JP2000000576A - Method for preventing adhesion of slime - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the lowering of a heat exchange rate by preventing the adhesion of slime to the wall of water facilities using open type circulating cooling water, especially, to a heat exchanger by continuously supplying a slime separating agent and a sterilizing/bacteriostatic agent to the open type circulating cooling water at the same time. SOLUTION: As a slime separating agent, a compsn. containing hydrazine and a carboxylic acid type polymer with a wt. average mol.wt. of 30,000 or less is especially used. As a sterilizing/bacteriostatic agent, zinc ions or silver ions not becoming a reducing catalyst with respect to the slime separating agent, that is, not accelerating the oxidative decomposition of hydrazine are especially used. The slime separating agent and the sterilizing/bacteriostatic agent are continuously added to cooling water at the same time and the concns. of both agents are kept almost constant. By this constitution, it is prevented that microorganisms living in water adhere to the wall of an aq. equipment to propagate and form slime. Especially, the lowering of a heat exchange rate, water flow inferiority and the acceleration of corrosion in a heat exchanger are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing slime from adhering to an open-type circulating cooling water system, and a slime adhesion inhibitor used in the method.

[0002]

2. Description of the Related Art In an open-type circulating cooling water system, microorganisms living in water adhere to and proliferate on the walls of water-based facilities and form slime, thereby causing various obstacles. Various obstacles include a decrease in the heat exchange rate of the heat exchanger, poor running water, and promotion of corrosion at the slime attachment portion.

[0003] In order to prevent slime damage, conventionally,
Disinfecting and bacteriostatic agents such as chlorine-based inorganic compounds, chlorine-based organic compounds, and surfactants are used. By using hydrazine or a salt thereof and hydrogen peroxide as the slime remover, the formed slime is peeled off from the wall.

[0004] Slime prevention treatment with a bactericidal / bacteriostatic agent
It is generally used because the method of intermittent batch injection is economical. However, in the open-circulation cooling water system, circulating cooling water is used to suppress scale disturbances such as calcium carbonate and calcium sulfate due to accumulation of calcium hardness and corrosion inhibition due to concentration of dissolved salts such as chloride ions and sulfate ions. Partially or intermittently blow out of the system. Since the concentration of the disinfectant / bacteriostatic agent in the cooling water after the batch injection decreases over time,
There is a period during which the bacteriostatic effect weakens. Therefore, microorganisms may grow and slime may be gradually formed.

[0005] The formed slime can be removed and removed with a slime remover. However, when the slime gradually accumulates in the heat exchanger, the tendency that the heat exchange rate decreases with time is inevitable as compared with when the slime is clean. Agents that prevent slime damage by being continuously supplied into cooling water include sodium hypochlorite and hydrazine. However, when the concentration of microorganisms in the water supplied to the system is high or the concentration of nutrients is high, it is necessary to use a drug at a high concentration. Since sodium hypochlorite is highly corrosive, its use at a high concentration causes corrosion damage. Hydrazine has a lower sterilizing and antibacterial activity than other drugs, and using a large amount of hydrazine is not practical because the cost is too high.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an aqueous system using open-circulating cooling water, and more particularly, to a method for preventing slime from adhering to a heat exchanger without generating slime and reducing the heat exchange rate for a long period of time. An object of the present invention is to provide a slime adhesion inhibitor to be used.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to simultaneously and continuously supply a slime remover and a disinfectant / bacteriostatic agent to open-type circulating cooling water to prevent slime from adhering to walls of water-based equipment. And a slime release agent and a bacteriostatic / bacteriostatic agent are contained in the same liquid, whereby the above-mentioned problems can be solved.

[0008] The slime release agent (hereinafter referred to as "release agent") used in the present invention is not particularly limited as long as it has a release effect on slime. Examples include hydrazine, carboxylic acid polymers, hydrogen peroxide, sodium hypochlorite, chlorinated isocyanuric acid, chlorine dioxide, glutaraldehyde, and the like. As the slime release agent, those containing hydrazine and a carboxylic acid polymer having a weight average molecular weight of 30,000 or less are particularly preferred. Hydrazine may be a salt or a hydrate. Examples of the carboxylic acid-based polymer include a polymer having acrylic acid, maleic acid, or methacrylic acid as a monomer, or a copolymer of two or more of these, and a salt thereof.
0 to 15000.

The bactericidal / bacteriostatic agent used in the present invention is not particularly limited as long as it has a slime preventing action or a bactericidal / bacteriostatic action on cooling water. Preferably, zinc ions or silver ions which do not act as a reduction catalyst for hydrazine when mixed with a release agent, ie, do not promote oxidative decomposition of hydrazine, are preferred. These ions can be obtained as aqueous solutions of the respective salts. Examples of zinc salts include zinc chloride, zinc sulfate, and zinc nitrate, and examples of silver salts include silver nitrate.

In the present invention, the stripping agent and the bacteriostatic / bacteriostatic agent are simultaneously and continuously supplied to the cooling water, whereby the concentrations of both agents in the cooling water are maintained substantially constant. At that time, these two agents may be used as a mixture or a single agent. The concentration of the stripping agent in the cooling water, for example, hydrazine is usually selected from 0.1 to 50 mg / L, and the concentration of the bactericidal / bacteriostatic agent, for example, zinc ion is
Usually, it is selected from 0.1 to 20 mg / L, and the silver ion is usually selected from 0.01 to 5.0 mg / L. When a carboxylic acid-based polymer and hydrazine are used in combination as the release agent, the hydrazine concentration is in the same range as described above, and the carboxylic acid-based polymer concentration range is usually
It is selected from 1.0 to 100 mg / L.

The present invention relates to a slime adhesion inhibitor containing the above-mentioned stripping agent and a bacteriostatic / bacteriostatic agent in the same liquid, and can be suitably used in the present invention. The mixing ratio is advantageously set to a mixing ratio proportional to each concentration in the cooling water, so that it can be used after being diluted to a desired concentration at the time of use.

[0012]

Hereinafter, specific examples of the present invention will be described.
The present invention is not limited to this. Example 1 General bacteria count 10^FourCFU / mL of drug-free cooling water
After dispensing 200 mL each, and adding various chemicals,
Shake continuously. Daily bacterial count is 10 ^ThreeCFU
The number of days of bacteriostasis was examined with a target of / mL or less. Table 1
The result is shown.

[0013]

[Table 1]

The bacteriostatic days when hydrazine alone is added at 2.5 mg / L and when silver alone is added at 0.1 mg / L are 0.5 days and 2 days, respectively. .5 days. In contrast, hydrazine was used for 2.
When 5 mg / L and 0.1 mg / L of silver were added, it was 5 days, which was doubled. In addition, zinc alone
The number of bacteriostatic days when mg / L was added was one day, which was 1.5 days in total when adding 0.5 mg / L of hydrazine for 0.5 day, whereas hydrazine and zinc were added. When 2.5 mg / L was added at a time, the bacteriostatic days were 3 days, which was also doubled.

Example 2 A slime adhesion prevention test was conducted using a small cooling tower. Sodegaura City water was used as make-up water, and the concentration multiple of circulating cooling water was doubled. Cooling water was continuously passed through the test tube (SUS-304) to measure the amount of slime adhering to the wall surface. The prevention rate was calculated. The test was performed under each condition for two weeks.

In the test, a release agent having the following formulation and silver were used in a ratio of 1: 1.
A slime anti-adhesive agent which was a mixture containing 3.3 to 1: 800 at a ratio, a release agent and zinc at a ratio of 1: 0.8 to 1:40 was used. Release agent) 60% by weight Hydrazine hydrated 65% by weight Sodium polyacrylate (weight average molecular weight 6,000) 10% by weight Water 25% by weight Total 100% by weight Table 2 shows the slime adhesion prevention ratio under the conditions in which a release agent and zinc are used in combination.

[0017]

[Table 2]

[0018]

[Table 3]

Under the condition that 10 mg / L is held by the release agent alone, the adhesion prevention ratio is 42%, and the silver alone is 0.1 m / L.
It was 30% under the condition of keeping g / L. When these were summed up to 72%, the release agent and silver were each 1%.
Under the conditions of 0 mg / L and 0.1 mg / L, the adhesion prevention rate was 91%, showing a synergistic effect. Further, under the condition that 10 mg / L is held by the release agent alone,
Anti-adhesion rate is 42%, zinc alone 2.5mg / L
It was 24% under the conditions kept. The sum of these was 66%, but the release agent and zinc were each 10 m
Under the conditions of holding each of g / L and 2.5 mg / L, the anti-adhesion ratio was 90%, which also showed a synergistic effect.

In the cooling water, a release agent of 4.0 mg / L or more and a concentration of silver or zinc of 0.05 mg / L, respectively.
By holding 1.0 mg / L or more, slime adhesion could be effectively prevented.

[0021]

The synergistic effect of using a stripping agent and a disinfectant / bacteriostatic agent as a mixture, which makes the heat exchanger longer compared to the method using a stripping agent or a disinfectant / bacteriostatic agent alone. It can be kept clean for a period. Furthermore, the process can be performed at a lower cost than the method of using the continuous supply of the release agent alone without causing any trouble such as corrosion in the open circulation cooling water system.

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Claims (4)

[Claims] 1. A method for preventing slime from adhering, comprising simultaneously and continuously supplying a slime remover and a bacteriostatic / bacteriostatic agent to the open-type circulating cooling water to prevent slime from adhering to the walls of the water-based equipment. Method. 2. A slime adhesion inhibitor comprising a slime release agent and a bacteriostatic / bacteriostatic agent contained in the same liquid. 3. The slime adhesion inhibitor according to claim 2, wherein the slime release agent contains hydrazine and a carboxylic acid polymer having a weight average molecular weight of 30,000 or less. 4. The slime adhesion inhibitor according to claim 2, wherein the bactericidal / bacteriostatic agent contains a zinc ion or a silver ion which does not act as a reduction catalyst for the slime remover.