Process for purifying hot waste air containing hydrofluoric acid or hydrofluoric acid and sulphur oxides, and clay- and/or glazing-containing effluent from the ceramic industry

摘要

In this process, on the one hand the waste air is purified by means of washing water and the hydrofluoric acid present in the effluent is then removed by precipitation of calcium fluoride. On the other hand, the clay- and/or glazing-containing effluent is neutralised and clarified in a settling tank. In order to reduce the water consumption and the investment costs, the washing water containing hydrofluoric acid is held at a pH of less than 3.5 by metered addition of water with simultaneous discharge of effluent containing hydrofluoric acid. The effluent containing hydrofluoric acid and the clay- and/or glazing-containing effluent are then combined in a tank and the clay- and/or glazing-containing effluent is cleaved by the effluent containing hydrofluoric acid, and both effluents are together neutratilised with milk of lime. The calcium fluoride and calcium sulphate formed in the neutralised effluents and the clay and/or glazing solids are separated off by sedimentation in a common settling tank. At least a part of the clarified water leaving the settling tank is added to the washing water containing hydrofluoric acid for dilution. <IMAGE>