CO_2矿化反应基础研究Ⅱ.有机胺介质中碳酸化反应热力学研究

CO_2 mineralization fundamental research Ⅱ.The thermodynamic equilibrium of carbonation in ternary amine

对有机胺介质中CaCl2与二氧化碳的碳酸化反应进行了研究,在二氧化碳压力为2 MPa～5 MPa、CaCl2浓度为1.31 mol/L～2.44 mol/L下考察了压力和浓度对该多相反应体系碳酸钙收率和有机胺萃取效率的影响。结果表明,碳酸化反应过程中碳酸钙收率和有机胺萃取效率随二氧化碳压力和CaCl2初始浓度的增大而增加。结合Pitzer电解质溶液模型、二氧化碳溶解模型对该多相反应进行热力学平衡分析。有机胺的萃取平衡决定了HCl在有机相和水相的分配平衡,水相中H+浓度限制H2CO3解离,制约碳酸钙沉淀反应。CaCl2浓度大小影响了HCO3-和CO32-的活度系数,对沉淀/溶解平衡也有一定影响。热力学平衡转化率与实验结果接近,表明该反应受化学反应平衡控制。

The reaction of CaCl2 solution with CO2 in ternary amine was studied.In this multiphase reaction,calcium carbonate yield and amine extraction efficiency increased with the increase of CO2 pressure and CaCl2 concentration.The equilibrium of the reaction was analyzed by thermodynamics model coupled with Pitzer electrolytic solution model and a modified Henry＇s law CO2 solubility model.The distribution of hydrochloric acid in aqueous and amine is restricted by extraction equilibrium.The concentration of H＋ could affect the dissociation of carbonic acid,which determines calcium carbonate precipitation/dissolution equilibrium.The activity coefficients of HCO3-and CO32-decreased with the increase of CaCl2 concentration at constant CO2 pressure condition,and influenced the equilibrium.The calcium carbonate yield and amine extraction efficiency were close to the calculated equilibrium values,and the reaction is controlled by chemical equilibrium.