JP2649107B2 - In-can treatment composition for boilers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates mainly to a treatment agent for water supplied to a steam boiler, and particularly to a strong anticorrosion coating on a metal surface inside a can placed in a high temperature environment. It relates to a composition that can be formed.

[0002]

2. Description of the Related Art There are two types of boiler water treatment agents, one used as a cleansing agent and the other used as a deoxidizer. Of these, the cleaning agent prevents the hardness and iron oxide that enter the can from being scaled inside the can, and adjusts the pH value to an appropriate range to suppress corrosion of the can. have. On the other hand, the oxygen scavenger achieves the anticorrosion function by removing dissolved oxygen in the can water. These two treatment agents are appropriately used in combination depending on the properties of water to be applied. In addition to the treatment agent, a multi-purpose boiler in-can treatment agent composed of a composite of a cleaning agent and a deoxidizer specifically adjusted to withstand a high-temperature environment for a high-pressure steam boiler is also known. is there.

[0003] According to the prior art, when adjusting the treatment agent, especially the treatment agent in the can for a multipurpose boiler, it is required to finely mix various kinds of agents, resulting in high costs.

In particular, when hydrazine is used as a deoxygenating agent, it is necessary to add a catalyst for promoting the reaction of hydrazine at a low water temperature. Bad), forcing even more practical problems.

[0005] In addition, it is known that hydrazine-based oxygen scavengers have disadvantages such as deterioration due to reaction with oxygen in the air during storage and volatilization during long-term storage.

[0006]

In general, not only the above-mentioned cleaning agent or oxygen scavenger but also the in-can treatment agent for a multipurpose boiler contains various types of components, and the various components are synergistically required. While achieving the desired objectives (scale suppression as well as deoxygenation), these known components lead to the aforementioned cost disadvantages and handling difficulties. Such a problem can be solved by itself if a sufficient and strong anticorrosion coating can be formed on the wall of the can or the wall of the water tube inside the can.

[0007]

Therefore, based on the above point of view, the inventors of the present invention have made many attempts to form a dense anticorrosion film of chelate on the surface of an iron-based metal material constituting a can body. As a result of the trials and experiments, the composition comprising at least one component selected from organic polybasic acids having two or more carboxyl groups or salts thereof, an alkali metal hydroxide and hydrated hydrazine is obtained. It has been found that it is suitable as an in-can treatment agent for boilers, especially for steam boilers placed in high-temperature environments.

The organic polybasic acids in the present invention include those having two carboxyl groups, such as succinic acid, malic acid, fumaric acid, and tartaric acid, and those having three or more carboxyl groups, such as citric acid and isocitric acid. Is mentioned.

The metal ions forming the salt include:
In addition to alkali metal ions such as Na ⁺ , K ⁺ , and Li ⁺ ,
^Examples thereof include alkaline earth metal ions such as a ²⁺ and Mg ^{2+. From the} viewpoint of high solubility or prevention of scaling, the use of the latter alkali metal provides more preferable results.

[0010] The treatment agent in the can according to the present invention comprises:
Any form of a solution such as an aqueous solution or a powder can be used.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described. Tables 1 and 2 show preferred embodiments of the present invention, and Tables 3 to 5 show conventional examples as comparative examples.

[0012]

[0013]

[0014]

[0015]

[0016]

In the case of the treatment agent in a can according to the present invention, the mechanism of corrosion prevention is as follows: iron ions and organic polybasic acids or their ions precipitate and form a thin film by adsorption on the metal surface; It is presumed that the acid or its ions form a dense thin film of the chelate on the metal surface, and that the reduction action of hydrazine forms a dense magnetite layer on the surface of the can body, and the removal of hydrazine. It is presumed to be due to the synergistic effect of the removal of dissolved oxygen by the oxygen function.

In particular, in the present invention, the alkali metal hydroxide promotes the deoxygenation and reduction of hydrazine by adjusting the pH of the still water, and the anti-corrosive property of the organic polybasic acid itself makes it possible to reduce the temperature at low temperatures. It compensates for the lack of anti-corrosion performance of hydrazine and exhibits anti-corrosion properties over a wide temperature range as a whole.

The above tendency can be understood from FIG. 1 showing the relationship between the water temperature and the number of pits generated on the metal surface. FIG. 1 shows the treating agents of the components shown in Table 1 (Example 1) and the treating agents of the conventional components shown in Tables 3 and 4 (Conventional Examples 1 and 2).
According to this, it was found that the use of the treating agent of the present invention significantly reduced the number of pits generated on the metal surface of the inner wall of the water pipe, regardless of the temperature of the water. I understand.

According to FIG. 2, another effect obtained by the treatment agent of the present invention, that is, scaling of a scale component (hardness, iron oxide, etc.) brought in from the outside of the can body (scaling to a can wall or the like) The effect of inhibiting the adhesion and growth of components is shown. FIG. 2 shows the thickness of the scale generated on the metal surface as the boiler combustion (operation) time increases, and FIG. 2 shows the effect of the treatment agent of the present invention to reduce the scale. Conventional treatment agents (Table 5
It is understood that the components are more remarkable than Comparative Example 3), and that the amount of generated scale is remarkably superior to the case where no chemical is added.

Furthermore, in the present invention, a trace amount of heavy metals (functioning as a catalyst for hydrazine) in the treating agent is blocked by the chelating action of an organic polybasic acid having two or more carboxyl groups such as citric acid. The hydrazine is excellent in stability during storage of the treating agent.

Further, since the organic polybasic acid prevents sludge formation corresponding to the hardness flowing into the can and disperses it, the scale can be discharged when the can water is blown, thereby effectively preventing scale formation. Will do.

[0023]

As described above, the in-can treatment composition for boilers of the present invention forms a stronger anticorrosion film on the metal surface inside the can body and exhibits a desired anticorrosion function. It is. Further, complicated operations such as the conventional complicated preparation of the medicine and the management of the dissolved oxygen concentration are not required, and it is only necessary to set a predetermined amount at first and maintain the amount thereafter.
Furthermore, there is no need to add expensive quinone-based catalysts and scale inhibitors such as phosphoric acid and polycarboxylic acid, which were conventionally required as treatment agents in cans. Can be greatly reduced.
Further, unlike the prior art, the treatment agent in the can for a multipurpose boiler, which is required for application to a high-pressure steam boiler, becomes unnecessary, which is extremely advantageous in handling and cost. In addition, hydrazine applied as a deoxygenating agent in the treating agent of the present invention is prevented from being deteriorated by the action of another component, that is, an organic polybasic acid, so that costs and labor required for storage can be reduced. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a relationship between water temperature and the number of pits generated on a metal surface.

FIG. 2 is an explanatory diagram showing a relationship between a boiler combustion (operation) time and a scale thickness generated inside a can body.

Claims (2)

(57) [Claims] (1) When operating a boiler, it is added to boiler can water and used.
A composition for use, main component and one or more components selected from the organic polybasic acid or salt thereof having two or more carboxyl groups, and an alkali metal hydroxide, and hydrazine hydrate
In- can treatment composition for boilers. 2. The organic polybasic acid is succinic acid, apple
Acid, fumaric acid, tartaric acid, citric acid, isocitric acid
The in-can treatment agent composition for a boiler according to claim 1.