Low-temperature rectification system and low-temperature rectification method
By employing multi-tower parallel operation and gradient cooling technology with refrigerants of different properties in the cryogenic distillation system, the problem of high production cost in cryogenic distillation was solved, and efficient, low-energy-consumption separation of light isotopes was achieved.
Patent Information
- Application Number
- CN202610375213.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-25
- Publication Date
- 2026-05-05
AI Technical Summary
Low-temperature distillation is used to separate light isotopes such as carbon (12C, 13C) and boron (10B, 11B). The production cost is high, mainly due to the difficulty of separation and the high energy cost. Traditional processes do not make full use of energy, resulting in large equipment and staggering energy consumption.
By employing multiple parallel upper and lower columns, combined with high-temperature circulation units, low-temperature circulation units, and thermal circulation units, and using gradient cooling of refrigerants with different properties, an intermediate reboiler is used to replace the traditional reboiler and condenser, forming a compact low-temperature distillation system that efficiently utilizes energy.
It reduces energy consumption of the cryogenic distillation system, improves separation efficiency and system operational flexibility, reduces equipment costs, and enhances separation capacity and production capacity.
Smart Images
Figure CN121972000A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of cryogenic distillation technology, and more specifically, to a cryogenic distillation system and a cryogenic distillation method. Background Technology
[0002] carbon( 12 C, 13 C), Boron ( 10 B, 11 Light isotopes (B) have irreplaceable value in fields such as nuclear medicine, semiconductor industry, and scientific research. Cryogenic distillation is one of the key technologies for separating these light isotopes. However, the biggest challenge of this process is its extremely high production cost, mainly due to two factors: (1) Difficult to separate: The relative volatility between light isotopes is extremely low (very close to 1). To achieve effective separation, a very high theoretical plate number and a very large reflux ratio are required, resulting in tall distillation column equipment and astonishing energy consumption.
[0003] (2) High energy cost: The distillation process needs to be carried out at extremely low temperatures (e.g., separation) 13 CO separation occurs at approximately -190°C. 10 At BF3 (around -100°C), the investment and operating costs of the large refrigeration units required to maintain such a low temperature environment constitute the majority of the production cost.
[0004] Therefore, it is necessary to provide a cryogenic distillation system that can reduce energy consumption. Summary of the Invention
[0005] To address the aforementioned shortcomings, this application provides a low-temperature distillation system and method that can reduce energy consumption.
[0006] This application is implemented as follows: In a first aspect, examples of this application provide a cryogenic distillation system, including a distillation unit, a high-temperature circulation unit, a low-temperature circulation unit, and a thermal circulation unit. The distillation unit includes a lower column and multiple upper columns arranged in parallel. The top of the lower column is connected to the multiple upper columns via an intermediate reboiler, and a bottom reboiler is provided at the bottom of the lower column. Each upper column is equipped with a top condenser.
[0007] The high-temperature circulation unit has a circulation channel for circulating high-temperature refrigerant, and the low-temperature circulation unit has a circulation channel for circulating low-temperature mixed refrigerant. The high-temperature refrigerant and the low-temperature mixed refrigerant exchange heat through an evaporator-condenser. The refrigerant outlet of the low-temperature circulation unit is connected to the low-temperature inlet of the condenser at the top of the tower.
[0008] The heat cycle unit includes heat exchanger one. The high-temperature outlet of the overhead condenser is connected to the low-temperature inlet of heat exchanger one. The high-temperature outlet of heat exchanger one is connected to the high-temperature inlet of the intermediate reboiler via compressor one. The low-temperature outlet of the intermediate reboiler is connected to the high-temperature inlet of the reboiler at the bottom of the column via compressor two. The low-temperature outlet of the reboiler at the bottom of the column is connected to the high-temperature inlet of heat exchanger one. The low-temperature outlet of heat exchanger one is connected to the refrigerant inlet of the low-temperature cycle unit.
[0009] In the above implementation process, compared with directly achieving a large-scale cooling capacity using a single refrigeration cycle unit, the cryogenic distillation system provided in this application utilizes the gradient cooling of refrigerants with different properties in the high-temperature cycle unit and the low-temperature cycle unit. This not only provides cooling capacity to the distillation unit more efficiently, but also reduces energy consumption due to its high refrigeration efficiency. Furthermore, in the cryogenic distillation system provided in this application, the high-temperature refrigerant collected from the high-temperature outlet of the column top condenser is transported to the thermal cycle unit. After preheating by heat exchanger one in the thermal cycle unit, it is transported to compressor one and compressed into a high-temperature, high-pressure refrigerant. This high-temperature, high-pressure refrigerant provides energy to the intermediate reboiler and exchanges heat with the material in the intermediate reboiler. After heat exchange, the refrigerant discharged from the intermediate reboiler is compressed and heated by compressor two to obtain a high-temperature medium, which is then transported to the reboiler at the bottom of the column to provide energy and exchange heat with the material there. It then returns to heat exchanger one to preheat the refrigerant discharged from the overhead condenser outlet, and then returns to the low-temperature circulation unit to exchange heat with the high-temperature circulation unit, forming a low-temperature refrigerant that provides cooling to the overhead condenser. This cycle continues. The thermal circulation unit can fully utilize the heat from the overhead condenser discharge to provide energy to the intermediate and reboiler refrigerants, reducing their energy consumption.
[0010] In addition, the distillation unit provided in this application employs multiple upper and lower columns arranged in parallel, with an intermediate reboiler installed between them. This intermediate reboiler replaces the traditional upper column reboiler and lower column condenser, eliminating some independent heat and cold sources. Energy utilization between the upper and lower columns is more efficient, and the parallel operation of multiple columns enhances separation efficiency and reduces system energy consumption. Furthermore, the organic integration of the distillation unit, cryogenic circulation unit, high-temperature circulation unit, and thermal circulation unit makes the cryogenic distillation system more compact, reducing the number of intermediate storage tanks, transfer pumps, and heat exchangers, thus lowering the cost of the cryogenic distillation system. The parallel operation of multiple upper columns enhances the system's operational flexibility and anti-interference capability.
[0011] In one alternative embodiment, the thermal cycle unit is further provided with a second heat exchanger. The low-temperature outlet of the intermediate reboiler may be selectively connected to the high-temperature inlet of the second heat exchanger, and the low-temperature outlet of the second heat exchanger is connected to the high-temperature inlet of the first heat exchanger.
[0012] In the above implementation process, heat exchanger 2 is set between the outlet of the intermediate reboiler and heat exchanger 1. When the reboiler in the column bottom does not require too much heat, part of the medium discharged from the outlet of the intermediate reboiler can be transported to heat exchanger 2 to preheat the remaining materials in the low-temperature distillation system and then flow back to heat exchanger 1 to mix with the medium discharged from the reboiler in the column bottom. After preheating the medium discharged from the condenser at the top of the column, it flows back to the low-temperature circulation unit.
[0013] In one optional embodiment, the high-temperature circulation unit includes a first compressor, a first condenser, and a first expansion device. The outlet of the first condenser is connected to the low-temperature inlet of the evaporative condenser via the first expansion device, the high-temperature outlet of the evaporative condenser is connected to the inlet of the first compressor, and the outlet of the first compressor is connected to the inlet of the first condenser, forming a circulation channel for the high-temperature refrigerant.
[0014] In the above process, the high-temperature refrigerant liquid condensed in the first condenser under high pressure can be transported to the first expansion device for pressure reduction, throttling, and cooling, forming a high-temperature refrigerant in a low-temperature, gas-liquid two-phase state. This high-temperature refrigerant enters from the low-temperature inlet of the evaporator-condenser, exchanges heat with the low-temperature mixed refrigerant gas entering from the high-temperature inlet of the evaporator-condenser, absorbs heat and vaporizes to form a high-temperature refrigerant gas, which is discharged from the high-temperature outlet of the evaporator-condenser, and then enters the first compressor to be compressed into a high-temperature, high-pressure refrigerant gas. The high-temperature, high-pressure refrigerant gas flows to the first condenser, exchanges heat with the refrigerant (such as air or water) at the first condenser, and condenses into a high-temperature refrigerant liquid, thus circulating in this manner.
[0015] In one alternative embodiment, the cryogenic cycle unit includes a first heat exchanger, a first gas-liquid separator, a second heat exchanger, a second expansion device, a third expansion device, and a second compressor connected by pipes.
[0016] The outlet of the second compressor is connected to the high-temperature inlet of the evaporator-condenser, and the low-temperature outlet of the evaporator-condenser is connected to the high-temperature inlet of the first heat exchanger. The high-temperature outlet of the first heat exchanger is connected to the inlet of the second compressor. The low-temperature outlet of the first heat exchanger is connected to the inlet of the first gas-liquid separator, and the gas outlet of the first gas-liquid separator is connected to the high-temperature inlet of the second heat exchanger. The liquid outlet of the first gas-liquid separator is connected to the low-temperature inlet of the second heat exchanger via a second expansion device. The high-temperature outlet of the second heat exchanger is connected to the low-temperature inlet of the first heat exchanger. The low-temperature outlet of the second heat exchanger is connected to the low-temperature inlet of the top condenser via a third expansion device. The high-temperature outlet of the top condenser is connected to the low-temperature inlet of heat exchanger one. The low-temperature outlet of heat exchanger one is connected to the low-temperature inlet of the second heat exchanger.
[0017] In the above-described process, the cryogenic mixed refrigerant includes at least two refrigerants with different evaporation temperatures. In the cryogenic cycle unit, the cryogenic mixed refrigerant gas discharged from the cryogenic outlet of the evaporator-condenser enters through the high-temperature inlet of the first heat exchanger, exchanging heat with the first working fluid entering from the cryogenic inlet of the first heat exchanger, absorbing cooling energy to form a first gas-liquid mixture. The first gas-liquid mixture flows to the first gas-liquid separator for gas-liquid separation. The first refrigerant gas discharged from the outlet of the first gas-liquid separator flows into the high-temperature inlet of the second heat exchanger, while the second refrigerant liquid discharged from the liquid outlet of the first gas-liquid separator flows into the cryogenic inlet of the second heat exchanger after being depressurized and cooled by the second expansion device. At this point, the first refrigerant gas absorbs the cooling energy of the second refrigerant, then exits from the cryogenic outlet of the second heat exchanger, and is then depressurized and cooled by the third expansion device before entering the top condenser through the inlet. The first refrigerant at the top condenser absorbs heat from the top layer of material and vaporizes, forming a high-temperature first refrigerant gas. The first refrigerant gas, in a high-temperature state, exits from the condenser outlet at the top of the column. After preheating at one heat exchanger, it flows into compressor one, where it is compressed into a high-temperature, high-pressure first refrigerant gas. This high-temperature, high-pressure first refrigerant gas flows to the intermediate reboiler, providing energy to it, and then exits from the intermediate reboiler outlet. The first refrigerant exiting the intermediate reboiler outlet is then compressed into a high-temperature, high-pressure state by compressor two, flowing to the reboiler at the bottom of the column, providing energy to it, and then exiting from the reboiler. It flows back to heat exchanger one, where it preheats the first refrigerant gas exiting from the condenser at the top of the column. Then, it flows back into the second heat exchanger through its low-temperature inlet, mixing with the second refrigerant, which also enters through its low-temperature inlet, to form the second working fluid. The second working fluid exchanges heat with the first refrigerant gas exiting the first gas-liquid separator at the second heat exchanger, absorbing heat, and then exits from the high-temperature outlet of the second heat exchanger. The second working fluid discharged from the high-temperature outlet of the second heat exchanger forms the first working fluid. The first working fluid enters through the low-temperature inlet of the first heat exchanger and exchanges heat with the low-temperature mixed refrigerant gas entering through the high-temperature inlet of the first heat exchanger, absorbing heat, and then exits through the high-temperature outlet of the first heat exchanger. The low-temperature mixed refrigerant exiting through the high-temperature outlet of the first heat exchanger is in a high-temperature, low-pressure state. This high-temperature, low-pressure low-temperature mixed refrigerant is sent to the second compressor and compressed into a high-temperature, high-pressure low-temperature mixed refrigerant gas. Then, this high-temperature, high-pressure low-temperature mixed refrigerant gas enters the evaporator-condenser through the high-temperature inlet, exchanges heat with the high-temperature refrigerant entering through the low-temperature inlet of the evaporator-condenser, absorbing cooling capacity, and then exits through the low-temperature outlet of the evaporator-condenser, thus completing the cycle.
[0018] In one optional embodiment, the cryogenic circulation unit further includes a second gas-liquid separator, a fourth expansion device, and a third heat exchanger connected by pipelines. The cryogenic outlet of the second heat exchanger is connected to the inlet of the second gas-liquid separator, the gas outlet of the second gas-liquid separator is connected to the high-temperature inlet of the third heat exchanger, and the liquid outlet of the second gas-liquid separator is connected to the cryogenic inlet of the third heat exchanger via the fourth expansion device. The cryogenic outlet of the third heat exchanger is connected to the cryogenic inlet of the top condenser via the second expansion device. The high-temperature outlet of the top condenser is connected to the cryogenic inlet of the first heat exchanger, and the cryogenic outlet of the first heat exchanger is connected to the cryogenic inlet of the third heat exchanger. The high-temperature outlet of the third heat exchanger is connected to the cryogenic inlet of the second heat exchanger.
[0019] In the above-described process, a second gas-liquid separator, a fourth expansion device, and a third heat exchanger are installed between the second heat exchanger and the third expansion device. This allows for a second gas-liquid separation of the refrigerant discharged from the low-temperature outlet of the second heat exchanger. The first refrigerant gas is discharged from the outlet of the second gas-liquid separator and transported to the high-temperature inlet of the third heat exchanger, while the third refrigerant liquid is discharged from the outlet of the second gas-liquid separator. After being throttled, depressurized, and cooled by the fourth expansion device, it is transported to the low-temperature inlet of the third heat exchanger, where it absorbs heat and cools down. Then, the first refrigerant liquid discharged from the low-temperature outlet of the third heat exchanger is transported to the third expansion device for throttling, depressurization, and cooling, before being delivered to the top condenser. Using this low-temperature distillation apparatus, the temperature gradient of the first refrigerant can be further increased, allowing for the delivery of a lower-capacity first refrigerant to the top condenser.
[0020] The high-temperature and low-temperature circulation units of this application can not only provide cooling capacity to the top condenser more efficiently and accurately, but also achieve low-temperature refrigeration with a large range by only setting up two sets of refrigeration units. During the cooling process, there is no need to compress the refrigerant multiple times with a large compression ratio, which can reduce energy consumption.
[0021] In one optional embodiment, the cryogenic cycle unit further includes a regenerator with a heat exchange channel. The high-temperature outlet of the first heat exchanger is connected to the inlet of the second compressor via the regenerator. The cryogenic distillation system also includes a feed delivery pipe that passes through the heat exchange channel and connects to the feed inlet of the upper column.
[0022] In the above implementation process, a regenerator is set between the high-temperature outlet of the first heat exchanger and the second compressor. The high-temperature gas discharged from the high-temperature outlet of the first heat exchanger can be used to preheat the raw material in the upper tower raw material conveying pipe. The preheated raw material is then conveyed to the upper tower to recover heat and further reduce energy consumption.
[0023] In one alternative embodiment, the cryogenic distillation system further includes an emergency unit, which includes a second condenser. The cryogenic outlet of the heat exchanger is optionally connected to the inlet of the second condenser, and the outlet of the second condenser is optionally connected to the cryogenic inlet of the top condenser.
[0024] In the above implementation process, an emergency unit is set up in the cryogenic distillation system. When the high-temperature circulation unit or the cryogenic circulation unit fails, the cryogenic mixed refrigerant in a high-temperature and high-pressure state discharged from the heat exchanger can be directly delivered to the second condenser. The cryogenic mixed refrigerant is cooled by a refrigerant (such as liquid nitrogen or liquid oxygen) and then delivered to the top condenser to condense the top product, which helps to stabilize the operation of the cryogenic distillation system.
[0025] In one alternative embodiment, the distillation apparatus includes six upper columns arranged in parallel, each upper column having a feed inlet. The refrigerant outlet of the cryogenic circulation unit is provided with a main pipe and six branch pipes connected to the main pipe, each of the six branch pipes corresponding to the cryogenic inlet of one of the six top condensers.
[0026] In the above implementation process, the "one-down-six-up" coupling structure can significantly enhance the separation capability of the low-temperature distillation system, effectively increase the isotope product production capacity per unit time, and further reduce the production energy consumption of the low-temperature distillation system.
[0027] In one alternative implementation, the main pipe is equipped with a circulation pump.
[0028] In the above implementation process, a circulation pump is installed at the pipeline connecting the refrigerant outlet of the low-temperature circulation unit and the low-temperature inlet of the tower top condenser, which can deliver the refrigerant in a low-temperature and low-pressure state to multiple tower top condensers one by one.
[0029] In one alternative implementation, the reboiler is provided with a discharge port.
[0030] In the above process, a discharge port is set in the reboiler of the column bottom so that the bottom product after distillation separation can be discharged from the reboiler.
[0031] In a second aspect, this application provides a method for performing cryogenic distillation using the cryogenic distillation system provided in the first aspect, comprising: The raw materials are delivered to the feed inlet of each of the upper towers.
[0032] High-temperature refrigerant is injected into the high-temperature circulation unit, and low-temperature mixed refrigerant is injected into the low-temperature circulation unit. This allows the low-temperature mixed refrigerant to exchange heat with the high-temperature refrigerant through the evaporator-condenser and absorb cold energy. The refrigerant is then delivered to the top condenser of each upper column through the refrigerant outlet of the low-temperature circulation unit.
[0033] The low-temperature mixed refrigerant discharged from the high-temperature outlet of the condenser at the top of the tower is transported to heat exchanger one for heat exchange and heat absorption, and then compressed by compressor one before being transported to the intermediate reboiler to provide heat to the intermediate reboiler.
[0034] The low-temperature mixed refrigerant discharged from the low-temperature outlet of the intermediate reboiler is sent to compressor two for compression, and then sent to the reboiler at the bottom of the column to provide heat to the reboiler.
[0035] The cryogenic refrigerant discharged from the cryogenic outlet of the reboiler in the tower is returned to the cryogenic circulation unit through the first heat exchanger.
[0036] In the above-described process, during cryogenic distillation, the raw material is fed to the feed inlet of each upper column, utilizing multiple upper columns and one lower column for cryogenic distillation. Furthermore, the cryogenic mixed refrigerant, cooled by the high-temperature refrigerant, is fed to the top condenser of each upper column. After heat exchange with the overhead material, the cryogenic mixed refrigerant is sequentially passed through heat exchanger one and compressor one before being sent to the intermediate reboiler. Utilizing this heat reduces the energy consumption of the intermediate reboiler. The cryogenic mixed refrigerant discharged from the intermediate reboiler is then compressed by compressor two and sent to the bottom reboiler, further reducing the energy consumption of the bottom reboiler. The cryogenic mixed refrigerant discharged from the bottom reboiler is then returned to the cryogenic circulation unit via heat exchanger one, achieving the circulation of the cryogenic mixed refrigerant. Attached Figure Description
[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.
[0038] Figure 1 This is a plan view of the cryogenic distillation system provided in the embodiments of this application; Figure 2 This is a schematic diagram showing the connection between the low-temperature cycling unit and the high-temperature cycling unit provided in an embodiment of this application; Figure 3 This is a connection diagram of the control unit provided in an embodiment of this application.
[0039] Icons: 100-Cryogenic Distillation System; 1-Distillation Unit; 11-Top Condenser; 12-Feed Feed Pipe; 13-Upper Column; 14-Lower Column; 15-Intermediate Reboiler; 16-Bottom Reboiler; 2-High Temperature Circulation Unit; 21-First Compressor; 22-First Condenser; 23-First Expansion Unit; 3-Cryogenic Circulation Unit; 31-First Heat Exchanger; 32-First Gas-Liquid Separator; 33-Second Heat Exchanger; 34-Second Expansion Unit; 35-Third Expansion Unit; 36-Second... Compressor; 37-Second gas-liquid separator; 38-Fourth expansion device; 39-Third heat exchanger; 40-Fifth expansion device; 41-Regenerator; 4-Evaporator-condenser; 5-Emergency unit; 51-Second condenser; 6-Control unit; 61-Controller; 62-Flow control valve; 63-Temperature sensor; 64-Pressure control valve; 65-Transfer pump; 66-Buffer tank; 7-Heat circulation unit; 71-Heat exchanger one; 72-Compressor one; 73-Compressor two; 74-Heat exchanger two. Detailed Implementation
[0040] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.
[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having”, and any variations thereof, in the specification and the foregoing description of the drawings are intended to cover non-exclusive inclusion.
[0042] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.
[0043] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0044] Cryogenic distillation is one of the key technologies for separating light isotopes. However, the biggest challenge facing this process is its extremely high production cost, which stems primarily from two aspects: (1) Difficult to separate: The relative volatility between light isotopes is extremely low (very close to 1). To achieve effective separation, a very high theoretical plate number and a very large reflux ratio are required, resulting in tall distillation column equipment and astonishing energy consumption.
[0045] (2) High energy cost: The distillation process needs to be carried out at extremely low temperatures (e.g., separation) 13 CO separation occurs at approximately -190°C. 10 At BF3 (around -100°C), the investment and operating costs of the large refrigeration units required to maintain such a low temperature environment constitute the majority of the production cost.
[0046] For temperatures where separation is challenging, a dual-tower or multi-tower series process is typically employed to improve efficiency. However, in traditional series methods, the towers are connected only by material streams, resulting in inefficient energy utilization. Furthermore, the condensers and reboilers of multiple distillation towers usually require independent cold and heat sources, leading to significant energy waste.
[0047] Therefore, this application further improves the cryogenic distillation system, thereby reducing the energy consumption of the cryogenic distillation system to a certain extent. To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.
[0048] Please see Figure 1 The cryogenic distillation system 100 provided in this application embodiment includes a distillation unit 1, a high-temperature circulation unit 2, a low-temperature circulation unit 3, and a thermal circulation unit 7.
[0049] Please continue reading for more details. Figure 1 The distillation unit 1 includes a lower column 14 and multiple upper columns 13 arranged in parallel. The top of the lower column 14 is connected to the multiple upper columns 13 through an intermediate reboiler 15, and a bottom reboiler 16 is provided at the bottom of the lower column 14. Each upper column 13 is provided with a top condenser 11.
[0050] The high-temperature circulation unit 2 is equipped with a circulation channel for circulating high-temperature refrigerant, and the low-temperature circulation unit 3 is equipped with a circulation channel for circulating low-temperature mixed refrigerant. The high-temperature refrigerant absorbs heat from the low-temperature mixed refrigerant. The refrigerant outlet of the low-temperature circulation unit 3 is connected to the low-temperature inlet of the top condenser 11.
[0051] The heat cycle unit 7 includes a heat exchanger 71. The high-temperature outlet of the top condenser is connected to the low-temperature inlet of the heat exchanger 71. The high-temperature outlet of the heat exchanger 71 is connected to the high-temperature inlet of the intermediate reboiler 15 via a compressor 72. The low-temperature outlet of the intermediate reboiler 15 is connected to the high-temperature inlet of the bottom reboiler 16 via a compressor 73. The low-temperature outlet of the bottom reboiler 16 is connected to the high-temperature inlet of the heat exchanger 71. The low-temperature outlet of the heat exchanger 71 is connected to the refrigerant inlet of the low-temperature cycle unit.
[0052] In the cryogenic distillation system 100 provided in this application, the refrigerant in a high-temperature state collected from the high-temperature outlet of the overhead condenser 11 is transported to the thermal circulation unit 7. After preheating by heat exchanger 71 in the thermal circulation unit 7, it is transported to compressor 72, where it is compressed into a high-temperature, high-pressure refrigerant. This high-temperature, high-pressure refrigerant provides energy to the intermediate reboiler 15, heating the material in the intermediate reboiler 15. After heating, it is discharged from the intermediate reboiler 15 and then compressed and heated by compressor 73 to obtain a high-temperature medium, which is transported to the bottom reboiler 16 to provide energy to the bottom reboiler 16, heating the material there. Then, it returns to heat exchanger 71 to preheat the refrigerant discharged from the outlet of the overhead condenser 11, and then returns to the cryogenic circulation unit 3 to exchange heat with the high-temperature circulation unit 2, forming a cryogenic refrigerant that provides cooling to the overhead condenser 11, thus completing the cycle. The heat cycle unit 7 can make full use of the heat discharged from the top condenser 11 to provide energy for the intermediate reboiler 15 and the bottom reboiler 16, thereby reducing the energy consumption of the intermediate reboiler 15 and the bottom reboiler 16.
[0053] If a single refrigeration cycle unit is used to directly achieve a large-scale cooling capacity, it typically requires a multi-stage compressor and an increased compression ratio, and it is difficult to select a suitable refrigerant. In contrast, the cryogenic distillation system 100 provided in this application utilizes a gradient cooling mechanism with refrigerants of different properties in the high-temperature cycle unit 2 and the low-temperature cycle unit 3. This not only provides cooling capacity to the distillation unit 1 more efficiently, but also reduces further energy consumption due to its high cooling efficiency.
[0054] In the distillation unit 1 provided in this application, multiple upper columns 13 and lower columns 14 are arranged in parallel. An intermediate reboiler 15 is set between the upper columns 13 and lower columns 14. The intermediate reboiler 15 replaces the traditional reboiler of the upper column 13 and the condenser of the lower column 14, eliminating some independent heat sources and some cold sources. The energy utilization between the upper columns 13 and lower columns 14 is more efficient, and the parallel operation of multiple columns enhances the separation efficiency and reduces the system energy consumption.
[0055] In the cryogenic distillation system 100 provided in this application embodiment, the organic combination of distillation unit 1, cryogenic circulation unit 3, high-temperature circulation unit 2, and thermal circulation unit 7 enables the cryogenic distillation system 100 to have a more compact structure, reducing a large number of intermediate storage tanks, transfer pumps, and heat exchangers, thereby lowering the cost of the cryogenic distillation system 100. The parallel operation of multiple upper columns 13 enhances the system's operational flexibility and anti-interference capability.
[0056] In some embodiments, please continue reading Figure 1 The distillation unit 1 includes six parallel upper columns 13, each with a feed inlet. The refrigerant outlet of the cryogenic circulation unit 3 is provided with a main pipe and six branch pipes connected to the main pipe. The six branch pipes are connected one-to-one to the cryogenic inlets of the six top condensers 11.
[0057] As an example, the intermediate reboiler 15 has six feed inlets at its top, and the bottoms of the six upper columns 13 are connected to the intermediate reboiler 15 through these six feed inlets. Each upper column 13 has a feed inlet located at the midpoint of its height. The distillation unit 1 is equipped with a feed delivery pipe 12, which has six delivery branches, each corresponding to one of the feed inlets of the six upper columns 13. The intermediate reboiler 15 has a discharge outlet at its bottom, and the top of the lower column 14 is connected to the discharge outlet at the bottom of the intermediate reboiler 15. The bottom of the lower column 14 is connected to the bottom reboiler 16, which also has a discharge outlet at its bottom.
[0058] During the operation of distillation unit 1, the raw material is conveyed one-to-one from the raw material conveying pipe 12 to the six upper columns 13. The condensate in the upper columns 13 flows downward to the intermediate reboiler 15, where it is heated. Part of the condensate absorbs heat and evaporates, flowing upward from the intermediate reboiler 15 back into the upper column 13, and is then collected from the top of the upper column 13 and condensed by the top condenser. Part of the condensate in the intermediate reboiler 15 continues to flow downward to the bottom reboiler 16 of the lower column 14, where it is heated, evaporates to form a gas phase, and flows upward to the intermediate reboiler 15. Because the heat at the intermediate reboiler 15 is lower than that at the bottom reboiler 16, some of the gas phase flowing upward to the intermediate reboiler 15 will condense and flow back to the bottom reboiler 16, while some of the gas phase continues to flow upward to the upper column 13. By adopting a "six-upper-one-lower" coupling structure, the separation capability of the cryogenic distillation system can be significantly enhanced, the isotope product production capacity per unit time can be effectively increased, and the production energy consumption of the cryogenic distillation system can be further reduced.
[0059] Furthermore, in some embodiments, please refer to Figure 2The high-temperature circulation unit 2 includes a first compressor 21, a first condenser 22, and a first expansion device 23 connected by pipes. The low-temperature circulation unit 3 includes a first heat exchanger 31, a first gas-liquid separator 32, a second heat exchanger 33, a second expansion device 34, a third expansion device 35, and a second compressor 36 connected by pipes.
[0060] Please continue reading for more details. Figure 2 The outlet of the first condenser 22 is connected to the low-temperature inlet of the evaporator-condenser 4 via the first expansion device 23. The high-temperature outlet of the evaporator-condenser 4 is connected to the inlet of the first compressor 21. The outlet of the second compressor 36 is connected to the high-temperature inlet of the evaporator-condenser 4, and the low-temperature outlet of the evaporator-condenser 4 is connected to the high-temperature inlet of the first heat exchanger 31. The high-temperature outlet of the first heat exchanger 31 is connected to the inlet of the second compressor 36. The low-temperature outlet of the first heat exchanger 31 is connected to the inlet of the first gas-liquid separator 32. The gas outlet of the first gas-liquid separator 32 is connected to the high-temperature inlet of the second heat exchanger 33, and the liquid outlet of the first gas-liquid separator 32 is connected to the low-temperature inlet of the second heat exchanger 33 via the second expansion device 34. The high-temperature outlet of the second heat exchanger 33 is connected to the low-temperature inlet of the first heat exchanger 31. The low-temperature outlet of the second heat exchanger 33 is connected to the low-temperature inlet of the top condenser 11 via the third expansion device 35. Please refer to... Figure 1 The high-temperature outlet of the top condenser 11 is connected to the low-temperature inlet of the heat exchanger 71.
[0061] In this application, "high-temperature refrigerant" and "low-temperature refrigerant" refer to the difference in evaporation temperature of the refrigerant. That is, the evaporation temperature of the high-temperature refrigerant is higher than that of the low-temperature refrigerant. Generally, the evaporation temperature of the refrigerant directly determines the cooling effect. As an example, a high-temperature refrigerant L1 is used in the high-temperature cycle, and a low-temperature mixed refrigerant L2 is used in the low-temperature cycle. The evaporation temperature of the high-temperature refrigerant L1 is higher than that of the low-temperature mixed refrigerant L2. When the low-temperature mixed refrigerant includes a first refrigerant L21 and a second refrigerant L22 with an evaporation temperature higher than that of the first refrigerant L1, the cycle process is as follows: High-temperature refrigerant L1 gas is compressed by the first compressor 21 to form high-temperature, high-pressure refrigerant L1 gas. This high-temperature, high-pressure refrigerant L1 gas is then condensed by the first condenser 22 to form low-temperature, high-pressure refrigerant L1 gas. After being throttled and depressurized by the first expansion device 23, the low-temperature, high-pressure refrigerant L1 gas is in a low-pressure, two-phase state. The high-temperature refrigerant L1 gas discharged from the outlet of the first expansion device 23 is transported to the low-temperature inlet of the evaporator-condenser 4, where it exchanges heat with the low-temperature mixed refrigerant gas L2 flowing into the evaporator-condenser 4 from the high-temperature inlet. It absorbs heat from the low-temperature mixed refrigerant L2 gas, re-evaporates, and becomes low-temperature high-temperature refrigerant L1 gas again, flowing back into the first compressor 21, thus completing the cycle.
[0062] The second compressor 36 compresses the low-temperature mixed refrigerant L2 into a high-temperature, high-pressure state of low-temperature mixed refrigerant L2 gas. The low-temperature mixed refrigerant L2 gas flows into the high-temperature inlet of the evaporator-condenser 4, exchanges heat with the high-temperature refrigerant L1 at the evaporator-condenser 4, absorbs cold energy, and is discharged from the low-temperature outlet of the evaporator-condenser 4 after the temperature has decreased, thus achieving the first cooling of the low-temperature mixed refrigerant L2.
[0063] The temperature of the low-temperature mixed refrigerant L2 gas discharged from the low-temperature outlet of the evaporator-condenser 4 is recorded as the first temperature. The low-temperature mixed refrigerant L2 at the first temperature flows into the high-temperature inlet of the first heat exchanger 31, where it exchanges heat with the first working fluid, absorbs cold energy, and achieves a second cooling of the low-temperature mixed refrigerant L2. Since the evaporation temperature of the second refrigerant L22 in the low-temperature mixed refrigerant L2 gas is higher than that of the first refrigerant L21, the second refrigerant L22 will condense first, forming the second refrigerant L2 liquid, while the first refrigerant L21 remains in a gaseous state.
[0064] The temperature of the first gas-liquid mixture discharged from the low-temperature outlet of the first heat exchanger 31 is denoted as the second temperature. The second temperature is lower than the first temperature but higher than the evaporation temperature of the first refrigerant L21. The first gas-liquid mixture enters the first gas-liquid separator 32, where the first refrigerant L21 gas and the second refrigerant L22 liquid are separated. After the second refrigerant L22 liquid is throttled, depressurized, and cooled by the second expansion device 34, it forms a second refrigerant L22 in a gas-liquid two-phase state at the third temperature. It can be understood that the third temperature is lower than the second temperature. The first refrigerant L21 gas at the second temperature flows into the high-temperature inlet of the second heat exchanger 33, where it exchanges heat with the second working fluid. The first refrigerant L21 with a lower temperature is discharged from the low-temperature outlet of the second heat exchanger 33 (denoted as the fourth temperature), and the first working fluid with a higher temperature is discharged from the high-temperature outlet of the second heat exchanger 33 (denoted as the fifth temperature), thus achieving the third cooling of the first refrigerant L21. The first refrigerant L21 at the fourth temperature undergoes throttling, depressurization, and cooling (fourth cooling) in the third expansion device 35 before flowing into the top condenser 11. At the top condenser 11, the first refrigerant L21 exchanges heat with the top layer of material, absorbing heat, and is discharged from the top condenser 11 as a heated first refrigerant L2 gas (referred to as the sixth temperature). The sixth temperature is approximately maintained at the evaporation temperature of the first refrigerant L2.
[0065] The first refrigerant gas at temperature 6 enters the low-temperature inlet of heat exchanger 71, where it exchanges heat with the first refrigerant gas (temperature 8) entering from the high-temperature inlet of heat exchanger 71. The first refrigerant gas at temperature 9 is then discharged from the high-temperature outlet of heat exchanger 71. The first refrigerant gas at temperature 9 is compressed by compressor 72 into a high-temperature, high-pressure state (temperature 10). The first refrigerant gas at temperature 10 flows to intermediate reboiler 15 to heat the material, and the first refrigerant gas at temperature 11 is discharged from the low-temperature outlet of intermediate reboiler 15. It is understood that the 11th temperature is lower than the 10th temperature. The first refrigerant gas at temperature 11 flows to compressor 73 for further compression and heating, forming the first refrigerant gas at temperature 12. It is understood that the 12th temperature is higher than the 10th temperature. The first refrigerant gas at temperature 12 flows into reboiler 16 at the bottom of the column, where it heats the material, and the first refrigerant gas at temperature 8 is discharged from reboiler 16 at the bottom of the column. The first refrigerant gas at temperature eight flows into the high-temperature inlet of heat exchanger 71, exchanges heat with the first refrigerant gas at temperature six, and discharges the first refrigerant gas at temperature thirteen. Temperature eight is higher than temperature six. Temperature thirteen is lower than temperature six.
[0066] The first refrigerant L21 at the thirteenth temperature and the first refrigerant L22 at the third temperature mix to form the second working fluid at the seventh temperature. This fluid flows into the low-temperature inlet of the second heat exchanger 33 to cool the first refrigerant L22 gas at the second temperature. The seventh temperature is lower than the second temperature.
[0067] After heat exchange at the second heat exchanger 33, the second working fluid, now at a higher temperature (fifth temperature), is discharged from the high-temperature outlet of the second heat exchanger 33. It is understood that the fifth temperature is lower than the second temperature, which is lower than the first temperature. Therefore, the first working fluid can cool the low-temperature mixed refrigerant L2 gas at the first temperature at the first heat exchanger 31. After heat exchange at the first heat exchanger 31, the first working fluid discharges the high-temperature, low-pressure low-temperature mixed refrigerant L2 gas from the high-temperature outlet of the first heat exchanger 31. The high-temperature, low-pressure low-temperature mixed refrigerant L2 gas is compressed by the second compressor 36 into a high-temperature, high-pressure low-temperature mixed refrigerant L2 gas, which is then transported to the high-temperature inlet of the evaporator-condenser 4, thus completing the cycle.
[0068] Furthermore, in some embodiments, please continue to refer to Figure 1 The heat circulation unit 7 is also equipped with a second heat exchanger 74. The low-temperature outlet of the intermediate reboiler 15 can be selectively connected to the high-temperature inlet of the second heat exchanger 74, and the low-temperature outlet of the second heat exchanger 74 is connected to the high-temperature inlet of the first heat exchanger 71.
[0069] A second heat exchanger 74 is installed between the outlet of the intermediate reboiler 15 and the first heat exchanger 71. When the reboiler 16 does not require excessive heat, a portion of the medium discharged from the outlet of the intermediate reboiler 15 can be transferred to the second heat exchanger 74 to preheat the remaining material in the cryogenic distillation system 100 before being returned to the first heat exchanger 71. There, it mixes with the medium discharged from the reboiler 16, preheats the medium discharged from the overhead condenser 11, and then returns it to the cryogenic circulation unit 3. Alternatively, the second heat exchanger 74 may not be installed.
[0070] Furthermore, in some embodiments, please continue to refer to Figure 2 The low-temperature circulation unit 3 also includes a second gas-liquid separator 37, a fourth expansion device 38, and a third heat exchanger 39 connected by pipes. The low-temperature outlet of the second heat exchanger 33 is connected to the inlet of the second gas-liquid separator 37, the gas outlet of the second gas-liquid separator 37 is connected to the high-temperature inlet of the third heat exchanger 39, and the liquid outlet of the second gas-liquid separator 37 is connected to the low-temperature inlet of the third heat exchanger 39 via the fourth expansion device 38. The low-temperature outlet of the third heat exchanger 39 is connected to the low-temperature inlet of the top condenser 11 via the second expansion device 34. The low-temperature outlet of heat exchanger 71 is connected to the low-temperature inlet of the third heat exchanger 39, and the high-temperature outlet of the third heat exchanger 39 is connected to the low-temperature inlet of the second heat exchanger 33.
[0071] In this way, three low-temperature refrigerants with different evaporation temperatures can be mixed to form a mixed low-temperature refrigerant. The refrigerant with the higher evaporation temperature is condensed and separated in sequence for throttling and cooling. It then exchanges heat with the refrigerant with the lower evaporation temperature at the heat exchanger, achieving a gradient cooling of the low-evaporation-temperature refrigerant. The energy consumption of the heat exchanger and expansion device is low, thus reducing the overall energy consumption of the low-temperature distillation system 100 and also contributing to the precise control of the refrigeration temperature.
[0072] To further precisely control the refrigeration temperature at the top condenser 11, in some embodiments, please refer to [the relevant documentation / reference needed]. Figure 2 The cryogenic cycle unit 3 also includes a fifth expansion device 40. The inlet of the fifth expansion device 40 is optionally connected to the outlet of the second compressor 36, and the outlet of the fifth expansion device 40 is connected to the cryogenic inlet of the overhead condenser 11. When the temperature at the overhead condenser 11 is too low, the opening of the fifth expansion device 40 can be controlled to supply an appropriate amount of cryogenic mixed refrigerant L2 at a high temperature to the overhead condenser 11, thereby increasing the temperature.
[0073] As an example, a check valve can be installed in the pipeline between the outlet of the fifth expansion unit 40 and the inlet of the top condenser 11.
[0074] To further precisely control the refrigeration temperature at the top condenser 11, in some embodiments, please refer to... Figure 3 ( Figure 3 The thermal cycle unit 7 is omitted. A buffer tank 66 is also provided between the outlet 35 of the third expansion unit and the inlet of the top condenser 11. The cryogenic distillation system 100 is also provided with a control unit 6. The control unit 6 includes a controller 61, a conveying device, a control device, and a temperature sensor 63 installed in the buffer tank 66. The conveying device includes a conveying pump 65 and a flow control valve 62 installed in the pipeline connecting the outlet of the buffer tank 66 and the cryogenic inlet of the top condenser 11. The control device includes a pressure control valve 64 installed in the pipeline connecting the cryogenic inlet of the heat exchanger 71 and the high-temperature outlet of the top condenser 11. The temperature sensor 63, the conveying pump 65, the flow control valve 62, and the pressure control valve 64 are all signal-connected to the controller 61.
[0075] The controller 61 is equipped with at least the following function: when the temperature sensor 63 detects that the temperature at the top of the upper column 13 is higher than the set value, the flow rate of the flow control valve 62 is increased; conversely, the flow rate of the flow control valve 62 is decreased.
[0076] As an example, the flow control valve 62 can be a flow meter or a solenoid valve.
[0077] Furthermore, the upper tower 13 needs to be controlled at a suitable tower pressure. The controller 61 can adjust the opening of the pressure control valve 64 according to the detection results of the pressure sensor at the upper tower 13, adjust the refrigerant discharge ratio, and thus adjust the gas pressure.
[0078] Furthermore, the controller 61 can be connected to various expansion devices (e.g., automatic throttle valves) and the compressor via signal connection. Based on the detection data from the temperature sensor 63 and pressure sensor, the controller 61 can adjust the opening degree of each control valve, the compression ratio of the compressor, and the opening degree of the expansion devices, thereby regulating the temperature of the refrigerant delivered to the top condenser 11 and achieving dynamic and precise adjustment. The temperature sensor 63 and pressure sensor can be selected from conventional temperature and pressure sensors; this application is not limited to any particular type. The controller 61 can be connected to the compressor, condenser, throttle valve, pressure sensor, and temperature sensor 63 according to conventional control methods in the art. The signal connection can be wired or wireless. Figure 3 The dashed lines in the diagram represent the limited signal connection paths.
[0079] For further information, please refer to [link / reference]. Figure 2 ( Figure 2The thermal cycle unit 7 is omitted. The cryogenic distillation system 100 also includes an emergency unit 5. The emergency unit 5 includes a second condenser 51. The cryogenic outlet of heat exchanger 71 can be selectively connected to the inlet of the second condenser 51, and the outlet of the second condenser 51 can be selectively connected to the cryogenic inlet of the top condenser 11. In the event of a failure in the high-temperature cycle unit 2 or the cryogenic cycle unit 3, the high-temperature and high-pressure cryogenic mixed refrigerant discharged from the cryogenic outlet of heat exchanger 71 can be directly delivered to the second condenser 51. The cryogenic mixed refrigerant is cooled using a refrigerant (such as liquid nitrogen or liquid oxygen), and then delivered to the top condenser 11 to condense the top product, thereby contributing to the stable operation of the cryogenic distillation system 100.
[0080] Furthermore, in some embodiments, the cryogenic circulation unit 3 further includes a regenerator 41. The regenerator 41 is provided with a heat exchange channel, and the high-temperature outlet of the first heat exchanger 31 is connected to the inlet of the second compressor 36 through the regenerator 41. The cryogenic distillation system 100 is also provided with a raw material delivery pipe 12, which passes through the heat exchange channel and is connected to the feed inlet of the upper column 13, which can preheat the raw material, recover heat, and reduce energy consumption.
[0081] The expansion device in this application can be a conventional throttling valve in the art, such as a manual throttling valve or an automatic throttling valve, as long as it can achieve the function of throttling and cooling. This application does not limit the specific type of heat exchanger; conventional heat exchangers in the art can be selected. As an example, the heat exchanger can be a co-tube heat exchanger, a plate heat exchanger, or a shell-and-tube heat exchanger. The compressor and condenser in this application are both conventional compressors and condensers in the art, and appropriate compressors and condensers can be selected according to compression and condensation requirements. The gas-liquid separator can be a commonly used gas-liquid separator in refrigeration systems; this application does not impose any restrictions. All components are connected by pipes, and the pipes are externally covered with insulation material.
[0082] Furthermore, embodiments of this application also provide a method for cryogenic distillation using the aforementioned cryogenic runoff system, comprising: The raw materials are delivered to the feed inlet of each of the upper towers.
[0083] High-temperature refrigerant is injected into the high-temperature circulation unit, and low-temperature mixed refrigerant is injected into the low-temperature circulation unit. This allows the low-temperature mixed refrigerant to exchange heat with the high-temperature refrigerant through the evaporator-condenser and absorb cold energy. The refrigerant is then delivered to the top condenser of each upper column through the refrigerant outlet of the low-temperature circulation unit.
[0084] The low-temperature mixed refrigerant discharged from the high-temperature outlet of the condenser at the top of the tower is transported to heat exchanger one for heat exchange and heat absorption, and then compressed by compressor one before being transported to the intermediate reboiler to provide heat to the intermediate reboiler.
[0085] The low-temperature mixed refrigerant discharged from the low-temperature outlet of the intermediate reboiler is sent to compressor two for compression, and then sent to the reboiler at the bottom of the column to provide heat to the reboiler.
[0086] The cryogenic refrigerant discharged from the cryogenic outlet of the reboiler in the tower is returned to the cryogenic circulation unit through the first heat exchanger.
[0087] It is understandable that the evaporation temperature of a high-temperature refrigerant is higher than that of a low-temperature mixed refrigerant. A low-temperature mixed refrigerant contains two refrigerants with different evaporation temperatures.
[0088] As an example, the low-temperature mixed refrigerant includes a first refrigerant and a second refrigerant, wherein the evaporation temperature of the first refrigerant is lower than the evaporation temperature of the second refrigerant, and the evaporation temperature of the second refrigerant is lower than the evaporation temperature of the high-temperature refrigerant.
[0089] As an example, high-temperature refrigerants include at least one of R404A, R507, R414A, R454C, or R448A.
[0090] As an example, the low-temperature mixed refrigerant includes at least two of R290, R170, R1150, R14, and R23.
[0091] As an example, low-temperature mixed refrigerants include R290, R14, and R23.
[0092] As an example, the high-temperature refrigerant is R404A, and the low-temperature mixed refrigerant includes R290, R14, and R23 configured in a certain proportion. During the low-temperature distillation process, the high-temperature refrigerant R404A gas flows sequentially through the first compressor, the first condenser, and the first expansion device to the evaporator-condenser, where it exchanges heat with the low-temperature mixed refrigerant gas of R290, R14, and R23 at the evaporator-condenser, absorbing heat and re-phaseing into high-temperature refrigerant R404A gas, thus completing the cycle. At the evaporator-condenser, the high-temperature refrigerant R404A can provide a cooling capacity of approximately -50°C to -30°C.
[0093] A mixture of low-temperature refrigerants R290, R14, and R23 sequentially exchanges heat with the high-temperature refrigerant R404A at the evaporator-condenser and the first working fluid at the first heat exchanger to form a first gas-liquid mixture. The first gas-liquid mixture is then separated into liquid refrigerant R290 and gases of refrigerants R14 and R23 using a first gas-liquid separator. The gases of refrigerants R14 and R23 are then condensed by heat exchange with the second working fluid at the second heat exchanger to form a second gas-liquid mixture. This second gas-liquid mixture is then separated into gaseous refrigerant R14 and liquid refrigerant R23 using a second gas-liquid separator. The gaseous refrigerant R14 is then exchanged with the third working fluid at the third heat exchanger, condensed, and then transported via a third expansion device to the top condenser of the distillation column. This condenser delivers approximately -100°C of cooling energy to the top of the distillation column, exchanging heat with the gas phase at the top of the column to achieve low-temperature distillation.
[0094] Refrigerant R14 exchanges heat with the overhead material at the top condenser and is discharged from the high-temperature outlet of the top condenser. The R14 discharged from the high-temperature outlet of the top condenser is then sent to heat exchanger one for heat exchange, absorbing heat and preheating before being sent to compressor one. After compression and heating by compressor one, it is sent to the intermediate reboiler to provide heat. The R14 discharged from the intermediate reboiler is then sent to compressor two, where it is compressed and heated before being sent to the bottom reboiler to provide heat. The R14 discharged from the bottom reboiler is then returned to the third heat exchanger via heat exchanger one, where it mixes with liquid R23, which has been throttled and cooled by the fourth expansion device, to form the third working fluid. The third working fluid flows through the third heat exchanger to the second heat exchanger, while liquid R290, after being throttled and cooled by the second expansion device, flows to the second heat exchanger, where they mix to form the second working fluid (containing portions of R290, R14, and R23). The second working fluid is heated by the second heat exchanger to form the first working fluid. The first working fluid is then heated by the first heat exchanger and the second compressor to form a low-temperature mixed refrigerant gas, and this cycle is repeated.
[0095] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A low-temperature distillation system, characterized in that, include: A distillation unit includes a lower column and multiple upper columns arranged in parallel. The top of the lower column is connected to the multiple upper columns through an intermediate reboiler, and a bottom reboiler is provided at the bottom of the lower column. Each of the upper columns is provided with a top condenser. The system includes a high-temperature circulation unit and a low-temperature circulation unit. The high-temperature circulation unit is equipped with a circulation channel for circulating high-temperature refrigerant, and the low-temperature circulation unit is equipped with a circulation channel for circulating low-temperature mixed refrigerant. The high-temperature refrigerant and the low-temperature mixed refrigerant exchange heat through an evaporator-condenser. The refrigerant outlet of the low-temperature circulation unit is connected to the low-temperature inlet of the top condenser of the tower; The heat cycle unit includes a heat exchanger, wherein the high-temperature outlet of the top condenser is connected to the low-temperature inlet of the heat exchanger, the high-temperature outlet of the heat exchanger is connected to the high-temperature inlet of the intermediate reboiler via a compressor, the low-temperature outlet of the intermediate reboiler is connected to the high-temperature inlet of the bottom reboiler via a compressor, and the low-temperature outlet of the bottom reboiler is connected to the high-temperature inlet of the heat exchanger; the low-temperature outlet of the heat exchanger is connected to the refrigerant inlet of the low-temperature cycle unit.
2. The low-temperature distillation system according to claim 1, characterized in that, The heat circulation unit is also provided with a second heat exchanger; the low temperature outlet of the intermediate reboiler can be selectively connected to the high temperature inlet of the second heat exchanger, and the low temperature outlet of the second heat exchanger is connected to the high temperature inlet of the first heat exchanger.
3. The low-temperature distillation system according to claim 1, characterized in that, The high-temperature circulation unit includes a first compressor, a first condenser, and a first expansion device; the outlet of the first condenser is connected to the low-temperature inlet of the evaporator-condenser through the first expansion device, the high-temperature outlet of the evaporator-condenser is connected to the inlet of the first compressor, and the outlet of the first compressor is connected to the inlet of the first condenser, forming a circulation channel for the high-temperature refrigerant.
4. The low-temperature distillation system according to claim 3, characterized in that, The cryogenic circulation unit includes a first heat exchanger, a first gas-liquid separator, a second heat exchanger, a second expansion device, a third expansion device, and a second compressor, all connected by pipes. The outlet of the second compressor is connected to the high-temperature inlet of the evaporator-condenser, and the low-temperature outlet of the evaporator-condenser is connected to the high-temperature inlet of the first heat exchanger; the high-temperature outlet of the first heat exchanger is connected to the inlet of the second compressor. The low-temperature outlet of the first heat exchanger is connected to the inlet of the first gas-liquid separator; the gas outlet of the first gas-liquid separator is connected to the high-temperature inlet of the second heat exchanger; the liquid outlet of the first gas-liquid separator is connected to the low-temperature inlet of the second heat exchanger via the second expansion device; and the high-temperature outlet of the second heat exchanger is connected to the low-temperature inlet of the first heat exchanger. The low-temperature outlet of the second heat exchanger is connected to the low-temperature inlet of the top condenser via the third expansion device; the high-temperature outlet of the top condenser is connected to the low-temperature inlet of the first heat exchanger; and the low-temperature outlet of the first heat exchanger is connected to the low-temperature inlet of the second heat exchanger.
5. The low-temperature distillation system according to claim 4, characterized in that, The cryogenic circulation unit also includes a second gas-liquid separator, a fourth expansion device, and a third heat exchanger connected by pipes. The low-temperature outlet of the second heat exchanger is connected to the inlet of the second gas-liquid separator; the gas outlet of the second gas-liquid separator is connected to the high-temperature inlet of the third heat exchanger; the liquid outlet of the second gas-liquid separator is connected to the low-temperature inlet of the third heat exchanger via the fourth expansion device; the low-temperature outlet of the third heat exchanger is connected to the low-temperature inlet of the top condenser via the second expansion device; the high-temperature outlet of the top condenser is connected to the low-temperature inlet of the first heat exchanger; the low-temperature outlet of the first heat exchanger is connected to the low-temperature inlet of the third heat exchanger; and the high-temperature outlet of the third heat exchanger is connected to the low-temperature inlet of the second heat exchanger.
6. The low-temperature distillation system according to claim 4, characterized in that, The low-temperature circulation unit also includes a regenerator, which is provided with a heat exchange channel. The high-temperature outlet of the first heat exchanger is connected to the inlet of the second compressor through the regenerator. The low-temperature distillation system is also provided with a raw material delivery pipe, which passes through the heat exchange channel and is connected to the feed inlet of the upper column.
7. The low-temperature distillation system according to claim 4, characterized in that, The cryogenic distillation system also includes an emergency unit, which includes a second condenser. The cryogenic outlet of the heat exchanger can be selectively connected to the inlet of the second condenser, and the outlet of the second condenser can be selectively connected to the cryogenic inlet of the top condenser.
8. The low-temperature distillation system according to claim 1, characterized in that, The distillation unit includes six parallel upper columns, each with a feed inlet; the refrigerant outlet of the low-temperature circulation unit is provided with a main pipe and six branch pipes connected to the main pipe, and the six branch pipes are connected one-to-one with the low-temperature inlets of the six top condensers.
9. The low-temperature distillation system according to claim 8, characterized in that, The main pipe is equipped with a circulation pump.
10. The cryogenic distillation system according to claim 1, characterized in that, The reboiler in the tower is equipped with a discharge port.
11. A low-temperature distillation method, characterized in that, The cryogenic distillation system according to any one of claims 1 to 10, wherein the cryogenic distillation method comprises: The raw materials are fed to the feed inlet of each of the upper towers; High-temperature refrigerant is injected into the high-temperature circulation unit, and low-temperature mixed refrigerant is injected into the low-temperature circulation unit, so that the low-temperature mixed refrigerant can exchange heat with the high-temperature refrigerant through the evaporator-condenser to absorb cold energy, and is delivered to the top condenser of each of the upper columns through the refrigerant outlet of the low-temperature circulation unit. The low-temperature mixed refrigerant discharged from the high-temperature outlet of the condenser at the top of the tower is transported to the heat exchanger to absorb heat, and then compressed by the compressor before being transported to the intermediate reboiler to provide heat to the intermediate reboiler. The low-temperature mixed refrigerant discharged from the low-temperature outlet of the intermediate reboiler is delivered to compressor two for compression, and then delivered to the reboiler at the bottom of the column to provide heat to the reboiler at the bottom of the column; The cryogenic refrigerant discharged from the cryogenic outlet of the reboiler in the tower is returned to the cryogenic circulation unit via the first heat exchanger.