Combustion behaviour of biomass fuels and their blends with lignite

The combustion characteristics of various biomass fuels from the Mediterranean region (olive prunnings, cotton residue, olive and peach kernels, pine needles, cardoon, and sewage sludge), one lignite and lignite/biomass blends were investigated and the compatibility of each component in the blend was studied. The experiments were conducted in a thermogravimetric analysis system. The effects of heating rate, oxygen concentration, particle size and moisture content of the fuels were examined. Combustion parameters were measured and ignition and combustion indices were calculated, in order to evaluate the performance of the process. The results showed that the combustion process was controlled by the emission of volatile matter. Ignition and burnout temperatures were slightly increased with particle size and moisture content of the fuels. An oxygen-enriched atmosphere reduced the ignition temperature and the burnout time and improved the combustion performance of the fuels. A higher heating rate delayed the process, but increased the burning rate. For the mixtures studied, it was found that the combustion characteristics of the blends followed those of parent fuels in both additive and non-additive manners. Blending lignite with biomass fuels increased its thermochemical reactivity.