(75d) Syngas Chemical Looping and Coal Direct Chemical Looping Processes for Hydrogen and Power Production with in-Situ Carbon Capture: Pilot Scale Development and Demonstration
Redox Chemical Looping processes use a metal oxide or metal sulfate to performed reduction and oxidation reactions with a carbonaceous fuel and air/steam, respectively. Redox chemical looping systems are advantageous in their ability to produce high purity products undiluted with nitrogen present in air, eliminating the need for energy intensive components such as a cryogenic air separation unit or an acid gas removal device. The Ohio State University (OSU) has advanced the redox chemical looping concept in the development of two, 250 kWth pilot-scale demonstration plants for coal combustion to produce heat for electricity generation, the coal direct chemical looping (CDCL) process, and for gaseous fuel conversion for producing high purity H2, the syngas chemical looping (SCL) process. In each of these processes, a countercurrent moving bed reducer reactor is used for full conversion of the carbonaceous fuels to a gas stream consisting predominantly of CO2 and H2O. A fluidized bed combustor reactor is used to regenerate the oxygen carriers to their original oxidation state. In the SCL process, a third countercurrent moving bed oxidizer reactor is used to produce high purity H2 from steam. The countercurrent moving bed reducer reactor design in the CDCL and SCL processes ensure nearly full fuel conversion to CO2 with minimal solid circulation requirement and have the capability of producing high purity H2. The SCL pilot plant was constructed and tested at the National Carbon Capture Center for processing coal-derived syngas to H2. The CDCL pilot plant was constructed with ongoing operations at the Babcock and Wilcox Research Center for coal combustion with carbon capture. The present paper discusses the development strategy in the design of both pilot plants, reviews the startup and operation challenges observed during the plant commissioning, and summarizes the demonstration results to date. Additional discussion is presented on the comparison the demonstration results with the theoretically expected performance. Overall, over 1,500 hours of operational experience were gained from these pilot plants.