FCCU旋风分离器壳体断裂失效的原因分析

针对目前FCC装置旋风分离器壳体和拉杆出现的断裂问题,依据气固两相流会诱发振动引起金属材料疲劳破坏的观点进行了分析.被分离的气固两相流进入旋风分离器后,在旋风分离器内形成的不稳定旋转和不稳定下料会产生低频脉动压力.这种脉动压力施加在旋风分离器壳体上形成了旋风分离器系统振动的激振力,诱发了旋风分离器系统发生共振响应,形成较大的交变应力,最后导致壳体和拉杆的高应力部位和高变形部位的疲劳断裂.预防这种断裂失效的措施应该是对旋风分离器系统进行结构改进,使其结构的固有频率远离激振力的频率,避免共振发生,不需要对旋风分离器壳体材料进行更换.

Analysis of cracking failure of shell of FCCU cyclone separator

The cracking failure of shell and rod of cyclone in FCCU is analyzed based on the gas solid two-phase flow in the cyclone which leads to vibration and fatigue cracks of the cyclone equipment.When gas solid two-phase flow enters the cyclone,the instability of swirling flow and particles flowing down in the cy clone generate the gas-solid flowing fluctuating pressure.The fluctuating pressure acting on the cyclone shell produces an induction force of cyclone shell vibration,which may induce the resonance vibration.During the resonance vibration,the fatigue cracks or fatigue fracture of the cyclone shell are formed under the effect of high alternating stress and high deformation within the cyclone shell and rod.The effective measure to prevent the fracture failure is to improve the structure of cyclone system so as to keep the fixed frequency of structure away from the frequency of exciting force and avoid the resonance vibration without the replacement of material.