乙烷-丙烷混合裂解反应机理的二维模拟

TWO-DIMENSIONAL SIMULATION OF THE REACTION MECHANISM OF ETHANE-PROPANE MIXED CRACKING

利用FLUENT软件构建乙烷-丙烷混合裂解反应一维模型和二维模型,分别模拟反应管物料径向流速、温度、浓度分布及自由基浓度分布对乙烷-丙烷混合裂解过程的影响。结果表明:传递过程与裂解过程有耦合作用,径向扩散过程使烷烃裂解温度降低;二维模拟时CH4和C2H4浓度比一维模拟时高,而H_(2),C_(2)H_(6),C_(3)H_(6)浓度略低;乙烷-丙烷混合裂解主要由丙烷断链实现链引发,乙烷与丙烷共同参与链传递过程;乙烷-丙烷混合裂解时体系中存在H·,CH_(3)·,C_(2)H_(5)·,i-C_(3)H_(7)·,n-C_(3)H_(7)·自由基,C_(2)H_(5)·,i-C_(3)H_(7)·,n-C_(3)H_(7)·自由基的浓度需要一定积累后才能生成烯烃,乙烯主要由C_(2)H_(5)·和n-C_(3)H_(7)·生成,丙烯主要由i-C_(3)H_(7)·和n-C_(3)H_(7)·生成。

Using FLUENT software to construct one dimensional model and two dimensional models of ethane and propane mixture cracking reaction,the effects of radial flow rate,temperature,concentration distribution and free radical concentration distribution on the mixed cracking process of ethane and propane were simulated respectively.The results showed that the transfer process was coupled with the cracking process,and the cracking temperature of alkanes was decreased by radial diffusion.The concentrations of CH_(4)and C_(2)H_(4)in 2-D simulation were higher than those in 1-D simulation,while the concentrations of H2,C2H6 and C3H6 were slightly lower.The mixed cracking of ethane and propane was mainly initiated by the chain initiation of propane,and both ethane and propane took part in the chain propagation process.During ethane and propane mixture cracking process,there were free radicals H·,CH_(3)·,C_(2)H_(5)·,i-C_(3)H_(7)·and n-C_(3)H_(7)·in the system.The concentrations of free radicals C_(2)H_(5)·,i-C_(3)H_(7)·and n-C_(3)H_(7)·need to be accumulated before olefin could be formed.Ethylene was mainly generated by C_(2)H_(5)·and n-C_(3)H_(7)·and propylene was mainly generated by i-C_(3)H_(7)·and n-C_(3)H_(7)·.