Mg(OH)_2浆液吸收脱碳过程的组分动态分析

Dynamic analysis of the main components of the absorption process of capturing CO_2 with Mg(OH)_2 slurry

为了探究Mg(OH)_2浆液在鼓泡塔中吸收CO_2的过程原理,采用实验和理论计算对Mg(OH)_2-CO_2-H_2O吸收体系进行了组分浓度动态分析。研究结果表明:该吸收过程依据反应产物可分为3个阶段,第一阶段为Mg(OH)_2与CO_2反应生成Mg(HCO_3)_2的过程,第二阶段为Mg(OH)_2将CO_2固定为MgCO_3的过程,第三阶段为MgCO_3对CO_2的吸收过程;随着气相CO_2浓度升高,可发现高浓度(体积分数20%~30%)吸收过程会出现第二阶段消失的特殊现象;当CO_2分压一定时,第一阶段反应时间长度几乎不随Mg(OH)_2浓度而变化,第二阶段和第三阶段反应时间长度则与Mg(OH)_2浓度成正比,平衡时生成的MgCO_3固体含量与浆液初始浓度成正比;20~50℃,第一阶段反应时间长度与温度成反比,低温区间(20~35℃),第二阶段和第三阶段反应时间长度随温度升高而缩短,高温区间(35~50℃)则相反,35℃左右,吸收达到平衡时间最短。

In order to explore the principle of CO2 capturing by Mg（OH）2 slurry in bubble column,experiments and theoretical simulation were selected to analyze the component concentration dynamic variation in Mg（OH）2-CO2-H2O system.The research revealed that there are three stages on the basis of the reaction products in absorption process,namely,CO2 reacting with dissolved Mg（OH）2 in the slurry to generate Mg（HCO3）2 in the first stage,Mg（OH）2 particles continueously dissolving and being carbonized into MgCO3 in the second stage,CO2 being captured by MgCO3 in the third stage.With CO2 concentration enrichment,the second stage disappeares in high CO2 concentration（volume fraction is 20%—30%）absorption process.When CO2 partial pressure is constant,reaction time of the first stage almost has noting to do with Mg（OH）2 concentrtion,reaction time of the second and third stage and MgCO3 solid content at quilibrium are proportional to Mg（OH）2 concentrtion.Reaction time of the first stage varies inversely to temperature（20—50℃）.Reaction time of the second and third stage are shortened with temperature increasing at low temperature zone（20—35℃）,while it is exactly the opposite at high temperature zone（35—50℃）.The shortest time it took to reach the quilibrium state occurs around 35℃.