Process for producing flue gas gypsum in the course of the flue gas desulphurisation of power station boiler firings

摘要

Process for producing flue gas gypsum in the course of the flue gas desulphurisation of power station boiler firings. 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 in 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 fed into the scrubbing tower via atomisation nozzles. A further crystal suspension stream is continuously drawn off from the bottom of the scrubbing tower and split by means of a cyclone separator into an underflow carrying crystal slurry and an overflow containing solid fines, with the underflow being dewatered, flue gas gypsum being drawn off and the resulting clear liquid being recirculated to the scrubbing tower and with the overflow containing solid fines likewise being recirculated to the scrubbing tower. At least 10% by weight of the solids contained in the crystal suspension have a particle diameter of less than 20 mu m and are carried along as solid fines in the overflow of the cyclone separator. A substream is separated from the overflow and replaced by a solids-free liquid. In this procedure, the particle size of the calcium sulphate dihydrate crystals drawn off is set by control of the amount of the substream, with, by means of throttling the amount of the substream, finer calcium sulphate dihydrate crystals and ... Original abstract incomplete. IMAGE