Study On The Phosphorus Volatile In The Process Of Pyrolyzing The Middle And Low Grade Phosphate Rock

Phosphate rock resources are rich in our country, but mainly is the low and medium grade collophanite. Referenced principle of producing calcium-magnesia phosphate fertilizer by blast furnace method, discussed melting the low and medium grade phosphate rocks, volatilizing the element phosphorus into steam and collecting, at the same time, residual solid as the trace elements in the citrate acid soluble fertilizer. The research on utilization of low grade phosphate rock resources directly increasingly highlights as the decreasing of phosphorus resource and phosphate rock grade gradually depleted.The research adopts the high temperature furnace, coke as the reducing agent, silica and alumina as fluxing agent. First, the research studies the main influence factors and pyrolysis reaction mechanism of tricalcium phosphate. Then, on this basis, research on the thermal phosphate-solubilizing volatilization process and its mechanism with the selected medium-low grade phosphate rock of Hu-bei province was conducted. The study supplies a tentative exploration for the feasibility of the new productive technology and provides some feasible basic data.The main research contents and conclusions as follows:1. In the reduction process of tricalcium phosphate, the results showed that the carbon is theory of the dosage of1.05times; Alumina and silica added respectively has promoting effect of reduction of tricalcium phosphate, and when the acidity index is1.5and aluminum-calcium ratio is1.5, the experimental results is optimal; When alumina and silica added at the same time, as the aluminum-calcium ratio is1.5and acidity index is2.0namely the melt factor is2.2, each material’s ratio (mass fraction) of total material is that silicon dioxide is24.49%; alumina is23.68%; calcium oxide is18.03%; then when the reaction temperature is1525℃and reaction time is90min, the experimental results is optimal.2. The result of the orthogonal experiment showed that the sequence of the various factors influenced on the reduction rate of reduction of the phosphate rock is: reaction time> reaction temperature> dosage of carbon> acidity index>coke particle diameter. According to single factor experiments, choose the best process condition for:acidity index:0.75, reaction temperature:1525℃, reaction time:90min, coke particle diameter:0.075mm, the carbon is theory of the dosage of1.05times.3. The addition of alumina not only can increase the reduction rate of phosphate rock but also can reduce the material’s melting point. Experimental results showed that:when the plus acidity index is2.0, the aluminum-calcium ratio0.75namely the melt factor is1.88as the main proportion of each reaction material in all materials is that aluminum oxide is19.31%; silicon dioxide is31.72%; calcium oxide is19.92%, then when the reaction temperature is1525℃and reaction time of90min, the experimental results is optimal.4. Through the thermodynamic analysis of the reduction process of tricalcium phosphate and phosphate rock, discussed its’reaction properties and reduction mechanism in the process of reduction. The change of calculation results of enthalpy and gibbs free energy showed that the initial temperature of the reduction reaction and the temperature at which the chemical reaction equilibrium, and has been confirmed reasonable in the test results.