JPS6035038B2 - Method of burning combustible radioactive organic waste - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for burning combustible radioactive organic waste.

The term used in the present invention - ``Flammable radioactive organic waste'' is combustible organic waste containing radioactive materials generated from nuclear combustion reprocessing plants, nuclear reactors, radiochemical laboratories, hot laboratories, nuclear fuel refining plants, etc. Flammable radioactive organic waste includes liquid and solid.Liquid waste includes kerosene, polishing oil, cutting oil, press oil, vacuum pump oil, etc., and solid waste includes epoxy resin. , ion exchange resin, vinyl chloride, neoprene rubber, etc. All of these organic wastes have solid constituent elements of carbon and hydrogen, and although they can be completely combusted by adding sufficient oxygen and heating, they are not flammable. Since organic waste is burned in a confined space such as a glove box, it is difficult to supply and exhaust air, and there are restrictions such as preventing high temperatures, making it difficult to achieve complete combustion.Incineration of combustible organic waste However, if the incineration is not complete, soot and tar are produced.These often cause problems such as clogging of high-performance filters in exhaust equipment in facilities that handle radioactive materials.On the other hand, it is possible to suppress the generation of soot and tar. To achieve this goal, it is necessary to achieve complete combustion of combustible organic waste.Complete combustion requires a large amount of oxygen supply, and the incineration process generates extremely high temperatures, which also affects the selection of incinerator materials. The conventional treatment method for ion exchange resin among such combustible radioactive organic wastes will be discussed below.

Conventionally, used ionized dried sardine resin has been treated by pyrolysis, acid digestion, plastic solidification, asphalt or cement solidification, but these conventional methods have drawbacks that should be improved as described below. Pyrolysis method, acid digestion method,
Disadvantages of conventional methods such as plastic compaction, asphalt or cement compaction methods are discussed.

The method of processing by combustion in oxygen generates high heat and may generate radioactive luminescent substances such as volatile oxides Ru04 and cesium sulfate CS2S04. In addition, it is not actually used because the hot exhaust gas contains soot, unburned organic gas, etc. A method has also been developed in which the material is heated in advance to 50,000 ℃ in an inert gas, non-oxidizing gas, thermally decomposed, the residue is transferred to a fluidized bed, and then burned at 750 to 109,300 ℃ while flowing oxygen. However, there is still room for further improvement in the treatment of hydrogen and volatile gases generated during thermal decomposition, and in the simplification of the process. Another method is to heat the used ion exchange resin to 500° C. in an inert gas and solidify the thermally decomposed residue into cement. This method is also not necessarily stable for long-term storage due to the treatment of volatile organic gas during thermal decomposition and the solidification of char. Concentrated sulfuric acid as acid digestion method,
There is a method of adding used ion exchange resin to concentrated nitric acid and decomposing it by heating. Since these methods generate a large amount of acidic waste liquid, this waste liquid treatment method must be considered. Furthermore, since the concentrated acid is heated and used, there is the problem of corrosivity caused by its vapor. Furthermore, solidifying into plastic, asphalt, or cement is not consumer friendly, and on the contrary, the use of solidifying agents increases waste. The inventor of the present invention aims to improve the shortcomings of the prior art.As a result of repeated studies, the inventors have found that by thermally decomposing combustible radioactive organic waste using catalysts such as oxidized steel, iron oxide, and nickel oxide, the volatile organic waste generated is , discovered that hydrogen, soot, etc. can be completely oxidized by passing them over a heated oxidation catalyst, and completed the present invention.

In practicing this invention, pyrolysis is carried out in the presence of oxygen, preferably in the presence of an amount of oxygen below atmospheric pressure.

When thermally decomposing organic substances, there is a risk of explosive combustion if there is a large amount of oxygen present, so it is necessary to suppress the oxygen partial pressure. For example, a mixed gas of 5 to 20% oxygen and 95 to 80% inert gas is preferable. . However, air oxidation is also possible if the furnace and reactor used are sufficiently strong. The oxidation catalyst used in the present invention is an isokinetic oxidation catalyst selected from the group consisting of steel oxide, iron oxide, cobalt oxide, nickel oxide, and mixtures thereof, heated to 600 to 700 qo.

The most preferred catalysts used in the present invention are copper net (50-80 mesh) and stainless steel net (50-80 mesh).
80 mesh) or nickel net (50-80 mesh) wrapped in layers and oxidized in the air, it does not lose its shape during use, is easy to use, and maintains its performance for a long time. In carrying out the present invention, the amount of combustible radioactive organic waste is 400 to 50
It is thermally decomposed at a temperature of 1,000 mils.

If it is less than 40,000, combustion is insufficient, and if it is less than 500,
If the temperature is above ℃, volatile radioactive organic waste may spread.

The method of the present invention simplifies the process, reduces the volume, stabilizes the residue, and suppresses the generation of dust compared to conventional methods.

An example of an apparatus for incinerating organic solid waste according to the present invention is shown in FIG. In Figure 1, 1 is the air intake port, for example 5 to 1
A mixed gas of 0% oxygen-95-80% inert gas is supplied. 2 is a pyrolysis furnace, 3 is a waste storage container, 4 is a catalytic furnace,
5 is an oxidation catalyst, 6 is glass wool, 7 is a bubbler, 8 is an exhaust gas outlet, and 9 is a thermocouple.

In the case of the apparatus illustrated in FIG. 1, the waste container, oxidation catalyst and glass wool are placed in a quartz tube. An example of an apparatus for incinerating organic liquid waste according to the present invention is shown in FIG.

In Figure 2, 10 is a waste storage container, 11 is a pump, 12 is a pyrolysis furnace, 13 is copper shavings, 14 is a heater, 15 is an air intake port, 16 is a thermocouple, 17 is a catalyst furnace, and 18 is an oxidation catalyst , 19 indicates an air intake port, and 20 indicates a bubbler. The results of experiments in which solid and liquid wastes were incinerated using the apparatus shown in FIGS. 1 and 2 are described.

In the examples, analytical values of exhaust gas are expressed in mol%. Example 1
The apparatus shown in FIG. 1 was used.

The 100-year-old ion exchange resin contaminated with radioactivity was placed in a container (3) and heated to 500°C while a mixed gas of 10% oxygen and 90% argon was flowed through (2).

When kept at 500° C. for about 30 minutes, the organic substances in the ion exchange resin completely disappeared. Volatile organic matter, soot, etc. were generated during this thermal decomposition, but when the material was introduced into a catalytic furnace (1) filled with an oxidized steel catalyst and heated to 700 pm, the following chemical reaction occurred and a stable oxide was formed. ■ CmHn 10 × Cu ○ → × C broadside ○ 10 m
C○20NH2○■ m'C10×Cu○→×Cboard○10m
'C○2■ n' day 20 Hydrocarbons, free carbon (soot) hydrogen, C
○, C02, day, etc. are generated.

These mixed gases are completely oxidized using an oxidized steel catalyst. Oxidized steel is partially reduced, but oxygen is always supplied, so ■
As shown in the formula, it acts as a catalyst continuously because it is compounded into oxidized steel.

After the organic substance decomposes, the metal bonded to the ion exchange resin becomes an oxide that is stable in reaction with oxygen, so it is easy to store it permanently. Example 2 Epoxy resin is thermally decomposed in air at about 320 qo, C ratio,
C2 day 2, C4 day, o, C6 ratio, C, ~2, C○, C0
2. Occurs on day 20 etc.

Resins generally generate hydrocarbons when thermally decomposed. These materials were incinerated using the apparatus shown in FIG. 1 using iron oxide as an oxidation catalyst. That is, put resin on container 3,
The pyrolysis furnace No. 2 was heated while flowing a mixed gas of 5% oxygen and 95% argon. The resin thermally decomposed to generate hydrocarbons, which reacted catalytically with the oxidation catalyst heated to about 6,000C to form water and carbon dioxide gas. The following results were obtained from exhaust gas analysis.

Ingredients 1st time 2nd time C ratio 0.06 0.05N2
76.62 76.0502
8.52 7.87AJ
7.30 8.24C02 7.
49 7.79 From the above results, it was obtained from the experimental results that iron oxide is extremely effective in completely burning combustible organic substances.

Example 3 In the apparatus shown in FIG. 1, an epoxy resin incineration experiment was conducted twice under the same conditions as in Example 2 using cobalt oxide as a catalyst.

The results are described below. Ingredients 1st time
Second C ratio 0.06 0.06N2
77.62 77.6502
7.52 7.77A stop
7.40 7-39C02
7.39 7.13 From the above results, it was found that epoxy resin, which is a solid waste, can be completely incinerated by using cobalt oxide as a catalyst.

Example 4 Three liquid waste incineration experiments were conducted using the apparatus shown in FIG.

The results will be described. The pyrolysis furnace 13 was heated to about 500 oo, and the catalytic furnace 18 was heated to about 600 oo. Pyrolysis furnace lower part 16
A mixed gas of 10% oxygen and 90% argon was flowed from the catalyst furnace inlet 17, and a mixed gas of 20% oxygen and 80% argon was flowed from the catalyst furnace inlet 17. Next, the polishing oil in the container 11 is dripped into the pyrolysis furnace using pump 12, and the vaporized liquid organic matter is introduced into the catalytic furnace with a mixed gas of oxygen and argon, where it undergoes a contact reaction with the nickel oxide catalyst, causing water and carbon dioxide gas. I made it. Water was collected from one bubbler. The results of gas analysis taken from exhaust gas are shown below. Ingredients 1st 2nd 3rd C ratio 0.05 0.04 0.03
N2 47.42 48.77 4
8.1202 17.91 17.6
4 17.22AJ 30.51
29.72 30.69C02 4.1
1 3.82 3.94 From the above results, using nickel oxide as a catalyst turns organic matter into water and carbon dioxide, and complete combustion was achieved, although only an extremely small amount of C ratio was detected for hydrocarbons. I can say that.

Moreover, this catalyst can be used normally without any change in shape after one year. Example 5 Copper net (50 mesh) and stainless steel net (80 mesh) were wrapped and oxidized in air, and the same conditions as in Example 4 were used, using the apparatus shown in Figure 2 as a catalyst. We conducted three experiments on incineration of polishing oil.

The results of analyzing the finally obtained exhaust gas are shown below. Ingredients 1st 2nd 3rd C 0.02 0.02 0.01
N2 47.45 48.79 4
8.1402 18.01 17.6
6 17.62AJ 30.41
29.70 30.09C02 4.2
0 3.83 4.14 From the above results, the waste becomes water and carbon dioxide by mixing oxidized steel and iron oxide, and only a very large amount of carbon dioxide was detected as a hydrocarbon. , it can be seen that complete combustion occurred.

Example 6 Polishing oil was heated under the same conditions as in Example 4 using the equipment shown in Figure 2, using as a catalyst a copper net (80 mesh) and a nickel net (70 mesh) wrapped around each other and oxidized in the air. The combustion experiment was conducted three times.

The results of exhaust gas analysis are shown. Ingredients 1st 2nd 3rd C ratio 0.01 0.01 0.02
N2 46.42 47.79 4
8.6802 18.91 18.6
6 17.77AJ 29.01
28.70 29.00C02 5.6
5 4.84 4.53 From the above results, by using a mixed catalyst of copper oxide and nickel oxide, the waste becomes water and carbon dioxide gas, and only a very large amount of C day was detected as hydrocarbons. It is clear that it was incinerated.

Example 7 Copper net (70 mesh), stainless steel net (65 mesh), and nickel net (55 mesh) were wrapped in layers and oxidized in air, and then used as a catalyst.
A polishing oil combustion experiment was conducted three times under the same conditions as in Example 4 using the apparatus shown in the figure.

The results of exhaust gas analysis are shown. Ingredients 1st 2nd 3rd C ratio 0.029 0.03 0.03
N2 46.32 49.12 4
8.0202 16.99 16.2
2 17.32~2 29.51 3
0.59 30.49C02 7.15
4.04 4.14 From the above results, by using a mixed catalyst consisting of oxidized steel, iron oxide, and nickel oxide, the waste was converted to water and carbon dioxide, and a very high C ratio was detected as a hydrocarbon. It is clear that it was completely incinerated.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of an apparatus for incinerating radioactive organic solid waste according to the present invention, and FIG. 2 is a sectional view of an example of an apparatus for incinerating liquid waste. Figure 2 Figure 1

Claims (1)

[Claims] 1. Combustible radioactive organic waste is thermally decomposed in the presence of an amount of oxygen below air pressure, and the volatile organic matter, hydrogen and dust generated are converted into copper oxide, iron oxide, cobalt oxide, nickel oxide and A method for burning combustible radioactive organic waste, which comprises completely oxidizing combustible radioactive organic waste by passing it over an oxidation catalyst selected from the group consisting of mixtures thereof. 2. The method according to claim 1, wherein the thermal decomposition is carried out at 400 to 500°C. 3. The method according to claim 1, wherein the oxidation catalyst is heated to 600 to 700°C.