Cooling Tower Systems

Abstract

To provide a cooling tower system that realizes water conservation by recovering evaporated water from a cooling tower and realizes sound facility maintenance by managing water quality. [Solution] A cooling tower 1 has a tower body 2 with louvers 3 on the sides, an exhaust fan 8 on the top, and a lower water tank 4 at the bottom, a filler 5 placed inside the tower body 2 onto which water is poured from above, and a controller 17 that controls a make-up water valve 15 based on the electrical conductivity detected by an electrical conductivity sensor 16. Condensed water generated by a heat exchanger 22 for cooling the exhaust air from the exhaust fan 8 is used as make-up water.

Description

[Technical field]

[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. [Background technology]

[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 runs down the packing material is cooled by the heat of vaporization and becomes cold water. The air that passes through the packing material is exhausted upward by the fan at the top of the tower.

[0003] The cold water that falls into the lower water tank of the cooling tower and is stored there is sent to the equipment to be cooled, such as a refrigerator, where it is heated by heat exchange, and then returns 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 provided at the top 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. Atmosphere or air at a lower temperature is ventilated through the low-temperature fluid passage of this heat exchanger.

[0006] In an open circulating cooling water system, water is lost due to evaporation, scattering, blowing, etc., so make-up water is supplied. The discharge of cooling water out of 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 the cooling water droplets generated when sprayed in the cooling tower splash outside the system and are discharged. Blow water and splash water are collectively called total blow water. The amount of make-up water is equal to the sum of the amount of evaporated water and the total amount of blow water.

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

[0009] [Patent Document 1] Special Publication No. 2006-502365 [Patent Document 2] Japanese Patent Application Publication No. 8-49989 [Patent Document 3] Japanese Patent Application Publication No. 6-109379 [Patent Document 4] JP 2003-207293 A [Patent Document 5] Patent No. 5773013 Summary of the Invention [Problem to be solved by the invention]

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

[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 make-up water supply means for supplying make-up 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 make-up water supply means, and a blow control means for controlling the concentration ratio of the cooling water to a predetermined range.

[0012] In a cooling tower system according to one embodiment of the present invention, the heat exchanger exchanges heat between 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 is made up of a plurality of flat, hollow chamber boxes arranged in parallel with gaps between them so that the plate surfaces are in the vertical direction, and the chamber boxes are open at their upper and lower ends and have a pair of closed side edges, and the exhaust air flows into the chamber boxes through an open opening at the upper end face of each chamber box and flows out through an open opening at the lower end face, with the air passing through the space between each chamber box.

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

[0016] The cooling tower system of the present invention combines a water recovery means for recovering evaporated water with a blowdown control means for maintaining constant water quality, such as the electrical conductivity of 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, the exhaust air from a cooling tower is ventilated to a heat exchanger by utilizing the blowing force of a cooling tower fan. Also, air that is attracted by the fan and attempts to flow into the cooling tower is circulated through the heat exchanger and exchanges heat with the exhaust air. In this way, both the exhaust air and the air are ventilated to the heat exchanger by the blowing force and suction force of the cooling tower fan, so there is no need to install a new blower device other than the fan. Therefore, the equipment cost and the power cost are low.

[0018] In one aspect of the present invention, the heat exchanger is located outside the cooling tower, so that existing cooling towers can be easily retrofitted with the cooling tower system of the present invention. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a configuration diagram of a cooling tower system according to an embodiment. [Diagram 2] FIG. 2 is a schematic perspective view of a heat exchanger. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, and a lower water tank (pit) 4 for storing cooling water is provided at the bottom of the casing 2. Louvers 3 are provided on two opposing side surfaces of the casing 2 as air intakes. Filler 5 is placed inside the casing 2, and an upper water tank 6 is placed above the filler 5. The bottom plate of the upper water tank 6 is composed of a spray plate 6a with many small holes. An empty chamber 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 empty chamber 7.

[0023] The suction side of a pump 9 for delivering 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 body 12 to be cooled, such as a heat exchanger, via a cooling water supply pipe 10. The other end of the body 12 to be cooled, 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 make-up water pipe 14 having a valve 15 such as an electromagnetic valve is connected to the lower water tank 4. The make-up water pipe 14 is connected to a make-up 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 described later. As the make-up raw water, groundwater, tap water, industrial water, etc. are used.

[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] 2, the heat exchanger 22 is a configuration in which a plurality of flat, hollow chamber boxes 22a are arranged in parallel with a gap between them. The upper and lower end faces of the chamber boxes 22a are open, and one pair of side edges is closed. Exhaust air from the fan 8 flows into the chamber box 22a from an open opening on the upper end face of the chamber box 22a and flows out from an open opening on the lower end 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-like material made of a material with high thermal conductivity such as aluminum or copper, with a pair of side edges joined together and the top edges and bottom edges not joined together. The chamber boxes 22a are arranged in parallel with their plate surfaces facing the louvers 3.

[0032] In this cooling tower system, a fan 8 is rotated by a motor (not shown), and a pump 9 is operated to spray water onto the filler 5 from a spray plate 6a of an 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. Then, the air, now highly humid, is exhausted from the chamber 7 through the fan 8 to the duct 21.

[0034] The water that runs down through the filler 5 becomes cold water 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 flows into the upper water tank 6, and 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 become condensed water.

[0036] This condensed water flows out 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 end of the overblow pipe 18 flows out from the overblow pipe 18. This outflow water is either desalted 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 make-up water, thereby reducing the amount of make-up raw water used, such as groundwater, tap water, and 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, make-up water is supplied to make the electrical conductivity equal to or lower than the upper limit, so that the quality of the cooling water is maintained good, scale problems are prevented, and the operation of the cooling tower system is stabilized.

[0040] The exhaust gas cooled by the heat exchanger 22 is released into the atmosphere through the 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 if the exhaust gas is released into the atmosphere.

[0041] In this cooling tower system, by operating the fan 8 of the cooling tower 1, the atmosphere is drawn in, and air as a low-temperature fluid flows into the heat exchanger 22, while the blowing force of the fan 8 causes the exhaust air from the fan 8 to be ventilated into the cooled fluid flow path of the heat exchanger 22. Therefore, a separate power device (i.e., other than the fan 8) for ventilating the heat exchanger 22 is not required.

[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 to 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 specified 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 the cooling water may be blown out so that the quality of the cooling water is 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 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] As the atmospheric cooler, an evaporative cooling device, a heat storage material, a heat exchanger, etc. can be used. An evaporative cooling device is a device that cools air by utilizing the heat of vaporization caused by the evaporation of water. The evaporative cooling device is not particularly limited as long as it is a device that uses the heat of vaporization to cool air, and it is sufficient that the water sprayed for cooling comes into contact with the air taken into the heat exchanger 22. In order to efficiently carry out the contact, the device may be a device that sprays water or a filler is placed on the intake side of the heat exchanger 22 and sprays 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] A thermal storage material can be used in the air cooler to cool the air using cold available at another location or time. Types of thermal storage materials include, but are not limited to, latent heat storage materials and sensible heat storage materials.

[0053] In the present invention, an exhaust cooler may be provided downstream of the fan exhaust flow from the heat exchanger 22 for further cooling the exhaust with a low-temperature fluid, thereby allowing 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 and may 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 roughly divided 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] Methods for collecting condensed water droplets include separating them from the air using a filter, collecting them on an electrode using electrostatic force by utilizing corona discharge, and separating and collecting the water and air using centrifugal force.

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

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

[0060] [Example 1] Equipped with a cooling tower, it holds 20m of water 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.

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

[0062] Raw water for make-up water: Industrial water (electrical conductivity: 20 mS / m) Cooling water circulation flow rate: 1000m 3 / h Cooling water inlet temperature of cooled body 12: 32°C Cooling water outlet temperature of cooled body 12: 37℃ (set ΔT=5℃) Cooling tower 1 fan power: 25W Electrical conductivity upper limit: 100S / m Evaporation volume: 8.6m 3 / h Evaporation water recovery rate: 20% Outside temperature (average): 27℃

[0063] Table 1 shows the amount of make-up water required when operating at various concentration rates.

[0064] [Example 2] Except for the water recovery rate being 30%, the operation was carried out under the same conditions as in Example 1. Table 1 shows the amount of makeup water when the concentration factor was changed.

[0065] [Example 3] Except for the water recovery rate being 40%, the operation was carried out under the same conditions as in Example 1. Table 1 shows the amount of make-up water when the concentration factor was changed.

[0066] [Comparative Example 1] The 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 amount of makeup water when the concentration factor was changed variously.

[0067] [Comparative Example 2] In Comparative Example 1, the blowdown water was treated by reverse osmosis (RO), the permeate was returned to the make-up water tank, and the water recovery rate [(RO permeate 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 reaction rate (rpm) was 1000 rpm and the reaction time (h) was 100 rpm.

[0068] Table 1 shows the amount of make-up water required when operating at various concentration rates.

[0069] [Table 1]

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

[0071] In addition, Comparative Example 2, which recovers blown water using RO, exhibits a large 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 in which evaporated water is recovered, 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 (evaporation water recovery rate of 40%), the 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. Other than that, the system was operated for 100 hours under the same conditions as Example 3. Then, it was measured whether the quality of the cooling water changed due to this change in recovery rate. The water quality measurement results after 100 hours are shown in Table 2. Table 2 also shows the water quality measurement results in 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. (Corrosion rate calculation method) Corrosion rate (mg / dm 2 / day) = (weight of test specimen before test - weight of test specimen after test) (mg) ÷ (surface area of ​​test specimen) (dm 2 )÷(corrosion test period)(days) The post-test weight of the test specimen is the weight of the test specimen after removing the corrosion products. Specimen surface area: 0.32 dm 2 Corrosion test period: 7 days

[0075] [Comparative Experiment Example 1] In the first experimental example, instead of controlling the opening of the make-up water valve 15 based on the detected electrical conductivity value, the amount of make-up water was set to 6.5 m 3 The opening of the valve 15 was fixed so as to keep the flow rate 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] [Table 2]

[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 blow control based on electrical conductivity was not performed, the cooling water became concentrated, the water quality fluctuated, and the corrosion rate increased.

[0078] Since the recovery rate of evaporated water varies greatly depending on the weather, it was found that in order to obtain a stable equipment maintenance effect, it is desirable to control the blower based on the detected value of the cooling water quality. [Explanation of symbols]

[0079] 1 cooling tower 3 Louver (air intake) 4 Lower tank 5 Filling material 6 Upper tank 6a Sprinkler plate 8. Exhaust Fan 12 Cooled object 14 Makeup water piping 15 Valve 16 Electrical conductivity sensor 17 Controller 18 Overblow pipe 21 Duct 22 Heat exchanger 22b Reclaimed water piping

Claims

1. a cooling tower in which water is sprayed onto a filler to cool it and produce cooling water; A make-up water supply means for supplying make-up water to the cooling tower; a heat exchanger that cools the exhaust air from the exhaust fan of the cooling tower to produce condensed water; a water recovery means for supplying condensed water generated in the heat exchanger to the makeup water supply means; A blow control means for controlling the concentration rate of the cooling water within a predetermined range; 1. A cooling tower system comprising: The heat exchanger is a cooling tower system in which the air drawn into the cooling tower by the operation of the exhaust fan is exchanged with the exhaust air from the exhaust fan to cool the exhaust air.

2. 2. The cooling tower system according to claim 1, 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.

3. The heat exchanger is a plurality of flat hollow chamber boxes arranged in parallel with intervals between each other so that the plate surfaces are in the up-down direction, The chamber box has an open upper end surface and a closed lower end surface, and a pair of closed side surfaces. The exhaust gas flows into each chamber box through an opening at an upper end surface thereof and flows out of the opening at a lower end surface thereof, 3. The cooling tower system of claim 2, wherein the air passes through spaces between each of the chamber boxes.

4. 4. The cooling tower system according to claim 1, wherein the blow control means comprises a water quality sensor that detects the quality of the cooling water, and a control means that controls the supply amount of makeup water or the blow water amount based on the detection value of the water quality sensor.

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