heated well

Abstract

To provide a heating well capable of further enhancing heating efficiency in view of the fact that in a conventional heating well, heat is transmitted to a processing object area by radiation, and heat transmission by radiation makes the efficiency of heat transmission (heating efficiency) inferior compared to heat transmission by conduction.SOLUTION: A heating well 1 to be used for original position purification of contaminated soil includes: an outer pipe 10; a heat conductive layer 30 comprising a heat conductive substance filled in the inside of the outer pipe 10; and an insulating heater 20. The heat conductive substance has a heat conductivity higher than that of air, and at least a part of the insulating heater 20 is inserted into the heat conductive layer 30.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heating well, more specifically, a heating well used for in-situ purification of contaminated soil.

Background Art

[0002] As a method for purifying contaminated soil contaminated with volatile organic compounds (VOCs) or the like, a method of excavating and removing (excavation removal method) is known. However, in the excavation removal method, a large amount of contaminated soil has to be carried out and transported, which requires enormous costs.

[0003] In response to such problems, for example, Patent Document 1 proposes an in-situ purification method for contaminated soil in which heat is applied to a treatment target area containing contaminants, a part of the contaminants is vaporized and sucked, and removed from the treatment target area. According to the invention of Patent Document 1, it is intended to improve the removal efficiency of contaminants by in-situ heating and steam extraction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the heating well (heating well) of Patent Document 1, a heating wire is arranged as a heater inside a sleeve pipe (outer pipe), and the outer pipe and the heating wire are insulated by air. The heat of the heating wire heated to a high temperature (for example, 100 ° C or higher) is transmitted to the treatment target area by radiation. Heat transfer by radiation is inferior in heat transfer efficiency (heating efficiency) compared to heat transfer by conduction.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a heating well with higher heating efficiency. [Means for solving the problem]

[0007] To solve the above problems, the present invention has the following aspects. [1] A heated well used for in-situ remediation of contaminated soil, It comprises an outer tube, a heat-conducting layer formed by filling the inside of the outer tube with a heat-conducting material, and an insulating heater. The aforementioned thermally conductive material has a higher thermal conductivity than air. A heating well in which at least a portion of the insulating heater is inserted into the heat conductive layer. [2] The heating well according to [1], wherein the thermally conductive material is inorganic granular material. [3] The heating well according to [1] or [2], wherein the thermally conductive material is one or more selected from iron sand, iron powder, iron granules, iron chips, iron oxide, non-ferrous metal powder and non-ferrous metal granules. [4] Further comprising a heat transfer element, The heating well according to any one of [1] to [3], wherein the heat transfer element extends in the axial direction of the outer tube within the heat conductive layer and is in contact with the insulating heater. [5] The heating well according to [4], wherein the thermal conductivity of the heat transfer body is higher than the thermal conductivity of the heat conduction layer. [6] The heating well according to [4] or [5], wherein the heat transfer body is an aluminum steel rod. [Effects of the Invention]

[0008] According to the heating well of the present invention, heating efficiency can be further improved. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing the configuration of a heating well according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view showing the configuration of an insulating heater according to one embodiment of the present invention. [Figure 3] This is a cross-sectional view of the CC line in Figure 2. [Figure 4]This graph shows the relationship between distance from the heat source and soil temperature in a simplified simulation. [Figure 5] This is a schematic diagram showing the heat distribution of the heated well and surrounding soil in Example 1. [Figure 6] This graph shows the relationship between the distance from the heat source center and the soil temperature in Example 1. [Figure 7] This is a schematic diagram showing the heat distribution of the heated well and surrounding soil in Comparative Example 1. [Figure 8] This graph shows the relationship between the distance from the heat source center and the soil temperature in Comparative Example 1. [Figure 9] This graph shows the relationship between the distance from the heat source center and the temperature in Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0010] The heated well of the present invention is used for in-situ remediation of soil by heating a treatment area containing contaminated soil with pollutants to increase fluidity by volatilizing the pollutants or reducing their viscosity by raising the temperature, thereby facilitating suction treatment (hereinafter also referred to as "volatilization, etc."). The heating well of the present invention comprises an outer tube, a heat conductive layer, and an insulating heater. The heat conductive layer is formed by filling the inside of the outer tube with a heat conductive material that has a higher thermal conductivity than air. Hereinafter, one embodiment of the heating well of the present invention will be described with reference to the drawings.

[0011] <Heated well> The heating well 1 in Figure 1 comprises an outer tube 10, an insulating heater 20, a heat conductive layer 30, and a heat transfer body 40. The heating well 1 is installed in the treatment area A where contaminated soil is present. The heating well 1 is positioned to extend downward in the depth direction from the ground surface G. The heating well 1 is connected to a power supply 50 installed on the ground surface.

[0012] The cylindrical outer pipe 10 is arranged to extend downward in the depth direction from the ground surface G. Inside the outer pipe 10, a heat-conductive substance is filled to form a heat-conduction layer 30. The insulating heater 20 is inserted into the heat-conduction layer 30 and extends in the axial direction (depth direction) of the outer pipe 10 from the ground surface G or from deep underground deeper than the ground surface G inside the outer pipe 10. The heat-transfer body 40 is inserted into the heat-conduction layer 30 and is arranged above and below the insulating heater 20. The lower end of the heat-transfer body 40 reaches near the bottom of the outer pipe 10. The power supply 50 is located on the ground surface G and is electrically connected to the insulating heater 20. The arrow Q in the figure indicates the direction of heat energy transfer.

[0013] The outer pipe 10 is the casing of the heating well 1. Examples of the outer pipe 10 include carbon steel pipes for piping (SGP pipes), stainless steel pipes, and the like. The bottom of the outer pipe 10 is preferably in a closed form. When the bottom of the outer pipe 10 is in a closed form, it is possible to prevent groundwater from entering the inside of the heating well 1. In addition, when the bottom of the outer pipe 10 is in a closed form, it is possible to prevent the heat-conductive substance from leaking to the outside of the heating well 1. The outer pipe 10 may be cylindrical or polygonal cylindrical.

[0014] The insulating heater 20 is an electric heating heater having insulation. Since the insulating heater 20 has insulation, it is possible to prevent electric leakage due to contact between the heating wire and the outer pipe 10. FIG. 2 shows an example of the insulating heater 20.

[0015] As shown in FIG. 2, the insulating heater 20 includes a heater sheath 22, a heating wire 24, and an insulator 26. The heater sheath 22 has a cylindrical shape extending in the axial direction. In the present embodiment, the insulating heater 20 has the axial direction of the heater sheath 22 as its longitudinal direction. Inside the heater sheath 22, a coiled heating wire 24 serving as a heating element is arranged, and the insulator 26 is filled.

[0016] As shown in Figure 3, the cross-sectional shape of the insulating heater 20 perpendicular to the tube axis is circular. The heater sheath 22 of the insulating heater 20 also has a circular cross-sectional shape perpendicular to the tube axis. A coiled heating wire 24 is arranged inside the heater sheath 22. The cross-sectional shape of the heating wire 24 is a curved ellipse. The heater sheath 22 and the heating wire 24 are insulated by an insulator 26.

[0017] The heater sheath 22 is the casing for the insulating heater 20. Examples of materials for the heater sheath 22 include metal tubes with high temperature resistance such as stainless steel, Inconel® steel, titanium, and aluminum. The outer diameter L22 of the heater sheath 22 is not particularly limited, but is preferably, for example, 5 to 20 mm. If the outer diameter L22 of the heater sheath 22 is greater than or equal to the lower limit, the heating efficiency of the heated well 1 can be further increased. If the outer diameter L22 of the heater sheath 22 is less than or equal to the upper limit, the amount of insulator 26 used can be reduced, which is advantageous in terms of cost.

[0018] The longitudinal length of the heater sheath 22 is not particularly limited, but is preferably 0.1 m or more. If the longitudinal length of the heater sheath 22 is greater than or equal to the lower limit mentioned above, heat can be transferred more efficiently in the depth direction of the processing area A. The upper limit of the length of the heater sheath 22 in the axial direction of the pipe is preferably as long as possible.

[0019] The heating element 24 is a heat source. The material of the heating element 24 is not particularly limited, but examples include metals such as nichrome, tungsten, and platinum. The material of the heating element 24 may also be a non-metallic compound such as silicon carbide.

[0020] The insulator 26 only needs to have insulating properties, and examples include magnesium oxide, mica, porcelain, glass powder, etc.

[0021] A thermally conductive material is a substance with a higher thermal conductivity than air. Because the heating well 1 has a thermally conductive material filled inside the outer tube 10, the heat generated by the insulating heater 20 can be transferred to the treatment area A by conduction rather than radiation. Therefore, the heating efficiency of the heating well 1 can be increased.

[0022] The thermal conductivity of air is 0.0257 W / m·K at 20°C. A thermally conductive material only needs to have a thermal conductivity higher than 0.0257 W / m·K at 20°C. Examples of thermally conductive materials include sand (0.3 W / m·K), soil (0.14 W / m·K), glass granules (0.2-0.8 W / m·K), alumina granules (5-30 W / m·K), iron-based materials (iron sand, iron powder, iron granules, iron scraps, iron oxide, 10-80 W / m·K), cement-based materials such as concrete (1.5 W / m·K), and inorganic granular materials such as non-ferrous metal powder and non-ferrous metal granules. The values ​​in parentheses indicate the thermal conductivity at 20°C or room temperature (5-30°C). The thermal conductivity shown here is an example and will vary depending on the shape of the thermally conductive material, its packing state, etc. For example, even with the same material, the thermal conductivity of granular material is thought to be only a fraction of that of a dense solid. Thus, since thermal conductivity changes depending on the shape and packing state of the thermally conductive material at the time of measurement, it is preferable to determine it by experimental measurement. One method for measuring thermal conductivity is the hot-wire method. In this specification, materials with an average particle diameter of less than 1 mm are referred to as "powder" (iron powder, non-ferrous metal powder), and materials with an average particle diameter of 1 mm or more are referred to as "granules" (iron particles, non-ferrous metal particles).

[0023] The thermal conductivity of the thermally conductive material is preferably 0.1 W / m·K or higher, more preferably 1 W / m·K or higher, and even more preferably 20 W / m·K or higher. If the thermal conductivity of the thermally conductive material is above the lower limit mentioned above, the heating efficiency of the heating well 1 can be further increased. A higher upper limit for the thermal conductivity of the thermally conductive material is preferable, but in this embodiment, it is substantially about 80 W / m·K.

[0024] As a thermally conductive material, sand and soil are preferred due to their low cost. Furthermore, as thermally conductive materials, iron-based materials, non-ferrous metal powders, and non-ferrous metal granules are preferred due to their high thermal conductivity, with iron-based materials being more preferred, and iron sand being even more preferred. Examples of non-ferrous metal powders include aluminum powder (10-40 W / m·K) and copper powder (20-80 W / m·K). Examples of non-ferrous metal granules include aluminum granules (5-30 W / m·K) and copper granules (10-60 W / m·K). When non-ferrous metal powder or non-ferrous metal granules are used as the thermally conductive material, they can be easily recovered with a magnet when the heated well 1 is dismantled and removed. Therefore, it is preferable that the non-ferrous metal be a magnetic metal. The thermally conductive material may be a single material or a combination of two or more materials.

[0025] The thermal conductive layer 30 is formed by filling the inside of the outer tube 10 with a thermally conductive material. In this embodiment, the thermal conductive layer 30 is stacked from the bottom of the outer tube 10 down to the ground surface G of the outer tube 10. The thermal conductivity of the thermal conductive layer 30 can be determined by actual measurement and can be adjusted by the type, shape, and filling state of the thermally conductive material. The thermal conductive material constituting the thermal conductive layer 30 may be one type or two or more types.

[0026] The heat transfer element 40 is located inside the heat conduction layer 30 and transfers the heat generated by the insulating heater 20 in the axial direction (depth direction) of the outer tube 10. The shape of the heat transfer element 40 can be a rod-like shape extending in the depth direction. The shape of the heat transfer element 40 is not limited to a rod-like shape, but may also be a wavy shape or a spiral shape.

[0027] As for the heat transfer element 40, it is preferable that the thermal conductivity of the heat transfer element 40 is higher than that of the heat conduction layer 30, since it is easier to transfer heat generated by the insulating heater 20 in the depth direction than in the direction perpendicular to the tube axis direction (horizontal direction) of the outer tube 10. For example, if the thermally conductive material is sand or soil, the heat transfer body 40 can be glass, asphalt, concrete, alumina, ferrous materials, non-ferrous metals, etc. For example, if the thermally conductive material is an iron-based material, the heat transfer body 40 can be a non-ferrous metal with a higher thermal conductivity than iron. Examples of non-ferrous metals with a higher thermal conductivity than iron include aluminum, copper, and silver. As these heat transfer elements 40, rod-shaped aluminum (aluminum steel rods) is preferred because it has high thermal conductivity, is lightweight, and is easy to install.

[0028] The difference between the thermal conductivity of the heat transfer element 40 and the thermal conductivity of the heat conduction layer 30 ((thermal conductivity of heat transfer element 40) - (thermal conductivity of heat conduction layer 30), also called the "thermal conductivity difference") is preferably as large as possible. A large thermal conductivity difference allows for a greater depth to cover the temperature rise required for the heating process, relative to the length of the insulating heater 20 in the axial direction of the tube (heater depth). Therefore, a large thermal conductivity difference allows for a higher heating efficiency in the depth direction of the processing area A. The thermal conductivity difference can be determined by measuring the thermal conductivity of the heat transfer element 40 and the thermal conductivity of the heat conduction layer 30, respectively.

[0029] When the heat transfer element 40 is rod-shaped, the length of the heat transfer element 40 in the depth direction is preferably about 2m from the lower end of the insulating heater 20. When the length of the heat transfer element 40 in the depth direction is as described above, the heat required for the heating process can be sufficiently transferred to the depth direction of the processing area A. It is preferable that the heat transfer element 40 and the insulating heater 20 are in physical contact with the largest possible contact area. The larger the contact area between the insulating heater 20 and the heat transfer element 40, the more heat generated by the insulating heater 20 can be conducted to the heat transfer element 40. This allows for a higher heating efficiency.

[0030] The power supply 50 is not particularly limited, and examples include a heating power supply device. The power supply 50 is electrically connected to the insulating heater 20. Because the power supply 50 is electrically connected to the insulating heater 20, a voltage can be applied to the heating element 24 of the insulating heater 20, thereby heating the heating element 24. The power supply 50 may be self-powered, or it may be powered by an external power supply facility via wiring or the like.

[0031] ≪How to use a heated well≫ The heated well 1 of this embodiment is used for in-situ remediation, which involves heating the treatment area A where contaminated soil is present to volatilize the contaminants and purify the soil. The in-situ remediation method in this embodiment is a so-called in-situ thermal desorption method. Examples of heating methods for the in-situ thermal desorption method include electric heater type, electric resistance type, and steam type. Among the heating methods for the in-situ thermal desorption method, the electric heater type is preferred because it allows for high heating temperatures and easy uniform heating of the soil. The heating well 1 in this embodiment uses an insulating heater 20, and therefore is classified as an electric heater type heating method.

[0032] When using the heating well 1 of this embodiment, first, a voltage is output from the power supply 50 and supplied to the heating element 24 of the insulating heater 20. The magnitude of the output voltage is set considering the size of the insulating heater 20, the size of the heating well 1, the target heating temperature, etc. For example, a voltage of 30 to 500V is preferable. The magnitude of the output voltage (applied voltage) is determined by the required output and the material, diameter, and length of the heating wire 24, but it is preferable to keep it as small as possible. A smaller applied voltage allows multiple insulating heaters 20 to be connected in series, reducing the number of terminals on the power distribution panel and increasing efficiency.

[0033] When voltage is applied to the heating element 24, it is energized and heated. The heat generated by heating the heating element 24 propagates through the heat conduction layer 30 and is transferred to the external processing area A via the outer tube 10 (heat treatment). In addition, the heat generated by heating the heating element 24 propagates through the heat transfer body 40 and the heat conduction layer 30 and is transferred to the external processing area A via the outer tube 10. In this case, since the heating well 1 has a heat conduction layer 30 inside the outer tube 10, the heat generated by the heating element 24 can be quickly transferred to the processing area A.

[0034] The heating temperature of the treatment area A during heat treatment is preferably 60°C or higher, more preferably 80°C or higher, and even more preferably above the boiling point of groundwater. When the heating temperature is above the lower limit, the vaporization and decomposition of pollutants are promoted, and more pollutants can be removed. In particular, when the heating temperature is above the boiling point of groundwater, the water contained in the pores of the soil is evaporated, the pores between soil particles are expanded, and the desorbed pollutants can be carried away by water vapor, so pollutants can be removed from the soil more efficiently. The upper limit of the heating temperature is up to about 350°C when targeting the unsaturated zone or on-site. The heating temperature during the heat treatment process can be measured using a monitoring well (not shown) equipped with a thermocouple or temperature sensor.

[0035] Examples of pollutants include volatile organic compounds (VOCs), oils, mercury, polychlorinated biphenyls (PCBs), and dioxins. Examples of VOCs include benzene, toluene, and halogenated hydrocarbons (e.g., trichloroethylene). Examples of oils include hydrocarbons with 5 to 44 carbon atoms. Hydrocarbons with 5 to 18 carbon atoms can be recovered mainly as a gas. Even hydrocarbons with 19 or more carbon atoms can be recovered as a liquid by reducing their viscosity. These hydrocarbons may be saturated or unsaturated. These hydrocarbons may be linear, branched, or cyclic. Specific examples of these hydrocarbons include 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., methylmercury, ethylmercury) and phenylmercury (e.g., phenylmercury acetate).

[0036] 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-tetrachloropradioxin and 2,3,4,7,8-pentachlorodibenzofuran.

[0037] The removal of contaminants can be carried out, for example, by using a suction well (not shown) to aspirate a fluid containing contaminants that have been desorbed from the soil by heating.

[0038] The heating well 1 of this embodiment has a heat conductive layer 30 inside the outer tube 10, which is filled with a heat conductive material that has a higher thermal conductivity than air. The heat conductive layer 30 has a higher thermal conductivity than air and can transfer heat by conduction in addition to radiation. Therefore, the heating efficiency of the treatment area A can be increased compared to conventional heating wells. Since the heating well 1 of this embodiment uses an insulating heater 20, heat can be transferred to the processing area A without leakage of electricity. Because the heating well 1 of this embodiment uses a heat transfer body 40, it can efficiently heat even deeper locations within the processing area A.

[0039] Although the heating well and method of using the heating well of the present invention have been described above, the present invention is not limited to the embodiments described above and can be modified as appropriate without departing from the spirit of the invention. For example, in heating well 1, the thermally conductive material is filled throughout the entire interior of the outer tube 10, but in heating wells, there may be areas within the outer tube where the thermally conductive material is absent. However, it is preferable that the thermally conductive material is filled throughout the entire interior of the outer tube in order to further improve heating efficiency. For example, in the heating well 1, the entire insulating heater 20 is inserted into the heat conduction layer 30, but it is sufficient if at least a portion of the insulating heater is inserted into the heat conduction layer. However, it is preferable that the entire insulating heater is inserted into the heat conduction layer in order to further improve heating efficiency. For example, the heating well 1 has a heat transfer element 40, but the heating well may not have a heat transfer element and may consist only of an insulating heater. However, it is preferable for the heating well to have a heat transfer element because it can heat to a deep location in the area to be processed. For example, in heating well 1, the heat transfer body 40 extends to the bottom of the outer tube 10, but in heating wells, the heat transfer body does not necessarily have to reach the bottom of the outer tube. However, it is preferable for the heat transfer body to reach the bottom of the outer tube in order to further improve heating efficiency. For example, the heating well 1 is positioned to extend downward in the depth direction from the ground surface, but the heating well may also be positioned to extend horizontally or diagonally downward in the ground. A single heating well may be installed, or two or more may be installed. [Examples]

[0040] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0041] First, to clarify the features of the present invention, a simple two-dimensional simulation was performed. The results are shown in Figure 4. Note that Figure 4 shows that the center of the heat source is located at a position of 2.5 m. As shown in Figure 4, when the temperature at the outer pipe of the heating well is the same, the temperature of the heating wire in the heating well of Patent Document 1 is 800°C or higher, whereas in the present invention, the temperature of the heating wire in the heating well is about 500°C for the same capacity. This means that in the present invention, the load on the heating wire is small, and the risk of problems such as the heating wire breaking can be reduced. Furthermore, when a voltage greater than the output shown in Figure 4 is applied, the heating element (nichrome wire) in Patent Document 1 approaches its usage limit (approximately 1000°C), resulting in only a slight increase in output. However, in the present invention, the margin before reaching the usage limit is greater than in the case of Patent Document 1, making it easier to increase the output.

[0042] We simulated the soil heating conditions using a heating well with the following configuration, employing thermal analysis software. This was done to confirm that the results obtained in the simplified two-dimensional simulation shown in Figure 4 could be reproduced in a three-dimensional simulation assuming realistic conditions. (Configuration of the heating well: Example 1) ·Outer pipe: SGP pipe, pipe diameter 0.1m, pipe length 10m. • Insulating heater: Heater length 10m, heat output 20.79W / kg. • Thermal conductive layer: Iron sand. Figure 5 shows the heat distribution in Example 1. Figure 6 shows the relationship between the distance from the heat source center (outer tube surface) and the temperature in Example 1.

[0043] As shown in Figure 5, it was found that the temperature is high at the center of the heat source and decreases as the horizontal distance from the center of the heat source increases. Furthermore, it was found that the temperature at the center of the heat source decreases as the depth (Z direction) of the heating well increases.

[0044] As shown in Figure 6, the maximum temperature at the center of the heat source was approximately 147°C.

[0045] (Conventional heating well configuration: Comparative Example 1) ·Outer pipe: SGP pipe, pipe diameter 0.03m, pipe length 10m. • Heater: Heater diameter 0.015m, heater length 10m, heat output 20.79W / kg. • Thermal conductive layer: Air (thermal conductivity 0.0241 W / m·K). Figure 7 shows the heat distribution in Comparative Example 1. Figure 8 shows the relationship between the distance from the heat source center (outer tube surface) and temperature in Comparative Example 1.

[0046] As shown in Figure 7, it was found that the temperature is high at the center of the heat source and decreases as the horizontal distance from the center of the heat source increases. Furthermore, it was found that the temperature at the center of the heat source decreases as the depth (Z direction) of the heating well increases.

[0047] As shown in Figure 8, the maximum temperature at the center of the heat source was approximately 528°C.

[0048] Figure 9 shows a graph illustrating the relationship between the heating temperature and the distance from the heat source center for the heated well used in the above simulation (Example 1) and a conventional heated well (Comparative Example 1). As shown in Figure 9, the temperature distribution was almost the same for Example 1 and Comparative Example 1 beyond the interface between the heated well and the soil, which is approximately 0.03 m from the center of the heat source. On the other hand, the maximum temperature at the center of the heat source was about 150°C in Example 1, while it was about 530°C in Comparative Example 1 when heated with the same energy as Example 1. This means that the load on the heating element is smaller in Example 1, which reduces the risk of problems such as the heating element breaking. Furthermore, when a voltage higher than the output shown in Figure 9 is applied, the heating element (nichrome wire) of Comparative Example 1 approaches its operating limit (approximately 1000°C). This indicates that Example 1 has a greater margin for output enhancement than Comparative Example 1, making it easier to increase the output. Thus, it was found that Example 1, to which the present invention is applied, can sufficiently heat the soil in the treatment area even when the temperature at the center of the heat source is lower than that of Comparative Example 1. In other words, it was found that Example 1, to which the present invention is applied, can achieve higher heating efficiency compared to conventional heated wells. [Explanation of Symbols]

[0049] 1…Heating well, 10…Outer pipe, 20…Insulating heater, 22…Heater sheath, 24…Heating wire, 26…Insulator, 30…Heat conductive layer, 40…Heat transfer element, 50…Power supply

Claims

1. A heated well used for in-situ remediation of contaminated soil, It comprises an outer tube, a heat-conducting layer formed by filling the inside of the outer tube with a heat-conducting material, and an insulating heater. The aforementioned thermally conductive material has a higher thermal conductivity than air. At least a portion of the insulating heater is inserted into the heat conductive layer, It further comprises a heat transfer element, The heat transfer element extends in the axial direction of the outer tube within the heat conductive layer and is in contact with the insulating heater, and is a heating well.

2. The heating well according to claim 1, wherein the thermally conductive material is inorganic granular material.

3. The heating well according to claim 1 or 2, wherein the thermally conductive material is one or more selected from iron sand, iron powder, iron granules, iron chips, iron oxide, non-ferrous metal powder, and non-ferrous metal granules.

4. The heating well according to any one of claims 1 to 3, wherein the thermal conductivity of the heat transfer element is higher than the thermal conductivity of the heat conduction layer.

5. The heating well according to any one of claims 1 to 4, wherein the heat transfer body is an aluminum steel rod.

Images