A method and apparatus for heavy water concentration and stripping of tritium containing waste water

Abstract

This invention provides a method and apparatus for heavy water concentration and desalination of tritium-containing wastewater. The method includes: performing N-stage distillation on raw water to obtain a rich solution and a lean solution; the N-stage distillation includes: using the i-th stage high-boiling liquid as the system to be distilled for the (i+1)-th stage distillation; pressurizing the first stage low-boiling gas; subjecting at least a portion of the reboiling system of at least one stage of the N-stage distillation to a first reboiling heat exchange treatment; and subjecting at least a portion of the reboiling system of the i-th stage distillation to a second reboiling heat exchange treatment using the (i+1)-th stage low-boiling gas; wherein the distillation pressure of the (i+1)-th stage distillation is higher than the distillation pressure of the i-th stage distillation. This method can reduce energy consumption in heavy water concentration and tritium-containing wastewater desalination with low investment.

Description

Technical Field

[0001] This invention relates to the nuclear industry, and more particularly to a method and apparatus for heavy water concentration and desalination of tritium-containing wastewater. Background Technology

[0002] Heavy water has significant applications in the nuclear industry, neutron moderators, and isotope separation, while tritium-containing wastewater is widely present in nuclear power plant operation, nuclear fuel reprocessing, and related nuclear industry processes. Due to the relatively small differences in physical properties between deuterium, tritium, and protium, their separation typically relies on efficient isotope separation technologies. Water distillation technology, with its mature process, stable flow, relatively simple equipment structure, high safety, and suitability for large-scale continuous operation, has been widely used in heavy water concentration and tritium-containing wastewater desalination.

[0003] Meanwhile, as the nuclear industry's requirements for separation efficiency, equipment scale, and operational economy continue to increase, reducing energy consumption and equipment investment during the separation process has become an important research direction in related fields. Currently, the use of water distillation technology for heavy water concentration and tritium-containing wastewater desalination presents problems such as large equipment scale, high system energy consumption, limited tower heat utilization efficiency, and insufficient overall operational economy, making it difficult to simultaneously meet the demands for low-energy operation and low investment costs.

[0004] Therefore, how to reduce energy consumption in heavy water concentration and tritium-containing wastewater desalination with low-cost investment remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a method for heavy water concentration and desalination of tritium-containing wastewater, which can reduce energy consumption in heavy water concentration and desalination of tritium-containing wastewater with low investment cost.

[0006] The present invention also provides an apparatus that can reduce energy consumption in heavy water concentration and desalination of tritium-containing wastewater with low-cost investment.

[0007] In a first aspect, the present invention provides a method for heavy water concentration and desalination of tritium-containing wastewater, comprising: performing N-stage distillation on raw water to obtain a rich liquid and a lean liquid; the N-stage distillation includes: using the i-th stage high-boiling liquid as the system to be distilled for the (i+1)-th stage distillation, pressurizing the first stage low-boiling gas, performing a first reboiling heat exchange treatment on at least a portion of the reboiling system of at least one stage of the N-stage distillation, and performing a second reboiling heat exchange treatment on at least a portion of the reboiling system of the i-th stage distillation by the (i+1)-th stage low-boiling gas; wherein the distillation pressure of the (i+1)-th stage distillation is higher than the distillation pressure of the i-th stage distillation; the rich liquid is the N-th stage high-boiling liquid, and the lean liquid is the liquid phase product of the first stage low-boiling gas after the first reboiling heat exchange treatment; N≥2, 1≤i≤N-1.

[0008] In one possible implementation, as described above, the low-boiling gas of the (i+1)th stage is subjected to the second reboiling heat exchange treatment on at least a portion of the reboiling system of the distillation process of the (i)th stage, to obtain the low-boiling liquid of the (i+1)th stage.

[0009] A portion of the low-boiling liquid from stage i+1 is returned to participate in the distillation process of stage i+1, while the remaining low-boiling liquid from stage i+1 participates in the distillation process of stage i.

[0010] In one possible implementation, as described above, the first reboiling heat exchange treatment includes: pressurizing the first-stage low-boiling gas to obtain a first-stage pressurized low-boiling gas.

[0011] The first-stage pressurized low-boiling gas is subjected to N-stage splitting to obtain N streams of first-stage sub-pressurized low-boiling gas;

[0012] Each of the first-stage sub-pressurized low-boiling gases is used to perform a first reboiler heat exchange treatment on at least a portion of the reboiling system in the N-stage distillation process.

[0013] In one possible implementation, as described above, the first-stage low-boiling gas is subjected to the first reboiling heat exchange treatment to obtain the first-stage low-boiling liquid.

[0014] The first-stage low-boiling liquid is subjected to recooling treatment to obtain a first-stage low-boiling recooled liquid;

[0015] A portion of the first-stage low-boiling recooled liquid is returned to participate in the first-stage distillation process, and the remaining first-stage low-boiling recooled liquid is the lean liquid.

[0016] In one possible implementation, as described above, the first-stage low-boiling liquid preheats the raw material water before performing the recooling treatment.

[0017] In one possible implementation, as described above, the distillation pressure of the first stage distillation process is 5-15 kPaA; and the distillation pressure of the Nth stage distillation process is 6-120 kPaA.

[0018] In one possible implementation, as described above, the pressure of the first-stage pressurized low-boiling gas is 101-600 kPaA.

[0019] In a second aspect, the present invention provides an apparatus for implementing the method described in any one of the first aspects of the present invention, comprising N stages of distillation columns; wherein each stage of the distillation column includes a raw material inlet, a high-boiling liquid outlet, and a low-boiling gas outlet, and N≥2; each stage of the distillation column includes a first reboiler, and the first to (N-1)th stages of the distillation column further include a second reboiler;

[0020] Each stage of the first reboiler includes a first heat exchange medium inlet and a first heat exchange medium outlet, and each stage of the second reboiler includes a second heat exchange medium inlet and a second heat exchange medium outlet.

[0021] The high-boiling liquid outlet of stage i and the raw material inlet of stage i+1 are connected, 1≤i≤N-1;

[0022] At least one of the low-boiling gas outlet of stage 1 and the inlet of the first heat exchange medium of stage N is connected;

[0023] The low-boiling gas outlet of the (i+1)th stage is connected to the inlet of the second heat exchange medium of the ith stage;

[0024] It also includes a booster compressor; the booster compressor includes a booster inlet and a booster outlet, the low boiling gas outlet of the first stage is connected to the booster inlet, and the booster outlet is connected to the heat exchange medium inlet of the Nth stage.

[0025] In one possible embodiment, as described above, the outlet of the second heat exchange medium in the i-th stage is connected to the raw material inlet of the (i+1)-th stage and the raw material inlet of the i-th stage, respectively.

[0026] In one possible embodiment, the apparatus as described above further includes a recooler, wherein the recooling inlet of the recooler is connected to the outlet of the first heat exchange medium in the Nth stage, and the recooling outlet of the recooler is connected to the raw material inlet in the first stage.

[0027] In one possible embodiment, the apparatus as described above further includes a raw water preheater; the raw water outlet of the raw water preheater is connected to the raw water inlet of the first stage, and the first heat exchange medium outlet of the Nth stage is connected to the recooling inlet through the heat exchange medium channel of the raw water preheater.

[0028] The method for heavy water concentration and desalination of tritium-containing wastewater provided by this invention adopts a multi-stage cascade distillation approach. By progressively increasing the pressure of the distillation process, the gas phase temperature of the subsequent distillation process meets the heat exchange requirements of the previous distillation process, realizing the cascade utilization of heat and reducing the system's operating energy consumption. At the same time, the low-boiling gas obtained from the first-stage distillation process is pressurized to raise its temperature, providing heat for each stage of distillation, further reducing the operating cost of the device. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0030] Figure 1 This is a schematic diagram of the device provided in Embodiment 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of the device provided in Embodiment 2 of the present invention.

[0032] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] Heavy water has important applications in nuclear reactor moderators, neutron shielding materials, and isotope research, while tritium-containing wastewater is widely generated from nuclear power plant operation, nuclear fuel reprocessing, and other nuclear industry processes. Because deuterium, tritium, and common hydrogen isotopes have similar physicochemical properties, their separation typically requires highly efficient isotope separation technologies.

[0035] In existing technologies, heavy water concentration and desalination of tritium-containing wastewater are typically achieved using multi-stage cascade water distillation, heat pump distillation, or inter-tower thermal coupling technologies. While these technologies can achieve heavy water concentration and desalination of tritium-containing wastewater to some extent and reduce some system energy consumption, their overall economic efficiency still needs further improvement.

[0036] The inventors analyzed that while conventional cascade distillation can improve separation efficiency, the system typically requires a high reflux ratio and a large vaporization rate, resulting in high steam consumption and cooling load. Traditional heat pump distillation, although able to recover some of the top heat, requires a large amount of circulating steam and compressor load, leading to increased column diameter, compressor size, and equipment investment. Furthermore, in conventional inter-column thermal coupling schemes, the direction of heat utilization is usually limited by the temperature relationship between columns, and the overall heat recovery capacity of the system remains limited, thus leaving room for further improvement.

[0037] To address the aforementioned issues, this invention employs a multi-stage cascaded distillation method. By progressively increasing the pressure of the distillation process, the gas phase temperature of the subsequent distillation stage meets the heat exchange requirements of the preceding stage, achieving cascaded utilization of heat and reducing system operating energy consumption. Simultaneously, the low-boiling gas obtained from the first-stage distillation process is pressurized to raise its temperature, providing heat for each stage of distillation and further reducing the operating cost of the device.

[0038] In a first aspect, the present invention provides a method for heavy water concentration and desalination of tritium-containing wastewater, comprising:

[0039] The raw water is subjected to N-stage distillation to obtain rich and lean liquor;

[0040] The N-stage distillation process includes: using the i-th stage high-boiling liquid as the system to be distilled for the (i+1)-th stage distillation process, pressurizing the 1-th stage low-boiling gas, performing a first reboiling heat exchange treatment on at least a portion of the reboiling system of at least one stage of the N-stage distillation process, and performing a second reboiling heat exchange treatment on at least a portion of the reboiling system of the i-th stage distillation process using the (i+1)-th stage low-boiling gas.

[0041] The distillation pressure of the (i+1)th stage distillation process is higher than that of the ith stage distillation process; the rich liquid is the Nth stage high-boiling liquid, and the lean liquid is the liquid phase product of the 1st stage low-boiling gas after the first reboiling heat exchange treatment; N≥2, 1≤i≤N-1.

[0042] In this invention, the raw water used for heavy water concentration and desalination of tritium-containing wastewater is mainly composed of H2O. The deuterium and tritium components in this water have higher boiling points and lower volatility, thus they are more easily enriched in the high-boiling liquid during distillation, while the lighter component H2O more easily enters the low-boiling gas. Based on this characteristic, the heavy water concentration in the (i+1)th stage high-boiling liquid obtained after the (i+1)th stage distillation is further increased compared to the (i)th stage distillation system, while the proportion of light water in the (i+1)th stage low-boiling gas is relatively increased. Through multi-stage continuous distillation, this invention can gradually amplify the volatility differences between different isotopic waters, thereby achieving heavy water enrichment and the gradual removal of heavy isotopic water from tritium-containing wastewater.

[0043] Specifically, the feed water first undergoes a first-stage distillation process, yielding a first-stage high-boiling liquid and a first-stage low-boiling gas. The first-stage high-boiling liquid is then used as the system to be distilled in the second-stage distillation process, while the first-stage low-boiling gas serves as the heat source for the subsequent first reboiling heat exchange process. Subsequently, the second-stage distillation process further separates the first-stage high-boiling liquid, yielding a second-stage high-boiling liquid and a second-stage low-boiling gas. The second-stage low-boiling gas then performs a second reboiling heat exchange process on at least a portion of the reboiling system from the first-stage distillation process.

[0044] Similarly, the i-th stage of distillation yields an i-th stage high-boiling liquid and an i-th stage low-boiling gas. The i-th stage high-boiling liquid serves as the system to be distilled in the (i+1)-th stage, and the i-th stage low-boiling gas is used for a second reboiling heat exchange treatment on at least a portion of the reboiling system from the (i-1)-th stage distillation. Finally, the N-th stage of distillation yields an N-th stage high-boiling liquid and an N-th stage low-boiling gas, with the N-th stage high-boiling liquid being output as a rich liquid. It should be noted that the rich liquid can be any one of the N-th stage high-boiling liquids or any combination thereof, determined by the isotopic content requirements of heavy water; this invention does not impose such limitations.

[0045] In this process, since the distillation pressure of the (i+1)th stage distillation process is higher than that of the i-th stage distillation process, the low-boiling gas of the (i+1)th stage has a higher temperature than the reboiling system of the i-th stage distillation process, thus providing reboiling heat to the i-th stage distillation process and realizing the cascade utilization of heat transfer along the distillation stages.

[0046] Meanwhile, the first-stage low-boiling gas is pressurized to obtain the first-stage pressurized low-boiling gas. Since the temperature of the first-stage pressurized low-boiling gas increases through pressurization, the heat it carries can be used to heat the subsequent distillation process, further optimizing the overall energy consumption. After completing the first reboiling heat exchange treatment, the first-stage low-boiling gas undergoes a phase change to form a liquid product, which is then output as lean liquor.

[0047] Furthermore, the high-boiling liquid in stage i serves as the distillation system for stage i+1. Therefore, as the number of distillation stages increases, some light components continue to separate in the form of low-boiling gas, and the amount of material entering the subsequent distillation process gradually decreases. This results in a gradual reduction in the feed load of the subsequent distillation processes, which in turn reduces the corresponding equipment specifications, heat exchange area, and system circulation load, thereby reducing equipment investment costs and operating energy consumption. This further improves the economic efficiency of the entire heavy water concentration and tritium-containing wastewater desalination process.

[0048] In one possible embodiment, as described above, the i+1th stage low-boiling gas is subjected to a second reboiling heat exchange treatment on at least a portion of the reboiling system of the i-th stage distillation process to obtain the i+1th stage low-boiling liquid; a portion of the i+1th stage low-boiling liquid is returned to participate in the i+1th stage distillation process, and the remaining i+1th stage low-boiling liquid participates in the i-th stage distillation process.

[0049] In this embodiment, the (i+1)th stage low-boiling gas first performs a second reboiling heat exchange treatment on at least part of the reboiling system of the i-th stage distillation process. The heat in the (i+1)th stage low-boiling gas is transferred to the reboiling system of the i-th stage distillation process to maintain the vapor-liquid circulation and separation process in the i-th stage distillation process, thereby realizing the stepwise transfer of heat from the high-pressure distillation process to the low-pressure distillation process.

[0050] After completing the second reboiling heat exchange process, the low-boiling gas in stage i+1 condenses to form a low-boiling liquid in stage i+1. Subsequently, a portion of the low-boiling liquid in stage i+1 returns to participate in the distillation process in stage i+1 to maintain the gas-liquid contact and separation stability within the distillation process; the remaining low-boiling liquid in stage i+1 participates in the distillation process in stage i, allowing a portion of the stream from stage i+1 to re-enter the previous distillation process for further separation. Through this stream reflux and cross-stage stream return structure, the material coupling between distillation processes can be improved, the loss of heavy components can be reduced, and the overall separation efficiency of the system can be improved.

[0051] In one possible embodiment, as described above, the first reboiling heat exchange treatment includes: pressurizing the first-stage low-boiling gas to obtain a first-stage pressurized low-boiling gas; performing an N-stage splitting treatment on the first-stage pressurized low-boiling gas to obtain N streams of first-stage sub-pressurized low-boiling gas; and causing each stream of first-stage sub-pressurized low-boiling gas to perform a first reboiling sub-heat exchange treatment on at least a portion of the reboiling system in the N-stage distillation treatment.

[0052] In this embodiment, the first-stage pressurized low-boiling gas is further subjected to N-stage splitting treatment to form N streams of first-stage sub-pressurized low-boiling gas. Each stream of first-stage sub-pressurized low-boiling gas performs first reboiler heat exchange treatment on at least a portion of the reboiling system in the N-stage distillation process. Since the temperature of the first-stage pressurized low-boiling gas increases through pressurization treatment, it can provide reboiling heat to multiple distillation processes after splitting treatment, so that the heat carried by the first-stage low-boiling gas is more fully utilized.

[0053] In one possible embodiment, as described above, the first-stage low-boiling gas undergoes a first reboiling heat exchange treatment to obtain a first-stage low-boiling liquid; the first-stage low-boiling liquid is then subjected to a recooling treatment to obtain a first-stage low-boiling recooled liquid; a portion of the first-stage low-boiling recooled liquid is returned to participate in the first-stage distillation treatment, and the remaining first-stage low-boiling recooled liquid is a lean liquid.

[0054] In this embodiment, the first-stage low-boiling gas undergoes a first reboiling heat exchange treatment to transform into a first-stage low-boiling liquid, which then enters a recooling treatment to control the temperature. Subsequently, a portion of the first-stage low-boiling recooled liquid is returned as reflux to participate in the first-stage distillation process, replenishing the low-boiling components in the system and maintaining the gas-liquid balance and composition gradient during the distillation process. The other portion serves as the final lean liquid discharged, achieving continuous removal of low-boiling components and system material renewal. This approach can improve the overall thermal integration efficiency of the system while maintaining compositional stability during the distillation process through the reflux and lean liquid discharge mechanism.

[0055] In one possible embodiment, as described above, the first-stage low-boiling liquid preheats the raw material water and then cools it again.

[0056] In this embodiment, after the first-stage low-boiling liquid enters the raw material preheating treatment, it indirectly exchanges heat with the raw material water, so that the sensible heat in the first-stage low-boiling liquid is directionally transferred to the raw material water, thereby realizing the heating pretreatment of the raw material water, reducing the heat load of the first-stage distillation treatment, while the first-stage low-boiling liquid cools down, further reducing the energy load of the recooling treatment.

[0057] In one possible embodiment, as described above, the distillation pressure of the first-stage distillation process is 5-15 kPaA; and the distillation pressure of the Nth-stage distillation process is 6-120 kPaA.

[0058] In this embodiment, the first-stage distillation process operates under deep low-pressure conditions of 5-15 kPaA, which can significantly reduce the relative volatility threshold of low-boiling components, enhance the gas-liquid phase equilibrium shift, and make it easier for light components to be removed from the liquid phase, thereby increasing the separation driving force and reducing boiling point-related energy consumption. Subsequently, the distillation process pressure is gradually increased to 6-120 kPaA, causing the gas-liquid equilibrium of the system to gradually shift towards high temperature and high pressure, thereby forming a stable pressure gradient. This ensures that the necessary phase equilibrium difference is maintained between each stage to drive separation, and that heat is transferred unidirectionally through pressure increase, reducing reflux disturbance or energy loss.

[0059] In one possible embodiment, as described above, the pressure of the first-stage pressurized low-boiling gas is 101-600 kPaA.

[0060] In this embodiment, after the first-stage pressurized low-boiling gas is boosted to 101-600 kPaA, its thermodynamic state is reasonably matched with the subsequent higher-stage operating pressure range. This allows it to release latent heat as an effective heat source when entering the subsequent distillation stage, achieving directional heating from the high-pressure side to the relatively low- or medium-pressure system. This improves the overall energy utilization rate and the stability of multi-stage continuous operation.

[0061] In a second aspect, the present invention provides an apparatus for implementing the method of any one of the first aspects of the present invention, comprising N stages of distillation columns; wherein each stage of distillation column includes a feed inlet, a high-boiling liquid outlet, and a low-boiling gas outlet, and N≥2; each stage of distillation column includes a first reboiler, and the first to (N-1)th stage distillation columns further include a second reboiler;

[0062] Each stage of the first reboiler includes a first heat exchange medium inlet and a first heat exchange medium outlet, and each stage of the second reboiler includes a second heat exchange medium inlet and a second heat exchange medium outlet.

[0063] The outlet of the i-th stage high-boiling liquid and the inlet of the (i+1)-th stage raw material are connected, 1≤i≤N-1;

[0064] At least one of the first-stage low-boiling gas outlet and the first-stage heat exchange medium inlet of the Nth stage is connected;

[0065] The low-boiling gas outlet of stage i+1 and the inlet of the second heat exchange medium of stage i are connected;

[0066] It also includes a booster compressor; the booster compressor includes a booster inlet and a booster outlet, the first-stage low-boiling gas outlet is connected to the booster inlet, and the booster outlet is connected to the N-stage heat exchange medium inlet.

[0067] In this invention, raw water enters the first-stage distillation column through the raw material inlet. Under the heat provided by the first and second reboilers, gas-liquid mass transfer separation occurs, forming a first-stage high-boiling liquid and a first-stage low-boiling gas. The first-stage low-boiling gas enters the booster inlet of the booster compressor from the first-stage low-boiling gas outlet. After boosting, it is output as first-stage boosted low-boiling gas from the booster outlet and is then delivered to the first heat exchange medium inlet of the N-stage first reboiler through the booster outlet to heat the reboiling system in each stage of distillation.

[0068] Meanwhile, the low-boiling gas of stage i+1 is drawn out from the outlet of stage i+1 and enters the second heat exchange medium inlet of the second reboiler of stage i to supplement the heat exchange of the reboiler system of stage i, thereby realizing heat coupling and cascade utilization between multiple stages.

[0069] In addition, the first-stage high-boiling liquid is discharged from the first-stage high-boiling liquid outlet and enters the second-stage distillation column. Similarly, the i-th stage high-boiling liquid is discharged from the i-th stage high-boiling liquid outlet and directly enters the i+1-th stage feed inlet as the feed system for subsequent distillation treatment, so as to realize the gradual enrichment of heavy components and the gradual removal of light components.

[0070] After releasing heat, the first-stage pressurized low-boiling gas gradually condenses into the first-stage low-boiling liquid and is discharged through the outlet of the first heat exchange medium of each stage. It then further participates in the subsequent material circulation and lean liquid formation process within the system. Through the above structure, the system achieves synergistic optimization of progressive enrichment of high-boiling liquid by step-by-step feeding and cross-stage heating of low-boiling gas.

[0071] In one possible embodiment, as described above, the outlet of the second heat exchange medium in the i-th stage is connected to the raw material inlet of the (i+1)-th stage and the raw material inlet of the i-th stage, respectively.

[0072] In this embodiment, the low-boiling gas of stage i+1, after heat exchange in the second heat exchanger of stage i, is discharged from the outlet of the second heat exchange medium of stage i and diverted for transport: part of it directly enters the first-stage distillation column from the feed inlet of stage i and participates in the first-stage distillation process as feedstock; the other part is transported to the feed inlet of stage i+1 and enters the first-stage distillation column to participate in the first-stage distillation process. Through the above-mentioned material reflux and cross-stage material return structure, the material coupling between distillation processes can be improved, the loss of heavy components can be reduced, and the overall separation efficiency of the system can be improved.

[0073] The (i+1)th stage raw material inlet can be further divided into the (i+1)th stage high-boiling liquid inlet and the (i+1)th stage reflux inlet. The (i)th stage high-boiling liquid outlet and the (i+1)th stage high-boiling liquid inlet are connected as channels for the transfer of high-boiling liquids at each stage. The (i)th stage second heat exchange medium outlet is connected to the (i+1)th stage reflux inlet to transport the (i+1)th stage low-boiling liquid to improve the overall separation efficiency of the system.

[0074] In one possible embodiment, the apparatus as described above further includes a recooler, the recooling inlet of which is connected to the outlet of the first heat exchange medium of the Nth stage, and the recooling outlet of which is connected to the inlet of the first stage raw material.

[0075] In this embodiment, the first-stage low-boiling gas heats each stage of the distillation column through the first reboiler of each stage, and then exits from the outlet of the first heat exchange medium of each stage. It then enters the recooler through the recooling inlet. After temperature control, part of it is discharged as lean liquid, and part is refluxed back to the first-stage feed inlet and enters the first-stage distillation column to replenish the low-boiling components in the system and maintain the gas-liquid balance and composition gradient during the distillation process. This structure can improve the overall thermal integration efficiency of the system while maintaining compositional stability during distillation through the reflux and lean liquid discharge mechanism.

[0076] In one possible embodiment, the apparatus as described above further includes a raw water preheater; the raw water outlet of the raw water preheater is connected to the first-stage raw material inlet, and the N-stage first heat exchange medium outlet is connected to the recooling inlet through the heat exchange medium channel of the raw water preheater.

[0077] In this embodiment, the raw water enters through the raw water channel of the raw water preheater and undergoes indirect heat exchange with the heat exchange medium from the outlet of the first heat exchange medium of the Nth stage in the heat exchange medium channel. After the raw water is heated, it is transported from the raw water outlet to the inlet of the first stage raw material, thereby completing the preheating and adjustment before the first stage distillation treatment.

[0078] Meanwhile, the material at the outlet of the first heat exchange medium of the N-stage does not directly enter the recooler. Instead, it first exchanges heat with the raw water through the heat exchange medium channel of the raw water preheater. After releasing some heat and reducing the temperature, it enters the recooler as the recooling inlet material, further improving the system's heat utilization efficiency and reducing energy consumption.

[0079] In this invention, packed distillation columns or plate distillation columns with similar structures can be selected for each stage to ensure the consistency and comparability of gas-liquid mass transfer models and parameters between stages; reboilers can be shell-and-tube heat exchange reboilers or forced circulation reboilers to adapt to heat exchange requirements under different pressure levels; booster compressors can be multi-stage centrifugal compressors or corrosion-resistant screw compressors to adapt to continuous compression conditions of water vapor or tritium-containing water vapor systems; recoolers should preferably adopt shell-side cooling structures or plate condensation structures to achieve sufficient removal of terminal heat and liquid phase stabilization.

[0080] The various stages of equipment are connected in series via gravity or pumping to form a continuous feed chain. The pressure of each distillation stage can be controlled by linking the back pressure valve with the feed flow rate to maintain a stable pressure gradient; the reboiler heat load is regulated through a closed-loop temperature feedback system to control the gas-liquid phase equilibrium; the booster outlet pressure is controlled by frequency converter control or guide vane adjustment to achieve constant pressure gas supply; and the recooler is controlled by both outlet temperature and liquid level parameters to ensure that the feed material returning to the first-stage feed inlet is in a stable liquid phase.

[0081] It should be noted that the above selections are merely some possible embodiments of the present invention, used to illustrate the process path, heat coupling relationship, and control logic achievable by the present invention, and do not constitute a limitation on the scope of protection of the present invention. Those skilled in the art can make equivalent substitutions or conventional adjustments to the equipment type, structural form, connection method, and control strategy according to the actual processing scale, operating pressure, heat exchange load, media corrosivity, radioactivity level, and system continuity requirements; all such substitutions should be considered to fall within the scope of protection of the present invention.

[0082] The present invention will be described in more detail below through specific embodiments.

[0083] Example 1

[0084] This embodiment is an application example of desalination treatment for wastewater containing tritium (HTO). Figure 1 The diagram shows a schematic of the apparatus for Embodiment 1 provided by the present invention. Tritium-containing wastewater is pumped to the first-stage distillation column, where the pressure at the top is 8 kPaA. The first-stage high-boiling liquid, obtained after preliminary concentration, enters the second-stage distillation column from the bottom for further distillation and concentration. The first-stage low-boiling gas at the top of the first-stage distillation column is pressurized to 120 kPaA by a booster compressor, and the superheated steam temperature reaches 150°C, simultaneously providing heat for the first-stage reboiler and the second-stage reboiler. Subsequently, the liquid product, after being heated by the two heat exchangers, is further cooled to 40°C by a recooler, and a portion is returned to the first-stage distillation column, while the remainder is collected and stored in a lean liquid tank. Finally, the second-stage low-boiling gas at 73°C at the top of the second-stage distillation column provides a heat source for the first-stage reboiler (60°C) of the first-stage distillation column, with a heat exchange temperature difference of ≥10°C. The condensed liquid portion is partially refluxed to the top of the second-stage distillation column, while the remaining portion enters the first-stage distillation column for further distillation and separation.

[0085] As shown in Table 1, compared to the single-stage water distillation process, this scheme reduces circulating water consumption by 92.5% and steam consumption by 100%. Although the use of a compressor increases power consumption, the overall energy consumption is still reduced by about 50%. Compared to the single-stage heat pump scheme, circulating water and power consumption are reduced by 7.2% and 7.5%, respectively. Furthermore, due to the two-stage cascade operation, the height of both distillation columns is significantly reduced while maintaining the same total packing height. In particular, the diameter of the second-stage distillation column is reduced by more than 40%, resulting in a reduction of investment costs by more than 30%.

[0086]

[0087] Example 2

[0088] This embodiment is an application example of heavy water (D2O) concentration. For example... Figure 2 The diagram shows a schematic of the apparatus in Embodiment 2 provided by the present invention. The deuterium-containing feed water is pumped to the first-stage distillation column. After preliminary concentration, the first-stage high-boiling liquid obtained from the preliminary concentration enters the second-stage distillation column for further distillation and concentration. The first-stage low-boiling gas at the top of the first-stage distillation column is pressurized to 1.5 bar by a booster compressor, simultaneously providing a heat source for the first-stage reboiler A, second-stage reboiler A, and third-stage reboiler. The heated liquid product preheats the feed water and is further cooled to 40°C by a recooler. Part of it is returned to the first-stage distillation column, and the remainder is collected and sent to a lean liquid tank, and finally sent to a dual-temperature exchanger for recycling. Then, the second-stage low-boiling gas (65℃) at the top of the second-stage distillation column provides a heat source for the first-stage reboiler B (52℃) of the first-stage distillation column, with a heat exchange temperature difference ≥10℃. Part of the condensed liquid is refluxed back to the second-stage distillation column, while the remainder continues distillation separation in the first-stage distillation column. The second-stage high-boiling liquid from the bottom of the second-stage distillation column enters the third-stage distillation column. The top temperature of the third-stage distillation column is 86℃, with a heat exchange temperature difference ≥10℃. The third-stage low-boiling gas provides a heat source for the second-stage reboiler B of the second-stage distillation column. After heat exchange, part of the liquid is refluxed back to the third-stage distillation column, while the remainder enters the second-stage distillation column. The qualified heavy water concentrate is collected from the bottom of the third-stage distillation column. As shown in Table 2, compared with the traditional three-stage cascade heavy water separation scheme, the overall energy consumption can be reduced by more than 50%.

[0089]

[0090] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A process for the concentration of heavy water and the stripping of tritium from waste water containing tritium, characterized in that, include: The raw water is subjected to N-stage distillation to obtain rich and lean liquor; The N-stage distillation process includes: using the i-th stage high-boiling liquid as the system to be distilled for the (i+1)-th stage distillation process; pressurizing the 1-th stage low-boiling gas; performing a first reboiling heat exchange treatment on at least a portion of the reboiling system of at least one stage of the N-stage distillation process; and performing a second reboiling heat exchange treatment on at least a portion of the reboiling system of the i-th stage distillation process using the (i+1)-th stage low-boiling gas. Wherein, the distillation pressure of the (i+1)th stage distillation treatment is higher than the distillation pressure of the ith stage distillation treatment; the rich liquid is the high-boiling liquid of the Nth stage, and the lean liquid is the liquid phase product of the low-boiling gas of the 1st stage after passing through the first reboiling heat exchange treatment; N≥2, 1≤i≤N-1.

2. The method according to claim 1, characterized in that, After subjecting at least a portion of the reboiling system of the i-th stage distillation process to the low-boiling gas of the i+1 stage through the second reboiling heat exchange treatment, the i+1 stage low-boiling liquid is obtained. A portion of the low-boiling liquid from stage i+1 is returned to participate in the distillation process of stage i+1, while the remaining low-boiling liquid from stage i+1 participates in the distillation process of stage i.

3. The method according to claim 1 or 2, characterized in that, The first reboiling heat exchange treatment includes: The first-stage low-boiling gas is pressurized to obtain first-stage pressurized low-boiling gas. The first-stage pressurized low-boiling gas is subjected to N-stage splitting to obtain N streams of first-stage sub-pressurized low-boiling gas; Each of the first-stage sub-pressurized low-boiling gases is used to perform a first reboiler heat exchange treatment on at least a portion of the reboiling system in the N-stage distillation process.

4. The method according to any one of claims 1-3, characterized in that, After the first reboiling heat exchange treatment, the low-boiling gas of the first stage is used to obtain the first stage low-boiling liquid. The first-stage low-boiling liquid is subjected to recooling treatment to obtain a first-stage low-boiling recooled liquid; A portion of the first-stage low-boiling recooled liquid is returned to participate in the first-stage distillation process, and the remaining first-stage low-boiling recooled liquid is the lean liquid.

5. The method according to claim 4, characterized in that, After the first-stage low-boiling liquid preheats the raw material water, the recooling treatment is performed.

6. The method according to any one of claims 1-5, characterized in that, The distillation pressure of the first stage distillation process is 5-15 kPaA; the distillation pressure of the Nth stage distillation process is 6-120 kPaA; and / or, the pressure of the first stage pressurized low-boiling gas is 101-600 kPaA.

7. An apparatus, characterized in that, The method for implementing any one of claims 1-6 includes N stages of distillation columns; wherein each stage of the distillation column includes a feed inlet, a high-boiling liquid outlet, and a low-boiling gas outlet, and N≥2; each stage of the distillation column includes a first reboiler, and the first to (N-1)th stages of the distillation column further include a second reboiler; Each stage of the first reboiler includes a first heat exchange medium inlet and a first heat exchange medium outlet, and each stage of the second reboiler includes a second heat exchange medium inlet and a second heat exchange medium outlet. The high-boiling liquid outlet of stage i and the raw material inlet of stage i+1 are connected, 1≤i≤N-1; At least one of the low-boiling gas outlet of stage 1 and the inlet of the first heat exchange medium of stage N is connected; The low-boiling gas outlet of the (i+1)th stage is connected to the inlet of the second heat exchange medium of the ith stage; It also includes a booster compressor, which has a booster inlet and a booster outlet. The low-boiling gas outlet of the first stage is connected to the booster inlet, and the booster outlet is connected to the heat exchange medium inlet of the Nth stage.

8. The apparatus according to claim 7, characterized in that, The outlet of the second heat exchange medium in the i-th stage is connected to the raw material inlet of the (i+1)-th stage and the raw material inlet of the i-th stage, respectively.

9. The apparatus according to claim 7 or 8, characterized in that, It also includes a recooler, the recooling inlet of which is connected to the outlet of the first heat exchange medium in the Nth stage, and the recooling outlet of which is connected to the raw material inlet in the first stage.

10. The apparatus according to claim 9, characterized in that, It also includes a raw water preheater; the raw water outlet of the raw water preheater is connected to the raw water inlet of the first stage, and the first heat exchange medium outlet of the Nth stage is connected to the recooling inlet through the heat exchange medium channel of the raw water preheater.

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