磁场对湿颗粒流化床系统中介尺度结构影响机制研究

doi:10.11949/0438-1157.20220158

摘要/Abstract

摘要：

湿颗粒系统在自然界及工业过程非常普遍，例如喷雾造粒、反应器中矿物黏结、催化以及制药等，这其中含有大量典型介尺度结构如颗粒聚团、结块以及气泡等结构，这些结构的存在导致颗粒系统的流动及热质传递特性发生明显改变。针对鼓泡流化床湿颗粒系统中颗粒聚团以及气泡等介尺度结构，应用离散单元模型并引入外加磁场，研究磁场作用下湿颗粒系统中介尺度结构的演化机制，探究磁场力、液桥力、接触力对气泡演化过程的影响。研究发现，在不考虑磁场的条件下，颗粒易形成聚团并存在气泡边界不规则等现象，引入外加匀强磁场后，磁场力对鼓泡流化床内气泡结构存在破坏和抑制作用。

关键词: 湿颗粒, 离散单元模型, 磁场, 介尺度

Abstract:

Wet particle systems are very common in nature and industrial processes, such as spray granulation, mineral bonding in reactors, pharmaceutical and catalyst. Due to the presence of liquid, the flow, heat and mass transfer characteristics are significantly changed compared with dry particle systems. For example, a large number of typical mesoscale structures, including particle agglomeration, clusters and bubbles, form and lead to different flow regime. Thus, mesoscale structure flow and evolution behaviors have attracted more and more attention, which might affect the design and operation of industrial reactors. In this paper, typical mesoscale structures are investigated in a bubbling fluidized bed by discrete element method (DEM), and effect of external magnetic field on mesoscale structure evolution process is explored. First, the numerical model for describing dry and wet particle system flow behaviors were established with magnetic field introduced. The numerical model has been validated and shown in our previous published investigations. Then, mesoscale structure flow behaviors were analyzed in dry and wet particle system without magnetic flied. Bubble evolution process was found clearly in a dry particle system, and the trajectory of the bubble was almost along the midline of fluidized bed. With the cohesive liquid introduced, that of bubble center was offset from the midline. Next, an external magnetic field was introduced based on DEM to study the evolution mechanism of the mesoscale structure in the wet particle system under the action of the magnetic field. We compared the dominant role of liquid bridge force, contact force, magnetic force and drag force in fluidized beds, and tried to analyze and explore the relationship among different forces. The study found that without considering the magnetic field, particles are easy to form agglomeration and have irregular bubble boundaries. After the introduction of an external uniform magnetic field, the magnetic field force will destroy and inhibit the bubble structure in the bubbling fluidized bed.

Key words: wet particle, discrete element method, magnetic field, mesoscale structure

中图分类号:

TK 11

唐天琪, 何玉荣. 磁场对湿颗粒流化床系统中介尺度结构影响机制研究[J]. 化工学报, 2022, 73(6): 2636-2648.

Tianqi TANG, Yurong HE. Effect of magnetic field on the mesoscale structure evolution process in a wet particle fluidized bed[J]. CIESC Journal, 2022, 73(6): 2636-2648.

图/表 11

图1 磁场作用下含湿磁性颗粒受力情况示意图

Fig.1 Schematic diagram of forces imposing on wet particles under effect of magnetic field

表1 模拟参数设置

Table 1 Parameters used in the simulation

变量	数值	单位	变量	数值	单位
流化床			气体
鼓泡床x、y、z方向尺寸	90×24×900	mm	气体密度	1.2	kg/m³
鼓泡床x、y、z方向网格	10×3×90		气体速度	1.2	m/s
颗粒			气体黏度	1.8×10^-5	Pa?s
颗粒数量	16000	个	出口压力	101325	Pa
颗粒直径	3	mm	液体
颗粒密度	420	kg/m³	相对液体量	0.01	%
恢复系数	0.97		液体密度	1000	kg/m³
颗粒间滑动摩擦系数	0.10		液体黏度	1.03	mPa?s
颗粒壁面间滑动摩擦系数	0.30		接触角	π/6	rad
法向弹簧刚度	800	N/m	表面张力系数	0.0721	N/m
切向弹簧刚度	286	N/m	磁场
颗粒磁化率	0.642		磁场强度	0.005，0.010，0.020	T

图2 流化床结构示意图

Fig.2 Structure of the bubbling fluidized bed

图3 无磁场作用下一个气泡生长周期内颗粒空间分布情况

Fig.3 Instantaneous particle distribution and bubble forming process without magnetic field in dry and wet particle systems (a cycle)

图4 无磁场作用下床层压降脉动及一个气泡生长周期内气泡生长情况

Fig.4 Distribution of pressure drop and bubble evolution process without magnetic field (a cycle)

图5 干、湿颗粒系统中气泡颗粒温度分布情况

Fig.5 Distribution of bubble granular temperature in dry and wet particle systems

图6 不同磁场强度下一个气泡生长周期内颗粒空间分布情况

Fig.6 Instantaneous particle distribution and bubble forming process under different magnetic field intensities in wet particle system

图7 不同磁场强度下气泡颗粒温度分布情况

Fig.7 Distribution of bubble granular temperature under different magnetic field intensities

图8 不同磁场强度下床层压降脉动及一个气泡生长周期内气泡生长情况

Fig.8 Distribution of pressure drop and bubble evolution process under different magnetic field intensities

图9 梯度磁场对一个气泡生长周期内气泡生长情况的影响

Fig.9 Effects of magnetic field gradient on bubble evolution process

图10 气泡区域垂直方向磁场力、接触力、曳力以及液桥力之间的相互作用机制

Fig.10 Interaction among magnetic field force, contact force, drag force and liquid bridge force for the bubble structure evolution process under different magnetic field intensities in vertical direction

参考文献 41

1	Ali H, Plaza F, Mann A. Numerical prediction of dust capture efficiency of a centrifugal wet scrubber[J]. AIChE Journal, 2018, 64(3): 1001-1012.
2	Cui H P, Grace J R. Fluidization of biomass particles: a review of experimental multiphase flow aspects[J]. Chemical Engineering Science, 2007, 62(1/2): 45-55.
3	Agrawal K, Loezos P N, Syamlal M, et al. The role of meso-scale structures in rapid gas-solid flows[J]. Journal of Fluid Mechanics, 2001, 445: 151-185.
4	李静海, 胡英, 袁权. 探索介尺度科学: 从新角度审视老问题[J]. 中国科学: 化学, 2014, 44(3): 277-281.
	Li J H, Hu Y, Yuan Q. Mesoscience: exploring old problems from a new angle[J]. Scientia Sinica Chimica, 2014, 44(3): 277-281.
5	王海峰. 气固流态化的多尺度非平衡特性研究[D]. 北京: 中国科学院大学(中国科学院过程工程研究所), 2020.
	Wang H F. Multiscale nonequilibrium features of gas-solid fluidization[D]. Beijing: Institute of Process Engineering, Chinese Academy of Sciences, 2020.
6	初广文, 廖洪钢, 王丹, 等. 微纳介尺度气液反应过程强化[J]. 化工学报,2021, 72(7): 3435-3444.
	Chu G W, Liao H G, Wang D, et al. Gas-liquid reaction process intensification at micro-/ nano-mesoscale[J]. CIESC Journal, 2021, 72(7): 3435-3444.
7	Boyce C M, Ozel A, Kolehmainen J, et al. Growth and breakup of a wet agglomerate in a dry gas-solid fluidized bed[J]. AIChE Journal, 2017, 63(7): 2520-2527.
8	Zhao M, Liu D Y, Ma J L, et al. CFD-DEM simulation of gas-solid flow of wet particles in a fluidized bed with immersed tubes[J]. Chemical Engineering and Processing-Process Intensification, 2020, 156: 108098.
9	Song C X, Liu D Y, Ma J L, et al. CFD-DEM simulation of flow pattern and particle velocity in a fluidized bed with wet particles[J]. Powder Technology, 2017, 314: 346-354.
10	Liu P Y, Kellogg K M, LaMarche C Q, et al. Dynamics of singlet-doublet collisions of cohesive particles[J]. Chemical Engineering Journal, 2017, 324: 380-391.
11	Balakin B V, Shamsutdinova G, Kosinski P. Agglomeration of solid particles by liquid bridge flocculants: pragmatic modelling[J]. Chemical Engineering Science, 2015, 122: 173-181.
12	Cheng J N, Fan X Q, Sun J Y, et al. Evolution and fluidization behaviors of wet agglomerates based on formation-fragmentation competition mechanism[J]. Chemical Engineering Science, 2022, 247: 116933.
13	Wang H T, Soria Verdugo A, Sun J Y, et al. Experimental study of bubble dynamics and flow transition recognition in a fluidized bed with wet particles[J]. Chemical Engineering Science, 2020, 211: 115257.
14	van Willigen F K, van Ommen J R, van Turnhout J, et al. Bubble size reduction in a fluidized bed by electric fields[J]. International Journal of Chemical Reactor Engineering, 2003, 1(1): 21-36.
15	van Willigen F K, van Ommen J R, van Turnhout J, et al. Bubble size reduction in electric-field-enhanced fluidized beds[J]. Journal of Electrostatics, 2005, 63(6/7/8/9/10): 943-948.
16	Zhu C, Liu G L, Yu Q, et al. Sound assisted fluidization of nanoparticle agglomerates[J]. Powder Technology, 2004, 141(1/2): 119-123.
17	Zhu Q H, Li H Z, Zhu Q S, et al. Hydrodynamic study on magnetized fluidized beds with Geldart-B magnetizable particles[J]. Powder Technology, 2014, 268: 48-58.
18	Zhu Q H, Li H Z, Zhu Q S, et al. Hydrodynamic behavior of magnetized fluidized beds with admixtures of Geldart-B magnetizable and nonmagnetizable particles[J]. Particuology, 2016, 29: 86-94.
19	李响. 外场作用下流化床中气固两相流动数值模拟[D]. 哈尔滨: 哈尔滨工业大学, 2010.
	Li X. Simulations of hydrodynamics of gas and particles in fluidized bed with additional extra field[D]. Harbin: Harbin Institute of Technology, 2010.
20	杨慧, 万东玉, 曹长青. 磁-流场耦合气-固流化床气含率的模拟[J]. 石油化工, 2014, 43(1): 51-55.
	Yang H, Wan D Y, Cao C Q. Simulation of gas holdup in a gas-solid fluidized bed with magnetic and fluid fields[J]. Petrochemical Technology, 2014, 43(1): 51-55.
21	Espin M J, Quintanilla M A S, Valverde J M. Magnetic stabilization of fluidized beds: effect of magnetic field orientation[J]. Chemical Engineering Journal, 2017, 313: 1335-1345.
22	毛志, 谭诗德, 柯春海, 等. 磁场对磁性湿颗粒运动机理的影响[J]. 重庆大学学报, 2018, 41(8): 17-25.
	Mao Z, Tan S D, Ke C H, et al. Influence of magnetic field on movement mechanism of wet magnetic particles[J]. Journal of Chongqing University, 2018, 41(8): 17-25.
23	Anderson T B, Jackson R. Fluid mechanical description of fluidized beds. Equations of motion[J]. Industrial & Engineering Chemistry Fundamentals, 1967, 6(4): 527-539.
24	Muguruma Y, Tanaka T, Tsuji Y. Numerical simulation of particulate flow with liquid bridge between particles (simulation of centrifugal tumbling granulator)[J]. Powder Technology, 2000, 109(1-3): 49-57.
25	Goniva C, Kloss C, Deen N G, et al. Influence of rolling friction on single spout fluidized bed simulation[J]. Particuology, 2012, 10(5): 582-591.
26	Zhang D, Whiten W J. The calculation of contact forces between particles using spring and damping models[J]. Powder Technology, 1996, 88(1): 59-64.
27	Israelachvili J N. Intermolecular and Surface Forces [M]. 3rd ed. London: Academic Press, 2011.
28	Lambert P, Chau A, Delchambre A, et al. Comparison between two capillary forces models[J]. Langmuir, 2008, 24(7): 3157-3163.
29	Liu P Y, Yang R Y, Yu A B. Dynamics of wet particles in rotating drums: effect of liquid surface tension[J]. Physics of Fluids, 2011, 23(1): 013304.
30	Lian G P, Thornton C, Adams M J. Discrete particle simulation of agglomerate impact coalescence[J]. Chemical Engineering Science, 1998, 53(19): 3381-3391.
31	Goldman A J, Cox R G, Brenner H. Slow viscous motion of a sphere parallel to a plane wall(Ⅰ): Motion through a quiescent fluid[J]. Chemical Engineering Science, 1967, 22(4): 637-651.
32	Lian G, Adams M J, Thornton C. Elastohydrodynamic collisions of solid spheres[J]. Journal of Fluid Mechanics, 1996, 311: 141-152.
33	Pinto-Espinoza J. Dynamic behavior of ferromagnetic particles in a liquid-solid magnetically assisted fluidized bed (MAFB): theory, experiment, and CFD-DPM simulation[D]. Corvallis: Oregon State University, 2003.
34	Beetstra R, van der Hoef M A, Kuipers J A M. Drag force of intermediate Reynolds number flow past mono-and bidisperse arrays of spheres[J]. AIChE Journal, 2007, 53(2): 489-501.
35	Jiang Z C, Rieck C, Bück A, et al. Modeling of inter- and intra-particle coating uniformity in a Wurster fluidized bed by a coupled CFD-DEM-Monte Carlo approach[J]. Chemical Engineering Science, 2020, 211: 115289.
36	Zhang Y, Zhao Y M, Lu L Q, et al. Assessment of polydisperse drag models for the size segregation in a bubbling fluidized bed using discrete particle method[J]. Chemical Engineering Science, 2017, 160: 106-112.
37	Wang B, Tang T Q, Yan S N, et al. Magnetic segregation behaviors of a binary mixture in fluidized beds[J]. Powder Technology, 2022, 397: 117031.
38	Tang T Q, He Y R, Ren A X, et al. Experimental study and DEM numerical simulation of dry/wet particle flow behaviors in a spouted bed[J]. Industrial & Engineering Chemistry Research, 2019, 58(33): 15353-15367.
39	Collier A P, Hayhurst A N, Richardson J L, et al. The heat transfer coefficient between a particle and a bed (packed or fluidised) of much larger particles[J]. Chemical Engineering Science, 2004, 59(21): 4613-4620.
40	刘亚丕, 何时金, 包大新, 等. 软磁材料的发展趋势[J]. 磁性材料及器件, 2003, 34(3): 26-29, 32.
	Liu Y P, He S J, Bao D X, et al. Developing tendency of soft magnetic materials[J]. Journal of Magnetic Materials and Devices, 2003, 34(3): 26-29, 32.
41	Jung J, Gidaspow D, Gamwo I K. Measurement of two kinds of granular temperatures, stresses, and dispersion in bubbling beds[J]. Industrial & Engineering Chemistry Research, 2005, 44(5): 1329-1341.

[1]	邢美波, 张中天, 景栋梁, 张洪发. 磁调控水基碳纳米管协同多孔材料强化相变储/释能特性[J]. 化工学报, 2023, 74(7): 3093-3102.
[2]	胡善伟, 刘新华. 气固流化系统多尺度跨流域EMMS建模[J]. 化工学报, 2022, 73(6): 2514-2528.
[3]	孔令菲, 陈延佩, 王维. 气固流态化中颗粒介尺度结构的动力学研究[J]. 化工学报, 2022, 73(6): 2486-2495.
[4]	王婵, 肖国锡, 郭小雪, 徐人威, 岳源源, 鲍晓军. 基于介尺度结构解聚-重组装的Beta分子筛的绿色合成及应用[J]. 化工学报, 2022, 73(6): 2690-2697.
[5]	王忠东, 朱春英, 马友光, 付涛涛. 并行微通道内液液两相流及介尺度效应[J]. 化工学报, 2022, 73(6): 2563-2572.
[6]	郑涛, 刘海燕, 张睿, 孟祥海, 岳源源, 刘植昌. 基于分子筛绿色合成的天然硅铝矿物介尺度活化研究进展[J]. 化工学报, 2022, 73(6): 2334-2351.
[7]	马永丽, 刘明言, 胡宗定. 气液固流化床流动介尺度模型研究进展[J]. 化工学报, 2022, 73(6): 2438-2451.
[8]	孟博, 刘艳萍, 蒋新科, 韩一帆. Fe₅C₂-MnO _x 尺度调控及催化合成气制烯烃性能研究[J]. 化工学报, 2022, 73(6): 2677-2689.
[9]	郑默, 李晓霞. ReaxFF MD模拟揭示的煤热解挥发分自由基反应的竞争与协调[J]. 化工学报, 2022, 73(6): 2732-2741.
[10]	李铁男, 赵碧丹, 赵鹏, 张永民, 王军武. 气固流化床启动阶段挡板内构件受力特性的CFD-DEM模拟[J]. 化工学报, 2022, 73(6): 2649-2661.
[11]	李丽媛, 王建强, 陈奕, 郭友娣, 周健, 刘志成, 王仰东, 谢在库. 甲醇制丙烯反应中ZSM-5分子筛催化剂积炭失活介尺度机制研究[J]. 化工学报, 2022, 73(6): 2669-2676.
[12]	朱嫣然, 葛亮, 李兴亚, 徐铜文. 三相结构离子交换膜的构筑及应用研究[J]. 化工学报, 2022, 73(6): 2397-2414.
[13]	蒋鸣, 周强. 气固流化床介尺度结构形成机制及过滤曳力模型研究进展[J]. 化工学报, 2022, 73(6): 2468-2485.
[14]	周晨阳, 贾颖, 赵跃民, 张勇, 付芝杰, 冯昱清, 段晨龙. 介尺度视角下干法重介流态化分选过程强化[J]. 化工学报, 2022, 73(6): 2452-2467.
[15]	王利民, 郭舒宇, 向星, 付少童. 湍流系统的能量最小多尺度模型研究进展[J]. 化工学报, 2022, 73(6): 2415-2426.