| 摘要 |
The invention relates to a process for preparing flue gas gypsum in the course of the flue gas desulphurisation of power station boiler furnaces, in which the flue gas is treated in a scrubbing tower with a scrub water suspension containing lime or limestone and the sulphur dioxide thus scrubbed out is converted in the bottom of the scrubbing tower, with feeding of atmospheric oxygen, by oxidation and by crystallisation into calcium sulphate dihydrate crystals. A circulating stream is drawn off from the bottom of the scrubbing tower and is fed via atomisation nozzles to the scrubbing tower. A further crystal suspension stream is continuously drawn off from the bottom of the scrubbing tower, fed to a cyclone separator and after separating off crystal slurry is recirculated to the bottom of the scrubbing tower. The material flowing from the bottom of the cyclone separator and carrying the crystal slurry is dewatered, flue gas gypsum is drawn off and the clear liquid is fed to the scrubbing tower. According to the teaching of the main patent, the proportion of fines in the bottom of the scrubbing tower is adjusted such that at least 10% by weight, preferably from 20 to 70% by weight, of the solids carried along in the crystal suspension stream remain in the material flowing from the top of the cyclone separator. In further embodiment and improvement of the process known from the main patent, lime or limestone in the form of a siliceous power station effluent treatment sludge having a pH between 8 and 10 is fed to the scrubbing tower. <IMAGE>
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