NAMS 2002 Workshop - ICOM 2008

Gas Separation V – 4
Friday July 18, 11:15 AM-11:45 AM, Kaua’i
Natural Gas Purification Using High Performance Crosslinked Hollow Fiber
Membranes: Effects of High Pressure CO2 and Toluene Feed.
I. Omole (Speaker), Georgia Institute of Technology, Atlanta, Georgia, USA
S. Miller, Chevron Energy Technology Company, Richmond, California, USA
W. Koros, Georgia Institute of Technology, Atlanta, Georgia, USA -
william.koros@chbe.gatech.edu
Natural gas is one of the fastest growing primary energy sources in the world
today. The increasing world demand for energy requires increased production of
high quality natural gas. For the natural gas to be fed into the mainline gas
transportation system, it must meet the pipe-line quality standards. Natural gas
produced at the wellhead is usually ‘sub-quality’ and contains various impurities
such as CO2, H2S, and higher hydrocarbons, which must be removed to meet
specifications.
Carbon dioxide is usually the largest impurity in natural gas feeds and high CO2
partial pressures in the feed can lead to plasticization, which causes loss of some
methane product and may ultimately render the membrane ineffective. Moreover,
the presence of highly sorbing higher hydrocarbons in the feed can further
reduce membrane performance.
Covalent crosslinking has been shown to increase plasticization resistance in
dense films by suppressing the degree of swelling and segmental chain mobility
in the polymer, thereby preserving the selectivity of the membrane. This research
focuses on extending the dense film success to asymmetric hollow fibers.
In this paper, the effect of high pressure CO2 (up to 400 psig CO2 partial
pressure) on CO2/CH4 mixed gas separation performance was investigated on
the hollow fiber membrane at different degrees of crosslinking. All the crosslinked
fibers were shown to exhibit good resistance to selectivity losses from CO2
induced plasticization, significantly more than the uncrosslinked fibers. Robust
resistance of the hollow fiber membranes in the presence of toluene (a highly
sorbing contaminant) was also demonstrated as the membranes showed no
plasticization even in toluene saturated feed streams.