Coupled simulations of an ethylene dichloride (EDC) cracking furnace and reactor are conducted using one-dimensional Lobo Evans and computational fluid dynamics (CFD) models. Optimization is performed using the first model, in which the fuel gas allocation operator a is investigated to improve performance indices such as selectivity, conversion, and fuel gas consumption (per vinyl chloride monomer production). The optimum coil outlet temperature (COT) is suggested to make a good compromise among the performance indices. The CFD model is used to validate the optimized results. A standard k-epsilon two-equation model is applied to simulate turbulence, and a finite-rate/eddy dissipation model is used to model a premixed combustion of the sidewall burners. The discrete ordinate model is applied to simulate the radiative heat transfer of a furnace in a CFD simulation. The EDC cracking process in the reactor, as well as the flow, combustion, and radiative heat transfer in the furnace, is provided in the CFD model.