Abstract:

The Level-set two-phase flow coupled component mass transfer equations were used to simulate the CO₂ absorption by alkali liquor in three-dimensional T-junction cylindrical microchannels. The bubble formation and flow process, the characteristics of interphase transfer and absorption were analyzed, and the effects of inlet gas velocity, liquid velocity and alkali concentration on the CO₂ chemical absorption and mass transfer were mainly discussed. The results show that, for gas velocity of 0.08 m/s and the liquid velocity of 0.03 m/s, the formation time of a single bubble is about 0.012 s, and the bubble moving speed is almost equal to the inlet gas velocity, showing the alternating Taylor flow characteristics of bubbles and liquid plugs. The CO₂ absorption rate reaches its maximum at the initial stage of bubble formation, and gradually decreases along the outlet direction along with the decrease of mass transfer force at gas-liquid interface. When the gas velocity increased from 0.05 m/s to 0.1 m/s, the CO₂ absorptivity decreased from 62.6% to 34.8%. Conversely, when the liquid velocity increased from 0.01 m/s to 0.05 m/s, the CO₂ absorptivity increased from 18.5% to 48.4%. Furthermore, increasing the absorbent concentration from 50 mol/m³ to 250 mol/m³ raises the absorptivity from 50.8% to 79.3%.

Key words: microchannel, absorption, mass transfer, CO₂ capture, numerical simulation

摘要：

采用水平集两相流耦合组分传质微分方程对三维T型微通道内的CO₂碱液吸收过程进行了数值模拟。分析了气泡形成及流动过程、相间传递及吸收特性，并重点探讨了进口气速、液速和碱液浓度对CO₂化学吸收传质的影响。结果表明，在气速0.08 m/s、液速0.03 m/s时，单个气泡形成时间约为0.012 s，气泡移动速率几乎等于进口气速，展现气泡和液塞交替的泰勒流特征。CO₂吸收溶解速率在气泡形成初始阶段溶解速率最大，随着气液相相互接触传质推动力逐渐降低，沿出口方向的气液两相界面上逐渐下降。气速0.05 m/s增加到0.1 m/s时，CO₂吸收率从62.6%降低到34.8%，当液速从0.01 m/s增加到0.05 m/s时，CO₂吸收率从18.5%提高48.4%。吸收剂浓度从50 mol/m³增加到250 mol/m³，吸收率由50.8%提高到79.3%。

关键词: 微通道, 吸收, 传质, 二氧化碳捕集, 数值模拟