Abstract: The desulfurated gypsum produced by a power station in Shandong is normally sold in lower price as common mixture of cement and the relate product, as well as raw material for making common gypsum product. In order to increase the added value of the desulfurated gypsum products, experiments on preparation of α-hemi-hydrate gypsum(α-HH) by NaCl salt solution at normal pressure were carried out. Based on the crystal water content and crystal microstructure of the product, the process was optimized to finally determine the concentration of salt solution 20%, slurry concentration 20%, natural pH value, and reaction temperature of 100 ℃ for 3 h. Under this condition, the cylindrical crystallization with crystal water content of 8.74% and average length to diameter ratio of 4∶1 were achieved. XRD analysis proved that the main phase in the product is α-HH indeed.

Key words: Desulfurated gypsum, α-hemi-hydrate gypsum, Hydrothermal method in salt solution at atmospheric pressure, Crystal water content, Microstructure