Amino Acid-Salt-Based Complex Absorbents for CO₂ Capture in a Membrane Contactor

Abstract

Phosphate or borate as an activating agent was added into the aqueous glycinate to form amino acid salt-based complex absorbents. Capture of CO2 by the complex absorbents was studied theoretically and experimentally using a hollow fiber membrane contactor. Reaction mechanism concerning the activation effect of phosphate and borate was presented theoretically. A mathematical model was developed to simulate mass transfer of the membrane contactor. The effects of absorbent and gas CO2 concentrations on mass transfer flux and CO2 capture efficiency were investigated. Surface tension of the complex absorbents and operational stability of the membrane contactor were also discussed in this work. Results show that the activation follows the sequence B4O7 2− > PO4 3− > HPO4 2− > H2PO4 −. The mathematical model was validated by comparing theoretical with experimental data. The mass transfer flux increased almost linearly with the increase of gas CO2 concentration. Surface tension data revealed that the complex absorbents could not wet the membrane micropores. The flux was basically kept constant during the prolonged period of operation. The complex absorbents modified by the phosphates and borates are good potential absorbents for CO2 capture.

Hollow fiber membrane contactor absorption of CO2 from the flue gas: Review and perspective

“…It can be seen that the surface tension follows the order: physical solutions<chemical solutions<amino acid salts<blended absorbents. The blend has the highest surface tension which is close to water (Lu et al, 2010a). Fu and Zhong (2010) found that the surface tension would follow a downward monotonic trend with increasing the temperature and the alcohol amine concentration.…”

“…Lu et al (2005Lu et al ( , 2010Lu et al ( , 2010a) studied the absorption performance of blended solutions based on the amino and inorganic-amino acid salts in a hydrophobic microporous membrane. Lin et al (2008) used AMP with the activator PZ and found that with an increase in the additive concentration, the CO 2 absorption rate constantly improved.…”

CO2 absorption into aqueous blends of ionic liquid and amine in a membrane contactor

“…MGA is a promising, competitive and alternative to conventional (e.g., tower techniques) process. Relevant investigations on MGA have made significant progress [5][6][7][8][9][10].…”

“…A good absorbent should be the liquid with high selectivity, good gas solubility, good reactivity, high absorption rate and high capacity, low volatility, low regeneration energy, no degradation, no corrosiveness [5]. It doesn't wet the membrane micropore in capture process [8]. Amine-based solvents and their blends as chemical absorbents are frequently used in MGA for CO 2 [4][5][6][7][8][9].…”

“…It doesn't wet the membrane micropore in capture process [8]. Amine-based solvents and their blends as chemical absorbents are frequently used in MGA for CO 2 [4][5][6][7][8][9]. However, their obvious shortcomings are degradability, producing stable salts, corrosiveness, foaming, energy dissipation, toxicity and high operation cost.…”