The Conversion,Modification And The Solubility Study Of Flue Gas Desulfurization Gypsum At Atmospheric Pressure

Gypsum is an industrial by-products produced from the calcium-based wet flue gas desulfurization process (FGD). The practical utilization of FGD gypsum is an effective way and a fundamental solution to secondary pollution of the desulfurization residue of calcium-based wet FGD process.This study focuses on the optimum conditions of FGD gypsum conversion intoα-calcium sulfite hemihydrate in salty solution at atmospheric pressure. At the same time, the change of solubility of reagent-grade calcium sulfate dihydrate and FGD gypsum are discussed and contrasted.The experiment is carried out in a batch reactor by using the method of hydrothermal mixed salt solution at atmospheric pressure. A 3-neck flask is used as the crystal reactor. In the experiment, the temperature and the concentration of salt solution which influence the transformation process are mainly discussed. With the samples analyzed by qualitatively and quantitatively, the progress of FGD Gypsum conversion intoα-calcium sulfate hemihydrate is studied. Sequentially to select the optimum condition of FGD Gypsum conversion. The experimental results show that the temperature, species and concentration of salt solution are the most sensitive factors in the process of FGD Gypsum transformation. In order to get theα-calcium sulfate hemihydrates crystals with high quality, the best condition is keeping the temperature range among 95℃~98℃and ensure the mixed salt solution concentration range among 25% ~31%.The research results demonstrate that calcium sulfate dehydrate(AR) has the same rules with FGD gypsum in the single-salt solutions. In CaCl2 solution, as the co-ions effect of Ca2+, higher the concentrations , lower the solubility; In MgCl2 solution, for the stable bitter salt formed by Mg2 + and SO42-, it could enhance the dissolution of FGD gypsum and solubilization obviously; In KCl solution, the KCl promotes dissolution of FGD gypsum by salt effect, its solubilization is less than MgCl2 solution. In the Ca-Mg-K mixed chloride salt solution, the solubility of calcium sulfate is affected most significant by co-ion effect.