Based on the computational fluid dynamics(CFD)method

a coupled simulation of combustion with heat transfer in the firebox radiation section and cracking reaction of naphtha in the reactor tube was carried out in a SL-Ⅱ industrial ethylene pyrolyzer by using CFX software.The standard k-ε turbulence model

eddy dissipation/finite rate chemistry combustion model(EDM/FRC)and discrete transfer(DT)radiation model

combined with multi-grey gas model for radiation properties of flue gas

were used to model the firebox.The molecular reactions model scheme proposed by Kumar was used to simulate cracking reaction of naphtha in the tubular reactor.Meanwhile

the Navier-Stokes equation system was solved by a so-called fully implicit coupled algorithm.Simulation results agreed very well with industrial data

which proved the reliability of the model.Simulation results showed that propylene and butylene yields firstly increased and then decreased

while methane and ethylene yields increased all the way.the addition of side burners brought the outlet tube skin temperature distribution to be more uniform.The flue gas recirculation made the temperature in the middle of firebox more uniform.The asymmetrical structure of the furnace led to the asymmetry of flue gas velocity at the top of the furnace

and further led to a lower efficiency of heat supply of the side burners on the rear wall than the ones on the front wall.The results could be helpful for engineers to design and optimize the  ethylene pyrolyzer.