SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2020, Vol. 28 ›› Issue (3): 777-784.doi: 10.1016/j.cjche.2019.12.002

• Separation Science and Engineering • Previous Articles     Next Articles

Classification performance of model coal mill classifiers with swirling and non-swirling inlets

Lele Feng1, Hai Zhang1, Lilin Hu1, Yang Zhang1, Yuxin Wu1, Yuzhao Wang2, Hairui Yang1   

  1. 1 Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China;
    2 Chengde Petroleum College, Chengde 067000, China
  • Received:2019-08-27 Revised:2019-11-26 Online:2020-03-28 Published:2020-06-11
  • Contact: Yang Zhang E-mail:yang-zhang@tsinghua.edu.cn
  • Supported by:
    The financial support from the National Key Technologies R&D Program of China (2018YFF0216002) is highly appreciated.

Abstract: The classification performance of model coal mill classifiers with different bottom incoming flow inlets was experimentally and numerically studied. The flow field adjacent to two neighboring impeller blades was measured using the particle image velocimetry technique. The results showed that the flow field adjacent to two neighboring blades with the swirling inlet was significantly different from that with the non-swirling inlet. With the swirling inlet, there was a vortex located between two neighboring blades, while with the nonswirling inlet, the vortex was attached to the blade tip. The vorticity of the vortex with the non-swirling inlet was much lower than that with the swirling inlet. The classifier with the non-swirling inlet demonstrated a larger cut size than that with the swirling inlet when the impeller was stationary (~0 r·min-1). As the impeller rotational speed increased, the cut size of the cases with non-swirling and swirling inlets both decreased, and the one with the non-swirling inlet decreased more dramatically. The values of the cut size of the two classifiers were close to each other at a high impeller rotational speed (≥120 r·min-1). The overall separation efficiency of the classifier with the non-swirling inlet was lower than that with the swirling inlet, and monotonically increased as the impeller rotational speed increased. With the swirling inlet, the overall separation efficiency first increased with the impeller rotational speed and then decreased when the rotational speed was above 120 r·min-1, and the variation trend of the separation efficiency was more moderate. As the initial particle concentration increased, the cut sizes of both swirling and non-swirling inlet cases decreased first and then barely changed. At a low initial particle concentration (<0.04 kg·m-3), the classifier with the swirling inlet had a larger cut size than that with the non-swirling inlet.

Key words: Coal mill classifier, Cut size, Non-swirling inlet, Particle image velocimetry, Impeller rotational speed