Water cooling system and air separation device comprising the same

Abstract

To provide a water cooling system with a dry-type water cooler and a wet-type water cooler, which can generate condensate water by a compressed air cooler to supply the condensate water to the wet-type water cooler.SOLUTION: A water cooling system A1 comprises: a compressed air cooler 12 that cools compressed air; a wet type water cooler 13 into which condensate water generated in the compressed air cooler 12 is introduced as make-up water; a cooling water pump 14 that sends cooling water derived from the wet type water cooler 13 to a cold end of the compressed air cooler 12 to cool the compressed air with the cooling water; a dry type water cooler 15 that cools warm water derived from a warm end of the compressed air cooler 12; and a first flow control valve 121 that adjusts a flow rate of the condensate water.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water cooling system, and more particularly to a water cooling system for cooling cooling water used, for example, in an air compressor.

Background Art

[0002] Cooling water used for cooling equipment is generally cooled by a wet water cooler and a dry water cooler (see, for example, Citation 1). A wet water cooler evaporates a part of the cooling water and cools the cooling water by its latent heat. There are configurations in which it is released to the atmosphere or is performed under reduced pressure while being blocked from the atmosphere (see, for example, Citation 2). However, it is necessary to replenish the cooling water lost by evaporation. The makeup water may be configured to be mixed with the cooling water or to be indirectly cooled through a heat exchanger without being mixed with the cooling water. However, in any configuration, the common problem is that there is evaporation loss of water. In addition, when the makeup water and the cooling water are mixed, there is also a problem of concentration of mineral components and the like contained in the water. A dry water cooler cools the cooling water by a heat exchanger with the atmosphere, and it is necessary to apply a blower or the like to improve the efficiency of heat exchange (see, for example, Citation 3).

[0003] In view of the supply capabilities of water resources and electric power, it has been known for a long time to optimize a water cooling system by combining a wet water cooler and a dry water cooler. However, in any case, supply of makeup water is required to operate the wet cooler. Especially these days when both water resources and electric power are in short supply, there is a demand for constructing a system that optimizes the use of water and electric power according to environmental conditions without adding equipment that requires cooling. This demand is particularly prominent in an air separation plant equipped with an air compressor. Generally, the temperature difference between the cooling water of the air compressor and the atmosphere is small. In the case of air cooling, the air volume increases and the load on the blower becomes large. Therefore, it is highly economically reasonable to use the latent heat of evaporation of water to cool the water and reduce the power consumption of the blower.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above problems and demands, the present disclosure provides a water cooling system that can suppress makeup water by generating condensed water with a compression gas cooler and supplying this condensed water to a wet water cooler in a system equipped with a dry water cooler and a wet water cooler. Also provided is an air separation device equipped with this water cooling system.

Means for Solving the Problems

[0006] The water cooling system of the present disclosure includes a compression gas cooler that cools the compressed gas compressed by a compressor that takes in the gas to be processed, a wet water cooler into which the condensed water generated in the compression gas cooler is introduced as makeup water, a cooling water pump that sends the cooling water derived from the wet water cooler to the cold end of the compression gas cooler to cool the compression gas, a dry water cooler that cools the cooling water derived from the hot end of the compression gas cooler, a first condensed water line pipe that sends the condensed water derived from the compression gas cooler, and a first flow rate adjustment valve provided in the first condensed water line pipe to adjust the flow rate of the condensed water.

[0007] The gas to be processed includes, for example, air (atmosphere), liquefied natural gas (LNG), natural gas (NG), boil-off gas, and the like. The compressed gas includes, for example, compressed air, compressed natural gas, compressed boil-off gas, and the like.

[0008] The water cooling system (A1, A2, A3) of the present disclosure A compressed air cooler (12) for cooling the compressed air compressed by an air compressor (11) that takes in the atmosphere, A wet water cooler (13) into which the condensed water generated in the compressed air cooler (12) is introduced as makeup water, A cooling water pump (14) that sends the cooling water derived from the wet water cooler (13) to the cold end of the compressed air cooler (12) to cool the compressed air, A dry water cooler (15) for cooling the warm water (heat-exchanged cooling water) derived from the warm end of the compressed air cooler (12), A first condensate line pipe (L2) that sends the condensed water derived from the compressed air cooler (12) (to the wet water cooler (13)), A first flow rate adjustment valve (121) provided in the first condensate line pipe (L2) to adjust the flow rate of the condensed water, may be provided.

[0009] The water cooling system (A1, A2, A3) of the present disclosure may include a cooling water line pipe (L3) that sends the cooling water derived from the wet water cooler (13) to the cold end of the compressed air cooler (12), sends it from the warm end of the compressed air cooler (12) to the dry water cooler (15), and sends the derived cooling water to the wet water cooler (13).

[0010] The water cooling system (A1, A2, A3) may include an atmosphere line pipe (L1) that sends the atmosphere to the air compressor (11) and sends the compressed air from the air compressor (11) to the compressed air cooler (12).

[0011] The compressed air (saturated with water vapor) derived from the compressed air cooler (12) may be supplied to the air separation device.

[0012] The water cooling system (A1, A2, A3) may include one or more of the storage part (12a) of the compressed air cooler (12) that stores the condensed water, or a separately provided buffer, the storage part (131) of the wet water cooler (13), or a separately provided buffer, and the storage part (161) of the water buffer (16) provided in the condensed water line pipe (L2). The water cooling system (A1) a second condensed water line pipe (L21) that sends condensed water from the water buffer (16) to the wet water cooler (13), and a second flow rate adjustment valve (122) provided in the second condensed water line pipe (L21) for adjusting the flow rate of the condensed water.

[0013] The water cooling system (A2) may include a first control unit (18) that controls the first flow rate adjustment valve (121) and / or the second flow rate adjustment valve (122) to control the supply amount of the condensed water. The water cooling system (A1) a first level meter (22) that measures the liquid volume of the cooling water in the cooling water storage part (131) of the wet water cooler (13), a second level meter (21) that measures the liquid volume of the water in the storage part (161) of the water buffer (16), and may include them. The first control unit (18) may control the driving of the cooling water pump (14).

[0014] The water cooling system (A3) may include a second control unit (19) that controls the operating rate of the dry water cooler (15) (controls the blower) in accordance with the increase or decrease of the power cost. The second control unit (19) may control the second flow rate adjustment valve (122) based on the data of the first level meter (22) and the data of the second level meter (21). The second control unit (19) may control the driving of the cooling water pump (14).

[0015] The air separation device of the present disclosure may include the water cooling system (A1, A2, A3).

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0017] Some embodiments of the present disclosure will be described below. The embodiments described below illustrate an example of the present disclosure. The present disclosure is not limited to the following embodiments, and also includes various modified forms implemented within the scope of not changing the gist of the present disclosure. Note that not all of the configurations described below are essential configurations of the present disclosure. The upstream and downstream are based on the flow direction of the gas flow.

[0018] (Embodiment 1) The water cooling system A1 of Embodiment 1 will be described with reference to FIG. 1. The water cooling system A1 includes a compressed air cooler 12, a wet water cooler 13, a cooling water pump 14, and a dry water cooler 15.

[0019] The compressed air cooler 12 cools the compressed air compressed by the air compressor 11 that takes in the atmosphere. The compressed air cooler 12 is provided with a condensed water storage part 12a that stores condensed water at the bottom. The compressed air compressed by the air compressor 11 is dried by the cooling water to a state of water vapor saturation, and condensed water is generated. The cooling water is sent from the storage part 131 of the wet water cooler 13 by the cooling water pump 14. The compressed air cooler 12 produces compressed air saturated with water vapor by exchanging heat between the atmosphere compressed by the air compressor 11 and the cooling water. The water condensed by cooling condenses on the surface of the heat exchanger and drips, or the mist or droplet-shaped condensed water floating in the compressed air is separated by a mist separator or the like and stored in the compressed air cooler 12.

[0020] The wet water cooler 13 has a storage part 131 and introduces the condensed water generated in the compressed air cooler 12 as makeup water through the first condensed water line pipe L2. The wet water cooler 13 evaporates a part of the cooling water and cools the cooling water by the latent heat of evaporation. In this embodiment, water is evaporated by contacting the atmosphere (natural convection or forced convection), but it is not necessary to release the atmosphere, and it may be evaporated under reduced pressure conditions blocked from the atmosphere, or the cooling water may be indirectly cooled by a heat exchanger cooled by the evaporation of water.

[0021] A flow rate adjustment valve 121 is provided in the first condensed water line pipe L2, and condensed water can be sent from the compressed air cooler 12 to the wet water cooler 13 by controlling the opening and closing of the valve. For example, the flow rate adjustment valve 121 may be opened and closed by timer control, may be opened and closed based on the condensed water liquid level in the compressed air cooler 12, or may be controlled by flow rate control by a condensed water flow meter (not shown) arranged in the condensed water line pipe L2.

[0022] The cooling water pump 14 is arranged in the cooling water line pipe L3 and sends the cooling water led out from the storage part 131 of the wet water cooler 13 to the cold end of the compressed air cooler 12 to cool the compressed air.

[0023] The dry water cooler 15 cools the cooling water derived from the hot end of the compressed air cooler 12. It drives the motor of the blower to perform cooling. The dry water cooler 15 cools by indirectly exchanging heat between the cooling water and the air sent from the blower.

[0024] The atmosphere line pipe L1 is a pipe that sends the atmosphere to the air compressor 11 and sends the compressed air from the air compressor 11 to the compressed air cooler 12. The first condensate line pipe L2 is a pipe that sends condensate from the storage part 12a of the compressed air cooler 12 to the wet water cooler 13. The cooling water line pipe L3 sends the cooling water from the storage part 131 of the wet water cooler 13 to the cold end of the compressed air cooler 12. Also, the cooling water line pipe L3 is a pipe that sends the cooling water from the hot end of the compressed air cooler 12 to the dry water cooler 15 and sends the cooled cooling water to the wet water cooler 13.

[0025] According to Embodiment 1, although compressed air has a wide range of industrial uses, when the compressed air is cooled, water vapor derived from the atmosphere condenses to obtain condensate. If this condensate is supplied to the wet cooler 13, a part of the evaporation loss of the cooling water can be compensated for, or the load of the wet water cooler 13 can be increased so as to suppress the cooling load of the dry water cooler 15, and the power consumption required for the blower used in the dry water cooler 15 can be reduced. Since the compressed air cooler 12 can be operated at a pressure higher than that of the cooling water line pipe L3, by arranging the flow rate adjustment valve 121 in the first condensate line pipe L2, it is possible to control to minimize the energy loss due to pressure reduction when deriving condensate from the compressed air cooler 12.

[0026] (Alternative Embodiment) The wet water cooler 13 and the dry water cooler 15 were arranged in series, but they may be arranged in parallel. Fig. 4 shows the parallel arrangement. The cooling water line pipe L3 has a branch pipe L31 that branches off on the way from the hot end of the compressed air cooler 12 to the dry water cooler 15. The branch pipe L31 is a pipe that sends the water from the hot end of the compressed air cooler 12 to the wet water cooler 13. Also, the cooling water cooled by the dry water cooler 15 merges into the cooling water line pipe L3 upstream of the cooling water pump 14.

[0027] (Embodiment 2) The water cooling system A2 of Embodiment 2 will be described with reference to FIG. 2. The water cooling system A2 includes a compressed air cooler 12, a wet water cooler 13, a cooling water pump 14, a dry water cooler 15, a water buffer 16, and a first control unit 18. Description of the same components as in Embodiment 1 will be omitted.

[0028] Since the access to services such as the power or water resources of the cooling water system A2 is not necessarily constant, it is preferable to have a buffer in order to stably operate the system in any situation. The water buffer 16 can store the supply water (such as industrial water) from outside the system and the condensed water together. Since the condensed water may contain components in the atmosphere as impurities, it may be purified alone or together with the supply water by a purification device or the like. The purification device may be disposed between the water buffer 16 and the wet water cooler 13. Since the condensed water is derived from the atmosphere, the amount that can be recovered is not necessarily stable. Therefore, by providing the water buffer 16, stable management of the condensed water becomes possible.

[0029] The water buffer 16 has a storage section 161. Water can be supplied to the water buffer 16. Also, the first condensed water line pipe L2 is connected from the storage section 12a of the compressed air cooler 12 to the storage section 161, and the condensed water is sent. The second condensed water line pipe L21 is a pipe for sending condensed water (make-up water) from the storage section 161 of the water buffer 16 to the storage section 131 of the wet water cooler 13. The second flow rate adjustment valve 122 is provided in the second condensed water line pipe L21. The second flow rate adjustment valve 122 adjusts the flow rate of the condensed water (make-up water). The second flow rate adjustment valve 122 may be opened and closed by timer control, or may be opened and closed based on the condensed water liquid level in the storage section 161 of the water buffer 16 and / or the liquid level in the storage section 131 of the wet water cooler 13, or may be controlled by flow rate control by a condensed water flow meter disposed in the second condensed water line pipe L21.

[0030] The first level meter 22 measures the liquid volume of the cooling water in the storage section 131 of the wet water cooler 13. The second level meter 21 measures the liquid volume of the water in the storage section 161 of the water buffer 16. Based on the data of the first level meter 22 and the second level meter 21, the first control unit 18 controls the first flow rate adjustment valve 121 and the second flow rate adjustment valve 122 to control the supply amount of the condensed water (make-up water). The first control unit 18 may control the driving of the cooling water pump 14.

[0031] (Embodiment 3) The water cooling system A3 of Embodiment 3 will be described with reference to FIG. 3. The water cooling system A3 includes a compressed air cooler 12, a wet water cooler 13, a cooling water pump 14, a dry water cooler 15, a water buffer 16, a first control unit 18, and a second control unit 19. The description of the same components as in Embodiments 1 and 2 is omitted.

[0032] The second control unit 19 controls the operating rate of the dry water cooler 15 in accordance with the increase or decrease of the power cost. Specifically, it controls the blower. The data of the power cost is sent from an external device that stores the fluctuations of the power cost. When the power cost is high, the operating rate of the dry water cooler 15 is adjusted. Also, the first control unit 18 introduces the condensed water from the water buffer 16 into the wet cooling water tower 13 to adjust its operating rate.

[0033] Also, when the power supply capacity such as solar power generation or wind power generation can change depending on the environment, it is necessary to adjust the loads of the dry water cooler 15 and the wet water cooler 13 respectively. For example, during the day when solar power generation is possible, the dry water cooler 15 is mainly operated with inexpensive power, and as the electricity unit price increases at night, the load of the wet water cooler 13 is increased for control. At this time, during the day, the condensed water obtained from the compressed air cooler 12 is stored in the water buffer 16, and at night, the water stored in the water buffer 16 is used to meet the water demand of the wet water cooler 13 for control. That is, by using the condensed water under the condition with the highest value in comparison with the electricity price, the economy of the cooling water system can be improved.

[0034] The economic data such as electricity unit price is used to determine the operation method of the cooling water system A3, that is, the load sharing between the dry-type water cooler 15 (mainly consuming electricity) and the wet-type water cooler 13 (mainly consuming water). When it is determined that the electricity cost is low, the dry-type water cooler 15 is mainly operated, and the condensed water is stored in the water buffer 16. When it is determined that the electricity cost is high, the load of the dry-type water cooler 15 is reduced and the load of the wet-type water cooler 13 is increased. Since the burden on the wet-type water cooler 13 can be detected by the loss of water due to evaporation, specifically, the decrease in the water level of the storage part 131 of the wet-type water cooler 13, makeup water (condensed water or a mixture of condensed water and service water) is supplied from the water buffer 16 so that the water level stays within the control value. The amount of water (water level) in the water buffer 16 may be considered for the determination of the load adjustment of the dry-type water cooler 15. By doing so, even when the water level in the water buffer 16 drops, the system can be operated so that the cooling water temperature is stabilized by increasing the load of the dry-type water cooler 15.

[0035] (Example) The results of the physical simulation of Embodiment 3 are shown. Air at an inlet condition temperature of 35°C, relative humidity of 80%, and 1 barA, 100,000 Nm 3 / h is compressed and cooled by an air compressor having 4 compression stages to obtain compressed air at an outlet condition of 42°C, relative humidity of 100%, and 10 barA. At the inlet condition, the water contained in the air is 3786 kg / h, but at the outlet condition, it is saturated and only 684 kg / h exists as water vapor. Therefore, the difference of 3102 kg / h can be recovered as condensed water. Since the latent heat of vaporization of water is 575 cal / g at 40°C, when the cooling water temperature is 40°C, the condensed water of 3102 kg / h can cool the cooling water by 1783 Mcal / h of latent heat of vaporization. The power required for a dry-type water cooler can vary depending on the difference between the atmospheric temperature and the cooling water temperature. Generally, the smaller the temperature difference, the greater the required air volume. For example, when blowing air at 35°C to obtain cooling water at 40°C, 0.052 kW of power is consumed for cooling of 1 Mcal / h. If the above condensate is used for water cooling, 93 kW of power can be reduced, i.e., 1783 Mcal / h × 0.052 kWh / Mcal = 93 kW.

[0036] Examine the optimization when the water cooling of a heat load of 7400 Mcal / h (equivalent to the cooling requirement of the above air compressor) is carried out using a dry-type water cooler and a wet-type water cooler using condensate, considering different electricity costs during day and night. Assume the daytime is 12 hours with an electricity cost of 20 yen / kWh at that time, and the nighttime is 12 hours with an electricity cost of 60 yen / kWh at that time. When continuously using condensate in the wet cooler day and night, the load of the dry-type water cooler is reduced by 93 kW, and 292 kW (= 7400 Mcal / h × 0.052 kWh / Mcal - 93 kW) of power is used. In this case, the electricity cost per day is 20 yen / kWh × 292 kW × 12 h + 60 yen / kWh × 292 kW × 12 h = 280320 yen. On the other hand, when only the dry-type water cooler operates during the day to store the condensate and both the condensate supplied at night and the stored condensate are used, the load of the dry-type water cooler is 385 kW during the day, while 199 kW (= 385 kW - 186 kW) of power is used at night. In this case, the electricity cost per day is 20 yen / kWh × 385 kW × 12 h + 60 yen / kWh × 199 kW × 12 h = 235680 yen. That is, by concentrating the use of condensate at night when the electricity cost is high, it is expected that the electricity cost can be reduced by about 16% per day.

[0037] In this embodiment, it is intended to reduce the power consumption and water supply load associated with water cooling by using the condensed water obtained along with the compression cooling of air. However, the timing of using the condensed water is adjusted according to the power supply capacity that can be generated by using renewable energy. In particular, when power is likely to be insufficient, the condensed water is actively used to reduce the power consumption related to water cooling, thereby reducing the power cost (this implicitly includes the installation cost of generators and storage batteries capable of stable power generation).

[0038] (Alternative Embodiment) (1) The compressed air generated in Embodiments 1 to 4 may be provided to the air separation device. (2) Embodiments 1 to 4 are not limited to compressed air and may be applied to compressed LNG gas and compressed boil-off gas.

Description of Reference Numerals

[0039] 11 Air compressor 12 Compressed air cooler 13 Wet water cooler 15 Dry water cooler

Claims

1. A compressed gas cooler that cools the compressed gas compressed by a compressor that takes in the gas to be processed, A wet water cooler that introduces the condensed water generated in the compressed gas cooler as makeup water, A cooling water pump that sends the cooling water derived from the wet water cooler to the cold end of the compressed gas cooler to cool the compressed gas, A dry water cooler that cools the cooling water derived from the hot end of the compressed gas cooler, A first condensate line pipe that sends the condensed water derived from the compressed gas cooler, A first flow rate adjustment valve provided in the first condensate line pipe to adjust the flow rate of the condensed water, comprising: A water cooling system.

2. A cooling water line pipe that sends the cooling water derived from the wet water cooler to the cold end of the compressed gas cooler, sends the cooling water from the hot end of the compressed gas cooler to the dry water cooler, and sends the derived cooling water to the wet water cooler, The water cooling system according to claim 1.

3. Comprising a water buffer for storing the condensed water, The water cooling system according to claim 1.

4. A second condensate line pipe that sends the condensed water from the water buffer to the wet water cooler, A second flow rate adjustment valve provided in the second condensate line pipe to adjust the flow rate of the condensed water, comprising: The water cooling system according to claim 3.

5. Comprising a first control unit that controls the first flow rate adjustment valve and controls the supply amount of the condensed water, The water cooling system according to claim 1.

6. Comprising a first control unit that controls the second flow rate adjustment valve and controls the supply amount of the condensed water, The water cooling system according to claim 4.

7. A second control unit that controls the operating rate of the dry water cooler in accordance with increases and decreases in power costs. The water cooling system according to claim 1.

8. An air separation apparatus comprising the water cooling system according to claim 1.

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