Mathematical modeling of the hydrocarbon (HC) pyrolysis kinetics has been performed using the propane-butane fraction as feedstock. The calculated data have been compared with the results of the examination of industrial pyrolysis furnaces after operation with a significant sporadic change in the feedstock composition. The mathematical model has been adapted to the operation of the real pyrolysis furnace. The adequacy of the adapted mathematical model and its suitability for the operational control of the pyrolysis process have been proved. Regression equations have been obtained for the subsequent use in automatic process control systems.