Refrigerant cooling device and refrigerant cooling method

Abstract

This invention provides a refrigerant cooling device and refrigerant cooling method that can reduce the consumption of liquefied gas by effectively utilizing the conventional exhaust gas pressure and low temperature for cooling. [Solution] A refrigerant cooling device 10 comprising a circulation path L1 for circulating a refrigerant to cool an object T1 to be cooled, a heat exchanger 2 provided in the circulation path L1, a low-temperature liquefied gas introduction path L2 for introducing low-temperature liquefied gas into the heat exchanger 2, an expansion turbine 6 for adiabatically expanding the low-temperature liquefied gas vaporized in the heat exchanger 2, and an expanded low-temperature gas introduction path L4 for introducing the expanded low-temperature gas adiabatically expanded in the expansion turbine 6 into the heat exchanger 2, wherein the heat exchanger 2 cools the refrigerant by indirect heat exchange with the low-temperature liquefied gas and the expanded low-temperature gas.

Description

Technical Field

[0001] The present invention relates to a refrigerant cooling device and a refrigerant cooling method, and more particularly to a refrigerant cooling device and a refrigerant cooling method for controlling the temperature of a cooling object such as a low-temperature reaction tank used in a chemical reaction process or the like.

Background Art

[0002] A refrigerant cooling device that uses the cold heat of liquefied gas to cool a liquid refrigerant and circulates the refrigerant to maintain a load part (a cooling object such as a reaction tank) at a low temperature is already known (see, for example, Patent Document 1). Such a method is particularly used when it is necessary to precisely control the temperature of the cooling object. That is, the refrigerant is cooled to a temperature as close as possible to the controlled temperature by the liquefied gas that is the cold heat source, and the cooling object is indirectly cooled by the refrigerant.

[0003] FIG. 3 is a system diagram of a conventional refrigerant cooling device of such a method. Generally, liquefied nitrogen (-196°C at atmospheric pressure) is used as the liquefied gas that is the cold heat source. Further, a liquid that does not solidify or vaporize within the temperature range to be used is used as the refrigerant, and for example, fluorinated ether (atmospheric boiling point +76°C, freezing point -138°C) etc. are typical.

[0004] In the refrigerant cooling device 1, the liquefied nitrogen and the refrigerant exchange heat in the heat exchanger 2, and the refrigerant is cooled to a predetermined temperature. The temperature of the refrigerant is adjusted by controlling the opening degree of the flow control valve 4 that adjusts the flow rate of the liquefied nitrogen with the temperature indicating regulator (TIC) 3 provided in the circulation path L1. In the heat exchanger 2, the liquefied nitrogen is heated by the refrigerant and vaporizes, and becomes nitrogen gas and is discharged to the atmosphere. Note that the nitrogen flowing through the heat exchanger 2 is generally designed to be less than 1 MPa so as not to be subject to the High Pressure Gas Safety Act.

[0005] The refrigerant, cooled to a predetermined temperature, cools the object to be cooled T1 (e.g., a low-temperature reaction vessel), maintaining the object T1 at a predetermined low temperature. The temperature of the refrigerant supplied from the heat exchanger 2 to the object to be cooled T1 is adjusted to be as close as possible to the temperature of the object to be cooled T1, for example, 20°C lower than the object to be cooled, so that the temperature can be precisely controlled. After cooling the object T1, the refrigerant's temperature rises slightly, for example, to 10°C lower than the object to be cooled, and it is pressurized by the circulation pump 5 and sent to the heat exchanger 2.

[0006] Furthermore, Figure 4 shows a conventional system diagram for cases where there are multiple objects to be cooled at different temperatures. In order to simplify the configuration and operation of the equipment, it is common to use only one type of cryogenic liquefied gas as the cooling source. In this case, objects to be cooled at different temperatures must be cooled with a cryogenic liquefied gas at a lower temperature than the object with the lowest temperature. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 4068108 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in the case of a refrigerant cooling system as shown in Figure 3, the nitrogen gas vaporized by cooling the refrigerant is released into the atmosphere at a lower temperature than the refrigerant introduced into the heat exchanger, and the exhaust gas pressure and low temperature are not effectively utilized before being released into the atmosphere.

[0009] Therefore, the present invention aims to provide a refrigerant cooling device and a refrigerant cooling method that can reduce the consumption of liquefied gas by effectively utilizing the conventional exhaust gas pressure and low temperature for cooling. [Means for solving the problem]

[0010] To achieve the above objective, the refrigerant cooling device of the present invention comprises a circulation path for circulating a refrigerant for cooling an object to be cooled, a heat exchanger provided in the circulation path, a low-temperature liquefied gas introduction path for introducing low-temperature liquefied gas into the heat exchanger, an expansion turbine for adiabatically expanding the low-temperature liquefied gas vaporized in the heat exchanger, and an expanded low-temperature gas introduction path for introducing the expanded low-temperature gas adiabatically expanded by the expansion turbine into the heat exchanger, wherein the heat exchanger cools the refrigerant by indirect heat exchange with the low-temperature liquefied gas and the expanded low-temperature gas.

[0011] Furthermore, it is preferable to introduce the expanded low-temperature gas discharged from the heat exchanger as a cooling source into a heat exchanger provided in a circulation path for circulating a refrigerant to cool other objects. The system is further characterized by being equipped with a generator that is driven by the expansion turbine and generates electricity.

[0012] Furthermore, in order to achieve the above objective, the refrigerant cooling method of the present invention is a refrigerant cooling method for cooling an object to be cooled by indirect heat exchange with a low-temperature liquefied gas, characterized in that the gas vaporized from the low-temperature liquefied gas by the indirect heat exchange is adiabatically expanded to become an expanded low-temperature gas, and in the indirect heat exchange, the expanded low-temperature gas is also used as a cooling source.

[0013] Furthermore, it is preferable to use the expanded low-temperature gas used in the indirect heat exchange as a cooling source for cooling a refrigerant used to cool other objects by indirect heat exchange. Additionally, the system is characterized by converting the work generated during adiabatic expansion into electricity. [Effects of the Invention]

[0014] According to the refrigerant cooling apparatus and method of the present invention, the consumption of cryogenic liquefied gas can be reduced by adiabatically expanding the cryogenic liquefied gas cooled by the refrigerant and further utilizing it as a cooling source. Furthermore, when there are multiple objects to be cooled, the total consumption of cryogenic liquefied gas can be reduced by further utilizing the cryogenic liquefied gas effectively. In addition, electricity can be recovered by converting the work generated by the expansion turbine into electricity using a generator. [Brief explanation of the drawing]

[0015] [Figure 1] This is a diagram illustrating a first embodiment of the refrigerant cooling device of the present invention. [Figure 2] This is a diagram illustrating a second embodiment of the refrigerant cooling device of the present invention. [Figure 3] This is a diagram of a conventional refrigerant cooling system. [Figure 4] This is a diagram of a conventional refrigerant cooling system. [Modes for carrying out the invention]

[0016] Figure 1 is a schematic diagram showing a first embodiment of the refrigerant cooling device of the present invention. Components similar to those in the conventional refrigerant cooling device shown in Figure 3 above are denoted by the same reference numerals. This refrigerant cooling device 10 is for cooling (temperature control) an object T1 to be cooled using a refrigerant, and includes a circulation pump 5 for supplying the refrigerant, a heat exchanger 2 which is a cooling means for cooling the refrigerant discharged from the circulation pump 5, and piping connecting these.

[0017] Each pipe forms a closed-cycle circulation path L1 through which the refrigerant is circulated back to the circulation pump 5 via the circulation pump 5, heat exchanger 2, and object to be cooled T1.

[0018] The heat exchanger 2 cools the circulating refrigerant to a predetermined temperature by indirect heat exchange between the low-temperature liquefied gas (liquid nitrogen in this embodiment), which is introduced into the heat exchanger 2 from the low-temperature liquefied gas introduction path L2 and led out to the expansion turbine introduction path L3, and the expansion low-temperature gas described later.

[0019] The cryogenic liquefied gas (liquid nitrogen) introduced into the heat exchanger 2 from the cryogenic liquefied gas introduction path L2 is heated up and vaporized by heat exchange with the refrigerant. Since the vaporized gas (nitrogen gas) is still in a low-temperature state and has a predetermined pressure, it is introduced into the expansion turbine 6 through the expansion turbine introduction path L3 and expanded. Thereby, a gas at a lower temperature (expansion cryogenic gas) can be obtained. The expansion cryogenic gas is introduced into the heat exchanger 2 through the expansion cryogenic gas introduction path L4, heated up by heat exchange with the refrigerant, led out to the exhaust gas path L5, and discharged into the atmosphere as exhaust gas.

[0020] The object to be cooled T1 is, for example, a reaction tank or the like including a reaction vessel provided with a jacket through which the refrigerant circulates on the outer periphery. The temperature of the refrigerant supplied to the object to be cooled T1 is adjusted by setting a predetermined cooling temperature in the temperature indicating controller (TIC) 3 provided in the circulation path L1 between the heat exchanger 2 and the object to be cooled T1, and the temperature indicating controller (TIC) 3 operates according to the temperature of the refrigerant to control the opening degree of the flow rate control valve 4 provided in the cryogenic liquefied gas introduction path L2.

[0021] Furthermore, it is provided with a generator G that is driven by the expansion turbine 6 to generate electricity. The gas vaporized through the heat exchanger 2 is introduced into the suction side of the expansion turbine 6, adiabatically expanded in the expansion turbine 6 to give driving energy to the expansion turbine 6, and flows out as a colder expansion cryogenic gas. Thereby, the expansion turbine 6 drives the generator G to generate electricity.

[0022] Therefore, by effectively using the expansion cryogenic gas for cooling the refrigerant, the consumption amount of the cryogenic liquefied gas can be reduced. In addition, since the work amount generated by the expansion turbine can be converted into electric power by the generator, the recovery of the consumed electric power is also possible.

Example

[0023] Example 1 assumes that the refrigerant cooling system 10 shown in Figure 1 is used, and liquid nitrogen with a saturation temperature of 0.7 MPa is used as the low-temperature liquefied gas to cool the refrigerant to -90°C, with a heat exchange capacity of 50 kW in the heat exchanger 2 and an exhaust gas temperature of -100°C after heat exchange. The nitrogen gas vaporized in the heat exchanger 2 is sent to an expansion turbine 6 with an efficiency of 80% for adiabatic expansion.

[0024] Furthermore, using the conventional refrigerant cooling device 1 shown in Figure 2, and similar to Example 1, liquid nitrogen with a saturation temperature of 0.7 MPa is used as the low-temperature liquefied gas that serves as the cooling source. To cool the refrigerant to -90°C, the heat exchange capacity of the heat exchanger 2 is assumed to be 50 kW, and the exhaust gas after heat exchange is assumed to be -100°C. This is designated as Comparative Example 1.

[0025] Table 1 shows the fluid consumption, temperature, and pressure in the piping for Example 1 and Comparative Example 1.

[0026] [Table 1]

[0027] As shown in Table 1, in the conventional Comparative Example 1, the consumption of liquid nitrogen was 714 kg / h, whereas in Example 1, the nitrogen gas vaporized in the heat exchanger 2 is adiabatically expanded in the expansion turbine 6, and the low-temperature expanded gas is used to cool the refrigerant, resulting in a consumption of 624 kg / h of liquid nitrogen. Therefore, Example 1 was able to reduce the consumption of liquid nitrogen by 87% compared to Comparative Example 1.

[0028] Figure 2 is a schematic diagram showing a second embodiment of the refrigerant cooling device of the present invention. Note that the refrigerant cooling device 20 in Figure 2 differs from the refrigerant cooling device 10 in Figure 1 in that it is a device that has multiple objects to be cooled at different temperatures.

[0029] The first object to be cooled T11 is cooled (maintained at a lower temperature) than the second object to be cooled T21. The first object to be cooled T11 has a circulation pump 15 that delivers refrigerant, a first heat exchanger 12 which is a cooling means for cooling the refrigerant discharged from the circulation pump 15, and piping connecting these. The piping forms a first circulation path L11 of a closed-cycle system that circulates the refrigerant back to the circulation pump 15 via the circulation pump 15, the first heat exchanger 12, and the first object to be cooled T11.

[0030] The second object to be cooled T21 includes a circulation pump 25 that delivers refrigerant, a second heat exchanger 22 which is a cooling means for cooling the refrigerant discharged from the circulation pump 25, and piping connecting these. The piping forms a closed-cycle second circulation path L21 that circulates the refrigerant back to the circulation pump 25 via the circulation pump 25, the second heat exchanger 22, and the second object to be cooled T21.

[0031] The refrigerant flowing through the first circulation path L11 and the refrigerant flowing through the second circulation path L21 can be the same refrigerant or different refrigerants, as long as they can circulate without freezing or vaporizing at their respective temperatures.

[0032] The first heat exchanger 12 cools the refrigerant circulating in the first circulation path L11 to a predetermined temperature by indirectly exchanging heat with the low-temperature liquefied gas introduced into the first heat exchanger 12 from the low-temperature liquefied gas introduction path L12 and led out to the expansion turbine introduction path L13, and the expanded low-temperature gas described later.

[0033] The cryogenic liquefied gas (liquefied nitrogen) introduced into the first heat exchanger 12 via the cryogenic liquefied gas introduction path L12 is heated and vaporized through heat exchange with the refrigerant. The vaporized gas (nitrogen gas), still at a low temperature and with a predetermined pressure, is introduced into the expansion turbine 16 via the expansion turbine introduction path L13 to expand. This yields an even lower temperature gas (expanded cryogenic gas). The expanded cryogenic gas is introduced into the first heat exchanger 12 via the expanded cryogenic gas introduction path L14 and is heated through heat exchange with the refrigerant.

[0034] The second heat exchanger 22 is cooled to a predetermined temperature by indirect heat exchange between the low-temperature liquefied gas introduced to the second heat exchanger 22 via a low-temperature liquefied gas introduction path L22 branched from the low-temperature liquefied gas introduction path L12 and the expanded low-temperature gas introduced from the first heat exchanger 12.

[0035] The expanded low-temperature gas, which has undergone indirect heat exchange with the refrigerant flowing through the first circulation path L11 in the first heat exchanger 12, is heated and led to the heat exchanger connection path L15. The heated expanded low-temperature gas can also be used to cool the refrigerant in the second circulation path L21 if its temperature is lower than the set temperature of the refrigerant in the second circulation path L21.

[0036] The expanded cryogenic gas introduced into the heat exchanger connection path L15 is introduced into the second heat exchanger 22, where it is heated through heat exchange with the refrigerant along with the cryogenic liquefied gas introduced from the cryogenic liquefied gas introduction path L22, and then introduced into the exhaust gas path L16 and released into the atmosphere as exhaust gas. Similarly, the cryogenic liquefied gas introduced from the cryogenic liquefied gas introduction path L22 is also heated through heat exchange with the refrigerant, vaporized, introduced into the exhaust gas path L26, and released into the atmosphere as exhaust gas.

[0037] The temperature of the refrigerant supplied to the first object to be cooled T11 is adjusted by setting a predetermined cooling temperature in a temperature indicator controller (TIC) 13 installed in the first circulation path L11 between the first heat exchanger 12 and the first object to be cooled T11, and by the temperature indicator controller (TIC) 13 operating according to the temperature of the refrigerant and controlling the opening degree of a flow control valve 14 installed in the low-temperature liquefied gas introduction path L12.

[0038] Furthermore, the temperature of the refrigerant supplied to the second object to be cooled T21 is adjusted by setting a predetermined cooling temperature in a temperature indicator controller (TIC) 23 installed in the second circulation path L21 between the second heat exchanger 22 and the second object to be cooled T21, and by the temperature indicator controller (TIC) 23 operating according to the temperature of the refrigerant and controlling the opening degree of a flow control valve 24 installed in the low-temperature liquefied gas introduction path L22.

[0039] Furthermore, the system is equipped with a generator G that is driven by the expansion turbine 16 to generate electricity. The gas vaporized after passing through the first heat exchanger 12 is introduced to the intake side of the expansion turbine 16, where it undergoes adiabatic expansion, providing driving energy to the expansion turbine 16, and also flows out as a lower-temperature expanded low-temperature gas. This causes the expansion turbine 16 to drive the generator G, which then generates electricity. [Examples]

[0040] Example 1 assumes that, using the refrigerant cooling device 20 shown in Figure 2, and using liquid nitrogen with a saturation temperature of 0.7 MPa as the low-temperature liquefied gas that serves as the cooling source, the refrigerant flowing through the first circulation path L11 is cooled to -90°C, and the refrigerant flowing through the second circulation path L21 is cooled to -50°C. The heat exchange capacities of the first heat exchanger 12 and the second heat exchanger 22 are set to 50 kW each, and the temperature of the nitrogen gas discharged from the first heat exchanger is set to -100°C, and the temperature of the nitrogen gas discharged from the second heat exchanger is set to -50°C. The nitrogen gas vaporized in the first heat exchanger 12 is sent to an expansion turbine 16 with an efficiency of 80% for adiabatic expansion.

[0041] Comparative Example 2 will use the conventional refrigerant cooling device 1' shown in Figure 4. In the conventional refrigerant cooling device 1' in Figure 4, components similar to those in the second embodiment are denoted by the same reference numerals. In Comparative Example 2, as in Example 2, in order to cool the refrigerant flowing through the first circulation path L11 to -90°C and the refrigerant flowing through the second circulation path L21 to -50°C, the heat exchange capacity of the first heat exchanger 12 and the second heat exchanger 22 is set to 50 kW, and the temperature of the nitrogen gas discharged from the first heat exchanger is assumed to be -100°C and the temperature of the nitrogen gas discharged from the second heat exchanger is assumed to be -50°C.

[0042] Table 2 shows the fluid consumption, temperature, and pressure in the piping for Example 2 and Comparative Example 2.

[0043] [Table 2]

[0044] As shown in Table 2, in the conventional Comparative Example 2, when the two refrigerants were cooled using only liquid nitrogen, the total consumption of liquid nitrogen was 1299 kg / h. In contrast, by using thermally low-temperature expanding gas to cool each refrigerant, the consumption of liquid nitrogen was reduced to 1102 kg / h. Therefore, Example 2 was able to reduce the consumption of liquid nitrogen by 85% compared to Comparative Example 2.

[0045] It should be noted that the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the invention. In the second embodiment, there are two objects to be cooled, but there may be three or more objects to be cooled. In that case as well, the vaporized gas of the cryogenic liquefied gas used to cool the refrigerant whose temperature is controlled to the lowest temperature is introduced into the expansion turbine, and the expanded cryogenic gas is used to cool that refrigerant. Instead of releasing the expanded cryogenic gas used for cooling as exhaust gas, it is used to cool other refrigerants whose temperature is controlled to a higher temperature, thereby reducing the overall consumption of cryogenic liquefied gas. [Explanation of symbols]

[0046] 1,1'...Refrigerant cooling system, 2...Heat exchanger, 3...Temperature indicator controller (TIC), 4...Flow control valve, 5...Circulation pump, 6...Expansion turbine, 10...Refrigerant cooling system, 12...First heat exchanger, 15...Circulation pump, 16...Expansion turbine, 20...Refrigerant cooling system, 21...First heat exchanger, 22...Second heat exchanger, 23...Temperature indicator controller (TIC), 24...Flow control valve, 25...Circulation pump, G...Generator, T1... object to be cooled, T11... first object to be cooled, T21... second object to be cooled. L1... Circulation path, L2... Cryogenic liquefied gas introduction path, L3... Expansion turbine introduction path, L4... Expanded cryogenic gas introduction path, L5... Exhaust gas path, L11... First circulation path, L12... Cryogenic liquefied gas introduction path, L13... Expansion turbine introduction path, L14... Expanded cryogenic gas introduction path, L21... Second circulation path, L22... Cryogenic liquefied gas introduction path, L26... Exhaust gas path,

Claims

1. A circulation path for circulating the refrigerant used to cool the object to be cooled, A heat exchanger provided in the aforementioned circulation path, A cryogenic liquefied gas introduction path for introducing cryogenic liquefied gas into the heat exchanger, An expansion turbine that adiabatically expands the low-temperature liquefied gas vaporized in the heat exchanger, An expanded cryogenic gas introduction path introduces the expanded cryogenic gas, which has been adiabatically expanded in the expansion turbine, into the heat exchanger. A refrigerant cooling system equipped with, The refrigerant cooling device is characterized in that the heat exchanger cools the refrigerant by indirect heat exchange with the low-temperature liquefied gas and the expanded low-temperature gas.

2. The refrigerant cooling apparatus according to claim 1, characterized in that the expanded low-temperature gas discharged from the heat exchanger is introduced as a cooling source into a heat exchanger provided in a circulation path for circulating a refrigerant to cool other objects to be cooled.

3. The refrigerant cooling device according to claim 1 or 2, characterized in that it comprises a generator that is driven by the expansion turbine and generates electricity.

4. A refrigerant cooling method in which a refrigerant used to cool an object is cooled by indirect heat exchange with a low-temperature liquefied gas, The low-temperature liquefied gas, vaporized by the aforementioned indirect heat exchange, is adiabatically expanded to become an expanded low-temperature gas. A refrigerant cooling method characterized in that the expanded low-temperature gas is also used as a cooling source in the indirect heat exchange described above.

5. The refrigerant cooling method according to claim 4, characterized in that the expanded low-temperature gas used in the indirect heat exchange is used as a cooling source for cooling a refrigerant for cooling another object to be cooled by indirect heat exchange.

6. The refrigerant cooling method according to claim 4 or 5, characterized in that the amount of work generated during the adiabatic expansion is converted into electricity.

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