A discharge system and method for an external cooler of a gas-based vertical furnace

Abstract

The present invention discloses a discharge system and method of an external cooler for a gas-based vertical furnace, which comprises a direct reduction vertical furnace, an external cooler, a pressure discharge tank, a washing quenching orifice plate, a washing venturi and a decompression scrubber; the feed port at the upper part of the external cooler is connected to the discharge port at the bottom of the direct reduction vertical furnace, the discharge port at the lower part of the external cooler is connected to the feed port of the pressure discharge tank, and the nitrogen port of the pressure discharge tank is connected to a high-pressure nitrogen source through a pipeline and a booster valve; the nitrogen port of the pressure discharge tank is also connected to the washing quenching orifice plate, the washing venturi and the decompression scrubber in sequence through a pipeline, and a decompression valve is provided on the pipeline between the nitrogen port of the pressure discharge tank and the washing quenching orifice plate; the lower part of the external cooler is connected to the high-pressure nitrogen source, and the upper part of the external cooler is connected to the pipeline between the pressure reducing valve and the washing quenching orifice plate through a pipeline and a nitrogen stop valve. This system can effectively control particulate matter emissions, achieve ultra-low particulate matter emissions, and improve the surrounding environment.

Description

Technical Field

[0001] The invention relates to a discharge system and method, in particular to a discharge system and method for an external cooler of a gas-based vertical furnace. Background Art

[0002] The short-process steelmaking process led by the direct reduction ironmaking process has replaced the long-process steelmaking process led by the traditional blast furnace ironmaking process. The emission reduction advantages have gradually become prominent and have been adopted by large domestic steel companies. The current mainstream direct reduction process is mainly based on the Midrex and HYL gas-based vertical furnace methods. Domestic steel companies are jointly building gas-based vertical furnace process projects with Midrex and HYL companies. The unit CO2 emissions generated by the traditional blast furnace method of smelting molten iron, even based on optimized processes, are about 1.6 tons of CO2 / t iron. Data show that the Midrex and HYL processes will significantly reduce the unit CO2 emissions per ton of pig iron produced. The Midrex process is about 0.5 tons of CO2 / t iron, and the HYL process is about 0.25 tons of CO2 / t iron.

[0003] In the direct reduction vertical furnace process, the temperature of the direct reduced iron discharged from the lower part of the vertical furnace is between 600 and 700°C; this results in two discharge methods for the vertical furnace: hot discharge and cold discharge. Hot discharge is suitable for the vertical furnace area and the electric furnace steelmaking area are close, and pneumatic conveying is used to reduce heat loss and input costs. The cold discharge method is suitable for the vertical furnace area and the electric furnace steelmaking area are far apart or for sales. Pneumatic conveying cannot be used, and only long-distance reverse transportation can be used to supply users. Using the cold discharge process, the gas-based vertical furnace needs to be equipped with an external cooler, which cools the direct reduced iron to below 50°C. When the external cooler is overhauled and purged, the discharged purge nitrogen will carry particulate matter; and the external cooler needs to be equipped with a discharge tank for discharge. Gas will be released during the discharge process, and the released gas will inevitably carry particulate matter.

[0004] The current particulate matter emission control technology of the vertical furnace reduction process discharge system is not mature yet, and the particulate matter generated during the maintenance and purge of the external cooler is directly discharged without treatment. This will cause the particulate matter content in the surrounding environment of the vertical furnace reduction plant to exceed the standard, causing environmental pollution and causing harm to the people working and living nearby. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an emission system of an external cooler of a gas-based vertical furnace with ultra-low particulate matter emission; the present invention also provides an emission method of an external cooler of a gas-based vertical furnace.

[0006] In order to solve the above technical problems, the technical solution adopted by the system of the present invention is: it includes a direct reduction vertical furnace, an external cooler, a pressure discharge tank, a washing quenching orifice plate, a washing venturi and a pressure reducing scrubber; the feed port at the upper part of the external cooler is connected to the discharge port at the bottom of the direct reduction vertical furnace, the discharge port at the lower part of the external cooler is connected to the feed port of the pressure discharge tank, and the nitrogen port of the pressure discharge tank is connected to a high-pressure nitrogen source through a pipeline and a booster valve; the nitrogen port of the pressure discharge tank is also connected to the washing quenching orifice plate, the washing venturi and the pressure reducing scrubber in sequence through a pipeline, and a pressure reducing valve is provided on the pipeline between the nitrogen port of the pressure discharge tank and the washing quenching orifice plate; the lower part of the external cooler is connected to the high-pressure nitrogen source, and the upper part of the external cooler is connected to the pipeline between the pressure reducing valve and the washing quenching orifice plate through a pipeline and a nitrogen stop valve.

[0007] The system of the present invention is also provided with a circulating water station and a circulating water pump; the liquid outlet of the vacuum washer, the circulating water pump, the circulating water station and the liquid inlet of the vacuum washer are sequentially connected through pipelines. The circulating water station is also connected to the liquid inlet of the washing quenching orifice plate through a pipeline.

[0008] The system of the present invention also includes a cooling gas quenching orifice plate, a cooling gas venturi, a separation tower, a quenching tower, a dehydrator, a filter, a compressor, an aftercooler and a secondary dehydrator; the lower part of the external cooler is provided with a cooling nitrogen inlet, and the upper part is provided with a cooling nitrogen outlet; the cooling nitrogen outlet is sequentially connected to the cooling gas quenching orifice plate, the cooling gas venturi, the separation tower, the quenching tower, the dehydrator, the filter, the compressor, the aftercooler and the secondary dehydrator through a pipeline, and the outlet of the secondary dehydrator is connected to the cooling nitrogen inlet.

[0009] The method of the present invention adopts the above-mentioned discharge system, and the method steps include: 1) high-quality pellets are added from the top of the direct reduction shaft furnace, and after reacting with the reducing gas in the direct reduction shaft furnace, the generated direct reduced iron enters the external cooler for cooling, and then enters the pressure discharge tank;

[0010] 2) The pressure discharge tank is pressurized by nitrogen sent from a high-pressure nitrogen source, and when the pressure inside the tank is equal to the pressure of the external cooler, loading is performed; when the pressure discharge tank is unloaded, nitrogen is first discharged to reduce the pressure to atmospheric pressure before discharging;

[0011] 3) During the decompression process of the pressure discharge tank, nitrogen carrying particulate matter is discharged; the nitrogen carrying particulate matter is discharged after the washing quenching orifice plate gas-liquid mixing, the washing venturi tube capturing dust, and the decompression scrubber washing the particulate matter.

[0012] The method of the present invention also includes the following steps: when the external cooler needs to be overhauled and purged, nitrogen is filled into the external cooler from a high-pressure nitrogen source for purging, and the nitrogen carrying particulate matter is discharged from the upper part of the external cooler after purging, and enters the washing quenching orifice plate through a nitrogen shut-off valve for gas-liquid mixing, the washing venturi captures dust, and the decompression scrubber washes the particulate matter, and then the clean nitrogen is discharged.

[0013] The method of the present invention also includes the following steps: the circulating water of the circulating water station is divided into two paths, one path enters the washing quenching orifice plate to merge with the nitrogen carrying particulate matter, captures dust through the washing venturi, separates gas and water in the vacuum scrubber, and the sewage is discharged from the vacuum scrubber and returned to the circulating water station through the circulating water pump; the other path of circulating water directly enters the vacuum scrubber to wash the gas, and the sewage formed after washing the gas is discharged from the vacuum scrubber and returned to the circulating water station through the circulating water pump.

[0014] The method of the present invention also includes the following steps: 1) the external cooler uses nitrogen as a cooling medium; the nitrogen after cooling the direct reduced iron is discharged from the cooling nitrogen outlet of the external cooler, mixed with gas and liquid through the cooling gas quenching orifice plate, and dust is captured by the cooling gas venturi, and the gas and liquid are separated by a separation tower, cooled by the quenching tower, and the water is removed by the dehydrator, and further filtered by the filter before entering the compressor; after the compressor compresses the gas, the gas is cooled again by the aftercooler, and then the remaining water is removed by the secondary dehydrator, and then the gas enters the external cooler through the cooling nitrogen inlet of the external cooler to cool the direct reduced iron, forming a closed loop;

[0015] 2) Adding fresh nitrogen from a high-pressure nitrogen source to the nitrogen circulated in step (2) as needed.

[0016] The nitrogen temperature at the cooling nitrogen inlet of the method of the present invention is 30-40°C, and the nitrogen temperature at the cooling nitrogen outlet is 200-220°C.

[0017] The beneficial effects of the above technical solution are as follows: the nitrogen carrying particulate matter discharged from the pressure discharge tank under reduced pressure of the present invention is injected with water in the quenching orifice plate, and the particulate matter is fully captured by the pressure change of the venturi tube, and then the gas and liquid are separated by the reduced pressure scrubber, and the particulate matter enters the water for subsequent treatment, and the discharged nitrogen is clean and harmless; when the external cooler is overhauled, the nitrogen used for nitrogen purging can also be treated by the above process, and no longer directly discharged. The present invention can effectively control particulate matter emissions, achieve ultra-low particulate matter emissions, improve the surrounding environment of the direct reduction shaft furnace plant, and allow production workers to breathe clean air.

[0018] The present invention adopts nitrogen to cool the direct reduced iron. The nitrogen after cooling the direct reduced iron is mixed with gas and liquid through the quenching orifice plate, the venturi captures dust, and the separation tower is used to achieve gas-liquid separation. After cooling through the quenching tower, the dehydrator removes moisture, and further filters through the filter to enter the compressor process. The compressor provides loop circulation power. After the compressor compresses the gas, the gas temperature will increase. The aftercooler is used to cool it again to 30-40°C, and then the secondary dehydrator is used to remove the remaining moisture. The cooling gas inlet of the cone of the external cooler enters the external cooler again to cool the direct reduced iron to form a closed loop. Therefore, the emission of particulate matter during the cooling process can be effectively controlled to achieve ultra-low emission of particulate matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] In the figure: 01 is a direct reduction vertical furnace, 02 is an external cooler, 03 is a pressure discharge tank, 04 is a transfer belt, 05 is a nitrogen storage tank, 06 is a washing quenching orifice plate, 07 is a washing venturi, 08 is a pressure reducing scrubber, 09 is a circulating water pump, 10 is a circulating water station, 11 is a nitrogen charging valve, 12 is a booster valve, 13 is a pressure reducing valve, 14 is a nitrogen shut-off valve, 15 is a purge nitrogen inlet, 16 is a purge nitrogen outlet, 17 is a cooling nitrogen inlet, 18 is a cooling nitrogen outlet, 19 is a cooling gas quenching orifice plate, 20 is a cooling gas venturi, 21 is a separation tower, 22 is a quenching tower, 23 is a dehydrator, 24 is a filter, 25 is a compressor, 26 is an aftercooler, and 27 is a secondary dehydrator. DETAILED DESCRIPTION

[0022] Figure 1As shown, the discharge system of the external cooler of the gas-based vertical furnace includes a direct reduction vertical furnace 01, an external cooler 02, a pressure discharge tank 03, a nitrogen storage tank 05, a washing quenching orifice plate 06, a washing venturi 07, a decompression scrubber 08, a circulating water station 10 and a circulating water pump 09. A discharge port is provided at the bottom of the direct reduction vertical furnace 01, and the external cooler 02 is located below the direct reduction vertical furnace 01. The feed port at the top of the external cooler 02 faces and is connected to the discharge port at the bottom of the direct reduction vertical furnace 01; in this way, the direct reduced iron generated by the reaction of the direct reduction vertical furnace 01 can be discharged and loaded into the external cooler 02. The discharge port at the bottom of the external cooler 02 is connected to the feed port of the pressure discharge tank 03; there are two pressure discharge tanks 03, and both feed ports of the two pressure discharge tanks 03 are connected to the discharge port at the bottom of the external cooler 02; in this way, the two pressure discharge tanks 03 can be discharged alternately to ensure continuous discharge. The pressure discharge tank 03 has a discharge port at its lower portion, and a transfer belt 04 is provided below the pressure discharge tank 03 , the transfer belt 04 being directly opposite to the discharge port of the pressure discharge tank 03 .

[0023] Figure 1 As shown, the two pressure discharge tanks 03 of the discharge system of the gas-based vertical furnace external cooler are both provided with nitrogen ports, and the nitrogen ports of the two pressure discharge tanks 03 can be connected to the nitrogen storage tank 05 through pipelines, and a booster valve 12 is provided on the pipeline between the pressure discharge tank 03 and the nitrogen ports of the nitrogen storage tank 05; the nitrogen storage tank 05 is a high-pressure nitrogen source, and can also be connected to a high-pressure nitrogen pipeline as a high-pressure nitrogen source. The pipeline between the nitrogen storage tank 05 and the booster valve 12 is connected to the middle and lower part of the external cooler 02 through a nitrogen filling valve 11. The nitrogen port of the pressure discharge tank 03 is connected to the air inlet of the washing quenching orifice plate 06 through a pipeline, the air outlet of the washing quenching orifice plate 06 is connected to the inlet of the washing venturi 07 through a pipeline, and the outlet of the washing venturi 07 is connected to the air inlet of the lower part of the pressure reducing scrubber 08 through a pipeline; an exhaust port is provided on the top of the pressure reducing scrubber 08; in this way, the nitrogen carrying particulate matter is injected with water in the washing quenching orifice plate 06, the particulate matter is fully captured by the pressure change of the washing venturi 07, and then the gas-liquid is separated by the pressure reducing scrubber 08, and the nitrogen free of particulate matter is discharged through the exhaust port of the pressure reducing scrubber 08.

[0024] Figure 1 As shown, the discharge system of the gas-based vertical furnace external cooler is provided with a purge nitrogen inlet 15 at the bottom and a purge nitrogen outlet 16 at the top of the external cooler 02; the purge nitrogen inlet 15 is connected to the high-pressure nitrogen source-nitrogen storage tank 05, and is provided with a nitrogen filling valve 11; the purge nitrogen outlet 16 pipeline and the nitrogen stop valve 14 are connected to the pipeline between the pressure reducing valve 13 and the washing quenching orifice plate 06, and are provided with a pressure reducing valve 14. In this way, a purge nitrogen pipeline is formed, and the nitrogen carrying particulate matter after purge can be discharged after being treated by the washing quenching orifice plate 06, the washing venturi 07 and the pressure reducing scrubber 08.

[0025] Figure 1 As shown, in the discharge system of the external cooler of the gas-based vertical furnace, the vacuum scrubber 08 is provided with a liquid outlet at the bottom and a liquid inlet at the top; the liquid outlet of the vacuum scrubber 08, the circulating water pump 09, the circulating water station 10 and the liquid inlet of the vacuum scrubber 08 are connected through a pipeline; the pipeline between the circulating water station 10 and the liquid inlet of the vacuum scrubber 08 is also connected to the liquid inlet of the washing quenching orifice plate 06; thus, two circulating water pipelines are formed; one path passes through the washing quenching orifice plate 06, the washing venturi 07, the vacuum scrubber 08, and the circulating water pump 09 and then returns to the circulating water station 10; the other path passes through the vacuum scrubber 08 and the circulating water pump 09 and then returns to the circulating water station 10.

[0026] Figure 1 As shown, the discharge system of the external cooler of the gas-based vertical furnace also includes a cooling gas quenching orifice plate 19, a cooling gas venturi 20, a separation tower 21, a quenching tower 22, a dehydrator 23, a filter 24, a compressor 25, an aftercooler 26 and a secondary dehydrator 27; the lower part of the external cooler 02 is provided with a cooling nitrogen inlet 17, and the upper part is provided with a cooling nitrogen outlet 18; the cooling nitrogen outlet 18 is connected to the cooling gas quenching orifice plate 19, the cooling gas venturi 20, the separation tower 21, the quenching tower 22, the dehydrator 23, the filter 24, the compressor 25, the aftercooler 26 and the secondary dehydrator 27 in sequence through a pipeline, and the outlet of the secondary dehydrator 27 is connected to the cooling nitrogen inlet 17; in this way, a circulating pipeline for nitrogen cooling is formed.

[0027] Figure 1 As shown, the process steps of the discharge method using a gas-based vertical furnace external cooler are as follows: 1) High-quality pellets are loaded from the top of the direct reduction vertical furnace 01, react with the reducing gas in the vertical furnace, and are discharged from the bottom of the vertical furnace to generate direct reduced iron. The temperature of the direct reduced iron is 600-700°C, which does not meet the conditions for cold discharge and must be further cooled.

[0028] 2) The direct reduced iron is discharged from the bottom of the direct reduction vertical furnace 01 and loaded into the external cooler 02, where it is further cooled by nitrogen, and then discharged from the bottom of the external cooler 02 and loaded into the pressure discharge tank 03. The temperature of the discharged direct reduced iron is below 50°C. The pressure discharge tank 03 discharges the material onto the transfer belt, which is then transported to the storage unit or used directly.

[0029] 3) The external cooler is cooled by nitrogen. Nitrogen at 30-40°C is injected from the cooling nitrogen inlet 17 of the lower cone of the external cooler, and flows in the opposite direction to the direct reduced iron that descends by gravity inside. The direct reduced iron is discharged from the bottom of the external cooler; the nitrogen that completes the cooling task is discharged from the upper part of the external cooler. The temperature of the discharged nitrogen is 200-220°C, and it carries dust, so the circulation power is reduced. To recycle it, dust removal and cooling are necessary to provide recycling power.

[0030] The high-temperature nitrogen discharged from the cooling nitrogen outlet 18 at the upper part of the external cooler after cooling the direct reduced iron first enters the cooling gas quenching orifice plate 19; the cooling gas quenching orifice plate 19 is a concentric tube structure, and uniform small holes are arranged at the upper end of the inner tube; the nitrogen passes through the inner tube from top to bottom; the circulating water is injected from the lower part of the shell side, injected through the small holes at the upper end of the inner tube to mix with the nitrogen carrying dust; the gas and water are mixed and enter the cooling gas venturi 20.

[0031] The gas-liquid mixture coming out of the cooling gas quenching orifice plate enters the cooling gas venturi 20; the cooling gas venturi 20 is a variable diameter structure. Due to the structural characteristics, after passing through the fixed throat of the cooling gas venturi 20, the gas flow rate increases, causing the water to be finely dispersed in small droplets, and the small droplets capture dust particles. Thereafter, the solid particles continue to be entrained in the liquid flow.

[0032] The gas-liquid mixture from the cooling gas venturi 20 enters the separation tower 21, where the gas is discharged from the top and the liquid carrying dust is discharged from the bottom. At this time, the nitrogen discharged from the separation tower 21 is clean nitrogen.

[0033] The nitrogen discharged from the separation tower 21 enters the quenching tower 22, where the nitrogen is cooled by cooling water to a temperature of 35-45° C. In the quenching tower 22, cooling water is injected from the top and nitrogen is injected from the west to form a countercurrent, and the cooled nitrogen is discharged from the top and water is discharged from the bottom.

[0034] The nitrogen discharged from the quench tower 22 is dehydrated by the dehydrator 23, and then filtered by the filter 24 to remove particulate matter, and then enters the compressor 25; the compressor 25 provides power for recycling, and the temperature of the compressed nitrogen will increase, normally to 70-80°C.

[0035] The nitrogen compressed by the compressor 25 is cooled again by the aftercooler 26 to 30-40° C. Considering the characteristics of the direct reduced iron in the external cooler 02, it is easily oxidized and cannot come into contact with water; the nitrogen discharged by the aftercooler 26 is deeply dehydrated by the secondary dehydrator 2.

[0036] After the above steps, the nitrogen meets the cooling gas condition again and is injected again from the cooling nitrogen inlet 17 of the lower cone of the external cooler 02 to form a closed circulation loop of the entire cooling gas.

[0037] During production, due to pipeline leakage or other reasons, it is detected that the nitrogen flow in the cooling gas closed circulation loop is significantly reduced, and the nitrogen filling valve 11 is opened to purge the nitrogen inlet 15 to supplement fresh nitrogen.

[0038] 4) The pressure discharge tank 03 switches between high pressure and normal pressure. When pressurizing, the nitrogen provided by the nitrogen storage tank 05 is used. The pressure boosting valve 12 is opened for punching. When the pressure reaches the pressure equal to the pressure of the external cooler 02, the material is loaded. After loading, the pressure boosting valve 12 is closed, and the pressure reducing valve 13 is opened to release the pressure until the internal pressure of the pressure discharge tank 03 is the same as the atmospheric pressure, and the material is discharged.

[0039] 5) The nitrogen generated by the decompression of the pressure discharge tank 03 enters the washing quenching orifice plate 06. The washing quenching orifice plate 06 is a concentric tube structure, and uniform small holes are arranged on the upper end of the inner tube; the nitrogen passes through the inner tube from top to bottom; the circulating water is injected from the lower part of the shell side, injected through the small holes on the upper end of the inner tube and mixed with the nitrogen carrying particulate matter; the gas and water are mixed and enter the washing venturi 07.

[0040] The washing venturi 07 is a variable diameter structure. Due to the structural characteristics, after passing through the fixed throat of the washing venturi 07, the gas flow rate increases, causing the water to be finely dispersed in small droplets, and the small droplets capture dust particles. Thereafter, the solid particles continue to be entrained in the liquid flow.

[0041] The gas-liquid mixed fluid is injected from the lower part of the vacuum scrubber 08. In the vacuum scrubber 08, the gas flows upward and is discharged from the top; the liquid flow accompanied by particulate matter flows downward and is discharged from the bottom. The vacuum scrubber 08 is a multi-layered packed tower, which can fully achieve gas-liquid separation and effectively control the particulate matter content in the gas.

[0042] 6) During normal production, the nitrogen filling valve 11 of the external cooler 02 is closed; when the external cooler 02 needs to be inspected and purged, the nitrogen filling valve 11 is opened to fill with nitrogen, and the used nitrogen is discharged from the upper part of the external cooler 02 (the nitrogen at this time carries a large amount of particulate matter), passes through the nitrogen stop valve 14 and enters the nitrogen pipeline after the pressure reducing valve, and then enters the washing quenching orifice plate 06 and subsequent devices, and the particulate matter carried in the gas is washed.

[0043] 7) The circulating water produced by the circulating water station 10 is divided into two paths. One path enters the washing quenching orifice plate 06 to merge with the nitrogen carrying particulate matter, and then passes through the washing venturi 07 to capture the particulate matter. The gas and water are separated in the vacuum scrubber 08, and the sewage is discharged from the lower part of the vacuum scrubber 08. The sewage discharged from the vacuum scrubber 08 is provided with circulation power by the circulating water pump 09 and returns to the circulating water station 10. The other path of circulating water directly enters the upper part of the vacuum scrubber 08 to wash the gas. The sewage formed after washing the gas is discharged from the lower part of the vacuum scrubber 08, and is provided with circulation power by the circulating water pump 09 and returns to the circulating water station 10.

[0044] Clean circulating water is injected into the upper part of the vacuum scrubber 08 and flows downward to form a countercurrent with the rising nitrogen carrying particulate matter. Due to the presence of multiple layers of filling pads in the vacuum scrubber 08, the two can fully contact each other to wash away the particulate matter in the nitrogen.

Claims

1. An exhaust system for an external cooler of a gas-based vertical furnace, characterized in that: It comprises a direct reduction vertical furnace (01), an external cooler (02), a pressure discharge tank (03), a washing quenching orifice plate (06), a washing venturi (07) and a pressure reducing scrubber (08); the feed port at the top of the external cooler (02) is connected to the discharge port at the bottom of the direct reduction vertical furnace (01), the discharge port at the bottom of the external cooler (02) is connected to the feed port of the pressure discharge tank (03), and the nitrogen port of the pressure discharge tank (03) is connected to a high-pressure nitrogen source through a pipeline and a booster valve (12); The nitrogen port of the pressure discharge tank (03) is also connected to the washing quenching orifice plate (06), the washing venturi (07) and the pressure reducing scrubber (08) in sequence through a pipeline, and a pressure reducing valve (13) is provided on the pipeline between the nitrogen port of the pressure discharge tank (03) and the washing quenching orifice plate (06); the lower part of the external cooler (02) is connected to the high-pressure nitrogen source, and the upper part of the external cooler (02) is connected to the pipeline between the pressure reducing valve (13) and the washing quenching orifice plate (06) through a pipeline and a nitrogen stop valve (14).

2. The exhaust system of the external cooler of a gas-based vertical furnace according to claim 1, characterized in that: A circulating water station (10) and a circulating water pump (09) are also provided; the liquid outlet of the reduced pressure scrubber (08), the circulating water pump (09), the circulating water station (10) and the liquid inlet of the reduced pressure scrubber (08) are connected in sequence through pipelines.

3. The exhaust system of the external cooler of a gas-based vertical furnace according to claim 2, characterized in that: The circulating water station (10) is also connected to the liquid inlet of the washing quenching orifice plate (06) through a pipeline.

4. The exhaust system of the external cooler of a gas-based vertical furnace according to claim 1, 2 or 3, characterized in that: It also includes a cooling gas quenching orifice plate (19), a cooling gas venturi (20), a separation tower (21), a quenching tower (22), a dehydrator (23), a filter (24), a compressor (25), an aftercooler (26) and a secondary dehydrator (27); the lower part of the external cooler (02) is provided with a cooling nitrogen inlet (17), and the upper part is provided with a cooling nitrogen outlet (18); the cooling nitrogen outlet (18) is connected to the cooling gas quenching orifice plate (19), the cooling gas venturi (20), the separation tower (21), the quenching tower (22), the dehydrator (23), the filter (24), the compressor (25), the aftercooler (26) and the secondary dehydrator (27) in sequence through a pipeline, and the outlet of the secondary dehydrator (27) is connected to the cooling nitrogen inlet (17).

5. A method for discharging an external cooler of a gas-based vertical furnace, using the discharge system according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: 1) high-quality pellets are added from the top of a direct reduction shaft furnace (01), react with reducing gas in the direct reduction shaft furnace (01), and the generated direct reduced iron enters an external cooler (02) for cooling, and then enters a pressure discharge tank (03); 2) The pressure discharge tank (03) is pressurized by nitrogen sent from a high-pressure nitrogen source, and when the pressure inside the tank is equal to the pressure of the external cooler (02), loading is performed; when the pressure discharge tank (03) is unloaded, the nitrogen is first discharged to reduce the pressure to atmospheric pressure before discharging; 3) During the decompression process of the pressure discharge tank (03), nitrogen gas carrying particulate matter is discharged; the nitrogen gas carrying particulate matter is discharged after being mixed with gas and liquid by the washing quenching orifice plate (06), being captured by the washing venturi (07), and being washed by the decompression scrubber (08) for particulate matter.

6. The method for discharging an external cooler of a gas-based vertical furnace according to claim 5, characterized in that: The method further comprises the following steps: when the external cooler (02) needs to be overhauled and purged, nitrogen is filled into the external cooler (02) from a high-pressure nitrogen source for purging, and the nitrogen carrying particulate matter after purging is discharged from the upper part of the external cooler (02), passes through a nitrogen shut-off valve (14), enters a washing quenching orifice plate (06) for gas-liquid mixing, a washing venturi (07) for capturing dust, and a pressure reducing scrubber (08) for washing particulate matter, and then the clean nitrogen is discharged.

7. The method for discharging an external cooler of a gas-based vertical furnace according to claim 5, characterized in that: The method further comprises the following steps: the circulating water of the circulating water station (10) is divided into two paths, one path enters the washing quenching orifice plate (06) to merge with the nitrogen carrying particulate matter, passes through the washing venturi (07) to capture dust, and separates gas and water in the vacuum scrubber (08), and the wastewater is discharged from the vacuum scrubber (08) and returned to the circulating water station (10) through the circulating water pump (09); the other path of circulating water directly enters the vacuum scrubber (08) to wash the gas, and the wastewater formed after washing the gas is discharged from the vacuum scrubber (08) and returned to the circulating water station (10) through the circulating water pump (09).

8. A method for discharging an external cooler of a gas-based vertical furnace according to claim 5, 6 or 7, characterized in that: The method further comprises the following steps: 1) the external cooler (02) uses nitrogen as a cooling medium; the nitrogen after cooling the direct reduced iron is discharged from the cooling nitrogen outlet (18) of the external cooler (02), mixed with gas and liquid through the cooling gas quenching orifice plate (19), and dust is captured by the cooling gas venturi (20), and gas-liquid separation is achieved by using a separation tower (21), and cooled by the quenching tower (22), and water is removed by a dehydrator (23), and further filtered by a filter (24) before entering a compressor (25); after the compressor (25) compresses the gas, the gas is cooled again by an aftercooler (26), and then the remaining water is removed by a secondary dehydrator (27), and then the gas enters the external cooler (02) through the cooling nitrogen inlet (17) of the external cooler (02) again to cool the direct reduced iron, thereby forming a closed loop; 2) Add fresh nitrogen from a high-pressure nitrogen source to the nitrogen circulated in the above steps as needed.

9. The method for discharging an external cooler of a gas-based vertical furnace according to claim 8, characterized in that: The nitrogen temperature at the cooling nitrogen inlet (17) is 30-40°C, and the nitrogen temperature at the cooling nitrogen outlet (18) is 200-220°C.

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