CN215965481U - Thermal desorption restoration backflash heating energy-saving system - Google Patents

Abstract

The utility model discloses a thermal desorption restoration backfire heating energy-saving system, wherein a gas-liquid separation unit is connected with a soil waste gas extraction unit and is in electrification control connection with an electric control unit, a backfire heating unit comprises a backfire pipeline, a burner device and a heating pipe group, one end of the backfire pipeline is communicated with a waste gas output end, the other end of the backfire pipeline is connected with the burner device and is mixed with gas entering the burner device for combustion, the heating pipe group is horizontally embedded in soil of a polluted land block or is positioned below an extraction pipe in the soil waste gas extraction unit, one end of the heating pipe group is communicated with a high-temperature gas output end of the burner device, and the other end of the heating pipe group is output to the ground through a tail gas pipeline. The utility model adopts a combustion mode to carry out combustion treatment on the soil extraction waste gas, the waste gas which is not fully combusted is decomposed at high temperature, and the heat energy of the soil extraction waste gas and the back combustion thereof are utilized to heat and save energy, thereby saving heating energy, saving energy, reducing emission and reducing repair cost.

Description

Thermal desorption restoration backflash heating energy-saving system

Technical Field

The utility model relates to the technical field of soil remediation, in particular to a thermal desorption remediation and backfire heating energy-saving system.

Background

The 'soil cleaning' work is one of three big environmental protection attack and solidness wars in China and is an important component for building beautiful China. With the promulgation and implementation of the soil pollution prevention and control law, the soil pollution prevention and control work is paid unprecedented attention at present. Contaminated soil restoration mode includes normal position restoration and ectopic restoration, and the construction drawbacks such as dystopy is restoreed and is related to earthwork excavation, soil transportation and temporary storage, and present soil normal position thermal desorption is restoreed and is gradually become contaminated soil restoration's hot technique.

The in-situ thermal desorption is basically a soil remediation method for promoting the volatilization of pollutants by heating soil and performing centralized treatment on the pollutants, and according to different heating modes, the commonly used in-situ thermal desorption comprises three types of heat conduction, resistance heating and steam heating, wherein the heat conduction comprises electric heating heat conduction and fuel gas heating heat conduction. The heat conduction has the advantage that heating temperature is high, and the factors influencing heat energy loss in the gas heating in-situ thermal desorption repair process are as follows: the heat preservation effect of the covering layer; the heat preservation effect of the burner main body; heat energy taken away by the emission of combustion exhaust gas; heat energy taken away by the soil extraction waste gas, and the like.

In the in-situ thermal desorption repair process, the direct treatment of the soil extraction waste gas has large heat energy loss and needs to increase energy consumption, the soil temperature rise is slow, the repair cycle time is long, the energy consumption is large, and the repair cost is high. Therefore, the heating utilization rate is improved in the thermal desorption repair process, and energy conservation and emission reduction are particularly important.

SUMMERY OF THE UTILITY MODEL

Aiming at the technical problems in the existing in-situ thermal desorption repair process, the direct treatment of the soil extraction waste gas has larger heat energy loss and needs to increase energy consumption, the soil temperature rise is slow, the repair period is long, the energy consumption is larger, and the repair cost is higher. Therefore, the utility model provides a thermal desorption restoration and back combustion heating energy-saving system, provides a practical and reliable back combustion measure, and reduces the heat energy loss of extracted waste gas and the waste gas treatment cost. The extraction waste gas is used for backflash, so that the heating efficiency can be improved, the heating energy can be saved, the emission is reduced, the heating time is optimized, the pollutant removal is improved, the repair period is shortened, the repair cost is reduced, and the green repair is realized.

The utility model adopts the following technical scheme:

a thermal desorption restoration backfire heating energy-saving system comprises a soil waste gas extraction unit, a gas-liquid separation unit and an electric control unit, wherein the gas-liquid separation unit is connected with the soil waste gas extraction unit, and forms an electrification control connection with the electric control unit, the system also comprises a back-burning heating unit, which comprises a back-burning pipeline, a burner device and a heating pipe set, wherein one end of the back-burning pipeline is communicated with a waste gas output end in the gas-liquid separation unit, the other end of the heating tube group is connected with the burner device and is used for mixing with gas entering the burner device and then burning the gas, the heating tube group is horizontally embedded in soil of the polluted land, or the heating pipe group is positioned below an extraction pipe in the soil waste gas extraction unit, one end of the heating pipe group is communicated with the high-temperature gas output end of the burner device, and the other end of the heating pipe group is output to the ground through a tail gas pipeline.

Preferably, the heating pipe set is provided with a plurality of heating pipes, each heating pipe is horizontally embedded in the polluted land at intervals, an inlet pipe section of each heating pipe adopts a stainless steel pipeline, an inlet end of each heating pipe is respectively connected with the burner device, and an outlet pipe section of each heating pipe is a carbon steel pipeline.

The tail gas pipeline comprises a tail gas fan, a tail gas main pipe and a plurality of tail gas branch pipes correspondingly connected with the outlet ends of the heating pipes, each tail gas branch pipe is correspondingly communicated with the tail gas main pipe, and the tail gas main pipe extends out of the polluted land on the ground and is connected with the tail gas fan.

Preferably, the exhaust branch pipe is a spiral air pipe.

The soil waste gas extraction unit comprises a first extraction pipe group, a second extraction pipe group, an extraction main pipe and an extraction fan communicated with the extraction main pipe, wherein one end of the first extraction pipe group and one end of the second extraction pipe group are respectively communicated with the extraction main pipe, and a plurality of extraction pipes I in the first extraction pipe group are horizontally embedded at intervals at the soil surface position of the polluted land block and are positioned right above the heating pipe group or are horizontally embedded at intervals at the soil surface position of the polluted land block; and a plurality of extraction pipes II in the second extraction pipe group are vertically embedded in the polluted land block at intervals, and extraction inlets at the lower ends of the extraction pipes II are arranged close to the heating pipes and are respectively positioned at the middle cold spot positions of two adjacent heating pipes or are vertically embedded in the polluted land block at intervals.

Longitudinal or transverse cutting seams are formed along the length direction of the extraction pipe I, the interval between every two adjacent cutting seams is 10-20cm, the width of each cutting seam is 1-2mm, an anti-blocking screen mesh is wrapped on the outer side surface of the extraction pipe I, and quartz sand or gravel with the particle size of 2-4mm is paved around the extraction pipe I.

The extraction pipe I is horizontally buried in an area with the depth of 50cm of the polluted land, and the extraction cutting seam at the lower part of the extraction pipe II is positioned in an area with the depth of 100cm of the polluted land.

The extraction main pipe is arranged on the ground, the gas-liquid separation unit comprises a heat exchanger, a cooling tower and a gas-liquid separator, the cooling tower is connected with the heat exchanger through a pipeline and used for cooling the heat exchanger, the extraction main pipe is connected with the inlet end of the heat exchanger and used for exchanging heat and cooling extraction waste gas, the outlet end of the heat exchanger is connected with the gas-liquid separator, the extraction fan is arranged at the gas outlet of the gas-liquid separator, and the liquid outlet of the gas-liquid separator is connected with wastewater treatment equipment.

The technical scheme of the utility model has the following advantages:

A. the thermal desorption restoration and backfire heating energy-saving system provided by the utility model preferably adopts gas as heating energy, connects the soil extraction waste gas of the restored land or another restored land with the air inlet of the burner main body of the horizontal heating pipe of the local land, enables the soil extraction waste gas to be burned in the burner main body, enables the part of the waste gas which is not fully burned to be mixed and reacted with high-temperature gas in the horizontal heating pipe, reduces air preheating by utilizing the heat energy in the extraction waste gas, simultaneously carries out backfire by taking the organic matters in the extraction waste gas as fuel and utilizes the heat energy to heat the polluted soil, so as to achieve the functions of utilizing the heat energy of the soil extraction waste gas and the backfire heating energy saving, thereby saving the heating energy, saving energy, reducing emission and reducing restoration cost.

B. The utility model adopts a plurality of horizontal extraction pipes I which are arranged on the surface layer of the soil and are distributed above the heating pipe group and a plurality of extraction pipes II which vertically extend to the position close to the heating pipe group, so that two types of extraction pipes are horizontally and vertically and symmetrically distributed on two sides of the extraction main pipe to form an extraction network and extract waste gas aiming at different soil layers, the waste gas generated by the heated soil is more comprehensively collected, the waste gas extraction efficiency is greatly improved, and the soil remediation progress is accelerated.

C. The utility model saves fixed waste gas treatment equipment, thereby saving cost, and all units can be connected by pipelines, and the equipment installation position is flexible, thereby being suitable for fields with different conditions.

Drawings

In order to more clearly illustrate the embodiments of the present invention, the drawings which are needed to be used in the embodiments will be briefly described below, and it is apparent that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained from the drawings without inventive labor to those skilled in the art.

Fig. 1 is a schematic structural diagram of the entire energy saving system provided by the present invention.

The labels in the figure are as follows:

1-soil waste gas extraction unit

11-first extraction tube set, 11 a-extraction tube I

12-second extraction tube set, 12 a-extraction tube II

13-extraction main pipe

14-extraction fan

2-gas-liquid separation Unit

21-heat exchanger, 22-cooling tower

23-gas-liquid separator

231-first gas-liquid separator, 232-second gas-liquid separator

24-exhaust gas treatment device

3-Back-fire heating Unit

31-backflash pipe, 32-burner device, 33-heating pipe set, 33 a-heating pipe

4-tail gas pipeline

41-tail gas fan, 42-tail gas main pipe, 43-tail gas branch pipe and 44-activated carbon box

5-chimney.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; the connection can be mechanical connection or electrical connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

As shown in fig. 1, the present invention provides a thermal desorption repair burn-back heating energy-saving system, which comprises a soil waste gas extraction unit 1, a gas-liquid separation unit 2, a burn-back heating unit 3 and an electrical control unit (not shown in the figure), wherein the gas-liquid separation unit 2 is connected with the soil waste gas extraction unit 1 and forms an electrical control connection with the electrical control unit, the burn-back heating unit 3 comprises a burn-back pipeline 31, a burner device 32 and a heating pipe set 33, one end of the burn-back pipeline 31 is communicated with a waste gas output end in the gas-liquid separation unit 2, the other end of the burn-back pipeline is connected with the burner device 32 for mixing with gas entering the burner device 32 and then burning, the heating pipe set 33 is horizontally embedded in soil heated by pollution, or is positioned below an extraction pipe in the soil waste gas extraction unit 1, that is to extract waste gas and heat a polluted land block on the same polluted land block, or can be carried out on different polluted land areas respectively. One end of the heating pipe set 33 is communicated with the high-temperature gas output end of the burner device 32, and the other end thereof is output to the ground through the tail gas pipeline 4. The back-burning pipeline 31 conveys the waste gas separated by the gas-liquid separation unit 2 to the air inlets of the burner devices connected with the horizontal heating pipe group, and the waste gas is processed by carbon steel pipes.

The heating pipe set 33 is provided with a plurality of heating pipes 33a, each heating pipe 33a is horizontally embedded in the polluted land at intervals, because the combustion temperature of the fuel gas and the extraction waste gas is higher than 800 ℃, the inlet pipe section of each heating pipe 33a adopts a stainless steel pipeline, each heating pipe 33a is respectively connected with a burner device 32, and the outlet pipe section of each heating pipe 33a is a carbon steel pipeline, the cost can be further reduced. The heating pipe 33a can make the extraction waste gas which is not fully combusted fully mix and react with the high-temperature fuel gas generated in the burner device, make the retention time of the waste gas in the waste gas reach the requirement, conduct the high-temperature heat energy to the polluted soil, and raise the temperature of the polluted soil to volatilize the pollutants and extract the pollutants. The horizontal heating pipe 33a is buried in the plot to a pollution depth of about 1 m, and burns the soil extraction waste gas to heat the plot soil.

The burner device 32 mainly includes a burner 321 and a burner body 322, and the burner 321 functions to supply the natural gas fuel and the oxidizer and to create conditions for mixing them or to mix them.

Burning the auxiliary fuel to generate high-temperature fuel gas; the burner 321 includes the following functions:

1) and (3) an ignition function: consists in igniting a mixture of air and fuel, the main components of which are an ignition transformer, an ignition electrode, an electric spark high-voltage cable. The flame length, cone angle and shape can be designed according to the requirements of users.

2) A monitoring function: the main components of the burner are a flame monitor, a pressure monitor, a temperature monitor and the like, so as to ensure the safe and stable operation of the burner.

3) Function of the fuel system: in order to ensure that the burner burns the required fuel. The fuel system of the fuel oil burner mainly comprises an oil pipe, a joint, an oil pump, an electromagnetic valve, a nozzle and a heavy oil preheater. The gas burner mainly comprises a filter, a pressure regulator, an electromagnetic valve group, an ignition electromagnetic valve group and a fuel butterfly valve.

The main body of the burner 321 is made of steel, and a refractory insulating material is installed inside the main body to serve as a lining. The function of the device is to complete the whole process of mixing fuel gas, waste gas and air and igniting and burning. The high-temperature fuel gas and the extraction waste gas are mixed and combusted to reach the reaction temperature.

The tail gas pipeline 4 comprises a tail gas fan 41, a tail gas main pipe 42, a plurality of tail gas branch pipes 43 correspondingly connected with the outlet ends of the heating pipes 33a and an activated carbon box 44, each tail gas branch pipe 43 is correspondingly communicated with the tail gas main pipe 42, the tail gas main pipe 42 extends out of the ground of the polluted land and is connected with the tail gas fan 41, under the action of the tail gas fan 41, waste gas combustion is realized in the burner main body 322, high-temperature heating and decomposition of the waste gas are completed in the heating pipe group 33, namely, the polluted soil is heated, decomposition of harmful substances in the polluted waste gas is also realized, and the waste gas is discharged to the atmosphere in a non-toxic manner through the activated carbon box 44, the tail gas fan 41 and the chimney 5 in sequence. The combustion exhaust branch pipe 43 is generally manufactured by a galvanized spiral duct.

The soil waste gas extraction unit 1 is mainly used for extracting waste gas containing pollutants volatilized from the heated polluted land. The soil waste gas extraction unit 1 comprises a first extraction pipe group 11, a second extraction pipe group 12, an extraction main pipe 13 and an extraction fan 14 communicated with the extraction main pipe 13, wherein one end of the first extraction pipe group 11 and one end of the second extraction pipe group 12 are respectively communicated with the extraction main pipe 13, a plurality of extraction pipes I11a in the first extraction pipe group 11 are horizontally embedded at intervals at the soil surface position of the polluted land block and are positioned right above the heating pipe group 33, and certainly, a plurality of extraction pipes I11a in the first extraction pipe group II can be horizontally embedded at intervals at the soil surface position of the polluted and heated soil. Namely, the same polluted land can be extracted, and the extracted waste gas is combusted to generate high-temperature fuel gas for carrying out back combustion heating on the same polluted land; the first extraction pipe group II can be arranged on a first pollution heating land, and high-temperature fuel gas obtained by burning extraction waste gas is used for heating a second pollution land, so that the pollution heating land of the extraction waste gas is associated with another pollution land to be heated; a plurality of extraction pipes II12a in the second extraction pipe group 12 are vertically embedded in the polluted land at intervals, an extraction inlet at the lower end of each extraction pipe II12a is arranged near the heating pipe 33a and is respectively located at the middle cold spot position of two adjacent heating pipes 33a, similarly, the second extraction pipe group 12 can also be located in the polluted land, so as to extract the waste gas generated on the polluted heating land, and then the extracted waste gas is combusted and heated to obtain high-temperature gas, and then the high-temperature gas is used to heat other polluted land to be heated. A plurality of extraction pipes I11a and extraction pipe II12a in fig. 1 are symmetrically arranged on both sides of the extraction main pipe 13. Of course, it is also possible to lay the upper and lower layers of horizontal extraction pipes I11a or the vertical extraction pipes II12a with different depths at different soil depth positions on the surface layer or shallow area of the soil.

The extraction pipe I11a is used for extracting the polluted gas on the surface layer of the soil and is processed by a carbon steel pipe. The longitudinal or transverse interval is 10-20cm, the width of the cutting seam is 1-2mm, the diameter of the cutting seam is 1/3 in the transverse direction, the longitudinal cutting seam is 90 degrees, the length of the cutting seam is 10-20cm, after the processing is finished, the outer surface of the cutting seam is wrapped with a 50-mesh stainless steel screen mesh to prevent the blockage of an extraction pipe, the buried polluted soil is about 50cm, quartz sand or gravel with the particle size of 2-4mm is paved around the cutting seam for filtering the waste gas of the soil and preventing the blockage of the extraction pipe, and the cutting seam-free vertical section comprises a surface extraction horizontal section with the cutting seam and a vertical section without the cutting seam, which is used for connecting a ground extraction main pipe.

The extraction pipe II12a is used for extracting the polluted gas in the deep layer of soil, is generally arranged at the middle cold spot position of the adjacent heating pipe to form convection heat conduction, improves the soil heating efficiency, is processed by carbon steel pipes, and is arranged vertically. The processing and installation method is the same as that of the extraction pipe I11a, and the cutting processing is not carried out when the extraction pipe is 100cm away from the ground, and the extraction pipe is used for connecting the ground extraction main pipe 13.

The extraction main pipe 13 is used for conveying waste gas extracted from the surface and the cold spot and is processed by a carbon steel pipe;

the extraction fan 14 is used for extracting the volatile waste gas of the pollutant after the polluted soil is heated for centralized treatment, and a roots fan is generally selected to provide power for an extraction system.

The gas-liquid separation unit 2 includes a heat exchanger 21, a cooling tower 22, and a gas-liquid separator 23, and the cooling tower 22 is connected to the heat exchanger 21 through a pipeline, so that high-temperature water after heat exchange is re-cooled and recycled, and cooling water is provided for the heat exchanger 21. The cooling water is consumed in the heat exchange process, and the automatic water replenishing device arranged on the cooling tower 22 automatically replenishes water. The extraction main pipe 13 is connected with the inlet end of the heat exchanger 21 and used for exchanging heat and reducing temperature for the extraction waste gas, the outlet end of the heat exchanger 21 is connected with the gas-liquid separator 23, and the extraction fan 14 is arranged at the air outlet of the gas-liquid separator 23. The heat exchanger 21 heats the contaminated soil to 90-100 ℃, the water content in the extracted waste gas increases, the extracted waste gas needs to be subjected to heat exchange and temperature reduction in order to better remove the pollutants in the waste gas and protect the extraction fan 14 (roots fan) from high-temperature operation, and the water content in the waste gas is reduced after the contaminated soil is heated to 100 ℃.

The gas-liquid separator 23 adopted in the present invention is preferably a two-stage gas-liquid separator, and comprises a first gas-liquid separator 231 and a second gas-liquid separator 232 connected in series, respectively, the first gas-liquid separator 231 receives the heat-exchanged extraction waste gas and performs gas-liquid separation on the heat-exchanged extraction waste gas, the second gas-liquid separator 232 further performs gas-liquid separation on the waste gas treated by the first gas-liquid separator 231, the separated waste gas enters the back combustion pipeline 31 through the extraction fan 14, and the cost separated by the two-stage gas-liquid separators is connected with the wastewater treatment equipment.

The first gas-liquid separator 231 is installed after the heat exchanger 21, and performs a first-stage gas-liquid separator on the off-gas, and delivers the separated off-gas to the second gas-liquid separator 232, and delivers the condensed waste water to the waste water treatment facility 24.

The second gas-liquid separator 232 is installed after the first gas-liquid separator 231, performs a two-stage gas-liquid separator on the exhaust gas, conveys the separated exhaust gas to the back-combustion heating unit 3, and conveys condensed wastewater to the wastewater treatment device 24.

The wastewater treatment apparatus 24 treats the wastewater collected by the gas-liquid separator 23.

The electrical control unit provides power supply, communication and monitoring control for the cooling tower 22, the wastewater treatment equipment 24, the extraction fan 14, the burner device 32 and other equipment of the system, and is a command center and a communication center of the units.

The soil extraction waste gas and the horizontal heating pipe are connected in series for use, the thermal desorption restoration backfire heating energy-saving system returns the soil extraction waste gas subjected to heat exchange and gas-liquid separation to the burner for burning, reduces air preheating by using the heat energy of the soil extraction waste gas, performs backfire treatment on the waste gas, and heats the polluted soil by using the heat energy of the waste gas, so that the heating energy is saved, the emission is reduced, and the restoration cost is reduced.

The utility model is suitable for in-situ thermal desorption restoration of the soil extraction waste gas of the vertical well heating plots and the heating pipes of the horizontal heating plots which are connected in series, and ex-situ pile thermal desorption or thermal desorption horizontal well heating restoration of the soil extraction waste gas of the plots and the horizontal heating pipes of the local plots which are connected in series.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are intended to be within the scope of the utility model.

Claims (8)

1. A thermal desorption restoration backfire heating energy-saving system comprises a soil waste gas extraction unit (1), a gas-liquid separation unit (2) and an electrical control unit, wherein the gas-liquid separation unit (2) is connected with the soil waste gas extraction unit (1) and forms an electrified control connection with the electrical control unit, and is characterized by further comprising a backfire heating unit (3) which comprises a backfire pipeline (31), a burner device (32) and a heating pipe set (33), one end of the backfire pipeline (31) is communicated with a waste gas output end in the gas-liquid separation unit (2), the other end of the backfire pipeline is connected with the burner device (32) and is used for mixing with gas entering the burner device (32) and then combusting, the heating pipe set (33) is horizontally embedded in soil of a polluted land block or positioned below an extraction pipe in the soil waste gas extraction unit (1), one end of the heating pipe set (33) is communicated with the high-temperature gas output end of the burner device (32), and the other end of the heating pipe set is output to the ground through a tail gas pipeline (4).

2. The thermal desorption repair flashback heating energy-saving system according to claim 1, wherein the heating tube set (33) is provided with a plurality of heating tubes (33a), each heating tube (33a) is horizontally embedded in the polluted land block at intervals, an inlet tube section of each heating tube (33a) adopts a stainless steel tube, an inlet end of each heating tube (33a) is respectively connected with the burner device (32), and an outlet tube section of each heating tube (33a) is a carbon steel tube.

3. The thermal desorption restoration and post-combustion heating energy-saving system according to claim 2, wherein the tail gas pipeline (4) comprises a tail gas fan (41), a tail gas main pipe (42) and a plurality of tail gas branch pipes (43) correspondingly connected with the outlet ends of the heating pipes (33a), each tail gas branch pipe (43) is correspondingly communicated with the tail gas main pipe (42), and the tail gas main pipe (42) extends out of the ground of the polluted land and is connected with the tail gas fan (41).

4. The thermal desorption restoration flashback heating energy-saving system according to claim 3, wherein the exhaust branch pipe (43) is a spiral duct.

5. The thermal desorption restoration flashback heating energy-saving system as set forth in claim 2, wherein the soil waste gas extraction unit (1) comprises a first extraction pipe group (11), a second extraction pipe group (12), an extraction main pipe (13) and an extraction fan (14) communicated with the extraction main pipe (13), one end of the first extraction pipe group (11) and one end of the second extraction pipe group (12) are respectively communicated with the extraction main pipe (13), a plurality of extraction pipes I (11a) in the first extraction pipe group (11) are horizontally spaced and buried at the soil surface level position of the polluted land block and are located right above the heating pipe group (33) or are horizontally spaced and buried at the soil surface level position of the polluted land block; a plurality of extraction pipes II (12a) in the second extraction pipe group (12) are vertically embedded in the polluted land block at intervals, and extraction inlets at the lower ends of the extraction pipes II (12a) are arranged close to the heating pipes (33a) and are respectively positioned at the middle cold spot positions of two adjacent heating pipes (33a) or are vertically embedded in the polluted land block at intervals.

6. The thermal desorption restoration and flashback heating energy-saving system as claimed in claim 5, wherein longitudinal or transverse slits are formed along the length direction of the extraction pipe I (11a), the interval between adjacent slits is 10-20cm, the width dimension of the slit is 1-2mm, the outer side surface of the extraction pipe I (11a) is wrapped with an anti-clogging screen, and quartz sand or gravel with the particle size of 2-4mm is laid around the extraction pipe I (11 a).

7. The thermal desorption restoration flashback heating energy-saving system as set forth in claim 6, wherein the extraction pipe I (11a) is horizontally buried in the area with the depth of 50cm of the contaminated land, and the extraction slits at the lower part of the extraction pipe II (12a) are located in the area with the depth of 100cm of the contaminated land.

8. The thermal desorption restoration flashback heating energy-saving system according to claim 7, wherein the extraction main pipe (13) is arranged on the ground, the gas-liquid separation unit (2) comprises a heat exchanger (21), a cooling tower (22) and a gas-liquid separator (23), the cooling tower (22) is connected with the heat exchanger (21) through a pipeline and used for cooling the heat exchanger (21), the extraction main pipe (13) is connected with an inlet end of the heat exchanger (21) and used for exchanging heat and cooling extraction waste gas, an outlet end of the heat exchanger (21) is connected with the gas-liquid separator (23), the extraction fan (14) is arranged at an outlet of the gas-liquid separator (23), and a liquid outlet of the gas-liquid separator (23) is connected with a wastewater treatment device (24).

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