A combustion heat conduction in-situ thermal desorption heating system and method of use thereof

Abstract

This invention provides an in-situ heat removal system for combustion heat conduction and its usage method. The system includes a square-wave reciprocating single-layer heating pipe, a burner, a terminal exhaust fan, connecting pipes, and a monitoring device. The heating pipes are located underground, and adjacent heating pipes are arranged in a counter-rotating, staggered pattern to form a uniformly distributed heating pipe network. Each heating pipe includes several U-shaped universal pipe sections and an upper connecting pipe. The inlet at the beginning of the pipe connects to the burner, and the outlet at the end connects in parallel to the terminal exhaust fan. In-situ soil heating is achieved through heat exchange via the reciprocating flow of high-temperature flue gas produced by the burner within the heating pipes. This invention improves the energy utilization efficiency of high-temperature flue gas, reduces the need for burner configuration, avoids the insufficient applicability of conventional double-layer pipe structures, improves the shortcomings of traditional vertical shaft heat conduction heating at the top and bottom, and achieves uniform heating and repair through the parallel, counter-rotating, staggered arrangement of the heating system.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to an in-situ heat removal system for combustion heat conduction and its usage method. Background Technology

[0002] With the acceleration of industrialization and urbanization in my country, the pollution of soil and groundwater from historical industrial sites during the development of construction land has become increasingly prominent. Typical pollutants in soil and groundwater are organic pollutants, including benzene compounds, chlorinated hydrocarbons, petroleum hydrocarbons, pesticides, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). The presence of these pollutants in soil and groundwater seriously endangers the health of surrounding people and the ecological environment. Therefore, it is necessary to remove pollutants from contaminated soil and groundwater through reasonable remediation technologies to effectively control the health and ecological risks of contaminated sites. In-situ thermal desorption technology involves heating the organic pollutants in the soil to a sufficiently high temperature through direct or indirect heating, causing them to volatilize into a gaseous state and separate from the soil. The volatilized pollutants are collected or directly incinerated and decomposed. Compared with other contaminated soil remediation technologies, thermal desorption technology has advantages such as a wide range of pollutant treatment, high treatment rate, and the reuse of remediated soil. Heating methods for in-situ thermal desorption include heat conduction heating, resistance heating, and steam-enhanced extraction, among which heat conduction heating includes electric heating and combustion heating. Combustion heat conduction heating is currently the mainstream heating method in in-situ thermal desorption technology and is widely used in in-situ soil remediation projects in my country.

[0003] However, current combustion heat conduction heating systems generally use double-casing heating wells. Due to limitations in flue gas injection methods, existing thermal desorption systems typically heat from the bottom up, resulting in uneven heating as the flue gas temperature gradually decreases. Furthermore, existing thermal desorption systems have high exhaust temperatures and low energy efficiency. The main method of flue gas reuse is re-injection underground for secondary use, but this results in significant energy loss during surface transmission. Therefore, developing an in-situ heat conduction heating system and method with high energy efficiency and uniform heating is particularly necessary. Summary of the Invention

[0004] This invention addresses the problems of low energy utilization efficiency and uneven heating range in the existing in-situ heat conduction desorption system. It provides a combustion heat conduction in-situ heat desorption heating system and its usage method, which aims to improve energy utilization efficiency, achieve uniform heating and repair, and make the installation and dismantling of the device more convenient.

[0005] To achieve the above objectives, the present invention mainly adopts the following technical solutions:

[0006] A combustion heat conduction in-situ heat removal and additional heating system is characterized by comprising: a square-wave reciprocating zigzag single-layer heating tube, a burner, a terminal exhaust fan, matching connecting pipes, and a monitoring device; the square-wave reciprocating zigzag single-layer heating tube is located underground, and adjacent parallel square-wave reciprocating zigzag single-layer heating tubes are arranged in a reverse staggered manner at their heads and ends to form a uniformly distributed heating pipe network.

[0007] Furthermore, the square-wave reciprocating single-layer heating tube includes several U-shaped universal pipe sections and an upper connecting pipe. The U-shaped universal pipe sections are connected in series with each other through the upper connecting pipe. The air inlet at the first end of the square-wave reciprocating single-layer heating tube is connected to the burner pipeline, and the air outlet at the end is connected to the air inlet of the end exhaust fan after being connected in parallel through the flue gas exhaust pipeline.

[0008] Furthermore, the air inlet of the terminal exhaust fan is connected in parallel to the outlet of the flue gas exhaust pipe of the square-wave reciprocating single-layer heating tube, and the air outlet of the terminal exhaust fan is connected to the flue gas exhaust pipe.

[0009] A further preferred embodiment is that the terminal exhaust fan is a high-temperature resistant exhaust fan with variable frequency to adjust the air pressure and air volume.

[0010] Furthermore, the U-shaped universal pipe section consists of a bottom horizontal pipe, a U-shaped arm pipe, and a support rod; the inlet and outlet of the top and bottom of the U-shaped arm pipe are flange structures, the bottom of the U-shaped arm pipe is connected to the bottom horizontal pipe through a flange, and the top of the U-shaped arm pipe is fixedly supported by a support rod, with a detachable support rod lifting ring in the middle of the support rod.

[0011] A further preferred embodiment is that both the bottom horizontal tube and the U-shaped arm tube are stainless steel round tubes with the same inner diameter and greater than 15cm.

[0012] A further preferred embodiment is that the U-shaped arm has a length of 2m, 4m or 6m, and one or more U-shaped arms are connected according to the target remediation depth, with the connection length being less than 2m or more of the thickness of the contaminated soil to be remediated.

[0013] Furthermore, the upper connecting pipe has flange interfaces at both ends, which are connected in series to the inlet and outlet ports of two U-shaped universal pipe sections.

[0014] Furthermore, the bottom horizontal tube has flange interfaces at both ends, and four steel plates are welded to the outside of the bottom horizontal tube to form a bidirectional V-shaped structure. The bottom horizontal tube is the same length as the support rod.

[0015] A further preferred embodiment is that the lengths of the upper connecting pipe, the bottom horizontal pipe, and the support rod are of standard specifications of 2m, 4m, or 6m.

[0016] A further preferred embodiment is that the number of the U-shaped universal pipe section and the upper connecting pipe, and the length of the upper connecting pipe and the bottom horizontal pipe are determined according to the target temperature difference between the inlet and outlet of the square waveform reciprocating single-layer heating pipe. In the low-temperature zone far from the burner, a smaller length of the upper connecting pipe and the bottom horizontal pipe can be selected, and the outlet temperature is greater than the target heating temperature.

[0017] Furthermore, the burner is installed at the top of the air inlet of the first U-shaped universal pipe section at the beginning of the square-wave reciprocating single-layer heating tube.

[0018] A further preferred embodiment is that the burner is a low-NOx type light oil burner or a natural gas burner, and the burner power can be adjusted between 20-80kW to meet the heating temperature requirements of heating tubes of different lengths.

[0019] Furthermore, the connecting pipes between the burner and the inlet of the square-wave reciprocating single-layer heating tube, and between the outlet of the square-wave reciprocating single-layer heating tube and the end exhaust fan, are equipped with threaded interfaces and replaceable thermocouple temperature detection probes; the thermocouples are of type N and type K. One-way valves for flue gas are installed at the inlet and outlet of the square-wave reciprocating single-layer heating tube, and the flue gas flow rate of the parallel heating tubes is adjusted through the outlet one-way valve. By detecting the inlet and outlet flue gas temperatures, the operating parameters of the burner and fan can be adjusted accordingly to ensure that the temperature meets the repair requirements. The one-way valves ensure that the high-temperature flue gas flows more stably according to the preset flow direction, effectively preventing backflow of flue gas after shutdown and cooling, and ensuring a more uniform temperature distribution in the heating area.

[0020] The present invention also provides a method for in-situ heat removal of additional heat from combustion heat conduction system, which employs the aforementioned in-situ heat removal system for combustion heat conduction and includes the following steps:

[0021] S1: Based on the target heating temperature and the influence radius of the square waveform reciprocating single-layer heating tube, determine the length of the U-shaped arm tube, the specifications of the bottom horizontal tube, and the parallel spacing of the square waveform reciprocating single-layer heating tube, and assemble the U-shaped general tube section structure.

[0022] S2: Based on the repair depth and the parallel spacing of the square-wave reciprocating single-layer heating tubes, use a chain grooving machine to open heating tube grooves. The groove width is greater than 20cm, the groove length is greater than the span of the square-wave reciprocating single-layer heating tube by 1m, the axial deviation does not exceed ±5cm, the groove depth is greater than or equal to the burial depth of the square-wave reciprocating single-layer heating tube and less than the heating repair depth by 1-2m, the spacing between adjacent grooves is the parallel spacing of the square-wave reciprocating single-layer heating tubes, and the adjacent parallel grooves are offset by the span of a U-shaped universal pipe section. The offset of the parallel heating tubes is achieved by the offset of the adjacent grooves.

[0023] S3: The assembled U-shaped universal pipe section is lifted into the trench using support rods and lifting rings, and statically pressed into the target depth for fixation. The upper connecting pipe is connected to form a square waveform reciprocating single-layer heating pipe. The adjacent parallel square waveform reciprocating single-layer heating pipes are offset by one span of the U-shaped universal pipe section. The original contaminated soil is backfilled into the heating pipe trench to above the bottom horizontal pipe for fixation. The offset of the adjacent parallel heating pipes achieves the complementarity of the heating range of the upper and bottom horizontal pipes, resulting in more uniform energy utilization and temperature distribution.

[0024] S4: Connect the burner to the air inlet of the underground corrugated reciprocating single-layer heating tube. Install it according to the principle of reverse direction of the first and last ends of the adjacent parallel square corrugated reciprocating single-layer heating tube. Connect the air outlet of the square corrugated reciprocating single-layer heating tube to the ground flue gas parallel pipeline. Connect the flue gas parallel pipeline to the end exhaust fan in parallel. Check the high temperature flue gas sealing performance.

[0025] S5: After all the parallel square waveform reciprocating single-layer heating pipe systems are installed, coarse-grained quartz sand is filled into the gaps in the trench as a heat-conducting material, a surface foam cement insulation layer is laid, and the power of the burner, the terminal exhaust fan and the flue gas one-way valve are adjusted to ensure that the flue gas temperature at the outlet of the square waveform reciprocating single-layer heating pipe is higher than the target heating temperature. This is combined with an in-situ extraction and treatment system for the remediation of contaminated soil.

[0026] S6: After the repair is completed and the soil has cooled, remove the burner and the terminal exhaust fan, break the surface insulation layer, remove the top layer of soil and quartz sand, remove the upper connecting pipe, disassemble the heating system into U-shaped universal pipe sections, and remove and clean the heating pipes by lifting them up.

[0027] The present invention has the following beneficial technical effects:

[0028] (1) The present invention improves the energy utilization efficiency of the high-temperature flue gas generated by the burner by the reciprocating flow of the high-temperature flue gas produced by the burner in the underground heating pipe, thereby reducing the burner configuration requirements and energy consumption.

[0029] (2) This invention improves the shortcomings of traditional vertical shaft heat conduction, which has poor heating effect at the top and bottom, by using a single-layer heating pipe structure with reciprocating waveforms underground. At the same time, the heating depth can be increased to 10m by connecting standard-specification arm pipes in series. Compared with a single horizontal pipe heating well, the coverage depth range is greatly improved, and the application range is wider. The bidirectional V-shaped structure reduces soil resistance, realizes trench hoisting, reduces the construction difficulty of simultaneous vertical and horizontal heating, and makes installation and dismantling more convenient.

[0030] (3) The present invention achieves complementarity between high temperature zone and low temperature zone, and upper and lower heating zone by parallel reverse staggered plane arrangement of adjacent heating tubes, offset of heating tubes and opposite flow of high temperature flue gas, and improves temperature uniformity by using gradient distribution of temperature field.

[0031] (4) This invention enables the reuse of heating well pipes in the remediation of shallow contaminated soil within 10m by standardizing the heating well pipes. The length of the heating pipes can be freely combined and extended by assembling the universal pipe sections, without the need to manufacture heating pipes separately according to site characteristics. At the same time, in the low-temperature section of the heating pipe far from the burner, short-specification upper connecting pipes and bottom horizontal pipes can be selected to freely adjust the spacing of the heating pipes, avoiding the insufficient applicability of the conventional double-layer sleeve complex structure.

[0032] (5) Compared with the ground secondary conduction heating system, the present invention reduces the ground heat transfer pipelines, making the repair construction site safer. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the composition and structure of the combustion heat conduction in-situ heat removal and additional heating system of the present invention in a specific embodiment;

[0034] Figure 2 This is a schematic diagram of the components of a single-set square waveform reciprocating folding single-layer heating tube in a specific embodiment of the combustion heat conduction in-situ heat removal and auxiliary heating system of the present invention;

[0035] Figure 3 This is a side view of the bottom horizontal pipe of the U-shaped universal pipe section in the combustion heat conduction in-situ heat removal system of the present invention in a specific embodiment.

[0036] Figure 4 This is a schematic diagram of the parallel reverse misaligned plane layout of the combustion heat conduction in-situ heat removal and additional heating system of the present invention in a specific embodiment;

[0037] The diagram shows: 1. Square-wave reciprocating single-layer heating tube; 2. Burner; 3. Terminal exhaust fan; 4. Flue gas exhaust stack; 5. U-shaped universal pipe section; 6. Upper connecting pipe; 7. Bottom horizontal pipe; 8. U-shaped arm pipe; 9. Support rod; 10. Connecting flange; 11. Support rod lifting ring; 12. Bottom horizontal pipe with bidirectional V-shaped structure; 13. Thermocouple temperature detection probe; 14. Heating tube groove; 15. Original contaminated soil; 16. Coarse quartz sand; 17. Flue gas one-way valve. Detailed Implementation

[0038] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0039] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0040] Please see Figure 1-4This invention provides an in-situ heat removal system for combustion heat conduction. In this embodiment, it mainly includes a square-wave reciprocating single-layer heating tube 1, a burner 2, a terminal exhaust fan 3, supporting connecting pipes, and a monitoring device. Six sets of parallel square-wave reciprocating single-layer heating tubes 1 located below ground are arranged with their adjacent heating tubes staggered in opposite directions to form a uniformly distributed heating pipe network. Each square-wave reciprocating single-layer heating tube 1 includes three U-shaped universal pipe sections 5 and two upper connecting pipes 6. The U-shaped universal pipe sections 5 are connected in series via the upper connecting pipes 6. The air inlet at the beginning of the series-connected square-wave reciprocating single-layer heating tube 1 is connected to the burner 2 via a pipe, and the air outlet at the end is connected to the terminal exhaust fan 3 via a parallel flue gas exhaust pipe. Each U-shaped universal pipe section 5 consists of a bottom horizontal pipe 7, a U-shaped arm pipe 8, and a support rod 9. The bottom horizontal pipe 7 and the U-shaped arm pipe 8 are stainless steel round pipes with an inner diameter of 16 cm. The top and bottom inlets and outlets of the U-shaped arm pipe 8 are flange structures, with a length of 4m and a target repair depth of 6m. The bottom of the U-shaped arm pipe 8 is connected to the bottom horizontal pipe 7 via a flange, and the top of the U-shaped arm pipe 8 is fixedly supported by a support rod 9. The support rod 9 has a detachable support rod lifting ring 11 in the middle. The bottom horizontal pipe 7 has flange interfaces at both ends, and four steel plates are welded to the outside of the bottom horizontal pipe 7 to form a bidirectional V-shaped structure 12. The bottom horizontal pipe 7 and the support rod 9 are available in two lengths: 2m and 4m. The upper connecting pipe 6 is 2m long, with flange interfaces at both ends, and is connected in series to the inlet and outlet of two adjacent U-shaped universal pipe sections 5. The target soil heating temperature is 90℃, the inlet temperature of the square waveform reciprocating single-layer heating pipe 1 is 1000℃, and the target outlet temperature is 200℃. In the low-temperature section after the first U-shaped universal pipe section, the length of the bottom horizontal pipe 7 and the support rod 9 is shortened from 4m to 2m. The burner 2 is installed at the top of the air inlet of the first U-shaped universal pipe section 5 at the beginning of the square-wave reciprocating single-layer heating tube 1. It is a low-NOx light oil burner with an adjustable power between 20-80kW. The terminal exhaust fan 3 is a high-temperature resistant exhaust fan with variable frequency to adjust the air pressure and air volume. Its air inlet is connected to the parallel outlet of the flue gas exhaust pipe of the square-wave reciprocating single-layer heating tube 1, and its outlet is connected to the external flue gas exhaust stack 4 through a pipe. The matching connecting pipes between the burner 2 and the air inlet of the square-wave reciprocating single-layer heating tube 1, and between the end outlet of the square-wave reciprocating single-layer heating tube 1 and the terminal exhaust fan 3, are equipped with threaded interfaces and replaceable thermocouple temperature detection probes 13. The thermocouples are of type N and type K. The inlet and outlet of the heating tube are equipped with flue gas one-way valves 17 to regulate the flue gas flow and prevent flue gas backflow from burning the burner. The flue gas flow of the parallel heating tubes is regulated by the flue gas one-way valve at the outlet.

[0041] The steps for in-situ thermal remediation of contaminated soil using the heating system described above are as follows:

[0042] Step 1: Based on the target heating temperature and the influence radius of the square waveform reciprocating single-layer heating tube 1, determine the length of the U-shaped arm tube 8 (in this embodiment, the length of the U-shaped arm tube is 4m, composed of a single 4m specification arm tube, which is less than the 2m thickness of the contaminated soil to be remediated), the specifications of the bottom horizontal tube 7 (in this embodiment, the length of the bottom horizontal tube is either 2m or 4m), and the parallel spacing of the square waveform reciprocating single-layer heating tube 1 (in this embodiment, the parallel spacing is 2m), and assemble the U-shaped universal tube section 5 structure.

[0043] Step 2: Based on the repair depth and the parallel spacing of the square-wave reciprocating single-layer heating tube 1, use a chain grooving machine to open the heating tube groove 14; the groove width should be greater than 20cm, preferably 25cm; the groove length is 14m, and the span of the square-wave reciprocating single-layer heating tube is 12m; the axial deviation should not exceed ±5cm; the groove depth is 5m, the burial depth of the square-wave reciprocating single-layer heating tube is 5m, and the heating repair depth is 6m; the spacing between adjacent grooves is 2m for the parallel spacing of the square-wave reciprocating single-layer heating tube; the offset between adjacent parallel grooves is one U-shaped universal pipe section span of 4m;

[0044] Step 3: Use the support rod and lifting ring 11 to lift the assembled U-shaped universal pipe section 5 into the trench, and statically press it into the target depth of 5m to fix it. Then connect the upper connecting pipe 6 in sequence to form a square waveform reciprocating single-layer heating pipe 1. The adjacent parallel square waveform reciprocating single-layer heating pipes are offset by 4m. Backfill the original contaminated soil 15 into the heating pipe trench 14 to 1m above the bottom horizontal pipe 7 and fix it.

[0045] Step 4: Connect the burner 2 to the air inlet of the underground corrugated reciprocating single-layer heating tube 1, and install it according to the principle of reverse direction of the first and last ends of adjacent parallel heating tubes. Connect the air outlet of the heating tube to the ground exhaust pipe, and connect the exhaust pipe in parallel to the end exhaust fan 3 to check the high temperature flue gas sealing.

[0046] Step 5: After all the parallel heating systems are installed, continue to fill the gaps in the trench with coarse quartz sand 16 as a heat-conducting material, lay a surface foam cement insulation layer, adjust the power of burner 2, terminal exhaust fan 3 and flue gas one-way valve 17 to ensure that the flue gas temperature at the outlet of the heating pipe is higher than the target heating temperature, and use the in-situ extraction and treatment system to remediate the contaminated soil.

[0047] Step 6: After the repair is completed and the soil has cooled down, remove the burner 2 and the terminal exhaust fan 3, break the surface insulation layer, remove the top layer of soil and quartz sand, remove the upper connecting pipe 6, and disassemble the heating system into U-shaped universal pipe sections 5. Remove and clean the heating pipes by lifting them up.

Claims

1. A method of using a combustion heat conduction in-situ thermal desorption heating system, comprising: The combustion heat conduction in-situ thermal desorption heating system comprises a square wave reciprocating return single-layer heating pipe (1), a burner (2), an end exhaust fan (3), a matching connecting pipeline and a monitoring device; the square wave reciprocating return single-layer heating pipe (1) is located underground, and the first and last ends of adjacent parallel square wave reciprocating return single-layer heating pipes (1) are arranged in reverse staggered positions to form a uniformly distributed heating pipe network. The square wave reciprocating return single-layer heating pipe (1) comprises a plurality of U-shaped universal pipe sections (5) and upper connecting pipes (6), the U-shaped universal pipe sections (5) are connected in series with each other through the upper connecting pipes (6); the first end gas inlet of the series-connected square wave reciprocating return single-layer heating pipe (1) is connected with the pipeline of the burner (2), and the end gas outlet is connected with the gas inlet of the end exhaust fan (3) after being connected in parallel through a flue gas exhaust pipeline. The U-shaped universal pipe section (5) is composed of a bottom horizontal pipe (7), a U-shaped arm pipe (8) and a support rod (9); the top and bottom inlets and outlets of the U-shaped arm pipe (8) are flange structures, the bottom of the U-shaped arm pipe (8) is connected with the bottom horizontal pipe (7) through a flange, the top of the U-shaped arm pipe (8) is fixedly supported through the support rod (9), and the middle of the support rod (9) is provided with a detachable support rod lifting ring (11). The matching connecting pipeline between the burner (2) and the gas inlet of the square wave reciprocating return single-layer heating pipe (1) and between the end gas outlet of the square wave reciprocating return single-layer heating pipe (1) and the end exhaust fan (3) is provided with a threaded joint, and a replaceable thermocouple temperature detection probe (13) is installed; the thermocouples are N-type and K-type. The use method comprises the following steps: S1: based on the target heating temperature and the influence radius of the square wave reciprocating return single-layer heating pipe, the length of the U-shaped arm pipe, the specification of the bottom horizontal pipe and the parallel spacing of the square wave reciprocating return single-layer heating pipe are determined, and the U-shaped universal pipe section structure is assembled; S2: according to the repair depth and the parallel spacing of the square wave reciprocating return single-layer heating pipe, a heating pipe slot is opened using a chain slot machine, the slot width is greater than 20 cm, the slot length is greater than the span of the square wave reciprocating return single-layer heating pipe by 1 m, the axis deviation is not more than ±5 cm, the slot depth is greater than or equal to the burial depth of the square wave reciprocating return single-layer heating pipe and less than the heating repair depth by 1-2 m, the adjacent slot spacing is the parallel spacing of the square wave reciprocating return single-layer heating pipe, and the adjacent parallel slots are offset by a U-shaped universal pipe section span; S3: the assembled U-shaped universal pipe section is hoisted into the slot using the support rod lifting ring, is pressed into the target depth statically and is fixed, the upper connecting pipes are connected in sequence to form the square wave reciprocating return single-layer heating pipe, the adjacent parallel square wave reciprocating return single-layer heating pipes are offset by a U-shaped universal pipe section span, and the heating pipe slot is backfilled with original contaminated soil to a position above the bottom horizontal pipe and is fixed; S4: the burner is connected to the gas inlet of the underground square wave reciprocating return single-layer heating pipe, is installed according to the principle that the first and last ends of adjacent parallel square wave reciprocating return single-layer heating pipes are in reverse, the gas outlet of the square wave reciprocating return single-layer heating pipe is connected to a ground flue gas parallel pipeline, the flue gas parallel pipeline is connected in parallel to the end exhaust fan, and the high-temperature flue gas tightness is checked. S5: After all the sets of parallel square wave reciprocating return single-layer heating pipe systems are installed, continue to fill coarse quartz sand as heat-conducting material in the gap in the tank, lay the ground surface foam cement insulation layer, adjust the power of the burner and the end exhaust fan and the one-way flue gas valve to ensure that the outlet flue gas temperature of the square wave reciprocating return single-layer heating pipe is higher than the target heating temperature, and the in-situ extraction treatment system is used for contaminated soil remediation; S6: After the remediation is completed and the soil is cooled, the burner and the end exhaust fan are removed, the ground surface insulation layer is broken, the upper layer of soil and quartz sand on the tank top is removed, the upper layer of connecting pipe is removed, the heating system is split into U-shaped universal pipe sections, and the heating pipe is lifted to remove and clean.

2. A method of using a combustion heat conduction in-situ thermal desorption heating system according to claim 1, wherein, The air inlet of the end exhaust fan (3) is connected in parallel with the outlet of the flue gas exhaust pipe of the square wave reciprocating return single-layer heating pipe (1), and the air outlet of the end exhaust fan (3) is connected with the flue gas exhaust pipe (4).

3. The method of claim 1, wherein the heating system is a combustion heat conduction in-situ thermal desorption heating system. The upper layer connecting pipe (6) has same-direction flange interfaces at both ends and is connected in series to the air inlets and outlets of the two U-shaped universal pipe sections (5).

4. The method of claim 1, wherein the system is a combustion heat conduction in-situ thermal desorption heating system. The bottom cross pipe (7) has same-direction flange interfaces at both ends, and four steel plates are welded outside the bottom cross pipe (7) to form a bottom cross pipe double-direction V-shaped structure (12), and the length of the bottom cross pipe (7) is the same as that of the support rod (9).

5. The method of claim 1, wherein the system is a combustion heat conduction in-situ thermal desorption heating system. The burner (2) is installed on the top of the air inlet of the first section U-shaped universal pipe section (5) at the first end of the square wave reciprocating return single-layer heating pipe (1).

6. The method of using a combustion heat conduction in-situ thermal desorption heating system of claim 1, wherein, The bottom cross pipe (7) and the U-shaped arm pipe (8) are both stainless steel pipes with the same inner diameter greater than 15 cm.

7. The method of using a combustion heat conduction in-situ thermal desorption heating system of claim 1, wherein, The U-shaped arm pipe (8) has a length of 2 m, 4 m or 6 m, and one or more U-shaped arm pipes (8) are connected according to the target remediation depth, and the connection length is less than 2 m of the thickness of the contaminated soil to be remediated.

8. The method of using a combustion heat conduction in-situ thermal desorption heating system of claim 1, wherein, The upper layer connecting pipe (6) has a standard length of 2 m, 4 m or 6 m.

9. The method of using a combustion heat conduction in-situ thermal desorption heating system of claim 1, wherein, The bottom cross pipe (7) and the support rod (9) have a standard length of 2 m, 4 m or 6 m.

10. The method of claim 1, wherein the system is a combustion heat conduction in-situ thermal desorption heating system. The number of U-shaped universal pipe sections (5) and upper layer connecting pipes (6) and the length of upper layer connecting pipes (6) and bottom cross pipes (7) are determined according to the target temperature difference of the air inlets and outlets of the square wave reciprocating return single-layer heating pipe, and shorter specifications of upper layer connecting pipes (6) and bottom cross pipes (7) can be selected for the low-temperature section away from the burner, and the outlet temperature is greater than the target heating temperature.

11. The method of using a combustion heat conduction in-situ thermal desorption heating system of claim 1, wherein, The burner (2) is a low-nitrogen light oil burner or a natural gas burner, and the power of the burner can be adjusted between 20-80 kW.

12. The method of using a combustion heat conduction in-situ thermal desorption heating system of claim 1, wherein, The end exhaust fan (3) is a high-temperature resistant exhaust fan.

13. The method of claim 1, wherein the system is a combustion heat conduction in-situ thermal desorption heating system. The air inlets and outlets of the square wave reciprocating return single-layer heating pipe (1) are provided with one-way flue gas valves.

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