Pyrolysis of wood pellets in the presence of oxygen carriers in a fluidised bed coupled with a DBD reactor for tar quantification
The pyrolysis of wood in the presence of chemical looping agents including Fe2O3, mayenite-supported CuO and mayenite-supported Cu2O was studied from 773 to 1173 K. A continuous tar quantification system, based on a DBD reactor downstream of the fluidised bed, was developed to allow quantification of the tar formed. An oxygen-containing plasma was used to convert volatiles and tars to measurable carbon-containing species, mainly CO, CH4, and CO2. It was found that pyrolysis of the wood in alumina sand produced CH4, CO, CO2, tar and char as the main products. Tar cracking was observed above 1073 K, and this mainly generated CH4. Both Fe2O3 and mayenite-supported Cu-based oxides were effective for in situ combustion of the pyrolysis products, particularly tar, at temperatures exceeding 873 K. Mayenite-supported CuO showed the highest reactivity. The results showed the potential of using metal oxides for direct combustion of biomass, and particularly converting the tarry products during devolatisation. The better activity of mayenite-supported CuO compared to Fe2O3 and Cu2O in these experiments was mainly due to the ability of CuO to release gaseous oxygen at higher temperatures.