Depth-determined precision thermal repair method and device

Abstract

The present invention provides a method and device for precise heat repair at a fixed depth, which is to lay out a multifunctional well and an extraction well in a contaminated area, wherein an electric heating device is laid out in the area corresponding to the contaminated stratum in the multifunctional well, and an injection pipe is arranged in the area corresponding to the clean stratum, and the injection pipe is connected to a DC cable; an oxidant is injected into the ground through the injection pipe, and then a DC electric field can be generated between adjacent injection pipes, thereby forming a chemical oxidation reaction zone under the clean area; the electric heating device is connected to an alternating current, and the contaminated area is precisely heated at a fixed depth, and a part of the pollutants are collected by the extraction well after being volatilized by heat, and the other part moves upward and enters the chemical oxidation reaction zone and is oxidized and degraded. The present invention only performs precise heating on the contaminated area according to the stratum distribution of the pollutants, and is particularly suitable for areas with "shallow cleaning and deep pollution", which can greatly reduce the volume of heated soil, reduce heating energy consumption and repair costs.

Description

Technical Field

[0001] The present invention relates to an in-situ heat treatment technology, and in particular to an in-situ heat treatment device and method for precisely heating only a contaminated area. Background Art

[0002] In-situ thermal treatment technology is a highly effective technology for treating organically contaminated sites, especially for pesticide, chemical, coking and other sites where volatile organic compounds exist. It can effectively reduce the risk of secondary pollution caused by ex-situ remediation and control odor problems.

[0003] In recent years, this technology has been highly favored in China and has been gradually promoted and applied. However, in actual engineering applications, in order to prevent the hot and volatilized polluted steam from condensing during the upward migration and causing secondary pollution to the clean area above, the generally used heating method is usually to heat the entire area from bottom to top, resulting in huge energy waste. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for precise thermal repair at a fixed depth, so as to solve the problems of high energy consumption and high cost in the prior art and reduce heating energy consumption and repair cost.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for precise thermal repair at a fixed depth, wherein the contaminated area has a contaminated stratum and a clean stratum located above the contaminated stratum, characterized in that the repair method comprises:

[0007] injecting an oxidant into the clean formation;

[0008] A direct current electric field is formed on the lower side of the clean formation, and the oxidant, driven by the direct current electric field, performs directionally migration and diffusion through the effects of electromigration and electroosmosis, thereby forming a chemical oxidation reaction zone on the lower side of the clean area;

[0009] The polluted stratum is heated, and the pollutants are volatilized by heat, a portion of which is collected by extraction wells arranged in the polluted area, and the other portion moves upward and enters the chemical oxidation reaction zone to be oxidized and degraded.

[0010] The method for precise thermal repair at a fixed depth comprises: a multifunctional well is arranged in the contaminated area, an electric heating device is arranged in the area corresponding to the contaminated formation in the multifunctional well, and the electric heating device is connected to alternating current for heating the contaminated formation.

[0011] The method for precise thermal repair at a fixed depth, wherein: an injection pipe is provided in the area corresponding to the clean formation in the multifunctional well, and the injection pipe is used to inject an oxidant into the clean formation;

[0012] The injection pipe is also connected to direct current, and the direct current electric field can be generated between the injection pipes of adjacent multifunctional wells.

[0013] The method for precise thermal repair at a fixed depth, wherein: the extraction well is a well cluster type extraction / injection multifunctional well, capable of injecting an oxidant into the clean formation;

[0014] Electrodes are arranged in the area corresponding to the clean formation in the multifunctional well, and the DC electric field can be generated between the electrodes of adjacent multifunctional wells.

[0015] A fixed-depth precision thermal repair device, wherein the contaminated area has a contaminated stratum and a clean stratum located above the contaminated stratum, characterized in that the device comprises:

[0016] Extraction wells arranged in contaminated areas;

[0017] injection equipment capable of injecting an oxidant into the clean formation;

[0018] A direct current device capable of forming a direct current electric field on the lower side of the clean formation, wherein the oxidant can be directed to migrate and diffuse through the effects of electromigration and electroosmosis under the driving action of the direct current electric field, thereby forming a chemical oxidation reaction zone on the lower side of the clean area;

[0019] The heating device can heat the contaminated formation so that the pollutants in the contaminated formation can be volatilized by heat. Part of the volatilized pollutants are collected by the extraction well, and the other part moves upward into the chemical oxidation reaction zone to be oxidized and degraded.

[0020] The fixed-depth precision thermal repair device, wherein: a multifunctional well is arranged in the contaminated area, the heating equipment is an electric heating device arranged in the multifunctional well and corresponding to the contaminated formation area, and the electric heating device is connected to alternating current.

[0021] The fixed-depth precision thermal repair device, wherein: the injection device is an injection pipe arranged in the multifunctional well and corresponding to the clean formation area;

[0022] The drug injection tube is also connected to direct current to form the direct current device.

[0023] The fixed-depth precision thermal repair device, wherein: the extraction well is a well cluster type extraction / injection multifunctional well, having both the injection equipment and the extraction well functions;

[0024] Electrodes are provided in the multifunctional well and in an area corresponding to the clean formation, and the electrodes are connected to direct current to form the direct current device.

[0025] The fixed-depth precision thermal repair device, wherein: the injection equipment has an injection screen slot, and the injection screen slot extends from the junction of the contaminated formation and the clean formation to one side of the clean area.

[0026] The fixed-depth precision thermal repair device, wherein: an extraction pipe is provided in the extraction well, and the extraction screen slot of the extraction pipe is arranged at the same height or a lower height position corresponding to the injection screen slot.

[0027] The present invention precisely heats only the polluted area according to the stratum distribution of pollutants. It is particularly suitable for areas with "shallow cleaning and deep pollution". It can greatly reduce the volume of heated soil, reduce heating energy consumption and remediation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 , Figure 2 , Figure 3 It is a schematic diagram of the steps of the fixed-depth precision thermal repair method of the present invention.

[0029] Figure 4 It is a schematic diagram of another embodiment of the fixed-depth precision thermal repair device of the present invention.

[0030] Figure 5 It is a schematic diagram of another embodiment of the fixed-depth precision thermal repair device of the present invention.

[0031] Explanation of the reference numerals: multifunctional well 10; electric heating device 11; AC cable 12; injection pipe 13; injection sieve slit 14; DC cable 15; DC electrode 16; extraction well 20; well cluster type extraction / injection multifunctional well 20a; extraction pipe 21; extraction sieve slit 22; contaminated formation 30; clean formation 40; chemical oxidation reaction zone A. DETAILED DESCRIPTION

[0032] The present invention provides a method for precise thermal repair at a fixed depth, comprising the following steps:

[0033] like Figure 1 As shown, a multifunctional well 10 and an extraction well 20 are arranged in the polluted area, wherein:

[0034] An electric heating device 11 is arranged in the area corresponding to the contaminated formation 30 in the multifunctional well 10, and the electric heating device 11 is connected to an AC cable 12; wherein the electric heating device 11 can be an electrode to realize resistance heating (the maximum heating temperature is below 100°C), or a heating rod to realize heat conduction heating (the maximum heating temperature can be higher than 100°C), so as to meet different heating temperature requirements;

[0035] An injection pipe 13 is provided in the area corresponding to the clean formation 40 in the multifunctional well 10, and an injection screen slit 14 (with a slit width of about 1 mm) is provided on the surface of the injection pipe 13. The injection screen slit 14 extends 0.5 to 2.0 m from the junction of the contaminated formation 30 and the clean formation 40 to one side of the clean area, and the injection pipe 13 is connected to a DC cable 15;

[0036] The extraction well 20 is provided with an extraction pipe 21, and the extraction pipe 21 is provided with an extraction screen slot 22 at a position at the same height or lower height corresponding to the injection screen slot 14;

[0037] like Figure 2 As shown, an oxidant is injected into the ground through an injection pipe 13, and then a DC cable 15 on the injection pipe 13 is connected to direct current to generate a DC electric field between adjacent injection pipes 13. Under the driving action of the DC electric field, the oxidant migrates and diffuses in a directional manner through the action of electromigration and electroosmosis, thereby forming a chemical oxidation reaction zone A at the lower side of the clean area;

[0038] like Figure 3 As shown, the electric heating device 11 is connected to AC power through the AC cable 12 to perform precise heating of the polluted area at a fixed depth. After the pollutants are volatilized by heat, most of them are collected by the extraction pipe 21 for centralized treatment, and a small part moves upward and enters the chemical oxidation reaction zone A to be oxidized and degraded.

[0039] like Figure 4 FIG. 1 is a schematic diagram of another embodiment of the fixed depth precision thermal repair device of the present invention. Figure 1-Figure 3 Compared with the embodiment shown, the difference is that the extraction well 20 is set as a well cluster extraction / injection multifunctional well 20a to establish a pressure gradient at different depths. In this way, the heat transfer of the pollutant layer can be promoted through injection / extraction, the heat transfer efficiency can be improved, which is beneficial to the uniform distribution of heat and the uniform dispersion of the oxidant.

[0040] like Figure 5 FIG. 1 is a schematic diagram of another embodiment of the fixed depth precision thermal repair device of the present invention. Figure 4 Compared with the embodiment shown in the figure, the difference is that the injection pipe 13 in the multifunctional well 10 is replaced by a DC electrode 16, and the injection function of the original injection pipe 13 is realized by the well cluster type pumping / injection multifunctional well 20a. Such an arrangement can reduce the corrosion of the chemical oxidizing agent to the heating equipment and facilitate the maintenance and management of the heating equipment.

[0041] The main advantages of the present invention are:

[0042] 1. By integrating the electric remediation technology (EK) with the in-situ chemical oxidation technology (ISCO), the directional migration and diffusion of the oxidant is achieved, thereby constructing a chemical oxidation reaction zone A above the heating area to effectively prevent and control the secondary pollution problem of the clean formation 40 caused by the upward migration of pollutants due to heat; and, through EK, the problem of poor mass transfer and dispersion of the oxidant in low-permeability formations is effectively solved. In addition, by controlling the direction of the DC electric field, the migration effect of the agent is made more uniform and can be directionally enhanced, thereby constructing a full-range and fully covered oxidation reaction zone above the contaminated formation 30 to eliminate dead corners.

[0043] 2. On the basis of solving the secondary pollution, the precise heating of the polluted area at a fixed depth is realized, and the heating energy consumption is significantly reduced by greatly reducing the heating volume of the clean area above.

[0044] 3. The integrated technology and device can further realize thermally coupled chemical oxidation technology. By low-temperature heating, the oxidant is activated and free radicals are generated, thereby performing advanced chemical oxidation on the pollutants, further improving the oxidation efficiency, reaction rate and reducing the amount of oxidant used. Low-temperature heating (for example, the target temperature is 40-50°C) can further reduce the heating energy consumption, and low-temperature heating can also reduce the amount of steam generated, thereby reducing the risk of upward migration of pollutants to the clean area.

[0045] 4. The present invention adopts a multifunctional well 10, and arranges the injection pipe 13 and the heating device in the same well, which brings the following beneficial effects: first, it can effectively prevent the pollutant vapor from migrating and diffusing upward along the priority channel formed by the multifunctional well 10 to pollute the clean area; second, it reduces the number of wells to be built, thereby reducing the cost of well construction.

[0046] 5. The extraction well 20 arranged in the present invention can establish a pressure gradient through extraction, and in the oxidant migration stage, can further enhance the horizontal migration distance and rate of the oxidant; in the precise heating stage, can inhibit the upward migration of pollutants and reduce the load of the chemical oxidation reaction zone A.

[0047] The above description is only illustrative rather than restrictive of the present invention. Those skilled in the art will understand that many modifications, changes or equivalents may be made without departing from the spirit and scope defined by the claims, but all will fall within the scope of protection of the present invention.

Claims

1. A method for precise thermal remediation at a fixed depth, wherein the contaminated area has a contaminated stratum and a clean stratum located above the contaminated stratum, characterized in that: The repair method comprises: injecting an oxidant into the clean formation; A direct current electric field is formed on the lower side of the clean formation, and the oxidant, driven by the direct current electric field, performs directionally migration and diffusion through the effects of electromigration and electroosmosis, thereby forming a chemical oxidation reaction zone on the lower side of the clean area; The polluted stratum is heated, and the pollutants are volatilized by heat, a portion of which is collected by extraction wells arranged in the polluted area, and the other portion moves upward and enters the chemical oxidation reaction zone to be oxidized and degraded.

2. The method for precise thermal repair at a fixed depth according to claim 1, characterized in that: A multifunctional well is arranged in the contaminated area, and an electric heating device is arranged in the area of ​​the multifunctional well corresponding to the contaminated formation. The electric heating device is connected to alternating current and is used to heat the contaminated formation.

3. The method for precise thermal repair at a fixed depth according to claim 2, characterized in that: An injection pipe is provided in the area of ​​the multifunctional well corresponding to the clean formation, and the injection pipe is used to inject an oxidant into the clean formation; The injection pipe is also connected to direct current, and the direct current electric field can be generated between the injection pipes of adjacent multifunctional wells.

4. The method for precise thermal repair at a fixed depth according to claim 2, characterized in that: The extraction well is a well cluster type extraction / injection multifunctional well, capable of injecting oxidant into the clean formation; Electrodes are arranged in the area corresponding to the clean formation in the multifunctional well, and the DC electric field can be generated between the electrodes of adjacent multifunctional wells.

5. A fixed-depth precision thermal repair device, wherein the contaminated area has a contaminated stratum and a clean stratum located above the contaminated stratum, characterized in that: The device comprises: Extraction wells arranged in contaminated areas; A drug injection device capable of injecting an oxidant into the clean formation, wherein the drug injection device has a drug injection sieve slot, and the drug injection sieve slot extends 0.5 to 2.0 m from the boundary between the contaminated formation and the clean formation to one side of the clean area; A direct current device capable of forming a direct current electric field on the lower side of the clean formation, wherein the oxidant can be directed to migrate and diffuse through the effects of electromigration and electroosmosis under the driving action of the direct current electric field, thereby forming a chemical oxidation reaction zone on the lower side of the clean area; A heating device capable of heating the contaminated formation so that the contaminants in the contaminated formation can be volatilized by heat, a part of the volatilized contaminants are collected by the extraction well, and another part moves upward into the chemical oxidation reaction zone to be oxidized and degraded; A multifunctional well is arranged in the contaminated area, and the heating equipment is an electric heating device arranged in the multifunctional well and corresponding to the contaminated formation area, and the electric heating device is connected to alternating current.

6. The depth-fixed precision thermal repair device according to claim 5, characterized in that: The drug injection equipment is a drug injection pipe arranged in the multifunctional well and corresponding to the clean formation area; The drug injection tube is also connected to direct current to form the direct current device.

7. The depth-fixed precision thermal repair device according to claim 5, characterized in that: The extraction well is a well cluster type extraction / injection multifunctional well, which has the functions of both the injection equipment and the extraction well; Electrodes are provided in the multifunctional well and in an area corresponding to the clean formation, and the electrodes are connected to direct current to form the direct current device.

8. The depth-fixed precision thermal repair device according to claim 5, characterized in that: An extraction pipe is provided in the extraction well, and the extraction screen slot of the extraction pipe is arranged at the same height or a lower height position corresponding to the injection screen slot.

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