A Comprehensive Study on the Combustion of Sunflower Husk Pellets by Thermogravimetric and Kinetic Analysis, Kriging Method

The combustion of sunflower husk pellets was investigated by kinetic analysis supplemented by the Kriging method. The nonisothermal thermogravimetric experiments in air were carried out at the temperatures from 20 to 700 degrees C and heating rates of 5, 10, and 20 degrees C/min. Kinetic analysis was carried out using the model-free OFW (Ozawa-Flynn-Wall) method and Coats-Redfern (CR) method. The activation energy values, calculated by the OFW method, ranged from 116.44 to 249.94 kJ/mol. These data were used to determine the combustion mechanism by the CR method. The kinetic triplet (E-alpha, A, g(alpha)) was determined in the conversion interval 0.2 to 0.8. The model of the chemical reaction F-8 was recommended to describe the mechanism of the thermochemical conversion process. The relationship between the kinetic parameters was analyzed using the Kriging method. The patterns between the kinetic parameters were represented as three-dimensional surfaces and two-dimensional projections. The distribution's surfaces were uniform; there were local extremes as well as linear regions. A new approach to the data analysis will allow predicting parameters of a thermochemical conversion of the various raw materials and contributes to a deeper understanding of the characteristics and mechanism of biomass combustion.