Effect of membrane separation process conditions on the recovery of syngas components

The presented study focuses on inspecting the dependency between process conditions, especially permeate and retentate pressure and component recovery of H2, CO, and CO2 during a membrane separation of model syngas. Experiments with both pure components and a model mixture were performed using a laboratory membrane unit Ralex GSU-LAB-200 with a polyimide hollow fibre module with 3000 hollow fibres. Permeability values were established at 1380 Barrer for H2, 23 Barrer for CO, and 343 Barrer for CO2. The measured selectivities differ from the ideal ones: the ideal H2/CO2 selectivity is 3.21, while the experimental values range from over 4 to as low as 1.2 (this implies that an interaction between the components occurs). Then, the model syngas, comprised of 16% H2, 34% CO, and 50% CO2, was tested. The recovery of each component decreases with an increasing permeate pressure. At a pressure difference of 2 bar, the recovery rate for H2, for a permeate pressure of 1.2 bar, is around 68%, for 2.5 bar, the values drop to 51%, and for 4 bar, the values reach 40% only. A similar trend was observed for CO2, with recovery values of 59%, 47% and 37% for permeate pressures of 1.2 bar, 2.5 bar and 4 bar, respectively.