Co-combustion of Biomass

Regenerative energy sources have gained importance during the last years. Co-combustion of biomass in a coal-fired burner is particularly attractive because the economic available biomass may be used in a large plant at high efficiencies. In the project a process was investigated where wood is pyrolysed and partial gasified in a fluidised bed gasifier. The gasifier produces a gas loaded with a fine dust of charcoal which is burned in the coal-fired boiler. Based on investigations carried out at the institute, a demonstration plant was erected and put into operation by Draukraft in Zeltweg. For the investigations the following facilities were used: Thermogravimetric Analysis (TGA): The ignition behaviour as well as the pyrolysis and gasification characteristics of the fuel particles were investigated by means of TGA at appropriate gas atmospheres and temperatures whereby the mass loss of the samples and the composition of the produced gas (CO, CO2, H2, CxHy, etc.) was measured as a function of time. Experimental fluidised-bed reactor: In order to find out the optimal operation conditions for maximum attrition an experimental fluidised-bed reactor was designed, erected and operated. In addition to high efficiencies one of the main advantages of this process is a comparable low investment (the gasifier may be design much smaller as usual). Furthermore the gas from the gasifier will reduce the NOx in the furnace of the coal-fired boiler due to reburning.