Pollution Prevention and Abatement Handbook WORLD BANK GROUP Effective July 1998

Iron and Manufacturing

Industry Description and Practices els of about 15 kg/t of steel. Air emissions from pig manufacturing in a include Steel is manufactured by the chemical reduction particulate matter (PM), ranging from less than of , using an integrated steel manufac- 10 kg/t of steel manufactured to 40 kg/t; sulfur turing process or a direct reduction process. In oxides (SOx), mostly from sintering or pelletiz- the conventional integrated steel manufacturing ing operations (1.5 kg/t of steel); nitrogen oxides process, the iron from the blast furnace is con- (NOx), mainly from sintering and heating (1.2 verted to steel in a basic oxygen furnace (BOF). kg/t of steel); hydrocarbons; monoxide; Steel can also be made in an in some cases dioxins (mostly from sintering op- (EAF) from steel and, in some cases, from erations); and hydrogen fluoride. . BOF is typically used for Air emissions from steel manufacturing using high-tonnage production of carbon , while the BOF may include PM (ranging from less than the EAF is used to produce carbon steels and low- 15 kg/t to 30 kg/t of steel). For closed systems, tonnage specialty steels. An emerging technol- emissions come from the desulfurization step be- ogy, direct steel manufacturing, produces steel tween the blast furnace and the BOF; the particu- directly from iron ore. This document deals only late matter emissions are about 10 kg/t of steel. with integrated iron and steel manufacturing; In the conventional process without recircula- that on Mini Steel Mills addresses the electric arc tion, wastewaters, including those from cooling steel process and steel finishing processes. Steel operations, are generated at an average rate of manufacturing and finishing processes discussed 80 cubic meters per metric ton (m3/t) of steel in that document are also employed in integrated manufactured. Major pollutants present in un- steel plants. See also Coke Manufacturing. treated wastewaters generated from pig iron In the BOF process, coke making and iron manufacture include total organic carbon (typi- making precede steel making; these steps are not cally 100–200 milligrams per liter, mg/l); total necessary with an EAF. Pig iron is manufactured suspended solids (7,000 mg/l, 137 kg/t); dis- from sintered, pelletized, or lump iron ores us- solved solids; cyanide (15 mg/l); fluoride (1,000 ing coke and limestone in a blast furnace. It is mg/l); chemical oxygen demand, or COD (500 then fed to a BOF in molten form along with scrap mg/l); and zinc (35 mg/l). metal, fluxes, alloys, and high-purity oxygen to Major pollutants in wastewaters generated manufacture steel. In some integrated steel mills, from steel manufacturing using the BOF include sintering (heating without melting) is used to total suspended solids (up to 4,000 mg/l, 1030 agglomerate fines and so recycle iron-rich mate- kg/t), lead (8 mg/l), chromium (5 mg/l), cadmium rial such as mill scale. (0.4 mg/l), zinc (14 mg/l), fluoride (20 mg/l), and oil and grease. Mill scale may amount to 33 kg/t. Waste Characteristics The process generates effluents with high tem- peratures. Sintering operations can emit significant dust lev- Process solid waste from the conventional pro- els of about 20 kilograms per metric ton (kg/t) cess, including furnace slag and collected dust, of steel. Pelletizing operations can emit dust lev- is generated at an average rate ranging from 300

327 328 PROJECT GUIDELINES: INDUSTRY SECTOR GUIDELINES kg/t of steel manufactured to 500 kg/t, of which Steel Manufacturing 30 kg may be considered hazardous depending on the concentration of heavy metals present. • Use dry dust collection and removal systems Approximately, 65% of BOF slag from steel manu- to avoid the generation of wastewater. Recycle facturing can be recycled in various industries collected dust. such as building materials and, in some cases, • Use BOF gas as fuel. mineral wool. • Use enclosures for BOF. • Use a continuous process for casting steel to Pollution Prevention and Control reduce energy consumption.

Where technically and economically feasible, di- Other rect reduction of iron ore for the manufacture of iron and steel is preferred because it does Use blast furnace slag in construction materials. not require coke manufacturing and has fewer Slag containing free lime can be used in iron environmental impacts. Wherever feasible, pel- making. letizing should be given preferences over sinter- ing for the agglomeration of iron ore. The Target Pollution Loads following pollution prevention measures should be considered. The recommended pollution prevention and con- trol measures can achieve the following target Pig Iron Manufacturing levels.

• Improve blast furnace efficiency by using Liquid Effluents and other fuels (such as oil or gas) for heating instead of coke, thereby minimizing air emis- Over 90% of the wastewater generated can be sions. reused. Discharged wastewaters should in all • Recover the thermal energy in the gas from the cases be less than 5 m3/t of steel manufactured blast furnace before using it as a fuel. Increase and preferably less than 1 m3/t. fuel efficiency and reduce emissions by im- proving blast furnace charge distribution. Solid Wastes • Improve productivity by screening the charge and using better taphole practices. Blast furnace slag should normally be generated • Reduce dust emissions at furnaces by cover- at a rate of less than 320 kg/t of iron, with a tar- ing iron runners when tapping the blast fur- get of 180 kg/t. The generation rate, however, nace and by using nitrogen blankets during depends on the impurities in the feed materials. tapping. Slag generation rates from the BOF should be • Use pneumatic transport, enclosed conveyor between 50 and 120 kg/t of steel manufactured, belts, or self-closing conveyor belts, as well as but this will depend on the impurity content of wind barriers and other dust suppression mea- feed materials. Zinc recovery may be feasible for sures, to reduce the formation of fugitive dust. collected dust.

• Use low- NOx burners to reduce NOx emissions from burning fuel in ancillary operations. Treatment Technologies • Recycle iron-rich materials such as iron ore fines, pollution control dust, and scale in a sin- Air Emissions ter plant. • Recover energy from sinter coolers and ex- Air emission control technologies for the removal haust gases. of particulate matter include scrubbers (or

• Use dry SOx removal systems such as caron semidry systems), baghouses, and electrostatic absorption for sinter plants or lime spraying precipitators (ESPs). The latter two technologies in flue gases. can achieve 99.9% removal efficiencies for par- Iron and Steel Manufacturing 329 ticulate matter and the associated toxic metals: Table 2. Target Load per Unit of Production, chromium (0.8 milligrams per normal cubic Steel Manufacturing meter, mg/Nm3), cadmium (0.08 mg/Nm3), lead (emissions per metric ton of product) 3 3 (0.02 mg/Nm ), and nickel (0.3 mg/Nm ). Blast Basic oxygen Sulfur oxides are removed in desulfurization Parameter furnace furnace plants, with a 90% or better removal efficiency. Wastewater 0.1 m3 0.5 m3 However, the use of low-sulfur fuels and ores Zinc 0.6 g 3 g may be more cost-effective. Lead 0.15 g 0.75 g The acceptable levels of nitrogen oxides can Cadmium 0.08 g n.a. be achieved by using low-NOx burners and other combustion modifications. n.a. Not applicable. For iron and steel manufacturing, the emis- sions levels presented in Table 1 should be achieved. vironmental assessment (EA) process on the ba- sis of country legislation and the Pollution Pre- Wastewater Treatment vention and Abatement Handbook, as applied to local conditions. The emissions levels selected Wastewater treatment systems typically include must be justified in the EA and acceptable to the sedimentation to remove suspended solids, physi- World Bank Group. cal or chemical treatment such as pH adjustment The guidelines given below present emis- to precipitate heavy metals, and filtration. sions levels normally acceptable to the World Bank Group in making decisions regarding The target levels presented in Table 2 can be provision of World Bank Group assistance. Any achieved for steel-making processes. deviations from these levels must be described in the World Bank Group project documenta- Solid Waste Treatment tion. The emissions levels given here can be consistently achieved by well-designed, well- Solid wastes containing heavy metals may have operated, and well-maintained pollution con- to be stabilized, using chemical agents, before trol systems. disposal. The guidelines are expressed as concentrations to facilitate monitoring. Dilution of air emissions Emissions Guidelines or effluents to achieve these guidelines is unac- ceptable. Emissions levels for the design and operation of All of the maximum levels should be achieved each project must be established through the en- for at least 95% of the time that the plant or unit is operating, to be calculated as a proportion of annual operating hours. Table 1. Load Targets per Unit of Production, Iron and Steel Manufacturing Air Emissions Parameter Maximum value For integrated iron and steel manufacturing PM 100 g/t of product (blast furnace, 10 plants, the emissions levels presented in Table 3 basic oxygen furnace); 300 g/t from sintering process should be achieved.

3 Sulfur oxides For sintering: 1,200 g/t; 500 mg/m Liquid Effluents Nitrogen oxides For pelletizing plants: 500 g/t; 250– 750 mg/Nm3; for sintering plants: The effluent levels presented in Table 4 should 750 mg/Nm3 be achieved. Fluoride 1.5 g/t; 5 mg/Nm3 330 PROJECT GUIDELINES: INDUSTRY SECTOR GUIDELINES

Table 3. Air Emissions from Iron and Steel at noise receptors located outside the project Manufacturing property boundary. (milligrams per normal cubic meter) Parameter Maximum value Maximum allowable log equivalent (hourly PM 50 measurements), in dB(A) Sulfur oxides 500 (sintering) Day Night Nitrogen oxides 750 Receptor (07:00–22:00) (22:00–07:00) Fluorides 5 Residential, institutional, educational 55 45 Sludges Industrial, commercial 70 70 Sludges should be disposed of in a secure land- fill after stabilization of heavy metals to ensure Monitoring and Reporting that heavy metal concentration in the leachates do not exceed the levels presented for liquid Air emissions should be monitored continuously effluents. after the air pollution control device for particu- late matter (or alternatively an opacity level of Ambient Noise less than 10%) and annually for sulfur oxides, ni- trogen oxides (with regular monitoring of sulfur Noise abatement measures should achieve either in the ores), and fluoride. Wastewater discharges the levels given below or a maximum increase in should be monitored daily for the listed param- background levels of 3 decibels (measured on the eters, except for metals, which should be moni- A scale) [dB(A)]. Measurements are to be taken tored at least on a quarterly basis. Frequent sampling may be required during start-up and upset conditions. Table 4. Effluents from Iron and Steel Monitoring data should be analyzed and re- Manufacturing viewed at regular intervals and compared with (milligrams per liter, except pH and temperature) the operating standards so that any necessary Parameter Maximum value corrective actions can be taken. Baseline data on fugitive PM emissions should be collected and pH 6–9 used for comparison with future emissions esti- TSS 50 mates, which should be performed every three Oil and grease 10 COD 250 years based on samples collected. Records of Phenol 0.5 monitoring results should be kept in an accept- Cadmium 0.1 able format. The results should be reported to the Chromium (total) 0.5 responsible authorities and relevant parties, as Lead 0.2 required. Mercury 0.01 Zinc 2 Key Issues Cyanide Free 0.1 Total 1 The key production and control practices that will Temperature increase £ 3oCa lead to compliance with emissions guidelines are summarized here. Note: Effluent requirements are for direct discharge to surface waters. • Prefer the direct steel manufacturing process a. The effluent should result in a temperature increase of no where technically and economically feasible. more than 3° C at the edge of the zone where initial mixing and dilution take place. Where the zone is not defined, use 100 • Use pelletized feed instead of sintered feed meters from the point of discharge. where appropriate. Iron and Steel Manufacturing 331

• Replace a portion of the coke used in the blast Sources furnace by injecting pulverized coal or by us- ing natural gas or oil. British Steel Consultants. 1993. “Research Study, In- • Achieve high-energy efficiency by using blast ternational Steel Industry.” Prepared for the Inter- furnace and basic oxygen furnace off-gas as national Finance Corporation, Washington, D.C. fuels. The Netherlands. 1991. “Progress Report on the Study • Implement measures (such as encapsulation) of the Primary Iron and Steel Industry.” Third Meet- ing of the Working Group on Industrial Sectors, to reduce the formation of dust, including iron Stockholm, January 22–24. oxide dust; where possible, recycle collected dust to a sintering plant. Paris Commission. 1991. Secondary Iron and Steel Pro- duction: An Overview of Technologies and Emission • Recirculate wastewaters. Use dry air pollution Standards Used in the PARCOM Countries. control systems where feasible. Otherwise, World Bank. 1996. “Pollution Prevention and Abatement: treat wastewaters. Iron and Steel Manufacturing”. Draft Technical Back- • Use slag in construction materials to the ex- ground Document. Environment Department, Wash- tent feasible. ington, D.C.