Effect of porosity on mass transfer of gas absorption in a hollow fiber membrane contactor

• A model was proposed for hollow fiber contactor (HFC) in consideration of porosity.
• Effect of porosity on mass transfer of gas absorption in HFC was elucidated.
• Effect of porosity at vertical and parallel diffusion dominant states was clarified.
• Increasing the pH or flow velocity of absorbent intensifies the effect of porosity.
• Effect of porosity grows with decreasing fiber length or enlarging pore size.

A mathematical model was proposed to elucidate the mass transfer of a hollow fiber membrane absorption process taking the effect of membrane porosity into account. This model was derived based on the mass transfer differential equation and discretized considering the micropores on the membrane wall. The model was numerically solved by using upwind difference technique, and the solute concentration profiles were obtained. Effects of porosity under various conditions, including membrane pore size, fiber length, pH of absorbent and liquid velocity on the mass transfer process, were quantitatively investigated. The results indicated that the porosity plays an important role in forming the solute concentration profile, and thus influenced the mass transfer performance. Low porosity (or high pH and liquid velocity, or low fiber length) corresponded to the heterogeneous profiles, while opposite conditions led to the homogeneous profiles. The model gave calculation results in good agreement with experimental results.