JP3858469B2 - Treatment method for nitrate asphalt mixed waste - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating nitrate asphalt mixed waste, and in particular, it is produced by evaporating moisture by kneading concentrated waste liquid mainly composed of sodium nitrate with asphalt, which occurs in the process of spent fuel reprocessing. The present invention relates to a method for treating nitrate asphalt mixed waste, which is suitable for converting the nitrate asphalt mixed waste into a more thermally stable and reduced volume waste form.
[0002]
[Prior art]
As the conventional technology, the document “Power Reactor / Nuclear Fuel Development Corporation Tokai Works, Reprocessing Plant, Technology Development Department, Test Operation Section 2: Operation of Reprocessing Plant, 11.2 Asphalt Solidification Technology Development Facility: Kinetics Technical Report, No. .55, pp. 64-66, 1985. 9 ”, a low radioactive waste liquid generated from a reprocessing facility and asphalt are heated and mixed, dehydrated, and filled into a drum as a stable asphalt solidified body. It has been. This method
(1) Asphalt is inexpensive.
[0003]
(2) The process is relatively simple.
[0004]
(3) The leachability of radioactive materials in the solidified body with respect to water is low.
[0005]
Has the following advantages.
[0006]
According to the published information “http: /www.pnc.go.jp/kenkyu/dbase/asf/a2.html”, the treatment waste liquid is a concentrated waste liquid containing sodium nitrate and sodium carbonate as main chemical components, The asphalt mixing ratio is 40/60 to 50/50 wt%. The asphalt solidified body filled in the drum can was stored in the asphalt solidified body storage facility. However, it is not known about the prior art that once solidified and stored asphalt solidified material is again processed in some way into a thermally stable, reduced volume waste form.
[0007]
[Problems to be solved by the invention]
The invention of claim 1 converts flammable nitrate asphalt mixed waste into non-oxidizing salt and carbon-based coke-like materials with excellent fire resistance and reduced flame retardant mixed waste. The purpose is to do.
[0008]
  The invention of claim 2HighThe purpose is to suppress a reaction that is accompanied by a large amount of foaming after the temperature has been reached.
[0010]
  Claim3An object of the present invention is to prevent the melt from overflowing from the reaction vessel due to foaming due to the interaction between the nitric acid component as the oxidizing agent and the asphalt volatile component as the reducing agent.
[0011]
  Claim4The purpose of this invention is to produce carbonate with a high melting point, prevent the formation of a molten phase, and promote the interaction between the nitric acid component and the asphalt volatile component, thereby suppressing the decomposition of the existing carbonate. It is.
[0012]
  Claim5This invention relates to the invention of claim 1 and aims to reduce the generation of secondary waste.
[0013]
  Claim6The object of the present invention is to oxidize and decompose a coke-like substance mainly composed of carbon that has become flame retardant into carbon dioxide gas, and to separate residual inorganic substances mainly as carbonates.
[0014]
  Claim7The object of the present invention is to provide heat resistance and leaching resistance by using a soluble inorganic substance mainly composed of carbonate as an insoluble inorganic crystal mineral substance.
[0015]
  Claim8The invention of claim7In relation to the invention, the purpose is to reduce the total amount of reprocessed waste by deriving the elements added for the heat resistance and leaching resistance of inorganic components from other reprocessed waste, etc. .
[0016]
  Claim9The invention of claim6It is an object of the present invention to provide an optimum apparatus for oxidatively decomposing asphalt distillation products.
[0017]
  Claim 10The invention claims9The purpose of this invention is to reduce the generation of waste gas.
[0018]
  Claim 11The purpose of the invention is to increase the energy efficiency of the heating means.
[0019]
[Means for Solving the Problems]
The feature of the invention of claim 1 is that the nitrate asphalt mixture, which is inherently flammable, is gradually raised in an oxygen-free atmosphere, so that the nitric acid component as an oxidizing agent and the asphalt volatile component as a reducing agent are reduced. It is intended to decompose and remove both by reacting in a controllable state to form a mixture of a non-oxidizing salt and a flame-retardant coke-like substance composed mainly of carbon.
[0020]
The feature of the invention of claim 2 is that nitrite is added in order to start the interaction between the nitric acid component as the oxidizing agent and the asphalt volatile component as the reducing agent from a relatively low temperature. The purpose is to suppress a reaction that involves a rapid and large amount of foaming.
[0021]
The special report of the invention of claim 3 relates to the invention of claim 4 and is to optimize the addition amount of nitrite.
[0022]
The feature of the invention of claim 4 is that the opening area of the container prevents the melt from overflowing from the reaction container due to foaming due to the interaction between the nitric acid component as the oxidizing agent and the asphalt volatile component as the reducing agent. Is to make it larger.
[0023]
The feature of the invention of claim 5 resides in that the concentration of carbon dioxide gas in the atmosphere is increased so that the decomposition product of the nitric acid component does not become meltable, so that it is easily converted to carbonate, and decomposition of the carbonate is suppressed.
[0024]
The feature of the invention of claim 6 relates to the invention of claim 1 and is that the dry-distilled condensed oil content of the asphalt component is used as a forming aid for the dry-distilled product.
[0025]
The feature of the invention of claim 7 resides in that the coke-like substance mainly composed of carbon which has become flame retardant is oxidized and decomposed mainly into carbon dioxide gas to obtain a residual inorganic substance mainly composed of carbonate.
[0026]
The feature of the invention of claim 8 resides in that a soluble inorganic substance mainly composed of carbonate is insoluble, and further, a constituent element is a crystalline mineral that is fixed by replacing with various and various elements.
[0027]
The feature of the invention of claim 9 relates to the invention of claim 8, and the element added for making the inorganic component insoluble material is included in the incinerated ash, nuclear fuel assembly metal waste, and waste solvent. It is to be derived from inorganic waste such as phosphoric acid.
[0028]
A feature of the invention of claim 10 relates to the invention of claim 7, and is to provide an optimum method for oxidatively decomposing asphalt dry distillation products.
[0029]
The feature of the invention of claim 11 relates to the invention of claim 10, and after removing the gas generated by oxidative decomposition of the asphalt dry distillation product, it is enriched with oxygen or oxygen and ozone and refluxed to the oxidizer. It is in.
[0030]
The feature of the invention of claim 12 is that the nitric acid component as an oxidizing agent and the asphalt volatile component as a reducing agent are allowed to proceed to each other, the oxidation reaction of the coke-like granule is advanced, And the heating means for sintering is a microwave heating method.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
A typical nitrate asphalt mixed waste is composed of 45% by weight of a salt mainly composed of sodium nitrate and 55% by weight of asphalt. Asphalt is the heaviest component contained in crude oil, and its structure is a high molecular compound having a complex (aromatic) polycyclic structure. Generally, asphalt is composed of an n-heptane soluble component and an n-heptane insoluble component (asphalten), and the former is further classified into a saturated fat component, a naphthene aromatic component, and a polar aromatic component.
[0032]
A typical asphalt weight composition is 25% saturated fat, 35% naphthenic aromatic, 15% polar aromatic and 25% asphaltene. The elemental composition of typical asphalt is 89.5% carbon and 10.5% hydrogen, the average element weight composition of saturated aliphatic components is 85% carbon, 15% hydrogen, and the average element weight composition of other aromatic components. Is 91% carbon and 9% hydrogen.
[0033]
Therefore, 1 kg of typical nitrate asphalt mixed waste includes 0.45 kg (5.29 g-mol) of sodium nitrate and 0.138 kg of saturated aliphatic component (C: 9.7 g-mol, H: 20.6 g-). mol) and 0.412 kg of aromatic components (C: 31.3 g-mol, H: 37.1 g-mol).
[0034]
The effects of the inventions of claims 1, 2, 3, 4 and 5 are based on the thermal decomposition characteristics of nitrate asphalt mixed waste.
[0035]
The softening point of asphalt itself is about 85 ° C, but nitrate asphalt mixed waste is melted at about 175 ° C and filled into containers. Nitrate asphalt mixed waste starts an exothermic reaction at 200 ° C, and is about 300 ° C (NaNO_ThreeAt a melting point of 306.8 ° C., the foamed layer due to the volatilization of asphalt decomposition products becomes about 50 mm and becomes steady, but around 380 ° C. (NaNO_ThreeAt a decomposition temperature of 380 ° C., it is said that a vigorous exothermic reaction occurs and a runaway reaction state occurs. Since asphalt itself does not thermally decompose at 300 ° C., the thermal decomposition at about 300 ° C. is dependent on the reaction with sodium nitrate.
[0036]
The oxidation reaction with nitrate increases rapidly to near the decomposition temperature of sodium nitrate, and when nitrite ions, which are reduction products of nitric acid, accumulate to a certain concentration or more, the reaction proceeds rapidly and becomes difficult to control. Therefore, if nitrite ions are present from the beginning, the oxidation reaction with nitric acid proceeds even at a low temperature, so that abrupt reaction can be avoided and controlled. Sodium nitrite (NaNO₂Of 270 ° C. to 320 ° C., which is lower than the decomposition temperature of sodium nitrate, can give a constant high reaction rate. The amount of nitrous acid required empirically is 1-5% of the amount of nitric acid.
[0037]
In general, nitrate ion is 1 g-mol NO according to the following reaction:_Three ^-Shows an oxidizing property equivalent to 1 g-mol of oxygen.
[0038]
2NO_Three ^--2e → NO + NO₂+ 2O
If 0.45 kg (5.29 g-mol) of sodium nitrate contained in 1 kg of typical nitrate asphalt mixed waste is preferentially reacted with saturated aliphatic components, the saturated aliphatic components are converted into carbon dioxide and water. Since it corresponds to 17.8% compared to the oxygen equivalent (29.7 g-mol) required for oxidation, 24.5 g of the saturated aliphatic component is decomposed by reaction with sodium nitrate. However, in reality, the reaction product may contain not only carbon dioxide and water but also vapors of carbohydrates, and it is considered that a larger amount of saturated aliphatic components are decomposed.
[0039]
If a nitrate asphalt mixture is heated to about 700 ° C in a non-oxidizing atmosphere, it will be thermally decomposed and condensed to a hydrocarbon with a low molecular weight, excluding at least 17.8% of saturated aliphatic components involved in the reaction with nitrate ions. It becomes a thing. On the other hand, aromatic components are mainly CH in the pyrolysis process up to 700 ° C._FourPolymerization is performed while generating hydrogen, and polymerization is performed while generating hydrogen at higher temperatures. When heating to 700 ° C, when 25% of the aromatic components are volatilized, the hydrogen content is reduced from 9% to 3.62%, and the remaining coke-like substance has a carbon content of 96.38%. . When heated to 851 ° C., which is the melting point of sodium carbonate, the hydrogen content is reduced to 1.86%, the amount of coke-like substance is 0.304 kg, and the carbon content is 98.14%. As a result, 4% of the asphalt component becomes carbon dioxide and water by reaction with nitrate ions, 41% volatilizes as some hydrocarbon or hydrogen, and 55% remains as a coke-like substance.
[0040]
On the other hand, sodium nitrate (NaNO_ThreeMelting point 306.8 ° C.) 5.29 g-mol reacts with hydrocarbon and decomposes to 5.29 g-mol of NOx, and reacts quantitatively with the generated carbon dioxide and water, so that sodium carbonate (Na₂CO_ThreeA melting point of 851 ° C.) of 1.83 g-mol and sodium hydroxide (NaOH melting point of 318.4 ° C.) of 1.64 g-mol. If there is an excess of carbon dioxide in the atmosphere, all of the reaction product of sodium nitrate is converted to sodium carbonate. Therefore, 0.45 kg (5.29 g-mol) of sodium nitrate and 0.55 kg of asphalt contained in 1 kg of the original nitrate asphalt mixed waste are 0.281 kg (2.65 g-mol) of sodium carbonate and coke-like dry distillation. A total of 0.305 kg is 0.585 kg.
[0041]
The specific gravity of the raw material asphalt is 1.04, the specific gravity of the mixture with sodium nitrate (specific gravity = 2.261) is 1.58, and the coke-type dry distillation product containing sodium carbonate (sg = 2.532) ( The specific gravity of 2.15) is 1.2, and the specific gravity of granules having a particle size of 30 mesh or less produced by crushing a coke-like dry distillation product is 1.5 (69.7%). . When 5% asphalt is added to the weight of the granule and mixed with heat, and then press-molded, the specific gravity of the compact becomes 1.8, and the temperature is gradually increased to 851 ° C in a non-oxidizing atmosphere. When combined, the weight is reduced by 2.3% and the specific gravity is 1.8. Initially, the nitrate asphalt mixed waste, which weighed 1 kg and had a volume of 0.633 liters, was finally reduced to a weight of 0.60 kg and a volume of 0.333 liters.
[0042]
Coke-shaped granules can be formed by using techniques usually used for the production of carbon products such as mold compression molding, extrusion molding, and briquette molding.
[0043]
The action of the invention of claim 7 is based on the oxidative decomposition characteristics of the coke-like dry distillation product containing sodium carbonate in heated oxygen at a relatively low temperature. Coke-like dry distillation product containing sodium carbonate is put into a granule container produced by crushing, and exposed to oxygen. The heating temperature is gradually increased, and the carbon component is oxidized when the temperature exceeds 300 ° C and below 500 ° C. First, the weight increases, and then the carbon oxide gas is generated to gradually decrease the weight. When ozone is contained in oxygen, the same oxidation reaction proceeds even at lower temperatures. However, if the ozone concentration is high, there is a possibility of explosion, so the ozone concentration needs to be 5% or less. If the temperature is too high until the weight increase due to oxidation of the carbon component reaches the maximum value, the reaction heat accumulates and ignites, and all the granules in the container burn. The granule is red hot and the carbon monoxide gas burns to generate a flame, which may cause inorganic components to scatter. When the weight increase due to the oxidation of the carbon component reaches the maximum value, the temperature of the carbon oxide gasification reaction can be accelerated without raising the temperature. If no flame is generated, inorganic components will not scatter. Nitrate asphalt mixed waste may contain carbonates containing radioactive carbon. Even if the temperature does not reach the so-called decomposition point, carbonate may react with a substance that easily forms a sodium salt exceeding the melting point and decompose. In the present invention, by keeping the temperature below the melting point of the carbonate, decomposition of the carbonate can be prevented, and liberation of radioactive carbon can be prevented. Finally, all carbon components except for carbonic acid components are lost as gas, and the nitrate asphalt mixed waste, which initially weighed 1 kg and had a volume of 0.633 liters, was carbonated with a weight of 0.281 kg. It becomes sodium.
[0044]
The action of the invention of claim 8 and claim 9 is that the inorganic substance produced by the invention of claim 7 converts sodium carbonate containing pollutants into a substance insoluble in water. Zirconium phosphate sodium (abbreviated as NZP) has the molecular formula NaZr₂P_ThreeO₁₂(Molecular weight: 490.34 g), ZrO₆The octahedron has 6 POs_FourEach tetrahedron and an oxygen atom share and bind to each PO._FourThe tetrahedron has four ZrO₆The octahedron and the oxygen atom are shared and bonded, and the basic structural unit is (Zr₂P_ThreeO₁₂ ^-) Is a ribbon structure, and the ribbon structure is PO_FourCombined by tetrahedron, it has a three-dimensional crystal structure. The crystal structure is generally M'M "_Three[A^IV ₂] [X^V _Three] O₁₂Zr ions occupy the A position and P ions occupy the X position. There is a hole M 'in the ribbon structure, and Na ions are coordinated. There is another hole M "between adjacent ribbon structures, but it is not filled in NZP.
[0045]
Each position of M ′, A, X, etc. is characterized in that the crystal structure does not change even if it is substituted with various heterovalent ions. The M ′ position is almost selectively replaced by the largest cation, the X position is the smallest cation, and the A position is replaced by an intermediate cation. In general, a substance whose structure does not change even when a constituent atom of NZP is substituted is denoted as [NZP].
[0046]
M 'position: Na⁺, Rb⁺, Cs⁺, Ag⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Cd²⁺, Pb²⁺
A position: Ti⁴⁺, Cr³⁺, Fe³⁺, Co²⁺, Ni²⁺, Y³⁺, Zr⁴⁺, Tc⁴⁺, Ru⁴⁺, Rh³⁺, In³⁺, La³⁺, Ce⁴⁺, Pr³⁺, Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺, U⁴⁺, Np⁴⁺, Pu⁴⁺, Am³⁺, Cm³⁺
X position: Al³⁺, Si⁴⁺, P⁵⁺, As⁵⁺, Se⁶⁺, Mo⁶⁺, Sn⁴⁺, Sb⁵⁺, Te⁴⁺
An ion in a multivalent valence state at the M ′ position replaces an equivalent amount of Na. At the M ″ position, an equivalent amount of a monovalent alkali metal is coordinated to compensate for the charge of the ion substituted at the A or X position.
[0047]
When [NZP] is synthesized with sodium ions, which are the main components of waste, it is possible to fix up to 4 atoms of Na per molecule of [NZP] by selecting other constituent elements. Almost all fission product elements contained as contaminating components are fixed by substituting elements in [NZP]. [NZP] can be synthesized with a wide variety of element combinations. Although the basic compound is composed of Na, Zr, and P, it is particularly desirable to synthesize Zr by replacing it with titanium or iron that is cheaper and has a smaller atomic weight. Phosphorus is an essential element, but may be replaced with silicon as necessary for the purpose of fixing a larger amount of Na.
[0048]
All fission product elements, MA elements, corrosion product elements, process chemical constituent elements, etc. contained in reprocessed waste are fixed by substituting constituent elements of [NZP] except those present as anions. .
[0049]
The additive elements for synthesizing [NZP] can be supplied from other reprocessing wastes. For example, Zr, Fe, Sn contained in Zircaloy (hull, channel box), Fe, Cr, Ni contained in stainless steel (end piece), Ni, Fe contained in nickel alloy (spacer), and miscellaneous solid incineration ash Ca, Al, Si, Zn, phosphate (waste solvent), etc. contained.
[0050]
The action of the invention of claim 10 is that a batch-type muffle furnace that controls the temperature rise rate and the maximum temperature respectively, and moves horizontally in the furnace at a constant speed while controlling the horizontal temperature distribution and the maximum temperature respectively. Either a continuous tunnel furnace or rotary inclined tubular tunnel furnace to be used, or a silo furnace that is loaded into the furnace continuously or batchwise and moved by gravity while controlling the temperature distribution in the height direction and the maximum temperature, respectively, etc. Good. In a tunnel furnace or silo-shaped furnace, it is preferable to supply oxygen or oxygen-containing oxygen from the oxidation reaction product take-out side.
[0051]
According to the eleventh aspect of the present invention, the gas containing the radioactive substance can be easily confined and managed in the circulation system by enriching and circulating the exhaust gas from the heating furnace with oxygen.
[0052]
The effects of the inventions of claims 12, 13 and 14 are based on microwave heating, which is characterized in that the heated object itself becomes a heating element. Since a normal heating method mainly uses heat conduction, the temperature distribution of the object to be heated is difficult to be uniform, a hot spot is generated, and a reaction may occur locally. On the other hand, in the microwave heating method, the temperature distribution of the object to be heated becomes more uniform, and local reactions hardly occur.
[0053]
Microwave heating is effective not only in promoting a chemical reaction by increasing the temperature but also in promoting energy-efficient solid phase diffusion reaction and sintering reaction between particles. The microwave heating method is suitable for heat-treating a radioactive substance in a container by placing a microwave generation source requiring maintenance outside the living body shield and guiding it into the living body shield by a waveguide.
[0054]
[Example 1]
A method for treating nitrate asphalt mixed waste, which is a preferred embodiment of the present invention, will be described with reference to FIG. 1 showing a nitrate asphalt mixed waste apparatus. A heat resistant metal muffle furnace 1 for treating a nitrate asphalt mixture includes a heat resistant metal container 2. Container 2 has an opening area of 0.2 m², The depth is 15 cm. A nitrate asphalt mixture, pre-fluidized and containing 1% sodium nitrite, is filled in container 2 to a depth of 7.5 cm. The nitrate asphalt mixture has a loading volume of 15 liters and a loading capacity of 23 kg. 3 is a gas circulation system, 4 is a carbon dioxide supply system, 5 is an oxygen supply system (including an ozone generator), 6 is an oil condenser, 7 is an adsorption tower, 8 is a gas condenser, 9 is an oil outlet, Reference numeral 10 denotes a washing water outlet, and 11 denotes an adsorption tower cleaning liquid supply port. The adsorption tower 7 is filled with a zeolite-based adsorbent.
[0055]
Carbon dioxide supplied from the carbon dioxide supply system 4 circulates through the muffle furnace 1, the oil condenser 6, the adsorption tower 7, the gas condenser 8, and the muffle furnace 1 as a circulation gas. In this state, the temperature in the muffle furnace 1 is gradually increased from 270 ° C. to 380 ° C., and the reaction of nitrate and hydrocarbon, which is a composition of the nitrate asphalt mixture, proceeds in the vessel 2. The oil contained in the nitrate asphalt mixture is volatilized by the heating and condensed in the oil condenser 6. The condensed oil is taken out from the apparatus through the oil take-out port 9. NOx generated by thermal decomposition in the muffle furnace 1 is adsorbed and removed by the zeolite adsorbent in the adsorption tower 7. The gas condenser 8 condenses the circulating gas and removes moisture and the like contained therein. Circulating gas containing no volatile matter and moisture is returned from the gas condenser 8 to the muffle furnace 1.
[0056]
After no volatile matter is generated, the temperature of the muffle furnace 1 is increased to 850 ° C., and the substance in the container 2 is heated. After this heating, 13.45 kg of coke-like substance remaining in the container 2 after the muffle furnace temperature returns to room temperature is taken out from the muffle furnace 1. The coke-like substance is pulverized to 30 mesh or less by a crusher (not shown) to form granules.
[0057]
The granules are heated to about 120 ° C. with 5% asphalt added. Granules and asphalt are mixed in this heating state. Thereafter, the mixture was cooled and then 0.3 ton / cm by a punch in a mold having an inner diameter of 30 cm.²Was compressed into a cylindrical molded body having a height of 11 cm. The bulk specific gravity of this molded body was 1.8. The molded body was placed in the container 2 and placed in the muffle furnace 1, and sintered in an inert atmosphere (carbon dioxide gas atmosphere) in 8 hours and finally gradually increased to 850 ° C. This sintered body is taken out from the muffle furnace 1. The sintered body had a weight of 13.8 kg, a diameter of 28.5 cm, a height of 10.5 cm, and a bulk density of 2.06. The nitrate asphalt mixture volume, which was 15 liters prior to treatment, was reduced to 6.7 liters by the treatment of this example.
[0058]
After the sintered body is taken out from the muffle furnace 1, an oxidation process is performed. In the oxidation step, oxygen containing ozone is supplied from the oxygen supply system 5 into the processing apparatus. NOx adsorbed on the zeolitic adsorbent is NO by the action of oxygen and ozone.₂It is oxidized to. By washing the adsorbent with the supply liquid supplied into the adsorption tower 7 from the cleaning liquid supply port 11, NO₂Is recovered as nitric acid. The nitric acid is taken out from the cleaning liquid outlet 10.
[0059]
The following effects can be obtained by this embodiment.
[0060]
(1) The flame-retardant nitrate asphalt mixed waste can be converted into a reduced carbonaceous waste solidified body.
[0061]
(2) The radioactive carbon contained in the nitrate asphalt mixed waste as a carbonate can be stored in the solidified carbonaceous waste.
[0062]
[Example 2]
The coke-like granule produced | generated in Example 1 is loaded into the container 2, and is put in the muffle furnace 1 in the apparatus shown in FIG. The filling volume of the granules was 9 liters and the filling depth was 4.5 cm. Oxygen containing 5% or less of ozone (supplied from the oxygen supply system 5) was used as a circulating gas to keep the muffle furnace temperature at 300 ° C. to advance the oxidation reaction. After raising the temperature to 500 ° C. over 24 hours, it was finally oxidized at 850 ° C. for 8 hours and then cooled to room temperature. In container 2, 6.5 kg (61.33 g-mol) of mineralized material mainly consisting of sodium carbonate remained.
[0063]
TiO in the mineralization residue₂(81.77 g-mol), SiO₂(81.77 g-mol) was added and wet-pulverized to homogenize sufficiently, and while stirring, H_ThreePO_Four(40.88 g-mol) was added to decompose the carbonate, kept at 90 ° C. and evaporated to dry. The dried product was pulverized to about 100 mesh, placed in an alumina crucible, and heated in air at 700 ° C. for 4 hours. The weight of the produced powder is 18.15 kg, and the elemental composition is Na_ThreeTi₂PSi₂O₁₂As a result of X-ray diffraction analysis, NaZr₂P_ThreeO₁₂It was found to be a single mineral phase of the same structure. The true specific gravity of the powder was 3.3.
[0064]
A small amount of vinyl alcohol aqueous solution is added to the powder as a binder, dried, and then 0.3 ton / cm with a punch in a 30 cm inner diameter mold.²The cylinder was formed by compression molding at a pressure of 10.7 cm in height. The bulk specific gravity of the molded body was 2.4. The molded body was placed on the container 2 and returned to the muffle furnace 1 and sintered in an air atmosphere by gradually raising the temperature to 1000 ° C. in 8 hours. The sintered body had a weight of 18.1 kg, a diameter of 28.5 cm, a height of 10.2 cm, and a bulk density of 2.78. The volume of the nitrate asphalt mixture before treatment was 15 liters, but this example reduced the volume to 6.5 liters.
[0065]
The effect similar to Example 1 was acquired by the present Example.
[0066]
Example 3
(Specific example 1)
The coke-like granule produced | generated in Example 1 was loaded into the container 2, and was returned in the muffle furnace 1 in the apparatus of FIG. The filling volume of the granules was 9 liters and the filling depth was 4.5 cm. Oxygen was used as a circulating gas to keep the muffle furnace temperature at 300 ° C. to advance the oxidation reaction. After raising the temperature to 500 ° C. over 24 hours, it was finally oxidized at 850 ° C. for 8 hours and then cooled to room temperature. In container 2, the mineralized material consisting of 6.5 kg (61.33 g-mol) of sodium carbonate remained.
[0067]
In addition to nitrate asphalt mixed waste, the reprocessing plant generates waste such as fuel assembly metal waste and miscellaneous solid incineration ash. The breakdown of each is as follows.
[0068]
(A) Fuel assembly metal waste
Zr 11.69 kg 128.15 g-mol
Fe 1.03 kg 18.44 g-mol
Cr 0.29 kg 5.57 g-mol
Ni 0.33kg 5.62g-mol
Sn 0.18kg 1.52g-mol
Total 13.52kg
(B) Miscellaneous solid incineration ash
CaO 2.04 kg 36.31 g-mol
SiO₂ 0.81 kg 12.26 g-mol
Al₂O_Three 0.57 kg 5.59 g-mol
Fe₂O_Three 0.20 kg 1.25 g-mol
ZnO 0.17kg 0.99g-mol
MgO 0.12 kg 2.98 g-mol
Total 3.91kg
3.01 kg of SiO2 as an additive to the residual sodium carbonate from the nitrate asphalt mixture, oxides produced from fuel assembly metal waste and oxides of miscellaneous solid incineration ash₂And mix, and finally 16.52 kg of H_ThreePO_FourAnd 40.79 kg of a single-phase mineral having the following composition formula (molecular weight = 505.53 g) was synthesized.
[0069]
Na₁.₅₂Ca₀.₄₅Zn₀.₀₁Mg₀.₀₄[Zr₁.₅₈Fe₀.₂₆Cr₀.₀₇Ni₀.₀₇
Sn₀.₀₂] Si₀.₁₅Al₀.₁₄(P₂.₀₉Si₀.₆₂) O₁₂
This solidified body is increased to 177% compared to the original nitrate asphalt mixed waste volume (23 kg), but the waste itself is solidified using reprocessed waste. The original weight ratio of waste is 58.7%. The phosphoric acid content contained in the waste solvent can also be used for this synthesis.
[0070]
According to this example, the following effects can be obtained. This example also produces the effect obtained in the first embodiment.
[0071]
(1) It is possible to convert nitrate asphalt mixture waste into an integrated waste solidified body having heat resistance and leaching resistance by using reprocessed waste that has been solidified individually.
[0072]
(Specific example 2)
Unlike the case of Example 1, when the amount of nitrate asphalt mixed waste generated is large compared to other wastes, the maximum amount of sodium carbonate, mineralized residue generated by the treatment of nitrate asphalt mixture, is maximized. As a solidified product, 2.41 kg of SiO2 as an additive to a mixture of 2.70 kg of oxide and miscellaneous solid incineration ash generated from 6.85 kg of metal waste constituting the fuel assembly₂And mix, and finally 4.82 kg of H_ThreePO_FourWas added, and 21.76 kg of a single-phase mineral (molecular weight = 532.30 g) having the following composition formula was synthesized.
[0073]
Na_Three.₀₀Ca₀.₄₅Zn₀.₀₁Mg₀.₀₄[Zr₁.₅₈Fe₀.₂₆Cr₀.₀₇Ni₀.₀₇
Sn₀.₀₂] Si₀.₁₅Al₀.₁₄(P₀.₆₁Si₂._Ten) O₁₂
This solidified product is only reduced to 94.6% compared with the original nitrate asphalt mixed waste (23kg), but the waste itself is solidified using reprocessed waste. Thus, the weight ratio of the original waste occupying the weight of the solidified body is 73.7%. The phosphoric acid content contained in the waste solvent can also be used for this synthesis.
[0074]
According to this example, the following effects can be obtained. Also in this specific example, the effect produced in the first embodiment can be obtained.
[0075]
(1) It is possible to convert nitrate asphalt mixture waste into a solidified waste with further reduced heat resistance and leaching resistance by using reprocessed waste that has been individually solidified.
[0076]
【The invention's effect】
According to the invention of claim 1, the volume of the nitrate asphalt mixture before processing can be reduced to 45% by using a mixture of nitrate and asphalt, which are inherently flammable dangerous substances, as a solidified body of a flame retardant coke-like substance.
[0077]
According to invention of Claim 2, the reaction rate of nitrate and asphalt can be controlled, and an explosive reaction can be prevented.
[0078]
According to the invention of claim 3, the effect of the invention of claim 2 can be optimized.
[0079]
According to invention of Claim 4, it can control so that a molten material may not overflow from a container by foaming by reaction of nitrate and asphalt.
[0080]
According to the invention of claim 5, it is possible to provide a means for the reaction product of nitrate and asphalt to be a carbonate having a higher melting point, so that the salt does not melt and does not inhibit the reaction, and is further fixed as a carbonate. The release of radioactive carbon can be suppressed.
[0081]
According to invention of Claim 6, generation | occurrence | production of a secondary waste can be suppressed by utilizing the dry distillation condensed oil content of asphalt as a shaping | molding agent of a coke-like granule.
[0082]
According to the invention of claim 7, only the salts mineralized by decomposing the coke-like granules into carbon oxide gas and water can be separated.
[0083]
According to the invention of claim 8, the mineralized salt is converted into a heat-resistant and leaching-resistant crystal mineral, and the volume of the nitrate asphalt mixture before processing can be reduced to 45%.
[0084]
According to the invention of claim 9, mineralized salts are mixed with other reprocessing wastes, converted into heat- and leaching-resistant crystalline minerals with a minimum of additives, and 73.7% of all wastes before processing It can be made into a solidified body.
[0085]
According to the invention of claim 10, it is possible to provide a means for industrially decarbonizing the coke-like granule by oxidation.
[0086]
According to the eleventh aspect of the present invention, the management of the gas containing radioactivity can be facilitated by recirculating the gas containing oxygen.
[0087]
According to the inventions of claims 12, 13 and 14, by applying microwave heating in all the heat treatment processes, in addition to saving energy consumption, the heating process can be easily controlled and the heating device can be easily maintained. can do.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a nitrate asphalt mixed waste apparatus to which a method for treating nitrate asphalt mixed waste according to a preferred embodiment of the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Muffle furnace, 2 ... Container, 3 ... Gas circulation system, 4 ... Carbon dioxide supply system, 5 ... Oxygen supply system (ozone generator), 6 ... Oil content condenser, 7 ... Adsorption tower, 8 ... Gas condenser, 9 ... Oil content outlet, 10 ... Wash water outlet, 11 ... Adsorption tower cleaning fluid supply port.

Claims (13)

The solidified asphalt waste mixed with sodium nitrate is heated at a first temperature between the melting point and the decomposition point of sodium nitrate in an oxygen-free atmosphere to react the sodium nitrate and the asphalt composition organic matter. Removing volatile products volatilized at the first temperature;
Subsequently heating at a second temperature above the decomposition point of sodium nitrate, the second and divided the volatile products volatilized at a temperature, a volume reduction coke-like substances containing sodium salt,
The coke-like substance is crushed into granules, and asphalt is molded into the granules hot as a molding aid, then molded, and the molded body is heated to remove the volatile content of the molding aid. A method for treating nitrate asphalt mixed waste. The method for treating a nitrate asphalt mixed waste according to claim 1, wherein sodium nitrite is added to the solidified waste when the solidified waste is heated to the first temperature. The reaction between the sodium nitrate and the organic composition of the asphalt performed by heating to the first temperature is performed by using a container having a depth and an open area so that the asphalt melt that expands and expands in volume does not overflow. The processing method of the nitrate asphalt mixed waste of Claim 1 performed by using. The oxygen-free atmosphere is carbon dioxide or a mixture of carbon dioxide and inert gas;
By generating sodium carbonate by reacting carbon dioxide with the decomposition component of sodium nitrate, the processing method of the nitrates asphalt wastes according to claim 1 for converting the degradation products of sodium nitrate to sodium carbonate.   The method for treating nitrate asphalt mixed waste according to claim 1, wherein the molding aid is a dry-distilled condensed oil of the volatile product of the asphalt. Nitrate asphalt mixing that heats the granules, touches oxygen or oxygen containing ozone, oxidizes and decomposes the granules into carbon oxide gas and water, etc. without igniting, and makes residual inorganic substances mainly consisting of sodium carbonate A method for treating waste, wherein the granule is heated at a temperature not exceeding the melting point of the sodium carbonate . The space group the previous Symbol residual inorganic

As the oxide or thermal decomposable element, the constituent elements necessary for obtaining the same crystal structure material of zirconium phosphate and sodium phosphate (NaZr ₂ (PO ₄ ) ₃ ) having the three-dimensional crystal structure having the symmetry indicated by the symbol Add,
The mixture is pulverized to form a water slurry in which the components are uniformly dispersed, and phosphoric acid is mixed while the slurry is stirred. The slurry is heated to below the boiling point of water to evaporate into a dry powder. Sintered to 1000 ° C to form the same crystal structure material of zirconium phosphate and sodium, and if necessary, sintered powder was sintered at high temperature after cold compression molding, or solidified at high density by high temperature hot compression molding A method for treating a nitrate asphalt mixed waste according to claim 6 . 8. The nitrate according to claim 7 , wherein the component element added to the residual inorganic substance as the oxide or the thermally decomposable salt includes those derived from incineration ash of miscellaneous solid waste, nuclear fuel assembly metal waste, and waste solvent. Asphalt mixed waste disposal method. The heating performed without igniting the granule while touching oxygen or oxygen containing ozone is performed while controlling the temperature rise rate and the maximum temperature, respectively, and the horizontal temperature distribution and the maximum temperature are controlled respectively. However, a continuous tunnel furnace that rotates horizontally in the furnace at a constant speed, a rotating inclined tubular tunnel furnace, or a silo furnace that moves by gravity while controlling the temperature distribution in the height direction and the maximum temperature respectively. The processing method of the nitrate asphalt mixed waste of Claim 6 performed by heating furnaces, such as. Oxygen containing oxygen or ozone is supplied to the heating furnace, carbon dioxide from the exhaust gas of the furnace is obtained by adding oxygen and oxygen and ozone after removal condensable gases such as water according to claim 9, Treatment method for nitrate asphalt mixed waste. The nitrate asphalt according to claim 1, wherein the solidified asphalt waste mixed with sodium nitrate is maintained at the first temperature or the second temperature, and the molded body is heated by microwave heating. Processing method of mixed waste. The method for treating nitrate asphalt mixed waste according to claim 6 , wherein the granule is maintained at a temperature not exceeding the melting point of sodium carbonate, and the molded body is heated by microwave heating. The nitrate asphalt according to claim 7 , wherein the powder obtained by evaporating and drying the water of the slurry below the boiling point of water is maintained at 700 ° C to 1000 ° C, and heating of the molded body is performed by microwave heating. Processing method of mixed waste.

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