US3078662A - Non-corrosive vanadiumcontaining fuels - Google Patents

Description

Feb. 26, 1963 A. G. RoccHlNl ETAL NoN-coRaosIvE vANADIUM-coNTAINING FUELS Filed Feb. 24. 1959 INVENTORS HlBE RT G. ROCCH/N/ By CHARLES E. TRAUTHHN v Arrows/Y Y a l? WN V States Patent @ffice 3,078,662 Patented Feb. 26, 1963 3,678,662 NQN-CORROSIVE VANADIUM- CONTAINNG FUELS Albert G. Rocchini, Oaicmont, and Charles E. Trautman,

Cheswiclr, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Feb. 24, 1959, Ser. No. 795,036 7 Claims. (Cl. eil-39.02)

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-vanadinni-containing ash upon combustion.

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 l.to materials of construction atelevated temperatures and attacks such parts as boiler tubes, hangers, turbine blades and the like. ingas turbines. Large gas turbines show promise of becoming an important type of industrial prime mover.-

However, economic considerations based on the eciency of, the gas turbinedictate the use of. a fuel for this purpose which is cheaper than a distillate diesel fuel; otherwise, other forms of power suchA as'diesel engines .becomes competitive withy gas turbines. a w

. One of the main problems arising inthe use :of `residual fuel `oils in gas turbines is the corrosiveness` induced by those residual fuels containing sufrlcientamounts` of vanadium -to` cause corrosion.

ciabl'eI corrosion is encountered. While many'residual fuel oils asnormally obtained in the renery'contain so`little vanadium,or none, as'to present Anofcorrosion problems, such non-corrosive fuel oils are not always available at the pointrwhe're the oil is to be used. In such instance, the cost of transportation of-the non-corrosive oilto the point of usel is often prohibitive, and` theresidual'oil losesits competitive advantage. These factors appear to militate against the extensive use ofI Aside from corroresidual fuel oils for gas turbines. l sion; the formation of deposits upon the burning'of a residual fuel in a gas turbine mayresult in unbalance ing such as deep vacuum reduction v-ofasphaltic crudes to obtain solid residues, visbreaking of :liquid distillation' bottoms followed by distillation to obtain. solid residues,

colcing ofyli'quid distillation bottoms and the like. fThe.

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 concentratey in the residual fractions, and' since the processing of the residual fractions to solid residues results inI further concentrationof the yanadium in the solid residues,

the vanadium` corrosion problem tends to-beintensilied inusingthe solidresidues as fuel.k

The vanadium-containing ash present inthe 4hot lluef gas obtained from, theburning of a residual fuel-,con-

taining substantial amounts of vanadiur'ri compoundscauses catastrophic. corrosion ofthe turbine blades and Iother metal parts Ain a gas turbine. The corrosive nature-of the ash appears to be due to its -vanadiu'm oxide content.- -Certain'inorganic compounds of vanadium, such*v as 'vanadiuml oxide (V205), which'vare formedo'n fcom'-v Theseieifects are particularly noticeable v Where vno vanadium `is' present or the amount of vanadium is small, noapprefbustion 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. lThe 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.

lt has already been proposed to employ in corrosive residual fuels small amounts of certain metal compounds to mitigate the vanadium corrosion. Such compounds are of varying effectiveness and it has not always been possible to reduce vanadium induced corrosion to a minimum amount.

It has now been discovered that residual petroleum fuels containing vanadium in an amount sufficient to yield a corrosive vanadium-containing ash upon combustion can be rendered substantially non-corrosive by incorporating therein to form a uniform bled (l) a small amount of a vanadium-free aluminum compound su'icient to, retardjthe corrosiveness of the ash, and (2) a small amount of a vanadium-free alkali metal compound sufiicient' to furtherreduce the corrosiveness of said ash to a minimum.' In they fuel compositions of the invention the coaction `of the two additive compounds is such that the corrosion 'is reducedto'negligible amounts.

VIn the accompanying drawing, thesingle FIGURE shows anfappa'ratusfor testing'thejcorrosivity of residual fuel oil'compositions. y v j l 'y Thetypeef residual fuel cils to which -the invention is directed'is exemplilied by No. 45,'No7 6 and Bunker C fuel oils which contain a suli'cjient' amount of vanadium to form acorrosive ash upon combustion.' These are residual type fuel voils obtained from petroleum by methods` known totheart. For example,`residual1fuel oils are `obtained as liquid residua` by the conventional distillation of total'cru'des, 'by atmospheric and vacuum reduction of total crudes, by thethermal crackingy of topped crude's,y by visbreakingheavypetroleum residua, and other conventional treatments of 'heavy petroleum oils. lesidua'k thus obtained are sometimes diluted with distillate fuel oil stocks, yknown as cutter -`stocks, and theinvention also includes residual fuel oils so obtained, provided that suchboils contain suiiicient 'vanadiumnormally to exhibitE the corrosion characteristics described V herein. It sl'oulilI be luxlderstood that distillatefuel oils themselves contain" either no vanadium yor* such small amounts'- as topresent nop'roblem of corrosion. 'I'hetotal ash from commercial residual fuel'oils usually ranges from about 0 .02to 0.2 percent by' weight; Thevvanadium pentoxide (V205) con` tent of such ashes ranges from -Zeroto trace amounts up' to about 5 percent by Weight for low Vanadium stocks,y ex;y hibitingl no signicant vanadium corrosion problem, toas" much as 8S percent by weight for some ofthe high vana# dium stocks, Y' exhibiting severe corrosion.

*The type of vanadium-containing' solid residual fuels' to.v 1 whichv the inventionis' directed is exemplified by the cokel obtained inknown manner by the rdelayed thermal "cokin'g or fluidi-Zed coking of topped or reduced crude oil'sand bye the pitches obtained in `known manner byl the deep vacu@ um reduction of asphaltic. crudes 'to obtainsolid residues'. v These materials have ash contents'` of the ordert of- 0.218

percent by weight,l more or-'1ess,` andrcontain Ycorrosivei amounts of vanadium when :prepared vfrom stocks-con# taining substantial amounts of vanadium". A typical pitch exhibiting corrosive characteristics uponcombustion had.- 1": a softening point lof1347 F; and arvanadiu'mcontent, as

vanadium,- of 578 parts permillion.

' I`A`ny"alurninum "compound, organic or inorganic,which'`r is" free from vanadium lis used as 'the `aluminumvadditive' of the inventions Similarly, anyforganic vorinorganic vanadium-free alkali metal. compound is employed. The alkali metals include sodium, potassium, lithium, cesium and rubidium; sodium and potassium compounds are referred. Such inorganic alkali metal and aluminum com-- pounds as` the. oxides, hydroxides,v acetates, carbonates, silicates, oxalates, sulfates, nitrates, halides and the like are successfully employed. In4 this` connection, the mixture., of` salts present in seawater, as disclosedV in: our` copending; application Serial No. 654,812, filed April 24,. 1957, now` U .S.. Patent 2,966,029, comprises a suitabley alkali metalA compound. Aluminum oxide isa preferred. inorganic aluminum compound. The organic compounds of 'aluminum and the alkali metals include the oil-soluble and oil-dispersible salts` of acidic, organic compounds such as: (1 the fatty acids, eg., valeric, caproic, 2-ethylhexanoic, oleic, palmitic, stearic linoleic, tall oil, and the like; (2) alkylaryl sulfonic acids,u e.g., oilfsoluble petroleum sulfonic acids and dodecylbenzene sulfonic acid;` (3)A longchain alkylsulfuric` acids, eg., lauryl sulfuric acid; (.Iipetroleum rraphthenic,acids;(5) rosinand-hydrogenatcd` rosin; (6);,alkyl phenols,A e.g., iso-octyl phenol, tbutyl phenolsandthe like;` (7) `alkylphenol t sulfides, e.g.,.bis(iso.`

otyl phenoDmonosulidc, bis(t-butylphenol)disulfide, and the likt?, (8)1hc acids-obtained by theoxidation ofpetroleumwaxesA and, other petroleum fractions;A andi` (9)- oilsoluble phenolfformaldehyde resins, e.g., the; Amberols suchj as;ltfbutylphenobformaldehyde resin, and the; like; Since the: salts or; soapsgofisuch acidicorganiecompounds t the` fatty, acids, naphthenic. acidsandY rosins are rela-` tively inexpensiveandV areeasily prepared,` these are pre-` ferredmaterials for` the, organic additives.-

When employingl in l residual ,fuels the inorganic addi-` tives of the invention, it is desirable to useviinely-diyided,V

materials. However, the; degrceof subdivisiontis notvcritical.l One1 requirement ,for usinga iinely-dividedmaterial.

isbased, upon, the i desirabilityof forming, a fairly stable dispersion or4 susp en sion, of the) additiyesfwhenv blended; with: a., residual fuell oil... Furthermore, the more.A nelyf dividedrnaterials; are moreeificient in forming.v uniform.

blends and 'rendering noncorrosiye the. relatively small amounts of vanadium in.a residualrfuel, whether the fuel .solid ,or-liquid, Theinorganic additives;- are ltherefore;

employed in t a` particle size rangeof less than 215() .micron s,= preferably less than.,5 0 microns. However, where'` the inorganic additiyes, are water-soluble, for example, in Vthe caseoftaluminumsulfate, sodium carbonate, and the like it is not-Y necessary to employ finely-dividedi materials desiredtheadditiyes can bedissolyed nwater. tognform, a more,or less, concentrated solution. andthe watersolution emulsiiied,in .the'fuelA The.- organic. additives of the invention i areoil-solubleA orfoil-dispersible': and are therefore ,readily blendedwithtv residual `:fuels to.,form uniformblends. Since on a weight,

basis. in' relation to the fuel, the'` amounts of the additives are,v small, itlmay be. desirableV tovtpreparev concentrated,

solutions.` or..dispersionsz of thevorganic additives a:

naphtha, kerosene or gas.` oil for. convenience. in. com` pounding;

In the practice of -theL invention with' vanadium-con-` taining residual-fuel-,oils, the'mixture of` additives is uniformly. blended with the oil. This is accomplished by; suspending the nely-divided. dry` additives-in theoil,`

densationiproducts thereof,gglycerol monooleate, and the.

like, which promote the ,stability of :the suspensions or emulsionscan be employed.

In .the 1 practice 'ofrthe invention .with .the ,solid residualY fuels, incorporation of .thexadditives `of the inventionV is.`

accomplished in severalways.' The additives can besuspended, emulsiiiedtor. l dissolved in .the liquid vanadium` containing residual stocksiorcrudeoil stocksifrom which:

the solid residual fuels of the invention are derived, and

the mixture can` then. be subjected to the refiningproceu which will produce the solid, fuel. For example, in the production of a pitch by the deep vacuum reduction of an asphaltic crude oil, the additives or a concentrate thereof are slurried with the oil in proportion to the vanadium content thereof, and the whole subjected to deep vacuum reductionV to obtain a pitch containing the additives uniformly dispersed therein. As stillV another alternative, particularly with a pitchl whichis withdrawn in molten form from the processing vessel, the additives` can be mixed withithe molten pitch and the mixture allowed to solidify afterA which it is ground -to the desired size.

In the` case of either liquid or solid residual fuels, theV additives: can be separately fed into the burnerast concentrated solutions or dispersions. In such a case, ity is preferred to meter the additives into the fuel line just prior to thecombustion zone. In a'gas turbine plant where the heat resisting metallic parts'are'exposedto hot combustion gasessat temperatures of the order ofi1200 F. andabove, the additivestcan be'added separately `fromy the fuel: either prior to` or during combustion itself, or even subsequent' to combustion; However they may specicallycbe addedwhether inadmixture with on separately form` the fuel, the' additives are introduced into said plant upstream ofthetheat resisting metal` parts `to` beprotected from corrosion.

The. aluminum compounds' and-r the alkali metal compoundsare. both employed in1smallcorrosion retarding amounts withrespect,tol'thelfuel, and'insuch amountsl with respect toeachV othery asI to `minimize the corrosive-v ness of the ash. Fortexample, when1 the aluminum com pound` is employed in; an t amountof abou-t4 atomiweights of. aluminum per atom. weight' off vanadium; ordinarily.` an. amount. ofalkali metal: compound yielding about 1 atom.- weight of; alkali metal is" suflcientto reduce' the corrosion to negligible amounts. Althoughlargen amounts :1 of,I theY alkali metal compound can' be; employed;y de;` sired; no additional advantage is usually obtained,A t

The following f examples are: further illustrative= oflfthe# invention;

EXAMPLEI With a .residual fuel oil uniformly blend 0.08 t" percent by weight of aluminum oxide and 0.02percentb`y weightf. of sodium carbonate. Theresidual fuel oil`cmployed"has. tlie` following inspection;

The resulting composition has an atom weight ratio of4 aluminum to vanadium of 4:1 andv an atomweight" ratiov of sodium to vanadium `of 1:1.

EXAMPLE A Il Tothe samexresidualfuel oiljof Example'l,- add andi uniformly blend 0.52' percent byweight of l aluminum.,` sulfate, Al2(SO)3.18H2O, and 0.12 percent by weight fo a solution of sodium petroleum naphthenate in naphtha containing 7 percent by weight of sodium. The resulting composition has an atom weight ratio of' aluminum to vanadium of `4:1 and an atom weight ratio of sodium toA vanadium of 1:1.

` III Meltl-asolid petroleum pitch obtainedjfromthedeepvacuum reduction of auf asphalticlcrude.- This i pitchl basa Lsofteningpoint off347 l?. and 1a vanadium contentl of 578 parts per million. While the pitch is in molten l form, add and uniformly blend therein 0.23 percent by weight lof aluminum oxide and v0.08 percent by weight of sodium sulfate. Upon Icooling and ,solidificatiom grind the mixture to about 150 mesh. The resulting fuel has an atom weightv 'ratio fof aluminum 4to vanadium of aos/see products ofa residual fuel oil, the specimen being maintained at a selected test temperature of, for example, 1350, 1450 or 1550 F. by the heat of the combustion products. The test is usually run for a period of 100 hours with the rateof fuel feed being 1/2 pound per hour 4:;1 and an atom we1ght rat1o of sodium to vanadium of and the rate of atomizln-g an' feed` being 2vpounds per 1`:1'. p hour. The .combustion air entering through air inlet 31 In order vto test the effectiveness of the additives of this is fedr at 25 pounds per bouh Atm@ end of the test 'mml invention under con-ditions v. of burning residual fuels` in the specimen isreweighed to determinethe Weight of de.` a gas turbine, the apparatus shownin the drawing is emposits `and is then descaled with a conventional alkalinez ployed. As shown therein, the residual oil under test is descaling salt in` molten lcondition at 475 C.. After introduced through line 10 into a heating coil 11 disposed ldesc'aling, the specimen is-dippedin-6 N hydrochloric acid in a tank of water 12 maintained at such temperature that containing a conventionalV pickling inhibitor, and isy then. the incoming fuel is preheated to a temperature of apwashed, driedand weighed. The lossl in weight of the proximately 212 F. From the heating coil 11 the pre- 15y specimen after ydescaling is the corrosion loss. u c heated oil is passed into an atomizing head designated gen- Tests are conducted in the apparatus just describedv erally as 13. The preheated oil passes through a passageusing a l257- stainless steel as `the test specimen. The way 14 into a nozzle 1S which consists of a #26 hypotests are run forA 4100 hours at a temperature of 1450"v F. dermic needle of approximately 0.008 inch LD. and 0.018 under the conditions described above. Tests are made` inch `O. D. The tip of the nozzle is ground square and 20. with `the fueloil `composition ofk Example Lwith similar allowed to project slightly through an oritice 16 of apfuel oil compositions but containing only oneof the addi-1 proximately 0.020 inch diameter. yThe oritice is supplied tives in varying proportions, and withthe uncompounded with l55 p.ls.`i.g. air for atomization of the fuel into the residualfuel'A oil of Example I.y The same base -fuel is com-bustion chamber 21. The air is introduced ythrough used inall thetests. The following table shows the cor-v line 17,` preheat coil 10 iny tank 12, and air passageways 2.5. rosion and deposits obtained. l 1

Table 1 i Atom Wt. Corrosion, Deposits Radio, Wt. Loss oi Fuel Additive Specimen,

Metal: V Mg/Sq. In. Amount, Nature Mg./sq.1n.

Uncompounded Fuel of Example I 1,430 l, 151 Hard Scale. Fuel+Sodium Carbonate 1:1 133 234 Hard Granular.

Do 91 205 Powdery. Fuel-{"Aluminum Oxide 710 165 Hard Scale.

Do 420 352 Scale. Dom.. 434 321 Hard Powdery. FuEH- luminum Oxide-i-Sodium Carbonate 19 100 powdery x.

19 and 20 in the atomizing head 13. The combustion chamber 21 is made up of two concentric cylinders 22 and 23, respectively, welded to two end plates 24 and 2'5. 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 2d has a central opening 26 into which the atomizing head is inserted. End plate has a one (l) inch opening 27 covered by a baille plate 28 mounted in front of it to prevent direct blast of flame 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. The specimen 29 is mounted near the downstream end of the cylinder approximately 1% inches from the outlet thereof. Combustion air is introduced by means of air inlet 3l into the annulus between cylinders 22 and 23, thereby preheating the combustion air, and then through three pairs of 3m; inch tangential air inlets 32 in the inner cylinder 22. The first pair of air inlets is spaced 1A inch from end plate 24; the second pair 3%: inch from the first; 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 33 surrounding the outer cylinder 23. The entire combustion assembly is surrounded by suitable insulation 34. The 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 to 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 weighed metal specimen is exposed to the combustion It will be seen from the preceding table that, although the alkali metal and aluminum additives individually tend to reduce corrosion and deposits, substantial corrosion and deposits are nevertheless obtained. This is apparent even when relatively larger amounts of the individual additives are employed, for example, in atom weight ratios of additive metal to vanadium on the order of 4:1 and 5:1. However, when the additives are employed in combination, corrosion and deposits are unexpectedly minimized. Thus, it will be noted that the aluminum additive and the alkali metal additive when individually employed in the same total additive content as the combination of additives do not minimize corrosion and deposits. Similar results to those shown for the specific additives employed in the examples and in the preceding table are obtained when using the other aluminum and alkali metal compounds disclosed.

A typical analysis of the 25-20 stainless steel employed in the testing described is shown in the following table in percent by weight:

Resort may be had to such modifications and variations l'. A fuel composition comprising a uniform blend ofi a' maior amount of a residual petroleum fuel' yielding a corrosive vanadium-containing ash upon combustion, anY arriountof a vanadium-free aluminum compound yielding about- 4' atom weights of aluminum per atom weight'of vanadium in said fuel, and an amount of a vanadium-free alkali metal compound yielding aboutv 1 atom weight ofalkali metal per atom weight of vanadium in s'aid fue1. 2. The fuel composition of claim 1, wherein tlie fuel isa solidresidual petroleum fuel.

3. The fuel composition of claim 1, wherein the fuel is a residual fuel oil and the alkali metal compound is aV 15 sodium compound. 4

4. The fuel compositionof claim 3, wherein the aluminum compound is aluminum oXideand the sodium compound is 'sodium carbonate.

51 Thefuelcomposition of` claim 3, wherein the alumin'um compoundis'aluminum sulfate and the-'sodium compoundissodium naphthenate.

6l The fuel composition ofA claim 3, wherein'the'alumi# num" compound `is aluminum oxide andthe sodium compound is sodium sulfate.

7. 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 combustion of said oil, the method of reducin'g'r said corrosion which comprises introducing intoA s'a'id plant upstream of said parts a small amount offal vanadium-free mixture of an aluminum compoundand an alkali metal compound, the amount of said aluminum compound being sufficient to yield about 4 atom weights ofV aluminum per atom weight of vanadium in said fuel oil and the amount of said alkali metal compound being sufcient to yield about 1 atom weight` of alkalimetal p er atom weight of vanadium insaid fuel oil.

References Cited in the tile of this patent UNITED STATES PATENTS 2,949,008 Rocchini et al Aug; 16, 1960 2,968,148 Rocchini et al. Jan.` 17, 1961 FOREIGN PATENTS 200,149' Australia Nov; 4, 1955 498,777 Belgium Feb.`15`, 1951 744,141 Great Britain Feb. 1, 1956 745,012 Great' Britain Feb. 15, 1956 745,818 Great Britain1 Mar. 21, 19516 761,378 Greatv Britain.A Nov.' 14,1956 781,581 Great Britain Aug. 21, 1957 1,117,896 France Mar. 5, 1956 327,289 Switzerland Mar. 15, 1958

Claims (1)

1. 7. IN A GAS TURBINE PLANT IN WHICH 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 RRESULTING FROM COMBUSTION OF SAID OIL, THE METHOD OF REDUCING SAID CORROSION WHICH COMPRISES INTRODUCING INTO SAID PLANT UPSTREAM OF SAID PARTS A SMALL AMOUNT OF A VANADIUM-FREE MIXTURE OF AN ALUMINUM COMPOUND AND AN ALKALI METAL COMPOUND, THE AMOUNT OF SAID ALUMINUM COMPOUND BEING SUFFICIENT TO YIELD ABOUT 4 ATOM WEIGHTS OF ALUMINUM PER ATOM WEIGHT OF VANADIUM IN SAID FUEL OIL AND THE AMOUNT OF SAID ALKALI METAL COMPOUND BEING SUFFICIENT TO YIELD ABOUT 1 ATOM WEIGHT OF ALKALI METAL PER ATOM WEIGHT OF VANADIUM IN SAID FUEL OIL.

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