Spray granulated Cu-Mn oxygen carrier for chemical looping with oxygen uncoupling (CLOU) process

Abstract

One form of Chemical Looping Combustion (CLC) with CO2 capture as an alternative to the burning of solid fuels is the Chemical Looping with Oxygen Uncoupling (CLOU) process. The CLOU process requires metal oxides with O2 release capacity at temperatures that are suitable for solid fuel combustion, e.g. copper and manganese oxides. A Cu-Mn mixed oxide comprising 34wt% CuO and 66wt% Mn3O4 and prepared by fluidized bed granulation was analysed for use as an oxygen carrier for the CLOU process. TGA and batch fluidized bed reactors were used to investigate oxygen generation rates, agglomeration behaviour and oxygen carrier attrition. A medium volatile coal from South Africa and its char were used as fuel in a batch fluidized bed reactor in a temperature range of 800–930°C. The Cu-Mn oxygen carrier showed good release O2 rate and a high rate of oxygen transfer by direct gas-solid reaction. The presence of CO as a combustion product appeared only at low oxygen carrier to coal ratios. This material has the capacity to generate O2 at lower temperatures than needed for Cu-based oxygen carriers, which suggests that this material is suitable for work at lower temperatures in a fuel reactor with complete combustion of the fuel. The low attrition rate and attrition index, together with the stable crushing strength of the particles with redox cycles, make this Cu-Mn oxygen carrier suitable for operation in a continuous CLOU unit.