Thermal calculation of the radiation chamber of a hydrocarbon pyrolysis furnace with a non-symmetric arrangement wall-mounted burners
Authors: Vafin D. B. , Vankov Y. V. 
Published: January 2024

RELEVANCE. The possibility of predicting the operating conditions of individual elements of high-temperature technological units of petrochemical industries even at the design or modernization stage is relevant for many reasons. THE PURPOSE. Carrying out numerical studies of thermal parameters and features of the turbulent movement of flue gases in the radiative part of the hydrocarbon pyrolysis furnace with a central arrangement of coils with an asymmetric arrangement of burners of low thermal power on the side lined walls and on the vault of the chamber. Such furnaces are used to produce lower olefins, which are the primary products for the production of synthetic resins, rubbers, plastics and fibers. METHODS. In the radiant chamber of the furnace, interrelated processes of combustion of gaseous fuel, turbulent flow of combustion products, radiant-convective heat exchange and cracking reactions of hydrocarbons in tubular coils occur with the formation of a mixture of light hydrocarbons rich in olefins. The formation of pyrolysis products of hydrocarbons becomes essential when the temperature of the vapor-gas mixture in tubular reactors is within 800-855 oC in the presence of dilution steam.. The heat required for this will be obtained mainly due to the thermal radiation of the combustion products and the hot lined surfaces of the radiation chamber. The physical processes taking place in the combustion chamber are modeled by two-dimensional equations of the model gorenje hydrocarbons in the air, energy transfer by radiation and equations of motion. The package of applied programs is used, which is based on the numerical solution of the mentioned system of transfer equations. As a result of numerical studies, the velocity and temperature fields of flue gases formed during the combustion of a fuel gas mixture in the furnace chamber of a tube furnace were constructed. In his work, it is assumed that on one side wall of the radiation chamber, wall burners in the amount of 64 pieces are placed in eight horizontal rows, and on the other wall of the chamber, the same burners are installed in seven tiers and one row of burners on the vault of the chamber. The combustion products emanating from these burners form complex velocity and temperature fields in the volume in both halves of the radiation chamber. RESULTS. As a result of numerical calculations, the fields of temperature and flue gas velocities in both parts of the radiation chamber are constructed. The temperatures of the inner surfaces of the lining walls are calculated. The distributions of the surface densities of radiant heat fluxes to the reaction pipes along the height of the pyrolysis furnace of the propane-butane fraction are determined. Comparisons of some of the results obtained were carried out for cases when all burners are installed only on the side walls of the chamber and with the above arrangement of burners. CONCLUSION. Calculations show that the use of a large number of low-power wall burners leads to the emergence of complex velocity and temperature fields in the radiation chambers of tubular furnaces. At the same time, the spread of temperature values in the volume of the furnace chamber is much smaller than for the case when all burners of higher power are installed only on the vault and on the hearth of the furnace. By changing the location of the tiers of burners, it is possible to achieve a relatively uniform supply of heat to the heated product along the length of the pyro coil.