UNSTEADY-STATE SIMULATION OF GASOLINE FRACTION PYROLYSIS

Abstract

The relevance of the research is caused by the need of alkenes production increase as well as deepening understanding of the coke formation. The direction of petrochemical complex development and increase of pyrolysis efficiency is resources-saving, minimizing the volume of operations cost and the probability of occurrence of accidents. The main aim of the research is to develop a mathematical model for gasoline fraction pyrolysis, which will consider coke formation and its effect on the kinetic, hydrodynamic and thermodynamic components of the process. Object of the research is gasoline fraction pyrolysis process; dynamic of hydrocarbon stream composition during the process and coke formation side process. Methods. The methodological basis of the research is the system analysis and the method of mathematical modeling. In addition, quantum-chemical methods are used to calculate the thermodynamic and kinetic parameters of target and side chemical reactions occurring during the processing of hydrocarbon raw materials, and electron-structural methods based on the density functional theory; methods of computational fluid dynamics for the study of flow regimes and the deposition of coke particles on the walls of the coil; developed experimental methods for determining the optimal consumption of hydrocarbon raw materials and steam, predicting the duration of the inter-regeneration cycle of the pyrolysis furnace. Results. A non-stationary model of gasoline fraction pyrolysis was created to describe the coking side process along the length of the pyrolysis tube and over time. With the model, the rate of coke layer formation was calculated considering the technological parameters and the composition of feedstock. The calculated rate is 3,12∙10–7 mm per second. The results also made it possible to obtain the thickness distribution of the coke layer in the radiant coil, which indicates the acceleration of side processes towards the end of the process. This is due to formation of a significant amount of unsaturated compounds. It was found that changing the main parameters has two opposite effects. Thus, with an increase in temperature and pressure, both the yields of target products and the growth rate of the coke layer increased. An increase in the consumption of raw materials leads to a decrease in both of these parameters.

Keywords

• pyrolysis
• hydrocarbon feedstock
• unsteady-state
• mathematical model
• gasoline fraction