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

Definitions

• This invention relates to the beneficiation of coal and more particularly to an improved process for the beneficiation of coal.
• coal or coal combustion products must be cleaned because they contain substantial amounts of sulfur, nitrogen compounds and mineral matter, including significant quantities of metal impurities. During combustion these materials enter the environment as sulfur dioxides, nitrogen oxides and compounds of metal impurities. If coal is to be accepted as a primary energy source, it must be cleaned to prevent pollution of the environment either by cleaning the combustion products of the coal or the coal prior to burning.
• Known chemical coal cleaning techniques include, for example, oxidative desulfurization of coal (sulfur is converted to a water-soluble form by air oxidation), ferric salt leaching (oxidation of pyritic sulfur with ferric sulfate), and hydrogen peroxide-sulfuric acid leaching.
• oxidative desulfurization of coal sulfur is converted to a water-soluble form by air oxidation
• ferric salt leaching oxidation of pyritic sulfur with ferric sulfate
• hydrogen peroxide-sulfuric acid leaching hydrogen peroxide-sulfuric acid leaching
• a process for beneficiating coal comprising admixing coal in an aqueous medium, under high shear admixing conditions with a polymerizable monomer, and a liquid organic carrier, thereby rendering said coal hydrophobic and oleophilic.
• U.S. Patent No. 4,304,573 discloses a highly desirable process for beneficiating coal which involves surface treating particles of coal in an aqueous medium with a surface treating admixture comprising a polymerizable monomer, a polymerization catalyst and a liquid organic carrier, thereby rendering said coal particles hydrophobic and oleophilic.
• the process provides a highly beneficiated coal product of relatively low water content which can be even further dehydrated (dried) to a remarkable degree without the use of thermal energy.
• the ash content of the coal prepared by the process is reduced to low levels and mineral sulfur compounds present are also removed.
• the final coal product has enhanced BTU content and can be burned as a solid or combined with fuel oil or water to produce highly desirable beneficiated coal mixtures or slurries which are readily transportable and cleanly burned.
• the term "beneficiation” is intended to include methods for cleaning or otherwise removing impurities from a substrate, such as coal and to the recovery of coal from coal streams, such as, for example, the recovery of coal from waste streams in coal processing operations and the concentration or dewatering of coal streams or slurries such as, for example, by the removal of water in, for example, coal slurry pipelines.
• any type coal can be employed in the process of the present invention.
• these include, for example, bituminous coal, sub-bituminous coal, anthracite, low rank coal, such as lignite and the like.
• Other solid carbonaceous fuel materials such as oil shale, tar sands, coke, graphite, mine tailings, coal from refuse piles, coal processing fines, vertical retort residues, coal fines from mine ponds or tailings, concentrated coal pipeline streams, carbonaceous fecal matter and the like are also contemplated for treatment by the process herein.
• the term "coal” is also intended to include these kinds of other solid carbonaceous fuel materials or streams.
• coal is pulverized and initially cleaned, usually in the presence of water, wherein the coal is suspended and/or sufficiently wetted to permit fluid flow.
• the coal is pulverized employing conventional equipment such as, for example, ball or rod mills, breakers and the like. It may also be desirable, although not necessary to the present process, to employ certain water conditioning (treating) additives in the pulverization operation.
• additives assist in rendering the ash more hydrophilic, which facilitates the separation thereof, in a manner that will be discussed hereinafter.
• typical additives which are useful for purposes of this invention include conventional inorganic and organic dispersants, surfactants, and/or wetting agents.
• Preferred additives for this purpose include sodium carbonate, sodium pyrophosphate and the like.
• the coal-aqueous slurry formed in the pulverization operation is typically one having a coal to water ratio of from about 0.5:1 to about 1:5 and preferably about 1:3 parts by weight, respectively.
• the water treating additives, hereinbefore described are employed in small amounts, usually, for example, from about 0.25 to about 5%, based on the weight of dry coal. While it is generally recognized that more impurities are liberated as the size of the coal is reduced, the law of diminishing returns applies in that there is an economic optimum which governs the degree of pulverization. In any event, for the purposes of this invention, it is generally desirable to crush the coal to a particle size of from about 48 to about less than 325 mesh, preferably about 80% of the particles being of about a 200 mesh size (Tyler Standard Screen Size).
• the aqueous coal slurry is initially contacted and admixed under ambient conditions and under high shear mixing conditions, with a polymerizable monomer and a liquid organic carrier, such as fuel oil, toluene, etc.
• high shear mixing requires the vigorous admixture, high agitation, or mixing or turbulence of the materials, such as in a high speed mixing (Waring blendor, for example) or other device adapted to impart high shear mixing or agitation such as a ball mill.
• a high speed mixing Waring blendor, for example
• the condition of high shear exceeds about 1000 reciprocal seconds and most preferably exceeds about 4500 reciprocal seconds.
• such monomers include ethylene, propylene, butylene, tetrapropylene, isoprene, butadiene, such as 1,4-butadiene, pentadiene, dicyclopentadiene, octadiene, olefinic petroleum fractions, styrene, vinyltoluene, vinylchloride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N-methylolacrylamide, acrolein, maleic acid, maleic anhydride, fumaric acid, abietic acid and the like.
• a preferred class of monomers for the purposes of the present invention are unsaturated carboxylic acids, esters, anhydrides or salts thereof, particularly those included within the formula wherein R is an olefinically unsaturated organic radical, preferably containing from about 2 to about 30 carbon atoms, and R' is hydrogen, a salt- forming cation such as alkali metal, alkaline earth metal or ammonium cation, or a saturated or ethylenically unsaturated hydrocarbyl radical, preferably containing from 1 to about 30 carbon atoms, either unsubstituted or substituted with one or more halogen atoms, carboxylic acid groups and/or hydroxyl groups in which the hydroxyl hydrogens may be replaced with saturated and/or unsaturated acyl groups, the latter preferably containing from about 8 to about 30 carbon atoms.
• R is an olefinically unsaturated organic radical, preferably containing from about 2 to about 30 carbon atoms
• R' is hydrogen,
• Specific monomers conforming to the foregoing structural formula include unsaturated fatty acids such as oleic acid, linoleic acid, linolenic, ricinoleic, mono-, di- and tri-glycerides, and other esters of unsaturated fatty acids, acrylic acid, methacrylic acid, methylacrylate, ethyacrylate, ethylhexylacrylate, tertiarybutyl- acrylate, oleylacrylate, methylmethacrylate, oleylmeth- acrylate, stearylacrylate, stearylmethacrylate, laurylmethacrylate, vinylacetate, vinylstearate, vinylmyristate, vinyllaurate, unsaturated vegetable seed oil, soybean oil, rosin acids, dehydrated castor oil, linseed oil, olive oil, peanut oil, tall oil, corn oil and the like.
• unsaturated fatty acids such as oleic acid, linoleic
• tall oil and corn oil have been found to provide particularly advantageous results. Corn oil is especially preferred.
• compositions containing compounds within the foregoing formula and in addition containing, for example, saturated fatty acids such as palmitic, stearic etc. are also contemplated herein.
• monomers are aliphatic and/or polymeric petroleum materials.
• the amount of polymerizable monomer will vary depending upon the degree of surface treatment desired. In general, however, monomer amounts of from about 0.005 to about 0.1%, by weight, of the dry coal are used.
• Catalysts and/or free-radical initiators may be employed in the beneficiation process of the present invention. That is, these catalysts and/or initiators may be added to the admixture during the afore-described high shear admixing of the aqueous coal slurry with the monomer and organic carrier.
• catalysts which may be employed in the beneficiation process of the present invention are any such materials commonly used in polymerization reactions. These include, for example, anionic, cationic or free radical catalysts. Free radical catalysts or catalyst systems (also referred to as addition.polymerization catalysts, vinyl polymerization catalysts or polymerization initiators) are preferred herein.
• free radical catalysts contemplated herein include for example, inorganic and organic peroxides such as benzoyl peroxide, methylethyl ketone peroxide, tert-butyl - hydroperoxide, hydrogen peroxide, ammonium persulfate, di- tert-butylperoxide, tert-butyl-perbenzoate, peracetic acid and including such non-peroxy free-radical initiators as the diazo compounds such as 1,1'-bisazoisobutyronitrile and the like.
• inorganic and organic peroxides such as benzoyl peroxide, methylethyl ketone peroxide, tert-butyl - hydroperoxide, hydrogen peroxide, ammonium persulfate, di- tert-butylperoxide, tert-butyl-perbenzoate, peracetic acid and including such non-peroxy free-radical initiators as the diazo compounds such as 1,1
• any catalytic amount e.g. 1 pound per ton of dry coal feed
• any catalytic amount e.g. 1 pound per ton of dry coal feed
• Free radical initiators which function to help initiate the free radical reaction, may also be used herein alone or in combination with the heretofore identified catalysts.
• some of these initiators include, for example, water soluble salts, such as sodium perchlorate and perborate, sodium persulfate, potassium persulfate, ammonium persulfate, silver nitrate, water soluble salts of noble metals such as platinum and gold, sulfites, nitrites and other compounds containing the like oxidizing anions, and water soluble salts of iron, nickel chromium, copper, mercury, aluminum, cobalt, manganese, zinc, arsenic, antimony, tin, cadmium, and the like.
• Particularly preferred initiators herein are the water soluble copper salts, i.e.
• cuprous and cupric salts such as copper acetate, copper sulfate and copper nitrate. Most advantageous results have been obtained herein with cupric nitrate, Cu(NO 3 ) 2 .
• Further initiators contemplated herein are disclosed in copending U.S: patent application Serial No. 230,063 filed January 29, 1981 incorporated herein by reference. Among others, these initiators include metal salts of organic moities, typically metal salts of organic acids or compositions containing organic acids, such as naphthenates, tallates, octanoates, etc. and other organic soluble metal salts, said metals including copper, chromium, mercury, aluminum,
• the amounts of free radical initiator contemplated herein are any catalytic amount and generally are within the range of from about 10-1000 ppm (parts per million) of the metal portion of the initiator preferably 10-200 ppm, based on the amount of dry coal.
• the beneficiation process herein also includes a liquid organic carrier.
• This liquid organic carrier is utilized to facilitate contact of the surface of the coal particles with the polymerization reaction medium.
• liquid organic carriers included within the scope of this invention are, for example, fuel oil, such as No. 2 or No.
• fuel oils other hydrocarbons including benzene, toluene, xylene, hydrocarbons fractions,such as naphtha and medium boiling petroleum fractions (boiling point 100°-180°C); dimethylformamide, tetrahydrofuran, tetrahydrofurfuryl alcohol, dimethylsulfoxide, methanol, ethanol, isopropyl alcohol, acetone, methylethyl ketone, ethyl acetate and the like and mixtures thereof.
• fuel oil is a preferred carrier.
• liquid organic carrier such as fuel oil
• utilized in the surface treatment reaction herein are generally in the range of fromabont0.25 to about 5% by weight,based on the weight of dry coal.
• the beneficiation process of the present process is carried out in an aqueous medium.
• the amount of water employed for this purpose is generally from about 65% to about 95%, by weight, based on the weight of coal slurry.
• the beneficiation process conditions will, of course, vary, depending upon the specific ingredients employed and results desired. Generally, however, any conditions, polymerization or otherwise, which result in the formation of a hydrophobic or oleophilic surface on the coal can be utilized. More specifically, typical conditions include, for example, temperatures in the range of from about 10°C to about 90°C, atmospheric to nearly atmospheric pressure conditions. High shear admixing is generally carried out from about 0.25 to about 5 minutes, preferably from about 0.5 to about 1 minute.
• the resultant coal particles After having been subjected to this afore-mentioned initially high shear admixing step, the resultant coal particles become hydrophobic and oleophilic and float to the surface of the liquid mass. The ash, still remaining hydrophilic, tends to settle and is removed to the water phase. Thus, the coal which results is extremely hydrophobic and oleophilic and consequently readily floats and separates from the aqueous phase, providing a ready water washing and for high recoveries of coal.
• the floating hydrophobic coal is also readily seperable from the queous phase (for example, a skimming screen may be used for the separation), which contains ash, sulfur and other impurities which have been removed from the coal. While it is not completely understood and while not wishing to be bound to any theory, it is believed that the treatment involves the formation of a polymeric organic coating on the surface of the coal by molecular grafting of polymeric side chains on the coal molecules.
• the surface treated coal is then preferably subjected to at least one further wash step wherein the coal phase or phases are redispersed, under high shear agitation, as a slurry in fresh wash water.
• the aqueous washings may be carried out with the treated coal slurry in the presence of simply water at temperatures of, for example, about 10° to about 90°C, preferably about 30°C, employing from about 99 to about 65 weight percent water, based on the weight of dry coal feed.
• additional amounts of any or all of the heretofore described surface treating ingredients i.e. polymerizable monomer, catalyst, initiator, liquid organic carrier may also be added to the wash water.
• the washing conditions e.g. temperatures, contact time, etc., utilized when these ingredients are employed can be the same as if only water is present or the washing conditions can be the same as those described heretofore with respect to surface treatment of the coal with the surface treating mixture.
• water conditioning additives may also be utilized during the washing steps, if desired.
• the beneficiated coal may be dried to low water levels simply by mechanical means, such as by centrifugation, pressure or vacuum filtration etc., thus avoiding the necessity for costly thermal energy to remove residual water.
• the beneficiated coal prepared by the process of this invention generally contains from about 0.5% to about 10.0% by weight ash, based on the weight or dry coal.
• the sulfur content is from about 0.1% to about 4% by weight, preferably about 0.3 to about 2%,.based on the weight of dry coal and the water content is from about 2% to about 25%, preferably from about 2% to about 15% by weight, based on the weight of dry coal.
• Recoveries of beneficiated coal are in the range of from about 85 to about 99%.
• the beneficiated coal can be used as a high energy content, ash and sulfur reduced, fuel product.
• This beneficiated fuel product can be utilized in a direct firing burner apparatus.
• the beneficiated particulate coal can be blended with a carrier such as oil and/or water to provide a highly stable and beneficiated coal slurry, such as a coal-oil mixture (COM) or coal-aqueous mixture (CAM).
• COM coal-oil mixture
• CAM coal-aqueous mixture
• Example 1 the reagents are mixed in by hand stirring.
• Example 2 the reagents are added and slurry is then subjected to 10 min. of high shear in a Waring Blendor, Model No. 5011G, at high speed, according to the present invention.
• the aqueous phase containing the high ash fraction is separated from the toluene phase, containing the high carbon fraction, by the use of a separatory funnel.
• the high carbon product is cleaned in each case by adding more water and reseparating in the funnel.
• the water added is mixed in by shaking.
• Example 2 the water added is mixed in for 2 min. of Waring Blendor, Model No. 5011G at high speed. Cleaning is repeated until the aqueous phase is quite free of suspended particles.
• the ash and carbon contents and carbon recovery for the products after filtration and drying are as follows:
• Black Mesa Pipeline centrate contains approximately 18% solids which consists of pigmentary size particles of coal.
• the ash content averages 24%.
• Reagents fuel oil, H202, Cu(N0 3 ) 2 and tall oil
• Example 3 the reagents are mixed in by hand stirring.
• Example 4 the reagents are added and the slurry is subjected to 60 seconds of high shear in a Waring Blendor, according to the present invention.
• the slurry is then transferred to a flotation cell and a frother (methyl isobutyl carbinol) is added.
• the coal is then removed as a froth from the aqueous phase which contains the majority of the ash.
• the froth is then cleaned again by adding fresh water to the unit and refloating. Cleaning is repeated untilthe aqueous phase is quite free of suspended particles.
• the ash contents and the coal recovery for the products after filtration and drying are as follows:
• Indianhead lignite does not respond at all to standard flotation - zero carbon recovery. However, by adding the reagents (fuel oil, H 2 0 2 , Cu(N0 3 ) 2 and corn oil) to the lignite before subjecting the lignite to comminution in the ball mill, the coal recovery is increased.
• reagents fuel oil, H 2 0 2 , Cu(N0 3 ) 2 and corn oil
• the coal is crushed 100% - 30 mesh and ground with the reagents and water in a ball mill for 15 minutes at 33% solids.
• the slurry is then transferred to a flotation cell and a frother (methyl isobutyl carbinol) is added.
• the coal is then removed as a froth from the aqueous phase which contains the majority of the ash.
• the froth is then cleaned again by adding fresh water to the unit and refloating. Cleaning is repeated until the aqueous phase is quite free of suspended particles.
• the ash contents before and after beneficiation and the coal recovery in the product after filtration and drying are as follows:

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• 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)
• Liquid Carbonaceous Fuels (AREA)
• Polymerisation Methods In General (AREA)

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Citations (4)

• 1983
  • 1983-09-08 CA CA000436298A patent/CA1214039A/fr not_active Expired
  • 1983-09-13 ZA ZA836782A patent/ZA836782B/xx unknown
  • 1983-09-13 AU AU19090/83A patent/AU1909083A/en not_active Abandoned
  • 1983-09-14 EP EP83109068A patent/EP0105237A3/fr not_active Withdrawn
  • 1983-09-19 ES ES525705A patent/ES525705A0/es active Granted
  • 1983-09-26 PT PT77396A patent/PT77396B/pt not_active IP Right Cessation
  • 1983-09-27 GR GR72547A patent/GR78723B/el unknown
  • 1983-09-29 DK DK447783A patent/DK447783A/da not_active Application Discontinuation
  • 1983-09-30 JP JP58180994A patent/JPS5987058A/ja active Pending

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