JP4708395B2 - Cooling system and operation management method thereof - Google Patents

Description

  The present invention relates to a cooling system and an operation management method thereof, and more particularly to a cooling system that performs cooling by circulating cooling water and an operation management method of such a cooling system.

  In plants of various industries such as thermal power generation, oil refining, and iron making, a cooling system using cooling water such as industrial water is indispensable. One of the cooling systems widely used at present is one using an open cooling tower. An open-type cooling tower is a device that cools water by dropping water from its upper part to its lower part and bringing it into contact with the atmosphere. In a cooling system, usually, water used for cooling an object such as a heat exchanger is cooled by such a cooling tower and recycled.

  In that case, in the cooling tower, part of the cooling water (circulating water) evaporates during the cooling process, and the circulating water is gradually concentrated. Such an operation method involving the concentration of circulating water is preferable from the viewpoint of effective use of water. However, on the other hand, when the circulating water is concentrated, the salts contained in the circulating water are concentrated, and scales are deposited in the piping through which the cooling water flows, etc. Serious failure may occur.

In order to avoid the occurrence of such scales, conventionally, the electrical conductivity of the replenishing water and the replenishing water replenished as the recirculating water and the ion concentration of the salts are measured, and the concentration rate of the recirculating water (what is the replenishing water? Add a chemical such as a dispersant or pH adjuster to the circulating water, or a method that controls the amount of blown water or make-up water so that the scale is less than the allowable value for scale generation. Methods have been proposed (see Patent Documents 1 and 2). In addition, as a method for detecting the presence or absence of a scale, a method in which a predetermined scale detector is provided in a portion where the scale should be confirmed and the state of scale adhesion is confirmed by visual observation (see Patent Document 3), There has been proposed a method for detecting a scale based on a change in thermal resistance caused when it adheres (see Patent Document 4).
Japanese Patent Laid-Open No. 2002-282892 JP 2004-177053 A Japanese Patent Application Laid-Open No. 07-253293 Japanese Patent Application Laid-Open No. 08-015189

  In general, in a cooling water circulation type cooling system using an open cooling tower as described above, tap water, industrial water, ground water, or the like is used as makeup water. In recent years, wastewater such as sewage is reclaimed and used as make-up water from the viewpoints of water saving and energy saving or cost reduction of make-up water.

  However, when such a sewage collection area is located in the coastal area, seawater or groundwater containing seawater permeates into the collection area when the collection pipe falls below the sea level due to rising tide levels, etc. It can happen that it is mixed into the sewage of the water collection area. In addition, such seawater mixing phenomenon can occur in well water in coastal areas as well.

  Seawater contains a high concentration of various salts, and salt removal is not performed in normal sewage treatment. If seawater enters the sewage, it will be contained in the water after sewage treatment (sewage treatment water). The salt concentration will suddenly increase. If water that may contain seawater is used as make-up water for the cooling system, the salt concentration in the circulating water rises as the circulating water cools and concentrates in the cooling tower, causing the risk of scale formation. Will increase.

  Since tap water, industrial water, and the like conventionally used as make-up water have little fluctuation in water quality, the salt concentration in the circulating water of the cooling system can be easily predicted from the concentration ratio in the cooling tower. Therefore, scale generation can be suppressed by controlling the concentration ratio within a predetermined range. In addition, in the case of tap water, industrial water, and the like, since components that generate scale are known to some extent, it is also possible to suppress scale generation using a dispersant corresponding to such components.

  On the other hand, sewage treated water has a large variation in water quality compared to conventional tap water, industrial water and the like. In addition, various salts are dissolved in the sewage treated water, and when such sewage treated water is concentrated, it is difficult to predict scale generation due to the interaction of these salts. In addition, as described above, when seawater is unsteadyly mixed into sewage, the water quality fluctuation is further increased, and only by controlling the concentration ratio in the cooling tower or adding a dispersant corresponding to a specific component. It is difficult to suppress scale generation.

  In addition, groundwater usually has little fluctuation in water quality, but when seawater is likely to be mixed with it, the salt concentration will change greatly. Difficult to do.

Note that the conventionally proposed scale detection method detects the scale after generation, and is unsuitable for preventive operation management of the cooling system that prevents the generation of scale in advance.
This invention is made | formed in view of such a point, and it aims at providing the cooling system which can suppress scale production | generation effectively, and its operation management method.

  In the present invention, in order to solve the above-described problem, in the cooling water circulation type cooling system in which the cooling water is circulated and the reduced amount of the circulating cooling water is replenished by the replenishing water, the cooling water that circulates in the system. A means for extracting a part, and a component that generates a scale that can be mixed into the makeup water is added to the extracted cooling water, and an addition amount of the component and a concentration of the added component in the cooling water There is provided a cooling system comprising: means for acquiring a relationship between the first and second components; and means for determining a risk that a scale is generated in the system using the acquired relationship.

  According to such a cooling system, a part of the cooling water circulating in the system is periodically sampled, and a component that generates a scale that can be mixed into the makeup water is added to the cooling water. It is possible to grasp whether or not scale precipitation is likely to occur due to the mixing of such components. The larger the amount of the component added until the scale is generated, the lower the scale generation risk because the scale is less likely to generate scale.

  As a result, taking into consideration the possibility that components that generate scale will be mixed into the makeup water, it is possible to grasp whether the system that actually circulates the cooling water is in a high or low scale generation risk state. Will come to be.

  Further, in the present invention, in order to solve the above-mentioned problem, in the operation management method of the cooling water circulation type cooling system, the cooling water is circulated and the reduced amount of the circulating cooling water is replenished by the replenishing water. A part of the circulating cooling water is extracted, a component that generates a scale that can be mixed into the makeup water is added to the extracted cooling water, the amount of the component, and the cooling of the added component A cooling system operation management method is provided, wherein a relationship with a concentration in water is acquired, and a risk that a scale is generated in the system is determined using the acquired relationship.

  According to such an operation management method for the cooling system, the system that actually circulates the cooling water is placed in a state in which the risk of scale generation is high in consideration of the possibility that the components that generate the scale are mixed into the makeup water. You will be able to figure out whether you are in a low state or not.

  That is, by adding in advance the sampled scale generation component to the sampled circulating cooling water, the control reference value of the addition amount at which precipitation starts (for example, when the scale generation component is seawater, The management reference value C0 of conductivity is determined.

And up to the amount of the reference value, even if the scale generation component is mixed in, the scale does not immediately occur, so that it is an allowable amount that allows the operation to be continued as it is.
The circulating water is sampled and the scale generation point is examined while adding the scale-generating component.

If the amount of the scale-generating component to be generated is greater than the control reference value, it is determined that the circulating water can be operated as it is.
If scale generation occurs with an amount of scale generation component added that is less than the control standard value, there is a risk that scale precipitation will occur if a smaller amount of scale generation component is mixed than the set allowable amount. By increasing the supply amount of makeup water, measures such as lowering the concentration of scale-generating components in the circulating water are taken.

  In the present invention, a part of the cooling water circulating in the system is extracted, and a component that generates a scale that can be mixed into the makeup water is added to the cooling water. The relationship with the concentration of the component dissolved in the system was obtained, and the scale generation risk in the system was determined using the relationship. This makes it possible to grasp the risk of scale generation in the system in consideration of the possibility that components that generate scale will be mixed in the makeup water. Therefore, even when makeup water that can contain such components is used, scale generation can be effectively suppressed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of a cooling system.
The cooling system 1 shown in FIG. 1 is a cooling water circulation type system. The cooling water (circulating water) 2 is circulated through the heat exchanger 3, and the circulating water 2 after passing through the heat exchanger 3 is cooled by the cooling tower 4. The configuration is such that it is circulated through the heat exchanger 3 again.

  As the cooling tower 4, an open type cooling tower is used, and the circulating water 2 that has been sent from the cooling tower 4 to the heat exchanger 3 using the circulating water pump 5 and then returned to the cooling tower 4 is returned to the cooling tower 4. As it falls from the top to the bottom, it cools in contact with the atmosphere. At that time, a part of the circulating water 2 is evaporated and concentrated.

  The cooling tower 4 is provided with a blow valve 6 for discharging the internal circulating water 2. In addition, the cooling tower 4 is supplied with supplementary water to make up for the reduced amount of the circulating water 2 in the system through which the circulating water 2 circulates, for example, the amount discharged by the blow valve 6 or the amount evaporated by the cooling tower 4. It has become so.

  In this cooling system 1, sewage treated water 7 is used as such makeup water, and the sewage treated water 7 after sewage treatment is stored in a makeup water tank 8. The sewage treatment water 7 in the makeup water tank 8 is supplied into the cooling tower 4 through a line equipped with a makeup water valve 10 by using a makeup water pump 9. Mixed with circulating water 2.

  As described above, the sewage treated water 7 has a large fluctuation in water quality compared to tap water, etc., and when the sewage collection area is in the coastal area, seawater is mixed into the collected sewage. If the salt is not removed during the sewage treatment, the salt concentration of the sewage treated water 7 increases. In the cooling system 1 in the present embodiment, the sewage treated water 7 obtained by treating the sewage in which the scale generating component such as seawater may be mixed is used as makeup water.

  Note that clean water such as tap water can be supplied to the makeup water tank 8. In the cooling system 1, the clean water is supplied to the make-up water tank 8 in which the sewage treated water 7 is stored, thereby diluting the scale generation component concentration (salt concentration in the case of seawater) in the make-up water tank 8. It is possible to do.

  The cooling system 1 also has a water sampling line 13 provided with a test water pump 11 and a test water valve 12 for sampling a part of the circulating water 2 in the cooling tower 4. Part of the collected circulating water 2 (test water) 14 passes through such a water sampling line 13 and enters a seawater addition tank 17 in which seawater 16 can be added using a seawater pump 15. It comes to be supplied.

  The seawater 16 has a solubility that generates scale in the system in which the circulating water 2 circulates, such as calcium, magnesium, silica, zinc, phosphoric acid, sulfuric acid, etc., which may be mixed into the sewage treatment water 7 of the makeup water tank 8. It is used for the purpose of adding the component (scale generating component) to the test water 14. The seawater 16 is preferably the same as that which can actually be mixed into the sewage used for the sewage treated water 7, but it is also possible to use a place where the water quality is less likely to be collected.

  In the seawater addition tank 17 to which the seawater 16 is added, in order to agitate the level sensor 18 for storing a certain amount of the test water 14 therein, and the test water 14 (including the seawater 16 added). A stirrer 19 is provided. Further, the seawater addition tank 17 is provided with a metallic pipe 20 at a position where it is completely immersed in the test water 14. In the pipe 20, a constant temperature water circulating device 21 is used in the heat exchanger 3. A liquid having the same water temperature as the high-temperature water is distributed.

  Instead of the pipe 20 and the constant-temperature water circulation device 21, a metal heater having an outer surface is inserted into the seawater addition tank 17, and the heater surface has a piping temperature through which high-temperature water flows in the heat exchanger 3. You may heat up so that it may become the same.

  A part of the test water 14 in the seawater addition tank 17 is supplied to a densitometer 22 for measuring the concentration of the scale generating component dissolved therein. Further, the seawater addition tank 17 is provided with a drain valve 23 for discharging the test water 14 in the seawater addition tank 17.

  Further, the cooling system 1 uses the amount of seawater 16 added to the seawater addition tank 17 and the scale generation component concentration measured by the densitometer 22 to obtain the relationship between the addition amount of seawater 16 and the scale generation component concentration, A risk determination processing unit 24 that determines the scale generation risk in the system based on the relationship is included. In other words, the risk determination processing unit 24 has a relationship between the amount of the scale generation component added to the test water 14 (corresponding to the amount of seawater 16 added) and the concentration of the scale generation component dissolved in the test water 14. The scale generation risk in the system is determined based on the relationship.

  The addition amount of the seawater 16 used for the determination in the risk determination processing unit 24 is calculated from, for example, the addition time of the seawater 16 to the seawater addition tank 17 using a constant flow pump for the seawater pump 15. Or the addition amount of the seawater 16 provides the electrical conductivity meter (not shown) in the seawater addition tank 17, the electrical conductivity of the test water 14 before and after the seawater 16 addition, and the seawater 16 measured beforehand. Is calculated from the change in electrical conductivity due to the addition of seawater 16. These calculation functions can be provided in the risk determination processing unit 24. Moreover, you may make it use the electrical conductivity itself measured in that way as the addition amount of the seawater 16.

Next, the operation flow of the cooling system 1 having the above configuration will be described.
First, the sewage treatment water 7 of the makeup water tank 8 is supplied to the cooling tower 4. The circulating water 2 at the lower part of the cooling tower 4 is sent to the heat exchanger 3 using the circulating water pump 5, passes through the heat exchanger 3, and is returned to the upper part of the cooling tower 4. In the heat exchanger 3, the hot water flowing through the heat exchanger 3 is cooled by the passage of the circulating water 2. In the cooling tower 4, the circulating water 2 after passing through the heat exchanger 3 returned to the upper part is cooled and concentrated while falling to the lower part.

  The decrease in the circulating water 2 due to such concentration is compensated by replenishing the sewage treatment water 7 of the makeup water tank 8. However, if only the reduced amount of the circulating water 2 is replenished with the sewage treated water 7, the concentration of the scale generating component of the circulating water 2 is increased, and the scale is easily generated in the system in which the circulating water 2 circulates. Therefore, when the sewage treated water 7 is replenished, a certain amount of circulating water 2 is discharged from the blow valve 6, and the amount of sewage treated water 7 that compensates for the discharged amount and the decrease due to concentration is replenished. The amount of circulating water 2 is controlled, and the concentration rate of circulating water 2 is controlled.

  In the cooling system 1, it is determined whether the scale generation risk is high or low at an appropriate timing, such as once a day or every several hours, for the system in which the circulating water 2 circulates. Based on the results, operation management is performed.

  In order to perform such operation management, the cooling system 1 firstly extracts a part of the circulating water 2 stored in the lower part of the cooling tower 4 from the water collection line 13 using the test water pump 11 at a predetermined timing. Extracted into the seawater addition tank 17 as test water 14.

  In that case, the water level of the test water 14 is detected by the level sensor 18, and when the seawater addition tank 17 is filled with a certain amount of circulating water 2, the test water valve 12 is closed, the test water pump 11 is stopped, The supply of the circulating water 2 to the seawater addition tank 17 is stopped. After the supply is stopped, the test water 14 in the seawater addition tank 17 is stirred by a stirrer 19. At the time of agitation, the test water 14 is brought to a temperature state equivalent to the circulating water 2 passing through the heat exchanger 3 by, for example, a pipe 20 through which a liquid having a predetermined temperature flows by the constant temperature water circulation device 21.

  Then, a part of the test water 14 in the seawater addition tank 17 is supplied to the densitometer 22 and the concentration of the scale generation component is measured. Moreover, an electrical conductivity meter is provided in the seawater addition tank 17 as necessary, and the electrical conductivity of the test water 14 at this time is measured. The concentration measurement value of the scale generation component of the test water 14 or the measurement value of the electrical conductivity of the test water 14 is sent to the risk determination processing unit 24.

  Next, seawater 16 containing a scale generating component that can be mixed into the sewage treatment water 7 of the makeup water tank 8 is used for the test water 14 in the seawater addition tank 17 using, for example, a seawater pump 15 capable of feeding at a constant flow rate. As a result, the scale-generating component is added to the test water 14. In the meantime, a part of the test water 14 to which the seawater 16 is added is supplied to the densitometer 22 and the concentration of the scale generation component is continuously measured. If necessary, the electrical conductivity of the test water 14 when the seawater 16 is added is continuously measured by an electrical conductivity meter provided in the seawater addition tank 17. Each concentration measurement value of the scale generation component of the test water 14 or each measurement value of the electrical conductivity of the test water 14 is sent to the risk determination processing unit 24.

  Note that there are usually multiple types of scale-generating components contained in the test water 14 before and after the addition of the seawater 16, and in the concentration measurement of the scale-generating components by the densitometer 22, all the concentrations of these components can be measured. preferable. However, if necessary, the concentration of only a specific scale generation component may be measured.

The density | concentration of the scale production | generation component (solubility) of the test water 14 changes with the addition of the seawater 16, ie, the addition of a scale production | generation component.
2 and 3 are diagrams showing an example of the relationship between the seawater addition amount and the scale-generating component concentration. 2 and 3, the horizontal axis represents the amount of seawater 16 added (the amount of seawater 16 added (the amount actually added or the amount obtained from the electrical conductivity)) or test water 14 to which seawater 16 was added. The vertical axis represents the concentration of the scale generating component.

  In the case of FIG. 2, when the seawater 16 is added, the concentration of the scale generation component X increases up to a certain addition amount C1, and thereafter becomes constant. Moreover, the density | concentrations of the scale production | generation components Y and Z increase with the addition amount of the seawater 16 increasing. When the concentration becomes constant when reaching a certain addition amount C1 as in the scale generation component X, it can be said that the scale starts to be generated from that point.

  In the case of FIG. 3, the concentration of the scale generation component X increases up to a certain addition amount C2 as the seawater 16 is added, and thereafter becomes constant. Moreover, the density | concentration of the scale production | generation component Y increases with the addition amount of the seawater 16 increasing. Further, the concentration of the scale generating component Z increases until a certain addition amount C2, and thereafter decreases. When the concentration becomes constant or decreases when a certain amount of addition C2 is reached as in the scale generation components X and Z, it can be said that the scale starts to be generated from that point.

  The risk determination processing unit 24 of the cooling system 1 first acquires the relationship as shown in FIGS. 2 and 3 using the added amount of the seawater 16 and the measured value of the scale generation component concentration. Then, the amount of seawater 16 added at the time when the concentration increase of the scale-generating component dissolved in the liquid is saturated (at the time when the concentration starts to decrease or begins to decrease) is specified, and the test water is based on the specified added amount. 14 scale generation risks, that is, the scale generation risk in the system in which the circulating water 2 is circulating are determined.

  At that time, a reference value (management reference value) C0 is set in advance for the amount of seawater 16 added, and the risk determination processing unit 24 specifies the concentration of scale generation components as shown in FIG. 2, for example. If the added amount C1 is higher than the control reference value C0, it is assumed that there is a low possibility that scale will be generated immediately even if scale generation components are mixed from the sewage treated water 7 into the system in which the circulating water 2 is circulating. It is determined that the scale generation risk in the system is low.

  Further, as shown in FIG. 3, for example, the risk determination processing unit 24 is a system in which the circulating water 2 is circulated when the addition amount C2 specified from the concentration change of the scale generation component is lower than the management reference value C0. If the scale generation component is mixed in from the sewage treated water 7, it is determined that the scale is likely to be generated, and it is determined that the scale generation risk in the system is high.

  The management reference value C0 used for the determination of such scale generation risk is set based on the operating conditions and operation management standards of the cooling system 1, the operating conditions and operation management standards of the plant to which the cooling system 1 is applied, and the like. The

  When it is determined by the seawater 16 addition test as described above that the scale generation risk is low, the cooling system 1 continues to operate. On the other hand, when it is determined that the scale generation risk is high, the cooling system 1 executes a process for reducing the concentration rate of the circulating water 2 circulating in the system.

  For example, when it is determined that the risk of scale generation is high, the cooling system 1 opens the blow valve 6 of the cooling tower 4 to discharge a part of the circulating water 2 and further opens the makeup water valve 10. By replenishing the sewage treated water 7, the concentration rate of the circulating water 2 circulating in the system is lowered and the risk of scale generation is reduced. At that time, even if the scale generation component is mixed in the sewage treated water 7 to be replenished, the possibility of such mixing has already been taken into account by using the seawater 16 for the determination of the scale generation risk. . In general, the circulating water 2 in the system is managed at a constant amount of water.

  In addition, when it is determined that the scale generation risk is high, the cooling system 1 adds sewage water such as tap water to the sewage treatment water 7 of the makeup water tank 8 and dilutes the sewage to be used as makeup water. The scale generation component concentration of the treated water 7 may be lowered to prevent scale generation. Furthermore, pretreatment such as ion exchange treatment using an ion exchange resin is performed on the sewage treated water 7 before replenishment to the cooling tower 4 (not shown), and the concentration of scale-generating components in the sewage treated water 7 is determined. The scale may be lowered to prevent scale generation.

  The operation management of the cooling system 1 by the seawater 16 addition test as described above is preferably performed at least once a day, and more preferably every several hours or continuously. After completion of the seawater 16 addition test, the seawater pump 15 is stopped to stop the addition of the seawater 16, the agitator 19 is stopped, the drain valve 23 is opened, and the test water 14 is discharged from the seawater addition tank 17.

It should be noted that the processing operation of each element constituting the cooling system 1 as described above and the operation management of the cooling system 1 can be controlled using a computer (not shown).
The operation management of the cooling system 1 can also be performed as follows. That is, a certain amount (for example, 1 L) of the circulating water 2 is weighed from a water sampling line 13 into a glass or metal container such as a beaker, and used as test water. A predetermined amount of seawater collected in advance is added to the test water while stirring with a stirrer or a stirring blade and performing predetermined heating. Meanwhile, the concentration of the scale-generating component in the test water is measured, the relationship between the seawater addition amount and the scale-generating component concentration is obtained, and the seawater addition amount at the time when scale generation starts is specified. Then, it is only necessary to compare the specified seawater addition amount with its management reference value and determine the scale generation risk in the system in which the circulating water 2 is circulating.

In the cooling system 1, the case where the heat exchanger 3 is used as an object to be cooled by the circulating water 2 is illustrated, but the object to be cooled is not limited to the heat exchanger 3.
As explained above, in order to manage the operation of a cooling system that uses water such as sewage treated water in which scale-generating components are unsteadyly mixed with seawater or the like as make-up water, it is actually circulated in the system. Using the circulating water, the addition test of water such as seawater containing the scale generation component that can be mixed is performed, and the scale generation risk in the system is determined based on the addition amount. Then, based on the determination result, the concentration ratio of circulating water circulating in the system is changed, and the quality of the makeup water is controlled. This makes it possible to easily and reliably perform operation management that suppresses the generation of scale in the system, even when using makeup water that varies in water quality.

It is a figure which shows the structural example of a cooling system. It is FIG. (1) which shows the example of the relationship between seawater addition amount and a scale production | generation component density | concentration. It is a figure (the 2) which shows the example of the relationship between seawater addition amount and a scale production | generation component density | concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cooling system 2 Circulating water 3 Heat exchanger 4 Cooling tower 5 Circulating water pump 6 Blow valve 7 Sewage treated water 8 Supply water tank 9 Supply water pump 10 Supply water valve 11 Test water pump 12 Test water valve 13 Water sampling line 14 Test Water 15 Seawater pump 16 Seawater 17 Seawater addition tank 18 Level sensor 19 Stirrer 20 Pipe 21 Constant temperature water circulation device 22 Concentration meter 23 Drain valve 24 Risk judgment processing section

Claims (4)

In a cooling water circulation type cooling system that circulates cooling water and replenishes the reduced amount of the circulating cooling water with makeup water,
Means for extracting a part of the cooling water circulating in the system;
Means for adding a component that generates a scale that can be mixed into the makeup water to the extracted cooling water, and obtaining a relationship between the added amount of the component and the concentration of the added component in the cooling water; ,
Means for determining the risk of scale generation in the system using the acquired relationship;
A cooling system comprising:   The means for determining the risk includes a reference value as the component addition amount set in advance by the system, the addition amount at the time when the concentration of the added component in the cooling water is saturated or the increase starts to decrease. 2. The cooling system according to claim 1, wherein the risk is determined based on a magnitude relationship between the reference value and an addition amount when the concentration of the component is reduced to saturation or increase. In the operation management method of the cooling water circulation type cooling system, circulating the cooling water and replenishing the reduced amount of the circulating cooling water with makeup water,
Extract a part of the cooling water circulating in the system,
To the extracted cooling water, a component that generates a scale that can be mixed into the makeup water is added, and the relationship between the amount of the component added and the concentration of the added component in the cooling water is obtained.
Using the acquired relationship to determine the risk of scale generation in the system,
An operation management method for a cooling system.   When determining the risk, the added amount at the time when the concentration of the added component in the cooling water is saturated or the increase starts to decrease is the reference value as the component added amount set in advance by the system. 4. The cooling system according to claim 3, wherein the risk is determined based on a magnitude relationship between an addition amount when the concentration of the component starts to decrease or the increase in concentration of the component and the reference value. 5. Operation management method.

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