Contaminated soil heating device, contaminated soil purification device, and contaminated soil purification method

Abstract

To provide a heating device of contaminated soil which can efficiently cope with a difference in temperature rise of soil for each depth.SOLUTION: A heating device 101 includes: an electric heating coil 110 formed in a heating well provided in contaminated soil so as to be capable of being inserted in a depth direction D1; a connection terminal 121 connected to the electric heating coil 110 between an upper end 111 and a lower end 112 of the electric heat coil 110; a power supply device for heating for applying a voltage to the lower end 112 of the electric heating coil 110 and the connection terminal 121; and a connection position changing device for changing a position of the connection terminal 121 to a predetermined connection position CX with the electric heating coil 110 according to thermal conductivity for each depth of the contaminated soil.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a heating device for contaminated soil, a purification device for contaminated soil, and a purification method for contaminated soil. [Background technology]

[0002] Conventionally, soil contaminated with volatile organic compounds (VOCs), heavy metals, perfluoroalkyl and polyfluoroalkyl compounds (PFAS), polychlorinated biphenyls (PCBs), dioxins, oils, etc. (hereinafter referred to as "target substances") has been purified by in-situ thermal desorption, a purification method in which the target substances are volatilized and recovered by heating them in situ, without excavating the contaminated soil.

[0003] The above-mentioned target substances are adsorbed to soil particles, causing soil contamination, and dissolve into groundwater, causing groundwater contamination. Various methods have been proposed for heating soil in a purification device using the conventional in-situ thermal desorption method. For example, a method of heating the soil to a predetermined temperature by installing a heating well (or a heating hole) that leads to the soil purification target range and inserting a heater into the hollow part of the heating well is exemplified. In this method, the temperature of the soil is raised to about 350°C, so that the target substances that are thermally decomposed in the ground or adsorbed to the soil particles are desorbed and the fluidity of the target substances is increased. As a result, the target substances are volatilized or eluted into the surrounding groundwater. The volatilized target substances are attracted to the ground from the recovery well and are thermally decomposed in an exhaust gas treatment device or the like installed on the ground, or are recovered by being adsorbed to activated carbon or the like. The target substances that have eluted into the liquid phase are pumped to the ground together with groundwater from the recovery well and detoxified in a wastewater treatment device or the like.

[0004] For example, Patent Document 1 discloses a purification system that is installed in a preheat hole (heating hole) excavated in contaminated soil around a recovery well and has a heater that preheats the groundwater that seeps into the preheat hole.

[0005] Patent Document 2 discloses a system (In-Situ Thermal Desorption: ISTD) that directly heats soil in situ using a heating well to desorb target substances from the soil or decompose them underground, and the shape of the heater used for heating.

[0006] Patent Document 3 discloses a system (In-Pile Thermal Desorption: IPTD) in which excavated contaminated soil is sealed in a space surrounded by structures such as walls and heated with a heater. Patent Document 4 shows the shape of a heater used to heat soil in situ. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-272273 A [Patent Document 2] Patent No. 4509558 [Patent Document 3] Patent No. 5486684 [Patent Document 4] U.S. Patent No. 10201042 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, when efficiently heating soil to a predetermined temperature in order to purify contaminated soil, heating and temperature management are required to match the rate of temperature rise at each depth according to the thermal conductivity, which differs depending on the soil's heterogeneity, porosity, saturation state, etc. However, in conventional heaters, the depth range of the heating well is fixed and the depth range is heated uniformly, which is inefficient. On the other hand, multi-stage heaters and heaters that can respond to changes in thermal conductivity at depth by changing the density in the longitudinal direction of the coil that constitutes the heater have been proposed, but there remains a problem of inefficiency due to the presence of unheated parts or the inability to easily change the heating range according to the temperature rise at depth.

[0009] In view of the above circumstances, the present invention provides a heating device for contaminated soil, a purification device for contaminated soil, and a purification method for contaminated soil that can efficiently deal with differences in temperature rise in soil at different depths. [Means for solving the problem]

[0010] The contaminated soil heating device of the present invention comprises a heating element formed so as to be insertable into a heating well provided in the contaminated soil, at least one connection terminal connected to the heating element between the upper and lower ends of the heating element, a power source which applies voltage to at least two of the upper end of the heating element, the lower end of the heating element, and the at least one connection terminal, and a connection position changing device which changes the connection terminal to a predetermined connection position with the heating element depending on the thermal conductivity of the contaminated soil at each depth.

[0011] According to the above-mentioned contaminated soil heating device, the heating range of the heating element can be easily adjusted by changing the connection position between the connection terminal and the heating element using the connection position changing device, taking into consideration the expected temperature rise rate at each depth or the temperature rise rate calculated using a temperature sensor or the like installed underground, depending on the thermal conductivity that differs at each depth due to the heterogeneity, porosity, saturation state, etc. of the contaminated soil. In addition, it is not necessary to generate unheated parts in the heating element. This makes it possible to efficiently respond to the difference in temperature rise at each depth in the contaminated soil.

[0012] The contaminated soil heating device according to the present invention may include a plurality of the connection terminals.

[0013] According to the above-mentioned heating device for contaminated soil, the total number and size of the heating ranges between the upper and lower ends of the heating element can be freely adjusted. The more the number of connection terminals increases, the more finely the total number and size of the heating ranges of the heating element can be adjusted. This makes it possible to more flexibly respond to the difference in temperature rise at each depth in the contaminated soil.

[0014] The contaminated soil purification apparatus of the present invention comprises the above-mentioned contaminated soil heating device, a heating well provided in the contaminated soil and configured to allow the heating device to be inserted, a recovery well provided in a location in the contaminated soil different from the heating well and configured to allow the recovery of at least one of the target substance vaporized from the contaminated soil heated by the heating well and the target substance eluted into groundwater, and a treatment device for treating the target substance recovered from the recovery well.

[0015] The above-mentioned contaminated soil purification device includes a heating device for the contaminated soil, so that the heating range of the heating element can be easily adjusted and the contaminated soil to be heated can be accurately heated through the heating well, taking into consideration the rate of temperature rise at each depth according to the thermal conductivity that differs at each depth depending on the heterogeneity, porosity, saturation state, etc. of the contaminated soil. This makes it possible to efficiently deal with the difference in temperature rise at each depth of the contaminated soil without having to prepare and reinstall heating devices individually.

[0016] The contaminated soil purification device of the present invention may include a temperature detector that detects the temperature at each depth within the contaminated soil, and a connection position control device that receives the temperature detected by the temperature detector as a post-detection temperature, calculates the connection position and the voltage to be applied to the heating element based on the difference between the post-detection temperature and the pre-detection temperature at the same depth, outputs the calculated connection position to the connection position changing device, and outputs the calculated applied voltage to the power source.

[0017] According to the above-mentioned contaminated soil purification device, during the operation period of the above-mentioned contaminated soil heating device, the temperature at each depth of the contaminated soil is detected using a temperature detector, and based on the detected temperature, the connection position control device can calculate the temperature rise rate at each depth of the contaminated soil in real time from the difference between the temperature before detection and the temperature after detection. Furthermore, according to the above-mentioned contaminated soil purification device, the connection position between the connection terminal and the heating element and the voltage applied to at least two of the upper end of the heating element, the lower end of the heating element, and the connection terminal can be changed according to the calculated temperature rise rate. By applying the changed connection position and applied voltage, it is possible to efficiently respond to the difference in temperature rise at each depth of the contaminated soil.

[0018] The method for purifying contaminated soil according to the present invention is a method for purifying contaminated soil using the above-mentioned contaminated soil purification device, and includes a temperature detection process for detecting the temperature at each depth in the contaminated soil, a set value calculation process for calculating each set value of the connection position and the applied voltage in accordance with the temperature detected in the temperature detection process, a position change process for changing the position of the connection terminal to the connection position calculated in the set value calculation process, and a voltage application process for applying the applied voltage calculated in the set value calculation process to at least two locations among the upper end of the heating element, the lower end of the heating element, and at least one of the connection terminals.

[0019] The method for purifying contaminated soil according to the present invention is a method for purifying contaminated soil using the above-mentioned contaminated soil purification device, wherein the contaminated soil heating device is provided with a plurality of the connection terminals, and the method comprises: a temperature detection process for detecting the temperature at each depth within the contaminated soil; a set value calculation process for calculating set values ​​of the applied voltage to the upper end of the heating element, the lower end of the heating element, and every two adjacent locations among the plurality of connection terminals in a direction along the heating element, according to the temperature detected in the temperature detection process; and a voltage application process for switching and applying the applied voltage calculated in the set value calculation process to the upper end of the heating element, the lower end of the heating element, and every two adjacent locations among the plurality of connection terminals in a direction along the heating element.

[0020] According to the above-mentioned method for purifying contaminated soil, the connection position between the connection terminal and the heating element can be calculated in accordance with the temperature rise rate at each depth of the contaminated soil, and the set value of the applied voltage to be applied to the heating element in the heating range determined by the changed connection position, by the temperature detection step and the set value calculation step. In addition, in the above-mentioned heating device for contaminated soil, the heating range of the heating element and the heat generation amount in the heating range are changed and adjusted according to the changed set value, and heating can be performed at each depth of the contaminated soil according to the changed set value, so that the target substance can be efficiently thermally desorbed and recovered from the heated contaminated soil. Effect of the Invention

[0021] According to the contaminated soil heating device, contaminated soil purification device, and contaminated soil purification method of the present invention, the heating range of the contaminated soil can be easily and freely adjusted, and differences in temperature rise at each depth in the contaminated soil can be efficiently addressed. [Brief description of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a purification apparatus for polluted soil according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of a heating device used in the contaminated soil purification apparatus shown in FIG. [Diagram 3] 4 is a cross-sectional view of a heating device used in a purification apparatus for polluted soil according to a second embodiment of the present invention. FIG. [Figure 4] FIG. 4 is a circuit diagram of a heating device of the contaminated soil purification apparatus shown in FIG. [Diagram 5] FIG. 1 is a cross-sectional view of a conventional heating device for contaminated soil. [Figure 6] FIG. 1 is a cross-sectional view of a conventional heating device for contaminated soil. [Figure 7] FIG. 1 is a cross-sectional view of a conventional heating device for contaminated soil. [Figure 8] FIG. 1 is a cross-sectional view of a conventional heating device for contaminated soil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a heating device for contaminated soil, a purification device for contaminated soil, and a purification method for contaminated soil according to the present invention will be described with reference to the drawings.

[0024] (First embodiment) As shown in FIG. 1, a first embodiment of a contaminated soil purification apparatus (hereinafter, sometimes simply referred to as a "purification apparatus") 200 according to the present invention is installed in contaminated soil 300 and purifies a target substance (not shown) contained in the contaminated soil 300.

[0025] The contaminated soil 300 has a stratum 351 and a stratum 352 having a thermal conductivity and properties different from those of the stratum 351. The contaminated soil 300 has a layered structure in which a plurality of stratums 351 and a plurality of stratums 352 are alternately repeated along a depth direction D1 from the ground 310. The stratum 351 is, for example, a permeable layer. The stratum 352 is, for example, an impermeable layer. The layered structure in which the stratums 351 and 352 are alternately layered as shown in FIG. 1 is an example of the structure of the contaminated soil 300. The structure of the contaminated soil 300 is not particularly limited as long as the purification device 200 can be installed therein, and the contaminated soil 300 is made up of a plurality of types of stratums having different thermal conductivities. The number of types of stratums constituting the contaminated soil 300 is not limited to a specific number.

[0026] As shown in FIG. 1, the purification device 200 includes a water barrier 10, a diffusion prevention cover 20, a heating well 40, a contaminated soil heating device (hereinafter sometimes simply referred to as the "heating device") 101, a temperature detector 160, a connection position control device 180, a recovery well 60, and an exhaust gas treatment device (treatment device) 80.

[0027] The impermeable wall 10 is provided to prevent the target substance contained in the contaminated soil 300 in the region A to be purified from diffusing outside the region A in a lateral direction D2 intersecting the depth direction D1. The impermeable wall 10 is provided to surround the region A of the contaminated soil 300 to be purified when viewed in a plan view. In the depth direction D1, the impermeable wall 10 penetrates at least the stratum 351 to be purified at the outer periphery of the region A and reaches the stratum 352. The diffusion prevention cover 20 is provided to prevent the target substance contained in the contaminated soil 300 in the region A from directly evaporating and diffusing from the contaminated soil 300 toward the ground as shown by the dashed arrow Z in FIG. 1. The diffusion prevention cover 20 is provided to cover the ground 310 in the region A. The impermeable wall 10 and the diffusion prevention cover 20 are not essential components of the purification device 200, so they may be installed as needed.

[0028] The heating well 40 is provided in a drilled hole 41 formed at a predetermined position in the contaminated soil 300 in the region A in the lateral direction D2. The drilled hole 41 extends from the ground surface 310 to the lower end of the stratum 351 in the depth direction D2. The heating well 40 includes a casing 42 and a lid 44. The casing 42 is formed with a bottom and no top, and is composed of a hollow pipe material made of a material having appropriate thermal conductivity, such as a steel pipe. The lid 44 closes an opening at the upper end of the casing 42, which protrudes slightly above the ground surface 310, and is provided so that it can be opened during maintenance of the heating well 40, etc.

[0029] The heating device 101 includes an electric heating coil (heat generating element) 110, one connection terminal 121, voltage supply lines 130, 131, a heating power supply device (power supply) 140, and a connection position changing device 150.

[0030] The electric heating coil 110 serves as a heater and is used to heat the target area P of the contaminated soil 300 in the area A. The electric heating coil 110 is formed so as to be insertable along the depth direction D1 into the hollow part of the casing 42 of the heating well 40, and is arranged over substantially the entire length of the hollow part of the casing 42 in the depth direction D1. The density of the electric heating coil 110 is substantially uniform in the depth direction D1, but may be non-uniform as necessary. The connection terminal 121 is connected to the electric heating coil 110 at a connection position CX between the upper end 111 and the lower end 112 of the electric heating coil 110. The connection terminal 121 is provided in a state in which it can move along the depth direction D1.

[0031] The lower end 112 of the electric heating coil 110 and the heating power supply device 140 are connected by a voltage supply line 130. The connection terminal 121 and the heating power supply device 140 are connected by a voltage supply line 131. The voltage supply lines 130 and 131 penetrate the lid 44 of the heating well 40 in the depth direction D1 without leaving a gap with the lid 44. The upper end 111 of the electric heating coil 11 is open. The material of the electric heating coil 110, the connection terminal 121, and the voltage supply lines 130 and 131 is, for example, a metal such as nichrome, tungsten, or platinum, or a nonmetallic compound such as silicon carbide, but is not particularly limited as long as it can generate heat by the voltage supplied from the heating power supply device 140.

[0032] The heating power supply device 140 outputs a voltage E to be applied to the electric heating coil 110. The heating power supply device 140 is configured with a power supply capable of adjusting the magnitude of the voltage E. The voltage output from the heating power supply device 140 is supplied to the lower end 112 of the electric heating coil 110 and the connection terminal 121, and is applied to the electric heating coil 110 between the lower end 112 of the electric heating coil 110 and the connection terminal 121 in the depth direction D1.

[0033] The connection position changing device 150 is provided to raise and lower the connection terminal 121 in accordance with the movement of the connection position CX1 between the connection terminal 121 and the electric heating coil 110. The connection position changing device 150 moves the connection terminal 121 to a connection position (predetermined connection position) CX1 in accordance with the thermal conductivity of each depth of the contaminated soil 300, and changes the connection position of the connection terminal 121 with the electric heating coil 110. The connection position changing device 150 is composed of, for example, a winding device and an unwinding device, an expansion device, or the like that can freely change the length of the portion of the voltage supply line 131 that extends along the depth direction D1.

[0034] The temperature detector 160 is provided to detect the temperature at each position in the depth direction D1 of the contaminated soil 300, i.e., at each depth. In FIG. 1, temperature detectors 161 and 162 are illustrated as examples of the temperature detector 160. The temperature detectors 161 and 162 are provided in the contaminated soil 300 on both sides of the heating well 40 in the region A in the lateral direction D2 as positions capable of detecting the temperature of the contaminated soil 300 heated by the heating device 101. Each of the temperature detectors 161 and 162 includes a plurality of temperature sensors 165 spaced apart in the depth direction D1, and a transmission line 166 for transmitting the temperature detected by each of the plurality of temperature sensors 165 to the connection position control device 180.

[0035] The connection position control device 180 receives the temperature at each depth of the contaminated soil 300 detected by each of the temperature detectors 161 and 162 as the post-detection temperature. The connection position control device 180 determines the connection position CX1 to be changed and the applied voltage E to the heating element according to the difference ΔT between the post-detection temperature at the detected depth and the pre-detection temperature at the same depth. The connection position control device 180 outputs the determined connection position CX1 to the connection position change device 150, and can change the position of the connection terminal 121 to the connection position CX1 to be changed using the connection position change device 150. In addition, the connection position control device 180 outputs the determined applied voltage E to the heating power supply device 140, and can change the voltage supplied to the lower end 112 of the electric heating coil 110 and the connection terminal 121 using the heating power supply device 140. The connection position control device 180 is composed of, for example, an integrated circuit, a processor, a calculator, or the like having a program capable of executing each of the above-mentioned processes built in.

[0036] The heating power supply device 140, the connection position changing device 150, and the connection position control device 180 are disposed on the ground 310, for example, on the diffusion prevention cover 20.

[0037] The recovery well 60 is provided to recover target substances that have volatilized into the gas phase (vaporized target substances) mainly from the target area P of the contaminated soil 300 heated by the heating device 101 of the heating well 40 and target substances that have dissolved into the groundwater W. The recovery well 60 is provided in the contaminated soil 300 in area A in the lateral direction D2, at least between the heating well 40 and the water shielding wall 10, and is provided in the contaminated soil 300 between either of the temperature detectors 161, 162 and the water shielding wall 10 that is closer to that temperature detector in the lateral direction D2.

[0038] As shown in FIG. 1, the recovery well 60 is formed so as to be able to mainly recover target substances volatilized into the gas phase from the heated contaminated soil 300. The recovery well 60 is provided in a borehole 61 formed in the contaminated soil 300 between one of the temperature detectors 161, 162 in the region A and the water impermeable wall 10 in the lateral direction D2. The borehole 61 extends from the ground 310 to the deepest part of the stratum 351 in the depth direction D2. The bottom of the borehole 61 is located at approximately the same position as the bottom of the borehole 41 in the depth direction D1. The recovery well 60 includes a casing 62, a ventilation filter 63, and a lid 64. The casing 62 is formed with a bottom and no top, and is made of, for example, a hollow steel pipe material. The ventilation filter 63 is provided to induce the target substance desorbed from the heated contaminated soil 300 to enter the recovery well 60 and to prevent soil, sand, etc. other than the target substance from entering the recovery well 60 from the contaminated soil 300. The ventilation filter 63 is provided on substantially the entire peripheral wall of the casing 62. The ventilation filter 63 is filled with a plurality of particles having a particle size larger than, for example, the soil and sand of the contaminated soil 300 and allowing groundwater W to pass through. The lid 64 is provided so as to close an opening at the upper end of the casing 62 which protrudes slightly above the ground surface 310.

[0039] The exhaust gas treatment device 80 is provided to treat the target substances recovered from the recovery wells 60. The exhaust gas treatment device 80 is disposed on the ground, for example, on the ground surface 310 outside the area A in the lateral direction D2. The hollow portion of the casing 62 of each recovery well 60 and the exhaust gas treatment device 80 are connected by an intake pipe 82. The intake pipe 82 penetrates the cover 64 of the recovery well 60 in the depth direction D1 without leaving a gap between the cover 64 and the exhaust gas treatment device 80. The target substances volatilized from the heated contaminated soil 300 into the gas phase and attracted to the hollow portion of the casing 62 of the recovery well 60 are led to the exhaust gas treatment device 80 through the intake pipe 82. The exhaust gas treatment device 80 includes a blower 84 that sucks in gas, and an adsorption tank (not shown) that contains an adsorbent such as a thermal oxidizer 86 or activated carbon. The target substances volatilized in the gas phase are either subjected to combustion decomposition processing by the thermal oxidizer 86 described above, or are captured by an adsorbent in an adsorption tank and are recovered (processed). However, the type of adsorbent in the adsorption tank may be appropriately selected according to the type of the target substances. The configuration of the exhaust gas treatment device 80 is not particularly limited as long as it can properly and safely treat the target substances.

[0040] Next, a method for purifying contaminated soil according to a first embodiment (hereinafter, may be referred to as a purification method) will be described. The purification method according to the first embodiment is a method for purifying contaminated soil 300 using the purification device 200 according to the first embodiment described above. The purification method according to the first embodiment includes at least a temperature detection step, a set value calculation step, a position change step, and a voltage application step, and further includes a pre-step and a target substance treatment step.

[0041] In the purification method of the first embodiment, as a pre-step, the connection terminal 121 of the heating device 101 disposed in the hollow portion of the casing 42 of the heating well 40 is disposed at an initial connection position CX0 in the depth direction D1 of the electric heating coil 110 as shown in Figures 1 and 2. The initial connection position CX0 may be set in consideration of various conditions such as the layered structure of the contaminated soil 300 previously investigated, the state and water content of the stratum 351, or may be set appropriately.

[0042] Next, a voltage is output from the heating power supply device 140 and supplied to the lower end 112 of the heating coil 110 and the connection terminal 121. The magnitude of the initial voltage is set taking into consideration the various conditions described above. In the depth direction D1, the heating range R1 of the electric heating coil 110 is the range between the lower end 112 of the electric heating coil 110 and the connection terminal 121. That is, a predetermined voltage value is applied to the electric heating coil 110 in the heating range R1.

[0043] Next, in the temperature detection step, the temperature is detected for each depth of the contaminated soil 300 in area A. Specifically, in the temperature detection step, information on temperatures detected at predetermined time intervals by each of the multiple temperature sensors 165 of each of the temperature detectors 161, 162 is output to the connection position control device 180.

[0044] Next, in the set value calculation step, the set value of the connection position CX to be changed according to the temperature of the contaminated soil 300 at each depth detected in the temperature detection step, and the set value of the applied voltage E to be applied to the electric heating coil 110 in the heating range R1 to be changed are calculated. Specifically, the connection position control device 180 receives the temperature of the contaminated soil 300 at each depth detected by the temperature detectors 161 and 162 at a predetermined time interval as the post-detection temperature. The connection position control device 180 calculates the temperature rise rate according to the difference between the pre-detection temperature and the post-detection temperature of the contaminated soil 300 at each depth, which is the same as the post-detection temperature, and obtains the applied voltage E to the connection position CX1 and the electric heating coil 110 in the heating range R1 after the change according to the calculated temperature rise rate. Note that if there is no change in the temperature rise rate of the contaminated soil 300 at each depth at a predetermined time interval, the applied voltage E to the connection position CX and the electric heating coil 110 in the heating range R1 before and after the change may be the same.

[0045] Next, in the position changing process, the position of the connection terminal 121 is changed to the connection position CX1 calculated in the set value calculation process. Specifically, the connection position control device 180 outputs information on the connection position CX1 calculated as described above to the connection position changing device 150. The connection position changing device 150 changes the position of the connection terminal 121 to the received connection position CX1 using the voltage supply line 131.

[0046] Next, in the voltage application step, the changed applied voltage E found in the set value calculation step is applied to the lower end 112 of the heating coil 110 and the connection terminal 121 connected to the heating coil 110 at the changed connection position CX1. Specifically, the connection position control device 180 outputs information about the applied voltage E to the heating coil 110 in the heating range R1 found as described above in accordance with the connection position CX1 in the set value calculation step to the heating power supply device 140. The heating power supply device 140 supplies the received applied voltage E from the voltage supply lines 130, 131 to the lower end 112 of the heating coil 110 and the connection terminal 121.

[0047] Next, in the target substance treatment process, the target substances volatilized from the heated contaminated soil 300 into the gas phase are recovered from the recovery well 60 through the intake pipe 82 to the exhaust gas treatment device 80. The recovered target substances are subjected to combustion decomposition treatment in the thermal oxidizer 86 of the exhaust gas treatment device 80, or are adsorbed onto an adsorbent in an adsorption tank, etc., and then subjected to appropriate recovery treatment.

[0048] As described above, by heating the contaminated soil 300 in accordance with the rate of temperature rise according to the thermal conductivity of the contaminated soil 300 at each depth, the target substances contained in the contaminated soil 300 are efficiently thermally desorbed and volatilized into the gas phase, and are then recovered and treated in the recovered exhaust gas treatment device 80. By continuing the temperature detection process, set value calculation process, position change process, voltage application process, and target substance treatment process within a specified purification period, purification of the contaminated soil 300 in area A is completed.

[0049] As described above, the first embodiment of the contaminated soil heating device 101 comprises an electric heating coil 110 formed so as to be insertable along the depth direction D1 in a heating well 40 provided in the contaminated soil 300, one connection terminal 121 connected to the electric heating coil 110 between an upper end 111 and a lower end 112 of the electric heating coil 110, a heating power supply unit 140 that applies a voltage to the lower end 112 of the electric heating coil 110 and the connection terminal 121, and a connection position changing device 150 that changes the position of the connection terminal 121 to a predetermined connection position CX with the electric heating coil 110 depending on the thermal conductivity of the contaminated soil 300 at each depth. According to the heating device 101 of the first embodiment, during operation, the heating range R1 of the electric heating coil 110 can be easily changed and adjusted by changing the connection position CX between the connection terminal 121 and the electric heating coil 110 using the connection position changing device 150 according to the rate of temperature rise of the contaminated soil 300 at each depth, following the thermal conductivity that differs depending on the depth due to the heterogeneity, porosity, saturation state, etc. of the contaminated soil 300. In addition, it is not necessary to generate non-heated parts of the electric heating coil 110 in the depth direction D1. According to such a heater length variable type heating device 101, it is possible to efficiently respond to the difference in temperature rise at each depth of the contaminated soil 300.

[0050] The first embodiment of the purification device 200 for contaminated soil includes the heating device 101 of the first embodiment, a heating well 40 that is provided in the contaminated soil 300 and is formed so that the heating device 101 can be inserted therein, a recovery well 60 that is provided in a location different from the heating well 40 in the contaminated soil 300 and is formed so that the target substance volatilized into the gas phase from the contaminated soil 300 heated by the heating well 40 can be recovered, and an exhaust gas treatment device 80 that treats (performs recovery treatment of) the target substance recovered from the recovery well 60. According to the purification device 200 of the first embodiment, since the heater length variable type heating device 101 is provided as described above, the heating range R1 of the electric heating coil 110 can be easily changed in consideration of the temperature rise rate for each depth according to the thermal conductivity that differs for each depth depending on the heterogeneity, porosity, saturation state, etc. of the contaminated soil 300, and the contaminated soil 300 to be heated can be efficiently and accurately heated via the heating well 40. This makes it possible to efficiently deal with the difference in temperature rise at each depth in the contaminated soil 300 without the need to prepare separate heating devices and reinstall them in the heating well 40 as in the conventional method.

[0051] The first embodiment of the purification device 200 for contaminated soil includes a temperature detector 160 that detects the temperature at each depth in the contaminated soil 300, and a connection position control device 180 that receives the temperature detected by the temperature detector 160 as a post-detection temperature, calculates the voltage E applied to the electric heating coil 110 at the connection position CX1 and the heating range R1 according to the difference between the post-detection temperature and the pre-detection temperature at the same depth, outputs the connection position CX1 to the connection position changing device 150, and outputs the applied voltage E to the heating power supply device 140. According to the purification device 200 of the first embodiment, during the operation period of the heating device 101 of the first embodiment, the temperature at each depth in the contaminated soil 300 is detected using the temperature detector 160 installed underground, and based on the detected temperature, the connection position control device 180 can calculate the temperature rise rate at each depth in the contaminated soil 300 in real time from the difference between the pre-detection temperature and the post-detection temperature. Furthermore, according to the purification device 200 of the first embodiment, the connection position CX1 and the applied voltage E to the lower end 112 of the electric heating coil 110 and the connection terminal 121 can be freely changed in accordance with the temperature rise rate calculated by the connection position control device 180. By applying the changed connection position CX1 and applied voltage E to the heating device 101, it is possible to efficiently and accurately respond to differences in temperature rise at each depth in the contaminated soil 300.

[0052] The method for purifying contaminated soil of the first embodiment is a method for purifying contaminated soil using the purification device 200 of the first embodiment, and includes a temperature detection step of detecting the temperature at each depth in the contaminated soil 300, a set value calculation step of calculating the set values ​​of the connection position CX1 and the applied voltage E according to the temperature detected in the temperature detection step, a position change step of changing the position of the connection terminal 121 to the connection position CX1, and a voltage application step of applying the applied voltage E to the lower end 112 of the electric heating coil 110 and the connection terminal 121. According to the method for purifying contaminated soil of the first embodiment, the connection position CX1 that matches the temperature rise rate at each depth in the contaminated soil 300 and the set value of the applied voltage E applied to the electric heating coil 110 in the heating range R1 determined by the connection position CX1 can be calculated by the temperature detection step and the set value calculation step. Furthermore, according to the method for purifying contaminated soil of the first embodiment, the heating range R1 of the electric heating coil 110 and the amount of heat generated in the heating range R1 are changed and adjusted in accordance with the changed set values ​​in the heating device 101 of the first embodiment, and the contaminated soil 300 can be efficiently heated at each depth according to the changed set values. Therefore, it is possible to efficiently thermally desorb and recover the target substance from the heated contaminated soil.

[0053] In the heating device 101 of the first embodiment, if necessary or preferable for purification of the contaminated soil 300, the upper end 111 of the electric heating coil 110 may be connected to the heating power supply device 140 by a voltage supply line 130 instead of the lower end 112 of the electric heating coil 110. The lower end 112 of the electric heating coil 11 may be open. In that case, the voltage output from the heating power supply device 140 is supplied to the upper end 111 of the electric heating coil 110 and the connection terminal 121, and can be applied to the electric heating coil 110 between the upper end 111 of the electric heating coil 110 and the connection terminal 121 in the depth direction D1.

[0054] Second embodiment Next, a contaminated soil heating device, a contaminated soil purification device, and a contaminated soil purification method according to a second embodiment of the present invention will be described. Note that, for the second embodiment, differences from the above-mentioned first embodiment will be described, and contents and explanations common to the first embodiment will be omitted. In addition, in the description of the configuration of each embodiment of the second embodiment, configurations common to the first embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted.

[0055] The second embodiment of the purification apparatus for contaminated soil is obtained by replacing the heating device 101 in the purification apparatus 200 shown in FIG. 1 with a heating device 102 for contaminated soil of the second embodiment shown in FIG. 3. The heating device 102 of the second embodiment includes an electric heating coil 110, a plurality of connection terminals 121, 122, . . . , a voltage supply line 130, 131, 132, . . . , 130-2 in the same number as the number of connection terminals, a heating power supply device 140, and a connection position changing device 150. In FIG. 3, two connection terminals 121, 122 are shown as an example of the plurality of connection terminals 121, 122, . . . The connection terminal 122 is connected to the electric heating coil 110 at a connection position CX between the upper end 111 and the lower end 112 of the electric heating coil 110. The connection terminal 122 is provided in a state in which it can move independently of the connection terminal 121 along the depth direction D1.

[0056] The upper end 111 of the electric heating coil 110 and the heating power supply device 140 are connected by a voltage supply line 130-2. The connection terminal 122 and the heating power supply device 140 are connected by a voltage supply line 132. The voltage supply lines 130-2 and 132 penetrate the lid 44 of the heating well 40 in the depth direction D1 without leaving a gap with the lid 44. In the heating device 102 of the second embodiment, compared to the heating device 101 of the first embodiment, the connection terminal 122 is added and the voltage supply line 130-2 is connected to the upper end 111 of the electric heating coil 110, so that up to three heating ranges R11, R12, and R13 can be set in the electric heating coil 110 in the depth direction D1 without any non-heatable area. Here, the heating range R11 is the area between the lower end 112 of the electric heating coil 110 and the terminal located lower among the connection terminals 121 and 122 (the connection terminal 122 in FIG. 3). Heating range R12 is the region between connection terminals 121, 122. Heating range R13 is the region between the upper one of connection terminals 121, 122 (connection terminal 121 in FIG. 3) and upper end 111 of heating coil 110. The material of connection terminal 122 and voltage supply lines 130-2, 132 is the same as the material of connection terminal 121 etc., but is not particularly limited as long as heat can be generated by the voltage supplied from heating power supply device 140.

[0057] The method for purifying contaminated soil according to the second embodiment includes a pre-process, a temperature detection process, a set value calculation process, a voltage application process, and a target substance treatment process. The pre-process and the temperature detection process are performed in the same manner as in the method for purifying soil according to the first embodiment.

[0058] In the previous step, the connection terminals 121, 122 of the heating device 101 are placed at initial connection positions CX0-1, CX0-2 in the depth direction D1 of the electric heating coil 110. The initial connection positions CX0-1, CX0-2 are preferably set at positions that are expected to be suitable for switching the temperature rise rate in the depth direction D1, taking into consideration various conditions such as the layered structure of the contaminated soil 300 that has been previously investigated, the state of the stratum 351, and the moisture content. However, even if the expected initial connection positions CX0-1, CX0-2 deviate from the suitable positions after actually starting to heat the contaminated soil 300, the connection positions CX1, CX2 between the connection terminals 121, 122 and the electric heating coil 110 can be freely adjusted independently of each other, as described below.

[0059] In the set value calculation step in the second embodiment, a set value to be changed for the applied voltage E applied to at least the electric heating coil 110 in the heating ranges R1, R2, and R3 is calculated according to the temperature at each depth of the contaminated soil 300 detected in the temperature detection step. Specifically, the connection position control device 180 calculates a temperature rise rate according to the difference between the pre-detection temperature and the post-detection temperature, and determines the applied voltages E1, E2, and E3 to the electric heating coil 110 in each of the heating ranges R11, R12, and R13 in accordance with the calculated temperature rise rate.

[0060] In the voltage application step in the second embodiment, the applied voltages E1, E2, and E3 calculated in the set value calculation step are applied to two locations adjacent in the depth direction D1, namely, the lower end 112 of the electric heating coil 110 and the connection terminal 122, the connection terminals 122 and 121, and the connection terminal 121 and the upper end 111 of the electric heating coil 110, by switching in the depth direction D1. Specifically, the connection position control device 180 outputs information on the applied voltages E1, E2, and E3 to the electric heating coil 110 in the heating ranges R11, R12, and R13 calculated as described above according to the connection positions CX0-1 and CX0-2 in the set value calculation step to the heating power supply device 140. The heating power supply device 140 supplies the received applied voltages E1, E2, and E3 to the three sets of two locations from the voltage supply lines 130, 131, 132, and 130-2.

[0061] The target substance treatment process is performed in the same manner as in the purification method of the first embodiment. By continuing the temperature detection process, the set value calculation process, the voltage application process, and the target substance treatment process within a predetermined purification period, purification of the contaminated soil 300 in the area A is completed.

[0062] An example of the switching operation of the applied voltages E1, E2, E3 to the electric heating coils 110 of the heating ranges R11, R12, R13 when performing the purification method of the second embodiment as described above will be described. In FIG. 4, the configuration of the heating device 102 is shown as an electric circuit 192. The electric circuit 192 has a DC power supply 501, switches SS1 to SS6, and heater parts RR1 to RR3, which are connected as shown in FIG. 4. The DC power supply 501 may be an AC power supply (not shown). The DC power supply 501 and the switches SS1 to SS6 are provided in, for example, the heating power supply device 140. The heater parts RR1 to RR3 correspond to the electric heating coils 110 of the heating ranges R11, R12, R13. An electric line 505 connecting at least two points among the DC power source 501, the switches SS1 to SS6, and the heater units RR1 to RR3 corresponds appropriately to any one of the voltage supply lines 130, 131, 132, and 130-2.

[0063] In order to desorb the target substance in the contaminated soil 300 by heating and recover it on the ground, it is said that an efficient purification method is to heat the soil from the deepest part of the stratum 351 where the groundwater W exists, and gradually raise the heating range in the depth direction D1 toward the ground 310, as shown in Figure 1. Therefore, the heating can be switched to the heater parts RR1 to RR3 in the following patterns.

[0064] [Table 1]

[0065] In the purification method of the second embodiment, when determining the applied voltages E1, E2, and E3 in the set value calculation step, if it is detected that changing the initial connection positions CX0-1 and CX0-2 will result in a more preferable heating distribution in the depth direction, the initial connection positions CX0-1 and CX0-2 may be changed and the heating ranges R11, R12, and R13 may be adjusted by an operation similar to that of the position changing step of the purification method of the first embodiment.

[0066] As described above, the contaminated soil heating apparatus 102 of the second embodiment and the purification apparatus of the second embodiment have a configuration similar to that of the contaminated soil heating apparatus 101 of the first embodiment and the purification apparatus 200 of the first embodiment, and therefore achieve the same effects as the heating apparatus 101 and the purification apparatus 200.

[0067] The contaminated soil heating device 102 of the second embodiment includes a plurality of connection terminals 121, 122. According to the heating device 102 of the second embodiment, the number of heating areas RX11, ... and the size in the depth direction D1 between the upper end 111 and the lower end 112 of the electric heating coil 110 can be freely adjusted by selecting any two of the upper end 111 and the lower end 112 of the electric heating coil 110 and the connection terminals 121, 122. The more the number of connection terminals increases, the more finely the total number and size of the heating areas of the electric heating coil 110 can be adjusted. Therefore, according to the heater switching type heating device 102 of the second embodiment, it is possible to more flexibly respond to the difference in temperature rise at each depth in the contaminated soil 300.

[0068] The method for purifying contaminated soil according to the second embodiment is a method for purifying contaminated soil using the purification device according to the second embodiment, and includes a temperature detection step, a set value calculation step for calculating set values ​​of applied voltages E1, E2, and E3 for each pair of adjacent positions in the depth direction D1 among the upper end 111 and the lower end 112 of the electric heating coil 110 and the connection terminals 121 and 122 according to the temperature detected in the temperature detection step, and a voltage application step for switching and applying the applied voltages calculated in the set value calculation step to each pair of positions among the above-mentioned three sets of two positions. According to the purification method according to the second embodiment, the set values ​​of applied voltages E1, E2, and E3 applied to the electric heating coil 110 in the heating ranges R11, R12, and R13 determined by the connection positions CX0-1 and CX0-2 according to the temperature rise rate for each depth of the contaminated soil 300 can be calculated by the temperature detection step and the set value calculation step. Furthermore, according to the method for purifying contaminated soil of the second embodiment, the heating amount in the heating ranges R11, R12, and R13 of the electric heating coil 110 is changed and adjusted in accordance with the changed set value in the heating device 101 of the first embodiment, and heating can be efficiently and accurately performed for each depth of the contaminated soil 300 according to the changed set value. Therefore, it is possible to efficiently thermally desorb and recover the target substance from the heated contaminated soil.

[0069] For example, in a conventional heating device 401 shown in FIG. 5, the heating wire 115 is formed in a U-shape when viewed from the side (for example, see FIG. 1 of Patent Document 2). The heating wire 115 descends from one upper end 111 along the depth direction D1, bends in a semicircular shape near the lower end of the casing 42 (i.e., the deepest part of the stratum 351), and then rises from there along the depth direction D1 to the other upper end 111 located at approximately the same height as the one upper end 111. Each of the two upper ends 111, 111 is connected to a voltage supply line 130-3. Also, in a conventional heating device 402 different from the heating device 401 of FIG. 5 as shown in FIG. 6, the voltage supply line 130-2 is connected to the upper end 111 of the electric heating coil 110, and the voltage supply line 130-2 is connected to the lower end 112. In the heating devices 401 and 402, when a voltage E is applied to the heating wire 115 via the voltage supply lines 130 and 130-2, the heated range RQ is forcibly fixed over substantially the entire length of the heating wire 115 in the depth direction D1.

[0070] On the other hand, the conventional heating device 403 shown in FIG. 7 is a device in which a plurality of heating devices 402 are miniaturized and arranged in series and in multiple stages along the depth direction D1. According to the heating device 403, the heating range RQ of the heating device 402 can be divided into heating ranges RS of the same number as the heating devices 402. However, in the heating device 403, the size of the heating range RS is fixed and cannot be adjusted, and a non-heated portion 450 is formed between the heating devices 402 adjacent to each other in the depth direction D1. In the conventional heating device 404 shown in FIG. 8, the density of the electric heating coil 110 from the upper end 111 to the lower end 112 is non-uniform (for example, see FIG. 1, FIG. 2, etc. of Patent Document 4). For example, in the depth direction D1, the density of the central portion of the electric heating coil 110 is higher than that of the upper and lower portions. The high density portion 117 and the low density portions 118-1 and 118-2 of the electric heating coil 110 form heating ranges RT due to the difference in the amount of heat generated. However, the size of the heating area RT is fixed also in the heating device 404. Furthermore, the amount of heat generated in the heating area RT is restricted by the density of the electric heating coil 110, and the adjustable range of the amount of heat generated is narrow.

[0071] The soil to be purified is composed of a plurality of types of strata (including the above-mentioned strata 351, 352, etc.) with different thermal conductivities. These strata are formed of loam, sand, gravel, silt, clay, or a mixture of these. As described above, the thermal conductivity of each layer of the contaminated soil 300 varies greatly depending on the constituent materials as well as the porosity, etc., so that even if the contaminated soil 300 is heated and warmed by the conventional heating devices 401-404, the variation in the temperature rise amount for each depth cannot be suppressed. In contrast to the conventional heating devices 401-404, the heater length variable type heating device 101 and the heater switching type heating device 102 to which the present invention is applied can follow the thermal conductivity of the contaminated soil 300, and can efficiently heat and warm the contaminated soil 300 at a desired speed for each depth. Furthermore, with the heating devices 101 and 102, the connection position control device 180 can be operated while monitoring the temperature detected in real time or the concentration of the target substance recovered in the exhaust gas treatment device 80, thereby changing and adjusting the heating conditions required for the purification of the contaminated soil 300. This increases the purification efficiency of the contaminated soil 300, reduces energy consumption and management costs, and enables purification at low cost and in a short period of time.

[0072] Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications are possible within the scope of the gist of the present invention described in the claims. In the above-mentioned embodiments, an electric heating coil is mentioned as the heating element of the heating device according to the present invention, but the heating element is not limited to the electric heating coil, and may be any element that allows the connection position with the connection terminal to be freely set in the depth direction. By using a spiral electric heating coil as the heating element, when multiple connection terminals are provided, the connection terminals can be easily arranged at different positions in the circumferential direction in a plan view, and contact between the contact terminals can be prevented. However, the heating element is not limited to the spiral electric heating coil as mentioned above, and may be, for example, a member made of metal or a heating material formed in a straight line, or a member made of metal or a heating material formed in an arbitrary shape.

[0073] In the heating device according to the present invention, the power source applies a voltage to at least two of the upper end of the heating element, the lower end of the heating element, and at least one connection terminal. The selection of the two locations and the number of connection terminals are appropriately determined taking into consideration the structure of the contaminated soil to be purified and the conditions required during purification.

[0074] In the above-mentioned embodiments, the recovery well has been described as having a hollow structure, but the recovery well may be formed so as to be capable of recovering target substances eluted into the liquid phase of the groundwater W. In that case, the recovery well includes a casing made of a steel pipe or the like, a water-passing filter, and a lid, similar to a known pumping well. The water-passing filter is provided to prevent impurities such as sand and gravel of the contaminated soil from entering the hollow portion of the recovery well from the contaminated soil. The water-passing filter is, for example, composed of a screen and a filter body adjacent to the screen in the horizontal direction. The filter body is filled with a plurality of particles having a particle size larger than the through holes formed in the screen. As the treatment device, a wastewater treatment device is provided instead of the above-mentioned exhaust gas treatment device. The hollow portion of the recovery well and the wastewater treatment device are connected by a water-passing pipe, and a pumping pump, for example, is provided at the tip of the water-passing pipe inserted into the hollow portion of the recovery well.

[0075] In each of the above-described embodiments, groundwater W exists in the stratum 351, but the stratum 351 may be an impermeable layer, and there may be cases where no groundwater exists depending on the remediation depth, or where new groundwater is prevented from flowing into the remediation target area A by the impermeable wall 10. In these cases, by pumping groundwater from the recovery well before heating the contaminated soil, it is possible to prevent excessive elution of the target substance into the groundwater and evaporation of the groundwater itself due to heating.

[0076] 1 exemplify a configuration in which the electric heating coil 110 can be arranged along the depth direction D1, which is the same as the extension direction of the heating well 40, and a configuration in which the electric heating coil 110 is arranged vertically from the original position. However, the direction in which the electric heating coil 110 and the multiple temperature sensors 165 are arranged is not limited to the depth direction D1, and may be a horizontal direction including the lateral direction D2, a diagonally upward direction, or any other direction, regardless of whether it is inside or outside the heating well 40. In other words, the electric heating coil 110 and the multiple temperature sensors 165 may be arranged in any desired direction in consideration of the heating conditions, etc., in the contaminated soil 300 (i.e., a sealed space) that is sealed by being surrounded by the water impermeable wall 10 and the diffusion prevention cover 20, etc.

[0077] In the electric circuit 192 of the second embodiment described above and illustrated in Fig. 4, the switches SS1 to SS6 are preferably made of, for example, semiconductors. That is, the portion of the electric circuit 192 surrounded by the dashed line is preferably a semiconductor switching circuit. By making the electric circuit 192 out of a semiconductor circuit, the circuit can be switched electronically, and electrical and physical wear and tear and the generation of sparks when a relatively large current flows through the electric heating coil 110 can be prevented. [Explanation of symbols]

[0078] 40 Heating Well 101 Heating equipment (heating equipment for contaminated soil) 110 Electric heating coil (heating element) 111 Upper end 112 Bottom end 121, 122 Connection terminal 140 Heating power supply 150 Connection position change device 200 Purification equipment (contaminated soil purification equipment) 300 Contaminated Soil D1 Depth direction

Claims

1. A heating element formed so as to be insertable into a heating well provided in the contaminated soil; At least one connection terminal connected to the heating element between an upper end and a lower end of the heating element; a power source that applies a voltage to at least two of the upper end of the heating element, the lower end of the heating element, and at least one of the connection terminals; a connection position changing device that changes a predetermined connection position of the connection terminal with the heating element in accordance with the thermal conductivity of the contaminated soil at each depth; Equipped with The connection position changing device is a contaminated soil heating device composed of a winding device and an unwinding device, or an expansion device, which can freely change the length of the voltage supply line extending along the depth direction.

2. A plurality of the connection terminals are provided.

2. The apparatus for heating contaminated soil according to claim 1.

3. a heating device for contaminated soil comprising: a heating element formed so as to be insertable into a heating well provided in the contaminated soil; at least one connection terminal connected to the heating element between an upper end and a lower end of the heating element; a power source that applies voltage to at least two of the upper end of the heating element, the lower end of the heating element, and the at least one connection terminal; and a connection position changing device that changes a predetermined connection position of the connection terminal with the heating element in accordance with the thermal conductivity of the contaminated soil at each depth; a heating well provided in the contaminated soil and configured so that the heating device can be inserted therein; A recovery well is provided at a location different from the heating well of the contaminated soil and is configured to recover at least one of the target substance vaporized from the contaminated soil heated by the heating well and the target substance dissolved into groundwater; a treatment device for treating the target substance recovered from the recovery well; Equipped with a temperature detector for detecting a temperature at each depth in the contaminated soil; a connection position control device that receives the temperature detected by the temperature detector as a post-detection temperature, calculates the connection position and an applied voltage to the heating element according to a difference between the post-detection temperature and a pre-detection temperature at the same depth, outputs the calculated connection position to the connection position changing device, and outputs the calculated applied voltage to the power source; The contaminated soil purification device further comprises:

4. A method for purifying contaminated soil using the contaminated soil purification apparatus according to claim 3, comprising: a temperature detection step of detecting temperatures at each depth in the contaminated soil; a set value calculation step of calculating set values ​​of the connection position and the applied voltage in accordance with the temperature detected in the temperature detection step; a position changing step of changing a position of the connection terminal to the connection position calculated in the setting value calculation step; a voltage application step of applying the applied voltage calculated in the set value calculation step to at least two of the upper end of the heating element, the lower end of the heating element, and at least one of the connection terminals, Methods for remediating contaminated soil.

5. A method for purifying contaminated soil using the contaminated soil purification apparatus according to claim 3, comprising: The contaminated soil heating device includes a plurality of the connection terminals, a temperature detection step of detecting temperatures at each depth in the contaminated soil; a set value calculation step of calculating set values ​​of the applied voltages to an upper end of the heating element, a lower end of the heating element, and two adjacent positions among the plurality of connection terminals in a direction along the heating element, according to the temperature detected in the temperature detection step; a voltage application process of switching and applying the applied voltage calculated in the set value calculation process to an upper end of the heating element, a lower end of the heating element, and every two adjacent positions among the plurality of connection terminals in a direction along the heating element; Equipped with Methods for remediating contaminated soil.

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