Modeling gas separation in flat sheet membrane modules: Impact of flow channel size variation

Abstract

Flat sheet membranes offer many advantages over other membrane configurations, (e.g. ease of maintenance and low pressure drops) that make them a strong candidate for post-combustion carbon capture. A performance model for a stacked flat sheet membrane module is reported in this work. The model is based on the reported specifications for the Gen 2 Polaris™ module developed by Membrane Technology & Research (MTR) and predicts performance based on solution of the governing momentum and mass balance equations. The model accounts for variability in flow channel heights within the module that can arise during module manufacturing. The model is first verified against similar membrane models. Simulations are then performed over a wide range of conditions to demonstrate how much performance declines as channel height variability increases. As per the performance metrics, the dimensionless feed flow rate processed per unit membrane area (f-curve) shows the greatest decline. The changes in performance are comparable to those that occur with hollow fiber membrane modules that possess similar fiber size variations. Together, the results of this study indicate that flow channel height variation in flat sheet membrane modules can hurt CO2 separation performance, but the impact is minor except at low CO2 retentate compositions with large channel height variation (e.g. a 10% decline in stage cut performance for a mixture with 94% CO2 in the permeate stream and 30% channel height variation). However, high variation has a significant impact on overall membrane area with a 30% increase at 30% variation.