Water quality diagnosis method

Abstract

To provide a water quality diagnostic method enabling the presence / absence of abnormality of water quality in a steam turbine plant to be more appropriately determined.SOLUTION: A water quality diagnostic method comprises: a step of obtaining a measurement value of an electrical conductivity and a measurement value of pH of sample water derived from steam or circulating water taken from a steam turbine plant using ammonia as a water conditioning agent; and a determination step of determining the presence / absence of abnormality of water quality in the steam turbine plant using at least a first determination condition of whether or not the measurement value of the electrical conductivity and the measurement value of the pH are included in a first determination region set in a first correlation map of the electrical conductivity and the pH in consideration of a carbonic acid concentration range that can be dissolved in the sample water.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a water quality diagnosis method.

Background Art

[0002] In a steam turbine power plant, it is required to appropriately diagnose the water quality of circulating water and steam in order to suppress corrosion of equipment and piping that make up the water circulation system including boilers and turbines.

[0003] Patent Document 1 describes a water quality diagnosis method for a power plant that uses ammonia as a water quality conditioner to suppress corrosion of equipment. In the method described in Patent Document 1, first, a reference value is obtained from the correlation between pH and electrical conductivity according to the ammonia concentration. Then, the pH and electrical conductivity of the circulating water in the power plant are measured, and the degree of water quality abnormality of the circulating water is determined based on the degree of deviation of the measured values from the reference value.

[0004] Patent Document 2 is not related to water quality diagnosis, but Patent Document 2 describes controlling an ammonia injection pump based on a measured value of electrical conductivity so that the pH of the plant circulating water is within a specified range, using the correlation between pH and electrical conductivity considering the carbon dioxide gas concentration.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, in a steam turbine power plant, the water quality of circulating water or steam (hereinafter referred to as circulating water, etc.) can change due to the mixing of acids, alkalis, salts, etc. from the outside, and such changes in water quality also cause changes in the electrical conductivity and pH of the circulating water, etc. Therefore, based on the measured values of electrical conductivity and pH, it is possible to detect water quality abnormalities caused by the mixing of substances as described above. On the other hand, the correlation between the electrical conductivity and pH in the circulating water, etc. is affected by the carbonic acid concentration in the water. The carbonic acid concentration in the circulating water, etc. corresponds to the amount of carbon dioxide in the atmosphere dissolved in the circulating water, etc., and thus can change depending on the operating state of the power plant, etc.

[0007] In this regard, in the method described in Patent Document 1, since the carbonic acid concentration in the circulating water is not considered, it is considered that the water quality diagnosis result may not be appropriate in some cases.

[0008] In view of the above circumstances, at least one embodiment of the present invention aims to provide a water quality diagnosis method capable of more appropriately determining the presence or absence of water quality abnormalities in a steam turbine power plant.

Means for Solving the Problems

[0009] The water quality diagnosis method according to at least one embodiment of the present invention is a step of obtaining a measured value of the electrical conductivity of sample water derived from steam or circulating water collected from a steam turbine power plant using ammonia as a water quality regulator, and a measured value of the pH of the sample water; a determination step of determining the presence or absence of water quality abnormalities in the steam turbine power plant using at least a first determination condition as to whether or not the measured value of the electrical conductivity and the measured value of the pH are included in a first determination region set in a first correlation map of the electrical conductivity and the pH in consideration of a carbonic acid concentration range soluble in the sample water; and includes.

Effects of the Invention

[0010] According to at least one embodiment of the present invention, there is provided a water quality diagnosis method capable of more appropriately determining the presence or absence of abnormal water quality in a steam turbine plant.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0012] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

[0013] (Configuration of Steam Turbine Plant) FIG. 1 is a schematic configuration diagram of a steam turbine plant to which a water quality diagnosis method according to some embodiments is applied. As shown in FIG. 1, a steam turbine plant 1 includes a boiler 2 for generating steam and a steam turbine 8 configured to be driven by the steam from the boiler 2. The steam turbine 8 may be configured to drive a generator. The boiler 2 may be a heat recovery steam generator configured to be supplied with exhaust gas from a gas turbine.

[0014] The boiler 2 includes steam drums (14, 22, 28) including a high-pressure drum 14, a medium-pressure drum 22, and a low-pressure drum 28, economizers (a high-pressure economizer 13, a medium-pressure economizer 20, and a low-pressure economizer 26), evaporators (not shown), and superheaters (a high-pressure superheater 16, a medium-pressure superheater 24, and a low-pressure superheater 30) provided corresponding to the respective steam drums (14, 22, 28), and a reheater 18. Note that during operation of the steam turbine plant 1, the internal pressure of the steam drum is highest in the high-pressure drum 14, second highest in the medium-pressure drum 22, and lowest in the low-pressure drum 28.

[0015] The economizers (13, 20, 26) are configured to heat the feed water from the feed water line 3 by heat exchange with exhaust gas or the like. The feed water heated by the economizers (13, 20, 26) is respectively guided to the steam drums (14, 22, 28) corresponding to the respective economizers.

[0016] Evaporators corresponding to the respective steam drums (14, 22, 28) are respectively connected to the steam drums (14, 22, 28) via downcomers (not shown) and evaporator tubes (not shown). The feed water in the steam drums (14, 22, 28) is guided to the evaporators via the downcomers.

[0017] The evaporator is configured to evaporate feed water by heat exchange with exhaust gas or the like to generate steam. The steam generated in the evaporator flows into the steam drums (14, 22, 28) together with the feed water (i.e., in the form of a two-phase flow) through the evaporation tubes. In the steam drums (14, 22, 28), the steam and the feed water are separated by a gas-liquid separator (not shown), and the steam thus separated is temporarily stored in the steam drums (14, 22, 28) as saturated steam. The saturated steam in the steam drums (14, 22, 28) is respectively guided to the superheaters (16, 24, 30) corresponding to the respective steam drums (14, 22, 28).

[0018] The superheaters (16, 24, 30) and the reheater 18 are configured to heat the steam from the steam drums (14, 22, 28) by heat exchange with exhaust gas or the like. The steam heated by the superheaters (16, 24, 30) and the reheater 18 is guided to the steam turbine 8 and is configured to rotationally drive the steam turbine 8.

[0019] The steam from the steam drums (14, 22, 28) is heated by the superheaters (16, 24, 30) corresponding to the respective steam drums, and then is respectively introduced into the high-pressure turbine section, the intermediate-pressure turbine section, and the low-pressure turbine section of the steam turbine 8. The steam that has passed through the high-pressure turbine section merges with the steam from the intermediate-pressure superheater 24 and is guided to the reheater 18. After being reheated by the reheater 18, it is introduced into the intermediate-pressure turbine section of the steam turbine 8. The steam that has passed through the intermediate-pressure turbine section merges with the steam from the low-pressure superheater 30 and is introduced into the low-pressure turbine section of the steam turbine 8.

[0020] The steam that has passed through the low-pressure turbine section of the steam turbine 8 is guided to the condenser 12 connected to the low-pressure turbine section, is condensed in the condenser 12, and this condensed water is supplied as feed water to the respective steam drums (14, 22, 28) via the feed water line 3 and the feed water pump 4.

[0021] In the exemplary embodiment shown in FIG. 1, a high and intermediate pressure feed water pump 10 is provided downstream of the low pressure economizer 26 in the feed water line 3, and the feed water pressurized by the high and intermediate pressure feed water pump 10 is supplied to the intermediate pressure drum 22 and the high pressure drum 14.

[0022] Also, in the exemplary embodiment shown in FIG. 1, a condensate receiver 6 for condensing the ground steam is provided downstream of the feed water pump 4 and upstream of the low pressure economizer 26 in the feed water line 3.

[0023] The steam turbine plant 1 shown in FIG. 1 includes a chemical supply unit 60 for supplying ammonia as a water quality conditioner (chemical) to the feed water in the feed water line 3. The chemical supply unit 60 includes a chemical tank 62, a chemical line 64 provided between the chemical tank 62 and the feed water line 3, and a chemical pump 66 provided in the chemical line 64.

[0024] The chemical line 64 is connected to the feed water line 3 at a position downstream of the condensate receiver 12 and upstream of the low pressure economizer 26. Therefore, the feed water mixed with the water quality conditioner from the chemical tank 62 and the chemical line 64 is supplied to the low pressure drum 28, the intermediate pressure drum 22, and the high pressure drum 14 via the feed water line 3. In the exemplary embodiment shown in FIG. 1, the chemical line 64 is connected to the feed water line 3 at a position downstream of the condensate receiver 12 and upstream of the condensate receiver 6 for the ground steam.

[0025] Ammonia as a water quality conditioner is supplied to the feed water for the purpose of suppressing corrosion of equipment (for example, economizers (13, 20, 26), steam drums (14, 22, 28), etc.) that come into contact with circulating water such as feed water or steam. The water quality conditioner may have a function as a pH adjuster capable of adjusting the pH of the feed water so as to suppress corrosion that is likely to occur when the pH of the feed water is within a predetermined range.

[0026] Note that the steam turbine plant to which the water quality diagnosis method according to the embodiment of the present invention is applied is not limited to the steam turbine plant 1 equipped with an exhaust heat recovery boiler. For example, it may be a steam turbine plant configured to drive a steam turbine by steam generated by a boiler that burns fuels such as coal, oil, liquefied natural gas, and heavy oil.

[0027] (Configuration of the measurement unit) FIG. 2 is a schematic diagram showing the configuration of a measurement unit for measuring water quality parameters of sample water collected from the steam turbine plant 1. In the water quality diagnosis method according to some embodiments, the water quality parameters of sample water collected from circulating water such as feed water or steam (hereinafter also referred to as circulating water etc.) of the steam turbine plant 1 are measured by the measurement unit 40 (40A, 40B), and based on the measured values, the presence or absence of abnormality in the water quality of the circulating water etc. is determined. Here, the water quality parameters include pH, electrical conductivity, or acid electrical conductivity.

[0028] As shown in FIG. 1, the sampling points of the sample water in the steam turbine plant 1 may be, for example, the condensate pump outlet P1, the low-pressure economizer inlet P2, the low-pressure steam drum P3, the medium-pressure steam drum P4, the high-pressure steam drum P5, the low-pressure steam drum outlet P6, the medium-pressure steam drum outlet P7, or the high-pressure steam drum outlet P8.

[0029] The sample water may be obtained from the feed water at the condensate pump outlet P1, the feed water at the low-pressure economizer inlet P2, the drum water in the low-pressure steam drum P3, the drum water in the medium-pressure steam drum P4, the drum water in the high-pressure steam drum P5, the steam at the low-pressure steam drum outlet P6, the steam at the medium-pressure steam drum outlet P7, or the steam at the high-pressure steam drum outlet P8.

[0030] A plurality of measurement units 40 for measuring water quality parameters may be provided so as to correspond to each of the above-described sampling points P1 to P8. Alternatively, one measurement unit 40 may be provided for two or more of the sampling points P1 to P8. That is, a certain measurement unit 40 may be configured to be able to measure the water quality parameters of the sample water from a plurality of sampling points P1 to P8, respectively. In FIG. 2, as an example, a measurement unit 40A for measuring the water quality parameters of the feed water (sample water) from the condensate pump outlet P1 and a measurement unit 40B for measuring the water quality parameters of the feed water (sample) at the low-pressure economizer inlet P2 are shown.

[0031] The measurement unit 40 (40A, 40B) includes a pH meter 46 (46A, 46B) for measuring the pH of the sample water, a conductivity meter 48 for measuring the electrical conductivity of the sample water, and / or an acid conductivity meter 50 (50A, 50B) for measuring the acid conductivity of the sample water. Here, the acid conductivity is the electrical conductivity measured for the sample water in which the cations in the sample water are exchanged with hydrogen ions.

[0032] The acid conductivity meter 50 (50A, 50B) includes an ion exchange unit 51 (51A, 51B) for exchanging the cations in the sample water with hydrogen ions and a conductivity meter 52 (52A, 52B) for measuring the electrical conductivity of the sample water after passing through the ion exchange unit 51. The ion exchange unit 51 may include an ion exchange resin or an electric ion exchanger.

[0033] Sample water from each sampling point (the condensate pump outlet P1 or the low-pressure economizer inlet P2 in FIG. 2) is supplied to the measurement unit 40 (40A, 40B) via a sample water supply line 42 (42A, 42B). The sample water from the sample water supply line 42 is branched and supplied to each measuring instrument (pH meter 46, conductivity meter 48, or acid conductivity meter 50), respectively.

[0034] In the example shown in FIG. 2, the sample water collected from the outlet P1 of the condensate pump is supplied to the measuring unit 40A via the sample water supply line 42A, and the sample water collected from the inlet P2 of the low-pressure economizer is supplied to the measuring unit 40B via the sample water supply line 42B.

[0035] When the water quality diagnosis target is steam (for example, steam at the outlet P6 of the low-pressure steam drum, the outlet P7 of the medium-pressure steam drum, or the outlet P8 of the high-pressure steam drum), the steam may be condensed by a condenser (not shown), and the condensate thus obtained may be supplied as sample water to the measuring unit 40. Also, the sample water from the drum water (for example, the low-pressure steam drum P3, the medium-pressure steam drum P4, or the high-pressure steam drum P5) may be cooled to normal temperature and normal pressure by a cooler (not shown) and supplied to the measuring unit 40.

[0036] The sample water that has passed through the measuring unit 40 (40A, 40B) is discharged via the sample water discharge line 54 (54A, 54B).

[0037] As shown in FIG. 2, the sample water supply lines 42 (42A and 42B) corresponding to the plurality of systems of the measuring unit 40 (that is, the measuring units 40A and 40B) may be connected to each other via the connection line 38. In this case, a valve 39 is provided in the connection line 38, and valves 43 (43A, 43B) and valves 44 (44A, 44B) are respectively provided on the upstream side and the downstream side of the connection point of each sample water supply line 42 (42A, 42B) with the connection line 38. Thereby, by appropriately operating the opening and closing of the valve 39, the valve 43, and the valve 44, the flow of the sample water can be switched so that the sample water collected at a certain sampling point is supplied to the plurality of systems of the measuring unit 40 (for example, the measuring units 40A and 40B) respectively.

[0038] For example, in the example shown in FIG. 2, to supply the sample water from the condensate pump outlet P1 to the measurement unit 40A and the sample water from the low-pressure economizer inlet P2 to the measurement unit 40B, open valves 43A, 44A, 43B, and 44B and close valve 39. Also, to supply the sample water from the condensate pump outlet P1 to both the measurement unit 40A and the measurement unit 40B, open valves 43A, 44A, 44B, and valve 39 and close valve 43B. Alternatively, to supply the sample water from the low-pressure economizer inlet P2 to both the measurement unit 40A and the measurement unit 40B, open valves 43B, 44B, 44A, and valve 39 and close valve 43A.

[0039] (Flow of water quality diagnosis) Hereinafter, the flow of the water quality diagnosis method according to several embodiments will be described. FIG. 3 is a diagram showing an example of the first correlation map used in the water quality diagnosis method according to one embodiment. FIG. 4 is a diagram showing an example of the second correlation map used in the water quality diagnosis method according to one embodiment.

[0040] In the water quality diagnosis method according to several embodiments, water quality diagnosis of circulating water or the like is performed using a first correlation map (see FIG. 3) showing the correlation between the electrical conductivity and pH of the sample water. In this embodiment, first, the measured value of the electrical conductivity of the sample water (for example, the sample water derived from the steam or circulating water collected from the steam turbine plant (for example, the above-mentioned steam turbine plant 1) using ammonia as a water quality conditioner, such as the circulating water or the sample water obtained from the steam at any of the above-mentioned sampling points P1 to P8)), and the measured value of the pH of the sample water are obtained. The measured values of the electrical conductivity and pH of the sample water can be obtained using, for example, the electrical conductivity meter 48 and the pH meter 46 of the above-mentioned measurement unit 40, respectively.

[0041] Next, at least using the first determination condition of whether the measured value of the electrical conductivity and the measured value of the pH are included in the first determination region set in the first correlation map in consideration of the carbonate concentration range soluble in the sample water, the presence or absence of water quality abnormality in the steam turbine plant is determined.

[0042] In this specification, the carbonic acid concentration refers to the total concentration of carbonic acid (H2CO3), bicarbonate ions (HCO3 - ), and carbonate ions (CO3 2- ), that is, the total carbonic acid concentration. In the steady state, the ratio of carbonic acid (H2CO3), bicarbonate ions (HCO3 - ), and carbonate ions (CO3 2- ) dissolved in water is a specified ratio according to the pH. Therefore, if the concentration of any one of carbonic acid (H2CO3), bicarbonate ions (HCO3 - ), and carbonate ions (CO3 2- ), and the pH are known, the total carbonic acid concentration in water can be calculated.

[0043] Here, with reference to FIG. 3, the first correlation map and the first determination region will be described. The first correlation map is a known map divided into regions where combinations of electrical conductivity and pH can be taken in association with the water quality state of sample water collected from a steam turbine plant. The water quality state can be grasped from the region to which the measured values of electrical conductivity and pH belong on the first correlation map.

[0044] In the graph shown in FIG. 3, curves C1 to C4 respectively show the correlation between electrical conductivity (horizontal axis) and pH (vertical axis) according to the carbonic acid concentration in sample water containing ammonia. Specifically, curves C1 to C4 respectively show the correlation between electrical conductivity and pH when the concentration of carbonate ions (CO3 2- ) in the sample water is 0 ppm (described as "ammonia theoretical value" in FIG. 3), 2 ppm, 4 ppm, and 6 ppm.

[0045] The correlation between the electrical conductivity and pH according to the carbonic acid concentration (e.g., the relationship shown by curves C1 to C4 in FIG. 3) is obtained in advance by an experimental method or calculation. In the case of an experimental method, the above-mentioned correlation can be obtained by measuring the electrical conductivity and pH at various ammonia concentrations and carbonic acid concentrations using circulating water when the water quality is normal. In the case of calculation, based on chemical equilibrium calculations, the acid dissociation equilibrium, the alkali dissociation equilibrium, the water dissociation equilibrium, the balance of positive and negative charges, and the mass balance of acids and alkalis, the ammonia concentration and the carbonate ion concentration are calculated, and from the calculated concentrations, the pH and the electrical conductivity can be calculated.

[0046] The electrical conductivity and pH of the sample water (such as circulating water) change according to the ammonia concentration of the sample water, but the relationship between the electrical conductivity and pH follows the correlation shown by curves C1 to C4 and the like. For example, when the carbonate ion (CO3 2- ) concentration in the sample water is 0 ppm, the electrical conductivity and pH change according to the ammonia concentration in the sample water, but the relationship between the electrical conductivity and pH follows curve C1. Note that as the ammonia concentration in the sample water increases, the electrical conductivity and pH tend to increase.

[0047] Here, the carbonic acid concentration in the sample water (such as circulating water) corresponds to the amount of carbon dioxide (CO2) in the atmosphere dissolved in the circulating water and the like, and thus can change depending on the operating state of the steam turbine plant and the like. For example, during the operation of the steam turbine plant, since the vacuum degree of the condenser is high, the carbonic acid concentration in the feed water and the sample water becomes low. On the other hand, when the vacuum of the condenser is broken when the steam turbine plant is stopped or the like, carbon dioxide in the atmosphere dissolves in the feed water, so the carbonic acid concentration in the feed water and the sample water becomes high.

[0048] In addition, the carbonate ion concentration in the sample water (such as circulating water) should be in the range of 0 ppm or more and about 6 ppm or less. This is because the upper limit value of the carbonate ion concentration when carbon dioxide (CO2) in the atmosphere dissolves in water is about 6 ppm. Therefore, the boundary indicating the relationship between the electrical conductivity and pH when the carbonate concentration in the sample water (such as circulating water) is zero is shown by curve C1, and the boundary indicating the relationship between the electrical conductivity and pH when the carbonate concentration is the upper limit soluble in the sample water (such as circulating water) is represented by curve C4. That is, in FIG. 3, the region between curves C1 and C4 is the region where combinations of electrical conductivity and pH can be obtained when there is no water quality abnormality in the sample water (when there is no contamination such as impurities).

[0049] Therefore, for example, using the above-mentioned curves C1 to C4, etc., a region for water quality abnormality determination (the above-mentioned first determination region) considering the range of carbonate concentration soluble in the sample water can be set within the first correlation map.

[0050] In a steam turbine plant, the water quality of the circulating water or steam (such as circulating water) can change due to the mixing of acids, alkalis, salts, etc. from the outside. For example, the water quality can fluctuate due to additives (such as rust inhibitors) introduced for the stable operation of the steam turbine plant, or the mixing of acids and salts from the outside (such as NaCl resulting from seawater leakage in the condenser). And such changes in water quality also cause changes in the electrical conductivity and pH of the circulating water, etc. For this reason, it is possible to detect water quality abnormalities due to the mixing of substances as described above based on the measured values of electrical conductivity and pH. On the other hand, as already described, the correlation relationship between the electrical conductivity and pH in the circulating water, etc. is affected by the carbonate concentration in the water. The carbonate concentration in the circulating water, etc. corresponds to the amount of carbon dioxide in the atmosphere dissolved in the circulating water, etc., and thus can change depending on the operating state of the plant, etc.

[0051] In this regard, in the water quality diagnosis method according to the above-described embodiment, in the first correlation map of electrical conductivity versus pH, it is determined whether there is an abnormality in the water quality of the sample water based on a first determination condition of whether the measured values of electrical conductivity and pH are included in a first determination region set in consideration of the carbonate concentration soluble in the sample water (such as circulating water). Therefore, even if the carbonate concentration in the sample water fluctuates due to the operating state of the plant or the like, the water quality diagnosis can be appropriately performed.

[0052] For example, on the first correlation map shown in FIG. 3, a region A1 (see FIG. 3) between a boundary (curve C1) showing the relationship between electrical conductivity and pH when the carbonate concentration in the sample water is zero and a boundary (curve C4) showing the relationship between electrical conductivity and pH when the carbonate concentration is the upper limit soluble in the sample water may be set as the first determination region. In this case, for example, when the measured values of the electrical conductivity and pH of the sample water are included in region A1, it may be determined that the water quality is normal, and when not included, it may be determined that the water quality is abnormal.

[0053] Alternatively, on the first correlation map, a region A2 (see FIG. 3) located on the opposite side of the above-described region A1 across a boundary (curve C4) showing the relationship between electrical conductivity and pH when the carbonate concentration is the upper limit soluble in the sample water may be set as the first determination region. In this case, for example, when the measured values of the electrical conductivity and pH of the sample water are included in region A2, it may be determined that the water quality is abnormal.

[0054] Alternatively, on the first correlation map, a region A3 (see FIG. 3) located on the opposite side of the above-described region A1 across a boundary (curve C1) showing the relationship between electrical conductivity and pH when the carbonate concentration is zero may be set as the first determination region. In this case, for example, when the measured values of the electrical conductivity and pH of the sample water are included in region A3, it may be determined that the water quality is abnormal.

[0055] In some embodiments, on the first correlation map, based on whether the measured value of the electrical conductivity and the measured value of the pH of the sample water are included in the above-mentioned region A1 (the first normal region) as the first determination region, the presence or absence of water quality abnormality in the steam turbine plant is determined.

[0056] Region A1 is a region between the boundary (curve C1) showing the relationship between the electrical conductivity and the pH when the carbonic acid concentration in the sample water is zero, and the boundary (curve C4) showing the relationship between the electrical conductivity and the pH when the carbonic acid concentration in the sample water is at the upper limit. Therefore, if no acid, salt, alkali, etc. other than carbonic acid are mixed into the circulating water or the like, the measured values of the electrical conductivity and the pH of the sample water should be included in region A1 on the first correlation map. Thus, based on whether the measured values of the electrical conductivity and the pH are included in region A1 (the first normal region), the presence or absence of water quality abnormality can be appropriately determined.

[0057] In one embodiment, on the first correlation map, when the measured value of the electrical conductivity and the measured value of the pH of the sample water are included in region A2, which is located on the opposite side of region A1 (the first normal region) as the first determination region, across the boundary (curve C4) showing the relationship between the electrical conductivity and the pH when the carbonic acid concentration is the upper limit soluble in the sample water, it is determined that there is a water quality abnormality caused by the mixing of an acid or a salt other than carbonic acid into the sample water.

[0058] In the steam turbine plant, when an acid or a salt is mixed into the circulating water or the like, the pH tends to decrease or the electrical conductivity tends to increase compared to the case where it is not. In this regard, according to the above embodiment, when the measured values of the electrical conductivity and the pH are included in region A2, which is on the opposite side of region A1 (the first normal region), across the boundary (curve C4) showing the relationship between the electrical conductivity and the pH when the carbonic acid concentration in the sample water is at the upper limit, the cause of the water quality abnormality can be identified. Specifically, in this case, it can be determined that the water quality abnormality is caused by the mixing of an acid or a salt other than carbonic acid into the sample water.

[0059] In one embodiment, when the measured electrical conductivity and pH values ​​of the sample water on the first correlation map are included in region A3 located on the opposite side of region A1 (first normal region) as the first judgment region, across the boundary (curve C1) showing the relationship between electrical conductivity and pH when the carbon dioxide concentration is zero, it is judged that there is an abnormality in the water quality due to the inclusion of a basic substance other than ammonia.

[0060] When a basic substance is mixed into the steam turbine plant, the pH tends to increase compared to when the basic substance is not mixed into the water sample. In this regard, according to the above-described embodiment, when the measured values ​​of electrical conductivity and pH are included in the region A3 on the opposite side of the region A1 (first normal region) across the boundary (curve C1) showing the relationship between electrical conductivity and pH when the carbon dioxide concentration in the water sample is zero, the cause of the water quality abnormality can be identified. Specifically, it can be determined that the water quality abnormality in this case is caused by the mixing of a basic substance other than ammonia into the water sample.

[0061] In some embodiments, in addition to the above-mentioned first correlation map, a second correlation map (see FIG. 4) showing the correlation between the acid conductivity and pH of the sample water is used to diagnose the water quality of circulating water, etc. In this embodiment, in addition to the above-mentioned measured values ​​of the electrical conductivity and pH of the sample water, a measured value of the acid conductivity of the sample water is obtained. The measured value of the acid conductivity of the sample water can be obtained, for example, by the acid conductivity meter 50 of the measuring unit 40.

[0062] Next, in addition to the above-mentioned first judgment condition, the presence or absence of an abnormality in the water quality in the steam turbine plant is judged using a second judgment condition of whether or not the measured values ​​of acid electrical conductivity and pH are included in a second judgment region set in the second correlation map taking into account the expected concentration range of ammonia in the sample water in the steam turbine plant.

[0063] Here, with reference to FIG. 4, the second correlation map and the second determination region will be described. The second correlation map is a known map divided into regions where combinations of acid conductivity and pH can be taken in association with the water quality state of the sample water collected from the steam turbine plant. The water quality state can be grasped based on the region to which the measured values of conductivity and pH belong on the second correlation map.

[0064] In the graph shown in FIG. 4, curves C5 to C7 respectively show the correlation between acid conductivity (horizontal axis) and pH (vertical axis) according to the ammonia concentration in the sample water containing ammonia. Specifically, curves C5 to C7 respectively show the correlation between acid conductivity and pH when the ammonia concentration in the sample water is 10 ppm, 15 ppm, and 30 ppm.

[0065] Note that the correlation between conductivity and pH according to the ammonia concentration (for example, the relationship shown by curves C5 to C7 in FIG. 4) is obtained in advance by an experimental method or calculation. In the case of an experimental method, the above-mentioned correlation can be obtained by measuring conductivity and pH at various ammonia concentrations and carbonate concentrations using circulating water when the water quality is normal. In the case of calculation, the ammonia concentration and carbonate ion concentration can be calculated based on the acid dissociation equilibrium, alkali dissociation equilibrium, water dissociation equilibrium, balance of positive and negative charges, and mass balance of acid and alkali by chemical equilibrium calculation, and pH and conductivity can be calculated from the calculated concentrations.

[0066] Although the acid conductivity and pH of the sample water (such as circulating water) change according to the carbonate concentration of the sample water, the relationship between acid conductivity and pH follows the correlation shown by curves C5 to C7 and the like. For example, when the ammonia concentration in the sample water is 30 ppm, the relationship between acid conductivity and pH follows curve C7.

[0067] Here, the ammonia concentration in the sample water (such as circulating water) falls within the range of about 10 ppm or more and 30 ppm or less. This is because when ammonia is used as a water quality conditioner, ammonia is injected into the feed water so that the pH falls within the range of about 9.9 or more and 10.3 or less when the carbonate concentration is almost zero, and in this case, the ammonia concentration falls within the range of about 10 ppm or more and 30 ppm or less. Therefore, the ammonia concentration range in the sample water assumed in a steam turbine plant using ammonia as a water quality conditioner is about 10 ppm or more and 30 ppm or less. In this case, the boundary when the ammonia concentration in the sample water (such as circulating water) is at the lower limit of the ammonia concentration range in the sample water assumed in the steam turbine plant is represented by curve C5 in FIG. 4, and the boundary when it is at the upper limit is represented by curve C7 in FIG. 4. That is, in FIG. 4, the region between curves C5 and C7 is the region where combinations of acid electric conductivity and pH can be taken when there is no water quality abnormality in the sample water (when there is no contamination by impurities, etc.).

[0068] Therefore, for example, using the above-mentioned curves C5 to C7, etc., a region for water quality abnormality determination (the above-mentioned second determination region) considering the ammonia concentration range in the sample water assumed in the steam turbine plant can be set within the second correlation map.

[0069] In a steam turbine plant, the ammonia concentration in circulating water, etc. can vary depending on the operating conditions of the plant, etc. In this regard, in the above-described embodiment, in addition to the above-described first determination condition, in the second correlation map of acid electric conductivity versus pH, based on the second determination condition of whether the measured values of acid electric conductivity and pH are included in the second determination region set considering the ammonia concentration range in the sample water (such as circulating water) assumed in the steam turbine plant, the presence or absence of water quality abnormality in the sample water is determined. Therefore, even if the ammonia concentration in the sample water fluctuates due to the operating conditions of the plant, etc., the water quality diagnosis can be made appropriate.

[0070] In addition, when salts or acids other than carbonic acid are mixed in the circulating water or the like, the acid electric conductivity is more likely to increase compared to the case where this is not the case. In this regard, in the above-described embodiment, since the abnormality of the water quality is determined based on whether or not the measured values of the acid electric conductivity and the pH are included in the second determination region in the second correlation map, for example, even when the concentrations of the acids and salts mixed in the circulating water or the like are low and it is difficult to determine the abnormality of the water quality with the first correlation map of the electric conductivity and the pH, the abnormality of the water quality can be determined more appropriately.

[0071] In addition, in some other embodiments, without using the above-described first correlation map, water quality diagnosis of circulating water or the like may be performed using a second correlation map (see FIG. 4) showing the correlation between the acid electric conductivity and the pH of the sample water. In the present embodiment, the measured value of the acid electric conductivity of the above-described sample water and the measured value of the pH of the sample water are acquired. Then, based on whether or not the measured value of the acid electric conductivity and the measured value of the pH are included in the second determination region set in the second correlation map in consideration of the concentration range of ammonia in the sample water assumed in the steam turbine plant, it is possible to determine whether or not there is an abnormality in the water quality in the steam turbine plant.

[0072] In some embodiments, based on whether or not the measured value of the acid electric conductivity of the sample water and the above-described measured value of the pH are included in a second normal region as the second determination region defined on the above-described second correlation map, the presence or absence of water quality abnormality is determined. The second normal region defined on the second correlation map may be, for example, a region B1 (see FIG. 4) between a boundary (curve C5) showing the relationship between the acid electric conductivity and the pH when the concentration of the ammonia in the sample water is the lower limit of the above-described concentration range (the concentration range assumed in the steam turbine plant) and a boundary (curve C7) showing the relationship between the acid electric conductivity and the pH when the concentration of the ammonia in the sample water is the upper limit of the above-described concentration range.

[0073] In the above-described embodiment, on the second correlation map, a region B1 between a boundary indicating the relationship between the acid conductivity and pH when the ammonia concentration in the sample water is at the lower limit of the above-described concentration range and a boundary indicating the relationship between the acid conductivity and pH when the ammonia concentration in the sample water is at the upper limit of the above-described concentration range is defined as the second normal region (second determination region). If no acid, salt, alkali, etc. other than carbonic acid are mixed into the circulating water or the like, the measured values of the acid conductivity and pH of the sample water should be included in the region B1 on the second correlation map. Therefore, based on whether the measured values of the acid conductivity and pH are included in the region B1 (second normal region), it is possible to appropriately determine the presence or absence of water quality abnormalities.

[0074] In one embodiment, on the second correlation map, when the measured value of the acid conductivity and the measured value of the pH are included in a region B2 (abnormal region) located on the opposite side of the region B1 (second normal region) as the second determination region across a boundary (curve C7) indicating the relationship between the acid conductivity and the pH when the concentration of ammonia in the sample water is at the upper limit of the above-described concentration range, it is determined that there is an abnormality in the water quality due to the mixing of an acid or salt other than carbonic acid into the sample water.

[0075] When an acid or salt is mixed into the circulating water or the like in a steam turbine plant, the acid conductivity tends to increase compared to the case where it is not. In this regard, in the above-described embodiment, on the second correlation map, when the measured values are included in a region B2 (abnormal region; that is, a region where the acid conductivity is relatively high) located on the opposite side of the region B1 (second normal region) across a boundary (curve C7) indicating the relationship between the acid conductivity and pH when the concentration of ammonia assumed in the steam turbine plant is at the upper limit of the concentration range, the cause of the water quality abnormality can be specified. Specifically, in this case, it can be determined that the water quality abnormality is due to the mixing of an acid or salt other than carbonic acid into the sample water.

[0076] As shown in FIG. 4, the region B2 (abnormal region) may include a region B2a which is a high pH region and a region B2b which is a low pH region having a lower pH than the region B2a (high pH region). In one embodiment, on the second correlation map, when the measured values of the acid conductivity and pH of the sample water are included in the above-mentioned region B2a (high pH region), it is determined that there is an abnormality in the water quality due to the mixing of salts, and when the measured values of the acid conductivity and pH of the sample water are included in the above-mentioned region B2b (low pH region), it may be determined that there is an abnormality in the water quality due to the mixing of acids other than carbonic acid.

[0077] When salts are mixed into circulating water or the like, the pH generally does not change (decrease) compared to the case where this is not the case. On the other hand, when acids are mixed into circulating water or the like, the pH decreases compared to the case where this is not the case. In this regard, when the measured values of the acid conductivity and pH are included in the above-mentioned region B2a (high pH region) or region B2b (low pH region) on the second correlation map in the above-mentioned embodiment, it is possible to appropriately identify whether the water quality abnormality is due to the mixing of salts or due to the mixing of acids other than carbonic acid.

[0078] In some embodiments, when it is determined that there is an abnormality in the water quality of the steam turbine plant using one of the above-mentioned first determination conditions (determination conditions using the first correlation map) or the above-mentioned second determination conditions (determination conditions using the second correlation map), it is determined whether there is an abnormality in the measuring instrument used to obtain the measured value of the water quality parameter of the sample water related to the one condition. The water quality parameter includes the conductivity, pH or acid conductivity of the sample water. The measuring instruments used for these water quality parameters are, for example, the above-mentioned pH meter 46, conductivity meter 48 or acid conductivity meter 50 (ion exchange unit 51 and conductivity meter 52).

[0079] When it is determined that there is an abnormality in the water quality using one of the first determination condition or the second determination condition, in addition to the possibility of an actual abnormality in the water quality, there is also a possibility of an abnormality in the measuring instrument used for measuring the water quality parameters (electrical conductivity, acid electrical conductivity, or pH). In this regard, according to the above-described embodiment, when it is determined that there is an abnormality in the water quality using one of the first determination condition or the second determination condition, the presence or absence of an abnormality in the measuring instrument used for measuring the water quality parameter related to the one condition is determined. Therefore, it is possible to specify whether the abnormality is in the water quality or in the measuring instrument.

[0080] In one embodiment, the presence or absence of an abnormality in the measuring instrument is determined by comparing the measured value of the water quality parameter of the sample water by the measuring instrument used for the determination of the first determination condition or the second determination condition with the measured value of the water quality parameter of the sample water by a comparative measuring instrument different from the measuring instrument.

[0081] According to the above-described embodiment, when the possibility of an abnormality in the measuring instrument is suspected, the presence or absence of an abnormality in the measuring instrument can be appropriately determined by comparing the measured value by the measuring instrument used for measuring the water quality parameter related to the first determination condition or the second determination condition with the measured value by a comparative measuring instrument different from the measuring instrument.

[0082] For example, here, the case where the feed water collected from the outlet P1 of the condensate pump is used as the sample water and the water quality diagnosis is performed using the first determination condition based on the measured values of the electrical conductivity and pH obtained using the electrical conductivity meter 48A and the pH meter 46A of the measurement unit 40A as the measuring instruments will be described. When measuring the electrical conductivity and pH using the electrical conductivity meter 48A and the pH meter 46A of the measurement unit 40A, the valves 43A and 44A shown in FIG. 2 are open and the valve 39 is closed.

[0083] If it is determined that there is an abnormality in the water quality using the first determination condition, there is a possibility that there is an abnormality in the water quality of the feed water and a possibility that there is an abnormality in the measuring instrument. Therefore, the electrical conductivity and pH of the sample water are measured using the electrical conductivity meter 48B and pH meter 46B of the measurement unit 40B, which is a measuring instrument (comparison measuring instrument) different from the above-mentioned measuring instrument. Specifically, the valve 43B is closed, the valve 39 is opened, and the feed water (sample water) collected from the condensate pump outlet P1 is led to the measurement unit 40B, and the electrical conductivity and pH of the sample water are measured using the electrical conductivity meter 48B and pH meter 46B as comparison measuring instruments.

[0084] When the difference between the measured value by the electrical conductivity meter 48A and the measured value by the electrical conductivity meter 48B is within the specified range, and the difference between the measured value by the pH meter 46A and the measured value by the pH meter 46B is within the specified range, it can be determined that there is no abnormality in the measuring instrument (electrical conductivity meter 48A and pH meter 46A), and there is an abnormality in the water quality of the sample water (feed water). When the difference between the measured value by the electrical conductivity meter 48A and the measured value by the electrical conductivity meter 48B exceeds the specified range, it can be determined that there is an abnormality in the electrical conductivity meter 48A (measuring instrument). When the difference between the measured value by the pH meter 46A and the measured value by the pH meter 46B exceeds the specified range, it can be determined that there is an abnormality in the pH meter 46A (measuring instrument).

[0085] In some embodiments, when it is determined that there is an abnormality in the water quality using one of the first determination condition or the second determination condition, and as a result of determining the presence or absence of an abnormality in the measuring instrument, it is determined that there is no abnormality in the measuring instrument, the type of abnormality in the water quality in the steam turbine plant is specified based on the first correlation map or the second correlation map related to the other of the first determination condition or the second determination condition.

[0086] According to the above-described embodiment, when it is determined that there is an abnormality in the water quality rather than an abnormality in the measuring instrument, the type of abnormality in the water quality can be specified based on the first correlation map or the second correlation map.

[0087] In some embodiments, the sample water is obtained from the boiler feed water of the steam turbine plant (for example, the sample water obtained from the low-pressure steam drum P3, the medium-pressure steam drum P4, or the high-pressure steam drum P5). When it is determined that there is an abnormality in the water quality using the first determination condition or the second determination condition, the abnormality in the water quality is specified as being caused by seawater leakage in the condenser of the steam turbine plant (for example, the condenser 12 described above).

[0088] According to the above-described embodiment, when the sample water is obtained from the boiler feed water, when it is determined that there is an abnormality in the water quality, it is specified that the abnormality in the water quality is caused by seawater leakage in the condenser of the steam turbine plant. That is, when seawater leakage occurs in the condenser, salts such as NaCl are mixed into the water supplied to the boiler. Therefore, in the case of abnormal feed water quality, it can be determined that it is caused by seawater leakage in the condenser.

[0089] In some embodiments, the sample water is obtained from the steam of the steam turbine plant (for example, the sample water obtained from the steam at the outlet of the low-pressure steam drum P6, the outlet of the medium-pressure steam drum P7, or the outlet of the high-pressure steam drum P8). When it is determined that there is an abnormality in the water quality using the first determination condition or the second determination condition, the abnormality in the water quality is specified as being caused by entrainment of drum water in the steam turbine plant.

[0090] According to the above-described embodiment, when the sample water is obtained from the steam, when it is determined that there is an abnormality in the water quality, it is specified that the abnormality in the water quality is caused by entrainment of drum water in the steam turbine plant. That is, when entrainment of drum water occurs, acids and salts other than carbonic acid contained in the drum water are mixed into the steam generated in the drum. Therefore, in the case of the above-described water quality abnormality, it can be determined that it is caused by entrainment of drum water.

[0091] Next, with reference to FIGS. 5 and 6, a specific flow of the water quality diagnosis method according to an embodiment will be described. FIGS. 5 and 6 are flowcharts of the water quality diagnosis method according to an embodiment. In the following description, a case where water quality diagnosis is performed using the feed water obtained from the feed water pump outlet P1 in the steam turbine plant 1 shown in FIG. 1 as sample water will be described.

[0092] First, the sample water from the feed water pump outlet P1 is introduced into the measurement unit 40A (first measurement system) shown in FIG. 2, and the water quality parameters of the sample water are measured using the measuring instruments (pH meter 46A, electric conductivity meter 48A, and acid electric conductivity meter 50A) of the measurement unit 40A. That is, the measured value of the pH of the sample water, the measured value of the electric conductivity, and the measured value of the acid electric conductivity are obtained (S2).

[0093] Next, it is determined whether the measured value of the electric conductivity and the measured value of the pH obtained in step S2 are included in the region A1 (first normal region), which is the first determination region set in the first correlation map of the electric conductivity and the pH shown in FIG. 3 (S4).

[0094] In step S4, when the measured value of the electric conductivity and the measured value of the pH are not included in the region A1 (first normal region) (No in step S4), it is determined that there is a possibility of water quality abnormality or abnormality of the measuring instrument (electric conductivity meter 48 or pH meter 46A) of the measurement unit 40A, and the process proceeds to step S12 (see FIG. 6) described later.

[0095] On the other hand, in step S4, when the measured value of the electric conductivity and the measured value of the acid electric conductivity are included in the region A1 (first normal region), it is determined whether the measured value of the acid electric conductivity and the measured value of the pH obtained in step S2 are included in the region B1 (second normal region), which is the second determination region set in the second correlation map of the acid electric conductivity and the pH shown in FIG. 4 (S6).

[0096] In step S6, when the measured value of the acid electrical conductivity and the measured value of the pH are included in region B1 (the second normal region) (that is, when the measured values of the water quality parameters are included in the normal region in both the first correlation map and the second correlation map; Yes in step S6), it is determined that the water quality is normal (S8), and the flow is terminated.

[0097] On the other hand, in step S6, when the measured value of the acid electrical conductivity and the measured value of the pH are not included in region B1 (the second normal region) (No in step S6), it is determined that there is an abnormality in the water quality (S10), and the flow is terminated. In step S10, based on the second correlation map, the cause of the water quality abnormality may be specified. For example, when the measured value of the acid electrical conductivity and the measured value of the pH measured in step S2 are included in region B2 (the abnormal region), it may be determined that there is an abnormality in the water quality due to the mixing of an acid or salt other than carbonic acid into the sample water (feed water). Also, for example, when the measured value of the acid electrical conductivity and the measured value of the pH are included in region B2a (the high pH region), it may be determined that there is an abnormality in the water quality due to the mixing of salt into the sample water (feed water). Also, for example, when the measured value of the acid electrical conductivity and the measured value of the pH are included in region B2b (the low pH region), it may be determined that there is an abnormality in the water quality due to the mixing of an acid other than carbonic acid into the sample water (feed water).

[0098] In step S4, when the measured value of the electrical conductivity and the measured value of the pH are not included in region A1 (the first normal region) (No in step S4), in step S12 (see FIG. 6), the sample water from the feed water pump outlet P1 is led to the measuring unit 40B (the second measuring system different from the measuring unit 40A (the first measuring system)) shown in FIG. 2, and the water quality parameters of the sample water are measured using the measuring instruments (pH meter 46B, electrical conductivity meter 48B, and acid electrical conductivity meter 50B; comparison measuring instruments) of the measuring unit 40B. That is, the measured value of the pH, the measured value of the electrical conductivity, and the measured value of the acid electrical conductivity of the sample water are obtained (S12).

[0099] Next, it is determined whether the difference between the measured value of the water quality parameter of the measuring instrument of the measurement unit 40A (first measurement system) and the measured value of the water quality parameter by the measuring instrument (comparative measuring instrument) of the measurement unit 40B (second measurement system) is within the specified range (S14). Specifically, it is determined whether the difference between the measured value by the pH meter 46A and the measured value by the pH meter 46B, the difference between the measured value by the electrical conductivity meter 48A and the measured value by the electrical conductivity meter 48B, and the difference between the measured value by the acid electrical conductivity meter 50A and the measured value by the acid electrical conductivity meter 50B are each within the specified range.

[0100] In step S14, if the difference in the measured value by any of the measuring instruments is outside the specified range (No in step S14), it is determined that there is an abnormality in the measuring instrument (pH meter 46A, electrical conductivity meter 48A, or acid electrical conductivity meter 50A) of the measurement unit 40A (first measurement system) (S22), and the flow ends. In step S22, it may be specified which of the pH meter 46A, the electrical conductivity meter 48A, and the acid electrical conductivity meter 50A has an abnormality. That is, in step S14, it may be specified that there is an abnormality in the measuring instrument for which the difference in the measured value was outside the specified range.

[0101] On the other hand, in step S14, if the difference in the measured value by each measuring instrument is within the specified range (Yes in step S14), it is determined that there is no abnormality in the measuring instrument (pH meter 46A, electrical conductivity meter 48A, or acid electrical conductivity meter 50A) (Yes in step S14), and the process proceeds to step S16.

[0102] In step S16, it is determined whether the measured value of the acid electrical conductivity and the measured value of the pH obtained in step S2 are included in the region B1 (second normal region), which is the second determination region set within the second correlation map of the acid electrical conductivity and the pH shown in FIG. 4 (S16).

[0103] In step S16, when the measured value of the acid conductivity and the measured value of the pH are included in region B1 (the second normal region) (Yes in step S16), it is determined that there is an abnormality in the water quality based on the first correlation map (S18), and the flow is terminated. In step S18, the cause of the water quality abnormality may be specified based on the first correlation map. For example, when the measured value of the conductivity and the measured value of the pH measured in step S2 are included in region A2, it may be determined that there is an abnormality in the water quality due to the mixing of an acid or salt other than carbonic acid into the sample water (feed water). Also, for example, when the measured value of the conductivity and the measured value of the pH are included in region A3, it may be determined that there is an abnormality in the water quality due to the mixing of a basic substance other than ammonia into the sample water (feed water).

[0104] On the other hand, in step S16, when the measured value of the acid conductivity and the measured value of the pH are not included in region B1 (the second normal region) (that is, when the measured values of the water quality parameters are included in the abnormal region in both the first correlation map and the second correlation map; No in step S16), it is determined that there is an abnormality in the water quality based on the first correlation map and the second correlation map (S20), and the flow is terminated. In step S20, the cause of the water quality abnormality may be specified based on the first correlation map and the second map. For example, when the measured value of the conductivity and the measured value of the pH measured in step S2 are included in region A2, and the measured value of the acid conductivity and the measured value of the pH measured in step S2 are included in region B2a, it may be determined that there is an abnormality in the water quality due to the mixing of a salt into the sample water (feed water). Also, for example, when the measured value of the conductivity and the measured value of the pH are included in region A2, and the measured value of the acid conductivity and the measured value of the pH are included in region B2b, it may be determined that there is an abnormality in the water quality due to the mixing of an acid other than carbonic acid into the sample water (feed water). Also, for example, when the measured value of the conductivity and the measured value of the pH are included in region A3, it may be determined that there is an abnormality in the water quality due to the mixing of a basic substance other than ammonia into the sample water (feed water).

[0105] The content described in each of the above embodiments is understood as follows, for example.

[0106] (1) The water quality diagnosis method according to at least one embodiment of the present invention includes acquiring a measured value of the electrical conductivity of sample water derived from steam or circulating water collected from a steam turbine plant (1) using ammonia as a water quality conditioner, and a measured value of the pH of the sample water (for example, step S2 described above); determining whether there is an abnormality in the water quality in the steam turbine plant using at least a first determination condition of whether the measured value of the electrical conductivity and the measured value of the pH are included in a first determination region set in a first correlation map of the electrical conductivity and the pH in consideration of the carbonate concentration range soluble in the sample water (for example, step S4 described above); and is provided with.

[0107] As described above, the correlation between the electrical conductivity and the pH in circulating water or the like is affected by the carbonate concentration in the water. In this regard, in the method of (1) above, in the first correlation map of electrical conductivity vs. pH, based on the first determination condition of whether the measured values of the electrical conductivity and the pH are included in the first determination region set in consideration of the carbonate concentration soluble in the sample water (circulating water or the like), the presence or absence of an abnormality in the water quality of the sample water is determined. Therefore, even if the carbonate concentration in the sample water fluctuates due to the operating state of the plant or the like, the water quality diagnosis can be appropriately performed.

[0108] (2) In some embodiments, in the method of (1) above, determining whether there is an abnormality in the water quality based on whether the measured value of the electrical conductivity and the measured value of the pH are included in a first normal region defined on the first correlation map as a region between a boundary indicating the relationship between the electrical conductivity and the pH when the carbonate concentration in the sample water is zero and a boundary indicating the relationship between the electrical conductivity and the pH when the carbonate concentration is the upper limit soluble in the sample water (for example, region A1 described above) as the first determination region.

[0109] In the method of (2) above, on the first correlation map, a region between the boundary indicating the relationship between the electrical conductivity and pH when the carbonic acid concentration in the sample water is zero and the boundary indicating the relationship between the electrical conductivity and pH when the carbonic acid concentration in the sample water is at the upper limit is defined as the first normal region (first determination region). Therefore, based on whether the measured values of the electrical conductivity and pH are included in the first normal region, it is possible to appropriately determine the presence or absence of water quality abnormalities.

[0110] (3) In some embodiments, in the method of (2) above, On the first correlation map, when the measured values of the electrical conductivity and the pH are included in a region (for example, region A2 described above) located on the opposite side of the first normal region across the boundary indicating the relationship between the electrical conductivity and the pH when the carbonic acid concentration is the upper limit that can be dissolved in the sample water, it is determined that there is an abnormality in the water quality due to the mixing of an acid or a salt other than carbonic acid into the sample water.

[0111] In a steam turbine plant, when an acid or a salt is mixed into the circulating water or the like, the pH tends to decrease or the electrical conductivity tends to increase compared to the case where it is not. According to the method of (3) above, when the measured values of the electrical conductivity and the pH are included in a region on the opposite side of the first normal region across the boundary indicating the relationship between the electrical conductivity and the pH when the carbonic acid concentration in the sample water is at the upper limit, the cause of the water quality abnormality can be specified. Specifically, it can be determined that the water quality abnormality is due to the mixing of an acid or a salt other than carbonic acid into the sample water.

[0112] (4) In some embodiments, in the method of (2) or (3) above, On the first correlation map, when the measured values of the electrical conductivity and the pH are included in a region (for example, region A3 described above) located on the opposite side of the first normal region across the boundary indicating the relationship between the electrical conductivity and the pH when the carbonic acid concentration is zero, it is determined that there is an abnormality in the water quality due to the mixing of a basic substance other than ammonia.

[0113] In a steam turbine plant, when a basic substance is mixed in, the pH tends to rise compared to the case where it is not. According to the method of (4) above, when the measured values of the electric conductivity and pH are included in the region on the opposite side of the first normal region across the boundary indicating the relationship between the electric conductivity and pH when the carbonate concentration in the sample water is zero, the factor causing the water quality abnormality can be specified. Specifically, in this case, it can be determined that the water quality abnormality is caused by the mixing of basic substances other than ammonia into the sample water.

[0114] (5) In some embodiments, in any of the methods of (1) to (4) above, it includes a step of obtaining a measured value of the acid electric conductivity of the sample water (for example, step S2 described above), in addition to the first determination condition, considering the concentration range of the ammonia in the sample water assumed in the steam turbine plant, using a second determination condition of whether the measured value of the acid electric conductivity and the measured value of the pH are included in a second determination region set in the second correlation map of the acid electric conductivity and the pH, to determine the presence or absence of abnormality in the water quality (for example, steps S6 and S16 described above).

[0115] In a steam turbine plant, the water quality of circulating water or the like can change due to the mixing of acids, alkalis, salts, etc. from the outside, and such a change in water quality also causes changes in the acid electric conductivity and pH of circulating water or the like. Also, the correlation between the acid electric conductivity and pH in circulating water or the like is affected by the ammonia concentration in the water. The ammonia concentration in circulating water or the like can change depending on the operating state of the plant or the like. In the method of (5) above, in addition to the above-described first determination condition, in the second correlation map of the acid electric conductivity and pH, based on a second determination condition of whether the measured values of the acid electric conductivity and pH are included in a second determination region set considering the concentration range of ammonia in the sample water (circulating water or the like) assumed in the steam turbine plant, the presence or absence of abnormality in the water quality of the sample water is determined. Therefore, even if the ammonia concentration in the sample water fluctuates due to the operating state of the plant or the like, the diagnosis of the water quality can be appropriately performed.

[0116] In addition, when salts or acids other than carbonic acid are mixed in circulating water or the like, the acid electrical conductivity (that is, the electrical conductivity measured for the sample water in which cations in the sample water are exchanged with hydrogen ions) is likely to be larger than in the case where this is not the case. In this regard, in the method of (5) above, since the abnormality of the water quality is determined based on whether or not the measured values of the acid electrical conductivity and pH are included in the second determination region in the second correlation map, for example, even when the concentration of the acid or salt mixed in the circulating water or the like is small and it is difficult to determine the abnormality of the water quality from the first correlation map of the electrical conductivity and pH, it becomes easier to more appropriately determine the abnormality of the water quality.

[0117] (6) In some embodiments, in the method of (5) above, Based on whether or not the measured value of the acid electrical conductivity and the measured value of the pH are included in a second normal region (for example, region B1 above) defined on the second correlation map as a region between a boundary indicating the relationship between the acid electrical conductivity and the pH when the concentration of ammonia in the sample water is the lower limit of the concentration range and a boundary indicating the relationship between the acid electrical conductivity and the pH when the concentration of ammonia in the sample water is the upper limit of the concentration range, the presence or absence of abnormality of the water quality is determined.

[0118] In the method of (6) above, on the second correlation map, a region between a boundary indicating the relationship between the acid electrical conductivity and the pH when the ammonia concentration in the sample water is the lower limit of the above concentration range and a boundary indicating the relationship between the acid electrical conductivity and the pH when the ammonia concentration in the sample water is the upper limit of the above concentration range is defined as the second normal region (second determination region). Therefore, based on whether or not the measured values of the acid electrical conductivity and pH are included in the second normal region, the presence or absence of abnormality of the water quality can be appropriately determined.

[0119] (7) In some embodiments, in the method of (6) above, When the measured values of the acid conductivity and the pH are included in an abnormal region (for example, the above-mentioned region B2) located on the side opposite to the second normal region across the boundary indicating the relationship between the acid conductivity and the pH when the concentration of ammonia in the sample water is at the upper limit of the concentration range on the second correlation map, it is determined that there is an abnormality in the water quality due to the mixing of an acid or a salt other than carbonic acid into the sample water.

[0120] In the method of (7) above, on the second correlation map, when the measured values are included in an abnormal region (that is, a region where the acid conductivity is relatively large) located on the side opposite to the second normal region across the boundary indicating the relationship between the acid conductivity and the pH when the concentration of ammonia assumed in the steam turbine plant is at the upper limit of the concentration range, the cause of the water quality abnormality can be specified. Specifically, in this case, it can be determined that the water quality abnormality is due to the mixing of an acid or a salt other than carbonic acid into the sample water.

[0121] (8) In some embodiments, in the method of (7) above, the abnormal region includes a high pH region (for example, the above-mentioned region B2a) and a low pH region where the pH is lower than that of the high pH region (for example, the above-mentioned region B2b), when the measured values of the acid conductivity and the pH are included in the high pH region on the second correlation map, it is determined that there is an abnormality in the water quality due to the mixing of the salt, when the measured values of the acid conductivity and the pH are included in the low pH region on the second correlation map, it is determined that there is an abnormality in the water quality due to the mixing of the acid.

[0122] When an acid mixes into the circulating water or the like, the pH of the circulating water or the like decreases. On the other hand, when a salt mixes into the circulating water or the like, the pH of the circulating water or the like does not change much (does not decrease). In this regard, according to the method of (8) above, depending on whether the measured values of the acid conductivity and pH are included in either the high pH region or the low pH region on the second correlation map, it is possible to specify whether the water quality abnormality is caused by the mixing of salts or by the mixing of acids other than carbonic acid.

[0123] (9) In some embodiments, in any of the methods of (6) to (8) above, when it is determined that there is an abnormality in the water quality using one of the first determination condition or the second determination condition, a step of determining the presence or absence of an abnormality in the measuring instrument used to obtain the measured value of the water quality parameter of the sample water related to the one condition (for example, step S14 described above) is provided, the water quality parameter includes the conductivity, pH, or acid conductivity of the sample water.

[0124] When it is determined that there is an abnormality in the water quality using one of the first determination condition or the second determination condition, in addition to the possibility of an actual abnormality in the water quality, there is also a possibility of an abnormality in the measuring instrument used to measure the water quality parameter (conductivity, acid conductivity, or pH). In this regard, according to the method of (9) above, when it is determined that there is an abnormality in the water quality using one of the first determination condition or the second determination condition, the presence or absence of an abnormality in the measuring instrument used to measure the water quality parameter related to the one condition is determined, so that it is possible to specify whether it is an abnormality in the water quality or an abnormality in the measuring instrument.

[0125] (10) In some embodiments, in the method of (9) above, the presence or absence of an abnormality in the measuring instrument is determined by comparing the measured value of the water quality parameter of the sample water measured by the measuring instrument with the measured value of the water quality parameter of the sample water measured by a comparison measuring instrument different from the measuring instrument.

[0126] According to the method of (10) above, when the possibility of an abnormality in the measuring instrument is suspected, by comparing the measured value obtained by the measuring instrument used for measuring the water quality parameter related to the first determination condition or the second determination condition with the measured value obtained by a comparative measuring instrument different from the measuring instrument, it is possible to appropriately determine whether there is an abnormality in the measuring instrument.

[0127] (11) In some embodiments, in the method of (9) or (10) above, When it is determined that there is no abnormality in the measuring instrument, based on the first correlation map or the second correlation map related to the other of the first determination condition or the second determination condition, the type of abnormality in the water quality in the steam turbine plant is specified.

[0128] According to the method of (11) above, when it is determined that the abnormality is not in the measuring instrument but in the water quality, the type of abnormality in the water quality can be specified based on the first correlation map or the second correlation map.

[0129] (12) In some embodiments, in any of the methods of (1) to (11) above, The sample water is obtained from the boiler feed water of the steam turbine plant, When it is determined in the determination step that there is an abnormality in the water quality, the abnormality in the water quality is specified as being caused by seawater leakage in the condenser of the steam turbine plant.

[0130] According to the method of (12) above, when the sample water is obtained from the boiler feed water, when it is determined that there is an abnormality in the water quality, it is specified that the abnormality in the water quality is caused by seawater leakage in the condenser of the steam turbine plant. That is, when seawater leakage occurs in the condenser, salts such as NaCl are mixed into the water supplied to the boiler. Therefore, when there is an abnormality in the water quality of the feed water, it can be determined that it is caused by seawater leakage in the condenser.

[0131] (13) In some embodiments, in any of the methods of (1) to (11) above, The sample water is obtained from the steam of the steam turbine plant, When it is determined in the determination step that there is an abnormality in the water quality, the abnormality in the water quality is specified as being caused by entrainment of the drum water of the steam turbine plant.

[0132] According to the method of (13) above, when the sample water is obtained from steam, when it is determined that there is an abnormality in the water quality, it is specified that the abnormality in the water quality is caused by entrainment of the drum water of the steam turbine plant. That is, when entrainment of the drum water occurs, acids and salts other than carbonic acid contained in the drum water are mixed into the steam generated in the drum. Therefore, in the case of the above water quality abnormality, it can be determined that it is caused by entrainment of the drum water.

[0133] (14) In some embodiments, in any of the methods of (1) to (13) above, The sample water is obtained from the boiler feed water at the condensate pump outlet (P1) of the steam turbine plant, the boiler feed water at the low-pressure economizer inlet (P2), the drum water of the low-pressure steam drum (P3), the drum water of the medium-pressure steam drum (P4), the drum water of the high-pressure steam drum (P5), the steam at the low-pressure steam drum outlet (P6), the steam at the medium-pressure steam drum outlet (P7), or the steam at the high-pressure steam drum outlet (P8).

[0134] According to the method of (14) above, it is possible to appropriately determine the water quality abnormality of the circulating water (feed water or drum water) or steam at the above-described position in the steam turbine plant by using the sample water obtained from the circulating water (feed water or drum water) or steam at the above-described position in the steam turbine plant.

[0135] (15) The water quality diagnosis method according to at least one embodiment of the present invention is A step of obtaining a measured value of the acid electric conductivity of sample water derived from steam or circulating water collected from a steam turbine plant using ammonia as a water quality conditioner, and a measured value of the pH of the sample water (for example, step S2 described above), Determining whether there is an abnormality in the water quality of the steam turbine plant by using at least a second determination condition as to whether the measured value of the acid electric conductivity and the measured value of the pH are included in a second determination region set in the second correlation map of the acid electric conductivity and the pH in consideration of the concentration range of the ammonia in the sample water assumed in the steam turbine plant (for example, step S16 described above); comprising.

[0136] In a steam turbine plant, the water quality of circulating water or the like can change due to the mixing of acids, alkalis, salts, etc. from the outside, and such a change in water quality also causes changes in the acid electric conductivity and pH of circulating water or the like. Further, the correlation between the acid electric conductivity and pH in circulating water or the like is affected by the ammonia concentration in the water. The ammonia concentration in circulating water or the like can change depending on the operating state of the plant or the like. In the method of (15) above, in the second correlation map of acid electric conductivity vs. pH, based on a second determination condition as to whether the measured values of the acid electric conductivity and pH are included in a second determination region set in consideration of the concentration range of ammonia in the sample water (circulating water or the like) assumed in the steam turbine plant, the presence or absence of an abnormality in the water quality of the sample water is determined. Therefore, even if the ammonia concentration in the sample water fluctuates depending on the operating state of the plant or the like, the water quality diagnosis can be made appropriate.

[0137] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and also includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0138] In this specification, expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states of relative displacement with tolerances or at angles and distances such that the same function can be obtained. For example, expressions indicating that things such as "identical", "equal", and "homogeneous" are in an equal state shall represent not only a strictly equal state but also a state in which there are tolerances or differences to the extent that the same function can be obtained. Also, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape shall represent not only the shapes such as a rectangular shape or a cylindrical shape in a geometrically strict sense but also shapes including uneven portions, chamfered portions, etc. within the range where the same effect can be obtained. Also, in this specification, the expressions "comprising", "including", or "having" for a component are not exclusive expressions excluding the existence of other components.

Explanation of Signs

[0139] 1 Steam turbine plant 2 Boiler 3 Feed water line 4 Feed water pump 6 Condenser 8 Steam turbine 10 High and medium pressure feed water pump 12 Condenser 13 High pressure economizer 14 High pressure drum 16 High pressure superheater 18 Reheater 20 Medium pressure economizer 22 Medium pressure drum 24 Medium pressure superheater 26 Low pressure economizer 28 Low pressure drum 30 Low pressure superheater 38 Connection line 39 Valve 40, 40A, 40B Measuring part 42, 42A, 42B Sample water supply line 43, 43A, 43B Valve 44, 44A, 44B Valve 46, 46A, 46B pH meter 48, 48A, 48B Electrical conductivity meter 50, 50A, 50B Acid electrical conductivity meter 51 Ion exchange part 52 Electrical conductivity meter 54 Sample water discharge line 60 Chemical supply section 62 Chemical tank 64 Chemical line 66 Chemical pump P1 - P8 Sampling points

Claims

1. A step of obtaining a measured value of the electrical conductivity of sample water derived from steam or circulating water collected from a steam turbine plant using ammonia as a water quality conditioner, and a measured value of the pH of the sample water; A determination step of determining the presence or absence of water quality abnormality in the steam turbine plant by using at least a first determination condition of whether the measured value of the electrical conductivity and the measured value of the pH are included in a first determination region set in a first correlation map of the electrical conductivity and the pH in consideration of the carbonate concentration range soluble in the sample water; comprising Based on whether the measured value of the electrical conductivity and the measured value of the pH are included in a first normal region defined on the first correlation map as a region between a boundary indicating the relationship between the electrical conductivity and the pH when the carbonate concentration in the sample water is a first concentration, which is the first determination region, and a boundary indicating the relationship between the electrical conductivity and the pH when the carbonate concentration is a second concentration higher than the first concentration, determine the presence or absence of water quality abnormality Water quality diagnosis method.

2. Based on whether the measured value of the electrical conductivity and the measured value of the pH are included in the first normal region defined on the first correlation map as a region between a boundary indicating the relationship between the electrical conductivity and the pH when the carbonate concentration in the sample water is zero, which is the first determination region, and a boundary indicating the relationship between the electrical conductivity and the pH when the carbonate concentration is the upper limit soluble in the sample water, determine the presence or absence of water quality abnormality The water quality diagnosis method according to claim 1.

3. On the first correlation map, if the measured value of the electrical conductivity and the measured value of the pH are included in a region located on the opposite side of the first normal region across the boundary indicating the relationship between the electrical conductivity and the pH when the carbonate concentration is the upper limit soluble in the sample water, it is determined that there is an abnormality in the water quality due to the mixing of an acid or salt other than carbonate into the sample water The water quality diagnosis method according to claim 2.

4. When the measured values of the electrical conductivity and the pH are included in a region located on the opposite side of the first normal region across the boundary indicating the relationship between the electrical conductivity and the pH when the carbonic acid concentration is zero on the first correlation map, it is determined that there is an abnormality in the water quality due to the mixing of basic substances other than ammonia. The water quality diagnosis method according to claim 2 or 3.

5. A step of obtaining a measured value of the electrical conductivity of sample water derived from steam or circulating water collected from a steam turbine plant using ammonia as a water quality conditioner, and a measured value of the pH of the sample water; A determination step of determining the presence or absence of water quality abnormality in the steam turbine plant by using at least a first determination condition as to whether the measured value of the electrical conductivity and the measured value of the pH are included in a first determination region set in a first correlation map of the electrical conductivity and the pH in consideration of the carbonic acid concentration range soluble in the sample water; A step of obtaining a measured value of the acid electrical conductivity of the sample water, and comprising: In addition to the first determination condition, in consideration of the concentration range of ammonia in the sample water assumed in the steam turbine plant, in a second determination region set in a second correlation map of the acid electrical conductivity and the pH, using a second determination condition as to whether the measured value of the acid electrical conductivity and the measured value of the pH are included, to determine the presence or absence of water quality abnormality Water quality diagnosis method.

6. Based on whether the measured value of the acid electrical conductivity and the measured value of the pH are included in a second normal region defined on the second correlation map as a region between a boundary indicating the relationship between the acid electrical conductivity and the pH when the concentration of ammonia in the sample water is the lower limit of the concentration range and a boundary indicating the relationship between the acid electrical conductivity and the pH when the concentration of ammonia in the sample water is the upper limit of the concentration range, to determine the presence or absence of water quality abnormality The water quality diagnosis method according to claim 5.

7. When the measured values of the acid conductivity and the pH are included in the abnormal region located on the opposite side of the second normal region across the boundary indicating the relationship between the acid conductivity and the pH when the concentration of the ammonia in the sample water is the upper limit of the concentration range on the second correlation map, it is determined that there is an abnormality in the water quality due to the mixing of an acid or a salt other than carbonic acid into the sample water. The water quality diagnosis method according to claim 6.

8. The abnormal region includes a high pH region and a low pH region where the pH is lower than the high pH region. When the measured values of the acid conductivity and the pH are included in the high pH region on the second correlation map, it is determined that there is an abnormality in the water quality due to the mixing of the salt. When the measured values of the acid conductivity and the pH are included in the low pH region on the second correlation map, it is determined that there is an abnormality in the water quality due to the mixing of the acid. The water quality diagnosis method according to claim 7.

9. When it is determined that there is an abnormality in the water quality using one of the first determination condition or the second determination condition, a step of determining the presence or absence of an abnormality in the measuring instrument used to obtain the measured value of the water quality parameter of the sample water related to the one condition is provided. The water quality parameter includes the conductivity, pH, or acid conductivity of the sample water. The water quality diagnosis method according to any one of claims 6 to 8.

10. The presence or absence of an abnormality in the measuring instrument is determined by comparing the measured value of the water quality parameter of the sample water by the measuring instrument with the measured value of the water quality parameter of the sample water by a comparative measuring instrument different from the measuring instrument. The water quality diagnosis method according to claim 9.

11. When it is determined that there is no abnormality in the measuring instrument, the type of abnormality in the water quality in the steam turbine plant is specified based on the first correlation map or the second correlation map related to the other of the first determination condition or the second determination condition. The water quality diagnosis method according to claim 9 or 10.

12. The sample water is obtained from the boiler feed water of the steam turbine plant. When it is determined that there is an abnormality in the water quality in the determination step, the abnormality in the water quality is specified as being caused by seawater leakage in the condenser of the steam turbine plant. The water quality diagnosis method according to any one of claims 1 to 11.

13. The sample water is obtained from the steam of the steam turbine plant, When it is determined in the determination step that there is an abnormality in the water quality, it is specified that the abnormality in the water quality is caused by entrainment of droplets of the drum water of the steam turbine plant. The water quality diagnosis method according to any one of claims 1 to 11.

14. The sample water is obtained from the boiler feed water at the outlet of the condensate pump of the steam turbine plant, the boiler feed water at the inlet of the low-pressure economizer, the drum water of the low-pressure steam drum, the drum water of the medium-pressure steam drum, the drum water of the high-pressure steam drum, the steam at the outlet of the low-pressure steam drum, the steam at the outlet of the medium-pressure steam drum, or the steam at the outlet of the high-pressure steam drum. The water quality diagnosis method according to any one of claims 1 to 13.

15. A step of obtaining a measured value of the acid electric conductivity of sample water derived from steam or circulating water collected from a steam turbine plant using ammonia as a water quality conditioner, and a measured value of the pH of the sample water; A step of determining the presence or absence of water quality abnormality in the steam turbine plant by using at least a second determination condition as to whether or not the measured value of the acid electric conductivity and the measured value of the pH are included in a second determination region set in a second correlation map of the acid electric conductivity and the pH in consideration of the concentration range of the ammonia in the sample water assumed in the steam turbine plant; comprising Based on whether or not the measured value of the acid electric conductivity and the measured value of the pH are included in a second normal region defined on the second correlation map as a region between a boundary indicating the relationship between the acid electric conductivity and the pH when the ammonia concentration in the sample water is a third concentration as the second determination region and a boundary indicating the relationship between the acid electric conductivity and the pH when the ammonia concentration is a fourth concentration higher than the third concentration, the presence or absence of water quality abnormality is determined. Water quality diagnosis method.

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