Cleaning system

Abstract

A cleaning system according to one embodiment of the present invention comprises: a chemical liquid supply pipe that is connected to one end, on the upstream side, of a portion to be cleaned and has a chemical injection port; a chemical addition device; a first pipeline that connects the chemical injection port to the chemical addition device and has a chemical collection port; a return pipeline that connects the other end, on the downstream side, of the portion to be cleaned to the chemical collection port; a circulation pump for circulating the chemical; an analyzer that is connected to a branch pipe branching off from the first pipeline and analyzes a waste liquid sent to the branch pipe, for component fluctuations with time; and a controller. The controller, on the basis of analytical results from the analyzer, predicts an outermost-surface component of a scale, determines one of at least three chemicals which is suited for the outermost-surface component, and controls the chemical addition device so as to supply the determined chemical.

Description

Cleaning System

[0001] The present invention relates to a cleaning system.

[0002] Geothermal power plants extract high-temperature geothermal fluids (geothermal water and geothermal steam) from production wells and generate electricity using the geothermal water or geothermal steam separated from the geothermal fluid.Geothermal fluids extracted from production wells contain more calcium and dissolved silica than well water or river water.

[0003] Calcium and dissolved silica in geothermal water collected from production wells are concentrated by reducing pressure in geothermal power plants, and are cooled as they flow through pipes, reducing their solubility. When the calcium and dissolved silica contained in the geothermal water become supersaturated, they polymerize to form calcium carbonate and amorphous silica, which precipitate as scale. Scale buildup is a problem in geothermal power plants because it can adhere to the inner walls of pipes and cause blockages.

[0004] Therefore, methods for preventing or removing scale in geothermal power plants have been studied. For example, in a geothermal power generation system described in Patent Document 1, hydrogen peroxide solution is supplied as an oxidizing agent to the separated hot water downstream of the steam separator to prevent the deposition of silica scale in the geothermal water system.

[0005] Japanese Patent Application Publication No. 2015-90147

[0006] However, in the geothermal power generation system described in Patent Document 1, no consideration is given to removing scale that has adhered to and accumulated on the inner walls of pipes, etc. Furthermore, since scale grows as its components change in stages and accumulate in layers, when using an oxidizing agent to remove scale that has adhered to and accumulated on the inner walls of pipes, etc. in a geothermal power generation plant, while it is possible to remove scale of one component, it is difficult to remove scale of other components, and there is a possibility of poor cleaning.

[0007] One aspect of the present invention provides a cleaning system that can sufficiently remove scale.

[0008] One aspect of the present invention is a cleaning system for removing scale that has adhered to the part to be cleaned in a geothermal power plant that includes a gas-liquid separator that separates geothermal water and geothermal steam from geothermal fluid that has been ejected from a production well, and a part to be cleaned that is provided downstream of the gas-liquid separator, the system comprising: a chemical supply pipe that is connected to one end of the part to be cleaned upstream and has a chemical injection port; a chemical addition device that injects chemicals into the chemical injection port; a first pipe that connects the chemical injection port and the chemical addition device and has a chemical recovery port; the chemical injection port and the chemical recovery port; a circulation pump provided midway on the first piping between the chemical injection port and the chemical recovery port and for circulating the chemical; an analyzer connected to a branch pipe branching off from the first piping and for analyzing changes over time in the components of the waste liquid sent to the branch pipe; and a control device, wherein the control device predicts the outermost surface components of the scale based on the analysis results of the analyzer, determines one chemical suitable for the outermost surface component from among at least three chemicals, and controls the chemical addition device to supply the determined chemical.

[0009] According to a geothermal power generation system according to one aspect of the present invention, scale can be sufficiently removed from the reduction line.

[0010] FIG. 1 is a schematic configuration diagram of a geothermal power plant according to one embodiment. FIG. 2 is a schematic configuration diagram of a cleaning system according to one embodiment. FIG. 3 is a schematic diagram showing a scale layer structure. FIG. 4 is a diagram showing a flow relating to chemical switching control by a control device. FIG. 5 is a diagram showing a processing flow of temperature control by a control device. FIG. 6 is a diagram showing the relationship between the temperature detected by a temperature measuring instrument and the output of a heater. FIG. 7 is a schematic diagram for explaining reverse direction cleaning. FIG. 8 is a diagram showing a flow relating to cleaning direction switching control by a control device. FIG. 9 is a diagram showing the relationship between elapsed time and scale elution rate.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] Fig. 1 is a schematic configuration diagram of a geothermal power plant 100 according to one embodiment, and Fig. 2 is a schematic configuration diagram of a cleaning system 1 according to one embodiment. As shown in Fig. 1 and Fig. 2, the cleaning system 1 removes scale adhered to the cleaning target C in the geothermal power plant 100, which includes a gas-liquid separator 103 that separates geothermal water and geothermal steam from a geothermal fluid spouted from a production well 102, and a cleaning target C provided downstream of the gas-liquid separator 103.

[0013] An example of a geothermal power plant 100 equipped with a cleaning system 1 will be described. As shown in Fig. 1 , the geothermal power plant 100 includes, for example, a gas-liquid separator 103, a power generation device 101, a retention tank 105, a return line L100, a return pump 106, and a cleaning system 1. In Fig. 1 , arrows indicate the flow of fluid.

[0014] In a geothermal power plant 100, geothermal fluid extracted from a production well 102 is sent to a gas-liquid separator 103. The gas-liquid separator 103 separates geothermal water and geothermal steam from the geothermal fluid ejected from the production well 102. The geothermal water and geothermal steam separated in the gas-liquid separator 103 are sent via piping to a power generation unit 101, which generates power using the geothermal water or geothermal steam separated in the gas-liquid separator 103 as a heat source. The geothermal water whose heat has been recovered in the power generation unit 101 is introduced into a retention tank 105 via piping.

[0015] In the example shown in Figure 1, the geothermal steam separated in the gas-liquid separator 103 is sent to a flash power generation plant 101a, which generates electricity using the geothermal steam separated in the gas-liquid separator 103 as a heat source, and the geothermal water separated in the gas-liquid separator 103 is sent to a binary power generation plant 101b, which generates electricity using the geothermal water separated in the gas-liquid separator 103 as a heat source.

[0016] The power generation device 101 is not particularly limited, and may include a flash power generation device 101a and a binary power generation device 101b, or may include either the flash power generation device 101a or the binary power generation device 101b.

[0017] The flash power generation system 101a includes a turbine that rotates when supplied with geothermal steam separated in the gas-liquid separator 103, a generator connected to the turbine, a condenser that condenses the geothermal steam discharged from the turbine, a cooling tower that cools the condensed water condensed in the condenser, etc. The binary power generation system 101b includes a medium evaporator that evaporates a low-boiling-point heat medium through heat exchange, a turbine that rotates when supplied with the vaporized heat medium, a generator, a medium condenser, etc.

[0018] The retention tank 105 stores the geothermal water whose heat has been recovered by the power generation device 101. The geothermal water is retained until a polymerization reaction of silica in the geothermal water progresses and the silica-based insoluble components are sufficiently coagulated and precipitated.

[0019] The reinjection line L100 is a line that connects the outlet of the retention tank 105 to the reinjection well 104.

[0020] The return pump 106 is provided midway along the return line L100 and returns the geothermal water discharged from the retention tank 105 to the return well 104. The geothermal water discharged from the retention tank 105 is returned to the return well 104 via the return line L100 by the return pump 106.

[0021] In the example shown in Figure 1, the part to be cleaned C is the reduction line L100 (piping), but it is not limited to this and can be any component or part that comes into contact with geothermal fluid in a geothermal power plant, such as piping, heat exchangers, valves, etc. at other locations.

[0022] Next, a description will be given of the cleaning system 1. As shown in Fig. 2, the cleaning system 1 includes a chemical supply pipe LS, a chemical addition device 30, a first pipe L1, a return pipe LR, a circulation pump P1, an analyzer 40, and a control device 50. The cleaning system 1 may further include a heater 4 and a temperature measuring device 5.

[0023] The chemical solution supply pipe LS is connected to one end upstream of the area to be cleaned C. The chemical solution supply pipe LS also has an chemical injection port 2. The chemical injection port 2 may be provided midway along the chemical solution supply pipe LS. The other end of the chemical solution supply pipe LS may be connected to the reduction line L100 of the geothermal power plant 100. The other end (upstream end) of the chemical solution supply pipe LS may be connected to a part of any geothermal power plant, not limited to the geothermal power plant 100. Geothermal fluid F flows in from the other end of the chemical solution supply pipe LS.

[0024] The chemical addition device 30 injects a chemical into the chemical injection port 2. Specifically, the chemical addition device 30 injects the chemical into the chemical injection port 2 via a first pipe L1, which will be described later. The chemical addition device 30 may include at least three chemical tanks 31a, 31b, and 31c that store chemicals, a second pipe L2 that connects the first pipe L1 to each of the chemical tanks 31a, 31b, and 31c, and a chemical injection pump P2 that discharges the chemical stored in each of the chemical tanks 31a, 31b, and 31c toward the chemical injection port 2. While the number of chemical tanks 31a, 31b, and 31c is three in the example shown in FIG. 2 , the number is not limited to three, and may be four or more.

[0025] The chemicals contained in the chemical tanks 31a, 31b, and 31c are chemicals for removing and cleaning scale adhering to the cleaning target area C. At least three chemical tanks 31a, 31b, and 31c may contain a first basic chemical, a mixed chemical of a second basic chemical, a chelating agent, and a dispersant, and an acidic chemical, respectively. In this embodiment, the first basic chemical is contained in the chemical tank 31a, the mixed chemical is contained in the chemical tank 31b, and the acidic chemical is contained in the chemical tank 31c. These three types of chemicals can be used depending on the components of the scale that change during the scale growth process.

[0026] Fig. 3 is a schematic diagram showing the layer structure of scale. As shown in Fig. 3, scale grows as its components change stepwise and accumulates in layers on a cleaning target C, such as the inner wall of a pipe. The inventors analyzed the components of each layer of scale and concluded that, when the cleaning target C is made of iron, scale grows and accumulates in the following order from the cleaning target C side: an initial layer X1 mainly composed of iron oxide; an intermediate layer X2 mainly composed of silica and impurities (calcium, aluminum, iron, etc.); and a growth layer X3 mainly composed of amorphous silica. The inventors also confirmed that the iron ion concentration decreases in the order of the initial layer X1, the intermediate layer X2, and the growth layer X3.

[0027] The first basic chemical can be used to dissolve the growth layer X3. Examples of the first basic chemical include sodium hydroxide, potassium hydroxide, and ammonium salts.

[0028] The mixed chemical can be used to dissolve the intermediate layer X2. The second basic chemical contained in the mixed chemical can be selected from the same chemicals as the first basic chemical described above, and may be the same chemical as the first basic chemical or a different chemical.

[0029] Examples of the chelating agent contained in the mixed drug include ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), hydroxyethylenediaminetriacetic acid (HEDTA), diethylenetriaminepentaacetic acid (DTPA), trimethanolamine, sodium gluconate, etc. Among these, the chelating agent is preferably EDTA, NTA, HEDTA, or DTPA.

[0030] Examples of dispersants contained in the mixed agent include sodium polyacrylate, maleic acid, and diallyldimethylammonium chloride / acrylamide copolymer.

[0031] The acidic agent can be used to dissolve the initial layer X1. Examples of the acidic agent include sulfuric acid, hydrochloric acid, acetic acid, and citric acid.

[0032] 2, the chemical addition device 30 may further include a water tank 32 that is located upstream of the chemical tanks 31a, 31b, and 31c and that stores water, a water pump P3 that introduces water into the second pipe L2, a drain pipe (drain line) LW that branches off from the second pipe L2 downstream of the chemical injection pump P2, and a wastewater tank 33 that is connected to the drain pipe LW and that stores the water that has passed through the second pipe L2. Here, the upstream side and downstream side of the chemical addition device 30 refer to the upstream side and downstream side relative to the direction in which the chemical or water flows.

[0033] The water stored in the water tank 32 is water used to wash away any previous drug remaining in the second pipe L2 when changing the type of drug to be injected into the drug injection port 2 via the second pipe L2, and may be, for example, one type selected from tap water, river water, and distilled water.

[0034] The chemical addition device 30 may have a third pipe L3 branching from the second pipe L2 and connected to the outlet of the chemical tank 31a, a fourth pipe L4 branching from the second pipe L2 and connected to the outlet of the chemical tank 31b, a fifth pipe L5 branching from the second pipe L2 and connected to the outlet of the chemical tank 31c, and a sixth pipe L6 branching from the second pipe L2 and connected to the outlet of the water tank 32. The chemical addition device 30 may also have a valve V1a provided midway along the third pipe L3 for opening and closing the flow path of the third pipe L3, a valve V1b provided midway along the fourth pipe L4 for opening and closing the flow path of the fourth pipe L4, a valve V1c provided midway along the fifth pipe L5 for opening and closing the flow path of the fifth pipe L5, a valve V2 provided midway along the sixth pipe L6 for opening and closing the flow path of the sixth pipe L6, and a valve V3 provided midway along the drainage pipe LW for opening and closing the flow path of the drainage pipe LW.

[0035] The first pipe L1 connects the chemical injection port 2 and the chemical addition device 30. Specifically, the first pipe L1 connects the chemical injection port 2 and the second pipe L2. The first pipe L1 also has a chemical recovery port 3. The chemical recovery port 3 may be provided midway along the first pipe L1. The other end of the chemical supply pipe LS may be connected to a pipe in the geothermal power plant.

[0036] The return pipe LR connects the other end downstream of the area to be cleaned C to the chemical recovery port 3. The return pipe LR circulates waste liquid that has passed through the area to be cleaned C and returns it to the first pipe L1 via the chemical recovery port 3. The section of the chemical solution supply pipe LS from the chemical injection port 2 to one end of the area to be cleaned C, the return pipe LR, and the section of the first pipe L1 from the chemical recovery port 3 to the chemical injection port 2 form a circulation line. The cleaning system 1 uses the circulation line to circulate the chemical to the area to be cleaned C in the forward direction D1.

[0037] The circulation pump P1 is provided in the first pipe L1 between the chemical injection port 2 and the chemical recovery port 3, and circulates the chemical. Specifically, the circulation pump P1 discharges the chemical supplied from the chemical addition device 30 toward the chemical injection port 2, thereby circulating the chemical in the circulation line.

[0038] The heater 4 is provided midway along the first pipe L1 between the circulation pump P1 and the chemical injection port 2. The heater 4 heats the chemical supplied from the chemical addition device 30 and flowing through the first pipe L1.

[0039] The temperature measuring device 5 is connected to the first pipe L1 between the heater 4 and the chemical injection port 2. The temperature measuring device 5 detects the temperature of the chemical supplied from the chemical addition device 30 and flowing through the first pipe L1, and transmits the detected data to the control device 50.

[0040] The analyzer 40 is connected to a branch pipe LB branching off from the first pipe L1, and analyzes changes over time in the components of the waste liquid sent to the branch pipe LB. The branch pipe LB may branch off from the first pipe L1 between the circulation pump P1 and the heater 4. The analyzer 40 transmits the analysis results to the control device 50. Specifically, the analyzer 40 measures changes over time in the iron ion concentration and transmits the measurement results to the control device 50. For example, a high-performance liquid chromatograph can be used as the analyzer 40.

[0041] The cleaning system 1 may include a valve V8 located upstream of the drug recovery port 3 of the first pipe L1 (towards the drug addition device 30) and opening and closing the flow path of the first pipe L1, a valve V9 located upstream of the drug injection port 2 of the chemical solution supply pipe LS and opening and closing the flow path of the chemical solution supply pipe LS, a seventh pipe L7 branched off from the branch 9 upstream of the branch 10 of the return pipe LR (the other end side of the cleaning target area C), and a valve V10 located midway along the seventh pipe L7 and opening and closing the flow path of the seventh pipe L7.

[0042] The cleaning system 1 may include an eighth pipe L8 that branches off from the branch pipe LB and is connected to the inlet of the analyzer 40, and a valve V11 that is provided midway along the eighth pipe L8 and that opens and closes the flow path of the eighth pipe L8. The cleaning system 1 may also include a waste liquid tank 6 that is connected to the end of the branch pipe LB and that stores waste liquid, and a valve V12 that is provided midway along the branch pipe LB and that opens and closes the flow path of the branch pipe LB.

[0043] The control device 50 controls the chemical additive device 30, the heater 4, and each valve. The control device 50 predicts the outermost surface component of the scale based on the analysis results of the analysis device 40, determines one chemical suitable for the outermost surface component from among at least three chemicals, and controls the chemical additive device 30 to supply the determined chemical.

[0044] Specifically, the control device 50 predicts the outermost surface components of the scale based on the iron ion concentration detected by the analysis device 40. The three types of chemicals may be a first basic chemical, a mixed chemical of a second basic chemical, a chelating agent, and a dispersant, and an acidic chemical. The control device 50 further controls the heater 4 based on the temperature detected by the temperature measuring device 5.

[0045] FIG. 4 is a diagram showing a flow of chemical switching control by the control device 50. At the start of treatment, the control device 50 assumes that the outermost surface component of the scale is primarily composed of amorphous silica (growth layer X3), and as shown in FIG. 4, of the valves V1a, V1b, and V1c, only valve V1a is opened and the chemical injection pump P2 is activated (step S11). Note that the water pump P3 is stopped, and valves V1b, V1c, and V2 are closed. This allows the control device 50 to inject the first basic chemical into the chemical injection port 2 via the first pipe L1 using the chemical addition device 30.

[0046] Next, the control device 50 sends a signal to the analyzer 40 to start measuring the iron ion concentration (step S12). The control device 50 then determines whether the measured value of the iron ion concentration received from the analyzer 40 is within a set value range (step S13). In step S13, the set value of the iron ion concentration can be determined based on the results of a prior survey of the cleaning target area C. In step S13, the set value of the iron ion concentration can be, for example, 1 ppm or more and less than 10 ppm. If the iron ion concentration is within the set value range, the control device 50 predicts that the outermost surface component of the scale is primarily composed of silica and impurities (calcium, aluminum, iron, etc.) (intermediate layer X2).

[0047] When the control device 50 determines that the iron ion concentration received from the analyzer 40 is within the set value range (step S13: Yes), it closes the valve V1a, stops the chemical injection pump P2, opens the valve V2, and activates the water pump P3 (step S15). This allows the cleaning system 1 to clean the first basic chemical remaining in the second pipe L2 before switching the chemical supplied by the chemical addition device 30 to another chemical.

[0048] If the control device 50 determines that the iron ion concentration received from the analyzer 40 is outside the set value range (step S13: No), it causes the timer to measure the elapsed time, and if it determines that one hour has elapsed (step S14: Yes), it sends a signal to the analyzer 40 to start measuring the iron ion concentration again (step S12). Then, the control device 50 proceeds to the process of step S13, and repeats the processes of steps S12, S13, and S14 until it determines that the iron ion concentration received from the analyzer 40 is within the set value range. Note that the control device 50 may have a timer.

[0049] After performing step S15, the control device 50 opens only valve V1b of valves V1a, V1b, and V1c and activates chemical injection pump P2 (step S16). Note that water pump P3 is stopped and valves V1a, V1c, and V2 are closed. This allows the control device 50 to inject the mixed chemical into chemical injection port 2 via first pipe L1 using chemical addition device 30.

[0050] Next, the control device 50 sends a signal to the analysis device 40 to start measuring the iron ion concentration (step S17). The control device 50 then determines whether the iron ion concentration received from the analysis device 40 is within a set value range (step S18). The set value of the iron ion concentration in step S18 can be determined based on the results of a prior survey of the cleaning target area C. In step S18, the set value of the iron ion concentration can be, for example, 10 ppm or more. If the iron ion concentration is equal to or greater than the set value, the control device 50 predicts that the outermost surface component of the scale is primarily composed of iron oxide (initial layer X1).

[0051] When the control device 50 determines that the iron ion concentration received from the analyzer 40 is equal to or greater than the set value (step S18: Yes), it closes the valve V1b, stops the chemical injection pump P2, opens the valve V2, and activates the water pump P3 (step S20). This allows the cleaning system 1 to clean the mixed chemical remaining in the second pipe L2 before switching the chemical supplied by the chemical addition device 30 to another chemical.

[0052] If the control device 50 determines that the iron ion concentration received from the analyzer 40 is less than the set value (step S18: No), it causes the timer to measure the elapsed time, and if it determines that one hour has elapsed (step S19: Yes), it sends a signal to the analyzer 40 to start measuring the iron ion concentration again (step S17).The control device 50 then proceeds to the process of step S18, and repeats the processes of steps S17, S18, and S19 until it determines that the iron ion concentration received from the analyzer 40 is equal to or greater than the set value.

[0053] After performing step S20, the control device 50 opens only valve V1c among valves V1a, V1b, and V1c and activates chemical injection pump P2 (step S21). Note that water pump P3 is stopped and valves V1a, V1b, and V2 are closed. This allows the control device 50 to inject the acidic chemical into chemical injection port 2 via first pipe L1 using chemical addition device 30.

[0054] Fig. 5 is a diagram showing the flow of the temperature control process by the control device 50, and Fig. 6 is a diagram showing the relationship between the temperature detected by the temperature measuring device and the output of the heater. The control device 50 may further control the heater 4 so that the temperature detected by the temperature measuring device 5 is 40°C or higher and 100°C or lower. As shown in Fig. 5, the control device 50 turns on the output of the heater 4 (step S41) and determines whether the temperature detected by the temperature measuring device 5 is 100°C or higher (step S42). In step S42, the set value of the detected temperature of the temperature measuring device 5, which serves as the determination criterion, is not limited to 100°C or higher and can be any temperature.

[0055] If the control device 50 determines that the detected temperature received from the temperature measuring device 5 is 100°C or higher (step S42: Yes), it turns off the output of the heater 4 (step S43). If the control device 50 determines that the detected temperature received from the temperature measuring device 5 is not 100°C or higher (step S42: No), it returns to the process of step S41 and repeats the processes of steps S41 and S42 until it determines that the detected temperature received from the temperature measuring device 5 is 100°C or higher.

[0056] After performing the process of step S43, the control device 50 determines whether the temperature detected by the temperature measuring device 5 is 40° C. or less (step S44). In step S44, the set value of the detected temperature by the temperature measuring device 5, which serves as the determination criterion, is not limited to 40° C. or less and can be any temperature.

[0057] If the control device 50 determines that the detected temperature received from the temperature measuring device 5 is 40° C. or less (step S44: Yes), it turns on the output of the heater 4 again (step S41). If the control device 50 determines that the detected temperature received from the temperature measuring device 5 is not 40° C. or less (step S44: No), it returns to the process of step S43 and repeats the processes of steps S43 and S44 until it determines that the detected temperature received from the temperature measuring device 5 is 40° C. or less. That is, the control device 50 controls the heater 4 to be turned on and off, as shown in FIG.

[0058] The control device 50 continues the above process until the operation of the washing system 1 is stopped, and ends the process when the operation of the washing system 1 is stopped.

[0059] Next, the configuration for reverse cleaning will be described. As shown in Fig. 2, the cleaning system 1 may further include a third pipe L3 branching from a branch point 7 of the chemical solution supply pipe LS and connected to a branch point 10 of the return pipe LR, and a fourth pipe L4 branching from a branch point 8 downstream of the branch point 7 of the chemical solution supply pipe LS and connected to a branch point 11 downstream of the branch point 10 of the return pipe LR.

[0060] The cleaning system 1 may further include a valve V4 provided in the chemical supply pipe LS between branching portion 7 and branching portion 8, a valve V5 provided in the return pipe LR between branching portion 10 and branching portion 11, a valve V6 provided midway along the third pipe L3, and a valve V7 provided midway along the fourth pipe L4.

[0061] The third pipe L3, the fourth pipe L4, the valve V4, the valve V5, the valve V6, and the valve V7 are configured to circulate the chemical in the reverse direction D2 to the area to be cleaned C. The third pipe L3, the return pipe LR between the branch 10 and the other end of the area to be cleaned C, the chemical supply pipe LS between one end of the area to be cleaned and the branch 8, the fourth pipe L4, and the portion of the return pipe LR from the branch 11 to the chemical recovery port 3 form a backwashing line.

[0062] 7 is a schematic diagram for explaining the reverse direction cleaning, and FIG. 8 is a diagram showing a flow of the cleaning direction switching control by the control device 50. When the cleaning target C is cleaned using a circulation line, the chemical agent is circulated in the forward direction D1 relative to the cleaning target C, so as shown in FIG. 7, a scale X is provided downstream of the forward direction D1. Ｆ Therefore, the cleaning system 1 cleans the cleaning target C by circulating the chemical agent in the forward direction D1, and then uses the reverse cleaning line to circulate the chemical agent in the reverse direction D2, thereby removing the scale X. Ｆ In addition, by flowing the agent in the reverse direction D2, the scale X can be removed upstream of the forward direction D1. Ｒ In this case, the cleaning system 1 uses the circulation line again to circulate the agent in the forward direction D1 to the area to be cleaned C, thereby removing the scale X Ｒ can be removed.

[0063] As shown in FIG. 8 , the control device 50 sends a signal to valves V4 and V5 to open them (step S31). At this time, valves V6 and V7 are closed. This allows the cleaning system 1 to circulate the chemical in the forward direction D1 to the cleaning target C using the circulation line. The control device 50 calculates the dissolution rate of the scale based on the analysis results of the analyzer 40 and determines whether the dissolution rate (Δy / Δx) is equal to or less than a set value (step S32). In step S32, the set value of the dissolution rate (Δy / Δx) can be, for example, 1% / h.

[0064] If the control device 50 determines that the dissolution rate (Δy / Δx) is equal to or less than the set value (step S32: Yes), it sends a signal to close valves V4 and V5 and a signal to open valves V6 and V7 (step S34). This allows the cleaning system 1 to circulate the chemical agent in the reverse direction D2 to the cleaning target C using the reverse cleaning line.

[0065] If the control device 50 determines that the dissolution rate (Δy / Δx) is not below the set value (step S32: No), it causes the timer to measure the elapsed time, and if it determines that 0.5 hours have elapsed (step S33: Yes), it performs the processing of step S32 again, and repeats the processing of steps S32 and S33 until it determines that the dissolution rate (Δy / Δx) is below the set value.

[0066] After performing the process of step S34, the control device 50 calculates the dissolution rate of the scale based on the analysis result of the analyzer 40, and determines whether the dissolution rate (Δy / Δx) is equal to or less than a set value (step S35). In step S35, the set value of the dissolution rate (Δy / Δx) can be, for example, 1% / h.

[0067] If the control device 50 determines that the dissolution rate (Δy / Δx) is equal to or less than the set value (step S35: Yes), it calculates the scale elution rate based on the analysis results of the analyzer 40 and determines whether the scale elution rate is equal to or greater than the set value (step S37). In step S37, the set value for the scale elution rate can be, for example, 95%. If the control device 50 determines that the scale elution rate is equal to or greater than the set value (step S37: Yes), it ends the process and completes cleaning.

[0068] If the control device 50 determines that the dissolution rate (Δy / Δx) is not below the set value (step S35: No), it causes the timer to measure the elapsed time, and if it determines that 0.5 hours have elapsed (step S36: Yes), it performs the processing of step S35 again, and repeats the processing of steps S35 and S36 until it determines that the dissolution rate (Δy / Δx) is below the set value.

[0069] If the control device 50 determines in step S37 that the scale elution rate is less than the set value (step S37: No), it performs the process of step S31 and then performs the processes of steps S31 to S37 again.

[0070] Next, a method for calculating the scale dissolution rate and scale elution rate will be described. FIG. 9 is a diagram showing the relationship between elapsed time and scale elution rate. The elapsed time shown in FIG. 9 means the time elapsed from the start of cleaning. The analyzer 40 calculates the amount of eluted scale using the following formula (1). Here, the concentration of the main scale component is, for example, the silica concentration. The analyzer 40 can collect waste liquid sent to the branch pipe LB and measure the silica concentration using, for example, the molybdenum yellow method. Amount of eluted scale = Concentration of the main scale component × Volume of the part to be cleaned C ... (1)

[0071] The analysis device 40 calculates the estimated amount of scale using the following formula (2). Here, the estimated amount of scale means the amount of scale that is estimated to have accumulated on the part to be cleaned C. The estimated amount of scale can be set in advance by conducting a preliminary survey of the part to be cleaned C. Note that the estimated amount of scale is not limited to the following formula (2), and may be calculated using other formulas or methods. Estimated amount of scale = area of ​​inner surface of part to be cleaned C × estimated thickness of scale × density of scale (2)

[0072] The analyzer 40 calculates the scale elution rate based on the calculated estimated scale amount and eluted scale amount using the following formula (3): Scale elution rate [%] = eluted scale amount / estimated scale amount × 100 (3)

[0073] The analyzer 40 calculates the scale elution rate versus elapsed time, and can obtain data such as that shown in Fig. 9. In Fig. 9, time t1 is the time when the process of step S34, i.e., the reverse cleaning process, starts, and time t2 is the time when the process shown in Fig. 8 ends.

[0074] The analyzer 40 calculates the scale dissolution rate based on the calculated scale dissolution rate using the following formula (4): Scale dissolution rate = Δy (change in scale dissolution rate) / Δx (change in elapsed time) (4)

[0075] As described above, the cleaning system 1 includes the chemical solution supply pipe LS, the chemical addition device 30, the first pipe L1, the return pipe LR, the circulation pump P1, the analyzer 40, and the control device 50. The control device 50 predicts the outermost surface components of the scale based on the analysis results of the analyzer 40, determines one chemical suitable for the outermost surface component from among at least three chemicals, and controls the chemical addition device 30 to supply the determined chemical.

[0076] With this configuration, the cleaning system 1 can clean scale adhering to or deposited on the cleaning target part C using an agent that is optimal for the outermost surface components of the scale. Therefore, the cleaning system 1 can sufficiently remove the scale.

[0077] The three types of chemicals can be a first basic chemical, a mixed chemical of a second basic chemical, a chelating agent, and a dispersant, and an acidic chemical. This allows the cleaning system 1 to clean the scale using the optimal chemical for each of the initial layer X1, which is primarily composed of iron oxide; the intermediate layer X2, which is primarily composed of silica and impurities (calcium, aluminum, iron, etc.); and the growth layer X3, which is primarily composed of amorphous silica. Therefore, the cleaning system 1 can sufficiently remove scale.

[0078] The control device 50 can predict the outermost surface components of scale based on the iron ion concentration detected by the analysis device 40. As a result, the cleaning system 1 can predict the outermost surface components of scale while keeping the geothermal power plant in a closed system state without opening or disassembling it, determine one chemical suitable for the outermost surface components from among at least three chemicals, and supply the chemical using the chemical addition device 30. Therefore, the cleaning system 1 can easily remove scale.

[0079] The cleaning system 1 includes a heater 4 and a temperature measuring device 5, and the control device 50 can control the heater 4 based on the temperature detected by the temperature measuring device 5. With this configuration, the cleaning system 1 can supply heated chemicals to the area to be cleaned C, thereby improving the cleaning effect of the chemicals.

[0080] The control device 50 can control the heater 4 so that the temperature detected by the temperature measuring device 5 is between 40° C. and 100° C. This allows the cleaning system 1 to supply the cleaning target area C with heated chemicals in a temperature range that enhances the cleaning effect of the first basic chemical, the mixed chemical, and the acidic chemical, thereby further enhancing the cleaning effect of the chemicals.

[0081] The first basic chemical and the second basic chemical may be sodium hydroxide, potassium hydroxide, or an ammonium salt, thereby enabling the cleaning system 1 to clean the scale growth layer X3 and the intermediate layer X2 using chemicals that are more optimal for each of them.

[0082] The acidic agent may be sulfuric acid, hydrochloric acid, acetic acid, or citric acid, which allows the cleaning system 1 to clean the initial scale layer X1 using an agent that is more optimal for the initial scale layer X1.

[0083] The chelating agent contained in the mixed chemical may be ethylenediaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylenediaminetriacetic acid, or diethylenetriaminepentaacetic acid, which allows the cleaning system 1 to clean the intermediate layer X2 of scale using a chemical that is more optimal for the scale.

[0084] The dispersant contained in the mixed chemical may be sodium polyacrylate, maleic acid, or diallyldimethylammonium chloride / acrylamide copolymer, which allows the cleaning system 1 to clean the intermediate layer X2 of scale using a chemical that is more optimal for the scale.

[0085] The chemical addition device 30 can have three chemical tanks 31a, 31b, and 31c, a second pipe L2, a chemical injection pump P2, a water tank 32, a water supply pump P3, a drain pipe LW, and a wastewater tank 33. With this configuration, the cleaning system 1 can flush out any chemicals remaining in the second pipe L2 before switching the type of chemical supplied by the chemical addition device 30. Therefore, the cleaning system 1 can prevent the cleaning effect of the determined chemical from being reduced due to contamination of the chemical determined by the control device 50 with other chemicals.

[0086] The geothermal power plant 100 includes a gas-liquid separator 103 that separates geothermal water and geothermal steam from geothermal fluid spouted from a production well, a cleaning target C located downstream of the gas-liquid separator 103, and a cleaning system 1. With this configuration, the geothermal power plant 100 can clean scale that has adhered to or accumulated on the cleaning target C using an agent that is optimal for the outermost surface components of the scale. Therefore, the geothermal power plant 100 can sufficiently remove the scale.

[0087] Although the embodiments have been described above, they are presented as examples and do not limit the present invention. The cleaning system 1 can be applied to any geothermal power plant, not just the geothermal power plant 100. The embodiments can be embodied in various other forms, and various combinations, omissions, substitutions, or modifications can be made without departing from the spirit of the invention. The 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 set forth in the claims.

[0088] The present embodiment disclosed above can be specified, for example, by the following aspects: [1] A cleaning system for removing scale adhering to a part to be cleaned in a geothermal power plant including a gas-liquid separator that separates geothermal water and geothermal steam from geothermal fluid spouted from a production well and a part to be cleaned located downstream of the gas-liquid separator, the system comprising: a chemical supply pipe connected to one end upstream of the part to be cleaned and having a chemical injection port; a chemical addition device that injects a chemical into the chemical injection port; a first pipe connecting the chemical injection port and the chemical addition device and having a chemical recovery port; a return pipe connecting the other end downstream of the part to be cleaned and the chemical recovery port; a circulation pump provided midway through the first pipe between the chemical injection port and the chemical recovery port and that circulates the chemical; an analyzer connected to a branch pipe branching off from the first pipe and that analyzes changes over time in components of waste liquid sent to the branch pipe; and a control device. The cleaning system includes a control device that predicts the outermost surface components of the scale based on the analysis results of the analyzer, determines one chemical suitable for the outermost surface components from among at least three chemicals, and controls the chemical adding device to supply the determined chemical. [2] The cleaning system described in [1], wherein the three chemicals are a first basic chemical, a mixed chemical of a second basic chemical, a chelating agent, and a dispersant, and an acidic chemical. [3] The cleaning system described in [1] or [2], wherein the control device predicts the outermost surface components of the scale based on the iron ion concentration detected by the analyzer. [4] The cleaning system described in any one of [1] to [3], further including: a heater provided midway along the first piping between the circulation pump and the chemical injection port; and a temperature measuring device connected to the first piping between the heater and the chemical injection port; and the control device controls the heater based on the temperature detected by the temperature measuring device. [5] The cleaning system described in [4], wherein the control device controls the heater so that the temperature detected by the temperature measuring device is 40°C or higher and 100°C or lower. [6] The cleaning system according to [2], wherein the first basic agent and the second basic agent include sodium hydroxide, potassium hydroxide, or ammonium salts.[7] The cleaning system according to [2], wherein the acidic chemical includes sulfuric acid, hydrochloric acid, acetic acid, or citric acid. [8] The cleaning system according to [2], wherein the chelating agent included in the mixed chemical includes ethylenediaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylenediaminetriacetic acid, or diethylenetriaminepentaacetic acid. [9] The cleaning system according to [2], wherein the dispersant included in the mixed chemical includes sodium polyacrylate, maleic acid, or diallyldimethylammonium chloride / acrylamide copolymer.

[10] The cleaning system described in any one of [1] to [9], wherein the chemical addition device has at least three chemical tanks for storing chemicals, a second pipe connecting the first pipe to each of the chemical tanks, a chemical injection pump for discharging the chemical stored in each of the chemical tanks toward the chemical injection port, a water tank arranged upstream of the chemical tanks for storing water, a water supply pump for introducing the water into the second pipe, a drainage pipe branching from the second pipe downstream of the chemical injection pump, and a wastewater tank connected to the drainage pipe for storing the water that has passed through the second pipe.

[0089] This application claims priority based on Japanese Patent Application No. 2024-99623, filed with the Japan Patent Office on June 20, 2024, and incorporates the entire contents of said application by reference.

[0090] REFERENCE SIGNS LIST 1 Cleaning system 2 Chemical injection port 3 Chemical recovery port 4 Heater 5 Temperature measuring device 30 Chemical addition device 40 Analytical device 50 Control device 100 Geothermal power plant 102 Production well 103 Gas-liquid separator 104 Reinjection well C Area to be cleaned L1 First pipe L2 Second pipe LS Chemical supply pipe LB Branch pipe LR Return pipe P1 Circulation pump

Claims

1. A cleaning system for removing scale adhering to the part to be cleaned in a geothermal power plant having a gas-liquid separator that separates geothermal water and geothermal steam from geothermal fluid spouted from a production well and a part to be cleaned located downstream of the gas-liquid separator, the system comprising: a chemical supply pipe connected to one end upstream of the part to be cleaned and having a chemical injection port; a chemical addition device that injects chemicals into the chemical injection port; a first pipe that connects the chemical injection port and the chemical addition device and has a chemical recovery port; a return pipe that connects the other end downstream of the part to be cleaned and the chemical recovery port; a circulation pump that is located midway through the first pipe between the chemical injection port and the chemical recovery port and circulates the chemical; an analyzer connected to a branch pipe branching off from the first pipe and that analyzes changes over time in the components of waste liquid sent to the branch pipe; and a control device. The control device predicts the outermost surface components of the scale based on the analysis results of the analysis device, determines one chemical suitable for the outermost surface components from among at least three chemicals, and controls the chemical addition device to supply the determined chemical.

2. The cleaning system according to claim 1, wherein the three types of chemicals are a first basic chemical, a mixed chemical of a second basic chemical, a chelating agent and a dispersing agent, and an acidic chemical.

3. A cleaning system according to claim 2, wherein the control device predicts the outermost surface components of the scale based on the iron ion concentration detected by the analysis device.

4. A cleaning system as described in claim 3, comprising: a heater provided midway along the first piping between the circulation pump and the chemical injection port; and a temperature measuring instrument connected to the first piping between the heater and the chemical injection port, wherein the control device controls the heater based on the temperature detected by the temperature measuring instrument.

5. A cleaning system according to claim 4, wherein the control device controls the heater so that the temperature detected by the temperature measuring device is between 40°C and 100°C.

6. The cleaning system of claim 2, wherein the first basic agent and the second basic agent include sodium hydroxide, potassium hydroxide, or ammonium salts.

7. The cleaning system of claim 2, wherein the acidic agent comprises sulfuric acid, hydrochloric acid, acetic acid, or citric acid.

8. The cleaning system of claim 2, wherein the chelating agent contained in the mixed chemical comprises ethylenediaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylenediaminetriacetic acid, or diethylenetriaminepentaacetic acid.

9. The cleaning system of claim 2, wherein the dispersant contained in the mixed agent comprises sodium polyacrylate, maleic acid, or diallyldimethylammonium chloride / acrylamide copolymer.

10. A cleaning system as described in any one of claims 1 to 9, wherein the chemical addition device comprises at least three chemical tanks for storing chemicals, a second pipe connecting the first pipe to each of the chemical tanks, a chemical injection pump for discharging the chemicals stored in each of the chemical tanks toward the chemical injection port, a water tank arranged upstream of the chemical tanks for storing water, a water supply pump for introducing the water into the second pipe, a drainage pipe branching off from the second pipe downstream of the chemical injection pump, and a wastewater tank connected to the drainage pipe for storing the water that has passed through the second pipe.

Images