(515c) A Computational Investigation of Hollow Fibers for Carbon Capture

Absorption of CO₂ in post combustion systems has recorded rapid development as a consequence of addressing increasing green-house gas emissions and requirements for achieving higher energy efficiency. Due to the low driving force for CO₂ separation in post-combustion flue gas, any membrane-based separation system that does not use flue gas compression must have modules with very low pressure drop. Hollow fiber modules based on membrane contactors have a higher surface area to volume ratio compared with flat sheet membranes, which makes them an attractive option for minimizing the cost of gas separations. A combination of factors including materials, device configurations and operating conditions, form a design space of many dependent parameters that needs to be examined to achieve device-and-system-scale improvements.

Computational Fluid Dynamics (CFD), is a powerful tool in retrieving detailed physics information and revealing the underlying mechanisms that dictate performance. A new computational framework is developed, based on models of fibers of increasing complexity and computational cost. Simple, yet accurate models of membranes and membrane modules that capture the temperature dependence of multiple membrane materials and the effects of geometry on performance are developed. First, a 2D axisymmetric model is studied that accounts for the momentum and mass transport of CO₂ in a mixture of gases inside the module. The concentration profiles on the shell and permeate side are quantifying the driving force as a function of the position along the fiber. Based on this model, scaling up of numerous fibers inside a module is sought to account for the effect of inflow CO₂ mass fraction, operating conditions and geometrical features of the module on the pressure drop and the overall performance of the separation process.