Catalytic thermal desorption remediation device and method for organic contaminated soil

Abstract

The invention relates to a catalytic thermal desorption remediation device and method for organic contaminated soil. The catalytic thermal desorption remediation device comprises a rotationally arranged thermal desorption barrel, a metal screen which is annularly arranged in the thermal desorption barrel and wraps the thermal desorption barrel to form a reaction cavity, a heating structure arranged on the inner wall of the thermal desorption barrel, and a catalyst filled between the heating structure and the metal screen. The reaction cavity is used for containing organic contaminated soil, and the filling rate of the catalyst is 75-95%; the method comprises the following steps: starting a heating structure to control the temperature at reaction temperature; feeding the organic contaminated soil into a reaction cavity and sealing; and then the thermal desorption cylinder is alternately rotated forwards and backwards so as to promote the reaction to remove organic pollutants in the organic contaminated soil, and the treated soil is obtained. Compared with the prior art, the method can be used in the soil thermal desorption process, and the recovery rate, activity, use conditions and practical engineering application effect of the catalyst are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of soil treatment, and relates to a catalytic thermal desorption repair device and method for organically contaminated soil. Background Art

[0002] Thermal desorption technology is one of the most advanced technologies for treating polluted waste in the world. It has a good degradation effect on pesticide-contaminated soil, oil-containing waste from oil fields, and oil sludge at the bottom of tanks. In the current domestic engineering application cases, the thermal treatment equipment for thermal desorption is usually rotary kilns, screw-propelled pyrolysis furnaces and other devices. These devices are relatively mature in application, but they generally have problems such as high energy consumption, large engineering workload, and carbonization of soil organic matter after restoration, which hinder the further development of thermal desorption technology. Therefore, reducing energy consumption and reaction temperature during thermal desorption will become a key link in breaking through technical bottlenecks.

[0003] In the chemical industry, adding catalysts is often used to reduce the pyrolysis temperature. However, in this field, catalysts are generally added directly to the materials, and the catalyst and material are separated after the reaction is completed. This method is applied to the field of soil remediation, and catalyst recovery becomes one of the technical difficulties; in the process of catalytic thermal desorption, as heat transfer heat loss continues to occur, maintaining the catalyst activation temperature will also become a technical problem that cannot be ignored; as the clay soil continuously wraps the catalyst during the reaction, the efficiency of the catalyst will continue to decrease, and maintaining the catalyst activity will also limit the engineering application of this technology.

[0004] CN202010029407.2 relates to a multiphase catalytic reactor, including a raw water chamber, at least one purification reaction chamber is connected below the raw water chamber, a water purification chamber is arranged below the purification reaction chamber, and a water passage is arranged between the bottom of the purification reaction chamber and the bottom of the water purification chamber; the purification reaction chamber is a vertical cylindrical body, a catalyst layer is arranged in the purification reaction chamber, the catalyst is a photocatalytic catalyst or an electrocatalytic catalyst, and a light generating device or an electric generating device or an ultrasonic generating device or a heating device is arranged inside or outside the purification reaction chamber. The invention filters the raw water by setting a perforated water-passing plate in the filter layer, and a closed air chamber is formed between the perforated water-passing plate and the liquid surface of the purification reaction chamber. The water flows down along the inner wall of the purification reaction chamber to form a water curtain, and the ultraviolet light generating device irradiates the catalyst coating through the water curtain to generate a catalytic reaction, thereby achieving the disinfection of water. The device can be used for fluid catalysis, but it cannot meet the application of restoration engineering for solid soil remediation.

[0005] CN202310321759.9 proposes a reactor and its application, the reactor includes: a metal shell, which includes: a metal tube bundle, arranged in the metal shell; the metal tube bundle includes metal tubes arranged in parallel; the two ends of the metal tube are connected to the first surface and the second surface; the metal shell includes a material inlet and a material outlet; a shell side is formed between the shell and the outer wall of the metal tube; the inner cavity of the metal tube forms a tube side; the shell side is filled with a granular first catalyst, and / or the tube side is filled with a granular and / or honeycomb second catalyst; a plurality of metal fins are arranged on the outer wall of the metal tube; the metal fins separate the shell side into sections connected to each other; the first material is output from the material outlet after reacting in the section; and / or the second material reacts through the tube side; when the reactor is operating, the material flow direction in the metal tube bundle in the shell side is perpendicular to the length direction of the metal tube. The invention has high compactness, good heat and mass transfer performance, and low cost. However, in the field of soil remediation, the invention cannot automatically add and discharge soil from the reactor tube bundle, and the reactor tube bundle is dense and has many dead corners, which cannot meet the engineering application of soil remediation. Summary of the invention

[0006] The purpose of the present invention is to provide a catalytic desorption and remediation device and method for organic contaminated soil, which is used to ensure the catalyst recovery rate, activity, use conditions and actual engineering application effects during the soil thermal desorption process.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The first aspect of the present invention provides a catalytic thermal desorption remediation device for organic contaminated soil, comprising:

[0009] The thermal desorption cylinder is rotatably arranged and wrapped by a built-in ring-arranged metal screen to form a reaction chamber, wherein the reaction chamber is used to contain organically contaminated soil;

[0010] A heating structure is arranged on the inner wall of the thermal desorption cylinder;

[0011] The catalyst is filled between the heating structure and the metal screen; the accumulated volume of the catalyst is 75-95% of the volume between the heating structure and the metal screen.

[0012] Furthermore, a vent is provided on the reaction chamber.

[0013] Furthermore, a process port for loading the catalyst is provided through the side wall and the heating structure of the thermal desorption cylinder.

[0014] Furthermore, a catalyst gate is provided at the process port for closing or opening the process port.

[0015] Further,

[0016] Furthermore, a soil feed port for loading organic contaminated soil into the reaction chamber is provided through the side wall and the heating structure of the thermal desorption cylinder.

[0017] Furthermore, a feed inlet gate is provided on the soil feed inlet.

[0018] Furthermore, the metal screen is cylindrical and arranged in the thermal desorption cylinder.

[0019] Furthermore, the radial cross section of the metal screen is ratchet-shaped.

[0020] Furthermore, the device also includes a rotating motor for driving the thermal desorption cylinder to rotate.

[0021] Furthermore, the device also includes a bracket, and a bearing and an exhaust pipe arranged on the bracket;

[0022] The thermal desorption cylinder is rotatably mounted on the bracket via a bearing;

[0023] A vent is provided at the rotation center of the end surface of the thermal desorption cylinder, and the exhaust pipe extends to the vent and is dynamically sealed and connected to the vent.

[0024] The second aspect of the present invention provides a catalytic thermal desorption remediation method for organic contaminated soil based on the above device, comprising the following steps:

[0025] S1: Start the heating structure and control the temperature at the reaction temperature;

[0026] S2: sending the organic contaminated soil into the reaction chamber, and then sealing the reaction chamber;

[0027] S3: The thermal desorption cylinder is rotated alternately in forward and reverse directions to promote the reaction to remove organic pollutants in the organically contaminated soil to obtain treated soil.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) The present invention arranges a heating structure on the inner wall of the thermal desorption cylinder, and fills the catalyst between the inner wall of the heating structure and the reaction chamber containing the organic contaminated soil, thereby ensuring the optimal operating temperature of the catalyst and improving the catalytic efficiency.

[0030] 2) Since the catalyst in the present invention is not fully filled during use, friction and collision will occur during the rotation process, which will stimulate the activity of the catalyst and enhance the activation energy of the catalyst.

[0031] 3) The collision between the catalyst of the present invention and the metal screen can cause the soil on the metal screen to fall off, thereby regenerating the metal screen and ensuring the contact area between the catalyst and the soil.

[0032] 4) The present invention adopts a polygonal turbine structure, that is, a ratchet-shaped metal screen, which can increase the basic area of ​​soil and catalyst. At the same time, the forward and reverse rotations are combined during operation to avoid soil accumulation in dead corners and further adjust the contact area between soil and catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic structural diagram of a catalytic thermal desorption remediation device for organic contaminated soil in the present invention;

[0034] Figure 2 is a radial cross-sectional view of a thermal desorption cylinder;

[0035] Description of the markings in the figure:

[0036] 1-metal screen, 2-catalyst, 3-heating structure, 4-thermal desorption cylinder, 5-process port, 6-vent, 7-external exhaust pipe, 8-bearing, 9-bracket, 10-catalyst gate, 11-rotating motor, 12-soil feed port, 13-feed port gate. DETAILED DESCRIPTION

[0037] The directions (up, down, left, right, front, back) in the description of the present invention are for the convenience of intuitive description of the technical solution of the present invention, rather than that the present invention has a specific orientation structure and operation, and should not be understood as a limitation of the present invention.

[0038] In the description of the present invention, “one section”, “two sections”, “first level” and “second level” are only used to distinguish technical features and cannot be understood as the number of technical features indicated by the present invention or the order of the indicated technical features.

[0039] In the present invention, the terms "set", "install", "connect" and the like should be understood in a broad sense, and may refer to direct connection, indirect connection, fixed connection, detachable connection, or integral molding.

[0040] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0041] In the following implementation manners or examples, unless otherwise specified, functional components or structures are conventional components or conventional structures used in the art to achieve corresponding functions.

[0042] In order to achieve efficient thermal desorption and removal of pollutants from organic contaminated soil, this embodiment provides a catalytic desorption and remediation device for organic contaminated soil, such as Figure 1As shown, it includes: a rotatable thermal desorption cylinder 4, which is a concentric circle structure, a heating structure 3 is installed between the outer concentric circles, the heating temperature can be controlled wirelessly from the outside, a metal screen 1 is installed on the innermost side of the thermal desorption cylinder 4, a catalyst 2 is filled between the metal screen 1 and the inner wall of the concentric circle, process ports 5 for catalyst input and discharge are opened at the top and bottom of the thermal desorption cylinder 4, and the process port 5 is equipped with a catalyst gate 10 that can be opened and closed, and a soil feed port 12 and a feed port gate 13 are provided in the middle of the length direction of the thermal desorption cylinder 4, one end of the thermal desorption cylinder 4 is connected to a rotating motor 11, and the other end is connected to a bearing 8, the rotating motor 11 and the bearing 8 are fixed on a bracket 9 together, and a vent 6 is opened at the rotation center of one end of the thermal desorption cylinder 4 connected to the bearing 8, and the vent 6 is dynamically sealed with an external exhaust pipe 7.

[0043] The present invention ensures the catalytic performance of the catalyst by maintaining the working temperature of the catalyst, increasing the activation energy of the catalyst, etc., and ensures the contact area between the soil and the catalyst by combining the structure and the use method, thereby achieving the purpose of reducing the thermal desorption remediation temperature of organic contaminated soil remediation. At the same time, low-temperature remediation not only reduces energy consumption, but also ensures the organic matter content in the soil, reducing the impact of the remediation process on the soil fertilizer efficiency.

[0044] The metal screen 1 is a polygonal wheel structure, the mesh equivalent diameter is slightly smaller than the D50 particle size of the catalyst 2, and the metal screen is fixed to the side walls of the thermal desorption cylinder 4. Function: to ensure that the catalyst 2 does not enter the repaired soil, and at the same time, the presence of the catalyst 2 also prevents soil particles from entering the catalyst.

[0045] Catalyst 2 only has requirements on the shape of the catalyst, specifically, the catalyst is in the form of particles, the particle size range is 5-20mm, the gap with the inner wall of the filter housing is not less than 20mm, and the filling rate of the catalyst in the equipment ranges from 70-90%. Function: The particle size of the catalyst particles is roughly the same as that of the soil particles. At the contact interface between the two, the catalytic effect is better. At the same time, during use, the catalysts constantly rub and collide with each other, which will stimulate the activation performance of the catalyst and strengthen the catalytic effect.

[0046] Heating structure 3, heating temperature range is room temperature - 200 ℃, the specific temperature is determined by the catalyst use temperature. Function: can maintain the optimal activation temperature of the catalyst in real time to ensure the catalyst performance. Specifically, the heating structure 3 is a heating jacket arranged on the inner wall of the thermal desorption cylinder 4 and a heating coil arranged in the heating jacket.

[0047] The rotating motor 11 has a speed range of 3-100r / min, and can be set to rotate in a forward and reverse direction as needed. Function: Strengthen thermal desorption, strengthen catalytic operation, purify the contact surface between the catalyst and the soil, and avoid repair dead corners.

[0048] A catalytic thermal desorption remediation method for organic contaminated soil, implemented based on the above device, comprises the following steps:

[0049] (1) Open the upper catalyst gate 10, place the catalyst inside the equipment through the upper process port 5, and close the top catalyst gate 10 when the filling amount is met;

[0050] (2) Turn on the heating structure 3 and control the temperature to a suitable temperature for the catalyst;

[0051] (3) Open the feed inlet gate 13, let the organic contaminated soil enter the equipment through the soil feed inlet 12, and close the feed inlet gate 13;

[0052] (4) Turn on the rotating motor 11, adjust the rotation speed and reversal frequency and time, and the thermal desorption cylinder 4 rotates alternately in the forward and reverse directions during the working process;

[0053] (5) The gas inside the thermal desorption cylinder 4 is discharged through the vent 6 and the external exhaust pipe 7;

[0054] (6) After the repair is completed, the rotating motor 11 is adjusted to rotate counterclockwise and the speed is adjusted to 10-30r / min. After about 0.5-2 minutes, the rotating motor is turned off, the discharge port is rotated to the lowest position, and the feed port gate 13 on the soil feed port 12 is opened to discharge the repaired soil;

[0055] (7) Open the upper catalyst valve 10 and add a portion of the catalyst as needed;

[0056] (8) According to the repair needs, the lower catalyst valve 10 can be opened to discharge the existing catalyst, and the valve can be closed to wait for the addition of new catalyst.

[0057] Embodiment 1:

[0058] In order to achieve thermal desorption treatment of organic contaminated soil, this embodiment adopts the above-mentioned catalytic thermal desorption remediation device and method for organic contaminated soil to remediate organic contaminated soil of a contaminated plot in Baoshan District, Shanghai, which contains about 800 mg / kg of o-xylene, to a level below the screening value for Class II land use.

[0059] The thermal desorption cylinder 4 has a diameter of about 1.5 meters and a length of 3 meters.

[0060] According to the types of soil pollutants and remediation requirements, Ce-Mn / α-Fe2O3 catalyst (preparation method refers to Example 1 in CN117797828A) is used to make the catalyst into uniform particles with an equivalent diameter of about 8 mm. The total amount of catalyst used accounts for about 3% of the total mass of the remediated soil.

[0061] The metal screen 1 has a ratchet-shaped radial cross-section, and the mesh is circular with a diameter of about 6 mm and is fixed to the side walls of the thermal desorption cylinder 4 at both ends.

[0062] Before use, the catalyst is first added into the interlayer between the metal screen 1 and the heating structure 3, with a filling rate of about 85%, and the heating is turned on and the temperature is preheated to 60°C.

[0063] The specific usage includes the following steps:

[0064] (1) Open the upper catalyst gate 10, place the determined Ce-Mn / α-Fe2O3 catalyst in the interlayer between the metal mesh and the outer wall of the equipment through the upper process port 5, and close the top catalyst gate 10 when the filling amount reaches 85%;

[0065] (2) Turn on the heating structure, control the temperature to 120°C, and maintain a constant temperature;

[0066] (3) Open the feed gate 13, and let the organic contaminated soil enter the equipment through the soil feed port 12, with a filling rate of about 65%. After the filling is completed, close the feed gate 13;

[0067] (4) Turn on the rotating motor 11, the working procedure is to rotate clockwise at a speed of 5 r / min, rotate for 2 min, then rotate counterclockwise for 1 min, the counterclockwise rotation speed is 10 r / min, and then continue to rotate alternately clockwise and counterclockwise;

[0068] (5) The gas inside the thermal desorption cylinder 4 is discharged through the vent 6 and the external exhaust pipe 7;

[0069] (6) After the repair is completed, the rotating motor 11 is adjusted to rotate counterclockwise and the speed is adjusted to 30r / min. After about 2 minutes, the bottom of the cylinder is aligned with the discharge port, the rotating motor is turned off, and the feed port gate 13 on the soil feed port 12 is opened to discharge the repaired soil;

[0070] (7) Open the upper catalyst valve 10, check and find that no catalyst needs to be added, then continue to feed and repeat the above steps;

[0071] (8) Finally, after the repair work is completed, open the lower catalyst valve 10 to discharge the existing catalyst, close this valve, and wait for the new catalyst to be added again.

[0072] A third-party test showed that the concentration of o-xylene in the soil after remediation was 283 mg / kg, meeting the requirements for Class II land use.

[0073] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A catalytic thermal desorption remediation device for organic contaminated soil, characterized in that: include The thermal desorption cylinder (4) is rotatably arranged and is wrapped by a built-in annular metal screen (1) to form a reaction chamber, wherein the reaction chamber is used to contain organically contaminated soil; A heating structure (3) is arranged on the inner wall of the thermal desorption cylinder (4); The catalyst (2) is filled between the heating structure (3) and the metal screen (1); the accumulated volume of the catalyst (2) is 75-95% of the volume between the heating structure (3) and the metal screen (1).

2. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 1 is characterized in that: A process port (5) for loading the catalyst (2) is provided through the side wall of the thermal desorption cylinder (4) and the heating structure (3).

3. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 2 is characterized in that: A catalyst gate (10) is provided at the process port (5) for closing or opening the process port (5).

4. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 1 is characterized in that: A soil feed port (12) for loading organic contaminated soil into the reaction chamber is provided through the side wall of the thermal desorption cylinder (4) and the heating structure (3).

5. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 4 is characterized in that: The soil feed port (12) is provided with a feed port gate (13).

6. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 1 is characterized in that: The metal screen (1) is in a cylindrical shape and is arranged in a thermal desorption cylinder (4).

7. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 6 is characterized in that: The radial cross section of the metal screen (1) is in the shape of a ratchet.

8. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 1 is characterized in that: The device also includes a rotating motor (11) for driving the thermal desorption cylinder (4) to rotate.

9. The catalytic thermal desorption remediation device for organic contaminated soil according to claim 1 is characterized in that: The device also includes a bracket (9), and a bearing (8) and an exhaust pipe (7) arranged on the bracket (9); The thermal desorption cylinder (4) is rotatably mounted on a bracket (9) via a bearing (8); A vent (6) is provided at the rotation center of the end surface of the thermal desorption cylinder (4), and the exhaust pipe (7) extends to the vent (6) and is dynamically sealed to the vent (6).

10. A catalytic thermal desorption remediation method for organic contaminated soil based on the device according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Start the heating structure (3) and control the temperature at the reaction temperature; S2: sending the organic contaminated soil into the reaction chamber, and then sealing the reaction chamber; S3: The thermal desorption cylinder (4) is rotated alternately in forward and reverse directions to promote the reaction to remove organic pollutants in the organically contaminated soil, thereby obtaining treated soil; and the reaction gas generated in the reaction chamber is discharged through the vent (6) for treatment.

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