A study of methane oxy-combustion characteristics inside a modified design button-cell membrane reactor utilizing a modified oxygen permeation model for reacting flows

This work studies numerically the use of a modified oxygen permeation equation in a modified button-cell ion transport membrane reactor (ITMR). The permeation equation is modified in order to account for Reynolds number variations and non-elementary surface reactions on both sides of the membrane. The near membrane zone in the ITMR is modified to create recirculation zones in the vicinity of the membrane to sustain stable flame. Air is fed to the ITMR feed side and a mixture of methane and CO₂ is fed to the sweep side. The ITMR is axisymmetric and the mesh was constructed using Gambit 2.2 before importing it to the CFD fluent 12.1. A series of user defined functions (UDFs) written in C++ were compiled and hooked to fluent to solve for oxygen permeation. Effects of reactivity on oxygen permeation characteristics are investigated over wide ranges of operating parameters. Considering reacting flow conditions, the effects of sweep flow rate and feed oxygen partial pressure are investigated. The results showed that two, inner and outer, recirculation zones were created in the vicinity of the membrane with a stable flame. Significant improvements in oxygen permeation and combustion temperature are encountered utilizing the present reactor design.