Geothermal power generation system

Abstract

To provide a geothermal power generation system that properly returns non-condensable gas together with reduced water into the ground in response to a variation in a flow rate of the non-condensable gas by using an existing device.SOLUTION: A geothermal power generation system 1 according to an embodiment comprises: a separator 11 which separates a geothermal fluid into steam and hot water; a returned water pipe 12 which guides the hot water to a reduction well 14; a steam turbine 20 into which the steam is introduced; a condenser 22 into which exhaust gas of the steam turbine 20 is introduced; a gas introduction pipe 37 which guides non-condensable gas separated from the steam in the condenser 22, to the returned water pipe 12; a gas compressor 38 which pressurizes the non-condensable gas in the gas introduction pipe 37; a pressure adjustment valve 33 which adjusts a pressure in the separator; a flow rate detection device 15 which detects information related to a flow rate of the geothermal fluid to be introduced into the separator 11; and a control device 40 which controls the pressure adjustment valve 33 and the gas compressor 38 on the basis of the flow rates of the non-condensable gas and the hot water calculated from detection information of the flow rate detection device 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a geothermal power generation system. [Background technology]

[0002] In a geothermal power plant, geothermal fluid extracted from a geothermal reservoir underground is introduced into a separator via a production well. The geothermal fluid, which is a gas-liquid two-phase flow, is separated into steam and hot water in the separator.

[0003] The separated steam is used to generate electricity. After power generation, the steam is introduced into a condenser where it is condensed to form water. Non-condensable gases (NCG) contained in the steam are separated from the water in the condenser. If non-condensable gases remain in the condenser, turbine output will decrease, so the non-condensable gases are released into the atmosphere via a gas extraction device.

[0004] On the other hand, the hot water separated in the separator and the condensed water produced in the condenser are returned to the ground as reduced water via a reduction well in order to prevent the depletion of underground resources.

[0005] The non-condensable gases contain large amounts of toxic H2S and CO2, a greenhouse gas. Releasing non-condensable gases into the atmosphere could become a problem as environmental pollution in the future. Therefore, a technology is being considered that would return the non-condensable gases underground along with the reduced water by injecting them into the reduced water.

[0006] When non-condensable gas is injected underground together with the injected water, a two-phase gas-liquid flow of injected water and non-condensable gas flows downward through the injection well. To properly inject this two-phase gas-liquid flow underground, it is necessary to consider the pressure, temperature, and flow rate of the injected water, the pressure and flow rate of the non-condensable gas, and the solubility of the non-condensable gas in the injected water.

[0007] The flow rate of non-condensable gas contained in geothermal fluid extracted from a geothermal reservoir is not always constant but fluctuates over time. For example, if the flow rate of non-condensable gas increases, the non-condensable gas may flow back up the reinjection well at the confluence where the non-condensable gas is injected into the reinjection water flowing down the reinjection well. This may cause the operation of the geothermal power plant to be stopped.

[0008] When the flow rate of non-condensable gases increases, it is necessary to increase the pressure of the reduced water to increase its solubility in order to suppress backflow of the non-condensable gases and return them underground together with the reduced water. Furthermore, if the required solubility cannot be achieved, hydrostatic pressure is utilized by creating a confluence deep underground. Another method involves increasing the pressure of the reduced water to turn the non-condensable gases into bubbles, reducing their volume and reducing buoyancy while returning them underground. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 2617533 [Patent Document 2] Patent No. 5578125 Summary of the Invention [Problem to be solved by the invention]

[0010] The above-mentioned conventional technique of injecting non-condensable gas into reduced water requires the addition of a pump to ensure the pressure required for reduction and a confluence deep underground to the configuration of a conventional geothermal power plant, which complicates the configuration of the geothermal power plant and increases the facility costs of the geothermal power plant.

[0011] The problem that the present invention aims to solve is to provide a geothermal power generation system that can appropriately return non-condensable gases together with reduced water into the ground in accordance with fluctuations in the flow rate of the non-condensable gases, while utilizing existing equipment of the geothermal power generation plant. [Means for solving the problem]

[0012] In one embodiment, a geothermal power generation system injects non-condensable gases separated from steam of geothermal fluid collected by a production well into the ground via a reinjection well together with hot water of the geothermal fluid. The geothermal power generation system includes a separator that separates the geothermal fluid collected by the production well into steam and hot water, a reinjection water pipe that guides the hot water separated by the separator to the reinjection well, a steam turbine to which the steam separated by the separator is introduced via a main steam pipe, a condenser to which exhaust gas from the steam turbine is introduced, a gas inlet pipe that guides the non-condensable gases separated from the steam in the condenser to the reinjection water pipe, and a gas compressor that pressurizes the non-condensable gases introduced to the reinjection water pipe via the gas inlet pipe.

[0013] The geothermal power generation system further includes a first regulating valve provided in a connecting pipe connected to the main steam pipe for adjusting the pressure within the separator, a flow rate detection device for detecting information related to the flow rate of geothermal fluid introduced into the separator, and a control device for controlling the first regulating valve and the gas compressor based on the flow rate of non-condensable gas and the flow rate of hot water introduced into the reduced water pipe calculated from the detection information of the flow rate detection device. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing a system configuration of a geothermal power generation system according to an embodiment; [Figure 2] 1 is a block diagram showing the configuration of a control device for a geothermal power generation system according to an embodiment; [Figure 3] 3 is a flowchart illustrating the operation of the geothermal power generation system according to the embodiment. [Figure 4] 4 is a flowchart for explaining the non-condensable gas increase response process in FIG. 3. [Figure 5] 4 is a control time chart for explaining the non-condensable gas increase response process in FIG. 3. [Figure 6]4 is a flowchart for explaining a non-condensable gas reduction response process in FIG. 3. [Figure 7] 4 is a control time chart for explaining the non-condensable gas reduction response process in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] 1 is a diagram showing the system configuration of a geothermal power generation system 1 according to an embodiment. The geothermal power generation system 1 injects non-condensable gas separated from steam of geothermal fluid collected by a production well 13 into the ground via an injection well 14 together with hot water of the geothermal fluid.

[0017] As shown in FIG. 1, the geothermal power generation system 1 includes a geothermal fluid pipe 10, a separator 11, and a reinjection water pipe 12. One end of the geothermal fluid pipe 10 is connected to a production well 13 that has been drilled deep underground to a geothermal reservoir, and the other end of the geothermal fluid pipe 10 is connected to the separator 11. One end of the reinjection water pipe 12 is connected to the separator 11, and the other end of the reinjection water pipe 12 is connected to a reinjection well 14 that has been drilled deep underground. The production well 13 and the reinjection well 14 are wells that have been drilled from the earth's surface to deep underground. The reinjection water pipe 12 is also equipped with a reinjection water pump 19 for sending hot water and non-condensable gases to the reinjection well 14.

[0018] The geothermal fluid pipe 10 is provided with a flow rate detection device 15 that detects information related to the flow rate of the geothermal fluid flowing through the geothermal fluid pipe 10. The flow rate detection device 15 may be a device that detects the total flow rate of the geothermal fluid, which is a two-phase gas-liquid flow. When the flow rate detection device 15 detects the total flow rate of the geothermal fluid, a fluid flow rate calculation unit 71 (described later) calculates the flow rates of the non-condensable gas and the hot water based on a preset flow rate ratio of the non-condensable gas to the hot water. The flow rate detection device 15 may also be a device that detects the total flow rate of the geothermal fluid and the flow rate ratio of the non-condensable gas to the hot water in the geothermal fluid. In this case, the fluid flow rate calculation unit 71 (described later) calculates the flow rates of the non-condensable gas and the hot water based on the detection information from the flow rate detection device 15.

[0019] The geothermal fluid piping 10 is provided with a pressure detection device 16 that detects information related to the pressure of the geothermal fluid in the production well 13. The pressure detection device 16 may be provided in the geothermal fluid piping 10 or in the production well 13. That is, the pressure detection device 16 only needs to be able to detect information related to the pressure of the geothermal fluid in the production well 13. The geothermal fluid piping 10 also has a pressure regulating valve 17 that adjusts the pressure of the geothermal fluid in the production well 13. The pressure regulating valve 17 also has the function of adjusting the flow rate of the geothermal fluid introduced into the separator 11. The pressure regulating valve 17 functions as a third regulating valve. The pressure detection device 16 functions as a geothermal fluid pressure detection device.

[0020] The separator 11 separates the geothermal fluid collected by the production well 13 and introduced through the geothermal fluid piping 10 into steam containing non-condensable gases and hot water. The hot water separated by the separator 11 is led to the reinjection well 14 via the reinjection water piping 12. The steam separated by the separator 11 is led to the steam turbine 20 via the main steam pipe 30, which will be described later.

[0021] The separator 11 is provided with a pressure detector 18 that detects information related to the pressure inside the separator 11. The pressure detector 18 functions as a separator pressure detector.

[0022] The geothermal power generation system 1 also includes a steam turbine 20, a generator 21, a condenser 22, a cooling tower 23, a gas extraction device 24, and a control device 40.

[0023] The steam outlet of the separator 11 and the steam inlet of the steam turbine 20 are connected by a main steam pipe 30. The main steam pipe 30 is provided with a steam control valve 31 that adjusts the flow rate of steam introduced into the steam turbine 20. In other words, the steam control valve 31 has the function of adjusting the rotation speed of the steam turbine 20. The steam control valve 31 is provided on the inlet side of the steam turbine 20 in the main steam pipe 30. The steam turbine 20 is provided with a rotation speed detection device 25 that detects information related to the rotation speed of the steam turbine 20. The steam control valve 31 functions as a second adjustment valve.

[0024] A connecting pipe 32 is connected to the main steam pipe 30 between the separator 11 and the steam control valve 31. One end of the connecting pipe 32 is connected to the main steam pipe 30, and the other end of the connecting pipe 32 is open to the atmosphere. The connecting pipe 32 is provided with a pressure regulating valve 33 that adjusts the pressure inside the separator 11.

[0025] That is, the connecting pipe 32 functions as a relief pipe that releases part of the steam in the main steam pipe 30 to the atmosphere in order to adjust the pressure in the separator 11. Therefore, the pressure regulating valve 33 also functions to adjust the pressure of the steam in the main steam pipe 30. The pressure regulating valve 33 also functions to adjust the flow rate of steam released to the atmosphere. Note that during normal operation, the pressure regulating valve 33 is opened to a predetermined degree. Therefore, part of the steam in the main steam pipe 30 is released to the atmosphere from the connecting pipe 32. The pressure regulating valve 33 also functions as a first regulating valve.

[0026] An exhaust pipe 34 connects the outlet of the steam turbine 20 and the steam inlet of the condenser 22. The condenser 22 includes a cooling pipe 22a through which cooling water from a cooling tower 23 circulates. The cooling water cools the steam and other components introduced into the condenser 22 via the cooling pipe 22a.

[0027] The condenser 22 is connected to the reduced water piping 12 via a condensate pipe 35. The condensate pipe 35 guides the condensate generated in the condenser 22 to the reduced water piping 12. The condensate pipe 35 is equipped with a condensate pump 36 that pumps the condensate. Note that the connection between the condensate pipe 35 and the reduced water piping 12 is located, for example, upstream (towards the separator 11) of the reduced water piping 12 relative to the connection between the gas introduction pipe 37 and the reduced water piping 12.

[0028] The condenser 22 is also connected to a gas extraction device 24 that extracts non-condensable gases from within the condenser 22. When the steam condenses to form condensed water, the non-condensable gases mixed in with the steam are separated from the steam and remain within the condenser 22. The gas extraction device 24 extracts the non-condensable gases remaining within the condenser 22 from within the condenser 22.

[0029] The gas extraction device 24 is connected to the reduced water piping 12 via a gas introduction pipe 37. The gas introduction pipe 37 introduces the non-condensable gas extracted by the gas extraction device 24 to the reduced water piping 12. The gas introduction pipe 37 is equipped with a gas compressor 38 that compresses the non-condensable gas. The connection between the gas extraction device 24 and the reduced water piping 12 is located, for example, on or above the ground surface.

[0030] The control device 40 controls the pressure regulating valve 33 and the gas compressor 38 based on, for example, the flow rate of the non-condensable gas and the flow rate of the hot water introduced into the reduced water pipe 12 calculated from the detection information of the flow rate detection device 15. The control device 40 then adjusts the pressure inside the separator 11 and the pressure of the non-condensable gas sprayed into the reduced water pipe 12.

[0031] 2 is a block diagram showing the configuration of a control device 40 of a geothermal power generation system 1 according to an embodiment. The control device 40 includes an input unit 50, a memory unit 60, a calculation unit 70, and an output unit 80. The control device 40 is capable of exchanging signals with detection devices such as a flow rate detection device 15, a pressure detection device 16, a pressure detection device 18, and a rotation speed detection device 25, devices such as a gas extraction device 24, a condensate pump 36, a gas compressor 38, and a reduced water pump 19, and adjustment valves such as a pressure adjustment valve 17, a steam control valve 31, and a pressure adjustment valve 33.

[0032] The input unit 50 receives detection signals from, for example, the flow rate detector 15, the pressure detectors 16 and 18, the rotation speed detector 25, and the like.

[0033] The storage unit 60 is realized by, for example, a hard disk drive, a nonvolatile memory device, etc. The storage unit 60 includes, for example, an input data storage unit 61, a calculation data storage unit 62, and a calculation result storage unit 63.

[0034] The input data storage unit 61 stores, for example, data input via the input unit 50.

[0035] The calculation data storage unit 62 stores calculation programs and calculation data used in the calculation process of the calculation unit 70. The calculation data storage unit 62 stores, for example, calculation formulas and calculation parameters for calculating the flow rates of noncondensable gas and hot water based on detection information from the flow detection device 15. The calculation data storage unit 62 also stores, for example, calculation formulas and calculation parameters for calculating the reducing water conditions for dissolving all of the noncondensable gas in the hot water and the reducing water conditions for converting the noncondensable gas into bubbles of a volume that does not backflow through the reinjection well 14. Here, bubbles of a volume that does not backflow through the reinjection well 14 are obtained, for example, by a gas-liquid two-phase flow in which the gas-liquid volume ratio is equal to or less than that of the slug flow. The gas-liquid volume ratio is the ratio, expressed as a percentage, of the gas phase volume to the sum of the gas and liquid phase volumes in a gas-liquid mixed-phase state in which noncondensable gas is mixed with the reducing water described below. That is, the gas-liquid volume ratio is expressed as (gas phase volume) / (gas phase volume+liquid phase volume)×100.

[0036] The calculation data storage unit 62 stores calculation formulas and calculation parameters for calculating the set pressure in the separator 11 for bringing the hot water into a state of reduced water conditions based on the reduced water conditions. The calculation data storage unit 62 stores, for example, data showing the relationship between the flow rate of the non-condensable gas introduced into the gas extraction device 24 and the operating capacity of the gas extraction device 24, and data showing the relationship between the flow rate or discharge pressure of the non-condensable gas and the operating capacity of the gas compressor 38.

[0037] The calculation data storage unit 62 stores, for example, calculation formulas and calculation parameters for calculating the rotation speed of the steam turbine 20 based on detection information from the rotation speed detection device 25. The calculation data storage unit 62 also stores, for example, calculation formulas and calculation parameters for calculating the pressure of the geothermal fluid in the production well 13 based on detection information from the pressure detection device 16.

[0038] The calculation result storage unit 63 stores, for example, the calculation results of the calculation unit 70.

[0039] The calculation unit 70 executes various calculation processes using, for example, input signals from the input unit 50, input data stored in the memory unit 60, calculation programs, calculation data, etc. The calculation unit 70 is a calculation block including a fluid flow rate calculation unit 71, a reduced water condition calculation unit 72, a separator pressure calculation unit 73, a rotation speed calculation unit 74, and a geothermal fluid pressure calculation unit 75.

[0040] The fluid flow rate calculation unit 71 reads out the calculation formulas and calculation parameters for calculating the flow rate of non-condensable gas and hot water from the calculation data memory unit 62, and calculates the flow rate of non-condensable gas and hot water introduced into the reduced water piping 12 based on the detection information of the flow detection device 15.

[0041] The fluid flow rate calculation unit 71 also determines whether the calculated flow rate of the non-condensable gas exceeds or falls below the reference flow rate threshold. Here, the reference flow rate threshold may be a predetermined flow rate value. Alternatively, the reference flow rate threshold may be a value having an allowable flow rate range centered on the predetermined flow rate value. The reference flow rate threshold is set, for example, based on the amount of non-condensable gas under optimal conditions for the geothermal fluid flow rate and pressure. The reference flow rate threshold is stored in the calculation data storage unit 62.

[0042] The fluid flow rate calculation unit 71 adjusts the operating capacity of the gas compressor 38 based on the calculated flow rate of the non-condensable gas and the reducing water conditions to make the pressure of the non-condensable gas the pressure under the reducing water conditions. The fluid flow rate calculation unit 71 adjusts the operating capacity of the gas extraction device 24 based on the calculated flow rate of the non-condensable gas. The fluid flow rate calculation unit 71 also adjusts the condensate pump 36 based on the reducing water conditions to make the pressure of the condensate the pressure under the reducing water conditions.

[0043] For example, if the amount of non-condensable gas in the condenser 22 increases, the pressure in the condenser 22 increases, resulting in a decrease in power generation output. That is, if the flow rate of the non-condensable gas introduced into the condenser 22 exceeds the reference flow rate threshold, the decrease in power generation output becomes significant. In this case, the fluid flow rate calculation unit 71 increases the operating capacity of the gas extraction device 24 to increase the amount of non-condensable gas extracted from the condenser 22. The fluid flow rate calculation unit 71 also increases the operating capacity of the gas compressor 38 to increase the pressure of the non-condensable gas to the same pressure as the pressure of the pressurized hot water.

[0044] On the other hand, when the amount of non-condensable gas in the condenser 22 decreases, the pressure in the condenser 22 tends to decrease. If the gas extraction device 24 and the gas compressor 38 are operated at normal operating capacity when the flow rate of the non-condensable gas introduced into the condenser 22 is below the reference flow rate threshold, the pressure in the condenser 22 will decrease more than necessary, and the gas extraction device 24 and the gas compressor 38 will enter an over-operating state. In this case, the fluid flow rate calculation unit 71 reduces the operating capacity of the gas extraction device 24 to reduce the amount of non-condensable gas extracted from the condenser 22. In addition, the fluid flow rate calculation unit 71 reduces the operating capacity of the gas compressor 38 to reduce the pressure of the non-condensable gas to the same pressure as the pressure of the decompressed hot water.

[0045] The reduced water condition calculation unit 72 reads out the calculation formulas and calculation parameters for calculating the reduced water conditions for dissolving all of the non-condensable gases in the hot water from the calculation data storage unit 62, and calculates the reduced water conditions for dissolving all of the non-condensable gases in the hot water based on the flow rates of the non-condensable gases and the hot water calculated by the fluid flow rate calculation unit 71. The reduced water conditions are the hot water pressure conditions for dissolving all of the non-condensable gases in the hot water introduced into the reduced water piping 12. Note that increasing the pressure of the hot water increases the amount of non-condensable gases that dissolve in the hot water.

[0046] The separator pressure calculation unit 73 reads out the calculation formula and calculation parameters for calculating the set pressure in the separator 11 to bring the hot water into a state of reduced water conditions from the calculation data storage unit 62, and calculates the set pressure in the separator 11 to bring the hot water into a state of reduced water conditions based on the reduced water conditions calculated by the reduced water condition calculation unit 72. The separator pressure calculation unit 73 also controls the pressure adjustment valve 33 based on the calculated set pressure in the separator 11 and the detection information from the pressure detection device 18 to bring the pressure in the separator 11 to the set pressure.

[0047] The rotation speed calculation unit 74 reads out an arithmetic expression and calculation parameters for calculating the rotation speed of the steam turbine 20 from the calculation data storage unit 62, and calculates the rotation speed of the steam turbine 20 from the detection information of the rotation speed detection device 25. Then, the rotation speed calculation unit 74 adjusts the steam control valve 31 based on the calculated rotation speed to maintain the rotation speed of the steam turbine 20 at a predetermined rotation speed. The predetermined rotation speed is set, for example, by the rated rotation speed of the steam turbine 20.

[0048] The geothermal fluid pressure calculation unit 75 reads out the calculation formula and calculation parameters for calculating the pressure of the geothermal fluid in the production well 13 from the calculation data storage unit 62, and calculates the pressure of the geothermal fluid from the detection information of the pressure detection device 16. Then, the geothermal fluid pressure calculation unit 75 controls the pressure regulating valve 17 based on the calculated geothermal fluid pressure to maintain the pressure of the geothermal fluid in the production well 13 at a predetermined pressure. Note that the predetermined pressure is set, for example, based on the optimal conditions for the flow rate and pressure of the geothermal fluid.

[0049] The output unit 80 outputs the control signal from the calculation unit 70 to, for example, the pressure regulating valve 17, the steam control valve 31, the pressure regulating valve 33, etc. The output unit 80 also outputs the control signal from the calculation unit 70 to, for example, the gas extraction device 24, the condensate pump 36, the gas compressor 38, etc.

[0050] (Overview of geothermal fluid flow) Here, an overview of the flow of geothermal fluid in the geothermal power generation system 1 will be described with reference to FIG.

[0051] Geothermal fluid collected by a production well 13 is introduced into a separator 11 via a geothermal fluid pipe 10. The geothermal fluid introduced into the separator 11 is separated into steam containing non-condensable gases and hot water.

[0052] The hot water is guided to the reinjection well 14 via the reinjection water piping 12. The steam is guided to the steam turbine 20 via the main steam pipe 30. The steam guided to the steam turbine 20 drives the steam turbine 20 to rotate. The steam discharged from the steam turbine 20 is introduced into the condenser 22 via an exhaust pipe 34.

[0053] The steam introduced into the condenser 22 is cooled and condensed to become condensed water. At this time, non-condensable gases mixed in the steam do not condense and are separated from the condensed water. The condensed water is pumped into the reduced water piping 12 via a condensate pipe 35 by a condensate pump 36. At this time, the condensed water is pressurized to the same pressure as the hot water flowing through the reduced water piping 12.

[0054] The separated non-condensable gas is extracted by the gas extractor 24 and introduced into the gas introduction pipe 37. The non-condensable gas introduced into the gas introduction pipe 37 is pressurized by the gas compressor 38 and ejected into the reduced water pipe 12. At this time, the non-condensable gas is pressurized to the same pressure as the pressure of the hot water flowing through the reduced water pipe 12.

[0055] The non-condensed gases ejected into the flow of reduced water consisting of hot water and condensate dissolve in the reduced water or become bubbles of a volume that will not flow back up the reduced water well 14, and then flow down the reduced water piping 12 together with the reduced water and are led to the reduced water well 14.

[0056] (Operation of Geothermal Power Generation System 1) Next, the operation of the geothermal power generation system 1 will be described.

[0057] Fig. 3 is a flowchart for explaining the operation of the geothermal power generation system 1 according to the embodiment. Fig. 4 is a flowchart for explaining the non-condensable gas increase response process in Fig. 3. Fig. 5 is a control time chart for explaining the non-condensable gas increase response process in Fig. 3. Fig. 6 is a flowchart for explaining the non-condensable gas decrease response process in Fig. 3. Fig. 7 is a control time chart for explaining the non-condensable gas decrease response process in Fig. 3.

[0058] First, the operation of the geothermal power generation system 1 will be described with reference to FIG.

[0059] The input unit 50 inputs the detection information of the flow rate detection device 15 (step S1). The input data storage unit 61 stores the input information such as the detection information inputted by the input unit 50.

[0060] The fluid flow rate calculation unit 71 calculates the flow rate of the non-condensable gas and the flow rate of the hot water introduced into the reduced water pipe 12 based on the detection information from the flow rate detection device 15 (step S2). The calculation result storage unit 63 stores the calculation results calculated by calculation units such as the fluid flow rate calculation unit 71.

[0061] The fluid flow rate calculation unit 71 determines whether the calculated flow rate of the non-condensable gas exceeds the reference flow rate threshold value (step S3).

[0062] In the determination of step S3, when it is determined that the flow rate of the non-condensable gas exceeds the reference flow rate threshold (Yes in step S3), the control device 40 executes a non-condensable gas increase response process, which will be described later.

[0063] If it is determined in step S3 that the flow rate of the non-condensable gas does not exceed the reference flow rate threshold (No in step S3), the fluid flow rate calculation unit 71 determines whether the calculated flow rate of the non-condensable gas is below the reference flow rate threshold (step S4).

[0064] In the determination of step S4, when it is determined that the flow rate of the non-condensable gas is lower than the reference flow rate threshold (Yes in step S4), the control device 40 executes a non-condensable gas decrease response process. The non-condensable gas decrease response process will be described later.

[0065] When it is determined in step S4 that the flow rate of the non-condensable gas is not below the reference flow rate threshold (No in step S4), the control device 40 ends the series of processes.

[0066] Note that even when it is determined in step S4 that the flow rate of the non-condensable gas is not below the reference flow rate threshold (No in step S4), the process from step S1 may be repeatedly executed.

[0067] (Treatment for increased non-condensable gases) Next, the non-condensable gas increase handling process will be described with reference to FIGS.

[0068] The non-condensable gas increase response process is executed when it is determined in step S3 shown in FIG. 3 that the flow rate of the non-condensable gas exceeds the reference flow rate threshold.

[0069] Based on the flow rate of the non-condensable gas and the flow rate of the hot water calculated by the fluid flow rate calculation unit 71, the reduced water condition calculation unit 72 calculates, for example, the reduced water conditions for dissolving the entire amount of non-condensable gas into the hot water, or the reduced water conditions for turning the non-condensable gas into bubbles of a volume that will not flow back up the reduced well 14 (step S10).

[0070] In the process of dealing with an increase in non-condensable gases, the amount of non-condensable gases dissolved in the reduced water, which is composed of hot water and condensate, increases, so it is necessary to increase the solubility of the non-condensable gases in the reduced water. Therefore, in order to increase the solubility, the calculated reduced water conditions result in an increase in the pressure of the reduced water. Furthermore, in the process of dealing with an increase in non-condensable gases, the non-condensable gases are converted into bubbles of a volume that will not cause them to flow back up the reduced well 14, and are then returned to the ground together with the reduced water. Therefore, in order to convert the non-condensable gases into bubbles of a volume that will not cause them to flow back up the reduced water, the calculated reduced water conditions result in an increase in the pressure of the reduced water.

[0071] The separator pressure calculation unit 73 calculates the set pressure in the separator 11 for bringing the hot water into a state of reduced water conditions based on the reduced water conditions calculated by the reduced water condition calculation unit 72 (step S11).

[0072] The fluid flow rate calculation unit 71 outputs a signal to the output unit 80 to increase the operating capacity of the gas extraction device 24 based on the calculated flow rate of the non-condensable gas (step S12). The output unit 80 outputs the signal to the gas extraction device 24 (step S12). Here, the operating capacity of the gas extraction device 24 is increased to a capacity capable of extracting an amount of non-condensable gas that exceeds the reference flow rate threshold introduced into the condenser 22. As shown in FIG. 5, at time T1, the operating capacity of the gas extraction device 24 increases.

[0073] Based on the calculated flow rate of the non-condensable gas and the reducing water conditions, the fluid flow rate calculation unit 71 outputs a signal to the output unit 80 to increase the operating capacity of the gas compressor 38 (step S13). The output unit 80 outputs the signal to the gas compressor 38 (step S13). Here, the operating capacity of the gas compressor 38 is increased to the capacity capable of pressurizing the non-condensable gas to the pressure of hot water, i.e., the reducing water conditions. As shown in FIG. 5, at time T1, the operating capacity of the gas compressor 38 increases.

[0074] Fluid flow rate calculation unit 71 outputs a signal to output unit 80 to increase the operating capacity of condensate pump 36 based on the reducing water conditions (step S14). Output unit 80 outputs the signal to condensate pump 36 (step S14). Here, the operating capacity of condensate pump 36 is increased to the capacity that can increase the pressure of condensate to the hot water pressure, i.e., the reducing water conditions. As shown in FIG. 5, at time T1, the operating capacity of condensate pump 36 increases.

[0075] In this way, increasing the operating capacity of the gas extraction device 24 suppresses an increase in the amount of non-condensable gas in the condenser 22. This ensures that the pressure in the condenser 22 is appropriate, and the specified power generation output is obtained. Furthermore, by increasing the operating capacity of the gas compressor 38, even if the flow rate of non-condensable gas in the gas introduction pipe 37 increases, non-condensable gas that has been pressurized to the reducing water condition is ejected into the reducing water pipe 12. Furthermore, by increasing the operating capacity of the condensate pump 36, condensate that has been pressurized to the reducing water condition is introduced into the reducing water pipe 12.

[0076] The separator pressure calculation unit 73 adjusts the pressure regulating valve 33 based on the calculated set pressure in the separator 11 and the detection information from the pressure detection device 18, to set the pressure in the separator 11 to the set pressure (step S15). At this time, the separator pressure calculation unit 73 outputs a signal for adjusting the pressure regulating valve 33 to the output unit 80. The output unit 80 then outputs that signal to the pressure regulating valve 33. As shown in FIG. 5, the pressure regulating valve 33 is throttled from time T1, and the throttling operation of the pressure regulating valve 33 is completed at time T2. At time T2, the pressure in the separator 11 reaches the set pressure. Note that throttling the pressure regulating valve 33 causes the pressure in the separator 11 to increase.

[0077] The rotation speed calculation unit 74 calculates the rotation speed of the steam turbine 20 from the detection information of the rotation speed detection device 25, and adjusts the steam control valve 31 based on the calculated rotation speed (step S16). Specifically, the rotation speed calculation unit 74 adjusts the steam control valve 31 so that the rotation speed of the steam turbine 20 is maintained at a predetermined rotation speed such as a rated rotation speed. At this time, the rotation speed calculation unit 74 outputs a signal for adjusting the steam control valve 31 to the output unit 80. Then, the output unit 80 outputs the signal to the steam control valve 31.

[0078] Here, when the pressure inside the separator 11 increases, the pressure of the steam inside the main steam pipe 30 also increases. As a result, the rotation speed of the steam turbine 20 increases, for example, above the rated rotation speed. Therefore, the rotation speed calculation unit 74 executes control to throttle the steam control valve 31 so that the rotation speed of the steam turbine 20 is maintained at a predetermined rotation speed such as the rated rotation speed.

[0079] 5, the steam control valve 31 is throttled from time T1, and the throttling operation of the steam control valve 31 is completed at time T2. At time T2, the rotation speed of the steam turbine 20 becomes the same as the rotation speed before time T1.

[0080] The geothermal fluid pressure calculation unit 75 calculates the pressure of the geothermal fluid from the detection information of the pressure detection device 16, and adjusts the pressure regulating valve 17 based on the calculated geothermal fluid pressure (step S17). Specifically, the geothermal fluid pressure calculation unit 75 adjusts the pressure regulating valve 17 so that the pressure of the geothermal fluid in the production well 13 is maintained at a predetermined pressure. At this time, the geothermal fluid pressure calculation unit 75 outputs a signal for adjusting the pressure regulating valve 17 to the output unit 80. The output unit 80 then outputs the signal to the pressure regulating valve 17.

[0081] Here, when the pressure in the separator 11 increases, if the opening of the pressure regulating valve 17 is kept constant, the pressure in the geothermal fluid piping 10, in other words, the pressure in the production well 13, increases. This reduces the flow rate of geothermal fluid introduced into the separator 11 from the production well 13 via the geothermal fluid piping 10. Therefore, by adjusting the pressure regulating valve 17 to maintain the pressure in the production well 13 at a predetermined pressure, an appropriate flow rate of geothermal fluid introduced into the separator 11, i.e., an appropriate flow rate of hot water, is maintained. As a result, even if the amount of non-condensable gas increases, the non-condensable gas dissolves in the hot water (reduced water) and is introduced to the reinjection well 14. Furthermore, even if the amount of non-condensable gas increases, the non-condensable gas becomes bubbles of a volume that does not flow back up the reinjection well 14, and is introduced to the reinjection well 14.

[0082] 5, the pressure regulating valve 17 is opened from time T1, and the opening operation of the pressure regulating valve 17 is completed at time T2. At time T2, the pressure of the geothermal fluid in the production well 13 becomes the same as the pressure of the geothermal fluid before time T1.

[0083] After adjusting the pressure of the geothermal fluid in step S17, the process from step S10 onwards may be repeated.

[0084] Here, the processing of steps S12 to S17 shown in Fig. 4 is executed simultaneously as shown in Fig. 5 based on the results calculated in steps S10 to S11. That is, in this embodiment, adjustment of the pressure inside the separator 11, adjustment of the rotation speed of the steam turbine 20, adjustment of the pressure of the geothermal fluid inside the production well 13, and adjustment of the operating capacities of the gas extraction device 24, the gas compressor 38, and the condensate pump 36 can be executed simultaneously.

[0085] As described above, in the process of dealing with an increase in non-condensable gases, even if the pressure in the separator 11 is increased to raise the pressure of the hot water in order to increase the solubility of the non-condensable gases in the reduced water, the increased non-condensable gases can be guided to the reduced well 14 together with the reduced water while maintaining an appropriate geothermal fluid flow rate and appropriate power generation output.

[0086] (Non-condensable gas reduction treatment) Next, the non-condensable gas reduction response process will be described with reference to FIGS.

[0087] The non-condensable gas decrease response process is executed when it is determined in step S4 shown in FIG. 3 that the flow rate of the non-condensable gas is lower than the reference flow rate threshold.

[0088] Based on the flow rate of the non-condensable gas and the flow rate of the hot water calculated by the fluid flow rate calculation unit 71, the reduced water condition calculation unit 72 calculates, for example, the reduced water conditions for dissolving the entire amount of non-condensable gas into the hot water, or the reduced water conditions for converting the non-condensable gas into bubbles of a volume that will not flow back up the reduced well 14 (step S20).

[0089] In the process of reducing non-condensable gases, the amount of non-condensable gases dissolved in the reduced water consisting of hot water and condensate is reduced, so the solubility of non-condensable gases in the reduced water can be reduced. Therefore, in order to reduce the solubility, the calculated reduced water conditions result in a reduction in the pressure of the reduced water.

[0090] The separator pressure calculation unit 73 calculates the set pressure in the separator 11 for bringing the hot water into a state of reduced water conditions based on the reduced water conditions calculated by the reduced water condition calculation unit 72 (step S21).

[0091] The fluid flow rate calculation unit 71 outputs a signal to the output unit 80 to suppress the operating capacity of the gas extraction device 24 based on the calculated flow rate of the non-condensable gas (step S22). The output unit 80 outputs the signal to the gas extraction device 24 (step S22). Here, the operating capacity of the gas extraction device 24 is suppressed to a level that does not reduce the pressure in the condenser 22 more than necessary. As shown in FIG. 7, at time T3, the operating capacity of the gas extraction device 24 is suppressed.

[0092] Based on the calculated flow rate of the non-condensable gas and the reducing water conditions, the fluid flow rate calculation unit 71 outputs a signal to the output unit 80 to suppress the operating capacity of the gas compressor 38 (step S23). The output unit 80 outputs the signal to the gas compressor 38 (step S23). Here, the operating capacity of the gas compressor 38 is suppressed to the capacity to pressurize the non-condensable gas to the pressure of the hot water, i.e., the reducing water conditions. As shown in FIG. 7, at time T3, the operating capacity of the gas compressor 38 is suppressed.

[0093] Fluid flow rate calculation unit 71 outputs a signal to output unit 80 to suppress the operating capacity of condensate pump 36 based on the reducing water condition (step S24). Output unit 80 outputs the signal to condensate pump 36 (step S24). Here, the operating capacity of condensate pump 36 is suppressed to the capacity that can increase the pressure of the condensate to the pressure of hot water, i.e., the reducing water condition. As shown in FIG. 7, at time T3, the operating capacity of condensate pump 36 is suppressed.

[0094] In this way, by suppressing the operating capacity of the gas extraction device 24, the pressure inside the condenser 22 is prevented from dropping more than necessary. This allows the pressure inside the condenser 22 to be maintained at an appropriate pressure. Furthermore, by suppressing the operating capacity of the gas compressor 38, non-condensable gas at a pressure corresponding to the reducing water conditions is ejected into the reducing water piping 12. Furthermore, by suppressing the operating capacity of the condensate pump 36, condensate at a pressure corresponding to the reducing water conditions is introduced into the reducing water piping 12.

[0095] The separator pressure calculation unit 73 adjusts the pressure regulating valve 33 based on the calculated set pressure in the separator 11 and the detection information from the pressure detection device 18, to set the pressure in the separator 11 to the set pressure (step S25). At this time, the separator pressure calculation unit 73 outputs a signal for adjusting the pressure regulating valve 33 to the output unit 80. The output unit 80 then outputs the signal to the pressure regulating valve 33. As shown in FIG. 7, the pressure regulating valve 33 opens from time T3, and the opening operation of the pressure regulating valve 33 is completed at time T4. At time T4, the pressure in the separator 11 reaches the set pressure. Note that opening the pressure regulating valve 33 reduces the pressure in the separator 11.

[0096] The rotation speed calculation unit 74 calculates the rotation speed of the steam turbine 20 from the detection information of the rotation speed detection device 25, and adjusts the steam control valve 31 based on the calculated rotation speed (step S26). Specifically, the rotation speed calculation unit 74 adjusts the steam control valve 31 so that the rotation speed of the steam turbine 20 is maintained at a predetermined rotation speed such as a rated rotation speed. At this time, the rotation speed calculation unit 74 outputs a signal for adjusting the steam control valve 31 to the output unit 80. Then, the output unit 80 outputs the signal to the steam control valve 31.

[0097] Here, when the pressure inside the separator 11 drops, the pressure of the steam inside the main steam pipe 30 also drops. As a result, the rotation speed of the steam turbine 20 drops below, for example, the rated rotation speed. Therefore, the rotation speed calculation unit 74 executes control to open the steam control valve 31 so that the rotation speed of the steam turbine 20 is maintained at a predetermined rotation speed such as the rated rotation speed.

[0098] 7, the steam control valve 31 opens from time T3, and the opening operation of the steam control valve 31 is completed at time T4. At time T4, the rotation speed of the steam turbine 20 becomes the same as the rotation speed before time T3.

[0099] The geothermal fluid pressure calculation unit 75 calculates the pressure of the geothermal fluid from the detection information of the pressure detection device 16, and adjusts the pressure regulating valve 17 based on the calculated geothermal fluid pressure (step S27). Specifically, the geothermal fluid pressure calculation unit 75 adjusts the pressure regulating valve 17 so that the pressure of the geothermal fluid in the production well 13 is maintained at a predetermined pressure. At this time, the geothermal fluid pressure calculation unit 75 outputs a signal for adjusting the pressure regulating valve 17 to the output unit 80. The output unit 80 then outputs the signal to the pressure regulating valve 17.

[0100] Here, when the pressure in the separator 11 decreases, if the opening of the pressure regulating valve 17 is kept constant, the pressure in the geothermal fluid piping 10, in other words, the pressure in the production well 13, decreases. This increases the flow rate of geothermal fluid introduced into the separator 11 from the production well 13 via the geothermal fluid piping 10. Therefore, by adjusting the pressure regulating valve 17 to maintain the pressure in the production well 13 at a predetermined pressure, an appropriate flow rate of geothermal fluid introduced into the separator 11, i.e., an appropriate flow rate of hot water, is maintained. As a result, even when the amount of non-condensable gas decreases, the non-condensable gas dissolves in the hot water (reduced water) and is introduced to the reinjection well 14. Furthermore, even when the amount of non-condensable gas decreases, the non-condensable gas becomes bubbles of a volume that does not flow back up the reinjection well 14, and is introduced to the reinjection well 14.

[0101] 7, the pressure regulating valve 17 is throttled from time T3, and the throttling operation of the pressure regulating valve 17 is completed at time T4. At time T4, the pressure of the geothermal fluid in the production well 13 becomes the same as the pressure of the geothermal fluid before time T3.

[0102] After adjusting the pressure of the geothermal fluid in step S27, the process from step S20 onwards may be repeated.

[0103] Here, the processing of steps S22 to S27 shown in Fig. 6 is executed simultaneously as shown in Fig. 7 based on the results calculated in steps S20 to S21. That is, in this embodiment, adjustment of the pressure inside the separator 11, adjustment of the rotation speed of the steam turbine 20, adjustment of the pressure of the geothermal fluid inside the production well 13, and adjustment of the operating capacities of the gas extraction device 24, the gas compressor 38, and the condensate pump 36 can be executed simultaneously.

[0104] As described above, in the process of dealing with the reduction of non-condensable gases, even if the pressure in the separator 11 is lowered to reduce the pressure of the hot water in order to reduce the solubility of the non-condensable gases in the reduced water, the reduced non-condensable gases can be guided to the reduced well 14 together with the reduced water while maintaining an appropriate geothermal fluid flow rate and appropriate power generation output.

[0105] As described above, according to the geothermal power generation system 1 of this embodiment, the pressure of the hot water introduced into the reduced water pipe 12 can be adjusted by adjusting the pressure inside the separator 11 with the pressure regulating valve 33. That is, by adjusting the pressure inside the separator 11, for example, the pressure of the hot water can be adjusted to a pressure that provides a solubility that can dissolve all of the non-condensable gases. Alternatively, the pressure of the hot water can be adjusted to a pressure that provides a volume of bubbles that will not cause the non-condensable gases to flow back up the reduced water well 14.

[0106] In this way, the geothermal power generation system 1 can adjust the pressure of the hot water by using the pressure regulating valve 33 of the connecting pipe 32 (relief pipe) that is provided in conventional geothermal power generation systems. This allows the geothermal power generation system 1 to adjust the pressure of the hot water without having to provide a pump or the like to ensure the pressure required for reduction. Furthermore, the geothermal power generation system 1 does not need to provide a confluence point deep underground where the reduced water and non-condensable gases meet in order to utilize hydrostatic pressure.

[0107] Therefore, in the geothermal power generation system 1, the pressure of the hot water (reduced water) can be adjusted to guide the entire amount of non-condensable gas to the reinjection well 14 without complicating the geothermal power generation plant configuration or increasing equipment costs.

[0108] Furthermore, even if the flow rate of the geothermal fluid fluctuates, the geothermal power generation system 1 can calculate, for example, the reduced water conditions for hot water that can dissolve all of the non-condensable gases, or the reduced water conditions for turning the non-condensable gases into bubbles of a volume that will not cause them to flow back up the reduced well 14. Then, by adjusting the pressure inside the separator 11 with the pressure regulating valve 33, the hot water can be brought into the reduced water conditions.

[0109] Furthermore, in geothermal power generation system 1, the operating capacity of gas compressor 38 and condensate pump 36 can be controlled based on the calculated flow rate of non-condensable gas and the reduced water conditions, so that even when the pressure of the hot water is adjusted, non-condensable gas and condensate can be reliably introduced into reduced water piping 12. In addition, the operating capacity of gas extraction device 24 can be controlled based on the calculated flow rate of non-condensable gas, so that an appropriate amount of non-condensable gas can be extracted from condenser 22 even when the flow rate of non-condensable gas fluctuates.

[0110] Furthermore, in the geothermal power generation system 1, the pressure in the production well 13 is maintained at a predetermined pressure by adjusting the pressure regulating valve 17 based on the detection information from the pressure detection device 16. Furthermore, in the geothermal power generation system 1, the rotation speed of the steam turbine 20 is maintained at a predetermined rotation speed by adjusting the steam control valve 31 based on the detection information from the rotation speed detection device 25.

[0111] According to the embodiment described above, it is possible to appropriately return non-condensable gases together with reduced water into the ground in accordance with fluctuations in the flow rate of non-condensable gases, while utilizing existing equipment in a geothermal power plant.

[0112] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0113] 1...Geothermal power generation system, 10...Geothermal fluid piping, 11...Separator, 12...Return water piping, 13...Production well, 14...Return well, 15...Flow rate detection device, 16, 18...Pressure detection device, 17, 33...Pressure regulating valve, 19...Return water pump, 20...Steam turbine, 21...Generator, 22...Condenser, 22a...Cooling pipe, 23...Cooling tower, 24...Gas extraction device, 25...Rotation speed detection device, 30...Main steam pipe, 31...Steam control valve, 32 ...Connecting piping, 34...Exhaust pipe, 35...Condensate pipe, 36...Condensate pump, 37...Gas introduction pipe, 38...Gas compressor, 40...Control device, 50...Input section, 60...Memory section, 61...Input data memory section, 62...Calculation data memory section, 63...Calculation result memory section, 70...Calculation section, 71...Fluid flow rate calculation section, 72...Reduced water condition calculation section, 73...Separator pressure calculation section, 74...Rotation speed calculation section, 75...Geothermal fluid pressure calculation section, 80...Output section.

Claims

1. A geothermal power generation system in which non-condensable gas separated from steam of geothermal fluid collected by a production well is injected underground via an injection well together with hot water of the geothermal fluid, a separator that separates the geothermal fluid collected by the production well into steam and hot water; a reduced water pipe that guides the hot water separated by the separator to the reduced water well; a steam turbine into which the steam separated by the separator is introduced via a main steam pipe; a condenser into which exhaust from the steam turbine is introduced; a gas introduction pipe that introduces non-condensable gas separated from the steam in the condenser into the reduced water pipe; a gas compressor that pressurizes the non-condensable gas introduced into the reduced water pipe through the gas introduction pipe; a first adjusting valve provided in a connecting pipe connected to the main steam pipe, the first adjusting valve adjusting the pressure inside the separator; a flow rate detection device that detects information related to the flow rate of the geothermal fluid introduced into the separator; a control device that controls the first regulating valve and the gas compressor based on the flow rate of the non-condensable gas and the flow rate of the hot water introduced into the reduced water pipe calculated from detection information from the flow rate detection device; A geothermal power generation system comprising:

2. The geothermal power generation system includes: The fuel cell system further includes a separator pressure detection device that detects information related to the pressure inside the separator, The control device a fluid flow rate calculation unit that calculates the flow rate of the non-condensable gas and the flow rate of the hot water introduced into the reduced water pipe based on the detection information of the flow rate detection device; a reduced water condition calculation unit that calculates reduced water conditions for dissolving the entire amount of non-condensable gas in hot water, or reduced water conditions for turning the non-condensable gas into bubbles of a volume that will not flow back through the reduced well, based on the flow rate of the non-condensable gas and the flow rate of the hot water calculated by the fluid flow rate calculation unit; a separator pressure calculation unit that calculates a set pressure in the separator for bringing hot water into a state of the reduced water condition based on the reduced water condition; Equipped with 2. The geothermal power generation system according to claim 1, wherein the separator pressure calculation unit adjusts the first regulating valve based on the set pressure and detection information from the separator pressure detection device to adjust the pressure inside the separator to the set pressure.

3. 3. The geothermal power generation system according to claim 2, wherein the fluid flow rate calculation unit adjusts the operating capacity of the gas compressor based on the calculated flow rate of the non-condensable gas and the reduced water conditions.

4. The geothermal power generation system includes: a gas extraction device that extracts non-condensable gas separated from the steam in the condenser and introduces the non-condensable gas into the gas introduction pipe; 4. The geothermal power generation system according to claim 3, wherein the fluid flow rate calculation unit adjusts the operating capacity of the gas extraction device based on the calculated flow rate of the non-condensable gas.

5. 3. The geothermal power generation system according to claim 2, wherein the reduced water condition is a pressure condition of the hot water introduced into the reduced water pipe.

6. The geothermal power generation system includes: a rotation speed detection device that detects information related to the rotation speed of the steam turbine; a second adjusting valve for adjusting the rotation speed of the steam turbine; Furthermore, The control device 2. The geothermal power generation system according to claim 1, further comprising a rotation speed calculation unit that adjusts the second regulating valve based on detection information from the rotation speed detection device to maintain the rotation speed of the steam turbine at a predetermined rotation speed.

7. The geothermal power generation system includes: a geothermal fluid pressure detection device that detects information related to the pressure of the geothermal fluid in the production well; a third regulating valve for regulating the pressure of the geothermal fluid in the production well; Furthermore, The control device 2. The geothermal power generation system of claim 1, further comprising a geothermal fluid pressure calculation unit that adjusts the third regulating valve based on detection information from the geothermal fluid pressure detection device to maintain the pressure of the geothermal fluid in the production well at a predetermined pressure.

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