(480h) Design and Operation of High Pressure and High Temperature Fluidization Systems for Chemical Looping Application

Authors: 
Tong, A., The Ohio State University
Wang, D., The Ohio State University
Chung, C., The Ohio State University
Hsieh, T. L., The Ohio State University
Xu, D., The Ohio State University
Fan, L. S., The Ohio State University
Chemical looping technologies have evolved into a promising alternative for the efficient conversion of carbonaceous fuels to electricity and/or high value chemicals with minimal carbon emissions. These processes utilize an oxygen carrier solid material to indirectly supply oxygen to the fuel source. With the exponential growth of research and publications in this field, chemical looping has expanded to encompass power and chemical production with in-situ gas separation. The Ohio State University (OSU) has advanced the chemical looping concept in the development of 2 pilot-scale demonstration plants for coal combustion with CO2 capture and gaseous fuel conversion to high purity H2 as well as multiple sub-pilot test units for syngas generation from biomass, natural gas, and coal. In each of these processes, a moving bed reducer reactor is used for partial or full conversion of the carbonaceous fuels to CO/H2 and CO2/H2O, respectively. A fluidized bed combustor reactor is used to regenerate the oxygen carriers to their original oxidation state. Interconnecting nonmechanical valves between reactors are used to control the solids circulation rate of the system for the mass balance of the redox reaction and heat balance for the system integration. This paper also summarizes the key developments of two chemical looping processes – the 250kWth-3MWth high pressure syngas chemical looping (SCL) pilot plant and the coal direct chemical looping (CDCL) 25 kWth sub-pilot unit and 250 kWth pilot plant. Key process design features and experimental results from over 1,500 hours of cumulative operation will be discussed. The counter-current moving bed reducer reactor design the CDCL and SCL process ensure nearly full fuel conversion to CO2 with minimal solid circulation and capability of producing high purity H2. During operation of the pilot plants, sliding mode control theory was adopted for modulating the aeration gas flow rate against the pressure fluctuations caused by the slugging bed combustor in order to maintain a constant solid circulation rate.