乙烯裂解炉的蒸汽-空气烧焦过程模拟

SIMULATION OF THE STEAM-AIR COMBINED COKE CLEANING PROCESS FOR THE ETHYLENE CRACKING COILS

裂解炉炉管内壁的蒸汽 空气烧焦操作是一个反应温度和浓度沿空间变化的动态过程。此过程可以用一组非线性双曲型偏微分方程描述。为了便于求解及积分的收敛 ,采用迎风差分格式计算。在烧焦过程模拟中 ,根据裂解炉炉管高温成焦的特点 ,采用了沿炉管不变的烧焦反应动力学参数和反应热 ,模拟计算 2 0h内裂解炉炉管不同时刻的焦层厚度、气固相温度、氧气和水蒸气分压沿炉管的变化 ,计算结果与工业测量结果相符合 ,为开发先进的裂解炉在线烧焦技术提供了更加可靠的基础。

Removal of coke layer deposited on the internal surface of the cracking coil is a dynamic process with the variation of temperature and concentration along the reactor length. For this purpose, a mathematical model was established by a set of hyperbolic partial differential equations. For the sake of convergence of integration, the windward difference from was adopted. In view of coke formation under high temperatures, constant combustion kinetic parameters and reaction heats were assumed independent of the tube length. An 20 h coke burning was simulated, which provided the time-varying behavior of the coke layer thickness, the gas and coke temperatures, the pressures of oxygen and steam along the reactor. The simulation was in good agreement with the available industrial data. This work provides some fundamental information to the development of advanced online coke-burning technology for the ethylene production.