Anticorrosive for boiler

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...

AI Technical Summary

Benefits of technology

[0011]The present invention enables provision of an anti-corrosive which can more effectively maintain the pH of boiler water and which can prevent corrosion of a boiler tank and 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, the anti-corrosive being generally for use in a boiler operated with a superheater or a steam turbine, such a boiler to which treated water is fed, etc.MODES FOR CARRYING OUT THE INVENTION

[0012]The modes of the boiler anti-corrosive of the present invention are (i) anti-corrosive I containing 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), and (ii) anti-corrosive II which further contains an oxygen scavenger.[Anti-Corrosive I]

[0013]The boiler anti-corrosive I of the present invention contains the aforementioned amine compound represented by formula (1). The amine compound is a low-volatility amine which has high thermal stability and high dissociation degree. Thus, the amine remains in boiler water rather than moving to the vapor phase, whereby the pH of boiler water can be effectively maintained.

[0014]Therefore, the amine compound itself can serve as an anti-corrosive and may also be used in combination with another volatile amine, such as an amine having a volatility higher than that of the aforementioned amine compound. In the latter case, the amount of amine transferred to the vapor generated in the boiler can be controlled, along with the pH of feed water and concentrated water, to thereby prevent corrosion of the entire boiler system.

[0015]The amine compound is preferably 2-(2-aminoethoxy)ethanol, in which each of m and n in formula (1) is 2,3-(3-aminopropoxy)ethanol, in which m is 3 and n is 2, or 3-(3-aminopropoxy)propanol, in which each of m and n is 3, from the viewpoint of anti-corrosion performance. Among them, 2-(2-aminoethoxy)ethanol is more preferred.

[0016]The anti-corrosive I may consist of the amine compound as a sole ingredient, or may be a combined agent further containing water, another solvent, and an optional ingredient. When the combined agent is used, these ingredients may be individually and separately supplied to a boiler, followed by mixing. Alternatively, the ingredients may be combined to provide a pre-mix type agent, which is added to a boiler.[Anti-Corrosive II]

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.