NOVEL COMPOSITE MEMBRANES FOR HYDROGEN SEPARATION IN GASIFICATION PROCESSES IN VISION 21 ENERGY PLANTS

This report describes the work performed, accomplishments and conclusion obtained from the project entitled ''Novel Composite Membranes for Hydrogen Separation in Gasification Processes in Vision 21 Energy Plants'' under the United States Department of Energy Contract DE-FC26-01NT40973. ITN Energy Systems was the prime contractor. Team members included: the Idaho National Engineering and Environmental Laboratory; Nexant Consulting; Argonne National Laboratory and Praxair. The objective of the program was to develop a novel composite membrane structure for hydrogen separation as a key technology module within the future ''Vision 21'' fossil fuel plants. The separation technology module is targeted for use within the gasification module of the ''Vision 21'' fossil fuel plant. The high performance and low-cost manufacturing of the proposed technology will benefit the deployment of ''Vision 21'' fossil fuel plant processes by improving the energy efficiency, flexibility and environmental performance of these plants. Of particular importance is that this technology will also produce a stream of pure carbon dioxide. This allows facile sequestration or other use of this greenhouse gas. These features will benefit the U.S. in allowing for the continued use of domestic fossil fuels in a more energy efficient and environmentally acceptable manner. The program developed and evaluated composite membranes and catalysts for hydrogen separation. Components of the monolithic modules were fabricated by plasma spray processing. The engineering and economic characteristics of the proposed Ion Conducting Ceramic Membrane (ICCM) approach, including system integration issues, were also assessed. This resulted in a comprehensive evaluation of the technical and economic feasibility of integration schemes of ICCM hydrogen separation technology within Vision 21 fossil fuel plants. Several results and conclusion were obtained during this program. In the area of materials synthesis, novel pyrochlore-based proton conductors were identified, synthesized and characterized. They exhibited conductivity as high as 0.03 S/cm at 900 C. Long-term stability under CO{sub 2} and H{sub 2} atmospheres was also demonstrated. In the area of membrane fabrication by plasma spray processing, the initial results showed that the pyrochlore materials could be processed in a spray torch. Although leak-tight membranes were obtained, cracking, most likely due to differences in thermal expansion, remained a problem. More modeling and experimental work can be used to solve this problem. Finally the techno-economic analyses showed that the ITN ICCM approach for separating H{sub 2} is comparable to conventional pressure swing adsorption (PSA) technology in efficiency and economics. Enhanced membrane flux and lower operating temperatures may make the ICCM approach superior to PSA