Reentrainment of fine particles of fly-ash and talc is experimentally studied by utilizing an electrical detection method. Micron order particles are packed in a cylindrical tube so as to make a thin powder layer on the inside wall. Then, the particles are reentrained by pure-air flow or gas-solid two phase flow containing large sand particles (300μm diameter). It is found that the reentrainment efficiency for fly-ash particles gradually increases with air flow velocity, while talc particles are perfectly detached at a certain air velocity. The current generated by the reentrained particles reveals the fact that aggregate particles are entrained intermittently by pure-air flow. On the other hand, fully dispersed or small aggregate particles are entrained continuously by the two-phase flow because the large sand particles in the flow frequently collide with the powder layer. Reentrainment velocity for the latter is reduced to about a quarter in comparison with the pure-air flow. It does not depend on the mass flow ratio of sand particles to air. This fact suggests a new method for efficient removal of a powder layer by adding a small amount of large particles to the air flow.

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The effects of high-temperature grinding on the rates of aragonite to calcite transformation and zinc ferrite formation were examined by using a laboratory-scale high-temperature mechanical mortar. The rates of reaction were compared with the cold dingring method, where reactants were ground beforehand and subsequently heated without any mechanical stressing. Remarkable enhancement was observed during high-temperature grinding between 400 and 450°C for the unitary, and 560 and 640°C for the binary reaction, respectively. The broader X-ray diffraction peak breadths from the products of high-temperature grinding suggest that the method enables not only enhancement of the reaction rate but also production of more active powdery materials.

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Suspensions containing 15% of binapacryl with a particle size range of 1-8μm in 0.2% aqueous Ca-ligunosulfonate were prepared by repeated wet-sedimentation. The concentration of 4, 6-dinitro-2-sec-butylphenol (DNBP, an impurity in technical grade binapacryl) in the dispersion medium was kept below 130ppm because the particle growth of binapacryl was found not to be enhanced by DNBP at concentrations below 130ppm.
The change in the particle size distribution of binapacryl was monitored by Coulter counter TA-II during the preservation of the suspensions at constant temperatures. Binapacryl particle growth occurred above 45°C and temperature accelerated the particle growth. A positive correlation was found between the growth rate of binapacryl particles and the vapor pressure of binapacryl above 50°C. From the microscopic observation of binapacryl particles during the particle growth and the high level of agreement with the experimental particle size distribution and the calculated one based on the hypothesis that binapacryl particles bond at random two by two and grow, it is apparent that the particle growth of binapacryl is attributed to the bonding of particles. No polymorphic change during particle growth was detected by X-ray diffractometry.
From these results, it is concluded that the particle growth of binapacryl in aqueous suspensions is caused by the bonding of binapacryl particles owing to a sintering phenomenon occuring above 45°C.

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Pneumatic Escalator was examined by pulsating air from the standpoint of heat transfer operation of particles. As a result, it was found that the apparent passing velocity of solids through the device in pulsed air flow was similar to that of as constant flow and that the frequency of pulsation did not affect heat transfer as much as expected. However smaller intermittency increased the rate of heat transfer, because the average relative velocity between solids and air was enhanced as compared with the constant air velocity. Thus, similarly to other simultaneous operation of solids-gas contact, Pneumatic Escarator was confirmed to provide better heat transfer results by adding pulsation to heating air.

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It is meaningful for the analysis of rolling resistance for an ordinary wheel running on soft ground to study the cylindrical wheel or the spherical wheel as a fundamental form of the ordinary wheel. The authors have presented several reports for the cylindrical wheel in this magazine. This time, experiments were made for a spherical wheel driven on soft ground to investigate the mean driving torque to the wheel, the slip ratio, and the amount of sinking, etc. caused by the load carried by the wheel axle. The result is reported on together with the measured result for the cylindrical wheel.

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