China Nonferrous Metallurgy

Generation of acid mist mainly occurs during electrowinning of the hydrometallurgical zinc refining process. Acid mist irritates respiratory tract and skin, corrodes teeth and contaminates ambient air and soil. Fugitive acid mist in zinc electrowinning operations has been a major concern in Danxia Refinery. Control measures are taken including strict control of the quality of purified solution, optimized ventilation system of electrolysis cells, improved liquid distribution system and spray trap of air-cooled tower and provision of foam trap. As a result, acid mist discharge to atmosphere decreases by more than 99.5%. Ambient acid mist concentration drops to lower than 0.025mg/m³ and acid mist discharge from air-cooled tower declines to 0.025mg/m³. It is not only in compliance with state discharge limits but also far ahead in the industry. Meanwhile, the increased height and optimized spray system of the air-cooled tower improves the cooling range to 5-6℃, which meets the requirements of normal and stable operations of zinc electrowinning.