Steam turbine system, geothermal power generation plant, and method for operating steam turbine system

Abstract

To improve accuracy of estimating the clogging state of a nozzle even when steam is guided to a plurality of spaces.SOLUTION: A steam turbine system 20 comprises: a steam pipe 7 through which steam jetted from a well flows; a steam turbine 8 having a nozzle to which the steam flowing through the steam pipe 7 is guided; a first steam pipe 21 that branches from the steam pipe 7 and guides steam to a first steam chamber S1; a second steam pipe 22 that branches from the steam pipe 7 and guides steam to a second steam chamber S2 having a smaller capacity than the first steam chamber S1; a steam chamber communication valve 23 that adjusts the flow rate of the steam flowing through the second steam pipe 22; a flowmeter 18 that detects the flow rate of the steam flowing through the steam pipe 7; a pressure gauge that detects the pressure of the steam guided to the first steam chamber S1; and a clogging state estimation unit that estimates the clogging state of the nozzle on the basis of the flow rate detected by the flowmeter 18, the pressure detected by the pressure gauge, and the opening degree of the steam chamber communication valve 23.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to steam turbine systems and geothermal power plants, as well as methods of operating steam turbine systems. [Background technology]

[0002] In geothermal power plants, power is generated by introducing steam separated from geothermal fluid (mainly a mixture of steam and hot water) that gushes out from a well (production well) into a steam turbine. Some geothermal power plants are provided with multiple steam chambers so that the introduction area of ​​the steam turbine can be adjusted according to the amount of steam (for example, Patent Document 1). Patent Document 1 discloses a turbine having a main steam chamber and a sub-steam chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-75189 A Summary of the Invention [Problem to be solved by the invention]

[0004] Steam separated from the geothermal fluid that gushes out of the well contains impurities such as silica. As a result, impurities precipitate in the nozzle located upstream of the steam turbine installed in the geothermal power plant. This narrows the nozzle opening area, which may make it difficult to introduce steam into the steam turbine. In addition, the scale causes airflow turbulence, which may reduce turbine efficiency. For this reason, it is considered to be possible to grasp the blockage situation from the nozzle opening area.

[0005] The nozzle opening area (A1) can be calculated from the steam flow rate (G) guided to the steam turbine, the steam chest pressure (P1), and the steam chest temperature (T1).

[0006] In a device having a main steam chamber and a sub-steam chamber as in Patent Document 1, the sub-steam chamber may not be provided with a detection device such as a pressure gauge. In such a case, if the nozzle opening area is derived using the pressure in the main steam chamber, it may not be possible to accurately grasp the nozzle clogging state.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a steam turbine system, a geothermal power plant, and an operating method for a steam turbine system that can improve the accuracy of estimating the nozzle blockage status even when steam is guided to multiple spaces. [Means for solving the problem]

[0008] In order to solve the above problems, the steam turbine system, geothermal power plant, and method of operating the steam turbine system disclosed herein employ the following measures. A steam turbine system according to one embodiment of the present disclosure includes a steam pipe through which steam separated from geothermal fluid sprayed from a borehole flows, a steam turbine having a nozzle to which the steam flowing through the steam pipe is guided, the nozzle having a first nozzle section and a second nozzle section, a first steam pipe branching off from the steam pipe and directing steam to the first nozzle section, a second steam pipe branching off from the steam pipe and directing steam to the second nozzle section, a flow control valve adjusting a flow rate of steam flowing through the second steam pipe, a flow detection unit detecting the flow rate of steam flowing through the steam pipe, a pressure detection unit detecting the pressure of steam guided to the first nozzle section, and a blockage status estimation unit estimating a blockage status of the nozzle based on the flow rate detected by the flow detection unit, the pressure detected by the pressure detection unit, and an opening degree of the flow control valve.

[0009] According to one aspect of the present disclosure, there is provided an operating method for a steam turbine system, the steam turbine system comprising: a steam pipe through which steam separated from geothermal fluid sprayed from a well flows; a steam turbine having a nozzle to which the steam flowing through the steam pipe is guided, the nozzle having a first nozzle section and a second nozzle section; a first steam pipe branching off from the steam pipe and directing steam to the first nozzle section; a second steam pipe branching off from the steam pipe and directing steam to the second nozzle section; and a flow control valve adjusting a flow rate of steam flowing through the second steam pipe, the operating method comprising the steps of: a flow rate detection step of detecting a flow rate of steam flowing through the steam pipe; a pressure detection step of detecting a pressure of the steam guided to the first nozzle section or the steam guided to the first nozzle section; and a clogging condition estimation step of estimating a clogging condition of the nozzle based on the flow rate detected in the flow rate detection step, the pressure detected in the pressure detection step, and an opening degree of the flow control valve. Effect of the Invention

[0010] According to the present disclosure, it is possible to improve the accuracy of estimating the nozzle blockage state even when steam is guided to a plurality of spaces. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing a schematic configuration of a geothermal power plant according to a first embodiment of the present disclosure. [Diagram 2] 1 is a vertical cross-sectional view showing a main portion of a steam turbine according to a first embodiment of the present disclosure. [Diagram 3] 1 is a diagram showing a schematic configuration of a steam turbine system according to a first embodiment of the present disclosure. [Figure 4] 1 is a diagram showing a schematic configuration of a steam turbine system according to a first embodiment of the present disclosure. [Diagram 5] FIG. 2 is a block diagram showing a control device according to the first embodiment of the present disclosure. [Figure 6] 4 is a graph showing a relationship between the opening degree of a steam chest connecting valve and an opening area correction value in the steam turbine system according to the first embodiment of the present disclosure. [Figure 7]4 is a graph showing a change in the opening area of ​​a nozzle in the steam turbine system according to the first embodiment of the present disclosure. [Figure 8] 4 is a graph illustrating a method for determining, by a mathematical formula, a correction curve in the steam turbine system according to the first embodiment of the present disclosure. [Figure 9] FIG. 4 is a diagram showing a schematic configuration of a steam turbine system according to a second embodiment of the present disclosure. [Figure 10] 10 is a graph illustrating a method for determining, by a mathematical formula, a correction curve in a steam turbine system according to a second embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram showing a schematic configuration of a steam turbine system according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [First embodiment] A first embodiment of a steam turbine system, a geothermal power plant, and an operating method of a steam turbine system according to the present disclosure will be described below with reference to the drawings. Note that the steam turbine system 20 can be widely applied to any geothermal power plant that generates power using geothermal fluid spouting from a well 2, and is not limited to application to only the geothermal power plant 1 having the configuration described below.

[0013] FIG. 1 is a diagram showing a schematic configuration of a geothermal power plant 1 including a well control system according to a first embodiment of the present disclosure. In this embodiment, a case where a plurality of wells 2 are provided, for example, two wells 2 are provided, will be described. Note that the geothermal power plant 1 shown in FIG. 1 is a flash cycle type geothermal power plant. Also, in FIG. 1, for example, two wells 2 are provided, two steam-water separators 5 are provided, and one reinjection well 19 is provided, but the present disclosure can be applied as appropriate without being limited to the above configuration and the number of components.

[0014] 1, a geothermal power plant 1 according to this embodiment mainly comprises a geothermal fluid transport pipe 3, a steam flow rate control valve 4, a steam-water separator 5, a hot water pipe 6, a steam pipe 7, a steam turbine 8, a condenser 10, and a cooling tower 11. The steam pipe 7 and the steam turbine 8 are included in a steam turbine system, which will be described later.

[0015] The geothermal fluid transport pipe 3 is a pipe that guides geothermal fluid spouted from the borehole (geothermal borehole) 2 to the steam-water separator 5. A magma reservoir is formed underground, and the heat from this reservoir heats rainwater that has seeped underground and groundwater that has flowed in, forming a geothermal reservoir. Geothermal fluid is stored in the geothermal reservoir, and is extracted to the surface via the borehole 2. The geothermal fluid transport pipe 3 transports the geothermal fluid from the geothermal reservoir to the steam-water separator 5 via the borehole 2. Note that geothermal fluid is a two-phase mixture fluid that is mainly composed of steam (gas) and hot water (liquid).

[0016] The gas flow rate control valve 4 is installed on the geothermal fluid transport pipe 3 and adjusts the total flow rate (the gas flow rate, the total flow rate of steam and hot water) of the geothermal fluid flowing from the borehole 2 to the steam-water separator 5.

[0017] In addition, an opening / closing valve 13 may be provided upstream of the geothermal fluid flow on the geothermal fluid transport pipe 3 (upstream of the gas flow control valve 4, for example, near the outlet of the borehole 2) to control the flow state (flowing state or non-flowing state) of the geothermal fluid.

[0018] The steam-water separator 5 is a device (separator) that separates the geothermal fluid, which is a two-phase mixed fluid supplied by the geothermal fluid transport pipe 3, into steam and hot water. The hot water separated by the steam-water separator 5 is guided to a hot water pipe 6, and the steam separated by the steam separator 5 is guided to a steam pipe 7.

[0019] The hot water pipes 6 are pipes that guide the hot water separated by the steam-water separators 5 to the reinjection wells 19. By returning the hot water to the underground geothermal reservoir via the reinjection wells 19, depletion of geothermal fluid in the underground geothermal reservoir is suppressed. The hot water separated by each steam-water separator 5 may be pumped to the reinjection wells 19 using a pump 14.

[0020] The steam pipe 7 is a pipe that guides the steam separated by the steam-water separator 5 to the steam turbine 8. The steam separated by each steam-water separator 5 is joined in the steam pipe 7 and supplied to the steam turbine 8. The flow rate of the steam sent to the steam turbine 8 is measured by a flow meter 18 provided on the steam pipe 7. Note that in this embodiment, a case will be described in which the flow rate (total flow rate) of the steam separated by each steam-water separator 5 is measured after the steam is joined, but the flow rate of the steam separated by each steam-water separator 5 may be measured individually. The steam pipe 7 may be provided with a flow control valve 15 for the steam separated by each steam-water separator 5 after the steam is joined, to control the supply flow rate of the steam to the steam turbine 8.

[0021] The condenser 10 is a device that condenses and condenses the steam that has completed its work of rotating the rotor blades 8d (see FIG. 3) in the steam turbine 8 by cooling it with cooling water. The condensed hot water is supplied to a cooling tower 11.

[0022] The cooling tower 11 is a device that evaporates and cools the hot water condensed in the condenser 10. Specifically, the hot water supplied to the cooling tower 11 is sprayed from a spray unit at the top of the cooling tower 11. A portion of the sprayed hot water evaporates when it comes into contact with air circulated by the blower of the cooling tower 11, and the latent heat associated with this evaporation cools the remaining hot water to become water. The cooled water is stored in the cooling tower 11 as cooling tower water. The cooling tower water stored in the cooling tower 11 is supplied to the condenser 10 as cooling water via a pump 12.

[0023] Next, the steam turbine 8 will be described with reference to Fig. 2 to Fig. 4. Note that in Fig. 3, for convenience of illustration, the stationary blades 8c are omitted. 2 and 3, the steam turbine 8 has a housing 8a with a space formed therein, a shaft portion 8b penetrating the housing 8a, stationary blades 8c provided inside the housing 8a and fixed to the inner peripheral surface of the housing 8a, and rotor blades 8d provided inside the housing 8a and attached to the outer peripheral surface of the shaft portion 8b. In the steam turbine 8, steam supplied from a steam pipe 7 is introduced through a nozzle into a space formed between the housing 8a and the shaft portion 8b, and the rotor blades 8d and the shaft portion 8b are driven to rotate by the energy of the steam flowing through the space, which in turn drives a generator 9 (see FIG. 1) connected to the shaft portion 8b to generate electricity.

[0024] The shaft portion 8b extends linearly in a predetermined direction and rotates about a central axis extending in the predetermined direction.

[0025] A plurality of stator blades 8c are provided. The plurality of stator blades 8c are arranged side by side at predetermined intervals along a predetermined direction. For example, the plurality of stator blades 8c are fixed to the inner peripheral surface of the housing 8a. The plurality of stator blades 8c are arranged side by side at predetermined intervals along the circumferential direction. The nozzle refers to a flow passage (opening) formed between two adjacent stator vanes 8c belonging to the most upstream stator vanes 8c in the steam flow direction, for example, and a plurality of nozzles are provided. The plurality of nozzles are arranged side by side at predetermined intervals along the circumferential direction.

[0026] A plurality of rotor blades 8d are provided. The rotor blades 8d are arranged in a line at a predetermined interval along a predetermined direction. Each rotor blade 8d has a plurality of blades arranged in a line in the circumferential direction on the outer circumferential surface of the shaft portion 8b. The stationary blades 8c and the moving blades 8d are arranged alternately in a predetermined direction.

[0027] A plurality of steam chambers (two, for example, in this embodiment) are formed upstream of the plurality of nozzles.

[0028] As shown in Fig. 4, the multiple steam chambers include a first steam chamber S1 and a second steam chamber S2 arranged in a circumferential direction centered on the central axis of the shaft portion 8b of the steam turbine 8. The first steam chamber S1 and the second steam chamber S2 are separated by two partition walls 8e spaced apart in the circumferential direction. The first steam chamber S1 and the second steam chamber S2 are formed upstream of the nozzle. The multiple nozzles include a first nozzle portion which is a nozzle connected to the first steam chamber S1 and through which steam is guided from the first steam chamber S1, and a second nozzle portion which is a nozzle connected to the second steam chamber S2 and through which steam is guided from the second steam chamber S2.

[0029] The opening area of ​​the nozzle (first nozzle portion) connected to the first steam chamber S1 (if there are multiple first nozzle portions, the sum of the opening areas of the multiple first nozzle portions) is larger than the opening area of ​​the nozzle (second nozzle portion) connected to the second steam chamber S2 (if there are multiple second nozzle portions, the sum of the opening areas of the multiple second nozzle portions). If the sum of the nozzle opening areas is 100%, for example, the opening area of ​​the first nozzle portion is about 70% to 80% of the total, and the opening area of ​​the second nozzle portion is about 20% to 30% of the total. Note that the ratio of the opening area of ​​each nozzle portion is not limited to this and may be set to any ratio.

[0030] Next, the steam turbine system 20 according to this embodiment will be described in detail. 3 and 4, the steam turbine system 20 includes a steam pipe 7 through which steam separated from the geothermal fluid spouted from the borehole 2 (see FIG. 1) flows, and a steam turbine 8 having a nozzle through which the steam that has flowed through the steam pipe 7 is guided. The steam turbine system 20 also includes a first steam pipe 21 that branches off from the downstream end of the steam pipe 7 and guides steam to the first steam chamber S1, and a second steam pipe 22 that branches off from the downstream end of the steam pipe 7 and guides steam to the second steam chamber S2. The steam turbine system 20 also includes a steam chamber connecting valve (flow rate control valve) 23 that adjusts the flow rate of steam flowing through the second steam pipe 22, a flow meter (flow rate detection unit) 18 that detects the flow rate of steam flowing through the steam pipe 7, a pressure gauge (pressure detection unit) 25 that detects the pressure of the steam led to the first steam chamber S1 (in other words, the steam in the first steam chamber S1), and a thermometer 26 that detects the temperature of the steam led to the first steam chamber S1 (in other words, the steam in the first steam chamber S1). The steam turbine system 20 also includes a control device 30 that receives measurement results from the flow meter 18 and the pressure gauge 25 and adjusts the opening degree of the steam chamber connecting valve 23.

[0031] In the geothermal power plant 1 of this embodiment, when the steam flow rate supplied to the steam turbine 8 decreases due to, for example, attenuation of geothermal fluid, additional drilling of wells, maintenance, or the like, or when the steam flow rate flowing into the steam turbine 8 decreases due to a reduction in the nozzle opening area caused by scale, the output of the steam turbine 8 (i.e., the amount of power generated by the generator 9) decreases and falls below a specified threshold value, the steam chamber connection valve 23 is opened (with an opening degree corresponding to the amount of reduction in output) and the second steam chamber S2 is partially used. By operating in this manner, the geothermal power plant 1 can operate while maintaining a stable output.

[0032] As shown in Fig. 5, the control device 30 has a blockage state estimation unit 31 and a cleaning necessity determination unit 32. The control device 30 receives information measured by various devices from the flowmeter 18, the pressure gauge 25, and the thermometer 26. The control device 30 also transmits and receives signals related to the opening degree to and from the steam chest connecting valve 23, and controls the opening degree of the steam chest connecting valve 23. The opening degree of the steam chest connecting valve 23 may be manually operated by an operator. In this case, the information measured by various devices from the flowmeter 18, the pressure gauge 25, and the thermometer 26 is output to a display or the like, and the operator operates the opening degree of the steam chest connecting valve 23 by checking the output information.

[0033] The control device 30 (Controller) includes, for example, a CPU (Central Processing Unit: Processor), a main memory, a secondary storage, etc. Furthermore, the control device 30 may include a communication unit for transmitting and receiving information to and from other devices. The main storage device is composed of writable memory such as cache memory and RAM (Random Access Memory), and is used as a working area for reading out programs executed by the CPU and writing data processed by the programs. The secondary storage device is a non-transitory computer readable storage medium, such as a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory. A series of processes for realizing various functions is stored in a secondary storage device in the form of a program, for example, and various functions are realized by the CPU reading the program into the main storage device and executing information processing and arithmetic processing. The program may be installed in the secondary storage device in advance, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0034] The clogging condition estimation unit 31 estimates the clogging condition of the nozzle based on the flow rate detected by the flow meter 18, the pressure detected by the pressure gauge 25, and the opening degree of the steam chest connecting valve 23. In detail, the clogging condition estimation unit 31 estimates the clogging condition of the nozzle by correcting data obtained based on the flow rate detected by the flow meter 18 and the pressure detected by the pressure gauge 25, based on the opening degree of the steam chest connecting valve 23. The clogging condition estimation unit 31 estimates the clogging condition of the nozzle when steam is being guided to the second steam chest S2 via the second steam pipe 22. The nozzle clogging state may be derived based on, for example, a change in the nozzle opening area (hereinafter referred to as the "nozzle opening ratio"). The nozzle opening ratio may be a ratio of the current nozzle opening area to the nozzle opening area in a predetermined state (for example, a state before the steam turbine system 20 starts operating or a state immediately after cleaning) set to 100%.

[0035] The cleaning necessity determining unit 32 determines whether or not to clean the nozzle based on the clogging state of the nozzle estimated by the clogging state estimating unit 31. The cleaning necessity determining unit 32 may determine to clean the nozzle when the nozzle opening rate estimated by the clogging state estimating unit 31 becomes equal to or lower than a predetermined threshold. Note that a final decision on whether or not to clean the nozzle may be made by an operator. In this case, the cleaning necessity determining unit 32 outputs the decision on whether or not to clean on a display or the like, and the operator confirms the output decision and makes a final decision on whether or not to clean the nozzle.

[0036] Next, a method for the clogged state estimation unit 31 to estimate the clogged state of the nozzle will be described. The steam separated from the geothermal fluid gushes out of the borehole 2 contains impurities such as silica. As a result, the impurities precipitate in a nozzle provided upstream of the steam turbine 8 in the geothermal power plant 1. This narrows the opening area of ​​the nozzle (i.e., the nozzle becomes clogged).

[0037] The nozzle clogging condition can be estimated by estimating the nozzle opening area based on the current operating state of the steam turbine 8. The nozzle opening area (A1) can be derived from the steam flow rate (G) guided to the steam turbine 8, the pressure (P1) of the first steam chamber S1, and the temperature (T1) of the first steam chamber S1. In the case of a geothermal power plant 1, since the temperature of the first steam chamber S1 changes little, the temperature of the first steam chamber S1 can be omitted and the nozzle opening area (A1) can be simply calculated from the ratio (P1) of the steam flow rate (G) and the pressure of the first steam chamber S1 (hereinafter referred to as the "G / P ratio"). In the case of a simple calculation, it can be specifically calculated by the following formula (1). c(T) in the following formula (1) is a proportionality constant and can be derived from the measured temperature. In the case of a geothermal power plant, the steam chamber temperature changes little and the proportionality constant c(T) has little temperature dependency, so the proportionality constant c(T) may be a fixed value.

[0038] A1 = c(T) × G / P1(1)

[0039] In the case of a structure in which a pressure gauge is not provided in the second steam chamber S2 and steam is supplied to both the first steam chamber S1 and the second steam chamber S2, as in this embodiment, if the opening area is estimated only based on the G / P ratio based on the first steam chamber S1, it will be affected by the opening area of ​​the second steam chamber S2, and there is a possibility that the consistency of the estimation standard (based on the first steam chamber S1) will be lost and the accuracy will decrease. Specifically, as shown by the dashed line in Figure 7, a value larger than the actual opening area is calculated depending on the opening degree of the steam chamber connection valve 23.

[0040] Generally, the larger the opening degree of the steam chest connecting valve 23, the larger the apparent opening area becomes, but the degree of this increase is uniquely determined by the opening degree of the steam chest connecting valve 23. Therefore, the control device 30 of this embodiment corrects the calculated value of the opening area obtained based on the flow rate detected by the flow meter 18 (i.e., the steam flow rate (G)) and the pressure detected by the pressure gauge 25 (i.e., the pressure (P1) of the first steam chamber S1) in accordance with the opening degree of the steam chamber connecting valve 23, thereby eliminating the influence of the opening area of ​​the second steam chamber S2, thereby maintaining consistency of the estimation criteria and enabling a more accurate estimation of the nozzle blockage condition.

[0041] The memory unit of the control device 30 stores a correction curve (see FIG. 6) that specifies the relationship between the opening of the steam chest connecting valve 23 and the correction value of the opening area, and determines a correction value according to the opening of the steam chest connecting valve 23 based on the correction curve. The calculated nozzle opening area is corrected with the determined correction value. In the correction curve of this embodiment, the correction value increases as the opening of the steam chest connecting valve 23 increases.

[0042] Specifically, when the opening degree of the steam chest connection valve 23 is 50%, it is derived from the correction curve that the correction value is C1, as shown in Fig. 6. In this case, the nozzle opening area (i.e., the blocked state) is estimated by subtracting C1 from the calculated nozzle opening area, as shown in Fig. 7. Similarly, when the opening degree of the steam chest connection valve 23 is 100%, it is derived from the correction curve that the correction value is C2, as shown in Fig. 6. In this case, the nozzle opening area (i.e., the blocked state) is estimated by subtracting C2 from the calculated nozzle opening area, as shown in Fig. 7.

[0043] In this embodiment, the correction is described using the opening degree of the steam chamber connecting valve 23 at 0% (i.e., fully closed) as the estimation standard (i.e., first steam chamber S1 standard), but the opening degree of the steam chamber connecting valve 23 at 100% (i.e., fully open) may also be used as the estimation standard (i.e., first steam chamber S1 + second steam chamber S2 standard), or a predetermined intermediate opening degree may be used as the estimation standard. Which opening degree is used as the estimation standard is arbitrary and is determined depending on the geothermal power plant 1.

[0044] The correction curve may be determined, for example, by learning from driving data. For example, during actual operation, the opening degree and calculated values ​​of the opening area of ​​the steam chest connecting valve 23 are recorded, and a correction curve can be determined from the change in the calculated value of the opening area according to the opening degree of the steam chest connecting valve 23. If this method is performed within a period that is sufficiently short compared to the growth rate of scale (for example, acquired within one hour), it is possible to determine a correction curve without being affected by the change in the opening area due to scale.

[0045] Also, the change in the calculated value of the opening area when the steam chest connecting valve 23 is operated to an open position (for example, the change in the calculated value of the opening area when operated from 50% to 100%) may be recorded, and the correction curve may be determined by learning from the data set. With this method, the correction curve can be determined more accurately, since it can be determined from data over a relatively long period of time during which scale would grow.

[0046] Depending on the operating history up to that point, it is possible that the degree of scale deposition in the nozzles of the first steam chamber S1 and the nozzles of the second steam chamber S2 will differ (for example, when the steam chamber connecting valve 23 has been operated in a fully closed state for a long period of time and then is operated in an open state, etc.).

[0047] Next, a method for cleaning the nozzle of the steam turbine 8 will be described. A cleaning necessity determining unit 32 determines whether or not the nozzle needs to be cleaned based on the blockage state estimated by the blockage state estimating unit 31. When the cleaning necessity determining unit 32 determines that the nozzle needs to be cleaned, the nozzle is cleaned. The method for cleaning the nozzle is not particularly limited, but examples of the nozzle cleaning method include online cleaning and open cleaning.

[0048] Online cleaning involves issuing a command to the geothermal power plant 1 to perform automatic cleaning, and by supplying a cleaning liquid (e.g., water or an aqueous sodium hydroxide solution) to the steam turbine 8 from a water supply line (not shown) connected to the steam pipe 7, etc. upstream of the steam turbine 8, scale adhering to the nozzles, etc. is dissolved and removed. Open cleaning is a method in which the steam turbine 8 is opened and scale adhering to the nozzles and the like is manually removed.

[0049] According to this embodiment, the following advantageous effects are obtained. In this embodiment, the clogging condition estimation unit 31 estimates the clogging condition of the nozzle based on the flow rate detected by the flowmeter 18, the pressure detected by the pressure gauge 25, and the opening of the steam chamber connection valve 23. By estimating the clogging condition based on the opening of the steam chamber connection valve 23 in this way, the accuracy of estimating the clogging condition of the nozzle can be improved even when steam is guided to the second steam chamber S2 via the steam chamber connection valve 23.

[0050] Furthermore, in this embodiment, even when steam is guided to the second steam chamber S2, the nozzle blockage state can be estimated without detecting the pressure of the steam flowing through the second steam pipe 22. Therefore, since there is no need to provide a device for detecting the pressure of the steam flowing through the second steam pipe 22, the number of parts can be reduced. This makes construction easier and reduces costs.

[0051] In this embodiment, the clogging condition estimation unit 31 performs correction based on the opening degree of the steam chest connection valve 23. This makes it possible to more accurately estimate the clogging condition of the nozzle, even when steam is guided to the second steam chest S2 via the steam chest connection valve 23.

[0052] Furthermore, in this embodiment, even when steam is guided to the first steam chamber S1 and the second steam chamber S2, it is possible to estimate the clogging state of the nozzle. Also, the number of parts can be reduced.

[0053] In this embodiment, the clogging state estimation unit 31 estimates the clogging state of the nozzle when the second steam pipe 22 leads to the second steam chamber S2. This makes it possible to accurately estimate the clogging state of the nozzle even when steam is led to the second steam chamber S2 via the steam chamber connection valve 23.

[0054] In addition, in this embodiment, a cleaning necessity determining unit 32 that determines whether or not to clean the nozzle is provided, so that it is possible to determine whether or not to clean the nozzle depending on the clogging state.

[0055] [Modifications] In the first embodiment, an example has been described in which the correction curve is determined by learning from the driving data, but the correction curve may be determined by a mathematical formula. A method for determining the value by a formula will be described below (see also FIG. 8).

[0056] As described above, with the proportionality constant being c, the following equations (2) and (3) hold.

[0057] A1 = c × G1 / P1(2) A2 = c × G2 / P2 (3) A1 is the opening area of ​​the nozzle corresponding to the first steam chamber S1 A2 is the opening area of ​​the nozzle corresponding to the second steam chamber S2 P1 is the pressure in the first steam chamber S1 P2 is the pressure in the second steam chamber S2 G1 is the steam flow rate introduced into the first steam chamber S1 G2 is the steam flow rate led to the second steam chamber S2

[0058] Furthermore, the steam chest connecting valve 23 has a valve capacity coefficient, Cv, that is determined according to the opening degree (X), and based on this, the following equation (4) is established. Note that a in equation (4) is an arbitrary coefficient.

[0059]

number

[0060] By eliminating P2 from equation (5), the following equation (5) is obtained.

[0061]

number

[0062] On the other hand, the flow rate actually measured by the flowmeter 18 is G0=G1+G2, and the apparent opening area (A0) calculated from this is given by the following formula (6). Note that G0 is the flow rate of steam flowing through the steam pipe 7.

[0063]

number

[0064] That is, the corrected area (the difference between the apparent opening area A0 and the nozzle opening area A1 of the first steam chamber S1) is calculated by the following formula (7).

[0065]

number

[0066] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to FIGS. This embodiment differs from the first embodiment in that the steam chamber is divided into three steam chambers. Accordingly, this embodiment also differs from the first embodiment in that a third steam pipe 43 that guides steam to the third steam chamber S3 is provided. Since other points are the same as those of the first embodiment, in the following description, the same components are denoted by the same reference numerals and detailed description thereof is omitted.

[0067] 9, a steam turbine system 120 of this embodiment includes a first steam pipe 21 that branches off from the downstream end of the steam pipe 7 and leads steam to a first steam chamber S1, a second steam pipe 22 that branches off from the downstream end of the steam pipe 7 and leads steam to a second steam chamber S2, and a third steam pipe 43 that branches off from the downstream end of the steam pipe 7 and leads steam to a third steam chamber S3. The steam turbine system 120 also includes a steam chamber connection valve 23 that adjusts the flow rate of steam flowing through the second steam pipe 22, and a steam chamber connection valve 44 that adjusts the flow rate of steam flowing through the third steam pipe 43.

[0068] The multiple steam chambers include a first steam chamber S1, a second steam chamber S2, and a third steam chamber S3 that are arranged in a circumferential direction around the central axis of the shaft portion 8b of the steam turbine 8. The capacity of the first steam chamber S1 is larger than the capacity of the second steam chamber S2. The capacity of the second steam chamber S2 is also larger than the capacity of the third steam chamber S3. For example, if the capacity of the entire steam chamber is 100%, the capacity of the first steam chamber S1 is about 70%, the capacity of the second steam chamber S2 is about 20%, and the capacity of the third steam chamber S3 is about 10%. Note that the ratio of the capacity of each steam chamber is not limited to this and may be set to any ratio.

[0069] In this embodiment, a method for determining the correction curve by a mathematical formula will be described (see also FIG. 10).

[0070] As described above, when the proportionality constant is c, the following equations (8), (9), and (10) hold.

[0071] A1 = c × G1 / P1(8) A2 = c × G2 / P2 (9) A3 = c × G3 / P3 (10) A1 is the opening area of ​​the nozzle corresponding to the first steam chamber S1 A2 is the opening area of ​​the nozzle corresponding to the second steam chamber S2 A3 is the opening area of ​​the nozzle corresponding to the third steam chamber S3 P1 is the pressure in the first steam chamber S1 P2 is the pressure in the second steam chamber S2 P3 is the pressure in the third steam chamber S3 G1 is the steam flow rate introduced into the first steam chamber S1 G2 is the steam flow rate led to the second steam chamber S2 G3 is the steam flow rate led to the third steam chamber S3

[0072] Furthermore, if the Cv value of the steam chest connecting valve 23 is Cv2 and the Cv value of the steam chest connecting valve 44 is Cv3, the following equations (11) and (12) are established. Note that a in equations (11) and (12) is an arbitrary coefficient.

[0073]

number

[0074]

number

[0075] On the other hand, the flow rate actually measured is G0=G1+G2+G3, and the apparent opening area (A0) calculated from this is given by the following formula (13). Note that G0 is the flow rate of steam flowing through the steam pipe 7.

number

[0076] That is, the corrected area is calculated by the following formula (14): The corrected area is a linear sum of the correction terms for the second steam chamber S2 and the third steam chamber S3.

[0077]

number

[0078] In addition, when the steam chamber is divided into three or more parts, the correction factor is similarly a linear sum of the correction terms of the valves provided in the piping that guides steam to chambers other than the first steam chamber S1.

[0079] In this way, even when the steam chamber is divided into three or more chambers, the same effects as those of the first embodiment can be achieved by making corrections based on the opening degrees of the respective steam chamber communication valves.

[0080] Third Embodiment Next, a third embodiment of the present disclosure will be described with reference to FIG. This embodiment differs from the first embodiment in that the steam chamber is not divided in the circumferential direction and in that the position to which the second steam pipe 52 is connected is different. Since other points are the same as those in the first embodiment, in the following description, the same components are denoted by the same reference numerals and detailed description thereof is omitted.

[0081] In the steam turbine system 220 of this embodiment, the steam chamber is not divided in the circumferential direction. The first steam pipe 21 is connected to the undivided steam chamber. Also, as shown in FIG. 11, the second steam pipe 52 is connected to a second nozzle section which is a nozzle provided on the most upstream side (in other words, an opening formed between the stator vanes 8c provided on the most upstream side) provided on the downstream side of the first nozzle section. The second steam pipe 52 is provided with a steam chamber connection valve 54 which adjusts the flow rate of steam flowing through the second steam pipe 52. Also, the steam turbine system 220 is provided with a pressure gauge (pressure detection section) 55 which detects the pressure of steam flowing through the second steam pipe 52, and a thermometer 56 which detects the temperature of steam flowing through the second steam pipe 52.

[0082] In this embodiment, a method for determining the correction curve by a mathematical formula will be described.

[0083] As described above, with the proportionality constant being c, the following equations (15) and (16) hold.

[0084] A1 = c × G1 / P1 (15) A1 is the opening area of ​​the nozzle (first nozzle portion) corresponding to the first steam chamber S1

[0085]

number

[0086] On the other hand, the flow rate actually measured by the flowmeter 18 is G0=G1+G2, and the apparent opening area (A0) calculated from this is given by the following formula (17). Note that G0 is the flow rate of steam flowing through the steam pipe 7.

[0087]

number

[0088] That is, the corrected area is calculated by the following equation (18).

number

[0089] In this embodiment as well, by making a correction based on the opening degree of the steam chest connection valve, the same effects as those of the first embodiment can be achieved.

[0090] The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present disclosure. For example, in each of the above embodiments, the pressure gauge 25 and the thermometer 26 are provided in the first steam chamber S1, but the present disclosure is not limited to this. For example, the pressure gauge 25 and the thermometer 26 may be provided in the first steam pipe 21.

[0091] The steam turbine system, the geothermal power plant, and the method of operating the steam turbine system described in the above-described embodiments can be understood, for example, as follows. A steam turbine system according to a first aspect of the present disclosure includes a steam pipe (7) through which steam separated from geothermal fluid spouted from a well (2) flows, a steam turbine (8) having a nozzle to which the steam flowing through the steam pipe (7) is guided and which has a first nozzle portion and a second nozzle portion, a first steam pipe (21) branching off from the steam pipe (7) and directing steam to the first nozzle portion (8c), and a second steam pipe (22) branching off from the steam pipe (7) and directing steam to the second nozzle portion (8c). The steam flow control valve (23) adjusts the flow rate of steam flowing through the second steam pipe (22), a flow rate detection unit (18) detects the flow rate of steam flowing through the steam pipe (7), a pressure detection unit (25) detects the pressure of the steam guided to the first nozzle portion, and a clogging state estimation unit (31) estimates a clogging state of the nozzle (8c) based on the flow rate detected by the flow rate detection unit (18), the pressure detected by the pressure detection unit (25), and the opening degree of the flow rate control valve (23).

[0092] In the above configuration, the clogging condition estimation unit estimates the clogging condition of the nozzle based on the flow rate detected by the flow rate detection unit, the pressure detected by the pressure detection unit, and the aperture of the flow rate control valve. In this way, by estimating the clogging condition based on the aperture of the flow rate control valve, it is possible to improve the accuracy of estimating the clogging condition of the nozzle even when steam is guided to the second turbine section via the flow rate control valve.

[0093] In addition, in the above configuration, even when steam is guided to the second turbine section, the nozzle blockage state can be estimated without detecting the pressure of the steam flowing through the second steam pipe. Therefore, since there is no need to provide a device for detecting the pressure of the steam flowing through the second steam pipe, the number of parts can be reduced, and therefore costs can be reduced.

[0094] In addition, the nozzle clogging status may be derived based on the opening rate of the gaps formed between the multiple blades (hereinafter referred to as the "nozzle opening rate"), for example, when the nozzle has multiple blades arranged side by side at a predetermined interval in the circumferential direction. The nozzle opening ratio may be the ratio of the current nozzle opening area to the nozzle opening area in a predetermined state (for example, a state before the steam turbine system starts operating or a state immediately after cleaning) being 100%.

[0095] In addition, in the steam turbine system according to the first aspect, the blockage condition estimation unit (31) estimates the blockage condition of the nozzle (8 c) by correcting data obtained based on the flow rate detected by the flow rate detection unit (18) and the pressure detected by the pressure detection unit (25) based on an opening degree of the flow rate control valve (23).

[0096] In the above configuration, the clogging state estimation unit performs correction based on the opening degree of the flow rate control valve. This makes it possible to more accurately estimate the clogging state of the nozzle even when steam is guided to the second space via the flow rate control valve.

[0097] In addition, in a steam turbine system according to a third aspect of the present disclosure, in the above-mentioned first or second aspect, the steam turbine (8) has a first steam chamber (S1) that guides steam to the first nozzle section (8c) and a second steam chamber (S2) that guides steam to the second nozzle section, and the first steam chamber (S1) and the second steam chamber (S2) are arranged in a circumferential direction around a central axis of the steam turbine (8).

[0098] In the above configuration, even when steam is guided to the first steam chamber and the second steam chamber, it is possible to estimate the clogging state of the nozzle, and the number of parts can be reduced.

[0099] In addition, in a steam turbine system according to a fourth aspect of the present disclosure, in any one of the first to third aspects, the blockage situation estimation unit (31) estimates a blockage situation of the nozzle (8c) when the second steam pipe (22) guides steam to the second nozzle section.

[0100] In the above configuration, the clogging state estimation unit estimates the clogging state of the nozzle when the second steam pipe is leading to the second turbine section. This makes it possible to accurately estimate the clogging state of the nozzle even when steam is led to the second turbine section via a flow rate control valve.

[0101] Furthermore, a steam turbine system according to a fifth aspect of the present disclosure, in any of the first to fourth aspects, includes a cleaning necessity determining unit (32) that determines whether or not to clean the nozzle (8c) based on the blockage state estimated by the blockage state estimation unit (31).

[0102] In the above-described configuration, a cleaning necessity determining unit is provided that determines whether or not to clean the nozzle, so that it is possible to determine whether or not to clean the nozzle depending on the clogging state.

[0103] Furthermore, in a steam turbine system according to a sixth aspect of the present disclosure, in the above-described fifth aspect, the blockage situation estimation unit (31) estimates an opening ratio of the nozzle (8c) and estimates a blockage situation based on the opening ratio, and the cleaning necessity determination unit (32) determines to clean the nozzle (8c) when the opening ratio of the nozzle (8c) estimated by the blockage situation estimation unit (31) becomes equal to or lower than a predetermined threshold value.

[0104] In the above configuration, the cleaning necessity determining unit determines to clean the nozzle when the nozzle opening ratio estimated by the blockage state estimating unit is equal to or smaller than a predetermined threshold value, thereby making it possible to more accurately determine whether or not to clean the nozzle.

[0105] Furthermore, a geothermal power plant according to a first aspect of the present disclosure includes a steam turbine system (20) described in any one of the first to sixth aspects above, a well from which steam is ejected and led to the steam turbine system (20), and a generator that generates electricity using the driving force of the steam turbine system (20).

[0106] A method for operating a steam turbine system according to a first aspect of the present disclosure is a method for operating a steam turbine system (20), the steam turbine system (20) including: a steam pipe (7) through which steam separated from geothermal fluid spouted from a well (2) flows; a steam turbine (8) having a nozzle to which the steam flowing through the steam pipe (7) is guided, the nozzle having a first nozzle portion and a second nozzle portion; a first steam pipe (21) branching off from the steam pipe (7) and guiding steam to the first nozzle portion (8c); the first nozzle portion (8c) and a flow rate control valve (23) that controls the flow rate of steam flowing through the second steam pipe (22), and the nozzle (8c) is provided with a flow rate detection step of detecting a flow rate of steam flowing through the steam pipe (7), a pressure detection step of detecting a pressure of the steam to be guided to the first nozzle portion or the steam guided to the first nozzle portion, and a clogging state estimation step of estimating a clogging state of the nozzle (8c) based on the flow rate detected in the flow rate detection step, the pressure detected in the pressure detection step, and the opening degree of the flow rate control valve (23). [Explanation of symbols]

[0107] 1: Geothermal power plant 2: Well 3:Geothermal fluid transport pipe 4: Gas flow control valve 5: Steam water separator 6:Hot water pipe 7: Steam pipe 8: Steam turbine 8a: Housing 8b:Shaft part 8c: Shizuka 8d: Moving blade 8e: Bulkhead 9: Generator 10: Condenser 11: Cooling tower 12: Pump 13: Opening and closing valve 14: Pump 15: Flow control valve 18:Flow meter 19: Reinjection well 20: Steam turbine system 21: First steam pipe 22: Second steam pipe 23: Steam chamber connection valve (flow control valve) 25: Pressure gauge (pressure detection part) 26:Thermometer 30: Control device 31: Blockage status estimation unit 32: Cleaning necessity determination unit 43: Third steam pipe 44: Steam chamber connection valve 52: Second steam pipe 54: Steam chamber connection valve 55: Pressure gauge (pressure detection part) 56: Thermometer 120: Steam turbine systems 220: Steam turbine systems S1: First steam room S2: Second steam room S3: Steam room no. 3

Claims

1. a steam pipe through which steam separated from the geothermal fluid spouted from the well flows; a steam turbine into which the steam flowing through the steam pipe is guided, the steam turbine having a nozzle including a first nozzle portion and a second nozzle portion; a first steam pipe branching from the steam pipe and directing steam to the first nozzle portion; a second steam pipe branching off from the steam pipe and directing steam to the second nozzle portion; a flow rate control valve that controls a flow rate of steam flowing through the second steam pipe; a flow rate detection unit that detects a flow rate of steam flowing through the steam pipe; a pressure detection unit that detects a pressure of the steam guided to the first nozzle unit; a clogging state estimation unit that estimates a clogging state of the nozzle based on the flow rate detected by the flow rate detection unit, the pressure detected by the pressure detection unit, and an opening degree of the flow rate control valve.

2. 2. The steam turbine system according to claim 1, wherein the blockage condition estimation unit estimates the blockage condition of the nozzle by correcting data obtained based on the flow rate detected by the flow rate detection unit and the pressure detected by the pressure detection unit based on an opening degree of the flow rate control valve.

3. the steam turbine has a first steam chamber that guides steam to the first nozzle portion and a second steam chamber that guides steam to the second nozzle portion, The steam turbine system according to claim 1 , wherein the first steam chamber and the second steam chamber are arranged side by side in a circumferential direction about a central axis of the steam turbine.

4. The steam turbine system according to claim 1 , wherein the blockage state estimation unit estimates the blockage state of the nozzle when the second steam pipe guides steam to the second nozzle portion.

5. The steam turbine system according to claim 1 , further comprising a cleaning necessity determining unit that determines whether or not to clean the nozzle based on the clogging state estimated by the clogging state estimating unit.

6. the clogging state estimation unit estimates an opening ratio of the nozzle and estimates a clogging state based on the opening ratio; The steam turbine system according to claim 5 , wherein the cleaning necessity determining unit determines to clean the nozzle when the nozzle opening ratio estimated by the blockage state estimating unit becomes equal to or smaller than a predetermined threshold value.

7. A steam turbine system according to any one of claims 1 to 6; a well through which steam flows to the steam turbine system; a generator that generates electricity using the driving force of the steam turbine system.

8. 1. A method for operating a steam turbine system, comprising: The steam turbine system includes: a steam pipe through which steam separated from the geothermal fluid spouted from the well flows; a steam turbine into which the steam flowing through the steam pipe is guided, the steam turbine having a nozzle including a first nozzle portion and a second nozzle portion; a first steam pipe branching from the steam pipe and directing steam to the first nozzle portion; a second steam pipe branching off from the steam pipe and directing steam to the second nozzle portion; a flow rate control valve for controlling a flow rate of steam flowing through the second steam pipe, a flow rate detection step of detecting a flow rate of steam flowing through the steam pipe; a pressure detection step of detecting a pressure of the steam being guided to the first nozzle portion or the steam having been guided to the first nozzle portion; and a clogging state estimating step of estimating a clogging state of the nozzle based on the flow rate detected in the flow rate detecting step, the pressure detected in the pressure detecting step, and an opening degree of the flow rate control valve.

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