JPH09177507A - Method for disposing non-condensable gas in geothermal power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform detoxicating treatment for non-condensable gas containing toxic gas without exhausting the gas into the atmosphere by injecting non- condensable gas generated in a condenser provided in the downstream side of a steam turbine into a heated water returning well and returning the gas together with returning heated water to the underground. SOLUTION: A geothermal fluid jetted out of a production well 1 is passed through an entrance separator 2 and a steam header 3 and then supplied to the stream entrance part of a steam turbine 5. The steam is introduced to the stream turbine 5 and used for power generation and heated water is returned through a returning well 7 to the underground. Especially, non-condensable gas generated in a condenser 8 provided in the downstream side of the steam turbine 5 is injected into the heated water returning well 7 and thus returned together with the returning heated water to the underground. Thus, since the gas is returned to the underground, no environmental problem such as an offensive odor or the like is prevented and the non-condensable gas is subjected to a detoxicating treatment without reducing the amount of returning heated water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a proposal for a technique for detoxifying non-condensable gas contained in geothermal fluid used for geothermal power generation, and in particular to open the self-injected geothermal fluid to the atmosphere. The present invention relates to a method for disposing non-condensable gas applied to a geothermal power generation facility related to a closed system for processing without treatment.

[0002]

2. Description of the Related Art A general geothermal power generation system, as shown in FIG. 1, excavates a well (production well) from the ground to a high-temperature geothermal fluid reservoir in the deep underground, and The fluid is self-injected to the ground through this production well 1, while on the other hand, it is separated into steam and hot water by a wellhead separator 2 (steam / water separator), and the steam is supplied to a steam turbine 5 via a steam header 3 and a separator 4. Then, the generator 6 is driven. On the other hand, hot water is a method of returning to the underground through the reducing well 7.

In such a geothermal power generation system, as a method of treating (reducing) the hot water separated by the wellhead separator 2, a so-called atmospheric opening system in which the hot water is once released to the atmosphere and then reduced is provided and a predetermined atmosphere without opening to the atmosphere. There are two methods, so-called closed systems, in which underground return is performed while maintaining pressure.

The above-mentioned atmosphere opening system requires a large circulating water tank for lowering the silica component in hot water by intentionally precipitating scale beforehand, and furthermore, due to the temperature drop of hot water, oxidation by aeration, etc. For example, the use of a scale inhibitor is indispensable in order to prevent the formation of scale that precipitates when the silica component contained in the geothermal fluid changes its form from monosilicic acid to polysilicic acid. Therefore,
There is a problem that labor and cost increase. In addition, despite these efforts, this open system requires rehabilitation of the reduction well and excavation of new wells in order to completely remove the scale, which contributes to the increase in geothermal power generation costs. Was becoming.

On the other hand, in the closed system as shown in FIG. 1, since there is no temperature drop of hot water and oxidation due to aeration that occurs in the case of the open-air type, the hot water is returned underground without causing scale. In fact, most geothermal power plants in recent years have begun to adopt this method. For example, this technology that was proposed by the present applicant (Japanese Patent Publication No. 62-18712).
”Geothermal power generation steam extraction A geothermal fluid consisting essentially of steam and hot water that self-injects from a well is introduced into a steam-water separator installed on the ground to separate it into steam and hot water. The method of substituting underground into deeply cracked strata with deep ground temperature of 180 ℃ or higher through reduction wells while maintaining temperature of 100 ℃ or higher and pressure of 1.5kg / cm ² or higher without releasing water to the atmosphere. " Is.

[0006]

In the case of the above-mentioned conventional power generation system, generally, a condenser 8 is usually provided on the downstream side of the steam turbine in order to improve the efficiency of the steam turbine. A jet type is usually used for the condenser 8, but it is a device having a function of sucking and condensing vapor together with gases such as carbon dioxide and hydrogen sulfide. The role of this device is to create a high vacuum in the condenser by the volume change that occurs when the steam discharged from the steam turbine 5 condenses when being introduced into the condenser 8. To keep turbine low to improve turbine efficiency. For example,
By efficiently discharging the non-condensable gas from the condenser 8,
In order to improve turbine efficiency, this non-condensable gas is introduced into the steam jet ejectors 9a and 9b or the compressor to improve the discharge efficiency of the non-condensable gas from the condenser 8. In the figure, 10 is an intercooler and 11 is an outer cooler, through which the non-condensable gas is discharged to the atmosphere.

By the way, geothermal steam has a very large amount of non-condensable gas as compared with ordinary thermal power generation, and sometimes exceeds 10% of the total steam amount. Since this non-condensable gas contains harmful gas, it must be detoxified and discharged. However, conventionally, a technology for economically removing (disposing) a harmful gas such as hydrogen sulfide from a non-condensable gas has not been established yet, and the condenser 8 and the steam jet ejectors 9a and 9b are directly exposed to the atmosphere. Cooling tower 12 for discharging or accelerating by turbo blower to circulate hot water for cooling
At present, it is emitted with a larger amount of exhaust gas.

As described above, according to the conventional technique,
As a result of the condenser being kept in a high vacuum, the efficiency of the steam turbine is also improved, but it often causes an environmental problem such as the generation of a bad odor due to the release of the non-condensable gas containing hydrogen sulfide gas.
There is a strong demand for the establishment of effective disposal methods for non-condensable gases.

A first object of the present invention is to propose a method for detoxifying a non-condensable gas containing a harmful gas.
A second object of the present invention is to propose a method of disposing non-condensable gases without releasing them into the atmosphere. A third object of the present invention is to use non-condensable gases without adversely affecting the underground reduction of hot water in a closed system,
We are proposing a suitable method of performing underground reduction together with the hot water.

[0010]

In order to achieve the above-mentioned object, the present invention proposes a means for solving the problems having the following items as its gist. (1) The geothermal fluid that self-injects from the steam extraction production well is separated into steam and hot water through a steam separator, and then the steam is introduced into a steam turbine for power generation without opening to the atmosphere. On the other hand, in the method of returning hot water to the underground through a reduction well, the non-condensable gas generated in the condenser installed on the downstream side of the steam turbine is injected into the reduction well for hot water reduction. A method for disposing of non-condensable gas generated in a geothermal power generation facility, which is characterized by performing underground reduction with the reduced hot water. (2) A method for disposing non-condensable gas, which comprises injecting the non-condensable gas into a piping for reduced hot water, joining the reduced hot water, and then performing underground reduction. (3) In returning the non-condensable gas to the underground, after compressing the non-condensable gas with a compressor, after combining with the reduced hot water through an ejector provided in the pipe for the reduced hot water or in the reduction well, the underground reduction is performed. A method for disposing of non-condensable gas, characterized by:

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the non-condensable gas extracted and separated by the condenser is basically mixed with the reduced hot water after the steam separation, and is reduced underground. When,
Gas and liquid will be separately returned underground without mixing. In such a case, the reduced hot water in the reduced hot water pipe or the reduced well is flown into the slag (bubble 1
7) and, depending on the case, hot water pulsation due to gas injection may occur, and the amount of reduced hot water may decrease.

Therefore, as a preferred embodiment of the present invention, the non-condensable gas is pressurized by a compressor or the like, and then the non-condensable gas is rapidly supplied to an ejector installed in the reduced hot water pipe or the reduction well. By injecting with, the mixture is mixed homogeneously with hot water for reduction and then reduced deep underground. As described above, it is preferable to mix the reduced hot water and the non-condensable gas by using the ejector because the non-condensable gas is mixed with the reduced hot water in the form of finer bubbles.

Further, in the present invention, when the amount of the non-condensable gas is large, it is possible to install the aged ejector down to the deep underground of the reduction well and inject the non-condensable gas into a deep position as close as possible to the reduction layer. More preferable.

[0014]

EXAMPLE FIG. 2 is a schematic diagram showing an example of a method for disposing of non-condensable gas according to the present invention. The geothermal fluid ejected from the production well 1 passes through the wellhead separator 2, the steam header 3, and is further supplied to the steam inlet portion of the steam turbine 5.
In this way, the high-pressure steam ejects the turbine 5
The rotor is rotated, and the generator 6 generates electric power.

The steam introduced into the steam turbine 5 is rarely overheated steam, but is generally saturated steam at 150 ° C. or higher, while the exhaust steam after driving the turbine has an outlet temperature of 5
It is a low temperature wet steam of about 0 ° C. At the rear of the turbine outlet side, a condenser 8 is provided in order to suck such low-temperature wet steam and improve power generation efficiency. Most of the low-temperature wet steam is stored in the condenser 8. The condenser 8 is cooled and condensed, while the inside of the condenser 8 is therefore in a reduced pressure atmosphere.

Reference numeral 12 in the figure is a cooling tower provided for cooling the cooling water of the condenser 8. Here, the non-condensable gas extracted by the condenser 8 is provided in the reduction hot water pipe 14 or the reduction well 7 through some compressors 13a and 13b and the intercooler 10 and the non-condensable gas pipe 16. It is supplied to the ejectors 15a and 15b, and is injected and merged with the hot water to be mixed. Note that the reduction hot water pipe 14 is used for underground reduction of the hot water after separating the geothermal fluid ejected from the production well 1 into steam and hot water into the reduction well 7 by a closed system without opening to the atmosphere. It is piping.

FIG. 3 is an explanatory view of a joining portion of the hot water pipe 14 and the non-condensable gas pipe 16. Ejectors 15a are respectively inserted in these or reduction wells 7. In addition, these ejectors 15a usually have a non-condensable gas flow path portion 17 and a reduced hot water intake port 18.

In the present invention, the ejector 15a having such a structure is disposed so as to be immersed in the reduced hot water in the pipe at the downstream side (close to the reduction well) of the reduced hot water pipe 14 and the ejector 15a is provided. The pipe 16 is connected to the non-condensable gas flow passage portion 17 provided at the center of the non-condensable gas flow passage portion 17, and the non-condensable gas is flown from the non-condensable gas flow passage portion 17 into the ejector 15a at high speed. As a result, the reduced hot water flowing through the reduced hot water pipe 14 is sucked into the ejector 15a through the reduced hot water intake port 18 provided around the ejector 15a, and the reduced hot water and the non-condensable gas fine particles are drawn. The non-condensable gas is reduced to a deep underground reducing layer through the reduced hot water pipe 14 or the reduction well 7, resulting in the adverse effect of hydrogen sulfide. Can be disposed of without.

FIG. 4 shows an example in which an ejector 15b similar to that shown in FIG. 3 is installed at a position of a predetermined depth in the reduction well 7, and the operation is the same as in FIG. Since the non-condensable gas can be directly reduced to a deep portion, it can be advantageously applied as a reduction method that does not cause pulsation of reduced hot water especially when the amount of the non-condensable gas is large.

[0020]

As described above, according to the present invention, the non-condensable gas contained in the geothermal fluid can be mixed with the reducing hot water for the underground reduction, so that the environment such as the generation of a bad odor can be achieved. The non-condensable gas can be detoxified without causing a problem or reducing the amount of reduced hot water.

[Brief description of the drawings]

FIG. 1 is a flow sheet for disposal of non-condensable gas generated during conventional geothermal power generation.

FIG. 2 is a flow sheet for disposal of non-condensable gas generated during geothermal power generation according to the present invention.

FIG. 3 is a schematic diagram showing the appearance of the mixing section of the reduced hot water pipe and the non-condensable gas pipe used in the present invention.

FIG. 4 is a schematic diagram showing how the reduced hot water used in the present invention and a non-condensable gas are mixed in a reducing well.

FIG. 5 is an explanatory diagram of a reduction well showing the flow of slag.

[Explanation of symbols]

1 Production well 2 Wellhead separator 3 Steam header 4 Separator 5 Steam turbine 7 Reduction well 8 Condenser 13a, 13b Compressor 14 Reduced hot water piping 15a, 15b Ejector 16 Non-condensable gas piping
17 Slag flow (air bubbles)

Claims (3)

[Claims] 1. A geothermal fluid self-injected from a steam sampling production well is separated into steam and hot water through a steam separator, and then the steam is introduced into a steam turbine without being released to the atmosphere. While supplying power, in the method of returning hot water to the underground through a reduction well, non-condensable gas generated in a condenser installed downstream of the steam turbine is injected into the reduction well for hot water reduction. The method for disposing of non-condensable gas generated in a geothermal power generation facility is characterized by performing underground reduction with the reduced hot water. 2. The non-condensable gas according to claim 1, wherein the non-condensable gas is injected into a piping for hot water for reduction, merged with the hot water for reduction, and then subjected to underground reduction. Disposal method. 3. When reducing the non-condensable gas underground, after compressing the non-condensable gas with a compressor, the non-condensable gas is joined with the reduced hot water through an ejector provided in a pipe for the reduced hot water or in a reduction well. The method for disposing of non-condensable gas according to claim 1 or 2, wherein the method is a underground reduction.