Electrothermal coupled chemical oxidation method and device

Abstract

The present invention provides an electrothermal coupled chemical oxidation method and device, the device includes an oxidant preparation and injection unit, a monitoring control unit and a power regulation unit, the oxidant preparation and injection unit can inject oxidant into contaminated soil; the monitoring control unit can detect the changes in conductivity and redox potential in the contaminated soil; the power regulation unit includes an isolation voltage regulator, a rectifier and a switching switch, the input end of the isolation voltage regulator is connected to an AC power supply, and the output end is selected to be directly connected to an electrode in the contaminated soil through a switching switch, or is selected to be connected to the electrode through a rectifier, so as to transmit AC or DC to the electrode. The present invention first passes DC power to make the oxidant migrate in a directional manner, and then passes AC power to make the oxidant activated under the heating action of the AC electric field, so as to efficiently oxidize the contaminated soil.

Description

Technical Field

[0001] The invention relates to the technical field of soil remediation. Background Art

[0002] In-situ chemical oxidation technology is a highly efficient in-situ remediation technology suitable for treating source areas. It injects oxidants into soil or groundwater contaminated areas, and the oxidants come into contact with pollutants to oxidize them, converting the pollutants into non-toxic or relatively less toxic substances. It has the characteristics of good economy, rapid remediation, and significant effects. However, for low-permeability formations, there is a problem of poor mass transfer of oxidants. Since the transmission and diffusion of oxidants are affected by the permeability of the soil, it is impossible to achieve sufficient contact between the oxidants and the pollutants, resulting in poor in-situ chemical oxidation effects.

[0003] Sodium persulfate is a new type of oxidant with strong oxidizing ability (E 0 =2.01V), can treat a wide variety of pollutants, has a wide pH range, strong stability, high solubility, low economic cost, and high safety. Especially after activation, it can form sulfate free radicals (E 0 =2.5~3.1V), the oxidation capacity is further improved, the types of pollutants that can be treated can be increased, the reaction rate can be accelerated, and the amount of oxidant used can be reduced. Therefore, the advanced oxidation technology based on sodium persulfate has been gradually widely used in the remediation of organic contaminated sites.

[0004] Sodium persulfate can be activated by heating or by adding an activator, such as iron (Fe 2+ / Fe 0+ ), strong oxidant activation (H 2 O 2 ) and alkali activation (NaOH), etc., but the latter has problems such as difficult to control the ratio of activator to persulfate (if too much activator is added, the activator will react with the generated sulfate radicals, resulting in unnecessary consumption of free radicals; if too little activator is added, the oxidant cannot be fully activated), low activation efficiency (one persulfate ion can only produce one sulfate radical), poor environmental friendliness (alkali activation requires pH>10). In comparison, thermal activation is a more efficient and environmentally friendly activation method. The bond energy of the OO bond in persulfate is 140kJ / mol. The energy input by heating (>50℃) will cause the OO bond to break and produce sulfate radicals. The temperature of thermal activation of persulfate is about 50℃. Since the free radicals generated by activation have poor stability and a short activation time (about 4s), for thermal activation of oxidants, the best activation time is to heat the oxidant after the oxidant is transported to the contaminated area, so as to achieve the purpose of improving the activation efficiency of the oxidant and reducing the amount of oxidant used.

[0005] Therefore, the key to in-situ chemical oxidation technology is to achieve uniform migration and dispersion technology of the oxidant and efficient heating activation technology. Summary of the invention

[0006] In order to solve the problems of poor mass transfer of low permeability formations and low oxidant activation efficiency in in-situ chemical oxidation technology, the present invention provides an electrothermal coupled chemical oxidation method and device.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] An electrothermal coupled chemical oxidation device, characterized in that it includes an oxidant preparation and injection unit, a monitoring control unit and a power regulation unit, wherein:

[0009] The oxidant preparation and injection unit is capable of injecting oxidants into the contaminated soil;

[0010] The monitoring control unit is capable of detecting changes in conductivity and redox potential in contaminated soil;

[0011] The power regulation unit includes an isolation voltage regulator, a rectifier and a switching switch. The input end of the isolation voltage regulator is connected to an AC power source, and the output end is selected through the switching switch to be directly connected to an electrode in the contaminated soil, or to be connected to the electrode through a rectifier, thereby transmitting AC or DC power to the electrode.

[0012] The electrothermal coupled chemical oxidation device, wherein: the electrodes are arranged in a manner that the basic unit is an equilateral triangle, and form an electrode matrix;

[0013] When the electrode is connected to direct current, there are multiple regular hexagonal units in the electrode matrix, wherein the six vertices of each regular hexagonal unit are negative poles, and the electrode at the center of the regular hexagonal unit is a positive pole; the remaining single electrodes are arranged in a staggered manner with positive and negative poles adjacent to each other;

[0014] When the electrodes are connected to alternating current, the phases of the three corners of each basic unit in the shape of an equilateral triangle are different.

[0015] The electrothermal coupled chemical oxidation device, wherein: the electrode matrix is ​​composed of an electrode injection well and an electrode well.

[0016] The electrothermal coupled chemical oxidation device, wherein: the electrode injection well is made of corrosion-resistant metal material.

[0017] An electrothermal coupled chemical oxidation method, using the electrothermal coupled chemical oxidation device, wherein: firstly, an oxidant is injected into the soil through an oxidant preparation and injection unit, and then the operation phase 1 and the operation phase 2 are sequentially performed, and the oxidant injection, the operation phase 1 and the operation phase 2 are repeated, wherein:

[0018] The first operation stage is the DC directional migration stage: the switch of the power regulation unit is connected to the rectifier to realize the conversion of AC power to DC power, and the DC power is transmitted to the electrode, thereby forming a DC electric field underground; the DC voltage is adjusted by the isolation voltage regulator, and the electric field strength of the DC electric field is adjusted to control the migration rate of the oxidant; driven by the DC electric field, the oxidant migrates and diffuses in a directional manner to the designated contaminated area;

[0019] The second operation stage is the AC heating activation stage: after the monitoring and control unit determines that the oxidant has been transmitted to the designated contaminated area, the switching switch of the power regulation unit is connected to another circuit, so that the AC power is directly transmitted to the electrode, thereby forming an AC electric field underground; the DC voltage is adjusted by the isolation voltage regulator, and the electric field strength of the AC electric field is adjusted to control the soil heating rate and heating temperature; the oxidant is activated under the heating action of the AC electric field to produce sulfate free radicals with stronger oxidation ability.

[0020] The electrothermal coupled chemical oxidation method, wherein: the electrodes are arranged in a manner that the basic unit is an equilateral triangle, and form an electrode matrix;

[0021] In the first operation stage, there are a plurality of regular hexagonal units in the electrode matrix, wherein the six vertices of each regular hexagonal unit are negative electrodes, and the electrode at the center of the regular hexagonal unit is a positive electrode;

[0022] In the second operation stage, the phases of the three corners of each basic unit in the shape of an equilateral triangle are different.

[0023] The electrothermal coupled chemical oxidation method, wherein: the electrode matrix is ​​composed of an electrode injection well and an electrode well.

[0024] The electrothermal coupled chemical oxidation method, wherein: the electrode injection well is made of corrosion-resistant metal material.

[0025] The electrothermal coupled chemical oxidation method, wherein: in the first operation stage, for the single electrode in the regular hexagonal layout, a rotation switching method is also used to spatially optimize the layout of the electrodes, so that the regular hexagonal electrode units are moved horizontally and vertically in the electrode matrix, and the single electrodes are incorporated into the new regular hexagonal units to eliminate blind spots in drug transmission.

[0026] The electrothermal coupled chemical oxidation method, wherein: the oxidant is re-injected, and the operation phase 1 and the operation phase 2 are performed sequentially.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention uses an electrode injection well, which can realize the composite functions of reagent injection and direct current and alternating current introduction, and the function integration reduces the cost and time of well construction;

[0029] (2) In the stage of direct current enhanced oxidant directional migration, by adjusting the distribution of the positive and negative electrodes of the direct current of the electrode, the electrode matrix can be formed into any number of regular hexagonal electrode units, so that the effective action area of ​​a single electrode is maximized and the average field strength induced is the highest, thereby reducing the operating energy consumption, improving the uniformity of the agent diffusion, and reducing the amount of the agent used;

[0030] (3) During the AC heating activation stage, by adjusting the AC phase distribution of the electrodes so that the electrodes form an equilateral triangle layout, the current can heat between any two adjacent electrodes, avoiding the generation of heating cold spots (if the AC phases of two adjacent electrodes are the same, there will be no current flow between the two and heating cannot be achieved), thereby making the heating effect more uniform, the oxidant activation efficiency higher, and reducing the heating energy consumption;

[0031] (4) In the first operation stage, the polarity of the electric field is periodically switched by using a rotation switching method, thereby eliminating the dead angle of drug transmission and making the drug diffusion more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structure of the electrothermal coupled chemical oxidation device provided by the present invention;

[0033] Figure 2 This is a working principle diagram of the electrothermal coupled chemical oxidation device provided by the present invention in the first operation stage;

[0034] Figure 3A is a schematic diagram of polarity distribution of the electrode matrix in operation phase 1;

[0035] Figure 3B yes Figure 3A Schematic diagram of polarity distribution of a hexagonal unit;

[0036] Figure 4 It is a working principle diagram of the electrothermal coupled chemical oxidation device provided by the present invention in the second operation stage;

[0037] Figure 5A is a schematic diagram of the polarity distribution of the electrode matrix in the second operation stage (①, ②, ③ represent the three-phase connection with the live wire respectively);

[0038] Figure 5B yes Figure 5A Schematic diagram of the polarity distribution of a triangular unit (①, ②, ③ represent the three-phase connection to the live wire respectively).

[0039] Figure 6It is a schematic diagram of the action of controlling the regular hexagonal electrode unit to move horizontally and vertically in the electrode matrix.

[0040] Explanation of the reference numerals: oxidant preparation and injection unit 1; oxidant storage stirring tank 11; pressurized injection pump 12; electrode injection integrated well 13; monitoring control unit 2; monitoring well 21; power regulation unit 3; isolation voltage regulator 31; rectifier 32; switching switch 33; electrode matrix 4. DETAILED DESCRIPTION

[0041] like Figure 1 As shown, the present invention provides an electrothermal coupled chemical oxidation device, comprising an oxidant preparation and injection unit 1, a monitoring control unit 2 and a power adjustment unit 3, wherein:

[0042] The oxidant preparation and injection unit 1 includes an oxidant storage stirring tank 11, a pressurized injection pump 12 and an electrode injection well 13. The electrode injection well 13 is made of corrosion-resistant metal and can be used as an oxidant injection well and an electrode to introduce direct current or alternating current into the ground.

[0043] The monitoring control unit 2 includes a monitoring well 21, a detector (capable of detecting the redox potential, pH value, conductivity, moisture content and / or temperature in the soil), a display and a memory (not shown), and is equipped with intelligent "positive and negative pole / phase time-sharing switching" control software;

[0044] The power regulation unit 3 includes an isolation voltage regulator 31, a rectifier 32 and a switching switch 33. The input end of the isolation voltage regulator 31 is connected to an AC power supply, and the output end can be directly connected to the electrode injection well 13 through the switching switch 33, or can be connected to the electrode injection well 13 and / or the electrode well through the rectifier 32, thereby transmitting AC or DC power to the electrode injection well 13 and / or the electrode well.

[0045] When the present invention is used:

[0046] First, the oxidant (sodium persulfate) is injected into the electrode injection well 13 through the oxidant preparation and injection unit, and then the operation phase 1 and the operation phase 2 are alternately performed, wherein:

[0047] The first operation stage is the DC directional migration stage: the switch 33 of the power regulation unit 3 is connected to the rectifier 32 to realize the conversion of AC power into DC power, and the DC power is transmitted to the electrode injection well 13 and / or the electrode well through the cable, so as to form a DC electric field underground; the DC voltage is adjusted by the isolation voltage regulator 31, and the electric field strength of the DC electric field is adjusted to control the migration rate of the oxidant; the oxidant (sodium persulfate) is driven by the DC electric field to perform directional migration and diffusion ( Figure 2); preferably, the electrode injection well 13 and / or the electrode well are arranged in a manner that the basic unit is an equilateral triangle. After the number is expanded, an electrode matrix 4 can be formed, and a regular hexagonal unit is formed in the electrode matrix 4, wherein the six vertex electrodes of each regular hexagonal unit are negative electrodes, the electrode at the center position of the regular hexagonal deformation unit is a positive electrode, and the remaining single electrodes are arranged in a manner that the positive and negative electrodes are staggered and adjacent; by monitoring the intelligent "positive and negative pole / phase time-sharing switching" control software of the control unit 2, the positive and negative poles of each electrode injection well 13 and / or the electrode well are adjusted (the positive and negative poles are staggered and adjacent to form Figure 3A , Figure 3B The regular hexagonal electrode unit shown in the figure can make the drug delivery effect more uniform and efficient;

[0048] The second operation stage is the AC heating activation stage: after the oxidant is transmitted to the designated contaminated area (determined by monitoring the changes in the conductivity and redox potential in the soil detected by the control unit 2), the switch 33 of the power adjustment unit 3 is connected to another circuit, so that the AC power is directly transmitted to the electrode matrix 4, thereby forming an AC electric field underground; the DC voltage is adjusted by the isolation voltage regulator 31, and the electric field strength of the AC electric field is adjusted to control the soil heating rate and heating temperature; the oxidant (sodium persulfate) is activated under the heating action of the AC electric field to produce sulfate radicals with stronger oxidizing ability (such as Figure 4 ); As mentioned above, the electrode matrix 4 is arranged in a way that the basic unit is an equilateral triangle. By monitoring the intelligent "positive and negative pole / phase time-sharing switching" control software of the control unit 2, the basic unit of each equilateral triangle is adjusted to have different phases at the three corners (such as Figure 5A , Figure 5B As shown), so that current can flow between any two adjacent electrodes, making the heating effect more uniform and efficient;

[0049] After running for a period of time, the oxidant is re-injected according to the pollutant removal effect, and the operation stage 1 and the operation stage 2 are repeated alternately until the remediation goal is achieved; wherein, during the repeated operation of the stage 1, the intelligent "positive and negative pole / phase time-sharing switching" control software of the monitoring control unit 2 can be used to optimize the layout of the electrodes in space by using a rotation switching method for the single electrodes in the regular hexagonal layout, so that the regular hexagonal electrode units can move horizontally and vertically in the electrode matrix (such as Figure 6 As shown in the figure, the single electrode is incorporated into a new regular hexagonal unit to eliminate the blind spots of drug transmission, thereby achieving the purpose of uniform drug diffusion; in addition, the present invention can narrow the repair range and perform precise repair on partial areas based on the precise control of a single electrode according to the pollutant removal situation.

[0050] The beneficial effects brought by the present invention are:

[0051] (1) The present invention uses an electrode injection well 13, which can realize the composite functions of injecting reagents and introducing direct current and alternating current, and the function integration reduces the cost and time of well construction;

[0052] (2) In the stage of direct current enhanced oxidant directional migration, by adjusting the distribution of the positive and negative electrodes of the direct current of the electrode, the electrode matrix 4 can be formed into any number of regular hexagonal electrode units, so that the effective action area of ​​a single electrode is maximized and the average field strength induced is the highest, thereby reducing the operating energy consumption, improving the uniformity of the agent diffusion, and reducing the amount of the agent used;

[0053] (3) During the AC heating activation stage, by adjusting the AC phase distribution of the electrodes so that the electrodes form an equilateral triangle layout, the current can heat between any two adjacent electrodes, avoiding the generation of heating cold spots (if the AC phases of two adjacent electrodes are the same, there will be no current flow between the two and heating cannot be achieved), thereby making the heating effect more uniform, the oxidant activation efficiency higher, and reducing the heating energy consumption;

[0054] (4) In the first operation stage, the polarity of the electric field is periodically switched by using a rotation switching method, thereby eliminating the dead angle of drug transmission and making the drug diffusion more uniform.

[0055] In general, the technical method and device of the present invention can solve the problem of poor mass transfer of oxidants in low permeability formations and the problem of efficient activation of persulfate after it reaches the contaminated area. By using a multifunctional injection / electrode well structure, a two-dimensional electrode configuration (regular hexagonal electrode unit), an equilateral triangle layout, electric field rotation switching, etc., it is possible to reduce the cost of well construction, reduce the amount of oxidant used, increase the oxidant transmission rate, and accelerate the oxidation reaction rate, thereby generally improving the in-situ chemical oxidation removal rate, reducing the repair cost and shortening the repair time.

Claims

1. An electrothermal coupled chemical oxidation device, characterized in that: It includes an oxidant preparation and injection unit, a monitoring control unit and a power regulation unit, wherein: The oxidant preparation and injection unit is capable of injecting oxidants into the contaminated soil; The monitoring control unit is capable of detecting changes in conductivity and redox potential in contaminated soil; The power regulation unit includes an isolation voltage regulator, a rectifier and a switch, wherein the input end of the isolation voltage regulator is connected to an AC power source, and the output end is selected to be directly connected to an electrode in the contaminated soil or to be connected to the electrode through a rectifier through the switch, thereby transmitting AC or DC power to the electrode; Wherein, the electrodes are arranged in a manner that the basic unit is an equilateral triangle, and form an electrode matrix; When the electrode is connected to direct current, there are multiple regular hexagonal units in the electrode matrix, wherein the six vertices of each regular hexagonal unit are negative poles, and the electrode at the center of the regular hexagonal unit is a positive pole; the remaining single electrodes are arranged in a staggered manner with positive and negative poles adjacent to each other; When the electrodes are connected to alternating current, the phases of the three corners of each basic unit in the shape of an equilateral triangle are different.

2. The electrothermal coupled chemical oxidation device according to claim 1, characterized in that: The electrode matrix is ​​composed of an electrode injection well and an electrode well.

3. The electrothermal coupled chemical oxidation device according to claim 2, characterized in that: The electrode injection well is made of corrosion-resistant metal.

4. An electrothermal coupled chemical oxidation method, using the electrothermal coupled chemical oxidation device as claimed in claim 1, characterized in that: First, the oxidant is injected into the soil through the oxidant preparation and injection unit, and then the operation phase 1 and the operation phase 2 are sequentially performed, and the oxidant injection, the operation phase 1 and the operation phase 2 are repeated, wherein: The first operation stage is the DC directional migration stage: the switch of the power regulation unit is connected to the rectifier to realize the conversion of AC power to DC power, and the DC power is transmitted to the electrode, thereby forming a DC electric field underground; the DC voltage is adjusted by the isolation voltage regulator, and the electric field strength of the DC electric field is adjusted to control the migration rate of the oxidant; driven by the DC electric field, the oxidant migrates and diffuses in a directional manner to the designated contaminated area; The second operation stage is the AC heating activation stage: after the monitoring and control unit determines that the oxidant has been transmitted to the designated contaminated area, the switching switch of the power regulation unit is connected to another circuit, so that the AC power is directly transmitted to the electrode, thereby forming an AC electric field underground; the DC voltage is adjusted through the isolation voltage regulator, and the electric field strength of the AC electric field is adjusted to control the soil heating rate and heating temperature; the oxidant is activated under the heating of the AC electric field, and produces sulfate free radicals with stronger oxidation ability; Wherein, the electrodes are arranged in a manner that the basic unit is an equilateral triangle, and form an electrode matrix; In the first operation stage, there are a plurality of regular hexagonal units in the electrode matrix, wherein the six vertices of each regular hexagonal unit are negative electrodes, and the electrode at the center of the regular hexagonal unit is a positive electrode; In the second operation stage, the phases of the three corners of each basic unit in the shape of an equilateral triangle are different.

5. The electrothermal coupled chemical oxidation method according to claim 4, characterized in that: The electrode matrix is ​​composed of an electrode injection well and an electrode well.

6. The electrothermal coupled chemical oxidation method according to claim 5, characterized in that: The electrode injection well is made of corrosion-resistant metal.

7. The electrothermal coupled chemical oxidation method according to claim 4, characterized in that: In the first operation stage, a rotation switching method is used to spatially optimize the layout of the electrodes for the lone electrodes in the regular hexagonal layout, so that the regular hexagonal electrode units can move horizontally and vertically in the electrode matrix, and the lone electrodes can be incorporated into the new regular hexagonal units to eliminate blind spots in drug transmission.

8. The electrothermal coupled chemical oxidation method according to claim 4, characterized in that: The oxidant is reinjected, and the operation phase 1 and the operation phase 2 are performed sequentially.

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