Nov. 17, 1959 C. E. TRAUTMAN 2,913,319 FUEL OLS IN/ENTOR CA/ARES.E. TRU7MA/y AYMS 4777OAPMMAFY 2,913,319 United States Patent Office Patented Nov. 17, 1959 2 other metal parts in a gas turbine. The corrosive na ture of the ash appears to be due to its vanadium oxide content. Certain inorganic compounds of vanadium, 2,913,319 such as vanadium oxide (V2O5), which are formed on FUEL OLS combustion of a residual fuel oil containing vanadium compounds, vigorously attack various metals, their al Charles E. Trautman, Cheswick, Pa., assignor to Gulf loys, and other materials at the elevated temperatures Research & Development Company, Pittsburgh, Pa., encountered in the combustion gases, the rate of attack a corporation of Delaware becoming progressively more severe as the temperature Application August 13, 1956, Serial No. 603,609 0 is increased. The vanadium-containing ash forms de 14 Claims. (Cl. 44-50) posits 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 This invention relates to vanadium-containing petro 5 temperatures by the hot ash resulting from the com leum fuels. More particularly, it is concerned with ren bustion of a vanadium-containing residual fuel is to be dering non-corrosive those residual fuels which contain distinguished from the type of corrosion occurring at at such an amount of vanadium as normally to yield a cor mospheric or slightly elevated temperatures, generally in rosive vanadium-containing ash upon combustion. the presence of air and moisture. Under the latter con It has been observed that when a residual type fuel 20 ditions, an ash containing vanadium oxide has no sig oil containing substantial amounts of vanadium is burned nificant corrosive effect. The corrosion problem de in furnaces, boilers and gas turbines, the ash resulting scribed herein may therefore properly be termed a prob from combustion of the fuel oil is highly corrosive to lem of “hot corrosion.” materials of construction at elevated temperatures and at The economic factors involved preclude any exten tacks such parts as boiler tubes, hangers, turbine blades, 25 sive treatment of vanadium-containing residual fuels to and the like. These effects are particularly noticeable remove the vanadium therefrom or to mitigate its effects. in gas turbines. Large gas turbines show promise of be The vanadium compounds in residual oils are not removed coming an important type of industrial prime mover. by centrifuging or by the conventional chemical refining However, economic considerations based on the efficiency treatments. of the gas turbine dictate the use of a fuel for this pur 30 I have now discovered that residual petroleum fuels' pose which is cheaper than diesel fuel; otherwise, other containing vanadium in an amount sufficient to yield a forms of power such as diesel engines become competi corrosive vanadium-containing ash upon combustion can tive with gas turbines. be rendered substantially less corrosive, notwithstanding One of the main problems arising in the use of residual the normally corrosive vanadium content, by incorporat fuel oils in gas turbines is the corrosiveness induced by 35 ing therein in a small amount sufficient to retard the those residual fuels containing sufficient amounts of corrosiveness of the ash a compound of a didymium rare vanadium to cause corrosion. Where no vanadium is earth element. In the fuel compositions of the inven present or the amount of vanadium is small, no apprecia tion, corrosion due to the vanadium-containing ash is ble corrosion is encountered. While many residual fuel substantially retarded. - oils as normally obtained in the refinery contain so lit 40 The single figure of the drawing shows an apparatus tle vanadium, or none, as to present no corrosion prob for testing the corrosiveness of residual fuel oil compo lems, such non-corrosive fuel oils are not always avail sitionas. able at the point where the oil is to be used. In such The type of residual fuel oils to which my invention is instance, the cost of transportation of the non-corrosive directed is exemplified by No. 5, No. 6 and Bunker “C” oil to the point of use is often prohibitive, and the 45 fuel oils which contain a sufficient amount of vanadium residual oil loses its competitive advantage. All of these to form a corrosive ash upon combustion. These are factors appear to militate against the extensive use of residual type fuel oils obtained from petroleum by meth residual fuel oils for gas turbines. Aside from corrosion, ods known to the art. For example, residual fuel oils the formation of deposits upon the burning of a residual are obtained as liquid residua by the conventional dis fuel in a gas turbine may result in unbalance of the tur 50 tillation of total crudes, by atmospheric and vacuum re bine blades, clogging of openings and reducing thermal duction of total crudes, by the thermal cracking of efficiency of the turbine. topped crudes, by visbreaking heavy petroleum residua, Substantially identical problems are encountered when and other conventional treatments of heavy petroleum using a solid residual petroleum fuel containing substan oils. Residua thus obtained are sometimes diluted with tial amounts of vanadium. These fuels are petroleum 55 distillate fuel oil stocks, known as "cutter" stocks, and residues obtained by known methods of petroleum refin the invention also includes residual fuel oils so obtained, ing such as deep vacuum reduction of asphaltic crudes provided that such oils contain sufficient vanadium nor to obtain solid residues, visbreaking of liquid distillation mally to exhibit the corrosion characteristics described bottoms followed by distillation to obtain solid residues, herein. It should be understood that distillate fuel oils coking of liquid distillation bottoms, and the like. The 60 solid residues thus obtained are known variously as themselves contain either no vanadium or such small petroleum pitches or cokes and find use as fuels. Since amounts as to present no problem of hot corrosion. The the vanadium content of the original crude oil tends to total ash from commercial residual fuel oils usually ranges concentrate in the residual fractions, and since the proc from about 0.02 to 0.2 percent by weight. The vanadium essing of the residual fractions to solid residues results 65 pentoxide (VOs) content of such ashes ranges from zero in further concentration of the vanadium in the solid to trace amounts up to about 5 percent by weight for low residues, the vanadium corrosion problem tends to be in vanadium stocks, exhibiting no significant vanadium cor tensified in using the solid residues as fuel. rosion problem, to as much as 85 percent by weight for The vanadium-containing ash present in the hot fiu some of the high vanadium stocks, exhibiting severe cor gas obtained from the burning of a residual fuel con 70 rosion. taining substantial amounts of vanadium compounds The type of vanadium-containing solid residual fuels causes 'catastrophic' corrosion of the turbine blades and to which the invention is directed is exemplified by the 2,918,819 3 4. coke obtained in known manner by the delayed thermal acids; (5) rosin and hydrogenated rosin; (6) alkyl phe coking or fluidized coking of topped or reduced crude nols, e.g., iso-octyl phenol, t-butylphenol and the like; oils and by the pitches obtained in known manner by (7) alkylphenol sulfides, e.g., bis (iso-octyl phenol)- the deep vacuum reduction of asphaltic crudes to obtain monosulfide, bis(t-butylphenol) disulfide, and the like; and solid residues. These materials have ash contents of the (8) oil-soluble phenol-formaldehyde resins, e.g., the Am order of 0.18 percent by weight, more or less, and con berols, such as t-butylphenol-formaldehyde resin, and the tain corrosive amounts of vanadium when prepared from like. Since the salts or soaps of such acidic organic stocks containing substantial amounts of vanadium. A compounds as the fatty acids, naphthenic acids and typical pitch exhibiting corrosive characteristics upon rosins are easily prepared, these are preferred materials. combustion had a softening point of 347 F. and a vana O When employing the inorganic didymium compounds dium content, as vanadium, of 578 parts per million. in residual fuels, it is desirable to use finely-divided ma As has been stated, the corrosion retarding additives of terials. However, the degree to which the materials are the invention are compounds of a didymium rare earth Subdivided is not critical. One requirement for using a element. As known commercially, the d'idymium ele finely-divided material is based upon the desirability of ments are the rare earth elements of atomic numbers forming a fairly stable dispersion or suspension of the 57 to 71, inclusive, with the exception of cerium. The inorganic didymium compounds when blended with a didymium elements thus include anthanum, praseodym residual fuel oil. Furthermore, the more finely-divided ium, neodymium, samarium, europium, gadolinium, materials are more efficient in forming uniform blends terbium, dysprosium, holmium, erbium, thulium, ytter and rendering non-corrosive the relatively small amounts bium and lutecium. 20 of vanadium in a residual fuel, whether the fuel be solid Commerical ores of the rare earth elements are pri or liquid. The inorganic didymium compounds are marily monazite and bastnasite. Monazite is an ortho therefore employed in a particle size range of less than phosphate of the rare earth elements and thorium. 250 microns, preferably less than 50 microns. Bastnasite is a cerium earth fluorocarbonate. In the work The organic didymium compounds of the invention ing of these ores to separate the thorium and cerium, the 25 are oil-soluble or oil-dispersible and are therefore readily remaining didymium elements are obtained.