JP4718823B2 - Boiler water treatment agent and boiler water treatment method using the same - Google Patents

Description

  The present invention relates to a method for treating a boiler water system, which provides an anti-corrosion effect and an anti-scale adhesion effect for operating boiler equipment, and in particular, iron sludge not only during operation of the boiler but also during operation as well as during shutdown. Therefore, the present invention relates to a boiler water-based treatment agent that does not generate corrosion even when the boiler is stopped, and a boiler water-based treatment method using the same.

  In many cases, the boiler is repeatedly operated and stopped according to the use state of the generated steam. Here, usually, an anticorrosive agent is added to an operating boiler water system, and other anticorrosive measures such as adding hydrazine or sulfite at a high concentration as a can-preserving agent at the time of long-term shutdown, At the time of restarting, it is necessary to replace the boiler water and add a new anticorrosive agent, which makes the operation complicated and increases the running cost.

  In addition to such problems, there may be a case where the stoppage period may be several days or several weeks depending on the situation depending on the number of installed boilers and the operation method. For this reason, the boiler aqueous processing agent which does not require a special treatment before a stop like this was calculated | required.

  Here, for example, in JP-A-6-108274, a natural product type corrosion inhibitor selected from tannins, lignins and saccharides, phosphonic acid or a salt thereof, and an unsaturated carboxylic acid polymer are added together. A boiler water treatment method has been proposed.

This method is a method that can achieve the anticorrosion effect by using a highly safe chemical and further stably dispersing the scale, but the anticorrosion property when the boiler is stopped is insufficient, and the above problem cannot be solved. .
JP-A-6-108274

  Here, when the technique described in Japanese Patent Laid-Open No. 6-108274 has been studied in detail, this technique generally prevents the adhesion of the iron scale scale that occurs during operation, but the iron in the boiler water system when stopped. Since sludge accumulates and this iron sludge prevents contact between the boiler inner surface portion and boiler water containing oxygen, oxygen is present between the boiler inner surface of the sludge accumulation portion and other boiler inner surface portions where iron sludge is not accumulated. It was found that a difference in concentration occurred, and as a result, electrochemical corrosion occurred on the inner surface of the boiler in the sludge accumulation portion.

Therefore, the present invention can exhibit the anticorrosion effect without taking any additional measures not only during boiler operation but also during boiler operation in boiler water systems that are frequently operated and stopped , Boiler water treatment agent that has a scale prevention effect and can prevent corrosion due to iron sludge accumulation at the time of stopping without causing any trouble even when entering, and a boiler water treatment method using the same Is to provide.

In order to solve the above-mentioned problem, the boiler water-based treatment agent of the present invention is a boiler water-based treatment agent used in a boiler water system having a high frequency of operation-stop, as described in claim 1, and is gallic acid and / or One or more selected from the salts thereof, polyacrylic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and bis (polycarboxyethyl) phosphinic acid and one or more is a boiler water treatment agent characterized by containing.

Moreover, in order to solve said subject, the processing method of the boiler water type | system | group of this invention is a processing method of boiler water type | system | group with high frequency of operation-stop as described in Claim 2 , Comprising: Gallic acid and / or its 1 selected from one or more selected from a salt, polyacrylic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and bis (polycarboxyethyl) phosphinic acid it is a processing method for a boiler water system which comprises adding a species or two or more, to the boiler water.

According to the boiler water-based treatment agent of the present invention and the boiler water-based treatment method of the present invention, in a boiler water system having a high frequency of operation-stop, not only during the operation of the boiler but also any additional measures are taken when the boiler is stopped. Therefore, the corrosion prevention effect can be exhibited as it is, and there is no trouble even if restarting, and the corrosion caused by the accumulation of iron sludge can be prevented. High anticorrosion effect is maintained even in

  The boiler water-based treatment agent of the present invention needs to contain one or more selected from gallic acid and / or a salt thereof and one or more of unsaturated carboxylic acid polymers. . Due to the synergistic effect of these two components, the generation of iron sludge is suppressed, and therefore, iron sludge accumulation in the boiler when the boiler is stopped is prevented. As a result, corrosion generation due to iron sludge accumulation is effectively prevented. Can be prevented.

  Here, the gallate must be a water-soluble salt, and examples thereof include general alkali metal salts, alkaline earth metal salts, and ammonium salts.

  In addition, the unsaturated carboxylic acid polymer in the present invention is a polymer having an unsaturated carboxylic acid monomer, and the unsaturated bond of the unsaturated carboxylic acid monomer usually indicates an unsaturated bond derived from an ethylene group. Such an unsaturated carboxylic acid polymer is used as a scale inhibitor in the boiler field, and functions as a scale inhibitor during operation in the present invention.

  Here, the unsaturated carboxylic acid polymer is a homopolymer of acrylic acid, methacrylic acid, or maleic acid, or two or more kinds of unsaturated compounds selected from acrylic acid, methacrylic acid, and maleic acid. Copolymers composed of carboxylic acid monomers, or one or more unsaturated carboxylic acid monomers selected from acrylic acid, methacrylic acid, and maleic acid, and other compounds that can be copolymerized with these unsaturated carboxylic acid monomers ( Monomer).

  Examples of such other compounds include fumaric acid, itaconic acid, acrylamide, acrylic acid ester, vinyl acetate, styrene, ethylene oxide, ethylene, n-butylene, isobutylene, allyl sulfonic acid, vinyl sulfonic acid, and styrene sulfonic acid. , Sulfopropyl acrylate, sulfopropyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid and the like.

  Here, since higher iron sludge dispersibility and corrosion resistance are obtained, the unsaturated carboxylic acid polymer is desirably polyacrylic acid. The unsaturated carboxylic acid polymer may contain a sulfonic acid group and / or a phosphinic acid group.

  The molecular weight of the unsaturated carboxylic acid polymer in the present invention is usually from 500 to 100,000, preferably from 1,000 to 20,000, in that an excellent anticorrosive effect is obtained.

  The amount of the above components used in the present invention to be added to the boiler water system is 5 mg / L to 500 mg / L for gallic acid and / or a salt thereof, and 1 mg / L to 200 mg / L for the unsaturated carboxylic acid polymer. It is preferable from the viewpoint of preventing the accumulation of iron sludge, the anticorrosion effect, and the economy. Each of the above components may be added separately so as to have a predetermined concentration, or may be added in advance by mixing. Each of the above components may be added to a boiler water-based makeup water line or may be added directly to the boiler.

  The boiler anticorrosive agent according to the present invention includes a boiler aqueous treatment agent in addition to one or more selected from gallic acid and / or a salt thereof and one or more of unsaturated carboxylic acid polymers. In order to enhance this effect or to impart other effects, an appropriate amount of other components that are usually blended may be included.

  As such other components, for example, other anticorrosives, scale inhibitors, condensate treatment agents, pH adjusters, etc., specifically, nitrites, zinc salts, tin salts, molybdic acid or salts thereof, hydrazine , Carbohydrazide, diethylhydroxylamine, methyl ethyl ketoxime, tannin, lignin, lignin sulfonic acid, saccharides, ascorbic acid or salt thereof, erythorbic acid or salt thereof, oxycarboxylic acid or salt thereof, phosphoric acid or salt thereof, aminotrimethylenephosphonic acid Or a salt thereof, hydroxyethylethylenediphosphonic acid or a salt thereof, phosphonobutanetricarboxylic acid or a salt thereof, ethylenediaminetetraacetic acid or a salt thereof, nitrilotriacetic acid or a salt thereof, aminomethylpropanol, octathesylamine, morpholine, alkali metal water Kind of oxide, alkali metal carbonate, etc. Mention may be made of two or more thereof.

  The boiler water treatment agent according to the present invention can be used by adding an appropriate amount to the boiler water system, as in the case of conventional anticorrosive agents for boilers. With such addition, when the boiler is stopped, or without special measures before stopping, the anticorrosion effect can be exhibited as it is even when the boiler is stopped, and there is no trouble even if it enters the restart, and In addition, it is possible to effectively prevent the occurrence of corrosion due to the accumulation of iron sludge when the boiler is stopped.

Examples of the boiler water-based treatment agent of the present invention will be specifically described below.
<Evaluation of iron sludge suppression ability>
As a basic study, the iron sludge generation prevention ability was evaluated about some boiler water-system processing agent compositions.

  Iron (II) chloride against softened water (referred to as "Tsukuba City softened water") whose cation is replaced with sodium ion by using a cation exchange resin in Tsukuba City tap water adjusted to pH 11.5 using potassium hydroxide. (Ferrous chloride) was added as an iron concentration to 40 mg / L, and then kept at 75 ° C. and stirred at 300 rpm for 2 hours. Thereafter, any one of 10 types of boiler water-based treatment agent samples shown in Table 1 and Examples 1 to 3 and Comparative Examples 1 to 7 were added and stirred at 300 rpm for 24 hours while maintaining at 75 ° C. did.

  Thereafter, the test water was filtered using a filter having a pore diameter of 0.45 μm or 0.2 μm, and the total iron concentration in the filtrate was measured by atomic absorption spectrophotometry. These experimental results are also shown in Table 1.

  In Table 1, polyacrylic acid is Aron A-20UK (average molecular weight: 6000) manufactured by Toa Gosei Co., Ltd., and AA-AMPS copolymer is a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid. The polymer (Aron A-6016 manufactured by Toa Gosei Co., Ltd., average molecular weight: 2000), bis (polycarboxyethyl) phosphinic acid, which is an acrylic acid copolymer containing a phosphinic acid group, is Versperse 164 manufactured by Great Lakes Chemical Co., Ltd. The average molecular weight is 1200), HEDP is hydroxyethylidene-1,1-diphosphonic acid, and PBTC is 2-phosphonobutane-1,2,4-tricarboxylic acid.

  Table 1 shows that in the system to which the boiler water treatment agent according to the present invention is added, the concentration of dissolved iron in the liquid is not at all or hardly decreases, and iron sludge is generated by the boiler water treatment agent according to the present invention. It can be seen that it can be kept low.

<Evaluation of iron sludge generation suppression and anti-corrosion ability when boiler stops>
The anti-corrosion ability was evaluated assuming the occurrence of corrosion due to iron sludge accumulation when the boiler was stopped.

  Adjust the pH to 11.5 by adding potassium hydroxide to the same Tsukuba softening water as above, then add iron (II) chloride so that the iron concentration becomes 40 mg / L, and then stir at 300 rpm. While maintaining at 75 ° C. for 2 hours, any one of a total of four types of boiler water-based treatment agent samples of Examples 4 and 5 and Comparative Examples 8 and 9 shown in Table 2 was added, and while maintaining at 75 ° C., 300 rpm And stirred for 24 hours.

  A test piece made of mild steel (40 mm x 60 mm x 2 mm) in a container containing the sample solution (1000 mL) containing iron is immersed in the bottom of the container so as to be horizontal, and kept at 60 ° C for 3 days. Then, the corrosion degree of the test piece at that time was measured. The results are also shown in Table 2. In Table 2, “No chemical added” is a result of a system in which no anticorrosive was added.

  It can be seen from Table 2 that in the system to which the boiler water-based treatment agent according to the present invention is added, the progress of corrosion can be remarkably suppressed even under conditions assuming the boiler stop. In addition, the corrosion in Comparative Examples 8 to 10 occurred significantly on the upper surface placed horizontally, and the accumulation of iron sludge was confirmed on those surfaces.

  On the other hand, in the system to which the boiler water-based treatment agent according to the present invention was added, almost no sludge accumulation was observed on the upper surface of the horizontally placed test piece, and corrosion was only observed at the fixed part of the test piece. Met.

In the boiler water system having a high frequency of operation-stop , the present invention can exhibit the anticorrosion effect as it is without stopping the boiler as well as during the operation of the boiler, and can be restarted. A boiler water-based treatment agent that maintains a high anti-corrosion effect and can prevent the occurrence of corrosion due to the accumulation of iron sludge during stoppage without causing any trouble, It is the processing method of the used boiler water system.

Claims (2)

Boiler water treatment agent used in boiler water systems with high frequency of operation-stop,
One or more selected from gallic acid and / or a salt thereof;
One or more selected from polyacrylic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and bis (polycarboxyethyl) phosphinic acid ;
A boiler water-based treatment agent comprising: A treatment method for a boiler water system with a high frequency of operation and shutdown,
One or more selected from gallic acid and / or a salt thereof;
One or more selected from polyacrylic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and bis (polycarboxyethyl) phosphinic acid ;
Is added to boiler water. A method for treating a boiler water system.