High gradient magnetic filtration of steel mill process and waste waters

Abstract

High gradient magnetic separation used in the kaolin industry to separate fine, weakly magnetic particles is applicable to the treatment of a variety of waste and process waters in steel mills. High efficiency and low space requirements make high gradient magnetic filtration capable of removing almost all suspended solids found in these waters. High gradient magnetic filtration devices operate much like automatic backflushing filters. The recovery of magnetic particles in these devices depends on the ratio of magnetic to hydrodynamic drag forces which is large for typical particles found in these waters. The cost and performance of high gradient magnetic filters depend on the magnetic field strength and the flow velocity used. Reduction in suspended solids contents of treated waste waters is typically greater than 90% and often exceeds 99%. A full scale treatment plant for basic oxygen furnace waters has been designed and would require a tenth of the land area of that used in a conventional treatment system.