Electrostatic beneficiation of fly ash in a free-falling system--颗粒学报PARTICUOLOGY

Zhang, L., Hou, J., Bi, X. T., Grace, J. R., Janke, T., & Arato, C. (2012). Electrostatic beneficiation of fly ash in a free-falling system. Particuology, 10(2), 154–160. https://doi.org/10.1016/j.partic.2011.07.006

Electrostatic beneficiation of fly ash in a free-falling system

Lifeng Zhang ^a, Jiangtian Hou ^a, Xiaotao T. Bi ^a *, John R. Grace ^a, Travis Janke ^b, Claudio Arato ^b

a Fluidization Research Centre, Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, Canada
b Sonoro Energy Ltd., Vancouver, Canada

10.1016/j.partic.2011.07.006

Volume 10, Issue 2, April 2012, Pages 154-160

Received 12 May 2011, Revised 27 July 2011, Accepted 28 July 2011, Available online 17 January 2012.

E-mail: xbi@chbe.ubc.ca

Highlights

► Fly ash beneficiation was systematically investigated in a free falling system.

► Larger particles showed better separation performance.

► Sonification reduced particle size and helped in improving separation efficiency.

► A simplified mechanic model was developed to predict separation efficiency and ash recovery.

Abstract

A systematic study of fly ash electrostatic beneficiation in a free-falling separation system was carried out to provide fundamental understanding of the separation efficiency for the design of a suitable process for industrial applications. The parameters investigated included feeding position, electric field strength, particle size and moisture content. Particles larger than 105 μm presented the best separation efficiency among four different size fractions, whereas particles smaller than 44 μm showed minimal separation. However, sonication treatments helped separation by liberating more carbon from ash particles, although particle sizes were reduced as well. Experiments also showed that exposure to moisture significantly altered charging behavior of fly ash and its subsequent separation due to more free mobile ion-induced charge exchanges. The optimal feeding position was found to be slightly on the side of the negative electrode, leading to a 30% reduction in loss-on-ignition (LOI) and a 45% recovery in a single pass. A simplified mechanical model based on trajectory analysis for charged particles in an electrical field was in reasonable agreement with experimental results.

Graphical abstract

Keywords

Fly ash; Electrostatic separation; Loss-on-ignition; Bi-polar charging; Vibratory feeder

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