JP2005507494A5 - - Google Patents

Description

Apparatus and method for vitrifying contaminated soil or waste

  The present invention relates to a method and apparatus for melting a material to be processed. Strictly speaking, the present invention relates to an apparatus with a container which melts in it and thus makes it possible to carry out a method in which the material to be treated is disposed in one stage.

  The use of the vitrification method to safely dispose of contaminated soil or waste (hereinafter referred to as material to be treated) is widely known in the art. Examples of such methods are provided in US Pat. Nos. 4,376,598, 5,024,556, 5,536,114, 5,443,618 and RE 35,782. Has been. The disclosures of these patents are incorporated herein by reference.

  In general, in known vitrification methods, the material to be treated is placed in a vitrification chamber or vessel. Next, an electrode is inserted into the material to be processed, and a high current is passed between the electrodes. The electric current is continuously applied until the temperature of the material to be processed rises to its melting start point, and is further applied until it is completely melted. In some cases, when the material to be treated does not have the proper conductivity, other additives are required to create the first conductive resistance path through the material to be treated. When a resistance path is created and the material starts to melt, the melted material itself continues to pass current.

In the process of melting the material, the organic components are destroyed or evaporated, and the gas is typically evacuated through a suitable gas precleaner, cooler, filter or other known device or method.
When the material is sufficiently melted and all organic components are processed, the electrical supply is stopped and the molten material is cooled. The result of cooling is a glassy and / or crystalline solid material. In this way, the inorganic contaminants are fixed in a hard glassy mass, ensuring that the contaminants are trapped and easily discarded.

  In known methods, vitrification takes place in complex refractory lining melters or in pits dug in the soil. In US Pat. No. 5,543,618, a vitrification apparatus having either a chamber in place permanently (such as in a processing facility) or a chamber that can be demolished and reconstructed in a desired location. An example is provided. In either case, the molten mass is removed from the chamber and processed further. Such another treatment involves the embedding of vitrified and / or crystalline mass or another type of disposal. Devices known in the art for performing vitrification processes are usually complex structures including various electrical supply systems, waste supply systems, molten glass discharge systems, cooling systems and exhaust systems. In such a system, the molten glass discharge system is necessary because the molten mass must be removed in a molten state. In these cases, the melt is poured or poured into the receiving container as a molten liquid.

  Vitrification in the pit is described in US Pat. No. 4,376,598 and RE 35,782. In this case, the material to be treated is dropped into underground pits or grooves, and dirt or other types of caps are hung as a cover. Next, an electrode is inserted and vitrification is performed as described above. When processing is complete, the vitrified and / or crystalline mass is left embedded in the ground. As can be appreciated, certain types of contaminants such as radioactive waste must be disposed of in a legally established burial site and cannot be safely disposed of in this manner.

In general, known methods are expensive and are used in difficult situations without alternatives. Accordingly, there is a need for vitrification apparatus and methods that overcome various disadvantages of the prior art.
US Pat. No. 4,376,598 US Pat. No. 5,024,556 US Pat. No. 5,536,114 US Pat. No. 5,443,618 RE 35,782

Thus, in one embodiment, the present invention provides a process for melting a material to be processed, said process generally comprising the following representative steps:
Installing the material to be processed in a container;
Heating the material to be treated in a container until it is melted to become a molten material;
The molten material is cooled in the container until solidified.

  The material to be treated is (a) contaminated soil such as soil containing radioactive or non-radioactive materials, (b) some kind of harmful material, or (c) some waste. The material to be treated varies depending on the heating method, but at least one heating element, that is, at least two electrodes, is arranged in the material to be treated, and an electric current is passed between the electrodes and thus through the material to be treated (or heated). It is desirable to heat the element). The current and / or heating element is sufficiently melted to heat the material to be treated and the molten material to be processed forms a solidified glassy and / or quartz mass after cooling. The solidified material may be disposed of in a container (ie, dispose of both the material and the container) or may be disposed of by removing it from the container after cooling and disposing of it alone.

  In another embodiment, the present invention provides a target material comprising a box having an internal lining comprised of one or more layers of thermal insulation and one or more layers of refractory, or combinations thereof. Provides containers for processing.

These and other features of preferred embodiments of the present invention will become apparent upon reading the following detailed description with reference to the accompanying drawings.
As mentioned above, conventional vitrification processes have been performed in pits or complex chambers. However, the present invention provides a container in which a material to be processed is placed and a melting process is performed therein. Furthermore, the container is manufactured at low cost so that it can be easily disposed of when the melting process is complete. This eliminates the need to remove and handle vitrified and / or crystalline masses, thus providing a safe and easy waste disposal means.

  The container of the present invention can be used for virtually all types of melt processing. The container of the present invention can be used with virtually any material that can be melted or treated with molten material. For example, the container and process can be used for various types of contaminants such as heavy metals, radionuclides, organic and inorganic compounds. The concentration of contamination can be in any range. Furthermore, the present invention can be used with any material that can be melted, such as sand, silt, clay, or other types of silica or soil. The target material may be wet or may contain sludge, deposits, or ash.

  As noted above, common melting processes are used to decompose organic contaminants and to fix harmful inorganic and radioactive materials within highly vitrified and / or crystalline products. It involves the step of electrically melting the material to be treated, such as contaminated soil or other underground material. The stage of electrical melting occurs using different types of heat treatments such as Joule heating and plasma heating. This process is initiated by placing at least two electrodes or at least one heating element in the material to be treated, and then optionally placing a conductive starting path material between the at least two electrodes. . When energized, current flows through the startup path, heating the path to a point where adjacent soil and waste melt. As adjacent soil and waste melt, they become conductive and from that point on, the melted material acts as a heating element for processing. Heat is transferred from the molten mass to the adjacent unmelted material and heated to the melting point, at which point the unmelted material becomes part of the conductive heating element. The process continues until the supply of power is finished by increasing the amount of material to be melted. During the melting process, all gaseous waste is captured and, if necessary, processed in a suitable known manner. The solidified mass resembles a vitrified and / or crystalline product and fixes non-gasified contaminants such as heavy metals and radionuclides. Melt processing is highly receptive to waste such as steel, wood, concrete, megaliths, plastics, bitumen, tires and the like.

  For typical naturally occurring soil materials, the melting process is carried out within a temperature range of about 1400 ° to 2000 °, depending mainly on the composition of the material being melted. Melts of various sizes and shapes can be made. It should be understood that there is no fixed range for the temperature at which the melting process of the present invention is performed. Rather, the temperature range will increase or decrease depending on the additive used in connection with the present invention. The higher the temperature, the more expensive the melting process.

  During the melting process, the volume is generally reduced by melting the material to be processed. Accordingly, in certain optional embodiments, active or passive feeding methods are used to add additional material to the container to maximize the amount of material to be processed in the container. Passive feeding occurs when additional material to be processed is stored at the top of the container before the melting process begins. When the processing target material is melted during the melting process, the additional processing target material is lowered into the container, and as a result, the additional processing target material is processed. In the case of active supply, additional material to be processed is added to the container during the melting process.

  In a preferred embodiment of the invention, the melt process will use a commercially available steel container such as a commercially available “roll-off box”. In accordance with the present invention, the container is insulated to prevent heat transfer, and a heat resistant lining is mounted inside the box to protect the box during the melting phase. The heat resistant lining and the heat insulating material may be composed of the same material or different materials. The refractory lining may consist of prefabricated or naturally produced refractory materials, such as brick, sand or concrete, mixtures thereof, insulation boards, or any other material with a high melting point. Good. At least two electrodes or at least one heating element are placed in the box. Next, the material to be processed is placed in the box, and the melting process is performed as described above. When melting is complete, the contents of the box cool and solidify. The box is then disposed with vitrified and / or crystalline contents. In an alternative embodiment, the box can be reused because the vitrified and / or crystalline contents can be removed from the box and disposed of separately.

  FIG. 1 illustrates a processing container according to an embodiment of the present invention. As shown, the container 10 is a box having a side wall 12 and a bottom 14. The container 10 is provided with a heat insulating layer 16 on each side wall 12 and bottom 14. The insulation 16 can be constructed of a material such as brick or sand, a mixture thereof, a thermal insulation board, or some other material having a high melting point. After placing the heat insulator, the container is lined with a heat-resistant material 18. The heat-resistant material is lined not only on the bottom but also on the side of the container. In this way, the space 20 is left, and the material to be processed is placed therein. In a preferred embodiment, when a free liquid is used in conjunction with the present invention, a liquid impervious liner 19 lining such as a plastic liner 19 is further applied over the refractory material.

  FIG. 2 illustrates an embodiment of the present invention. As shown, the container of FIG. 1 is provided with a lid or cover 22. The lid or cover 22 is disposed on the container 10 and seals the upper part thereof. The lid or cover is provided with an opening 24 through which at least two electrodes or at least one heating element 26 extends.

A connector 28 that connects the lid or cover 22 to the container 10 may be disposed between the lid or cover 22 and the container 10.
As shown in the example illustrated in FIG. 2, after the heat insulator 16 and the heat-resistant material 18 are mounted in the container 10, the processing target material 30 is placed in the space 20. For example, when using a drum can in connection with the present invention, the drum can is a standard 55 or 30 gallon drum. However, it should be understood that there is no limitation on the size of the drum or container used with the present invention. The space between the drums 30 is filled with soil 32. Such soil 32 is further placed over the drum. In addition, a layer of overburden 34 rests on the covered drum and extends into the connector 28. The electrode or heating element installation tube 36 extends through the cover 34. At least two electrodes or at least one heating element 24 for the treatment process extends through the installation tube 36.

  FIG. 3 shows another exemplary embodiment of the present invention. In the container 10, a compressed drum tube 30a or some material to be treated is placed in place of the cylindrical drum shown in FIG. It has been.

  Hereinafter, the present invention will be described step by step. First, as described above, the container is lined with a heat insulating board, and then a sliding mold is installed to facilitate mounting of the heat-resistant material layer. Next, a liquid impervious liner is installed in the container so that the material to be treated and the soil can be packed in the liquid impervious liner. Liquid impervious liners can also be used to fill the liquid prior to processing if the material being processed contains significant liquid. Once the material to be treated is installed, the sliding form may be removed.

  As will be described below by way of example, the material to be processed can be put in a drum can and placed in a container. Within the drum, the material to be processed can be compressed to maximize the amount of material to be processed. Instead, in another embodiment, the material to be processed can be placed directly into the container without using a drum. In another embodiment, the material to be processed can be placed in a container in a bag or box. In yet another embodiment, liquid waste can be mixed with soil or other absorbent and placed in a container.

As will be appreciated by those skilled in the art, various additives can be added to the material to be treated to improve or enhance the treatment of the present invention. For example, such an additive increases the electrical conductivity of the material to be treated (for example, Na ⁺ ), or promotes oxidation of a metal contained in the material to be treated (for example, saccharose, KMnO ₄ ). Such as additives to improve the durability of vitrified and / or crystalline masses (ie solidified materials), or chemicals added to promote the decay of chlorinated organics such as PCBs Other additives may be used. Furthermore, the additive may affect the melting temperature by raising or lowering the melting temperature.

  In some embodiments, the container of the present invention may be a standard “roll-off” box having a volume in the range of 10 to 40 cubic yards. Such containers or boxes vary in length, width and height dimensions. As will be appreciated by those skilled in the art, the dimensions of the box are limited only by the requirements of the equipment that must be attached to the box. In another embodiment, the container of the present invention includes a metal drum such as a standard 55 gallon steel drum. Such drums are provided with the necessary insulation and / or refractory layers as discussed herein. The wall thickness of the container of the present invention may also vary. A typical box typically has a wall thickness in the range of 10 to 12 gauge, but other dimensions may be used, as will be apparent to those skilled in the art.

Generally speaking, pre-fabricated thermal and refractory materials form a liner or liner system inside the container. Such a liner serves to maintain heat in the container and increase the efficiency of the melting process. If this is taken into consideration, it will be understood that the heat-resistant material also works as a heat-insulating layer. In such a case, the necessary heat insulation value can be obtained by increasing the thickness of the heat-resistant material in the container. Alternatively, the heat-resistant material may be omitted and only the heat insulating layer may be provided in the container. When both a heat-resistant layer and a separate heat-insulating layer are used, the heat-resistant material also functions to slow down the heat transfer to the heat-insulating layer. In such a case, the thermal insulation layer can be removed from the container after the melting process and reused. In another embodiment, multiple thermal insulation layers and / or heat resistant liners are used. As can be appreciated, the amount of thermal insulation and / or refractory material depends, among other criteria, on the nature of the soil and material being treated. For example, when the melting temperature of such soil and the material to be treated is high, extra heat insulation and / or heat resistant material is required.
EXAMPLES The present invention will be described with reference to specific examples involving radioactive materials such as uranium pieces present in the soil. It should be understood that this example is not intended to limit the scope of the invention in any way.

  First, the material to be treated is placed in a 30 gallon drum. Next, the drum can containing the material to be treated is compressed or reduced, placed in a 50 gallon drum, and filled with soil and sealed. The 50 gallon drum is then placed in the processing container 10. As will be described in detail below, while compressing the smaller drum, the oil in the material to be treated must be removed and treated separately.

  Putting a drum of compressed material to be processed (eg, uranium and oil) into the container 10 can be performed in two ways. The first method is to place the contents of the compressed smaller drum and the 55 gallon drum holding the soil into the container 10. The compressed drum is immediately covered with soil and is not freely exposed to air. In this way, the compressed drums can be placed closer together for processing and can be packed with more uranium. Further, removing the compressed drum from the 55 gallon drum eliminates the need to break or unseal the 55 gallon drum to escape the vapor during the vitrification stage.

  Alternatively, a 55 gallon drum containing the compressed drum can be placed directly into a waste disposal container for processing. In this case, a vent hole is provided in the drum to facilitate escape of steam during processing.

  A portion of the contaminated oil removed during the compression phase of the smaller (30 gallon) drum can be added to the soil in the container processing volume and processed with the uranium drum. The liquid impervious liner 19 prevents free oil from moving from the material to be treated to the heat resistant sand material 18. The sliding formwork is raised until the level of waste, soil and refractory sand is increased and at the same time the container is filled to the desired level. At that point, the sliding formwork is removed to the storage location.

  A clean soil layer is placed on the installed waste and heat-resistant sand. The electrodes are then placed in the soil layer. The electrode is installed using a previously installed tube that reserves a space for the electrode 26 to be placed later. Alternatively, a pair of electrodes is placed in the installed waste and heat resistant sand before the clean soil layer is placed on the installed waste and heat resistant sand. Next, a starting path is disposed in the soil between the electrodes. Finally, an additional clean cover 34 is placed over the starting path 31. This completes the installation of the waste in the processing container. The configuration of the waste treatment container after the waste is installed is shown in FIGS.

  When waste is installed in the waste treatment container 10 as described above, the gaseous waste collection hood 22 connected to the gaseous waste treatment system is then covered. Next, in order to support the electrode feeder 29, the electrode feeder support frame 27 is disposed on the container hood assembly 22, provided that both are already disposed at predetermined positions when they are integral parts of the hood assembly. Will be. At least two electrodes 26 are then inserted through the feeder 29 into the hood 22 and into the tube 36 located at the end of the starting path 31. Placing additional start path material in the tube 36 ensures a good connection with the start path 31. Finally, the remaining part of the tube is filled with a clean cover 34. This completes the preparation of the material for melting. As can be appreciated, the above discussion has been done for at least two electrodes, but as will be apparent to those skilled in the art, at least one heating element may be used in the system.

  Before starting the melting process, the gaseous waste starts flowing and ready for testing. The melting process is powered by a certain rate of increase (starting ramp) over a period of time and at a given power output value. For example, power is applied to a total power level of about 500 kW for about 15 hours. Depending on the type of waste to be treated, the level of power used and the size of the container, it may take 2 to 5 days in total to process uranium waste drums and oil. is expected. Processing is performed on a 24 hour basis until complete.

FIGS. 4 a to 4 d show the progress stages of melting of the material in the container 10.
Although the present invention has been described in terms of certain specific embodiments, it will be apparent to those skilled in the art that these embodiments can be made without departing from the spirit and scope of the invention as outlined in the following claims. Various modifications can be made to.

2 is an end cross-sectional elevation view of a container according to an embodiment of the present invention. FIG. FIG. 2 is an end cross-sectional elevation view of an apparatus including the container of FIG. 1 in use, according to an embodiment of the present invention. FIG. 2 is an end cross-sectional elevation view of an apparatus including the container of FIG. 1 in use according to another embodiment of the present invention. 4A-4D are end cross-sectional elevational views of the apparatus of FIG. 3 at each stage of the melting process of the present invention.

Claims (26)

In the process for melting the material to be processed,
Placing the waste and / or hazardous material to be treated into a container that is not a pit dug in the soil ;
Heating the waste and / or hazardous material in the container until the material melts into molten waste and / or hazardous material ;
Cooling the molten waste and / or hazardous material into vitrified waste and / or hazardous material in the container ;
A process consisting of: The process of claim 1, further comprising discarding the container in which the waste and / or hazardous material is contained. The process of claim 2 , wherein the waste and / or hazardous material in the container is heated at a temperature of about 1400 ° C to 2000 ° C. The process of claim 1 , wherein the waste and / or hazardous material is heated to form a molten state without the addition of a temperature reducing additive . The process according to claim 4 , wherein the container has a structure for collecting a gas . 6. The process of claim 5 , wherein after the molten material has cooled, the gas recovery structure is removed from the container and the container containing the waste and / or hazardous material is discarded . The process of claim 1 , wherein the waste and / or hazardous material is heated by passing a current between at least two electrodes removably disposed within the material . 8. The process of claim 7 , wherein a starting path member is disposed between the at least two removable electrodes prior to heating the material . The process of claim 1, wherein the container further comprises a hood and at least one heating device that penetrates the hood and enters the material . The process of claim 1, wherein the waste and / or hazardous material includes a contaminant selected from the group consisting of hydrocarbons, radioactive materials, radionuclides, carcinogens, or combinations thereof. The process of claim 1, wherein the container has an insulating layer. The process according to claim 11, wherein the heat insulating layer is a heat insulating board. The process of claim 12, wherein the container comprises a refractory material. The process of claim 1, wherein an additive is added to the material prior to heating the material. The process of claim 14, wherein the additive increases the conductivity of the material to be treated. 15. The process of claim 14, wherein the additive promotes oxidation of the metal contained in the material to be treated. The process of claim 1, wherein the material is heated to a temperature of at least about 1400 ° C. The process of claim 1, wherein the container has a cavity, and a sliding formwork is installed in the cavity. The process of claim 18, wherein sand material is placed in the container behind the sliding formwork. 20. The process of claim 19, wherein the sliding form is removed from the container and the sand material remains in the container before heating the material to be treated. The process of claim 1 wherein a liquid impermeable liner is disposed within the container and the material to be treated is disposed within the nailer. The process of claim 1, wherein the material to be processed is packed into one or more containers disposed within the container. The process according to claim 22, wherein a plurality of containers are disposed in the container, and soil is disposed in a space between the containers. The process according to claim 1, wherein the material to be treated is covered with soil before heating. The process according to claim 1, wherein the material to be treated is mixed with soil. The process according to claim 1, wherein the material to be treated is a soil material.