JPH0556477B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for treating radioactive waste, and more particularly to a method for treating organic materials containing phosphorus. (Conventional technology) In facilities that handle radioactive materials, organic substances containing phosphorus, such as phosphate ester oil (EHC oil), which is a control system hydraulic oil, and extractants (TBP/kerosene) discarded from the reprocessing process, are radioactive. Discarded as waste. (Problem to be Solved by the Invention) When these organic substances containing phosphorus are incinerated, the phosphorus undergoes an oxidation reaction and produces phosphorus pentoxide or phosphoric acid, which easily produces glass-like substances with a relatively low melting point. Phosphorous pentoxide or phosphoric acid is present on the surface of the ceramic filter element of the filter (ceramic filter, bag filter, metal mesh filter, etc.) used to remove radioactive particulate matter in the exhaust gas treatment facility, especially the high-temperature dust remover located on the most upstream side. , reacts with the incineration ash or filter-forming components collected on the surface of the filter element to produce glassy substances, and these glassy substances strongly adhere to the filter aggregate and increase clogging of the ceramic filter element. This increases the pressure loss, and it is difficult to effectively regenerate the filter even by backwashing the filter with compressed air or the like, and the ceramic filter element has to be replaced in a relatively short period of time. The purpose of the present invention is to eliminate the above-mentioned problems by providing a coating layer of a specific component on the surface of a ceramic filter element to prevent clogging of the filter, thereby stabilizing the combustion exhaust gas of radioactive organic substances containing phosphorus for a long period of time. The aim is to provide a method for disposing of radioactive waste that can be disposed of using radioactive waste. (Means for Solving the Problems) The radioactive waste processing method of the present invention is a method for burning phosphorus-containing organic materials generated in radioactive material handling facilities. A first coating layer made of a powdery filter aid made of silica, alumina, or both is provided on the filter, and when the high-temperature exhaust gas after combustion of the organic substance is filtered by the dust remover, the phosphorus content in the exhaust gas is reduced. the first part of the filter surface
It is characterized in that it is collected by a coating layer to prevent clogging of the filter. (Function) In the present invention, a first coating layer made of silica, alumina, or both, which does not easily react with phosphorus, is applied to the surface of a ceramic filter element of a high-temperature dust remover installed immediately after a radioactive waste incinerator. As a result, the phosphorus content in the exhaust gas is collected by this first coating layer, and there is no generation of glassy substances in the ceramic filter element, which tends to occur in the past, thereby preventing clogging of the ceramic filter. It can be prevented. Additionally, when substances containing calcium or potassium are added to organic substances containing phosphorus and incinerated, calcium and potassium, which are highly reactive with phosphorus, are released.
It becomes a reactant of Ca ₂ P ₂ O ₇ or K ₄ P ₂ O ₇ and can be collected in the first coating layer. Furthermore, when a powdery second coating layer made of calcium oxide, potassium oxide, or both is provided on the surface of the first coating layer, Ca ₂ P ₂ O ₇ , K ₄ Since P ₂ O ₇ and the like are generated and collected, this can be achieved even more favorably. (Embodiment) FIG. 1 is a perspective sectional view showing an embodiment of a high-temperature dust remover used in the present invention. In this embodiment, the dust remover 1 has an exhaust gas inlet 3 and a combustion burner 4 in the lower part, an exhaust gas outlet 5 in the upper part, and an air inlet 6 for backwashing in the upper part. It has a structure in which 100 bottomed cylindrical ceramic filter elements 8 are suspended. Combustion exhaust gas from an incinerator that incinerates radioactive waste is supplied from the exhaust gas inlet 3 into the dust remover 1, passes through a ceramic filter element 8 from the outside, and after filtering radioactively contaminated dust, etc., the exhaust gas is released. It has a structure in which it is discharged outside the machine from an outlet 5, and has the functions of removing dust from combustion exhaust gas, reburning unburned dust, and completely burning unburned gas. When the ceramic filter element 8 becomes clogged and the differential pressure reaches approximately 700 mmAq, backwashing is performed to regenerate the filter element 8.
To perform backwashing, first, for example, with the exhaust gas outlet 5 closed and the air inlet 6 connected to an air tank (not shown) via a shutoff valve, the exhaust gas inlet 3 is
Connect a vacuum pump etc. to the inside of dust remover 1 to -1000mm.
Create a negative pressure of about Aq. In this state, by opening the shutoff valve and instantaneously flowing compressed air from the inner circumferential side to the outer circumferential side of the cylindrical body of the filter element 8, the dust layer on the surface of the filter element is peeled off and falls, allowing regeneration processing. FIG. 2 is a diagram showing one embodiment of the filter element 8 used in the present invention. The filter element 8 of this embodiment is preferably made of porous ceramics in which fine particles such as SiC are bonded with an inorganic binder, and has a length of 1000 mm or 1500 mm.
It has a bottomed cylindrical shape with a diameter of 60 mm and a wall thickness of about 10 mm, and the structure is such that exhaust gas passes through from the outer periphery of the cylindrical body to the inside. FIG. 3 is an enlarged sectional view showing one embodiment of the filter element 8 used in the present invention. In this example, a first coating layer 11 made of a powdery filter aid made of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), or both is provided on the entire outer surface of the filter element 8. There is. At this time, Al ₂ O ₃ ,
The average particle size of the powder-like filter aid made of _SiO2 is 10μ
The thickness of the first coating layer 11 is preferably about 1 to 5 mm, and preferably contains about 10% of Kanto Rohm JIS Class 8 as a binder. The reason for this is that if the thickness of the first coating layer 11 is less than 1 mm, it will not be effective, and if it is more than 5 mm, the initial pressure loss will become too large. In the above structure in which the first coating layer 11 is provided, the first coating layer 11 made of silica and/or alumina hardly reacts with phosphorus, so the phosphorus content in the exhaust gas is absorbed on the first coating layer 11. Not only can it be collected, but its melting point is 1000 even when it reacts.
Since the temperature is higher than 0.degree. C. and does not become glassy, clogging of the filter element 8 can be prevented and backwashing can also be carried out suitably. Furthermore, in the filter element 8 shown in FIG. 3, calcium or potassium, which is highly reactive with phosphorus, is added in advance to the phosphorus-containing radioactive waste material in a stoichiometric excess amount. When adding a compound containing Ca or K such that Ca/P≧1.0 or K/P≧2.0,
Fine powder Ca ₂ P ₂ O ₇ or K ₄ P ₂ O ₇ is produced,
It can be suitably collected on the first coating layer 11. Therefore, phosphorus does not enter the pores of the filter element 8, and the filter element 8
In addition to better preventing clogging, the coating layer 11 also has good removability, so backwashing can be carried out even better. FIG. 4 is an enlarged sectional view showing another embodiment of the filter element 8 used in the present invention. In this example, the first coating layer 11 is first provided as in the example shown in _FIG . A powdery second coating layer 12 is provided. The thickness of this second coating layer 12 is preferably about 1 to 5 mm, and Kanto Rohm
It is desirable that the binder contains about 10% of JIS class 8. The reason for this is that if it is less than 1 mm, it will not be effective as a second coating layer, and if it is more than 5 mm, the initial pressure loss will be too large. When the second coating layer 12 is provided on the first coating layer 11 as described above, the second coating layer 12 reduces the amount of gas contained in the combustion exhaust gas.
P ₂ O ₅ reacts with CaO or K ₂ O to create a phosphorus compound, and this phosphorus compound is generated on the second coating layer 12 and is not in direct contact with the filter element 8. The releasability between the surface and the first coating layer is further improved, and backwashing can be carried out more favorably, and there is no need to previously introduce calcium and potassium compounds into the waste. In the following, waste oil made from radioactive waste containing 1% phosphorus was actually incinerated in a miscellaneous solid incinerator, and the dust remover shown in Fig. 1 was installed with each of the four types of ceramic filter elements shown in Table 1. The results of filtration and dust removal are shown as the time required for the filter differential pressure to decrease from 300 mmAq to an unusable 700 mmAq, and the effect of backwashing with pressurized air as changes in the filter differential pressure.

[Table] As is clear from Table 1, compared to the conventional example in which no coating layer is provided on the filter element,
40 times more in the example with the first coating layer of Al ₂ O ₃ and SiO ₂ ;
In addition, there is an example in which a second coating layer of CaO and K ₂ O is provided.
Lifespan increased by 76 times. Moreover, while the conventional example had almost no backwashing effect, all the methods of the present invention were able to perform backwashing favorably. (Effects of the Invention) As is clear from the detailed explanation above, according to the method for treating radioactive waste of the present invention,
By providing a first coating layer of Al ₂ O ₃ and/or SiO ₂ on the surface of the filter element, the phosphorus in the exhaust gas can be collected by the first coating layer, which prevents the filter from clogging with phosphorus. As a result, radioactive organic substances containing phosphorus can be treated stably for a long period of time. Further, according to the present invention, backwashing during filter element regeneration can be suitably performed. Furthermore, in the above embodiments, in which Ca and K are mixed and burned, or in which a second coating layer of CaO and K ₂ O is provided, radioactive organic substances containing phosphorus can be more effectively stabilized for a long period of time. In addition, backwashing can be carried out more suitably.

[Brief explanation of drawings]

Fig. 1 is a perspective sectional view showing an embodiment of a high-temperature dust remover used in the present invention, Fig. 2 is a diagram showing an embodiment of a filter element used in the invention, and Fig. 3 is a diagram showing an embodiment of the filter element used in the present invention. FIG. 4 is an enlarged sectional view showing one embodiment of the filter element used in the present invention. FIG. 4 is an enlarged sectional view showing another embodiment of the filter element used in the present invention. 1...Dust remover, 2...Ash removal port, 3...Exhaust gas inlet, 4...Secondary combustion burner, 5...Exhaust gas outlet, 6...Air inlet for backwashing, 7...Refractory ,
8... Filter element, 11... First coating layer, 12... Second coating layer, 13... Support plate.

Claims (1)

[Scope of Claims] 1. In a method for burning organic materials containing phosphorus generated in a radioactive material handling facility, powder particles made of silica, alumina, or both are coated on the surface of a ceramic filter element of a high-temperature dust remover. providing a first coating layer consisting of a filter aid;
When filtering the high-temperature exhaust gas after the combustion of the organic substance with the dust remover, the radioactive substance is characterized in that phosphorus in the exhaust gas is collected by a first coating layer on the surface of the filter to prevent clogging of the filter. How to dispose of waste. 2. Radioactive waste according to claim 1, in which the phosphorus-containing organic substance is mixed in advance with a compound containing a stoichiometrically excessive amount of calcium or potassium relative to phosphorus and then burned. processing method. 3. Claim 1, wherein a powdery second coating layer made of calcium oxide, potassium oxide, or both is provided on the surface of the first coating layer.
Radioactive waste disposal method described in Section 1.