Blast furnace shutdown nitrogen purging method and blast furnace nitrogen purging system

Abstract

This invention belongs to the technical field of blast furnaces for ironmaking, and discloses a method and system for nitrogen introduction during blast furnace shutdown. The method includes: before shutting down the blast furnace, discharging dust from the gravity dust collector through the ash discharge valve; when the blast furnace air volume is less than a first threshold, discharging a small amount of gas from the downcomer; opening the residual gas diversion valve to introduce nitrogen into the gravity dust collector; when the pressure in the residual gas diversion pipe is greater than or equal to the pressure in the main combustion gas pipe, opening the residual gas shut-off valve; when the gas concentration in the residual gas diversion pipe is 0, gradually reducing the opening of the nitrogen valve; when the pressure in the residual gas diversion pipe is equal to the pressure in the main combustion gas pipe, closing the residual gas shut-off valve, and then closing the nitrogen valve. This invention can reduce the amount of nitrogen used and recover and reuse the residual gas in the gravity dust collector.

Description

Technical Field

[0001] This invention relates to the technical field of blast furnaces for ironmaking, and more particularly to a method for nitrogen purging during blast furnace shutdown and a nitrogen purging system for blast furnaces. Background Technology

[0002] The blast furnace gravity dust collector is the first dust removal device for the raw gas from the blast furnace top. Due to its high flow velocity and high dust concentration, the blast furnace top gas passes through a downcomer and reaches the gravity dust collector. Most of the dust and particulate matter in the gas falls to the bottom of the collector under its own gravity. The gas, now free of dust and particulate matter, then flows through a bag filter system for further dust removal, resulting in clean gas. The dust and particulate matter that falls to the bottom of the gravity dust collector are discharged thereafter.

[0003] During blast furnace production, the gravity dust collector is sealed and isolated from the outside atmosphere. The internal pressure of the gravity dust collector can reach 200 kPa or even higher. It contains a large amount of blast furnace gas. When the blast furnace is shut down, due to the large amount of gas inside, the gas temperature and pressure drop significantly after shutdown, easily creating negative pressure that draws outside air into the gravity dust collector. If this air encounters the gas, an explosion is likely. The negative pressure can also cause the outer shell of the gravity dust collector to deform under pressure. Therefore, during blast furnace shutdown, nitrogen must be introduced into the gravity dust collector to maintain pressure and purge the gas inside. Using nitrogen to maintain pressure and purge the gravity dust collector during shutdown is a crucial step in the blast furnace shutdown process.

[0004] In existing technology, when the blast furnace shuts down and the blowdown begins, nitrogen is introduced into the gravity dust collector. This nitrogen is transported along with the gas flow to the bag filter system and finally to the gas pipeline. All the nitrogen introduced at this stage is wasted and not truly utilized. In addition, after the blast furnace shuts down, the gravity dust collector is opened, and nitrogen is used to blow the residual gas inside the gravity dust collector into the atmosphere. This gas pollutes the atmosphere and is difficult to recover. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for nitrogen introduction during blast furnace shutdown, which can reduce the volume of nitrogen introduced into the gravity dust collector during blast furnace shutdown and can also recover residual coal gas in the gravity dust collector.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for nitrogen purging during blast furnace shutdown includes the following steps:

[0008] S1. Before shutting down the blast furnace, clean the dust out of the gravity dust collector;

[0009] S2. When the blast furnace air volume is less than the first threshold, the gas in the downcomer connecting the blast furnace and the gravity dust collector is discharged.

[0010] S3. Open the residual gas diversion valve located on the residual gas diversion pipe. The residual gas diversion pipe is used to connect the gravity dust collector and the combustion gas main pipe. Nitrogen gas is introduced into the gravity dust collector. When the pressure in the residual gas diversion pipe is greater than or equal to the pressure in the combustion gas main pipe, open the residual gas shut-off valve on the residual gas diversion pipe.

[0011] S4. Maintain the pressure in the residual gas diversion pipe at a level greater than the pressure in the main furnace gas pipe.

[0012] S5. When the gas concentration in the residual gas inlet pipe is 0, gradually reduce the opening of the nitrogen valve on the nitrogen pipeline that introduces nitrogen into the gravity dust collector. When the pressure in the residual gas inlet pipe is equal to the pressure in the main gas pipe of the furnace, close the residual gas shut-off valve, and then close the nitrogen valve.

[0013] Preferably, the first threshold is 600m 3 / min.

[0014] Preferably, step S2 specifically includes:

[0015] When the blast furnace air volume is less than the first threshold, steam is introduced into the top of the blast furnace, the blast furnace top vent valve is opened, the bag filter pipe valve on the bag filter pipe connected to the gravity dust collector is closed, the gas shut-off valve located at the top of the gravity dust collector is closed, and the dust collector vent valve is opened to allow the gas in the downcomer pipe to be discharged to the outside through the dust collector vent valve.

[0016] Preferably, step S3 specifically includes:

[0017] Open the residual gas diversion valve and the nitrogen valve, control the pressure of the nitrogen entering the gravity dust collector to the second threshold, and the flow rate of the nitrogen to the third threshold; when the pressure in the gas diversion pipe is the same as the pressure in the main gas pipe of the furnace, open the residual gas shut-off valve.

[0018] Preferably, the second threshold is 0.4–1 MPa; the third threshold is 20–50 mPa. 3 / min.

[0019] Preferably, step S4 specifically involves:

[0020] Gradually increase the opening of the nitrogen valve to gradually increase the flow rate of nitrogen until the pressure in the residual gas inlet pipe is greater than the pressure in the main gas pipe of the furnace, which is the fourth threshold. Then fix the opening of the nitrogen valve at this time so that the pressure in the gas inlet pipe is kept above the fourth threshold of the pressure in the main gas pipe of the furnace.

[0021] Preferably, the fourth threshold is 10-20 kPa.

[0022] Preferably, step S6 is also included:

[0023] Open the ash discharge valve on the gravity dust collector and the gas shut-off valve, so that part of the nitrogen in the gravity dust collector is discharged from the ash discharge valve, and the other part is discharged into the atmosphere through the furnace top vent valve at the top of the gravity dust collector along the downcomer, waiting for the blast furnace to restart.

[0024] Another object of the present invention is to provide a blast furnace nitrogen purging system for implementing the above-described blast furnace shutdown nitrogen purging method.

[0025] Preferably, the system includes a blast furnace, a gravity dust collector, and a hot blast stove; the blast furnace is connected to the gravity dust collector via a downcomer; the hot blast stove is equipped with a main combustion gas pipe, and a pressure gauge is installed inside the main combustion gas pipe; the gravity dust collector is connected to the main combustion gas pipe via a residual gas diversion pipe; a residual gas diversion valve is installed at one end of the residual gas diversion pipe near the gravity dust collector, and a residual gas shut-off valve is installed at the other end of the residual gas diversion pipe near the main combustion gas pipe; a gas detector and a pressure gauge are installed inside the residual gas diversion pipe; the gravity dust collector is connected to an external nitrogen source via a nitrogen pipeline.

[0026] The beneficial effects of this invention are:

[0027] The blast furnace shutdown nitrogen purging method and system of this invention perform nitrogen purging operations on the blast furnace. The nitrogen introduced into the gravity dust collector "pushes" the coal gas within the dust collector, guiding it through the residual coal gas diversion pipe to the main combustion gas pipe, and then through the main combustion gas pipe to the hot blast stove for coal gas recovery and utilization. When the coal gas concentration in the diversion pipe is detected to be 0, the nitrogen input is gradually reduced until it stops being introduced into the gravity dust collector. This eliminates the need to continuously introduce nitrogen into the gravity dust collector during blast furnace shutdown, ensuring that all nitrogen introduced into the gravity dust collector is used to vent coal gas and is not wasted, thus reducing nitrogen consumption to a low level. This reduces nitrogen usage to as low as 500 m³ / hour. 3 The nitrogen consumption is approximately 1500 m³ / h, while the existing blast furnace shutdown nitrogen purging method consumes approximately 1500 m³ / h of nitrogen. 3Compared to existing technologies, this invention significantly reduces nitrogen usage, thereby lowering costs and conserving nitrogen. Furthermore, this invention enables the recovery and reuse of residual coal gas within the gravity dust collector, preventing coal gas from being released into the atmosphere and polluting the environment, and also reducing the amount of additional coal gas supplied to the hot air furnace, thus achieving energy savings. Attached Figure Description

[0028] Figure 1 This is a flowchart of an embodiment of the blast furnace shutdown and nitrogen purging method of the present invention;

[0029] Figure 2 This is a schematic diagram of the overall structure of an embodiment of the blast furnace nitrogen purging system of the present invention.

[0030] In the diagram: 1. Blast furnace; 2. Gravity dust collector; 3. Hot blast stove; 4. Furnace top vent valve; 5. Downcomer; 6. Gas shut-off valve; 7. Dust collector vent valve; 8. Ash discharge valve; 9. Nitrogen pipeline; 10. Bag filter pipeline; 11. Bag filter pipeline valve; 12. Residual gas diversion pipe; 13. Residual gas diversion valve; 14. Residual gas shut-off valve; 15. Gas detector; 16. Pressure gauge; 17. Main blast furnace gas pipe; 18. Nitrogen valve. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0032] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] In the description of this embodiment, terms such as "upper" and "lower" refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0034] Reference Figure 1 This is an embodiment of the blast furnace shutdown and nitrogen purging method of the present invention, which includes the following steps:

[0035] S1. 30 minutes before the shutdown of blast furnace 1, open the ash discharge valve 8 to discharge the dust in the gravity dust collector 2 through the ash discharge valve 8. After the dust in the gravity dust collector 2 is discharged, close the ash discharge valve 8.

[0036] S2. When the blast furnace 1 air volume is less than 600m³ 3 When the flow rate is 1 / min, steam is introduced into the top of blast furnace 1, and the blast furnace top vent valve 4 is opened. The bag pipe valve 11 on the bag pipe 10 connected to the gravity dust collector 2 is closed, and the gas shut-off valve 6 at the top of the gravity dust collector 2 is closed. At this time, the gas shut-off valve 6 descends to below the downcomer pipe 5 to cut off the connection between the downcomer pipe 5 and the bottom area of ​​the gravity dust collector 2. The dust collector vent valve 7 is opened so that the gas in the downcomer pipe 5 can be discharged to the outside through the dust collector vent valve 7.

[0037] S3. Open the residual gas diversion valve 13 and the nitrogen valve 18, controlling the nitrogen pressure input to the gravity dust collector 2 to 0.6 MPa and the nitrogen flow rate to 30 m³ / h. 3 / min; When the pressure in the residual gas diversion pipe 12 is the same as the pressure in the main gas pipe 17 of the furnace, open the residual gas shut-off valve 14.

[0038] S4. Gradually increase the opening of nitrogen valve 18 to gradually increase the flow rate of nitrogen until the pressure in the residual gas inlet pipe 12 is greater than the pressure in the main gas pipe 17 of the furnace by 15 kPa. Then fix the opening of nitrogen valve 18 at this time so that the pressure in the residual gas inlet pipe 12 is kept greater than the pressure in the main gas pipe 17 of the furnace by 15 kPa. At this time, the gas in gravity dust collector 2 can be stably introduced into hot blast stove 3.

[0039] S5. When the gas detector 15 detects that the gas concentration in the gas inlet pipe is 0, the opening of the nitrogen valve 18 on the nitrogen pipeline 9 that introduces nitrogen into the gravity dust collector 2 is gradually reduced. When the pressure in the residual gas inlet pipe 12 is equal to the pressure in the main gas pipe 17 of the furnace, the residual gas shut-off valve 14 is closed, and then the nitrogen valve 18 is closed.

[0040] S6. Open the ash discharge valve 8 on the gravity dust collector and open the gas shut-off valve 6, so that part of the nitrogen in the gravity dust collector 2 is discharged from the ash discharge valve 8, and the other part is discharged into the atmosphere from the vent valve 4 at the top of the blast furnace 1 along the downcomer 5. At this time, the environment inside the gravity dust collector 2 is the same as the outside atmosphere until the blast furnace 1 is restarted.

[0041] In another embodiment, step S3 is as follows: open the residual gas diversion valve 13, open the nitrogen valve 18, and control the pressure of the nitrogen entering the gravity dust collector 2 to be 0.4 MPa and the flow rate to be 20 m³ / h. 3 / min; When the pressure in the residual gas diversion pipe 12 is the same as the pressure in the main gas pipe 17, open the residual gas shut-off valve 14 to allow the gas in the gravity dust collector 2 to enter the hot blast stove 3.

[0042] In another embodiment, step S3 is as follows: open the residual gas diversion valve 13, open the nitrogen valve 18, and control the pressure of the nitrogen entering the gravity dust collector 2 to be 1 MPa and the flow rate to be 50 m³ / h. 3 / min; When the pressure in the residual gas diversion pipe 12 is the same as the pressure in the main gas pipe 17, open the residual gas shut-off valve 14 to allow the gas in the gravity dust collector 2 to enter the hot blast stove 3.

[0043] In another embodiment, step S4 is: gradually increase the opening of nitrogen valve 18 to gradually increase the flow rate of nitrogen until the pressure in the residual gas inlet pipe 12 is greater than the pressure in the main gas pipe 17 of the furnace by 10 kPa, then fix the opening of nitrogen valve 18 at this time so that the pressure in the residual gas inlet pipe 12 is kept greater than the pressure in the main gas pipe 17 of the furnace by 10 kPa.

[0044] In another embodiment, step S4 is: gradually increase the opening of nitrogen valve 18 to gradually increase the flow rate of nitrogen until the pressure in the residual gas inlet pipe 12 is greater than the pressure in the main gas pipe 17 of the furnace by 20 kPa, then fix the opening of nitrogen valve 18 at this time so that the pressure in the residual gas inlet pipe 12 is kept greater than the pressure in the main gas pipe 17 of the furnace by 20 kPa.

[0045] In steps S3 and S4, if the pressure in the residual gas diversion pipe 12 is less than the pressure in the main gas pipe 17, the residual gas shut-off valve 14 will be opened, which will cause the gas in the main gas pipe 17 to flow back into the gravity dust collector 2. Therefore, the residual gas diversion valve 13 needs to be opened first to make the pressure in the residual gas diversion pipe 12 equal to the pressure in the main gas pipe 17 before the residual gas shut-off valve 14 is opened.

[0046] In order to ensure that the residual gas in the gravity dust collector 2 can be stably fed into the main gas pipe 17 of the furnace, the pressure in the residual gas diversion pipe 12 should be 10 to 20 kPa greater than the pressure in the main gas pipe 17 of the furnace. If the pressure difference is too large, it will be difficult to operate the opening and closing of the valves; if the pressure difference is too small, the gas in the residual gas diversion pipe 12 will be difficult to be stably discharged into the hot blast stove 3.

[0047] In actual operation, blast furnace 1 can officially enter the shutdown state at any time between step S3 and step S6. The specific shutdown time depends on the actual operation of blast furnace 1.

[0048] The blast furnace shutdown nitrogen charging method and system of this invention perform nitrogen charging operations on the blast furnace. Before introducing nitrogen, the filter bag valve is closed, thus avoiding nitrogen waste caused by nitrogen entering the filter bag system. At this time, the nitrogen "pushes" the gas in the gravity dust collector, guiding it through the residual gas diversion pipe to the main blast furnace gas pipe, and then transporting it to the hot blast stove for gas recovery. When the gas concentration in the gas diversion pipe is detected to be 0, the nitrogen input is gradually reduced until it stops. This eliminates the need to continuously supply nitrogen to the gravity dust collector during blast furnace shutdown, ensuring that all nitrogen entering the gravity dust collector is used for blast furnace gas discharge and is not wasted. This reduces nitrogen consumption to a minimum, allowing nitrogen usage to be reduced to 500 m³ / hour. 3 The nitrogen consumption is approximately 1500 m³ / h, while the existing blast furnace shutdown nitrogen purging method consumes approximately 1500 m³ / h of nitrogen. 3 Compared to existing technologies, this invention significantly reduces nitrogen usage, thereby lowering costs and conserving nitrogen. Furthermore, this invention enables the recovery and reuse of residual coal gas within the gravity dust collector, preventing coal gas from being released into the atmosphere and polluting the environment, and also reducing the amount of additional coal gas supplied to the hot air furnace, thus achieving energy savings.

[0049] Reference Figure 2 This embodiment of the blast furnace nitrogen purging system of the present invention includes a blast furnace 1, a gravity dust collector 2, and a hot blast stove 3. A top vent valve 4 is provided at the top of the blast furnace 1. The top of the blast furnace 1 is connected to the top of the gravity dust collector 2 via a downcomer 5. A gas shut-off valve 6 and a dust collector vent valve 7 are provided at the top of the gravity dust collector 2. The gas shut-off valve 6 is in the open state during blast furnace 1 operation. An ash discharge valve 8 is provided at the bottom of the gravity dust collector 2, through which accumulated dust is discharged to the outside.

[0050] The gravity dust collector 2 is connected to an external nitrogen source via a nitrogen pipeline 9. The nitrogen pipeline 9 is equipped with a nitrogen valve 18 to control the opening and closing of the nitrogen pipeline 9. The nitrogen pipeline 9 is located near the ash discharge valve 8 in the gravity dust collector 2. Because nitrogen has a low density, introducing nitrogen from the bottom of the gravity dust collector 2 ensures that nitrogen gradually fills the entire interior of the gravity dust collector 2 and forces the coal gas inside the gravity dust collector 2 to the top of the gravity dust collector 2.

[0051] The gravity dust collector 2 is connected to a bag filter pipe 10 leading to the bag filter system at the position between the downcomer pipe 5 and the nitrogen pipe. The bag filter pipe 10 is equipped with a bag filter pipe valve 11 and a residual gas drainage pipe 12, which is connected to the hot air furnace 3, allowing the residual gas in the gravity dust collector 2 to enter the hot air furnace 3. The residual gas in the gravity dust collector 2 is compressed by nitrogen and discharged into the hot air furnace 3 to become fuel for the hot air furnace 3, thus realizing the recovery and utilization of the gas in the gravity dust collector 2.

[0052] A residual gas diversion pipe 12 is equipped with a residual gas diversion valve 13 at one end near the gravity dust collector 2, and a residual gas shut-off valve 14 at the other end near the hot blast stove 3. A gas detector 15 and a pressure gauge 16 are installed inside the residual gas diversion pipe 12. The gas detector 15 is a commercially available carbon monoxide detector, and the pressure gauge 16 is also a commercially available pressure gauge. The pressure gauge 16 is used to measure the pressure inside the residual gas diversion pipe 12 in real time.

[0053] The hot blast stove 3 is connected to a main combustion gas pipe 17, which is connected to an external gas source. A residual gas drain pipe 12 is directly connected to the main combustion gas pipe 17. A pressure gauge 16 is also installed inside the main combustion gas pipe 17. When gas is introduced into the main combustion gas pipe 17 through the residual gas drain pipe 12, the pressure inside the residual gas drain pipe 12 must be no less than that in the main combustion gas pipe 17 to prevent backflow of gas from the main combustion gas pipe 17 into the residual gas drain pipe 12. The gas drawn from the residual gas drain pipe 12 merges with the gas introduced into the main combustion gas pipe 17 before being introduced into the hot blast stove 3. Therefore, the amount of gas introduced into the main combustion gas pipe 17 from the outside can be appropriately reduced, achieving energy savings.

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method of nitrogen flushing during a blast furnace outage, characterized by, The method comprises the following steps: S1. Before the blast furnace is blown down, the dust in the gravity dust collector is discharged clean; S2. When the blast furnace air volume is less than a first threshold value, the gas in the downcomer connecting the blast furnace and the gravity dust collector is discharged; S3. The residual gas drainage pipe near the gravity dust collector is provided with a residual gas drainage valve, and the residual gas drainage pipe near the blast furnace gas main pipe is provided with a residual gas cut-off valve. The residual gas drainage valve on the residual gas drainage pipe is opened, the residual gas drainage pipe is used to connect the gravity dust collector and the blast furnace gas main pipe, nitrogen is introduced into the gravity dust collector, and when the pressure in the residual gas drainage pipe is greater than or equal to the pressure in the blast furnace gas main pipe, the residual gas cut-off valve on the residual gas drainage pipe is opened; S4. The pressure in the residual gas drainage pipe is kept greater than the pressure in the blast furnace gas main pipe; S5. When the gas concentration in the residual gas drainage pipe is 0, the opening of the nitrogen valve on the nitrogen pipeline introducing nitrogen into the gravity dust collector is gradually reduced, when the pressure in the residual gas drainage pipe is equal to the pressure in the blast furnace gas main pipe, the residual gas cut-off valve is closed, and then the nitrogen valve is closed.

2. The blast furnace nitrogen flushing method of claim 1, wherein, The first threshold value is 600 m³ / min.

3. The blast furnace nitrogen flushing method of claim 1, wherein, The step S2 is specifically: When the blast furnace air volume is less than the first threshold value, steam is introduced into the blast furnace top, the blast furnace top diffuser valve is opened, the bag filter pipeline valve on the bag filter pipeline connecting the gravity dust collector is closed, the gas cut-off valve at the top of the gravity dust collector is closed, the dust collector diffuser valve is opened, and the gas in the downcomer is discharged from the dust collector diffuser valve to the outside.

4. The blast furnace nitrogen flushing method of claim 1, wherein, The step S3 is specifically: The residual gas drainage valve is opened, the nitrogen valve is opened, the pressure of the nitrogen introduced into the gravity dust collector is controlled to be a second threshold value, and the flow of the nitrogen is controlled to be a third threshold value; when the pressure in the residual gas drainage pipe is equal to the pressure in the blast furnace gas main pipe, the residual gas cut-off valve is opened.

5. The blast furnace nitrogen flushing method of claim 4, wherein, The second threshold value is 0.4-1 MPa, and the third threshold value is 20-50 m³ / min.

6. The blast furnace nitrogen flushing method of claim 1 wherein, The step S4 is specifically: The opening of the nitrogen valve is gradually increased to gradually increase the flow of the nitrogen, and when the pressure in the residual gas drainage pipe is greater than the pressure in the blast furnace gas main pipe by a fourth threshold value, the opening of the nitrogen valve is fixed, and the pressure in the residual gas drainage pipe is kept greater than the pressure in the blast furnace gas main pipe by the fourth threshold value.

7. The blast furnace nitrogen flushing method of claim 6, wherein, The fourth threshold value is 10-20 kPa.

8. The blast furnace nitrogen flushing method of claim 3, wherein, The method further comprises the following step S6: The ash discharge valve on the gravity dust collector is opened, the gas cut-off valve is opened, part of the nitrogen in the gravity dust collector is discharged from the ash discharge valve, another part of the nitrogen is discharged from the blast furnace top diffuser valve along the downcomer into the atmosphere, and the blast furnace is blown up.

9. A nitrogen pass system for a blast furnace, characterized by, The blast furnace nitrogen system is used for implementing the blast furnace nitrogen blowing method as claimed in any one of claims 1-8, comprising a blast furnace, a gravity dust collector and a hot blast stove; the blast furnace is communicated with the gravity dust collector through a downcomer; the hot blast stove is provided with a stove gas main pipe, and a pressure gauge is arranged in the stove gas main pipe; the gravity dust collector is communicated with the stove gas main pipe through the residual gas flow pipe; a residual gas flow valve is arranged at one end of the residual gas flow pipe close to the gravity dust collector, and a residual gas cut-off valve is arranged at one end of the residual gas flow pipe close to the stove gas main pipe; a gas detector and a pressure gauge are arranged in the residual gas flow pipe; and the gravity dust collector is communicated with an external nitrogen source through a nitrogen pipeline.

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