CN115069754A - Electrode well structure and repair system for in-situ thermal desorption-electrocatalytic oxidation - Google Patents
Electrode well structure and repair system for in-situ thermal desorption-electrocatalytic oxidation Download PDFInfo
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- CN115069754A CN115069754A CN202210557896.8A CN202210557896A CN115069754A CN 115069754 A CN115069754 A CN 115069754A CN 202210557896 A CN202210557896 A CN 202210557896A CN 115069754 A CN115069754 A CN 115069754A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/06—Reclamation of contaminated soil thermally
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/002—Reclamation of contaminated soil involving in-situ ground water treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/005—Extraction of vapours or gases using vacuum or venting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
- B09C1/085—Reclamation of contaminated soil chemically electrochemically, e.g. by electrokinetics
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C2101/00—In situ
Abstract
The invention discloses an electrode well structure and a repair system for in-situ thermal desorption-electrocatalytic oxidation, which comprises: an electrode well; a special electrode is arranged in the electrode well and is respectively connected with the SCR alternating current voltage regulating unit and the bidirectional direct current pulse unit through a circuit switching unit; when the electrode well works as an in-situ thermal desorption mode, the circuit switching unit is switched to the SCR alternating current voltage regulating unit; when the electrode well works in an electrocatalytic oxidation mode, the circuit switching unit is switched to the bidirectional direct-current pulse unit; the special electrode comprises an aluminum alloy row, a pair-clamping graphite electrode plate is arranged on the aluminum alloy row at a preset distance along the height direction, the graphite electrode plate is fixed with the aluminum alloy row through a pair-clamping bolt, and the surface of a non-heating area of the aluminum alloy row is coated with an insulating sheath. The invention meets the use requirements under two working conditions of resistance heating and electrocatalytic oxidation by improving the design of the special electrode and the electrode well, and provides a larger space for the selection and optimization of the technical process.
Description
Technical Field
The invention relates to the technical field of in-situ remediation, in particular to an electrode well structure and a remediation system for in-situ thermal desorption-electrocatalytic oxidation, which are suitable for remediation of organic contaminated soil and underground water.
Background
The in-situ thermal desorption technology has good applicability to remediation of soil and underground water polluted by VOCs and SVOCs. The in-situ resistance heating technology adopts an alternating current power supply system, takes an electrode well as a phase electrode and utilizes the electric heating effect of soil and underground water to realize heating. Electrocatalytic oxidation technology, as an advanced oxidation technology, is widely used in the field of sewage treatment, which requires direct current as a power source.
The in-situ thermal desorption technology is used as a soil and underground water treatment technology, has high efficiency and thorough treatment degree, but has relatively high energy consumption to influence one of the factors of technical selection under the background of carbon emission reduction; the electrocatalytic oxidation technology is not used in the field of soil and underground water before, and a plurality of challenges are faced in design and construction cost.
Disclosure of Invention
In view of the above problems in the prior art, the present invention provides an electrode well structure and repair system for in situ thermal desorption-electrocatalytic oxidation.
The invention discloses an electrode well structure for in-situ thermal desorption-electrocatalytic oxidation, which comprises: an electrode well;
the special electrode capable of realizing in-situ thermal desorption and electrocatalytic oxidation is arranged in the electrode well and is respectively connected with the SCR alternating current voltage regulating unit and the bidirectional direct current pulse unit through the circuit switching unit; when the electrode well works in an in-situ thermal desorption mode, the circuit switching unit is switched to the SCR alternating current voltage regulating unit; when the electrode well works in an electrocatalytic oxidation mode, the circuit switching unit is switched to the bidirectional direct current pulse unit;
the special electrode comprises an aluminum alloy row, a pair-clamp graphite electrode plate is arranged at a preset distance along the height direction at intervals on the aluminum alloy row, the graphite electrode plate is detachably fixed to the aluminum alloy row through a pair-clamp bolt, and the surface of a non-heating area of the aluminum alloy row is coated with an insulating sheath.
As a further improvement of the invention, the graphite electrode plate is required to have an electric conductivity of not less than 25A/cm 2 And coating an anti-oxidation protective layer on the surface.
As a further development of the invention, the electrode well comprises: a well body;
the special electrode is arranged in the well body, the graphite electrode plate is arranged in a plane of a pollution area, quartz sand and conductive liquid are filled in the plane of the corresponding pollution area in the well body, and bentonite is filled in the plane of the corresponding pollution-free area.
As a further improvement of the invention, when the special electrode is used as a heating electrode or an advanced oxidation electrode, carbon powder is released, and the released carbon powder can be dispersed in peripheral heating soil.
As a further improvement of the invention, the electrode well can be used as an in-situ thermal desorption heating well, an in-situ electrocatalytic oxidation electrode or used as the in-situ thermal desorption heating well and the in-situ electrocatalytic oxidation electrode in combination at different stages respectively.
As a further improvement of the invention, in an in-situ thermal desorption mode, the SCR ac voltage regulation unit regulates the inter-phase voltage between the electrode wells to control the heating process; under the electrocatalytic oxidation mode, the bidirectional direct current pulse unit realizes the anode-cathode conversion between the electrodes.
The invention also discloses an in-situ remediation system for the organic contaminated soil and underground water, which comprises the following steps: the electrode well structure comprises an extraction well, a vapor extraction component, a liquid extraction component and the electrode well structure;
the electrode well and the extraction well are arranged in a preset area of the organic polluted soil and the underground water;
the extraction well is respectively connected with a gas phase extraction assembly and a liquid phase extraction assembly, the gas phase extraction assembly comprises a vacuum pump, an atomization spraying unit, a steam-water separator and a tail gas treatment unit which are sequentially connected, and the liquid phase extraction assembly comprises an extraction pump, a mass flow meter, a condenser, a three-phase separator and a sewage treatment unit which are sequentially connected; the liquid outlet of the steam-water separator is connected with the liquid inlet of the condenser, the gas outlet of the three-phase separator is connected with the gas inlet of the tail gas treatment unit, and the oil outlet of the three-phase separator and the oil outlet of the tail gas treatment unit are both connected to the storage tank.
As a further improvement of the invention, the method also comprises the following steps: an intelligent control unit;
the intelligent control unit is respectively connected with one or more of the electrode well, the circuit switching unit, the SCR alternating current pressure regulating unit, the bidirectional direct current pulse unit, the vacuum pump, the atomization spraying unit, the steam-water separator, the tail gas treatment unit, the extraction pump, the mass flow meter, the condenser, the three-phase separator, the sewage treatment unit and the storage tank, and is used for realizing intelligent control of in-situ thermal desorption and electrocatalytic oxidation.
As a further improvement of the present invention, the intelligent control unit is specifically configured to:
based on the sampling monitoring data in the repairing process, the circuit switching unit is intelligently controlled to realize the switching between the SCR alternating current voltage regulating unit and the bidirectional direct current pulse unit;
intelligently controlling working parameters of the SCR alternating current voltage regulating unit and the bidirectional direct current pulse unit based on underground parameters of the electrode well;
and intelligently controlling the working parameters of the gas phase extraction assembly and the liquid phase extraction assembly based on the detection parameters of the mass flow meter.
Compared with the prior art, the invention has the beneficial effects that:
the invention meets the use requirements under two working conditions of resistance heating and electrocatalytic oxidation by improving the design of the special electrode and the electrode well, and provides a larger space for the selection and optimization of the technical process.
Drawings
FIG. 1 is a schematic structural diagram of an in-situ remediation system for organically-polluted soil and groundwater according to an embodiment of the present disclosure;
FIG. 2 is a schematic structural diagram of an electrode according to an embodiment of the present invention; wherein a is a front view; b is a side view;
FIG. 3 is a schematic structural diagram of an electrode well according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a three-phase separator disclosed in an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an electrode well intelligent control system for in-situ thermal desorption-electrocatalytic oxidation according to an embodiment of the present invention.
In the figure:
1. an electrode well; 2. an extraction well; 3. a circuit switching unit; 4. an SCR AC voltage regulation unit; 5. a bidirectional DC pulse unit; 6. an intelligent control unit; 7. a vacuum pump; 8. an atomization spraying unit; 9. a steam-water separator; 10. a tail gas treatment unit; 11. an extraction pump; 12. a mass flow meter; 13. a condenser; 14. a three-phase separator; 15. a sewage treatment unit; 16. a storage tank; 17. a power supply device;
1-1, special electrodes; 1-1-1, aluminum alloy row; 1-1-2, graphite electrode plate; 1-1-3, oppositely clamping bolts; 1-1-4, aluminum row connecting holes; 1-1-5, insulating sheath; 1-2, pollution-free area; 1-3, a contaminated area; 1-4, well body; 1-5, bentonite; 1-6 parts of quartz sand and a conductive liquid; 1-7, an injection pipe;
14-1, a sand blocking plate; 14-2, a sand discharge valve; 14-3, a water regulating valve; 14-4, a heavy component regulating valve; 14-5, an oil baffle plate; 14-6, pressure regulating valve; 14-7, a demister; 14-8, a float level meter; 14-9, a temperature sensor; 14-10 parts of a water tank; 14-11, a grit chamber; 14-12 and a shell.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention is described in further detail below with reference to the attached drawing figures:
as shown in fig. 1-3 and 5, the present invention provides an electrode well structure for in-situ thermal desorption-electrocatalytic oxidation, comprising: the electrode well 1, the special electrode 1-1, the circuit switching unit 3, the SCR alternating current voltage regulating unit 4 and the bidirectional direct current pulse unit 5; wherein the content of the first and second substances,
the electrode well 1 is internally provided with a special electrode 1-1 which can realize in-situ thermal desorption and electrocatalytic oxidation, the special electrode is respectively connected with an SCR alternating current voltage regulating unit 4 and a bidirectional direct current pulse unit 5 through a circuit switching unit 3, and the SCR alternating current voltage regulating unit 4 and the bidirectional direct current pulse unit 5 are respectively connected with a power supply device 17 (for power supply of the city network); when the electrode well 1 works in an in-situ thermal desorption mode, the circuit switching unit 3 is switched to the SCR alternating current voltage regulating unit 4, the SCR alternating current voltage regulating unit 4 starts to work, alternating current is supplied to the electrode well 1, and soil and underground water serving as conductors are heated based on current thermal effect; when the electrode well 1 works in an electrocatalytic oxidation mode, the circuit switching unit 3 is switched to the bidirectional direct current pulse unit 5, the bidirectional direct current pulse unit 5 applies positive and negative direct current pulse voltage to the electrode well 1, and a high-density and full-coverage electric field is applied to a repair area for electrocatalytic oxidation; based on the method, the in-situ thermal desorption, the electrocatalytic oxidation and the in-situ thermal desorption-electrocatalytic oxidation combined remediation of the organic polluted soil and the underground water can be realized.
As shown in figure 2, the electrode of the invention adopts a special electrode 1-1 which can be used as a heating SCR alternating current voltage regulation and electrocatalytic oxidation bidirectional direct current pulse integrated electrode, and the special electrode 1-1 comprises: 1-1-1 parts of aluminum alloy rows, 1-1-2 parts of graphite electrode plates, 1-1-3 parts of oppositely clamped bolts and 1-1-5 parts of insulating sheaths; the aluminum alloy row 1-1-1 is provided with oppositely-clamped graphite electrode plates 1-1-2 at intervals of a preset distance in the height direction, aluminum row connecting holes 1-1-4 are formed in corresponding positions on the aluminum alloy row 1-1-1, the graphite electrode plates 1-1-2 are detachably fixed with the aluminum alloy row 1-1-1 through oppositely-clamped bolts penetrating through the corresponding aluminum row connecting holes 1-1-4, and the surface of a non-heating area of the aluminum alloy row 1-1-1 is coated with an insulating sheath 1-1-5.
Further, the aluminum alloy row 1-1-1 has the characteristics of low density and high strength, and has excellent conductivity of 2.2 multiplied by 10 -8 Ω m, thermal conductivity and corrosion resistance, tensile ductility; compared with a common copper column electrode, the aluminum alloy row 1-1-1 has lower density, so that the aluminum alloy row is lighter in weight and smaller in longitudinal stress, and can effectively cope with stress deformation caused by soil heating. The electrical conductivity of the high-power graphite electrode plate 1-1-2 is not less than 25A/cm 2 The surface of the steel plate is coated with an anti-oxidation protective layer, so that the steel plate has the characteristics of light weight, corrosion resistance, high temperature resistance and the like.
Further, according to the type and concentration of pollutants, calculating the heating power of soil in unit volume, and designing the area of the graphite electrode plate 1-1-2 used in unit length of the aluminum alloy row, so as to adjust the size of the gap between the graphite electrode plates 1-1-2 on the aluminum alloy row 1-1-1, and the gap is protected by a high-temperature insulating sheath 1-1-5; meanwhile, multiple sections of aluminum alloy rows can be connected through bolts according to the depth of the well, and only the aluminum rows are reserved for a stratum which does not need to be heated and are used as frameworks to wrap the high-temperature insulating sheaths 1-1-5. Furthermore, the special electrode is used for installation in soil, the alternating current voltage AC is 30-600V, and the direct current pulse voltage DC is 0-100V; preferably, the width of the aluminum alloy row is 100cm, the thickness is 6cm, and the width of the graphite electrode plate is 200cm, and the thickness is 10 cm.
On the basis of the scheme, as shown in figure 3, the electrode well comprises a well body 1-4, a special electrode 1-1 is arranged in the well body 1-4, and a graphite electrode plate 1-1-2 is arranged in a plane where a pollution area 1-3 is located; meanwhile, the plane of the pollution areas 1-3 corresponding to different depths in the well body 1-4 is filled with quartz sand and conductive liquid 1-6, and the plane of the pollution-free areas 1-2 corresponding to different depths in the well body 1-4 is filled with bentonite 1-5.
Further, when the special electrode 1-1 is used as a heating electrode and an advanced oxidation electrode, carbon powder is released and gradually dispersed in peripheral heating soil, so that the conductivity is increased, and the heating and oxidation effects are enhanced; meanwhile, if the conductivity can not meet the requirement, the carbon powder-containing conductive liquid can be supplemented into the polluted soil and underground water through the injection pipes 1-7. Meanwhile, the invention can also supplement water to the special electrode well through the injection pipes 1-7 according to the extracted water amount of the extraction well, so as to maintain the underground water level.
As shown in fig. 1, the present invention provides an in-situ remediation system for organic contaminated soil and groundwater, which comprises, in addition to the above electrode well structure designed and constructed according to site geological features and contamination conditions: designing an extraction well 2 and a monitoring well (not shown in the figure) according to site geological characteristics and pollution conditions; wherein the content of the first and second substances,
the multiphase extraction well 2 is respectively connected with a gas phase extraction assembly and a liquid phase extraction assembly, the gas phase extraction assembly comprises a vacuum pump 7, an atomization spraying unit 8, a steam-water separator 9 and a tail gas treatment unit 10 which are sequentially connected, and the liquid phase extraction assembly comprises an extraction pump 11, a mass flow meter 12, a condenser 13, a three-phase separator 14 and a sewage treatment unit 15 which are sequentially connected; the liquid outlet of the steam-water separator 9 is connected with the liquid inlet of the condenser 13, the gas outlet of the three-phase separator 14 is connected with the gas inlet of the tail gas treatment unit 10, and the oil outlet of the three-phase separator 14 and the oil outlet of the tail gas treatment unit 10 are both connected to the storage tank 16.
The specific extraction method comprises the following steps: extracting a gas phase from an extraction well 2 by gas phase extraction, enabling the gas phase to enter a steam-water separator 9 through a vacuum pump 7 and an atomization spraying unit 8, separating the gas phase by the steam-water separator 9 to remove a liquid phase, enabling the gas phase to enter a tail gas treatment unit 10, and discharging the gas phase after the treatment is finished; liquid phase extraction is carried out on liquid phase extracted from the extraction well 2, the liquid phase passes through an extraction pump 11 and a mass flow meter 12 and then enters a condenser 13 together with a liquid phase separated by a steam-water separator 9, and then three-phase separation is carried out by a three-phase separator 14; the separated gas phase enters a tail gas treatment unit 10 for treatment, the separated heavy component oil phase and the heavy component oil phase collected by the tail gas treatment unit 10 enter a storage tank 16 for collection and centralized treatment at the same time, and the separated water phase enters a sewage treatment unit 15 for treatment.
On the basis of the scheme, as shown in FIG. 4, the three-phase separator 14 comprises a sand baffle plate 14-1, a sand discharge valve 14-2, a water regulating valve 14-3, a heavy component regulating valve 14-4, an oil baffle plate 14-5, a pressure regulating valve 14-6, a demister 14-7, a float level meter 14-8, a temperature sensor 14-9, a water tank 14-10, a grit chamber 14-11 and a shell 14-12; wherein, a sand baffle 14-1 is arranged in the shell 14-12 close to the liquid inlet, a sand discharge valve 14-2 is arranged on a sand discharge pipe at the bottom of a grit chamber 14-11 formed by the sand baffle 14-1 and the inner wall of the shell, and when sand is accumulated to a certain height, the sand discharge valve 14-2 is opened for sand discharge; a water tank 14-10 and an oil baffle 14-5 are sequentially arranged at the downstream of the sand baffle 14-1 in the shell 14-12, a water discharge pipe at the bottom of the water tank 14-10 is provided with a water regulating valve 14-3, and an oil outlet pipe at the bottom of an oil outlet pool formed by the oil baffle 14-5 and the inner wall of the shell is provided with a heavy component regulating valve 14-4; a demister 14-7 is arranged at the top of the shell 14-12, and a pressure regulating valve 14-6 is arranged on an air outlet pipe connected with the demister 14-7; meanwhile, a buoy liquid level meter 14-8 and a temperature sensor 14-9 for detecting the liquid levels and temperatures of the water phase and the heavy component oil phase are also arranged on the shell 14-12.
When the three-phase separator 14 is used, water layered up and down in the shell 14-12 enters the water tank 14-10 and is connected with the sewage treatment unit 15 through a drain pipe; the heavy component oil phase layered up and down in the shell 14-12 enters an oil outlet pool and is connected with a storage tank 16 through an oil outlet pipe; gas generated by three-phase separation in the shell passes through a demister 14-7 and then enters the tail gas treatment unit 10 through a gas outlet pipe.
On the basis of the scheme, the mass flowmeter 12 can monitor the flow rate and the density temperature of the fluid, the mass flowmeter 12 is provided with a driving coil, the two ends of the driving coil are provided with detection coils, when excitation voltage provided by a transmitter is applied to the driving coil, the vibrating tube vibrates in a reciprocating period, fluid media in the working process flow through the vibrating tube of the sensor to generate a Coriolis force effect on the vibrating tube so that the two vibrating tubes vibrate in a torsional mode, the detection coils arranged at the two ends of the vibrating tube generate two groups of signals with different phases, and the phase difference of the two signals is in proportional relation with the mass flow rate of the fluid flowing through the sensor. The computer calculates the mass flow passing through the vibrating tube; meanwhile, when different media flow through the sensor, the main vibration frequencies of the vibration tubes are different, and the density of the media is calculated according to the main vibration frequencies. The platinum resistor installed on the vibrating tube of the sensor can indirectly measure the temperature of the medium.
The technical requirements of the mass flowmeter are as follows:
the mass flow precision is +/-0.002 multiplied by the flow +/-zero drift;
the density measurement precision is +/-0.003 g/cm 3 ；
The density measurement range is 0.5-1.5 g/cm 3 。
In order to realize the intelligent control of the repairing process, the repairing system of the invention further comprises: an intelligent control unit 6; the intelligent control unit 6 is respectively connected with one or more of the electrode well 1, the circuit switching unit 3, the SCR alternating current pressure regulating unit 4, the bidirectional direct current pulse unit 5, the vacuum pump 7, the atomization spraying unit 8, the steam-water separator 9, the tail gas treatment unit 10, the extraction pump 11, the mass flowmeter 12, the condenser 13, the three-phase separator 14, the sewage treatment unit 15 and the storage tank 16, and is used for realizing intelligent control of each stage of in-situ thermal desorption and electrocatalytic oxidation.
Further, in the three-phase separator 14, a float level meter 14-8 and a temperature sensor 14-9 are connected with the input end of the intelligent control unit 6, and a water regulating valve 14-3 and a heavy component regulating valve 14-4 are connected with the output end of the intelligent control unit 6.
The specific functions of the intelligent control unit 6 of the present invention may include:
1) based on the sampling monitoring data in the repairing process, the intelligent control circuit switching unit 3 realizes the switching between the SCR alternating current voltage regulating unit 4 and the bidirectional direct current pulse unit 5; for example, when the soil pollutant is detected to reach within 10 times of the remediation target, which indicates that the thermal desorption is completed, the circuit switching unit 3 is switched to the bidirectional direct current pulse unit 5, and the remediation is continued through the electrocatalytic oxidation technology.
2) Based on the underground detection parameters (such as resistance and conductivity) of the electrode well 1, intelligently controlling the working parameters (such as working voltage and working time) of the SCR alternating current voltage regulating unit 4 and the bidirectional direct current pulse unit 5; for example, parameters such as the forward and reverse working time, the voltage, the power and the like of the bidirectional direct current pulse unit 5 can be automatically adjusted according to the field resistance, so that the output voltage is ensured to be constant.
3) Based on the detection parameters (such as mass flow, density and temperature) of the mass flowmeter 12, intelligently controlling the working parameters (such as whether to start, when to start, working time and intermittent time) of each device of the gas phase extraction assembly and the liquid phase extraction assembly; for example:
firstly, when liquid phase extraction is carried out, an extraction pump 11, a mass flow meter 12, a condenser 13, a three-phase separator 14, a sewage treatment unit 15 and a storage tank 16 are controlled to be started; meanwhile, in the liquid phase extraction process, the extraction pump is controlled to perform staged intermittent work based on the change of the liquid phase temperature and the density;
and controlling the vacuum pump 7, the atomizing and spraying unit 8, the steam-water separator 9 and the tail gas treatment unit 10 to be started when the thermal desorption temperature reaches the set temperature (40 ℃) to perform vapor extraction.
Regulating working parameters of equipment such as a condenser 13 and the like based on oil phases with different heavy components;
and fourthly, intelligently controlling the flow regulation of the water regulating valve 14-3 and the heavy component regulating valve 14-4 based on the liquid level and the temperature detected by the float level meter 14-8 and the temperature sensor 14-9.
Specifically, the method comprises the following steps:
as shown in fig. 5, the present invention provides an electrode well intelligent control system for in-situ thermal desorption-electrocatalytic oxidation, comprising: the electrode well comprises an electrode well 1, a circuit switching unit 3, an SCR alternating current voltage regulating unit 4, a bidirectional direct current pulse unit 5 and an intelligent control unit 6; wherein the content of the first and second substances,
electrode well 1 of the present invention as an in situ thermal desorptionWhen the electrode well works in the attached mode, the intelligent control unit 6 controls the circuit switching unit 3 to be switched to the SCR alternating current voltage regulating unit 4, the SCR alternating current voltage regulating unit 4 starts to work, alternating current is supplied to the electrode well 1, and soil and underground water serving as conductors are heated based on current heat effect; in the heating process, when the site temperature delta t is monitored on site to meet the following conditions: t is t 0 ≤Δt＜t 1 The intelligent control unit 6 controls the SCR alternating current voltage regulating unit 4 to output constant power; when the field monitoring temperature deltat satisfies: t is t 1 ≤Δt＜t 2 The intelligent control unit 6 controls the SCR AC voltage regulation unit 4 to output constant voltage; wherein, t 0 Initial temperature for repairing the site, t 1 The temperature t corresponding to the deviation value between the actual measurement field resistance and the initial field resistance is larger than a first threshold value 2 Is the set temperature at which the heating mode is stopped.
On the basis of the scheme, the SCR alternating current voltage regulating unit 4 comprises a measuring instrument, a voltage measuring instrument, a power measuring instrument, a temperature measuring instrument, a pressure measuring instrument and the like, wherein the measuring instrument is used for measuring parameters such as current, voltage, power, temperature and pressure of a repair site and providing linkage protection; the SCR units of the SCR alternating current voltage regulating unit 4 are overlapped by adopting SCR modules, the front end of the SCR alternating current voltage regulating unit is provided with fast melting protection, and the cooling mode is water cooling; the power supply of the SCR AC voltage regulating unit 4 is an isolated power supply and provides 4 voltage levels according to the system requirements.
On the basis of the scheme, the invention discloses 1 The determining method is a temperature corresponding to the condition that the deviation value of the actually measured field resistance and the initial field resistance is greater than 10%, and comprises the following steps:
collecting undisturbed soil of the stratum i according to a geological survey report; measuring the resistivity rho of the undisturbed soil of each stratum at different temperatures it (ii) a At temperature t, the resistance R between wells t And each floor thickness L i And resistivity ρ it The relationship of (1) is:
as the heating process progresses, the temperature t 1 Time-to-well resistance R t1 With initial temperature t 0 Inter-well resistance R of time t0 The ratio of the components is as follows:
according to current and voltage data in the heating process, real-time monitoring is carried out
When the deviation of the two is more than 10%, marking the temperature t at the time 1 。
On the basis of the scheme, when the SCR alternating-current voltage regulating unit 4 outputs constant power, the output power P is output 1 Constant and adjustable from 0 to 500kVA, I 1 For field-detected values as arguments, U 1 In the first stage, the energy is input and the temperature is rapidly increased in order to set the voltage as the regulating variable; when the SCR AC voltage regulating unit 4 outputs constant voltage, the output voltage U 2 Constant and adjustable from 0 to 1000V, I 2 For field-detected values as arguments, P 2 In the second stage of energy input stage, the electrode well is protected from being damaged and the temperature is raised stably in order to set the power as the regulating quantity.
When the electrode well 1 of the invention is operated as electrocatalytic oxidation mode, when t 2 Delta t is less than or equal to delta t, the thermal desorption mode of the SCR alternating current voltage regulating unit 4 is ended, the circuit switching unit 3 is controlled to be switched to the bidirectional direct current pulse unit 5 through the intelligent control unit 6, the system enters an electrocatalytic oxidation mode, and a high-frequency power electronic conversion technology is adopted to output pulses. The intelligent control unit 6 of the invention controls the constant voltage output of the bidirectional direct current pulse unit 5.
On the basis of the scheme, the bidirectional direct current pulse unit 5 is composed of a control circuit, a human-computer interface and a bidirectional pulse adjustable power supply, wherein the human-computer interface is a touch screen, has a configuration function, displays running pictures and realizes manual operation and automatic program control; in the operation process of the system, the electrocatalytic oxidation environment is very unstable due to the changes of moisture, pollutant ions, temperature and the like in soil, and the system adopts constant voltage control, namely, the output voltage U is output 3 Constant and adjustable from 0 to 24V, I 3 For field measurements as independent variables, t 3 Set positiveThe reverse working time is used as an adjustment quantity, and forward and reverse pulses with different amplitudes meeting the system operation requirements can be obtained. The input end of the bidirectional pulse adjustable power supply is power frequency alternating current, the output is bidirectional direct current pulse, and the bidirectional pulse adjustable power supply can be controlled by a program; the input power frequency alternating current passes through a direct current converter to generate bidirectional direct current pulses, and a rectifier in the converter adjusts unstable current and corrects input power factors.
The invention provides an organic contaminated soil and underground water remediation method based on the in-situ remediation system, which comprises the following steps:
and 4, after the in-situ thermal desorption is finished (for example, when the content of the soil pollutants reaches within 10 times of the remediation target), the circuit switching unit 3 is switched to the bidirectional direct-current pulse unit 5, positive and negative direct-current pulse voltage is applied to the electrode well 1, and a high-density and full-coverage electric field is applied to the remediation area for electrocatalytic oxidation.
Example (b):
the average nitrobenzene soil content in a certain polluted land is 350mg/kg, the remediation target is 4.46mg/kg, the remediation target is 1200mg/kg, the remediation target is 38mg/kg, and the pollution depth is 20 meters.
Target pollutant nitrobenzene: relative density 1.205(15/4 deg.C), melting point 5.7 deg.C, boiling point 210.9 deg.C, and colorless or yellowish (containing nitrogen dioxide impurity) oily liquid;
the target pollutant 4-chloroaniline, with a relative density of 1.43, a melting point of 72.5 ℃, a boiling point of 232 ℃, is white or light yellow crystal in appearance, and is dissolved in hot water.
The geological structure of the site is a miscellaneous filling layer, a clay layer and a silt layer, because the resistivity of each section is different, 3 sections of wells are built, special electrodes are arranged according to the density of the pollution range, aluminum bars among the three sections are connected with heat shrinkable sleeves for insulation, the electrodes are isolated by quartz sand and bentonite outside, and the multiphase extraction and layering arrangement is realized.
The method for repairing the combined pollution of nitrobenzene and 4-chloroaniline comprises the following steps:
and 3, extracting the nitrobenzene according to the physical characteristics of the nitrobenzene as shown in the table 1:
TABLE 1
| Temperature of | Density set g/cm 3 | Density detection value > set value | Density detection value<Set value |
| 20 | 1.18 | Pump extraction operation | Standing for 30 minutes |
| 25 | 1.15 | Pump extraction operation | Standing for 45 minutes |
| 30 | 1.12 | Pump extraction operation | Standing for 110 minutes |
| 35 | 1.1 | Pump extraction operation | Standing for 120 minutes |
| 40 | 1.07 | Pump extraction operation | Standing for 150 minutes |
| 45 | 1.05 | Pump extraction operation | Standing for 180 minutes |
The water inlet of the extraction pipeline is arranged at the bottom of the multiphase extraction well 2, and can preferentially extract a medium with high density, the mass flow meter 12 can detect the temperature and density of the extracted liquid in real time, the intelligent control unit 6 can compare the detection value of the mass flow meter 12 with the value in the table 1, automatically control the operation of the extraction pump 11 and reserve standing time for underground water; after each standing is finished, starting the extraction pump to operate for at least 10 min;
continuously electrifying the special electrode 1-1 to heat the soil and the underground water in situ, heating the soil and the underground water to 60 ℃, dissolving the 4-chloroaniline in hot water, and then starting extraction; when the detected relative density is more than 1.2, continuously extracting, wherein the relative density is less than 1.2, standing for 30min, and then starting to circularly extract for at least 10 min; raising the temperature to 65 ℃, detecting that the relative density is more than 1.1, continuously extracting, starting to circularly extract when the relative density is less than 1.1, and increasing the standing time to 60 min; heating to 70 deg.C, detecting relative density of more than 1.05, continuously extracting, detecting relative density of less than 1.05, starting circular extraction, and standing for 120 min; heating to 75 deg.C, maintaining the temperature, extracting the liquid phase with relative density greater than 1.0, continuously extracting with relative density less than 1.0, circularly extracting for 30min, and standing for 150 min; and continuously and circularly extracting for 15 days until the relative density of the extract reaches 0.98.
Further, when the 4-chloroaniline solution was treated, the temperature was controlled at 65 ℃ by a condenser. The pipeline is blocked by crystallization at too low temperature, and layering and sedimentation are not facilitated by too high temperature; meanwhile, the heavy component and the water outlet regulating valve are controlled to maintain the interface constant.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. An electrode well structure for in situ thermal desorption-electrocatalytic oxidation, comprising: an electrode well;
the special electrode capable of realizing in-situ thermal desorption and electrocatalytic oxidation is arranged in the electrode well and is respectively connected with the SCR alternating current voltage regulating unit and the bidirectional direct current pulse unit through the circuit switching unit; when the electrode well works in an in-situ thermal desorption mode, the circuit switching unit is switched to the SCR alternating current voltage regulating unit; when the electrode well works in an electrocatalytic oxidation mode, the circuit switching unit is switched to the bidirectional direct current pulse unit;
the special electrode comprises an aluminum alloy row, a pair-clamp graphite electrode plate is arranged at a preset distance along the height direction at intervals on the aluminum alloy row, the graphite electrode plate is detachably fixed to the aluminum alloy row through a pair-clamp bolt, and the surface of a non-heating area of the aluminum alloy row is coated with an insulating sheath.
2. The electrode well structure of claim 1, wherein the graphite electrode plate requires an electrical conductivity of not less than 25A/cm 2 And coating an anti-oxidation protective layer on the surface.
3. The electrode well structure of claim 1, wherein the electrode well comprises: a well body;
the special electrode is arranged in the well body, the graphite electrode plate is arranged in a plane of a pollution area, quartz sand and conductive liquid are filled in the plane of the corresponding pollution area in the well body, and bentonite is filled in the plane of the corresponding pollution-free area.
4. The electrode well structure of claim 1, wherein when the special electrode is used as a heating electrode or an advanced oxidation electrode, carbon powder is released, and the released carbon powder is dispersed in the peripheral heating soil.
5. The electrode well structure of claim 1, wherein the electrode well can be used as an in-situ thermal desorption heater well, an in-situ electrocatalytic oxidation electrode, or a combination of an in-situ thermal desorption heater well and an in-situ electrocatalytic oxidation electrode at different stages.
6. The electrode well structure of claim 1, wherein in an in-situ thermal desorption mode, the SCR AC voltage regulator unit controls the heating process by modulating the phase-to-phase voltage between the electrode wells; under the electrocatalytic oxidation mode, the bidirectional direct current pulse unit realizes the anode-cathode conversion between the electrodes.
7. An in situ remediation system for organically contaminated soil and groundwater, comprising: an extraction well, a vapor extraction component, a liquid extraction component and an electrode well structure as claimed in any one of claims 1 to 6;
the electrode well and the extraction well are arranged in a preset area of the organic polluted soil and the underground water;
the extraction well is respectively connected with a gas phase extraction assembly and a liquid phase extraction assembly, the gas phase extraction assembly comprises a vacuum pump, an atomization spraying unit, a steam-water separator and a tail gas treatment unit which are sequentially connected, and the liquid phase extraction assembly comprises an extraction pump, a mass flow meter, a condenser, a three-phase separator and a sewage treatment unit which are sequentially connected; the liquid outlet of the steam-water separator is connected with the liquid inlet of the condenser, the gas outlet of the three-phase separator is connected with the gas inlet of the tail gas treatment unit, and the oil outlet of the three-phase separator and the oil outlet of the tail gas treatment unit are both connected to the storage tank.
8. The in situ repair system of claim 7, further comprising: an intelligent control unit;
the intelligent control unit is respectively connected with one or more of the electrode well, the circuit switching unit, the SCR alternating current pressure regulating unit, the bidirectional direct current pulse unit, the vacuum pump, the atomization spraying unit, the steam-water separator, the tail gas treatment unit, the extraction pump, the mass flow meter, the condenser, the three-phase separator, the sewage treatment unit and the storage tank, and is used for realizing intelligent control of in-situ thermal desorption and electrocatalytic oxidation.
9. The in situ remediation system of claim 8, wherein the intelligent control unit is specifically configured to:
based on the sampling monitoring data in the repairing process, the circuit switching unit is intelligently controlled to realize the switching between the SCR alternating current voltage regulating unit and the bidirectional direct current pulse unit;
intelligently controlling working parameters of the SCR alternating current voltage regulating unit and the bidirectional direct current pulse unit based on underground parameters of the electrode well;
and intelligently controlling the working parameters of the gas phase extraction assembly and the liquid phase extraction assembly based on the detection parameters of the mass flow meter.
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