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

doi:10.1016/j.cjche.2019.12.002

中国化学工程学报 ›› 2020, Vol. 28 ›› Issue (3): 777-784.DOI: 10.1016/j.cjche.2019.12.002

• Separation Science and Engineering • 上一篇下一篇

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 Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China;
2 Chengde Petroleum College, Chengde 067000, China

收稿日期:2019-08-27 修回日期:2019-11-26 出版日期:2020-03-28 发布日期:2020-06-11
通讯作者: Yang Zhang
作者简介:Lele Feng,E-mail addresses:feng-ll15@mails.tsinghua.edu.cn;Hai Zhang,E-mail addresses:haizhang@mail.tsinghua.edu.cn;Lilin Hu,E-mail addresses:hll17@mails.tsinghua.edu.cn;Yuxin Wu,E-mail addresses:wuyx09@mail.tsinghua.edu.cn;Hairui Yang,E-mail addresses:yhr@mail.tsinghua.edu.cn
基金资助:
The financial support from the National Key Technologies R&D Program of China (2018YFF0216002) is highly appreciated.

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 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
Supported by:
The financial support from the National Key Technologies R&D Program of China (2018YFF0216002) is highly appreciated.

摘要/Abstract

摘要： 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.

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

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

Lele Feng, Hai Zhang, Lilin Hu, Yang Zhang, Yuxin Wu, Yuzhao Wang, Hairui Yang. Classification performance of model coal mill classifiers with swirling and non-swirling inlets[J]. 中国化学工程学报, 2020, 28(3): 777-784.

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

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

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