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CLIMIT-Forskning, utvikling og demo av CO2-håndtering

Novel molten/solid composite oxygen transport membranes for CO2 capture

Alternative title: Smelte/faststoff-kompositt oxygentransportmembraner for CO2 fangst

Awarded: NOK 11.4 mill.

MOC-OTM focuses on the development of novel composite oxygen separation membranes used at intermediate temperatures. These novel membranes will benefit the implementation of CCS-related technologies such as oxy-fuel combustion by reducing the energy penalty and improving membrane stability due to lower operating temperatures. Moreover, the knowledge gained in this project will contribute to the cathode development of novel fuel cells at intermediate temperatures for power generation that avoid degradation issues observed for conventional SOFCs. We are developing the composite membranes along two approaches. 1) In the case of ceramic composites membranes: a) We have developed thermochemically stable membranes based on mixture of oxide ion conductors such as Bi2O3 and electronic conductors such as Sr-doped LaMnO3 (LSM) and LaFeO3 (LSF). These membranes showed high oxygen fluxes comparable to state-of-the-art single-phase membranes such as Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF), and with much better stability in the presence of CO2. Some results were published in 'Chem. Commun., 2019, 55, 3493', and comprehensive evaluations about this kind of membranes were submitted to 'Journal of Membrane Sciences'. Bi2O3 were co-doped by Ta, Pr and Tm to form single-phase oxygen separation membranes. The measured oxygen flux density of single-phase membrane was much lower than that of cer-cer membranes, indicating the importance of electronic conducting phase in membranes' transport. b) The oxygen surface exchange kinetics plays an important role in the performance of oxygen transport membranes (OTMs). We employ pulse-response isotope exchange (PIE) measurements, isotope exchange gas phase analysis (IE-GPA), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study the mechanisms governing oxygen exchange kinetics of pure and doped Bi2O3, LSM, and composites based on them. The results from this work are summarized for publication in a scientific journal, and the title is 'Oxygen surface exchange kinetics in Bi2O3-based mixed conductors'. 2)For the solid/molten phase composites membranes: a) One solid/molten composite system based on molten Bi2O3 has been tested and it was shown that oxygen is transported in the presence of molten Bi2O3. Emphasis has been put on searching for a suitable oxide to form eutectic mixture system with Bi2O3 to achieve a lower melting point, which is compatible with ceramic matrices. b) Eutectic salts based on K2SO4 and V2O5 with a lower melting point of ~500 °C have been tested for infiltration into various ceramic porous supports including pure electronic conductors, and composite of electronic and oxide ion conductors. The composite membranes have shown oxygen permeation in the low temperature range of 500-650°C, which is promising to lower down the operating temperature of oxygen transport membranes. However, the stability of ceramic supports is still a challenge. c) A ZrV2O7-30mol%V2O5 solid/molten composite has been studied intensively by means of electromotive force (EMF) measurements and electrochemical impedance spectroscopy (EIS). When V2O5 melts and increases the V2O5 volume percolation, the electrical conductivity increases with a factor of 10 and the activation energy increases from 0.21 to ~0.7 eV. The oxygen red-ox reaction at the surface changes from being rate limited by charge transfer processes to mass transfer processes as a consequence of fast oxygen exchange in molten V2O5 as compared to the all-solid composite. This work, with the title ?Electrical transport in a V2O5-ZrV2O7 molten/solid composite?, was published in Journal of Materials Chemistry A on the 16th of August, 2021. d) Defect chemistry and transport properties in ZrV2O7 have been investigated by experimental and computational approaches such as DFT. A scientific contribution with the title 'Defects and transport in ZrV2O7' is under preparation for submission. e) Porous supports are very important for developing solid/liquid membranes. A dusty gas model has been used to simulate gas transport in porous media. To better understand its properties such as permeability, tortuosity etc., deep learning is implemented to generate 3D porous structure from a 2D training image. Moreover, such a method is also utilized to analyze triple phase boundary on membrane surfaces. When it comes to process integrations, performance evaluations of the composite membranes in terms of energy efficiency were performed by calculating the material and energy balances for the processes in oxy-combustion gas turbine cycles and in hydrogen production. A systematic approach to the integration of membranes in these processes was developed, showing the potential for efficiency improvement. Analyses indicated that the optimal operations of OTMs are at 750°C for Oxy-GT and 800°C for ATR, and a high recovery and feed pressure in the ranges of 5-10 bars are also required for the competitiveness of OTMs.

The results obtained in this project have significant benefit for the field of oxygen separation membranes. We have shown the importance of super coherent interface on fast oxygen transport. Commercialization of such a membrane system could be potentially achieved upon development of a suitable catalyst for low temperature surface activation. Novel solid/molten membrane systems would make oxygen separation possible at lower temperatures (500-600°C). Through this project, we also found the enhancement of molten phase on surface kinetics, transport, and electrochemical performance of composite systems. Developed modelling for porous transport and 3D reconstruction will support future research on dual-phase material systems. In this sense, knowledge built in this project will be essential to reaching commercialization of future green energy related technologies such as novel chemical processes, e.g. membrane reactors, molten carbonate fuel cells (MCFCs), SOFCs and catalysis.

Many of current energy conversion and storage technologies utilize the fine interfaces between porous solid and functional ion-conducting liquid phases. Fundamental and microscopical understanding of how they work is, however, limited. Understanding of the properties of materials confined in constrained geometry is of fundamental interest, as surface interactions due to spatial restriction and low dimensionality of the confining matrix result in the physical and chemical behavior of the confined systems much different from the bulk. The MOC-OTM project addresses these challenges and takes as starting point the recent discoveries of new systems (e.g. dual phase gas separation membranes and apparent proton conduction in ceramics at room temperature pursued separately in preceding RCN projects) and advances in theory, modelling, and high resolution and in-situ instrumentation to call for a deeper and more generic investigation of the principles at hand. This will be exemplified in the present project with the development of high flux oxygen transport membranes operating at intermediate temperature to increase efficiency of oxygen combustion in CCS integrated power plants. The membranes will be designed as molten/solid composite systems exhibiting high oxygen flux density through confinement effects in microstructured solid phases. The project will contain theoretical and modelling activities, experimental studies of key materials systems and fabrication of microstructured ceramic matrices and composite membranes. Membranes will be tested in relevant conditions to evaluate their operating window and address stability of operation over 500h. The project is led by SINTEF, with UiO, Colorado School of Mines, Imperial College London, University Twente, as national and international collaborators, and has an advisory board including Air Liquide, CoorsTeK Membrane Sciences and Cerpotech to ensure industrial relevance. It trains one PhD candidate and lasts for 3 years.

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CLIMIT-Forskning, utvikling og demo av CO2-håndtering