Study On The Analysis And Fluidization Decomposition Of Calcium Sulfate In Phosphogysum

With the rapid development of phosphorous chemical industry, the amount of the phosphogypsum is growing year by year. The treatment and utilization of phosphogypsum become a problem that the human have to cope with. The process for sulfuric acid and cements based on phosphogypsum can not only eliminate environment pollution, but also achieve the circulating utilization of sulfur resource. But the traditional technology could not be applied extensively because of some disadvantages such as the low concentration of formed SO2, low equipment efficiency, great investment and much energy requirment. Therefore, there were important practical value and theoretical significance at the the research of the phosphogypsum fluidization decomposition characteristics.Calcium sulfate in phosphogypsum was measured by gravimetric and EDTA titration methods. It was discovered that relatively big error for calcium sulfate content was caused by EDTA titration method because of difficult ascertainment of the end point color during analysis. At the same time, analytical value gained by gravimetric method was obviously smaller than that of calcium sulfate in the traditional phosphogypsum. This phenomenon may be caused by incomplete solution of calcium sulfate. So the appropriate hydrochloric acid was added and then heated to increase dissolubility of calcium sulfate when distilled water and phosphogypsum were mixed in a beaker. It turned out that analytical error was relatively small. Finally, it was concluded that the improved gravimetric method is appropriate to analyse calcium sulfate in phosphogypsum.The decomposition characteristics of phosphogypsum in fluidized beds were studied using orthogonal experiments, the reaction temperature, the reaction time, the phase concentration of reducing gas and the gas flow velocity was discussed. The optimal reaction conditions of decomposition rate was obtained:temperature 950℃,reaction time 30 min,the phase concentration of CO 15%,gas flow velocity 1966 mL/min.The optimal reaction conditions of the desulphurization rate was defined:temperature 1010℃,reaction time 5 min,the phase concentration of CO 5%,gas flow velocity 885 mL/min.But the the fluidization quality of fluidized bed was low,The reaction stability affects the result. It can not truly reflect the decomposing efficiency of phosphogypsum. So, the device should be improved to advance its fluidization.