Affiliation: | Nisshin Flour Milling Co., Ltd., 5 - 3 - 1 Tsurugaoka Ohi, Iruma, Saitama, 354 Japan Nisshin Engineering Co., Ltd., 19 - 12 Koamicho Nihonbashi, Chuoku, Tokyo, 103 Japan Society of Powder Technology, Shibunkaku-kaikan 2 - 7, Tanaka-Sekidencho, Sakyoku, Kyoto, 606 Japan |
Abstract: | To classify fine powders with particles smaller than 1 μm in diameter, air classifier design must take three factors into consideration: dispersion of feed powders, air flow uniformity in the classification zone, and recovery of fine particles adhering to the coarse fraction. The effects on the classification performance of a centrifugal air classifier using a dispersion nozzle for particle dispersion and a circulation mechanism using channel air jets for the recovery of fine particles are discussed. By using a dispersion nozzle, the classification sharpness index was improved below 0.8 (Dp/Dp50) and the fine fraction yield was improved by 64% without changing size distribution. The circulation mechanism using channel air improved classification performance by 58% of the classification sharpness index and 65% of the fine fraction yield, although the particle size distribution of the fine fraction became 0.1 μm coarser than that without channel air. |