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过程工程学报 ›› 2020, Vol. 20 ›› Issue (7): 757-769.DOI: 10.12034/j.issn.1009-606X.219296

• 流动与传递 • 上一篇    下一篇

双层喷嘴提升管进料区内气固流动特性的数值模拟

傅梦倩1, 姚秀颖1, 范怡平2*, 卢春喜2   

  1. 1. 中国石油大学(北京)机械与储运工程学院,北京 102249 2. 中国石油大学(北京)化学工程与环境学院,北京 102249
  • 收稿日期:2019-09-06 修回日期:2019-11-06 出版日期:2020-07-22 发布日期:2020-07-21
  • 通讯作者: 范怡平
  • 基金资助:
    中石油重大专项催化轻馏分油组合进料技术研究

Simulation of gas-solid flow characteristics in feedstock injection zone for risers with double-layer nozzles

Mengqian FU1, Xiuying YAO1, Yiping FAN2*, Chunxi LU2   

  1. 1. College of Mechanical and Transportation Engineering, China University of Petroleum, Beijing 102249, China 2. College of Chemical Engineering and Environment, China University of Petroleum, Beijing 102249, China
  • Received:2019-09-06 Revised:2019-11-06 Online:2020-07-22 Published:2020-07-21

摘要: 为了改善催化裂化工艺的产品分布,提出了一种双层喷嘴提升管进料方案,即在原有喷嘴层下方加设2个对称的“副喷嘴”,目前尚缺少此类双层喷嘴结构提升管内气固流动特性的研究。采用能量最小化方法考虑介尺度非均匀结构的影响,气固相间曳力采用EMMS曳力模型,采用了适用于模拟提升管内油剂混合和流动规律的数学模型。为保证模拟的准确性,确定了适宜的颗粒与壁面间镜面反射系数。主副喷嘴间距为0.5 m,同时改变主副喷嘴进料方向,形成了4种组合结构,即down?down结构、down?up结构、up?down结构和up?up结构。通过比较双层喷嘴与单层喷嘴提升管进料段内油剂混合和流动特性发现,双层喷嘴结构对提升管进料区气固流动的影响较大,尤其对于主喷嘴向上的传统进料结构,副喷嘴射流能加快气固两相达到均匀稳定。副喷嘴射流会加剧进料区副喷嘴以上高度处固含率分布的不均匀程度。当主喷嘴向下时,单层喷嘴down结构具有较小的平均停留时间和停留时间分布的离散程度,当主喷嘴向上时,双层喷嘴up?up结构的平均停留时间和离散程度最小,表明两种结构能使油剂在较短的接触时间内实现强混合,同时抑制目标产品继续裂解,降低生焦量。

关键词: 提升管, 进料区, 双层喷嘴, 流动特性

Abstract: A new structure of injection zone with double-layer nozzles has been proposed in order to improve the product distribution of FCC process. Two supplementary nozzles are added below the primary nozzles. However, the research on gas?solid flow characteristics in this novel injection zone is rarely reported. In this study, the numerical investigation of the mixing and flow of catalyst/particles and oil/gas in the novel injection zone was carried out using the combination of two-fluid model with the energy minimization multi-scale (EMMS)-based drag model. The particle?wall specularity coefficient was first determined by comparing with experimental data. Four combination types of double-layers nozzles with a distance of 0.5 m between primary and supplementary nozzles were investigated, i.e. down?down, down?up, up?down and up?up types with different feeding directions. The hydrodynamic behaviors of gas and solid in the feedstock injection zone with these four nozzle combinations were investigated and further compared with the results with the single-layer nozzles. The results showed that the introduction of the supplementary nozzles had a great influence on the gas?solid flow in the feedstock injection zone, especially in the injection region with the primary upward feeding nozzles. The jet from supplementary nozzles can accelerate gas and solid phase to reach the uniform and stable state at the region above the primary nozzles. But an uneven distribution of solids volume fraction occurred at the zone above secondary nozzles. When the main nozzles were downward, the injection zone with single-layer nozzles showed the smaller mean residence time and heterogeneity. When the main nozzles were upward, the double-layers nozzles with the up?up structure showed the smallest mean residence time and heterogeneity. These results indicated that the feeding using double-layer nozzles can achieve the strong mixing within a shorter contact time and inhibit the over-cracking of desired products, thus increasing the yield of desired products.

Key words: Riser, Feedstock injection zone, Double-layers nozzles, Flow characteristics