JP5117666B2 - Treatment method for boiler water system - Google Patents

Description

The present invention relates to a boiler water treatment technology, and not only high anticorrosion effect and scale prevention effect can be obtained in an operating boiler device, but also iron sludge is prevented from being generated even when the boiler is stopped. About the processing method of the boiler water system which does not cause corrosion

  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 boiler water and add a new anticorrosive agent, which not only complicates driving operations but also increases running costs.

  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 (Patent Document 1), a natural product type corrosion inhibitor selected from tannins, lignins and saccharides, phosphonic acid or a salt thereof, and an unsaturated carboxylic acid polymer A method for treating boiler water is also 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. .

In JP-A-51-108101 (Patent Document 2), hydroxylamines such as diethylhydroxylamine are described as oxygen scavengers (referred to as “oxygen scavengers” in Patent Document 2) for water-based corrosion prevention methods. However, the above-mentioned problem cannot be solved.
JP-A-6-108274 JP 51-108101 A

The present invention improves the above-mentioned conventional problems, that is, it can exhibit the anticorrosion effect as it is without taking any additional measures even when the boiler is stopped, and it will cause any trouble even if it enters the restart. There is provided a method for treating a boiler water system that can prevent the occurrence of corrosion due to accumulation of iron sludge at the time of stoppage and further has a scale prevention effect.

In order to solve the above-described problems, the boiler water treatment method of the present invention has a high frequency of operation-stop as described in claim 1 , and additional anti-corrosion means at the time of stoppage and replacement of boiler water at the time of re-operation. Boiler water-based treatment method that does not perform the treatment, which is diethylhydroxylamine, polyacrylic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and bis (polycarboxylethyl) phosphinic acid 1 or 2 or more of unsaturated carboxylic acid polymers selected from the above, and a boiler water-based treatment method in which 10 mg of the diethylhydroxylamine is added so as to prevent the accumulation of iron sludge. / L or more 500 mg / L or less, and adding the unsaturated carboxylic acid polymer below 10 mg / L or more 200 mg / L, the boiler water system It is a processing method for a boiler water system wherein Rukoto.

According to the boiler water treatment method of the present invention , the anticorrosion effect can be exhibited as it is without taking any additional measures not only during boiler operation, but also when the boiler is stopped. There will be no trouble. Furthermore, according to the boiler water processing method of the present invention, it is possible to prevent the occurrence of corrosion due to the accumulation of iron sludge, and therefore, a high anticorrosion effect is maintained even in a boiler water system with a lot of iron sludge.

  The boiler aqueous treatment agent of the present invention needs to contain diethylhydroxylamine and one or more 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.

  The diethylhydroxylamine in the present invention is known to have an effect as an oxygen scavenger in the field of boilers. In the present invention, in addition to the effect, diethylhydroxylamine is present in the boiler when the boiler is stopped in the presence of an unsaturated carboxylic acid polymer. It functions to prevent iron sludge accumulation inside.

  Further, the unsaturated carboxylic acid polymer in the present invention is a polymer composed of 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 preferably 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 500 or more and 100,000 or less, preferably 1000 or more and 20,000 or less, in that an excellent anticorrosive effect is obtained.

  The amount of the above components used in the present invention to the boiler water system is such that diethylhydroxylamine is 1 mg / L or more and 500 mg / L or less, and the unsaturated carboxylic acid polymer is 1 mg / L or more and 200 mg / L or less. It is preferable from the viewpoint of preventing sludge accumulation and anticorrosion, or economically. 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 aqueous treatment agent according to the present invention enhances the effect of the boiler aqueous treatment agent or imparts other effects in addition to diethylhydroxylamine and one or more of unsaturated carboxylic acid polymers. In general, it may contain an appropriate amount of other components to be blended.

  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, methyl ethyl ketoxime, gallic acid, tannin, lignin, lignin sulfonic acid, saccharide, ascorbic acid or salt thereof, erythorbic acid or salt thereof, oxycarboxylic acid or salt thereof, phosphoric acid or salt thereof, aminotrimethylene phosphonic acid or Salt thereof, hydroxyethylidene diphosphonic acid or salt thereof, phosphonobutanetricarboxylic acid or salt thereof, ethylenediaminetetraacetic acid or salt thereof, nitrilotriacetic acid or salt thereof, aminomethylpropanol, octadecylamine, morpholine, alkali metal hydroxide, List one or more alkali metal carbonates It is possible.

  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. By adding such boiler water treatment agent to the boiler water system, the anti-corrosion effect can be exerted as it is even when the boiler is stopped, without any special measures being taken before or after the boiler is stopped. However, it is possible to effectively prevent the occurrence of corrosion due to the accumulation of iron sludge when the boiler is stopped without causing any trouble.

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 compared to softened water (referred to as "Tsukuba City softened water") in which Tsukuba City tap water was adjusted to pH 11.5 using potassium hydroxide and the cation was replaced with sodium ion by a cation exchange resin. (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 a total of 10 types of boiler water-based treatment agent samples shown in Table 1 and Examples 1 to 4 and Comparative Examples 1 to 6 were added, and the mixture was 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. Further, the total iron concentration “<0.5” in the filtrate filtered in the table indicates that the iron concentration was less than the detection lower limit of 0.5 mg / L (hereinafter the same).

  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 5 and 6 and Comparative Examples 7 and 8 shown in Table 2 was added and kept at 75 ° C. And stirred for 24 hours.

  A test piece made of mild steel of 40 mm x 60 mm x 2 mm in a container containing the sample solution (1000 mL) containing iron is immersed horizontally on the bottom of the container, kept at 60 ° C, and left to stand 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 boiler water-based treatment agent composition 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 7 to 9 was severely generated 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.

  The present invention is capable of exhibiting the anticorrosion effect as it is without stopping the boiler as well as during the operation of the boiler, and without causing any trouble even when the operation is restarted. It is a boiler water treatment agent that can prevent the occurrence of corrosion due to the accumulation of iron sludge at the time, maintains a high anti-corrosion effect, and also has a scale prevention effect, and a boiler water treatment method using the same. It can be suitably used in boiler water systems that are frequently operated and stopped.

Claims (1)

A treatment method for a boiler water system that has a high frequency of operation-stop, does not perform additional anti-corrosion means at the time of stop, and does not replace boiler water at the time of restart,
One kind of unsaturated carboxylic acid polymer selected from diethylhydroxylamine, polyacrylic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and bis (polycarboxylethyl) phosphinic acid Or it is the processing method of the boiler water system which adds 2 or more types to a boiler water system, and
Add the diethylhydroxylamine at 10 mg / L or more and 500 mg / L or less and the unsaturated carboxylic acid polymer at 10 mg / L or more and 200 mg / L or less to the boiler water system so as to prevent the accumulation of iron sludge. A method for treating a boiler water system.