Journal of the Society of Powder Technology, Japan

Classification Mechanism of an Air Classifier Using Centrifugal Force (Part I)

Calculations of Particle Trajectories

Yuichi SATO, Yukiyoshi YAMADA

1987 Volume 24 Issue 11 Pages 693-699
Published: November 10, 1987
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.24.693

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Trajectories of particles thrown into a forced vortex type centrifugal air classifier are presented to clarify the causes of classification error. The cascade flow is calculated with a finite element method applied to the potential equation. The analysis of particle trajectories rests on the assumption of low volumetric solid/gas ratios so that the flow field is not appreciably disturbed. The obtained results show that a trajectory is affected significantly by the position of the collisions with the blade-walls. A particle thrown in a classifier with a narrow blade interval generally moves outside of a cascade and travels a very long distance before it is classified.

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A Coagulation Method for the Preparation of Pellet Particles from Polymer Latex

Hideo YASUI, Wataru OKADA, Yasuhiro MIKI, Hisashi MORIKAWA

1987 Volume 24 Issue 11 Pages 700-706
Published: November 10, 1987
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.24.700

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A new coagulation method which consists of two stages the generation of seed particles and the growth of particles, was developed for the preparation of pellet-like particles from polymer latex.
In this report, first the mechanism of this coagulation was studied through an examination of the coagulating velocity during each stage. Then the pellet-like particles were characterized by a SEM observation of the inside of a particle and a measurement of particle properties.
As a result, experimental equations on the amount of generated seed particles and rate of growth of the particles were obtained. The phenomena in which the latex particles inside the coagulated particle are packed closely by drying and are fused homogeneously by sintering, was confirmed.

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Effects of the Particle Size on the Circulating Time in a Powder Mixer

Segregation Due to the Size-Difference and Circulating Time Ratio

Munetake SATOH, Yuichiro DEGUCHI, Hajime TSUMURA, Kei MIYANAMI

1987 Volume 24 Issue 11 Pages 707-712
Published: November 10, 1987
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.24.707

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To investigate the characteristics of the flow and the mixing and/or demixing of particles in the powder mixer, the relationship between the circulating time and the particle size for the cases of various combinations of binary components has been measured by using an optical method. A mechanical agitation type of mixer with a vibrating vessel has been employed, and six pairs of optical fiber made of plastics were inserted in the particle bed as a detector of the tracer concentration. The particle bed in the vessel during the mixing operation showed a fluid-like behavior in the limited region of the operating conditions, both for the impeller speed and frequency of vessel vibration. The larger particles in the smaller particle bed showed a smaller circulating time. On the other hand, the circulating time for the smaller particles in the larger particle bed showed the opposite tendency. A new parameter Θ defined as the ratio of the circulating time θ(N_R) for the tracer particles at impeller speed N_R and θ_O(N_R) for the bulk particles at the same operating conditions has been introduced as an index of the segregating or demixing tendencies due to the difference in the particle size. The effects of the size ratio of the tracer and bulk particles, d_PB/d_PA and the size of bulk particles bed on the parameter Θ have been examined.

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Measurements of the Wall Friction Coefficients of Powders by an Inclined Plate Method

Effect of the Weight of a Cell

Rikuo TAKAI, Kazuya INUI, Hiroshi MURATA, Ryuuichi AOKI

1987 Volume 24 Issue 11 Pages 713-719
Published: November 10, 1987
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.24.713

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To determine the wall friction coefficients of powders, the traditonal inclined plate method is simple, and its powder bed works actively in the test. However, in this method, the weight of the test cell must be negligibly small. In this report, we proposed a new method and a test apparatus which had two inclined plates with the same base angles. During measurement, the weight of the test cell could be cancelled by the dummy weight which was connected with the test cell by a string and placed on one of the plates. The wall friction coefficients of Sohma sand, wheat flour and corn starch, which were determined by the traditional method (the single-cell method) using heavier cells, decreased with the increasing weight of test cell. On the other hand, the wall friction coefficients of those powders determined by the new method (counter balance method) show the constant values for each powder.

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[title in Japanese]

Takashi MORIYAMA

1987 Volume 24 Issue 11 Pages 733-735
Published: November 10, 1987
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.24.733

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[title in Japanese]

Zennosuke TANAKA

1987 Volume 24 Issue 11 Pages 736-739
Published: November 10, 1987
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.24.736

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