(195b) Non-Cryogenic Oxygen Production Technology Using Ion-Transport Membranes

DOE is supporting the development of an Ion-Transport Membrane (ITM) air separation technology for large, tonnage-quantity oxygen as stand-alone plants and for integration of ITM Oxygen with power generation systems. A multi-disciplinary effort was launched that required the simultaneous development of ceramic materials and manufacturing methods, engineering fundamental studies, energy cycle analyses, and ceramic oxygen conductor module design, construction and operation. The project has since reached the prototype phase. ITM Oxygen will enable advancement of energy production systems by achieving step change improvements in efficiency, environmental performance, and cost. It has broad applications to coal gasification and combustion systems, coal-to-hydrogen and electricity co-production plants, and has the potential to provide a technology-based response to global climate change concerns by improving the economics and emission performance of oxygen-enriched combustion in coal-based power plants.

The compositions of ITM materials are complex and application dependent, and are based on required operating temperature and environment. Generically, ITMs are engineered ceramics that operate at 700 to 1,000°C and at high pressures, and can be fabricated in tubular or planar configurations. Depending on the applications, ITMs can be pressure driven or chemical potential driven. In general, these materials allow the rapid transfer of oxygen ions, achieving very high flux which is orders of magnitude higher than polymeric membranes, with theoretically infinite selectivity. This property enables compact and efficient gas separator equipment designs. ITMs produce oxygen from air in a single separation stage under the gradient of oxygen partial pressure.

The application of ITMs to important industrial needs requires the design and fabrication of membrane modules that address both mechanical and process conditions. The ITM effort has led to compact, ceramic separator module and equipment designs and fabrication methods. Ceramic module architecture is typically either tubular or planar; however, for oxygen applications the full potential of ITMs is obtained through planar designs that rely on advanced lamination fabrication techniques. Laminated structures composed of layers of featured ceramic materials are joined to form an engineered structure. Layers are used to fabricate large, multi-passage membrane architectures satisfying all flow distribution, heat exchange, and mechanical strength requirements.

In partnership with DOE, Air Products has developed high-flux compact oxygen ion conductors in planar configurations to separate oxygen from air and achieved production flux exceeding commercial performance targets with excellent product purity. The research team built the first commercial-scale ITM Oxygen air separation module. A 5 ton-per-day subscale engineering prototype (SEP) facility has been successfully commissioned. The prototype achieved target performance for system pressure, temperature, and airflow rates typical of commercial operating conditions. Designed experiments assessed module performance through a series of scheduled process variable changes, eventually producing oxygen of more than 99 percent purity. Two commercial-scale modules in the SEP have been successfully cycled between operating and idle conditions. The modules gave the same or better performance when cycled between commercially-relevant operating conditions and idle states attesting that the materials and architecture of the new technology can withstand the stresses accompanying anticipated operational transients.

ITM Oxygen integrates well with turbine based power cycles. Successful embodiment of ITM Oxygen with advanced power cycles will increase efficiencies and environmental performance while reducing the capital and operating costs of coal-based energy plants. System and experimental studies confirm the economic benefits of ITM Oxygen technology. Process economic analyses to date have been mainly focused on the coal-fed IGCC power plant application. Other studies have detailed the use of ITM Oxygen in other applications, such as, oxygen-enriched combustion. These process economic analyses illustrate that the benefits of the ITM Oxygen technology relative to cryogenic air separation technology are significant. For example, an ITM Oxygen plant integrated with an IGCC facility could reduce the air separation plant capital and power requirement by over one-third each compared to IGCC-cryogenic facilities. ITM Oxygen can reduce the parasitic power load of coal boilers by over thirty percent.

Advanced energy production systems and future environmental mandates would require use of more oxygen rather than air. Today's cryogenic technologies are challenged to produce affordable oxygen for energy and other oxygen-intensive industries. The planned accomplishments of the follow-on project include the commissioning a nominal 150 ton-per-day (TPD) test facility comprising an integrated ITM Oxygen separator with a gas turbine. The nominal 150 TPD unit will provide scale-up data to allow the design and construction of a nominal 2000 TPD facility that could be tested as part of the DOE's FutureGen plant for co-producing hydrogen and electricity from coal. This presentation will give a technology overview and present some on-going R&D results.