Abstract:Soluble phosphorus, fluorine, organic matter, gypsum phase composition and gelling properties of phosphogypsum which was fluidized heat treatment by controlling the parameters were determined, and specific surface area and the microcosmic morphology of the sample also were analyzed by using the BET and SEM. The results show that the fluidization process is continuous and stable by controlling the parameters of the gas flow velocity 35m/s and the stay time 30s. With the increase of fluidization temperatures, the content of soluble phosphorus, fluorine and organic impurities in the sample decrease gradually and then pH value increases. In the fluidized heat treatment process, phosphogypsum forms complex phases undergoing transformation of CaSO4·2H2O to CaSO4·05H2O, Ⅲ CaSO4 and Ⅱ CaSO4 Under the fluidization temperature less than 400℃, the hemihydrate gypsum phase increases with the rise of temperatures. However, anhydrite phase increases with the rise of temperatures at the fluidization temperature over 400℃. During the fluidized heat treatment process, phosphogypsum forms hemihydrate gypsum or anhydrite phase through surface dehydration, and a large number of cracks are formed on its surface. The specific surface area of gypsum powders increase gradually, because the particles collided with each other and the crystal grains became smaller. Under the control of fluidization temperature 400℃, and time 30s, the mechanical strength of gypsum powders are as follows, the flexural strength 21MPa, the compressive strength 43MPa in the hydration period of 2h.