In a wildland fire, the thermal decomposition of biomass supports the burning of wildland material, while the pyrolysis of shallow soil has a considerable impact on the underground smoldering. So far, the interaction between biomass and shallow soil has been scarcely studied. This work presents an effort on this problem. The thermal behaviors of pine needle, pine bark, pine branch, shallow soil and their mixtures are investigated using a thermogravimetric analyzer under nitrogen and air atmospheres. The calculated TG curves of the forest combustible mixtures, obtained with the mixing ratios and experimental data of individual materials, agree well with the experimental data. This indicates that the interaction among biomass and shallow soil mixture is negligible under nitrogen and air atmospheres. The deviation parameter and the deviation of residue yield between the calculated and experimental curves are used to evaluate the influence of interactions on the organic and inorganic components, respectively. The calculated lower values of these parameters (<3%) confirm insignificant effect of interaction between biomass and shallow soil on pyrolysis and combustion. In addition, results further indicate that the effect of interactions on the thermal decomposition of the organic component is closely associated with the atmosphere and mixing ratio, while the effect on inorganic component has no perceptible relationship with these two factors. A kinetic model, involving nth-order independent parallel reactions, is applied to verify the reliability of the evaluation result. The pyrolysis rate of biomass is considered as the sum of the three pseudo-components, namely cellulose, hemicellulose, and lignin. While in the pyrolysis of shallow soil, the three pseudo-components are composed of labile, intermediate, and stable organic materials. The major mass loss of single material in combustion is interpreted as the sum of the parallel reactions of the above three pseudo-components as well as char. The theoretical TG curves of the mixtures, based on mixing ratio and kinetic parameters of individual materials, are in good agreement with experimental data, which also suggests an insignificant interaction effect on pyrolysis and combustion.

International Seminar on Fire and Explosion Hazards (9; 2019; Saint Petersburg, Russia). Proceedings of the Ninth International Seminar on Fire and Explosion Hazards [Электронный ресурс]: 21-26 April 2019, Saint Petersburg, Russia. Vol. 2 / Peter the Great St. Petersburg Polytechnic University, Autonomous Non-Profit Organization "Fire and Explosion Safety", Gefest Holding Ltd ; [edited by A. Snegirev [et al.]. — Электрон. текстовые дан. (1 файл : 98,7 Мб). — Saint Petersburg, 2019. — Загл. с титул. экрана. — Свободный доступ из сети Интернет (чтение, печать, копирование). — Adobe Acrobat Reader 7.0. — <URL:http://elib.spbstu.ru/dl/2/k19-97.pdf>. — <URL:http://doi.org/10.18720/SPBPU/2/k19-97>.