Characterisation of the Bipolar Electrostatic Charging of Powders
Characterisation of the Bipolar Electrostatic Charging of Powders
Electrostatic charging theories and charging in powder handling operations is reviewed. The causes of bipolar powder charging and its influence on powder behaviour are considered. Various techniques are used to measure bipolar charging of powders. A microprobe, differential charge/mass meter, but the main technique is the electrostatic deflection in an electrostatic field.
The charge distribution of powders after various charging mechanisms is examined, and an explanation of how charge is distributed and how this distribution is affected by powder load is given.
The charge distributions of powders handled with the same techniques show the same basic charge pattern. The degree of magnitude of charge differs, but the basic charge distribution is the same with all powders charged by the same technique.
When transport or handling results in mainly particle-particle contact, the charging is bipolar, with logarithmically decaying presence of charged particles. When the handling is mainly particle-equipment wall, the charge distribution is Gaussian, and mainly unipolar.
The influence of particle size, surface area, morphology and chemistry has also been investigated, but the differences between oppositely charged fractions are very small. If differently charged powder fractions are recharged, the powder is seen to have the same charge pattern as before. Particle properties and chemistry therefore only determine the polarity of charge and charge distribution to very small degrees.
This work indicates that the shape of charge distribution is dependent on the handling of the powder and not powder properties. Powder properties do however determine the magnitude and polarity of charging.
University of Southampton
Ose, Sivert
6b81866b-3481-42f4-8428-2551b110df27
2001
Ose, Sivert
6b81866b-3481-42f4-8428-2551b110df27
Ose, Sivert
(2001)
Characterisation of the Bipolar Electrostatic Charging of Powders.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Electrostatic charging theories and charging in powder handling operations is reviewed. The causes of bipolar powder charging and its influence on powder behaviour are considered. Various techniques are used to measure bipolar charging of powders. A microprobe, differential charge/mass meter, but the main technique is the electrostatic deflection in an electrostatic field.
The charge distribution of powders after various charging mechanisms is examined, and an explanation of how charge is distributed and how this distribution is affected by powder load is given.
The charge distributions of powders handled with the same techniques show the same basic charge pattern. The degree of magnitude of charge differs, but the basic charge distribution is the same with all powders charged by the same technique.
When transport or handling results in mainly particle-particle contact, the charging is bipolar, with logarithmically decaying presence of charged particles. When the handling is mainly particle-equipment wall, the charge distribution is Gaussian, and mainly unipolar.
The influence of particle size, surface area, morphology and chemistry has also been investigated, but the differences between oppositely charged fractions are very small. If differently charged powder fractions are recharged, the powder is seen to have the same charge pattern as before. Particle properties and chemistry therefore only determine the polarity of charge and charge distribution to very small degrees.
This work indicates that the shape of charge distribution is dependent on the handling of the powder and not powder properties. Powder properties do however determine the magnitude and polarity of charging.
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Published date: 2001
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Local EPrints ID: 464468
URI: http://eprints.soton.ac.uk/id/eprint/464468
PURE UUID: 09d619e3-8ac6-4d81-9e57-e077e962db3c
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Date deposited: 04 Jul 2022 23:39
Last modified: 16 Mar 2024 19:32
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Author:
Sivert Ose
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