Sand recycling and reuse saves foundry hazardous waste disposal, cleanup costs
Rather than keep spending three-quarters of a million dollars a year for hazardous waste disposal, a foundry implements a sand recycling process.
The Conbraco Industries foundry in Matthews, N. C., casts industrial valves from brass ingots containing 85 percent copper and 5 percent each of tin, zinc, and lead. Conbraco makes valve casting molds from a mixture of 70- to 100-mesh sand [silica], bentonite clay, organic fillers, and other minor ingredients. Resin-coated sand cores in the mold form the valves' hollow interiors. Conbraco pours molten brass into the completed molds; after the brass hardens, the valves are removed from the molds, blasted with iron shot, and ground to finish. The casting process results in 6 to 7 tons per day of used sand that contains scrap brass and iron shot.