Abstract
Hydrogen purification and CO2 capture are of great significance in refineries and pre-combustion power plants. A dual membrane separator offers an alternative approach for improving H2/CO2 separation efficiency. In this work, H2/CO2/CH4 ternary gas mixtures separation can be achieved by a dual membrane separator with an integrated polyimide (PI) membrane and polydimethylsiloxane/polyetherimide (PDMS/PEI) composite membrane. A hollow fiber dual membrane separation equipment is designed and manufactured. Through the self-designed device, the effects of stage cut, operating temperature, operating pressure, and membrane area ratio on separation performance of dual membrane separator have been studied. The results indicate that, at a high stage cut, a dual membrane separator has obvious advantages over a single membrane separator. Operating temperature has a significant impact on gas permeation rates. At 25 °C, a dual membrane separator can obtain the highest purity of H2 and CO2. By increasing operating pressure, the purity and recovery of H2 and CO2 can be improved simultaneously. The effect of the membrane area ratio on the performance of the dual membrane separator was studied. When the permeate flows of two membranes are approximately equal by changing the membrane area ratio, the overall performance of the dual membrane separator is the best. On the basis of its synergy in promoting separation, the dual membrane separator holds great industrial application potential.
Highlights
Hydrogen purification and CO2 capture are vital processes in the chemical industry and integrated gasification combined cycle (IGCC) power plants [1,2]
2 /CO2 selectivity of PI membranes in the dual membrane separator were similar to the concentration polarization by reducing the CO2 concentration in feed gas, and the product purity was significantly improved compared with the PI single membrane separator
With the increase of operating pressure, the purity and recovery of H2 and CO2 increased at the same time
Summary
Hydrogen purification and CO2 capture are vital processes in the chemical industry and integrated gasification combined cycle (IGCC) power plants [1,2]. Syngas is first produced by the steam methane reforming or coal gasification process, and converted to a mixture containing H2 , CO2 , CH4 , CO, H2 O, and hydrocarbons by water–gas shift reaction [3,4]. The concentration of CO2 in the shifted syngas may be high (up to 45%), which would require large equipment and high energy consumption for desorption [6]. Gas membrane separation has great prospects in the petrochemical industry owing to extensibility and modularity, cost efficiency, and lower energy requirement [7,8,9]. H2 -selective membranes are widely used in the field of H2 /N2 and H2 /hydrocarbon separation, which could reach
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