Effect of different carbon sources on vacuum carbothermal reduction of low-grade phosphorus ore

Abstract

In this study, the effect of different carbon sources on the carbothermal reduction of low-grade phosphate ore were examined using FactSage7.2 calculations and vacuum reduction experiments. The thermodynamic calculations showed that the trend of the effect for three types of reducing agents was generally consistent under 1 Pa pressure and 14% carbon dosage. The reduction effect was maximum when graphite was used as the reducing agent, and a maximum mass of P was obtained at 1250 ?C. The vacuum experiment results showed that the reduction and volatilization ratios of phosphate rock increased with temperature for different carbon sources. Maximum reduction ratio was obtained using graphite in the temperature range 1250-1300?C. The reduction effect of pulverized coal was optimal at 1350?C, when SiO2, Al2O3, and MgO in the pulverized coal ash were exposed to form low-melting eutectics with CaO due to the increased degree of reaction, and the heat and mass transfer rates were increased. At this time, a maximum reduction ratio of 51.77% of the sample and a maximum volatilization ratio of 82.44% of P were achieved. Considering the cost effectiveness, pulverized coal was the optimum carbon source for the treatment of low-grade phosphate rock using vacuum carbothermal reduction.