Abstract:

In order to solve the potential harm to the environment caused by the large amount of desulfurization gypsum,improve the added value of desulfurization gypsum,the atmospheric salt solution water thermal method was used to explore the optimal synthesis process of α-hemihydrate gypsum with the desulfurization gypsum of power plant as raw material.The effect of salt solution type and concentration on the synthesis process,synthesis product composition and structure of α-semi-water desulfurization gypsum was studied.The results showed that in the CaCl₂ and MgCl₂ salt solutions,the formation process of hemihydrate gypsum was hindered due to the same ion effect and the formation of magnesium sulfate ion pairs.The higher concentration of KCl and NaCl salt solution can transform the dihydrate gypsum,wherein KCl will cause the hemihydrate gypsum to be excessively dehydrated to form anhydrous potassium gypsum.The NaCl salt solution can convert the dihydrate gypsum into hemihydrate gypsum and maintain it for a long time.By comparing the optimal synthesis process was obtained as follows：NaCl solution mass fraction was 15%,system reaction temperature was 95 ℃,mass ratio of solid to water was 1∶4,stirring rate was 150 r/min and synthesis time was 3 h.Under the conditions,hexagonal short columnar α-hemihydrate gypsum with an aspect ratio of about 5∶1 was obtained.

Key words: hydrothermal method, type of salt solution, concentration of salt solution, α-hemihydrate gypsum