CH623603A5 - Fuel for gas turbines - Google Patents

Description

The invention relates to fuels for gas turbines and methods for operating gas turbines with fuels, in particular fossil fuels, such as petroleum fuels and combustible waste materials, which can be used on their own or together with fossil fuels, and additives for liquid fuels. The s

10th

IS

20th

25th

30th

35

40

45

50

55

60

65

3rd

623603

The invention is particularly applicable to fuels and the combustion of such fuels for operating gas turbines for power generation, drive systems and the like.

Magnesium-containing compounds have been used as corrosion retarders in the combustion of non-distilled fuels that contain ash or inorganic contaminants, especially metallic contaminants, for the operation of gas turbines. When such ash-containing fuels are used as gas turbine fuels, it has heretofore been necessary to pretreat these fuels to minimize their alkali metal content to obtain combustion gases that are less than about 1.0 ppm, preferably less than 0.5 ppm, of alkali metal ( Sodium and / or potassium) on a weight basis. The removal of the alkali metal from the fuel and / or avoidance of its presence in the combustion products when using the fuel to operate gas turbines with the addition of magnesium compounds has heretofore been considered necessary to remove the metal alloys of the nozzles and blades of turbines at temperatures of around 760 ° C and more work to protect against high temperature corrosion.

Although magnesium is generally regarded as an effective additive to gas turbine fuels in order to reduce the high temperature corrosion of the gas turbine blades by vanadium, which assumes particular importance at temperatures above 760 ° C., the effectiveness of magnesium as an additive is reduced even by small amounts of alkali metals, such as Sodium, in the fuel or in the combustion gases impaired; because if the fuel contains both sodium and vanadium, an ash is formed which contains a high content of corrosive, low-melting sodium vanadates with the exclusion of magnesium vanadate, since vanadium reacts selectively with sodium but not with magnesium.

So far it has not been possible to suppress the tendency of sodium to form undesirable corrosive compounds in the presence of vanadium. More importantly, the magnesium is unable to provide effective protection against the sulfidation attack of the turbine blades and nozzles by sodium sulfate, an attack that occurs at the current and planned higher working temperatures that result from the constant effort to increase the performance and efficiency of gas turbines has become a very serious and even destructive problem. The presence of alkali metals in the combustion products also adversely affects the nature of the turbine ash deposits, leading to increased pollution and narrowing of the flow channels for the combustion gases through the turbine, so that the performance of the turbine quickly decreases and the need and / or frequency of washing the Turbine is increased with water in order to remove the deposits and restore the original performance.

When burning ash-containing or alkali-containing fuels to a combustion gas for the operation of gas turbines, it was previously common to use the fuel, e.g. B. by washing with water to pretreat to remove the alkali compounds and the water-soluble ash-forming compounds therefrom. Plants for washing fuels with water, however, require a lot of space and contribute significantly to the total plant costs. So z. B. when washing such fuels with water often difficult to destroy water-in-oil emulsions.

These emulsions require the use of de-emulsifiers, which are commonly used with centrifugal or electrostatic devices to complete the removal of the aqueous phase containing the water-soluble salts extracted from the oil phase.

Alkali metal, such as sodium, not only needs to get into the combustion zone and the combustion products as an impurity of the fuel, but also occurs as an impurity of the combustion air, especially when combusting fuels in systems which are located on or on the water, such as e.g. . B. on board ships or in port. Alkali metals, such as sodium, can also enter the combustion products from the air in the form of salt particles (NaCl) or salt-containing mists. In order to avoid such contamination with alkali metals, measures have hitherto been taken to remove the contaminants contained in the air therefrom by means of coalescing or filter devices. Another possible source of alkali metal contamination in the operation of gas turbines may be the water injected into the primary combustion zone of the turbine to reduce the emission of nitrogen oxides in the combustion gases, especially when used for this purpose Water contains alkali salts in solution. The removal of alkali metals such as sodium and other metals in order to obtain practically metal-free water or water of the desired degree of purity also requires special pretreatment, such as demineralization.

In the A.S.M.E. publication by E.E. Knills,

entitled "Gas Turbine Liquid Fuel Treatment and Analysis", publication No. 74-GT-44, presented at the gas turbine conference in Zurich, Switzerland, from March 31 to April 4, 1974, is a fuel treatment plant including the washing of fuels and others' factors related to the selection and treatment of fuels for the operation of gas turbines. Special reference is made to this publication here.

As mentioned above, the problems associated with burning ash-containing fuels, particularly sodium-containing fuels, for the operation of gas turbines are already known, and the use of magnesium as an additive to such fuels to extend the life of the gas turbine blades is also known. Current practice of using magnesium as an additive requires that the sodium content of the fuels be minimized to provide effective protection against the high temperature corrosion of the alloys from which the turbine parts operating at high temperatures of 760 ° C or more, such as nozzles and blades. In all cases, except in the case of distillate fuels, washing the fuel to remove the sodium is considered essential in order to obtain fuels suitable for gas turbines, and this has so far primarily prevented the professional world from using inexpensive, low-ash oils and gas turbines to be used extensively for power generation in fields such as those of the utility vehicles, the manufacturing and processing industries, transportation, etc. Fuel washers are costly and add significantly to the installation cost per kWh of turbines that burn heavy oil by increasing capital costs, space requirements (which is particularly important for marine facilities), complexity of work, and the work box including labor costs. Therefore, the simplification s

10th

15

20th

25th

30th

35

40

45

50

55

60

65

623 603

4th

or the elimination of such washing systems represents a significant technical advance and provides a means to significantly improve the competitiveness of the gas turbine against the diesel engine and the steam-generating systems, which do not require any fuels, which must meet the stringent standard requirements with regard to their alkali content . Improving the process for burning significant amounts of alkali metal containing fuels would result in satisfactory fuel usage as supplied by the supplier, i. H. Fuels that contain both vandium and sodium enable and have a profound effect on the general usability of gas turbines.

The need for effective high-temperature corrosion retarders and ash modifiers to avoid the difficulty resulting from the alkali content of the combustion gases is also becoming critical, especially because fuels that are ash-free, such as petroleum distillates, are becoming scarcer and / or more expensive, and because fuels and mixtures containing ash residues they are more readily available and less expensive with distillate fuels. Furthermore, the corrosion values show that at higher gas turbine operating temperatures, e.g. B. metal temperatures of 925 ° C, the magnesium, when used in a weight ratio of magnesium to vanadium of 3: 1, is no longer able to provide the required protection when using a substantially alkali-free fuel.

Additives for fossil fuel and their use are described in US Pat. No. 3,817,722. These additives consist of silicon and magnesium compounds, which have the task of combating the high-temperature corrosion of the turbine alloys exposed to the combustion gases and of acting as a modifier for the ashes produced in the combustion products when ash-containing fuels are combusted if the fuels comprise one or more elements the group of vanadium, alkali metal such as sodium, and sulfur. In particular, the cited patent discloses a significant inhibition of corrosion and ash deposition in combustion plants for the combustion of fossil fuels when using additives which contain sources of silicon and magnesium in proportions such that the ratio Si02: Mg0 is greater than 2: 1. When burning fossil fuels in ovens, steam boilers, diesel engines or when operating gas turbines, it is desirable that the additional components are present in such quantities that each part by weight of ash in the fuel accounts for at least 0.50 part by weight of the combined SÌO2 and MgO equivalent . Furthermore, the patent discloses that in the combustion of ash-containing fuels for the operation of gas turbines, if the combustion products contain vanadium and / or alkali metals, the additional constituents should be present in such proportions that at least 2 parts by weight of magnesium are present in each part by weight of vanadium in the fuel, whereby, as stated above, the SiO 2: MgO ratio of these components is such that at least 2 parts by weight of silicon are accounted for by each part by weight of alkali metal in the fuel and / or in the air to be added during the combustion. The cited patent specification also mentions that it is desirable and economically feasible to operate gas turbines when using sodium-rich fuels with ratios of SiO 2: MgO of 6: 1 and more.

The invention has for its object improved fuels, the alkali content, such as. B. sodium content,

is more than 2 ppm by weight, especially fuels for the operation of gas turbines which contain up to about 50 to 100 ppm alkali metal, e.g. As sodium and / or potassium, may contain on a weight basis, an improved method for operating gas turbines that at temperatures above 760 ° C, such as. B. 925 ° C or more, work in which the hot combustion gases used to operate the gas turbine have an alkali content of over 2 ppm, such as. B. have more than about 5 ppm by weight.

It has now been found that fuels with an alkali metal content (e.g. sodium and potassium) of at least 2 ppm, e.g. B. those containing more than 5 ppm sodium on a weight basis, or distillate fuels which are practically free of alkali metals but are burned under conditions such that alkali metals occur in the combustion products or exhaust gases, can advantageously be burned in the presence of additives, which essentially consist of compounds of silicon and magnesium which form SÌO2 and MgO at the combustion temperatures, the proportions of the compounds being such that, calculated on the SiOz and MgO produced during the combustion, a SiOz: MgO weight ratio is produced which is greater than 2: 1. The amount of the additional constituents present during the combustion is such that the weight ratio of silicon to alkali metal in the fuels is greater than 2: 1, in particular greater than 6: 1, and that at least 2 parts by weight of magnesium are present in each part by weight of vanadium in the fuel if it contains vanadium.

The additional components can be added to the fuel before the combustion or separately brought into contact with the fuel during the combustion in the combustion zone or injected directly into the flame or the primary hot combustion gases.

The invention is generally applicable to ash-containing fuels and fuels which have alkali metal in the combustion products or combustion exhaust gases. The fuels which can be used according to the invention include possible hydrocarbon fuels, such as possible petroleum fuels, especially normally liquid petroleum fuels, namely petroleum distillates or petroleum residues. The normally gaseous and liquid distillate fuels are essentially ash-free and are mostly trouble-free fuels for gas turbines. However, even with ash-free fuels, such as distillate fuels, gas turbine operation can be difficult if they are burned under conditions such that the combustion products are alkali metals included, such as B. if the fuels have come into contact with salt water and the salt water has not been removed from them sufficiently, or if such fuels z. B. burned on board ships or in the port, where the air required for combustion contains fine, almost microscopic salt particles or salty fog, or if water is injected into the combustion chamber to reduce the flame temperature and thereby the NOx emission if this water contains small amounts of ash-forming constituents or metals such as sodium. For the purposes of the invention, gaseous fuels, such as natural gas, liquefied petroleum gases, the normally gaseous or easily liquefiable hydrocarbons and synthetic liquid and / or gaseous fuels, eg. B. CO, H2, CH4, C2H6 and mixtures der5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

The same, which have been generated by liquefaction or by gasification of solids, such as coal, petroleum coke, combustible waste, petroleum residues, liquid petroleum fractions, etc.

Numerous different compounds can be used as silicon and magnesium components in the context of the invention. Virtually all compounds or mixtures of compounds of silicon and magnesium can be used, provided that SÌO2 and MgO are only produced at the temperatures that occur during the combustion of the fuels. The silicon and magnesium can be added in the form of organic compounds, inorganic compounds, or mixtures of such compounds, and such mixtures can be water-soluble or water-dispersible or oil-soluble or oil-dispersible or both. The components can be added individually or together to the fuel prior to combustion, or they can be fed separately from the fuel to the combustion zone, or one or more of these methods for adding the additives can be used, provided only the combustion of the fuels in the presence of the Additive is made.

Easily available compounds such as magnesium sulfate, magnesium acetate and magnesium chloride, all of which are water-soluble, can be used as sources of magnesium or the magnesium component. The readily available water-insoluble magnesium compounds, such as magnesium hydroxide and magnesium carbonate, can also be used, preferably in dispersible or finely divided form. Other magnesium compounds, such as talc, magnesium-containing clays, natural or synthetic magnesium silicate,

which then simultaneously provides the magnesium and the silicon. Organic magnesium compounds can also be used, such as magnesium salts of organic acids, e.g. B. of aliphatic, naphthenic or petroleum sulfonic acids, for. B. Magnesium petroleum sulfonates, magnesium naphthenates, also the magnesium salts of carboxylic acids of high molecular weight, such as magnesium oleate, magnesium caprylate and the like;

all of these compounds are suitable as a magnesium component for the silicon and magnesium-containing additives according to the invention.

Finely divided inorganic silicates are suitable as a source of silicon. Organic silicon compounds are particularly valuable, especially the silicones, the polysilicones, the lower silicic acid alkyl esters with 1 to 6 carbon atoms in the alkyl group, such as the tetra-lower alkyl orthosilicates, the mixed polysilicic acid alkyl esters, e.g. B. Ethyl polysilicate. The suitable silicon compounds provide all or part of the silicon of the additives according to the invention, which essentially consist of compounds of silicon and magnesium which form SÌO2 and MgO at the combustion temperatures.

The preparation of aqueous solutions or aqueous dispersions which contain the additional components according to the invention can be carried out by any suitable and / or conventional method. It is also possible to use processes for the preparation of solutions or suspensions in organic solvents. If an additive is used in distillate fuels or other high quality petroleum fuels, the suspensions or solutions can be made in various light petroleum fractions such as light oil, distillate oil # 2 and the like. If the additive is to be used in fuels of lower quality, such as petroleum residues, an aromatic one is preferably used

623603

Solvent or an aromatic petroleum fraction to facilitate even mixing with the fuel. Suitable aromatic solvents are the high-boiling substituted napthalene compounds or the disubstituted benzene compounds. Typical suitable aromatic solvents that are commercially available

are (1) aromatic solvents containing methylnaphthalene or naphthalene fractions regardless of their origin, i.e. H. regardless of whether they are derived from coal or petroleum, (2) methylated naphthalenes, such as mixtures of a- and ß-methylnaphthalene, and derivatives thereof, and (3) chlorinated solvents, such as o-dichlorobenzene. Other solvents are also suitable.

The advantages of the additives according to the invention can be used by various methods. A main method is the use of additives in Forni combined or mixed with the fuel, mechanically mixing the sources of silicon and magnesium with the fuel, or liquid preparations of the additive components in aqueous or organic liquid phase, in which the sources of magnesium and silicon are evenly dissolved and / or dispersed. Such additives can easily be produced in such a way that they meet the respective requirements of the fuel to be burned and the incineration plant.

However, it is by no means necessary for the sources of silicon and magnesium to be added simultaneously. They can also be added separately to the fuel or the combustion zone, and if a fuel is used which already contains a sufficient amount of either the magnesium or the silicon, the invention can be carried out by adding the missing silicon or magnesium in such an amount adds that the ratio Si02: Mg0 in the combustion gas is greater than 2: 1.

If the treated fuel is to be used in large plants or a number of small plants,

it may also be expedient that the additional components have already been added to the fuel by the supplier.

The methods of applying the invention may vary somewhat depending on the type of combustion device, i.e. that is, they can depend on whether the turbine is fed directly with liquid or gaseous fuel,

whether it is operated together with a pressurized steam boiler in such a way that the combustion in the boiler takes place under pressure and the combustion exhaust gases are fed to the turbine with or without previous additional combustion, or whether water is injected. For the purposes of the invention, the additional components are expediently present in amounts such that at least 2 parts by weight of magnesium and 2 parts by weight of silicon are present in each part by weight of vanadium and sodium in the fuel or in the combustion gases fed to the turbine. This ratio can be increased to 3 parts by weight and possibly even more, since any such increase in the amount of additional components further improves the modification of the ashes and the fight against corrosion. From a practical point of view, the upper limit for the amount of additional components depends on economic considerations, taking into account the costs of the additive, the fuel costs, the fuel quality, i.e. H. the ash content and composition, and the desired degree of suppression of corrosion and pollution of the hot turbine parts.

If the additives are introduced into the combustion zone independently of the fuel, the dosage should be dimensioned in the same way as if they were added directly to the fuel.

5

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

623 603

6

The operation of gas turbines poses a particular problem, because metal temperatures occur significantly higher than in other combustion devices for power generation. If, during the combustion of fuel in gas turbines, vanadium and alkali metals are contained in the combustion products, the additional components should be present in such amounts that at least 2 parts by weight and preferably about 3 parts by weight of magnesium are present for each part by weight of vanadium in the fuel or the combustion gases, and the ratio SiChrMgO should be such that in the fuel and in the air to be added during the combustion and / or in the water • injected into the combustion zone, more than 6 parts by weight of silicon are accounted for by each part by weight of alkali metal. With plants on the mainland far from the sea, alkali metal is unlikely to be in the combustion air. On the other hand, in gas turbines for propelling ships or in land-based plants near salt water, the amount of alkali metal contained in the combustion air as a salt spray can contribute significantly to the amount of alkali metal contained in the combustion products. As already mentioned, the combination of sulfur, which is always present in traces in petroleum fuels, and alkali metal leads to destructive sulfidation corrosion when gas turbines with such fuels are operated at temperatures in the range from 760 to 9250 C or more. Sulphidation, also known as hot corrosion, leads to an extremely severe deterioration in the alloys exposed to hot gases used for the nozzles and blades of gas turbines as a result of the chemical attack by Na2S04, which is either in the flame forms or is otherwise contained in the combustion gases on the alloy metals, such as chromium and nickel, which leads to the precipitation of round-grain metal sulfides, predominantly chromium sulfide, whereby the metal is depleted of chromium and the oxidation resistance of these alloys is destroyed. It is also important to recognize that this sulfidic corrosion is independent of the presence of vanadium compounds in the fuel and is in no way related to the corrosion caused by the low-melting vanadates. The accelerated oxidation and severe exfoliation caused by the sulfidation can lead to the failure of such gas turbine alloys after only a short operating time of a few thousand hours.

In the A.S.M.E. publication by C.T. Sims, No. 70-GT-24, presented at the gas turbine conference in Brussels, Belgium, May 24-28, 1970, describes the morphological mechanism of sulfidation corrosion of nickel alloys in gas turbines. This publication is expressly referred to here. In order to reduce or prevent this destructive sulfidation of turbine alloys, it is necessary to provide additional components according to the invention, expediently with an increased ratio of S1O2 to MgO, in such a way that the weight ratio Si: Na is greater than 6: 1. If the additives according to the invention are used in dosages and SiOs.'MgO ratios corresponding to or proportional to the amount of vanadium and alkali metal in the combustion products, the alkali content of the combustion products can be significantly, e.g. B. can rise to over 20 or even 50 ppm alkali metal on a weight basis or even higher without this having a particularly harmful effect. Considerable savings can be made in this way, since the need to remove the alkali metal practically completely from the fuel and / or the combustion air and from the water injected to reduce the nitrogen oxide content of the combustion products, which contributes considerably to the cost, is reduced or eliminated.

The use of the combination of magnesium and silicon in the additives according to the invention not only solves the serious problem of sulfidation corrosion in gas turbines operating at high temperatures, even if the fuels of high quality recommended for this purpose are used, but the additives also make it possible the use of fuels of significantly lower quality for the operation of gas turbines at high temperatures.

The additives and fuels according to the invention can also contain other additional components which have known beneficial effects on the fuels in question. So you can z. B. small amounts of manganese, barium or iron, which are used to improve combustion and / or to suppress smoke formation, as well as boron as a biocide and other substances such as emulsifiers or de-emulsifiers, if this is given the nature of the used Fuel appears. If only the additives and / or the fuels mixed with them contain sources of magnesium and silicon and / or it is ensured that SiO 2 and MgO are present in the prescribed proportions and amounts in the combustion product or in the hot combustion zone, these fall Additives and the fuels mixed with them within the scope of the invention.

By applying the invention, i. H. by incorporating the additives into alkali-containing fuels or by burning the fuels in the presence of the additives, which essentially consist of compounds of silicon and magnesium in amounts such that a weight ratio of silicon to alkali metal of more than 6: 1, preferably, is obtained in the combustion products more than 10: 1, the need to wash the alkali metal depletion fuel with water is avoided or at least reduced. In the sense of the invention it would be possible to burn fuels under conditions under which a high alkali content, e.g. B. to about 20 to 100 ppm Na, occurs in the combustion products without excessive corrosion or contamination of the turbine blades when the combustion products are used to drive a gas turbine. The ASTM standards for gas turbine fuels currently set limits of 5 ppm sodium and 2 ppm vanadium for GT1, GT2 and GT3 fuels, which are intended for combustion without additives to combat corrosion or ash deposition. Although these fuel standards have been set by turbine manufacturers, technical experience has shown that the fuels,

even if they contain these relatively small and previously considered harmless amounts of impurities, are completely unacceptable and lead to the rapid destruction of turbine blades in turbines which are operated at metal temperatures of 760 ° C. and more. By using the fuels and burning the fuels according to the invention, these difficulties are eliminated.

Furthermore, when using the invention, there is no need to wash sodium-containing fuels with water in order to practically remove the alkali content from them. The invention enables the use of a relatively simple method in which a short, sufficient residence time of the fuel is provided in stock so that the water entrained by the fuel can settle out

10th

15

20th

25th

30th

35

40

45

50

55

60

65

7

623 603

and can essentially separate. Such a method enables the removal of a substantial portion of sea water or aqueous salt solutions which are usually entrained in the fuel and, if the fuel is filtered or centrifuged as required, leads to the withdrawal of a high and fluctuating concentration of sodium, thereby reducing the sodium content of such fuels is reduced to about 10 to 20 ppm, a range which can easily be permitted within the scope of the invention. Using the invention, it is also possible to allow higher sodium levels io in the combustion products entering the turbine caused by the sea salt content in the combustion air or, if water is injected, a lower purity water without using it Measures of expensive pretreatments, such as demineralization, are to be taken in order to essentially remove the metallic impurities from the water before its use in the turbine, provided that only the sodium content in the hot combustion products does not exceed a maximum of about 20 to 50 ppm. According to the invention, the sodium content of the fuel or of the combustion products entering the turbine need not be reduced to a negligible level.

if the additional components according to the invention are only present when the fuel is burned. This finding is of considerable technical value.

Attempts have been made to demonstrate the value of the invention; in particular, a combination of the components according to the invention was added to form a sodium-rich fuel. With special equipment, a number of tests were performed on metal samples to mimic the conditions that gas turbine blades are exposed to in practice. These

Special equipment is featured in Publication No. 70-WA / CD-2, an ASME publication, presented at the American Society of Mechanical Engineers Annual Meeting in New York from November 30 to December 3, 1970, entitled "Laboratory Procédures for Evaluating High-Temperature Corrosion Resistance of Gas Turbine Alloys », described and illustrated. The metal samples to be examined consisted of "Udimet 500", a nickel alloy containing Co, Cr, Al and Ti, and a cobalt alloy X-45 containing Cu, Ni and W, all of which are described in the work mentioned.

In the experiments, a fuel oil was used as fuel, which contained different amounts of sodium in the range from 1.5 to 20 ppm and different amounts of vanadium in the range from 2 to 20 ppm. The additional components according to the invention were added in amounts such

that there were different weight ratios of magnesium to vanadium and from silicon to sodium. The additive components, which consisted essentially of compounds of silicon and magnesium, which form SÌO2 and MgO at the combustion temperature, were added in the form of a magnesium sulfonate containing 12 percent by weight of MgO and a silicone polymer containing 60 percent by weight of SÌO2, both of which were in a temperature above 2320 ° C boiling aromatic petroleum fraction were dissolved. The additives were added to the fuel in such quantities that the Mg: V and Si02: Mg0 ratios given in the table below were obtained. The results of the tests are also reported in the table. The tests were carried out for a period of about 150 hours at a combustion gas temperature of 870 ° C. and a pressure of about 3 at. The results can be found in the table below.

Fuel composition ratio of additives weight loss due to corrosion,

Ratio mg / cm2

V, ppm Na. ppm Na: V Mg: V Si02: Mg0 U500 X-45 sulfidation

0

0

0

0

5.5 +

8 +

no

2nd

2nd

1.0

0

0

13

13

no

20 *

1.5

0.075

3rd

0

4.5

10.6

no

20th

20th

1.0

0

0

extremely strong

very strong

20th

20th

1.0

3rd

0

not determined

unacceptable

20th

20th

1.0

6

3rd

7.6

17.5

no

* Test temperature 8150 C. + oxidation.

The test results clearly show that at 870 ° C even a small amount of ash in the fuel, such as 2 ppm vanadium and 2 ppm sodium, leads to a considerable increase in corrosion, expressed as the weight loss of the alloy samples, compared to the weight loss that occurs when an ash-free distillate fuel ss is burned under the same test conditions, with only normal high-temperature oxidation occurring. If a magnesium additive in a weight ratio of Mg: V of 3: 1 is added to a vanadium-rich fuel,

vanadium corrosion is suppressed at 815 ° C with a minimum 60 sodium concentration in the fuel. With a high sodium concentration in the fuel, however, the alloy metals are rapidly destroyed despite the presence of magnesium in the weight ratio Mg: V of 3: 1 which has normally been recommended up to now. In contrast to the ineffectiveness which the magnesium additive shows on its own, the additional combination according to the invention prevents the use of a fuel which

Contains 20 ppm vanadium and 20 ppm sodium and therefore has a Na: V weight ratio of 1, under the same conditions the attack by sulfidation completely and reduces the weight loss of the alloy samples to a value that approximates that for an ash-free fuel, in which case U500 nickel alloy even reduces the rate of corrosion of a fuel containing 2 ppm vanadium and 2 ppm sodium. Previous experiments had shown that a content of 2 ppm each of vanadium and sodium represents the maximum permissible concentration of these metals in a fuel that is to be used for the operation of turbines at high temperatures without additives. The most significant advantage that results from the additive according to the invention is the suppression of sulfidation, which is shown in a fuel with a sodium content of 20 ppm, which is 20 times as high as the maximum sodium content of 1 ppm, which the standard regulations of Most turbine manufacturers allow the sulfidation of the metal alloys

623603

8th

Avoid in the nozzles and blades of turbines operated at temperatures of 760 ° C and more.

The experimental results in the table show that when using the special additional combination according to the invention, the fuel can have high levels of alkali metals, such as sodium, which are much higher than was previously thought to be permissible, provided only the fuel is present in the presence of the special additional combination is combusted according to the invention, thereby avoiding the destructive sulfidation attack and excessive corrosion of the turbine blades.

Compositions of additives according to the invention are given below. An additive consists of about 54 percent by weight of a petroleum hydrocarbon fraction, such as an aromatic petroleum fraction, about 25 percent by weight of one or more organic silicon compounds, such as a silicone, and about 21 percent by weight of one or more organic magnesium compounds, such as the magnesium salt of petroleum sulfonic acid. in a weight ratio Si02: Mg0 of 6: 1 with a total metal oxide content of about 17.5 percent by weight. This composition is suitable as an additive for the combustion of a normally liquid distillate fuel, such as a normally liquid petroleum distillate fuel, for the operation of gas turbines. Another composition which is suitable for the combustion of vanadium-containing fuels, such as vanadium-containing liquid petroleum fuels for gas turbines, in the sense of the invention consists of 34 percent by weight of a liquid hydrocarbon or petroleum fraction, 25 percent by weight of one or more organic silicon compounds and 41 weight percent of one or more organic magnesium compounds with a weight ratio Si02: Mg0 of 3: 1 and a total metal oxide concentration of about 20 weight percent.

B

Claims (15)

623 603 2nd PATENT CLAIMS 1. Fuel for gas turbines operating at temperatures of 760 ° C and more, based on a fuel with an alkali metal content of more than 2 parts by weight per million, characterized in that it is mixed with one that suppresses the sulfidation and the formation of turbine deposits There is an amount of additional constituents, which essentially consist of compounds of silicon and magnesium, which form SiCte and MgO at the combustion temperature and are present in such amounts that, calculated on the SiCh and MgO produced during combustion, a SiCh: MgO weight ratio is formed which is greater than 2: 1, the amount of the additional components added to the fuel being such that the weight ratio of silicon to alkali metal in the fuel mixture is more than 2: 1. 2. Fuel according to claim 1, characterized in that the weight ratio of Si to alkali metal in the fuel mixture is more than 6: 1. 3. Fuel according to claim 2, characterized in that the fuel base has a vanadium content of more than 2 parts by weight per million and contains the additional components in such quantities that at least 2 parts by weight of magnesium are present for each part by weight of vanadium. 4. Fuel according to claim 2, characterized in that the fuel base is a material obtained from petroleum. 5. Fuel according to claim 1, for gas turbines working at 7 60 0 C or more, based on liquid hydrocarbons with an alkali metal content of more than 2 parts by weight per million, characterized in that it is mixed with a sulfidation and Formation of turbine deposits suppressing amount of additional components is present, which are dispersed or dissolved in hydrocarbons and essentially consist of compounds of silicon and magnesium, which form S bildenO2 and MgO at the combustion temperature, the magnesium compound is selected from the group consisting of magnesium acetate, magnesium chloride, magnesium sulfonate, magnesium naphthenate and the magnesium salts of higher molecular weight carboxylic acids and the silicon compound is selected from the group consisting of Ci-Cö-alkyl silicates, polysilicic acid alkyl esters and silicones, and the compounds in such proportions are present that, based on the SÌO2 and MgO produced during combustion, a weight ratio Si02: Mg0 is formed which is greater than 2: 1, and the amount of the additive mixed with the fuel is dimensioned such that the weight ratio of silicon to alkali metal in the fuel is greater than 2: 1. 6. Fuel according to claim 5, characterized in that the magnesium compound is a magnesium sulfonate, which preferably contains about 12 weight percent MgO and the silicon compound is a silicone, which preferably contains about 60 weight percent SÌO2. 7. Fuel according to claim 5 or 6, characterized in that the fuel base contains ash-containing liquid hydrocarbons and the magnesium and silicon compounds are present in such amounts, that it corresponds to at least 0.05 parts by weight of SÌO2 and MgO per part by weight of ash in the liquid hydrocarbons. 8. A method for operating gas turbines at temperatures of 760 ° C and more with a fuel with an alkali metal content in the fuel gas of more than 2 parts by weight per million, or wherein the fuel is burned under such conditions that in the Combustion gases more than 2 ppm alkali metal occur, characterized in that the fuel is burned in the presence of additional components in the sulfidation and the formation of turbine deposits suppressing amounts, the additional components consisting essentially of compounds of silicon and magnesium, which at the combustion temperatures SÌO2 and Form MgO and are present in such quantities that, calculated on the SÌO2 and MgO produced during combustion, a weight ratio Si02: Mg0 is formed which is greater than 2: 1, and that the amount of the additional components is dimensioned such that the amount of silicon leads to a weight ratio of silicon to alkali metal in the combustion gases of more than 6: 1. 9. The method according to claim 8, characterized in that the fuel is an ash-containing petroleum fuel with a vanadium content of more than 2 parts by weight per million are used and the amount of the additional components is measured so that at least 2 parts by weight of magnesium are accounted for by each part by weight of vanadium in the fuel. 10. The method according to claim 8, characterized in that an oil distillate is used as fuel. 11. The method according to claim 9, characterized in that the fuel is first withdrawn from the fuel by settling during storage and / or centrifuging and / or passing through coalescing filters, so that the pretreated fuel has an alkali metal content of not more than 50 parts by weight per million. 12. The method according to claim 9, characterized in that occurs during the combustion of the fuel alkali metal in the combustion gases in amounts of more than 2 to 50 parts by weight per million. 13. Additive for liquid hydrocarbon-based fuels for operating gas turbines at temperatures of 760 ° C and more to suppress corrosion and ash deposition, characterized in that it contains sources of silicon and magnesium in such quantities that, calculated on the basis of the Combustion SÌO2 and MgO creates a weight ratio Si02: Mg0, which is greater than 2: 1, the source of magnesium being selected from the group consisting of magnesium acetate, magnesium chloride, magnesium sulfonate, magnesium naphthenate and the magnesium salts of carboxylic acids of higher molecular weight and the source of silicon being selected from the group consisting of silicic acid Ci-Cs alkyl esters, polysilicic acid alkyl esters and silicones, and the sources of silicon and magnesium are dispersible or oil-soluble in oil. 14. Additive according to claim 13, characterized in that the weight ratio Si02: Mg0 is 3: 1. 15. Additive according to claim 13 or 14, characterized in that the source of magnesium is a magnesium sulfonate and the source of silicon is a silicone, wherein the magnesium sulfonate preferably contains about 12 weight percent MgO and the silicone preferably contains about 60 weight percent SÌO2.