JPS6384697A - Scale inhibitor - Google Patents

Abstract

PURPOSE:To prevent the growth of silica scale for a long period of time by adding a small amt. of a scale inhibitor consisting of a copolymer of an unsatd. quaternary ammonium compd., hydrophobic unsatd. compd. and hydrophilic unsatd. compd. to terrestrial heat water, etc. CONSTITUTION:This scale inhibitor consists of the copolymer of 10-95wt% unsatd. quaternary ammonium compd. (e.g., acryloyloxyethyltrimethyl ammonium chloride), 5-90wt% hydrophobic unsatd. compd. (e.g., methyl acrylate) and 0-85wt% hydrophilic unsatd. compd. (e.g., acrylic acid). Such scale inhibitor is added to the terrestrial heat water, etc., at such a ratio at which content thereof is 3-200ppm. As a result, the deposition of silica scale to equipment and piping to handle the terrestrial heat water, hot spring water, cooling water, etc., is prevented and the operation and utilization of heat exchangers, terrestrial water transport pipes and reduction wells for a long period of time are permitted.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to production wells, transport pipes, and heat exchangers for river water, ground water, hot spring water, geothermal water, etc. containing silica.

This invention relates to a method for efficiently preventing scale mainly composed of silica on contact surfaces of reinjection wells, etc.

By effectively preventing clicascale, we can generate electricity using geothermal water, which was previously impossible, and exchange heat with fresh water through a heat exchanger for space heating, greenhouses, fish farming, etc.
It can now be used for multiple purposes such as snow melting and heated pools, making it possible to effectively utilize geothermal water at temperatures around 100 degrees Celsius. Furthermore, even in cooling water systems that use ground water, tap water, etc., climatic scale accumulates due to the warping force components that are dissolved in fi.

It becomes possible to prevent the generation and accumulation of this silica scale.

(Conventional technology) Conventionally, geothermal water has been used to generate electricity using only steam components, and hot water contains harmful components such as arsenic and scale-forming components such as chloride. Therefore, it cannot be used as is, and the heat is used by exchanging heat with fresh water.

In this case, scale adhesion to the tube walls or corrosion of the heat exchanger tubes, etc. occur, reducing the efficiency of heat exchange, and furthermore, the passageway becomes blocked, which is a major problem, and it is not fully utilized. .

In addition, silica scale forms on the pipe walls of geothermal water return wells, and blockages occur underground, requiring the wells to be re-drilled periodically.

Therefore, various measures were taken to prevent scale.

For example, a method has been proposed in which a Ca+" compound is added (Japanese Patent Application Laid-open No. 145554/1983; 156094/1983), but the former requires a very large amount of Ca+1 compound and the resulting calcium silicate Even if the compound is separated, it is difficult to dispose of it, and if it is returned underground, there is a great risk of blocking the reinjection well.

The latter is effective for calcite-type scales (such as CaCO3), but its effectiveness against amorphous scales such as silica is questionable.

(Problems to be solved by the invention) As mentioned above, in order to effectively utilize geothermal water, it is necessary to exchange heat with fresh water. However, it requires periodic cleaning, which limits its use.

In addition, in the underground restoration of geothermal water that is currently being carried out, scale adhesion to the pipe walls and underground blockage are progressing, and there is an urgent need to resolve these problems.

The present invention attempts to effectively utilize geothermal water and extend the life of the equipment by suppressing and preventing scales mainly composed of silica.

(Means for solving the problems) The present inventor conducted various studies to solve these problems. As a result, 1. By adding a small amount of the scale inhibitor of the present invention, the scale mainly composed of silica can be reduced. The present invention was completed based on the discovery that generation can be prevented and heat exchangers, geothermal water transport pipes, and Sagimoto wells can be operated and utilized for a long period of time.

That is, one aspect of the present invention is.

a) 10 to 95% by weight, preferably 20 to 90% by weight
b) 5 to 90% by weight, preferably 5 to 50% by weight, of hydrophobic unsaturated compounds; c) 0 to 85% by weight, preferably 0 to 75% by weight, of hydrophilic unsaturated compounds ; relates to a scale inhibitor comprising a copolymer of;

Here, the unsaturated quaternary ammonium compound is expressed by the general formula (1) (wherein R1 is hydrogen or a methyl group, R2, R3, and R4 are lower alkyl groups, Y is 0 or NH, and A has 1 to 4 carbon atoms. Polymerizable monomers represented by an alkylene group, a hydroxyalkylene group or a haphenylene group, X- represents a counter anion, and the like can be mentioned.

In addition, as a hydrophobic unsaturated compound, general formula (2) (in the formula R
1 is hydrogen or a methyl group; 5 is an alkyl group, an aralkyl group, or an aryl group having 1 to 12 carbon atoms; and acrylonitrile, methacrylonitrile, and styrene.

Examples include vinyl acetate.

Also, as a hydrophilic unsaturated compound, acrylic acid is used.

Methacrylic acid and their salts, acrylamide.

methacrylamide, N,N-dimethylacrylamide,
Diacetone acrylamide, N-methylol acrylamide, N-vinylpyrrolidone, 2-hydroxyethyl methacrylate, diethylene glycol monomethacrylate, 2-hydroquinethyl acrylate, diethylene gelicol monoacrylate, vinyl ether, allyl alcohol, methyl vinyl ether, etc. It will be done.

Representative examples of the unsaturated quaternary ammonium compounds include acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium bromide, methacryloyloxyethyltrietherammonium chloride, 3
- methacroyloxy-2-hydroxyglobiltrimetherammonium chloride, etc. and monomers having a tertiary amine group, such as N,N-dimethylaminoethyl acrylate, N,N-diethylaminoethyl acrylate,
N,N-dimethylaminoether methacrylate), N,N
- Monomers such as diethylaminoether methacrylate, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, N,N-diethylaminopropylmethacrylamide, and methyl chloride.

Methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, dimethyl sulfate.

Examples include unsaturated quaternary ammonium salt compounds obtained by reacting with diethyl sulfate and the like.

Further, typical examples of the hydrophobic unsaturated compounds include methyl acrylate, ethyl acrylate, butyl acrylate,
Acrylic 2-ethylhexyl.

Examples include methyl methacrylate, ethyl methacrylate, butyl methacrylate, acrylonitrile, methacrylonitrile, styrene, and vinyl acetate.

Any of the unsaturated quaternary ammonium compounds, hydrophobic unsaturated compounds, and hydrophilic unsaturated compounds (optional components) can be used alone or as a mixture of two or more.

These monomers can be polymerized to form a copolymer by a conventional polymerization method, but water is mainly used as a polymerization solvent.

In addition to water, alcohols such as methanol, ethanol, impropatol, methyl cellosolve, ethyl cellonorb, diacetone alcohol, and acetone, acetonitrile, and methyl acetate.

Organic solvents such as dimethylformamide and dimethylsulfoxide can also be used.

Note that instead of the unsaturated quaternary ammonium compound,
After copolymerizing using the above monomer having a tertiary amine group, the polymer is reacted with methyl chloride, methyl bromide, dimethyl sulfate, diethyl sulfate, etc. to synthesize the copolymer of the present invention having a quaternary ammonium base. You can also.

Regarding the mechanism of scale adhesion mainly composed of silica, silica dissolved in geothermal water, i.e., monomeric silicic acid, becomes supersaturated due to a decrease in concentration, adheres to pipe walls, etc., and polymerizes, forming polymerizable silica. This is thought to generate a scale.

When using the scale inhibitor of the present invention, the monomeric silicic acid combines with the quaternary ammonium base before adhering to the pipe wall.
It is thought that this prevents silica from polymerizing and adhering to the vessel wall, or that the scale inhibitor of the present invention is adsorbed to the vessel wall and prevents silica from adhering.

Furthermore, one case in which the scale inhibitor of the present invention is used.

The combination of copolymer and silica does not adhere to the vessel wall.

The amount of the scale inhibitor of the present invention added to the silica-containing aqueous solution is not particularly limited, but depends on the type of copolymer and the type of cooling water, geothermal water, and hot spring water.

It varies depending on the silica content, but in any case it is a very small amount.
The silica content of the silica-containing aqueous solution may be up to 5 o
o ppm of geothermal water, etc. 3-200 I) 1)!
n may be used, and a range of 10 to 100 ppm is particularly preferred.

Even if it is added in an amount of 200 ppm or more, the expected effect will not be obtained. Considering the effect and economical efficiency, it is desirable to keep the amount within the range of 2 (10 ppm).

By adding a small amount of the scale inhibitor of the present invention to a silica-containing aqueous solution, it is possible to prevent the 7-lica scale from adhering to the vessel walls and tube walls.

The method for adding the scale inhibitor to the aqueous solution is to first prepare a 1-50 weight aqueous solution of the scale inhibitor, add the prepared aqueous solution to the above-mentioned usage concentration range, and stir uniformly. Mainly employed is a method in which the silica-containing aqueous solution flowing through the pipes is continuously injected using a liquid injection pump or a syringe.

The materials for equipment and piping that handle the silica-containing aqueous solution to which the scale inhibitor of the present invention is added may be any commonly used materials, and the materials are not limited. Examples include iron, stainless steel, copper, brass, aluminum, galvanized titanium and other metals, glass, plastic, and ceramic.

According to the present invention, there is provided a container or a kettle in which a scale inhibitor can be handled simply by adding it to an aqueous solution containing silica.

There is no fault. Therefore, it was cleaned regularly.

In addition to extending the lifespan of heat exchangers, water pipes, etc. that were being replaced, the system also prevents their performance from deteriorating and enables long-term operation.

(Examples) The present invention will be explained in detail below using examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 Methacryloyloxyethyltrimethylammonium chloride 902 methyl acrylate
102nd saliva rinse 2
2 Deionized water 1201 A mixture of the above composition is placed in a 500 d round bottom separable flask, nitrogen gas is blown into it and the temperature is raised to 70°C.

A solution of ammonium persulfate 2y dissolved in deionized water 302 is added dropwise to this over 2 hours to effect polymerization. The temperature at the rear end of the catalyst drop f was raised to 100°C and heated for 3 hours to complete the polymerization.

The viscosity of a 40% water bath solution of this copolymer is 900p at 25°C.
It was 8.

The above copolymer (1) was added at 10.30°60 ppm to geothermal water containing about 400 ppn of supersaturated silica.
m was added and the state of adhesion of silica scale was measured.

The test device is diameter 12Rs and length 400 #1ffi.
7 Lika-containing geothermal water was applied to the outside of the steel pipe at 100°C at a rate of 0.
Inside the sink, fresh cooling water is poured at the inlet to a depth of 5 m.
Heat exchange was performed by flowing the solution so that the temperature at the outlet was 50°C. The amount of silica scale attached after 8 hours was measured and compared with a blank to which no copolymer was added.

For comparison, a sample containing 30 ppm of sodium polyacrylate and polyacrylamide was also included.

From the results shown in Table 1, copolymer (1) shows an extremely excellent effect on preventing silica scale adhesion.

On the other hand, the silica scale of sodium polyacrylate, which is an anionic polymer, is increased compared to that of the blank, indicating a rather negative effect.

In addition, polyacrylamide, which is a nonionic polymer,
is almost ineffective.

Example 2 Rimethacrylamidopropyltrimethylammonium chloride 802 ethyl acrylate 2Qf sodium hypophosphite aquarium
5? Ammonium persulfate 5
2 Deionized water 1502 A mixture having the above composition was placed in a 5001 Lt round bottom separable flask, nitrogen gas was introduced, the temperature was raised to 90°C and polymerization was carried out for 5 hours to obtain a copolymer (2).

The viscosity of 40% water solution of this copolymer is 140 ape/
The temperature was 25°C.

Similarly, the ratio of acrylamide propyltrimethylammonium chloride, styrene, and diethylene glycol monomethacrylate was 7+1:20 copolymer (
3).

10:1 copolymer of methacryloyloxyethyltrimethylammonium chloride and acrylonitrile (4
).

Acryloyloxyethyltrimethelammonicum chloride, methyl methacrylate and vinylpyrrolidone 7
;1:2 copolymer (5).

81111 copolymer of methacrylamide propyltrimethylammonium chloride and methyl acrylate, 2-hydroxyethyl methacrylate (6), 5:2 copolymer of acryloyloxyethyltrimethylammonium chloride and vinyl acetate (7).

A copolymer (8) in which the ratio of methacryloyloxyethyltrimethylammonium chloride to ethyl acrylate and acrylamide was 7:1:2 was synthesized.

The above copolymer was prepared using the same equipment as in Example 1.

The amount of silica scale attached was measured by adding 30 ppm of each to geothermal water, and the silica scale prevention rate was calculated by comparing it with a blank. The results and the viscosity of the copolymer are shown in the second column.

From the results shown in Table 2, copolymers (2) to (8) show good results in preventing the adhesion of silica scale.

Prevents 7 Lika scale from adhering to equipment and pipes that handle hot spring water, cooling water, etc.

Claims (1)

[Scope of Claims] 1. a) 10 to 95% by weight of unsaturated quaternary ammonium compounds; b) 5 to 90% by weight of hydrophobic unsaturated compounds; and c) 0 to 85% by weight of hydrophilic unsaturated compounds. A scale inhibitor consisting of a copolymer of a saturated compound.