| 摘要 |
Raw gypsum, which is separated in a cyclone separator (3) after flue gas desulphuration in a flue gas desulphuration plant (1), is laid on a vacuum belt filter (5) and washed with water in the second stage of said filter. The washing water has previously been enriched in a water tank (13) with gaseous SO2 from an SO2 source (11) to such an extent that the SO2 in the washing water can react with the colouring components Fe<3+> and manganese dioxide of the filter cake. Said substances are thereby converted into colourless substances (Mn<2+> and Fe<2+>). The entire plant may be of the prior art type and, to enrich the washing water with SO2, requires only the technologically trivial addition of the SO2 source with a metering device (12). The result is pure gypsum with a substantially greater brightness of considerably over 80 %. |
