Application of Microwave Heating for Reduction of Tricalcium Phosphate with Carbon

Recently, recycling of phosphorus from the wastes containing phosphorous compounds is being attempted. In this study, carbo-thermic reduction of TriCalcium Phosphate (TCP) by microwave heating was investigated as one of the fundamental reaction processes of the phosphorus recycling. In this study, the reduction of TCP which contains iron oxides was also investigated. In the experiments, carbothermic reduction of TCP, Fe304 and TCP/Fe304 mixture were performed by microwave heating. The maximum temperature, the heating rate and the carbon equivalent was varied, and the reduction ratio was determined. First, reduction ratio of phosphorus in TCP decreased with increasing the heating rate and with decreasing the attained maximum temperature. Second, the reduction reaction rate of Fe304 at temperature higher than 1100°C is relatively rapid that it is not affected well by the heating rate. And third, reduction ratio of phosphorus from TCP/Fe304 mixture is dependent on the amount of phosphorus dissolution into iron, and carbon equivalent influences its kinetics. Considering the obtained reduction rates, the amount of phosphorus dissolving into the reduced iron is supposed to decrease with increasing the carbon equivalent and the heating rate.