The effects of shell-side flows and fiber property variations on hollow fiber membrane module performance.

摘要

Hollow fiber membrane modules are used for a variety of separations, contacting, and reactor applications. Most modules contain common design elements, but the effects of these elements on performance are poorly understood. Here we develop methods for quantifying the effects of many design factors on module performance. We consider explicitly how fiber bundle geometry affects the shell-side fluid distribution and module performance, and how variations in fiber material properties within the bundle affect module performance.; To incorporate the effects of fiber bundle properties into a performance model, we volume average the relevant transport relationships to form a set of partial differential equations describing mass and momentum transport in the shell (outside of the fibers) and the lumen (inside the fibers) regions. Fiber bundle properties appear in the form of Darcy permeabilities. Evaluation of these parameters as a function of fiber packing and alignment is accomplished using standard methods developed to predict flows in porous media. Feed properties and other module properties, including bundle case and port geometries, appear in the boundary conditions. The resulting set of equations is solved for two different applications.; For applications in which a dilute solute is removed from the shell fluid, the lumen fluid concentration does not change appreciably, and permeation resistance is membrane dominant, module performance was found to depend on two dimensionless groups that quantify bundle properties and operating conditions. Varying these dimensionless groups over typical ranges resulted in module performance predictions that varied by 40% depending on the module properties and operating conditions. This large predicted performance variation was attributed to the effects of bundle geometry on the shell-side fluid distribution.; The analysis was also used to predict air separation performance, and the results were compared to experimental measurements. Our analysis was found to predict performance more accurately than simpler, more commonly used models.; The effects of fiber material property variations in size, permeance, and selectivity were analyzed for lumen-fed gas separators. Variation in any of these properties is detrimental, but size variations decrease performance most at comparable variation levels.