CFD (computational fluid dynamics) analysis of a novel reactor design using ion transport membranes for oxy-fuel combustion

Conventional two-channel ITM (ion transport membrane) reactors applied to oxy-combustion, face the potential drawback of high thermal gradients and high local temperatures, which can result in membrane damage. In such reactors, air flows on the feed side and fuel are introduced on the permeate side, where it reacts with the permeated oxygen. In this work, we propose to use a three-channel configuration in which a porous plate is used to separate the permeate stream from the fuel stream, allowing the fuel to diffuse gradually into the permeate side. The gradual combustion of the fuel results in a slow temperature rise and a more spatially uniform temperature distribution along the membrane. We model this three-channel reactor using computational fluid dynamics and compare its performance to a conventional two-channel reactor. It is shown that, indeed, in case of a two-channel reactor, a high temperature zone is concentrated near the inlet, whereas the three-channel reactor produces a milder temperature gradient along the reactor length. The more-uniform heat flux associated with the latter results in a moderate temperature distribution and reduction in the wall shear stress along the channels and the associated pressure drop. The more uniform temperature distribution should be less damaging to the membrane. The reaction zone associated with the gradual fuel diffusion into the sweep side improves the membrane performance by maintaining a more uniform oxygen flux.