Please wait a minute...
浙江大学学报(工学版)
Journal of ZheJiang University (Engineering Science)  2020, Vol. 54 Issue (7): 1347-1354    DOI: 10.3785/j.issn.1008-973X.2020.07.013
    
CFD-DEM investigation on mixing of rod-like particles in spout-fluid bed
Hua-qing MA(),Yong-zhi ZHAO*()
Institute of Process Equipment, Zhejiang University, Hangzhou 310027, China
Download: HTML     PDF(1070KB) HTML
Export: BibTeX | EndNote (RIS)      

Abstract  

The flow of rod-like particles in a spout-fluid bed was simulated by computational fluid dynamics/discrete element method (CFD-DEM), with rod-like particles being modeled by super-ellipsoids. The impacts of fluidization gas velocity, spout gas velocity and particle shape on the flow and mixing of rod-like particles were analyzed. The simulation results showed that the flow behaviors of rod-like particles in a spout-fluid bed basically accorded with the typical spout characteristics. Increasing fluidization gas velocity and spout gas velocity both can improve particle mixing, and the fluidization gas velocity has more effect on the particle mixing than the spout gas velocity does. The impact of particle shape on the particle mixing is mainly realized through the factors of consistency of particle orientation that is quantified by the proposed method and interlock between rod-like particles, so that the mixing degree decreases firstly and then increases with the particle aspect ratio.

Key words： computational fluid dynamics/discrete element method (CFD-DEM)      spout-fluid bed      particle mixing      rod-like particles      non-spherical particles     
Received: 24 June 2019      Published: 05 July 2020
CLC:  TK 6  
Corresponding Authors: Yong-zhi ZHAO     E-mail: 21528010@zju.edu.cn;yzzhao@zju.edu.cn
Service
E-mail this article
Add to my bookshelf
Add to citation manager
E-mail Alert
RSS
Articles by authors
Hua-qing MA
Yong-zhi ZHAO
Cite this article:

Hua-qing MA,Yong-zhi ZHAO. CFD-DEM investigation on mixing of rod-like particles in spout-fluid bed. Journal of ZheJiang University (Engineering Science), 2020, 54(7): 1347-1354.

URL:

http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2020.07.013     OR     http://www.zjujournals.com/eng/Y2020/V54/I7/1347


喷动流化床中杆状颗粒混合特性的CFD-DEM模拟

采用计算流体力学-离散单元法（CFD-DEM）模型对杆状颗粒在喷动流化床中的流动及混合行为进行数值模拟研究，其中杆状颗粒采用超椭球模型进行描述. 通过模拟结果，考察流化气速、喷动气速和颗粒形状对流动与混合的影响. 结果表明，杆状颗粒在喷动流化床中的流动具有典型喷动床的喷动特性；提高喷动气速与流化气速均有助于颗粒混合，且流化气速对流动与混合的影响大于喷动气速. 颗粒形状主要通过颗粒互锁与颗粒长轴取向一致性这2个因素影响颗粒混合，提出较简单的方法用以量化颗粒长轴取向的一致性. 在上述2个因素的作用下，当杆状颗粒长径比较小时，增加长径比会抑制颗粒混合；当长径比较大时，增加长径比会促进颗粒混合.


关键词： 计算流体力学-离散单元法（CFD-DEM）,  喷动流化床,  颗粒混合,  杆状颗粒,  非球形颗粒 
Fig.1 Geometry of spout-fluid bed and CFD grid
杆 长径比 a/mm b/mm c/mm s1 s2
杆1 1 1.748 1.748 1.748 20 2
杆2 2 1.387 1.387 2.775 20 2
杆3 3 1.212 1.212 3.636 20 2
杆4 4 1.101 1.101 4.405 20 2
杆5 5 1.022 1.022 5.111 20 2
Tab.1 Particle shape and sizes
参数 数值
颗粒密度/(kg·m?3) 638
弹性恢复系数 0.8
颗粒-颗粒间摩擦系数 0.5
颗粒-壁面间摩擦系数 0.3
气体密度/(kg·m?3) 1.21
气体黏度/(Pa·s) 1.83 × 10?5
颗粒数量 28 000
CFD时间步长/s 2 × 10?4
DEM时间步长/s 2 × 10?5
流化气体us umf、1.25umf
喷动气速uj/（m·s?1） 5、8
Tab.2 Parameters used in CFD-DEM simulations
Fig.2 Initial states of granular beds
杆 气速条件A
(us = umf,
uj = 5 m/s) 		气速条件B
(us = umf,
uj = 8 m/s) 		气速条件C
(us = 1.25umf,
uj = 5 m/s) 		气速条件D
(us = 1.25umf,
uj = 8 m/s)
杆1 A1 B1 C1 D1
杆2 A2 B2 C2 D2
杆3 A3 B3 C3 D3
杆4 A4 B4 C4 D4
杆5 A5 B5 C5 D5
Tab.3 Cases of CFD-DEM simulations
Fig.3 Comparisons of flow patterns between simulations and experiments
us/(m·s?1) H/m
实验值 模拟值
0.7 0.309±0.020 0.291±0.028
1.0 0.346±0.039 0.358±0.057
Tab.4 Comparisons of bed heights between CFD-DEM simulations and corresponding experiments
Fig.4 Snapshots of flow patterns for Rod 2 and Rod 4 at different gas velocities
Fig.5 Variation of mixing index with time for Rod 3 at different gas velocities
Fig.6 Time-averaged particle velocity during 2-10 s
Fig.7 Variation of mixing index with respect to time at B-gas velocity for particles with different shapes
Fig.8 Schematic diagram of divided subcells in spout-fluid bed
Fig.9 Quantification of consistency of particle orientation
[1]   张勇, 金保升, 钟文琪 喷动气固流化床颗粒混合规律的实验研究[J]. 中国电机工程学报, 2008, 28 (20): 8- 12
ZHANG Yong, JIN Bao-sheng, ZHONG Wen-qi Experimental investigation on particle mixing in spout-fluid bed[J]. Proceedings of the CSEE, 2008, 28 (20): 8- 12
doi: 10.3321/j.issn:0258-8013.2008.20.002
[2]   张勇, 金保升, 钟文琪, 等 喷动流化床颗粒混合特性的三维直接数值模拟[J]. 中国电机工程学报, 2008, 28 (2): 33- 38
ZHANG Yong, JIN Bao-sheng, ZHONG Wen-qi, et al Three-dimensional DEM simulation on particle mixing characteristics of spout-fluid bed[J]. Proceedings of the CSEE, 2008, 28 (2): 33- 38
doi: 10.3321/j.issn:0258-8013.2008.02.006
[3]   ANDERSON T B, JACKSON R Fluid mechanical description of fluidized beds[J]. Industrial and Engineering Chemistry Fundamentals, 1967, 6 (4): 527- 539
doi: 10.1021/i160024a007
[4]   TSUJI Y, KAWAGUCHI T, TANAKA T Discrete particle simulation of two-dimensional fluidized bed[J]. Powder Technology, 1993, 77 (1): 79- 87
doi: 10.1016/0032-5910(93)85010-7
[5]   XU B, YU A Numerical simulation of the gas-solid flow in a fluidized bed by combining discrete particle method with computational fluid dynamics[J]. Chemical Engineering Science, 1997, 52 (16): 2785- 2809
doi: 10.1016/S0009-2509(97)00081-X
[6]   CUNDALL P A, STRACK O D A discrete numerical model for granular assemblies[J]. Geotechnique, 1979, 29 (1): 47- 65
doi: 10.1680/geot.1979.29.1.47
[7]   周池楼, 赵永志 离散单元法及其在流态化领域的应用[J]. 化工学报, 2014, 65 (7): 2520- 2534
ZHOU Chi-lou, ZHAO Yong-zhi Discrete element method and its applications in fluidization[J]. CIESC Journal, 2014, 65 (7): 2520- 2534
doi: 10.3969/j.issn.0438-1157.2014.07.014
[8]   ZHU H, ZHOU Z, YANG R, et al Discrete particle simulation of particulate systems: a review of major applications and findings[J]. Chemical Engineering Science, 2008, 63 (23): 5728- 5770
doi: 10.1016/j.ces.2008.08.006
[9]   LU G, THIRD J, MüLLER C Discrete element models for non-spherical particle systems: from theoretical developments to applications[J]. Chemical Engineering Science, 2015, 127: 425- 465
doi: 10.1016/j.ces.2014.11.050
[10]   ZHONG W, YU A, LIU X, et al DEM/CFD-DEM modelling of non-spherical particulate systems: theoretical developments and applications[J]. Powder Technology, 2016, 302: 108- 152
doi: 10.1016/j.powtec.2016.07.010
[11]   ZHAO Y, XU L, UMBANHOWAR P B, et al Discrete element simulation of cylindrical particles using super-ellipsoids[J]. Particuology, 2019, 46: 55- 66
doi: 10.1016/j.partic.2018.04.007
[12]   MA H, XU L, ZHAO Y CFD-DEM simulation of fluidization of rod-like particles in a fluidized bed[J]. Powder Technology, 2017, 314: 355- 366
doi: 10.1016/j.powtec.2016.12.008
[13]   HOPKINS M A Polyhedra faster than spheres?[J]. Engineering Computations, 2014, 31 (3): 567- 583
doi: 10.1108/EC-09-2012-0211
[14]   NING Z, BOEREFIJN R, GHADIRI M, et al Distinct element simulation of impact breakage of lactose agglomerates[J]. Advanced Powder Technology, 1997, 8 (1): 15- 37
doi: 10.1016/S0921-8831(08)60477-X
[15]   KODAM M, BHARADWAJ R, CURTIS J, et al Cylindrical object contact detection for use in discrete element method simulations. Part I: contact detection algorithms[J]. Chemical Engineering Science, 2010, 65 (22): 5852- 5862
doi: 10.1016/j.ces.2010.08.006
[16]   CAI J, LI Q, YUAN Z Orientation of cylindrical particles in gas-solid circulating fluidized bed[J]. Particuology, 2012, 10 (1): 89- 96
doi: 10.1016/j.partic.2011.03.012
[17]   OSCHMANN T, VOLLMARI K, KRUGGEL-EMDEN H, et al Numerical investigation of the mixing of non-spherical particles in fluidized beds and during pneumatic conveying[J]. Procedia Engineering, 2015, 102: 976- 985
doi: 10.1016/j.proeng.2015.01.220
[18]   REN B, ZHONG W, JIANG X, et al Numerical simulation of spouting of cylindroid particles in a spouted bed[J]. The Canadian Journal of Chemical Engineering, 2014, 92 (5): 928- 934
doi: 10.1002/cjce.21900
[19]   ZHONG W Q, ZHANG Y, JIN B S, et al Discrete element method simulation of cylinder-shaped particle flow in a gas-solid fluidized bed[J]. Chemical Engineering and Technology, 2009, 32 (3): 386- 391
doi: 10.1002/ceat.200800516
[20]   NAN W, WANG Y, WANG J Numerical analysis on the fluidization dynamics of rodlike particles[J]. Advanced Powder Technology, 2016, 27 (5): 2265- 2276
doi: 10.1016/j.apt.2016.08.015
[21]   VOLLMARI K, OSCHMANN T, WIRTZ S, et al Pressure drop investigations in packings of arbitrary shaped particles[J]. Powder Technology, 2015, 271: 109- 124
doi: 10.1016/j.powtec.2014.11.001
[22]   VOLLMARI K, JASEVI?IUS R, KRUGGEL-EMDEN H Experimental and numerical study of fluidization and pressure drop of spherical and non-spherical particles in a model scale fluidized bed[J]. Powder Technology, 2016, 291: 506- 521
doi: 10.1016/j.powtec.2015.11.045
[23]   OSCHMANN T, HOLD J, KRUGGEL-EMDEN H Numerical investigation of mixing and orientation of non-spherical particles in a model type fluidized bed[J]. Powder Technology, 2014, 258: 304- 323
doi: 10.1016/j.powtec.2014.03.046
[24]   MAHAJAN V V, NIJSSEN T M J, KUIPERS J A M, et al Non-spherical particles in a pseudo-2D fluidised bed: modelling study[J]. Chemical Engineering Science, 2018, 192: 1105- 1123
doi: 10.1016/j.ces.2018.08.041
[25]   MA H, ZHAO Y CFD-DEM investigation of the fluidization of binary mixtures containing rod-like particles and spherical particles in a fluidized bed[J]. Powder Technology, 2018, 336: 533- 545
doi: 10.1016/j.powtec.2018.06.034
[26]   MA H, ZHAO Y, CHENG Y CFD-DEM modeling of rod-like particles in a fluidized bed with complex geometry[J]. Powder Technology, 2019, 344: 673- 683
doi: 10.1016/j.powtec.2018.12.066
[27]   CUI H, GRACE J R Spouting of biomass particles: a review[J]. Bioresource Technology, 2008, 99 (10): 4008- 4020
doi: 10.1016/j.biortech.2007.04.048
[28]   LIU X, ZHONG W, JIANG X, et al Spouting behaviors of binary mixtures of cylindroid and spherical particles[J]. AIChE Journal, 2015, 61 (1): 58- 67
doi: 10.1002/aic.14636
[29]   LIU X, ZHONG W, YU A, et al Mixing behaviors in an industrial-scale spout-fluid mixer by 3D CFD-TFM[J]. Powder Technology, 2017, 314: 455- 465
doi: 10.1016/j.powtec.2016.10.046
[30]   ZHANG Y, ZHONG W, JIN B Experimental investigation on the translational and rotational motion of biomass particle in a spout-fluid bed[J]. International Journal of Chemical Reactor Engineering, 2013, 11: 453- 468
doi: 10.1515/ijcre-2013-0067
[31]   MA H, ZHAO Y Investigating the flow of rod-like particles in a horizontal rotating drum using DEM simulation[J]. Granular Matter, 2018, 20 (3): 41
doi: 10.1007/s10035-018-0823-0
[32]   ZHAO Y, JIANG M, LIU Y, et al Particle-scale simulation of the flow and heat transfer behaviors in fluidized bed with immersed tube[J]. AIChE Journal, 2009, 55 (12): 3109- 3124
doi: 10.1002/aic.11956
[33]   XU L, ZHANG Q, ZHENG J, et al Numerical prediction of erosion in elbow based on CFD-DEM simulation[J]. Powder Technology, 2016, 302: 236- 246
doi: 10.1016/j.powtec.2016.08.050
[34]   ZHAO Y, XU L, ZHENG J CFD-DEM simulation of tube erosion in a fluidized bed[J]. AIChE Journal, 2017, 63: 418- 437
doi: 10.1002/aic.15398
[35]   YOU Y, LIU M, MA H, et al Investigation of the vibration sorting of non-spherical particles based on DEM simulation[J]. Powder Technology, 2018, 325: 316- 332
doi: 10.1016/j.powtec.2017.11.002
[36]   ZHU H, ZHOU Z, YANG R, et al Discrete particle simulation of particulate systems: theoretical developments[J]. Chemical Engineering Science, 2007, 62 (13): 3378- 3396
doi: 10.1016/j.ces.2006.12.089
[37]   XU B H, YU A B, CHEW S J, et al Numerical simulation of the gas-solid flow in a bed with lateral gas blasting[J]. Powder Technology, 2000, 109 (1–3): 13- 26
[38]   DI FELICE R The voidage function for fluid-particle interaction systems[J]. International Journal of Multiphase Flow, 1994, 20 (1): 153- 159
doi: 10.1016/0301-9322(94)90011-6
[39]   H?LZER A, SOMMERFELD M New simple correlation formula for the drag coefficient of non-spherical particles[J]. Powder Technology, 2008, 184 (3): 361- 365
doi: 10.1016/j.powtec.2007.08.021
[40]   ZHAO Y, DING Y, WU C, et al Numerical simulation of hydrodynamics in downers using a CFD-DEM coupled approach[J]. Powder Technology, 2010, 199 (1): 2- 12
doi: 10.1016/j.powtec.2009.04.014
[41]   MAHAJAN V V, PADDING J T, NIJSSEN T M, et al Nonspherical particles in a pseudo-2D fluidized bed: experimental study[J]. AIChE Journal, 2018, 64 (5): 1573- 1590
doi: 10.1002/aic.16078
[42]   LACEY P M C Developments in the theory of particle mixing[J]. Journal of Applied Chemistry, 1954, 4 (5): 257- 268
[43]   赵永志, 张宪旗, 刘延雷, 等 滚筒内非等粒径二元颗粒体系增混机理研究[J]. 物理学报, 2009, 58 (12): 8386- 8393
ZHAO Yong-zhi, ZHANG Xian-qi, LIU Yan-lei, et al Augmenting the mixing of size-type binary granular systems in a rotating horizontal drum[J]. Acta Physica Sinica, 2009, 58 (12): 8386- 8393
doi: 10.3321/j.issn:1000-3290.2009.12.042
[44]   朱润孺, 朱卫兵, 邢力超, 等 矩形喷动床混合特性的三维数值研究[J]. 中国电机工程学报, 2010, 30 (17): 12- 16
ZHU Run-ru, ZHU Wei-bing, XING Li-chao, et al A three-dimensional numerical investigation on particle mixing characteristics in rectangular spouted beds[J]. Proceedings of the CSEE, 2010, 30 (17): 12- 16
[1] REN Li-bo, HAN Ji-tian, ZHAO Hong-xia. Numerical simulation of discrete particles in fluidized bed with immersed tube[J]. Journal of ZheJiang University (Engineering Science), 2015, 49(1): 150-156.