CN1683091A

CN1683091A - Waste processing method and waste processing apparatus

Info

Publication number: CN1683091A
Application number: CNA2005100754334A
Authority: CN
Inventors: 赤井芳惠; 松林义和; 山口恭志; 山田和矢; 小原敦
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1997-08-20
Filing date: 1998-08-20
Publication date: 2005-10-19
Anticipated expiration: 2018-08-20
Also published as: CN1208938A; CN1213097C; CN100344386C

Abstract

The invention provides a waste processing method and a waste processing apparatus. The waste processing method decomposes an organic substance or an inorganic substance contained in organic wastes or inorganic wastes by holding a mixture of the organic wastes or the inorganic wastes and a medium, which is in its supercritical state, for a pre-determined time period, in which the hydrogen ion concentration of the medium is 10<-4>mol or more to 1kg of the medium. The waste processing method has a step of decomposing all or almost all of an organic substance included in organic wastes into lower-molecular-weight products by holding the organic wastes in a medium, which is in its supercritical state, for a pre-determined time and a step of oxidizing the lower-molecular-weight products by holding a mixture of an oxidant and the lower-molecular-weight products in the medium, which is in its subcritical state, for a pre-determined time period.

Description

Waste treatment method and waste treatment apparatus

The present application is a divisional application entitled "method and apparatus for treating waste", having an application date of 8/20/1998 and an application number of 98117610.0.

Technical Field

The present invention relates to a method and an apparatus for treating organic waste, and a method and an apparatus for treating inorganic waste.

Background

In recent years, disposal of organic waste containing polymer containers, resins such as polyvinyl chloride, and radioactive substances has caused a great problem in the global environment. Generally, organic waste is incinerated, and toxic substances such as dioxide and nitrogen oxides are generated by the incineration process, and a large-scale apparatus is required for recovering these toxic substances.

Inorganic waste in the atomic energy field contains not only radioactive substances but also a large amount of sodium nitrate salts. These materials are buried in underground disposal sites as solidified bodies. Recently, according to studies on underground environment, it has been reported that nitrate ions may become ammonia underground as a reductive enclosure gas having a low partial pressure of oxygen. Thus, the nuclear substance such as plutonium may form ammonia or a complex, and may be eluted from the solidified body.

In recent years, attention has been paid to a method of using water (supercritical water) at a high temperature and a high pressure exceeding the critical point of water (temperature 374 ℃ C., pressure 22.1MPa) as a method of decomposing organic substances.

The supercritical state is a state of a substance at a temperature and a pressure equal to or higher than a critical temperature and a critical pressure, which are physical quantities inherent to a compound. The substance in this state is called a supercritical fluid.

A method of mixing an organic substance, water and an oxygen-containing fluid to oxidatively decompose the organic substance in a supercritical state exceeding the critical point of water is known ("organic substance oxidation method in supercritical water", Japanese patent application No. 56-68414, registration No. 1551862). Supercritical water has an intermediate property between liquid and gas, and can oxidize and decompose organic substances in a short time by arbitrarily mixing organic substances, oxygen, and the like.

However, in the supercritical state, the solubility of inorganic substances is significantly reduced, and the inorganic substances contained in the organic waste are deposited on the surface of the reactor to close the reactor. In particular, the solubility of the inorganic oxide is low, and the above-mentioned problems are more likely to occur.

For example, when waste generated in a nuclear power plant is treated, it is difficult to treat the waste because radioactive substances are deposited, and a large amount of cost is required for maintenance of the waste treatment apparatus.

Therefore, a method and an apparatus for decomposing organic waste, which can utilize a supercritical state without precipitating inorganic substances, are desired.

As described above, if ammonia is present in the solidified body, nuclear substances such as plutonium may be eluted from the solidified body. Therefore, it is desired to develop a waste treatment method and apparatus for preventing nitrate ions from being mixed into a solidified material by converting nitrate ions or nitrates in waste into nitrogen gas even when waste containing only inorganic substances is treated.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a method and an apparatus for efficiently decomposing organic waste or inorganic waste in a short time.

In order to achieve the purpose, the invention adopts the following technical scheme:

the waste treatment method of the present invention is characterized by comprising a low molecular weight step and an oxidation step; in the low molecular weight step, a mixture of the organic waste and the medium in a supercritical state is maintained for a predetermined period of time to reduce all or most of the organic substances contained in the organic waste to low molecular weight; in the oxidation step, the product produced in the low molecular weight step is mixed with an oxidizing agent, and the mixture is maintained in the subcritical medium for a predetermined time to be oxidized.

The waste treatment method is characterized by comprising a medium supercritical step and a mixing step; in a medium supercritical step, the medium is brought into a supercritical state; in the mixing step, a mixture of the organic waste and the supercritical medium is obtained.

The method for treating waste is characterized in that the organic waste contains 2 or more kinds of nitrate, sulfate, chloride, phosphate or silicate.

The method of treating waste is characterized in that the medium is water, carbon dioxide or hydrocarbon, or a mixture of 2 or more thereof.

The waste treatment method is characterized in that the oxidant is oxygen, air, hydrogen peroxide or ozone, or more than 2 of the oxygen, air, hydrogen peroxide or ozone; the amount of these oxidants is more than 1 time the stoichiometric amount required for complete oxidation of the organic waste.

The method of treating waste is characterized in that the concentration of hydrogen ions in the supercritical medium is 10% to 1kg of the supercritical medium^-4And (3) molar ratio.

The waste treatment method is characterized in that at least one of sulfuric acid and hydrochloric acid is added to the supercritical medium, and the hydrogen ion concentration of the supercritical medium is adjusted to 10 relative to 1kg of the supercritical medium^-4And (3) molar ratio.

The method for treating waste further comprises a separation step of separating insoluble impurities contained in the organic waste.

The waste treatment method is characterized by comprising a medium supercritical step and a mixing step; in a medium supercritical step, the medium is brought into a supercritical state; in the mixing step, a mixture of the organic waste and the medium in a supercritical state is obtained.

The waste treatmentmethod is characterized in that the oxidant is oxygen, air, hydrogen peroxide or ozone, or more than 2 of the oxygen, air, hydrogen peroxide or ozone; the amount of these oxidants is more than 1 time the stoichiometric amount required for complete oxidation of the organic waste.

The method of treating waste is characterized in that the concentration of hydrogen ions in the supercritical medium is 10 relative to 1kg of the supercritical medium^-4And (3) molar ratio.

The waste treatment method is characterized in that at least one of sulfuric acid and hydrochloric acid is added to the supercritical medium, and the hydrogen ion concentration of the supercritical medium is 10 relative to 1kg of the supercritical medium^-4And (3) molar ratio.

The waste treatment method of the present invention is a waste treatment method for decomposing waste by maintaining a mixture of the waste and a supercritical medium for a predetermined time, the method being characterized in that the waste is decomposed in the presence of oxygenIn the case of the agent, the hydrogen ion concentration of the supercritical medium is 10 relative to 1kg of the medium^-4And (3) molar ratio.

The waste treatment method is characterized in that the waste is organic waste, and organic matter contained in the organic waste is decomposed.

The method for treating organic waste is characterized by comprising a medium supercritical step and a mixing step; in a medium supercritical step, the medium is brought into a supercritical state; in the mixing step, a mixture of the organic waste and the medium in a supercritical state is obtained.

The method for treating waste is characterized in that the supercritical medium contains an oxidizing agent.

The method for treating waste is characterized in that the supercritical medium contains at least 2 of oxygen, air, hydrogen peroxide, ozone, or the like, and the content of the supercritical medium is 1 time or more of the stoichiometric amount required for completely oxidizing the organic waste.

The waste treatment method is characterized in that the waste is inorganic waste, and inorganic substances contained in the inorganic waste are decomposed.

The waste treatment method is characterized by comprising a medium supercritical step and a mixing step; in a medium supercritical step, the medium is brought into a supercritical state; in the mixing step, a mixture of the inorganic waste and the medium in a supercritical state is obtained.

The waste treatment method is characterized in that the inorganic waste contains nitric acid and/or nitrate.

The method for treating waste is characterized inthat the supercritical medium contains at least 2 of oxygen, air, hydrogen peroxide, ozone, or the like, and the content thereof is 1 time or more of the stoichiometric amount required for completely oxidizing the inorganic waste.

The waste treatment apparatus of the present invention is characterized by comprising:

a reactor for reducing the molecular weight of all or most of the organic substances contained in the organic waste in a supercritical medium;

an organic waste supply device for supplying the organic waste to the reactor;

a media supply for supplying the media to the reactor;

an oxidation reactor for oxidizing a product produced by the reactor in a subcritical state;

an oxidant supply means for supplying an oxidant to the oxidation reactor;

and a recovery device for recovering the product fluid generated in the oxidation reactor.

The waste treatment apparatus is characterized by comprising: and the adjusting device is used for adjusting the hydrogen ion concentration in the reactor.

The waste treatment apparatus is characterized in that the reactor includes a separator for separating insoluble impurities contained in the organic waste.

The waste treatment apparatus described above, wherein the organic waste supply device, the medium supply device, and the oxidizing agent supply device are provided with a pressurizing device and a preheating device forpressurizing and preheating the organic waste, the medium, and the oxidizing agent, respectively;

the recovery device is provided with a pressure reducing device for reducing the pressure of the fluid generated in the reactor and a cooling device for cooling the fluid.

The waste treatment apparatus is characterized by comprising a device for detecting the state of the medium in the reactor.

The waste treatment apparatus is characterized in that the reactor includes a device for irradiating the contents with ultraviolet rays or radiation.

The waste treatment apparatus is characterized in that the recovery treatment apparatus comprises a gas-liquid separation device, a gas treatment device, and a liquid treatment device.

The waste treatment apparatus is characterized in that the gas treatment apparatus comprises a filter and a scrubber; the filter is used for removing solid particles, radioactive substances or harmful substances in the gas; the scrubber is used for recovering radioactive or harmful substances in the gas.

The waste treatment apparatus is characterized in that the liquid treatment apparatus includes a device for coagulating and precipitating inorganic ions in the liquid.

The waste treatment apparatus is characterized in that the liquid treatment apparatus includes a device for separating solid particles in a liquid.

The waste treatment apparatus is characterized in that the liquid treatment apparatus includes an ion exchange apparatus for removing an ion component in the liquid.

The waste treatment apparatus is characterized in that the liquid treatment apparatus includes an extraction and recovery treatment apparatus for extracting and recovering inorganic ions in aliquid by bringing the liquid into contact with an extractant.

The waste treatment apparatus is characterized in that carbon dioxide is used as a diluent of the extractant.

The waste treatment apparatus is characterized in that the liquid treatment apparatus includes a solidification device for solidifying the liquid or the sludge.

The waste treatment apparatus is characterized in that the liquid treatment apparatus comprises a solidification device for solidifying the liquid or the sludge and a drying device for drying the liquid or the sludge.

The waste treatment apparatus is characterized in that the solidification device solidifies a mixture of the liquid or the sludge or the mixture thereof and the solidifying agent in the container.

a reactor for decomposing waste in a supercritical medium;

a waste supply device for supplying the waste to the reactor;

a media supply for supplying the media to the reactor;

an oxidizing agent supply device for supplying an oxidizing agent to the reactor;

a regulating device for regulating the hydrogen ion concentration in the reactor;

and a recovery device for recovering the product fluid generated in the reactor.

The waste treatment apparatus described above is characterized in that the waste is an organic waste, the reactor is a reactor for decomposing the organic waste, and the waste supply apparatus is an organic waste supply apparatus for supplying the organic waste to the reactor.

The waste treatment apparatus is characterized in that the adjusting device mixes the inorganic acid and the medium and supplies the mixture to the reactor so as to obtain a predetermined hydrogen ion concentration.

The waste treatment apparatus is characterized in that the adjusting device comprises:

an acid supply device for supplying inorganic acid to the reactor;

a hydrogen ion concentration measuring device for measuring the hydrogen ion concentration in the reactor;

and a controller for supplying a calculated amount of the inorganic acid from the acid supply device to the reactor based on a signal from the hydrogen ion concentration measuring device.

The waste treatment apparatus described above, wherein the adjusting device adjusts the hydrogen ion concentration in accordance with the type of the organic waste and the supply amount of the oxidizing agent.

The waste treatment apparatus is characterized in that a pressurizing device and a preheating device for pressurizing and preheating the organic waste, the medium and the oxidant are respectively arranged in the organic waste supply device, the medium supply device and the oxidant supply device; the recovery device is provided with a depressurizing device and a cooling device for depressurizing and cooling the fluid generated in the reactor.

The waste treatment apparatus is characterized in that the recovery treatment apparatus comprises a gas-liquid separation device, a gas treatment device and a liquid treatment device.

The waste treatment apparatus is characterized in that the liquid treatment apparatus includes an extraction/recovery treatment apparatus for contacting the liquid with an extractant to extract and recover inorganic ions in the liquid.

The waste treatment apparatus is characterized in that the waste is an inorganic waste, the reactor is a reactor for decomposing inorganic substances contained in the inorganic waste, and the waste supply apparatus is an inorganic waste supply apparatus for supplying the inorganic waste to the reactor.

The waste treatment apparatus is characterized in that the adjusting device mixes the inorganic acid and the medium at a predetermined hydrogen ion concentration and supplies the mixture to the reactor.

The waste treatment apparatus described above, wherein the adjusting device adjusts the hydrogen ion concentration in accordance with the type of the inorganic waste and the supply amount of the oxidizing agent.

an acid supply device for supplying inorganic acid to the reactor,

A hydrogen ion concentration measuring device for measuring the hydrogen ion concentration in the reactor,

a reactor for converting all or most of organic substances contained in organic waste into low molecular weight substances in a supercritical medium, and then mixing the resultant with an oxidizing agent in a subcritical state to oxidize the resultant;

an organic waste supply device for supplying the organic waste to the reactor;

a media supply for supplying the media to the reactor;

an oxidant supply means for supplying an oxidant to the reactor;

a recovery device for recovering the product fluid generated in the reactor.

The waste treatment method 1 of the present invention is characterized by comprising a low molecular weight step and an oxidation step; in the low molecular weight step, the mixture of the organic waste and the medium is maintained in a supercritical state for a predetermined period of time to reduce all or most of the organic substances contained in the organic waste to low molecular weight; in the oxidation step, the product produced in the low molecular weight step is mixed with an oxidizing agent and is maintained in a subcritical state for a predetermined time to be oxidized.

According to this method, the organic substance is reduced in molecular weight in the absence of the oxidizing agent in the supercritical state, and then the oxidizing agent is added to decompose the organic substance under subcritical conditions in which the inorganic substance is less likely to precipitate, so that the organic substance can be effectively decomposed and the precipitation of the inorganic substance can be prevented.

The organic waste is not particularly limited, and examples thereof include paper, rags, activated carbon, pitch, various resins, and the like. The organic waste may contain nitrate, sulfate, chloride, phosphate, or silicate, or 2 or more thereof.

Organic waste may contain insoluble substances such as sand, gravel, and pebbles.

Further, the resin may contain an inorganic additive or an organic metal salt additive such as polyethylene, propylene, PET resin, various ion exchange resins, and the like, or an inorganic additive or an organic metal salt additive such as vinyl chloride, silicon, Fiber Reinforced Plastic (FRP), and the like.

Inorganic additives, stabilizers for lead salts, Sn salts, etc., CaCO₃Or SiO₂Such filler, Al₂(OH)₃、Sb₂O₃Flame retardants such as MgO, and conductive or reinforcing carbon. The organic metal salt additive may be, for example, lead stearate.

When the organic waste contains a large amount of impurities, inorganic additives or organic metal salt additives, it is desirable to reduce the amount of the primary treatment in order to prevent precipitation of inorganic substances.

The invention of the 2 nd waste treatment method, characterized by, have low molecular weight process, separation process and oxidation process; in the low molecular weight step, the mixture of the organic waste and the medium is maintained in a supercritical state for a predetermined period of time to reduce all or most of the organic substances contained in the organic waste to low molecular weight; separating insoluble impurities contained in the organic waste in a separation step; in the oxidation step, the product produced in the low molecular weight step is mixed with an oxidizing agent and is maintained in a subcritical state for a predetermined time to be oxidized.

According to this method, even if the organic waste contains a large amount of insoluble impurities, inorganic additives or organic metal salt additives, the organic waste is treated in a supercritical state, and then after removing these impurities and the like, the organic waste is oxidized by adding an oxidizing agent in a subcritical state, so that the organic waste can be effectively decomposed and the precipitation of inorganic substances in a subcritical state can be prevented. It is not necessary to reduce the amount of one process.

In these waste treatment methods, the hydrogen ion concentration of the medium is preferably 10 relative to 1kg of the medium^-4And (3) molar ratio. The precipitation of the inorganic substance can be further reduced by increasing the solubility of the inorganic substance.

According to the inventionA3 rd waste treatment method for decomposing organic substances contained in an organic waste by maintaining a mixture of the organic waste and a medium in a supercritical state for a predetermined period of time, wherein the hydrogen ion concentration of the medium is 10 relative to 1kg of the medium^-4And (3) molar ratio.

According to this method, the hydrogen ion concentration of the medium is 10 relative to 1kg of the medium^-4The amount of the inorganic compound is not less than the molar ratio, and thus precipitation of the inorganic compound can be prevented.

The medium may also contain an oxidizing agent.

The object to be treated may be the same organic waste as in the method for treating

waste

1 or 2, and the organic waste may contain an oxide. According to the waste treatment method, these substances can be effectively treated.

The 4 th waste treatment method of the present invention is a waste treatment method for decomposing inorganic substances contained in inorganic waste by maintaining a mixture of the inorganic waste and a medium in a supercritical state for a predetermined time, wherein the hydrogen ion concentration of the medium is 10 relative to 1kg of the medium^-4And (3) molar ratio.

In the supercritical medium, inorganic substances are effectively decomposed. The hydrogen ion concentration per 1kg of the medium was 10^-4Since the amount of the inorganic substance is not less than the molar ratio, the inorganic substance after decomposition does not precipitate and may exist in the fluid according to the present waste treatment method.

The object to be treated is preferably a waste containing only inorganic substances, for example, a solidified matter of α -containing waste may be treated, the inorganic waste may contain nitric acid and/or nitrate, but the object to be treated is not limited to this, and a waste containing some organic substances may be treated.

The medium may also contain an oxidizing agent.

In the waste treatment method of the present invention, the medium supercritical step and the mixing step may be provided: in the medium supercritical step, the medium is brought into a supercritical state; in the mixing step, a mixture of the supercritical medium and the organic waste or inorganic waste is obtained. Organic waste or inorganic waste is continuously supplied to a supercritical medium, and waste treatment can be continuously performed with high efficiency.

Of course, the medium may be mixed with the organic waste or the inorganic waste, and the resulting mixture may be heated and pressurized to be in a supercritical state.

The medium may be water, carbon dioxide or hydrocarbon, or a mixture of 2 or more thereof.

Generally, in a supercritical medium, a gaseous or liquid substance can be uniformly mixed in any ratio at normal temperature and pressure. In addition, in the supercritical medium, a higher substance transfer rate can be expected as compared with the case of using a liquid solvent. Therefore, the supercritical medium of the present invention can use water, carbon dioxide, or hydrocarbon having the above-described characteristics according to the object to be treated.

By mixing them, the critical point of the medium can be changed.

The oxidant can be oxygen, air, hydrogen peroxide or ozone, or more than 2 of the above; the amount of these oxidizing agents is preferably 1 or more times the stoichiometric amount required for complete oxidation of the organic or inorganic waste. Preferably, 1.2 to 10 times the stoichiometric amount is used.

When the hydrogen ion concentration is adjusted, an inorganic acid is preferably used. Sulfuric acid, hydrochloric acid, etc. are preferably used. It is not suitable to use an acid such as nitric acid which thermally decomposes at high heat.

The invention provides a waste treatment apparatus 1, comprising:

an organic waste supply device for supplying organic waste to the reactor;

a medium supply device for supplying the medium to the reactor;

an oxidation reactor for oxidizing a product produced in the reactor in a subcritical state;

an oxidant supply device for supplying an oxidant to the oxidation reactor;

The invention provides a waste treatment apparatus 2, comprising:

a reactor for converting all or most of organic substances contained in organic waste into low molecular weight substances in a supercritical medium, and then mixing the resultant with an oxidizing agent in a subcritical state to perform an oxidation reaction;

an organic waste supply device for supplying organic waste to the reactor;

a medium supply device for supplying the medium to the reactor;

an oxidant supply means for supplying an oxidant to the reactor;

a recovery device for recovering the product fluid generated in the reactor.

The 3 rd waste treatment apparatus of the present invention is characterized by comprising:

a reactor for decomposing organic substances contained in the organic waste in a supercritical medium;

an organic waste supply device for supplying organic waste to the reactor,

A medium supply device for supplying the medium to the reactor,

A regulating device for regulating the hydrogen ion concentration in the reactor,

A recovery device for recovering the product fluid generated in the reactor.

The 4 th waste treatment apparatus of the present invention is characterized by comprising:

an organic waste supply device for supplying organic waste to the reactor,

A medium supply device for supplying the medium to the reactor,

An oxidizing agent supply device for supplying an oxidizing agent to the reactor,

A recovery device for recovering the product fluid generated in the reactor.

The 5 th waste treatment apparatus of the present invention is characterized by comprising:

a reactor for reducing all or most of organic substances contained in the organic waste into low molecular weight substances in a supercritical medium,

An organic waste supply device for supplying organic waste to the reactor,

A medium supply device for supplying the medium to the reactor,

An oxidation reactor for oxidizing a product produced in the reactor in a subcritical state,

An oxidizing agent supply device for supplying an oxidizing agent to the oxidation reactor,

The 6 th waste treatment apparatus of the present invention is characterized by comprising:

a reactor for decomposing inorganic substances contained in the inorganic waste in a supercritical medium;

an inorganic waste supply device for supplying inorganic waste to the reactor,

A medium supply device for supplying the medium to the reactor,

A recovery device for recovering the product fluid generated in the reactor.

The

waste treatment apparatuses

1, 2, 3, 4 and 5 of the present invention may further comprise a neutral salt adding device for adding a neutral salt to the medium supplied to the reactor.

The reactor may be provided with a device for irradiating ultraviolet rays or radiation rays to the contents.

The liquid treatment apparatus may further include a neutralization device for neutralizing an acid in the liquid.

In the waste treatment apparatuses of the

present invention

3, 4, 5 and 6, the adjusting means mixes the inorganic acid and the medium at a predetermined hydrogen ion concentration and supplies the mixture to the reactor.

The above-mentioned adjusting device may be provided with: an acid supply device for supplying an inorganic acid to the reactor, a hydrogen ion concentration measuring device for measuring the hydrogen ion concentration in the reactor, and a control device for supplying the calculated amount of the inorganic acid from the acid supply device to the reactor based on a signal from the hydrogen ion concentration measuring device.

The inorganic acid is preferably at least one of sulfuric acid and hydrochloric acid.

The reactor is provided with a gas agent supply device for supplying an oxidizing agent, and the adjusting device adjusts the hydrogen ion concentration according to the type of the organic waste or inorganic waste and the supply amount of the oxidizing agent. Various wastes can be effectively treated.

The waste treatment apparatusof the present invention may further comprise a separation device for separating insoluble impurities contained in the organic waste or the inorganic waste in the reactor.

Preferably, means are provided for detecting the state of the medium in the reactor. Thus, it is possible to accurately determine whether or not the medium in the reactor is in a supercritical state, and to treat the waste in an optimum state. For example, if a device for measuring the temperature and pressure in the reactor is provided, the state of the medium can be detected. Instead of directly measuring the temperature and pressure in the reactor, the temperature and pressure of the mixture of the waste and the medium before being supplied to the reactor may be measured.

A pressurizing device and a preheating device for pressurizing and preheating the organic waste or the inorganic waste and the medium are respectively arranged in the organic waste or the inorganic waste supply device and the medium supply device; the recovery device is provided with a depressurizing device and a cooling device for depressurizing and cooling the fluid generated in the reactor. When the acid supply device or the oxidizing agent supply device is provided, a pressurizing device and a preheating device for pressurizing and preheating the acid or the oxidizing agent may be provided. With such a structure, waste can be continuously supplied, collected, and treated, thereby improving the treatment efficiency.

The above oxidant may be oxygen, air, hydrogen peroxide or ozone, or 2 or more thereof; the amount of these oxidizing agents is preferably 1 or more times the stoichiometric amount required for complete oxidation of the organic or inorganic waste. Preferably, 1.2 to 10 times the stoichiometric amount is used.

Preferably, means are provided to cover at least a portion of the organic waste or inorganic waste supply means. For example, at least a part of the organic waste or inorganic waste supply device is preferably disposed in a spherical tank or a hood.

The covering device is preferably explosion-proof.

The recovery device preferably includes a gas-liquid separation device, a gas treatment device, and a liquid treatment device.

The gas treatment device preferably comprises a filter and a scrubber; the filter is used for removing solid particles, radioactive substances or harmful substances in the gas; the scrubber is used to recover radioactive or harmful substances in the gas.

The solution used in the scrubber is preferably at least one of water, an alkaline solution containing sodium hydride, or water containing a reducing agent.

The liquid processing apparatus preferably includes a device for collecting the liquid and analyzing the liquid.

The liquid treatment apparatus preferably includes a stirring device for stirring the liquid.

The liquid treatment apparatus preferably includes a cooling device for cooling the liquid.

The liquid treatment apparatus preferably includes a device for coagulating and precipitating inorganic ions in the liquid.

The liquid treatment apparatus preferably has a device for separating the fixed component in the liquid.

The liquid treatment apparatus preferably has an ion exchange device for removing an ionic component in the liquid.

The liquid treatment apparatus preferably includes an extraction/recovery treatment apparatus for contacting the liquid with an extractant to extract and recover inorganic ions in the liquid.

The extractant is preferably at least one of a neutral organic phosphorus compound and an acidic organic phosphorus compound.

The diluent of the above extractant is preferably carbon dioxide.

The liquid treatment apparatus preferably includes a drying device for drying the liquid or the sludge.

The liquid treatment apparatus preferably has a solidification device for solidifying the liquid or the sludge.

The curing device preferably cures a kneaded product of the liquid or sludge or a mixture thereof and the curing agent in a container.

Therefore, according to the present invention, when organic waste or inorganic waste is treated by using a supercritical medium, precipitation of inorganic substances can be effectively prevented, and a large amount of waste can be effectively treated. The construction cost and the operation cost of the device can be greatly reduced.

Drawings

FIG. 1 is a process diagram of a waste treatment method according to example 1 of the present invention.

FIG. 2 is a process diagram of a conventional waste treatment method.

Fig. 3 is a graph showing the solubility of lead oxide under supercritical and subcritical conditions.

Fig. 4 is a graph showing changes in water ion product when temperature and pressure are changed.

FIG. 5 is a graph showing the cerium precipitation rate when the amount of the oxidizing agent added was changed.

FIG. 6 is a schematic view showing a waste treatment apparatus according to example 3.

FIG. 7 is a view showing a separator provided in thelower part of the reactor.

Fig. 8 is a critical curve showing the critical point of the water-and-hydrocarbon mixture.

FIG. 9 is a schematic view showing a waste treatment apparatus according to example 4.

FIG. 10 is a schematic view showing a waste treatment apparatus according to example 5.

FIG. 11 is a schematic view showing a waste treatment apparatus according to example 6.

FIG. 12 is a view showing the structure of an α nuclear seed recovery apparatus in example 6.

FIG. 13 is a schematic view showing a waste treatment apparatus according to example 7.

FIG. 14 is a view showing a part of a waste treatment apparatus according to example 8.

Fig. 15 is a state diagram of water.

FIG. 16 is a view showing a part of a waste treatment apparatus according to example 9.

FIG. 17 is a view showing a part of a waste treatment apparatus according to example 10.

FIG. 18 is a view showing a part of a waste treatment apparatus according to example 11.

FIG. 19 is a view showing a part of a waste treatment apparatus according to example 12.

FIG. 20 is a view showing a part of a waste treatment apparatus according to example 13.

FIG. 21 is a view showing a part of a waste treatment apparatus according to example 14.

FIG. 22 is a view showing a part of a waste treatment apparatus according to example 15.

FIG. 23 is a view showing a part of a waste treatment apparatus according to example 16.

FIG. 24 is a view showing a part of a waste treatment apparatus according to example 17.

Fig. 25 is a graph showing the partition ratio of 30% TBP-nitrate-based radioactive (アクチノイド) element.

FIG. 26 is a graph showing the partition ratio of HDEHP-nitric acid-based radioactive (アクチノイド) elements.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In the following embodiments and drawings, the same components are denoted by the same reference numerals, and their repetitive description will be omitted.

(example 1)

FIG. 1 shows a process diagram of embodiment 1 of the present invention. Fig. 2 is a process diagram of a conventional example.

As shown in fig. 2, in the conventional method, water as a medium is brought into a supercritical state in the medium supercritical step 1. In the mixing step 2, the sulfate-containing organic waste is added to the supercritical water. In the supercritical decomposition step 6, the obtained mixture is kept together with the oxidizing agent at a high temperature and a high pressure exceeding the critical point of water for a predetermined period of time. The organic waste containing sulfate is oxidatively decomposed in water in a supercritical state.

The generated decomposed gas and decomposed liquid, and inorganic substances (oxides and the like) such as sulfates contained in the organic waste are sent to the recovery step 5, and subjected to treatments such as recovery of harmful substances and solidification.

In contrast, in the method of example 1, in the medium supercritical step 1, water as the medium is brought into a supercritical state. In the mixing step 2, the sulfate-containing organic waste is added to the supercritical water.

Alternatively, instead of mixing the organic waste with the medium in a supercritical state, the medium and the organic waste may be mixed first, and then the mixture may be heated to bring the medium into a supercritical state.

In the low molecular weight step 3, the mixture obtained is held in water in a supercritical state without an oxidizing agent for a predetermined period of time to reduce the molecular weight of all or most of the organic substances in the sulfate-containing organic waste.

Next, in the oxidation step 4, the product produced in the low molecular weight step is mixed with an oxidizing agent and kept in a subcritical state for a predetermined time.

The generated decomposed gas and decomposed liquid, and inorganic substances (ions) such as sulfate contained in the organic waste are sent to the recovery step 5, and subjected to treatments such as recovery of harmful substances and solidification.

Although the conventional method can effectively oxidize and decompose the organic substances in the organic waste, when the organic waste contains inorganic substances, the inorganic substances are more likely to form oxides and precipitate in a supercritical state than in a subcritical state.

Lead is taken as an example for explanation. FIG. 3 is a graph showing the solubility curves of lead oxide under supercritical and subcritical conditions (63 rd annual meeting of the chemical society, department of engineering of the northeast university, Tata "subcritical,Solubility determination of metal oxides in supercritical water "). As shown by the curve, the solubility of lead oxide is small in thesupercritical region of 374 ℃ or higher, and is 0.5X 10 at 450 DEG C^-3mol/kg. However, in the subcritical region, the solubility increased by about 10 times to 0.5X 10^-2mol/kg. When oxygen is present, the solubility tends to be further reduced.

Therefore, if the organic waste containing the inorganic additive or the organic metal salt additive is treated in a supercritical state in the presence of the oxidizing agent as in the conventional art, the inorganic substance contained in the inorganic additive or the organic metal salt additive is precipitated as the oxide.

In this embodiment, since the oxidizing agent is not present in the low molecular weight step, inorganic substances such as sulfate contained in the organic waste are not oxidized, and therefore, precipitation of inorganic oxides can be prevented.

Then, an oxidizing agent is added in a subcritical state to oxidize the organic matter, thereby effectively decomposing the organic matter.

When an organic substance is mixed with water before being mixed with an oxidizing agent and oxidized to react with the oxidizing agent in a supercritical state, the organic substance having a high molecular weight can be converted into a low molecular weight by selective thermal decomposition or hydrolysis of the small binding energy existing in the organic substance. Then, an oxidizing agent is added to the organic material having a low molecular weight, and the organic material is reacted in a subcritical state, so that the organic material can be oxidized in a short time because of its small molecular weight and high reaction speed with oxygen.

Therefore, the organic waste is reacted in the supercritical state for a predetermined time and then maintained in the subcritical state for a predetermined time, whereby the organic waste can be effectively decomposed and precipitation of inorganic substances can be prevented.

In example 1, hydrogen peroxide was used as the oxidizing agent, but the present invention is not limited thereto. Oxygen, air, ozone, or 2 or more kinds of oxygen, air, hydrogen peroxide, and ozone may be used.

The organic material is generally decomposed by reaction with the group (ラジカル). In the case of organic substances, the reactive group is a hydroxyl group (. OH: hereinafter referred to as OH group). OH groups have an oxidation-reduction potential shown in formula I in an acidic solution at 25 ℃, and are stronger oxidants than ozone.

2.85V.vs.NHE …I

Therefore, the generation of OH groups is critical for the effective decomposition of organic substances.

In supercritical water, water reacts with oxygen to generate OH groups represented by formula II and hydroperoxy groups (. OOH).

H₂O+O₂→HO₂·+OH· …II

According to Baulch et al, the reaction rate constant of formula II is 10 at 500 ℃^-10.5The mol/s ratio is very slow. (0.00631 mol of oxygen gas and 6.31mol of water), and the hydroperoxyl group reacts as in the formula (III) to produce hydrogen peroxide and oxygen gas, which are decomposed as in the formula (IV) to produce OH groups.

…III

…IV

In general, the reaction of the groups with each other is fast, and the decomposition reaction of hydrogen peroxide is easy at a temperature of 100 ℃ or higher, so that the reaction speed of the formulae III and IV is fast.

When organic substances are decomposed with oxygen in supercritical water, since the reaction rate of formula II is slow, when hydrogen peroxide is added to directly generate OH groups, the decomposition reaction of organic substances can be efficiently caused.

The following are the results of decomposition of polyethylene by the method of example 1.

10mg of polyethylene having 2mg of cerium sulfate attached thereto and 2ml of water were put into a reactor (5.6ml), and reacted at 400 ℃ and 30MPa for 30 minutes.

After the reaction, the reaction mixture is returned to normal temperature and pressure, and as a result, 99% or more of the polyethylene initially present as a solid is thermally decomposed to form alkanes and alkenes each having c of 1 to 30, and the alkanes and alkenes are present in a gas or a liquid.

Then, 0.3g of hydrogen peroxide and 1.6g of water (3.6 g in total) were added thereto, and the mixture was held at 350 ℃ and 30MPa for 60 minutes. After the reaction, the reaction was returned to normal temperature and pressure, and the amount of organic carbon in the gas and liquid was measured, whereby 99% or more of the organic substances were oxidatively decomposed.

After the reaction, the reaction mixture was returned to normal temperature and pressure, and the decomposed solution was filtered, and cerium in the filtrate was measured by ICP (inductively coupled Plasma Spectroscopy). Further, cerium was measured by ICP similarly by dissolving the filter paper with an acid, and as a result, no precipitate was obtained. Thus, cerium is all present in ionic form and does not precipitate as an oxide.

As a comparative example,polyethylene was decomposed in supercritical water in the presence of an oxidizing agent as in the prior art.

10mg of polyethylene having 2mg of cerium sulfate attached thereto, 2ml of water and 0.3g of hydrogen peroxide were charged into a reactor (5.6ml), and reacted at 400 ℃ and 30MPa for 30 minutes.

As a result, 99% or more of the polyethylene was oxidized to generate carbon dioxide. Half of the cerium precipitates as oxides.

From the above, it is understood that the organic waste can be efficiently decomposed without precipitating inorganic substances by the method of example 1.

(example 2)

In the method of example 2, in the conventional supercritical medium conversion step 1 shown in FIG. 2, hydrogen ions were set to 10 for 1kg of water^-4The solution is brought into a supercritical state by adding an inorganic acid in a molar ratio of at least one mole, and is used as a supercritical medium in the subsequent step.

According to the study of Smith et al, the metal elements in the nitric acid waste liquid are hydrolyzed as shown by formula V at high temperature and high pressure, and then are thermally decomposed as shown by formula VI to finally become oxides.

The nitric acid formed in formula V generates oxygen gas after thermal decomposition, and thus, an oxide is easily formed.

… formula V

… formula VI

To prevent such hydrolysis, it is necessary to add an acid to shift the equilibrium of formula V to the left.

The concentration of hydrogen ions in water is closely relatedto the ion accumulation of water. Fig. 4 shows the change in ionic product of water as the temperature and pressure change.

For example, at a pressure of 25MPa, the ion product of water is 10, which is the maximum at around 300 ℃^-11(mol/kg)². Therefore, the hydrogen ion concentration in supercritical water when no acid or the like is present is 3.3X 10^-6mol/kg. Under the supercritical water condition of 374 ℃ or above, the ion product of water is less than 10^-11(mol/kg)²At 600 ℃ of 10^-24(mol/kg)². Thus, the hydrogen ion concentration at 600 ℃ is 10^-12mol/kg, much less than at 300 ℃.

Conventionally, when organic substances are decomposed by supercritical water, conditions of high temperature and low pressure (for example, 600 ℃ C., 25MPa) are often employed. Therefore, when water alone is added to an organic substance containing an inorganic substance and the reaction is carried out at a high temperature, the hydrogen ion concentration in the reactor becomes extremely low, the equilibrium of formula V shifts to the right, and the inorganic substance precipitates as an oxide.

In order to increase the ion concentration in supercritical water, the ion product must be increased. As shown in fig. 4, the ion product increases with the increase in pressure, and the pressure that can be actually used is 50MPa or less.

For example, at 350 ℃ and 50MPa, the ion product is 10^-12(mol/kg)² Ion deposition 10 in comparison with normal temperature and pressure^-14(mol/kg)²100 times larger, hydrogen ion concentration of 10^-6mol/kg. Thus, by selecting the temperature and pressure, it is notThe hydrogen ion concentration in the supercritical water is extremely increased, and in this embodiment, the hydrogen ion concentration can be adjusted by adding an acid to the supercritical water, thereby preventing precipitation of inorganic substances.

The method of this example was used to investigate the conditions under which the addition of acid to supercritical water did not precipitate inorganic substances.

Adding 5X 10^-5Molar sulfuric acid to obtain water with a hydrogen ion concentration of 10^-4mol/kg of medium.

The obtained medium was mixed with cerium nitrate (cerium 1mg), reacted at 400 ℃ under 25MPa for 30 minutes, returned to normal temperature and pressure, the decomposition solution was filtered, and cerium in the filtrate was measured by ICP. Further, the filter paper was dissolved with an acid, and cerium was measured by ICP in the same manner to confirm the presence or absence of a precipitate. The results are shown in Table 1.

In addition, as a conventional example, results of using two media are shown. One is the result of using water as the medium without adding sulfuric acid. Another is to add 5X 10 for 1kg of water^-6The molar concentration of sulfuric acid, i.e. hydrogen ions, being 10^-5Results in mol/kg of medium.

As shown in Table 1, in the conventional example, 100% of cerium precipitated as cerium oxide and 5X 10 cerium oxide was added^-5The precipitation rate was 0% by mol of sulfuric acid, and the entire amount of cerium remained in the solution in a dissolved state. In addition, 5X 10 is added^-6At mole of sulfuric acid, 70% of the cerium precipitated.

As can be seen from the above, the hydrogen ion concentration was adjusted to 10^-4When acid was added in mol/kg, no cerium precipitated.

TABLE 1

Amount of sulfuric acid added to 1kg of water	0 mole	5×10^-6Mole of	5×10^-5Mole of
Amount of sulfuric acid added to 1kg of water	0 mole	5×10^-6Mole of	5×10^-5Mole of	Rate of cerium precipitation	100％	70％	0％
Remarks for note	Description of the Prior Art		The invention	Rate of cerium precipitation	100％	70％	0％

When oxygen is present in the inorganic substance, the inorganic substance is oxidized to an oxide. In the method of this example, conditions were examined under which organic substances could be decomposed without precipitating inorganic substances when an oxidizing agent was present in the medium.

FIG. 5 shows the results of a reaction at 400 ℃ and 25MPa for 30 minutes in which cerium nitrate (cerium: 1mg) was added with water, sulfuric acid and an oxidizing agent. For 1kg of water 5X 10 wasadded^-3Molar sulfuric acid. As a result of measurement by ICP, cerium precipitated as the amount of the oxidizing agent added increased. When the amount of oxidant added exceeded 600 times the stoichiometry (assuming cerium to be ceria) (0.3 g of hydrogen peroxide), 97% of the cerium precipitated.

Therefore, in the presence of an oxidizing agent, the amount of acid added must be increased as the amount of the oxidizing agent added increases.

Table 2 shows the reaction conditions in cerium nitrate(cerium: 1mg) was added with 4 times the stoichiometric amount of an oxidizing agent, and the mixture was reacted at 400 ℃ and 25MPa for 30 minutes. The addition amount of sulfuric acid to water was 5X 10^-2At mol/kg, the precipitation rate of cerium was 0%.

Therefore, in the presence of an oxidizing agent, 5X 10 must be added to 1kg of water^-2mol/kg sulfuric acid (hydrogen ion concentration of 10)^-1mol/kg)。

TABLE 2

Added in 1kg of water Amount of sulfuric acid	5×10^-4Mole of	5×10^-3Mole of	5×10^-2Mole of
Added in 1kg of water Amount of sulfuric acid	5×10^-4Mole of	5×10^-3Mole of	5×10^-2Mole of	Rate of cerium precipitation	98％	70％	0％

As described above, when the oxidizing agent is present, the hydrogen ion concentration in 1kg of the medium is 10^-1Adding acid on a molar basisIn this case, the organic material can be decomposed without precipitating inorganic material.

In the method of the present example, the case where inorganic salts other than nitrate are contained in the organic waste was examined.

To nitrate, sulfate, chloride, phosphate and oxide (cerium 1mg) of cerium, an oxidizing agent was added in an amount 4 times the stoichiometric amount to be treated. In water is added with 5 x 10^-2The reaction was carried out at 400 ℃ and 30MPa for 30 minutes using mol/kg sulfuric acid as a medium.

The results are shown in Table 3.

In the case of nitrate, sulfate, chloride and phosphate, the amount of cerium present as ions in water was 100% and the precipitation rate of cerium was 0% as measured by ICP. In addition, 50% of the oxide originally present as a solid dissolves in the liquid, and even a small amount of the oxide can be recovered in the liquid.

TABLE 3

Form of cerium	Nitrate salt	Sulfates of sulfuric acid	Chloride compound	Phosphate oxide
Form of cerium	Nitrate salt	Sulfates of sulfuric acid	Chloride compound	Phosphate oxide	Amount of cerium present in water	100％	100％	100％	100％ 50％

As described above, according to the method of the present embodiment, not only nitrate but also inorganic substances can be decomposed without precipitating even if sulfate, chloride, phosphate, or oxide is contained.

For example, when organic waste containing plutonium oxide is processed, plutonium can be recovered as ions in a liquid, and therefore, organic waste contaminated with plutonium (for example, rags and gloves) can be changed to non- α waste (waste containing only non-emission α ray elements), and the processing cost can be reduced.

In the method of the present example, it was examined whether or not organic waste could be treated without precipitating inorganic substances by using sulfuric acid or hydrochloric acid as an inorganic acid for adjusting the concentration of hydrogen ions in the medium.

Adding 4 times of stoichiometric amount of oxidant into cerium nitrate, and adding 5 × 10 of oxidant into 1kg of water^-2Sulfuric acid, hydrochloric acid, and nitric acid in mol/kg as a medium. The reaction was carried out at 400 ℃ and 30MPa for 30 minutes, and the results are shown in Table 4.

As a result of the ICP measurement, when sulfuric acid or hydrochloric acid was used, no precipitation of cerium was observed, but when nitric acid was added, 100% of cerium was precipitated. Since nitric acid is thermally decomposed at a high temperature, the hydrogen ion concentration is 10 in 1kg of water^-4At below mol, the solubility of the inorganic substance is low, and precipitation occurs.

As described above, when sulfuric acid or hydrochloric acid is used as the inorganic acid, the organic waste can be decomposed without precipitating inorganic substances.

TABLE 4

Kind of acid	Sulfuric acid	Hydrochloric acid	Nitric acid
Kind of acid	Sulfuric acid	Hydrochloric acid	Nitric acid	Rate of cerium precipitation	0％	0％	100％

(example 3)

FIG. 6 is a schematic view showing a waste treatment apparatus according to the present embodiment.

The waste treatment apparatus of the present embodiment includes: a reactor 11 for treating organic waste in a supercritical state of water, an organic waste supply device 12 for introducing the organic waste into the reactor 11, a water supply device 13 for supplying water as a medium to the reactor 11, an oxidation reactor 14 for oxidizing low molecular weight organic substances produced in the reactor 11, an oxidizing agent supply device 15 for supplying an oxidizing agent to the oxidation reactor 14, and a recovery device 30 for recovering a product produced by the oxidation reactor 14.

The recovery apparatus 30 includes a gas-liquid separator 33, a gas treatment apparatus 34, and a liquid treatment apparatus 40.

The liquid treatment device 40 has a dryer 45 and a solidifier 46 that dry and solidify the liquid sludge.

In this embodiment, the reactor 11 and the oxidation reactor 14 are provided separately and connected by a pipe or the like, and the product produced in the reactor 11 is sent to the oxidation reactor 14. However, a structure in which one container is divided into 2 compartments by a partition plate or the like may be employed. It is also possible to use one vessel as the reactor 11 and the oxidation reactor 14 by appropriately adjusting the pressure and temperature.

The object to be treated is not particularly limited. The organic waste may be organic waste containing resin or the like, organic waste contaminated with radioactive substances, or the like, and various organic wastes can be treated.

When organic waste containing insoluble impurities such as sand and gravel, or organic waste containing inorganic additives or organic metal salt additive resins is treated, the organic matter is first reduced in molecular weight in a supercritical state and then oxidized in a subcritical state, thereby sufficiently preventing precipitation of inorganic matter.

In this case, it is preferable to reduce the amount of organic waste to be treated at one time. As shown in fig. 7, a separator 18 may be provided at the lower part of the reactor 11 to remove inorganic substances precipitated in a supercritical state by weight or inertia. This prevents the precipitation of inorganic substances in a subcritical state.

As shown in fig. 7, the separator 18 may be provided inside the reactor 11 or between the reactor 11 and the oxidation reactor 14.

In the present embodiment, water is used as the supercritical medium, but the supercritical medium is not limited thereto, and carbon dioxide, various kinds of hydrocarbons, or a mixture thereof may be used.

Fig. 8 is a critical curve showing the critical point of the water and hydrocarbon mixture. Reference numeral 116 is a critical curve of water-benzenes, reference numeral 117 is a critical curve of heavy water-benzenes, reference numeral 118 is a critical curve of water-toluenes, reference numeral 119 is a critical curve of water-o-xylenes, reference numeral 120 is a critical curve of water-1, 3, 5-trimethylbenzenes, reference numeral 121 is a critical curve of water-cyclohexanes, reference numeral 122 is a critical curve of water-ethanes, reference numeral 123 is a critical curve of water-n-butanes, reference numeral 124 is a critical curve of water-naphthalenes, reference numeral 125 is a critical curve of water-biphenyls, and reference numeral 126 is a critical curve of water. The critical point of water is 374 ℃ and 22MPa, and in FIG.8, for example, in water-benzene, 2 components are mixed at a specific ratio, and the critical point can be lowered to 300 ℃ or higher. Therefore, if a mixture of water, carbon dioxide and hydrocarbon is used as a medium, the organic waste can be treated under mild conditions at a lower temperature and a lower pressure while maintaining the supercritical state.

In the present embodiment, hydrogen peroxide is used as the oxidizing agent, but the oxidizing agent is not limited thereto, and oxygen, air, or ozone, or a mixture of 2 or more kinds of oxygen, air, hydrogen peroxide, or ozone may be used.

When hydrogen peroxide is used, organic substances can be effectively decomposed.

In order to completely decompose the organic substances, the amount of hydrogen peroxide added is preferably 1 time or more of the amount required for making the organic substances into carbon dioxide or water. Preferably 1.2 to 10 times.

When organic waste is treated by this apparatus, water as a medium is supplied from the water supply apparatus 13 to the reactor 11. In the reactor 11, the organic waste is supplied to the water in the supercritical state by the organic waste supply device 12, mixed with supercritical water, and maintained in the supercritical state for a predetermined time.

The organic waste is reduced in molecular weight in the reactor 11 in a supercritical state of medium water. The resultant is transferred to the oxidation reactor 14, and after the addition of the oxidizing agent, is oxidized in a subcritical state.

The product produced in the oxidation reactor 14 is sent to the recovery device 30, separated into gas and liquid by the gas-liquid separator 33, and sent to the gas treatment device 34 and the liquid treatment device 40, respectively, to recover harmful substances.

The solid phase or liquid phase generated by the decomposition is dried by the dryer 45, and then a curing agent is mixed into the curing device 46, and the mixture is cured in a processing container such as a drain tank, thereby forming a stable cured body. Thus, safety in handling can be ensured, and management is easy. The curing agent is preferably cement paste.

By providing the organic waste supply device 12, the water supply device 13, and the oxidizing agent supply device 15, the organic waste, the water, and the oxidizing agent can be continuously supplied to the reactor 11, and the product can be continuously taken out from the recovery device 30. Therefore, the organic waste can be continuously treated.

As described above, according to the waste treatment apparatus of the present embodiment, when organic waste is treated in a supercritical state, the problem of precipitation of inorganic substances which has been conventionally observed can be prevented.

Therefore, troubles such as clogging of the reactor due to precipitation of inorganic substances can be avoided. The running cost and the maintenance cost of the device can be reduced. In addition, when the inorganic substance is a radioactive substance, the harm to the operator can be reduced.

When hydrogen peroxide is added as an oxidizing agent, OH groups are generated in a short time, and therefore a large amount of organic substances can be decomposed in a short time.

The inorganic salt is recovered in an ionic state without being converted into an oxide, and the inorganic substance existing as an oxide from the beginning can be recovered into a liquid, so that the organic waste can be converted into a homogeneous waste.

(example 4)

FIG. 9 is a schematic view of the wastetreatment apparatus according to the present embodiment.

The waste treatment apparatus of example 4 includes: a reactor 11 for treating organic waste in a supercritical state of water, an organic waste supply device 12 for introducing the organic waste into the reactor 11, a water supply device 13 for supplying water as a medium to the reactor 11, a pH meter 23 for measuring a hydrogen ion concentration of water in the reactor 11, an acid supply device 16 for supplying an acid to the reactor 11, a controller 24 for controlling the acid supply device 16 based on a measurement value of the pH meter 23 and supplying the calculated amount of acid to the reactor 11, and a recovery device 30 for recovering a product of the reactor 11.

The acid supplied from the acid supply device 16 is an inorganic acid ionized in the medium water, but is not suitable for use with an acid thermally decomposed at high temperature such as nitric acid. Sulfuric acid or hydrochloric acid is preferably used.

As described in example 2, when the organic waste is decomposed, if the hydrogen ion concentration of water is 10^-4When the molar ratio is not less than kg, precipitation of inorganic substances in a supercritical state can be suppressed.

However, the influence of the decomposition product of various organic wastes on the hydrogen ion concentration of water is considered.

For example, a polymer container made of polyethylene or polyvinyl chloride is reacted at 374 ℃ and 22.1MPa in the presence of water to hydrolyze polyethylene and produce ethanol, organic acid, and the like, but polyvinyl chloride produces hydrochloric acid in addition to ethanol and organic acid. The chlorine content in polyvinyl chloride was 56% by weight, and if 0.006g of polyvinyl chloride was added to 1kg of water, the hydrogen ion concentration in the reactor was 10^-4Mol/kg.

Therefore, when 0.006g of polyvinyl chloride was added to 1kg of water, no acid was added. However, since polyethylene does not generate an acid, an acid is added so that the hydrogen ion concentration in 1kg of water becomes 10^-4Mol/kg.

In addition, when decomposing a waste mixture of polyethylene that does not generate an acid and polyvinyl chloride that generates an acid, the mixing ratio is clarified, and the amount of acid generated from organic matter is grasped.

In this example, the hydrogen ion concentration in the reactor 11 was measured in real time by the pH meter 23, and based on the measured value, the hydrogen ion concentration per 1kg of water was calculated by the controller 24 to be 10^-4The amount of acid required in moles or more is controlled by controlling the acid supply device 16 to supply the calculated amount of acid to the reactor 11.

According to this configuration, the hydrogen ion concentration in the reactor can be maintained at an optimum state regardless of the type of organic waste.

The amount of acid supplied can be greatly reduced by supplying an optimum amount of acid depending on the object to be treated.

Further, for the following reasons, the gas-liquid separator 33 can be made smaller than the conventional example.

Carbon dioxide dissolves in water as shown by formula VII to become carbonic acid, and carbonic acid decomposes in water to ions shownby formulae VIII and XI.

…VII

…VIII

…IX

In order to shift the equilibrium of formulae VII, VIII, IX to the left, separating carbon dioxide and water, the hydrogen ion concentration in the liquid must be increased. Acid separation constant of formula VIII is 10 at 20 ℃^-3.6(mol/l). When hydrogen ion concentration is varied [ HCO]₃ ^-〕/〔H₂CO₃The ratios are shown in Table 5.

Due to H₂CO₃In equilibrium with carbon dioxide in the gas phase, HCO when dissolved in liquid₃ ^-Is greater than H₂CO₃In time, separation of water from carbon dioxide is difficult. In the conventional method, the hydrogen ion concentration in the liquid is 10^-7mole/Kg, so that H in the solution₂CO₃The ratio of (3) is small, and when separating carbon dioxide, it is necessary to contact a large amount of air, and a relatively large gas-liquid separator is required.

However, in the present invention, since the hydrogen ion concentration is 10^-4The molar ratio is not less than Kg, so that a small-sized gas-liquid separator can be used as compared with the conventional example, and the facility cost can be reduced. In addition, air is not needed to be added, the processing capacity of the gas processor is reduced, and the equipment cost and the operation cost are reduced.

TABLE 5

Hydrogen ion concentration (mol/l)	[HCO₃ ^-]/[H₂CO₃]Ratio of
Hydrogen ion concentration (mol/l)	[HCO₃ ^-]/[H₂CO₃]Ratio of	10^-1	0.0025
10^-2	0.025	10^-1	0.0025
10^-2	0.025	10^-3	0.25
10^-4	2.5	10^-3	0.25
10^-4	2.5	10^-7(conventional example)	2500

In this example, the depth of hydrogen ions in the reactor 11 was directly measured by the PH meter 23, but actually, the inside of the reactor was at high temperature and high pressure, and it was sometimes difficult to provide the PH meter.

The amount of acid added to the water may be calculated according to the type and amount of the waste to be treated, and the required amount of acid may be mixed with the water and then supplied to the reactor 11. Thus, the hydrogen ion concentration can be controlled without directly measuring the hydrogen ion concentration of the medium in the reactor, and therefore, a pH meter is not required.

As described above, in the organic waste decomposition device of the present embodiment, the supply amount of the inorganic acid is adjusted according to the type of the organic waste, and the optimum hydrogen ion concentration state for preventing the precipitation of the inorganic substance is controlled, so that the waste mixed with various organic substances can be easily treated.

The amount of inorganic acid in the organic waste water in the apparatus was controlled to 10 kg in 1kg of water in terms of hydrogen ions^-4More than mole, can effectively prevent the precipitation of inorganic matters without large equipment investment. In addition, the gas-liquid separator can be miniaturized.

(example 5)

FIG. 10 is a schematic view of the waste treatment apparatus according to the present embodiment.

The waste treatment apparatus of the present example was the waste treatment apparatus of example 4, which was provided with an oxidizing agent supply device 15 for supplying an oxidizing agent to the reactor 11.

In the waste treatment apparatus of the present embodiment, the organic matter is first reduced in molecular weight in the supercritical state of water in the reactor 11, and then the pressure and temperature in the reactor 11 are reduced to oxidize the organic matter in the subcritical state.

The hydrogen ion concentration in the reactor 11 was adjusted to 10 per 1kg of water by controlling the acid supply device 16 by the controller 24 based on the measured value of the pH meter 23^-4And (3) molar ratio.

The organic waste preferably contains a large amount of inclusions, inorganic additives or organic metal salt additives. If the organic waste contains a large amount of inorganic additives, the amount of the organic waste to be treated at one time is reduced, or a precipitate separating apparatus is provided, and after the treatment in a supercritical state, the precipitated inorganic substances are removed and the organic waste is treated in a subcritical state.

As described above, in the organic waste treatment apparatus of the present embodiment, the organic material is reduced in molecular weight in the supercritical state, and then is oxidatively decomposed in the subcritical state, thereby preventing the precipitation of the inorganic material.

Since the supercritical state treatment and the subcritical state treatment are carried out in the same reactor, the cost of the apparatus is suppressed and the operation is simple.

Further, the hydrogen ion concentration per 1kg of water was adjusted to 10^-4More than molar, the precipitation of inorganic substances can be more effectively prevented.

The supply amount of the inorganic acid is adjusted according to the kind and amount of the organic waste, the amount of the oxidizing agent used, and the like, so that the hydrogen ion concentration can be controlled to an optimum state, and the waste mixed with various organic substances can be easily treated.

By adding the oxidizing agent, a large amount of organic matter can be decomposed and treated in a short time.

(example 6)

FIG. 11 is a schematic view of the waste treatment apparatus according to the present embodiment.

The waste treatment apparatus of this example is the same as the waste treatment apparatus of example 5 except that the organic waste supply apparatus 12 is not provided, but an inorganic waste supply apparatus 51 for supplying inorganic waste to the reactor 11 is provided, an ammonia treatment apparatus 52 is provided in the gas treatment apparatus 34, and an α nuclear species recovery apparatus 53 is provided in the liquid treatment apparatus 40, and the nuclear species recovery apparatus 53 of α is constituted by a coagulation sedimentation apparatus 43 and a separator 44 for separating solid particles in a liquid, as shown in fig. 12.

In addition, the inorganic waste supply device 51 may not be provided, and the organic waste supply device 12 may supply the inorganic waste. Thus, both organic and inorganic wastes can be treated by the same apparatus, which is advantageous for reducing the cost.

For example, a solidified body of α -containing waste may be treated, but the present invention is not limited thereto, and waste containing organic matter may be treated.

When inorganic waste containing radioactive substances such as α nuclei or nitrates is treated by this apparatus, water as a medium is supplied to the reactor 11 by the water supply apparatus 13, and the inorganic waste is supplied to water which has been brought into a supercritical state in the reactor 11 by the inorganic waste supply apparatus 51, mixed with supercritical water, and held in the supercritical state for a predetermined period of time.

The inorganic waste is oxidatively decomposed in the presence of an oxidizing agent in the supercritical state of medium water in the reactor 11.

In this example, the hydrogen ion concentration per 1kg of water was adjusted to 10^-4The radioactive substance (for example, α nuclei such as plutonium) is not precipitated and can be recovered in a liquid, and nitric acid or nitrate contained in the inorganic waste is decomposed without being precipitated and recovered as ammonia in a gas.

The product thus produced is sent to the recovery apparatus 30, separated into gas and liquid by the gas-liquid separator 33, and sent to the gas treatment apparatus 34 and the liquid treatment apparatus 40, respectively.

The ammonia-containing gas is heated to 310 ℃ or higher in the presence of a platinum catalyst in the ammonia treatment device 52, and the ammonia becomes nitrogen gas.

A liquid containing α nuclei such as plutonium is precipitated by adding barium to a coagulating sedimentation apparatus 43 of a α nucleus recovering apparatus 53 to produce insoluble barium sulfate, α nuclei having valence III and IV are precipitated together with barium sulfate, α nuclei having valence V and VI are reduced to valence III and IV by a reducing agent, and then precipitated together with barium sulfate.

When the liquid contains ammonia, sodium hydroxide is added to adjust the PH of the liquid to 9, and then ammonia is removed from the liquid by replacing it with a vapor phase.

The barium sulfate salt containing α precipitated nuclei may be separated by the separator 44 and recovered to be a glass solidified body or a cement solidified body.

In addition to barium, iron may be added to adjust the pH to 4 or higher, α seeds may be precipitated together with the generated iron hydroxide to form a cement solidified body, or the iron hydroxide may be precipitated together with a lanthanum phosphorus salt.

The liquid from which α nuclei have been removed is dried by a dryer 45, mixed with a curing agent in a curing device 46, and cured in a treatment vessel such as a discharge tank to form a cured product of non- α waste.

As described above, in the waste treatment apparatus of the present embodiment, the concentration of hydrogen ions in the medium in the supercritical state is adjusted to 10 per 1kg of water^-4The precipitation of radioactive substances or inorganic substances such as nitrates can be prevented. Therefore, troubles such as clogging of the reactor due to precipitation of inorganic substances can be avoided. Not only can reduce the running cost and the maintenance cost of the device, but also can reduce the harm of radioactive substances to operators.

According to this example, since nitrate ions are decomposed into most of nitrogen gas, and the solidified α waste after the supercritical treatment does not contain nitrate, ammonia is not generated even when the solidified product is buried under a reducing atmosphere, and it is possible to prevent nuclear substances such as plutonium from being eluted from the solidified product.

Further, since the solidified body obtained by solidifying the liquid and the sludge from which the α nuclei have been removed is non- α waste, it can be treated in a shallow ground, whereby the treatment of waste is easy.

For example, a solidified body of radioactive waste is obtained by a usual method, and α seeds such as plutonium are collected from the solidified body to be a glass solidified body, so that the amount of α waste can be greatly reduced.

In this example, α nuclei were precipitated and separated and recovered, but the present invention is not limited to α nuclei, and precipitation treatment may be performed by condensing inorganic ions of metals and the like dissolved in a liquid phase.

The treatment apparatus of example 3 or 4 may be provided with a device for coagulating and precipitating these inorganic ions.

(example 7)

In the waste treatment apparatus of the present example, as shown in fig. 13, in the waste treatment apparatus of example 3, heaters 25a to c and pressers 26a to c are provided in the organic waste supply device 12, the water supply device 13, and the oxidizing agent supply device 15, respectively, and a pressure reducer 31 and a cooler 32 are provided in the recovery device 30.

In the waste disposal apparatus of example 4 or example 5, the same heater and pressurizer may be provided in the organic waste supply apparatus 12, the water supply apparatus 13, the oxidizing agent supply apparatus 15, and the acid supply apparatus 16, and the same pressure reducer and cooler may be provided in the recovery apparatus 30.

In the waste treatment apparatus of example 6, the same heater and pressurizer may be provided in the inorganic waste supply device 51, the water supply device 13, the oxidizing agent supply device 15, and the acid supply device 16, and the same decompressor and cooler may be provided in the recovery device 30.

Heaters 25a to c heat the organic waste, the medium, and the oxidizing agent, respectively, and pressurizers 26a to c pressurize the organic waste, the medium, and the oxidizing agent, respectively. With this structure, the organic waste, water and the oxidizing agent can be continuously supplied to the reactor 11, and the organic waste can be continuously treated without lowering the reaction temperature and pressure.

The decomposition product produced in the oxidation reactor 14 is sent to the recovery device 30, and is depressurized and cooled by the decompressor 31 and the cooler 32. With this configuration, the product fluid is continuously withdrawn from the oxidation reactor 14, and then the gas-liquid separator 33 efficiently separates the fluid into gas and liquid.

When oxygen is added to the organic matter and decomposed, carbon becomes carbon dioxide and hydrogen becomes water. Under supercritical water conditions, water as a medium and carbon dioxide generated by decomposition are mixed at will and are not easily separated. However, when the temperature of the fluid generated by decomposition is reduced to normal temperature and pressure by reducing the pressure to normal pressure, most of water and carbon dioxide can be separated.

Thus, according to the present embodiment, the treatment speed is higher than that of the batch treatment, and the running cost can be greatly reduced. Further, the gas-liquid separation by the gas-liquid separator 33 can be performed efficiently.

(example 8)

As shown in fig. 14, the waste treatment apparatus of the present example is the waste treatment apparatus of example 3, in which a temperature sensor 21 and a pressure sensor 22 are provided in a reactor 11.

The waste treatment apparatuses of examples 4, 5, 6, and 7 may have the same structure.

Fig. 15 shows a state diagram of water. Since the state of water depends on the temperature and pressure, it can be determined whether the inside of the reactor 11 is in a supercritical state or a subcritical state by monitoring the temperature and pressure inside the reactor.

By monitoring the temperature and pressure in the reactor 11 by the temperature sensor 21 and the pressure sensor 22, it is possible to accurately determine whether or not the medium in the reactor 11 is in a supercritical state, and thus, it is possible to treat the waste in an optimum state.

It is preferable to provide the same temperature sensor and pressure sensor in the oxidation reactor 14 as well as the reactor 11, so that whether the inside of the oxidation reactor 14 is in the subcritical state can be grasped.

In the apparatus having the heaters 25a to c and the pressers 26a to c as in the waste treatment apparatus of example 7, the temperature and pressure of the heated or pressed waste, medium, and the like may be measured before being supplied to the reactor. The state in the reactor can be grasped without directly measuring the temperature and pressure in the reactor.

(example 9)

The waste treatment apparatus according to example 9 is the waste treatment apparatus according to example 3, in which at least a part of the reactor 11 and the organic waste supply apparatus 12 is disposed in the drying box (グロ - ブボツクス)27, as shown in fig. 16.

The waste treatment apparatuses of examples 4, 5, 6, 7, and 8 may have the same structure.

When organic waste contaminated with radioactive substances or harmful substances is treated, it is necessary not to leak the radioactive substances or harmful substances to the outside. The waste treatment apparatus according to example 3 is mostly a closed system for treatment, but a part of the organic waste supply apparatus 12 is an open system for receiving organic waste. Therefore, when organic waste contaminated with radioactive substances or harmful substances is treated, the organic waste supply device 12 serving as an open system is installed in a shield (フ - ド) or a component such as a drying oven, thereby preventing the contamination from spreading.

Further, it is preferable that the covering member such as the drying box or the hood is explosion-proof. The organic waste may be treated when volatile organic compounds that may cause explosion risk are generated by decomposition of the organic waste or when volatile organic compounds that may cause explosion risk are attached to the organic waste.

According to the present embodiment, since a part of the processing apparatus is disposed in the spherical box, the apparatus can be downsized as compared with disposing the entire apparatus in the covering member.

(example 10)

In this embodiment, as shown in fig. 17, the waste treatment apparatus according to embodiment 3 is provided with a neutral salt supply device 29, and the neutral salt supply device 29 is used for adding neutral salt to the medium water.

The waste treatment apparatuses of examples 4, 5, 7, 8, and 9 may have the same structure.

In general, salts M which are poorly soluble_nL_mThe solubility Ks of (A) is shown by the formula X in terms of active amount.

，Ks＝a1^m·a2ⁿ…X

a1：M^m+Activity of, a 2: l is^n-Activity of

The activity a is shown by the formula XI with an activity coefficient gamma and a concentration C.

a＝γ·C …XI

When the temperature and the pressure are constant, the activity a is constant, and the Ks has a constant value. In a dilute solution, γ is 1 and the activity a is equal to the concentration C. However, when the ionic strength increases, γ<1, resulting in an increase in the concentration C, M dissolved in the solution^m+And L^n-The solubility tends to increase as the amount increases.

Therefore, when a neutral salt is added, the solubility of the sparingly soluble salt increases, and precipitation can be suppressed.

The neutral salt can be sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium sulfate, potassium sulfate, etc.

According to this embodiment, the addition of the neutral salt can more effectively suppress the precipitation of the inorganic substance.

(example 11)

As shown in fig. 18, the waste treatment apparatus of the present embodiment is the waste treatment apparatus of embodiment 3, which is provided with a radiation irradiation device 28 for irradiating the contents of the reactor 11 with radiation.

The same structure can be applied to the waste treatment apparatuses of examples 4, 5, 7, 8, 9, and 10.

Instead of theradiation irradiation device, an ultraviolet irradiation device for irradiating ultraviolet rays may be used.

When water is irradiated with radiation, OH groups are generated as shown in the formula XII.

…XII

OH groups act as strong oxidants as shown in formula I, and therefore, can decompose organic substances without adding an oxidizing agent.

In addition, in the presence of an oxidizing agent, if ultraviolet rays or radiation rays are irradiated, the reaction is further accelerated. For example, when irradiated with radiation, oxygen generates radicals and finally hydrogen peroxide. The hydrogen peroxide reacts with the organic compound in the presence of radiation as in the formula XIII to form OH groups, which can decompose the organic compound.

H₂O₂+hv→2OH· …XIII

Ozone reacts with ultraviolet light as shown in formula XIIII to produce hydrogen peroxide. The hydrogen peroxide is further reacted with ultraviolet rays as shown in the formula XIII to form OH groups.

…XIIII

Further, as shown in XV, the hydrogen atom generated in VII is reacted with oxygen to generate hydroperoxyl, and further reacted with ozone to generate OH group as shown in XVI.

…XV

…XVI

Therefore, by irradiation with radiation, OH groups can be efficiently generated, and organic substances can be more efficiently decomposed.

When waste containing radioactive substances is treated, a radiation field can be easily formed without irradiating radiation from the outside, and therefore, the above-described effects can be obtained without providing a radiation irradiation apparatus.

(example 12)

As shown in fig. 19, the waste treatment apparatus of the present example is the waste treatment apparatus of example 3, wherein the gas treatment apparatus 34 is provided with a filter 35 and a scrubber 36, the filter 35 is used for removing solid particles and harmful components in the gas, and the scrubber 36 is used for recovering the harmful components.

The same structure can be applied to the waste treatment apparatuses of examples 4, 5, 6, 7, 8, 9, 10, and 11.

For example, when waste contaminated with radioactive substances in a reprocessing plant is processed, volatile elements such as technetium and ruthenium are transferred to a gas phase.

Ruthenium transitions into the gas phase as ruthenium tetroxide, but is reduced to ruthenium dioxide in the presence of organics. Ruthenium dioxide is solid at ordinary temperature, and therefore, can be removed by a filter for removing solid particles.

Technetium is transferred to the gas phase as technetium heptaoxide or pertechnetium percolates, but when contacted with water, as shown by formulas XVII and XVIII, it dissolves in water in the form of ions.

…XVII

…XVIII

Thus, where a scrubber is provided, technetium may be recovered into the liquid.

In order to recover the element such as technetium more efficiently, it is preferable to use an alkali solution containing sodium hydroxide or water containing a reducing agent in addition to water in the scrubber.

When technetium is contacted with water, it dissolves in the form of an anion as shown by formulas XVII and XVIII. Since this anion reacts with sodium ion to form a salt, technetium can be recovered as a salt in the solution.

…XVIIII

In the presence of the reducing agent, technetium is reduced from pertechnetic acid (valency VII) to technetium dioxide (valency IV). Technetium dioxide is less soluble in water at normal temperature and pressure, and therefore technetium can be recovered as a solid in water.

As described above, according to this embodiment, solid or volatile harmful elements that migrate into the gas phase by the splash accompanying can be removed, and even waste contaminated with radioactive substances can be safely disposed of.

(example 13)

As shown in fig. 20, the waste treatment apparatus according to example 13 is the waste treatment apparatus according to example 3, and the liquid treatment apparatus 40 includes an agitator 41 for agitating the liquid and a collection analyzer 42 for collecting and analyzing the liquid.

The waste treatment apparatuses of examples 4, 5, 6, 7, 8, 9, 10, 11, or 12 may have the same structure.

The liquid sent from the gas-liquid separator 33 to the liquid treatment apparatus 40 is stirred by the stirrer 41, and the liquid phase becomes uniform. The composition of the liquid phase can be clarified by collecting a part of the homogeneous liquid by thecollection and analysis device 42 and analyzing the collected part. The most suitable curing apparatus for storage and handling may be selected for the curing device 46. Further, since the content of the cured product after the curing treatment is clear, the storage and management at the time of the treatment are easy.

Even if the liquid contains suspended solids, the liquid can be uniformly stirred by the stirrer 41, and the solidification treatment can be easily performed in the solidification vessel 46.

If the collection analyzer 42 is not provided, the contents of the solidified body are not known, and the contents are measured by some method for management. However, in the measurement of the content of the solidified material, it is difficult to take a representative sample, and therefore, the accuracy is poor, and there is a problem in waste management.

(example 14)

As shown in fig. 21, the waste treatment apparatus according to the present embodiment is the waste treatment apparatus according to embodiment 3, wherein the liquid treatment apparatus 40 includes a neutralization treatment apparatus 50, and the neutralization treatment apparatus 50 is configured to neutralize an acid or an alkali contained in a treatment liquid.

The waste treatment apparatuses of examples 4, 5, 7, 8, 9, 10, 11, 12, and 13 may have the same structure.

For example, in the treatment of radioactive solid waste containing technetium, the transition of technetium to technetium heptaoxide into the gas phase.

However, when a base such as sodium hydroxide is added to the neutralization apparatus 50 after the decomposition product is recovered from the oxidation reactor 14 to the recovery apparatus 30, as shown by formula XVIII, a trace amount of technetium remaining in theliquid after gas-liquid separation can be stabilized in the liquid phase.

Therefore, according to the present embodiment, harmful substances such as radioactive substances contained in the liquid are stabilized, and the solidification treatment is facilitated in the solidification device.

(example 15)

In the waste treatment apparatus according to example 15, as shown in fig. 22, a cooler 47 for cooling a liquid phase is provided in the liquid treatment apparatus 40 in the waste treatment apparatus according to example 3.

The waste treatment apparatuses of examples 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14 may have the same structure.

When radioactive waste is treated, the radioactive material in the liquid treatment apparatus 40 generates heat, and the liquid is not cooled and boils, which may increase contamination of the radioactive material. This risk is avoided when the liquid is cooled by the cooler 47, so that the radioactive material remains stable in the liquid phase.

(example 16)

In the waste treatment apparatus according to the present embodiment, as shown in fig. 23, an ion exchange column 48 is provided in the liquid treatment apparatus 40 in the waste treatment apparatus according to embodiment 3.

The waste treatment apparatuses of examples 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 may have the same structure.

For example, when waste contaminated with radioactive substances in a reprocessing plant is processed, a part of volatile elements such as technetium and ruthenium is transferred to a gas phase, but the volatile elements remain in a liquid phase, technetium is present in a solution as pertechnetic acid, and ruthenium is present in a solution as a complex of chloride ions and nitrateions.

Since pertechnetic acid is an anion, it can be removed using an anion exchange resin. Ruthenium is a cation and can be removed using a cation exchange resin.

Therefore, according to this embodiment, harmful ion components such as radioactive substances contained in the solution of the decomposition product can be removed, and the remaining solution can be discharged to the outside of the system, thereby reducing the cost for disposing of waste.

In addition, after the harmful ion components in the liquid are removed in this way, the liquid phase and the solid phase of the waste liquid supplied from the liquid treatment line to the solidification equipment become uniform and homogeneous. The waste liquid can be formed into a homogeneous solidified body by mixing a curing agent, and the stable solidified body can be stored and handled in a simple process.

(example 17)

As shown in fig. 24, the waste treatment apparatus of the present example is the waste treatment apparatus of example 3, wherein an extraction and recovery apparatus 49 is provided in the liquid treatment apparatus 40, and the extraction and recovery apparatus 49 is used for bringing the liquid into contact with the extractant to recover the harmful inorganic ions in the water into the extractant.

The waste treatment apparatuses of examples 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, and 15 may have the same structure.

For example, nuclear fuel materials such as uranium and plutonium are contained in radioactive wastes generated from reprocessing plants, and if organic wastes containing these elements are directly solidified, α wastes are generated, and the solidified material processing cost is increased.

As the extractant, a neutral organic phosphorus compound such as tributyl phosphate (hereinafter referred to as TBP) or an acidic organic phosphorus compound such as dihexyl phosphoric acid (HDEHP) can be used.

FIG. 25 shows the distribution coefficient of 30 vol% of TBP-nitrate based radioactive (アクチノイド) element. At a nitric acid concentration of 3 mol/liter (リツトル), the partition coefficients of uranium, plutonium and neptunium are 10 or more, and the partition coefficient of thorium is 3 or more.

The concentration of the liquid acid recovered in the liquid treatment apparatus is adjusted to 3g mol/l by the extraction and recovery apparatus 49, and then the liquid acid is brought into contact with TBP, whereby radioactive elements such as plutonium can be recovered in the TBP. Further, by bringing a TBP containing radioactive elements such as plutonium into contact with a dilute acid, the radioactive elements such as plutonium can be recovered in the dilute acid.

Fig. 26 shows the distribution coefficient of the radioactive element using HDEHP. Nitric acid concentration is even 10^-1The distribution coefficient of plutonium, uranium and americium is above 100 below mol/liter, and the plutonium, uranium and americium can be recycled into HDEHP. Further, hydrazine (ヒドラジン) or the like is containedWhen about 1 mol/liter of acid of the reducing agent contacts HDEHP, the VI valence of plutonium or uranium is reduced to the III valence, and recovered in the acid.

If HDEHP is used, the acid concentration is 10^-1Since the radioactive element can be recovered at about mol/liter, the amount of acid to be added to the separation/recovery unit can be reduced and the running cost can be reduced as compared with the case of using a neutral organic phosphorus compound such as TBP.

The diluent for the extractant such as TBP or HDEHP is preferably supercritical carbon dioxide. Because the amount of the used organic solvent can be reduced, the cost for treating the secondary waste is greatly reduced.

TBP at normal temperature and pressure has a specific gravity of 1g/ml, which is the same as that of water, and when n-dodecane (ノルマルドデカン) is added as a diluent to TBP, the organic phase and the aqueous phase can be easily separated. When radioactive substances such as plutonium are recovered in TBP, the TBP or n-dodecane after use is radioactive, and therefore, must be disposed of as radioactive organic waste.

Usually, the n-dodecane is mixed in a ratio of 30 vol% of TBP and 70 vol% of n-dodecane, and therefore, the amount of n-dodecane to be treated is 2 times or more the TBP. Therefore, if n-dodecane does not need to be treated, the treatment cost can be reduced by 3.

Since carbon dioxide is in a supercritical state under conditions of 31 ℃ and 7.4MPa or more and is mixed with an organic substance at will, when TBP is brought into contact with carbon dioxide in a supercritical state, radioactive elements such as plutonium can be recovered from the decomposed solution into TBP. After use, carbon dioxide is converted into a gas at normal temperature and pressure, and can be easily separated from TBP, so that carbon dioxide treatment is not required.

Therefore, when carbon dioxide in a supercritical state is used as a diluent, the treatment cost can be greatly reduced.

As described above, according to the present embodiment, harmful inorganic ions in the liquid are recovered into the extractant, and the cost for treating the solidified body can be reduced.

In addition, after the harmful ion components in the liquid are removed in this way, the liquid phase and the solid phase ofthe waste liquid supplied from the liquid treatment apparatus to the solidification equipment become uniform and homogeneous. The waste liquid can be formed into a homogeneous solidified body by mixing a curing agent, and the stable solidified body can be stored and handled in a simple process.

Claims

1. A waste treatment method for decomposing inorganic substances contained in inorganic waste by maintaining a mixture of the inorganic waste and a medium in a supercritical state for a predetermined period of time, wherein the hydrogen ion concentration of the medium is 10 relative to 1kg of the medium^-4And (3) molar ratio.

2. The waste treatment method according to claim 1, comprising a medium supercritical step and a mixing step; in a medium supercritical step, the medium is brought into a supercritical state; in the mixing step, a mixture of the inorganic waste and the medium in a supercritical state is obtained.

3. The waste treatment method according to claim 1, wherein the inorganic waste contains nitric acid and/or nitrate.

4. The method of treating waste according to claim 1, wherein the medium is water, carbon dioxide or hydrocarbon, or a mixture of 2 or more thereof.

5. The waste treatment method according to claim 1, wherein the supercritical medium contains an oxidizing agent.

6. The method of treating waste according to claim 1, wherein the supercritical medium contains at least 2 of oxygen, air, hydrogen peroxide, ozone, or the like, and the content thereof is 1 time or more of the stoichiometric amount required for completely oxidizing the inorganic waste.

7. The waste disposal of claim 1The method for treating a substance is characterized in that at least one of sulfuric acid and hydrochloric acid is added to the supercritical medium, and the hydrogen ion concentration of the supercritical medium is 10 relative to 1kg of the supercritical medium^-4And (3) molar ratio.