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Anticorrosive for boiler

a technology for anticorrosion and boilers, applied in the direction of corrosion diminishing boiler components, specific water treatment objectives, other chemical processes, etc., can solve the problems of phosphate salt hiding phenomenon or alkali corrosion, increasing the amount of organic substances unintentionally transferred to the boiler tank, and reducing the ph of the boiler water. achieve the effect of effective maintenance of the ph prevent the corrosion of the boiler tank, and high thermal stability

Inactive Publication Date: 2013-06-06
KURITA WATER INDUSTRIES LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides an anti-corrosive for boilers that can maintain the pH of boiler water and prevent corrosion of the boiler tank and entire boiler system without adding a large amount of phosphate salt or elevating the Na / PO4 mole ratio to 3 or higher. The anti-corrosive contains a low-volatility amine compound, which remains in boiler water and prevents the pH of boiler water from dropping. The amine compound can be used alone or in combination with another volatile amine to control the pH of feed water and concentrate water, which prevents corrosion of the entire boiler system. The anti-corrosive can be a single ingredient or a combined agent containing water, another solvent, and an optional ingredient.

Problems solved by technology

In recent years, however, the amounts of organic substances unintentionally transferred to a boiler tank have increased due to use of various water sources and impaired water quality.
Under such circumstances, the pH of boiler water often lowers problematically.
In the above case, a phosphate salt hide-out phenomenon or alkali corrosion may problematically occur.
The hide-out phenomenon adversely affects a boiler member, and an example thereof is impairment of thermal conduction.
However, these compounds cannot fully elevate the pH of boiler water.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples

[0032]The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

[0033]In the Examples, compound (A) was 2-(2-aminoethoxy)ethanol represented by the following formula (A), and compound (B) was 3-(3-aminopropoxy)propanol represented by the following formula (B).

NH2—(CH2)2—O—(CH2)2—OH  (A)

NH2—(CH2)3—O—(CH2)3OH  (B)

experiment 1

[0034]A corrosion test was carried out through employment of a test boiler which was operated under the following conditions: a pressure of 4 MPa, a blow rate of 1%, a condensate recovery of 20%, pure water (ion-exchange water) feed, and use of a heater-degasser [outlet degassing capacity (dissolved oxygen level: DO) of 0.03 mg / L]. In the corrosion test, to feed water, sodium phosphate having an Na / PO4 mole ratio of 2.7 was added in an amount of 0.1 mg / L as phosphate ion, and monoisopropanolamine (MIPA) was added in an amount of 1.5 mg / L. As a result, the pH of boiler water was 10.0.

[0035]When a microamount of organic matter originating from feed water is thermally decomposed in boiler water, an organic acid is conceivably formed. Thus, 0.06 mg / L of acetic acid was added to feed water as the organic acid. In this case, the pH (25° C.) of boiler water was lowered to 9.2, lower than 9.4, which the lower limit of JIS standard value under such a pressure (Comparative Example 1). Then, M...

experiment 2

[0037]To a test boiler, pure water (ion-exchange water) having a dissolved oxygen concentration of 0.010 mg / L after degassing was fed. The boiler was operated at a pressure of 11 MPa and a blow rate of 1%, without recovering condensate. In the Comparative Examples, the boiler was operated while each of monoethanolamine (MEA), MIPA, MDEA, and 3-methoxypropylamine (MOPA) was added in an amount of 1.5 mg / L. When the pH of boiler water was stabilized, measurement was performed (Comparative Examples 3 to 6). In the Examples, the boiler was operated while the compound (A) or (B) was added in an amount of 1.5 mg / L. When the pH of boiler water was stabilized, measurement was performed (Examples 2 and 3). Table 2 shows the results.

[0038]As is clear from Table 2, in Examples 2 and 3, in which compounds (A) and (B) were added, a higher pH elevating effect was attained, as compared with Comparative Examples 3 to 6.

TABLE 2Comp.Comp.Comp.Comp.Ex. 3Ex. 4Ex. 5Ex. 6Ex. 2Ex. 3AddedMEAMIPAMDEAMOPAComp...

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Abstract

The boiler anti-corrosive of the present invention contains an amine compound represented by formula (1):NH2—(CH2)m—O—(CH2)n—OH  (1)(wherein each of m and n is an integer of 1 to 3), or contains an oxygen scavenger and the amine compound represented by formula (1).The anti-corrosive is generally used in a boiler operated with a superheater or a steam turbine, or in such a boiler to which treated water is fed, and can more effectively maintain the pH of boiler water and can prevent corrosion not only of the boiler tank but also in the entire boiler system including a feed-condensate system, without adding a large amount of phosphate salt or elevating the Na / PO4 mole ratio to 3 or higher.

Description

TECHNICAL FIELD[0001]The present invention relates to an anti-corrosive for a boiler (hereinafter may be referred to as a “boiler anti-corrosive”) and, more particularly, to a boiler anti-corrosive suitably used in a boiler operated with a superheater and a steam turbine.BACKGROUND ART[0002]Boilers have a structure for heating boiler water to generate vapor, and an anti-corrosive is applied to such boilers for preventing corrosion of metal members of the boilers. Particularly, in boilers for power generation, garbage incineration, etc., operated with a superheater or a steam turbine, ion-exchange water or desalinated water is generally used as a supplementary feed. Such boilers are generally operated at a concentration factor of about 30 to about 100, which is one of the water quality control factors. In such boilers, a phosphate salt, instead of a caustic alkali substance, is added so as to adjust the pH of boiler water for corrosion prevention, and a neutralizable amine or ammonia...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C09K15/20
CPCC23F11/08C23F11/141F22B37/025C09K5/048C09K15/20C02F5/12C23F11/142C23F11/149C02F2303/08C02F1/70C23F11/10C23F11/14F22B37/52
Inventor MORI, SHINTAROUSHIMURA, YUKIMASA
Owner KURITA WATER INDUSTRIES LTD
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