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
  • C10L1/32—Liquid carbonaceous fuels consisting of coal-oil suspensions or aqueous emulsions or oil emulsions
  • C10L1/322—Coal-oil suspensions

Definitions

• This invention relates to a process for the beneficiation of solid carbonaceous fuel materials and more particularly to a process for the beneficiation of low rank coals.
• coal-oil and coal-aqueous mixtures are described in the literature.
• Such liquid coal mixtures offer considerable advantages.
• they are more easily storable, and less subject to the risks of explosion by spontaneous ignition.
• providing coal in a fluid form makes it feasible for burning in conventional apparatus used for burning fuel oil.
• Such a capability can greatly facilitate the transition from fuel oil to coal as a primary energy source.
• coal-oil and coal-aqueous mixtures and their preparation are disclosed in U.S. Patent No. 3,762,887, U.S. Patent No. 3,617,095 and U.S. Patent No. 4,217,109 and British Patent No. 1,523,193.
• coal Regardless of the form in which the coal is ultimately employed, the coal must be cleaned because it con­tains 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 or the coal prior to burning.
• chemical coal cleaning techniques are in a very early stage of development.
• 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.
• Other methods are disclosed in the above-noted reference to the Encyclopedia of Chemical Technology , Volume 6, pages 314-322.
• hydrophobic coal can be readily further dehydrated to very low water levels without employing costly thermal energy.
• the clean, very low moisture content coal, resulting from this process can then be employed as is, i.e., a dry solid product, or used to form advantageous coal-oil or coal-­aqueous mixtures.
• each class responds differently to beneficiation.
• the so-called low rank coals i.e. low rank bituminous, sub-bituminous, lignite and peat, contain water of hydration, which impairs and at times prevents, beneficiation by conventional froth flotation processes.
• these coals do not respond to conventional oil agglomeration, nor do they respond satisfactorily to the so-called Otiska process. Accordingly, the yields from these processes are very poor. While these low rank coals may be beneficiated according to the process disclosed in said U.S. Patent Nos. 4,332,593 and 4,304,573, the results achieved employing this process have not been entirely satisfactory, either.
• Still another object of this invention is to provide a process for the beneficiation of low rank coal which provides a beneficiated product which is highly suitable for forming coal-aqueous and coal-oil mixtures.
• a still further object of the present invention is to provide a process for the beneficiation of low rank coal which results in a high recovery of beneficiated product.
• coal derived oils also known as coal tar oils and/or coal tar de­rivatives
• coal tar oils also known as coal tar oils and/or coal tar de­rivatives
• improved beneficiation results are achieved with low rank coals.
• coal derived oils also known as coal tar oils and/or coal tar de­rivatives
• the surface treatment according to this invention also involves the formation of a polymeric coating on the surface of the coal by molecular grafting of polymeric side chains on the coal molecules.
• raw mined low rank coal it is initially preferred to reduce raw mined low rank coal to a fine diameter size and to remove the unwanted rock, heavy ash and the like materials collected in the mining operation.
• the raw coal is crushed and ground in the presence of water, employing conventional equipment such as, for example, ball or rod mills, breakers and the like.
• additives assist in rendering the ash more hydrophilic which facilitates the separation thereof.
• these additives can 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 by the heretofore pulverization operation is typically one having a coal to water ratio of about 1:3 parts by weight, respectively.
• the water conditioning 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 is applicable 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 desired to crush the coal to a particle size of from about 48 to about 300 mesh, preferably about 80% of the particles being of about a 200 mesh size.
• the pulverized coal-aqueous slurry is then con­tacted and admixed with a surface treating mixture com­prising a coal derived oil, a polymerizable monomer, a polymerization catalyst and optionally, a further organic liquid carrier, such as fuel oil.
• a surface treating mixture com­prising a coal derived oil, a polymerizable monomer, a polymerization catalyst and optionally, a further organic liquid carrier, such as fuel oil.
• the coal derived oil may be admixed with the coal before or in combination with or after the remaining surface treating ingredients are contacted and admixed with the coal.
• the coal is admixed with the surface treating admixture, including the coal derived oil, under any polymerization conditions, for example, temperatures ranging from about 20° to about 70°C at atmospheric or nearly atmospheric conditions for from about 1 second to about 30 minutes, preferably from about 1 second to about 3 minutes.
• the resultant surface treated coal is extremely hydrophobic and oleophilic and thus a coal froth phase ensues which is readily removed from the remaining aqueous ash containing phase.
• such monomers include ethylene, propylene, butylene, tetrapropylene, isoprene, butadiene, such as 1,4-butadiene, pentadiene, dicyclopentadiene, octadiene, olefinic petroleum fractions, sytrene, vinyltoluene, vinyl­chloride, vinylbromide, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N-methylolacrylamide, acrolein, maleic acid, 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, or salts thereof, particularly, those included within the formula R -OR' 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 an 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 preferivelyably 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
• Specific monomers conforming to the foregoing structural formula include unsaturated fatty acids such as oleic acid, linoleic acid, linolenic, ricinoleic, mono-, di-, and tri­glycerides, and other esters of unsaturated fatty acids, acrylic acid, methacrylic acid, methylacrylate, ethylacrylate, ethylhexylacrylate, tertiarybutyl acrylate, oleylacrylate, methylmethacrylate, oleylmethacrylate, stearylacrylate, stearyl­methacrylate, laurylmethacrylate, vinylstearate, vinylmyristate, vinyllaurate, soybean oil, dehydrated castor oil, tall oil, corn oil and the like.
• unsaturated fatty acids such as oleic acid, linoleic acid, linolenic, ricinoleic, mono-, di-, and tri­glycerides
• 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.
• the amount of polymerizable monomer will vary de­pending upon the results desired. In general, however, monomer amounts of from about 0.005% to about 1.0% by weight, preferively from 0.02 to 0.1 percent by weight of the dry coal are used.
• the catalysts employed in the coal surface treat­ing beneficiation reaction of the present invention are any such materials commonly used in polymerization reactions.
• any catalytic amount of those catalysts which are commonly referred to as free radical catalysts or catalyst system (which can also be referred to as addition polymerization catalysts, vinly polym­erization catalysts or polymerization initiators) are preferred.
• catalysts contemplated herein include benzoyl peroxide, methylethyl ketone peroxide, tert-butyl­hydroperoxide, hydrogen peroxide, ammonium persulfate, di­tert-butylperoxide, tert-butylperbenzoate, peracetic acid and including such non-peroxy free radical initiators as the diazo compounds, such as 1,1'bis-azoisobutyronitrile, and the like
• free radical polymerization systems commonly employ free radical initiators which function to help initiate the free radical reaction.
• free radical initiators include, for example, sodium perchlorate and perborate, sodium persulfate, potas­sium persulfate, ammonium persulfate, silver nitrate, water soluble salts of noble metals such as platinum and gold, water soluble salts of iron, zinc, arsenic, antimony, tin, cadmium and mixtures thereof.
• 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(NO3)2.
• Further initiators contemplated herein are also disclosed in U.S. Patent Application Serial No. 230,063, filed January 29, 1981 and incorporated herein by reference. These initiators include metal salts of naphthenates, tallates, octanoates, etc., said metals including copper, cobalt, manganese, nickel, tin, lead, zinc, iron, rare earth metals, mixed rare earths and mixtures thereof.
• the amounts of catalysts contemplated herein include 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 advantages of the present invention are derived principally from the utili­zation of coal derived oil, i.e. coal tar or coal tar derivative, in the beneficiation process.
• coal derived oils contemplated for use in the process of this invention are those liquid products which result from the dry distillation or carbonization (coking) of coal and which, generally, are products having a boiling point in the range of from about 100-500°C. That is, the dry distillation or carbonization of coal yields a liquid condensate, most of which is coal tar.
• crude coal tar may be employed herein as a coal derived oil it is preferred to employ coal tar derivatives which are commercially provided by the distillation or topping of the crude coal tar.
• the distillate from this procedure i.e. chemical oil, generally has an upper boiling point of about 250°C and contains:
• the amount of coal derived oil used in the present process is small and is, for example, from about 0.5% to about 5%, preferably about 2-3% by weight of the amount of dry coal. If the coal derived oil is employed in conjunction with a further liquid organic carrier such as fuel oil, like No. 2 fuel oil, the amount of coal derived oil may be less, wherein the total content of coal derived oil and fuel oil employed is preferably about 2.5% by weight based on the amount of dry coal.
• the resulting low rank coal is, in contrast to prior art processes, extremely hydrophobic and oleophilic and consequently, readily floats and separates from the aqueous phase.
• the floating hydrophobic oleophilic coal is thusly readily removed from the aqueous phase, for example, by skimming, and is thereafter, if desired, readily introduced for further treat­ment, e.g. dried and used as is, or further washed and/or surface treated, or admixed with oil or water in the prep­aration of desirable coal-oil or coal-aqueous mixtures.
• the surface treating reaction mixture of the present invention may also optionally include an additional liquid organic carrier.
• This liquid organic carrier is utilized to further facilitate contact of the surface of the coal particles with the polymerization reaction medium.
• optional 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 optional carrier.
• the amounts of optional liquid organic carrier, such as fuel oil, contemplated herein are generally in the range of from about 0.5 to about 5% by weight of dry coal.
• Water is a further ingredient which is utilized in the surface treatment reaction mixture of the present process. Amounts of water contemplated for this purpose are from about 65% to about 95% by weight of the amount of dry coal.
• the low rank coal resulting from the beneficiation process of this invention is very low in ash, sulfur and moisture content.
• the beneficiated low rank coal prepared by the process of the present invention has an ash content of from 5 to about 10%, a sulfur content of from about 0.5 to about 1.0% and a moisture content of from about 15 to about 30%,based on the dry coal weight.
• recovery of beneficiated product in accordance with the present invention is also very good and is generally from about 50% to about 60%.
• a particularly effective technique for separating the treated coal particles from unwanted ash and sulfur in the water phase is an aeration spray technique wherein a coal froth phase is formed by spraying or injecting the treated coal-water slurry into the surface of cleaning water as is described and claimed in U.S. Patent Nos. 4,347,126 and 4,347,127 incorporated herein by reference.
• the coal slurry is injected through at least one spray nozzle at pressures, for example, at from about 15-20 psi at a spaced-apart distance above the water sur­face into the water surface producing aeration and a frothing or foaming of the coal particles, causing these particles to float to the water surface for skimming off.
• the coal froth phase which results from the initial surface treating step, as hereinbefore described may be further washed and/or surface treated by admixing the same with a further aqueous medium which can comprise simply clean water or water and water conditioning agents or water and any or all of the ingredients which comprise the initial surface treating admixture, including the coal derived oil.
• a further aqueous medium which can comprise simply clean water or water and water conditioning agents or water and any or all of the ingredients which comprise the initial surface treating admixture, including the coal derived oil.
• any number of these additional washings and/or surface treat­ments may be utilized for the purposes of this invention before recovering the beneficiated coal product.
• these aqueous phases may be surface treated and/or washed as hereinbefore described and the residual beneficiated coal may be recovered for increased yields.
• Aerofroth-65 (5 mg/ml) (a propylene oxide reaction product with ethylene glycol mol. wt. 400-450, available from American Cynamid Company) and 1 cc. pine oil.
• the resultant admixture is permitted to react at 30°C and atmospheric pressure for about 5 minutes.
• the ensuing coal froth phase is separated and introduced to another vessel containing an aqueous medium comprising 500 grams of clean water.
• the resultant coal froth phase therein is again removed and introduced to a second aqueous medium comprising 500 grams of clean water.
• the coal froth phase is removed and the beneficiated coal is recovered.
• the product is found to have a reduced ash content of 6.22% and a reduced sulfur content of 0.76%.
• the % recovery is excellent and is determined to be 58.3%.
• the strained coal froth phase is again placed in the separatory funnel containing 5000 grams of clean water at 30°C and agitated. 0.034%,by weight dry coal, of the Neutral oil and 0.034%, by weight dry coal, of pine oil are added and admixed therewith. The resultant coal froth is removed and the aqueous phase is discarded. The coal froth is again placed in the funnel containing 5000 grams of clean water at 30°C and agitated. Another 0.034%,by weight dry coal, of Neutral oil and 0.034%,by weight dry coal, of pine oil are admixed therewith, and the resultant coal froth is removed.
• the aqueous phase is stirred and 0.034%, by weight dry coal, of Neutral oil and 0.034%, by weight dry coal, of pine oil are added thereto.
• a froth with coal floating within it is obtained and removed. Additional Neutral oil is added to the aqueous phase but no more coal floated.
• the water is discarded and the froth is filtered.
• the coal froth phases are combined and the following physical results are determined. % recovery - 25.6 % final ash - 6.91 % final sulfur - 0.83

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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)
• Liquid Carbonaceous Fuels (AREA)
• Emulsifying, Dispersing, Foam-Producing Or Wetting Agents (AREA)

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• 1985
  • 1985-10-23 EP EP85113452A patent/EP0219569B1/fr not_active Expired
  • 1985-10-23 DE DE8585113452T patent/DE3562627D1/de not_active Expired
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