Development of oxygen transport membranes for coal-based power generation

Abstract

Praxair is developing an Advanced Zero Emission Coal Fired Power Plant (Advanced Power Cycle) that enables carbon capture and sequestration (CCS) at a “levelized” cost of electricity below the U.S. Department of Energy’s target for CO2 capture from coal fired power plants. The power cycle utilizes a gasifier, partial oxidation units, power recovery turbines and an oxygen fired boiler to yield a process that meets the DOE’s goal of <35% increase in cost of electricity with CCS. Through the use of Praxair’s reactively driven Oxygen Transport Membrane (OTM) technology, the parasitic load of the oxygen supply system to both the partial oxidation reactors and boiler is reduced by approximately 75%. The Advanced Power Cycle uses coal gasification to produce a gaseous fuel that is then combusted in an oxygen fired supercritical boiler. Low cost oxygen is made available by integrating Praxair’s OTMs into the boiler and, depending on the gasifier selected, into a post gasification partial oxidation system to convert tars and methane to CO and hydrogen. Praxair has completed a detailed techno-economic analysis of the performance of the Advanced Power Cycle (APC) and achieved significant breakthroughs in the OTM architecture and gas separation layer chemistry to achieve the commercial flux targets under phase 1 of a cooperative research agreement with the United States Department of Energy (DOE). Phase 2 of this agreement, currently underway, is focused on developing a detailed cost estimate of key components of the cycle as well as developing fabrication cost estimates of the membranes. While the APC is targeted at coal based CCS, the key components of the APC can offer benefits to integrated gasification fuel cell cycles, natural gas combined cycle plants as well as other processes. These additional processes represent opportunities to demonstrate key components of the APC prior to demonstrating the technology in its entirety. These opportunities not only allow investment dollars to be leveraged for additional benefits but also allow critical performance and reliability to be gained at commercial scale in an industrial environment–a critical hurdle that must be crossed for any new technology to be implemented at utility scale. Praxair is encouraged by the progress made to date and believes that great progress has been made in the area of materials and cycle development. The newly developed materials and membrane architecture have met commercial flux targets while demonstrating robust performance. The APC holds great promise to address the needs of CCS, while minimizing the cost of compliance.