Studies on carbon flotation from fly ash

Wencai Zhang, Rick Honaker

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


The separation of carbon from fly ash significantly improves the potential end-us of combustion byproducts. Froth flotation is the most effective separation technique for ultrafine material. Diesel dosages, conditioning time, and impeller rotating speeds' influences on carbon flotation performance were studied. From flotation products, + 25 and − 25 μm fractions were screened out to study their different flotation behaviors. At a given impeller speed, carbon recovery of +25 μm fraction increased significantly from 38.46% to 74.22% over a range of diesel dosage from 0.5 to 4.5 kg/t, while that of -25 μm fraction was relatively constant at 85% over the same diesel dosage range. Morphologies and microstructures of coarse and fine carbon were studied by using scanning electron microscope. Porous structures of coarse carbon were observed. It's difficult for diesel droplets of several microns to penetrate the pores of coarse carbon particles, which increases diesel consumption. Increasing impeller speeds from 1200 to 1600 rpm during conditioning improved the carbon recovery and separation efficiency of + 25 μm fraction by 79% and 110%, respectively, which significantly reduced diesel consumption. Flotation kinetic studies indicate that increasing impeller speeds during conditioning stage can improve the flotation rate constant and maximum carbon recovery for both + 25 and − 25 μm fractions.

Original languageEnglish
Pages (from-to)236-241
Number of pages6
JournalFuel Processing Technology
StatePublished - Nov 2015

Bibliographical note

Publisher Copyright:
© 2015 Elsevier B.V.


  • Carbon
  • Flotation
  • Fly ash
  • Separation

ASJC Scopus subject areas

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology


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