Suppression of cone discharges in a powder silo using a grounded metal rod |
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| Authors: | M. Yamaguma K.S. Choi T. Mogami |
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| Affiliation: | 1. National Institute of Occupational Safety and Health, Electrical Safety Research Group, Umezono 1-4-6, Kiyose, Tokyo 204-0024, Japan;2. Kasuga Denki, Inc., Minami Kamata 2-4-19, Ota-ku, Tokyo 144-0035, Japan;1. Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409, United States;2. Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415, United States;1. HAE Research and Development Center, LG Electronics, Seoul 153-802, Republic of Korea;2. School of Mechanical Engineering, Yonsei University, Seoul 120-749, Republic of Korea;3. Yonsei Center for Clean Technology, Yonsei University, Seoul 120-749, Republic of Korea;1. School of Chemical Engineering, The University of Adelaide, SA 5005, Australia;2. Ian Wark Research Institute, University of South Australia, SA 5095, Australia;3. Laboratorio de Materiales Avanzados, Departamento de Química Inorgánica, Universidad de Alicante, Apartado 99, E-03080, Spain;4. Sansom Institute, University of South Australia, SA 5001, Australia;5. School of Agriculture, Food and Wine, The University of Adelaide, SA 5005, Australia;6. School of Science, Loughborough University, Leicestershire LE11 3TU, UK;1. Department of Chemical Engineering, National Institute of Technology-Calicut, Kozhikode, Kerala, 673601 India;2. Department of Biosciences and Bioengineering, Indian Institute of Technology-Guwahati, Guwahati, Assam, 781039, India |
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| Abstract: | While filling a large silo with coarse nonconductive powders, strong electrostatic sparks known as a cone discharge, which can become sufficiently energized to ignite a flammable dust cloud, often occur on the surface of a powder heap. In an attempt to mitigate or eliminate a cone discharge, a long metal rod with a pointed tip or a flat tip was vertically installed in the center of an experimental silo (1.5 m in diameter, 2 m in effective height) with the objective that the static charge might be released by the corona discharges or the surface potential of the powder heap reduced by the electric field reducing effect. The experimental results are summarized as follows:(1) No cone discharges were observed while the silo was being filled with polypropylene pellets when either a pointed tip or a flat-tip rod was installed so that its lower end was located 10 cm above or 30 cm below the heap surface level. A corona discharge that occurred on the pointed tip was shown to be effective to some extent in reducing the charge of the powder heap.(2) Brush discharges were observed near the metal rod and its support. However, we assume that the maximum energy was not high enough to ignite a dust cloud with minimum ignition energy greater than 3 mJ. |
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