BlueScope Steel plant report_Final

24
2012 COMPOSED BY: Angela Chen (z3189156) UNSW - MATS5394 Pollution Control in Industry 10/5/2012 PLANT REPORT FOCUS: POLLUTION CONTROL

Transcript of BlueScope Steel plant report_Final

Page 1: BlueScope Steel plant report_Final

COMPOSED BY: Angela Chen (z3189156)

UNSW - MATS5394 Pollution Control in

Industry

10/5/2012

2012PLANT REPORT FOCUS: POLLUTION CONTROL

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Table of Contents

ABSTRACT 1

PORT KEMBLA PLANT TRIP SUMMARY 2

BASIC OXYGEN STEEL-MAKING (BOS) 3OVERVIEW 3

POLLUTANTS 4

HEALTH AND HAZARDS 4

EMISSION OVERVIEW AND NPI DATA5

CLEANING AND REDUCTION CONTROL METHODS 5

CASTING PROCESS - OVERVIEW 6POLLUTANTS 6

DUST TREATMENTS AND CONTROL METHODS 7

ROLLING PROCESS - OVERVIEW 8POLLUTANTS 8

MONITORING AND CONTROL METHODS 9

RECYCLING and REUSE PROCESSES 10OVERVIEW 10

WATER AND ENERGY CONSUMPTIONS 11

MONITORING AND CONTROL METHODS 12

INNOVATION AND EMERGING TECHNOLOGIES 12

CONCLUSION 13

REFERENCES 15

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ABSTRACT

The main types of plants involved in iron and steel industry are blast furnaces, steel works and sintering plants, direct reduction plants, ferroalloy production, coking plants, rolling, iron and steel foundry, and other technologies such as: argon-oxygen decarburization, ladle metallurgy vacuum degassing1. Due to large scale manufacturing plant and high volume output, the iron and steel industry causes significant effects on environmental media – air, water and soil.

Figure 1 - Night view of Port Kembla Steelwork Plant and smog emissions

This report will examine the dominant emissions generated from material handling; wind-box exhausts, discharge end, and cold screen are particulate emissions. These mainly consist of iron oxides, sulphur oxides, calcium oxides, hydrocarbons, carbonaceous compounds, and chlorides1. Emissions from the Blast Furnace are generated from the top, in the casting stages, by drilling and plugging the taphole. During the casting operations, iron-oxides, magnesium oxides and carbonaceous compounds are generated. The most significant emissions from the Basic Oxygen Process are emitted during the oxygen blowing period where iron oxides, mainly heavy metals and fluorides are released into air. Furthermore, during the semi-finished product preparation the pollution is produced from the pouring of the molten steel into ingot moulds and when semifinished steel is scarfed.

Another section of the report will also investigate the control methods for polluting emissions in the iron and steel industry. These monitoring and control methods include various technology and devices such as: cyclone cleaners, dry or wet

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electrostatic precipitators, scrubbers, bag house, hoods, furnace enclosures; chemical, catalytic and biological methods.

PORT KEMBLA PLANT VISIT

This report is based on a plant visit to BlueScope Steel in Port Kembla, NSW. It is a large scale steel and iron making industry that has the steel-making capacity of 5 million tonnes a year, on an area of 800 hectares and has up to 6000 employees2.

The tour started at the Visitors Centre and all participants were fitted with safety glasses, gloves, helmet, high visibility vest, and hearing protection with communication devices2. Then the tour entered through the BlueScope Steel Northgate, went past buildings, gardens, also between the immense blast furnace, massive stockpiles of coal and other raw materials. It was pointed out that the No.6 Blast Furnace recently had all their alignment done and is in full operation where it was initially commissioned in 1996 at a cost of $460 Million2.

It was evident on the tour that BlueScope Steelworks made significant efforts to protect and sustain ecologically local flora and fauna. Continuous improvements in the past two decades, 441000 trees, shrubs and ground cover were planted2. Along the drive, there were about 180 individual gardens, and designated resting areas for employees, restricted areas for a rare colony of green and golden bell frogs where their health is now subjected to ongoing monitoring by joint project with Southern Cross University2. Also a recent census showed that 39 species of birds live and or visit the site. However, it was also noted that open dust sources include vehicle traffic, raw material handling and wind erosion from storage piles all contribute to the atmospheric pollutions.

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Figure 2 - Blast Furnace and Emission stack at BlueScope Steelworks, Port Kembla

BASIC OXYGEN STEEL-MAKING (BOF)

The tour continued to the first visiting site which is the Basic Oxygen Steelmaking Plant. This is one of the critical steps in making steel where iron is proportionally mixed with small quantities of carbon and other additives. The group went up the external staircase to the furnace floor to witness the 1600 degree Celsius process that makes steel in this vessel. The raw materials include molten iron and scrap that consists of 1/5 of the total volume is placed in the vessel, combined with heat and oxygen blast to create and refine carbon in steel2. At Port Kembla there are three Basic Oxygen Steelmaking apparatus each with capacity of 5 mega-tonne per annum, which can be seen from the following image (Figure 3)2.

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Figure 3 - BOS Vessel at BlueScope Steelworks

In Basic Oxygen Steelmaking Plant there are also two air separation units producing gaseous oxygen and nitrogen along with liquid oxygen, nitrogen and argon. Typical operational capacities are about 1,080 tonnes per day of gaseous oxygen and 220 tonnes per day of gaseous nitrogen2. Due to such large volume of gaseous substances being added to the steelmaking process each day, there is no doubt the amount of air pollutant emitted into the atmosphere. Hence there are monitoring systems and preventative techniques in place to reduce pollutants and health hazards.

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Figure 4 – General Process of Basic Oxygen Steelmaking flowchart – Specifying individual operations and the input and output mass streams

Pollution Prevention in the BOF

Slag is a major component of the waste produced in BOFs. Due to its composition, this slag, unlike that from the blast furnace, is best used as an additive in the sintering process. Since metallic content is lower, hence is not a good raw material for the construction industry3.

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Hot gases are also produced by the BOF. Furnaces are equipped with air pollution control equipment that contains and cools the gas3. The gas is quenched and cooled using water and cleaned of suspended solids and metals. This process produces air pollution control dust and water treatment plant sludge (Figure 5). For instance, typical pollution control equipment like: Top Gas Recovery Turbine (TRT); Hot stoves waste – Gas Heat Recovery Systems; using EFA (Entrained Flow Absorber) - Sintering Off-gas treatment; also De-dusting and Air Pollution Control Systems (i.e. Stock-house facilities) 4.

Figure 5 - Recycled water used for cooling and de-dusting hot steel slabs

It is evident that in the iron and steel making industry, the manufacturing process (which is clearly explained by the flowchart in Figure 4) does generate significant amount of pollutants in the environment specifically in air, water and landfills2. Thus, Australia has a nationally pollution monitoring system known as NPI where the general public can all access up to data emission data and be aware of hazardous pollutants caused by particular industries. This report will also discuss specific emission data in the next section and their effect on health. BlueScope Steelworks have inputted tremendous efforts where they implemented many techniques to reduce the pollutant effects and protect the environment.

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BlueScope Steel is part of the “World-steel Climate Action Programme”: that is a measurement and benchmarking of greenhouse gases. It is a crucial pathway towards encouraging, developing and enacting company-specific and industry-wide initiatives for reducing CO2 emissions6. This is a scheme which recognises that a steel producer has fulfilled its commitment to take part in the World-steel CO2 data collection program. The data collection program is at the core of the steel industry's global steel sectoral approach to climate change6. Based on a common methodology and agreed definitions and boundaries, the data collection programme enables individual steel plants to compare themselves against both average and best performance and to identify scope for improvement. 

EMISSIONS & HEALTH HAZARDS

BlueScope Steelworks Emission Data obtained from NPI websites shows that the major air pollutant emission is carbon monoxide (CO) totally of (1.55e8 kg = 155 tonnes per annum into air)5. Hence, it is crucial to have awareness of the potential hazards and health risks associated with CO.

Carbon monoxide gas is produced in substantial amounts by a variety of furnaces. It may also be released during the pouring of molten metal. Inhaled carbon monoxide prevents the blood from carrying a normal supply of oxygen. Exposure to concentrations of 500 to 1000 parts per million (ppm) for approximately 30 minutes may precipitate headache, accelerated breathing, nausea, dizziness and mental confusion6. Thus a possible secondary effect of exposure is an increased risk of accident and injury to the worker. Exposure to higher concentrations (approx.. 1000 ppm) may result in the appearance of symptoms after several minutes, or unconsciousness may occur rapidly without any warning symptoms5.

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Since Carbon Monoxide is a colourless and odourless substance so it has no warning properties when inhaled or in contact3. The only way to determine the concentration of the gas is by regularly monitoring the foundry air. Automatic alarms are in place to warn workers of the dangerous Co levels, provided they are correctly adjusted10.

Exhaust ventilation is an effective controlling carbon monoxide emissions at the source. For all potential exposed workers should be instructed in the dangers, recognition and treatment of CO poisoning. The biological monitoring of carbon monoxide via blood sampling or in exhaled air samples maybe a useful technique. The samples should be taken at the end of the working shift6.

Various metal fumes may be generated during founding processes, especially during melting and pouring operations. Lead, magnesium, zinc, copper, aluminium, cadmium, antimony, tin and beryllium fumes are commonly present in non-ferrous foundries. Iron oxide is the major fume generated in iron and steel operations4. ‘Metal fume fever’ may result from exposure to these contaminants. This is an acute illness of short duration which commences some hours after inhalation of the metallic fumes. The initial symptoms are flu-like: nausea, headache, dry throat and coughing, and muscular pains. Chills and sweating may occur later. Recovery is usual within 24 hours after removal from exposure3-5. The fumes of zinc and copper are the most common causes of metal fume fever. The fumes and dust of cadmium, beryllium, nickel and chromium, contained in some alloys, are very toxic.

Figure 6 - Air emissions from Blast Furnace gas tower at BlueScope Steel, Port Kembla

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0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

9000000

VOC Sulfuric Acid

Sulfur Dioxide

PM2.5

PM10

Nitrogen Oxides

Lead&CompoundsHydrochloric Acid

Ammonia

NPI Data: Other Pollutant Substances emitted from Iron/Steel Industries (Total Air and Water in Kilograms )

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CONTINUOUS SLAB CASTING PROCESS

The plant trip continued after the molten metal is released from BOF, to the second visiting site where it must be formed into its final shape and finished to prevent corrosion. Traditionally, steel was poured into convenient shapes called ingots and stored until further shaping was needed3. Current practices favour continuous casting methods, where the steel is poured directly into semi-finished shapes. Continuous casting saves time by reducing the steps required to produce the desired shape.

Figure 7 - Continuous casting and cutting of Steel slab as semi-finished product

Due to the excessive heat required to heat up for continuous casting and cutting large energy expenditure are required. All BlueScope facilities harness as much energy as is economically feasible from the gases generated by on-site activities: gaseous by-products are cleaned, and then used to generate energy for the plant7-9. This not only utilises the by-products of the steelmaking process, but also contributes to resource sustainability and greenhouse gas (GHG) emission reduction. 80% per cent of the energy required to power the coke ovens at Port Kembla Steelworks is derived from gases produced in the blast furnace. The other 20% of the energy required comes from gases recovered from the coke ovens themselves8.

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BlueScope Steel industry is also the leading the water recycling project, commissioned in partnership with Sydney Water, now recycles wastewater from across the Illawarra region and treats it for re-use at Port Kembla Steelworks. The introduction of recycled water reduced the Steelworks' fresh water consumption and has saved more than 21 billion litres of fresh water to date (2010)6. At Port Kembla Steelworks the great majority of water used is seawater (96 per cent), which displaces the need to use fresh water for much of the site’s cooling requirements7.

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ROLLING / HOT STRIP MILL PROCESS

Primary wastes produced in the metal forming process include contact water, oil, grease, and mill scale4-5. All are collected in holding tanks. The scale settles out and is removed. It can be reused in sintering plants or, if the metal content is sufficient, may be sold as a raw material elsewhere8.

The remaining liquid leaves the process as waste treatment plant sludge6-7. As the waste results in a small portion of pollution produced by steelmaking, pollution prevention and process modification opportunities are not a top priority.

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THE RECYCLING PROCESS

There are two methods of steel production: Blast Furnace-Basic Oxygen Steelmaking (BF-BOS) and Electric Arc Furnace (EAF) production8. The BF-BOS process uses virgin material, including iron ore, coke and fluxes, as well as scrap steel. Scrap is added to the BOS vessel to maintain thermal balance. All flat steel products (e.g. automobile panels and roofing and fencing materials) and some long products (e.g. railway tracks) made in Australia are produced through the BF-BOS route7. EAF steel can be produced from up to 100% recovered material. However, EAF production is limited by the worldwide availability of scrap, and is therefore insufficient to meet market needs8.

BF-BOS recycled content proportions may also be limited by the availability of scrap; however, there are also technical limitations. These factors result in the proportion of recovered material in the steel produced in the BF-BOS process by BlueScope Steel in Australia being, on average, 17–20%.7-8 The majority of this material is classed as reutilised scrap, not pre-consumer or post-consumer recycled content. From a sustainability point of view, the proportion of steel that is recovered for recycling at the end of each use phase is more relevant than the recycled content in any one product at a particular point in time10.

Figure 8 - BlueScope Steel-works external conveyor to melting vessels, Port Kembla

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INNOVATION & EMERGING TECHNOLOGY

BlueScope Steel has successfully developed high-strength steel products, so that the same function is achieved using fewer raw materials. Roofing that was once manufactured at 0.55 mm thick, is today made from high-strength COLORBOND® steel 0.42 mm thick – a reduction of 24% without any sacrifice in performance8.

Improvements have also been made in terms of the coatings that go on our steel. A highly corrosion resistant aluminium/zinc (AZ) mixture is used to coat some products that were once treated with zinc alone (traditional galvanised products). The AZ coating is lighter (on a volume basis) than a pure zinc coating, the same coating thickness can be achieved using less material. The standard 20 μm thick coating requires approximately 45% less coating material when AZ is used compared to zinc alone8. This translates to a 75% reduction in the amount of zinc used per square metre of coated steel. Further, the increased durability of the AZ coating means that the final product lasts longer, which gives a lower environment footprint8.

CONCLUSION

The iron and steel industry causes significant effects on environment media: for air emissions of SO2, NOx, CO, H2S, PAH, Lead, Ni, As, Cd, Cr, Cu, Zn, Se, Hg, PM10, PM2.5

etc. For water pollutant emissions include: organic matter, oil, metals, suspended solids, benzene, phenol, acids, sulphides, sulfates, ammonia, cyanides, thiocyanates, thiosulfates, fluorides (scrubber effluent)15. Last but not least, land pollutants of slag, sludge, sulphur compounds, heavy metals, oils and grease, residues, salts.

This report discussed the aforementioned pollutants, their threatening effects on health and preventative techniques to reduce and monitor various hazardous emission levels. Examples were given by detailed observations and information gained from plant trip around BlueScope Steelworks at Port Kembla, NSW and literature values from NPI database. Typical polluting emissions generated in the iron and steel industries are controlled by a variety of evacuation systems, devices and methods16. These include cyclone enclosures, dry or wet electrostatic precipitators (EC), scrubbers, bag houses, hoods, vegetation planation, and furnace enclosures implementations etc. In essence, with the new millennium there must be an awareness to make improvements and developments of modern, sustainable iron and steel technology within human activity in coexistence with environment on a global-scale17-18.

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REFERENCES

1. NPI: Emission Estimation Technique Manual (NPI Gov. website database)

2. Lecture Handout – BlueScope Steelworks Briefings and Field Trip info

3. European Commission – (BAT): “Iron and Steel Production”, Industrial Emission Directive EU: Integrated Pollution Prevention and Control

4. http://www.istc.illinois.edu/info/library_docs/manuals/primmetals/chapter2.htm

5. Pollution Prevention and Abatement Handbook - WORLD BANK GROUP: Effective July 1998

6. http://www.sydneywater.com.au/Publications/Reports/AnnualReport/2007/menu/performance/goal2/recycling.cfm

7. http://www.paulwurth.com/en/Our-Activities/Energy-environment/Blast-Furnace-gas-cleaning-systems

8. http://annualreport2005.bluescopesteel.com/results/port-kembla-steelworks.html

9. Chatterjee, Amit. "Recent Developments in Ironmaking and Steelmaking." Iron and Steelmaking. 22:2 (1995), pp. 100-104.

10.Frukawa, Tsukasa. "5000 Daily Tons of Direct Iron-Ore Smelting by 2000." New Steel. 10:11 (November, 1994), pp. 36-38.

11.McManus, George, ed. "Replacing Coke With Pulverized Coal." New Steel. 10:6 (June, 1994), pp. 40-42.

12.Ritt, Adam. "DRI comes to the Gulf Coast." New Steel. January, 1996, pp. 54-58.

13.Strohmeier, Gerolf, and John Bonestell. "Steelworks Residues and the Waelz Kiln Treatment of Electric Arc Furnace Dust." Iron and Steel Engineering. April, 1996, pp. 87-90.

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14.U.S. Department of Commerce. 1992 Census of Manufacturers — Blast Furnaces, Steel Works and Rolling and Finishing Mills. 1992.

15.USEPA. "Profile of the Iron and Steel Industry." EPA/310-R-95-010, U.S. Environmental Protection Agency. Washington, D.C., September 1995.

16.Andres, A., et al. "Long-term Behavior of Toxic Metals in Stabilized Steel Foundry Dust." Journal of Hazardous Waste Materials. 40 (1995)

17.Berry, Brian. "Hoogovens Means Blast Furnaces — And Clean Air." New Steel. December, 1994. pp. 26-30. McManus, G.J. "The Direct Approach to Making Iron." Iron Age. July, 1993. pp. 20-23.

18.Mohla, Prem. "New Ductile Iron Process Meets the Challenge of the 1990's Head On." Foundry Management and Technology. 121:4 (April, 1993), pp. 52-56.

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