− In this research, hollow fiber membranes were used in order to investigate to permeation and selectivity of the CH 4 and N 2 . Polyimide and polyethersulfone hollow fiber membrane were prepared by the dry-wet phase inversion method and the module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy (SEM) studies showed that the produced fibers typically had an asymmetric structure. The permeance of CH 4 and N 2 were increased with pressure and temperature. However, the selectivity was decreased with increasing temperature. The permeances of CH 4 and N 2 were decreased with increasing the air gap and the effect of posttreatment on membrane showed the increase in permeance up to 3.2~7.0 times.
− In this study, by using the polymeric membrane separation process, the CO 2 /CH 4 separation and H 2 S removal from biogas were performed in order to CH 4 purification and enrichment for the fuel cell energy source application. Fibers were spun by dry/wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a porous, sponge substructure. The permeance of CO 2 and CO 2 /CH 4 selectivity increased with pressure and temperature. Mixture gas with increasing pressure and temperature, removal efficiency of the CO 2 and H 2 S were decreased while concentration of CH 4 was increased up to 100%. When retentate flow rate was increased with the decreasing of pressure and temperature the CH 4 recovery ratio in retentate side was increased while the CH 4 purity in retentate side was decreased.
A general finite element model and a new solution method were developed to simulate the permeances of Lintz Donawiz converter gas (LDG) components and the performance of a polysulfone membrane separation unit. The permeances at eight bars of CO, N2, and H2 in LDG simulated using the developed model equations employing the experimental mixed gas data were obtained by controlling the finite element numbers and comparing them with pure gas permeation data. At the optimal finite element numbers (s = 15, n = 1), the gas permeances under the mixed-gas condition were 6.3% (CO), 3.9% (N2), and 7.2% (H2) larger than those of the pure gases, On the other hand, the mixed-gas permeance of CO2 was 4.5% smaller than that of pure gas. These differences were attributed to the plasticization phenomenon of the polysulfone membrane used by CO2. The newly adopted solution method for the stiff nonlinear model functions enabled the simulation of the performance (in terms of gas recovery, concentration, and flow rate) of the first-stage membrane within two seconds under most gas flow conditions. The performance of a first-stage membrane unit separating LDG could be predicted by the developed model with a small error of <2.1%. These model and solution methods could be utilized effectively for simulating gas permeances of the membrane that is plasticized severely by the permeating gas and the separation performance of two- or multi-stage membrane processes.
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