【摘要】 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。更多还原

【Abstract】 The behavior of MgO in Mg extraction by carbothermic reduction in vacuum was studied in thermodynamic theory. The impacts of reduction conditions,including the pressure and temperature,on the reaction pathway and reduction temperature were theoretically calculated and experimentally evaluated. The condensate and slag were characterized with X-ray diffraction. The calculated results show that the MgO reduction with carbon easily occurs in vacuum,and the reduction temperature drops down with a decreasing pressure. At a pressure ranging from 30Pa to 100 Pa,the main reaction MgO(s)+ C(s)= Mg(g)+ CO(g)starts at 1573 K;and the indirect reaction MgO(s)+ CO(g)= Mg(g)+ CO2(g)never occurs. The experimental results reveal that at 1553 K and a pressure of 30~ 100 Pa,metallic Mg coexists with carbon and un-reacted MgO in the C-coated condensate,possibly because of the reverse reaction,Mg( g) + CO( g) = MgO( s) + C( s). No magnesium carbides were observed in the slag.更多还原