JP2631421B2 - Can water treatment agent composition for boiler - 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 boiler, and forms a strong anticorrosion film on a metal surface, particularly in a can body placed in a high-temperature environment. Compositions that can be used.

[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 above treating agents, a multipurpose boiler treating agent comprising a composite of a cleaning agent and an oxygen scavenger specially adjusted to withstand a high temperature environment for a high-pressure steam boiler is also known.

[0003] According to the prior art, when adjusting the treatment agent, it is required to finely mix various agents, resulting in high costs. In addition, when a deoxidizer is applied, the amount of supply corresponding to the dissolved oxygen concentration of the supply water must be determined, and the measurement is a very complicated operation. The dissolved oxygen concentration in water greatly varies depending on the external environment such as temperature.This is because when the oxygen absorber is added, the residual amount of deoxidized components in the can is checked together with the external environmental conditions to determine the total amount of oxygen. This means that a difficult operation of adjusting is required.

[0004] As a simple method for eliminating the complicated and difficult operations as described above, attempts have been made to set the amount of the oxygen absorber to be supplied at a time when the dissolved oxygen concentration is highest throughout the year. However, in this case, when the dissolved oxygen concentration is low, the drug becomes excessive and the cost increases. In addition, in the case of a sulfurous acid type oxygen scavenger, excess chemicals increase the electrical conductivity of the can water, increasing not only the chance of blow processing (the processing of discharging concentrated water generated in the can), but also the carryover. Cause. Similar problems can occur with hydrazine-based oxygen scavengers. Further, it is also known that conventional oxygen scavengers have disadvantages such as deterioration due to reaction with oxygen in the air during storage and deterioration due to long-term storage.

In addition, when the above-mentioned multipurpose boiler treating agent is used for a steam boiler or the like, the M alkalinity of the can water and the blow amount (the discharge amount of concentrated water generated in the can) are taken into consideration. It is necessary to determine the input amount. In this case, in order to avoid a more complicated operation, conventionally, there are provided various kinds of medicines that can be selected according to the place of use. Another problem with using this kind of drugs is that they are mainly hydrazine,
The steam delivered from the boiler contains a compound that is not preferable for the human body or a processed product (food, etc.), and causes a problem in terms of safety.

[0006]

Generally, the cleaning agent or the oxygen scavenger contains various types of components, and the desired purpose (scale suppression function and deoxygenation function) is achieved by synergistic action of each component. ), But these known components lead to cost disadvantages and handling difficulties as described above. 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 inventor has made many attempts to form a dense anticorrosive coating of a chelate on the surface of an iron-based metal material constituting a can body. As a result of a trial and an experiment, a composition containing at least one component selected from an organic polybasic acid having two or more carboxyl groups or a salt thereof, a reducing saccharide and an alkali metal hydroxide was obtained. The present invention has been found to be suitable as a can water treatment agent for steam boilers which are 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 water treatment agent of the present invention is
Any form of a solution such as an aqueous solution or a powder can be used.

[0011]

The present invention will be described in detail with reference to the following Examples. Table 1 shows an example of the use of an organic polybasic acid having two carboxyl groups.

[0012]

In the case of the water treatment agent according to the present invention, the mechanism of anticorrosion is as follows: iron ions and organic polybasic acids or their ions are precipitated to form a thin film by adsorption on the metal surface; It is presumed that the acid or its ion is in a state of forming a dense chelate thin film on the metal surface.

In particular, in the present invention, by containing a reducing saccharide, when heated in the presence of an alkali,
The film forming action and the deoxidizing action are promoted, and the anticorrosive effect is enhanced together with the organic polybasic acid. At this time, another additional component, an alkali metal hydroxide, helps the reducing saccharide to exhibit deoxidizing properties, and at the same time suppresses oxidation (pitting) of the metal surface in combination with an organic polybasic acid. Causes the action of As a result, a stronger and more heat-resistant coating can be obtained on the metal surface. Therefore, the anticorrosion film to be formed inside the can body can be actually realized by maintaining an organic polybasic acid or a salt thereof at a certain concentration (amount) or more in the can water. It does not depend on the concentration. This tendency can be understood from FIG. 1 showing the relationship between the dissolved oxygen concentration and the number of generated pits on the metal surface.

According to FIG. 1, the use of the treating agent of the present invention shows a large change in the state of occurrence of the number of pits on the metal surface of the inner wall of a water pipe, etc., even if the dissolved oxygen concentration in the can water becomes high. It turns out that there is no.

FIG. 2 shows a comparison between the citric acid component alone and the one obtained by adding an alkali metal hydroxide (sodium hydroxide) to the citric acid component, showing the effect when the latter component is added. It is.

Further, according to FIG. 3, another effect obtained by the treatment agent of the present invention, that is, scaling of scale components (hardness, iron oxide, etc.) brought in from the outside of the can body (scaling to the can wall etc.) The effect of inhibiting the adhesion and growth of components is shown. FIG. 3 shows the thickness of the scale generated on the metal surface as the boiler combustion (operation) time increases, and FIG. 3 shows the effect of the treatment agent of the present invention to reduce the scale. It is understood that the treatment is remarkable as compared with the conventional sulfurous acid-based treatment agent, and that the amount of scale generation is remarkably superior to the case where no chemical is added.

[0018]

As described above, the boiler boiler water treatment composition of the present invention forms a stronger and more heat-resistant anticorrosive coating on the metal surface inside the can body, and dissolves the dissolved oxygen in the boiler. The desired anticorrosive function is exhibited with little influence from the rust. 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 incorporate a scale inhibitor such as phosphoric acid or polycarboxylic acid, which was conventionally required as a treatment agent in a can, and the number of components in the entire treatment agent can be reduced, thereby greatly reducing product cost. . Furthermore, the conventional multipurpose boiler treating agent required for application to a high-pressure steam boiler is not required, which is extremely advantageous in handling and cost. Moreover, the treating agent of the present invention has a significantly lower electric conductivity than a sulfurous acid-based agent, so that the number of times of the blow treatment (concentrated water discharge treatment) is reduced, and the carryover is reduced. Not only does it contribute to the suppression of generation, but in the case where sodium hydroxide is selected as the alkali metal hydroxide, all components have safety as a food additive. In addition, since the organic polybasic acid is chemically stable even in powder or aqueous solution, there is no need to worry about deterioration such as in sulfites and hydrazines as oxygen scavengers, and the cost required for storage can be reduced. Can also.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a difference in effect between a citric acid component alone and a solution obtained by adding sodium hydroxide to the citric acid component.

FIG. 3 is an explanatory diagram showing a relationship between a boiler combustion (operation) time and a thickness of a scale generated inside a can body.

Continuation of the front page (56) References JP-A-1-212781 (JP, A) JP-A-55-89478 (JP, A) JP-A-59-92097 (JP, A) JP-A-51-59447 (JP, A) JP-A-55-106589 (JP, A) JP-B-49-18338 (JP, B1)

Claims (2)

(57) [Claims] 1. A tannic acid comprising as a main component at least one component selected from an organic polybasic acid having two or more carboxyl groups or a salt thereof , a reducing saccharide, and an alkali metal hydroxide.
A boiler can water treatment composition containing no acid or a salt thereof. 2. The organic polybasic acid is succinic acid, apple
Acid, fumaric acid, tartaric acid, citric acid, isocitric acid
The boiler can water treatment composition according to claim 1, which is
Stuff.