Potentialities of a dense skin hollow fiber membrane contactor for biogas purification by pressurized water absorption

Abstract

Gas purification technologies are a key step in the technological chain using energy sources such as natural gas, coal gas or biogas, and represent a significant part of production costs. Numerous separation technologies exist to achieve required purity specifications depending on the particular application (absorption, adsorption, cryogenic, membranes). The objective of this work is to present an evaluation of the potentialities of using a membrane contactor based on a dense skin Poly (Phenylene Oxide) (PPO) hollow fiber module for CO2 absorption from biogas by pressurized water through simulations and experiments. In this system, the liquid flowing on the shell-side is in direct contact with the dense skin, thus enabling pressurization and avoiding membrane wetting in order to maintain stable absorption performances.The overall mass transfer coefficient Kov, CO2 removal efficiency, and CH4 loss are evaluated for a range of liquid and gas flow rates. A one-dimensional (1D) model based on resistance in series provides very good predictions of the experimental results when the Graetz approach is used for shell-side mass transfer calculations.Membrane mass transfer resistance is shown to be negligible compared to the liquid resistance. Consequently, the overall mass transfer performances of the dense skin contactor are close to typical values of packed columns (10−5–10−4m/s). Thanks to the increased gas-liquid interfacial area offered by the membrane contactor, a significant volume reduction of the absorption unit (up to 15 process intensification factor) is potentially achievable. Moreover, a selective dense skin could minimize methane losses.