Phosphogypsum Process Of Preparation Of Thiourea

Phosphogypsum is one kind of dangerous solid slag produced in the production process of phosphoric acid industry and ammonium phosphate industry. Thiourea is an important chemical raw material, also is an important organic chemical intermediates. In this paper, we analyzed the actuality of the production and unilization of phosphogypsum and the future of thiourea production comprehensivly. Based on the analysis and the development trend of phosphorus chemical industry, the way to produce thiourea by use of phosphogypsum as a raw material was set down. After CaS was sinteringed out by use of phosphogypsum, two technologies processes of synthesis thiourea by use of CaS as an initial material were made out.Process 1: Produce Ca(HS)₂ by CaS and CO₂.,and then the thiourea was produced by use of Ca(HS)₂ as one of material. In this part, the process parameters of producing Ca(HS)₂ by use of CaS was studed on. The optimum process parameters of producing Ca(HS)₂ have found out by the orthogonality design. The optimum process parameters are that the reaction time is 1.5 hours, the temperature is 30℃and the stream velocity is 80 air bubbles/min. With this optimum process parameter, the sulfur conversion rate reaches 88.90% and the purity quotient of thiourea which is made by the Ca(HS)₂ is 93.21%.Process 2: Produce H₂S by CaS and CO₂, and then the thiourea was produced by use of H₂S.and calcium cyanamide. In this part, the process parameters of producing H₂S were found out, also is the process parameters of synthesis thiourea. The optimum process parameters of producing H₂S are that the stream velocity is 110 air bubbles/min, the temperature is 60℃and the reaction time is 5 hours. With this optimum process parameter, the sulfur conversion rate reaches 93%.The optimum process parameters of synthesis thiourea are that H₂S and calcium cyanamide in the ratio is 1:1 to 1.8:1, the temperature is 70～80℃and synthesis time is 4 hours. With this optimum process parameter, the purity quotient of thiourea is up to 91%.The study on this paper not only has found a way out for the comprehensive utilization of phosphogypsum, but also found a new source of sulfur for thiourea industrial. In this way, we can get great valuable production by use of phosphogypsum. The rsearch results in this paper have the vital significance to circulation economy, resources using and environmental protection.