SUSTAINABLE PRODUCTION IN THE MINING INDUSTRY: BY-PRODUCT RECOVERY

The U.S. mining industry produces over 7,000,000 tons/yr of process residue that may contain hazardous species as well as valuable by-products. Process residues are generated by (a) smelter off-JDVFOHDQLQJ WRQV\UDQGEEDJKRXVHGXVWDQG ZDVWHZDWHUWUHDWPHQW WRQV\U 7KHULJKWWHFKQRORJ\PD\EHDEOHWR recover marketable by-products from this process residue to generate revenue and reduce disposal costs for the mining industry. In fact, such a technology was invented by a small U.S. business, SepraDyne, and is being developed and commercialized at an Arizona copper mine to treat smelter off-gas cleaning sludge. The process separates mercury from lead, copper, gold and silver so the residue is either recycled to recover additional copper or sold to recover lead, bismuth, and trace gold and silver. (2) The following paper reviews the processing steps used to mine and refine copper. This overview provides background for understanding the source of the process residue being treated by SepraDyne – smelter off-gas cleaning sludge called acid plant blow-down. Mineral-rich process residues generated by copper refining step may also be amenable to by-product recovery. The paper deVFULEHVWKH6HSUD’\QHSURFHVV WKHKLJKYDFXXP indirectly heated, rotary kiln operates at temperatures up to 750oC. The paper also summarizes factors that influence the economics of by-product recovery. If, for example, 30 % of the industry’s residues were to be processed, then mercury removal could generate $400M/year in revenue from the recovered metals, and avoid $1B in waste disposal and energy costs