Compression cycle heat supply heavy water rectification process

Abstract

The invention relates to the field of heavy water production, and discloses a compression cycle heat supply heavy water rectification process which comprises the following steps: 1, carrying out primary rectification on feed water; 2, condensing tower top steam by a first-stage cooler to obtain tower top produced liquid, enabling one part of the produced liquid to flow back to a first-stage rectifying tower, discharging the other part of the produced liquid, pressurizing and heating a working medium heated by the first-stage cooler by a compressor, and feeding the working medium into a first-stage reboiler; 3, feeding one part of deuterium-enriched water of the tower kettle into a first-stage reboiler, boiling, returning to the bottom of the rectifying tower, taking the rest part as feed water for next-stage rectification, and returning a working medium cooled by the first-stage reboiler into a first-stage cooler through a first-stage expansion valve to be heated and evaporated; and 4, performing N-stage rectification and purification until the heavy water meets the purity requirement. By utilizing the characteristics that the boiling difference between water and heavy water is extremely small and the condensation heat of the tower kettle is equivalent to the heat source required by the tower kettle, the condensation heat of tower top steam is transferred to the tower kettle through the circulating working medium, the energy consumption is greatly reduced, and a large amount of heat sources can be provided for the system by a small amount of power consumption of the compressor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heavy water production, and particularly relates to a compression cycle heat supply heavy water rectification process. BACKGROUND

[0002] Heavy water is a key raw material for the preparation of deuterium gas and deuterium solvent, and has wide application in the fields of electronic semiconductors, medical and pharmaceuticals, nuclear industry, scientific research, etc.

[0003] In industrial production, heavy water and ordinary water are usually separated and purified by taking advantage of their differences in physical and chemical properties. Common methods include rectification, electrolysis, double-temperature hydrogen sulfide-water exchange, double-temperature hydrogen-water exchange, ammonia-hydrogen exchange, and liquid hydrogen low-temperature fractionation. Among them, electrolysis takes advantage of the fact that heavy water molecules are more difficult to electrolyze than ordinary water molecules, and enriches heavy water by electrolyzing ordinary water. This method requires a large amount of electrical energy and time, and has low efficiency. When the electrolysis feed water is partially enriched, the cost performance of the electrolysis method improves; the double-temperature hydrogen sulfide-water exchange method is based on the hydrogen and deuterium isotope exchange between water and hydrogen sulfide in a series of multi-stage towers. Deuterium migrates to water at low temperature, and to hydrogen sulfide at high temperature. This method has low energy consumption, but the medium is toxic, flammable and corrosive, and has high requirements for production process and equipment; the double-temperature hydrogen-water exchange method uses the isotope exchange between water and hydrogen gas. Similar to the hydrogen sulfide-water exchange method, through countercurrent contact in the tower equipment, deuterium in the low-temperature tower is transferred from hydrogen gas to liquid water, and deuterium in the high-temperature tower is transferred from water to hydrogen gas. This method also faces the risk of flammable and explosive medium, and the catalyst for isotope exchange has a large amount and high cost; the ammonia-hydrogen exchange method is a method for extracting deuterium from synthetic gas by liquid ammonia under the action of a catalyst. In the exchange tower, the gas flows from the tower bottom to the top, and the liquid ammonia flows from the top to the bottom. Deuterium is washed from the hydrogen of the synthetic gas and enriched in the liquid ammonia. This method often relies on the scene of synthetic gas, and has a large ammonia-hydrogen separation coefficient. However, the catalyst loses activity when it gets wet, and a high-performance hydrophobic catalyst needs to be developed. At the same time, it also faces the dilemma of toxic, flammable and explosive medium; the liquid hydrogen low-temperature fractionation method uses the difference in vapor pressure between liquid hydrogen and deuterium to achieve separation at low temperature. At a temperature of about 22K, the vapor pressure ratio of liquid hydrogen and liquid deuterium is H2 / HD = 1.6 and H2 / D2 = 2.5. The higher relative volatility can achieve higher separation efficiency, but the low-temperature liquefaction requirement also puts new requirements on industrial refrigeration and material performance.

[0004] As can be seen, the above methods have problems such as high energy consumption, high process equipment requirements, toxic, flammable and explosive process medium, high catalyst cost, and easy deactivation, etc. Therefore, it is urgent to develop a low-energy-consumption process to simplify the process requirements and control the production cost. SUMMARY

[0005] The present application aims to provide a heavy water separation process to solve the problems of high energy consumption, high process equipment requirements, toxic, flammable and explosive process medium, high catalyst cost and easy deactivation in the current heavy water separation process.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solution: a compressed cycle heat supply heavy water rectification process, comprising the following steps:

[0007] (1) feeding the feed water into the middle section of the first-stage rectification tower for primary rectification;

[0008] (2) condensing the first-stage rectification tower overhead vapor by the first-stage cooler to obtain the first-stage rectification overhead take-off liquid, part of which is returned to the first-stage rectification tower as reflux, and the rest is discharged as the first-stage rectification distillate, wherein the liquid phase working medium in the first-stage cooler is evaporated into a gas phase working medium which is pressurized and heated by a compressor and then enters the first-stage reboiler as a heat source;

[0009] (3) part of the deuterium-rich water in the first-stage rectification tower is sent to the first-stage reboiler for heating, and then returned to the rectification tower after boiling, and the rest is used as the feed water for the next-stage rectification or as heavy water take-off, and the liquid phase working medium cooled in the first-stage reboiler is depressurized and cooled by the first-stage expansion valve and then returned to the first-stage cooler to be heated into a gas phase, completing the working medium cycle.

[0010] The above process can further purify the heavy water treated by other concentration methods, or can preliminarily treat the feed water, and can be widely applied to heavy water at different treatment stages. Since heavy water separation is isotopic separation, light water with a low deuterium content is obtained at the top of the rectification tower, and heavy water with a high deuterium content is obtained at the bottom. The present application takes advantage of the fact that the temperature difference between the top and the bottom of the heavy water rectification tower is very small, and the condensation heat at the top is equivalent to the heat required at the bottom, fully utilizes the large amount of heat released by the condensation of the tower top vapor, and makes the circulating working medium evaporate into a gas phase which is pressurized and heated by a compressor to supply heat to the reboiler, without the need for additional heat sources. Only a small amount of energy is needed to drive the compressor to obtain a large amount of heat source, and a large amount of low-grade heat is recovered and utilized by the circulating working medium. Specifically, the gas phase working medium is pressurized and heated by the compressor to supply heat to the reboiler at the bottom, the working medium is condensed into a liquid phase in the reboiler, the liquid phase working medium is then depressurized and throttled to reduce the temperature, and then sent to the top cooler to cool the tower top vapor. At the same time, the working medium evaporates into a gas phase which is then compressed and pressurized by the compressor to complete the working medium cycle. The process of the present application does not involve high-cost catalysts, and the process can be carried out at normal pressure, without toxic, flammable and explosive substances, which is beneficial to effectively control the production cost and improve the safety.

[0011] As a preferred solution, the above process further comprises step (4), that is, when the deuterium-rich water in step (3) continues to be used as feed water for the next stage of rectification, the overhead vapor of the second-stage rectification column is condensed by the second-stage cooler to obtain the overhead distillate of the second-stage rectification, part of the overhead distillate of the second-stage rectification is returned to the rectification column as reflux, the rest is returned to the first-stage rectification as raw material, the working medium heated by the second-stage cooler is pressurized and heated by the compressor and then enters the second-stage reboiler as a heat source, the liquid-phase working medium cooled by the second-stage reboiler is depressurized and cooled by the second-stage expansion valve and then returns to the second-stage cooler to be heated into a gas phase, completing the working medium cycle, part of the deuterium-rich water in the column sump of the second-stage rectification column is boiled and heated by the second reboiler and then returned to the rectification column, and the rest is used as feed water for the next stage of rectification, and the total number of stages of rectification is N, the rectification process of each stage is consistent with that of the previous stage, and the heavy water collected from the column sump of the Nth-stage rectification column is collected until it meets the purity requirement. By using the multi-stage rectification mode as a whole, heavy water can be directly obtained from ordinary feed water, the structure of the entire process is simpler, and the number of stages of rectification can be flexibly adjusted according to different raw materials, and the adaptability is stronger.

[0012] As a preferred solution, the working medium is water, which is not only environmentally friendly, safe and stable, but also has a very high latent heat of vaporization and heat transfer coefficient, which can significantly improve the heat transfer efficiency; more importantly, in the heavy water rectification process of the present application, water as a circulating working medium has a high degree of matching between the evaporation temperature and the condensation temperature of the overhead vapor, and the condensation temperature is also accurately coupled with the reboiling temperature of the deuterium-rich water at the bottom, so that the condensation heat at the top of the rectification column is fully recovered, thereby greatly reducing the energy consumption of the system.

[0013] As a preferred solution, the first-stage rectification distillate discharged in step (2) is used to preheat the feed water in step (1) to reduce the energy consumption of the rectification column.

[0014] As a preferred solution, the feed water in step (1) is preheated to 80-101℃, which is close to the operating temperature of the rectification column, so that the temperature gradient in the column can be effectively reduced, thereby improving the separation efficiency and operation stability of the rectification process and reducing the risk of product quality fluctuation.

[0015] As a preferred solution, part of the heavy water with a deuterium content greater than 99.8% after purification by the rectification system is transported to a heavy water storage tank.

[0016] As a preferred solution, part of the overhead distillate of the second-stage rectification column to the Nth-stage rectification column is returned to the rectification column as reflux, and the rest is returned to the previous stage of rectification as raw material. After the feed water is subjected to multi-stage rectification, a large amount of light water is discharged out of the system, and the deuterium content of the overhead distillate gradually increases. Returning the overhead distillate of the rectification column to the previous stage of rectification as raw material avoids returning the deuterium-containing water to the first-stage rectification and increases the rectification process.

[0017] As a preferred solution, the reflux ratio of the overhead stream in the primary rectification in step (2) is 10-200.

[0018] As a preferred solution, the deuterium content in the feed water is at least 0.014%, and impurities are removed in advance.

[0019] As a preferred solution, the rectification column uses carbon steel wire mesh packing to provide higher mass transfer efficiency while ensuring lower pressure drop, facilitating the realization of multi-column series for rectification, thereby facilitating the separation of heavy water and ordinary water with close boiling points.

[0020] The present solution has the following technical advantages:

[0021] (1) By taking advantage of the fact that the boiling point difference between water and heavy water is very small and the condensation heat at the top of the column is equivalent to the heat required at the column bottom, the large amount of latent heat released by the condensation of the vapor at the top of the column is fully utilized to evaporate the circulating working medium into a gas phase, which is then compressed to provide heat for the reboiler. No additional heat source is required, only a small amount of energy is needed to drive the compressor, a large amount of heat source can be obtained, the energy consumption is only 1 / 20-1 / 30 of the heat required for rectification, a large amount of low-grade heat is recycled through the circulating working medium, energy is used efficiently, and energy consumption is greatly reduced.

[0022] (2) The present application uses water as the circulating working medium to construct a closed loop of condensation heat at the top of the column-heat exchanger heat absorption-compressor pressure increase-reboiler heat release-column bottom reboiling, which precisely matches the evaporation temperature of the working medium with the condensation temperature of the vapor at the top of the rectification column, and couples the condensation temperature with the reboiling temperature of the heavy water at the bottom of the column, effectively realizing the full recovery of the condensation heat and reducing the energy consumption.

[0023] (3) Compared with other isotopic exchange methods and low-temperature distillation processes, the operating medium of the present application is ordinary water or low-concentration heavy water, which does not require catalysts and toxic, flammable, explosive and corrosive media, and the production process is safer and more environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The figure is a process flow diagram of an embodiment of the present application. DETAILED DESCRIPTION

[0025] The following will be further described in detail through specific embodiments:

[0026] The reference signs in the attached drawings of the specification include: first-stage rectification tower 11, first-stage cooler 12, first-stage separator 13, first-stage reflux pump 14, first-stage heavy water pump 15, feed water preheater 16, first-stage compressor 17, first-stage heavy boiler 18, first-stage expansion valve 19, Nth-stage rectification tower 51, Nth-stage cooler 52, Nth-stage separator 53, Nth-stage reflux pump 54, Nth-stage heavy water pump 55, Nth-stage compressor 57, Nth-stage heavy boiler 58, Nth-stage expansion valve 59.

[0027] Embodiment:

[0028] A compressed cycle heat supply heavy water rectification process, as shown in the attached drawings, comprises the following steps: Figure 1

[0029] (1) The feed water with deuterium content of at least 0.014% is heated to 80-101℃, and then supplied to the middle section of the first-stage rectification tower 11, for first-stage rectification, so that the light components in the feed water are further purified in the rectification section, and the heavy components are further removed from the light components in the stripping section, to obtain low-deuterium overhead vapor and heavy water in the tower kettle.

[0030] In this embodiment, the feed water is heated to near its boiling point before being introduced into the rectification tower, which not only makes the raw material temperature more stable, reduces the sharp change of the temperature gradient in the tower, and ensures the operation stability.

[0031] In this step, the overhead temperature of the first-stage rectification tower 11 can be selected to be 50-105℃, the kettle temperature of the first-stage rectification tower 11 is 52-107℃, and the operating pressure of the first-stage rectification tower 11 can be 10-110kPa, which is controlled to be 100-110kPa in this embodiment, and the equipment is simpler under near atmospheric pressure. In this embodiment, the overhead operating temperature is preferably controlled to be slightly lower than the boiling point of heavy water, and the kettle operating temperature is controlled to be slightly higher than the boiling point of heavy water. In this step, when the entire system is initially started, external steam is introduced to heat the first-stage cooler 12, and the first-stage compressor 17 is started to pressurize, and after the system is stably operated, the supply of external steam is stopped, to ensure the stable operation of the system.

[0032] ​(2) The overhead vapor of the first stage rectifying column 11 is condensed by the first stage cooler 12 to obtain the first stage rectified overhead liquid, which is first separated into gas and liquid in the first stage separator 13, and then is pumped by the first stage reflux pump 14. A part of the overhead liquid is refluxed to the upper rectifying section of the first stage rectifying column 11, and the reflux ratio is controlled to be 10-80. The refluxed overhead liquid fully contacts with the ascending vapor at the top of the first stage rectifying column 11, and the overhead liquid carrying high-boiling-point components flows downward and exchanges with the low-boiling-point components in the ascending vapor, so that the concentration of water in the overhead vapor is gradually increased, and the heavy water carried by the vapor is reduced. The unrefluxed overhead liquid is used as the first stage rectified distillate, which is heated with the feed water in the feed water preheater 16 and then is discharged, so that the residual heat of the overhead liquid is recovered, and the energy consumption is saved. The circulating working medium is converted from liquid to gas by being heated by the overhead vapor in the first stage cooler 12, is pressurized and heated by the first stage compressor 17, and then is introduced into the first stage reboiler 18.

[0033] (3) A part of the deuterium-rich water in the column sump of the first stage rectifying column 11 is introduced into the first stage reboiler 18 to be heated and then is refluxed to the first stage rectifying column. The remaining deuterium-rich water is used as the feed water of the next stage rectifying column or is discharged as heavy water. The circulating working medium is converted from gas to liquid by being cooled in the first stage reboiler 18, is depressurized and cooled by the first stage expansion valve 19, and then is refluxed to the first stage cooler 12, so that the circulation of the working medium is realized. The working medium in the embodiment is preferably water or pure water, and the pure water is beneficial to the stable heat transfer and circulation of the working medium and avoids blockage.

[0034] In this step, the deuterium-rich water in the column sump of the first stage rectifying column 11 exchanges heat with the circulating working medium in the first stage reboiler 18 to be vaporized to form a steam-water mixture. The liquid is refluxed to the column sump, and the steam ascends in the first stage rectifying column 11. The ascending steam contacts with the liquid phase in the first stage rectifying column 11 to exchange mass and heat. The heavy components are continuously enriched downward, and the light components are continuously enriched upward. Finally, the low-deuterium overhead vapor is obtained at the top of the first stage rectifying column 11, and the deuterium-rich water is obtained at the column sump.

[0035] The first three steps can be used as a separate process to purify the heavy water that has been preliminarily treated, and then part of the heavy water with a deuterium content greater than 99.8% after being purified by the rectifying system is transported to a heavy water storage tank, or to preliminarily treat the feed water to increase the concentration of heavy water in the feed water. The embodiment also includes a subsequent step (4) to directly extract the required heavy water from the feed water.

[0036] (4) The deuterium-rich water in step (3) is used as feed water for the next stage of rectification. The overhead vapor of the second-stage rectification column is condensed by a second-stage condenser to obtain the overhead draw of the second-stage rectification, part of which is returned to the column as reflux, and the rest is returned to the first-stage rectification column 11 as raw feed water. The working medium in the second-stage condenser is heated while condensing the overhead vapor of the second-stage rectification column, and the working medium is further pressurized and heated by a second-stage compressor, and then enters the second-stage reboiler as a heat source to heat the deuterium-rich water. The working medium is cooled by the second-stage reboiler and changes from a gaseous state to a liquid state, and then is depressurized and cooled by a second-stage expansion valve, and then returns to the second-stage condenser to complete the working medium cycle. Part of the deuterium-rich water in the column sump of the second-stage rectification column is returned to the column after being boiled and heated by the second reboiler, and the rest is used as feed water for the next stage of rectification. The total number of stages of rectification is N, where N is a positive integer, and the flow of each stage of rectification is consistent with the previous stage of rectification, and the heavy water drawn from the column sump of the Nth-stage rectification column meets the purity requirements. This step further purifies the heavy water to obtain heavy water of the corresponding purity requirements. The overhead temperature of the second-stage rectification column to the Nth-stage rectification column can be 50-105°C, the column sump temperature of the second-stage rectification column to the Nth-stage rectification column is 52-110°C, the operating pressure of the second-stage rectification column to the Nth-stage rectification column can be 10-110 kPa, and the overhead reflux ratio of the second-stage rectification column to the Nth-stage rectification column can be 10-200. In this scheme, according to the purity requirements of the feed water and the product heavy water, the enrichment effect of the second-stage rectification system to the Nth-stage rectification system is used, and the heavy water drawn from the column sump of the Nth-stage rectification column meets the purity requirements of the heavy water and is transported to the heavy water storage tank.

[0037] In this embodiment, a total of five-stage rectification systems are used, and the flow of the second-stage rectification to the fifth-stage rectification is consistent with the flow of the first-stage rectification system in steps (1)-(3). The overhead draw of the second-stage rectification to the fifth-stage rectification is returned to the previous stage of rectification as feed water, and the deuterium-rich water in the column sump of the fifth-stage rectification column 51 is discharged as heavy water.

[0038] In this embodiment, the operating parameters of the five-stage rectification and the effects of purifying heavy water are as follows:

[0039] First stage Second stage Third stage Fourth stage Fifth stage Operating pressure kPa 101 101 101 101 101 Overhead temperature °C 99.6 99.9 100.1 100.2 100.3 Bottom temperature °C 102.3 102.4 102.5 103.7 103.9 Overhead recovery % 7.58 6.60 6.60 5.61 2.19 Reflux ratio 26 40 41 52 188 Recovered heat kW 1728554 222721 22035 2458 480 Compressor energy consumption kW 60400 7650 890 89 16 Deuterium content % 0.129 1.295 12.883 86.700 99.8

[0040] In this embodiment, the feed water deuterium content is preferably 0.015%, 5-stage rectification is set and the recovery rate of the first 4 stages is controlled to be between 5.61% and 7.58%; the reflux ratio is between 26 and 52, which is conducive to improving the separation efficiency; the distillate of the last stage of rectification is recycled to the first stage of rectification, reducing the loss of deuterium; the rectification process operating pressure is 101 kPa, and normal pressure operation is conducive to simplifying the equipment, without the need for additional equipment to maintain system negative pressure, which can effectively reduce the investment in equipment; the column top operating temperature is controlled to be between 99.6 and 100.3°C, and the column bottom operating temperature is controlled to be between 102.3 and 103.9°C, the boiling point difference between water and heavy water is small, and by utilizing the large amount of latent heat released by the condensation of the column top vapor, the circulating working medium is evaporated into a gas phase to provide heat for the reboiler after compression, heating and pressure increase, only a small amount of energy is required to drive the compressor, and a large amount of heat source is obtained without other additional heat sources.

[0041] The present scheme also provides a system for implementing the above process, including N rectification units, N = 5, such as the first-stage rectification unit, which includes a first-stage rectification column 11, a first-stage cooler 12, a first-stage separator 13, a first-stage reflux pump 14, a first-stage heavy water pump 15, a feed water preheater 16, a first-stage compressor 17, a first-stage reboiler 18, a first-stage expansion valve 19, and the Nth-stage rectification unit, which includes an Nth-stage rectification column 51, an Nth-stage cooler 52, an Nth-stage separator 53, an Nth-stage reflux pump 54, an Nth-stage heavy water pump 55, an Nth-stage compressor 57, an Nth-stage reboiler 58, and an Nth-stage expansion valve 59, and the material flow path is as shown. Figure 1

[0042] Specifically, the pipeline for conveying the feed water is in communication with the middle section of the first-stage rectification column 11, and the rectification column can adopt a conventional sieve tray column or a packed column, and in this embodiment, carbon steel wire mesh packing is used in the first-stage rectification column 11 to the Nth-stage rectification column 51, the vapor outlet at the top of the first-stage rectification column 11 is connected to the high-temperature fluid inlet of the first-stage cooler 12, the high-temperature fluid outlet of the first-stage cooler 12 is connected to the first-stage separator 13, the separated liquid is communicated with the upper rectification section of the first-stage rectification column 11 and the hot fluid inlet of the feed water preheater 16 through the first-stage reflux pump 14, respectively; the heavy water outlet interface of the first-stage rectification column 11 is connected to the first-stage reboiler 18 and the first-stage heavy water pump 15 through a pipeline, respectively, the heavy water outlet of the first-stage reboiler 18 is connected to the rectification section of the first-stage rectification column 11, and the outlet of the first-stage heavy water pump 15 is connected to the pipeline for the feed water of the next-stage rectification column. The circulating working medium is sequentially connected in series through a pipeline to form a closed loop, including the first-stage cooler 12, the first-stage compressor 17, the first-stage reboiler 18, and the first-stage expansion valve 19, to transfer heat from the column top vapor to the heavy water at the column bottom. The structures of the remaining rectification units are similar to that of the first-stage rectification unit, and the main difference is that, in addition to a part of the column top distillate being returned to the rectification section of the rectification column, the remaining part is directly used as the feed water of the upper rectification column without being heated by the raw material preheater.​

[0043] The rectifying column involved in the embodiment is a common device for separating liquid mixture in chemical production, which separates the mixture by using the different boiling points of various components, and the low-boiling components are easily volatilized into the gas phase and rise with the gas flow; the high-boiling components are more easily condensed in the liquid phase and flow downward along the column body. Through the repeated gas-liquid contact, mass transfer and heat transfer process, the light components with high purity are finally obtained at the top of the column, and the heavy components with high purity are obtained at the column bottom.

[0044] The above is only the embodiment of the present application, and the common knowledge of specific structures, properties and reactant ratios in the scheme is not described in detail. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, such as simple adjustment of the process flow and the structure of the equipment, simple adjustment of the selection of parameters within or near the specified parameter range, etc., and the technical effects are similar to those of the embodiments of the present application. These should be considered as the protection scope of the present application, and these will not affect the effect and practicality of the patent. The protection scope of the present application should be subject to the content of its claims, and the specific embodiments in the specification can be used to explain the content of the claims.

Claims

1. A compressed cycle heat supply heavy water rectification process, characterized by, The method comprises the following steps: (1) feeding feed water into the middle section of a first rectification tower for primary rectification; (2) condensing the overhead vapor of the first rectification tower by a first cooler to obtain the overhead product of the primary rectification, part of the overhead product is returned to the first rectification tower as reflux, and the rest is discharged as primary rectification distillate, the liquid phase working medium in the first cooler is evaporated into a gas phase working medium, which is pressurized and heated by a compressor and then enters the first reboiler as a heat source; (3) part of the deuterium-rich water in the bottom of the first rectification tower is sent to the first reboiler for heating, and then returned to the rectification tower after boiling, and the rest is used as feed water for the next stage of rectification or as heavy water product, the liquid phase working medium cooled in the first reboiler is reduced in pressure and cooled by a first expansion valve, and then returned to the first cooler to be heated into a gas phase, completing the working medium cycle.

2. A compressed cycle heat-supply heavy water distillation process according to claim 1, characterized in that: The method further comprises step (4), when the deuterium-rich water in step (3) is used as feed water for the next stage of rectification, the overhead vapor of the second rectification tower is condensed by a second cooler to obtain the overhead product of the secondary rectification, part of the overhead product of the secondary rectification is returned to the rectification tower as reflux, and the rest is returned to the primary rectification as feed water, the working medium heated in the second cooler is pressurized and heated by a compressor and then enters the second reboiler as a heat source, the liquid phase working medium cooled in the second reboiler is reduced in pressure and cooled by a second expansion valve, and then returned to the second cooler to be heated into a gas phase, completing the working medium cycle, part of the deuterium-rich water in the bottom of the second rectification tower is returned to the rectification tower after boiling and heating by the second reboiler, and the rest is used as feed water for the next stage of rectification, the total number of rectification stages is N, the rectification process of each stage is consistent with that of the previous stage, and the heavy water product in the bottom of the Nth rectification tower is discharged when the purity requirement is met.

3. A compressed cycle heat supplied heavy water distillation process according to claim 1 or 2, characterized in that: The working medium is water.

4. A compressed cycle heat-supply heavy water distillation process according to claim 1, characterized in that: The primary rectification distillate discharged in step (2) is heat-exchanged with the feed water in step (1) by a raw water preheater.

5. A compressed cycle heat supplied heavy water distillation process according to claim 2, characterized in that: The heavy water with a deuterium content of more than 99.8% purified by the rectification system is transported to a heavy water storage tank in step (4).

6. A compressed cycle heat supplied heavy water distillation process according to claim 2, characterized in that: Part of the overhead product of the second rectification tower to the Nth rectification tower is returned to the rectification tower as reflux, and the rest is returned to the previous stage of rectification as raw material.

7. A compressed cycle heat supplied heavy water distillation process according to claim 1, characterized in that: The reflux ratio of the overhead product of the primary rectification in step (2) is 10-200.

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