(433a) Simulation of Flow Through Spacers Used in Membrane Modules for Carbon Dioxide Capture

Carbon dioxide (CO₂) emissions from coal-fired power plants may lead to significant global climate change if not controlled. CO₂ capture and sequestration (CCS) is one of many solutions being considered to mitigate emissions.

Membrane based processes potentially are a cost-effective option for CO₂ capture. Spacers are a critical component of membrane modules. Spacers create and maintain uniform flow channels during module fabrication and operation for the permeate and feed flows. Spacers also may be used to mix fluid within the channels to eliminate concentration polarization and increase mass transfer rates. Unfortunately, spacers increase pressure drop. This increase is strongly dependent on spacer geometry and is especially important in the membrane modules used for CO₂ capture. Process economics require the pressure difference that drives transport across the membrane to be as small as possible due to flue gas compression costs. Pressure drop that accompanies flow through a spacer will reduce this driving force and represents an additional parasitic energy load on the plant.

Computational fluid dynamics (CFD) is used to investigate the flow within a spacer-filled channel. The effect of mesh refinement and use of a periodic cell to represent the entire spacer are examined to determine the fidelity of the results. The results are compared to experimental measurements of pressure drop to validate the simulations.

The dependence of velocity fields and pressure drop on spacer geometry is examined to determine spacer configurations that offer the lowest pressure drops. Variables considered include diameter of each filament, filament spacing, angle between filaments, and fluid attack angle. The configurations considered include the low pressure drop configurations described in the patent literature. The results allow determination of the features that lead to the lowest pressure drops and the associated velocity fields.