JP6844880B1 - Geothermal exchanger and geothermal power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To install even in an environment where it is difficult to prepare a large amount of cooling water, to utilize a large latent heat of steam emitted from a turbine without waste, and to take out the temperature of geothermal energy is not stable. Provided is a geothermal exchanger capable of stabilizing the temperature and flow rate of produced steam even under such circumstances. The steam exiting the outlet of a turbine 12 is guided to a primary condensate heat exchanger 18a and exchanges heat with a working fluid having a boiling point lower than that of water. The steam remaining without heat exchange in the primary condensate heat exchanger 18a is sent to the turbine 13 to form a steam circulation path. The water discharged from the primary condensate heat exchanger 18a and the returned water obtained by removing the steam boiled under reduced pressure from the steam generator 10 are guided to the secondary condensate heat exchanger 18b and operate at a boiling point lower than that of water. Heat exchange is performed with the fluid, and the working fluid produces binary power. [Selection diagram] Fig. 1

Description

The present invention relates to a geothermal exchanger and a geothermal power generation device capable of efficiently extracting geothermal energy.

Geothermal power generation, which uses geothermal energy to generate electricity, uses a high-temperature magma layer as a heat source, can be used as semi-permanent thermal energy, and does not generate greenhouse gases in the process of power generation. In recent years, it has been attracting attention as an alternative means of fuel.

In the conventional geothermal power generation, the geothermal power is bored, and the natural steam and hot water existing in the geothermal power are extracted by using the natural pressure to generate electricity. Therefore, the extracted steam and hot water contain a large amount of sulfur and other impurities peculiar to the tropics. These impurities become scales and adhere to hot wells, pipes, turbines, and the like. If the scale adheres, the power generation output decreases over time, making it difficult to use for a long period of time.

Patent Document 1 and Patent Document 2 describe geothermal exchangers that employ a method of sending water from the ground to extract energy in order to solve the problem of this scale. Further, Patent Document 3 describes an invention relating to a geothermal exchanger provided with a means for improving the flash rate underground for the purpose of effectively extracting geothermal energy.

Japanese Patent No. 4927136 Japanese Patent No. 5731051 Japanese Patent No. 6176890

One of the causes that hinders the promotion of geothermal power generation is the problem of procuring cooling water. In Japan, most of the geothermal resources exist in hot spring areas, often in national parks, and in these areas with excellent natural landscapes, famous water is also a tourism resource, and the area is large. It is a property.

In most geothermal areas where geothermal power can be planned, the function of a condenser that cools the steam coming out of the turbine and returns it to hot water is an essential condition for improving the efficiency of the turbine, so secure cooling water. The need for power plants limits the locations where power plants are planned, which hinders the promotion of geothermal power generation.

In general geothermal power generation, a condenser is installed to cool the steam discharged from the turbine and return it to water, and a negative pressure is applied to the turbine outlet to increase the pressure difference between the inlet and outlet in the turbine. Then, the efficiency of the turbine is improved. In this case, since it is steam at the outlet of the turbine and the latent heat of the steam is about 6 times or more that of saturated water, not only a large amount of cooling water is required, but also the latent heat of the steam that is heat-exchanged in the condenser is generated. It will be thrown away in vain.

Further, in any of the methods disclosed in Patent Documents 1, 2 and 3, a double-tube type geothermal exchanger buried underground is used, and a common drawback caused by this is the geothermal energy to be taken out. The temperature is not constant. In particular, in geothermal development, it is important to develop a geothermal power generation system for the mid-low temperature zone of about 180 ° C or less, which is overwhelmingly present all over the country. The problem caused by the instability of the temperature of geothermal energy becomes remarkable. Therefore, there is a problem that the temperature and flow rate of the produced steam are not stable and the power generation output is not stable. In addition, the flow of geothermal fluid in the geotropics also causes the geothermal temperature to not stabilize.

The present invention has been made in consideration of such circumstances, and can be installed even in an environment where it is difficult to prepare a large amount of cooling water, and the large latent heat of the steam emitted from the turbine is not wasted. Using a geothermal exchanger that can be used and that can stabilize the temperature and flow rate of the steam produced even under the condition that the temperature of the geothermal energy to be extracted is not stable, and this geothermal exchanger. The purpose is to provide a geothermal power generation device that can efficiently generate a large amount of power and effectively utilize the geothermal resources in the power generation area.

In order to solve the above problems, the geoheat exchanger of the present invention is a steam generator in which pressure water obtained by heating water injected from the ground to the ground by the geotropa is sent to a steam generator. A geothermal exchanger that is taken out as steam inside and sent to the turbine, where the steam exiting the turbine outlet is guided to exchange heat with the working fluid, which has a lower boiling point than water. In addition to being equipped with a vessel, the water that has left the primary condensate heat exchanger and the return water that is obtained by removing the steam that has been boiled under reduced pressure from the steam generator are guided to exchange heat with the working fluid that has a lower boiling point than water. It is equipped with a secondary condensate heat exchanger to be performed, and is characterized in that binary power generation is performed by a working fluid.

In a general geothermal power generation system, a condenser is installed to cool the steam discharged from the turbine and return it to water, and apply negative pressure to the turbine outlet to improve the efficiency of the turbine. However, in this case, since it is steam at the outlet of the turbine and the latent heat of the steam is about 6 times or more that of saturated water, a large amount of cooling water is required. Furthermore, a large amount of latent heat remains in the steam that has been heat-exchanged in the condenser, and this is wasted.

In the present invention, instead of the condenser, a condenser heat exchanger that can be used for binary power generation is installed in two stages, and latent heat is exchanged by binary power generation to replace the condenser. As a result, since cooling water is not required, it can be installed in the mountains where it is often difficult to prepare a large amount of water. In addition, the energy of the steam exchanged for heat in the condenser is not wasted, and the energy can be effectively used.

In the geothermal exchanger of the present invention, the steam remaining without heat exchange in the primary condensate heat exchanger is sent to the turbine via the steam heater and the steam tank to form a steam circulation path. Can be.

By forming the steam circulation path and forming the reheating line in this way, the flush rate of the entire system is greatly improved, so that the flow rate of the circulating water line via the geothermal exchanger can be greatly reduced. Therefore, the capacity of the well circulation pump can be greatly reduced, and the amount of heat required for heating the pressure water in the pressure water tank and the circulation water in the circulation water tank can be greatly reduced, so that the efficiency of the entire system can be greatly improved. Can be done. Further, heating steam requires less heat from an external heat source than heating water having a large specific heat.

In the geothermal exchanger of the present invention, heating by the steam heater can be performed by an external heat source other than geothermal heat. As an example of the external heat source, it can be based on the surplus heat of biomass power generation, any of renewable fuels, or a combination thereof.

In the present invention, a steam circulation path is formed to form a reheating line, which is reheated by a steam heater. Since this reheating is performed by an external heat source other than geothermal heat, the temperature and flow rate of the steam produced can be stabilized even in a situation where the temperature of the geothermal energy to be taken out is not stable.

In the geothermal exchanger of the present invention, the pressure water can be assumed to be hot water generated by supplying heat from the geotropics and rising to the ground without containing steam.
Further, in the geothermal exchanger of the present invention, the pressure water can be obtained by separating steam from a gas-liquid two-phase flow taken out to the ground.

The geothermal power generation device of the present invention is characterized in that power is generated using the geothermal power exchanger of the present invention.

Since the geothermal exchanger of the present invention can improve the flash rate, it is possible to generate a large amount of power. Further, even when the geothermal heat is insufficient as a heat source, it is possible to quickly respond to the temperature change of the geothermal heat and the power generation output is stable.

According to the present invention, it can be installed even in an environment where it is difficult to prepare a large amount of cooling water, the large latent heat of the steam emitted from the turbine can be utilized without waste, and the temperature of the geothermal energy to be extracted can be increased. A geothermal exchanger that makes it possible to stabilize the temperature and flow rate of the steam produced even under unstable conditions, and this geothermal exchanger can be used to efficiently generate a large amount of power in the power generation area. It is possible to realize a geothermal power generation device that can effectively utilize geothermal resources.

It is a figure which shows the structure of the ground equipment of the geothermal exchanger and the geothermal power generation apparatus of this invention. It is a figure which shows the 1st Embodiment about underground equipment. It is a figure which shows the 2nd Embodiment about underground equipment.

Hereinafter, the geothermal exchanger and the geothermal power generation device of the present invention will be described based on the embodiment thereof.
FIG. 1 shows the configuration of the ground equipment of the geothermal exchanger and the geothermal power generation device of the present invention.

In the geothermal exchanger 1, the pressure water obtained by heating the water injected from the ground to the ground by the geotropa is sent to the steam generator 10 and taken out as steam in the steam generator 10, and the steam is taken out. Is sent to the turbine 12. The steam exiting the outlet of the turbine 12 is guided to the primary condensate heat exchanger 18a, exchanges heat with a working fluid having a boiling point lower than that of water, and binary power generation is performed by the working fluid.

The steam remaining without heat exchange in the primary condensate heat exchanger 18a is sent to the turbine 13 via the steam heater 23 and the steam tank 24 to form a steam circulation path. The heating by the steam heater 23 is performed by an external heat source other than geothermal heat, and the external heat source is the surplus heat of biomass power generation, any of renewable fuels, or a combination thereof.

The water discharged from the primary condensate heat exchanger 18a and the returned water obtained by removing the steam boiled under reduced pressure from the steam generator 10 are guided to the secondary condensate heat exchanger 18b and operate at a boiling point lower than that of water. Heat exchange is performed with the fluid, and the working fluid produces binary power. By controlling the rotation speed of the return water pump 27, the circulating water can be greatly stirred to increase the heat exchange ratio.

The pressure water taken out from the underground is stored in the pressure water tank 22 and sent to the steam generator 10 by the pressure water pump 21. A sufficient amount is stored in the pressure water tank 22 so as to be able to cope with the temperature change of the well. The pressure water stored in the pressure water tank 22 is taken out by the pressure water pump 21 in an amount determined by the flush rate calculated based on the steam flow rate, the steam temperature, and the steam pressure. The pressure water is heated in the pressure water tank 22, and this heating is performed by an external heat source other than the heat source obtained from the geotropa, and surplus heat of biomass power generation or renewable fuel can be used as the external heat source.

The steam generated by the steam generator 10 can be converted from saturated steam to superheated steam by the steam heater 23, whereby the efficiency of the turbine 12 can be improved. Superheated steam sets the vapor pressure below the critical pressure, which allows the adoption of high temperature turbines that are not applicable in conventional geothermal power generation. The superheated steam is introduced into the turbine 12 via the steam tank 24 and the steam valve 26 to drive the turbine 12, and the generator generates electricity.

The water discharged from the secondary condensate heat exchanger 18b is guided to the circulating water tank 16. The water stored in the circulating water tank 16 is heated, and this heating is performed by an external heat source other than the heat source obtained from the geotropics, and surplus heat of biomass power generation or renewable fuel can be used as the external heat source.

The circulating water in the circulating water tank 16 is pressurized by the well circulation pump 9 and is supplied to the underground well again. By repeating this process, geothermal heat is continuously extracted.

FIG. 2 shows a first embodiment relating to underground equipment.
The geothermal exchanger 1 is arranged in the outer pipe 2 provided in the ground and supplied with water pressurized by the well circulation pump 9, and inside the outer pipe 2, and extends through the outer pipe 2 to the tropics. It is provided with an inner pipe 3 in which hot water generated by supplying heat from the geothermal region rises in a state where steam is not contained in the falling pressure water. The pressure water taken out from the inner pipe 3 is stored in the pressure water tank 22, sent to the steam generator 10, and taken out as steam in the steam generator 10. A heat insulating portion 20 is formed at a place where the outer pipe 2 is in contact with a low temperature zone near the ground surface.

FIG. 3 shows a second embodiment relating to underground equipment.
The geothermal exchanger 1 has a double pipe structure including an outer pipe 2 provided underground and water is supplied from the ground, and an inner pipe 3 arranged inside the outer pipe 2. It is provided with a pressure valve 6 provided inside the pressure valve 6. A high-pressure area 5 is formed in which heat is supplied from the geotropa to the water in the outer pipe 2 to generate high-pressure hot water without boiling, and in the high-pressure area 5 at the position where the pressure valve 6 is installed. The pressure valve 6 opens when the pressure difference between the pressure of the high-pressure hot water and the pressure-reducing area 8 in the inner pipe 3 exceeds the set reference value, and when the pressure valve 6 opens, the high-pressure hot water enters from the high-pressure area 5. It flows into the pipe 3, and the upper part of the decompression area 8 of the inner pipe 3 is depressurized near the pressure required by the turbine and converted into a gas-liquid two-phase flow. The pressure valve 6 is opened by setting the pressure for pressurizing the water injected into the outer pipe 2 by the well circulation pump 9. A heat insulating portion 20 is formed at a place where the outer pipe 2 is in contact with a low temperature zone near the ground surface.

To set the reference value for opening the pressure valve 6, the pressure of the high-pressure hot water in the high-pressure area 5 at the position where the pressure valve 6 is installed is set as the saturation pressure at the water saturation temperature determined from the temperature conditions of the geotropics. , The pressure valve 6 can be opened beyond the set reference value of the pressure difference.

Further, for setting the reference value for opening the pressure valve 6, the pressure of the high-pressure hot water in the high-pressure area 5 at the position where the pressure valve 6 is installed is set to be near the critical pressure of water, and the setting reference value of the pressure difference is set. It is also possible to open the pressure valve 6 beyond that.

The pressure water obtained by separating steam from the gas-liquid two-phase flow taken out to the ground is stored in the pressure water tank 22. The separated steam is sent to the steam heater 23.

A system that produces steam by reducing the pressure of pressure water as in the present invention is a system that utilizes the pressure difference due to the temperature difference of the pressure water.
It is calculated by flash rate (%) = (latent heat of high temperature saturated water-latent heat of low temperature saturated water) / latent heat of vaporization at low temperature, but this formula can be replaced with the following formula.
Flash rate (%) = steam generation amount / circulating water amount

In the geothermal exchanger of the present invention, the amount of steam generated by boiling under reduced pressure can be subtracted from the amount of circulating steam, so that the flash rate of the entire system can exceed 40%. This value is equivalent to decompressing pressure water in a temperature range close to supercritical, and can contribute to next-generation energy, which is a national policy.

The present invention can be installed even in an environment where it is difficult to prepare a large amount of cooling water, the large latent heat of the steam emitted from the turbine can be utilized without waste, and the temperature of the geothermal energy to be taken out is stable. A geothermal exchanger that makes it possible to stabilize the temperature and flow rate of the steam produced even under such circumstances, and this geothermal exchanger can be used to efficiently generate a large amount of power and generate geothermal heat in the power generation area. It can be widely used as a geothermal power generation device that can effectively use resources.

1 Geothermal exchanger 2 Outer pipe 3 Inner pipe 5 High pressure area 6 Pressure valve 8 Decompression area 9 Well circulation pump 10 Steam generator 12 Turbine 16 Circulation water tank 18a Primary condensate heat exchanger 18b Secondary condensate heat exchanger 20 Insulation Part 21 Pressure water pump 22 Pressure water tank 23 Steam heater 24 Steam tank 26 Steam valve 27 Return water pump

Claims (5)

A geoheat exchanger in which pressure water obtained by heating water injected from the ground to the ground by the geotropa is sent to a steam generator, taken out as steam in the steam generator, and this steam is sent to a turbine. It is equipped with a primary condensate heat exchanger in which steam exiting the turbine outlet is guided to exchange heat with a working fluid having a boiling point lower than that of water, and water exiting the primary condensate heat exchanger. guided and the Modomizu from steam generator obtained by removing the flash boiling vapor, a secondary condensate heat exchanger lower than that of water boiling the working fluid and heat exchange is performed by the working fluid Binary-a geothermal exchanger that produces power
A geothermal exchanger characterized in that steam remaining without heat exchange in the primary condensate heat exchanger is sent to a turbine via a steam heater and a steam tank to form a steam circulation path. The heating by steam heaters, geothermal exchanger according to claim 1, characterized in that made by an external heat source other than geothermal. The geothermal exchanger according to claim 1 or 2, wherein the pressure water is hot water generated by supplying heat from the tropics and rising to the ground without containing steam. The geothermal exchanger according to claim 1 or 2, wherein the pressure water is obtained by separating steam from a gas-liquid two-phase flow taken out to the ground. A geothermal power generation device characterized in that power is generated using the geothermal exchanger according to any one of claims 1 to 4.

Images