CO2 Absorption Using Hollow Fiber Membrane Contactors: Introducing pH Swing Absorption (pHSA) to Overcome Purity Limitation

Abstract

Recently, membrane contactors have gained more popularity in the field of CO2 removal; however, achieving high purity and competitive recovery for poor soluble gas (H2, N2, or CH4) remains elusive. Hence, a novel process for CO2 removal from a mixture of gases using hollow fiber membrane contactors is investigated theoretically and experimentally. A theoretical model is constructed to show that the dissolved residual CO2 hinders the capacity of the absorbent when it is regenerated. This model, backed up by experimental investigation, proves that achieving a purity > 99% without consuming excessive chemicals or energy remains challenging in a closed-loop system. As a solution, a novel strategy is proposed: the pH Swing Absorption which consists of manipulating the acido–basic equilibrium of CO2 in the absorption and desorption stages by injecting moderate acid and base amount. It aims at decreasing CO2 residual content in the regenerated absorbent, by converting CO2 into its ionic counterparts (HCO3− or CO32−) before absorption and improving CO2 degassing before desorption. Therefore, this strategy unlocks the theoretical limitation due to equilibrium with CO2 residual content in the absorbent and increases considerably the maximum achievable purity. Results also show the dependency of the performance on operating conditions such as total gas pressure and liquid flowrate. For N2/CO2 mixture, this process achieved a nitrogen purity of 99.97% with a N2 recovery rate of 94.13%. Similarly, for H2/CO2 mixture, a maximum H2 purity of 99.96% and recovery rate of 93.96% was obtained using this process. Moreover, the proposed patented process could potentially reduce energy or chemicals consumption.

The Effect of Sweeping Media and Temperature on Aqueous CO2 Removal Using Hollow Fiber Membrane Contactor (HFMC): An Experimental Determination

“…Among them, hollow fber membrane contactors (HFMCs) are commonly employed in medical, pharmaceutical, biological, and environmental applications. Extracorporeal membrane oxygenation (e.g., biohybrid oxygenators [6][7][8], extracorporeal CO2 removal (ECCO2R) [9,10], arterio-venous CO 2 removal (AVCO2R) and venovenous CO 2 removal (VVCO2R) devices [11][12][13]), hemodialysis [14,15], tissue culturing [16], membrane bioreactors used for wastewater treatment [17][18][19][20], air purifcation (e.g., fue gas absorbing and CO 2 capturing [21][22][23][24][25][26][27]), and reverse osmosis applied in, e.g., water purifcation [28] and concentration process [29] are various examples where HFMCs are employed as one of their major components. In several applications, such as AVCO2R and VVCO2R, aqueous CO 2 removal is considered the signifcant performance objective of HFMCs [30].…”

CO2/CH4 separation performance of SiO2/PES composite membrane prepared by gas phase hydrolysis and grafting coating in gas-liquid membrane contactor: A comparative study

“…The hydrophobic microporous hollow fiber membrane is typically used as an interface barrier in gas-liquid contactors, where it can act as a carrier for the two phases while separating the liquid and gas phases. It allows for efficient mass transfer between the gas and liquid phases while preventing them from mixing [ 12 ]. Throughout the whole mass transfer process, the mixed gas passes through the hollow fiber membrane on its way from the gas phase side of the membrane surface to the liquid phase side under the effect of shear force.…”

CO2 Capture and H2 Recovery Using a Hollow Fiber Membrane Contactor

“…Absorption on amino acid salts or highly viscous liquid such as glycerol solution in membrane contactors has been studied, leading to the creation of a numerical model of absorption with wetting characteristics such as surface tension and breakthrough pressure and the mass transfer phenomena [21,22]. Recently, a theoretical model of CO 2 absorption on acid-base equilibrium was calculated depending on pH swing and compared with the experimental and calculated results of a membrane contactor system coupled with an absorption, desorption, and loop system [23].…”