Design and Operation of a Coal-fired 50 kWth Chemical Looping Combustor

A 50 kWth pilot plant for solid fuels have been designed and constructed to be operated in both iG-CLC and CLOU modes for solid fuel combustion. The design of the concept was based on two interconnected circulating fluidized beds reactors. A carbon stripper has been included between fuel and air reactors to increase the residence time of char particles in the fuel reactor, thus allowing high CO2 capture rates. The char particles are separated and recirculated to the fuel reactor. In this device, the solid flow exiting from the fuel reactor splits into two different streams. One goes to the carbon stripper and the other is recirculated to the fuel reactor. In this way it is possible to have an independent control of solid inventory in the fuel reactor and the global solid circulation flowrate between fuel and air reactors. Startup and experimental results obtained in this unit during combustion of a subbituminous coal with ilmenite by iG-CLC are presented. Low oxygen demand values were found (5.2%) in gases coming from the fuel reactor. This value agrees with the predictions obtained with a previously validated model. Moreover carbon capture efficiencies of 95% were found due to the high separation efficiency of the carbon stripper.