Study On Calcium Sulfate Whiskers Preparation From Desulphurization Gypsum

Desulphurization gypsum is main by-product of the flue gas desulfurization. With the increasing of the sulfur dioxide output, the yield of desulphurization gypsum increases. If desulphurization gypsum isn't dealt with in time, it not only wastes the land, but also pollutes environment. If high value added desulphurization gypsum product is utilized, it could reduce the exploitation of natural gypsum resources, as well as protect environment.In the paper, hydrothermal method was applied in the preparation of calcium sulfate whiskers using desulphurization gypsum as primary materials. Effect of reaction temperature, raw material's grain size and additive on the calcium sulfate whisker was studied. The samples were characterized by the mean length and aspect ratio of calcium sulfate whiskers.Under this experimental condition, the conclusions were obtained as follows:(1) By hydrothermal method, calcium sulfate whiskers can be prepared from desulphurization gypsum, whose aspect ratio arrives 50～60.(2) Without any additives, the mean length increases with the increasing of reaction temperature. The mean length and aspect ratio show uptrend as the reaction time increases and the grain size of raw materials decreases. While the mean length and aspect ratio show descending trend as slurry concentration increases. When the slurry concentration is 14.28%, both the mean length and the aspect ratio arrive the maximum.(3) In the absence of additives, the optimum conditions are obtained, the reaction temperature is 140℃, the reaction time is 180min and slurry concentration is 14.28%.(4) Citric acid and neopelex can accelerate the growth of whiskers, the proper amount are 0.3%and 0.2%, respectively. The mean length of calcium sulfate whisker is over 60μm, the aspect ratio is approximately 58. The growth of Calcium sulfate whiskers is restrained by magnesium chloride.(5) When the concentration of neopelex reaches to 0.2%, the contribution of citric acid on whisker is better than that of sodium chloride. In addition, the contents of citric acid and neopelex are 0.3%and 0.2%, respectively. The mean length of calcium sulfate whisker arrives 60-80μm, the aspect ratio arrives approximately 70.