The effect of an improved hopper and of the materials of the hopper wall on the bridge in coal bunkers.

概要

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Experiments were carried out on the discharge of wet coals from experimental bunkers with a capacity of about 4m3. These bunkers were reduced to a scale of one-sixth the actual size of those in a coal thermal power station. Consequently, the coal bunker must be completely designed as a type of mass flow.An improved hopper was proposed in order to reduce the critical size of hopper outlet. The improved hopper was a regular pyramidal hopper joined to a conical hopper, and a prismatic insert was installed between each opposite wall of the pyramidal hopper.A method is described for the estimation of the critical size of the bridge in the hoppers at the commencement of flow on the basis of the conditions of the static state of stresses exerted by the bulk solid. The estimated values of the critical outlet size, using the fixed volume shear cell results, were in good agreement with the experimental results of the discharge.The experimental results also indicate that the slope angle of the hopper walls was reasonably determined from both the angle of internal friction and the angle of wall friction according to Jenike's approach. Moreover, remnants of coal that adhered to the bunker walls were strongly affected by the wall materials used, such as steel and ultra high molecular weight polyethylene.
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