JP3344999B1 - Melt processing method and processing container - Google Patents

Abstract

An object of the present invention is to improve the energy efficiency and the surrounding soil by preventing the release of gas generated from the melting area to the surroundings and the influence of water from the surroundings when melting the contaminated soil. The present invention provides a melting treatment method and a treatment container for preventing the contamination of the material. SOLUTION: A water-impervious outer container 1 is embedded in the ground, and an inner container 2 is disposed in the container via a clean soil CS. The contaminated soil is accommodated in the inner container, and the electrodes ME1 and ME2 are energized to melt the contaminated soil to form a vitrified body. The inner container is composed of a porous air-permeable inner layer body and an outer layer body having a sealing property against generated gas up to a temperature at which pollutants decompose and volatilize. The gas generated in the process of melting contaminated soil is
In addition to the path in the direction a, the gas passes through the inner layer body and is discharged into the off-gas hood H.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting method and a processing container therefor, and more particularly to a method for melting contaminants in soil using in situ vitrification (ISV) technology.
TECHNICAL FIELD The present invention relates to a melting method and a processing container which eliminate the influence of generated gas or the like accompanying melting of contaminants.

[0002]

2. Description of the Related Art Recently, environmental problems such as contamination of soil by spills of used harmful chemicals or residues containing harmful substances have been increasing in factories and laboratories in various places. . Therefore, a technique for restoring the contaminated soil to its original state or removing contaminants is required, and various studies have been made for that purpose.

Under such circumstances, as one of the countermeasures,
In situ vitrification (ISV) technology has been developed that purifies contaminated soil by melting and vitrifying the soil itself in situ where the contaminants are present in the soil. FIG. 3 shows a procedure of a melting treatment system for vitrifying contaminated soil itself using the ISV technology.

[0004] As shown in FIG. 3 (A), first, the surrounding soil S on which the contaminated soil S2, which is the original position to be melted, exists.
In 1, the off-gas hood H is covered with clean soil so as to cover the entire upper part of the contaminated soil S2 to be purified.
Is installed. Further, the melting electrodes ME1 and ME2 are inserted into the clean earth covering soil. Next, a conductive resistance path R for enabling initial energization is formed between the melting electrodes ME1 and ME2.

Here, each melting electrode withstands high temperatures.
For example, a rod-shaped electrode made of graphite is used. The offgas hood H is connected to a pipe for discharging gas generated during the purification process from the contaminated soil S2 to be purified to the offgas treatment system.

When the preparation for melting is completed, the melting electrode M
Electric power supplied from a generator or system power is supplied to E1 and ME2. At this time, since the conductive resistance path R exists, Joule heat is generated in the resistance path R, and the Joule heat causes the resistance path and the surrounding soil to be melted and become magma-like.

As shown in FIG. 3 (B), when the energization is continued and the soil is melted, the electric resistance of the melted portion is greatly reduced, so that the electric power supplied from the melting electrodes ME1 and ME2 causes the resistance to decrease. The road R and the soil adjacent thereto are melted one after another, and a melting area MG is formed. The melting region MG gradually expands downward from above.

In accordance with the expansion of the melting, the melting electrode ME
1 and ME2 are also inserted further down. At this time, the melting electrode is inserted so as to sink downward according to the melting of the soil due to the weight of the electrode itself.

In this way, if the entire area including the entire contaminated soil S2 requiring the purification treatment can be melted,
The power supply to the melting electrodes ME1 and ME2 is stopped.
As shown in FIG. 3 (C), the volume of the molten area MG in which the contaminated soil S2 has been melted is 25% to 50% when viewed from the initial state.
Therefore, the depressed portion is back-filled with new soil S3.

[0010] Since one batch process for the contaminated soil S2 to be purified is completed, the offgas hood H is moved to the next batch process.

According to the ISV technology described above, detoxification processing can be executed at the original position by using portable equipment. Contaminated soil that is difficult to dig can be treated as it is. Contaminated soil that can be dug up is stored in a special partition, melted in that partition, and clean soil can be backfilled, so transport it to another location such as a disposal site. No need.

When the ISV technology is used for melting and solidifying contaminated soil, for example, heavy metals and radioactive substances in soil are confined in the molten and solidified vitrified material, or hardly decomposable harmful organic substances such as dioxin. When the soil is melted, it can be detoxified by thermal decomposition at a high temperature of 1600 to 2000 ° C.

Furthermore, in addition to the contaminated soil, solid substances such as incineration ash, refractory bricks, drums, and the like, and combustible substances such as plastics can be collectively treated in the same shape. Moreover, by melting and solidifying the soil, not only can the volume be reduced significantly to reduce the volume,
It has the characteristic that a long-term stable state can be maintained by vitrification.

[0014]

SUMMARY OF THE INVENTION However, the ISV
When using technology to contaminate soil or soil embedded with solids, etc., when melting and vitrifying, the contaminants, solids, etc. contained in the soil burn, evaporate, evaporate, Alternatively, gas is generated in the melting process due to thermal decomposition or the like.
Since this generated gas contains a trace amount of harmful components, as shown in FIG. 3, the contaminated soil to be subjected to the melting process should not be released into the atmosphere during the melting process. An off-gas hood H covering S2 is provided. The generated gas collected in the off-gas hood H is sent to the off-gas processing device, and is discharged to the atmosphere through a secondary heat treatment, a filter, and the like.

Here, as shown in FIG. 3, the generation of gas during the melting process of the contaminated soil S2 will be described by taking as an example the case where the contaminated soil S2 is melted by the ISV technique. 4 (A) to 4 (C) each show a state during the melting process in FIG. 3 (B).

FIG. 4A shows that the contaminated soil S2 is melted,
This shows a state in which the melting region MG is formed. During the melting process, the gas generated from the melting region MG is:
The gas is released into the off-gas hood H as generated gas a mainly from the upper surface of the area MG. However, during the melting process, the gas generated in the melting area MG is not only the generated gas a, but also the surrounding soil S surrounding the area.
In the case of 1, the gas is diffused as the generated gas b through the side surface or the lower surface of the region. It is conceivable that the diffused generated gas b permeates the surrounding soil S1 and is released as the generated gas c.

As shown in FIG. 4B, the surrounding soil S1 is also heated during the melting process, and as a result, the surrounding soil S1 around the melting area MG is dried to form a dry zone D. is there. This dry zone D has better air permeability than before drying due to drying of the soil itself. Therefore, the generated gas b coming out of the melting area MG is diffused around the area MG.
Passes through the dry zone D and is released as generated gas d.

As described above, while the contaminated soil S2 is being melted, the generated gases a to d are generated and released or diffused. However, the generated gas contains harmful components as described above. Therefore, the generated gases a and d are captured by the off-gas hood H, so that there is no problem. However, as shown in FIG. 4A, the generated gas c is directly released to the atmosphere.
Environmental pollution problems occur. Further, a part of the generated gas b may become the generated gas c, or may remain in the surrounding soil S1 even after the melting area MG is cooled. Assuming that the harmful components remain in the surrounding soil S1, there is a problem that even if the contaminated soil itself can be treated, the surrounding soil is contaminated.

On the other hand, when the melting treatment of the contaminated soil is performed in rainy weather, since the upper part of the treatment target area is covered with the off-gas hood H for capturing generated gas, rainwater does not directly enter the melting area MG. . However, depending on the state of the surrounding soil S1, rainwater may penetrate into the soil and reach around the melting area MG. In such a case, the melting energy is consumed by the evaporation of the infiltrating rainwater, and extra power must be supplied from the melting electrodes ME1 and ME2. There is a problem that the melting efficiency is deteriorated, and the melting process is difficult in rainy weather.

Further, the infiltration of water into the melting area MG is not limited to rainwater, and the contaminated soil S2 may be close to groundwater as shown in FIG. 4C. In this case, the water W rises one by one from the groundwater to the melting area MG via the surrounding soil S1, and the melting energy is greatly consumed for the evaporation of the rising water W. In addition, there is a problem that the time of the melting process becomes long.

In some cases, the contaminated soil itself is a wetland that must be melted, or, as described above, solids and the like are dumped in the wetland, and these are collectively melted together with the soil. You may have to deal with it. However, even in these cases, the melting energy is largely consumed for evaporating the water contained in the wetland, which makes it difficult to melt the contaminants in situ.

Therefore, the present invention does not diffuse the gas generated from the melting region to the surroundings when melting the contaminants by using the ISV technology, and prevents the gas from being affected by the water from the surroundings. It is an object of the present invention to provide a melting treatment method and a treatment container for preventing the contamination of surrounding soil in a specific manner.

[0023]

In order to solve the above-mentioned problems, the present invention provides a method for melting an object, comprising melting a gas-permeable layer member in a container having an inner wall surface. By storing the target object and energizing the target object, the target object is melted in the container, and the gas generated in the melting process of the target object is captured, and the melting process of the target object is performed. And

The object is contaminated soil,
Alternatively, as a soil containing solid matter, the wall of the container includes an inner layer of the layer member and an outer layer that seals a gas generated in a process of melting the object, and the inner layer is formed in a porous shape, The outer layer is formed of a material having a gas sealing property at least up to a decomposition temperature of a substance contained in the object.

Further, the container is disposed in an outer container formed in the soil, and the space between the container and the outer container is filled with a filler, and the filler is clean soil. .

Further, in the present invention, in order to melt and solidify the object by energizing the object, in the melting processing container for storing the object, an inner layer made of a gas-permeable layer member and a gas generated from the object are provided. And an outer layer having a function of sealing a gas to be sealed.

The space between the wall and the outer container, including the outer container surrounding the outer periphery of the wall, is filled with a filler, and the object is contaminated soil or solid material. Soil.

Further, the layer member is formed in a porous shape, is formed of a material having a sealing property up to the decomposition temperature of the substance a contained in the object, and clean soil is used for the filler. And

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a melting treatment method and a treatment container according to the present invention for melting and contaminating contaminants together with soil and vitrification will be described with reference to FIGS. 1 and 2. FIG.

As shown in FIG. 3 or FIG. 4, in the conventional vitrification of contaminants by melting using the ISV technique, the contaminants are melted in situ and vitrified. Utilizing the feature of performing the melting, the melting electrode is directly inserted into the contaminant to be melt-processed in the surrounding soil, and power is supplied thereto. There, the contaminants are melted by the power and a melting zone is formed in the soil, which is in direct contact with the surrounding soil. For this reason, the gas generated from the melting region is diffused into the surrounding soil, or is affected by moisture contained in the surrounding soil during the melting process.

Therefore, in the process of melting contaminants using the ISV technology according to the present embodiment, in the original position where the contaminants are present, a processing container capable of storing the contaminants to be melted in a state isolated from the surrounding soil. Was used. In this processing container, a contaminant is formed by a power supplied from the melting electrode to form a melting region.

Further, the processing container used in the present embodiment has an inner container and an outer container, and the inner container comprises an inner layer and an outer layer, and the inner layer is formed of a layer member having air permeability. And the outer layer body is made of a material having a function of sealing gas generated from contaminants to be melt-processed.

FIG. 1 shows a method for melting contaminants using the ISV technology according to the present embodiment. In FIG.
Similar to FIG. 3, an example is shown in which the contaminated soil S2 exists in the clean surrounding soil S1. This contaminated soil S2 is
We are trying to melt and reduce the volume by V technology.
Here, the difference between the melting method of FIG. 1 and the conventional method of FIG. 3 is that the contaminated soil S2 is melted after being stored in the processing container.

Next, a specific example of a procedure according to the melting treatment method according to the present embodiment will be described. Here, the contaminated soil S
2 is buried in the surrounding soil S1, and it is not possible to excavate the contaminated soil S2 and carry it to another place for environmental protection. Therefore, the treatment for the contaminated soil S2 must be performed in the site where the contaminated soil S2 exists, and the above-described processing container is installed in an area adjacent to the contaminated soil S2.

Therefore, the operation of installing the processing container will be described first. In the surrounding soil S1 in which the contaminated soil S2 is buried, a hole having a size enough to bury the outer container 1 of the processing container is dug.
The excavated clean soil is stored and later used for backfilling this hole. The excavated clean soil is also used as a filler between the outer container and the inner container.

The outer container 1 is placed in the dug hole. This outer container 1 is made of a shielding material that does not allow generated gas or moisture to pass through,
For example, it is formed of a plate made of steel or the like. This outer container 1
Converts the gas generated in the process of melting contaminated soil into surrounding soil S1.
In the surrounding soil S1 during the melting process.
It has a role in preventing water from entering.

As long as the volume of the contaminated soil S2 is known, the outer container 1 may be manufactured in advance according to the volume, or may be assembled at the site with a steel plate or the like. . Then, when the outer container 1 can be installed in the hole, a part of the clean soil CS dug out before is spread over the bottom of the outer container 1 with a constant thickness, and then the inner container 2 is placed thereon. Further, the space formed between the outer container 1 and the inner container 2 is filled with the previously excavated clean soil CS. In this way, the space between the outer container 1 and the inner container 2 filled with the excavated clean soil CS is left as it is at the treatment site, including the outer container 1 together with the molten vitrified contaminated soil. This is because it can be assumed. Note that the clean soil CS may be a separately prepared filler, or may be recycled for the next melting process.

When the outer circumference of the inner container 2 is filled with the clean soil CS, as shown in FIG. 1, the processing vessel is set in the surrounding soil S1. Therefore, the contaminated soil S2 is dug out, and the contaminated soil S2 is stored in the inner container 2. Thus, as shown in FIG. 3A, a state similar to that of the contaminated soil S2 being buried in the surrounding soil S1 is obtained, and then the clean soil is covered on the contaminated soil S2. 3A is different from the case of FIG. 3A in that the contaminated soil S2 is isolated in the surrounding soil S1 by the surrounding soil S1, the outer container 1, and the inner container 2.

Now that the preparation for melting treatment of the contaminated soil S2 is completed, the entire upper opening of the outer container 1 is covered with the off-gas hood H in the same manner as shown in FIG.
The electrodes ME1 and ME2 for melting are inserted, and a conductive resistance path R is laid between the electrodes ME1 and ME2 for melting.
Then, electricity is supplied to the melting electrodes ME1 and ME2 to start melting the contaminated soil S2. The subsequent melting process is performed in the same manner as in the conventional case. When the melting electrodes ME1 and ME2 sink down by their own weight and reach the bottom of the inner container 2, the melting process in the depth direction of the contaminated soil S2 ends. Suppose you did. As shown in FIG. 1, the contaminated soil S2
The inside is a melting area MG. In this case, the contaminated soil S2 stored in the inner container 2 is melted, but the clean soil CS spread on the bottom of the outer container 1 is not melted.

Here, the structure of the inner container 2 will be described with reference to FIG. FIG. 2 shows an enlarged partial cross-section. The wall of the inner container 2 is formed of a composite layer, for example, an inner layer 3 and an outer layer 4. The inner layer body 3 and the outer layer body 4 may be fixed and combined, or may be overlapped during construction. The inner layer body 3 is formed of a member that is permeable to the gas b generated by the decomposition or volatilization of the pollutant in the process of melting the contaminated soil S2. This air permeability can be achieved, for example, by forming a porous material. This inner layer body 3
Because it is in contact with the contaminated soil S2, during the melting process of the contaminated soil S2, the entire thickness of the layer is not melted,
Be sure to maintain air permeability.

On the other hand, the outer layer body 4 is formed of a material having a sealing property against gas generated at least up to a temperature at which the contaminants contained in the contaminated soil S2 are decomposed or volatilized. For example, a metal plate made of aluminum, steel, or the like, a composite ceramic, or the like can be selected according to the type of contaminant.

As shown in FIG. 2, the inner container 2 is disposed in contact with the contaminated soil S2 on one side and the clean soil CS on the other side. Then, when the melting process for the contaminated soil S2 is started, an evolved gas is generated with the melting. At this time, an evolved gas a that is directly discharged upward of the contaminated soil S2 and an evolved gas b that are generated laterally are generated. The generated gas b is discharged into the inner layer body 3 and
The gas passes through the inner layer body 3 and is discharged to the off-gas hood H.

As described above, in the inner container 2, during the melting treatment of the contaminated soil S2, the inner layer body 3 is moved to the high-temperature melting region MG.
Is formed, the entire layer is not melted, and the function of releasing the generated gas b into the off-gas hood H is maintained. Even if the outer layer body 4 is melted at a temperature at which the molten region MG is generated, the contaminants have already been decomposed or volatilized at this point. For this reason, there is no problem even if the outer layer body 4 is melted and thus has no sealing property against generated gas.

The treatment container as described above is installed as shown in FIG. 1, and the contained contaminated soil is melt-processed by the ISV technique so that the contaminated soil can be detoxified, and the volume reduction process is performed. It can be performed. And
After the melting treatment, it can be made into a harmless vitrified body, so that it can be easily taken out of the processing container and the subsequent handling becomes simple. When a large amount of contaminated soil is buried, the capacity of the processing container may be dug out one after another in a batch manner, and the melting process may be repeated successively.

[0045]

As described above, in the melting treatment of contaminated soil according to the present invention, since a treatment container having an inner container for storing the contaminated soil and an outer container is used, the melting treatment including the treatment container is performed. Not only can the generated gas be prevented from diffusing out of the facility, but also the generated gas can be prevented from diffusing into the surrounding soil or the atmosphere, and secondary contamination due to the melting process can be prevented.

Further, since the outer container is made of a water-blocking material, it is possible to prevent moisture or water from entering the surrounding soil, and the outer container is affected by water even in a place with a high groundwater level or in a wetland. Instead, the melting treatment can be performed, so that the electric energy input for the melting can be efficiently used for the treatment of the contaminants.

Further, by using the inner container composed of the inner layer body and the outer layer body, the decomposition gas generated in the melting process is reliably captured in the off-gas hood. Moreover, when the generated gas contains an organic compound, the flow path through which the gas passes can be limited to a high-temperature region, so that the efficiency of the detoxification treatment of the organic compound can be improved.

[0048] The presence of the inner container makes it possible to clearly separate the range of the formation of the molten vitrified body produced after the contaminant melting treatment and the range of the sintered body produced by sintering the clean soil. The amount of the vitrified molten material can be minimized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view in soil illustrating an embodiment of a melting treatment method according to the present invention.

FIG. 2 is an enlarged view showing a partial cross section of an inner container used in the embodiment.

FIG. 3 is a longitudinal sectional view illustrating an application example of a conventional melting treatment method using an in-situ vitrification (ISV) technique.

FIG. 4 is a diagram for explaining the influence of generated gas and the like in a conventional melting treatment method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Outer container 2 ... Inner container 3 ... Inner layer body 4 ... Outer layer body a-d ... Generated gas CS ... Clean soil H ... Off gas hood ME1, ME2 ... Melting electrode MG ... Melting area S1 ... Peripheral soil S2 ... Contaminated soil

Continuation of front page (56) References US Pat. No. 6,120,430 (US, A) James E. Hansen, Patrick S .; Lowery, Craig L. Timmerman, New GeoMeltTMvitrification technologies for difficult dosing site remediation needs, Proceedings of SPECTRUM'98 International Conference of National Conventions. . , United States, American Nuclear Society, 1998, Vol. 1034-1039 Motoshi Muraoka et al., Dioxin removal by geomelt technology, 100 selected environmental technology for protecting the earth, revised edition, Japan, Pollution Control Technology Co., Ltd., 2000, pp. 118-119 Shigeharu Nakachi, Considering Dioxin Contamination Treatment by the Geomelt Method, Environmental Monitoring, Japan, Medical Laboratories, Minamirokai, Environmental Monitoring Research Institute, 2001, No. 78, pp. 100 1-7 (58) Fields surveyed (Int. Cl. ⁷ , DB name) B09C 1/06 E02D 3/11 JICST file (JOIS) WPI (DIALOG)

Claims (15)

(57) [Claims] An object to be melted is stored in a container having a layer member having air permeability on an inner wall surface, and the object is melted in the container by energizing the object. While capturing the gas generated in the process of melting the material,
A melting method for performing a melting process on the object. 2. The method according to claim 1, wherein the object is contaminated soil. 3. The method according to claim 1, wherein the object is soil containing solid matter. 4. The container according to claim 1, wherein the wall of the container has an inner layer formed by the layer member and an outer layer sealing a gas generated in a process of melting the object. 3. The melt processing method according to item 1. 5. The method according to claim 4, wherein the inner layer is formed in a porous shape. 6. The melting process according to claim 4, wherein the outer layer is formed of a material having a sealing property against the gas at least up to a decomposition temperature of a substance contained in the object. Method. 7. The container according to claim 1, wherein the container is disposed in an outer container formed in soil, and a filling material is filled between the container and the outer container. The melt processing method according to claim 1. 8. The method according to claim 7, wherein the filling is clean soil. 9. A fusion processing container for accommodating an object to be melted by energizing the object, wherein the container is configured to seal an inner layer of a gas-permeable layer member and a gas generated from the object. A melt processing container comprising an outer layer having a function. 10. The melt processing container according to claim 9, further comprising an outer container surrounding the outer periphery of the wall, wherein a filling is filled between the wall and the outer container. 11. The melting processing container according to claim 9, wherein the object is contaminated soil. 12. The melting processing container according to claim 9, wherein the object is soil containing solid matter. 13. The melt processing container according to claim 9, wherein the inner layer is formed in a porous shape. 14. The melting process according to claim 9, wherein the outer layer is formed of a material having a sealing property up to a decomposition temperature of a substance contained in the object. container. 15. The melting processing container according to claim 10, wherein the filling is clean soil.