Effect of temperature on the vacuum carbothermal reduction of low-grade phosphate ore

The effect of temperature on the vacuum carbothermal reduction of low-grade phosphate ore was investigated by FactSage 7.0 and experimental studies. The calculation indicated that the mass of PO and PO2 in the gas phase increased with the increase of temperature, while the volatilization ratio of phosphorus initially increased and then decreased under fixed carbon dosage and pressure. The maximum theoretical volatilization ratio of phosphorus was 96.70% at 1250 degrees C. Experimental results showed that the volatilization ratio of phosphorus obviously increased as the reduction temperature was increased from 1200 degrees C to 1250 degrees C, and the tendency slowed down subsequently. Theoretical calculation and experimental results were in fairly good agreement that the optimum reduction temperature was between 1250 degrees C and 1300 degrees C. The Ca-5(PO4)(3)F and SiO2 in the ore were converted to Ca2SiO2F2, and the phosphorus in the ore was reduced to phosphorus vapor during the reduction.