Thermal desorption treatment contaminated soil thermal conductivity test system and test method

Abstract

The application discloses a kind of thermal desorption treatment contaminated soil thermal conductivity test system and test method, test system includes test cavity, heating furnace, gas pressure control system and soil sample thermal conductivity test system, gas pressure control system includes gas pressure sensor, gas pressure control valve, nitrogen source, tail gas processor and vacuum pump, soil sample thermal conductivity test system includes double probe, wire, direct current power supply, multichannel temperature recorder and thermal conductivity calculation system, the double probe insertion to be measured soil sample and place in test cavity, the application can operate under high temperature environment, simultaneously, two different test methods are used to calculate two thermal conductivities for the same to-be-tested soil sample respectively, and the mean value is obtained by comparison and verification, effectively save the time of parallel test under high temperature environment, reduce the experimental error of calculating thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of high-temperature thermal desorption and thermal property measurement, specifically to a system and method for testing the thermal conductivity of contaminated soil treated by thermal desorption. Background Technology

[0002] Thermal desorption technology is one of the most effective methods for treating organically contaminated sites, widely used due to its advantages of short treatment time, high efficiency, and high safety. However, current understanding of the heat transfer characteristics and evolution mechanism of organically contaminated soil in thermal desorption technology is insufficient in China, lacking corresponding theories and experience to guide engineering design. Therefore, it is necessary to develop a device capable of measuring the thermal conductivity of contaminated soil under high-temperature environments, ultimately simulating the evolution of heat transfer characteristics in the remediation of contaminated soil during thermal desorption. However, current thermal probes on the domestic market have the following shortcomings: 1. Small testing temperature range, and difficulty in normal operation under ultra-high temperature environments; 2. Each measurement can only measure the thermal conductivity once. To reduce experimental errors in thermal conductivity calculation, parallel tests of the soil sample are often required. Parallel tests require the thermal probe to cool to the same temperature as the soil sample, consuming a significant amount of time. Furthermore, the higher the ambient temperature of the soil sample or the greater the temperature rise of the thermal probe, the longer the cooling time required. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a thermal conductivity testing system and method for contaminated soil undergoing thermal desorption treatment. This system can operate in high-temperature environments and simultaneously calculates two different thermal conductivity values ​​for the same soil sample using two different testing methods for comparison and verification, thereby saving time in conducting parallel experiments at high temperatures and reducing experimental errors in calculating thermal conductivity.

[0004] This invention is achieved using the following technical solution: a thermal desorption treatment system for testing the thermal conductivity of contaminated soil, comprising a test chamber, a heating furnace, a gas pressure control system, and a soil sample thermal conductivity testing system. The specific structure and connection relationships of the components are as follows:

[0005] The test chamber is placed inside a heating furnace. The thermocouple inside the test chamber is connected to the heating furnace temperature control system. The air inlet of the air pressure control system is connected in sequence to the first air pressure control valve and the nitrogen source. The air outlet of the air pressure control system is connected in sequence to the air pressure sensor, the second air pressure control valve, the exhaust gas processor and the vacuum pump.

[0006] The soil sample thermal conductivity testing system includes dual probes, wires, a DC power supply, a multi-channel temperature recorder, and a thermal conductivity calculation system. The dual probes are inserted into the soil sample to be tested and placed together in the test chamber. The dual probes are connected to the DC power supply and the multi-channel temperature recorder through wires. The thermal conductivity calculation system is externally connected to the multi-channel temperature recorder.

[0007] The dual probe consists of two parallel probes. Both the first and second probes include a stainless steel needle tube, a stainless steel conical needle tip, a thermocouple, a ceramic insulating coating, an insulating spherical alumina powder filler, a sealing head, and a convex needle cap. The first probe has an alloy heating wire built in. A solid capillary steel tube is welded at the center of the stainless steel conical needle tip at the lower end of the first probe.

[0008] The first and second probes are fixed to the lower end of the convex needle cap by welding. The parallel distance between the two probes is 15±1mm. The alloy heating wire and thermocouple wire are led out from the upper end of the convex needle cap.

[0009] The upper end of the stainless steel needle tube of the first and second probes is a sealed head, and the lower end is a stainless steel conical needle tip.

[0010] The first and second probes are fully filled with insulating spherical alumina powder filler, and the solid capillary steel tube and alloy heating wire are coated with ceramic insulating coating.

[0011] A solid capillary steel tube with a diameter of 0.3-0.5 mm and a length of 90-140 mm is welded to the center of the stainless steel conical tip at the lower end of the first probe.

[0012] The temperature measuring points of the two thermocouples of the first and second probes extend to the middle height position of the stainless steel needle tube. The alloy heating wire is spirally wound and built into the surface of the solid capillary tube of the first probe in parallel, with the same length as the solid capillary tube.

[0013] The stainless steel needle tubes of the first and second probes have the same diameter and thickness, with an outer diameter of 2-3 mm, an inner diameter of 1.8-2.8 mm, and a length of 100-150 mm.

[0014] The diameter of the alloy heating wire is 0.3-0.5 mm; the diameter of the thermocouple is 0.3-0.5 mm, and the accuracy is 0.01 K.

[0015] The thermal conductivity calculation system calculates the thermal conductivity of the soil sample based on the temperature change data of the first and second probes under constant current recorded by the multi-channel temperature recorder, according to the principles of the thermal probe method and the parallel hot wire method.

[0016] The calculation formula for the thermal probe method is as follows:

[0017]

[0018]

[0019] In the formula, ΔT and lnt1 are linearly related on the coordinate axis, λ is the thermal conductivity, in W / (m·K), q is the heating power per unit length of the first probe, in W / m, t1 is the interval from the start of the test to the start of temperature change of the second probe, in s, ΔT is the temperature rise of the first probe within time t1, in K, I is the current through the alloy heating wire, in A, R is the resistance of the alloy heating wire, in Ω, and H is the length of the stainless steel needle tube of the first probe, in m.

[0020] The calculation formula for the parallel hot-wire method is as follows:

[0021]

[0022] In the formula, λ is the thermal conductivity, with units of W / (m·K), q is the heating power per unit length of the first probe, with units of W / m, and E i The function is an exponential integral function, where r is the distance between the first and second probes (15 ± 1 mm), and α is the thermal diffusivity of the soil sample (in m³). 2 / s, t2 is the total test time from the start to the end of the test, in seconds, and Δθ is the temperature rise of the second probe within time t2, in K.

[0023] All high-temperature resistant components refer to those that can withstand temperatures above 600℃.

[0024] The beneficial results of this invention are as follows:

[0025] 1. By heating and depressurizing the soil sample under test through a high-temperature heating furnace and a gas pressure control system, the soil heating process under various high-temperature and negative-pressure conditions of in-situ thermal desorption can be simulated; the soil sample thermal conductivity testing system can measure the thermal conductivity under a series of complex high-temperature conditions during the thermal desorption process, and ensure that the components in the dual probe operate normally at high temperatures.

[0026] 2. The dual probe of this invention benefits from the use of two different testing methods to calculate two thermal conductivity values ​​for the same soil sample, and then compares and verifies them to obtain the average value. This effectively saves the time of conducting parallel tests in a high-temperature environment and reduces the experimental error in calculating the thermal conductivity. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the thermal conductivity testing system for contaminated soil undergoing thermal desorption treatment as described in this invention.

[0028] Figure 2 This is a schematic diagram of the dual-probe system for testing the thermal conductivity of contaminated soil undergoing thermal desorption treatment, as described in this invention.

[0029] The components marked in the diagram are: Heating Furnace-101, First Pressure Control Valve-105, Second Pressure Control Valve-102, Pressure Sensor-103, Nitrogen Source-104, Exhaust Gas Processor-106, Vacuum Pump-107, Silicon Carbide Rod-108, Thermocouple-109, Activated Carbon-110, Filter Plate-111, Inlet Pipe-112, Outlet Pipe-113, Reserved Hole-114, Exhaust Gas Processor Inlet Pipe-115, Exhaust Gas Processor Outlet Pipe-116. 1. Soil sample testing chamber - 117. Dual probes - 201. Wires - 202. DC power supply - 203. Multi-channel temperature recorder - 204. Thermal conductivity calculation system - 205. Stainless steel needle tube - 301. Stainless steel conical needle tip 1 - 302. Stainless steel conical needle tip 2 - 303. Alloy heating wire - 304. Thermocouple - 305. Sealing head - 306. Insulating spherical alumina powder filler - 307. Convex needle cap - 308. Solid capillary steel tube - 309 Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Example 1

[0032] like Figure 1 As shown, the thermal desorption treatment contaminated soil thermal conductivity testing system of the present invention includes a soil sample test chamber 117, a heating furnace 101, a gas pressure control system, and a soil sample thermal conductivity testing system.

[0033] The heating furnace 101 is equipped with a silicon carbide heating source 108 and a thermocouple 109, which are used to heat up and monitor the temperature inside the furnace. They are wired to the intelligent temperature control program module of the high-temperature heating furnace 101. The heating method is controlled by setting the intelligent temperature control program module, which controls the heating rate, heating temperature range, heating dwell time, and heating power.

[0034] The air pressure control system includes an air pressure sensor 103, a first air pressure control valve 105, a second air pressure control valve 102, a nitrogen source 104, a tail gas processor 106, and a vacuum pump 107. The air pressure sensor 103 is installed next to the furnace outlet pipe 113 and can monitor the air pressure inside the high-temperature furnace in real time. The nitrogen source 104 is connected in sequence to the first air pressure control valve 105 and the inlet pipe 112. Adjusting the control valve releases nitrogen, allowing air inside the furnace to escape through the outlet pipe 113 and maintaining an inert gas atmosphere for the experimental soil sample inside the furnace. The second air pressure control valve 102 is installed in the outlet pipe 113 and is used to control the air pressure inside the high-temperature furnace 101. If the air pressure inside the furnace... During the test, the pressure will automatically release if it exceeds the set value; the upper air inlet pipe 115 of the exhaust gas processor 106 is connected to the air outlet pipe 113 of the high-temperature heating furnace 101. The exhaust gas processor 106 contains activated carbon 110 and filter plate 111 to adsorb and purify the waste gas generated during the test; the vacuum pump 107 is connected to the lower air outlet pipe 116 of the exhaust gas processor 106. The vacuum pump 107 can not only speed up the extraction of waste gas in the heating furnace, but also create a negative pressure condition in the heating furnace 101.

[0035] The soil sample thermal conductivity testing system includes a dual probe 201, a wire 202, a DC power supply 203, a multi-channel temperature recorder 204, and a thermal conductivity calculation system 205. The dual probe 201 body includes a stainless steel needle tube 301, stainless steel conical needle tips 1-302, stainless steel conical needle tips 2-303, an alloy heating wire 304, a thermocouple 305, a ceramic insulating coating, insulating spherical alumina powder filler 307, a sealing head 306, and a convex needle cap 308. The stainless steel conical needle tip 1-302 is welded to the lower end of the stainless steel needle tube 301 for easy insertion into the material to be tested. The alloy heating wire 304 is spirally wound around the solid capillary steel tube 309 of the stainless steel conical needle tip 1-302, with the winding length consistent with that of the solid capillary steel tube 309, to ensure sufficient heat and uniform temperature distribution within the first probe. The thermocouple 305 is inserted into the stainless steel needle tube 301, with the measuring point extending to the middle height of the needle tube, used to measure the temperature change of the dual probes 201. The ceramic coating is applied to the surfaces of the alloy heating wire 304 and the solid capillary steel tube 309, and the coating can maintain high thermal conductivity and provide insulation and shielding current at high temperatures. The insulating spherical alumina powder filler 307 is fully compacted into the gaps of the stainless steel needle tube 301, and then the top of the stainless steel needle tube 301 is sealed with the sealing head 306 to... Thermocouple 305 and sealing filler 307 are fixed in stainless steel needle tube 301; the double probe 201 is fixed to the lower end of the convex needle cap 308 by welding, the two are 15±1mm apart and kept perpendicular and parallel, and the alloy heating wire 304 and thermocouple 305 wires are led out through the upper end of the convex needle cap 308; the DC power supply 203 is connected to the alloy heating wire 304 by wire 202, and the DC power supply 203 provides an adjustable and stable current to the alloy heating wire 304; the multi-channel temperature recorder 204 is connected to the thermocouple 305 wire, and the multi-channel temperature recorder 204 records the temperature change data of the thermocouple 305 over time; the thermal conductivity calculation system 205 receives and processes the temperature signal of the multi-channel temperature recorder 204, and calculates the thermal conductivity of the soil sample after data processing by combining the principles of thermal probe method and parallel hot wire method.

[0036] The dual-probe 201 needle tube has the same diameter and thickness, with an outer diameter of 2-3 mm, an inner diameter of 1.8-2.8 mm, and a length of 100-150 mm.

[0037] The alloy heating wire 304 is a nickel-chromium alloy heating wire with a diameter of 0.3-0.5 mm, and the thermocouple 305 is a custom-made K-type thermocouple with a diameter of 0.3-0.5 mm and an accuracy of 0.01 K.

[0038] The solid capillary steel tube 309 has a diameter of 0.3-0.5 mm and a length of 90-140 mm.

[0039] The sealing head 306 is made of ceramic insulating coating.

[0040] The thermal conductivity calculation system 205 calculates the thermal conductivity of the soil sample to be tested based on the temperature change data of the first and second probes under constant current recorded by the multi-channel temperature recorder 204, according to the principles of the thermal probe method and the parallel hot wire method.

[0041] All high-temperature resistant components refer to those that can withstand temperatures above 600℃.

[0042] Example 2

[0043] This embodiment describes the testing method for the thermal conductivity testing system for contaminated soil undergoing thermal desorption treatment as described in this invention. The specific operating steps are as follows:

[0044] (1) Before heating, the cylindrical soil sample to be tested is placed in the soil sample test chamber 117. The double probe 201 is inserted vertically into the cylindrical soil sample. The first probe with the alloy heating wire needs to be inserted into the center of the cylindrical soil sample. The wire 202 of the double probe 201 is led out from the reserved hole 114 at the top of the heating furnace 101 and connected to the DC power supply 203 and the multi-channel temperature recorder 204 respectively. Then, the reserved hole is blocked with heat insulation cotton. The thermal conductivity calculation system 205 is connected to the multi-channel temperature recorder 204.

[0045] (2) Input instructions into the intelligent temperature control program module of the heating furnace according to the heating conditions to control the heating rate, heating time, heating temperature and holding time.

[0046] (3) Open the first pressure control valve 105 and the second pressure control valve 102 to release nitrogen, so that the air in the furnace is discharged from the exhaust pipe 113 through the tail gas processor 106 and the vacuum pump 107, so that the soil sample in the furnace is in an inert gas atmosphere. Then close the first pressure control valve 105, adjust the second pressure control valve 102 to the required pressure setting value, turn on the vacuum pump 107 to draw air to form a negative pressure environment in the heating furnace, and read the pressure value in the furnace through the pressure sensor 103. When the read pressure value is consistent with the pressure setting value of the second pressure control valve 102, turn off the vacuum pump 107. After the adjustment is completed, turn on the heating switch of the heating furnace to start heating.

[0047] (4) After the furnace is heated to the set temperature, the soil sample is kept at a constant temperature for a period of time to ensure that it is heated evenly. When the temperature difference between the two thermocouples in the dual probe 201 read by the multi-channel temperature recorder 204 does not exceed 0.05℃, it indicates that the soil sample temperature is stable.

[0048] (5) After meeting the requirements of step (4), turn on the DC power supply 203 and manually adjust the set constant current to power the alloy heating wire 304. At the same time, the multi-channel temperature recorder 204 will continuously record the temperature rise and corresponding time of the two thermocouples 305 and feed it back to the thermal conductivity calculation system 205 to obtain the temperature rise curves of the first probe and the second probe. The thermal conductivity of the soil sample is calculated back according to the formulas of the thermal probe method and the parallel hot wire method.

[0049] The calculation formula for the thermal probe method is as follows:

[0050]

[0051]

[0052] In the formula, ΔT and lnt1 are linearly related on the coordinate axis, λ is the thermal conductivity, in W / (m·K), q is the heating power per unit length of the first probe, in W / m, t1 is the interval from the start of the test to the start of temperature change of the second probe, in s, ΔT is the temperature rise of the first probe within time t1, in K, I is the current through the alloy heating wire, in A, R is the resistance of the alloy heating wire, in Ω, and H is the length of the stainless steel needle tube of the first probe, in m.

[0053] The calculation formula for the parallel hot-wire method is as follows:

[0054]

[0055] In the formula, λ is the thermal conductivity, with units of W / (m·K), q is the heating power per unit length of the first probe, with units of W / m, and E i The function is an exponential integral function, where r is the distance between the first and second probes (15 ± 1 mm), and α is the thermal diffusivity of the soil sample (in m³). 2 / s, t2 is the total test time from the start to the end of the test, in seconds, and Δθ is the temperature rise of the second probe within time t2, in K.

[0056] (6) After the thermal conductivity measurement is completed, a large amount of waste gas will be generated after the contaminated soil is heated. The vacuum pump 107 is turned on, and the waste gas is extracted from the heating furnace 101 by the vacuum pump 107 and discharged through the exhaust pipe 113 and the tail gas treatment box 106 for adsorption and purification.

[0057] Example 3

[0058] This embodiment is an application example of the testing method of the thermal conductivity testing system for contaminated soil undergoing thermal desorption treatment described in this invention. The specific operation steps are as follows:

[0059] The experiment was conducted according to the experimental steps of Example 2. The experimental conditions were: furnace temperature 400℃, furnace pressure 101.325kPa, the soil to be tested was silty clay, the length of the stainless steel needle tube of the first probe was 100mm, and the resistance of the alloy heating wire was 1Ω. The calculation process for the thermal conductivity of the soil to be tested using the thermal probe method is as follows: First, manually adjust the DC power supply 203 to provide a current of 1A to the alloy heating wire 304. Calculate the heating power per unit length of the first probe as: q = 10W / m. The first derivative of the temperature rise of the first probe with respect to the logarithm of time is given. Therefore, the slope of the fitted line obtained by linear fitting of the temperature rise of the first probe and the logarithm of the test time using the least squares method of the thermal conductivity calculation system is 3.446. The thermal conductivity calculation results of the thermal probe method are as follows:

[0060]

[0061] Meanwhile, the thermal conductivity of the soil under test, obtained using the parallel hot-wire method, is calculated as follows:

[0062] First, determine the thermal conductivity calculation system. The ratio, and then according to Table 2 of the standard "Test Method for Thermal Conductivity of Refractory Materials" (GTB 5990-2006). and The function relationship table is used to determine the corresponding Δθ(t2). Value, will Substitute Δθ(t2) and q into formula (3) to calculate the thermal conductivity of the soil to be tested. For the specific calculation process, please refer to "Test Method for Thermal Conductivity of Refractory Materials" (GTB 5990-2006). It will not be described in detail here. The calculation result of this method is λ=0.235W / (m·K). The final thermal conductivity of the soil to be tested is

Claims

1. A method for testing the thermal conductivity of contaminated soil treated by thermal desorption, characterized in that, The specific steps are as follows: (1) Before heating, put the cylindrical soil sample to be tested into the soil sample test chamber, insert the double probe vertically into the cylindrical soil sample, and insert the first probe with the alloy heating wire into the center of the cylindrical soil sample. The wires of the double probe are led out from the reserved hole at the top of the heating furnace and connected to the DC power supply and the multi-channel temperature recorder respectively. Then, the reserved hole is blocked with heat insulation cotton. The thermal conductivity calculation system is connected to the multi-channel temperature recorder. (2) Input instructions into the intelligent temperature control program module of the heating furnace according to the heating conditions to control the heating rate, heating time, heating temperature and holding time; (3) Open the first pressure control valve and the second pressure control valve to release nitrogen, so that the air in the furnace is discharged from the exhaust pipe through the tail gas processor and the vacuum pump, so that the soil sample in the furnace is in an inert gas atmosphere. Then close the first pressure control valve, adjust the second pressure control valve to the required pressure setting value, turn on the vacuum pump to draw air to form a negative pressure environment in the heating furnace, and read the pressure value in the furnace through the pressure sensor. When the read pressure value is consistent with the pressure setting value of the second pressure control valve, turn off the vacuum pump. After the adjustment is completed, turn on the heating switch of the heating furnace to start heating. (4) After the furnace is heated to the set temperature, the soil sample is kept at a constant temperature for a period of time to ensure that it is heated evenly. When the temperature difference between the two thermocouples in the dual probe is no more than 0.05℃, it indicates that the soil sample temperature is stable. (5) After meeting the requirements of step (4), turn on the DC power supply and manually adjust the set constant current to power the alloy heating wire. At the same time, the multi-channel temperature recorder will continuously record the temperature rise and corresponding time of the two thermocouples and feed it back to the thermal conductivity calculation system to obtain the temperature rise curves of the first probe and the second probe. The thermal conductivity of the soil sample is calculated back according to the formulas of the hot probe method and the parallel hot wire method. The calculation formula for the thermal probe method is as follows: ， (2) ， In the formula They exhibit a linear relationship on the coordinate axes. Thermal conductivity, in units of The heating power per unit length of the first probe is given by [unit]. The interval from the start of the test to the point where the temperature of the second probe begins to change, in units of... The temperature rise of the first probe within a time period, in units of The current passing through the alloy heating wire is expressed in units of . The resistance of the alloy heating wire, in units of... The length of the stainless steel needle tube of the first probe is in meters. The calculation formula for the parallel hot-wire method is as follows: (3)， In the formula Thermal conductivity, in units of The heating power per unit length of the first probe is given by [unit]. Let r be the exponential integral function, and r be the distance between the first and second probes. , The thermal diffusivity of the soil sample to be tested is given in units of 1000 ppm. The test duration is the total time from start to finish, expressed in seconds. The temperature rise of the second probe within a given time period, expressed in Kelvin (K). (6) After completing the thermal conductivity measurement, since a large amount of waste gas will be generated after the contaminated soil is heated, the vacuum pump is turned on. The waste gas is extracted from the heating furnace through the vacuum pump and discharged through the exhaust pipe and tail gas treatment box for adsorption and purification.

2. A testing system applicable to the method for testing the thermal conductivity of contaminated soil subjected to thermal desorption treatment as described in claim 1, characterized in that: It includes a test chamber, a heating furnace, a pneumatic control system, and a soil sample thermal conductivity testing system. The specific structure and connections are as follows: The test chamber is placed inside a heating furnace. The thermocouple inside the test chamber is connected to the heating furnace temperature control system. The air inlet of the air pressure control system is connected in sequence to the first air pressure control valve and the nitrogen source. The air outlet of the air pressure control system is connected in sequence to the air pressure sensor, the second air pressure control valve, the exhaust gas processor and the vacuum pump. The soil sample thermal conductivity testing system includes dual probes, wires, a DC power supply, a multi-channel temperature recorder, and a thermal conductivity calculation system. The dual probes are inserted into the soil sample to be tested and placed together in the test chamber. The dual probes are connected to the DC power supply and the multi-channel temperature recorder through wires. The thermal conductivity calculation system is externally connected to the multi-channel temperature recorder.

3. The testing system according to claim 2, characterized in that: The dual probe consists of two parallel first probes and second probes. Both the first probe and the second probe include a stainless steel needle tube, a stainless steel conical needle tip, a thermocouple, a ceramic insulating coating, an insulating spherical alumina powder filler, a sealing head, and a convex needle cap. The first probe has an alloy heating wire built in. A solid capillary steel tube is welded to the center of the stainless steel conical needle tip at the lower end of the first probe. The first and second probes are fixed to the lower end of the convex needle cap by welding, and the parallel distance between the two probes is [missing information]. The alloy heating wire and thermocouple wire extend from the top of the convex needle cap.

4. The testing system according to claim 3, characterized in that: The upper end of the stainless steel needle tube of the first and second probes is a sealed head, and the lower end is a stainless steel conical needle tip. The interior of the first and second probes is fully filled with insulating spherical alumina powder filler.

5. The testing system according to claim 3, characterized in that: Both the solid capillary steel tube and the alloy heating wire are coated with ceramic insulating coating.

6. The testing system according to claim 3, characterized in that: A solid capillary steel tube with a diameter of 0.3-0.5 mm and a length of 90-140 mm is welded to the center of the stainless steel conical tip at the lower end of the first probe.

7. The testing system according to claim 3, characterized in that: The temperature measuring points of the thermocouples of the first and second probes extend to the middle height of the stainless steel needle tube. The alloy heating wire is spirally wound and built into the surface of the solid capillary tube of the first probe, with a length consistent with that of the solid capillary tube.

8. The testing system according to claim 3, characterized in that: The stainless steel needle tubes of the first and second probes have the same diameter and thickness, with an outer diameter of 2-3 mm, an inner diameter of 1.8-2.8 mm, and a length of 100-150 mm.

9. The thermal conductivity testing system for contaminated soil undergoing thermal desorption treatment according to claim 2, characterized in that: The diameter of the alloy heating wire is 0.3-0.5 mm; the diameter of the thermocouple is 0.3-0.5 mm, and the accuracy is 0.01 K.

10. The testing system according to claim 2, characterized in that: The thermal conductivity calculation system calculates the thermal conductivity of the soil sample based on the temperature change data of the first and second probes under constant current recorded by the multi-channel temperature recorder, according to the principles of the thermal probe method and the parallel hot wire method.

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