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基于线性接触模型、库仑滑移接触模型以及平行黏结三种接触模型的组合, 利用离散元法对包衣结构的湿颗粒聚团与壁面碰撞解聚的物理过程进行了数值模拟, 研究了碰撞过程中湿颗粒聚团解聚模式、解聚过程中聚团内各颗粒的速度变化以及颗粒间液桥断裂的规律, 分析了聚团的碰撞速度、黏附小颗粒的重力以及中心大颗粒的旋转对聚团解聚的影响. 研究发现: 聚团的碰撞解聚呈现出碰撞式、重力-碰撞式和剪切-碰撞式三种解聚模式. 湿颗粒聚团与壁面的碰撞打破了聚团内颗粒速度的一致性, 颗粒间出现相对运动而使颗粒间的液桥发生拉伸断裂. 液桥的断裂由聚团的碰撞点向外、由底部向上、由内层向外扩展. 聚团内液桥的断裂经历了缓慢断裂、快速断裂和完全断裂三个阶段. 碰撞速度越大, 黏附的小颗粒质量越大、大颗粒的转速越高, 湿颗粒聚团的缓慢断裂阶段越短暂且解聚程度越高. 模拟结果和实验符合.Based on the combination of linear contact model, Coulomb slip contact model and parallel bond contact model, a discret element model (DEM) of wet granule agglomerates with coating structure is constructed. Disaggregation processes of wet agglomerates in impacting to a horizontal plate are performed by applying particle flow code (PFC). Three failure patterns are obtained corresponding to those in experiment. The variation of velocities and rupture characteristics of liquid bridge in disaggregation process are investigated. Effects of impact velocity, gravity of adhered granules, and rotation of core granule are analyzed. DEM simulations show that there are three disaggregation patterns in the coating structure of agglomerates: impact disaggregation, gravity-impact disaggregation and shear-impact disaggregation, depending on the size of primary particles and the rotation of the core granules. With the enlargement of size, gravity plays an increasingly important role and the impact disaggregation pattern shifts to gravity-impact disaggregation. The rotation of core can generate a shear force to separate the fine and disaggregation pattern to turn to shear-impact disaggregation. Impacting results in a heterogeneous distribution of granule velocities and a tendency of relative movement in agglomerates. Relative movement will bring about the stretch of liquid bridge between granules. If the maximum separation distance of wet granules exceeds the rupture distance of liquid bridge, disaggregation happens. The ruptures of liquid bridge start from impact point and expand to outward, from bottom to up, from inside to outside in coating agglomeration. It is found that the rupture of liquid bridge needs time for accumulation and goes through three stages termed as slow rupture stage, quick rupture stage and entire rupture stage. With the increase of impact velocity, particle gravity, and rotating speed of core granules, disaggregation processes of wet granule agglomerates become fast and thorough. Impact velocity plays a primary role in disaggregation. DEM simulations are consistent with the experimental results.
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Keywords:
- wet granulation /
- agglomerates /
- disaggregation /
- DEM
[1] Fu J S, Cheong Y S, Adams M J, Reynolds G K 2004 Powder Technology 140 24
[2] Jinsheng F, Gavin K R, Michael J A 2005 Chemical Engineering Science 60 4005
[3] Gao H L, Chen Y C, Zhao Y Z, Zhen J Y 2011 Acta Phys. Sin. 60 124501 (in Chinese) [高红利, 陈友川, 赵永志, 郑津洋 2011 60 124501]
[4] Zhao L L, Zhao Y M, Liu C S, Li J 2014 Acta Phys. Sin. 63 034501 (in Chinese) [赵啦啦, 赵跃民, 刘初升, 李珺 2014 63 034501]
[5] Radl S, Kalvoda E, Glasser B J, Khinast J G 2010 Powder Technology 200 171
[6] Zhu R R, Zhu W B, Xing L C, Sun Q Q 2011 Powder Technology 210 73
[7] He Y, Peng W, Wang T, Yan S 2014 Mathematical Problems in Engineering 31 568
[8] Thornton C, Liu L 2004 Powder Technology 143 110
[9] Sergiy A, Manoj K, Jurgen T 2006 Chemical Engineering and Processing 45 838
[10] Mishra B K, Thornton C 2001 International Journal of Mineral Processing 61 225
[11] Liu L, Kafui K D, Thornton C 2010 Powder Technology 199 189
[12] Xu Y, Sun Q C, Zhang L,Huang W B 2003 Advanced in Mechanics 33 253 (in Chinese) [徐泳,孙其诚,张凌,黄文彬 2003 力学进展 33 253]
[13] Christopher D, Michael J 2000 Langmuir 16 9396
[14] Hotta K, Taked A K, Iinoya K 1974 Powder Technology 10 231
[15] Lian G, Adamsand M J, Thornton C 1996 Journal of Fluid Mechanics 311 141
[16] Davis R H, Serayssol J M, Hinch E J 1986 Journal of Fluid Mechanics 163 479
[17] Zhang R 2005 Ph. D. Dissertation (Jilin: Ji Lin University) (in Chinese) [张锐 2005 博士学位论文(吉林:吉林大学)]
[18] Zhang R, Li J Q, Zhou C H, Xu S C 2007 Transactions of the Chinese Society of Agricultural Engineering 23(9) 13 (in Chinese) [张锐,李建桥,周长海,许述财 2007 农业过程学报 23(9) 13]
[19] Itasca C 2004 Particle flow code, PFC2D 3.1 (Minneapolis, Minnesota Press) p123
[20] Shen Z F, Jiang M J, Zhu F Y, Hu H J 2011 Northwestern Seismological Journal 33(8) 160 (in Chinese) [申志福,蒋明镜,朱方园,胡海军 2011 西北地震学报 33(8) 160]
[21] Cundall P A, Strack O L 1997 Geotechnique 29(1) 47
[22] Yang Y, Tang S G, Wang J L 2007 Computer Aider Engineering 16 (3) 65 (in Chinese) [杨洋, 唐寿高,王居林 2007 计算机辅助工程 16 (3) 65]
[23] Iwashita K, Oda M 1998 Journal of Engineering Mechanics 124 285
[24] Jiao Y , Zhang X X , Kong F C 2014 Journal ofChina Coal Society 39 2092 (in Chinese) [焦杨,章新喜,孔凡成 2014 煤炭学报 39 2092]
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[1] Fu J S, Cheong Y S, Adams M J, Reynolds G K 2004 Powder Technology 140 24
[2] Jinsheng F, Gavin K R, Michael J A 2005 Chemical Engineering Science 60 4005
[3] Gao H L, Chen Y C, Zhao Y Z, Zhen J Y 2011 Acta Phys. Sin. 60 124501 (in Chinese) [高红利, 陈友川, 赵永志, 郑津洋 2011 60 124501]
[4] Zhao L L, Zhao Y M, Liu C S, Li J 2014 Acta Phys. Sin. 63 034501 (in Chinese) [赵啦啦, 赵跃民, 刘初升, 李珺 2014 63 034501]
[5] Radl S, Kalvoda E, Glasser B J, Khinast J G 2010 Powder Technology 200 171
[6] Zhu R R, Zhu W B, Xing L C, Sun Q Q 2011 Powder Technology 210 73
[7] He Y, Peng W, Wang T, Yan S 2014 Mathematical Problems in Engineering 31 568
[8] Thornton C, Liu L 2004 Powder Technology 143 110
[9] Sergiy A, Manoj K, Jurgen T 2006 Chemical Engineering and Processing 45 838
[10] Mishra B K, Thornton C 2001 International Journal of Mineral Processing 61 225
[11] Liu L, Kafui K D, Thornton C 2010 Powder Technology 199 189
[12] Xu Y, Sun Q C, Zhang L,Huang W B 2003 Advanced in Mechanics 33 253 (in Chinese) [徐泳,孙其诚,张凌,黄文彬 2003 力学进展 33 253]
[13] Christopher D, Michael J 2000 Langmuir 16 9396
[14] Hotta K, Taked A K, Iinoya K 1974 Powder Technology 10 231
[15] Lian G, Adamsand M J, Thornton C 1996 Journal of Fluid Mechanics 311 141
[16] Davis R H, Serayssol J M, Hinch E J 1986 Journal of Fluid Mechanics 163 479
[17] Zhang R 2005 Ph. D. Dissertation (Jilin: Ji Lin University) (in Chinese) [张锐 2005 博士学位论文(吉林:吉林大学)]
[18] Zhang R, Li J Q, Zhou C H, Xu S C 2007 Transactions of the Chinese Society of Agricultural Engineering 23(9) 13 (in Chinese) [张锐,李建桥,周长海,许述财 2007 农业过程学报 23(9) 13]
[19] Itasca C 2004 Particle flow code, PFC2D 3.1 (Minneapolis, Minnesota Press) p123
[20] Shen Z F, Jiang M J, Zhu F Y, Hu H J 2011 Northwestern Seismological Journal 33(8) 160 (in Chinese) [申志福,蒋明镜,朱方园,胡海军 2011 西北地震学报 33(8) 160]
[21] Cundall P A, Strack O L 1997 Geotechnique 29(1) 47
[22] Yang Y, Tang S G, Wang J L 2007 Computer Aider Engineering 16 (3) 65 (in Chinese) [杨洋, 唐寿高,王居林 2007 计算机辅助工程 16 (3) 65]
[23] Iwashita K, Oda M 1998 Journal of Engineering Mechanics 124 285
[24] Jiao Y , Zhang X X , Kong F C 2014 Journal ofChina Coal Society 39 2092 (in Chinese) [焦杨,章新喜,孔凡成 2014 煤炭学报 39 2092]
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