乙烯裂解炉空气烧焦过程模拟及其应用

Simulation of Decoking Process of Ethylene Cracking Coils by Air and Its Application to Process of Decoking

裂解炉炉管内壁的空气烧焦过程是个炉管温度、压力、浓度和焦炭厚度随时间沿空间变化的动态过程,因此其机理模型是一组非线性双曲线偏微分方程。以某化工研究院的乙烯裂解炉装置为研究对象,利用选定后的假设沿炉管不变的烧焦反应动力学参数和反应热,使用隐式差分格式模拟计算炉管出口处二氧化碳浓度,得到空气烧焦过程的内在特性,根据模拟计算,提出了一种在线自动闭环控制方法,所提方法不同于传统的顺序开环烧焦控制,它以二氧化碳浓度和裂解炉管壁温度的变化作为反馈来实时地调整入口空气流量和壁管温度,实验结果证实了所提方法的可行性和有效性。

Air decoking process on the inner surface of the cracking coil is a dynamic process with the variation of temperature, pressure, concentration and coke layer thickness along the reactor length. For the air decoking process, a mathematical model was derived by a set of hyperbolic partial differential equations. According to a real ethylene cracking furnace by choosing the reaction kinetic parameters and reaction heat along the furnace tube, simulation of the concentration dynamic change for carbon dioxide which was the index of the decoking process with implicit difference algorithm was done. Based on the simulation results, a method of online-decoking automatic closed-loop control was proposed. On-line changes in concentration of carbon dioxide and temperature along the cracking furnace tube were used as the Jeedbacks to adjust the airflow at the entry of the furnace tube and its temperature in real time. The application results have verified the feasibility and effectiveness of the proposed method.