旋转流化床粉体混合机混合效果数值模拟和实验验证
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摘要
为了对旋转流化床粉体混合机进行优化设计,采用CFD-DEM联合仿真的方法,对旋转流化床粉体混合机内球形颗粒的混合过程进行数值模拟,通过Lacey指数具体评价颗粒的混合效果,研究了进气管倾斜角度、进气管布置方式、进气方式对球形颗粒混合效果的影响,并进行球形颗粒混合实验验证。结果表明,进气管最合适的倾斜角度应保证气流作用区域面积恰好为底部颗粒物料区域面积的一半。进气管水平布置时能够保证很好的混合质量及较快的混合速率。脉冲及连续方式进气均能实现均匀混合,脉冲进气方式比连续进气方式耗气量更低。颗粒混合实验有很好的混合效果,与数值模拟的结果具有较高的一致性,从而获得了一种混合效果优越的结构形式,进气管倾斜角度α=35°,水平布置。
In order to get structure optimal design of a rotating fluidized bed powder mixer, the mixing progress of spherical powder granules in a rotating fluidized bed powder mixer was simulated by a combined approach of computational fluid dynamics(CFD) and discrete element method(DEM). Lacey mix index was used to quantitatively analyze the mixing degree of granules in the mixer. The effects of different parameters including the tilt angle of the intake pipe, the arrangement of the intake pipe and intake method were studied respectively. To verify the mixing performance of the rotating fluidized bed powder mixer, a granule mixing experiment was carried out. Simulation results showed that the most appropriate angle of intake pipe should ensure the area of airflow is just half of the area of granular materials in the bottom of the mixer. Besides, if the intake pipe is horizontal arranged, effective mixing quality and mixing rate could be achieved. Moreover, whether the intake is continuous or pulsed, spherical granules could achieve uniform mixing. Compared with the continuous intake,the air comsumption of pulsed intake was less. Finally, the powder mixing experimental results showed a positive mixing quality, which were in good agreement with the numerical data. It could be drawn that it is a structure with superior mixing effect if the intake pipe is tilted at an angle of 35 degrees and horizontal arranged.
In order to get structure optimal design of a rotating fluidized bed powder mixer, the mixing progress of spherical powder granules in a rotating fluidized bed powder mixer was simulated by a combined approach of computational fluid dynamics(CFD) and discrete element method(DEM). Lacey mix index was used to quantitatively analyze the mixing degree of granules in the mixer. The effects of different parameters including the tilt angle of the intake pipe, the arrangement of the intake pipe and intake method were studied respectively. To verify the mixing performance of the rotating fluidized bed powder mixer, a granule mixing experiment was carried out. Simulation results showed that the most appropriate angle of intake pipe should ensure the area of airflow is just half of the area of granular materials in the bottom of the mixer. Besides, if the intake pipe is horizontal arranged, effective mixing quality and mixing rate could be achieved. Moreover, whether the intake is continuous or pulsed, spherical granules could achieve uniform mixing. Compared with the continuous intake,the air comsumption of pulsed intake was less. Finally, the powder mixing experimental results showed a positive mixing quality, which were in good agreement with the numerical data. It could be drawn that it is a structure with superior mixing effect if the intake pipe is tilted at an angle of 35 degrees and horizontal arranged.
引文
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[2]沈俊兰,王春芳,陈安石,等.脉冲式气流混合机的设计与应用[J].浙江化工,2011,42(1):21-22.SHEN J L,WANG C F,CHEN A S,et al.Design and application of impulse type air flow mixer[J].Zhejiang Chemical Industry,2011,42(1):21-22.
[3]叶涛.多组分粉体混合过程的理论分析与实验研究[D].武汉:武汉理工大学,2009.YE T.Theoretical analysis and experimental study on mixing process of multi component powders[D].Wuhan:Wuhan University of Technology,2009.
[4]ZHANG Y,ZHONG W,JIN B,et al.Mixing and segregation behavior in a spout-fluid bed:effect of the particle density[J].Industrial and Engineering Chemistry Research,2013,52(15):5489-5497.
[5]CHEN H Z,GUO Z K.Characteristics of mixing/segregation in a bubbling/slugging fluidized bed with binary mixtures[J].Advanced Materials Research,2012,396(4):322-325.
[6]张俊强,纪律,李斌,等.单孔射流流化床内颗粒混合特性的数值模拟[J].化工学报,2017,68(3):879-888.ZHANG J Q,JI L,LI B,et al.Numerical simulation of particle mixing in single jet fluidized bed[J].CIESC Journal,2017,68(3):879-888.
[7]张俊强,纪律,李斌,等.双孔射流流化床内颗粒混合特性的离散单元法数值模拟[J].动力工程学报,2017,37(2):91-97.ZHANG J Q,JI L,LI B,et al.DEM simulation on mixing characteristics of particles in double jets fluidized bed[J].Journal of Chinese Society of Power Engineering,2017,37(2):91-97.
[8]CHAIKITTISILP W,TAENUMTRAKUL T,BOONSUWAN P,et al.Analysis of solid particle mixing in inclined fluidized beds using DEM simulation[J].Chemical Engineering Journal,2006,122(1):21-29.
[9]LUO K,WU F,YANG S,et al.CFD–DEM study of mixing and dispersion behaviors of solid phase in a bubbling fluidized bed[J].Powder Technology,2015,274(4):482-493.
[10]JIN B,YONG Z,ZHONG W,et al.Experimental study of the effect of particle density on mixing behavior in a spout-fluid bed[J].Industrial and Engineering Chemistry Research,2009,48(22):10055-10064.
[11]LIU D,XIAO S,CHEN X,et al.Investigation of solid mixing mechanisms in a bubbling fluidized bed using a DEM-CFD approach[J].Asia-Pacific Journal of Chemical Engineering,2012,7(2):237-244.
[12]李斌,宋小龙.循环流化床内颗粒混合特性的数值模拟[J].动力工程学报,2013,33(10):759-764.LI B,SONG X L.Numerical simulation on mixing characteristics of particles in circulating fluidized bed[J].Journal of Chinese Society of Power Engineering,2013,33(10):759-764.
[13]LUO K,FAN W,YANG S,et al.Numerical investigation of the time-related properties of solid phase in a 3-D spout-fluid bed[J].Chemical Engineering Journal,2015,267(5):207-220.
[14]李斌,于洋,马梦祥,等.三维喷动床内异径干湿颗粒混合特性数值模拟[J].化工学报,2017,68(12):4545-4555.LI B,YU Y,MA M X,et al.Numerical simulation of mixing different sized wet and dry particles in three-dimensional spouted bed[J].CIESC Journal,2017,68(12):4545-4555.
[15]WU H,GUI N,YANG X,et al.Numerical simulation of heat transfer in packed pebble beds:CFD-DEM coupled with particle thermal radiation[J].International Journal of Heat and Mass Transfer,2017,110(5):393-405.
[16]LI Y,JI W.Acceleration of coupled granular flow and fluid flow simulations in pebble bed energy systems[J].Nuclear Engineering and Design,2013,258(2):275-283.
[17]BLAIS B,Bertrand O,FRADETTE L,et al.CFD-DEM simulations of early turbulent solid-liquid mixing:prediction of suspension curve and just-suspended speed[J].Chemical Engineering Research and Design,2017,123(7):388-406.
[18]李斌,纪律.流化床炉内颗粒混合的离散单元法数值模拟[J].中国电机工程学报,2012,32(20):42-48.LI B,JI L.Numerical simulation of particle mixing in circulating fluidized bed with discrete element method[J].Proceedings of the CSEE,2012,32(20):42-48.
[19]ZHANG Y,JIN B,ZHONG W,et al.DEM simulation of particle mixing in flat-bottom spout-fluid bed[J].Chemical Engineering Research and Design,2010,88(5):757-771.
[20]胡国明.颗粒系统的离散元素法分析仿真[M].武汉:武汉理工大学出版社,2010:301.HU G M.Analysis and simulation of particle system by discrete element method[M].Wuhan:Wuhan University of Technology Press,2010:301.
[21]LACEY P M C.Developments in the theory of particle mixing[J].Journal of Chemical Technology and Biotechnology,2010,4(5):257-268.
[22]FENG Y Q,XU B H,ZHANG S J,et al.Discrete particle simulation of gas fluidization of particle mixtures[J].AICh E Journal,2004,50(8):1713-1728.
[23]ERGUN S,ORNING A A.Fluid flow through randomly packed columns and fluidized beds[J].Industrial and Engineering Chemistry,1949,41(6):1179-1184.