Study Of The Intensification Of Mass Transfer In The Membrane Gas Absorption Process

Membrane gas absorption technology is one of the most promising alternatives to conventional technologies in carbon dioxide (CO2) capture. However, the heterogenous concentration profile near the membrane surface caused by inducing the microporous membrane decrease the mass transfer rate, and the non-ideal flow condition in the hollow fiber module shell-side also deteriorate the overall mass transfer. For the purpose of overcoming theses issues, experimental and modeling study on intensification of mass transfer in the membrane gas absorption process has been carried out in this work.Mathematical model considering the effect of porosity and mathematical model for the intensification process based on surface renewal theory are developed. The effects of solid loading, membrane porosity, absorbent pH value and particle diameter have been investigated. The calculated results have a good agreement with the experimental results.Pure CO2 was absorbed by de-ionized water or NaOH aqeous solution using membranes with different porosities in the flat-sheet membrane contactor. In order to improve the distribution of the concentration of solute near the membrane surface, solid particles are added into the absorbent liquid to enhance the turbulence in the boundary layer. The difference of mass transfer coefficient obtained by varied porosities declined by adding solid particles into the absorbent liquid. The higher enhancement factor is obtained at lower porosity.A method of improving the absorption performance in hollow fiber contactor by adding the third solid phase into the shell-side absorbent is proposed. Ultrasound is used in this work as an approach to make the solid particles suspending in the absorbent. The mass transfer rate is enhanced above 40% by adding solid particles into the absorbent, and the enhancement factors increase with an increase of the packing density. The residence time distributions (RTD) curves are measured, which demonstrate that the addition of the solid particles can improve the flow conditions in the shell-side.The influence of shaking on the flow condition in the shell-side of the module and the mass transfer of hollow fiber membrane gas absorption process has been investigated. The results of absorption experiments indicate that the shaking of module raises the mass transfer coefficient above 50%. The mass transfer improvement is higher when the shaking direction vertical to the liquid velocity direction. The shaking of the module can improve the flow status in the shell side of the hollow fiber modules.