Multilateral Investment Guarantee Agency Environmental Guidelines for Mini Steel Mills

Industry Description and Practices lead baths are used for cooling and to impart desired features. Mini steel mills normally use the electric arc To prepare the steel for cold rolling or furnace (EAF) to produce steel from returned drawing, acid pickling is performed to steel, scrap, and direct reduced iron. EAF is a chemically remove oxides and scale from the batch process with a cycle time of about two to surface of the steel through use of inorganic three hours. Since the process uses scrap metal acid water solutions. Mixed acids (nitric and instead of molten iron, coke making or iron hydrofluoric) are used for stainless steel making operations are eliminated. These pickling, and sulfuric or hydrochloric acid is operations are discussed in separate documents. used for other steels. Other methods to remove Electric arc furnaces (EAFs) can serve smaller, scale include salt pickling, electrolytic pickling, local markets. and blasting which is environmentally Further processing of steel can include desirable, where feasible. continuous casting, hot rolling and forming, cold rolling, wire drawing, coating, and Waste Characteristics pickling. The continuous casting process bypasses several steps of the conventional ingot EAF produces metal dusts, slag and gaseous teeming process by casting steel directly into emissions. The primary hazardous components semi-finished shapes. The casting, rolling, and of EAF dust are zinc, lead, and cadmium (nickel steel finishing processes are also used in iron and chromium are present when stainless steels and steel manufacturing. are manufactured), but its composition can vary Hot steel is transformed in size and shape greatly depending on the scrap composition through a series of hot rolling and forming steps and furnace additives. EAF dust from a to manufacture semi-finished and finished steel majority of the furnaces have a zinc content in products. The hot rolling process consists of excess of 15 percent (with a range of 5 to 35 slab-heating (as well as billet and bloom), percent). Other metals present in the EAF dust rolling, and forming operations. Several types of include: lead (2 to 7 percent); cadmium hot forming mills (primary, section, flat, pipe (generally 0.1 to 0.2 percent but can be up to 2.5 and tube, wire, rebar, and profile) manufacture percent where stainless cases of nickel-cadmium a variety of steel products. batteries are melted); chromium (up to 15 For the manufacture of a very thin strip or a percent); and nickel (up to 4 percent). Generally, strip with high quality finish, cold rolling must EAF produces 10 kilograms (kg) (with a range follow the hot rolling operations. Lubricants of 5 to 30 kg depending on factors such as the emulsified in water are usually used to achieve furnace characteristics and scrap quality) of high surface quality and to prevent overheating dust per metric ton of steel. Major pollutants of the product. present in the air emissions include particulates Wire drawing includes heat treatment of rods, (1,000 milligrams per normal cubic meter cleaning, and sometimes coating. Water, oil, or (mg/Nm3)), nitrogen oxides, from cutting,

417 418 Mini Steel Mills

scarfing and pickeling opertions; nitrogen • Recycle mill scale to the sinter plant in an operations, and acid fumes (3,000 mg/Nm3) integrated steel plant. from pickling operations. Both nitrogen oxides • Use acid free methods (i.e., mechanical and acid fumes vary with the steel quality. methods) for descaling (for example, blasting) Mini mills generate up to 80 m3 of where feasible. wastewater per metric ton of steel product. • In the pickling process, use countercurrent Untreated wastewaters contain high levels of flow of rinse water. Use indirect method for total suspended solids (up to 3,000 milligrams heating and pickling baths. per liter (mg/L)), copper (up to 170 mg/L), lead • Use closed-loop systems for pickling; (10 mg/L), total chromium (3,500 mg/L), regenerate and recover acids from spent hexavalent chromium (200 mg/L), nickel (4,600 pickling liquor using resin bed, retorting or mg/L), and oil and grease (130 mg/L). Chrome other regeneration methods (such as vacuum and nickel concentrations mostly result from crystalization of sulfuric acid baths). pickling operations. The characteristics of the • Use electrochemical methods in wastewater will depend on the type of steel, combination with pickling to lower acid forming and finishing operations and the consumption. quality of scrap used as feed to the process. • Reduce nitrogen oxide (NOx) emissions by Solid wastes (excluding EAF dust and use of natural gas as fuel, use low NOx burners, wastewater treatment sludges) are generated at and use hydrogen peroxide and urea in a rate of 20 kg/t of steel product. Sludges and stainless steel pickling baths (containing nitric scale from acid pickling (especially stainless and hydrofluoric acids). steel) contain heavy metals such as chromium • Recycle and re-use slags and other (up to 700 mg/kg), lead (up to 700 mg/kg), and residuals from the manufacturing operations in nickel (400 mg/kg). These levels may be even construction and other industries. higher for some stainless steels. • Recover zinc from EAF dust containing more than 15 percent total zinc. Recycle EAF Pollution Prevention and Control dust to the exten feasible.

The following pollution prevention measures Target Pollution Loads should be considered: • Locate EAFs enclosed buildings The recommended pollution prevention • Improve feed quality - use selected scrap measures can achieve the following target to reduce the release of pollutants to the levels: environment. • Use dry dust collection methods such as Wastewaters fabric filters. • Replace ingot teeming with continuous Recycle wastewaters to reduce the discharge casting. Use continuous casting for semi- rate to less than 5 m3/t of steel produced finished and finished products, wherever including indirect cooling waters. High water feasible. use is associated with cooling. • In some cases, continuous charging may be feasible and effective for controlling dust Treatment Technologies emissions. • Use bottom tapping of EAFs to prevent Air Emissions dust emissions. • Control water consumption by proper Dust emission control technologies include design of spray nozzles, and cooling water cyclones, baghouses, and ESPs. Scrubbers are systems. used to control acid mists. Fugitive emissions • Segregate wastewaters containing from charging and tapping of EAF should be lubricating oils from other wastewater streams controlled by locating EAF in an enclosed and remove oil. building or hoods and the dust evacuated to the

419 Mini Steel Mills

dust arrestment equipment to achieve an Air Emissions emission level of less than 0.25 kg/t. Air emissions of particulate matter (PM) should Wastewater Treatment be below 20 mg/Nm3 where toxic metals are present and 50 mg/Nm3 in other cases. This Spent pickle liquor containing hydrochloric acid would correspond to a total dust emission of is treated by spraying into a roasting chamber less than 1 kg/t of steel. SOx should be 2000 3 and scrubbing the vapors. If hexavalent chrome mg/ Nm and NOx should be controled to less is present in salt pickling or electrolytical than 750 mg/ Nm3. pickling baths, it can be reduced with a sulfide reagent, iron salts, or other reducing agents. Liquid Effluents Remaining wastewaters are typically treated using oil-water separation flotation, For mini steel mills, the following effluent levels precipitation, chemical flocculation, should be achieved: sedimentation/parallel plate separation/ hydrocycloning, and filtration. Methods such as Effluents from the Mini Steel Mill ultrafiltration may be used for oil emulsions. Parameter Maximum value For continuous casting and cold rolling, oil and milligrams per liter total suspended solids should be less than 5 g /t (mg/L) and 10 g/t; and for hot rolling, the corresponding values are 10 g/t and 50 grams pH 6 - 9 per metric ton (g/t), respectively. Total suspended 50 solids Emissions Guidelines Oil and grease 10 Cadmium 0.1 Emission levels for the design and operation of Chromium 0.1 each project must be established through the (hexavalent) Environmental Assessment (EA) process, based Chromium (total) 0.5 on country legislation and the Pollution Copper 0.5 Prevention and Abatement Handbook as applied to Lead 0.1 local conditions. The emission levels selected Nickel 0.5 must be justified in the EA and acceptable to Temperature less than or equal to MIGA. increase 3oC1 The following guidelines present emission 1 levels normally acceptable to the World Bank The effluent should result in a temperature increase of no more than 3 degrees Celsius at the edge of the zone Group in making decisions regarding provision where initial mixing and dilution takes place. Where of World Bank Group assistance, including the zone is not defined, use 100 meters from the point MIGA guarantees; any deviations from these of discharge. Solid wastes such as slag, dust, and scale levels must be described in the project should be sent for meals recovery or recycled to the documentation. extent feasible. The guidelines are expressed as concentrations to facilitate monitoring. Dilution Sludges from wastewater treatment and steel of air emissions or effluents to achieve these finishing operations should be disposed of in a guidelines is unacceptable. secure landfill after chrome reduction and All of the maximum levels should be stabilization. Levels of heavy metals in the achieved for at least 95% of the time that the leachates should be less than those presented plant or unit is operating, to be calculated as a for liquid effluents. proportion of annual operating hours. Ambient Noise

Noise abatement measures should achieve either the following levels or a maximum

420 Mini Steel Mills

increase in background levels of 3 dB(A). Measurements are to be taken at noise receptors Key Issues located outside the project property boundary. The following box summarizes the key production and control practices that will lead Ambient Noise to compliance with emission guidelines:

Maximum Allowable Leq (hourly), in dB(A) • Replace ingot teeming with continuous Receptor Daytime Nighttime casting. 07:00 - 22:00 22:00 - 07:00 • Locate EAFs in enclosed buildings or install Residential; 55 45 dry dust collection systems such as bag institutional; filters. educational • Use countercurrent flow of rinse water in Industrial; 70 70 acid pickling. commercial • Regenerate and reuse acid from spent pickle liquor or sell pickle liquor for use as The emission guidelines given here can be wastewater treatment reagent. consistently achieved by well-designed, well- • Recycle at least 90 percent of the wastewater. operated and well-maintained pollution control systems. • Use hydrogen peroxide or urea to reduce NOx emissions from nitric and hydrofluoric Monitoring and Reporting acid pickling baths.

Stack air emissions should be monitored continuously for PM using an opacity meter (for Further Information an opacity level of less than 10 percent) or dust detector. The following are suggested as sources of Wastewater discharges should be monitored additional information (these sources are daily for the above-mentioned parameters provided for guidance and are not intended to except metals, which should be monitored at be comprehensive): least on a weekly basis or when there are process changes. British Steel Consultants. 1993. Research Study, Monitoring data should be analyzed and International Steel Industry. Prepared for the reviewed at regular intervals and compared International Finance Corporation. with the operating standards so that any necessary corrective actions can be taken. A Paris Commission. 1991. Secondary Iron and base line data set should be developed for Steel Production: An Overview of Technologies fugitive emissions and periodic review of (once and Emission Standards Used in the PARCOM every three years) such emissions be performed. Countries. Records of monitoring results should be kept in an acceptable format. These should be reported World Bank, Environment Department. 1996 to the responsible authorities and relevant “Pollution Prevention and Abatement: Mini parties, as required, and provided to MIGA if Steel Mills.” Technical Background Document. requested..