Cooling tower system

Abstract

A cooling tower 1 comprises: a tower body 2 which has louvers 3 on a side surface, an exhaust fan 8 in a top portion, and a lower water tank 4 in a lower portion; a filler 5 which is disposed within the tower body 2 and onto which water is poured from above; and a controller 17 for controlling a makeup water valve 15 on the basis of a detected electrical conductivity from an electrical conductivity sensor 16. Condensed water generated by a heat exchanger 22 for cooling exhaust gas from the exhaust fan 8 is used as a makeup water.

Description

Cooling Tower System

[0001] The present invention relates to a cooling tower system having a cooling tower and a water recovery mechanism that recovers moisture in the exhaust gas from the cooling tower.

[0002] In an open circulation cooling tower, the fan at the top of the tower is operated and water is sprayed onto the packing material placed inside the tower. The water that flows down the packing is cooled by the heat of evaporation and becomes cold water. The air that passes through the packing is exhausted upward by the fan at the top of the tower.

[0003] The cold water that falls into and accumulates in the lower water tank of the cooling tower is sent to the equipment to be cooled, such as a refrigerator, where it is heated by heat exchange before returning to the cooling tower.

[0004] The cooling tower exhaust contains a large amount of water vapor and other moisture, and in winter, the water vapor may condense and produce white smoke.

[0005] As a cooling tower equipped with a mechanism for preventing such white smoke, Patent Document 1 describes an air-cooled heat exchanger installed in the upper part of the cooling tower, which cools the water vapor-containing air rising inside the tower and condenses the water vapor, thereby reducing the amount of moisture in the cooling tower exhaust. Atmospheric air or air at a lower temperature is ventilated through the low-temperature fluid passage of this heat exchanger.

[0006] In an open-circulation cooling water system, water is lost due to evaporation, scattering, blowing, etc., and therefore make-up water is supplied. The discharge of cooling water outside the system due to evaporation occurs when liquid water turns into water vapor and is released into the atmosphere. Patent Documents 2 to 4 describe the condensation and recovery of this water vapor for use as cooling water.

[0007] The discharge of cooling water outside the system as blow water is carried out to properly manage the concentration of cooling water due to evaporation. The discharge of cooling water outside the system as splash water occurs when cooling water droplets generated when sprayed in a cooling tower splash outside the system and are discharged. Blow water and splash water are collectively referred to as total blow water. The amount of makeup water is equal to the sum of the amount of evaporated water and the amount of total blow water.

[0008] When a portion of the cooling water evaporates in a cooling tower, the cooling water becomes concentrated. If the concentration of dissolved salts in the cooling water increases due to the concentration of the cooling water, these salts may precipitate as scale in heat exchangers, cooling towers, etc. To prevent this, concentrated cooling water is blown out from pits, etc., to prevent excessive concentration, and makeup water is supplied to the cooling water system in an amount commensurate with the amount of blown out. A scale dispersant is also added (Patent Document 5). Patent Document 5 also describes treating the blown out water with a reverse osmosis membrane device and returning the treated water to the cooling water system.

[0009] Japanese Patent Publication No. 2006-502365 Publication of Japanese Patent Application Publication No. 8-49989 Publication of Japanese Patent Application Publication No. 6-109379 Publication of Japanese Patent Publication No. 2003-207293 Publication of Patent No. 5773013

[0010] An object of the present invention is to provide a cooling tower system that can achieve water conservation by recovering evaporated water from a cooling tower and can also achieve sound equipment maintenance through water quality management.

[0011] The cooling tower system of the present invention comprises a cooling tower in which water is sprayed onto a filler material to cool it and produce cooling water; a makeup water supply means for supplying makeup water to the cooling tower; a heat exchanger for cooling exhaust air from an exhaust fan of the cooling tower to produce condensed water; a water recovery means for supplying the condensed water produced in the heat exchanger to the makeup water supply means; and a blowdown control means for controlling the concentration ratio of the cooling water to a predetermined range.

[0012] In one aspect of the cooling tower system of the present invention, the heat exchanger exchanges heat between the air drawn into the cooling tower by the operation of the exhaust fan and the exhaust air from the exhaust fan, thereby cooling the exhaust air.

[0013] In one aspect of the present invention, the heat exchanger is arranged facing the air intake on the side of the cooling tower so that air drawn toward the air intake passes through the heat exchanger.

[0014] In one aspect of the present invention, the heat exchanger comprises a plurality of flat, hollow chamber boxes arranged in parallel with gaps between them so that the surfaces of the chamber boxes are in the vertical direction, the chamber boxes having open upper and lower end faces and a pair of closed side edges, the exhaust air flowing into each chamber box through an open opening in the upper end face and flowing out through an open opening in the lower end face, and the air passing through the space between each chamber box.

[0015] In one aspect of the present invention, the blow control means includes a water quality sensor that detects the quality of the cooling water, and control means that controls the amount of makeup water supplied or the amount of blown water based on the value detected by the water quality sensor.

[0016] The cooling tower system of the present invention uses a combination of a water recovery means for recovering evaporated water and a blowdown control means for maintaining constant water quality, such as electrical conductivity, in the cooling water system. This not only achieves water conservation by recovering evaporated water, but also ensures sound equipment maintenance through water quality management.

[0017] In one aspect of the present invention, exhaust gas from a cooling tower is ventilated to a heat exchanger using the blowing force of a cooling tower fan. Furthermore, air drawn into the cooling tower by the fan is circulated through the heat exchanger and exchanges heat with the exhaust gas. Because both the exhaust gas and the air are ventilated to the heat exchanger using the blowing force and induced force of the cooling tower fan, there is no need to install a separate blower other than the fan. This reduces both equipment costs and power costs.

[0018] In one aspect of the present invention, the heat exchanger is located outside the cooling tower, which allows existing cooling towers to be easily retrofitted with the cooling tower system of the present invention.

[0019] 1 is a configuration diagram of a cooling tower system according to an embodiment. FIG. 2 is a schematic perspective view of a heat exchanger.

[0020] Hereinafter, an embodiment will be described with reference to the drawings.

[0021] FIG. 1 is a configuration diagram of a cooling tower system according to a first embodiment, showing a cooling tower as a schematic vertical cross section.

[0022] This cooling tower 1 comprises a casing (tower body) 2, with a lower water tank (pit) 4 for storing cooling water provided at the bottom of the casing 2. Louvers 3 are provided on two opposing side surfaces of the casing 2 as air intakes. A filler material 5 is placed inside the casing 2, and an upper water tank 6 is installed above the filler material 5. The bottom plate of the upper water tank 6 is composed of a spray plate 6a with many small holes. A void 7 is provided in the center of the casing 2 (the center when viewed from above), and an exhaust fan 8 is provided above this void chamber 7.

[0023] The suction side of a pump 9 for supplying cooling water is connected to the bottom of the lower water tank 4, and the discharge side of the pump 9 is connected to one end of a cooled body 12 such as a heat exchanger via a cooling water supply pipe 10. The other end of the cooled body 12 such as a heat exchanger is connected to the upper water tank 6 of the cooling tower 1 via a cooling water return pipe 13.

[0024] A makeup water pipe 14 having a valve 15 such as an electromagnetic valve is connected to the lower water tank 4. The makeup water pipe 14 is connected to a makeup water tank (not shown).

[0025] The make-up water tank is connected to a pipe for introducing raw make-up water (make-up raw water) and a recovered water pipe 22b, which will be described later. Note that groundwater, tap water, industrial water, etc., can be used as the make-up raw water.

[0026] An electric conductivity sensor 16 is installed as a water quality sensor in the lower water tank 4. A detection signal from this electric conductivity sensor 16 is input to a controller 17, and the valve 15 is controlled to open and close by a signal from the controller 17.

[0027] In order to maintain the water level in the lower water tank 4 within a set range, the lower water tank 4 is provided with an overblow pipe 18 .

[0028] The sides of the fan 8 are surrounded by a cylindrical shroud 20 .

[0029] One end of a duct 21 is connected to the upper end of the shroud 20, and the other end of the duct 21 is connected to a heat exchanger 22. The heat exchanger 22 is disposed outside the casing (tower body) 2, facing the louvers 3 on one side of the casing 2.

[0030] As shown in Figure 2, the heat exchanger 22 is made up of multiple flat, hollow chamber boxes 22a arranged in parallel with gaps between them. Each chamber box 22a is open at its top and bottom, and one pair of sides is closed. Exhaust air from the fan 8 flows into the chamber box 22a through an opening in the top face of the chamber box 22a and flows out through an opening in the bottom face. Air (atmospheric air) passes through the spaces between the chamber boxes 22a and flows into the casing 2 through the louvers 3.

[0031] The chamber boxes 22a are made of a substantially rectangular plate-shaped material with high thermal conductivity, such as aluminum or copper, and are configured by joining a pair of sides together, but not joining the top sides together or the bottom sides together. The chamber boxes 22a are arranged in parallel with their plate surfaces facing the louvers 3.

[0032] In this cooling tower system, the fan 8 is driven to rotate by a motor (not shown), and the pump 9 is operated to spray water onto the filler material 5 from the spray plate 6 a of the upper water tank 6 .

[0033] The attractive force of the fan 8 causes the air (atmospheric air) to pass through the heat exchanger 22, the louvers 3, and the filler 5. The air, now highly humid, is then discharged from the chamber 7 through the fan 8 to the duct 21.

[0034] The water that flows down through the filler 5 becomes cold due to the heat of vaporization when it evaporates, and falls into the lower water tank 4. The water in the lower water tank 4 flows through the pump 9, piping 10, cooled body 12, and piping 13, and then flows into the upper water tank 6, where it is sprayed onto the filler 5 again.

[0035] The high-humidity exhaust air discharged into the duct 21 by the blowing force of the fan 8 passes through the heat exchanger 22, where it exchanges heat with the air and is cooled. Then, the water vapor contained in the exhaust air condenses to form condensed water.

[0036] This condensed water flows into the recovered water pipe 22b through a water collector (not shown) provided below the heat exchanger 22. The water from the recovered water pipe 22b is sent to the make-up water tank (not shown) and used as make-up water for the cooling tower.

[0037] In this cooling tower system, when the electrical conductivity detected by the electrical conductivity sensor 16 exceeds a preset upper limit, a valve open signal is sent from the controller 17 to the valve 15, which opens and supplies makeup water to the lower water tank 4. This causes the water level in the lower water tank 4 to rise, and water that exceeds the water level at the top of the overblow pipe 18 flows out from the overblow pipe 18. This outflow water is either desalinated and reused, or sent to the discharge process.

[0038] When the electrical conductivity detected by the electrical conductivity sensor 16 falls below the upper limit, the controller 17 closes the valve 15 .

[0039] In this embodiment, the water vapor in the exhaust gas from the cooling tower 1 is condensed in the heat exchanger 22 and reused as makeup water, thereby reducing the amount of makeup water used, such as groundwater, tap water, or industrial water. Also, the water quality (electrical conductivity) in the lower water tank 4 is monitored by the electrical conductivity sensor 16, and when the electrical conductivity exceeds an upper limit, makeup water is supplied to keep the electrical conductivity below the upper limit. This maintains good quality of the cooling water, prevents scale problems, and ensures stable operation of the cooling tower system.

[0040] The exhaust gas cooled by the heat exchanger 22 is released into the atmosphere through a duct 23. Since a large portion of the water vapor in the fan exhaust gas has been removed from this exhaust gas, the generation of white smoke is prevented or suppressed even when the exhaust gas is released into the atmosphere.

[0041] In this cooling tower system, by operating the fan 8 of the cooling tower 1, atmospheric air is drawn in, and air as a low-temperature fluid flows into the heat exchanger 22, and the airflow force of the fan 8 causes the exhaust air from the fan 8 to flow into the cooled fluid flow path of the heat exchanger 22. Therefore, no separate power device (i.e., other than the fan 8) is required for ventilation to the heat exchanger 22.

[0042] In this cooling tower system, the duct 21 and the heat exchanger 22 are arranged outside the casing 2, so that the cooling tower system of the present invention can be constructed even in an existing cooling tower by attaching the duct 21 and the heat exchanger 22.

[0043] In FIG. 1, the heat exchanger 22 is installed only on the outside of one of the louvers 3, but it is also possible to install a heat exchanger 22 on the outside of each louver 3 and ventilate the exhaust air from the fan 8 through each heat exchanger 22.

[0044] In the above embodiment, the electrical conductivity sensor 16 is installed in the lower water tank 4, but it may be installed in other locations such as the pipes 10 and 13 (or pipes branching therefrom).

[0045] In the above embodiment, the electrical conductivity sensor 16 is used as the water quality sensor, but other sensors or devices such as an ion electrode or an automatic chemical analyzer may also be used.

[0046] In the present invention, in addition to a water quality sensor such as an electrical conductivity sensor, a water level sensor may be installed in the lower water tank 4, and the valve 15 may be controlled so that the water quality is within a specified range and the water level in the lower water tank 4 is within a predetermined range.

[0047] In the present invention, instead of the overblow pipe, a blow pipe having a blow valve or a blow pump may be connected to the lower water tank 4, and cooling water may be blown out so that the quality of the cooling water falls within a specified range, and makeup water may be supplied to the lower water tank 4 by makeup water supply means (makeup water pipe 14 having a makeup water valve 15, a ball tap, etc.).

[0048] In FIG. 1, atmospheric air is assumed to pass through the heat exchanger 22 as the air, but air at a lower temperature than the atmospheric air may be supplied to the heat exchanger 22 .

[0049] In the present invention, in order to lower the temperature of the air passing through the heat exchanger 22 and achieve more efficient evaporation water recovery, an air cooler may be installed on the intake side of the heat exchanger 22 as long as it does not significantly impede ventilation.

[0050] The atmospheric cooler may be an evaporative cooling device, a heat storage material, a heat exchanger, or the like. An evaporative cooling device is a device that cools air by utilizing the heat of vaporization produced by the evaporation of water. The evaporative cooling device is not particularly limited as long as it has a mechanism for cooling air by utilizing the heat of vaporization, and may be one in which the water sprayed for cooling comes into contact with the air taken into the heat exchanger 22. The evaporative cooling device may have a mechanism for spraying water to efficiently achieve contact, or for installing a filler on the intake side of the heat exchanger 22 and spraying water on the filler.

[0051] The water used in the evaporative cooling device is not particularly limited, and industrial water, tap water, well water, recycled wastewater water, cooling water, condensed water, etc. can be used.

[0052] To cool the air using cold available at another location or time, a heat storage material can be used in the air cooler, including, but not limited to, latent heat storage materials and sensible heat storage materials.

[0053] In the present invention, an exhaust cooler may be installed downstream of the heat exchanger 22 in the fan exhaust flow to further cool the exhaust with a low-temperature fluid, thereby allowing for further recovery of evaporated water.

[0054] The low-temperature fluid used to cool the exhaust gas in the exhaust gas cooler is not particularly limited, and may be industrial water, tap water, well water, recycled wastewater, cooling water, condensed water, brine, process fluid, etc. However, the exhaust gas cooler cools the exhaust gas using cold energy, and the cold energy source is not limited to a liquid, but may also be a gas.

[0055] In the present invention, a heat exchanger having a configuration other than that shown in FIG. 2, such as a corrugated fin type heat exchanger, may be used.

[0056] Generally, evaporation water recovery equipment technologies are broadly classified into two types: one is a technology that recovers droplets of condensed water generated by lowering the dew point of the air at the cooling tower outlet, which contains evaporated water, and the other is a technology that recovers water molecules that exist as a gas in the air as water vapor.

[0057] There are several methods for collecting condensed water droplets, including separating them from the air using a filter, collecting them on an electrode using electrostatic force by utilizing corona discharge, and separating and collecting water and air using centrifugal force.

[0058] There are several ways to recover gaseous water vapor, including cooling the air and using chemical adsorption. Methods for recovering water vapor by cooling include using a heat exchanger like a dehumidifier, or mixing cold air or cold water with air to cool it. Chemical adsorption involves absorbing water vapor with a highly hygroscopic chemical such as calcium chloride, and extracting it as water by applying heat or other energy.

[0059] In the present invention, among these, the means for recovering water vapor by cooling air is preferred, and the means described in the above embodiment is particularly preferred.

[0060] [Example 1] Equipped with a cooling tower, water capacity 20 m ３ A simulation was performed on a cooling tower system in which a duct 21 and a heat exchanger 22 were installed externally as shown in FIG. 1 to the cooling tower facility.

[0061] This cooling tower system was operated under the following conditions. The evaporation water recovery rate is given below: [(amount of evaporated water recovered (m ３ / h)) / (Supplementary water amount (m) ３ / h)] × 100%.

[0062] Raw water for makeup water: Industrial water (electrical conductivity: 20 mS / m) Circulating flow rate of cooling water: 1000 m ３ / h Cooling water inlet temperature of cooled body 12: 32°C Cooling water outlet temperature of cooled body 12: 37°C (set at ΔT = 5°C) Fan power of cooling tower 1: 25 W Upper limit of electrical conductivity: 100 S / m Evaporation amount: 8.6 m ３ / h Evaporation water recovery rate: 20% Outside temperature (average): 27°C

[0063] Table 1 shows the amount of make-up water when the concentration factor was changed.

[0064] [Example 2] Operation was carried out under the same conditions as in Example 1, except that the evaporation water recovery rate was set to 30%. Table 1 shows the amount of makeup water when operation was carried out with various concentration factors.

[0065] Example 3 The operation was carried out under the same conditions as in Example 1, except that the evaporation water recovery rate was set to 40%. Table 1 shows the amount of makeup water when the concentration factor was changed.

[0066] Comparative Example 1 Operation was carried out under the same conditions as in Example 1, except that the ducts 21, 23 and the heat exchanger 22 were not installed. Table 1 shows the amounts of makeup water when the concentration factor was changed variously.

[0067] [Comparative Example 2] In Comparative Example 1, the blow water was treated by reverse osmosis (RO), and the permeated water was returned to the make-up water tank. The blow water recovery rate [(RO permeated water volume (m ３ / h)) / (Supplementary water amount (m) ３ The operation was carried out under the same conditions as in Comparative Example 1, except that the ratio of the temperature to the temperature of the fuel cell was 75%.

[0068] Table 1 shows the amount of make-up water when the concentration factor was changed.

[0069]

[0070] As shown in Table 1, Examples 1 to 3 in which evaporated water is recovered and Comparative Example 2 in which blown water is recovered all require less makeup water than Comparative Example 1 in which water recovery is not performed, and have a water-saving effect.

[0071] In addition, Comparative Example 2, which recovers blown water using RO, exhibits a significant water-saving effect at low concentrations (when the concentration factor is small), but the water-saving effect decreases as the concentration factor increases.

[0072] In Examples 1 to 3, which recover evaporated water, the water-saving effect is inferior to that of blown water recovery using RO (Comparative Example 2) at low concentrations. However, by increasing the concentration factor, a greater water-saving effect can be obtained than that of blown water recovery using RO (Comparative Example 2).

[0073] [Experimental Example 1] In a cooling tower system operated under the conditions of Example 3 (evaporated water recovery rate of 40%), the evaporated water recovery rate was changed to 10%, and the pH of the water system was adjusted to pH = 8.2 (constant) using sulfuric acid to prevent calcium carbonate precipitation. The system was operated for 100 hours under the same conditions as Example 3 except for this. It was then measured whether the quality of the cooling water changed due to this change in evaporated water recovery rate. The water quality measurement results after 100 hours are shown in Table 2. Table 2 also shows the water quality measurement results for Example 3.

[0074] In addition, to examine the corrosion prevention effect of cooling water under each water quality condition, the corrosion rate was measured using carbon steel test pieces according to the following method. The results are shown in Table 2. (Method for calculating corrosion rate) Corrosion rate (mg / dm ２ / day) = (weight of test piece before test - weight of test piece after test) (mg) ÷ (surface area of ​​test piece) (dm ２ ) ÷ (corrosion test period) (days) The weight of the test specimen after the test is the weight of the test specimen after removing the corrosion products. Test specimen surface area: 0.32 dm ２ Corrosion test period: 7 days

[0075] Comparative Experimental Example 1 In Experimental Example 1, instead of controlling the opening of the make-up water valve 15 based on the detected value of electrical conductivity, the amount of make-up water was set to 6.5 m ３ The opening of the valve 15 was fixed so that the temperature was constant at 1 / h. Other than that, the measurements were carried out under the same conditions as in Experimental Example 1. The results are shown in Table 2.

[0076]

[0077] As shown in Table 2, the water quality remained constant even when the evaporation water recovery rate was varied as in Experimental Example 1. In contrast, in Comparative Experimental Example 1, in which automatic control of blowing based on electrical conductivity was not performed, the cooling water became concentrated, causing fluctuations in water quality and an increase in the corrosion rate.

[0078] Since the recovery rate of evaporated water varies greatly depending on the weather, it was found that controlling the blowdown based on the detected value of the cooling water quality is desirable in order to obtain stable equipment maintenance effects.

[0079] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2023-214069, filed on December 19, 2023, and is incorporated by reference in its entirety.

[0080] REFERENCE SIGNS LIST 1 Cooling tower 3 Louver (air intake section) 4 Lower water tank 5 Filler 6 Upper water tank 6a Spray plate 8 Exhaust fan 12 Cooled body 14 Make-up water piping 15 Valve 16 Electrical conductivity sensor 17 Controller 18 Overblow pipe 21 Duct 22 Heat exchanger 22b Recovered water piping

Claims

1. A cooling tower system comprising: a cooling tower in which water is sprayed onto a filler material to cool it and produce cooling water; a make-up water supply means for supplying make-up water to said cooling tower; a heat exchanger for cooling exhaust air from an exhaust fan of said cooling tower to produce condensed water; a water recovery means for supplying the condensed water produced in the heat exchanger to said make-up water supply means; and a blow control means for controlling the concentration rate of said cooling water to a predetermined range.

2. The cooling tower system of claim 1, wherein the heat exchanger exchanges heat between the air drawn into the cooling tower by the operation of the exhaust fan and the exhaust air from the exhaust fan, thereby cooling the exhaust air.

3. A cooling tower system according to claim 2, wherein the heat exchanger is disposed facing the atmospheric air intake on the side of the cooling tower so that air drawn toward the atmospheric air intake passes through the heat exchanger.

4. The cooling tower system of claim 3, wherein the heat exchanger is a plurality of flat, hollow chamber boxes arranged in parallel with gaps between them so that the plates are in the vertical direction, the chamber boxes have open upper and lower end faces and a pair of side edges are closed, the exhaust air flows into each chamber box from the open opening on the upper end face and flows out from the open opening on the lower end face, and the air passes through the space between each chamber box.

5. A cooling tower system according to any one of claims 1 to 4, wherein the blow control means comprises a water quality sensor which detects the quality of the cooling water, and a control means which controls the amount of makeup water supplied based on the detection value of the water quality sensor.

6. A cooling tower system according to any one of claims 1 to 4, wherein the blow control means comprises a water quality sensor for detecting the quality of the cooling water, and a control means for controlling the amount of blow water based on the detection value of the water quality sensor.

7. The cooling tower system of claim 5, wherein said water quality sensor is an electrical conductivity sensor.

8. The cooling tower system of claim 6, wherein said water quality sensor is an electrical conductivity sensor.

9. The cooling tower system according to claim 3, wherein the exhaust fan is provided at the top of the cooling tower, and the exhaust air from the exhaust fan is guided to the heat exchanger by a duct.

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