Non-condensable gas reduction system

Abstract

This disclosure provides a non-condensable gas reduction system for efficiently processing non-condensable gases in geothermal power plants. [Solution] A non-condensable gas reduction system for a geothermal power plant, which returns non-condensable gas that remains after cooling in a first gas contained in geothermal fluid that springs from a production well to a reinjection well, comprising: a first pump that pressurizes a first liquid sent to the reinjection well; an ejector driven by the first liquid that induces the non-condensable gas and discharges a second liquid which is a mixture of the first liquid and the non-condensable gas; a first tank which temporarily stores the second liquid discharged from the ejector and discharges a third liquid to the reinjection well; a chemical injection unit for injecting a chemical into the first tank; and a reuse unit which returns the third liquid discharged from the first tank to the first tank.

Description

Technical Field

[0001] The present disclosure relates to a non-condensable gas reduction system.

Background Art

[0002] Patent Document 1 discloses a method for disposing of non-condensable gas generated in a geothermal power generation facility, in which the non-condensable gas generated in a condenser provided downstream of a steam turbine is injected into a reduction well for hot water reduction, and is reduced underground together with the reduced hot water.

[0003] Patent Document 2 discloses a geothermal power generation plant including a reduction water flow path for transporting reduction water to a reduction well, a gas extraction device for extracting gas from a condenser, and a gas flow path for supplying the gas extracted from the condenser to the reduction water flow path and mixing it into the reduction water.

[0004] Patent Document 3 discloses a non-condensable gas reduction system used in a so-called binary geothermal power plant, which sends non-condensable gas remaining uncondensed in an evaporator to a reduction well.

[0005] Patent Document 4 discloses a non-condensable gas reduction system used in a so-called flash geothermal power plant, which sends non-condensable gas remaining uncondensed in a condenser to a reduction well. Each of Patent Document 3 and Patent Document 4 discloses that the non-condensable gas reduction system includes an ejector that attracts non-condensable gas and discharges a liquid mixed with the pressurized liquid, and returns the liquid discharged by the ejector to the reduction well, thereby returning the non-condensable gas to the reduction well.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] As disclosed in Patent Documents 1 and 2, it has been proposed that non-condensable gases such as carbon dioxide or hydrogen sulfide be reduced in a reinjection well along with reinjecting hot water in geothermal power generation. For example, when reducing non-condensable gases in a reinjection well, there is a need for efficient reduction of the gases into the reinjection well. For example, in the non-condensable gas reduction systems disclosed in Patent Documents 3 and 4, respectively, it has been proposed to spray alkali to dissolve undissolved non-condensable gases that cannot be completely dissolved by the ejector and result in insufficient dissolution. However, Patent Documents 3 and 4 do not specify detailed methods or controls. If the amount of alkali is not adjusted, excess alkali will be produced, resulting in high costs, so a more efficient processing method is needed.

[0008] This disclosure provides a non-condensable gas reduction system for efficiently processing non-condensable gases in geothermal power plants. [Means for solving the problem]

[0009] This disclosure provides a non-condensable gas reduction system for a geothermal power plant, which returns non-condensable gas, which remains uncondensed when cooled in a first gas contained in geothermal fluid flowing from a production well, to a reinjection well, comprising: a first pump for pressurizing a first liquid sent to the reinjection well; an ejector driven by the first liquid for inducing the non-condensable gas and for discharging a second liquid which is a mixture of the first liquid and the non-condensable gas; a first tank for temporarily storing the second liquid discharged from the ejector and for discharging a third liquid to the reinjection well; a chemical injection unit for injecting a chemical into the first tank; and a reuse unit for returning the third liquid discharged from the first tank to the first tank. [Effects of the Invention]

[0010] The non-condensable gas reduction system disclosed herein can efficiently process non-condensable gases in geothermal power plants. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram of the configuration of a geothermal power plant equipped with a non-condensable gas reduction system according to the first embodiment. [Figure 2] Figure 2 is a schematic diagram showing the configuration of the ejector in the non-condensable gas reduction system according to the first embodiment. [Figure 3] Figure 3 is a schematic diagram showing the configuration of the dissolution determination unit included in the non-condensable gas reduction system according to the first embodiment. [Figure 4] Figure 4 illustrates the dissolution determination process in the non-condensable gas reduction system according to the first embodiment. [Figure 5] Figure 5 is a flowchart illustrating the processing of the non-condensable gas reduction system according to the first embodiment. [Figure 6] Figure 6 is a diagram illustrating the processing of the non-condensable gas reduction system according to the first embodiment. [Figure 7] Figure 7 is a schematic diagram showing the configuration of a geothermal power plant equipped with a non-condensable gas reduction system according to the second embodiment. [Modes for carrying out the invention]

[0012] The embodiments will be described below with reference to the attached drawings. However, this disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the claims as indicated by the claims.

[0013] In addition, regarding the descriptions and drawings of each embodiment, components having substantially the same or corresponding functional configurations may be denoted by the same reference numerals, thereby omitting redundant explanations. Furthermore, for ease of understanding, the scale of each part in the drawings may differ from that of the actual parts.

[0014] A non-condensable gas reduction system according to an embodiment of this disclosure will now be described. The non-condensable gas reduction system according to an embodiment of this disclosure is a system used in a geothermal power plant to return non-condensable gas, which remains uncondensed when cooled in a first gas contained in the geothermal fluid that springs from a production well, back to an injection well. The non-condensable gas reduction system according to an embodiment of this disclosure includes a first pump that pressurizes a first liquid sent to an injection well, and an ejector driven by the first liquid that induces non-condensable gas and discharges a second liquid which is a mixture of the first liquid and the non-condensable gas. The non-condensable gas reduction system according to an embodiment of this disclosure also includes a first tank in which the second liquid discharged from the ejector is temporarily stored and a third liquid is discharged to the injection well, and a chemical injection unit that injects a chemical into the first tank. Furthermore, the non-condensable gas reduction system according to an embodiment of this disclosure includes a reuse unit that returns the third liquid discharged from the first tank back to the first tank.

[0015] From another perspective, the non-condensable gas reduction system according to an embodiment of the present disclosure will be described. The non-condensable gas reduction system according to an embodiment of the present disclosure is a non-condensable gas reduction system that returns, in a geothermal power plant, non-condensable gas remaining without being condensed when cooled in a first gas contained in geothermal fluid gushing out from a production well to a reinjection well. The non-condensable gas reduction system according to an embodiment of the present disclosure includes a first pump that pressurizes a first liquid sent to the reinjection well, and an ejector that is driven by the first liquid, attracts non-condensable gas, and discharges a second liquid in which the first liquid and the non-condensable gas are mixed. Further, the non-condensable gas reduction system according to an embodiment of the present disclosure includes a first tank in which the second liquid discharged from the ejector is temporarily stored and a third liquid is discharged to the reinjection well, and a chemical injection unit that injects a chemical into the first tank. Also, the non-condensable gas reduction system according to an embodiment of the present disclosure includes a sensor that measures the liquid property of the liquid stored in the first tank, and a control device that controls the chemical injection unit based on the detection result of the sensor.

[0016] ≪First Embodiment≫ The non-condensable gas reduction system according to the first embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the configuration of a geothermal power plant 1 including a non-condensable gas reduction system 50 which is an example of the non-condensable gas reduction system according to the first embodiment.

[0017] The geothermal power plant 1 includes a gas-liquid separator 10, a power generation unit 20, a condenser 30, a cooling unit 40, a non-condensable gas reduction system 50, and a control unit 60. The geothermal power plant 1 is a geothermal power plant using a so-called flash-type geothermal power generation method. Also, the geothermal power plant 1 includes valves 81 and 82, and a pump 91.

[0018] [Gas-Liquid Separator 10] The gas-liquid separator 10 separates the geothermal fluid GF ejected from the production well PWL into steam ST and hot water HW. The geothermal fluid GF ejected from the production well PWL is either allowed to flow or blocked by the valve 81. The steam ST discharged from the gas-liquid separator 10 is sent to the power generation unit 20. The hot water HW discharged from the gas-liquid separator 10 is discharged into the reinjection well RWL. The pressure gauge 71, described later, measures the pressure of the hot water HW.

[0019] Here, steam ST is not pure water vapor, but includes gases emitted from the production well PWL, such as carbon dioxide and hydrogen sulfide.

[0020] [Power generation unit 20] The power generation unit 20 generates electricity using steam ST. The power generation unit 20 comprises a turbine 21 and a generator 22. The turbine 21 is rotated by the steam ST. More specifically, the turbine 21 rotates due to the pressure difference between the pressure from the steam ST and the pressure reduced by the condensation of water vapor contained in the steam ST in the condenser 30. The generator 22 is connected to the turbine 21. When the turbine 21 rotates, the rotating shaft of the generator 22 rotates and generates electricity. The electricity generated by the generator 22 is supplied to the outside.

[0021] [Condenser 30] The condenser 30 cools the steam ST discharged from the turbine 21 with coolant CW supplied from the cooling unit 40, more specifically, coolant CW1. The condenser 30 is a so-called surface contact condenser. The condenser 30 performs heat exchange between the coolant CW1 and the steam ST. By performing heat exchange between the coolant CW1 and the steam ST, the steam ST is cooled. As the steam ST is cooled in the condenser 30, it condenses into water. In the surface contact condenser 30, for example, the coolant CW1 cools the steam ST by flowing inside the piping of the heat exchanger, and the coolant CW1 does not come into direct contact with the steam ST.

[0022] Non-condensable gases (NCGs) such as carbon dioxide and hydrogen sulfide contained in the steam ST accumulate at the top of the condenser 30. When non-condensable gases NCG accumulate, the pressure in the condenser 30 increases. When the pressure in the condenser 30 increases, the driving force for rotating the turbine 21 decreases. When the driving force for rotating the turbine 21 decreases, the power generation efficiency of the power generation unit 20 decreases. Therefore, it is desirable to discharge the non-condensable gases NCG accumulated in the condenser 30 from the condenser 30.

[0023] In geothermal power plant 1, the non-condensable gas (NCG) that accumulates in the condenser 30 is drawn in by the non-condensable gas reduction system 50 and discharged into the reinjection well (RWL).

[0024] [Cooling section 40] The cooling unit 40 supplies coolant CW to cool the steam ST in the condenser 30. The cooling unit 40 is, for example, a cooling tower. The coolant CW1 cooled in the cooling unit 40 is sent to the condenser 30 by the pump 91. In the condenser 30, the coolant CW2 whose temperature has risen due to heat exchange with the steam ST returns to the cooling unit 40 to be cooled.

[0025] [Non-condensable gas reduction system 50] The non-condensable gas reduction system 50 induces and discharges non-condensable gas NCG from the condenser 30. The non-condensable gas reduction system 50 includes an ejector 54, a dissolution determination unit 57, a control device 58, pressure gauges 71, 72, and 73, a valve 83, and a pump 55. The ejector 54 is driven by coolant CW, more specifically by coolant CWa, which is a part of coolant CW1. Coolant CWa is pumped by the pump 55. The ejector 54 discharges a mixture MW, which is a mixture of non-condensable gas NCG and coolant CWa.

[0026] (Ejector 54) The structure of the ejector 54 will now be described. Figure 2 is a schematic diagram of the configuration of the ejector 54 provided in the noncondensable gas reduction system 50, which is an example of a noncondensable gas reduction system according to the first embodiment.

[0027] The ejector 54 comprises an induction section 51, a drive nozzle 52, and an expansion section 53. The induction section 51 has an induction port 51a. Non-condensable gas NCG is drawn in from the induction port 51a. The drive nozzle 52 is inserted into the induction section 51. Pressurized coolant CWa is supplied to the drive port 52a of the drive nozzle 52 by the pump 55. As the high-speed coolant CWa is discharged from the tip of the drive nozzle 52, a pressure drop occurs inside the ejector, the induction section 51 becomes a vacuum space, and non-condensable gas NCG is drawn in.

[0028] The ejector 54 mixes the non-condensable gas NCG and the coolant CWa and discharges the mixed liquid MW through the expanded pipe section 53.

[0029] In ejector 54, the non-condensable gas NCG and coolant CWa are mixed and discharged, and the resulting mixture MW is sent to the reinjection well RWL.

[0030] The ejector 54 is installed on the ground. Installing the ejector 54 on the ground facilitates maintenance of the ejector 54. Multiple ejectors may also be installed. Installing multiple ejectors allows maintenance to be performed without shutting down the system.

[0031] (Dissolution determination section 57) The dissolution determination unit 57 determines whether the non-condensable gas NCG is dissolved in the coolant CWa in the mixed liquid MW. The dissolution determination unit 57 also promotes the dissolution of the non-condensable gas NCG so that it dissolves in the coolant CWa.

[0032] The details of the dissolution determination unit 57 will now be explained. Figure 3 is a schematic diagram of the configuration of the dissolution determination unit 57 included in the noncondensable gas reduction system 50, which is an example of a noncondensable gas reduction system according to the first embodiment.

[0033] The dissolution determination unit 57 includes a dissolution determination tank 57a, a chemical tank 57b, a pump 57c, a valve 57d, a pump 57e, and a valve 57f. The dissolution determination unit 57 also includes a flow meter 57m, a flow meter 57n, a pH meter 57p, and a level meter 57q.

[0034] The control device 58 controls pump 57c, valve 57d, pump 57e, and valve 57f, respectively. The control device 58 also acquires measurement results from flow meter 57m, flow meter 57n, pH meter 57p, and level meter 57q, respectively.

[0035] The dissolution determination tank 57a is located downstream of the ejector 54. The dissolution determination tank 57a is equipped with a level gauge 57q. In the dissolution determination tank 57a, liquid Lq accumulates at the bottom and gas Gs accumulates at the top. The level gauge 57q measures the liquid level of liquid Lq stored in the dissolution determination tank 57a. The result (liquid level) measured by the level gauge 57q is output to the control device 58. The control device 58 performs a dissolution determination of the non-condensable gas NCG.

[0036] In the non-condensable gas reduction system according to the embodiments of this disclosure, the determination of the dissolution of non-condensable gas in the mixed liquid discharged by the ejector will be explained. Figure 4 is a diagram illustrating the dissolution determination process in a non-condensable gas reduction system 50, which is an example of a non-condensable gas reduction system according to the first embodiment.

[0037] As shown in Figure 4(A), if the non-condensable gas NCG is completely dissolved in the mixed liquid MW, the inside of the dissolution determination tank 57a will be filled with the mixed liquid MW. On the other hand, as shown in Figure 4(B), if the non-condensable gas NCG is not completely dissolved in the mixed liquid MW, the non-condensable gas NCG will accumulate at the top of the dissolution determination tank 57a. Therefore, when the non-condensable gas NCG accumulates, the liquid level measured by the level gauge 57q will decrease by a height of ΔL. Thus, by measuring the level of the mixed liquid MW in the dissolution determination tank 57a using the level gauge 57q, it is possible to determine whether the non-condensable gas NCG is dissolved in the mixed liquid MW.

[0038] The chemical tank 57b stores the chemical. The chemical is, for example, an alkaline agent. The non-condensable gas reduction system 50 is equipped with a pump 57c, a valve 57d, and a flow meter 57m in the flow path 57A from the chemical tank 57b to the dissolution determination tank 57a. The pump 57c, valve 57d, and flow meter 57m installed in the flow path 57A are collectively called the chemical injection section 57i.

[0039] Pump 57c delivers the drug from the drug tank 57b to the dissolution determination tank 57a. Pump 57c is, for example, an axial flow pump. Pump 57c is controlled by the control device 58. Valve 57d adjusts the flow rate of the drug flowing through the flow path 57A. Flow meter 57m measures the flow rate of the drug flowing through the flow path 57A. Flow meter 57m is, for example, an electromagnetic flow meter. When adjusting the flow rate of the drug flowing through the flow path 57A, the opening of valve 57d may be adjusted based on the result measured by the flow meter 57m.

[0040] The chemical agent sent from the flow path 57A is sprayed into the dissolution determination tank 57a from a nozzle provided in the dissolution determination tank 57a.

[0041] Furthermore, the chemical supplied from the chemical injection unit 57i is not limited to an alkaline agent; any desired chemical may be injected. Also, the configuration of the chemical injection unit 57i is not limited to the example described above and may be changed as appropriate. For example, the flow rate of the chemical flowing through the channel 57A may be adjusted by adjusting the rotation speed of the pump 57c.

[0042] The non-condensable gas reduction system 50 includes a pump 57e, a valve 57f, and a flow meter 57n in a channel 57C that returns the mixed liquid MWa from the discharge channel 57B to the dissolution determination tank 57a. The pump 57e, valve 57f, and flow meter 57n provided in channel 57C are collectively referred to as the reuse section 57r.

[0043] Pump 57e sends the mixed liquid MWa discharged from the dissolution determination tank 57a back to the dissolution determination tank 57a. Pump 57e is, for example, an axial flow pump. Pump 57e is controlled by a control device 58. Valve 57f adjusts the flow rate of the mixed liquid MWa flowing through the flow path 57C. Flow meter 57n measures the flow rate of the mixed liquid MWa flowing through the flow path 57C. Flow meter 57n is, for example, an electromagnetic flow meter. When adjusting the flow rate of the mixed liquid MWa flowing through the flow path 57C, the opening of valve 57f may be adjusted based on the result measured by the flow meter 57n.

[0044] The mixed liquid MWa sent from the flow path 57C is sprayed into the inside of the dissolution determination tank 57a from a nozzle provided in the dissolution determination tank 57a.

[0045] The configuration of the reuse section 57r is not limited to the example described above and may be changed as appropriate. For example, the flow rate of the mixed liquid MWa flowing through the flow path 57C may be adjusted by adjusting the rotation speed of the pump 57e.

[0046] (Control device 58) The control device 58 is primarily composed of a computer, including, for example, a processor, memory or other storage devices, auxiliary storage devices, and an external input / output interface device. The processor is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an MPU (Micro Processing Unit). The control device 58 may also be, for example, a programmable logic controller (PLC).

[0047] During power generation, if the pressure P1 at the pressure gauge 71 becomes higher than the pressure P2 at the pressure gauge 73, the control device 58 controls the valve 83 to close in order to prevent hot water HW from flowing into the condenser 30. The valve 83 is located in the flow path of non-condensable gas NCG between the condenser 30 and the ejector 54. The pressure P1 at the pressure gauge 71 is the pressure of the hot water HW, and the pressure P2 at the pressure gauge 73 is the discharge pressure of the pump 55.

[0048] The control device 58 may also monitor the pressure of the non-condensable gas NCG using the pressure gauge 72.

[0049] The process performed by the control device 58 will now be described. The control device 58 controls the dissolution determination unit 57. Figure 5 is a flowchart illustrating the process of a non-condensable gas reduction system 50, which is an example of a non-condensable gas reduction system according to the first embodiment. In Figure 5, valve 57d is shown as valve V1, valve 57f as valve V2, pump 57c as pump PM1, and pump 57e as pump PM2.

[0050] (Step S1) The control device 58 acquires the liquid level of the dissolution determination tank 57a. The control device 58 controls the level gauge 57q to measure the liquid level. Then, the control device 58 acquires the liquid level measured by the level gauge 57q.

[0051] (Step S2) Next, the control device 58 determines whether the dissolution determination tank 57a is full based on the liquid level obtained in step S1. For example, if the liquid level obtained in step S1 is higher than a predetermined threshold liquid level, the control device 58 determines that the dissolution determination tank 57a is full. If the liquid level obtained in step S1 is equal to or lower than a predetermined threshold liquid level, the control device 58 determines that the dissolution determination tank 57a is not full.

[0052] If the dissolution determination tank 57a is full (YES in step S2), the control device 58 proceeds to step S9. If the dissolution determination tank 57a is not full (NO in step S2), the control device 58 proceeds to step S3.

[0053] (Step S3) Next, the control device 58 acquires the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a. The control device 58 controls the pH meter 57p to measure the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a. Then, the control device 58 acquires the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a as measured by the pH meter 57p.

[0054] (Steps S4 and S5) The control device 58 compares the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a, acquired in step S3, with a threshold value.

[0055] If the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3 is less than 4 (YES in step S4, liquid Lq is acidic), the control device 58 proceeds to step S6. If the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3 is 4 or higher (NO in step S4), the control device 58 proceeds to step S5.

[0056] If the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3 is 4 or greater and less than 7 (YES in step S5, liquid Lq is neutral), the control device 58 proceeds to step S7. If the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3 is 7 or greater (NO in step S5, liquid Lq is alkaline), the control device 58 proceeds to step S8.

[0057] (Step S6) If the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3 is less than 4 (YES in step S4, liquid Lq is acidic), the control device 58 controls the system to neutralize the liquid Lq. In order to neutralize the liquid Lq, the control device 58 controls the system to spray the chemical agent into 57a using the chemical injection unit 57i.

[0058] Specifically, the control device 58 controls valve V1 (valve 57d) and valve V2 (valve 57f) respectively to fully open valve V1 (valve 57d) and fully close valve V2 (valve 57f). Then, the control device 58 controls pump PM1 (pump 57c) and pump PM2 (pump 57e) respectively to operate pump PM1 (pump 57c) and stop pump PM2 (pump 57e) (off).

[0059] If the liquid Lq in the dissolution determination tank 57a is acidic, it is considered that the amount of chemical supplied from the chemical injection unit 57i is insufficient. Therefore, the non-condensable gas reduction system 50 controls the dissolution determination unit 57 to supply as much chemical as possible from the chemical injection unit 57i.

[0060] Then, the control device 58 proceeds to step S9.

[0061] (Step S7) If the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3 is 4 or greater and less than 7 (YES in step S5, liquid Lq is near neutral), the control device 58 controls the system to bring the pH of liquid Lq closer to 7. In order to bring the pH of liquid Lq closer to 7, the control device 58 uses the chemical injection unit 57i to spray the chemical into 57a and controls the system to reuse the discharged mixed liquid MWa.

[0062] Specifically, the control device 58 controls valve V1 (valve 57d) and valve V2 (valve 57f) to adjust their opening degrees based on the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3. The control device 58 then controls pump PM1 (pump 57c) and pump PM2 (pump 57e) to activate (turn ON) pump PM1 (pump 57c) and pump PM2 (pump 57e) respectively.

[0063] If the liquid Lq in the dissolution determination tank 57a is near neutral, the non-condensable gas reduction system 50 adjusts the amount of chemical supplied from the chemical injection unit 57i to an appropriate amount. The non-condensable gas reduction system 50 also adjusts the amount of mixed liquid MWa returned from the reuse unit 57r to the dissolution determination tank 57a to an appropriate amount.

[0064] Then, the control device 58 proceeds to step S9.

[0065] (Step S8) If the pH (hydrogen ion concentration) of the liquid Lq in the dissolution determination tank 57a obtained in step S3 is 7 or higher (NO and liquid Lq in step S5 are alkaline), the control device 58 controls the system to reuse the discharged mixed liquid MWa.

[0066] Specifically, the control device 58 controls valve V1 (valve 57d) and valve V2 (valve 57f) respectively to fully close valve V1 (valve 57d) and fully open valve V2 (valve 57f). Then, the control device 58 controls pump PM1 (pump 57c) and pump PM2 (pump 57e) respectively to stop pump PM1 (pump 57c) and start pump PM2 (pump 57e).

[0067] If the liquid Lq in the dissolution determination tank 57a is alkaline, it is considered that the amount of chemical supplied from the chemical injection unit 57i is excessive. Therefore, the non-condensable gas reduction system 50 controls the dissolution determination unit 57 to stop supplying chemical from the chemical injection unit 57i. In addition, the non-condensable gas reduction system 50 controls the dissolution determination unit 57 to supply as much of the mixed liquid MWa returned from the reuse unit 57r as possible in order to reuse the excess chemical.

[0068] Then, the control device 58 proceeds to step S9.

[0069] (Step S9) The control device 58 determines whether a power generation stop command has been issued. If a power generation stop command has been issued (YES in step S9), the control device 58 proceeds to step S10. If there is no power generation stop command (NO in step S9), the control device 58 returns to step S1 and repeats the process.

[0070] (Step S10) The control device 58 performs post-processing to stop the process.

[0071] Specifically, the control device 58 controls valve V1 (valve 57d) and valve V2 (valve 57f) to completely close each of them. Then, the control device 58 controls pump PM1 (pump 57c) and pump PM2 (pump 57e) to stop (turn off) each of them.

[0072] Then, the control device 58 terminates the process.

[0073] The opening degrees of valves V1 (valve 57d) and V2 (valve 57f) will be explained. Figure 6 is a diagram illustrating the processing of a non-condensable gas reduction system 50, which is an example of a non-condensable gas reduction system according to the first embodiment. Specifically, it is a diagram showing the opening degrees of valves V1 (valve 57d) and V2 (valve 57f) in relation to the hydrogen ion concentration (pH) in the non-condensable gas reduction system 50.

[0074] In Figure 6, the horizontal axis represents the pH (hydrogen ion concentration) of the liquid in Lq in the dissolution determination tank 57a obtained in step S3, and the vertical axis represents the opening degree of valve V1 (valve 57d) and valve V2 (valve 57f), respectively. On the vertical axis, "Open" indicates that valve V1 (valve 57d) or valve V2 (valve 57f) is fully open, and "Close" indicates that valve V1 (valve 57d) or valve V2 (valve 57f) is fully closed.

[0075] Line LV1 in Figure 6 indicates the opening degree of valve V1 (valve 57d). Line LV2 in Figure 6 indicates the opening degree of valve V2 (valve 57f).

[0076] The process in step S6 corresponds to the range RA in Figure 6. The process in step S7 corresponds to the range RB in Figure 6. The process in step S8 corresponds to the range RC in Figure 6.

[0077] In Figure 6, within range RB, the openings of valves V1 (valve 57d) and V2 (valve 57f) change linearly with respect to the hydrogen ion concentration (pH). However, the openings are not limited to changing linearly with respect to the hydrogen ion concentration (pH). For example, based on experimental results, the openings of valves V1 (valve 57d) and V2 (valve 57f) may be made to change based on a desired function.

[0078] Furthermore, the control is not limited to controlling the opening degrees of valve V1 (valve 57d) and valve V2 (valve 57f), but may also be controlled by the flow rate through valve V1 (valve 57d) and valve V2 (valve 57f).

[0079] According to the non-condensable gas reduction system of the first embodiment, non-condensable gases in a flash-type geothermal power plant can be processed efficiently.

[0080] According to the non-condensable gas reduction system of the first embodiment, non-condensable gases in a geothermal power plant can be efficiently treated by reusing the mixed liquid discharged from the dissolution determination tank and dissolving the non-condensable gas in the dissolution determination tank. In particular, according to the non-condensable gas reduction system of the first embodiment, when an excess of the chemical agent is supplied, the excess chemical agent can be reused to efficiently treat non-condensable gases in a geothermal power plant.

[0081] Furthermore, according to the non-condensable gas reduction system of the first embodiment, since the dissolution determination tank performs processing based on the hydrogen ion concentration of the mixed liquid, the consumption of the chemical agent can be optimized, and non-condensable gases in geothermal power plants can be processed efficiently.

[0082] ≪Second Embodiment≫ The non-condensable gas reduction system according to the second embodiment uses the non-condensable gas reduction system according to the first embodiment in geothermal power plants with different power generation methods. Figure 7 is a schematic diagram showing the configuration of a geothermal power plant 2 equipped with a non-condensable gas reduction system 50, which is an example of a non-condensable gas reduction system according to the second embodiment.

[0083] Geothermal power plant 2 comprises a gas-liquid separator 10, a power generation unit 120, a condenser 130, an evaporator 135, a cooling unit 140, a non-condensable gas reduction system 50, and a control unit 160. Geothermal power plant 2 is a so-called binary geothermal power generation system.

[0084] For geothermal power plant 2, please refer to the description of geothermal power plant 1 for details regarding its common configuration. Detailed explanations are omitted here.

[0085] [Power generation unit 120] The power generation unit 120 generates electricity using the working medium RF, which has been heated by steam ST and turned into a gas. The power generation unit 120 comprises a turbine 121 and a generator 122. The turbine 121 is rotated by the working medium RF. More specifically, the turbine 121 rotates due to the pressure difference between the working medium RF, which has been converted from liquid to gas by heat exchange with steam ST in the evaporator 135, and the working medium RF, which has been converted from gas to liquid by cooling liquid CW1 in the condenser 130. The generator 122 is connected to the turbine 121. When the turbine 121 rotates, the rotating shaft of the generator 122 rotates and generates electricity. The electricity generated by the generator 122 is supplied to the outside.

[0086] The working fluid RF is a medium with a lower boiling point than water, such as ammonia, pentane, or a fluorocarbon alternative. The working fluid RF condenses from gas to liquid when cooled in the condenser 130. The working fluid RF also evaporates from liquid to gas when heated in the evaporator 135. The working fluid RF is circulated by the pump 92 in the order of evaporator 135, turbine 121, and condenser 130.

[0087] [Condenser 130] The condenser 130 cools the working medium RF discharged from the turbine 121 with coolant CW supplied from the cooling unit 140. The working medium RF condenses in the condenser 130, changing from a gas to a liquid. The condenser 130 is, for example, a multi-tube heat exchanger, a plate heat exchanger, etc.

[0088] [Evaporator 135] The evaporator 135 heats the working medium RF with steam ST supplied from the gas-liquid separator 10. As the evaporator 135 heats the working medium RF, it evaporates and changes from a liquid to a gas. The evaporator 135 is, for example, a multi-tube heat exchanger. Heat exchange occurs between the steam ST and the working medium RF in the evaporator 135, causing the steam ST to cool. When the steam ST cools, it condenses into a condensate HWa.

[0089] Non-condensable gases (NCG), such as carbon dioxide and hydrogen sulfide, contained in the steam ST accumulate at the top of the evaporator 135. When non-condensable gases NCG accumulate, the liquid level of the condensate HWa formed from the condensation of steam ST in the evaporator 135 decreases. When the liquid level of the condensate HWa formed from the condensation of steam ST in the evaporator 135 decreases, the heat exchange efficiency between steam ST and the working fluid RF in the evaporator 135 decreases. Therefore, it is desirable to discharge the non-condensable gases NCG accumulated in the evaporator 135 from the evaporator 135.

[0090] In geothermal power plant 2, the non-condensable gas NCG that accumulates in the evaporator 135 is drawn in by the non-condensable gas reduction system 50 and discharged into the reinjection well RWL.

[0091] According to the non-condensable gas reduction system of the second embodiment, non-condensable gases in a binary-type geothermal power plant can be efficiently processed.

[0092] According to the non-condensable gas reduction system of the second embodiment, non-condensable gases in a geothermal power plant can be efficiently treated by reusing the mixed liquid discharged from the dissolution determination tank and dissolving the non-condensable gas in the dissolution determination tank. In particular, according to the non-condensable gas reduction system of the second embodiment, when an excess of the chemical agent is supplied, the excess chemical agent can be reused to efficiently treat non-condensable gases in a geothermal power plant.

[0093] Furthermore, according to the non-condensable gas reduction system of the second embodiment, since the dissolution determination tank performs processing based on the hydrogen ion concentration of the mixed liquid, the consumption of the chemical agent can be optimized, and non-condensable gases in geothermal power plants can be processed efficiently.

[0094] Note that dissolution determination tank 57a is an example of the first tank, and chemical tank 57b is an example of the second tank. Also, pump 55 is an example of the first pump, pump 57c is an example of the second pump, pump 57e is an example of the third pump, valve 57d is an example of the first valve, and valve 57f is an example of the second valve.

[0095] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0096] 1, 2 Geothermal power plants 10 Gas-liquid separator 20, 120 Power Generation Unit 21, 121 Turbine 22, 122 generators 30 Condenser 40, 140 Cooling section 50 Non-condensable gas reduction system 54 Ejectors 55 pumps 57 Dissolution determination section 57a Dissolution determination tank 57b Chemical tank 57c, 57e, PM1, PM2 pumps 57d, 57f, V1, V2 valves 57A, 57B, 57C channel 57i Drug injection site 57m, 57n flow meter 57p pH meter 57q level meter 57r Reuse section 58 Control device 60, 160 Control Unit 71, 72, 73 Pressure gauges 130 Condenser 135 Evaporator CW, CW1, CW2, CWa Coolant GF geothermal fluid HW hot water HWa condensate Lq liquid MW, MWa mixture NCG (Non-condensable gas) PWL production well RWL Reinforcement Well ST Steam RF working medium

Claims

1. In a geothermal power plant, a non-condensable gas reduction system returns the non-condensable gas that remains after cooling in the first gas contained in the geothermal fluid that springs from the production well to the reduction well. A first pump pressurizes the first liquid sent to the injection well, An ejector driven by the first liquid, which attracts the non-condensable gas and discharges a second liquid which is a mixture of the first liquid and the non-condensable gas, A first tank in which the second liquid discharged from the ejector is temporarily stored and the third liquid is discharged into the injection well, The first tank includes a chemical injection unit for injecting chemicals, A reuse unit that returns the third liquid discharged from the first tank back to the first tank, Equipped with, Non-condensable gas reduction system.

2. A sensor for measuring the properties of the liquid stored in the first tank, The system further comprises a control device for controlling the reuse unit, The control device controls the reuse unit based on the detection result of the sensor. The non-condensable gas reduction system according to claim 1.

3. The control device further controls the drug injection unit, The control device controls the drug injection unit based on the detection result of the sensor. The non-condensable gas reduction system according to claim 2.

4. The drug injection section is, A second tank for storing the aforementioned chemical, A second pump that sends the chemical from the second tank to the first tank, The system includes a first valve for adjusting the flow rate of the agent supplied from the second pump, The control device controls the opening degree of the first valve. The non-condensable gas reduction system according to claim 3.

5. The aforementioned reuse unit is A third pump that sends the third liquid discharged from the first tank back to the first tank, The system includes a second valve for adjusting the flow rate of the third liquid supplied from the third pump, The control device controls the opening degree of the second valve. A non-condensable gas reduction system according to any one of claims 2 to 4.

6. In a geothermal power plant, a non-condensable gas reduction system returns the non-condensable gas that remains after cooling in the first gas contained in the geothermal fluid that springs from the production well to the reduction well. A first pump pressurizes the first liquid sent to the injection well, An ejector driven by the first liquid, which attracts the non-condensable gas and discharges a second liquid which is a mixture of the first liquid and the non-condensable gas, A first tank in which the second liquid discharged from the ejector is temporarily stored and the third liquid is discharged into the injection well, The first tank includes a chemical injection unit for injecting chemicals, A sensor for measuring the properties of the liquid stored in the first tank, A control device that controls the drug injection unit based on the detection results of the sensor, Equipped with, Non-condensable gas reduction system.

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