JPWO2010016434A1 - Boiler water treatment agent and water treatment method - Google Patents

Abstract

Provided a boiler water treatment agent and a water treatment method capable of obtaining an excellent scale suppression effect without deterioration in performance during storage and distribution even when phosphoric acid or a salt thereof and a natural product-based oxygen scavenger are contained To do. The boiler water treatment agent is blended with polymerized phosphoric acid and / or a salt thereof as a phosphoric acid component, and a natural product oxygen scavenger containing a polyhydric phenol organic compound and / or a polysaccharide organic compound. And this boiler water treatment agent and an alkali agent are added to a boiler water system, and the water treatment of a boiler water system is performed.

Description

  The present invention relates to a technique for suppressing scale in a boiler water system.

  With energy saving and cost saving, it is desired to save the amount of water used in various water systems such as a cooling water system, a boiler water system, and an exhaust gas dust collecting water system. For this reason, in recent years, techniques for reducing the amount of water blown out of the system and operating with high concentration have been developed.

  In the aqueous system, scale components such as calcium and magnesium in the water increase in concentration. As a result, they are scaled and deposited, causing problems such as a decrease in thermal efficiency and blockage of the water flow path. In particular, in a boiler water system, when scale components such as calcium, magnesium, and iron brought into a boiler can scale on a heat transfer surface with a high heat load and adhere to the heat transfer surface, heat transfer inhibition is induced. This heat transfer inhibition may cause expansion, bending, rupture, and a decrease in thermal efficiency due to overheating of the steel material.

  In order to suppress such a problem, it is necessary to add a water treatment agent having a scale-inhibiting action to the aqueous system to suppress the adhesion of the scale component into the system and to discharge it outside the aqueous system by blowing. For this reason, phosphates such as trisodium phosphate and dipotassium phosphate, which are excellent in corrosion inhibition, are blended with conventional water treatment agents.

  On the other hand, the dissolved oxygen contained in the water flowing through the boiler water system causes corrosion of the boiler can body, steam condensate piping and other water plant equipment. Therefore, in general, a water treatment agent containing an oxygen scavenger having an action of removing dissolved oxygen is added to water supplied to a water supply system or a steam generation facility.

  Conventionally, hydrazine has been frequently used as the oxygen scavenger, but from the viewpoint of improving safety to the human body, the use of natural materials in place of hydrazine has been studied. At present, attention has been focused on polyhydric phenol-based organic substances such as tannins having a corrosion-inhibiting film-forming ability on the metal surface in addition to the action of removing oxygen as a component of the oxygen scavenger (Patent Document 1).

JP-A-6-108274

  However, the conventional techniques described above have the following problems. In polyhydric phenol-based organic substances such as tannins derived from natural materials, ions that react with phosphate ions to form insoluble salts, such as calcium ions and magnesium ions, are mixed. For this reason, water treatment agents containing both polyphenolic organic substances and phosphates have reduced scale-inhibiting functions that should be exhibited after they are added to the aqueous system due to the precipitation of insoluble salts during storage and distribution. There is a problem that it sometimes happens.

  As a method for solving this problem, it is conceivable to separate and store and distribute polyphenolic organic substances and phosphates to prevent the precipitation of sparingly soluble salts. It is cumbersome to perform, and the operation of mixing both components at the site of use is also complicated.

  Therefore, the present invention provides a boiler water treatment agent that can provide an excellent scale suppression effect without deterioration in performance during storage and distribution even if it contains phosphoric acid or a salt thereof and a natural product-based oxygen scavenger. And it aims at providing a water treatment method.

  The present inventors have found that polymerized phosphoric acid and / or a salt thereof under normal storage conditions can be stably present even when present together with calcium ions, magnesium ions, etc., and have completed the present invention.

That is, the water treatment agent according to the present invention contains polymerized phosphoric acid and / or a salt thereof, and a natural product-based oxygen scavenger containing a polyhydric phenol-based organic compound and / or a polysaccharide-based organic compound. is there.
The polymerized phosphoric acid and its salt blended in the water treatment agent of the present invention are stable regardless of the presence of calcium ions, magnesium ions, etc. mixed in the natural product-based oxygen scavenger, so during storage and distribution Scale suppression performance is not reduced. Further, when polymerized phosphoric acid and its salt are added to a boiler water system having a high temperature and a high pressure, the polymer phosphoric acid and its salt are decomposed into orthophosphate and exhibit a sufficient corrosion inhibiting action.
In this water treatment agent, as the polyhydric phenol organic compound, for example, one or more compounds selected from the group consisting of tannins, lignins and catechins can be used, and as the polysaccharide organic compound, For example, chitosans can be used.
Moreover, it is preferable that this water treatment agent does not contain orthophosphoric acid and its salt substantially. Here, “substantially not containing” includes not only containing at all, but also containing a small amount inevitably mixed in, or containing an amount within an allowable limit for detour purposes.
Furthermore, an alkali agent can be contained. In that case, it is preferable to use, for example, sodium hydroxide and / or potassium hydroxide as the alkali agent.

The water treatment method according to the present invention is a water treatment method in a boiler water system, in which the above-described water treatment agent and an alkali agent are added to the boiler water system.
In the present invention, since a water treatment agent containing polymerized phosphoric acid and / or a salt thereof that can be stably present even when coexisting with calcium ions, magnesium ions, etc. is used, the scale can be sufficiently suppressed. .

  According to the present invention, since polymerized phosphoric acid and / or a salt thereof is used as the phosphoric acid component, even if it contains a natural product-based oxygen scavenger, there is no performance deterioration during storage and distribution, and it is excellent. Scale suppression effect is obtained.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

[Boiler water treatment agent]
First, the boiler water treatment agent according to the first embodiment of the present invention will be described. The boiler water treatment agent according to the present embodiment contains polymerized phosphoric acid and / or a salt thereof, and a natural product-based oxygen scavenger, and is added to the boiler water system and has effects such as scale inhibition and corrosion inhibition. Play.

(Natural product oxygen scavenger)
Natural product oxygen scavengers contain polyhydric phenolic organic compounds and / or polysaccharide organic compounds produced from natural materials, and naturally contain calcium ions, magnesium ions, etc. that are mixed in during the production process. Yes. Moreover, since a natural product type oxygen absorber is derived from a natural material, it is excellent in safety.

  The polyhydric phenol-based organic compound contained in the natural oxygen scavenger is not particularly limited as long as it has an action of reducing dissolved oxygen in water. For example, gallic acid or the like may be used. From the point which is excellent in it, it is desirable that it is 1 or more types of compounds chosen from the group which consists of tannins, lignins, and catechins.

  Examples of tannins used here include hydrolyzable tannins such as gallotannins and polymerized tannins such as quebracho tannins. Examples of the lignins include alcohol lignin, dioxane lignin, phenol lignin, hydrotropic lignin, mercaptrignine, thioglycolic acid lignin, lignin sulfonic acid, alkali lignin, thioalkali lignin, acid lignin, copper oxide-ammonia lignin. And periodate lignin and the like. Furthermore, examples of catechins include epigallocatechin, epigallocatechin gallate, epicatechin, and epicatechin gallate.

  On the other hand, the polysaccharide organic compound contained in the natural oxygen scavenger is preferably chitosans from the viewpoint of excellent oxygen scavenging action, but is not limited thereto, and may be starch or the like. Good. Examples of the chitosans used here include chitosan, glycerylated chitosan, carboxymethyl chitosan, cationized chitosan, and hydroxyalkyl chitosan.

(Polymerized phosphoric acid, polymerized phosphate)
Calcium ions, magnesium ions, and the like contained in the natural product-based oxygen absorber easily react with phosphate ions to form hardly soluble salts (for example, calcium phosphate, magnesium phosphate, hydroxyapatite). When the water treatment agent in which such a salt is formed is added to the boiler water system, the amount of phosphate ions is insufficient, and the scale suppressing effect may be insufficient. Therefore, in the boiler water treatment agent of this embodiment, polymerized phosphoric acid and / or a salt thereof is blended as the phosphoric acid component.

  Examples of polymerized phosphoric acid blended in the boiler water treatment agent of the present embodiment include pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid, but under non-high temperature or non-high pressure conditions. From the viewpoint of excellent stability, it is preferable to use tripolyphosphoric acid. Examples of the polymerized phosphate include the alkali metal salts (for example, sodium salt and potassium salt) and alkaline earth metal salts (for example, magnesium salt and calcium salt) of the polymerized phosphoric acid described above.

  Among these polymerized phosphates, it is preferable to use an alkali metal salt (for example, sodium salt or potassium salt) because it is difficult to cause an increase in scale by reacting with phosphate ions during use, and sodium tripolyphosphate. It is more preferable. The crystal of sodium tripolyphosphate has two types, that is, a type I crystal form and a type II crystal form, and both forms of crystals are readily soluble in water. For this reason, type I and / or type II sodium tripolyphosphates can be used alone or in combination with sodium tripolyphosphate hexahydrate.

  The above-mentioned polymerized phosphoric acid and its salt decompose into orthophosphate under high temperature and high pressure conditions. For this reason, when added to the boiler water system, an orthophosphate is generated, and a sufficient scale inhibiting action is exhibited by this orthophosphate. For example, in the case of sodium tripolyphosphate, the decomposition reaction shown in the following chemical formulas 1 and 2 occurs.

  On the other hand, polymerized phosphoric acid and its salt hardly decompose and exist stably under non-high temperature (including normal temperature and low temperature) or non-high pressure conditions. For this reason, in the boiler water treatment agent of this embodiment, the production | generation of a phosphate ion is suppressed during storage and distribution | circulation, and formation of a hardly decomposable salt can be suppressed.

  Moreover, it is preferable that the boiler water treatment agent of this embodiment does not contain orthophosphoric acid and its salt substantially. Thereby, the situation where the poorly soluble salt formed by the reaction between calcium ions, magnesium ions, etc. and phosphate ions is mixed into the boiler water system can be prevented. “Substantially not containing” includes not only containing it at all, but also containing a small amount inevitably mixed in, or containing an amount within an allowable limit for detour purposes.

(Alkaline agent)
Furthermore, it is desirable that the boiler water treatment agent of this embodiment contains an alkali agent in addition to the above-described components. The alkaline agent has an effect of neutralizing the organic acid generated with the removal of dissolved oxygen by the oxygen scavenger. Thereby, since the pH fall in a boiler water system is suppressed, a corrosion inhibitory effect can be heightened.

  The alkaline agent blended in the boiler water treatment agent of the present embodiment is not particularly limited as long as it is alkaline. For example, an alkali metal (for example, sodium, potassium) or an alkaline earth metal (for example, magnesium, calcium) is used. Examples thereof include hydroxides and carbonates. Among these, an alkali metal hydroxide is particularly preferable, and sodium hydroxide and / or potassium hydroxide is more preferable. Thereby, the scale suppression effect can be improved.

  The content of the alkaline agent can be appropriately set according to the quality of water supplied to the boiler water system, the operating pressure of the boiler, the content of polymerized phosphoric acid and its salt, and the like.

(Other)
The boiler water treatment agent of this embodiment may further contain optional components such as a scale dispersant and an anticorrosive agent.

  The scale dispersant disperses the scale and suppresses the adhesion of the scale to the boiler water system. The scale dispersant blended in the boiler water treatment agent of the present embodiment is not particularly limited, and for example, a well-known one such as a high molecular polymer containing a sulfonic acid group or a carboxylic acid group can be used. .

  The anticorrosive agent prevents corrosion by forming an anticorrosive film in the boiler water system. The anticorrosive agent blended in the boiler water treatment agent of the present embodiment is not particularly limited. For example, neutralizing amines such as cyclohexylamine, diethylethanolamine and morpholine, and long-chain aliphatic amines such as octadecylamine. Well-known things such as can be used.

  Thus, in the boiler water treatment agent of this embodiment, since the polymerization phosphoric acid and / or its salt are mix | blended as a phosphoric acid component, the performance fall during storage or distribution | circulation can be suppressed. In addition to polymerized phosphoric acid and / or its salt, it also contains a natural product-based oxygen scavenger, so that the phosphoric acid component and oxygen scavenger can be stored and distributed separately or mixed at the site of use. Since there is no need to do this, the complexity of the work can be eliminated.

[Water treatment method]
Next, a water treatment method according to the second embodiment of the present invention will be described. The water treatment method of the present embodiment is a method for suppressing the occurrence of scale and corrosion in the boiler water system by using the water treatment agent of the first embodiment described above. Specifically, the water treatment method of the present embodiment includes a step of adding a boiler water treatment agent containing polymerized phosphoric acid and / or a salt thereof and a natural product-based oxygen scavenger, and an alkaline agent to the boiler water system. Have.

  The boiler water treatment agent and the alkaline agent may be added at any location in the boiler water system, and is usually at a location where scale and corrosion should be suppressed or upstream thereof. Moreover, the addition of the alkaline agent to the boiler water system may be performed after mixing with the boiler water treatment agent, or may be performed independently of the boiler water treatment agent. Here, adding independently means adding to an independent timing and / or an independent location.

  In addition, since the detail of the component added to a boiler water system is the same as that of what was described by the boiler water processing agent, it abbreviate | omits.

  In the water treatment method of this embodiment, polymerized phosphoric acid and / or a salt thereof is blended as the phosphoric acid component, and further, a boiler water treatment agent blended with a natural product-based oxygen scavenger is used. An excellent scale suppression effect can be obtained stably, and no mixing work is required at the site of use.

  Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. First, as a first example of the present invention, storage stability was compared between a water treatment agent using polymerized phosphoric acid (Example) and a water treatment agent using non-polymerized phosphoric acid (Comparative Example). In this example, sodium tripolyphosphate, which is a salt of polymerized phosphoric acid, is used as the phosphoric acid component, and a natural product oxygen scavenger containing tannin or sodium lignin sulfonate, and potassium hydroxide and / or water. The water treatment agent of Examples 1-16 was prepared by mix | blending the alkaline agent which consists of sodium oxide.

  Further, trisodium phosphate which is a salt of non-polymerized phosphoric acid (orthophosphoric acid) is used as a phosphoric acid component, and natural product-based oxygen scavenger containing tannin or sodium lignin sulfonate, potassium hydroxide and / or Or the alkaline agent which consists of sodium hydroxide was mix | blended, and the water treatment agent of Comparative Examples 1-16 was prepared.

  Table 1 below shows the calcium concentration contained in the natural product-based oxygen scavenger used in each of the water treatment agents of these Examples and Comparative Examples.

  Then, 150 g of the water treatment agent prepared by the above-described method is put into a polypropylene container having a capacity of 250 mL, and a lid with a hole having a diameter of 5 mm is put on the container, and the temperature is −5 ° C. (low temperature) or 40 ° C. (normal temperature). After standing still for 4 weeks, precipitation in each container and the state of precipitation were observed. The evaluation criteria for the stability of each water treatment agent were “◯” when neither precipitation nor precipitation was observed, and “X” when precipitation or precipitation was observed. The above results are summarized in Tables 2 and 3 below.

  As shown in Tables 2 and 3 above, the boiler water treatment agents of Examples 1 to 16 were stable at both −5 ° C. and 40 ° C., whereas the boiler water treatment of Comparative Examples 1 to 16 The agent was unstable at -5 ° C. By using sodium tripolyphosphate, which is polymerized phosphoric acid, instead of orthophosphoric acid, which is non-polymerized phosphoric acid, performance degradation can be suppressed regardless of whether it is stored or distributed at low or normal temperature, improving versatility. It was confirmed that it was possible.

  In addition, as a result of analyzing the deposit which generate | occur | produced with the boiler water treatment agent of the comparative example 6 using the fluorescent-X-ray-analysis apparatus, it turned out that the main components of a deposit are phosphorus and calcium. Thereby, it was strongly suggested that precipitates are generated by the reaction of calcium ions mixed in the natural product-based oxygen scavenger with phosphate ions.

  Moreover, since any boiler water treatment agent of Examples 1-16 was stable, sodium tripolyphosphate which is polymeric phosphoric acid can be used together with a variety of natural product oxygen scavengers and alkaline agents, It was confirmed that it was excellent in performance. In particular, it has been found that sodium tripolyphosphate, which is a polymerized phosphoric acid, can stabilize the boiler water treatment agent regardless of the amount of calcium ions and the like mixed in the natural product oxygen scavenger.

Next, as a second embodiment of the present invention, the scale suppression performance was compared between a water treatment agent using polymerized phosphoric acid (Example) and a water treatment agent using non-polymerized phosphoric acid (Comparative Example). . In this example, water treatment agents of Example 17 and Comparative Examples 17 and 18 shown in Table 4 below were added to city water softened water (soft water 90% and city water 10%) adjusted to 40 ° C., respectively, at 140 mg / L. Added. This was supplied to a test boiler having a retained water amount of 5.7 L and operated under the conditions of a pressure of 0.7 MPa, an evaporation amount of 4.5 L / hour, and a blow rate of 10% (but no blow for 7 hours after the start of operation). Then, after operation for 168 hours, the boiler was stopped and three heat transfer tubes (carbon steel SS400) were taken out. About 5 cm of both ends of these tubes were wound with a vinyl tape, the scale attached to the portion between the tapes (surface area 133 cm ² , length 170 mm × diameter 25 mm) was scraped off, and the mass was measured. The results are shown in Table 5 below.

  As shown in Table 5 above, the boiler water treatment agent of Example 17 was equivalent to Comparative Example 17 and suppressed scale adhesion better than Comparative Example 18. Thereby, it was confirmed that even if sodium tripolyphosphate which is polymerized phosphoric acid is used instead of orthophosphoric acid which is non-polymerized phosphoric acid, the adhesion of scale can be suppressed to the same level or more.

Claims (6)

Polymerized phosphoric acid and / or salt thereof;
A natural product oxygen scavenger containing a polyphenolic organic compound and / or a polysaccharide organic compound;
A boiler water treatment agent containing   The boiler water according to claim 1, wherein the polyhydric phenol-based organic compound is one or more compounds selected from the group consisting of tannins, lignins, and catechins, and the polysaccharide-based organic compound is chitosans. Processing agent.   The boiler water treatment agent according to claim 1 or 2, which is substantially free of orthophosphoric acid and salts thereof.   The boiler water treatment agent according to any one of claims 1 to 3, further comprising an alkali agent.   The boiler water treatment agent according to claim 4, wherein the alkaline agent includes sodium hydroxide and / or potassium hydroxide. A water treatment method in a boiler water system,
A water treatment method in which the boiler water treatment agent according to any one of claims 1 to 3 and an alkali agent are added to the boiler water system.