Study On Vacuum Carbothermal Reduction Of Medium And Low Grade Phosphate Ore

Although China is rich in phosphate resources,it is mainly poor.Especially with the depletion of high grade ore,it is very important to develop the mining and comprehensive utilization of medium and low grade phosphate ore,which will provide strong guarantee and significance for the sustainable development of phosphorus chemical industry in China.In this paper,the vacuum carbothermal reduction of low and medium grade phosphate rock is studied,and the effects of carbon content,reduction temperature and holding time on the vacuum carbothermal reduction of low and medium grade phosphate rock are explored.Firstly,the vacuum carbothermal reduction of low and medium grade phosphate rock was calculated by thermodynamics software FactSage7.0.On the basis of theoretical calculation,the experimental research is carried out,and the conclusions are as follows:The theoretical calculation shows that in the relationship between the Gibbs free energy and the temperature in the P₂O₅ carbothermal reduction,the minimum reaction temperature of P₂O₅ carbothermal reduction can be reduced under vacuum conditions.In the vacuum carbon heat reduction of low grade phosphate ore,the yield of phosphorus increases gradually with the increase of carbon distribution,but the increment is small after the amount of carbon distribution is over 14%.The harvest is the first to rise and then decrease.When the temperature is at 1250?-1300?,the harvest rate reaches the highest.In a comprehensive way,the theoretical calculation shows that the best reduction condition of low grade phosphate rock is,the amount of carbon distribution is 14%,and the temperature is between 1250?and 1300?.According to the experimental scheme,the experiment was carried out under different factors,then the content of phosphorus in the reduced sample was measured.The weight loss rate of the reduced sample was calculated,the yield of phosphorus was calculated and the XRD phase analysis was used.The results showed that the weight loss rate of the reduced material increased with the increase of temperature,from the reduction temperature of 1200.The increase of 19.1%to 1350 degrees centigrade is 35.54%,which indicates that the increase of carbon distribution is beneficial to the production of meteorological materials in the reduced sample;the reduction temperature is 1300 and the carbon distribution is 14%,and the amount of phosphorus in the sample is reduced when the heat preservation time is increased.The dephosphorization rate of phosphate rock increases with the increase of heat preservation time.The optimum holding time is 120 minutes and the dephosphorization rate is 87.58%.From the XRD map phase analysis,it is found that Ca₅?PO₄?₃F,Ca₂?SiO₄?and SiO₂ in the original ore are reacted with the reductant coke to produce Ca₄Si₂O₇F₂,Ca₂SiO₄ and Ca₂SiO₂F₂,and the phosphorus elements in Ca₅?PO₄?are reduced.