A soil heating and volatile organic matter collection device

Abstract

A soil heating and volatile organic compound collection device comprises a ceramic shell, the end face of the ceramic shell is arranged perpendicular to the ground, a composite filter membrane is sealed in the cavity of the ceramic shell, and a gas collection cover is fixedly connected to the end face of the ceramic shell on the side away from the soil; the ceramic shell comprises a flexible heating element, and the flexible heating element is embedded in the inner end face of the ceramic breathable cover; the composite filter membrane comprises a water conducting layer, a heat insulating layer and a VOCs separation membrane, and the three are connected as a whole, and the heat insulating layer is sandwiched between the water conducting layer and the VOCs separation membrane; when the collection operation is started, the VOCs gas passes through the water conducting layer, the heat insulating layer and the VOCs separation membrane in sequence; the present invention is used in conjunction with a drilling rig and a measuring device to detect VOCs on site, and on the premise of improving the collection efficiency, it has more advantages such as wear resistance, impact resistance, high temperature resistance, and long service life; the device has a very high degree of structural integration, is easy to customize according to the size of the drilling rig, is simple to install, and can ensure working stability in different soil environments and different drilling rig working conditions.

Description

Technical Field

[0001] The invention relates to the technical field of soil pollution monitoring, and in particular to a soil heating and volatile organic matter collecting device. Background Art

[0002] Volatile Organic Compounds (hereinafter referred to as "VOCs") are a typical soil pollutant. With the rapid development of the petroleum and petrochemical industry and other chemical and pesticide production, a large amount of VOCs are discharged into the soil, changing the composition and structure of soil organic matter and aggravating soil pollution. How to effectively detect VOCs is a prerequisite for accelerating the solution to the problem of soil VOCs governance.

[0003] At present, VOCs detection methods mainly include post-sampling laboratory detection (also known as ex situ detection) and field detection (also known as in situ detection). The laboratory detection method is cumbersome and time-consuming, and only samples a few discrete locations. It cannot accurately assess the changes in soil pollution in the depth direction, which limits its application and development. At the same time, the on-site detection method has the advantages of better real-time, high efficiency and continuity, so it is considered to be a more advanced detection method and has been more widely studied and applied in recent years.

[0004] Chinese patent CN107084862B proposes a soil VOCs collection device, which has a structure of a heating element arranged in the middle of a drill bit, an air hole arranged on the annular surface of the drill bit tail, and the air hole covered by a waterproof and breathable membrane; the working principle is that under different soil conditions and working conditions, the drill rig carrying the VOCs collection device is drilled into the ground to a specified depth and heat the soil, and the VOCs volatilize and flow through the air hole to be analyzed by an online detection system, but its accuracy, reliability and service life will be affected to varying degrees: for example, the heating element and the gas channel are located at different soil depths, the heating position and the collection position are different, and the VOCs are different from each other. There is a certain height difference between the two positions, which makes it easy to collect VOCs in the soil outside the heating position, resulting in errors; the collection device is generally embedded in the side wall of the drill bit or drill rod, and its outer shell is in direct contact with the soil and should have good wear resistance; when the soil moisture content is high or the soil particles are small, the gas channel is easily blocked by liquid water or soil particles, reducing the collection efficiency; when the soil is firm, the drilling rig itself vibrates to a large extent, and the core component of the collection device—the VOCs separation membrane—is likely to be greatly deformed or even damaged; when the heating temperature is high and the drilling speed is fast, there are correspondingly higher requirements for the heat resistance and fatigue resistance of the collection device.

[0005] Existing collection devices only consider the functional requirements of gas collection, lack specific design and optimization in terms of accuracy, reliability, and service life. They are difficult to adapt to complex and changeable soil conditions and harsh working conditions, resulting in unsatisfactory results in actual collection work. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a soil heating and volatile organic compound collection device, which is used in conjunction with a drilling rig and measuring equipment to detect VOCs on site. On the premise of improving the collection efficiency, it has more advantages such as wear resistance, impact resistance, high temperature resistance, and long service life; the device has a high degree of structural integration, is easy to customize according to the size of the drilling rig, is simple to install, and can ensure working stability in different soil environments and different drilling rig working conditions.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A soil heating and volatile organic matter collection device comprises a ceramic shell 1, a composite filter membrane 2 and a gas collection cover 3. The end face of the ceramic shell 1 is arranged perpendicular to the ground, the composite filter membrane 2 is sealed in the cavity of the ceramic shell 1, and the gas collection cover 3 is fixedly connected to the end face of the ceramic shell 1 away from the soil.

[0009] The ceramic housing 1 comprises a ceramic breathable cover 10, a flexible heating element 11 and a ceramic barrel 12, wherein the flexible heating element 11 is embedded in the inner end surface of the ceramic breathable cover 10, and the ceramic breathable cover 10 and the ceramic barrel 12 are fixedly connected;

[0010] The composite filter membrane 2 includes a water-conducting layer 20, a heat-insulating layer 21 and a VOCs separation membrane 22, which are connected as a whole. The heat-insulating layer 21 is sandwiched between the water-conducting layer 20 and the VOCs separation membrane 22. The water-conducting layer 20 is close to the ceramic breathable cover 10, and the VOCs separation membrane 22 is close to the gas collection cover 3. After the collection operation is started, the VOCs gas passes through the water-conducting layer 20, the heat-insulating layer 21 and the VOCs separation membrane 22 in sequence.

[0011] The gas collection hood 3 is a thin-walled container with openings on both sides, which is combined with the ceramic shell 1 to form a larger gas storage cavity.

[0012] The ceramic breathable cover 10 includes a breathable cover plate 100 and an annular plug 101. The breathable cover plate 100 is provided with a plurality of inclined holes 102 which are parallel to each other and have an angle of 45° with the axis. The inner end surface is provided with a "loop curve-shaped" groove 103. The flexible heating element 11 is arranged in the groove 103. Two circular through holes are also provided on the side of the breathable cover plate 100. The wires of the flexible heating element 11 extend out of the circular through holes and are connected to a DC power supply. The annular plug 101 is interference fit with the inner wall of the ceramic barrel 12. A series of notches are provided on the end surface of the annular plug 101. The water-conducting layer 20 is nested in the notch and the end surfaces of the two are kept flush.

[0013] The groove 103 is designed in a specific shape according to the heating area and temperature requirements, and does not intersect with the inclined hole 102 in space.

[0014] The flexible heating element 11 is formed by etching a thin metal foil, which is pressed into the groove 103 of the ceramic breathable cover 10, and then wires are welded at the first outlet point 110 and the second outlet point 111, and finally a layer of epoxy cement is coated on the surface for insulation treatment.

[0015] The inner wall diameter of the ceramic barrel 12 changes once to form a step. On the side that cooperates with the ceramic breathable cover 10, the inner diameter of the ceramic barrel 12 is larger and equal to the outer diameter of the annular plug 101; the ceramic barrel 12 also includes a first flow channel 120 and a second flow channel 121. The first flow channel 120 is close to the ceramic breathable cover 10 and is used to export liquid water in the collection device; the second flow channel 121 is close to the composite filter membrane 2 and is used to accelerate the transmission of VOCs. The second flow channel 121 and the first flow channel 120 are independent of each other in space and are not connected to each other.

[0016] The first flow channel 120 is symmetrically arranged, and the symmetry plane is a plane passing through the axis of the ceramic barrel 12. One side of the symmetry plane is provided with a first air inlet hole 120-1, a first arc-shaped inner flow channel 120-2 and 12 first air outlet holes 120-3; the other side of the symmetry plane is provided with 12 water inlet holes 120-4, a second arc-shaped inner flow channel 120-5 and a water outlet hole 120-6, the first air outlet hole 120-3 has the same structure as the water inlet hole 120-4, and the first air inlet hole 120-1 has the same structure as the water outlet hole 120-6; the second flow channel 121 includes a second air inlet hole 121-1, an annular inner flow channel 121-2 and 8 second air outlet holes 121-3, the second air inlet hole 121-1 has the same structure as the first air inlet hole 120-1, and the second air outlet holes 121-3 are evenly distributed along the circumferential direction.

[0017] The water-conducting layer 20 includes a grid 201 cut into a circular shape and a capillary tube 200. The grid 201 is nested in the notch of the annular plug 101, and the end faces of the two parts remain flush. The grid 201 is hollow inside and has openings on the upper and lower sides. The openings are connected to the first air outlet 120-3 and the water inlet 120-4 of the ceramic body 12; the capillary tube 200 is arranged perpendicular to the grid 201.

[0018] The heat insulation layer 21 is made of porous heat insulation materials, including honeycomb heat storage body, foam ceramics, etc.

[0019] The VOCs separation membrane 22 is composited with a polymer membrane on the basis of a metal skeleton, wherein the metal skeleton is a porous lattice structure as a base membrane support and is manufactured using 3D printing technology. The polymer membrane is any dense polymer material that works using a dissolution-diffusion mechanism, and the thickness of the metal skeleton is greater than that of the polymer membrane.

[0020] The soil heating and volatile organic compound collection device is used in conjunction with a gas circulation device. The gas circulation device must provide two air flows, wherein the pressure of the first air flow is less than the pressure of the second air flow, and the output end of the gas circulation device is connected to the first air inlet 120-1 and the second air inlet 121-1; after the collection operation is started, the second air flow is blown in from the second air inlet 121-1, and blows VOCs to the outlet of the gas collection hood 3 through the eight second air outlets 121-3; after the drainage operation is started, the first air flow is blown in from the first air inlet 120-1, and blows the water inside the grille 201 to the water outlet 120-6, and is discharged to the outside or collected.

[0021] The fixed connection between the gas collecting hood 3 and the ceramic shell 1, and between the ceramic breathable cover 10 and the ceramic cylinder body 12 can prevent gas leakage, and the sealing ring is installed and locked with bolts.

[0022] The beneficial effects of the present invention are:

[0023] 1. The flexible heating element 11 is curled and covered on the inner end surface of the ceramic breathable cover 10. Compared with the general heating wire, it has a larger surface area, provides higher power density and more uniform heat distribution.

[0024] 2. Using the infiltration principle, the capillary 200 draws water into the flow channel in the grille 201. Together with the first airflow, the liquid water entering the collection device can be quickly discharged, thereby reducing the impact on VOCs gas detection and improving the sampling sensitivity of the equipment.

[0025] 3. The composite filter membrane 2 and the ceramic housing 1 have a close fit, with higher positioning accuracy, and can better adapt to the vibration environment during the movement of the drilling rig, and are less likely to move in position.

[0026] 4. The heat insulation effect of the heat insulation layer 21 improves the temperature environment of the VOCs separation membrane 22 during operation and prolongs its service life.

[0027] 5. When used in conjunction with the gas circulation device, the airflow passes through the gas channel on the ceramic shell 1, carrying VOCs and blowing them evenly toward the gas collection hood 3. Due to the large pressure difference between the inlet and outlet, the collection efficiency of VOCs is greatly accelerated.

[0028] 6. The supporting function of the metal skeleton in the VOCs separation membrane 22 absorbs energy through folding and deformation, thereby enhancing the mechanical properties of the membrane, being able to resist a certain degree of vibration and impact, and not being easily deformed or damaged.

[0029] 7. The device has a high degree of structural integration. The VOCs separation membrane 22 is manufactured using 3D printing technology and is easy to customize according to the size of the drilling rig. It can be used in conjunction with the drilling equipment and VOCs online detection system with only simple installation and fixation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall explosion of the present invention.

[0031] Figure 2 It is a schematic cross-sectional view of the overall structure of the present invention.

[0032] Figure 3 It is a schematic structural diagram of the ceramic breathable cover 10 and the flexible heating element 11 of the present invention.

[0033] Figure 4 It is a schematic diagram of assembling the ceramic breathable cover 10 and the water-conducting layer 20 of the present invention.

[0034] Figure 5 It is a schematic cross-sectional view of the ceramic barrel 12 of the present invention.

[0035] Figure 6 It is a schematic diagram of the structure of the first flow channel 120 and the second flow channel 121 of the present invention.

[0036] Figure 7 It is a schematic diagram of the structure of the water-conducting layer 20 of the present invention.

[0037] Figure 8 Schematic diagram of the structure of the VOCs separation membrane 22 of the present invention.

[0038] Fig. 9 This is a schematic diagram of the "gas collection" functional principle of the present invention.

[0039] Fig.10 for Fig. 9 A partial enlarged view to illustrate the principle of the "drainage" function. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0041] like Figure 1 As shown, a soil heating and volatile organic matter collection device includes a ceramic housing 1, a composite filter membrane 2 and a gas collection cover 3; Figure 2 As shown, the end face of the ceramic shell 1 is arranged perpendicular to the ground, the composite filter membrane 2 is pressed into the cavity of the ceramic shell 1, the gas collection cover 3 and the right end face of the ceramic shell 1 are locked with bolts, and the above connection positions are sealed with rubber rings.

[0042] like Figure 2 As shown, the ceramic housing 1 includes a ceramic breathable cover 10, a flexible heating element 11 and a ceramic barrel 12. The flexible heating element 11 is embedded in the inner end surface of the ceramic breathable cover 10. A sealing ring is placed between the ceramic breathable cover 10 and the ceramic barrel 12 and then locked with bolts.

[0043] like Figure 2As shown, the composite filter membrane 2 includes a water conducting layer 20, a heat insulating layer 21 and a VOCs separation membrane 22, which are connected as a whole. The heat insulating layer 21 is sandwiched between the water conducting layer 20 and the VOCs separation membrane 22. The water conducting layer 20 is close to the ceramic breathable cover 10 side, and the VOCs separation membrane 22 is close to the gas collection cover 3 side; the heat insulating layer 21 is made of porous heat insulating material, such as honeycomb heat storage body, foam ceramic, etc., which has good heat insulating effect without affecting the air permeability; after the collection operation is started, the VOCs gas passes through the water conducting layer 20, the heat insulating layer 21 and the VOCs separation membrane 22 in sequence.

[0044] like Figure 2 As shown, the gas collection hood 3 is a thin-walled container with openings on both sides, which is combined with the ceramic shell 1 to form a larger gas storage cavity. The outlet of the gas collection hood 3 is connected to the VOCs online detection system through a pipeline to transfer VOCs for analyzing the component content.

[0045] like Figure 3 As shown, the ceramic breathable cover 10 includes a breathable cover plate 100 and an annular plug 101. The annular plug 101 is installed on the inner side of the breathable cover plate 100; the breathable cover plate 100 is provided with a plurality of inclined holes 102 which are parallel to each other and have an angle of 45° with the axis, forming an "uphill slope". During the descent of the drilling rig, it is difficult for soil particles to pass through the inclined holes 102; the inner end surface of the breathable cover plate 100 is provided with a "loop curve-shaped" groove 103 for arranging the flexible heating element 11, which makes full use of the inner end surface space of the breathable cover plate 100. The groove 103 can be freely adjusted according to the heating area and temperature requirements to ensure that it does not intersect with the inclined hole 102 in space.

[0046] The flexible heating element 11 can be manufactured and installed as follows: the shape of the groove 103 is designed into CAD and transferred to a thin metal foil, a heating sheet is formed by etching the pattern, and after pressing it into the groove 103, wires are welded at the first outlet point 110 and the second outlet point 111, and finally a layer of epoxy cement is coated on the surface for insulation treatment.

[0047] like Figure 4 As shown, two circular through holes are arranged on the side of the breathable cover plate 100, and the wires of the flexible heating element 11 extend from the circular through holes and are connected to a DC power supply; the annular plug 101 is interference fit with the inner wall of the ceramic barrel 12, and a series of notches are arranged on the end face of the annular plug 101. The shape of the notches is designed according to the shape of the water-conducting layer 20, so that the water-conducting layer 20 can be nested in the notches and the end faces remain flush, thereby effectively avoiding the movement of the composite filter membrane 2 caused by the vibration of the drilling rig.

[0048] like Figure 5As shown, the inner wall diameter of the ceramic barrel 12 changes once to form a step, the inner diameter on the left side is larger than the inner diameter on the right side, and the inner diameter on the left side is equal to the outer diameter of the annular plug 101 of the ceramic breathable cover 10, so that the annular plug 101 can be inserted into the ceramic barrel 12 to cooperate and further compress the water-conducting layer 20; the ceramic barrel 12 also includes a first flow channel 120 and a second flow channel 121, the first flow channel 120 is close to the ceramic breathable cover 10, and is used to guide the liquid water in the collection device, and the second flow channel 121 is close to the composite filter membrane 2, and is used to accelerate the transmission of VOCs, and the second flow channel 121 and the first flow channel 120 are independent of each other in space and do not communicate with each other.

[0049] like Figure 5 , Figure 6 As shown, the first flow channel 120 is symmetrically arranged, and the symmetry plane is a plane passing through the axis of the ceramic barrel 12. A first air inlet hole 120-1, a first arc-shaped inner flow channel 120-2 and 12 first air outlet holes 120-3 are arranged on the upper side of the symmetry plane, forming a "one-in and multiple-out" gas channel; similarly, 12 water inlet holes 120-4, a second arc-shaped inner flow channel 120-5 and a water outlet hole 120-6 are arranged on the other side of the symmetry plane, forming a "multiple-in and one-out" liquid channel; the first air outlet hole 120-3 has the same structure as the water inlet hole 120-4, and the cross-section area of ​​both is 0.9mm 2 The first air inlet 120-1 has the same structure as the water outlet 120-6, and is a circular hole with an inner diameter of 3 mm.

[0050] The second flow channel 121 includes a second air inlet hole 121-1, an annular inner flow channel 121-2 and eight second air outlet holes 121-3. The second air inlet hole 121-1 has the same structure as the first air inlet hole 120-1, and the second air outlet holes 121-3 are evenly distributed along the circumferential direction.

[0051] like Figure 7 As shown, the water-conducting layer 20 includes a grid 201 cut into a circle and a capillary 200. The grid 201 is hollow inside and open on both sides. The capillary 200 is arranged perpendicular to the grid 201 and has a diameter of 0.8 mm. The distance between each two adjacent capillaries is no more than 3 mm, forming a large number of "L"-shaped flow channels.

[0052] like Figure 8 As shown, the VOCs separation membrane 22 is composited with a polymer membrane on the basis of a metal skeleton, wherein the metal skeleton is a porous lattice structure as a base membrane support and is manufactured using 3D printing technology. The polymer membrane is any dense polymer material that works using a dissolution-diffusion mechanism, and the thickness of the metal skeleton is greater than the thickness of the polymer membrane.

[0053] The basic unit of the porous lattice structure (also called the cell structure) is similar to the ball-and-stick model that characterizes the spatial structure of chemical molecules. Specifically, the upper and lower vertices are in the shape of a hemisphere, with the plane on the outside and the spherical surface on the inside. The total area of ​​the plane of the lattice structure accounts for no more than 25% of the total area of ​​the membrane. There are a large number of gaps inside to fill dense polymer materials, thereby ensuring the effect of separating VOCs. Dynamic folding will occur under impact loads, and large elastic deformation will occur inside the structure, thereby absorbing most of the impact energy. This enables the VOCs separation membrane 22 to obtain good vibration and impact resistance and is not easily damaged.

[0054] like Fig. 9 As shown, the soil heating and volatile organic compound collection device is used in conjunction with a gas circulation device, and the gas circulation device must provide two air flows, which can be nitrogen or other gases, wherein the pressure of the first air flow is less than the pressure of the second air flow; the output end of the gas circulation device is connected to the first air inlet 120-1 and the second air inlet 121-1 through a hose; after the collection operation is started, the second air flow is blown in from the second air inlet 121-1, enters the annular inner flow channel 121-2, and blows toward the outlet of the gas collection hood 3 through the eight second air outlets 121-3 carrying VOCs.

[0055] like Fig. 9 As shown, the upper and lower openings of the grille 201 are respectively connected to the first air outlet 120-3 and the water inlet 120-4 of the ceramic body 12. After the drainage operation is started, the first air flow is connected to the first air inlet 120-1, enters the first arc-shaped inner flow channel 120-2, and blows into the interior of the grille 201 through the first air outlet 120-3.

[0056] like Fig.10 As shown, when liquid water enters the cavity of the collection device or water vapor is liquefied in the cavity, due to the infiltration effect, the capillary 200 draws water into the grille 201, and flows downward along the "L"-shaped inner flow channel under the action of gravity. After the drainage operation is started, the first airflow blows the water inside the grille 201 from the water inlet hole 120-4 to the second arc-shaped inner flow channel 120-5 from top to bottom, and is discharged to the outside or collected through the water outlet hole 120-6.

[0057] The working principle of the present invention is:

[0058] The soil heating and volatile organic compound collection device is integrated into the drilling equipment, which can be the side wall of the drill bit or drill rod. When the work starts, the drill drills downward, and the impact and vibration at this time are very large. Since the composite filter membrane 2 has been completely fixed on the ceramic shell 1, the position displacement caused by the vibration of the drill is prevented; the presence of the metal skeleton in the VOCs separation membrane 22 will dynamically fold under the impact load, absorb most of the impact energy, and avoid large deformation or even damage to the membrane; soil particles are squeezed upward along the ceramic protective shell, and due to the large slope of the inclined hole 102, the soil particles can hardly enter the collection device; after reaching the height of the soil layer to be detected, the flexible heating element 11 starts to heat, and as the soil temperature rises, VOCs and other gases escape, all gases pass through the gaps in the water-conducting layer 20, and then pass through the holes in the heat-insulating layer 21. The heat-insulating layer 21 isolates most of the heat to ensure that the VOCs separation membrane 22 is effective, and finally only VOCs can pass through the polymer membrane of the VOCs separation membrane 22.

[0059] After heating the soil for a specified time, the collection operation can be started. The gas circulation device continuously blows the second air flow into the second air inlet 121-1, and carries VOCs to the outlet of the gas collection hood 3 through the eight second air outlets 121-3. Due to the large pressure difference between the inlet and outlet, the collection efficiency of VOCs is greatly accelerated, and the VOCs flowing out of the outlet of the gas collection hood 3 are transmitted to the online detection system to analyze the component content.

[0060] However, during the collection process, liquid water may enter the collection device, and the water-conducting layer 20 utilizes the wetting effect to enrich the water droplets at the opening of the capillary 200, and under the action of gravity, the water drops flow downward along the flow channel in the grille 201; after the drainage operation is turned on, the first airflow generated by the gas circulation device is connected to the first air inlet 120-1, and the water inside the grille 201 is blown to the water outlet 120-6, and discharged to the outside or collected; after the drainage operation is turned off, the first airflow is immediately turned off, and the second airflow is kept on, which does not affect the VOCs collection; the drainage operation is turned on or off according to the water inflow condition in the collection device. For example, a water immersion sensor can be set on the inner wall of the ceramic shell 1 to detect the water inflow condition.

[0061] After the VOCs online detection system obtains the analysis results, the collection operation is closed, the second airflow is immediately closed, the drilling depth into the soil layer is changed, and the above process is repeated until the end.

[0062] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A soil heating and volatile organic matter collection device, comprising a ceramic housing (1), a composite filter membrane (2) and a gas collection cover (3), characterized in that: The end face of the ceramic housing (1) is arranged perpendicular to the ground, the composite filter membrane (2) is sealed in the cavity of the ceramic housing (1), and the gas collection cover (3) is fixedly connected to the end face of the ceramic housing (1) away from the soil; The ceramic housing (1) comprises a ceramic breathable cover (10), a flexible heating element (11) and a ceramic barrel (12); the flexible heating element (11) is embedded in the inner end surface of the ceramic breathable cover (10); and the ceramic breathable cover (10) and the ceramic barrel (12) are fixedly connected; The composite filter membrane (2) comprises a water-conducting layer (20), a heat-insulating layer (21) and a VOCs separation membrane (22), the three of which are connected as a whole, the heat-insulating layer (21) is sandwiched between the water-conducting layer (20) and the VOCs separation membrane (22), the water-conducting layer (20) is close to the ceramic air-permeable cover (10) side, and the VOCs separation membrane (22) is close to the gas collection cover (3) side; after the collection operation is started, the VOCs gas passes through the water-conducting layer (20), the heat-insulating layer (21) and the VOCs separation membrane (22) in sequence; The gas collection hood (3) is a thin-walled container with openings on both sides, and is combined with the ceramic shell (1) to form a larger gas storage cavity.

2. The device according to claim 1, characterized in that: The ceramic breathable cover (10) comprises a breathable cover plate (100) and an annular plug (101); the breathable cover plate (100) is provided with a plurality of mutually parallel inclined holes (102) with an angle of 45° to the axis; the inner end surface is provided with a "loop curve-shaped" groove (103); the flexible heating element (11) is arranged in the groove (103); the side surface of the breathable cover plate (100) is also provided with two circular through holes; the wires of the flexible heating element (11) extend out of the circular through holes and are connected to a DC power supply; the annular plug (101) is interference-fitted with the inner wall of the ceramic barrel (12); a series of notches are provided on the end surface of the annular plug (101); the water-conducting layer (20) is nested in the notches and the end surfaces of the two are kept flush.

3. The device according to claim 2, characterized in that: The groove (103) is designed in a specific shape according to the heating area and temperature requirements, and does not intersect with the inclined hole (102) in space.

4. The device according to claim 1, characterized in that: The flexible heating element (11) is formed by etching a thin metal foil, which is pressed into the groove (103) of the ceramic breathable cover (10), and then wires are welded at the first outlet point (110) and the second outlet point (111), and finally a layer of epoxy cement is coated on the surface for insulation treatment.

5. The device according to claim 1, characterized in that: The inner wall diameter of the ceramic barrel (12) changes once to form a step. On the side that matches the ceramic breathable cover (10), the inner diameter of the ceramic barrel (12) is larger and is equal to the outer diameter of the annular plug (101). The ceramic barrel (12) also includes a first flow channel (120) and a second flow channel (121). The first flow channel (120) is close to the ceramic breathable cover (10) and is used to guide the liquid water in the collection device. The second flow channel (121) is close to the composite filter membrane (2) and is used to accelerate the transmission of VOCs. The second flow channel (121) and the first flow channel (120) are independent of each other in space and are not connected to each other.

6. The device according to claim 5, characterized in that: The first flow channel (120) is symmetrically arranged, and the symmetry plane is a plane passing through the axis of the ceramic barrel (12); one side of the symmetry plane is provided with a first air inlet hole (120-1), a first arc-shaped inner flow channel (120-2), and 12 first air outlet holes (120-3); the other side of the symmetry plane is provided with 12 water inlet holes (120-4), a second arc-shaped inner flow channel (120-5), and a water outlet hole (120-6); the first air outlet holes (120- 3) has the same structure as the water inlet hole (120-4), and the first air inlet hole (120-1) has the same structure as the water outlet hole (120-6); the second flow channel (121) includes one second air inlet hole (121-1), an annular inner flow channel (121-2) and eight second air outlet holes (121-3), the second air inlet hole (121-1) has the same structure as the first air inlet hole (120-1), and the second air outlet holes (121-3) are evenly distributed along the circumferential direction.

7. The device according to claim 6, characterized in that: The water-conducting layer (20) comprises a grid (201) cut into a circular shape and a capillary tube (200); the grid (201) is nested in the notch of the annular plug (101), and the end faces of the two parts are kept flush; the grid (201) is hollow inside and has openings on the upper and lower sides, and the openings are connected to the first air outlet (120-3) and the water inlet (120-4) of the ceramic cylinder body (12); and the capillary tube (200) is arranged perpendicular to the grid (201).

8. The device according to claim 1, characterized in that: The heat insulation layer (21) is made of porous heat insulation material, including honeycomb heat storage body and foam ceramic.

9. The device according to claim 1, characterized in that: The VOCs separation membrane (22) is composited with a polymer membrane on the basis of a metal skeleton, wherein the metal skeleton is a porous lattice structure as a base membrane support and is manufactured using 3D printing technology, and the polymer membrane is any dense polymer material that works using a dissolution-diffusion mechanism, and the thickness of the metal skeleton is greater than the thickness of the polymer membrane.

10. The device according to claim 7, characterized in that: The soil heating and volatile organic compound collection device is used in conjunction with a gas circulation device. The gas circulation device must provide two air flows, wherein the pressure of the first air flow is lower than the pressure of the second air flow, and the output end of the gas circulation device is connected to the first air inlet (120-1) and the second air inlet (121-1); after the collection operation is started, the second air flow is blown in from the second air inlet (121-1), and blows through the eight second air outlets (121-3) to carry VOCs to the outlet of the gas collection hood (3); after the drainage operation is started, the first air flow is blown in from the first air inlet (120-1), and blows the water inside the grille (201) to the water outlet (120-6), and is discharged to the outside or collected.

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