US2845338A

US2845338A - Fuel additive for removing and inhibiting fireside deposits

Info

Publication number: US2845338A
Application number: US386383A
Authority: US
Inventors: John W Ryznar; Thompson Harris
Original assignee: National Aluminate Corp
Current assignee: ChampionX LLC
Priority date: 1953-10-15
Filing date: 1953-10-15
Publication date: 1958-07-29
Anticipated expiration: 1975-07-29

Description

United States Patent O FUEL ADDITIVE FOR REMDVING AND INHIBIT- ING FIRESIDE DEPOSITS John W. Ryznar, La'Grange Park,'and-Harris1l1ompson, Downers Grove, Ill., assignorsto- National Aluminate Corporation, Chicago,"Ill., acorporationof Delaware :No Drawing. Application October 15, 1953 v Serial No. 386,383

24 Claims. (Cl. 44-5) -Th is inventionrclates to afuel additive ,for. removing and lnhibiting the formation of firesidedeposits, more particularly'fireside deposits in.oil. and coal firedxfurnaces.

. The invention also relates to a method of .burning.,.car-

bonaceous fuels.

It is well recognized that the burning of many: fuels 7 causes troublesome fireside-deposits, such as: slag,which are difficult to remove.

This is. particularly .true..in.-.the case of fuel oils and the formation of. suchtdeposits is also prevalent with other carbonaceous. fuels,..such.as

- coal.

The exact cause of theformation offireside. deposits is not clearly understood and their removal presents .a, diffi- -cult problem. Most of the troublesome deposits. are .mamly Inorganic compositions such as slag and, their formation is undoubtedly. due to:inorganic:contaminants r in the'fuel. These contaminants are present insuch small :amounts and in such chemical combinations thatmethods for their removal from the fuel: are difiic ult. toapply cconomicallyon a commercial scale.

One of the objects of the present inventionis to .pro-

. videznew and improved fuel additives .for .dirninutionof 1 :fireside deposits which can be added-readily to the fuel or directly to the furnace.

. A further object of the invention is to provide a method of preventing or minimizing fireside deposits. ofmainly :inorganie compositions, such=as slag, in. the radiant,

1 superheater, economizer, or. air. preheater ,section'. of a wboiler. furnace or in similar .locations inothertypes of furnaces by feeding with the fuel. orninto the.combustion chamber a chemical composition.

Another object of the invention is to .provide a method of the. typedescribed inwhich the quantity, of the chemi- ..cal composition required is relatively small.

An additional object of the invention is to provide a method of the type described which iseffective in removing old slag deposits or in reducing them to a form in which they are readily removed by blowingthem-with .air.

Another object of the'invention' is toprovidea newand improved method of reducing-corrosionin-economizer and air preheater sections of a boiler furnace,

. Amore specific object ofthe"invention"is- -toprovide a chemical composition which can'be suitably blended with ..-pulverized -coal andwhen so blendedis effective in. preventing orminimizing theformation of fireside depositions without interfering with thecombustion of the. coal. 'A further specific object is to provide a chemical composition which'can' be dispersed in fuel oil and whenso dispersed is effective in preventing or diminishing-the formation of-fireside deposits withoutinterferingx with the combustion of the fuel oil. Other objects willaappear hereinafter. v I

ln accordance with the invention it has been found-that theoccurrence of fireside deposits of mainly inorganic cbmpositions, such as slags, in the radiant, superheater,

economizer or air preheater of a boiler furnace ori 2,845,338 Eatented July 29, 1958 similar locations in other types offurnaces areprevented -or greatly reduced by feeding with the fuel or;into ..the

combustion chamber a compound from the. group consist- .ing of magnesium oxide and compounds decomposing to preferred components of the composition are magnesiu'm oxide in the form of a very finely divided, highgnelting point powder and copper oxychloride. {Ilie'setwo components when blended together form an Qexcellerit additive for pulverized coal.

Where the composition is to be radded to a fpeljoil, it isdesirable to include a dispersingagenbgfld for this purpose in the practice of the invention it is preferred to .use magnesium. stearate which isnot lonly effective, a dispersing agent but alsodecomposes during combustion to magnesium oxide. The compositionswhich are togbe limited by the following examples in whichjth added to fuel oil are preferably.prepared initially as a blend of finely divided solid components, for example, magnesium oxide, copper oxychloride and magnesium stearate. The blend is then prefcrablwt lade intoja slurry in a suitable liquid carrier, for example, the f uel oil used in the furnace or a fuel oil compatible with the fuel oil used in the furnace. The resultant slurry is then fed insmall amounts either to thecombustion zone :or to l the fuel oil which is to housed in thecombustion.

The invention will be furtherillustrated but islnot quantit are given in parts by weight unless,otherwise indicated.

Example I To evaluate a typical composition of this ii yention a test was conducted using a boiler ,located jin a llarge capacity of 150,000 pounds of steam jpe pressure of 740 pounds per square inch ,and 1a superheater temperature of 750 F. Under normal conjditions it -operates at rated temperature and pressuiresywith a load manufacturing concern. The particularfboiler was gcliosen for. several reasons, the most important; one, being the troublesome nature of the slag deposits f ormedin the furnace and superheater areas. 'Ihisboilerwas ra d a t a ith a of 130,000 pounds of steam per hour. Thefuel may, be

, pulverized coal as its main source;

days there is a limited supply. ofnaturaLgasav on Sundays natural gas is generally the only no either pulverizedcoal or gas with .lthe four firing burners being capable of utilizing either coal or natural gas.

During the winter months thisjboiler primarily uses f fuel buton satur- Natural gas is almost exclusively burned duriiiglfthe sum mermonths. Slag formations present in theboileiiprior to thetest were caused by the combustion of pulverized coil. Accordingly, .it was decided to conduct 'altest of three months duration that would be; concluded in the spring, at which time the boiler would be shut down for its annual inspection and cleaningpperations .The condition of the boiler befo'rethe test was 'm ost unsatisfactory with large accumulations of slag having been deposited on the various, surfaces of the furna ce and the superheater. In particular, ther ew as a' la'rge -islag deposit that nearly covered the entirerear furnace wall.

' This .deposit was thick, hard and brittle in nature. Similarly, there were heavy incrustations onthe 'superheater tubes and slag screen tubes. These deposits for theimost .partwere difiicult to remove during priors'hutdown's. .The deposit on the rear furnace wall was at onetime so thick and bulky it fell onto the floor tubes necessitating a costly shutdown and repairs. I

3 The treatment used in this test was a formulation that consisted of 96% by weight of commercial magnesium oxide and 4% by weight of commercial copper oxychloride (CuCl .3Cu(OH) or 3CuO.CuCl .3H O). This material was fed directly into the furnace by blowing it through a piece of pipe located directly adjacent to one of the burners, thus allowing a uniform mixing of the treatment with the pulverized coal. Dosage was on the basis of the amount of pulverized coal burned during a given period of time and was computed to be /3 pound of treatment per ton of coal consumed. it was found that it was not necessary to constantly feed the composition to the coal but three 20 to 30 minute dosings per day gave adequate results.

At the end of the three month test period a thorough inspection of the furnace and superheater sections of the boiler was made and the observed results were excellent. The large deposit on the rear furnace wall was substantially reduced in size with but a small residuum of slage remaining. Some of the previously slagged areas were completely freed of the troublesome deposits with only a gray powdery coating remaining. The roof tubes previously covered with deposits, were freed of slag. The most satisfactory results were found in the superheater tubes. Nearly all the slag had been dissipated and the small amounts remaining were negligible. The usual cleaning operations that were required in the past, to rid the superheater of the deposits, were not necessary and the superheater tubes were ready to resume their normal operations.

Example 11 This example illustrates the application of the invention to a fuel oil. In this case the boiler had a capacity of 250,000 pounds of steam per hour with an operational pressure of 900 pounds per square inch and a rated superheater temperature of 900 F. The furnace was lit and put on a load of 200,000 pounds of steam per hour.

The fuel used was mostly asphalt containing some No. 6 fuel oil. Analyses of the asphalt used as fuel showed an ash content of 0.059% by weight and of the No. 6 fuel oil an ash content of 0.076% by weight.

The quantity of fuel used at a load of 200,000 pounds of steam per hour was approximately 12,250 pounds of fuel per hour or 294,000 pounds of fuel per day. 7

Before the operation began deposits were noted in both the furnace and super-heater areas of the boiler. These deposits were particularly heavy on the rear furnace wall tubes opposite the four burners. A section approximately 400 square feet in area was covered with black friable material that extended A to inch from the surface of the tubes. Similar type deposits were attached to the side wall tubes at the elevation of the lower burners. The remainder of the furnace wall tubes were covered with a light powdery coating which was easily removed. There were also dense non-porous deposits which covered the lower half of the slag screen tubes. The trailing edges of the first bank of superheater tubes were covered with a A; to /2 inch thick deposit, which was similar in nature to the slag adhering to the rear furnace wall tubes opposite the burners.

The existing deposits were removed from the furnace and superheater tubes so that the bare metal surfaces were again exposed. The boiler was fired at a low rate and was brought up to load within about a 36 hour period. During this relatively short time small deposits had begun to form on the slag screen tubes. As the boiler reached normal conditions the treatment, hereinafter described, was begun and within four hours a fine protective dust had formed on nearly all of the tubes. 1

The chemical composition employed for the purpose of the invention was prepared by intimately blending together 91% by weight of commercial magnesium oxide, 4% by weight of commercial-copper oxychloride and by weight of magnesium stearate.

The resultant powdered blend was made into a slurry by mixing it with the oil used for burning in the furnace to produce a composition containing about 5% by weight of the blend and by weight of the fuel oil. The slurry was prepared in a separate tank and the slurry tank was insulated and provided with a steam coil for maintaining the temperature at approximately 180 F. The slurry was pumpedfrom the slurry tank by a positive displacement pump into the oil going to the burners at a point beyond where the fuel oil was recirculated to the storage tank. The slurry tank was also equipped with a stirrer to keep the slurry liquid in continuous agitation.

The chemical composition prepared as above described was introduced into the fuel at a dosage rate of pounds per day.

At the end of seven days the furnace walls, slag screen and superheater tubes were examined and found to have only a film of dust adhering thereto. No slag was found in any section.

The initial dosage of 100 pounds per day of the additive was continued for 15 days and then reduced to 50 pounds per day. After an additional operational period of 7 days, the furnace walls were inspected and showed no sign of deposit other than a light colored dust film. 'Ihe slag screen was clean except for a few pieces of slag on the tubes nearest the back wall. The superheater tubes were clean.

After an additional operational period of 6 days the dosage of the additive was reduced from 50 pounds per day to 25 pounds per day. After a further operational period of 8 days the fireside of the furnace and the superheater were inspected and it was observed that the tubes in both sections contained only a dust film.

The operation was continued at a dosage of 25 pounds per day of the additive for an additional period of 19 days when the fireside of the furnace and superheater were again observed. The furnace had some slag on the rear wall opposite the burners about the size of buttons. The superheater showed no fireside deposit. The slag screen had small amounts of fireside deposits on the top closest to the rear wall.

The operation was continued at a dosage of 25 pounds of the additive per day and 26 days later was observed again. The boiler had button-shaped deposits on the rear wall, thin and about inch in diameter. The leading edge of the slag screen tubes showed a slight accumulation but generally the boiler was in clean condition. The slight deposits were powdery and had little bonding strength with the tubes.

In the foregoing examples the commercial magnesium oxide used had the following composition and physical characteristics Percent SiO 0.9

F8 0 w n 0.2 CaO 1.5 MgO 93.9 Ignition loss 3.0 Through 325 mesh screen 98.0

The commercial copper oxychloride used in the foregoing examples had the following composition and physical characteristics:

have been obtained by employing about 100 parts by Weight, expressed as Mg, of themagnesium compound permillion parts of coal, and abo,ut 4 parts by weight, expressed as Cu, of a copper. compound per million parts of coal. In the treatment of a fuel oil for instance, as disclosed in Example II, the quantity of the magnesium compound, expressed as Mg, is about 50 parts per million parts of fuel oil andthe quantity of the copper compound,

expressed as Cu, is about 2'parts per million parts of fuel oil.

The dosage range required for the purpose of the inventionmay also vary depending upon service conditions but with.:compositions of the type disclosediinExample I is usuallywithin the range of /6' pound to 1 poundper ton of coal burned, and with compositions of the type employed in Example II isjusually Within therange of A1 pound to .2 pounds per thousand gallons of fuel,oil. The optimum amounts are readily determined by usage. Once the minimum effective amount has been deterrnined for a particular installation the amount can be increased in order to ascertainthe optimum amount for the best over.- all operation. An increase beyond the optimum amount is not advantageous fromthe cost standpoint. In all cases minute amounts of the additive are used and the-quantities .of additive are only a fraction of a percentiofthe Weight of the carbonaceous fuel. I

In general, the quantity of the magnesium compound, expressedas Mg, will predominate over the quantity of the copper compound, expressed as Cu, and the preferred weight ratio ofthe respective compounds, expressed as MgzCu, is approximately 25:1 but can vary within a relatively wide range, for example -5 :1 to 35:1.

Although magnesium oxide is the preferredtype of magnesium compound employed in the practice of the invention, it will. be understood that the magnesium oxide may be replaced whollyor in part by other magnesium compounds, either organic or inorganic, which decompose under the combustion conditions to form magnesium oxide. for this purpose are magnesium hydroxide, magnesium carbonate .and magesium salts of fatty acids, including magnesium octoate (the magnesium salt of 2-ethyl hexanoic acid), magnesium .lau-rate, magnesium stearate, magnesium linoleate, magnesium oleate, and the like.

Likewise, although copperoxych'loride is preferably employed in the. practice of the invention other compounds of metals which are effective in lowering the ignition temperature ofcarbon can be employed in chemically equivalent amounts. Examples of other copper compounds which can be employed arecopper naphthenate, cuprous chloride, cupricv chloride, copper oleate, copper linoleate, copper stearate, copper octoate, copper salts of mahogany acids and copper salts of petroleum naphthenic acids. Where-the composition is used as a fueloil additive, good results are obtained by employing as the copper component a coppersalt of 2-ethyl hexanoicacid'or a copper salt of another branched chain acyclic aliphatic carboxylic acid containing 5 to 12 carbon atoms as disclosed in U. S. Patent 2,622,671".

The; amounts of thecopper compounds required-in the practice of the invention are less than the effective amounts normally required when the same copper'compounds are used, as additives to fuel oil to prevent or reduce the formation of soot. In most instances these quantities are 20% to 50% less than the effective quantitiesfor preventing or reducing the formation of soot. Since many copper compounds tendto produce sludgingin fuel oil, the,

Among thecompounds which may be mentioned G the invention reduces thetendency towards sludging and makes it possible to use copper compounds that would' have undesirable .side effects if they were employed in larger amounts as soot inhibitors.

The inorganic compounds of both magnesium and copper have the advantage that they do not introduce deleterious byproducts into the fuel oil or coal to which they v are added.

Chemically equivalent quantities of cobalt compounds may be substituted Wholly or in part for the corresponding copper compounds in thev practice of the invention. Examples of suitable cobalt compounds are cobalt naphthenate, cobalt oxychloride, cobaltic chloride, cobaltous chloride, cobalt tallate, the cobalt salt of 2-ethyl hexanoic acid,

cobalt oleate, cobalt 'stearate, cobalt linoleate, cobalt.

lin-olenate and the cobalt salts of branched chain acyclic aliphatic carboxylic acids having 5 to 12 carbonatomsani containing a carboxylgroupattached to the -carbon atom other than the central carbon atom of the longest hydro carbon chain.

The. corresponding compounds of manganese, iron and manganese octoate, iron octoate, calcium octoate and the homologues thereof.

Where the slag inhibiting compositions are to be add d,

to fuel oil it may be desirable in some. instances to include reducers of the polymerizationof the oil, for example, nitrobenzene, the nitrophenols and alpha, or, be,ta-.

naphthol. Likewise, sludge inhibitors may be incorporated with the concentrates, as, for example, 'tricresyl phosphate, hydroquinone, phenylenediamine and its derivatives, and the phosphorous-organic 'sulfur compounds de; rived by the reaction of par-affin or aliphatic alcoholic substances and phosphorus pentasulfide.

The invention also contemplates that. the additive com-. positions. be prepared in the form of briquettes containing an oil soluble binder such as, for example, parafiin heavy fueloils .and/ or microcrystalline wax with or without dispersants, such as, for instance, magnesium stearate, magnesium'laurate and the like. Similarly, the com-,. positions of the invention can be incorporated in coal briquettes where the finer coal particles are bound to:. gether by a suitable binder such as an asphaltic binderin which the compositions of the invention are dispersed.

The term carbonaceous fuel is employed herein to describe fuels in which carbon is the principal constituent, and is intended to cover'both powdered fuels suchas coal. and petroleum fuel oils which are primarily hydrocarbons.

The term fuel oil is intendedto include combustible. oils which are liquid or are capable of being liquefied: when preheated. Thus, many of the residual oils are, semi-solid in nature and areheated to temperaturesof say F. in order to increase theirfluidity before they are used as burning fuels. It will be understood that the term fuel-oil includes these semi-solid types of residual oils as well as the liquid types of fuel oils.

While the invention is not limited to any theory, itis believed that the combined action .of the active essential ingredients of the slag inhibiting additive compositionrin, some wayinterferes with or altersv the formation of sul; fates of a typewhich would ordinarily produce adherent slag deposits. That the result-is due to a combined or, synergistic effect of the active essential components is indicated by the fact that neither magnesium oxide, alone nor copper oxychloride alone will produce the desired result. I

The invention is especially advantageous in making it possible to operate large steam boiler plants in power. generating stations, refineries and otherindustrial and" municipal locations for long periods of time without the necessity for discontinuing the operation to remove fireside deposits. Heretofore slag deposits in steam generating units have presented a very troublesome problem. The problem has been especially acute where fuel oils have been employed. These slag deposits are not only difficult to remove but the outage or discontinuance of the steam generating operation during the period of removal of the slag deposits represents a great economic loss. The slag deposits reduce the efficiency of the operation and tend to decrease the life of the equipment.

The practice of the present invention reduces or prevents splash sticking of low melting ash particles and reduces or prevents sulfatic deposits. The practice of the invention also reduces adherent acidic deposits and provides a neutralizing action in economizer and air preheater sections of boiler furnaces whereby corrosion is reduced. The compositions employed in the practice of the invention are readily prepared in a form in which they can be fed to the combustion chamber or to the fuel while maintaining freedom from feeding difficulties in chemical vats, pumps, distribution lines and in fuel burners.

By making it possible to operate steam generating units over much longer periods of time, the invention greatly assists in alleviating the difficulties encountered in the operation of steam generating units. The invention also makes it possible to remove old slag deposits that are not removable by ordinary cleaning methods.

The invention is hereby claimed as follows:

1. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of a compound of a metal selected from the group consisting of copper, cobalt, manganese, iron and calcium which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decom posing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said compound of a metal, expressed as said metal, being within the range of :1 to 35 :1, and said additive composition being effective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

2. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of a compound of copper which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said copper compound, expresed as Cu, being within the range of 5:1 to 35:1 and said additive composition being efiective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

3. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of a compound of copper which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said copper compound, expressed as Cu, being approximately 25:1, said additive composition being effective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

4. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of a compound of cobalt which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said cobalt compound, expressed as Co, being within the range of 5:1 to 35:1 and said additive composition being effective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

5. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of copper oxychloride and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to copper oxychloride, expressed as Cu, being within the range of 5:1 to 35:1 and said additive composition being efiective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

6. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of copper oxychloride and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium com pound, expressed as Mg, to copper oxychloride, expressed as Cu, being approximately 25:1 and said additive composition being effective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

7. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of copper oxychloride and magnesium oxide, the weight ratio of magnesium oxide, expresesd as Mg, to copper oxychloride, expressed as Cu, being within the range of 5 :1 to 35 :1 and said additive composition being effective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

8. An additive composition for a carbonaceous fuel consisting essentially of an intimate mixture of copper oxychloride and magnesium oxide, the weight ratio of magnesium oxide, expressed as Mg, to copper oxychloride, expressed as Cu, being approximately 25:1 and said additive composition being effective to inhibit slag formation when a fraction of a percent thereof by weight is added to a carbonaceous fuel.

9. A fuel additive consisting essentially of an intimate mixture of about 96% by weight commercial magnesium oxide and about 4% by weight of commercial copper oxychloride.

10. A fuel additive consisting essentially of an intimate mixture of approximately 91% by weight commercial magnesium oxide, 5% by weight magnesium stearate and 4% by weight commercial copper oxychloride.

11. A method of burning a carbonaceous fuel which comprises burning said fuel in the presence of a fraction of a percent by weight of said fuel of a composition of a compound of a metal selected from the group consisting of copper, cobalt, manganese, iron and calcium which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said compound of a metal, expressed as said metal, being within the range of 5 :1 to 35 :1, the combined quantity of said first named metal compound and said magnesium compound being effective to inhibit slag formation.

12. A method of removing and of inhibiting the formation of fireside deposits in the burning of a carbonaceous fuel which comprises burning said fuel in the presence of a fraction of a percent by weight of said fuel of a composition of a copper compound which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide, under combustion conditions, the weighttratiot of said magnesium compound, expressed as Mg, tosaid copper compound, expressed as Cu, being within the range, of :1 to 35:1, the combined quantity of said'copper compound and said magnesium compound being effective to inhibit slag formation.

13. A method'of removing and of inhibiting the formation of fireside deposits in the burning of a carbonaceous fuel which comprises burning said fuel in the presence of a fraction of a percent by weight of said fuel of an intimate mixture of a copper compound which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said copper compound, expressed as Cu, being within the range of 5 :1 to 35:1, the quantity of said copper compound, expressed as Cu, being at least 2 parts per million parts by weight of fuel and the quantity of said magnesium compound, expressed as Mg, being at least 50 parts per million parts by weight of said fuel.

14. A method which comprises incorporating with pulverized coal a quantity of an intimate mixture of a copper compound which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, said quantity containing approximately 4 parts, expressed as Cu, of said copper compound per million parts by weight of said coal, and approximately 100 parts, expressed as Mg, of said magnesium compound per million parts by weight of said coal, and burning said coal.

15. A method which comprises incorporating with a fuel oil a quantity of an intimate mixture of a copper compound which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, said quantity containing approximately 2 parts, expressed as Cu, of said copper compound per million parts by weight of said fuel oil, and approximately 50 parts, expressed as Mg, of said magnesium compound per million parts by weight of said fuel oil, and burning said fuel oil.

16. A method which comprises incorporating withv pulverized coal a quantity of an intimate mixture consisting essentially of approximately 96% by weight commercial magnesium oxide and 4% by weight commercial copper oxychloride, said quantity being between /6 pound of said mixture and 1 pound of said mixture per ton of said coal, and burning said coal.

17. A method which comprises incorporating with a fuel oil a quantity of a composition composed of approximately 5% by weight of an intimate blend of approximately 91% by weight commercial magnesium oxide, 4% by weight commercial copper oxychloride and 5% by weight magnesium stearate, said quantity being between fit pound and 2 pounds per thousand gallons of fuel oil, and burning the resultant composition.

18. A carbonaceous fuel containing an intimate mixture of a compound of a metal selected from the group consisting of copper, cobalt, manganese, iron and calcium which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said compound of a metal, expressed as said metal, being within the range of 5 :1 to 35 1, the combined quantity of said first named metal compound and said magnesium compound being a 10 fraction of a percent by weight: of said fuel suificient to inhibit slag formationwhen said fuel is burned.

19. A carbonaceous fuel containing an intimate mixture of a compound of a metal selected from the group consisting ofL'coppeI, cobalt manganese, iron and calcium which is ,efiectivein lowering the ignition temperature of carbon andwamagnesium compound from the group c0nsisting..of magnesium oxide and magnesium compoundsldecomposing to magnesium oxide under combustion; conditions,. the .quantity. of saidjfirst named metal compound, expressed as Cu, being at least 2 parts per million parts by weight of said fuel and the quantity of said magnesium compound, expressed as Mg, being at least 50 parts per million parts by weight of said fuel.

20. Pulverized coal containing a quantity of an intimate mixture of a copper compound which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the quantity of said copper compound, expressed as Cu, being at least 4 parts per million parts by weight of said coal and the quantity of said magnesium compound, expressed as Mg, being at least parts per million parts by weight of said coal.

21. A fuel oil containing an intimate mixture of a copper compound which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the quantity of said copper compound, expressed as Cu, being at least 2 parts per million parts by weight of said fuel oil and the quantity of said magnesium compound, expressed as Mg, being at least 50 parts per million parts by weight of said fuel oil.

22. A method for inhibiting slag formation on elements contacted by the combustion gases from burning a carbonaceous fuel which comprises burning said fuel while providing on said elements a protective coat resulting from exposure to said gases of a composition of a compound of a metal selected from the group consisting of copper, cobalt, manganese, iron and calcium which is effective in lowering the ignition temperature of carbon and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said compound of a metal, expressed as said metal, being within the range of 5:1 to 35:1.

23. A method for inhibiting slag formation on elements contacted by the combustion gases from burning pound, expressed as Mg, to said copper halide, expressed as Cu, being within the range of 5:1 to 35:1.

24. A method for inhibiting slag formation on elements contacted by the combustion gases from burning a carbonaceous fuel which comprises burning said fuel while providing on said elements a protective coat resulting from exposure to said gases of a composition of a cobalt halide, and a magnesium compound from the group consisting of magnesium oxide and magnesium compounds decomposing to magnesium oxide under combustion conditions, the weight ratio of said magnesium compound, expressed as Mg, to said cobalt halide, ex-

pressed as Co, being within the range of 5:1 to 35:1.

(References on following page) UNITED STATES PATENTS Boggs Sept. 14, 1909 Tropsch Feb. 21, 1939 Bartleson et a1. July 17, 1951 Roque Sept. 4, 1951 Chenicek Sept. 9, 1952 Johnson Dec. 23, 1952 Taylor et a1. Feb. 12, 1957 OTHER REFERENCES Reference Book of Inorganic Chemistry, Latimer and Hildebrand, 3rd ed., 1951, The MacMillan 00., N. Y., pages 62-64.

Removal of Soot from Furnaces and Flues by the use of Salts or Compounds, U. S. Dept. of Commerce, Bur. of Mines Bulletin 360, 1932 (pp. 21-26).

Claims

1. AN ADDITIVE COMPOSITION FOR A CARBONACEOUS FUEL CONSISTING ESSENTIALLY OF AN INTIMATE MIXTURE OF A COMPOUND OF A METAL SELECTED FROM THE GROUP CONSISTING OF COPPER, COBALT, MANGANESE, IRON AND CALCIUM WHICH IS EFFECTIVE IN LOWERING THE IGNITION TEMPERATURE OF CARBON AND A MAGNESIUM COMPOUND FROM THE GROUP CONSISTING OF MAGNESIUM OXIDE AND MAGNESIUM COMPOUNDS DECOMPOSING TO MAGNESIUM OXIDE UNDER COMBUSTION CONDITIONS, THE WEIGHT RATIO OF SAID MAGNESIUM COMPOUND, EXPRESSED AS MG, TO SAID COMPOUND OF A METAL, EXPRESSED AS SAID METAL, BEING WITHIN THE RANGE OF 5:1 TO 35:1, AND SAID ADDITIVE COMPOSITION BEING EFFECTIVE TO INHIBIT SLAG FORMATION WHEN A FRACTION OF A PERCENT THEREOF BY WEIGHT IS ADDED TO A CARBONACEOUS FUEL.