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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。
In the prior art, dolomite was used to prepare metallic magnesium. The problems of inadequate utilization of energy resources such as thermal decomposition and thermal reduction, heavy environmental load and low production efficiency were put forward. After the mixture of dolomite and carbon was charged for one time, The thermal decomposition and thermal reduction were completed to obtain the new method of magnesium and calcium metal. The Gibbs free energy and critical conditions of atmospheric thermal decomposition and vacuum thermal decomposition of simple dolomite and dolomite-carbon system were calculated and analyzed, and the calcined dolomite carbothermal reduction Gibbs Free Energy and Critical Conditions for Preparation of Metallic Magnesium and Metallic Calcium. The results show that both the pyrolysis reaction of dolomite-carbon system and the carbothermal reduction of calcined dolomite are thermodynamically feasible at higher reaction temperature and lower system pressure (degree of vacuum); the critical of dolomite-carbon system The thermal decomposition temperature is slightly higher than the thermal decomposition temperature of dolomite, but the maximum critical decomposition temperature is only increased by 17.04 K, and the by-product CO value is high. The degree of vacuum can significantly reduce the thermal decomposition and calcination of dolomite carbon The Gibbs free energy of the thermal reduction reaction significantly reduces the critical temperature for thermal decomposition and thermal reduction. When the system vacuum is 10 Pa, the maximum critical thermal decomposition temperature, the critical reduction temperature of MgO and the critical reduction temperature of CaO are 754.38, 1353.95 and 1531.41 K, respectively Respectively, which are 369.38, 765.26 and 897.26 K lower than those under atmospheric pressure respectively. The critical reaction conditions for carbothermal reduction of MgO and CaO are quite different. By controlling the appropriate temperature, degree of vacuum and their combinations, Obtaining the metallic magnesium to obtain the metallic calcium, and simultaneously obtaining the reaction conditions of the metallic magnesium and the metallic calcium to realize the reasonable and efficient utilization of the dolomite resource.