Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L9/00—Treating solid fuels to improve their combustion
  • C10L9/02—Treating solid fuels to improve their combustion by chemical means

Definitions

• the present invention relates to a method for the removal of iron pyrites from coal and carbon structures during ash removal by chemical means.
• Pyrites is commonly distributed within the coal matrix as pyrites particles laminated to the organic coal matrix, often with intermediate bonding by inorganic mineral matter such as aluminosilicates.
• Our invention has as its objective a method which liberates pyrites from coal without the necessity for fine grinding.
• the invention provides a method for liberating pyrites from coal comprising crushing coal to a suitable particle size; leaching the crushed coal with hydrofluoric acid, and treating the leached solids using otherwise conventional pyrites removal s.
• the suitable particle size range varies from coal to coal, however it is coarser in size than.that necessary for satisfactory conventional liberation of pyrites.
• the hydrofluoric acid dissolves most of the inorganic minerals within the coal matrix, including the predominant aluminosilicates, but not the pyrites thereby breaking the bond between the pyrites and the organic coal matrix, and liberating the pyrites particles.
• Conventional pyrites removal methods such as gravity separation, magnetic separation, and flotation can then be employed. Gravity separation is particularly enhanced as the organic coal matrix achieves a lower than normal density after hydrofluoric acid leaching, due to the dissolution of ash-forming minerals, thereby increasing the density difference between the pyrites refuse and the coal accepts.
• hydrofluoric acid leaching conditions are not critical with respect to acid concentration, temperature or leaching time. We have successfully employed acid concentrations of about 3 to 70 w/w%, temperatures of 20 to 100°C and leaching times from about 10 minutes to 48 hours.
• the raw coal must be crushed to a particles size suitable for hydrofluoric acid leaching. It is necessary to reduce the particle size only to that extent required to provide access for the hydrofluoric acid leach liquor to the mineral matter associated with the coal matrix. It is not necessary to completely liberate the mineral particles, which would require finer grinding. Accordingly, relatively coarse coal particles can be acid leached and then treated for pyrites removal. Liberation of pyrites by grinding alone would only be achieved at much finer particle sizes. We have achieved excellent pyrites removal from coal by hydrofluoric acid leaching raw coal at particle sizes as coarse as 5mm, and then using conventional separation methods.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)

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Publications (2)

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Citations (3)

• 1983
  • 1983-03-28 AU AU26200/84A patent/AU2620084A/en not_active Abandoned
• 1984
  • 1984-03-27 EP EP84103390A patent/EP0120499A3/fr not_active Withdrawn

Patent Citations (3)

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