JP2005046809A - Scale prevention apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scale prevention apparatus capable of stably preventing scale deposition composed essentially of metal ions of calcium and magnesium etc. or silica which are dissolved in water to be treated. <P>SOLUTION: One sheet of large-sized flat plate anode 11 and four sheets of small-sized flat plate cathodes 12a-12d are arranged oppositely to each other in a chamber 4. These electrodes are arranged in such a manner that the cathode on the downstream side in the water passage direction comes nearer to the anode 11 as compared to the cathodes on the upstream side. The water is electrolyzed and fine particles of carbonate salt of the metal ions in the cathodes 12a-12d are produced. A scale prevention component such as mellitic acid is produced by oxidation reaction in the vicinity of the anode 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for preventing scale generated in a cooling water circulation line, a boiler line or the like in a factory or a building.

  Heat exchangers in open circulation cooling water lines such as cooling towers, boiler towers in boiler towers such as cooling towers and piping, or once-through boilers are mainly composed of metal ions such as calcium and magnesium or silica contained in water. Scales may adhere, resulting in a decrease in heat transfer efficiency, blockage of piping, and the like.

  In order to prevent this scale adhesion, more types of scale preventive agents have been used than before. Recently, devices that prevent scale by applying an electric or magnetic field have been developed and sold.

  Japanese Patent No. 2912809 describes a method of preventing scale generation by treating boiler water with electric and magnetic fields.

In Japanese Patent Publication No. 2001-502229, a pair of electrodes made of graphite is disposed in a cylindrical container, and conductive particles made of a carbonaceous material such as graphite, silica, glass, and plastic are disposed between the electrodes. A method is described in which scale formation is reduced by mixing and filling non-conductive particles such as water and passing water through a cylindrical container while energizing between the electrodes. According to the description of the same issue, alkali is generated by this energization treatment, crystal nuclei are generated by this alkali (page 12, lines 17-18), and the scale generation tendency decreases (page 7, lines 5-6). ).
Japanese Patent No. 2912809 Special table 2001-502229 gazette

  Scale can be prevented by adding an appropriate amount of appropriate chemicals to the open circulating cooling water line or boiler line, but the concentration of circulating water or boiler can water can be accidentally operated above the specified level, or vice versa. If the engine is operated at a significantly lower concentration than specified, or if the load on the heat exchange side is larger than specified, the scale may adhere to the heat exchange section where the temperature is high or the cooling tower where water evaporates. This is because if the operation is continued under the condition exceeding the above-mentioned regulation, it will deviate from the scale prevention ability range of the added drug. In order to avoid such a situation, it is only necessary to always add a drug that can cope with an operating condition such as a high load. However, the cost of the drug becomes enormous and is difficult in practice.

  Furthermore, when the raw water quality is very high, such as calcium hardness, silica, total iron concentration, etc., or when the heat load is high, such as a resin polymerization reaction tower, the currently available anti-scale agents may not be applicable. is there.

  In the apparatus for applying an electric field and a magnetic field of the above-mentioned Japanese Patent No. 2912809, since the scale prevention mechanism is hardly clarified, there is a possibility that scale prevention is insufficient.

  According to the method of JP-T-2001-502229, as the water flow continues, the carbonaceous material particles are selected from the mixed packed bed of the particles made of the carbonaceous material filled between the electrodes and the non-conductive particles. Wears down and the particle size decreases. And for this reason, the particle | grain space | interval of a packed bed becomes small and water flow resistance increases.

  Therefore, the present applicant has previously proposed scale prevention devices that can solve such problems (Japanese Patent Application Nos. 2003-066184, 2003-061815, and 2003-100526).

  This scale prevention device exhibits an excellent scale prevention effect over a long period of time, but it is desirable that practically the scale prevention effect can be exhibited more efficiently.

  Accordingly, as a result of various studies on the growth mechanism of the scale by the present inventors, the scale is deposited with carbonates such as calcium carbonate and magnesium in the circulating water, which grows and deposits on or adheres to the inner surface of the device. Therefore, if a high pH region is formed on the cathode side in the electrolysis and the scale component is generated in advance as fine particles, and this is rapidly processed by the scale preventing component to maintain the fine particles, It has been found that even if the hardness component in the circulating water is supersaturated, the fine particles do not grow and do not become scale.

  This invention is made | formed in view of the said subject, and aims at providing the scale prevention apparatus which exhibits the scale prevention effect efficiently over a long period of time.

  The scale prevention apparatus of the present invention is a scale prevention apparatus for preventing scale deposition from water, comprising an electrode comprising an anode and a cathode, and means for applying a voltage between the electrodes, at least the cathode being in the direction of water flow. A plurality of the cathodes are arranged in multiple stages apart from each other, and the cathode is different from the cathodes in the other stages in the arrangement position in the direction perpendicular to the water flow direction. In the present invention, “prevention” includes “suppression”.

  In the apparatus of the present invention, when water is passed between the anode and the cathode, water is electrolyzed and the vicinity of the cathode becomes a high pH, and in the vicinity of the cathode, carbonic acid such as calcium or magnesium dissolved in the water is dissolved. Salt fine particles are generated, and scale precipitation from water is sufficiently prevented.

  That is, in the apparatus of the present invention, a high pH region is formed near the cathode. When the water passes through this region, carbonates mainly of metal ions such as calcium and magnesium contained therein are deposited. By generating a large amount of the fine particles of the scale component in the water in advance, the solubility calcium hardness in the circulating water is lowered, and the heat exchange part and the cooling tower can pass with less than the solubility, and the scale is formed in the heat exchange part and the cooling tower. It does not precipitate. The generated fine particles of the scale component circulate in the line along the water flow, but do not deposit on the inner surface of the apparatus, and are eventually discharged out of the line together with the blow.

<Mechanism for preventing scale by precipitation of fine particles>
The mechanism for preventing scale by fine particle precipitation in the present invention will be described in detail below based on the theory of scale precipitation from water.

(I) In general, the mechanism of scale precipitation from water (mechanism) is as follows.
As the water temperature increases, the solubility of carbonates such as calcium carbonate decreases. In the heat exchange part of the cooling water system or boiler water system, if the surface temperature is high and the solubility in that part is smaller than the concentration of carbonate such as calcium carbonate in circulating water or can water, that is, if it becomes supersaturated, this high temperature Scale deposits in the heat exchange section. Even if a scale-preventing agent is used, the ability to prevent scale per unit mass of the agent has been determined, and abnormal line management was performed for some reason, resulting in a carbonate concentration such as calcium carbonate in circulating water that exceeded this limit. In this case, the scale is deposited in the high temperature heat exchange part by the same mechanism.

  The filler part of the cooling tower of the circulating cooling water system has a structure that evaporates water in order to reduce the temperature of the circulating water. When water evaporates, the concentration of carbonate such as calcium carbonate in the circulating water increases, and when the concentration reaches a supersaturated state with a solubility or higher, scale is deposited on the filler. Moreover, in the filler part, in order to evaporate water efficiently, the flow-down speed of circulating water is made slow, and a scale tends to deposit on a filler.

(Ii) In the scale prevention apparatus of the present invention, the dissolved calcium hardness in water is reduced by electrolyzing water (hereinafter sometimes referred to as water to be treated) to form fine particles of metal carbonate. , Prevent scale precipitation.

  In general, the solubility of carbonates such as calcium carbonate and magnesium carbonate is affected by pH, and the solubility decreases as the pH increases.

  When the water to be treated is electrolyzed using the apparatus of the present invention, the pH in the vicinity of the cathode becomes high pH, and carbonates of metals such as calcium and magnesium in the water to be treated are deposited in the vicinity of the cathode. These precipitated fine particles circulate in the line along the flow of cooling water and boiler water, and are discharged to the outside of the line along with the blow, so the concentration of hardness components such as calcium and magnesium in the cooling water and boiler system decreases, Scale deposition in the heat exchange section and cooling tower is prevented.

  For example, in the case of the calcium carbonate component, a sufficient number of scale component fine particles are generated, so that the soluble calcium hardness in the circulating water is lowered, and the soluble calcium hardness component concentration is less than the solubility even in the heat exchange section and the cooling tower. Thus, scale deposition in the heat exchange section and cooling tower is prevented.

  In the present invention, the cathodes are arranged in multiple stages in the water passing direction, and the positions of the cathodes in each stage in the direction perpendicular to the water passing direction are different. (In addition, it is preferable that the positions of the cathodes in all the stages are different in the direction perpendicular to the water flow direction, but in some stages, the positions in the orthogonal direction to the water flow direction of the cathodes may overlap.) By varying the position of the cathode, the fine particles of the scale component are generated over a wide range in the direction perpendicular to the water flow direction, the dissolved calcium hardness in the circulating water is reduced uniformly, and scale precipitation prevention is improved.

<Effect of scale prevention when anode is made of carbonaceous material>
In the present invention, when the anode is made of a carbonaceous material, a chemical component for scale prevention such as melittic acid is generated by an electrolytic reaction at the anode, so that even if the hardness component in water is in a supersaturated region, the generated fine particles are It is prevented from growing excessively and depositing or adhering to the inner surface of the device. The anti-scale agent generated by this anodic reaction and added to the water to be treated is adsorbed by the fine particles. Since the scale component fine particles adsorbing the scale preventive agent hardly grow even when exposed to a supersaturated state in a heat exchange section, a cooling tower or the like, the fine particles exist in the circulating water as fine particles and are discharged out of the line together with the blow.

  In order to allow the scale-preventing drug component and the scale component fine particles to efficiently associate with each other, in the stage adjacent to the water flow direction, on the downstream side of the upstream stage electrode, on the downstream side of the water flow direction. It is preferable to arrange the electrodes at the opposite potential of the steps. That is, the cathode of the next stage is arranged downstream of the anode of a certain stage, and the anode of the next stage is arranged downstream of the cathode of a certain stage. In particular, it is preferable to arrange the anode of the next stage downstream of the cathode of the upstream stage. By comprising in this way, the chemical | medical component for scale prevention comes to adsorb | suck efficiently with respect to the scale component microparticles | fine-particles produced | generated by the cathode vicinity, and the scale prevention effect improves.

<Electrolytic substance with scale-inhibiting action produced by reaction at anode>
The electrolytic substance produced by the electrolytic reaction at the anode contains an aromatic carboxylic acid.

  It is known that higher-order carboxylic acids having a large number of carboxyl groups have a scale-dispersing effect, and among them, benzenehexacarboxylic acid (mellitic acid) has been reported to be effective as a scale-preventing agent (The Inhibition of Dicalcium Phosphate Dihydrate Crystal Growth by Polycarboxylic Acids Z. AMJAD Journal of Colloid and Interface Science, Vol. 117, No. 1, May 1987).

  In particular, by using a carbonaceous material having a six-membered ring structure as the carbonaceous material as the anode material and anodizing it in water, an aromatic carboxylic acid can be produced inexpensively and efficiently.

  The carbonaceous material having a six-membered ring structure constituting the anode is preferably a carbonaceous material having a six-membered ring network plane three-dimensionally laminated and having a carbon content of 80% or more. In particular, in order to produce higher-order carboxylic acids such as melittic acid, it is desirable that the condensation rate of the surface layer is higher. Moreover, if a carbon content rate is high, there exists an advantage that a by-product is hard to produce | generate, and it is preferable. As such a carbonaceous material, graphites such as graphite, calvin, coke, charcoal, activated carbon, anthracite, carbon black, and the like can be used. The electrode may be composed of the carbonaceous material near the surface.

  When this six-membered ring-structured carbonaceous material is subjected to an electrolytic reaction using an anode, aromatic carboxylic acids such as various benzene carboxylic acids can be easily generated using mellitic acid as a main product. This product usually contains 30-50% of melittic acid based on the total organic carbon content. In addition, benzenecarboxylic acids having one or more carboxyl groups in the benzene ring, condensation of naphthalene, phenanthrene, etc. Aromatic carboxylic acids having one or more carboxyl groups in the ring are included.

  The cathode material is not particularly limited. However, in the present invention, as described later, it is preferable to perform pole reversal, and therefore, the cathode is preferably composed of a carbonaceous material similar to the anode.

  The shape of the anode and the cathode is not particularly limited, but a flat electrode arranged facing each other is preferable for reducing the pressure loss in the electrolytic cell.

  In one aspect of the present invention, the anode is composed of only one flat plate, and a plurality of plate-like cathodes are arranged in multiple stages so as to face the anode, and the cathode is arranged in a direction perpendicular to the water flow direction. The positions are configured to be different at each stage.

  In this case, since the distance between the electrodes is different in each stage, a correction resistor may be provided in each circuit so that the voltages between the electrodes in each stage are equal.

  In another embodiment of the present invention, the anode and the cathode are separated in each stage. In this case, it is preferable that the distance between the electrodes in each stage is the same, and the water flow direction and the orthogonal direction of the anode and the cathode are different in each stage. Thereby, it becomes possible to generate scale component fine particles and scale preventive drug components uniformly.

  In this case, as described above, in the adjacent stage, it is preferable to dispose the electrode having the opposite potential of the next stage on the downstream side of the electrode of the upstream stage.

  The applied voltage between the electrodes is preferably 1.3 V or more, particularly about 5 to 30 V. This voltage may be either alternating current or direct current, and may be an alternating current, but it is preferable from the viewpoint of generation efficiency to apply the voltage so that the current flows in the same direction for 10 minutes or more, more preferably for 1 hour or more. .

  In addition, it is preferable to reverse the polarity from the viewpoint of preventing scale failure due to impurities on the cathode surface. In this case, since the generation efficiency decreases when the inversion interval is short, it is desirable to take an inversion interval of 1 hour or more, for example, about 1 to 24 hours.

Although there is no particular limitation on the current value, the amount of electricity input and the amount of melittic acid produced are in a proportional relationship, so it is better to increase the current value in order to increase the production efficiency. However, since there is a limit current density, it is preferable that the range be 5.0 A / dm ² or less.

  ADVANTAGE OF THE INVENTION According to this invention, scale precipitation which has as a main component metal ions, such as calcium and magnesium, and silica which are melt | dissolving in to-be-processed water can be prevented stably.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a schematic longitudinal sectional view of a scale prevention device according to an embodiment.

  A cylindrical chamber 4 is installed between flanges 1a, 3a and 4a between pipes 1 and 3 for passing cooling water, boiler water and the like. In the chamber 4, one large flat plate anode 11 and four small flat plate cathodes 12 a to 12 d are arranged facing each other. A voltage is applied from the power source 7 to the cathodes 12a to 12d and the anode 11 to be energized. Between this cathode 12a-12d and the anode 11, it is the space part for water flow in which a filler does not exist.

  The plate surface of the anode 11 and the plate surfaces of the cathodes 12a to 12d are along the direction of water flow.

  The cathodes 12a to 12d are sequentially arranged in the direction of water flow. The water flow direction and the orthogonal direction of each of the cathodes 12a to 12d are different from each other. In this embodiment, the cathode on the downstream side in the water passage direction is disposed closer to the anode 11.

  In this embodiment, the anode 11 and the cathodes 12a to 12d are made of graphite on which six-membered ring network planes are regularly stacked.

  When electricity is passed between the cathodes 12a to 12d and the anode 11 by the power source 7 while passing through the pipes 1 and 3 to the chamber 4, the vicinity of the cathodes 12a to 12d is alkaline, and the vicinity of the anode 11 is acidic. Become. On the acidic side, oxygen is generated at the same time as the vicinity of the electrode is acidic, and the oxidation of the graphite electrode is promoted. The graphite electrode is decomposed to produce benzene polycarboxylic acid. Since benzene polycarboxylic acids have carboxyl groups like polymaleic acid and polyacrylic acid, which are typical scale preventing agents, they have a scale preventing effect.

  In the high pH region near the cathodes 12a to 12d, fine particles of scale components are generated. Thereby, the soluble calcium hardness in the water taken out from the pipe 3 is lowered, and scale deposition is prevented.

  In particular, in this embodiment, since the water flow direction and the orthogonal direction of the anode 11 are different from each other, the water that passes through the scale prevention device 18 uniformly contains fine particles of scale components.

  In addition, in order to improve the contact efficiency of an electrode and water, it is preferable to set water flow volume so that water flow may become a turbulent flow.

  FIG. 2 is a longitudinal sectional view of a scale prevention device 18A according to another embodiment.

  In this embodiment, instead of the anode 11, four small plate-like anodes 11a to 11d are arranged. Other configurations are the same as those in FIG.

  The anodes 11a to 11d are arranged to face the cathodes 12a to 12d. The distances between the electrodes of the anode 11a, the cathode 12a, the anode 11b, the cathode 12b, the anode 11c, the cathode 12c, the anode 11d, and the cathode 12d are substantially the same.

  The second-stage cathode 12b is disposed downstream of the first-stage anode 11a in the water flow direction, and the subsequent-stage cathodes 12b to 12d are disposed on the downstream side of the upstream-side anodes 11a to 11c. . Each of the cathodes 12b, 12c, and 12d is positioned slightly closer to the upper cathodes 12a, 12b, and 12c than the upper anodes 11a, 11b, and 11c by one stage. For example, the distance (inter-plate distance) between the plate surfaces of the anode 11a and the cathode 12b in the direction perpendicular to the water flow direction is preferably 10 cm or less, particularly about 1 to 2 cm.

  Also in this embodiment, benzene polycarboxylic acid is produced in the vicinity of the anodes 11a to 11d, and scale component fine particles are produced in the cathodes 12a to 12d. Then, the scale component fine particles generated in the cathodes 12a to 12d come into contact with and adsorb benzene polycarboxylic acid generated in the vicinity of the anodes 11a to 11c passing from the upstream side. In this way, the water is efficiently subjected to the scale component prevention treatment.

[Example 1]
The scale preventive device 18 of the present invention shown in FIG. 1 was incorporated in the open system circulating cooling water line shown in FIG.

  A scale prevention device 18 was incorporated in a water storage tank 16 installed under the cooling tower 14 to continuously treat the circulating water. The water in the water storage tank 16 is sent to the double-pipe heat exchanger 20 through the pump 17, is heat-exchanged by the hot water flowing outside the double pipe, is cooled in the cooling tower 14, and is circulated. The water in the water storage tank 16 is circulated through the scale prevention device 18 via the pump 19 and processed.

In addition, the area of the anode 11 of the device 18 was 300 cm ² , the areas of the cathodes 12 a to 12 d were 75 cm ² , and the distance between the anode 11 and the cathodes 12 a to 12 d was 4 cm, 3 cm, 2 cm, and 1 cm, respectively. The applied voltage is about 10 V, the current density is 0.5 A / dm ² (current value is 1.5 A), the inversion frequency is once / Hr, and the water flow rate (linear velocity) is 2.0 m / sec.

The calcium hardness (CaH) and acid consumption (pH 4.8 / MA) of the circulating water are 300 mg / l as CaCO _{3 and the} surface temperature of the heat exchange part is 80 ° C. This is a condition for precipitating on the heat exchange surface. This apparatus was operated for 96 hours with a residence time of circulating water of 24 hours.

[Example 2]
The open system circulating cooling water line was operated in the same manner as in Example 1 except that the scale prevention device 18A of FIG. 2 was used instead of the scale prevention device 18.

  The size of the anodes 11a to 11d was the same as that of the cathodes 12a to 12d. The interelectrode distance was all 15 cm.

[Comparative Example 1]
For comparison, the same operation was performed under the same conditions except that the scale prevention devices 18 and 18A were not operated.

  Table 1 shows the results of water quality analysis. As shown in Table 1, the water quality is maintained in the present invention, and scale precipitation in the system is suppressed.

  Next, Table 2 shows the results of measuring the amount of scale deposited on the heat exchange section.

  As shown in Table 2, according to the scale prevention device of the present invention, scale deposition on the heat exchange part that becomes high temperature is prevented. The energization current value was constant at 1.5 A during the water flow period.

It is a schematic longitudinal cross-sectional view of the scale prevention apparatus which concerns on embodiment. It is a schematic longitudinal cross-sectional view of the scale prevention apparatus which concerns on another embodiment. It is a system flow figure of an open system circulation cooling water line to which the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,3 Piping 7 Power supply 11,11a-11d Anode 12a-12d Cathode 14 Cooling tower 16 Water tank 18 Scale prevention apparatus 20 Double pipe type heat exchanger

Claims (9)

In a scale prevention device that prevents scale deposition from the water,
An electrode comprising an anode and a cathode, and means for applying a voltage between the electrodes,
At least a plurality of cathodes are spaced apart in the direction of water flow and arranged in multiple stages.
The scale prevention device according to claim 1, wherein the cathode is different from the cathode in the other stage in the arrangement position in the direction perpendicular to the water flow direction.   2. The scale prevention apparatus according to claim 1, wherein the cathode has a flat plate shape and is disposed with the plate surface passing through the water.   3. The scale prevention apparatus according to claim 1, wherein the distance between the electrodes at each stage is different.   3. The scale prevention device according to claim 1, wherein the anode and the cathode at each stage are separately provided, and the arrangement positions of the anode and the cathode in the direction perpendicular to the water flow direction are different at each stage.   5. The scale prevention apparatus according to claim 4, wherein the distance between the electrodes at each stage is equal.   The scale prevention apparatus according to any one of claims 1 to 5, wherein the electrode is provided in four or more stages in the water flow direction.   7. In any one of Claims 4 thru | or 6, in the stage adjacent to a water flow direction, the electrode of the opposite electric potential of a downstream stage is located in the water flow direction downstream of the electrode of an upstream stage. The scale prevention apparatus characterized by the above-mentioned.   The scale prevention device according to any one of claims 1 to 7, wherein the anode is made of a carbonaceous material.   9. The scale prevention apparatus according to claim 8, wherein the carbonaceous material has a carbon six-membered ring structure.

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