Kinetic study of the co-firing of bagasse-sludge blends

Abstract

Thermogravimetry was used for the thermal and kinetic characterization of waste biomass as bagasse and sewage sludge and their blends, during the co-firing process for power generation. The kinetic evaluation was performed by a linear integral isoconversional method, applying different conditions of heating. In higher heating rates, kinetic process of combustion of all tested biomasses showed the lower values and the lower changes in activation energy up to 70 % for the conversion of all samples. Above this point, there was a continuous increase in this parameter for bagasse and the bagasse-sludge blends up to the end of the processes. However, in the case of sludge, there was a continuous decrease in energy, which suggests the occurrence of catalytic reactions. The results showed that under low heating rates, the sludge-bagasse blends exhibit profiles of kinetic decomposition very similar to bagasse, regardless the proportion of sludge employed, which may be due the contribution of the high amount of volatile organic materials present in bagasse (30 % higher than the sludge), which increase the reactivity of the sample during the devolatilization process. On the other hand, the kinetic study confirmed the occurrence of the kinetic compensation effect, which suggests a similar scheme of degradation between the biomass samples. Thermal characterization and kinetic study may surely provide valuable information to support the co-processing of waste biomass in order to maximize their fuel performance, ensuring its efficient use of both the environmental and the economic point of view.