JPS5931396B2 - Dissolved oxygen removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing dissolved oxygen in water. Indicates an alkyl group with a prime number of 3 or less.

) using one or more selected from the hydroxylamines or salts thereof, and one selected from trihydric phenols and their derivatives, naphthoquinones and their derivatives, or anthraquinones and their derivatives as an activator. Or it relates to a method of removing dissolved oxygen in water using two or more types.

Removal of dissolved oxygen in water is carried out in many industrial fields, particularly for the purpose of corrosion protection of iron and steel that come into contact with water.

In addition, air oxidation is carried out for the purposes of stabilizing aqueous solutions containing oxidative substances and substances, and preventing oxidation of chemical reaction systems.

It is well known that aqueous solutions containing dissolved oxygen easily oxidize iron and steel, causing accidents due to corrosion.

Removal of dissolved oxygen in water for the purpose of preventing corrosion of iron and steel is carried out by boiler-related methods, such as boiler water supply, boiler canned water, full storage of idle boilers, soda boiling in cans, alkaline washing, and neutralization treatment. This method is also used in small closed cooling water systems.

Hydrazine and sodium sulfite have conventionally been mainly used as oxygen scavengers to remove dissolved oxygen from water.

Hydroxylamine, diethylhydroxylamine, etc. have also been proposed.

Hydrazine has a sufficient deoxidizing effect at high temperatures of 300°C or higher, such as in high-pressure boilers, but at temperatures below 200°C,
For example, in medium- and low-pressure boilers, soda boiling in cans, alkaline washing and neutralization treatment in cans at room temperature, storage of idle boilers with water, closed cooling water, etc., the reaction rate with dissolved oxygen is extremely slow and sufficient desorption is not possible. Oxygen effect cannot be obtained.

For this purpose, a large number of substances have been proposed as activators for hydrazine, but the activation effect may be insufficient, or even if the activation effect is good, it may cause secondary corrosion of iron and steel. There are drawbacks and no fully satisfactory activator has been found so far.

Sodium sulfite has a good reaction rate with dissolved oxygen and a good deoxidizing effect, but since the reaction product becomes sodium sulfate,
Depending on the type of water used, there is a risk of scale formation within the equipment.

In particular, it causes scale formation in boiler feed water, etc., and has disadvantages such as solid residue.

Furthermore, hydroxylamine or diethylhydroxylamine has drawbacks such as a slow reaction rate with dissolved oxygen, particularly at low temperatures of 100° C. or lower, and a sufficient deoxidizing effect cannot be obtained.

For this purpose, a method of adding copper ions as an activator has been proposed, but the added copper ions cause an ion substitution reaction with iron or steel and adhere to the inside of the equipment, resulting in secondary corrosion of the equipment. It has drawbacks such as causing a problem, and is not practical.

As a result of intensive studies to solve the drawbacks of conventional methods for removing dissolved oxygen using oxygen scavengers, the inventors of the present invention were able to quickly and efficiently remove dissolved oxygen even at room temperature, and in addition, remove residue and scale. The present invention has been completed which has a remarkable effect that there is no generation and there is no risk of secondary corrosion.

That is, the present invention uses one or more selected from hydroxylamines or salts thereof as an oxygen scavenger, and trihydric phenols and their derivatives, naphthoquinones and their derivatives, and anthraquinones and their derivatives as the activator. The present invention provides a method for removing dissolved oxygen in water using one or more selected from the following.

General formula ゛＼, -8□ used as an oxygen scavenger in the present invention
.

picture,. 02.2゜, yomoe 3□eme. Examples of the hydroxylamines represented by R2/3 or less (representing an alkyl group) include hydrosylamine, N-methylhydroxylamine, N,N-dimethylhydroxylamine, N-methyl, N-ethylhydroxylamine,
Examples include N-ethylhydroxylamine, N,N-diethylhydroxylamine, N,N-dipropylhydroxylamine, and the like.

Examples of hydroxylamine salts include sulfates, nitrates, hydrochlorides, phosphates, sulfaminates, acetates,
These include oxalate, maleate, fumarate, sulfosalicylate, salicylate, and chloroacetate.

Examples of trihydric phenols and derivatives thereof used as activators in the present invention include pyrogallol, gallic acid,
Tannic acid, phloroglucin, fluzlogalin, pyrogallol 1-methyl ether, pyrogallol 2-methyl ether, chloroglyside, dihydropyrogallol,
Examples of pyrogallol carbonate include 4-(3,4,5-trioxyphenyl)1,2-dioxynaphthalene and 5-nitropyrogallol.

Examples of naphthoquinones and derivatives thereof include 1,
4-naphthoquinone, 1,2-naphthoquinone, ■, 2-naphthoquinone-4-sodium sulfonate, ■, 4-naphthohydroquinone, 1,2-naphthohydroquinone, 2,6-naphthoquinone, 3-chlor・1,2-naphthoquinone , naphthopurpurin, 5.8-dihydro・1,4-naphthoquinone, 5°6, 7.8-tetrahydro, ■, 4-naphthoquinone, 3,4-dihydroxy・1,4-naphthoquinone, 4-amino・1 , 2-naphthoquinone, 2-amino 1
, 4-naphthoquinone, 4-benzyl 1゜2-naphthoquinone, 2-methyl 1,4-naphthoquinone, 2-methyl 1,4-naphthoquinone 3-sodium sulfonate, 2,
3-dimethyl 1,4-naphthoquinone, 2,7-dimethyl 1,4-naphthoquinone, 2-chloro 1,4-naphthoquinone, 2,3-dichloro 1,4-naphthoquinone,
3-methyl/1,2-naphthoquinone, 4-methyl/1°2-naphthoquinone, 5-methyl/1,2-naphthoquinone, 3,6-dimethyl/1,2-naphthoquinone, 3,4.
8-trimethyl・1,2-naphthoquinone, 4-chlor・
1,2-naphthoquinone, 2-hydroxy 1,4-naphthoquinone, nigerone, 3-amino 2-hydroxy 1
, 4-naphthoquinone, 2,3-dioxy/1,4-naphthoquinone, 5,8-dihydroxy/1,4-naphthoquinone, 1,4,5,8-naphthoquinone, and the like.

Examples of anthraquinones and their derivatives include anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, anthraquinone β-carboxylic acid, anthraquinone/sodium 1-sulfonate, anthraquinone/
Sodium 2-sulfonate, sodium anthraquinone/1,8-disulfonate, sodium anthraquinone/2,6-disulfonate, 1-amino/4-hydroxyanthraquinone,
1゜4-dihydroxyanthraquinone, 1,5-dihydroxyanthraquinone, quinizarin, anthragallol, anthragallol, purpurin, 2-aminoanthraquinone, 1,2-diaminoanthraquinone, 1,4-diaminoanthraquinone, 1゜5-diamino Examples include anthraquinone, 2,6-diaminoanthraquinone, leucoquinizarin, alizarin/sodium 5-sulfonate, 2-chloroanthraquinone, 1,4-dihydroxy/5,8-dichloroanthraquinone, and the like.

Although the activating agent of the present invention has an activating effect at any pH, its effect is particularly strong at neutral to alkaline pH.

Although the effect of the activator of the present invention can be recognized in any amount, it is preferable to
00TII! /l, and usually 0.1 to 10 /l is sufficient.

The amount of hydroxylamine added is preferably 0.0001 to 20% by weight.

The activator can be added as it is or as a solution, but it is also possible to mix the precursor with the oxygen scavenger in the necessary proportion and then add this.

The theoretically required amount of hydroxylamine or its salt as an oxygen scavenger varies depending on the amount of dissolved oxygen.

For example, in the case of the reaction of N,N-diethylhydroxylamine at room temperature, the reaction ratio of both is expressed as a weight ratio of oxygen/N,
0.4 in N-diethylhydroxylamine and can react with even more oxygen at high temperatures.

Generally speaking, the amount of the oxygen scavenger added is about 0.1 to 1000 ml per water to be treated.

The processing temperature is not particularly limited either, but the function can be sufficiently exerted at a low temperature of usually 100°C or lower, for example, usually about 70°C.

As described above, the dissolved oxygen removal method according to the present invention can quickly and efficiently remove dissolved oxygen even at low temperatures, and there is no generation of residue or scale, and there is no risk of secondary corrosion.

Therefore, it can be used not only as a deoxidizing method at high temperatures such as high pressure boilers, but also for medium and low pressure boilers, soda boiling in cans, alkali washing and neutralization treatment in cans, storage of idle boilers with water, closed cooling water, air oxidation. It is also a sufficiently effective method for removing dissolved oxygen at low temperatures in stabilizing aqueous solutions and preventing oxidation in chemical reaction systems.

For detailed explanation of the present invention, hydroxylamine and N,
The oxygen scavenging effect of N-diethylhydroxylamine alone is cited as a reference example.

Next, Examples will be given to explain the present invention more specifically, but the present invention is not limited thereto.

Reference example Disodium hydrogen phosphate 300% as a pH buffer in pure water
After dissolving 7119/l, the pH was adjusted to a predetermined value using caustic soda or phosphoric acid.

Attach this solution to a pH electrode and a dissolved oxygen electrode.
00ml! The mixture was placed in a glass container and stirred well at a specified temperature to dissolve the oxygen in the air, then sealed with a rubber stopper so that no air phase remained and was stirred with a magnetic stirrer before measuring dissolved oxygen. .

Next, the injection needle of the microsyringe was inserted from above the rubber stopper to prevent air from entering, and a predetermined amount of hydroxylamine was injected.

The amount of residual oxygen was measured at predetermined intervals after injection.

Note that N,N-diethylhydroxylamine is injected directly as industrial aquarium crystal, and hydroxylamine salt is hydroxylamine 150, which has been adjusted to the same pH as the aqueous solution to be added.
Injected as a 1A aqueous solution.

Dissolved oxygen measurement at Yellow Springs In
A dissolved oxygen meter model 54 manufactured by Strument Co., Inc. was used.

The results are shown in Table I.

Example 1 Disodium hydrogen phosphate 300111 fl/l in pure water,
After dissolving a predetermined amount of activator, adjust the pH to a predetermined value in the same manner as in the reference example, and then measure dissolved oxygen, inject an oxygen scavenger, and measure dissolved oxygen at predetermined time intervals after injection in the same manner as in the reference example. Ta.

In addition, for those using hydroxylamine salts as oxygen scavengers, the purity level is 15, which is adjusted to the same pH as the aqueous solution to which it is added.
Injected as an aqueous solution at 0 f /l.

The results are shown in Table H. Example 2 Pure water was supplied and degassed using a heating deaerator, the dissolved oxygen concentration at the deaerator outlet was 0.5 ppm, and the evaporation temperature was 197'C (15
Ky/cA), the concentration of N, N in the aqueous solution of feed water containing diethylhydroxylamine and 1,2-naphthoquinone mixed and dissolved in the deaerator outlet water supply line of a boiler operated under conditions of evaporation rate of 12 t/hr. -diethylhydroxylamine 2.0 ppm11, 2-nafdoquinone 0. l
Continuously inject boiler water to a pH of 10 ppm;
It was operated continuously for 90 days while maintaining the temperature between 5 and 11.0.

Part of the steam generated here was cooled to form condensed water, and dissolved oxygen in this water was continuously measured using an electrode-type dissolved oxygen meter, but no dissolved oxygen could be detected.

Before conducting this test, the inside of the boiler was cleaned with acid to completely remove internal scale, and after 90 days of continuous operation, the inside of the boiler was inspected, but the internal conditions did not change compared to before the test. No corrosion or scale formation was observed.

Claims (1)

[Scope of Claims] 1. One or two kinds of oxygen scavengers selected from hydroxylamines represented by the general formula (wherein R0 and R2 are hydrogen or an alkyl group having 3 or less carbon atoms) or salts thereof. In addition, one or more selected from trihydric phenols and derivatives thereof, naphthoquinones and derivatives thereof, and anthraquinones and derivatives thereof are used as an activator, and oxygen-dissolved water is not treated. Characteristic dissolved oxygen removal method.