(487a) Bypass in Hollow Fiber Gas Separation Membrane Modules

Membrane gas separation processes most commonly utilize hollow fiber membrane modules. Experimental performance of these modules can differ dramatically from theoretical predictions based on independent experimental measurements of membrane transport properties. One of the most significant sources of these deviations is flow maldistribution that prevents uniform counter-current contacting between retentate and permeate.

Previous work has demonstrated the impact of fiber size uniformity on flow distribution and performance for lumen-fed modules. While poor packing of the fiber bundle adjacent to the enclosing case has been hypothesized as another significant factor for shell-fed modules, the impact of gas bypass in this region has not been investigated thoroughly.

Simulations of flow through fiber bundles with non-uniform wall packing are reported. Results are reported for planar and circular fiber bundles possessing a regular square or triangular packing. Determination of the length scale over which the case influences flow distribution, as a function of fiber packing fraction, is emphasized.

Full three-dimensional simulations compare well with an approximate solution that assumes the fibers within the central part of the bundle perform like an ideal counter current module. Additionally, the planar bundle simulations provide a good approximation to the circular bundle simulations using the average distance between the case and fiber bundle.

The results can provide guidance for establishing module manufacturing guidelines to minimize the effect of gas bypass on performance. Additionally, the procedures can be adapted to evaluate the effect of shell-side sweep by-pass on performance.