Abstract:
A significant improvement in the combustion properties of liquid hydrocarbon furnace fuel, perceived as a marked reduction in the rate and quantity of tarry, cokelike deposits formed on combustion of the fuel in conventional burner equipment, is obtained by adding to said fuel from about 1.0×10 -6  to about 1.0×10 -3  parts by weight of at least one isomer of dinitrotoluene. Optionally, combustion deposit formation can be further inhibited by the addition of at least one metal acetylacetonate to furnace fuel containing dinitrotoluene in the aforesaid amount.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to liquid fuels for use in furnaces and, more particularly, to such fuels containing an additive ingredient which significantly improves their combustion efficiency and reduces their consumption. 
     2. Description of the Prior Art 
     With the accelerating rate of consumption of liquid hydrocarbon fuels derived from economically recoverable petroleum deposits, much emphasis has been placed as of late on conserving such fuels through improved design of equipment utilizing them and/or improving the combustion characteristics of the fuels with a view to exploiting their potential energy to a still greater degree. Furnace fuels for space heating and power generation account for a considerable portion of liquid hydrocarbon fuels consumed by the industrial nations of the world. Many of these fuels, especially those of the heavier types, burn only incompletely forming tarry, cokelike deposits which collect on the internal parts of burners. The formation of such deposits not only results in a significant loss of energy-producing material but requires their periodic removal, the frequency of which is proportionate to the rate of accumulation of the deposits. In utility and industrial power plants, the frequency and duration of furnace down-time occasioned by the excessive accumulation of combustion deposits in the fuel burner equipment can be directly translated into higher costs for all energy users. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a liquid hydrocarbon furnace fuel having significantly improved combustion characteristics is provided by the addition to said fuel of from about 1.0×10 -6  to about 1.0×10 -3  parts by weight thereof of at least one isomer of dinitrotoluene. The presence of dinitrotoluene in furance fuel in accordance with this invention has been found to exert a catalyst-like effect upon combustion of the fuel such that in known and conventional burner equipment, fuel combustion takes place with very little of the formation of tarry and cokelike deposits associated with the furnace fuels heretofore in use. 
     It is an additional feature of the invention herein to further enhance the reduction combustion deposit formation by further including in the furnace fuel at least one metal acetylacetonate. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The combustion characteristics of any of the known and conventional liquid furance fuels can be significantly improved by the addition of dinitrotoluene in accordance with this invention. Table I below sets forth some average physical and chemical properties of furnace fuels in accordance with U.S. government specification, Fuel Oil, Burner, VV-F-815. 
     
                                           TABLE I__________________________________________________________________________                Water                    Carbon                and Residue Distillation                Sedi-                    on 10%  temperatures, °F.Grade of fuel oil        Flash            Pour                ment,                    resid-                         Ash                            10%                               90%                                  EndGrade        point,            point,                %   uum, %                         %  point                               point                                  pointNo. Description        °F.            °F.                Max Max  Max                            Max                               Max                                  Max__________________________________________________________________________2   Distillate oil        100  5  0.10                    0.33 . . .                            . . .                               675                                  . . .    for general pur-        or    pose domestic        legal    heating for use    in burners not    requiring No. 14   Oil for burner        130 20  0.50                    . . .                         0.10                            . . .                               . . .                                  . . .    installations        or    not equipped        legal    with preheating    facilities5   Residual-type        130 . . .                1.00                    . . .                         0.10                            . . .                               . . .                                  . . .    oil for  or    burner   legal    installations    equipped with    preheating    facilities6   Oil for use in        150 . . .                2.00                    . . .                         . . .                            . . .                               . . .                                  . . .    burners equipped        or    with preheaters        legal    permitting a    high-viscosity    fuel__________________________________________________________________________        Viscosity        SayboltGrade of fuel oil        Universal              Furol Kinematic centistokes                                GravityGrade        at 100° F.              at 122° F.                    At 100° F.                          At 122° F.                                °APINo. Description        Max           Min              Max                 Min                    Max                       Min                          Max                             Min                                Min__________________________________________________________________________2   Distillate oil         40           . . .              . . .                 . . .                     4.3                       . . .                          . . .                             . . .                                26    for general pur-    pose domestic    heating for use    in burners not    requiring No. 14   Oil for burner        125            45              . . .                 . . .                    26.4                        5.8    installations    not equipped    with preheating    facilities5   Residual-type        . . .           150               40                 . . .                    . . .                       32.1                           81    oil for    burner    installations    equipped with    preheating    facilities6   Oil for use in        . . .           . . .              300                 45 . . .                       . . .                          638                             92    burners equipped    with preheaters    permitting a    high-viscosity    fuel__________________________________________________________________________ 
    
     Any of the dinitrotoluene isomers set forth in Table II below can be used herein, singly or in admixture: 
     
                       TABLE II______________________________________dinitrotolueneisomer         melting point °C.______________________________________2,4-dinitrotoluene          712,3-dinitrotoluene          632,5-dinitrotoluene          482,6-dinitrotoluene          663,4-dinitrotoluene          593,5-dinitrotoluene          92______________________________________ 
    
     For the sake of economy and convenience, it is preferred to employ the most commonly available isomer, 2,4-dinitrotoluene, which is commerce, is frequently supplied in admixture with a minor amount of 2,6-dinitrotoluene, the latter occurring in the manufacture of the former. In the present invention, a commercially available 80:20 weight mixture of the 2,4 and 2,6 isomers which melts at approximately 56° C. has been found to provide entirely acceptable results. 
     By themselves, none of the foregoing dinitrotoluene isomers are soluble in furnace fuel and they must therefore be incorporated into the fuel with the aid of a mutual solvent. The choice of mutual solvent is not a critical requirement of the present invention, it only being necessary that the solvent effect the complete dissolution of the dinitrotoluene at its level of concentration in a particular furnace fuel medium. Whether a particular substance is suitable for use as a mutual solvent herein can be readily determined employing standard techniques, i.e., solubility testing. Among the mutual solvents which can be advantageously used for this purpose, alone or in admixture, are dimethylformamide, halogenated hydrocarbons such as ortho-dichlorobenzene, trichloropropane and methylene chloride, cyclic ethers such as tetrahydrofuran and dioxolane, tricresyl phosphate, and the like. In general, the minimum amount of mutual solvent which results in complete dissolution of the selected isomer or isomer mixture in a given furnace fuel is preferred. Concentrations of isomer in the foregoing solvents ranging from about 5 to about 25 weight percent isomer are usually suitable. 
     An amount of dinitrotolune isomer/mutual solvent solution is added to the furnace fuel to provide a final concentration of isomer in the fuel of from about 1.0×10 -6  to about 1.0×10 -3  parts by weight and preferably from about 1.5×10 -6  to about 1.0×10 -5  parts by weight. At levels significantly below 1.0×10 -6  parts by weight of furnace fuel, the dinitrotoluene isomer will usually be present in the fuel in too small an amount to provide a noticeably improved effect on combustion performance. While amounts of dinitrotoluene in excess of 1.0×10 -3  parts by weight of fuel are usually effective, they confer no particular advantage over the lesser concentrations and considerations of economy militate against their use. 
     If desired, the dinitrotoluene/mutual solvent solution can be introduced into a small quantity of furnace fuel to provide an additive concentrate and this concentrate can thereafter be combined with a larger quantity of furnace fuel to provide the fuel of this invention. 
     By way of example, a concentrate of dinitrotoluene/mutual solvent solution in no. 2 heating oil can be prepared as follows. 
     
         ______________________________________Component          Amount (weight ounces)______________________________________80:20 weight mixture of              482,4-dinitrotoluene and2,6-dinitrotoluenedimethylformamide  64ortho-dichlorobenzene              64methylene chloride 64tricresyl phosphate               8no. 2 heating oil  53.3 gallons              55 gallons (approx.)______________________________________ 
    
     The above formulation can be admixed with liquid hydrocarbon furnace fuel at a level of from about 1 gallon additive to about 5,000 gallons fuel, and preferably, from about 1 gallon additive to about 4,000 gallons fuel. 
     In accordance with a further embodiment of the present invention, the combustion characteristics of a furnace fuel containing from about 1.0×10 -6  to about 1.0×10 -3  parts by weight of at least one isomer of dinitrotoluene is further improved by adding to said fuel, a combustion deposit inhibiting amount of at least one metal acetylacetonate. The useful metal acetylacetonates are in themselves well known compounds (viz. U.S. Pat. No. 2,086,775 (1936)) and are preferably selected from among the metal derivatives of the beta diketones. The metal moieties of such compounds can be advantageously selected from the group consisting of cobalt, nickel, manganese, iron, copper, uranium, molybdenum, vanadium, zirconium, beryllium, platinum, palladium, thorium, chromium, aluminum and the rare earth metals. Beta diketones useful in the preparation of the metal acetyl acetonates can be represented by the structural formula: 
     
         R.sub.1 --CO--CHR.sub.2 --COR.sub.3 
    
     wherein R 1  and R 3  are hydrocarbon radicals which may carry halogen atoms as substituents, and R 2  is a hydrocarbon radical or a hydrogen atom. Specific beta diketones include acetylacetone, which is preferred, benzoylacetone and their alkyl aralkyl or aryl homologs. Useful metal acetylacetonates which can be used herein with good results include, singly or in admixture: nickel propionylacetonate, cobaltous propionylacetonate, cobaltic acetylacetonate, ferric acetylacetonate, cerous propionylacetonate, thorium acetylacetonate, zirconium acetylacetonate, chromic acetylacetonate, aluminum acetylacetonate, and the like. The metal acetylacetonates herein are generally quite effective when employed within the same ranges of concentration as the dinitrotoluene. It is preferred to incorporate from about 5.0×10 -6  to about 1.0×10 -5  parts by weight of metal acetylacetonate part by weight of fuel. If soluble in furnace fuel, the metal acetylacetonate can be incorporated directly therein but more usually, the metal acetylacetonate will be dissolved in one or a mixture of mutual solvents, together with the dinitrotoluene isomer, optionally with one or more detergents, and the resulting solution will be mixed with a minor quantity of base fuel to form an additive concentrate just as in the case of dinitrotoluene alone, supra. 
     In accordance with this invention, the following additive formulation, employed at a level of 1 gallon per 4,000 gallons of no. 2 heating oil can be employed with good results. 
     
         ______________________________________Component          Amount (weight ounces)______________________________________ferric acetylacetonate              30zirconium acetylacetonate              4aluminum acetylacetonate              4cobaltic acetylacetonate              4chromic acetylacetonate              4ortho-dichlorobenzene              56dimethylformamide  56dimethylsulfoxide  7toluene            56butyl cellosolve   56methylene chloride 12880:20 mixture of 2,4-dinitrotoluene              48and 2,6-dinitrotoluenetricresyl phosphate              8Witconate 1840 (sulfonate fatty              2acid of Witco Chemical Corp.)triethylamine      7Class 2 diesel oil 51      gallons              55      gallons (approx.)______________________________________