Method for adjusting low nitrogen oxide emission of heating furnace

Abstract

The low nitrogen oxide emission adjusting method for the heating furnace is characterized in that the heating furnace adopts a multi-section control system, and the method comprises the following steps of 1, feedback adjustment of the relation between the furnace temperature of each section and the power of a burner, 2, in-furnace oxygen component detection and air-fuel ratio fine adjustment, and 3, in-furnace atmosphere detectors and calorific value instruments are arranged between the sections of the heating furnace. And the calorific value instrument, the pore plate and the oxygen analyzer are matched to work. The method for adjusting the low nitrogen oxide emission of the heating furnace has the advantages that the influence of various factors causing the increase of the NOX emission is overcome, the normal heating requirement is kept, and the NOX emission is stable and low in nitrogen.

Description

Technical Field

[0001] The present invention relates to a heating furnace in the metallurgical industry, and specifically, to a method for adjusting low nitrogen oxide emissions of a heating furnace. Background Art

[0002] The main function of a metallurgical heating furnace is to heat steel billets (slab billets, square billets, round steel, round tubes, etc.) to a high temperature to meet the requirements of the next rolling process, and it can also be the furnace type of a heat treatment furnace. Its purpose is to maintain low NOX emissions during the heating process.

[0003] In low nitrogen control, there are currently many strategies, such as using low nitrogen burners, performing flue gas recirculation, high-temperature denitrification in the furnace, and low-temperature denitrification technology in the flue. Using a low nitrogen burner is to fundamentally reduce NOX emissions, which is an essential strategy. Compared with other compensatory measures, it has the advantages of low transformation cost, low maintenance cost, energy conservation, and no secondary pollution. Therefore, for the current low nitrogen transformation of heating furnaces, replacing them with low nitrogen burners is a better method.

[0004] Combustion is a very complex thermal process. When the burner is working, specific conditions are required to maintain the low nitrogen effect of combustion. In actual operation, due to the continuous change and variation of the operating conditions of the heating furnace, even with low nitrogen burners, there will be fluctuations in NOX, and even situations where it exceeds the standard.

[0005] There are many factors affecting the combustion conditions, such as fluctuations in gas calorific value and pressure, fluctuations in air pressure and flow rate, changes in production volume, changes in furnace temperature, etc., which bring various uncertain problems to the nitrogen oxide emissions of the heating furnace.

[0006] Therefore, the known combustion methods of heating furnaces have the above-mentioned various inconveniences and problems. Summary of the Invention

[0007] The purpose of the present invention is to propose a method for adjusting low nitrogen oxide emissions of a heating furnace that can maintain normal heating requirements and at the same time keep the NOX emissions stably low.

[0008] To achieve the above purpose, the technical solution of the present invention is: A method for adjusting low nitrogen oxide emissions of a heating furnace, wherein the heating furnace adopts a multi-section control system, and is characterized by including the following steps: The first step is the feedback adjustment of the relationship between the furnace temperature and the burner power in each section, including the following steps: a. Determine whether the control process is a heating process or a cooling process Compare the detected value of the soaking section furnace temperature with the set value of the preset soaking section furnace temperature of the furnace temperature. If the soaking section furnace temperature > the preset soaking section furnace temperature, it is determined as a cooling process, and vice versa, it is a heating process; b. Determine the current status and simultaneously determine the heating and cooling multiples When the temperature difference between the soaking zone furnace temperature and the preset furnace temperature in the soaking zone is less than 5°C and greater than 2°C, use a 1-fold speed increment for heating and cooling. When the temperature difference is less than 10°C and greater than or equal to 5°C, use a 2-fold speed increment for heating and cooling. When the temperature difference is greater than 10°C, use a 3-fold speed for heating and cooling. When the temperature difference is less than 2°C, it is in the heat preservation state, maintaining the valve opening unchanged; c. Determine the gas increment The preset gas increment is 1%, and it is adjusted adaptively according to different furnace types or sections; d. Determine the air-fuel ratio When the calorific value Q of the gas is a known value, the theoretical air-fuel ratio n0 = 0.0018*(Q / 1000)^2 + 0.2154*(Q / 1000) is calculated. This formula is suitable for high-coke mixed gas, and the calorific value Q is in the unit of KJ / Nm3; e. Determine the maximum and minimum gas volumes in each section The maximum gas volume is determined by the rated power of the burner. The burner is designed to allow a 20% power overrun. The maximum gas volume in the section = the rated gas consumption of a single burner X (1 + 20%), where X is the number of burners in the section; The minimum gas volume is determined. The parameter settings of the flow orifice plate need to be set in the form of a polynomial; the system is set to calculate the minimum gas flow as 15% of the maximum flow; f. Proportional adjustment of the gas volume The branch pipes in each section of the heating furnace are equipped with flow orifice plates for detecting the gas flow and air flow in the branch pipes. Using the proportional adjustment module of the programmable logic controller, the target flow is used as the input value, the actual flow is used as the feedback value, and the valve opening is used as the output control value to establish a proportional adjustment system. When the target flow is less than the actual flow, the system automatically closes the valve opening; when the target flow is greater than the actual flow, the system automatically opens the valve opening; g. Calculate the air target value Calculate the air target value: To ensure the full combustion of the gas, the product of the gas target value and the air-fuel ratio is used to obtain the theoretical air calculation value; the product of the actual gas flow and the air-fuel ratio is used to obtain the actual air calculation value; Calculate the required air volume V in each section according to the air-fuel ratio: V = gas flow x no x k, When the theoretical air calculation value is less than the actual air calculation value, the air target value takes the actual air calculation value; when the theoretical air calculation value is greater than or equal to the actual air calculation value, the theoretical air calculation value is taken. When the air target value is less than or equal to the minimum air flow, the minimum air flow is taken to ensure the full combustion of the gas; using the proportional adjustment module, the accurate gas and air flows are calculated for controlling the valve; Second step, in-furnace oxygen component detection and air-fuel ratio fine-tuning. Install in-furnace atmosphere detectors and calorimeters between different sections of the heating furnace to detect the O2 content (%) and CO content. The calorimeter, orifice plate, and oxygen analyzer work together, including the following steps: a. Determine the preliminary theoretical air-fuel ratio and its variation range based on the calorimeter Based on the calorimeter data, determine the common value and fluctuation range; calculate the maximum gas flow rate, minimum gas flow rate, maximum air-fuel ratio, and minimum air-fuel ratio according to the calorific value; The maximum output power of each section of the heating furnace combustion system is affected by the gas calorific value and the main pipe pressure. Increase the calorific value and the main pipe pressure to increase the heat output power and production. For a single heating furnace, the air flow rate in the air pipeline can only be increased by increasing the pressure; The air volume V = gas calorific value Q * air-fuel ratio n, where the air-fuel ratio n = theoretical air-fuel ratio n0 * air excess coefficient k of the section; b. Feedback adjustment of the detected oxygen content of the components Install component detectors at the outlet position of each section to detect the comprehensive combustion effect of the section; combine the data of the flue gas component detector, and during the production of the heating furnace, make a judgment based on the component detection values and combustion states of each section.

[0009] The method for adjusting the low NOx emissions of the heating furnace of the present invention can also be further realized by adopting the following technical measures.

[0010] In the foregoing method, the preset gas increment is 1% of the rated power of the burner.

[0011] In the foregoing method, the proportional adjustment is to adjust the corresponding proportional coefficient and integral time, and finally a fast-converging flow control curve needs to be obtained.

[0012] In the foregoing method, when the gas target value is calculated to be less than the minimum value or greater than the maximum value, the system issues an alarm, and at the same time assigns the pre-set limit value to the target value to avoid system errors and ensure the safety of the heating furnace.

[0013] In the foregoing method, the unit of the CO content is mg or ppm.

[0014] After adopting the above technical solutions, the method for adjusting the low NOx emissions of the heating furnace of the present invention has the following advantages: 1. Overcome the influence of various factors that cause an increase in NOx emissions; 2. Maintain normal heating requirements; 3. Keep the NOx emissions stable and low in nitrogen. Description of the Drawings

[0015] Figure 1Schematic diagram of the two-stage heating furnace according to an embodiment of the present invention, which is provided with a soaking section and a heating section; Figure 2 Schematic diagram of the three-stage heating furnace according to an embodiment of the present invention, which is provided with a soaking section, a heating section and a preheating section; Figure 3 Schematic diagram of the four-stage heating furnace according to an embodiment of the present invention, which is provided with a soaking section, a second heating section, a first heating section and a preheating section; Figure 4 Schematic diagram of the control system of the four-stage heating furnace according to an embodiment of the present invention; Figure 5 Example diagram of the orifice plate differential pressure-flow relationship according to an embodiment of the present invention; Figure 6 Combustion system diagram of the two-stage heating furnace according to an embodiment of the present invention. Detailed implementation manners

[0016] The present invention will be further described in detail below in conjunction with embodiments and their accompanying drawings.

[0017] Embodiment 1 The heating furnace of the present invention adopts multi-stage control and is divided into 3 types of sectional furnace types according to different heating requirements and product characteristics.

[0018] Now please refer to Figures 1-3 , Figure 1 Schematic diagram of the two-stage heating furnace according to an embodiment of the present invention, which is provided with a soaking section and a heating section, Figure 2 Schematic diagram of the three-stage heating furnace according to an embodiment of the present invention, which is provided with a soaking section, a heating section and a preheating section, Figure 3 Schematic diagram of the four-stage heating furnace according to an embodiment of the present invention, which is provided with a soaking section, a second heating section, a first heating section and a preheating section.

[0019] The heating furnace implemented by the present invention adopts a four-stage heating furnace, and the preheating section is also equipped with burners to illustrate the low nitrogen oxide emission adjustment method and strategy. For the convenience of narration, the codes and meanings specified in Table 1 are adopted in this embodiment.

[0020] Table 1 Summary list of codes and meanings

[0021] The heating furnace of the present invention adopts a four-stage heating furnace, and the method for adjusting the low nitrogen oxide emission of the heating furnace includes the following steps: I. Feedback adjustment of the relationship between the furnace temperature of each section and the burner power The first step is to judge whether the control process is a heating process or a cooling process Compare the furnace temperature detection value T40 with the furnace temperature set value T4. If T40 > T4, it is judged as a cooling process, otherwise it is a heating process.

[0022] Step 2: Determine the current state and the heating and cooling multiple When the temperature difference between T40 and T4 is less than 5°C and greater than 2°C, use 1x speed increment for heating and cooling; when the temperature difference is less than 10°C and greater than or equal to 5°C, use 2x speed increment for heating and cooling; when the temperature difference is greater than 10°C, use 3x speed for heating and cooling; when the temperature difference is less than 2°C, it is in the heat preservation state, maintaining the valve opening unchanged.

[0023] Step 3: Determine the gas increment The smaller the gas increment, the finer the adjustment, but the longer the adjustment time. It is recommended to preset 1% (1% of the burner rated power), and at the same time give a modification screen for adaptive adjustment according to different furnace types or sections.

[0024] Step 4: Determine the air-fuel ratio When the gas calorific value Q is a known value, the theoretical air-fuel ratio n0 = 0.0018*(Q / 1000)^2 + 0.2154*(Q / 1000) is calculated. This formula is suitable for high-coke mixed gas. The calorific value Q unit is KJ / Nm3; For different positions of each zone in the heating furnace, different air excess coefficient k settings are given. The general principle is to control the oxygen content in the flue gas leaving the furnace within 3%, higher at both ends and lower in the middle. Table 2 shows the air excess coefficient settings for each zone of three furnace types.

[0025] Table 2 Air excess coefficient settings for each zone of three furnace types

[0026] The air-fuel ratio n = theoretical air-fuel ratio n0 x air excess coefficient k.

[0027] Step 5: Determine the maximum and minimum gas volumes for this zone The maximum gas volume is determined by the burner rated power. Generally, the burner design allows a power overrun of 20%. Therefore, the maximum gas volume in this zone = single-burner rated gas consumption X (1 + 20%) X the number of burners in this zone.

[0028] The minimum gas flow needs to consider two aspects. One is the detection limit of the orifice plate for gas flow. When the gas flow is lower than a certain amount, the measurement accuracy of the orifice plate will be very poor. As shown in the following figure, the differential pressure-flow curve of a certain orifice plate. If the orifice plate flow parameters are set linearly, there will be an increasing deviation when it is below 20%. Therefore, the parameter settings of the flow orifice plate need to be set in the form of a polynomial. Specifically for a certain orifice plate, it needs to be calculated separately and the calculation formula is given. Figure 5 It is an example diagram of the orifice plate differential pressure-flow relationship.

[0029] Second, for burners of certain structures, there is a possibility of flashback when the gas flow rate is less than a certain value. Therefore, the system is set to calculate the minimum gas flow rate as 15% of the maximum flow rate, and at the same time, a modification screen is given to allow the operator to make corrections according to the actual situation.

[0030] Step 6: PID regulation of gas volume Since each branch pipe in each combustion section of all heating furnaces is equipped with an orifice plate for detecting the gas flow rate and air flow rate in the branch pipe, we can use this flow rate as the flow feedback to control the gas regulating valve and air regulating valve of each branch pipe respectively. The specific method is as follows: Using the PID regulation module of the PLC, taking the target flow rate as the input value, the actual flow rate as the feedback value, and the opening degree of the valve as the output control value, a PID regulation system is established. When the target flow rate is less than the actual flow rate, the system automatically closes the valve opening degree; when the target flow rate is greater than the actual flow rate, the system automatically opens the valve opening degree. According to the characteristics of different valves, adjust the corresponding proportional coefficient and integral time, and finally a fast-converging flow control curve needs to be obtained.

[0031] When the gas target value is calculated to be less than the minimum value or greater than the maximum value through calculation, the system will issue an alarm. At the same time, the preset limit value is assigned to the target value to avoid system errors and ensure the safety of the heating furnace.

[0032] Step 7: Calculate the air target value Calculate the air target value: To ensure the full combustion of the gas, we use the product of the gas target value and the air-fuel ratio to obtain the theoretical air calculation value; use the product of the actual gas flow rate and the air-fuel ratio to obtain the actual air calculation value; Calculate the air volume required for each section according to the air-fuel ratio: V = gas flow rate x no x k When the theoretical air calculation value is less than the actual air calculation value, our air target value takes the actual air calculation value; when the theoretical air calculation value is greater than or equal to the actual air calculation value, take the theoretical air calculation value. At the same time, when the air target value is less than or equal to the minimum air flow rate, take the minimum air flow rate. This can not only ensure the full combustion of the gas but also ensure that the required air flow rate will not be too low due to the too small target gas flow rate, resulting in the failure of burning out the burner.

[0033] Using the PID regulation module, calculate the accurate gas and air flow rates for controlling the valves.

[0034] II. Detection of oxygen content in the furnace and fine-tuning of air-fuel ratio In the heating furnace, atmosphere detectors are installed between each partition to mainly detect the O2 content (%) and CO content (mg or ppm). 10,000 ppm of CO content = 1%, which means incomplete combustion and the fuel burnout rate is 99%.

[0035] CO is a reducing agent. At high temperatures, the reaction CO + NO = CO2 + N2 exists, which is very important for reducing NOX in the combustion products. Therefore, the heating furnace is considered as a whole, and a certain amount of CO can be maintained in the furnace before discharging, and its concentration is greater than that of NO. Then, the excess air coefficient is appropriately increased before the heating furnace is discharged, so that the oxygen content in the flue gas discharged from the heating furnace as a whole is controlled within 3%. Based on this conclusion, the recommended excess air coefficients for each zone are shown in Table 2.

[0036] The inaccurate measurement or detection lag of the gas calorific value will bring large fluctuations to the control of the heating furnace, which requires correction according to the oxygen content detected in each zone.

[0037] The measurement accuracy of the orifice flowmeter is affected by many factors, such as changes in fluid temperature, the reduction of the inner diameter of the pipeline caused by the adhesion of tar and other substances on the inner wall of the pipeline, the accumulation of sundries before and after the orifice plate, air leakage in the pressure-taking pipe, instrument drift, etc. This also requires correction according to the oxygen content detected in each zone.

[0038] At the same time, the oxygen analyzer itself will also be affected by some factors in its measurement accuracy, such as: the instrument crashing due to a short-term CO explosion, the instrument crashing due to the interruption of nitrogen backwashing, the expiration of the life of the instrument detection module, etc. All of the above factors indicate that for the continuous and stable operation of the heating furnace combustion system, the calorimeter, orifice plate, and oxygen analyzer need to work in cooperation.

[0039] Determine the preliminary theoretical air-fuel ratio and its variation range based on the calorimeter Through the calorimeter data, the common values and fluctuation ranges can be determined. For heating furnaces without a display screen, manual input can be used.

[0040] Calculate the maximum gas flow rate, minimum gas flow rate, maximum air-fuel ratio, and minimum air-fuel ratio based on the calorific value The maximum output power of each zone of the heating furnace combustion system is affected by the gas calorific value and the main pipe pressure. Increasing the calorific value and the main pipe pressure can both increase the heat output power and increase the output. However, the air pipeline of the single heating furnace can only increase the air flow rate by increasing the pressure. If the air flow rate is insufficient, it will cause incomplete combustion of the gas, and even too much unburned components in the flue gas will bring safety risks.

[0041] The control idea is to use gas as the main control and air as the follow-up control. When the required air volume corresponding to the gas volume reaches the maximum air volume, the gas will no longer increase.

[0042] Air volume V = gas calorific value Q * air-fuel ratio n Among them, the air-fuel ratio n = theoretical air-fuel ratio n0 * excess air coefficient k of this zone Feedback adjustment of the detected oxygen content of the components The component detector installed at the exit of each zone can detect the comprehensive combustion effect of the zone and provide intuitive feedback for the adjustment of the air-fuel ratio of the zone. However, the accuracy of the detection is greatly affected by the installation position, burner characteristics and burner power adjustment. Therefore, the general heating furnace is not used as a control factor for automated production, but to guide the operator in the setting of other parameters, such as correcting the air-fuel ratio.

[0043] Table 3 shows the component detection values ​​and combustion status judgments of each section. Combined with the data from the flue gas component detector, the heating furnace makes a combustion status judgment during production.

[0044] Table 3 Component detection values ​​of each zone and combustion state determination

[0045] Note: The increase and decrease of the air-fuel ratio can be entered and modified in the setting area.

[0046] Example 2 Figure 6 The combustion system diagram of the two-stage heating furnace of the embodiment of the present invention. The heating furnace of the present invention adopts a two-stage heating furnace, which is respectively a heating zone and a soaking zone. The heating zone is divided into two temperature control zones, upper heating and lower heating, and the soaking zone is divided into four temperature control zones, upper two sides, upper center, lower two sides, and lower center. There is no calorific value meter. According to the results reported by the Ministry of Energy and Environment, the calorific value of commonly used gas is 11500KJ / Nm3, with a normal fluctuation of 10%. The designed gas power and flow rate of each part are shown in Table 4 below.

[0047] Table 4 shows the air gas flow parameters for each zone

[0048] Based on the orifice plate parameters of each zone, the flow range of the orifice plate is calculated and summarized in Table 5 in combination with the actual flow range.

[0049] From the summary table, the green area is the gas adjustment range, and the blue area is the air adjustment area. This is a typical case of narrowing the gas adjustment range by greatly increasing the calorific value of the gas. In operation, the gas valve opening is small, the flow is not easy to be stably adjusted, the oxygen content in the exhaust fluctuates greatly, and NOX will remain high. The solution is to reduce the diameter of the gas orifice plate and increase the opening range of the gas valve.

[0050] Considering the nonlinear performance curve of the orifice plate below 20% differential pressure, the differential pressure-flow curve formula of the gas orifice plate needs to be refitted according to the calculated data. The recommended linear formula provided by the PLC system cannot be used.

[0051] Table 5 Calculation of orifice flow and differential pressure relationship based on the new calorific value of 2700

[0052] The method for adjusting the low nitrogen oxide emission of the heating furnace in the two-stage heating furnace combustion system according to the embodiment of the present invention includes the following steps: 1. The program detects the current furnace temperature detection value T40, compares it with the furnace temperature set value T4 in this area, and determines whether it is a heating or cooling operation; 2. Determine whether rapid heating or cooling is required according to the difference, and determine the heating or cooling multiple.

[0053] 3. Change the value of S43 by adjusting the opening of the gas valve 43, and the orifice plate 44 detects the change in the flow value V44; 4. Calculate the target air volume according to the value of V44; 5. According to the target air volume, use the PID of the PLC to adjust the opening value S45 of the air valve 45 so that the value of the orifice plate 46 is close to the target value; 6. When the valve opening value S45 = 100%, if the flow value V46 of the orifice plate 46 cannot reach the target air volume, stop increasing the gas; for example, in the upper part of the heating section, when the gas flow reaches 3936 Nm3 / h, the air flow reaches the maximum value of 10830. At this time, the gas flow cannot be increased anymore, otherwise there will be incomplete combustion and waste of gas.

[0054] 7. In actual operation, since the heating section is designed with an air excess coefficient of 1.1, there is still a 10% increase in gas, and the component detection value A41 will not reach 0%.

[0055] 8. To correct the deviation of the furnace gas component detection at the outlet of each area, with the help of the oxygen component detection value A51 in the flue gas on the chimney, considering reasons such as flue leakage, control the oxygen content A51 below 8%, and at the same time the value of the CO content A52 in the flue gas component is less than 1000 ppm, so as to correct and adjust the air excess coefficient value of each area.

[0056] 9. The same adjustment is carried out in other areas so that the heating furnace can automatically burn steel. Control the flue gas NOX index within a lower range.

[0057] The above embodiments are only for illustrating the present invention, rather than limiting the present invention. Those skilled in the relevant technical fields can also make various transformations or changes without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the scope of the present invention and should be defined by each claim.

Claims

1. A method for adjusting low nitrogen oxide emissions in a heating furnace, wherein the heating furnace adopts a multi-segment control system, characterized in that The following steps are involved: The first step is to feedback and adjust the relationship between the furnace temperature and the burner power in each section, including the following steps: a. Determine whether the control process is a heating process or a cooling process The detected value of the furnace temperature in the soaking section is compared with the set value of the preset furnace temperature in the soaking section. If the soaking section temperature is greater than the preset furnace temperature in the soaking section, it is judged as a cooling process, otherwise it is a heating process. b. Determine the current state and determine the temperature rise and fall multiples When the temperature difference between the soaking section furnace temperature and the preset soaking section furnace temperature is less than 5℃ and greater than 2℃, use 1x speed increment to increase or decrease the temperature; when the temperature difference is less than 10℃ and greater than or equal to 5℃, use 2x speed increment to increase or decrease the temperature; when the temperature difference is greater than 10℃, use 3x speed to increase or decrease the temperature; when the temperature difference is less than 2℃, it is in the insulation state, and the valve opening is maintained unchanged; c. Determine the gas increment The preset gas increment is 1%, which can be adjusted adaptively according to different furnace types or sections; d. Determine the air-fuel ratio When the gas calorific value Q is a known value, the theoretical air-fuel ratio n0=0.0018*(Q / 1000)^2+0.2154*(Q / 1000) is calculated. This formula is suitable for high-coke mixed gas. The calorific value Q unit is KJ / Nm 3 ; e. Determine the maximum and minimum gas volume in the section The maximum gas volume is determined by the rated power of the burner. The burner design allows 20% power overshoot. The maximum gas volume of the section = the rated gas consumption of a single burner X (1 + 20%), where X is the number of burners in the section. The minimum value of the gas volume is determined, and the parameters of the flow orifice plate need to be set in the form of a polynomial; the system setting is calculated based on the minimum gas flow being 15% of the maximum flow; f. Proportional adjustment of gas volume The branch pipes of each section of the heating furnace are equipped with flow orifice plates to detect the gas flow and air flow of the branch pipes. The proportional regulation system is established by using the proportional regulation module of the programmable logic controller, taking the target flow as the input value, the actual flow as the feedback value, and the valve opening as the output control value. When the target flow rate is less than the actual flow rate, the system automatically closes the valve opening; when the target flow rate is greater than the actual flow rate, the system automatically opens the valve opening; g. Calculate air target value Calculate the air target value: To ensure the full combustion of the gas, the theoretical air calculation value is obtained by multiplying the gas target value by the air-fuel ratio; the actual air calculation value is obtained by multiplying the actual gas flow by the air-fuel ratio; Calculate the required air volume V for each section according to the air-fuel ratio: V = gas flow x no xk, When the theoretical air calculation value is less than the actual air calculation value, the air target value is the actual air calculation value; when the theoretical air calculation value is greater than or equal to the actual air calculation value, the theoretical air calculation value is taken; when the air target value is less than or equal to the minimum air flow, the minimum air flow is taken to ensure full combustion of the gas; the proportional adjustment module is used to calculate the precise gas and air flow for controlling the valve; The second step is to detect the oxygen composition in the furnace and fine-tune the air-fuel ratio. An atmosphere detector and a calorific value meter are set between each section of the heating furnace to detect the O2 content and CO content. The calorific value meter, orifice plate and oxygen analyzer work together, including the following steps: a. Determine the preliminary theoretical air-fuel ratio and its variation range based on the calorific value meter Determine the common value and fluctuation range through the calorific value meter data; calculate the maximum gas flow, minimum gas flow, maximum air-fuel ratio, and minimum air-fuel ratio based on the calorific value; The maximum output power of each section of the heating furnace combustion system is affected by the calorific value of the gas and the main pipe pressure. Increasing the calorific value and the main pipe pressure can increase the heat output power and increase the output. The air duct of a single heating furnace can only increase the air flow by increasing the pressure. Air volume V = gas calorific value Q * air-fuel ratio n, where air-fuel ratio n = theoretical air-fuel ratio n0 * air excess coefficient of the section is k; b. Feedback adjustment of oxygen content in component detection A component detector is installed at the exit of each section to detect the comprehensive combustion effect of the section; Combined with the data from the flue gas composition detector, the heating furnace makes judgments during production based on the component detection values ​​of each zone and the combustion status.

2. The method for adjusting low nitrogen oxide emissions of a heating furnace according to claim 1, characterized in that: The preset gas increment is 1% of the rated power of the burner.

3. The method for adjusting low nitrogen oxide emissions of a heating furnace according to claim 1, characterized in that: The proportional regulation is to adjust the corresponding proportional coefficient and integral time, and finally a fast-converging flow control curve needs to be obtained.

4. The method for adjusting low nitrogen oxide emissions of a heating furnace according to claim 1, characterized in that: When the gas target value is calculated to be less than the minimum value or greater than the maximum value, the system issues an alarm and assigns a preset limit value to the target value to avoid system errors and ensure the safety of the heating furnace.

5. The method for adjusting low nitrogen oxide emissions of a heating furnace according to claim 1, characterized in that: The unit of the CO content is mg or ppm.

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