Computational Analysis and Modeling Techniques for Monolithic Membrane Reactors Related to CO2 Free Power Processes

University dissertation from Heat Transfer

Abstract: Funded by European Community and Swiss government research project AZEP (Advanced Zero Emission Power Plant), the project was carried out at the Department of Energy Sciences at Lund Faculty of Engineering (LTH). The project addressed the development of a specific, zero emissions, gas turbine-based, power generation process to reduce local and global emissions in a cost-effective way. In this project a unique monolith heat and mass exchanger reactor with an oxygen permeable membrane was proposed by the Norsk Hydro Oil and Energy Research Center in Norway. The aim of this thesis is to describe a complete design of a monolithic reactor where both heat and oxygen transport takes place. This led to the development of a mathematical model of an oxygen membrane reactor which fulfils the boundary conditions set by the AZEP process. Further, an investigation of the total pressure drop and pressure distribution of the manifolding system using the Computational Fluid Dynamics (CFD) tool FLUENT was carried out. A further goal was also to perform dynamic analysis of the AZEP reactor. In order to perform such analysis, calculation tools were needed to describe the performance of CO2 capture. The object-oriented programming languages Modelica and Dymola were used to describe dynamic behavior of the oxygen transfer reactor. Sensitivity studies performed with the membrane model showed that a high inlet sweep temperature would raise the magnitude of the oxygen permeation flux through the MCMmembrane. At the same time high inlet air temperatures would be necessary to keep the driving potential through the length of the membrane at a higher level which would be important for achieving the targeted industrial values of oxygen fluxes. The dynamic simulations showed that disturbances on sweep flow had larger impact on the membranes performance than disturbances introduced on the air side of the reactor. By introduction of a new solution of flow manifolds (linear channel arrangement) a less complex header system than the one in the AZEP solution was achieved. Since the implementation of detailed membrane model in heat and mass balance calculations for system studies would result in excessive calculation time, results from this study were utilized for the generation of correlations describing the oxygen transfer as a function of operating parameters such as temperature and partial pressure. This modeling approach was expected to improve the accuracy of the system studies.