Lateral dispersion coefficient of large solid particles in CFB dense zone using CPFD method

doi:10.11949/j.issn.0438-1157.20170394

Abstract

Abstract:

Computational particle fluid dynamics (CPFD),a discrete element method (DEM),was utilized to simulate the lateral diffusion behavior of large solid particles in a 900 mm×100 mm×1200 mm quasi-three dimensional fluidized-bed.Before the simulating,verification had been performed in accordance with previous experimental studies to ensure the reliability of CPFD.The effects of the tracer particle diameter and the fluidizing air velocity on lateral dispersion coefficient of large solid particles in dense zone were investigated by the method of tracer particle.The results showed that the bubble behavior was the major factor of solid mixing in dense zone,which had been confirmed in many literatures.An increased gas velocity or a reduced tracer particle diameter resulted in an increased lateral dispersion coefficient.

Key words: fluidized-bed, dense zone, CPFD, bubble, diffusion, fluidization air velocity

摘要：

运用一种离散单元法（DEM）计算颗粒流体力学（CPFD）对尺寸为900 mm×100 mm×1200 mm的准三维流化床的密相区大颗粒扩散行为进行研究。模拟之前，依照前人实验研究对CPFD方法进行验证，模拟结果与实验结果符合较好，证明了CPFD方法模拟的有效性。模拟中通过注入示踪粒子的方法来研究大颗粒在密相区中的横向扩散系数，研究了流化风速、颗粒直径对颗粒横向扩散系数的影响。模拟结果显示，气泡是引起密相区内颗粒混合的主要因素；随着流化风速增加，颗粒横向扩散系数变大；随着颗粒直径增大，颗粒横向扩散系数减小。

关键词: 流化床, 密相区, CPFD, 气泡, 扩散, 流化风速

CLC Number:

TK224.1

ZHANG Xian, GE Rongcun, ZHANG Shouyu, LIU Qing, ZHANG Man, YANG Hairui, LÜ Junfu. Lateral dispersion coefficient of large solid particles in CFB dense zone using CPFD method[J]. CIESC Journal, 2017, 68(10): 3725-3732.

张贤, 葛荣存, 张守玉, 刘青, 张缦, 杨海瑞, 吕俊复. CFB密相区大颗粒横向扩散系数的CPFD模拟[J]. 化工学报, 2017, 68(10): 3725-3732.

References 30

[1]	刘道银, 陈晓平, 唐智, 等. 侧面进料在循环流化床密相区混合特性的试验研究[J]. 工程热物理学报, 2009, 30(3):529-532. LIU D Y, CHEN X P, TANG Z, et al. Experimental study on the mixing of particles feeding into the bottom zone of a CFB[J]. Journal of Engineering Thermophysics, 2009, 30(3):529-532.
[2]	肖显斌, 杨海瑞, 吕俊复, 等. CFB密相区内颗粒横向扩散对燃烧的影响[J]. 煤炭转化, 2003, 26(4):55-59. XIAO X B, YANG H R, LÜ J F, et al. Effect of the solid lateral dispersion on combustion in the dense zone of CFB[J]. Coal Conversion, 2003, 26(4):55-59.
[3]	杨海瑞, 吕俊复, 刘青, 等. 循环流化床锅炉密相区内颗粒的横向扩散研究[J]. 热能动力工程, 2001, 16(4):395-399. YANG H R, LÜ J F, LIU Q, et al. Study on the solid lateral dispersion in the dense zone of circulating fluidized bed[J]. Thermal and Power Engineering, 2001, 16(4):395-399.
[4]	刘宝勇, 魏绪玲, 张斌, 等. 气-固循环流化床底部密相区研究进展[J]. 化工技术与开发, 2014, 43(3):38-42. LIU B Y, WEI X L, ZHANG B, et al. Research development of bottom dense phase zone of gas-solid circulating fluidized bed[J]. Technology & Development of Chemical Industry, 2014, 43(3):38-42.
[5]	王翀. 流化床气固两相流数值模拟及实验研究[D]. 重庆:重庆大学, 2011. WANG C. Numerical simulation and experimental for flow characteristics in fluidized-bed[D]. Chongqing:Chongqing University, 2011.
[6]	汪琦. 气固流化床两相流动的CFD模型研究和实验验证[D]. 武汉:华中科技大学, 2012. WANG Q. Comparative analysis of CFD models of gas-solid fluidized bed and experimental verification[D]. Wuhan:Huazhong University of Science and Technology, 2012.
[7]	闫盛楠. 鼓泡流化床不规则形状颗粒气固两相流动特性研究[D]. 哈尔滨:哈尔滨工业大学, 2014. YAN S N. Investigation on gas-solid two-phase flow characteristics of irregularly shaped particle in a bubbling fluidized bed[D]. Harbin:Harbin Institute of Technology, 2014.
[8]	刘道银, 陈晓平, 陆利烨, 等. 流化床密相区颗粒扩散系数的CFD数值预测[J]. 化工学报, 2009, 60(9):2183-2190. LIU D Y, CHEN X P, LU L Y, et al. Prediction of solids dispersion coefficient in fluidized bed dense zone using CFD simulation[J]. CIESC Journal, 2009, 60(9):2183-2190.
[9]	OKE O, LETTIERE P, SALATINO P, et al. Eulerian modeling of lateral solid mixing in gas-fluidized suspensions[J]. Procedia Engineering, 2015, 102:1491-1499.
[10]	SNIDER D M, O'ROURKE P J, ANDREWS M J. Sediment flow in inclined vessels calculated using a multiphase particle-in-cell model for dense particle flows[J]. International Journal of Multiphase Flow, 1998, 24(8):1359-1382.
[11]	SNIDER D M. An incompressible three-dimensional multiphase particle-in-cell model for dense particle flows[J]. Journal of Computational Physics, 2001, 170(2):523-549.
[12]	SHI X, LAN X, LIU F, et al. Effect of particle size distribution on hydrodynamics and solids back-mixing in CFB risers using CPFD simulation[J]. Powder Technology, 2014, 266:135-143.
[13]	CHEN C, WERTHER J, HEINRICH S, et al. CPFD simulation of circulating fluidized bed risers[J]. Powder Technology, 2013, 235(2):238-247.
[14]	XU B H, YU A B. 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.
[15]	沈来宏, 章名耀. 鼓泡流化床内颗粒混合的对流-扩散模型[J]. 中国电机工程学报, 1995, 15(1):45-53. SHEN L H, ZHANG M Y. Modeling for solids mixing in bubbling fluidized beds[J]. Proceeding of The Chinese Society for Electrical Engineering, 1995, 15(1):45-53.
[16]	李炳顺, 孙运凯, 雍玉梅,等. 二维循环流化床密相区物料扩散冷态试验与模型建立[J]. 锅炉技术, 2007, 38(2):28-31. LI B S, SUN Y K, YONG Y M, et al. Coal-feeding diffusion cold experiment and model-building in dense phase of two-dimensional circulating fluidized bed[J]. Boiler Technology, 2007, 38(2):28-31.
[17]	MOSTOUFI N, CHAOUKI J. Local solid mixing in gas-solid fluidized beds[J]. Powder Technology, 2001, 114(1/2/3):23-31.
[18]	YUE G X, LU J F, ZHANG H, et al. Design theory of circulating fluidized bed boilers[C]//18th International Conference on Fluidized Bed Combustion. Fairfield, NJ:American Society of Mechanical Engineers, 2005:135-146.
[19]	杨石, 杨海瑞, 吕俊复, 等. 新一代节能型循环流化床锅炉燃烧技术[J]. 动力工程学报, 2009, 29(8):728-732. YANG S, YANG H R, LÜ J F, et al. The new generation combustion technology for energy saving circulating fluidized bed boilers[J]. Journal of Power Engineering, 2009, 29(8):728-732.
[20]	RHODES M J, ZHOU S, HIRAMA T, et al. Effects of operating conditions on longitudinal solids mixing in a circulating fluidized bed riser[J]. AIChE Journal, 1991, 37(10):1450-1458.
[21]	KOJIMA T, ISHIHARA K I, GUILIN Y, et al. Measurement of solids behaviour in a fast fluidized bed[J]. Journal of Chemical Engineering of Japan, 1989, 22(4):341-346.
[22]	SHI Y F, FAN L T. Lateral mixing of solids in batch gas-solids fluidized beds[J]. Industrial & Engineering Chemistry Process Design and Development, 1984, 23(2):337-341.
[23]	金涌. 流态化工程原理[M]. 北京:清华大学出版社, 2002. JIN Y. Theory of Fluidized Engineering[M]. Beijing:Tsinghua University Press, 2002.
[24]	徐旭常. 燃烧理论与燃烧设备[M]. 北京:机械工业出版社, 1990. XU X C. Combustion Theory and Combustion Equipment[M]. Beijing:China Machine Press, 1990.
[25]	胡南, 郭兆君, 杨海瑞, 等. CFB锅炉炉膛内颗粒横向扩散系数研究[J]. 动力工程学报, 2016, 36(3):168-171. HU N, GUO Z J, YANG H R, et al. Experimental study on lateral dispersion coefficient of solid particles in a CFB boiler[J]. Chinese Journal of Power Engineering, 2016, 36(3):168-171.
[26]	SALAM T F, REN Y, GIBBS B M. Lateral solid and thermal dispersion in fluidized bed combustors[C]//9th International Conference on Fluidized Bed Combustion. New York:American Society of Mechanical Engineers, 1987:541-545.
[27]	WINAYA I N S, SHIMIZU T, YAMADA D. A new method to evaluate horizontal solid dispersion in a bubbling fluidized bed[J]. Powder Technology, 2007, 178(3):173-178.
[28]	BERRUTI F, SCOTT D S, RHODES E. Measuring and modelling lateral solid mixing in a three-dimensional batch gas-solid fluidized bed reactor[J]. Canadian Journal of Chemical Engineering, 2010, 64(1):48-56.
[29]	XIAO P, YAN G, WANG D. Investigation on horizontal mixing of particles in dense bed in circulating fluidized bed (CFB)[J]. Journal of Thermal Science, 1998, 7(2):78-84.
[30]	SCHLICHTHAERLE P, WERTHER J. Solids mixing in the bottom zone of a circulating fluidized bed[J]. Powder Technology, 2001, 120(1):21-33.