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

Abstract

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.