Chemical Enhancement for CO2 Absorption into Dilute Aqueous Amine Solutions

以稀薄醇胺水溶液吸收二氧化碳時之化學促進作用

沈瑞富(Jui-FU Shen) ； 楊毓民(Yu-MIn Yang) ； 馬哲儒(Jer-Ru Maa)

《Journal of the Chinese Institute of Chemical Engineers》 31卷1期 (2000/01) Pp. 11-18

https://doi.org/10.6967/JCICE.200001.0011

摘要

本文以批式攪拌吸收器量測稀薄之醇胺(MEA)及二乙醇胺(DEA)水溶液吸收二氧化碳時反應促進因子。同時進行熱力模擬計算，結果顯示：在眾多反應中，濃醇胺溶液內之化學反應可以簡化由單一氨基甲酸根(carbamate)生成反應來代表，即此時氨基甲酸根很穩定；但稀薄溶液內大部份的氨基甲酸根卻會進一步水解，再生成自由醇胺，所以它的化學吸收模式江比濃溶液吸收系統更複雜。本文利用實驗數據檢驗兩項分別代表氨基甲酸根水解程度處於上下限的吸收機制：(a)代表水解反應已達化學平衡之大部平衡機制(bulk-equilibrium mechanism)與(b)代表水解反應完全沒進行之兩性離子機制(zwitterions mechanism)。結果顯示：由於當吸收負載小於0.3的情況，MEA和DEA水溶液內氨基甲酸根水解程度還很低，所以兩性離子機制的預測準確度最高，但當吸收負載繼續增加後，其累積的水解程度已漸漸顯著地影響化學吸收，所以在高吸收負載時期，大部平衡機制的預測準確度反而更高。

並列摘要

Chemical enhancement factors for CO2 absorption into dilute aqueous MEN/DEA solutions in a batch stirred-cell absorber were experimentally determined over a wide range of CO2 loadings. The experimental data are used to examine the validity of two promotion mechanisms: the zwitterion mechanism, by which the carbamate formation is the sole main reaction occurring in the liquid, and the bulk-equilibrium mechanism, by which both the carbamate formation and the carbamate hydrolysis are two fast main reactions to enable the chemical equilibrium to prevail in the bulk-liquid. The results reveal that the zwitterion mechanism satisfactorily predicts the experimental data for CO2 loadings below 0.3, while the bulk-equilibrium mechanism is more competent in describing those for CO2 loadings larger than 0.5. A detailed rigorous thermcx1ynamic simulation shows that the equilibrium extent of the carbamate hydrolysis, which generates free amine in the bulk and hence promotes absorption, increases with the decrease of the initial amine concentration and with the proceeding of CO2 loadings. The experimental re-suits of absorption, therefore, indicate that the extent of the carbamate hydrolysis is insignificant in systems with low CO2 loadings however becoming significant in higher C2 loading systems. The difference between the promotion mechanisms for the absorption of CO2 by dilute aqueous NH3 solutions as previously reported by us and that by MENDEA solutions in this work is also discussed .

並列關鍵字

Gas Absorption ； Chemical Enhancement ； Carbon Dioxide ； Aqueous Amine Solution ； Garbamate Hydrolysis