聚乙烯流化床反应器气-液-固流场中升力模型的影响研究

doi:10.11949/0438-1157.20221147

摘要/Abstract

摘要：

气相法聚乙烯工艺在冷凝模式操作下，液相在床层内部蒸发使流体流型转变为旋转型，升力的影响不可忽略。建立了气-液-固三相流聚乙烯流化床反应器CFD模型，并探究Saffman-Mei、Legendre-Magnaudet和Moraga三种不同升力模型对聚乙烯流化床反应器多相流体流动的影响。模拟结果表明，升力模型对于流化稳定后床层平均高度、反应器平均温度无明显影响，但在床层不同高度区域内颗粒相分布和低区域内温度分布存在差别。不同粒径固相颗粒在升力的影响下具有不同的流化过程，小粒径颗粒在流化过程中易产生较大的气泡，大粒径颗粒在壁面处的聚集现象更为明显。Saffman-Mei模型使得颗粒沿着壁面以及向较高床层运动更为明显，在低床层趋于温度较低；Saffman-Mei模型和Moraga模型具有相似的液相蒸发速率；Moraga模型的颗粒和气泡运动最为剧烈；Legendre-Magnaudet模型预测的床层压降最为准确，并且流化过程中的相分布和温度分布等更为均匀。

关键词: 计算流体力学, 流化床, 多相流, 流体力学, 升力模型

Abstract:

When the gas-phase polyethylene process is operated in the condensation mode, the liquid phase evaporates in the bed and the fluid flow pattern changes to the rotary type, and the effect of lift force can't be ignored. In this paper, the CFD model of the gas-liquid-solid three-phase flow polyethylene fluidized bed reactor was established, and the effects of three different lift models of Saffman-Mei, Legendre-Magnaudet and Moraga on the multiphase fluid flow of the polyethylene fluidized bed reactor were explored. The simulation results show that the lift model has no significant effect on the average bed height and the average reactor temperature after fluidization stabilization, but there are differences in the particle phase distribution in different height regions of the bed and the temperature distribution in the low region. The different particle sizes of solid phase particles have different fluidization processes under the influence of lift, small particles tend to produce larger bubbles in the fluidization process, and the aggregation phenomenon of large particles at the wall is more obvious. The Saffman-Mei and Moraga models have similar evaporation rates of the liquid phase. The Moraga model has the most intense particle and bubble motion. The bed pressure drop predicted by the Legendre-Magnaudet model is the most accurate, and the phase distribution and temperature distribution during the fluidization process are more uniform.

Key words: computational fluid dynamics, fluidized bed, multiphase flow, fluid mechanics, lift model

中图分类号:

TQ 021.1

李永帅, 郑毅, 李岚, 李新爽, 赵馨怡, 潘慧, 凌昊. 聚乙烯流化床反应器气-液-固流场中升力模型的影响研究[J]. 化工学报, 2022, 73(12): 5355-5366.

Yongshuai LI, Yi ZHENG, Lan LI, Xinshuang LI, Xinyi ZHAO, Hui PAN, Hao LING. Influence of lift model on gas-liquid-solid flow field in polyethylene fluidized bed reactor[J]. CIESC Journal, 2022, 73(12): 5355-5366.

图/表 12

图1 聚乙烯工业流化床反应器示意图

Fig.1 Geometries of the simulated fluidized bed reactor

表1 气、液、固三相的性质及工业操作条件

Table 1 Physical properties of three phases and operation conditions from industrial data

参数设置	数值
气相
c_p,_g/(J·kg^-1·K^-1)	1780
ρ_g/(kg·m^-3)	26.7
μ_g/(kg·m^-1·s^-1)	1.4×10^-5
k_g/(W·m^-1·K^-1)	3.18 ×10^-2
扩散系数/(m²·s^-1)	4×10^-7
液相
直径/m	8×10^-5 m
ρ_l /(kg·m^-3)	541
c_p,l /(J·kg^-1·K^-1)	2400
固相
直径/m	1×10^-4、5×10^-4、1×10^-3
ρ_s/(kg·m^-3)	919
c_p,_s/(J·kg^-1·K^-1)	2550
入口颗粒温度/K	328
入口气相温度/K	328
入口液相温度/K	328
入口气相速度/(m·s^-1)	0.5928
入口液相速度/(m·s^-1)	0.5928
入口液相质量分数	0.1243%
初始固相体积分数	0.5
初始床层高度/m	3.5
压力/MPa	2
动力学参数
E_A/(J·mol^-1)	50400
E_D/(J·mol^-1)	1000
ΔH/(J·kg^-1)	3.843×10⁶
ΔH_vap/(J·kg^-1)	2.84×10⁵
ρ_cat/(g·m^-3)	2.84×10⁶
k_p0/(m³·mol^-1·s^-1)	4.49×10⁶
k_d0/(m³·mol^-1·s^-1)	1.6×10^-4

表2 模型参数

Table 2 Numerical parameters

参数	数值
入口边界条件	速度入口
出口边界条件	压力出口
壁面边界条件	气液相壁面无滑移，固相部分滑移
壁面热条件	Adiabatic
颗粒碰撞恢复系数	0.9
颗粒黏度	文献[26]
颗粒体积黏度	文献[28]
摩擦黏度	文献[30]
内摩擦角	30°
固相填料极限	0.63
最大迭代次数	50
收敛标准	10^-5
时间步长 (s)	10^-3

图2 FBR中流化过程的床层压降

Fig.2 The pressure drop with the fluidization proceeding in the FBR

图3 不同升力模型流化过程

Fig.3 Fluidization process of different lift models

图4 流化过程中固相体积分数径向分布

Fig.4 Radial distribution of solid phase volume fraction in the fluidization process

图5 不同粒径固相颗粒在Saffman-Mei模型下的流化过程

Fig.5 Fluidization process of different particle sizes in Saffman-Mei model

图6 不同粒径颗粒在Saffman-Mei模型下流化过程中固相体积分数径向分布

Fig.6 Radial distribution of solid phase volume fraction in Saffman-Mei model fluidization process for different particle sizes

图7 固相体积分数轴向分布

Fig.7 Axial distribution of solid volume fraction

图8 固相体积分数径向分布

Fig.8 Radial distribution of solid volume fraction

图9 FBRs中液相蒸发速率

Fig.9 Evaporation rate of liquid phase in FBRs

图10 FBR中固相颗粒径向温度分布

Fig.10 Radial temperature distribution of solid phase particles in FBR

参考文献 34

1	夏勇, 黄昌猛, 吕海霞, 等. 聚乙烯的结构、性能与应用[J]. 橡塑技术与装备, 2017, 43(16): 42-45.
	Xia Y, Huang C M, Lyu H X, et al. Structure, properties and applications of polyethylene[J]. China Rubber/Plastics Technology and Equipment, 2017, 43(16): 42-45.
2	Soares J B P, McKenna T F. Polyolefin Reaction Engineering[M]. Weinheim: Wiley-VCH, 2012.
3	孙海涛. 气相流化床法聚乙烯工艺技术比较[J]. 石化技术, 2019, 26(2): 133.
	Sun H T. Comparison of polyethylene process technologies by gas-phase fluidized bed process[J]. Petrochemical Industry Technology, 2019, 26(2): 133.
4	Yang Y, Yang J, Chen W, et al. Instability analysis of the fluidized bed for ethylene polymerization with condensed mode operation[J]. Industrial & Engineering Chemistry Research, 2002, 41(10): 2579-2584.
5	Pan H, Liang X F, Luo Z H. CFD modeling of the gas-solid two-fluid flow in polyethylene FBRs: from traditional operation to super-condensed mode[J]. Advanced Powder Technology, 2016, 27(4): 1494-1505.
6	Zhou Y F, Wang J D, Yang Y R, et al. Modeling of the temperature profile in an ethylene polymerization fluidized-bed reactor in condensed-mode operation[J]. Industrial & Engineering Chemistry Research, 2013, 52(12): 4455-4464.
7	Zhou Y F, Shi Q, Huang Z L, et al. Effects of liquid action mechanisms on hydrodynamics in liquid-containing gas-solid fluidized bed reactor[J]. Chemical Engineering Journal, 2016, 285: 121-127.
8	Zhou Y F, Shi Q, Huang Z L, et al. Realization and control of multiple temperature zones in liquid-containing gas-solid fluidized bed reactor[J]. AIChE Journal, 2016, 62(5): 1454-1466.
9	Zhou Y F, Shi Q, Huang Z L, et al. Effects of interparticle forces on fluidization characteristics in liquid-containing and high-temperature fluidized beds[J]. Industrial & Engineering Chemistry Research, 2013, 52(47): 16666-16674.
10	范小强, 韩国栋, 黄正梁, 等. 气相法聚乙烯工艺冷凝态操作模式的稳定性和动态行为[J]. 化工学报, 2018, 69(2): 779-791.
	Fan X Q, Han G D, Huang Z L, et al. Stability and dynamic behaviors of gas-phase ethylene polymerization process under condensed mode operation[J]. CIESC Journal, 2018, 69(2): 779-791.
11	Pan H, Liang X F, Zhu L T, et al. Important analysis of liquid vaporization modeling scheme in computational fluid dynamics modeling of gas-liquid-solid polyethylene fluidized bed reactors[J]. Industrial & Engineering Chemistry Research, 2017, 56(36): 10199-10213.
12	张仪, 李兵, 白玉龙, 等. 液固流态化动态过程中相间作用力的数值模拟及实验验证[J]. 化工学报, 2020, 71(11): 5129-5139.
	Zhang Y, Li B, Bai Y L, et al. Numerical simulation and experimental validation of inter-phase forces in dynamic process of liquid-solid fluidization[J]. CIESC Journal, 2020, 71(11): 5129-5139.
13	Pang M J, Wei J J. Analysis of drag and lift coefficient expressions of bubbly flow system for low to medium Reynolds number[J]. Nuclear Engineering and Design, 2011, 241(6): 2204-2213.
14	毛在砂. 颗粒群研究: 多相流多尺度数值模拟的基础[J]. 过程工程学报, 2008, 8(4): 645-659.
	Mao Z S. Knowledge on particle swarm: the important basis for multi-scale numerical simulation of multiphase flows[J]. The Chinese Journal of Process Engineering, 2008, 8(4): 645-659.
15	Wang Q G, Yao W. Computation and validation of the interphase force models for bubbly flow[J]. International Journal of Heat and Mass Transfer, 2016, 98: 799-813.
16	Yao Y, He Y J, Luo Z H, et al. 3D CFD-PBM modeling of the gas-solid flow field in a polydisperse polymerization FBR: the effect of drag model[J]. Advanced Powder Technology, 2014, 25(5): 1474-1482.
17	Hibiki T, Ishii H. Lift force in bubbly flow systems[J]. Chemical Engineering Science, 2007, 62(22): 6457-6474.
18	Zhang X B, Yan W C, Luo Z H. CFD-PBM simulation of bubble columns: sensitivity analysis of the nondrag forces[J]. Industrial & Engineering Chemistry Research, 2020, 59(41): 18674-18682.
19	Yamoah S, Raúl M C, Guillem M, et al. Numerical investigation of models for drag, lift, wall lubrication and turbulent dispersion forces for the simulation of gas-liquid two-phase flow[J]. Chemical Engineering Research and Design, 2015, 98: 17-35.
20	Koerich D M, Lopes G C, Rosa L M. Investigation of phases interactions and modification of drag models for liquid-solid fluidized bed tapered bioreactors[J]. Powder Technology, 2018, 339: 90-101.
21	Jin D, Xiong J B, Cheng X. Investigation on interphase force modeling for vertical and inclined upward adiabatic bubbly flow[J]. Nuclear Engineering and Design, 2019, 350: 43-57.
22	Zhang X, Yu T, Cong T L, et al. Effects of interaction models on upward subcooled boiling flow in annulus[J]. Progress in Nuclear Energy, 2018, 105: 61-75.
23	Schiller L. Uber Die grundlegenden berechnungen Bei der schwerkraftaufbereitung[J]. Z. Vereines Deutscher Inge., 1933, 77:318-321.
24	Gidaspow D. Multiphase Flow and Fluidization: Continuum and Kinetic Theory Descriptions[M]. New York: Academic Press, 1994.
25	Morsi S A, Alexander A J. An investigation of particle trajectories in two-phase flow systems[J]. Journal of Fluid Mechanics, 1972, 55(2): 193.
26	Gidaspow D, Bezburuah R, Ding J. Hydrodynamics of circulating fluidized beds: kinetic theory approach[R]. Chicago: Illinois Inst. of Tech., 1991.
27	Chapman S, Cowling T G. The Mathematical Theory of Non-uniform Gases: Notes Added in 1951[M]. New York: Cambridge University Press, 1953.
28	Lun C K K, Savage S B, Jeffrey D J, et al. Kinetic theories for granular flow: inelastic particles in Couette flow and slightly inelastic particles in a general flowfield[J]. Journal of Fluid Mechanics, 1984, 140: 223-256.
29	Boemer A, Qi H, Renz U. Eulerian simulation of bubble formation at a jet in a two-dimensional fluidized bed[J]. International Journal of Multiphase Flow, 1997, 23(5): 927-944.
30	Schaeffer D G. Instability in the evolution equations describing incompressible granular flow[J]. Journal of Differential Equations, 1987, 66(1): 19-50.
31	Saffman P G. The lift on a small sphere in a slow shear flow[J]. Journal of Fluid Mechanics, 1965, 22(2): 385-400.
32	Mei R W, Klausner J F. Shear lift force on spherical bubbles[J]. International Journal of Heat and Fluid Flow, 1994, 15(1): 62-65.
33	Legendre D, Magnaudet J. The lift force on a spherical bubble in a viscous linear shear flow[J]. Journal of Fluid Mechanics, 1998, 368: 81-126.
34	Moraga F J, Bonetto F J, Lahey R T. Lateral forces on spheres in turbulent uniform shear flow[J]. International Journal of Multiphase Flow, 1999, 25(6/7): 1321-1372.

[1]	张思雨, 殷勇高, 贾鹏琦, 叶威. 双U型地埋管群跨季节蓄热特性研究[J]. 化工学报, 2023, 74(S1): 295-301.
[2]	肖明堃, 杨光, 黄永华, 吴静怡. 浸没孔液氧气泡动力学数值研究[J]. 化工学报, 2023, 74(S1): 87-95.
[3]	宋瑞涛, 王派, 王云鹏, 李敏霞, 党超镔, 陈振国, 童欢, 周佳琦. 二氧化碳直接蒸发冰场排管内流动沸腾换热数值模拟分析[J]. 化工学报, 2023, 74(S1): 96-103.
[4]	温凯杰, 郭力, 夏诏杰, 陈建华. 一种耦合CFD与深度学习的气固快速模拟方法[J]. 化工学报, 2023, 74(9): 3775-3785.
[5]	岳林静, 廖艺涵, 薛源, 李雪洁, 李玉星, 刘翠伟. 凹坑缺陷对厚孔板喉部空化流动特性影响研究[J]. 化工学报, 2023, 74(8): 3292-3308.
[6]	杨越, 张丹, 郑巨淦, 涂茂萍, 杨庆忠. NaCl水溶液喷射闪蒸-掺混蒸发的实验研究[J]. 化工学报, 2023, 74(8): 3279-3291.
[7]	汪林正, 陆俞冰, 张睿智, 罗永浩. 基于分子动力学模拟的VOCs热氧化特性分析[J]. 化工学报, 2023, 74(8): 3242-3255.
[8]	邢雷, 苗春雨, 蒋明虎, 赵立新, 李新亚. 井下微型气液旋流分离器优化设计与性能分析[J]. 化工学报, 2023, 74(8): 3394-3406.
[9]	何晓崐, 刘锐, 薛园, 左然. MOCVD生长AlN单晶薄膜的气相和表面化学反应综述[J]. 化工学报, 2023, 74(7): 2800-2813.
[10]	董明, 徐进良, 刘广林. 超临界水非均质特性分子动力学研究[J]. 化工学报, 2023, 74(7): 2836-2847.
[11]	牛超, 沈胜强, 杨艳, 潘泊年, 李熠桥. 甲烷BOG喷射器流动过程计算与性能分析[J]. 化工学报, 2023, 74(7): 2858-2868.
[12]	杨峥豪, 何臻, 常玉龙, 靳紫恒, 江霞. 生物质快速热解下行式流化床反应器研究进展[J]. 化工学报, 2023, 74(6): 2249-2263.
[13]	郑志航, 马郡男, 闫子涵, 卢春喜. 提升管射流影响区内压力脉动特性研究[J]. 化工学报, 2023, 74(6): 2335-2350.
[14]	陈巨辉, 张谦, 舒崚峰, 李丹, 徐鑫, 刘晓刚, 赵晨希, 曹希峰. 基于DEM方法的旋转流化床纳米颗粒流动特性研究[J]. 化工学报, 2023, 74(6): 2374-2381.
[15]	于源, 陈薇薇, 付俊杰, 刘家祥, 焦志伟. 几何相似涡流空气分级机环形区流场变化规律研究及预测[J]. 化工学报, 2023, 74(6): 2363-2373.