An investigation of steam production in chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) for solid fuels

Chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) are being actively explored as solid fuel combustion technologies that have the potential to facilitate CO₂ capture. While CLC and CLOU have similarities operationally, there are some key differences. In particular, the CLC process requires a coal gasification step where coal is first broken down into a syngas with the use of steam or CO₂. The resulting syngas is then oxidized with the metal oxide to release energy. In the CLOU process the metal oxide releases oxygen that combusts the solid fuel, resulting in a lower residence time, as the coal gasification reactions are avoided. The CLC and CLOU systems were modeled with ASPEN Plus at a 10MW_th scale, and the process streams were analyzed by ASPEN Energy Analyzer to determine the amount of industrial process steam that could be generated from CLC or CLOU. Both the air and fuel reactor were analyzed as two circulating fluidized beds, with metal oxide circulating between the two reactors. The air reactor, where metal oxide is oxidized, was fluidized with air. The fuel reactor, where the metal oxide is reduced, was fluidized with steam for CLC and recirculated CO₂ for CLOU. It was identified that the CLOU process had the potential to produce more steam, approximately 7920kg/h, as compared to CLC (6910kg/h).