Economic Bottom of the Barrel Processing to Minimize Fuel Oil Production

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In parallel to this phenomenon,there is another challenge, whichhas developed through the years.

As the world recognizes the benefitsof using natural gas as fuel, demandfor fuel oil has seen a drop, adverse-ly affecting fuel oil prices. This inturn has weakened the economicsof those refiners with limited fueloil outlets, and has reached a level

where changes are needed.These are the major factors driv-

ing refiners to look at ways to processalternative lower costs crude oils,and the primary cause of the wave ofinterest in bottom of the barrel solu-tions. Most refineries will need toinstall new units using either carbonrejection or / and hydrogen additiontechnologies to convert fuel oil intomore valuable products. Many ofthe traditional solutions will resultin capital intensive projects. Withcoke disposal being a problem forcertain refiners and the high costof hydrogen consumption becomingan increasing burden, refiners often

wonder what other alternatives theymay have.

TWO CRITICAL ISSUES:

CRUDE OILS & FUEL OILAs security of supply and rising

crude prices are becoming greaterconcerns, refiners attention turn toless traditional crude oils. As crudeprice differentials also continue to

widen due to the direct link of sup-ply shortage & demand increase,refiners see in less traditional crudeoils another venue to maximize mar-gins; but how to get there is the key

question. These crude oils could behigh in Sulfur, low in API, contain-ing high Total Acid Number (TAN).Production of less traditional crudeoils is also on the rise.

The net result of processing ahigher volume of heavy or extraheavy crudes in the refinery diet isan increase in Vacuum Residue (VR)

volume and a decrease in feed sup-ply to the existing conversion units.

The disposition of this high sul-fur fuel oil will become difficultdue to new environmental require-ments. Moreover, with the decline

in fuel oil demand and the naturalgas switch, fuel oil pricing couldcontinue to drop in the long run.

The best projects of the futureshould not only allow processing ofless expensive, opportunistic crudeoils but should be able to reducefuel oil make without compromisingrefinery reliability. In order to meetthe above objectives the new proj-ects may include some or all of thefollowing elements:

Allow shift to less expensiveheavier, sour crude oils and otheropportunity crude oils.

Convert all or a high percent-age of fuel oils, particularly highsulfur fuel oil, into more valuable

products.Reduce processing cost by using

more optimized processing scheme. Reduce utility costs and keep

emissions low.

TYPICAL RESIDUE

PROCESSING

CONFIGURATIONS

Simple Refinery

Representative of many Indianrefineries, these do not include anyconversion or upgrading facilitiesfor the bottom of barrel streams. Theentire vacuum residue (VR) is typi-cally disposed off by blending intohigh sulfur fuel oil product. Whenavailable, decant and cycle oils fromfluid cracking units, unconvertedoil from hydrocrackers, heavy gasoils, etc. can be used as cutter stocksto produce a high sulfur fuel oil.Sometimes even higher value distil-lates have to be blended into fuel oilto meet viscosity specifications.

Fuel oil producers will also find itdifficult to sell large volumes of highsulfur fuel oil as new regulationshave already been introduced whichlimit sulfur in fuel oil. These refiner-ies typically look for the additionof cost effective residue upgradingoptions.

Some of the potential technolo-gies that are available to the refinerfor achieving the above goals are asfollows.

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Economic Bottom of theBarrel ProcessingTo Minimize Fuel Oil

Production

Vasant Patel*, Rashid Iqbal, Odette Eng, AnandSubramanianKellogg Brown & Root, Inc.

Houston, Texas USA

The recent years have been marked by global uncertaintiesranging from economic to geopolitical. These uncertaintieshave resulted in a steep rise in crude prices affecting world-

wide refinery operations. Faced with the burden of skyrock-eting feedstock prices and uncertainty of supplies, refinersare much more conscious of these issues than in years past.As feedstock prices play a crucial part to the profitability ofrefiners the natural thought is to find ways to process lessexpensive crude oils. As crude prices increase so does thecost for refiners to bring in feed to process at the refinery.There are around 160 types of crude oils being producedworldwide and the price differentials between crude oils canbe $15 /barrel or higher. Refiners find themselves facedwith the difficult question of searching for crude blends tomaximize the use of their existing assets or to choose crudeblends, which will require additional capital investment butwill offer opportunity to increase return on investment.

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Technologies that reject car-bon:

- Solvent deasphalting (ROSETM)and Pelletizer (AQUAFORMTM)

- Thermal cracking processes(coking, thermal cracking, & vis-breaking)

Technologies that add hydro-gen:

- Fixed bed hydrotreating /hydrocracking

- Ebullated bed hydrotreating /hydrocracking

- Fluidized bed hydrocrackingAll of the above technologies

except the fluidized bed hydroc-racking are well established and arein use today. This paper will focuson the ROSE and AQUAFORMtechnology option, the effects of theDAO on FCC and the options for thedisposition of Asphaltenes.

Carbon Rejection

Delayed coking is the most com-monly used carbon rejection pro-cess. Roughly half of the US refiner-

ies have cokers. Visbreaking andthermal cracking are less severethermal processes than delayedcoking and more popular in Europe.Thermal cracking is normally usedfor cracking distillates. Visbreak-ing is used for reducing viscosity ofresidue by thermal cracking. Theserefineries include visbreaking/ther-mal cracking operations to reducerequirements for cutter stock forblending into fuel oil.

In delayed coking, VR feed can betypically cracked up to 65-80% with20-35% of the feed being rejected aslow value petroleum coke. The liq-

uid products are further convertedinto transportation fuels while gasproducts are used as fuel.

The cokers are capital intensive,require large real estate, and willproduce hydrogen deficient productstreams that would require hydro-gen addition prior to being blendedin to the product streams or pro-cessed in the existing reformers andFCC units.

In refineries with no FCC pre-treatment, a significant debit in FCCperformance will occur. In general,a negative impact on existing sec-ondary processing units hydro-processing, FCC, reformer, sulfurplant and amine system will occur.

Hydrogen Addition

Liquid Product

LSFO

VacuumColumn

Vac residHydrocracker

Vacuum residues can behydrotreated or even hydrocrackedusing either fixed bed or more typi-cally in an ebullated bed reactor.The high metal content of the VR

require use of guard beds or one ofthe online catalyst removal / addi-tion systems to achieve long runs.Unfortunately both options signifi-cantly increase capital and operat-ing costs.

The ebullated bed reactor designsinclude provision for online catalystaddition and removal. Resid hydro-processing units are generally veryexpensive and require significantplot space. The products from theebullated bed units normally requirefurther treating in fixed bed reac-tors. In most of the cases upgrading

the heaviest portion of the residuethrough hydrogen addition will con-sume large amounts of hydrogenand catalysts, and the incrementalbenefits derived will not justify theincremental investment require-ments.

SOLVENT DEASPHALTING

WITH PELLETIZATION

The option to use Solvent Deas-phalting in combination with thegeneration of solid fuels is a verycost effective means of dealing withatmospheric or vacuum residues andreducing the fuel oil production.

Typically 40 -70% of the VR can beeconomically extracted at a qualitysuitable for processing in an FCCunit. The pitch can be pelletized forsale as solid fuel in the cement, steelor power industry.

The sulfur or metals content inthe feed is attractive to the cementindustry, which currently thrives onlow BTU coal and petroleum cokefuel sources. Specifically for theIndian market, where the fuel needsfor the cement industry are enor-mous, the partial switch to high BTUasphaltenes represents an attractivesynergistic opportunity for bothindustries.

This paper will focus on the tech-nologies involved highlighting theperformance, benefits and limita-tions for the specific applicationsunder consideration.

Supercritical Solvent Deasphalt-

ing Unit - ROSETMSolvent extraction was first intro-

duced in the 1930s as a means ofextracting paraffinic lube oil blend-ing stocks from mixed base andnaphthenic crude oils. After wide-spread implementation of fluid cata-lytic cracking, refiners soon recog-nized the negative impact on FCCyield performance from processingaromatic feed stocks. Recogniz-ing an opportunity soon thereafter,refiners turned to solvent extractionas a means of producing viable high

Watson K FCC feedstock from resi-

due that was otherwise too contami-nated for economic FCC processing(see Table 1).

It was discovered that residualoils could be decarbonized withparaffin solvents to produce FCCfeeds with sufficiently low concen-trations of carbon residue and met-als to allow economic processing inthe FCC units. In the 1970s, KerrMcKee developed a solvent deas-phalting process, the ROSE Process,that separates most of the solventfrom the deasphalted oil (DAO) inthe supercritical phase regime rath-er than utilizing energy intensive

boil-off and condensation for sol-vent recovery. The supercritical sol-vent recovery breakthrough greatlyreduced the utilities expense asso-ciated with operation of the units,and the ROSE process quicklybecame the dominant residue deas-phalting process. ROSE technology

was acquired by The M.W. KelloggCompany in 1995 and now it is partof the refining technology portfoliooffered by Kellogg Brown & RootLLC (KBR).

The solvent deasphalting (SDA)process removes asphaltenes from

atmospheric and vacuum residuesusing solvent extraction. Most ofmetal, sulfur and carbon (Conrad-son carbon -CCR) is concentrated in

Table 1 Watson K for typical FCC feedstocks

FeedstockSource Atm Resid VacuumGas Oil PropaneDAO ButaneDAO CokerGas Oil

Arabian Light 11.60 11.68 11.81 11.74 11.4

Arabian Heavy 11.44 11.62 11.86 11.78 11.4

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the asphaltenes. The deasphaltedoil (DAO), which contains very lowquantities of metals, low sulfur, andCCR, is an excellent feedstock forprocessing in conventional refin-ery units, such as, fixed bed VGOhydrotreatreaters and the FCC.They can also be processed in highpressure hydrocrackers and ther-mal cracker units. Typical yield andquality are shown in Table 2.

Several SDA units (mostly ROSEunits offered by KBR of Houston,Texas) are operating successfullyin combination with hydrocrackers,hydrotreaters, and FCC units. Thisis an important aspect of ROSE unitsas refiners move towards heaviercrude oils. The contaminants, if leftin the processing chain, will becomethe limiting factors of downstreamunits.

FCC Feedstock ConsiderationsFeed properties that are most

important to consider when process-ing residue in an FCC unit are (1)asphaltenes (C7 insolubles) whichcause deactivation of downstreamcatalyst systems (2) vanadium,

which is the controlling parametersetting FCC catalyst make-up rates,(3) carbon residue which is the majorfactor affecting coke burning andcatalyst cooling requirements, and(4) hydrogen content which impactsFCC conversion and yield selectiv-ity.

Atmospheric or Vacuum Residueswith lower concentrations of carbonresidue and metals, particularly par-affinic, low vanadium crude oils, arenaturally better suited to upgradingin FCC units, and often significant

volumes of such residues or even 100percent atmospheric residue can be

charged to FCC units with little orno changes to the FCC hardware.However, the availability of thesehigh quality crude oils is diminish-ing and more contaminated, heaviercrude oils are making up an increas-ing proportion of the worlds crudeoil supply.

Even if blended in small concen-trations into FCC feedstocks, atmo-spheric or vacuum residues fromlower quality crude oils often con-tain higher concentrations of met-als and carbon residue than wouldbe economic for FCC processingbecause of the contaminants impacton required catalyst make-up rateand FCC yields; therefore beforeprocessing in the FCC unit, the resi-dues from such crude oils must firstbe upgraded with such processes as

vacuum distillation, coking, residuehydrotreating or solvent deasphalt-ing to reduce carbon residue and

metals content.While directly processing resi-

due from some high quality crudeoils in the FCC unit can be eco-nomic, this option is not very flex-ible with respect to refinery crudeoil supply.

Vacuum distillation can sepa-rate vacuum gas oil from atmospher-ic residue, but vacuum distillationleaves potential FCC feed behind inthe vacuum residue.

Coking eliminates vanadiumand carbon residue from its gas oilproducts but the coker gas oils are

hydrogen deficient, resulting in pooryield selectivity when processed inan FCC unit.

Residue hydrotreating canreduce contaminants to economiclevels while increasing FCC feedhydrogen content but the capi-tal and operating costs of residuehydrotreating are high.

ROSE solvent deasphalting sepa-rates a less contaminated, hydro-gen rich material (DAO) from atmo-spheric or vacuum residue thatcan be economically cracked in anFCC unit, mitigating issues associ-ated with the processing schemes

described above. The increasedhydrogen content and lower con-taminants of the DAO relative to theresidue together with low invest-ment and operating costs oftenmakes ROSE an economical optionfor producing good quality FCCfeed from residue.

It is interesting to note that thecontaminants that are most detri-mental to the FCC unit operation arealso the ones that show the sharpestpartitioning in the ROSE unit. e.g.metals > carbon residue > nitrogen> sulfur, resulting in a natural syn-

ergy between these processes.The contribution of DAO andCGO added to VGOs is shown inTable 3. For the same operating

Table 2 ROSE Yields and QualitiesFeed: Middle East Vacuum Residue

VR Feed Asphaltene DAO

Yield, wt% 100 51 49

SG, at 15.5oC 1.043 1.118 0.974

Sulfur, wt% 5.7 7.3 4.0

Conradson carbon, wt% 23.8 40.0 6.6

Nickel+Vanadium, ppmw 222 425 11

C7 Insolubles


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severity, the conversion, yields, andproduct quality from processing

VGO and DAO are about the same.A very interesting obser vation is theCCR content of the DAO; an equiva-lent CCR in the VGO would havemade this an unacceptable FCCfeed; but not so for DAO. This obvi-ously confirms that coke precursorsin the FCC feed are obviously bet-ter correlated by asphaltene con-centration as opposed to the coarserdetermination of carbon residue byConradson Carbon measurementmethod.

ASPHALTENE UTILIZATIONEconomic utilization of the

asphaltene product from a ROSEunit is the key to ROSE processeconomics. Listed below are someof the options refineries are utiliz-ing to maximize the value of ROSE

asphaltene product followed by adiscussion of each option, with spe-cial emphasis on solid fuels which

we believe will be very attractive forthe Indian market.

Fuel oil blend component Specialty commercial

asphaltenesConversion (coker) feedstockPartial oxidation feedstockSolid fuel

Asphaltene Product to Fuel OilIt is sometimes possible to burn

the asphaltene product directly

as fuel oil, but in most cases, it isfirst blended with other low-valuestreams to produce a lower viscosityproduct that meets fuel oil speci-fications. The fuel oil productioncan often be cut to less than half byinstalling a ROSE unit and blend-ing asphaltenes instead of vacuumresiduum into fuel oil.

Some refiners blend theasphaltenes with distillate materi-als to produce No. 6 fuel oil. Lightcycle oil and slurry oil from theFCCU makes excellent blendingstocks because of their high aro-matic content. A visbreaker canbe used to reduce the viscosity ofthe asphaltene and thus reduce therequired amount of blending stock.However, the high sulfur content ofthe asphaltene may limit its use inNo. 6 fuel oil production.

Asphaltene quality depends oncrude slate, and as the crude slatebecomes heavier and more sour, theasphaltene produced from thesecrude oils will also contain a higherquantity of sulfur. Environmentalregulations will therefore dictate howmuch flue gas cleanup is requiredand, hence, the viability of direct

firing burning of asphaltenes.

Commercial Asphaltenes

Specialty products, such as pav-ing asphalt or roofing asphalt, canbe made by blending the ROSEasphaltenes with suitable aromaticoils.

Asphaltene CokingAsphaltenes may be successfully

coked in refineries with existingcokers. Many refiners are now suc-cessfully cracking asphaltenes intheir cokers. Normally asphalteneis blended with vacuum residuumto achieve good flow properties.The blend is then cracked in cok-ers. Asphaltene cracking is beingcarried out by both delayed andfluid coker operators. CrackingROSE asphaltene instead of vacuumresiduum reduces total coke makeby 10-20%. The liquid yield alsoimproves. At the 2003 NPRA, somerefiners have reported the use ofmore than 50 percent asphaltenes in

their coker feedstocks.KBR has pro-cessed asphaltene in the coker pilotplant. Typical pilot plant yields fromcoking the asphaltenes are providedin Table 4.

Note that the coke yield is muchless than would be expected from atraditional feed with high CCR. The

ratio of feed CCR to coke yield isabout 1.2 for this feedstock. LowerCCR feedstocks can be expected tohave a feed CCR to coke yield ratioof 1.5 to 1.6 under similar condi-tions.

Asphalteneto Partial Oxidation UnitThe asphaltene can be fed to a

partial oxidation unit to producesynthesis gas. Hydrogen in the syn-thesis gas can be used for hydropro-cessing units. The remaining syn-thesis gas is fired to produce steamand power. There are presently twoROSE units in operation feedingpartial oxidation units and threemore planned as the prime outlet fortheir asphaltene product.

Solid fuelThis represents the most sim-

ple and cost effective option for

asphaltene disposition for the Indianmarket, where a large demand forhigh BTU solid fuel exists.

The heating value, organic car-bon and chemical properties suchas sulfur, nickel and vanadium aregoverned by the feed properties.The asphaltene pellets can be used

Table 4 - Data from KBR Delayed Coker Pilot Plant

Feed

Source Pentane asphaltene

Conradson carbon, wt% 38

Yields, wt%

Gas 6.9

C3-C3 3.8

C5-205C 12.1

205-343C 16.4

343C+ 15.0

Coke 45.8

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as solid fuel in the cement kilns,the steel industry, and in the utilityindustries. The pellets can be addedto fuel grade coke or coal as additiveto enhance combustion character-istics. The asphaltene pellets have20%-50% higher heating value thanpetroleum coke.

The high HGI value of the pelletsindicates easy grindability. Unlikecoal, the asphaltene pellets havelow ash content and high organiccarbon content (high boiling hydro-carbons, typically >1000 F) thatprovide improved combustion char-acteristics.

In view of the superior heatingvalue, combustion characterist ics,ease of grinding, the asphaltene pel-lets should demand a higher valueper ton when compared to fuel gradecoke and coal.

AQUAFORMTM

There are existing older commer-cial technologies to produce solidfuel from the solvent asphaltene.However, these processes are gener-ally high in maintenance, low in reli-ability and are manpower intensive.

KBRs AQUAFORM technol-ogy is an ideal solution to solidifyasphaltenes and other heavy hydro-carbons. AQUAFORM is a low costprocess, easy to operate, and hasa high expected on-stream factor.This unit can process a variety offeedstocks and is self cleaning dur-ing shutdown.

The pellets produced by theAQUAFORM process are resistantto dusting and can be easily han-

dled, stored, and transported. Theasphaltene pellets have a higherheating value and better fuel prop-erties compared to petroleum cokeand thus represent improved fuel

value.A simplified flow diagram for the

AQUAFORM process is presentedbelow. Hot liquid asphaltenes arepumped to a pelletizer vessel atthe optimal temperature requiredfor successful pelletization. Liquidasphaltenes are converted to drop-lets in the vapor space of the pellet-izer vessel using a proprietary highcapacity feed distributor.

The surface hardened pelletsfall in to a water bath and on to a

vibrating screen where the pelletsare dewatered. The pellets may betransported to a silo or pit or otherloading facilities by a conveyor.

KBRs proprietary feed distribu-tor is the heart of the system, giv-

ing substantial capacity, flexibility,and reliability improvements versusother solidification process technol-ogies. The feed distributor can beadjusted to vary the size of the pel-lets as well as unit capacity.

The pellets are near sphericalwith an expected size distributionbetween 1 and 3 mm and have goodgrindability, storage and transpor-tation characteristics as indicatedby the high Hargrove GrindabilityIndex (HGI), storage test tempera-ture and low friability. The highangle of repose provides high capac-

ity on conveyors. The small amountof residual moisture on the pellets

helps to minimize dust formationduring transport.

CONCLUSIONThe combination of solvent deas-

phalting and asphaltene pelletizertechnologies represents an econom-ic solution to upgrade vacuum resi-

dues and reduce or eliminate fuel oilproduction that can be implementedat a fraction of the cost of all otherresid processing options.

The deasphalted oil is an excel-lent feedstock and can be easilyprocessed in the existing refineryFCC or other conversion units, andthe solid asphaltene pellets can besold to the cement, steel and powerindustries.

Since the contaminants (metals,sulfur etc.) are rejected in the solidfuel to the cement industry, there is

very minimal impact to the auxiliaryunits (sulfur plant, amine regenera-

tion etc.) within the refinery.The Indian refiner and cement

producer can benefit enormous-ly from the synergies that existbetween the two industries.

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Economic Bottom of the Barrel Processing to Minimize Fuel Oil Production

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