Tribo-charging of binary mixtures composed of coarse and fine particles in gas

Wang, H., Fotovat, F., Bi, X. T., & Grace, J. R. (2019). Tribo-charging of binary mixtures composed of coarse and fine particles in gas–solid pipe flow. Particuology, 43, 101-109. https://doi.org/10.1016/j.partic.2018.07.001

Tribo-charging of binary mixtures composed of coarse and fine particles in gas–solid pipe flow

Haifeng Wang ^a, Farzam Fotovat ^b *, Xiaotao T. Bi ^c, John R. Grace ^c

a Department of Chemical Engineering, China University of Mining and Technology, Xuzhou 221166, China
b Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Avenue, P.O. Box 11365-9465, Tehran, Iran
c Fluidization Research Centre, Department of Chemical and Biological Engineering, University of British Columbia, Vancouver V6T 1Z3, Canada

10.1016/j.partic.2018.07.001

Volume 43, April 2019, Pages 101-109

Received 28 October 2017, Revised 9 May 2018, Accepted 2 July 2018, Available online 4 December 2018, Version of Record 19 February 2019.

E-mail: fotovat@sharif.edu

Highlights

• The effect of adding fines on tribo-charging of coarse glass beads was investigated.

• The mixture composition with the highest amount of charge was determined.

• The effect of the total particle surface area on particle mixture electrification was explored.

• Electrification of particle mixtures was compared with that of fine and coarse materials alone.

• A model was proposed to predict charge density of mixtures as a function of their composition.

Abstract

Experiments were conducted to investigate the effect of adding fines on the tribo-charging of coarse glass beads. Four types of fines, i.e., copper, stainless steel, uncoated and silver-coated fine glass beads, mixed with 240–830 μm glass beads were conveyed by air through a stainless-steel spiral pipe acting as a tribo-charger. Regardless of the type or electrical conductivity of the fine particles tested, adding small amounts of fines (up to 10 wt%) to coarse glass beads resulted in a sharp increase in the mass and surface charge densities of the particles. In general, the profiles of the mass and surface charge densities of the fine–coarse particle mixtures as a function of the mixture composition were determined by the relative magnitude of contact potential differences and the total surface areas of all the components. The dominant particle tribo-electrification mechanism switched from coarse particle–wall contacts to fine particle–wall contacts when the fines weight percentage in the mixture exceeded 10%. A model was developed to predict the mass charge density of binary mixtures as a function of the mixture composition.

Graphical abstract

Keywords

Tribo-charging; Electrostatics; Fine particles; Binary mixture; Gas–solid flow

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