Air cooling device, air cooling method and air separation system

Abstract

To lower a temperature of air to be supplied to an air compressor by using a simple facility configuration.SOLUTION: An air cooling device 10 includes: a first heat exchanger 11 that exchanges heat between a first refrigerant comprising any of liquid nitrogen, liquid oxygen and liquid air and a second refrigerant comprising water to cool the second refrigerant; a second heat exchanger 12 that exchanges heat between the cooled second refrigerant and air to cool the air; a cold refrigerant supply system 13 for causing the first refrigerant to flow in the first heat exchanger 11 and diffusing the first refrigerant that has undergone the heat exchange with the second refrigerant in the first heat exchanger 11 to the outside on the downstream side of the first heat exchanger 11; an intermediate refrigerant supply system 14 for causing the second refrigerant to flow in the first heat exchanger 11 and the second heat exchanger 12 in this order and discharging the second refrigerant that has undergone the heat exchange with the air in the second heat exchanger to a drainage tank on the downstream side of the second heat exchanger; and an air supply system 15 for supplying the air to the second heat exchanger 12.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an air cooling device, an air cooling method and an air separation system. [Background technology]

[0002] Air compressors that compress air are widely used in air separation units and gas turbine generators used in industrial plants. Air separation units use air compressors to liquefy air. Gas turbine generators also use air compressors to pressurize the air supplied to the combustor. It is known that the operating efficiency of air compressors decreases as the temperature of the air they take in increases. In particular, in the summer when the air temperature is high, the operating efficiency of an air compressor can decrease by approximately 2 to 10% compared to the winter when the air temperature is low. Therefore, various technologies have been proposed to reduce the temperature of the air supplied to the air compressor in order to prevent a decrease in the operating efficiency of the air compressor.

[0003] For example, Patent Document 1 discloses cooling air taken in from the outside using circulating water at a predetermined temperature and supplying the cooled air to an air compressor. Patent Document 2 discloses cooling combustion air using an intermediate refrigerant cooled by heat exchange with liquefied natural gas (hereinafter sometimes referred to as LNG) and supplying the cooled combustion air to a gas turbine. Patent Document 3 discloses cooling dehumidified air using mixed alcohols cooled by LNG. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-207267 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-155689 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-116198 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, Patent Document 1 discloses a technology for cooling taken-in air using circulating water cooled to about 12 to 13°C as a refrigerant, but there is a problem in that it is difficult to efficiently cool the air when a refrigerant of 10°C or higher is used. In particular, when a large amount of air is required, such as in an air separation unit or gas turbine generator installed in an industrial plant, or when the outside air temperature is high, such as in summer, there is a risk that the supply of cooled air will be insufficient.

[0006] Furthermore, Patent Document 2 discloses a technique for cooling air using the cold energy of liquefied natural gas, in which the cold energy of LNG is exchanged with an intermediate refrigerant and the cooled intermediate refrigerant is used to cool the air. The technique disclosed in Patent Document 2 does not directly exchange heat with air using cryogenic fluid such as LNG. Therefore, it is possible to prevent moisture contained in the air from adhering to the heat exchanger as frost, which would hinder the cooling of the air. However, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs) used as intermediate refrigerants are known as fluorocarbons. These fluorocarbons are potent greenhouse gases, and their release into the atmosphere harms the environment. Therefore, when these refrigerants are used as cold / hot refrigerants, they must be circulated and the piping system must be strictly maintained. As a result, the equipment becomes larger and the equipment costs become higher.

[0007] Furthermore, Patent Document 3 discloses that when mixed alcohol is used as a liquid refrigerant, air can be cooled to -100°C or below, and when alcohol water is used as a liquid refrigerant, air can be cooled to approximately -30°C. However, in equipment that uses mixed alcohol as a liquid refrigerant, particularly equipment where the destination of the cooled air is exposed to a high-temperature atmosphere, the location where heat exchange between the liquid refrigerant and the air takes place must be located away from the area where the high-temperature atmosphere occurs, taking into consideration the risk of fire. As a result, there are problems such as an increase in the size of the equipment and an increase in equipment costs.

[0008] In addition, in facilities that use alcoholic water as a liquid refrigerant, although the risk of fire is reduced, there is a risk of fire occurring if the alcoholic water leaks outside due to evaporation of the alcoholic components. Therefore, a circulation path is required to circulate the alcoholic water so that it does not leak outside. As a result, the equipment becomes larger and the equipment costs become higher.

[0009] The present invention has been made in view of the above-mentioned problems, and aims to provide an air cooling device and an air cooling method that can lower the temperature of air supplied to an air compressor with a simple equipment configuration. Another object of the present invention is to provide an air separation system that has excellent power consumption per unit of electricity by maintaining the temperature of air supplied to the air compressor at a stable low temperature. [Means for solving the problem]

[0010] An air cooling device according to one aspect includes: a first heat exchanger that exchanges heat between a first refrigerant made of any one of liquid nitrogen, liquid oxygen, and liquid air and a second refrigerant made of water, thereby cooling the second refrigerant; a second heat exchanger that exchanges heat between the cooled second refrigerant and air, thereby cooling the air; a first supply system that flows the first refrigerant through the first heat exchanger and dissipates the first refrigerant that has exchanged heat with the second refrigerant in the first heat exchanger to the outside downstream of the first heat exchanger; a second supply system that flows the second refrigerant through the first heat exchanger and then the second heat exchanger, and discharges the second refrigerant that has exchanged heat with the air in the second heat exchanger into a drainage tank downstream of the second heat exchanger; and a third supply system that supplies air to the second heat exchanger.

[0011] Furthermore, it is preferable that the first supply system is connected upstream of the first heat exchanger to a delivery pump that delivers the first refrigerant toward the first heat exchanger, and that the first supply system has a dissipation section downstream of the first heat exchanger that dissipates the first refrigerant that has been heat exchanged by the first heat exchanger to the outside.

[0012] Furthermore, it is preferable that the second supply system is connected upstream of the first heat exchanger to a water intake pump that takes in at least one of groundwater, seawater, and industrial water, and that the second supply system has a discharge section downstream of the second heat exchanger that discharges the second refrigerant that has been heat exchanged by the second heat exchanger into a drainage tank.

[0013] Furthermore, it is preferable that the third supply system be connected to a suction blower that draws in outside air upstream of the second heat exchanger, and be connected to an air compressor that compresses the air that has been heat exchanged by the second heat exchanger downstream of the second heat exchanger.

[0014] Also, an air cooling method according to one aspect is characterized by having a first heat exchange step in which heat is exchanged between a first refrigerant made of any one of liquid nitrogen, liquid oxygen, and liquid air and a second refrigerant made of water in a first heat exchanger to cool the second refrigerant, and a second heat exchange step in which heat is exchanged between the second refrigerant cooled in the first heat exchange step and air in a second heat exchanger different from the first heat exchanger to cool the air.

[0015] In addition, an air separation system according to one aspect includes an air cooling device that cools air, and an air separation unit that uses the air cooled by the air cooling device to rectify and separate oxygen and nitrogen, the air separation system including: a compressor that compresses the air cooled by the air cooling device and sends the compressed air to the air separation unit; and a delivery pump that sends a first refrigerant made of any of liquid nitrogen, liquid oxygen, and liquid air generated by the air separation unit to the air cooling device, wherein the air cooling device exchanges heat between the first refrigerant and a second refrigerant made of water, and a first heat exchanger that cools the cooled second refrigerant; The cooling system is characterized by comprising: a second heat exchanger that exchanges heat between a second refrigerant and air taken into the air cooling device to cool the air taken into the air cooling device; a first supply system that flows the first refrigerant through the first heat exchanger and dissipates the first refrigerant that has exchanged heat with the second refrigerant in the first heat exchanger to the outside downstream of the first heat exchanger; a second supply system that flows the second refrigerant through the first heat exchanger and then the second heat exchanger and discharges the second refrigerant that has exchanged heat with the air in the second heat exchanger to a drainage tank downstream of the second heat exchanger; and a third supply system that supplies the air taken into the air cooling device to the second heat exchanger. [Effects of the Invention]

[0016] According to the present disclosure, it is possible to provide an air cooling device and an air cooling method that can lower the temperature of air supplied to an air compressor with a simple equipment configuration. Also, by maintaining the temperature of the air supplied to the air compressor at a stable low temperature, it is possible to provide an air separation system that is excellent in terms of power consumption. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of an air separation system according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of an air cooling device. [Figure 3] FIG. 3 is a schematic diagram showing an example of the configuration of an air separation unit. DETAILED DESCRIPTION OF THE INVENTION

[0018] The air separation system according to this embodiment will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing an example of the configuration of an air separation system. As shown in Fig. 1, the air separation system SYS includes an air cooling device 10, an air separation device 30, and a refrigerant storage tank 60.

[0019] Hereinafter, the refrigerant delivered from the refrigerant storage tank 60 to the air cooling device 10 will be referred to as a cold / warm refrigerant. Also, the refrigerant delivered from the water storage tank 64 described below to the air cooling device 10 will be referred to as an intermediate refrigerant. Note that the cold / warm refrigerant refers to a refrigerant that is in a liquid state in an environment of 0°C or below and normal pressure. Of the above-mentioned refrigerants, the cold / warm refrigerant corresponds to the first refrigerant recited in the claims, and the intermediate refrigerant corresponds to the second refrigerant recited in the claims.

[0020] The air cooling device 10 is a device that cools outside air (hereinafter sometimes referred to as air) taken in by a suction blower 61, using an intermediate refrigerant cooled by a low-temperature refrigerant. Details of the air cooling device 10 will be described later. The low-temperature refrigerant is supplied to the air cooling device 10 from a refrigerant storage tank 60 by driving a delivery pump 62. The intermediate refrigerant is supplied to the air cooling device 10 from a water storage tank 64 by driving a water intake pump 63.

[0021] The air cooled in the air cooling device 10 is mixed with outside air in the process of being supplied to the air separation device 30. The air mixed with the outside air is supplied to the air separation device 30 after fine dust and the like are collected by a bag filter 65.

[0022] 1 illustrates an air separation system SYS in which air cooled in one air cooling device 10 is supplied to one air separation device 30, but the air separation system may also be an air separation system in which air cooled in two or more air cooling devices 10 is supplied to one air separation device 30. In this case, if the total amount of air cooled per unit time in the two or more air cooling devices 10 matches or exceeds the amount of air processed per unit time in the air separation device 30, it is not necessary to mix the air cooled by each of the two or more air cooling devices 10 with outside air.

[0023] Hereinafter, the air separation unit 30 is a unit that separates air supplied to the air separation unit 30 into oxygen, nitrogen, argon, etc. Details of the air separation unit 30 will be described later. Hereinafter, the air supplied to the air separation unit 30 may be referred to as feed air.

[0024] The refrigerant storage tank 60 separately stores the liquid nitrogen, liquid oxygen, and liquid air produced in the air separation unit 30 .

[0025] 2, the air cooling device 10 includes a first heat exchanger 11, a second heat exchanger 12, a cold / hot refrigerant supply system 13, an intermediate refrigerant supply system 14, an air supply system 15, and a control device 16. Here, the cold / hot refrigerant supply system 13 corresponds to the first supply system set forth in the claims, the intermediate refrigerant supply system 14 corresponds to the second supply system set forth in the claims, and the air supply system 15 corresponds to the third supply system set forth in the claims.

[0026] The first heat exchanger 11 exchanges heat between the cold / warm refrigerant and the intermediate refrigerant to cool the intermediate refrigerant. The second heat exchanger 12 exchanges heat between the cooled intermediate refrigerant and air to cool the air. Here, the first heat exchanger 11 and the second heat exchanger 12 can be a plate heat exchanger or a multi-tube heat exchanger (shell and tube heat exchanger). Note that, since the second heat exchanger 12 exchanges heat between air and a liquid intermediate refrigerant, it is preferable to use a fin-tube heat exchanger with a large contact area on the air side. Here, the cold / warm refrigerant corresponds to the first refrigerant in the claims, and the intermediate refrigerant corresponds to the second refrigerant in the claims.

[0027] The cold / warm refrigerant supply system 13 includes a pipe 21, for example, a vacuum insulated pipe. The pipe 21 is a discharge-type pipe in which an upstream end 21a of the pipe 21 is connected to a delivery pump 62. Here, a discharge-type pipe refers to a pipe whose downstream end 21b is open, for example. When the delivery pump 62 is driven, the cold / warm refrigerant flows from the upstream end 21a of the pipe 21 toward the first heat exchanger 11. By using the pipe 21 as a vacuum insulated pipe, the cold / warm refrigerant is supplied to the first heat exchanger 11 while being maintained at a constant temperature. The cold / warm refrigerant is heated by heat exchange with the intermediate refrigerant in the first heat exchanger 11, and then dissipated to the outside from the downstream end 21b of the pipe 21. In other words, the downstream end 21b of the pipe 21 functions as a dissipation section. Because liquid nitrogen, liquid oxygen, or liquid air is used as the cold / warm refrigerant, dissipating the cold / warm refrigerant to the outside at the downstream end 21b of the pipe 21 does not affect the external environment.

[0028] Here, the above-mentioned cold / warm refrigerant is diffused from the downstream end 21b of the pipe 21 in any one of a gaseous state, a liquid state, or a mist state in which these are mixed. For example, when the cold / warm refrigerant is diffused in a gaseous state, it is preferable to provide an evaporator at the downstream end 21b of the pipe 21. When the cold / warm refrigerant is diffused, it is preferable to set the height from the surface on which the worker walks to the downstream end 21b of the pipe 21 to, for example, about 3 to 5 m in order to avoid direct contact with the worker.

[0029] A control valve 22 and a flow meter F1 are provided upstream of the first heat exchanger 11 in the hot / cold refrigerant supply system 13. The control valve 22 can switch between an open state and a closed state, as well as adjust the opening degree. The switching control and opening degree adjustment control of the control valve 22 are performed by the control device 16. The flow meter F1 measures the flow rate of the hot / cold refrigerant flowing toward the first heat exchanger 11. A measurement signal from the flow meter F1 is output to the control device 16.

[0030] The intermediate refrigerant supply system 14 includes a pipe 23. The pipe 23 is a discharge pipe having an upstream end 23a connected to a water intake pump 63. When the water intake pump 63 is driven, the intermediate refrigerant flows from the upstream end 23a of the pipe 23 through the first heat exchanger 11 and the second heat exchanger 12 in this order. The intermediate refrigerant is cooled by heat exchange with the low-temperature refrigerant in the first heat exchanger 11, and then heated by heat exchange with air in the second heat exchanger 12. The heated intermediate refrigerant is discharged from the downstream end 23b of the pipe 23 into the drainage tank 24. That is, the downstream end 23b of the pipe 23 functions as a drain. Because water is used as the intermediate medium, discharging the low-temperature refrigerant from the downstream end 23b of the pipe 23 into the drainage tank 24 does not affect the external environment.

[0031] In the intermediate refrigerant supply system 14, for example, a control valve 25 and a flow meter F2 are provided between the water intake pump 63 and the first heat exchanger 11. The control valve 25 can switch between an open state and a closed state, as well as adjust the opening degree. The switching control and opening degree adjustment control of the control valve 25 are performed by the control device 16. The flow meter F2 measures the flow rate of the intermediate refrigerant flowing toward the first heat exchanger 11. A measurement signal from the flow meter F2 is output to the control device 16.

[0032] Furthermore, in the intermediate refrigerant supply system 14, a thermometer T1 is provided between the first heat exchanger 11 and the second heat exchanger 12. The thermometer T1 measures the temperature of the intermediate refrigerant cooled in the first heat exchanger 11. A measurement signal from the thermometer T1 is output to the control device 16.

[0033] The air supply system 15 has a pipe 26 whose upstream end 26a is connected to a suction blower 61 and whose downstream end 26b is connected to a bag filter 65. The air supply system 15 supplies air taken in by, for example, the suction blower 61 to the second heat exchanger 12. In the air supply system 15, a control valve 27 and a flow meter F3 are provided upstream of the second heat exchanger 12. Note that not only cases in which the pipe 26 is provided as the air supply system 15, but also cases in which the pipe 26 is not provided are envisioned. Therefore, in Figures 1 and 2, the pipe 26 provided in the air supply system 15 is shown by a dotted line instead of a solid line.

[0034] The control valve 27 can be switched between an open state and a closed state, and can also adjust the degree of opening. The control of the switching and adjustment of the degree of opening of the control valve 27 is performed by a control device 16, which will be described later. The flow meter F3 measures the flow rate of air flowing toward the second heat exchanger 12. A measurement signal from the flow meter F3 is output to the control device 16.

[0035] Furthermore, a thermometer T2 is provided in the air supply system 15 downstream of the second heat exchanger 12. The thermometer T2 measures the temperature of the air cooled in the second heat exchanger 12. A measurement signal from the thermometer T2 is output to the control device 16.

[0036] The control device 16 controls the switching of the control valves 22, 25, 27 and the opening degree of these valves based on measurement signals from the flow meters F1, F2, F3 and thermometers T1, T2 provided in the supply systems 13, 14, 15 described above.

[0037] The control device 16 adjusts the opening of the control valves 22, 25 so that the temperature of the intermediate refrigerant after heat exchange by the first heat exchanger 11 becomes a predetermined temperature (0°C or higher and 5°C or lower), and adjusts the flow rate of the cold / warm refrigerant flowing through the cold / warm refrigerant supply system 13 and the flow rate of the intermediate refrigerant flowing through the intermediate refrigerant supply system 14.

[0038] For example, when the temperature of the intermediate refrigerant measured by thermometer T1 is lower than the target temperature, controller 16 adjusts the aperture of control valve 25 to increase the flow rate of the intermediate refrigerant, or adjusts the aperture of control valve 22 to decrease the flow rate of the cold / warm refrigerant. Also, when the temperature of the intermediate refrigerant measured by thermometer T1 is higher than the target temperature, controller 16 adjusts the aperture of control valve 25 to decrease the flow rate of the intermediate refrigerant, or adjusts the aperture of control valve 22 to increase the flow rate of the cold / warm refrigerant.

[0039] Furthermore, the control device 16 adjusts the aperture of the control valve 27, for example, so as to reduce fluctuations in the temperature of the air after heat exchange by the second heat exchanger 12. For example, the temperature of the air taken in by the suction blower 61 varies depending on the season and weather conditions. Therefore, the control device 16 adjusts the aperture of the control valve 27 so that the temperature of the air after heat exchange by the second heat exchanger 12 falls within a predetermined temperature range. In addition, the apertures of the control valves 22 and 25 can also be adjusted in accordance with the adjustment of the aperture of the control valve 27.

[0040] Specifically, control device 16 adjusts the apertures of control valves 22, 25 so that the flow rate of the cold / hot refrigerant flowing through first heat exchanger 11 is, for example, 3 to 20 L / min, and the flow rate of the intermediate refrigerant is, for example, 100 to 300 L / min. When the temperature of the water supplied from water intake pump 63 is, for example, 10 to 34°C, the temperature of the intermediate refrigerant after heat exchange in first heat exchanger 11 is adjusted to a temperature higher than 0°C and lower than the temperature of the air being drawn in. In other words, the temperature of the intermediate refrigerant after heat exchange in first heat exchanger 11 is adjusted to a temperature higher than 0°C and equal to or lower than 5°C.

[0041] The control device 16 also controls the flow rate of the intermediate refrigerant flowing through the second heat exchanger 12 to be 100 to 300 L / min, and the flow rate of the air sucked by the suction blower 61 to be 6 to 30 kNm. 3 / h. When the temperature of the air sucked by the suction blower 61 is 30 to 38°C, the temperature of the air after heat exchange by the second heat exchanger 12 is adjusted to 9 to 13°C.

[0042] The temperature of the air that has passed through the second heat exchanger 12 can be further reduced by appropriately changing the flow rate of the cold / hot refrigerant or the intermediate refrigerant and the flow rate of the drawn air.

[0043] The cold / warm refrigerant and intermediate refrigerant used in the above-described air cooling device 10 will now be described. As the cold / warm refrigerant, any of liquid nitrogen, liquid oxygen, and liquid air, which are stored individually in a refrigerant storage tank 60, is used. Note that liquid nitrogen, liquid oxygen, and liquid air are not toxic even when released into the atmosphere, so the cold / warm refrigerant supply system 13 does not need to be a circulating system, and can be an open system as shown in Fig. 2. As a result, there is an advantage in that the routing of the piping 21 of the cold / warm refrigerant supply system 13 can be simplified.

[0044] Of the above-mentioned cryogenic refrigerants, liquid nitrogen has a boiling point of -196°C at normal pressure, so when used as a cryogenic refrigerant, it is preferable to use it in a state where it is kept at -196°C or lower. Furthermore, liquid oxygen has a boiling point of -183°C at normal pressure, so when used as a cryogenic refrigerant, it is preferable to use it in a state where it is kept at -183°C or lower. Liquid air has a boiling point of -190°C at normal pressure, so when used as a cryogenic refrigerant, it is preferable to use it in a state where it is kept at -190°C or lower.

[0045] Examples of the intermediate refrigerant include groundwater, seawater, industrial water, water taken from a river, and water purified at a water purification facility. Furthermore, circulating water circulated within a factory to cool equipment can also be used as the intermediate refrigerant. Preferably, the water used as the intermediate refrigerant is temporarily stored in a water tank 64 and then taken in by a water intake pump 63. This ensures a sufficient amount of intermediate refrigerant to be used in the air cooling device 10, and storing the water in the water tank 64 suppresses temperature changes in the water used as the intermediate refrigerant. Using water as the intermediate refrigerant prevents the intermediate refrigerant from leaking to the outside, eliminating the need for a circulating system for the intermediate refrigerant supply system, and allowing it to be an open system as shown in FIG. 2. This has the advantage of simplifying the layout of the piping 23 of the intermediate refrigerant supply system 14.

[0046] 3, the air separation unit 30 includes an air compressor 31, a water wash column 32, an MS adsorber (molecular sieve adsorber) 33, a heat exchanger 34, an expansion turbine 35, a rectification column 36, and a secondary rectification column 37. The heat exchanger 34, the expansion turbine 35, the rectification column 36, and the secondary rectification column 37 are housed inside a cold box 39.

[0047] The air compressor 31 compresses the raw air supplied to the air separation unit 30 via the bag filter 65 to, for example, about 0.5 MPa.

[0048] The water washing tower 32, for example, sprays cooling water from the top of the tower to wash and cool the raw air compressed by the air compressor 31. The water washing tower 32 cools the compressed raw air, for example, from about 80°C to about 10°C.

[0049] The MS adsorber 33 adsorbs and removes CO2, H2O, and the like contained in the feed air that has been washed and cooled by the water washing tower 32. By using the MS adsorber to adsorb and remove CO2, H2O, and the like, it becomes possible to prevent the piping that constitutes the air separation unit 30, particularly the piping housed inside the cold box 39, from freezing.

[0050] Heat exchanger 34 cools the feed air by exchanging heat between the feed air from which CO2, HO, etc. have been adsorbed and removed and the low-temperature nitrogen gas and oxygen gas separated by fractionator 36. Heat exchanger 34 cools the feed air by exchanging heat between the feed air and the low-temperature argon gas separated by side fractionator 37. Connected to heat exchanger 34 are an air supply passage 41 to which the feed air is supplied, a nitrogen recovery passage 42 from which nitrogen gas is recovered, an oxygen recovery passage 43 from which oxygen gas is recovered, and an argon recovery passage 45 from which argon gas is recovered.

[0051] For example, the temperature of the raw air supplied to the heat exchanger 34 through the air supply passage 41 is, for example, about 10°C (specifically, 10°C). When the raw air is heat exchanged with nitrogen gas, oxygen gas, and argon gas in the heat exchanger 34, the raw air is cooled to about -170°C.

[0052] The air supply passage 41 connected to the heat exchanger 34 branches off into a branch passage 44 connected to the low-pressure column 36b of the rectification column 36 downstream of the heat exchanger 34. The branch passage 44 is provided with an expansion turbine 35. The expansion turbine 35 adiabatically expands the feed air flowing from the air supply passage 41 to the branch passage 44, thereby generating low-temperature, low-pressure feed air. The low-temperature, low-pressure feed air is supplied to the low-pressure column 36b of the rectification column 36.

[0053] The rectification column 36 has a high-pressure rectification column (high-pressure column) 36a for separating nitrogen gas and oxygen-enriched liquefied air, and a low-pressure rectification column (low-pressure column) 36b for separating the oxygen-enriched liquid air obtained from the high-pressure column 36a into nitrogen and oxygen. A condenser 46 is provided inside the low-pressure column 36b.

[0054] In the high-pressure column 36a, oxygen, a high-boiling component in the supplied feed air, is liquefied and accumulates at the bottom as oxygen-enriched liquid air, while nitrogen, a low-boiling component, accumulates at the top of the high-pressure column as a high-purity gas. The oxygen-enriched liquid air that accumulates at the bottom of the high-pressure column 36a is introduced into the center of the low-pressure column 36b. The high-purity nitrogen gas is once cooled in a condenser 46 located at the bottom of the low-pressure column 36b, and then refluxed to the high-pressure column 36a as reflux liquid (liquid nitrogen). In addition, the high-purity nitrogen gas is supplied to the top of the low-pressure column 36b and to a liquid nitrogen storage tank 60a provided in the refrigerant storage tank 60.

[0055] In the low-pressure column 36b, oxygen, a high-boiling-point component in liquid air, is liquefied by cryogenic liquefaction separation, and liquid oxygen accumulates at the bottom, while nitrogen gas accumulates at the top. For example, the liquid oxygen accumulated at the bottom of the low-pressure column 36b is converted into oxygen gas by heat exchange with nitrogen gas in the condenser 46, and the converted oxygen gas flows into the oxygen recovery line 43 and is also supplied to the liquid oxygen storage tank 60b provided in the refrigerant storage tank 60. The oxygen gas flowing through the oxygen recovery line 43 is heated in the heat exchanger 34 and then compressed by the oxygen compressor 47. The compressed oxygen gas is then supplied to other facilities in the plant. Specifically, the compressed oxygen gas is supplied to an ironmaking plant, a steelmaking plant, or the like, and used as oxygen to promote reactions in blast furnaces and converters.

[0056] The nitrogen gas accumulated at the top of the low-pressure column 36b flows into the nitrogen recovery line 42. The nitrogen gas flowing through the nitrogen recovery line 42 is heat exchanged in the heat exchanger 34 and then compressed by the nitrogen compressor 48. The compressed nitrogen gas is then supplied to other facilities in the plant. Specifically, the compressed nitrogen gas is supplied to, for example, an ironmaking plant, a steelmaking plant, or a cold rolling plant, and is used as an inert gas.

[0057] The side rectification column 37 is supplied with gas extracted from the central portion of the low-pressure column 36b of the rectification column 36. This gas contains oxygen gas in addition to argon gas. Therefore, in the side rectification column 37, the gas extracted from the central portion of the low-pressure column 36b is cryogenically distilled. As a result of the cryogenic distillation, argon gas accumulates at the top and liquid oxygen accumulates at the bottom. The argon gas that accumulates at the top of the side rectification column 37 flows to the argon recovery line 45 described above. The argon gas flowing through the argon recovery line 45 is heat exchanged in the heat exchanger 34 and then compressed by the argon compressor 49. The compressed argon is then filled into a cylinder or the like. The argon filled into a cylinder or the like is traded, for example, in the market.

[0058] The refrigerant storage tank 60 has a liquid nitrogen storage tank 60a, a liquid oxygen storage tank 60b, and a liquid air storage tank 60c. The liquid nitrogen storage tank 60a stores liquid nitrogen that has been cooled by heat exchange with liquid oxygen in the condenser 46. The liquid oxygen storage tank 60b stores liquid oxygen that accumulates at the bottom of the low-pressure column 36b of the rectification column 36. During start-up of the air separation unit 30, liquid air may be discharged from the rectification column 36. Therefore, the liquid air storage tank 60c is provided in the refrigerant storage tank 60 to store the liquid air discharged from the rectification column 36.

[0059] The air separation unit 30 described above is a unit that operates to produce nitrogen gas, oxygen gas, and argon gas from air, which is used as a raw material. Therefore, when the air separation unit 30 is operating, liquid nitrogen is stored in the liquid nitrogen storage tank 60a, and liquid oxygen is stored in the liquid oxygen storage tank 60b. In some cases, the stored liquid nitrogen or liquid oxygen may become surplus. In this embodiment, either liquid oxygen or liquid nitrogen, which has conventionally been discarded (dissipated into the atmosphere), can be effectively utilized as the cold / warm refrigerant in the air cooling unit 10. Furthermore, not only liquid oxygen or liquid nitrogen but also liquid air can be effectively utilized as the cold / warm refrigerant.

[0060] In this embodiment, the feed air is cooled using an intermediate refrigerant that is cooled using a low-temperature refrigerant, and then supplied to the air compressor 31. For example, supplying cooled feed air to the air compressor 31 has the advantage of reducing the power consumption of the air compressor 31 compared to supplying feed air to the air compressor 31 without cooling it. The temperature of the air taken in by the suction blower 61 varies depending on weather conditions. In this embodiment, the feed air is cooled to within a predetermined temperature range by the air cooling device 10, and then supplied to the air compressor 31. The air compressor 31 compresses the feed air to a predetermined pressure value. Therefore, the power consumption of the air compressor 31 can be stabilized.

[0061] Hereinafter, the air separation unit 30 described above will be described. 3 / h, 48kNm 3 The air separation unit 30 had an air compressor 31 capable of producing 230 kNm of compressed air. 3 The equipment was designed to generate water at a flow rate of 1000kJ / h and have a rated power of 21,000kWh.

[0062] The air compressor 31 supplies raw air at a temperature of 30°C at a flow rate of 200 kNm 3 / h to the air separation unit 30, and the air separation unit 30 supplies oxygen gas at a flow rate of 42 kNm 3The air separation system SYS was operated under conditions whereby the liquid oxygen produced in the air separation unit 30 was produced at a rate of 1000 kJ / h. At this time, the liquid oxygen produced in the air separation unit 30 was stored in the liquid oxygen storage tank 60b, and the stored liquid oxygen was supplied to the air cooling unit 10 as a cold / hot refrigerant.

[0063] In the air cooling device 10, liquid oxygen stored in the liquid oxygen storage tank 60b is supplied to the first heat exchanger 11 via the cold / warm refrigerant supply system 13 using the delivery pump 62. In detail, liquid oxygen at −190° C. is used as the cold / warm refrigerant, and the liquid oxygen is supplied to the first heat exchanger 11 at a flow rate of 15 L / h.

[0064] In the air cooling device 10, groundwater is used as an intermediate refrigerant and is supplied to the first heat exchanger 11 via the intermediate refrigerant supply system 14 using the water intake pump 63. The temperature of the groundwater is, for example, 16 to 18°C ​​throughout the year. At this time, the flow rate of the intermediate refrigerant is set to 140 to 160 L / min so that the temperature of the intermediate refrigerant becomes 3 to 5°C through heat exchange in the first heat exchanger 11.

[0065] At this time, in the air cooling device 10, the air drawn in by the suction blower 61 is blown at a flow rate of 30 kNm 3 When the air was supplied to the second heat exchanger 12 via the air supply system 15 at 1 / h, the air temperature could be lowered from 34°C to 11°C by heat exchange in the second heat exchanger 12.

[0066] As shown in Figure 1, the cooled air was mixed with outside air during the process of supplying the cooled air from the air cooling device 10 to the air separation device 30. At this time, the air at 34°C was mixed with 170 kNm 3 In this case, the air compressor 31 of the air separation unit 30 was fed with a mixture of air having a temperature of 30°C and a flow rate of 200 kNm 3 / h of mixed air was supplied as raw air. That is, while the temperature of the outside air was 34°C, the air cooled to 30°C by the air cooling device 10 was supplied from the air cooling device 10 to the air compressor 31 of the air separation unit 30. That is, in the air separation system SYS in this embodiment, the temperature was 34°C, the flow rate was 200 kNm 3It was found that the power consumption of the air compressor 31 was reduced by 1% compared to when air was supplied at 1000 kJ / h.

[0067] In this embodiment, the configuration of the air supply system 15 is exemplified, which has a pipe 26 whose upstream end 26a is connected to a suction blower 61 and whose downstream end 26b is connected to a bag filter 65. However, the air supply system 15 is not limited to the one in which the suction blower 61, the second heat exchanger 12, and the bag filter 65 are connected by the pipe 26. For example, the air supply system 15 may have the suction blower 61, the second heat exchanger 12, and the bag filter 65 arranged in series, so that a unidirectional air flow is formed by the suction blower 61, and the second heat exchanger 12 and the bag filter 65 are arranged in the flow path of the formed air flow.

[0068] That is, the air supply system 15 can be configured not only by a closed flow path using piping or ducts, but also by an open flow path that forms an air flow so that the air sucked in by the suction blower 61 can pass through the second heat exchanger 12 and the bag filter 65. In this case, it is preferable to arrange the suction blower 61, the second heat exchanger 12, and the bag filter 65 in close proximity. When the air supply system 15 is configured by an air flow path, that is, when the piping 26 is not used, the air sucked in by the suction blower 61 is mixed with the air inside the air cooling device 10 and sent to the bag filter 65 in a cooled state. In this case, there is no need to provide not only the piping 26 but also the control valve 27 and the flow meter F3, which further simplifies the configuration of the air cooling device 10.

[0069] <Summary of effects> The system is characterized by comprising: a first heat exchanger 11 that exchanges heat between a cold / warm refrigerant made of one of liquid nitrogen, liquid oxygen, and liquid air and an intermediate refrigerant made of water, thereby cooling the intermediate refrigerant; a second heat exchanger 12 that exchanges heat between the cooled intermediate refrigerant and air, thereby cooling the air; a cold / warm refrigerant supply system 13 that flows the cold / warm refrigerant through the first heat exchanger 11 and dissipates the cold / warm refrigerant that has exchanged heat with the intermediate refrigerant in the first heat exchanger 11 to the outside downstream of the first heat exchanger 11; an intermediate refrigerant supply system 14 that flows the intermediate refrigerant through the first heat exchanger 11 and then the second heat exchanger 12, and discharges the intermediate refrigerant that has exchanged heat with the air in the second heat exchanger 12 into a drainage tank downstream of the second heat exchanger 12; and an air supply system 15 that supplies air to the second heat exchanger 12.

[0070] Conventionally, liquefied natural gas (LNG) is used as the cold / hot refrigerant, and specific chlorofluorocarbons such as hydrochlorofluorocarbons (HCFCs), alternative chlorofluorocarbons such as hydrofluorocarbons (HFCs), mixed alcohol, or alcohol water are generally used as the intermediate refrigerant that receives the cold energy from the cold / hot refrigerant. However, in this embodiment, one of liquid nitrogen, liquid oxygen, and liquid air is used as the cold / hot refrigerant, and water is used as the intermediate refrigerant. As a result, no harmful substances are used as the substances used to cool the air, so there is no risk of fire, destruction of the ozone layer, or contribution to the generation of greenhouse gases.

[0071] The cold / warm refrigerant supply system 13 is preferably connected upstream of the first heat exchanger 11 to a delivery pump 62 that delivers the cold / warm refrigerant toward the first heat exchanger 11, and the cold / warm refrigerant supply system 13 preferably has a downstream end 21b that functions as a dissipation section that dissipates the cold / warm refrigerant that has been heat exchanged by the first heat exchanger 11.

[0072] This allows an open type supply system to be used as the hot / cold refrigerant supply system 13, which simplifies the layout of the piping of the supply system.

[0073] In addition, it is preferable that the intermediate refrigerant supply system 14 is connected upstream of the first heat exchanger 11 to a water intake pump 63 that takes in at least one of groundwater, seawater, and industrial water, and that the intermediate refrigerant supply system 14 has a downstream end 23b that functions as a discharge section that discharges the intermediate refrigerant that has been heat exchanged by the second heat exchanger 12.

[0074] This allows an open type supply system to be used as the intermediate refrigerant supply system 14, which simplifies the layout of the piping of the supply system.

[0075] In addition, it is preferable that the air supply system 15 is connected to a suction blower 61 that draws in outside air upstream of the second heat exchanger 12, and is connected to an air compressor 31 that compresses the air that has been heat exchanged by the heat exchanger 12 downstream of the second heat exchanger 12.

[0076] This allows air maintained at a low temperature to be stably supplied to the air compressor 31, thereby reducing the amount of power consumed when the air compressor 31 is operating.

[0077] The air separation system SYS of this embodiment is an air separation system SYS having an air cooling device 10 that cools air, and an air separation unit 30 that uses the air cooled by the air cooling device 10 to rectify and separate oxygen and nitrogen, and has an air compressor 31 that compresses the air cooled by the air cooling device 10 and sends the compressed air to the air separation unit 30, and a delivery pump 62 that sends out a cold / warm refrigerant made of any of liquid nitrogen, liquid oxygen, and liquid air generated by the air separation unit 30 to the air cooling device 10, and the air cooling device 10 exchanges heat between the cold / warm refrigerant and an intermediate refrigerant made of water, and the intermediate refrigerant a second heat exchanger 12 that exchanges heat between the cooled intermediate refrigerant and air to cool the air; a cold / warm refrigerant supply system 13 that flows the cold / warm refrigerant through the first heat exchanger 11 and dissipates the cold / warm refrigerant that has exchanged heat with the intermediate refrigerant in the first heat exchanger 11 to the outside downstream of the first heat exchanger 11; an intermediate refrigerant supply system 14 that flows the intermediate refrigerant through the first heat exchanger 11 and then the second heat exchanger 12 and discharges the intermediate refrigerant that has exchanged heat with the air in the second heat exchanger 12 to a drainage tank downstream of the second heat exchanger 12; and an air supply system 15 that supplies air to the second heat exchanger 12.

[0078] This makes it possible to maintain the temperature of the air supplied to the air compressor 31 at a stable low temperature, thereby providing an air separation system with excellent power consumption rate. [Explanation of symbols]

[0079] 10 Air Cooler 11 1st heat exchanger 12 Second heat exchanger 13. Hot and cold refrigerant supply system 14 Intermediate refrigerant supply system 15 Air supply system 30 Air Separation Unit 31 Air compressor 60 Refrigerant storage tank 61 Suction blower 62 Delivery pump 63 Water intake pump SYS Air Separation System

Claims

1. a first heat exchanger that exchanges heat between a first refrigerant made of any one of liquid nitrogen, liquid oxygen, and liquid air and a second refrigerant made of water, thereby cooling the second refrigerant; a second heat exchanger that exchanges heat between the cooled second refrigerant and air to cool the air; a first supply system that causes the first refrigerant to flow through the first heat exchanger and dissipates the first refrigerant that has exchanged heat with the second refrigerant in the first heat exchanger to the outside downstream of the first heat exchanger; a second supply system that causes the second refrigerant to flow through the first heat exchanger and then the second heat exchanger, and that discharges the second refrigerant that has exchanged heat with the air in the second heat exchanger into a drainage tank downstream of the second heat exchanger; a third supply system that supplies the air to the second heat exchanger; An air cooling device comprising:

2. the first supply system is connected to a delivery pump that delivers the first refrigerant toward the first heat exchanger, on the upstream side of the first heat exchanger; 2. The air cooling device according to claim 1, wherein the first supply system has a dissipation section downstream of the first heat exchanger that dissipates the first refrigerant that has undergone heat exchange by the first heat exchanger to the outside.

3. the second supply system is connected to a water intake pump that takes in at least one of groundwater, seawater, and industrial water, on the upstream side of the first heat exchanger; 2. The air cooling device according to claim 1, wherein the second supply system has a discharge part downstream of the second heat exchanger that discharges the second refrigerant that has been heat exchanged by the second heat exchanger into a drainage tank.

4. 2. The air cooling device according to claim 1, wherein the third supply system is connected to a suction blower that draws in outside air on the upstream side of the second heat exchanger, and is connected to an air compressor that compresses the air that has been heat exchanged by the second heat exchanger on the downstream side of the second heat exchanger.

5. 1. A method of cooling air, comprising: a first heat exchange step of exchanging heat between a first refrigerant made of any one of liquid nitrogen, liquid oxygen, and liquid air and a second refrigerant made of water in a first heat exchanger, thereby cooling the second refrigerant; a second heat exchange step of performing heat exchange between the second refrigerant cooled in the first heat exchange step and the air in a second heat exchanger different from the first heat exchanger, thereby cooling the air; 1. An air cooling method comprising:

6. An air separation system including an air cooling device that cools air, and an air separation device that uses the air cooled by the air cooling device to rectify and separate oxygen and nitrogen, a compressor that compresses the air cooled by the air cooling device and sends the compressed air to the air separation unit; a delivery pump that delivers a first refrigerant, which is any one of liquid nitrogen, liquid oxygen, and liquid air produced by the air separation unit, to the air cooling unit; Equipped with The air cooling device is a first heat exchanger that exchanges heat between the first refrigerant and a second refrigerant made of water and cools the second refrigerant; a second heat exchanger that exchanges heat between the cooled second refrigerant and the air taken into the air cooling device, thereby cooling the air taken into the air cooling device; a first supply system that causes the first refrigerant to flow through the first heat exchanger and dissipates the first refrigerant that has exchanged heat with the second refrigerant in the first heat exchanger to the outside downstream of the first heat exchanger; a second supply system that causes the second refrigerant to flow through the first heat exchanger and then the second heat exchanger, and that discharges the second refrigerant that has exchanged heat with the air in the second heat exchanger into a drainage tank downstream of the second heat exchanger; a third supply system that supplies the air taken in by the air cooling device to the second heat exchanger; 1. An air separation system comprising:

Images