Relevance. Numerical modeling is becoming an increasingly popular tool for studying and analyzing various thermochemical processes, among which pyrolysis is of the greatest interest due to the variety and complexity of chemical reactions. In addition, this process is environmentally friendly, as it does not produce harmful emissions into the atmosphere. The results obtained by numerical simulation of pyrolysis of worn tires make it possible to obtain reliable data on the composition of released gaseous substances, optimize and predict the behavior of the process under various configurations of equipment, which significantly reduces the time of experimental studies. Aim. To determine the composition of the pyrolysis gas and to identify the temperature dependences of the yield of volatile components using numerical simulation methods for the thermal decomposition of rubber chips densely packed in a cylindrical flow reactor. Methods. To solve this problem, a numerical method based on the application of finite element analysis in the Ansys application software package is used. Results and conclusions. The paper provides a literature review of pyrolysis research by domestic and foreign authors. The results of numerical simulation of thermal decomposition in a cylindrical reactor with a fixed dense layer for crushed spent large-sized tires of 3 mm fraction in the temperature range from 350 to 650°C. The results obtained demonstrate a change in the yield of volatile substances depending on temperature, as well as qualitatively and quantitatively consistent with experimental data with an error of no more than 15%. It is noted that with temperature growth in the studied gas, an increase in the hydrogen content and a decrease in the proportion of C₁–C₄ hydrocarbons are observed. According to the derivatogram of the rubber crumb in the helium current, the value of the activation energy is determined, which is 188.6 kJ/mol.