Soil in-situ remediation tail gas backdraft treatment TO furnace

Abstract

The utility model relates to the technical field of soil pollutant remediation, and discloses a soil in-situ remediation tail gas backdraft treatment TO furnace which comprises an outer heating pipe and a collecting mechanism, the outer heating pipe is pre-buried in soil, and the collecting mechanism is installed on one side of a control box through a supporting frame. According to the utility model, decomposed water is attached to the inner walls of the inner heating pipe and the outer heating pipe, and water drops attached to the inner walls of the inner heating pipe and the outer heating pipe drop into the water collecting tank along the inner walls along with gravity, so that the water collecting tank can conveniently collect the water; water in the water collecting tank is sucked into the cooling pipeline through the cooling pipeline and the water conveying pipeline by suction force, the fan is powered on and operates to generate wind power to conduct air cooling on the water in the cooling pipeline, and the cooled water in the cooling pipeline is conveyed into the water storage tank through the suction force of the water suction pump after air cooling. The function of discharging water collected in the outer heating pipe is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of soil pollutant remediation, and specifically, to a soil in-situ remediation tail gas afterburning treatment TO furnace. Background Art

[0002] Polluted soil remediation refers to technical measures that, through physical, chemical, biological, and ecological principles and by adopting artificial control measures, reduce the concentration of soil pollutants, realize the harmlessness and stabilization of pollutants, and achieve the desired detoxification effect.

[0003] After further searching, it is found that a soil in-situ remediation tail gas afterburning treatment device disclosed in the authorized publication number CN214391606U, through specific technical structure settings, effectively solves the technical drawbacks in the conventional technology that the polluted gas extracted from the extraction pipe needs to pass through a steam-water separator, and then the tail water and tail gas are respectively treated. The tail gas needs to enter the secondary combustion chamber, be fully burned and then discharged into the atmosphere, and the tail water needs to be added with corresponding agents to be treated cleanly, which will increase the cost of soil remediation.

[0004] However, when the above-mentioned prior art is actually used, there are still many defects. For example, in the above technology, the high-temperature tail gas passes through the through holes in the gravel filter layer and enters the inside of the extraction pipe. At this time, the high-temperature tail gas enters the inside of the inner pipe of the heating pipe from the extraction gas afterburning pipe, so as to facilitate the secondary combustion of gaseous organic pollutants. The inner pipe of the heating pipe will completely decompose and burn them into carbon dioxide and water. The carbon dioxide and water exchange heat with the polluted soil through the outer pipe of the heating pipe along with the hot flue gas, and finally are discharged from the tail gas outlet pipe, adsorbed by activated carbon and finally discharged into the atmosphere from the chimney, making the treatment of polluted soil cleaner. However, the decomposed water cannot be completely burned, and the water is heavier than the gas and will not be discharged through the tail gas outlet pipe along with the hot flue gas. The decomposed water droplets fall on the bottom of the outer pipe of the heating pipe and cannot be discharged, resulting in excessive water accumulation inside the outer pipe of the heating pipe, thus affecting the heat conduction effect of the outer pipe of the heating pipe. Therefore, it is necessary to have a function of discharging and collecting the water accumulated inside the outer pipe of the heating pipe. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a soil in-situ remediation tail gas afterburning treatment TO furnace, which solves the problems in the prior art that the decomposed water cannot be completely burned, the water is heavier than the gas and will not be discharged through the tail gas outlet pipe along with the hot flue gas, the decomposed water droplets fall on the bottom of the outer pipe of the heating pipe and cannot be discharged, resulting in excessive water accumulation inside the outer pipe of the heating pipe and affecting the heat conduction effect of the outer pipe of the heating pipe. Therefore, it is necessary to have a function of discharging and collecting the water accumulated inside the outer pipe of the heating pipe.

[0006] The utility model provides the following technical solutions: a soil in-situ remediation tail gas backburning treatment TO furnace, comprising an external heating pipe and a collecting mechanism, the external heating pipe is pre-buried in the soil, the inner part of the external heating pipe is fixedly sleeved with the inner heating pipe, the top of the inner heating pipe is fixedly connected with a connecting pipe, the top of the connecting pipe is fixedly installed with a control box, one side of the control box is fixedly installed with an extended gas pipe, one end of the gas pipe is fixedly installed with a solenoid valve, the output end of the solenoid valve is through-connected with a connecting cavity, the collecting mechanism is installed on one side of the control box through a supporting frame, one side of the external heating pipe is provided with an extraction gas backburning pipe, and the extraction gas backburning pipe is also pre-buried in the soil.

[0007] As a preferred embodiment of the above technical solution, a low-nitrogen burner is fixedly installed inside the control box, and the output end of the low-nitrogen burner is through-connected with the other side of the connecting cavity. An air inlet pipe extending from the outer wall of the control box is fixedly installed on the output end of the low-nitrogen burner, and a combustion gun extending to the inside of the internal heating tube is fixedly installed on the bottom end of the connecting cavity. The operator turns on the controller to control the low-nitrogen burner to power on and operate. The powered-on low-nitrogen burner draws external air into the connecting cavity through the air inlet pipe. At the same time, the powered-on low-nitrogen burner ignites the air and gas inside the connecting cavity, thereby igniting, and transmits firepower to the inside of the internal heating tube through the combustion gun for combustion.

[0008] The top of the extraction gas reburning pipe is fixedly connected to an extraction pipeline, and a reburning valve is fixedly installed on the outside of the extraction pipeline, and the extraction pipeline is connected to a side of the inner heating pipe away from the top of the extraction gas reburning pipe, and a sealing sleeve is fixedly sleeved on the outside of the top of the extraction gas reburning pipe, and a filter cover is fixedly sleeved on the outside of the extraction gas reburning pipe. When organic pollutants in the soil are formed into a gaseous state due to temperature increase, the high-temperature exhaust gas passes through the through hole of the filter cover and enters the interior of the extraction gas reburning pipe, and the reburning valve is opened to allow the exhaust gas inside the extraction gas reburning pipe to enter the interior of the inner heating pipe through the extraction pipeline, so that the fire inside the inner heating pipe burns again, and the top of the extraction gas reburning pipe is sealed by the sealing sleeve, so that the extraction gas reburning pipe and the extraction pipe can be tightly connected, and the soil is isolated on the outside of the filter cover by the filter cover to prevent the soil from blocking the through hole of the extraction gas reburning pipe and affecting the high-temperature exhaust gas from entering the interior of the extraction gas reburning pipe.

[0009] As a preferred embodiment of the above technical solution, the collecting mechanism includes a water collecting trough, a cooling pipe and a water storage tank. The water collecting trough is fixedly installed on the lower side of the external heating pipe, and one side of the water collecting trough is fixedly connected to a water supply pipe extending from one side of the external heating pipe. The water decomposed inside the external heating pipe is collected by the water collecting trough, and the water in the water collecting trough is transported to the inside of the cooling pipe through the water supply pipe.

[0010] Preferably, as the above technical solution, the water storage tank is installed on the surface of the soil through a support frame. A water pump is fixedly installed on the lower side of the water storage tank through a mounting plate. A cooling box is arranged on one side of the water storage tank close to the support frame and is installed on the surface of the soil. A cooling pipe is fixedly installed inside the cooling box. A fan is fixedly installed on the outer wall of one side of the cooling box. The cooling box provides an installation position for the cooling pipe and the fan. The operator turns on the controller to control the fan to operate electrically. The electrically operated fan generates wind to air-cool the water inside the cooling pipe, avoiding damage to the water pump due to the overheated water suctioned in the water collecting tank. Then, the suction force of the water pump is used to transport the cooled water inside the cooling pipe into the water storage tank for storage.

[0011] Preferably, as the above technical solution, the input end of the cooling pipe is fixedly connected to the top end of the water delivery pipe through a pipe, and the output end of the cooling pipe is fixedly connected to the input end of the water pump through a pipe. The electrically operated water pump generates suction force, and the suction force sucks the water stored in the water collecting tank through the cooling pipe and the water delivery pipe. The sucked water is transported into the cooling pipe through the water delivery pipe.

[0012] Preferably, as the above technical solution, air outlet holes are formed at the top end of the outer heating pipe wall and extend out of the soil interior. A box door is installed on the outside of the control box through a hinge, and a controller is fixedly installed on the outer wall of the box door. An activated carbon adsorption layer is arranged inside the air outlet holes. The decomposed carbon dioxide and hot flue gas are adsorbed by the activated carbon adsorption layer inside the air outlet holes, and the waste heat flue gas after adsorption by the activated carbon adsorption layer is discharged through the outlet of the air outlet holes. By the operator opening the box door, it is convenient for the operator to start the solenoid valve. The controller is electrically connected to the solenoid valve, low-nitrogen burner, fan, and water pump through wires, facilitating the operator to control the device to operate electrically through the controller.

[0013] Compared with the prior art, the beneficial effects of the present utility model are:

[0014] After the decomposition of the present utility model, water adheres to the inner walls of the inner heating pipe and the outer heating pipe. The water droplets adhering to the inner walls of the inner heating pipe and the outer heating pipe drip along the inner walls to the inside of the water collecting tank due to gravity, which facilitates the water collecting tank to collect the decomposed water, realizes the function of collecting the decomposed water, and the operator turns on the controller to control the water pump to run with power on. The water pump running with power on generates suction, and the suction sucks the water stored inside the water collecting tank through the cooling pipe and the water delivery pipe. The sucked water is transported to the inside of the cooling pipe through the water delivery pipe. At the same time, the operator turns on the controller to control the fan to run with power on. The fan running with power on generates wind to cool the water inside the cooling pipe, preventing the water sucked inside the water collecting tank from damaging the water pump due to excessive temperature. Then, the water pump sucks the cooled water inside the cooling pipe into the water storage tank for storage through its suction, which facilitates the reuse of the collected water, realizes the function of discharging the water collected inside the outer heating pipe, and avoids the problem that excessive water accumulation inside the outer heating pipe affects the heat conduction effect of the outer heating pipe. Description of the Drawings

[0015] Figure 1 It is a three-dimensional structural schematic diagram of a TO furnace for treating tail gas by back burning in in-situ soil remediation;

[0016] Figure 2 It is a sectional structural schematic diagram of a TO furnace for treating tail gas by back burning in in-situ soil remediation;

[0017] Figure 3 It is a structural schematic diagram of the control box of a TO furnace for treating tail gas by back burning in in-situ soil remediation;

[0018] Figure 4 It is a structural schematic diagram of the collection mechanism of a TO furnace for treating tail gas by back burning in in-situ soil remediation.

[0019] In the figure: 1. Outer heating pipe; 101. Air outlet; 2. Inner heating pipe; 3. Control box; 301. Box door; 302. Connecting pipe; 4. Gas pipe; 401. Electromagnetic valve; 5. Connecting cavity; 501. Low-nitrogen burner; 502. Combustion gun; 503. Inlet pipe; 6. Extraction gas back-burning pipe; 601. Sealing sleeve; 602. Extraction pipe; 603. Back-burning valve; 7. Filter material cover; 8. Collection mechanism; 801. Water collecting tank; 802. Water delivery pipe; 803. Cooling box; 804. Cooling pipe; 805. Fan; 806. Water pump; 807. Water storage tank; 9. Controller. Detailed Embodiment

[0020] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model.

[0021] Such as Figures 1-4As shown in the figure, the utility model provides a technical solution: a TO furnace for afterburning treatment of tail gas in in-situ soil remediation, which includes an external heating pipe 1 and a collection mechanism 8. The external heating pipe 1 is buried inside the soil. An internal heating pipe 2 is fixedly sleeved inside the external heating pipe 1. A connecting pipe 302 is fixedly connected to the top of the internal heating pipe 2. A control box 3 is fixedly installed at the top of the connecting pipe 302. A low-nitrogen burner 501 is fixedly installed inside the control box 3. The output end of the low-nitrogen burner 501 is connected through to the other side of the connecting cavity 5. An air inlet pipe 503 extending out of the outer wall of the control box 3 is fixedly installed at the output end of the low-nitrogen burner 501. A combustion gun 502 extending into the internal heating pipe 2 is fixedly installed at the bottom end of the connecting cavity 5. The operator turns on the controller 9 to control the low-nitrogen burner 501 to operate electrically. The electrically operating low-nitrogen burner 501 sucks and conveys the outside air to the inside of the connecting cavity 5 through the air inlet pipe 503. At the same time, the electrically operating low-nitrogen burner 501 ignites the air and gas inside the connecting cavity 5, thereby igniting, and conveys the firepower to the inside of the internal heating pipe 2 through the combustion gun 502 for combustion, so that heat is generated inside the internal heating pipe 2. The heat generated inside the internal heating pipe 2 is transferred to the soil through the external heating pipe 1, thereby performing thermal radiation on the soil and achieving the effect of heating the soil. A gas pipe 4 extending out is fixedly installed on one side of the control box 3. A solenoid valve 401 is fixedly installed at one end of the gas pipe 4. The output end of the solenoid valve 401 is connected through to the connecting cavity 5. The collection mechanism 8 is installed on one side of the control box 3 through a support frame. The collection mechanism 8 includes a water collection tank 801, a cooling pipe 804 and a water storage tank 807. The water collection tank 801 is fixedly installed on the lower side inside the external heating pipe 1. A water delivery pipe 802 extending out of one side of the external heating pipe 1 is fixedly connected to one side of the water collection tank 801. The water storage tank 807 is installed on the surface of the soil through a support frame. A water pump 806 is fixedly installed on the lower side of the water storage tank 807 through a mounting plate. A cooling box 803 is provided on one side of the water storage tank 807 close to the support frame, and the cooling box 803 is installed on the surface of the soil. A cooling pipe 804 is fixedly installed inside the cooling box 803. A blower 805 is fixedly installed on the outer wall on one side of the cooling box 803. The input end of the cooling pipe 804 is fixedly connected to the top end of the water delivery pipe 802 through a pipe. The output end of the cooling pipe 804 is fixedly connected to the input end of the water pump 806 through a pipe. The decomposed water adheres to the inner walls of the internal heating pipe 2 and the external heating pipe 1. The water droplets adhering to the inner walls of the internal heating pipe 2 and the external heating pipe 1 drip along the inner walls to the inside of the water collection tank 801 due to gravity, facilitating the water collection tank 801 to collect the decomposed water, realizing the function of collecting the decomposed water, and the operator turns on the controller 9 to control the water pump 806 to operate electrically. The electrically operating water pump 806 generates suction, and the suction sucks the water stored inside the water collection tank 801 through the cooling pipe 804 and the water delivery pipe 802. The sucked water is conveyed to the inside of the cooling pipe 804 through the water delivery pipe 802.Meanwhile, the operator turns on the controller 9 to control the fan 805 to run with power on. The fan 805 running with power on generates wind to cool the water inside the cooling pipe 804, preventing the water sucked into the water collecting tank 801 from damaging the water pump 806 due to excessive temperature. Then, the cooled water inside the cooling pipe 804 is transported into the water storage tank 807 for storage by the suction force of the water pump 806, facilitating the reuse of the collected water. One side of the external heating pipe 1 is provided with an extraction gas recirculation combustion pipe 6, and the extraction gas recirculation combustion pipe 6 is also buried inside the soil. When the organic pollutants in the soil form a gas due to temperature rise, the high-temperature exhaust gas passes through the filter material cover 7 and enters the extraction gas recirculation combustion pipe 6 through the through hole, facilitating the exhaust gas inside the extraction gas recirculation combustion pipe 6 to enter the internal heating pipe 2 through the extraction pipe 602, enabling the fire inside the internal heating pipe 2 to burn again.,

[0022] It should be noted that: The working principle of the low-nitrogen burner 501 is mainly to reduce the oxygen concentration in the flue gas, lower the maximum flame temperature, and shorten the residence time of the gas in the high-temperature zone by improving the structure of the burner, so as to achieve the purpose of reducing the concentration of nitrogen oxides in the exhaust gas. Specifically, the low-nitrogen burner adopts the principle of staged combustion, enabling the fuel and air to be mixed and burned in stages, deviating from the theoretical equivalence ratio, thereby reducing the generation of NOx.

[0023] As an implementation manner in this embodiment, as Figure 1 、 Figure 2 and Figure 3 shown, the top end of the extraction gas recirculation combustion pipe 6 is fixedly connected with an extraction pipe 602. A recirculation combustion valve 603 is fixedly installed on the outer side of the extraction pipe 602. The top end of the extraction pipe 602 away from the extraction gas recirculation combustion pipe 6 is connected in communication with one side of the internal heating pipe 2. A sealing sleeve 601 is fixedly sleeved on the outer side of the top end of the extraction gas recirculation combustion pipe 6. A filter material cover 7 is fixedly sleeved on the outer side of the extraction gas recirculation combustion pipe 6. When the organic pollutants in the soil form a gas due to temperature rise, the high-temperature exhaust gas passes through the filter material cover 7 and enters the extraction gas recirculation combustion pipe 6 through the through hole, and by opening the recirculation combustion valve 603, the exhaust gas inside the extraction gas recirculation combustion pipe 6 enters the internal heating pipe 2 through the extraction pipe 602, enabling the fire inside the internal heating pipe 2 to burn again. The top of the extraction gas recirculation combustion pipe 6 is sealed by the sealing sleeve 601, enabling the extraction gas recirculation combustion pipe 6 and the extraction pipe 602 to be tightly connected. The soil is isolated outside the filter material cover 7 by the filter material cover 7, preventing the soil from blocking the through hole of the extraction gas recirculation combustion pipe 6 and affecting the entry of the high-temperature exhaust gas into the extraction gas recirculation combustion pipe 6.

[0024] As an implementation manner in this embodiment, as Figure 1 、 Figure 2 and Figure 3As shown in the figure, an air outlet hole 101 is opened at the top end of the outer heating pipe 1, and the air outlet hole 101 extends out of the soil interior. A cabinet door 301 is installed on the outside of the control box 3 through a hinge, and a controller 9 is fixedly installed on the outer wall of the cabinet door 301. An activated carbon adsorption layer is arranged inside the air outlet hole 101. The decomposed carbon dioxide and hot flue gas are adsorbed through the activated carbon adsorption layer inside the air outlet hole 101, and the adsorbed activated carbon adsorption layer and the hot flue gas are discharged through the outlet of the air outlet hole 101. By the operator opening the cabinet door 301, it is convenient for the operator to start the solenoid valve 401. The controller 9 is electrically connected to the solenoid valve 401, the low-nitrogen burner 501, the fan 805, and the water pump 806 through wires, facilitating the operator to control the power-on operation of the device through the controller 9.

[0025] Working principle: By the operator opening the cabinet door 301 and starting the solenoid valve 401, the gas inside the gas pipe 4 enters the connection cavity 5. Then the operator turns on the controller 9 to control the power-on operation of the low-nitrogen burner 501. The powered-on low-nitrogen burner 501 sucks and conveys the outside air to the inside of the connection cavity 5 through the air inlet pipe 503. At the same time, the powered-on low-nitrogen burner 501 ignites the air and gas inside the connection cavity 5, thereby igniting, and conveys the firepower to the inside of the inner heating pipe 2 through the combustion gun 502 for combustion, causing heat to be generated inside the inner heating pipe 2. The heat generated inside the inner heating pipe 2 is transferred to the soil through the outer heating pipe 1, thereby performing heat radiation on the soil to achieve the effect of heating the soil. As the temperature of the soil rises, the organic pollutants in the soil change state. When the organic pollutants in the soil form a gas state due to the temperature rise, the high-temperature tail gas passes through the filter hood 7 through the through hole and enters the extraction gas re-burning pipe 6, and by opening the re-burning valve 603, the tail gas inside the extraction gas re-burning pipe 6 enters the inner heating pipe 2 through the extraction pipeline 602, enabling the firepower inside the inner heating pipe 2 to burn it again. The re-burning decomposes the gaseous organic pollutants into carbon dioxide and water, and the decomposed carbon dioxide is adsorbed by the activated carbon adsorption layer inside the air outlet hole 101, and the adsorbed gas is discharged through the air outlet hole 101.

[0026] The decomposed water adheres to the inner walls of the inner heating pipe 2 and the outer heating pipe 1. The water droplets adhering to the inner walls of the inner heating pipe 2 and the outer heating pipe 1 drip along the inner walls to the inside of the water collecting tank 801 under the action of gravity, facilitating the collection of the decomposed water by the water collecting tank 801, realizing the function of collecting the decomposed water. Then, the operator turns on the controller 9 to control the water pump 806 to operate energized. The energized water pump 806 generates suction, and the suction sucks the water stored inside the water collecting tank 801 through the cooling pipe 804 and the water delivery pipe 802. The sucked water is transported to the inside of the cooling pipe 804 through the water delivery pipe 802. At the same time, the operator turns on the controller 9 to control the fan 805 to operate energized. The energized fan 805 generates wind to air-cool the water inside the cooling pipe 804, preventing the water sucked inside the water collecting tank 801 from damaging the water pump 806 due to excessive temperature. Then, the water cooled inside the cooling pipe 804 is transported to the inside of the water storage tank 807 for storage by the suction of the water pump 806, facilitating the reuse of the collected water.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it.

Claims

1. A TO furnace for treating the tail gas of in-situ soil remediation by afterburning, comprising an external heating pipe (1) and a collection mechanism (8), characterized in that: The external heating pipe (1) is embedded inside the soil. An internal heating pipe (2) is fixedly sleeved inside the external heating pipe (1). A connecting pipe (302) is fixedly connected to the top of the internal heating pipe (2). A control box (3) is fixedly installed at the top of the connecting pipe (302). A gas pipe (4) extending out is fixedly installed on one side of the control box. An electromagnetic valve (401) is fixedly installed at one end of the gas pipe (4). The output end of the electromagnetic valve (401) is connected through to a connecting cavity (5). The collection mechanism (8) is installed on one side of the control box (3) through a support frame. A extraction gas return combustion pipe (6) is arranged on one side of the external heating pipe (1), and the extraction gas return combustion pipe (6) is also embedded inside the soil.

2. The TO furnace for treating the tail gas by back burning during in-situ soil remediation according to claim 1, wherein: A low-nitrogen burner (501) is fixedly installed inside the control box (3). The output end of the low-nitrogen burner (501) is connected through to the other side of the connecting cavity (5). An air inlet pipe (503) extending out of the outer wall of the control box (3) is fixedly installed at the output end of the low-nitrogen burner (501). A combustion gun (502) extending into the internal heating pipe (2) is fixedly installed at the bottom end of the connecting cavity (5).

3. The in-situ soil remediation tail gas recirculation treatment TO furnace according to claim 1, characterized in that: The top end of the extraction gas return combustion pipe (6) is fixedly connected to an extraction pipe (602). A return combustion valve (603) is fixedly installed on the outside of the extraction pipe (602). The top end of the extraction pipe (602) away from the extraction gas return combustion pipe (6) is connected through to one side of the internal heating pipe (2). A sealing sleeve (601) is fixedly sleeved on the outside of the top end of the extraction gas return combustion pipe (6). A filter material cover (7) is fixedly sleeved on the outside of the extraction gas return combustion pipe (6).

4. A TO furnace for treating the tail gas of in-situ soil remediation by afterburning, according to claim 1, characterized in that: The collection mechanism (8) includes a water collection tank (801), a cooling pipe (804) and a water storage tank (807). The water collection tank (801) is fixedly installed on the lower side inside the external heating pipe (1). A water delivery pipe (802) extending out of one side of the external heating pipe (1) is fixedly connected to one side of the water collection tank (801).

5. A soil in-situ remediation tail gas afterburning treatment TO furnace according to claim 4, characterized in that: The water storage tank (807) is installed on the surface of the soil through a support frame. A water pump (806) is fixedly installed on the lower side of the water storage tank (807) through a mounting plate. A cooling box (803) is arranged on one side of the water storage tank (807) close to the support frame, and the cooling box (803) is installed on the surface of the soil. A cooling pipe (804) is fixedly installed inside the cooling box (803). A fan (805) is fixedly installed on the outer wall of one side of the cooling box (803).

6. A TO furnace for treating the tail gas of in-situ soil remediation by afterburning, as described in claim 4, characterized in that: The input end of the cooling pipe (804) is fixedly connected to the top end of the water delivery pipe (802) through a pipe. The output end of the cooling pipe (804) is fixedly connected to the input end of the water pump (806) through a pipe.

7. A TO furnace for treating the tail gas of in-situ soil remediation by afterburning, as described in claim 1, wherein: An air outlet hole (101) is opened at the top end of the outer wall of the external heating pipe (1), and the air outlet hole (101) extends out of the soil. A box door (301) is installed on the outside of the control box (3) through a hinge. A controller (9) is fixedly installed on the outer wall of the box door (301).

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