JP6786157B2 - Scale inhibitor for geothermal power generation equipment and scale prevention method for geothermal water - Google Patents

Description

The present invention relates to a scale inhibitor for a geothermal power generation device and a method for preventing scale of geothermal water. More specifically, the present invention relates to a scale inhibitor for a geothermal power generation device used for preventing silica scale of geothermal water used in a geothermal power generation device, and a scale prevention method for geothermal water.

In recent years, geothermal power generation has been attracting attention as a power generation using natural energy that does not emit CO _{2 and} has a greenhouse effect. Geothermal power generation uses the steam of geothermal water pumped from the geothermal reservoir in the stratum to generate electricity, and this steam contains not only water but also silica and sodium carbonate contained in the stratum. , There is a problem that these scales are generated and accumulated in the piping of the geothermal power generation device and block the piping. In particular, silica scale tends to precipitate when the temperature of high-temperature steam drops to the state of liquid water at 80 to 100 ° C, and scale precipitation in the piping through which the liquid geothermal water flows in the equipment. Becomes a problem. The problem with this silica scale is that the geothermal water pumped from the geothermal reservoir is divided into steam and liquid water, and the steam is used for power generation, and the liquid water is also used for power generation. This becomes a bigger problem in power generation equipment (see Patent Document 1).
As a method of suppressing such silica scale, a method of injecting acid into hot water flowing in the piping of a geothermal power generation device (see Patent Document 2), or a method of adding a cationic nitrogen-containing compound, an acid, and an antiscale agent is added. (See Patent Document 3) and a method of using a polymer having a predetermined structure as a scale inhibitor for geothermal power generation (see Patent Documents 4 to 7) have been proposed.

International Publication No. 2013/05/1265 Japanese Unexamined Patent Publication No. 2012-202179 U.S. Pat. No. 4,328,106 Japanese Unexamined Patent Publication No. 2013-226526 Japanese Unexamined Patent Publication No. 2016-64382 Japanese Unexamined Patent Publication No. 4-78494 Japanese Unexamined Patent Publication No. 2011-52235

As described above, various methods have been proposed as methods for preventing the precipitation of silica scale in the geothermal power generation device, but none of them is sufficient in terms of effectiveness, and the precipitation of silica scale can be prevented more effectively. There is a need to develop a way to do this.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a method for effectively preventing the precipitation of silica scale in a geothermal power generation device.

The present inventor has studied various methods for effectively preventing the precipitation of silica scale in a geothermal power generation device, and found that at least one of a polymer having a cationic group and a polymer having a nonionic group and an inorganic acid. When is added to geothermal water, precipitation of silica scale in the geothermal power generation device can be effectively prevented, and at least one of a polymer having a cationic group and a polymer having a nonionic group is used. On the other hand, it has been found that a polymer to which an inorganic acid is added is useful as a scale inhibitor used in a geothermal power generation device, and the present invention has been reached.

That is, the present invention is an anti-scale agent used in a geothermal power generation device, and the anti-scale agent is (a) a polymer having a cationic group and / or a polymer having a nonionic group and (b) an inorganic acid. It is a scale inhibitor for geothermal power generation equipment, which is characterized by containing.
The present invention is also a method of preventing scale of water used in a geothermal power generation device, wherein the method comprises (a) a polymer having a cationic group and / or a polymer having a nonionic group. b) It is also a method for preventing scale of water used in a geothermal power generation device, which is characterized by adding an inorganic acid to water.
The present invention will be described in detail below.
It should be noted that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

<Scale inhibitor for geothermal power generation equipment>
The scale inhibitor for a geothermal power generation device of the present invention is characterized by containing (a) a polymer having a cationic group and / or a polymer having a nonionic group, and (b) an inorganic acid.
It is considered that the precipitation of silica scale is caused by the polymerization of the silica component contained in the geothermal water pumped from the geothermal reservoir to generate large molecules of silica. A polymer having a cationic group is adsorbed on silica before polymerization to prevent the polymerization reaction from occurring, and a polymer having a nonionic group is adsorbed on a growth point of silica during the polymerization reaction to be a silica polymer. It is considered that by inhibiting the growth of silica, large molecules of silica are generated to prevent the precipitation of silica scale. Further, since the silica scale precipitates when the liquid property of water becomes alkaline, the silica scale can be prevented by adding an inorganic acid to make the liquid property acidic.
Here, adding an acid to make the liquid acidic is one method of preventing silica scale, but if the pH is lowered too much, the geothermal power generator may be corroded by the acid, so only the use of acid is used. There is a limit to preventing silica scale. Further, as described in Patent Documents 4 to 7 described above, a sufficient silica scale prevention effect cannot be obtained only by a method using a polymer that functions as a scale prevention agent. On the other hand, the scale inhibitor for geothermal power generation equipment of the present invention has an acid or a synergistic effect of (a) a polymer having a cationic group and / or a polymer having a nonionic group and (b) an inorganic acid. It is possible to obtain an excellent silica scale prevention effect that cannot be achieved when the polymer is used alone.

In the scale inhibitor for geothermal power generation equipment of the present invention, (a) the ratio of the mass of the inorganic acid to the mass of the polymer having a cationic group and / or the polymer having a nonionic group (b) / (a). ) Is preferably 0.001 to 200. At such a ratio, the anti-scale effect of the polymer having a cationic group and / or the polymer having a nonionic group and the anti-scale effect of using an acid are exhibited in a well-balanced manner, and the anti-scale agent can be used. The scale prevention effect by using it will be more fully exhibited.
The ratio of the mass of (b) the inorganic acid to the mass of (a) the polymer having a cationic group and / or the polymer having a nonionic group is more preferably 0.007 to 150, still more preferably. It is 0.01 to 100, and particularly preferably 0.1 to 80.
Here, the "mass of a polymer having a cationic group and / or a polymer having a nonionic group" means either a polymer in which the antiscale agent has a cationic group or a polymer having a nonionic group. When only one is contained, it means the mass of the polymer, and when the antiscale agent contains both a polymer having a cationic group and a polymer having a nonionic group, the total mass of those polymers is taken. means.

(Polymer having a cationic group, polymer having a nonionic group)
The scale inhibitor for a geothermal power generation device of the present invention includes (a) a polymer having a cationic group and / or a polymer having a nonionic group. That is, either one of the polymer having a cationic group and the polymer having a nonionic group may be contained, or both may be contained.
The polymer having a cationic group may have a nonionic group or an anionic group as long as it has a cationic group in the structure, but the cationic group is the entire functional group (cationic group, nonionic group). And anionic groups) are preferably the main components. That is, it is preferable that the cationic group is 50 mol% or more with respect to the total of 100 mol% of the functional groups (cationic group, nonionic group and anionic group) contained in the polymer. More preferably, it is 60 mol% or more, further preferably 70 mol% or more, particularly preferably 80 mol% or more, and most preferably 90 mol% or more.

Similar to the above-mentioned polymer having a cationic group, the polymer having a nonionic group may have a cationic group or an anionic group as long as it has a nonionic group. Above all, it is one of the preferable embodiments of the scale inhibitor for the geothermal power generation device of the present invention that the polymer having a nonionic group further has an anionic group.
In the present invention, when the polymer having a nonionic group further has an anionic group, it is preferable that the nonionic group and the anionic group are the main components of the entire functional group. That is, it is preferable that the total amount of the nonionic group and the anionic group is 50 mol% or more with respect to the total of 100 mol% of the functional groups (cationic group, nonionic group and anionic group) of the polymer. .. More preferably, it is 60 mol% or more, and even more preferably 70 mol% or more.
When the polymer having a nonionic group has a nonionic group and an anionic group, it is based on 100 mol% of the total of the functional groups (cationic group, nonionic group and anionic group) of the polymer. The proportion of anionic groups is preferably 10-98 mol%. It is more preferably 20 to 95 mol%, and even more preferably 30 to 92 mol%.

Further, the fact that the polymer having a nonionic group is a polymer having no anionic group is also one of the preferred embodiments of the scale inhibitor for a geothermal power generation device of the present invention. In this case, the nonionic group is preferably the main component of the entire functional group. That is, it is preferable that the nonionic group is 50 mol% or more with respect to 100 mol% of the total of the cationic group and the nonionic group contained in the polymer. More preferably, it is 60 mol% or more, further preferably 70 mol% or more, particularly preferably 80 mol% or more, further particularly preferably 90 mol% or more, and most preferably 100. Mol%, that is, the polymer having a nonionic group has neither a cationic group nor an anionic group.

Examples of the polymer having a cationic group include a polymer having a primary 1-3 amino group or a quaternary ammonium base in the structure. Examples of such a polymer include polyalkyleneimine, a polymer having a structural unit derived from an ethylenically unsaturated monomer having a tertiary amino group or a quaternary ammonium base in its structure, and the like. ..
As the polyalkyleneimine, polyalkyleneimine derived from alkyleneimine having 2 to 4 carbon atoms such as polyethyleneimine is preferable.

Examples of the ethylenically unsaturated monomer having a primary 1-3 amino group or a quaternary ammonium base in the above structure include the following formula (1-1) or (1-2);

(In the formula, R ¹ and R ² represent the same or different hydrogen atoms and hydrocarbon groups having 1 to 20 carbon atoms. R ^{3 to} R ⁵ represent the same or different hydrocarbon groups having 1 to 20 carbon atoms. Represents a hydrogen group. R ^{6 to} R ⁸ represent the same or different alkyl atoms or alkyl groups having 1 to 10 carbon atoms. X represents a direct bond or a divalent linking group). Examples include monomers.

Examples of the divalent linking group in the above formulas (1-1) and (1-2) include the following formulas (2-1) or (2-2);

(In the formula, m represents an integer of 0 to 4).

A polymer having a structural unit derived from an ethylenically unsaturated monomer having a primary to tertiary amino group or a quaternary ammonium base in the above structure contains a primary to tertiary amino group or a quaternary ammonium base. It may have a structural unit derived from a monomer other than the ethylenically unsaturated monomer.
Other monomers include carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid and its alkali metal salts and ammonium salts; vinyl sulfonic acid, styrene sulfonic acid, (meth) allyl sulfonic acid, 3- Sulfonic acid group-containing monomer such as allyloxy-2-hydroxypropanesulfonic acid and its alkali metal salt and ammonium salt; aminoalkyl ester of (meth) acrylic acid such as diethylaminoethyl acrylate and its quaternary ammonium derivative; methyl acrylate , Alkyl ester of (meth) acrylic acid such as ethyl acrylate; Aromatic vinyl monomer such as styrene; Olefin monomer such as ethylene and propylene; Alkyl vinyl ether such as methyl vinyl ether and ethyl vinyl ether; Vinyl acetate, vinyl Examples thereof include stearate, glycol diacrylate, glycol dimethacrylate, divinylbenzene, glycol diallyl ether and the like, and one or more of these can be used.
If the polymer having a structural unit derived from an ethylenically unsaturated monomer having a primary to tertiary amino group or a quaternary ammonium base in the structure has a structural unit derived from another monomer, the other simple Among the above-mentioned polymers, ethylene having no functional group, alkyl ester of (meth) acrylic acid, aromatic vinyl-based monomer, olefin-based monomer other than ethylene, alkyl vinyl ether, vinyl acetate, vinyl Nonionic group-containing monomers such as stearate, glycol diacrylate, glycol dimethacrylate, divinylbenzene, and glycol diallyl ether are preferable.

A polymer having a structural unit derived from an ethylenically unsaturated monomer having a primary to tertiary amino group or a quaternary ammonium base in the above structure has the first to third to 100% by mass based on 100% by mass of the entire structural unit. It is preferable to have 20 to 100% by mass of a structural unit derived from an ethylenically unsaturated monomer having a secondary amino group or a quaternary ammonium base. By having such a ratio, the polymer can more sufficiently exert the scale prevention effect. It is more preferably 30 to 100% by mass, and even more preferably 50 to 100% by mass.

Examples of the polymer having a nonionic group include a polymer having a structure derived from an unsaturated monomer having a nonionic group.
Examples of the unsaturated monomer having a nonionic group include those described above and the following formula (3);

(In the formula, R ^{9 to} R ¹² are the same or different and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. X represents an integer of 0 to 4. y represents an integer of 1 to 3. A monomer having a lactam ring represented by (represented) and an ethylenically unsaturated hydrocarbon group, or the following formula (4);

(In the formula, R ^{13 to} R ¹⁵ represent the same or different alkyl atoms or alkyl groups having 1 to 10 carbon atoms. R ¹⁶ represents alkyl groups having 1 to 20 carbon atoms. N represents 0 to 0. A monomer represented by (representing an integer of 4) can be mentioned.
As the monomer represented by the above formula (3), vinylpyrrolidone is preferable. As the monomer represented by the above formula (4), 1-allyloxy-3-butoxypropan-2-ol (PAB) represented by the following formula (5) is preferable.

When the polymer having a nonionic group is a polymer having a structural unit derived from a monomer having a lactam ring represented by the above formula (3) and an ethylenically unsaturated hydrocarbon group, the polymer is , The K value is preferably 5 to 500. It is more preferably 7 to 300, still more preferably 10 to 100.
The K value of the polymer can be measured by the method described in Examples.

The polymer having a nonionic group may have a structural unit derived from a monomer other than the unsaturated monomer having a nonionic group.
Other monomers include carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid and its alkali metal salts and ammonium salts; vinyl sulfonic acid, styrene sulfonic acid, (meth) allyl sulfonic acid, 3- Sulfonic acid group-containing monomers such as allyloxy-2-hydroxypropanesulfonic acid and its alkali metal salts and ammonium salts; aminoalkyl esters of (meth) acrylic acids such as diethylaminoethyl acrylate and their quaternary ammonium derivatives; diethylaminoethyl Tertiary ammonium compounds of (meth) acrylate and methyl sulphate; N-vinylimidazole, N-vinylacetamide, N-vinylformamide, N-vinylcarbazole, acrylamide, methacrylicamide, N-alkylacrylamide, N-methylolacrylamide, Examples thereof include N, N-methylenebisacrylamide, and one or more of these can be used.

As described above, in the present invention, the fact that the polymer having a nonionic group is a polymer having no anionic group is one of the preferred embodiments of the present invention, and the nonionic property is also described above. It is also one of the preferred embodiments of the present invention that the polymer having a group further has an anionic group.
When the polymer having a nonionic group is a polymer having a nonionic group and no anionic group, the structure derived from the unsaturated monomer having a nonionic group in the polymer having a nonionic group. The ratio of the units is preferably 70% by mass or more with respect to 100% by mass of all the structural units constituting the polymer. It is more preferably 80% by mass or more, further preferably 90% by mass or more, and most preferably 100% by mass, that is, it is composed of only unsaturated monomers having a nonionic group.

When the polymer having a nonionic group is a polymer having an anionic group, the proportion of the structural unit derived from the unsaturated monomer having a nonionic group in the polymer having a nonionic group is the polymer. It is preferably 1 to 95% by mass with respect to 100% by mass of all the structural units constituting the above. It is more preferably 2 to 90% by mass, further preferably 3 to 80% by mass, particularly preferably 5 to 80% by mass, and particularly preferably 8 to 70% by mass, most preferably. Preferably, it is 10 to 70% by mass.
The proportion of the structural unit derived from the unsaturated monomer having an anionic group in the polymer having a nonionic group is 5 to 99% by mass with respect to 100% by mass of all the structural units constituting the polymer. Is preferable. It is more preferably 5 to 98% by mass, still more preferably 10 to 97% by mass, particularly preferably 20 to 95% by mass, and particularly preferably 30 to 92% by mass, most preferably. Preferably, it is 30 to 90% by mass.
The anionic group may be any group having an anion or a group that generates an anion in water, and may be any of a carboxyl group, a sulfonyl group and the like, and has one of these. Also, it may have two or more kinds.

Examples of the unsaturated monomer having an anionic group include carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid and its alkali metal salt, and ammonium salt; vinyl sulfonic acid, styrene sulfonic acid, and (meth). Examples thereof include sulfonic acid group-containing monomers such as allylsulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, alkali metal salts thereof, and ammonium salts.

The polymer having a cationic group and the polymer having a nonionic group preferably have a weight average molecular weight of 500 to 1,000,000. It is more preferably 800 to 700,000, still more preferably 1,000 to 500,000, and particularly preferably 1,200 to 200,000. When the polymer having a cationic group or the polymer having a nonionic group has such a molecular weight, it is superior in preventing precipitation and adhesion of silica scale.
The weight average molecular weight of the polymer having a cationic group or the polymer having a nonionic group can be measured by the method described in Examples.

The method for producing the polymer having a cationic group or the polymer having a nonionic group in the present invention is not particularly limited, and the polymer can be produced by using a commonly used polymerization reaction.
The polymerization initiator used in the above polymerization reaction is not particularly limited, and is, for example, hydrogen peroxide; persulfate such as sodium persulfate, potassium persulfate, ammonium persulfate; 2,2'-azobis (2-amidinopropane) hydrochloride. , 4,4'-azobis-4-cyanovaleric acid, azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) and other azo compounds; benzoyl peroxide, peroxymonosulfurate. Organic peroxides such as lauroyl oxide, peracetic acid, di-t-butyl peroxide, and cumene hydroperoxide can be used.
The amount of the polymerization initiator used is not particularly limited as long as it can initiate the polymerization reaction, but is appropriately in the range of 1 to 12 g with respect to 1 mol of the total amount of all the monomers used in the polymerization reaction. It can be adjusted and used.

A chain transfer agent may be used in the polymerization reaction, if necessary. The chain transfer agent is not particularly limited, and is, for example, a thiol-based chain transfer agent such as mercaptoethanol, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid; halogen such as carbon tetrachloride and methylene chloride. Compounds; Secondary alcohols such as isopropanol and glycerin; Hypophosphate, hypophosphite and salts thereof (sodium bisulfite, potassium hypophosphate, etc.), sulfite, hydrogen sulfite, dithionic acid, meta Lower oxides such as sodium bisulfite and salts thereof (sodium bisulfite, potassium hydrogen sulfite, sodium dithionate, potassium bisulfite, sodium metabisulfite, potassium metabisulfite, etc.) and salts thereof may be used. it can.
The amount of the chain transfer agent used is not particularly limited and can be appropriately adjusted according to the required molecular weight of the polymer and the like. For example, with respect to 1 mol of the total amount of all the monomers used in the polymerization reaction. It can be appropriately adjusted and used in the range of 1 to 20 g.

The above polymerization reaction may be carried out using a solvent. The solvent is not particularly limited, but for example, lower alcohols such as water, methanol, ethanol and isopropyl alcohol; lower ketones such as acetone, methyl ethyl ketone and diethyl ketone; ethers such as dimethyl ether and dioxane; amides such as dimethyl formaldehyde and the like. One or more of the above can be used.

The temperature of the polymerization reaction is not particularly limited, but can be appropriately adjusted in the range of 0 to 150 ° C., and the polymerization time can be appropriately adjusted in the range of, for example, 30 to 3000 minutes.

(Inorganic acid)
The inorganic acid (b) in the present invention is not particularly limited, and any inorganic acid such as hydrochloric acid, sulfuric acid, and nitric acid can be used, and one or more of these can be used.

<Liquid composition for geothermal power generation equipment>
As described above, when at least one of a polymer having a cationic group and a polymer having a nonionic group and an inorganic acid are added to the geothermal water used in the geothermal power generation device, the silica scale in the geothermal power generation device is added. The composition obtained by adding these to water can be suitably used in a geothermal power generation device as a liquid composition in which precipitation of silica scale is effectively prevented. .. Such a liquid composition, that is, a liquid composition used in a geothermal power generation device, which is (a) a polymer having a cationic group and / or a polymer having a nonionic group (a). A liquid composition for a geothermal power generation device, which comprises b) an inorganic acid and (c) water, is also one of the present inventions.

The liquid composition for a geothermal power generation device preferably has a content of (a) a polymer having a cationic group and / or a polymer having a nonionic group of 0.1 to 990,000 ppm. By including a polymer having a cationic group and / or a polymer having a nonionic group in such a ratio, the scale prevention effect of these polymers will be more sufficiently exhibited. The content of the polymer having a cationic group and / or the polymer having a nonionic group is more preferably 1 to 900,000 ppm.
In particular, when a polymer having a cationic group is used, the content of the polymer having a cationic group is preferably 10 to 900,000 ppm. It is more preferably 15 to 900,000 ppm, and even more preferably 20 to 900,000 ppm.
Further, particularly when a polymer having a nonionic group is used, the content of the polymer having a nonionic group is preferably 0.1 to 800,000 ppm. It is more preferably 0.2 to 600,000 ppm, and even more preferably 0.5 to 500,000 ppm.
Further, considering economic efficiency, the content of the polymer having a cationic group and / or the polymer having a nonionic group is particularly preferably 0.1 to 1000 ppm. Most preferably, it is 0.1 to 100 ppm.
Here, the "content of the polymer having a cationic group and / or the polymer having a nonionic group" refers to only one of the polymer having a cationic group and the polymer having a nonionic group. When it is contained, it means the content of the polymer, and when the antiscale agent contains both a polymer having a cationic group and a polymer having a nonionic group, it means the total content of those polymers. To do. The same applies to the content of the polymer having a cationic group and / or the polymer having a nonionic group in water in the scale prevention method of the present invention described later.

The pH of the liquid composition for a geothermal power generation device is preferably 1.5 to 10. When the pH of the liquid composition is in such a range, it is possible to more effectively suppress the precipitation of silica scale while preventing the corrosion of the geothermal power generation device by acid. The pH of the liquid composition is more preferably 2.0 to 9.5, even more preferably 2.5 to 9.0, and particularly preferably 3.0 to 8.5, most preferably. Preferably, it is 5.0 to 8.0.
The pH of the liquid composition for a geothermal power generation device can be measured by a pH meter using a pH electrode.

When the above liquid composition for a geothermal power generation device is used in a geothermal power generation device, geothermal water pumped from a geothermal storage layer in the geothermal layer can be used as the water contained in the composition. Geothermal water contains about 10 to 2000 ppm of silica and about 1 to 1000 ppm of sodium carbonate.
Therefore, the water contained in the liquid composition for the geothermal power generation device may contain 10 to 2000 ppm of silica and 1 to 1000 ppm of sodium carbonate.

<Method of preventing scale of water used in geothermal power generation equipment>
In the water scale prevention method used in the geothermal power generation device of the present invention, (a) a polymer having a cationic group and / or a polymer having a nonionic group, and (b) an inorganic acid are added to water. Although it is a method, the method of adding the polymer or the inorganic acid is not particularly limited, and these may be added at the same time or separately. Further, both the polymer and the inorganic acid may be added all at once, or may be added in small portions.
Further, the polymer or the inorganic acid may be added to the water in the state where only the water in the liquid state is present, and at least as long as the water in the liquid state is present, both the water in the liquid state and the vapor can be added. It may be added to the existing water.

The scale prevention method includes (a) a polymer having a cationic group and / or a polymer having a nonionic group, and (b) an inorganic acid with respect to water having a silica content of 300 ppm or more in water. Is preferably a method of adding. Since the scale prevention method of the present invention is a method capable of effectively preventing the precipitation of silica scale, its effect when used for water having a high silica content such as containing 300 ppm or more of silica in water. Will be exhibited more prominently. More preferably, it is used for water having a silica content of 500 ppm or more in water, and more preferably it is used for water having a silica content of 700 ppm or more in water.
The silica content in water is measured by quantifying the amount of Si in the filtrate using a plasma emission spectrophotometer (ICP) (SPS4000 manufactured by Seiko Denshi Kogyo Co., Ltd.) and converting it to the SiO ₂ concentration. be able to.

The scale prevention method is preferably a method of adjusting the content of (a) a polymer having a cationic group and / or a polymer having a nonionic group in water to 0.1 to 990,000 ppm. By adjusting the content of the polymer having a cationic group and / or the polymer having a nonionic group in water within such a range, the effect of preventing the precipitation of silica scale by these polymers is more sufficiently exhibited. Will be. The more preferable contents of these polymers in water and the like are the same as those after the more preferable contents of these polymers in the above-mentioned liquid composition for geothermal power generation equipment of the present invention, and the polymer having a cationic group can be used. The same applies to the preferable content when used and the preferable content when a polymer having a nonionic group is used.

The scale prevention method is preferably a method of adjusting the pH of water to 1.5 to 10. By adjusting the content of the polymer having a cationic group and / or the polymer having a nonionic group in water within such a range, the effect of preventing precipitation of silica scale can be more sufficiently exhibited. After the more preferable range of pH of water is the same as after the more preferable range of pH in the above-mentioned liquid composition for geothermal power generation equipment of the present invention.

The scale prevention method is preferably used for water at 80 to 120 ° C. The temperature of the geothermal water in the geothermal power generation device is in the range of about 80 to 120 ° C., and the scale prevention method of the present invention exerts its effect more remarkably when used for water at such a temperature. It will be. In particular, since silica scale is more likely to be generated when the temperature of water is 80 to 100 ° C., it is more preferably used for water at 80 to 100 ° C., and further generated when the temperature is 80 to 90 ° C. Since it is easy, it is more preferably used for water at 80 to 90 ° C.
When the scale prevention method is used for water at 80 to 120 ° C., it means that (a) a polymer having a cationic group and / or a polymer having a nonionic group for water at 80 to 120 ° C. (B) It does not mean only the addition of an inorganic acid, and even if the temperature is outside the range of 80 to 120 ° C. at the time of addition, (a) a polymer having a cationic group and / or a nonionic group. When the temperature of the water containing (b) the inorganic acid and the polymer having (b) is 80 to 120 ° C., the scale prevention method of the present invention is used for water at 80 to 120 ° C. become.

The scale prevention method is preferably used for a binary system type geothermal power generation device.
As described above, the binary system type geothermal power generation device divides the geothermal water pumped from the geothermal reservoir into steam and liquid water and uses the steam for power generation, and also vaporizes the liquid water again. Furthermore, it is a device with a structure used for power generation. In a binary system type geothermal power generation device, more parts of the geothermal power generation device are in a liquid state than a normal geothermal power generation device that uses only the vapor content of the geothermal water pumped from the geothermal reservoir for power generation. It will come into contact, and there will be many parts of the geothermal power generation equipment where the problem of silica scale precipitation can occur. Therefore, it can be said that the scale prevention method of the present invention can exert the effect of the invention more remarkably when it is used for such a binary system type geothermal power generation device among the geothermal power generation devices, and it can be said that the effect of the invention is more remarkable. Used in a geothermal power generation device is one of the preferred embodiments of the scale prevention method of the present invention.

Since the scale inhibitor for a geothermal power generation device of the present invention has the above-mentioned configuration and can effectively prevent the precipitation of silica scale in the geothermal power generation device, it can be suitably used for a geothermal power generation device. It can be particularly suitably used for a binary system type geothermal power generation device in which a larger part of the geothermal power generation device is in contact with geothermal water in a liquid state.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "part" means "part by weight" and "%" means "mass%".

Various measurements in the synthetic example were performed as follows.
<K value of polymer>
When the K value was less than 20, the viscosity of the 5% (g / 100 ml) solution was measured, and when the K value was 20 or more, the viscosity of the 1% (g / 100 ml) solution was measured. The sample concentration was converted to dry matter. When the K value is 20 or more, weigh 1.0 g of the sample precisely, put it in a 100 ml volumetric flask, add distilled water at room temperature, dissolve it completely while shaking, and add distilled water to make exactly 100 ml. did. This sample solution was left in a constant temperature bath (25 ± 0.2 ° C.) for 30 minutes, and then measured using an Ubbelohde viscometer. Measure the time it takes for the solution to flow between the two markings. It was measured several times and the average value was taken. In order to measure the relative viscosity, distilled water was measured in the same manner. The two obtained flow times were corrected based on the Hagenbach-Coutete correction.

<Amount of residual monomer of polymer>
The amount of residual monomer of the polymer was measured by HPLC (High Performance Liquid Chromatography).
<Weight average molecular weight of polymer>
The weight average molecular weight of the polymer was measured by GPC (gel permeation chromatography) under the following conditions.
Equipment: HLC-8320GPC manufactured by Tosoh Corporation
Detector: RI
Column: Showa Denko Co., Ltd. Shodex Asahipak GF-310-HQ,
GF-710-HQ, GF-1G 7B
Column temperature: 40 ° C
Flow velocity: 0.5 ml / min
Calibration curve: POLYACRYLIC ACID STANDARD manufactured by Sowa Kagaku Co., Ltd.
Eluent: 0.1N sodium acetate aqueous solution

Synthesis example 1
In a SUS304 reaction vessel equipped with a Max Blend (registered trademark of Sumitomo Heavy Industries, Ltd.) type stirring blade and a glass lid, 430.0 parts by weight of ion-exchanged water and a 48% sodium hydroxide aqueous solution (hereinafter, "48"). % NaOH ") 0.16 parts by weight, sodium hypophosphate monohydrate (hereinafter referred to as" SHP ") 4.25 parts by weight (acid type equivalent (hypophosphorous acid equivalent) 2.65 weight Part) was charged and the temperature was raised to 90 ° C. A monomer aqueous solution consisting of 500 parts by weight of N-vinylpyrrolidone (hereinafter referred to as "NVP") and 55.6 parts by weight of ion-exchanged water was applied over 180 minutes over 2,2'-azobis-2-amidinopropane dihydrochloric acid. An aqueous polymerization initiator solution consisting of 1.5 parts by weight of salt (hereinafter referred to as “V-50”) and 8.5 parts by weight of ion-exchanged water was added to the reaction vessel over 210 minutes. 240 minutes after the start of polymerization, 3.05 parts by weight of an 88% formic acid aqueous solution was added, and the temperature was maintained at 90 ° C. for 80 minutes to obtain a 50.9% solid polymer aqueous solution (1) containing the polymer (1). Got The K value of the polymer (1) was 28, and the polymer (1) had a hypophosphorous acid (salt) group in the main chain.

Synthesis example 2
Polyethyleneimine SP018 manufactured by Nippon Catalyst Co., Ltd. was diluted with ion-exchanged water to a solid content of 50.0% to obtain a polymer aqueous solution (2) containing polyethyleneimine as the polymer (2).

Synthesis example 3
(Synthesis of monomer)
370.0 g of n-butyl alcohol and 4.27 g of pelletized sodium hydroxide were placed in a 500 mL glass four-necked flask equipped with a reflux condenser and a stirrer (paddle blade), and the temperature was raised to 60 ° C. with stirring. It was warm. Next, 57.0 g of allyl glycidyl ether (hereinafter, also referred to as “AGE”) was added over 30 minutes, and then the reaction was carried out for 5 hours. The solution was transferred to a 1,000 mL eggplant flask and desolvated with a rotary evaporator. The precipitated salt was removed by filtration to obtain a monomer (1).

(Synthesis of polymer)
128.4 g of pure water and 0.0187 g of molle salt were placed in a glass separable flask with a capacity of 1,000 mL equipped with a reflux condenser and a stirrer (paddle blade), and the temperature was raised to 85 ° C. while stirring for polymerization. It was used as a reaction system. Next, 270.0 g of an 80% aqueous acrylic acid solution (hereinafter, also referred to as "80% AA") and sodium 3-allyloxy-2-hydroxypropanesulfonate were placed in a polymerization reaction system maintained at 85 ° C. under stirring. 192.0 g of 40% aqueous solution (hereinafter, also referred to as "40% HAPS"), 15.0 g of monomer (1), 100 g of 15% sodium persulfate aqueous solution (hereinafter, also referred to as "15% NaPS"), In addition, 40 g of a 35% aqueous sodium hydrogen sulfite solution (hereinafter, also referred to as “35% SBS”) was added dropwise from separate nozzles. The dropping time of each solution was 180 minutes for 80% AA, 120 minutes for 40% HAPS, 120 minutes for monomer (1), 190 minutes for 15% NaPS, and 175 minutes for 35% SBS. did. In addition, the dropping rate of each solution was constant, and each solution was dropped continuously. After the completion of the dropping of 80% AA, the reaction solution was held (aged) at 85 ° C. for another 30 minutes to complete the polymerization. After completion of the polymerization, 193.3 g of a 48% aqueous sodium hydroxide solution (hereinafter, also referred to as “48% NaOH”) was gradually added dropwise while stirring and allowing the polymerization reaction solution to cool to neutralize the polymerization reaction solution. In this way, a polymer aqueous solution (3) containing the polymer (3) of the present invention having a solid content concentration of 45% was obtained. The weight average molecular weight of the polymer (3) was 8,200. The residual acrylic acid was 80 ppm, the residual HAPS was 850 ppm, and the residual monomer (1) was 0.21%.

Synthesis example 4
128.4 g of pure water and 0.0187 g of molle salt were placed in a glass separable flask with a capacity of 1,000 mL equipped with a reflux condenser and a stirrer (paddle blade), and the temperature was raised to 85 ° C. while stirring for polymerization. It was used as a reaction system. Next, 270.0 g of an 80% aqueous acrylic acid solution (hereinafter, also referred to as "80% AA") and sodium 3-allyloxy-2-hydroxypropanesulfonate were placed in a polymerization reaction system maintained at 85 ° C. under stirring. 192.0 g of 40% aqueous solution (hereinafter, also referred to as "40% HAPS"), 15.0 g of monomer (1), 20 g of 15% sodium persulfate aqueous solution (hereinafter, also referred to as "15% NaPS"), In addition, 20 g of a 35% aqueous sodium hydrogen sulfite solution (hereinafter, also referred to as “35% SBS”) was added dropwise from separate nozzles. The dropping time of each solution was 180 minutes for 80% AA, 120 minutes for 40% HAPS, 120 minutes for monomer (1), 190 minutes for 15% NaPS, and 175 minutes for 35% SBS. did. In addition, the dropping rate of each solution was constant, and each solution was dropped continuously. After the completion of the dropping of 80% AA, the reaction solution was held (aged) at 85 ° C. for another 30 minutes to complete the polymerization. After completion of the polymerization, 193.3 g of a 48% aqueous sodium hydroxide solution (hereinafter, also referred to as “48% NaOH”) was gradually added dropwise while stirring and allowing the polymerization reaction solution to cool to neutralize the polymerization reaction solution. In this way, a polymer aqueous solution (4) containing the polymer (4) of the present invention having a solid content concentration of 45% was obtained. The weight average molecular weight of the polymer (4) was 46,000. The residual acrylic acid was 100 ppm, the residual HAPS was 900 ppm, and the residual monomer (1) was 0.11%.

Synthesis example 5
6024 g of 40% HAPS was charged into a 25 L SUS reaction vessel equipped with a reflux condenser and a stirrer, and the temperature was raised to a boiling point reflux state under stirring. Then, under stirring, 5670 g of 80% AA, 6024 g of 40% HAPS, and 2128 g of 15% NaPS were added dropwise to the polymerization reaction system in a boiling point reflux state. Based on the time point at which the addition of 80% AA was started (0 minutes), 80% AA was added dropwise over 0 to 90 minutes, and 40% HAPS was added dropwise over 0 to 60 minutes at regular intervals. The initiator, 15% NaPS, was added dropwise at 9.7 g / min, and at 55 minutes after the start, the dropping rate was tripled to 29.1 g / min, and the mixture was added dropwise between 0 and 110 minutes. Then, 4940 g of deionized water was added dropwise at a constant rate for 50 to 90 minutes. The reaction solution was dropped from separate nozzles, and the reaction solution was kept in a boiling point reflux state under stirring. After the completion of the dropping of 15% NaPS, the reaction solution was kept in a boiling point reflux state for another 30 minutes to complete the polymerization, and an aqueous polymer solution (5) having a solid content of 40% by weight was obtained. The weight average molecular weight of the polymer (5) was 95,000.

Example 1
Test water having a silica concentration of 1000 mg / L (converted to SiO ₂ and adjusted with sodium metasilicate / 9hydrate) and a sodium carbonate concentration of 300 mg / L was placed in a 250 ml polypropylene container. The polymer aqueous solution (1) was added thereto so as to have a solid content of 5 mg / L, and sulfuric acid was added so as to have a pure content of 200 mg / L.
This solution was charged into a sealable 120 ml polypropylene solution having an internal volume so as not to mix air, sealed, and allowed to stand at 85 ° C. for 4 hours. Then, it is filtered using a 0.1 μm membrane filter, and the amount of Si in the filtrate is quantified using a plasma emission spectrophotometer (ICP) (SPS4000 manufactured by Seiko Denshi Kogyo Co., Ltd.) and converted to SiO ₂ concentration. The scale suppression rate (scale prevention ability) (%) was calculated by the following formula. In addition, the pH of the solution was measured with a pH meter.
Scale suppression rate (%) = ((XY) / (ZY)) × 100
X: SiO ₂ concentration (mg / L) in the filtrate after the test
Y: SiO ₂ concentration (mg / L) in the filtrate tested without the addition of polymer
Z: SiO ₂ concentration (mg / L) before the test
The evaluation results are shown in Table 1.

Examples 2-5
In Example 1, instead of using 5 mg / L of the polymer aqueous solution (1) in terms of solid content, the polymer aqueous solutions (2)-(5) shown in Table 1 were used in the amounts shown in Table 1. The experiment was carried out in the same manner as in Example 1 except that. The results are shown in Table 1.

Comparative Example 1
In Example 1, the experiment was carried out in the same manner as in Example 1 except that sulfuric acid was not used. The results are shown in Table 1.

Comparative Example 2
The experiment was carried out in the same manner as in Example 1 except that the aqueous polymer solution (1) was not used in Example 1. The results are shown in Table 1.

From the results of Examples 1 to 5 and Comparative Examples 1 and 2, by adding both a polymer having a cationic group or a polymer having a nonionic group and an inorganic acid, either the polymer or the inorganic acid can be added. It was confirmed that an excellent anti-scale ability was exhibited as compared with the case where only was added.

Claims (11)

An anti-scale agent used in geothermal power generation equipment
The scale inhibitor contains (a) a polymer having a cationic group and / or a polymer having a nonionic group and (b) an inorganic acid.
The ratio (b) / (a) of the mass of (b) the inorganic acid to the mass of (a) the polymer having a cationic group and / or the polymer having a nonionic group is 8 to 200. Anti-scale agent for geothermal power generation equipment. The scale inhibitor for a geothermal power generation device according to claim 1, wherein the polymer having a nonionic group further has an anionic group. A liquid composition used in geothermal power generation equipment.
The liquid composition comprises (a) a polymer having a cationic group and / or a polymer having a nonionic group, (b) an inorganic acid and (c) water.
The ratio (b) / (a) of (b) the mass of the inorganic acid to the mass of (a) the polymer having a cationic group and / or the polymer having a nonionic group is 8 to 200. Liquid composition for geothermal power generation equipment. The liquid composition for a geothermal power generation device is characterized in that (a) the content of the polymer having a cationic group and / or the polymer having a nonionic group is 0.1 to 990,000 ppm. The liquid composition for a geothermal power generation device according to 3. The liquid composition for a geothermal power generation device according to claim 3 or 4, wherein the liquid composition for a geothermal power generation device has a pH of 1.5 to 10. A way to prevent scale of water used in geothermal power plants
The method comprises (a) a polymer having a cationic group and / or a polymer having a nonionic group and (b) an inorganic acid, and (a) a polymer having a cationic group and / or a nonionic group. (B) Water used in a geothermal power generation device, which is added to water so that the ratio (b) / (a) of the mass of the inorganic acid to the mass of the polymer having the above is 8 to 200. How to prevent scale. The scale prevention method includes (a) a polymer having a cationic group and / or a polymer having a nonionic group and (b) an inorganic acid with respect to water having a silica content of 300 ppm or more in water. The method for preventing scale of water used in the geothermal power generation device according to claim 6, wherein the method is a method of adding water. The scale prevention method is characterized in that (a) the content of the polymer having a cationic group and / or the polymer having a nonionic group in water is adjusted to 0.1 to 990,000 ppm. The method for preventing scale of water used in the geothermal power generation device according to claim 6 or 7. The method for preventing scale of water used in a geothermal power generation device according to any one of claims 6 to 8, wherein the method for preventing scale is a method for adjusting the pH of water to 1.5 to 10. The method for preventing scale of water used in a geothermal power generation device according to any one of claims 6 to 9, wherein the scale prevention method is used for water at 80 to 120 ° C. The method for preventing scale of water used in a geothermal power generation device according to any one of claims 6 to 9 , wherein the scale prevention method is used in a binary system type geothermal power generation device.