A continuous annealing furnace radiant tube online combustion monitoring system and control method

Abstract

The application discloses a kind of continuous annealing furnace radiation tube on-line combustion monitoring system and control method, the system includes continuous annealing furnace, gas main, flue gas main, air main and data acquisition processing system, and the hearth of continuous annealing furnace is provided with several radiation tubes;Gas main is connected with the gas inlet of radiation tube by gas branch pipe, flue gas main is connected with the flue gas outlet of radiation tube by flue gas branch pipe, and air main is connected with the air inlet of radiation tube by air branch pipe;First pressure sensor is arranged on gas main, second pressure sensor and flue gas analyzer are arranged on flue gas main, third pressure sensor is arranged on air main, and fourth pressure sensor and temperature sensor are arranged on flue gas branch pipe.The combustion state data of radiation tube is acquired in real time by constructing monitoring system in the application, and the combustion process is accurately regulated by using control method, so as to improve the operation efficiency, safety and energy consumption level of annealing furnace.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiation tube combustion monitoring, and particularly relates to a continuous annealing furnace radiation tube online combustion monitoring system and a control method. BACKGROUND

[0002] Continuous annealing furnaces are widely used in the metal processing industry, and the radiation tubes, as key components, directly determine the working performance of the annealing furnaces. The traditional combustion monitoring methods have problems such as poor real-time performance, insufficient precision, and inaccurate control, and cannot meet the needs of modern industrial production.

[0003] In the prior art, a Chinese patent with the publication number CN 106801139 A discloses an annealing furnace air-fuel ratio optimization method, which includes the following steps: step 1: adjusting the air flow pressure difference of each burner of the annealing furnace when the annealing furnace is stopped; step 2: adjusting the gas flow pressure difference of each burner of the annealing furnace in the running state of the annealing furnace; and step 3: performing waste gas analysis in the running state of the annealing furnace. A Chinese patent with the publication number CN 110306017 A discloses an annealing furnace proportional control type burner air-fuel ratio control method and system, which monitors the current heating power, the current air flow set value and the current actual air value in real time or periodically, sets a preset condition according to the working condition of the annealing furnace, timely compensates the air flow or gas flow, and timely corrects the set value of the air flow transmitter and the gas flow transmitter. A Chinese patent with the publication number CN 106906339 A discloses a control method, which includes: determining the air-fuel ratio with excess combustion air according to the theoretical air / gas ratio value, the theoretical dry flue gas / gas ratio value and the oxygen content set value in the dry flue gas; obtaining the air-fuel ratio correction coefficient of the unlit burner; and determining the corrected air-fuel ratio according to the air-fuel ratio with excess combustion air and the air-fuel ratio correction coefficient of the unlit burner. However, the above-mentioned methods cannot guide the adjustment of the gas main and the air main pressure adjustment by monitoring the flue gas temperature and the flue gas composition, and realize online optimization monitoring of the air-fuel ratio. Therefore, it is particularly important to develop an efficient and accurate online combustion monitoring system and control method. SUMMARY

[0004] The present application aims to overcome the deficiencies of the above background art, and provides a continuous annealing furnace radiation tube online combustion monitoring system and control method, which acquires the combustion state data of the radiation tube in real time by constructing a monitoring system, and accurately regulates the combustion process by using a control method, so as to improve the operation efficiency, safety and energy consumption level of the annealing furnace.

[0005] In order to achieve the above object, the continuous annealing furnace radiation pipe online combustion monitoring system comprises a continuous annealing furnace, a gas main pipe, a flue gas main pipe, an air main pipe and a data acquisition and processing system, a plurality of radiation pipes are arranged in the hearth of the continuous annealing furnace, the gas main pipe is connected with the gas inlets of the radiation pipes through gas branch pipes, the flue gas main pipe is connected with the flue gas outlets of the radiation pipes through flue gas branch pipes, and the air main pipe is connected with the air inlets of the radiation pipes through air branch pipes.

[0006] A first pressure sensor is arranged on the gas main pipe, a second pressure sensor and a flue gas analyzer are arranged on the flue gas main pipe, a third pressure sensor is arranged on the air main pipe, a fourth pressure sensor and a temperature sensor are arranged on the flue gas branch pipe, and the data output ends of the first pressure sensor, the second pressure sensor, the flue gas analyzer, the third pressure sensor, the fourth pressure sensor and the temperature sensor are connected with the data input end of the data acquisition and processing system.

[0007] Further, a radiation pipe heat exchanger is arranged at the flue gas outlet of the radiation pipe, the air input into the air branch pipe exchanges heat with the flue gas discharged from the radiation pipe in the radiation pipe heat exchanger, the air after being heated is input into the air inlet of the radiation pipe, and the flue gas after being cooled is collected through the flue gas branch pipe and then discharged to the flue gas main pipe.

[0008] Further, a first quick cut-off electromagnetic valve and a first manual regulating valve are arranged on the gas branch pipe, and a first flow orifice plate is arranged on the pipeline between the first quick cut-off electromagnetic valve and the first manual regulating valve.

[0009] Further, a second quick cut-off electromagnetic valve and a second manual regulating valve are arranged on the air branch pipe, and a second flow orifice plate is arranged on the pipeline between the second quick cut-off electromagnetic valve and the second manual regulating valve.

[0010] Further, a gas pressure stabilizing device is arranged on the gas main pipe, and the gas pressure stabilizing device is used for stabilizing the gas pressure in the pipeline.

[0011] Further, a variable frequency induced draft fan is arranged on the flue gas main pipe, the control signal input end of the variable frequency induced draft fan is connected with the control signal output end of the data acquisition and processing system, the variable frequency induced draft fan is used for extracting the flue gas in the flue gas main pipe and discharging the flue gas, and the variable frequency induced draft fan is used for keeping the flue gas negative pressure in the flue gas main pipe stable according to the control signal of the data acquisition and processing system.

[0012] Further, a variable frequency air blower is arranged on the air main pipe, the control signal input end of the variable frequency air blower is connected with the control signal output end of the data acquisition and processing system, the variable frequency air blower is used for blowing the air with pressure into the air main pipe, and the variable frequency air blower is used for keeping the air pressure in the air main pipe stable according to the control signal of the data acquisition and processing system.

[0013] Further, the flue gas branch pipe is provided with an artificial detection opening, which is an opening for detecting the flue gas composition of a single radiant tube.

[0014] The application also provides a method for controlling the on-line combustion monitoring system of the continuous annealing furnace radiant tube, which uses the data acquisition and processing system to acquire the data of the first pressure sensor, the second pressure sensor, the flue gas analyzer, the third pressure sensor, the fourth pressure sensor and the temperature sensor, judges the combustion state of the radiant tube and adjusts the first quick cut-off electromagnetic valve, the first manual regulating valve, the second quick cut-off electromagnetic valve, the second manual regulating valve, the variable frequency induced draft fan and the variable frequency air blower to adjust the total air pipe pressure and the total coal gas pipe pressure.

[0015] Further, when the flue gas composition of the total flue gas pipe is CO:<50ppm, the total air pipe pressure is reduced at a pressure reduction rate of 0.5Kpa / min until the CO is 50ppm-100ppm; when the CO is >50ppm, the total air pipe pressure is increased at a pressure increase rate of 0.5Kpa / min until the CO is 50ppm-100ppm.

[0016] When the average value of the radiant tube exhaust gas temperature is <630℃, the total coal gas pipe pressure is increased at a pressure increase rate of 0.5Kpa / min until the exhaust gas temperature is 630-650℃; when the average value of the radiant tube exhaust gas temperature is >650℃, the total coal gas pipe pressure is reduced at a pressure reduction rate of 0.5Kpa / min until the exhaust gas temperature is 630-650℃.

[0017] Compared with the prior art, the application has the following advantages:

[0018] Firstly, the application acquires the combustion state data of the radiant tube in real time by constructing a monitoring system and accurately controls the combustion process by using a control method, thereby improving the operation efficiency, safety and energy consumption level of the annealing furnace.

[0019] Secondly, the application aims at the on-line combustion optimization control problem of the radiant tube burner group in the pulse combustion control mode, adjusts the total coal gas pipe pressure and the total air pipe pressure according to the monitoring of the flue gas O2, CO and CO2 compositions at the total flue gas pipe to realize the on-line optimization monitoring of the air-fuel ratio, and identifies and judges the radiant tube fault condition according to the change condition of the flue gas pressure and temperature after the heat exchanger of each set of radiant tube burner.

[0020] Thirdly, the on-line combustion monitoring system of the continuous annealing furnace radiant tube of the application improves the operation efficiency and safety of the continuous annealing furnace and reduces the energy consumption, and has a wide application prospect. The system of the application has been successfully tried out on a cold-rolled continuous annealing furnace, and the scientificity, accuracy and applicability effect have been verified. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a continuous annealing furnace radiation tube online combustion monitoring system structure diagram;

[0022] In the figure, the continuous annealing furnace 1, the gas main pipe 2, the flue gas main pipe 3, the air main pipe 4, the data acquisition processing system 5, the radiation tube 6, the gas branch pipe 7, the flue gas branch pipe 8, the air branch pipe 9, the first pressure sensor 10, the second pressure sensor 11, the flue gas analyzer 12, the third pressure sensor 13, the fourth pressure sensor 14, the temperature sensor 15, the radiation tube heat exchanger 16, the first quick cut-off electromagnetic valve 17, the first manual regulating valve 18, the first flow orifice plate 19, the second quick cut-off electromagnetic valve 20, the second manual regulating valve 21, the second flow orifice plate 22, the gas pressure stabilizing device 23, the variable frequency induced draft fan 24, the variable frequency blower 25, the manual detection port 26. DETAILED DESCRIPTION

[0023] The implementation of the present application will be described in detail below in conjunction with the implementation cases, but they do not constitute a limitation on the present application, but only serve as an example. At the same time, the advantages of the present application will become more clear and easy to understand through the description.

[0024] As Figure 1 shown, the continuous annealing furnace radiation tube online combustion monitoring system of the present application includes a continuous annealing furnace 1, a gas main pipe 2, a flue gas main pipe 3, an air main pipe 4, and a data acquisition processing system 5. The continuous annealing furnace is mainly composed of a furnace body, an air supply system, a gas supply system, a radiation tube combustion heating system, a furnace chamber arranged with a plurality of radiation tube combustion heaters, an exhaust system, etc. The main purpose is to ensure that the gas is fully burned in the radiation tube burner during the indirect heating process of the continuously moving strip steel between the continuous annealing furnace radiation tubes to achieve the annealing heat treatment effect. The furnace chamber temperature of the continuous annealing furnace should be controlled within 900℃, the furnace chamber is filled with protective gas of nitrogen (95%) + hydrogen (5%), and the furnace pressure is controlled at a slight positive pressure (130-200pa). The gas main pipe is used to distribute high-pressure gas (about 10000pa) to each gas branch pipe, and each gas radiation tube gas branch pipe is provided with gas. The air main pipe pressurizes the combustion-supporting air to the required pressure through the variable frequency blower, and distributes it to each air branch pipe for combustion-supporting of each gas radiation tube. The flue gas main pipe collects the flue gas from each flue gas branch pipe and discharges it through the variable frequency induced draft fan.

[0025] The radiation tube 6 is mainly composed of a tube body, a burner, a waste heat recovery device heat exchanger and a combustion control unit. The gas is completely combusted in the radiation tube made of heat-resistant steel or heat-resistant ceramic material, and the radiation heat emitted by the heated tube is used to heat the workpieces or materials to be processed in the furnace. The gas main 2 is connected to the gas inlet of the radiation tube 6 through the gas branch pipe 7, and the gas is distributed to each gas radiation tube through the gas main. The flue gas main 3 is connected to the flue gas outlet of the radiation tube 6 through the flue gas branch pipe 8, and the flue gas generated by the combustion of the gas in each radiation tube is collected into the flue gas main through the flue gas branch pipe. The air main 4 is connected to the air inlet of the radiation tube 6 through the air branch pipe 9, and the air is distributed to each gas radiation tube through the air main.

[0026] The first pressure sensor 10 is arranged on the gas main 2, the second pressure sensor 11 and the flue gas analyzer 12 are arranged on the flue gas main 3, the third pressure sensor 13 is arranged on the air main 4, and the fourth pressure sensor 14 and the temperature sensor 15 are arranged on the flue gas branch pipe 8. The data output ends of the first pressure sensor 10, the second pressure sensor 11, the flue gas analyzer 12, the third pressure sensor 13, the fourth pressure sensor 14 and the temperature sensor 15 are connected to the data input end of the data acquisition and processing system 5. The pressure sensor is used for measuring and collecting the pressure parameters of the medium in the pipeline. The temperature sensor is used for measuring and collecting the temperature parameters of the medium in the pipeline. The flue gas analyzer is arranged on the flue gas main, and the O2, CO and other components of the flue gas are extracted online and directly through the opening method. The cold drying method is adopted: after the flue gas is cooled, purified, transported, separated by steam, dried by cooling, extracted and pressurized, desulfurized and dusted, and stabilized, it enters the gas analyzer for analysis. Technical performance: repeatability error: Cv≤1%, linear error: ≤1% FS.

[0027] The flue gas outlet of the radiation tube 6 is provided with a radiation tube heat exchanger 16, which is a waste heat recovery device of the radiation tube. The high-temperature flue gas generated by combustion heats the combustion air, achieving the effect of waste heat utilization. The air introduced by the air branch pipe 9 exchanges heat with the flue gas discharged from the radiation tube 6 in the radiation tube heat exchanger 16. The heated air is input into the air inlet of the radiation tube 6, and the cooled flue gas is collected to the flue gas main 3 through the flue gas branch pipe 8 and discharged.

[0028] The first quick cut-off electromagnetic valve 17 is arranged on the coal gas branch pipe 7, and the first manual regulating valve 18 is arranged on the coal gas branch pipe 7. The first flow orifice plate 19 is arranged on the pipeline between the first quick cut-off electromagnetic valve 17 and the first manual regulating valve 18. The second quick cut-off electromagnetic valve 20 is arranged on the air branch pipe 9, and the second manual regulating valve 21 is arranged on the air branch pipe 9. The second flow orifice plate 22 is arranged on the pipeline between the second quick cut-off electromagnetic valve 20 and the second manual regulating valve 21. The gas pressure stabilizing device 23 is arranged on the coal gas main pipe 2, and is used for stabilizing the gas pressure in the pipeline. The quick cut-off electromagnetic valve is arranged on the coal gas branch pipe and the air branch pipe, and is used for realizing the quick use and cut-off of each gas radiation pipe. The flow orifice plate reflects the medium flow by measuring the difference between the total pressure and the static pressure. The manual regulating valve is adjusted according to the indication of the flow orifice plate.

[0029] The variable frequency induced draft fan 24 is arranged on the flue gas main pipe 3, and the control signal input end of the variable frequency induced draft fan 24 is connected with the control signal output end of the data acquisition and processing system 5. The variable frequency induced draft fan 24 is used for extracting the flue gas in the flue gas main pipe 3 and discharging the flue gas, and the flue gas negative pressure in the flue gas main pipe is kept stable by the variable frequency control technology according to the control signal of the data acquisition and processing system 5.

[0030] The variable frequency induced draft fan 24 is arranged on the flue gas main pipe 3, and the control signal input end of the variable frequency induced draft fan 24 is connected with the control signal output end of the data acquisition and processing system 5. The variable frequency induced draft fan 24 is used for extracting the flue gas in the flue gas main pipe 3 and discharging the flue gas, and the flue gas negative pressure in the flue gas main pipe is kept stable by the variable frequency control technology according to the control signal of the data acquisition and processing system 5.

[0031] In this embodiment, the combustion-supporting air is sent into the air main pipe after being pressurized by the variable frequency air blower, and is distributed to each radiant tube burner through each air branch pipe. The air branch pipe is provided with a flow orifice plate and a manual regulating valve to adjust the flow. The air is heated by the radiant tube heat exchanger and then enters the radiant tube for combustion-supporting. The air main pipe is provided with a pressure sensor to guide the variable frequency air blower to realize stable adjustment of the air main pipe pressure. The pressurized coal gas is sent to each gas branch pipe through the gas main pipe, and is distributed to each radiant tube burner. The gas branch pipe is provided with a flow orifice plate and a manual regulating valve to adjust the flow. The gas main pipe is provided with a gas pressure stabilizing device to realize constant pressure of each gas branch pipe. The air branch pipe and the gas branch pipe corresponding to each gas radiant tube are provided with a quick cut-off electromagnetic valve to realize quick commissioning (combustion) and cut-off of each gas radiant tube. The flue gas generated by the combustion of each gas radiant tube is cooled by the radiant tube heat exchanger, is collected through the flue gas branch pipe to the flue gas main pipe, and is then extracted by the variable frequency induced draft fan and discharged. Before the variable frequency induced draft fan, the gas main pipe is provided with a pressure sensor to guide the variable frequency induced draft fan to adjust and realize constant negative pressure control of the flue gas main pipe pressure. The flue gas analysis instrument is arranged on the flue gas main pipe after the collection of each flue gas branch pipe. The flue gas temperature and pressure sensors are arranged on the flue gas branch pipe after each gas radiant tube heat exchanger to realize online identification and diagnosis of the combustion state of each gas radiant tube. The flue gas analysis instrument, the variable frequency induced draft fan, the variable frequency air blower, and the online temperature, pressure, and flow sensors are connected to the data acquisition and processing system through data lines.

[0032] A method for controlling the above continuous annealing furnace radiant tube online combustion monitoring system, the data acquisition and processing system 5 collects data of the first pressure sensor 10, the second pressure sensor 11, the flue gas analysis instrument 12, the third pressure sensor 13, the fourth pressure sensor 14, and the temperature sensor 15, judges the radiant tube combustion state, and adjusts the first quick cut-off electromagnetic valve 17, the first manual regulating valve 18, the second quick cut-off electromagnetic valve 20, the second manual regulating valve 21, the variable frequency induced draft fan 24, and the variable frequency air blower 25 to adjust the air main pipe pressure and the gas main pipe pressure. The data acquisition and processing system collects the detection data from the pressure sensors, the temperature sensors, and the gas analysis instrument in real time, calculates the CO2 fluctuation range through a software model, compares the result with the online flue gas CO2 analysis result, guides the correction feedback of the air-fuel ratio, and optimizes the combustion control.

[0033] The real-time flue gas temperature, components (O2, CO, NOx, etc.), and concentration change, the air branch pipe and the gas branch pipe flow meter data returned by the data acquisition and processing system are used to judge the radiant tube combustion state and guide the adjustment of the air blower air volume and the gas flow to realize the air-fuel ratio optimization adjustment and the radiant tube combustion power. x The radiant tube burner heat exchanger rear flue gas pressure and temperature returned by the data acquisition and processing system are used to identify and judge the radiant tube fault condition according to the data fluctuation.

[0034] The control logic of the on-line combustion monitoring system of the continuous annealing furnace radiation tube of the present application:

[0035] (1) Coal gas heat value, adjusted total gas pipe, air pipe, flue gas pipe pressure determination:

[0036] a) Coal gas heat value: 2200-2400 Kcal / m 3 ;

[0037] b) Total gas pipe pressure: 10 Kpa ± 5%, air pipe pressure: 10 Kpa ± 5%;

[0038] c) Flue gas pipe pressure -13 Kpa ± 5%.

[0039] (2) Each radiation tube combustion state (air-fuel ratio) adjustment solidification:

[0040] Cold state adjustment, one by one individual adjustment, manual ignition of the radiation tube, through adjustment of the radiation tube air, coal gas manual regulating valve, to ensure:

[0041] a) Flue gas O2: >2%, CO: 50 ppm-100 ppm;

[0042] b) Flue gas temperature: 630-650℃;

[0043] c) Flue gas pressure: -10--12 Kpa.

[0044] (3) On-line monitoring under normal production state: ensure that each radiation tube works normally: when some radiation tube flue gas temperature and flue gas pressure deviate greatly from other radiation tube parameters (more than 20% difference from the average value), check and adjust the corresponding radiation tube, if necessary, cut off the system;

[0045] a) When the flue gas composition of the flue gas main pipe: CO: <50 ppm, reduce the air main pipe pressure: according to the pressure reduction rate of 0.5 Kpa / min until CO: 50 ppm-100 ppm; when CO: >50 ppm, increase the air main pipe pressure: according to the pressure increase rate of 0.5 Kpa / min until CO: 50 ppm-100 ppm.

[0046] b) When the average value of each radiation flue gas temperature: <630℃, increase the total gas pipe pressure: according to the pressure increase rate of 0.5 Kpa / min until the flue gas temperature: 630-650℃; when the average value of the radiation tube flue gas temperature: >650℃, reduce the total gas pipe pressure: according to the pressure reduction rate of 0.5 Kpa / min until the flue gas temperature: 630-650℃.

[0047] c) The above steps are repeated to realize on-line monitoring and ensure the safety and efficiency of the system.

[0048] The above merely illustrates the specific embodiments of the present application. It should be noted that any changes or replacements within the technical scope disclosed by the present application can be easily conceived by any person skilled in the art, and should be covered within the protection scope of the present application. The rest of the prior art is not described in detail.

Claims

1. An online combustion monitoring system for radiant tubes in a continuous annealing furnace, characterized in that: The system includes a continuous annealing furnace (1), a gas main pipe (2), a flue gas main pipe (3), an air main pipe (4), and a data acquisition and processing system (5). The furnace chamber of the continuous annealing furnace (1) is equipped with several radiant tubes (6). The gas main pipe (2) is connected to the gas inlet of the radiant tubes (6) through a gas branch pipe (7). The flue gas main pipe (3) is connected to the flue gas outlet of the radiant tubes (6) through a flue gas branch pipe (8). The air main pipe (4) is connected to the air inlet of the radiant tubes (6) through an air branch pipe (9). A first pressure sensor (10) is installed on the main gas pipe (2), a second pressure sensor (11) and a flue gas analyzer (12) are installed on the main flue gas pipe (3), a third pressure sensor (13) is installed on the main air pipe (4), and a fourth pressure sensor (14) and a temperature sensor (15) are installed on the branch flue gas pipe (8); the data output terminals of the first pressure sensor (10), the second pressure sensor (11), the flue gas analyzer (12), the third pressure sensor (13), the fourth pressure sensor (14), and the temperature sensor (15) are respectively connected to the data input terminal of the data acquisition and processing system (5); A radiant tube heat exchanger (16) is provided at the flue gas outlet of the radiant tube (6). The air introduced by the air branch pipe (9) and the flue gas discharged from the radiant tube (6) exchange heat in the radiant tube heat exchanger (16). The heated air is input into the air inlet of the radiant tube (6), and the cooled flue gas is collected through the flue gas branch pipe (8) and discharged to the flue gas main pipe (3). The gas branch pipe (7) is equipped with a first fast-cut-off solenoid valve (17) and a first manual regulating valve (18), and a first flow orifice plate (19) is provided on the pipeline between the first fast-cut-off solenoid valve (17) and the first manual regulating valve (18). The air branch pipe (9) is provided with a second fast shut-off solenoid valve (20) and a second manual regulating valve (21), and a second flow orifice plate (22) is provided on the pipeline between the second fast shut-off solenoid valve (20) and the second manual regulating valve (21); A variable frequency induced draft fan (24) is installed on the flue gas main pipe (3). The control signal input terminal of the variable frequency induced draft fan (24) is connected to the control signal output terminal of the data acquisition and processing system (5). The variable frequency induced draft fan (24) is used to extract the flue gas in the flue gas main pipe (3) and discharge it to the outside. According to the control signal of the data acquisition and processing system (5), the negative pressure of the flue gas in the flue gas main pipe is kept stable by frequency conversion control. A variable frequency blower (25) is installed on the air main (4). The control signal input terminal of the variable frequency blower (25) is connected to the control signal output terminal of the data acquisition and processing system (5). The variable frequency blower (25) blows pressurized air into the air main (4) and keeps the air pressure in the air main stable by frequency conversion control according to the control signal of the data acquisition and processing system (5).

2. The online combustion monitoring system for the radiant tubes of a continuous annealing furnace according to claim 1, characterized in that: A gas pressure stabilizing device (23) is installed on the main gas pipe (2), which is used to stabilize the gas pressure in the pipe.

3. The online combustion monitoring system for the radiant tubes of a continuous annealing furnace according to claim 1 or 2, characterized in that: The flue gas branch pipe (8) is provided with a manual detection port (26), which is an opening for detecting the composition of flue gas on a single radiant pipe.

4. A method for controlling the continuous annealing furnace radiant tubes using the online combustion monitoring system according to any one of claims 1 to 3, characterized in that: The data acquisition and processing system (5) collects data from the first pressure sensor (10), the second pressure sensor (11), the flue gas analyzer (12), the third pressure sensor (13), the fourth pressure sensor (14), and the temperature sensor (15), determines the combustion status of the radiant tube, and adjusts the first quick-cut-off solenoid valve (17), the first manual regulating valve (18), the second quick-cut-off solenoid valve (20), the second manual regulating valve (21), the variable frequency induced draft fan (24), and the variable frequency blower (25) to adjust the pressure of the air main pipe and the gas main pipe.

5. The method according to claim 4, characterized in that: When the flue gas composition in the main flue gas pipe is CO: <50ppm, reduce the main air pipe pressure at a rate of 0.5 kPa / min until CO: 50ppm~100ppm; when CO: >50ppm, increase the main air pipe pressure at a rate of 0.5 kPa / min until CO: 50ppm~100ppm. When the average exhaust temperature of the radiant tubes is <630℃, increase the pressure of the main gas pipe at a rate of 0.5 kPa / min until the exhaust temperature reaches 630-650℃; when the average exhaust temperature of the radiant tubes is >650℃, decrease the pressure of the main gas pipe at a rate of 0.5 kPa / min until the exhaust temperature reaches 630-650℃.

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