Method and system for evaluating scale prevention and suppression effects

Abstract

The present invention enables the effects of scale prevention and suppression in a geothermal power plant to be evaluated more rapidly. Provided is a method for evaluating the effects of preventing and suppressing scale adhesion in a geothermal power plant (100), the effects of preventing and suppressing scale adhesion being evaluated using a scale sensor device (120) that detects the degree of scale adhesion to the surface of a sensing unit by immersing the sensing unit, which is formed by exposing the core of an optical fiber in one or more locations, in a geothermal fluid produced from a production well (101) of the geothermal power plant. The scale sensor detects the degree of adhesion of scale at the production well (101) and an injection well (102) of the geothermal power plant and at any location therebetween, and detects the degree of adhesion of scale at any location after, for example, adding a chemical agent for preventing and suppressing the formation of scale into the geothermal fluid, or after changing the production method.

Description

Method and System for Evaluating Scale Prevention and Inhibition Effects

[0001] The present invention relates to a method and a system for evaluating scale prevention and inhibition effects.

[0002] Inorganic salts and the like dissolved in geothermal fluid become supersaturated with changes in temperature, pH, pressure and the like, precipitate as scale, and adhere to above-ground facilities, pipes, wellbores and the like of a geothermal power plant. Adhesion of such scale causes a reduction in the efficiency of heat exchangers and the flow rate of hot water in above-ground pipes in geothermal power generation, and hinders the operation and power generation efficiency of geothermal power generation. Therefore, as countermeasures against scale in geothermal power plants, many related techniques for scale prevention and inhibition have been developed, such as mechanical scale removal, scale inhibition by chemical addition, high-temperature reduction of hot water, and changes to production methods.

[0003] As a related technique for scale prevention and inhibition in geothermal power plants, for example, Patent Document 1 discloses a silica scale modifier that facilitates removal of silica scale. Meanwhile, Patent Document 2 discloses a scale inhibition device that can suppress the generation of silica-based scale and calcium-based scale at a low cost for influent water containing a silica component and a calcium component. Further, Patent Document 3 discloses a scale inhibition device that can spray a scale inhibitor in accordance with the scale component contained in steam.

[0004] Japanese Patent Application Laid-Open No. 2023-008593; US 2015 / 0121867 A1; Japanese Patent No. 7077169

[0005] When implementing scale prevention and inhibition countermeasures in a geothermal power plant, it is a challenge to evaluate the effect of scale prevention and inhibition more quickly.

[0006] The present invention has been made in view of the above problem, and an object thereof is to enable more rapid evaluation of the effect of scale prevention and inhibition in a geothermal power plant.

[0007] One aspect of the present invention is a method for evaluating the effectiveness of preventing and suppressing scale buildup in a geothermal power plant, wherein a sensing section formed by exposing the core of an optical fiber at at least one or more locations is immersed in geothermal fluid produced from a production well of the geothermal power plant, and the effectiveness of preventing and suppressing scale buildup is evaluated using a scale sensor that detects the degree of scale buildup on the surface of the sensing section.

[0008] According to one aspect of the present invention, the effectiveness of preventing and suppressing scale formation in geothermal power plants can be evaluated more quickly by using a scale sensor.

[0009] Another aspect of the present invention relates to an evaluation system for evaluating the effectiveness of preventing and suppressing scale buildup in a geothermal power plant, comprising: a production well for producing geothermal fluid to be retained in a geothermal reservoir in a geothermal area; and a scale sensor for detecting the degree of scale buildup on the surface of the sensing part, by immersing a sensing part, formed by exposing the core of an optical fiber at at least one or more locations, in the geothermal fluid produced from the production well, wherein the scale sensor evaluates the effectiveness of preventing and suppressing scale buildup based on the detection result of the degree of scale buildup on the surface of the sensing part.

[0010] According to another aspect of the present invention, the effectiveness of preventing and suppressing scale formation in geothermal power plants can be evaluated more quickly by using a scale sensor.

[0011] This is a block diagram illustrating the schematic configuration of an evaluation system to which the scale prevention and suppression effect evaluation method according to the first embodiment of the present invention is applied. This is a schematic diagram showing a scale sensor device used in the scale prevention and suppression effect evaluation method according to the first embodiment of the present invention. (A) is an enlarged schematic diagram of the sensing part of the scale sensor device used in the scale prevention and suppression effect evaluation method according to the first embodiment of the present invention, (B) is a schematic diagram showing the detection principle by the sensing part, and (C) is a schematic diagram showing the detection principle by the sensing part in a state where scale is attached. This is a block diagram illustrating the schematic configuration of an evaluation system to which the scale prevention and suppression effect evaluation method according to the second embodiment of the present invention is applied. This is a block diagram illustrating the schematic configuration of an evaluation system to which the scale prevention and suppression effect evaluation method according to the third embodiment of the present invention is applied. This is a schematic diagram showing a high-temperature, high-pressure scale sensor device used in the scale prevention and suppression effect evaluation method according to the third embodiment of the present invention.

[0012] Preferred embodiments of the present invention will be described in detail below. It should be noted that the embodiments described below are not intended to unduly limit the scope of the present invention as described in the claims, and not all of the configurations described in these embodiments are necessarily essential as solutions to the present invention.

[0013] In the following description, the terms "up," "down," "left," and "right" are used for explanatory purposes only and do not limit the method or manner of use. The terms "first" and "n" (where n is an integer) following "first" as described herein and in the claims are used as identifying terms to distinguish different elements and do not indicate any particular order or superiority.

[0014] [First Embodiment] The schematic configuration of an evaluation system to which the scale prevention and suppression effect evaluation method according to the first embodiment of the present invention is applied will be described with reference to the drawings. Figure 1 is a block diagram showing the schematic configuration of an evaluation system to which the scale prevention and suppression effect evaluation method according to this embodiment is applied.

[0015] The evaluation system 1 to which the scale prevention and suppression effect evaluation method of this embodiment is applied evaluates the scale prevention and suppression effect at a geothermal power plant 100 that generates electricity using thermal energy contained in geothermal reservoirs in geothermal areas. The evaluation system 1 comprises a geothermal power plant 100, a scale sensor device 120, and a control unit 130.

[0016] As shown in Figure 1, the geothermal power plant 100 comprises a production well 101, an injection well 102, and a geothermal power generation facility 110. The production well 101 is a well that produces geothermal fluids such as high-temperature, high-pressure hot water and steam that are retained in the geothermal reservoir of the geothermal area. The injection well 102 is a well that returns the injected water, which contains condensed steam and other water, to the ground after the geothermal fluid produced from the production well 101 has been used for power generation in the geothermal power generation facility 110. In other words, the injection well 102 is a well that returns the injected water, which is discharged after heat exchange with the geothermal fluid in the geothermal power generation facility 110, back into the ground.

[0017] The geothermal power generation equipment 110 is a facility that takes in geothermal water containing high-temperature steam at approximately 200 to 350°C as a geothermal fluid and has the function of obtaining electricity from this geothermal water. The geothermal power generation equipment 110 mainly comprises a first flasher 111, a second flasher 112, a turbine 113, a generator 114, a condenser 115, a container 116, and a pound 117, as shown in Figure 1.

[0018] The geothermal power generation equipment 110 takes in geothermal fluid heated by geothermal energy, and feeds it into a first flusher 111, which is a steam-water separator that functions as a separator, to separate it into steam and hot water. The separated steam is sent to the turbine 113. Alternatively, the steam is separated into steam and water by a second flusher 112, which also functions as a separator, to obtain secondary steam, which is similarly sent to the turbine 113, and the rotation of the turbine 113 generates electricity with the generator 114. The steam consumed by the turbine 113 is condensed in a condenser 115, and the condensed geothermal water is used as cooling wastewater, cooled and used as cooling water for the condenser 115, or used for return to the geothermal zone by an injection well 102.

[0019] In this embodiment, the hot water obtained by separating the gas and water again by the second flusher 112 is transferred to a container 116 which serves as a storage tank, and then to a pond 117 which serves as a storage pool. In the pond 117, the precipitated and settled scale components such as silica and metal sulfides are recovered, and then the liquid layer is sent to the reinjection well 102 by a high-pressure circulation pump (not shown).

[0020] Furthermore, the geothermal power generation equipment 110 is not limited to the configuration described above, and other components may be replaced with other equipment or additional equipment may be added. In addition, although the geothermal power generation equipment 110 in this embodiment is shown as a double-flash system as shown in Figure 1, it is also applicable to a single-flash system in which the steam-water separated hot water in the first flasher 111 is returned directly to the geothermal area from the reinjection well 102.

[0021] Furthermore, as mentioned above, the evaluation system 1 applies a flash-type geothermal power generation facility as the geothermal power generation facility 110, which generates electricity using high-temperature, high-pressure steam contained in the geothermal fluid produced from the production well 101. The evaluation system 1 of this embodiment is not limited to a flash-type geothermal power generation facility as the geothermal power generation facility 110, but can also be applied to a binary-type geothermal power generation facility that generates electricity using steam obtained by boiling a medium with a lower boiling point than water using the geothermal fluid produced from the production well 101.

[0022] The scale sensor device 120 functions as a scale sensor to evaluate the state of scale formation on the surface of equipment such as pipes, which are pipelines through which hot water, such as geothermal water for geothermal power generation or hot spring water, comes into contact. In this embodiment, the scale sensor device 120 is applied to the hot water that has been separated into gas and water by the second flusher 112 and transferred to the container 116 to detect the degree of scale adhesion.

[0023] At the geothermal power plant 100, chemicals such as sulfuric acid, inhibitors, and precipitation accelerators are added to the geothermal fluid produced from the production well 101 to prevent and suppress scale buildup on the surfaces of equipment such as piping in the geothermal power generation facility 110. Therefore, by applying the scale sensor device 120 to detect the degree of scale buildup, it becomes possible to evaluate the effectiveness of the chemical additive in preventing and suppressing scale buildup.

[0024] In this embodiment, a chemical agent is added to the first pipeline PL1 that transfers the geothermal fluid produced from the production well 101 to the first flusher 111, and the scale prevention and suppression effect is evaluated on the geothermal brine transferred to the container 116 using a scale sensor device 120. The scale sensor device 120 can be installed at any point in the geothermal power plant 100 after the chemical agent has been added, such as between the production well 101 and the injection well 102, in order to evaluate the scale prevention and suppression effect of the chemical agent. Therefore, the installation location of the scale sensor device 120 can be any point downstream from the chemical agent addition point, and is not limited to the container 116.

[0025] In other words, the scale sensor device 120 only needs to be installed in at least one of the following locations: the production well 101, the first pipeline PL1 connecting the production well 101 and the first flusher 111, the second pipeline PL2 connecting the first flusher 111 and the second flusher 112, the third pipeline PL3 connecting the second flusher 112 and the container 116, the fourth pipeline PL4 connecting the container 116 and the pound 117, the fifth pipeline PL5 connecting the pound 117 and the reinjection well 102, the container 116, the pound 117, and the reinjection well 102. It may be installed in two or more locations.

[0026] Similarly, the chemical agent can be added from at least one of the following locations: the production well 101, the first pipeline PL1, the second pipeline PL2, the third pipeline PL3, the fourth pipeline PL4, the fifth pipeline PL5, the container 116, the pound 117, and the injection well 102. It may also be added from two or more locations. In order to ensure that the scale sensor device 120 can reliably evaluate the scale prevention and suppression effect, the chemical agent should be added upstream of the installation location of the scale sensor device 120.

[0027] The control unit 130 has the function of controlling all or part of the components of the evaluation system 1. The control unit 130 includes components such as a processor 131, a storage unit 132, and a connector 133, which are connected to each other via a bus. The processor 131 includes, for example, a CPU (Central Processing Unit). The storage unit 132 includes, for example, a hard disk, a ROM (Read Only Memory) for storing programs, and a RAM (Random Access Memory) as a work area. The control unit 130 communicates with each component of the evaluation system 1 via the connector 133. The control unit 130 may further include other components such as a display device such as a liquid crystal display or a touch panel, and an input device such as a keyboard, buttons, or a touch panel. The operation of the control unit 130 may be realized, for example, by having the processor 131 execute a program stored in the storage unit 132.

[0028] In this embodiment, the control unit 130 has a function to evaluate the conditions under which the scale sensor device 120 can best prevent or suppress scale buildup by changing the type, location, and amount of the drug. Specifically, the control unit 130 controls the system to change the type and amount of the drug depending on the location where the drug is added to prevent or suppress scale buildup. The control unit 130 then has a function to evaluate the conditions under which scale buildup can best prevent or suppress scale buildup based on the detection results of the degree of scale buildup detected by the scale sensor device 120 by changing the location, type, and amount of the drug.

[0029] In this embodiment, by changing the type of chemical agent (sulfuric acid, inhibitor, precipitation accelerator, etc.), the location of addition, and the amount added when adding chemicals to prevent and suppress scale adhesion, the conditions that best suppress the precipitation of scales such as silica scale and metal sulfide scale can be evaluated by the scale sensor device 120 downstream of container 116 or pound 117. In other words, in this embodiment, the scale sensor device 120 makes it possible to efficiently evaluate the scale prevention and suppression effect of chemicals. Furthermore, the scale prevention and suppression effect of suitable chemicals can be efficiently evaluated depending on the type of scale. In addition, other scale prevention and suppression effects such as mechanical scale removal, high-temperature reduction of hot water, and changes in production methods can also be efficiently evaluated using the scale sensor device 120. "Changes in production methods" as referred to here include, for example, stopping double flashing and switching to single flashing, or changing the injection temperature into the injection well (injection well).

[0030] Next, with reference to Figures 2 and 3, the configuration and detection principle of the scale sensor device 120 used in the scale prevention and suppression effect evaluation method according to this embodiment will be described in detail.

[0031] The scale sensor device 120 is a device that evaluates the state of scale formation on the surface of equipment such as pipes, which are conduits through which hot water such as geothermal water for geothermal power generation or hot spring water passes, in equipment that uses hot water. In particular, in this embodiment, the scale sensor device 120 is used to evaluate the effectiveness of scale prevention and suppression measures more quickly when implementing scale prevention and suppression measures in a geothermal power plant.

[0032] As shown in Figure 2, the scale sensor device 120 comprises a light source 121, an optical fiber 122, and a spectral analyzer 123. The light source 121 is connected to one end of the optical fiber 122, and the spectral analyzer 123 is connected to the other end of the optical fiber 122.

[0033] The light source 121 has the function of emitting light with a wavelength within a predetermined bandwidth. In this embodiment, the light source 121 is, for example, one in which the wavelength of the peak value of the light intensity is in the range of 550 nm to 750 nm, and a white light source is preferred. As such a light source 121, for example, a white light source such as an LED light source with a predetermined bandwidth can be used. Alternatively, monochromatic light may be used as the light source 121.

[0034] As shown in Figure 2, the method for evaluating the scale prevention and suppression effect using the scale sensor device 120 is to use an evaluation hot water path 124 for monitoring geothermal fluid GF, such as geothermal water or hot spring water used for geothermal power generation, as the scale detection target area. The geothermal fluid GF is passed through this evaluation hot water path 124, and the sensing part 122a of the optical fiber 122 is immersed in the geothermal fluid GF of the evaluation hot water path 124 to measure and evaluate the scale.

[0035] The geothermal fluid GF is supplied from a condenser 125 such as an intake well to an evaluation hot water path 124 provided in a predetermined piping, which is a hot water supply path 126. The geothermal fluid GF that has passed through the evaluation hot water path 124 is then returned to the original hot water supply path 126. The evaluation hot water path 124 may also be branched, and the branched geothermal fluid GF may be discarded. In addition to continuously flowing the geothermal fluid GF to be used for evaluation, it may also be stored in the evaluation hot water path 124 for a certain period of time for scale measurement and evaluation.

[0036] Next, with reference to Figure 3(A), the optical fiber 122 used in the scale sensor device 120 will be described. The optical fiber 122 is a multimode optical fiber, and it is preferable to use a silica core optical fiber. One end of the optical fiber 122 is connected to the light source 121, and light of a predetermined bandwidth wavelength is transmitted through it. As shown in Figure 3(A), the jacket 122c, which is the outer sheath, and the cladding 122b, which is the intermediate layer, are partially removed from the optical fiber 122 to expose the core and form the sensing portion 122a.

[0037] The spectral analyzer 123 functions as a general-purpose spectrometer that detects the spectrum of light that has passed through the sensing unit 122a of the optical fiber 122. The spectral analyzer 123 detects the change over time in the absorbance spectrum of white light or the like that transmitted from the light source 121 to the optical fiber 122, and displays a predetermined spectrum on a display, enabling evaluation and determination of the scale composition and formation state. In this embodiment, the scale sensor device 120 is configured such that the sensing unit 122a is placed within the scale detection target area, light from the light source 121 is transmitted through the optical fiber 122, and the spectral analyzer 123 detects the change over time in the transmittance and spectrum of the light transmitted through the sensing unit 122a, thereby enabling evaluation of the scale adhesion prevention and suppression effect.

[0038] Next, the principle of scale adhesion evaluation by the scale sensor device 120 will be explained with reference to Figures 3(B) and (C). As shown in Figure 3(B), when no scale is attached to the surface of the sensing portion 122a of the optical fiber 122, the refractive index of water is smaller than the refractive index of the core of the sensing portion 122a. Therefore, the propagating light L undergoes total internal reflection at the inner surface of the sensing portion 122a and passes through the optical fiber 122. The spectral analyzer 123 then detects the time-dependent change in the spectrum of the propagating light L that has been transmitted while undergoing total internal reflection.

[0039] On the other hand, as shown in Figure 3(C), when scale SC adheres to the surface of the sensing portion 122a of the optical fiber 122, the refractive index of scale SC is greater than that of the core of the sensing portion 122a. Therefore, the total internal reflection of the propagating light L at the inner surface of the sensing portion 122a is inhibited, and the propagating light L is attenuated. The spectral analyzer 123 then detects the change in the spectrum of the attenuated propagating light L over time. This attenuation of the propagating light L, that is, the change in the intensity of the propagating light L, is correlated with the amount of scale SC attached, and the amount of scale SC attached is expressed as a change in the peak wavelength of the light irradiated from the light source 121.

[0040] In the scale sensor device 120, the amount of scale adhering to the surface of the sensing unit 122a is measured by the spectral analyzer 123 as a change in the peak wavelength of light transmitted through the optical fiber 122 over time. By measuring the scale adhesion state, the scale sensor device 120 can detect the scale formation state adhering to equipment through which the geothermal fluid GF passes in near real time and evaluate the degree of that formation state. In other words, the scale sensor device 120 can detect the scale adhesion state in real time by immersing the sensing unit 122a in the geothermal fluid produced from the production well 101. Therefore, by using the scale sensor device 120, it becomes possible to quickly evaluate the effectiveness of scale prevention and suppression measures such as adding chemicals to prevent or suppress scale adhesion.

[0041] The geothermal fluid GF referred to here includes geothermal water and hot spring water used for geothermal power generation, as well as steam erupting from underground. It may also include carbon dioxide injected underground for the purpose of CCS (Carbon Dioxide Capture and Storage) or EGS (Enhanced Geothermal Systems), or other injected fluids. The equipment includes piping such as pipes and heat exchangers that carry the geothermal fluid GF. Furthermore, for the identified products, by using monochromatic light from the light source 121 and detecting the transmittance of the light that has passed through the sensing unit 122a, it is possible to easily detect scale and recognize changes in the adhesion state, thereby enabling the evaluation of scale formation.

[0042] According to the method for evaluating the scale prevention and suppression effect using the scale sensor device 120 of this embodiment, it is possible to measure scale adhesion more quickly and evaluate the scale prevention and suppression effect. It is also possible to detect changes in the spectrum over time based on the absorbance of the spectrum and identify a wider range of scale types. In particular, it enables rapid detection and evaluation of silica scale, allowing for timely and appropriate scale countermeasures.

[0043] It should be noted that the method for evaluating scale generation by the scale sensor device 120 is not limited to the above-described embodiment. The optical bandwidth of the light source 121 and the type of the light source 121 can be appropriately set, and the material and structure of the optical fiber 122 can also be selected according to the application of the sensor and the hot water to be used. Furthermore, the applicable groundwater such as hot water includes geothermal water for geothermal power generation, hot spring water and other groundwater, and also includes water vapor.

[0044] Next, the operation and effects of the scale prevention and suppression effect evaluation method and evaluation system according to the present embodiment will be described.

[0045] The inventors of the present invention have conducted intensive studies to solve the problem of evaluating the effect of preventing and suppressing scale in geothermal power plants more quickly, and have found the following phenomenon. That is, the inventors have found that by utilizing a scale sensor capable of detecting scale generation more quickly, the effect of preventing and suppressing scale adhesion due to chemical addition and the like performed in geothermal power plants can be evaluated in real time.

[0046] In order to prevent and suppress the adhesion of precipitates called scale derived from geothermal fluid to above-ground facilities, pipes, wellbores and the like of geothermal power plants, many scale prevention and suppression methods such as chemical injection have been developed and proposed. However, as conventional methods for evaluating the effect of scale prevention and suppression methods, for example, a hot water flow test in which water is passed through an actual pipe requires a three-month test period and high cost. A column water flow test, in which water is passed through a column simulating a formation, requires a test period of about one week. In the case of a test using a coupon (a metal piece), evaluation is performed based on the weight difference before and after scale adhesion, which takes time and effort to evaluate the effect of the scale prevention and suppression method.

[0047] In contrast, in the present embodiment, by utilizing an optical fiber scale sensor, the presence or absence of scale generation from geothermal fluid, the generation rate thereof, the type of generated scale, and the like can be rapidly evaluated from the attenuation of light transmitted through the optical fiber obtained in real time. For this reason, in the present embodiment, by utilizing the scale sensor, the scale generation status can be detected in a short period of several hours to about one day, so that the effect of appropriate scale suppression, prevention and control methods can be evaluated under many test conditions. Furthermore, by reducing the amount of scale precipitation, cleaning of pipelines, wells, above-ground facilities, etc. of a geothermal power plant can be easily performed

[0048] Furthermore, in the present embodiment, in order to prevent and suppress scale generation and adhesion, the effect of scale prevention and suppression methods under many test conditions is evaluated by changing the type, addition location and addition amount of the added chemical. That is, in the present embodiment, by changing the installation location of the scale sensor or providing multiple chemical addition locations, the effect of appropriate scale suppression and prevention methods under more test conditions can be evaluated. For this reason, by finding optimal conditions that can prevent and suppress scale precipitation, it becomes possible to reduce the amount of scale precipitation and facilitate cleaning of above-ground facilities, pipes, wells, and the like of a geothermal power plant.

[0049] [Second Embodiment] Next, with reference to FIG. 4, a schematic configuration of an evaluation system to which the method for evaluating scale prevention and suppression effect according to the second embodiment of the present invention is applied will be described.

[0050] The evaluation system 2 to which the method for evaluating scale prevention and suppression effect of the present embodiment is applied evaluates the prevention and suppression effect of scale adhesion in a geothermal power plant 100 that generates power using thermal energy contained in geothermal reservoirs and the like in geothermal zones. As shown in FIG. 4, the evaluation system 2 includes a geothermal power plant 100, a scale sensor device 120, and a control unit 130. Note that in the evaluation system 2 of the present embodiment, the configuration of each component of the geothermal power plant 100, the scale sensor device 120, and the control unit 130 is the same as that of the evaluation system 1 of the first embodiment described above, so description thereof is omitted.

[0051] In this embodiment, a chemical agent is added to the second pipeline PL2, which transfers the geothermal fluid produced from the production well 101 from the first flusher 111 to the second flusher 112. The scale prevention and suppression effect is then evaluated on the geothermal brine transferred to the container 116 using a scale sensor device 120. The scale sensor device 120 can be installed at any point after the chemical agent is added between the production well 101 and the injection well 102 of the geothermal power plant 100, in order to evaluate the effect of chemical agent addition in preventing and suppressing scale buildup. Therefore, the installation location of the scale sensor device 120 can be any point downstream from the chemical agent addition point, and is not limited to the container 116.

[0052] In other words, the scale sensor device 120 only needs to be installed in at least one of the first pipeline PL1, second pipeline PL2, third pipeline PL3, fourth pipeline PL4, fifth pipeline PL5, container 116, and pound 117, and may be installed in two or more locations. Similarly, the chemical agent can be added from at least one of the first pipeline PL1, second pipeline PL2, third pipeline PL3, fourth pipeline PL4, fifth pipeline PL5, container 116, and pound 117, and may be added from two or more locations. In order to ensure that the scale sensor device 120 can reliably evaluate the effect of preventing and suppressing scale buildup, the chemical agent should be added upstream of the installation location of the scale sensor device 120.

[0053] In this embodiment, the control unit 130 has a function to evaluate the conditions under which the scale sensor device 120 precipitates scale in different locations according to the type of scale by changing the type of agent, the location of addition, and the amount of addition. Specifically, the control unit 130 controls the type and amount of agent to change according to the location of addition of the agent for preventing and suppressing scale adhesion. The control unit 130 then has a function to evaluate the conditions under which scale precipitates in different locations according to the type of scale by changing the location, type, and amount of addition of the agent, based on the detection results of the degree of scale adhesion detected by the scale sensor device 120.

[0054] For example, the scale sensor device 120 evaluates whether silica scale is being deposited in container 116 and metal sulfide scale in pound 117 by changing the location, type, and amount of the chemical agent added. Specifically, first, a chemical agent that reacts with silica is added to the geothermal fluid produced from production well 101, and the scale sensor device 120 evaluates whether silica scale is being selectively deposited in container 116. Then, after the geothermal fluid remaining after silica scale deposition is transferred to pound 117, the scale sensor device 120 evaluates whether metal sulfide scale is being deposited in pound 117 by adding a chemical agent that reacts with metal sulfides to the transferred geothermal fluid.

[0055] Thus, in this embodiment, by changing the type of chemical agent (sulfuric acid, inhibitor, precipitation accelerator, etc.), the location of addition, and the amount of addition in the chemical agent used to prevent and suppress scale adhesion, the scale sensor device 120 can evaluate the conditions for precipitation in different locations according to the type of scale, such as silica scale or metal sulfide scale. In other words, in this embodiment, by using the scale sensor device 120, if two or more types of scale are generated, each scale can be precipitated separately in different locations, thereby facilitating the recovery of each scale as a valuable mineral resource.

[0056] Next, the operation and effects of the scale prevention and suppression effect evaluation method and evaluation system according to this embodiment will be described.

[0057] In this embodiment, by utilizing a scale sensor, the effectiveness of chemicals in preventing and suppressing scale buildup can be efficiently evaluated in real time. Furthermore, by reducing the amount of scale deposited, cleaning of pipelines, wells, and surface facilities becomes easier. In addition, in this embodiment, the effectiveness of suitable chemicals in preventing and suppressing scale buildup can be efficiently evaluated depending on the type of scale. In particular, in this embodiment, when two or more types of scale are generated, the system controls the deposition of each type of scale separately in different locations, making it easier to recover each type of scale as a mineral resource and enabling efficient and effective utilization of each type of scale as a valuable resource.

[0058] [Third Embodiment] Next, with reference to Figure 5, the schematic configuration of an evaluation system to which the scale prevention and suppression effect evaluation method according to the third embodiment of the present invention is applied will be described.

[0059] The evaluation system 3 to which the scale prevention and suppression effect evaluation method of this embodiment is applied evaluates the scale prevention and suppression effect of a geothermal power plant 100 that generates electricity using thermal energy contained in geothermal reservoirs in the geotropical region. The evaluation system 3 comprises a geothermal power plant 100, a scale sensor device 120, a control unit 130, and a simulated plant 140. In the evaluation system 3 of this embodiment, the configuration of each component of the geothermal power plant 100, the scale sensor device 120, and the control unit 130 is the same as that of the evaluation system 1 of the first embodiment described above, so their description is omitted.

[0060] In this embodiment, as shown in Figure 5, a simulated plant 140 is introduced, which branches off a portion of the fluid from the first pipeline PL1, a two-phase flow pipeline connecting the production well 101 and the first flusher 111, via a branch valve (not shown), and the effectiveness of the scale suppression and prevention method is evaluated. The simulated plant 140 is a scale measurement facility that uses a scale sensor device 120 to detect the degree of scale adhesion after adding a chemical agent for preventing and suppressing scale adhesion to the geothermal fluid produced from the production well 101, and evaluates the effectiveness of the scale prevention and suppression method. The simulated plant 140 is about 1 / 100 the size of the actual geothermal power generation equipment 110, for example, on a scale of 50 cm × 50 cm × 50 cm.

[0061] The control unit 130 sets the appropriate type, location, and amount of chemical agent to prevent and suppress scale buildup in the actual geothermal power generation equipment 110 based on the measurement results in the simulated plant 140, and controls the system to add the chemical agent to prevent and suppress scale buildup. In this embodiment, a portion of the geothermal fluid produced from the production well 101 is transferred to the simulated plant 140, and in the simulated plant 140, the scale sensor device 120 detects the degree of scale buildup after the chemical agent is added to the transferred geothermal fluid, and then sets the type, location, and amount of chemical agent to be added in the actual geothermal power generation equipment 110.

[0062] Next, the operation and effects of the scale prevention and suppression effect evaluation method and evaluation system according to this embodiment will be described.

[0063] In this embodiment, by utilizing a scale sensor, the effectiveness of preventing and suppressing scale buildup by chemicals can be efficiently evaluated in real time. Furthermore, by reducing the amount of scale deposited, cleaning of wells, pipelines, and surface equipment at geothermal power plants becomes easier. In addition, it becomes possible to monitor the degree and type of scale buildup, such as silica scale and metal sulfide scale, in real time under many test conditions in a short period of time.

[0064] In particular, in this embodiment, a simulated plant smaller in size than the actual geothermal power generation facility can be branched off and installed on the upstream side of the transfer of geothermal fluid produced from production wells to the actual geothermal power generation facility, as a scale measurement facility for evaluating the effectiveness of preventing and suppressing scale buildup. Therefore, in the simulated plant, in parallel with geothermal power generation at the actual facility, a chemical agent can be added to the geothermal fluid produced from production wells, and the degree of scale buildup can be quickly detected by a scale sensor device. This makes it possible to measure and monitor the effectiveness of scale suppression, prevention, and suppression in real time, even with a relatively small amount of chemical agent added.

[0065] Thus, in this embodiment, by providing a simulated plant, the appropriate type, location, and amount of chemical agent to be added to the geothermal fluid produced from the production well to prevent and suppress scale buildup can be selected in advance using small amounts of chemical agent. In other words, in this embodiment, the components and properties of the geothermal fluid produced from the production well can be confirmed in advance using the simulated plant. As a result, the appropriate type, location, and amount of chemical agent can be added to the geothermal fluid to be transported to the geothermal power generation facility with greater certainty, thus enabling effective prevention and suppression of scale buildup according to the type of scale, and allowing for efficient scale control at geothermal power plants at a lower cost.

[0066] Furthermore, in this embodiment, by introducing a portion of the geothermal fluid from a two-phase flow pipeline into a simulated plant and varying various test conditions for chemical addition (type of chemical, location of addition, amount of addition, etc.), the degree of prevention and suppression of scale (silica scale, metal sulfide scale, etc.) precipitation can be measured in real time over a short period of time. As a result, the effectiveness of scale prevention and suppression at a geothermal power plant can be evaluated more quickly without stopping the actual geothermal power generation operation of the geothermal power plant. Thus, in this embodiment, scale countermeasures at a geothermal power plant can be efficiently implemented without stopping the actual geothermal power generation, thereby improving geothermal power generation efficiency with less time and cost.

[0067] Furthermore, as the scale sensor device used in the evaluation system 3 of this embodiment, the high-temperature, high-pressure scale sensor device 220, which can be used in a high-temperature, high-pressure environment as shown in Figure 6, may be used. As shown in Figure 6, the high-temperature, high-pressure scale sensor device 220 comprises a light source 221, an optical fiber 222, and a spectral analyzer 223, with the light source 221 connected to one end of the optical fiber 222 and the spectral analyzer 223 connected to the other end of the optical fiber 222.

[0068] The high-temperature, high-pressure scale sensor device 220 has a sensing section 222a of an optical fiber 222 located in the reactor 224. The reactor 224 is supplied with geothermal fluid produced from the production well 101 via a supply line L1 equipped with a pump 227 and valve V1 from a supply port 225, and the scale components contained in the geothermal fluid can be monitored. The monitored geothermal fluid is then discharged from the outlet 226 via a discharge line L2 equipped with valves V2, V3, and V4 and returned to the original hot water supply path.

[0069] As shown in Figure 6, the high-temperature, high-pressure scale sensor device 220 includes a temperature control unit 228 for controlling the temperature inside the reactor 224 and a pressure adjustment unit 229 for adjusting the pressure inside the reactor 224.

[0070] The temperature control unit 228 has the function of controlling the temperature inside the reactor 224 so that it ranges from 0°C to a maximum of 250°C. The temperature inside the reactor 224 can be measured by a thermometer T1. The pressure adjustment unit 229 has the function of adjusting the pressure inside the reactor 224 so that the lower limit of the pressure is between vacuum and atmospheric pressure (0.1 MPa) and the upper limit is a maximum of 15 MPa, by supplying an inert gas such as Ar gas to a gas line L3 connected to a discharge line L2, which is equipped with valves V5, V6, and V7. The pressure inside the reactor 224 can be measured, for example, by a P1 provided between valves V2 and V3 in the discharge line L2. In addition, a pressure gauge P2 for measuring the pressure of the supplied gas is provided in the gas line L3.

[0071] In the method for evaluating the scale prevention and suppression effect using the high-temperature, high-pressure scale sensor device 220 configured in this way, first, geothermal fluid is supplied into the reactor 224 from the supply port 225 and collected from the discharge port 226. Next, the valve V4 located upstream of the discharge port 226 is closed, and the pressure rise is checked using the pressure gauge P1 located in the discharge line L2 to confirm whether the reactor 224 is filled with geothermal fluid.

[0072] Subsequently, when the pressure measured by pressure gauge P1 reaches 4 MPa, the supply of geothermal fluid is stopped, and Ar gas is supplied from the pressure adjustment unit 229 via the gas line L3. The pressure inside the apparatus is adjusted to 4-6 MPa while measuring the pressure of the supplied gas using pressure gauge P2 installed in the gas line L3. The temperature inside reactor 224 is then gradually raised to a maximum of 250°C to enable batch and water flow tests. At this time, the reaction temperature inside reactor 224 is measured by thermometer T1. The progress of the scale precipitation reaction is then confirmed by the spectral analyzer 223, which acts as a detector in the sensing unit 222a.

[0073] In this way, the high-temperature, high-pressure scale sensor device 220 enables monitoring of scale formation in response to temperature and pressure changes in the reactor 224. The high-temperature, high-pressure scale sensor device 220 can reproduce the conditions for the formation of various scales by adjusting the temperature (maximum 250°C) and pressure (maximum 15 MPa), and this can be used to consider prevention and suppression measures. The high-temperature, high-pressure scale sensor device 220 incorporates a sensing unit 222a, which acts as a scale sensor, into the reactor 224, enabling real-time monitoring of scale formation while geothermal fluid is flowing under high temperature and pressure.

[0074] Generally, when the solubility of a mineral decreases, it becomes supersaturated, making it easier for scale to form. However, the effects of temperature and pressure differ depending on the type of scale, so it is important to correctly understand the precipitation conditions for each. For example, silica scale precipitates when it becomes supersaturated due to a decrease in temperature and pressure, while sulfide scale is more likely to form when it becomes supersaturated in an environment with high temperature and low pressure. Therefore, by using the high-temperature, high-pressure scale sensor device 220, the sensing unit 222a can be immersed in the geothermal fluid in the local environment, allowing for real-time monitoring of the scale formation state.

[0075] Although each embodiment of the present invention has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel aspects and effects of the present invention. Therefore, all such modifications are considered to fall within the scope of the present invention.

[0076] For example, any term that appears at least once in the specification or drawings alongside a broader or synonymous term may be replaced with that different term anywhere in the specification or drawings. Furthermore, the configuration and operation of the evaluation system are not limited to those described in the embodiments of the present invention, and various modifications are possible.

[0077] According to the present invention, the effectiveness of preventing and suppressing scale formation in geothermal power plants can be evaluated more quickly.

Claims

1. A method for evaluating the effectiveness of scale prevention and suppression in preventing and suppressing scale buildup at a geothermal power plant, wherein a sensing unit formed by exposing the core of an optical fiber at at least one or more locations is immersed in geothermal fluid produced from a production well of the geothermal power plant, and a scale sensor is used to detect the degree of scale buildup on the surface of the sensing unit, thereby evaluating the effectiveness of scale prevention and suppression.

2. The method for evaluating the scale prevention and suppression effect according to claim 1, wherein the scale sensor detects the degree of scale buildup at the production wells and injection wells of the geothermal power plant and at any point between them.

3. The method for evaluating the scale prevention and suppression effect according to claim 2, wherein the scale sensor detects the degree of scale adhesion at any point after the addition of the agent that suppresses the formation of scale to the geothermal fluid.

4. The method for evaluating the scale prevention and suppression effect according to claim 3, wherein the scale sensor evaluates the conditions that best suppress scale adhesion by changing the type, location, and amount of the agent.

5. The method for evaluating the scale prevention and suppression effect according to claim 3, wherein the scale sensor evaluates the conditions for precipitation in different locations according to the type of scale by changing the type, location, and amount of the agent.

6. A method for evaluating the scale prevention and suppression effect according to claim 3, wherein a portion of the geothermal fluid produced from the production well is transferred to a simulated plant, and in the simulated plant, the scale sensor detects the degree of scale adhesion after the agent is added to the geothermal fluid.

7. The method for evaluating the scale prevention and suppression effect according to claim 2, wherein the scale sensor is provided at one or more locations in the production well, the injection well, or any location between them.

8. The method for evaluating the scale prevention and suppression effect according to claim 3, wherein the agent is added at one or more locations in the production well, the injection well, or any location between them.

9. The method for evaluating the scale prevention and suppression effect according to any one of claims 1 to 8, wherein the scale sensor comprises a light source connected to one end of the optical fiber and transmitting light of a predetermined bandwidth wavelength through the optical fiber, and a spectrometer connected to the other end of the optical fiber and detecting the spectrum of light that has passed through the sensing part of the optical fiber, and the scale sensor evaluates the scale prevention and suppression effect by transmitting light from the light source through the optical fiber with the sensing part immersed in the geothermal fluid and detecting the change in the transmittance and spectrum of the light that has passed through the sensing part over time.

10. The method for evaluating the scale prevention and suppression effect according to any one of claims 1 to 8, wherein the scale sensor uses a scale sensor that detects the degree of scale adhesion to the surface of the sensing part under a high temperature and high pressure environment to evaluate the effect of preventing and suppressing scale adhesion.

11. An evaluation system for evaluating the effectiveness of preventing and suppressing scale buildup in a geothermal power plant, comprising: a production well for producing geothermal fluid that remains in a geothermal reservoir in a geothermal region; and a scale sensor for detecting the degree of scale buildup on the surface of the sensing part by immersing a sensing part, formed by exposing the core of an optical fiber at at least one or more locations, into the geothermal fluid produced from the production well, wherein the scale sensor evaluates the effectiveness of preventing and suppressing scale buildup based on the detection result of the degree of scale buildup on the surface of the sensing part.

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