Unsteady state simulation of gasoline fraction pyrolysis

•Coke settles on the walls of pyrolysis furnace coil due to side reactions.•Coke deposition significantly decrease the process efficiency.•A non-stationary model was suggested as the mean to predict state of the process.•Calculated with model value of coke deposition rate is 3.12 ∙ 10–7 mm per second.•Percentage error is still high due to incomplete data about the process. Pyrolysis of various hydrocarbon feedstock is one of the key processes for production of monomers for polymer industry. During this process mixture of hydrocarbons is heated at high temperatures and in the absence of oxygen in furnace coil. However, coke settles on the inner walls of the coil due to side reactions of polymerization and consecutive polycondensation. This phenomenon decreases efficiency of process, thus, making it unstable. Therefore, existing stationary models might not be suitable for simulation of the process as they do not usually take into account influence of coke formations on kinetic, hydrodynamic or thermal aspects of pyrolysis. In this paper, development of unsteady-state model is presented as incremental improvement towards the solution of process optimization and forecasting of its performance. Thus, the model provides ability to understand deeper the influence of operating parameters on the coke formation process. The model allows to simulate coke deposition along the coil through intergeneration cycle, considering composition of provided feedstock. Dependencies of target products yields and coke layer growth rate on such operating parameters as inlet pressure, temperature and feedstock mass flow rate were determined. The inlet pressure varied from 0.3 to 0.75 MPa, the temperature varied from 780 to 850 °C and the flow rate – from 3600 to 5000 kg/h.