FILLERS MADE FROM FGD GYPSUM

So far FGD gypsum has been used mainly in the construction materials i ndustry, and in fact all the FGD gypsum from coal-fired power stations is used for this purpose. For FGD gypsum from lignite-fired power sta tions it is necessary to look for further possible applications becaus e of the large quantities generated. One of these options could be the manufacture of calcium sulphate fillers and their application in adhe sives, paints and plastics. Processing, grinding and classifying proce sses for FGD gypsum to produce dihydrate fillers have been developed i n extensive laboratory and pilot-plant trials. Cleaning, drying, grind ing and classifying has led to two industrially interesting types of f iller made from FGD gypsum; these were produced and characterized, and their application in adhesives and paints was investigated. Because o f the thermal stressing involved, anhydrite fillers are the only ones suitable for use in plastics, especially in PVC (polyvinyl chloride), so a process was also developed for producing FGD anhydrite Filer from FGD gypsum. This FGD anhydrite filler exhibited excellent properties, in particular high levels of whiteness and high fineness in the 2 mu m range, and its application in PVC and other thermoplastics and durop lastics was investigated with good results. This cart be summarized by stating that, in principle, it is possible to produce calcium sulphat e fillers from FGD gypsum. The high quality specifications for fillers were met, especially with respect to fineness and colour. The applica tion tests in the application medium gave results equally as good as t hose of competing Filers.