JPH02144191A - Method for purifying water circulating in cooling tower - Google Patents

Abstract

PURPOSE:To effectively utilize ozone by purifying circulating water with dissolved ozone in the bottom water tank of a cooling tower, allowing undissolved ozone to rise in the tower with air and dissolving the ozone in circulating water falling in a packed bed by contact to sterilize the packed bed and to kill algae. CONSTITUTION:Part of water circulating in a cooling tower 2 is brought into contact with ozone-contg. air fed from an ozonizer 1 to dissolve 70-90% of the ozone in the circulating water. This circulating water is blown into the bottom water tank 3 of the tower 2 together with the air contg. the undissolved ozone and ozone-contg. air rising from the water tank 3 is brought into contact with circulating water in a packed bed 6. Expensive ozone is effectively consumed without waste and can be made more effective in sterilizing the water tank and the packed bed and killing algae.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to cooling water circulating in wet wall cooling towers for cooling and reusing cooling water in air conditioning equipment, industrial equipment, plants, etc. by contacting it with outside air. The present invention relates to a purification method and a method for sterilizing and algaecide packed beds used in wet walls.

(Conventional technology) A cooling tower has a water tank at the bottom, and a packed bed filled with plastic filler or backing to form a wet wall at the top. It has a structure that exchanges heat by bringing outside air and water into contact with each other in a packed bed. However, bacteria and algae tend to grow and multiply in the circulating water of cooling towers, and the use of ozone as a preventive measure is a well-known method that takes advantage of ozone's strong oxidizing and sterilizing powers.

As an example of this method, a part of the circulating water is taken out of the system and brought into contact with ozone-containing air obtained from an ozone generator to sterilize bacteria in the water, and then the water is separated into gas and liquid.
The ozone-dissolved water is returned to the system, and the ozone gas-containing air that cannot be dissolved in the water is exhausted after residual ozone is rendered harmless using an ozone decomposition catalyst such as activated carbon.

(Problem to be Solved by the Invention) However, in this method of simply bringing ozone-containing air into contact with water, no matter what efficient gas-liquid contacting device currently in use is used, 90% of the ozone generated is Only about % of ozone can be dissolved in water, so the remaining ozone is not effectively utilized and is wasted. Furthermore, although ozone itself is not harmful to the human body at extremely low concentrations, it is highly toxic and harmful if it is disposed of as is at high concentrations.
The gas must be decomposed and rendered harmless using an ozone-decomposing solvent such as activated carbon before being exhausted.

In addition, the packed bed of a cooling tower constantly forms a wet wall, which makes it easy for bacteria and algae to grow, which causes the packed bed to become dirty and clogged, resulting in a decrease in cooling efficiency. However, at present, it cannot be said that sterilization and algaecide measures for the packed bed have been carried out by -1.

(Means for solving the problem) The present inventors used ozone as effectively as possible to sterilize and kill algae in the circulating water of a cooling tower, and also to sterilize and kill algae in the packed bed that forms the wet wall. As a result of careful consideration of possible methods, we decided to extract a portion of the circulating water from the cooling tower, bring it into gas-liquid contact with ozone-containing air, and then blow the gas-liquid mixed water containing undissolved ozone into the bottom water tank. In addition, by adjusting the amount of ozone dissolved during gas-liquid contact, and allowing a small amount of ozone to remain in the air rising through the cooling tower, and bringing it into contact with the circulating water flowing down in the packed bed, the sterilization effect in the packed bed will be increased. Knowing this, I arrived at the present invention.

The source of ozone used in the present invention is not particularly limited, but
It is usually convenient to use ozone-containing air obtained from an ozone generator producing hundreds to thousands of ppm of ozone. In the present invention, instead of blowing ozone-containing air directly into the water tank at the bottom of the cooling tower, first, a part of the circulating water of the cooling tower is extracted and introduced into a gas-liquid contacting device to contact with the ozone-containing air to form this gas-liquid mixture. Blow into the water tank at the bottom of the cooling tower. According to the method of the present invention, circulating water is purified by dissolved ozone in the bottom water tank, and undissolved ozone goes up the tower along with the air, comes into contact with the circulating water flowing down in the packed bed, and is dissolved. Since a phase ozone atmosphere is maintained, the packed bed can be sterilized and algaecide.

The ratio of ozone-containing air and water that come into contact with the gas-liquid contact device is adjusted so that 70 to 90% of the ozone is dissolved. If all the ozone is dissolved, the sterilization and algaecide effects of the packed bed will not be obtained, and if there is a large amount of undissolved ozone, the sterilization and algaecide in the bottom water tank will not be sufficient, and the upper fan will This is undesirable because excess ozone is exhausted. By adjusting the solubility of ozone to the above value, it is possible to purify circulating water with dissolved ozone, sterilize packed beds with undissolved ozone,
Algaecide can also be used.

The gas-liquid contact device used in the present invention can be any device that efficiently dissolves ozone in the air by contacting the ozone-containing air with water.

Specifically, ejectors, static mixer spray towers, packed towers, tray towers, etc. may be mentioned, and an appropriate one may be selected from among them, taking into account the capacity of the cooling tower, the capacity of the bottom water tank, etc.

The present invention will be explained below with reference to FIG.

The ozone-containing air supplied from the ozone generator 1 is brought into contact with and mixed with a part of the circulating water sucked by the pump 4 from the bottom of the bottom water tank 3 of the cooling tower 2 by the ejector 5,
After most of the ozone is dissolved in the circulating water, the discharge pressure of the pump 4 is used to force the ozone into the water tank 3 at the bottom of the cooling tower again in a gas-liquid mixed state.

In this way, the ozone dissolved in the water is used for sterilization, algaecide, etc. of the water stagnant in the aquarium. Further, the undissolved ozone that is pressurized into the water tank rises inside the cooling tower due to the flow of outside air from bottom to top sucked in by the fan 7 at the top of the cooling tower, and passes between the packed beds 6. At this time, ozone comes into contact with the circulating water flowing down the packed bed 6 and dissolves in the water, and also kills bacteria, algae, etc. that grow around the filled part 6 due to the oxidizing and sterilizing power of gaseous ozone. be able to.

(Example) Next, the present invention will be explained in more detail based on FIG.

Cooling tower 2 has a capacity of 40 refrigeration tons and a water circulation rate of 30 rrl/H. Ozone generator 1 is pneumatic 18. ! By flowing M/min, the concentration is 8.
It has the ability to generate 50ppm of ozone.

Cooling tower bottom water tank 3 to 301 by pump 4
/min of circulating water is sucked and introduced into the ejector 5,
Here, it was brought into contact with and mixed with ozone-containing air from the ozone generator 1. 85% of the generated ozone was dissolved in the circulating water, and the ozone remaining in the gas phase was 130 ppm.

In this state, when the gas/liquid mixture at the ejector outlet was pressurized into the water tank 3 at the bottom of the cooling tower, the mixture was transferred to the pump 4.
It was observed that the ozone-dissolved water was blown into the aqueous phase vigorously by the discharge pressure, and the ozone-containing air that was blown in at the same time effectively stirred the water and mixed it uniformly into the accumulated water.

On the other hand, the air containing undissolved ozone blown out from the bottom water tank rises up the cooling tower due to the suction of the top fan 7 and comes into contact with the flowing circulating water in the packed bed 6, during which time the ozone is dissolved in the water and the air is Maintain a phase ozone atmosphere.

After gas-liquid contact, the air substantially free of ozone is exhausted to the atmosphere.

When the method of the present invention was carried out, the number of general bacteria in the bottom water tank was 1 x 1-04 bacteria/ml before ozone injection, but it increased to I x 102 bacteria/ml two weeks after the start of ozone injection.
After one month, the number decreased to 0 pieces/ml, demonstrating that ozone is working effectively. On the other hand, the adhesion of green algae, which was observed before ozone injection near the packed bed, began to decrease as ozone was injected, and after about one month, the algae died, so the algicidal effect of ozone in the packed bed was clearly recognized.

Furthermore, when the ozone concentration was measured in the vicinity of the fan 7 at the top of the cooling tower, it was found to be 0.0 ippm or less, confirming that the supplied ozone was effectively consumed and reduced to below the safe concentration.

(Effects of the Invention) According to the method of the present invention, when ozone was conventionally used for water sterilization, algaecide, etc., the utilization efficiency of ozone was poor. It is also possible to use undissolved ozone more effectively, effectively consuming expensive ozone without wasting it, and increasing the bactericidal and algicidal effects of the bottom water tank and the packed bed.

In addition, conventionally, air containing undissolved ozone was detoxified using a separate ozone decomposition catalyst such as activated carbon, but the method of the present invention eliminates the need for S incidental equipment, making it more economical. can provide an advantageous method.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of an embodiment of the present invention. Figure-1 Applicant: Steel Chemical Industry Co., Ltd. Representative Yuji Masuda

Claims (1)

[Claims] Part of the cooling tower circulating water and ozone-containing air are brought into gas-liquid contact in advance to dissolve 70 to 90% of the ozone in the circulating water, and then the circulating water is blown into the bottom water tank of the cooling tower together with the undissolved ozone-containing air. A method for purifying circulating water in a cooling tower, sterilizing the packed bed, and killing algae, characterized by bringing the ozone-containing air rising from the air into gas-liquid contact with the circulating water in a packed bed.