JPH10277560A - Method for preventing attaching of slime to seawater cooling water system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain improved attaching prevention effects using a small quantity of hydrogen peroxide by adding quaternary ammonium salt to a seawater cooling water system beforehand at a sterilization concentration of aerobic bacteria and then adding hydrogen peroxide agents so that the concentration of hydrogen peroxide of the cooling water system becomes a specific value. SOLUTION: For preventing slime due to microorganisms from attaching to the interior of a piping of a seawater cooling water system, quaternary ammonium salt is added to the cooling water system beforehand at a sterilization concentration of aerobic bacteria and a hydrogen peroxide agent is then added so that the concentration of hydrogen peroxide in the cooling system becomes 0.01-0.5 mg/L. That is, when quaternary ammonium salt and hydrogen peroxide agent are added, in the case that, for example, seawater is used in an one-through manner in the seawater cooling water system, quaternary ammonium salt of predetermined concentration is added on the upstream side of the system beforehand, following which a hydrogen peroxide agent is added so that the concentration thereof on the downstream side of the system, in which the quaternary ammonium salt is dispersed, becomes a predetermined concentration.

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 which is an obstacle in a seawater cooling water system. More specifically, the present invention remarkably suppresses adhesion of slime mainly derived from microorganisms, which causes heat conduction inhibition in piping of a seawater cooling water system using seawater as cooling water, particularly in a metal thin tube of a heat exchanger. On how to prevent.

[0002]

2. Description of the Related Art In recent years, slimes of various types of industrial water have been frequently caused due to microbial contamination, causing various harmful effects. For example, in various plants such as petrochemical plants and chemical plants, and thermal and nuclear power plants, heat exchangers, condensers,
A large amount of industrial water is required for cooling a drainage system and the like. In addition to industrial tap water, seawater, lake water, river water, and groundwater are mainly used. Microorganisms in these industrial waters are adsorbed on the walls and pipes of the water supply equipment, secrete a large amount of adhesive substances, and form a slime layer. Further, microorganisms propagate in the slime layer to form a microorganism coating. These slime layers and microbial coatings cause adverse effects such as lowering the heat exchange rate during cooling and blocking the strainer with the exfoliated slime.

[0003] With respect to the adverse effects of these slimes, a method of preventing slime adhesion by adding hydrogen peroxide has been proposed.
It is heavily used. This method is environmentally preferable because hydrogen peroxide is decomposed into oxygen gas and water. However, in a seawater cooling water system that uses seawater in a transient manner, the amount of hydrogen peroxide to be added naturally increases with the increase in the amount of seawater to be used. It is rare. On the other hand, the emergence of bacteria that are considered to be resistant to hydrogen peroxide has caused cases in which the intended effect cannot be exhibited even if a larger amount of hydrogen peroxide is added.

[0004] Japanese Patent Publication No. 51-16703 discloses a method for disinfecting water and water, which comprises simultaneously adding a quaternary ammonium salt (n-alkyl-dimethylbenzylammonium chloride) and hydrogen peroxide, and for eliminating algae. Proposed.

[0005]

Therefore, the present invention provides
It is an object of the present invention to provide a more economical method for preventing slime adhesion, which uses hydrogen peroxide that does not adversely affect the environment and exhibits an effective slime adhesion prevention effect even if the amount of hydrogen peroxide is further reduced. And

[0006]

Thus, according to the present invention, a quaternary ammonium salt is added to a seawater cooling water system in advance at a sterilizing concentration of aerobic fungi, and then the hydrogen peroxide concentration of the cooling water system is reduced to 0.01%. A method for preventing slime from adhering to a seawater cooling water system is provided, wherein a hydrogen peroxide agent is added so as to be 0.5 mg / liter to prevent slime from adhering to the cooling water system.

Here, "adding a quaternary ammonium salt in advance and then adding a hydrogen peroxide agent" means that seawater cooling water is treated in advance with a quaternary ammonium salt, and the treated seawater cooling water is then peroxided. It means adding a hydrogenating agent. For example, in the case of a seawater cooling water system in which seawater is used in a transient manner, a quaternary ammonium salt having a predetermined concentration is added in advance on the upstream side of the cooling water system, and the added quaternary ammonium salt is added to the flow or physical flow of the aqueous system. The hydrogen peroxide agent may be added to a predetermined concentration on the downstream side dispersed by various means.

According to the study of the present inventors, the effects intended in the present invention cannot be obtained when the two kinds of agents are added simultaneously or when the hydrogen peroxide agent is added first, and the above-mentioned effects are not obtained. Such processing is essential. And, in the method of the present invention, by adding a hydrogen peroxide agent to seawater cooling water treated with a quaternary ammonium salt having a bactericidal concentration of aerobic fungi, the amount of added hydrogen peroxide is surprisingly low. It has also been found that a drastically smaller amount than the added amount produces a sufficient effect.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The quaternary ammonium salt which can be used in the present invention is, for example, a compound represented by the following general formula (I):

[0010]

Embedded image

(Wherein R has a hydroxy group at the β-position
Or saturated or unsaturated linear aliphatic having 8 to 28 carbon atoms
Hydrocarbon group, R¹Is a lower alkyl group, or a
C8-C28 saturated or unsaturated which may have a xy group
A linear aliphatic hydrocarbon group of R ^TwoAnd R^ThreeAre the same or different
Is a lower alkyl group, X is an acid residue or a hydroxyl group), or
General formula (II):

[0012]

Embedded image

(Wherein R and X have the same meanings as in formula (I),
R ⁴ is represented by a hydrogen atom or a methyl group).

In the general formula (I), "C8-C28"
Saturated or unsaturated linear aliphatic hydrocarbon group '', octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, docosyl, tricosyl, Linear saturated hydrocarbon groups such as tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl and the like;

Octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl,
Pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl (oleyl = 9-cis-octadecenyl), nonadecenyl, icosenyl, henicocenyl, docosenyl,
Tricosenyl, tetracosenyl, pentacosenyl, hexacosenyl, heptacosenyl, octacosenyl, octadecadienyl (linoleyl = 9,12-octadecadienyl) and the like;

Octazinyl, nonazinyl, decadinyl,
Undecadinyl, dodecadinyl, tridecadinyl, tetradecadinyl, pentadecadinyl, hexadecadinyl,
Heptadecazinyl, octadecadinyl, nonadecadinyl, icosazinyl, henicosazinyl, docosazinyl, tricosazinyl, tetracosazinyl, pentacosazinyl,
Linear unsaturated hydrocarbon groups such as hexacosazinyl, heptacosazinyl, octacosadinyl and the like; coconut alkyl, tallow alkyl, hardened tallow alkyl, soybean alkyl and the like.

Here, coconut alkyl, tallow alkyl, hardened tallow alkyl, and soybean alkyl are alkyl groups constituting higher aliphatic mono- or polyamines produced from coconut oil or coconut fat, tallow or soybean oil by known means. is there. In addition, these alkyl groups have a carbon number of 8 to
It may contain a plurality of linear saturated or unsaturated aliphatic hydrocarbon groups having an arbitrary value between 28.

The "saturated or unsaturated straight-chain aliphatic hydrocarbon group having 8 to 28 carbon atoms having a hydroxy group at the β-position" includes the aforementioned "saturated or unsaturated straight-chain aliphatic hydrocarbon group having 8 to 28 carbon atoms". Groups having a hydroxy group at the β-position of the `` chain aliphatic hydrocarbon group '', among which β-hydroxydodecyl, β
-Hydroxyhexadecyl is preferred.

Further, the "lower alkyl group" of the formula (I)
Is preferably an alkyl group having 1 to 4 carbon atoms, specifically, methyl, ethyl, n-propyl, iso-propyl,
n-butyl, iso-butyl, sec-butyl, tert-butyl. X in the general formulas (I) and (II) represents hydrochloric acid, hydrobromic acid, nitric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oleic acid, naphthenic acid, adipic acid, lactic acid, citric acid, benzoic acid , Saccharin and the like, and a hydroxyl group. Among them, a residue of hydrochloric acid or hydrobromic acid is particularly preferable.

The quaternary ammonium salt represented by the general formula (I) which can be used in the present invention includes dodecyltrimethylammonium salt, dodecyltriethylammonium salt, tetradecyltrimethylammonium salt, tetradecyltriethylammonium salt, Decyl trimethyl ammonium salt, hexadecyl triethyl ammonium salt, octadecyl trimethyl ammonium salt, octadecyl triethyl ammonium salt, coco alkyl trimethyl ammonium salt, coco alkyl triethyl ammonium salt, tallow alkyl trimethyl ammonium salt, tallow alkyl triethyl ammonium salt;

Dioctyl dimethyl ammonium salt, didecyl dimethyl ammonium salt, decyl tetradecyl dimethyl ammonium salt, didodecyl dimethyl ammonium salt, dihexadecyl dimethyl ammonium salt, dioctadecyl dimethyl ammonium salt, ditallow alkyl dimethyl ammonium salt; β-hydroxy Dodecyltrimethylammonium salt, β-hydroxyhexadecyltrimethylammonium salt, β-hydroxydodecyltriethylammonium salt, β-hydroxyhexadecyltriethylammonium salt are exemplified.

The quaternary ammonium salts represented by the general formula (II) which can be used in the present invention include dodecyl pyridinium salt, hexadecyl pyridinium salt,
Octadecylpyridinium salt, cocoalkylpyridinium salt, tallowalkylpyridinium salt and the like can be mentioned. These quaternary ammonium salts may be used as a mixture of two or more.

Among the above quaternary ammonium salts, octadecyltrimethylammonium chloride, hexatrimethylammonium chloride, tallowalkyltrimethylammonium chloride, dodecyltriethylammonium bromide and hexadecylpyridinium bromide are selectively used for aerobic bacteria, especially actinomycetes. It is preferable because it sterilizes.

The hydrogen peroxide agent usable in the present invention is commercially available at a concentration of 3 to 60 for industrial use.
% Hydrogen peroxide solution or a compound capable of releasing hydrogen peroxide in water. Examples of the compound capable of releasing hydrogen peroxide in water include inorganic peracids such as perboric acid, percarbonate and peroxysulfate, organic peracids such as peracetic acid, and salts thereof. In addition, when the hydrogen peroxide agent is added to the seawater cooling water system, it may be appropriately diluted with seawater or freshwater. Further, hydrogen peroxide generated by electrolysis or the like in a cooling water system or another water system can also be used.

Although the details of the mechanism of action of the present invention are unclear, first, the bactericidal concentration of aerobic fungi which contains a large amount of catalase (enzyme) that decomposes hydrogen peroxide and reduces the bactericidal efficacy of hydrogen peroxide. By adding a quaternary ammonium salt, aerobic bacteria that are not effective with hydrogen peroxide alone, especially actinomycetes, are selectively sterilized by low-concentration contact. It is thought that the addition of the quaternary ammonium salt and the hydrogen peroxide can be reduced as a result. In particular, the addition amount of the hydrogen peroxide agent is usually 1/3 of the used amount.
１／1/10 or less.

The concentration of the quaternary ammonium salt is a bactericidal concentration of aerobic fungi, for example, 0.005 to seawater.
0.2 mg / liter, preferably 0.01-0.1 m
g / liter. If the amount of the quaternary ammonium salt is less than 0.005 mg / l, it is not preferable because aerobic bacteria, especially actinomycetes, cannot be selectively killed. If it is more than 0.2 mg / l, it is not economical. In addition, seawater foams, which is not preferable. The quaternary ammonium salt is preferably added at the above concentration over a period of 8 to 24 hours a day.

The concentration of hydrogen peroxide depends on the type of microorganisms constituting the slime, the type of seawater, the state of pollution, the content of organic substances in the water system, the water temperature, etc., and cannot be uniquely limited. On the other hand, it is 0.01 to 0.5 mg / liter, preferably 0.1 to 0.5 mg / liter. If the concentration of hydrogen peroxide is less than 0.01 mg / liter, the effect of preventing slime adhesion is not exhibited, which is not preferable. If it is more than 0.5 mg / liter, it is not economical and not preferable.

The quaternary ammonium salt and the hydrogen peroxide added in the present invention are easily dispersed in the fluidized seawater, but conventional physical means are used for rapid and substantially uniform dispersion. be able to. Specifically, installation of a diffuser, a stirrer, a baffle plate, and the like in the seawater cooling water system may be mentioned. In addition, since the equipment corresponding to these is attached to the seawater cooling water system, it can be diverted.

The method of the present invention can be particularly preferably used for preventing slime derived from aerobic fungi mainly comprising actinomycetes.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the scope of the present invention is not limited thereby.

Example 1 In summer when the water temperature is high (25-28 ° C.) and slime formation is remarkable, seawater is pumped by a submersible pump from a depth of 2 m on the quay of a certain steelworks, and is passed through a model waterway shown in FIG. , And each drug was injected in a predetermined amount and in a predetermined order from the front injection point 1 and the rear injection point 2 (see Table 1). After 30 days, the state of slime formation and the amount of adhesion were examined. The model channel shown in FIG. 1 has a PVC pipe 3 downstream of the rear injection point 2.
A titanium test plate 4 (25 mm square × 0.5 mm thick) was placed in parallel with the water flow (inside diameter 65 mm × length 20 cm), and a titanium tube 5 (inside diameter 15 mm) was further downstream.
× length 1 m, wall thickness 0.5 mm). Arrows in the figure indicate the direction of seawater flow.

A pipe 3 made of vinyl chloride with a test plate attached
The average flow velocity in the tube was about 0.1 cm / sec, and the average flow velocity in the titanium tube 5 was about 1.6 cm / sec. After the completion of the water passage for a predetermined time, the titanium test plate 4 was collected, fixed with 2% glutaraldehyde-containing sterilized filtered seawater, freeze-dried, and subjected to SEM observation. The slime adhered to the inside of the titanium tube 5 was scraped off with a brush, placed in a measuring cylinder, and the slime wet volume after standing for 24 hours was measured. Table 1 shows the results of SEM observation and measurement of slime wet volume.
Shown in

[0033]

[Table 1]

Example 2 In a steel mill (water passing 10,000 tons / hour) in which a seawater cooling water system is treated with a chlorine agent, a normal operation using a chlorine agent, a quaternary ammonium salt and a peroxide Slime adhesion was compared with the case where a hydrogen agent was used in combination. Seawater is taken out from the inlet of a condenser at a certain steelworks and passed through a titanium pipe 5 (inner diameter 15 mm x length 1 m, wall thickness 0.5 mm) so that the average flow rate in the pipe is about 1.6 cm / sec. Watered. Then, 30 days later, the slime adhered in the titanium tube was scraped off with a brush, placed in a graduated cylinder, and allowed to stand for 24 hours, and the wet slime volume was measured. In addition, sodium hypochlorite was used as the chlorine agent, and the injection concentration was such that residual chlorine was not detected at the water outlet of the factory so that the chlorine was injected from the tip of the headrace to 0.2 ppm in terms of chlorine.

The test was conducted in the same manner as the test using a chlorine agent, except that injection points were provided at two places in the seawater headrace and two kinds of chemicals were injected with a metering pump. In addition, the chemical was injected from the end of the seawater headrace so that tallow alkyltrimethylammonium chloride became 0.05 ppm.
% Aqueous solution was continuously injected with a metering pump. In addition, a 35% hydrogen peroxide solution was continuously injected at a concentration of 1 ppm from just before berth screen 2 m downstream from the tip. Table 2 shows the measurement results of the infused drug, the infusion conditions, and the slime wet volume.

[0036]

[Table 2]

[0037]

According to the present invention, a quaternary ammonium salt is added to a seawater cooling water system in advance at a bactericidal concentration of aerobic fungi, and then the hydrogen peroxide concentration in the cooling water system is adjusted to a predetermined concentration. Since the hydrogen agent is added, the addition of trace amounts of the quaternary ammonium salt and the hydrogen peroxide can prevent strong slime from adhering to the cooling water system piping. In particular, the addition amount of the hydrogen peroxide agent is set to 1 /
It can be reduced to 3 to 1/10 or less.

[Brief description of the drawings]

FIG. 1 is a schematic view of a test device (model waterway) for confirming a slime adhesion preventing effect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front injection point 2 Rear injection point 3 Vinyl chloride pipe 4 Titanium test plate 5 Titanium pipe

Claims (3)

[Claims] 1. A quaternary ammonium salt is added in advance to a seawater cooling water system at a bactericidal concentration of aerobic bacteria, and then the hydrogen peroxide concentration of the cooling water system is adjusted to 0.01 to 0.5 mg / liter. A method for preventing slime from adhering to a seawater cooling water system, comprising adding a hydrogen oxide agent to prevent slime from adhering to the cooling water system. 2. The method according to claim 1, wherein the quaternary ammonium salt is present in an amount of from 0.005 to
The method for preventing slime adhesion according to claim 1, wherein the slime is added at a concentration of 0.2 mg / liter. 3. The method according to claim 1, wherein the aerobic fungi is mainly actinomycetes.