Chemical feed control method of cooling-water system and chemical feed control apparatus of cooling-water system

Abstract

To provide a chemical feed control method of a cooling-water system and a chemical feed control apparatus of a cooling-water system, capable of efficiently injecting a chemical following a change in water temperature of circulation cooling-water, when controlling an injection rate of the chemical to the circulation cooling-water in the cooling-water system having a cooling tower and a refrigerator.SOLUTION: A chemical feed control method of a cooling-water system is configured to control a cooling-water system 1 including: a cooling tower 10 configured to perform a heat exchange using circulation cooling-water; and a refrigerator 12 including a condenser 24 for the heat exchange between the circulation cooling-water and a coolant. On the basis of a first optimum chemical injection rate at a prescribed first temperature of the circulation cooling-water and a second optimum chemical injection rate at a prescribed second temperature higher than the first temperature, an injection rate of a chemical to the circulation cooling-water is proportionally controlled.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a chemical injection control method and a chemical injection control device for controlling chemical injection (chemical injection) in a cooling water system equipped with a cooling tower and a refrigerator. [Background technology]

[0002] In conventional cooling water systems equipped with a cooling tower and a chiller, automatic blowdown control is performed to control the concentration of the circulating cooling water by monitoring the electrical conductivity of the circulating cooling water, and chemicals are injected into the circulating cooling water at predetermined concentrations to suppress slime and scale.

[0003] In addition, to estimate the state of fouling in the condenser of a refrigerator, the outlet temperature of the circulating cooling water in the condenser and the temperature of the refrigerant after condensation are measured, and if the LTD (Leaving Temperature Difference) value, calculated as [temperature after condensation of the refrigerant - outlet temperature of the circulating cooling water], becomes large, it is assumed that fouling has occurred in the heat exchanger, and chemicals containing slime inhibitors, scale inhibitors, etc. are injected into the circulating cooling water.

[0004] For example, Patent Document 1 describes a cooling water system control method that controls the amount of chemicals injected into circulating cooling water based on the LTD value, and controls the supply of makeup water in a cooling tower and the discharge of circulating cooling water based on the electrical conductivity of the circulating cooling water.

[0005] However, control based solely on the LTD value may not be able to keep up with fluctuations in the temperature of the circulating cooling water, for example, when the temperature of the circulating cooling water is high, such as in summer, and may not be able to sufficiently suppress the increase in the LTD value.

[0006] Patent Document 2 describes a cooling water system control method in which the amount of chemical agent injected into circulating cooling water is controlled based on the LTD value, and when the LTD value exceeds an upper limit value for a predetermined period of time, the amount of chemical agent injected into the circulating cooling water is increased for a predetermined period of time by forced injection of the chemical agent.

[0007] However, the method of Patent Document 2 has a problem in that once the LTD value rises above the upper limit, the LTD value does not decrease even with forced injection control.

[0008] Patent Document 3 describes that the amount of disinfectant added is controlled based on the temperature and / or pH value of the circulating water (circulating cooling water), specifically, that when the temperature of the circulating water is within a predetermined range, only disinfectant is added to the circulating water, that the amount of disinfectant added to the circulating water is determined comprehensively based on the temperature of the circulating water, the pH value of the circulating water, and the residence time of the circulating water, and that this control is not performed for water treatment agents containing disinfectants, scale inhibitors, and corrosion inhibitors.

[0009] However, the method of Patent Document 3 does not perform the above-mentioned control for water treatment agents containing scale inhibitors and corrosion inhibitors, and therefore has the problem of being unable to respond to fluctuations in corrosion and scaling due to temperature fluctuations. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2022-042815 [Patent Document 2] Japanese Patent Publication No. 2022-042816 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-127810 Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide a chemical injection control method for a cooling water system and a chemical injection control device for a cooling water system that can efficiently inject chemicals in response to temperature fluctuations in the circulating cooling water in controlling the amount of chemicals injected into the circulating cooling water in a cooling water system equipped with a cooling tower and a chiller. [Means for solving the problem]

[0012] The present invention provides a chemical injection control method for a cooling water system, which controls a cooling water system including a cooling tower that performs heat exchange using circulating cooling water, and a refrigerator 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 is a chemical injection control method for a cooling water system, which proportionally controls the amount of chemical injected into the circulating cooling water based on a first optimal chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimal chemical injection amount at a predetermined second temperature higher than the first temperature.

[0013] In the method for controlling chemical injection into a cooling water system, it is further preferable that, when an upward trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] continues for a predetermined time, forced injection of chemical is performed to increase the amount of chemical injected into the circulating cooling water for a predetermined time.

[0014] In the chemical injection control method for a cooling water system, a first chemical containing a scale inhibitor and a corrosion inhibitor and a second chemical containing a slime inhibitor are used as the chemicals, and the injection amount of the second chemical into the circulating cooling water is proportionally controlled based on the first optimal chemical injection amount and the second optimal chemical injection amount for the second chemical, or the injection amount of the second chemical into the circulating cooling water is proportionally controlled based on the first optimal chemical injection amount and the second optimal chemical injection amount for the second chemical, and further, when an upward trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] continues for a predetermined time, it is preferable to perform forced injection of a chemical to increase the injection amount of the second chemical into the circulating cooling water for a predetermined time.

[0015] In the chemical injection control method for a cooling water system, a first chemical containing a scale inhibitor and a corrosion inhibitor and a second chemical containing a slime inhibitor are used as the chemicals, and the injection amount of the first chemical into the circulating cooling water is proportionally controlled based on the first optimal chemical injection amount and the second optimal chemical injection amount for the first chemical, and the injection amount of the second chemical into the circulating cooling water is proportionally controlled based on the first optimal chemical injection amount and the second optimal chemical injection amount for the second chemical, and further, when an upward trend in the LTD value calculated from the outlet temperature of the refrigerant and the outlet temperature of the circulating cooling water in the condenser as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] continues for a predetermined time, it is preferable to perform forced injection of a chemical to increase the injection amount of the second chemical into the circulating cooling water for a predetermined time.

[0016] In the method for controlling chemical injection in a cooling water system, it is preferable that the first chemical contains a tracer substance, and the concentration of the first chemical is measured by measuring the concentration of the tracer substance, and the injection amount of the first chemical into the circulating cooling water is proportionally controlled based on the measured concentration of the first chemical, the first optimal chemical injection amount based on the first optimal chemical concentration at the first temperature, and the second optimal chemical injection amount based on the second optimal chemical concentration at a predetermined second temperature higher than the first temperature, or the injection amount of the second chemical into the circulating cooling water is proportionally controlled based on the first optimal chemical injection amount based on the first optimal chemical injection time for the second chemical at the first temperature and the second optimal chemical injection time at a predetermined second temperature higher than the first temperature.

[0017] The present invention is a chemical injection control device for a cooling water system that controls a cooling water system that includes a cooling tower that performs heat exchange using circulating cooling water, and a chiller that includes a condenser that has 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, and the chemical injection control device for a cooling water system includes a control means that proportionally controls the amount of chemical injected into the circulating cooling water based on a first optimal chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimal chemical injection amount at a predetermined second temperature higher than the first temperature.

[0018] In the chemical injection control device for the cooling water system, it is preferable that the control means further performs forced chemical injection by increasing the amount of chemical injected into the circulating cooling water for a predetermined time when the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] shows an increasing trend for a predetermined time.

[0019] In the chemical injection control device for the cooling water system, the chemicals used are a first chemical containing a scale inhibitor and an anticorrosive agent, and a second chemical containing a slime inhibitor, and the control means proportionally controls the injection amount of the second chemical into the circulating cooling water based on the first optimal chemical injection amount and the second optimal chemical injection amount for the second chemical, or the control means proportionally controls the injection amount of the second chemical into the circulating cooling water based on the first optimal chemical injection amount and the second optimal chemical injection amount for the second chemical, and further, when an upward trend in the LTD value calculated from the outlet temperature of the refrigerant and the outlet temperature of the circulating cooling water in the condenser as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] continues for a predetermined time, it is preferable that the chemical injection control device performs forced injection of chemical to increase the injection amount of the second chemical into the circulating cooling water for a predetermined time.

[0020] In the chemical injection control device for the cooling water system, it is preferable that the chemicals used are a first chemical containing a scale inhibitor and an anticorrosive agent, and a second chemical containing a slime inhibitor, and that the control means proportionally controls the injection amount of the first chemical into the circulating cooling water based on the first optimal chemical injection amount and the second optimal chemical injection amount for the first chemical, and that the control means proportionally controls the injection amount of the second chemical into the circulating cooling water based on the first optimal chemical injection amount and the second optimal chemical injection amount for the second chemical, and further, when an upward trend in the LTD value calculated from the outlet temperature of the refrigerant and the outlet temperature of the circulating cooling water in the condenser as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] continues for a predetermined time, forced chemical injection is performed to increase the injection amount of the second chemical into the circulating cooling water for a predetermined time.

[0021] In the chemical injection control device for the cooling water system, the first chemical contains a tracer substance, and is provided with a chemical concentration measuring means for measuring the concentration of the first chemical by measuring the concentration of the tracer substance, and the control means proportionally controls the injection amount of the first chemical into the circulating cooling water based on the concentration of the first chemical measured by the chemical concentration measuring means, the first optimal chemical injection amount based on the first optimal chemical concentration at the first temperature, and the second optimal chemical injection amount based on the second optimal chemical concentration at a predetermined second temperature higher than the first temperature, or the control means proportionally controls the injection amount of the second chemical into the circulating cooling water based on the first optimal chemical injection amount based on the first optimal chemical injection time for the second chemical at the first temperature and the second optimal chemical injection time at the predetermined second temperature higher than the first temperature. [Effects of the Invention]

[0022] The present invention provides a chemical injection control method for a cooling water system and a chemical injection control device for a cooling water system that can efficiently inject chemicals in response to temperature fluctuations in the circulating cooling water in controlling the amount of chemical injected into the circulating cooling water in a cooling water system equipped with a cooling tower and a chiller. [Brief explanation of the drawings]

[0023] [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] 1 is a graph showing the number of days (days) of operation in Comparative Example 1, the LTD (° C.) of the refrigerator, the cooling water outlet temperature (° C.), and the agent concentration (mg / L). [Figure 3] 1 is a graph showing the number of days (days) elapsed since operation in Example 1, the LTD (° C.) of the refrigerator, the cooling water outlet temperature (° C.), and the drug concentration (mg / L). DETAILED DESCRIPTION OF THE INVENTION

[0024] 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.

[0025] An example of a cooling water system according to an embodiment of the present invention is illustrated 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, such as a scale inhibitor and a corrosion inhibitor, into the circulating cooling water, and a second chemical storage tank 15 as a second chemical injection means for injecting a second chemical, such as a slime inhibitor, into the circulating cooling water. Cooling water system 1 also includes a control device 20 as a control means for proportionally controlling the amount of chemical injected into the circulating cooling water based on a first optimal chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimal chemical injection amount at a predetermined second temperature higher than the first temperature.

[0026] 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.

[0027] 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 cold water inlet and outlet and a refrigerant inlet and outlet for heat exchange between the cold 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 is equipped 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The chemical injection control device for a cooling water system according to this embodiment includes a control device 20. The chemical injection control device for a cooling water system according to this embodiment may further include a circulating cooling water outlet temperature measuring device 32 and a refrigerant outlet temperature measuring device 34. The chemical injection control device for a cooling water system may also include a chemical concentration measuring device 18.

[0033] The chemical injection control method for a cooling water system, the chemical injection control device for a cooling water system, and the operation of the cooling water system 1 according to this embodiment will be described.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The temperature of the circulating cooling water varies depending on the season (e.g., summer and winter), and the amount of scale inhibitor, anticorrosive agent, slime inhibitor, etc. required to maintain a low LTD value varies. Conventional control of the LTD value alone may result in the same LTD value in summer and winter, making it impossible to keep up with the seasonal fluctuations mentioned above. This is thought to be because water temperature primarily affects the risk of scale and corrosion, slime activity, and slime inhibitor stability.

[0039] In this embodiment, the amount of chemicals injected into the circulating cooling water is proportionally controlled based on a first optimal chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimal chemical injection amount at a predetermined second temperature higher than the first temperature. This allows for efficient injection of chemicals in accordance with temperature fluctuations in the circulating cooling water. Treatment can be performed to maintain the amount of active ingredients, such as scale inhibitors, anticorrosive agents, and slime inhibitors, in the circulating cooling water in accordance with water temperature fluctuations, such as seasonal fluctuations.

[0040] For example, the lowest temperature of the circulating cooling water in winter, etc. can be set as the first temperature, the highest temperature of the circulating cooling water in summer, etc. can be set as the second temperature, the optimal injection amount of the drug at the first temperature can be set as the first optimal drug injection amount, and the optimal injection amount of the drug at the second temperature can be set as the second optimal drug injection amount, and a control formula can be determined to proportionally control the injection amount of the drug between the first optimal drug injection amount and the second optimal drug injection amount based on the temperature of the circulating cooling water.

[0041] For example, in an actual cooling water system, a first temperature, which is the lowest temperature of the circulating cooling water in winter, etc., and a second temperature, which is the highest temperature of the circulating cooling water in summer, etc., can be specified based on data measured based on the temperature of the circulating cooling water measured over, for example, a year, specifically the temperature of the circulating cooling water in winter, etc., when it is expected to be the lowest temperature, and the temperature of the circulating cooling water in summer, etc., when it is expected to be the highest temperature. Then, a first optimal chemical injection rate, which is the optimal injection rate of the chemical at the first temperature, and a second optimal chemical injection rate, which is the optimal injection rate of the chemical at the second temperature, can be determined in advance by experiment, etc. Then, a control formula can be determined from the first temperature, the second temperature, the first optimal chemical injection rate, and the second optimal chemical injection rate.

[0042] For example, the control device 20 controls the first chemical injection pump 51, or the second chemical injection pump 52, or both the first chemical injection pump 51 and the second chemical injection pump 52, in accordance with a control equation determined based on a first optimal chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimal chemical injection amount at a predetermined second temperature higher than the first temperature, thereby proportionally controlling the amount of chemical injected into the circulating cooling water.

[0043] The first temperature may be the lowest temperature of the circulating cooling water in a year, or may be the average temperature of the circulating cooling water during low temperature periods such as winter. The first temperature may be set within the range of 15 to 45°C, for example, depending on the installation environment of the cooling water system 1, etc.

[0044] The second temperature may be the highest temperature of the circulating cooling water over the course of a year, or may be the average temperature of the circulating cooling water during high temperature periods such as summer. The second temperature may be set within the range of 15 to 45°C, for example, depending on the installation environment of the cooling water system 1, etc.

[0045] For scale inhibitors, the first optimal chemical dosage may be, for example, the dosage of the chemical containing the scale inhibitor required to maintain the residual active ingredient concentration in a range of, for example, 0.1 to 1000 mg / L when the temperature of the circulating cooling water is a first temperature, and the second optimal chemical dosage may be, for example, the dosage of the chemical containing the scale inhibitor required to maintain the residual active ingredient concentration in a range of, for example, 0.1 to 1000 mg / L when the temperature of the circulating cooling water is a second temperature.

[0046] With regard to the anticorrosive agent, the first optimal drug injection amount may be, for example, the amount of drug containing the anticorrosive agent required to maintain the residual active ingredient concentration in a range of, for example, 0.1 to 1000 mg / L when the temperature of the circulating cooling water is a first temperature, and the second optimal drug injection amount may be, for example, the amount of drug containing the anticorrosive agent required to maintain the residual active ingredient concentration in a range of, for example, 0.1 to 1000 mg / L when the temperature of the circulating cooling water is a second temperature.

[0047] Regarding the slime inhibitor, when an oxidizing agent-based slime inhibitor is used, the first optimal chemical injection amount may be, for example, the amount of chemical containing slime inhibitor required to maintain the residual free oxidant concentration in the range of 0.1 to 1.0 mg / L, preferably 0.1 to 0.5 mg / L, when the temperature of the circulating cooling water is a first temperature, and the second optimal chemical injection amount may be, for example, the amount of chemical containing slime inhibitor required to maintain the residual free oxidant concentration in the range of 0.1 to 1.0 mg / L, preferably 0.1 to 0.5 mg / L, when the temperature of the circulating cooling water is a second temperature.

[0048] The temperature of the circulating cooling water may be the temperature of the circulating cooling water measured at a predetermined position in the cooling water system 1. The temperature of the circulating cooling water may be the circulating cooling water outlet temperature measured by the circulating cooling water outlet temperature measuring device 32, the circulating cooling water inlet temperature measured by the circulating cooling water inlet temperature measuring device 30, or the temperature of the circulating cooling water stored in the cooling tower 10. From the viewpoint of being able to use the circulating cooling water outlet temperature measuring device installed to determine the LTD value, it is preferable to use the circulating cooling water outlet temperature measured by the circulating cooling water outlet temperature measuring device 32 as the temperature of the circulating cooling water.

[0049] 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.

[0050] In the present embodiment, the control of "proportionally controlling the amount of chemicals injected into the circulating cooling water based on a first optimum chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimum chemical injection amount at a predetermined second temperature higher than the first temperature" may be performed by determining a control formula for the chemicals containing a scale inhibitor, anticorrosive, and slime inhibitor using a single-component process, or by determining a control formula for either or both of the first chemical containing a scale inhibitor and anticorrosive and the second chemical containing a slime inhibitor using a two-component process, or by determining a control formula for either, any two, or all of the first chemical containing a scale inhibitor, the second chemical containing a slime inhibitor, and the third chemical containing a corrosion inhibitor using a three-component process. For chemicals not subject to the above control, a fixed amount of a predetermined amount may be injected.

[0051] In the case of single-component treatment, for example, a tracer-containing agent may be used, and the agent concentration may be measured by the agent concentration measuring device 18. The measured value may be transmitted to the control device 20. The agent injection amount may be controlled using a control equation determined based on the measurement results, a first optimal agent injection amount based on a first optimal agent concentration at a first temperature, and a second optimal agent injection amount based on a second optimal agent concentration at a second temperature higher than the first temperature. Alternatively, a tracer-containing agent may be used in single-component treatment, and the agent concentration may be measured by the agent concentration measuring device 18. The measured value may be transmitted to the control device 20. The agent injection amount may be controlled using a control equation and a timer determined based on the measurement results, a first optimal agent injection amount based on a first optimal agent injection time at a first temperature, and a second optimal agent injection amount based on a second optimal agent injection time at a second temperature higher than the first temperature. In the case of two-component treatment, for example, a tracer-containing agent may be used as the first agent, including a scale inhibitor and a corrosion inhibitor, and the same control as in single-component treatment may be performed. The second chemical containing a slime inhibitor does not contain a tracer and is controlled using a determined control formula and timer based on a first optimal chemical injection amount based on a first optimal chemical injection time at a first temperature and a second optimal chemical injection amount based on a second optimal chemical injection time at a predetermined second temperature higher than the first temperature.

[0052] In the chemical injection control method and chemical injection control device for a cooling water system according to this embodiment, if the LTD value calculated from the refrigerant outlet temperature T1 and the circulating cooling water outlet temperature T2 in the condenser 24 of the chiller 12 as [refrigerant outlet temperature T1 - circulating cooling water outlet temperature T2] shows a continuing upward trend for a predetermined period of time, forced chemical injection may be performed to increase the amount of chemical injected into the circulating cooling water for a predetermined period of time. This LTD value serves as an indicator of the state of contamination of the condenser 24.

[0053] For example, as in Patent Document 2, when the amount of chemical injected into the circulating cooling water is controlled based on the LTD value, if the LTD value exceeds the upper limit for a predetermined period of time, the LTD value may not decrease even if forced injection of the chemical is performed to increase the amount of chemical injected into the circulating cooling water for a predetermined period of time.

[0054] Therefore, by detecting an increase in the LTD value as soon as possible and injecting chemicals, such as slime inhibitors, into the circulating cooling water as soon as possible, the LTD value can be maintained low. Even if the LTD value increases due to factors other than water temperature fluctuations, such as seasonal fluctuations, it is possible to restore the treatment state to a good state.

[0055] For example, the refrigerant temperature at the refrigerant outlet (refrigerant outlet temperature T1) is measured by the refrigerant outlet temperature measuring device 34 (refrigerant outlet temperature measuring step), and the circulating cooling water temperature at the circulating cooling water outlet (circulating cooling water outlet temperature T2) is measured by the circulating cooling water outlet temperature measuring device 32 (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. If the calculated LTD value shows an upward trend for a predetermined time, forced chemical injection is performed, increasing the amount of chemical injected into the circulating cooling water for a predetermined time. This state is called the "forced chemical injection mode."

[0056] For example, when the increase in LTD value is between 0.1°C and 2.0°C above the reference LTD value, it can be determined that "there is an increasing trend," and when the period during which the LTD value continues to rise is between 12 and 168 hours, it can be determined that "the increasing trend in LTD value has continued for a predetermined period of time." In forced drug infusion, the drug infusion amount can be, for example, 1.1 to 20.0 times, and preferably 2.0 to 10.0 times, the normal drug infusion amount. The reference LTD value can be the average LTD value during periods other than forced drug infusion mode.

[0057] In forced chemical injection mode, if the LTD value is elevated due to slime, a chemical containing a slime inhibitor can be forcibly injected into the circulating cooling water. A determination of whether the LTD value is elevated due to slime can be made, for example, by looking at whether the LTD value drops due to the addition of a high concentration of slime inhibitor or physical cleaning of the heat exchanger. Furthermore, if the LTD value is elevated due to scale, it is difficult to remove even with the addition of a high concentration of scale inhibitor, so it is best to add a scale cleaner. Examples of scale cleaners include compounds containing hydrochloric acid or sulfuric acid.

[0058] The control device 20 may issue an alarm when the LTD value calculated 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 continues to increase for a predetermined period of time. Examples of the method of issuing an alarm include notifying a control screen on a cloud or the like via internet communication, or notifying an operator or the like by linking the notification to an email or the like.

[0059] Forced chemical injection is performed by increasing the amount of chemical injected into the circulating cooling water for a predetermined period of time, and if the LTD value drops to the reference LTD value, the system can return to normal operating mode. Forced chemical injection may be performed a predetermined number of times. If the LTD value does not drop to the reference LTD value even after the predetermined number of forced chemical injections, the forced chemical injection may be stopped, an alarm may be issued, and normal operation may be resumed. If the forcedly injected chemical contains a slime inhibitor and the LTD value does not drop even after forced chemical injection, it is assumed that the increase in the LTD value is due to scale buildup, and the forced chemical injection may be stopped, and a scale cleaning agent or the like may be separately injected into the circulating cooling water.

[0060] The slope of the calculated LTD value increase may vary depending on the scale or slime produced. In this case, the ingredients of the chemicals used may be changed depending on the slope of the calculated LTD value increase.

[0061] In this embodiment, the electrical conductivity of the circulating cooling water may be 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 may be 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 measurement 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 reaches a predetermined upper limit, the valve 46 is opened to supply makeup water into the cooling tower 10 and discharge the circulating cooling water by overflow through the pipes 69 and 66. When the predetermined electrical conductivity is reached, the valve 46 is closed. Alternatively, valve 42 may be 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. In other words, "control of the supply of makeup water and the discharge of circulating cooling water" 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.

[0062] 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.

[0063] The control device 20 may issue an alarm when the electrical conductivity of the circulating cooling water measured by the electrical conductivity measuring device 16 exceeds a predetermined upper limit. The control device 20 may issue an alarm when the drug concentration of the circulating cooling water measured by the drug concentration measuring device 18 exceeds a predetermined upper limit or falls below a predetermined lower limit.

[0064] When the circulating cooling water is discharged through pipes 69 and 66 in cooling tower 10, it is preferable to reduce or stop the injection of the first chemical into the circulating cooling water by first chemical injection pump 51 from first chemical storage tank 14 and the injection of the second chemical into the circulating cooling water by second chemical injection pump 52 from second chemical storage tank 15. Furthermore, when the operation of cooling tower 10 is stopped, it is preferable to stop the injection of the chemical into the circulating cooling water by first chemical injection pump 51 from first chemical storage tank 14 and the injection of the second chemical into the circulating cooling water by second chemical injection pump 52 from second chemical storage tank 15. This allows the amount of chemical used to be reduced.

[0065] The cooling tower 10 in the cooling water system according to this embodiment may be an open circulation type (direct cooling) that evaporates a portion of the circulating cooling water and cools the circulating cooling water by the latent heat of evaporation.

[0066] The chiller 12 is not particularly limited as long as it has an evaporator 22, a condenser 24, a compressor 26, and an expansion valve 28. Examples of the chiller 12 include a turbo chiller that uses a turbo compressor and an absorption chiller that uses an absorption liquid. The cooling water system control method and cooling water system control device according to this embodiment can be suitably applied to a cooling water system that uses a turbo chiller, in which the LTD value is likely to change due to the adhesion of dirt, etc., and in which the impact on LTD due to factors other than the dirt on the heat exchanger is relatively small.

[0067] 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.

[0068] 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.

[0069] The expansion valve 28 is not particularly limited as long as it can reduce the pressure of the refrigerant.

[0070] 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.

[0071] 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.

[0072] The chemical concentration measuring device 18 is not particularly limited 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, and preferably can measure the concentrations of scale inhibitors and anticorrosive agents 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.

[0073] 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.

[0074] The control device 20 is composed of a microcomputer and electronic circuits, which include, for example, a calculation means such as a CPU that calculates a program, and storage means such as ROM and RAM that store the program and calculation results, and has the function of proportionally controlling the amount of drug injected into the circulating cooling water based on a first optimal drug injection amount at a first temperature and a second optimal drug injection amount at a second temperature.

[0075] Control device 20 may have a function to calculate an LTD value based on the circulating cooling water outlet temperature and the refrigerant outlet temperature measured by circulating cooling water outlet temperature measuring device 32 and refrigerant outlet temperature measuring device 34, and if the calculated LTD value shows an upward trend for a predetermined time, to perform forced chemical injection to increase the amount of chemical injected into the circulating cooling water for a predetermined time by adjusting the flow rates of first chemical injection pump 51 and second chemical injection pump 52, etc. Control device 20 may have a function to control the supply of makeup water to the circulating cooling water by adjusting the opening / closing degree of valve 46, etc., based on the electrical conductivity of the circulating cooling water measured by electrical conductivity measuring device 16.

[0076] The valves 42 and 46 are, for example, valves whose opening and closing degrees can be adjusted manually or automatically.

[0077] 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.

[0078] 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.

[0079] The agents include scale inhibitors, slime inhibitors, anticorrosive agents, etc. In the case of a two-agent treatment, for example, the first agent includes a scale inhibitor and may also include an anticorrosive 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 oxidizers such as hypochlorous acid, bromine-based oxidizers such as hypobromous acid, stabilized hypobromous acid compositions containing a bromine-based oxidizer and a sulfamic acid compound, stabilized hypochlorous acid compositions containing a chlorine-based oxidizer and a sulfamic acid compound, etc. When the slime inhibitor is an oxidizer-based slime inhibitor such as a chlorine-based oxidizer, a bromine-based oxidizer, a stabilized hypochlorous acid composition, or a stabilized hypobromous acid composition, which has a relatively fast acting effect when dirt adheres, the cooling water system chemical injection control method and cooling water system chemical injection control device according to this embodiment can be suitably applied.

[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. [Example]

[0084] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0085] <Comparative Example 1> Using the cooling water system 1 shown in Figure 1, a single-agent treatment was performed using a stabilized hypobromous acid composition containing bromine and sulfamic acid as a slime inhibitor, and an aqueous solution containing benzotriazole and a polycarboxylic acid polymer as a scale inhibitor and anticorrosion agent. Chemical injection was controlled solely by the LTD value, and the operation was carried out for 60 days. In addition to controlling chemical injection, concentration control for automatic blowdown control was also carried out by monitoring electrical conductivity. Figure 2 shows the changes in the LTD value (°C) at the chiller condenser, the cooling water outlet temperature (°C), and the chemical concentration (mg / L) over the number of days of operation (days).

[0086] An automatic cooling water system control device (Olchaser, manufactured by Organo Corporation) was used for chemical injection, and an automatic cooling water blower (with an electrical conductivity meter) (manufactured by Organo Corporation) was used for controlling the blowing of the circulating cooling water by measuring electrical conductivity. Pipe contact type resistance thermometers were used as the temperature measuring device for the circulating cooling water outlet and the refrigerant outlet.

[0087] The LTD value tends to rise, but in the case of chemical control linked to the LTD value, the increase in chemical concentration was delayed, and the LTD could not be sufficiently reduced. Also, because the chemical was forcedly injected after the LTD value had peaked, the LTD value could not be completely suppressed. Furthermore, the cooling water outlet temperature rose, and the slime load in the system increased.

[0088] Example 1 Using the cooling water system 1 shown in Figure 1, a two-agent treatment was performed using an aqueous solution containing benzotriazole and a polycarboxylic acid polymer as the scale inhibitor and anticorrosive agent (first agent), and a stabilized hypobromous acid composition containing bromine and sulfamic acid as the slime inhibitor (second agent).The treatment was run for 50 days.The amount of the first agent containing the scale inhibitor and anticorrosive agent injected into the circulating cooling water was proportionally controlled according to the control formula below.The amount of the second agent containing the slime inhibitor injected into the circulating cooling water was proportionally controlled according to the control formula below.If the LTD value continued to increase for a predetermined period of time, a forced injection of the agent was performed, increasing the amount of agent injected into the circulating cooling water for a predetermined period of time.

[0089] Based on past circulating cooling water measurement data, a first temperature (25°C), which represents the lowest circulating cooling water temperature in winter, and a second temperature (35°C), which represents the highest circulating cooling water temperature in summer, were defined. The first optimal chemical dosage at the first temperature and the second optimal chemical dosage at the second temperature were determined experimentally. A control formula was determined from the first temperature, second temperature, first optimal chemical dosage, and second optimal chemical dosage. The first and second optimal chemical dosages were determined as the dosage of the second chemical, including a slime inhibitor, necessary to maintain the residual free oxidant concentration in the circulating cooling water within the range of 0.2 to 0.5 mg / L. The first chemical was injected so that the active ingredient content in the circulating cooling water was 10 to 1,000 mg / L, as a compound containing the above ingredients. Figure 3 shows the variation in the LTD value (°C) at the chiller condenser, the cooling water outlet temperature (°C), and the chemical concentration (mg / L) over the number of days of operation.

[0090] For the first 20 days after the start of operation, the injection of the second chemical containing the slime inhibitor was intentionally stopped for a comparison test of the forced injection mode, causing the LTD value to rise, which resulted in a gradual increase in the LTD value. On the 24th day, the second chemical containing the slime inhibitor was forced into the forced injection mode (five times the normal injection concentration (four times in total)), which suppressed the increase in the LTD value and reduced the LTD value. Furthermore, as the cooling water temperature rose, the increase in the LTD value was suppressed by increasing the concentration of the second chemical containing the slime inhibitor.

[0091] In the control of Example 1, the amount of chemicals injected into the circulating cooling water in a cooling water system equipped with a cooling tower and a chiller was controlled by tracking the temperature fluctuations of the circulating cooling water, enabling optimal chemical injection tailored to the load of slime, corrosion, and scale. As a result, the LTD was able to be maintained low. Furthermore, even if an unexpected load occurred and the LTD rose, the increase in LTD was detected early and the increase in LTD was suppressed.

[0092] In this way, the control of Example 1 enabled efficient injection of chemicals in accordance with fluctuations in the temperature of the circulating cooling water in controlling the amount of chemicals injected into the circulating cooling water in a cooling water system equipped with a cooling tower and a chiller. [Explanation of symbols]

[0093] 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 chemical injection control method for a cooling water system, comprising: a cooling tower that performs heat exchange using circulating cooling water; and a refrigerator 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 control method for a cooling water system, characterized by proportionally controlling the amount of chemical injected into the circulating cooling water based on a first optimal chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimal chemical injection amount at a predetermined second temperature higher than the first temperature.

2. 2. The chemical injection control method for a cooling water system according to claim 1, Furthermore, the chemical injection control method for a cooling water system is characterized in that, when an increasing trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of the refrigerant - outlet temperature of the circulating cooling water] continues for a predetermined time, forced chemical injection is performed to increase the amount of chemical injected into the circulating cooling water for a predetermined time.

3. 2. The chemical injection control method for a cooling water system according to claim 1, As the chemicals, a first chemical containing a scale inhibitor and an anticorrosive agent and a second chemical containing a slime inhibitor are used, The injection amount of the second drug into the circulating cooling water is proportionally controlled based on the first optimal drug injection amount and the second optimal drug injection amount for the second drug. or The second chemical is proportionally controlled in the amount of the second chemical injected into the circulating cooling water based on the first optimum chemical injection amount and the second optimum chemical injection amount for the second chemical, and further, when an increasing trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of the refrigerant - outlet temperature of the circulating cooling water] continues for a predetermined time, a forced chemical injection is performed to increase the amount of the second chemical injected into the circulating cooling water for a predetermined time. A chemical injection control method for a cooling water system.

4. 2. The chemical injection control method for a cooling water system according to claim 1, As the chemicals, a first chemical containing a scale inhibitor and an anticorrosive agent and a second chemical containing a slime inhibitor are used, The injection amount of the first chemical into the circulating cooling water is proportionally controlled based on the first optimal chemical injection amount and the second optimal chemical injection amount for the first chemical; The second chemical is proportionally controlled in the amount of the second chemical injected into the circulating cooling water based on the first optimum chemical injection amount and the second optimum chemical injection amount for the second chemical, and further, when an increasing trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of the refrigerant - outlet temperature of the circulating cooling water] continues for a predetermined time, a forced chemical injection is performed to increase the amount of the second chemical injected into the circulating cooling water for a predetermined time. A chemical injection control method for a cooling water system.

5. 5. The chemical injection control method for a cooling water system according to claim 4, the first agent comprises a tracer substance; measuring the concentration of the first agent by measuring the concentration of the tracer substance, and proportionally controlling the injection amount of the first agent into the circulating cooling water based on the measured concentration of the first agent, the first optimum agent injection amount based on the first optimum agent concentration at the first temperature, and the second optimum agent injection amount based on the second optimum agent concentration at a predetermined second temperature higher than the first temperature; or proportionally controlling the injection amount of the second drug into the circulating cooling water based on the first optimum drug injection amount based on a first optimum drug injection time at the first temperature for the second drug and the second optimum drug injection amount based on a second optimum drug injection time at a predetermined second temperature higher than the first temperature; A chemical injection control method for a cooling water system.

6. A chemical injection control device for a cooling water system that controls a cooling water system including: a cooling tower that performs heat exchange using circulating cooling water; and a refrigerator 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 control device for a cooling water system, characterized in that it is equipped with a control means for proportionally controlling the amount of chemical injected into the circulating cooling water based on a first optimal chemical injection amount at a predetermined first temperature of the circulating cooling water and a second optimal chemical injection amount at a predetermined second temperature higher than the first temperature.

7. The chemical injection control device for a cooling water system according to claim 6, The control means further comprises a chemical injection control device for a cooling water system, wherein when an increasing trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of the refrigerant - outlet temperature of the circulating cooling water] continues for a predetermined time, the control means performs forced chemical injection to increase the amount of chemical injected into the circulating cooling water for a predetermined time.

8. The chemical injection control device for a cooling water system according to claim 6, As the chemicals, a first chemical containing a scale inhibitor and an anticorrosive agent and a second chemical containing a slime inhibitor are used, The control means proportionally controls the injection amount of the second drug into the circulating cooling water based on the first optimal drug injection amount and the second optimal drug injection amount for the second drug. or The control means proportionally controls the injection amount of the second chemical into the circulating cooling water based on the first optimum chemical injection amount and the second optimum chemical injection amount for the second chemical, and further performs forced chemical injection to increase the injection amount of the second chemical into the circulating cooling water for a predetermined time when an increasing trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] continues for a predetermined time. A chemical injection control device for a cooling water system.

9. The chemical injection control device for a cooling water system according to claim 6, As the chemicals, a first chemical containing a scale inhibitor and an anticorrosive agent and a second chemical containing a slime inhibitor are used, the control means proportionally controls the injection amount of the first drug into the circulating cooling water based on the first optimal drug injection amount and the second optimal drug injection amount for the first drug; The control means proportionally controls the injection amount of the second chemical into the circulating cooling water based on the first optimum chemical injection amount and the second optimum chemical injection amount for the second chemical, and further performs forced chemical injection to increase the injection amount of the second chemical into the circulating cooling water for a predetermined time when an increasing trend in the LTD value calculated from the outlet temperature of the refrigerant in the condenser and the outlet temperature of the circulating cooling water as [outlet temperature of refrigerant - outlet temperature of circulating cooling water] continues for a predetermined time. A chemical injection control device for a cooling water system.

10. The chemical injection control device for a cooling water system according to claim 9, the first agent comprises a tracer substance; a drug concentration measuring means for measuring the concentration of the first drug by measuring the concentration of the tracer substance; the control means proportionally controls the injection amount of the first drug into the circulating cooling water based on the concentration of the first drug measured by the drug concentration measurement means, the first optimum drug injection amount based on the first optimum drug concentration at the first temperature, and the second optimum drug injection amount based on the second optimum drug concentration at a predetermined second temperature higher than the first temperature; or the control means proportionally controls the injection amount of the second drug into the circulating cooling water based on the first optimum drug injection amount based on a first optimum drug injection time at the first temperature for the second drug and the second optimum drug injection amount based on a second optimum drug injection time at a predetermined second temperature higher than the first temperature; A chemical injection control device for a cooling water system.

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