Reducing noxious emissions in acid pickling plants for metals - by injecting controlled amt. of steam into air above pickling bath

摘要

The emission of noxious substances is reduced in plants used for the pickling of metals with acid in an enclosed bath fitted with controlled fume extn. Steam is blown into the air space above the pickling bath inside the plant. The amt. of steam employed pref. provides a partial pressure equal to the vapour pressure provided by the surface of the bath or on the wet surfaces of the workpieces. Alternatively, the partial pressure due to the steam may be above the vapour pressure provided by the bath surface or the wet workpieces. The process can be used, e.g. when metals are pickled with HCl or HNO3, where fumes of HCl or NOx are obtd. The invention can be applied to almost any modern plant using pickling tanks which are enclosed so they can be provided with fume extn. plant.