The Study On Gas-Liquid Two-Phase Flow And Mass Transfer Of CO₂ Absorption Into Mixed-Amine Aqueous Solutions In Microchannels

Microreactor shows great application potential in the processes of gas absorption,mixture and chemical reaction.In recent years,the study on the two-phase flow and mass transfer performance in microchannel has become a frontier and hotspot in the field of chemical engineering.In this paper,the microchannel,the fluid control system,the image acquisition and recording system,and the pressure measurement system were used to investigate the gas-liquid two-phase flow and mass transfer of CO₂absorptionintoN-MethyldiethanolaMine/2-amino-2-methyl-1-propanol?MDEA/AMP?aqueous solution and N-MethyldiethanolaMine/Diethanolamine?MDEA/DEA?aqueous solution in microchannel.The flow pattern and bubble formation frequency of gas-liquid two-phase flow in microchannel with mass transfer process were studied.The slug-bubbly flow,the slug flow and the slug-annular flow were observed.The effects of the gas and liquid phase flow rates and the liquid phase property on the bubble formation frequency were investigated.Then a correlation for predicting the bubble formation frequency was proposed,which indicated a good prediction performance.The void fraction and pressure drop of gas-liquid two-phase flow in microchannel were studied by the image acquisition and recording system.The results showed that,the void fraction increased with increasing the gas phase flow rate,or decreasing the liquid phase flow rate and the liquid phase concentration.Based on the experimental data,the Lockhart-Martinelli prediction model for void fraction was optimized.The results also showed that,when increasing the flow rates of gas and liquid phases and the liquid phase concentration of alcohol amine,the pressure drop increased.On the basis of the Lockhart-Martinelli model,Cp was modified to improve the predictive performance for pressure drop.In addition,the physical pressure drop model was modified through taking the effect of chemical reaction on the length of the bubble into consideration,the modified model showed a good prediction performance.The mass transfer performances of CO₂ absorption into MDEA/AMP aqueous solution and MDEA/DEA aqueous solution were investigated.An online method was used to obtain the mass transfer coefficient k,the specific interfacial area a and the volumetric mass transfer coefficient ka.The enhancement factor E was calculated based on the Higbie theory.The results showed that,the mass transfer coefficient k,the volumetric mass transfer coefficient ka and the enhancement factor E increased with increasing the gas phase or liquid phase flow rates and increasing the liquid phase concentration.The specific interfacial area a increased with increasing the gas phase or liquid phase flow rate,but decreased with increasing the liquid phase concentration.A new model of volumetric mass transfer coefficient was proposed on the basis of the surface renewal model,by which the enhancement factor E could be predicted.Moreover,the energy dissipation model and the dimensionless predictive model were modified,respectively.All three predictive models indicate good prediction performance for the volumetric mass transfer coefficient.