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This work describes the capability of a novel chemical looping system that utilizes CO2 as a feedstock for methane reforming.

The coal direct chemical looping (CDCL) combustion process using an iron-based oxygen carrier has been developed and demonstrated in a 25-kW th subpilot unit. The CDCL subpilot unit is the first chemical looping demonstration unit with a circulating moving bed for the solid fuel conversions. To date, the CDCL subpilot unit at OSU has been operated for more than 550 h. The feasibility of the subpilot unit with various types of solid fuels including sub-bituminous coal and lignite coal has been tested. This article discusses the operational experience of a successful 200-h integrated, continuous demonstration with sub-bituminous coal and lignite coal. Throughout the 200-h continuous operation, the CDCL subpilot unit showed steady behavior in terms of solid circulation, coal handling, and oxygen carrier reactivity and recyclability. Tests with both coals confirmed more than 90% coal conversion with 99.5 vol % purity of CO 2 achieved in the reducer. The sound design of the reducer allowed for nearly full coal conversion with a high purity of CO 2 , eliminating the need for additional downstream fuel polishing and separation units. The combustor gas contained lean oxygen concentrations with minute amounts of carbonaceous gases (CO 2 , CO, and CH 4 ) detected. The combustor gas analysis implied the proper regeneration of iron-based oxygen carriers, good gas sealing between the reducer and combustor, and no indication of unconverted carbon carry-over. Moreover, the fates of coal pollutants such as NO x and SO x that are commonly observed in the conventional coal combustion process were also investigated during the subpilot unit operation. The NO x analysis showed that the CDCL process is capable of significantly reducing NO x emissions by avoiding thermal NO x formation. The sulfur analysis indicated SO 2 generation in both reducer and combustor, agreeing with the sulfur chemistry in the CDCL scheme.

The syngas chemical looping (SCL) process has been demonstrated at The Ohio State University for the conversion of gaseous fuels, such as natural gas and syngas, to sequestration-ready carbon dioxide (CO 2 ) and high-purity hydrogen (H 2 ) in a 25 kW th sub-pilot-scale unit operation. The present work focuses on parametric studies of the unique moving-bed reducer reactor operation for the conversion of methane to a concentrated stream of CO 2 . The variables studied include the reactor operating temperature, the gas hourly space velocity (GHSV), and the oxygen carrier/methane mass flow ratio. The results show that nearly full methane conversion (∼98%) can be achieved in the process with a GHSV of 395 h −1 . Additionally, the post experiment oxygen-carrier analysis indicated that the oxygen-carrier conversion reached nearly 50%. Comparatively, the resulting oxygen-carrier conversion for the moving-bed reducer design is nearly 5 times greater than that theoretically achievable in a fluidized-bed reducer. The oxygen-carrier conversion profile along the height of the bed indicates that the conversion from Fe 3 O 4 to FeO occurs at a much faster rate than the conversion from FeO to Fe in the reactor system. A multi-stage equilibrium simulation model for the reducer performance was developed using ASPEN Plus to compare against the experimental results. The simulation and experiment show a good match for oxygen-carrier and methane conversion results based on the testing conditions used. The parametric studies performed show promising results, indicating that the SCL technology can be used for the conversion of natural gas with CO 2 readily separated.