Experimental and theoretical study on gas-solid flow characteristics in feedstock injection zone of FCC riser with double-layer nozzles

doi:10.11949/0438-1157.20201442

Abstract

Abstract:

In order to improve the product distribution of FCC process, on the basis of the traditional single-layer upward feedstock nozzle feed structure, two symmetrical and downward “sub-nozzles” have been added. The gas-solid flow characteristics of the double-layer nozzles were experimentally investigated in a large-scale cold model. The occurrence of the secondary flow of the downward nozzle jet in the riser was analyzed by using “secondary flow” theory. The results showed that, the double-layer nozzle structure can improve the matching of oil & catalyst particles and improve the gas-solid contact efficiency compared with the traditional single-layer nozzle structure. Furthermore, the secondary nozzle can shorten the mixing height of riser by 1/3, reduce the mixing time of oil & catalyst particles, accelerate the uniformity and stabilization of gas-solid phase, realize the purpose of restraining over-cracking of oil, improving the target product yield and reducing coke generation.

Key words: FCC, riser reactor, feed injection zone, double-layer nozzles, multiphase flow, hydrodynamics

摘要：

为改善催化裂化工艺的产品分布，在传统单层向上原料喷嘴进料结构基础上，增加了2个对称、向下的“副喷嘴”。通过一套大型冷模实验装置，考察这种新型双层喷嘴进料段结构内气固流动混合特性，同时利用射流“二次流”理论，分析了逆向喷嘴射流二次流在提升管内的形成发展过程。实验结果表明，与传统单层向上喷嘴（主喷嘴）结构相比，双层喷嘴结构能够改善主喷嘴附近油剂匹配程度，提高气固接触效率。同时副喷嘴的加入可以将提升管进料段长度缩短1/3，减少油剂混合时间，加快气固相达到均匀稳定，实现抑制油气过度裂解，提高目标产品收率，降低生焦量的目的。

关键词: 催化裂化, 提升管反应器, 进料段, 双层喷嘴, 多相流, 流体动力学

CLC Number:

TQ 016

Jun XU, Zhifeng WANG, Kaijun HOU, Yongfu GAO, Yiping FAN, Chunxi LU. Experimental and theoretical study on gas-solid flow characteristics in feedstock injection zone of FCC riser with double-layer nozzles[J]. CIESC Journal, 2021, 72(8): 4019-4029.

许峻, 王智峰, 侯凯军, 高永福, 范怡平, 卢春喜. 双层喷嘴进料提升管内气固流动混合特性的大型冷模实验研究[J]. 化工学报, 2021, 72(8): 4019-4029.

Figures/Tables 7

Fig.1 Schematic diagram of gas-solid phase mixing process of nozzle upward riser feed section

Fig.2 Schematic diagram of particle group motion process

Fig.3 Schematic diagram of gas-solid phase momentum transfer model

Fig.4 Schematic diagram of experimental apparatus

Fig.5 Radial distribution of solid holdup, velocity and jet characteristic concentration in the feed injection at three nozzle velocities

Fig.6 Distribution and matching of oil and catalysts in feed injection at three nozzle velocities

Fig.7 Distribution of oil/catalyst matching index in feed injection of double nozzle and traditional single upward nozzle (Uj=80 m/s)

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