Detailed electrical characterization of PMR membranes

In order to further understand the electrical and electrochemical properties of the PMR membranes, detailed electrical characterization was performed on single-tube membranes supplied by CoorsTek, as a function of steam pressure (0.05-5 bar) and temperature (600-800°C). Using impedance spectroscopy, ohmic and electrode polarization resistances could be extracted, which serve as basis for further improvement of performance of the membranes see Figure.

Chemical and electrochemical degradation studies

Further experimental work in NCCS will focus on investigating potential chemical and electrochemical degradation of the PMR materials in relevant atmospheres as well as impurities in the natural gas such as H₂S. The work so far has been to prepare different types of samples required for the chemical and electrochemical degradation experiments, and to make a test matrix including the relevant post-characterization methods. These have been chosen to address hypothesis regarding the degradation mechanism based on previous experimental and computational work in Task 3.

Hybrid PMR and CO₂ liquefaction process

A hybrid process comprising PMR technology and CO₂ liquefaction is being developed in the MACH-2 KSP spin-off project. By exploiting the advantages of both technologies and applying them in their preferred window of operation, significant cost and efficiency gains are expected. In optimizing the process, the configuration of the hybrid process was varied with respect to the type of liquefaction process for CO₂ capture and the treatment methods of the residual gas from the low-temperature process. The latter is critical for optimal design of the hybrid system with a high H₂ recovery rate as the PMR retentate gas may contain considerable amounts of hydrogen and CO if the PMR is not operated at high conversion. The detailed process flow diagram of the hybrid process with the liquefaction system is illustrated in the figure below. In the selected hybrid process, a mixed refrigerant liquefaction system is used for the carbon capture part, and a water gas shift reactor for the retentate gas is included to reduce the CO content in the feed and achieve a high CO₂ capture rate and high H₂ recovery rate by recycling the residual gas. Based on the performance analysis of the hybrid process, the configuration of the liquefaction process will be further modified to minimize the overall cost of the system. The heat recovery method of the warm hydrogen product and retentate gas from the PMR will also be further developed in the MACH-2 project to improve the energy efficiency of the hybrid system for hydrogen production with low carbon footprint. 

In 2020, results originating from the MACH-2 project were presented at the 30th European Virtual Symposium on Computer Aided Process Engineering (ESCAPE-30) in September, and during the NCCS-organized webinar in October. A scientific article detailing the low temperature process was published in the Elsevier journal Computer Aided Chemical Engineering.

PMR experiments at lower temperatures for the first time

In 2019, we managed to perform catalytic PMR experiments at lower temperatures (750 and 700°C) for the first time, for comparison with the standard operation at 800°C (left figure). Methane conversion of 98.7% was achieved and the catalytic data corresponds well with thermodynamic equilibrium at the highest hydrogen recoveries (>95%). These results are important for further optimization of the PMR operating conditions. Specifically, lower operating temperature may translate to improved lifetime and reduced cost of materials and components in the PMR modules.

Improvements to experimental setup

The task-team has made several upgrades to the setup for detailed characterization of PMR membranes. We achieved high quality electrical measurements which provides the main input for further development of membrane cells with improved electrochemical performance. This work also benefits the long-term PMR testing that is planned within KPN MACH-2.

Modelling of membranes and modules

Simulations of PMR membranes and thermally integrated modules are being pursued to benchmark and improve the PMR hydrogen production process. Single-tube PMR simulations were performed for detailed temperature and gas composition profiles along membrane length, and for the role of gas inlet temperature. The results demonstrated the importance of thermal integration of PMR modules, and a simulation framework for a thermally integrated SEU – containing 36 membrane segments – was established for isothermal conditions.

Main Results

• Performance targets defined for a single PMR membrane for testing in NCCS, and for commercial deployment of the PMR technology.
• Several modification and improvements to the experimental setup have been performed amid significant challenges with the experimental setup.
• Simulation model for CoorsTek membranes was developed for modelling of PMR membrane and reactor.
• Paper on theoretical studies of CO₂ and H₂O co-adsorption on membrane surface accepted for publication.

Impact and innovations

• Knowledge of possible critical role of coke deposition in membrane anode.

The task deals with development of the Protonic Membrane Reformer (PMR) technology by CoorsTek Membrane Sciences which allows hydrogen production with CO₂ capture in a modular steam methane reformer.

The work aims to identify and improve material stability and performance issues of the ceramic membrane and seals under PMR operating conditions and thermal cycling.

A membrane unit at SINTEF was upgraded for testing of electrochemical membranes provided by CoorsTek and commissioned for PMR test conditions (800 °C and 10 bar pressure with a steam to carbon ratio of 2.5). A single-segment tubular membrane was tested under PMR conditions and further improvements were made to the setup.

A paper was submitted on atomistic studies of CO₂ adsorption on the BaZrO₃-based membrane material in connection with a research visit at MIT supported by CLIMIT and other RCN projects.

Journal Publications

2019: 

• Surface reactivity and cation non-stoichiometry in BaZr1-xYxO3-δ (x=0-0.2) exposed to CO₂ at elevated temperature - R. Sažinas, M.F. Sunding, A. Thøgersen, I. Sakaguchi, T. Norby, T. Grande, J.M. Polfus
• Factors Limiting the Apparent Hydrogen Flux in Asymmetric Tubular Cercer Membranes Based on La27W3.5Mo1.5O55.5−δ and La0.87Sr0.13CrO3−δ - Z. Li , J.M. Polfus , W. Xing, C. Denonville, M.-L. Fontaine, R. Bredesen

2018: 

• Adsorption of CO₂ and Facile Carbonate Formation on BaZrO3 Surfaces - J.M. Polfus, B. Yildiz, H. L. Tuller,  R. Bredesen
• Interplay between H₂O and CO₂ coadsorption and space-charge on Y-doped BaZrO3 surfaces - Polfus, Jonathan M., Yang, Jing, Yildiz, Bilge