JPH1119510A - Disoxidant for boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disoxidation agent for a boiler in which corrosion of the whole boiler system can be prevented by exerting enough disoxidation force at less additional concentration. SOLUTION: The disoxidation agent for a boiler contains (A) at least one kind selected from a group consisting of aliphatic dicarboxylic acid and its salt shown in a formula M<1> OOC-(CH2 )n -COOM<2> (M<1> and M<2> in formula denote hydrogen atom, sodium atom, potassium atom or ammonium atom and these may be mutually same or different and (n) is an integer of 1-10) and (B) at least one kind selected from groups consisting of sulfurous acid, metabisulfurous acid and its salt and (c) neutral amine as effective components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deoxidizer for a boiler, and more particularly, to a boiler system capable of efficiently removing dissolved oxygen in water. The present invention relates to a deoxidizer for boilers that can effectively prevent corrosion.

[0002]

2. Description of the Related Art In general, dissolved oxygen contained in water supplied to a boiler is not only supplied to a boiler main body but also to a heat exchanger, an economizer, a steam condensing system pipe, etc. disposed upstream of the boiler main body. May cause corrosion. Therefore, in order to prevent the corrosion of these boiler systems, it is necessary to remove the dissolved oxygen in the boiler feed water by performing a deoxygenation treatment on the boiler feed water used.

[0003] Conventionally, chemical treatment and physical treatment have been carried out as such a deoxygenation treatment. Examples of the chemical treatment include hydrazine (N ₂ H ₄ ) and sodium sulfite (Na). A method of adding ₂ SO ₃ ) as a deoxidizer to boiler feedwater has been widely adopted.

[0004] However, hydrazine is suspected to be involved in carcinogenesis of the human body, and its handling has been regarded as a problem. On the other hand, sodium sulfite has no problem in safety to the human body, but its reaction rate with oxygen is too fast.Before adding sodium sulfite to water in the dissolution tank, Sodium reacts with dissolved oxygen to cause a decrease in its concentration, resulting in insufficient injection, which eventually leads to a problem that the corrosion of the boiler system is rather promoted. Further, since sulfuric acid ions are newly generated in the boiler feed water treated with sodium sulfite, there is a problem that corrosion and scale adhesion easily occur in the boiler system.

Therefore, as a substitute for such a drug,
At least one selected from the group consisting of aliphatic dicarboxylic acids and salts thereof represented by the following general formula, and sulfurous acid;
An oxygen scavenger comprising at least one selected from the group consisting of metabisulfite and salts thereof as an active ingredient has been proposed (JP-A-6-240476).

[0006]

Embedded image M ¹ OOC— (CH ₂ ) _n —COOM ² (wherein M ¹ and M ² are a hydrogen atom, a sodium atom,
A potassium atom or an ammonium group, which may be the same or different, and n is an integer of 1 to 10; )

[0007]

However, by adding the above-mentioned oxygen scavenger to the boiler feed water, it reacts with dissolved oxygen to exhibit excellent oxygen scavenging ability and contributes to prevention of corrosion of the boiler system. However, there is a problem that the amount required for exhibiting an effective effect is relatively large.

[0008] In view of such circumstances, an object of the present invention is to provide a deoxidizer for boilers which can exhibit sufficient deoxygenating power with a lower addition concentration and can prevent corrosion of the entire boiler system. .

[0009]

The present invention for solving the above-mentioned problems comprises: (A) at least one selected from the group consisting of aliphatic dicarboxylic acids represented by the following general formula and salts thereof;

[0010]

Embedded image M ¹ OOC— (CH ₂ ) _n —COOM ² (wherein M ¹ and M ² are a hydrogen atom, a sodium atom,
A potassium atom or an ammonium group, which may be the same or different, and n is an integer of 1 to 10; An oxygen absorber for a boiler, comprising (B) at least one selected from the group consisting of sulfurous acid, metabisulfite and salts thereof, and (C) a neutralizing amine as active ingredients. It is in.

The aliphatic dicarboxylic acid and its salt represented by the above general formula used in the present invention exhibit an excellent deoxygenation effect due to its catalytic action due to the presence of sulfurous acid, metabisulfite and their salts. However, the presence of the neutralizing amine further enhances the deoxidizing power of dicarboxylic acid by its catalytic action. Therefore, when the oxygen scavenger of the present invention is used, a sufficient oxygen scavenging effect can be obtained with a lower addition concentration. Further, since the neutralizing amine moves to the steam condensate system and raises the condensate pH, the neutralizing amine has an effect of further improving the anticorrosion effect in the steam condensate system.

The aliphatic dicarboxylic acid used in the present invention is a dicarboxylic acid having n = 1 to 10, for example, malonic acid (n = 1), succinic acid (n = 2), glutamic acid (n = 3), Adipic acid (n = 4), pimelic acid (n =
5), suberic acid (n = 6), sebacic acid (n = 8),
Decanedicarboxylic acid (n = 10) and the like can be mentioned, and those having n in the range of 1 to 6 are particularly preferable. Examples of the salts of these aliphatic dicarboxylic acids include sodium salts, potassium salts and ammonium salts, and these may be mono-salts or di-salts. Further, these aliphatic carboxylic acids and salts thereof may be used alone, or two or more of them may be used as an appropriate mixture.

In the present invention, sulfurous acid, metabisulfite and salts thereof are used. These may be used alone or in combination of two or more. The salt of sulfurous acid or metabisulfite is not particularly limited as long as it has high water solubility, and for example, a sodium salt, a potassium salt, an ammonium salt and the like are preferably used.

Examples of the neutralizing amine used in the present invention include 2-amine-2-methyl-1-propanol, cyclohexylamine, monoethanolamine, diethylethanolamine, morpholine, monoisopropanolamine and mixtures thereof. Preferred examples include, but are not limited to, these.

The oxygen scavenger of the present invention is prepared by mixing the above-mentioned agent (A), the agent (B), and the agent (C). Component 10 of the drug
Usually, 1 to 1 part by weight of the drug component (A) is added to 0 parts by weight.
000 parts by weight, preferably 3 to 1,000 parts by weight,
It is preferable that the drug component (C) is used in an amount of 0.1 to 10,000 parts by weight, preferably 1 to 500 parts by weight.
If the ratio is outside these ranges, the synergistic effect of the three will not be remarkably exhibited.

The amount of the oxygen absorber used in the present invention is appropriately determined according to the concentration of dissolved oxygen in the target boiler feed water and other water quality conditions. 0.001 to 1000 mg, preferably 0.01 to 300 mg, more preferably 0.02 to 10 mg
The ratio may be set to be 0 mg.

The oxygen scavenger of the present invention comprises the above-mentioned agent (A), the agent (B) and the agent (C) as essential components. In addition, hydrazine, sodium sulfite, and gluconic acid Such known oxygen scavengers or corrosion inhibitors, as well as known dispersants, chelating agents, scale inhibitors, or mixtures thereof may be blended.

The oxygen scavenger of the present invention can be used in all low-pressure, medium-pressure or high-pressure boiler systems, and its use is not limited by boiler pressure, boiler type, water supply type and the like.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.

(Corrosion test method) A 5 liter experimental electric boiler was supplied with Atsugi-shi water softened water saturated with oxygen in the air at 40 ° C, and the boiler was operated under the following conditions to generate steam. Raised. Thereafter, the generated steam was completely condensed, and the concentration of dissolved oxygen in the obtained condensed water was measured using a dissolved oxygen meter.

Further, the condensed water is heated to 50 ° C. and passed through a test piece camula, and a test piece (50 × 15 × 1 m) made of carbon steel (SS400) is previously introduced into the camula.
m) was arranged, the corrosion amount of these test pieces for 96 hours was measured, and the corrosion rate was calculated from the results.

Test conditions Pressure: 1.0 MPa Steam generation amount: 4 liter / h Blow rate: 10%

(Examples 1 to 3) In this example, succinic acid, potassium metabisulfite and 2-amino-2-methyl-1-propanol (AMP) are shown in Table 1 below as oxygen scavengers. The concentration of dissolved oxygen in the condensed water and the corrosion rate of carbon steel were measured.

Comparative Example 1 In this comparative example, the same measurement as in the example was performed without adding any chemical to the water supply.

Comparative Examples 2 to 6 In each of Comparative Examples, succinic acid and potassium metabisulfite were used as oxygen scavengers in Table 1 below.
And the same measurement as in the example was performed.

In Comparative Examples 2 to 4, succinic acid and potassium metabisulfite were added at the same concentrations as in Examples 1 to 3 except that AMP was not added. , The amount of the added drug was increased.

(Test Results) The above results are shown in Table 1, and FIG. 1 shows a comparison of the dissolved oxygen concentration in the steam condensed water of each of the examples and comparative examples. FIG. 2 shows a steam of each of the examples and comparative examples. 3 shows a comparison of corrosion rates of carbon steel in condensed water.

As shown in Table 1 and FIG. 1, the chemicals of the examples of the present invention were significantly condensed in vapor by adding 2-amino-2-methyl-1-propanol to the chemicals of the comparative example. It was found to reduce the dissolved oxygen concentration in water. In addition, the drug of the present invention exhibited a high effect even at a low concentration. For example, in Example 1, the effect was at least three times that of Comparative Example 2. Further, in Example 3 in which the concentration was increased, almost all of the dissolved oxygen in the steam condensate used in the test could be decomposed, and the effect of Comparative Example 6 using succinic acid about 1.7 times was obtained. .

Further, as shown in Table 1 and FIG. 2, it was found that the chemicals of each example of the present invention can significantly suppress the corrosion rate of carbon steel in steam condensed water as compared with the chemicals of the comparative example. For example, in Example 1, approximately six times the effect of Comparative Example 2 was obtained, and a better result was obtained than in Comparative Example 6 in which succinic acid was used in an amount of 5 times, and a high effect was obtained even at a low concentration. Was confirmed.

From the above test results, the oxygen scavenger according to the present invention can be obtained by adding 2-amino-2-methyl-1-propanol, which is a neutralizing amine, to succinic acid and potassium metabisulfite. It has been clarified that the oxygen scavenging power can be greatly improved, and a high effect can be obtained even with a low-concentration oxygen scavenger.

[0031]

[Table 1]

[0032]

As is apparent from the above description, the oxygen scavenger for boilers of the present invention exerts sufficient oxygen scavenging power at a lower addition concentration, and further improves the anticorrosion effect of steam condensate water piping. Thus, there is an effect that the entire boiler system can be efficiently protected from corrosion.

[Brief description of the drawings]

FIG. 1 is a graph showing the concentration of dissolved oxygen in steam condensed water.

FIG. 2 is a graph showing a corrosion rate of carbon steel in steam condensed water.

Claims (1)

[Claims] (A) at least one selected from the group consisting of an aliphatic dicarboxylic acid represented by the following general formula and a salt thereof, and M ¹ OOC- (CH ₂ ) _n -COOM ² (Wherein M ¹ and M ² are a hydrogen atom, a sodium atom,
A potassium atom or an ammonium group, which may be the same or different, and n is an integer of 1 to 10; An oxygen absorber for a boiler, comprising (B) at least one selected from the group consisting of sulfurous acid, metabisulfite and salts thereof, and (C) a neutralizing amine as active ingredients.