Deposition of unipolarly charged particles by their own space charge from laminar flow in a cylindrical tube is investigated both experimentally and theoretically. Experimental deposition efficiencies for fly-ash particles agree well with Wilson's analytical solutions. The distribution of the deposited mass of particles in an axial direction in a brass tube is also well predicted by Wilson's equation. The polarity of charged particles has no effect on the deposition efficiencies. It is also found that the size distributions of deposited particles are almost the same for any axial position in the tube. This experimental fact shows that the deposition efficiencies are independent of the particle size, which is also predicted by Wilson's equation in so far as the field charging is predominant. Effects of the particle inertia, Brownian diffusion and image force are also discussed, showing that the effects of these physical phenomena on the deposition of charged particles are negligible in the experimental range.

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It in known that the method of feeding powder into split cell affects the adhesion forces of powder beds, especially in fine particle powders. But the effect of the agglomeration phenomenon on the adhesion forces has not been investigated systematically.
The adhesion forces of powder beds have been measured by a split cell type tensile strength meter. The powder beds consisted of several size agglomerations which were prepared with sieves having a larger opening size than the primary particle diameter. The void fractions of powder beds were prepared with compression. Kanto loam powder, limestone powder and fused almina powder were used as samples and their primary diameter are several μm. It is found from these measurements that the adhesion forces of powder beds are decreased by the effect of the agglomeration phenomenon, especially in high voidage, and the adhesion forces have constant values when the void fractions of the powder bed is equal to the void fractions of the agglomerations in the powder bed. The mechanisms of the effect of agglomeration phenomenon are tentatively analysed.

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A data reduction method is presented for instrumental measurement of aerosol particle size distribution by an Andersen sampler with wall loss or bounce-off, and an electrical aerosol size analyzer. The method is based on Twomey's non-linear iteration algorithm, and estimation of aerosol particle size distribution is made without assuming its form. Overfitting for size distribution data involving random noise is elimininated by using an χ²-test for convergence criterion of iteration.
It is concluded that this method is more effective for the estimation of aerosol particle size distribution than the conventional method, if the response function of the instrument is known.

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The movement of particles and a change of internal stress in the beds of an atomized copper powder wat followed under a random vibration (6-180Hz) with a small amplitude and under a vibrationless state on a bibration proof stage by visual inspection and by measuring the static wall pressure.
The internal stress in standing beds decreases with standing time. Two types of particle movements were observed in the deposition beds: the one was massive displacement, the so called settling phenomenon, and the other was random displacements of particles into the nearest void space. The latter was always observed the powders of 67.5-125.5μm in mean particle diameter.
The flow-patterns in the discharge of the powder from a cylindrical tets bin changed with standing time:
1. mass-flow immediately after the filling; 2. plug-flow after longer standing time (more than 30 minetes); 3. trasient type at medium standing time.
A connection between the variation of flow-pattern and the change in the internal stress due to random displacement of individual particles is discussed.

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The shearing process diagram and normal stress distribution in the vicinity of the shearing area of several kinds of fine powders have been measured by means of a direct shear test. A tensile test has been also carried out and the tensile strength of the powders can be described in terms of an initial void fraction in the powders phase. Stick-slip friction characteristics have been found to depend on the solids powders, and the stick-slip phenomenon is found to increase more appreciably with the applied normal stress on the fine powders. When the powders have a small internal friction factor which is computed on the basis of the actual normal stress measured, the powders show smaller values of cohesion and tensile strength and resulting better flowability. The flowability of the fine powders has been systematically evaluated in terms of tensile strength, cohesion, internal friction factor and their combination.

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The elutriation of dust from a batch fluidized bed consisting of fine and coarse particles was investigated. The materials used were dust (JIS Z-8901 (1974), No. 11) for fine particles and sand and glass beads for coarse ones.
The elutriation rate coefficient k was defined as V=kw₀exp(-kt), where V=elutriation rate of fine particles, w₀=initial holdup of fines and t=time.
The experiment was to determine the effects of the experimental conditions and materials on the elutriation rate coefficient k.
The results were as follows;
(1) k was not affected by the initial holdup of dust and the column length.
(2) k was affected by the holdup of the coarse particles and the humidity in the air as the fluidizing medium.
(3) k was proportional to u^2.5 (u=superficial air velocity).
(4) k was affected by the kinds of coarse particles with humid air and was not affected by them with dry air.
(5) The estimated value of k, which was calculated from the reported equation for fine particles above 100μm in diameter, coincided roughly with the one used in the experiment.
(6) The generated dusts were throughly deagglomerated, and their size distribution were independent of time.

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In order to estimate and control the levels of indoor pollutant's concentration, the mechanism of the concentration formation with large particles as well as small ones should be made clear. In this experimental study, we tried to clarify the dispersion range of large particles generated by dropping a weight onto a cushion placed on the floor.
The horizontal and vertical distributions of settled particles were microscopically examined, and the distance of dispersed particles larger than 10μm in size was found to be only 1-1.5m from the source with out air mouement or ventiration.

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A fabric filter is a high efficiency dust collector. However, large penetration is observed during the use of a virgin fabric and at the beginning of the filtration cycle after the cleaning operation.
In this paper, the characteristics of penetration of felt fabrics, i. e. changes in diameter and concentration of dust penetrating the fabric, are discussed based on the data obtained using the isokinetic sampling technique with a small probe and a particle counter with light scattering. The following conclusions are obtained:
1) Penetrations become larger as dust particle size and the weight of felt fabrics decrease.
2) Instantaneous penetrations for various particle sizes decrease almost exponentially with dust load. The decrease rates depend not on particle diameter, but on the kind of fabrics.
3) Air humidity does not have much effect on particle penetration.

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Separation performance of a cyclone was tested with airborne kanto loam, dust which is the powder for industrial testing No. 11, JIS Z 8941, dispersed by an ejector and an orifice. The electric charge quantity of those dusts were measured by the Faraday cage method. The results of this experiment are as follows: Airborne dust is well dispersed by both methods and in both cases it shows similar tendency of dispersion. But an ejector needs only about one-fifth of the air flow rate which an orifice needs.
When using dusts dispersed by an orifice, the observed collection efficiencies agree with the estimates fairly well, which are calculated from the size disributions of dusts measured by a cascade impactor. But, under the condition of 45-55% air humidity, the observed collection efficiencies for the dusts dispersed by the ejector are much larger than the estimates.
The dust kanto loam is charged minus by the dispersing device which is made from brass. The charge quantities of the dust dispersed by the ejector are much larger than that by the orifice and those values are more than 10^-6C/g. The more airborne dust disperses the larger the quantity is.
The larger the charge quantity of dust is, the more the observed collection efficiency of the cyclone differs from the estimate.

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