Numerical Simulation of Mixed Conducting Membranes for CO2 Capturing Using Synthetic Microstructures

Abstract

A side effect of the industrial revolution is the significant increase in atmospheric concentration of CO2 and subsequent greenhouse effects, which necessitated the need for developing technologies for extracting CO2 from high temperature flue gases [1]. Using dense membranes to separate and transport CO2 is promising because of their high selectivity and ability to operate under high temperatures compared to other methods[2]. CO2 permeation flux through dense membranes can be improved significantly by using multiphase composite materials, one promising example of which is Molten Carbonate/Solid Oxide membranes [2, 3]. The topological characteristics of the composite material’s microstructure has a significant impact on the overall effective conductivity of the membrane as the volume fraction and tortuosity of each phase affect the charge carrier pathways. It is difficult to quantify the impact of different features of the microstructure using homogeneous simulations or experimental methods, which necessitates the use of heterogeneous simulations to provide a better understanding on how the different microstructural features affect the overall macroscopic performance [4, 5, 6].In this work, the effect of microstructure on the performance of Molten carbonate/Solid Oxide mixed oxide-ionic and carbonate-ionic conductor (MOCC) will be studied. Unlike previous work presented in the literature, which was limited to one microstructure obtained experimentally by focused ion beam and scanning electron microscope [7, 8], a range of microstructures will be generated synthetically using Dream3D software. The generated microstructures will have different particle sizes and volume fractions for each phase. In addition, the variations that can occur within the same volume fraction ratio will be also considered. COMSOL will be used to solve the Nernst-Plank equations using Finite Element Method for each phase. The detailed simulation results 1) will be compared to the conventional homogeneous simulations; 2) will be validated by experimental CO2 capturing flux; 3) will be used to assess the effect of the microstructure parameters on the performance of the membrane when paired with a Methane oxidative coupling reactor as shown in Fig. 1.