JPS6114198B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to fuel additives and methods for reducing corrosion of petroleum fuel oils and nickel and cobalt based alloys containing the same, and more particularly to corrosion reduction of metal alloys in hot gas streams due to the presence of alkali metal and vanadium contaminants. The present invention relates to a method for reducing intercalary corrosion. Nickel-based superalloys and cobalt-based superalloys that can withstand high temperatures are used as materials for casting or forging gas turbine blades and vanes. The gas flow in the turbine contains about 15% oxygen, and its inlet temperature is e.g. 926.7~1260℃ (1700~
2300〓), and the surface temperature of the blades and vanes at the first stage averages 899℃ (1650〓), reaching about 954℃ (1750〓) at the apex. Because this relatively high velocity flow of oxidizing combustion gases is a severe condition, the components must be made from superalloys that can withstand high temperatures. Various grades of petroleum fuels, from crude oil to hot distillates, can be used in gas turbines, and there is a problem with trace impurities that become part of the gas stream and corrode materials exposed to it. arise.
Contaminants such as alkali metals (sodium and potassium) and vanadium in fuel are known to cause such corrosion problems. Higher grades of fuel oil, such as hot distillate, usually contain low amounts of contaminants. Since alkali metal contaminants are usually present as soluble chloride salts, water washing is primarily performed before and after the distillation operation to reduce the alkali metal concentration. In order to keep corrosion to a minimum in high-temperature parts, gas turbine fuel specifications must be made of both alkali metals and vanadium.
Must be kept below 0.5ppm.
This method of reducing contaminants at high temperatures is expensive as it requires far more processing operations than the production of more impure low-end, resid and crude oils, and this cost is and other parts, especially those in the first stage. Corrosion rates can also be reduced by reducing the temperature of the gas stream, but the reduction in efficiency of the gas turbine at lower temperatures must be economically justified. It should be noted that alkali metal contaminants can also enter the gas stream from sources other than fuel. Alkali metal salts are naturally also present in salt water operating environments. These salts are also present in the combustion air or combustion cooling water in marine equipment, equipment located on the coast or in saline environments. After studying the individual corrosion mechanisms of (1) alkali metals and (2) vanadium at high temperatures, we discovered that there are other useful methods to reduce the corrosion caused by these contaminants. Alkali metals in the combustion or inlet air are introduced into the combustion process and combine with the sulfur normally present in the fuel to form alkali metal sulfates (eg, Na ₂ SO ₄ ). When these sulfates come into contact with hot alloy components, they degrade by a mechanism known as sulfidation. The addition of chromium and certain other metal elemental compounds to provide metal oxides (e.g. Cr ₂ O ₃ ) in the gas stream reduces the corrosion of coated and uncoated superalloy components due to the aforementioned sulfidation. It has been described in the prior art that it is effective for reducing or preventing. Chromium oxide is also not presented as being effective in preventing deterioration or corrosion from vanadium-contaminated fuel, and in fact only chromium oxide is added to a gas stream obtained from a fuel containing, for example, a few ppm of vanadium. In some cases, unacceptable quality deterioration occurs. Deterioration of superalloys occurs through different mechanisms, mostly due to severe oxidation due to vanadium contamination. Vanadium in fuel is oxidized to molten vanadium pentoxide (melting point 690
℃). When this melt of vanadium pentoxide is exposed to hot metal surfaces such as turbine blades and vanes or boiler tubes, rapid oxidation of the alloy occurs. However, it is known that this oxidative deterioration due to vanadium contamination can be overcome by introducing magnesium compounds into the gas stream. Magnesium oxide formed in the hot gas stream reacts with vanadium pentoxide to form magnesium orthovanadate (3MgO.
V ₂ O ₅ ), this compound is harmless to the superalloy at normal operating temperatures of gas turbines and boilers. The effectiveness of magnesium additives is significantly reduced if alkali metal contaminants such as sodium and potassium are also present. Accordingly, alkali metal contaminants are removed by water treatment from fuels containing relatively high concentrations of vanadium contaminants until the amount of sodium does not promote the progression of alteration. Normally, the fuel put into the gas turbine combustor contains 0.5 ppm of sodium + potassium.
It is determined as follows. The amount of alkali metal contaminants in the fuel or more importantly in the gas stream becomes even more critical when vanadium exceeds the upper limit of 0.5 ppm in the fuel. The degree of corrosion of the alloy in the hot section is several orders of magnitude greater when both the alkali metal and vanadium are present in concentrations greater than 0.5 ppm each than the mere sum of the degree of corrosion when each is present alone. This undesirable corrosion synergy is difficult to study but is believed to be due to the formation of highly corrosive low melting point sodium vanadate. This increased rate of corrosion is often experienced. Corrosive compounds with lower melting points corrode more gas turbine components. U.S. Pat. No. 3,581,491 discloses a method for preventing sulfidation corrosion of nickel-based and cobalt-based alloys in gas turbine engines by treating a gas stream containing alkali metal salts with oxides of chromium, tin, samarium, and columbium. is listed. “Rx for Sodium” by RC Farmer
``Sulfidation'' (Gas Turbine International, September-October 1974, Volume 15, Issue 5, pp. 32-35). of Cr ₂ O ₃ and describes curing by adding a chromium-containing organic compound to the fuel in a solvent soluble in the fuel. “Evaluation of Additives for Prevention of
High Temperature Corrosion of Super Alloys
in GasTurbines” (Journal, a newsletter of ASME)
of Engineering For Power, Vol.95, Series A,
No. 4, pp. 333-339, October 1973) describes certain additives containing magnesium to reduce vanadium corrosion. “Environmental Effects on the High−” by SYLee, WE Young, and CE Hussy.
TemperatureCorrosion of Super Alloys in
“Present and Future Gas Turbines” (ASME newsletter, Journal of Engineering for Power,
Vol.94, Series A, No.2, pp. 149-153, 1972
(April 2010) describes the problem of high temperature corrosion of certain superalloys due to contaminants in the fuel. “Effect of
sulfate salts on Corrosion Resistance of Gas
Turbine Alloys” (Hot Corrosion Problems)
Associated with Gas Turbines，ASTM Special
Technical Publication No. 421, pages 223-245,
(1967) describes the results of corrosion tests on alloys exposed to magnesium sulfate and sodium sulfate, which form low melting point eutectics. The main object of the present invention is to add relatively high concentrations of alkali metal salts and vanadium compounds as impurities to petroleum fuels and to eliminate the presence of said impurities in the hot gas stream that impinges on the superalloys of combustion chambers or gas turbine components. The present invention provides a composition for preventing corrosion caused by such corrosion. Another object of the invention is to provide petroleum fuels containing relatively high concentrations of sodium and vanadium, especially
A method of reducing the rate at which turbine blades and blades are altered by gas streams produced by burning high grade crude oil containing concentrations of sodium+potassium greater than 0.5 ppm and vanadium greater than 0.5 ppm. It provides: According to the present invention, the alkali metal and vanadium contaminated petroleum fuel additive composition consists of a petroleum fuel distillate solvent soluble in petroleum fuels and a solution of chromium and magnesium in the form of oil soluble organic salts. Another object of the present invention is to provide a petroleum fuel oil containing more than 0.5 ppm of alkali metals and more than 0.5 ppm of vanadium, wherein said fuel oil inhibits corrosion of metals by the gas stream produced by burning said fuel oil. The present invention provides a petroleum fuel oil containing effective amounts of chromium and magnesium in the form of oil-soluble organic salts. The present invention further provides a method for reducing corrosion of nickel-based and cobalt-based alloys by a hot gas stream containing combustion products of petroleum fuel oil containing alkali metal contaminants and vanadium contaminants. A method for reducing corrosion of nickel-based alloys and chromium-based alloys is included, which comprises adding an oil-soluble organic salt and an oil-soluble organic salt of magnesium. When fuel oil is combusted, the chromium and magnesium in the form of oil-soluble organic salts of the additive composition provide chromium and magnesium oxides in the hot gas stream. The combination of these oxides is caused by the presence of relatively large amounts of sodium and vanadium in the fuel oil, typically a combination of sodium and vanadium (3 ppm sodium and 5 ppm vanadium) in Saudi crude oil. Prevent or reduce rapid corrosion. That is, when Saudi crude oil or other economical fuels containing more than 0.5 ppm of alkali metals and more than 0.5 ppm of vanadium are burned and used as a gas stream to drive a gas turbine, the composition of the present invention can be added. This reduces corrosion or deterioration of coated or uncoated blades, vanes, or other components made from nickel-based or cobalt-based superalloys. According to the invention, concentrations of alkali metals (sodium + potassium) higher than 0.5 ppm and 0.5 ppm
Alteration of nickel- and cobalt-based superalloys by exposure to a gas stream obtained by burning petroleum fuels containing higher concentrations of vanadium results in the removal of chromium compounds in the form of oil-soluble organic salts and soluble chromium compounds prior to combustion. It has been discovered that this can be reduced by adding a combination of magnesium compounds to fuel oil. The water washing operation reduces the concentration of alkali metals.
Although this is a relatively simple and economical method for reducing concentrations below 0.5 ppm (because alkali metals exist as water-soluble salts),
Readily available wash water may itself be contaminated with alkali metal salts, thus impeding effective washing operations. Fuel that has already been cleaned can also become contaminated with residual alkali metal salts from cleaning tank cars, tanks and pipelines with seawater. In the absence of potable wash water, several light Arabian crude oils,
Especially sodium + potassium and more than 0.5ppm
It would be highly desirable to be able to reduce corrosion at high temperatures when using fuel oils such as Saudi crude containing 0.5 ppm or more of vanadium. Both chromium and magnesium are added, preferably dissolved in the contaminated fuel oil.
Magnesium is added to the fuel oil as an oil-soluble organic salt such as magnesium naphthenate or magnesium sulfonate, preferably in an amount such that the Mg:V ratio is about 3:1 by weight (all Concentrations and ratios are by weight unless otherwise specified). Chromium is preferably added to the fuel oil in the form of an oil-soluble organic salt such as chromium octoate, preferably with a Cr:Na+K ratio of about
It is added in an amount such that the ratio is 4.5:1. The ratios of Mg:V and Cr:Na+K may vary considerably from the preferred ratios and still have the advantage of reducing corrosion or alteration. Although the use of fuel with lower Mg:V and Cr:Na+K ratios than the preferred ratio increases the frequency of gas turbine blade and vane replacement, the combined additives of the present invention can be used at lower ratios. The lifespan is longer than without additives. If the additives of the present invention are used in proportions higher than the preferred ratios mentioned above, they will have sufficient ability to reduce corrosion and increase the temperature of the incoming gas and blades, but will not cause large amounts of It has the disadvantage of forming deposits. As a result, deposits on the gas turbine must be frequently cleaned. If the fuel oil contains 10 ppm or even 100 ppm of vanadium, even if the Mg:V ratio is favorable, it has the drawback of forming large amounts of deposits. However, the effect of reducing corrosion is achieved. The simplest method for injecting the additive of the present invention into fuel oil is to dissolve magnesium and chromium in a fuel oil-soluble solvent and add them as a solution. The solvent is a petroleum fuel distillate or preferably a solvent soluble in the fuel, such as kerosene, mineral spirits or benzene.
These latter solvents have significantly lower pour points and viscosities, providing solutions that are more easily pumpable and injectable and easier to handle. These advantages are why it is desirable to use the additive composition of the present invention as a solution of chromium and magnesium in the form of oil-soluble organic salts in a fuel-soluble petroleum distillate solvent. The concentration of chromium and magnesium in the solution is not critical. For convenience and to reduce the volume of the solution to be handled, it is desirable to have a relatively high concentration. Chromium octoate and magnesium sulfonate can be dissolved in relatively common, inexpensive, oil-soluble solvents to provide a solution containing about 8% chromium and 8% magnesium. Chromium and/or
The solubility of various organometallic compounds containing either magnesium or magnesium can be easily determined by tests. Solvent petroleum solubility for these compounds can be determined as well. The quantitative ratio of chromium and magnesium in the oil-soluble solvent is preferably Mg:V=3:1, Cr:Na when the ratio of V:Na+K in the fuel is known.
It is adjusted so that +K=4.5:1. For example, for Saudi crude oil containing 3 ppm Na+K and 5 ppm vanadium, chromium in oil solution:
The weight ratio of magnesium is 13.5:15. Therefore, as long as the concentration and quantitative ratio of sodium + potassium and vanadium do not substantially change, the above-mentioned preferred quantitative ratio can be adopted. It can be added as If the concentrations or quantitative ratios of these impurities vary significantly, it is convenient to use two separate oil-soluble solutions, one containing magnesium and the other containing chromium, and then The amount of each solution added can be changed depending on the change. It should be recognized that alkali metals can be introduced into the hot gas stream from sources other than fuel oil. In coastal and marine installations, alkali metal impurities get mixed into the air used for combustion or the water that is injected into the combustion chamber to regulate the temperature of the flame. Regardless of the origin of the impurities, alkali metal impurities in the gas stream, along with vanadium impurities, rapidly alter the superalloy component. This deterioration or corrosion can of course be reduced or prevented by adding a combination of soluble magnesium and chromium compounds to the fuel oil.
The concentrations and quantitative ratios of magnesium and chromium in the fuel are selected in such a way that Cr:Na+K is the aforementioned preferred quantitative ratio, taking into account all alkali metals that are mixed into the gas stream, regardless of their source. This is done by measuring the sodium + potassium in the combustion air and converting it to the equivalent concentration in the fuel, which is relatively easy since the fuel:air ratio is known. The effects of the invention can also be obtained by coating the metal parts with a substance containing chromium and magnesium. In fact, according to the invention, the alkali metals and vanadium (each in the fuel
This has the effect of reducing the extent of corrosion wherever combustion gases containing 0.5 ppm or more impinge on components made from nickel-based or cobalt-based superalloys. Specifically regarding gas turbines,
When using fuels containing 0.5 ppm or more of alkali metals and 0.5 ppm or more of vanadium (or gas streams containing equivalent amounts of impurities), the chromium:alkali metal ratio is approximately 4.5:1 and the magnesium: Preferably, chromium and magnesium are each added to the fuel in amounts such that the vanadium ratio is about 3:1. Even when these fuels are used in gas turbines with nickel-based superalloy blades and cobalt-based alloy vanes, the average temperature of the blades and vanes is 899°C (1650°C) and the peak temperature at one point is 954°C (1750°C). In the case of 〓), the life of the first stage is long and good. Currently in commercial gas turbine technology, the nominal inlet gas stream temperature, which corresponds to the temperature of the first stage metal member, is approximately
1132℃ (2070〓), and this gas flow is nominally ±
It varies in a range of 149℃ (300〓). The invention is further explained according to the following examples. EXAMPLE A laboratory turbine was used to perform corrosion tests on samples of commonly used gas turbine nickel-based and cobalt-based superalloys by exposing them to a gas stream containing vanadium and sodium impurities. The fuel used in these tests contained less than 0.5 ppm of sodium and vanadium. It was a fraction of No. 2 petroleum fuel. The actual concentrations of these impurities in the test fractions were analytically determined to mimic the aforementioned natural crude oils. After that,
By appropriately adding sodium carboxylate and vanadium carboxylate to the test fuel oil, a test fuel was obtained in which the amounts of sodium and vanadium were adjusted to appropriate concentrations. The test fuel also contained 0.5% sulfur. Chromium was added to the test fuel as chromium naphthenate. Magnesium is Petrolite
Commercially available from Tretolite Division of Corp.
It was added as a soluble solution in a fuel oil known as KI-16. The amount of additives administered to the test fuel was determined to be Cr:Na = 4.5:1 and Mg:V = 3:1. Oxidation results were obtained in the case of natural gases containing no sodium or vanadium. The test sample alloy was a 6.4 mm (1/4 inch) diameter pin. The test pin was installed in the high pressure corrosion test passageway where it was exposed to a test gas flow having the characteristics of a conventional gas turbine gas flow. More detailed descriptions of test equipment and operating procedures can be found at SYLee, SMDeCorso and WE.
“Laboratory Procedures for
Evaluating High−Temperature Corrosion
"Resistance of Gas Turbine Alloys" (Journal of Engineeribng for ASME's newsletter)
Power, Vol.93, SeriegA, No.1, No. 313-320
Page, July 1971). The article also describes the composition of nickel-based and cobalt-based superalloys. As a result of the corrosion test on the cleaned and descaled metal, the degree of weight loss and reduction in sample diameter was determined. Figures 1 and 2 show the test results at 899℃ (1650〓) for the cobalt matrix alloy X-45 of a typical gas turbine blade and the nickel matrix alloy U-500 of a typical rotating blade, respectively. show.
These test results demonstrate that when the magnesium and chromium combination of the present invention is included in a fuel, the corrosion rate due to vanadium and sodium is significantly reduced. The chromium and magnesium combination of the present invention provides some protection to the superalloy from simple oxidation, such as occurs in tests using pure natural gas. The effects of the additives of the present invention extend equally to a variety of other nickel-based and cobalt-based superalloys used in gas turbine engines. The additives of the present invention are equally effective on coated blades and vanes. Tables 1 and 2 below show the magnesium and chromium combination additives of the present invention as described above.
The effects when used at Cr:Na and Mg:V ratios are shown.

【table】

【table】

[Table] The effects of the present invention extend to fuels containing lead as an impurity. Lead contamination occurs when petroleum fuel oil is shipped or transported in tanks with residual gasoline. Magnesium additives are also effective in reducing corrosion caused by lead in the fuel. If lead is present, the concentration of lead may be added to the concentration of vanadium, and the amount of magnesium to be added may be calculated from the total amount.

[Brief explanation of the drawing]

Figure 1 shows the results of a corrosion test at 899°C (1650°C) for cobalt-based alloy X-45 for gas turbine blades. Curve A ₁ ... Treated with chromium and magnesium additives (Cr:Na=4.5:1,
Mg:V=3:1) Results obtained using a fuel containing 3 ppm Na and 5 ppm V are shown. curve
B ₁ ...5ppm Na and 2ppm not treated with additives
The results obtained using a fuel containing V are shown. Curve C ₁ ... shows the corrosion results due to oxidation of natural gas fuel. Figure 2 shows the nickel-based alloy U-
Corrosion test results for 500 at 899℃ (1650〓) are shown. Curve A ₂ ... Treated with chromium and magnesium additives (Cr:Na=4.5:1, Mg:V
= 3:1) Results obtained using a fuel containing 3 ppm Na and 5 ppm V are shown. Curve B ₂ ...
...5ppm Na and 2ppm V without additive treatment
The results obtained using a fuel containing
Curve C ₂ ... shows the corrosion results due to oxidation of natural gas fuel.

Claims (1)

[Scope of Claims] 1. A fuel additive composition for petroleum fuel oil contaminated with alkali metals and vanadium, wherein the composition comprises a petroleum distillate solvent soluble in the petroleum fuel oil and an oil-soluble organic salt. A fuel additive composition characterized in that it consists of a solution of chromium and magnesium in the form. 2. The fuel additive composition according to claim 1, wherein the chromium is chromium octoate. 3. The fuel additive composition according to claim 1, wherein the magnesium is magnesium sulfonate. 4. The fuel additive composition according to claim 1, 2 or 3, wherein the weight ratios of chromium and magnesium are substantially equal. 5 Claim 1 in which the solvent is kerosene
The fuel additive composition according to any one of items 1 to 4. 6. In petroleum fuel oils containing more than 0.5 ppm of alkali metals and more than 0.5 ppm of vanadium, said fuel oil is used to prevent or reduce corrosion of metals by gas streams produced by burning said fuel oil. A petroleum fuel oil characterized in that it contains an effective amount of chromium and magnesium in the form of oil-soluble organic salts. 7. The petroleum fuel oil according to claim 6, wherein the quantitative ratio of Cr:Na+K is about 4.5:1. 8. The petroleum fuel oil of claim 6, wherein the Mg:V ratio is about 3:1. 9. The petroleum fuel oil according to claim 8, wherein the amount of lead is included as V in the Mg:V quantitative ratio. 10 In a method for reducing corrosion of nickel-based and cobalt-based alloys by a hot gas stream containing combustion products of petroleum fuel oil containing alkali metal contaminants and vanadium contaminants, the oil-soluble organic salt of chromium is added to the fuel oil. and a method for reducing corrosion of nickel-based alloys and chromium-based alloys, the method comprising adding an oil-soluble organic salt of magnesium. 11. The method of claim 10, wherein the hot gas stream contains more than 0.5 ppm alkali metal and more than 0.5 ppm vanadium. 12 Claim 10, wherein the petroleum fuel oil has a chromium:alkali metal ratio of about 4.5:1 and a magnesium:vanadium ratio of about 3:1.
The method described in section. 13. The method according to claim 10, wherein the alloy is a member of a gas turbine. 14. The method of claim 10, wherein the temperature of the hot gas stream is about 1132°C.