Comparative Evaluation of the Performance of Coal Combustion in 0.5 and 50 kWth Chemical Looping Combustion Units with Ilmenite, Redmud or Iron Ore as Oxygen Carrier

Abstract

Chemical Looping Combustion (CLC) is one of the most promising technologies to achieve the CO2 capture at a low economic and energetic penalty. In CLC the combustion is split in two steps: fuel combustion assisted by an oxygen carrier in the fuel reactor, and oxygen carrier regeneration in the air reactor by oxygen in air. Usually, the air and fuel reactors are interconnected fluidized beds, with the oxygen carrier circulating between them. Thus, the CO2 capture is inherent to the CLC process. The use of solid fuels in CLC is attracting great attention due to coal is the most abundant fuel, and burning biomass with CO2 capture would allow to reduce the atmospheric CO2 concentration. The in situ Gasification CLC (iG-CLC) allows the conversion of the solid fuel by performing both gasification and combustion of gasification products in the fuel reactor. In iG-CLC complete combustion is not reached, and an oxygen polishing step is required downstream by using a small fraction of pure oxygen.In this work, an overview of the operational experience in ICB-CSIC is presented. Results obtained in 0.5 kWth and 50 kWth CLC units burning different coals with ilmenite, redmud or iron ore are compiled and critically compared. Insights were obtained in order to achieve high CO2 capture and combustion efficiency values. Eventually, the use of ring-type internals in the fuel reactor of the 50 kWth CLC unit was accomplished to promote the gas-solid contact, thus increasing the combustion efficiency.