Many agro-industrial companies grow amaranth for the subsequent production of amaranth oil, flour, cereals, flakes, and bran. After the grain is extracted, waste in the form of inflorescences remains, which can be used to obtain useful new products. This work investigated the use of pyrolysis to recycle amaranth inflorescence wastes (AIW). Thermochemical conversion experiments in an inert medium were carried out in a laboratory setup at 550 °C and a heating rate of 10 °C/min. It was found that the AIW pyrolysis produced 37.1 wt.% bio-oil, 35.8 wt.% pyrogas and 27.1 wt.% biochar. The oil fraction of the obtained bio-oil contains 41.8% of hydrocarbons. Thermogravimetric analysis of AIW was performed in the temperature range from 40 to 1000 °C at heating rates of 10, 15, and 20 °C/min in argon medium (75 mL/min). The kinetic parameters were determined by the model-free Friedman, Ozawa-Flynn-Wall, and Kissinger-Akahira-Sunose methods. The average activation energy values are in the range of 208.44–216.17 kJ/mol, and they were used to calculate the thermodynamic parameters. The results indicate that the pyrolysis application will allow efficient conversion of AIW into value-added products.

The thermal decomposition of two types of peat from the Vladimir oblast of Russia in an inert atmosphere of argon was studied for the first time with the c

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 °C and heating rates of 5, 10, and 20 °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_α, A, g(α)) was determined in the conversion interval 0.2 to 0.8. The model of the chemical reaction F₈ 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.

The aim of this work was to experimentally study the oxidative torrefaction of sunflower husk pellets in a kaolin layer. The kaolin layer was used to limit oxygen access to the biomass to prevent it from self-ignition. The changes in mass yield, volatiles, ash content, high calorific value (HHV), hydrophobicity, and morphology of the biomass were investigated at torrefaction temperatures 240, 260, and 280 °C, process durations 30–60 min, and kaolin layer heights 3–5 cm. The Van Krevelen diagram and the CHO index based on atomic C, H, and O data were also used for explanation. As a result of oxidative torrefaction in the kaolin layer, the atomic O/C and H/C ratios decreased and the sunflower husk position shifted towards peat. During torrefaction at 260 °C for 1 h (kaolin layer height of 3 cm) the O/C decreased by 26.9% and the H/C by 18.8%. Reducing the height of kaolin layer, as well as increasing the temperature and time of torrefaction, led to a decrease in mass yield and an increase in ash content. Torrefaction increased the FC/VM ratio from 50 to 225%, which improved the fuel properties of the biomass. A 16.5% increase in HHV was achieved compared to untreated sunflower husk. As the torrefaction intensity increased, drier fuel was formed, the moisture absorption of which decreased from 213 to 25.8%.

The results of studies of the thermal transformations of granulated wood biofuel performed by thermogravimetry and differential scanning calorimetry in an atmosphere of argon at heating rates of 5, 10, 20, and 30 K/min are reported in this paper. The results of the analysis were used for the determination of the preexponential factor and activation energy of the thermal decomposition of wood biofuel based on the Kissinger, Kissinger–Akahira–Sunose, and Ozava–Flynn–Wall isoconversion model-free methods. The values of activation energy for the release of volatile substances in the course of the thermal decomposition of wood granules varied in ranges of 87–250 and 76–242 kJ/mol.