Waste management and pollution prevention opportunities in the iron and steel industry.

The types of emissions generated by the iron and steel industry and the methods of managing these types of industrial waste are the subjects of this summary article.

The iron and steel industry involves a myriad of operations which generate vast volumes of air emissions, liquid effluents and solid wastes. This article presents an overview of waste management and pollution prevention opportunities in this industry, with the primary focus on this industry in Ontario. However, these opportunities are equally applicable to the iron and steel industry in Canada as well as in a global context as well as other metallurgical operations. Although this article will be of most interest to the iron and steel industry, it will also be valuable for discussions between various parties involved and interested in the clean up of the Great Lakes, eliminating persistent toxics and achieving economically feasible (and/or zero discharge) technology trains.

To appreciate the magnitude, diversity and complexity of process effluents, an overview of iron and steel production processes and effluents is presented. These operations include the subcategories: cokemaking, ironmaking (blastfurnace, sintering, etc.), steelmaking, casting, hotforming and finishing. Also presented are assessments of the pollution prevention opportunities and the Best Available Treatment Technologies (BATT) for the abatement and treatment of various effluents, air emissions and solid wastes.

Air emissions are generated as both particulate and gaseous emissions in the transportation of raw materials and in processing operations. It is imperative to control dust by water spraying and by adequate covering of conveyer belts and drop points. By far the largest source of air pollution is sulfur dioxide generated in the combustion of coke oven gas (COG) and liquid fuels used in various operations for heating. S[O.sub.2] emissions generated by the combustion of COG can be reduced by desulfurizing the COG using the Stretford and Zimpro processes. Other air emissions include hydrogen sulfide gas generated during the blast furnace slag cooling by water spray, volatile organic compounds emitted from cokemaking by-products, and nitrogen oxides released during hotforming and other reheating operations.

An enormous volume of non-contact cooling water (NCCW) is also used in the various operations. It is important that process streams be segregated at their source (process/operation), whichever possible, and treated separately from the NCCW streams. It is also important that the NCCW be separated and recycled where applicable, to decrease the volume of the effluent to be treated.