A nitrogen-oxygen integrated liquefaction device and liquefaction method thereof

Abstract

The present invention proposes a nitrogen-oxygen integrated liquefaction device and a liquefaction method thereof, which specifically relate to the field of liquefaction technology. The nitrogen-oxygen integrated liquefaction device comprises a refrigeration unit and a throttling liquefaction unit, wherein: the refrigeration unit comprises a compressor, an oil filter and a cold box, a heat exchanger group and an expander are arranged inside the cold box, the heat exchanger group comprises a first heat exchanger, a second heat exchanger and a third heat exchanger, the throttling liquefaction unit comprises the first heat exchanger, the second heat exchanger, the third heat exchanger, a liquid oxygen dewar, a liquid nitrogen dewar and a plunger pump. The present invention performs heat exchange on oxygen and nitrogen respectively through three different levels of heat exchangers, namely the first heat exchanger, the second heat exchanger and the third heat exchanger, which can overcome the difference in the liquefaction points of oxygen and nitrogen, and can also make full use of the cold capacity to reduce energy consumption, and the liquefaction efficiency is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of liquefaction, and in particular to a nitrogen-oxygen integrated liquefaction device and a liquefaction method thereof. Background Art

[0002] Liquid nitrogen and liquid oxygen are widely used cold sources in cryogenic refrigeration systems, especially in aerospace, machinery manufacturing, military and other technical fields. At present, a variety of cryogenic technologies can realize the liquefaction of oxygen and nitrogen. The most important refrigeration technologies include: mixed working fluid compression refrigeration technology, Stirling refrigeration technology, GM refrigeration technology and turbine expansion refrigeration technology. Among them, the turbine expander refrigeration machine has a simple structure, long life and a high degree of localization. The turbine expansion refrigeration machine adopts static pressure turbine technology. The main components include compressors, turbine expanders, heat exchangers and other components. The gas working fluid mainly uses inert gases such as helium, neon and nitrogen. The turbine expansion refrigeration technology adopts the reverse Brayton cycle or Kraut cycle. Its theoretical cycle is close to the Carnot efficiency. With the advancement of processing and manufacturing technology, the efficiency of compressors and turbine expansions still has a lot of room for improvement.

[0003] Since nitrogen and oxygen have different liquefaction points, in the prior art, oxygen and nitrogen are usually processed and liquefied separately. However, the energy consumption required to liquefy nitrogen and oxygen separately is relatively high. Secondly, different working parameters need to be set when liquefying oxygen and nitrogen, which is inconvenient. Summary of the invention

[0004] In order to solve the problem in the prior art that oxygen and nitrogen have different liquefaction points and need to be liquefied separately, resulting in high energy consumption, the present invention proposes a nitrogen-oxygen integrated liquefaction device and a liquefaction method thereof.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention proposes that the nitrogen-oxygen integrated liquefaction device comprises a refrigeration unit and a throttling liquefaction unit, wherein:

[0007] The refrigeration unit includes a compressor, an oil filter and a cold box, and a heat exchanger group and an expander are arranged inside the cold box, and the heat exchanger group includes a first heat exchanger, a second heat exchanger and a third heat exchanger;

[0008] The throttling liquefaction unit includes the first heat exchanger, the second heat exchanger, the third heat exchanger, a liquid oxygen dewar, a liquid nitrogen dewar and a plunger pump;

[0009] The refrigerant is isothermally compressed in the compressor to form a high pressure. The high-pressure refrigerant enters the cold box after being deoiled by the oil filter, and then enters the expander for adiabatic expansion refrigeration after being cooled by the refluxed refrigerant through the first heat exchanger. The formed low-temperature and low-pressure refrigerant then enters the low-pressure side inlet of the second heat exchanger, and then flows back to the low-pressure suction end of the compressor after passing through the second heat exchanger, the third heat exchanger and the first heat exchanger in sequence for recirculation.

[0010] The high-pressure oxygen is cooled to a supercooled state by the reflux refrigerant through the first heat exchanger and the second heat exchanger, and then enters the liquid oxygen dewar to form liquid oxygen; the high-pressure nitrogen is cooled to a supercooled state by the reflux refrigerant through the first heat exchanger and the third heat exchanger, and then enters the liquid nitrogen dewar to form liquid nitrogen. The liquid nitrogen and the liquid oxygen are then pressurized by the plunger pumps to form high-pressure gases for the packaging of high-pressure nitrogen and high-pressure oxygen.

[0011] Furthermore, the refrigeration unit further includes a regulating valve CV6. After the refrigerant passes through the first heat exchanger 32, it enters into the first heat exchanger of the expander through the regulating valve CV6.

[0012] Furthermore, the throttling liquefaction unit also includes an inlet regulating valve CV4 and a first outlet throttling valve CV8. The high-pressure oxygen enters the first heat exchanger through the inlet regulating valve CV4. After the high-pressure oxygen completes heat exchange in the second heat exchanger 33, it flows into the liquid oxygen dewar through the first outlet throttling valve CV8.

[0013] Furthermore, the throttling liquefaction unit also includes an inlet regulating valve CV5 and a second outlet throttle valve CV7. The high-pressure nitrogen enters the first heat exchanger through the inlet regulating valve CV5. After the high-pressure nitrogen completes heat exchange in the third heat exchanger, it flows into the liquid nitrogen dewar through the second outlet throttle valve CV7.

[0014] Furthermore, it also includes a buffer unit, which includes a buffer tank and a three-way pipe, and the three-way pipe is respectively connected to a loading valve CV2, an unloading valve CV3 and a buffer tank, the buffer gas in the buffer tank enters into the first heat exchanger through the loading valve CV2, and the refrigerant in the first heat exchanger enters into the buffer tank through the unloading valve CV3.

[0015] Furthermore, the buffer unit further includes a bypass valve CV1, and the refrigerant filtered by the oil filter enters into the compressor through the bypass valve CV1 to stabilize the high and low pressures of the refrigerant.

[0016] Furthermore, the refrigerant is one or both of helium and neon.

[0017] Furthermore, the compressor is a low-pressure screw compressor.

[0018] Furthermore, the operation method of the nitrogen-oxygen integrated liquefaction device includes:

[0019] Furthermore, a liquefaction method of a nitrogen-oxygen integrated liquefaction device is characterized by comprising the following steps:

[0020] The refrigerant is isothermally compressed in the compressor to form a high-pressure refrigerant and then passes through the oil filter for precise oil removal. The buffer tank controls the refrigerant gas pressure to be stable. The high-pressure refrigerant enters the cold box. The refrigerant cooled to a certain temperature after heat exchange in the first heat exchanger enters the expander for adiabatic expansion refrigeration to form a low-temperature and low-pressure refrigerant. At this time, the temperature of the refrigerant is lower than the saturation temperature of liquid oxygen or liquid nitrogen and enters the second heat exchanger, the third heat exchanger, and the first heat exchanger in sequence to cool the oxygen and nitrogen, and at the same time cool the compressed high-pressure refrigerant, and finally flows back to the compressor;

[0021] After being cooled to a supercooled state by the first heat exchanger and the second heat exchanger, the high-pressure oxygen enters the liquid oxygen dewar and is converted into liquid oxygen for storage. After being cooled to a supercooled state by the first heat exchanger and the third heat exchanger, the high-pressure nitrogen enters the liquid nitrogen dewar and is converted into liquid nitrogen for storage.

[0022] Beneficial effects of the present invention:

[0023] The nitrogen-oxygen integrated liquefaction device and its operation method proposed in the present invention can respectively perform heat exchange on the oxygen liquefaction pipeline and the nitrogen liquefaction pipeline by setting a first heat exchanger, a second heat exchanger and a third heat exchanger, thereby cooling and liquefying oxygen and nitrogen. On the one hand, it can overcome the difference in liquefaction points of oxygen and nitrogen, and can simultaneously realize the liquefaction of oxygen and nitrogen or two other gases with different liquefaction points, and the structure is simpler. On the other hand, it can make full use of the cooling capacity of the refrigerant and reduce energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of the nitrogen-oxygen integrated liquefaction device of the present invention;

[0025] In the figure: compressor 1, oil filter 2, cold box 3, expander 31, first heat exchanger 32, second heat exchanger 33, third heat exchanger 34, liquid oxygen dewar 5, liquid nitrogen dewar 6, plunger pump 7, buffer tank 8.

[0026] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0027] In order to more clearly and completely illustrate the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings.

[0028] Please refer to Figure 1 The present invention proposes a nitrogen-oxygen integrated liquefaction device including a refrigeration unit and a throttling liquefaction unit, wherein:

[0029] The refrigeration unit includes a compressor 1, an oil filter 2 and a cold box 3. A heat exchanger group and an expander 31 are arranged inside the cold box 3. The heat exchanger group includes a first heat exchanger 32, a second heat exchanger 33 and a third heat exchanger 34.

[0030] The throttling liquefaction unit includes a first heat exchanger 32, a second heat exchanger 33, a third heat exchanger 33, a liquid oxygen dewar 5, a liquid nitrogen dewar 6 and a plunger pump 7;

[0031] The refrigerant is isothermally compressed in the compressor 1 to form a high pressure. The high-pressure refrigerant enters the cold box 3 after being deoiled by the oil filter 2, and then enters the expander 31 for adiabatic expansion refrigeration after being cooled by the refluxed refrigerant through the first heat exchanger 32. The formed low-temperature and low-pressure refrigerant then enters the low-pressure side inlet of the second heat exchanger 33, and then flows back to the low-pressure suction end of the compressor 1 after passing through the second heat exchanger 33, the third heat exchanger 34 and the first heat exchanger 32 in sequence to circulate again.

[0032] The high-pressure oxygen is cooled to a supercooled state by the reflux refrigerant through the first heat exchanger 32 and the second heat exchanger 33, and then enters the liquid oxygen dewar 5 to form liquid oxygen; the high-pressure nitrogen is cooled to a supercooled state by the reflux refrigerant through the first heat exchanger 32 and the third heat exchanger 34, and then enters the liquid nitrogen dewar to form liquid nitrogen. The liquid nitrogen and liquid oxygen are then pressurized by the plunger pump 7 to form high-pressure gas for the bottling of high-pressure nitrogen and high-pressure oxygen.

[0033] In this embodiment:

[0034] The first heat exchanger 32, the second heat exchanger 33 and the third heat exchanger 34 in the cold box 3 are used for heat exchange and cooling of the liquefied oxygen and nitrogen;

[0035] The oxygen liquefaction device is used to liquefy oxygen;

[0036] The throttling liquefaction unit is used to liquefy nitrogen;

[0037] Compressor 1 is used to isothermally compress the working fluid for refrigeration;

[0038] Oil filter 2 is used for precise oil removal of refrigeration circuit;

[0039] The expander 31 is used for adiabatic expansion refrigeration;

[0040] The plunger pump 7 is used to pressurize the liquid oxygen and liquid nitrogen;

[0041] Liquid oxygen dewar 5 is used to store liquid oxygen after liquefaction;

[0042] Liquid nitrogen Dewar 6 is used to store liquid nitrogen after liquefaction of nitrogen gas;

[0043] Specifically, the compressor 1 is a low-pressure screw compressor, and the oil filter 2 can filter out impurities in the refrigerant to prevent the impurities in the refrigerant from affecting the refrigeration efficiency of the refrigerant. The expander 31 can be used. The compressor 1 adopts a low-pressure screw compressor 1, and can also be selected according to actual needs. The compressor 1 isothermally compresses the refrigerant to form a high pressure. The high-pressure refrigerant enters the cold box 3 and passes through one side of the first heat exchanger 32. The first heat exchanger 32 performs heat exchange on the refrigerant. After the refrigerant is cooled to a certain temperature, the refrigerant enters the expander 31 for adiabatic expansion and refrigeration, so that its temperature is lower than the saturation temperature of liquid oxygen or liquid nitrogen. Then, the low-temperature and low-pressure refrigerant enters the inlet of the second heat exchanger 33, and passes through the second heat exchanger, the third heat exchanger, and the other side of the first heat exchanger in turn, and is cooled and heat exchanged with the second heat exchanger, the third heat exchanger, and the first heat exchanger. After completing the heat exchange, the refrigerant returns to the inlet of the compressor 1 for recirculation. Due to the liquefaction point of oxygen and nitrogen Different, nitrogen is easier to liquefy than oxygen at low temperatures. The cooling effect of the first heat exchanger 32 in the cold box 3 is the largest, and the cooling effects of the second heat exchanger 33 and the third heat exchanger 34 are the smallest. After oxygen enters the first heat exchanger 32 through the inlet regulating valve CV4 for heat exchange, it enters the second heat exchanger 33 for heat exchange to become liquid oxygen, and finally flows out from the second outlet throttle valve CV7. After nitrogen enters the first heat exchanger 32 through the inlet regulating valve CV5 for heat exchange, it enters the third heat exchanger 34 for heat exchange to form liquid nitrogen, and finally flows out from the first outlet throttle valve CV8. The separate liquefaction of oxygen and nitrogen by three heat exchangers of different levels can overcome the difference in the liquefaction points of oxygen and nitrogen. Different levels of heat exchangers are used to liquefy oxygen and nitrogen, and the liquefaction of oxygen and nitrogen can be achieved at the same time, which simplifies the structure of the liquefaction device. At the same time, the liquefaction efficiency is higher and the energy consumption is lower. Secondly, the nitrogen-oxygen integrated liquefaction device provided by the present invention can also realize the liquefaction of two other gases with different liquefaction points.

[0044] In a real-time example: liquid oxygen dewar 5 and liquid nitrogen dewar 6 can store liquid oxygen and liquid nitrogen, the second outlet throttle valve CV7 and the first outlet throttle valve CV8 are opened, and then the liquefied nitrogen and oxygen enter the liquid nitrogen dewar 6 and liquid oxygen dewar 5 respectively for storage for use.

[0045] In another embodiment: the plunger pump 7 is also connected to a gas outlet pipe. When liquid nitrogen and liquid oxygen need to be used or filled, the liquid oxygen and liquid nitrogen can be pressurized by the plunger pump 7 and then transported to an external vaporizer through the gas outlet pipe to become high-pressure gas. The high-pressure nitrogen and high-pressure oxygen are then filled for use by other equipment.

[0046] Furthermore, the refrigeration unit also includes a regulating valve CV6. After the refrigerant passes through the first heat exchanger 32, it enters the first heat exchanger 32 of the expander 31 through the regulating valve CV6. The throttling liquefaction unit also includes an inlet regulating valve CV4 and a first outlet throttle valve CV8. The high-pressure oxygen enters the first heat exchanger 32 through the inlet regulating valve CV4. After the high-pressure oxygen completes heat exchange in the second heat exchanger 33, it flows into the liquid oxygen dewar 5 through the first outlet throttle valve CV8. The throttling liquefaction unit also includes an inlet regulating valve CV5 and a second outlet throttle valve CV7. The high-pressure nitrogen enters the first heat exchanger 32 through the inlet regulating valve CV5. After the high-pressure nitrogen completes heat exchange in the third heat exchanger 34, it flows into the liquid nitrogen dewar 6 through the second outlet throttle valve CV7.

[0047] In this embodiment:

[0048] The regulating valve CV6 is used to block and open the refrigeration unit;

[0049] The inlet regulating valve CV4 and the inlet regulating valve CV5 are used to regulate the inlet nitrogen and oxygen respectively;

[0050] The second outlet throttle valve CV7 and the first outlet throttle valve CV8 are used to adjust the delivery of liquid oxygen and liquid nitrogen respectively;

[0051] Specifically, the second outlet throttle valve CV7 and the first outlet throttle valve CV8 can open and close the nitrogen outlet and the oxygen outlet to control the liquid oxygen and liquid nitrogen to flow into the liquid oxygen dewar 5 and the liquid nitrogen dewar 6, the inlet regulating valve CV4 and the inlet regulating valve CV5 can open the nitrogen inlet and the oxygen inlet to control the oxygen and nitrogen to flow into the oxygen liquefaction pipeline and the nitrogen liquefaction pipeline respectively, the regulating valve CV6, the inlet regulating valve CV4, the inlet regulating valve CV5, the second outlet throttle valve CV7 and the first outlet throttle valve CV8 can be intelligently controlled by an external control panel or a PLC system to realize the opening and closing of the refrigeration unit, the throttling liquefaction unit and the oxygen liquefaction device.

[0052] Furthermore, it also includes a buffer unit, which includes a buffer tank 8 and a three-way pipe, on which a loading valve CV2, an unloading valve CV3 and the buffer tank 8 are respectively connected. The buffer gas in the buffer tank 8 enters into the first heat exchanger 32 through the loading valve CV2, and the refrigerant in the first heat exchanger 32 enters into the buffer tank 8 through the unloading valve CV3. The buffer unit also includes a bypass valve CV1, and the refrigerant filtered by the oil filter 2 enters into the compressor 1 through the bypass valve CV1 to stabilize the high and low pressures of the refrigerant.

[0053] In this embodiment:

[0054] The buffer tank 8 is used to control the stability of the high and low pressures of the working fluid in the refrigeration circuit;

[0055] The loading valve CV2 and the unloading valve CV3 are used to open and close the buffer tank 8;

[0056] Bypass valve CV1 is used to open the circuits on both sides of compressor 1;

[0057] Specifically, the external gas management panel can control the opening and closing of the bypass valve CV1, the loading valve CV2 and the unloading valve CV3, and the buffer unit can adjust and control the inlet and outlet pressures of the compressor 1 to stabilize the gas pressure of the refrigerant to maintain stable operation of the refrigeration circuit.

[0058] Furthermore, the refrigerant is one or both of helium and neon.

[0059] In this embodiment:

[0060] The refrigerant is used to provide a cold source for the heat exchanger for heat exchange;

[0061] Specifically, the refrigerant can cool down to complete the heat exchange. The refrigerant can be helium, neon, or a mixture of nitrogen and neon. The type of the refrigerant can be selected according to actual needs.

[0062] Furthermore, the operation method of the nitrogen-oxygen integrated liquefaction device includes:

[0063] Expansion refrigeration: The refrigerant is compressed at a constant temperature in the compressor 1 to form a high-pressure refrigerant and then flows out from the outlet. After the refrigerant is precisely deoiled by the oil filter 2, the buffer tank 8 controls the refrigerant gas pressure to be stable. The high-pressure refrigerant is in the cold box 3. After heat exchange in the first heat exchanger 32, the refrigerant cooled to a certain temperature enters the expander 31 for adiabatic expansion refrigeration to form a low-temperature and low-pressure refrigerant. At this time, the temperature of the refrigerant is lower than the saturation temperature of liquid oxygen or liquid nitrogen and enters the second heat exchanger, the third heat exchanger, and the first heat exchanger in turn to cool the oxygen and nitrogen, and at the same time cool the compressed high-pressure refrigerant, and finally flows back into the compressor 1.

[0064] Oxygen liquefaction: After external high-pressure treatment, oxygen enters from the oxygen inlet of the oxygen liquefaction pipeline, and then is converted into liquid oxygen after being cooled by the first heat exchanger 32 and the second heat exchanger 33 and enters from the oxygen outlet into the liquid oxygen dewar 5 for storage.

[0065] Nitrogen liquefaction: After external high-pressure treatment, nitrogen enters from the oxygen inlet of the nitrogen liquefaction pipeline, and then is converted into liquid oxygen after being cooled by the first heat exchanger 32 and the third heat exchanger 34 and enters from the oxygen outlet into the liquid nitrogen dewar 6 for storage.

[0066] In a real-time example: control operation parameters, where: oxygen inlet pressure: 0.4MPa, liquid oxygen pressure: 1.2bar, nitrogen inlet pressure: 0.6MPa, liquid nitrogen pressure: 1.2bar, liquid oxygen temperature: 88.69K, liquid nitrogen temperature: 78.82K, refrigerant helium circulation volume: 35g / s, 0.4MPa high-pressure oxygen passes through the first heat exchanger 32 and the second heat exchanger 33 and is cooled to a supercooled state by the refrigerant, and then enters the liquid oxygen dewar 5 through the first outlet throttle valve CV8, 0.6MPa high-pressure nitrogen passes through the first heat exchanger 32 and the third heat exchanger 34 and is cooled to a supercooled state by the refrigerant, and enters the liquid nitrogen dewar 6 through the second outlet throttle valve CV7, and finally the following parameters are calculated: oxygen liquefaction rate: 11.97Nm3 / h, nitrogen liquefaction rate: 22.79 Nm3 / h, total UA value 6.888KJ / KS, expected power consumption: 47.76KW. It can be seen that the liquefaction efficiency of the nitrogen and oxygen integrated liquefaction device proposed in the present invention is higher than that of the traditional liquefaction device, and the energy consumption is lower.

[0067] In summary, in a specific implementation, the refrigerant is compressed in the compressor 1 to form a high pressure, and the high-pressure refrigerant is deoiled by the oil filter 2, and then enters one side of the first heat exchanger 32 for heat exchange. After the heat exchanged refrigerant is cooled to a certain temperature by the first heat exchanger 32, it passes through the regulating valve CV6 and enters the expander 31 for adiabatic expansion refrigeration. After cooling again by expansion refrigeration, the temperature of the refrigerant is lower than the saturation temperature of liquid oxygen or liquid nitrogen, and the low-temperature and low-pressure refrigerant is formed, and then enters the second heat exchanger 33 for heat exchange, the third heat exchanger 34, and the other side of the first heat exchanger 32 in sequence. Heat exchange cooling is carried out on the side, and the refrigerant after cooling is circulated again from the inlet end of the compressor 1. The refrigeration unit provides cold capacity for the first heat exchanger 32, the second heat exchanger 33 and the third heat exchanger 34. Then, the oxygen enters the first heat exchanger 32 and the second heat exchanger 33 in turn through the regulating valve CV4 for heat exchange, and finally flows into the liquid oxygen dewar 5 through the second outlet throttle valve CV7 for storage. The nitrogen enters the first heat exchanger 32 and the third heat exchanger 34 in turn through the regulating valve CV5 for heat exchange, and finally flows into the liquid nitrogen dewar 6 through the first outlet throttle valve CV8 for storage.

[0068] Of course, the present invention may have many other implementations. Based on this implementation, other implementations obtained by ordinary technicians in this field without any creative work are all within the scope of protection of the present invention.

Claims

1. A nitrogen and oxygen integrated liquefaction device, characterized in that: The nitrogen and oxygen integrated liquefaction device comprises a refrigeration unit and a throttling liquefaction unit, wherein: The refrigeration unit comprises a compressor (1), an oil filter (2) and a cold box (3); a heat exchanger group and an expander (31) are provided inside the cold box (3); the heat exchanger group comprises a first heat exchanger (32), a second heat exchanger (33) and a third heat exchanger (34); The throttling liquefaction unit comprises the first heat exchanger (32), the second heat exchanger (33), the third heat exchanger (34), a liquid oxygen dewar (5), a liquid nitrogen dewar (6) and a plunger pump (7); The refrigerant is isothermally compressed in the compressor (1) to form a high pressure. The high-pressure refrigerant is deoiled by the oil filter (2) and enters the cold box (3). It is then cooled by the reflowing refrigerant through the first heat exchanger (32) and enters the expander (31) for adiabatic expansion refrigeration. The low-temperature and low-pressure refrigerant then enters the low-pressure side inlet of the second heat exchanger (33), and sequentially passes through the second heat exchanger (33), the third heat exchanger (34) and the first heat exchanger (32) before returning to the low-pressure suction end of the compressor (1) for recirculation. The high-pressure oxygen is cooled to a supercooled state by the reflux refrigerant through the first heat exchanger (32) and the second heat exchanger (33), and then enters the liquid oxygen dewar (5) to form liquid oxygen; the high-pressure nitrogen is cooled to a supercooled state by the reflux refrigerant through the first heat exchanger (32) and the third heat exchanger (34), and then enters the liquid nitrogen dewar (6) to form liquid nitrogen. The liquid nitrogen and the liquid oxygen are then pressurized by the plunger pump (7) to form high-pressure gas, which is used for the bottling of the high-pressure nitrogen and the high-pressure oxygen.

2. The nitrogen and oxygen integrated liquefaction device according to claim 1, characterized in that: The refrigeration unit further comprises a regulating valve (CV6), and after the refrigerant passes through the first heat exchanger (32), it enters the first heat exchanger (32) of the expander (31) through the regulating valve (CV6).

3. The nitrogen and oxygen integrated liquefaction device according to claim 1, characterized in that: The throttling liquefaction unit further comprises an inlet regulating valve (CV4) and a first outlet throttling valve (CV8); the high-pressure oxygen enters the first heat exchanger (32) through the inlet regulating valve (CV4); after the high-pressure oxygen completes heat exchange in the second heat exchanger (33), it flows into the liquid oxygen dewar (5) through the first outlet throttling valve (CV8).

4. The nitrogen and oxygen integrated liquefaction device according to claim 3, characterized in that: The throttling liquefaction unit further comprises an inlet regulating valve (CV5) and a second outlet throttling valve (CV7); the high-pressure nitrogen enters the first heat exchanger (32) through the inlet regulating valve (CV5); after the high-pressure nitrogen completes heat exchange in the third heat exchanger (34), the high-pressure nitrogen flows into the liquid nitrogen dewar (6) through the second outlet throttling valve (CV7).

5. The nitrogen and oxygen integrated liquefaction device according to claim 1, characterized in that: The invention also comprises a buffer unit, the buffer unit comprising a buffer tank (8) and a three-way pipe, the three-way pipe being respectively connected to a loading valve (CV2), an unloading valve (CV3) and the buffer tank (8), the buffer gas in the buffer tank (8) entering into the first heat exchanger (32) through the loading valve (CV2), and the refrigerant in the first heat exchanger (32) entering into the buffer tank (8) through the unloading valve (CV3).

6. The nitrogen and oxygen integrated liquefaction device according to claim 5, characterized in that: The buffer unit further comprises a bypass valve (CV1), through which the refrigerant filtered by the oil filter (2) enters the compressor (1) to stabilize the high and low pressures of the refrigerant.

7. The nitrogen and oxygen integrated liquefaction device according to claim 1, characterized in that: The refrigerant is one or both of helium and neon.

8. The nitrogen and oxygen integrated liquefaction device according to claim 1, characterized in that: The compressor (1) is a low-pressure screw compressor.

9. A liquefaction method according to the nitrogen-oxygen integrated liquefaction device according to any one of claims 1 to 8, characterized in that: The steps include: The refrigerant is isothermally compressed in the compressor (1) to form a high-pressure refrigerant, which is then precisely degreased by the oil filter (2). The buffer tank (8) controls the refrigerant gas pressure to be stable. The high-pressure refrigerant enters the cold box (3). The refrigerant is cooled to a certain temperature after heat exchange in the first heat exchanger (32). The refrigerant enters the expander (31) to undergo adiabatic expansion and refrigeration to form a low-temperature and low-pressure refrigerant. At this time, the temperature of the refrigerant is lower than the saturation temperature of liquid oxygen or liquid nitrogen and enters the second heat exchanger (33), the third heat exchanger (34), and the first heat exchanger (32) in sequence to cool the oxygen and nitrogen and the compressed high-pressure refrigerant, and finally flows back into the compressor (1); After the high-pressure oxygen is cooled to a supercooled state by the first heat exchanger (32) and the second heat exchanger (33), it enters the liquid oxygen dewar (5) and is converted into liquid oxygen for storage. After the high-pressure nitrogen is cooled to a supercooled state by the first heat exchanger (32) and the third heat exchanger (34), it enters the liquid nitrogen dewar (6) and is converted into liquid nitrogen for storage.

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