The influence of sludge ash and its active species on the combustion characteristics and kinetics of biomass: application of model-fitting method combined with master-plots method

Combustion characteristics and kinetics of camellia seed shell (CS) with additions of sludge ash (SA) and its active species of CaO, Fe2O3, and SiO2 were analyzed by thermogravimetry. The combustion paths of CS with the additives fell between "in situ combustion of carbon-containing components" and "complete volatiles release + char combustion." In the view of heat release, the additions of SA active species increased the combustion performance of CS. A higher heating rate greatly increased the combustion performance, but the addition of CaO decreased the combustion performance. The combustion kinetic parameters of CS with the 10% additions of SA, CaO, Fe2O3, and SiO2 were analyzed by combining Coats-Redfern and Malek methods. The distributions of the activation energies of the second combustion zone with certain additives were more centralized. It was found that the second combustion zones all followed f(x) = (1 - x)(2) at varied heating rates, while those of the third zone were not identical, and those of the fourth zone of CS + 10%CaO followed f(x) = (1 - x)(2/3).