Mass Transfer Performance For CO₂ Absorption Into MEA-based Compound Solution In A Hollow Fiber Membrane Contactor

The combustion of fossil fuels resulted in a large amount of CO₂ gas emitted into the atmosphere,causing a series of problems such as global warming and melting of glaciers.Therefore,it is extremely urgent to reduce CO ₂ emissions from coal-fired power plants.The chemical absorption method based on alkanolamine solution is one of the most widely used CO₂ capture technologies in the industrial application.Effective absorbent coupled with effective mass transfer equipment can greatly reduce the operational cost of CO₂ capture process.Monoethanolamine?MEA?,as the most commonly used CO₂ absorbent,has the advantages of fast absorption rate and strong adaptability.Compared with traditional tower equipment,the hollow fiber membrane contactor has a large gas-liquid contact area and large operational flexibility,which can be regardesd as an efficient mass transfer device.However,due to the limitation of its own property,when the MEA solution captures CO₂ in the hollow fiber membrane contactor,it will face the problems of small absorption capacity,large regenerative energy consumption,and the possibility of wetting the hollow fiber membrane contactor.In order to optimize the absorption performance of absorbents,reduce the desorption energy of absorbents,and reduce the wettability of the membrane contactor,mass transfer performance for CO₂ absorption into MEA-based solution in hollow fiber membrane contactor was investigated.The main research content is as follows:?1?The effect of the molar ratio of potassium glycinate?PG?on the surface tension of 2.0 mol/L MEA/PG solution was investigated;The CO₂ absorption performance of mixed MEA/PG solution was tested under different operating conditions in a PTFE hollow fiber membrane contactor.The experimental results show that the higher the molar ratio of PG,the greater the surface tension of MEA/PG solution,and the less the possibility of wetting of the membrane material.For the system of MEA-PG-CO₂,the CO₂ absorbtion flux increases with the increasing inlet gas velocity,the CO₂ partial pressure,and the liquid velocity;and decreases with the increasing CO₂ loading of the lean liquid and the height of the contactor.In addition,two developed correlations for the prediction of CO ₂ absorption flux and CO₂removal rate of MEA/PG-CO₂ system in PTFE hollow fiber membrane contactor were proposed,and the predicted values obtained from the model were in good agreement with the experimental values.?2?A noval rapid screening method was proposed to investigate the influence of different molar ratios of mixed MEA/DMEA solution on the CO₂ absorption rate,desorption rate and cycle capacity.Solvent screening experimental results showed that blended MEA/DMEA solution with molar ratio of 1.0:1.0 exhibited the higher CO₂ absorption rate,desorption rate,as well as the highest CO₂ cyclic capacity.In addition,the experimental results also presented that the synergistic effect was observed during CO₂ absorption into MEA/DMEA solution,resulting in the increasing absorption and desorption rates.Then,the mass transfer performance of CO₂absorption into 1.0 mol/L MEA+1.0 mol/L DMEA solution was also investigated in a PTFE hollow fiber membrane contactor.The effects of liquid flow rate,feed temperature range,lean CO₂ loading,inlet gas flow rate and CO₂ partial pressure on the mass transfer performance were evaluated in terms of CO₂ absorption flux and overall gas phase mass transfer coefficient?K_G?.Furthermore,a developed correlation was proposed for prediction of mass transfer coefficient?K_G?for CO₂ absorption into MEA/DMEA solution in a hollow fiber membrane contactor.The predicted values determined from the correlations are in relatively good agreement with the experimental values,with average absolute relative deviation?AAR D?of 8.31%.This correlation is of great significance to the application of the hollow fiber membrane contactor in the field of CO₂ capture.