JP2001327994A - Apparatus for treating open circulating cooling water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion in an open circulating cooling water system by the reduction of the concentration of corrosion-proof ions, the rising of pH and the concentration of corrosive anions in the system, in preventing the adhesion of scale of the system by calcium carbonate precipitation type scale preventing technique. SOLUTION: An apparatus for treating open circulating cooling water has a means 5 for precipitating calcium carbonate in cooling water to prevent the adhesion of calcium carbonate scale and an anion exchange means 6 for exchanging corrosive anions in cooling water with corrosion-proof anions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an open circulating cooling water treatment apparatus for preventing scale from adhering to an open circulating cooling water system and preventing corrosion in the system.

[0002]

2. Description of the Related Art In an open-circulating cooling water system, the concentration of salts in make-up water increases as water is circulated and the concentration increases, and scale components such as calcium carbonate and silica are transferred to tubes of a heat exchanger. Adhesion causes heat transfer inhibition and deposits in the system, causing various obstacles.

Conventionally, as a technique for preventing calcium carbonate scale from adhering to a heat exchanger, a method of giving magnetism to an aqueous system using a permanent magnet or a solenoid coil type magnet, and elution of metal ions into an aqueous system using an electrode in which different metals are combined are used. There is known a so-called calcium carbonate precipitation-type scale prevention technique such as a method of immersing a ceramic ball in an aqueous system. In the calcium carbonate precipitation-type scale prevention technology, calcium carbonate is precipitated as crystals in the system and suspended in an aqueous system, so that even in a highly concentrated system in which scale prevention is difficult with a scale dispersant such as a low molecular weight polymer, Since scaling of calcium carbonate can be prevented and the problem of scale adhesion can be eliminated, high-concentration operation of the cooling water system becomes possible.

[0004]

However, according to the conventional calcium carbonate precipitation-type scale prevention technology, calcium ions, carbonate ions, and hydrogen carbonate ions in the system due to precipitation of calcium carbonate crystals (these ions act on the metal surface). Is an anticorrosive ion that prevents corrosion.)
As a result, there is a problem that the base material of piping and equipment in the system is easily corroded.

[0005] Particularly, in a cooling water system in which high concentration operation is performed, corrosion is further promoted because corrosive anions such as chloride ions and sulfate ions are concentrated while these anticorrosive ions are reduced. Therefore, there is a problem that the service life of the piping, the heat exchanger, and the like is shortened due to corrosion.

The present invention solves the problems of the calcium carbonate precipitation-type scale prevention technology, and provides an open-circulating cooling water treatment apparatus that prevents scale trouble in an aqueous system and also prevents corrosion trouble. The purpose is to do.

[0007]

According to the present invention, there is provided an apparatus for treating open-circulating cooling water, comprising means for preventing calcium carbonate scale from adhering by depositing calcium carbonate in the cooling water, and removing corrosive anions in the cooling water. It has an anion exchange means for performing ion exchange with the anticorrosive anion.

[0008] In the apparatus for treating open circulation cooling water of the present invention,
By using a combination of means for precipitating calcium carbonate to prevent adhesion of calcium carbonate scale and anion exchange means for ion-exchanging corrosive anions into anticorrosive anions, scale obstacles and corrosion disorders are prevented.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an apparatus for treating open circulation cooling water according to the present invention;

FIG. 1 is a system diagram showing an embodiment of an apparatus for treating open circulation cooling water of the present invention.

In this open circulating cooling water system, circulating cooling water is supplied from a cooling tower 1 to a heat exchanger 3 by a circulating pipe 2 having a pump P, and return water is returned to the cooling tower 1 from a pipe 4. The circulation pipe 2 is provided with a calcium carbonate scale preventing device 5, and the makeup water introduction pipe 7 is provided with an anion exchange tower 6. 8 is a blow pipe.

In the present invention, for example, the following can be used as the calcium carbonate deposition type scale prevention device 5, and two or more of these may be combined. Means for giving magnetism to circulating water by permanent magnets or solenoid coil type magnets. Means for allowing metal ions such as aluminum to be present in circulating water. Means for dissolving metals such as aluminum by short-circuiting different metals, for example. Means for placing ceramic balls in circulating water.

[0013] On the other hand, the anion exchange column 6, OH ^- and HC
O ₃ ^- anion exchange resin anticorrosive anion by ion exchange carrier, such as, packed column specifically filled with HCO ₃ form or OH type anion exchange resin is used.

As shown in FIG. 1, make-up water is supplied to the anion exchange tower 6.
Treated to make Cl in makeup water⁻, SO ₄ ^2-Etc.
Neon to OH⁻, HCO₃ ⁻Ion to anticorrosive anions such as
After the heat exchange, it is introduced into the cooling tower 1,
Prevents the concentration of corrosive ions and prevents corrosion.
With the introduction of, corrosion in the system can be effectively prevented.

[0015] Further, by providing a scale prevention device 5 in the circulating water system to precipitate calcium carbonate and make it float in water, it is possible to effectively prevent adhesion failure of calcium carbonate scale.

FIG. 1 shows an example of an embodiment of an open-circulating cooling water treatment apparatus according to the present invention, and the present invention is not limited to the illustrated ones unless it exceeds the gist thereof. is not.

For example, the scale prevention device 5 may be provided directly on the circulation pipe of the cooling water, or a bypass pipe may be provided on the circulation pipe, and a process may be performed on a part of the circulating water passing through the bypass pipe. good. However, from the viewpoint of the scale prevention effect, as shown in the figure, it is preferable to provide the scale prevention device 5 directly in the circulation pipe to treat the entire amount of the circulating water.

The anion exchange tower 6 may be provided in a circulation pipe or a bypass pipe provided in the circulation pipe in addition to the supply water supply pipe, and an anion exchange may be performed on all or a part of the circulating water.

The type of the anion exchange column is not particularly limited, and may be a packed bed type, a fluidized bed type, or the like. Further, even water flow conditions anion exchange column is not particularly limited, in the present invention, the anion exchange treatment, Cl in the cooling water system ^-, the total concentration of SO ₄ ^2-corrosive anion is 5ppm or less It is preferable to perform the anion exchange treatment as described above.

The means for exchanging corrosive ions for anticorrosive anions is not limited to a means for treating the anion exchange tower by passing makeup water and / or circulating water therethrough. The method of treating by passing water through a tower is the most simple and industrially advantageous.

Further, in the present invention, a water-soluble polymer which does not inhibit the precipitation of calcium carbonate such as a nonionic or cationic low molecular weight polymer or a copper anticorrosive such as a triazole is added to the cooling water system. good.

By adding such a water-soluble polymer, it is possible to stabilize the suspended state of the precipitated calcium carbonate to prevent sludge from accumulating in the aqueous system and to effectively prevent silica scale from adhering. Can be. Further, in the presence of a low molecular weight polymer, Ca ²⁺ and HCO ₃ ^−, which are anticorrosive ions, form a uniform precipitation film of CaCO _{3 on} the metal surface and prevent diffusion of dissolved oxygen which is a factor of promoting corrosion. This makes it possible to more reliably prevent corrosion.

In this case, the water-soluble polymer to be added may be any one which does not inhibit the precipitation of calcium carbonate. For example, the following cationic water-soluble polymer or nonionic water-soluble polymer having a molecular weight of 500 to 100 , 0
00, especially about 1,000 to 20,000. One of these water-soluble polymers may be used alone, or two or more thereof may be used in combination. (Cationic polymer) polyvinylamine, polyethyleneimine (nonionic polymer) polyacrylamide, polyvinyl alcohol, polyethylene oxide, polyvinylformamide, polyvinylpyrrolidone, silicone oil It is not suitable for the present invention because it is not adsorbed and cannot effectively exhibit the scale prevention effect.

If the concentration of such a water-soluble polymer is too low, a sufficient effect cannot be obtained, whereas if it is too high, the cost of the drug rises. Therefore, the concentration in the circulating water is 1 to 100 mg / L. , Particularly preferably in the range of 5 to 50 mg / L, especially 10 to 30 mg / L.

On the other hand, examples of the anticorrosive include inorganic phosphates (normal phosphates and polymerized phosphates), organic phosphates, phosphonic acids, zinc, nickel salts, tungstates, molybdenum hydrochloride, nitrite, borates and the like. Corrosion inhibitors such as acid salts, silicates, oxycarboxylates, benzotriazole, and mercaptobenzothiazole.

In the present invention, a scale inhibitor such as lignin derivatives, tannic acids and polysaccharides such as starch may be used in combination. Further, a slime control agent may be used in combination.

[0027]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 An experiment was conducted to examine the scale and the state of occurrence of corrosion by the open-circulating cooling water treatment apparatus shown in FIG.

As the scale preventing device, those shown in Table 1 were used, and as the anion exchange tower, a strong basic anion exchange resin ("Diaion SA20" manufactured by Mitsubishi Chemical Corporation) was used.
A)) HCO adjusted by packing 1 L into an acrylic column having an inner diameter of 38 mm and a length of 1000 mm, regenerating with a 5% NaHCO ₃ aqueous solution to form HCO ₃ and washing with water.
_{A type 3} anion exchange tower was used.

The treated water pipe obtained by passing Atsugi-shi water through the HCO type ₃ anion exchange tower is as follows:
By using the water subjected to the anion exchange treatment in this way as makeup water, Cl ⁻ ions and SO ₄
The total concentration of ^2- ions was kept below 1 ppm.

[Treated water quality] pH: 7.8 Calcium hardness: 40 mg-CaCO ₃ / L M alkalinity: 80 mg-CaCO ₃ / L Silica: 25 mg-SiO ₂ / L Cl ⁻ + SO ₄ ^2- : 1 mg / L The apparatus was continuously operated under the following operating conditions, and the corrosion loss of the test piece (SPCC) installed in the water system after one month was examined. The results are shown in Table 1.

Also, one month later, the presence or absence of scale attached to the filler in the cooling tower was examined. The results are shown in Table 1.

[Operating conditions] Retained water volume: 300 L Circulating water volume: 20 L / min Blow water volume: 4.6 L / hour Replenishment water volume: 46 L / hour Flow rate: 0.5 m / sec Concentration magnification: 10 times Heat exchanger inlet water temperature: 30 ℃ Heat exchanger outlet water temperature: 50 ° C (steam heating) Water temperature difference Δt: 20 ° C

Comparative Examples 1 and 2 In Examples 1 and 2, except that the anion exchange tower was not provided and the anion exchange treatment of the makeup water was not carried out, the same operation was carried out to determine whether corrosion loss and scale adhesion were present. And the results are shown in Table 1.

[0035]

[Table 1]

As is clear from Table 1, scale failure is prevented in each of Examples and Comparative Examples. However, in Examples 1 and 2 in which anion exchange treatment was performed, compared to Comparative Systems 1 and 2, metal scale was reduced. Corrosion weight loss is extremely low, and good corrosion prevention results are obtained. This indicates that the combined use of the anion exchange treatment can significantly extend the life of metals such as pipes.

[0037]

As described above in detail, according to the apparatus for treating open circulation cooling water of the present invention, scale failure and corrosion failure of the open circulation cooling water system can be effectively prevented, and high concentration operation can be performed for a long period of time. It is possible to continue stably throughout.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of an apparatus for treating open circulation cooling water of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cooling tower 3 Heat exchanger 5 Scale prevention device 6 Anion exchange tower

Claims (1)

[Claims] 1. An apparatus for treating open-circulation cooling water, comprising: means for preventing calcium carbonate scale from adhering by precipitating calcium carbonate in said cooling water; An open-circulating cooling water treatment apparatus, comprising: