Heating well

Abstract

To provide a heating well that can increase the heating efficiency of an in-situ purification method for contaminated soil.SOLUTION: A heating well used in in-situ purification of contaminated soil includes an outer pipe installed downwardly, an inner pipe accommodated in the outer pipe, a heater arranged in contact with an inner surface of the outer pipe or in the immediate vicinity of the inner surface of the outer pipe, and a sleeve inserted between the heater and the outside surface of the inner pipe, wherein the sleeve is a member for assisting in arranging the heater in contact with the inner surface of the outer pipe or in the immediate vicinity of the inner surface of the outer pipe.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to heating wells used in the in situ remediation of contaminated soil. [Background technology]

[0002] As a method for purifying soil contaminated with volatile organic compounds (VOCs), etc., a method of excavating and removing the contaminated soil (excavation and removal method) is known. The excavation and removal method is said to be a reliable method for purifying contaminated soil. However, the excavation and removal method required the removal and transportation of large amounts of contaminated soil, resulting in enormous transportation and disposal costs.

[0003] From the perspective of reducing costs such as transportation and processing costs, it may be possible to use in-situ purification methods that remove contaminants in-situ. Known in-situ purification methods include bioremediation, which activates microorganisms to decompose pollutants, and chemical decomposition methods (such as the Fenton process) that use hydrogen peroxide. However, even when in-situ remediation methods are used, if the local soil is clayey or silty, which has low permeability, it is extremely difficult for the treatment chemicals to reach the contaminated areas, and remediation takes a long time.

[0004] Another method for removing pollutants in situ is known as in situ thermal desorption. There are three common in situ thermal desorption methods: electric heater type, electric resistance type, and steam type. Among these, the in-situ thermal desorption method using an electric heater can heat the local soil to over 100°C, expanding the soil skeleton pores as the soil pore water evaporates, and enabling the contaminants to be desorbed and carried away by the water vapor. This makes it a method that can efficiently remove contaminants from the soil.

[0005] For example, Patent Document 1 has been proposed as an in-situ thermal desorption method using an electric heater. Patent Document 1 describes a method in which heat is applied to a treatment target area containing contaminants to vaporize part of the contaminants, which are then sucked in and removed from the treatment target area. According to the invention of Patent Document 1, it is intended to increase the efficiency of contaminant removal by in-situ heating and steam extraction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4509558 Summary of the Invention [Problem to be solved by the invention]

[0007] The heating well (heating well) of Patent Document 1 has an electric heating wire disposed as a heater inside a sleeve pipe (outer pipe), and the outer pipe and the electric heating wire are insulated by air. In this configuration, the heat of the heating wire heated to a high temperature (e.g., 100°C or higher) is transferred to the area to be treated by radiation. Heat transfer by radiation is less efficient (heating efficiency) than heat transfer by conduction.

[0008] The present invention has been made in consideration of the above circumstances, and has as its object to provide a heating well that can further improve the heating efficiency of a method for in-situ remediation of contaminated soil. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following aspects. [1] A heating well used for in-situ remediation of contaminated soil, comprising: an outer pipe installed facing downward; an inner pipe housed within the outer pipe; a heater positioned in contact with or in close proximity to the inner surface of the outer pipe; and a sleeve inserted between the heater and the outer surface of the inner pipe, wherein the sleeve is a member that assists the heater in contacting or being positioned in close proximity to the inner surface of the outer pipe. [2] A heating well as described in [1], wherein a portion of the sleeve is in close contact with the outer surface of the inner tube, a biasing means is inserted between the sleeve and the heater, and the biasing means applies a force to separate the sleeve and the heater, thereby pressing the heater against the inner surface of the outer tube. [3] A heating well as described in [2], wherein a spacer is inserted between the sleeve and the outer surface of the inner tube, and a biasing means is inserted between the sleeve and the heater, and the biasing means applies a force to separate the sleeve and the heater, thereby pressing the heater against the inner surface of the outer tube. [4] A heating well as described in [1], wherein multiple heaters are installed between the outer tube and the inner tube, and each heater is evenly spaced apart. [5] The heating well described in [2] or [3], wherein the biasing means is a leaf spring. Effect of the Invention

[0010] The heating well of the present invention can further increase the heating efficiency of the method for in-situ remediation of contaminated soil. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic diagram of a first embodiment of a heating well of the present invention. [Diagram 2] FIG. 2 is a plan view showing an example of a heating well of the first embodiment. [Diagram 3] FIG. 2 is a plan view showing an example of a heating well of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The heating well of the present invention is used for in-situ purification of soil by heating the treatment area where contaminated soil containing pollutants is present, thereby volatilizing the pollutants or increasing the temperature to reduce the viscosity of the pollutants, thereby increasing their fluidity and facilitating suction treatment (hereinafter also referred to as "volatilization, etc."). The heating well of the present invention comprises an outer pipe, an inner pipe, a heater, and a sleeve. The outer pipe is provided so as to separate the soil to be purified from the heater, which is a heating device disposed inside the outer pipe. The inner pipe is housed within the outer pipe. The inner pipe has openings at the top and bottom. Hereinafter, one embodiment of the heating well of the present invention will be described with reference to the drawings.

[0013] [Heating well] The heating well of this embodiment has an outer tube 10, an inner tube 12, a heater 20, and a sleeve 30, as shown in FIG. In the illustrated example, the outer pipe 10 and the inner pipe 12 are cylindrical and are arranged to extend in the depth direction downward from the ground surface G. The inner pipe 12 is housed within the outer pipe 10. The heater 20 is located between the inner pipe 12 and the outer pipe 10 and is arranged so as to contact the outer pipe 10. The sleeve 30 is arranged around the heater 20 and inserted between the outer surface (radially outer surface) of the inner pipe 12 and the heater 20 to facilitate contact between the heater 20 and the outer pipe 10.

[0014] The heating well is installed in the treatment target area A where contaminated soil exists. The heating well is arranged so as to extend in the depth direction downward from the ground surface G. The upper surface of the heating well is covered with a concrete layer 40. The concrete layer 40 is preferably made of air mortar with high thermal insulation properties from the viewpoint of energy efficiency. Although not shown, a suction well that sucks up contaminants in the ground may be provided separately from the heating well.

[0015] The outer tube 10 is the casing of the heating well. The outer pipe 10 is provided for the purpose of isolating the soil to be purified from the heater 20, which is a heating device disposed inside the outer pipe 10. The bottom of the outer pipe 10 is of a closed type, and is closed (blocked) at the bottom surface 10a.

[0016] Although not shown, the upper part of the outer pipe 10 may be closed by a lid member or the like. The lid member may be further covered with a concrete layer 40. The material of the lid member may be the same as that of the outer pipe 10.

[0017] The length of the outer pipe 10 can be set arbitrarily depending on the treatment target area A where the contaminated soil exists. For example, it may be 3 to 10 m, or when the purification target depth is about 20 to 30 m, it may be about 22 to 32 m, or about 21 to 31 m. If the length of the outer pipe 10 is too long, construction becomes difficult or construction costs increase, so it is preferable to set the length within a range where these inconveniences are unlikely to occur.

[0018] The shape of the outer tube 10 may be, for example, cylindrical or polygonal. A cylindrical shape is particularly preferable. With this shape, when installing multiple heaters 20 in one heating well, the heaters 20 can be easily arranged at positions spaced evenly apart from each other. With this arrangement, heating can be performed uniformly, and the heating efficiency can be further improved. The outer pipe 10 may be, for example, a carbon steel pipe for piping (SGP pipe), a stainless steel pipe, or the like.

[0019] The inner tube 12 is housed inside the outer tube 10. The outer tube 10 and the inner tube 12 are preferably coaxial. The outer diameter of the inner tube 12 is smaller than the inner diameter of the outer tube 10, so that a heater 20 and a sleeve 30 can be installed between the outer tube 10 and the inner tube 12. The inner diameter of the outer tube 10 is, for example, 0.05 m to 0.2 m. A thermocouple 50, a temperature sensor, or the like for measuring temperature can be installed inside the inner tube 12. The inside diameter of the inner tube 12 may be any size that allows the installation of a thermocouple 50, a temperature sensor, or the like, and may be, for example, 0.05 m to 0.1 m.

[0020] The material of the inner pipe 12 may be any material that has heat resistance at the heating temperature of the heater 20. For example, carbon steel pipes for piping (SGP pipes), stainless steel pipes, etc. may be mentioned. The length of the inner pipe 12 may be shorter than or approximately the same as the length of the outer pipe 10. It is preferable that the length is approximately the same. With this configuration, the sleeve 30 provided in close contact with the outer surface of the inner pipe 12 is A plurality of sleeves can be disposed at regular intervals over the entire heater 20. This allows the sleeve 30 to more easily fulfill its role of ensuring the linearity of the heater 20, in addition to its role of bringing the heater 20 into contact with the outer tube 10. The upper and lower ends of the inner tube 12 may be open or closed.

[0021] The inner tube 12 may be, for example, cylindrical or polygonal, with the cylindrical shape being preferred. A configuration in which both the inner tube 12 and the outer tube 10 are cylindrical is particularly preferred. With this configuration, when installing multiple heaters 20 in one heating well, it becomes easy to install the sleeve 30 or another type of sleeve (fixing jig) made of a metal rod and a semicircular metal, which will be described later, without interfering with each other. This makes it easy to arrange the heaters 20 at positions that are evenly spaced apart from each other without having to worry about the arrangement of the sleeve 30 or the fixing jig. With the heaters 20 arranged in this way, they can be heated evenly, thereby further improving the heating efficiency.

[0022] Although not shown, the lower part of the inner pipe 12 may be fixed to the outer pipe 10 by a fixing member or the like. In this case, the material of the fixing member 14 may be the same as that of the inner pipe 12. The fixing member 14 and the inner pipe 12 may be integral with each other.

[0023] The heater 20 is cylindrical along the longitudinal direction of the outer tube 10, and includes a heater sheath (outer cover) and a heating wire. The heater 20 is an insulating heater having insulating properties. In addition, it is preferable that the heater 20 is an electric heating type. That is, it is preferable that the heater 20 is an electric heating type insulating heater. The gap between the heating wire and the heater sheath is filled with a material having insulating properties and thermal conductivity. As a material having both insulating and thermal conductivity, magnesium oxide is preferable because it is inexpensive and has high insulating properties and thermal conductivity.

[0024] The heater 20 is located between the inner tube 12 and the outer tube 10 and is disposed so as to be in contact with the outer tube 10 . With this arrangement, the heat generated by the heater 20 can be transferred to the outer pipe 10 by thermal conduction, which has excellent heat transfer efficiency (heating efficiency). Therefore, heat can be transferred with good heating efficiency to the treatment target area A where contaminated soil exists.

[0025] The heater 20 may not strictly be in contact with the outer tube 10, or may be arranged in close proximity to the outer tube 10 and capable of transferring heat by thermal conduction.

[0026] There is no particular limitation on the material of the heating wire that is the heat source of the heater 20. Examples include metals such as nichrome, tungsten, graphite, and platinum, ceramics, and carbon fibers. In addition, it may be a non-metallic compound such as silicon carbide.

[0027] The length of the heater 20 can be set arbitrarily according to the treatment target area A where the contaminated soil exists. In addition, for example, when the purification target depth is about 20 m to 30 m, multiple heaters 20 can be installed in one heating well according to the treatment target area A where the contaminated soil exists.

[0028] The heater 20 is preferably installed so that it maintains its state (linearity) along the longitudinal direction of the outer tube 10 even during heating. In particular, when multiple heaters 20 are installed in one heating well, it is preferable to install the heaters 20 with their longitudinal directions approximately parallel to each other. With this arrangement, there is little risk of the heaters 20 being positioned in contact with each other, and problems with temperature control such as localized high temperatures are unlikely to occur. In other words, the heating effect of the heaters 20 can be made more uniform, and heating efficiency can be improved.

[0029] When multiple heaters 20 are installed in one heating well, the heaters 20 are preferably arranged so as to be evenly spaced from each other, and the multiple heaters are preferably arranged so as to maintain an evenly spaced positional relationship even when heating with the heaters. In other words, the heaters 20 are preferably arranged so that the distance between the centers of the heaters 20 is equal in the cross-sectional direction perpendicular to the longitudinal direction of the outer tube 10. With this arrangement, uniform heating can be achieved without causing temperature control problems such as localized high temperatures, and the heating efficiency can be further improved.

[0030] Although not shown, the heater 20 can be electrically connected to a power source located on the surface. The power source is not particularly limited, and examples thereof include a heating power source device. In this case, by electrically connecting the power source to, for example, the electric insulating heater 20, a voltage can be applied to the heating wire of the electric insulating heater 20, thereby heating the heating wire. The power source may be one that can supply power by itself, or may be one that receives power from an external power supply facility or the like via wiring or the like.

[0031] The sleeve 30 is disposed around the heater 20 and inserted between the heater 20 and the outer surface of the inner tube 12. In the embodiment illustrated in FIG. 2, in a cross-sectional view of the outer tube 10 cut in the longitudinal direction, the sleeve 30 is a thick, short cylinder (thick-walled ring) toward the depth direction of the paper. The inner surface of the sleeve 30 is in close contact with the outer surface (outer surface) of the inner tube 12. A semicircular recess 30a is provided on the outer surface of the sleeve 30 along the contour of the heater 20 in the cross-sectional view. A part of the cylindrical heater 20 fits into the recess 30a, and a part of the side surface of the heater 20 is surrounded by the recess 30a. Since the sleeve 30 is a thick-walled ring, it fills most of the gap between the outer tube 10 and the inner tube 12. In the cross-sectional view of the outer tube 10, the inner tube 12, the sleeve 30 (recess 30a), a leaf spring 32 as an example of a biasing means, the heater 20, and the outer tube 10 are arranged in this order from the center to the outside. The leaf spring 32 is disposed on a straight line connecting the center of the inner tube 12 and the center of the heater 20 , and is inserted into the gap between the recess 30 a and the heater 20 . The sleeve 30 can bias the heater 20 toward the outer tube 10 (applying a force that separates the sleeve 30 and the heater 20) via the leaf spring 32. This allows the heater 20 to be configured to easily come into contact with the inner surface (inner side surface) of the outer tube 10, and can help the heater 20 to come into contact with the inner surface of the outer tube 10 or to be positioned very close to the inner surface of the outer tube 10. When the heater 20 and the outer pipe 10 are in contact with each other or arranged in close proximity to each other, the heat generated by the heater 20 can be transferred to the outer pipe 10 by thermal conduction, which has better heat transfer efficiency (heating efficiency) than radiation. Therefore, heat can be transferred more efficiently to the treatment target area A where contaminated soil exists.

[0032] The force with which the sleeve 30 urges the heater 20 towards the outer tube 10 via the leaf spring 32 (the force that separates the sleeve 30 and the heater 20) can be adjusted by changing the repulsive force, etc., of the leaf spring 32. Since the heater 20 expands in the extension direction during the heating process, it is particularly preferable to use a leaf spring 32 whose repulsive force, etc., is adjusted to an extent that does not impede this expansion and that comes into contact with the outer tube 10.

[0033] As shown in FIG. 1, a plurality of sleeves 30 are disposed at regular intervals along the longitudinal direction of the outer tube 10 . There is no particular limitation on the number of sleeves 30. For example, the number of sleeves 30 can be set arbitrarily depending on the length of the heater 20.

[0034] The sleeve 30 has a role of making the heater 20 contact the outer tube 10, and also a role of making it easier to ensure the linearity of the heater 20. For example, as shown in FIG. 1, by arranging a plurality of sleeves 30 at regular intervals, the linearity of the heater 20 can be easily maintained. With this configuration, when a plurality of heaters are provided, the plurality of heaters can be kept evenly spaced apart from each other even when heated by the heaters. This reduces the risk of the heaters 20 being in a positional relationship where they come into contact with each other, and makes it difficult for problems in temperature management, such as localized high temperatures, to occur. That is, the heating effect of the heater 20 can be made more uniform, and the heating efficiency can be improved. In particular, as in the example shown in FIG. 1, when a plurality of sleeves 30 are arranged at regular intervals over the entire heater 20, the effect of improving the heating efficiency can be further obtained.

[0035] The shape of the sleeve 30 is not particularly limited, but is preferably, for example, an annular plate-like shape. If it is annular, the sleeve 30 can be easily disposed at a position where the heater 20 can easily come into contact with the outer tube 10. If it is plate-like, it is easy to form recesses (holes) in the sleeve 30. 2, a more preferable embodiment has a recess (hole) for passing the heater 20. In this embodiment, the sleeve 30 can be disposed so as to partially surround the heater 20, and the sleeve 30 can more easily perform its function of bringing the heater 20 into contact with the outer tube 10 or ensuring the linearity of the heater 20. In this case, it is preferable that the leaf spring 32 is provided in a recess (hole) of the sleeve 30. When the heater 20 is passed through the recess (hole), the leaf spring 32 is compressed and then installed, so that the heater 20 can be easily brought into contact with the outer tube 10 by the repulsive force of the leaf spring 32, etc.

[0036] Another embodiment is illustrated in FIG. 3. The outer tube 10, the inner tube 12, the heater 20, and the leaf spring 32 are the same as those in the embodiment in FIG. 2. In a cross-sectional view of the outer tube 10 cut in the longitudinal direction, the inner tube 12, a metal rod 34 as an example of a spacer, the sleeve 30 (recess 30a), the leaf spring 32, the heater 20, and the outer tube 10 are arranged in this order from the center to the outside. The sleeve 30 in this embodiment is a member made by bending a metal plate, and is a semicircular member in the cross-sectional view. A part of the cylindrical heater 20 fits into the recess 30a surrounded by the curved surface of the sleeve 30, and a part of the side surface of the heater 20 is surrounded by the recess 30a. The leaf spring 32 as an example of a biasing means is inserted and arranged in the gap between the sleeve 30 and the heater 20 on a straight line connecting the center of the inner tube 12 and the center of the heater 20. The metal rod 34 is arranged in the gap between the sleeve 30 and the inner tube 12 on a straight line connecting the center of the inner tube 12 and the center of the heater 20. The metal rod 34 serves as a spacer. The cross-sectional shape of the metal rod 34 is not particularly limited, and may be circular, elliptical, polygonal, or any other arbitrary shape. The spacer metal rod 34 is preferably welded, and is preferably joined to the inner tube 12 and the sleeve 30 by welding. The sleeve 30 can bias the heater 20 toward the outer tube 10 via the leaf spring 32. This makes it easier for the heater 20 to come into contact with the inner surface of the outer tube 10, and can help the heater 20 to come into contact with the inner surface of the outer tube 10 or to be positioned very close to the inner surface of the outer tube 10.

[0037] The material of the sleeve 30 may be any material that has heat resistance at the heating temperature of the heater 20. Examples of the material include metal, ceramic, and stainless steel. It is preferably the same as the material of the inner tube 12. If the sleeve 30 and the inner tube 12 are made of the same material, it becomes easy to join the sleeve 30 and the inner tube 12 by welding.

[0038] The leaf spring 32 is not particularly limited as long as it is a compression spring that can bias the heater 20 toward the outer tube 10 so as to assist the heater 20 in contacting the inner surface of the outer tube 10 or being disposed very close to the inner surface of the outer tube 10. For example, instead of a leaf spring, a coil spring, a heat-resistant spring, or the like can be used as the biasing means. It can be selected according to the required purpose, and for example, a heat-resistant spring can be selected for the purpose of avoiding the spring from becoming worn due to high temperatures.

[0039] The leaf spring 32 may or may not be provided in the following configurations. For example, in the case of a configuration in which "the heater 20 is not in contact with the outer tube 10 strictly speaking, but is arranged in a position very close to the outer tube 10 and heat can be transferred by thermal conduction." In this way, in a configuration in which the heater 20 is arranged in a position very close to the outer tube 10 without the leaf spring 32, the leaf spring 32 can be eliminated.

[0040] [How to install a heating well] Next, an example of a method for installing the heating well of the present embodiment will be described. The heating well of this embodiment is used for in-situ remediation in which a treatment target area A containing contaminated soil is heated to volatilize contaminants, thereby purifying the soil. The in-situ purification method of this embodiment is a so-called in-situ thermal desorption method. Examples of heating methods for the in-situ thermal desorption method include an electric heater type, an electric resistance type, and a steam type. As the heating method for the in-situ thermal desorption method, an electric heater type is preferable because it has a high heating temperature and is easy to heat the soil uniformly. The heating well of this embodiment uses a heater 20, so it is classified as an electric heater type heating method.

[0041] The method for installing the heating well of this embodiment is not particularly limited, and may be, for example, a method including the following steps (a) to (c). Step (a): The outer pipe 10 is installed underground by boring work. Step (b): A recess (hole) for passing the heater 20 is provided in the sleeve 30. A leaf spring 32 is welded to the recess (hole). The sleeve 30 with the recess (hole) and the leaf spring 32 joined by welding is then joined to the inner tube 12 by welding. Step (c): The inner tube 12 and the sleeve 30 are installed inside the outer tube 10. A thermocouple 50 for measuring temperature is installed inside the inner tube 12. The heater 20 is inserted into the recess (hole) of the sleeve 30 and installed.

[0042] The purpose of the above step (a) is to separate the area to be treated A from the inside surrounded by the outer tube 10.

[0043] The above step (b) is mainly a step of installing the sleeve 30. There is no particular limitation on the method of providing the recesses (holes) in the sleeve 30. For example, a plurality of recesses (holes) may be provided in the sleeve 30 which is an annular plate, or the sleeve 30 may be divided into two or four parts and then the recesses (holes) are provided therein, and the sleeve 30 may then be joined by welding. In particular, when division is desired for convenience of installation, the joining by welding after division is preferably performed on-site.

[0044] The sleeve 30 is joined to the inner pipe 12, and this welding is preferably performed on-site. Furthermore, if the sleeve 30 and the inner pipe 12 are made of the same material, it becomes easier to join the sleeve 30 and the inner pipe 12 by welding.

[0045] A compression spring such as a leaf spring 32 is welded and joined to the recess (hole) of the sleeve 30. This makes it easy to bring the heater into contact with the outer tube 10 by compressing the spring before installing it when passing the heater through.

[0046] The sleeve 30 may be a semicircular metal or the like that surrounds a part of the heater 20 as shown in FIG. 3. The semicircular metal is a member obtained by bending a metal plate, and is a member that is semicircular in the cross-sectional view. The sleeve 30 may be a member to which a metal rod 34, which is an example of a spacer, is joined. In this case, the metal rod 34 and the sleeve 30 are welded, and the leaf spring 32 is welded to the fixing jig formed by the above. Furthermore, the end of the metal rod 34 is welded to the inner tube 12. As a result, the sleeve 30 can be configured to be provided in the inner tube 12 via the metal rod 34 as in the illustrated example. The spacer metal rod 34 is preferably welded, and is preferably joined to the inner tube 12 and the sleeve 30 by welding.

[0047] In the above step (c), the inner tube 12 joined in step (b) and the sleeve 30 are installed. In addition, by compressing the leaf spring 32 and then installing the heater 20 through the recess (hole) of the sleeve 30, it becomes easy to bring the heater 20 into contact with the outer tube 10.

[0048] Contaminant removal can be achieved, for example, by using a suction well (not shown) to suck up fluid containing contaminants that have been desorbed from the soil by heating.

[0049] Examples of pollutants include volatile organic compounds (VOCs), oil, mercury, polychlorinated biphenyls (PCBs), and dioxins. Examples of VOCs include benzene, toluene, and halogenated hydrocarbons (eg, trichloroethylene). The oil component may be, for example, a hydrocarbon having 5 to 44 carbon atoms. A hydrocarbon having 5 to 18 carbon atoms can be mainly recovered as a gas. Even a hydrocarbon having 19 or more carbon atoms can be recovered as a liquid by reducing the viscosity. These hydrocarbons may be saturated or unsaturated. These hydrocarbons may be linear, branched, or cyclic. Specific examples of these hydrocarbons include, for example, n-pentane, isopentane, n-hexane, and cyclohexane. Examples of mercury include metallic mercury, inorganic mercury, and organic mercury. Examples of inorganic mercury include mercury oxide, mercury sulfide, mercury chloride (Hg2Cl2, HgCl2), and mercury nitrate. Examples of organic mercury include alkyl mercury (e.g., methyl mercury, ethyl mercury), and phenyl mercury (e.g., phenyl mercury acetate).

[0050] Examples of PCBs include 3,3',4,4'-tetrachlorobiphenyl, 3,4,4',5-tetrachlorobiphenyl, 3,3',4,4',5-pentachlorobiphenyl, 3,3',4,4',5,5'-hexachlorobiphenyl, 2,3,3',4,4'-pentachlorobiphenyl, 2,3,3',4,4',5-hexachlorobiphenyl, and 2,3,3',4,4',5,5'-heptachlorobiphenyl. Examples of dioxins include 2,3,7,8-tetrachloroparadioxin and 2,3,4,7,8-pentachlorodibenzofuran. [Explanation of symbols]

[0051] 10, 10a... outer tube, 12... inner tube, 20... heater, 30, 30a... sleeve, 32... leaf spring, 34... metal rod, 40... concrete layer, 50... thermocouple

Claims

1. A heating well used for in-situ remediation of contaminated soil, comprising: An outer tube that is installed facing downward; an inner tube housed within the outer tube; a heater disposed in contact with or in close proximity to an inner surface of the outer tube; a sleeve inserted between the heater and an outer surface of the inner tube; A heating well, wherein the sleeve is a member that assists in positioning the heater in contact with or in close proximity to the inner surface of the outer tube.

2. a portion of the sleeve contacts an outer surface of the inner tube; A biasing means is interposed between the sleeve and the heater; The heating well of claim 1 , wherein the biasing means applies a force to separate the sleeve and the heater, thereby forcing the heater against the inner surface of the outer tube.

3. A spacer is inserted between the sleeve and an outer surface of the inner tube; A biasing means is interposed between the sleeve and the heater; The heating well of claim 2 , wherein the biasing means applies a force to separate the sleeve and the heater, thereby forcing the heater against the inner surface of the outer tube.

4. The heating well of claim 1 , wherein a plurality of said heaters are installed between said outer tube and said inner tube, and each heater is evenly spaced apart.

5. 4. A heating well according to claim 2 or 3, wherein the biasing means is a leaf spring.

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