Membrane stripping is a promising method for carbon dioxide (CO 2 ) desorption with low energy demand. We developed a mathematical model to simulate the CO 2 stripping from the CO 2 -rich monoethanolamine (MEA) solvent in a hollow fiber membrane contactor. The modeling results agreed well with literature experimental results. To improve the understanding and facilitate the optimization of the membrane based CO 2 stripping process, we investigated the effects of different operating variables including liquid flow velocity, sweeping gas flow rate, regeneration pressure, and temperature on CO 2 desorption performance. The effects of membrane's length and diameter of membrane fiber on CO 2 desorption were also studied. Results showed that increasing membrane's length will improve CO 2 stripping performance, but not infinitely, because of the thermodynamic limitation of absorbent, and shorter membrane module is preferred for thinner membrane. Membranes with a smaller diameter favor CO 2 desorption. To predict the influence of membrane wetting on CO 2 stripping performance, the change of CO 2 lean loading with the wetting ratio was investigated. Membrane wetting significantly deteriorates CO 2 membrane desorption performance, with CO 2 lean loading increasing suddenly once the membrane is wetted.

CO 2 membrane stripping is a novel method for CO 2 desorption at low temperature (around 348K) for amine-based CO 2 capture, which has the potential to reduce regeneration energy requirement. In this work, we investigated CO 2 membrane stripping with two different commercial hollow fiber membranes, polypropylene (PP) and Polyvinylidene fluoride (PVDF). CO 2 membrane stripping in PVDF membrane showed a faster CO 2 desorption rate than in PP membrane, but PP membrane presented a better stability on long-term running. Energy consumption for CO 2 membrane stripping with 20 wt% MEA solvent was evaluated. Compared with conventional thermal regeneration, 28% energy can be saved if regeneration pressure of CO 2 membrane stripping operated at 20 kPa.

CO2 absorption at the temperature of flue gas inlet could reduce the costs related to flue gas cooling systems and improve the economic feasibility of the postcombustion carbon capture processes. Amino acid salts are considered as promising absorbents to absorb CO2 in a membrane contactor at elevated temperatures because of their advantages of lower volatility, less degradation, and higher surface tension. In this study, 24 common amino acids have been screened for their potential to absorb CO2 at the temperature of flue gas inlet in a membrane contactor. These screening processes involved examination of the water solubility of amino acids, measurement of surface tension and viscosity of their potassium salts, CO2 capacity, and CO2 membrane absorption test. Taurine, sarcosine, and glycine were identified as performing well in all the screening tests and were further investigated for CO2 membrane absorption at high temperatures up to 80 °C and various CO2 loadings in a polypropylene hollow fiber membrane module. The results show that those amino acid salts are feasible to absorb CO2 at high temperatures in a membrane contactor. Potassium sarcosinate is identified as the most promising absorbent for high-temperature CO2 absorption with a better absorption performance than monoethanolamine and other amino acid salts.

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Nanoparticles suspended in solutions are considered to have the potential to enhance gas‐liquid mass transfer and have been studied for gas separation. In order to reveal the mechanisms of kinetics enhancement, the diffusion and reaction process should be carefully examined. In this paper, CO2 absorption kinetics of amine‐based solutions with additive of SiO2 and Al2O3 nanoparticles were investigated by wetted‐wall column experiments. Measurements at different conditions, including solid loading, pressure, and solvent flow rate, show a significant enhancement on CO2 absorption kinetics. The experiment and model analysis indicate that the micro convective motion induced by particle Brownian movement plays a primary role in mass transfer enhancement. Three solutions, MEA, MDEA, and PZ which have different kinetics were selected to study the impact of nanoparticles on absorption kinetics of solutions with different reaction rate. It is interesting to find that the increased ratio of absorption kinetics by nanoparticle follows the same order with increased solvent reaction rate with CO2, which is PZ > MEA > MDEA. The wetted‐wall kinetic model indicates that a diffusion controlled kinetics for PZ solution could result in much more significant kinetic enhancement with additives of nanoparticles. By operation conditions optimization, the liquid side mass transfer rate of MEA solution can be increased over 15%.© 2015 Society of Chemical Industry and John Wiley & Sons, Ltd