Separation of acidic gases using hollow fibre membrane contractors

El-Amari, AA

Abstract

Gas absorption in hollow fibre contactors is being increasingly used due to
their enormous surface area/volume ratio. The capability of the hollow fibre
membrane modules for the removal of CO 2 and SO2 from a binary gas
mixture has been investigated experimentally. Four different modules were
used in this study. The membranes in modules one and two were made of
microporous polypropylene. The third module was made of non-porous
silicone rubber (polydimethylsiloxane) while the latter one was a
polyvinylidenefluoride (PVDF) asymmetric hollow fibre membrane.
The gas mixtures used in the experiments were composed of 9.5% CO2 and
1% SO2 in N 2 , which was introduced into the hollow fibre lumen, while the
absorbent liquid was fed into the shell side of module. The absorbent liquids
used were water, aqueous solutions of diethanolamine (DBA) and ammonia
at different concentrations (5, 10 and 20 wt%). The effects of different
operating conditions on the permeation process have been investigated for
co-current and counter-current flow patterns. In addition, to improve the
silicone rubber hollow fibre membrane performance, baffles were installed
within the shell of the permeator to increase liquid fibre contact.
The results obtained showed that the use of baffles within the shell of the
permeator improved the separation performance of the non-porous
membrane module without any substantial increase in the physical size of
the contacting device. Studies also showed that improved performance was
observed when the system was operated under a counter-current flow
pattern. The results showed that the use of an absorbent liquid in the permeate side
of the fibres increased the selectivity of the membranes used, and reduced
the need to maintain a high pressure ratio across the membrane. A
decrease in the feed gas flow rate or increase in liquid flow rate generally
improved the removal of gases.
The results showed that the use of aqueous reactive solutions as an
absorbing medium in the permeate side of the hollow fibre permeator can
significantly improve CO2 removal from the gas mixture. However, the main
problem when using a microporous membrane coupled with aqueous
solutions of diethanolamine as absorbent was wetting of the microporous
membrane by amine solutions. For 862 separation, the highest removal was
attained using the microporous membrane coupled with water as absorbent
liquid. This demonstrates that a hollow fibre based device can be a very
efficient gas liquid contactor.
The separation process was simulated with a numerical model based on the
effective permeabilities of gases and compared with the experimental
results. The model simulations showed good agreement with the
experimental observations.

Citation

El-Amari, A. Separation of acidic gases using hollow fibre membrane contractors. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 2002