Abstract:

This study implemented the structure optimization and operational status evaluations on the cyclone separation system of the 3.6 million tons per annum catalytic cracking unit through a combined approach of numerical simulation and industrial experiments, with the aim of ensuring that the separation efficiency complies with operational requirements and industry standards. Firstly, numerical simulation was employed to optimize the flow field within the third stage cyclone separator (three-cyclone). The simulation results indicated that when the cone angle was 19°, the overall pressure drop within the three-cyclone and the energy consumption required for the pressure drop were minimized. The tangential velocity of the fluid was maximized, enhancing the centrifugal separation effect. The axial velocity of the fluid was minimized, prolonging the residence time of the particles within the separator, and the overall separation performance was quite satisfactory. Subsequently, industrial experiments were carried out based on catalytic cracking systems with a third stage cyclone separator with a 19° cone angle. The results demonstrated that the concentration of catalyst particles in the flue gas at the outlet of the two-stage cyclone separators within the regenerator was relatively stable and decreased over the operation time. The particle concentration was 320.16mg/m³ (wet basis under operating conditions), and the maximum particle size was less than 53.94μm, which was far below the threshold stipulated in the design, indicating that the separation efficiency of the regenerator cyclone for catalyst particles met the production operation requirements. The catalyst concentration at the outlet of the three-cyclone was stable within a narrow distribution range of 75.34—83.71mg/m³ (wet basis under operating conditions), and the concentration under standard conditions (dry basis) was 83.77—91.45mg/m³. The maximum particle size was less than 10 microns, suggesting that the separation efficiency of the three-cyclone met the index requirements for the concentration and particle size of the catalyst at the inlet of the gas turbine in the "Technical conditions for gas turbines" (HG/T 3650—2012) of China's chemical industry standard. Simultaneously, the particle size distribution of the equilibrium agent in the reaction-regeneration system was reasonable. The catalyst particles were regular in shape without obvious fragmentation. The catalyst experienced relatively light abrasion during the circulation process, and the device operated in a favorable state.

Key words: catalytic cracking, flue gas, cyclone separator, particle size distribution, separation efficiency, abrasion

摘要：

通过数值模拟与工业实验相结合的方法，对3.6Mt/a催化裂化装置的旋风分离系统进行了结构优选与运行状态评估，以保证分离效率满足运行要求及行业标准。首先，使用数值模拟对三级旋风分离器（三旋）内的流场进行优化，模拟结果显示锥角为19°时三旋内整体压降及压降所需能耗最小，流体切向速度最大，增强了离心分离作用，流体轴向速度最小，延长了颗粒在分离器中的停留时间，总体分离效果较好。然后，基于增加19°锥角的三级旋风分离器的催化裂化系统开展工业实验，结果表明，再生器内两级旋风分离器出口烟气中催化剂颗粒浓度较稳定并随运行时间延长而下降，颗粒工况下浓度（湿基）为320.16mg/m³，最大粒径小于53.94μm，远低于设计要求的阈值，表明再生器旋风分离器对催化剂颗粒的分离效率满足生产运行要求。三旋出口催化剂工况下浓度（湿基）稳定在75.34~83.71mg/m³的窄分布范围内，标况下催化剂浓度（干基）为83.77~91.45mg/m³，最大粒径小于10μm，表明三旋分离效率满足我国化工行业标准《烟气轮机技术条件》（HG/T 3650—2012）对烟气轮机入口催化剂浓度与粒度的指标要求。同时，反应-再生系统中催化剂粒度分布合理，催化剂颗粒形状规则、无明显破碎，催化剂在循环过程中磨损较轻，装置运行状态良好。

关键词: 催化裂化, 烟道气, 旋风分离器, 粒度分布, 分离效率, 磨损