JP2922996B2 - Scale dissolving removal composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composition for dissolving and removing a scale containing a metal oxide from a metal surface.

[Conventional technology]

Table 1 shows conventional general scale dissolving and removing agents. The type and concentration of the agent are selected according to the type and condition of the object to be cleaned.

[Problems to be Solved by the Invention] Conventional scale dissolving and removing agents have the following problems, respectively.

(1) Pickling with inorganic acid 1) The acidity is high, and there is a concern about peracid cleaning.

 2) There is a risk of hydrogen embrittlement.

3) After the scale is removed, the object to be cleaned needs to be neutralized.

 4) There is danger in handling.

 5) A heating operation is required.

 6) Effluent pH treatment is required.

 7) Generates acidic gas and pollutes the environment.

(2) Pickling with Organic Acid In addition to the same problems as pickling with inorganic acids, there are the following problems.

 1) The COD load of drainage is large.

 2) The cost of the drug is high.

The present invention has been made in view of the above problems of the conventional scale dissolving and removing agent, and has as its object to provide a scale dissolving and removing composition containing a metal oxide which does not have these problems.

[Means for solving the problem]

The present invention comprises mixing one or more chelating agents with a relatively large amount of chloride ions and / or sulfate ions and adjusting the pH to 5.
A scale dissolution and removal composition containing a metal oxide, which is adjusted to 5 to 9.5.

As the chelating agent used in the dissolving and removing composition of the scale of the present invention, malonic acid, itaconic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, thioglycolic acid, polymer system such as polymaleic acid, 1 hydroxyethylidene 1,1 diphosphonic acid, Phosphonic acids such as phytic acid, amines such as ethylenediamine and triethanolamine, amino acids such as alanine and glutamic acid, aldehydes such as salicylaldehyde, ketones such as acetylacetone, etc., and water-soluble at pH of 5.5 to 9.5 Any chelating agent can be used.

As the chlorine ion, any one may be used as long as it is dissolved in water with an alkali metal salt such as sodium chloride, sodium chloride and potassium chloride, or a salt of an organic cation such as amine and ammonia to generate chlorine ion. The sulfate ion may be any alkali metal salt such as sodium sulfate, potassium sulfate or the like, or a salt of an organic cation such as amine, ammonia or the like, which can be dissolved in water to generate sulfate ion.

The combination ratio of the chelating agent and the chloride ion and / or sulfate ion is 95: 5 to 5:95 by weight, preferably 90:10 to 10:90. The concentration of the chelating agent, chloride ion and / or sulfate ion in the composition of the present invention is 0.1 to 50%, preferably 0.5 to 50%.
~ 10% is good. The pH value of the composition is adjusted to 5.5-9.5,
For this adjustment, an inorganic acid or an inorganic alkali agent such as sulfuric acid, hydrochloric acid, sodium hydroxide, or potassium hydroxide, or an organic acid or an organic alkali agent such as gluconic acid, citric acid, oxalic acid, acetic acid, alkanolamine, or ammonia can be used. . When the pH value is 5.5 or less, descaling by conventional pickling is performed, and these disadvantages cannot be improved. On the other hand, when the pH value is 9.5 or more, the removing power of the scale is greatly reduced, so that it is not appropriate. In order to promote the descaling effect, a surfactant such as an anionic, cationic or nonionic surfactant may be used in combination.

[Action]

Although the action of the composition of the present invention is not clear, the chelating agent and the chloride ion and / or sulfate ion in the composition alone have little or no scale removing action. It is presumed to be due to the synergistic action of objects.

〔Example〕

In a 500 ml beaker, add the composition according to the present invention (solids concentration of 5
%) And a test piece with a mill scale attached on its surface. Hot rolled steel sheet JIS-G-3131, 2 types, 3 types
5 × 50 × 1.2 (mm) テ ス ト Test piece that forcibly generated red rust ｛Structural steel, JIS-G-3101, 2 types, 40 × 75 ×
4 (mm), 3 weeks after blasting
The test piece to which the mill scale is attached is subjected to an immersion test (room temperature, stationary state) for 3 days, and the test piece with red rust generated for 10 minutes, and the scale of the test piece after the immersion test is observed.

Examples of the descaling agent according to the present invention include: Example 1: a mixture of malonic acid and sodium chloride (weight ratio).
Example 2: Mixture of malonic acid and sodium sulfate (weight ratio)
75:25) Example-3: Malonic acid, sodium chloride and sodium sulfate (weight ratio 75:15:10) Example-4: Mixture of ethylenediamine and sodium chloride (weight ratio 50:50) Example-5: Ethylenediamine Mixture of tetraacetic acid and sodium chloride (weight ratio 25:75) Example-6: Mixture of alanine and sodium chloride (weight ratio)
Example 7: Mixture of polyacrylic acid (molecular weight 5000) and sodium chloride (weight ratio 65:35) Example 8: Mixture of gluconic acid and sodium chloride (weight ratio 95: 5) Example- 9: Mixture of nitroacetic acid and sodium chloride (weight ratio 10:90) Example-10: Mixture of oxalic acetic acid and sodium chloride (weight ratio 40:60) Example-11: Mixture of salicylaldehyde and sodium chloride (weight ratio) Example 12: A mixture of 12: 1 hydroxyethylidene 1.1 diphosphonic acid and sodium chloride (weight ratio 85:15) Example 13: A mixture of acetylacetone and sodium chloride (weight ratio 75:25) was used.

As a comparative example, Comparative Example-1: Sodium chloride Comparative Example-2: Sodium sulfate Comparative Example-3: Malonic acid Comparative Example-4: Ethylenediamine Comparative Example-5: Ethylenediaminetetraacetic acid Comparative Example-6: Alanine Comparative Example- 7: Polyacrylic acid (molecular weight: 5000) Comparative Example-8: Gluconic acid Comparative Example-9: Nitroacetic acid Example-10: Oxalacetic acid Example-11: Salicylaldehyde Example-12: 1: 1 Hydroxyethylidene 1.1 diphosphonic acid Example -13: acetylacetone was used. The total concentration of each solution was 5%. The pH values of the Examples and Comparative Examples were adjusted to predetermined pH values using sulfuric acid or sodium hydroxide.

The descaling effects of the examples and comparative examples are as shown in Table 2.

[Effect of the Invention] The scale removing composition of the present invention has the following advantages.

1) The composition of the present invention exhibits a descaling effect even near neutrality (pH 5.5 to 9.5).

2) High safety.

3) The cost of chemicals is lower than that of conventional organic acid type cleaning agents.

4) It has a sufficient descaling effect even at room temperature, and does not necessarily require a heating operation.

5) There is no need for pH treatment of waste liquid.

6) Since no pickling gas is generated, the environment is not polluted.

7) Neutral, no need for neutralization after descaling.

8) There is no danger of causing hydrogen embrittlement.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Sakanishi 1-1, Akunouracho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute (72) Inventor Munetaka Tsuro 9-1, Tanimachi, Chuo-ku, Osaka-shi, Osaka No. 18 Kyoeisha Yushi Kagaku Kogyo Co., Ltd. (72) Inventor Shigenori Fukuoka 9-1-18 Tanimachi, Chuo-ku, Osaka City, Osaka Prefecture Kyoeisha Yushi Kagaku Kogyo Co., Ltd. (56) References A) Japanese Patent Publication No. 53-22546 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) C23G 1/00-1/24

Claims (1)

(57) [Claims] (1) mixing at least one chelating agent with a relatively large amount of chloride ions and / or sulfate ions, and adjusting the pH value;
A scale dissolution / removal composition containing a metal oxide, which is adjusted to 5.5 to 9.5.