Numerical investigation of a hybrid polymeric-ceramic membrane unit for carbon-free oxy-combustion applications

This work aims at developing a hybrid polymeric/ceramic membrane unit for oxy-fuel combustion applications. A ceramic oxygen transport membrane (OTM) unit is integrated numerically with a polymeric membrane unit to form the hybrid polymeric-ceramic membrane reactor. Oxygen-enriched air out of the polymeric membrane unit is fed to a ceramic membrane oxy-fuel based reactor. A detailed numerical study is performed to investigate oxy-fuel combustion in a tubular oxygen transport reactor (OTR) that is fed by oxygen-enriched air. CH4/CO2 mixture with various concentrations is swept inside the tubular OTR, where CO2 serves as a diluent. The effects of sweep gas flow rate, feed gas flow rate, fed O2 mass fraction, and swept CH4 mass fraction on permeation fluxes and combustion process are investigated. Energy and design analyses of the hybrid membrane unit are conducted and the ratio between the required fiber polymeric membranes area to the ceramic membranes area is calculated as a function of the sweep flow rate. It was found that stoichiometric combustion within the OTR is achievable at a certain feed flow rate. The output power of the hybrid membrane unit is calculated and compared with the output power in case of air fed unit (without the polymeric membranes).