两种结构临界喷嘴内气固两相流动对比研究

为分析催化裂化能量回收系统中临界喷嘴的磨损问题,采用计算流体力学CFD数值模拟软件Fluent中的标准k-ε湍流模型和随机轨道模型(DPM)对孔板式、拉瓦尔式两种结构的临界喷嘴内气固两相进行耦合计算。结果表明:颗粒相对两种临界喷嘴的磨损位置差异较大,孔板式临界喷嘴磨损区域主要在主烟道壁面,距临界喷嘴插入点1 000~1 500 mm区域,产生磨损的颗粒主要为大于5μm颗粒;而催化剂颗粒对拉瓦尔式临界喷嘴磨损区域在喷嘴扩散后段,距临界喷嘴插入点0~500 mm区域,磨损颗粒主要为小于10μm粒径颗粒,颗粒对拉瓦尔喷嘴主烟道不产生磨损;两种临界喷嘴磨损存在差异的原因:孔板式临界喷嘴不存在扩散减速段,颗粒以90 m/s的速度冲刷主烟道壁面;拉瓦尔式扩散段内出现旋转涡流携带催化剂颗粒冲刷壁面产生磨损。

Comparative study on in critical nozzles gas-solid two-phase flow of two constructions

To analyze abrasion problem in FCC power recovery system, the gas-solid flow in critical nozzles of two constructions i.e. orifice plate and Laval type is coupling calculated by using κ-ε model and DPM model in the computational fluid dynamics （CFD） numerical software--Fluent. The results indicate that the positions of abrasion by particles are greatly different in the critical nozzles of two constructions. The abraded area of orifice plate is mainly located in the wall of the main flue gas stack, 1 000 - 1 500 mm from the critical nozzle insertion point. The particles that produce abrasion are mainly the particles with sizes bigger than 5. The area that is subject to catalyst particle abrasion of Laval type critical nozzle concentrates in the post section of the nozzle, 0 -500 mm from the critical nozzle insertion point. The particles are mainly the particles with sizes smaller than 10 . The catalyst particles do not abrade the main flue gas stack of Laval nozzle. The causes of differences of abrasion in two kinds of critical nozzles are ： In critical nozzle of orifice plate, there is no diffusion section, and the catalysts particles rush to the wall of main flue gas stack at a velocity of 90 m/s. In the diffusion section of Laval type nozzle, the rotating vortex with carry-over catalyst particles washes the wall and produces abrasion.