A device and method for remediating soil contaminated by mercury and polycyclic aromatic hydrocarbons

Abstract

This application discloses a device and method for remediating soil contaminated with mercury and polycyclic aromatic hydrocarbons (PAHs), relating to the technical field of contaminated soil remediation and treatment. The device not only effectively treats contaminated soil but also has the advantages of a simple structure, easy operation, and the ability to perform soil remediation and treatment on-site at the contamination site. The device comprises a thermal desorption chamber, a power chamber, a dust removal chamber, an air-cooled hydrocarbon removal chamber, a water-cooled mercury removal chamber, a water-cooled hydrocarbon removal chamber, an adsorption chamber, and a spray chamber. The thermal desorption chamber is capable of thermal desorption remediation of the soil; the power chamber is capable of transmitting gas; the dust removal chamber is capable of removing dust from the gas; the air-cooled hydrocarbon removal chamber is capable of removing polycyclic aromatic hydrocarbons (PAHs) with four or more rings from the gas; the water-cooled mercury removal chamber is capable of removing elemental mercury from the gas; the water-cooled hydrocarbon removal chamber is capable of removing polycyclic aromatic hydrocarbons with three or fewer rings; the adsorption chamber is capable of removing residual mercury vapor; and the spray chamber is capable of removing residual PAHs from the gas. This application also discloses a method for remediating soil contaminated with mercury and PAHs.

Description

Technical Field

[0001] The present application relates to the technical field of contaminated soil remediation and treatment, and in particular to a device and method for remediating soil contaminated by mercury and polycyclic aromatic hydrocarbons. Background Art

[0002] With the rapid development of society, many sites left behind by oil, timber, and tobacco processing enterprises after closure and relocation are contaminated with polycyclic aromatic hydrocarbons (PAHs). This type of soil is contaminated with both PAHs and heavy metals. PAHs are persistent organic pollutants that are toxic, carcinogenic, teratogenic, mutagenic, and difficult to degrade. Heavy metal contaminants are deposited into environmental media, where they enter and accumulate in organisms. Mercury, a typical heavy metal contaminant, can enter the food chain through plants and aquatic animals and rapidly transfer to higher trophic levels, ultimately harming human health through amplification within the food chain. Currently, commonly used remediation methods for soil contaminated with both mercury and PAHs include chemical remediation, bioremediation, solidification and stabilization, and thermal desorption, all of which are associated with high treatment costs.

[0003] The Chinese patent, "Combined Chemical-Microbial Remediation Method for Soil from Sites Contaminated with Polycyclic Aromatic Hydrocarbons and Heavy Metals" (Publication No. CN102941225A), discloses a remediation technology and process for soil contaminated with heavy metals and organic matter. Specifically, the remediation technology includes crushing and screening the contaminated soil, placing soil particles with a size of less than 2 mm in a blender; the remediation system setup includes adding a methyl β-cyclodextrin eluent to the blender; adjusting the reaction temperature to 50±2°C; and simultaneously adjusting the ultrasonic transmitter to 35kHz ultrasound for 30 minutes; continuous leaching: repeating the above steps for three consecutive leaching and remediation cycles; and deep remediation with degrading bacteria: inoculating the soil after continuous leaching and remediation with polycyclic aromatic hydrocarbon-degrading bacteria, adjusting the N / P ratio to 10:1, and continuing degradation for 90 to 140 days. The disadvantages of this technology are that the leaching process involves the use of heating and ultrasonic equipment, making it difficult and costly to implement in large-scale remediation projects. Summary of the Invention

[0004] The embodiments of the present application provide a device and method for remediating soil contaminated with mercury and polycyclic aromatic hydrocarbons, which can not only effectively treat the composite contaminated soil, but also have the advantages of simple structure, easy operation, and the ability to perform soil remediation on-site at the contamination site.

[0005] To achieve the above-mentioned objectives, on the one hand, an embodiment of the present application provides a device for remediating soil contaminated with mercury and polycyclic aromatic hydrocarbons, comprising a thermal desorption chamber, a power chamber, a dust removal chamber, an air-cooled hydrocarbon removal chamber, a water-cooled mercury removal chamber, a water-cooled hydrocarbon removal chamber, an adsorption chamber and a spray chamber, which are arranged in sequence from bottom to top; the thermal desorption chamber can perform thermal desorption remediation on the soil to be remediated; the power chamber can transmit the mixed gas generated in the thermal desorption chamber to the dust removal chamber; the dust removal chamber can remove dust from the mixed gas; the air-cooled hydrocarbon removal chamber can remove polycyclic aromatic hydrocarbons with four or more rings from the mixed gas treated by the dust removal chamber; the water-cooled mercury removal chamber can remove elemental mercury from the mixed gas treated by the air-cooled hydrocarbon removal chamber; the water-cooled hydrocarbon removal chamber can remove polycyclic aromatic hydrocarbons with three or less rings from the mixed gas treated by the water-cooled mercury removal chamber; the adsorption chamber can adsorb mercury vapor remaining in the mixed gas treated by the water-cooled hydrocarbon removal chamber; and the spray chamber can absorb polycyclic aromatic hydrocarbons remaining in the mixed gas treated by the adsorption chamber.

[0006] Furthermore, the thermal desorption chamber includes an outer shell, an insulation layer and a metal isolation net; the insulation layer is attached to the inner wall of the outer shell; a heating ring cavity is formed between the insulation layer and the metal isolation net; a soil cavity is formed inside the metal isolation net; a heating ring cavity air inlet connected to an external air source is provided on the side wall of the heating ring cavity; a first temperature controller and an electric heater are provided in the heating ring cavity; and an air-conducting spiral agitator is provided in the soil cavity.

[0007] Furthermore, the shell and the metal isolation net are both cylindrical and through-through, and are coaxially arranged; a soil feed port and a soil discharge port are provided on the side wall of the shell; and a sealing door is provided at the soil feed port.

[0008] Furthermore, the air-guiding spiral agitator includes a core shaft and a spiral agitator wheel arranged on the core shaft; the core shaft and the spiral agitator wheel are both hollow structures, and the interiors of the two are connected; the spiral agitator wheel is provided with a groove in the opposite direction of rotation, and the bottom of the groove is provided with an air inlet hole that allows the mixed gas in the soil cavity to enter; the upper end of the core shaft is provided with an exhaust port.

[0009] Furthermore, a drive motor and a fan are provided in the power chamber; the output end of the drive motor is connected to the air-guiding spiral agitator; the air inlet pipe of the fan is connected to the exhaust port of the air-guiding spiral agitator, and the exhaust pipe of the fan is connected to the entrance of the dust removal chamber.

[0010] Furthermore, the air-cooled hydrocarbon removal chamber is provided with a first condensation spiral tube and a first condensate discharge pipe; the bottom inlet of the first condensation spiral tube is connected to the outlet of the dust removal chamber; the first condensate discharge pipe is connected to the condensate outlet of the first condensation spiral tube; an air inlet of the air-cooled hydrocarbon removal chamber and an air outlet of the air-cooled hydrocarbon removal chamber are provided on the side wall of the air-cooled hydrocarbon removal chamber; the air inlet of the air-cooled hydrocarbon removal chamber and the air outlet of the air-cooled hydrocarbon removal chamber are relatively staggered; the air outlet of the air-cooled hydrocarbon removal chamber can be selectively connected to the air inlet of the heating ring cavity and the external air source; a second temperature controller is provided in the air-cooled hydrocarbon removal chamber; a second condensation spiral tube and a second condensate discharge pipe are provided in the water-cooled mercury removal chamber; the bottom inlet of the second condensation spiral tube is connected to the upper outlet of the first condensation spiral tube; the second cooling The condensate discharge pipe is connected to the condensate outlet of the second condensation spiral tube; a first cooling water inlet and a first cooling water outlet are provided on the side wall of the water-cooled mercury removal chamber; the first cooling water inlet and the first cooling water outlet are relatively staggered; a third temperature controller is provided in the water-cooled mercury removal chamber; a third condensation spiral tube and a third condensate discharge pipe are provided in the water-cooled hydrocarbon removal chamber; the bottom inlet of the third condensation spiral tube is connected to the upper outlet of the second condensation spiral tube; the third condensate discharge pipe is connected to the condensate outlet of the third condensation spiral tube; a second cooling water inlet and a second cooling water outlet are provided on the side wall of the water-cooled hydrocarbon removal chamber; the second cooling water inlet and the second cooling water outlet are relatively staggered; a fourth temperature controller is provided in the water-cooled hydrocarbon removal chamber.

[0011] Furthermore, the adsorption chamber is filled with an adsorbent having a strong adsorption effect on mercury vapor; or, a leaching liquid sprayer is provided at the top of the spray chamber, and a leaching liquid collector and a liquid storage tank are provided at the bottom of the spray chamber; the leaching liquid sprayer is capable of spraying carbon tetrachloride solution.

[0012] Furthermore, a demisting chamber is provided above the spray chamber, and a baffle demister is provided in the demisting chamber; an exhaust fan is provided on the top of the demisting chamber.

[0013] Furthermore, a plurality of rollers evenly distributed along the circumference of the thermal desorption chamber are provided at the bottom of the thermal desorption chamber.

[0014] On the other hand, the embodiment of the present application also provides a remediation method based on the above-mentioned mercury and polycyclic aromatic hydrocarbons composite contaminated soil remediation device, comprising the following steps: S1, placing the crushed and screened soil to be remediated into a thermal desorption chamber, controlling the temperature in the thermal desorption chamber to 550°C and maintaining it for 25 minutes, so that the mercury and polycyclic aromatic hydrocarbons in the soil are heated and desorbed into the air to form a mixed gas; S2, the power chamber drives the mixed gas generated in the thermal desorption chamber into the dust removal chamber; S3, the dust removal chamber removes dust from the mixed gas; S4, the mixed gas after dust removal enters the air-cooled hydrocarbon removal chamber, and controls the temperature in the air-cooled hydrocarbon removal chamber to 370°C. The polycyclic aromatic hydrocarbons with four or more rings in the gas are condensed and discharged; S5, the mixed gas treated in the air-cooled hydrocarbon removal chamber enters the water-cooled mercury removal chamber, and the temperature in the water-cooled mercury removal chamber is controlled to 350°C, so that the elemental mercury in the mixed gas is condensed and discharged; S6, the mixed gas treated in the water-cooled mercury removal chamber enters the water-cooled hydrocarbon removal chamber, and the temperature in the water-cooled hydrocarbon removal chamber is controlled to 330°C, so that the polycyclic aromatic hydrocarbons with three or less rings in the mixed gas are condensed and discharged; S7, the mixed gas treated in the water-cooled hydrocarbon removal chamber enters the adsorption chamber, and the residual mercury vapor is adsorbed; S8, the mixed gas treated in the adsorption chamber enters the spray chamber, and the residual polycyclic aromatic hydrocarbons are absorbed.

[0015] This application has the following beneficial effects:

[0016] 1. The mercury and polycyclic aromatic hydrocarbons composite contaminated soil remediation device of the embodiment of the present application has a simple structure and does not require expensive equipment such as ultrasonic instruments. It has the advantages of low manufacturing cost and easy operation.

[0017] 2. The mercury and polycyclic aromatic hydrocarbons composite contaminated soil remediation device of the embodiment of the present application can perform soil remediation and treatment on-site at the contaminated site, without the need to transport the soil to be remediated to a treatment site, thus saving costs.

[0018] 3. The mercury and polycyclic aromatic hydrocarbons composite contaminated soil remediation device of the embodiment of the present application connects the air outlet of the air-cooled hydrocarbon removal chamber with the air inlet pipe of the heating ring cavity, recovers and utilizes the waste heat generated by the air-cooled hydrocarbon removal chamber, and saves energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 This is a schematic diagram of the structure of the mercury and polycyclic aromatic hydrocarbons composite contaminated soil remediation device according to an embodiment of the present application;

[0021] Figure 2 This is a cross-sectional view of the spiral stirring wheel in the mercury and polycyclic aromatic hydrocarbons complex contaminated soil remediation device in an embodiment of the present application. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0023] In the description of this application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0024] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0025] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0026] Reference Figure 1 An embodiment of the present application provides a mercury and polycyclic aromatic hydrocarbons composite contaminated soil remediation device, comprising a thermal desorption chamber 1, a power chamber 2, a dust removal chamber 3, an air-cooled hydrocarbon removal chamber 4, a water-cooled mercury removal chamber 5, a water-cooled hydrocarbon removal chamber 6, an adsorption chamber 7, a spray chamber 8 and a demisting chamber 9, which are arranged in sequence from bottom to top.

[0027] The thermal desorption chamber 1 includes a housing 11, an insulation layer 12, and a metal isolation screen 13. Both the housing 11 and the metal isolation screen 13 are vertical cylindrical and coaxially arranged. To enhance strength, the housing 11 is constructed of stainless steel. A soil feed port 111 is provided at the upper sidewall of the housing 11, where a slidable sealed door is located. A switchable soil discharge port 112 is provided at the lower sidewall of the housing 11. This facilitates feeding while preventing heat dissipation and contamination.

[0028] A thermal insulation layer 12 is attached to the inner wall of the outer shell 11. This layer is made of a ceramic fiber layer with excellent thermal insulation properties. A heating ring cavity 14 is formed between the thermal insulation layer 12 and the metal isolation mesh 13, and a soil cavity 15 is formed within the metal isolation mesh 13. This improves the thermal desorption chamber 1's thermal insulation performance and prevents large particles in the soil to be remediated from entering the heating ring cavity 14.

[0029] A heating ring cavity air inlet 141 is provided on the side wall of the heating ring cavity 14. A heating ring cavity air inlet pipe 16 connected to the external atmosphere is provided at the heating ring cavity air inlet 141. A first temperature controller (not shown) and a plurality of electric heaters 17 are provided in the heating ring cavity 14. The first temperature controller is electrically connected to the heater 17. The heater 17 heats the air entering the heating ring cavity 14. The first temperature controller regulates the temperature of the heating ring cavity 14 to 550°C by controlling the start and stop of the heater 17. The hot air then passes through the metal isolation mesh 13 into the soil cavity 15 to heat the soil in the soil cavity 15. The desorption and remediation time of the contaminated soil in the soil cavity 15 is 25 minutes.

[0030] In order to allow the mixed gas containing mercury and polycyclic aromatic hydrocarbons desorbed from the soil to quickly enter the dust removal chamber 3, a gas-guiding spiral stirrer 18 is coaxially provided in the soil inner cavity 15. The gas-guiding spiral stirrer 18 includes a core shaft 181 and a spiral stirring wheel 182 wound around the core shaft 181. The core shaft 181 and the spiral stirring wheel 182 are both hollow structures, and the interiors of the two are connected. Figure 2 The spiral stirring wheel 182 is provided with a groove in the opposite direction of rotation, and a plurality of air inlet holes 183 are provided on the bottom of the groove to allow the mixed gas in the soil cavity 15 to enter. Figure 1 , the upper end of the core shaft 181 forms an exhaust port.

[0031] Thus, the air-conducting spiral agitator 18 stirs and mixes the soil, heating the mercury and polycyclic aromatic hydrocarbons in the soil and desorbing them into the air. Furthermore, to facilitate transport, the bottom of the thermal desorption chamber 1 is equipped with four rubber rollers 19 evenly distributed along the circumference of the chamber.

[0032] Continue to refer to Figure 1, the power chamber 2 is connected to the upper part of the thermal desorption chamber 2. The outer shape of the power chamber 2 is also cylindrical. A drive motor 21 and a fan 22 are axially arranged in the power chamber 2. Among them, the lower output end of the drive motor 21 is connected to the core shaft 181 of the air-guiding spiral agitator 18. The air inlet pipe of the fan 22 is connected to the exhaust port on the upper part of the air-guiding spiral agitator 18, and the exhaust pipe of the fan 22 is connected to the entrance of the dust removal chamber 3. Thus, the drive motor 21 can drive the air-guiding spiral agitator 18 to rotate, suck the mixed gas into the cavity of the air-guiding spiral agitator 18, and then the fan 22 transports the mixed gas to the dust removal chamber 3.

[0033] The dust removal chamber 3 is connected to the upper portion of the power chamber 2. A bag dust collector 31 is provided in the dust removal chamber 3 to remove dust from the mixed gas entering the dust removal chamber 3. The inlet of the bag dust collector 31 is connected to the exhaust pipe of the ventilator 22, and the outlet is connected to the ventilation and cooling hydrocarbon removal chamber 4.

[0034] The air-cooled hydrocarbon removal chamber 4 is connected to the upper portion of the dust removal chamber 3. A first condensation coil 41 and a first condensate discharge pipe 42 are provided in the air-cooled hydrocarbon removal chamber 4. The first condensation coil 41 extends vertically, and the first condensate discharge pipe 42 extends horizontally. The first condensation coil 41 includes a bottom inlet, a condensate outlet, and a top outlet. The bottom inlet of the first condensation coil 41 is connected to the outlet of the bag filter 31, the condensate outlet of the first condensation coil 41 is connected to the inlet of the first condensate discharge pipe 42, and the top outlet of the first condensation coil 41 is connected to the water-cooled mercury removal chamber 5. The outlet of the first condensate discharge pipe 42 is connected to the outside of the air-cooled hydrocarbon removal chamber 4.

[0035] An air-cooled hydrocarbon removal chamber air inlet 43 and an air-cooled hydrocarbon removal chamber air outlet 44 are also provided on the side wall of the air-cooled hydrocarbon removal chamber 4. The air-cooled hydrocarbon removal chamber air inlet 43 is located at the lower part of the side wall of one side of the air-cooled hydrocarbon removal chamber 4, and the air-cooled hydrocarbon removal chamber air outlet 44 is arranged on the side opposite to the air-cooled hydrocarbon removal chamber air inlet 43, and is arranged near the top. The air-cooled hydrocarbon removal chamber air outlet 43 can be selectively connected to the heating ring cavity air inlet pipe 16 or the outside air. In this way, the air with waste heat generated in the air-cooled hydrocarbon removal chamber 4 can enter the heating ring cavity 14 for waste heat recovery and utilization. Compared with directly entering the atmosphere at normal temperature, air with waste heat can save energy. A second temperature controller (not shown in the figure) for adjusting the temperature in the cavity is provided in the air-cooled hydrocarbon removal chamber 4. It should be noted that valves are provided on the pipe for entering the outside air and the pipe for the heating ring cavity air inlet pipe 16. The second temperature controller is electrically connected to the valve on the air inlet duct. By controlling the opening of the valve at the air inlet through the second temperature controller and adjusting the amount of fresh air entering, the temperature in the air-cooled hydrocarbon removal chamber can be adjusted to 370°C, so that the polycyclic aromatic hydrocarbons with four or more rings in the mixed gas are condensed and changed from gas to liquid, and then received and discharged by the first condensate discharge pipe 42.

[0036] The water-cooled mercury removal chamber 5 is connected to the upper portion of the air-cooled hydrocarbon removal chamber 4 and has the same structure as the air-cooled hydrocarbon removal chamber 4. Specifically, a second condensation coil 51 and a second condensate drain pipe 52 are provided within the water-cooled mercury removal chamber 5. The bottom inlet of the second condensation coil 51 communicates with the upper outlet of the first condensation coil 41. The condensate outlet of the second condensation coil 51 communicates with the second condensate drain pipe 52. The fixed inlet of the second condensation coil 51 communicates with the inlet of the water-cooled hydrocarbon removal chamber 6. The outlet of the second condensate drain pipe 52 communicates with the exterior of the water-cooled mercury removal chamber 5.

[0037] A first cooling water inlet 53 and a first cooling water outlet 54 are provided on the side wall of the water-cooled mercury removal chamber 5. The first cooling water inlet 53 is located at the lower portion of the side wall of one side of the water-cooled mercury removal chamber 5, and the first cooling water outlet 54 is provided on the side opposite to the first cooling water inlet 53, and is provided near the top. A third temperature controller (not shown) is provided in the water-cooled mercury removal chamber 5. It should be noted that valves are provided at both the first cooling water inlet 53 and the first cooling water outlet 54. The third temperature controller is electrically connected to the valve on the water inlet pipe. By regulating the amount of cooling water entering, the temperature in the water-cooled mercury removal chamber 5 can be regulated to 350°C, causing the elemental mercury in the mixed gas to condense and change from gas to liquid, which is then received and discharged by the second condensate discharge pipe 52.

[0038] The water-cooled hydrocarbon removal chamber 6 is connected to the upper portion of the water-cooled mercury removal chamber 5 and has the same structure as the air-cooled hydrocarbon removal chamber 4. Specifically, a third condensation coil 61 and a third condensate discharge pipe 62 are provided within the water-cooled hydrocarbon removal chamber 6. The bottom inlet of the third condensation coil 61 communicates with the upper outlet of the second condensation coil 51, and the condensate outlet of the third condensation coil 61 communicates with the third condensate discharge pipe 62. The top outlet of the third condensation coil 61 communicates with the second cooling water inlet and outlet provided on the sidewall of the water-cooled hydrocarbon removal chamber 6, which are connected to the inlet of the adsorption chamber 7. The outlet of the third condensate discharge pipe 62 communicates with the exterior of the water-cooled hydrocarbon removal chamber 6.

[0039] A second cooling water inlet 63 and a second cooling water outlet 64 are provided on the side wall of the water-cooled hydrocarbon removal chamber 6. The second cooling water inlet 63 is located at the lower part of the side wall of one side of the water-cooled hydrocarbon removal chamber 6, and the second cooling water outlet 64 is provided on the side opposite to the second cooling water inlet 63, and is provided close to the top. A fourth temperature controller (not shown in the figure) is provided in the water-cooled hydrocarbon removal chamber 6. It should be noted that valves are provided at the second cooling water inlet 63 and the second cooling water outlet 64. The fourth temperature controller is electrically connected to the valve on the water inlet pipe, and by regulating the amount of cooling water entering, the temperature in the water-cooled hydrocarbon removal chamber 6 can be regulated to 330°C, so that the three-ring and less polycyclic aromatic hydrocarbons in the mixed gas are condensed and changed from gas to liquid, and then received and discharged by the third condensate discharge pipe 62.

[0040] Adsorption chamber 7 is connected to the upper portion of water-cooled hydrocarbon removal chamber 6. It is filled with manganese dioxide granules. Manganese dioxide granules have a strong adsorption effect on mercury vapor, capable of absorbing any remaining mercury vapor in the mixed gas after treatment in water-cooled hydrocarbon removal chamber 6. During use, the dynamic adsorption capacity of the adsorbent must be regularly tested. When the dynamic adsorption capacity drops to 80% of the designed value, the adsorbent must be replaced.

[0041] The spray chamber 8 is connected to the upper portion of the adsorption chamber 7. The top of the spray chamber 8 is equipped with an eluent sprayer 81, and the lower portion is equipped with an eluent collector 82 and a liquid reservoir 83. The liquid reservoir 83 is located near the bottom of the spray chamber 8. The eluent sprayer 81 sprays a carbon tetrachloride solution, which absorbs residual polycyclic aromatic hydrocarbons (PAHs) in the mixed gas after treatment in the adsorption chamber 7. The eluent collector 82 collects the reacted carbon tetrachloride solution and accumulates it in the liquid reservoir 83.

[0042] Attached to the top of the spray chamber 8 is a demisting chamber 9 equipped with a baffled demister 91. The top of the chamber is conical, with an exhaust fan 92 located at its highest point. This fan draws air upward from the entire repair system, intercepting any droplets in the air within the chamber. Finally, clean air is discharged through the exhaust fan 92.

[0043] On the other hand, an embodiment of the present application further provides a method for remediating soil contaminated by mercury and polycyclic aromatic hydrocarbons, comprising the following steps:

[0044] Step 1: The crushed and screened soil to be repaired is placed into the soil cavity 15 through the soil feed port 111, and the electric heater is controlled to heat the air. The first temperature controller adjusts the temperature in the thermal desorption chamber 1 to 550°C. Under the suction and exhaust action of the fan 22 and the exhaust fan 92, the hot air enters the soil cavity 15 through the metal isolation mesh 13 and heats the soil. The desorption and repair time of the soil to be repaired in the soil cavity 15 is 25 minutes.

[0045] Step 2: The motor 21 starts and drives the air-guiding spiral stirrer 18 to stir and mix the soil. The mercury and polycyclic aromatic hydrocarbons in the soil are heated and desorbed into the air, enter the core shaft 181 through the air inlet 183 on the spiral stirring wheel 182, and enter the dust removal chamber 3 under the action of the fan 22.

[0046] Step 3: The bag filter 31 removes dust from the mixed gas.

[0047] Step 4: The mixed gas after dust removal enters the air-cooled hydrocarbon removal chamber 4. The second temperature controller adjusts the temperature in the air-cooled hydrocarbon removal chamber 4 to 370° C. to condense and discharge the polycyclic aromatic hydrocarbons with four or more rings in the mixed gas.

[0048] Step 5: The mixed gas after being treated in the air-cooled hydrocarbon removal chamber 4 enters the water-cooled mercury removal chamber 5. The third temperature controller adjusts the temperature in the water-cooled mercury removal chamber 5 to 350° C. to condense and discharge the elemental mercury in the mixed gas.

[0049] Step 6: The mixed gas treated in the water-cooled mercury removal chamber 5 enters the water-cooled hydrocarbon removal chamber 6. The fourth temperature controller adjusts the temperature in the water-cooled hydrocarbon removal chamber 6 to 330° C. to condense and discharge the three-ring and lower polycyclic aromatic hydrocarbons in the mixed gas.

[0050] Step 7: The mixed gas treated in the water-cooled hydrocarbon removal chamber 6 enters the adsorption chamber 7, and the residual mercury vapor is adsorbed by the adsorbent.

[0051] Step 8: The mixed gas treated in the adsorption chamber 7 enters the spray chamber 8, and the residual polycyclic aromatic hydrocarbons are absorbed by the eluent.

[0052] Step 9: The mixed gas treated by the spray chamber 8 enters the demisting chamber 10 , where the liquid droplets in the gas are intercepted and the clean gas is discharged by the exhaust fan 92 .

[0053] Step 10: The repaired soil is discharged from the soil discharge port 112 and backfilled into the original location.

[0054] The above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A device for remediating soil contaminated by mercury and polycyclic aromatic hydrocarbons, characterized in that: It includes a thermal desorption chamber, a power chamber, a dust removal chamber, an air-cooled hydrocarbon removal chamber, a water-cooled mercury removal chamber, a water-cooled hydrocarbon removal chamber, an adsorption chamber and a spray chamber, which are arranged in sequence from bottom to top; The thermal desorption chamber can perform thermal desorption remediation on the soil to be remediated; The power chamber is capable of transmitting the mixed gas generated in the thermal desorption chamber into the dust removal chamber; The dust removal chamber is capable of removing dust from the mixed gas; The air-cooled hydrocarbon removal chamber can remove polycyclic aromatic hydrocarbons with four or more rings from the mixed gas after being treated in the dust removal chamber; The water-cooled mercury removal chamber can remove elemental mercury from the mixed gas treated by the air-cooled hydrocarbon removal chamber; The water-cooled hydrocarbon removal chamber can remove polycyclic aromatic hydrocarbons (PAHs) with three rings or less from the mixed gas treated by the water-cooled mercury removal chamber. The adsorption chamber is capable of adsorbing the mercury vapor remaining in the mixed gas after being treated by the water-cooled hydrocarbon removal chamber; The spray chamber can absorb the polycyclic aromatic hydrocarbons remaining in the mixed gas after being treated by the adsorption chamber.

2. The mercury and polycyclic aromatic hydrocarbons composite contaminated soil remediation device according to claim 1 is characterized in that: The thermal desorption chamber includes an outer shell, an insulation layer and a metal isolation net; the insulation layer is attached to the inner wall of the outer shell; a heating ring cavity is formed between the insulation layer and the metal isolation net; a soil cavity is formed inside the metal isolation net; a heating ring cavity air inlet connected to an external air source is provided on the side wall of the heating ring cavity; a first temperature controller and an electric heater are provided in the heating ring cavity; and an air-conducting spiral agitator is provided in the soil cavity.

3. The mercury and polycyclic aromatic hydrocarbons combined contaminated soil remediation device according to claim 2 is characterized in that: The shell and the metal isolation net are both cylindrical and penetrate from top to bottom, and are coaxially arranged; a soil feed port and a soil discharge port are provided on the side wall of the shell; and a sealing door is provided at the soil feed port.

4. The mercury and polycyclic aromatic hydrocarbons combined contaminated soil remediation device according to claim 2 is characterized in that: The air-guiding spiral agitator includes a core shaft and a spiral agitator wheel arranged on the core shaft; the core shaft and the spiral agitator wheel are both hollow structures, and the interiors of the two are connected; the spiral agitator wheel is provided with a groove in the opposite direction of rotation, and the bottom of the groove is provided with an air inlet hole that allows the mixed gas in the soil cavity to enter; the upper end of the core shaft is provided with an exhaust port.

5. The mercury and polycyclic aromatic hydrocarbons combined contaminated soil remediation device according to claim 2, characterized in that: A drive motor and a fan are provided in the power chamber; the output end of the drive motor is connected to the air-guiding spiral stirrer; the air inlet pipe of the fan is connected to the exhaust port of the air-guiding spiral stirrer, and the exhaust pipe of the fan is connected to the entrance of the dust removal chamber.

6. The mercury and polycyclic aromatic hydrocarbons combined contaminated soil remediation device according to claim 1 is characterized in that: The air-cooled hydrocarbon removal chamber is provided with a first condensation spiral tube and a first condensate discharge pipe; the bottom inlet of the first condensation spiral tube is connected to the outlet of the dust removal chamber; the first condensate discharge pipe is connected to the condensate outlet of the first condensation spiral tube; an air inlet for the air-cooled hydrocarbon removal chamber and an air outlet for the air-cooled hydrocarbon removal chamber are provided on the side wall of the air-cooled hydrocarbon removal chamber; the air inlet for the air-cooled hydrocarbon removal chamber and the air outlet for the air-cooled hydrocarbon removal chamber are relatively staggered; the air outlet for the air-cooled hydrocarbon removal chamber can be selectively connected to the air inlet of the heating ring cavity and an external air source; a second temperature controller is provided in the air-cooled hydrocarbon removal chamber; The water-cooled mercury removal chamber is provided with a second condensation coil and a second condensate discharge pipe; the bottom inlet of the second condensation coil is connected to the upper outlet of the first condensation coil; the second condensate discharge pipe is connected to the condensate outlet of the second condensation coil; a first cooling water inlet and a first cooling water outlet are provided on the side wall of the water-cooled mercury removal chamber; the first cooling water inlet and the first cooling water outlet are relatively staggered; a third temperature controller is provided in the water-cooled mercury removal chamber; A third condensation coil and a third condensate discharge pipe are provided in the water-cooled hydrocarbon removal chamber; the bottom inlet of the third condensation coil is connected to the upper outlet of the second condensation coil; the third condensate discharge pipe is connected to the condensate outlet of the third condensation coil; a second cooling water inlet and a second cooling water outlet are provided on the side wall of the water-cooled hydrocarbon removal chamber; the second cooling water inlet and the second cooling water outlet are relatively staggered; a fourth temperature controller is provided in the water-cooled hydrocarbon removal chamber.

7. The mercury and polycyclic aromatic hydrocarbons combined contaminated soil remediation device according to claim 1 is characterized in that: The adsorption chamber is filled with an adsorbent having a strong adsorption effect on mercury vapor; or, a leaching liquid sprayer is provided on the top of the spray chamber, and a leaching liquid collector and a liquid storage tank are provided at the bottom of the spray chamber; the leaching liquid sprayer can spray carbon tetrachloride solution.

8. The mercury and polycyclic aromatic hydrocarbons combined contaminated soil remediation device according to claim 1 is characterized in that: A demisting chamber is further provided above the spray chamber, wherein a baffle demister is provided in the demisting chamber; and an exhaust fan is provided on the top of the demisting chamber.

9. The mercury and polycyclic aromatic hydrocarbons combined contaminated soil remediation device according to claim 1, characterized in that: The bottom of the thermal desorption chamber is provided with a plurality of rollers evenly distributed along the circumference of the thermal desorption chamber.

10. A method for repairing soil contaminated by mercury and polycyclic aromatic hydrocarbons based on the device for repairing soil contaminated by mercury and polycyclic aromatic hydrocarbons according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Place the crushed and sieved soil to be remediated into a thermal desorption chamber, control the temperature in the thermal desorption chamber to 400-550°C and maintain it for 20-30 minutes, so that the mercury and polycyclic aromatic hydrocarbons in the soil are heated and desorbed into the air to form a mixed gas; S2. The power chamber drives the mixed gas generated in the thermal desorption chamber into the dust removal chamber; S3, the dust removal chamber removes dust from the mixed gas; S4. The mixed gas after dust removal enters the air-cooled hydrocarbon removal chamber, and the temperature in the air-cooled hydrocarbon removal chamber is controlled to 370-380°C to condense and discharge the polycyclic aromatic hydrocarbons with more than four rings in the mixed gas; S5. The mixed gas treated in the air-cooled hydrocarbon removal chamber enters the water-cooled mercury removal chamber, where the temperature is controlled to 350-355°C to condense and discharge elemental mercury in the mixed gas. S6. The mixed gas treated in the water-cooled mercury removal chamber enters the water-cooled hydrocarbon removal chamber, and the temperature in the water-cooled hydrocarbon removal chamber is controlled to 300-335° C. to condense and discharge the three-ring and lower polycyclic aromatic hydrocarbons in the mixed gas; S7, the mixed gas after being treated in the water-cooled hydrocarbon removal chamber enters the adsorption chamber, and the residual mercury vapor is adsorbed; S8. The mixed gas treated in the adsorption chamber enters the spray chamber, and the residual polycyclic aromatic hydrocarbons are absorbed.

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