Search

• Membrane contactor was used as a gas-liquid separator in pressure swing process. • The two mass transfer mechanisms were analysed through calculation of viscous flux and mass transfer coefficients. • When integrated with membrane contactor for CO 2 absorption, stable and consistent performance was observed. A new method to regenerate high pressure CO 2 absorbent is presented in this paper, where PTFE hollow fiber membrane contactor was used as a gas–liquid separator in pressure swing process. CO 2 desorption happened in the membrane contactor at the same time. The two mass transfer mechanisms were analysed through calculation of viscous flux and mass transfer coefficients. Experimental results showed that CO 2 loading in regenerated absorbent increased with absorbent flow rate. This was due to decrease in membrane area available for CO 2 desorption, as most of the membrane area was utilized for gas-liquid separation. Co-current configuration exhibited higher CO 2 desorption driving force compared to counter-current configuration, hence its CO 2 loading in regenerated absorbent was lower. When integrated with membrane contactor for CO 2 absorption, stable and consistent performance was observed. Unlike conventional flash drum, membrane contactor did not have requirement on flashed gas velocity, because the membrane itself functioned as a screen to prevent fine liquid droplets from escaping the system along with flashed gas. Results from this study show that vessel size reduction up to 2.5 times could be achieved when PTFE membrane contactor was used, with absorbent regeneration energy as low as 0.94 GJ/ton CO 2. [ABSTRACT FROM AUTHOR]

• Deep CO 2 removal using high pressure membrane contactor was proven able to reduce CO 2 content to < 0.005 mol% level, meeting requirement for atural Gas process. • Liquid phase mass transfer resistance was the highest compared to membrane phase and gas phase, showing that liquid was the bottleneck for mass transfer. • High liquid velocity was favored for better liquid phase mass transfer, resulted in high L/G ratio in deep CO 2 removal using membrane contactor. • Liquid flow rate reduction could not reduce L/G effectively as this led to more reduction in CO flux than L/G. • Membrane module length increase was able to achieve 70% reduction in L/G, with only 16% reduction in flux, offering lower energy consumption compared to conventional packed column in LNG process. Membrane contactor is a technology that intensifies conventional absorption column. However, liquid-to-gas ratios (L/G) of membrane contactor in existing reports are much higher compared to CO 2 absorption column, which results in higher solvent circulation rate and higher consumption in heating energy. This makes the technology less attractive for deep CO 2 removal. Direct reduction of liquid flow rate was not effective in lowering down L/G. Experimental results showed that 50% reduction in liquid flow rate could reduce L/G by 25%, but the reduction in CO 2 flux (33%) was higher due to decrease in liquid phase mass transfer coefficient which was dependent on liquid velocity. An alternative method to reduce L/G through membrane module length increase was proven, where L/G was reduced 70% with only 16% flux reduction. The flux reduction was only observed when L/G dropped below 0.80 L/mol and it was due to depletion of unreacted amine for CO 2 absorption. The lowest L/G value obtained in this study was 36% lower than the conventional absorption column in liquefied natural gas (LNG) process, showing that membrane contactor technology is not only energy-viable and more compact for deep CO 2 removal, but it also offers energy saving advantage. [ABSTRACT FROM AUTHOR]