Abstract
Porous asymmetric polyetherimide (PEI) hollow fiber membranes with various non-solvent additives, e.g. lithium chloride, methanol and phosphoric acid (PA) were prepared for CO2 absorption and stripping process in a membrane contractor. The PEI membranes were characterized via gas permeation, liquid entry pressure of water (LEPw), contact angle and field emission scanning electronic microscopy analysis. The CO2 absorption and stripping performance was evaluated via the membrane contactor system. Addition of non-solvent additives increased the LEPw and membrane porosity of the PEI membrane with the formation of various membrane microstructures and contact angles. Absorption test was performed at 40 °C showed that the PEI–PA membrane produced the highest absorption flux of 2.7 × 10−2 mol m−2 s−1 at 0.85 m s−1 of liquid velocity. Further testing on PEI–PA membrane was conducted on CO2 stripping at 60 °C, 70 °C to 80 °C and the results indicated that the stripping flux was lower compared to the absorption flux. Stripping tests at 80 °C produced the highest stripping flux which might due to the increase in equilibrium partial pressure of CO2 in the liquid absorbent. Modification of PEI membrane via incorporation of additive can enhanced the performance of a membrane contactor via increasing the absorption and stripping flux.
Highlights
In the conventional absorption process for CO2 removal, physical and chemical solvents are used extensively as liquid absorbents for the removal of acid gases especially in the petrochemical industry
We focused on the performance of a PEI hollow ber membrane for absorption and stripping in a membrane contactor system with the presence of non-solvent additives in the polymer dope
Tap water was used as the coagulation bath medium for the spinning process. 99% MEA purchased from Merck was used to prepare 1 M aqueous solution as the liquid absorbent and 99% CO2 was used as the loading gas
Summary
A combination of microporous membrane and amine solution standing side by side without mixing with each other; have been a centre of attention due to its favourable features such as modular design, emulsion free, easy scaling-up, known surface area that remains undisturbed at high and low ow rates and no moving parts.[3] This is in contrast with conventional methods which constantly creates technical problems such as ooding, entrainment and foaming The highlight of this system is the membrane itself where it should remain non-wetted by the liquid absorbent when operated at prolong hours. A previous study by Bakeri et al.[10] implemented various nonsolvent additives such as methanol, ethanol, glycerol and acetic acid in polyetherimide (PEI) hollow ber membrane for CO2 absorption in distilled water They highlighted that the highest absorption ux achieved was 1.85 Â 10À3 mol mÀ2 sÀ1 for PEI– methanol which produced the lowest membrane mass transfer resistance. The membrane properties were examined, and the CO2 absorption and stripping performance was further evaluated based on the speci c operating condition in the membrane contactor system
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