JP4177369B2 - A method for treating silica-containing water and an open circulation type cooling water system using the treated water. - Google Patents

Description

  The present invention relates to a treatment method for removing suspended silica contained in service water such as groundwater to make the water quality suitable for industry, commerce, etc., and also relates to an open circulation type cooling water system using treated water. is there.

  Conventionally, surface water such as rivers, underground water, underground water, lake water, and the like are used for industrial, commercial, beverage, irrigation, fire extinguishing and the like. Of these, water used in industrial equipment and commercial equipment is mainly used as cooling water in large amounts in cooling devices, cooling devices, and (boiler devices). The water contains slight scale components such as silica component and hardness component, but the scale adheres to the metal heat transfer surface of the heat exchanger and the inner surface of the pipe in these devices, resulting in poor heat transfer. A scale failure occurs. In particular, in an open circulation type cooling water system, cooling water is cooled by utilizing the latent heat of evaporation of water, but recently, water is used only for replenishing the amount of cooling water evaporated from the viewpoint of resource saving and energy saving. In many cases, high concentration operation is performed with a reduced amount of waste (blow) to the outside of the system. In this case, the silica component and the hardness component contained in the irrigation water are concentrated. In such a high concentration operation, the silica component and hardness component in the cooling water system become high in concentration, and scales such as calcium silicate and magnesium silicate are generated and adhered.

  Conventionally, phosphonic acids and carboxylic acid-based low molecular weight polymers are generally used as prescriptions that can be used for highly concentrated cooling water systems. However, the scale prevention effect of phosphonic acids and carboxylic acid polymers can be seen in the calcium carbonate scale generally generated in cooling water systems, but there is a drawback that the effect gradually decreases as the concentration of the coexisting silica increases. is there. In addition, silicate scales that combine silica with magnesium or calcium often do not work at all. Therefore, even when the cooling water system is highly concentrated, it is common to set and manage the concentration factor so that the silica concentration in the water does not exceed about 200 ppm.

  In view of the above circumstances, the current water treatment method for the cooling water system appropriately selects the chemical according to the operation management status such as the quality of the cooling water and makeup water, the concentration factor of the cooling water, and the silica concentration in the cooling water. The actual situation is that the operating conditions are set so that the value does not exceed about 200 ppm. (Ref. 1)

  In order to prevent the scale from adhering, various chemicals are injected into the cooling water system. (Refer to Document 2) That is, the time required for adding a drug composed of an amide compound of polyalkylene polyamine and a quaternary ammonium salt of an anionic group-containing polymer to sample water containing 60 to 100 ppm, calcium salt, magnesium salt and silica. A technique is disclosed in which the scale is not scaled since there is no change in the concentration of these scale-generating components after the passage.

JP-A-7-256266 ([0011-13]) Japanese Patent Laying-Open No. 2005-46679 ([0005], [0055] Table 2)

  Conventionally, industrial water mainly composed of surface water has been used as water for cooling systems in industrial facilities and commercial facilities, but in recent years, it is cheaper than industrial water and is obtained from deep wells obtained near the place of use. The use of groundwater has increased. Since these groundwaters generally contain more silica components and hardness components than surface water, scale failures are likely to occur in an open circulation type cooling water system. In order to prevent this, it is necessary to use a large amount of chemicals, and since the concentration factor cannot be increased, it is necessary to increase the amount of blow, so that not only operations but also economical problems have arisen.

  The present invention has been made in order to solve such problems, and removes suspended silica and ionic silica contained in water for use in groundwater and the like, so that the water quality is suitable for a cooling system in industrial equipment and commercial equipment. Another object of the present invention is to provide an open circulation type cooling water system that uses the obtained treated water as makeup water for the cooling water system.

  In order to achieve the above object, the invention of claim 1 is characterized in that after the silica-containing water is softened, a strong cationic polymer flocculant is added to agglomerate the silica in the water, A method for treating silica-containing water, which is collected and removed by a filter. The invention according to claim 2 is characterized in that, in the method for treating silica-containing water according to claim 1, calcium and magnesium ions in the water are removed as water softening treatment.

  The invention of claim 3 is characterized in that, in the method for treating silica-containing water according to claim 1 or 2, a low molecular weight homopolymer of diallyldimethylammonium chloride is used as the polymer flocculant. The invention of claim 4 is the method for treating silica-containing water according to claim 3, wherein the amount of the low molecular weight homopolymer of diallyldimethylammonium chloride, which is a polymer flocculant, is added to the silica-containing water as an active ingredient. It is characterized by being in the range of 0.5 to 10.0 μg / kg in terms of conversion. Further, the invention of claim 5 is the method for treating silica-containing water according to any one of claims 1 to 4, wherein the filter is a filter capable of collecting aggregates having a particle diameter of 1 to 5 μm. It is characterized by using.

  Usually, in working water such as groundwater, calcium ions and magnesium ions, which are hardness components, are 40 to 120 mg / l, suspended silica (having a particle diameter of 0.01 to 0.45 μm) is 20 to 80 mg / l and ionic 10-100 mg / l of silica is present. In adopting the configuration of the present invention, a strong cationic polymer flocculant is used to charge-neutralize and aggregate the suspended silica particles. In order to make it work well, calcium ions and magnesium ions are ion-exchanged and removed in advance by water softening treatment in advance so that the suspended silica particles can be effectively removed with a small amount of the polymer flocculant added. It was found that the particles were aggregated in a 5 μm diameter range. By adopting these constitutions, filtered water having almost no silica content, that is, treated water, is obtained by a filter capable of removing the aggregated 1-5 μm diameter silica particles by filtering the 1-5 μm particles in the subsequent step. Can do.

  Further, by adopting a low molecular weight homopolymer flocculant having diallyldimethylammonium chloride as a monomer as a strong cationic polymer flocculant, the homopolymer has a surface charge of the suspended particles with respect to the suspended silica particles. Is neutralized to be destabilized and agglomerated so that it can be easily captured by the filter medium. That is, the homopolymer molecule is adsorbed on the surface of the suspended silica particle having the opposite charge by the charge attractive force and also adsorbed on the surface of the filter medium. Further, the addition amount of the low molecular weight homopolymer flocculant of diallyldimethylammonium chloride is sufficient to agglomerate suspended silica particles in the range of 0.5 to 10 μg / kg in terms of active ingredient, and agglomerated particles having a diameter of 1 to 5 μm. Then, the agglomerated particles are adsorbed and removed on the surface of the filter medium of the filter to obtain filtered water with little or no silica content. In addition, the low molecular weight of a homopolymer means the thing of the range of molecular weight 20000-200000.

  The invention of claim 6 is an open circulation type cooling water system comprising an open watering type cooling tower, one or a plurality of cooling heat exchangers, a circulation cooling water pump, and a circulation pipe. 6. An open circulation type cooling water system characterized in that treated water obtained in the method for treating silica-containing water according to any one of items 1 to 5 is used as makeup water for the system. The invention of claim 7 is the open circulation type cooling water system of claim 6, wherein the treated water is replenished by blowing the circulating cooling water so that the electrical conductivity of the circulating cooling water does not exceed 800 μS / cm. -It is an open circulation type cooling water system characterized by replacement.

  According to the method of the present invention of claims 1 to 5, since there is almost no content of not only silica in water but also calcium and magnesium ions as hardness components, a small amount of treated water can be obtained. Based on the configuration of claim 6, by using this treated water as make-up water to make up for the evaporation loss of the cooling water in the open circulation type cooling water system, the silica component, calcium ion and magnesium ion component are added to the cooling water system. Scale generation can be prevented by reducing the degree of accumulation. That is, since this system evaporates a part of the cooling water and cools the cooling water by the latent heat of vaporization, components other than water are concentrated in the remaining cooling water. As described above, when scale-generating components such as silica component, calcium ion and magnesium ion component are present in the makeup water, they are concentrated to promote the generation of scale and cause scale failure, but the treated water of the method of the present invention is a scale-generating component. There is almost no concentration, so there is little concentration, or concentration does not proceed easily and scale failure does not occur easily. Also, cooling water disposal (blowing) that reduces the concentration of scale-generating components can be reduced compared to the conventional method. Also, administration of a drug that prevents scale generation is not required, or even if necessary, a minimum amount is sufficient.

According to the open circulation type cooling water system of claim 7, the electric conductivity of the circulating cooling water is measured for the contents of silica, calcium and magnesium which are the scale generating components, and the electric conductivity is set to 800 μS / cm. Adjust or control the amount and timing of circulating cooling water blow so that it does not exceed (Micro Siemens · cm ⁻¹ ), and supply or replace treated water to prevent scale failure in an open circulating cooling water system. It can be surely prevented. Moreover, it can also be applied to means for managing the quality of treated water to be replenished.

  According to the method for treating silica-containing water according to claims 1 to 5 according to the present invention, since the treatment is performed in a range where the content of calcium ions and magnesium ions as well as silica in the water is small, the polymer flocculant to be administered These scale-generating components can be surely removed even if the amount of is small. In particular, by removing calcium ions and magnesium ions in advance, the agglomeration of suspended silica particles with a particle size of 1 to 5 μm can be reliably performed even with the addition of a small amount of a strong cationic polymer flocculant. By capturing and removing the silica agglomerated particles with a filter, the suspended silica can be efficiently removed from the silica-containing water.

  Further, according to the open circulation type cooling water system of claims 6 and 7, since the treated water by the treatment method is used as makeup water for the evaporation loss of the system, silica as a scale generating component contained in the circulating cooling water, It is easy to maintain the calcium and magnesium contents at low levels, so that it is not necessary to administer a large amount of scale formation inhibitory drug as in the conventional system, and the amount of blow is inevitably reduced by increasing the concentration factor. Moreover, in order to make the measured value of the electrical conductivity of the circulating cooling water within a certain range, the effect can be ensured by controlling the blow amount.

  Therefore, the scale can be reliably scaled even if the dose of the drug is small, compared to the system that prevents the scale formation failure by administering the drug to the circulating cooling water as in the open circulation type cooling water system of conventional industrial equipment and commercial equipment. Generation failures can be prevented, and the heat transfer efficiency of the heat exchanger can be reduced and the inner surface of the pipes can be prevented. Therefore, running costs and maintenance costs can be reduced, and convenient and inexpensive groundwater can be used. It is excellent in economic efficiency.

  The best mode of the present invention will be described below. Water used as a target of the treatment method of the present invention is underground water including underground water, surface water, lake water, etc., and is used as cooling water for cooling equipment and cooling equipment in industrial equipment and commercial equipment, and partly in boiler equipment. Is also used. Conventionally, surface water such as rivers has been used as industrial water for these waters. However, in recent years, groundwater obtained from deep wells with a depth of 200 to 300 m is compared to industrial water and water at the place where water is used. However, it is evaluated as being inexpensive and suitable for cooling water because of its low water temperature, and has been widely used in open circulation type cooling water systems that use a large amount of water. However, since groundwater penetrates deeply into the ground and stays for a long time, it is generally rich in silica and hardness components such as calcium ions and magnesium ions. When used in a type cooling water system, scales such as calcium silicate and magnesium silicate are generated from the silica component and hardness component on the heat transfer surface of the heat exchanger that is the object of cooling, reducing the thermal efficiency. Since the scale failure occurred, the function of the open circulation type cooling water system was deteriorated.

  The treatment method of the present invention is mainly intended for groundwater, and raw water (water) containing 20 to 80 mg / kg as a silica component and 40 to 120 mg / kg as a calcium + magnesium (calcium carbonate equivalent) component. The silica component is processed so as to be 0 to 20 mg / kg, and the calcium + magnesium component is almost zero. In addition, as the form of the silica component, there are suspended (colloidal) silica and ionic silica having a particle diameter in the range of 0.01 to 0.45 μm. In the present invention, the main purpose is removal of suspended silica. In addition, ionic silica is also removed.

  In the treatment method of the present invention, a strong cationic polymer flocculant is applied to the suspended silica particles to perform charge neutralization and agglomerate into particles having a diameter of 1 to 5 μm. In order to efficiently act on suspended silica, it is necessary to perform a water softening treatment to remove calcium ions and magnesium ions in advance. This is not clear, but when diallyldimethylammonium chloride is used as a strong cationic polymer flocculant, it is more effective to remove calcium ions and magnesium ions that react quickly with the polymer molecules. It is considered that the surface charge of the suspended silica is neutralized to destabilize the suspended state, and at the same time, it is adsorbed on the surface of the suspended silica and facilitates aggregation.

  In addition, a strong cationic polymer flocculant having diallyldimethylammonium chloride as a monomer is used, but it is preferable to use a homopolymer solution having a concentration of 10% active ingredient in diluting the solution and adding / diffusing it into the water. desirable. There is FILTERREX 5110 as a trade name of the homopolymer solution. In addition, the amount added to the raw water after water softening to neutralize the suspended silica particles into aggregated particles having a particle diameter of 1 to 5 μm varies depending on the charge density of the suspended particles, but the active ingredient (diallyldimethyl) It is in the range of 0.5 to 10 μg / kg with respect to the raw water after water softening in terms of (a homopolymer of ammonium chloride). In addition, when the addition amount is in the range of 8 to 10 μg / kg, when the addition amount becomes excessive with respect to the agglomeration of the suspended silica particles, there arises a problem that it becomes difficult to filter with a filter in the next step. . Therefore, the addition amount is desirably in the range of 0.5 to 5 μg / kg. As other agglomeration conditions, the pH of the raw water after softening is suitably in the range of 6.0 to 8.5 and the liquid temperature in the range of 10 to 30 ° C.

  In addition, it is important for the addition position of the strong cationic polymer flocculant to ensure sufficient time for contact with the suspended silica particles to achieve charge neutralization and agglomeration. It is desirable for agglomeration of suspended silica particles to maintain a state in which the long chains of adsorbed homopolymer are not broken. That is, the addition position is downstream of the pump, and the addition is performed at a place where the flow is not turbulent. After the addition, the flow rate of 0.1 to 0.5 m / sec is applied for 2 seconds or more in a laminar flow state until the next filter. Determining the diameter and length of the pipe that can be secured is important in promoting the agglomeration reaction.

  The silica aggregate particles having a particle size of 1 to 5 μm are trapped and removed by a filter medium through a filter capable of filtering a particle size of 1 to 5 μm, a so-called microfilter. When paper, polyester, polypropylene, or the like is used as the filter medium, the silica aggregated particles are easily adsorbed on the surface of the filter medium by the action of the homopolymer molecules adsorbed on the particle surface, so that filtration can be performed reliably. Further, it is desirable that the filter has a structure in which the filtration capacity is not lowered by the silica aggregated particles trapped in the filter medium, and further a structure in which the trapped silica aggregated particles can be easily removed. Therefore, a plurality of filtration units are provided inside the filter, each filtration unit is cylindrical, has a porous water collection tube in the center, and has a convex polygonal cross section so that a large filtration area can be taken around it. It is preferable to have a structure provided with a filter medium having a shape (presenting a bowl-like shape) and an angle at which the filtration surface is inclined with respect to the center of the cylinder. Since the filter medium surface is disposed in a tangential direction with respect to the center of the filtration unit, the filtration efficiency can be improved by introducing the silica-containing aggregated particle liquid in this direction. The trapped silica agglomerated particles can be removed from the filter medium surface with water from a washing nozzle. Therefore, in this case, it is better to have a plurality of filters and to clean up the filters with water intermittently one by one.

  Referring to FIG. 1, a treatment method for containing silica water and an open circulation cooling system using the treated water according to an embodiment of the present invention will be described. In the water treatment system 1, water (raw water) 11 is a raw water receiving tank. 2 and sent to the water softening device 3 by the pump 7. Here, the calcium ions and magnesium ions, which are hardness components, are removed to 30 mg / kg or less, and the raw water 12 after the water softening treatment is sent to the filter 5 called a microfilter by the pump 8, After the pump 8, the strong cationic polymer flocculant is added to the raw water 12 by the flocculant injection pump 9 from the flocculant tank 4 in which diallyldimethylammonium chloride, which is a strong cationic polymer flocculant, is stored. Then, after the suspended silica particles having a diameter of 0.01 to 0.5 μm are aggregated to agglomerated silica particles having a diameter of 1 to 5 μm and expanded, the raw water 13 containing the aggregated silica particles having a diameter of 1 to 5 μm is filtered through the filter 5. Hang on. The treated water 14 obtained by capturing and removing the agglomerated silica with the filter 5 and removing the silica content from the raw water 13 is stored in the treated water tank 6. In addition, when calcium ion and magnesium ion in the treated water are set to about 30 mg / kg, a protective film is formed in the piping of the open circulation type cooling water system 20 described later, which is preferable in terms of the life of the piping.

  The water softening apparatus 3 is filled with a cationic resin (for example, trade name SST-60) as a filter medium in the resin tank. By passing the raw water through the resin tank, calcium ions and magnesium ions, which are hardness components in the raw water, are ion-exchanged with resin ions (Na ions), and the cations are attached to the resin surface. Can be almost completely removed. The resin is regenerated by salt water (saline concentration 17 wt%) by a conventional method.

The flocculant tank 4 stores a product obtained by diluting a trade name FILTERREX 5110 (a homopolymer solution of diallyldimethylammonium chloride having an active ingredient concentration of 10%) 50 to 100 times, which is a strong cationic polymer flocculant. Is done. The flocculant liquid is preferably added to the raw water 12 after being softened by the flocculant injection pump 9 within the range of 0.5 to 3 μg / kg in terms of active ingredient. The strong cationic polymer flocculant is a practically immediate reaction with the suspended silica particles, but it is desirable to take a long contact time in order for the injected flocculant and the suspended silica particles to react completely. Therefore, it is preferable to inject into a straight pipe portion having a flow rate of 0.1 to 0.5 m / sec at a location as far as possible from the filter 5. Further, unless the amount of the unreacted flocculant is within 0.001 μg / kg in terms of the active ingredient, a trouble due to the muddy balls occurs in the subsequent filtering operation. In addition, if the molecular and homopolymer chains that are characteristic of the flocculant are divided by shearing force, the aggregation reaction efficiency of the flocculant is reduced, so that the shearing force does not act, a stirring pipe, a storage tank with stirring blades, Application of a pump with an impeller is not preferable.

  The filter 5 collects suspended silica particles having a diameter of 0.01 to 0.5 μm into agglomerated silica particles having a diameter of 1 to 5 μm and collected by a microfilter capable of filtering the particles having a diameter of 1 to 5 μm. Then, it is applied to obtain a filtrate containing no silica as treated water 14 while being discharged out of the system. The best embodiment of the present invention uses a filter 5 capable of agglomerating and expanding suspended silica particles having a diameter of 0.01 to 0.5 μm to agglomerated silica particles having a diameter of 3 to 4 μm and filtering 1 μm diameter particles. Is the best form for silica removal. The filter 5 is preferably structured so that the captured aggregated silica particles can be backwashed and removed manually or automatically, and the filtration flow rate should not continuously decrease with the passage of the collection time of the aggregated silica. . For example, it is preferable to use a paper filter material with a trade name HURRICANE filter of HARMSCO (USA). This is provided with a plurality of integrated cylindrical filtration units with a large filtration area. Each filtration unit has a fold bent in the tangential direction to introduce fluid in the direction of fluid rotation (fluid is introduced tangential to the filter). And when the fluid force is applied, the wrinkles come off and the particles are uniformly dispersed, so that the particle separation efficiency is high and the life of the filter medium is prolonged.

  The open circulation type cooling water system 20 includes an open watering type cooling tower 21 having a cooling tower fan 21a, a heat exchanger 23 in the cooling device or the cooling device, and the circulating cooling water 25 into the cooling tower 21 and the heat exchanger 23. It is comprised from the circulation pump 22 which sends water to these, and those piping. The water storage section of the cooling tower 21 is provided with an electric conductivity meter 26, and a blow valve 24 for blowing the circulating cooling water 25 manually or automatically is provided in order to maintain the measured value within a predetermined range. Further, a replenishment adjustment valve 10 for replenishing the treated water 14 to the cooling tower 21 is provided to supplement the amount of the circulating cooling water 25 that has been evaporated and blown.

In order to adjust the amount of scale-generating components (silica, calcium ions, magnesium ions, etc.) of the circulating cooling water 25 within limits that prevent scale generation, the circulating cooling water 25 is measured using an electric conductivity meter 26. The blow amount is preferably adjusted and controlled so that the measured value does not exceed 800 μS / cm (micro Siemens · cm ⁻¹ ). That is, a part of the circulating cooling water 25 is blown by a predetermined amount by opening the blow valve 24, and the replenishment adjusting valve 10 is opened by using the treated water 14 as make-up water to compensate. With this system, it is possible to use the treated water 14 with very little scale generation component in the open circulation type cooling water system 20 without causing a scale failure, and to eliminate or extremely reduce the injection of medicine. In this case, the concentration factor (≈ (evaporation loss amount + blow amount) ÷ blow amount) can be in the range of 6 to 10, so that the blow amount can be reduced. Can be reduced.

  Removal of the silica component from the silica-containing water was confirmed by applying the method of the present invention to the raw water pumped from the deep well. The silica-containing water containing 27 mg / kg of suspended silica and 15.3 mg / kg of ionic silica is subjected to water softening treatment to remove calcium ions and magnesium ions (hereinafter referred to as hardness components), and then a strong cationic polymer. The product name FILTERREX 5110 (a homopolymer solution of diallyldimethylammonium chloride having a 10% active ingredient concentration) that is a flocculant is diluted 100 times as a flocculant in the range of 0.5 to 3.0 μg / kg in terms of active ingredient. A stepwise addition was performed to remove the agglomerated silica with agglomerated back paper (pore size 1 μm), and the silica residue of the treated water was determined. The analysis of silica was performed according to JISK0101 44.12. The total amount of silica and the amount of ionic silica were determined, and the amount of suspended silica was calculated therefrom. The results of the examples are shown in Table 1 (the hardness component after water softening treatment was adjusted to 30 mg / kg) and Table 2 (the hardness component after water softening treatment was adjusted to 1 mg / kg).

  From the results of Tables 1 and 2, silica-containing water containing 27 mg / kg of suspended silica and 15.3 mg / kg of ionic silica was treated to obtain 3.1 to 10.9 mg / kg of suspended silica and ionic Treated water of 2.5 to 11.2 mg / kg of silica was obtained, and a suspended silica removal rate of 89 to 60% and an ionic silica removal rate of 84 to 27% were obtained. It has been found that according to the method of the present invention, not only suspended silica but also ionic silica can be removed.

  Regardless of industrial and commercial facilities, the present invention can be widely used for a cooling water system or a water treatment system for a heat exchanger of a cooling or refrigeration equipment, a lubricating oil of a mechanical equipment or a heat exchanger of a cooling system.

It is explanatory drawing of the removal method of the suspended silica in the water which is the best embodiment of this invention, and the open circulation type cooling method using the treated water, Comprising: It is a typical flowchart.

Explanation of symbols

1: Water treatment system 2: Raw water receiving tank 3: Soft water treatment device 4: Coagulant tank 5; Filter 6: Treated water tank 7: Pump 8: Raw water pump
9: Coagulant injection pump 10: Supply adjustment valve 11: Water (raw water)
12: Raw water after softening 13: Raw water 14: Treated water 20: Open circulation type cooling system 21: Cooling tower 21a: Cooling tower fan 22: Circulation pump 23: Heat exchanger 24: Blow valve 25: Circulating cooling water 26: Electric conductivity meter

Claims (7)

  The silica-containing water is characterized by adding a strong cationic polymer flocculant after the water containing the silica-containing water is softened to aggregate the silica in the water, and collecting and removing the aggregate with a filter. Processing method.   The method for treating silica-containing water according to claim 1, wherein calcium and magnesium ions in the water are removed as water softening treatment.   3. The method for treating silica-containing water according to claim 1 or 2, wherein a low molecular weight homopolymer of diallyldimethylammonium chloride is used as the polymer flocculant.   The method for treating silica-containing water according to claim 3, wherein the addition amount of the low molecular weight homopolymer of diallyldimethylammonium chloride, which is a polymer flocculant, is 0.5 to 10.0 μg in terms of active ingredient relative to the silica-containing water. A method for treating silica-containing water, characterized by being in the range of / kg.   The silica-containing water treatment method according to any one of claims 1 to 4, wherein a filter capable of collecting aggregates having a particle diameter of 1 to 5 µm is used as the filter. Water treatment method.   6. An open circulation type cooling water system comprising an open sprinkling type cooling tower, one or a plurality of cooling heat exchangers, a circulating cooling water pump, and a circulation pipe. An open circulation type cooling water system characterized in that the treated water obtained in the method for treating silica-containing water according to the item is used as makeup water for the system.   The open circulation type cooling water system according to claim 6, wherein the circulating cooling water is blown so that the electric conductivity of the circulating cooling water does not exceed 800 μS / cm, and the treated water is replenished and replaced. It is a circulating cooling water system.

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