Improvement in the Circulating Efficiency By Radial Flow Impellers in Vacuum Pans Operated in Horizontal Cascade Crystallizers

摘要

For decades the impellers in vacuum pans have been installed within the central draft tube of the calandria. The axial flow impellers - so called "Kaplan type" - are nowadays the standard impellers in vacuum pans. In comparison with this standard type, the performance of radial flow impellers installed below the heating chambers of two vacuum pans at Goslawice Sugar Factory was investigated during the 2004 campaign. The two vacuum pans were operated continuously as the 3rd as well as the 2nd stage of B (raw-sugar) and C (afterproduct) cascade crystallizers. The investigations included running each impeller at three different values of the rotational speed and measuring the power consumption of the agitator drive while determining the heat transfer coefficient in the respective pan. In a similar manner, the performance of standard Kaplan Impellers installed in the central tubes of the heating chambers of both pans was investigated. rnIn relation to Kaplan impellers, the radial flow impellers made it possible to attain markedly higher heat transfer coefficients at lower values of the rotational speed. By comparing their power consumption at similar levels of the heat-transfer intensity, a comparison between the two impeller types with respect to the circulating efficiency was also made. In B3 vacuum pan, the circulating efficiency of the radial flow impeller was higher than that of the Kaplan impeller by a factor of 2.8. In C2 vacuum pan, the corresponding factor was 2.6.