Gas phase extraction system for polluted soil, gas phase extraction treatment method and application

Abstract

The invention belongs to the technical field of soil and groundwater pollution remediation, and discloses a gas-phase extraction system for polluted soil, a gas-phase extraction treatment method and application. The gas phase extraction system for the polluted soil comprises at least one extraction well, a gas-liquid separation device, a negative pressure extraction device, a catalytic combustion device and at least one injection well, wherein the gas-liquid separation device, the negative pressure extraction device, the catalytic combustion device and the at least one injection well are sequentially communicated with a gas outlet section of the extraction well through pipelines in the flowing direction of gas flow; the air inlet section of the extraction well is in contact with the contaminated soil, and the air outlet section of the injection well is in contact with the contaminated soil. According to the vapor extraction treatment method applying the system, the extraction efficiency of organic pollutants is greatly improved. Moreover, on the basis of greatly improving the organic matter pollution extraction efficiency, decomposition and purification of organic pollutants are achieved through a simple method, heat of purified high-temperature gas is reused, purified gas containing carbon dioxide is guided into the ground, and the effects of saving energy and reducing carbon are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil and groundwater pollution remediation, and in particular relates to a gas phase extraction system for contaminated soil, a gas phase extraction treatment method and an application thereof. Background Art

[0002] Organic pollutants in soil are mainly volatile organic pollutants and semi-volatile organic pollutants, including petroleum hydrocarbons, halogenated hydrocarbons, pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, phthalates, etc. Most of them are carcinogenic, teratogenic and mutagenic, and are easily accumulated in the environment, causing long-term impacts on the ecological environment and human health. At present, the commonly used methods for soil organic pollution remediation mainly include gas phase extraction, thermal desorption, chemical oxidation, etc. Among them, gas phase extraction and thermal desorption are used for the treatment of volatile organic compounds and semi-volatile organic compounds, respectively.

[0003] CN105234166A provides a system for in-situ solar energy enhanced gas phase extraction to repair soil organic pollutants, including a gas phase extraction pipeline, a water circulation system pipeline, a solar energy heat collection system, an insulated water tank, a gas purification system and a soil water replenishment system. Among them, the water circulation system pipeline is connected to the ground solar energy heat collection system to form a solar energy circulating water heating system, the water circulation system pipeline is connected to the insulated water tank to form an insulated water tank heat storage circulating water system, and the solar energy heat collection system is connected to the insulated water tank to form a solar energy-insulated water tank combined circulating water heating system. The whole system uses solar energy to enhance in-situ gas phase extraction to repair soil organic pollutants. The system is compact, easy to operate, and energy-saving.

[0004] CN103350104A provides an integrated equipment and application method for in-situ thermal enhanced gas phase extraction and remediation of contaminated sites, including a high-pressure blower, a gas-liquid separation tank, an activated carbon absorption tower, a heating electrode, a temperature sensor, etc. The heating electrode is mainly buried in the contaminated area to increase the soil temperature of the site, promote the desorption of pollutants in the soil, and then a negative pressure is formed in the extraction pipeline by a high-pressure blower to generate gas flow from the extraction well to the outside, and the pollutants in the soil are taken away from the soil as the gas flows. The invention can reduce the impact of low temperature conditions on gas phase extraction and extend the effective remediation work time in winter.

[0005] CN103447291A discloses a device for strengthening gas phase extraction and remediation of chlorobenzene contaminated soil and a method for treating chlorobenzene contaminated soil with the device. The device includes a plurality of heating extractors arranged in an equilateral triangle or square; the heating extractor includes a heating source and an extraction tube, the heating source is placed in the extraction tube, and the heating source is a resistance wire; the extraction tube is filled with fillers and catalysts. On-site, a plurality of heating extractors are arranged in an equilateral triangle or square at a distance of 2-5 meters in the remediation site, intermittent extraction, and the temperature of the heating source is controlled at 400°C, and heating is performed for 120 hours. The device has an obvious effect on the remediation of chlorobenzene contaminated soil in a short time, and the pollutant removal rate is high.

[0006] In summary, existing technologies usually enhance the soil vapor extraction process by heating with external heat sources, including electrodes, gas, steam, solar energy, etc. Although external heating improves the efficiency of vapor extraction to a certain extent, it also greatly increases equipment and operating costs. Therefore, on the basis of maintaining high extraction efficiency, it is of great significance to develop green and energy-saving vapor extraction technology for removing soil organic pollutants. Summary of the invention

[0007] The inventor of the present invention has invented a new type of gas phase extraction system and gas phase extraction treatment method for contaminated soil through research. The gas phase extraction system purifies the waste gas of volatile and semi-volatile organic matter extracted from the contaminated site through catalytic combustion, and the purified high-temperature gas is then injected back into the soil of the contaminated area in situ. The gas phase extraction treatment method of the gas phase extraction system is applied to greatly improve the extraction efficiency of organic pollutants. Not only that, on the basis of greatly improving the extraction efficiency of organic pollution, the present invention realizes the decomposition and purification of organic pollutants through a simple method, not only reusing the heat of the purified high-temperature gas, but also introducing the purified gas containing carbon dioxide into the underground, which plays a role in energy saving and carbon reduction. In summary, the gas phase extraction treatment method of the present invention has the characteristics of green, energy-saving and environmental protection, and overcomes the problems of low efficiency of volatile and semi-volatile organic contaminated site treatment, complex removal of organic pollutants, and large energy consumption of heating enhancement in the prior art, and has extremely high promotion and application value in the application of contaminated soil remediation.

[0008] The first aspect of the present invention is to provide a gas phase extraction system for contaminated soil, such as Figure 1As shown, it includes at least one extraction well 1, a gas-liquid separation device 2, a negative pressure extraction device 3, a catalytic combustion device 4 and at least one injection well 6 which are connected to the gas outlet section of the extraction well through pipelines in sequence according to the flow direction of the gas flow; the air inlet section of the extraction well 1 is in contact with the contaminated soil, the catalytic combustion device can decompose the organic pollutants extracted from the contaminated soil to obtain purified high-temperature gas, and the purified high-temperature gas can be passed into the injection well 6 through the pipeline, and the gas outlet section of the injection well is in contact with the contaminated soil.

[0009] As described above, the gas phase extraction treatment method using the gas phase extraction system greatly improves the extraction efficiency of organic pollutants. Not only that, on the basis of greatly improving the extraction efficiency of organic pollution, the present invention realizes the decomposition and purification of organic pollutants through a simple method, not only reusing the heat of the purified high-temperature gas, but also introducing the purified gas containing carbon dioxide into the underground, which plays a role in energy saving and carbon reduction. The above technical effects are achieved, and the inventors of the present invention believe through research that the various devices of the gas phase extraction system of the present invention cooperate with each other, and use an extremely simple method to decompose organic pollutants, not only utilizing the heat of the purified high-temperature gas obtained by the decomposition and purification of organic pollutants, but more importantly, after the purified high-temperature gas is introduced into the underground, it plays a role in strengthening the flow of airflow. In the process of extraction, the gas introduced into the underground promotes the extraction of volatile and semi-volatile organic matter, thereby greatly improving the extraction efficiency of organic pollutants.

[0010] In one embodiment of the present invention, Figure 1 As shown, it is possible but not necessary to further provide an induced draft device 5 on the pipeline between the catalytic combustion device 4 and the injection well 6, and the induced draft device 5 includes but is not limited to an induced draft fan.

[0011] According to the present invention, Figure 1 As shown, the pipeline between the catalytic combustion device 4 and the injection well 6 is also provided with a branch pipeline, and the branch pipeline is optionally connected to the outside world above the ground through a valve.

[0012] According to the present invention, the air inlet section and the air outlet section of the extraction well and the injection well can take in and out air, and the air inlet section and the air outlet section include but are not limited to porous screen pipes and / or multi-slit screen pipes, that is, the corresponding air inlet section / air outlet section is distributed with through holes and / or multiple slits.

[0013] According to the present invention, the ratio of the total effective area of ​​the gas outlet section of the injection well to the total effective area of ​​the gas intake section of the extraction well can be selected within a wide range. In a preferred embodiment of the present invention, the ratio of the total effective area of ​​the gas outlet section of the injection well to the total effective area of ​​the gas intake section of the extraction well is not less than 1.5. In this preferred embodiment, the efficiency of organic pollution extraction is further improved. More preferably, the ratio of the total effective area of ​​the gas outlet section of the injection well to the total effective area of ​​the gas intake section of the extraction well is 2-3. In this more preferred embodiment, the efficiency of organic pollution extraction is further improved. The reason may be that, in this more preferred embodiment, it is more conducive to the purification gas introduced into the underground to heat the contaminated soil, and at the same time has a higher effect of strengthening the flow of air.

[0014] According to the present invention, the distance between the gas outlet section of the injection well and the gas inlet section of the extraction well can be selected within a wide range. In a preferred embodiment of the present invention, the distance between the gas outlet section of the injection well and the gas inlet section of the extraction well is 1-5 meters. In this preferred embodiment, the gas phase extraction treatment method using the gas phase extraction system has a higher extraction efficiency of organic pollutants.

[0015] The inventors have found through research that adjusting the distance between the outlet section of the injection well and the inlet section of the extraction well according to the soil quality of the contaminated soil can further improve the extraction efficiency of organic pollutants. In a more preferred embodiment of the present invention, when the contaminated soil is sandy soil, the distance between the outlet section of the injection well and the inlet section of the extraction well is 2.5-5 meters.

[0016] In another preferred embodiment of the present invention, when the contaminated soil is silty and / or clayey soil, the distance between the gas outlet section of the injection well and the gas inlet section of the extraction well is 1-2.5 meters.

[0017] According to the present invention, the negative pressure extraction device includes but is not limited to a vacuum pump.

[0018] According to the present invention, the function of the gas-liquid separation device is to achieve gas-liquid separation, wherein the liquid is mainly water, therefore, the gas-liquid separation device includes but is not limited to a gas-water separation device. The gas-liquid separation device is a conventional device, and those skilled in the art can select a specific type as needed, which will not be described in detail here.

[0019] According to the present invention, the catalytic combustion device can realize the present invention as long as it can decompose the organic pollutants extracted from the contaminated soil to obtain purified high-temperature gas. This catalytic combustion device belongs to the conventional device in the field, including but not limited to catalytic burners.

[0020] The second aspect of the present invention is to provide a gas phase extraction treatment method for contaminated soil treatment using the gas phase extraction system of the first aspect, comprising the following steps:

[0021] (1) contacting the air intake section of the extraction well with the contaminated soil, and extracting under negative pressure to obtain a mixed gas containing organic pollutants;

[0022] (2) first subjecting the mixed gas to gas-liquid separation pretreatment, and then subjecting the mixed gas to catalytic combustion to obtain purified high-temperature gas;

[0023] (3) introducing the purified high-temperature gas into the contaminated soil through the gas outlet section of the injection well;

[0024] Repeat steps (1), (2), and (3).

[0025] According to the present invention, the gas phase extraction treatment method is suitable for volatile organic compounds and / or semi-volatile organic compounds. In a preferred embodiment of the present invention, the organic pollutants in the contaminated soil are halogen-free volatile organic compounds and / or semi-volatile organic compounds.

[0026] In a more preferred embodiment of the present invention, the organic pollutant is at least one of an aliphatic hydrocarbon and an aromatic hydrocarbon with a carbon number of 5-16, that is, an aliphatic hydrocarbon with a carbon number of 5-16, and / or an aromatic hydrocarbon with a carbon number of 6-16.

[0027] The organic pollutant is at least one of an aliphatic hydrocarbon and an aromatic hydrocarbon having a carbon number of 5-16, and the carbon number may be, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16.

[0028] In a preferred embodiment of the present invention, the concentration of total non-methane hydrocarbons in the mixed gas containing organic pollutants obtained in step (1) is less than 5000 mg / Nm 3 .

[0029] According to the present invention, preferably, the purified high-temperature gas is introduced into the contaminated soil through the gas outlet section of the injection well to heat the soil, so that the temperature of the mixed gas containing organic pollutants (i.e., the extracted waste gas) reaches above 50°C, for example, 50-90°C.

[0030] In order to facilitate understanding of the present invention, the following Figure 1 The gas phase extraction treatment method of the present invention is described, comprising the following steps:

[0031] (1) bringing the air intake section of the extraction well 1 into contact with the contaminated soil, and extracting under negative pressure by a negative pressure extraction device 3 to obtain a mixed gas containing organic pollutants;

[0032] (2) The mixed gas is first subjected to gas-liquid separation pretreatment in a gas-liquid separation device 2, and then subjected to catalytic combustion in a catalytic combustion device 4 to obtain purified high-temperature gas;

[0033] (3) introducing the purified high-temperature gas into the contaminated soil through the gas outlet section of the injection well 6;

[0034] Repeat steps (1), (2), and (3).

[0035] In this way, the present invention injects the extracted waste gas (i.e., the mixed gas containing organic pollutants) back into the soil of the polluted area in situ after catalytic combustion purification, not only reusing the heat of the purified high-temperature gas, but also introducing the purified gas containing carbon dioxide into the underground, which plays a role in strengthening the flow of air. During the extraction process, the gas introduced into the underground promotes the extraction of volatile and semi-volatile organic matter, thereby greatly improving the extraction efficiency of organic pollutants.

[0036] The third aspect of the present invention is to provide an application of the gas phase extraction system described in the first aspect or the gas phase extraction treatment method described in the second aspect in the field of contaminated soil remediation.

[0037] The gas phase extraction treatment method for contaminated soil described in the present invention can be used for the remediation of soil or groundwater contaminated by volatile and semi-volatile organic compounds, and has good application prospects in the green and sustainable remediation of related contaminated sites.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] The gas phase extraction treatment method using the gas phase extraction system greatly improves the extraction efficiency of organic pollutants. In addition, on the basis of greatly improving the extraction efficiency of organic pollution, the present invention achieves the decomposition and purification of organic pollutants through a simple method, not only reusing the heat of the purified high-temperature gas, but also introducing the purified gas containing carbon dioxide into the ground, which plays a role in energy saving and carbon reduction.

[0040] In summary, the gas phase extraction treatment method of the present invention is green, energy-saving and environmentally friendly. It overcomes the problems of low efficiency in the treatment of volatile and semi-volatile organic pollutant contaminated sites, complex removal of organic pollutants, and high energy consumption of heating enhancement in the prior art, and has extremely high promotion and application value in the application of contaminated soil remediation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of gas phase extraction treatment method for contaminated soil:

[0042] 1-extraction well; 2-gas-liquid separation device; 3-negative pressure extraction device; 4-catalytic combustion device; 5-inducing wind device; 6-injection well. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0044] like Figure 1 As shown, the volatile or semi-volatile organic matter in the soil is extracted from the extraction well 1 by suction of the negative pressure extraction device 3; trace water in the exhaust gas is removed by the gas-liquid separation device 2; the exhaust gas enters the catalytic combustion device 4, and the organic matter in the exhaust gas is burned to generate carbon dioxide at a certain temperature; the high-temperature gas discharged from the catalytic burner is directly introduced into the underground soil contaminated area through the induced draft device 5 and the injection well 6, so that the contaminated soil is heated, and the introduced gas also plays a role in strengthening the flow of air flow, thereby improving the extraction efficiency of volatile or semi-volatile organic matter in the soil.

[0045] In the following embodiments, the method for detecting the concentration of total non-methane hydrocarbons in the inlet and outlet gas of the catalytic burner is: "Gas Chromatography for Determination of Total Hydrocarbons, Methane and Non-methane Hydrocarbons in Waste Gas from Stationary Pollution Sources" (HJ 38-2017).

[0046] Example 1

[0047] The gas phase extraction and treatment method for contaminated soil of the present invention was used to repair the sandy soil 1-3m underground that was seriously contaminated by isoprene, n-pentane, benzene, etc. at a chemical site in Tianjin. One extraction well and one injection well with a diameter of 100mm were built on site.

[0048] The air inlet section of the extraction well and the air outlet section of the injection well both extend 3.2 m downward from 0.8 m underground; the distance between the air outlet section of the injection well and the air inlet section of the extraction well is 3.5 m;

[0049] The total effective area of ​​the gas outlet section of the injection well is 0.3m 2 The total effective area of ​​the air intake section of the extraction well is 0.12m 2 , the ratio of their areas is 2.5.

[0050] Turn on the catalytic burner to preheat the system to 260°C; start the extraction fan to start extraction, with an air volume of 200m 3 / h, the concentration of non-methane total hydrocarbons in the extracted exhaust gas is about 1500mg / Nm 3 ; The preheated exhaust gas enters the catalytic burner for treatment, and the catalyst bed is heated to 380°C; the concentration of non-methane total hydrocarbons in the catalytic burner outlet gas is reduced to 50mg / Nm 3The temperature is about 180℃, and the exhaust gas is discharged to the atmosphere through the exhaust port. After running for 1 hour, the concentration of non-methane total hydrocarbons at the inlet and outlet of the catalytic burner is basically stable (the concentration of non-methane total hydrocarbons in the extracted exhaust gas is about 1500mg / Nm 3 ), the fluctuation does not exceed 10%. Close the discharge port, inject the catalytic burner outlet gas into the ground through the injection well, and increase the concentration of the extracted exhaust gas to about 3000mg / Nm 3 , temperature 60-80℃; continuous operation for 1h, the total non-methane hydrocarbon concentration at the outlet of the catalytic burner is maintained at 50mg / Nm 3 the following.

[0051] Example 2

[0052] The gas phase extraction treatment method of the contaminated soil of a chemical site in Beijing was used to treat benzene, toluene, ethylbenzene, petroleum hydrocarbons (C6-C 16 ) and other severely contaminated clay soils 2.5-5m underground. Three extraction wells with a diameter of 75mm and four injection wells with a diameter of 100mm were built on site. The extraction wells and injection wells were arranged in a hexagonal shape, with the extraction wells located at the three spaced vertices of the hexagon and the injection wells at the other three spaced vertices and the center of the hexagon.

[0053] The air inlet section of the extraction well and the air outlet section of the injection well both extend 5.5m downward from 2m underground; the distance between the air outlet section of the injection well and the air inlet section of the extraction well is 2m;

[0054] The total effective area of ​​the gas outlet section of the injection well is 2.4m 2 The total effective area of ​​the air intake section of the extraction well is 0.75m 2 , the area ratio is 3.2.

[0055] Turn on the catalytic burner to preheat the system to 300°C; start the extraction fan to start extraction, with an air volume of 500m 3 / h, the concentration of non-methane total hydrocarbons in the extracted exhaust gas is about 800mg / Nm 3 ; The preheated exhaust gas enters the catalytic burner for treatment, and the catalyst bed is heated to 420°C; the concentration of non-methane total hydrocarbons in the catalytic burner outlet gas is reduced to 50mg / Nm 3 Below, the temperature is about 180℃, and it is discharged to the atmosphere through the discharge port. After continuous operation for 1 hour, the concentration of non-methane total hydrocarbons at the inlet and outlet of the catalytic burner is basically stable (the concentration of non-methane total hydrocarbons in the extracted exhaust gas is about 800mg / Nm 3 ), the fluctuation does not exceed 10%. Close the discharge port, inject the catalytic burner outlet gas into the ground through the injection well, and increase the concentration of the extracted exhaust gas to about 2000mg / Nm 3, temperature 55-70℃; continuous operation for 1h, the total non-methane hydrocarbon concentration at the outlet of the catalytic burner is maintained at 50mg / Nm 3 the following.

[0056] Example 3

[0057] The soil in the same area of ​​this embodiment was repaired in the same manner as in embodiment 1, except that the total effective area of ​​the gas outlet section of the injection well was 0.18 m 2 The total effective area of ​​the air intake section of the extraction well is 0.12m 2 , the ratio of their areas is 1.5.

[0058] It has been verified that the exhaust gas concentration of the catalytic burner is increased to about 2000mg / Nm by injecting the gas from the catalytic burner into the ground through the injection well. 3 .

[0059] Example 4

[0060] The soil in the same area of ​​this embodiment was repaired according to the same method as in embodiment 2, except that the distance between the air outlet section of the injection well and the air inlet section of the extraction well was 3 meters.

[0061] It has been verified that the concentration of the extracted exhaust gas can be raised to about 1400 mg / Nm by injecting the gas from the catalytic burner outlet into the ground through an injection well. 3 .

[0062] Comparative Example 1

[0063] The soil in the same area of ​​Example 2 was repaired by using electrodes to directly heat the soil, and the injection well was replaced with a heating tube heated by electrodes. The temperature of the heating tube was controlled to keep the temperature of the extracted exhaust gas at 55-70°C.

[0064] It has been verified that the concentration of the extracted waste gas rises to about 1200mg / Nm 3 .

[0065] It can be seen from the contents described in Examples 1 and 2 that after the purified high-temperature gas is introduced into the contaminated soil, the concentration of the extracted waste gas is significantly increased compared to the case where the contaminated soil is not introduced (ie, the extracted waste gas is discharged into the atmosphere).

[0066] It can be seen from Example 2 and Comparative Example 1 that, compared with the method of directly heating the contaminated soil, the present invention passes the purified high-temperature gas into the contaminated soil, and the concentration of the extracted waste gas is significantly improved, achieving an unexpected technical effect. It also shows that the technical effect of the present invention is not only achieved by heating the contaminated soil with high-temperature gas to promote the extraction of organic pollutants, but also by the purified high-temperature gas strengthening the airflow during extraction.

[0067] By comparing Examples 1 and 2 with Examples 3 and 4, it can be seen that in a more preferred embodiment of the present invention, for example, by using a more preferred ratio of the total effective area of ​​the gas outlet section of the injection well to the total effective area of ​​the gas intake section of the extraction well, and by using a more preferred distance between the gas outlet section of the injection well and the gas intake section of the extraction well, the extraction efficiency of organic pollutants can be further improved, and Examples 1 and 2 have achieved further significant technical effects.

[0068] The parts not described in detail in the present invention belong to the well-known technology in the art.

[0069] The above descriptions are only some specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

[0070] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0071] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0072] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0073] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0074] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0075] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A gas phase extraction system for contaminated soil, comprising at least one extraction well, a gas-liquid separation device, a negative pressure extraction device, a catalytic combustion device and at least one injection well, which are connected to the gas outlet section of the extraction well through pipelines in sequence according to the flow direction of the gas flow; The air inlet section of the extraction well is in contact with the contaminated soil, the catalytic combustion device can decompose the organic pollutants extracted from the contaminated soil to obtain purified high-temperature gas, and the purified high-temperature gas can be passed into the injection well through the pipeline, and the air outlet section of the injection well is in contact with the contaminated soil.

2. The gas phase extraction system according to claim 1, characterized in that: The ratio of the total effective area of ​​the gas outlet section of the injection well to the total effective area of ​​the gas intake section of the extraction well is not less than 1.5, and is preferably 2-3.

3. The gas phase extraction system according to claim 1 or 2, characterized in that: The distance between the gas outlet section of the injection well and the gas inlet section of the extraction well is 1-5 meters.

4. The gas phase extraction system according to claim 1 or 2, characterized in that: When the contaminated soil is sandy soil, the distance between the gas outlet section of the injection well and the gas inlet section of the extraction well is 2.5-5 meters.

5. The gas phase extraction system according to claim 1 or 2, characterized in that: When the contaminated soil is silty and / or clayey soil, the distance between the gas outlet section of the injection well and the gas inlet section of the extraction well is 1-2.5 meters.

6. A gas phase extraction treatment method for contaminated soil treatment using the gas phase extraction system according to any one of claims 1 to 5, comprising the following steps: (1) contacting the air intake section of the extraction well with the contaminated soil, and extracting under negative pressure to obtain a mixed gas containing organic pollutants; (2) first subjecting the mixed gas to gas-liquid separation pretreatment, and then subjecting the mixed gas to catalytic combustion to obtain purified high-temperature gas; (3) introducing the purified high-temperature gas into the contaminated soil through the gas outlet section of the injection well; Repeat steps (1), (2), and (3).

7. The gas phase extraction treatment method according to claim 6, characterized in that: The organic pollutants in the contaminated soil are halogen-free volatile organic compounds and / or semi-volatile organic compounds.

8. The gas phase extraction treatment method according to claim 7, characterized in that: The organic pollutant is at least one of aliphatic hydrocarbons and aromatic hydrocarbons having a carbon number of 5-16.

9. The gas phase extraction treatment method according to claim 7, characterized in that: The concentration of non-methane total hydrocarbons in the mixed gas containing organic pollutants obtained in step (1) is less than 5000 mg / Nm 3 .

10. Use of the gas phase extraction system according to any one of claims 1 to 5 or the gas phase extraction treatment method according to any one of claims 6 to 9 in the field of contaminated soil remediation.

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