The formation of red gypsum suspension at Cinkarna Celje d.d. has been a major technological problem in the last few years. Due to the increasing demand of the by- product Cegips, the amount of red gypsum produced is decreasing and, as a consequence, its concentration is decreasing. Red gypsum suspension is too depleted to achieve normal settling, so we resort to the addition of various additives.In this thesis, we have tried to find out how different parameters influence the course of the red gypsum suspension thickening. In the laboratory, the settling of gypsum suspension from production samples was monitored using heated glass cylinders at different temperatures, pH values, dilution rates and different additions of production coagulant and flocculant samples. We found that temperature has no particular influence on the course of thickening and that significantly better settling can be achieved at higher dilution rates with coagulant additions and in particular flocculant additions. The pH value is an important parameter in thickening of the red gypsum suspension, but it is not crucial as it is difficult to regulate in such a large production.
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