JP2971827B2 - Treatment method of hot water flowing out from geothermal steam sampling well - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating hot water flowing out of a geothermal steam sampling well. For more information,
The present invention has a problem in that when hot water flowing out accompanying geothermal steam from a geothermal steam sampling well used for geothermal power generation is returned to the underground, it adheres to a hot water piping system or a reducing well. The present invention relates to a method for treating hot water, which effectively suppresses precipitation of magnesium-containing clay mineral mainly composed of stevensite.

[0002]

2. Description of the Related Art A few kilometers underground in a volcanic area, 100
There is a heat source of about 0 to 1200 ° C., that is, a so-called magma chamber. When rainwater penetrates to a deep reservoir (generally 1 to 3 km in depth), it is heated by the magne pool, and 200 to 300 ° C. It is ejected to the ground or stored in the ground as a degree of hot water or steam. In geothermal power generation, geothermal steam stored in the ground is blown out by boring, and a steam turbine is operated to generate power. However, in many geothermal steam sampling wells, several times the amount of hot water spouts together with the geothermal steam, so the steam and hot water are separated on the ground, and the steam is used for power generation. Since arsenic often exceeds the emission standard, it is usually reduced to underground through a reduction well.

[0003] This hot water contains silica, calcium ions, magnesium ions, iron ions, manganese ions, bicarbonate ions and the like. Therefore, for example, by flashing in a wellbore, hardly soluble calcium carbonate is produced. When colloidal silica is deposited and deposited as calcium scale in a geothermal well or when steam and hot water are separated into steam and water, and then reduced to hot water, colloidal silica is generated. This causes problems such as the inability to smoothly operate the geothermal power generation due to adhesion to the like. Therefore, various measures have been taken to solve such a problem. For example, (1) an average molecular weight of 1 adjusted to pH 8.5 to 11.0 in a geothermal well;
A method of preventing adhesion of calcium scale by injecting 500 to 20,000 sodium polyacrylate (JP-B-63-25157). (2) Reducing hot water separated from steam by a steam separator to the underground At this time, an acid is added to the hot water while maintaining a sealed state with the atmosphere to adjust the pH to 4 to 4.
6, a closed reduction system method (Japanese Patent Publication No. 61-53514) for preventing the adhesion of silica scale, and the like are performed.

[0004] However, the above method (1) is very effective for preventing adhesion of calcium scale, and the method (2) is a very effective method for preventing adhesion of silica scale. According to the method (2), the smectite-based scale is effectively prevented from adhering, but the piping and equipment are easily corroded. With silica in hot water,
In geothermal steam sampling wells containing a large amount of magnesium ions, iron ions, manganese ions, etc., when hot water is reduced to the underground, smectite scale mainly consisting of stevensite adheres to the inner wall of the piping system, reducing the inner diameter of the piping. Not only can it be narrowed, but in extreme cases the piping system can be blocked. In addition, this smectite scale is attached not only to the piping system, but also to the inner wall of the reducing well when hot water is reduced from the reducing well to the underground, and further, a hole or a hole for conducting the hot water from the reducing well to the underground. The crevices and the like are also closed, and as a result, the function as a reduction well may be lost. Therefore, development of a method for effectively suppressing the adhesion of smectite scale has been desired.

[0005]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a method for reducing underground hot water flowing out from a geothermal steam sampling well used for geothermal power generation along with geothermal steam. A method of effectively suppressing the precipitation of magnesium-containing clay minerals such as smectite-based minerals, mainly stevensite, which has become a problem by adhering to hot water piping systems and reducing wells without corroding pipes and various equipment. The purpose is to provide.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that when reducing hot water separated from steam to the underground by a closed system, the hot water or It has been found that the purpose can be achieved by adding an acid to the gas-liquid two-phase flow before gas-liquid separation to adjust the pH to a predetermined range. The present invention has been completed based on such findings. That is, the present invention separates steam and hot water from a high-temperature high-pressure fluid flowing out of a geothermal steam sampling well into steam and hot water, and then returns the hot water to the underground while keeping the hot water sealed with the atmosphere. Add acid to hot water after steam-water separation to adjust pH to the range of 6.3 to 6.7 ,
Alternatively, (2) a part of the hot water after the gas-water separation is extracted, and an acid added thereto is circulated in a gas-liquid two-phase flow before the gas-water separation to adjust the pH of the hot water phase to 6.3 to 6; The present invention provides a method for treating hot water flowing out of a geothermal steam sampling well, which is adjusted to a range of 0.7 to suppress precipitation of a magnesium-containing clay mineral.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a preferred embodiment of the present invention will be described with reference to the accompanying drawings. The magnesium-containing clay mineral referred to in the present invention is a smectite-based mineral mainly composed of stevensite. FIG. 1 is an example of a flow sheet for carrying out the method of the present invention. As shown in the figure, the present invention employs a closed reduction system. First, a high-temperature and high-pressure fluid composed of geothermal steam and hot water ejected from a geothermal steam sampling well 1 is supplied to a steam-water separator 3 by a pipe 2 to separate geothermal steam and hot water,
Geothermal steam is supplied from a pipe 4 projecting from the bottom center of the steam separator 3
And sent to a steam turbine (not shown). On the other hand, hot water is taken out through a pipe 5 attached to the steam separator 3. Note that reference numeral LH in the figure is a level header attached to the steam separator 3. The hot water taken out through the pipe 5 is added with an acid from an acid container 6 connected to the pipe 5, whereby the pH is higher than 6
It is adjusted to a lower (6 <pH value <7) range. When the pH is out of this range, the effect of suppressing precipitation of the magnesium-containing clay mineral is not sufficiently exhibited, and the object of the present invention cannot be achieved. In addition, when the pH is 6 or less, the piping and equipment are easily corroded. In order to particularly effectively suppress the precipitation and corrosion of the magnesium-containing clay mineral, it is advantageous to adjust the pH of the hot water to around 6.5, particularly to 6.3 to 6.7.

[0008] The acid used for the pH adjustment is not particularly limited, for example, preferably strongly acidic ones such as hydrochloric acid, sulfuric acid, nitric acid and the like. Particularly, from the viewpoint of economy and handling, hydrochloric acid and sulfuric acid are preferred. Is preferred. These acids may be used alone or in combination of two or more. The concentration of the acid is not particularly limited, and may be appropriately selected according to the situation. Since the pipe 2 before the steam-water separator 3 is in a gas-liquid two-phase flow in which steam and hot water are mixed, acid may be mixed into the pipe 4 through which steam flows. Additive mixing of the acid by the method is not preferred. In addition, since the scale is easily generated due to a rise in pH or a decrease in temperature due to a decrease in pressure, it is advantageous to add the acid in the pipe 5 between the steam separator 3 and the LH immediately after the steam separation. . However, in the case where scale deposition is already observed not only from the pipe 5 where the hot water flows but also from the pipe 2, it is necessary to add an acid from the pipe 2 to suppress this. In this case, it is preferable to add an acid as shown in FIG. FIG. 2 is a flow sheet showing another example of the method for adding an acid according to the present invention, in which a part of hot water is withdrawn from a pipe 5, pressurized by a pump P, and then acid is added from an acid container 6; back to the pipe 2 near the geothermal steam adoption toy 1,
Mix. By using such a method, the acid can be added to and mixed with the gas-liquid two-phase flow of the pipe 2 without mixing the acid into the pipe 4 through which the steam flows.

The hot water whose pH has been adjusted in this manner is guided to a heat exchanger 7 by a pipe 5, heat-exchanged, guided to a reduction well 8 through a pipe 9, and further reduced to the underground. . On the other hand, the hot water heat-exchanged by the heat exchanger 7 can be effectively used, for example, for industrial water, house cultivation, and other purposes such as heating various buildings. According to the method of the present invention, precipitation of the magnesium-containing clay mineral in the hot water is suppressed, so that the magnesium-containing clay mineral is formed in the heat exchanger 7 and the inner wall of the pipe 9 connecting the heat exchanger 7 and the reduction well 8. The scale of the clay mineral is hard to adhere, and as a result,
The heat efficiency of the heat exchanger can be maintained high, and the heat exchanger can be used for a long time. In addition, since the magnesium-containing clay mineral hardly adheres to the pores and crevices inside the reduction well 8 and the hot water from the reduction well 8 to the underground, the reduction well 8
Can also be used for a long time.

[0010]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 and Comparative Examples 1 and 2 The same scale suppression test equipment was provided in three lines, and the tests of Example 1, Comparative Examples 1 and 2 were performed, respectively. FIG.
The simplified flow sheet of the scale suppression test equipment used for this test is shown below. The raw hot water A is continuously supplied to the test facility, and 1 wt% hydrochloric acid B is continuously supplied so that the pH measured by the pH meter 16 becomes a predetermined value. The raw hot water and 1% by weight hydrochloric acid are mixed in a line mixer 11 and further sufficiently mixed in a buffer tank 12, and then discharged to a pit C via a flash tank 17. Two test pieces 13 for corrosion test are installed in the buffer tank 12, and a cylindrical test piece 14 for attaching scale is installed on the line. The supply amount of the raw hot water is controlled so that the flow rate measured by the flow meter 15 becomes a predetermined value.

<Operating conditions> Raw hot water (origin: Morikawa, Morimachi, Hokkaido): primary hot water separated by a steam separator, SiO ₂
Content 410-450 mg / l, Mg content 0.6-1.
7 mg / liter, pH 8.2, temperature 150 to 160 ° C. Hot water flow rate: 2.5 tons / hour Line pressure: 4.5 to 5.0 kg / cm ² G pH: 7.5 (Comparative Example 1), 6. 5 (Example 1),
5.5 (Comparative Example 2) Operating period: 62 days As a test piece for corrosion test to be installed in the buffer tank, a SUS304 test piece (weight about 9) was used.
9g, wall thickness about 6mm, surface area 24.5cm ² ) and SS4
Using a 00 test piece (weight about 96 g, wall thickness about 6 mm, surface area 24.5 cm ² ), a SUS316 cylindrical test piece (weight about 410 g, inner diameter about 26 mm) was used as a scale-attaching test piece installed in the line. Using. After the operation, take out each test piece,
Visual observation and weight measurement were performed, and the degree of corrosion was evaluated for the test piece for corrosion test. The results are shown in Tables 1 and 2.

[0012]

[Table 1]

[0013]

[Table 2]

(Note) 1) If scale is attached, measure after removing it. 2) Corrosion rate (%) = [reduced weight before and after test (g) / weight before test (g)] × 100 Further, with respect to the test piece for scale adhesion, the change in inner diameter was further measured to evaluate the degree of scale adhesion. The results are shown in Tables 3 and 4.

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

According to the method of the present invention, when the hot water flowing out from the geothermal steam sampling well used for geothermal power generation along with the geothermal steam is returned to the underground, the hot water piping system and the reducing well are used. It is possible to effectively suppress the precipitation of magnesium-containing clay minerals such as smectite-based minerals, which are mainly composed of stevensite, which has become a problem by adhering to the pipes. The smooth operation of geothermal power can be secured.

[Brief description of the drawings]

FIG. 1 is an example of a flow sheet for implementing the method of the present invention.

FIG. 2 is a flow sheet showing another example of the method for adding an acid in the present invention.

FIG. 3 is a simplified flow sheet of a scale suppression test facility used in Examples and Comparative Examples.

[Description of Signs] 1: Geothermal steam sampling well 3: Steam / water separator 6: Acid vessel 7: Heat exchanger 8: Reduction well 11: Line mixer 12: Buffer tank 13: Corrosion test test piece 14: Scale adhesion Test piece 15: Flow meter 16: pH meter 17: Flash tank A: Raw water B: 1% by weight hydrochloric acid C: Pit LH: Level header P: Pump

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E21B 43/40 E21B 43/00

Claims (3)

(57) [Claims] After separating high-temperature and high-pressure fluid flowing out of a geothermal steam sampling well into steam and hot water, the hot water is returned to the underground while being kept sealed with the atmosphere. A method for treating hot water flowing out of a geothermal steam sampling well, comprising adding an acid to the hot water to adjust the pH to a range of 6.3 to 6.7 to suppress precipitation of a magnesium-containing clay mineral. . 2. After separating the high-temperature and high-pressure fluid flowing out of the geothermal steam sampling well into steam and hot water, the hot water is returned to the underground while being kept sealed with the atmosphere. A portion of the hot water is extracted, and an acid added to the hot water is circulated through a gas-liquid two-phase flow before gas-water separation.
A method for treating hot water flowing out of a geothermal steam sampling well, wherein H is adjusted to a range of 6.3 to 6.7 to suppress precipitation of a magnesium-containing clay mineral. 3. The method for treating hot water according to claim 1, wherein the acid is hydrochloric acid and / or sulfuric acid.