KR20230010419A - Circulating salt waste treatment method and device - Google Patents

Abstract

The present invention relates to a cyclic salt waste treating method and device and, more specifically, to a cyclic salt waste treating method, which comprises the following steps of: inputting salt waste, a desalination medium, and a carrier gas into a desalination device to fluidize the salt waste, desalination medium, and carrier gas; heating the desalination device to desalinate the salt waste and the desalination medium to produce a desalination reaction product and a chlorine gas; separating unreacted salt waste, an unreacted demineralization medium, the desalination reaction product, the carrier gas and the chlorine gas into a gaseous mixture and a solid mixture; and inputting the separated solid mixture to the desalination device again.

Description

Cyclic salt waste treatment method and device {CIRCULATING SALT WASTE TREATMENT METHOD AND DEVICE}

The present invention relates to a method and apparatus for treating cyclic salt waste.

Pyroprocessing is a process that separates and recycles TRU (transuranium), a useful component, from spent nuclear fuel. This process consists of unit processes such as pretreatment, electrolytic reduction, electrolytic refining, electrolytic smelting, and waste treatment. Among them, the electrolytic reduction process and the electrolytic refining process are processes of applying a voltage to an oxide and a metal, respectively, and for this purpose, the use of an electrolyte is essentially required. In general, LiCl molten salt is used in the electrolytic reduction process, and LiCl-KCl mixed eutectic salt is used as the electrolyte in the electrolytic refining process. As these two electrolytic processes proceed, radioactive materials are concentrated in each electrolyte, and at some stage, the electrolyte is required to be disposed of.

Disposal of these electrolytes has been studied in two directions. It is divided according to whether or not chlorine is removed from chlorine compounds, which are the main components of electrolytes, and is (1) a method of disposing of chlorine compounds and (2) a method of removing chlorine from chlorine compounds (desalination reaction) and then disposing of them. The electrolyte can be vitrified through a solidification medium in an unchlorinated or dechlorinated state (demineralized state) for final disposal.

If chlorine is not removed from the electrolyte to be disposed of, there are disadvantages such as weakening chemical stability and increasing the volume of waste. In order to overcome these disadvantages, a process of removing chlorine from the electrolyte (desalination reaction) and then vitrifying it has been researched and developed.

For example, Korean Patent Publication KR10-2012-0071602A suggests a desalination reaction using a desalination medium. However, the existing process is a batch-type process, and it is difficult to increase the capacity and requires a long reaction time. In the present invention, it is intended to present a desalination process capable of continuous process and mass production, breaking away from the existing batch-type desalination process.

An object of the present invention is to provide a cyclic salt waste treatment method capable of treating salt waste generated in a pyroprocessing waste treatment process.

Another object of the present invention is to provide a circulating salt waste treatment device in which the salt waste is treated.

One aspect of the present invention comprises the steps of fluidizing salt waste, desalination medium and carrier gas into a desalination device; heating the desalination device to desalinate the salt waste and the desalination medium to produce a desalination reaction product and chlorine gas; Separating unreacted salt waste, unreacted desalination medium, desalination reaction products, carrier gas, and chlorine gas into a solid mixture and a gaseous mixture; and re-injecting the separated solid mixture into a desalination device.

Another aspect of the present invention is a desalination device in which salt waste, a desalination medium and a carrier gas are introduced and fluidized, and a desalination reaction product and chlorine gas are generated by reacting the salt waste and the desalination medium by heating; a first flow path connected to the desalination device and transporting unreacted salt waste, unreacted desalination medium, desalination reaction products, carrier gas, and chlorine gas discharged from the desalination device; a gas-solid-phase separator connected to the first flow path and separating the unreacted salt waste, the unreacted desalination medium, the desalination reaction product, the carrier gas, and the chlorine gas into a solid mixture and a gas mixture; and a second flow path connected to the gas-solid separation device and reintroducing the separated solid mixture into the desalination device.

According to the cyclic salt waste treatment method of the present invention, the salt waste treatment capacity can be increased by treating the salt waste in a continuous process.

In addition, according to the cyclic salt waste treatment method of the present invention, since each process can be performed sequentially or continuously as a unit process, the closeness between unit processes can be increased, and thus the salt waste treatment capacity can be increased. .

1 is a diagram showing a circulating salt waste treatment apparatus according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified in various forms, and the scope of the present invention is not limited to the embodiments described below.

According to the present invention, a cyclic salt waste treatment method capable of treating salt waste in a continuous process and increasing the capacity for treating salt waste is provided.

Hereinafter, the present invention will be described with reference to FIG. 1 shows a cycle salt waste treatment apparatus 100 in which the cycle salt waste treatment process of the present invention is performed.

The circulating salt waste treatment method of the present invention includes the steps of fluidizing salt waste, a desalination medium, and a carrier gas into a desalination device 110; heating the desalination device 110 to react the salt waste and the desalination medium to produce a desalination reaction product and chlorine gas; Separating unreacted salt waste, unreacted demineralization medium, desalination reaction products, carrier gas and chlorine gas into a gaseous mixture and a solid mixture; and re-injecting the separated solid mixture into the desalination device 110.

In the present invention, salt waste and desalination medium may be introduced from the top of the desalination device 110. The salt waste may be waste discharged from pyroprocessing, and may be, for example, an electrolyte containing chlorine ions. The electrolyte containing these chlorine ions may be at least one selected from the group consisting of LiCl, LiCl-KCl mixed salt, CsCl, SrCl ₂ , BaCl ₂ and RECl ₃ , but is not limited thereto.

Meanwhile, the demineralization medium may include a SiO ₂ -Al ₂ O ₃ -P ₂ O ₅ (SAP) composite. The structure of the SAP complex used in the present invention and the content of each component constituting the SAP complex are not particularly limited.

In the present invention, the carrier gas may be introduced into the desalination apparatus 110 through the carrier gas inlet provided at the lower part of the desalination apparatus 110 . The carrier gas introduced into the desalination device 110 is supplied into the desalination device 110, and the salt waste and the desalination medium can be fluidized by the carrier gas. The demineralization device may further include a dispersion plate 150. The dispersion plate 150 is not particularly limited as long as it is shaped and made of a material that allows the carrier gas to be injected more uniformly.

At this time, as the carrier gas, a gas that does not affect the desalination reaction, such as argon gas, may be used.

As the fluidization process progresses, the salt waste and the demineralization medium can become a homogeneous mixture.

Meanwhile, the desalination device 110 may be heated to react the salt waste with the desalination medium. At this time, the demineralization device 110 may be heated above the melting point of the salt waste, preferably at 300°C to 900°C. If the heating temperature is less than 300 ° C., the desalination reaction may not occur, and if it exceeds 900 ° C., a large amount of salt waste may be vaporized, which is not preferable because the efficiency of the desalination reaction may be reduced.

When the desalination device 110 is heated, the salt waste and the desalination medium react, resulting in a desalination reaction. Products and chlorine gas can be formed. The reaction in which the chlorine component contained in the salt waste is removed is called a desalination reaction. Desalination may be carried out at 300 ° C to 900 ° C for 0.01 to 100 hours.

The desalination reaction using the SAP complex may proceed according to the following reaction schemes 1 to 4, but is not limited thereto, and any chemical reaction scheme capable of separating a chlorine component from a metal chloride into chlorine gas may be applied.

[Scheme 1]

LiCl + SAP → Li ₃ PO ₄ + Li _x Al _x Si _1-x O _2-x + Cl ₂

[Scheme 2]

LiCl + CsCl + SAP → Li ₃ PO ₄ + Cs ₂ AlP ₃ O ₁₀ + (Li, Cs)-aluminosilicate + Cl ₂

[Scheme 3]

LiCl + SrCl ₂ + SAP → Li ₃ PO ₄ + Li _x Al _x Si _1-x O _2-x + Sr ₅ (PO ₄ ) ₃ Cl + Cl ₂

[Scheme 4]

LiCl + BaCl ₂ + SAP → Li ₃ PO ₄ + Li _x Al _x Si _1-x O _2-x + Ba ₅ (PO ₄ ) ₃ Cl + Cl ₂

After the desalination reaction, unreacted salt waste, unreacted desalination medium, desalination reaction products, carrier gas, and chlorine gas exist in the desalination device 110, and they pass through the first flow path 210 to the gas-solid phase separator 120. ) can be transferred. At this time, the unreacted salt waste may be in a high-viscosity liquid state, but may be cooled while passing through the first flow path 210 and become a solid state.

Unreacted salt waste, unreacted demineralization medium, desalination reaction products, carrier gas, and chlorine gas may be separated into a solid mixture and a gas mixture in the gas-solid phase separator 120. The gaseous mixture may include a carrier gas and chlorine gas, and the solid mixture may include unreacted salt waste, unreacted desalination medium, and desalination reaction products.

The gas-solid phase separator 120 is not particularly limited as long as it can separate unreacted salt waste, unreacted desalination medium, desalination reaction product, carrier gas, and chlorine gas into a solid mixture and a gas mixture, but, for example, a cyclone can be

The solid mixture separated in the gas-solid phase separation process may be reintroduced into the desalination device 110 through the second flow path 220 . The solid mixture reintroduced into the desalination device 110 may be mixed with salt waste and desalination medium introduced from the top of the desalination device 110, and then fluidized again by a carrier gas. Salt waste and desalination medium present in the desalination device 110 undergo a desalination reaction to produce desalination reaction products and chlorine gas, and unreacted salt wastes, unreacted desalination medium, desalination reaction products, carrier gas, and chlorine gas pass through a first flow path. After being transferred to the gas-solid separator 120 through 210 and separated into a solid mixture and a gas mixture, a process of re-injecting the solid mixture into the desalination apparatus 110 may be repeated.

Meanwhile, the gas mixture separated in the gas-solid phase separation process may be transferred to the chlorine regeneration device 130 through the third flow path 230. The chlorine regeneration device 130 may have a chlorine regeneration medium. At this time, the chlorine regeneration device may further include a dispersion plate 150'.

The chlorine regeneration medium may react with chlorine gas to generate a regenerated electrolyte. This is called the chlorine recovery process.

The chlorine regeneration medium used in the chlorine regeneration process may be at least one selected from LiOH and KOH. Preferably, the chlorine regeneration medium may be determined according to the type of regenerated electrolyte to be produced in the chlorine regeneration process. For example, LiOH may be used as a chlorine regeneration medium when LiCl is to be produced, and KOH may be used as a chlorine regeneration medium when KCl is to be produced. The chlorine regeneration process may be performed in a medium such as water.

During the chlorine regeneration process, as shown in Scheme 5 below, chlorine gas (Cl ₂ ) is dissolved in water (H ₂ O) to form hydrochloric acid (HCl).

[Scheme 5]

Cl ₂ + H ₂ O → HCl + HOCl (solubility of chlorine gas at 25°C: 6.3 mg/ml)

The hydrochloric acid reacts with the chlorine regeneration medium according to Formula 6 or 7 to produce a regenerated electrolyte.

[Scheme 6]

Li ⁺ + OH ^- + H ⁺ + Cl ^- → Li ⁺ + Cl ^- + H ₂ O

[Scheme 7]

K ⁺ + OH ^- + H ⁺ + Cl ^- → K ⁺ + Cl ^- + H ₂ O

The reaction according to Schemes 5 to 7 is a reaction that occurs spontaneously at room temperature and normal pressure, and does not require separate process conditions, but temperature may be increased or pressure may be applied to increase the reaction rate. At this time, the temperature and pressure ranges and temperature raising and pressurization methods are not particularly limited.

Chloride generated through the chlorine regeneration process may be discharged to the outside through a regenerated electrolyte outlet provided in the chlorine regeneration device 130 . In addition, the regenerated electrolyte may be recycled in an electrolytic reduction process or an electrolytic refining process of pyroprocessing. Meanwhile, the carrier gas may be discharged to the outside through the carrier gas outlet.

As the desalination process and the gas-solid phase separation process are repeated as described above, the concentration of the desalination reaction product present in the desalination device 110 may increase. When the concentration of the desalination reaction product present in the desalination device 110 exceeds a preset concentration, the desalination reaction product may be transferred to the vitrification device 140 through the fourth flow path 240 connected to the desalination device 110. . At this time, the preset concentration may be determined according to the type and amount of salt waste, desalination medium, carrier gas, and desalination reaction product, and the relative ratio of each component present in the desalination device.

In the present invention, whether or not the desalination reaction is completed is determined by taking a sample from the desalination device 110 and then performing XRD (X-Ray Diffraction) analysis, or by determining the concentration of chlorine ions or the concentration of hydrogen ions (pH) in the chlorine regeneration device 130. can be determined by analyzing.

When the desalination reaction is completed, the desalination reaction product may exist as a glassy solid, liquid, or a mixture of the solid and liquid. Therefore, by performing XRD analysis on the desalination reaction product, the completion of the desalination reaction can be determined according to whether a peak is observed. For example, when all desalination reaction products are in the glass phase, no peak will be observed as a result of XRD analysis, and from this, it can be seen that all salt wastes and desalination medium present in the desalination device are converted into desalination reaction products.

Meanwhile, the desalination reaction product may also exist in a crystalline phase depending on the type and amount of salt waste and desalination medium. In this case, it is possible to determine whether the desalination reaction is completed by analyzing the concentration of chlorine ions or the concentration of hydrogen ions (pH) in the chlorine regeneration device 130. For example, when the number of moles of chlorine ions generated in the desalination device 110 is equal to the number of moles of chlorine ions in the chlorine regeneration device 130, it can be determined that the desalination reaction is completed.

The desalination reaction product transferred to the vitrification device 140 may be vitrified by heat treatment at 300° C. to 14OO° C. for 0.01 hour to 100 hours, which is referred to as a vitrification process.

In the vitrification process, if the heat treatment temperature is less than 300°C, the desalination reaction product may not be vitrified, and if it exceeds 1400°C, components constituting the desalination reaction product may volatilize, which is not preferable.

In addition, if the heat treatment time is less than 0.01 hour, the desalination reaction product may not be vitrified, and if the heat treatment time exceeds 100 hours, the time for the reaction to reach equilibrium may be exceeded, which is not preferable in terms of process economy.

A vitrification medium may be used to more efficiently vitrify the demineralization reaction product. At this time, the vitrification medium is not particularly limited as long as it is a material capable of vitrifying the demineralization reaction product. For example, SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ , B ₂ O ₃ and Fe ₂ O ₃ It may be at least one.

The material used in the vitrification process may be discharged to the outside through a glass outlet provided at the lower end of the vitrification device 140 .

Each process of the above-described cyclic salt waste treatment method may be performed as a unit process. In addition, each of the above processes may be performed sequentially or continuously.

On the other hand, in the circulating salt waste treatment apparatus 100 of the present invention, salt waste, desalination medium and carrier gas are introduced and fluidized, and salt waste and desalination medium react by heating to generate desalination reaction products and chlorine gas. device 110; a first flow path 210 connected to the desalination device 110 and transporting unreacted salt waste, unreacted desalination medium, desalination reaction products, carrier gas, and chlorine gas discharged from the desalination device 110; A gas-solid-phase separator ( 120); and a second flow path 220 connected to the gas-solid separation device 120 and reintroducing the separated solid mixture into the desalination device 110 .

In addition, the circulating salt waste treatment device 100 may further include a chlorine regeneration device 130 connected to the gas-solid separation device 120 through the third flow path 230.

In addition, the circulating salt waste treatment device 100 may further include a vitrification device 140 connected to the desalination device 110 through the fourth flow path 240 .

According to the present invention, the scale of the salt waste treatment process is not limited by the size of the desalination device, and the capacity of the desalination process can be increased through the implementation of a continuous process.

100 Circulating salt waste treatment system
110 demineralizer
120 Gas-Solid Separator
130 Chlorine Regeneration Device
140 vitrification apparatus
150, 150' dispersion plate
210 1st Euro
220 2nd Euro
230 third euro
240 4th Euro

Claims (10)

Fluidizing by introducing salt waste, desalination medium and carrier gas into a desalination device;
heating the desalination device to desalinate the salt waste and the desalination medium to produce a desalination reaction product and chlorine gas;
Separating unreacted salt waste, unreacted demineralization medium, desalination reaction products, carrier gas and chlorine gas into a gaseous mixture and a solid mixture; and
Re-introducing the separated solid mixture into the desalination device
Containing, cyclic salt waste treatment method. According to claim 1,
The demineralization medium comprises a SiO ₂ -Al ₂ O ₃ -P ₂ O ₅ complex, a cyclic salt waste treatment method. According to claim 1,
The salt waste is at least one selected from the group consisting of LiCl, LiCl-KCl mixed salt, CsCl, SrCl ₂ , BaCl ₂ and RECl ₃ , cyclic salt waste treatment method. According to claim 1,
The demineralization device is heated to 300 ℃ ~ 900 ℃, circulating salt waste treatment method. According to claim 1,
Cyclic salt waste treatment method further comprising the step of transferring the separated gaseous mixture to a chlorine regeneration device equipped with a chlorine regeneration medium, and reacting the chlorine regeneration medium and chlorine gas to produce chloride. According to claim 5,
The chlorine regeneration medium is at least one selected from LiOH and KOH, circulating salt waste treatment method. According to claim 1,
Cyclic salt waste treatment method further comprising the step of heat-treating and vitrifying the desalination reaction product transferred from the desalination device. a desalination device in which salt waste, a desalination medium and a carrier gas are introduced and fluidized, and a desalination reaction product and chlorine gas are generated by reacting the salt waste and the desalination medium by heating;
a first flow path connected to the desalination device and transporting unreacted salt waste, unreacted desalination medium, desalination reaction products, chlorine gas, and carrier gas discharged from the desalination device;
a gas-solid phase separator connected to the first flow path and configured to separate the unreacted salt waste, the unreacted desalination medium, the desalination reaction product, the chlorine gas, and the carrier gas into a gas mixture and a solid mixture; and
A second flow path connected to the gas-solid separation device and reintroducing the separated solid mixture into the desalination device.
Containing, circulating salt waste treatment device. According to claim 8.
Further comprising a chlorine regeneration device, wherein the chlorine regeneration device is connected to the gas-solid phase separation device by a third flow path. According to claim 8.
Further comprising a vitrification device, wherein the vitrification device is connected to the desalination device by a fourth flow path.

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