JPH1119636A - Method for transporting solid to reaction field of supercritical water atmosphere and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively execute the complete decomposition of hardly decomposable org. matter by adding a thickener consisting of an org. compd. for increasing the viscosity of transporting fluid contg. powder and granular solids to this transporting fluid when the transporting fluid is supplied continuously to a reaction field maintained in a supercritical water atmosphere. SOLUTION: At the time of treating ion exchange resins, etc., by supercritical hydroxylation, a prescribed amt. of the used waste ion exchange resins are added from a sample tank 2 to a mixing vessel 1 and a prescribed amt. of the thickener is added from a thickener tank 3 thereto. Next, a liquid mixture contg. the ion exchange resins and the thickener is stirred and mixed by a stirring device 4 and is slurried to the state of the ion exchange resin uniformly dispersed into the water. This slurry is fed by a slurry pump 5 to the suction side of a high-pressure pump 6 via a transporting pipe 7. The slurry is pressurized by this high-pressure pump 6 and is supplied via a high-pressure transporting pipe 9 to a reactor 10. The supercritical water reaction forming fluid discharged from the reactor 10 to a discharge pipe 13 is discharged through the process of cooling, pressure reducing, etc., to the outside of the system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for transporting a substance to be decomposed used for decomposing a powdery organic solid in a supercritical water atmosphere. TECHNICAL FIELD The present invention relates to a method and an apparatus for transporting a substance to be decomposed, which are preferably used when supercritically hydroxylating a solid that precipitates in water.

[0002]

BACKGROUND OF THE INVENTION The prior art and problems in the field to which the present invention is applied will be described below by taking as an example the case where the volume of an ion exchange resin is reduced by oxidative decomposition.

[0003] Conventionally, in power generation facilities such as thermal power plants,
Ion exchange resin is used in the condensate system to remove impurities (cladding, ions, etc.) contained in condensate water, and this ion exchange resin deteriorates over time and is discarded when it reaches a certain use limit Is done. It has been conventionally desired that the waste ion-exchange resin be reduced in volume and disposed of in the same manner as in general waste. But,
The ion-exchange resin is often a hardly decomposable substance, and an industrial-scale volume reduction technology capable of reducing the volume and treating at low cost has not been realized so far. For ion exchange resins used in condensate systems at nuclear power plants,
In addition to the above-mentioned problem that the ion exchange resin is hardly decomposable, since the radioactive material is contained in the cladding etc. that is adsorbed and adhered to the waste ion exchange resin, the radioactive material is stored in a sealed manner. There is a demand for downsizing of equipment. In view of the need for a technique for reducing the volume of waste ion-exchange resin generated from power plant facilities as described above, the present inventor studied an effective method for reducing the volume.

The direct combustion method known as a general volume reduction method is a method in which an ion exchange resin is oxidatively decomposed at a high temperature of, for example, 800 ° C. or more in an incinerator, and complete decomposition of an object can be realized. However, NO _X, and that there is a generation of SO _X, when such radioactive materials are the combustion gases required to take measures to ensure that radioactive materials when released to the atmosphere are not included in the waste gas Problem. In addition, since incineration is performed at a high temperature, there is a problem that equipment costs and operation costs increase in terms of durability of the incinerator and consumption of fuel (heavy oil or the like) used for incineration. The wet oxidation method, which is known as another method, has no problem in that NO _x , SO _x and radioactive substances are released into the atmosphere, but the decomposition of ion-exchange resin, which is hardly decomposable, is incomplete and dioxin and the like are not obtained. This may cause another problem of by-producing toxic substances.

[0005] Because of these problems, the direct combustion method and the wet oxidation method described above are limited to objects that are relatively easy to decompose.

On the other hand, the supercritical water oxidation treatment method is attracting attention as a technique for treating a hardly decomposable substance such as a chlorine compound, a nitrogen compound or a sulfur compound in the chemical structure of the substance (for example, See Japanese Patent Publication No. 38532/1993.

In this treatment method by supercritical water oxidation, an object to be decomposed is supplied to a reaction field in a supercritical water atmosphere, and at the same time, an oxidizing agent such as oxygen and supercritical water are supplied. This method oxidizes and decomposes substances to be decomposed under supercritical conditions. The generated fluid is cooled, the gas (mainly carbon dioxide) is depressurized by a decompression mechanism, and then discharged to the atmosphere through an exhaust pipe. This removes the inorganic substances and the like contained therein and discharges the condensed water through a drain pipe. In this method, water (supercritical water) under the critical condition of water, that is, under the condition that the critical temperature is 374 ° C. and the critical pressure is 22 MPa is exceeded.
Of organic matter can be controlled by temperature and pressure, so that non-polar substances such as paraffinic hydrocarbons and benzene can be dissolved. It shows extremely excellent properties as a reaction solvent for decomposition, and if the decomposition target has a carbon content of several percent, it can maintain the reaction temperature only by its own heat of oxidation (or supply of a small amount of auxiliary fuel). Decomposable organic substances and toxic organic wastes can be completely decomposed by appropriately controlling hydrolysis and thermal decomposition reactions in supercritical water, and in particular, harmful organic substances can be treated in closed systems. It is very suitable for the decomposition process. In addition, even when a radioactive substance is contained, the radioactive substance can be reliably and efficiently captured in the water or gas discharge system, so that it is also suitable for the oxidative decomposition treatment of ion exchange resin from nuclear power plant equipment. It has the advantage of being used.

[0008]

The above-mentioned ion-exchange resin is a solid in the form of powder and granules. When this is treated by supercritical water oxidation, the following problems arise. That is, the treatment method of supercritical water oxidation is characterized by maintaining the reaction temperature using the heat of oxidation generated when the decomposition target is oxidatively decomposed, and when processing hardly decomposable organic substances,
If this is incompletely decomposed, the above-mentioned toxic substance such as dioxin may be by-produced. Therefore, it is necessary to avoid as much as possible the occurrence of uneven reaction temperature in the reaction field for complete decomposition. For this reason, in the supercritical water oxidation treatment, it is necessary to avoid fluctuations in the amount of heat of oxidation generated in the reaction field, and it is important to avoid fluctuations in the concentration of the decomposition target (concentration unevenness) that directly affect the fluctuations in the heat generation. Become. However, it is not always easy to transport (supply) the ion-exchange resin without pulverizing the ion-exchange resin into the reaction field in a state where the concentration is not uneven.

The reason why the density unevenness is likely to occur is considered as follows. In other words, the supercritical water oxidation treatment is a special treatment condition that supercritical water oxidation is performed by supplying a decomposition target at a relatively low speed to a reaction field under a pressure exceeding the critical pressure of water. This is one of the causes. In general, in the transportation of a granular material, the specific gravity, the shape, the particle size, the physical properties of the granular material such as a dispersion type or an integrated type, and the transport fluid (fluid)
Properties, transport pressure, transport speed, etc. are related as factors of transport efficiency, for example, transport fluid and transported material (granules)
If there is a difference in specific gravity, the discharge pressure of the pump is increased to increase the transport speed, etc., to prevent the sedimentation of the granular material, which leads to the accumulation of the granular material in the transport pipe and the stagnation in the pump. Methods of transportation are conceivable. However, in the case of transporting solids from a low pressure to a high pressure in order to perform supercritical water oxidation, a positive displacement pump (plunger pump, piston pump, diaphragm pump) is usually used. This is because it is inevitable to generate transport unevenness (pulsation) peculiar to the positive displacement pump during the continuous transport of.

In a general transport system, a secondary fluid can be supplied to a position where the granular material is likely to settle to fluidize the granular material, or gas can be bubbled to fluidize. In the transport system for supercritical water oxidation, a separate high-pressure pump is required to supply the secondary fluid, which incurs equipment costs and control burdens. The adoption is difficult because there is a great risk of causing trouble.

[0011] Apart from the above problems, the above-mentioned unevenness in concentration is caused by the addition of a neutralization salt to neutralize the generated acid in the case of a decomposition target in which a neutralized salt must be formed by the reaction. Although it is desired from the viewpoint of volume reduction to add the neutralizing agent as close to the equivalent as possible, it is necessary to excessively add the neutralizing agent based on the upper limit value of the density unevenness that fluctuates. In particular, when performing processing such as concentrating and storing the reaction product solution containing a radioactive substance or the like, the concentration of inorganic salts contained in the solution increases, so that the subsequent concentration reduction process becomes disadvantageous. There are also bugs that can lead to problems.

[0012] From the above, for example, when supercritical water oxidation treatment is performed on a granular material (solid matter) such as an ion exchange resin,
It is necessary to prevent adverse effects due to accumulation and stagnation in the supply pipe and pump, and to prevent uneven concentration of the decomposition target that is continuously supplied to the reaction field. It is thought to increase.

However, this method is not advantageous as an industrial facility because a device for crushing and pulverizing is required, and control of the pulverized particle size is required, so that this step is omitted if possible. It is desirable to reduce the burden. In addition, since ion-exchange resins are difficult to be wet-pulverized, pretreatment for drying is required prior to pulverization, and the method of performing pulverization is more burdensome.

The present invention overcomes the above-mentioned problems peculiar to the treatment in a supercritical water atmosphere as described above, typically in the treatment of supercritical water, and particularly, makes it possible to efficiently decompose the hardly decomposable organic substances. The purpose of the present invention is to provide a method and an apparatus for transporting an object to be decomposed which are suitable for realizing the method.

Another object of the present invention is to reduce the burden of pulverization processing without pulverization, particularly when the used waste ion exchange resin is oxidatively decomposed and reduced in volume by a supercritical water oxidation method. It is an object of the present invention to provide a transport method and an apparatus which can be efficiently transported to a reaction field without concentration unevenness and can realize a suitable treatment.

Still another object of the present invention is to provide a supercritical water oxidation method for oxidatively decomposing solid matter such as waste ion exchange resin, in which the amount of a neutralizing agent added for neutralizing the generated acid is reduced as much as possible. It is an object of the present invention to provide a transportation method and apparatus capable of reducing the volume of waste as much as possible.

[0017]

The above objects of the present invention are as follows.
This is achieved by the invention described in each claim of the above claims.

A feature of the method for transporting solids to a reaction field in a supercritical water atmosphere according to claim 1 of the present application is that a transport fluid containing powdery solids to be decomposed is subjected to low pressure (generally, normal pressure). A transport method for continuously supplying a reaction field maintained in a supercritical water atmosphere exceeding a critical pressure of water from below, wherein the transport fluid includes an organic compound that increases the viscosity of the transport fluid. It is characterized by adding an agent.

In the above invention, the reaction carried out in the reaction field in a supercritical water atmosphere is carried out under either a non-oxidizing atmosphere in which no oxidizing agent is present or an oxidizing atmosphere in which an oxidizing agent is present. Is also good. The reaction in a non-oxidizing atmosphere is generally performed for the purpose of recovering oil, and the reaction in an oxidizing atmosphere is generally performed for the purpose of complete decomposition. As the oxidizing agent used for performing the oxidation reaction, generally, air, oxygen, an oxygen-enriched gas can be used, and a liquid oxidizing agent such as hydrogen peroxide solution or a solid oxidizing agent can also be used. it can. The supercritical water atmosphere is given by setting the reaction field to a critical temperature of water of 374 ° C. or more and a critical pressure of 22 MPa or more, preferably 22 to 25 MPa, 400 to 250 MPa.
650 ° C. The reaction is carried out for 1 to 10 minutes, preferably 1 to 10 minutes.
It takes 2 minutes.

The reaction field in the supercritical water atmosphere is formed in a reactor such as a tubular (pipe) reactor or a vertical cylindrical so-called Bessel reactor, and contains a fluid containing solid matter to be decomposed. The reaction is performed using a known apparatus in which a supply system for supplying supercritical water, an oxidizing agent, a neutralizing agent, and the like as necessary, a heating unit, a cooling unit, a pressurizing unit, and a depressurizing unit are arranged at appropriate positions. Can be done.

As a transport fluid for the decomposition target, water is generally used industrially, but is not limited thereto. In the following description, a case where general “water” is used as a transport fluid will be described.

The present invention is intended to enable the transport of solids which are difficult to transport evenly with a positive displacement pump without causing unevenness in concentration over time. Among solids, those with the same specific gravity as water can be transported without causing concentration unevenness over time.However, in general, solids often have a specific gravity difference with water, and these settle in still water. Alternatively, suspended, especially sedimentable solids may not be transported by high pressure pumps. Representative examples of the sedimentable organic solid include used waste ion exchange resin, waste activated carbon, and waste sedimentation aid having large sedimentation. In addition, examples of the floating solid include plastic and the like. However, the object of the present invention is not limited to this.

The size of the granular material is not particularly limited as long as it does not hinder the supply to the above-mentioned reaction field. Specific gravity and the like cannot necessarily be determined uniformly, but generally those having an upper limit of 1 mm or less, preferably 0.5 mm or less are targeted. If the decomposition target is small, there is little possibility of a problem due to the sedimentation in the transport system unless the specific gravity is extremely large. Conversely, if the decomposition target is too large, there is a high possibility that clogging in the positive displacement pump or the piping will cause poor transport. Solids that can be transported by the method of the present invention generally have a specific gravity of 3
The following can be mentioned.

As the thickener comprising an organic compound used in the above-mentioned invention, starch, sugar, or an organic polymer compound shown in Table 1 below is preferably used. The thickener may or may not be water-soluble and may disperse solids in colloidal form.

[0025]

[Table 1]

The reason why an organic compound is used as a thickener in the present invention is that this thickener is also decomposed by a reaction in a supercritical water atmosphere. Therefore, those which are easily decomposed by an oxidation reaction or the like are preferably used.

[0027] The degree of thickening depends on the size and specific gravity of the solid, but if the viscosity is too high, it will hinder the transport of the fluid in the pipe and the pump discharge, so that the transport of the fluid containing the solid to the reaction field will be hindered. The thickener can be selected and the amount added can be adjusted within a range where there is no such amount, and is generally 50 to 250 cP, preferably 100 to 150 cP, but the amount added can also be confirmed experimentally. In addition, by mixing a substance that makes the specific gravity of the fluid the same as that of the organic solid, the powdery organic solid can be transported by a fluid without sedimentation. In general, substances generally also have a thickening effect, and substances having an action of adjusting specific gravity together with thickening are not excluded from the thickener of the present invention.

The thickening effect of water due to the addition of a thickener decreases as the temperature rises. However, the occurrence of uneven transport during the transport of solid matter is mainly caused by passing through a high-pressure pump. Since it passes through the process at a low temperature, even if the temperature rises due to preheating or the like in the vicinity of the reactor, the supercritical reaction proceeds immediately thereafter, so there is no significant effect. Either addition or mixing of the organic solid and the thickener to the transport fluid may be performed first.

According to the method of the present invention, the concentration unevenness when the powdery organic solid is transported under a high pressure at a relatively low speed (0.1 m / s or less) by a positive displacement pump such as a plunger pump is large. To be reduced. Therefore, the temperature fluctuation when the reaction is maintained by the heat generated during the decomposition can be prevented, and the risk of incomplete decomposition can be reduced or eliminated. Further, since the concentration unevenness can be suppressed, it is possible to prevent a disadvantage that the amount of the neutralizing agent when the acid is contained in the generated fluid must be excessively added.

[0030] The invention of claim 3 of the present application is characterized in that the above-mentioned thickener does not contain an element which generates a corrosive acid for metals, and the invention of claim 4 is the above-mentioned thickener. Does not contain a substance that generates a neutralized salt of an acid and an alkali. As such a thickener,
For example, starch, sugar, polyacrylamide and the like can be mentioned.

According to these inventions, for example, by using a thickener which does not contain an element such as Cl or S which generates hydrochloric acid or sulfuric acid, when the decomposition target does not similarly generate an acid, It is not necessary to add a neutralizing agent (alkali), and it is not necessary to use an excessively large amount of the neutralizing agent even when the decomposition target is an acid. In addition, the amount of salt generated can be suppressed, so that the final amount of waste can be reduced, and especially the volume of hardly decomposable substances or the waste waste ion exchange resin discharged from nuclear power plants by supercritical water oxidation. It is effective for conversion processing.

According to the invention of claim 5 of the present application, the reaction performed in the reaction field maintained in the supercritical water atmosphere is an oxidation reaction (supercritical water oxidation reaction) performed in the presence of an oxidizing agent, or an oxidizing agent. Is a non-oxidative decomposition reaction (supercritical water decomposition reaction) in which is not present.

According to the present invention, for example, as set forth in claim 7, the used waste ion exchange resin can be completely oxidized and decomposed to greatly reduce the volume, and the crushing treatment of the ion exchange resin can be performed. This is extremely useful when used in a method for reducing the volume of an ion-exchange resin, which is not easily crushed, because it is unnecessary or the burden of crushing can be reduced. In general, the specific gravity of the ion exchange resin in the form of powder is 1.1 to 1.3.
The present invention is applicable to both cation exchange resins and anion exchange resins. In addition, when these are mixed and transported,
The present invention can be applied to any of the cases where they are separately transported.
In the case of transporting separately, since the anion exchange resin and the cation exchange resin generally have a difference in specific gravity (usually, the specific gravity of the cation exchange resin is large), the specific gravity difference may be separated by backwashing and sedimentation.

Since the anion exchange resin of the above does not generally contain a substance which generates an acid, it does not contain an element which generates a corrosive acid for metals as the above-mentioned claim 3 as a thickener. By using a material that does not contain a substance that forms a neutralized salt of an acid and an alkali according to the fourth aspect, it is possible to make it free of salt that is a final waste.

The invention of an apparatus for transporting solids to a reaction field in a supercritical water atmosphere according to claim 8 of the present invention is a method for transporting a transporting fluid containing powdered solids to be decomposed under low pressure (usually normal pressure). A fluid transport device for continuously supplying a reaction field maintained in a supercritical water atmosphere exceeding the critical pressure of water from a fluid, comprising a thickening organic compound that increases the viscosity of the transport fluid. Thickening agent adding means for adding an agent, and pressurizing the transport fluid containing the thickener and the decomposition target from a low pressure to a pressure exceeding the critical pressure of water, and providing a transport force to be supplied to the reaction field. A high-pressure transport pump.

In the above structure, the solids can be mixed with the transport fluid generally in a mixing tank under normal pressure, or can be mixed in a pipe. It is preferable to provide an appropriate stirring device in these mixing tanks and mixing pipes. The mixing of the solids may be performed before or after the addition of the thickener to the transport fluid.

As the high-pressure pump, a positive displacement pump such as a plunger pump, a piston pump, or a diaphragm pump is used, and the supply of fluid from the mixing tank or the like to the high-pressure pump can be performed using a slurry pump.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

Embodiment 1 FIG. 1 shows that supercritical water oxidation treatment of an ion exchange resin is performed.
FIG. 1 is a diagram showing an outline of the flow of each substance when an apparatus to which the transportation method of the present invention is applied, in which 1 is an open-to-atmosphere type mixing tank, which is filled with a predetermined amount of water; A predetermined amount of the used waste ion exchange resin is added from the sample tank 2 and a predetermined amount of the thickener is added from the thickener tank 3. Reference numeral 4 denotes a stirring device provided in the mixing tank 1, and
The mixed liquid containing the ion exchange resin and the thickener is sufficiently stirred and mixed in the slurry to form a slurry in a state where the ion exchange resin is substantially uniformly dispersed in water (hereinafter referred to as “slurry”).
I do.

Reference numeral 5 denotes a slurry pump. The slurry is sent to the suction side of the high-pressure pump 6 by the slurry pump 5 via the transport pipe 7, and the excess is returned to the mixing tank 1 by the return pipe 8.

The high-pressure pump 6 is configured as a positive displacement plunger pump, for example, and pressurizes the slurry sent to the suction side by the transport pipe 7 and discharges the slurry to the high-pressure transport pipe 9. The high-pressure transport pipe 9 transports and discharges the discharged slurry to a reactor 10 for performing supercritical water oxidation. In the case of a hardly decomposable ion exchange resin (for example, a cation exchange resin), a vessel type is preferably used for the reactor 10, and a neutralizing agent is added to neutralize the generated acid. An agent supply pipe can be provided. In addition, in the case of an anion exchange resin, it is often unnecessary to add a neutralizing material, so a pipe-type reactor can be used, but none of them is limited.

A pre-heater (not shown) may be arranged in the middle of the high-pressure transport pipe 9 (preferably near the reactor) to pre-heat the mixture to a predetermined temperature.

The high-pressure transport pipe 9 is provided so that air pressurized to a high pressure on the way is joined from the oxidant supply pipe 11 as an oxidant, and supercritical water is joined from the supercritical water supply pipe 12. The supercritical water reaction product fluid discharged from the reactor 10 to the discharge pipe 13 is discharged out of the system through a predetermined process such as cooling and decompression.

According to the apparatus of this embodiment, since the thickener is added to the water containing the ion exchange resin in the mixing tank 1 under normal pressure, sedimentation of the ion exchange resin is suppressed by the thickening action,
The slurry is satisfactorily transported by the transport pipe 7, and is satisfactorily transported in the high-pressure pump 6 and the high-pressure transport pipe 9 discharged from the slurry without causing stagnation or accumulation. Thereby, the mixed solution continuously transported from the high-pressure pump 6 to the reactor 10 is supplied to the reactor 10 in a state of a stable ion exchange resin concentration without causing large concentration unevenness, and is supercritically hydroxylated. It does not cause a large fluctuation of the reaction temperature. Therefore, in particular, it is possible to completely decompose the hardly decomposable ion-exchange resin by supercritical water oxidation, and to reduce the risk of inconvenience of generating harmful substances due to insufficient decomposition.

Although the apparatus of this example has the above-described configuration, the apparatus of the present invention is not limited to this example, and variously modified embodiments can be used. For example, it is also possible to continuously supply and mix the ion exchange resin while flowing water added with a thickener in advance into the transport pipe.

REFERENCE EXAMPLE 1 In this example shown in FIG. 3, the system for adding the thickener from the thickener tank 3 is omitted, and the route for adding the used waste ion exchange resin from the sample tank 2 to the mixing tank 1 is omitted. The example in which the crushing device 14 is provided in the middle of FIG. Other configurations are the same as those in FIG. 1, and the same devices and members are denoted by the same reference numerals.

According to this example, since the ion exchange resin is crushed by the crushing device 14, the fluidity of the solid material increases,
The risk of malfunctions such as clogging in the high pressure pump is reduced.

That is, since the ion-exchange resin has sedimentation properties with respect to water as a transport fluid, the ion-exchange resin stays in the high-pressure pump 6 in a non-pulverized state, and the stay may cause clogging. In addition, the slurry discharged also in the high-pressure pump 6 is deposited in the high-pressure transport pipe 9 and
May be blocked, but these crushing processes reduce these risks.

However, the above-described apparatus 14 for crushing (crushing) the ion exchange resin is required, and since the ion exchange resin is generally dried after wet crushing is generally difficult, a drying step is further required. In this point, the burden on equipment and the burden on operation increase. In particular, in the case of an ion exchange resin containing a radioactive substance, it is difficult to adopt the ion exchange resin because an increase in the handling load in processes such as drying and crushing is a serious problem.

[0050]

【Example】

Example 1 Using the apparatus shown in FIG. 1, under the following conditions, a supercritical water treatment was carried out using water as a transport fluid without crushing the ion-exchange resin into a reactor for supercritical water oxidation treatment. An oxidation treatment was performed.

Transport system Mixing amount with ion exchange resin: Type: anion exchange resin (Amberlite (registered trademark) IRA-400T): (specific gravity: 1.1, particle size: 0.4 to 0.6 mm)・ ・ 2wt% Thickener and amount added: Type ・ ・ ・ Polyacrylamide concentration ・ ・ ・ 0.1% Slurry pump: Transport amount ・ ・ ・ 50ml / min (return amount 22ml
/ Min) Type of high-pressure pump and discharge rate: High-pressure pump: 2 syringe pumps Discharge rate: 28 ml / min Reactor and supercritical water oxidation treatment Reactor: tubular reactor (diameter 6.8 mm) , Length 15
m) Temperature: 650 ° C. Pressure: 25 MPa Oxidizing agent: 30% H ₂ O ₂ , oxygen ratio: 1.5 Transport of ion-exchange resin under the conditions above, supercritical performed in the reaction vessel FIG. 2 shows the results of measuring the temperature of the hydroxylation reaction for each distance from the slurry supply port to 8 m.
The temperature was measured using a large number of thermocouples installed on the outer wall of the reactor.

As can be seen from the results, the temperature rises smoothly in the reactor and reaches a predetermined target temperature (600 in this example).
〜650 ° C.) was obtained stably over a relatively long range in the reactor.

Comparative Example 1 Using the apparatus of FIG. 1, the same type of ion exchange resin of the same type as in Example 1 was subjected to supercritical water oxidation treatment under the same conditions except that no thickener was added. As a result, the ion exchange resin was clogged in the pump and the piping, that is, could not be sent to the reactor.

Comparative Example 2 Using the apparatus shown in FIG. 3, the same amount and the same amount of ion exchange resin were crushed so as to be 0.1 mm or less, and the same supercritical water oxidation treatment was carried out without adding a thickener. Was done. As a result, as shown in FIG. 4 (the temperature distribution from the slurry supply port to 8 m from the slurry supply port as in FIG. 3), the reaction temperature during the operation became lower at the inlet.

It is considered that the reason for this is that, even though the material was crushed, the concentration of the substance to be decomposed was uneven unless the thickener was added. When the inflow of the object of the subcommittee decreases due to the occurrence of unevenness, the calorific value corresponding to the decrease decreases, so that the temperature at the reactor inlet decreases as shown in FIG. Oxidative decomposition becomes unstable.

[0056]

As described above, according to the present invention which provides a method or an apparatus for transporting a powdery solid to a reaction field in a supercritical water atmosphere, the following effects are obtained as compared with the conventional method. Is played.

By adjusting (enhancing) the viscosity of the transport fluid, it is possible to transport and supply the sedimentable or buoyant powdery solids to the reaction field in a state of being uniformly dispersed in the transport fluid. it can. Therefore, it is possible not only to prevent the decomposition target substance, which is the above-mentioned powder and granules, from staying and clogging in the middle of the transport system applied to the treatment in the supercritical water atmosphere. It is possible to reduce or eliminate the concentration unevenness of the decomposition target supplied to the furnace, thereby preventing incomplete decomposition due to instability of the reaction temperature in the case of oxidation treatment, and in the case where an element that generates an acid is contained. Excellent effects, such as a reduction in the amount of added humectant, can be achieved.

According to the third and fourth aspects of the present invention, it is possible to reduce the amount of the salt substance finally produced by the neutralization, and particularly to reduce the volume of the substance containing a radioactive substance (for example, an ion exchange resin). It is extremely useful for conversion.

When the ion-exchange resin is used as the decomposition target, the burden on the processing operation for the material which is not easily crushed and pulverized can be reduced. It is very effective when used in a process for reducing the volume of an ion-exchange resin containing a radioactive substance by oxidizing, for example.

Since the thickener added in the present invention is an organic compound, the heat of its decomposition reaction is also used as the heat of reaction for maintaining the supercritical water reaction.
For example, there is also an advantage that the amount of addition can be reduced when an auxiliary heat generating substance is used in the treatment of a solid material having a relatively low heat generation.

[Brief description of the drawings]

FIG. 1 is a flow chart showing a schematic configuration of a supercritical water oxidation apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a temperature distribution in a reaction vessel during supercritical water oxidation treatment of Example 1 performed using the apparatus of Embodiment 1.

FIG. 3 is a flowchart showing a schematic configuration of a supercritical water oxidation apparatus of Reference Example 1.

FIG. 4 is a view showing a temperature distribution in a reaction vessel during supercritical water oxidation treatment of Comparative Example 1 performed using the apparatus of Reference Example 1.

[Explanation of symbols]

Reference Signs List 1 mixing tank, 2 sample tank, 3 thickener tank, 4 stirring device, 5 slurry pump,
6 ... High pressure pump, 7 ... Transport pipe, 8 ... Return pipe, 9 ... High pressure transport pipe, 10 ... Reactor, 11 ...
・ Neutralizer supply pipe, 12 ・ ・ ・ Supercritical water supply pipe, 13 ・ ・
· · · · · · · · · Discharge pipe, 15 · · · crushing device.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinichi Ohashi 1-4-9 Kawagishi, Toda City, Saitama Prefecture Inside Organo Research Institute (72) Inventor Taro Kuramochi 1-4-9 Kawagishi, Toda City, Saitama Prefecture Organo Research Institute

Claims (9)

[Claims] 1. A transport method for continuously supplying a transport fluid containing a particulate solid substance to be decomposed from a low pressure to a reaction field maintained in a supercritical water atmosphere exceeding a critical pressure of water. A method of transporting a solid to a reaction field in a supercritical water atmosphere, wherein a thickener comprising an organic compound that increases the viscosity of the transport fluid is added to the transport fluid. 2. The method according to claim 1, wherein the substance to be decomposed is a substance having a sedimentation property with respect to a transport fluid before adding a thickener, or a substance having a floating property. A method of transporting solid matter to a reaction field in a critical water atmosphere. 3. The method according to claim 1, wherein the thickener does not contain an element that generates a corrosive acid for a metal. how to. 4. The method according to claim 1, wherein
A method for transporting a solid substance to a reaction field in a supercritical water atmosphere, wherein the thickener does not contain a substance that generates a neutralized salt of an acid and an alkali. 5. The method according to claim 1, wherein
The reaction performed in the reaction field maintained in the supercritical water atmosphere is
A method for transporting a solid substance to a reaction field in a supercritical water atmosphere, which is either an oxidation reaction performed in the presence of an oxidizing agent or a non-oxidative decomposition reaction in the absence of an oxidizing agent. 6. The method according to claim 1, wherein
A method for transporting a solid to a reaction field in a supercritical water atmosphere, wherein the transport fluid is water. 7. The method according to claim 1, wherein
A method for transporting a solid to a reaction field in a supercritical water atmosphere, wherein the powdery and solid matter to be decomposed is an ion exchange resin, and the supercritical water atmosphere is maintained under oxidizing conditions. 8. Fluid transport for continuously supplying a transport fluid containing a particulate solid as a decomposition target to a reaction field maintained in a supercritical water atmosphere exceeding a critical pressure of water from a low pressure. An apparatus, comprising: a thickener adding means for adding a thickener made of an organic compound that increases the viscosity of the transport fluid; and transporting the transport fluid containing the thickener and the decomposition target from normal pressure to water. A high-pressure transport pump that pressurizes to a pressure exceeding the critical pressure and supplies a transport force to the reaction field, and transports solids to the reaction field in a supercritical water atmosphere. 9. The method according to claim 8, further comprising a storage tank for storing a transport fluid containing the decomposition target, and a means for adding the decomposition target and / or a thickener to the storage tank. A device that transports solids to a reaction field in a supercritical water atmosphere.