NAMS 2002 Workshop - ICOM 2008

Membrane Contactors – 3
Friday July 18, 3:30 PM-4:00 PM, O’ahu/Waialua
Operational Flexibility of Gas-Liquid Membrane Contactors for CO2
Separation
K. Fischbein (Speaker), University of Twente, Enschede, The Netherlands -
k.fischbein@utwente.nl
K. Nijmeijer, University of Twente, Enschede, The Netherlands
M. Wessling, University of Twente, Enschede, The Netherlands
Objective CO2 is one of the major contributors to the greenhouse effect: the
power and industrial sectors combined, account for about 60% of global CO2
emissions [1]. To prevent the emissions of CO2, capture and sequestration of
CO2 from gas streams is essential. The traditional method of separating CO2
from other gases is amine scrubbing. Although high product yields and purities
can be obtained, the disadvantage of this method is its high energy consumption
- especially during desorption - in combination with a high liquid loss due to
evaporation of the solvent. Membrane technology is a promising method of
replacing conventional absorption technology. It has a high energy efficiency, is
easy to scale-up because of its modular design, and it has a high area-to-volume
ratio [2]. These advantages suggest that membrane separation is a viable
alternative to conventional gas separation techniques. In this work, we use a
membrane contactor to separate CO2 from natural gas. A membrane contactor
combines the advantages of membrane technology with those of an absorption
liquid. In a membrane contactor, CO2 diffuses from the feed gas side through the
membrane and is then absorbed in the selective absorption liquid. The loaded
liquid is circulated from the absorber to the desorber, which can be a traditional
desorber or a second membrane contactor, in which desorption of CO2 occurs.
The membrane acts as an interface between the feed gas and the absorption
liquid. The selectivity of the process is not only determined by the membrane, but
also the absorption liquid plays a significant role and contributes to the selectivity.
Gas-liquid membrane contactors offer a unique way to perform gas- liquid
absorption processes in a controlled fashion and they have a high operational
flexibility. In this work, we investigate the effect of these operating parameters on
the CO2/CH4 separation performance of the membrane contactor and identify the
operating window for such a process.
Experimental Part Porous polypropylene hollow fibers (Accurel S6/2, obtained
from Membrana GmbH, Germany) and asymmetric poly phenylene oxide
membranes (normally used for gas separation; kindly provided by Parker Gas
Separation, The Netherlands) were used as absorber and desorber in a
membrane contactor for the separation of CO2/CH4 (20/80 vol.%). The use of
asymmetric membranes with a dense top layer prevents penetration of the