Effect of hydrophobicity and frother concentration on bubble-particle interactions in turbulent flow

B. Omelka*, N. Schreithofer, K. Heiskanen

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

10 Citations (Scopus)

Abstract

The different zones of a flotation cell are characterised by varying flow regimes, particle populations and consequently different types of bubble-particle interactions. Theories have been presented both for the attachment and for the detachment of particles from bubbles based on the treatment of bubble-particle aggregates as single entities. This paper describes the effects of hydrophobicity and frother concentration on particle-bubble aggregate behaviour in turbulent conditions. The interactions were studied with high speed imaging in a laboratory scale stationary turbulence device, where the turbulent energy intensity could be varied to match the values found in industrial flotation cells. The experimental results showed, that in ultra pure water the frequency of surface vibrations of the bubbles was in the same order of magnitude as the Kolmogorov time scale turnover frequency. Very small frother concentrations rapidly decreased the surface vibration frequency. This frequency decrease had an effect on the particle- bubble stability. The aggregates showed a marked tenacity when subjected to turbulent energy. During turbulent acceleration, the particles moved at high local velocities on the bubble surface. The difference of velocities between spherical glass spheres and particles crushed from the same glass material was so small that no statistically meaningful difference could be obtained from the videos made. There seems to be only a small, even negligible, force preventing the particles to slide on the surface. The increase of frother concentration seems to increase this force as expected. The results of the experimental campaign have shown, that bubble-particles aggregates in turbulence are influenced by the complex interplay of hydrodynamics and surface chemistry. The complexity of the system is not reflected in the currently available models. The detachment phenomenon predicted by the current models could not be found. The mechanism of detachment proved to be profoundly different.

Original languageEnglish
Title of host publicationXXV International Mineral Processing Congress 2010, IMPC 2010
Pages2205-2214
Number of pages10
Volume3
Publication statusPublished - 1 Dec 2010
MoE publication typeA4 Article in a conference publication
EventInternational Mineral Processing Congress - Brisbane, Australia
Duration: 6 Sep 201010 Sep 2010
Conference number: 25

Conference

ConferenceInternational Mineral Processing Congress
Abbreviated titleIMPC
CountryAustralia
CityBrisbane
Period06/09/201010/09/2010

Keywords

  • High speed imaging
  • Hydrophobicity
  • Particle-bubble interactions
  • Surfactant concentration
  • Turbulence

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