Energy-saving rectification heavy water separation process

Abstract

The invention relates to the field of heavy water production, and discloses an energy-saving rectification heavy water separation process which comprises the following steps: (1) heating feed water, and carrying out primary rectification; (2) compressing steam at the top of the first-stage rectifying tower, then supplying heat to a first reboiler, performing heat exchange condensation on the compressed steam to form tower top produced liquid for first-stage rectification, enabling one part of the tower top produced liquid to flow back to the first-stage rectifying tower, and discharging the other part of the tower top produced liquid as first-stage rectification distillate; (3) a stripping section base solution of the first-stage rectifying tower flows into a first reboiler, and a part of the stripping section base solution is boiled to form rising steam; the rest part enters a tower kettle and is extracted as heavy water or used as feeding water for next-stage rectification; and (4) carrying out N-stage rectification and purification until the heavy water meets the purity requirement. According to the scheme, the boiling difference between water and heavy water is extremely small, tower top condensation heat is equivalent to a heat source required by a tower kettle, tower top steam is used for providing heat for the tower kettle, latent heat of steam is fully utilized, energy consumption is greatly reduced, and a large number of heat sources can be obtained with a small amount of power consumption.

Description

Technical Field

[0001] The present invention relates to the field of heavy water production, and in particular to an energy-saving distillation heavy water separation process. Background Art

[0002] Heavy water, a key raw material for the preparation of deuterium gas and deuterated solvents, is widely used in electronics, semiconductors, medicine, the nuclear industry, and scientific research. Industrial production utilizes the differences in the physical and chemical properties of heavy water and ordinary water to separate and purify it. Common methods include distillation, electrolysis, dual-temperature hydrogen sulfide-water exchange, dual-temperature hydrogen-water exchange, ammonia-hydrogen exchange, and cryogenic fractionation of liquid hydrogen.

[0003] The electrolysis method enriches heavy water by electrolyzing ordinary water, taking advantage of the fact that heavy water molecules are more difficult to electrolyze than ordinary water molecules. This method requires a large amount of electricity and time, and is relatively inefficient. The cost-effectiveness of electrolysis improves only after the feed water for electrolysis has been partially enriched. The dual-temperature hydrogen sulfide-water exchange method is based on the exchange of hydrogen and deuterium isotopes between water and hydrogen sulfide within a series of multi-stage towers. At low temperatures, deuterium migrates to water, while at high temperatures, deuterium migrates to hydrogen sulfide. This method is energy-efficient, but the medium is toxic, flammable, and somewhat corrosive, placing high demands on production processes and equipment. The dual-temperature hydrogen-water exchange method utilizes isotope exchange between water and hydrogen. Similar to the hydrogen sulfide-water exchange method, countercurrent contact is achieved within the towers, with deuterium transferring from hydrogen to liquid water in the low-temperature tower and from water to hydrogen in the high-temperature tower. This method also faces the risk of flammable and explosive media, and the isotope exchange catalyst requires large quantities and isotope exchange costs. The ammonia-hydrogen exchange method extracts deuterium from syngas using liquid ammonia in the presence of a catalyst. Within the exchange column, gas flows from the bottom to the top, while liquid ammonia flows from the top to the bottom. Deuterium is washed from the hydrogen in the syngas and concentrated in the liquid ammonia. This method often relies on the presence of syngas, resulting in a high ammonia-hydrogen separation coefficient. However, the catalyst loses its activity when exposed to moisture, necessitating the development of a high-performance hydrophobic catalyst. It also faces the dilemma of toxic, flammable, and explosive media. Liquid hydrogen cryogenic fractionation utilizes the difference in vapor pressure between liquid hydrogen and deuterium at low temperatures to achieve separation. At approximately 22K, the vapor pressure ratios of liquid hydrogen and deuterium (H2 / HD) are 1.6 and 2.5, respectively. The higher relative volatility results in higher separation efficiency. However, the requirement for cryogenic liquefaction also places new demands on industrial refrigeration and material properties.

[0004] In summary, the above methods have problems such as high energy consumption, high requirements for process equipment, toxic, flammable and explosive process media, high catalyst cost and easy deactivation. It is urgent to develop a low-energy consumption process to simplify process requirements and control production costs. Summary of the Invention

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

[0006] To achieve the above object, the present invention adopts the following technical solution: an energy-saving distillation heavy water separation process, comprising the following steps:

[0007] (1) After heating the feed water, it is fed into the middle section of the first-stage distillation tower for primary distillation;

[0008] (2) compressing the steam from the top of the first-stage distillation tower and using the compressed steam to heat the first-stage reboiler. The compressed steam is condensed through heat exchange to form the top produced liquid of the first-stage distillation tower. A portion of the top produced liquid is refluxed to the first-stage distillation tower, and the rest is discharged as the first-stage distillation distillate.

[0009] (3) The bottom liquid of the stripping section of the first-stage distillation tower flows into the first-stage reboiler. A portion of it boils to form rising steam and re-enters the stripping section of the distillation tower of this stage; the rest enters the tower kettle and is extracted as heavy water or as deuterium-enriched water for the next stage of distillation.

[0010] In this application, the bottom liquid of the stripping section refers to the liquid phase leaving the last packing or sieve plate of the stripping section.

[0011] The above process can not only further purify heavy water that has been treated by other concentration methods, but also perform preliminary treatment on feed water, and can be widely used for heavy water in different treatment stages; feeding from the middle of the first-stage distillation tower allows the light components in the feed water to continue to be purified in the distillation section, and the heavy components are further removed from the light components in the stripping section. At the same time, the traditional method of direct condensation of the overhead produced liquid is abandoned, but the opposite approach is taken, and the overhead steam is directly pressurized, and the pressurized steam is cooled and condensed by a reboiler, thereby further saving the energy consumption of the traditional reboiler, and the overall process can greatly save energy. In addition, compared with traditional electrolysis, dual-temperature hydrogen sulfide-water exchange, dual-temperature hydrogen-water exchange, ammonia-hydrogen exchange, and liquid hydrogen low-temperature fractionation, the process of this application does not involve high-cost catalysts, does not contain toxic, flammable, and explosive substances, and is conducive to effectively controlling production costs and improving safety.

[0012] Preferably, the above process further comprises step (4), that is, when the water in step (3) is used as feed water for the next stage of distillation, a portion of the overhead liquid of the secondary distillation is refluxed to the distillation tower of that stage, and the rest is returned to the primary distillation as a raw material. After the bottom liquid of the stripping section of the second-stage distillation tower is boiled and heated in the second-stage reboiler, a portion is vaporized into steam and returned to the stripping section of the distillation tower of that stage, and the rest is extracted as heavy water or as deuterium-enriched water for the next stage of distillation. The total number of distillation stages is N, and the distillation process of each stage is consistent with the first stage distillation, until the heavy water extracted from the bottom of the N-stage distillation tower meets the purity requirements and is transported to the heavy water storage tank. The optimized process adopts a multi-stage distillation method as a whole to achieve direct production of heavy water from ordinary feed water. The structure of the entire process is simpler, and the number of distillation stages can be flexibly adjusted according to different raw materials, making it more adaptable.

[0013] Preferably, in step (4), a portion of the heavy water having a deuterium content greater than 99.8% after being purified by the distillation system is transported to a heavy water storage tank.

[0014] Preferably, a portion of the overhead produced liquid from the third to Nth stage distillation towers is refluxed back to the distillation towers of that stage, with the remainder returned to the previous stage distillation as feedstock. After the feed water undergoes multiple stages of distillation, a large amount of light water is discharged from the system, and the deuterium content of the resulting overhead produced liquid gradually increases. Returning the overhead produced liquid from the distillation tower to the previous stage distillation tower as feedstock avoids returning this deuterium-containing water to the first stage distillation, thereby avoiding additional distillation steps.

[0015] Preferably, the first-stage reboiler is arranged in the first-stage distillation tower, and the compressed steam condenses and releases heat through the heat exchange tubes of the first-stage reboiler to heat the bottom liquid of the stripping section of the distillation tower. The heat exchange tubes of the first-stage reboiler are arranged horizontally, and the compressed steam condenses and releases heat through the inside of the horizontal heat exchange tubes. The medium in the distillation tower falls freely as a cold fluid and sprays on the surface of the horizontal heat exchange tubes to be heated and evaporated. Alternatively, the first-stage reboiler is arranged in the first-stage distillation tower, and the compressed steam condenses and releases heat through the outside of the heat exchange tubes of the first-stage reboiler to heat the bottom liquid of the stripping section of the distillation tower. The heat exchange tubes of the first-stage reboiler are arranged vertically, and the compressed steam condenses and releases heat through the outside of the vertical heat exchange tubes, and the medium in the tower forms a film inside the tubes to be heated and evaporated. The above two solutions achieve better energy saving and consumption reduction by placing the reboiler inside the distillation tower. This is because this method can prevent the medium in the tower from forming a static liquid column in the falling film evaporation reboiler. The static pressure brought by the static liquid column will increase the boiling point of the medium, resulting in the need for higher temperature steam as a heat source; the above technical features reduce the requirements for the outlet pressure of the compressor, and at the same time can effectively reduce the heat transfer temperature difference of the reboiler, saving energy.

[0016] Preferably, the top temperature of the first-stage distillation tower is 50-105°C, the bottom temperature of the first-stage distillation tower is 52-107°C, and the operating pressure of the first-stage distillation tower is 10-110 kPa. In this solution, the distillation process has a low operating pressure, the top operating temperature is slightly lower than the boiling point of heavy water, and the bottom operating temperature is slightly higher than the boiling point of heavy water, and extreme temperature and pressure conditions are not required. Due to the small difference in boiling points between water and heavy water, the temperature difference between the top and bottom of the distillation tower is extremely small, so the heat source required for condensation at the top and the bottom is equivalent. By compressing the steam at the top and simultaneously increasing the steam temperature and pressure, the latent heat of the steam is fully utilized. The condensation of the top steam and the heating of the bottom are coupled through the reboiler, and only a small amount of energy needs to be supplied by the compressor, effectively reducing energy consumption.

[0017] Preferably, the reflux ratio of the overhead produced liquid in the first-stage distillation in step (2) is 10-200.

[0018] Preferably, in step (1), the feed water is heated to 80-101°C before being introduced into the distillation tower. The preheated feed water temperature is more stable, which can reduce the drastic changes in the temperature gradient in the tower, making the distillation process easier to control and reducing the risk of product quality fluctuations.

[0019] Preferably, the deuterium content in the feed water is at least 0.014%, and impurities are removed in advance.

[0020] Preferably, the distillation tower uses carbon steel wire mesh filler to provide higher mass transfer efficiency while ensuring lower pressure drop, making it easy to connect multiple towers in series for distillation, thereby facilitating the separation of heavy water and ordinary water with similar boiling points.

[0021] Preferably, the reboiler is also used as the overhead steam condenser of the corresponding distillation column, saving the installation and maintenance costs of the condenser.

[0022] This solution has the following technical advantages:

[0023] (1) By taking advantage of the fact that the boiling point difference between water and heavy water is extremely small and the condensation heat at the top of the tower is equivalent to the heat source required by the bottom of the tower, the traditional method of heat exchange and condensation of the steam at the top of the tower is abandoned, and the method of pressurizing the steam at the top of the tower to provide heat for the bottom of the tower is adopted. A large amount of heat source can be obtained with a small amount of electricity consumption, and the energy consumption is usually only 1 / 40 to 1 / 60 of the heat required by the traditional distillation method; by compressing the steam at the top of the tower to increase the pressure and temperature of the steam, a higher-grade heat source is obtained, and the compressed steam is used to provide heat for the bottom of the tower. A large amount of low-grade heat is converted into high-grade heat for recycling, and energy is used efficiently, reducing the energy consumption of the device; by compressing the steam at the top of the tower and increasing the temperature and pressure of the steam, the latent heat of the steam is fully utilized, and energy consumption is greatly reduced;

[0024] (2) There is no need to set up a condenser at the top of the tower to condense the top steam. The reboiler acts as both the top condenser and the bottom reboiler, which saves equipment investment and reduces costs. In particular, the reboiler is built into the distillation tower, which better avoids the formation of a static liquid column in the falling film evaporation reboiler by the medium in the tower, and reduces the impact of the traditional reboiler on the increase in boiling point due to the pressure of the liquid column. The reduction in the heat transfer temperature difference also reduces the requirements for the outlet pressure of the compressor, thereby reducing the energy consumption of the compressor.

[0025] (3) Compared with other isotope exchange methods and low-temperature fractionation processes, the operating medium of this application is ordinary water or low-concentration heavy water, which does not require catalysts and toxic, flammable, explosive, and corrosive media, making the production process safer and more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process flow of Example 1 of the present invention.

[0027] Figure 2 This is a schematic diagram of the process flow of Example 2 of the present invention. DETAILED DESCRIPTION

[0028] The following is further described in detail through specific implementation methods:

[0029] The reference numerals in the drawings of the specification include: a first-stage distillation tower 11, a first-stage compressor 12, a first-stage reboiler 13, a first-stage reflux pump 14, a first-stage heavy water pump 15, a first-stage reflux tank 16, a fifth-stage distillation tower 51, a fifth-stage compressor 52, a fifth-stage reboiler 53, a fifth-stage reflux pump 54, a fifth-stage heavy water pump 55, and a fifth-stage reflux tank 56.

[0030] Example 1:

[0031] An energy-saving distillation heavy water separation process, as shown in the following Figure 1 As shown, the following steps are included:

[0032] (1) Feed water having a deuterium content of at least 0.014% is heated to 80-101°C, which is slightly lower than the boiling point of ordinary water, and then fed into the middle section of the first-stage distillation tower 11 for primary distillation. The light components in the feed water are further purified in the distillation section, and the heavy components are further removed from the light components in the stripping section, thereby achieving efficient separation to obtain deuterium-low overhead vapor and deuterium-rich water in the bottom of the tower.

[0033] Among them, heating the feed water to 80-101°C before passing it into the distillation tower can not only make the raw material temperature more stable, but also reduce the drastic changes in the temperature gradient in the tower.

[0034] In this step, the top temperature of the first-stage distillation tower 11 is 50-105° C., and the bottom temperature of the first-stage distillation tower 11 is 52-107° C. The operating pressure of the first-stage distillation tower 11 can be 10-110 kPa. In this embodiment, the operating pressure is controlled at 100-110 kPa, operating at near-normal pressure, and simplifying the equipment. The top operating temperature is controlled at 98-108° C., slightly below the boiling point of heavy water, and the bottom operating temperature is controlled at 100-110° C., slightly above the boiling point of heavy water. The steam at the top of the tower is compressed to heat the reboiler, fully utilizing the latent heat of the steam.

[0035] In this step, when the entire system is initially started, external steam is introduced to heat the first-stage reboiler 13. After the system is running stably, the supply of external steam is stopped to ensure the stable operation of the system.

[0036] (2) The overhead steam of the first-stage distillation tower 11 is compressed, and the compressed steam is used to heat the first-stage reboiler 13. The compressed steam is condensed by heat exchange to form the overhead produced liquid of the first-stage distillation. A portion of the overhead produced liquid is refluxed to the first-stage distillation tower 11, and the rest is discharged as the first-stage distillation distillate. The overhead reflux ratio is 10 to 80. Specifically, in this step, the overhead produced liquid is first passed into the first-stage reflux tank 16 for buffering, and then pumped to the upper distillation section of the first-stage distillation tower 11 by the first reflux flow pump 14, so that the refluxed overhead produced liquid is fully in contact with the rising steam in the distillation tower at the top of the tower. The overhead produced liquid carries high-boiling-point components and flows downward, exchanging with low-boiling-point components in the rising steam, so that the water concentration in the overhead steam is gradually increased, and the heavy water carried in the steam is reduced. The discharged distillate is first mixed with the feed water of the distillation tower of this stage and then added to the distillation tower. The heat of the produced liquid at the top of the tower is used to preheat the feed water, recover heat and save energy.

[0037] In this step, the tower top vapor is compressed by the first stage compressor 12 and then heat is supplied to the first stage reboiler 13. The compressor used is a common device for increasing gas pressure, which reduces the volume of the gas by compressing it, thereby increasing the pressure and temperature.

[0038] (3) The bottom liquid of the stripping section of the first-stage distillation tower 11 flows into the first-stage reboiler 13, a portion of which boils to form rising steam and re-enters the bottom of the stripping section of the distillation tower of this stage; the rest enters the tower kettle and is extracted as heavy water or as deuterium-enriched water for the next stage of distillation.

[0039] In this step, a portion of the bottom liquid of the stripping section of the distillation tower is vaporized in the first-stage reboiler 13 by heat exchange with the tower top steam compressed by the compressor to form steam, and another portion of the deuterium-enriched water flows downward along the heat exchange tube of the first-stage reboiler 13 to the tower bottom. The steam rises in the first-stage distillation tower 11, and the rising steam contacts the liquid phase in the first-stage distillation tower 11 for mass and heat transfer. The heavy components are continuously enriched downward, and the light components are continuously enriched upward. Finally, low-deuterium tower top steam is obtained at the top of the first-stage distillation tower 11, and deuterium-enriched water is obtained in the tower bottom.

[0040] The first three steps can be used as a separate process to purify the preliminarily treated heavy water, and then transfer the portion of heavy water with a deuterium content greater than 99.8% after purification by the distillation system to a heavy water storage tank, or to preliminarily treat the feed water to increase the concentration of heavy water in the feed water. This embodiment also includes a subsequent step (4) to directly extract the required heavy water from the feed water.

[0041] (4) A portion of the overhead liquid from the secondary distillation is refluxed back to the distillation tower of that stage, and the remainder is returned to the primary distillation as a feedstock. The bottom liquid from the stripping section of the second distillation tower is heated by boiling in the second-stage reboiler, and a portion of it is returned to the stripping section of that distillation tower, while the remainder is used as deuterium-enriched water for the next stage of distillation. The total number of distillation stages is N, where N is a positive integer. The distillation process for each stage is the same as that for the primary distillation, until the heavy water produced from the bottom of the N-stage distillation tower meets the purity requirements and is then transported to the heavy water storage tank. This step further purifies the heavy water to obtain heavy water of the corresponding purity requirements. The top temperature of the second through Nth distillation towers is 50-105°C, the bottom temperature of these towers is 52-110°C, the operating pressure of these towers is 10-110 kPa, and the top reflux ratio of these towers is 10-200. The top operating temperature is controlled at 50-105°C, and the bottom operating temperature is controlled at 50-110°C. In this solution, heavy water extracted from the bottom of the Nth distillation tower meets the purity requirements for feed water and product heavy water through enrichment from the second to Nth distillation systems. The heavy water is then transferred to the heavy water storage tank after meeting the purity requirements.

[0042] In this embodiment, a five-stage distillation system is used. Each stage of the distillation system is composed of a distillation tower, a compressor, a reboiler, a reflux pump, a reflux tank and a heavy water pump. The process of the secondary distillation to the fifth stage distillation is consistent with the process of the first stage distillation system in the aforementioned steps (1) to (3). In addition to being used as the top reflux liquid, the top produced liquid of the second stage distillation is returned to the first stage distillation as a raw material; in addition to being used as the top reflux liquid, the top produced liquid of the third stage distillation to the fifth stage distillation is returned to the previous stage distillation as a raw material; in addition, the deuterium-enriched water in the bottom of the fifth stage distillation tower 51 is discharged as heavy water.

[0043] The operating parameters of the five-stage distillation and the effects of purifying heavy water in this embodiment are as follows:

[0044]

[0045]

[0046] In this embodiment, the deuterium content of the feed water is 0.015%. A five-stage distillation process is provided, and the recovery rate of the first four stages is controlled between 5% and 8%. The reflux ratio is preferably between 20 and 190, which is beneficial for improving separation efficiency. The distillate from the last stage of distillation is recycled to the previous stage of distillation, reducing deuterium loss. The distillation process operating pressure is 100 to 110 kPa, close to atmospheric pressure. Normal pressure operation facilitates equipment simplification and eliminates the need for additional equipment to maintain a negative pressure in the system, effectively reducing equipment investment. The tower top operating temperature is controlled between 99.5 and 100.5°C, slightly below the boiling point of heavy water, and the tower bottom operating temperature is controlled between 101.0 and 104.0°C, slightly above the boiling point of heavy water. Utilizing the small difference in boiling points between water and heavy water, the tower top vapor is pressurized and used as a heat source for the reboiler, eliminating the need for additional condensing equipment to condense the tower top vapor. This not only effectively utilizes the latent heat of the tower top vapor, reducing energy consumption, but also simplifies the process flow and makes operation easier.

[0047] The present solution also provides a system for implementing the above-mentioned process, comprising at least two stages of distillation units, each of which is mainly composed of a distillation tower, a compressor, a reboiler, a reflux pump and a heavy water pump, with similar structures and principles. For example, the first-stage distillation unit comprises: a first-stage distillation tower 11, a first-stage compressor 12, a first-stage reboiler 13, a first-stage reflux pump 14, a first-stage heavy water pump 15 and a first-stage reflux tank 16.

[0048] Specifically, a pipeline for conveying feed water is connected to the middle section of the first distillation tower. The distillation tower can be a traditional packed tower or a sieve plate tower. In this embodiment, the first-stage distillation tower 11 preferably uses carbon steel wire mesh packing. The inlet end of the first-stage compressor 12 is connected to the steam outlet at the top of the first-stage distillation tower 11. The outlet end of the first-stage compressor 12 is connected to the heating medium inlet of the first-stage reboiler 13. The bottom of the kettle of the first-stage distillation tower 11 is connected to the middle section of the distillation tower of the next-stage distillation system via the first-stage heavy water pump 15. The gas-liquid mixture at the top outlet of the first reboiler 13 rises to the distillation section of the first-stage distillation tower 11, and the condensate outlet of the heating medium of the first-stage reboiler 13 is connected to the first-stage reflux tank 16. The first-stage reflux tank 16 is connected to the upper distillation section of the first-stage distillation tower 11 and the external system through the first-stage reflux pump 14. A part of the bottom liquid of the distillation section forms steam under the action of the first reboiler 13, and the other part flows downward from the first reboiler 13 to the bottom of the first-stage distillation tower 11 to form deuterium-enriched water in the bottom. Here, the first-stage reboiler 13 is also used as a condenser, so that the top of the first-stage distillation tower 11 no longer needs to be equipped with an additional condenser to condense the top steam, reducing the complexity of the equipment.

[0049] In this embodiment, a total of five stages of distillation are employed, which can be adjusted according to actual needs. In this solution, the fifth-stage distillation system includes a fifth-stage distillation tower 51, a fifth-stage compressor 52, a fifth-stage reboiler 53, a fifth-stage reflux pump 54, a fifth-stage heavy water pump 55, and a fifth-stage reflux tank 56. The second-stage distillation system differs from the first-stage distillation system in that the condensate outlets of the heating medium of the corresponding reboilers are connected to the upper portion of the corresponding distillation tower and the middle portion of the first-stage distillation tower 11 respectively through reflux pumps. In the third-stage distillation system, which is the fifth-stage distillation system, the condensate outlets of the heating medium of the corresponding reboilers are connected to the upper portion of the corresponding distillation tower and the middle portion of the distillation tower of the previous stage of distillation respectively through reflux pumps. In addition, the bottom of the fifth distillation tower of the fifth-stage distillation system is connected to the fifth reboiler 53 and the heavy water storage tank via a heavy water pump.

[0050] The distillation tower used in this example is a common device used in chemical production to separate liquid mixtures. This separation is achieved by exploiting the different boiling points of the various components in a mixture. Low-boiling-point components readily evaporate into the gas phase and rise with the gas flow, while high-boiling-point components more readily condense in the liquid phase and flow downward along the tower. Through this repeated process of gas-liquid contact, mass transfer, and heat transfer, high-purity light components are ultimately obtained at the tower top and high-purity heavy components in the tower bottom.

[0051] The reboiler used in this embodiment is a vertical reboiler. The heat exchange tubes of the reboiler are arranged vertically. The pressurized top steam is used as the heating medium to flow through the shell side. The bottom liquid of the distillation tower is transported to the stripping section of the reboiler from the bottom part as the process fluid and flows through the inner side of the tube. The top steam and the deuterium-enriched water are not in direct contact. The bottom liquid of the stripping section is vaporized and boiled in the tube, and the top steam is condensed by heat exchange on the shell side.

[0052] Example 2

[0053] The difference between this embodiment and embodiment 1 is that a horizontal reboiler is used in this embodiment. Figure 2 As shown, the heat exchange tubes of the reboiler are arranged horizontally, the pressurized top steam is used as the heating medium to flow through the inner side of the tube, the bottom liquid of the distillation tower is transported to the stripping section of the reboiler as the process fluid to flow through the shell side of the tube, and part of the deuterium-enriched water falls into the tower bottom.

[0054] The above is only an embodiment of the present invention, and the common sense such as the known specific structure, characteristics and reactant ratio in the scheme are not described too much here. It should be pointed out that for those skilled in the art, without departing from the inventive concept, some deformations and improvements can also be made, such as simple adjustments to the process flow and equipment structure, such as simply adjusting the selection of parameters within or near a specified parameter range, etc., and the technical effect can be expected to be similar to the embodiment of the present invention, and these should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation methods in the description and other records can be used to explain the content of the claims.

Claims

1. An energy-saving distillation heavy water separation process, characterized in that: The following steps are involved: (1) After heating the feed water, it is fed into the middle section of the first-stage distillation tower for primary distillation; (2) compressing the steam from the top of the first-stage distillation tower and using the compressed steam to heat the first-stage reboiler. The compressed steam is condensed through heat exchange to form the top produced liquid of the first-stage distillation tower. A portion of the top produced liquid is refluxed to the first-stage distillation tower, and the rest is discharged as the first-stage distillation distillate. (3) The bottom liquid of the stripping section of the first-stage distillation tower flows into the first-stage reboiler, where a portion of it boils to form rising steam; the rest enters the tower kettle and is extracted as heavy water or as deuterium-enriched water for the next stage of distillation.

2. The energy-saving distillation heavy water separation process according to claim 1, characterized in that: The method further includes the following steps: when the deuterium-enriched water in the bottom of the tower in step (4) is subjected to the next stage of distillation, a portion of the overhead liquid of the secondary distillation is refluxed to the distillation tower of this stage, and the remaining portion is returned to the first distillation as a raw material; after the bottom liquid of the stripping section of the second-stage distillation tower is boiled and heated in the second-stage reboiler, a portion of it forms rising steam and returns to the distillation tower of this stage, and the remaining portion enters the bottom of the tower to be extracted as heavy water or to be subjected to the next stage of distillation as deuterium-enriched water; the total number of distillation stages is N, and the distillation process of each stage is consistent with the first stage distillation, until the heavy water extracted from the bottom of the N-stage distillation tower meets the purity requirement and is then extracted.

3. The energy-saving distillation heavy water separation process according to claim 2, characterized in that: In the step (4), the heavy water with a deuterium content greater than 99.8% after being purified by the distillation system is transported to a heavy water storage tank.

4. The energy-saving distillation heavy water separation process according to claim 2, characterized in that: A portion of the overhead liquid from the third-stage distillation tower to the N-stage distillation tower is refluxed to the distillation tower of this stage, and the rest is returned to the previous stage distillation as raw material.

5. The energy-saving distillation heavy water separation process according to claim 1, characterized in that: The first-stage reboiler is arranged in the first-stage distillation tower, and the compressed steam condenses and releases heat through the heat exchange tube of the first-stage reboiler to heat the bottom liquid of the stripping section of the distillation tower.

6. The energy-saving distillation heavy water separation process according to claim 1, characterized in that: The first-stage reboiler is arranged in the first-stage distillation tower, and the compressed steam condenses and releases heat outside the heat exchange tube of the first-stage reboiler to heat the bottom liquid of the stripping section of the distillation tower.

7. An energy-saving distillation heavy water separation process according to claim 1 or 2, characterized in that: The distillation tower is filled with wire mesh.

8. The energy-saving distillation heavy water separation process according to claim 1, characterized in that: The reflux ratio of the overhead liquid produced in the first-stage distillation in step (2) is 10-200.

9. An energy-saving distillation heavy water separation process according to claim 1 or 2, characterized in that: The reboiler also serves as a condenser at the top of the distillation tower.

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