Device and method for preventing carbon deposition of hot gas valve of hydrogen-rich carbon circulating oxygen blast furnace

Abstract

The invention belongs to the technical field of hot gas valves, and particularly discloses a device for preventing carbon deposition of a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace, which comprises a hot gas valve, a PLC (programmable logic controller) and a nozzle, a hot gas pipe, a magnetostrictive sensor and the nozzle are arranged on the hot gas valve, and a pressure sensor and a gas component analyzer are arranged on the hot gas pipe. The nozzle is provided with a nitrogen pipe, the nitrogen pipe is provided with a safety valve, a check valve, an electromagnetic valve, a nitrogen valve, a flow regulating valve and a pressure regulating valve, and the magnetostriction sensor, the pressure sensor, the check valve, the electromagnetic valve, the flow regulating valve and the pressure regulating valve are all electrically connected with the PLC; the PLC controls the pressure and flow of nitrogen according to the content of carbon dioxide and the offset distance of the valve rod, and blowing nitrogen blows carbon deposit in the hot gas valve until the carbon deposit is cleaned, so that the problem that the hot gas valve is not opened and closed in place due to the fact that carbon separated out when mixed hot gas is conveyed is accumulated at the bottom of the hot gas valve is solved; and the service life of the valve is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of hot gas valves, and in particular to a device and method for preventing carbon deposition in a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace. Background Art

[0002] The hydrogen-rich carbon circulating oxygen blast furnace is currently the most effective innovative technology for achieving carbon emission reduction in traditional ironmaking processes. After removing carbon dioxide from the coal gas, it is heated to 1200℃ and then recycled to the hydrogen-rich carbon circulating oxygen blast furnace. During this period, a large amount of hydrogen-rich coal gas is also used, and the hydrogen-rich coal gas is also heated and recycled to the hydrogen-rich carbon circulating oxygen blast furnace. The existing gas heating furnace uses three to four gas heating furnaces to heat the coal gas. During this period, there is always one gas heating furnace in the hot gas delivery stage, and the remaining gas heating furnaces are in the furnace burning and heat storage stage. Three to four gas heating furnaces rotate to deliver hot gas, and it is necessary to ensure both the temperature of the hot gas and the continuous delivery of gas. During this period, a hot gas valve is installed at the outlet of each gas heating furnace. The hot gas valve is opened when delivering hot gas and closed when the hot gas delivery is stopped.

[0003] However, in actual operation, the mixing of highly reducing decarbonized coal gas and hydrogen-rich coal gas with heating easily leads to carbon deposition. This deposited carbon gradually accumulates at the bottom of the hot gas valve. This deposit can cause the hot gas valve to open and close improperly and fail to close properly. It can also damage the valve's sealing structure, causing gas leaks and potentially safety accidents. Furthermore, the long-term presence of this deposit accelerates corrosion of the valve's bottom components, shortening the valve's service life and increasing equipment maintenance costs. Currently, the main method for cleaning hot gas valves is manual disassembly and cleaning, which is labor-intensive and inefficient, requiring the blast furnace to shut down and interrupt production. Furthermore, the disassembly process carries the risk of gas leakage, posing a threat to the operator's safety. Summary of the Invention

[0004] The object of the present invention is to provide a device and method for preventing carbon deposition in the hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace, so as to solve the problem that carbon precipitated during the delivery of mixed hot gas accumulates at the bottom of the hot gas valve, causing the hot gas valve to not open and close properly, resulting in gas leakage and shortening the service life of the valve.

[0005] To achieve the above objectives, the present invention provides a basic solution: a device for preventing carbon deposition on a hot gas valve in a hydrogen-rich carbon circulating oxygen blast furnace, comprising a hot gas valve, a PLC controller, and a nozzle. The hot gas valve is provided with a hot gas pipe, a magnetostrictive sensor, a pressure sensor, and a gas composition analyzer. The nozzle and the hot gas valve are fixedly connected. A nitrogen pipe is connected to the nozzle, and the other end of the nitrogen pipe is connected to a nitrogen tank. The nitrogen pipe is sequentially provided with a safety valve, a check valve, a solenoid valve, a nitrogen valve, a flow regulating valve, and a pressure regulating valve. The magnetostrictive sensor, pressure sensor, check valve, solenoid valve, flow regulating valve, and pressure regulating valve are all electrically connected to the PLC controller.

[0006] The principles and beneficial effects of the present invention are as follows: during installation, the magnetic ring of the magnetostrictive sensor is mounted on the valve stem of the hot gas valve. When carbon deposits appear in the hot gas valve, the valve stem of the hot gas valve deflects. The PLC controller controls the opening of the nitrogen valve based on the carbon dioxide content, and then controls the flow regulating valve and the pressure regulating valve based on the deflection distance of the valve stem. The carbon deposits in the hot gas valve are purged by injecting nitrogen until the carbon deposits are cleared and the valve stem of the hot gas valve does not deflect. When the gas heating furnace stops supplying hot gas and the hot gas valve is closed, the introduction of nitrogen effectively prevents leakage of high-temperature gas from the hot gas valve. The real-time purging and cleaning effectively prevents carbon deposits at the bottom of the hot gas valve, reduces valve operating resistance, ensures smooth valve opening and closing, avoids sealing failure and leakage caused by carbon deposits, and improves the operational reliability and safety of the valve.

[0007] Option 2 is the preferred basic option. The hot gas valve is a high-temperature water-cooled gate valve, the nozzle is a ceramic nitrogen nozzle, the check valve is a swing check valve, model Neway Valve H44H, the solenoid valve is a direct-acting solenoid valve, model FestoMS6-LFE, the flow control valve is an intelligent electric control valve, model Siemens SIPART PS2 with SITRANS F, and the pressure control valve is an electric pressure control valve, model Emerson Fisher GX series; swing check valve has the advantages of low flow resistance, high pressure adaptability, impurity resistance and easy maintenance. It is easy to install and takes up little space. It responds quickly and can realize switching action in a short time to meet the needs of rapid control. The direct-acting solenoid valve is easy to operate and can realize automatic control without a complex control system. It has low cost. The intelligent electric control valve can adjust the flow rate with high precision to meet the precise control needs of complex working conditions. It has a high degree of automation and can be linked with the host computer system to realize remote monitoring and automatic adjustment, greatly reducing the intensity of manual operation. The electric pressure regulating valve has the advantage of precise pressure control. Through the linkage of the electric actuator and the intelligent control system, the system pressure can be accurately adjusted in real time to meet the high-precision pressure control needs under different working conditions. It has a high degree of automation and supports remote monitoring and automatic adjustment without the need for frequent manual intervention.

[0008] Solution 3: The basic solution provided by the present invention is: a method for preventing carbon deposition in a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace, comprising the following steps: S1. The pressure sensor transmits the real-time hot gas pressure to the PLC controller, sets the hot gas valve stem offset distance interval, the magnetostrictive sensor transmits the real-time hot gas valve stem offset distance to the PLC controller, and the gas composition analyzer transmits the real-time gas composition in the hot gas to the PLC controller; S2. The PLC controller controls the nitrogen valve according to the carbon dioxide content in the hot coal gas. If the nitrogen valve is open, the process proceeds to the next step. If not, the process ends. S3. After the nitrogen valve opens, the PLC controller controls the flow control valve based on the real-time offset of the hot gas valve stem in S1, purging the carbon deposits in the hot gas valve with nitrogen. S4. When the real-time offset distance of the hot gas valve stem is not 0, the PLC controller controls the pressure regulating valve according to the carbon purging condition and the hot gas pressure, and adjusts the nitrogen pressure to purge the carbon deposits in the hot gas valve; S5. If the purge time in S4 is ≥ 30 minutes, the process ends when the real-time offset distance of the hot gas valve stem is 0. If the real-time offset distance of the hot gas valve stem is not 0, the process loops back to step S4 and adjusts the nitrogen pressure until the real-time offset distance of the hot gas valve stem is 0.

[0009] Solution 4 is a preferred solution of Solution 3. In step S1, the valve stem offset distance intervals of the hot gas valve are 0-10 mm, 10-15 mm and ≥15 mm respectively.

[0010] Option 5 is a preferred option of Option 3. When the carbon dioxide content in step S2 is ≥1%, the nitrogen valve is opened. If the carbon dioxide content is <1%, the nitrogen valve does not need to be opened.

[0011] Option 6, which is a preferred option of Option 3, the method for controlling the nitrogen flow rate in step S3 is: When the valve stem offset distance of the hot gas valve is 0-10mm, the flow regulating valve controls the nitrogen flow rate to be 100-200m³ / h, the nitrogen pressure is 0.3Mpa higher than the hot gas pressure, and the purge time is 6 minutes; When the valve stem offset distance of the hot gas valve is 10-15mm, the flow regulating valve controls the nitrogen flow rate to be 200-300m³ / h, the nitrogen pressure is 0.5Mpa higher than the hot gas pressure, and the purge time is 10min; When the valve stem offset distance of the hot gas valve is ≥15mm, the flow regulating valve controls the nitrogen flow rate to be 300-500m³ / h, the nitrogen pressure is 0.7Mpa higher than the hot gas pressure, and the purge time is 20min.

[0012] Option 7, which is a preferred option of Option 3, the method for controlling the nitrogen pressure in step S4 is: When the valve stem offset distance of the hot gas valve is 0-10mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 0.5Mpa, and the purge time is extended to 10min; When the valve stem offset distance of the hot gas valve is 10-15mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 0.7Mpa, and the purge time is extended to 15min; When the valve stem offset distance of the hot gas valve is ≥15mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 1Mpa, and the purge time is extended to 25min.

[0013] Option 8 is a preferred option of Option 3. The method for adjusting the nitrogen pressure during the cycle in step S5 is: the PLC controller controls the nitrogen pressure to increase by 0.01 MPa / min until the real-time offset distance of the valve stem of the hot gas valve is 0. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a left view of a device and method for preventing carbon deposition on a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace according to the present invention; Figure 2 This is a schematic diagram of the installation of a device and method for preventing carbon deposition in a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace according to the present invention; Figure 3 The present invention discloses a flow chart of a device and method for preventing carbon deposition in a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below through specific embodiments: The figure marks in the drawings of the specification include: 1. hot gas valve, 2. nozzle, 3. safety valve, 4. check valve, 5. solenoid valve, 6. nitrogen valve, 7. flow regulating valve, 8. pressure regulating valve, 9. nitrogen tank, 10. nitrogen pipe, 11. pressure sensor, 12. hot gas pipe, 13. magnetostrictive sensor, 14. gas composition analyzer.

[0016] Example 1 like Figure 1 and Figure 2As shown: A device for preventing carbon deposition of a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace, comprising a hot gas valve 1, a PLC controller and a nozzle 2. The hot gas valve 1 is a high-temperature water-cooled gate valve, the nozzle 2 is a ceramic nitrogen nozzle, a hot gas pipe 12 is provided on the hot gas valve 1, a magnetostrictive sensor 13 is provided on the hot gas valve 1, a pressure sensor 11 and a gas composition analyzer 14 are provided on the hot gas pipe 12, a pressure regulating valve 8 is an electric pressure regulating valve, model is Emerson Fisher GX series, the nozzle 2 and the hot gas valve 1 are fixedly penetrated, a nitrogen pipe 10 is connected to the nozzle 2, the other end of the nitrogen pipe 10 is connected to a nitrogen tank 9, a safety valve 3, a check valve 4, a solenoid valve 5, a nitrogen valve 6, a flow regulating valve 7 and a pressure regulating valve 8 are provided on the nitrogen pipe 10 in sequence, the check valve 4 is a swing check valve, model is Neway Valve H44H, the solenoid valve 5 is a direct-acting solenoid valve, model is Festo MS6-LFE, the flow control valve 7 is an intelligent electric control valve, model Siemens SIPART PS2 with SITRANS F, the magnetostrictive sensor 13, the pressure sensor 11, the check valve 4, the solenoid valve 5, the flow control valve 7 and the pressure control valve 8 are all electrically connected to the PLC controller.

[0017] This embodiment operates as follows: during installation, the magnetic ring of the magnetostrictive sensor 13 is mounted on the valve stem of the hot gas valve 1. When carbon deposits form in the hot gas valve 1, the magnetostrictive sensor 13 transmits the detected valve stem offset distance of the hot gas valve 1 to the PLC controller. The PLC then controls the opening of the nitrogen valve 6 based on the carbon dioxide content. The PLC then controls the flow control valve and the pressure control valve based on the valve stem offset distance to purge the carbon deposits in the hot gas valve 1 until the carbon deposits are cleared and the valve stem offset distance of the hot gas valve 1 is zero. When the gas heater stops supplying hot gas and the hot gas valve 1 is closed, nitrogen is introduced to effectively prevent high-temperature gas leakage from the hot gas valve 1.

[0018] Example 2 like Figure 3 A method for preventing carbon deposition in a hot gas valve of a hydrogen-rich carbon circulating oxygen blast furnace is shown, comprising the following steps: S1. The pressure sensor transmits the real-time hot gas pressure to the PLC controller. The hot gas valve stem offset distance ranges are set to 0-10mm, 10-15mm, and ≥15mm. The magnetostrictive sensor transmits the real-time hot gas valve stem offset distance to the PLC controller. The gas composition analyzer transmits the real-time gas composition of the hot gas to the PLC controller. S2. The PLC controller opens the nitrogen valve when the carbon dioxide content in the hot gas is ≥1%. If the carbon dioxide content is <1%, there is no need to open the nitrogen valve. S3. After the nitrogen valve opens, the PLC controller controls the flow control valve based on the real-time offset of the hot gas valve stem in S1. When the hot gas valve stem offset is 0-10 mm, the flow control valve controls the nitrogen flow rate to 100-200 m³ / h, the nitrogen pressure is 0.3 MPa higher than the hot gas pressure, and the purge time is 6 minutes. When the valve stem offset distance of the hot gas valve is 10-15mm, the flow regulating valve controls the nitrogen flow rate to be 200-300m³ / h, the nitrogen pressure is 0.5Mpa higher than the hot gas pressure, and the purge time is 10min; When the valve stem offset distance of the hot gas valve is ≥15mm, the flow regulating valve controls the nitrogen flow rate to 300-500m³ / h. The nitrogen pressure is 0.7Mpa higher than the hot gas pressure. The purge time is 20min. The carbon deposits in the hot gas valve are purged with nitrogen. S4. When the hot gas valve stem offset is not zero, the PLC controller controls the pressure regulating valve based on the carbon purging status and the hot gas pressure. When the hot gas valve stem offset is between 0 and 10 mm, the PLC controller adjusts the nitrogen pressure to 0.5 MPa above the hot gas pressure and extends the purge time to 10 minutes. When the valve stem offset distance of the hot gas valve is 10-15mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 0.7Mpa, and the purge time is extended to 15min; When the stem offset of the hot gas valve is ≥15mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 1Mpa, and the purge time is extended to 25min; S5. If the purge time in S4 is ≥ 30 min, the process ends when the real-time offset distance of the hot gas valve stem is 0. If the real-time offset distance of the hot gas valve stem is not 0, the process loops back to step S4, where the PLC controller increases the nitrogen pressure by 0.01 MPa / min until the real-time offset distance of the hot gas valve stem is 0.

[0019] The implementation method of this embodiment is as follows: the valve stem offset distance intervals of the hot gas valve are set in the PLC controller to 0-10mm, 10-15mm, and ≥15mm, respectively. When the hot gas valve is delivering hot gas and the carbon dioxide content is less than 1%, the nitrogen valve does not need to be opened. When the carbon dioxide content in the hot gas is ≥1%, the nitrogen valve is opened to purge the hot gas valve. During the purge process, the PLC controller controls the flow control valve according to the real-time valve stem offset distance of the hot gas valve: when the valve stem offset distance of the hot gas valve is 0-10mm, the flow control valve controls the nitrogen flow rate to 100-200m³ / h, the nitrogen pressure is 0.3MPa higher than the hot gas pressure, and the purge time is 6 minutes. If valve stem offset still exists after 6 minutes, the nitrogen pressure is controlled to be higher than the hot gas pressure to 0.5MPa, and the purge time is extended to 10 minutes. If valve stem offset still exists after 10 minutes, the nitrogen pressure is cyclically increased by 0.01MPa / min until the valve stem of the hot gas valve stops offsetting. When the hot gas valve stem deflection distance is 10-15mm, the flow control valve controls the nitrogen flow rate to 200-300m³ / h, the nitrogen pressure is 0.5Mpa higher than the hot gas pressure, and the purge time is 10 minutes. If the valve stem still deflects after 10 minutes, the nitrogen pressure is controlled to be 0.7Mpa higher than the hot gas pressure, and the purge time is extended to 15 minutes. If the valve stem still deflects after 15 minutes, the nitrogen pressure is increased by 0.01Mpa / min until the hot gas valve stem stops deflecting. When the valve stem offset distance of the hot gas valve is ≥15mm, the flow regulating valve controls the nitrogen flow rate to 300-500m³ / h, the nitrogen pressure is 0.7Mpa higher than the hot gas pressure, and the purge time is 20min; if the valve stem offset still exists after 20min, the nitrogen pressure is controlled to be 1Mpa higher than the hot gas pressure, and the purge time is extended to 25min. If the valve stem offset still exists after 25min, the nitrogen pressure is cyclically increased by 0.01Mpa / min until the valve stem of the hot gas valve stops offsetting.

[0020] When the hot gas valve stops delivering hot gas and is closed, the nitrogen flow rate is 100-200m 3 / h, the pressure is 0.25-0.45MPa, which can effectively prevent the leakage of high-temperature gas from the hot gas valve.

[0021] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A device for preventing carbon deposition on hot gas valves of hydrogen-rich carbon circulating oxygen blast furnaces, characterized in that: The invention comprises a hot gas valve (1), a PLC controller and a nozzle (2), wherein the hot gas valve (1) is provided with a hot gas pipe (12), the hot gas valve (1) is provided with a magnetostrictive sensor (13), the hot gas pipe (12) is provided with a pressure sensor (11) and a gas composition analyzer (14), the nozzle (2) and the hot gas valve (1) are fixedly penetrated, the nozzle (2) is connected with a nitrogen pipe (10), the other end of the nitrogen pipe (10) is connected with a nitrogen tank (9), the nitrogen pipe (10) is provided with a safety valve (3), a check valve (4), a solenoid valve (5), a nitrogen valve (6), a flow regulating valve (7) and a pressure regulating valve (8) in sequence, and the magnetostrictive sensor (13), the pressure sensor (11), the check valve (4), the solenoid valve (5), the flow regulating valve (7) and the pressure regulating valve (8) are all electrically connected to the PLC controller.

2. The device for preventing carbon deposition of hot gas valves in hydrogen-rich carbon cycle oxygen blast furnaces according to claim 1 is characterized in that: The hot gas valve (1) is a high-temperature water-cooled gate valve, the nozzle (2) is a ceramic nitrogen nozzle, the check valve (4) is a swing check valve, the solenoid valve (5) is a direct-acting solenoid valve, the flow regulating valve (7) is an intelligent electric regulating valve, and the pressure regulating valve (8) is an electric pressure regulating valve.

3. A method for preventing carbon deposition in hot gas valves of hydrogen-rich carbon circulating oxygen blast furnaces, characterized in that: The following steps are involved: S1. The pressure sensor (11) transmits the real-time pressure of the hot gas to the PLC controller, sets the valve stem offset distance interval of the hot gas valve (1), the magnetostrictive sensor (13) transmits the real-time valve stem offset distance of the hot gas valve (1) to the PLC controller, and the gas composition analyzer (14) transmits the real-time gas composition in the hot gas to the PLC controller; S2. The PLC controller controls the nitrogen valve (6) according to the carbon dioxide content in the hot coal gas. If the nitrogen valve (6) is opened, the process proceeds to the next step. If the nitrogen valve (6) is not opened, the process ends. S3. After the nitrogen valve (6) is opened, the PLC controller controls the flow control valve (7) according to the real-time offset distance of the valve stem of the hot gas valve (1) in S1, and purges the carbon deposits of the hot gas valve with nitrogen; S4. When the real-time offset distance of the valve stem of the hot gas valve (1) is not 0, the PLC controller controls the pressure regulating valve (8) according to the carbon deposit purge condition and the hot gas pressure, and adjusts the nitrogen pressure to purge the carbon deposits of the hot gas valve; S5. If the purge time in S4 is ≥ 30 min, the process ends when the real-time offset distance of the valve stem of the hot gas valve (1) is 0. If the real-time offset distance of the valve stem of the hot gas valve (1) is not 0, the process loops back to step S4 and adjusts the nitrogen pressure until the real-time offset distance of the valve stem of the hot gas valve (1) is 0.

4. The method for preventing carbon deposition in hot gas valves of hydrogen-rich carbon circulating oxygen blast furnaces according to claim 3, characterized in that: In step S1, the valve stem offset distance intervals of the hot gas valve (1) are 0-10 mm, 10-15 mm and ≥15 mm respectively.

5. The method for preventing carbon deposition in hot gas valves of hydrogen-rich carbon circulating oxygen blast furnaces according to claim 3, characterized in that: In step S2, when the carbon dioxide content is ≥1%, the nitrogen valve (6) is opened; if the carbon dioxide content is <1%, the nitrogen valve (6) does not need to be opened.

6. The method for preventing carbon deposition in hot gas valves of hydrogen-rich carbon circulating oxygen blast furnaces according to claim 3, characterized in that: The method for controlling the nitrogen flow in step S3 is: When the valve stem offset distance of the hot gas valve (1) is 0-10 mm, the flow regulating valve (7) controls the nitrogen flow rate to be 100-200 m³ / h, the nitrogen pressure is 0.3 MPa higher than the hot gas pressure, and the purge time is 6 minutes; When the valve stem offset distance of the hot gas valve (1) is 10-15 mm, the flow regulating valve (7) controls the nitrogen flow rate to be 200-300 m³ / h, the nitrogen pressure is 0.5 MPa higher than the hot gas pressure, and the purge time is 10 min; When the valve stem offset distance of the hot gas valve (1) is ≥15 mm, the flow regulating valve (7) controls the nitrogen flow rate to be 300-500 m³ / h, the nitrogen pressure is 0.7 MPa higher than the hot gas pressure, and the purge time is 20 min.

7. The method for preventing carbon deposition in hot gas valves of hydrogen-rich carbon circulating oxygen blast furnaces according to claim 3, characterized in that: The method for controlling the nitrogen pressure in step S4 is: When the valve stem offset distance of the hot gas valve (1) is 0-10 mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 0.5 MPa, and the purge time is extended to 10 minutes; When the valve stem offset distance of the hot gas valve (1) is 10-15 mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 0.7 MPa, and the purge time is extended to 15 minutes; When the valve stem offset distance of the hot gas valve (1) is ≥15 mm, the PLC controller controls the nitrogen pressure to be higher than the hot gas pressure and adjusts it to 1 MPa, and the purge time is extended to 25 minutes.

8. The method for preventing carbon deposition in hot gas valves of hydrogen-rich carbon circulating oxygen blast furnaces according to claim 3, characterized in that: The method for adjusting the nitrogen pressure during the cycle in step S5 is: the PLC controller controls the nitrogen pressure to increase by 0.01 MPa / min until the real-time offset distance of the valve stem of the hot gas valve (1) is 0.

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