Integrated flow field adjustable soil thermal desorption pilot plant and multi-working condition operation method

Abstract

The present application belongs to the technical field of contaminated soil remediation, and discloses an integrated soil thermal desorption pilot plant with adjustable flow field and a multi-working-condition operation method. A protection tube corresponding to an electric heating rod is vertically arranged in the thermal desorption soil column, the electric heating rod is arranged in the protection tube and has a gap with the protection tube, and the protection tube indirectly heats the soil in the thermal desorption soil column; a hydraulic system is connected with the electric heating device and is used to drive the electric heating device and the electric heating rod to vertically lift as a whole, and the electric heating rod can be inserted into the protection tube; a multi-mode flow field control system includes a blower, a vacuum pump and a plurality of air distribution plates; a tail gas multi-stage separation and purification unit is connected behind the vacuum pump; a plurality of air pipes are connected to the air distribution plates, the air pipes vertically extend upwards and are staggered with the protection tubes. The present application has small land occupation, is convenient to move and arrange, has high experimental data repeatability, and is suitable for various working condition simulation and engineering scale-up research.

Description

Technical Field

[0001] This invention belongs to the field of contaminated soil remediation technology, and in particular relates to an integrated pilot-scale soil thermal desorption device with adjustable flow field and a multi-condition operation method. Background Technology

[0002] With the increase in industrial activities and the use of hazardous chemicals, the accumulation of volatile and semi-volatile organic pollutants in soil is becoming increasingly serious. Thermal desorption technology is widely used in contaminated soil remediation projects due to its high treatment efficiency and wide applicability. Before the implementation of the project, it is usually necessary to simulate and optimize key parameters such as temperature gradient, gas flow rate, extraction intensity, and pollutant migration path through pilot-scale experimental equipment to verify the feasibility of the remediation process and provide data support for the scale-up of the project.

[0003] Existing pilot-scale soil thermal desorption devices have the following technical problems in practical applications: 1. The loading and unloading structure is poorly designed. The thermal desorption column usually contains heating rods and gas distribution pipes, making its structure complex. Traditional structures often use a top-mounted disassembly method, which requires repeated disassembly and reassembly of the high-temperature sealing flange, easily causing flange deformation and affecting sealing reliability. Another type of fixed cylinder structure, although with good sealing performance, is extremely inconvenient to fill and empty the soil, and is prone to damaging the internal pipelines, reducing the service life of the equipment.

[0004] 2. Direct contact heating methods suffer from localized overheating. In traditional devices, the heating element is in direct contact with the soil, causing a rapid rise in local temperature and creating hot spots. This localized overheating not only damages the soil structure but may also induce pyrolysis side reactions of pollutants, generating secondary pollutants and affecting the authenticity of the experiment and the reliability of the data.

[0005] 3. The flow field mode is singular and cannot simulate complex working conditions. Traditional devices are mostly single blower mode or single extraction mode, which cannot simulate complex flow field environments such as alternating positive and negative pressure and strong convection scavenging, thus limiting the extrapolation of experimental data to engineering applications.

[0006] Therefore, a pilot-scale soil thermal desorption device and a multi-condition operation method are needed, which are highly integrated in structure, have uniform heating, adjustable flow field, convenient loading and unloading, and high data repeatability, in order to meet the needs of various operating condition simulation and engineering scale-up research. Summary of the Invention

[0007] The purpose of this invention is to provide an integrated, flow-field-adjustable soil thermal desorption pilot plant and a multi-condition operation method to solve the following technical problems existing in the prior art: (1) The internal heating rod and gas distribution pipe of the hot desorption column have a complex structure. The traditional top disassembly or fixed dead cylinder structure is inconvenient for filling soil, which can easily damage the internal pipeline. The sealing flange is easily deformed by repeated disassembly, which affects the sealing reliability. (2) The heating element comes into direct contact with the soil, causing the local temperature to rise rapidly, creating hot spots, damaging the soil structure, inducing pyrolysis side reactions of pollutants, and affecting the authenticity of the experiment and the reliability of the data. (3) Traditional devices have a single flow field mode, which cannot simulate complex flow field environments such as alternating positive and negative pressures and strong convection scavenging, thus limiting the extrapolation of experimental data to engineering applications.

[0008] The specific technical solution adopted in this invention is as follows: In a first aspect, the present invention provides an integrated flow field adjustable soil thermal desorption pilot device, comprising a thermal desorption soil column, an electric heating device, a hydraulic system, a multimodal flow field control system, and a tail gas multi-stage separation and purification unit integrated within a support frame. The upper end of the thermally desorbed soil column is sealed to the electric heating device via a flange. Several electric heating rods extend downward from the bottom of the electric heating device. A protective tube corresponding to each electric heating rod is vertically installed inside the thermally desorbed soil column. The electric heating rods pass through the protective tubes and maintain a gap with the protective tubes, thereby indirectly heating the soil inside the thermally desorbed soil column through the protective tubes. The hydraulic system is connected to the electric heating device and is used to drive the electric heating device and the electric heating rod to rise and fall vertically as a whole, and to insert the electric heating rod into the protective tube. The bottom of the support frame is provided with a guide structure, and the thermally desorbed soil column can be translated horizontally along the guide structure; The multimodal flow field control system includes a first blower, a vacuum pump, and several air distribution plates arranged along the length of the thermally desorbed soil column and connected to the thermally desorbed soil column; the first blower is connected to the air distribution plates through an air inlet pipe, the vacuum pump is connected to the thermally desorbed soil column through an air outlet pipe, and the exhaust gas multi-stage separation and purification unit is connected after the vacuum pump; the air inlet pipe is provided with a bypass air pipe connected to each air distribution plate, and each bypass air pipe is provided with a control valve. The air distribution plate is connected to several air pipes, which extend vertically upwards and are arranged alternately with the protective pipe.

[0009] Optionally, the air distribution plate is provided with a swirling guide cavity, and the swirling guide cavity is provided with a plurality of spiral guide blades. The spiral guide blades form an angle of 30° to 45° with the horizontal plane, so that the incoming gas forms a rotating upward airflow.

[0010] Optionally, the thermally desorbed soil column is divided into an upper desorption strengthening zone, a middle homogenization transition zone, and a lower preheating zone along the axial direction from top to bottom, and the zones are separated by heat insulation plates. Each zone has an independent air inlet pipe, an independent air distribution plate, an independent air outlet pipe, and an independent electric heating circuit. Each zone's independent air inlet pipe is connected to the first blower via a solenoid valve, each zone's independent air extraction channel is connected to the vacuum pump via a proportional regulating valve, and each zone's independent electric heating circuit is connected to the power supply via a temperature control module. In other words, each zone has an independent air distribution plate at its bottom, the electric heating rods in different zones are connected to the power supply via temperature control modules to achieve independent temperature control for each zone, and each zone's air outlet pipe, equipped with a proportional regulating valve, is connected to the vacuum pump to achieve independent air extraction for each zone.

[0011] Optionally, the outer wall of the protective tube is provided with annular heat-conducting ribs or spiral heat-conducting fins along the axial direction; a heat-conducting filling layer is provided between the outer side of the protective tube and the soil.

[0012] Optionally, multiple inclined disturbance jet pipes are arranged along the circumferential direction on the sidewall of each zone of the thermally desorbed soil column. The inclined disturbance jet pipes are connected to the second blower after passing through the air inlet pipe. The axial direction of each inclined disturbance jet pipe forms an acute angle with the diameter of the thermally desorbed soil column. All the inclined disturbance jet pipes in each zone are connected together to form an air inlet ring, which is used to construct a three-dimensional composite disturbance flow field.

[0013] Optionally, the bottom of the thermally desorbed soil column is provided with a water collection chamber, which is located below the lowest air distribution plate and is sealed to the thermally desorbed soil column through a flange. The bottom of the water collection chamber is provided with a water outlet pipe.

[0014] Optionally, the exhaust gas multi-stage separation and purification unit includes a cyclone separator, a heat exchanger, a bag filter, a precision filter, and an activated carbon filter connected in sequence.

[0015] Optionally, an insulation layer is provided around the thermally desorbed soil column.

[0016] Optionally, the sidewall of the thermally desorbed soil column is provided with several pressure sensors, temperature sensors and sampling tubes along the axial direction; the pipelines of the multimodal flow field control system and the exhaust gas multi-stage separation and purification unit are provided with flow meters, temperature sensors and sampling ports.

[0017] Secondly, the present invention provides a multi-condition operation method for an integrated, flow-field-adjustable soil thermal desorption pilot plant, comprising the following steps: S1. Collaborative filling: The electric heating device is lifted by the hydraulic system, the thermally desorbed soil column is moved horizontally out of the filling soil and returned to its position, and the electric heating device is lowered to achieve precise insertion and sealing of the electric heating rod and the protective tube. S2, Indirect Uniform Heating: When the electric heating device is activated, heat is transferred to the protective tube via the electric heating rod and diffused into the soil through the thermally conductive filling layer; S3. Flow field mode switching: Select positive pressure stripping mode, negative pressure extraction mode or bidirectional coupling mode as needed; wherein, positive pressure stripping mode is achieved by closing the control valve of the bypass air pipe and starting the first blower, negative pressure extraction mode is achieved by opening the control valve of the bypass air pipe and starting the vacuum pump, and bidirectional coupling mode is achieved by closing the control valve of the bypass air pipe and starting the first blower and the vacuum pump simultaneously.

[0018] Compared with the prior art, the present invention has the following advantages: (1) Loading and unloading efficiency is greatly improved and the internal structure is not easily damaged. The electric heating device is driven by the hydraulic system to lift vertically as a whole, and in conjunction with the soil column horizontal translation guide structure, a dual-degree-of-freedom coordinated motion mode of "vertical lifting + horizontal translation" is formed, which realizes high-precision non-destructive alignment and rapid loading and unloading under complex interpolation structure, avoids the risk of deformation caused by repeated disassembly of high temperature sealing flange, and improves sealing reliability.

[0019] (2) The heating uniformity is significantly improved, avoiding local overheating and pyrolysis side reactions. The electric heating rod is inserted into the protective tube and fitted with it with a gap. It indirectly heats the soil through the protective tube. The heat transfer path is "electric heating rod - protective tube wall - thermally conductive filling layer - soil particles". With the thermally conductive ribs or spiral thermally conductive fins on the outer wall of the protective tube, the thermally conductive filling layer and the uniform temperature base structure, the probability of local hot spots is effectively reduced, the radial temperature uniformity is improved, and the authenticity of the experiment and the integrity of the soil structure are guaranteed.

[0020] (3) Enhanced flow field control capability and improved reliability of experimental data extrapolation. The multimodal flow field control system constructs three flow field modes—positive pressure stripping, negative pressure extraction, and bidirectional coupling—through the coordinated operation of the first blower, bypass air inlet, and vacuum pump. This can simulate complex flow field environments on site, improve the reliability of experimental data extrapolation, and enhance the adaptability of engineering applications.

[0021] (4) Improved energy utilization efficiency and desorption effect. The zoned heat-fluid coupling structure divides the soil column into an upper desorption enhancement zone, a middle homogenization transition zone and a lower preheating zone along the axial direction. Each zone independently controls the heating power, gas supply flow rate and extraction intensity, forming a controllable longitudinal temperature gradient and pressure gradient, avoiding energy waste caused by overall uniform heating, and significantly improving energy utilization efficiency and desorption effect.

[0022] (5) The mass transfer efficiency is significantly improved, making it suitable for low-permeability or heterogeneous soils. The three-dimensional composite disturbance flow field structure forms a spiral upward mainstream through the swirling guide cavity and spiral guide blades in the bottom air distribution plate, and the inclined disturbance jet pipe on the side wall of the soil column forms a lateral disturbance flow. The superposition forms a three-dimensional composite flow field, which destroys the chimney effect, eliminates the flow dead zone, increases the gas-solid contact frequency, and enhances the pollutant migration rate. The effect is particularly obvious in low-permeability or heterogeneous soils.

[0023] (6) The system has a high degree of integration, a small footprint, and good repeatability of experimental data. All functional units are highly integrated within the support frame, including thermal desorption soil column, hydraulic system, multimodal flow field control system, exhaust gas multi-stage separation and purification unit, etc. It has a small footprint, is easy to move and arrange, has high repeatability of experimental data, is suitable for simulation and engineering scale-up research under various working conditions, and has good adaptability to engineering scale-up. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention under a preferred embodiment; Figure 2 This is a schematic cross-sectional view of a thermally desorbed soil column under a preferred configuration. Figure 3 This is a schematic diagram of a thermally desorbed soil column under a preferred method; Figure 4 This is a schematic diagram of the air distribution plate and spiral guide vane structure in a preferred configuration. Figure 5 This is a schematic diagram of the ventilator structure in a preferred configuration.

[0025] Reference numerals: 1. First blower; 2. Thermal desorption soil column; 3. Cyclone separator; 4. Heat exchanger; 5. Bag filter; 6. Precision filter; 7. Activated carbon filter; 8. Vacuum pump; 9. Hydraulic system; 10. Water pump; 11. Support frame; 12. Insulation layer; 13. Water collection chamber; 14. Sampling tube; 15. Central controller; 16. Water outlet pipe; 17. First through hole; 18. Cyclone guide cavity; 19. Annular air distribution chamber; 20. Inclined disturbance jet pipe; 21. Spiral guide vane; 22. Air inlet ring; 23. Air inlet pipe; 24. Second blower; 201. Electric heating device; 202. Electric heating rod; 203. Air outlet pipe; 204. Support; 205. Protective pipe; 206. Air distribution plate; 207. Vent pipe; 208. Connecting rod; 209. Slide rail. Detailed Implementation

[0026] The following is in conjunction with the appendix Figure 1-5 The present invention will be described in further detail below.

[0027] This invention discloses an integrated, flow-field-adjustable soil thermal desorption pilot-scale device.

[0028] like Figure 1 The image shows an integrated, flow-field adjustable soil thermal desorption pilot plant, comprising a support frame 11, a thermal desorption soil column 2, an electric heating device 201, a hydraulic system 9, a multimodal flow field control system, and a multi-stage exhaust gas separation and purification unit. All functional units of the plant are integrated within the support frame 11. The support frame 11 is a box-type metal frame structure, approximately 2m × 1m × 2.5m in length × width × height, welded from angle steel, used to support and fix all components.

[0029] The thermally desorbed soil column 2 is a cylindrical stainless steel container with a diameter of 500 mm, a height of 1500 mm, and a wall thickness of 5 mm. An electric heating device 201 is sealed to the upper end of the thermally desorbed soil column 2 via a flange. The electric heating device 201 is an integrated heating unit comprising a heating power supply, a temperature control system, and electric heating rods 202. Several electric heating rods 202 extend downwards from the bottom of the electric heating device 201. In this embodiment, 15 stainless steel electric heating rods 202 are provided, each with a diameter of 20 mm. The portion of the rod located inside the thermally desorbed soil column 2 has a length of 1500 mm. The electric heating rods 202 are distributed at the bottom of the electric heating device 201, and are arranged in two concentric circles: 10 rods are evenly distributed in the outer circle, 4 rods are evenly distributed in the inner circle, and 1 rod is located in the center.

[0030] Inside the thermally desorbed soil column 2, there are vertically installed protective tubes 205, each corresponding to an electric heating rod 202. The protective tube 205 is made of stainless steel, with an inner diameter of 25mm, a wall thickness of 2mm, and a length of 1500mm. The electric heating rod 202 passes through the protective tube 205, maintaining a gap between it and the tube. The outer diameter of the electric heating rod 202 is 20mm, the inner diameter of the protective tube 205 is 25mm, and the gap is 2.5mm. A thermally conductive filling layer is provided between the outer side of the protective tube 205 and the soil. The soil inside is indirectly heated through the protective tube 205, with the heat transfer path being "electric heating rod 202 - protective tube 205 wall - thermally conductive filling layer - soil particles," effectively avoiding localized overheating caused by direct contact between the heating element (i.e., the electric heating rod 202) and the soil.

[0031] Furthermore, the thermally desorbed soil column 2 is divided axially from top to bottom into an upper desorption enhancement zone, a middle homogenization transition zone, and a lower preheating zone, each zone being 500mm high. The zones are separated by ceramic fiber insulation plates (in this embodiment, the ceramic fiber insulation plate can also be used as an air distribution plate, meaning air distribution plates are installed at the bottom of all three zones), with a thickness of 30mm. Each zone has an independent inlet pipe, an independent air distribution plate, an independent outlet pipe, and an independent electric heating circuit. Specifically, each zone has an independent air distribution plate 206 at its bottom. The portions of the electric heating rod 202 located in different zones are connected to a power supply via a temperature control module to achieve independent temperature control for each zone. Each zone is connected to a vacuum pump 8 via an outlet pipe 203 equipped with a proportional regulating valve to achieve independent air extraction for each zone. The independent inlet pipes of each zone are connected to the first blower 1 via solenoid valves, the outlet pipes of each zone are connected to the vacuum pump 8 via proportional regulating valves, and the independent electric heating circuits of each zone are connected to a power supply via a temperature control module (PID controller). During operation, the heating power, gas flow rate and extraction intensity of each zone can be adjusted separately to form a controllable longitudinal temperature gradient (upper zone 300-400℃, middle zone 200-300℃, lower zone 100-200℃) and pressure gradient, avoiding energy waste caused by uniform heating and significantly improving energy utilization efficiency and desorption effect.

[0032] like Figure 4 As shown, the gas distribution plate 206 has a first through hole 17 and a swirling guide cavity 18. The electric heating rod 202 passes through the first through hole 17 on the gas distribution plate 206 in sequence through the desorption enhancement zone and the homogenization transition zone, and finally reaches the first through hole 17 of the gas distribution plate 206 in the preheating zone. The protective tube 205 is interference-fitted with the first through hole 17. The gas distribution plate 206 has several swirling guide cavities 18 arranged circumferentially between the inner and outer rings of electric heating rods 202. The swirling guide cavities 18 are connected through an annular gas distribution cavity 19, which is in turn connected to the air inlet pipe 23. The swirling guide cavity 18 has spiral guide vanes 21, which form an angle of 30° to 45° with the horizontal plane, causing the incoming gas to form a rotating upward airflow. This swirling guide structure causes the gas to form a spiral upward mainstream, laying the foundation for constructing a three-dimensional composite disturbance flow field and increasing the gas-solid contact frequency.

[0033] like Figure 5 As shown, several vent pipes 207 are connected to the air distribution plate 206. In this embodiment, 10 stainless steel vent pipes 207 are provided, each with a diameter of 15 mm and a length of 450 mm. One end of each vent pipe 207 is inserted into the vortex guide cavity 18 and extends vertically upward from the air distribution plate 206. The vent pipes 207 and the protective tube 205 are arranged alternately to form a complex internal tube structure, such as... Figure 2 As shown.

[0034] The outer wall of the protective tube 205 is provided with annular heat-conducting ribs or spiral heat-conducting fins along the axial direction; a heat-conducting filling layer is provided between the outer side of the protective tube 205 and the soil. Specifically: Annular copper heat-conducting ribs are welded along the axial direction to the outer wall of the protective tube 205, with a height of 10mm, a thickness of 2mm, and a spacing of 20mm; or spiral copper heat-conducting fins are welded, with a pitch of 30mm, a height of 15mm, and a thickness of 2mm, to increase the heat exchange area. Quartz sand, with a particle size of 1-3mm and a filling thickness of 20mm, is filled between the outer side of the protective tube 205 and the soil as a heat-conducting filling layer to enhance heat transfer.

[0035] The thermally desorbed soil column 2 has a water collection chamber 13 at its bottom. The water collection chamber 13 is a semi-circular stainless steel container with a diameter of 500 mm and a height of 200 mm. It is located below the bottom air distribution plate 206 and is sealed to the thermally desorbed soil column 2 via a flange. The bottom of the water collection chamber 13 has a water outlet pipe 16 with a diameter of 20 mm, which is used to collect and discharge water or leachate from the soil to prevent water from accumulating inside the soil column and affecting the desorption effect.

[0036] An insulation layer 12 is provided around the thermally desorbed soil column 2. The insulation layer 12 is a ceramic fiber insulation layer with a thickness of 50mm. It wraps around the thermally desorbed soil column 2 and is fixed with a stainless steel shell to reduce heat loss, improve energy utilization efficiency, and ensure the temperature stability inside the soil column.

[0037] The sidewall of the thermally desorbed soil column 2 is axially equipped with several first pressure sensors, first temperature sensors, and sampling tubes 14. In this embodiment, three first pressure sensors are installed, with a range of -10 kPa to 10 kPa and an accuracy of 0.1 kPa, at the top, middle, and bottom positions of the thermally desorbed soil column 2 (heights of 1200 mm, 750 mm, and 300 mm, respectively). Three first temperature sensors are installed, with a range of 0-500℃ and an accuracy of 1℃, at the top, middle, and bottom positions of the thermally desorbed soil column 2 (heights of 1200 mm, 750 mm, and 300 mm, respectively). Three sampling tubes 14, with a diameter of 10 mm, are installed at the top, middle, and bottom positions of the thermally desorbed soil column 2 (heights of 1200 mm, 750 mm, and 300 mm, respectively), for collecting soil or gas samples. All first pressure sensors and first temperature sensors are connected to an external central controller 15 for automated control.

[0038] Hydraulic system 9 is installed on the upper part of support frame 11. Hydraulic system 9 is a hydraulic cylinder drive cylinder with an effective stroke of 2000mm and a maximum lifting force of 5000N. It is connected to electric heating device 201 through connecting rod 208 and is used to drive electric heating device 201 and electric heating rod 202 to vertically lift and lower as a whole. The bottom of support frame 11 is provided with a guide structure, specifically including bracket 204. Horizontal groove is opened on bracket 204 for placing the hot desorbed soil column 2. The frame has slide rail 209, which is inserted into the horizontal groove to form a sliding pair. Handles are provided on the side wall of hot desorbed soil column 2, which can be translated horizontally along the groove, with a movement distance of about 1m. When hydraulic system 9 drives electric heating device 201 to descend vertically, electric heating rod 202 is accurately inserted into protective tube 205 with an alignment accuracy of ±2mm, forming a "vertical lifting + horizontal translation" dual-degree-of-freedom coordinated motion mode, realizing high-precision non-destructive alignment and rapid loading and unloading under complex insertion structure.

[0039] The multimodal flow field control system includes a first blower 1, a vacuum pump 8, and several air distribution plates 206 arranged along the length of the thermally desorbed soil column 2 and connected to the thermally desorbed soil column 2. The first blower 1 is a centrifugal blower with a maximum air volume of 100 m³ / h. 3 The maximum air pressure is 5000Pa. The first blower 1 is connected to the air distribution plate 206 via the air inlet pipe. An electric ball valve is installed on the bypass air pipe as a switch. A bypass air pipe connected to each air distribution plate 206 is provided on the air inlet pipe 23. The bypass air pipe is equipped with a control valve, which is an electric ball valve. The vacuum pump 8 is a rotary vane vacuum pump with a maximum pumping capacity of 80m³ / h. 3 / h, ultimate vacuum degree -80kPa, vacuum pump 8 is connected to the thermally desorbed soil column through the outlet pipe. The first blower 1, the bypass pipe and vacuum pump 8 work together to construct three flow field modes: positive pressure stripping, negative pressure extraction and bidirectional coupling. The three modes are as follows: Positive pressure stripping mode: Close the electric ball valve of the bypass air pipe, start the first blower 1, and the gas enters the air distribution plate 206 from the first blower 1 through the pipeline, flows upward from the bottom of each zone of the thermal desorbed soil column 2, and carries the pollutants out from the air outlet pipe.

[0040] Negative pressure extraction mode: Open the electric ball valve of the bypass gas pipe, start the vacuum pump 8, and the atmosphere enters the pipeline through the bypass gas pipe, then enters the gas distribution plate 206, flows upward from the bottom of each zone of the thermal desorbed soil column 2, carries pollutants out from the outlet pipe, and is extracted by the vacuum pump 8.

[0041] Two-way coupling mode: Close the electric ball valve of the bypass gas pipe, and start the first blower 1 and vacuum pump 8 at the same time to form forced convection. The gas enters the gas distribution plate 206 from the first blower 1 through the pipeline, flows upward from the bottom of each zone of the thermal desorbed soil column 2, carries pollutants and is discharged from the gas outlet pipe, and is extracted by vacuum pump 8 to achieve the coupling effect of positive pressure and negative pressure.

[0042] In each zone of the thermally desorbed soil column 2, multiple inclined disturbance jet pipes 20 are arranged circumferentially on the sidewall. These inclined disturbance jet pipes 20 are connected to an air inlet pipe 23. The axial direction of each inclined disturbance jet pipe 20 forms an acute angle with the diameter of the thermally desorbed soil column 2. All the inclined disturbance jet pipes 20 in each zone are connected to form an air inlet ring 22, used to construct a three-dimensional composite disturbance flow field, such as... Figure 3 As shown.

[0043] Furthermore, several air intake rings are arranged axially along the sidewall of the thermally desorbed soil column 2. In this embodiment, three air intake rings are arranged, corresponding to the three zones of the thermally desorbed soil column 2. Each ring has six inclined disturbance jet pipes evenly distributed, with each inclined disturbance jet pipe forming a 45° angle with the diameter of the thermally desorbed soil column. These are controlled by independent valves to construct a three-dimensional composite disturbance flow field. The air intake rings are connected to the second blower 24, and the air intake rings and air intake pipes are independently connected to the two blowers. The inclined disturbance jet pipes on the sidewall of the thermally desorbed soil column 2 superimpose with the bottom swirling mainstream to form a three-dimensional composite flow field consisting of the bottom swirling mainstream, the lateral lateral disturbance flow, and the top concentrated extraction flow. This disrupts the chimney effect, eliminates dead zones in the flow, increases the gas-solid contact frequency, and enhances the pollutant migration rate, with particularly significant effects in low-permeability or heterogeneous soils.

[0044] The multi-stage exhaust gas separation and purification unit includes a cyclone separator 3, a heat exchanger 4, a bag filter 5, a precision filter 6, and an activated carbon filter 7, all connected sequentially via pipelines. The cyclone separator 3 has a diameter of 300mm and a height of 800mm, and is used to separate solid particles from the exhaust gas, achieving solid-liquid-gas three-phase separation. The heat exchanger 4 is a shell-and-tube heat exchanger with a heat exchange area of ​​2m². 2 Cooling water is supplied by water pump 10 to cool the high-temperature gas to room temperature. Bag filter 5 has a filtration accuracy of 10μm and is used to remove fine particulate matter from the exhaust gas. Precision filter 6 has a filtration accuracy of 1μm and is used to further remove fine particles from the exhaust gas. Activated carbon filter 7 is filled with 10kg of granular activated carbon to adsorb organic pollutants in the exhaust gas. The exhaust gas is sequentially treated by cyclone separator 3, heat exchanger 4, bag filter 5, precision filter 6, and activated carbon filter 7 before being safely discharged as clean gas.

[0045] The multimodal flow field control system and the exhaust gas multi-stage separation and purification unit are equipped with flow meters, temperature sensors, and sampling ports on their pipelines. The first flow meter is installed on the inlet pipe of the first blower 1, with a measuring range of 0-120m. 3 / h, used to monitor the gas flow rate at the outlet of the first blower 1. The second flow meter and the second temperature sensor are installed on the pipeline between the thermal desorbent column 2 and the cyclone separator 3. The second flow meter has a range of 0-100m. 3The second temperature sensor, with a range of 0-500℃, is used to monitor the gas flow rate and temperature at the outlet of soil column 2. The third flow meter and sampling port are installed on the pipeline between precision filter 6 and activated carbon filter 7; the third flow meter has a range of 0-100m³ / h. 3 / h, sampling port diameter 10mm, used to monitor the gas flow rate at the outlet of precision filter 6 and to connect to detection instruments such as GC-MS to monitor pollutant concentration in real time.

[0046] Reference Figure 1 The central controller 15 adopts a PLC (Programmable Logic Controller) to receive signals from all pressure and temperature sensors and control equipment such as the hydraulic system 9, electric heating device 201, first blower 1, vacuum pump 8, solenoid valve, and proportional regulating valve to realize the automated control of the device.

[0047] Implementation Principle: When filling with soil, open the top flange of the thermal desorption soil column 2. Control the hydraulic system 9 via the central controller 15 to raise the electric heating device 201 by 2000mm. The operator pulls the handle of the thermal desorption soil column 2, moving it horizontally 1m along the guide structure. Fill the column with contaminated soil. The hydraulic system 9 lowers the electric heating device 201, allowing the electric heating rod 202 to be precisely inserted into the protective tube 205, achieving a seal. Close the flange and return the thermal desorption soil column 2 to its original position. Start the electric heating device 201, setting the target temperature to heat the soil. The electric heating rod 202 indirectly heats the soil through the protective tube 205. Heat is transferred through the wall of the protective tube 205 to the thermally conductive filling layer and then to the soil particles, avoiding localized overheating caused by direct contact with the soil and ensuring uniform soil heating. Depending on the experimental requirements, the following modes were selected: positive pressure stripping (bypass air pipe closed, first blower 1 corresponding to the inlet pipe started, gas blown in from the bottom), negative pressure extraction (bypass air pipe 18 opened, vacuum pump 8 started, gas extracted from the top), or bidirectional coupling (bypass air pipe closed, first blower 1 and vacuum pump 8 started simultaneously, forming forced convection) to simulate different on-site remediation conditions. The high-temperature gas generated by desorption entered the cyclone separator 3 through the outlet pipe, achieving solid-liquid-gas three-phase separation. Solids and liquids were collected and centrally processed separately. The gas entered the heat exchanger 4 to cool to room temperature, then passed through the bag filter 5 and precision filter 6 for further dust removal and solid impurity removal. Finally, it entered the activated carbon filter 7 to adsorb and remove organic pollutants, and the clean gas was safely discharged. Throughout the process, pressure and temperature changes within the soil column were monitored in real time using pressure and temperature sensors. Soil or gas samples were collected for analysis using sampling tubes and sampling ports as needed. Gas flow was monitored using a flow meter to ensure the reliability of experimental data and compliance with emission standards for exhaust gas.

[0048] In the description of this invention, it should be understood that the terms "upper," "lower," "left," and "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or a specific orientational structure and operation. Therefore, they should not be construed as limitations on the invention. Furthermore, "first" and "second" are only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means two or more.

[0049] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A pilot-scale integrated soil thermal desorption device with adjustable flow field, characterized in that: Includes a thermally desorbed soil column (2) integrated into the support frame (11), an electric heating device (201), a hydraulic system (9), a multimodal flow field control system, and a multi-stage exhaust gas separation and purification unit; The upper end of the thermally desorbed soil column (2) is sealed to the electric heating device (201) through a flange. Several electric heating rods (202) extend downward from the bottom of the electric heating device (201). A protective tube (205) corresponding to each electric heating rod (202) is vertically arranged inside the thermally desorbed soil column (2). The electric heating rod (202) passes through the protective tube (205) and maintains a gap with the protective tube (205). The soil inside the thermally desorbed soil column (2) is indirectly heated through the protective tube (205). The hydraulic system (9) is connected to the electric heating device (201) and is used to drive the electric heating device (201) and the electric heating rod (202) to rise and fall vertically as a whole, and to insert the electric heating rod (202) into the protective tube (205); The bottom of the support frame (11) is provided with a guide structure, and the thermally desorbed soil column (2) can be translated horizontally along the guide structure; The multimodal flow field control system includes a first blower (1), a vacuum pump (8), and several air distribution plates (206) arranged along the length direction inside the thermal desorption soil column (2) and connected to the thermal desorption soil column (2); the first blower (1) is connected to the air distribution plate (206) through an air inlet pipe (23), the vacuum pump (8) is connected to the thermal desorption soil column (2) through an air outlet pipe (203), and the exhaust gas multi-stage separation and purification unit is connected behind the vacuum pump (8); the air inlet pipe (23) is provided with a bypass air pipe connected to each air distribution plate (206), and each bypass air pipe is provided with a control valve; The air distribution plate (206) is connected to several air pipes (207), which extend vertically upward and are arranged alternately with the protective pipe (205).

2. The integrated, flow-field-adjustable soil thermal desorption pilot-scale device according to claim 1, characterized in that: The gas distribution plate (206) is provided with a swirling guide cavity (18), and the swirling guide cavity (18) is provided with a number of spiral guide blades (21). The spiral guide blades (21) form an angle of 30° to 45° with the horizontal plane, so that the incoming gas forms a rotating upward airflow.

3. The integrated, flow-field-adjustable soil thermal desorption pilot-scale device according to claim 1, characterized in that: The thermally desorbed soil column (2) is divided into a desorption strengthening zone, a homogenization transition zone and a preheating zone along the axial direction from top to bottom, and the zones are separated by a heat insulation plate. Each zone has an independent air distribution plate (206) at the bottom. The electric heating rod (202) in different zones is connected to the power supply through a temperature control module to achieve independent temperature control in each zone. Each zone is connected to the vacuum pump (8) through an outlet pipe (203) with a proportional regulating valve to achieve independent air extraction in each zone.

4. The integrated flow field adjustable soil thermal desorption pilot plant according to claim 1, characterized in that: The outer wall of the protective tube (205) is provided with annular heat-conducting ribs or spiral heat-conducting fins along the axial direction; a heat-conducting filling layer is provided between the outer side of the protective tube (205) and the soil.

5. The integrated flow field adjustable soil thermal desorption pilot plant according to claim 3, characterized in that: The sidewalls of each zone of the thermally desorbed soil column (2) are arranged with multiple inclined disturbance jet pipes (20) along the circumferential direction. The inclined disturbance jet pipes (20) are connected to the second blower (24) through the air inlet pipe (23). The axial direction of each inclined disturbance jet pipe (20) forms an acute angle with the diameter of the thermally desorbed soil column (2). All the inclined disturbance jet pipes (20) in each zone are connected together to form an air inlet ring (22) for constructing a three-dimensional composite disturbance flow field.

6. The integrated, flow-field-adjustable soil thermal desorption pilot-scale device according to claim 1, characterized in that: The bottom of the thermally desorbed soil column (2) is provided with a water collection chamber (13). The water collection chamber (13) is located below the lowest air distribution plate (206) and is sealed to the thermally desorbed soil column (2) through a flange. The bottom of the water collection chamber (13) is provided with a water outlet pipe (16).

7. The integrated, flow-field-adjustable soil thermal desorption pilot-scale device according to claim 1, characterized in that: The exhaust gas multi-stage separation and purification unit includes a cyclone separator (3), a heat exchanger (4), a bag filter (5), a precision filter (6), and an activated carbon filter (7) connected in sequence.

8. The integrated, flow-field-adjustable soil thermal desorption pilot-scale device according to claim 1, characterized in that: The thermal desorbed soil column (2) is surrounded by an insulation layer (12).

9. The integrated flow field adjustable soil thermal desorption pilot plant according to claim 1, characterized in that: The sidewall of the thermally desorbed soil column (2) is provided with several pressure sensors, temperature sensors and sampling tubes (14) along the axial direction; the pipelines of the multimodal flow field control system and the exhaust gas multi-stage separation and purification unit are provided with flow meters, temperature sensors and sampling ports.

10. A multi-condition operation method for an integrated, flow-field-adjustable soil thermal desorption pilot plant as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Cooperative filling: The electric heating device (201) is lifted by the hydraulic system (9), the thermal desorbed soil column (2) is moved horizontally out of the filling soil and returned to its position, and the electric heating device (201) is lowered to achieve precise insertion and sealing of the electric heating rod (202) and the protective tube (205); S2, Indirect Uniform Heating: The electric heating device (201) is activated, and the heat is transferred to the protective tube (205) through the electric heating rod (202) and diffused into the soil through the thermally conductive filling layer; S3. Flow field mode switching: Select positive pressure stripping mode, negative pressure extraction mode or bidirectional coupling mode as needed; wherein, positive pressure stripping mode is achieved by closing the control valve of the bypass air pipe and starting the first blower (1), negative pressure extraction mode is achieved by opening the control valve of the bypass air pipe and starting the vacuum pump (8), and bidirectional coupling mode is achieved by closing the control valve of the bypass air pipe and starting the first blower (1) and the vacuum pump (8) at the same time.

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