JPH09104880A - Prevention of high-temperature corrosion of fuel oil burning gas turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing high-temperature corrosion of a gas turbine for burning a low-quality fuel such as a fuel oil C. SOLUTION: In order to reduce high-temperature corrosion in a gas turbine for burning a low-quality fuel containing a large amount of impurities with high-temperature corrosiveness, an Na compound alone or a mixture of the Na compound and an alkaline earth metal compound is added to a fuel and a fuel ash composition to be stuck to a high-temperature part is made rich in a sulfate so as to make Np/V or [Na+Ca(mg)]/V (weight ratio) to 1-5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing high-temperature corrosion of a gas turbine that burns low-quality fuel oil such as C heavy oil.

[0002]

2. Description of the Related Art The temperature of a gas at the inlet of a recent industrial gas turbine of high efficiency represented by a combined cycle plant has risen significantly to 1300 ° C. or more. Heat-resistant alloys used for moving and stationary blades exposed to such high-temperature gas have undergone vigorous research and development, and their allowable operating temperatures are increasing year by year.
About 900 ° C. For this reason, a thin-walled internal air cooling blade is used in the actual gas turbine, but since high-temperature oxidation and high-temperature corrosion cannot be avoided on the blade surface in contact with the high-temperature gas, MCrAlY (M = Ni, Co, etc.) , A thermal barrier coating (TBC) in which a ZrO ₂ -based ceramic having a low thermal conductivity is coated on the MCrAl coating or the MCrAlY coating is used. On the other hand, the fuel used is LNG, by-product gas or heavy oil, and recently, it has been researched to utilize coal by liquefying or gasifying it. In this case, coating of a corrosion resistant alloy such as NiCoCrAlY or CoCrAlY is performed by a thermal spraying method (hereinafter referred to as VPS).

[0003]

In a high temperature gas turbine, the moving and stationary blades that come into direct contact with the combustion gas increase in oxidation rate and corrosion rate as the gas temperature increases.
Even when the above corrosion resistance, oxidation resistance, and coating are applied, when burning low-quality fuel such as C heavy oil containing a large amount of S, Na, V, etc., Na ₂ SO ₄ and V compounds are used as fuel ash for moving and stationary vanes, etc. Adheres to the high temperature parts of the
It is known to significantly accelerate its wear. As a method of reducing corrosiveness when using this type of fuel oil, a method of removing Na content by washing with water is known, but a practical removal method for V content has not been established yet. Therefore, as a method of suppressing the corrosive action (vanadium attack or accelerated oxidation corrosion) due to V content, Mg compounds [mostly Mg compounds
(OH) ₂ or MgO] is added to fuel oil to form an xMgO · V ₂ O ₅ compound having a high melting point and low corrosiveness. This xMgO · V ₂ O ₅ compound is a combustor or a turbine. It has the drawback that it adheres to the moving and stationary blades and blocks the gas flow path, greatly reducing gas turbine efficiency. As described above, the fact that there is no deciding measure against high temperature corrosion by the mixed ash of Na ₂ SO ₄ and V compound, especially the ash composition is V
When it becomes minutely rich, there is a problem that the corrosion rate is remarkably increased. An object of the present invention is to provide a method for preventing high-temperature corrosion of a gas turbine that burns low-quality fuel such as C heavy oil, which can solve the above problems.

[0004]

The present invention provides high temperature corrosion resistance.
Gas that burns low-quality fuel such as heavy oil containing a large amount of impurities
Combustion for the purpose of reducing hot corrosion damage in the turbine
No Na / V or [Na + Ca (Mg)] / V in the ingredients
These are also N in a weight ratio of 1 to 5, preferably 3 to 5.
a compound, for example Na_TwoSO_Four, Na_TwoCO_Three, Na
HCO_Three, NaHSO_Four, NaOH, Na-based surfactant
(Na-soap or Na-based synthetic detergent) etc. alone or in alkali
Earth metal compounds such as CaSO_Four, CaCO_Three, C
a (HCO_Three)_Two, Ca (HSO_Four)_Two, Ca (OH)
_Two, MgCO_Three, Mg (HCO_Three)_Two, Mg (HS
O_Four)_Two, Mg (OH)_Two, MgSO_Four, Ca-stone
High temperature when added to fuel as a mixture with saponifier, Mg-soap, etc.
Fuel ash assembly attached to parts such as combustors, moving and stationary vanes, etc.
Na for growth_TwoSO_Four, CaSO_Four, MgSO_FourSulfate of etc.
Gas fueled by low-quality fuel oil such as heavy oil characterized by being rich
A method for reducing high temperature corrosion of a sturbine is provided. That is,
Contains a large amount of impurities with high temperature corrosivity such as S, Na and V
In gas turbines that use low-quality fuels such as heavy oil,
If the fuel ash composition is expected to become V rich, the product
Extremely Na_TwoSO_FourAnd Na compounds such as Na-based surfactants
Alone or CaSO_Four(MgSO_Four), Ca (Mg)
Na as a mixture with an alkaline earth metal compound such as sodium bicarbonate
/ V or [Na + Ca (Mg)] / V is the weight
Fuel ash composition by adding to fuel etc. in a ratio of 1 to 5
To Na _TwoSO_FourAnd CaSO_Four, MgSO_FourWith sulphate etc.
It will be enriched.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The above Na compound alone or in a mixture with an alkaline earth metal compound such as Ca or Mg into a fuel used such as C heavy oil is used as Na / V or [Na + Ca (M
g)] / V = 1 to 5 (weight ratio) is added so that the ash composition (V ₂ O ₅ / Na ₂ SO ₄ ) adhering to the gas turbine moving blade or the stationary blade is 1.0. Below (weight)
It can be. As a result, the high temperature corrosive effect of the ash content is significantly reduced as compared with the case where (V ₂ O ₅ / Na ₂ SO ₄ ) is 1.0 or more (weight ratio). The present invention is based on Mg compounds and C
Compared to the method of injecting only the a compound, since a Na compound is added as a main component, a high melting point compound of Mg or Ca and V (for example, 3MgO.V ₂ O ₅ , mp. 1191 ° C.,
3CaO · V ₂ O ₅ , mp. (1019 ° C.) is not formed, and most of the ash becomes a melt on the blade surface controlled at 850 to 900 ° C., and the gas flow passage is not blocked. Here, the addition ratio of the Ca (Mg) compound to the Na compound, Ca (Mg) compound / Na compound (molar ratio), is preferably 0 to 1.0.

[0006]

EXAMPLES In order to confirm the effects of the present invention, a combustion gas environment of a gas turbine that burns high V heavy oil was simulated, air-cooled test pieces were used under the conditions shown in Table 1, and the gas and the test piece were each set to a predetermined value. The temperature was controlled, and a 300-hour test including starting and stopping twice was performed. S, Na, V,
Considering the pressure difference between the simulated test (1ata) and the actual plant (12ata), the additive components such as Ca and Mg were added in an amount equivalent to 12 times the actual machine conditions. * High V heavy oil simulation example: Simulates heavy oil with a higher V content than Na (conventional example) In this example, the fuel condition in the actual machine is S = 0.5
%, Na = 1 ppm, V = 10 ppm equivalent amount, 12 times equivalent amount of SO ₂ gas, 0.5% NaVO ₃ ,
It was injected as 0.5% VOSO ₄ from the tip of the burner.
That is, S = 6%, V = 120 ppm, and Na = 12 ppm.

Example 1 In addition to the conventional example (Na = 1 ppm), Na ₂ SO ₄ was used, and an amount equivalent to Na = 19 ppm was added to obtain 20 ppm. The data in Table 1 is obtained by multiplying this by 12 to 240 ppm. Na / V
= 2 (weight ratio). Example 2 In addition to the conventional example (Na = 1 ppm), sodium alkylbenzene sulfonate (R—C ₆ H ₄ —SO)
₃ Na) and Na = 29 ppm equivalent amount, and Mg
Mg (10 ppm) equivalent amount was added using (OH) ₂ .
Table 1 shows the values obtained by multiplying these values by 12. (Na
+ Mg) / V = 4 (weight ratio). Instead of Mg (Example 3) Example 2, was added Ca = 10 ppm equivalent amount with calcium stearate [2 (CH ₃ (CH _{2) 16} COO) Ca]. In Table 1, this was multiplied by 12 to 120 ppm. (Na + Ca) / V
= 4 (weight ratio).

[0008]

[Table 1] * 1 Indicates the amount added (weight ratio) to fuel kerosene. * 2 ECY 768: Co-based superalloy used for stator blades, etc. * 3 In Example 3, the additive component Mg of Example 2 was replaced with Ca.

Table 2 shows the results of investigations on the corrosion conditions of the test pieces (ECY763) obtained in Examples 1 to 3 and the high V heavy oil simulation example.

[0010]

[Table 2] * 1 The value of each high V heavy oil simulated example was set to 100.

As a result, Na or Na + Ca (or Mg)
Example 1 in comparison with a high V heavy oil simulation example in which
The corrosion weight loss (maximum corrosion depth) is 25% (30%), or in Examples 2 and 3, the corrosion weight loss is about 10% and the maximum corrosion depth is about 15%. Was recognized. (The corrosion weight loss and maximum corrosion depth in Table 2 are shown with the value of the high V heavy oil simulated example being 100.)

[0012]

EFFECTS OF THE INVENTION Corrosion at high temperature of a gas turbine that burns low-quality fuel oil such as C heavy oil can be effectively prevented.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideyuki Ota, 1-1, Niihama, Arai-cho, Takasago-shi, Hyogo Prefecture 2-1-1, Takasago Laboratory, Mitsubishi Heavy Industries, Ltd. No. 1 Mitsubishi Heavy Industries Takasago Research Center

Claims (1)

[Claims] 1. In order to reduce high-temperature corrosion in a gas turbine that burns low-quality fuel such as heavy oil containing a large amount of impurities having high-temperature corrosiveness, Na / V or [Na + Ca in the fuel is used.
(Mg)] / V (weight ratio) of 1 to 5 is added to the fuel as a Na compound alone or as a mixture with an alkaline earth metal compound, and the fuel ash composition adhering to the high temperature component is sulfate rich. A method for reducing high temperature corrosion of a gas turbine burning low quality fuel oil such as heavy oil.