H2 separation from H2/N2 and H2/CO mixtures with co-polyimide hollow fibre module

A lab-scale membrane module, packed with more than 150 hollow fibers of P841 co-polyimide, was used for the separation of hydrogen mixtures. The ideal membrane performance was analysed with pure gases (H2, N2, CO, CO2, CH4) and H2/N2 and H2/CO mixtures at 50C and up to 6 bar. Significant differences were observed between ideal selectivities and separation factors of mixtures. In gas mixture experiments, no variation of hydrogen flux was observed among the different feeds, whereas the permeance of the less permeating species, i.e., N2 and CO, was significantly higher than that measured with pure gases. A linear dependence of H2 recovery on the stage cut was observed in the whole feed pressure range investigated. No differences in the behavior of the membrane versus the two different mixtures were observed. A higher separation factor was obtained when H2 was mixed with N2 rather than CO, in agreement with the trend followed by ideal selectivity values, since the one of H2/N2 was 78, a bit higher than that of H2/CO (60). However, the hydrogen concentration in the permeate also reached 90% molar. The performances of a membrane system were compared with PSA and cryogenic, considering two metrics of process intensification.