Boron isotope rectification separation method and device
By incorporating condensers and reboilers in the distillation column through low-temperature distillation and utilizing a circulating working fluid for heat recovery, the problems of complex equipment and high energy consumption in chemical exchange distillation are solved. This achieves low-energy, high-efficiency boron isotope separation, simplifies the process, and reduces production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-03
AI Technical Summary
Existing chemical exchange distillation methods for separating boron isotopes involve complex equipment, high control requirements, high energy consumption, and decomposition losses, making it difficult to achieve efficient and low-cost industrial production.
The low-temperature distillation method is adopted. By setting up condensers and reboilers in the distillation column, heat is recovered and circulated using the circulating working fluid, which simplifies the process, reduces the number of equipment, and uses the heat released by the condensation of the top steam and the pressure and temperature increase of the circulating working fluid for heating, thereby reducing energy consumption.
This method achieves low-energy separation of boron isotopes, simplifies the process, reduces production costs, improves separation efficiency, avoids complex decomposition and subsequent impurity removal processes, and consumes only about 1/10 of the power of traditional methods.
Smart Images
Figure CN121775657A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of separation and purification technology, and more specifically, to a method and apparatus for the distillation separation of boron isotopes. Background Technology
[0002] Thirteen isotopes of boron have been discovered, while natural boron has two stable isotopes. 10 B and 11 B, with abundances of 19.8% and 80.2%, respectively. 10 B compared to 11 B has a very strong ability to absorb neutrons. 10 These excellent properties of B make it suitable for a wide range of applications in the nuclear industry. High abundance 11 Boron trifluoride gas, produced from boron (B), is used as a specialty electronic gas in the high-end semiconductor manufacturing industry. Additionally, both boron-10 and boron-11 have applications in nuclear magnetic resonance (NMR) research.
[0003] Currently, various methods for separating boron isotopes have been developed, such as low-temperature distillation of boron trifluoride, chemical exchange distillation of boron trifluoride, and ion exchange of boric acid solution. However, the main methods for industrial production of boron isotopes are the chemical exchange distillation of boron trifluoride-anisole and the chemical exchange distillation of boron trifluoride-methyl ether.
[0004] Chemical exchange distillation is a method for separating boron isotopes based on the difference in complexing ability of gases within liquid-phase complexes. In the distillation column, a countercurrent, staged contact mass transfer between the gas and liquid phases is formed, resulting in higher affinity... 10 BF3 is enriched in liquid-phase complexes, exhibiting poor affinity. 11 BF3 accumulates in the gas phase. This method requires the complexation of raw materials, isotope exchange, and pyrolysis separation of liquid products to be carried out between different types of tower equipment, resulting in a large number of process devices and complex process parameter control. The selection of complexes has evolved from diethyl ether and methyl ether to anisole, but problems such as the need for depressurization during separation, low production capacity, and complex decomposition still exist.
[0005] In summary, chemical exchange distillation suffers from problems such as complex equipment, high control requirements, negative pressure process conditions, and decomposition losses. There is an urgent need to develop an energy-efficient, low-temperature distillation device for boron isotope purification to reduce energy consumption, simplify the process, and control production costs.
[0006] In view of this, the present invention is proposed. Summary of the Invention
[0007] The purpose of this invention is to provide a distillation separation method and apparatus for boron isotopes, aiming to provide an isotope separation process with lower energy consumption, so as to simplify the process and reduce the process cost while ensuring the separation effect.
[0008] This invention is implemented as follows: In a first aspect, the present invention provides a method for distillation separation of boron isotopes, comprising: passing isotopic raw materials into a distillation column for separation, setting a condenser at the top of the distillation column for condensing the top vapor, and setting a reboiler at the bottom of the distillation column for heating the bottom material. The circulating working fluid is heated and pressurized to provide heat to the reboiler, where it condenses into a liquid phase. The liquid working fluid is then depressurized and throttled before being sent to the condenser to cool the top steam of the cooling tower, causing the working fluid to evaporate into a gas phase. After being heated and pressurized again, the working fluid cycle is completed.
[0009] In an optional embodiment, the distillation column includes multiple distillation columns connected in series, with a condenser installed at the top of the first distillation column and a reboiler installed at the bottom of the last distillation column.
[0010] In an optional implementation, feed is introduced from a middle distillation column, and a transfer pump is installed at the bottom of each distillation column to send the liquid phase from the bottom of the previous distillation column to the top of the next distillation column. The transfer pump of the last distillation column outputs the liquid product. The vapor phase from the top of the next distillation column is returned to the bottom of the previous distillation column. The vapor phase output from the top of the first distillation column is condensed by a condenser, with part of it flowing back to the top of the first distillation column and the other part being collected after exchanging heat with the feed.
[0011] In an optional implementation, the working fluid cooler and the reboiler are connected in parallel. After being heated and pressurized, part of the working fluid enters the reboiler for heating, and part enters the working fluid cooler for cooling. The cooled working fluid is mixed with the working fluid output from the reboiler and then subjected to pressure reduction and throttling. And / or, use an expansion valve for pressure reduction and throttling.
[0012] In an optional embodiment, the boron isotope raw material is... 10 BF3 and 11 A mixture of BF3.
[0013] In an optional implementation, each distillation column operates at a pressure of 101 kPaA to 150 kPaA and an operating temperature of -101°C to -92°C, and the number of distillation columns is greater than two.
[0014] In an optional implementation, the reflux ratio of the first distillation column is 150~2000, and different reflux ratios are controlled to obtain an abundance of 30%~99% in the column bottom. 10 BF3, with an abundance of 99%~99.99% at the top of the tower. 11 BF3.
[0015] In an optional embodiment, the temperature of the material after being heated by the reboiler is controlled to be -92℃ to -100℃, and the temperature of the material after being cooled by the condenser is controlled to be -93℃ to -101℃, by adjusting the flow rate of the circulating working fluid.
[0016] In an optional embodiment, a compressor is used to heat and pressurize the circulating working fluid, and the temperature of the working fluid after heating and pressurizing is controlled to be 2-3°C higher than the temperature of the bottom of the column. And / or, control the working fluid temperature output by the working fluid cooler to be 2~3℃ lower than the temperature at the top of the tower; And / or, the circulating working fluid is ethylene.
[0017] In a second aspect, the present invention provides a boron isotope distillation separation apparatus for implementing any of the aforementioned boron isotope distillation separation methods, comprising: Distillation column, isotopic raw materials are fed into the distillation column for separation; A condenser, located at the top of a distillation column, is used to condense the vapor at the top of the column. A reboiler, located at the bottom of a distillation column, is used to heat the material in the bottom of the column. The working fluid circulation device includes a heating and pressurizing device and a depressurizing and throttling device. The gaseous circulating working fluid enters the reboiler for heating after passing through the pressurizing and heating device, and is then obtained as the liquid working fluid. The liquid working fluid is then sent to the condenser to cool the top steam of the tower after passing through the depressurizing and throttling device, and is then obtained as the gaseous working fluid. The gaseous working fluid is pressurized and heated again to complete the working fluid circulation.
[0018] This invention offers the following advantages: It employs distillation to separate boron isotopes, eliminating the need for complexation and cracking equipment, resulting in a simpler process, avoiding the introduction of impurities, and eliminating the need for subsequent impurity removal processes, thus facilitating better control. Heat is released by condensing the top steam of the column; the circulating working fluid is evaporated into a gaseous phase, compressed, heated, and pressurized, and then used to heat the reboiler, eliminating the need for additional heat sources and cooling sources. The method provided by this invention achieves a large amount of cooling capacity with minimal power consumption, requiring only ~1 / 10 of the power load required for distillation. A significant amount of cooling capacity is recovered and reused through the circulating working fluid, efficiently utilizing energy and reducing the energy consumption of the equipment. Attached Figure Description
[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 A single-tower separation process flow diagram provided by the present invention; Figure 2 The multi-tower separation process flow diagram provided by the present invention.
[0021] Explanation of main component symbols: 101-Raw material precooler; 102-Distillation column; 103-Condenser; 104-Separator; 105-Reflux pump; 106-Pressure reduction and throttling device; 107-Heating and pressurizing device; 108-Reboiler; 109-Working fluid cooler; 110-Transfer pump. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0023] This invention employs cryogenic distillation to separate boron isotopes. Compared to chemical exchange distillation, it has a lower separation coefficient and is more difficult to separate. Although it requires more trays, it eliminates the need for complexation and pyrolysis equipment, resulting in a simpler process. Furthermore, cryogenic distillation avoids introducing impurities, eliminating the need for subsequent impurity removal processes, thus simplifying the process and making it easier to control.
[0024] like Figure 1 As shown, this embodiment of the invention provides a method for distilling and separating boron isotopes, comprising: passing boron isotope raw material into a distillation column 102 for separation; setting a condenser 103 at the top of the distillation column 102 for condensing the top vapor; setting a reboiler 108 at the bottom of the distillation column 102 for heating the bottom material; and returning the heated material to the bottom.
[0025] This invention optimizes the heat exchange method between the reboiler 108 and the condenser 103 by using a circulating working fluid to heat the reboiler 108 and cool the condenser 103. Specifically, the circulating working fluid is heated and pressurized by the heating and pressurizing device 107 to heat the reboiler 108, where it condenses into a liquid phase. The liquid working fluid is then depressurized and cooled by the depressurization and throttling device 106 before being sent to the condenser 103 to cool the top steam of the cooling tower, causing the working fluid to evaporate into a gas phase. After being heated and pressurized again, the working fluid cycle is completed.
[0026] It should be noted that for boron isotope separation, high abundance is obtained at the top of the distillation column. 11 BF3, high abundance at the base of the tower. 10 BF3. Utilizing 11 BF3 and 10BF3 has a very small boiling point difference, so the temperature difference between the top and bottom of distillation column 102 is minimal. Simultaneously, the heat of condensation at the top and the heat source required at the bottom are comparable. The heat released by condensing the vapor at the top of the column is used to heat the reboiler 108 after the circulating working fluid is evaporated into a gaseous phase, compressed, heated, and pressurized, eliminating the need for additional heat sources or cooling sources.
[0027] In some embodiments, the working fluid cooler 109 and the reboiler 108 are connected in parallel. After being heated and pressurized, part of the working fluid enters the reboiler 108 for heating, and part enters the working fluid cooler 109 for cooling. The cooled working fluid mixes with the working fluid output from the reboiler 108 and then enters the pressure-reducing and throttling device 106 for pressure reduction and throttling. The method of cooling and throttling is not limited; for example, an expansion valve can be used for pressure reduction and throttling, but it is not limited to this. The circulating working fluid heat exchange method provided by the embodiments of the present invention can obtain a large amount of cooling capacity with a small amount of power consumption. The power consumption is only ~1 / 10 of the load required for distillation. A large amount of cooling capacity is recovered and reused through the circulating working fluid, which efficiently utilizes energy and reduces the energy consumption of the device.
[0028] When high separation precision is required and a single tower is too tall, the tower can be split into multiple towers, such as... Figure 2 As shown, a cascade distillation method is adopted, in which multiple distillation columns 102 are connected in series and the feed is selected from the middle column. This middle position is not an absolute middle position, and the feed can be selected from the distillation columns 102 located near the middle position (such as 1-3 columns before and after).
[0029] like Figure 2 As shown, the leftmost distillation column is the first-stage distillation column, the rightmost distillation column is the last-stage distillation column, and the distillation column with feed in the middle is the m-th stage distillation column. There are multiple distillation columns between the first-stage and m-th stage distillation columns, and multiple distillation stages between the m-th and last stage distillation columns. The number of distillation columns is greater than two, and the specific number of stages is not limited, such as 2-20 stages (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 stages, etc.), that is, 2-20 distillation columns, the number of separation stages being determined according to the separation requirements. A condenser 103 is installed at the top of the first distillation column 102. After condensation by the condenser 103, the product enters the separator 104 for gas-liquid separation, and is basically all liquid phase. A reboiler 108 is installed in the bottom of the last distillation column 102 to heat the liquid in the bottom and return it to the bottom.
[0030] Furthermore, each distillation column 102 is equipped with a transfer pump 110 at the bottom of the column. The transfer pump 110 is used to transfer the liquid phase from the bottom of the previous distillation column 102 to the top of the next distillation column 102. The transfer pump 110 of the last distillation column 102 outputs the liquid product (high abundance). 10BF3). In other words, the liquid phase at the bottom of the first distillation column 102 is sent to the second distillation column 102, and so on, until the liquid phase at the bottom of the last distillation column 102 is output through the corresponding transfer pump 110 (also called the extraction pump), thus realizing the bottom distillation extraction.
[0031] Furthermore, the vapor from the top of the next distillation column 102 is returned to the bottom of the previous distillation column 102. The vapor output from the top of the first distillation column 102 is condensed by condenser 103 and then separated in separator 104. Part of it is returned to the top of the first distillation column 102 by reflux pump 105, and the other part is collected after heat exchange with the feed in feed precooler 101, thus achieving high-abundance distillate from the top of the column. 11 Extraction of BF3.
[0032] In some embodiments, the isotope in the isotopic raw material is boron, and the corresponding isotopic raw material can be boron trifluoride, to achieve... 10 BF3 and 11 The separation of BF3, i.e., boron isotope raw material is 10 BF3 and 11 A mixture of BF3.
[0033] Furthermore, when the isotopic feedstock is boron trifluoride, the feedstock can be naturally abundant boron trifluoride or boron trifluoride that has been separated and enriched. The operating pressure of each distillation column 102 is 101 kPaA to 150 kPaA, such as 101 kPaA, 105 kPaA, 110 kPaA, 115 kPaA, 120 kPaA, 125 kPaA, 130 kPaA, 135 kPaA, 140 kPaA, 145 kPaA, 150 kPaA, etc. The operating temperature is -101℃ to -92℃, such as -101℃, -100℃, -95℃, -92℃, etc. The operating pressure and temperature of each column are similar, and the transfer pump 110 is only used to overcome the liquid column pressure at the top of the column. The reflux ratio of the first distillation column 102 is 150~2000, such as 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, etc. Controlling different reflux ratios yields a reboiler abundance of 30%~99%. 10 BF3, with an abundance of 99%~99.99% at the top of the tower. 11 BF3.
[0034] In some embodiments, the feed rate of the isotopic raw material is 10 kg / h to 15 kg / h, such as 10 kg / h, 11 kg / h, 12 kg / h, 13 kg / h, 14 kg / h, 15 kg / h, etc., and the feed state can be gaseous, liquid, or a gas-liquid mixture. The bottom product rate of the last distillation column 102 is 1 kg / h to 4 kg / h, such as 1 kg / h, 2 kg / h, 3 kg / h, 4 kg / h, etc. The top product rate of the first distillation column 102 is 8 kg / h to 12 kg / h, such as 8 kg / h, 9 kg / h, 10 kg / h, 11 kg / h, 12 kg / h, etc.
[0035] Furthermore, by adjusting the flow rate of the circulating working fluid, the temperature of the material heated by the reboiler 108 is controlled to be -92℃ to -100℃, such as -92℃, -95℃, -98℃, or -100℃; the temperature of the material cooled by the condenser 103 is controlled to be -93℃ to -101℃, such as -93℃, -95℃, -98℃, -100℃, or -101℃. The circulating working fluid is heated and pressurized using a compressor, and the temperature of the working fluid after heating and pressurizing is controlled to be 2-3℃ higher than the bottom temperature of the column; the working fluid temperature output from the working fluid cooler 109 is controlled to be 2-3℃ lower than the top temperature of the column.
[0036] It should be noted that by adjusting the feed rate of isotope raw materials, the output rate of products, and the operating temperatures of reboiler 108 and condenser 103, the efficiency can be further improved. 10 BF3 and 11 BF3's separation effect improves product purity.
[0037] Furthermore, the circulating working fluid can be ethylene to meet process requirements. After heat exchange in reboiler 108, it becomes a liquid working fluid, and after heat exchange in condenser 103, it becomes a gaseous working fluid.
[0038] This invention also provides a boron isotope distillation separation apparatus for the above-described boron isotope distillation separation method, such as... Figure 1 and Figure 2 As shown, it includes: Distillation column 102 is used to separate isotopic raw materials. The structure of distillation column 102 can be a plate distillation column.
[0039] Condenser 103, located at the top of distillation column 102, is used to condense the top vapor of the column and liquefy it.
[0040] The reboiler 108 is located at the bottom of the distillation column 102 and is used to heat the material in the bottom of the column, which is then returned to the bottom of the column after heating.
[0041] The working fluid circulation device includes a heating and pressurizing device 107 and a depressurizing and throttling device 106. The gaseous circulating working fluid enters the reboiler 108 for heating after passing through the pressurizing and heating device, and becomes the liquid working fluid. The liquid working fluid is sent to the condenser 103 to cool the top steam of the tower after passing through the depressurizing and throttling device 106, and becomes the gaseous working fluid. The gaseous working fluid is pressurized and heated again to complete the working fluid circulation.
[0042] Specifically, the heating and pressurizing device 107 can be a cryogenic compressor, but is not limited to this. The circulating working fluid, such as ethylene gas, evaporated at the top of the tower directly enters the compressor for compression. The compressed ethylene directly heats the reboiler. The entire system operates below the ambient temperature. Heat is input into the system from the outside, and the compressor also inputs heat into the system. Therefore, an ethylene cooler (i.e., working fluid cooler 109) is installed at the compressor outlet in parallel with the reboiler 108. A portion of the ethylene does not enter the reboiler 108 but is cooled in the ethylene cooler to maintain the heat balance of the entire system.
[0043] The other structures of the isotope distillation and separation apparatus are described above in the instruction manual and will not be repeated here.
[0044] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0045] Examples 1-4 This embodiment provides a method for the distillation separation of boron isotopes, utilizing... Figure 2 The apparatus shown separates boron trifluoride, with ethylene as the circulating working fluid.
[0046] In the boron trifluoride raw materials processed in each embodiment 10 The abundance of BF3 was 19.8% in all cases.
[0047] The isotopic feedstock is fed into N-stage distillation columns for separation. A condenser 103 is installed at the top of the first distillation column, and a reboiler 108 is installed at the bottom of the last distillation column. A transfer pump 110 is installed at the bottom of each distillation column 102 to transfer the liquid phase from the bottom of the previous distillation column 102 to the top of the next distillation column 102. The transfer pump 110 of the last distillation column 102 outputs the liquid product (high abundance 10BF3). The vapor phase from the top of the next distillation column 102 is returned to the bottom of the previous distillation column 102. The vapor phase output from the top of the first distillation column 102 is condensed by the condenser 103 and then separated in the separator 104. Part of it is returned to the top of the first distillation column 102 by the reflux pump 105, and the other part is collected after heat exchange with the feedstock in the feedstock precooler 101.
[0048] The circulating working fluid, after being heated and pressurized by the compressor, supplies heat to the reboiler 108. In the reboiler 108, it condenses into a liquid phase. The liquid working fluid passes through an expansion valve, where it is depressurized and cooled before being sent to the condenser 103 to cool the top steam of the tower, causing the working fluid to evaporate into a gaseous phase. After being heated and pressurized again, the working fluid cycle is completed. A working fluid cooler 109 is connected in parallel with the reboiler 108. After being heated and pressurized, part of the working fluid enters the reboiler 108 for heating, and part enters the working fluid cooler 109 for cooling. The cooled working fluid mixes with the working fluid output from the reboiler 108 and then enters the pressure-reducing and throttling device 106 for pressure reduction and throttling.
[0049] The operating parameters and energy consumption of each embodiment are shown in Table 1.
[0050] Table 1. Operating parameters and energy consumption of each embodiment
[0051] It should be added that if direct cooling at the top of the tower is used, with a coefficient of performance of approximately 2.5, the power consumption would be about four times that of the present invention under the same scale and separation effect.
[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for the distillation separation of boron isotopes, characterized in that, include: Boron isotope raw material is fed into a distillation column for separation. A condenser is installed at the top of the distillation column to condense the top vapor, and a reboiler is installed at the bottom of the distillation column to heat the bottom material. The circulating working fluid is heated and pressurized to supply heat to the reboiler, where it condenses into a liquid phase. The liquid working fluid is then depressurized and throttled before being sent to the condenser to cool the top steam of the cooling tower, causing the working fluid to evaporate into a gas phase. After being heated and pressurized again, the working fluid cycle is completed.
2. The method for distillation separation of boron isotopes according to claim 1, characterized in that, The distillation column includes multiple distillation columns connected in series, with the condenser installed at the top of the first distillation column and the reboiler installed at the bottom of the last distillation column.
3. The method for distillation separation of boron isotopes according to claim 2, characterized in that, Feed is fed from a middle distillation column, and a transfer pump is installed at the bottom of each distillation column to send the bottom liquid phase of the previous distillation column to the top of the next distillation column. The transfer pump of the last distillation column outputs the liquid product. The vapor phase from the top of the next distillation column is returned to the bottom of the previous distillation column. The vapor phase output from the top of the first distillation column is condensed by the condenser, with a portion flowing back to the top of the first distillation column and the other portion being collected after heat exchange with the feedstock.
4. The method for distillation separation of boron isotopes according to claim 3, characterized in that, The working fluid cooler is connected in parallel with the reboiler. After being heated and pressurized, part of the working fluid enters the reboiler for heating, and part enters the working fluid cooler for cooling. The cooled working fluid is mixed with the working fluid output from the reboiler and then subjected to pressure reduction and throttling. And / or, use an expansion valve for pressure reduction and throttling.
5. The method for distillation separation of boron isotopes according to claim 4, characterized in that, The boron isotope raw material is 10 BF3 and 11 A mixture of BF3.
6. The method for distillation separation of boron isotopes according to claim 5, characterized in that, The operating pressure of each distillation column is 101 kPaA to 150 kPaA, the operating temperature is -101℃ to -92℃, and the number of distillation columns is greater than 2.
7. The method for distillation separation of boron isotopes according to claim 6, characterized in that, The reflux ratio of the first distillation column is 150~2000, and by controlling different reflux ratios, an abundance of 30%~99% can be obtained in the reboiler. 10 BF3, with an abundance of 99%~99.99% at the top of the tower. 11 BF3.
8. The method for distillation separation of boron isotopes according to claim 6, characterized in that, By adjusting the flow rate of the circulating working fluid, the temperature of the material heated by the reboiler is controlled to be -92℃ to -100℃, and the temperature of the material cooled by the condenser is controlled to be -93℃ to -101℃.
9. The method for distillation separation of boron isotopes according to claim 6, characterized in that, The circulating working fluid is heated and pressurized using a compressor, and the temperature of the working fluid after heating and pressurization is controlled to be 2-3°C higher than the temperature of the column bottom. And / or, control the working fluid temperature output by the working fluid cooler to be 2~3℃ lower than the temperature at the top of the tower; And / or, the circulating working fluid is ethylene.
10. A boron isotope distillation separation apparatus for implementing the boron isotope distillation separation method according to any one of claims 1-9, characterized in that, include: A distillation column is used to separate isotopic feedstocks. A condenser, located at the top of the distillation column, is used to condense the top vapor of the column; A reboiler, located at the bottom of the distillation column, is used to heat the material in the bottom of the column. The working fluid circulation device includes a heating and pressurizing device and a depressurizing and throttling device. The gaseous circulating working fluid enters the reboiler for heating after passing through the pressurizing and heating device, and is then obtained as a liquid working fluid. The liquid working fluid is then sent to the condenser to cool the top steam of the tower after passing through the depressurizing and throttling device, and is then obtained as a gaseous working fluid. The gaseous working fluid is pressurized and heated again to complete the working fluid circulation.