Heating well

Abstract

To provide a heating well in which failure due to heat generation of an electric heater hardly occurs.SOLUTION: A connection sleeve 31 installed on an 10a of an upper end portion of the outer pipe 10, and a heat-resistant sleeve 32 disposed in the outer pipe 10, wherein a wire 61 electrically connected to a power source installed outside the outer pipe 10 is connected to the 31a of the upper end portion of the connection sleeve 31; An electric heater 20 extending along the longitudinal direction of the outer tube 10 is connected to the 32b of the lower end of the heat-resistant sleeve 32, and a heat-resistant wire 62 is electrically connected between the 31b of the lower end of the connection sleeve 31 and the 32a of the upper end of the heat-resistant sleeve 32.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to heating wells. [Background technology]

[0002] Soil can be contaminated with volatile organic compounds (VOCs), oil, mercury, polychlorinated biphenyls (PCBs), dioxins, and other substances. One known method for purifying contaminated soil is to excavate and remove the contaminated soil (excavation and removal method). The excavation and removal method is the simplest and most reliable method for purifying contaminated soil. However, the excavation and removal method requires the removed contaminated soil to be removed, transported, and treated. This has the disadvantage of requiring huge transportation and treatment costs.

[0003] Another method for purifying contaminated soil is in-situ remediation, which removes contaminants in situ. Known in-situ remediation methods include bioremediation, which activates microorganisms to decompose contaminants, and chemical decomposition (Fenton process) using hydrogen peroxide and other chemicals. However, when using in-situ remediation, if the soil in the area where the contaminated soil is located is clayey or silty with low permeability, it becomes extremely difficult for the treatment chemicals to reach the contaminated soil. For this reason, it can take a long time to remediate the contaminated soil using in-situ remediation.

[0004] Another known in-situ remediation method is in-situ thermal desorption, which uses heat to desorb contaminants from contaminated soil. There are three types of in-situ thermal desorption methods: the electric heater method, the electric resistance method, and the steam method.

[0005] Unlike the electrical resistance and steam methods, the in-situ thermal desorption method using an electric heater can uniformly heat the contaminated soil in situ to above 100°C. Therefore, in-situ thermal desorption using an electric heater can sufficiently expand the pore spaces between soil particles as the pore water in the soil in the treatment area turns to water vapor. Furthermore, the water vapor generated by heating the soil in the treatment area desorbs contaminants vaporized from the soil particles and entrains the contaminants. As a result, in-situ thermal desorption using an electric heater can efficiently remove contaminants from the contaminated soil in the treatment area.

[0006] An example of an in-situ thermal desorption method using an electric heater is the method described in Patent Document 1. Patent Document 1 describes a method in which heat is applied to a treatment target area containing contaminants to vaporize some of the contaminants, which are then sucked up and removed from the treatment target area. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4509558 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in heating wells equipped with electric heaters, problems can arise when the temperature inside the heating well is increased in order to ensure remediation performance according to the contamination state of the contaminated soil and the type of contaminant. For this reason, it has been necessary to suppress the power supplied to the electric heater and limit the output of the electric heater.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a heated well that is less likely to suffer from problems caused by heat generated by an electric heater. [Means for solving the problem]

[0010] In order to solve the above problem, the inventors have conducted extensive research into the causes of malfunctions in heating wells equipped with electric heaters due to heat generated by the electric heaters. As a result, it was found that the main cause of damage was the wiring that supplies electricity to the electric heater, which is installed at the upper end of the outer pipe of the heating well and is connected to the connecting sleeve and / or the wiring that supplies electricity to the electric heater, which was damaged by the heat generated by the electric heater.

[0011] Therefore, the inventors of the present invention have focused on the arrangement of the wiring that supplies electricity to the electric heater, the connection sleeve, and the electric heater, and have conducted extensive research. As a result, we discovered that it is possible to position the connection sleeve and the electric heater at a distance by installing a connection sleeve at the upper end of the heating well and placing a heat-resistant sleeve connected to the electric heater and heat-resistant wiring electrically connecting the heat-resistant sleeve and the connection sleeve between the connection sleeve and the electric heater, and thus arrived at the present invention. In order to solve the above problems, the present invention has the following aspects.

[0012] [1] A heating well installed in an area of ​​contaminated soil to be treated; an outer pipe installed facing downward in the treatment target area; a connecting sleeve installed at an upper end of the outer pipe; a heat-resistant sleeve disposed within the outer tube; A wiring electrically connected to a power source installed outside the outer tube is connected to an upper end of the connection sleeve, an electric heater extending along the longitudinal direction of the outer tube is connected to a lower end of the heat-resistant sleeve; A heating well, wherein a heat-resistant wiring is electrically connected between the lower end of the connection sleeve and the upper end of the heat-resistant sleeve.

[0013] [2] A heating well according to [1], wherein the lower end surface of the electric heater and the bottom surface of the outer tube are spaced apart. [3] The heating well according to [1], wherein the distance between the lower end surface of the connecting sleeve and the lower end surface of the heat-resistant sleeve is 40 cm to 150 cm. [4] The heating well according to [1], wherein the distance between the lower end surface of the electric heater and the bottom surface inside the outer tube is 100 mm to 500 mm.

[0014] [5] The heating well described in [1], wherein the heat-resistant wiring comprises a metal sheath, a conductive wiring housed within the metal sheath, and an inorganic insulating material filled in the gap between the conductive wiring and the metal sheath.

[0015] [6] The electric heater is integrated with the heat-resistant sleeve having an outer shape that surrounds the outer shape of the electric heater in a plan view, a sheath pipe extending along the longitudinal direction of the outer pipe to a bottom surface inside the outer pipe is provided inside the outer pipe, The electric heater is installed inside the sleeve pipe, A plate-shaped washer is placed on the upper end surface of the sleeve pipe, the washer has an outer shape that surrounds the sleeve tube in a plan view, and is surrounded by the outer shape of the heat-resistant sleeve in a plan view, and has a through hole that surrounds the electric heater; The heating well described in [1], wherein the heat-resistant sleeve is placed on the washer, thereby suspending the electric heater within the sheath pipe.

[0016] [7] A heating well as described in [1], wherein the heat-resistant sleeve has connection portions arranged at the upper and lower ends, respectively, a metal sheath, a conductive connection member housed within the metal sheath and electrically connecting the connection portion arranged at the upper end and the connection portion arranged at the lower end, and an inorganic insulating material filled in the gap between the conductive connection member and the metal sheath within the metal sheath. [Effects of the Invention]

[0017] The heating well of the present invention has a connecting sleeve installed at the upper end of the outer pipe and a heat-resistant sleeve arranged inside the outer pipe, with wiring electrically connected to a power source installed outside the outer pipe connected to the upper end of the connecting sleeve, an electric heater extending along the longitudinal direction of the outer pipe connected to the lower end of the heat-resistant sleeve, and heat-resistant wiring electrically connected between the lower end of the connecting sleeve and the upper end of the heat-resistant sleeve. Therefore, in the heating well of the present invention, the connecting sleeve and the electric heater are spaced apart by the heat-resistant wiring and the heat-resistant sleeve.

[0018] As a result, in the heating well of the present invention, the impact of heat generated by the electric heater on the connecting sleeve and the wiring connected to the upper end of the connecting sleeve is mitigated by the heat-resistant wiring and heat-resistant sleeve, making it less likely that the connecting sleeve and the wiring connected to the upper end of the connecting sleeve will be damaged by heat generated by the electric heater. As a result, the heating well of the present invention is less likely to suffer from problems caused by heat generated by the electric heater, and there is no need to suppress the power supplied to the electric heater and limit the output of the electric heater, allowing the temperature of the heating well to be sufficiently high. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a heating well of the first embodiment. [Figure 2] Figure 2(a) is a schematic cross-sectional view of the heating well of the first embodiment shown in Figure 1, taken along line II' shown in Figure 1. Figure 2(b) is a schematic cross-sectional view of the heating well of the first embodiment shown in Figure 1, taken along line II-II' shown in Figure 1. [Figure 3]Figure 3 is an enlarged cross-sectional view illustrating the dimensional relationship between the electric heater 20, the lower end 32b of the heat-resistant sleeve 32, the sheath pipe 50, and the washer 80 in the heating well 1 of the first embodiment shown in Figure 1. Figure 3(a) is a cross-sectional view taken along the vertical direction of the heating well. Figure 3(b) is a cross-sectional view taken along line III-III' shown in Figure 3(a). DETAILED DESCRIPTION OF THE INVENTION

[0020] The heating well of the present invention will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts enlarged for the sake of clarity. Therefore, the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them. Appropriate changes can be made within the scope of the present invention.

[0021] [Heating well] Figure 1 is a schematic cross-sectional view showing a heating well of the first embodiment. Figure 2(a) is a schematic cross-sectional view of the heating well of the first embodiment shown in Figure 1, taken along line II' shown in Figure 1. Figure 2(b) is a schematic cross-sectional view of the heating well of the first embodiment shown in Figure 1, taken along line II-II' shown in Figure 1.

[0022] The heating well 1 of this embodiment is installed and used in a contaminated soil treatment area A where contaminants are present, as shown in Figure 1. It is preferable that a known suction well (not shown) is provided around the heating well 1 to suck and collect the contaminants vaporized by heating the contaminated soil with the heating well 1.

[0023] As shown in Fig. 1, the heating well 1 of this embodiment has an outer pipe 10, an inner pipe 90, and a heating unit 11. As shown in Fig. 1, the heating unit 11 has wiring 61 electrically connected to a power source (not shown), a connection sleeve 31, heat-resistant wiring 62, a heat-resistant sleeve 32, an electric heater 20, and a sheath pipe 50.

[0024] In this embodiment, as shown in Figures 1, 2(a) and 2(b), an example will be described in which the heating well 1 has one outer pipe 10, one inner pipe 90 and four heating units 11. However, the number of heating units 11 in the heating well 1 of this embodiment is not limited to four, and may be one to three, or five or more, and is not particularly limited.

[0025] When the heating well 1 has multiple heating units 11, it is preferable that the heating units 11 be installed so that they are evenly spaced apart in a plan view and so that their longitudinal directions are approximately parallel to each other, as shown in Figures 1, 2(a), and 2(b). This arrangement allows the electric heaters 20 of each heating unit 11 to uniformly heat the soil, and the heating well 1 can efficiently heat the contaminated soil around the outer pipe 10. When the heating well 1 has multiple heating units 11, it is most preferable that the number of heating units 11 be four, as shown in Figures 1, 2(a), and 2(b). This is because the heating units 11 can be easily installed so that they are evenly spaced apart in a plan view.

[0026] As shown in FIG. 1, the area of ​​the surface G of the treatment target area A near the heating well 1 is covered with a concrete layer 40. The concrete layer 40 is preferably made of air mortar. The concrete layer 40 made of air mortar has good insulating properties, so heat radiation from the heating well 1 can be suppressed. Therefore, the heat generated by the electric heater 20 can heat the contaminated soil treatment target area A more efficiently, and the amount of energy required to purify the contaminated soil can be reduced.

[0027] The outer pipe 10 in the heating well 1 of this embodiment is the casing of the heating well 1. As shown in Figures 1, 2(a) and 2(b), the outer pipe 10 has a substantially cylindrical shape and is installed facing downward in the treatment target area A. Examples of the outer pipe 10 include carbon steel pipes for piping (SGP pipes) and stainless steel pipes. In the heating well 1 of this embodiment, as shown in Figure 1, the bottom surface 10b of the outer pipe 10 is closed.

[0028] As shown in Figures 1, 2(a) and 2(b), the inner pipe 90 in the heating well 1 of this embodiment has a substantially cylindrical shape and is provided in the outer pipe 10 at a position substantially at the center in a plan view, along the longitudinal direction of the outer pipe 10. As shown in Figure 1, the inner pipe 90 extends from a position above the upper end surface of the outer pipe 10 to the bottom surface 10b within the outer pipe 10. Examples of the inner pipe 90 include carbon steel pipes for piping (SGP pipes), stainless steel pipes, etc. The outer pipe 10 and the inner pipe 90 may be made of the same material or different materials.

[0029] 1, 2(a) and 2(b), a temperature measuring device 91 is installed inside the inner pipe 90. The temperature measuring device 91 may be any device that can measure the temperature inside the inner pipe 90, and may be, for example, a known temperature measuring device such as a thermocouple or a temperature sensor.

[0030] As shown in Fig. 1, the connection sleeve 31 has a generally cylindrical shape with the outer diameter of the upper end 31a and the lower end 31b being smaller than that of the central portion. As shown in Fig. 1, the lower end 31b of the connection sleeve 31 is installed inside the outer pipe 10. The central portion and the upper end 31a of the connection sleeve 31 are installed above the upper end 10a of the outer pipe 10 and are exposed from the outer pipe 10.

[0031] A wiring 61 electrically connected to a power source (not shown) installed outside the outer tube 10 is connected to the upper end 31a of the connection sleeve 31. The power source is not particularly limited, and for example, a heating power supply device or the like can be used. The wiring 61 is for supplying electricity to the electric heater 20.

[0032] As shown in Figure 1, a case 70 is installed on the upper end 10a of the outer pipe 10 to protect the components exposed from the outer pipe 10 of the heating well 1. As shown in Figure 1, the case 70 houses the upper ends of the inner pipe 90 and temperature measuring device 91, the center and upper end 31a of the connection sleeve 31, and the connection between the upper end 31a of the connection sleeve 31 and the wiring 61.

[0033] A known material used for electrically connecting conductive wires can be used as the connection sleeve 31. For example, it is preferable to use a connection sleeve 31 that includes connection portions consisting of terminals or the like arranged at the upper end 31a and the lower end 31b, a sheath member, a conductive connection member housed within the sheath member and electrically connecting the connection portions arranged at the upper end 31a and the lower end 31b, and an insulating material filled in the gap between the conductive connection member and the sheath member.

[0034] The sheath member of the connection sleeve 31 may be made of, for example, resin, metal, or ceramic. The conductive connection member may be made of, for example, copper wire, iron wire, stainless steel wire, or nichrome wire. The insulating material may be, for example, known materials such as epoxy resin, alumina, cement, or magnesium oxide.

[0035] As shown in Fig. 1, the heat-resistant sleeve 32 is disposed inside the outer tube 10. As shown in Fig. 1, the heat-resistant sleeve 32 has a generally cylindrical shape in which the outer diameters of the upper end 32a and the lower end 32b are smaller than that of the central portion. An electric heater 20 extending along the longitudinal direction of the outer tube 10 is connected to the lower end 32b of the heat-resistant sleeve 32. The heat-resistant sleeve 32 has excellent heat resistance, and is therefore unlikely to be damaged even if the electric heater 20 generates heat.

[0036] A known material having excellent heat resistance and used for electrically connecting conductive wires can be used as the heat-resistant sleeve 32. For example, it is preferable to use a heat-resistant sleeve 32 that includes connection portions consisting of terminals or the like arranged at the upper end 32a and the lower end 32b, a metal sheath, a conductive connection member housed in the metal sheath and electrically connecting the connection portions arranged at the upper end 32a and the lower end 32b, and an inorganic insulating material filled in the gap between the conductive connection member and the metal sheath.

[0037] The metal sheath of the heat-resistant sleeve 32 may be made of, for example, resin, metal, or ceramic. The conductive connecting member may be made of, for example, copper wire, iron wire, stainless steel wire, or nichrome wire. The inorganic insulating material may be, for example, magnesium oxide, alumina, epoxy resin, or cement, with magnesium oxide being preferred.

[0038] Such a heat-resistant sleeve 32 has excellent heat resistance, and is therefore less likely to be damaged even if the inside of the outer tube 10 below the heat-resistant sleeve 32 reaches a high temperature of 500°C to 800°C due to heat generated by the electric heater 20, which is preferable. The heat-resistant sleeve 32 may be a commercially available product.

[0039] In the heating well 1 of this embodiment, as shown in Figure 1, a heat-resistant wiring 62 is electrically connected between the lower end 31b of the connection sleeve 31 and the upper end 32a of the heat-resistant sleeve 32. The heat-resistant wiring 62 has excellent heat resistance, so it is unlikely to be damaged even if the electric heater 20 generates heat and is heated through the heat-resistant sleeve 32.

[0040] A known wiring having excellent heat resistance can be used as the heat-resistant wiring 62, and it is preferable that the wiring has heat resistance and insulating properties and includes conductive wiring with a large cross-sectional area, thereby suppressing electrical resistance and heat generation. As the heat-resistant wiring 62, for example, as shown in Fig. 2(a), it is preferable to use a wiring having a substantially cylindrical shape that is made of a metal sheath 62a, a conductive wiring 62b housed in the metal sheath 62a, and an inorganic insulating material 62c filled in the gap between the conductive wiring 62b and the metal sheath 62a.

[0041] The metal sheath 62a of the heat-resistant wiring 62 may be made of, for example, stainless steel or carbon steel. The conductive wires 62b may be made of a conductive material such as copper wire, iron wire, stainless steel wire, nichrome wire, etc. The number of conductive wires 62b included in each heat-resistant wire 62 may be one, or as shown in FIG. 2(a), may be two, or may be three or more, and is not particularly limited. The inorganic insulating material 62c may be, for example, magnesium oxide or alumina.

[0042] A commercially available product may be used as the heat-resistant wiring 62. Examples of commercially available heat-resistant wiring 62 include OKAZAKI MI Cable (product name: manufactured by Okazaki Manufacturing Co., Ltd.), SHEATH (product name: manufactured by Omega Engineering Co., Ltd.), and MI Cable (product name: manufactured by Yamazato Sangyo Co., Ltd.).

[0043] These heat-resistant wirings 62 have excellent heat resistance and insulation properties and heat generation is sufficiently suppressed, so that they are preferable because they will not be damaged even if the temperature inside the outer tube 10 below the heat-resistant sleeve 32 reaches high temperatures of 800°C to 1000°C due to heat generation by the electric heater 20, for example.

[0044] In the heating well 1 of this embodiment, the distance L1 (see FIG. 1) between the lower end surface of the connecting sleeve 31 and the lower end surface of the heat-resistant sleeve 32 is preferably 40 cm to 150 cm. When the distance L1 is 40 cm or more, the heat-resistant wiring 62 and the heat-resistant sleeve 32 can effectively mitigate the influence of heat generated by the electric heater 20 on the connecting sleeve 31 and the wiring 61.

[0045] Specifically, for example, when heat-resistant wiring 62 is used in which magnesium oxide is filled as inorganic insulating material 62c in the gap between conductive wiring 62b and metal sheath 62a within metal sheath 62a, if the distance L1 is 40 cm or more, the temperature of lower end 31b of connection sleeve 31 can be kept below 70°C even if the temperature inside outer tube 10 below heat-resistant sleeve 32 reaches a high of 800°C due to heat generated by electric heater 20. Therefore, damage to connection sleeve 31 and wiring 61 caused by heat generated by electric heater 20 is even less likely to occur. It is more preferable that distance L1 be 100 cm or more.

[0046] Furthermore, if the distance L1 is 150 cm or less, the upper end 31a of the connection sleeve 31 is not positioned too high from the surface G of the treatment target area A, which is preferable because it does not hinder the workability when connecting the upper end 31a of the connection sleeve 31 to the wiring 61. It is more preferable that the distance L1 is 120 cm or less.

[0047] As shown in FIGS. 1 and 2(b), the electric heater 20 has a generally cylindrical shape and is connected to the lower end 32b of the heat-resistant sleeve 32, thereby being integrated with the heat-resistant sleeve 32. As the electric heater 20, it is preferable to use an electric insulating heater, which is an electric heater having good safety.

[0048] As the electric heater 20, it is preferable to use an electric insulating heater having a heater sheath 21a (outer cover), a heating wire 21b housed within the heater sheath 21a, and an insulating and thermally conductive material 21c filled in the gap between the heating wire 21b and the heater sheath 21a within the heater sheath 21a, as shown in Figure 2(b).

[0049] The heater sheath 21a forming the electric insulating heater may be made of a metal such as stainless steel (SUS304, SUS310, SUS316, etc.). Furthermore, the insulating and thermally conductive material 21c forming the electric insulating heater is preferably magnesium oxide, because magnesium oxide is inexpensive and has good insulating and thermal conductivity.

[0050] The heating wire 21b forming the electric insulating heater may be any known material and is not particularly limited. Examples of the heating wire 21b include those made of metals such as nichrome, tungsten, graphite, and platinum, and those made of non-metallic compounds such as ceramics, carbon fiber, and silicon carbide, with nichrome wire being preferred. The heating wire 21b may be housed in a heater sheath in a spiral shape, for example.

[0051] In the heating well 1 of this embodiment, as shown in Figures 1 and 2(b), a sheath pipe 50 having a substantially cylindrical shape is provided inside the outer pipe 10. The sheath pipe 50 extends along the longitudinal direction of the outer pipe 10 to the bottom surface 10b inside the outer pipe 10. An electric heater 20 is installed inside the sheath pipe 50. Examples of the sleeve pipe 50 include carbon steel pipes for piping (SGP pipes), stainless steel pipes, etc. The outer pipe 10 and the sleeve pipe 50 may be made of the same material or different materials.

[0052] In the heating well 1 of this embodiment, as shown in Figures 1 and 2(b), a plate-shaped washer 80 is placed on the upper end surface 50a of the sheath pipe 50. The washer 80 may be made of a metal such as stainless steel (SUS304, SUS310, SUS316, etc.) or carbon steel. The washer 80 may also be made of a material with low thermal conductivity, such as ceramic.

[0053] Here, the dimensional relationship between the electric heater 20, the lower end 32b of the heat-resistant sleeve 32, the sheath pipe 50, and the washer 80 in the heating well 1 of the first embodiment shown in FIG. 1 will be explained using the drawings. 3 is an enlarged cross-sectional view illustrating the dimensional relationship between the electric heater 20, the lower end 32b of the heat-resistant sleeve 32, the sheath pipe 50, and the washer 80 in the heating well 1 of the first embodiment shown in FIG. 1. FIG. 3(a) is a cross-sectional view of the heating well cut in the vertical direction. FIG. 3(b) is a cross-sectional view cut along line III-III' shown in FIG. 3(a). In FIG. 3(b), D80 indicates the outer diameter of the washer 80, D50 indicates the outer diameter of the sheath pipe 50, D32b indicates the outer diameter of the lower end 32b of the heat-resistant sleeve 32, D80a indicates the inner diameter of the through hole 80a of the washer 80, and D20 indicates the outer diameter of the electric heater 20.

[0054] 3(a) and 3(b), the washer 80 has a generally circular outer shape in plan view with an outer diameter D80 larger than the outer diameter D50 of the sleeve tube 50. The washer 80 also has a generally circular through-hole 80a in its center with an inner diameter D80a in plan view that is smaller than the outer diameter D32b of the lower end 32b of the heat-resistant sleeve 32 and larger than the outer diameter D20 of the electric heater 20.

[0055] In the heating well 1 of this embodiment, the dimensional relationship between the outer diameter D80 of the washer 80, the outer diameter D50 of the sheath pipe 50, the outer diameter D32b of the lower end 32b of the heat-resistant sleeve 32, the inner diameter D80a of the through hole 80a of the washer 80, and the outer diameter D20 of the electric heater 20 is as described above, so that as shown in Figure 3(a), the electric heater 20 is inserted into the through hole 80a of the washer 80, and the heat-resistant sleeve 32 integrated with the electric heater 20 is placed on the washer 80, thereby suspending the electric heater 20 at approximately the center position within the sheath pipe 50 when viewed from above.

[0056] In this embodiment, as shown in Figures 3(a) and 3(b), the outer diameter D80 of the washer 80, the outer diameter D50 of the sheath tube 50, the outer diameter D32b of the lower end 32b of the heat-resistant sleeve 32, the inner diameter D80a of the through hole 80a of the washer 80, and the outer diameter D20 of the electric heater 20 are approximately concentric, but the center positions of some or all of these components may be different.

[0057] The planar shape of the washer 80 in the heating well 1 of this embodiment is not limited to the examples shown in FIGS. 3(a) and 3(b). That is, the outer diameter of the washer 80 may be any shape that surrounds the sheath pipe 50 in a planar view. Therefore, the outer diameter D80 of the washer 80 may be smaller than the outer diameter D32b of the lower end 32b of the heat-resistant sleeve 32 in a planar view. The shape of the through-hole 80a may be any shape that is surrounded by the outer shape of the heat-resistant sleeve 32 and surrounds the electric heater 20 in a planar view. The location of the through-hole 80a in the washer 80 in a planar view does not have to be at the center of the washer 80 and can be determined appropriately depending on the location of the electric heater 20 within the sheath pipe 50 in a planar view. The outer shape of the washer 80 and / or the shape of the through-hole 80a in a planar view are not limited to a substantially circular shape and may be, for example, a substantially polygonal shape or a substantially elliptical shape.

[0058] As described above, the washer 80 in the heating well 1 of this embodiment functions as a suspending member for suspending the electric heater 20 within the sheath pipe 50. Furthermore, if the washer 80 is made of a material with low thermal conductivity, such as ceramic, it also functions as a member for suppressing heat radiation upward from within the sheath pipe 50. Therefore, by placing the washer 80 on the upper end surface 50a of the sheath pipe 50, damage to the connection sleeve 31 and wiring 61 due to heat generated by the electric heater 20 can be more effectively prevented, and the heat generated by the electric heater 20 can be used more efficiently to heat the contaminated soil treatment target area A, thereby reducing the amount of energy required for remediation of the contaminated soil.

[0059] In the heating well 1 of this embodiment, as shown in Figure 1, the lower end surface 20b of the electric heater 20 is spaced apart from the bottom surface 10b inside the outer tube 10. Therefore, even if the electric heater 20 generates heat and the temperature inside the sheath tube 50 becomes sufficiently high, damage to the electric heater 20 due to thermal expansion of the electric heater 20 can be prevented, as will be described below.

[0060] That is, when the electric heater 20 generates heat, the electric heater 20 expands due to thermal expansion. In the heating well 1 of this embodiment, problems caused by heat generation by the electric heater 20 are unlikely to occur, and there is no need to limit the output of the electric heater 20 by suppressing the power supplied to the electric heater 20. Therefore, the temperature inside the sheath tube 50 can be sufficiently high. As a result, the thermal expansion of the electric heater 20 caused by generating heat may become more pronounced than in the past, and the electric heater 20 may expand significantly. In this case, in the heating well 1 of this embodiment, the lower end surface 20b of the electric heater 20 and the bottom surface 10b inside the outer tube 10 are arranged at a distance from each other. Therefore, the expansion of the electric heater 20 due to thermal expansion is prevented by the bottom surface 10b inside the outer tube 10, preventing deformation and damage of the electric heater 20.

[0061] Furthermore, in the heating well 1 of this embodiment, the heat-resistant sleeve 32 separates the electric heater 20 from the heat-resistant wiring 62, and also suppresses heat generation by the heat-resistant wiring 62. Therefore, even if the electric heater 20 generates heat, the heat-resistant wiring 62 is less likely to thermally expand, and even if, for example, the electric heater 20 generates heat and the temperature inside the outer pipe 10 below the heat-resistant sleeve 32 reaches a high temperature of 800°C, the heat-resistant wiring 62 is less likely to expand and break, resulting in problems.

[0062] In the heating well 1 of this embodiment, the distance L2 between the lower end surface 20b of the electric heater 20 and the bottom surface 10b inside the outer pipe 10 is preferably 100 mm to 500 mm. If the distance L2 is 100 mm or more, even if the electric heater 20 expands due to thermal expansion, the lower end surface 20b of the electric heater 20 is less likely to come into contact with the bottom surface 10b inside the outer pipe 10. Therefore, damage to the electric heater 20 due to thermal expansion and expansion of the electric heater 20 can be more effectively prevented.

[0063] For example, when the electric heater 20 has a length of 10 m and a heater sheath 21a made of stainless steel, the latent thermal expansion coefficient of stainless steel is 16.7 × 10 -6 / °C, when the temperature inside the outer tube 10 is raised from 20°C to 800°C, the electric heater 20 will expand by 130 mm. Therefore, when the distance L2 is 130 mm or more and the electric heater 20 has a heater sheath 21a made of stainless steel and is 10 m or less in length, even when the temperature inside the outer tube 10 is raised from 20°C to 800°C, the expansion of the electric heater 20 due to thermal expansion will not be impeded by the bottom surface 10b inside the outer tube 10. The distance L2 is more preferably 130 mm or more, and even more preferably 150 mm or more.

[0064] Furthermore, if the distance L2 is 500 mm or less, it is possible to prevent an increase in the amount of excavation required to install the heating well 1, which would otherwise be required if the lengths of the outer pipe 10 and the sheath pipe 50 were to be increased. This reduces the amount of work and energy required to install the heating well 1. It is more preferable that the distance L2 be 500 mm or less.

[0065] The length of the electric heater 20 in the heating well 1 of this embodiment can be, for example, 1 m to 20 m, or may be 10 m to 15 m, and can be determined appropriately depending on the depth from the surface G of the contaminated soil where the contaminants are present. In the heating well 1 of this embodiment, when the length of the electric heater 20 is 10 m or more, the effect of efficiently purifying the contaminated soil becomes significant when compared to, for example, when purifying the contaminated soil using an excavation and removal method.

[0066] Furthermore, when the length of the electric heater 20 is 10 m or more, the distance between the lower end surface 20 b of the electric heater 20 and the bottom surface 10 b inside the outer tube 10 is greater, which is likely to prevent damage to the electric heater 20. In particular, when the length of the electric heater 20 is 15 m or more and the electric heater 20 is heated to a temperature of 600°C or higher, the distance L2 between the lower end surface 20 b of the electric heater 20 and the bottom surface 10 b inside the outer tube 10 is greater, which is likely to prevent damage to the electric heater 20 when the distance between the lower end surface 20 b of the electric heater 20 and the bottom surface 10 b inside the outer tube 10 is greater.

[0067] The heating well 1 of this embodiment is less susceptible to problems caused by heat generated by the electric heater 20, and can be heated so that the temperature inside the outer pipe 10 reaches 800°C or higher. Therefore, the temperature inside the outer pipe 10 forming the heating well 1 can be appropriately determined depending on factors such as the vaporization temperature of the contaminants present in the contaminated soil treatment target area A. In contrast, in conventional heating wells, problems occur due to heat generated by the electric heater 20, making it difficult to heat the well to temperatures above 500°C.

[0068] When using the heating well 1 of this embodiment to purify contaminated soil in the treatment area A, the temperature inside the outer pipe 10 can be heated by the electric heater 20 to, for example, 300°C to 1100°C, or it may be heated to 500°C to 1050°C, or it may be heated to more than 700°C and less than 1000°C, or it may be heated to more than 800°C and less than 900°C.

[0069] [How to install a heating well] Next, an example of a method for installing the heating well 1 shown in Figures 1, 2(a) and 2(b) in contaminated soil will be described. The method for installing the heating well 1 of this embodiment in contaminated soil is not particularly limited, and for example, the following method can be used.

[0070] In this embodiment, multiple heating wells 1 are installed at predetermined intervals in a plan view in a contaminated soil treatment target area A where contaminants exist in an area from the surface G to a certain depth. The number of heating wells 1 installed in the treatment target area A is determined according to the area of ​​the treatment target area A and the distance between adjacent heating wells 1.

[0071] The distance between adjacent heating wells 1 installed in the treatment target area A can be, for example, 2 m to 4 m, and preferably 3 m to 3.5 m. The distance between adjacent heating wells 1 is determined appropriately depending on the type of contaminants contained in the treatment target area A, the soil quality of the treatment target area A, the temperature inside the outer pipe 10 of the heating well 1 heated by the electric heater 20, and other factors. The heating well 1 of this embodiment can raise the temperature inside the outer pipe 10 to a high temperature of 800°C or higher using the electric heater 20. Therefore, by increasing the temperature inside the outer pipe 10, the distance between adjacent heating wells 1 installed in the treatment target area A can be increased, and the number of heating wells 1 installed in the treatment target area A can be reduced.

[0072] To install the heating well 1 of this embodiment in the treatment target area A, first, the treatment target area A is excavated using a known boring method to form a substantially cylindrical hole of a predetermined depth and diameter in the treatment target area A.

[0073] The structure that will become the heating well 1 is manufactured by the following method. First, an outer pipe 10 is prepared, with a predetermined inner pipe 90 fixed at the center and four sheath pipes 50 fixed thereto so that they are evenly spaced from each other in a plan view. The number of sheath pipes 50 may be one to three, five, or six. The connection sleeve 31, heat-resistant wiring 62, heat-resistant sleeve 32, and electric heater 20 are electrically connected and integrated. The electric heater 20 is then inserted into the through-hole 80a of the washer 80. The integrated connection sleeve 31, heat-resistant wiring 62, heat-resistant sleeve 32, and electric heater 20 are then inserted into the outer pipe 10, and the washer 80 is placed on the upper end surface 50a of the sheath pipe 50. The heat-resistant sleeve 32 is then installed on the washer 80, as shown in FIG. 3(a). This allows the electric heater 20 to be suspended within the sheath pipe 50. Through the above steps, a structure that will become the heating well 1 is obtained.

[0074] Next, a structure to become the heating well 1, in which an electric heater 20 is suspended in a sheath pipe 50 inside an outer pipe 10, is installed in a hole provided in the treatment target area A by a known method. Next, in this embodiment, as shown in FIG. 1, air mortar is poured onto the top surface of the soil near the heating well 1 to form a concrete layer 40.

[0075] Thereafter, a temperature measuring device 91 is installed inside the inner pipe 90 of the structure that will become the heating well 1. In addition, the upper end 31a of the connection sleeve 31 is electrically connected to wiring 61 that is electrically connected to a power source (not shown) installed outside the outer pipe 10. Then, as shown in FIG. 1, the upper ends of the inner pipe 90 and the temperature measuring device 91, the center and upper end 31a of the connection sleeve 31, and the connection part between the upper end 31a of the connection sleeve 31 and the wiring 61 are housed inside the case 70. This completes the installation of the heating well 1.

[0076] Furthermore, in this embodiment, before heating the contaminated soil with the heating well 1, it is preferable to provide a known suction well (not shown) around the heating well 1 to suck and collect the contaminants vaporized by heating the contaminated soil. It is preferable to install a plurality of suction wells in the treatment target area A using a known method, spaced apart at predetermined intervals in a plan view.

[0077] [Recoverable pollutants] Next, contaminants that can be recovered by purifying contaminated soil using the heating well 1 of this embodiment will be described. Such contaminants include, for example, volatile organic compounds (VOCs), oils, mercury, polychlorinated biphenyls (PCBs), dioxins, and organofluorine compounds (PFASs) such as perfluoroalkyl compounds and polyfluoroalkyl compounds.

[0078] Examples of VOCs include benzene and halogenated hydrocarbons (such as tetrachloroethylene and trichloroethylene). Examples of oils include hydrocarbons having 5 to 18 carbon atoms. Hydrocarbons having 5 to 18 carbon atoms can be recovered mainly as gas. These hydrocarbons may be saturated hydrocarbons or unsaturated hydrocarbons. These hydrocarbons may have a linear structure, a branched structure, or a cyclic structure. Examples of hydrocarbons having 5 to 18 carbon atoms include n-pentane, isopentane, n-hexane, and cyclohexane.

[0079] Examples of mercury include metallic mercury, inorganic mercury, and organic mercury. Examples of inorganic mercury include mercury oxide, mercury sulfide, mercury chloride (HgCl, HgCl), and mercury nitrate. Examples of organic mercury include alkyl mercury (e.g., methyl mercury, ethyl mercury), and phenyl mercury (e.g., phenyl mercury acetate).

[0080] 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.

[0081] Examples of PFASs include perfluorooctane sulfonic acid (PFOS), perfluorosulfonic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), PFHxA, PFHpS, and PFHpA.

[0082] The heating well 1 of this embodiment can raise the temperature inside the outer tube 10 to a high temperature of, for example, 800°C or higher using the electric heater 20. For this reason, it can be preferably used when removing contaminants with high boiling points, such as PFASs and polychlorinated biphenyls (PCBs), among the above-mentioned contaminants.

[0083] The heating well 1 of this embodiment has a connection sleeve 31 installed at the upper end 10a of the outer pipe 10 and a heat-resistant sleeve 32 arranged inside the outer pipe 10, and the upper end 31a of the connection sleeve 31 is connected to wiring 61 electrically connected to a power source installed outside the outer pipe 10, and the lower end 32b of the heat-resistant sleeve 32 is connected to an electric heater 20 extending along the longitudinal direction of the outer pipe 10, and between the lower end 31b of the connection sleeve 31 and the upper end 32a of the heat-resistant sleeve 32, a heat-resistant wiring 62 is connected that electrically connects the wiring 61 connected to the connection sleeve 31 and the electric heater 20. Therefore, in the heating well 1 of this embodiment, the connection sleeve 31 and the electric heater 20 are spaced apart by the heat-resistant wiring 62 and the heat-resistant sleeve 32.

[0084] As a result, in the heating well 1 of this embodiment, the impact of heat generated by the electric heater 20 on the connecting sleeve 31 and the wiring 61 connected to the upper end 31a of the connecting sleeve 31 is mitigated by the heat-resistant wiring 62 and the heat-resistant sleeve 32, making it less likely that the connecting sleeve 31 and the wiring 61 connected to the upper end 31a of the connecting sleeve 31 will be damaged by heat generated by the electric heater. As a result, the heating well 1 of this embodiment is less likely to suffer from problems caused by heat generated by the electric heater 20, and there is no need to suppress the power supplied to the electric heater 20 to limit the output of the electric heater 20, allowing the temperature of the heating well 1 to be sufficiently high.

[0085] Therefore, when using the heating well 1 of this embodiment to purify a treatment target area A of contaminated soil containing contaminants, the temperature inside the heating well 1 can be set to an appropriate temperature depending on the state of contamination of the contaminated soil and the type of contaminant, etc., and the contaminated soil can be effectively purified. Specifically, for example, when contaminated soil is purified using a conventional heating well, even if the contaminated soil contains contaminants that could not be sufficiently vaporized, it may be possible to purify the contaminated soil by heating it at a high temperature using the heating well 1 of this embodiment. Furthermore, by using the heating well 1 of this embodiment to heat contaminated soil at high temperatures, the contaminated soil can be purified more efficiently and in a shorter time than when contaminated soil is purified using a conventional heating well.

[0086] Furthermore, the heating well 1 of this embodiment can heat contaminated soil to a higher temperature than conventional heating wells, so the area of ​​contaminated soil that can be heated to a predetermined temperature in a plan view by a single heating well 1 can be increased. This allows the distance between adjacent heating wells installed in the treatment target area A to be increased in order to purify the contaminated soil, and the number of heating wells 1 installed in the treatment target area A can be reduced. Therefore, when using the heating well 1 of this embodiment to purify contaminated soil, the effort and energy required to install the heating well 1 can be reduced compared to when conventional heating wells are used.

[0087] (Other examples) The present invention is not limited to the first embodiment described above, and for example, the following embodiments are also included within the technical scope of the present invention. In the first embodiment of the heating well 1 described above, an example was given in which the inner pipe 90 and the temperature measuring device 91 are provided, but the inner pipe 90 and the temperature measuring device 91 are provided as needed, and the inner pipe 90 and / or the temperature measuring device 91 do not have to be provided.

[0088] Furthermore, in the heating well 1 of the first embodiment described above, an example was given in which a temperature measuring device 91 is installed in the inner pipe 90, but the temperature measuring device 91 may be installed not only in the inner pipe 90 but also in the sheath pipe 50 as necessary, or it may be installed only in the sheath pipe 50 without being installed in the inner pipe 90.

[0089] Furthermore, in the heating well 1 of the first embodiment described above, an example has been given in which the electric heater 20 is suspended at approximately the center position in a planar view within the sheath pipe 50, but the arrangement of the electric heater 20 in a planar view on the inner surface of the sheath pipe 50 can be changed by, for example, appropriately adjusting the outer diameter D80 of the washer 80, the outer diameter D50 of the sheath pipe 50, the outer diameter D32b of the lower end 32b of the heat-resistant sleeve 32, the inner diameter D80a of the through hole 80a of the washer 80, and their arrangements.

[0090] Specifically, it is preferable that the outer surface of the electric heater 20 is disposed near the inner surface of the sheath pipe 50 or so as to be in contact with the inner surface of the sheath pipe 50. In this case, heat can be efficiently transferred from the electric heater 20 to the outer pipe 10 via the sheath pipe 50, and the contaminated soil can be efficiently heated. Furthermore, when the outer surface of the electric heater 20 is disposed near the inner surface of the sheath pipe 50 or so as to be in contact with the inner surface of the sheath pipe 50, a biasing means for pressing the outer surface of the electric heater 20 against the inner surface of the sheath pipe 50 may be provided within the sheath pipe 50.

[0091] Furthermore, in the heating well 1 of the first embodiment described above, the outer diameter D80 of the washer 80 and the outer diameter D50 of the sheath pipe 50 are approximately concentric, but the central positions of these components may be different. Specifically, it is preferable that the outer surface of the sheath pipe 50 be positioned near the inner surface of the outer pipe 10 or be positioned so as to contact the inner surface of the outer pipe 10. In this case, heat can be efficiently transferred from the electric heater 20 to the outer pipe 10 via the sheath pipe 50, and the contaminated soil can be efficiently heated. [Explanation of symbols]

[0092] A...treatment area, G...surface, 1...heating well, 10...outer pipe, 10a, 31a, 32a...upper end, 10b...bottom surface, 11...heating unit, 20...electric heater, 20b...lower end surface, 21a...heater sheath, 21b...heating wire, 21c...insulating and thermally conductive material, 31...connecting sleeve, 31b, 32b...lower end, 32...heat-resistant sleeve, 40...concrete layer, 50...sheath pipe, 50a...upper end surface, 61...wiring, 62...heat-resistant wiring, 62a...metal sheath, 62b...conductive wiring, 62c...inorganic insulating material, 70...case, 80...washer, 80a...through hole, 90...inner pipe, 91...temperature measuring device.

Claims

1. A heating well installed in the area of ​​contaminated soil to be treated; an outer pipe installed facing downward in the treatment target area; a connecting sleeve installed at an upper end of the outer pipe; a heat-resistant sleeve disposed within the outer tube; A wiring electrically connected to a power source installed outside the outer tube is connected to an upper end of the connection sleeve, an electric heater extending along the longitudinal direction of the outer tube is connected to a lower end of the heat-resistant sleeve; A heating well, wherein a heat-resistant wiring is electrically connected between the lower end of the connection sleeve and the upper end of the heat-resistant sleeve.

2. A heating well as described in claim 1, wherein the lower end surface of the electric heater and the bottom surface inside the outer tube are spaced apart.

3. 2. The heating well according to claim 1, wherein the distance between the lower end surface of the connecting sleeve and the lower end surface of the heat-resistant sleeve is 40 cm to 150 cm.

4. 2. The heating well of claim 1, wherein the distance between the lower end surface of the electric heater and the bottom surface inside the outer tube is 100 mm to 500 mm.

5. 2. The heating well of claim 1, wherein the heat-resistant wiring comprises a metal sheath, a conductive wiring housed within the metal sheath, and an inorganic insulating material filled in the gap between the conductive wiring and the metal sheath.

6. the electric heater is integrated with the heat-resistant sleeve having an outer shape that surrounds the outer shape of the electric heater in a plan view, a sheath pipe extending along the longitudinal direction of the outer pipe to a bottom surface inside the outer pipe is provided inside the outer pipe, The electric heater is installed inside the sleeve pipe, A plate-shaped washer is placed on the upper end surface of the sleeve pipe, the washer has an outer shape surrounding the sleeve tube in a plan view, and is surrounded by the outer shape of the heat-resistant sleeve in a plan view, and has a through hole surrounding the electric heater; The heating well of claim 1 , wherein the heat-resistant sleeve is placed on the washer, thereby suspending the electric heater within the sheath pipe.

7. 2. A heating well as described in claim 1, wherein the heat-resistant sleeve has connection portions located at the upper and lower ends, a metal sheath, a conductive connection member housed within the metal sheath and electrically connecting the connection portion located at the upper end and the connection portion located at the lower end, and an inorganic insulating material filled in the gap between the conductive connection member and the metal sheath within the metal sheath.

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