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
  • C10L1/00—Liquid carbonaceous fuels

Definitions

• This invention relates to fuel compositions which are dispersions of solid fuel in an alcohol and to a method for their preparation.
• Coal oil-slurries have previously been disclosed, see for example, British Patent Specification No. 975687. Whilst these have behaved as near-Newtonian non-settling fluids in pipelines, they separate on standing. Thus such slurries are suitable for use immediately after preparation or pipelining but are not suitable for transportation by tanker nor for storage.
• GB 1514888 - Keller Corporation discloses a fuel composition comprising a combustible, pseudo-thixotropic liquid-solid suspensoid including a critical proportion of coal particles having a critical settling velocity uniformly dispersed in a solution of methyl fuel including methanol, water and other alcohol soluble constituents of the coal.
• the coal particles have a relatively wide range of particle sizes and a majority are less than 150 micron in lateral dimensions. Because of surface area considerations, 1514888 warns that not more than 1% of the coal should have a particle size below 10 micron.
• the storage period may vary from one to many days or weeks.
• the particles in the final suspensoids remain in suspension wi.th low intensity stirring on storage and in motion through a pipe line. They do, however, settle out on standing but can be redispersed by stirring.
• dispersions of improved stability can be prepared by reducing the mean particle size to below 10 micron and furthermore, that if this is done, the lengthy storage step is not necessary.
• a fuel composition containing 15 to 65% by weight of a friable solid fuel., preferably 25 to 40%, uniformly dispersed in a lower alcohol, the mean particle size of the solid fuel being in the range 1 to 10 micron, preferably 2 to 5 micron, the percentage being expressed as a percentage by weight of the dispersion.
• lower alcohol we mean an alcohol containing from 1 to 6 carbon atoms per molecule.
• the preferred lower alcohol is methanol.
• Suitable friable solid fuels include coals of various ranks, solvent refined coal, coal coke and petroleum coke.
• a very suitable coal is bituminous coal.
• compositions are prepared by grindi.ng solid friable fuel in the alcohol in the absence of air.
• a method for the preparation of a uniform dispersion of a friable solid fuel in a lower alcohol comprises grinding the solid fuel in the alcohol until the mean particle size of the solid fuel particles is reduced to a value in the range 1 to 10 micron, preferably 2 to 5 micron, and the dispersion contains 15 to 65% solid fuel, preferably 25 to 40%, the percentage being expressed as a percentage by weight of the total dispersion, air being excluded during the grinding operation.
• the solid fuel supplied to the grinding process is pre-ground to a particle size not greater than 250 micron.
• Grinding can be carried out in vibratory, agitatory or tumbling ball mills.
• the pre-ground solid fuel is preferably pre-mixed with the alcohol before grinding, e.g. in a high speed vortex mixer.
• the grinding time will depend on the nature of the mill.
• Ball mills When using a ball mill it is, of course, desirable to use balls made of a material which does not react with the solid and which does not wear unduly either itself or the interior surface of the mill during the grinding. Ball mills usually contain steel or glass balls and these are suitable for the present purpose.
• the stability of the solid fuel dispersion is a function of three variables - the method of grinding, the final particle size and the final concentration of solid in alcohol. If all three are chosen correctly, then the resulting dispersion at ambient temperature is in the form of a gel in which a physical network is formed by solid particles in alcohol. It is a uniform structure from which the solid particles cannot settle out because they form part of it.
• the gel will not form. If the solid particle-size is too great, then the gel will not form. The concentration of the solid particles is also critical. If it is too low, the gel will not form. If it is too high, the gel will be too solid-like for pumping.
• Such solid fuel alcohol dispersions are suitable for use in blast furnaces, cement kilns, industrial boilers, marine boilers and utility boilers.
• coal was a bituminous coal ex Durham coal field of Rank 501 and with the following ultimate and initial analyses:
• the coal (1050 g) was mixed with methanol (1950 g) with continuous stirring using a high-speed vortex mixer.
• the resulting slurry which was extremely unstable (i.e. the coal settled rapidly out of suspension), was pumped at a rate of 300 ml/m giving a nominal residence time of one minute to a stirred ball mill sold under the name Dyno Mill Type KDL by Willy Bachofen Maschinenfabrik, Basle, Switzerland.
• the mill grinding chamber, a horizontally mounted cylinder of capacity 600 ml contained 1 mm steel balls (nominally 500 ml). After allowing for the void volume between the balls the volume of the grinding chamber actually available to the feed was 300 ml.
• the balls were stirred by agitator discs mounted on a horizontal shaft running parallel to the axis of the cylinder.
• the shaft speed was set at 4500 rpm giving a disc peripheral speed of 15 mm -1 .
• the product was collected as it emerged from the mill and was passed through the mill for a second time, at the same flow rate.
• the double-pass product emerged from the mill as a mobile liquid which showed no increase in coal content at the base of a test sample after storage at ambient temperatures for seven days.
• the mean parti.cle size of the coal particles in the dispersion was 3.7 micron as determined by an optical microscope technique.

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

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Publications (2)

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Citations (2)

• 1981
  • 1981-06-05 ZA ZA00813789A patent/ZA813789B/xx unknown
  • 1981-06-05 AU AU71397/81A patent/AU7139781A/en not_active Abandoned
  • 1981-06-17 EP EP81302732A patent/EP0042726A3/de not_active Ceased
  • 1981-06-17 BR BR8103840A patent/BR8103840A/pt unknown
  • 1981-06-18 NZ NZ197465A patent/NZ197465A/xx unknown

Patent Citations (3)

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