JP5037175B2 - Cooling water supply method and apparatus for large capacity transformer - Google Patents

Description

  The present invention relates to a cooling water supply method and apparatus for a large capacity transformer for cooling water supplied to a cooling tower.

  In order to cool a large-capacity transformer used in an ultrahigh voltage underground substation or the like, heat exchange with cooling water in a cooling tower is used. The cooling water warmed by heat exchange is cooled in the cooling tower. During the heat exchange, the cooling water evaporates and takes heat from the transformer. Due to the evaporation of the cooling water, the cooling water in the cooling tower is concentrated. When concentrated, the cooling water is scaled. This scale is scale, which is mainly calcium and silica contained in tap water. If the scaled cooling water is left as it is, the cooling tower is corroded and the cooling efficiency is lowered.

  In order to prevent this, the conductivity of the cooling water in the cooling tower is measured, and if it is higher than the predetermined conductivity, the cooling water is drained and new cooling water is replenished. If this new cooling water is supplied with low conductivity, the cooling water exchange interval with gradually increasing conductivity can be lengthened, but the amount of water used increases. Moreover, since the said cooling water will be used over a long period of time when the cooling water with too low electrical conductivity is used, algae generate | occur | produces in cooling water. The generation of algae is not preferable for operation.

  For this reason, the optimum water quality of the replenishing cooling water is obtained based on the evaporation amount and the drainage amount of the cooling water and supplied. In order to obtain such cooling water, first, a method of changing the water quality by using a chemical is conceivable. However, chemical treatment is costly for a cooling tower with a large amount of cooling water for cooling a transformer. Have difficulty. Therefore, the cooling water of this specified quality is treated with raw water such as tap water by UF (ultra filter) that performs physical filtration to remove dirt, and then ions are removed by RO membrane (reverse osmosis membrane). Formed.

  However, this RO membrane is likely to be clogged, and when clogging occurs, the flow rate decreases, the pump output increases, and the operation efficiency deteriorates. For this reason, periodic chemical cleaning is required, and maintenance costs are required.

  On the other hand, Patent Document 1 discloses a cooling device for reducing the makeup water to the cooling tower, maintaining the scale component concentration of the cooling water low, and preventing scale generation.

JP 2002-310595 A

  However, the cooling device described in Patent Document 1 uses an RO membrane for blow processing for reusing cooling water that has been scaled after use. For this reason, the RO membrane is likely to be clogged, and it is necessary to periodically maintain the RO membrane, and the interval is short.

  The present invention takes the above prior art into consideration, and suppresses clogging of the RO membrane, thereby preventing a decrease in the flow rate of new cooling water to be supplied to the cooling tower and reducing the pump output for that purpose. It is an object of the present invention to provide a cooling water supply method and apparatus for a large-capacity transformer for realizing improvement in planned operation efficiency.

  In order to achieve such an object, the applicant of the present application wonders what will happen to the clogging of the RO membrane if the water quality of the cooling water is intentionally deteriorated, that is, if the amount of ions to be removed is increased. When sodium chlorate was added, it was found that the clogging of the RO membrane was reduced without algae growing in the cooling water.

  This is because the addition of sodium hypochlorite caused the RO membrane to react with sodium hypochlorite and cause chemical damage, resulting in holes in the RO membrane. In other words, sodium hypochlorite reduces the generation of algae by its bactericidal action, and chemically reacts with the RO membrane, and the reacted part becomes a hole, so that cooling water easily passes through the RO membrane. This is because the.

  Therefore, the applicant of the present application has created that cooling water is formed by allowing raw water to pass through after opening the RO membrane. Furthermore, by adjusting the amount of sodium hypochlorite aqueous solution added, the amount of ions passing through the RO membrane can be adjusted, and cooling water having a desired water quality can be obtained. As a result, the clogging of the RO membrane can be suppressed, the decrease in the flow rate of the cooling water can be prevented, and the pump output can also be reduced. Therefore, the maintenance of cooling water could be reduced. Specifically, the following inventions have been created.

In order to achieve the above object, in the invention of claim 1, the raw water supplied from the raw water supply source is passed through an RO membrane made of a reverse osmosis membrane to form cooling water, and the cooling water is used to increase the capacity. In the cooling water supply method for cooling the transformer, the raw water has a sterilizing action on the cooling water and causes chemical damage to the RO membrane so that the raw water easily passes through the RO membrane. Reducing the generation of algae in the cooling water and reducing clogging of the RO membrane by passing an aqueous solution of a chlorine-based inorganic compound that forms holes in the RO membrane in advance. A cooling water supply method for a large-capacity transformer is provided.

Further, in the invention of claim 2, in the invention of claim 1, by adjusting the amount of the compound on the RO membrane is characterized that you adjust the damage rate of the RO membrane.

Further, in the invention of claim 3, in the invention of claim 1 or 2, wherein the chlorine-based inorganic compounds are characterized by sodium hypochlorite der Rukoto.

Moreover, in invention of Claim 4 , with respect to the raw | natural water supply source, the raw | natural water supplied from the said raw | natural water supply source, the filtration apparatus for performing ultrafiltration, and the raw | natural water which passed the said filtration apparatus are supplied from a reverse osmosis membrane. A cooling water supply device for a large-capacity transformer to a cooling tower for cooling a large-capacity transformer having an RO device that passes through the RO membrane, wherein the RO membrane passes through a chlorine-based inorganic compound aqueous solution 4. A cooling water apparatus for use in a cooling water supply method for a large capacity transformer according to claim 1, wherein the cooling water is pretreated and the dechlorination rate is 95.05%. I will provide a.

Further, the invention of claim 5 is characterized in that , in the invention of claim 4, the aqueous chlorine-based inorganic compound is an aqueous sodium hypochlorite solution.

Furthermore, in the invention of claim 6, in the invention of claim 4 or 5, the pretreatment is performed by adding 0.167 mg / l sodium hypochlorite aqueous solution at a flow rate of 2.4 m ³ / h for 90 days. It is characterized by being passed through a membrane .

According to the first aspect of the present invention, since a chlorine-based inorganic compound having a bactericidal action against cooling water and chemically damaging the RO membrane is passed through the RO membrane in advance, a large capacity transformation The cooling water supplied as the cooling water of the vessel has a sterilizing action, and more ions pass through the RO membrane without damage. Therefore, it is possible to suppress the growth of algae in the cooling water due to the sterilization action, and further, it is possible to suppress clogging of the RO membrane, prevent a decrease in the flow rate of the cooling water, and reduce the pump output. Furthermore, the maintenance unnecessary period can be lengthened.

According to the invention of claim 2, since the amount of compound added to the RO membrane is adjusted to adjust the RO membrane damage ratio, the amount of ions passing through the RO membrane can be adjusted, and cooling of the desired water quality can be achieved. You can get water. Adjustment of this addition amount can be adjusted with the density | concentration with respect to the mass of a compound, addition time, or addition days.

According to the invention of claim 3 , since sodium hypochlorite is used to damage the RO membrane, the RO membrane can be surely chemically damaged to provide an opening in the RO membrane.

According to the invention of claim 4 , after the pretreatment is performed on the RO membrane through the chlorine-based inorganic compound aqueous solution, the RO membrane is supplied to the cooling water supply device for supplying the RO membrane to the cooling tower of the large-capacity transformer. Use. For this reason, chemical damage is caused by the chlorine-based inorganic compound and an opening is formed. For this reason, by changing the aperture ratio of the opening to the RO membrane, the amount of ions passing through the RO membrane can be adjusted, and cooling water having a desired water quality can be obtained. By this pretreatment, clogging of the RO membrane can be suppressed. Therefore, a decrease in the flow rate of the cooling water can be prevented, and the pump output can also be reduced.

In addition, while the desalination rate of a normal RO membrane is 99.15%, the desalination rate is decreased by 4.1% by performing pretreatment with a chlorine-based inorganic compound. For this reason, when it is desired to obtain the same flow rate as that of the RO membrane not subjected to pretreatment, the RO membrane is opened by the amount corresponding to the decrease in the desalination rate, so that the pump output can be reduced.

According to the invention of claim 5 , since sodium hypochlorite is used to damage the RO membrane, it is possible to reliably cause chemical damage to the RO membrane and provide an opening in the RO membrane.

According to the invention of claim 6 , the pre-processing can be performed by a simple method.

  The present invention has a sterilizing effect on the cooling water when the raw water supplied from the raw water supply source is passed through an RO membrane made of a reverse osmosis membrane to form cooling water, and the RO membrane An aqueous solution of a compound that damages the membrane can be passed through the RO membrane in advance to prevent clogging of the RO membrane, prevent a decrease in the flow rate of cooling water, reduce pump output, and generate algae of cooling water. This is a cooling water supply method and apparatus for a large-capacity transformer capable of suppressing the above.

  FIG. 1 is a schematic view of a cooling water supply apparatus according to the present invention.

  As illustrated, the cooling water supply device 1 according to the present invention includes a raw water storage tank 2, an activated carbon filtration device 3, a UF device 4, a filtrate storage tank 5, and an RO device 6. The raw water storage tank 2 stores raw water such as tap water. The raw water in the raw water storage tank 2 is sent to the activated carbon filtration device 3 by the pump 10. The activated carbon filtration device 3 uses activated carbon as a filter medium, and has an activated carbon layer. By passing the raw water through the activated carbon filtration device 3, residual chlorine contained in the raw water is removed. The activated carbon filtration tank 3 is periodically backwashed with water flowing from the reverse side.

  The raw water that has passed through the activated carbon filtration tank 3 flows into the UF device 4. The UF device 4 includes a UF (ultra filter), and removes suspended substances in the raw water. That is, the UF device 4 performs ultrafiltration on the raw water. Similarly to the activated carbon filtration tank 3, the UF device 4 is regularly backwashed. The raw water that has passed through the UF device 4 is stored in the filtrate storage tank 5.

  The raw water in the filtrate storage tank 5 is pumped to the RO device 6 by the pump 11. The RO device 6 includes an RO membrane (reverse osmosis membrane), and raw water fed at a pressure higher than the osmotic pressure becomes deionized water. Pretreatment is performed on the RO membrane provided in the RO device 6. This preprocessing will be described later.

  The conductivity of the cooling water that has passed through the RO device 6 is measured by the conductivity measuring device 9. If this conductivity is optimal for supply to the cooling tower 8 obtained by calculation or simulation, it is stored in the mat water tank 7. If the predetermined conductivity is not reached, the water is returned from the return passage 12 to the filtrate storage tank 5 and again subjected to deionization processing by the RO device 6. The cooling water stored in the mat water tank 7 is appropriately supplied to the cooling tower 8 when the water level in the cooling tower 8 is lowered or when the conductivity of the cooling water is increased. The cooling tower 8 cools the large-capacity transformer 18 (see FIG. 3).

  The pretreatment of the RO membrane will be described below.

  If a normal RO membrane is passed through, the cooling water passing through the RO membrane has a considerably low conductivity because of its high desalting ability. However, as described above, since the generation of algae is a concern even if the conductivity is too low, it is necessary to increase the conductivity to some extent. For this reason, an arbitrary water quality can be obtained by changing the aperture ratio of the RO membrane. As a specific method, tap water to which a chlorinated inorganic compound is added is flowed in advance through the RO membrane. As a result, the RO membrane is chemically damaged and has an opening. By adjusting the addition amount of the chlorine-based inorganic compound, the aperture ratio of the RO membrane can be changed. Therefore, the amount of ions passing through the RO membrane can be adjusted, and cooling water with a desired water quality can be obtained.

  By performing such pretreatment, clogging can be suppressed and the life of the RO membrane can be prolonged. Therefore, a decrease in the flow rate of the cooling water can be prevented, and the pump output of the pump 11 can also be reduced. That is, the cooling water supply method for a large-capacity transformer according to the present invention is to cause damage to the RO membrane in advance before supplying the cooling water to the cooling tower. Thereby, the maintenance unnecessary period regarding the RO membrane can be lengthened.

  From the above, in order to perform the pretreatment, it can be said that the RO membrane is chemically damaged (oxidized) and further has a bactericidal action in terms of suppressing the generation of cooling water algae. In this regard, sodium hypochlorite is preferable as the chlorine-based inorganic compound, but it is not limited to the sodium hypochlorite aqueous solution as long as it is a chemical (compound) having such an action.

  As what has the above effects, there are chloramine, N chloroisocyanurate, and chlorine dioxide. The chemical damage to these RO membranes varies with concentration and pH.

  It is preferable to use the above-mentioned sodium hypochlorite because it does not require pH control, has a large bactericidal effect, and is considered from the viewpoint of cost and ease of handling.

The addition of sodium hypochlorite to tap water can be adjusted by changing the amount of addition depending on the number of days of addition, etc., but 0.167 mg / l sodium hypochlorite aqueous solution was added to 2.4 m ³ / h. It is preferable to pass through the RO membrane at a flow rate for 90 days. In addition, when this pretreatment is performed, the desalination rate is reduced from 99.15% to 95.05%.

  The applicant of the present application experimented by comparing the flow rate (l / min) and pump output (%) of the RO membrane subjected to such pretreatment and the RO membrane not subjected to the pretreatment. When the RO membrane is applied to the cooling water supply device and the flow rate of 30 (l / min) is maintained after 9 days from use, the pump output of the RO membrane without pretreatment is 75.3%. The RO membrane after the pretreatment was 66.2%. After 49 days, the pump output of the RO membrane that had not been pretreated at the same flow rate was 83.4%, whereas that of the RO membrane after the pretreatment was 73.0%. In any case, the pre-processed RO membrane has less pump output and contributes to power saving. In addition, when the pump output was set to 100% after 104 days, the flow rate of only 20.0 (l / min) was obtained with the RO membrane that was not subjected to the pretreatment, whereas the pretreatment was performed. In the RO membrane, a flow rate of 29.1 (l / min) can be obtained, and it can be seen that a larger flow rate can be flowed with less pump output if pretreatment is performed.

  The experimental results are shown in Table 1.

  FIG. 2 is a graph showing the relationship between the amount of water used and the concentration ratio. The horizontal axis indicates the concentration ratio, and the vertical axis indicates the amount of water used. Note that the concentration ratio is obtained by dividing the conductivity value determined to be replaced by the conductivity value of the supply cooling water. Therefore, when the concentration factor is high, the conductivity of the supplied cooling water is low.

  As shown in the figure, when the concentration ratio is high (conductivity is low), the amount of water used, that is, the amount of raw water is reduced, so that water is saved. However, it turns out that the amount of water used does not change so much when it becomes higher than a predetermined concentration ratio (point T in the figure). As described above, there is a concern about the generation of algae in the cooling water with a very low conductivity. Therefore, it can be said that the cooling water at the T point is the optimum water quality as the cooling water that can suppress the generation of algae with a small amount of water.

  When raw water treatment is performed using a normal RO membrane, cooling water having a higher concentration ratio than the T point can be obtained. Therefore, by performing the pretreatment, the concentration rate can be lowered to the point T, water can be saved, and pump output can be reduced. The optimum water quality standard changes depending on the amount of cooling water evaporated in the cooling tower to be used, and can be obtained by calculation or simulation.

  FIG. 3 is a schematic view showing a part of the cooling water supply apparatus according to the present invention.

  The RO membrane subjected to the pretreatment as described above is disposed in the RO device 6 and raw water such as tap water or groundwater is allowed to pass through. Cooling water having a predetermined conductivity that has passed through the RO device 6 is stored in the mat water tank 7. The cooling water is fed from here to the replenishing water tank 14 by the pump 13. From this replenishing water tank 14, the cooling water is replenished to the water storage tank 15 provided at the lower part of the cooling tower 8 as make-up water. Cooling water in the water storage tank 15 is sprinkled by a pump 16 from a sprinkling pipe 17 at the top of the cooling tower 8.

  The cooling object 18, which is a large-capacity transformer, is provided with outgoing and return chilled water pipes 19, 20 passing through the cooling tower 8. The cold water in the cold water pipes 19 and 20 is heat-exchanged with the cooling water cooled by the fan 22 rotated by the motor 21 in the cooling tower 8. That is, the chilled water heated by cooling the cooling object 18 enters the cooling tower 8 through the forward chilled water pipe 19, is cooled by heat exchange with the chilled water, and then cooled through the return chilled water pipe 20. The object 18 is cooled again.

  When the cooling water evaporates due to heat exchange in the cooling tower 8 and the conductivity becomes high, the water is drained from the water storage tank 15.

  On the other hand, as a method for obtaining cooling water having an optimal water quality, there is a method of blending raw water with cooling water that has passed through an RO membrane that is not subjected to pretreatment, in addition to the above method. That is, the raw water supply source, the filtration device for performing ultrafiltration on the raw water supplied from the raw water supply source, and the RO that passes the raw water that has passed through the filtration device through the RO membrane made of a reverse osmosis membrane A cooling water supply device for a cooling tower provided with a device, wherein raw water is supplied from the raw water supply source to cooling water that has passed through the RO device to form blend water.

  Even by such a method, the conductivity can be reduced as compared with the cooling water that has passed through the normal RO membrane, and the same effect can be obtained. In addition, cooling water having a desired water quality can be obtained with a simple configuration by simply mixing raw water.

It is the schematic of the cooling water supply apparatus which concerns on this invention. It is a graph which shows the relationship between electrical conductivity and concentration magnification. It is the schematic which shows a part of cooling water supply apparatus which concerns on this invention.

Explanation of symbols

1: Cooling water supply apparatus, 2: Raw water storage tank, 3: Activated carbon filtration apparatus, 4: UF apparatus, 5: Filtration water storage tank, 6: RO apparatus, 7: Mat water tank, 8: Cooling tower, 9: Conductivity measurement apparatus 10: pump, 11: pump, 12: return passage, 13: pump, 14: make-up water tank, 15: water tank, 16: pump, 17: sprinkling pipe, 18: object to be cooled, 19: outgoing cold water pipe, 20 : Return cold water piping, 21: Motor, 22: Fan

Claims (6)

In a cooling water supply method for forming cooling water by passing an RO membrane made of a reverse osmosis membrane against raw water supplied from a raw water supply source, and cooling a large-capacity transformer using the cooling water. ,
An aqueous solution of a chlorine-based inorganic compound that has a bactericidal action on the cooling water and that forms holes so that the raw water easily passes through the RO membrane by chemically damaging the RO membrane, A cooling water supply method for a large-capacity transformer, characterized by reducing the generation of algae in the cooling water and reducing clogging of the RO membrane by passing the RO membrane. Wherein by adjusting the amount of the compound to the RO membrane, the cooling water supply method of a transformer of large capacity according to claim 1, characterized that you adjust the damage rate of the RO membrane. The chlorinated inorganic compound, the cooling water supply method of a transformer of large capacity according to claim 1 or 2, characterized in sodium der Rukoto hypochlorite. Raw water source,
A filtration device for performing ultrafiltration on the raw water supplied from the raw water supply source;
A cooling water supply device for a large-capacity transformer for a cooling tower for cooling a large-capacity transformer provided with an RO device that allows the raw water that has passed through the filtration device to pass through an RO membrane made of a reverse osmosis membrane. And
4. The large-capacity transformer according to claim 1, wherein the RO membrane is pretreated through a chlorine-based inorganic compound aqueous solution and has a dechlorination rate of 95.05%. Cooling water device used for cooling water supply method. 5. The cooling water supply device for a large-capacity transformer according to claim 4 , wherein the chlorine-based inorganic compound aqueous solution is a sodium hypochlorite aqueous solution . The pretreatment, sodium hypochlorite aqueous solution of 0.167 mg / l is at a flow rate of 2.4 m ³ / h, 90 days, according to claim 4 or 5, characterized in Rukoto passed through the RO membrane Cooling water supply device.

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