【作者】 陈秋芬；

【导师】 王建军； 吴明；

【作者基本信息】 中国石油大学(华东) ， 动力工程， 2014， 硕士

【摘要】 本文采用Fluent软件对催化裂化三旋泄气系统内气固两相流动特性进行了研究,包括三种四旋分离系统、两种临界喷嘴内气相流场分布及催化剂颗粒运动特性,为泄气系统结构进一步改进提供了参考依据,本文将数值计算结果与理论计算结果进行了对比,证明模拟结果的准确性。通过研究表明:传统1型四旋分离系统收料罐对烟气中催化剂颗粒有预分离作用,但收料罐内压力高于四旋料腿内压力,易造成收料罐中气流反窜进入四旋及料腿的堵塞,该结构适用于颗粒浓度较高场合;传统2型四旋分离系统相对于传统1型工作状况较为稳定,四旋单管内气相流场规律性较强,正常运行,料腿内出现周期性二次涡,颗粒停留时间较长,易造成料腿壁面的磨损,颗粒浓度较高时,料腿易堵塞;新型内置式四旋分离系统工作状况较传统型安全稳定,解决了四旋料腿堵塞与磨损问题,四旋分离系统中四旋与独立四旋单管相比分离效率有所提高,但平衡管处颗粒逃逸降低了四旋分离系统分离效率,可以在收料罐内加锥形挡灰板以解决,四旋环形空间及灰斗锥段颗粒浓度较高,易将四旋壁面磨穿磨漏。孔板式临界喷嘴在0.14MPa前后压差下形成了高速可压缩流动,气流经喉部高速喷射入主烟道,以84m/s的速度喷射到主烟道壁面;喷嘴磨损区域主要在主烟道壁面,沿主烟道轴向距临界喷嘴插入点1000~1500mm区域,产生磨损的颗粒为大于5μm颗粒,减小烟气中含尘颗粒粒径能降低颗粒对临界喷嘴主烟道的磨损;拉瓦尔式临界喷嘴扩散段出现了激波现象,边壁处出现了旋转涡流,涡核中心位置在x=-254mm,距壁面13mm处,小于10μm粒径颗粒对拉瓦尔式临界喷嘴磨损较为严重,磨损区域在喷嘴扩散后段0~500mm区域,颗粒相对拉瓦尔喷嘴主烟道不产生磨损,减小烟气含尘浓度能有效的对其起到保护作用。更多还原

【Abstract】 In this dissertat ion a detailed st udy on ga s-solid two-phase flow behavior, which includes three type s of structure of the fourth st age separation system s, gas flow field distribution in two type s of critical nozzle struct ures and catal yst particle motion chara cteristics, i n frustrated sys tem of the third st age separator of FC CU, was made wi th Fluent software. The study provides valuable guida nce for further improvement i n frustrated system structure. Validity of the simulat ed re sults has been substantiat ed by compar ison with theoretic al ca lc ul ation resul ts.The results indicate that, for Type 1 of the tradit ional fourth stage separation system, the rece iving tank has t he function of pre-separa ti on t o catalys t particl es in the fl ue gas. However,pressure in the receiving tank is much highe r than that in dipleg of the fourth stage s eparator,which is prone to reve rse flow from the receiving tank to the fourth stage separat or and blocking in the dipleg. The structure is suitable for working conditions where particle concentrati on is dense. Compared wi th Type 1 of the traditional fourth stage separ ation sys tem, Type 2 is more stabl e in working condit ion. R egularity is relatively st rong for gas flow field in the fourth stage separator tube. The operation i n the fourth stage separator tube is normal. Periodic secondary vortex, making particle residenc e time longe r, happens in the dipleg, the ex istence of which may lead to wear of the wall. When part icle concentration is very dense, dipleg can block up easily. The working condition in new typ e of the buil t-in fourth stage separ ation system is safer than the t raditional ones, sol ving the problem of wear of the wall and blocking in the dipleg. The fourth stage separator has a higher separation efficiency than the fourth stage separator tube. But escape of part icles at the balance tube low the separation efficiency of the fourth stage separat ion system, which can be solved by adding a conical ash dam per in t he receivi ng tank. The dense particle concentration in annular space and conical section of the ash hopper is prone t o wear out the wall of t he fourth st age separa tor. For the orifi ce plate type critical nozzle, high speed compres sible flow comes into bei ng under pressure difference of 0.14 MPa. Gas flow jets in t he main flue collector through throat and at a speed of 84 m/s on the wall. The wear z one of the nozzle is mainly on the wall of the main flue collector, with a distance of 1000~1500 mm from the critical nozzle insertionpoint along the main flue collector ax ially. The worn-out parti cles are larger than 5 μm.Reducti on of parti cle diameter in t he flue ga s can decrease erosion of particles t o the flue col lector of the critical noz zle. For the Laval type critical nozzle, shock wave phenomenon happens i n t he diffuser. Rotary eddy ex ists on the wall, the cent er of whi ch locates at x=-254 mm, away from the wall about 13 mm. Particl es smaller than 10 μm wear the wall more severe ly. The wear zone is on the back end of the di ffuser of the nozz le, at the zone of 0~500mm. Particle abrasion doesn’t happen in the main flue collect or for the La val type critical noz zle. The nozzl e can be protected by decreasing particle concentration in the flue gas.更多还原