Cooling tower system

Abstract

To provide a cooling tower system that enables water saving by recovering evaporation water from a cooling tower and enables sound facility maintenance through water quality management.SOLUTION: A cooling tower 1 includes: a tower body 2 having a side surface with a louver 3, a top part with an exhaust fan 8 and a lower part with a lower water tank 4; a filler 5 that is disposed in the tower body 2 and to which water is poured from the upper side; and a controller 17 that controls a makeup water supply valve 15 on basis of detection electric conductivity from an electric conductivity sensor 16. Condensation water generated by a heat exchanger 22 for cooling exhaust gas from the exhaust fan 8 is used as makeup water.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cooling tower system having a cooling tower and a water recovery mechanism for recovering moisture in the exhaust gas of the cooling tower.

Background Art

[0002] In an open-circulation cooling tower, by operating a fan at the top of the tower and spraying water onto a filler disposed inside the tower, the water flowing down through the filler is cooled by the latent heat of vaporization to become cold water. The air passing through the filler is discharged upward by the fan at the top of the tower.

[0003] The cold water that has fallen and is stored in the lower water tank of the cooling tower is sent to a device to be cooled such as a refrigerator, and after heat exchange and temperature rise, it returns to the cooling tower.

[0004] The above-mentioned cooling tower exhaust gas contains a large amount of moisture such as water vapor, and in winter or the like, the water vapor may condense to generate white smoke.

[0005] As a cooling tower provided with a mechanism for preventing such white smoke, Patent Document 1 describes that an air-cooled heat exchanger is provided at the upper part inside the cooling tower, and the water vapor-containing air rising inside the tower is cooled to condense the water vapor, thereby reducing the amount of moisture in the cooling tower exhaust gas. The low-temperature fluid passage of this heat exchanger is ventilated with air at or lower than the temperature of the atmosphere.

[0006] In an open-circulation cooling water system, water is lost due to evaporation, scattering, blowing, etc., so makeup water is supplied. The discharge of cooling water to the outside of the system due to evaporation is due to the liquid water becoming water vapor and being released into the atmosphere. Patent Documents 2 to 4 describe that this water vapor is condensed and recovered for use in cooling water.

[0007] The discharge of cooling water to the outside of the system by blowdown water is carried out to properly manage the concentration of cooling water due to evaporation. The discharge of cooling water to the outside of the system by splashed water is such that the water droplets of the cooling water generated when sprinkled in the cooling tower are splashed and discharged to the outside of the system. The blowdown water and the splashed water are collectively referred to as total blowdown water. The makeup water volume is equal to the sum of the evaporation water volume and the total blowdown water volume.

[0008] When a part of the cooling water evaporates in the 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 on heat exchangers, cooling towers, etc. To prevent this, in order to prevent excessive concentration from occurring, blowdown is performed to discharge the concentrated cooling water from a pit or the like, and makeup water in an amount corresponding to the blowdown amount is supplied to the cooling water system. In addition, a scale dispersant is added (Patent Document 5). Note that Patent Document 5 describes treating blowdown 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

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0011] The cooling tower system of the present invention includes a cooling tower in which water is sprayed onto a filler and cooled to become cooling water, a makeup water supply means for supplying makeup water to the cooling tower, a heat exchanger for cooling the exhaust from the exhaust fan of the cooling tower to generate condensed water, a water recovery means for supplying the condensed water generated in the heat exchanger to the makeup water supply means, and a blowdown control means for setting the concentration ratio of the cooling water within a predetermined range.

[0012] In the cooling tower system according to one aspect of the present invention, the heat exchanger cools the exhaust by exchanging heat between the air drawn into the cooling tower when the exhaust fan operates and the exhaust from the exhaust fan.

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

[0014] In one aspect of the present invention, the heat exchanger is formed by arranging a plurality of flat and hollow chamber boxes in parallel at intervals with their disk surfaces in the vertical direction. The chamber boxes have open upper and lower end surfaces, and a pair of side edges are closed. The exhaust flows into each chamber box through the opening at the upper end surface of the chamber box and flows out through the opening at the lower end surface, and the air passes through the space between the chamber boxes.

[0015] In one aspect of the present invention, the blowdown control means includes a water quality sensor for detecting the water quality of the cooling water and a control means for controlling the supply amount of the makeup water or the blowdown amount based on the detection value of the water quality sensor.

Advantages of the Invention

[0016] The cooling tower system of the present invention is used in combination with a water recovery means for recovering evaporated water and a blowdown control means for keeping the water quality such as the electrical conductivity of the cooling water system constant, realizing water conservation by recovering the evaporated water and realizing sound equipment maintenance through water quality management.

[0017] In one aspect of the present invention, the exhaust gas of the cooling tower is ventilated to the heat exchanger by utilizing the blowing force of the fan of the cooling tower. Further, the air that is attracted by the fan and is about to flow into the cooling tower is circulated through the heat exchanger and heat-exchanged with the exhaust gas. In this way, since both the exhaust gas and the air are ventilated to the heat exchanger by the blowing force and suction force of the fan of the cooling tower, it is unnecessary to install a new blowing device other than the fan. Therefore, the equipment cost is low and the power cost is also low.

[0018] In one aspect of the present invention, the heat exchanger is arranged outside the tower of the cooling tower. Therefore, an existing cooling tower can be easily modified to the cooling tower system of the present invention.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

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

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

[0022] This cooling tower 1 is equipped with a casing (tower body) 2, and at the bottom of the casing 2, a lower water tank (pit) 4 for storing cooling water is provided. Louvers 3 are provided as air intake parts on two opposite side surfaces of the casing 2. A packing material 5 is installed inside the casing 2, and an upper water tank 6 is installed above the packing material 5. The bottom plate of the upper water tank 6 is composed of a water distribution plate 6a having a large number of small holes. An empty chamber 7 is provided at the central part (central part in plan view) of the casing 2, and an exhaust fan 8 is provided above this empty chamber 7.

[0023] The suction side of a pump 9 for sending 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 object 12 such as a heat exchanger via a forward pipe 10 for cooling water. The other end of the cooled object 12 such as a heat exchanger is connected to the upper water tank 6 of the cooling tower 1 via a return pipe 13 for cooling water.

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

[0025] A pipe for introducing raw water of makeup water (makeup raw water) and a recovery water pipe 22b described later are connected to the makeup water tank. Note that groundwater, tap water, industrial water, etc. are used as the makeup raw water.

[0026] An electric conductivity sensor 16 is installed in the lower water tank 4 as a water quality sensor. The detection signal of 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] An overblow pipe 18 is provided in the lower water tank 4 in order to maintain the water level of the lower water tank 4 within a set range.

[0028] The peripheral side of the fan 8 is surrounded by a cylindrical shroud 20.

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

[0030] As shown in FIG. 2, the heat exchanger 22 is formed by arranging a plurality of flat-plate-shaped and hollow chamber boxes 22a in parallel at intervals. The chamber boxes 22a have open upper and lower end faces, and a pair of side edges are closed. The exhaust air from the fan 8 flows into the chamber box 22a through the open port on the upper end face of the chamber box 22a and flows out through the open port on the lower end face. Air (atmosphere) passes through the space between the chamber boxes 22a and flows into the casing 2 through the louver 3.

[0031] The chamber box 22a is formed by connecting a pair of side edges of a substantially square plate-shaped material made of a material with high thermal conductivity such as aluminum or copper, and not connecting the upper and lower sides. Each chamber box 22a is arranged in parallel so that its plate surface (board surface) faces the direction of the louver 3.

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

[0033] Due to the suction force of the fan 8, air (atmosphere) passes through the heat exchanger 22, the louver 3, and the packing 5. Then, the high-humidity air is discharged from the empty chamber 7 through the fan 8 to the duct 21.

[0034] The water flowing down through the packing 5 becomes low-temperature cold water due to the heat of vaporization during evaporation and falls into the lower water tank 4. The water in the lower water tank 4 flows through the pump 9, the pipe 10, the object to be cooled 12, and the pipe 13 and flows into the upper water tank 6, and is sprinkled onto the packing 5 again.

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

[0036] This condensed water flows out into the recovered water pipe 22b through a water collector (not shown) provided on the lower side of the heat exchanger 22. The water from the recovered water pipe 22b is sent to the replenishment water tank (not shown) and used as the replenishment 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 value, an opening signal is given from the controller 17 to the valve 15, the valve 15 opens, and the replenishment water is supplied to the lower water tank 4. As a result, the water level in the lower water tank 4 rises, and the water exceeding the upper end water level of the overflow pipe 18 flows out from the overflow pipe 18. This outflow water is either desalinated and reused or sent to the discharge process.

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

[0039] In this embodiment, since the water vapor in the exhaust gas of the cooling tower 1 is condensed by the heat exchanger 22 and reused as the replenishment water, the usage amount of replenishment raw water such as groundwater, tap water, and industrial water is reduced. 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 becomes higher than the upper limit value, replenishment water is supplied to make the electrical conductivity below the upper limit value. Therefore, the water quality of the cooling water is maintained well, scale damage is prevented, and the operation of the cooling tower system becomes stable.

[0040] The exhaust gas cooled by the heat exchanger 22 is discharged into the atmosphere through the duct 23. Since a considerable part of the water vapor in the fan exhaust gas is removed, white smoke is prevented or suppressed from being generated even when it is discharged into the atmosphere.

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

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

[0043] In FIG. 1, the heat exchanger 22 is installed only outside one of the louvers 3, but the heat exchanger 22 may be installed outside each louver 3, and the exhaust air of the fan 8 may be vented to each heat exchanger 22.

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

[0045] In the above embodiment, the electric conductivity sensor 16 is used as the water quality sensor, but other sensors or devices such as ion electrodes and automatic chemical analyzers may be used.

[0046] In the present invention, in addition to the water quality sensor such as the electric 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 the specified range and the water level in the lower water tank 4 is within the predetermined range.

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

[0048] In FIG. 1, it is assumed that the atmosphere passes through the heat exchanger 22 as air, but air having a temperature lower than the atmosphere may be supplied to the heat exchanger 22.

[0049] In the present invention, in order to lower the temperature of the atmosphere 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 within a range that does not significantly impede ventilation.

[0050] As the air cooler, a vaporization cooling device, a heat storage material, a heat exchanger, or the like can be used. The vaporization cooling device is a device that cools air by utilizing the latent heat of vaporization due to the evaporation of water. The vaporization cooling device is not particularly limited as long as it is based on a mechanism that cools air by utilizing the latent heat of vaporization, and it may be one in which the water sprayed for cooling comes into contact with the air taken into the heat exchanger 22, and it may be a mechanism that sprays water or installs a filler on the intake side of the heat exchanger 22 and waters the filler.

[0051] The water used for the vaporization cooling device is not particularly limited, and industrial water, tap water, well water, recycled drainage water, cooling water, condensate, or the like can be used.

[0052] In order to cool air by using the cold heat obtained at another location or at another time, a heat storage material can be used for the air cooler. Examples of the type of heat storage material include, but are not limited to, latent heat storage materials and sensible heat storage materials.

[0053] In the present invention, an exhaust cooler for further cooling the exhaust with a low-temperature fluid may be installed on the downstream side of the fan exhaust flow of the heat exchanger 22 to further recover the evaporation water.

[0054] The low-temperature fluid used for cooling the exhaust by the exhaust cooler is not particularly limited, and industrial water, tap water, well water, recycled drainage water, cooling water, condensate, brine, process fluid, or the like can be used. However, the exhaust cooler cools the exhaust by using cold heat, and the cold heat 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] In general, the technology of an evaporation water recovery device is roughly classified into two types. One is a technology for recovering condensed water droplets generated by bringing the air at the outlet of a cooling tower containing evaporation water below the dew point, and the other is a technology for recovering water molecules existing as a gas in the air as water vapor.

[0057] As methods for recovering condensed water droplets, there are methods of separating and recovering from air using a filter or the like, methods of recovering to an electrode by electrostatic force utilizing corona discharge, methods of separating and recovering water and air by centrifugal force, and the like.

[0058] As means for recovering water vapor existing as a gas, there are means for cooling and recovering air, means for recovering using chemical adsorption, and the like. As means for cooling and recovering, there are means for cooling with a heat exchanger like a dehumidifier, means for mixing cold air or cold water with air for cooling, and the like. The means for recovering using chemical adsorption is a means for absorbing water vapor with a highly hygroscopic chemical substance such as calcium chloride and taking it out as water by applying energy such as heat.

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

Example

[0060] [Example 1] A cooling tower system in which a duct 21 and a heat exchanger 22 were externally installed as shown in FIG. 1 in a cooling tower facility having a holding water volume of 20 m 3 and equipped with a cooling tower was simulated.

[0061] This cooling tower system was operated under the following conditions. The following evaporation water recovery rate is a value calculated by [(evaporation water amount recovered (m 3 / h)) / (make-up water amount (m 3 / h))]×100%.

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

[0063] Table 1 shows the makeup water amounts when operating with various concentration multiples changed.

[0064] [Example 2] Operation was carried out under the same conditions as in Example 1 except that the water recovery rate was set at 30%. Table 1 shows the makeup water amounts when operating with various concentration multiples changed.

[0065] [Example 3] Operation was carried out under the same conditions as in Example 1 except that the water recovery rate was set at 40%. Table 1 shows the makeup water amounts when operating with various concentration multiples 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 makeup water amounts when operating with various concentration multiples changed.

[0067] [Comparative Example 2] In Comparative Example 1, the blowdown water was treated by reverse osmosis (RO), and the permeated water was returned to the makeup water tank. Operation was carried out under the same conditions as in Comparative Example 1 except that the water recovery rate [(RO permeated water volume (m 3 / h)) / (makeup water volume (m 3 / h)]×100% was set at 75%.

[0068] Table 1 shows the makeup water amounts when operating with various concentration multiples changed.

[0069]

Table 1

[0070] As shown in Table 1, Examples 1 to 3 and Comparative Example 2 where water recovery is carried out all have less makeup water amount compared to Comparative Example 1 where no water recovery is carried out, and have a water-saving effect.

[0071] Note that Comparative Example 2 where blowdown water recovery is carried out using RO exhibits a large water-saving effect at low concentration (when the concentration multiple is small), but the water-saving effect becomes small as the concentration multiple increases.

[0072] In Examples 1 to 3 where evaporation water recovery is carried out, although the water-saving effect is inferior to that of blowdown water recovery using RO (Comparative Example 2) at low concentration, a larger water-saving effect can be obtained compared to blowdown water recovery using RO (Comparative Example 2) as the concentration multiple is increased.

[0073] [Experimental Example 1] In the cooling tower system operating under the conditions of Example 3 (evaporation water recovery rate 40%), the recovery rate was changed to 10%, and in order to prevent the precipitation of calcium carbonate, sulfuric acid was used to adjust the pH of the water system to pH = 8.2 (constant). Otherwise, it was operated for 100 h under the same conditions as Example 3. Then, it was measured whether the water quality of the cooling water changed due to this change in the recovery rate. The water quality measurement results after 100 h are shown in Table 2. Note that Table 2 also shows the water quality measurement results in Example 3.

[0074] Also, in order to observe the corrosion prevention effect of the cooling water under each water quality condition, a carbon steel test piece was used, and the corrosion rate was measured 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) (day) The weight of the test piece after the test is the weight after removing the corrosion products of the test piece. Test piece 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 degree of the makeup water valve 15 based on the detected value of the electrical conductivity, the opening degree of the valve 15 was fixed so that the makeup water volume was constant at 6.5 m 3 / h. Other conditions were the same as in Experimental Example 1, and each measurement was carried out. 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 where automatic blow control based on the 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 the evaporation water varies greatly depending on the weather, it was recognized that blow control based on the detected value of the cooling water quality is desirable to obtain a stable equipment maintenance effect.

Explanation of Signs

[0079] 1 Cooling tower 3 Louver (atmospheric intake section) 4 Lower water tank 5 Filling material 6 Upper water tank 6a Water distribution plate 8 Exhaust fan 12 Object to be cooled 14 Makeup water pipe 15 Valve 16 Electrical conductivity sensor 17 Controller 18 Overblow pipe 21 Duct 22 Heat exchanger 22b Recovered water pipe

Claims

1. A cooling tower in which water is sprinkled on a filler material for cooling to become cooling water, make-up water supply means for supplying make-up water to the cooling tower, a heat exchanger that cools the exhaust from the exhaust fan of the cooling tower to generate condensed water, water recovery means for supplying the condensed water generated by the heat exchanger to the make-up water supply means, blow control means for setting the concentration ratio of the cooling water within a predetermined range, A cooling tower system having the above.

2. The cooling tower system according to claim 1, wherein the heat exchanger exchanges heat between the air drawn into the cooling tower when the exhaust fan operates and the exhaust from the exhaust fan to cool the exhaust.

3. The cooling tower system according to claim 2, wherein the heat exchanger is arranged facing the air intake part on the side surface of the cooling tower so that the air drawn toward the air intake part passes through.

4. The heat exchanger is a plurality of flat and hollow chamber boxes arranged in parallel with a space therebetween so that the disk surfaces are in the vertical direction, the chamber box has an open upper end surface and a lower end surface, and a pair of side edges are closed, the exhaust flows into the chamber box through the opening at the upper end surface of each chamber box and flows out through the opening at the lower end surface, The cooling tower system according to claim 3, wherein the air passes through the space between the chamber boxes.

5. The blow control means according to any one of claims 1 to 4, comprising a water quality sensor for detecting the water quality of the cooling water and control means for controlling the supply amount of make-up water or the blow-off water amount based on the detection value of the water quality sensor.

Images