JPH0373359B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a deposit dissolving agent. In air conditioning equipment and factory process piping, corrosion occurs due to hardness components brought in from water and air and corrosion of the pipes, including inorganic scale mainly composed of calcium carbonate and iron oxide. The product precipitates and accumulates. Such deposits must be removed as much as possible since they significantly degrade operating efficiency. Conventionally, inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid have been frequently used to remove such deposits inside piping. However, these inorganic acids have an extremely low pH and are not only dangerous to handle, but also have the problem of being extremely corrosive to materials such as piping. On the other hand, organic acids such as oxalic acid and citric acid are also generally known as cleaning agents. Among these, oxalic acid has a strong dissolving power for iron oxide, so it is often used as an acid cleaning agent.However, especially when targeting calcium-based scale, the dissolving efficiency is not very sufficient and it is not practical. There was a problem above. Furthermore, when other organic acids are used alone, they do not have a sufficient dissolving effect on both inorganic scales, and cannot be said to be practical. This invention was completed as a result of intensive research to solve the problems of the prior art, and its purpose is to provide an extremely efficient deposit dissolving agent. That is, this invention provides HOOC-( _CH2 )n-
It is an inorganic deposit dissolving agent containing calcium carbonate or iron oxide containing two or more organic acids represented by COOH (n represents an integer from 0 to 4). Specific examples of the dibasic acid represented by the above structural formula include oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid. In this invention, it is essential to contain a plurality of these dibasic acids, but it is sufficient to contain two or more types, and it may be three or five types. The blending ratio is not particularly limited either, and as is clear from the Examples described later, even if a small amount of different components are added, the dissolution efficiency can be greatly improved due to the synergistic effect. In implementation, first, the organic acids to be used are mixed in appropriate proportions to form an aqueous solution. It is desirable for the concentration to be 0.01% or more, preferably 0.1% or more in terms of dissolution efficiency. The solubilizer thus obtained is then supplied to the target system and circulated using a pump or the like. The liquid temperature is usually about room temperature to 30°C, and the circulation time is about 0.5 to several hours. After completion of the dissolution, the entire amount of the solution is discharged and separately treated and disposed of as necessary. The solubilizing agent of the present invention may further contain other known cleaning agents, such as organic acids such as citric acid and malic acid, inorganic acids such as hydrochloric acid, and known corrosion inhibitors for pickling, if necessary. I can do it. Systems targeted by this invention include air conditioning equipment for buildings, apartments, factories, etc., factory process piping, cooling water systems, and the like. By blending two or more specific dibasic acids, a previously unknown synergistic effect can be obtained, and as a result, deposits attached to piping systems etc. can be efficiently dissolved and removed. Example 1 10g of iron rust collected from the building's water supply piping was placed in a beaker, an aqueous solution of organic acid (5W/V%) 1 was added at the mixing ratio listed in Table 1, and the mixture was stirred at room temperature for 3 hours. Made it react. After 3 hours, the beaker was left still and the iron ion concentration in the supernatant water was measured. The results are shown in Table 1. From Table 1, it can be seen that the amount dissolved is much greater when different types of organic acids are blended than when oxalic acid is used alone.

[Table] Example 2 10g of scale mainly composed of calcium carbonate attached to the cooling tower packing of an oil refinery was taken into a beaker and treated in the same manner as in Example 1 using the dissolving agent shown in Table 2. carried out. The results are shown in Table 2. From Table 2, it can be seen that the dissolving agent of the present invention is much more effective than the comparative example.

[Table] Example 3 A cleaning test was conducted on an air conditioning cooling water system (water capacity: 100) in a factory where scale had precipitated. The scale was analyzed and found to be calcium carbonate 60.
%, and 10% iron oxide. The solubilizer used was 10% adipic acid + 65% glutaric acid.
% + 25% succinic acid. 10 kg of this solubilizer was supplied to the cooling water system by pump circulation. The dissolution reaction was carried out at 25°C for 1 hour. After 1 hour, the dissolved solution was drained and analyzed, and 3.000 mg of calcium ions and 250 mg of iron ions were detected. When the cooling system was restarted after washing, electricity consumption was 10% lower than before washing. In addition, test pieces (mild steel, pure copper, aluminum brass, SUS) immersed in the cooling water system during cleaning.
The corrosion rate of each is less than 1 mg/cm ² /hr,
It was found that there were no corrosion problems at all. For comparison, another air conditioning cooling water system at the same factory was cleaned in the same manner as above using only 10 kg of glutaric acid, and the calcium hardness in the liquid was 100 mg/kg.
-It was only CaCO ₃ .

Claims (1)

[Claims] 1. An inorganic deposit dissolving agent containing calcium carbonate or iron oxide, characterized by containing two or more organic acids represented by HOOC-( _CH2 )n-COOH (n represents an integer from 0 to 4) .