Fallwinter2014

C o v e r i n g M a i n t e n a n C e S o l u t i o n S f o r t h e i n d u S t r yKeystone PublishingP.O. Box 3502Covington, LA70434

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Sulfuric Acidwww.H2S04Today.com Fall/Winter 2014

IN THIS ISSUE > > > > global sulfuric acid – 2014 in review and outlook 2

Solid sulfur handling at sulfuric acid plants: an update Page 25

Solvr™ technology provides welcome solution for Southern States Page 30

H2SO4 + Fe -> FeSO4 + H2

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C o v e r i n g M a i n t e n a n C e S o l u t i o n S f o r t h e i n d u S t r y

Keystone PublishingP.O. Box 3502Covington, LA70434

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Sulfuric Acidwww.H2S04Today.com Fall/Winter 2014

IN THIS ISSUE > > > > global sulfuric acid – 2014 in review and outlook Page 12


Solvr™ technology provides welcome solution for Southern States 0


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Vol. 20 No. 2 Covering Maintenance Solutions for the Industry Fall/Winter 2014

froM the PuBliSherKeystone PublishingP.O. Box 3502Covington, LA70434

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Solvr™ technology provides welcome solution for Southern States Page 30

Dear Friends, Welcome to the Fall/Winter 2014 issue of Sulfuric Acid Today magazine. We have dedicated ourselves to covering the latest products and technology in our industry over the

last two decades, and hope you find this issue both helpful and informative. In this issue, you will find several articles regarding the latest technological information available to the sulfuric acid industry. For example, our cover story details the findings of a special Hydrogen Safety Committee that investigated recent hydrogen explosions in sulfuric acid plants across the globe. The article delves into the mechanisms behind the formation

of hydrogen as well as provides practical steps that you can take to mitigate the chances of hydrogen-based incidents

at your facility. To follow up on this important top-ic, the Hydrogen Safety Committee will provide an update with their latest findings at the Sulfuric Acid Roundtable to be held March 23-26, 2015, in Stream-song, Fla. Beyond safety concerns, this issue covers many other subjects to help inform your work in the indus-try. Be sure to read: “Global sulfuric acid–2014 in re-view and outlook” (page 12), “Increasing efficiency of spent acid oxidation facilities” (page 14), “SNC-Lava-lin: proven technology through years of innovation” (page 18), “Restoration technology for polymer con-crete” (page 20), “Anodic protection–proven corro-sion prevention for storage tanks” (page 21), “A simple

and effective tower upgrade: NORAM HP™ saddle packing” (page 22), “Solid sulfur handling at sulfuric acid plants: an up-date” (page 25), “SolvR™ Technology provides welcome solu-tion for Southern States Chemical” (page 30), “The dangers of pirated parts” (page 32), “WESP economics: how wet electro-static precipitators reduce gas cleaning costs, offer competi-tive edge” (page 34), “Roberts continues to expand offerings to phosphate industry” (page 35) and “Advancements in sulfur spraying: new hybrid gun and predictive modeling” (page 36). I would like to thank our new and returning Sulfuric Acid Today advertisers, including Acid Piping Technology Inc., BASF, Beltran Technologies, CECO Filters, Central Maintenance & Welding, Chemetics Inc., Corrosion Services, Combustion Solutions GmbH, El Dorado Metals Inc., Haldor Topsøe A/S, Kimre, Koch Knight LLC, MECS Inc., NORAM Engineering & Constructors, Outotec, Powell Fabrication & Manufacturing, Roberts Company, Sauereisen, Siemens, Southern Environmental Inc., Southwest Refractory of Texas, Spraying Systems Co., SNC-Lavalin, VIP International and Weir Minerals Lewis Pumps. We are currently compiling information for our Spring/Summer 2015 issue. If you have any suggestions for articles or other information you would like included, please feel free to contact me via e-mail at [email protected]. I look forward to hearing from you.

Sincerely,Kathy Hayward

on the Cover7 hydrogen formation in

sulfuric acid plants and considerations for risk mitigation

dePartMentS4 industry insights news items about the sulfuric

acid and related industries

16 lessons learned Case histories from the

sulfuric acid industry

41 faces & Places Covering sulfuric acid industry

events

42 Calendar of events upcoming industry events

12 Global sulfuric acid–2014 in review and outlook

14 Increasing efficiency of spent acid oxidation facilities

18 SNC-Lavalin: proven technology through years of innovation

20 Restoration technology for polymer concrete

21 Anodic protection–proven corrosion prevention for storage tanks

22 A simple and effective tower upgrade: NORAM HP™ saddle packing

25 Solid sulfur handling at sulfuric acid plants: an update

30 SolvR™ Technology provides welcome solution for Southern States Chemical

32 The dangers of pirated parts

34 WESP economics: how wet electrostatic precipitators reduce gas cleaning

costs, offer competitive edge

35 Roberts continues to expand offerings to phosphate industry

36 Advancements in sulfur spraying: new hybrid gun and predictive modeling

38 An institution in Clearwater: conference convenes for 38th year

38 DuPont, MECS host annual best practices workshop

40 Australasia workshop informs with wealth of experience

PUBLISHED BYKeystone Publishing L.L.C.

PUBLISHERKathy Hayward

EDITORApril Kabbash

ASSISTANT EDITORApril Smith

DESIGN & LAYOUT

Mailing Address: P.O. Box 3502Covington, LA 70434

Phone: (985) 893-8692 Fax: (985) 893-8693

E-Mail: [email protected]

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U.S. Subscription —- $39 per year (2 issues)Internat’l Subscription —-$59 per year (2 issues)

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Sulfuric AcidT O D A Y

INdUSTry INSIgHTS

Ma’aden selects MeCS® Sulfuric acid technology for phosphate fertilizer complexWILMINGTON, Del.—DuPont Sus-tainable Solutions announced in March that MECS, Inc., a wholly owned sub-sidiary of DuPont, has been awarded the sulfuric acid technology license by the Saudi Arabian Mining Com-pany (Ma’aden) for its Waad Al Sha-mal Phosphate Project. MECS, Inc., will provide the sulfuric acid technol-ogy and proprietary equipment for this three-line, 15,150 metric-tonne-per-day sulfuric acid facility. Ma’aden has se-lected a consortium led by long-time MECS licensee SNC-Lavalin Group Inc. to perform engineering, procure-ment and construction of the sulfuric acid and power segments of the com-plex. When operational in 2016, the facility will be one of the largest world-class phosphate fertilizer complexes, positioning Ma’aden as a significant global producer of fertilizers and other phosphate-based products. “We are proud to partner with Ma’aden and SNC on this landmark project and look forward to supporting Ma’aden in its endeavor to be a world-class minerals enterprise,” said Kirk Schall, vice president of licensing, MECS, Inc. MECS® Sulfuric Acid Technology is marketed and licensed by MECS, Inc., a global leader in the design of sulfuric acid plants and related high-performance products for the phosphate fertilizer, oil refining, general chemical and metal smelting industries. MECS has a long and successful history of providing best-in-class sulfuric acid plant processes, clean technologies and specialty products for more than 80 years, with 1,000 acid plants worldwide. MECS offers proven and reliable solutions that feature breakthrough technologies, many of which have revolutionized performance, quality and cost-effectiveness for the sulfuric acid industry. For more information, please visit www.mecsglobal.com.

aSarCo plans $110 million upgrade of hayden smelterHAYDEN, Ariz.—To meet new, more stringent emissions rules issued in 2011 by the U.S. Environmental Protection Agency (EPA), ASARCO has drafted plans for a $110 million upgrade of the Hayden copper smelter to bring the apparatus in compliance. The project will enable the smelter to meet EPA

rules limiting SO2 emissions from 140 ppb (parts per billion) to 75 ppb during a 24-hour period. The Hayden smelter has until Oct. 3, 2018 to meet this standard. ASARCO’s plan, which it filed on June 24 with the Arizona Department of Environmental Quality (ADEQ), will replace the smelter’s five current 13-ft. diameter converters with three 15-ft. diameter converters. Also included in the plan are the installation of improved primary and secondary hoods, and an electrostatic precipitator for solids removal prior to SO2 recapture at the smelter’s existing acid plants. Larger ladles (300 cu. ft. instead of 200 cu. ft.) will be installed to reduce the number of hot metal transfers. Additional upgrades will capture secondary gases and direct them to the acid plant for conversion to a sulfuric acid product. Overall, the plan aims to reduce SO2 emissions at the Hayden smelter by 85 percent, with a total SO2 capture rate of 99.7 percent of what is produced during the copper smelting process. ADEQ is expected to rule on the ASARCO plan early this fall. If approved, the plan will then go to the EPA for an additional 45-day comment period. With EPA approval, ASARCO could begin work on the upgrades before year’s end. Each year the Hayden smelter produces more than 300 million tons of 99 percent pure copper, along with more than 575,000 short tons of sulfuric acid. For more information, please visit www.asarco.com.

Surplus on the horizon for Chile’s sulfuric acid market SANTIAGO, Chile—After a decades-long deficit, Chile’s sulfuric acid market is expected to turn a net surplus by 2020 on a future decrease in consumption due to lower production of copper in cathodes, said state copper commission Cochilco. Chile’s sulfuric acid is obtained mainly from seven copper smelters, four of which are run by state giant Codelco, one by state minerals firm Enami, and the Chagres and Alto Norte smelters owned by Anglo American and Glencore, respectively. There are a number of other facilities that also produce sulfuric acid, including roasters and metallurgy plants. Chile’s sulfuric acid production was 5.4 million tons in 2013, while consumption was 8.36 million tons, creating a deficit of 2.93 million tons. Some 2.83 million tons were imported, mainly from Peru, Japan and South

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Korea, according to a Cochilco report.Cochilco said that the deficit

condition is expected to continue through 2020, the year in which production is expected to surpass consumption.

The decline in consumption is explained by a decline in the production of copper in cathodes, expected to fall to 1.13 million tons in 2023 compared to 1.93 million tons produced in 2013.

Cochilco noted that there’s only one large scale cathode production ex-pected to come online in the coming years—Antofagasta Minerals’ Antu-coya. Meanwhile, Collahusi, Uebrada Blanca, Mantos Blancos, Michilla and Mantoverde are all expected to close down operations before 2023.

Other factors expected to contribute to the surplus are an increase in acid production as a result of process optimization due to new smelter emission standards that will enter into effect in 2018, and a voluntary increase in production from two new sulfur roasters expected to go online in 2016.

Part of Mexican copper mine closed after spillCANANEA, Mexico—Mexican author-ities have closed part of a huge copper mine at the heart of a major chemical spill in August, which prompted offi-cials to turn off the water supply in sev-eral towns and forced dozens of schools to close.

“Various irregularities” found at the Buenavista mine in the northwest of the country pose an “imminent risk” of more problems, said the prosecutor’s office for environmental issues, known as PROFEPA.

On August 6th, 10.6 million gallons of sulfuric acid used to dissolve copper from ore leaked out of a holding tank at the Buenavista mine, which is one of the largest in the world. The chemical turned a 640-mile stretch of the Sonora River orange, causing authorities to shut off the water supply to 20,000 people in seven towns. Around 80 schools were closed for a week.

The mine is owned by Latin American mining giant Grupo Mexico, which released a statement blaming the leak on heavy rains, although for the first time it also said another factor was a construction flaw in a pipe.

The Buenavista mine produces 200,000 tonnes of copper a year, and is seeking to increase annual output to 510,000 tonnes by 2016 with a $3.2 billion investment.

In the acid spill case, Mexican law limits the maximum fine to the equivalent of $224,000. But PROFEPA is presenting arguments to try to

increase the fine to at least $3 million. For more information, please visit www.gmexico.com.

Solvay to sell its u.S.-based eco Services business unit to CCMP CapitalBRUSSELS—Solvay has signed a binding agreement to sell its sulfuric acid virgin production and regeneration business, Eco Services, to affiliates of CCMP Capital Advisors, LLC. “The divestment of Eco Services is another step in Solvay’s transformation aimed at achieving higher growth and greater returns. Eco Services has a market leading position and generates stable cash flows, but its business profile differs from Solvay’s strategic ambitions,” said Jean-Pierre Clamadieu, CEO of Solvay. “CCMP Capital is committed to working with the management team to make the investments necessary to support the long term growth of the business.” The transaction terms correspond to an enterprise value of $890 million. CCMP specializes in middle market buyouts and growth equity investments of $100-$500 million in North America and Europe. CCMP’s core strategy is to enhance the value of its portfolio companies through an active approach to operational transformation. As an international chemical group, Solvay assists industries in finding and implementing ever more responsible and value-creating solutions. Solvay generates 90 percent of its net sales in activities where it is among the world’s top three players. It serves many markets, varying from energy and the environment to automotive and aeronautics to electricity and electronics, with one goal: to raise the performance of its clients and improve society’s quality of life. The group, which employs 29,400 people, is headquartered in Brussels. Solvay Eco Services, headquartered in Cranbury, N. J., with 500 employees, is the U.S. leader in technologies that sustainably regenerate sulfuric acid for oil refineries. It also produces virgin sulfuric acid that is used in a range of applications, including mining, water treatment and other industrial chemical processes. Thanks to its network of six large-scale manufacturing plants, Eco Services supplies most of the largest refineries in the U.S. West Coast, Midwest, the Gulf of Mexico and Canada. For more information, please visit www.solvay.com.

(Continued on page 32)

INdUSTry INSIgHTS

Sulfuric Acid Today • Fall/Winter 2014 PAGE 5

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World-class Technologyfor Worldwide Markets

We deliver a wide range of products and services, from engineering studies through to full EPC projects for the Sulphuric Acid Industry

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Chemetics Inc.(headquarters)Suite 200 – 2930 Virtual WayVancouver, BC, Canada, V5M 0A5Tel: +1.604.734.1200 Fax: +1.604.734.0340email: [email protected]

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Chemetics Inc., a Jacobs companywww.jacobs.com/chemetics

Acid Plants▪ Sulphur Burning▪ Metallurgical▪ Spent Acid Regeneration▪ Acid Purification & Concentration▪ Wet Gas

Proprietary Equipment▪ Converter▪ Gas-Gas Exchanger▪ Acid Tower (brick lined and alloy)▪ Acid Cooler▪ Furnace▪ SARAMET® piping & acid distributor▪ Venturi Scrubber

Technical Services▪ Turnaround inspection▪ Operations troubleshooting▪ Process optimization▪ Feasibility studies▪ CFD (Fluent) analysis▪ FEA (Ansys) study

introductionThe formation of hydrogen in sulfuric acid plants

is a known phenomenon resulting from the corrosion of metallic materials under specific conditions. Those conditions are strongly dependent on acid strength and temperature. As a result, a mixture of hydrogen and oxygen containing process gas can occur with the potential risk of a hydrogen explosion.

Over the last few years, several incidents related to this have been reported. The majority of the reported hydrogen events took place in intermediate absorption systems, converters or heat recovery systems. In general, the incidents occurred during maintenance or after stopping the gas flow through the plant. In all cases, water ingress, resulting in low acid concentration, caused the formation of the hydrogen. In most of the cases, the water ingress was ignored or not noted and mitigation measures were not in place. As a result, plant equipment was severely damaged.

An international group from the sulfuric acid industry formed an expert committee dedicated to this topic. The members of this committee are from plant operation, consultancy as well as equipment/plant design disciplines.

The aim of the group was to analyze well documented hydrogen incidents in acid plants and identify high level considerations to assist operators and plant designers in avoiding/minimizing risk and mitigating potential consequences. This document summarizes the findings, considering:

• Theoreticalbackground “Understand the causes of hydrogen incidents.”• Plantandequipmentdesign “Issues and facts to consider when designing/modifying

a plant or equipment.”• Operationalandmaintenancepractices “How do you know that there is an issue and do you

know how to respond if there is an issue?” The intention of this work is to bring awareness to this important topic and provide high level recommendations and support for decision and concept finding, training of personnel and/or establishing mitigation measures. Firstly, an understanding of the chemistry and the root causes for such events is fundamental. The measures to be undertaken to avoid or mitigate such events must cover a multitude of aspects that can’t be covered in one general document. One has to be aware that there are, to each and every plant, details that need to be elaborated individually.

theoretical considerations The risk of a hydrogen explosion basically depends on three factors, which have to happen in sequence:

—Hydrogen generation (corrosion).—Formation of an explosive mixture of hydrogen and

oxygen containing process gas.—Ignition of the hydrogen/oxygen/process gas mixture.

While the formation of hydrogen and the explosion limits are well known and based on hydrogen release as an effect of corrosion products, there are no hard facts

about the possible sources and mechanism of the ignition.

explosion limitsThis section discusses the factors relating to hydrogen’s explosion limits. Explosion limits of hydrogen in air and air/nitrogen at room temperature, measured by various standards (in mole-%)

The case with 40 percent by volume N2 leaves a residual oxygen content of about 13 percent by volume, which is about double to triple the content usually experienced at the

DIN 51649 EN 1839(T) EN 1839(B) ASTM E681

LEL (H2 in air) 3.8 3.6 4.2 3.75

UEL (H2 in air) 75.8 76.6 77.0 75.1

LEL (40% N2 +air) 3.6 3.6 4.4 3.65

UEL (40% N2 + air) 38.2 38.4 38.2 37.3

Influence of temperature on explosion limits of hydrogen/air mixturesTemperature in °C LEL (mole-%) UEL (mole-%)20 3.9 75.2100 3.4 77.6200 2.9 81.3300 2.1 83.9400 1.5 87.6

Hydrogen formation in sulfuric acid plants and considerations for

risk mitigation

By: Members of the Hydrogen Safety Committee: Len Friedman (Acid Engineering & Consulting), Rick Davis (Davis & Associates Consulting), Steven M. Puricelli

(DuPont MECS), Michael Fenton (Jacobs Chemetics), Rene Dijkstra (Jacobs Chemetics), James W. Dougherty (Mosaic), Hannes Storch (Outotec), Collin Bartlett

(Outotec), Karl Daum (Outotec) and George Wang (Solvay).



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intermediate absorber. Thus, it is to be expected that the UEL in this case will be below the tabled figures.

It appears that the explosion range widens with increased temperature, which is important to consider at the prevailing conditions of acid plant operation. The minimum self-ignition temperature amounts to 585 degrees C.

Fig. 1 shows the variation of the explosion limits as a function of the temperature (H2 in air).

The presence of additional N2 or CO2 in the gas (air) will reduce the oxygen content. Subject to the residual O2, the explosion limits vary significantly, as presented in Fig. 2.

The diagram in Fig. 2 is based on a NASA report (1993) and suggests that the LEL remains virtually stable and constant with increased N2 content, while the UEL significantly decreases. Once the oxygen content of the gas reaches a level below 4-5 percent, the H2 is outside of any critical composition. This is very close to a typical gas at the exit of an intermediate absorber and hence one must not expect the formation of an explosive gas composition at “normal” operation. Obviously, no considerable amount of H2 would be released at such “normal” operation. However, release of H2 is much more important during plant shutdown and periods of maintenance.

explosion pressure and ignition energy

The energy involved in a hydrogen explosion/reaction is determined by the equations:

2H2 + O2 = 2H2O ∆H=-483,652kJ/mol The reaction is highly exothermic and the high valueofreactionenthalpy∆Hindicatesthattheresultof an explosion can be devastating. Fig. 3 shows the

explosion pressure generated. Ignition of hydrogen/air mixtures, particularly when these mixtures are within the flammability limits, takes place with only a very slight input of energy. A spark with such low energy that it is invisible in a dark room can ignite such a mixture. Common sources of ignition are sparks from electrical equipment, and sparks caused by the discharge of a small accumulation of static electrical charges. Even though a mixture is below the limit of flammability, some combustion can occur with a source of sufficient size and intensity. The minimum energy of ignition at a volumetric hydrogen concentration of 30 percent (stoichiometric) is only 0.02 mJ (while in pure oxygen, it is only 0.007 mJ). The ignition energy sharply increases at leaner or richer hydrogen concentrations and reaches 10 mJ, which represents a typical static discharge from a human body. This example shows that when there is the accumulation of an explosive hydrogen/oxygen mixture the likelihood of an ignition is extremely high.

hydrogen formation rate Stoichiometric corrosion chemistry is trivial and conforms to the following equations: H2SO4 + Fe –> FeSO4 + H2 3 H2SO4 + 2Cr –> Cr2(SO4)3 + 3H2 H2SO4 + Ni –> NiSO4 +H2 In practical terms, those equations describe that: —For each 1 kg of Fe, an amount of 0.0361 kg of H2 is

generated (equivalent to 0.40 Nm³). —For each 1 kg of Cr an amount of 0.0582 kg of H2 is

generated (equivalent to 0.65 Nm³). —For each 1 kg of Ni an amount of 0.0344 kg of H2 is

generated (equivalent to 0.38 Nm³). Typical corrosion rates of usual metals in acid plants are known, for example, as shown in Fig. 5 through Fig. 8. These diagrams can be used to quantify the amount of hydrogen generated.

Based on those data, the amount of hydrogen generated can basically be determined, at least as an order of magnitude. For example, the corrosion rate of a 1000 m² heat exchanger when exposed to 100 degrees C acid at 80 percent H2SO4 is in the range of 10 mm/year. Low alloy stainless steel, e.g. 304 or 316 type, offers slightly less corrosion, but still in the range of 6 mm/year. If such a heat exchanger is exposed to 80 percent acid at 100 degrees C for about 4 hours, then the amount of hydrogen produced would amount to 37 kg or 406 Nm³. When a plant is idle for such time and the hydrogen accumulates at the top of the intermediate absorption tower, which may have a volume of 700 m³ (or even less when considering only the “dead” volume on top of the gas exit duct, say 150 m³), then the H2-concentration can be anywhere from 50-100 percent. The rest of the gas obviously must contain some oxygen, which is the case when <100 percent H2 is present. These figures are well within the range to generate an explosion, provided that sufficient oxygen is present. Obviously it has to be considered that such an explosive mixture could accumulate—depending on the plant configuration—in other areas. For example, in one reported case the explosion occurred not in the top of the tower, but below the candle filter tube sheet.

normal variation or excursion of acid concentration during operation The earlier example and case studies clearly show that such events occur only under atypical conditions. It has to be understood that variations of acid concentration at normal operation, e.g. failure to control process water addition, can be regarded as non-critical with regard to the potential formation of hydrogen as a result of corrosion. Despite the higher corrosion rate as a function of operating outside the pre-determined design figures/operating windows, and as long as the possible material window of concentration and temperature are adhered to, the potential amount of hydrogen formed is negligible. It can be concluded that: 1. The small amount of H2 will not reach the

explosion range during operation. 2. Normal operation offers a gas composition where

the O2 content is very low. 3. By having a continuous gas flow through the plant,

the hydrogen concentration will be negligible and well below the lower explosive limit.

Fig.1: Explosion limits of H2 as function of temperature.

Fig.4: Ignition energy of H2 in air as function of pressure and composition.

Fig.5: Iso-corrosion of carbon steel general.

Fig.6: Iso-temperature corrosion of carbon steel at higher acid concentrations.

Fig.7: Typical corrosion rate of carbon steel

Fig.8: Typical corrosion rate of stainless steel

Fig.2: Explosion limits of H2 as function of additional nitrogen or carbon dioxide.

Fig.3: Explosion pressures of hydrogen/air and hydrogen/oxygen mixtures at 1 bar and room temperature.


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Operating windows are to be determined in accordance with process boundaries, e.g. an absorber cannot be operated outside of 98.0-99.0 percent H2SO4 and a drying tower not outside of 92-98.5 percent H2SO4, without generating other detrimental effects, such as extreme SO3 plume or heavy condensate formation. Obviously such circumstances would force a plant shutdown prior to entering into the tolerable material window. The material window is defined to be the range where the corrosion rate is still tolerable for a short period of time (up to, say, 1 mm/year), despite being the typically acceptable range of 0.1 mm/year. As long as operation parameters are contained within said limits, one must not expect an exceeding formation of hydrogen during operation. Shut down conditions are very different, however, as the hydrogen may accumulate and thus form an explosive composition.

Plant and equipment design considerations

It is a given that, in every plant, equipment can fail due to nearing the end of operational life, malfunction or defect. For the formation of hydrogen, the equipment that causes excessive water ingress is most relevant. That equipment is mainly steam related (waste heat boilers, economizers or superheaters) or water related (acid coolers or water dilution control valves).

As explained earlier, hydrogen is formed by the reaction of weak and/or hot acid with stainless steel, e.g. acid coolers, economizers, stainless steel towers, piping and other metallic components. The formed hydrogen will find, in every plant, stagnant areas where gas can accumulate and form an explosive hydrogen/oxygen/process gas mixture.

As all of that equipment is required and the plant layout will not allow an elimination of those stagnant areas (e.g. in one reported incident, the hydrogen reacted below the tube sheet), different measures that can be taken during design or operation to minimize risk need to be discussed. Of course, based on the studied cases, there are contributing factors to consider. For example:—Delayed leak detection, e.g. due to leak size or not

maintaining/installing instruments.—Inability to isolate/separate the water from the acid

system.—Inability to remove weak acid from the system, which

causes further corrosion.—Insufficient operation manuals addressing such events.

Keeping those generic aspects in mind will certainly help to increase the awareness of the issue of hydrogen incidents. The expert committee elaborated on more specific high level considerations. Those considerations should serve as a help for designers, operators and consultants in the sense of …am I aware of the potential consequences… or …have I considered that….. Please note that obviously such a list cannot cover all the specific elements of a plant, equipment, etc., and is meant as a list of typical considerations that complement rather than replace design guidelines, operation manuals or procedures. Such plant-specific documents can and should be expanded with regard to the hydrogen issue during the respective project-specific discussions.

high level considerationsAvoiding hydrogen formation

The mechanism of hydrogen formation is well understood, as described earlier. It is crucial to transfer this knowledge into the design and operation in order to minimize the risk of hydrogen formation, which actually

means avoiding rapid corrosion. It is of utmost importance to consider the entire plant/operation and understand potential effects of local modifications to other plant areas.• Considerthecharacteristicsofconstructionmaterials:

—Bricklined vs. stainless steel towers/vessels (material resistance, drain concept, etc.).

—Cast iron vs. stainless steel equipment (irrigation system, piping, etc.).

• Ensure separation of weak acid from metallurgicalsurfaces, for example:—Drain acid from acid coolers; consider drain valve

location and size of valve and ensure drain piping is sufficiently dimensioned.

—Acid can be drained from other stainless steel equipment, e.g., towers, pump tank, piping, etc.

—Acid distributors, tube sheet can be drained to avoid risk of local hydrogen formation.

• Minimizewateringressusingthesedesignconsiderations:—Cooling water isolation.—Boiler feed water bypasses around economizer.

• Considermeasurestoidentifywateringressearlyon,forexample:—Additional instrumentation to measure, e.g., dew point

and opacity.—Intelligent data management system for analyzing

flow rate, temperature, production deviation, etc.• Consider related infrastructure inplant safetyconcept/

HAZOP studies, especially the cooling water system:—Ensure that water pressure is always lower than acid

pressure.—Ensure that acid contaminated cooling water can be

drained.—Ensure cooling water quality is monitored.

Avoid hydrogen accumulation The key to safe operation is avoiding hydrogen formation. However, one has to consider that despite all efforts, the risk of hydrogen formation exists–even only nominally. Hence the design of plant/equipment as well as operational procedures must take this into consideration. • Use these design considerations to minimize areas of

potential hydrogen accumulation:—Fit acid tower with top, not lateral, gas outlet. —Minimize volumes of gas accumulation through the

design of the equipment, see example later in this article.

• Ensurethatpropershutdownandpurgeproceduresareinplace:—Those procedures have to be established considering

the individual plant characteristics and local standards.—Potential procedure: ongoing purging of the plant by

main blower following an event, until all weak acid is removed from system and equipment is isolated.

• MinimizepotentialH2 accumulation by, for example: —Purging blower.—Installing high point vents.—Purging nitrogen (depending on local infrastructure).

Equipment specific aspects Equipment design and operation should consider specific aspects for risk mitigation. Listed below are three examples of equipment that represent prominent sources of hydrogen formation, accumulation and ultimately explosion. Please note that equipment other than those listed could also be analyzed in a similar fashion.

Acid coolers Acid coolers offer a huge surface area, and hence have the highest potential for hydrogen formation. However weak acid in cooling water circuits can also result in hydrogen formation in the respective equipment (e.g., air coolers with closed loops). Consider the following aspects of acid cooler operation:• The main reason for an acid cooler leak is related to

water quality.—Is the cooler chosen for the cooling water quality?—Does the actual and the specified quality of the cooling

water match?—Is the cooling water quality regularly monitored and

are treatment procedures in place and maintained?• The acid pressure should be higher than the water

pressure.—While this is correct at start-up, is this still valid after

years of operation?—How is this considered/mitigated at heat recovery

coolers/evaporators, where this demand can generally not be adhered to?

—How is this ensured in abnormal situations, e.g., acid pump shutdown, filling of tanks etc?

• As plant capacities increase, acid coolers are gettinglarger. Is the increased capacity considered in the design?—Is the drain number and size correctly dimensioned?—Is a vent valve installed to support faster drainage?—Where are water and acid drained to?

• Isthemaintenanceofacidcoolersdoneinaproperway?• Are there procedures available and are personnel

aware of them?• Thewashingofcoolerscanresultin:

—Residual water in plugged tubes. Note: Tubes can be blocked by fouling on the water side, which creates a corrosive environment (hot spots).

—Residual water in the shell.• Isanadequateleakresponseensured?• Can the water side of the cooler be isolated and

drained?• Are the drains/vents easily accessible even during

upset conditions?

Economizer In economizers the water pressure is always significantly higher than the gas pressure, so a leak will force water into the gas stream. Once water has entered the gas stream weak sulfuric acid will potentially be formed. The result can be rapid corrosion (hydrogen formation) of the finned tubes and other downstream equipment.• Waterenteringthegasstreamcanendinacidtowersand

dilute the acid strength.• Considerdrainingtheeconomizer.

—Bottom drains can easily be blocked by small debris or sulfate.

—Is it part of maintenance practice to inspect such drains at every shut down?

—Is there a safe location to drain to?• Areupsetoperationsandcooldownphasesadequately

considered?—Can the water side be fully isolated?—Is a gas or water bypass around the economizer needed

for the cool down procedure?

Absorption towers Irrespective of a leak occurring in an economizer, waste heat boiler or acid cooler, ultimately the water will enter the absorption tower, eventually resulting in circumstances where the acid strength can’t be controlled anymore, hence the sub-system of the intermediate absorption tower is the


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area of the highest potential for hydrogen formation.• Whatareimplicationsofconstructionmaterials?

—Stainless steel towers are easy to install, however they offer a reduced operation window. Can it be ensured that the towers can be drained in case of upset operation (weak acid)?

—Bricklined towers are significantly more robust and less exposed to corrosion and so weak acid could remain stored in the tower sump or pump tank for some time. Has the material decision been triggered by the draining concept?

—Consider a design to minimize vapor and stagnant gas spaces.

—Consider standing vs. hanging candle filters, as in Fig. 9.

—Consider top vs. lateral gas outlet, as in Fig. 10.—Consider the maintenance concept: in-tower candle

replacement vs. cutting of roof.—Consider options to remove hydrogen from the

potential areas in the tower:—Purging using main blower after acid pumps are out

of operation.—Purging using nitrogen (if available).—Purging using high point purging vents.

operation and maintenanceIrrespective of implementing previous suggestions, the

key to avoiding such events is operator and maintenance personnel awareness of the theory behind hydrogen formation and the potential consequences. Operators have to plan and be prepared for such events, ensuring early detection, mitigation and prevention.• Do the following operational/maintenance procedures

cover such events?—Regular and emergency shutdown procedures.—Equipment evacuation procedures.

• Dooperatorshavethechancetopracticeforsuchevents?º How is it is ensured that the procedures will work?

—Transfer experience (legacy planning).—Test operator skills.

º Do operators understand to look out for early warning signals?

º How are new operators trained?º Is the equipment regularly inspected/tested?

—Ensure that bypass and drain valves work.—Ensure the drain line and disposal area is not

blocked.—Ensure that drains are cleaned at every shut down.

• Earlywarningofaproblemisvital. º Are sufficient instruments installed?

—Analyzers on cooling water return, one per cooler.—Consider water and acid temperature measurement. —Redundancy of acid measurement in cooling water

(pH-meter, conductivity, etc.).º Are instruments maintained regularly, including

cooling water loops?• Istheavailableinformationusedina“smart”way?

º Is a data management system used, e.g., acid plant water balance system?

º Are historical trends used?º Is the anodic protection understood? Changes in

current/voltage indicate a problem at a very early stage.

• Domaintenanceproceduresconsideradequatepurgingand flammable gas testing?

Conclusion Generation of hydrogen in a sulfuric acid plant is a well-known phenomenon, but for some unknown reason, the incidence of hydrogen explosions has recently been on the rise. Fortunately, there have been no serious injuries to date. But, unless hydrogen safety is brought to the forefront of our thinking, the consequences could become more dire.There are many potential causes for the increased incidence of hydrogen explosions, including the age of operating sulfuric acid plants, the increased use of stainless steel equipment in lieu of traditional brick and cast iron materials, new maintenance practices, new safety and environmental regulations that limit the ability of operators to perform traditional operational checks (such as draining drip acid from equipment) and a loss of operating experience, due to demographics. Moving forward, all parties involved must recognize that equipment failures are inevitable and when water is involved, a weak acid excursion can occur. This article has shown that the conditions leading to the formation of an explosive mixture can occur rapidly and immediate action is required that can only be achieved via thorough planning and procedures. By disseminating this information, the hope is that operators and designers alike become more aware of the hazards, making new plants better equipped for hydrogen safety and helping existing plants stay out of potentially dangerous situations. Any questions pertaining to hydrogen-related incidents, redesigns or operations can be brought to the attention of the Hydrogen Safety Committee by contacting any member of the group via email. Len Friedman, email: [email protected]; Rick Davis, email: [email protected]; Steven Puricelli, email: [email protected]; Michael Fenton, email: [email protected]; Rene Dijkstra, email: [email protected]; James W. Dougherty, email: [email protected]; Hannes Storch, email: [email protected]; Collin

Bartlett, email: [email protected]; Karl Daum, email: [email protected]; and George Wang, email: [email protected]. q

referencesV.Scroeder and K Holtappels, Explosion Characteristics of

Hydrogen-Air and Hydrogen-Oxygen Mixtures at Elevated

Pressures

Z. M. Shapiro and T. R. Moffette, Hydrogen Flammability

Data and Application to PWR Loss of Coolant Accident-

WAPD-SC -545 1957

HF Coward and GW Jones, Limits of Flammability of Gases

and Vapors-Bureau of Mines Bulletins 503-1952

I.L. Drell and F.E. Belles, Report 1383, Survey of Hydrogen

Combustion Properties NACA Lewis Lab-1957

MG Fontana IEC Vol 43, Aug 1951 P65A

General Chemical Data

N.D. Tomashov, Theory of Corrosion and Protection of

Metals

Inco CEB-1-1983, The Corrosion Resistant of Nickel

Containing Alloys in Sulfuric Acid and Related Compounds

2015 Sulfuric acid roundtable set for floridaCOVINGTON, La.—Sulfuric Acid Today is pleased to announce that the 2015 Sulfuric Acid Roundtable is scheduled for March 23-26, 2015. This year’s roundtable will take place at the newly constructed Streamsong Resort in central Florida. Attracting an international audience of professionals in the phosphate, metallurgical/smelting and acid regeneration industries, this biennial conference provides a venue for participants to learn the latest sulfuric acid technologies and exchange best practices. The schedule will closely follow the model of previous meetings. It will consist of two and a half days of informative presentations from the conference’s co-sponsoring firms along with insightful producing plant presentations, maintenance panel discussions, a keynote address on the global sulfuric acid market for 2015 and an update on hydrogen safety. There will be ample networking opportunities to meet co-sponsor representatives and peruse their exhibits of acid plant supplies and services. This year’s location will also allow roundtable attendees to take advantage of many recreational activities, including golf, fishing, hiking and clay shooting. An exciting new feature of this year’s roundtable will be a tour of Mosaic’s New Wales Phosphate Fertilizer Complex in Mulberry, Fla. The New Wales site, which has been in operation since 1975, sports five sulfuric acid plants producing 14,000 TPD and three turbine generators capable of producing over 100 MW of electricity. The site manufactures over 4 million TPY of phosphate fertilizers and is also one of the largest producers of animal feed supplements in the world. For more information on the roundtable or to register, please visit www.acidroundtable.com. For sponsorship opportunities, please contact Kathy Hayward, (985) 807-3868 or email [email protected]. q

Fig. 9: Standing candle filters (left) versus hanging candle filters.

Fig. 10: Top gas outlet (left) versus lateral outlet.


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In the Fall 2013 issue of Sulfuric Acid Today, excess supply was beginning to emerge that resulted in weaker sulfuric acid market prices throughout the fourth quarter before a recovery in February 2014.

One of the factors that contributed to increased supply toward the end of 2013 was reduced demand from phosphate fertilizer producers. While most sulfuric acid used by phosphate fertilizer producers is produced internally through the burning of elemental sulfur, producers still purchase incremental sulfuric acid volume in the merchant market, which plays a role in balancing global trade.

Compared with the second half of 2013, conditions in the phosphate fertilizer market during the second half of 2014 are stronger in terms of demand, and subsequently, prices. For example, the Tampa diammonium phosphate (DAP) export price from the start of the third quarter 2013 through the first week of September was in the $395-465/tonne freight-on-board (fob) range with the high exhibited the first week of July and the low during the first week of September. For the same time period this year, prices were in the $490-513/tonne fob range, representing higher prices and less volatility than the prior-year period. As a result, this has provided some sulfuric acid demand support to the merchant market.

Meanwhile, supply from base metals smelters, the primary source of acid traded in the market, has been stable. On the consumption side, market participants report industrial demand for sulfuric acid has been stronger than last year although in key markets, such as the United States, there is no significant sector or driver being cited.

So while the stronger phosphate fertilizer market and apparent firmer demand from industrial sulfuric acid consumers in 2014 would suggest higher prices than in 2013, there have been factors resulting in greater availability of sulfuric acid compared with last year, which has limited potential for upward price movement.

South Korea and Japan are sources of significant volumes of sulfuric acid traded in the global market because of the prevalence of base metal smelters in the region. In 2013, South Korea exported close to 2.9 million tons of sulfuric acid, or 19 percent of total global exports, while Japan exported around 2.6 million tons, or 17 percent of the global total. For both countries, Chile was the second-largest market served with it taking 17 percent of South Korea’s export volume and 25

percent of the volume exported from Japan. The supply from the two countries accounted for close to 1.2 million tons of the 2.8 million tons Chile imported in 2013. Clearly, Chile has been key for Asian smelter acid producers as an outlet for their involuntary production. Conditions in 2014 have been markedly different, however, as a result of freight costs from the key supply region to the largest import market. The freight costs have been outstripping prices that Chilean buyers were willing to pay. The annual contract price in Chile for 2014 is $60-69/tonne cost-in-freight (cfr), compared with the 2013 annual price of $90-100/tonne cfr. As of early September 2014, sulfuric acid vessel freight rates from South Korea/Japan to Chile were in the $70-80/tonne cfr range, implying any shipments under the 2014 annual price would result in a loss as

high as $20/tonne based on freight alone. As of the end of July, Chile’s imports from Japan for the first seven months of the year were down 47 percent compared with the prior-year period and imports from South Korea were down close to 51 percent. Imports from the two countries accounted for only 27 percent of the 1.3 million tons of acid Chile imported in 2013, compared with the 47 percent supplied in 2013 as a whole. To deal with the loss of Chile as an outlet for its production, suppliers in South Korea and Japan have had to increase volumes to alternative markets, mainly within the Asian region, including China and Thailand. This has often been at the expense of price, with assessed prices reaching negative levels in January 2014. Since moving out of the -$5/tonne fob range as February commenced, prices have only reached a peak of $10/tonne fob as of early

September. In comparison, prices were in the $0-10/tonne fob range for most of 2013. Some market participants have been surprised at the level of price support without the typical trade movement of South Korean and Japanese acid making its way to Chile. This implies that factors including improved demand from phosphate fertilizer producers and industrial consumers in 2014 over 2013 have effectively counterbalanced the loss of demand from Chile. Moving forward, Chile’s requirements will remain a critical factor in balancing the global market as Chile’s domestic production increases and the level of growth in consumption exhibited in prior years is not sustained as some consuming facilities close. This will result in Chile’s offshore import needs peaking, resulting in the need for key exporting regions continuing to rely on alternative markets.

Chile’s import requirements, along with whether or not the contract price in the primary import market will remain below freight rates from the key South Korea/Japan market, will be relevant in 2015. Meanwhile, factors in changing supply and demand in other regions will also impact the market in 2015. For example, the PASAR smelter in the Philippines is expected to double its capacity during the first half of next year from around the current 600,000 tonnes/year. A natural destination for this volume would be southeast Asia. But if competing against supply from South Korea and Japan (if Chile once again is not a viable outlet in 2015) the additional supply could put downward pressure on prices. Adding another layer of complexity is a primary sulfuric acid consuming site in the Philippines, the Philphos fertilizer plant, remains down following damage sustained

from Typhoon Yolanda in November 2013. It is unclear if the facility will resume operations in 2015. An extended outage would result in even more pressure to place the PASAR volume offshore. At the same time, the Taganito nickel leach project in the Philippines, which began consuming sulfuric acid in 2013, could consume more acid in 2015. However, increased supply from China is expected too, with the addition of new smelting capacity there, which could limit the country’s ability to absorb offshore imports. In other regions of the world, however, there is an increase in demand emerging. In the United States, the closure of PotashCorp’s (PCS) sulfur-based sulfuric acid plant in Geismar, La., by the end of the first half of 2015 will result in the need for acid to be purchased in the merchant market to fulfill demand rather than use acid produced internally. This is expected to tighten supply in the U.S. Gulf coast region and potentially allow for a higher volume of offshore imports. While overall consumption of sulfuric acid is forecast to increase, a significant portion of this will come through sulfur-based production for internal consumption, which will have a limited impact on the traded market. This includes addition of new capacity in Morocco to support OCP’s phosphate fertilizer operations. At the same time, new sulfur production capacity as new sour gas processing and oil refining capacity comes on stream is forecast to result in a surplus in supply in 2015 following deficit years in 2010-13 and forecast for 2014. This could result in downward pressure on sulfur prices, although this is expected to be more pronounced going into 2016 as the forecast surplus increases. This could impact the sulfuric acid market in terms of influencing price ideas or, for regions where sulfur is used as an index to represent costs for the raw material such as in the United States, limiting potential increases. Argus Media publishes weekly global reports on sulfur and sulfuric acid as well as reports on fertilizer-related products including nitrogen, ammonia, potash and phosphate. North American-specific publications for both fertilizers and the sulfur/sulfuric acid markets are also available. Argus also offers consulting services, including single-client studies and presentation services, for sulfur and sulfuric acid supported by our proprietary supply and demand model. For more information on Argus and its portfolio of fertilizer publications, please visit www.argusmedia.com/fertilizer. q

By: Fiona Boyd, Argus Media

global sulfuric acid–2014 in review and outlook


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t INdUSTry OUTLOOK

Effectively completing the oxidation process of spent acid formerly required a heating system containing a standing com-bustion chamber built in two separate sec-tions. A burner for pre-heating to support fuel injection along with nozzles for injec-tion of sulfuric acid are positioned at the be-ginning of the first section of the combus-tion chamber. In this system, the spent acid is injected top down into the first chamber section where it is vaporized, after which it is carried into the second chamber sec-tion where it is oxidized. The two chamber sections are linked with a short horizontal duct. The entire system requires plenty of space, materials and residence time.

CS Combustion Solutions GmbH (CS) worked for and with the Danish technology company, Haldor Topsøe AS, to improve the process of separating sulfuric acid. The main requirements of the WSA (wet sulfu-ric acid) process developed by Haldor Top-søe AS are the complete oxidation of spent acid and a compact horizontal combustion chamber. Additional requirements are:

• Regenerationofcontaminatedsulfuricacid by injecting with ultrafine atom-izing technology.

• Supportingfuelstoincludecokeovengas and vaporized waste liquids con-taining hydro-carbon combinations and carbon disulfide.

• Completevaporizationofthesulfuricacid without droplet formation.

• Space reductionwith the heat recov-ery boiler axially and the combustion chamber on the same horizontal axis.

• Protection of components located in-side the WHB with a special checker wall located in the combustion cham-

ber exit and directly in front of the boiler tubes.

With CS’s new concept, the combus-tion chamber is installed in a horizontal position. The pre-heating and support com-bustion burner and the nozzles for injecting the sulfuric acid are located on the front plate of the combustion chamber. Injection of sulfuric acid is done using just a few dual fluid lances located concentrically around the burner. Process parameters—time, temperature and turbulence—are guaran-teed with this system. The high-turbulence burner ensures excellent mixing while the ultrasonic nozzles realize the proper va-porization. Thus the residence time of the flue gas inside the combustion chamber can be reduced. Both the retention during the oxidation process and the combustion chamber physical dimensions are greatly reduced. CS’s own acid nozzles require consid-erably less pressure for the injection of the spent acid. Therefore the mixing and sup-ply pumps for the spent acid work with a very small rise in medium-pressure, which results in operating and maintenance cost reduction for pumps. Also the nozzles life-time will be increased. Obviously, a smaller, horizontal com-bustion chamber is cheaper and lighter. Also it is now possible to install a self sup-porting brick lining, field or shop installed. Furthermore, by eliminating the transition duct inside the combustion chamber, it is possible to use standard sized bricks, not to mention reduction of the dead space in the flue gas path. Further savings are achieved by eliminating the compensator between the combustion chamber and the boiler since they are aligned and bolted/welded together. Site construction costs and time are both reduced with fewer required steel structures, access platforms, stairs, etc. Inspection and servicing of the brick lining and combustion chamber are more easily facilitated by the chamber’s horizon-tal arrangement. This is also true for the burner and the spent acid lances, which are located at ground level of the plant. In short, the horizontal construction and unique design of CS’s combustion chamber components bring the following benefits to facilities operating in the field of spent acid oxidation:• Compactconstructionofthecombus-

tion chamber.• Simplification of servicing and facil-

ity modifications.• Comparatively lower CAPEX and

OPEX.

• Reducedprojectschedule.• A choice of pre-fabricated or on site

assembly of the brick lining.• Longerlifetimeofacidnozzles. This technology can be incorporated into new facilities as well as retrofitted into existing spent acid oxidation equipment.

about Combustion Solutions CS Combustion Solutions GmbH (CS) is an expert in the thermal oxidation of liquids, gases and powdered solids de-rived from by-products in the refinery, pet-rochemical, chemical and pharmaceutical industries. CS has a team of senior specialists dedicated to innovation and reliability in combustion/incineration and burner design. CS’s 25 years of expertise in engineering, supplying and commissioning combustors and oxidizers for a wide range of applica-tions are paramount to finding the best re-sults for each project’s requirements. Specializing in combustion systems for the refinery and chemical industries, CS has developed tailor made solutions for burning industrial by-products. In the chemical industry these are mainly waste gas, waste air or solvents, whereas in the refinery industry this is more and more tail gas from SRU plants. Over the past year, CS has introduced an improved generation of tail gas oxidiz-ers. The unique design of the CS combus-tion chamber creates new possibilities for refitting, optimizing and debottlenecking existing sulfuric compound separation fa-cilities. CS Combustion Solutions is part of the Unitherm Group, celebrating, in 2015, 70 years designing and providing combustion equipment. For more information, in Europe contact Thomas Bartonek at [email protected] or Andreas Kraxner at [email protected]. In North America, contact X. D. Hubert at (502) 819-0614. Visit our company website at www.comb-sol.com. q

Increasing efficiency of spent acid oxidation facilities

CS high efficiency spent acid combustor.

SAR plant in Poland for Haldor Topsøe A/S.


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Softened refractory Sulfur and spent acid regeneration fur-

naces are generally lined with refractory to provide thermal protection to the steel shell, in addition to keeping the heat within the fur-nace. The lining usually consists of two layers of refractory bricks or monolithic refractory. The insulating layer, which is closest to the steel shell, provides most of the thermal gradi-ent while the hot face layer, which is exposed to the process, provides thermal resistance, chemical resistance, mechanical stability and abrasion resistance.

Selection of the lining materials is critical for the longevity of the lining system and the steel shell. The materials and thicknesses of the insulating and hot face layers are selected to ensure the layers are kept in compression during operation and to ensure that the steel shell temperature is high enough to prevent condensation of acid vapors while preventing excessive strength loss of the steel shell. Refractory material selection is normally based on the maximum service temperature that is listed on the refractory data sheet. Bas-ing the selection entirely on this information, however, could lead to disastrous consequenc-es. One has to also consider the atmosphere in which the refractory operates. For example, a 60 percent alumina brick that has operated

successfully in a 2,250 degrees F (1,232 de-grees C) sulfur furnace may not necessarily work in a spent acid regeneration furnace at the same temperature. In addition, one has to consider the vol-ume stability (refractoriness under load) of the material. All things being equal, the refracto-riness under load, although tested in air, pro-vides the best indication of the performance of the refractory material against similar ma-terials. Of course, there is no substitute for a cup test. This test provides an indication of the material’s resistance to the damaging effects of slags or molten ash in your process.

Lesson learned When selecting refractory materials, do not rely just on maximum service temperature data. Also consider the proper steel shell tem-perature, the atmosphere in which the refrac-tory operates, and the volume stability of the hot face layer. Not considering these factors could lead to the refractory failures shown in Figures 1 and 2.

falling object Plant stacks are designed as self-sup-porting, all-welded steel structures. They are equipped with a tuned mass damper near the top (Fig. 3) or with guy wires (Fig. 4) to mini-mize movements from high winds or seismic loads. Because of their height, they are usually fabricated in manageable sections, so they can be shipped to the site for assembly. To speed up the erection process, one designer had a

better idea: bolt the sections together instead of welding. So, bolting flanges were welded to each section prior to shipping to the site. The bottom section was bolted onto the foundation and the other sections were bolted one on top of the other. The bolted joints were sealed with RTV silicone; no gaskets were installed. The stack was in service for eleven years until one morning the top section was found lying at grade between the intermediate and final absorbing towers. The bolts were cor-roded. Luckily, the fall did not damage any property or take a human life.

Lesson learned Like any acid plant equipment, inspec-tion and maintenance of the stack is necessary for trouble-free operation. Bolts have to be inspected and replaced as required; guy wires have to be lubricated every three years and inspected with an electromagnetic flux sensor for discontinuities. New designs have to be fully vetted for operability, maintainability and safety im-plications before implementing the design change.

More is not necessarily better Plate & Frame exchangers are compact in size because of their high heat transfer coef-ficient. They require turbulent flow to reduce fouling, which interferes with heat transfer. Plate & Frame exchangers are usually pro-vided with an in-line spare, so one could eas-ily make a switch should the other need to be overhauled for mechanical cleaning. Maintaining the design flow rates, espe-cially in the waterside, is required to minimize fouling, as shown in Fig. 5. And bypassing or throttling the water flow during cold weather to control the acid outlet temperature will do just the opposite–increase fouling. A similar effect happened in an acid plant where the op-erator placed the in-line spare in service with the running unit because the unusually hot weather was affecting the cooling water inlet

temperature. The thought process was: more area is better. While the strategy worked for a while, the reduced cooling water flow caused heavy fouling in the waterside, necessitating emergency cleaning.

Lesson learned Always maintain the design water flow into the exchanger to minimize fouling. In-stalling strainers upstream to capture piping corrosion products and debris is highly recom-mended.

lost in translation Engineering an acid plant within a proj-ect complex usually involves working with the major engineering contractor in charge of the whole complex. The technology provider’s scope of supply is usually limited to the acid plant’s battery limits, while the major engi-neering contractor does everything else. Even with fully defined division of responsibilities in place, there are always things that can fall through the cracks when the responsibility for a piece of equipment is shared. While this is not common, critical information that is trans-mitted by one office can be missed entirely by the other office. Such is the case with an acid cooler that was used for preheating boiler feedwater. The acid cooler was within the acid plant’s bat-tery limit, but the boiler feedwater system was within the scope of the major engineering contractor. And although the data sheet clearly specified the acid pressure to be higher than the boiler feedwater pressure, the major engi-neering contractor overlooked this informa-tion. The project went on and the discrepancy was not caught during the hazard and oper-ability review (HAZOP). Less than three years after commission-ing, an incident involving the acid cooler oc-curred. The operators never knew that the cause of the incident was the acid cooler be-cause the pH probe in the waterside that was supposed to provide early warning of a tube breach never went off. The boiler feedwater pressure was found higher than the acid pres-sure. The incident caused damage to the econ-omizers and boiler feedwater piping system.

Lesson learned To ensure critical information is not missed, HAZOP reviews must be attended by all disciplines that share responsibility for the same equipment. For more information, contact Or-lando Perez at 360-746-8028 or [email protected], or visit www.h2so4consultants.com. q

Fig. 1: Hot face layer subsidence

Fig. 2: Furnace choke ring failure due to refractory subsidence

Fig 4: Guyed stack

Fig. 3: Freestanding stack

Tuned MassDamper

Fig. 5: Plate & Frame exchanger showing condition of plates in acid- and watersides

Watersidefouling


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Case histories from the sulfuric acid industry By: Orlando Perez, H2SO4 Consultants

Since 1911, SNC-Lavalin Group Inc. has been a global service provider and world leader of engineering and construction groups, as well as a major player in the ownership of infrastructure. Being active for more than 100 years, SNC-Lavalin has established a multicultural network that spans every continent, and is currently carrying out more than 10,000 projects in over 100 countries.

SNC-Lavalin is built on a synergy of experience, evolution and excellence, which allows the company to maintain and strengthen its core business, develop new skills and activities, and to respond to the changing needs of clients and markets. With local office presence in over 50 countries, approximately 45,000 employees provide EPC and EPCM services in a wide variety of industry sectors, including mining and metallurgy, oil and gas, environment and water, infrastructure and clean power. SNC-Lavalin offers clients the full spectrum of technical expertise with complete end-to-end project solutions including project financing and operations and maintenance of infrastructure assets.

On August 22nd, 2014, SNC-Lavalin Group Inc. announced the complete acquisition of Kentz Corporation Limited, a global company with 15,500 employees currently operating in 36 countries. Kentz provides industry-leading engineering, construction management and technical support services to clients.

SNC-Lavalin strives to maintain exceptionally high standards for quality, health and safety and environmental protection while being committed to delivering projects on budget and on schedule to the

complete satisfaction of their clients. The Center of Excellence for Sulphur-Treating and Sulphuric Acid Plants within SNC-Lavalin, known as the Sulphur and Emissions Solutions (SES) Division extends as far back as 1969, formerly known as Fenco Engineering. They are a global leader in the design and construction of sulfuric acid processing plants with complete in-house capabilities for turnkey mandates. Supported by MECS-DuPont as well as other technology and major equipment and system suppliers, SES ensures that only experienced technologies are considered for their projects. With experience in delivering state-of-the-art plants worldwide for over 50 years, SES’s full sulfur lifecycle project expertise includes: sulfur burning acid plants, metallurgical acid plants, refinery acid regeneration plants, sulfur recovery units, power plants/power distribution cogeneration plants, heat recovery systems (HRS), sulfur transformation and logistics, gas-gas cleaning and effluent treatment plants. SNC-Lavalin can handle all clients’ sulfur lifecycle and emissions solutions needs. The company’s breadth of experience allows it to confidently deliver projects of any size, location and characteristics. SES specializes in servicing processes for their fertilizer, mining and metallurgy, power and oil and gas clients, supported by other SNC-Lavalin divisional strengths. Its global project footprint includes new plants, upgrades, revamps, sustaining capital work and expert advisory services. SNC-Lavalin’s several thousand experts apply their knowledge from execution in small and large scale projects, in which they are able to deliver comprehensive services to the sulfur industry.

SES is well experienced in treating the off-gas from pyrometallurgical processes for the smelting and refining of nickel, copper, leads and zinc or sulfide ores through metallurgical sulfuric acid plants. The company’s plant design takes into account all factors in order to produce the most desired sulfuric acid quality for their clients. SNC-Lavalin’s sulfur specialists are highly experienced and can answer any design specifications, from low-high gas strengths to an increased amount of water. Gas cleaning services are also available for clients who require gas cleaning systems to clean and condition plant gases in all brownfield, tie-in brownfield and greenfield projects. Additionally, SNC-Lavalin also has effluent/waste-water treatment specialists who have experience on greenfield projects and tying into brownfield projects. All of SES’s designs are built to produce quality sulfur and acid and to diminish clients’ operating difficulties. SES is proven capable of carrying out studies and assessments for many project sizes, having executed plants sizes from 60 MTPD to 3 x 5050 MTPD. This technical capability allows for specialization in all sorts of plant servicing, operations improvements, revamps, upgrades, logistics and management. Successful projects executed globally attest to the international experience and expertise within the group, and have firmly established SNC-Lavalin’s credentials as a stable and reliable contractor with total in-house capability. With the continued evolution of its expertise, SNC-Lavalin is here to deliver on any sulfur projects, anywhere. For more information, please visit www.snclavalin.com. q

SNC-Lavalin: proven technology through years of innovation


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Beltran’s advanced WESP technology captures fine particulates, acid mists and condensed organics with maximumefficiency and lower cost.

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Beltran Sulfuric Acid Today Full Page Rev2 9/16/14 6:46 AM Page 1

Polymer concrete is one of the most durable, longest-lasting and cor-rosion-resistant materials available for industrial in-frastructure. This class of products consists of a ma-trix composed of heavy-duty aggregate and either chemical-resistant resin or cement binder. These cast-able materials may offer up to five times the physi-cal strength compared to standard portland-based concrete.

Polymer concretes are designed to give supe-rior mechanical properties similar to masonry. Be-cause of chemical resis-tance throughout the entire thickness, polymer con-cretes may preclude the ne-cessity of barrier coatings and linings. They offer a one-step approach to solv-ing corrosion and provide

superior compressive, flex-ural, and tensile strength. In addition, select fillers enable physical proper-ties such as absorption and freeze-thaw durability to far exceed most inorganic counterparts. Application of poly-mer concrete offers ad-vantages since the product develops strength rapidly. Most castables in this category set through a catalyzed chemical reac-tion. This thermo-setting process occurs within 24-48 hours, primarily. Compared to the 28-day hydration/curing down-time of standard concrete, construction may proceed much more rapidly. When properly speci-fied and installed, polymer concrete provides a solu-tion for some of the most difficult corrosion prob-

lems. Understanding the capabilities and limitations of the different fillers and resin systems within the polymer concrete family is important. As technolo-gies evolve, the chemistry of various formulations proliferates as well. En-gineers, architects, main-tenance personnel and

contractors can create a value-added solution to their corrosion problems when knowing what to recommend. The wide va-riety of polymer concrete formulations can make se-lecting the correct materi-als a challenge. Ultimately, selecting the right chemis-try can translate into sub-stantial cost savings as determined by increased longevity or decreased construction downtime. A few of the more common formulations of polymer concretes include silicates, epoxies, calci-um-aluminates and vinyl esters. Sauereisen, Inc. of Pittsburgh, PA specializes in corrosion resistant mate-rials and produces a broad selection of polymer con-cretes to supplement other product lines including refractories, mortars and monolithic barriers of vari-ous thickness. For environments subject to the highest tem-peratures and acid concen-trations, Potassium Silicate polymer concretes provide optimum protection. The silicates can withstand temperature ranges in ex-cess of 1,400 degrees F (760 degrees C). This chemistry will also with-stand most solvents, oils, acids, and acid salts (ex-cept hydrofluoric) over a pH range of 0.0 to 7.0. For years, Silicate-based refractories have

provided thermal insula-tion and chemical protec-tion for flue gas structures subject to hot, acidic gasses commonly found in coal burning power generation facilities. Recently, poly-mer concretes have been specified for horizontal applications, such as chim-ney floors, where greater compressive strength is beneficial compared to the gunite-applied refrac-tory. In either case, these acidproof concretes pos-sess resistance to full con-centrations of sulfuric acid and up to oleum. Typical applications are construc-tion of sumps, containment pads, dikes, trenches, and support columns or bases. One novel installation in South America involved the formation of a potas-sium silicate polymer con-crete “jacket” around the exterior surface of a sulfu-ric acid drying tower. Epoxy polymer con-cretes, as a group, offer low permeability and broad chemical resistance. Ep-oxies exhibit greater bond strength, lower porosity, and more broad chemical resistance than inorganic varieties. Typically, com-pressive strength of epoxies is greater than 10,000 psi. This classification of poly-mer concretes shows toler-ance to a wide spectrum of acids and alkalis over a pH range of 0.0 to 14.0. These products are often catego-rized as either general pur-pose epoxy polymer con-crete or as a novolac epoxy. The novolac epoxy resin possesses a greater degree of cross-linking than the standard Bisphenol-A ep-oxy. Consequently, the novolac resin system offers an upgrade in properties. Among epoxies, novolac systems will tolerate great-er chemical concentrations while exhibiting compres-sive strength of 16,000 psi. Further up the line

of organic polymer con-cretes is the vinylester family. Novolac vinylesters are specified where certain chemicals such as bleaches or oxidizing solutions are present. Like epoxy-resin based polymer concrete, vinylester polymer con-cretes can be of a general purpose grade as well as a novolac vinylester formu-lation. Often the temperature environment is a determin-ing factor in selecting one of the organic polymer concretes. Sauereisen’s epoxy, novolac epoxy, vi-nylester, and novolac vi-nylester polymer concretes resist maximum service temperatures of 200 de-grees F, 250 degrees F, 220 degrees F, and 350 degrees F, respectively. The materials indus-try continues to develop new varieties of polymer concrete. Sauereisen re-ports recent advances in working with calcium alu-minate formulations for substrates where thermal shock is a concern and with polyurethane where a higher level of flexibility is desired. In either case, ma-terial formulators working in conjunction with instal-lation contractors are able to deliver a material that is easy to apply and durable enough to last a generation. For more information, please visit www.sauerei-sen.com. q

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Chemical Resistant Polymer Concretes

ULTIMATE CORROSION PROTECTION

SauereisenChemicalResistantPolymerConcrete

Faced with the urgency of a corrosive environment, but little if anydowntime, process industries are turning to Sauereisen polymerconcrete technology to protect their infrastructure. Multipleformulations enable rapid installation and prolonged service life.This user-friendly solution offers greater durability than the traditionalfix of combining new concrete with a thin coating.

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restoration technology for polymer concreteConsideration for the selection of materials for corrosion protection, versatilityBy: John Davis, Inside Sales & Marketing Specialist, Sauereisen, Inc.

Tank pad and pump base poured with polymer concrete.

Concrete pad rehabilitation with polymer concrete around a sulfuric acid tank.


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Anodic protection (AP) has been used effectively on concentrated sulfuric acid storage tanks for over 25 years. Leading companies across many industries have adopted AP to prevent corrosion to their tanks and maintain the purity of their product.

The economic benefit is clear. Corrosion is reduced significantly (often by a factor of 10), extending the service life of the tank. For many companies, the purity of the product is of utmost importance–AP greatly reduces the iron pickup, ensuring the acid remains clear.

For a typical storage tank, AP hardware can be installed conveniently; no tank entry is required. An AP system consists of cathode and reference electrode hardware installed through the tank roof and an automatic potential controlled rectifier situated adjacent to the vessel. Unlike expensive applied coatings, the system can be installed on acid tanks that are in operation, reducing the need for costly shutdowns. Any maintenance (replacing reference electrodes or cathodes) can be done on the fly.

Operating parameters can be tied into an existing DCS system using 4-20 mA signal outputs, where custom events can be programmed. For peace of mind, remote monitoring service is offered where a corrosion systems specialist monitors the data via remote internet connection and advises action as needed.

Corrosion Service Company Limited (CSCL) has over 60 years of corrosion mitigation experience, applying

Anotection® Anodic Protection systems for acid tanks and piping globally. Anotection® increases the life span of infrastructure and the quality of the acid with respect to iron content; an important criterion for acid purchasers. This makes Anotection® particularly beneficial in the manufacturing, storage and transport of acids. Anotection® systems feature complete automatic system operation. Remote monitoring service is available

at a low cost to ensure the system operation is optimal, with minimal maintenance requirements. For more information, contact Corrosion Service Co. Ltd. at (416) 630-2600 or email [email protected]. q

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A s s o c i A t e ssulfuric Acid

A s s o c i A t e ssulfuric Acid

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anodic protection–proven corrosion prevention for storage tanks

Powell Sulfuric Acid Dilution System

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The Powell Sulfuric Acid Dilution Systems are engineered to continuously dilute 93% or 98% sulfuric acid to any lower strength. The systems are automatic and include pumps and cooling water systems for the safe, accurate dilution of the concentrated acid. Systems are available for all flow rates and diluted acid strengths.

Features• Automatic Dilution• PLC Based Control System• Adjustable Batch Amounts or Flow Rates• Strong Acid and Water Supply Pumps• Skid Mounted, Fully Assembled

Anodic protection has been used effectively on concentrated sulfuric acid storage tanks for over 25 years.


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Are your acid tow-ers performing the way you want them to? If you are looking to increase your plant production rate, reduce the cost of energy or reduce stack emissions, then start by looking at the type of packing inside the acid towers.

Installing high performance, low pres-sure drop packing, such as the NORAM HP™ saddle, offers a low cost and effective way to up-grade your acid towers and acid plant by reducing packing pressure drop by up to 50 percent.

reactionWhen gas and acid streams come into contact, there is

a reaction. The reaction is a chemical operation known as absorption. Packing is installed in acid towers to provide a contact surface to enhance the reaction of the gas and liq-uid streams. Better contact of the two streams means better tower performance.

NORAM offers the patented High Performance (HP™) Saddle Packing as a way to achieve better perfor-mance in the operation of the acid towers in a sulfuric acid plant. NORAM packing has proven to be an effective prod-uct to debottleneck acid plants, and to improve tower per-formance.

Slip casting awayNORAM HP™ Saddle Packing is a ceramic pack-

ing made from quality clay material. It is manufactured through a slip casting process assuring uniformity in prod-uct composition and physical properties. In addition, its high crush strength properties and manufacturing process results in fewer chips, thereby minimizing plugging of the acid distributor, acid pumps and acid coolers.

ShapelyNORAM HP™ Saddle Packing shape and size are two

important features that make it an ideal packing for use in new acid towers or for repacking existing towers. Its slightly larger than standard 3” size together with the notches at the edge of the wings promote mass transfer and break up the gas and acid streams, which reduces gas flow resistance and increases gas throughput by 25 percent. The sculpted shape of the packing together with the openings significantly reduces the pressure

drop across the packing height by about 50 percent. The more open structure of the NORAM HP™ pack-ing, as compared to the standard 3” saddles, allows operat-ing with gas velocities that are typically about 20 percent higher. The reason is that the liquid hold-up for HP™ pack-ing is lower, which in turn lowers the superficial gas veloc-ity. These features benefit the client greatly by providing the advantages of either increasing the plant production rate or, for the same throughput, reducing energy costs in oper-ating the blower.

Works wellAs an example, an increase in the gas flow rate to a cli-

ent’s sulfuric acid plant would increase the gas throughput and pressure drop in the existing final tower. After evaluat-ing many options, the client chose to replace the existing standard packing with NORAM low-pressure drop ceramic HP™ saddle packing. As the graph in Fig. 1 shows, the pressure drop across

the packing is reduced significantly compared to a stan-dard 3” saddle packing. Actual pressure drop measurements taken after about six months of operation with the NORAM packing show that at peak gas flow rates, the pressure drop is about 100 mm (4”) WC. The client was able to successfully operate the acid plant at the in-creased gas flow rates and ex-pand the plant production rate.

front rowTo reduce pressure drop even further, special attention

is paid toward reducing the pressure drop at the packing support interface. NORAM provides customized installa-tion guidelines to fit the purpose of the change and support the specific tower design and duty. NORAM HP™ saddle packing is successfully used with grid blocks, cross parti-tion rings or metal grids.

no floodingUnlike small packing, which has a relatively large sur-

face area per unit and a correspondingly large liquid hold-up, NORAM HP™ saddle packing will not flood under normal operating conditions encountered in sulfuric acid plants. Flooding in small packing is usually an intermit-tent localized phenomenon where the liquid becomes the continuous phase and gas bubbles rise through the liquid. In general, well before flooding conditions are reached in acid towers, spray entrainment caused by excessive gas velocities will cause overload conditions for the mist elimi-nators and make a tower inoperable.

less foulingFouling of packing from sulfate or sulfur sublimation

in acid towers and through the breakage of packing will have a very significant effect on the superficial gas velocity and may cause localized flooding and give rise to spray en-trainment and insufficient absorption. The open structure and superior strength of NORAM HP™ packing makes this packing more resistant to fouling. And the HP saddle will have reduced chips compared to conventional packing, which can plug distributors, acid coolers and pump suc-tions.

Wrap upNORAM HP™ packing improves the performance

of acid towers because it brings into contact gas and acid to promote an efficient mass and heat transfer. Different saddles may appear similar, but the product may not per-form the same. This is because of the basic characteristics of NORAM HP™ packing, which are: number of pieces per volume, specific surface area, bulk density, and dimen-sions and wall thickness of the saddle. These measurements exceed all other products. Additionally, as Table 1 shows, the mechanical and chemical properties of NORAM HP™ packing make it more robust and less subject to chipping and breakage compared to other manufacturer’s products.

In conclusion, packing is a key component in the de-sign and operation of acid towers. The patented NORAM HP™ packing has proven to be very successful in achiev-ing better performance in the operation of both existing and new acid towers.

For more information or to receive a quotation for NORAM HP™ packing, please visit www.noram-eng.com or call (604) 681-2030. q

a simple and effective tower upgrade: NOraM HP™ saddle packing By: John Orlando, P. Eng., NORAM Engineering and Constructors Ltd.

NORAM Size No. 3 HP™ (High Performance) Ceramic Saddle Packing

HP™ saddle on standard grid block

Fig. 1: Lower pressure drop with NORAM HP™ saddle packing vs. standard 3” packing.

Table 1: Attributes of NORAM HP™ saddle packing


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siemens.com/energy/stc-sof

High-level production capacities in the processing of sulfurous gases

Your reliable partner for turning sulfur into profit

Siemens supplies the perfect solution for sulfuric acid production with pre-designed turbocompressors. Outstanding expertise and comprehensive R&D work at Siemens have made possible compressor technology that guarantees mechanical durability and wear resistance, in particular under complex operating conditions. The handling of corrosive gases represents a major challenge in the production of sulfuric acid, which Siemens has successfully

mastered. The STC-SOF series of products meets and even exceeds the demanding requirements for quality, such as reliability and en-ergy-sensitive operation. Pre-designed turbocompressors from Siemens have proven to be more efficient than conventional solutions, from the long-term as-pect. This is how Siemens is already meeting the future demands of the sulfur industry.

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Where the supply of liquid sulfur, mostly originating from refineries, is not available due to lack of infrastructure, solid sulfur has increasingly become a dominant source of supply for acid plants. This is particularly the case at remote locations where the acid production is located close to a metallurgical operation, e.g. a nickel leaching plant or a fertilizer manufacturing facility where the acid plant is close to the phosphate mine.

This article focuses on the melting of solid sulfur for sulfuric acid production plants. It presents various devices, design features and philosophies and a review of the historic development over the last few decades. It also covers some aspects of the handling of solid sulfur upstream and downstream from the melting unit, such as storage, transport and filtration.

Finally, Outotec’s state of the art process flowsheet is presented and described, covering the entire sulfur melting and filtration section of an acid plant.

fundamentals and basic sulfur properties

The energy demand of a sulfur melting unit comprises a number of individual items, as presented below.

Example: Energy required to melt sulfur in a 50 t/h melting unit.

Typical figures vary in practice between 100 and 130 kg/t. The latter would include the steam required to keep all other vessels in the section at the desired temperature, i.e. to compensate for the heat losses.

The capacity of the melter very much depends on the moisture content of the raw sulfur. Fig. 1 presents the qualitative relationship of a typical standard melter.

The viscosity of the molten sulfur must be kept within an acceptable range, i.e. between the melting temperature of about 119 degrees C and the upper figure of about 159

degrees C, where the liquid becomes very viscous, based on the change of the molecular structure of the sulfur. The viscosity increases sharply at temperatures greater than 159 degrees C. The molten sulfur above 159 degrees consists of a mixture of S8 rings and Sx polymers, which greatly increase the viscosity. Fig. 2 presents the characteristics. Melting of sulfur lumps or pellets is a major parameter when designing melting devices. Subject to the size of the particles, the impact of the residence time required for complete melting dramatically increases with size. Crushed bulk sulfur, e.g. frash sulfur, is not widely used anymore. It showed particle sizes up to 100 mm, partly well above this. It contained large amounts of fines, 20-35 percent, which made melting more difficult, as the fines with the significantly lower bulk density tend to swim on top of the liquid and form “ice bergs,” which could agglomerate to large lumps. Slates became more common in the late 1970s. They are 3-5 mm thick and contained fewer fines (4-7 percent), but fines increased whenever the material was handled. Today, prills, granules or pastilles are widely used, with particles typically 2-6 mm, which contain very few fines, typically less than 1 percent. The moisture content also has an impact on the melting characteristics, i.e. time required to completely liquefy the sulfur. Fig. 3 shows the typical required residence time of pure sulfur (no moisture) as a function of the raw solid sulfur particle size.

impurities of commercial solid sulfurThe characteristics of commercial sulfur vary in terms

of density, moisture content and purity. Typical figures are:

• Thetypicalbulkdensityisnotlessthan1,040kg/m³,mostly around 1,200 kg/m³. The angle of repose is not less than 25 degrees; sometimes up to 35 degrees (when wet).

• Purityandimpuritiesasspecifiedbysulfursuppliers: A typical purity figure amounts to > 99.8 percent S. The ash is typically specified in the range of 200-

2000 ppm.• Typically,thewatermoisturecontentamountstoabout

0.5-1 percent, subject to storage conditions, but can be as much as 3-4 percent.

• Theacidityalsodependsontimeandhumidityduringstorage, typically 500-1000 ppm (as H2SO4). The longer the exposure of stored sulfur to atmosphere and humidity, the more acidic material will be formed.

Melting and handling of liquid sulfur mainly employs carbon steel vessels and piping. Neutralization of the acid with lime Ca(OH)2 or aqueous NH3 for protection of carbon steel materials is mandatory. Some equipment will be made of stainless material, e.g. the sleeves of the agitator shafts. This neutralization takes place in the melting vessel and enough neutralizing agent must be added to the solid sulfur prior to entering the melting vessel. Overdosing is recommended, so that a pH of 8-9 of the liquid will result. Any residual lime and the reactant gypsum will be segregated from the liquid at the downstream leaf filter. Some sulfur contains organic matter. Typically this is well below 100 ppm, but low quality material can have several thousand ppm. Such sulfur has a brownish color. When molten, it has a slimy consistency and requires a larger filtration surface. Only a small fraction of the organic substances can be separated from the liquid sulfur and eventually it results in moisture generation when burned in a sulfur combustion furnace. This in turn can create a high acid dewpoint in the gas prior to entering the intermediate absorption. As most sulfur originates from SRUs, some residual H2S may be present. Typically this is below 10 ppm. Sulfur is usually degassed downstream of SRUs, so that the H2S content can generally be kept at single digit ppm figures. The typical sulfur specification calls for As, Te, Se, all less than 1 ppm. Generally the delivered quality has even fewer impurities. The water content not only affects the capacity of the melting device, but also impacts transportability and accretion. Prior to the melting, “wet” sulfur is often subject to transportation and handling in bins, screw conveyors and belt conveyors. The corrosive nature of sulfur requires that some parts of the solid handling equipment be protected against corrosion. The water content of the bulk sulfur impacts the required freeboard of the melter, that is, the distance above the liquid surface to the roof of the melting vessel. When bulk material is drowned, water will evaporate, form small bubbles and rise through the liquid, eventually arriving at the top surface and generating foam. This foam may occupy a significant volume above the liquid and impede the feeding and distribution of fresh bulk sulfur to the melter, or overflow the vessel. The greater the moisture content, the greater the freeboard must be for trouble-free operation.

Ambient (25°C) to rhombic . . . . . . . . . . 3,199,000 kJ/h (=889 kW)Rhombic to liquid . . . . . . . . . . . . . . . . . 3,455,500 kJ/h (=960 kW)Liquid to 140°C . . . . . . . . . . . . . . . . . . . 1,260,000 kJ/h (=350 kW)Energy required for evaporating moisture . . . . . . . . . . . . . . . .1.5%H2O ambient liquid to 140°C vapor . . . . 1,987,500 kJ/h (=552 kW)Heat loss melting area, say 3% . . . . . . . . . 297,000 kJ/h (= 83 kW)Total energy required . . . . . . . . . . . . .10,199,000 kJ/h (=2,834 kW)Steam (6barg ~2065 kJ/kg) required . . . . . . . . . . . . . . . 4,939 kg/hSpecific steam demand for melting . . . . . . . 99 kg steam/t of sulfur

Fig. 1

Fig. 2 Viscosity of liquid sulfur. Vertical axis shows viscosity cPoise, horizontal axis shows temperature, degrees C.

Fig. 3

Solid sulfur handling at sulfuric acid plants: an update By: Karl H. Daum, Stefan Bräuner and Dr. Hannes Storch, Outotec


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Managing the explosion hazards of dust Dust generation occurs whenever sulfur is handled, such as with front-end loaders, belt conveyors and other transportation devices. The self-ignition temperature of sulfur dust is about 240 degrees C, while the dust explosion limits are LEL: 35 g/m³ and UEL: 1400 g/m³. As the particle size of the dust decreases, the available surface area increases, making it much easier for the dust to explode. The presence of water reduces the explosion hazard, as it makes dust particles more cohesive. Naked flames and hot surfaces must be avoided. Care must be taken to prevent static electricity accumulation. Machinery, such as hoppers, conveyors and chutes must be earthed and regularly checked. Electrical wiring and equipment must be adequately designed in accordance with regulations. In the vicinity of solid sulfur handling equipment, electrical equipment must be explosion proof. Dust suppression systems (DSS) are in use by some suppliers. DSS agents apply small amounts of surfactants to suppress dust formation. Pyrophoric iron sulfide can be formed when sulfur and water are in contact with steel. Iron sulfide can ignite H2S, even if no ignition source is present.

fumes treatment For environmental reasons, the treatment of vent fumes from the melter is mandatory. Fumes originate from the water content of the solid feed material, the H2S contained therein and sulfur according to the vapor pressure over the liquid. Not only is such sulfur lost, but it is irritating to humans if not properly removed from the vent gas. A slight negative pressure at the top of the melting device can be kept with fume stacks, thus preventing fumes from exiting the vessel at uncontrolled locations. The fumes can be treated with a scrubber, preferably a venturi type, which not only enables the neutralization of the H2S or other acidic substances, but also removes small particles of sublimed sulfur formed when cooled below its melting temperature. Typically NaOH is used and the pH of the circulating liquid is kept constant. Sulfur fumes can block vents if not adequately heat jacketed.

Solid sulfur storage and handling Indoor storage shields bulk sulfur from wind, reduces fugitive sulfur dust emissions and protects stockpiles from contamination. It also avoids accumulation of water from rain, which must be evaporated at the melter, thereby reducing the melter’s capacity or throughput. However, such enclosures are expensive and a location shielded from prevailing winds is sometimes selected as an alternative. An urban environment would make covered storage obligatory. At dry and remote locations, uncovered storage is most common, although environmental restrictions may force the operation to be at least partly covered. Fig. 4 presents a covered storage facility. The storage is managed by various stationary belt conveyors. Reclaiming of the sulfur is by front end loaders. If a storage bin upstream of the melter is installed, it is fed by a belt conveyor and discharged by a screw conveyor (or rotating valve). Such bins are often subject to corrosion by wet sulfur from outdoor storage. Appropriate selection of construction materials is required. The dosing of lime is synchronized with a pre-set lime/sulfur ratio, subject to acidity. It must be ensured that the pH of the molten material is measured twice per shift and the ratio adjusted if required. Reasonable overdosing of lime prevents corrosion of downstream filtration equipment,

though increases the load on filtration. It is well known that naturally occurring bacteria, thiobacilli oxidans, attack stockpiled sulfur and cause acidification by excretion of sulfuric acid. These bacteria thrive at 20-35 degrees C and can acidify sulfur to a level that can cause severe corrosion to steel. Some vendors therefore add a biocide (for example, sodium lauryil sulfate), but this can be washed away since it is soluble. Also, the more often the sulfur is handled, the less effective the biocide treatment, as individual pellets get crushed and thus expose additional “untreated” surface. Fire detection is difficult, but thermocouples and SO2 analyzers at appropriate locations can provide adequate warning. Automatic fire extinguishing devices, such as sprinklers are less effective but can be installed. As a minimum, fire extinguishers and water hoses should be provided for manual operation.

Sulfur filtration Filtration of the molten sulfur is mandatory to remove impurities (ash, surplus lime and gypsum) from the liquid. Those substances must be segregated to prevent catalyst plugging downstream at the acid plant and hence extend the time between maintenance shutdowns for catalyst screening. Various types of filters are on the market with different concepts. The traditional leaf filter is characterized by moving internals and a stationary shell, as in Fig. 5. Others come with a moveable shell, supported from the ground as in Fig. 6 and Fig. 7. A design with the filter suspended from a steel structure is presented in Fig. 8. This is particularly operation friendly, with easy access for cleaning of the filter plates. Thus it is similar in concept to the traditional version of Fig. 5. All leaf filters are equipped with hydraulic opening/closure devices to ensure proper sealing. A typical filter size is 0.7 m² per t/h of feed liquid, but this figure can vary widely. Obviously, it depends very much on the amount of impurities, the quality of precoating, bitumous content of the sulfur and other factors, such as the degree of lime. Prior to use, the filter leaves must be pre-coated to enable the filtration of the small/fine particles, such as ash, lime and gypsum. Typically, finely ground diatomaceous earth is used as a filter aid, using approximately 1 kg/m² of filter area. In addition, lime is also added in an amount of about 0.5 kg/m² to protect the fine stainless steel gaze on the filter leaves just in case some residual acidic material is present in the sulfur. The initial total concentration of filter aid and lime at the precoating liquid is preferable in the range of greater than 0.5 percent. The volume flow of the precoating pump will typically be designed for 1 m³/h per each m² of filter area.

A separate precoat tank is desired, using clean sulfur as feedstock and a properly sized agitator with adequate feeding devices for the filter aid and lime. In order to achieve the most uniform and homogeneous precoat at the filter leaves, dirty sulfur must not be used for this purpose, although this is frequently observed in operating plants. Despite neutralization of the raw sulfur, temporary acidic material is sometimes fed to the filter and leads to corrosion of the filter plates. Also, those plates may be subject to mechanical damage during cleaning and handling. Damaged or corroded leaves will permit dirty sulfur to bypass or slip and contaminate the otherwise clean material. To prevent this, polishing (or police) filters, as shown in Fig. 9, have been used for many years in the industry.

Fig. 4

Fig. 8

Fig. 7

Fig. 5

Fig. 6


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However, polishing filters are installed for added protection, not for ongoing removal of impurities. As an alternative to the use of a polishing candle filter, one can consider installing a second leaf filter in series. Although an excellent suggestion technically, the economics will be difficult to justify. Sulfur filtration is still a very labor intensive activity based on its batch character. A typical design filtration cycle would be 16 hours for the daily capacity, whereas the rest of the time must be sufficient to clean the filter, prepare the precoating and get it ready for the next batch. High loads of ash or acid and excess lime will shorten the cycle length. So far, no continuous filtration process has been established in the industry, although various trials have been made in the past, for example, with centrifuges. The operation of sulfur filtration is an art, and operators will need to acquire some experience before the unit can work smoothly on a sustainable basis.

The filter cake typically consists of about 60 percent sulfur, while the rest is ash, lime and gypsum. Removal of this filter cake is performed when opening the filter casing, but manually assisted as sulfur and impurities are sometimes of “sticky” character. Fig. 10 shows the area where the filter cake is discharged. Even though the filtration is operated correctly, the filter cake dump area looks somewhat messy, which is normal in the industry. When the setup and operation of the filtration unit is correct, the quality of the filtrate can achieve an ash content of less than 10–15 ppm. With additional polishing filters, this amount can be reduced to single-digit figures, such as 5–8 ppm.

Clean sulfur storage tank A buffering tank is required between the acid plant and the melting/filtration section that operates partly in batches. The tank size depends on the infrastructure and nature of the entire operation. Typically, storage tanks hold three full days’ demand.

The tank is made of carbon steel, usually sitting on a sand bed and completely insulated to avoid excessive heat loss. Fig. 11 shows a tank farm for liquid clean sulfur, each tank with 20,000 t capacity. Since the sulfur must be kept liquid at about 130-140 degrees C, a heating device must be used. Typically this is a steam heated coil immersed in the tank, removable from the top during operation. Overheating must be avoided, as it may support corrosion and formation of pyrosulfide. Venting of the tank is to the atmosphere. Intertisation, that is flushing or sweeping with nitrogen N2, is occasionally used to prevent possible fire. Fire detection is difficult, but thermocouples have been used and steam flushing is then applied to dislodge the presence of oxygen and purge the vessel. Good insulation minimizes the required heating surface and thus “hot spots” where pyrophoric iron sulfide can be formed. In the case of multiple acid plants, each plant should be equipped with an additional day-tank in the vicinity of the sulfur combustion unit.

Sulfur melting devices

Sulfur pits

When solid sulfur was commonly used as raw material in the past, most sulfur melters were designed as pits. Large pits were of square or rectangular shape and made of concrete walls, partly or entirely lined with acid resistant bricks. These pits were equipped with a number of heating coils to provide the energy for melting and the enormous heat losses to the surrounding areas, as well as numerous agitators to support the heat transfer and prevent solids from settling at undesired locations. A sketch of a typical arrangement of a large pit consisting of several compartments is shown in Fig. 12. The heating coils are made of carbon steel, and are

subject to wear and tear and must be replaced regularly. The heating coils appear to have poor, unpredictable and undefined heat transfer and their size and arrangement are often based on empiric design. The pits are covered with large insulated roofs for weather protection, to prevent dust ingress and to reduce heat losses. The internal large steel surfaces are exposed to a corrosive atmosphere and thus present a hazardous area for maintenance. Despite the application of several agitators, sulfur impurities tend to accumulate at “dead” zones and accrue to form solid and hard deposits at various locations within the pits. Sedimentation of solids will also affect the heat transfer and thus, the melting capacity. Thus, at regular intervals, the pits must be mechanically cleaned in miner’s fashion, e.g. by hammer drill, at least the melting and settling pit. This is time consuming and requires extensive work, as the pit must be emptied and the roof removed for better access. Coils and walls can be damaged by the cleaning action. Melting pits are still widely used in the industry, simply because they were initially designed as such. New, modern sulfur handling plants avoid this technology entirely because of the many disadvantages.

Above ground melters with flat bottom

The heavy maintenance of the pit design led to the design of above ground melting devices, basically as presented in Fig. 13. Hybrid installations, consisting of above ground melting tanks and clean sulfur pits (pump pits) were still common for many years. Separate precoat tanks were used to facilitate the sulfur filtration. Relatively clean sulfur, mostly from undercover storage with little debris, enabled the flat bottom design, with melting capacities up to around 40 t/h. Individual sections or coils had to be removable for maintenance or replacement, which required extensive piping & valves for steam and condensate as well as good access to the top of the tank. Parts of the heat insulation had to be designed to be removable to enable access to the internals. Compared to a pit, an above ground melting system has an improved flow pattern, much better heat transfer and solids will remain in suspension more easily. These melters are equipped with a drain system (lateral opening) to facilitate the removal of any settled material. These melters also require substantially less space as compared to pits. Fig. 13 shows an installation with flat bottom melting tank and separate precoat vessel.

Above ground melters with conical bottom

In cases where there is more debris or greater amounts of impurities in the raw sulfur, melting tanks with conical

Fig. 11

Fig. 13Fig. 12

Fig. 10

Fig. 9


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bottoms are being used. Debris can easily be removed during operation without interruption of the melting. Fig. 14 shows a typical melting device with a conical bottom.

Solid sulfur is added from the top and liquefied molten sulfur overflows through a lateral nozzle. Heavy solids can settle and remain in the melter. The conical bottom is fit with a set of valves to enable the discharge of accumulated debris and cleaning of the nozzle. A typical capacity of this melter would be about 50 t/h sulfur.

Later installations also integrated the precoat tank into the melting vessel, so that all liquid sulfur handling functions are focused at this single vessel. This requires a greater capacity pump because it has to serve the precoating operation, as well as the normal filtration service. Appropriate specification for the pump supplier and the use of variable speed drive and orifice plates will solve this issue.

For larger capacities, several melting devices are used in parallel, now combined with separate associated pump tanks. Overflow from the melter is received by the pump tank. The liquid level in the melter is thus kept constant allowing large debris to settle and be removed from the bottom of the melter. The remaining impurities can be kept in suspension at the separate pump tank. It would also be used simultaneously as a precoat tank, which, again, creates a challenge for the pump. A plant designed and built with two parallel melters, pump tanks and filters is presented in Fig. 15.

A disadvantage of this design is that the precoating operation will be at least partially with “dirty” sulfur, which is not the best way to achieve a uniform and homogeneous precoat at the leaf filter. However, usually those compromises are the result of cost saving measures.

Generally, this arrangement can be designed to handle a 100 t/h melting capacity.

Melter with external heat exchanger Designing melters with larger capacities led to very large and inefficient melting vessels, because the space required for the internal coils increases the size of the tank. Installing multiple parallel units is one solution, but not the most economical. Outotec has therefore developed an external heater, simply in the form of a shell and tube heat exchanger, with the steam/condensate on the shell side. No submerged coils are located in the melting tank, making for a much smaller tank that need only handle the hydraulic requirements. The size of the melting tank must cover the agitator and circulation pump only, and ensure sufficient residence time to melt the solid sulfur particles. The heater is located outside at a convenient location that is easily accessible for maintenance. It can be drained and replaced without accessing or removing the roof of the melting tank or any other part of the tank. The absence of coils in the melter avoids areas for accretions of solids and other foreign material. The heater is fed with liquid sulfur by a circulation pump and by passing through the tubes; it heats up the sulfur in accordance with the required energy for the process. As with submerged coils, the control philosophy allows for adjustments in steam pressure so that the performance matches the desired capacity. Fig. 16 shows the installation of an external heater in an industrial acid plant of 2,100 t/d capacity. With the external heater, the throughput of the melting devices can be significantly larger as compared to the internal coil design. The limit extends well beyond 100 t/h per unit.

State of the art sulfur handling The sulfur melting and filtration chain consists of numerous individual units, all operating in individual vessels/equipment, as shown in Fig. 17. These individual units are as follows:

• Conical bottom melting tank withexternal shell and tube heater, overflowing to pump tank. The tank contains a single central agitator and a pump, designed for a constant throughput to the external heater. Also, internal baffles are installed to prevent circulating movement of the liquid content. The design is capable of melting a typical daily demand within 16 hours. Capacities well above 100 t/h per unit can be designed.

• Pumptankwithsinglecentralagitator,ensuring that any solid impurities are kept in suspension. The pump is designed to feed the sulfur leaf filter and has two distinct operating conditions, namely at the beginning of the filtration cycle (low pressure drop, high throughput) and towards the end of the cycle (high pressure drop, low flow).

• Separate precoat tank fedwith cleansulfur only and sized to cope with the requirements of the leaf filter in terms

of filter aid and lime addition, as well as proper mixing and concentrations of these additions. The pump is designed for precoating operation only, i.e. large throughput, subject to the filter area, and low pressure drop. Using clean sulfur ensures a homogeneous and uniform precoat of the filter leaves. Only this homogeneous layer

will enable good filtration. Filter precoating is not only a matter of material (e.g. lime and diatomaceous earth) per m² of filter area, but also depends on the concentration of those substances. A smaller pre-coat tank is better than a large unit. A return line from the clean sulfur tank to the leaf filter and pre-coat tank are included.

• Leaf filter designed to follow thecapacity of the melter, i.e. filtering the daily demand within 16 hours. First class filtration can achieve 10-15 ppm residual ash in the filtrate. Parallel leaf filters can be installed, so that the plant capacity, size and maintenance requirements can be optimized. Prior to opening and cleaning the filter, it must be drained into the pump tank, which must be adequately sized to hold the full content.

• Polishing filter, preferably with highefficiency candles made of ceramic material. Excellent clean sulfur quality can be achieved in the single-digit ppm range of residual ash.

• Clean sulfur tank with magneticdrive pump to feed the sulfur to the sulfur burner and combustion furnace. The centrifugal pump is fully encapsulated, made of stainless steel, steam jacketed and directly connected to the tank. This pump requires very little discharge head, as the Outotec LURO2™ burner does not need sulfur to be pressurized, other than the system pressure inside the furnace. A low discharge pressure of about 1 barg is sufficient.

• All other pumps in the melting andfiltration area are submerged type pumps with steam jacket heating.

Obviously all tanks are equipped with external or internal heating coils to compensate for heat loss. External heating is preferred, as in some cases where internal coils would obstruct the purpose of the unit. For more information, please visit www.outotec.com. q

Fig. 14

Fig. 15

Fig. 17

Fig. 16

External heater


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Partners, Professionals, Problem-Solvers...Check.

Safety: CMW’s MOD rate for 2014 is 0.65. Results exhibit the difference between talk and

action. CMW has a company wide behavior-based training system that drives safety at every

level of the organization. With over 100 turnarounds under our belt, we are proud of our

dedication to keeping our employees safe.

Scheduling: CMW has a dedicated scheduling/planning division with decades of

experience in developing project master schedules that have consistently removed hours,

if not days, of wasted time and resources. From work scope outlines to complete project

tracking through Microsoft Project and/or Primavera, CMW will deliver the master schedule

that makes a difference.

Fabrication: CMW’s ASME code shop has the S and U stamps along with the NBIC R

stamp for all your fabrication requirements. Our state-of-the-art 75,000 square foot facility

has produced hundreds of sulfuric pieces of equipment such as converters, heat exchangers,

pressure vessels, acid towers, ducts, expansions joints, and much more for whatever your

specifi c requirements may be.

Field Installation: CMW has an impeccable reputation for expert quality workmanship

and fi nishing on time and on budget. Our fi eld crews are some of the best in the business

and our close to 50 years of making sure your plant is back on line provides the confi dence

you need in making your contractor decision.

Maintenance: CMW believes in full service for your sulfuric acid plant. Our maintenance

crews ensure that your plant operates at peak effi ciency on a daily basis while also providing

the best preparation for all outage related work.

When it comes to exceeding the qualifi cations to perform your plant’s turnaround or outage, CMW tops the list:

Check us out at www.cmw.ccFor detailed capabilities, scan the QR Codeor go to: http://www.cmw.cc/additionalinfo.aspx

Toll-free in the USA: (877) 704-7411International: (813) 737-1402

Problem-Solvers... Problem-Solvers...

ALABAMA OFFICE2090 Schillinger Road • Ste A • Mobile, AL 36695

251-378-5471

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225-673-5452

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813-737-1402

When Southern States Chemical, Inc. decided to reduce emissions from their Savannah, Ga. sulfuric acid plant, they didn’t take the decision lightly. With so many technology options available, ranging from double absorption systems to caustic or hydrogen peroxide tail gas scrubbers, it was not a clear cut choice. But, after gathering all possible information, one option stood out: MECS’® SolvR™ Regenerative Technology. Southern States, a subsidiary of Dulany Industries, Inc., is the largest on-purpose producer of sulfuric acid for the merchant market on the east coast. The Savannah plant, which began production in the late 60s, needed an SO2 abatement solution that would fit into the existing facility, without requiring extensive retrofits. The benefits of MECS’® SolvR™ Tech-nology include modular design, low cost of ownership, robust process design and the ability to use waste energy. These were all important factors in the decision making process. According to Bryan Beyer, Acid Operations Manager at Southern States, the decision came down to two major points: “We really liked the minimal byproduct generated from the process and the ease of tying it into the existing equipment,” Beyer said. The SolvR™ retrofit was a fast track project. The contract was signed in August of 2013 and the first skids began arriving onsite in December 2013. The plant was mechanically complete by the end of the January 2014 outage and start-up occurred in April of 2014. The SolvR™ Technology start-up had the normal shakedown issues to contend with but quickly demonstrated its capabilities. The plant is currently operating at its design rate and meeting emission tar-gets. While the installation and startup of the first commercial SolvR™ plant has been a great success, it does not happen without a lot of behind the scenes work. Many re-generative SO2 technologies have come and gone over the years, but none so far have enjoyed significant commercial success. Therefore, it would be useful to understand the underlying issues in order to better un-derstand why MECS® SolvR™ Technology is poised for success. Regenerative absorption and desorp-

tion systems have been used extensively for CO2 and H2S removal for many years, so it is no coincidence that the MECS® SolvR™ re-generative sulfur dioxide system looks very similar to classical systems on the outside. What is different is the solvent.

the Solvr™ solvent In the search for the new sulfur dioxide solvent, MECS, Inc. (MECS) set the follow-ing criteria as the key performance metrics:• Lowertotalinstalledcostthan: — current regenerative sulfur dioxide

technologies. — double absorption (sulfuric) or

SCOT (Claus) plants.• Lower operating costs than currently

available regenerative technology, with: — steam consumptions in the range

of 5-10 kg steam/kg SO2. — minimal losses of solvent in the

treated gas. — solvent that is not degradable by

sulfuric acid.• Significantlyreducedemissions,toless

than 20 ppm sulfur dioxide in the ex-haust gas.

After an extensive computer-aided search, MECS identified a family of non-toxic, non-corrosive solvents, with a high affinity for sulfur dioxide. Since this solvent has not been used in sulfur dioxide service before, the first step was to develop the vapor liquid equilibrium (VLE) for comparison to the theoretical values. As expected, the solvent exhibited a strong affinity for sulfur dioxide at moder-ate temperatures, up to 50 degrees C (122 degrees F), and readily released the sulfur dioxide when the solution was heated to the boiling point, slightly above 100 degrees C (212 degrees F). A bench scale unit has been operating continuously, 24/7, since 2009. The goal was to establish and optimize the control pa-rameters, check the stability of the solvent, develop the performance characteristics of the mass transfer equipment and determine the suitability of various construction mate-rials for this service. The process flow scheme of the bench scale unit follows the same exact flow scheme of the commercial unit (see fig. 1). Synthetic sulfuric acid exhaust gas is first

quenched and hydrated via evaporative cool-ing to a temperature of about 30 degrees C. Excess water is added in the quench vessel to control the weak acid concentration. For gases contaminated with particulate, halo-gens, volatile metals, etc., a more extensive gas cleaning system must be incorporated for their removal. The saturated gas is then fed to the absorber for contact with the lean solvent. The solvent has a high capacity for sulfur dioxide, thus reducing the amount of liquid needed to irrigate the packing. The absorber can economically operate at temperatures as high as 50 degrees C, which is easily and economically attained in most areas using cooling water. The solvent is capable of se-lectively and cost effectively operating over

a wide range of concentrations, from as low as 200 ppmv to as high as 40 percent by vol-ume (see fig. 2). The treated gas, with very low levels of sulfur dioxide, is vented to the atmosphere. The original SO2 emissions goal was 20 ppm, but levels substantially below this were achieved in the lab (see fig. 3). The rich solvent leaving the absorber is then regenerated in the stripper by applying mild heat and/or reducing pressure. Vacuum is not preferred because air in-leakage intro-duces oxygen into the stripper, which pro-motes sulfuric acid formation. The amount of steam used during re-generation is proportional to the desired lev-el of sulfur dioxide emissions in the treated exhaust gas. Lower exhaust gas emissions

The unit’s modular build made installation less time consuming.

Installation went smoothly, with the completed SolvR™ system lifted into place.

Fig. 2: Solvent absorption and desorption curvesFig. 1: SolvR™ flow scheme Fig. 3: SolvR™ emissions vs. stripper performance

Solvr™ Technology provides welcome solution for Southern States Chemical


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require more thorough stripping of sulfur dioxide from the lean solvent resulting in higher steam to sulfur dioxide ratios. The required steam pressure for the stripper reboiler is quite low, since the stripper operates at 100 degrees C to 110 de-grees C. Initial indications from the commercial unit are that the steam usage is lower than predicted.

The stripper overhead contains sulfur dioxide saturated with water vapor. The solvent is highly selective, so minimal amounts of other inerts like CO2, O2 or N2, are present in the sulfur dioxide product. The water-saturated sulfur dioxide gas is partially condensed and sent to the rectifier column, where the condensed water is stripped of sulfur dioxide prior to recycling to the process or disposal in waste treatment. The recovered sulfur dioxide can be recycled and con-verted to sulfuric acid, or sulfur in the case of a Claus plant, thus increasing process yields. Alternatively, the sulfur diox-ide can be used to produce other products, such as sodium bi-sulfite or can be sold directly as a refined product. Oxygen that is commonly present in feed gas streams will oxidize sulfur dioxide to sulfur trioxide. The solvent is indif-ferent to the presence of sulfur trioxide because it reacts with a sodium adjunct of the solvent, forming sodium sulfate. A solvent purification system is incorporated into the system to remove sulfates when it reaches high levels. Typically, the amount of sulfate produced represents less than one half of one percent of the sulfur dioxide treated. Caustic is added to the solvent on pH control to maintain solvent effectiveness. The sulfate byproduct is non-toxic and can be sold, disposed of as a solid or, depending on local regulations, sent directly to the sewer. Extensive corrosion coupon testing was conducted dur-ing the initial two years of bench scale operation. Low cost 300 series stainless and FRP exhibited very low corrosion rates. The non-corrosive properties of the solvent minimized the initial capital cost. Pressure drop through the regenerative process is sig-nificantly lower than in sulfuric acid double absorption sys-tems because the tail gas is treated in a single, low pressure

drop absorbing tower with structured packing, thus reducing the power and volume requirements on the main gas com-pressor. This will greatly reduce the modifications needed to the compressor when treating the tail gas from an existing plant. Alternatively, existing units can be debottlenecked by increasing the gas strength and utilizing the SolvR™ system to treat the higher concentration tail gases.

a wise choiceThe 200 MTPD single absorption acid plant at

Southern States is the first commercial SolvR™ Technol-ogy installation. At Southern States, the SolvR™ system treats a tail gas of 25,000 NM3/hr (15,000 SCFM), con-taining 2,100 ppmv of sulfur dioxide. MECS® SolvR™ Technology was chosen over double absorption because of its significantly lower capital costs and high sulfur dioxide recovery capabilities. No compressor modifications and minimal other changes were required in the sulfuric acid plant. The SolvR™ stripper uses a combination of low pressure 0.2 barg (3 psig) steam from the exhaust of the main compressor and 14 barg (200 psig) steam to operate the stripper reboiler. The sulfur dioxide recovered from the stripper is returned to the drying tower for recovery as sulfuric acid. Water recovered from the process can be used as dilution water in the sulfuric acid plant. All the time spent exploring different choices was worth it for Southern States. Installation at the Savannah facility went smoothly. “The system was built in a modular format. Overall, the equipment fit together smoothly,” Bey-er said. “We did have a chimney tray that allowed solvent to pass between the absorbing section and the humidification section. MECS responded quickly though, and re-routed some process streams to continue operation.” Positive changes have been seen since the unit came online, as well. “Our plant yield has improved by about

1 percent since the installation of the SolvR™ system,” Beyer said.

disruptive technologyMECS® SolvR™ Technology is poised to become a

disruptive technology. With the capability to handle a wide range of inlet sulfur dioxide concentrations and no catalytic equilibrium limitations, the sulfuric acid process can be greatly simplified with more attention paid to significantly increasing energy recovery. To put this in perspective, classic double absorption requires a cold interpass heat exchanger, hot interpass heat exchanger, after interpass absorption converter pass(es), economizer, final absorber (including mist eliminator, distributors, packing, etc.) and acid cooler. In all, six pieces of equipment are required, five of which are large, because they must be sized for the gas volume. In contrast, the SolvR™ system consists of a quench/absorber (with internals), stripper/rectifier column (with internals), solvent interchanger, overhead condenser and solvent purification system. In all, six pieces of equipment are required, but only the quench/absorber is sized for the gas volume. Preliminary estimates indicate that the capital cost of a SolvR™ plant will be significantly less than double absorption. Given that double absorption accounts for 25 percent of the total cost of a new plant, the overall capital savings will be notable. Optimization may further improve the savings. Over the years, there have been many attempts to commercialize a regenerative sulfur dioxide technology, but for the most part, the solvent failed to provide the economic incentive for widespread commercialization. “SolvR™ technology gives us the flexibility to control our emissions,” Beyer said. “It is a viable option that should be considered by other plants looking for SO2abatement options.” q

Our Latest Installation Didn’t Take a CraneJust a Great Team of People

Recently, Roberts completed a different kind of installation – two new offices, in Florida and Texas. While our new locations didn’t require any heavy equipment, they are staffed with a team of heavily experienced people, ready to serve the sulfuric acid industry.

ROBERTS…A fully integrated engineering, fabrication, construction and plant maintenance services solutions company.

For more information, visit www.robertscompany.com | www.ppsengineers.com

Safe + Reliable + Creative + Competitive




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INdUSTry INSIgHTS

teck trail operations completes new acid plant, expected to reduce emissions by up to 15 percent

TRAIL, British Columbia—Teck Trail Operations has completed construction of its No. 1 acid plant, which has begun operation and is working at designed rates. The new acid plant improves environmental performance and operational reliability while reducing downtime and maintenance costs.

The new plant is expected to reduce sulfur dioxide (SO2) emissions from Trail Operations by up to 15 percent. “Safety is a core value at Teck. Our employees and contractor partners have exemplified this value on the project, which was completed with zero lost time injuries,” said Greg Belland, general manager, Teck Trail Operations. “The environmental and operational improvements that this new plant provides will support the long-term viability of Trail Operations.” The No. 1 acid plant replaces two older plants on the zinc processing side of the operation.

For more information, please visit www.teck.com.

freeport-McMoran announces smelter expansion project in Miami

MIAMI—Freeport-McMoRan has announced a smelter expansion project at its Miami operations which will increase copper production and also comply with new EPA standards. Upon completion of the project, the copper concentrate throughput for the smelter will increase by approximately 30 percent to a capacity of 900,000 tons per year from the current average of 700,000 tons per year. The expanded smelter capabilities will comply with the new EPA ambient air quality standard for sulfur dioxide (SO2) emissions. A major component of the project is to install a new smelting vessel which, along with modifications to other facilities in the smelter, will allow for increased copper production. Much of the construction work will be related to emission control systems in order to capture virtually all fugitive gases and particulate emissions. The resulting system will capture over 99 percent of the SO2 and other emissions from the Miami operations. The additional concentrate to feed the

expanded smelter will come primarily from Freeport-McMoRan’s Morenci (Arizona) and Chino (New Mexico) operations. The smelter will continue to be base-loaded with concentrate from the company’s Sierrita and Bagdad mines in Arizona. Engineering work is currently underway. While some construction will commence later this year, the bulk of the work is expected to begin in 2015. The new smelting vessel is scheduled to be commissioned in the second quarter of 2017 with production ramping up shortly thereafter. The construction workforce will vary greatly and is expected to number from 40 to 500 over a two-year period. Freeport-McMoRan plans to hire about 20 new employees to operate and maintain the new emission control systems and facilities. For more information, please visit www.fcx.com.

J.r. Simplot to build new ammonia plant in rock Springs, Wyo.

BOISE, Idaho—The J. R. Simplot Company is beginning construction on an ammonia plant adjacent to its existing phosphate fertilizer complex in Rock Springs, Wyo. This new plant will supply both the Rock

Springs and Pocatello phosphate fertilizer production locations, while having the capacity to meet the company’s next phase of anticipated phosphate expansion plans at Rock Springs. Construction activities for the new plant have begun, with completion scheduled for late 2016. “Output from the new ammonia plant will significantly enhance our long term sustainability in the phosphate marketplace,” said Bill Whitacre, president and CEO of the J. R. Simplot Company. “This capital investment is a big step for us; one that is key to our future in ensuring long-term, low cost raw materials to our facilities.” This investment will create approximately 25 permanent positions at the Rock Springs location, along with more than 400 construction jobs through the building process. The new plant will take approximately two years to complete. “After completion of this plant, we will be self-sufficient on ammonia, which is a key raw material in the production of fertilizer,” said Klaas Hutter, vice president of mining and manufacturing for Simplot’s AgriBusiness group. “Our process improvements will increase our efficiencies, therefore reducing our production costs as we continue to grow our commitment to the phosphate business.” For more information, please visit www.simplot.com. q

A major international fertilizer company was experiencing short sulfuric acid pump operating life after maintenance, which caused unexpected plant shutdowns. Weir Minerals Lewis Pumps (WMLP) was asked to study their operation and provide recom-mendations to increase pump reliability and reduce maintenance costs. A senior WMLP field service engineer was engaged by the company to present a clinic and maintenance training as well as take part in rebuilding a pump. This particular example is similar to claims in which the original new pumps received from WMLP were trouble free dur-ing the first several years, until they were removed from service for routine maintenance. Once they had been maintained, the pumps never seemed to achieve their initial operating life cycle. The investigation started with classroom sessions which included both operations and maintenance personnel—not just the engineers, but the millwrights who actually maintained the equipment. Open dialogue was encouraged in the classroom ses-sion, and it was discovered that the customer was purchasing the pump thrust ball bearing from a local supplier. Unfortunately, the procured bearing did not duplicate the thrust capability of the original equipment. WMLP normally uses a shielded maximum-capacity dou-ble-row ball bearing having a C-3 internal fit in its pumps 150 millimeters and larger. The customer was purchasing a bearing of identical physical dimensions, but with a smaller ball comple-ment, which dramatically lowered the thrust-loading capability of the bearing. Consequently, the pump service life was abbreviated due to early failures. When seeking replacement parts for pumps, customers

sometimes believe any part that will fit in the pump is a good option. Pirated parts may look

identical to original equipment manufacturer (OEM) parts and may indeed be a sufficient fit, but there are numerous dangers associated with installing pirated parts instead of those provided by the OEM. WMLP parts are made to exacting tolerances. Even though a pirated part may appear dimensionally similar, critical tolerances are nearly impossible to duplicate without the benefit of manufacturing drawings. These dimensional errors may not be catastrophic, but will often degrade the performance charac-teristics of the part. Choosing correct materials is critical to ensuring the long life of pumps in highly corrosive fluids. Pirated parts are not made from our proprietary Lewmet® material, which provides significant corrosion, erosion and galling resistance (see Fig. 1). A Lewmet® part possesses 20 to 25 times the corrosion resis-tance of alloy 20 in hot concentrated H2SO4. This translates to additional cost savings from the increased longevity of the OEM parts. After a pirated part is installed, the customer may find that the head vs. capacity of the part is within a few percentage points of the original WMLP part. What is typically lacking is efficien-cy. Pirated parts provided to WMLP by customers unhappy with their performance have been shown to be nearly 10 percent less

efficient than the OEM parts we provide. Based on a year’s worth of operation, this results in thousands of dollars in additional elec-trical costs for the customer. Despite an initial purchase cost that may be less than buying OEM parts, various factors result in a higher cost when expressed in “dollars per day of service.” A combination of inferior materi-als, reduced efficiency and degraded part performance can wreak havoc on the budget of the unsuspecting operator. Another danger often overlooked by customers seeking to purchase pirated or “bootleg” parts is the potential for catastroph-ic failure. With pumps operating in extreme conditions and often pumping corrosive fluids such as acid or oleum, a poorly made pirated part can lead to a full system breakdown. A broken part, depending on its location within the pump, can allow the release of deadly chemicals or fumes that can injure or otherwise harm workers. Although there is no way to eliminate the danger of working with such chemicals, using poorly engi-neered parts from a replicator facility can significantly increase the likelihood of a catastrophic failure leading to a deadly out-come. For more information, please contact Dolon Silimon at (314) 272-6224 or [email protected]. q

The dangers of pirated parts

Fig. 1: This comparison chart illustrates the corrosion resis-tance of various stainless steels including Lewmet®. From left to right, 316 Stainless Steel, CD4MCu, Alloy 20, Hastelloy C and Lewmet®, which shows the lowest corrosion. These corrosion rates are from static tests conducted in 98 percent sulfuric acid.

By: Dolon Silimon, Area Manager, Weir Minerals Lewis Pumps

Stop-gap measures like building up the shaft through welding or epoxy putties cannot take the place of OEM parts.

(Continued from page 5)


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t PUMP MaINTENaNCE

Electrostatic precipitators (ESPs) have been used for years to reduce dust and fumes from industrial exhaust and process gases. However, the technological innovations avail-able in today’s ESP designs are also yielding major cost reductions in capital equipment, operating expenses, energy use and main-tenance. In particular, wet electrostatic pre-cipitators (WESPs), when configured in a multistage system, can remove difficult-to-capture submicron particulates, aerosols and condensed organics with up to 99.9 percent efficiency and extremely low pressure drops. Suitable for a wide range of operating condi-tions, modern WESPs are currently produc-ing excellent results worldwide for a host of industrial applications, including sulfuric acid plants, mining and metallurgy, power generation, petroleum refining, industrial boilers and more.

A basic WESP is comprised of an array of negative discharge electrodes surrounded by grounded collection surfaces. Source gas is passed through the array, which induces a negative charge in even the most minute, sub-micron-size particles, impelling them toward the collection surfaces, where they adhere as the cleaned gas is passed through. The par-

ticle residues are purged from the plates by recirculating water sprays. Although they may share similar oper-ating principles and basic structures, WESPs can vary greatly in design, materials, gas flow rate and durability, as well as collection efficiency. It is important for engineers to recognize key differences among precipitator systems. Today’s intelligent WESP designs incorporate several features that can save your company significant sums. These fea-tures include:• Cost-effective on PM 2.5: Other gas

cleaning equipment and techniques, in-cluding scrubbers, cyclones and fabric filters, are usually less efficient or inef-fective on submicron particulates and mists.

• Uniqueelectrodedesignandmultistagesystems: Features custom-designed ion-izing rods with star-shaped discharge points, enclosed within square or hex-agonal tubes. This configuration gen-erates a stronger corona field without significantly increasing electrical load; it achieves superior collection efficiency using less energy.

• Low pressure drop: With virtually no

mechanical impedance, there is very little pressure drop through the WESP. This supports higher gas velocities and volumes and enables plant engineers to use smaller-scale, less costly equipment and still achieve collection efficiencies of 99.9 percent—far superior to wet or dry scrubbers, cyclones, fabric filters and other equipment.

• Aqueousflushingsystem:Thispreventsparticle re-entrainment, residue build-up and resistivity—thus increasing cost-efficiency per gas stream volume. Aque-ous flushing also eliminates the need for mechanical or acoustical rappers to dislodge particulate residues, saving money on power consumption, and on mechanical equipment maintenance and replacement costs due to wear and dete-rioration.

• Sophisticated electronic controls: Con-trols are linked to a close-coupled gas flow management system and can squeeze even more efficiency out of the system by continuously optimizing such operating parameters as gas velocity, gas composition, saturation, temperature, corona intensity, etc.

• Construction materials: To preventcostly, premature deterioration, critical WESP surfaces can be constructed with modern, corrosion-resistant alloys and fiber-reinforced plastics (FRPs).

• Cool, saturated WESP environment:This environment is more effective on condensable, oily, sticky contaminants, requiring less extensive treatment.

WeSP economics benefit mining/metals operations Advanced WESP systems demonstrate uniquely versatile applicability over a broad range of industries, operating conditions, lo-cations and gas chemistries. Mining, smelting

and metallurgical operations, for example, face some of the most complex and onerous air pollution-control challenges, and some of the tightest environmental regulations. In a recent case, Mopani Copper Mines Plc, in Zambia’s mineral-rich Copperbelt region, was producing high levels of sulfur dioxide, acid mists, particulates and other emissions from its pyrometallurgical smelters. Glencore International AG, the mine’s owner, had built a sulfuric acid plant to convert SO3 and SO2

gas emissions into purified sulfuric acid, but required more extensive cleaning of impuri-ties in the input gas stream. In 2007, the company added a pair of WESPs engineered and constructed onsite by Beltran Technologies, Inc. of Brooklyn, NY. Due to the corrosive nature of the Mopani smelter emissions, the Beltran WESPs were custom fabricated using fiberglass reinforced plastic (FRP) and high nickel-chromium al-loys. The new gas cleaning equipment was handling sulfuric acid mists, reducing the aerosols and particulates by 99.5 percent. Smelting operations at the Mopani Cop-per Mine were expanded again in early 2014. To handle the significantly increased gas vol-umes, Beltran was hired to construct and in-stall six more advanced WESPs for Mopani’s newly added sulfuric acid plants. Today, Mo-pani is again meeting emission control re-quirements set by the Zambian government, while saving money on its gas cleaning and acid manufacturing operations. Due to their versatility and efficiency on a wide variety of problematic emission com-ponents, and under diverse operating condi-tions, WESPs are becoming the proven spec-ification worldwide for collection efficiency, reliable performance—and cost savings that translate directly to the bottom line. For more information, contact Michael R. Beltran at (718) 338-3311 or [email protected], or visit the company’s website at www.beltrantechnologies.com. q

WESP economics: how wet electrostatic precipitators reduce gas cleaning costs, offer competitive edge

Mopani Copper Mines, Zambia: Beltran high-efficiency WESPs reduce costs of removing acid mists and fine particulates.

By: Michael R. Beltran, President and CEO, Beltran Technologies, Inc.


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Roberts and their partner, PPS Engineers, a full-ser-vice engineering firm, work as an integrated team to offer total service solutions to the phosphate/sulfuric acid in-dustry from project conception through project execution. Capabilities include scope development, detailed design, cost estimating, procurement, fabrication, construction, commission and start-up. With extensive experience in the phosphate/sulfuric industry, Roberts continues to not only expand services, but has added locations to provide even better service to their phosphate/sulfuric customers.

The addition of two new locations, ideally suited to serve the phosphate industry, is just one more way in which Roberts continues to enhance and build lasting relation-ships with its clients.

floridaThe new Mulberry, Fla., location, in the heart of the

Florida phosphate industry, is being led by WB Chambless. Chambless, who attended the University of South Florida, will serve as Roberts’ Florida Operations Manager. He has 39 years of experience in industrial engineering, construc-tion and maintenance project execution, as well as multi-of-fice execution for engineering and direct hire construction and maintenance. Chambless specializes in the phosphate fertilizer, plastics, power, pharmaceutical, petrochemical and waste water facility industries. He can be reached at (863) 207-3702 or [email protected].

texasRoberts’ Pasadena, Texas, office is conveniently locat-

ed to serve the Gulf Coast phosphate industry. Sam Parks, a graduate of Texas A&M University, will serve as the Gulf Coast Operations Manager. Parks has 35 years of experience working in the oil and gas industry, executing engineering and construction projects from upstream to downstream. He can be reached at (281) 705-2598 or [email protected]. Bob DeNeve, a graduate of Georgia Southern, is Senior Director of Business Development for Gulf Coast Operations. DeNeve has more than 20 years of experience in business de-velopment working in the downstream engineering, construc-tion and maintenance fields throughout North America, with a key focus on the U.S. Gulf Coast. Contact DeNeve at (832) 723-5423 or [email protected].

Project highlightsRoberts has many on-going projects that include fab-

rication, field erection of fabricated components, construc-tion, plant turnarounds and maintenance repairs, as well as fast track and emergency response services for a variety of customers. During the past several months the company completed the following projects specific to the sulfuric acid industry: The Texas office, led by Sam Parks, recently completed installation of a new converter for a facility on the Houston Ship Channel. A new foundation was installed adjacent to

the existing converter. Roberts assembled shop-fabricated components on the new foundation. During a turnaround, Roberts disconnected the ductwork from the old converter and connected new ductwork to the new converter. This ap-proach minimized the down-time required. Roberts also completed the mechanical installation of a Heat Recovery System for a Florida phosphate facility. The work consisted of steel erection as well as equipment and piping installation, and was completed prior to a plant turnaround. In other phosphate work, Roberts installed an alloy acid cooler in North Carolina, performing engineering, fab-rication, installation and associated services. The company was able to reuse foundations from a previous acid cooler installation and design the piping to minimize the amount of new piping required. Roberts completed the bulk of the work prior to a plant turnaround and completed tie-ins dur-ing the turnaround. Roberts knows the importance of focusing on core values, one of which is to build long-term customer rela-tionships. Key to this is an emphasis on integrity, superior quality, employee well-being and creating a safe work envi-ronment for all involved. These core values ultimately lead to customer satisfaction—and at Roberts, that’s what it’s all about. For more information, please visit www.robertscompany.com. q

roberts continues to expand offerings to phosphate industry

WB Chambless Sam Parks Bob DeNeve

Sulphuric Acid Coolers

Experience:• 2000+ Chemetics® (CIL) Anodically Protected Acid Coolers installed since 1968• ANOTROL® the premier name in anodic protection since 1970• Seawater acid coolers using CIRAMET® alloy since 1977• Introduced Silicon Stainless steel (SARAMET®) to the sulphuric acid industry in 1982• SARAMET® alloy Acid Coolers since 1989• Latest development: MEMORY SEAL™ cathode gland parts introduced in 2012Design and Manufacturing:• Every acid cooler is manufactured in Chemetics’ state-of-the-art facility in Canada • Materials and thermal designs selected to ensure optimal performance and reliability • Chemetics acid coolers regularly last over 30 yearsService/Feedback:• Over 200 years of acid cooler site technical service experience • 45 years of continuous improvement via feedback ensures customer focused solutions

Chemetics Inc.(headquarters)Vancouver, British Columbia, CanadaTel: +1.604.734.1200 Fax: +1.604.734.0340email: [email protected]

Chemetics Inc.(fabrication facility)Pickering, Ontario, Canada, Tel: +1.905.619.5200 Fax: +1.905.619.5345email: [email protected]

Chemetics Inc., a Jacobs companywww.jacobs.com/chemetics

More than 60% of the worlds sulphuric acid iscooled by Chemetics Acid Coolers


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EXPERTISEMining & Metallurgy Fertilizer Power

www.snclavalin.com

Oil & Gas

Sulphuric Acid > Sulphur Recovery > Gas Handling > LogisticsGreenfield > Revamps > Upgrades > AdvisoryAny size > Anywhere [email protected]

SULPHUR & EMISSIONSSOLUTIONS

Hydraulic nozzles have long been the standard for spraying molten sulfur, but the benefits of using air atomizing nozzles can be significant. The smaller drops produced by air atomizing nozzles typically improve combustion and eliminate carryover and damage to downstream equipment. Until now, testing guns equipped with air atomizing nozzles required purchasing new guns to equip an entire furnace.

A new hybrid sulfur gun has been introduced by Spraying Systems Co. The guns can be easily converted from hydraulic operation with WhirlJet® BA nozzles to air atomizing operation with FloMax® nozzles. In addition, the guns can be converted back to hydraulic operation if

air atomizing performance doesn’t meet expectations. The hybrid guns offer producers an easy and risk-free way to evaluate air atomizing nozzles in their operations.

using modeling tools to optimize spray performance and identify potential failures

Optimizing molten sulfur spraying is dependent on many variables including atomization, drop size, residence time, placement of the gun, furnace baffle locations and operating conditions in the furnace. Many producers are turning to Computational Fluid Dynamics (CFD) modeling to improve performance. Common studies look at both gun placement to avoid sulfur impingement on walls and drop size to determine the optimal size for complete vaporization

and full combustion. Fluid Structure Interaction (FSI) modeling is also gaining rapid acceptance. One recent study looked at the thermal and structural properties of a sulfur gun and the effect of flow-induced vibrations. The study validated the thermal integrity of the sulfur gun but identified a structural weakness that could result in gun failure. The gun was redesigned to include support collars to counteract the vibrations.

More information on sulfur gun technology is available at www.spray.com/hybridgun including the following topics:— Animation of hybrid sulfur gun conversion from hydraulic to air atomizing— Presentation: Optimizing Sulfur Spraying, Sulfuric Acid Roundtable 2013 —Sulfurgunfluidinteractionstudy— Sulfur gun and spray nozzle overview q

advancements in sulfur spraying: new hybrid gun and predictive modeling

CFD shows impingement with base of combustion chamber using hydraulic nozzle (left) and no impingement using air atomizing nozzle (right).

Hydraulic nozzles can be replaced with air atomizing nozzles on hybrid sulfur guns providing producers with an easy and economical way to compare performance between nozzle types. See animation at www.spray.com/hybridgun.


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Every year for over three decades the central Florida section of the Ameri-can Institute of Chemical Engineers plays host to the AIChE Clearwater Convention in Clearwater Beach, Fla. This year was no exception as hundreds of professionals from the fertilizer, mining and spent-acid regeneration industries gathered for the 38th annual convention held over two days last June.

Through the course of multiple ses-sions on June 6th and 7th, chemical pro-cess technology professionals explored the production of phosphoric acid, phosphate fertilizers and sulfuric acid. On day one of the conference, those interested in sulfuric acid attended the Sulfuric Acid Workshop

chaired by Rick Davis of Davis & Associ-ates Consulting and Josh Every of Mosaic. The workshop delved into the mechanisms surrounding recent hydrogen incidents that have been occurring in the acid industry worldwide and what can be done to miti-gate them. Participants heard case studies of actual field incidents as well as presen-tations detailing hydrogen formation, early detection and mitigation; optimal equip-ment design; best maintenance practices, as well as protocols for communicating events across the industry. Presentations were given by Steve Puricelli of DuPont MECS, Josh Every of Mosaic, George Wang of Solvay, Rene Dijkstra of Chemetics and Dr. Hannes Storch of Outotec.

The next day offered additional pre-sentations on a variety of topics related to sulfuric acid. These included: — “Computer Simulation of Sulfuric

Acid Plants: How to Make it Meaning-ful,” by Gary Lee of NORAM

— “A Virtual ‘Try Before You Buy’ Ap-proach: Better Plants Through Dy-namic Logistical Simulation,” by Guillaume Rivest of Hatch Ltd.

— “Case Study on Mosaic’s use of MECS Heat Recovery System (HRS) Operator Training Simulator (OTS) for Training at New Wales Facility,” by Dave Dericotte of DuPont MECS and Dave Sheffield of Mosaic

— “Commercialization of MECS SolvR™ Regenerative SO2 Recovery Technology,” by Steve Puricelli of DuPont MECS and Bryan Beyer of Southern States Chemical

— “Reduction of Magnesium Oxide in Fertilizer Grade Phosphoric Acid,” by

Tino Prado of Prado Technology Group— “Maximizing Power Generation from

Metallurgical Sulfuric Acid Plants,” by Dr. Hannes Storch of Outotec

— “Developing an Effective Strategy for Commissioning Capital Projects in Existing Process Facilities,” by Ran-dolph Williams of Hatch Ltd.

— “Polishing Filters, the Answer to the Increasing Need for Cleaner Sulfur,” by Jeroen Bouwman of Twin Filter

As in past years, the conference venue, the Sheraton Sand Key Resort, provided a relaxing beachside backdrop for partici-pants and their families to enjoy the various hospitality events spanning the two days. Attendees also used the ample networking time provided to exchange valuable indus-try information with their peers. Planning is already in progress for next year’s conference, to be held June 5-6, 2015, at the Sheraton Sand Key. Check www.aiche-cf.org for further details. q

DuPont Sustainable Solutions Clean Technologies hosted its 28th Annual Best Practices Workshop this year in Coeur d’Alene, Idaho attracting nearly 190 industry professionals. The workshop consisted of two distinct events, each highlighting a different technology. The two events, the STRATCO® Alkylation Workshop and the MECS® Sulfuric Acid Regeneration (SAR) Workshop, both took place at the Coeur d’Alene Resort during an overlapping period from Sept. 8-12. The DuPont conference brought to-gether customers from around the world for focused learning, information sharing and networking. Topics covered alkyla-tion process, technology configuration and selection, technical design consid-erations, operations and maintenance, as

well as technology troubleshooting and performance optimization. Workshop at-tendees included operations personnel, process and mechanical engineers, engi-neering supervisors and technology spe-cialists.

The primary goal of the MECS® SAR Best Practices Workshop was to al-low plant attendees to walk away with a better understanding of the sulfuric acid regeneration technology. The workshop is an important part of the MECS Inc. (MECS) customer service commitment. Participants were able to seek answers to any technical issues they might be hav-ing as well as gain better familiarity with the services and support that MECS pro-vides. The resort venue also enabled at-tendees to network with their peers in a relaxed setting. Topics for the SAR workshop in-cluded decomposition furnace operation and maintenance; NOx and niter in sul-furic acid plant operations; SAR and Al-kylation interactions; sulfuric acid safety;

sulfuric acid storage tanks; sulfuric acid safety; materials, corrosion and fouling; gas cleaning systems; strong acid systems, hydrogen safety; plate heat exchangers; anodically protected acid coolers; con-verters; turnaround maintenance plan-ning; SolvR™ regenerative SO2 scrubbing technology; mist eliminators; acid pumps; introduction to hydrogen peroxide tailgas scrubbing; advancements in MECS® cata-lyst technology; and an acid plant CFD modeling case study. In additional to technical aspects of the conference, participants were able pe-ruse vendor exhibits during hospitality re-ceptions as well as attend special planned dinners throughout the week. q

an institution in Clearwater: conference convenes for 38th year

duPont, MECS host annual best practices workshop

DuPont Sustainable Solutions Clean Technologies hosted its 28th Annual Best Practices Workshop this year in Coeur d’Alene, Idaho.

Dave Sheffield, left, and Mike Pubillones, right, of Mosaic share their experience of the MECS® heat recovery system operator training simulator at the company's New Wales, Fla. facility with participants at the 2014 AIChE Clearwater Convention.

CONfErENCE rEvIEW

The 2014 Sulfuric Acid Workshop focused on the mechanisms surrounding recent hydrogen incidents that have been occurring in the acid industry worldwide and what can be done to mitigate them. Chairing the session’s discussions are, from left, Dr. Hannes Storch of Outotec, Rene Dijkstra of Chemetics, George Wang of Solvay, Steve Puricelli of DuPont MECS and Josh Every of Mosaic.


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It will take more than just a single adjective to describe the 2014 Australasia Sulfuric Acid Workshop, held in Glenelg, South Australia, this spring. But even com-bining “useful” with “informative” plus “relevant” doesn’t quite do the job. At-tendee feedback to Kathy Hayward, con-ference organizer and Sulfuric Acid Today publisher, highlighted the workshop’s con-tent as exactly the sort of information acid producers can use back at their plants.

Fifteen acid producing companies were in attendance this year, as well as 19 conference co-sponsor firms, who provide expertise, equipment and services to the sulfuric acid industry. Co-sponsors pre-sented a variety of topics to inform and assist acid production. These topics ranged from material selection to maintenance to optimization and more. The specific pre-sentations were as follows:

—Keynote Address: “The Global Sul-phuric Acid Market,” presented by Robert Boyd, Elkbury Sulphur —“Sulfuric Acid Urban Myths and Legends (And Other Things Ob(li)vious to Us),” presented by Steve Puricelli, DuPont MECS —“Important Factors to Consider Be-fore Making a Decision in Sulphuric Acid Plant Equipment Replacement Projects,” presented by Michael Fenton, Chemetics —“Maximize Your Maintenance Out-age for a Longer Production Campaign,” presented by Stan Miller, VIP International —“Aspects of Sulfuric Acid Mist Precipitator Design, Materials and Main-tenance,” presented by Swapan Mitra, Bel-tran Technologies —“HRS in a Brownfield Plant,” pre-sented by Senada Dunjic, SNC-Lavalin —“Mist Eliminator Troubleshooting–A Selection of Case Studies and General Information to Help Guide You Through the Problems of Troubleshooting Mist Eliminator Operation,” presented by Graeme Cousland, Begg Cousland Enviro-tec Ltd. —“Revamp and Upgrade Possibilities in Sulphuric Acid Plants,” presented by Jan Albrecht, Outotec

—“On-Line Simultaneous Measuring of High Purity Sulfuric Acid Concentra-tion and Volume Flow with Non-Intrusive Ultrasonic Technology,” presented by Dr. JoergWylamrzy,FLEXIMGmbH —“Understanding Spray Technology to Optimize Sulfur Burning,” presented by Dan Vidusek and Chuck Munro, Spraying Systems —“Better Management of Sulphur Section,” presented by Jan Hermans, Sul-phurnet —“Get the Most Out of Your Cata-lyst,” presented by Allan Godsk Larsen, Haldor Topsøe A/S —“Maintenance Considerations for Mondi Piping Systems,” presented by Skip Unger, Acid Piping Technology —“Insulation and Cladding–(the un-recognized source of gas leaks and other plant damage),” presented by John Wood-head, Specialised Engineering Services Pty Ltd. In addition to the presentations, plant personnel participated in Q&A-style pan-els that generated discussion among all in attendance. The free exchange of informa-tion at panels like these is an important part of the workshop. “Particularly notable this year,” ex-plains Hayward, “was the variety of expe-rience levels. We had people who have been in the industry for 40 years, and others just a few months. The newer people tended to

ask a lot of questions, which prompted the sharing of knowledge from the more sea-soned experts.” There were eleven panel discussion topics this year. The topics, se-lected by plant personnel, were as follows: —Gas Cleaning (scrubber/quench tower, ESP wet and dry, gas cooler/gas cooling tower) —Acid Towers (acid towers/coolers/pump tanks/piping/valves/pumps for hi temp) —Sulfur Handling and Storage Sys-tems —Converter (replacement / mainte-nance / catalyst screening and disposal) —Materials of Construction (acid towers/coolers/pump tanks/piping/valves/pumps for hi-temp) —Maintenance Inspections / Testing Methods —Acid Resistant Linings/Bricks/Mor-tars and Furnace Refractory —Safety Issues and Incident Reviews —Weak and Strong Acid Pumps (ver-tical/horizontal/sulfur/corrosion/mainte-nance/materials of construction) —Heat Exchangers (acid coolers, shell and tube/plate/gas-gas) —Steam Systems (boilers/economiz-ers/superheaters) The Australasia conference, in its seventh year, drew an international crowd with over sixty people from six continents. Spanning four days from March 24-27, there was ample opportunity for partici-pants to mingle outside of the conference room. An important feature of the work-shop, social time enables participants to follow up on information presented during meetings as well as build relationships that promote beneficial business exchanges in the future. Held just steps from the Gulf of

St. Vincent in South Australia at the scenic Stamford Grand Adelaide Hotel, confer-ence goers relaxed during several hospi-tality events. These activities included the kick-off welcome reception, dinner at a nearby marina, and a friendly competition involving wine trivia. On the final day, five lucky participants also earned door prizes to take home as conference souvenirs. The conference ended with a friendly round of golf at the nearby Glenelg Golf Club. A Sulfuric Acid Today anniversary cake, commemorating the magazine’s 20th year in production, was a delicious addition to this year’s event. To accompany their dessert, conference participants received a copy of the 20th anniversary issue. Outside of the meetings and social agenda, the conference offered twelve co-sponsor booths, where plant personnel could learn about the latest technologies and services available in the industry. The Australasia Sulfuric Acid Work-shop is offered in even years in Austra-lia and alternates with the Sulfuric Acid Roundtable, which is offered in odd years in the United States. The 2015 Sulfu-ric Acid Roundtable will be held at the Streamsong Resort in Central Florida from March 23-26, 2015. Sulfuric acid producers can register online at www.acidroundtable.com. If you are a vendor that supports the sulfuric acid industry and you are interest-ed in attending the roundtable, please con-tact Kathy Hayward at [email protected] or (985) 807-3868. q

Kathy Hayward, publisher of Sulfuric Acid Today, celebrated her magazine’s 20th anniversary with attendees of the 2014 Australasia Sulfuric Acid Workshop in Glenelg, South Australia.

George Wang of Solvay co-chaired the panel discussion regarding maintenance inspections and testing methods.

Denis Gervais of Vale gave a brief presentation of his facility’s experience with acid towers and packing during a panel discussion.

The 2014 Australasia Sulfuric Acid Workshop was attended by 15 acid producing companies, as well as 19 conference co-sponsor firms, who provide expertise, equipment and services to the sulfuric acid industry.

Part of the workshop agenda included co-sponsor presentations. Jan Albrecht of Outotec presented a paper on the latest technology regarding revamps and upgrade possibilities in sulfuric acid plants.

John Woodhead of Specialised Engineering Services shared his vast knowledge of insulation and cladding with participants of the 2014 Australasia Sulfuric Acid Workshop.

australasia workshop informs with wealth of experience


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Faces & Places

Skip Unger of Acid Piping Technology, Brian Webster of Solvay, Howard Tenney of Tenney & Co. and Natalie and Gene Tenney of Tenney & Co. (with daughter Emma) enjoyed the festivities of the MECS, Tenney & Co., Acid Piping Technology and Weir Minerals Lewis Pumps Customer Appreciation Day.

The acid tower panel discussion at the 2014 Australasia Sulfuric Acid Workshop included a talk by Jared Exton, right, and Brett Marsh of First Quantum Minerals Australia Nickel who spoke about their facility’s recent drying tower downcomer replacement.

The 2014 Sulfuric Acid Workshop provided informative talks by acid industry suppliers, including this one, given by Allan Godsk Larsen of Haldor Topsøe A/S, who detailed how to get the most out of your catalyst.

Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day. Lewis Pumps Customer Appreciation Day.

FLEXIM participated as an exhibitor at the 2014 Sulfuric Acid Workshop in Glenelg, South Australia. Perusing the company’s booth are, from left, Joerg Wylamrzy of FLEXIM, Deono Suryadi of FLEXIM, Rob Schlegel of Solvay and Elisabeth Schlegel.

In a dramatic physical display not soon to be forgotten, the corporate hosts of this year’s Customer Appreciation Day demonstrate that when it comes to serving their customers, it’s all about family. A recent Houston Astros baseball game provided the venue for the event sponsored by MECS, Tenney & Co., Acid Piping Technology and Weir Minerals Lewis Pumps.

Social opportunities at the 2014 Australasia Sulfuric Acid Workshop included a friendly round of golf at the beautiful Glenelg Golf Course. Players are, front row from left, Nic Howard of Ravensdown Skip Unger of Acid Piping Technology, Mick Cooke of Weir Minerals Lewis Pumps and Stan Miller of VIP International; second row from left, Kay Dickinson, Peter Gaborit of James Walker and Ossama Al Ghamdi of Ma’aden; back row from left, Tyler Caviglia of Chemetics, Phill Dickinson of Ravensdown, Colin Clifton of Ravensdown, Corey Muller of Outotec, Graeme Cousland of Begg Cousland Envirotec, Michael Fenton of Chemetics and Kevin Nee of Ramco.

Participants of the 2014 Australasia Sulfuric Acid Workshop enjoyed many opportunities to chill. Here, pictured from left, are Brian Hill, Aaron Flood and Andrew Tieleman from Minara Resources/Glencore enjoying the workshop’s welcome cocktail reception.

Enjoying the Astros baseball game for the MECS, Tenney & Co., Acid Piping Technology and Weir Minerals Lewis Pumps Customer Appreciation Day are, from left, Gene Tenney and Drew Tenney of Tenney & Co., Matthew Miller, Howard Tenney of Tenney & Co., Stan Miller of VIP International, and Steve Williams of MECS.

Sulfuric acid producers shared their experiences with participants of the 2014 Australasia Sulfuric Acid Workshop. Here, Franz Schnetler of Incitec Pivot described his facility’s recent experience with stick tests during the acid towers panel discussion.

The 2014 Australasia Sulfuric Acid Workshop offered several discussion panels including one pertaining to sulfur during which Ron Larman, left, and Colin Tuck of Ballance Agri-Nutrients presented on molten sulfur acidity.

Co-sponsors of the 2014 Australasia Sulfuric Acid Workshop generously donated door prizes for the producing plant attendees. Brett Marsh, center, of First Quantum Minerals Australia Nickel was one of the lucky winners, scoring a Seagate Central media storage system, which he accepted from Steve Puricelli, left, of DuPont MECS and Darren Bridges of Specialised Engineering Services.

Haldor Topsøe hosted a dinner at the Lobster Pot restaurant in conjunction with the 2014 AIChE Clearwater Convention in Florida. Attending the dinner are, from left side of table, Patrick Polk of Haldor Topsøe, Betty Polk, Josh Every of Mosaic, Sarah Every, Nolan Blackwelder and Lian Blackwelder. From the right side of table, Sam Chidester of Haldor Topsøe, Darwin Passman of VIP International,Jon Wyatt, Mosaic, Scott Doty, Mosaic, and Stan Miller of VIP International.

International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.International, and Steve Williams of MECS.

Acid technology suppliers not only share information, but their appreciation for the clients they serve. Recently MECS, Tenney & Co., Acid Piping Technology and Weir Minerals Lewis Pumps combined forces to host a Customer Appreciation Day for nearly 200 customers at a Houston Astros baseball game. Pictured are, from left, Helen Cardwell and Paul Wibbenmeyer of MECS, Jim Clements of Solvay, Howard Tenney of Tenney & Co. and Brian Webster of Solvay.

Participants relaxed at the 2014 Sulfuric Acid Workshop’s closing dinner reception held at the Wine Centre in downtown Adelaide, South Australia. Pictured are, from left, Carol Cooke, Mick Cooke of Weir Minerals Lewis Pumps, Anders Ohlin of Outotec AB, S.G. Park of Sun Metals Corp., Deval Modi of Metz Specialty Materials, Senada Dunjic of SNC-Lavalin, Randy Stanfill of Weir Minerals Lewis Pumps and Ruth Stanfill.

Colleagues from Spraying Systems Co. relaxed together at the welcome cocktail reception of the 2014 Australasia Sulfuric Acid Workshop in Glenelg, South Australia. Pictured, from left, are Chuck Munro, Christy Hoffnerr and Dan Vidusek.


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Register On-Line Today! www.acidroundtable.com

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T O D A YSulfuric Acid

The 2015 Sulfuric Acid Roundtable will offer:— Keynote Address on the Global Sulfuric Acid Market— Producing Plant Panel Discussions & Presentations— New Technology Developments— Safety Issues & Incident Reviews

fifth South african conference supports growing industryJOHANNESBURG, South Africa—The Southern African Institute of Mining and Met-allurgy (SAIMM) has slated its 5th Sulphur and Sulphuric Acid Conference for April 8-10, 2015. The conference will take place in KwaZulu-Natal.

The production of SO2

and sulfuric acid remains a pertinent topic in the South-ern African mining, minerals and metallurgical industry. The Sub-Saharan region has seen a dramatic increase in the number of new plants in recent years. The design capacity of each of the new plants is in excess of 1,000 tons per day. This event provides a forum for producers, technology sup-pliers, consumers, legislators and other role players in the industry to discuss relevant issues on the topics related to acid and SO2 production.

Through the conference, SAIMM aims to expose its members to issues relating to the generation and handling of sulfur, sulfuric acid and SO2

abatement in metallurgical and other industries. The event will also provide an opportunity for producers and consumers of sulfur and sulfuric acid and related products to be exposed to new technologies and equip-ment in the field. Attendees will also share best practices and real-world experience. For more information or to register, please visit www.saimm.co.za or email [email protected].

Clearwater 2015 offers opportunity for learning, socializingCLEARWATER BEACH, Fla.—The American Insti-tute of Chemical Engineers (AIChE) Central Florida Chapter is pleased to announce its 39th Annual International Phosphate Fertilizer and Sul-

furic Acid Technology Confer-ence. The conference will take place at the Sheraton Sand Key Resort in Clearwater Beach June 5-6, 2015, marking the event’s 38th year at the resort.

The AIChE Central Flori-da section and colleagues from around the world enjoy gather-ing each year at Clearwater Beach to share ideas regard-ing chemical process technol-ogy specifically related to the production of phosphoric acid, phosphate fertilizers and sul-furic acid. In addition to the informative technical sessions, attendees look forward to the chance to mingle with friends old and new, enjoying the beautiful setting and wonder-ful Florida hospitality. This year, there will be two sessions on Friday af-ternoon. Rick Davis and Jim Dougherty will chair the sul-furic acid technology session. The topic and chairs for the second session will be an-nounced shortly. For more information or to register, please visit www.aiche-cf.org. q

CaLENdar Of EvENTS

WILMINGTON, Del.,—MECS, Inc. (MECS), a wholly owned sub-sidiary of DuPont, has entered into a collaboration agreement with W.L. Gore & Associates Inc. (Gore) to enhance customer access to world-class sealant technologies in the sul-furic acid industry. “This agreement deepens our commitment to helping our cus-tomers better maintain their assets by further integrating Gore’s best-in-class sealant technologies into MECS® plant designs,” said Brian Lamb, business unit supervisor, Clean Technologies, DuPont Sus-tainable Solutions. “Our customers will benefit from the shared exper-tise of MECS and Gore improving their safety and mechanical integ-rity performance.” Gore is the world’s leading sup-plier of expanded PTFE gaskets and packings. Products include GORE® Universal Pipe Gasket (Style 800), GORE® GR Sheet Gasketing, GORE® Series 500 Gasket Tape and GORE® Joint Sealant. For more than 40 years, the Sealant Technologies Group of W.L.

Gore & Associates has built a solid knowledge of factors that influence the sealing of piping systems, ves-sels, heat exchangers, pumps and valves across industries. Gore also has established a comprehensive technical services program, spe-cially designed to help customers determine the best solutions for their critical sealing applications. “We are pleased to formal-ize this cooperation with MECS, combining the technology and ex-perience of MECS with Gore’s in-novative Sealing Solutions. This collaboration agreement goes a long way towards increasing the reli-ability and safety of sulfuric acid processes,” said John Czerwinski, sulfuric acid segment leader, W.L. Gore & Associates. MECS is the global leader in the design of sulfuric acid plants and related high-performance products for the phosphate fertilizer, oil refin-ing and metal smelting industries. For more information about MECS® products and services, please visit www.mecs.dupont.com. q

MeCS, inc. and W.l. gore & associates inc. sign collaboration agreement to improve sulfuric acid plant operations and safety

INdUSTry NEWS


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Lewis® Pumps comprehensive product line includes:

Sulphuric Acid Pumps

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Weir Minerals Lewis Pumps is known internationally in the sulphur, sulphuric acid and phosphoric acid industries with equipment installed in more than 120 countries worldwide. Founded in 1891 as Chas. S. Lewis & Co., Inc., today Weir Minerals Lewis Pumps is the recognized world leader for pumps and valves in these difficult pumping applications.

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Weir Minerals Lewis Pumps8625 Grant Rd.St. Louis, MO 63123

T: +1 314 843-4437F: +1 314 843-7964Email: [email protected]

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