JPH0874075A - Steam turbine system - Google Patents

Abstract

(57) [Summary] [Purpose] By injecting an appropriate amount of a chemical for corrosion prevention suitable for a corrosion mode, corrosion damage of turbine structural materials is prevented in advance and effectively. [Constitution] A condensed water storage unit 17 for temporarily storing condensed water discharged from the low-pressure turbine 4 is provided. Condensed water storage unit 17
A sample electrode made of a material having the same composition as the structural material of the low-pressure turbine 4 and a reference electrode serving as a potential reference are immersed in the condensed water. And the chemical injection control device 19
, The potential difference between the reference electrode and the sample electrode is measured, and the kind and the amount of the injected chemical are calculated so that the measured potential difference falls within the predetermined potential range for the structural material of the low-pressure turbine 4. The calculation result is sent to the chemical injection device 16, and the chemical injection device 16 injects an appropriate amount of the optimum chemical into the inlet side steam pipe of the low-pressure turbine 4 based on the calculation result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine system for power generation, for ships, and for driving various rotary machines.

[0002]

2. Description of the Related Art In the case of a thermal power plant, for example, a water treatment method called AVT (All Volatile Treatment) has been put into practical use as a method of protecting structural materials such as a boiler from corrosion damage. AVT uses ammonia and hydrazine to supply water to the boiler, and the pH of the water is 9.0.
From 9.5 to 9.5, the DO (Dissolved Oxygen) concentration is controlled to be 7 ppb or less. This method is mainly designed to prevent corrosion of boiler materials, and does not attempt to prevent turbine materials from being positively protected.

Recently, CWT (Combined Water T
A water treatment method called "reatment" has become widespread instead of the conventional AVT method. This is because the AVT processing method has the following problems. When the AVT-treated feed water is sent to the boiler, the corrosion products produced in the boiler evaporation tube accumulate in a wavy manner in the tube. The corrugated deposits hinder the movement of the water supply, increasing the differential pressure of the boiler, and consequently deteriorating the power generation efficiency. Also, in AVT processing, CW
It requires about 10 times as much ammonia as compared to T treatment. Furthermore, in order to avoid the increase in the differential pressure of the boiler, it is necessary to regularly descale the corrosion product,
There was an economical problem such as the cost for this.

The CWT method is a method of controlling pH from 8.0 to 8.5 and DO concentration from 50 to 200 ppb, and is effective for the above problems. However, this method is also AVT
Like the law, it does not attempt to prevent the corrosion of turbine materials. Further, when considering this water treatment method from the corrosiveness of the turbine material, conversely, the corrosive environment is considered to be more severe than that of the AVT method.

In such a situation, the turbine material such as the moving blade, the stationary blade and the rotor may be corroded and damaged. Particularly in a thermal power plant that consists of high-pressure, medium-pressure and low-pressure turbines, steam condenses and droplets are generated in the latter stage of the low-pressure turbine, which is the dry-wet cross seeding area of steam, and corrosive media mixes with this to promote corrosion There is something to do. Further, when the plant is started and stopped, condensed water is generated in the main turbine (high, medium and low pressure turbines) and the turbine for driving the feed water pump, which may cause corrosion damage as in the low pressure turbine. In addition, as the water treatment method shifts from AVT to CWT, the shift from AVT pH 9.5 to pH 8.5, which has low corrosion resistance and low pH, may cause more and more corrosion damage to turbine materials. Has occurred.

Therefore, there has been proposed a steam turbine in which wet steam or a chemical for corrosion prevention is sprayed on the turbine to wash away and prevent corrosion of the corrosive medium adhering to the turbine (for example, Japanese Patent Laid-Open No. 3-12120).
No. 2).

[0007]

However, in the above-mentioned conventional techniques, the amount of moist steam or chemicals for preventing corrosion sprayed on the turbine per unit time is constant, and the type of chemicals for preventing corrosion can be changed once set. There is no such thing. Therefore, if the amount of moist steam or chemicals to prevent corrosion is too small, there is no anticorrosion effect, and if it is too large, it is not economical, and if a corrosion inhibitor suitable for the corrosion type is not used. Has a problem that the anticorrosion effect is weak.

An object of the present invention is to provide a steam turbine system capable of preventing corrosion damage to a turbine structural material in advance and effectively by injecting a proper amount of a corrosion preventing chemical suitable for a corrosion mode. It is to be.

[0009]

In order to achieve the above object, the first invention of the present application is a boiler for heating feed water to generate steam, and a steam turbine driven by the steam generated in the boiler. In a steam turbine system including a condenser that condenses steam after driving the steam turbine into condensed water, and a pump that returns the condensed water to the boiler, discharge from the steam turbine or the condenser. Between the reference electrode and the sample electrode, at least one sample electrode made of a material having the same composition as that of the steam turbine structural material and a reference electrode serving as a potential reference are immersed in condensed water to be condensed. Potential measuring means for measuring the potential difference of the steam turbine, and chemical injection means for injecting a chemical for preventing corrosion of the steam turbine structural material into the steam pipe on the inlet side to the steam turbine or into the steam turbine. , The kind of the chemical injected from the chemical injection means is selected so that the potential difference measurement result measured by the potential difference measurement means is taken and the potential difference measurement result is within the predetermined potential range for the steam turbine structural material. And a chemical injection control means for controlling the quantity of the chemical.

According to a second aspect of the present invention, in the steam turbine system having the above structure, pH measuring means for measuring the pH of the condensed water discharged from the steam turbine or the condenser is added, and the chemical injection control means comprises: Incorporating the potential difference measurement result measured by the potential difference measurement means and the pH measurement result measured by the pH measurement means, the potential difference measurement result and the pH measurement in the oxide stable region of the potential-pH diagram of the constituent elements of the steam turbine structural material The kind of the medicine injected from the medicine injection means is selected and the amount of the medicine is controlled so that the intersection with the result is located.

A third aspect of the present invention is the steam turbine system configured as described above, wherein it is detected that the steam is condensed in any of the steam turbine, the steam inlet to the steam turbine, and the steam outlet from the steam turbine. Condensation detection means is added, the chemical injection control means takes in the potential difference measurement result measured by the potential difference measurement means, and when the coagulation detection means detects vapor condensation, the potential difference measurement result is the steam turbine structure. The kind of the medicine injected from the medicine injecting means is selected and the amount of the medicine is controlled so as to be within a predetermined potential range for the material.

[0012]

[Function] First, corrosion fatigue and stress corrosion cracking, which are one of the corrosion damages, will be described. Fatigue is a phenomenon in which cracking progresses when metal undergoes alternating stress and repeated stress.
Each metal has its own fatigue limit, and at stresses below the fatigue limit, fracture does not occur even if stress cycles are repeatedly applied. On the other hand, corrosion fatigue causes fracture in a corrosive environment if the number of stress cycle repetitions is sufficiently large, no matter how small the stress is. Corrosion fatigue may also cause fracture due to stress corrosion cracking at the same time. Corrosion fatigue generally shortens the fatigue life as the degree of general corrosion increases. Also, the resistance to corrosion fatigue depends on the strength of the metal, rather than the mechanical strength. Therefore, the metal can be protected from corrosion fatigue by mitigating the corrosive environment in contact with the metal material.

Stress corrosion cracking is a crack that occurs when a corrosive action and a static stress act simultaneously. Unlike corrosion fatigue, stress corrosion cracking occurs when tensile stress is applied in a specific environment. It is known that martensitic stainless steel, which is one of the turbine materials, undergoes stress corrosion cracking in an environment in the presence of chloride ions and ammonia. Further, the stress corrosion cracking has a critical potential for stress corrosion cracking occurrence of each material.

[0014] In addition, crevice corrosion, pitting corrosion, and hydrogen embrittlement cracking can be cited as forms that are problematic in corrosion of turbine materials. Crevice corrosion is particularly problematic in the dovetail section between the blade and rotor. Pitting is a problem when corrosive anions such as chloride are present in the environment. If seawater leaks from the condenser from time to time in the power plant,
Chloride ions may fly into the turbine system. Similar to stress corrosion cracking, there is a critical potential for these corrosions. Hydrogen embrittlement cracking is different from corrosion, and is a phenomenon in which atomic hydrogen resulting from the progress of corrosion enters the steel and embrittles the material. This is especially noticeable with hard materials such as martensitic stainless steel used for rotor blades. In the present invention, these corrosions are generally called corrosion damages.

The next problem is how to determine an effective injection amount without excess or deficiency. The injection volume is determined as follows. A test electrode having the same composition as the material forming the turbine material and a reference electrode serving as a reference for the potential are immersed in the condensed water discharged from the steam turbine or the condenser. Then, the type and amount of the injected chemicals are controlled so that the potential of the test electrode measured by the reference electrode is present in a potential region where the turbine structural material is not corroded and damaged in advance. Metallic materials generally have a unique corrosion initiation critical potential for each corrosion form. For example, in the case of pitting corrosion and crevice corrosion, pitting corrosion and crevice corrosion occur respectively when the natural potential exceeds the pitting corrosion occurrence or crevice corrosion occurrence potential. Therefore, the turbine material can be kept sound by monitoring the potential of the test electrode and controlling the type and amount of the injected chemical so that the natural potential exists in the potential region where the turbine structural material is not corroded and damaged. .

According to the first aspect of the present invention, if the potential difference measured by the potential difference measuring means is outside the predetermined potential range for the steam turbine structural material, the chemical injection means determines that the measured potential difference is within the potential range. Select the type of drug to be injected and control the amount of drug injected. For example, p
By selecting a chemical that enhances H and injecting an appropriate amount of it, the corrosion resistance of the iron-based metal can be improved.

Further, according to the second aspect of the invention, the type and amount of chemical injection are controlled so that the corrosion potential exists within the oxide stable region in the potential-pH diagram of the elements constituting the turbine material. Can maintain a turbine that is resistant to corrosion.
Since the passive film existing on the surface of the structural material is mainly composed of oxide, the constituent elements of the turbine material-potential of the water system-
If the corrosion potential lies in the oxide stability region in the pH diagram, thermodynamically the structural material will not corrode. In order to achieve this, it is necessary to know the corrosion potential of the structural material and the pH of the liquid with which the structural material is in contact, and in the present invention, the pH of the condensed water discharged from the steam turbine or the condenser is adjusted to pH.
It is measured by measuring means.

However, since this potential-pH diagram can be used when corrosive ions such as chloride ions are not contained, when chloride ions sometimes flow into the turbine as in a thermal power plant, the turbine cannot be used. Material constituent elements −
It is necessary to use a potential-pH diagram of the water-chloride ion ternary system.

Next, according to the third aspect, the chemical is injected only when the steam is condensed in the turbine to be injected, so that the consumption of the chemical can be suppressed.

Whether or not the steam in the turbine casing is condensed depends on the load of the boiler. Corrosion does not proceed because water is not generated when the steam in the turbine casing to be injected is in the dry region. At this time, injecting chemicals is useless. Therefore, it is possible to suppress the waste of the chemical by providing the condensation detecting means for grasping the vapor condensation state and injecting the chemical only when the vapor is condensed. If, for example, a conductivity meter is used as the condensation detection means, the conductivity increases due to the adhesion of condensed water to the electrodes of the conductivity meter, so that it is possible to detect whether or not the vapor has condensed.

The chemical to be injected is a chemical substance having an oxidizing property, a reducing property, or a property of dissolving in condensed water to cause a pH change, or a property of making a passive film existing on the surface of a metal material highly resistant to corrosion. By selecting the chemical substance, the corrosion resistance of the turbine material can be kept high.

A chemical substance such as oxygen gas having an oxidizing property has the effect of promoting the formation of a passive film and improving the corrosion resistance. However, oxygen also has the opposite effect of promoting corrosion. In the case of a reducing hydrogen gas or the like, it does not have the property of making the coating highly corrosion resistant, but has the effect of lowering the spontaneous potential of the material. When the natural potential becomes low, for example, S
The difference between the CC generation potential and the natural potential becomes large, and as a result, SCC becomes difficult to occur. In the case of ammonia having the property of causing pH change, the pH of condensed water increases due to the addition of ammonia, and the iron-based alloy works in a stable direction against corrosion. In the case of a chemical species having a property of stabilizing a passive film such as molybdate, the passive film that influences the corrosion resistance becomes strong against the corrosion, so that the corrosion resistance is improved.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram of a thermal power plant. This power plant is provided with a high-pressure turbine, a medium-pressure turbine, and a low-pressure turbine so that the feed water can be treated by CWT. As shown in the figure, this power plant is composed of three systems: a water supply system (path shown by a thin solid line), a steam system (path shown by a broken line), and a chemical injection system (path shown by a thick solid line).

First, the operation of the water supply system and the steam system will be described, and then the chemical injection system will be described. The water supply is boosted by each pump of the condensate pump 7, the condensate booster pump 11, and the water feed pump 14, and is supplied from the condenser 6 to the boiler 1. A gland condenser 8, a condensate filter 9 and a condensate demineralizer 10 are provided on the way from the condensate pump 7 to the condensate booster pump 11. Also, the condensate booster pump 11
Ammonia injection device 2 for injecting ammonia in order to adjust the pH of the feed water in the way from the water supply pump 14 to the water supply pump 14.
9, a low-pressure feed water heater 12, a deaerator 13 for removing gas dissolved in the feed water, and an oxygen injection device 28 for injecting oxygen into the feed water are provided. Further, a high-pressure feed water heater 15 is provided on the way from the feed water pump 14 to the boiler 1.

The boiler 1 turns the feed water into a vapor phase, which is supplied to the high pressure turbine 2 and the feed water driving turbine 5. The steam supplied to the high-pressure turbine 2 releases kinetic energy for rotating the turbine 2, and then part of the steam is returned to the boiler 1 and reheated. The rest is supplied to the medium-pressure turbine 3, performs the same work, and then is sent to the low-pressure turbine 4. Part of the steam discharged from the intermediate-pressure turbine is also supplied to the feedwater-driven turbine 5, but whether or not to supply the steam varies depending on the load state of the boiler. Most of the steam used in the low-pressure turbine 4 consumes most of its energy (temperature of about 30 degrees, pressure of 0.
(05 atm), and condensed and collected in the condenser 6. The condensed water becomes supply water again, is supplied to the boiler 1, and circulates in this cycle.

Next, the chemical injection system will be described. The inlet side pipe of the low-pressure turbine 4 is connected to the chemical injection device 16 so that the chemical is injected into the inlet side pipe. Since the water phase in the low-pressure turbine 4 in the base load state (during rated operation) hits the wet-dry alternating region, part of the steam is condensed. The condensed water adhering to the surface of the rotor blade is repelled in the circumferential direction by the centrifugal force of the rotor blade rotating at high speed. The low pressure turbine 4 is provided with a condensed water introduction pipe 21 for discharging the above-mentioned condensed water generated in the low pressure turbine 4, and the condensed water is guided to a condensed water tank 17 by using a condensed water pump 18.
The type and amount of the chemical injected from the chemical injection device 16 are determined based on the potential of the test electrode installed in the condensed water tank 17 described below.

FIG. 2 shows the details of the condensed water tank 17. The condensed water tank 17 has a structure capable of withstanding pressure, and is provided with a condensed water introduction pipe 21 and a condensed water discharge pipe 26. Further, the condensed water tank 17 is provided with a sample electrode 22 and a reference electrode 23 which serves as a potential reference of the sample electrode 22. The composition of the sample electrode 22 is the same as that of the turbine structural material. If the turbine is composed of multiple materials,
Add the number of sample electrodes corresponding to each material, or
Alternatively, a noteworthy material may be selected and installed. Here, for the sake of simplicity, the martensitic stainless steel of 12% chromium forming the moving blade is selected from the turbine materials. Further, in order to measure the potential of the sample electrode 22 with respect to the reference electrode 23, a potential signal line 24 is connected to the electrodes 22 and 23, and a potential signal is sent to the drug injection control device 19. In addition, 25 is condensed water.

FIG. 3 is a detailed view of the chemical injection control device 19. The chemical injection control device 19 has a built-in potentiometer 27 for measuring the sample electrode 22 with respect to the reference electrode 23. The potential of the sample electrode 22 measured by the potentiometer 27 is sent to the comparison unit 30 and it is determined whether it is within a preset potential range.

Here, the condensed water tank 17, the sample electrode 22, the reference electrode 23, the potentiometer 27, etc. are a potentiometric measuring means,
The chemical injection device 16 constitutes a chemical injection means, and the comparison part 30 and the control part 31 in the chemical injection control device 19 respectively constitute a chemical injection control means.

The chemicals may be injected not only from the inlet side pipe of the low-pressure turbine 4 but also from a nozzle provided on the stationary blade as shown in FIG. In FIG. 4, 36 is a rotor, 37 is a moving blade, 38 is a stationary blade, and 39 is a generator.
The stationary blade 38 is provided with a nozzle 40 for ejecting a chemical into the turbine, and the nozzle 40 is connected to the chemical injection device 16.

FIG. 5 shows the relationship between the pitting corrosion generation potential and the chloride ion concentration of 12% chromium martensitic stainless steel at a temperature of 90 ° C. as a function of pH. When the potential of the sample electrode 22 exceeds the position shown by the solid line to the plus side, that is, when the oxidizing atmosphere becomes strong, pitting corrosion occurs. Pitting tends to be the starting point of stress corrosion cracking and corrosion fatigue, so it is necessary to operate the turbine in an environment where pitting does not occur. Corrosion potential is p for safety
H4.7, chloride ion concentration 1 mol / dm ⁻³ Potential indicated by -0.25 V vs. SHE If the injected chemicals and amount are controlled to be below, then the rotor blade (turbine material)
Can be protected against corrosion.

Based on the above, when the measured potential of the sample electrode 22 exceeds the set range to the plus side, it is considered that the environment of the low-pressure turbine has a strong oxidizing atmosphere, and therefore hydrogen having a reducing property is injected. Thus, the control unit 31 sends a signal to the control unit 31, and the control unit 31 controls the medicine injection device 16. On the contrary, when the measured corrosion potential exceeds the negative side of the set region, the reducing atmosphere becomes strong and there is a concern that the blade may be cracked due to hydrogen embrittlement. Therefore, the chemical injection device 16 is controlled so as to inject oxygen having the effect of increasing the potential. By injecting a chemical according to the corrosion potential, it is possible to protect the turbine material from corrosion damage.

As is clear from FIG. 5 shown above, the pitting corrosion potential is expressed as a function of pH and chloride ion concentration (provided that the temperature of the turbine and the temperature of the condensed water tank 17 are substantially equal). . In order to evaluate the corrosive environment more accurately, it is desirable to measure pH and chloride ion concentration. There is no problem if the pH and chloride ion concentration of the condensed water are known and there is no change over time, but these may change depending on the load condition of the boiler such as start and stop of the plant. In FIG. 6, a pH meter 32 and a chloride ion concentration meter 33 are added to the condensed water tank 17. With such a configuration, the pH of the condensed water and the chloride ion concentration can be obtained, and the accurate potential for pitting corrosion can be known from the relationship in FIG. For example, the pitting corrosion generation potential when the measured pH is 8.5 and the chloride ion concentration is 0.01 mol / dm to ³ is about 0.1 V from the figure, and the spontaneous potential is below this pitting corrosion generation potential. If held at, no pitting corrosion will occur on the blade.

Although pitting corrosion is taken as an example in this embodiment, various corrosion modes such as crevice corrosion, stress corrosion cracking, and corrosion fatigue exist in addition to pitting corrosion in an actual environment, and no countermeasure is taken against these corrosion modes. And can not completely prevent the corrosion damage of turbine material. In general, similar to pitting corrosion, there is a critical potential for corrosion occurrence in these types of corrosion. Therefore, chemicals should be injected so that the natural potential exists in the potential region where these corrosions do not occur, thereby highly protecting turbine materials from corrosion damage. Is possible.

In this embodiment, the test electrode 22 is installed in the condensed water tank 17 and the corrosion potential is measured by the reference electrode 23. Instead of the test electrode 22, the corrosion potential of the piping material through which the condensed water passes is measured. Substitution is also possible.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Figure 7 shows the potential-pH of iron at 25 ° C.
FIG. This figure shows the thermodynamic stability of iron compounds, and the hatched portion is a region in which it can exist stably as an oxide. Therefore, if the corrosion potential of the sample electrode 22 in the condensed water tank 17 exists in the hatched portion, the passive film formed of oxide (correctly, hydroxide and oxyhydroxide may also exist). Can exist stably and is not corroded.

Potential-pH by the comparison unit 30 in FIG.
As a result of the comparison between the figure and the corrosion potential, when the corrosion potential deviates from the oxide stable region, the control unit 30 causes the pH change so that the corrosion potential falls within the oxide stable region, or the chemical that changes the potential. Is instructed to be injected using the chemical injection device 16. This FIG. 7 can be applied only when a corrosive substance such as chloride ion does not exist. Therefore, when chloride ion or sulfide ion exists in the condensed water, a newly calculated or actually measured iron-water- A potential-pH diagram of chloride ion system or iron-water-sulfur system is used as a criterion for chemical injection. The potential-pH diagram for chromium is shown in FIG.

(Third Embodiment) Next, a third embodiment of the present invention will be described. In the first embodiment, oxygen and hydrogen were used as the chemicals to be injected according to the state of the self-potential, but any chemical having an oxidizing property such as oxygen may be used. Any chemical may be used as long as it is a reducing agent. Further, when the turbine environment is an oxidizing atmosphere or a reducing atmosphere, a chemical that removes substances causing these by a chemical reaction may be used. For example, oxygen having an oxidizing property reacts with hydrazine to decompose into non-oxidizing nitrogen and water. Even a chemical that changes pH can prevent corrosion. The higher the pH of an iron-based material, the less likely it is to corrode. Ammonia dissolves in the condensed water and raises the pH, so it has an anticorrosive effect on the turbine material. In addition, corrosion damage can be prevented by injecting a chemical that improves the corrosion resistance of the turbine material itself. For example, molybdate ions serve to strengthen the passive film of iron-based materials and suppress corrosion.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. Whether the steam in the turbine condenses changes depending on the load state of the boiler. If the steam does not condense, the water required for the corrosion cannot be supplied, so the corrosion does not proceed. At this time, it is useless to inject the chemical. Figure 9
This is an example in which, in the thermal power plant having the same configuration as in FIG. 1, a conductivity meter 34 that senses the wetness of steam in the low pressure turbine 4 is provided in the low pressure turbine 4 as condensation detection means. That is, in FIG. 9, when the steam gets wet, condensed water adheres to the electrode surface of the conductivity meter 34 and the conductivity increases. The conductivity signal of the conductivity meter 34 is transmitted to the drug injection controller 19 via the conductivity signal line 35. And the chemical injection control device 1
9 permits the chemical injection to the chemical injection device 16 only when the conductivity meter 34 detects water. As described above, in this embodiment, without paying attention to the load state of the boiler 1, the chemical is injected only when the steam of the turbine to be protected against corrosion enters the condensation environment, that is, the chemical is injected while the steam is not condensed. Since the injection is stopped, it is possible to prevent waste of chemicals.

Although the conductivity meter 34 is installed in the low-pressure turbine 4 in this embodiment, it may be located at any place where the condensed water flows out, such as the condensed water introducing pipe 21 and the condensed water tank 17. In the present embodiment, the conductivity meter 3 measures the condensed state of vapor.
Although it was detected in step 4, any means can be used as long as it can detect that the vapor has condensed.

Although the chemical injection device 16 described in the first to fourth embodiments has been exemplified for the low pressure turbine, the present invention is not limited to this, and the high pressure, medium pressure, feed water drive turbine may be used if necessary. Can also be applied to. Further, although the injection point of the chemical is provided at the turbine inlet, it may be injected from the jet port provided at the stationary blade. Similarly, the condensed water tank 17 for measuring the corrosion potential may be installed in a high-pressure, medium-pressure, feedwater drive turbine.

Although the condensed water is sampled through the condensed water introducing pipe 21 provided in the turbine to which the chemical is injected, the method is not limited to this method. When it is difficult to provide a pipe (condensed water introduction pipe 21) for extracting condensed water in the turbine casing, the test electrode 22 and the reference electrode 23 may be installed in the condenser 6 itself. Further, the condensed water tank 17 may be installed on the way from the condenser 6 to the condensate pump 7 or at any place in the water supply system. Furthermore, the present invention can be implemented by newly providing an extraction pipe in the steam system and using condensed water obtained by condensing the extracted steam in a heat exchanger as a target of corrosion potential measurement.

[0043]

As described above, according to the present invention,
Since an appropriate amount of anticorrosive chemicals suitable for the type of corrosion is injected,
Corrosion damage to the steam turbine structural material can be prevented effectively before it becomes possible to provide a highly reliable steam turbine system.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a steam turbine system according to a first embodiment of the present invention.

FIG. 2 is a detailed view of the condensed water tank portion of FIG.

FIG. 3 is a detailed view of a medicine injection control unit of FIG.

FIG. 4 is a view showing a chemical injection unit into the steam turbine.

FIG. 5 is a diagram showing the influence of chloride ion concentration and pH on the pitting corrosion generation potential.

FIG. 6 is a view showing a condensed water tank equipped with a pH meter according to a second embodiment of the present invention.

FIG. 7 is a potential-pH diagram of iron.

FIG. 8 is a potential-pH diagram of chromium.

FIG. 9 is a configuration diagram of a steam turbine system according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Boiler 2 High Pressure Turbine 3 Medium Pressure Turbine 4 Low Pressure Turbine 5 Feed Water Drive Turbine 6 Condenser 7 Condensate Pump 8 Ground Capacitor 9 Condensate Filter 10 Condensate Desalination Device 11 Condensate Booster Pump 12 Low Pressure Feed Heater 13 Deaerator 14 Water supply pump 15 High-pressure feed water heater 16 Chemical injection device 17 Condensed water tank 18 Condensate pump 19 Chemical injection control device 20 Chemical injection control signal 21 Condensate introduction pipe 22 Sample electrode 23 Reference electrode 24 Potential signal line 25 Condensed water 26 Condensed water discharge pipe 27 Potentiometer 28 Oxygen injection device 29 Ammonia injection device 30 Comparison part 31 Control part 32 pH meter 33 Chloride ion concentration meter 34 Conductivity meter 35 Conductivity signal line 36 Rotor 37 Stationary blade 38 Moving blade 39 Power generation Machine 40 nozzles

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuo Shimizu Inventor 3-1, 1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Tetsuo Yamaguchi 3-chome, Sachimachi, Hitachi, Ibaraki No. 1 Hitachi Ltd. Hitachi factory

Claims (7)

[Claims] 1. A boiler for heating feed water to generate steam, a steam turbine driven by steam generated in the boiler, and a condenser for condensing steam after driving the steam turbine into condensed water. And a pump for returning the condensed water to the boiler, wherein the condensed water discharged from the steam turbine or the condenser is made of a material having the same composition as the steam turbine structural material. At least one sample electrode and a reference electrode serving as a potential reference are immersed, and a potential difference measuring means for measuring a potential difference between the reference electrode and the sample electrode; and an inlet side steam pipe to the steam turbine Alternatively, a chemical injection means for injecting a chemical for preventing corrosion of the steam turbine structural material, and a potential difference measurement result measured by the potential difference measurement means are taken into the steam turbine. At the same time, the chemical injection control means for selecting the type of chemical injected from the chemical injection means and controlling the amount of the chemical so that the potential difference measurement result falls within the predetermined potential range for the steam turbine structural material. And a steam turbine system. 2. A boiler for heating feed water to generate steam, a steam turbine driven by the steam generated by the boiler, and a condenser for condensing steam after driving the steam turbine into condensed water. And a pump for returning the condensed water to the boiler, wherein the condensed water discharged from the steam turbine or the condenser is made of a material having the same composition as the steam turbine structural material. At least one sample electrode and a reference electrode serving as a potential reference are immersed, and a potential difference measuring means for measuring a potential difference between the reference electrode and the sample electrode; and discharge from the steam turbine or the condenser PH measuring means for measuring the pH of condensed water to be stored, and a chemical for preventing corrosion of steam turbine structural material in the steam pipe on the inlet side to the steam turbine or in the steam turbine. A chemical injection means for injecting a product, a potential difference measurement result measured by the potential difference measurement means, and the p
While incorporating the pH measurement result measured by the H measuring means, the intersection of the potential difference measurement result and the pH measurement result is located in the oxide stable region of the potential-pH diagram of the constituent elements of the steam turbine structural material, And a chemical injection control means for selecting the type of chemical injected from the chemical injection means and controlling the amount of the chemical. 3. A boiler for heating feed water to generate steam, a steam turbine driven by the steam generated by the boiler, and a condenser for condensing steam after driving the steam turbine into condensed water. And a pump for returning the condensed water to the boiler, wherein the condensed water discharged from the steam turbine or the condenser is made of a material having the same composition as the steam turbine structural material. At least one sample electrode and a reference electrode serving as a potential reference are immersed, and a potential difference measuring means for measuring a potential difference between the reference electrode and the sample electrode; and steam in the steam turbine and to the steam turbine Condensation detection means that is provided at any one of the inlet part and the steam outlet part from the steam turbine, and detects the condensation of the steam at the part, and the steam on the inlet side to the steam turbine In the pipe or in the steam turbine, a chemical injection means for injecting a chemical for preventing the corrosion of the steam turbine structural material, and the potential difference measurement result measured by the potential difference measurement means are taken in, and the solidification detection means When the condensation is detected, the kind of the chemical injected from the chemical injection means is selected and the amount of the chemical is controlled so that the potential difference measurement result is within a predetermined potential range for the steam turbine structural material. A steam turbine system comprising: a chemical injection control means. 4. The steam turbine system according to claim 3, wherein the condensation detecting unit is a conductivity meter that measures conductivity at the location. 5. The steam turbine system according to claim 1, 2, or 3, wherein the potential difference measuring means has a storage means for temporarily storing condensed water discharged from the steam turbine or the condenser. Steam turbine system characterized by. 6. The steam turbine system according to claim 1, 2, or 3, wherein the chemical injected by the chemical injection means is an oxidizing agent, a reducing agent, or a substance having a property of dissolving in condensed water to cause a pH change, or A steam turbine system, which is a substance having a property of making a passive film existing on the surface of the steam turbine structural material highly corrosion resistant. 7. The steam turbine system according to claim 1, 2, or 3, wherein the chemical injection means injects a chemical into the steam turbine from a nozzle provided in a stationary blade of the steam turbine. Steam turbine system.