CASE STUDY No. 9719
KEY WORDS BASIC OXYGEN FURNACE (BOF) SLUDGE, REUSE
Inland Steel Co.
3210 Watling St., MC 8130
East Chicago, IN 46312
Contact: Tom Barnett. Tel: 219-399-6296. Fax: 219-399-6039.
Summary
By introducing a process to form briquettes out of basic oxygen furnace (BOF) sludge, the company is able to use this former waste as feedstock for the steelmaking process, avoiding off-site landfill disposal of some 450,000 tons of sludge and dust per year and saving about $17 million.
Action
Inland Steel Co., one of the nation's largest producers, has been under considerable pressure for some years to address both environmental and competitive concerns. Ironmaking and steelmaking operations generate large volumes of baghouse and wet sludges. The wet sludges are generated from water spray scrubbing systems used to remove airborne particulates contained in the operations exhaust gas streams. These waste oxide dusts and sludges contain 90% to 95% iron along with other recoverable elements including lower concentrations of metals such as chromium, lead, and nickel.
The company evaluated waste stream handling and disposal practices to determine whether process changes were feasible. After normal dewatering to 80%-85% solids, residual sludge is still too wet to allow direct return to the BOF, and the zinc content precluded reintroduction to ironmaking operations. Landfilling seemed the only alternative.
Then, National Recovery Systems, in cooperation with Inland and two other steel companies, developed a process to make briquetting possible. The factors to control included chemical composition, particle size, reduction of heat-producing oxidation, plus size and strength characteristics required for physical handling of the material.
The resulting process now includes delivery and storage of individual waste elements for later blending; conveyor belt feeding to dryers; and blending with molasses, which acts as a moistener and binder. This blend of plastic material is dropped into the briquetter feeder chute which employs counter-rotating rolls with half-cavity pockets, 45 per roll. As the rolls turn, fully formed briquettes drop out of the other side and are conveyed away for cooling and curing. They are small, measuring 3 by 1-1/4 by 1-7/8 inches.
Payback
Using this process, Inland during 1996 saved $23.2 million dollars in raw material costs and avoided $12.4 in off-site disposal costs. Minus additional operations and material handling costs, the company's net saving for the year was $17.3 million.
Other benefits
