JPS5963301A - Geothermal turbine rotor - Google Patents

Abstract

PURPOSE:To improve the resistivity against corrosion caused by sulfide by thermally spraying material which has electrically poor characteristics compared with low alloy steel, namely, the material of a turbine rotor, onto it so as to form a uniform-thickness film on said turbine rotor with ease. CONSTITUTION:Al is flame-sprayed or plasma-sprayed onto the wheel part 24 of a low alloy steel turbine which turns inside a turbine casing 2, forming an Al thermally sprayed film layer 21. Therefore, a film of uniform thickness may be easily formed by the flame spraying or the plasma spraying and the basic material of a rotor may be prevented from corrosion because the Al film layer acts as a sacrificial annode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in turbine rotors used in geothermal turbines.

Geothermal power plants generate electricity using high-temperature steam and hot water that exist underground, using them as thermal energy sources for steam turbines, and are currently being developed to effectively utilize natural energy. ,however,
Since geothermal power plants use natural steam containing corrosive gases as a working medium, turbine parts that are in direct contact with the natural steam are placed in a severe corrosive environment.

In thermal power generation, water before entering the boiler to prevent corrosion! PH9.3-9.5, dissolved oxygen 7pp
The iron content is kept below 10ppb. On the other hand, geothermal steam differs depending on the well 52, but 15~
It contains a scum component composed of about 30% hydrogen sulfide gas and the remaining carbon dioxide. In addition, the hot water that spouts out along with the steam has a pH of 3 to 10. Hanion ion 100-4000p
pm l sulfate ion 10-110000pp, potassium ion in sodium ion 100-4. It is about OOppm.

Therefore, exposure to geothermal steam having such components i]
The materials used for the turbine rotor are subject to severe corrosion, which poses a problem for long-term operation.

In particular, since oxygen is a major factor contributing to corrosion, the labyrinth seal of the shaft seal and its surrounding areas, where steam and the atmosphere come into contact, tend to corrode more than other parts. For example, if the steam temperature is 150°C In the case of a geothermal steam turbine of
．． A decrease in wall thickness due to corrosion of 5yJ is observed. This
It is known that L is caused by the fact that the working medium, geothermal steam, condenses and accumulates due to the low temperature of the shaft seal, and that oxygen from the atmosphere dissolves into the condensation.

In the shaft sealing portion C2 of the geothermal steam turbine shown in Fig. 1, geothermal steam is introduced into the turbine casing 1 and efficiently turns the turbine rotor 2 into a rotation source. The steam that has completed its work is condensed from within the turbine casing l by a condenser (not shown) and returned to the ground. On the other hand, the sealing steam enters the grand seal chamber 3, flows through the left and right labyrinth packings 4Q and 4b, and seals the inside of the turbine casing 1 from the atmosphere. Furthermore, the sealing steam that has passed through the labyrinth packing 4b and the outside air that has passed through the labyrinth packing 4c and the balance weight 5 are dissolved, and the air is drawn into the grand vent chamber 6 (for two people), and then to an air extractor (not shown).

In addition, the ground vent chamber 6 is raised so that outside air and seal oil leaking from the bearing 7 through the oil seal portion 8 will not flow back. The shaft seal part and its vicinity under such conditions of φ exhibit severe corrosion due to geothermal steam and oxygen in the atmosphere. Therefore, the following problems exist as drawbacks of conventional geothermal turbines.

(1) Because the labyrinth gasket is corroded 6)k, the clearance increases, so the air suction rate increases by 1ρ, and as a result, the air extractor becomes the fire engine
Compared to this, the volume h'4- becomes larger.

(2) The labyrinth seal, which is integrally machined with the turbine rotor, will need to be reworked.

(8) The vibration correction balance weight 5 of the turbine rotor installed in the ground vent chamber 6 is corroded, and as a result, the vibration of the turbine rotor increases during operation.

Conventional solutions to these problems include the use of high-cobalt alloys, FA-nickel-chromium-molybdenum alloys, and stainless steel overlay-sprayed turbine rotor materials; It is being considered that an inert gas can be used as a fluid to cut off contact with air. However, the inner coating thermal spraying method is
Thermal spraying process takes time, it is difficult to form a uniform film and machining is required after spraying, pores are formed and sealing cannot be done, and the adhesive strength is high and the film is hard. Therefore, there are drawbacks such as difficulty in removing the sprayed film during disassembly and repair. Furthermore, the air shutoff method using nitrogen gas has economical problems in terms of the cost of equipment and slag.

A first object of the present invention is to provide a turbine rotor in which a thermally sprayed layer JI'A can be easily and uniformly formed and has excellent sulfide corrosion resistance.

The present invention is characterized by a low alloy material (1) base material of the turbine rotor, 2)
This relates to the formation of a thermally sprayed coating of a less noble material on the turbine rotor.

In the present invention, aluminum (
A1) can be achieved by flame spraying or plasma spraying on low alloy steel. A
No. 1 was selected from among the four thermal spray materials based on the results of the #j base test in hot steam.

Af thermal sprayed film t: Added excellent sulfurization resistance 1-,
It was experimentally found that ζ2 is less electrically grounded (in steam) than low-alloy steel. It was found that the Ai melting layer acts as a sacrificial anode and has a synergistic effect of preventing corner wall thinning (of the base material).

In an embodiment of the present invention, after degreasing the area to be treated with anti-corrosion using trichloride, shot, doplast or sandblasting is performed to remove surface oxidation scale and improve the mechanical adhesion of the sprayed layer. Process 1]° now. A1 is thermally sprayed using this Iyu g2 thermal spraying device, and the bath spraying method includes metallizing using MuJ1liil, thermospraying using AJ'(5) powder, or (d[plasma spraying). Both methods can be expected to have the same effect.

Example 1 Sample 1ii, 7 pieces I of the turbine rotor shell having the composition shown in Table 1 were thermally sprayed with A2 by plasma with some of the C2 (not shown in Fig. 1) exposed at pC. hV radiation + tq
IH': Overturned for the first time in 2.

For the implementation of Table 1, after degreasing and cleaning sweet sweet sample piece 1 with Trichlor,
Mask the area other than the surface to be thermally sprayed with metal tape,
Blast with alumina powder.

After this, spraying of 70 to 80 μm at a time was repeated 7 to 8 times using a thermal spraying machine so that the final thickness was 0.5 mm. The composition of the thermal spray powder used is shown in Table 2.

Table 2 Test piece 1 after intoxication was exposed to a geothermal environment for 3 to about 6 months and then measured. This environment 6, geothermal steam (all gas kj
0.03-0.15%, H2S it 0.008
-0.17%.

co2 JM: 0.02-0.13%, inert gas, z,
0.0002-0.02%), PH5.2, 025.9ppm, BO2゜16
．． 5 ppm, Has 80'ppm T S-. The test results are shown in Table 3.

As is clear from the results in Table 3 above, the turbine rotor material thermally sprayed with AL has significantly improved corrosion resistance, and also Compared to the one that had been diluted, %Al acted as a negative oxide, and no visible part of the exposed part of the test piece (2) was observed.

Therefore, in the present invention 1-, by coating the turbine rotor material with A1 powder wood, Ji
'! + Excellent corrosion resistance even under adverse food environment conditions, and even if some of the sprayed layer peels off during heavy operation, A4# +
Since the coating layer 21 acts as a sacrificial anode and maintains the mother@20, the lifespan is much longer than in the past, and an excellent effect is exhibited.

Example 2 In Example C2 shown in FIG. 3, the wheel portion 24 of the turbine rotor 23 rotating inside the turbine casing 22
2AJ, a thermally sprayed coating layer 21 has been applied.

The wheel portion 24 coated with this AL sprayed coating layer 21 is
This is a location where erosion and corrosion are likely to occur due to the drain that has passed through the nozzle labyrinth 25, but this can be effectively prevented by the coating layer 21, and cracking due to corrosion can also be prevented. In addition to this, C2 can also be applied to geothermal environments in turbines to provide better corrosion resistance.

As described above (according to the present invention), by applying the A4 heat-resistant coating to the special C2 geothermal environment part of the turbine, the sulfide corrosion resistance of this part is significantly improved, and the safety of the turbine itself is improved. can maintain strength and durability.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the 11η (1 sealing part) of the turbine rotor, and Fig. 2 is a perspective view showing a test piece of the A1 thermally sprayed sheath of the geothermal turbine rotor according to the present invention C2. ”
+ Figure 3 is an i-r plane view showing a wheel portion of a geothermal turbine rotor according to the present invention. 20... Trial piece piece material 21... A1 welding + It
Membrane 22...Turbine casing 23...Turbine rotor 24...Wheel 25...
... Nozzle labyrinth ... Turbine casing 2 ... Turbine rotor 3 ... Grand seal chamber 4
a~4c...Labyrinth packing 5...Balance weight 6...Grand vent chamber (8733) Agent: Yoshiaki Inomata (1 other person) Figure 1

Claims (2)

[Claims] (1) A geothermal turbine rotor characterized in that a part used in a geothermal environment is coated with a coating layer of a material having less electrical characteristics than the part's matrix. (2) A geothermal turbine rotor according to claim 1, wherein the coating layer is formed by thermal spraying high-purity aluminum containing few impurities such as iron and copper.