US2943925A - Residual fuel oils - Google Patents

Description

July 5, Y1960 H. A. AMBRosE RESIDUAL FUEL oILs Filed lAug 27, 1956 United States Patent RESIDUAL FUEL OILS Henry A. Ambrose, Penn Township, Allegheny County,

Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Aug. 27, 1956, Ser. No. 606,413

9 Claims. (Cl. 44-66) This invention relates to vanadium-containing petroleum fuels. More particularly, it is concerned with rendering non-corrosive those residual fuels which contain such an amount of vanadium as normally to yield a corrosive vanadium-containing ash upon combustion.

This application is a continuation-in-part of my prior copencling application Serial No. 227,108, tiled May 18,

It has been observed that when a residual type fuel oil containing substantial amounts of vanadium is burned infurnaces, boilers and gas turbines, the ash resulting from combustion of the fuel oil is highly corrosive to materials of construction at elevated temperatures and attacks such parts as boiler tubes, hangers, turbine blades, and the like. These effects are particularly noticeable in gas turbines. Large gas turbines show promise of becoming an important type of industrial prime mover. However, economic considerations based on the eiciency of the gas turbine dictate the use of a fuel for this purpose which yis cheaper than a distillate diesel fuel; otherwise, other forms of power such as diesel engines become competitive with gas turbines.

One of the main problems arising in the use of residual fuel oils in gas turbines is the corrosiveness induced by those residual fuels containing suicient amounts of vanadium to cause corrosion problems. Where no vanadium is present or the amount of vanadium is small, no appreciable corrosion is encountered. While many residual fuel oils as normally obtained in the refinery contain so little vanadium, or none, as to present no corrosion problems, such non-corrosive fuel oils are not a1- Ways available at the point where the oil is to be used. In such instance, the cost of transportation of the noncorrosive oil to the point of use is often prohibitive, and the residual oil loses its competitive advantage. These factors appear to militate against the extensive use of residual fuel oils for gas turbines. Aside from corrosion, the formation of deposits upon the burning of a residual fuel in a gas turbine may result in unbalance of the turbine blades, clogging of openings and reducing thermal efliciency of the turbine.

Substantially identical problems are encountered when using a solid residual petroleum fuel containing substantial amounts of vanadium. These fuels are petroleum residues obtained by known methods of petroleum rening such as deep vacuum reduction of asphaltic crudes to obtain solid residues, visbreaking of liquid distillation bottoms followed by distillation to obtain solid residues, coking of liquid distillation bottoms, and the like. The solid residues thus obtained are known variously as petroleum pitches or cokes and find use as fuels. Since the vanadium content of the original crude oil tends to concentrate in the residual fractions, and since the processing yof the residual fractions to solid residues results in further concentration of the vanadium in the solid residues, the vanadium corrosion problem tends to be intensified cin `using the solid residues as fuel.

The vanadium-containing ash present in the hot ilue HCS gas obtained from the burning of a residual fuel containing `substantial `arnounts of vanaditun compounds causes catastrophic corrosion of the turbine blades yand other metal parts in a gas turbine. The corrosive nature of the ash appears to be due to its vanadium oxide content. Certain inorganic compounds of vanadium, such as vanadium oxide (V205), which are formed on combustion of a residual fuel oil containing vanadium compounds', vigorously attack various metals, their alloys, and other materials at the elevated temperatures encountered in the combustion gases, the rate of attack becoming progressively more severe as the temperature is increased. The vanadium-containing ash forms deposits on the parts affected `and corrosively reacts with them. It is a hard, adherent material when cooled to ordinary temperatures.

It is to be noted that the corrosion of materials at high temperatures by the hot ash resulting from the combustion of a vanadium-containing residual fuel is to be distinguished from the type of corrosion occurring at atmospherfic or .slightly elevated temperatures, generally in the presence of air and moisture. Under the latter conditions, an ash containing vanadium oxide has no signiiicant corrosive eifect. The corrosion problem described herein may therefore properly be termed a problem of hot corrosion.

The economic factors involved preclude any extensive treatment of vanadium-containing residual fuels Vto remove the vanadium therefrom or to mitigate -its effects. The vanadium compounds in residual oils are not removed by centrifuging or by the conventional chemical refining treatments.

In my prior copending application Serial No. 227,108, previously referred to, I have shown that 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 Groups I, II, IH, IV, VI, VII and VIII of the Periodic Table of Mendeleef, can be employed in minor amounts in a residual fuel oil yielding `a corrosive vanadium-containing ash upon combustion to retard the corrosiveness of the ash.

I have now diswvered that not all of the metal salts 1of my copending application are of equal effectiveness and that manganese salts of an acidic organic compound show outstanding superiority in retarding, and in fact, substantially preventing corrosion. The present invention therefore relates to residual petroleum fuels containing vanadium in an amount sufficient to yield a corrosive vanadium-containing ash upon combustion, and containing, in a minor amount suicient to retard the corrosiveness of the ash, an oil-soluble or oil-dispersible manganese salt of an acidic organic compound.

The single gure of the drawing shows an apparatus for testing the corrosiveness of residual fuel oil compo- ,sitions.

The type of residual fuel oils to which my invention is directed 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. For example, residual fuel oils are obtained as liquid residua by the conventional distillation of total crudes, by atmospheric and vacuum reduction of total crudes, by the thermal cracking of topped crudes, by visbreaking heavy petroleum residua, and other conventional treatments of heavy petroleum oils. Residua thus obtained are sometimes diluted with distillate fuel oil stocks, known as cutter stocks, and the invention also includes residual fuel oils so obtained, provided that such oils contain suicient vanadium normally t'o exhibit the corrosion characteristics described herein. It should be understood that distillate fuel oils themselves contain either no vanadium or such small amounts as Patented July 5, 1960 from comercial' residual' 'fuel oilsusually ranges fromA about 0.02 to 0.2 percent by Weight. The vanadium pentoxide. (V205)k content of such ashes .ranges from zero' 'to trace amounts upv to about `5"percent nby Weight for low vanadium stocks, exhibiting Vno significant Vanadiurncorrosion problem, to as. muchv as 85` percent 'by Weight forsome of the high vanadium stocks, exhibiting severe corrosion.

The 'type of vanadium-'containing'solid residual fuels towhich the invention is directed is exemplified bythe coke' obtained in known manner by the delayed thermal coking .or uidized coking of Vtopped or reduced crudeY oils" and bythe pitches obtained in known manner by the deep vacuum reduction of asphaltic crudes to obtain solid residues. These materials have ash` contents of the order ofV 0.18 'percent Aby weight, more or less, and contain corrosive amounts of .vanadium rwhen prepared from stocks containing substantial amounts of Vanadium. Aty'p'ical Vpitch exhibitingv corrosive characteristics upon combustion had a softening point of 347 F. and a vanadiurnontent, as vanadium, of 578 parts per million."

As disclosed in -my prior copending application, the manganese salts .of the invention can be prepared from any acidic Yorg'anicrcompound that forms oil-soluble or oilldis'persible metal compounds. Representative examplesof the salts of the invention include oil-soluble Yand Vthenate. Alternatively, particles Vof the solid residual fuels'inrquestion Vcan be -coated orimpregnated lwith-a concentrated naphtha solution of the manganese salt in the proportion required in relation to the vanadium content, and the aggregate then dried to obtain solid fuel particles impregnated with the additive. As still another alternative, particularly withra pitch which is withdrawn in molten form from the processing vessel, the additive can be mixed with Athe-molten pitch'and lthe mixture alloweduto solidiiyaftenwhichf-itis ground to thedesired.- size.: ofcourse, .in the casev of 'either liquid or-solidre-Y sidualf-.fue1s`,.theradditive: can; be .separately fed into the burner as a concentrated solution, -preferably. in admixture with the fuel;

As has been statedfthe manganese-salts are employed in a small amount with respect to the vanadium-containing residual fuel, sufficient to retard the corrosiveness of the ash. Ordinarily, to -achieve practical corrosion retarda'tion, iti'is 'desirable yto employ such an vamount/of additive asit,oA resulti in at least about 3 atom weights -of the vmanganese of the Vsalt per-atom -weight of the vana` dium'in the fuel oil; Preferably,- the atom weight ratio, Mn:V, Yis"6:^1,V although larger amounts 'of thesaltfs'can be employed. Since V'on a -wei'ght basis' in relation'to the oil-dispersible manganese salts of (l) the fatty acids of Y at :least..5 carbonA atoms, eg., valerie, caproic, Z-ethylhexanonid'oleic, palmitic,vstearic, linoleic, tall oil, and the like; -(2)V oil-soluble alkylaryl sulfonic acids, e.g., oil'soluble petroleumY sulfonic acids and dodecylbenzenesulfonic acid; (3) long chain Yalkylsulfuric acids, e.g., lauryl sulfuric acid; (4) petroleum naphthenic acids; (5.) rorsin andhydrogenated rosin; (6) alkyl phenols, e.g., isooctyl .phenoLt-butylphenol and the like; (7) alkylphenol suldes,'e.g., bis(isooctyl phenol)monosulde, bis (t'tbutylphenol) disulfide, and the like; and (8) oilsoluble phenolformaldehyde resins, e.g., the Amberols, suchas t-butylphenol-formaldehyde resin, and the like. Since-the'salts or soaps of such acidic organic comounds as the fatty acids, naphthenic acids and rosins are readily available ror can easily be prepared, these are preferred materials.Y Particularly preferred are manganese naphthenate, manganese oleate, manganese tallate (tall oil soaps) and manganese rosinate.

The` requirement for oil-solubility or dispersibility-of the manganese salts of the-invention is to insureauniform blendingA thereof when employed with a residual-fuel oil. It would `obviously be undesirable for the bulk of theadditive -tobeconcentrated in a small portion of the fuel Aoil. while the remainder of the oil contained-,little or no additive. The requirementV for uniformy blending of the manganese salts :is ltherefore satisl'ed by the use of oil-soluble or oil-dispersible compounds. As willbe .apparent to those skilled inthe art, the distinction beftween oil-solubility and oil-dispersibility is a matterof degree, vit being suicient forpresent purposes that a yfairly stabledispersion of the dispersible additives be obtained, or that redispersion of a settled additive can beeasily'accomplished by simple agitation.

With .the solid residual fuels, incorporation of the oilsolubleor oil-dispersible manganese salts is accomplished in several ways. The salts can be suspended or dissolved in the liquid vanadium-containing residual stocks or crude oilstocks from which the solid residual fuels of theinvention are derived, and the mixture can then ybe subjectedqto the refining process which will produce-*fthe solid fuel; For example, in the production of Va vpitch by the deep vacuum reduction of an asphalticrcrudefoil, manganese naphthenate is slurried with the oil inproportionV to the vanadium content thereof, and the whole sub# iccted 4to deep Vacuum'reduction to jobtain a pitch con'- taining uniformly dispersed thereiuthe4 manganesenaph YIn. a -gram portion of a No. residual fuel oil having an-.ash c ontentof 0.055 .percent by Weight and a vanadium content of `0.015 percent byY Weight, there is dispersedA 0.5 percent by weight of manganese naphthenate. The'atom ratio of .manganese to vanadium in the dispersion is .2:71.

Example 2 With a residual fuel oil having anash content of 0.037 percent by weight and containing 166 parts per. million of vanadium, uniformly blend 0.9 percent by Weight of a. 6: percent. concentrate of manganese naphthenate in naphtha. This yields. an atom ratio, Mn:V, Vof about 3:1.

Example 3 r'Ifo'. the .same residual 'fuelV oil of Example 2, .add 1.8 percent by weight vof the .same concentrate of manganese naphthenatein naphtha. Thisl yields a Mn:V:atom ratio of about 6:1.'V l 'Example 4 A fuell 'oil composition accordingZ to the inventionis pre- Y pared byfblending 2.23 percent by weight of a. concentrate in naphltha of .manganese linoleate (Mn content 4.35 percent) -withiafresidual fuel oil having anash'content of 0.04 percentbyweightand a vanadium contentv of r lparts=per million. An atom ratio, Mn:V, of 5:'1 is obtained' Example 5 Y Another composition according to the invention is prepared byj blending manganese tallate in a vanadium-containing, residual fuel oil to obtain a Mnz-V atom rratio Aof 4.5 :.1.`

v Example 6 Y Melt2a.;solid"petroleum"pitch obtainedfrom the deep vacuumvlreduction' of :anv asphaltie crude. This'` pitch .has -asofteningnpoint of347. anda vanadium content of `57.8'fparts perimilliomi While .the pitchi is in molten :form add: andruniformly blendtherein 3.1 percent byweight :of the'manganese-naphthenate concentrate of Example. 'Upon cooling.V and solidication, grind the mixture to about -150V mesh. The resulting fuel'has an atom ratio, VMui-V, of "about 3:-1.

Similar compositions are 'prepared using manganese bctoate (2-ethylhexanoate), stearate, oc'tylphenolate, as well as the other acidic organic compounds disclosed herein.

In order to demonstrate the effectiveness of the manganese salts of the invention, the composition of Example 1 is placed in a 4 diameter 18-8 stainless steel dish and the dish is heated until the fire temperature of the oil is reached'and the oil ignites. After the oil has burned itself out, the dish containing the residue from the ignition is placed in a mufe furnace and heated for 8 hours'at l350 'F. At the end of this time, the dish is allowed to cool slowly and the nature of lthe ash is determined by inspection. An identical residual fuel oil without the manganese naphthenate in run for purposes of compari- In order to test the eifectiveness of the additives of this invention under conditions of burning residual fuels in a gas turbine, the apparatus shown in the drawing is ernployed. As shown in the drawing, the residual oil water tests is introduced through line 10 into a heating coil 11 disposed in a tank of water 12 maintained at such temperature that the incoming fuel is preheated to a temperature of approximately 212 F. From the heating coil 11 the preheated oil is passed into an atomizing head designated generally as 13. The preheated oil passes through a passageway 14 into a nozzle 15 which consists of a #26 hypodermic needle of approximately 0.008 inch I.D. and 0.018 inch O D. The tip of the nozzle is ground square and allowed to project slightly through an orifice 16 of approximately 0.020 inch diameter. The orifice is supplied with 65 p.s.i.g. air for atomization of the fuel into the combustion chamber 21. The air is introduced through line 17, preheat coil 18 in tank 12, and air passageways 19 and 20 in the atomizing head 13. lThe combustion chamber 21 is made up of two concentric cylinders 22 and 23, respectively, welded to two end plates 24 and 25. Cylinder 22 has a diameter of 2 inches and cylinder 23 has a diameter of 3 inches; the length of the cylinders between the end plates is 81/2 inches. End plate 24 has a central opening 26 into which the atomizing head is insented. End plate 25 has a one (l) inch opening 27 covered by a baffle plate 28 mounted in front of it to prevent direct blast of tlame on the test specimen 29. Opening 27 in end plate 25 discharges into a smaller cylinder 30 having a diameter of 11/2 inches and a length of 6 inches. 'Ihe specimen 29 is mounted near Ithe downstream end of the cylinder approximately 1% inches from the outlet thereof. Combustion air is introduced by means of air inlet 31 into the annulus between cylinders 22 and 23, thereby preheating 'the combustion air, and then through three pairs of 3/16 inch tangential air inlets 32 in the inner cylinder 22. The rst pair of air inlets are spaced 1A inch from end plate 24; the second pair inch from the rst; and the third 3 inches from the second. The additional heating required to bring the combustion products to test temperature is supplied by an electric heating coil `33a surrounding the outer cylinder 23. The entire combustion assembly is surrounded by suitable insulation 34. lThe test specimen 29 is a metal disc one inch in diameter by 0.125 inch thick, with a hole in the center by means of which the specimen is attached fto a tube 35 containing thermocouples. The specimen and tube assembly are mounted on a suitable stand 36.

In conducting a test in the above-described apparatus, a Weighted metal specimen is exposed to the combustion products of a residual fuel oil, the specimen being maintained at a selected test temperature of 1350, 1450 oi'l 1550 F. by the heat of the combustion products. The test is usually run for a period of hours with the rate of fuel feed being 1/2 pound per hour and the rate of atomizing air feed being 2 pounds per hour. The com- |bustion `air entering through air inlet 31, is fed at 25 pounds per hour. At the end of the test run the specimen is reweighed to determine the Weight of deposits and is then descaled with a conventional alkaline descaling salt in molten condition at 475 C. After descaling, the speci-- men is dipped in 6 N hydrochloric =acid containing a conventional pickling inhibitor, and is then washed, dried and weighed. The loss in weight of the specimen after descaling is the corrosion loss.

A test is conducted in the apparatus just described using a 25-20 stainless steel as the test specimen. The test is run for 100 hours at a temperature of 1450 F. under the conditions described above. The oil employed is a residual fuel oil having an ash content of 0.037 percent and containing 166 parts per million of vanadium. Comparartive tests are run with the oil containing no additive and with the compositions of Examples 2. and 3.

In order to demonstrate the superior effectiveness of the manganese additives of the invention, comparative tests are run under identical conditions in the apparatus described herein with corrosive vanadium-containing residual oils containing manganese naphthenate, calcium naphthenate and oil-soluble barium petroleum sulfonate as corrosion retarding additives. The test specimens are 25-20 stainless steel, and as described above, the test is run for 100 hours at a temperature of 1450 F. Each additive, i.e., the manganese naphthenate, calcium naphthenate and barium petroleum sulfonate, is employed in an amount suicient to give an identical atom weight ratio of metal to the vanadium of 6:1. 'Ihe results obtained are shown in the following table:

The above results clearly show the superiority of the manganese salts of the invention to other corrosion retarding additives. Corrosion has been reduced to a negligible amount, and deposit formation has been minimized.

Typical analyses of the stainless steels employed in the above description are shown in the following table in percent by weight:

Cr 18. 91 25 N1 8. 62 20 C. 0. 12 o. 08 Mn 0.62 2. 0 Si 0. 60 1. 5 S 0. 03 P 0. 04 Fe Balance Balance Y wflhe; above examples fcleanly Ydemonstate -the u effective- 3. The composition of claml, wherein the fuel is a 25 solid residuapetrde'um'fueL rosins.

nmcnfainingfashupon combustian and an amo' "untiiof i'n'gne's'e Salt' suieient `to7 yield from `about 3 to about 6 tom weights of manganese per atom weightof vanaaf; 10 urn in said oilysaid fs'alt lbeing selectedfrom 'theclasseom s'istng of oil-soluble- 'and /oil-dis'persible 'manganese 15 saltis 'manganesenaphthenatm v 7. The composition of claim 5', wherein the manganese' salt'ismangazuese' tallace.

8. The 'composition of claim 5, Wherein'themanganese slt is manganese'fosinate.

2Q 9". 'Ihe'oomposition of claim V5*,-wherein1theinrl'amgariese salt manganese'linoleate; Y

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,943,925 July 5, 1960 Henry A; Ambrose It is herebjr certified that error appears in the-printed specification of the above l'I 1um`oerec1 patent requiring correction and that the said Letters Patent should read as corrected below.;

Column 3, line 38, for "(t-tbutylphenoD" read (tbutylphenol) column 5i line 14, for Mn" read is line 27, for "water" read under --9 Signed and sealed this 20th day of December 1960.a

(SEAL) Attest:

KARL H. AXLINE Attesting Ocer ROBERT C. WATSON Commissioner of Patents

Claims (1)

1. A FUEL COMPOSITION COMPRISING A MAJOR AMOUNT OF A RESIDUAL PETROLEUM FUEL YIELDING A CORROSIVE VANADIUMCONTAINING ASH UPON COMBUSTION, AND A SMALL AMOUN OF A SALT SELECTED FROM THE CLASS CONSISTING OF OIL-SOLUBLE AND OIL-DISPERSIBLE MANGANESE SALTS OF AN ACIDIC ORGANIC COMPOUND SUFFICIENT TO RETARD THE CORROSIVENESS OF SAID ASH.

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