Environmental Code of Practice for Non-Integrated Steel Mills: section 3

Section 3: Environmental Concerns

• 3.1 Raw Materials Handling and Storage
• 3.2 Direct Reduction of Iron
• 3.3 Steelmaking
• 3.4 Continuous Casting
• 3.5 Hot Forming
• 3.6 Cold Forming
• 3.7 Pickling and Cleaning
• 3.8 Coating
• 3.9 Environmental Release Inventories

The major activities and processes of relevance to this Code of Practice and the associated environmental releases are illustrated in Figures 2.1 and 2.2.

3.1 Raw Materials Handling and Storage

The main environmental issue relating to raw materials handling and storage is the fugitive emission of particulate material arising from material transfers, truck traffic, and wind erosion of raw material storage piles. A secondary issue is the suspended solids and, in some cases, oil, contained in the runoff water from the storage areas.

Fugitive emissions of particulate are usually controlled by spraying stockpiles with water or crusting agents and ensuring that roadways and vehicle wheels are kept clean. The water runoff is usually directed to a wastewater treatment plant.

3.2 Direct Reduction of Iron

Emissions from the direct reduction process arise primarily from materials-handling operations, which result in airborne dust, and from the exhaust gases from the shaft furnace. These exhaust gases carry entrained particulate. The exhaust gases are typically cleaned by fabric filters or water scrubbers.

3.3 Steelmaking

Electric Arc Furnaces (EAFs) use one or three anodes. The exhaust gases are evacuated from most EAFs through a "fourth hole" in the roof (Direct Evacuation System). Primary emissions from the electric arc furnace include particulate matter and gases. Particulate matter, including metal oxides, is generated during the melting and refining phases and is exhausted from the furnace. Carbon monoxide (CO) and carbon dioxide (CO₂) are generated in the furnace from combustion of auxiliary fuel, oil contained in the scrap, and decarburization of some of the scrap. Dioxins and furans are also generated. The exhaust gases are cleaned by fabric filters.

Secondary emissions of particulate matter, including metal oxides, are generated during the charging and tapping of the furnace, and a small quantity may be emitted during furnace operations. The secondary emissions are usually collected by hoods above the furnace or in the roof structure and are typically cleaned by fabric filters.

Minor emissions of particulate matter and metal oxides arise from the secondary steel making processes (ladle metallurgy and vacuum degassing) are collected and typically cleaned by fabric filters.

The only wastewater effluents from electric arc furnace operations are leaks from hydraulic systems or cooling water systems.

Solid waste generated by electric arc furnace steelmaking includes slag, dust collected by the fabric filters, and used refractory materials.

3.4 Continuous Casting

Air emissions of particulate matter and metals arise from the transfer of molten steel to the mould and from the cutting to length of the product by oxy-fuel torches.

Wastewater effluents are generated during the cooling of the hot metal and include scale particles and oil.

Solid waste is generated from the cutting of the steel but is minor in amount and is usually recycled within the plant.

3.5 Hot Forming

Air emissions from hot forming include gases generated by the combustion of fuel in the heating furnaces and volatile organic compounds (VOCs) from rolling and lubrication oils.

Wastewater effluents are generated from the high-pressure water descaling of the hot steel and include suspended solids, oil, and grease.

Solid waste is primarily waste iron oxides recovered from the descaling and wastewater treatment operations and includes oil and grease.

3.6 Cold Forming

Air emissions from cold forming are primarily VOCs from rolling and lubrication oils. Some minor emissions result from the combustion of annealing furnace fuel.

Wastewater effluents are generated from rolling oilfiltering systems, leaks, and spills and include oil and minor amounts of suspended solids.

3.7 Pickling and Cleaning

The major air emissions are acid aerosols from the acid pickling operations and the acid regeneration plant, if acid regeneration is used. There are also solvent emissions from the solvent cleaning of stainless steel strip at Atlas Stainless Steels.

The major sources of wastewater effluents are the acid pickling rinse water and acid fume scrubber, acid regeneration plant scrubber, stainless steel pickling wastewater treatment plant and alkaline cleaning. Acid pickling rinse water discharges can be minimized by counter flow cascading and, in some cases, recycling to the acid regeneration plant. The wastewater effluents contain suspended solids, oil and grease, metals and acids.

The major sources of solid wastes are iron oxide from the acid regeneration process and sludge from wastewater treatment facilities.

3.8 Coating

The major air emissions from the off-site galvanizing plant operated by Ispat Sidbec Inc. and Dofasco Inc. are the combustion gases from the heating furnace and zinc fumes from the zinc pot.

Wastewater effluent is minimal and will contain oil and grease and suspended solids including zinc.

3.9 Environmental Release Inventories

The National Pollutant Release Inventory (NPRI) is a federal government regulatory initiative designed to collect annual, comprehensive, national data on releases to air, water, and land, and transfers for disposal or recycling of specified substances. The NPRI data support a wide range of environmental initiatives, including toxic substance assessment, and pollution prevention and control. NPRI data are accessible by the public and provide information on all sectors - industrial, government, commercial, and others.

The Accelerated Reduction/Elimination of Toxics (ARET) is an initiative dedicated to decreasing the adverse effects of toxic substances on human health and the environment. ARET especially targets toxic substances that persist in the environment and bioaccumulate in living organisms. Through voluntary action, organizations that use, generate, or release toxic substances strive to reduce or eliminate their emissions of these substances. According to the 1998 ARET report, 14 of the 17 steel plants participated in ARET for the 1997 calendar year. The substances reported by non-integrated mills in 1997 are identified in the ARET list of substances.