Abstract:

Abnormal gas-solid two-phase flow states inside the disengager impair the unit's separation capacity and cause substantial catalyst loss. Abnormal operating conditions of the catalyst loss severely affect the long-term safe and stable operation of the unit. This study employs numerical simulation to investigate the variation laws of gas-solid two-phase flow, heat transfer, and separation processes inside the disengager under conditions of changes in the oil gas flow, changes in catalyst circulation flow, and mechanical failures in the separation system. Additionally, a method for diagnosing abnormal catalyst loss in the disengager is established. The results show that changes in the disengager's operating parameters alter the internal gas-solid content. When the inlet conditions of the top cyclone deviate from the normal operating range, the disengager exhibits intermittent abnormal catalyst loss. Mechanical failures in the disengager cause abnormal gas-solid fluidization states such as gas in-leakage and short-circuit flows, which further disturb the velocity, temperature, and pressure distributions inside. This disruption sharply reduces the top cyclone's separation capacity, leading to sustained abnormal catalyst loss.Based on the catalyst loss mechanism and numerical simulation results, a diagnostic method is established for catalyst loss caused by changes of the operating parameters and equipment mechanical failure. Its accuracy is validated through industrial cases. This study provides theoretical support for preventing and handling catalyst loss in the disengager, facilitating the efficient operation of fluidized catalytic cracking units.

Key words: fluidized catalytic cracking (FCC) disengager, operating parameter, mechanical failure of equipment, catalyst loss, numerical simulation, abnormal diagnosis

摘要：

沉降器内部异常的气固两相流动状态会影响装置的分离能力，造成催化剂大量跑损，严重影响装置长周期安全稳定的运行。本文采用计算流体力学（CFD）模拟的方法考察装置原料处理量变化、催化剂循环量变化以及分离系统出现磨损穿孔、堵塞等机械故障时装置内部气固两相流动、传热和分离过程，并建立一种沉降器跑剂异常诊断的方法。研究结果表明，沉降器操作参数改变时装置内气固含量发生变化，顶旋入口条件偏离正常运行范围时，装置会出现阵发性的跑剂异常；沉降器发生机械故障时，内部出现窜气、短路流等异常气固流化状态，进而影响装置内速度、温度和压力分布，导致顶旋的分离能力急剧降低，装置出现持续性的跑剂异常。基于沉降器跑剂机理和数值模拟结果，建立了针对沉降器操作参数改变和设备机械故障跑剂的诊断方法，并通过工业实例证实了该方法的准确性。本文为沉降器跑剂问题的预防及应急处理提供理论支持，有助于催化裂化装置高效运行。

关键词: 催化裂化沉降器, 操作参数, 设备机械故障, 跑剂, 数值模拟, 异常诊断