A new tensile tester has been developed for the purpose of studying the tensile fracture behavior of a powder bed consolidated with a low normal stress of from 1 to 30kPa. Using this tester, the tensile fracture behavior was examined for three kinds of powder. The tensile strength of the powder bed was calculated by two methods. One is an ordinary method, i. e., the tensile strength is calculated from the maximum tensile force of the powder bed. The other is our method in which the reduced tensile strength is calculated from the fracture energy of the powder bed. As a result of comparison between them, we showed that the latter is more reliable than the former.

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To investigate the pneumatic conveying characteristics at high solid-gas loading ratios and high conveying pressures, the floating velocity of a polyester chip was measured at a pressure not exceeding 300kPa_(gage). Pneumatic conveying experiments were carried out on a nearly practical scale within solid-gas loading ratios <45 and conveying pressures <214kPa_(gage).
The floating velocity w_f decreases gradually with the increase of pressure in the pipe, and at 300kPa_(gage) falls to 50% of the value at atmospheric pressure. Pressure drop ratio α is proportional to the factor μ/Fr*Fr_wf, which consists of loading ratio μ, Froude number Fr* and Fr_wf, up to μ=40 as shown by Owen. The relationship between Froude number Fr* and the friction factor λ_k is nearly represented by the equation obtained by Morikawa et al. independent of the solid-gas loading ratio and pressure in the pipe. The solid-gas loading ratio μ_c at the choking limit increases exponentially to 45 independent of pipe inner diameter.

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At present, dry powders are mainly classified using a vortex centrifge or sieving equipment, in which the lowest 50% cut size is still greater than one micrometer. Inpactor-type classifiers are capable of operating in the submicron range, but have low throughput and high energy consumption.
Our new free vortex cyclones are capable of excellent sharp classification of dry powders in submicron cut sizes, especially by the use of a 5% to 15% blow-down flow rate from the dust collector chamber. A specified cyclone has been experimentally studied under various operating conditions using several kinds of test powders.

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Cluster formation of iron ore pellets causes serious trouble in the operation of direct reduction furnaces. In this study, the clustering behavior of iron ore pellets in a shaft furnace was considered, and the functions of the burden feeder which prevents cluster formation were experimentally analyzed. Namely, the gravity flow of ore pellets in a shaft furnace was visually observed by using a two dimensional model furnace. The powder pressure was also measured by using a three dimensional model furnace. Then, it was suggested that insertion of a grizzly type burden feeder would be effective to avoid cluster formation by reducing the plug flow region and to avoid cluster strengthening by decreasing the powder pressure.

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