JP2002361287A - Method for treating cooling water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling water treating method capable of simultaneously preventing the generation of scale and slime of a cooling water system without using a chemical agent. SOLUTION: In the cooling water treating method, the cooling water is treated by combining a scale preventing treatment device, a sludge removing device and a slime preventing device in the cooling water system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating cooling water. More specifically, the present invention relates to a method for treating cooling water that can simultaneously prevent scale and slime generation in the cooling water system without using chemicals.

[0002]

2. Description of the Related Art Cooling water is used in various industrial fields such as the petrochemical industry and the steel industry for the purpose of indirectly or directly cooling an object to be treated, or for air conditioning, cooling and heating of a building,
It is widely used in related devices. In recent years, from the viewpoint of water resources shortage and effective utilization, in order to reduce the amount of cooling water used, advanced utilization of cooling water has been performed, such as reduction of the forced blow amount in high concentration operation of open circulation cooling water system. I have. When the cooling water is used in such a high degree, the quality of the circulating cooling water deteriorates due to the concentration of dissolved salts and nutrients, and the insoluble salt is easily scaled.
Slime formed by mixing microorganisms such as bacteria, molds and algae with earth and sand, dust and the like is likely to be generated. The generation of scale and slime causes a decrease in heat efficiency and deterioration of water flow in the heat exchanger, and also causes local corrosion of equipment and piping. Therefore, in order to prevent such an obstacle due to scale or slime, a cooling water treatment agent such as a scale inhibitor or a slime inhibitor is widely used. For example, in order to prevent calcium-based scale, a polymer having a carboxyl group, a polymer having a sulfonic acid group, a polyphosphoric acid, a precipitation-inhibiting agent such as phosphonic acid is used, and in order to prevent slime, sodium hypochlorite is used. And an oxidizing agent such as hydrogen peroxide solution. These medicines are stored in a medicine tank, and are injected into the cooling water system at a constant speed by a medicine injection pump. However, when using drugs to prevent scale and slime, it takes time to check the remaining amount of drugs and replenish them regularly.
There are problems such as the need for labor, such as lorry transportation and container transportation. The polymer or phosphonic acid used as the scale inhibitor causes an increase in the load on the environment, such as an increase in the COD concentration and the phosphorus concentration in the waste water when blow water is generated due to the maintenance and management of the cooling water. The oxidizing agent used as an anti-slime agent has a risk of causing a leak or the like during handling of the chemical and damaging a human body. For this reason, there is a need for a method of treating cooling water that does not use any chemicals, and can solve problems such as the complexity of transporting and arranging chemicals in cooling water treatment, the effects on the environment, and the danger of handling. I have.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for treating cooling water which can simultaneously prevent scale and slime generation in the cooling water system without using chemicals. It is.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a combination of a scale prevention treatment device, a sludge removal device and a slime prevention device treats cooling water. As a result, it has been found that the scale of cooling water and the generation of slime can be prevented at the same time without using any chemical, and the present invention has been completed based on this finding. That is, the present invention provides (1)
In the cooling water system, a cooling water treatment method characterized by treating the cooling water by combining a scale prevention treatment device, a sludge removal device, and a slime prevention device. (2) The scale prevention treatment device is a permanent magnet, a solenoid coil type. 2. The method for treating cooling water according to claim 1, wherein the method is a combination of a magnet, a combination of different kinds of electrodes, a metal eluting device, or a ceramic ball.
3. The method for treating cooling water according to claim 1 or 2, wherein the sludge removing device is a filtration device or a sedimentation tank, and (4) the slime preventing device is an oxidizing agent generating device by electrolysis. The method for treating cooling water according to any of the items, and
(5) The method for treating cooling water according to item 4, wherein the oxidizing agent is chlorine, hydrogen peroxide or ozone.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the cooling water treatment method of the present invention, in a cooling water system, cooling water is treated by combining a scale prevention treatment device, a sludge removal device and a slime prevention device. The method of the present invention is easy to generate scales such as calcium carbonate, calcium sulfate, calcium sulfite, calcium phosphate, calcium silicate, magnesium silicate, magnesium hydroxide, zinc phosphate, zinc hydroxide, basic zinc carbonate, and water. Nutrients are dissolved in
The present invention can be suitably applied to a cooling water system in which microorganisms such as bacteria, filamentous fungi, and algae proliferate and mix with inorganic substances such as earth and sand and dust to form slime. There is no particular limitation on the scale prevention treatment apparatus used in the method of the present invention,
For example, a permanent magnet, a solenoid coil type magnet, a combination of different kinds of electrodes, a metal eluting device, a ceramic ball and the like can be used. One of these scale prevention treatment apparatuses can be used alone, or two or more can be used in combination. There is no particular limitation on the permanent magnet used in the method of the present invention, and examples thereof include alnico, barium-ferrite, iron-neodymium-boron, and samarium-cobalt. The permanent magnet is
The water containing the scale component is installed in the pipe so that it flows across the magnetic field at right angles. It is preferable to appropriately select the pipe diameter of the permanent magnet installation portion so that the flow rate of water is 1.5 m / sec or more. When a magnetic field is formed in water by a permanent magnet and the magnetic flux is cut by the flow of water, an ionic current of about several mA is generated, and the cluster of water becomes finer.
Not only can scale components in water be dispersed to prevent adhesion, but also scales that have already adhered can be softened and peeled off.

[0006] The solenoid coil type magnet used in the method of the present invention is used by winding a coil around the outside of the cooling water system pipe, so that it can be installed in the existing cooling water system without modification. There is no particular limitation on the material of the piping, for example,
Examples include copper, stainless steel, bronze, and plastic piping. An alternating current is applied to the solenoid coil, and a frequency of 2,000 to
It is preferable that the modulation be performed in the range of 7,000 Hz and the amplitude be modulated. When a magnetic field is formed in water by the solenoid coil type magnet, the electric charge on the surface of the fine particles of the scale component present in the water is increased, and they repel each other. It does not adhere to the wall. The condition of the magnetic field for charging the fine particles varies depending on the size of the fine particles, but the surface charge of all the fine particles can be increased by modulating the frequency and amplitude of the current applied to the solenoid coil. There is no particular limitation on the combination of different types of electrodes used in the method of the present invention, and examples thereof include a combination of an aluminum electrode and a carbon electrode, a combination of a silver electrode and a copper electrode, and the like. The combined heterogeneous electrodes are
Since it is preferable that there be no bubbles and no air pockets in the water, it is preferable to install the cooling water system pipe at a position where the pipe is vertical and the water flows upward from below. When water flows between the combined heterogeneous electrodes, a minute voltage of 1 V or less is generated,
An ultra-low current of μA or less flows, and water molecules are ion-activated and polarized. The scale components such as calcium, magnesium and silicic acid are sequestered by the hydration energy of the polarized water molecules. As a result, the crystallization of the scale is suppressed, the particles are dispersed in the form of amorphous fine particles, and the adhesion of the scale is prevented.

The metal eluting apparatus used in the method of the present invention is not particularly limited. For example, an apparatus for eluting metal ions by electrolyzing a metal electrode of aluminum, iron, zinc or the like in a circulating water by an external power supply, A device in which a carbon electrode is arranged at the counter electrode and short-circuited through a variable resistor to elute metal ions can be used. Examples of the ceramic ball used in the method of the present invention include a composite porous ceramic ball obtained by sintering and magnetizing a ceramic containing a positive magnetic compound and a diamagnetic compound. The installation position of the ceramic ball is not particularly limited. For example, the ceramic ball can be immersed in a pit of a cooling tower. In order to have the electromagnetic wave function, the ceramic ball generates oxygen ions and negative metal ions, finely clusters water, and prevents scaling of positive metal ions of scale components such as calcium and magnesium. Furthermore, the scale which has already adhered can be softened and peeled off.

[0008] The sludge removing apparatus used in the method of the present invention is not particularly limited, and examples thereof include a filtration apparatus and a sedimentation tank. One of these sludge removing devices can be used alone, or two or more thereof can be used in combination. It is preferable that the sludge removing device is installed by providing a bypass line in a cooling water system pipe. When a scale prevention treatment device is used, the scale component is suspended in water and sludges without adhering to the wall surface of the device, and can be removed using a sludge removal device. Examples of the filtration device used in the method of the present invention include, for example, a filtration device using a filter medium such as anthracite, sand, silica sand, gravel, activated carbon, and plastic, a filtration membrane such as a microfiltration membrane, an ultrafiltration membrane, and a reverse osmosis membrane. The membrane filtration device to be used can be mentioned. If the suspension is likely to settle out with large particles, or if the concentration of the suspension is high, it is preferable to provide a settling tank and use it in combination with a filtration device.

The slime preventing device used in the method of the present invention is not particularly limited, and examples thereof include an oxidizing agent generating device by electrolysis.
For example, chlorine, hydrogen peroxide, ozone, and the like can be given. In the electrolysis, cooling water can be directly electrolyzed, or water of another system can be electrolyzed and the water can be passed to the cooling water system. When the cooling water is directly electrolyzed, the type of electrode immersed in cooling tower pits is good in terms of simplicity, but the amount of oxidant generated is measured and the performance of the device is reliably managed while grasping the performance of the device. For this purpose, it is preferable that the electrode is of a water-passing type in which the electrode is housed in a casing through which cooling water can pass. In the method of the present invention, when chlorine is generated by electrolysis, a pair of electrodes including an anode and a cathode is immersed in cooling water containing chloride ions, and a DC voltage is applied between the terminals of these electrodes using an external power supply. Apply. As a result, chloride ions in the cooling water are oxidized on the surface of the anode, generating chlorine-based chemical species having oxidizing power, such as hypochlorite ions, and when hypochlorite is added to the cooling water. Similarly, slime can be prevented.

In this case, the material of the electrode is not particularly limited, but an electrode such as titanium, stainless steel, aluminum or silver can be used as the cathode. Further, as the anode, an electrode in which a metal material is coated with a simple substance or oxide of a platinum group element can be used. Examples of the platinum group element include ruthenium, rhodium, palladium, osmium, iridium and platinum, and among them, platinum, iridium and ruthenium can be particularly preferably used. By using an electrode coated with a simple substance or an oxide of a platinum group element for the anode, the generation efficiency of the oxidizing agent can be improved by the catalytic action of the platinum group element. The cathode and anode can be different materials, or they can be the same material. Further, the voltage applied to the electrode is not particularly limited,
V is preferred. If the voltage is less than 1 V, the generation efficiency of the oxidizing agent may be reduced. Voltage is 40V
If it exceeds, danger to the human body may occur.
Further, it is preferable to control the intensity of the current such that the concentration of the oxidizing agent becomes a predetermined value while measuring the concentration of the oxidizing agent in the cooling water. For example, when the water quality of the cooling water fluctuates greatly, stable maintenance can be achieved by adding a system that automatically controls the intensity of the current based on the measured value of the oxidant concentration. In the method of the present invention, when hydrogen peroxide is generated by electrolysis, oxygen is supplied to the cathode using an electrolytic cell using a porous gas diffusion electrode or a gas-liquid mixed electrolytic cell in which an oxygen-containing gas is blown into the cathode portion. To generate hydrogen peroxide, and the generated hydrogen peroxide is dissolved in cooling water to prevent slime. In the method of the present invention, when ozone is generated by electrolysis, slime can be prevented by generating ozone from oxygen in the atmosphere by silent discharge and dissolving it in cooling water. According to the method for treating cooling water of the present invention, despite the fact that no chemical is used, it is comparable to the conventional method using a scale inhibitor such as a polymer and a slime inhibitor such as a hypochlorite. In addition, the generation of scale and slime in the cooling water system can be prevented.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In Examples and Comparative Examples, the effect of preventing scale adhesion was evaluated using a circulating cooling water system having a pilot-scale heat exchanger. The cooling water system used had a water holding volume of 300 L and an outer diameter of 19 L.
0.3 mm heat transfer area with SUS304 tube
A 2 m ² heat exchanger is provided. Calcium hardness 50mgC
aCO ₃ / L, city water having a chloride ion concentration of 10 mgCl / L as makeup water, and a circulating cooling water flow rate of 1,680 L / h.
The 5-fold concentration operation was performed for 30 days. The temperature at the heat exchanger inlet of the circulating cooling water was maintained at 30 ° C., and the temperature at the heat exchanger outlet was maintained at 50 ° C. After the operation for 30 days, the tube of the heat exchanger was removed, dried and weighed, and the scale deposition rate was calculated from the weight difference before and after the test. In addition, for three days from the 20th day to the 23rd day after the start of operation, the cooling tower pit was 75mm x 25mm.
3 x 1.5 mm rubber plates were immersed and the slime that had adhered and grown was collected and dried at 105 ° C until a constant weight was obtained.
The slime deposition rate was determined from the average value of the measured weights. As the permanent magnet, a magnet unit (nominal diameter: 1.5 inches) of DNA Magtec Japan Co., Ltd. was used, and was mounted on the upstream side immediately adjacent to the heat exchanger. The metal elution apparatus used an external power supply for a pair of aluminum electrodes, and applied 10 mA between the electrodes. As the membrane filtration device, a filtration device provided with a microfiltration membrane having a membrane area of 3 m ² was used. The sedimentation tank is provided with a cooling water bypass line installed, and the bypass line has 300 L of cooling water /
h. For chlorine, an electrolytic cell provided with two titanium electrodes coated with platinum in a bypass line was provided, and a direct current of 3 A was used.
To generate hypochlorite ions. Hydrogen peroxide was added to the cooling water by using an electrolytic cell having a porous gas diffusion electrode and applying a current of 15 A between the electrodes to generate hydrogen peroxide.

Example 1 A permanent magnet was used as a scale prevention treatment device, a membrane filtration device was used as a sludge removing device, and a chlorine generator was used as a slime prevention device, and the system was operated for 30 days. The scale deposition rate was 5 mg / cm ² / month, and no slime was deposited. Example 2 A metal elution device was used as a scale prevention treatment device, a membrane filtration device was used as a sludge removal device, and a chlorine generation device was used as a slime prevention device. Scale does not adhere, slime deposition rate 1mg / dm ² / 3day
Met. Example 3 A metal elution device was used as a scale prevention treatment device, a sedimentation tank was used as a sludge removal device, and a chlorine generator was used as a slime prevention device. The scale deposition rate was 2 mg / cm ² / month, and the slime deposition rate was 4 mg / dm ² / 3day. Example 4 A metal elution device was used as a scale prevention treatment device, a membrane filtration device was used as a sludge removal device, and a hydrogen peroxide generator was used as a slime prevention device, and the system was operated for 30 days. The scale deposition rate was 3 mg / cm ² / month and the slime deposition rate was 2 mg / dm ² / 3day.

Comparative Example 1 Sludge removal without using a scale prevention treatment device
Membrane filtration device as device, chlorine generation as slime prevention device
The raw devices were combined and operated for 30 days. Scale
The attachment speed is 28mg / cm^Two/ Month with slime
No dressing occurred. Comparative Example 2 Scale prevention treatment without using a sludge removing device
Metal elution device as device, chlorine as slime prevention device
The generator was combined and operated for 30 days. Scale
10mg / cm^Two/ Month with slime
The wearing speed is 8mg / dm^Two/ 3day. Comparative Example 3 Scale prevention treatment without using a slime prevention device
Metal elution device as device, membrane filter as sludge removal device
The operation was performed for 30 days in combination with the filtration device. Scale
1mg / cm^Two/ Month, slime deposition speed
The degree is 15mg / dm ^Two/ 3day. Comparative Example 4 20 mg of polymaleic acid as a scale inhibitor in cooling water
/ L, sodium hypochlorite as anti-slime agent
mg / L was added and the operation was performed for 30 days. Scale adhesion
Speed is 2mg / cm^Two/ Month, slime adheres
Did not. Comparative Example 5 Scale prevention treatment device, sludge removal device and slime
Do not use any of the protective devices and do not add drugs.
I ran for 30 days. 93 mg scale deposition rate
/cm^Two/ Month and the slime deposition rate is 43mg / dm^Two
/ 3day. Results of Examples 1-4 and Comparative Examples 1-5
Are shown in Table 1.

[0014]

[Table 1]

As shown in Table 1, in Examples 1 to 4 in which a scale prevention treatment device, a sludge removal device and a slime prevention device were combined, no chemical was used, but the scale deposition speed, slime deposition Both the speeds were slow, and a scale prevention effect and a slime prevention effect almost equivalent to those of the prior art of Comparative Example 4 in which the polymer and hypochlorite were added were obtained. On the other hand, in Comparative Example 1 in which no scale prevention treatment device was used, the scale deposition speed was high, and in Comparative Example 3 in which no slime prevention device was used, the slime deposition speed was high. Further, even though the scale prevention treatment device and the slime prevention device were used, in Comparative Example 2 having no sludge removal device, both the scale deposition speed and the slime deposition speed were relatively high. It is considered that due to the presence of the turbid matter, scale and slime adhered in a mixed state with the slime, and the prevention effect became insufficient.

[0016]

According to the method for treating cooling water of the present invention, scale prevention and slime prevention can be simultaneously achieved without using any chemicals.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01D 24/02 C02F 1/44 E C02F 1/44 1/46 Z 1/46 1/48 A 1/48 1/50 510C 1/50 510 510D 520K 520 531M 531 531Q 531R 540B 540 560E 560 560F 560G 1/72 Z 1/72 1/78 1/78 5/08 B 5/08 F25B 43/00 V F25B 43/00 B01D 23/14 F28F 19/01 23/16 23/10 Z F28F 19/00 501A 501B (72) Inventor Tetsuro Sakamura F-term in Kurita Kogyo Co., Ltd. 4D006 GA03 GA06 GA07 HA41 KA01 KA71 KB01 KB02 MA03 PB07 PC80 4D041 BB02 BB03 BB04 BB06 CA04 CA07 4D050 AA08 AB06 BB02 BB04 BB09 CA09 CA10 CA11 CA15 4D061 DA05 DB02 DB05 EA02 EA18 EB01 EB04 EB14 EB17 EB27 EB28 EB29 EB31 EC01 EC05 EC11 EC18

Claims (5)

[Claims] 1. A method for treating cooling water, comprising treating a cooling water in a cooling water system by combining a scale prevention treatment device, a sludge removal device and a slime prevention device. 2. The cooling water treatment method according to claim 1, wherein the scale prevention treatment device is a permanent magnet, a solenoid coil type magnet, a combination of different types of electrodes, a metal elution device, or a ceramic ball. 3. The method for treating cooling water according to claim 1, wherein the sludge removing device is a filtering device or a settling tank. 4. The method for treating cooling water according to claim 1, wherein the slime preventing device is an oxidizing agent generating device by electrolysis. 5. The method according to claim 4, wherein the oxidizing agent is chlorine, hydrogen peroxide or ozone.