Mass transfer study and modeling of gas–liquid membrane contacting process by multistage cascade model for CO 2 absorption

Abstract

The objective of this work was to characterize the main mass transfer resistance for CO 2 capture in the gas–liquid membrane contacting process by both physical and chemical absorption conditions. The characterization was performed based on the resistance-in-series model as well as the Wilson-plot method. In addition, a multistage cascade model, which is able to predict the time for the system to reach a steady-state condition, was developed to describe CO 2 absorption in the membrane contacting process. The cascade model was numerically solved by using the MATLAB program. It was found that the main mass transfer resistance of the physical absorption (using pure water as an absorbent) and the chemical absorption (using 2 M NaOH as an absorbent) was in the liquid phase and in the membrane, respectively. The membrane mass transfer resistance in the case of physical absorption presented approximately 36% of the total resistances at a liquid velocity of 2.13 m/s. For the chemical absorption condition applied, the membrane mass transfer resistance occupied around 99% of the total resistance. The results of simulation by the cascade model agreed well with the experimental results when the overall mass transfer coefficient obtained form the experiment was employed. The model can potentially be used with various operating conditions including the liquid velocity, gas concentration, and reactive absorbent used.