JPS5840034B2 - Treatment method for hot water that flows out accompanying geothermal steam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating hot water flowing out from a geothermal steam extraction well along with geothermal steam, and its purpose is to treat hot water attached to the earth's surface. This is to prevent scale from forming within the transport piping system.

Geothermal power generation using geothermal steam has already been carried out, but it is ideal for geothermal power generation to emit only geothermal steam.

However, in Japan, the only example of such eruptions of geothermal steam is currently seen at the geothermal power plant in Matsuyo, Iwate Prefecture, and in many cases, hot water is accompanied by several times the amount of geothermal steam. For,
In geothermal power generation, it is necessary to separate the above-mentioned hot water from geothermal steam.

Currently, when geothermal steam and hot water are ejected as described above, geothermal fluid (hereinafter referred to as geothermal fluid) consisting of gas-liquid two phases of geothermal steam and hot water is ejected from surface heat extraction wells. A steam separator separates the water into geothermal steam and hot water, and the geothermal steam is directly sent to the power generation turbine, while the hot water is sent to the piping system (hereinafter referred to as piping system) connected to the level header of the steam water separator. By injecting the reduction into the reduction well through the
Measures are being taken to prevent pollution problems associated with hot water and the depletion of underground heat sources.

However, when hot water is transferred through a piping system as described above, scale accumulates on the inner walls of the pipes, making it difficult to transfer the hot water smoothly, and in extreme cases, the piping system becomes blocked, resulting in continuous and This may hinder the smooth extraction of geothermal steam and may even make regular geothermal power generation impossible.

The present invention prevents the formation of scale within the piping system by taking the control described in the claims, thereby smoothing the transfer of hot water through the piping system, thereby allowing the continuous flow of geothermal steam. Moreover, it enables smooth collection.

The amount of hot water that flows out along with geothermal steam varies considerably depending on the region, but examples are shown in Table 1.

Among the strings shown in Table 1, it is recognized from the scale analysis results that silicic acid and calcium are responsible for scale formation.

Further, as a result of research by the present inventors, the mechanism of precipitation with silicic acid and calcium in hot water is considered to be as follows.

In other words, silicic acid is formed when hot water that exists under high temperature and high pressure underground flows out onto the ground surface, resulting in a decrease in temperature and pressure, and as these decreases, silicic acid in the hot water polymerizes. It is thought that this forms a high molecular weight silicic acid polymer, which precipitates from the hot water.

On the other hand, calcium is dissolved mainly as calcium bicarbonate in hot water, but as shown in Table 1, there is a considerable amount of dissolved carbon dioxide in hot water, which exceeds the equilibrium solution pressure at high temperatures and high pressures underground. It is preserved and contained.

However, when hot water flows to the earth's surface, causing a pressure drop on the hot water and causing flashing, the equilibrium solubility pressure of dissolved carbon dioxide in the hot water collapses at the same time as steam is generated, and the dissolved carbon dioxide is released into gas. Therefore, calcium bicarbonate in the hot water decomposes as shown below to release carbon dioxide, and the calcium bicarbonate turns into poorly soluble calcium carbonate.

Even if the concentration of calcium carbonate is below its solubility, its dissolution rate is low, so it is thought that it adheres and deposits as scale on the inner wall of the piping system before dissolving in hot water.

As a result of the above analysis, the present invention prevents scale within the piping system by maintaining the hot water flowing out from the geothermal well at high temperature and high pressure as described later, and by adding soluble humates to the hot water. succeeded in.

That is, if hot water flowing out from a geothermal extraction well is kept at high temperature and high pressure as described below, almost no silicic acid will precipitate in the hot water.

The inventor's research has shown that if hot water is maintained at a temperature of 100°C or higher and a pressure of 1.5 ky/iG or higher, the silicic acid in the hot water will polymerize and become a silicic acid polymer, but ,
Even if this is transferred through a piping system, scale will not adhere to the inner wall of the piping system, and if it is maintained at a temperature of 135°C or higher and approximately 2kg/iG (equivalent to saturated vapor pressure) or higher, it will not heat up for a long period of time. Water is allowed to remain clear.

Therefore, scaling caused by hot water can be prevented by maintaining the hot water at a high temperature of 100° C. or higher and a high pressure of 1.5 ky/cIILG or higher, preferably at a temperature of 135° C. or higher and a pressure of 2 kg/cvF, G or higher.

However, even when hot water is held at high temperatures and high pressures as described above, if the hot water contains calcium, scales due to calcium carbonate will form due to the release of dissolved carbon dioxide in the hot water. do.

Since the pressure at the wellhead of a geothermal steam extraction well is as high as 6 to 7 kg/ff1G, the release of dissolved carbon dioxide in the hot water is inevitable due to the relative relationship between the pressure at the wellhead and the pressure within the piping system. Because of this, the pressure of hot water is 1.
Even if the temperature is 5 ky/iG or more, calcium carbonate precipitates in the hot water, and this deposits on the inner wall of the piping system, and it is thought that some of the silicic acid is incorporated into this, forming scale. It will be done.

In the present invention, the above-mentioned calcium carbonate in hot water is adsorbed and removed by a soluble humate salt.

The water-soluble humates are water-soluble humates such as sodium, potassium, and ammonium of natural humic acid or nitrofumic acid.

The above-mentioned soluble humate salt is added to hot water as an aqueous solution having a concentration by weight of 0.1 to 10.

In this case, the amount of soluble humate to be used can be appropriately selected depending on the amount of calcium contained in the hot water and the type of humic acid used, but in general, the amount of calcium contained in the hot water is It is sufficient to use the same amount or less, preferably 1/10 or more.

In addition, the soluble humate may be added immediately after the geothermal fluid is spouted from the geothermal well, or it may be added directly to the hot water after the geothermal fluid is separated into geothermal steam and hot water. It's okay.

As mentioned above, by adding soluble humates to hot water, calcium carbonate, which is generated simultaneously with the release of dissolved carbon dioxide in hot water, can be absorbed into the hot water before it adheres to the inner wall of the piping system. Calcium carbonate can form metastable colloidal particles by forming chelate bonds with soluble humates, or by adsorbing suspended calcium carbonate precipitated in hot water. This is thought to be able to prevent adhesion and deposition on the inner walls of the pipes of the system.

As described above, the present invention can prevent scale formation in the piping system due to silicic acid and calcium in hot water, so that the hot water flowing out along with geothermal steam from the geothermal steam extraction well can be removed from the piping system. can be transferred smoothly through the
Therefore, geothermal steam can be collected continuously and smoothly.

Next, the present invention will be specifically explained with reference to Examples.

The drawing shows an example of an apparatus for a scale generation test in a piping system, in which geothermal fluid ejected from a geothermal extraction well 1 is sent to a main pipe 2 and to a pipe 3 connected to a bypass. A portion is distributed, transferred, and introduced into the steam/water separator 4.

At the same time as the geothermal fluid is introduced into the pipe 3, the 0.5 aqueous solution of soluble humate stored in the tank 5 is metered by the metering pump 6, and the geothermal fluid in the pipe 3 is passed through the pipe 7. All soluble humic acids are added to the hot water by feeding it into the hot water.

The geothermal fluid to which soluble humic acid has been added is sent to a steam separator 4.
The steam is separated into steam and hot water, and the steam passes through the steam pipe 8 in the steam separator 4 and reaches the silencer 9.

On the other hand, hot water is supplied to the level header 10 through valves 11. Pipe 12. Pipe 13. Valve 14.
Pipe 15. Pipe 16. Reduction well 20 via piping system consisting of valve 17 and pipe 18 and valve 19
Reduction is injected underground.

The hot water transferred via these piping systems is maintained at a pressure of 1.5 kv/crit, 0 or more by appropriately adjusting the valves 11, 14, 17 and valve 19 provided in the piping system. Furthermore, by appropriately applying heat insulation treatment (cooling treatment if necessary) to the piping system, it is possible to maintain a temperature of 100° C. or higher.

Each pipe 3, 12, 13, 15, 16, 18 in the scale generation test equipment shown in the drawing has a diameter of 5 cr.
rL steel pipe was used.

Furthermore, the temperatures and pressures at points A, B, C, and D in the apparatus shown in the drawings are shown in Table 2.

After conducting hot water all day and night under the above conditions, scale formation in the piping system was observed, and the results are shown in Table 3.

The hot water shown in Table 1 was used for the scale generation equation test, and Table 3 also shows the case where no soluble humate was added.

Furthermore, when potassium humate salt and ammonium humate salt were used in place of the above-mentioned sodium humate salt, no scale was observed at all when 5 ppffl and 10 ppl were added, respectively.

Further, when the test was continued for several months using the test equipment shown in the drawing, no scale formation was observed within the piping system.

The scale adhesion test device described above can be applied to the actual production of geothermal steam by scaling up the various equipment to match the amount of geothermal fluid ejected from the geothermal extraction well and directly connecting it to the main pipe 2.

As described above, the present invention prevents the formation of scale caused by silicic acid in the piping system by maintaining the hot water flowing out accompanying geothermal steam at a temperature of 100°C or higher and a pressure of 1.5kg/Cr1LG or higher. By adding soluble humates to hot water, it is also possible to prevent the formation of calcium-based scales, thereby facilitating the smooth transfer of hot water through piping systems and ensuring continuous and smooth flow of geothermal steam. It is possible to collect.

[Brief explanation of drawings]

The drawing shows an example of an apparatus for scale generation testing. 1... Geothermal steam extraction well, 2... Main pipe, 3.7, 12, 13, 15, 16...
・Pipe, 4...Steam water separator, 5...
Humate aqueous solution tank, 6... quantitative phonf,
10...Level header-IL14, 17, 19
...Valve, 20...Reduction well.

Claims (1)

[Claims] 1. Hot water flowing out accompanying geothermal steam gushing out from a geothermal steam extraction well for geothermal power generation is heated to a temperature of 100°C or higher and 1.
．． After maintaining the hot water under a pressure of 5 kg/crit G or higher and adding soluble humates to the hot water, the hot water is connected to a level header of a steam separator attached above the ground surface. A method for treating hot water that flows out accompanied by geothermal steam, which is characterized by injecting reduction into a reduction well through a piping system in which the hot water flows out along with geothermal steam.