Dynamic Study Of Membrane Wetting In The Hollow Fiber Membrane Contacting Process For CO₂ Absorption

Recently,the greenhouse effect caused by CO2 gas is becoming more and more serious,so finding an effective method to separate and absorb C02 gas in order to cope with global warming is an urgency.Membrane contactor capture C02 technology is recognized as the most feasible and effective method,which has aroused the concern of many scholars.However,membrane wetting phenomenon has been the biggest bottleneck of this technology,which may cause a significant decline in the total mass transfer coefficient and a sharp rise of membrane resistance.Therefore,it is imminent to study how to slow down the membrane wetting and establish the dynamic equation of the membrane resistance and the experimental run time.In this paper,the aqueous diethanolamine solution was selected as the absorbent to capture C02 in the PVDF hollow fiber membrane contactor.Sodium chloride was employed as an additive in DEA solutions.The effects of temperature,concentration,liquid flow rate and the pressure difference of gas-liquid two-phase on the total mass transfer coefficient and the membrane resistance were investigated.The dynamic equations of membrane resistance and experimental run time were established by two regression methods.The experimental results show that:(1)It is the exaltation of temperature,speed-up of liquid flow,amplification of the pressure difference between gas and liquid that will lead to the decline in total mass transfer mass and the rise of membrane resistance rise.(2)The effect of concentration on membrane wetting is relatively complicated.When the concentration of solution increases in 15℃,the total mass transfer coefficient decreases and membrane resistance increases.When the temperature is 35℃,increasing the concentration of solution leads to the increase of the total mass transfer coefficient and the reduction of membrane resistance.(3)Sodium sulfate as an additive employed to DEA solution can not slow the membrane wetting;but adding a certain concentration of sodium chloride,to some extent,can slow down the film wetting.When 0.25 mol·L-1 of sodium chloride was added in 1 mol·L-1 DEA solution in 35 ℃,the effect of slowing the film wetting is the most obvious.Adding a small amount of sodium alginate the DEA solution at a temperature of 35℃,to a certain extent,can slow down the membrane wetting.(4)When the concentration of DEA solution is 2 mol·L-1,the parameter values change from 2.41×10-3 to 3.06×10-3 in the empirical model similar to the Arrhenius equation.The overall change of the model parameters is small.Whereas,the model parameter values of the first-order kinetics equation change from 3.33×10-3 to 5.04×10-3,the overall variation is larger.Similarly,the correlation coefficient of the parameter values in the empirical model similar to the Arrhenius equation is in the range of 0.954-0.994.While the correlation coefficient of the parameter value of the first-order kinetic equation is in the range of 0.900-0.984.Both kinetic equations can accurately and effectively predict and calculate the mass transfer resistance at any time.