PURPOSE:To eliminate the uneven presence of powder and to suppress the decrease in separating performance by providing dummies of ducts for transporting coarse powder between the outside and inside cylinders of a coarse powder separator. CONSTITUTION:A dummy duct 8 having the same shape as the shape of a duct 6 for transporting coarse powder is provided between an outside cylinder 3 and an inside cylinder 4 of a separator A. A piece of such duct is provided in approximately the same position as the duct 6 (the position symmetrical with respect to the central shaft of the separator). A pair of dummy ducts 8', 8' are provided between the inlet of the separator and the inlet of the cylinder 4 with deviation of a phase by + or -90 deg. from the position of the duct 6. Then if a ground raw material such as coal or cement is fed by pneumatic transport through a duct 2 to the separator A, a solid-air ratio distribution on the rear flow side of each dummy is made uniform.
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