US3272605A - Fuel oils - Google Patents

Description

United States Patent ()ffice 3,272,6fl5 Patented Sept. 13, 1966 3,272,605 FUEL OILS Henry A. Ambrose, Penn Township, Allegheny County,

Pa, assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed May 18, 1951, Ser. No. 227,108 6 tilaims. (Cl. 44-51) This invention relates to fuel oils, and more particularly it is concerned with preventing the corrosion occurring in furnaces, boilers, gas turbines and the like employing certain residual type oils derived from petroleum as fuel.

It has been observed that when a residual type fuel oil containing substantial amounts of vanadium is burned in furnaces, boilers and gas turbines, the ash resulting from combustion of the fuel oil is highly corrosive to materials at elevated temperatures and attacks such parts as boiler tubes, hangers, turbine blades, etc. These effects are particularly noticeable in gas turbines and therefore militate against the use of what would otherwise be a cheap and desirable fuel for this purpose.

The corrosive nature of an ash obtained upon the combustion of a residual type fuel oil is due to its vanadium oxide content. Vanadium oxide (V which is formed on combustion of a fuel oil containing vanadium compounds, vigorously attacks various metals, their alloys, and other materials at the elevated temperatures encountered in combustion, the rate of attack becoming progressively more severe as the temperature is increased. The ash formed upon combustion of a fuel oil containing substantial amounts of vanadium is a hard adherent material which forms deposits on the parts affected and corrosively reacts with them. At the high temperature encountered in combustion, it is believed that the vanadium oxide in the ash reacts with the parts corrosively affected to form vanadates.

The problem with which this invention is concerned is the corrosion of materials at elevated temperatures by the hot ash resulting from the combustion of a vanadiumcontaining residual type fuel oil. This is to be distinguished from the type of corrosion occurring at atmospheric or somewhat elevated temperatures, generally in the presence of air and moisture. Under such conditions, a vanadium oxide containing ash has no significant corrosive effect. The corrosion problem dealt with herein may therefore properly be termed a problem of hot corrosion.

It is an object of this invention to retard the corrosion obtained upon combustion of a fuel oil yielding an ash containing substantial amounts of vanadium oxide.

It is a further object of this invention so to act upon the vanadium constituents of a fuel oil normally yielding a corrosive vanadium-containing ash as to enable the use of such fuel oil in furnaces, boilers, gas turbines and the like without excessive corrosion.

These and other objects are achieved by the present in vention wherein I provide a fuel oil composition comprising a major amount of a residual fuel oil yielding a corrosive vanadium-containing ash upon combustion, and a minor amount, sufiicient to retard the corrosiveness of said ash, of a metal-containing organic compound selected from the group consisting of oil-soluble and oil-dispersible metal salts of an acidic organic compound, the metal of said metal salts being selected from the group consisting of the metals of Group I and calcium.

I have found that the hot corrosiveness of an ash containing vanadium oxide can be substantially inhibited by the addition of the oil-soluble or oil-dispersible metalcontaining organic compounds referred to. While I do not desire to be bound by any theory as to the action taking place, it is my present belief that the metal-containing organic compounds of my invention react during combustion of the fuel oil with the vanadium component in the fuel oil ash to form a stable vanadium compound which is not decomposed to vanadium oxide under the conditions of combustion of the fuel oil. It is my further belief that the reaction of the metal-containing organic compound with the vanadium component of the fuel takes place prior to the time any substantial amount of vanadium oxide ash comes into contact with the parts of the equipment otherwise corrosively affected. In any event, I have demonstrated that the addition of the above identified metal-containing organic compounds to a residual type petroleum fuel oil normally yielding a corrosive vanadium-containing ash completely changes the character of the ash from a hard adherent deposit to a light, loose and powdery material which can easily be blown out by the combustion draft in a turbine, furnace or boiler, or which falls to the floor of a furnace or boiler. I have also demonstrated that the addition of such metalcontaining organic compounds eliminates or materially retards the corrosion normally obtained from the ash of a residual type fuel oil containing substantial amounts of vanadium.

The oil-soluble or oil-dispersible metal-containing organic compounds of my invention are themselves well known in the art. As has been indicated, the metal-containing organic compounds of my invention include the oil-soluble and oil-dispersible metal salts of the common oil-soluble acidic organic compounds, such as those having a carboxy, sulfo, hydroxy, mercapto or carbamyl group.

Representative examples of the metal-containing organic compounds of my invention are the oil-soluble and oil-dispersible metal salts of fatty acids, e.g., valeric, caproic, oleic, palmitic, stearic, linoleic, tall oil, etc.; the oil-soluble petroleum sulfonic acids; petroleum naphthenic acids; long chain alkyl sulfuric acids, e.g., lauryl sulfuric acid; rosin and hydrogenated rosin; alkyl phenols, e.g., iso-octyl phenol, t-butyl phenol, etc.; alkyl phenol sulfides, e.g., bis(iso-octyl phenol) monosulfide, bis(t-butyl phenol) disulfide, etc.; oil-soluble phenol-formaldehyde resins, e.g., the Amberols such as t-butyl phenol-formaldehyde resin; and the like.

From the foregoing, it will be apparent to those skilled in the art that the additives of my invention can be formed from any acidic organic compound that forms oilsoluble or oil-dispersible metal compounds. Since metal salts or soaps of such acidic organic compounds as the fatty acids, naphthenic acids, and sulfonic acids are relatively cheap and readily available, these are preferred materials.

The requirement for oil-solubility or dispersibility of the metal containing organic compounds of my invention is to insure uniform blending of the compounds throughout the body of the fuel oil to which they are added. It would obviously be undesirable for the bulk of the additive to be concentrated in a small portion of the fuel oil While the remainder of the oil contained little or no additive. The requirement for uniform blending of the metal-containing organic compounds is therefore satisfied by the use of oil-soluble or oil dispersible compounds. As will be apparent to those skilled in the art, the distinction between oil-solubility and oil-dispersibility is a matter of degree, it being sufficient for the purposes of this invention that a fairly stable dispersion of the dispersible additives be obtained, or that redispersion of a settled additive can be easily accomplished by simple agitation.

The metals which are employed in the metal-containing organic compound of my invention are selected from the metals of Group I of the Periodic Table according to Mendeleef and calcium. The list of metals that are included therefore are lithium, sodium, potassium and calcium.

The type of fuel oil to which the corrosion retarding agents of my invention are added is exemplified by No. 5, No. 6 and Bunker C fuel oils which contain a sufficient amount of vanadium to form a corrosive ash upon combustion. These are residual type fuel oils obtained from petroleum by methods known to the art. However, not all residual fuel oils exhibit the hot corrosiveness described herein. Some residual type fuel oils contain such minor amounts of vanadium, or stated in another way, the ash of such fuel oils contains such minor amounts of vanadium oxide, that the problem of hot corrosion of the materials with which the hot ash comes into contact is not encountered. My invention, therefore, is concerned with retarding the corrosion exhibited by a residual type fuel oil normally yielding a corrosive vanadiumcontaining ash upon combustion. Such fuel oils need not be completely of the residual type; the invention also contemplates residual fuel oils diluted with distillate fuel oil stocks, provided that the fuel oil so obtained exhibits the corrosion characteristics described herein. It should be understood that distillate fuel oils themselves contain either no vanadium or such small amounts as to present no problem of hot corrosion.

In general, minor amounts of the metal-containing organic compound additives of my invention, sufiicient to retard the corrosiveness of the vanadium-containing ash, are added to the corrosion inducing fuel oils in accordance with my invention. Since the vanadium content of various residual type fuel oils varies from negligible amounts (such fuel oils do not exhibit a hot corrosion problem and are not encompassed by this invention) to additive to employ will vary, depending not only on the specific vanadium content of the fuel oil, but on the molecular weight of the metal-containing organic compound. Obviously, a smaller weight of the metal-containing organic compound will be required for a low molecular weight metal combined with a low molecular weight organic compound, than for a high molecular weight metal combined with a high molecular weight organic compound. From the foregoing and the simple, routine corrosion tests described hereafter, the amounts of metal-containing organic compound required to be added to a corrosive vanadium-containing fuel oil to retard corrosion will be obvious to those skilled in the art. Since such amounts of additive are generally small, sometimes as little as 0.05 percent by weight of the fuel oil, it is desirable to make concentrated solutions or dispersions of them in a naphtha, kerosine or gas oil for convenience in compounding with the corrosive vanadium-containing fuel oil.

The following examples are further illustrative of the invention.

EXAMPLE 1 Fifty grams portions of a No. 6 fuel oil with and without the metal additives described herein were placed in 4-inch diameter stainless steel dishes. The fuel oil employed had the following inspection data:

Gravity, A.P.I 12.3 Viscosity, S.U.S.:

210 F. 178 Flash, F. 320 Fire, F. 405 Carbon residue, percent 11.8 Precipitation number, B.S. & W. Trace Sulfur, percent 3.45 Ash, percent 0.025 Vanadium, percent 0.0075

The dishes were then heated until the fire temperature of the oil was reached and the oil ignited. After the oil had burned itself out, the dishes containing the residue from this ignition were placed in a mutfie furnace and heated for 8 hours at the desired test temperature. Tests were made at 700 F., 1000 F. and 1350 F. The results of these tests are shown in the following table.

r QQCAIO 00010 0000 Do. Loose and light powdery residue. Loose and very light powdery residue. 1, 350 Do.

As will be Observed from the foregoing table, it was found that, at the end of eight hours heating at all the test temperatures, the character of the ash obtained from the fuel oil containing the calcium was strikingly different from that obtained from the uncompounded fuel oil. The ash obtained when the additive was present was light, loose and powdery; in a condition in which it could easily be blown out by the combustion draft in a turbine. On the contrary, the ash from the uncompounded fuel oil was hard and adhered firmly to the walls of the it will be obvious that the exact weight percentage of stainless steel dish.

5 EXAMPLE 2.

Experiments similar to those set forth in the preceding example were carried out using a test temperature of 1350 F, but varying the amount and nature of the adsalts of refined grades of tall oil, refined to improve color and odor. The calcium salt of Staybelite is the calcium salt of hydrogenated rosin. The calcium salt of Amberol is the calcium salt of a condensation product of alkyl phenols and formaldehyde in which there is an average of about five phenol nuclei per molecule.

ditive. The results are shown in the following table. 5

Table 11 Percent Additive by Wt. of Nature of Ash or Residue Fuel Oil None Hardhresidue adhering to walls of steel Calcium Naphthenate 0.02 Very slight improvement over base oil.

D 0. Loose powdery residue.

Do 0.1 Loose, light powdery residue.

Do 0.2 Do. Calcium Pctronate. 0.02 No change over base oil.

Do 0.05 Loose powdery residue.

Do 0.2 Loose, light, powdery residue. Calcium salt of Opoi 0.2 Loose powdery residue. Calcium salt of Facoil GN 0.2 Do. Calcium salt of Facoil CB 0.2 Do. Calcium salt of Staybehte 0.2 Do. Calcium salt of AmberoL. 0.2 Do.

EXAMPLE 3 In order to demonstrate the corrosiveness of a residual fuel oil ash containing high amounts of vanadium and to determine the corrosion inhibiting effects of the additives of this invention the following tests were performed. An Eastern Venezuela No. 6 fuel oil was fired at 1600 F. to obtain an ash having a vanadium content, determined by analysis, of 36.75 percent. Half sections of Stellite blades from Westinghouse gas turbines and strips of inch thick 19*9 DL stainless steel sheet were cleaned by sand blasting in order to insure clean and uniform surfaces. The sections of Stellite turbine blades and the strips of alloy steel were then roasted in contact with the vanadium-containing ash for seven days in an electrically heated muflie furnace held at 1350 F. At the end of seven days heating the specimens were allowed to cool and were then examined for corrosion. Tests were made on the ash alone and on ash containing one of the additive compounds disclosed herein. In order to insure complete removal of all oragnic or carboniferous material, the ash was roasted for two hours at 1350 F. prior to being employed in the tests. In cases where an additive compound was also employed, it was added to the ash and well mixed prior to this preliminary heating. The additives were used in the amounts indicated.

The foregoing examples clearly show the beneficial effects of the additives of my invention on fuel oils yielding a corrosive vanadium-containing ash. Since it is difficult, if not impossible, to reduce the ash content of residual fuel oils without an uneconomic increase in cost, the use of the minor amounts of additive in accordance with my invention provides a solution to the problem of hot corrosion which is not only simple but is economically feasible.

Resort may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended claims.

What I claim is:

1. A fuel oil composition comprising a major amount of a residual fuel oil yielding a corrosive vanadiumcontaining ash upon combustion and a minor amount, sufficient to retard the corrosiveness of said ash, of a metal-containing organic compound selected from the group consisting of oil-soluble and oil-dispersible metal salts of an acidic organic compound, the metal of said metal salts being selected from the group consisting of the metals of Group I and calcium.

2. A composition according to claim 1 wherein said metal is sodium.

3. A composition according to claim 1 wherein said metal is calcium.

Table III Percent by Additive Wt. of Test Metal Appearance of Metal after Test Mixture None Stellit Very badly corroded. Tip corroded away. Rest of strip had heavy deposit of corrosion products. Calcium Naphthenate 56 d0 Light corrosion but great improvement over uninhibited ash. Do 80 d0 'Iarnished but no visual corrosion. Calcium Petronate 81 o Tarnished but no visual pitting. Non e 19-9 DL Stainless steeL. Very badly corroded with deep pits. Calcium Naphthenate Tarnished but no visual pitting. Calcium Suli'onate (Calcium Petroleum Do.

Sulfonate). Sodium Sulfonate (Sodium Petroleum Do.

Sulfonate; Petronate).

As will be seen from the above table, the Stellite and 19-9 DL strips in the uninhibited ash were very badly corroded, while the same strips roasted in the inhibited ash showed little corrosion, if any.

In the foregoing tables, the Petronate referred to at the end of Table III is the sodium salt of oil-soluble petroleum sulfonic acids. Calcium Petronate is an oilsoluble petroleum sulfonic acid. The calcium salt of Opoil is the calcium salt of crude tall oil. The calcium salts of Facoil GN and Facoil CB are the calcium 4. In a gas turbine plant in which a fuel oil containing vanadium is burned and which includes heat resisting metallic parts exposed to hot combustion gases and liable to be corroded by the corrosive vanadium-containing ash resulting from the combustion of said oil, the method of reducing said corrosion which comprises introducing into said plant a metal-containing organic compound selected from the group consisting of oil-soluble and oildispersible metal salts of an acidic organic compound,

3,272,605 7 8 the metal of said metal salts being selected from the group OTHER REFERENCES consisting of the metalspf Group calcium. Dunstan et al.: The Science of Petroleum, Oxford g g}: p i gi f fig y y i g i g g ii g gg gfil Univ. Press, New York, 1938, vol. 2, pages 1054-55. Symposium on Corrosion of Materials at Elevated cium. 5

References Cited by the Examiner Temperatures, Special Technlcal Publicat on No. 108 of the American Society for Testing Materials, 1916 Race UNITED STATES PATENTS St., Philadelphia 3, Pa., pp. 59 to 103; copyright 1951.

1,770,181 7/1930 Morrell 4451 2,141,848 12/ 1938 Adams 44 68 DANIEL E. WYMAN, Primary Examiner. 2 230 642 2/1941 Fischer et a1 4458 P. M. NASH, JULIUS GREENWALD, GEORGE A. 2,533,303 12/1950 Watkms GORECKI, F. L. MATTESON, w. KAUFMAN, F. CROWLEY, S. STAHL, M. LIEBMAN, Y. M. FOREIGN PATENTS HARRIS, Assistant Examiners. 561,328 5/1944 Great Britain. 15

Claims (1)

1. A FUEL OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A RESIDUAL FUEL OIL YIELDING A CORROSIVE VANADIUMCONTAINING ASH UPON COMBUSTION AND MINOR AMOUNT, SUFFICIENT TO RETARD THE CORROSIVENESS OF SAID ASH, OF A METAL-CONTAINING ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF OIL-SOLUBLE AND OIL-DISPERSIBLE METAL SALTS OF AN ACIDIC ORGANIC COMPOUND, THE METAL OF SAID METAL SALTS BEING SELECTED FROM THE GROUP CONSISTING OF THE METALS OF GROUP I AND CALCIUM.