JP5699445B2 - Water treatment chemical injection management method and apparatus for open circulation cooling water system - Google Patents

Description

  The present invention relates to a chemical injection control method and apparatus for an open circulating cooling water system.

  In an open circulation cooling water system for industrial use or air conditioning, water whose temperature has been raised by heat exchange in a heat exchanger such as a refrigerator is evaporated in a cooling tower, and cooled and released by releasing latent heat of evaporation. Since the open circulation cooling water system uses water in a circulating manner, the water is concentrated by evaporation, and corrosion failure, scale failure, and slime failure are likely to occur. In order to prevent these obstacles, various water treatment chemicals such as a corrosion inhibitor, a scale inhibitor, and a slime adhesion inhibitor are added to the circulating water in the open circulation cooling water system.

  These drugs do not exhibit sufficient effects unless they are constantly maintained above a certain concentration. On the other hand, excessive injection is not only economically wasteful but also harmful. Therefore, when a drug is used, it is desirable to manage the drug concentration in the circulating water so that the purpose of use is achieved most effectively and economically.

  As a means for injecting such a water treatment chemical into the circulating water and maintaining a constant concentration of the water treatment chemical in the circulating water, a chemical addition control method is known in which the amount of chemical lost by blow discharge is added. In this case, the chemical addition amount can be determined regardless of the concentration factor of circulating water, but a blow amount measuring device for measuring the blow discharge amount is required. Blow water is often discharged by overflow using an overflow pipe provided at a constant water level in the cooling water pit. In this case, not only cooling water (circulated water) but also air is entrained in the blow water. There is a problem that the blow amount cannot be measured. There is a water meter that can measure the amount of blow water even if air is involved, but it is expensive, and it is not desirable because a space for installing the water meter in an existing blow pipe cannot always be secured or a large-scale work may be required.

  As another conventional water treatment chemical addition control method, a replenishment water replenishment amount is measured with a pulse transmission type flow meter or the like, and a fixed amount of water treatment chemical is proportionally injected to the replenishment water (for example, Japanese Patent No. 2594224). Etc.) has been carried out. This method (hereinafter sometimes referred to as “replenishment water volume proportional drug injection control method”) is combined with automatic blow control that maintains the electrical conductivity in the circulating water to maintain the drug concentration in the circulating water constant. It is possible to do this, and it is relatively simple and the reliability of the apparatus is high.

  Also, water treatment chemicals can be used as tracer substances, or tracer substances with a concentration proportional to the water treatment chemicals can be added, the tracer substances can be continuously measured, and water treatment chemicals can be injected (hereinafter referred to as “tracer method”). (For example, Japanese Patent No. 3751655, Japanese Patent No. 434916, etc.).

  Since this method measures and controls the tracer substance concentration contained in the water treatment chemical in the circulating water, it is possible to maintain the water treatment chemical concentration in the circulating water constant.

Japanese Patent No. 2594224 Japanese Patent No. 3751655 Japanese Patent No. 4344916

  From the viewpoint of saving water and zero emissions, various types of wastewater are collected and reused as make-up water for cooling towers. In such a water system, the amount and quality of recovered water vary greatly depending on the operating conditions of the recovery source equipment. In addition, there are water systems in which groundwater, clean water, industrial water, and the like are mixed in addition to wastewater, and the quality of makeup water supplied to the cooling tower is not constant.

  The combination of the conventional makeup water proportion proportional chemical injection control method and automatic blow management that keeps the electrical conductivity of the circulating water constant, the chemical concentration in the circulating water is constant when the concentration factor of the circulating water remains constant. Can be maintained. However, when the makeup water quality changes, the concentration factor varies, so the chemical concentration cannot be kept constant.

For example, in an open circulating cooling water system in which X (g) chemicals are injected with respect to the makeup water amount M (m ³ ), the electrical conductivity of makeup water is a (mS / m), and the electrical conductivity of circulating water is When b (mS / m) is set, the chemical concentration Y (mg / L) in the circulating water is expressed by the following equation (1).

  The chemical concentration Y 'in the circulating water when the makeup water quality fluctuates and the electrical conductivity of the makeup water decreases and becomes a / n is expressed by the following equation (2)

となり、Ｙのｎ倍の濃度になり、薬品濃度を一定に維持できない。

Therefore, the concentration is n times that of Y, and the chemical concentration cannot be kept constant.

  Moreover, in the conventional tracer method, it is possible to keep the chemical concentration in the circulating water constant without being affected by the quality of the makeup water and the concentration factor. However, advanced measurement equipment such as an absorptiometer and an ion electrode is required to measure the chemical concentration. Although these devices can measure with high accuracy, maintenance such as frequent calibration and replacement of parts is necessary to maintain the performance. For this reason, the introduction and operation of the apparatus are costly and troublesome.

  The present invention provides a water treatment chemical injection management method and apparatus for an open circulating cooling water system that can inject a chemical so as to maintain a constant chemical concentration in the circulating water by a simple method even in an aqueous system in which the quality of makeup water is changed. The purpose is to provide.

Water treatment chemical injection management method of the present invention (claim 1) is a chemical addition method for keeping the water treatment chemical concentration of circulating water in an open circulation cooling water system constant electricity circulating water by the automatic blowing manager Keeping the conductivity constant, target chemical concentration in circulating water is Y (mg / L), makeup water volume is M (m ³ ), electrical conductivity of makeup water is a (mS / m), electricity of circulating water When the conductivity is b (mS / m) and the electrical conductivity due to the chemical in the circulating water is c (mS / m), the chemical X (g) to be injected into the makeup water is determined by the following formula (4). It is characterized by this.

The water treatment chemical injection management method according to claim 2 is the makeup water supply method according to claim 1, wherein the difference in cooling water temperature entering and exiting the cooling tower is ΔT (° C.) and the scattering loss ratio with respect to the circulating water amount is z (%). When the electrical conductivity of the water is higher than the value obtained by the equation (10) described later, the chemical amount X (g) to be injected into the makeup water is determined by the equation (4), and the electrical conductivity of the makeup water is represented by the equation (10). When the amount is less than or equal to the obtained value, the amount X (g) of the medicine to be injected is determined by the following equation (11) .

The water treatment chemical injection management device of the present invention (Claim 3 ) is a chemical addition device for maintaining a constant concentration of water treatment chemical in the circulating water in the open circulating cooling water system , and detects the amount of makeup water M (m ³ ). A means for detecting the electrical conductivity a (mS / m) of the makeup water, a means for detecting the electrical conductivity b (mS / m) of the circulating water, and for maintaining the electrical conductivity b of the circulating water constant. An automatic blow management device, a means for detecting electrical conductivity c (mS / m) due to chemicals in the circulating water, and a chemical amount determining means for determining chemical X (g) to be injected into the replenishing water according to the following equation (4): It is characterized by comprising.

The water treatment chemical injection management device according to claim 4 is the water treatment chemical injection management device according to claim 3 , further comprising a detecting means for a cooling water temperature difference ΔT (° C.) entering / exiting the cooling tower, wherein the chemical amount determining means When the degree is higher than the value obtained by the equation (10) described later, the chemical amount X (g) to be injected into the makeup water is determined by the equation (4), and the electrical conductivity of the makeup water is less than the value obtained by the equation (10). In this case, the chemical amount X (g) to be injected is determined by the following equation (11) .

  In the present invention, when the water quality (salt concentration) of circulating water is set with an automatic blow device based on electrical conductivity so as to keep the water quality (salt concentration) constant, the concentration factor is known even if the makeup water quality (salt concentration) changes. The amount of chemical added per make-up water is changed by the amount by which the concentration factor has changed.

  In the normal case, the replenishment water is replenished using a ball tap in conjunction with opening and closing of the replenishment water supply valve, as described in the following embodiments. Often changes. Therefore, in order to determine the chemical addition amount more accurately, it is desirable to change the chemical addition amount according to the measurement result of the makeup water amount.

  In order to detect the concentration of circulating water, it is better to detect how much the circulating water is concentrated with respect to makeup water. For example, ion electrode measurement, ion chromatograph measurement, which can detect a specific ion concentration, Although a colorimetric method or the like can be used, it is desirable that the concentration is determined from the electric conductivity of makeup water and circulating water because it is inexpensive and simple. In this case, the concentration factor can be determined from the ratio between the electrical conductivity of the circulating water and the electrical conductivity of the makeup water, but the amount of chemical added can be determined by continuously determining the ratio of the electrical conductivity of the circulating water and the makeup water. It is not necessary to determine the electrical conductivity of the circulating water and make-up water, and then how much the electrical conductivity of the make-up water has changed based on the electrical conductivity of the make-up water at that time. If it can be calculated, the chemical addition amount can be determined similarly.

  In the present invention, in addition to the conventional flow rate proportional chemical injection control method and automatic blow management for keeping the electrical conductivity of the circulating water constant, by performing the control to inject an amount of chemical according to the electrical conductivity of the makeup water Even if the quality of the makeup water fluctuates, it is possible to keep the chemical concentration in the circulating water constant.

  When the water quality of the make-up water changes and the electrical conductivity decreases, the chemical concentration in the circulating water can be maintained by reducing the amount of chemical injection according to the ratio of the electrical conductivity of the make-up water and the circulating water. Similarly, when the electrical conductivity of the makeup water increases, the chemical concentration in the circulating water can be maintained by increasing the chemical injection amount.

  In the formula (2), when the electric conductivity of the makeup water becomes a / n, the chemical concentration can be kept constant by setting the chemical injection amount to X / n.

  The electrical conductivity meter used in the present invention is simple, hardly affected by dirt, and can be measured with high accuracy by using multiple electrodes. Therefore, the electrical conductivity meter is lower in price and more reliable than the tracer method.

  The present invention can be applied not only to newly installed equipment, but also to the existing automatic blow management and flow proportional chemical injection control equipment by adding a make-up water conductivity meter with analog output to easily change the pump to an analog signal control type. By applying various improvements, it can be applied to existing facilities.

It is a flowchart of the facility to which the water treatment chemical injection management method of the open circulation cooling water system according to the embodiment is applied. It is a graph which shows the result of an Example. It is a graph which shows the result of a comparative example.

  FIG. 1 is a system diagram showing a circulating cooling water system, in which a cooling tower 1, a circulating pump 2 and a heat exchanger 3 are connected by a circulating water channel 4.

  In the cooling tower 1, the cooling water sprayed from the water spray plate 1a is cooled in contact with the air introduced from the louver 1c while flowing down the filler 1b, and is stored in the pit 1d. Discharged inside. Normally, steam and splashed water accompany this exhaust air.

  Cooling water in the pit 1 d is introduced from the circulation pump 2 to the heat exchanger 3. The cooling water having a high temperature in the heat exchanger 3 is cooled by partially evaporating in the cooling tower 1, flows down into the pit 1d, and circulates again.

  The pit 1d is provided with an over blow tube 1f and a ball tap 5. A supply water channel 6 is connected to the ball tap 5. When the water level in the pit 1d is lowered due to the evaporation and scattering of the cooling water, the ball tap 5 is opened, the makeup water is supplied from the makeup water channel 6, and the water level of the pit 1d is kept constant.

  A second supply water channel 7 branches from the supply water channel 6, and a valve 8 provided in the second supply water channel 7 is controlled by the automatic blow management device 9. A detection signal of an electric conductivity meter 10 installed so as to measure the electric conductivity of water in the pit 1 d is input to the automatic blow management device 9.

  In the cooling tower 1, the circulating cooling water is concentrated by evaporating a part of the cooling water, and the salinity concentration is increased. Further, foreign matters such as dust are mixed from the atmosphere, the scale and slime of the circulating cooling water system are peeled off, and the circulating cooling water system contains turbidity. In order to prevent the generation of corrosion, scale, slime and the like due to such circulating cooling water, a water treatment chemical is injected into the replenishment water channel 6 through the chemical tank 12, the chemical pump 13 and the chemical injection channel 14. The medicine may be poured into the cooling water pit 1d instead of the replenishment water channel 6.

  As will be described in detail later, in this embodiment, the medicinal pump 13 has a pulse transmission type flow meter 15 that measures the flow rate of the replenishment water channel 6 and a pulse amount proportional medicinal controller 16, and the electrical conductivity of the replenishment water channel 6. It is controlled by the electric conductivity meter 17 to be measured.

  Next, the chemical injection control of the circulating cooling water system will be described in detail. In this embodiment, an amount of chemical corresponding to the ratio of the amount of makeup water to the electrical conductivity of makeup water is added so that the concentration of the medicine in the circulation water is kept constant under the condition of keeping the conductivity of circulating water constant. Inject for a predetermined amount of makeup water.

The target chemical concentration in circulating water is Y (mg / L), the amount of makeup water is M (m ³ ), the electrical conductivity of makeup water is a (mS / m), and the electrical conductivity of circulating water is b (mS / m). m), the chemical X (g) to be injected into the makeup water is calculated from the above equation (1).

にて算出することができる。

Can be calculated.

  Y and b are constants and X is defined by M and a in order to perform control to keep the chemical concentration of circulating water and the electrical conductivity of circulating water constant. Therefore, by injecting an amount of chemical obtained by multiplying the makeup water flow rate and the electrical conductivity of makeup water, the concentration of the medicine in the circulating water can be kept constant even if the makeup water quality varies.

  In order to execute this chemical injection control, in this embodiment, a control device constituted by the following four means (i) to (iv) is used.

(I) Automatic blow management device 9 for controlling the electrical conductivity of the circulating water so as to keep it constant.
This automatic blow management device 9 is for automatically blowing when the electrical conductivity measured by the electrical conductivity meter 10 exceeds a set value, and for keeping the electrical conductivity of the circulating water constant, When the detected value of the electric conductivity meter 10 exceeds a preset value, the valve 8 is opened to start water supply, and a part of circulating water is discharged from the overblow pipe 1f by overblow. And when the electrical conductivity of circulating water falls below a threshold value, the valve 8 is closed and makeup water is stopped. Instead of opening and closing the replenishing water valve 8, a blow valve may be provided and the automatic blow management device 9 may open and close the blow valve.

(ii) Electrical conductivity meter 17 for measuring and outputting makeup water electrical conductivity
The electrical conductivity meter 17 continuously measures and outputs the electrical conductivity of the makeup water. The electrical conductivity meter 17 may be installed in a makeup water inlet other than the makeup water channel 6, a makeup water tank, or the like. In this embodiment, the make-up water from the ball tap 5 and the make-up water from the automatic blow management valve 8 are independent from each other. An electric conductivity meter 17 is installed in the center. However, when injecting chemicals into the replenishment water channel 6, it is desirable to install an electrical conductivity meter 17 upstream from the injection point in order to avoid the influence of an increase in electrical conductivity due to the addition of chemicals. In addition, it is possible to inject the chemicals into the cooling tower pit 1d instead of the replenishment water channel 6, and this is desirable from the viewpoint that the electrical conductivity of the replenishment water does not increase.

(Iii) Means for measuring and outputting the flow rate of makeup water The flow meter 15 continuously measures and outputs the flow rate of makeup water. As the flow meter 15, for example, a pulse transmission type flow meter or a flow meter such as a gear type, electromagnetic type, or ultrasonic type equipped with a flow rate output signal is used, but is not limited thereto. Since the make-up water from the ball tap 5 and the make-up water from the automatic blow management valve 8 are independent, a flow meter 15 is installed upstream of the branch portion of the water channel 7 in order to measure the amount of both make-up water. Has been.

(Iv) The controller 16 and the drug injection pump 13 for determining the amount of medicine to be injected based on the output signals of both (ii) and (iii) above.
Based on the signals (ii) and (iii), the controller 16 determines the amount of chemical to be injected according to the electrical conductivity of a certain amount of makeup water based on the calculation result of the equation (3). The pump 13 performs drug injection based on this control. The electrical conductivity of make-up water can be determined with an instantaneous value, but in systems where fluctuations in the quality of make-up water occur in a short period of time, dosing is performed with respect to the average value of the electrical conductivity of a certain amount of make-up water. It is desirable to do.

  In this embodiment, in addition to the arithmetic unit, the controller 16 uses a pulse amount proportional medicine injection controller 16 that instructs to inject an amount of medicine proportional to the pulse amount, but is proportional to the analog signal. An analog signal proportional drug injection device that instructs to inject a predetermined amount of medicine can be used, and a plurality of control devices can be used in combination. A pump with a built-in control device may be used.

In addition, when the makeup water from the ball tap 5 and the makeup water from the automatic blow management valve 8 are independent, the amount of makeup water or the electrical conductivity of both cannot be measured.
[1] A method in which two control devices and two pumps are provided, and the chemical injection amount is determined from the amount of replenishing water and electrical conductivity of each, and injected separately.
[2] A method in which two control devices and one pump are installed, the amount of chemicals to be injected is determined from the amount of replenishment water and electrical conductivity, and the medicines are dispensed in a batch.
[3] With a single control device and pump, it is possible to cope with three methods of determining the amount of medicine to be injected by calculating both the amount of replenishment water and the electrical conductivity, and then injecting the medicine in a batch. .

[Application to existing equipment]
It is possible to change to the method of the present invention with a simple modification to existing facilities that have been managed by conventional flow rate proportional chemical injection control and automatic blow. In existing cooling tower equipment with a makeup water flow rate proportional chemical injection control device, for example, an electrical conductivity meter with analog signal output can be added as an electrical conductivity meter in (ii), or a chemical injection pump in (iv) can be installed. By changing to the analog signal input control type, it becomes possible to inject an amount of medicine based on the chemical injection signal from the existing makeup water flow rate proportional chemical injection control device and the analog signal from the electrical conductivity meter.

[Correction of drug dosage]
Since the above method does not consider the increase in the electrical conductivity of the circulating water due to the addition of the chemical, when the electrical conductivity of the circulating water increases greatly due to the addition of the chemical, the chemical concentration in the circulating water becomes lower than the set value. For this reason, it is desirable to correct the drug injection amount by adding the electrical conductivity of the chemical to the electrical conductivity of the circulating water.

The target chemical concentration in circulating water is Y (mg / L), the amount of makeup water is M (m ³ ), the electrical conductivity of makeup water is a (mS / m), and the electrical conductivity of circulating water is b (mS / m). m) If the electrical conductivity of the chemical in the circulating water is c (mS / m), the chemical X (g) injected into the makeup water should be expressed as the following formula (4) based on the formula (3): Can do.

また、上記方法では飛散損出が考慮されていないため、補給水の電気伝導度が極めて低くなった場合、薬注量が極めて少量になる。しかし実際は、循環水量に対して一定量の飛散損出が冷却塔からあるため、補給水の電気伝導率が極めて低く飛散損出量が全ブロー量となる場合(ノンブロー運転の領域)は、設定した電気伝導度と補給水電気伝導度の比に基づいた薬注では循環水中の薬品濃度が設定値より低くなる課題がある。また、ブローを行わないノンブロー運転の領域では、循環水の電気伝導度が設定値まで上昇しない現象が生じる。そのため、電気伝導度と薬注量を補正して飛散損出により系外へ排出される薬品を補給する制御を行うことが望ましい。

In addition, since the above method does not take into account the scattering loss, when the electrical conductivity of make-up water becomes extremely low, the amount of chemical injection becomes extremely small. However, in reality, there is a certain amount of splashing loss from the cooling tower with respect to the circulating water volume, so if the make-up water electrical conductivity is very low and the splashing loss is the total blow rate (non-blow operation area), set In the chemical injection based on the ratio between the electrical conductivity and the electrical conductivity of the makeup water, there is a problem that the chemical concentration in the circulating water is lower than the set value. Further, in a non-blow operation region where no blow is performed, a phenomenon occurs in which the electrical conductivity of the circulating water does not increase to the set value. Therefore, it is desirable to perform control to correct the electrical conductivity and the amount of medicine to be supplied and supply chemicals discharged out of the system due to scattering loss.

The total blow amount TB (m ³ / h) is the evaporation amount E (m ³ / h), the electrical conductivity of makeup water is a (mS / m), the electrical conductivity of circulating water is b (mS / m), If the electrical conductivity of the chemical in the circulating water is c (mS / m), it can be expressed as the following equation (5).

ここで、飛散損出量Ｗ（ｍ^３／ｈ)が全ブロー量ＴＢ(ｍ^３／ｈ)に等しい場合の補給水の電気伝導度ａは（６）式のように表わすことができる。

Here, the electrical conductivity a of the makeup water when the scattering loss amount W (m ³ / h) is equal to the total blow amount TB (m ³ / h) can be expressed by the following equation (6).

補給水の電気伝導度が、（６）式で求まるａ以下では飛散損出量が全ブロー量となるため、飛散損出により系外へ排出される薬品を補給するように薬注量を補正する必要がある。この時の補給水に注入する薬品Ｘ(ｇ)は（４）式および（６）式より、次の（７）式のように求まる。

When the electrical conductivity of make-up water is less than or equal to a obtained by equation (6), the amount of splash loss is the total blow amount. Therefore, the chemical dose is corrected to replenish the chemicals discharged from the system due to the splash loss. There is a need to. The chemical X (g) to be injected into the replenishing water at this time can be obtained from the equations (4) and (6) as the following equation (7).

ここで、循環水量をＲ(ｍ^３／ｈ)、冷却塔入出の冷却水温度差をΔＴ（℃）、循環水量に対する飛散損出割合をｚ（％）とすると、蒸発量Ｅ(ｍ^３／ｈ)および飛散損出量Ｗ(ｍ^３／ｈ)はそれぞれ次の（８），（９）式で規定できる。

Here, assuming that the circulating water amount is R (m ³ / h), the cooling water temperature difference between entering and exiting the cooling tower is ΔT (° C.), and the scattering loss ratio with respect to the circulating water amount is z (%), the evaporation amount E (m ³ / h) and the scattering loss amount W (m ³ / h) can be defined by the following equations (8) and (9), respectively.

この（８），（９）式より、（６），（７）式はそれぞれ次の（１０），（１１）式のように表わすことができる。

From the equations (8) and (9), the equations (6) and (7) can be expressed as the following equations (10) and (11), respectively.

したがって、補給水の電気伝導度が（１０）式で求まるａよりも高い場合は（４）式で求まる薬品量を、また、補給水の電気伝導度が（１０）式で求まるａ以下の場合は（１１）式で求まる薬品量を、一定量の補給水に対して注入することにより、補給水の電気伝導度によらず循環水中の薬品濃度を一定に維持管理することができる。

Therefore, when the electrical conductivity of make-up water is higher than a obtained by equation (10), the amount of chemical obtained by equation (4), and when the electric conductivity of make-up water is less than a obtained by equation (10) By injecting the chemical amount obtained by the equation (11) into a certain amount of make-up water, the concentration of the medicine in the circulating water can be maintained and managed constant regardless of the electrical conductivity of the make-up water.

  As a simple countermeasure when it is difficult to calculate the chemical loss, such as when the scattering loss changes, a certain amount of chemical is injected when the electrical conductivity of the makeup water falls below the specified value for a certain period of time. It is possible to respond by performing such control.

  In the case of a general cooling tower, when the circulation pump 2 is stopped, the water flowing through the water spray plate 1a and the filler 1b falls, and a part of the circulating water is discharged out of the system by overblow. Therefore, when the pump is restarted, the amount of supplementary water that supplements the circulating water discharged to the outside due to the falling water flows in, so that the electrical conductivity and chemical concentration of the circulating water are reduced. Particularly in the non-blow operation region, the proportion of discharge due to overblowing in the blow amount is large, and if the circulation pump is frequently started and stopped, the circulating water is diluted with make-up water and the concentration decreases. For this reason, when the electrical conductivity of the circulating water is lowered, it is desirable to perform control to additionally inject the insufficient chemical concentration.

  The start / stop of the circulation pump 2 can be known by the interlock signal of the pump 2. If the electrical conductivity of the circulating water decreases after the pump 2 is restarted, the discharge amount due to overblowing is estimated from the decrease in the electrical conductivity of the circulating water and the amount of makeup water that has flowed in, and the corresponding chemicals are added. The chemical concentration in the circulating water can be kept constant. It is also possible to add a certain amount of chemicals when restarting the pump, assuming that the amount of discharge due to overblow when the pump is stopped is constant.

When the circulation pump 2 is restarted, makeup water flows in and the electrical conductivity of the circulating water decreases beyond the setting of the automatic blow management device 9. Therefore, even when the interlock signal of the circulation pump 2 cannot be obtained, since the makeup water flow rate and the circulation water electrical conductivity are measured, it is possible to capture the characteristics of the discharge due to the overblow. The chemical concentration in the circulating water can be kept constant by estimating the discharge amount due to overblow from the decrease in the electrical conductivity of the circulating water and the amount of replenished water that has flowed in, and adding chemicals accordingly. Similarly, a fixed amount of chemicals may be added when the amount of discharge due to overblowing due to the pump stop is constant and the pump 2 is restarted.
In addition, as a method for detecting the concentration of circulating water in the present invention, various conventional methods can be used in addition to the above-described method using electric conductivity of makeup water and circulating water, In addition, it is also possible to use the concentration obtained from the water balance by detecting the amount of evaporated water or the amount of blown water.

[Example 1]
In the circulating cooling water system shown in FIG. 1, chemicals are injected by the method of the present invention, and the transition results of the chemical concentration in the circulating water are shown in FIG.

  The equipment specifications of the cooling tower 1 are as follows.

Cooling capacity: 360kW
Retained water volume: 1.2m ³
Circulating water volume: 20 m ³ / hr
Cooling target: Plate heat exchanger for steam condensation Makeup water: Nogicho tap water (about 25mS / m) and pure water (about 0mS / m) mixed at an arbitrary ratio Circulating water electric conductivity setting: 55mS / m
Moreover, the following was used as a chemical injection control apparatus.

Pulse transmission type flow meter 15: FMDS20II manufactured by Aichi Watch Electric Co., Ltd.
Pulse proportional time chemical injection controller 16 and automatic blow management device 9: Kurita CT-R manufactured by Kurita Kogyo Co., Ltd.
Makeup water conductivity meter 17 with analog signal output: WBM-100 manufactured by Toa DKK Corporation
Analog signal input type chemical injection pump 13: PZDM-30 manufactured by Takumina Co., Ltd.
As shown in FIG. 2, the chemical concentration in the circulating water remained stable within the range of the set value ± 10% with respect to the set value of 400 mg / L even when the electrical conductivity of the makeup water varied.

[Comparative Example 1]
In the cooling tower facility where the operation of Example 1 was performed, chemicals were injected by a makeup water flow rate proportional chemical injection control system. Fig. 3 shows the transition results of the chemical concentration in the circulating water. As shown in FIG. 3, the chemical concentration of the circulating water greatly fluctuated due to fluctuations in the electrical conductivity of the makeup water.

Claims (4)

A chemical addition method for maintaining a constant concentration of water treatment chemical in the circulating water in an open circulating cooling water system,
Automatic blow management device keeps the electrical conductivity of circulating water constant,
The target chemical concentration in circulating water is Y (mg / L), the amount of makeup water is M (m ³ ), the electrical conductivity of makeup water is a (mS / m), and the electrical conductivity of circulating water is b (mS / m). m) Water treatment characterized by determining the chemical X (g) to be injected into the makeup water by the following equation (4), where c (mS / m) is the electrical conductivity of the chemical in the circulating water. Chemical injection management method.

In claim 1,
When the cooling water temperature difference between the cooling tower and the cooling tower is ΔT (° C.) and the scattering loss ratio with respect to the circulating water amount is z (%), the electric conductivity of makeup water is higher than the value obtained by the following equation (10). Sometimes the chemical amount X (g) to be injected into the makeup water is determined by the above equation (4),

A water treatment chemical injection management method, wherein the chemical amount X (g) to be injected is determined by the following equation (11) when the electric conductivity of the makeup water is not more than the value obtained by the above equation (10) .

A chemical addition device for maintaining a constant concentration of water treatment chemical in circulating water in an open circulating cooling water system,
Means for detecting the amount of makeup water M (m ³ );
Means for detecting the electrical conductivity a (mS / m) of makeup water;
Means for detecting the electrical conductivity b (mS / m) of the circulating water;
An automatic blow management device for keeping the electrical conductivity b of the circulating water constant;
A means for detecting electrical conductivity c (mS / m) by chemicals in the circulating water;
A water treatment chemical injection management apparatus comprising: a chemical amount determination means for determining a chemical X (g) to be injected into makeup water according to the following equation (4):

However, in formula (4), Y is the target chemical concentration (mg / L) in the circulating water. In claim 3 , further
It has a means for detecting the cooling water temperature difference ΔT (° C.) entering and exiting the cooling tower,
The chemical amount determining means determines the chemical amount X (g) to be injected into the makeup water when the electrical conductivity of the makeup water is higher than the value obtained by the following equation (10) according to the equation (4):

(However, z is the scattering loss rate (%) with respect to the amount of circulating water.)
A water treatment chemical injection management apparatus characterized in that when the electrical conductivity of makeup water is equal to or less than the value obtained by the above formula (10), the chemical amount X (g) to be injected is determined by the following formula (11) .

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