滚筒内柱体内构件对二元颗粒体系混合的影响
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摘要
针对滚筒内二元颗粒体系在混合过程中产生的混合死区现象,提出在混合死区位置设置柱体内构件的增混方式,以接触数作为混合评价指标,采用离散单元法研究柱体内构件对二元颗粒体系运动混合的影响,并分析其增混机理。研究结果表明:柱体内构件很大程度上破坏了聚集小颗粒的混合死区,强化了二元颗粒间的对流和扩散机制,同时抑制了颗粒的离析作用,提高了颗粒体系整体混合程度,同时,柱体内构件提高了二元颗粒体系的混合效率,改变了颗粒体系混合的稳定性;在一定的范围内,柱体内构件的数量越多,颗粒体系的混合效果越好,但如果数量过多,反而不利于二元颗粒间的混合;在滚筒开始转动的短暂时间内,柱体内构件反而抑制颗粒体系的混合,滚筒继续转动,才起到增混的效果。本研究可为二元颗粒物料增混设备的改进提供参考和依据。
Accounting for the phenomenon of mixed dead zone in mixing process of binary granular systems,column internals wee set in the horizontal drum to augment mixing.The contact number was taken as a particle mixing indicator.The discrete element method was employed to study mixing of the binary particles with the column internals.The mechanisms of augmenting mixing of the column internals were discussed in this paper.The results showed that the column internals can destroy the mixed dead zone of the aggregated particles.When the components are set in the drum,the mechanisms of convection and diffusion are enhanced,and the segregation of the binary particles is suppressed.Moreover,the column internals can improve the mixing efficiency and change the stability of mixing.It was noted that the mixing effect of binary particles improves with the increase of the number of cylinder components in the drum in a certain range,and excessive number of internals are unfavorable for mixing.The column internals inhibit mixing of particle system when the drum starts to rotate,and the internals achieve the purpose of augment mixing after a period of movement.The results can provide theoretical guidance for equipment improvement of particle material in the industry of the augmenting mixing.
Accounting for the phenomenon of mixed dead zone in mixing process of binary granular systems,column internals wee set in the horizontal drum to augment mixing.The contact number was taken as a particle mixing indicator.The discrete element method was employed to study mixing of the binary particles with the column internals.The mechanisms of augmenting mixing of the column internals were discussed in this paper.The results showed that the column internals can destroy the mixed dead zone of the aggregated particles.When the components are set in the drum,the mechanisms of convection and diffusion are enhanced,and the segregation of the binary particles is suppressed.Moreover,the column internals can improve the mixing efficiency and change the stability of mixing.It was noted that the mixing effect of binary particles improves with the increase of the number of cylinder components in the drum in a certain range,and excessive number of internals are unfavorable for mixing.The column internals inhibit mixing of particle system when the drum starts to rotate,and the internals achieve the purpose of augment mixing after a period of movement.The results can provide theoretical guidance for equipment improvement of particle material in the industry of the augmenting mixing.
引文
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[2]SHI Q,YAN X,HOU M,et al.Experimental study of segregation patterns in binary granular mixtures under vertical vibration[J].Science Bulletin,2003,48(7):627-629.
[3]LIU R,LI Y C,HOU M Y.Phase separation in a three-dimensional granular gas system[J].Acta Physica Sinica,2008,57(8):4660-4666.
[4]SHI Q,SUN G,HOU M,et al.Density-driven segregation in vertically vibrated binary granular mixtures[J].Physical Review E:Statistical Nonlinear&Soft Matter Physics,2007,75(6):061302.
[5]SHI Q F,SUN G,HOU M Y,et al.Segregation in vertically vibrated binary granular mixtures with same size[J].Chinese Physics Letters,2006,23(11):3080-3083.
[6]LIU R,LI Y,HOU M.Oscillatory phenomena of compartmentalized bidisperse granular gases[J].Physical Review E:Statistical Nonlinear&Soft Matter Physics,2009,79(5):052301.
[7]李少华,张立栋,余侃胜,等.回转干馏炉内油页岩颗粒群断续给料混合运动模式[J].化工进展,2010,29(8):1433-1437.LI S H,ZHANG L D,YU K S,et al.Experimentals on mixed motion with discontinuous feed for oil shale particle group in rotary kiln[J].Chemical Industry and Engineering Progress,2010,29(8):1433-1437.
[8]朱立平,秦霞,袁竹林,等.丝状颗粒在滚筒横向截面中的传热传质特性[J].东南大学学报(自然科学版),2014,44(4):756-763.ZHU L P,QIN X,YUAN Z L,et al.Heat and mass transfer characteristics of filamentous particles in transverse section of rotary dryer[J].Journal of Southeast University(Natural Science Edition),2014,44(4):756-763.
[9]王擎,肖冠华,孔祥钊,等.固体热载体干馏桦甸油页岩试验研究[J].东北电力大学学报,2013,33(5):15-21.WANG Q,XIAO G H,KONG X Z,et al.Experimental investigation of solid heat carrier retorting of Huadian oil shale[J].Journal of Northeast Dianli University,2013,33(5):15-21.
[10]FIGUEROA I,VARGAS W L,MCCARTHY J J.Mixing and heat conduction in rotating tumblers[J].Chemical Engineering Science,2010,65(2):1045-1054.
[11]张立栋,李连好,秦宏,等.多粒径颗粒在圆形偏心滚筒内的运动混合[J].化工进展,2017,36(2):451-456.ZHANG L D,LI L H,QIN H,et al.Research on motion and mixing of polydisperse particles in a circular eccentric drum[J].Chemical Industry and Engineering Progress,2017,36(2):451-456.
[12]张立栋,韦庆文,秦宏,等.柱状生物质颗粒与钢球颗粒在滚筒中的混合特性[J].化工进展,2016,35(10):3057-3064.ZHANG L D,WEI Q E,QIN H,et al.Mixing characteristics in a rotary drum filled with cylindrical biomass and spherical steel particles[J].Chemical Industry and Engineering Progress,2016,35(10):3057-3064.
[13]闫明,段文山,陈琼,等.不同形状混合器中二元颗粒的分聚与混合研究[J].力学学报,2016,48(1):64-75.YAN M,DUAN W S,CHEN Q,et al.The segregation and mixing of binary granular systems in rotating mixer with different cross-sections[J].Chinese Journal of Theoretical and Applied Mechanics,2016,48(1):64-75.
[14]GUI N,FAN J.Numerical study of heat conduction of granular particles in rotating wavy drums[J].International Journal of Heat&Mass Transfer,2015,84:740-751.
[15]李少华,张立栋,张轩,等.回转式干馏炉内影响颗粒混合运动因素的数值模拟[J].中国电机工程学报,2011,31(2):32-38.LI S H,ZHANG L D,ZHANG X,et al.Numerical analysis of particle mixing and movement in rotary retorting[J].Proceedings of the CSEE,2011,31(2):32-38.
[16]SUNKARA K A,HERZ F,SPECHT E,et al.Influence of flight design on the particle distribution of a flighted rotating drum[J].Chemical Engineering Science,2013,90(10):101-109.
[17]JIANG M Q,ZHAO Y Z,LIU G S,et al.Enhancing mixing of particles by baffles in a rotating drum mixer[J].Particuology,2011,9(3):270-278.
[18]BHATTACHARYA T,HAJRA S K,MCCARTHY J J.A design heuristic for optimizing segregation avoidance practices in horizontal drum mixers[J].Powder Technology,2014,253(2):107-115.
[19]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 Y Z,ZHANG X Q,LIU Y L,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.
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