Research On Preparation And Trans-crystal Technology Of α- Hemihydrate Flue Gas Desulfurization Gypsum With The Hydrothermal Method

Flue gas desulfurization gypsum (FGD) is a product from wet limestone flue gas desulfurization technology which is one of the main technologies environmental protection to control countermeasure of SO2 pollution.With the development of Energy saving and emissions reduction, flue gas desulfurization has become the coercive measure.the FGD's utilization is critical because emissions and the rate of rise increase swiftly and violently.Preparation ofα-hemihydrate gypsum by FGD which has the purity to be high, the quality is stable, the crystal granularity small, the undesirable impurities are few, and assumes characteristics and so on.Theα-Hemihydrate FGD gypsum was prepared in aqueous salt solustion with the hydrothermal method, by taking full advantage of the characteristics of FGD gypsum such as high grade and powder in hygrometric state. The influences of salt solution concentration, the reaction temperature and time, slurry concentration and pH value on the dehydration reaction dynamics process and theα-Hemihydrate FGD gypsum were studied. The optimal technological conditions were determined as follows: the concentration of salt solution is 15%, reaction temperature≥95℃, reaction time 2 hours, pH = 5 ~ 7, slurry concentration is 20%.Adding crystal modifier is a effective method to improve the formation ofα-form calcuim sulfate hemhydra, inorganic salt, polybasic acids (Salts), macromolecule and surfactant are the most commonly used crystal modifier. Pure crystal modifier have certain improvement effect on theα-form calcuim sulfate hemhydra`s crystal morphology, the standard consistency of gypsum, the compressive strength was ideal by adding the organic and inorganic composite modifier.According to the former experiments, we finally attain the high-strength material which compressive strength of3 days is 32.25MPa and the standard consistency is 32%.The mechanism of action of the crystal modifier is not known, it was generally supposed theα-form calcuim sulfate hemhydra take shape in dissolution-recrystallization process. Crystal modifier has a effect on growth speed as a result of adsorption, Various crystal faces growth speed's difference urges the crystal to the stub column. The research supply supporting technology to develop high efficiency crystal modifier and super-strength gypsum, and it will guide resource utilization of FGD gypsums.