Process for treating cold rolling mill effluent containing oil emulsified in water

摘要

PICT:1083243/C1/1 Oil is removed from the cooling and lubricating effluent of a cold-rolling mill by forming in the effluent an insoluble floc to coagulate and concentrate the oil, placing the effluent under pressure and dissolving pressurized air therein, releasing the pressure on the effluent liquid so that the air returns to the gaseous state and removes the floc and thus the oil upwardly by flotation, and skimming off the resultant layer of floc and oil. The floc may be formed by adding NaOH, KOH, or NH4OH to FeSO4 dispersed in the effluent. In the Figure, waste pickle liquor is metered by pump 10 into agitation tank 11, and caustic cleaning line waste is metered by pump 13 so that effluent pressurized by pump 12 to 40-80 p.s.i.g. is at pH 5-6.