JPS61277877A - Offshore geothermal power generating system - Google Patents

Abstract

PURPOSE:To enhance the generating efficiency as a whole and to effectively utilize the geothermal energy stored under the sea-bed by constructing a power generating base on the sea-bed and providing a generating equipment which allows the electric power to be generated at each temperature range covering a high temperature range to a low temperature range. CONSTITUTION:A power generating base 1, which is constructed on the land and is transported on the sea, is lowered to the sea-bed at the site in order to establish a generating base 1. This generating base 1 is equipped with both a production well 3 and a return well 4 in order to transfer the steam and hot water extracted from the production well 3. Out of this steam and hot water, that whose temperature belongs to a high temperature range of 150 deg.C or higher is used at generating equipment 10-13 for conventional steam generation or flashing power generation. On the other hand, the saturated steam whose temperature belongs to an intermediate range of around 100 deg.C is used by an atmospheric pressure turbine to generate power. While the steam or hot water whose temperature belongs to a low temperature range of about 65 deg.C is used in indirect generating equipment, in which CO2 is used as the medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a submarine geothermal power generation system that excavates a geothermal production well on the seabed and uses geothermal energy to generate electricity.

[Conventional technology]

Geothermal energy is a natural energy resource that is available in much larger quantities than solar heat, wind power, etc., and is a type of energy that is highly expected to be used effectively as a new, domestically produced energy that will not run out. It is. Currently, most of the uses of geothermal energy are for power generation. Although there are some geothermal power plants that have started operation so far, the geothermal fluid that is mainly used is so-called dry steam with a temperature of 150° C. or higher and almost no moisture, which is of good physical quality. In addition, depending on the chemical properties such as temperature and acidity of the geothermal fluid, it may be used in agriculture, heating, etc.
It is also used for snow melting and other multipurpose purposes. Conventionally, in what cases is the thermal energy of geothermal fluid used for power generation?
When geothermal fluid is used for purposes other than power generation, it is classified based on the temperature in the underground reservoir of geothermal fluid.

[Problem that the invention seeks to solve]

In the past, as mentioned above, geothermal energy has been actively developed on the ground and used for power generation, hot springs, and other heat sources. However, regarding the utilization of geothermal energy under the sea,
Maintenance and management of hot water production, transportation of hot water, seawater pollution (hazardous substances,
It has not received much attention due to problems such as prevention of heat (heat) and low utilization efficiency due to limited operating temperature range.

The present invention solves the above problems and aims to provide a submarine geothermal power generation system that can effectively utilize geothermal heat and is easy to maintain.

[Means for solving problems]

To this end, the submarine geothermal power generation system of the present invention constructs a power generation base on the seabed, installs power generation equipment capable of generating power in each temperature range of geothermal fluid from high temperature to low temperature, and also installs geothermal production wells. The feature is that it is excavated and generates electricity using geothermal fluid down to a low temperature range.

[Effect]

In the submarine geothermal power generation system of the present invention, geothermal fluid is extracted from the production well and power generation from high temperature to low temperature ranges is performed at the submarine power generation base, so high power generation efficiency can be obtained and the release temperature of the geothermal fluid can be lowered.

Furthermore, by constructing a power generation base equipped with power generation equipment on land, transporting it over the sea, and sinking it there, it is possible to facilitate the construction of a power generation base on the ocean floor.

〔Example〕

Examples will be described below with reference to the oral surface.

FIG. 1 is a diagram showing an embodiment of the submarine geothermal power generation system according to the present invention, where l is a power generation base, 2 is a power transmission base, 3 is a production well, 4 is a reinjection well, 5 is a gas, a scale removal section, 6 is a discharge port, 7 is a separator, 8 is a water collection tank, 9 is a flasher, 110 is a pole check valve, 11 is a drain tank, 12 is a turbine, 13 is a generator, 14 is a condenser, 1
5 is a return pump, 16 is a condensate pump, 17 is a hot water pump, 18 is a cooler, 19 is a power transmission cable, and 20 is a transformer.

In Fig. 1, a power generation base 1 is constructed on the seabed, has the necessary equipment as a power generation facility as explained below, and is equipped with a geothermal production well 3 and a return well 4, whose outer wall serves as a cooling surface. It is. This power generation base 1 may be constructed by constructing a set of power generation equipment and other equipment on land, and then transporting it by sea and sinking it to the seabed. Power generation base 1
Then, the two-phase flow of steam and hot water extracted from the production well 3 is guided to the gas/scale removal section 5, where non-condensable gas and scale contained in the two-phase flow are removed, and then passed to the separator 7. send. The two-phase flow sent to the separator 7 is first separated into steam and hot water here, and the steam is sent to the high-pressure stage of the turbine 12 and the hot water to the furano shear 9. Further, the steam obtained by flanching in the flannel shear 9 is also sent to the intermediate pressure stage of the turbine 12. Further, the hot water separated by the flasher 9 is returned underground from the reinjection well 4 through the drain tank 11. On the other hand, the steam that has done work in the turbine 12 is condensed in a condenser 14 to become hot water, and is sent by a hot water pump 17 to a cooler 18 installed outside (under the sea) of the power generation base 1 to be cooled. The cold water produced here is sent to the condenser 14 by the condensate pump 16, used to cool the steam from the turbine 12, and returned underground from the reinjection well 4 through the return pump 15. Electric power generated by the generator 13 connected to the turbine 12 is transmitted through the power transmission cable 1
9 from the power transmission base 2 constructed on land to the transformer 20
The voltage is then boosted and transmitted to the area of consumption. Note that the outlet 6 is for carrying out scale and the like removed from the two-phase flow by the gas/scale removing section 5. By providing such an exit port 6, maintenance can be facilitated because scales and the like need only be taken out periodically.

The submarine geothermal power generation system according to the present invention is based on the above-mentioned configuration, but in order to effectively utilize geothermal energy over a wide temperature range, it has a temperature range from a high temperature range (300°C) to a low temperature range (65°C). ) It will be constructed with multiple power generation facilities corresponding to each temperature range, so that it can generate electricity using geothermal fluid up to As power generation equipment compatible with each of these temperature ranges, power generation equipment such as steam power generation, flash power generation, total flow power generation, etc. that have been conventionally employed in the high temperature range may be used.

Conventionally, these geothermal power generation systems are targeted at cases where the geothermal temperature is 150°C or higher. Therefore, in order to generate electricity using geothermal fluid even in a temperature range lower than the temperature range targeted for conventional power generation, the submarine geothermal power generation system of the present invention has a
Indirect generation using an atmospheric pressure turbine that uses saturated steam at 00℃ as input energy, and CO□ as a medium in a lower temperature range! Indirect power generation using CO□ as a medium uses geothermal fluid to heat and pressurize CO□ to 65℃ and 130 kg/cnt through indirect contact to drive a turbine. In addition to supplying CO□ to the evaporator, it also supplies geothermal fluid at a low temperature of about 65 to 80°C, which was used in the geothermal production well and the previous medium-temperature region power generation equipment. And in this preheating/evaporator, 6
The medium COt exchanges heat between the geothermal fluid at a low temperature of about 5 to 80 degrees Celsius and the medium CO□, which has a critical temperature of 35 degrees Celsius and 70 k.
g/cd, which is 65℃, 130kg/cxl
It is stable without thermal decomposition even when the temperature and pressure are increased.

Therefore, by utilizing the characteristics of this critical temperature of 35°C and 170 kg/cJ and the stable properties of CO□, the CO□ of the medium was reduced to 6
The temperature and pressure are increased to 5°C, 130 kg/cd, and then supplied to the turbine.

By configuring power generation using multiple power generation facilities corresponding to each temperature range in this way, geothermal energy can be utilized even in low-temperature ranges, increasing power generation efficiency and reducing costs. It is possible to increase the performance and lower the emission temperature.

In addition, while geothermal fluid is stored underground, various substances dissolve, and non-condensable gases such as II and S (hydrogen sulfide) are discharged, and scale is precipitated. 5 removes such gas and scale, and FIG. 2 is a diagram for explaining an example of scale removal using an adsorbent in the gas/scale removal section. 22 is a container, 23 is a bentonite inlet, 24 is an axial mixer, 25 is a conveyor, and 26 is a bentonite outlet.

The scale of CaC01 (calcium carbonate) etc. that occurs in geothermal hot water is found in the shell of red shell 2 as shown in Figure 2 + al.
When passed through the container 22 containing 1, it adheres very well to the hairs of the red shell 21 and is removed. Therefore, the scale can be attached to the hairs of the red shell 21 and removed all at once in the form of a certain amount of lumps. Further, since the red shell 21 forms an appropriate space in the container 22, a smooth filtering action can be expected.

As mentioned above, the red shell 21 is effective as a scale adsorbent, but bentonite can also be used as a similar adsorbent as shown in FIG. 2 Tol. In the case of the example shown in FIG. 2, bentonite is mixed into the ground water 243 from the bentonite inlet 23. and,
By kneading hentonite into geothermal hot water using an axial flow mixer 24, scale is attached and mixed with bentonite, and the scale is taken out from a bentonite takeout port 26 by a conveyor 25.

Also, 11. As a method for removing non-condensable gases such as S, H2S may be removed by reacting a slab containing scraps such as Fe (iron) and Cu (copper). That is, (]2s contained in the geothermal fluid is IIzS + Fe −e FeS 1 H211, s
FeS (
Iron sulfide) and Cub (sulfide w4) are generated and removed from the geothermal fluid.

In FIG. 1, when the above-mentioned removal device is employed in the gas/scale removal section 5, red shells, bentonite, slabs containing FeS and CuS, etc. are periodically carried out from the carrying out port 6. It should be noted that such a removal device has low material costs and a simple device, and can reduce the burden of gas and gas removal in the entire system.

As a scale measure, it would also be beneficial to take measures for production well 3. In other words, the occurrence of scaling in the production well 3 causes a situation such as closure of the casing. Therefore, the avoidance of scaling in production well 3 is
This will extend the life of the production well. One example of a measure to avoid such scaling is to reduce C(h gas) near the scale precipitation point of production well 3. In other words, geothermal hot water contains Ca(HCOz)z (calcium hydrogen carbonate). The melt is mixed in. This is always CO2 and Ca.
It has the property of separating into CO5 (calcium carbonate) and HzO. Therefore, when hot water flashes and expands, CO□ also expands and spews out to the ground together with steam, causing CO
The balance between Oz and CaCO3 is disrupted, and as a result, CaCO3 remains as a scale and adheres to the flash point. Therefore, by supplying and returning Cow to the vicinity of the flash point where this CaCO2 remains and adheres as scale, CO2 and CaC0 are returned to the balance state before the flash, and the adhesion of scale is prevented.

In general, production wells consist of a conductor canong, an anchor casing connected underneath it, and a production casing, which are used to protect the soft strata near the surface, block groundwater, and serve as a base for installing a blowout preventer. It is fixed entirely with cementing. However, particularly in the production casing section, moisture permeates into the voids in the mortar and expands due to geothermal heat, compressing the casing and causing uneven deformation. Therefore, a problem arises in that scale is likely to adhere to the uneven deformed portion. Therefore, the anchor casing part is fixed by cementing, and the production casing part is loosely fitted without cementing. By doing so, deformation of the production casing is eliminated and scaling caused by deformation of the casing is prevented.

Note that the present invention is not limited to the above-described embodiment (and various modifications are possible. For example, although the cooler 18 shown in FIG. 1 is installed outside the power generation base I, , the cooler 18 may be installed in the power generation base I so that a part of the wall surface of the cooler 18 is used as the cooling wall surface of the cooler 18.By doing this, all the equipment can be installed in the power generation base 1. This allows the construction of a power generation base system on the seabed to be easily constructed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the power generation base can be constructed as a centrifugal structure equipped with various equipment, transported by sea, and installed by sinking to the seabed, which facilitates construction. Moreover, since geothermal fluid is used for power generation even down to the low temperature range using power generation equipment suitable for each temperature range, it is possible to increase total power generation efficiency and improve cost performance.
It is possible to effectively utilize geothermal heat in undeveloped seabed areas. Furthermore, by making it possible to release hot water at low temperatures into reinjection wells and seawater, and by preventing and removing scale, pollution problems can be avoided and the system can be made maintenance-free. Furthermore, since it is configured with an undersea base,
The surrounding wall can be used to cool the entire surface, and since the seawater that comes into contact with the cooling surface undergoes natural convection due to residual heat, cooling efficiency can be improved and cooling water for condensate can be easily generated.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the submarine geothermal power generation system according to the present invention, and FIG. 2 is a diagram for explaining an example of scale removal using an adsorbent in a gas scale removal section. l...Power generation base, 2...Power transmission base, 3...Production well, 4...Reduction well, 5...Gas/scale removal section, 6
... Carrying out port, 7... Separator, 8... Water collection tank, 9... Flasher, 10... Pole check valve, 11... Drain tank, 12... Turbine, 13 ... Generator, 14 ... Condenser, 15 ... Return pump, 16 ... Condensate pump, 17 ... Hot water pump, 18 ... Cooler, 19 ... Power transmission cable, 20
...Transformer, 21...Ark shell, 22...Container,
23... Bentonite inlet, 24... Axial flow mixer, 25... Conveyor, 26... Bentonite outlet. Figure 2

Claims (6)

[Claims] (1) Build a power generation base on the seabed, install power generation equipment that can generate electricity in each temperature range of geothermal fluid from high temperature to low temperature, and drill geothermal production wells to generate geothermal energy up to low temperature. A submarine geothermal power generation system that uses fluid to generate electricity. (2) The submarine geothermal power generation system according to claim 1, characterized in that the production casing of the production well is non-cemented. (3) The submarine geothermal power generation system according to claim 1, characterized in that carbon dioxide gas is fed to the vicinity of the scale generation point of the production well. (4) The submarine geothermal power generation system according to claim 1, characterized in that a scale adsorbent is interposed in the geothermal fluid conveyance path. (5) Submarine geothermal power generation according to claim 1, characterized in that a slab containing iron or copper is placed in a geothermal fluid conveyance path and reacted to extract hydrogen sulfide gas as iron sulfide or copper sulfide. system. (6) An atmospheric pressure turbine is used to generate electricity for geothermal fluid in a medium temperature range, and a carbon dioxide gas turbine is used to generate electricity for geothermal fluid in a low temperature range. Submarine geothermal power generation system.