(286c) Designing Flat Sheet Membrane Modules for Counter-Current Fluid Contacting

High-performance membranes are typically made in the form of hollow fibers or flat sheets. Hollow fiber modules inherently offer the potential for counter-current contacting. Flat sheet modules, in a plate and frame or spiral wound configuration, do not offer the same capability – crossflow contacting is inherent in standard designs, and additional features are required to promote counter-current flow. The effectiveness of these features in achieving counter-current flow without introducing overly parasitic fluid pressure drop is not understood well.

Glue lines or dots are commonly added within a membrane leaf to impart counter-current contacting in spiral wound modules. The glue forces fluid to flow parallel to the central permeate collection tube (i.e., in counter-current flow) within the leaf. However, crossflow is not eliminated completely and must occur to distribute fluid along the length of the leaf.

Glue lines have two detrimental effects: 1) reduction of membrane area for permeation and 2) introduction of additional pressure drop. These effects are examined for three different glue configurations taken from the literature: 1) a single glue line along the length of the leaf, 2) multiple glue lines that define a plurality of flow channels, and 3) the use of glue dots to create flow manifolds along the leaf.

The performance of these configurations is simulated using COMSOL Multiphysics for carbon capture from a concentrated point source. Module stage cut, feed flow rate, and pressure drop are compared for a range of stage cuts that provide up to 90% carbon capture. Performance with and without a sweep also is compared.

At low capture rates, differences between the configurations are small. However, as the capture rate increases, significant differences appear. The relative contributions of imperfect counter-current contacting, increased pressure drop, and membrane area loss are quantified and used to develop strategies for the effective use of glue lines.