Modeling Study On The Gas Phase Mass Transfer Behavior In Embrane Absorption Process

During the1990s, Since Qi and Cussler firstly proposed themembrane gas absorption technology, many researchers worked onmembrane gas absorption process, which has been considered to be apromising and potential large-scale application had technology for therecovery of CO₂. The membrane gas absorption technology wasconsidered to be one of the most effective methods to trapping thegreenhouse gases. The gas phase resistance became the major resistancein a membrane based gas absorption process when the absorbent had thecharacteristic of quick absorption, and larger absorption capacity. Inaddition, the micro scales of the membrane had significant effect on masstransfer.CO₂/N₂mixture with a volume ratio of1/1¹/99was used as thefeed gas while de-ionized water and the NaOH aqueous solution wereemployed as absorbents. The effects of membrane porosity, pore radius,absorbent pH value, liquid velocity and fiber length on mass transferprocess were investigated. The model results show that by increasing theabsorbent pH, liquid velocity or decreasing CO₂partial pressure, the mass transfer coefficient increased, and the membrane micro-structure hassignificantly influences on mass transfer performance.Based on the flat sheet membrane mass transfer model, a hollowfober mass transfer model is established. The effects of membraneporosity, pore radius, absorbent pH value, liquid velocity and fiber lengthon mass transfer process are investigated. The model was validated withthe experimental results using PVDF hollow fiber membrane contactorwith distilled water and NaOH aqueous solution as the liquid solvent. Themodeling predictions were in good agreement with the experimentalresults for different liquid velocity.