Investigation of the effects of operating parameters on the local mass transfer coefficient and membrane wetting in a membrane gas absorption process

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• Local overall gas side mass transfer coefficients and membrane wetting were investigated.
• The experimental KG was compared with the simulation results from a rate-based model.
• The wetting fractions along the length of membrane modules were not constant.
• The membrane wetting was affected by liquid velocity at a low wetting fraction.
• The use of CO2 loaded MEA solution could significantly reduce membrane wetting.

This work presents an investigation of local gas side overall mass transfer coefficient (KG) of the membrane gas absorption process determined from CO2 concentration gradients. The experimental KG was compared with simulation results of non-wetted and partially wetted modes of operation from a plug flow and rated based model to study the effects of various operating parameters on the partial wetting of the membrane and its process performance. The experiments were performed using two types of membranes (polytetrafluoroethylene, PTFE and polyvinylidene fluoride, PVDF), and two absorbents (monoethanolamine, MEA and 2-amino-2-methyl-1-propanol, AMP). A comparison showed that the membrane wetting fraction was lowest at the liquid outlet and varied along the length of the membrane module due to the effect of pressure drop. The effect of liquid velocity on membrane wetting was very obvious at a low membrane wetting fraction whereas it was less noticeable at a higher membrane wetting fraction. The average membrane wetting fractions were lower when PTFE was used with MEA solution than when PVDF and AMP solutions were used in experiments. In addition, the results further showed that the use of CO2 loaded MEA solution could significantly reduce membrane wetting.