KR101654700B1 - Water treatment composition containing diethyl hydroxylamine for power plant boiler system - Google Patents

Abstract

The present invention relates to a water treatment composition for a boiler for a power plant containing diethylhydroxylamine (DEHA) and hexamethylenetetramine as an active ingredient, and a method for removing dissolved oxygen using the same, It is effective not only to solve corrosion at the same time but also to prepare for environmental regulation in the future, and it is economical and easily available.

Description

[0001] The present invention relates to a water treatment composition for a power plant boiler system comprising diethylhydroxyamine,

The present invention relates to a composition capable of inhibiting oxygen corrosion and carbon dioxide corrosion in power plant boiler system water, which has a high dissolved oxygen removal rate and low toxicity, and a method for inhibiting oxygen corrosion and carbon dioxide corrosion using the same.

A boiler is a device that heats water to make necessary steam or hot water. There are various types of boilers depending on the purpose of use. Domestic power generation facilities are mostly using high-capacity, high-pressure boilers and water treatment for water quality control of water supply and boiler water. The purpose of water treatment is to increase the operation efficiency and extend the life span of power generation facilities.

Water treatment improves the quality of the system water and prevents the corrosion of system components. Each power plant adopts a water treatment method suitable for the characteristics and conditions of the power plant boiler.

Damage of the boiler tube due to corrosion of the boiler system is the biggest cause of the operation stoppage of the power generation facility, which causes a great economic loss such as the cost loss due to the operation stoppage and the maintenance cost. There are many factors such as the presence of corrosive ions and the presence of dissolved gas in the system water. However, it is known that the dissolved oxygen present in the boiler system water of the power plant has the greatest influence on the corrosion of the system material. have.

As a method to remove dissolved oxygen in the boiler system, it is necessary to remove the primary dissolved oxygen by deaerator which is a mechanical dissolved oxygen removing method and secondary chemical dissolution using deoxidizer to remove residual dissolved oxygen which is not removed by deaerator There is an oxygen removal method.

Currently, most domestic power generation boilers use hydrazine (N ₂ H ₄ ), which is also used as fuels for deoxidizing fuels, but hydrazine is toxic substance that has high human carcinogenicity and may affect respiratory, skin, .

Since the discovery that hydrazine is a pseudo-carcinogen, advanced countries require extreme caution when using hydrazine and have strict regulations on hydrazine emissions and storage. However, according to the Chemical Safety Agency, the amount of hydrazine hydrazine (hydrazine hydrate form) in Korea in 2013 is 1,992 kg per year, and the amount of waste water and waste including hydrazine is 16,954 kg and 56,794 kg per year, Regulation is expected to become strict.

The United States and other countries have developed alternate deoxidizing agents that can replace hydrazine for decades ago and have been applied to power boilers and industrial boilers.

Major alternative deoxygenators that are currently being developed and commercialized or being promoted for commercial use include Carbohydrazide, Hydroquinone, Diethyl hydroxylamine (DEHA), Methyloethyl ketoxime (MEKO), Ascorbic acid Acid).

The carbohydrazide in the alternative deoxygenating agent reacts with dissolved oxygen to produce water and carbon dioxide as shown in the following reaction formula. Carbohydrazide is known to have a higher dissolved oxygen removal rate than hydrazine up to 85 ° C. It hydrolyzes to 150 ° C to generate hydrazine and carbon dioxide, and decomposes to ammonia, nitrogen and hydrogen at temperatures above 200 ° C. Unlike hydrazine, however, carbohydrazide is not recognized as a carcinogen and is less toxic than hydrazine.

(H ₂ N-NH) ₂ CO + 2O ₂ → 2N ₂ + 3H ₂ O + CO ₂

Diethyl hydroxylamine reacts with dissolved oxygen to produce acetic acid and water as shown in the following reaction formula. DEHA is also not recognized as a carbal substance as carbohydrazide, and is less toxic than hydrazine.

4 (C ₂ H ₅ ) ₂ NOH + 9O ₂ → 8CH ₃ COOH + 2N ₂ + 6H ₂ O

Morpholine is a typical additive for compositions comprising deacidified materials as C ₄ H ₉ NO compounds as volatile amines.

On the other hand, the steam generated from the industrial boiler used for the process heat exchange and power generation is advantageous in saving energy and water consumption by being condensed after being used and then being recovered to the boiler water supply. Therefore, in the field where the boiler is located, the recovery rate of the condensate should be increased as much as possible.

However, in the heat exchanger and condensation line where the condensate is generated, the carbon dioxide generated due to pyrolysis of sodium carbonate and sodium borate contained in the boiler system water moves together with steam and is dissolved in the condensed water, thereby lowering the overall pH of the condensed water . Further, in the case of the above-mentioned carbohydrazide, carbon dioxide is generated as a by-product of the reaction. Therefore, a separate method for lowering it is needed.

Generally, it is advantageous to keep the pH of the boiler water between 11 and 11.8 in the case of boilers below 10kgf / ㎠ to prevent corrosion trouble. However, undesirable phenomenon may occur when the pH is lowered due to the inflow of carbon dioxide as described above. However, it has been reported that when the pH is more than 9, the metal has a negative effect.

Corrosion caused by this phenomenon is referred to as carbon dioxide corrosion, and if exposed to carbon dioxide corrosion for a long time, it will lead to a very lethal consequence to the material of the copper alloy as well as the steel material, and in some cases, the heat exchanger ruptures in severe cases. In addition, acetic acid is generated by the reaction of DEHA with oxygen, which lowers the pH and adversely affects the boiler system.

[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2012-21215 [Patent Document 2] Registered Patent Publication No. 10-0315496

[Non-Patent Document 1] Kwangwoo Park, "Dissolved Oxygen Control for Corrosion Prevention of Power Plant Boiler System", Suncheon University Graduate School of Industry Master's Thesis (August 2008). [Non-Patent Document 2] Essam Abdul Jalil Saeed and Najwa Sabir Majeed, "Use of hexamine to control properties of water condensate system of medical city hospitals", Baghdad: Foundation of technical education, Vol.21, P 120-131, 2008

The present invention provides a water treatment composition for a boiler of a power plant that solves carbon dioxide corrosion as well as corrosion by dissolved oxygen, and is low in toxicity in preparation for future environmental regulations.

The first aspect of the present invention provides a power plant boiler water treatment composition comprising diethylhydroxylamine (DEHA) and hexamethylenetetramine (hexamine) as an active ingredient.

The second aspect of the present invention provides a water treatment composition for power plants, which further comprises morpholine as an active ingredient.

A third aspect of the present invention is a method for producing a polyurethane foam, comprising: 0.1 to 10 parts by weight of diethylhydroxylamine (DEHA); 0.1 to 20 parts by weight of hexamethylenetetramine; 0.1 to 10 parts by weight of an additive including a scale inhibitor, a corrosion inhibitor, a pH adjuster, and a chelating agent; When 60 to 99.7 parts by weight of water is applied to a boiler of a power plant boiler, the diethylhydroxylamine (DEHA) is maintained at 0.05 to 600 ppm and the hexamethylenetetraamine is maintained at 0.2 to 15 ppm The present invention provides a corrosion inhibiting method for a boiler water treatment system of a power plant.

A fourth aspect of the present invention provides a method for inhibiting corrosion of a power plant boiler water treatment system, which further comprises morpholine.

Hereinafter, the present invention will be described in detail.

The present invention uses diethylhydroxylamine (DEHA) as an effective oxygen scavenger. DEHA has been used as a deoxidizer in boilers for over 20 years and has been used in many places due to its low toxicity. DEHA is used as a substitute for hydrazine because of its low toxicity, high volatility and low ammonia production in the case of pyrolysis, although it requires 40% more amount than hydrazine for the same deoxidation effect. DEHA removes dissolved oxygen through the following reaction.

4 (C ₂ H ₅ ) ₂ NOH + 9O ₂ → 8CH ₃ COOH + 2N ₂ + 6H ₂ O

Normally, DEHA maintains 300 ~ 500ppm in the input and 80 ~ 120ppm in the boiler system.

Typically, amine-based materials are used to increase corrosion and carbon dioxide corrosion by dissolved oxygen and lowered pH. In addition, corrosion inhibitors such as chromates, nitrites, molybdates, polymeric phosphates, phosphates, organic phosphates, zinc salts, trifluorothenoyl acetone, benzethonium chloride and 2-mercaptothiazole are used.

As a further additive, an anti-scale agent such as phosphoric acid, polyacrylic acid, polymaleic acid, ethylenediaminetetraacetic acid, acrylate-based polymer, diethylenetriaminepentamethylenephosphonic acid and the like, or an antioxidant such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium tertiary phosphate PH adjustment systems such as sodium monophosphate, potassium monophosphate, potassium dibasic potassium phosphate, potassium dihydrogenphosphate, sodium hexametaphosphate, sodium tripolyphosphate, and potassium sorbate may be used.

Hexamethylenetetramine (Hexamethylenetetramine) is a compound having a lattice structure as shown below and easily dissolves in water. Hexamethylenetetraamine is also known as hexamine, and it can be taken in the body if it is a small amount, and it is a urine antiinflammatory agent, which is not toxic enough to be used for the manufacture of medicines, and is cheap and easy to purchase.

Amines such as diethylhydroxylamine, cyclohexylamine, and dimethylaminopropylamine, which are amine compounds used in deoxidizers in the past, differ greatly in the types of hexamethylenetetramines and amines, which are quaternary amines as primary or secondary amines Not only the blade, but also hexamethylenetetramine, has a melting point far lower than 280 ° C and flip point of 250 ° C. As a result, it has a much higher volatility and has a disadvantage of requiring continuous replenishment as a deoxidizer.

Carbon dioxide dissolved in water is in the form of carbonate, which is involved in corrosion. Amine-based materials increase the pH while suppressing the corrosion of carbonate through the following reaction. In addition, the pH can be increased through a similar mechanism in acetic acid generated during deoxygenation of DEHA.

R - NH ₂ + H ₂ O -> R - NH ₃ ⁺ + OH ^-

R - NH ₃ ⁺ + OH ^- + H ₂ CO _{3 -} > R - NH ₃ ⁺ + HCO ₃ ^- + H ₂ O

In non-patent document 2, only corrosion inhibition by carbon dioxide in condensed water was studied using hexamethylenetetramine, and hexamethylenetetramine was found to be effective against this. Further, it is described that hexamethylenetetramine should be added after deaerating because of its sublimation properties. However, the above-mentioned research articles do not mention the deoxidizing agent at all and do not suggest a combination or the like, nor describe the embodiment.

In the present invention, DEHA having a low toxicity acts as a deoxidizing agent. On the other hand, attention is paid to the fact that acetic acid is produced, and hexamethylenetetraamine added with hexamethylenetetraamine, which is capable of removing acetic acid, (EN) Disclosed is a composition for water treatment of a boiler of a power plant comprising ethylhydroxylamine (DEHA) and hexamethylenetetramine as an active ingredient, and a method for inhibiting corrosion of a boiler water treatment system using the same.

The composition and method according to the present invention solve both acetic acid and carbon dioxide corrosion as well as dissolved oxygen, and have low toxicity in preparation for future environmental regulations. Also, the materials used are economical and readily available.

FIG. 1 shows the result of measuring the concentration of dissolved oxygen with time.
FIG. 2 shows the result of measuring pH over time.
Fig. 3 shows the result of measuring the conductivity with time.

Hereinafter, the present invention will be described in more detail with reference to examples. However, these examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples.

[ Example ]

Examples: Dissolved Oxygen, pH, Conductivity Measurements

To measure the dissolved oxygen concentration, pH, and conductivity with the addition of deoxidizing agent, iSTEK Multi Meter K7000-PDC was used. The specifications of the devices used are shown in the table below.

Metrics K7000-PDC (3 Channel) DO range 0.00 to 19.99 mg / l Resolution 0.001 / 0.01 / 0.1 accuracy ± 0.5 mg / l pH
range -2,000 ~ 19.999 Resolution 0.001 / 0.01 / 0.1 accuracy ± 0.002 pH Buffer automatic recognition 2/4/7/10/12 conductivity range 0.0 to 199,999 ss / cm Resolution 0.01 / 0.1 accuracy ± 0.5%

The distilled water used in the apparatus was a distilled water producing apparatus using reverse osmosis pressure, and the chemical used in the analysis had the following purity.

Analytical sample Sales company phase water Carbohydrazide sigma-ardrich powder 98% N, N-Diethylhydroxylamine sigma-ardrich Liquid phase ≥ 98% Hydrazine monohydrate JUNSEI Liquid phase ≥ 98% Hydroquinone JUNSEI powder ≥99% Morpholine JUNSEI Liquid phase ≥99% Hexamethylenetetramine KANTO CHEMICAL powder ≥99% Tannic Acid Duksan Pharmaceutical powder 100%

To measure dissolved oxygen, pH and conductivity, distilled water was added to a composition such as the following deoxidizer to make a total of 100 ml of solution. The temperature was maintained at room temperature (22 ° C) and normal pressure.

Composition Composition content One Diethylhydroxylamine +
Distilled water 1g
5g
10g
2 Diethylhydroxylamine + Hexamethylenetetramine +
Distilled water 0.5 g
0.5 g
2.5 g
2.5 g
5g
5g
3 Diethylhydroxylamine +
Morpholine +
Distilled water 0.5 g
0.5 g
2.5 g
2.5 g
5g
5g

Measurement result: Dissolved oxygen concentration measurement

(A), (b) and (c) of FIGS. 1, 2 and 3 are the results of measuring the dissolved oxygen concentration, pH and conductivity of each of the compositions 1 to 3, respectively. The concentration of dissolved oxygen decreased with time in all analytical compositions, and the rate of decrease of dissolved oxygen was also higher as the amount of deoxidizer was higher. The addition of hexamine to DEHA showed no significant change in dissolved acidity, suggesting that there is no problem in applying hexamine to DEHA deoxygenating agent. The amine type morpholine is a stronger base than hexamine and has a higher reactivity, so that the equilibrium dissolved pH, concentration, pH, and conductivity reach a shorter time. However, since morpholine has a lower flashpoint and spontaneous ignition temperature than hexamine, care must be taken to apply it to high-temperature power plant boilers. Other studies have indicated that base solutions with a pH of greater than 9 may adversely affect metals and that compositions containing morpholine have a pH greater than 10, It seems appropriate.

As described above, the concentration of dissolved oxygen was not significantly changed by the hexamine which can remove acetic acid which may occur during deacidification of DEAH, and there was no problem in use. Addition of morpholine shortened the reaction time It can be said that there is an effect that can be made.

Claims (4)

delete delete 0.1 to 10 parts by weight of diethylhydroxylamine (DEHA); 0.1 to 20 parts by weight of hexamethylenetetramine; 0.1 to 10 parts by weight of an additive including a scale inhibitor, a corrosion inhibitor, a pH adjuster, and a chelating agent; When 60 to 99.7 parts by weight of water is applied to a boiler of a power plant boiler, the diethylhydroxylamine (DEHA) is maintained at 80 to 120 ppm and the hexamethylenetetraamine is maintained at 0.2 to 15 ppm Wherein the corrosion inhibiting method is applied to a boiler water treatment system of a power plant.
The method of claim 3,
A method for inhibiting corrosion of a boiler water treatment plant of a power plant, which further comprises morpholine.

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