Upgrading difficult-to-float coal using microemulsion

Hussain Ahmad, Jan Drzymala

Research output: Contribution to journalJournal articlepeer-review

34 Scopus citations


Oxidized coals are difficult to float. Therefore, in this paper, a special flotation procedure was investigated for upgrading this type of coal. The procedure is called direct contact flotation. It relies on mixing dry coal either with pure (anhydrous) flotation reagent(s) or microemulsion. By applying the new direct contact flotation procedure, a coal yield reaching >95% using anhydrous flotation reagents was achieved, but with relatively high consumption of reagents (up to 30g/kg). This high reagent consumption may be attributed to the fines included in the flotation feed (100% less than 0.5 mm, with 40% less than 75 pm). On the other hand, the clean coal yield was found to be approximately 88% when mixing dry oxidized coal with microemulsion droplets from dodecane and dodecyl tetra (ethylene glycol) ether (C12E 4) in water at a total reagent dosage of 10g/kg. The direct contact of coal either with unhydrous reagents or microemulsion also provided a high flotation selectivity.

Original languageEnglish
Pages (from-to)88-96
Number of pages9
JournalMinerals and Metallurgical Processing
Issue number2
StatePublished - May 2012


  • Flotation
  • Microemulsion
  • Oxidized coal
  • Surfactants


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