An external liquefaction device

Abstract

The utility model discloses an external liquefied device relates to low temperature liquid preparation technical field. The device includes raw material nitrogen compressor and cold box, is equipped with main heat exchanger, high temperature expander, low temperature expander, two pressure boosters and low temperature ice machine in cold box, and the raw material nitrogen compressor export is connected high temperature expander pressure boosters, first pressure booster cooler, main heat exchanger in proper order, after low temperature ice machine, return to main heat exchanger again, the main heat exchanger export is divided into two ways, one way is through high temperature expander expansion end, low temperature expander pressure boosters, second pressure booster cooler, low temperature expander expansion end etc. and returns to raw material nitrogen compressor entrance, and the other way outputs liquid nitrogen product, and the device cancels circulating nitrogen compressor, and low temperature expander expands and is normal pressure, reduces equipment pressure, improves refrigerating capacity, reduces investment, and the operation is more simple and safe.

Description

Technical Field

[0001] This utility model relates to the technical field of low-temperature liquid production, specifically to an external liquefaction device. Background Technology

[0002] In current industrial production, the technology of conventional external liquefaction for producing large quantities of liquid products has been widely used. Its processes (such as...) Figure 2 Specifically: First, the raw material nitrogen compressor plays a crucial role in initially pressurizing the nitrogen gas. After entering the raw material nitrogen compressor, the nitrogen gas undergoes three stages of compression, gradually increasing its pressure to 0.49 MPaA. This pressure increase lays the foundation for the subsequent liquefaction process. The nitrogen gas, after completing the three-stage compression, enters the circulating nitrogen compressor, which further pressurizes the nitrogen gas to meet the pressure requirements of subsequent processes. The pressurized nitrogen enters the final cooler for cooling, lowering its temperature. A portion of the nitrogen exiting the final cooler is extracted and enters the main heat exchanger. In the main heat exchanger, the nitrogen exchanges heat with the cryogenic fluid, significantly reducing its own temperature. This cooled nitrogen then enters the high-temperature expander for expansion. During expansion, the nitrogen performs work, reducing its internal energy and further lowering its temperature. The expanded nitrogen is then reheated and returned to the inlet of the circulating nitrogen compressor to continue the cycle. The remaining nitrogen gas enters the pressurization ends of the high-temperature and low-temperature expanders. At the pressurization ends, the nitrogen gas is continuously pressurized, further increasing its pressure. After secondary pressurization, the nitrogen gas is cooled by a cooler at the pressurization end to lower its temperature, preventing excessively high temperatures from adversely affecting subsequent equipment and processes. The cooled nitrogen gas then enters the main heat exchanger for further cooling; some of the cooled nitrogen gas, after reaching a certain temperature, enters the low-temperature expander for expansion. The expanded nitrogen gas returns to the inlet of the circulating nitrogen compressor, while the remainder continues to cool until it becomes a completely liquid, produced as a liquefied product. Problems with existing technology: Although existing conventional external liquefaction production technologies can meet production needs to a certain extent, they have revealed many problems in practical applications, affecting the economy and efficiency of production. In terms of equipment investment costs and land area, pressurizing nitrogen to the required pressure generally requires both a raw material compressor and a circulating nitrogen compressor, leading to an increase in the number of devices. This increase not only significantly raises equipment procurement costs but also necessitates larger spaces to house these devices, thus increasing the land area required. For example, in some large liquefaction plants, accommodating numerous compressors and related equipment necessitates the construction of large factory buildings, undoubtedly increasing construction and land use costs. In conventional technologies, since the inlet pressure of the circulating nitrogen compressor and the discharge pressure of the raw material nitrogen compressor are equal, the inlet pressure of the expansion end of the high and low temperature expander is relatively high in order to achieve a cooling balance. This results in high actual working pressures for the circulating nitrogen compressor, the high and low temperature expander, and the high-pressure plate type. The higher working pressure places higher demands on the materials and manufacturing processes of the equipment. The equipment needs to be manufactured using higher quality and more expensive materials to withstand the high-pressure environment, which further increases the investment cost of the equipment. The high-pressure environment also accelerates the wear and aging of the equipment, shortens its service life, and thus increases the maintenance and replacement costs. The high operational difficulty is also a major problem with existing technologies. Because the entire system involves multiple devices and complex processes, and the equipment operates under high pressure, it requires operators to possess higher levels of skill and experience. During actual operation, operators need to constantly monitor the operating parameters of each device, such as pressure, temperature, and flow rate, and make timely adjustments based on the actual situation. Improper operation can lead to equipment malfunctions or even safety accidents. For example, improper adjustment of the expander's air intake can cause the expander to run at overspeed, thereby damaging the equipment. Utility Model Content

[0003] The core objective of this invention is to provide an external liquefaction device that effectively addresses numerous problems existing in conventional external liquefaction production technologies. Through unique design and process optimization, this device can significantly reduce the discharge pressure of the circulating nitrogen compressor, thereby reducing the operating pressure of key equipment such as the high and low temperature expander and high-pressure platen compressor. This not only reduces the risks and losses associated with equipment operation under high pressure but also lowers the stringent requirements on equipment materials and manufacturing processes, thus reducing equipment investment costs. This device improves the unit cooling capacity of the expander by optimizing the gas expansion process. Higher cooling capacity means more gas can be liquefied with the same energy consumption, significantly improving production efficiency and economic benefits. This invention aims to make the equipment easy to operate, reducing the workload and skill requirements for operators, lowering the risk of equipment failures and safety accidents caused by improper operation, and providing a safer, more stable, and more efficient external liquefaction solution for industrial production.

[0004] This utility model discloses an external liquefaction device, aiming to solve the problems of high operating pressure, high investment cost, and high operational difficulty in existing technologies. The specific technical solution of the device is as follows: An external liquefaction device includes a raw material nitrogen compressor and a cold box. The cold box is equipped with a main heat exchanger, a high-temperature expander, a low-temperature expander, a first pressurization end cooler, a second pressurization end cooler, and a low-temperature ice machine.

[0005] The connection relationships of each component are as follows: The outlet of the raw material nitrogen compressor is connected to the inlet of the high-temperature expander.

[0006] The outlet of the high-temperature expander is connected to the inlet of the first pressure-boosting cooler.

[0007] The outlet of the first booster cooler is connected to the first inlet of the main heat exchanger.

[0008] The first outlet of the main heat exchanger is connected to the inlet of the cryogenic ice machine.

[0009] The outlet of the cryogenic ice machine is connected to the second inlet of the main heat exchanger.

[0010] The second outlet of the main heat exchanger is divided into two paths: The first path connects to the expansion end inlet of the high-temperature expander, and the second path is used to output liquid nitrogen products.

[0011] The expansion end outlet of the high-temperature expander is connected to the third inlet of the main heat exchanger.

[0012] The third outlet of the main heat exchanger is connected to the inlet of the pressure boosting end of the cryogenic expander.

[0013] The outlet of the cryogenic expander is connected to the inlet of the second pressurized cooler.

[0014] The outlet of the second booster cooler is connected to the fourth inlet of the main heat exchanger.

[0015] The fourth outlet of the main heat exchanger is connected to the expansion end inlet of the cryogenic expander.

[0016] The expansion end outlet of the cryogenic expander is connected to the fifth inlet of the main heat exchanger.

[0017] The fifth outlet of the main heat exchanger is connected to the inlet of the raw material nitrogen compressor.

[0018] As a preferred embodiment, both the high-temperature expander and the low-temperature expander include a pressurization end and an expansion end. The pressurization end is used to pressurize nitrogen, and the expansion end is used to expand and cool nitrogen.

[0019] As a preferred option, the main heat exchanger is a plate heat exchanger, which is used to achieve heat exchange between nitrogen gases.

[0020] As a preferred embodiment, both the first and second pressurization end coolers are shell-and-tube coolers used to cool the pressurized nitrogen gas.

[0021] As a preferred option, the raw material nitrogen compressor is a centrifugal compressor used to compress and pressurize nitrogen gas.

[0022] As a preferred option, the low-temperature ice machine is a screw-type refrigeration unit used for deep cooling of nitrogen.

[0023] As a preferred option, the outlet pressure of the raw material nitrogen compressor is 0.49 MPaA.

[0024] As a preferred option, the nitrogen pressure at the expansion end outlet of the cryogenic expander is atmospheric pressure.

[0025] In summary, this application includes the following beneficial technical effects: This invention, through the combined use of various components, can design the pressure of the cryogenic expander after expansion to be at atmospheric pressure. By reducing the discharge pressure of the raw material nitrogen compressor, the expansion ratio is increased, which significantly reduces the working pressure of the raw material nitrogen compressor, the high and low temperature expander, and the main heat exchanger, thereby increasing the unit cooling capacity of the expander and facilitating nitrogen liquefaction. By eliminating the use of the circulating nitrogen compressor, the operating cost of the device is reduced, and it is also convenient for staff to perform maintenance. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the novel liquefied nitrogen process of this application; Figure 2 This is a schematic diagram of a conventional liquefied nitrogen process.

[0027] Explanation of reference numerals in the attached figures: 1. Raw material nitrogen compressor; 2. Low temperature ice machine; 3. Main heat exchanger; 4. High temperature expander; 5. Low temperature expander; 6. First pressurization end cooler; 601. Second pressurization end cooler. Detailed Implementation

[0028] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0029] Reference Figure 1 This application discloses an external liquefaction device, including a raw material nitrogen compressor 1 and a cold box. The cold box is equipped with a main heat exchanger 3, a high-temperature expander 4, a low-temperature expander 5, a first pressurization end cooler 6, a second pressurization end cooler 601, and a low-temperature ice machine 2. The outlet of the raw material nitrogen compressor 1 is connected to the inlet of the high-temperature expander 4, the outlet of the high-temperature expander 4 is connected to the inlet of the first pressure-boosting cooler 6, the outlet of the first pressure-boosting cooler 6 is connected to the first inlet of the main heat exchanger 3, the first outlet of the main heat exchanger 3 is connected to the inlet of the low-temperature ice machine 2, and the outlet of the low-temperature ice machine 2 is connected to the second inlet of the main heat exchanger 3. The second outlet of the main heat exchanger 3 is divided into two paths. One path connects to the expansion end inlet of the high-temperature expander 4. The expansion end outlet of the high-temperature expander 4 connects to the third inlet of the main heat exchanger 3. The third outlet of the main heat exchanger 3 connects to the pressure boosting end inlet of the low-temperature expander 5. The pressure boosting end outlet of the low-temperature expander 5 connects to the inlet of the second pressure boosting end cooler 601. The outlet of the second pressure boosting end cooler 601 connects to the fourth inlet of the main heat exchanger 3. The fourth outlet of the main heat exchanger 3 connects to the expansion end inlet of the low-temperature expander 5. The expansion end outlet of the low-temperature expander 5 connects to the fifth inlet of the main heat exchanger 3. The fifth outlet of the main heat exchanger 3 connects to the inlet of the raw material nitrogen compressor 1. The outlet pressure of the main heat exchanger 3 is higher than the inlet pressure of the raw material nitrogen compressor 1, so it can enter without backflow. The same applies to the others.

[0030] Raw material nitrogen compressor 1: A centrifugal compressor is selected, with a designed outlet pressure of 0.49 MPaA and a flow rate determined according to actual production needs. It is used for the preliminary compression of nitrogen.

[0031] High-temperature expander 4 and low-temperature expander 5: Both adopt an integral structure with a pressure boosting end and an expansion end. The high-temperature expander 4 is used for expansion and refrigeration at higher temperatures, and the low-temperature expander 5 is used for expansion and refrigeration at lower temperatures. The expansion end outlet of the low-temperature expander 5 is designed to be at atmospheric pressure.

[0032] Main heat exchanger 3: A plate heat exchanger is selected, which has the characteristics of high heat transfer efficiency and compact structure, and can effectively realize heat exchange between nitrogen gases.

[0033] First booster end cooler 6 and second booster end cooler 601: Both are shell-and-tube coolers, using water or air as the cooling medium, to cool the pressurized nitrogen and reduce its temperature.

[0034] Low-temperature ice machine 2: A screw-type refrigeration unit is selected, which can provide a lower temperature to deeply cool the nitrogen gas, creating favorable conditions for the subsequent liquefaction process.

[0035] The installation of the equipment should follow relevant industrial equipment installation standards to ensure its stability and safety. All equipment is connected by pipes; the pipe material should be selected based on the operating temperature and pressure, generally stainless steel, to ensure good low-temperature performance and corrosion resistance.

[0036] The following points should be noted when connecting: Pipe connections should be airtight to prevent leaks, especially in low-temperature areas. Leaks can not only affect the efficiency of the equipment but also pose safety hazards.

[0037] Piping should be laid out reasonably, minimizing bends and valves to reduce resistance loss.

[0038] Pressure gauges, thermometers, and other monitoring instruments should be installed in appropriate locations to monitor the operating parameters of the device in real time.

[0039] The installation of cold boxes should include proper insulation measures to minimize cold loss.

[0040] Check that all equipment is in good working order and that all valves are in the correct open / closed positions.

[0041] Check whether the cooling system, lubrication system and other auxiliary systems are normal.

[0042] The device was purged with nitrogen to remove air and moisture from the system.

[0043] Set the operating parameters for each piece of equipment, such as the outlet pressure of the raw material nitrogen compressor 1 and the refrigeration temperature of the low-temperature ice machine 2.

[0044] Start the raw material nitrogen compressor 1 and gradually increase its outlet pressure to the set value.

[0045] Start the high-temperature expander 4 and the low-temperature expander 5 to gradually bring them into normal operation.

[0046] Turn on the low-temperature ice machine 2 to start its cooling operation.

[0047] Slowly open the relevant valves to allow nitrogen to flow through the device according to the set process.

[0048] Closely monitor the operating parameters of each piece of equipment, such as pressure, temperature, and flow rate, and make adjustments as needed.

[0049] During normal operation of the device, all operating parameters should be monitored regularly to ensure they remain within the set range.

[0050] Pay close attention to the operating status of each piece of equipment, noting any abnormal vibrations or noises.

[0051] Regularly check the cooling system to ensure it is functioning properly.

[0052] Adjust the opening of relevant valves appropriately based on the output of liquid nitrogen products to ensure product yield and quality.

[0053] When shutting down, gradually reduce the load on the raw material nitrogen compressor 1, close its outlet valve, and then stop the raw material nitrogen compressor 1.

[0054] Stop the high-temperature expander 4, the low-temperature expander 5, and the low-temperature ice machine 2 in sequence.

[0055] Close the relevant valves to cut off the nitrogen supply.

[0056] Perform necessary purging and maintenance on the equipment.

[0057] The implementation principle of the external liquefaction device in this application embodiment is as follows: Nitrogen initial compression and pressurization: The raw nitrogen first enters the raw nitrogen compressor 1 and is compressed to 0.49 MPaA, completing the initial pressurization. Then, it all enters the pressurization end of the high-temperature expander 4, where the pressure is further increased by the mechanical work of the pressurization end of the expander, providing a sufficient pressure basis for subsequent cooling and liquefaction.

[0058] Staged cooling and deep cooling: After being pressurized by the high-temperature expander 4, the nitrogen enters the first pressurization end cooler 6 to lower its temperature. The cooled nitrogen then enters the main heat exchanger 3 to exchange heat with the low-temperature nitrogen circulating in the unit, achieving initial cooling. Subsequently, the nitrogen enters the low-temperature ice machine 2, where the deep cooling effect of the refrigeration unit lowers the nitrogen temperature to a level closer to its liquefaction point. The nitrogen exiting the low-temperature ice machine 2 re-enters the main heat exchanger 3 to continue exchanging heat with the low-temperature circulating nitrogen, further reducing its temperature.

[0059] Expansion refrigeration and recycling: The nitrogen gas at the outlet of the main heat exchanger is divided into two paths: First path (circulating refrigeration path): Part of the nitrogen enters the expansion end of the high-temperature expander 4, and performs work through the adiabatic expansion process, resulting in a significant temperature reduction (achieving first-stage refrigeration); the expanded low-temperature nitrogen enters the main heat exchanger 3, serving as a cold source for heat exchange with nitrogen in other flow paths (reheating process), and then enters the pressurization end of the low-temperature expander 5 for further pressurization; the pressurized nitrogen is cooled by the second pressurization end cooler 601, and then re-enters the main heat exchanger 3 for further cooling, before entering the expansion end of the low-temperature expander 5 for secondary adiabatic expansion. Because the expansion end outlet is designed at atmospheric pressure, the expansion ratio is larger, resulting in a stronger refrigeration effect (achieving second-stage refrigeration); the nitrogen after secondary expansion re-enters the main heat exchanger 3 for reheating, and finally returns to the inlet of the raw material nitrogen compressor 1, completing the cycle.

[0060] Second path (product output path): The remaining nitrogen continues to be cooled in the main heat exchanger 3 until it reaches the liquefaction temperature, and is finally output as liquid nitrogen product.

[0061] Summary of core principles: This device eliminates the circulating nitrogen compressor and utilizes the "pressurization end-expansion end" of the high-temperature expander 4 and the low-temperature expander 5. The integrated design combines nitrogen pressurization and refrigeration processes. Simultaneously, the cryogenic expander 5 expands the nitrogen to atmospheric pressure. Expanding to atmospheric pressure means a greater pressure change, resulting in greater cooling capacity for a given volume of expanded gas compared to when the pressure is higher after expansion. Since the pressure after expansion is lower than that of a conventional expander, the system operating pressure is reduced while achieving efficient nitrogen liquefaction. The entire process utilizes the heat exchanger 3 to recover and utilize cooling capacity, reducing cooling loss and improving energy efficiency. The reduced operating pressure lowers the design and manufacturing requirements, allowing for the use of more economical materials and manufacturing processes. Furthermore, the elimination of the circulating nitrogen compressor reduces the number of devices, lowering initial investment and floor space requirements. The reduced operating pressure also enhances operational safety, mitigating the safety risks associated with high-pressure equipment. Additionally, the reduced number of devices and lower operating pressure simplify operation, reducing operator workload and complexity. Lower operating pressure also reduces wear and fatigue, extending equipment lifespan, improving overall system reliability, and reducing maintenance costs and downtime.

[0062] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change. Secondly: The accompanying drawings of the embodiments disclosed in this utility model only involve the structures involved in the embodiments disclosed in this utility model. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this utility model can be combined with each other. Finally: The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

[0063] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An external liquefaction device, characterized in that, It includes a raw material nitrogen compressor (1) and a cold box, wherein the cold box is equipped with a main heat exchanger (3), a high-temperature expander (4), a low-temperature expander (5), a first pressurizing end cooler (6), a second pressurizing end cooler (601), and a low-temperature ice machine (2). The outlet of the raw material nitrogen compressor (1) is connected to the inlet of the high-temperature expander (4), the outlet of the high-temperature expander (4) is connected to the inlet of the first pressure-boosting cooler (6), the outlet of the first pressure-boosting cooler (6) is connected to the first inlet of the main heat exchanger (3), the first outlet of the main heat exchanger (3) is connected to the inlet of the low-temperature ice machine (2), and the outlet of the low-temperature ice machine (2) is connected to the second inlet of the main heat exchanger (3).

2. The external liquefaction device according to claim 1, characterized in that: The second outlet of the main heat exchanger (3) is divided into two paths.

3. An external liquefaction device according to claim 2, characterized in that: One of the second outlets of the main heat exchanger (3) is used to output liquid nitrogen products, and the other is connected to the expansion end inlet of the high temperature expander (4). The expansion end outlet of the high temperature expander (4) is connected to the third inlet of the main heat exchanger (3).

4. An external liquefaction device according to claim 3, characterized in that: The third outlet of the main heat exchanger (3) is connected to the inlet of the pressure boosting end of the cryogenic expander (5), the outlet of the pressure boosting end of the cryogenic expander (5) is connected to the inlet of the second pressure boosting end cooler (601), and the outlet of the second pressure boosting end cooler (601) is connected to the fourth inlet of the main heat exchanger (3).

5. An external liquefaction device according to claim 4, characterized in that: The fourth outlet of the main heat exchanger (3) is connected to the expansion end inlet of the cryogenic expander (5), the expansion end outlet of the cryogenic expander (5) is connected to the fifth inlet of the main heat exchanger (3), and the fifth outlet of the main heat exchanger (3) is connected to the inlet of the raw material nitrogen compressor (1).

6. An external liquefaction device according to claim 5, characterized in that: The fifth outlet pressure of the main heat exchanger (3) is higher than the inlet pressure of the raw material nitrogen compressor (1).

7. An external liquefaction device according to claim 1, characterized in that: Both the high-temperature expander (4) and the low-temperature expander (5) include a pressurizing end and an expanding end, with the expanding end located inside the cold box.

8. An external liquefaction device according to claim 1, characterized in that: The outlet pressure of the raw material nitrogen compressor (1) is 0.49 MPaA.

9. An external liquefaction device according to claim 1, characterized in that: The nitrogen pressure at the expansion end outlet of the cryogenic expander (5) is atmospheric pressure.

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