JP2002146563A - Deoxidizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deoxidizer by which dissolved oxygen in water, particularly, in boiler feed water can efficiently be removed, and which has high safety. SOLUTION: This deoxidizer contains one or more kinds selected from the groups consisting of 1,3-dimethyl-5-pyrazolone, urazole 6-azauracil, 3-methyl-5- pyrazolone and 3-methyl-5-pyrazoline-5-one 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, and more particularly to a deoxidizer capable of efficiently removing dissolved oxygen in water, and particularly effective for preventing corrosion of a boiler system by removing dissolved oxygen in boiler feed water. Related to various oxygen absorbers.

[0002]

2. Description of the Related Art Dissolved oxygen contained in boiler feedwater is:
This constitutes a cause of corrosion of the boiler main body, a heat exchanger, an economizer, a steam condensing pipe, etc. disposed in a stage preceding the boiler main body. 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] Therefore, chemical treatment and physical treatment have been conventionally performed as deoxygenation treatment. For example, as a chemical treatment, a method of adding hydrazine (N ₂ H ₄ ) and sodium sulfite (Na ₂ SO ₃ ) to a boiler feedwater as a deoxidizer has been widely adopted.

[0004]

However, in the above-mentioned chemical treatment, the method using hydrazine or sodium sulfite as an oxygen scavenger has the following problems.
First, hydrazine is regarded as a problem in terms of safety for the human body. Further, in the case of sodium sulfite, the following problem occurs because the reaction rate with oxygen is too high.

That is, prior to the addition to the boiler feed water,
When dissolving sodium sulfite in water in the dissolution tank,
The sodium sulfite reacts with the dissolved oxygen to cause a decrease in the concentration thereof, resulting in an insufficient injection amount, which ultimately promotes the corrosion of the boiler system. Furthermore, since sulfuric acid ions are newly generated in the boiler feedwater treated with sodium sulfite, corrosion and scale adhesion are likely to occur in the boiler system.

Therefore, the method using hydrazine or sodium sulfite as the oxygen scavenger is not necessarily industrially advantageous. The present invention solves the above-mentioned problems in conventional oxygen absorbers used when performing deoxidation of boiler feedwater by chemical treatment, for example, and can efficiently remove dissolved oxygen in boiler feedwater, and can provide high safety. The purpose of the present invention is to provide a new oxygen scavenger having a property.

[0007]

In order to achieve the above-mentioned object, in the present invention, 1,3-dimethyl-5-pyrazolone, urazole, 6-azauracil, 3-methyl-5-pyrazolone, and 3-methyl-5-pyrazolone are used. An oxygen scavenger characterized by containing, as an active ingredient, one or more members selected from the group consisting of methyl-5-pyrazolin-5-one.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The oxygen scavenger of the present invention has N-
It contains the following heterocyclic compound having an N bond as an active ingredient. That is,

[0009]

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[0010] These heterocyclic compounds may be used alone or in combination of two or more. Further, the oxygen scavenger of the present invention includes a heterocyclic compound having an N-substituted amino group (hereinafter, referred to as a heterocyclic compound A);

[0011]

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(Wherein a and b are each an integer of 0 to 5 and an integer satisfying a relationship of 2 ≦ a + b ≦ 5) (hereinafter referred to as a heterocyclic compound). Formula B), the following formula:

[0013]

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(Wherein R ₁ , R ₂ , R ₃ , and R ₄ may be the same or different and each represents hydrogen or a lower alkyl group or an aryl group having 1 to 8 carbon atoms) ,
X represents any of hydrogen, an amino group, an alkylamino group or a dialkylamino group having 1 to 8 carbon atoms, or a lower alkyl group or an aryl group having 1 to 8 carbon atoms)
(Hereinafter, referred to as heterocyclic compound C), and azodicarbonamide (NH ₂ CON
= NCONH ₂ ) or 2 selected from the group consisting of
It may be used in combination with a deoxidizer containing at least one compound as an active ingredient.

In this case, the following heterocyclic compound is preferable as the heterocyclic compound A. That is,

[0016]

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The following are preferred examples of the heterocyclic compound B.

[0018]

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The following are preferred examples of the heterocyclic compound C.

[0020]

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The amount of each of the active ingredients listed above is not particularly limited since it is appropriately determined according to the amount of dissolved oxygen in the target water. 0.001 to 1000 mg, preferably 1 to 30
Desirably, it is 0 mg.

[0022]

EXAMPLES Examples 1 to 10 The effects of the oxygen scavenger of the present invention were confirmed as follows. Softened water saturated with oxygen in the air at room temperature was supplied to a 5-liter steam generation test autoclave and operated under the following conditions to generate steam.

Temperature: 185 ° C., pressure: 1 MPa, evaporation amount:
12 liters / hr, blow rate: 10% The generated steam was completely condensed, and the concentration of dissolved oxygen in the obtained condensed water was measured using a dissolved oxygen meter. This value is used as data of Comparative Example 1. Next, a deoxidizer was added to the feed water to generate steam under the same conditions, and the concentration of dissolved oxygen in the condensed water of the steam was measured. Then, the difference from the data of Comparative Example 1 was calculated as the removal amount, and the removal amount was compared with that of Comparative Example 1.
Was calculated as the removal rate (%).

As for the addition of the oxygen scavenger to the feed water, the heterocyclic compound shown in Table 1 was dissolved in the softened water to prepare an aqueous solution having a predetermined concentration, and the aqueous solution was added to the feed water by a constant volume pump. The concentration of the heterocyclic compound in the feed and feed water was adjusted as shown in Table 1. Table 1 shows the above results.

[0025]

[Table 1]

[0026]

As is apparent from the above description, the oxygen scavenger of the present invention can efficiently remove dissolved oxygen in water. In particular, when used as a deoxidizer for boiler feed water, corrosion of the boiler body and steam condensing system piping due to dissolved oxygen can be prevented, and its industrial value is extremely large.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F22D 11/00 F22D 11/00 B

Claims (1)

[Claims] 1. A member selected from the group consisting of 1,3-dimethyl-5-pyrazolone, urazole, 6-azauracil, 3-methyl-5-pyrazolone, and 3-methyl-5-pyrazolin-5-one, or An oxygen scavenger comprising two or more active ingredients.