白云石-碳体系热分解及热还原的热力学分析  

Thermodynamics Analysis for Thermal Decomposition and Thermal Reduction of Dolomite-Carbon Hybrid System

作　　者：陈杰[1] 胡发平[1] 潘佳[1] 马欣[1] 彭晓东[1,2] 谢卫东[1,2] 

机构地区：[1]重庆大学材料科学与工程学院,重庆400045 [2]重庆大学国家镁合金材料工程技术研究中心,重庆400044

出　　处：《稀有金属》2014年第2期306-311,共6页Chinese Journal of Rare Metals

基　　金：国家科技部国际科技合作计划项目(2010DFR50010);国家大学生创新性实验计划项目(1210611007)资助

摘　　要：分析了以白云石制备金属镁的现有技术中,热分解、热还原等环节资源能源利用不充分、环境载荷重、生产效率低等问题,提出了白云石与碳的混合物一次装料后先后完成热分解和热还原,获得金属镁、钙的新方法,计算分析了单纯白云石和白云石-碳体系常压热分解、真空热分解的Gibbs自由能和临界条件,以及煅烧白云石碳热还原制备金属镁及金属钙的Gibbs自由能和临界条件。结果表明,在较高的反应温度、较低的系统气压(真空度)下,白云石-碳体系热分解反应、煅烧白云石碳热还原反应均具备热力学可行性;白云石-碳体系的临界热分解温度略高于单纯白云石热分解温度,但最高临界分解温度仅增加17.04 K,且副产物CO的利用价值高;真空度可显著减小白云石-碳体系热分解和煅烧白云石碳热还原反应的Gibbs自由能,显著降低热分解、热还原临界温度,当系统真空度为10 Pa时,最高临界热分解温度、MgO临界还原温度、CaO临界还原温度分别为754.38,1353.95,1531.41 K,分别较常压大气环境中低369.38,765.26,897.26 K;碳热还原MgO,CaO的临界反应条件差异较大,可通过调控适宜的温度、真空度及其组合,创造只获得金属镁、先获得金属镁再获得金属钙、同时获得金属镁和金属钙等反应条件,实现白云石资源的合理、高效利用。The thermal decomposition and thermal reduction procedures of present magnesium manufacture technique, based on dolo- mite minerals, had numerous issues on the depletion of resource and energy, the heavy environmental loading and the low production efficiency. A new method of preparing metallic magnesium and calcium was proposed, by putting dolomite-carbon hybrids into a vacu- um pot where the thermal decomposition and thermal reductions of hybrids were completed sequentially in once loading. The Gibbs free energy and critical reaction conditions of sole dolomite＇s and dolomite-carbon hybrids＇ decomposition at atmospheric pressure and under vacuum condition were calculated and analyzed, and that of preparing metallic magnesium and calcium through carbothermal reduction of calcined dolomite was calculated and analyzed as well. The results indicated that the thermal decomposition reaction of dolomite-car- bon hybrids and the thermal reduction reaction of calcined dolomite under higher reaction temperature and lower system gas pressure （ the vacuum degree） were feasible from the perspective of thermodynamics. The critical thermal decomposition reaction temperature of dolomite-carbon hybrids was slightly higher than that of the sole dolomite thermal decomposition reaction, however, the highest criticaldecomposition temperature just increased by 17.04 K and the by-product CO had high utilization value. Besides, the vacuum degree could largely diminish the Gibbs free energy of dolomite-carbon hybrids＇ thermal decomposition reaction and calcined dolomite＇ carboth- ermal reduction reaction; when the system vacuum degree was 10 Pa, the highest critical temperature of decomposition reaction, the critical reduction temperature of MgO and CaO, was 754.38, 1353.95, 1531.41 K, respectively, compared with that at atmospheric pressure, which was lowered by 369.38,765.26, 897.26 K. In addition, the difference between the critical reduction temperature of carbothermal reduction MgO and CaO was quite great, and the prep

关 键 词：白云石 热力学 Gibbs自由能 真空 碳 

分 类 号：TG292[金属学及工艺—铸造] TG316.3