从FGD残渣中制备高强型α半水石膏的研究

探索了溶液结晶法从烟气脱硫残渣中制备α半水石膏的机理及过程晶形的控制,结果表明:pH值、温度和盐溶液是影响α型半水石膏产品性能的最重要因素。由于α型半水石膏的强度取决于制浆需水量,而制浆需水量又取决于其晶体形态,当晶形从针状向短柱状转化时,其制品强度逐渐增大,这是制备高强α型半水石膏的必要条件,本研究借助了差示微分扫描量热仪等分析手段,得出了溶液结晶法从烟气脱硫残渣中制备α半水石膏的机理。

The Research on Producing α-form Calcium Sulfate Hemihydrate from the FGD Sludge

The paper has studied the mechanism and ideal crystalline shape of crystallization of α-form calcium sulfate hemihydrate from the FGD sludge. The experiments showed that the concentration of salts, pH value and the temperature of reaction are the important factors for this process. It can make the crystals of products grow in stubby columnar directions through adding the crystal habit modifiers and show an extremely low water carrying capacity. It can increase strength of the α-form calcium sulfate hemihydrate. Additionally, the type of alkali earth metal ions also strongly affects modification of crystal habit. The paper obtains mechanism of crystallization of producing flue gas desulfurization sludge waste into α-form calcium sulfate hemihydrate. The mechanism is conversion of FGD gypsum by dehydration into β-form hemihydrate at first, and then conversion of β-form hemihydrate into α-form hemihydrate.