摘要
Magnesium hydroxide(Mg(OH)2)has been considered as a potential solvent for CO2 removal of coal-fired power plant and biomass gas.The chemistry action and mass to transfer mechanism of CO2-H2O-Mg(OH)2 system in a slurry bubble column reactor was described,and a reliable computational model was developed.The overall mass transfer coefficient and surface area per unit volume were obtained using experimental approach and simulation with software assistance.The results show that the mass transfer process of CO2 absorbed by Mg(OH)2 slurry is mainly liquid-controlled,and slurry concentration and temperature are main contributory factors of volumetric mass transfer coefficient and liquid side mass transfer coefficient.High concentration of CO2 has an adverse effect on its absorption because it leads to the fast deposition of MgCO3·3H2O crystals on the surfaces of unreacted Mg(OH)2 particles,reducing the utilization ratio of magnesium hydroxide.Meanwhile,high CO3^2– ion concentration limits the dissolution of MgCO3 to absorb CO2 continually.Concentration of 0.05 mol/L Mg(OH)2,15%vol CO2 gas and operation temperature at 35℃are recommended for this CO2 capture system.
氢氧化镁被认为是燃煤电厂和生物质气脱碳的潜在溶剂。本文描述了浆态床鼓泡反应器中CO2-H2O-Mg(OH)2体系的化学作用和传质机理,建立了可靠的计算模型。利用实验方法和软件辅助仿真,得到了总传质系数和单位体积表面积。结果表明:Mg(OH)2浆体吸收CO2的传质过程主要是液膜控制过程,其中浆液浓度和反应温度是影响气泡塔反应器体积传质系数和液相传质系数的主要因素。高浓度的二氧化碳对其吸收有不利影响,因其导致MgCO3·3H2O晶体快速沉积在未反应的Mg(OH)2颗粒表面,降低了氢氧化镁的利用率。同时,高CO3^2–离子浓度限制了MgCO3的溶解,使其不能持续吸收CO2。建议二氧化碳捕集系统的反应条件为氢氧化镁溶液浓度0.05 mol/L,二氧化碳体积浓度15%,反应温度35℃。
基金
Project(21878338)supported by the National Natural Science Foundation of China
Project(2015BAL04B02)supported by the National key Technology R&D Program of China
Project(2018K2038)supported by the key Research and Development Project of Hunan Province,China
Project supported by Hunan Collaborative Innovation Center of Building Energy Conservation&Environmental Control,China
