Cooling-water system control method and cooling-water system control apparatus

Abstract

To provide a cooling-water system control method and a cooling-water system control apparatus, capable of promptly detecting an occurrence of abnormality in such as various sensors or a blow-purpose valve potentially leading to a fault occurrence such as scales with a smaller number of sensors at a lower cost in a control of a cooling-water system having a cooling tower and a refrigerator.SOLUTION: A cooling-water system control method is configured to control a cooling-water system 1 including a cooling tower 10 and a refrigerator 12 including a condenser 24. A chemical is injected to circulation cooling-water, and on the basis of electrical conductivity of the circulation cooling-water, a supply of make-up water and a discharge of the circulation cooling-water at the cooling tower 10 are controlled. In the method, an alarm is issued, if there is a continued state for a prescribed duration at which at least one of the electrical conductivity of the circulation cooling-water and a chemical concentration is below or above a predetermined threshold value, when an operation signal at the cooling tower 10 is at an on-state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling water system control method and a cooling water system control device for controlling a cooling water system including a cooling tower and a chiller. [Background technology]

[0002] In conventional cooling water systems equipped with cooling towers and chillers, in order to prevent the circulating cooling water from concentrating, make-up water is supplied to the circulating cooling water and blowdown control is performed to discharge the concentrated circulating cooling water.In addition, chemical injection control is performed to inject chemicals such as slime inhibitors and scale inhibitors into the circulating cooling water to prevent slime and scale formation.

[0003] For example, automatic blowdown control for the concentration of circulating cooling water is performed by monitoring the electrical conductivity of the circulating cooling water using an electrical conductivity measuring device such as an electrical conductivity sensor, and the concentration of chemicals such as slime inhibitors and scale inhibitors in the circulating cooling water is measured using a chemical concentration measuring device such as a chemical concentration sensor, and chemical injection control into the circulating cooling water is performed by setting a predetermined concentration.

[0004] Conventionally, abnormalities in electrical conductivity sensors and drug concentration sensors have been detected by the following methods (see, for example, Patent Document 1).

[0005] This was determined based on (a) the chemical concentration of the circulating cooling water measured by the chemical concentration sensor, (b) the electrical conductivity of the circulating cooling water measured by the electrical conductivity sensor, (c) the cumulative flow rate of the makeup water, (d) the liquid level of the chemical in the chemical tank, and the calculated chemical concentration calculated using (b) to (d) according to the following formula (1). Calculated chemical concentration (g / m 3 ) = Amount of chemical used calculated from the chemical liquid level difference (g) / Total flow rate of makeup water (m 3 ) × concentration factor calculated from the electrical conductivity of the circulating cooling water (1)

[0006] However, this method can only determine whether the electrical conductivity sensor is dirty, and cannot detect abnormalities such as when the blow valve that discharges the circulating cooling water breaks down, so it does not adequately avoid the risk of abnormalities in the concentration control of the circulating cooling water due to a faulty electrical conductivity sensor.In addition, it is necessary to introduce a relatively expensive flow meter to accurately calculate the chemical concentration, and an ultrasonic level meter to quantify the amount of chemical solution. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-200982 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a cooling water system control method and cooling water system control device that can quickly detect abnormalities in various sensors and blow valves that can lead to problems such as scale, using fewer sensors and at low cost, in controlling a cooling water system that includes a cooling tower and a chiller. [Means for solving the problem]

[0009] The present invention is a cooling water system control method for controlling a cooling water system including a cooling tower that performs heat exchange using circulating cooling water, and a chiller that includes a condenser having an inlet and outlet for the circulating cooling water and an inlet and outlet for the refrigerant for performing heat exchange between the circulating cooling water and the refrigerant, the method comprising the steps of: injecting a chemical into the circulating cooling water; measuring the electrical conductivity of the circulating cooling water, and controlling the supply of makeup water in the cooling tower and the discharge of the circulating cooling water based on the measured electrical conductivity of the circulating cooling water; and issuing an alarm when, when the operation signal of the cooling tower is on, at least one of the electrical conductivity of the circulating cooling water and the chemical concentration remains below or above a predetermined threshold for a predetermined period of time.

[0010] In the cooling water system control method, if the electrical conductivity of the circulating cooling water remains below the predetermined threshold for the predetermined period of time, it is preferable to determine that an abnormality has occurred in the electrical conductivity measuring device that measures the electrical conductivity of the circulating cooling water.

[0011] In the cooling water system control method, if the electrical conductivity of the circulating cooling water continues to exceed the predetermined threshold value for the predetermined period of time, it is preferable to determine that there is an abnormality in the supply of makeup water or the discharge of the circulating cooling water in the cooling tower.

[0012] In the cooling water system control method, it is preferable to determine that an abnormality has occurred in the injection of the chemical agent when the chemical agent concentration in the circulating cooling water remains below the predetermined threshold value for the predetermined period of time.

[0013] The present invention provides a cooling water system control device for controlling a cooling water system including a cooling tower that performs heat exchange using circulating cooling water, and a chiller that includes a condenser having an inlet and an outlet for the circulating cooling water and an inlet and an outlet for the refrigerant for performing heat exchange between the circulating cooling water and the refrigerant, This cooling water system control device comprises: a chemical injection means for injecting a chemical into the circulating cooling water; an electrical conductivity measurement means for measuring the electrical conductivity of the circulating cooling water; a chemical concentration measurement means for measuring the chemical concentration in the circulating cooling water; and a control means for controlling the supply of makeup water in the cooling tower and the discharge of the circulating cooling water based on the measured electrical conductivity of the circulating cooling water, wherein the control means issues an alarm when at least one of the electrical conductivity and chemical concentration of the circulating cooling water remains below or above a predetermined threshold for a predetermined period of time when the operation signal of the cooling tower is on.

[0014] In the cooling water system control device, it is preferable that the control means determines that there is an abnormality in the electrical conductivity measuring means when the electrical conductivity of the circulating cooling water remains below the predetermined threshold for the predetermined period of time.

[0015] In the cooling water system control device, it is preferable that the control means determines that there is an abnormality in the supply of makeup water or the discharge of the circulating cooling water in the cooling tower when the electrical conductivity of the circulating cooling water remains above the predetermined threshold for the predetermined period of time.

[0016] In the cooling water system control device, it is preferable that the control means determines that there is an abnormality in the chemical injection means when the chemical concentration in the circulating cooling water remains below the predetermined threshold for the predetermined period of time. [Effects of the Invention]

[0017] The present invention provides a cooling water system control method and cooling water system control device that can quickly detect abnormalities in various sensors and blow valves that can lead to problems such as scale, using fewer sensors and at low cost, when controlling a cooling water system that includes a cooling tower and a chiller. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic configuration diagram illustrating an example of a cooling water system according to an embodiment of the present invention. [Figure 2] 3 is a flowchart illustrating an example of a cooling water system control method according to an embodiment of the present invention. [Figure 3] 10 is a flowchart illustrating another example of a cooling water system control method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0020] An example of a cooling water system according to an embodiment of the present invention is shown in FIG. 1, and its configuration will be described. Cooling water system 1 includes a cooling tower 10 that performs heat exchange using circulating cooling water, and a chiller 12 equipped with a condenser 24 having an inlet and outlet for circulating cooling water and an inlet and outlet for refrigerant for heat exchange between the circulating cooling water and the refrigerant. Cooling water system 1 also includes a first chemical storage tank 14 as a first chemical injection means for injecting a first chemical containing, for example, a scale inhibitor and an anticorrosive agent into the circulating cooling water, and a second chemical storage tank 15 as a second chemical injection means for injecting a second chemical containing, for example, a slime inhibitor into the circulating cooling water. The cooling water system 1 is equipped with a control device 20 as a control means that issues an alarm when the operation signal of the cooling tower 10 is on and the time period during which the ``electrical conductivity of the circulating cooling water < the electrical conductivity at which the supply of makeup water and the discharge of circulating cooling water start'' continues for a predetermined time, or when the operation signal of the cooling tower 10 is on and the makeup water supply signal and the circulating cooling water discharge signal are on and the ``electrical conductivity of the circulating cooling water ≧ the electrical conductivity at which the supply of makeup water and the discharge of circulating cooling water start'' continues for a predetermined time.

[0021] The cooling tower 10 is equipped with an electrical conductivity measuring device 16 having an electrical conductivity measuring electrode 38 as an electrical conductivity measuring means for measuring the electrical conductivity of the circulating cooling water, and a drug concentration measuring device 18 having a drug concentration measuring electrode 40 as a drug concentration measuring means for measuring the drug concentration of the circulating cooling water.

[0022] The chiller 12 includes a condenser 24 having a circulating cooling water inlet and outlet and a refrigerant inlet and outlet for heat exchange between the circulating cooling water and the refrigerant, an evaporator 22 having a chilled water inlet and outlet and a refrigerant inlet and outlet for heat exchange between chilled water and the refrigerant, a compressor 26 for compressing the refrigerant, and an expansion valve 28 for decompressing and expanding the refrigerant. The circulating cooling water inlet of the condenser 24 may be provided with a circulating cooling water inlet temperature measuring device 30 as a circulating cooling water inlet temperature measuring means for measuring the temperature of the circulating cooling water at the circulating cooling water inlet, a circulating cooling water outlet temperature measuring device 32 as a circulating cooling water outlet temperature measuring means for measuring the temperature of the circulating cooling water at the circulating cooling water outlet, and a refrigerant outlet temperature measuring device 34 as a refrigerant outlet temperature measuring means for measuring the temperature of the refrigerant at the refrigerant outlet.

[0023] First drug storage tank 14 is provided with first drug amount measuring device 49 as first drug amount measuring means for measuring the first drug amount in first drug storage tank 14. Second drug storage tank 15 is provided with second drug amount measuring device 50 as second drug amount measuring means for measuring the second drug amount in second drug storage tank 15.

[0024] In the cooling water system 1 of Fig. 1, the circulating cooling water outlet of the cooling tower 10 and the circulating cooling water inlet of the condenser 24 of the chiller 12 are connected by piping 53 via the circulation pump 36. The circulating cooling water outlet of the condenser 24 of the chiller 12 and the circulating cooling water inlet of the cooling tower 10 are connected by piping 54. The chilled water inlet of the evaporator 22 is connected by piping 56, and the chilled water outlet is connected by piping 58. The refrigerant outlet of the condenser 24 and the refrigerant inlet of the evaporator 22 are connected by piping 60 via the expansion valve 28, and the refrigerant outlet of the evaporator 22 and the refrigerant inlet of the condenser 24 are connected by piping 62 via the compressor 26.

[0025] The first chemical outlet of first chemical storage tank 14 and the first chemical inlet of cooling tower 10 are connected by piping 64 via first chemical injection pump 51. The second chemical outlet of second chemical storage tank 15 and the second chemical inlet of cooling tower 10 are connected by piping 65 via second chemical injection pump 52. A piping 66 is connected to the cooling water outlet of cooling tower 10 via valve 42 and flow meter 44, and a piping 69 for overflowing the circulating cooling water in cooling tower 10 is connected to piping 66 between valve 42 and flow meter 44. A piping 68 is connected to the makeup water inlet of cooling tower 10 via valve 46 and flow meter 48.

[0026] The control device 20 is connected to each of the circulating cooling water inlet temperature measuring device 30, circulating cooling water outlet temperature measuring device 32, refrigerant outlet temperature measuring device 34, electrical conductivity measuring device 16, drug concentration measuring device 18, flow meter 48, flow meter 44, valve 42, valve 46, first drug amount measuring device 49, second drug amount measuring device 50, first drug injection pump 51, and second drug injection pump 52 so as to be able to communicate with each other via wired or wireless electrical connections, etc.

[0027] The cooling water system control device according to this embodiment includes a control device 20. The cooling water system control device according to this embodiment may further include an electrical conductivity measuring device 16 and a chemical substance concentration measuring device 18.

[0028] The cooling water system control method, the cooling water system control device, and the operation of the cooling water system 1 according to this embodiment will be described.

[0029] The cooling tower 10 is, for example, an open-circulation cooling water system cooling tower that cools the circulating cooling water by contacting the circulating cooling water with outside air. In the cooling tower 10, the circulating cooling water stored in the cooling tower 10 is sent from the circulating cooling water outlet to the condenser 24 of the chiller 12 through a piping 53 by a circulation pump 36 via a circulating cooling water inlet. In the condenser 24, the water exchanges heat with a high-temperature, high-pressure refrigerant sent from the compressor 26, producing cooling water with an increased temperature. The circulating cooling water is then sprayed from the top of the cooling tower 10 through a circulating cooling water outlet via a piping 54. The sprayed circulating cooling water comes into contact with air taken in from the outside by a fan 70, partially evaporates, and releases latent heat of evaporation, becoming cooling water with a lowered temperature. The sprayed circulating cooling water falls to the bottom of the cooling tower 10, where it is stored. After being sent from the circulating cooling water outlet to the condenser 24 of the chiller 12 through a piping 53 by a circulation pump 36, the circulating cooling water is circulated.

[0030] Meanwhile, in the chiller 12, the refrigerant, whose temperature has been reduced by heat exchange with the circulating cooling water, is sent from the refrigerant outlet to the expansion valve 28 through piping 60. In the expansion valve 28, the high-pressure refrigerant sent from the condenser 24 is decompressed, expanding and further reducing its temperature, changing into a low-temperature, low-pressure liquid. The expanded refrigerant, whose temperature has been further reduced, is sent from the refrigerant inlet through piping 60 to the evaporator 22. In the evaporator 22, the refrigerant sent from the expansion valve 28 exchanges heat with chilled water sent from the chilled water inlet through piping 56 from an air conditioner or the like, evaporates, and changes into a low-temperature, low-pressure gas. The chilled water, whose temperature has been reduced by heat exchange with the refrigerant, is sent from the chilled water outlet through piping 58 to the air conditioner or the like. The refrigerant, which has exchanged heat with the chilled water and become a gas, is sent from the refrigerant outlet through piping 62 to the compressor 26. In the compressor 26, the refrigerant is compressed and changes into a high-temperature, high-pressure gas. High-temperature, high-pressure refrigerant is sent from the refrigerant inlet through the pipe 62 to the condenser 24, where a refrigeration cycle of condensation → expansion → evaporation → compression is repeated.

[0031] As the circulating cooling water circulates, water evaporates, concentrating salts such as calcium salts and magnesium salts, as well as scale components such as silica, in the circulating cooling water. The concentration of these salts and other scale components can then become supersaturated and precipitate in the circulating cooling water, resulting in the formation of scale. Slime can also be generated by microorganisms that grow in the circulating cooling water. Furthermore, corrosion of equipment, piping, and the like can occur. To prevent water concentration and slime formation, the cooling tower 10 supplies makeup water to the circulating cooling water and discharges the circulating cooling water, replacing it with fresh water for dilution. To prevent scale formation, corrosion, slime formation, and other problems, chemicals, such as scale inhibitors, anticorrosives, and slime inhibitors, are injected into the circulating cooling water. When the circulating cooling water in the cooling tower 10 is diluted as described above, the amount of chemicals in the circulating cooling water decreases, so chemicals are replenished.

[0032] For example, a predetermined amount of a first chemical containing a scale inhibitor and an anticorrosive agent is injected from first chemical storage tank 14 by first chemical injection pump 51 through piping 64 into the circulating cooling water (first chemical injection step). Also, a predetermined amount of a second chemical containing, for example, a slime inhibitor is injected from second chemical storage tank 15 by second chemical injection pump 52 through piping 65 into the circulating cooling water (second chemical injection step). The concentration of the chemical in the circulating cooling water is measured, for example, by chemical concentration measuring device 18 having chemical concentration measuring electrode 40.

[0033] In this embodiment, the electrical conductivity of the circulating cooling water is measured to detect the concentration of salts and the like in the circulating cooling water, and the supply of makeup water and the discharge of the circulating cooling water in the cooling tower 10 are controlled based on the measured electrical conductivity of the circulating cooling water (blow control). For example, the electrical conductivity of the circulating cooling water in the cooling tower 10 is measured by an electrical conductivity measuring device 16 having an electrical conductivity measuring electrode 38 (electrical conductivity measuring step). When the electrical conductivity of the circulating cooling water measured by the electrical conductivity measuring device 16 is equal to or greater than a predetermined upper limit, the control device 20 opens the valve 46 to supply makeup water into the cooling tower 10 through the pipe 68 (makeup water supply step). Then, a portion of the circulating cooling water in the cooling tower 10 is discharged through the pipes 69 and 66 (discharge step). For example, when the electrical conductivity of the circulating cooling water in the cooling tower 10 is equal to or greater than a predetermined upper limit (EC start ), the valve 46 is opened to supply makeup water into the cooling tower 10, and the circulating cooling water is overflowed and discharged through the pipes 69 and 66, and the predetermined electrical conductivity (EC end ), valve 46 is closed. Alternatively, valve 42 is opened to discharge a portion of the circulating cooling water in cooling tower 10 through pipe 66. Valve 42 may be opened to discharge a portion of the circulating cooling water, and valve 46 may be opened to supply makeup water into cooling tower 10 through pipe 68. That is, "control of the supply of makeup water and the discharge of circulating cooling water (control of blowing)" by control device 20 includes a case in which the supply of makeup water into cooling tower 10 is controlled by opening and closing valve 46, which inevitably controls the discharge of a portion of the circulating cooling water due to overflow, etc., and a case in which the supply of makeup water into cooling tower 10 is controlled by opening and closing valve 46 and the discharge of a portion of the circulating cooling water is controlled by opening and closing valve 42. When performing forced chemical injection, it is preferable to stop the supply of makeup water and the discharge of circulating cooling water in cooling tower 10. The supply of makeup water and the discharge of circulating cooling water may be stopped while the cooling tower 10 is out of operation.

[0034] By controlling chemical injection and managing the concentration of the automatic blower control by monitoring electrical conductivity, it is possible to maintain optimal refrigerator efficiency.

[0035] In this embodiment, the control device 20 performs control to issue an alarm when at least one of the electrical conductivity and the chemical concentration of the circulating cooling water remains below or above a predetermined threshold for a predetermined period of time while the operation signal of the cooling tower 10 is on. An example of control to issue an alarm when the electrical conductivity of the circulating cooling water remains below or above a predetermined threshold for a predetermined period of time while the operation signal of the cooling tower 10 is on will be described with reference to the flowchart shown in Figure 2.

[0036] The control device 20 acquires an operation signal for the cooling tower 10 from the control panel of the circulating cooling water pump or the like (S10). When the operation signal for the cooling tower 10 is ON and blow control is being performed automatically, the control device 20 acquires the electrical conductivity EC of the circulating cooling water measured by the electrical conductivity measuring device 16 (S12). When the operation signal for the cooling tower 10 is OFF, the control device 20 ends the control. When the control ends, the control returns to the start, and the control may be circulated (the same applies below).

[0037] The control device 20 determines whether the electrical conductivity EC of the circulating cooling water reaches a predetermined electrical conductivity (EC end ) is smaller than (EC <EC end ("The electrical conductivity of the circulating cooling water is less than the electrical conductivity at which the supply of makeup water and the discharge of circulating cooling water are stopped"), the automatic supply of makeup water and the discharge of circulating cooling water are stopped for a period of time (automatic blow-off stop time) t bs Then, counting is started (S14).

[0038] The control device 20 counts the automatic blow stop time t bs is the upper limit of the blow stop time t bs limit greater than (t bs >t bs limit ), an electrical conductivity measuring device fault alarm is issued to notify that a fault such as a decrease in sensitivity of the electrical conductivity measuring electrode 38 may have occurred in the electrical conductivity measuring device 16 (S16). start) exceeds (EC>EC start ) (S18), the electrical conductivity measuring device malfunction alarm is cleared (S20), and the control is terminated. bs The control device 20 may reset the count of the automatic blow stop time t bs is the upper limit of the blow stop time t bs limit Below(t bs ≦t bs limit ), control ends.

[0039] The control device 20 determines whether the electrical conductivity EC of the circulating cooling water reaches a predetermined electrical conductivity (EC end ) or more (EC≧EC end ("Electrical conductivity of circulating cooling water ≧ electrical conductivity at which supply of makeup water and discharge of circulating cooling water are terminated"), and the electrical conductivity of circulating cooling water EC is the electrical conductivity at which a predetermined blow is initiated (EC start ) or more (EC≧EC start ), the operating time for automatic supply of makeup water and discharge of circulating cooling water (automatic blow operation time) t bc The controller 20 starts counting the number of times the electrical conductivity EC of the circulating cooling water reaches a predetermined electrical conductivity (EC start ) smaller than (EC <EC start ), control ends.

[0040] The control device 20 counts the automatic blow operation time t bc is the predetermined upper limit of blow operation time t bc limit greater than (t bc >t bc limit ), a blow valve failure alarm is issued to notify that a failure may have occurred in the blow valve 42 (S24). bc is the predetermined upper limit of blow operation time t bc limit Below(t bc ≦t bc limit ), control ends.

[0041] After issuing the blow valve failure alarm (S24), the control device 20 performs a predetermined action to stop the electric conductivity EC of the circulating cooling water from reaching a predetermined electric conductivity (EC end ) became smaller than (EC <EC end If the electrical conductivity of the circulating cooling water is less than the electrical conductivity at which the supply of makeup water and the discharge of circulating cooling water are stopped, the blow valve failure alarm is reset (S26) and the control is terminated. bs The count may be reset.

[0042] The control device 20 determines whether the electrical conductivity EC of the circulating cooling water reaches a predetermined electrical conductivity (EC end ) or more (EC≧EC end If the electrical conductivity of the circulating cooling water is greater than or equal to the electrical conductivity at which the supply of makeup water and the discharge of circulating cooling water are to be terminated, the control is terminated.

[0043] The control device 20 acquires an operation signal for the cooling tower 10 from the control panel of the circulating cooling water pump or the like (S10), and when the operation signal for the cooling tower 10 is ON and when the blow control is not performed automatically but is performed manually, the control device 20 calculates the operation time (manual blow operation time) t' for manually supplying makeup water and discharging circulating cooling water. bc Then, counting begins (S28).

[0044] The control device 20 counts the manual blow operation time t'. bc is the predetermined upper limit of blow operation time t bc limit greater than (t' bc >t bc limit ), an abnormal blow continuation alarm is issued to notify that the abnormal blow may be continuing (S30), and the control mode is switched to the automatic blow mode (S32), after which the abnormal blow continuation alarm is cancelled (S34), and the control ends. bc is the predetermined upper limit of blow operation time t bc limit Below(t' bc ≦t bc limit ), control ends.

[0045] The control device 20 acquires the operation signal of the cooling tower 10 from the control panel of the circulating cooling water pump or the like (S10), and when the operation signal of the cooling tower 10 is ON and the blow control is not performed automatically or manually, the control device 20 determines the stop time (manual blow stop time) t' of the manual supply of makeup water and the discharge of circulating cooling water. bs Then, counting begins (S36).

[0046] The control device 20 counts the manual blow stop time t'. bs is the upper limit of the blow stop time t bs limit greater than (t' bs >t bs limit ), an abnormal blow stop alarm is issued to notify that blowing may have been stopped abnormally (S38), and after transitioning to automatic blow mode (S40), the abnormal blow stop alarm is cancelled (S42) and control is terminated. bs is the upper limit of the blow stop time t bs limit Below(t' bs ≦t bs limit ), control ends.

[0047] In this way, the electrical conductivity (EC) of the circulating cooling water is set to a predetermined threshold value (e.g., the above EC end ) for a predetermined time (for example, the above t bs limit ) continues, it is determined that there is an abnormality in the electrical conductivity measuring device that measures the electrical conductivity of the circulating cooling water. end ) for a predetermined time (for example, the above t bc limit If the problem persists, it is determined that there is an abnormality in the supply of makeup water in the cooling tower, or an abnormality in the discharge of circulating cooling water, such as a malfunction of the blow valve.

[0048] Through such control, with a small number of sensors and at low cost, it is possible to quickly detect the occurrence of abnormalities that lead to the occurrence of obstacles such as scale, such as a decrease in the sensitivity of the electrical conductivity measurement electrode 38 and an abnormality in the blow valve or makeup water valve, and it is possible to prevent the deposition of scale and the like.

[0049] It is possible to determine an abnormality from the operating signal of the cooling tower, which is essential for controlling the electrical conductivity measured by the electrical conductivity measuring device and the circulating cooling water, with fewer sensors than in the prior art such as the method of Patent Document 1. Also, it is possible to detect an abnormality in the valve used for blow, which was difficult to detect in the prior art such as the method of Patent Document 1.

[0050] Next, an example of performing control to issue an alarm when the operating signal of the cooling tower 10 is in the ON state and the state where the chemical concentration of the circulating cooling water is below or above a predetermined threshold value continues for a predetermined time will be described with reference to the flowchart shown in FIG. 3.

[0051] The control device 20 acquires the operating signal of the cooling tower 10 from the control panel of the circulating cooling water pump or the like (S50). When the operating signal of the cooling tower 10 is ON and the chemical injection control is performed automatically, the control device 20 acquires the chemical concentration C measured by the first chemical dosage measuring device 49 and the second chemical dosage measuring device 50 (S52). When the operating signal of the cooling tower 10 is OFF, the control device 20 ends the control. When the control ends, the control returns to the start and may circulate (hereinafter, the same).

[0052] When the chemical concentration C is less than the predetermined target chemical concentration C' (C < C' ("chemical concentration in circulating cooling water < target chemical concentration")), the control device 20 starts a chemical injection command for performing chemical injection to chemical injection pumps such as the first chemical injection pump 51 and the second chemical injection pump 52 (S54), and starts counting the automatic chemical injection operation time (automatic chemical injection operation time) t ic (S56). When the chemical concentration C is equal to or greater than the predetermined target chemical concentration C' (C ≧ C' ("chemical concentration in circulating cooling water ≧ target chemical concentration")), the control device 20 ends the control.

[0053] The control device 20 counts the automatic chemical injection operation time t ic is the upper limit of the chemical injection operation time (t ic limit ) is greater than (t ic >t ic limit ), a drug injection device abnormality alarm is issued to notify that there may be an abnormality in the drug concentration measuring device 18, such as a decrease in sensitivity of the drug concentration measuring electrode 40, or that the drug may have run out due to an abnormal discharge in the drug injection pumps such as the first drug injection pump 51 and the second drug injection pump 52 (S58), and predetermined measures are taken.If the drug concentration C exceeds the predetermined target drug concentration C' (C>C' ("drug concentration in the circulating cooling water>target drug concentration")), the drug injection device abnormality alarm is canceled (S60) and control is terminated.

[0054] The control device 20 counts the automatic chemical injection operation time t ic is the upper limit of the chemical injection operation time (t ic limit ) or less (t ic ≦t ic limit ), control is terminated. Furthermore, the control device 20 issues a drug injection device abnormality alarm (S58), and terminates control if the drug concentration C is below the predetermined target drug concentration C' (C≦C' ("drug concentration in circulating cooling water≦target drug concentration")) even after taking the prescribed measures.

[0055] The control device 20 acquires the operation signal of the cooling tower 10 from the control panel of the circulating cooling water pump or the like (S50), and when the operation signal of the cooling tower 10 is ON and when the chemical injection control is not performed automatically but is performed manually, the control device 20 acquires the operation time of the manual chemical injection (manual chemical injection operation time) t' ic Then, counting begins (S62).

[0056] The control device 20 counts the manual chemical injection operation time t'. ic is the predetermined upper limit of chemical injection operation time t ic limit greater than (t' ic >t ic limit), an abnormal chemical injection continuation alarm is issued to notify that abnormal chemical injection may be continuing (S64), and after transitioning to automatic chemical injection mode (S66), the abnormal chemical injection continuation alarm is cancelled (S68) and control is terminated. ic is the predetermined upper limit of chemical injection operation time t ic limit Below(t' ic ≦t ic limit ), control ends.

[0057] The control device 20 acquires the operation signal of the cooling tower 10 from the control panel of the circulating cooling water pump or the like (S50), and when the operation signal of the cooling tower 10 is ON, and when the blow control is not performed automatically and when the blow control is not performed manually, the ... is Then, counting is started (S70).

[0058] The control device 20 counts the manual chemical feeding stop time t'. is is the predetermined upper limit of the chemical dosing stop time t is limit greater than (t' is >t is limit ), an abnormal chemical feeding stop alarm is issued to notify that chemical feeding may have been stopped abnormally (S72), and after transitioning to automatic chemical feeding mode (S74), the abnormal chemical feeding stop alarm is cancelled (S76), and control ends. is is the predetermined upper limit of the chemical dosing stop time t is limit Below(t' is ≦t is limit ), control ends.

[0059] In this way, the state in which the drug concentration (C) of the circulating cooling water is below a predetermined threshold (for example, the above C') is maintained for a predetermined time (for example, the above t ic limit ) If this continues, it is determined that there is an abnormality in the drug injection.

[0060] This type of control makes it possible to quickly detect abnormal chemical dosing, reduced sensitivity of the chemical concentration measurement electrode 40, chemical shortages due to abnormal discharge from the chemical dosing pump, and abnormal occurrence of chemicals, including scale inhibitors, with fewer sensors and at low cost, and to prevent scale deposition due to chemical shortages. Abnormalities can be determined from the chemical concentration measured by the chemical concentration measurement device, the cooling tower operation signal essential for controlling the circulating cooling water, and the operating status of the chemical dosing pump, and abnormalities can be determined with fewer sensors than with conventional techniques such as the method of Patent Document 1.

[0061] In this embodiment, the amount of chemical agent injected into the circulating cooling water may be controlled based on the LTD value calculated from the refrigerant outlet temperature T1 and the circulating cooling water outlet temperature T2 as [refrigerant outlet temperature T1 - circulating cooling water outlet temperature T2] in the condenser 24 of the refrigerator 12. This LTD value serves as an indicator of the state of contamination of the condenser 24.

[0062] For example, the refrigerant outlet temperature measuring device 34 measures the temperature of the refrigerant at the refrigerant outlet (refrigerant outlet temperature T1) (refrigerant outlet temperature measuring step), and the circulating cooling water outlet temperature measuring device 32 measures the temperature of the circulating cooling water at the circulating cooling water outlet (circulating cooling water outlet temperature T2) (circulating cooling water outlet temperature measuring step). The control device 20 calculates the LTD value [refrigerant outlet temperature T1 - circulating cooling water outlet temperature T2] from the refrigerant outlet temperature T1 measured by the refrigerant outlet temperature measuring device 34 and the circulating cooling water outlet temperature T2 measured by the circulating cooling water outlet temperature measuring device 32. The amount of chemical agent injected into the circulating cooling water can be controlled based on this calculated LTD value. The amount of chemical agent injected into the circulating cooling water can be controlled based on a predetermined relationship between the LTD value and the amount of chemical agent injected.

[0063] In this embodiment, the amount of agent injected into the circulating cooling water may be controlled based on the temperature of the circulating cooling water, in addition to or instead of the control based on the LTD value.

[0064] The cooling tower 10 in the cooling water system according to this embodiment may be an open circulation type (direct cooling) in which a portion of the circulating cooling water is evaporated and cooled by the latent heat of evaporation, or a closed circulation type (indirect cooling) in which the circulating water is passed through a copper pipe coil or the like and cooled by spray water.

[0065] There are no particular limitations on the refrigerator 12, as long as it has an evaporator 22, a condenser 24, a compressor 26, and an expansion valve 28. Examples of the refrigerator 12 include a turbo refrigerator using a turbo compressor and an absorption refrigerator using an absorption liquid.

[0066] The evaporator 22 and the condenser 24 are not particularly limited as long as they are heat exchangers that can exchange heat between the circulating cooling water and the refrigerant, and between the cold water and the refrigerant.

[0067] There are no particular limitations on the compressor 26 as long as it can compress the refrigerant. Examples of the compressor 26 include a positive displacement compressor and a centrifugal compressor.

[0068] The expansion valve 28 is not particularly limited as long as it can reduce the pressure of the refrigerant.

[0069] There are no particular limitations on the circulating cooling water inlet temperature measuring device 30, the circulating cooling water outlet temperature measuring device 32, and the refrigerant outlet temperature measuring device 34, as long as they can measure the temperatures of the circulating cooling water and the refrigerant. Examples of the circulating cooling water inlet temperature measuring device 30, the circulating cooling water outlet temperature measuring device 32, and the refrigerant outlet temperature measuring device 34 include temperature sensors such as thermometers, thermocouples, thermistors, and resistance thermometers.

[0070] There are no particular limitations on the electrical conductivity measuring device 16, as long as it can measure the electrical conductivity of the circulating cooling water. Examples of the electrical conductivity measuring device 16 include a device equipped with an electrical conductivity measuring electrode 38, a device attached to a two-electrode / four-electrode electrical conductivity meter, and a device attached to a dielectric electrical conductivity meter.

[0071] There are no particular limitations on the chemical concentration measuring device 18, as long as it can measure the concentrations of scale inhibitors, anticorrosive agents, slime inhibitors, etc. in the circulating cooling water of the cooling tower 10. Measurement methods include measuring the concentration of each chemical, or measuring the concentration of a tracer substance mixed with the chemical. However, since it is difficult to directly measure the concentration of anticorrosive agents and scale inhibitors, measurement of the concentration of the tracer substance is the main method. For slime inhibitors, it is possible to measure the concentration of the slime inhibitor itself. Specifically, tracer substances include Li, dyes, fluorescent substances, etc., and if the slime inhibitor is an oxidizing agent-based slime inhibitor, a polarographic method can be used.

[0072] The first drug amount measuring device 49 and the second drug amount measuring device 50 may be any device capable of measuring the amount of drug in the first drug storage tank 14 or the second drug storage tank 15, and are not particularly limited, but examples include a float-type level switch, an electrode-type level switch, an ultrasonic level switch, etc.

[0073] The control device 20 is composed of, for example, a microcomputer and electronic circuits that include a calculation means such as a CPU that calculates a program, and storage means such as a ROM and RAM that store the program and calculation results, and has the function of issuing an alarm when the operation signal of the cooling tower 10 is on and the time period in which the ``electrical conductivity of the circulating cooling water < the electrical conductivity at which the supply of make-up water and the discharge of circulating cooling water start'' continues for a predetermined time, or when the operation signal of the cooling tower 10 is on and the make-up water supply signal and the circulating cooling water discharge signal are on and the ``electrical conductivity of the circulating cooling water ≧ the electrical conductivity at which the supply of make-up water and the discharge of circulating cooling water start'' continues for a predetermined time.

[0074] The control device 20 may further have the function of issuing an alarm when the operation signal of the cooling tower 10 is on, the LL signal of the drug storage tank that stores the drug is off, and the drug concentration in the circulating cooling water is less than the target drug concentration for a predetermined period of time.

[0075] The valves 42 and 46 are, for example, valves whose opening and closing degrees can be adjusted manually or automatically.

[0076] There are no particular limitations on the flow meters 44 and 48, as long as they can measure the flow rate of the circulating cooling water being discharged or the makeup water being supplied.

[0077] Circulation pump 36, first chemical injection pump 51, and second chemical injection pump 52 are pumps that are driven at a rotational speed corresponding to, for example, an input drive frequency, and suck in and discharge liquid. Circulation pump 36, first chemical injection pump 51, and second chemical injection pump 52 may be equipped with, for example, an inverter that outputs a drive frequency corresponding to an input command signal to the pump. The amount of chemical injected into the circulating cooling water by first chemical injection pump 51 and second chemical injection pump 52 is preferably controlled by at least one of timer injection (minutes / hours), which injects a predetermined amount for a predetermined period of time, and continuous injection (mg / L), which varies the injection amount depending on the pump stroke.

[0078] In the example of Figure 1, a two-component process is used, in which a first chemical containing a scale inhibitor and an anticorrosive agent and a second chemical containing a slime inhibitor are used, and injection is controlled using separate chemical storage tanks and chemical injection pumps. However, a single-component process may also be used, in which an agent containing a scale inhibitor, an anticorrosive agent, and a slime inhibitor is used, and injection is controlled using a single chemical storage tank and chemical injection pump. By separating the treatment of the scale inhibitor and anticorrosive agent from the treatment of the slime inhibitor, two-component treatment allows for treatment that is appropriate for each. In single-component treatment, when controlling the injection amount of the slime inhibitor, the injection amount of the scale inhibitor and anticorrosive agent may exceed or fall below the optimal amount. However, by performing two-component treatment, the injection amounts of the scale inhibitor and anticorrosive agent and the slime inhibitor can be optimized, respectively, thereby reducing the usage and cost of the scale inhibitor, anticorrosive agent, and slime inhibitor. A three-agent treatment may be performed using a first agent containing a scale inhibitor, a second agent containing a slime inhibitor, and a third agent containing an anticorrosion agent, with each agent being injected and controlled using separate agent storage tanks and chemical injection pumps.

[0079] The agents include scale inhibitors, slime inhibitors, anticorrosion agents, etc. In the case of a one-agent treatment, the agents include scale inhibitors, slime inhibitors, anticorrosion agents, etc. In the case of a two-agent treatment, for example, the first agent includes a scale inhibitor and may also include an anticorrosion agent, and the second agent includes a slime inhibitor.

[0080] Examples of scale inhibitors include acrylic acid polymers, maleic acid polymers, methacrylic acid polymers, sulfonic acid polymers, phosphoric acid polymers, itaconic acid polymers, isobutylene polymers, and water-soluble salts thereof.

[0081] Examples of slime inhibitors include ammonium-based compounds, amine-based compounds, nitrogen-sulfur-based compounds, organometallic compounds, chlorine-based oxidizing agents such as hypochlorous acid, bromine-based oxidizing agents such as hypobromous acid, stabilized hypobromous acid compositions containing a bromine-based oxidizing agent and a sulfamic acid compound, and stabilized hypochlorous acid compositions containing a chlorine-based oxidizing agent and a sulfamic acid compound.

[0082] Examples of scale cleaning agents include amine polymers such as ethylenediamine and diethylenetriamine, aminocarboxylic acid polymers such as nitrilotriacetic acid, ethylenediaminetetraacetate and diethylenetriaminepentaacetic acid, and organic carboxylic acids such as gluconic acid, citric acid, oxalic acid, formic acid, tartaric acid, phytic acid, succinic acid and lactic acid.

[0083] Examples of anticorrosive agents for iron include phosphates, phosphonic acid, zinc, molybdic acid, and nitrous acid. Examples of anticorrosive agents for copper-based metals such as copper and copper alloys include azole compounds. The azole compounds are not particularly limited, but examples include 1,2,3-benzotriazole, tolyltriazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, imidazole, 2-mercaptobenzimidazole, and 2-mercaptobenzothiazole. One compound may be used alone, or two or more compounds may be used in combination. Among these, benzotriazole and tolyltriazole are preferred from the viewpoint of production costs, etc. [Explanation of symbols]

[0084] 1 Cooling water system, 10 Cooling tower, 12 Chiller, 14 First chemical storage tank, 15 Second chemical storage tank, 16 Electrical conductivity measuring device, 18 Chemical concentration measuring device, 20 Control device, 22 Evaporator, 24 Condenser, 26 Compressor, 28 Expansion valve, 30 Circulating cooling water inlet temperature measuring device, 32 Circulating cooling water outlet temperature measuring device, 34 Refrigerant outlet temperature measuring device, 36 Circulation pump, 38 Electrical conductivity measuring electrode, 40 Chemical concentration measuring electrode, 42, 46 Valve, 44, 48 Flow meter, 49 First chemical amount measuring device, 50 Second chemical amount measuring device, 51 First chemical dosing pump, 52 Second chemical dosing pump, 53, 54, 56, 58, 60, 62, 64, 65, 66, 68, 69 Piping, 70 Fan.

Claims

1. A cooling water system control method for controlling a cooling water system including a cooling tower that performs heat exchange using circulating cooling water, and a chiller that includes a condenser having an inlet and an outlet for the circulating cooling water and an inlet and an outlet for the refrigerant for performing heat exchange between the circulating cooling water and the refrigerant, Injecting a chemical into the circulating cooling water; measuring the electrical conductivity of the circulating cooling water, and controlling the supply of makeup water and the discharge of the circulating cooling water in the cooling tower based on the measured electrical conductivity of the circulating cooling water; A cooling water system control method characterized by issuing an alarm when, when the cooling tower operation signal is on, at least one of the electrical conductivity and chemical concentration of the circulating cooling water remains below or above a predetermined threshold for a predetermined period of time.

2. 2. The cooling water system control method according to claim 1, A cooling water system control method characterized by determining that an electrical conductivity measuring device that measures the electrical conductivity of the circulating cooling water is abnormal when the electrical conductivity of the circulating cooling water remains below the predetermined threshold for the predetermined period of time.

3. 2. The cooling water system control method according to claim 1, A cooling water system control method characterized by determining that there is an abnormality in the supply of makeup water or the discharge of the circulating cooling water in the cooling tower when the electrical conductivity of the circulating cooling water remains above the predetermined threshold for the predetermined period of time.

4. 2. The cooling water system control method according to claim 1, A cooling water system control method characterized in that, when the concentration of the chemical in the circulating cooling water remains below the predetermined threshold for the predetermined period of time, it is determined that there is an abnormality in the injection of the chemical.

5. A cooling water system control device for controlling a cooling water system including a cooling tower that performs heat exchange using circulating cooling water, and a chiller that includes a condenser having an inlet and an outlet for the circulating cooling water and an inlet and an outlet for the refrigerant for performing heat exchange between the circulating cooling water and the refrigerant, a chemical injection means for injecting a chemical into the circulating cooling water; an electrical conductivity measuring means for measuring the electrical conductivity of the circulating cooling water; a drug concentration measuring means for measuring the drug concentration in the circulating cooling water; a control means for controlling the supply of makeup water and the discharge of the circulating cooling water in the cooling tower based on the measured electrical conductivity of the circulating cooling water; Equipped with A cooling water system control device characterized in that the control means issues an alarm when, when the cooling tower operation signal is on, at least one of the electrical conductivity and pesticide concentration of the circulating cooling water remains below or above a predetermined threshold for a predetermined period of time.

6. The cooling water system control device according to claim 5, A cooling water system control device characterized in that the control means determines that there is an abnormality in the electrical conductivity measuring means when the electrical conductivity of the circulating cooling water remains below the predetermined threshold for the predetermined period of time.

7. The cooling water system control device according to claim 5, The cooling tower is provided with a cooling water system control device, and the control means determines that there is an abnormality in the supply of makeup water or the discharge of the circulating cooling water in the cooling tower when the electrical conductivity of the circulating cooling water remains above the predetermined threshold for the predetermined period of time.

8. The cooling water system control device according to claim 5, The cooling water system control device is characterized in that the control means determines that there is an abnormality in the chemical injection means when the chemical concentration in the circulating cooling water remains below the predetermined threshold for the predetermined period of time.

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