碳热还原SO2反应选择性的热力学分析及实验探究

A thermodynamical and experimental study on selectivity of the carbothermal reduction of sulfur dioxide

中文关键词: 碳热还原  化学热力学  吉布斯自由能  固定床  FTIR

英文关键词: carbothermal reduction  chemical thermodynamics  gibbs free energy  fixed bed  FTIR

中文摘要:

      针对燃煤烟气SO2脱除技术面临的可持续发展困境,以固体碳材料为还原剂的碳热SO2还原制硫磺技术具有重要发展前景,其中抑制非目标副产物的伴生是实现SO2定向还原的关键。基于吉布斯自由能最小原理对碳热还原SO2反应进行平衡产物量的计算,并通过固定床-FTIR实验分析反应的气相产物,探究了硫产率、副产物CO、COS和CS2的生成的规律。基于温度对反应热力学平衡的影响,结合副反应,来推断出合理的反应机理。在摩尔比n(C):n(SO2)≤1.0时体系中主要发生反应C + SO2→ S+ CO2副产物CS2生成量级仅为10^-4,理论硫产率可维持在0.9以上。过量的碳会促进COS由主反应物一步生成,高温、碳过量会促进COS向CS_2的转化反应。相关研究结果对实际应用时最佳工况的选取以及单质硫选择性的提高具有重要指导意义。

英文摘要:

      In view of the sustainable development predicament faced by SO2 removal technology of coal-fired flue gas, the technology of preparing sulfur through the Carbothermal reduction of SO2 with solid carbon materials as reducing agenthas an important development prospect. And the inhibition of the by-products is the key to realize SO2 directional reduction. Based on the principle of minimum Gibbs free energy, the equilibrium product of the carbon thermal reduction of SO2 was calculated, and the gaseous products of the reaction was analyzed by fixed bed-FTIR experiment to explore the sulfur yield and the law of CO, COS and CS2 formation. Based on the effect of temperature on the thermodynamic equilibrium, a reasonable reaction mechanism was deduced, combined with the side reactions proposed by previous researchers. The reaction of C + SO2→S + CO2 mainly took place atn(C):n(SO2)≤1.0, the magnitude of the byproduct CS2 was only 10-4 mol, and the theoretical sulfur yield was above 0.9. Excess carbon would promote COS generated by the main reactants in one step, and high temperature and carbon excess would promote the conversion reaction of COS to CS2. The results are of important to the selection of the best working conditions and the improvement of the elemental sulfur’s selectivity.