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Preparation of superfine calcium carbonate and calcium hydrosulfide from waste gypsum

wallpapers News 2021-11-23
Preparation of superfine calcium carbonate and calcium hydrosulfide from waste gypsum
Waste gypsum is a waste residue produced by industries such as phosphate fertilizers. Its main component is calcium sulfate. China emits a large amount every year, which not only pollutes the environment, but also occupies a large amount of land. Therefore, new processes should be developed as soon as possible to find a comprehensive utilization of waste gypsum with higher added value. The new approach is of great significance. A new process for the recovery of calcium and sulfur resources in waste gypsum is introduced, that is, waste gypsum undergoes reduction roasting, leaching, carbon dioxide replacement and other processes to recover calcium and sulfur resources to produce ultrafine calcium carbonate and calcium hydrosulfide. Good results.
A new method for preparing thiourea from waste gypsum is studied. Calcium sulfide is prepared by carbonization and roasting of waste gypsum, calcium sulfide is prepared by carbonation and leaching, and thiourea is prepared by wet reaction between calcium sulfide and lime nitrogen. This process eliminates the need for traditional thiourea The hydrogen sulfide preparation link in the synthesis process. At the same time, the influence of the reaction conditions of the waste gypsum carbonization and roasting on the output rate of calcium sulfide was investigated, and the optimal conditions for the efficient utilization of waste gypsum were proposed as follows: according to the mass ratio of waste gypsum to carbon: 1: 2.5. When roasting in a tube furnace at 920 C for 2.5 hours, the conversion rate of waste gypsum to calcium sulfide is 95%, and the purity of the further synthesized thiourea reaches 92%.
Industrial waste gypsum is used as raw material, and the solubility of calcium sulfate in a specific acid solution changes significantly with temperature to purify industrial waste gypsum. The purified filtrate is adjusted by the solid-liquid ratio and pH value, which plays a role in the structure-directing agent. Next, hydrothermal synthesis of calcium sulfate whiskers with high purity and high whiteness. The present invention uses a variety of industrial waste gypsum to prepare calcium sulfate whiskers, and fundamentally solves the bottleneck problem of complex types of waste gypsum impurities for large-scale industrial utilization. , To achieve the purpose of energy saving and emission reduction, and turning waste into treasure, with broad application prospects and market prospects.
 

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