Design and operation of a 50 kWth Chemical Looping Combustion (CLC) unit for solid fuels

Abstract

A Chemical Looping Combustion (CLC) unit for solid fuels has been designed, erected and operated. The design was based on a thermal power of 20kWth for in-situ Gasification Chemical Looping Combustion (iG-CLC) or 50kWth for Chemical Looping with Oxygen Uncoupling (CLOU). Fuel and air reactors are two interconnected circulating fluidized beds reactors, with the coal being fed at the bottom of the fuel reactor to maximize the contact between the volatile matter and the oxygen carrier particles. A carbon stripper has been included between fuel and air reactors to increase the CO2 capture rates. In this unit, the char particles are separated from the oxygen carrier particles and recirculated to the fuel reactor. The solids flow exiting from the fuel reactor is split into two different streams by using a double loop seal down the fuel reactor cyclone. 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 solids inventory in the fuel reactor and the global solids circulation flow rate between fuel and air reactors. First operational results at steady state have been obtained with stable operation in iG-CLC mode during combustion of a bituminous coal with ilmenite being the oxygen carrier. A CO2 capture value of 88% at 991°C and a total oxygen demand value of 8.5% were obtained with a solids inventory in the fuel reactor of 470kg/MWth.