The Research On The Effect Of Gas Phase Resistance On The Intrinsic Kinetics Of Carbon Dioxide Absorption

The intrinsic kinetics of gas-liquid reactions have been widely studied in stirred cell reactor experiments.In this work,in order to be able to understand and compensate for the mass transfer effects on the reaction kinetics that typically occur in these studies,the influences of diffusion and gas phase resistance on the measurement of kinetics have been investigated.Carbon dioxide（CO₂）absorption into monoethanolamine（MEA）and N-methyldiethanolamine（MDEA）,have been respectively taken as the fast and slow reaction cases in this work.Firstly,the investigation of CO₂ absorption rates under different initial CO₂ partial pressures was carried out in both MEA and MDEA systems.The inflection point between diffusion control and reaction control regions was found in the fast reaction case,but not in the slow one.This indicates that P_CO2 should be maintained below the inflection point in the cases of fast reaction systems,but that this is not necessary in slow reaction cases.Secondly,a series of CO₂ absorption experiments under different inert gas partial pressures(P_inert)was performed.The mass transfer in the faster reaction case is much more sensitive to P_inert than it is in the slow reaction case,which indicates P_inert should be controlled to be as low as possible in order to keep this effect negligible in the case of the fast reaction system.Conversely,the critical value of P_inert in the slow reaction system can be much higher.Finally,credible intrinsic kinetics of CO₂ absorption into aqueous MEA and MDEA solution have been obtained under optimum conditions based on the conclusions above,respectively,thus expanding the temperature range to lower than what is available in the literature.Based on the theory of gas-liquid mass transfer permeability,this work established a preliminary gas-liquid mass transfer model by using fick’s law and navier-stokes equation.Matlab was used to calculate the data of the model,and the model was verified and modified by combining with experimental data.The average absolute deviation between the predicted data of the mathematical model and the experimental data is only 5.2%.The model can not only fully describe the gas-liquid mass transfer process,but also the influence of the gas-phase resistance in the mass transfer process can be observed.At the same time,it can also be used as a calculation method of the intrinsic kinetics of the gas-liquid reaction,laying a foundation for the calculation of various data in the gas-liquid mass transfer process in the future.