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对氧化镁在真空碳热还原过程中的行为进行了热力学分析,研究表明真空条件下氧化镁易于被碳还原,还原温度随着体系压力的降低逐渐降低。在系统压力30~100 Pa的条件下,通过计算确定还原过程的主反应是MgO(s)+C(s)=Mg(g)CO(g),反应起始温度为1573 K。而反应MgO(s)+CO(g)=Mg(g)+CO2(g)在该体系条件下并未发生,此外碳热还原过程中生成镁的碳化物的反应也不会发生。实验研究表明,在温度1553 K,系统压力30~100 Pa的条件下,碳热还原反应开始进行,冷凝区得到金属Mg,这与热力学计算的参数相吻合。反应剩余渣经检测主要为未反应的氧化镁与碳,并未检测到碳化Mg。由于冷凝区发生逆反应Mg(g)+CO(g)=MgO(s)+C(s),得到的冷凝物表面有碳吸附,经检测冷凝物含有金属镁、氧化镁以及碳,通过进一步处理可得到纯度较高的金属Mg。
The thermodynamic analysis of the behavior of magnesia during the carbothermal reduction in vacuum was carried out. The results show that magnesia is easily reduced by carbon in vacuum and the reduction temperature decreases with the decrease of system pressure. Under the condition of system pressure of 30 ~ 100 Pa, the main reaction of the reduction process was calculated by the calculation of MgO (s) + C (s) = Mg (g) CO (g) and the initial reaction temperature was 1573K. The reaction MgO (s) + CO (g) = Mg (g) + CO2 (g) does not occur under the conditions of the system. In addition, the reaction of carbides that generate magnesium during the carbothermal reduction does not occur. Experimental results show that the carbothermal reduction reaction starts at a temperature of 1553 K and a pressure of 30 to 100 Pa, and the metal Mg in the condensation zone, which is consistent with the calculated thermodynamic parameters. The residue of the reaction was mainly detected as unreacted magnesia and carbon, and no carbonized Mg was detected. Because of the reverse reaction of Mg (g) + CO (g) = MgO (s) + C (s) in the condensing zone, the obtained condensate has carbon adsorption on the surface and the detected condensate contains metallic magnesium, magnesia and carbon, Can get high purity metal Mg.