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 OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L9/00—Treating solid fuels to improve their combustion
  • C10L9/02—Treating solid fuels to improve their combustion by chemical means

Definitions

• US. Pat. No. 1,098,359 teaches the adding of such phosphorus compounds as lime phosphate, phosphate chalk or apatite, to coal prior to coking. The purpose of this addition was to form a ferro-phosphorus compound so that any iron in the coke would-be deprived of taking up any further sulfur in the coking process.
• U.S. Pat. No. 2,057,486 teaches the use of hydrochloric acid in desulfurizingcoal.
• U.S. Pat. No. 2,166,321 discloses a method where a carbonizable extract of coal is produced. The extract is then treated with diluted inorganic acids and finally the extract is coked in the absence of the acids.
• Other inventors have attempted to produce low sulfur containing coke by carbonizing in a moving stream of reducing gases. See for example U.S. Pat. No. 3,117,918.
• char in contradistinction to the usual coke product is characterized as the solid carbonaceous residue of coal which has been distilled between about 400 and 800 C. and containing residual volatile matter of at least about 5% by weight.
• Coke normally contains less than about 2% by weight volatile matter and is the product of destructive distillation of coal at temperatures above about 1000 C.
• Char may find particular use by power companies in the generation of electricity.
• a low sulfur char will substantially assist in reducing atmospheric pollution normally' caused by utilization of coal for such purposes.
• sulfur in coal exists in several forms.
• sulfur may be found in coal in the form'of pyrites, gypsum or calcium sulfate and organic sulf'ur.
• Organic sulfur is combined with the carbon hydrogen and oxygen of the coal.
• Organic sulfur is believed to-be associated directly with the carbonaceous matter by incorporation of thesulfur atoms into the'aro-' matic molecular structure, although the particular way in' which the sulfur is bound in the molecular structure is not known.
• the removal of organic sulfur by hydrogen is a reversible reaction. This reaction is Sulfur is transferred from the gas phaseto thecarbona ceous phase at relatively high ratios of hydrogen sulfide to hydrogen.
• orthophosphoric acid commonly called phosphoric acid
• any of the polyphosphoric acids or phosphorus acids or mixtures thereof may be used.
• the polyphosphoric acids may be represented by the formula H P O wherein n is greater than 1. Examples of these polyphosphoric acids are metaphosphoric acid pyrophosphoric acids.
• phosphoric will be used and it is to be understood that all such phosphoric acids, phosphorus acids and mixtures thereof, described above can be used.
• a 5 or aqueous solution of phosphoric acid is slurried with crushed coal.
• the slurry is then filtered to remove excess acid.
• the coal will contain from about 10 to about 30% liquid based on the weight of the coal. Twenty weight percent liquid on the crushed coal is preferred. Experiments have shown that as little as 0.25 weight percent phosphoric acid based on the coal weight can be used in effecting the removal of sulfur from the coal during the carbonization thereof. Amounts of phosphoric acid up to about by weight on the coal or more may be used. However the preferred range for economic consideration is between about 1 and about 5% based upon the weight of the coal.
• the coal is crushed in any convenient manner in crushers or grinding mills. Preferably the coal will be reduced to a size between about 100 and 10 mesh U.S. Sieve Series. Larger particles of coal may be desulfurized using this invention but the time at temperature is thereby increased.
• the coal after it has been slurried with phosphoric acid and the excess acid, if any, removed therefrom, is fed to a suitable vessel for heating.
• the coal-phosphoric acid mixture may be heated to a range of between about 400 and 1300 F. with the preferred range being between 700 and 1200 F.
• the time taken to heat the coal slowly up to the desired temperature appears to have a minimal effect on the sulfur removal, it is preferred to heat at a relatively slow heating rate. It appears that a slow heating rate allows the sulfur compounds to leave the coal while charring is proceeding in a uniform and effective manner. It is believed that the most rapid sulfur removal occurs at around 700' F. .At this temperature the evolution of volatile matter, including some organic sulfur compounds, begins together with pyrite decomposition to pyrrhotite. Once the selected temperature has been reached it should be maintained for a period of time of at least 15 to minutes or longer.
• the inert atmosphere may be carbon dioxide or an atmosphere of spent gas from a coal combustion.
• a reducing atmosphere is introduced into the vessel.
• the reducing atmosphere is a continuously changing one in order to remove the sulfur compounds as they are released from the charring coal.
• the reducing atmosphere may be any combination of hydrogen, carbon monoxide, methane and an inert gas such as nitrogen.
• a convenient way in reducing atmosphere is tofeed steam and carbon monoxide simultaneously into and through the heating vessel.
• the gas in the reaction vessel will be changed every few seconds such that the gas space velocity will be between about 0.1 and 1.0.
• Example 1 Fifteen grams of Western Kentucky #11 coal was ground to a minus mesh and slurried with 12 milliliters of an aqueous 5 or 10% phosphoric acid solution for 15 minutes. The slurry was then filtered to remove excess acid and approximately half of the sample was weighed into a silica boat inside a tubular furnace.
• the furnace train consisted of compressed gas tanks, a regulator, a flow meter, a tube reactor, tar traps and a cadmium scrubber.
• the flowing gas was set to 360 mlsJmin. through the 18" x 0.8" inside diameter quartz tube reactor.
• the inert gas was pre-purified nitrogen and the reducing gas consisted of 5.5% hydrogen, 23.6% carbon monoxide, and the balance argon.
• the furnace was turned on and brought to 500 C. in about 15 minutes and held there for an additional 15 minutes. The results are tabulated below.
• the phosphoric acid pretreatment material ly assists in removing the sulfur thermal treatment.
• Example III Illinois No. 6 coal containing 4.33% by weight sulfur was crushed and 15 gram samples thereof slurried with 12';
• Example IV Further experiments on treatment of coal with phosphoric acid were conducted in a packed bed. Two 150 gram lots of 10 x 35 mesh (4.0% sulfur) and 60 x 100 mesh (4.3% sulfur) coal were taken from a larger lot of Illinois coal. These samples were slurried with 120 mls. of 10% phosphoric acid and stirred for minutes. The slurry was filtered and the wet solids dried at 220 F. to drive off excess water but to leave the acid in the coal. Fifteen gram portions of these samples were then carbonized in the packed bed. The samples in the packed bed were heated from room temperature to about 700 F. using a carbon dioxide atmosphere. Since this atmosphere is slightly oxidizing, it was expected to open up the pore structure of the coal making it more reactive.
• the process of desulfurizing coal while producing a low sulfur char which comprises the steps of (a) mixing crushed coal with an acid selected from the group consisting of orthophosphoric acid, .polyphosphoric acids, phosphorous acids and mixtures thereof,

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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)
• Coke Industry (AREA)

Priority Applications (2)

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Cited By (24)

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• 1972
  • 1972-07-26 US US00275119A patent/US3812017A/en not_active Expired - Lifetime
• 1973
  • 1973-07-26 JP JP48084541A patent/JPS4945101A/ja active Pending

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