JP2005211831A - Scale prevention device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scale prevention device which is capable of stably preventing scale deposition and prevents carbonaceous fine particles from being incorporated into treated water. <P>SOLUTION: A cylindrical chamber 4 of this scale prevention device 2 is disposed via flanges 1a, 3a, 4a between pipes 1, 3 for allowing cooling water, boiler water, or the like, to pass therethrough. In the cylindrical chamber 4, electrode chambers 16, 17 and a water flow space 18 between the electrode chambers are formed by a pair of porous membranes 13, 14. An electrode 11 is arranged in the electrode chamber 16 and an electrode 12 is arranged in the electrode chamber 17. The particulate carbonaceous material 20 such as coke is packed in the respective electrode chambers 16, 17. The electrodes 11, 12 are energized by a power source 7. A scale prevention component such as a mellitic acid is produced by anodic oxidation. Because the porous membranes 13, 14 are disposed, fine particles produced upon the production reaction are not incorporated during water passage. <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.

  A heat exchanger in an open circulation cooling water line incorporating a cooling tower, a cooling tower or piping, or a boiler line such as a once-through boiler has a scale mainly composed of metal ions such as calcium and magnesium contained in water or silica. Adhesion may cause reduction 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.

  JP-T-2001-502229 discloses that 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 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 between the electrodes while passing water through a cylindrical container. 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 is reduced (page 7, lines 5-6). ).

Aromatic carboxylic acids having a large number of carboxyl groups are known to have a scale-dispersing effect, and among them, benzenehexacarboxylic acid (mellitic acid) has been reported to be effective as an anti-scale 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).
Japanese Patent No. 2912809 Special table 2001-502229 gazette 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

  Scales can be prevented by adding an appropriate amount of appropriate chemicals to the open circulation cooling water line or boiler line, but the concentration of circulating water or boiler can water can be accidentally operated above the specified level, If the load on the exchange side is larger than specified, the scale may adhere to the heat exchange section that becomes high temperature 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 sufficient to always put in a medicine that can cope with operating conditions such as a high load. However, the cost of the medicine becomes excessive, which is practically difficult.

  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, the conductive carbonaceous material particles filled between the electrodes gradually wear with the passage of water, and the particle size becomes smaller. And for this reason, the particle | grain space | interval of a packed bed becomes small and water flow resistance increases. In addition, the resistance to water flow also increases when dirt components and scale components in water adhere to the surface of the filler. Further, when the height of the packed bed is lowered with the depletion of the conductive carbonaceous material particles, it is necessary to supply a new filler to the packed bed from above in order to compensate for this. In addition, when the carbonaceous material particles are depleted, the resistance value between the electrodes changes. For this reason, it is difficult to stably energize a constant current and pass a constant amount of water, and the scale generation reduction effect tends to be insufficient.

  In addition, in the case of a scale prevention device that generates an aromatic carboxylic acid by anodizing an electrode made of a carbonaceous material, fine particles of the carbonaceous material are generated and mixed in the water to be passed, such as a heat exchanger. It may adhere to the inner surface of equipment and piping and cause various obstacles.

  An object of the present invention is to solve the above-mentioned conventional problems, and to provide a scale prevention device that exhibits a stable scale prevention action over a long period of time and prevents the carbonaceous material fine particles from being mixed into the treated water. .

  The scale prevention device of the present invention (Claim 1) is a scale prevention device for preventing scale deposition from water, at least an electrode whose anode is made of a carbonaceous material, and means for applying a voltage between the electrodes, In the scale prevention device, which comprises a water passage means for passing water between the electrodes, and generates a scale-preventing agent comprising an electrolytic substance by a reaction at the anode, the fine particles of the carbonaceous material generated from the electrodes are disposed between the electrodes. Means for preventing the water from being mixed into the water is provided.

  According to a second aspect of the present invention, the scale prevention apparatus according to the first aspect is characterized in that the means is a filter means.

  According to a third aspect of the present invention, the scale preventing apparatus according to the second aspect is characterized in that the filter means is a porous membrane.

  According to a fourth aspect of the present invention, the scale prevention apparatus according to the third aspect is characterized in that the porous film is a resin film or a ceramic film.

  The scale prevention device according to claim 5 is characterized in that, in any one of claims 2 to 4, the filter means is disposed so as to separate the water passage area between the electrodes and the electrodes. Is.

  The electrolytic substance produced by the electrolytic reaction of the carbonaceous material at the anode contains an aromatic carboxylic acid. Scale generation is prevented by the scale dispersion effect of the aromatic carboxylic acid. Although the carbonaceous material fine particles are generated along with the electrolytic reaction of the carbonaceous material, in the present invention, the carbonaceous material fine particles are prevented from being mixed into the water flow. It is possible to prevent troubles in the piping.

  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 of the scale prevention device 2 is installed between the pipes 1 and 3 for passing cooling water and boiler water through flanges 1a, 3a and 4a. In the chamber 4, electrode chambers 16 and 17 and a water passage space 18 therebetween are formed by a pair of porous membranes 13 and 14. The electrode 11 is disposed in the electrode chamber 16, and the electrode 12 is disposed in the electrode chamber 17. Each electrode chamber 16, 17 is filled with a granular carbonaceous material 20 such as coke. The electrodes 11 and 12 are configured to be energized by the power supply 7.

  For example, when the electrode 11 is used as an anode and the electrode 12 is used as a cathode to conduct electrolysis by the power source 7, the vicinity of the anode 11 becomes acidic and the vicinity of the cathode 12 becomes alkaline. On the acidic side, the vicinity of the electrode is acidic and oxygen is generated, so that the oxidation of the carbonaceous material 20 is promoted. When the carbonaceous material 20 is partially oxidized, an aromatic carboxylic acid such as benzene polycarboxylic acid is generated. Since benzene polycarboxylic acids have carboxyl groups like polymaleic acid and polyacrylic acid which are typical scale inhibitors, they have a scale preventing effect.

  The produced aromatic carboxylic acid is diffused and permeated through the porous membranes 13 and 14 and added to the water in the water flow space 18.

  The vicinity of the cathode 12 is a high pH region, and scale component fine particles are generated in this region. In this high pH region, carbonates mainly of metal ions such as calcium and magnesium contained in water are precipitated. By generating fine particles of this scale component, the concentration of dissolved calcium ions in the circulating water is lowered, it can pass through the heat exchange part and the cooling tower with less solubility, and no scale is deposited on the heat exchange part or the cooling tower. The generated fine particles of the scale component circulate in the line on the water flow, and are discharged out of the line together with the blow.

  In addition, by using a carbonaceous material having a six-membered ring structure as the carbonaceous material, it is possible to generate aromatic carboxylic acid efficiently at low cost.

  As the carbonaceous material having a six-membered ring structure, a carbonaceous material having a six-membered ring network plane three-dimensionally laminated and having a carbon content of 80% or more is preferable. 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. As an electrode, you may use what the surface vicinity is comprised with the said carbonaceous material.

  In addition, since it is preferable to carry out a reversal in this scale prevention apparatus, it is preferable to fill the carbonaceous material 20 in both electrode chambers 16 and 17.

  The electrodes 11 and 12 may be a carbonaceous material as described above. However, when a corrosion-resistant metal material is used, there is no wear of the filler due to operation, and a scale prevention effect can be obtained stably over a long period of time. it can.

  The applied voltage between the electrodes 11 and 12 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. The current value is preferably set so as to prevent the produced aromatic carboxylic acid from becoming difficult to diffuse due to the electrophoresis phenomenon.

  According to the electrolytic reaction at the anode, aromatic carboxylic acids such as various benzenecarboxylic 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.

  Along with the decomposition reaction of the carbonaceous material 20, fine particles of the carbonaceous material are generated, but the porous membranes 13 and 14 prevent the fine particles from entering the water passing space 18.

  As the porous films 13 and 14, a polymer resin film having a pore diameter of 10 to 50 μm and a thickness of 1 to 4 mm is suitable. A ceramic film can also be used, but a polymer resin film is preferred because of its high bending strength.

  The apparatus of the present invention is preferably installed in an open circulating cooling water line as an apparatus for producing chemicals on site. The installation location is not limited at all, and can be applied to both the makeup water line and the circulation line.

[Example 1]
In the apparatus of FIG. 1, the horizontal cross-sectional area of the water flow space 18 is 5 cm ² , and the horizontal cross-sectional areas of the electrode chambers 16 and 17 are 10 cm ² , respectively. Platinum-iridium-coated titanium electrodes (dimensions of 150 × 50 × 2 mm) were used as the electrodes 11 and 12, and 50 g of coke having an average particle diameter of 5 mm was filled in the electrode chambers 16 and 17 as the carbonaceous material 20. As the porous membranes 13 and 14, polyethylene membranes (thickness 2.0 mm) having a pore diameter of 20 μm were used.

The distance between the porous membranes 13 and 14 is 10 mm. The cooling tower cooling water is passed as raw water through the water passing space 18 at a water line speed of 0.1 m / sec, a voltage of 15 V is applied between the electrodes 11 and 12, and a current is supplied at a current density of 1.0 A / dm ^2. Shed. FIG. 2 (a) shows the weight distribution of the carbonaceous material fine particles in the treatment liquid when treated in this way for 24 hours.

[Comparative Example 1]
In the apparatus of FIG. 1, water is passed under the same conditions except that a plastic plate having a hole diameter of 2 mmφ at a pitch of 5 mm is arranged in place of the porous membranes 13 and 14 and fine particles are not removed. The weight distribution of the fine particles in the treatment liquid was measured. The results are shown in FIG. 2 (b).

  As shown in FIG. 2 (b), it can be seen that most of the fine particles produced from coke have a particle size of 10 μm or more. As shown in FIG. 2 (a), according to Example 1, 93% of the fine particles are removed by the porous film.

  In addition, using porous membranes 13 and 14 having different pore diameters, water was passed in the same manner as in Example 1 and Comparative Example 1, and the production rate of aromatic carboxylic acid (gTOC / F) at that time was measured. . The results are shown in FIG. The unit gTOC / F is the amount of TOC generated per input electric amount. The production rate of aromatic carboxylic acid in the case of Comparative Example 1 not using the porous membrane was 0.6 gTOC / F. It is desirable to determine the pore size of the porous membrane so that the diffusion rate is equal to the generation rate. From FIG. 3, it can be seen that a porous membrane having a pore diameter of 10 μm or more does not inhibit diffusion rate limiting. However, as shown in the particle size distribution measurement result of FIG. 2 (a), a very large number of fine particles having a size of 10 μm or more are generated. Therefore, if the pore diameter is increased, a large number of fine particles permeate the porous membrane. Accordingly, it can be said that the pore diameter is preferably 10 to 20 μm.

  When the flow velocity to the film surface is 0, it is affected by electrophoresis rather than diffusion, but it has been found that the diffusion of the film surface is promoted only by applying a flow rate of only 0.013 m / sec, and the diffusion is governed.

It is a schematic longitudinal cross-sectional view of the scale prevention apparatus which concerns on embodiment. It is a particle size distribution map of fine particles generated from a carbonaceous material. It is a graph which shows the relationship between the production | generation rate of aromatic carboxylic acid, and the pore diameter of a porous membrane.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,3 Piping 4 Chamber 7 Power supply 11,12 Electrode 13,14 Porous membrane 16,17 Electrode chamber 18 Water flow space 20 Carbonaceous material

Claims (5)

A scale prevention device for preventing scale deposition from the water,
An electrode having at least an anode made of a carbonaceous material, means for applying a voltage between the electrodes, and water passing means for passing water between the electrodes,
In the scale prevention device that generates a scale prevention chemical consisting of an electrolytic substance by reaction at the anode,
A scale preventing apparatus comprising means for preventing fine particles of the carbonaceous material generated from the electrodes from being mixed into water passed between the electrodes.   2. A scale preventing apparatus according to claim 1, wherein said means is a filter means.   3. The scale prevention apparatus according to claim 2, wherein the filter means is a porous film.   4. The scale prevention apparatus according to claim 3, wherein the porous film is a resin film or a ceramic film.   5. The scale prevention apparatus according to claim 2, wherein the filter means is disposed so as to separate the water passage region between the electrodes and the electrode.

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