System and method for repairing soil through combination of low-temperature thermal desorption and ozone

Abstract

The invention provides a system and a method for repairing soil by combining low-temperature thermal desorption with ozone, and relates to the technical field of soil remediation, the system comprises a low-temperature heating well, a multiphase extraction well, a gas-liquid separator, a sewage treatment system and a waste gas treatment system; the low-temperature heating well comprises a conductive rod which is arranged in a well pit and formed by porous conductive particles, heating electrodes which are electrically connected are vertically arranged on the surface of the conductive rod at intervals, and an ozone device is arranged at the position, at the lower end of the conductive rod, of the well pit of the low-temperature heating well and used for guiding out ozone gas upwards; the multiphase extraction well comprises a gravel filter material layer, a hollow slotted steel pipe and a slotted screen pipe which are arranged in a well pit; the inlet end of the gas-liquid separator is in liquid communication with a slotted screen pipe of the multiphase extraction well, and the outlet end of the gas-liquid separator is in liquid communication with the sewage treatment system and the waste gas treatment system respectively. By adopting the system provided by the invention, the soil remediation efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil remediation, and particularly relates to a system and method for low-temperature thermal desorption combined with ozone to remediate soil. BACKGROUND

[0002] At present, remediation of organic contaminated soil includes in-situ remediation and ex-situ remediation. Although the ex-situ remediation has a lower cost, it needs to excavate and transport the contaminated soil, which not only destroys the soil structure, but also exposes the pollutants to the atmosphere, so that the risk of secondary pollution is greatly increased compared with the in-situ remediation, and the diffusion risk of volatile organic compounds is significantly increased.

[0003] The in-situ thermal desorption technology has become an optimal solution for remediation of high-concentration organic contaminated sites due to its high remediation efficiency and complete removal of pollutants. However, this technology has a prominent problem of energy consumption and cost: a large amount of energy needs to be continuously input during the heating process, and a large amount of consumables such as supporting insulation materials and conductive media need to be input, which leads to a unit remediation cost significantly higher than that of conventional remediation technologies, thereby forming a significant cost barrier.

[0004] Therefore, a system and method for low-temperature thermal desorption combined with ozone to remediate soil are needed to at least partially solve the above technical problems. SUMMARY

[0005] In view of this, the embodiments of the present application provide a system and method for low-temperature thermal desorption combined with ozone to remediate soil to at least solve one of the problems in the prior art.

[0006] In a first aspect, the embodiments of the present application provide a system for low-temperature thermal desorption combined with ozone to remediate soil, which comprises: a low-temperature heating well, a multiphase extraction well, a gas-liquid separator, a sewage treatment system and a waste gas treatment system; the low-temperature heating well comprises a conductive rod formed by porous conductive particles filled from bottom to top in succession, which is arranged in a well pit; heating electrodes are arranged on the surface of the conductive rod in a vertical direction; an ozone device is arranged at the lower end of the conductive rod in the well pit of the low-temperature heating well, and is used to guide ozone gas upward; the porous conductive particles are conductive particles with a porous structure, and the components of the conductive particles at least include ferrous ions; the multiphase extraction well comprises annular crushed stone filter layers, hollow split steel pipes and split screen pipes arranged in the well pit in a radial direction from outside to inside in sequence, and a gap is left between the split screen pipes and the split steel pipes; the inlet end of the gas-liquid separator is connected to the split screen pipe of the multiphase extraction well in liquid communication, and the outlet end of the gas-liquid separator is connected to the sewage treatment system and the waste gas treatment system in liquid communication, respectively; wherein the low-temperature heating well and the multiphase extraction well are arranged in the soil of the area to be remediated in a staggered grid pattern; when the heating electrodes of the low-temperature heating well are powered on, a conductive path is formed between adjacent low-temperature heating wells and the soil, so that the soil is heated by power supply.

[0007] According to the system of the present application, low-temperature heating wells, multi-phase extraction wells, water quality monitoring wells and temperature monitoring wells are arranged in the area to be repaired. When the heating electrodes of the low-temperature heating wells are powered on, an electrically conductive path is formed between adjacent low-temperature heating wells and the soil, so that the soil is heated by power on. After the soil reaches a temperature threshold, it enters a heat preservation stage. In the low-temperature environment formed by the self-heating of the soil, ozone gas is introduced, and the oxidation and degradation and volatilization of pollutants are accelerated under the catalysis of ferrous ions provided by the porous conductive particles in the low-temperature heating wells. At the same time, the gas-water mixed phase extracted from the multi-phase extraction well is separated by a gas-liquid separator and then introduced into a sewage treatment system and a waste gas treatment system respectively for treatment. The system repeatedly performs the operation process of heating and temperature control, ozone oxidation and extraction and separation to degrade the pollutants in the soil, thereby achieving energy-saving, efficient and environmentally friendly repair of the organic contaminated soil.

[0008] Preferably, the porous conductive particles comprise cement, ferrous sulfate solution, fly ash, carbon powder, foaming agent and foam stabilizer; the cement, ferrous sulfate solution, fly ash and carbon powder are mixed and stirred uniformly according to a mass ratio to prepare a mixed slurry; the foam stabilizer is added to the mixed slurry and stirred until the foam stabilizer is completely dispersed; the foaming agent is diluted and whipped to form stable foam; the stable foam is added to the mixed slurry and stirred until the foam and the mixed slurry are uniformly mixed to obtain a foam slurry; after the foam slurry is stably placed, it is poured into a pre-set mold to prepare foamed pellets which are then dried and formed. The mass ratio of the cement, ferrous sulfate solution, fly ash and carbon powder is 4:2:1:1; the mass ratio of the mixed slurry to the foam stabilizer is 1:0.01-0.08; and the mass ratio of the mixed slurry to the foam is 1:1-3.

[0009] Preferably, the ozone device is configured as a porous aeration plate which is connected to an ozone generator on the ground via a pipeline.

[0010] Preferably, the heating electrode is a power-adjustable heating electrode.

[0011] Preferably, the system further comprises a backflow pipeline, and the sewage treatment system is liquidly connected to the low-temperature heating well via the backflow pipeline.

[0012] Preferably, the system further comprises a barrier wall arranged outside the area to be repaired, and the barrier wall is a solidified impermeable containment structure.

[0013] Preferably, the system further comprises a temperature monitoring well, and the temperature monitoring well comprises a plurality of temperature sensors arranged in the well pit and spaced vertically to sense the soil temperature value at the corresponding depth region. When the soil temperature value of the corresponding depth region sensed by a certain temperature sensor is lower than the set threshold value, the heating electrode of the corresponding depth region increases the power until the soil temperature value of the corresponding depth region reaches the set threshold value.

[0014] Preferably, the system further comprises water quality monitoring wells, a hollow slotted screen pipe is arranged in the well pit of the water quality monitoring well, and the outside of the slotted screen pipe is filled with gravel; the water quality monitoring wells are arranged in the soil of the area to be repaired at a predetermined density.

[0015] Preferably, the system further comprises a heat preservation layer arranged outside the area to be repaired, and the heat preservation layer is formed by cement pouring.

[0016] According to another aspect of the present application, a method for repairing soil by low-temperature thermal desorption combined with ozone is also provided, the method comprising: A barrier wall and a heat preservation layer are arranged outside the area to be repaired, and low-temperature heating wells, multi-phase extraction wells, water quality monitoring wells and temperature monitoring wells are arranged in the area to be repaired; the low-temperature heating wells and the multi-phase extraction wells are arranged in a grid pattern with a set interval, and the water quality monitoring wells and the temperature monitoring wells are arranged at a set density. The power supply system is started, the conductive rod formed by the porous conductive particles in the low-temperature heating well supplies power to the heating electrode, the heating electrode conducts the electric energy to the soil, and the soil is heated and warmed by the electric conduction; The temperature monitoring wells monitor the soil temperature in real time, when the soil temperature of each depth region reaches the set threshold value, the heating electrode switches to a low-power output mode and enters a heat preservation stage; when the soil temperature of a certain depth region is lower than the set threshold value, the heating electrode of the corresponding depth region restores a high-power output mode, the power of the heating electrode is increased, and the soil temperature of the corresponding depth region reaches the set threshold value; After the soil temperature of each depth region reaches the set threshold value, the ozone generator is started, the generated ozone gas is introduced into the porous aeration plate through the conduit, and the ozone bubbles formed by the aeration effect enter the inside of the porous conductive particles while diffusing to the surrounding soil in the rising process; The ferrous ions of the porous conductive particles enter the surrounding soil with the groundwater or the backflow replenishment water, and catalyze the organic pollutants in the soil to oxidize with the ozone in the low-temperature environment; The ground vacuum pump is started to extract the contaminated water and the contaminated gas in the multi-phase extraction well, and a negative pressure field is formed in the multi-phase extraction well in the extraction process, guiding the surrounding contaminated gas and the contaminated water to migrate to the direction of the multi-phase extraction well; The extracted contaminated water and the contaminated gas mixture are transported to the gas-liquid separator through the conduit, and the water phase and the gas phase products are obtained after the gas-liquid separator treatment, the water phase is transported to the sewage treatment system, and the gas phase is transported to the waste gas treatment system; The water phase enters the sewage treatment system to remove the pollutants and is then injected into the low-temperature heating well through the backflow pipeline again; The system repeatedly performs the operation process of heating temperature control, ozone oxidation, extraction separation, and water phase reflux to degrade the pollutants in the soil. The groundwater pollutant concentration data is continuously collected through the water quality monitoring well. When the pollutant concentration reaches the preset repair target value, the whole system is shut down.

[0017] Additional advantages, objects, and features of the application will be set forth in part by the description that follows, and will become apparent to those skilled in the art upon examination of the following detailed description and drawings in which

[0018] Those skilled in the art will appreciate that the objects and advantages of the application can be practiced without resorting to the details of the specific implementation described herein, and that the full scope of the application can be understood by reference to the following detailed description and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present application and, together with the description given below, serve to explain the principles of the application. The components in the drawings are not drawn to scale, but are merely intended to illustrate the principles of the application. Some parts of the drawings can be enlarged for the purpose of illustrating and describing certain portions of the application, i.e., can become larger in relation to other components in the exemplary devices actually made in accordance with the application. In the drawings: Figure 1 A schematic diagram of a system for soil remediation by low-temperature thermal desorption combined with ozone according to an embodiment of the application; Figure 2 A schematic diagram of a low-temperature heating well in a system for soil remediation by low-temperature thermal desorption combined with ozone according to an embodiment of the application; Figure 3 A schematic diagram of a multi-phase extraction well in a system for soil remediation by low-temperature thermal desorption combined with ozone according to an embodiment of the application; Figure 4 A schematic diagram of a temperature monitoring well in a system for soil remediation by low-temperature thermal desorption combined with ozone according to an embodiment of the application; Figure 5 A schematic diagram of a water quality monitoring well in a system for soil remediation by low-temperature thermal desorption combined with ozone according to an embodiment of the application; BRIEF DESCRIPTION OF DRAWINGS 100, system; 110, low-temperature heating well; 111, porous conductive particles; 112, heating electrode; 113, porous aeration plate; 114, pipeline; 115. ozone generator 120. multi-phase extraction well 121. crushed stone filter layer 122. slotted steel pipe 123. slotted screen pipe 124. power supply system 125. vacuum pump 130. gas-liquid separator 140. sewage treatment system 141. return line 150. exhaust gas treatment system 160. barrier wall 170. temperature monitoring well 171. temperature sensor 180. water quality monitoring well 181. slotted screen pipe 182. crushed stone 190. thermal insulation layer DETAILED DESCRIPTION

[0020] The purposes and functions of the present application, and the method for achieving the purposes and functions will be clarified by referring to exemplary embodiments. However, the present application is not limited to the exemplary embodiments disclosed below; it can be implemented in various forms. The substance of the specification is merely to help those skilled in the relevant art to comprehensively understand the specific details of the present application.

[0021] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, it means that there is a presence of the features, integers, steps, operations, elements, and / or components, but it does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0022] The ordinal numbers such as "first" and "second" cited in the present application are merely for identification and have no other meaning, such as a specific order, etc. Also, for example, the term "first means" itself does not imply the existence of "second means", and the term "second means" itself does not imply the existence of "first means".

[0023] It should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", and similar expressions used herein are for illustrative purposes only, not limiting.

[0024] This application provides a system 100 for soil remediation using low-temperature thermal desorption combined with ozone. The soil remediation system 100 provided by this application can be applied in the field of soil remediation, and can achieve energy-saving, water-saving, efficient and environmentally friendly soil remediation.

[0025] It is understandable that the system 100 according to this application can also be used to remediate organically contaminated groundwater, etc.

[0026] In a preferred embodiment, such as Figure 1 As shown, the system for soil remediation using low-temperature thermal desorption combined with ozone may include a low-temperature heating well 110, a multiphase extraction well 120, a gas-liquid separator 130, a wastewater treatment system 140, and a waste gas treatment system 150.

[0027] The low-temperature heating well 110 can be used to electrically heat the soil in the area to be remediated and inject ozone gas into the soil, integrating low-temperature thermal remediation and ozone oxidation technologies to accelerate the oxidative degradation of pollutants and improve soil remediation efficiency. The multiphase extraction well 120 can be used to extract contaminated water and gases from the soil. The gas-liquid separator 130 can be used to separate the extracted contaminated water and gas mixture to obtain aqueous and gaseous products. The wastewater treatment system 140 can be used to treat the extracted contaminated water. The exhaust gas treatment system 150 is used to treat the extracted contaminated gases.

[0028] Specifically, the low-temperature heating well 110 may include conductive rods formed by porous conductive particles 111 continuously filled from bottom to top within the well pit. Heating electrodes 112, electrically connected, are arranged at vertical intervals on the surface of the conductive rods. The porous conductive particles 111 may be spherical, cylindrical, or irregularly polyhedral. The porous conductive particles 111 may be uniformly filled throughout the well section. To ensure a more stable structure between the porous conductive particles 111 in the conductive rods, a binder may be added after filling to firmly connect the particles. The heating electrodes 112 may be rod-shaped metal electrodes, or sheet-like or mesh-like electrodes. The heating electrodes 112 may be arranged at equal intervals or with varying intervals, suitable for locations with varying pollution concentration gradients, enabling on-demand energy distribution.

[0029] like Figure 3As shown, the multiphase extraction well 120 may include an annular layer of crushed stone filter media 121, a hollow slotted steel pipe 122, and a slotted screen pipe 123 arranged radially from the outside to the inside within the well pit. The crushed stone filter media 121 may be made of uniform crushed stone particles, or multi-grade crushed stone particles may be selected according to soil characteristics. The slotted steel pipe 122 and the slotted screen pipe 123 may be made of stainless steel, or other materials that balance filtration efficiency, clogging resistance, and corrosion resistance.

[0030] like Figure 1 As shown, the gas-liquid separator 130 is used to separate the extracted polluted water and polluted gas mixture to obtain aqueous and gaseous products. A suitable gas-liquid separator can be selected based on the soil characteristics.

[0031] like Figure 1 As shown, the wastewater treatment system 140 is used to treat the extracted polluted water. The treatment process can be physical (e.g., sedimentation, filtration), chemical (e.g., oxidation, neutralization) or biological (e.g., anaerobic, aerobic biological treatment). High-concentration organic wastewater can be degraded by advanced oxidation processes, and heavy metal polluted wastewater can be treated with chelation precipitation or adsorption processes to ensure that the treated polluted water meets the discharge standards.

[0032] like Figure 1 As shown, the exhaust gas treatment system 150 is used to treat the extracted polluting gas. The volatile organic compounds in the gas can be treated by adsorption, catalytic combustion or biological filter processes. Dust-containing exhaust gas requires a pre-dust removal device to ensure that the treated gas meets emission standards.

[0033] As described above, a low-temperature heating well 110, a multiphase extraction well 120, a gas-liquid separator 130, a sewage treatment system 140, and an exhaust gas treatment system 150 are deployed in the area to be remediated. When the heating electrode of the low-temperature heating well 110 is energized, a conductive path is formed between adjacent low-temperature heating wells 110 and the soil, enabling the soil to generate heat through electrical current. After reaching the temperature threshold, the system enters a heat preservation stage, and ozone gas is introduced to accelerate the oxidation and volatilization of pollutants. Simultaneously, the gas-water mixture extracted from the multiphase extraction well 120 is separated by the gas-liquid separator 130 and then fed to the sewage treatment system 140 and the exhaust gas treatment system 150 for treatment. The treated water is then reinjected into the low-temperature heating well 110. The system repeatedly executes the heating and temperature control, ozone oxidation, and extraction separation processes to degrade organic pollutants in the soil, achieving energy-saving, efficient, and environmentally friendly soil remediation.

[0034] In a preferred embodiment, the porous conductive particles 111 can be prepared by mixing cement, fly ash, ferrous sulfate solution, carbon powder, foaming agent, and foam stabilizer in a certain proportion. The ferrous sulfate concentration in the ferrous sulfate solution is controlled at approximately 5%. The foaming agent is diluted and then aerated with high-pressure air to prepare foam. A foam stabilizer is added during the aeration process to enhance foam quality. Environmentally friendly foaming agents such as tea saponins and saponins can be selected. The dilution ratio of the stock solution to water is 1:30~40. The foam stabilizer can be a 1% sodium carboxymethyl cellulose solution. Specifically, the preparation method is as follows: first, cement, ferrous sulfate solution, fly ash, and carbon powder are mixed evenly in a mass ratio of 4:2:1:1 to form a mixed slurry. Then, a foam stabilizer is added, with the ratio of the mixed slurry to the foam stabilizer being 1:0.01~0.08. The diluted foaming agent is whipped to form stable and abundant foam. The foam is then added to the mixed slurry and stirred evenly. The mass ratio of the mixed slurry to the foam can be controlled at 1:1~3. After stabilization, the whipped foam slurry is poured into a mold to prepare foamed spheres with a diameter of about 1~3cm. After drying, it can be used as a porous conductive material.

[0035] like Figure 2 As shown, the ozone device can be a porous aeration plate 113. The porous aeration plate 113 is connected to an ozone generator 115 on the ground via a pipe 114. The porous aeration plate 113 can cut and disperse the ozone introduced by the ozone generator 115 into a large number of tiny, uniform ozone bubbles. The ozone bubbles are in an omnidirectional diffusion state, which greatly increases the contact area with polluted soil and groundwater, and enhances the effect of oxidizing and degrading pollutants. The porous aeration plate 113 can be a plate-type aeration plate, and its shape can be long and narrow, square, or fan-shaped. The porous aeration plate 113 can be made of porous ceramic, stainless steel, or rubber.

[0036] like Figure 2As shown, the heating electrode 112 can be a power-adjustable heating electrode 112. In the initial stage of remediation, the heating electrode 112 operates in high-power mode, rapidly heating the soil medium to a preset threshold temperature range. When the temperature sensor 171 in the temperature monitoring well 170 reports that the soil temperature has reached the set threshold, the output power of the heating electrode 112 is reduced, and the soil enters a heat preservation stage, during which high-power heating is not required. During the heat preservation stage, the temperature sensor 170 continuously collects temperature data from different soil depths. When the soil temperature within a certain range is detected to be within the preset threshold range, the heating electrode 112 within that range maintains a low-power operation. When the soil temperature is detected to be below the lower threshold limit, the power of the corresponding depth heating electrode 112 can be adjusted to increase its output power to supplement heat. Once the temperature rises back to the threshold range, the power is reduced again, thus forming a closed-loop temperature control to ensure that the soil temperature in the remediation area remains stable within the threshold range, guaranteeing efficient desorption and degradation of organic pollutants, while also considering the economic and environmental benefits of the remediation process.

[0037] like Figure 1 As shown, the system may also include a return pipeline 141. The wastewater treatment system 140 is liquid-connected to the low-temperature heating well 110 via the return pipeline 141. After the wastewater treatment system 140 treats the extracted contaminated water, the effluent still maintains a temperature matching the soil remediation threshold. The warm water is transported to the low-temperature heating well 110 via the return pipeline 141 and evenly infiltrates into the surrounding soil through the porous structure of the porous conductive particles in the well. On the one hand, the return water with residual heat can replace part of the electrical energy for heating, helping to maintain the soil temperature within the preset threshold range, avoiding a sudden drop in temperature caused by heat loss to deeper soil or the surrounding environment, significantly reducing the power output of the heating electrodes during the heat preservation stage, and reducing the energy consumption of the entire system; on the other hand, the infiltration of the return water can replenish the moisture lost from the soil due to the extraction operation, maintain the porosity and permeability of the soil medium, ensure the uniform diffusion of ozone gas and the efficient migration of pollutants, and improve the remediation efficiency. In addition, the treated reflux water meets environmental protection requirements, and the reflux process will not cause secondary pollution to the soil and groundwater. At the same time, it can avoid the additional costs and energy consumption brought about by external clean water replenishment, thus achieving a balance between the economy, environmental protection and efficiency of the remediation process.

[0038] like Figure 1 As shown, the system also includes a barrier wall 160 set outside the area to be repaired. The barrier wall 160 is a solidified seepage-proof enclosure structure that establishes a physical isolation boundary between the repair area and the external environment. It effectively prevents the migration of volatile organic compounds and heavy metal contaminated groundwater that are activated by temperature rise during the repair process to the outside. At the same time, it avoids the risk of pollutant diffusion caused by changes in soil pore water pressure due to heating. It spatially locks in the contamination range, prevents secondary pollution, and ensures the safety and controllability of the repair process.

[0039] like Figure 1 and Figure 4 As shown, the system may also include a temperature monitoring well 170. The temperature monitoring well 170 includes multiple temperature sensors 171 arranged vertically at intervals within the well pit, used to sense soil temperature values ​​at corresponding depths. The temperature monitoring well 170 is a vertically deployed monitoring structure. The spacing between the multiple temperature sensors 171 arranged vertically along the well pit can be designed in layers according to the depth of site contamination, thereby achieving refined temperature monitoring of the target remediation area. After all temperature sensors 171 are deployed, soil can be backfilled into the well pit of the temperature monitoring well 170 to restore the original appearance as much as possible. The temperature sensors 171 can adopt a high-temperature resistant and corrosion-resistant encapsulation structure, which can withstand temperature fluctuations and pollutant erosion during in-situ thermal desorption, ensuring long-term stable operation. Each temperature sensor 171 can be connected to a ground data acquisition terminal using a waterproof cable. It can feed back soil temperature data at different depths to the system in real time, providing a precise basis for the dynamic adjustment of the power of the heating electrode. When the soil temperature value of the corresponding depth area sensed by a certain temperature sensor 171 is lower than the set threshold, the system will trigger a power adjustment command to control the heating electrode 112 of the corresponding depth area to increase the power and continuously replenish the heat until the soil temperature value of the corresponding depth area reaches the set threshold, thereby achieving precise and dynamic control of the temperature of each soil layer in the repair area.

[0040] like Figure 1 and Figure 5 As shown, the system may also include a water quality monitoring well 180. A hollow slotted screen tube 181 is installed within the well pit of the water quality monitoring well 180, and the outside of the slotted screen tube 181 is filled with gravel 182. The water quality monitoring well 180 is arranged in the soil of the area to be remediated at a preset density. The water quality monitoring well 180 is a vertically arranged long-term groundwater quality monitoring structure. The slotted screen tube 181 can be made of corrosion-resistant material. The slits on the surface of the slotted screen tube 181 allow groundwater to seep smoothly into the screen tube while effectively blocking soil particles from entering, preventing screen tube blockage and affecting monitoring operations. The gravel 182 filling the outside of the screen tube forms a stable filter and guide layer, which can further optimize the infiltration path of groundwater into the slotted screen tube 181, while enhancing the structural stability of the well wall and preventing well pit collapse. The density and location of the 180 water quality monitoring wells can be set according to the hydrogeological conditions, pollution range and pollution concentration gradient of the area to be remediated, so as to realize the dynamic tracking of soil pollutant indicators during the remediation process, timely grasp the changes in pollutant concentration, and provide data support for soil remediation.

[0041] like Figure 1As shown, the system also includes an insulation layer 190 located on the outside of the area to be repaired. The insulation layer 190 is cast in cement. By optimizing the proportions of the cement-based materials (lightweight insulating aggregates such as expanded perlite and vitrified microspheres can be added as needed), the thermal conductivity can be reduced while ensuring structural strength, achieving a balance between insulation performance and load-bearing capacity. The insulation layer 190 and the barrier 160 work together to form a closed system isolated from the outside environment, creating a dual protective barrier of "insulation + anti-diffusion," effectively preventing heat loss from the repair area and the outward diffusion of pollutants.

[0042] This application also provides a method 200 for soil remediation using low-temperature thermal desorption combined with ozone, the method including the following steps: In step S210, a barrier wall 160 and an insulation layer 190 are installed outside the area to be repaired. Low-temperature heating wells 110, multiphase extraction wells 120, temperature monitoring wells 170 and water quality monitoring wells 180 are installed within the area to be repaired. The low-temperature heating wells 110 and multiphase extraction wells 120 are arranged in a grid pattern at a set interval, and the temperature monitoring wells 170 and water quality monitoring wells 180 are arranged at a set density.

[0043] In step S220, the power supply system 124 is started, and power is supplied to the heating electrode 112 through the conductive rod formed by porous conductive particles 111 in the low temperature heating well 110. The heating electrode 112 conducts electrical energy to the soil, and the soil heats up when energized.

[0044] In step S230, the temperature monitoring well 170 monitors the soil temperature in real time. When the soil temperature in each depth area reaches the set threshold, the heating electrode 112 switches to low-power output mode and enters the heat preservation stage. When the soil temperature in a certain depth area is lower than the set threshold, the heating electrode 112 in the corresponding depth area resumes high-power output mode, increasing the power of the heating electrode 112 so that the soil temperature in the corresponding depth area reaches the set threshold.

[0045] In step S240, after the soil temperature in each depth area reaches the set threshold, the ozone generator is started. The generated ozone gas is introduced into the porous aeration plate 113 through the conduit 114. The ozone bubbles formed by the aeration process enter the interior of the porous conductive particles 111 during the rising process and diffuse to the surrounding soil.

[0046] In step S250, the ferrous ions of the porous conductive particles 111 enter the surrounding soil with groundwater or recirculated water, catalyzing the reaction of organic pollutants in the soil with ozone oxidation under low temperature conditions.

[0047] In step S260, the ground vacuum pump 125 is started to extract the polluted water and polluted gas in the multiphase extraction well 120. During the extraction process, a negative pressure field is formed in the multiphase extraction well 120 to guide the surrounding polluted gas and polluted water to migrate towards the multiphase extraction well 120.

[0048] In step S270, the extracted mixture of polluted water and polluted gas is transported to the gas-liquid separator 130 via a conduit. After being processed by the gas-liquid separator 130, aqueous and gaseous products are obtained. The aqueous phase is transported to the wastewater treatment system 140, and the gaseous phase is transported to the waste gas treatment system 150.

[0049] In step S280, after the aqueous phase enters the sewage treatment system 140 to remove pollutants, it is injected back into the low-temperature heating well 110 through the return pipe 141.

[0050] In step S290, the system repeatedly performs the operation process of heating and temperature control, ozone oxidation, extraction and separation, and aqueous phase reflux to degrade pollutants in the soil. Groundwater pollutant concentration data are continuously collected through water quality monitoring well 180. When the pollutant concentration reaches the preset remediation target value, the entire system is shut down.

[0051] Other embodiments of this application will be readily conceived and understood by those skilled in the art in conjunction with the description and practice disclosed herein. The descriptions and embodiments are to be considered exemplary only, and the true scope and spirit of this application are defined by the claims.

Claims

1. A system for soil remediation using low-temperature thermal desorption combined with ozone, characterized in that, The system includes a low-temperature heating well (110), a multiphase extraction well (120), a gas-liquid separator (130), a wastewater treatment system (140), and a waste gas treatment system (150). The low-temperature heating well includes a conductive rod formed by porous conductive particles (111) continuously filled from bottom to top and disposed in a pit. Heating electrodes (112) are arranged vertically at intervals on the surface of the conductive rod. An ozone device is provided at the lower end of the conductive rod in the pit of the low-temperature heating well for exporting ozone gas upward. The porous conductive particles are conductive particles with a porous structure containing at least ferrous ions. The multiphase extraction well (120) includes an annular gravel filter material layer (121) arranged radially from the outside to the inside, a hollow slotted steel pipe (122) and a slotted screen pipe (123) arranged in the well pit, with a gap between the slotted screen pipe and the slotted steel pipe. The inlet of the gas-liquid separator (130) is connected to the slotted screen (123) of the multiphase extraction well (120), and the outlet of the gas-liquid separator (130) is connected to the sewage treatment system (140) and the waste gas treatment system (150). The low-temperature heating well (110) and the multiphase extraction well (120) are buried in the soil of the area to be repaired in a grid-like staggered arrangement; When the heating electrode (112) of the low-temperature heating well (110) is energized, a conductive path is formed between the adjacent low-temperature heating wells (110) and the soil, thereby enabling the soil to generate heat through electricity.

2. The system according to claim 1, characterized in that, The porous conductive particles (111) include cement, ferrous sulfate solution, fly ash, carbon powder, foaming agent and foam stabilizer; Cement, ferrous sulfate solution, fly ash, and carbon powder are mixed and stirred evenly according to a mass ratio to obtain a mixed slurry. A foam stabilizer is added to the mixed slurry and stirred until the foam stabilizer is completely dispersed. A foaming agent is diluted and aerated until stable foam is formed. The stable foam is added to the mixed slurry and stirred until the foam and the mixed slurry are evenly mixed to obtain a foam slurry. After the foam slurry has been allowed to stand and stabilize, it is poured into a pre-set mold to obtain foamed small balls, which are then dried and shaped. The mass ratio of cement, ferrous sulfate solution, fly ash, and carbon powder is 4:2:1:

1. The mass ratio of the mixed slurry to the foam stabilizer is 1:0.01~0.08; The mass ratio of the mixed slurry to the foam is 1:1 to 3.

3. The system according to claim 1, characterized in that, The ozone device is constructed as a porous aeration plate (113), which is connected to an ozone generator (115) on the ground via a pipeline (114).

4. The system according to claim 1, characterized in that, The heating electrode (112) is a power adjustable heating electrode (112).

5. The system according to claim 1, characterized in that, The system also includes a return pipe (141), through which the wastewater treatment system (140) is liquid connected to the cryogenic heating well (110).

6. The system according to claim 1, characterized in that, The system also includes a barrier wall (160) set outside the area to be repaired, the barrier wall (160) being a solidified seepage-proof enclosure structure.

7. The system according to claim 4, characterized in that, The system also includes a temperature monitoring well (170), which includes multiple temperature sensors (171) arranged vertically at intervals in the well pit to sense the soil temperature value of the corresponding depth area. When the soil temperature value of the corresponding depth area sensed by a certain temperature sensor (171) is lower than the set threshold, the heating electrode (112) of the corresponding depth area increases the power until the soil temperature value of the corresponding depth area reaches the set threshold.

8. The system according to claim 1, characterized in that, The system also includes a water quality monitoring well (180), the well pit of which is provided with a hollow slotted screen tube (181), and the outside of the slotted screen tube (181) is filled with gravel (182); the water quality monitoring well (180) is arranged in the soil of the area to be repaired at a preset density.

9. The system according to claim 1, characterized in that, The system also includes an insulation layer (190) disposed on the outside of the area to be repaired, the insulation layer (190) being formed by cement casting.

10. A method for soil remediation based on low-temperature thermal desorption combined with ozone based on the system described in any one of claims 1 to 9, characterized in that, The method includes: A barrier wall (160) and an insulation layer (190) are set up outside the area to be repaired. Low temperature heating well (110), multiphase extraction well (120), temperature monitoring well (170) and water quality monitoring well (180) are set up in the area to be repaired. The low temperature heating well (110) and multiphase extraction well (120) are arranged in a grid pattern at a set interval. The temperature monitoring well (170) and water quality monitoring well (180) are arranged at a set density. The power supply system (124) is started, and power is supplied to the heating electrode (112) through the conductive rod formed by porous conductive particles (111) in the low temperature heating well (110). The heating electrode (112) conducts electrical energy to the soil, and the soil heats up when energized. The temperature monitoring well (170) monitors the soil temperature in real time. When the soil temperature in each depth area reaches the set threshold, the heating electrode (112) switches to low power output mode and enters the heat preservation stage. When the soil temperature in a certain depth area is lower than the set threshold, the heating electrode (112) in the corresponding depth area resumes high power output mode, increases the power of the heating electrode (112), and makes the soil temperature in the corresponding depth area reach the set threshold. Once the soil temperature in each depth region reaches the set threshold, the ozone generator is activated. The generated ozone gas is introduced into the porous aeration plate (113) through the conduit (114). The ozone bubbles formed by the aeration process enter the interior of the porous conductive particles (111) and diffuse to the surrounding soil during the rising process. Ferrous ions from porous conductive particles (111) enter the surrounding soil with groundwater or recharge water, catalyzing the reaction of pollutants in the soil with ozone oxidation under low temperature conditions. Start the ground vacuum pump (125) to extract the polluted water and polluted gas in the multiphase extraction well (120). During the extraction process, a negative pressure field is formed in the multiphase extraction well (120) to guide the surrounding polluted gas and polluted water to migrate towards the multiphase extraction well (120). The extracted polluted water and polluted gas mixture is transported to the gas-liquid separator (130) via a conduit. After being processed by the gas-liquid separator (130), aqueous and gaseous products are obtained. The aqueous phase is transported to the wastewater treatment system (140), and the gaseous phase is transported to the waste gas treatment system (150). After the water phase enters the sewage treatment system (140) to remove pollutants, it is injected back into the low-temperature heating well (110) through the return pipe (141); The system repeatedly performs the operation process of heating and temperature control, ozone oxidation, extraction and separation, and water phase reflux to degrade pollutants in the soil. Groundwater pollutant concentration data are continuously collected through water quality monitoring well (180). When the pollutant concentration reaches the preset remediation target value, the entire system is shut down.

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