JPH11108589A - Slime peeling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely peel off the slime in a short time without using any chemical of poor handleability, or generating any erosion by charging and circulating the granular body consisting of a soft organic gel containing water into a water system. SOLUTION: The slime is generated around heat exchanging tubes 15a, 15b, 15c of heat exchangers 2a, 2b, 2c, the granular body consisting of a soft organic gel containing water is charged from a charging passage 16, the dispersant, the control agent, etc., is poured in a pit 8 together with supplemental water as necessary, and fed in a circulation system 11 by a pump 10, and circulated through the heat exchangers 2a, 2b, 2c. When the mixture is passed through the heat exchanging tubes 15a, 15b, 15c, the granular body is collided with the slime to peel off the slime. The slime can be completely peeled off in a short time without using any chemical of poor handleability, or without generating any erosion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing aqueous slime produced by slime mainly composed of microorganisms.

[0002]

2. Description of the Related Art In a system in which water stays such as an open-circulation type cooling water system, slime mainly composed of microorganisms is generated, and this slime adheres to a heat exchange surface to lower heat transfer efficiency.
In a system in which such slime is generated, the heat transfer efficiency can be maintained high by removing the attached slime.

A conventional method of injecting a chemical such as hydrogen peroxide or hydrazine, which is a slime stripping method, involves a large amount of chemicals and is difficult to work. As a physical separation method, there is a method in which a sponge with a larger diameter is inserted into the heat exchanger and the water is reciprocated in the heat exchange tube.However, since this method requires the water to flow backward, the operation of the apparatus is stopped. In addition to the necessity, sponge is expensive, and when used in a heat exchanger for several years, the sponge dissolves in the chemical,
There are problems such as deterioration.

[0004] On the other hand, as a method for removing the scale, pellets having a particle diameter of 1/3 to 1/10 of the diameter of the heat exchange tube and having a specific gravity different from that of the heat exchange fluid are introduced into the heat exchanger to remove the scale. (Japanese Patent Publication No. 57-129)
No. 57). Since this method removes scale mainly composed of metal oxides instead of slime mainly composed of microorganisms, it is necessary to use relatively hard pellets. Therefore, erosion (physical corrosion) occurs in heat exchange tubes and the like. Easy to occur. In addition, since a heat exchange fluid, that is, a pellet having a specific gravity different from that of water is used, there is a problem that it is difficult to flow in a state of being dispersed in water for a long time.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to remove slime safely and in a short time by a simple operation during driving without using a poorly handled chemical and without causing erosion. It is to propose a slime stripping method that can be used.

[0006]

The present invention is the following slime stripping method. A slime exfoliating method for exfoliating aqueous slime generated by slime mainly composed of microorganisms, wherein a granular material composed of a soft hydrous organic gel is charged into an aqueous system and circulated.

[0007] In the present invention, the system to be subjected to slime separation is a system in which slime mainly composed of microorganisms is generated, and the slime usually adheres to a heat exchanger or other walls, resulting in poor water flow or heat exchange efficiency. Causes a decrease in Examples of such a system include an open circulation type cooling system, a refrigerator cooling water system, a hot water supply system, and a process line of a food factory.

In the present invention, the granular material used for peeling slime has a specific gravity of 0.9 to 1.1, preferably 0.95 to 1.05,
More preferably, 0.98 to 1.02, diameter 0.1 to 5
mm, preferably 0.5 to 3 mm, is a granular material composed of a soft hydrous organic gel, and is preferably flexible enough to be deformed by pushing with a fingertip. The shape of the granular material can be any shape such as a spherical shape and a cubic shape.

Examples of the hydrous organic substance gel constituting such a granular material include polysaccharide gels such as agar gel and glucomannan gel, and polysaccharide derivative gels such as cellulose acetate gel.
Gels composed of natural organic substances or derivatives thereof, such as protein gels such as gelatin gels, are preferred. These gels are heated and dissolved by adding agar, glucomannan, gelatin and the like to water, and the concentration of the agar is 1 to 5% by weight, preferably 1.
The specific gravity is adjusted to be 5 to 2.5% by weight, gelled by cooling or the like, and cut into the above-mentioned particle size before use.

The slime can be removed by adding the above granular material to an aqueous system and circulating it. The added amount of the granular material is 50 to 5 as a granular gel with respect to the water in the aqueous system.
000 mg / l (0.5 to 250 mg / dry weight)
l), preferably about 100 to 1000 mg / l. Addition of the granules can be performed during operation of the aqueous system, and the granules are circulated using an aqueous circulation pump. In this case, it is preferable to use a material having a particle size smaller than the opening of the strainer, for example, a particle size of 0.5 to 1.5 mm so as not to clog the strainer of the pump. If a strainer having a large opening is used, a particle having a larger particle size can be used.

In general, such a water system employs a system in which circulating water is circulated between a heat exchanger and a cooling tower by a circulation pump. In this case, the granular material may be circulated throughout the entire water system. Since slime adheres mainly to the heat exchanger, the slime may be circulated around the heat exchanger by bypassing the cooling tower.

In any case, by circulating the granular material together with water, the granular material collides with the slime and the slime is peeled off. The soft water-containing organic gel particles are flexible and deformed, so that they do not damage heat exchange tubes and other walls, do not cause erosion, and do not pass through narrow portions to cause clogging.

Along with the addition of the granules, a polymer electrolyte (for example, sodium polyacrylate) or 2-methyl-4-isothiazolin-3-one, 5-chloro-2- as a dispersant to promote peeling. Methyl-4-
Isothiazolin-3-one, dibromonitrilopropionamide, o-phthalaldehyde, 2-bromo-2-nitropropane-1,3-diol, hydrogen peroxide, chlorine,
A slime control agent such as hypochlorite or a surfactant such as dioctyl sulfosuccinate or alkylaminoethylglycine can also be added.

Since the above granular material has a specific gravity close to that of water,
It does not separate from water but circulates with the circulation of water to remove slime. The exfoliated slime is discharged out of the system together with the water by blowing the circulating water. The granules do not need to be present in the aqueous system after the slime is peeled off, and can be discharged together with the blow water. However, they can be separated and treated or reused by a screen smaller than the particle size of the granules.

The use of a natural product or a derivative gel thereof is highly biodegradable, so that the granular material can be treated by activated sludge treatment or the like, and if there is a blow water treatment device, it can be treated by that device. In any case, the treatment of the granular material is easy.

[0016]

According to the slime peeling method of the present invention, a soft granular material having a specific gravity close to that of water is put into an aqueous system and circulated, so that a chemical having poor handling properties is not used, and erosion does not occur. By a simple operation, the slime can be safely removed in a short time. In addition, by using a gel of a natural organic substance or a derivative thereof as the granules, the safety is high and the treatment of the granules becomes easy.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a circulating cooling water system showing a slime peeling method according to an embodiment. In FIG. 1, 1 is a cooling tower, 2a, 2b, 2c is a heat exchanger. Cooling tower 1
The cooling water is sprayed from the watering nozzle 4 onto the filler 3, the air 7 is taken in from the louver 6 by suction by the fan 5 and cooled, and the cooling water 9 is stored in the pit 8.

A cooling water 9 is supplied to a circulating water system 11 by a pump 10.
And heat exchanges (cools) the process water 12a, 12b, 12c, etc. in the process of passing through the heat exchangers 2a, 2b, 2c, and the heated cooling water is sprayed onto the filler 3 from the watering nozzle 4. , A part of which is cooled by evaporation and returns to the pit 8. A part of the concentrated cooling water 9 is discharged from the blow water channel 13, and the insufficient cooling water is supplied from the supply water channel 14.

In such a circulating cooling water system, the slime is supplied to the heat exchange tubes 15a, 15a of the heat exchangers 2a, 2b, 2c.
b, 15c. When slime is generated, the granular material is introduced from the introduction path 16 and, if necessary, a dispersant, a slime control agent and the like are injected into the pit 8 together with make-up water. When passing through the heat exchange tubes 15a, 15b, 15c, which are circulated through the exchangers 2a, 2b, 2c, the granular material collides with the slime and separates the slime.
Since the granular material is soft and flexible, the slime is exfoliated and erosion does not occur without damaging heat exchange tubes and other walls.

The granular material that has passed through the heat exchangers 2a, 2b, and 2c returns to the cooling tower 1 in a state of being dispersed in the cooling water together with the separated slime particles, and is cooled therein. Granules and slime particles enter the pits 8 without being captured by the filler 3. Here, since the granular material has a specific gravity close to that of water, the granular material is kept in a state of being dispersed in water, and the circulating water
It is circulated to 1 and used for slime exfoliation.

In the circulating water system 11, blow water is always discharged in a fixed amount, and separated slime particles and granular materials are mixed therein. When blow water is treated by a wastewater treatment device, the gel of a natural organic substance or a derivative thereof is directly treated by a wastewater treatment device, but when there is no wastewater treatment device, it is separated by a screen or the like and separately treated, or slime is used. It can be recycled to a circulating water system for stripping.

When slime exfoliation is performed by charging the granular material,
As the slime peels, the turbidity of the circulating water increases. After the turbidity reaches the maximum value, the turbidity gradually decreases because the exfoliated slime particles re-aggregate. When circulating while performing normal blowing as it is, the separated slime may be deposited again. Therefore, it is preferable to increase the blow water amount to 1.2 to 2 times the normal amount and discharge the granular material and the separated slime. . Alternatively, the blow may be performed after the operation for 2 to 3 hours without blowing.

The above embodiment is an example in which the granular material is circulated through the cooling tower 1. The granular material separating device 21 and the bypass 22 are provided in the circulating water system 11, and the granular material is circulated to the circulating water system 11 by the pump 23. And the cooling tower 1 can be bypassed. In this case, the granular material separating device 21 is provided with a screen 24 that captures the granular material and allows water and slime particles to pass through, so that only the granular material is captured and circulated. Here, new granules can be introduced from the introduction path 25. Further, after the peeling, the granular material can be taken out from the bypass passage 22 and processed, or collected and reused.

The slime is intermittently separated, for example, 1
It is preferable to carry out the treatment at a rate of about once every two months, but it is also possible to continuously circulate a small amount of the granular material to prevent the slime from being peeled off or adhered continuously.

[0025]

Embodiments of the present invention will be described below. Example 1 A carbon steel tube subjected to anticorrosion treatment is inserted into a glass tube as a heat exchange tube to form a double tube structure, high-temperature water (60 ° C.) is flowed inside the heat exchange tube, and the heat exchange tube is cooled between the glass tube Heat exchange was performed by circulating cooling water from the water tank. The heat transfer area of the heat exchange tube is 418 cm ² , the water volume is 50 liter,
Circulating water temperature 25-30 ° C, flow rate of evaluation section 0.2m / sec
It is. 100 mg / l of the anticorrosive dispersant Cryroyal (registered trademark, manufactured by Kurita Kogyo Co., Ltd.) in tap water as the cooling water
Addition, backwash water of the industrial water filter 1 liter of water
It was added in four portions, once every two to three days, so that the solid content per iter was 200 mg. After 10 days, the attachment of slime to the surface of the heat exchange tube was confirmed.

With the slime adhered, the agar gel was put into the circulating water system, and the slime was peeled off. The agar gel was prepared by dissolving agar in heated ultrapure water to a concentration of 1.5% by weight, cooling to gel, and cutting into a cube of 1-2 mm square. 500mg / agar gel
l (vs. agar gel weight relative to water possession; 7.5 mg / l dry weight). After a predetermined time from the agar introduction, circulating water was collected, the agar gel was removed with an 80 mesh, the turbidity was measured, and the residual slime adhesion amount on the heat exchange tube surface was visually observed. displayed. Table 1 shows the results.

[0027]

[Table 1]

Comparative Example 1 In the same manner as in Example 1, hydrazine was added to a circulating water system to which slime was attached so that the amount of hydrazine was 120 mg / l with respect to the amount of water retained, and slime was peeled off. Table 2 shows the results.

[0029]

[Table 2]

From the above results, it can be seen that agar gel has a higher slime exfoliating effect than hydrazine, and exfoliates rapidly in a short time to increase turbidity.

[Brief description of the drawings]

FIG. 1 is a system diagram of a circulating cooling water system showing a slime peeling method according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cooling tower 2a, 2b, 2c Heat exchanger 3 Filler 4 Sprinkling nozzle 5 Fan 6 Louver 7 Air 8 Pit 9 Cooling water 10, 23 Pump 11 Circulating water system 12a, 12b, 12c Process water 13 Blow water line 14 Refill water line 15a, 15b, 15c Heat exchange tubes 16, 25 Input path 21 Granular material separation device 22 Bypass path 24 Screen

Claims (1)

[Claims] 1. A method for exfoliating an aqueous slime produced by a slime mainly composed of microorganisms, wherein a granular material comprising a soft hydrous organic gel is charged into an aqueous system and circulated. .