JP7021015B2 - Geothermal binary power generation system and its operation method - Google Patents

Description

An embodiment of the present invention relates to a system of a binary power generation cycle using geothermal heat as a heat source and an operation method thereof.

Geothermal power generation is a power generation method in which steam or hot water is extracted from a geothermal reservoir that is a heat source, and the extracted heat is used to operate a turbine to obtain electric power. Geothermal power generation is roughly classified into a steam direct power generation method adopted in the case of a heat source in a high temperature region and a binary cycle method adopted in the case of a heat source in a low temperature region, depending on the temperature of the heat source.

In the binary cycle method, the power generation cycle is further selected according to the properties of the heat source (hot water single-phase flow, steam dryness in the case of hot water and steam two-phase flow, etc.).

Here, when the property of the heat source is a two-phase flow in which hot water and steam are mixed, the generated two-phase flow is separated into steam and hot water by a steam water separator, and the separated steam is separated into hot water by an evaporator. A method is known in which a preheater exchanges heat with a low-boiling medium that powers a power generation turbine, and generates power using the low-boiling medium evaporated by heat exchange. In the prior art, the low temperature hot water that has completed heat exchange with the low boiling point medium is directly sent to the reduction well.

Japanese Patent No. 5763495 Japanese Patent No. 5563854

In a known technique using a two-phase flow as a heat source, it is necessary to design and manufacture a brackish water separator capable of responding to natural fluctuations in the flow rate and pressure of the two-phase flow generated from a production well. Furthermore, the amount of evaporation and pressure generated from the brackish water separator fluctuate greatly depending on the state change of the two-phase flow. That is, there is a problem that the power generation output is not stable due to a large fluctuation in the flow rate and pressure of the steam flowing into the evaporator. In addition, since it is required to design and manufacture equipment, piping, instruments, etc. that can tolerate the fluctuation, an increase in equipment cost at the time of plant construction has become a problem.

Further, in the case of the conventional binary power generation cycle, since the temperature of the hot water returned to the underground after heat exchange is low, the solubility of silica contained in the geothermal water decreases, and silica scale is generated in the reduction well. Cheap. Since the closure of the reduction well directly leads to the shutdown of the plant, the problem of silica scale is considered to be one of the greatest risks of the binary cycle method. In order to solve this problem, in the conventional technology, measures such as PH control of hot water by a chemical injection system are taken to prevent silica scale, which leads to an increase in plant equipment costs and operating costs. ..

An object of the present invention is to make it possible to provide compact equipment with little output fluctuation in a binary power generation cycle using geothermal heat.

In order to solve the above problems, the geothermal binary power generation system according to the embodiment of the present invention has a geothermal water supply pipe for taking out a two-phase stream of steam and hot water taken out from a geothermal production well, and the geothermal water supply pipe. A mixer that accepts a two-phase flow of steam and hot water supplied from the mixer and stores it in a two-phase state, a hot water pipe that takes out hot water from the mixer, and heat taken out from the mixer through the hot water pipe. An evaporator that heats a medium having a boiling point lower than that of water using water as a heat source to evaporate the medium, a hot water return pipe that returns a part of the hot water radiated by the evaporator to the mixer, and the evaporation. A reduction pipe that returns a part of the hot water radiated by the vessel to the reduction well without returning it to the mixer, a turbine driven by a medium heated and evaporated by the evaporator, and a turbine driven by the turbine. A generator, a medium return pipe that returns the medium after working in the turbine to the evaporator, a water level gauge that measures the water level in the mixer, a reduced water amount control valve provided in the reduction pipe, and the like. It is characterized by having a reduced water amount control valve control unit that adjusts the opening degree of the reduced water amount control valve so that the water level in the mixer measured by the water level gauge falls within a predetermined water level range .

The method for operating a geothermal binary power generation system according to an embodiment of the present invention includes a geothermal water supply pipe that takes out a two-phase stream of steam and hot water taken out from a geothermal production well, and steam and steam supplied from the geothermal water supply pipe. A mixer that accepts a two-phase flow of hot water and stores it in a two-phase state, a hot water pipe that takes out hot water from the mixer, and hot water taken out from the mixer through the hot water pipe as a heat source from water. An evaporator that heats a medium having a low boiling point to evaporate the medium, a hot water return pipe that returns a part of the hot water radiated by the evaporator to the mixer, and the heat radiated by the evaporator. A reduction pipe that returns a part of water to the reduction well without returning it to the mixer, a turbine driven by a medium heated and evaporated by the evaporator, a generator driven by the turbine, and the turbine. It is an operation method of a geothermal binary power generation system having a medium return pipe for returning the medium after work to the evaporator and a reduced water amount control valve provided in the reduction pipe, and the water level in the mixer. The water level measurement step for measuring the temperature and the reduction water amount control valve opening adjustment step for adjusting the opening degree of the reduced water amount control valve so that the water level in the mixer measured in the water level measurement step falls within a predetermined water level range. It is characterized by having and.

According to the embodiment of the present invention, it is possible to provide compact equipment with little output fluctuation in a binary power generation cycle using geothermal heat.

It is a system diagram which shows the structure of the geothermal binary power generation system which concerns on 1st Embodiment of this invention. It is a system diagram which shows the structure of the geothermal binary power generation system which concerns on the 2nd Embodiment of this invention.

Hereinafter, embodiments of the geothermal binary power generation system and the method thereof according to the present invention will be described with reference to the drawings. Here, common reference numerals are given to parts that are the same as or similar to each other, and duplicate description is omitted.

[First Embodiment]
FIG. 1 is a system diagram showing a configuration of a geothermal binary power generation system according to the first embodiment of the present invention.

In this geothermal binary power generation system 11, a two-phase stream composed of steam and hot water is taken out from a production well (geothermal production well) 12, the heat is transferred to a low boiling point medium, and the turbine 13 is rotated by the low boiling point medium. It is a system that rotates the generator 14 thereby. In FIG. 1, the piping of the steam and hot water system is shown by a solid line, and the piping of the low boiling point medium system is shown by a broken line. The signal line is indicated by a two-dot chain line.

The steam and hot water taken out from the production well 12 are supplied to the mixer 16 through the geothermal water supply pipe 15 and stored. A geothermal water supply control valve 40 is arranged in the geothermal water supply pipe 15.

The hot water stored in the mixer 16 is sent to the evaporator 18 through the hot water pipe 17. A hot water pump 19 is provided in the hot water pipe 17, and the hot water in the hot water pipe 17 is boosted. Steam and hot water are in a mixed state in the mixer 16, and the hot water taken out from the mixer 16 through the hot water pipe 17 is in a substantially saturated water state.

The evaporator 18 is a non-mixed heat exchanger that evaporates a low boiling point medium using hot water supplied through a hot water pipe 17 as a heat source. The low boiling point medium is a medium having a boiling point lower than that of water, such as chlorofluorocarbons and ethylene.

The turbine 13 is driven by the low boiling point medium vaporized by the evaporator 18, and the generator 14 is driven by the turbine 13.

The low boiling point medium after working in the turbine 13 is condensed and liquefied in the condenser 21. The condenser 21 dissipates heat by the atmosphere, cooling water, or the like. The low boiling point medium condensed and liquefied by the condenser 21 is boosted by the medium pump 22 and sent to the preheater 23. The preheater 23 is a non-mixing type heat exchanger that transfers the heat of hot water after heat dissipation by the evaporator 18 to a low boiling point medium. The low boiling point medium preheated by the preheater 23 is sent to the evaporator 18 via the medium return pipe 20.

The hot water taken out from the mixer 16 through the hot water pipe 17 is pressurized by the hot water pump 19 and then dissipated by the evaporator 18 and the preheater 23 to become relatively low temperature. The relatively low-temperature hot water that has left the preheater 23 branches on the downstream side of the preheater 23, and a part of the hot water is returned to the mixer 16 through the hot water return pipe 24. The remaining hot water branched on the downstream side of the preheater 23 is returned to the reduction well 31 through the reduction pipe 30. A reduction water amount control valve 32 is arranged in the reduction pipe 30.

A gas discharge pipe 50 is connected to the top of the mixer 16, and a gas discharge valve 51 is installed in the gas discharge pipe 50. The tip of the gas discharge pipe 50 is open to the atmosphere. The gas discharge valve 51 is normally closed, but is opened when non-condensable gas such as corrosive non-condensable gas is accumulated in the upper part of the mixer 16 so that the non-condensable gas does not accumulate in the mixer 16. To.

A water level gauge 45 is installed to measure the water level in the mixer 16, and a pressure gauge 46 is installed to measure the pressure in the mixer 16.

The opening degree of the reduced water amount control valve 32 is such that the water level in the mixer 16 measured by the water level gauge 45 is substantially constant, specifically, the reduced water amount is within a predetermined water level range. It is controlled by the control valve control unit 47. For example, when the water level in the mixer 16 is lower than the predetermined water level range, the opening degree of the reduced water amount control valve 32 is lowered to reduce the flow rate of the hot water flowing through the reduction pipe 30, and more hot water is supplied. By returning the water to the inside of the mixer 16 through the hot water return pipe 24, the water level in the mixer 16 is controlled to rise. In this way, the water level in the mixer 16 can be kept substantially constant regardless of the fluctuation of the pressure of the two-phase flow supplied from the production well 12 and the dryness (mass ratio of steam).

The opening degree of the geothermal water supply control valve 40 is set so that the pressure in the mixer 16 measured by the pressure gauge 46 is substantially constant, specifically, the pressure is within a predetermined pressure range. It is controlled by the geothermal water supply control valve control unit 48. For example, when the pressure in the mixer 16 is lower than a predetermined pressure range, the opening degree of the geothermal water supply control valve 40 is increased to supply steam and heat to the mixer 16 through the geothermal water supply pipe 15. By increasing the flow rate of water, the pressure in the mixer 16 is controlled to increase.

The bypass pipe 52 branches from the upstream side of the geothermal water supply control valve 40 of the geothermal water supply pipe 15, and the tip of the bypass pipe 52 is guided to the reduction well 31. A bypass valve 53 is provided in the middle of the bypass pipe 52. The bypass valve 53 is normally closed, but the steam and hot water supplied from the production well 12 are abnormally increased when the steam and hot water supplied from the production well 12 through the geothermal water supply pipe 15 are abnormally increased. Part or all of the above can be returned to the reduction well 31 without passing through the mixer 16 or the like.

According to this embodiment, the pressure in the mixer 16 is kept substantially constant by adjusting the opening degree of the geothermal water supply control valve 40. As a result, the saturation temperature in the mixer 16 is substantially constant, and the temperature of the hot water supplied to the evaporator 18 is substantially constant. Thereby, the output of the generator 14 can be kept substantially constant regardless of the fluctuation of the pressure and the dryness of the two-phase flow supplied from the production well 12. In order to increase the output of the generator 14 in response to an increase in power generation demand, it is possible to increase the set value of the pressure in the mixer 16 to increase the saturated water temperature.

According to this embodiment, the temperature and flow rate of the hot water supplied to the evaporator 18 can be stabilized at a desired value regardless of the fluctuation of the pressure and the dryness of the two-phase flow supplied from the production well 12. can. Therefore, it is possible to design, manufacture, and select equipment, piping, instruments, etc. that limit the range of design conditions to a relatively narrow range. As a result, the equipment cost at the time of plant construction can be reduced. In addition, since the power generation output is stable, it contributes to the improvement of the quality of the electric power system and also contributes to the reduction of the equipment cost for stabilizing the electric power system.

Further, since the non-condensable gas can be discharged through the gas discharge pipe 50, the corrosive non-condensable gas such as hydrogen sulfide and carbon dioxide contained in the steam supplied from the production well 12 can be removed. Then, the hot water circulates from the mixer 16, that is, through the hot water pipe 17, the hot water pump 19, the evaporator 18, the preheater 23, and the hot water return pipe 24, and returns to the mixer 16. It is not necessary to deal with corrosive non-condensable gases such as hydrogen sulfide and carbon dioxide in each device and piping, and therefore the construction cost can be reduced.

In the example shown in FIG. 1, the evaporator 18 and the preheater 23 are provided separately, but as a modification, the evaporator 18 and the preheater 23 may be integrated. In that case, for example, an evaporator in which the evaporator 18 and the preheater 23 are integrated can be called an evaporator.

Further, in the above description, the reduction water amount control valve control unit 47 automatically adjusts the opening degree of the reduction water amount control valve 32 according to the output of the water level gauge 45. It is also possible to manually adjust the opening degree of the reduced water amount control valve 32 while observing the display of the output of the water level gauge 45.

Similarly, in the above description, the geothermal water supply control valve control unit 48 automatically adjusts the opening degree of the geothermal water supply control valve 40 according to the output of the pressure gauge 46, but as a modification. The worker can also manually adjust the opening degree of the geothermal water supply control valve 40 while observing the display of the output of the pressure gauge 46.

[Second Embodiment]
FIG. 2 is a system diagram showing a configuration of a geothermal binary power generation system according to a second embodiment of the present invention.

This second embodiment is a modification of the first embodiment, in order to prevent silica scale from being generated in the reduction well when the temperature of the reduced water returned to the reduction well 31 through the reduction pipe 30 is low. , The reduction pipe heating water pipe 60 is provided. The reduction pipe heating water pipe 60 branches from the upstream side of the geothermal water supply control valve 40 in the middle of the geothermal water supply pipe 15 and is connected to the reduction pipe 30. The reduction pipe heating water pipe 60 is provided with a reduction pipe heating water valve 61. Further, a thermometer 62 for measuring the temperature of the reduced water in the reducing pipe 30 is installed. Further, a reduction pipe heating water valve control unit 63 for controlling the reduction pipe heating water valve 61 according to the output of the thermometer 62 is provided.

Other configurations are the same as those of the first embodiment.

When the temperature of the reduced water in the reduction pipe 30 detected by the thermometer 62 drops below a predetermined range, the reduction pipe heating water valve control unit 63 opens the reduction pipe heating water valve 61. As a result, a part of the steam and hot water flowing through the geothermal water supply pipe 15 flows into the reduction pipe 30 through the heated water pipe 60. As a result, the temperature of the reduced water in the reducing pipe 30 rises. As a result, it is possible to prevent silica scale from being generated in the reduction well 31.

According to this second embodiment, not only the same effect as that of the first embodiment can be obtained, but also measures such as chemical injection and periodic cleaning to prevent silica scale are not required, and silica scale is not required. It is possible to avoid plant shutdown due to.

Here, flowing a part of the steam and hot water flowing in the geothermal water supply pipe 15 into the reduction pipe 30 through the heated water pipe 60 results in a loss of geothermal energy. Therefore, it is desirable that the flow rates of steam and hot water flowing through the heated water pipe 60 be minimized in order to prevent silica scale in the reduction well 31. For that purpose, it is preferable to control the reduction pipe heating water valve 61 so that the temperature detected by the thermometer 62 falls within an appropriate temperature range.

The reduction pipe heating water valve 61 may be a flow rate adjusting valve or an on-off valve that does not adjust the flow rate.

Further, instead of the method of automatically performing the reduction pipe heating water valve 61 by the reduction pipe heating water valve control unit 63, the operator manually operates the reduction pipe heating water valve 61 by looking at the output display of the thermometer 62. You may.

[Other embodiments]
In the description of the first and second embodiments, the reduction water amount control valve control unit 47, the geothermal water supply control valve control unit 48, and the reduction pipe heating water valve control unit 63 are separately provided, but hardware. These control units may be collectively incorporated as each function of one control device.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

11 ... Geothermal binary power generation system, 12 ... Production well (geothermal production well), 13 ... Turbine, 14 ... Generator, 15 ... Geothermal water supply pipe, 16 ... Mixer, 17 ... Hot water pipe, 18 ... Evaporator, 19 ... Hot water pump, 20 ... Medium return pipe, 21 ... Condenser, 22 ... Medium pump, 23 ... Preheater, 24 ... Hot water return pipe, 30 ... Reduction pipe, 31 ... Reduction well, 32 ... Reduced water amount control valve , 40 ... Geothermal water supply control valve, 45 ... Water level gauge, 46 ... Pressure gauge, 47 ... Reduced water amount control valve control unit, 48 ... Geothermal water supply control valve control unit, 50 ... Gas discharge pipe, 51 ... Gas discharge Valve, 52 ... Bypass pipe, 53 ... Bypass valve, 60 ... Reduction pipe heating water pipe, 61 ... Reduction pipe heating water valve, 62 ... Thermometer, 63 ... Reduction pipe heating water valve control unit

Claims (11)

Geothermal water supply piping that takes out the two-phase flow of steam and hot water taken out from the geothermal production well,
A mixer that accepts the two-phase flow of steam and hot water supplied from the geothermal water supply pipe and stores them in a two-phase state.
A hot water pipe that takes out hot water from the mixer, and
An evaporator that heats a medium having a boiling point lower than that of water using hot water taken out from the mixer through the hot water pipe as a heat source to evaporate the medium.
A hot water return pipe that returns a part of the hot water radiated by the evaporator to the mixer, and
A reduction pipe that returns a part of the hot water radiated by the evaporator to the reduction well without returning it to the mixer, and
A turbine driven by a medium heated and evaporated by the evaporator,
The generator driven by the turbine and
A medium return pipe that returns the medium after working in the turbine to the evaporator, and
A water level gauge that measures the water level in the mixer, and
The reduced water amount control valve provided in the reduction pipe and
A reduced water amount control valve control unit that adjusts the opening degree of the reduced water amount control valve so that the water level in the mixer measured by the water level gauge falls within a predetermined water level range.
A geothermal binary power generation system, characterized by having. A pressure gauge that measures the pressure inside the mixer, and
The geothermal water supply control valve provided in the geothermal water supply pipe and
A geothermal water supply control valve control unit that adjusts the opening degree of the geothermal water supply control valve so that the pressure in the mixer measured by the pressure gauge falls within a predetermined pressure range.
The geothermal binary power generation system according to claim 1, wherein the system comprises. Geothermal water supply piping that takes out the two-phase flow of steam and hot water taken out from the geothermal production well,
A mixer that accepts the two-phase flow of steam and hot water supplied from the geothermal water supply pipe and stores them in a two-phase state.
A hot water pipe that takes out hot water from the mixer, and
An evaporator that heats a medium having a boiling point lower than that of water using hot water taken out from the mixer through the hot water pipe as a heat source to evaporate the medium.
A hot water return pipe that returns a part of the hot water radiated by the evaporator to the mixer, and
A reduction pipe that returns a part of the hot water radiated by the evaporator to the reduction well without returning it to the mixer, and
A turbine driven by a medium heated and evaporated by the evaporator,
The generator driven by the turbine and
A medium return pipe that returns the medium after working in the turbine to the evaporator, and
A pressure gauge that measures the pressure inside the mixer, and
The geothermal water supply control valve provided in the geothermal water supply pipe and
A geothermal water supply control valve control unit that adjusts the opening degree of the geothermal water supply control valve so that the pressure in the mixer measured by the pressure gauge falls within a predetermined pressure range.
A geothermal binary power generation system, characterized by having. A reduction pipe heated water pipe that branches off from the geothermal water supply pipe on the upstream side of the geothermal water supply control valve and is connected to the reduction pipe.
The reduction pipe heating water valve provided in the reduction pipe heating water pipe,
A thermometer that measures the temperature inside the reduction pipe,
A reduction pipe heating water valve control unit that controls the opening of the reduction pipe heating water valve when the temperature inside the reduction pipe measured by the thermometer drops below a predetermined temperature.
The geothermal binary power generation system according to claim 2 or 3 , further comprising. The reduction pipe heating water valve control unit is characterized in that it controls the reduction pipe heating water valve so that the temperature in the reduction pipe measured by the thermometer falls within a predetermined temperature range. The geothermal binary power generation system according to claim 4. Any of claims 1 to 5, further comprising a preheater for preheating the medium before being sent to the evaporator by utilizing the residual heat of the hot water after being dissipated by the evaporator. The geothermal binary power generation system described in the first paragraph. The geothermal binary power generation system according to any one of claims 1 to 6, further comprising a hot water pump provided in the hot water pipe. A condenser that condenses the medium after working in the turbine,
A medium pump provided in the medium return pipe, which boosts the medium condensed by the condenser and sends it to the evaporator.
The geothermal binary power generation system according to any one of claims 1 to 7, further comprising. Geothermal water supply piping that takes out the two-phase flow of steam and hot water taken out from the geothermal production well,
A mixer that accepts the two-phase flow of steam and hot water supplied from the geothermal water supply pipe and stores them in a two-phase state.
A hot water pipe that takes out hot water from the mixer, and
An evaporator that heats a medium having a boiling point lower than that of water using hot water taken out from the mixer through the hot water pipe as a heat source to evaporate the medium.
A hot water return pipe that returns a part of the hot water radiated by the evaporator to the mixer, and
A reduction pipe that returns a part of the hot water radiated by the evaporator to the reduction well without returning it to the mixer, and
A turbine driven by a medium heated and evaporated by the evaporator,
The generator driven by the turbine and
A medium return pipe that returns the medium after working in the turbine to the evaporator, and
The reduced water amount control valve provided in the reduction pipe and
Is a method of operating a geothermal binary power generation system that has
A water level measurement step for measuring the water level in the mixer, and
A reduction water amount control valve opening adjustment step that adjusts the opening degree of the reduction water amount control valve so that the water level in the mixer measured in the water level measurement step falls within a predetermined water level range.
A method of operating a geothermal binary power generation system, characterized by having. Geothermal water supply piping that takes out the two-phase flow of steam and hot water taken out from the geothermal production well,
A mixer that accepts the two-phase flow of steam and hot water supplied from the geothermal water supply pipe and stores them in a two-phase state.
A hot water pipe that takes out hot water from the mixer, and
An evaporator that heats a medium having a boiling point lower than that of water using hot water taken out from the mixer through the hot water pipe as a heat source to evaporate the medium.
A hot water return pipe that returns a part of the hot water radiated by the evaporator to the mixer, and
A reduction pipe that returns a part of the hot water radiated by the evaporator to the reduction well without returning it to the mixer, and
A turbine driven by a medium heated and evaporated by the evaporator,
The generator driven by the turbine and
A medium return pipe that returns the medium after working in the turbine to the evaporator, and
The reduced water amount control valve provided in the reduction pipe and
With the geothermal water supply control valve provided in the geothermal water supply pipe
Is a method of operating a geothermal binary power generation system that has
A pressure measurement step for measuring the pressure in the mixer, and
A geothermal water supply control valve opening adjustment step that adjusts the opening degree of the geothermal water supply control valve so that the pressure in the mixer measured in the pressure measurement step falls within a predetermined pressure range.
Geothermal binary power generation system operating method. The method for operating a geothermal binary power generation system according to claim 10.
The geothermal binary power generation system is
A reduction pipe heated water pipe that branches off from the geothermal water supply pipe on the upstream side of the geothermal water supply control valve and is connected to the reduction pipe.
The reduction pipe heating water valve provided in the reduction pipe heating water pipe,
Have more
The operation method of the geothermal binary power generation system is
The temperature measurement step in the reduction pipe, which measures the temperature inside the reduction pipe,
A reduction pipe heating water valve opening step that opens the reduction pipe heating water valve when the temperature inside the reduction pipe measured in the reduction pipe temperature measurement step drops below a predetermined temperature.
A method of operating a geothermal binary power generation system, characterized by having more.

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