JP3442955B2 - Anticorrosive for soft water boiler - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in boilers using soft water such as city water and ground water when operating at relatively high temperature and high load, and is particularly useful for metals such as steam generators and heat exchangers. The present invention relates to an anticorrosive agent used for preventing corrosion of steel.

[0002]

2. Description of the Related Art Soft water boilers use chlorine ions, sulfate ions,
Due to the use of water containing interfering ions which promote so-called metal corrosion, such as nitrate and carbonate ions, metal corrosion has always been a problem. In particular, in recent years, there is a tendency to operate the boiler efficiently, and higher temperature and high load operation is performed. Therefore, naturally, the corrosion acceleration effect due to the high temperature becomes large and the corrosion acceleration effect due to the concentration of interfering ions in the boiler water occurs, and the synergistic effect of these causes the corrosion to become significantly large, and in some cases fatal corrosion troubles of the boiler may occur. Will be generated.
In order to prevent these corrosion, hydrazine,
Organic acid salts such as sulfites, polymeric phosphates and gluconates, monosaccharides such as tannins, lignin sulfonates, ascorbates, erythobinates, glucose and fructose are used as they are or as alkali-treated products. .

[0003]

However, these conventionally used anticorrosive agents have the following problems: operating cost, toxicity,
It has some drawbacks in terms of carcinogenicity, pollution, anticorrosion effect, liquid management, etc. Among these anticorrosive agents, the anticorrosive agent composed of a monosaccharide or an alkali-treated monosaccharide is excellent in anticorrosion property, and has a tendency to be particularly frequently used in recent years because of its features such as easy management, low cost and low pollution. However, these anticorrosive agents have the drawback that they generate a volatile odorous component such as aldehydes and ketones by causing a complicated chemical reaction during the operation of the boiler to generate volatile odorous components such as generated steam. In addition, some products may cause toxicity problems. In particular, when using live steam as it is, such as humidification in air-conditioning equipment, sterilization of equipment in hospitals, and food processing, it has become a serious problem, which is a factor that greatly limits the use.

In view of the above-mentioned state of the art, the present invention is to provide an anticorrosive agent for a soft water boiler, which is inexpensive, has a high anticorrosive property, and does not carry an odorous substance in steam.

[0005]

According to the present invention, (1) a 5 to 30% aqueous solution of a mixture of a monosaccharide and 0.5 to 5% by weight of a monosaccharide of iron gluconate is mixed with 85 parts of an alkali metal hydroxide. ±
The soft water boiler anticorrosive comprising a product obtained by reacting at 5 ° C. and (2) the compounding ratio of the alkali metal hydroxide to the monosaccharide is 80:20 to 10:90 (weight ratio). The anticorrosive agent for a soft water boiler according to (1) above, which is characterized in that.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Monosaccharides used in the present invention include glucose, mannose, galactose, fructose, etc., alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and iron gluconate as iron gluconate. A ferrous salt or ferric salt of gluconic acid may be used. The mixing ratio of the monosaccharide and the alkali hydroxide is 80:20 by weight.
The range of 10:90 is good, preferably 75:25 to 1
The range is 0:90. This ratio is largely unaffected by the type of alkali. Also, the alkali metal hydroxide can be used as it is as a solid, but since it is rinsed with a heterogeneous reaction,
It is preferably used in a 25 to 50% aqueous solution. The addition ratio of iron gluconate to monosaccharide is 0.5 to 5 to monosaccharide.
%, Preferably 1-2% by weight.

The mixture of monosaccharide and iron gluconate is 5 to 30
% Aqueous solution, to which alkali metal hydroxide 85 ±
While maintaining the temperature at 5 ° C., preferably 85 ± 3 ° C., an alkali metal hydroxide is gradually added and reacted. If the temperature is above or below the range of the present invention, the degree of generation of odorous components in the product is high, which is not preferable. Since the reaction between the monosaccharide and the alkali metal hydroxide is an exothermic reaction, it should be possible to externally cool the reaction. The reaction between the monosaccharide and the alkali metal hydroxide is completed in 20 to 60 minutes after the total amount of the alkali metal hydroxide is added.

Further, a polyacrylic acid salt, a polymaleic acid salt, a phosphonic acid salt, or the like, which can be used together with a scale dispersant which does not generate a volatile odor component in the boiler, a supplementary anticorrosive agent, etc. can be added to the water. .

(Action) Although the mechanism of the present invention is not clear, the presence of iron gluconate and the temperature of 85 in the process in which the monosaccharide reacts with the alkali metal hydroxide and decomposes.
By strictly maintaining the temperature at ± 5 ° C, almost no odorous component is generated, and an anticorrosive agent for a soft water boiler having an excellent anticorrosion effect can be obtained. During the reaction between the monosaccharide and the alkali metal hydroxide, iron gluconate remains unchanged and remains dissolved in the aqueous solution.

[0010]

Example: 0.8 liter of anticorrosion solution obtained by adding 0.3% by weight of the anticorrosive agent according to the present invention shown in the following (1) to (5) to tap water having the analysis values shown in Table 1 Take the autoclave with the product. Next, test pieces (structural steel, JIS-G-3101, SS-400,
35 × 50 × 1.2 mm) was immersed in the anticorrosive liquid. Then, the autoclave was set and allowed to stand at 180 ± 5 ° C. for 2 days. Two days later, steam is blown out from the autoclave to sniff odor, and its strength is evaluated. Then, the test piece was taken out and observed for rust.

[0011]

[Table 1]

The anticorrosive agent according to the present invention includes (1)
Glucose: 20 g, ferric gluconate: 0.4 g, sodium hydroxide: 9.6 g, water: 70 g, (2) fructose: 15 g, ferrous gluconate:
A composition comprising 0.08 g, sodium hydroxide: 14 g and water: 70 g, (3) mannose: 10 g, ferric gluconate: 0.1 g, potassium hydroxide: 19 g, water: 70
(4) glucose: 5 g, fructose: 5 g, ferrous gluconate: 0.1 g, sodium hydroxide: 19 g, water: 70 g, and (5)
Glucose: 23 g, ferric gluconate: 0.35 g,
A composition comprising 6 g of potassium hydroxide and 70 g of water,
For each example, a monosaccharide and an aqueous solution of iron gluconate were gradually added with stirring to an alkali metal hydroxide so that the temperature was 85 ± 5 ° C., and 30 minutes after adding the total amount of the alkali metal hydroxide. Stirring was continued at 85 ± 5 ° C. to obtain an anticorrosive agent according to the present invention.

On the other hand, as a comparative example, (1) 'glucose: 20 g, ferric gluconate: 0.04 g, sodium hydroxide: 9.6 g, water: 70 g of an anticorrosive agent in the preparation method of the embodiment. Made in. (2) 'Glucose: 20 g, ferric gluconate: 0.4 g, sodium hydroxide: 9.6 g, water: 70 g
A product manufactured at a reaction temperature of 90 ± 5 ° C. (3) 'Glucose: 20 g, ferric gluconate: 0.4 g, sodium hydroxide: 9.6 g, water: 70 g, which is an anticorrosive agent produced at a reaction temperature of 70 ° C or lower.
(4) ′ Glucose: 20 g, sodium hydroxide: 9.
6 g, water: 70 g of an anticorrosive compound, produced by the method according to the example. (5) ′ Glucose: 27 g, ferrous gluconate: 0.03 g, sodium hydroxide: 2
g, water: 70 g, an anticorrosive compound produced by the method according to the example, and (6) ′ glucose: 2 g, ferric gluconate: 0.1 g, sodium hydroxide: 27 g,
Water: An anticorrosive agent having a composition of 70 g, which was produced by the production method according to the example. Table 2 shows the effect of suppressing odorous components and the effect of preventing corrosion between the examples and the comparative examples.

[0014]

[Table 2]

[0015]

EFFECTS OF THE INVENTION The anticorrosive agent of the present invention does not have an odor, which was a drawback of the anticorrosive agent using a monosaccharide, and has very stable anticorrosion performance. The anticorrosive agent using a monosaccharide can be applied to applications where its use is limited due to odor, and it can be used in a wider range of applications.

Front page continued (72) Inventor Akihiro Sakanishi 5-171-1 Fukahori-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Research Laboratory (72) Inventor Shigenori Fukuoka 5-5-2, Nishikujo-cho, Nara, Nara Kyoeisha Chemical Co., Ltd., Nara Research Institute (72) Inventor Hideki Tezuka 5-2-5, Nishikujo-cho, Nara City, Nara Kyoeisha Chemical Co., Ltd., Nara Research Institute (56) Reference Japanese Patent Laid-Open No. 4-232286 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23F 11/10 F28G 9/00

Claims (2)

(57) [Claims] 1. A product obtained by reacting a 5 to 30% aqueous solution of a mixture of a monosaccharide and 0.5 to 5% by weight of monosaccharide with iron gluconate with an alkali metal hydroxide at 85 ± 5 ° C. An anticorrosive agent for a soft water boiler, which is made of a material. 2. The corrosion inhibitor for a soft water boiler according to claim 1, wherein the compounding ratio of the alkali metal hydroxide to the monosaccharide is 80:20 to 10:90 (weight ratio).