Numerical Simulation On The Combustion And Cracking Reaction Of Ethylene Cracking Furnace

The thermal cracking process of ethylene is an important process in the ethylene industry, and the cracking furnace is the key unit. Only some foreign corporations hold the whole technique of cracking process at present. Lacking of the knowledge of hydro-flow,combustion and cracking reaction,mass transfer and heat transfer in the furnace, it is difficult to get the operation analysis and the furnace design optimization. Thus,it is very significant for us to study details of the combustion and cracking reaction,transfer process in the cracking furnace.History and developments of simulation on ethylene cracking furnace are reviewed and analyzed.Based on those,taking complex flow,heat tranfer,mass tranfer combustion reaction process of hearth and flow,heat tranfer,mass tranfer,cracking reaction process of tube , as well as coupling relation of those processes, together with non-premixed PDF model, discrete ordinates model, turbulence model and 25 molecule kinetic reaction model,a k-εcoupling furnace-reactor mathematical model was developed. Meanwhile,the simulation calculation of CBL cracking furnace are put forward.The rationality of the mathematical model was testified by the approximate agreement of industrial data and simulation result data.The detailed information of the velocity, concentration and temperature,heat fulx distribution was obtained,which raveals the basic characteristics of the flow,mass and heat transfer processes in the cracking furnace and their relation and reciprocity.The information privided basic data and guidance for the design and improvement of ethylene cracking furnace.The established mathematical model for ethylene cracking furnace was applied to simulate hydrodynamic and reation behavior at different operation conditions(hydrocrbon flow rate,heat flux,dilution ratio)and different gepmetrical parameters.Through the comparsion among the simulated rasults,the qualitative effects of operation conditions and gepmetrical parameters on the processes of combustion and cracking reactions were revealed,the result of which used in reasonable design and optimum operation of industrialethylene cracking furnace.Through the analysis of advantage and disadvantage on the separate alternate arithmetic, a new coupling simulation calculation was put forward. Meanwhile, the simulation calculation of shrunken,simple industrial cracking furnace was carried out . The results indicated that flow,heat tranfer,mass transfer of fule and hydrocarbon in the separated space,that heat fulx among furnace and tube change with three-dimensional space. This method really coupled a series of processes on the cracking furnace and overleap complicated alternation.