JP6730815B2 - Volume reduction processing method and volume reduction apparatus for hardly decomposable waste - Google Patents

Description

The technique disclosed in the present specification relates to a technique for reducing the volume of hardly decomposable waste containing lithium. In particular, the present invention relates to a technique that can be suitably used for volume reduction treatment of an ion exchange resin having lithium attached thereto, which is used in a nuclear power plant.

As the hardly decomposable waste, for example, an ion exchange resin used in a nuclear power plant is known. That is, in a nuclear power plant, a large amount of ion exchange resin is used for purification of system water and purification of water to be injected into the system in order to prevent corrosion of equipment. Since the performance of these ion exchange resins deteriorates with age, they become waste after being used for a predetermined period. Conventionally, used ion-exchange resins generated in nuclear power plants have been sorted according to the level of radioactivity and stored together with water in storage tanks. Ion exchange resins have the property that they are stable and hardly decomposed in the natural state, but since they are organic substances, they may deteriorate in the long term. Therefore, when the used ion exchange resin is disposed of as waste, it is necessary to make it inorganic and to stabilize it.

As a method for treating used ion-exchange resin generated in a nuclear power plant, various mineralization volume reduction techniques such as incineration treatment, thermal decomposition treatment and oxidative decomposition treatment have been developed. Currently, at some nuclear power plants, high-temperature incineration treatment of 800°C or higher is carried out for those with low radioactivity levels. On the other hand, those with relatively high levels of radioactivity have problems such as the treatment of refractories that make up the treatment furnace used during high-temperature incineration and the problem of cesium (Cs) scattering associated with high-temperature incineration. It is difficult to adopt the treatment and it is currently stored in the storage tank together with water. In order to solve these problems, a technique for mineralizing and reducing the volume of a used ion exchange resin by using a carbonization device has been developed (for example, Patent Document 1).

JP-A-63-171400

In a nuclear power plant, lithium hydroxide (LiOH) is usually added to neutralize boric acid, which is an acidic substance of boron (B) added to system water. Therefore, lithium (Li) is attached to the used ion exchange resin. As a result of intensive studies by the inventors, it has been found that when lithium is attached to the ion exchange resin, the residues may combine with each other to form a lump when the ion exchange resin is subjected to dry distillation. In this case, the thermal decomposition of the residue becomes insufficient, and as a result, the volume reduction rate of the used ion exchange resin cannot be sufficiently improved.

The present specification discloses a technique capable of further increasing the volume reduction rate of a hardly decomposable waste containing lithium.

A method of reducing the volume of a lithium-containing hardly-decomposable waste disclosed in the present specification includes a step of adding an additive containing an alkaline earth metal and not containing CO ₃ to the hardly-decomposable waste, And a step of thermally decomposing the hardly-decomposable waste material to which the additive has been added by a dry distillation treatment.

In this volume reduction treatment method, an additive that contains alkaline earth metal and does not contain CO ₃ is added to a hardly-decomposable waste containing lithium, and the hardly-decomposable waste added with the additive is subjected to dry distillation treatment. Pyrolysis by. As will be described later, according to an experiment conducted by the inventors of the present application, when the persistent decomposition waste is subjected to carbonization treatment by adding an additive containing an alkaline earth metal and not containing CO ₃ , the residues are bound to each other. It was found that the lumps caused by the are less likely to occur. In the above volume reduction treatment method, since it is difficult for lumps to be formed due to the binding of the residues to each other, the volume reduction rate of the hardly decomposable waste can be improved.

Various methods can be used for adding the additive to the hardly-decomposable waste containing lithium. Specifically, the additive may be added to the hardly decomposable waste in advance, and the hardly decomposed waste to which the additive has been added may be supplied to a dry distillation furnace or the like, or the additive may be added together with the hardly decomposed waste. The agents may be individually supplied to a carbonization furnace or the like.

In addition, the present specification discloses a novel apparatus for reducing the volume of persistent waste that can solve the above problems. This volume reduction apparatus comprises a carbonization part, a slurry supply means for supplying a slurry of hardly-decomposable waste containing lithium to one end of the carbonization part, and an alkaline earth metal to the slurry supplied to one end of the carbonization part. And an additive adding means for adding an additive that does not contain CO ₃ . According to this volume reduction processing apparatus, the volume reduction processing method disclosed in the present specification described above can be suitably implemented.

Details of the technology disclosed in this specification and further improvements will be described in detail in the modes for carrying out the invention and in the examples.

It is a figure for demonstrating the whole structure of the volume reduction processing system which concerns on an Example. It is a figure for demonstrating the ball type carbonization furnace which concerns on an Example. It is a figure for demonstrating the other example of a ball type carbonization device.

The main features of the embodiments described below are listed. The technical elements described below are technical elements that are independent of each other, and exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Absent.

(Characteristic 1) In the method for reducing the volume of hardly-decomposable waste containing lithium disclosed in the present specification, even if the additive contains at least one of calcium hydroxide, calcium oxide and barium hydroxide. Good.

(Example) Hereinafter, a volume reduction processing system according to an example will be described. In the volume reduction system of this example, the volume of the ion exchange resin used for purification of system water in a nuclear power plant is reduced. Since lithium (Li) is added to the system water, Li is attached to the used ion exchange resin. As shown in FIG. 1, the volume reduction processing system includes a resin receiving tank 1, a superheated steam supply device 4, a ball type carbonization furnace 3, an exhaust gas processing device 5, and a control device 2. In the following, the used ion exchange resin may be simply referred to as “ion exchange resin”.

The resin receiving tank 1 stores the used ion exchange resin generated in the nuclear power plant as a 5 to 15% slurry (5 to 15% of resin and 85 to 95% of water content). The amount and concentration of the slurry stored in the resin receiving tank 1 are input to the control device 2. A supply pump 6 is connected to the resin supply port of the resin receiving tank 1. When the supply pump 6 operates, the slurry in the resin receiving tank 1 is supplied to the ball-type carbonization furnace 3 through the supply passage.

An electric conductivity measuring device 30 is connected to the resin receiving tank 1. A predetermined amount of the ion-exchange resin slurry in the resin receiving tank 1 is extracted and sent to the electric conductivity measuring device 30. The electrical conductivity measuring device 30 measures the electrical conductivity of the slurry while dropping a Li solution having a known concentration into the slurry. When the used ion exchange resin contains an unreacted sulfo group (—SO ₃ H) (that is, when it has ion exchange ability), Li in the dropped Li solution is ion-exchanged by the sulfo group. The electric conductivity of the non-electrolyte slurry does not change. When the addition of the Li solution is continued and the ion-exchange resin is saturated, the electrical conductivity of the slurry (strictly speaking, a mixture of the slurry and the Li solution) rises according to the amount of the Li solution dropped thereafter.

The electric conductivity measuring device 30 controls the total amount of the Li dissolved liquid when the electric conductivity starts to increase, the concentration of the Li dissolved liquid, and the amount of the slurry sent from the resin receiving tank 1 to the measuring device 30. Input to device 2. In the control device 2, these three values, the amount and concentration of the slurry stored in the resin receiving tank 1 input from the outside, and the content rate of sulfur (S) in the ion exchange resin input from the outside. , The amount of Li substance adhering to the ion exchange resin in the resin receiving tank 1 (mol) is calculated.

Not all sulfo groups of the ion exchange resin react with Li. For example, in an ion exchange resin having a S content of about 8.7 wt %, the amount of Li is 8.7 wt%×6.941/when all of the sulfo groups of the ion exchange resin are assumed to react with Li. 32.07=about 1.9 wt %. Here, 6.941 is the atomic weight of Li and 32.07 is the atomic weight of S. However, in reality, the amount of Li attached to the ion exchange resin having an S content of about 8.7 wt% is less than the theoretical value of about 1.9 wt %. Therefore, the sulfo group remains in the ion exchange resin even when the electric conductivity starts to increase due to the dropping of the Li solution. Therefore, the substance amount (mol) of Li attached to the used ion exchange resin is not based on the theoretically maximum amount (mol) of attachable Li, but actually attached to the ion exchange resin. It is calculated based on the maximum amount (mol) of possible Li. That is, calculated by (amount of Li adhering to the used ion exchange resin)=(maximum amount of Li actually adhering to the ion exchange resin)−(amount of Li added by dropping the Li solution) To be done. Since the maximum amount (mol) of Li actually attached to the ion exchange resin is determined by the S content rate of the ion exchange resin, the maximum Li attachment amount (mol) changes depending on the S content rate. .. It is empirically said that the maximum amount of Li deposited is about 1.3 wt% in an ion exchange resin having a S content of about 8.7 wt %. From such an empirical rule, the maximum amount (mol) of Li adhering to the ion exchange resin can be specified.

An additive supply device 24 is connected to the resin receiving tank 1. The additive supply device 24 supplies the additive to the resin receiving tank 1. As the additive, powdery calcium hydroxide (Ca(OH) ₂ ) is used. The additive supplied from the additive supply device 24 is mixed with the slurry of the ion exchange resin in the resin receiving tank 1. The slurry of the ion exchange resin mixed with the additive is supplied to the ball type carbonization furnace 3.

The additive amount of the additive is determined according to the substance amount (mol) of Li adhering to the ion exchange resin stored in the resin receiving tank 1. As described above, the substance amount (mol) of Li attached to the ion exchange resin can be calculated from the measurement result of the electric conductivity measuring device 30. When the substance amount (mol) of Li is calculated, the added amount (mol) of Ca(OH) ₂ can be determined by using the calculated substance amount (mol) of Li. Specifically, 1 mol of Li and equivalent to 2 times (that is, 0.5 to 1 mol) of Ca(OH) ₂ are added. In this example, the amount of Li substance adhering to the ion exchange resin (mol) was calculated by measuring the electric conductivity with the electric conductivity measuring device 30, and the calculated amount of Li substance ( Although the addition amount (mol) of the additive is determined according to (mol), the technique disclosed in the present specification is not limited to such an example. For example, if the content (wt%) of Li adhering to the used ion-exchange resin is empirically known, the amount of the additive added depends on the amount of the ion-exchange resin (used It may be determined according to the content rate (wt%) of Li adhering to the ion exchange resin). 1 wt% Li and equivalent Ca(OH) ₂ are 1 wt%×0.5×74.09/6.941=5.3 wt %. Here, 74.09 is the formula weight of Ca(OH) ₂ . As described above, since Ca(OH) ₂ equivalent to Li which is attached to the used ion exchange resin is doubled, the Li content (wt %) of the used ion exchange resin is a (wt %). ), approximately 5.3×a to 10.6×a (wt%) of Ca(OH) ₂ may be added. Specifically, when the Li content of the used ion exchange resin is empirically 1 wt %, Ca(OH) ₂ of about 5 to 10 wt% of the used ion exchange resin may be added.

The superheated steam supply device 4 includes a water tank 7, a supply pump 8, a steam generator 9, and a steam superheater 10. A supply pump 8 is connected to the supply port of the water tank 7. When the supply pump 8 operates, the water in the water tank 7 is supplied to the steam generator 9. The steam generator 9 converts the water supplied from the water tank 7 into steam. A steam superheater 10 is connected to the steam generator 9, and the steam generated by the steam generator 9 is supplied to the steam superheater 10. The steam superheater 10 superheats the steam supplied from the steam generator 9 into superheated steam. The superheated steam generated by the steam superheater 10 is supplied to the ball type carbonization furnace 3.

The ball-type carbonization furnace 3 brings the slurry of the ion exchange resin stored in the resin receiving tank 1 into contact with the superheated steam supplied from the superheated steam supply device 4 to thermally decompose the ion exchange resin. The gas generated by the thermal decomposition is sent to the exhaust gas treatment device 5, and the residue after the thermal decomposition of the ion exchange resin is sent to the solidification equipment. The detailed structure of the ball-type carbonization furnace 3 will be described later.

The exhaust gas processing device 5 processes the exhaust gas supplied from the ball-type carbonization furnace 3, detoxifies it, and exhausts it to the atmosphere. The exhaust gas treatment device 5 includes a secondary combustor for burning combustible components in the exhaust gas supplied from the ball-type carbonization furnace 3, and a plurality of HEPA filters for removing fine particles in the exhaust gas exhausted from the secondary combustor. have. By discharging the gas that has passed through the HEPA filter to the atmosphere, it is possible to prevent the fine particles contained in the exhaust gas from diffusing into the atmosphere.

The control device 2 is a control device that controls each device that constitutes the volume reduction processing system. The control device 2 uses, for example, the additive supply amount supplied to the resin receiving tank 1, the ion exchange resin supply amount (supply amount per hour) supplied to the ball-type carbonization furnace 3, and the ball-type carbonization furnace. The amount of superheated steam supplied to the No. 3 (the amount of supply per hour) and the atmospheric temperature in the ball-type carbonization furnace 3 are controlled. That is, the control device 2 controls the additive supply device 24 to control the additive supply amount, controls the supply pump 6 to control the ion exchange resin supply amount, and controls the superheated steam supply device 4. By controlling it, the supply amount of superheated steam is controlled, and by controlling the heater output of the ball-type carbonization furnace 3, the ambient temperature is controlled. The operation of the control device 2 will be described later in detail.

Next, the detailed configuration of the ball-type carbonization furnace 3 will be described with reference to FIG. As shown in FIG. 2, the ball-type carbonization furnace 3 includes a metal closed reaction vessel 11 which is a ball filling portion, an external heater 25 (shown in FIG. 1) for heating the inside of the reaction vessel 11 from outside the vessel. , Ceramic or metal balls 12 filled in the reaction vessel 11, stirring blades 13 capable of mechanically stirring the balls 12, and ions for supplying an ion exchange resin from the upper portion of the reaction vessel 11 to the balls 12 It is composed of an exchange resin supply nozzle 16 and a superheated steam supply nozzle 15 for supplying superheated steam from the upper part of the reaction vessel 11 onto the balls 12.

Whether or not the superheated steam is supplied from the superheated steam supply nozzle 15 is arbitrary, and can be appropriately determined according to the water content of the ion exchange resin supplied from the ion exchange resin supply nozzle 16. For example, when the water content of the ion exchange resin is high, the supply of superheated steam from the superheated steam supply nozzle 15 may be stopped, while when the water content of the ion exchange resin is low, the superheated steam supply nozzle 15 may be used. Superheated steam may be supplied.

The closed reaction vessel 11 is composed of a metal cylindrical body having a diameter of 400 mm and a length of 500 mm, for example, and is provided with a pressure control mechanism for maintaining the pressure inside the reaction vessel 11 at −0.5 to −10 kPa. There is. The length of the reaction vessel 11 is not limited to 500 mm and can be appropriately determined according to the type of ion exchange resin to be treated. In addition, when the slurry of the ion exchange resin having a high water content is directly charged into the reaction vessel 11, the temperature of the ion exchange resin is hard to rise, so that the length of the reaction vessel 11 is preferably 500 mm or more. By setting the length of the reaction vessel 11 to 500 mm or more, the reaction time can be sufficiently lengthened, and the charged ion exchange resin can be preferably thermally decomposed.

A rotary shaft 14 is provided at the axial center of the reaction container 11. The rotating shaft 14 is rotated at a predetermined speed (about 0.1 to 2.0 rpm, preferably 0.5 rpm or more) by a drive motor (not shown). A spiral stirring blade 13 is attached to the peripheral portion of the rotary shaft 14. The stirring blade 13 has a spiral outer frame portion 13 a extending so as to surround the rotating shaft 14, and a plurality of plate-shaped blade portions 13 b connecting the outer frame portion 13 a and the rotating shaft 14. The outer frame portion 13 a is located near the inner peripheral surface of the reaction container 11. The plurality of wings 13b are arranged in a distributed manner at intervals from the upper end to the lower end of the outer frame portion 13a. Therefore, a space is formed between the two adjacent blades 13b. The wing portion 13b may have a flat plate shape or a curved plate shape.

The balls 12 in the reaction vessel 11 are made of corrosion-resistant ceramic balls or high nickel alloy Hastelloy or Inconel, and have a particle size of 10 to 25 mm. The balls 12 ascend along the periphery of the reaction vessel 11 while being stirred by the agitating blades 13, and the balls located at the upper portion of the reaction vessel 11 descend sequentially in the space formed with this. Go

A holding plate 23 for holding the balls 12 in the reaction container 11 is arranged at the lower end of the reaction container 11 (illustrated in FIG. 1 ). The holding plate 23 prohibits the balls 12 from passing therethrough, while allowing the gas and the residue of the ion exchange resin to pass therethrough. This prevents the balls 12 filled in the reaction container 11 from falling into the powder storage portion 19, while the residue not thermally decomposed in the reaction container 11 and the gas generated by the thermal decomposition are powdered. It can be moved to the storage unit 19.

A temperature sensor 22 (shown in FIG. 1) is arranged substantially at the center of the lower surface of the holding plate 23. The temperature sensor 22 detects the temperature of the lower end of the reaction container 11 (that is, the lower end of the dry distillation section). The temperature sensor 22 is connected to the control device 2. The temperature detected by the temperature sensor 22 is input to the control device 2.

A powder storage section 19 is provided below the reaction container 11. The powder storage unit 19 separates solids (powder such as residue of ion exchange resin) from the gas discharged from the reaction container 11 and stores the separated powder. A superheated steam supply nozzle 21 is provided at the lower end of the powder reservoir 19. Superheated steam is supplied from the superheated steam supply device 4 to the superheated steam supply nozzle 21. The superheated steam supplied from the superheated steam supply nozzle 21 into the powder reservoir 19 is used for decomposing undecomposed components contained in the residue of the ion exchange resin. In addition, a part of the superheated steam supplied into the powder reservoir 19 flows into the reaction vessel 11, contacts the ion exchange resin in the reaction vessel 11, and is used for the thermal decomposition of the ion exchange resin.

An external electric heater 20 is provided on the wall surface of the powder storage portion 19 (shown in FIG. 1). The heater 20 controls the atmospheric temperature in the powder storage portion 19 to a temperature at which the residue of the ion exchange resin can be thermally decomposed.

The sintered metal filter 17 is arranged on the upper surface of the powder reservoir 19. The gas in the powder reservoir 19 is filtered by the sintered metal filter 17. The exhaust gas filtered by the sintered metal filter 17 is sent from the exhaust gas outlet 18 to the exhaust gas processing device 5. Although the sintered metal filter is used in this embodiment, the present invention is not limited to this, and a ceramic filter may be used, for example.

Next, a method of reducing the volume of the ion exchange resin by the volume reduction processing system according to the present embodiment will be described. First, the electric conductivity measuring device 30 is operated to measure the amount of Li substance adhering to the ion exchange resin stored in the resin receiving tank 1. The control device 2 controls the additive supply device 24 to supply Ca(OH) ₂ having a substance amount of 0.5 to 1 times the substance amount of Li to the resin receiving tank 1 as an additive. In the resin receiving tank 1, the ion-exchange resin slurry and the additive are agitated by an agitator (not shown), and both are uniformly mixed. Next, the controller 2 drives the supply pump 6 to supply the ion-exchange resin slurry to the reaction vessel 11 of the ball-type carbonization furnace 3, and drives the superheated steam supply device 4 to supply the superheated steam to the ball-type carbonization furnace 3. To the powder storage section 19 of At this time, the water content of the ion exchange resin supplied to the reaction vessel 11 per unit time and the water content of the superheated steam fed to the powder storage unit 19 per unit time are adjusted to adjust the ball-type carbonization furnace. The ambient temperature in 3 is preferably maintained at the temperature (about 460 to 700° C.) necessary for thermally decomposing the ion exchange resin.

The ion-exchange resin slurry supplied to the reaction container 11 is supplied from the ion-exchange resin supply nozzle 16 into the reaction container 11. The ion exchange resin supplied into the reaction vessel 11 initially has a water content of 5 to 15% slurry, and basically adheres to the surface of the balls 12 and moves in the furnace. Therefore, the residence time of the ion exchange resin in the reaction container 11 is the same as the descent time of the balls 12. The descent time of the balls 12 can be freely adjusted by the dimensions of the stirring blade 13, the number of revolutions, the dimensions of the balls 12, and the height of the packed bed. The longer the retention time is, the better for improving the volume reduction rate. Specifically, a method of reducing the diameter of the ball, reducing the number of rotations of the rotating shaft 14, and increasing the length of the filling layer filled with the ball 12 can be adopted.

The superheated steam supplied into the powder reservoir 19 is supplied from the superheated steam supply nozzle 21 into the powder reservoir 19. A part of the water vapor supplied into the powder reservoir 19 enters the reaction container 11 and is supplied to the ion exchange resin attached to the surface of the ball 12.

In the present embodiment, the control device 2 supplies the amount of the ion-exchange resin slurry supplied to the reaction container 11 and the powder storage unit 19 so that the temperature detected by the temperature sensor 22 becomes an appropriate temperature. The amount of superheated steam to be generated and the outputs of the various heaters 20 and 25 are controlled. As a result, the temperature of the lower end of the reaction vessel 11 is maintained at a sufficient temperature necessary for decomposing the ion exchange resin, and the volume of the ion exchange resin in the reaction vessel 11 can be sufficiently reduced.

The residue generated by the decomposition in the reaction container 11 is discharged to the powder storage section 19. In this embodiment, superheated steam is supplied to the lower portion of the powder storage portion 19, and the powder storage portion 19 is heated by the heater 20. As a result, the undecomposed portion in the residue discharged to the powder reservoir 19 is decomposed, and the volume reduction rate of the ion exchange resin can be further improved.

Decomposition gas (CO, CxHy, etc.) generated by decomposition in the reaction vessel 11, sulfuric acid gas, sulfurous acid gas, etc. are discharged from the exhaust gas outlet 18 through the sintered metal filter 17, and are processed by the exhaust gas processing device 5. .. Therefore, the used ion exchange resin generated in the nuclear power plant can be safely volume-reduced without the risk of environmental pollution due to radioactivity.

Further, by determining the additive amount of the additive according to the amount of the Li substance adhering to the ion exchange resin stored in the resin receiving tank 1, it becomes possible to supply the additive without excess or deficiency. It is possible to suppress the excessive supply of the additive.

The present inventors have used the above volume-reducing treatment system to provide (i) an unused ion exchange resin, (ii) a used ion exchange resin to which Ca(OH) ₂ has not been added, and (iii) Volume reduction processing was performed on a total of three types of samples, that is, a used ion exchange resin to which Ca(OH) ₂ was added (Experiment 1). In addition, Li is not attached to the unused ion exchange resin, and Li is attached to the used ion exchange resin. In Experiment 1, the temperature of the reaction container 11 was set to 550°C. S contained in the ion exchange resin used in Experiment 1 is about 8.7 wt% of the unused ion exchange resin. Further, Li attached to the used ion exchange resin is about 1 wt% of the unused ion exchange resin. In Experiment 1, Ca(OH) ₂ of about 7 wt% of the used ion exchange resin was added as an additive.

As a result of Experiment 1, in (i), the weight loss rate was 98% (on a dry weight basis), and no lump was formed due to the binding of the residues. In (ii), the weight loss rate was 90%, and lumps were formed due to the binding of the residues. In (iii), the weight loss rate was 95%, and no lumps due to the binding of the residues were generated. In Experiment 1, the weight reduction index was evaluated by the weight of the sample before and after the treatment (dry basis) as an index of volume reduction. When the residue generated in (iii) was analyzed by XRD (X-ray diffraction analysis), medium-scale amounts of Li ₂ SO ₄ and CaSO ₄ were detected. On the other hand, unreacted Ca was not detected. Further, in (iii), it was confirmed that the gas (SOx) sent to the exhaust gas treatment device 5 decreased. The “medium-scale amount” here is an evaluation of the relative amount in the target sample, and does not represent the amount compared with other samples. The same applies to "large amount" and "small amount" described later.

From the experimental results, it is considered that Li is the cause of the formation of lumps due to the bonding of the residues (described later). It is also found that even if Li is attached to the ion exchange resin, the addition of Ca(OH) ₂ can suppress the generation of lumps due to the binding of the residues. Further, in the ion exchange resin to which Li is attached, it can be seen that the volume reduction rate can be improved by adding Ca(OH) ₂ . The above-mentioned lump of residue was brittle and easily broken. From this, it is speculated that the lump of the residue is not caused by melt-fixing but is caused by sintering (or a phenomenon similar thereto). The inventors of the present invention also conducted an experiment in the case where the addition amount of Ca(OH) ₂ in (iii) of Experiment 1 was about 5 wt% and about 10 wt% of the used ion exchange resin. It was As a result of the experiment, it was confirmed that sintering (or a phenomenon similar thereto) did not occur in any case.

In the volume reduction treatment system of this example, calcium hydroxide (Ca(OH) ₂ ) was added to the ion exchange resin as an additive, and the ion exchange resin added with this additive was subjected to dry distillation treatment in the ball-type dry distillation furnace 3. To do. As is clear from the above experimental results, according to the volume reduction processing system of the present embodiment, it is possible to suppress the occurrence of lumps (typically, sintering or a similar phenomenon) due to the bonding of residues. .. Therefore, the residue can be sufficiently thermally decomposed, and the volume reduction rate of the used ion exchange resin can be further improved as compared with the conventional case.

In addition, the inventors of the present invention have (i) powdery lithium sulfate (Li ₂ SO ₄ ) (melting point 859° C.) and (ii) a mixture of Li ₂ SO ₄ and an unused ion exchange resin. , (Iii) solid lithium hydroxide (LiOH) (melting point 477° C.), and (iv) a mixture of unused LiOH and an ion-exchange resin, a total of four types of samples were prepared, and superheated steam and An experiment of reacting was conducted (Experiment 2). Experiment 2 was carried out at a temperature of 550°C. As a result of Experiment 2, in (i), the sample did not change and remained in powder form. In (ii), brittle lumps that appeared to be sintered were formed. In addition, a large amount of Li ₂ SO ₄ was detected by XRD. In (iii), a hard lump that appears to have solidified after melting occurred. In (iv), a hard lump that appeared to be fixed after melting occurred. In addition, a small amount of Li ₂ SO ₄ and LiOH and a mesoscale amount of lithium oxide (Li ₂ O) were detected by XRD.

From the experimental results, it was found that although Li ₂ SO ₄ has a melting point higher than the experimental temperature and does not change by itself, sintering (or a phenomenon similar thereto) occurs when the ion exchange resin is mixed. On the other hand, since the melting point of LiOH is lower than the experimental temperature, it was found that the sample melts and solidifies (fixes) either alone or in a mixture with the ion exchange resin. The cause of the residue lumps in Experiment 1 is that the residue lumps produced in Experiment 1 are most similar to the lumps produced by reacting (ii) in Experiment 2 with superheated steam. It is considered that the substance that becomes is Li ₂ SO ₄ instead of LiOH. Specifically, Li ₂ SO ₄ is separated from R—SO ₃ Li (R is a matrix of the ion exchange resin) under an atmosphere of superheated steam or a decomposition atmosphere of the ion exchange resin, and the separated Li ₂ SO _{4 is used.} It is considered that the residues are sintered together.

Further, according to Experiment 1, as a result of the volume reduction treatment of the used ion exchange resin added with Ca(OH) ₂ , Li ₂ SO ₄ and CaSO ₄ are detected from the residue and are sent to the exhaust gas treatment device 5. Gas (SOx) decreased. From this, it is considered that CaSO ₄ is produced by reacting the additive Ca(OH) ₂ with the sulfo group remaining in the ion exchange resin. According to Experiments 1 and ₂ , Li ₂ SO ₄ is considered to be a substance that causes the residue to sinter, but if CaSO ₄ is produced during the volume reduction treatment, Li ₂ SO ₄ remains even if it is produced. However, it is considered that the sintering of the residues can be suppressed. Further, since the gas sent to the exhaust gas treatment device 5 is reduced by adding Ca(OH) ₂ , the exhaust gas treatment device 5 can be downsized.

In addition, the present inventors conducted an experiment to dry-distill a used ion exchange resin to which Ca(OH) ₂ was not added under a nitrogen atmosphere instead of superheated steam. The experiment was carried out at a temperature of 550°C. As a result of the experiment, under the nitrogen atmosphere, the residue did not sinter even though Ca(OH) ₂ was not added. From this, it is considered that the reaction of the residue with the superheated steam is one of the causes of the sintering of the residue.

(Modification 1) The present inventors conducted an experiment of reacting an ion exchange resin added with calcium oxide (CaO) as an additive with superheated steam (Experiment 3). Experiment 3 was carried out at a temperature of 550°C. The amount of the additive added was a substance amount equivalent to twice the amount of the substance of Li adhering to the ion exchange resin in the resin receiving tank 1. As a result of Experiment 3, sintering did not occur.

From the results of Experiment 3, it can be seen that even when the additive is calcium oxide (CaO), the same operational effects as those of the example can be obtained.

From Experiments 1 and 3, it was found that when calcium hydroxide or calcium oxide was used as an additive, the sintering of the residues could be suppressed and the volume reduction rate of the used ion exchange resin could be improved. The present inventors conducted an experiment under the same conditions as Experiment 3 using calcium carbonate (calcium carbonate (CaCO ₃ )) as an additive (Experiment 4). As a result of Experiment 4, it was found that the residues were sintered and the volume reduction rate of the used ion exchange resin could not be improved.

(Modification 2) With respect to barium and magnesium which are the same Group 2 elements as calcium, the present inventors have prepared hydroxides thereof (that is, barium hydroxide (Ba(OH) ₂ ), magnesium hydroxide ( An experiment was conducted under the same conditions as in Experiment 3 (Experiment 5) also when Mg(OH) ₂ ) was used as an additive. As a result of Experiment 5, sintering did not occur with barium hydroxide (Ba(OH) ₂ ), but sintering did occur with magnesium hydroxide (Mg(OH) ₂ ).

Based on the results of Experiment 4, the present inventors have found that when barium and magnesium carbonates (ie, barium carbonate (BaCO ₃ ), magnesium carbonate (MgCO ₃ )) were used as additives, respectively. The experiment was performed under the same conditions as in Experiment 3 (Experiment 6). As a result of Experiment 6, as in Experiment 4, in each case, sintering of the residues occurred.

From the above experiment, it was found that when the hydroxides of calcium and barium which are alkaline earth metals and the oxide of calcium are used as the additives, sintering of the residues does not occur. On the other hand, when magnesium hydroxide, which is a Group 2 element but not an alkaline earth metal, is used as an additive, it was found that the residues sinter. Further, in the case of carbonate, it was found that the residues sinter with each other when any of calcium, barium and magnesium carbonate is used as an additive. From this, it was found that by using an additive containing an alkaline earth metal and not containing CO ₃ , sintering of the residues can be suppressed and the volume reduction rate of the used ion exchange resin can be improved.

Although one embodiment of the technology disclosed in the present specification has been described above in detail, this is merely an example and does not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

In the above-mentioned examples, the additive amount of the additive was determined according to the amount of Li adhering to the ion-exchange resin, but there are various determining methods for the additive amount. For example, when the Li content in the ion exchange resin having an S content of about 8.7 wt% is unknown, it is twice as much as the equivalent amount of Li (that is, about 1.3 wt%), which is the maximum deposition amount. Ca(OH) ₂ (that is, about 6.8 to 13.7 wt%) may be uniformly added.

Further, the additives (Ca(OH) ₂ , CaO and Ba(OH) ₂ ) listed in the examples and the modified examples may be used not only individually but also as a mixture.

Further, the additive may be directly charged into the ball type carbonization furnace 3. By stirring the balls 12 in the reaction container 11, the additive appropriately contacts and reacts with the ion exchange resin in the reaction container 11. Therefore, even if the additive is directly charged into the ball-type carbonization furnace 3, the same effect as that of the embodiment can be obtained.

Further, in the above-described examples, the ion exchange resin was treated using the ball type carbonization furnace, but various types of carbonization devices can be used. For example, a screw feeder type dry distillation device may be used, and the ion exchange resin may be supplied to one end of the screw feeder and the decomposition gas and the residue may be discharged from the other end of the screw feeder.

Further, in the above-described examples, the slurry of the ion exchange resin at room temperature was supplied to the reaction vessel 11, but a heater is provided in a device or the like for supplying the slurry of the ion exchange resin to remove the ion exchange resin slurry supplied to the reaction vessel 11. The slurry may be heated. As a result, the temperature of the upper layer of the reaction container 11 is suppressed from decreasing, and the reaction container 11 can be downsized.

Further, in the above-described embodiment, the ball-type carbonization furnace 3 in which the reaction vessel 11 for performing the carbonization treatment, the powder storage portion 19 for storing the residue, and the sintered metal filter 17 for removing foreign matters from the exhaust gas are integrated is provided. Although used, the technique disclosed in this specification is not limited to such an example. For example, as shown in FIG. 3, a dry distillation apparatus 31 in which a dry distillation furnace 32 and a filter section 34 are separate bodies may be used. That is, the carbonization device 31 is composed of a carbonization furnace 32 having a ball-type reaction section 38, and a filter section 34 having a filter 40 for filtering the exhaust gas from the carbonization furnace 32. The dry distillation furnace 32 and the filter section 34 are connected by a gas pipe 36. By making the dry distillation furnace 32 and the filter part 34 separate from each other in this way, the dry distillation furnace 32 is brought to a temperature suitable for the thermal decomposition of the object to be treated and the filter part 34 is made a temperature suitable for the treatment of the exhaust gas. You can As a result, the volume reduction process of the object to be processed can be appropriately performed.

The technical elements described in the present specification or the drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technique illustrated in the present specification or the drawings achieves a plurality of purposes at the same time, and achieving the one purpose among them has technical utility.

1 Resin Receiving Tank 2 Control Device 3 Ball Type Carbon Distillation Furnace 4 Superheated Steam Supply Device 5 Exhaust Gas Treatment Device 6 Supply Pump 7 Water Tank 8 Supply Pump 9 Steam Generator 10 Steam Superheater 11 Sealed Reaction Vessel 12 Ball 13 Stirring Blade 14 Rotation Shaft 15 Superheated steam supply nozzle 16 Ion exchange resin supply nozzle 17 Sintered metal filter 18 Exhaust gas outlet 19 Powder reservoir 20 External electric heater 21 Superheated steam supply nozzle 22 Temperature sensor 23 Holding plate 24 Additive supply device 25 External electric type Heater 30 electric conductivity measuring device

Claims (3)

A method for reducing the volume of an ion exchange resin containing lithium,
A step of measuring the electric conductivity of the ion exchange resin,
A step of adding an additive containing an alkaline earth metal and not containing CO ₃ to the ion exchange resin,
A step of thermally decomposing the ion exchange resin to which the additive is added by a dry distillation treatment,
In the adding step, the addition amount of the additive is adjusted based on the electrical conductivity measured in the measuring step to an amount that suppresses binding of the residue of the ion-exchange resin subjected to dry distillation treatment. There is a volume reduction method. The volume reduction method according to claim 1, wherein the additive contains at least one of calcium hydroxide, calcium oxide, and barium hydroxide. It is a device to reduce the volume of ion exchange resin,
The carbonization section,
A slurry supply means for supplying a slurry of an ion exchange resin containing lithium to one end of the carbonization section,
An electrical conductivity measuring means for measuring the electrical conductivity of the ion-exchange resin slurry,
An additive adding means for adding an additive containing an alkaline earth metal and containing no CO ₃ to the slurry supplied to one end of the carbonization section,
The additive addition means, based on the electric conductivity measured by the electric conductivity measuring means, the amount of added pressurizing agent, the amount suppresses the residue of the ion exchange resin to be carbonized processed binds Adjust the volume reduction device.

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