Please wait a minute...
浙江大学学报(工学版)
J4  2009, Vol. 43 Issue (09): 1703-1708    DOI: 10.3785/j.issn.1008-973X.2009.
    
Micro-scale simulation and analysis of gas-solid fluidized bed with multi-density distribution of particles
 JIANG Mao-Jiang, DIAO Yong-Zhi, ZHENG Jin-Xiang
(State Key Laboratory of Chemical Engineering, Zhejiang University, Hangzhou 310027, China)
Download:   PDF(2087KB) HTML
Export: BibTeX | EndNote (RIS)      

Abstract  

A three-dimensional multi-density fluidized bed was simulated by using computational fluid dynamics-discrete element method (CFD-DEM)  at two superficial gas velocities. The mixing and segregation behavior of particles at two different superficial gas velocities was compared. Results showed that different degree of segregation phenomenon existed in the fluidized bed. The obviously segregation phenomenon that heavy particles moved down and light particles moved up occurred when the superficial gas velocity was low, being larger than the critical fluidization velocity of the lightest particles but smaller than that of the heaviest particles. But the segregation phenomenon was not clear when the superficial gas velocity was higher than the maximum critical fluidization velocity. The mixing and segregation behavior of particles at two different superficial gas velocities was described by Lacey indexes. Results show that particles with smaller density difference have larger mixing index and are more difficult to be segregated, and that with larger density difference have smaller mixing index and can be segregated much more completely．

CLC:  TQ 018  
Service
E-mail this article
Add to my bookshelf
Add to citation manager
E-mail Alert
RSS
Articles by authors
Cite this article:

JIANG Mao-Jiang, DIAO Yong-Zhi, ZHENG Jin-Xiang. Micro-scale simulation and analysis of gas-solid fluidized bed with multi-density distribution of particles. J4, 2009, 43(09): 1703-1708.

URL:

http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2009.     OR     http://www.zjujournals.com/eng/Y2009/V43/I09/1703


非等密度颗粒气固流化床的微观尺度模拟与分析

采用计算流体力学与离散单元法相耦合的CFD-DEM方法对两种表观气速下三维非等密度颗粒流化床内的气固运动进行了数值模拟研究,对比了两种气速下流化床内颗粒的分层和混合现象,发现在非等密度颗粒流化床内,有不同程度的颗粒分层现象存在。当表观气速较低,处于最小密度颗粒的临界流化速度和最大密度颗粒的临界流化速度之间时,颗粒体系出现了较为明显的分层现象,整体上为重颗粒在下、轻颗粒在上的分层结构；当表观气速较高,大于最大密度颗粒的临界流化速度时,分层现象不再明显。采用Lacey混合指数分析了流化床内颗粒之间的混合状况,发现颗粒密度差越小,混合指数越大,越难分离；颗粒密度差越大,则混合指数越小,分离越完全.

[1] 何玉荣,陆慧林,别如山,等.鼓泡流化床宽筛分颗粒气固两相流动的流体动力学[J].动力工程,2003,23(5):2646-2651.
HE Yu-rong, LU Hui-lin, BIE Ru-shan, et al. Hydrodynamics of gas-solid flow in bubbling fluidized bed with wide particle size distribution [J].Power Engineering, 2003, 23(5): 2646-2651.
[2] 吴锦坤,罗坤,胡桂林,等.鼓泡流化床流动特性的直接数值模拟[J].浙江大学学报:工学版,2007, 41(3): 504-508.
WU Jin-kun, LUO Kun, HU Gui-lin, et al. Direct particle simulation of flow characteristics in bubbling fluidized bed [J].Journal of Zhejiang University: Engineering Science, 2007, 41(3): 504-508.
[3] TSUJI Y,KAWAGUCHI T,TABAKA T.Discrete particle simulation of two-dimensional fluidized bed [J].Powder Technology, 1993, 77(1):79-87.
[4] HOOMANS B P B,KUIPERS J A M,BRIELS W J,et al.Discrete particle simulation of bubble and slug formation in a two-dimensional gas-fluidized bed:a hard sphere approach [J].Chemical Engineering Science, 1996, 51(1):99-118.
[5] XＵ B H,YＵ A B.Numerical simulation of the gas-particle flow in a fluidized bed by combining discrete particle method with computational fluid dynamics [J].Chemical Engineering Science, 1997, 52(16):2785-2809.
[6] OUYANG J,LI J.Discrete simulations of heterogeneous structure and dynamic behavior in gas-solid fluidization [J].Chemical Engineering Science, 1999, 54(22):5427-5440.
[7] ZHU H P,ZHOU Z Y,YANG R Y,et al.Discrete particle simulation of particulate systems: theoretical developments [J].Chemical Engineering Science, 2007,62(13):3378-3396.
[8] FENG Y Q,XU B H,ZHANG S J,et al.Discrete particle simulation of gas fluidization of particle mixtures [J].AIChE Journal, 2004, 50(8): 1713-1728.
[9] FENG Y Q,YU A B.Micro-dynamic modeling and analysis of the mixing and segregation of binary mixtures of particles in gas fluidization [J].Chemical Engineering Science, 2007, 62(1-2):256-268.
[10] 周浩生,陆继东,钱诗智.宽筛分流化床气-固两相流动结构离散颗粒模拟[J].燃烧科学与技术,1999,5(3):270-275.
ZHOU Hao-sheng,LU Ji-dong,QIAN Shi-zhi.Discrete particle simulation of flow structure in gas fluidized bed with particle size distribution [J].Journal of Combustion Science and Technology,1999,5(3):270-275.
[11] 袁竹林. 流化床中颗粒流化运动的直接数值模拟[J].燃烧科学与技术,2001,7(2): 120-122.
YUAN Zhu-lin.Study on fluidized region of particles using direct simulation method [J].Journal of Combustion Science and Technology, 2001, 7(2):120-122.
[12] 刘阳,刘文铁,何玉荣,等.流化床内非等密度双组分颗粒流动特性研究[J].热能动力工程,2005,20(6): 615-618.
LIU Yang,LIU Wen-tie,HE Yu-rong,et al. Flow pattern in Fluidized beds of two solids differing in density [J].Journal of Engineering for Thermal Energy and Power, 2005, 20(6): 615-618.
[13] 赵永志,程易,金涌.提升管与下行床颗粒团聚行为的离散颗粒模拟[J].化工学报,2007,58(1):44-53.
ZHAO Yong-zhi,CHENG Yi,JIN Yong.CFD-DEM simulation of clustering phenomena in riser and downer [J].Journal of Chemical Industry and Engineering,2007,58(1):44-53.
[14] PATANKAR S V.Numerical heat transfer and fluid flow [M].Washington: Hemisphere, 1980.
[15] VAN DOORMAL J P,RAITHBY G D.Enhancements of the SIMPLEC method for predicting incompressible fluid flow [J].Numerical Heat Transfer,1984,7(2):147-163.
[16] 陶文铨.数值传热学[M].西安:西安交通大学出版社,2001.
[17] CUNDALLl P A,STRACK O D L.A discrete numerical model for granular assemblies [J].Geotechnique, 1979, 29(1):47-65.
[18] WEN C Y, YU Y H. A generalized method for predicting the minimum fluidization velocity [J].AIChE Journal, 1966; 12: 610-612.
[19] 黄卫星,漆小波,潘永良,等.气固循环提升管内的局部颗粒浓度及流动发展[J].高校化学工程学报, 2002, 16 (6): 626-631.
HUANG Wei-xing , QI Xiao-bo , PAN Yong-liang , et al. Local solid particle concentration and flow development in a long CFB riser [J].Journal of Chemical Engineering of Chinese University, 2002, 16 (6): 626-631.
[20] LACEY P M C.Developments in the theory of particle mixing [J].Journal of Applied Chemistry,1954,4(2):257-268.
[1] DIAO Yong-Zhi, JIANG Mao-Jiang, XU Beng, ZHENG Jin-Xiang. Micro-scale simulation of heat transfer behavior in fluidized bed with immersed tube[J]. J4, 2010, 44(6): 1178-1184.