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Mixing
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
The degree of mixing was analyzed using three different agitator blades: a blade type with 30 and 15 degrees and a rotating plate without blade. As seen in Figure 5.8.10, the degree of mixing was different, when the agitator blade type varied. The agitator blade with 30 degrees indicates the highest value of the terminal degree of mixing, followed by the values of the agitator blade type with 15 degrees and the disk. The disk type indicates the lowest value of the terminal degree of mixing, implying that the mixing progresses with the movement of the agitator blade and vertically upward movement of particles caused by the rotation of the inclined blade. In this way, the DEM simulation can be used to analyze the mixing condition and behavior of particle segregation due to size, density and shape. In addition, it is possible to design the mixing equipment. The simulation can be a promising tool to numerically analyze the mixing process.
Particle Characterization and Dynamics
Published in Wen-Ching Yang, Handbook of Fluidization and Fluid-Particle Systems, 2003
particle segregation. It is not unusual to have one part of the fluidized bed reactor operated in mixing mode while the other part of the same reactor is in segregation mode. It is important to point out that the segregation pattern or the particle distribution profile in the bed is set up by the dynamic equilibrium between the two competing mechanisms of solids mixing and particle segregation. Particle segregation can usually be prevented by operating a fluidized bed at a sufficiently high fluidizing velocity. On the other hand, a bed with particle size ratio between the largest and the smallest as small as 3 can be made to segregate by operating at a small enough fluidizing velocity (Wen and Yu, 1966b).
Frictional Mechanics of Granular Materials
Published in Y. Kishino, Powders and Grains 2001, 2020
Jean-Christophe Géminard, Wolfgang Losert, Jerry P. Gollub
We have analyzed in the preceding sections the frictional properties of roughly monodisperse granular materials. We extend this study to the case of binary mixtures. It is well known that granular mixtures submitted to shear tend to segregate. The physical mechanisms and patterns of segregation of particles by size, shape, or weight have been investigated in many experimental and theoretical studies. A number of mechanisms for particle segregation have been found, but models with broad predictive powers have not yet been developed. Most experiments have focussed on the steady segregated state, and, to our knowledge, measurements of the frictional properties of the initial mixed state have not yet been performed.
Sintering anisotropy of binder jetted 316L stainless steel: part I – sintering anisotropy
Published in Powder Metallurgy, 2022
Alberto Cabo Rios, Eduard Hryha, Eugene Olevsky, Peter Harlin
The anisotropic factors evolution during sintering is typically related to a non-homogeneous initial green porous structure, produced during the printing process [14]. Recoating process may produce particle segregation and heterogeneities. Besides, the binder deposition process may produce periodical voids during the interaction with the powder bed. Likewise, layered binder regions could be produced if binder cannot fully infiltrate within the powder bed. In Figure 5(a,b), the monotonous evolution of the factor from 1000°C to 1370°C and from 1 to 1.15 could be related with similar non-homogeneities along the X and Z direction, which are eliminated at low temperatures. However, results showed a larger final value than which indicate lower shrinkages along the Y direction (∼0.4%). This could be related to the anisotropic powder particles/binder distribution and particle contact number along the X and Y directions, caused by binder droplets being deposited along the X direction. However, the small difference between the shrinkages along X and Y direction and the lack of consistency with results from literature makes it difficult to reach a conclusion on this question. A comprehensive and more detailed discussion regarding the microstructural evolution during sintering is published in the companion article [17].
Inclined-flow segregation characteristics of multi size particles in a moving granular bed
Published in Particulate Science and Technology, 2023
Nan Qiu, Lige Tong, Qianwei Ma, Hongsheng Ding, Shaowu Yin, Chuanping Liu, Li Wang, Yulong Ding
In this paper, the flow segregation behavior of mixed particles with equal mass and multiple particle sizes on rough inclined surface is studied. The following conclusions are drawn by discussing the influencing factors such as inclined length and continuous degree of particle size distribution and studying the flow morphology of particles:Under the same replacement velocity, the displacement rate of granular beds with different incline flowing lengths is about 60% when they reach a steady state. In the process of moving bed operation, the formation of steady layered structure of granular bed can be realized by monitoring and controlling particle replacement rate.The inclined multi size granular bed has a critical incline length of particle segregation. When the incline length is less than this length, the degree of particle segregation increases with the increase of the incline length; when the incline length is greater than this length, the degree of segregation no longer increases. In the inclined granular bed, the incline length only needs to reach the critical length to achieve the best layering effect. For the ternary granular bed in this study, the critical incline length is 600 mm.Two mechanisms in the process of multi size particle segregation are proposed, one is the segregation mechanism based on the difference in particle diameter, and the other is the unidirectional segregation of the surface layer. When the two mechanisms work at the same time, the particles with the largest and smallest particle sizes have the best separation effect. The particle size distribution of the multi size particles is close to a continuous distribution, which will adversely affect the segregation of the granular bed.The segregation effect of the vertical zone is better than that of the inclined zone in granular bed. The particle diameter distribution of the vertical zone is close to that of the inlet particles. By changing the proportion of inlet particle, real-time control of the thickness of each particle diameter layer in the vertical zone can be achieved.