JPS6138499A - Method and device for treating used ion exchange resin by steam decomposition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method and apparatus for processing used ion exchange resin, particularly radioactive used ion exchange resin generated from nuclear power plants (hereinafter referred to as waste resin). More specifically, the present invention relates to a method and apparatus for thermally decomposing waste resin in a steam atmosphere.

[Background of the invention]

During the operation of nuclear power plants, etc., waste fluids containing all kinds of radioactive substances are generated, but these waste fluids are often treated using ion exchange resins. After use, this ion exchange resin is ion exchange resin). for example,
In boiling water nuclear power plants, a significant portion of the amount of radioactive waste generated is waste resin. Disposal of this waste resin is considered to be one of the operational issues of nuclear power plants.

Conventionally, this waste resin is mixed with a solidifying agent such as cement or asphalt, solidified in a drum, and stored within a facility. However, the amount of radioactive waste is increasing year by year, and since waste resin is an organic substance, it may decompose and rot if stored for a long time. Therefore, securing a storage location and maintaining safety during storage have become important issues. Therefore, when assimilating waste resin, the volume should be made as small as possible (volume reduction), and
Much attention has been paid to the so-called volume reduction mineralization treatment of waste resin, which converts waste resin into stable inorganic substances (mineralization).

Volume reduction mineralization treatment can be roughly divided into oxidative decomposition methods that decompose the resin in an oxygen atmosphere as shown in equation (1), and steam decomposition methods that decompose the resin in a steam atmosphere as shown in equation (2). Both methods convert carbon in waste resin into carbon dioxide.

C (waste resin) + O□→Co2+ 100 kcnl
l/mob −= (1) C (waste resin) + 2H2
0-+ Co2+ 2H2-30k-mot...
-(2) A typical example of the oxidative decomposition method is the fluidized bed method disclosed in Japanese Patent Application Laid-open No. 12400/1983. However, as is clear from Equation (1), the oxidative decomposition method is an exothermic reaction and generates as much as 100 k, d of heat per mole of carbon, which may lead to deterioration and damage to the decomposition reaction vessel. In order to remove the generated heat, it is necessary to use means such as flowing nitrogen gas, but this temperature control is difficult, and the amount of oxygen must be limited to avoid temperature runaway.
As a result, processing speed no longer increases.

In order to solve these drawbacks, the endothermic reaction of the resin as shown in equation (2) (endothermic amount: 30 ka4/mot) k
AECL as a method for decomposing waste resin in a steam atmosphere
There is. Details of the AECL method, Procedurengs
ofInternatlonal Conferences
nee on RadloactiveWaste
Management (Canadian Nuc)
layer 5ociety).

P, 174-178 (1982) K.

In this method (steam decomposition method), the resin decomposes under an endothermic reaction, so unlike the oxidative decomposition method that makes full use of the exothermic reaction, it is easy to control the temperature inside the reaction vessel and there is no need to limit the titf of steam. As a result, high processing speed can be obtained.

However, steam decomposition methods also have drawbacks.

The reason is that when trying to decompose waste resin in a steam atmosphere and atmospheric pressure, a decomposition temperature of 1000°C or higher is required, and the reaction vessel material deteriorates early (in the rR decomposition method, the decomposition temperature is approximately 600°C). . To solve this, AE
In the CL method, the decomposition pressure is set to a high pressure of 28 atmospheres or more, and the decomposition temperature of waste resin is reduced from 1000°C to 700°C. However, in this case, there is a drawback that the reaction vessel is large-scale due to the high decomposition pressure.

[Object of the Invention] In view of the problems of the prior art, an object of the present invention is to reduce the decomposition temperature '1lo when decomposing waste resin by steam decomposition.
The present invention provides a method for treating waste resin that makes it possible to reduce the decomposition pressure to below 0.0°C and to atmospheric pressure, and an apparatus for carrying out the treatment method.

[Summary of the invention]

The method for treating waste resin by steam decomposition according to the present invention is characterized in that all alkaline earth ions or all alkaline earth ions are adsorbed onto one waste resin before steam decomposition.

Further, the apparatus for carrying out all of the above treatment methods according to the present invention includes a tank that receives waste resin and an aqueous solution of alkali metal ions or alkaline earth metal ions and mixes the two, a reaction vessel that receives all of the waste resin that has been used in the tank, It is characterized by comprising a heating device for the reaction vessel, means for supplying all of the heated steam to the reaction vessel, and a system for removing exhaust gas from the reaction vessel.

Next, the idea of the present invention will be explained in detail.

It has a crosslinked structure in which a copolymer with CH2) is used as a polymer base, and sulfonic acid groups (So, H), which are ion exchange groups, are bonded to it, and it has a three-dimensional plum structure, and has the following structure. It will be hailed in a ceremony.

The 1+ molecular formula is represented by (C47H1706S2)n. The outline of the reaction equation for total steam decomposition of such an ion exchange resin has already been shown in equation (2), but in more detail it is shown in equation (2).
3) The decomposition products include carbon dioxide (CO2), -carbon oxide (Co), and hydrogen (
H2), producing sulfur oxides (5OX).

(C47H4706S2)n+H20→CO2+CO+
■Work 2 + SOX ・・・・-(3) Figure 2 shows the water vapor atmosphere of an ion exchange resin with such a molecular structure,
Figure 2, which shows the results of thermogravimetric analysis under atmospheric pressure as a solid line, shows that the ion exchange resin decomposes in two stages: approximately 350°C and 000°C. Of these, 350℃ is a reaction in which two sulfonic acid groups decompose and SO is generated, and 1000℃
The polymer base decomposes and Co2. Analysis of the cracked gas revealed that it was caused by a reaction that generated Co2 and (2) gold. From the above, it can be seen that the decomposition temperature must be 1000°C or higher in order to completely decompose waste tree fat by steam decomposition under atmospheric pressure.

As methods for lowering such high decomposition temperatures, methods of increasing the decomposition pressure and methods of adding a catalyst are known.

The former is the AECL method mentioned earlier.

On the other hand, the latter is a technology used in coal sulfurization. From research on coal sulfurization, ff1M for reducing decomposition temperature
It is known that carbonates of alkali metals or alkaline earth metals are effective.

The most typical of these is sodium carbonate (Na2C
It is known to reduce the decomposition temperature by adding O3) to finely powdered whole coal.

Therefore, the inventor attempted to add finely powdered carbonic acid (IJ) to the waste resin during steam decomposition of the waste resin. The curve with white circles in Figure 1 shows this catalyst (Na2
This figure shows the temperature in minutes/ffff1 of the waste resin under atmospheric pressure when the amount of added CO3 powder is varied. From this, it was found that the decomposition temperature of waste resin can be reduced from 1000°C to 800°C even under atmospheric pressure by adding more than 3m5q/1-resin (in other words, 20% mat%) of NIL2C03 powder, and the decomposition temperature of waste resin can be reduced from 1000°C to 800°C even under atmospheric pressure. The effect was confirmed.

On the other hand, the curve with black circles in FIG. 1 shows the decomposition temperature of the cradle to which sodium sulfate (Na2S04) powder was added as a catalyst, and it can be seen that there is no Na2SO4-catalytic effect.

In this way, even though they are the same sodium salt, Na2CO3 shows a catalytic effect, whereas Na2SO4 has a solvation effect? The reason why it is not shown is that Na2CO3 reacts with carbon in the waste resin to produce sodium gold, which is highly active with water vapor, as shown in equation (4), whereas Na2SO4
D, W, Mckee (Car
bon, Vat 16°53 (1978)).

As shown above, waste resin 1c3meq-/f-resin (20wt4
) or more can reduce the decomposition temperature of waste resin in a steam atmosphere from 1000°C to 800°C even under atmospheric pressure, but it has been found that Na and SO4 do not have such a catalytic effect.

However, in consideration of deterioration of the reaction vessel material, etc., it is more desirable to reduce the decomposition temperature of the waste resin to about 700° C., and in consideration of operating costs, it is more desirable to reduce the amount of catalyst added as much as possible. Therefore, the inventors reversed the previous experiment by devising a catalyst addition method to achieve all of these two requirements. As a result, it was found that as long as the catalyst was added in the form of fine powder, it was not possible to change the catalyst.

The reason for this is that even if a fine powder catalyst (particle size 0.1 to 10 μm) is added to waste resin with a particle size of 20 to 500 μm, if each piece of waste resin is considered t, the contact surface between the waste resin and the catalyst is This is because the fusion is limited to only the surface of the particles, and the contact area between the waste resin and the catalyst is not sufficient. The third one shows this situation.
In the figure, 1 is waste resin particles and 20 is fine powder catalyst water.

In order to improve this problem, it is necessary to uniformly disperse the catalyst within the waste resin particles, but this cannot be achieved by physical methods (such as further reducing the particle size of the catalyst).

Therefore, the inventors took advantage of all the properties of ion exchange resin,
In other words, if the melting medium is in ionic form, the catalyst will be uniformly incorporated into the waste resin particles by ion exchange,
Uniform dispersion of the catalyst becomes possible. This situation is shown in FIG. 4, which shows that the catalyst 20 is uniformly dispersed within the particles of the waste resin 1.

However, only Na can adsorb ions.
Since Na2Co3 has high catalytic activity, it cannot be applied to ion exchange resins.

Therefore, the inventors investigated how the chemical form of ion-adsorbed Na changes depending on temperature. As a result, Na
2 In addition to the formation of SO4, as the temperature increases, Na
It was newly discovered that 2CO3 is generated. Figure 5 shows Na in a water vapor atmosphere under atmospheric pressure at approximately 0.6 mec.
4/f-Substances produced from Na when waste resin on which ions have been adsorbed only by resin are decomposed are shown. From this figure, at decomposition temperatures below 600°C, Na reacts with the sulfonic acid group (-8o3H), which is an ion exchange group, and once Na2S0
4 (the curve with a white circle superimposed in the figure), but the decomposition temperature is 60
At temperatures above 0°C, Na2SO4 reacts with carbon in the waste resin to convert Na2c04 (curve with a black circle in the figure) into K, which has high catalytic activity.
Even if it is not added in the form of 2CO, if ions are adsorbed in the form of Na+, N has high catalytic activity at decomposition temperatures of 600°C or higher.
a) Steam decomposition is possible at low temperatures without producing 2CO3. .

Based on this newly discovered fact, the inventors investigated the thermal decomposition characteristics of waste resin under atmospheric pressure and in a steam atmosphere, and the results shown by the curve marked with a triangle in Figure 1 were obtained. A good friend. That is, it was found that the decomposition temperature of the waste resin after adsorbing sodium ions could be lowered to 700° C. by adding a melting medium of 0.5 to 1 meq/P-resin. This temperature is higher than 600°C, where the formation of Na 2 CO 5 increases as seen in Figure 3, and the Na
It can be seen that it changes to a2CO3 and exhibits catalytic activity. Further, in FIG. 12, the thermal M total analysis results when ion adsorption of Na+ by 1+n+sq/P2 resin are shown by broken lines for reference. From the results shown in these figures, it can be seen that all waste resin decomposes at 700°C.

In addition, in the case of Na+ ion adsorption as described above, the required amount of catalyst is 23 meq/P- resin when added as a fine powder Na2CO5k catalyst, whereas the required amount of catalyst is 10.5 to 10.5 meq/P- resin. 1.0 meq/P-Resin requires less amount of catalyst.

As a result of the above, when Na+ ions are adsorbed to waste resin as a catalyst, Na+ is uniformly dispersed within the waste resin particles, and at a decomposition temperature of 600°C or higher, this Na+ is converted to Na2CO5 with high catalytic activity. As a result, the Na uniformly dispersed in the waste 1'LJ fat
Because of 2C05, the decomposition temperature of the resin in a steam atmosphere and atmospheric pressure can be reduced from tiooo°C to 700°C, and the required amount of catalyst at that time is 0.5 to 1.0□. It turns out that it is a q4-resin〇Furthermore, as a catalyst for reducing the decomposition temperature during aquatic and fish reactions, carbonic acid is used as well as IJium.
Finely powdered alkali metal and alkaline earth metal carbonates are also known to be effective. Therefore, we also determined the decomposition temperatures of other alkali metals and alkaline earth metals when ions were adsorbed. The results are summarized in the 6th section.
As shown in the figure. Figure 6. Catalytic activity n Ll+, K+,
Na+ is the highest, followed by Cg+.

It can be seen that the order is 2+ Mg and Ca. In addition, the required amount of catalyst is approximately 0.5 to 1. Omeq/
It can also be seen that it is P-resin. Therefore, it can be seen that Li+, K", and Na are suitable as catalysts, but Na+ is the cheapest.
Na+ is optimal for the catalyst.

In addition, as starting materials for alkali metal and alkaline earth metal ions, taking Na+1 as an example, NaOH+NaC1
, Na2SO4, Na2CO3, etc. are possible, but Na
0f (otherwise, ions such as ct-, so4'''', co, etc. remain in the solution even after Na+i ions are adsorbed), which ultimately becomes radioactive secondary waste such as tic HCl. On the other hand, when NaOHf is used, the remaining OH- is finally converted into KE-H2OK. Therefore, when considering all secondary wastes, it is necessary to use an alkali metal or alkaline earth metal hydroxide compound such as NaOH as a starting material. is desirable.

From the above results, when carrying out the present invention, waste resin should be mixed with 1 g (dry weight) of 0.5 to 1. .

It can be seen that it is sufficient to adsorb the alkali metal or alkaline earth metal ion of meq., and then decompose it in a full steam atmosphere at atmospheric pressure. At this time, the temperature inside the reaction vessel (decomposition temperature) is set at 700°C or higher, and the supplied steam is also set at 700°C or higher. FIG. 7 is a system diagram of the processing system, and FIG. 8 is a schematic sectional view of a batch processing type fixed bed furnace used in the reaction vessel. Since the waste resin 1 is discarded from the condensate demineralizer through the backwash operation button, it is in the form of a slurry, and this is stored in the waste resin tank 2. A predetermined amount (30 ky in dry weight) of the waste resin 1 in the waste resin tank 2 is transferred to the stirring tank 4 via the pulp 3. An aqueous solution of sodium hydroxide (NaOH) is added to the stirring tank 4 from the medium tank 5.
30 mol (-30 eq.) is added, and these are stirred by the stirring blade 6 in the stirring tank 4 for about 1 hour. As a result, Na is uniformly dispersed in the waste resin as a melting medium by ion adsorption. This waste resin is centrifugally dehydrated by a dehydrator 17 and then supplied to a reaction vessel 8 through the entire pulp 7.

A schematic cross-sectional view of reaction vessel 8 is shown in FIG. The waste resin 1 supplied to the reaction vessel 8 is first passed through the heater 9.
Heated to 00t:. Thereafter, water vapor is supplied, and K is supplied to the reaction vessel 8 via the valve 12 after the water vapor generated in the evaporator 10 is heated to 00° C. by the heater 1g. This water vapor is uniformly supplied to the waste resin 1 in the reaction container 8 via a 13-metal dispersion plate provided in the reaction container 8. As a result, the waste resin is decomposed by steam, and an exhaust gas containing CO□rH2'e as a main component is generated as a decomposition product. This exhaust gas is valve 14'r
Prefilter 15 and HEPA filter 161C
After completely removing the radioactive substances in the exhaust gas, it is diluted into atmospheric pressure and released.

As a result of supplying water vapor at a rate of 10 kP/h, the initially supplied waste resin of 30 kP was decomposed in about 5 hours, and only 2 kg of residue remained in the reaction vessel 8. Furthermore, since steam decomposition is an endothermic reaction as described above, it is easy to control the decomposition temperature, and the decomposition temperature could always be controlled at 700±lθ°C.

Example 2 This example deals with steam decomposition of waste resin generated from the purification system of a boiling water nuclear reactor, and FIG. 9 is a system diagram of the treatment system used in this example.

Since the amount of waste resin generated from boiling water reactors is generally larger than that from pressurized water reactors, this embodiment is designed to allow continuous processing rather than patch processing. Continuous processing methods use fluidized bed furnaces, rotary kilns, multi-stage furnaces, etc.

After transferring the waste resin 1 stored in the waste resin tank 2 to the stirring tank 4, sodium hydroxide was added from the catalyst tank 5, and the mixture was stirred for about 1 hour using the stirring blade 6 until the Na ions were adsorbed into the waste resin. is exactly the same as in Example 1. Thereafter, this slurry-like waste resin was quantitatively supplied from the metering tank 18 to the fluidized bed furnace 19 at a rate of y/h (however, the value converted to the amount of dry resin). The fluidized bed furnace 19, which is commonly known, used steam as a fluidizing agent. The steam is heated to 00°C by a steam generator 10 and a heater 1g.71. After that, it is supplied to the fluidized bed furnace 19. Further, the temperature inside the fluidized bed furnace J9 is 700°C. As a result, one portion of the waste resin was decomposed with steam, and a flurry of exhaust gas was generated as decomposition products, including CO2 and H2. The treatment of this exhaust gas is exactly the same as in Example 1.

As a result of steam decomposition of waste resin by the above method, 20 ky of waste resin could be processed per hour, and 20kp of waste resin was reduced to only about 1.5kp of sand, resulting in the same effect as in Example 1. was recognized. In this way, even when a fluidized bed sound is used as a reaction vessel, waste resin can be decomposed with steam at a decomposition temperature of 700°C and a decomposition pressure of atmospheric pressure.Moreover, by performing continuous treatment, the treatment speed can be increased to about the same level as in Example 1. It was found that it can be improved by 3 times.@Also, the same effect can be obtained by using a rotary kiln, multi-stage furnace, etc. instead of a fluidized bed.

In addition, as already shown in detail in [Summary of the Invention] using FIG. 6 etc., as the melting medium, K
Alkali gold such as L1+, K+, Cs+ etc.
+ ion or an alkaline earth metal ion such as IdMg or Ca'l can also be used. These Na
As a result of steam decomposition of all melting media using the apparatus shown in Example 1, the decomposition temperature was 70 at Ll,K.
At 0℃, C8+, Mg2+lCa2+ have a total decomposition temperature of 8
It was confirmed that steam decomposition is possible even under atmospheric pressure by setting the temperature to 00 to 900°C. In these cases as well, the catalyst was supplied to the stirring tank 4 in the form of an aqueous solution of a hydroxide compound such as KOH or LiOH.

〔Effect of the invention〕

According to the present invention, the steam decomposition of waste resin, which allows stable control of the decomposition temperature and has a high processing speed, can be carried out at about 70% at atmospheric pressure.
．． It can be carried out at 0°C, and it is possible to prevent metal deterioration of the reactor material. Furthermore, the amount of catalyst can be reduced compared to the conventional example in which a powdered catalyst is added.

[Brief explanation of drawings]

Figure 1 is a diagram comparing the decomposition temperatures of the present invention and the conventional method.
The figure shows the change in weight of waste resin with respect to temperature. Figures 3 and 4 show the dispersion of the catalyst by the fine powder addition method and the ion adsorption method, respectively.
Figure 6 is a diagram showing the generation rate of a2CO, l NIL2SO4, Figure 6 is a diagram showing the effect of fences on the decomposition temperature, and Figures 7 and 8 are a system diagram of an embodiment of the present invention. A schematic cross-sectional view of the reaction vessel, and FIG. 9 is a system diagram of another embodiment. [Explanation of symbols] 1... Waste resin 4... Stirring tank 5...
・Catalyst tank 8... Reaction vessel 10... Evaporator 19... Fluidized bed furnace 20... Catalyst Figure 1 Catalyst addition ((new evyt-phase↑fat) Figure 2 External sales 3kL ('c) Figure 3 Figure 4 Figure 5 40υ waC)C)
50U 6th [4 07f It ltl st /10 t Cse'i
/1-kNRh) 7th figure 8th figure 9th figure procedural amendment concave (method) February 12, Showa Tough, Showa Ke 9 special 5'"Wish No. 16 cro? (Mr. 9)
Name (Name) - OF, Shizensha Mikuhe Sakutang 4 Agent address 2-6-2 Kuunouchi, Chiyo 01-ku, Tokyo Shigesu BiJshi 3305 Marunouchi Date of amendment order 1989 1g month near 0, :/ 7, 1g correction of amendment We will amend the following matters in the specification of this application. 1, page 5, line 12 [For details of the AECL method, see the Procedures of
``Details of the AECL method can be found in the Proceedings Op. International Conference on
Love or Active Waste Management (Canadian Nuclear Society) P, 174
~178 (1982) (Proceedingsof
Correct it with J. 2, page 5, line 15, 1'- (1982). "A certain gold 1'-
(1982):l. ” he corrected.

Claims (1)

[Scope of Claims] 1. A method for decomposing a used ion exchange resin by steam decomposition, characterized in that, prior to the steam decomposition, an alkali metal or an alkaline earth metal is ion-adsorbed onto the used ion exchange resin in advance. How to dispose of used ion exchange resin. 2. The spent ion according to claim 1, in which the alkali metal or alkaline earth metal is adsorbed at a rate of 0.5 to 1.0 milliequivalent per 1 g (dry weight) of the used ion exchange resin. How to process replacement resin. 3. The method for treating a used ion exchange resin according to claim 2, wherein sodium is ion adsorbed at a rate of 0.5 to 1.0 milliequivalent per 1 g (dry weight) of the used ion exchange resin. 4. The method for treating a used ion exchange resin according to claim 2 or 3, wherein the steam decomposition is carried out at a temperature of 700°C or higher and lower than 1000°C. 5. The method for treating a used ion exchange resin according to claim 4, wherein the steam decomposition is performed under atmospheric pressure. 6. A tank that receives and mixes used ion exchange resin and an aqueous solution of alkali metal ions or alkaline earth metal ions, a reaction vessel that receives the used ion exchange resin that has passed through the tank, and a heating device for the reaction vessel; A steam decomposition treatment apparatus for used ion exchange resin, comprising: a steam supply device for supplying heated steam to the reaction vessel; and a system for removing exhaust gas from the reaction vessel. 7. Claim 6, wherein the reaction vessel is of a fixed bed type.
A steam decomposition treatment device for used ion exchange resin as described in 2. 8. The steam decomposition treatment apparatus for used ion exchange resin according to claim 6, wherein the reaction vessel is of a fluidized bed type using the steam as a fluidizing agent.