LNG (Liquefied Natural Gas) cold energy gradient utilization device
By leveraging the LNG cooling capacity grading for air separation, cold chain refrigeration and cooling water supply in the LNG cooling stage utilization device, the problems of high energy consumption and cold energy waste in the prior art are solved, and more efficient Energy utilization.
Patent Information
- Application Number
- CN202323580160.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-26
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2033-12-26
AI Technical Summary
The prior art heaters LNG liquids have high energy consumption and poor economicality during the production process, and lead to a large amount of LNG cooling energy waste.
A LNG cooling energy cascade utilization device is designed. By sequentially using the LNG cooling capacity in the air separation system, cold chain refrigeration and cooling water supply system during the vaporization process, the cooling energy is realized and the energy utilization rate is improved.
Effectively utilize LNG cold energy, reduce energy consumption, improve the economy of the production process, and reduce cold energy waste.
Smart Images
Figure CN222257870U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of liquefied natural gas cold energy utilization, in particular to a LNG cold energy cascade utilization device. Background Art
[0002] Natural gas is the cleanest fossil energy in the world. Compared with liquefied petroleum gas, it is safer, cleaner and more environmentally friendly. After combustion, the carbon dioxide is only 40% of coal, and sulfur dioxide is also very low. No waste water or waste residue is generated after combustion. It is easy to operate and use, and is widely used in chemical industry, smelting, and daily life. In the process related to glass production, natural gas is usually used as a dye for melting glass.
[0003] When natural gas is used in large quantities, it is difficult to transport, so it is liquefied and compressed to a great extent to facilitate large-scale industrial production. In short, LNG is the product of natural gas (methane CH4) that has been purified and cooled and liquefied at ultra-low temperatures. LNG must be reheated to room temperature before it can be put into production.
[0004] Currently, in the production process, the common process for heating LNG liquid is to directly use water bath, electric heating or steam auxiliary heating, which has high energy consumption, poor economy and will cause a large amount of LNG cold energy to be wasted. Utility Model Content
[0005] The main purpose of the utility model is to provide a LNG cold energy cascade utilization device, which aims to utilize different temperature ranges of LNG cold energy to achieve graded utilization of LNG cold energy, so as to fully utilize a large amount of LNG cold energy.
[0006] To achieve the above-mentioned purpose, the utility model proposes a LNG cold energy cascade utilization device, which includes an LNG gas source, a gas trunk line, an air separation system, a cold chain refrigeration system, and a cooling water supply system;
[0007] The LNG gas source delivers fuel to the process production area through the gas trunk line, and the gas trunk line is sequentially provided with a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger along the fuel delivery direction;
[0008] The air separation system is connected to the primary heat exchanger, and the primary heat exchanger is capable of exchanging heat between the fuel in the gas trunk line and the gas in the air separation system;
[0009] The cold chain refrigeration system is connected to the secondary heat exchanger, and the secondary heat exchanger can exchange heat between the fuel in the gas trunk line and the gas in the cold chain refrigeration system;
[0010] The cooling water supply system is connected to the three-stage heat exchanger, and the three-stage heat exchanger can exchange heat between the fuel in the gas trunk line and the liquid in the cooling water supply system.
[0011] Optionally, the cold source outlets of the first-stage heat exchanger, the second-stage heat exchanger and the third-stage heat exchanger are all provided with temperature control valves, and the LNG cold energy cascade utilization device also includes a central control system, which is electrically connected to the temperature control valve so as to be able to control the opening of the temperature control valve.
[0012] Optionally, the cold source outlets and cold source inlets of the primary heat exchanger, the secondary heat exchanger and the tertiary heat exchanger are all provided with methane detection probes, and the methane detection probes are electrically connected to the central control system.
[0013] Optionally, the preset temperature of the temperature control valve at the primary heat exchanger is -150°C to -140°C.
[0014] Optionally, the preset temperature of the temperature control valve at the secondary heat exchanger is -100°C to -90°C.
[0015] Optionally, the preset temperature of the temperature control valve at the tertiary heat exchanger is 10°C to 20°C.
[0016] Optionally, the air separation system includes a distillation tower and a first air compressor, the oxygen outlet of the distillation tower, the first air compressor and the gas inlet of the first-stage heat exchanger are connected in sequence, and the gas outlet of the first-stage heat exchanger is connected to a liquid oxygen tank.
[0017] Optionally, an expansion valve is provided between the gas outlet of the primary heat exchanger and the liquid oxygen tank.
[0018] Optionally, the cold chain refrigeration system includes a refrigeration unit, and the refrigeration unit includes a second air compressor and an air purifier. After passing through the second air compressor, the air passes through the air purifier and the secondary heat exchanger in sequence.
[0019] Optionally, the cold chain cooling system also includes a cold storage system, an office area air-conditioning system and a production area air-conditioning system, and the gas outlet of the secondary heat exchanger is respectively connected to the cold sides of the cold storage system, the office area air-conditioning system and the production area air-conditioning system.
[0020] Optionally, a flow-limiting temperature control valve is provided between the air purifier and the gas inlet of the secondary heat exchanger, and the flow-limiting temperature control valve is used to control the air flow entering the secondary heat exchanger, and the preset temperature of the flow-limiting temperature control valve is 25°C to 35°C.
[0021] Optionally, a cold source temperature control valve is provided between the gas outlet of the secondary heat exchanger and the cold side of the cold storage system, the office area air-conditioning system and the production area air-conditioning system. The cold source temperature control valve is used to limit the temperature of the cold source entering the cold storage system, the office area air-conditioning system and the production area air-conditioning system.
[0022] Optionally, the cooling water supply system includes a return water pipe and a circulating water pool, the circulating water pool is connected to the return water pipe, and the three-stage heat exchanger is arranged between the return water pipe and the circulating water pool.
[0023] Optionally, the LNG cold energy cascade utilization device also includes a buffer tank, which is arranged in the gas trunk line and connected to the cold source outlet of the three-stage heat exchanger, and the buffer tank is used to buffer the LNG gas.
[0024] Optionally, the LNG cold energy cascade utilization device also includes a four-stage heat exchanger and a gas branch. The LNG gas source is connected to the gas branch via a control valve. The gas branch transports fuel to the process production area. The four-stage heat exchanger is arranged on the gas branch.
[0025] The technical solution of the utility model combines the demand for cold energy from factory operation and, according to the different required cooling temperatures, uses the cold energy released during the vaporization process of LNG in the air separation system, cold chain refrigeration and cooling water supply system in sequence, thereby realizing the cascade utilization of LNG cold energy and improving energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.
[0027] Figure 1 It is a structural schematic diagram of an embodiment of the LNG cold energy cascade utilization device of the utility model.
[0028] Description of Figure Numbers:
[0029]
[0030] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0031] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0032] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.
[0033] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0034] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.
[0035] The utility model provides a LNG cold energy cascade utilization device.
[0036] In the embodiment of the utility model, the LNG cold energy cascade utilization device is as follows Figure 1 As shown, it includes an LNG gas source, a gas trunk line 20, an air separation system 30, a cold chain refrigeration system 40, and a cooling water supply system 50;
[0037] The LNG gas source delivers fuel to the process production area through the gas trunk line 20, and the gas trunk line 20 is sequentially provided with a primary heat exchanger 21, a secondary heat exchanger 22 and a tertiary heat exchanger 23 along the fuel delivery direction;
[0038] The air separation system 30 is connected to the primary heat exchanger 21, and the primary heat exchanger 21 can exchange heat between the fuel in the gas trunk line 20 and the gas in the air separation system 30;
[0039] The cold chain refrigeration system 40 is connected to the secondary heat exchanger 22, and the secondary heat exchanger 22 can exchange heat between the fuel in the gas trunk line 20 and the gas in the cold chain refrigeration system 40;
[0040] The cooling water supply system 50 is connected to the tertiary heat exchanger 23 , and the tertiary heat exchanger 23 can exchange heat between the fuel in the gas trunk line 20 and the liquid in the cooling water supply system 50 .
[0041] The technical solution of the utility model combines the demand for cold energy from factory operation and uses the cold energy released by LNG during the vaporization process in the air separation system 30, cold chain refrigeration and cooling water supply system 50 in turn according to the different required cooling temperatures, thereby realizing the cascade utilization of LNG cold energy and improving energy utilization.
[0042] Optionally, the cold source outlets of the primary heat exchanger 21, the secondary heat exchanger 22, and the tertiary heat exchanger 23 are all provided with temperature control valves 24, and the LNG cold energy cascade utilization device further comprises a central control system, which is electrically connected to the temperature control valve 24 to control the opening of the temperature control valve 24. The temperature control valve 24 can detect the temperature in the primary heat exchanger 21, the secondary heat exchanger 22, and the tertiary heat exchanger 23. When the temperature in the primary heat exchanger 21, the secondary heat exchanger 22, and the tertiary heat exchanger 23 is lower than a preset temperature, the central control system will control the opening of the temperature control valve 24 to decrease, so as to prevent more low-temperature LNG cold sources from entering; when the temperature in the primary heat exchanger 21, the secondary heat exchanger 22, and the tertiary heat exchanger 23 is higher than a preset temperature, the central control system will control the opening of the temperature control valve 24 to increase, so as to allow more low-temperature LNG cold sources to enter. Further optionally, the LNG gas source is an LNG storage tank, and a temperature control valve 24 is provided between the LNG storage tank and the primary heat exchanger 21, and the temperature control valve 24 can be electrically connected to the central control system to control whether the gas trunk line 20 is running and to adjust the temperature in the primary heat exchanger 21. In other embodiments, the cold source outlets of the primary heat exchanger 21, the secondary heat exchanger 22, and the tertiary heat exchanger 23 can also be provided with ordinary valves, and temperature sensors are provided in the primary heat exchanger 21, the secondary heat exchanger 22, and the tertiary heat exchanger 23, and the temperature in the primary heat exchanger 21, the secondary heat exchanger 22, and the tertiary heat exchanger 23 can be adjusted by the staff manually opening and closing the valves.
[0043] Optionally, the cold source outlet and cold source inlet of the primary heat exchanger 21, the secondary heat exchanger 22 and the tertiary heat exchanger 23 are all provided with a methane detection probe 25, and the methane detection probe 25 is electrically connected to the central control system. To prevent methane leakage, for example, when the methane detection probe 25 detects methane leakage between the primary heat exchanger 21 and the secondary heat exchanger 22, the central control system closes the valve of the temperature control valve 24 between the primary heat exchanger 21 and the secondary heat exchanger 22 to prevent further leakage of methane. In other embodiments, the LNG cold energy cascade utilization device can also have an alarm light, and the methane detection probe 25 is electrically connected to the alarm light, and the flashing of the alarm light indicates that the staff manually close the valve.
[0044] Optionally, the air separation system 30 includes a distillation tower 32 and a first air compressor 31, the oxygen outlet of the distillation tower 32, the first air compressor 31 and the gas inlet of the first-stage heat exchanger 21 are connected in sequence, and the gas outlet of the first-stage heat exchanger 21 is connected to the liquid oxygen tank 33. When LNG flows out of the LNG storage tank into the first-stage heat exchanger 21, the temperature is about -162°C, and the temperature of oxygen when it flows out of the distillation tower 32 is about 10°C. It is necessary to make oxygen into liquid for easy storage and transportation. The boiling point of oxygen is -186°C at one atmospheric pressure (0.1MPa), so it is necessary to pressurize oxygen. When oxygen is compressed to 0.7MPa by the first air compressor 31, the boiling point of oxygen is -159.5°C, and it can be liquefied in the first-stage heat exchanger 21. In other embodiments, the nitrogen outlet of the distillation tower 32, the first air compressor 31 and the gas inlet of the primary heat exchanger 21 may be connected in sequence, and the first air compressor 31 can compress the air to 1 MPa or higher to make the boiling point of nitrogen above -162°C.
[0045] Optionally, the preset temperature of the temperature control valve 24 at the primary heat exchanger 21 is -150°C to -140°C. Since the temperature of oxygen liquefaction is -159.5°C at 0.7MPa, and the oxygen at the gas inlet of the primary heat exchanger 21 is about 10°C, assuming that the flow direction of LNG in the primary heat exchanger 21 is opposite to the flow direction of oxygen, the LNG cold source at the cold source outlet can effectively cool the oxygen, and the LNG cold source near the cold source inlet can liquefy the oxygen, so that the primary heat exchanger 21 can achieve sufficient heat exchange. Therefore, the preset temperature of the temperature control valve 24 between the primary heat exchanger 21 and the secondary heat exchanger 22 is any value between -150°C and -140°C.
[0046] Optionally, an expansion valve 34 is provided between the gas outlet of the primary heat exchanger 21 and the liquid oxygen tank 33. The expansion valve 34 can further increase the gas pressure, assist in the liquefaction of oxygen, and increase the efficiency of the oxygen liquefaction. In other embodiments, the expansion valve 34 may not be provided.
[0047] Optionally, the cold chain cooling system 40 includes a refrigeration unit 41, which includes a second air compressor 411 and an air purifier 412. After passing through the second air compressor 411, the air passes through the air purifier 412 and the secondary heat exchanger 22 in sequence. The temperature of the LNG flowing out of the cold source outlet of the primary heat exchanger 21 is between -150°C and -140°C. The second air compressor 411 can compress the outside air and exchange heat with the earphone heat exchanger, and the cooled air is used as the cold source of the cold chain cooling system 40. The air purifier 412 can filter the moisture and tiny solid particles in the outside air to prevent the moisture from freezing when the compressed air passes through the secondary heat exchanger 22, thereby affecting the heat exchange efficiency of the secondary heat exchanger 22. Compressing the outside air and serving as the cooling medium between the LNG cold source and the cold chain cooling system 40 can reduce the length of the gas trunk 20, reduce the probability of methane leakage, and have a low cost. In other embodiments, a cryogenic liquid with a freezing point of -160°C-150°C may be used as a cooling medium between the LNG cold source and the cold chain cooling system 40 .
[0048] Optionally, the cold chain cooling system 40 also includes a cold storage system 42, an office area air conditioning system 43 and a production area air conditioning system 44, and the gas outlet of the secondary heat exchanger is respectively connected to the cold side of the cold storage system 42, the office area air conditioning system 43 and the production area air conditioning system 44. Since the second air compressor 411 is pressurized, the outside air is transported for heat exchange with the LNG cold source with a temperature of -150°C to -140°C of the secondary heat exchanger 22, which can fully meet the use needs of a large cold storage, and based on the daily production of 1 million cubic meters of LNG, 500 cubic meters of ice can be produced per day, and there is also a surplus to provide the cooling capacity required for cooling the high-temperature production plant equipment and office space.
[0049] Optionally, the preset temperature of the temperature control valve 24 at the secondary heat exchanger 22 is -100°C to -90°C. Optionally, a flow-limiting temperature control valve 413 is provided between the air purifier 412 and the gas inlet of the secondary heat exchanger, and the flow-limiting temperature control valve 413 is used to control the air flow entering the secondary heat exchanger, and the preset temperature of the flow-limiting temperature control valve 413 is 25°C to 35°C. The flow-limiting temperature control valve 413 controls the air temperature at the gas inlet of the secondary heat exchanger 22 within the range of 25°C to 35°C, and the temperature of the cold source used to make ice for the cold storage system 42 must be at least below 0°C. Therefore, assuming that the flow direction of LNG in the secondary heat exchanger 22 is opposite to the flow direction of air, the LNG cold source at the cold source outlet can effectively initially cool the air, and the LNG cold source near the cold source inlet can effectively reduce the air to below 0°C, so that the secondary heat exchanger 22 can achieve sufficient heat exchange. Therefore, the preset temperature of the temperature control valve 24 between the secondary heat exchanger 22 and the tertiary heat exchanger 23 is any value between -100°C and -90°C.
[0050] Optionally, a cold source temperature control valve 414 is provided between the gas outlet of the secondary heat exchanger and the cold side of the cold storage system 42, the office area air conditioning system 43 and the production area air conditioning system 44, and the cold source temperature control valve 414 is used to limit the temperature of the cold source entering the cold storage system 42, the office area air conditioning system 43 and the production area air conditioning system 44. The cold source temperature control valve 414 can make the temperature of the cold source entering the cold storage system 42, the office area air conditioning system 43 and the production area air conditioning system 44 within the effective temperature reduction temperature range, wherein the preset temperature of the cold source temperature control valve 414 at the cold storage system 42 is between 0°C and -5°C, and the preset temperature of the cold source temperature control valve 414 at the office area air conditioning system 43 and the production area air conditioning system 44 is about 0°C. And the current limiting temperature control valve 413 and the cold source temperature control valve 414 are both electrically connected to the central control system so as to be able to intelligently control the opening of the current limiting temperature control valve 413 and the cold source temperature control valve 414. In other embodiments, ordinary valves may be provided between the gas outlet of the secondary heat exchanger and the cold sides of the cold storage system 42, the office area air-conditioning system 43 and the production area air-conditioning system 44, and temperature sensors may be provided in the cold sides of the cold storage system 42, the office area air-conditioning system 43 and the production area air-conditioning system 44. The temperature of the cold sides of the cold storage system 42, the office area air-conditioning system 43 and the production area air-conditioning system 44 may be regulated by the staff manually opening and closing the valves.
[0051] Optionally, the cooling water supply system 50 includes a return water pipe 51 and a circulating water pool 52, the circulating water pool 52 is connected to the return water pipe 51, and the tertiary heat exchanger is arranged between the return water pipe 51 and the circulating water pool 52. In the production plant, cooling water is needed to cool the equipment. In the circulating water system, the water temperature in the return water pipe 51 is usually around 50°C after heat exchange with the equipment. It needs to be cooled down to below 33°C by heat exchange with the tertiary heat exchanger 23, and then stored in the circulating water pool 52 for reuse. Combining LNG low-temperature heat exchange with circulating water cooling helps save production costs. In other embodiments, the tertiary heat exchanger 23 can also be arranged in the circulating water pool 52.
[0052] Optionally, the preset temperature of the temperature control valve 24 at the tertiary heat exchanger 23 is 10°C to 20°C, and the LNG cold source temperature at the cold source inlet of the tertiary heat exchanger 23 is in the range of -100°C to -90°C. Water has a high specific heat capacity and can absorb a large amount of heat to raise the temperature of the LNG cold energy to 10°C to 20°C. Methane gas at this temperature can be used as fuel.
[0053] Optionally, the LNG cold energy cascade utilization device also includes a buffer tank 60, which is arranged on the gas trunk line 20 and connected to the cold source outlet of the three-stage heat exchanger, and the buffer tank 60 is used to buffer the LNG gas. The buffer tank 60 is used to temporarily store the natural gas after heating and gasification, because the gas directly flowing out of the three-stage heat exchanger 23 is affected by the temperature control valve 24, and the gas flow size of the methane gas will fluctuate, and it is difficult to control the temperature when used directly. Among them, the gas inlet and other outlets of the buffer tank 60 are provided with a methane detection probe 25 to detect whether there is a methane leak. In other embodiments, the buffer tank 60 may not be provided.
[0054] Optionally, the LNG cold energy cascade utilization device further includes a four-stage heat exchanger 71 and a gas branch 70, the LNG gas source and the gas branch 70 are connected by a control valve 72, the gas branch 70 transports fuel to the process production area, and the four-stage heat exchanger 71 is arranged on the gas branch 70. When any one or more of the first-stage, second-stage heat exchangers 22 and third-stage heat exchangers 23 on the gas trunk 20 fails or the temperature control valve 24 needs to be repaired, the gas trunk 20 is closed, and the control valve 72 between the gas branch 70 and the LNG gas source is opened to allow the LNG liquid to flow to the gas branch 70, and the LNG liquid is directly heated from -162°C to 20°C through the four-stage heat exchanger 71 to avoid affecting the combustion and use of LNG. Further, the control valve 72 is electrically connected to the central control system, which can reduce the probability of frostbite of the staff and is easy to operate. In other embodiments, the four-stage heat exchanger 71 and the gas branch 70 may not be provided.
[0055] The above description is only an optional embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.
Claims
1. A LNG cold energy cascade utilization device, characterized in that: Including LNG gas source, gas trunk line, air separation system, cold chain refrigeration system, and cooling water supply system; The LNG gas source delivers fuel to the process production area through the gas trunk line, and the gas trunk line is sequentially provided with a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger along the fuel delivery direction; The air separation system is connected to the primary heat exchanger, and the primary heat exchanger is capable of exchanging heat between the fuel in the gas trunk line and the gas in the air separation system; The cold chain refrigeration system is connected to the secondary heat exchanger, and the secondary heat exchanger can exchange heat between the fuel in the gas trunk line and the gas in the cold chain refrigeration system; The cooling water supply system is connected to the three-stage heat exchanger, and the three-stage heat exchanger can exchange heat between the fuel in the gas trunk line and the liquid in the cooling water supply system.
2. The LNG cold energy cascade utilization device according to claim 1, characterized in that: The cold source outlets of the first-stage heat exchanger, the second-stage heat exchanger and the third-stage heat exchanger are all provided with temperature control valves. The LNG cold energy cascade utilization device also includes a central control system, which is electrically connected to the temperature control valve so as to be able to control the opening of the temperature control valve.
3. The LNG cold energy cascade utilization device according to claim 2, characterized in that: The cold source outlet and cold source inlet of the first-stage heat exchanger, the second-stage heat exchanger and the third-stage heat exchanger are all provided with methane detection probes, and the methane detection probes are electrically connected to the central control system; And / or, the preset temperature of the temperature control valve at the primary heat exchanger is -150°C to -140°C; And / or, the preset temperature of the temperature control valve at the secondary heat exchanger is -100°C to -90°C; And / or, the preset temperature of the temperature control valve at the three-stage heat exchanger is 10°C to 20°C.
4. The LNG cold energy cascade utilization device according to claim 1, characterized in that: The air separation system includes a distillation tower and a first air compressor. The oxygen outlet of the distillation tower, the first air compressor and the gas inlet of the first-stage heat exchanger are connected in sequence. The gas outlet of the first-stage heat exchanger is connected to a liquid oxygen tank.
5. The LNG cold energy cascade utilization device according to claim 4, characterized in that: An expansion valve is provided between the gas outlet of the primary heat exchanger and the liquid oxygen tank.
6. The LNG cold energy cascade utilization device according to claim 1, characterized in that: The cold chain refrigeration system includes a refrigeration unit, and the refrigeration unit includes a second air compressor and an air purifier. After passing through the second air compressor, the air passes through the air purifier and the secondary heat exchanger in sequence.
7. The LNG cold energy cascade utilization device according to claim 6, characterized in that: The cold chain cooling system also includes a cold storage system, an office area air conditioning system and a production area air conditioning system. The gas outlet of the secondary heat exchanger is respectively connected to the cold sides of the cold storage system, the office area air conditioning system and the production area air conditioning system.
8. The LNG cold energy cascade utilization device according to claim 7, characterized in that: A flow-limiting temperature control valve is provided between the air purifier and the gas inlet of the secondary heat exchanger, and the flow-limiting temperature control valve is used to control the air flow entering the secondary heat exchanger, and the preset temperature of the flow-limiting temperature control valve is 25° C. to 35° C.; And / or, a cold source temperature control valve is provided between the gas outlet of the secondary heat exchanger and the cold side of the cold storage system, the office area air-conditioning system and the production area air-conditioning system, and the cold source temperature control valve is used to limit the temperature of the cold source entering the cold storage system, the office area air-conditioning system and the production area air-conditioning system.
9. The LNG cold energy cascade utilization device according to claim 1, characterized in that: The cooling water supply system comprises a return water pipe and a circulating water pool, the circulating water pool is communicated with the return water pipe, and the three-stage heat exchanger is arranged between the return water pipe and the circulating water pool.
10. The LNG cold energy cascade utilization device according to claim 1, characterized in that: The LNG cold energy cascade utilization device further includes a buffer tank, which is arranged on the gas trunk line and communicated with the cold source outlet of the three-stage heat exchanger, and is used to buffer the LNG gas; And / or, the LNG cold energy cascade utilization device also includes a four-stage heat exchanger and a gas branch, the LNG gas source is connected to the gas branch via a control valve, the gas branch transports fuel to the process production area, and the four-stage heat exchanger is arranged on the gas branch.