Heating furnace uniformity strengthening and NOx emission reduction system based on pulse combustion principle

Abstract

The invention discloses a heating furnace uniformity strengthening and NOx emission reduction system based on the pulse combustion principle. Belongs to the technical field of industrial heating furnaces. According to the system, the traditional steady-state combustion concept is broken through, the flow of fuel and air is periodically controlled through the pulsation combustion generation and control device, the fuel and the air are supplied in a pulsation mode according to the frequency of 1-50 Hz and the adjustable phase difference, and strong disturbance is generated in the furnace; dynamic matching of pulsation parameters and a hearth is achieved by combining hearth characteristic monitoring and a self-adaptive algorithm; a differential pulsation process is adopted for each stage of steel billet heating. The convection heat transfer coefficient in the furnace can be increased by 30%-50%, the slab temperature difference is reduced to 20-30 DEG C, meanwhile, thermal NOx emission is reduced by 40%-60%, and the method is suitable for a heat treatment furnace and a slab heating furnace with the extremely high requirement for furnace temperature uniformity.

Description

Technical Field

[0001] This application relates to the field of industrial heating furnace combustion control and energy saving and emission reduction technology, and in particular to a heating furnace uniformity enhancement and NOx emission reduction system based on the principle of pulsed combustion. Background Technology

[0002] In industrial production, heating furnaces are core equipment in processes such as slab heat treatment and metal forging. The uniformity of furnace temperature directly determines product quality, while NOx produced during combustion is one of the main pollutants. Traditional industrial heating furnaces generally employ a steady-state combustion mode, maintaining combustion through a continuous and stable supply of fuel and air. However, this combustion method has significant drawbacks:

[0003] On the one hand, under steady-state combustion, the airflow inside the furnace is slow and the convective heat transfer intensity is limited. Local stagnant gas films are easily formed on the surface of the slab, which leads to obstructed heat transfer and uneven temperature distribution inside the furnace. Especially for large-sized slabs, there is often a problem of excessive temperature difference between the edge and the center, which affects the subsequent processing accuracy and product performance, while also prolonging the heating cycle and increasing energy consumption.

[0004] On the other hand, steady-state combustion easily creates localized high-temperature zones, with flame core temperatures often exceeding 1500℃. Under these conditions, nitrogen and oxygen readily undergo violent reactions to generate large amounts of thermal NOx, making it difficult to meet current stringent environmental emission standards. Existing improvement technologies, such as flue gas recirculation and low-NOx burners, can reduce NOx emissions to some extent, but their effect on improving furnace temperature uniformity is limited, and they also suffer from high retrofitting costs and poor adaptability.

[0005] As a non-steady-state combustion method, pulsed combustion technology forms a pulsed flame through the periodic supply of fuel and oxidant, which can generate strong fluid disturbance and acoustic effects. It has shown potential for enhanced heat transfer and low pollution emissions in small heating equipment. However, a mature technical solution has not yet been formed for how to systematically apply it to industrial heating furnaces and solve problems such as pulsed parameter matching, furnace adaptability and process integration. Summary of the Invention

[0006] Based on this, this application provides a heating furnace uniformity enhancement and NOx emission reduction system based on the principle of pulsed combustion. It achieves the dual goals of enhancing furnace temperature uniformity and reducing NOx emissions through controllable pulsed combustion, meeting the application requirements of high furnace temperature uniformity scenarios such as heat treatment furnaces and slab heating furnaces.

[0007] Firstly, a heating furnace uniformity enhancement and NOx emission reduction system based on the principle of pulsed combustion is provided. This system includes a pulsed combustion generation and control device, a furnace characteristic monitoring module, and an adaptive control module, wherein:

[0008] The pulsed combustion generator and control device is used to generate controllable pulsed combustion. It periodically controls the flow rate of fuel and air through pulsed parameters, and supplies fuel and air in a pulsed manner according to a set frequency and adjustable phase difference, thereby generating disturbances in the furnace.

[0009] The furnace characteristic monitoring module is used to acquire the furnace's natural frequency and internal temperature data.

[0010] The adaptive control module is used to optimize the pulsation parameters of the pulsation combustion generation and control device based on the data obtained by the furnace characteristic monitoring module. It dynamically adjusts the pulsation frequency, amplitude and phase difference through the PID neural network algorithm to achieve enhanced furnace temperature uniformity and NOx emission reduction.

[0011] The pulsed combustion generation and control device supplies fuel and air in a pulsed manner according to the optimized parameters output by the adaptive control module. The furnace characteristic monitoring module feeds back furnace state data to the adaptive control module in real time. The adaptive control module dynamically adjusts the pulsed parameters according to the feedback data to achieve uniform temperature distribution in the furnace and reduce NOx emissions.

[0012] Optionally, the pulsed combustion generation and control device includes an execution unit and a control unit, wherein:

[0013] The execution unit consists of a high-speed switching valve and a variable frequency fan, which respectively control the flow pulsation of fuel and air; the control unit outputs a periodic function control signal with a frequency of 1-50Hz, an amplitude of 5%-30%, and a waveform of sine wave, square wave, or trapezoidal wave; the phase difference between the pulsation signals of fuel and air can be adjusted within the range of 0-180°.

[0014] Optionally, the response time of the high-speed switching valve is ≤10ms, and the frequency conversion range of the variable frequency fan is 10-50Hz, to ensure accurate transmission of the pulsating signal and flow control.

[0015] Optionally, the furnace characteristic monitoring module specifically includes:

[0016] Three to five acoustic sensors are arranged on the side wall of the furnace to collect sound wave signals inside the furnace;

[0017] Temperature sensors are placed in different areas of the furnace and on the surface of the steel billet to monitor temperature data in real time;

[0018] The frequency matching unit obtains the furnace's natural frequency through Fourier transform analysis and adjusts the combustion pulsation frequency to avoid the natural frequency within ±5%, or to 1 / 2 or 1 / 3 times the natural frequency, in order to enhance heat transfer through resonance.

[0019] Optionally, the adaptive control module employs a PID neural network algorithm. The input parameters include the temperatures of different areas inside the furnace, the surface temperature of the billet, the billet arrangement information, and the target temperature curve. The output parameters are the adjustment values ​​of the pulsation frequency and amplitude. When the surface temperature difference of the billet is >50℃, the output parameters have an amplitude of 20%-30% and a frequency of 1-10Hz. When the surface temperature difference of the billet is ≤20℃, the output parameters have an amplitude of 5%-15% and a frequency of 10-30Hz.

[0020] Optionally, the system also includes a web front-end display module for visually displaying the operating status, temperature distribution, and NOx emission data of the heating furnace through a web interface.

[0021] Optionally, the Web front-end display module includes:

[0022] The 3D visualization unit is used to display the temperature distribution and pulsating combustion state of the heating furnace in a three-dimensional form.

[0023] The data interaction unit allows users to query data in real time, adjust parameters, and review historical data through a web interface.

[0024] Optionally, the system is suitable for volumes of 50-500m³. 3 The heat treatment furnace and slab heating furnace can be adapted to the heating requirements of steel billets of different specifications.

[0025] In a second aspect, a pulsed combustion process for use in a heating furnace is provided, implemented in any of the systems described in the first aspect above, the process comprising:

[0026] Preheating section: billet temperature 20-400℃, using pulsating parameters of frequency 10-50Hz and amplitude 5%-15%, with a phase difference of 30-60° between fuel and air;

[0027] Heating section: billet temperature 400-1000℃, using pulsating parameters with frequency 1-10Hz and amplitude 15%-25%, and fuel-air phase difference 60-90°;

[0028] Soaking zone: billet temperature 1000-1250℃, using pulsating parameters of frequency 1-5Hz and amplitude 20%-30%, fuel and air phase difference 80-120° and dynamically adjusted according to NOx concentration;

[0029] Stop phase: After the amplitude drops below 5%, maintain the frequency of 5-10Hz for 3-5 minutes and then stop the fuel supply.

[0030] Optionally, the preheating section enhances convective heat transfer through high-frequency, low-amplitude pulsations, while the heating section and the homogenizing section promote temperature homogenization and suppress NOx generation through low-frequency, high-amplitude pulsations.

[0031] The beneficial effects of the technical solution provided in this application include at least the following:

[0032] Significantly improved furnace temperature uniformity: The acoustic disturbance and eddy current generated by controllable pulsed combustion increase the convective heat transfer coefficient in the furnace by 30%-50%, break the stagnant gas film on the slab surface, and reduce the maximum temperature difference of the slab from 80-120℃ in the traditional process to 20-30℃, which is especially suitable for uniform heating of thick slabs.

[0033] The NOx emission reduction effect is outstanding: Pulsed combustion changes the flame structure, avoids local high temperature zones (the core flame temperature is reduced by 100-200℃), and accelerates the discharge of combustion products. The thermal NOx generation is reduced by 40%-60%, and the emission standard of GB 31573-2015 can be met without additional denitrification equipment.

[0034] Highly adaptable: Through frequency matching and adaptive algorithms, it can adapt to different volumes (50-500m²). 3 For heating furnaces with different billet specifications, the parameter adjustment response time is ≤1s to meet dynamic production needs;

[0035] Reduced energy consumption: Improved furnace temperature uniformity shortens the heating cycle by 15%-20%, and combined with the efficient combustion characteristics of pulsed combustion, overall energy consumption is reduced by 10%-15%, which has significant economic value. Attached Figure Description

[0036] To more clearly illustrate the embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0037] Figure 1 This application provides a flowchart of an implementation of a heating furnace uniformity enhancement and NOx emission reduction system based on the principle of pulsed combustion. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0039] In the description of this application, the terms "comprising," "having," and any variations thereof are intended to cover non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those steps or units that are expressly listed, but may also include other steps or units that are not expressly listed but are inherent to these processes, methods, products, or apparatuses, or steps or units added based on further optimizations conceived in this application.

[0040] This invention aims to break through the limitations of the traditional steady-state combustion concept and provide a heating furnace system based on the principle of pulsed combustion. Through controllable pulsed combustion, it achieves the dual goals of enhancing furnace temperature uniformity and reducing NOx emissions, meeting the application requirements of high furnace temperature uniformity scenarios such as heat treatment furnaces and slab heating furnaces.

[0041] The present invention relates to a heating furnace uniformity enhancement and NOx emission reduction system based on the principle of pulsed combustion, comprising a pulsed combustion generation and control device, a furnace characteristic monitoring module, an adaptive control module, and a matching combustion and heat transfer system. The specific technical solution is as follows:

[0042] The pulsed combustion generator and control device is used to generate controllable pulsed combustion. It periodically controls the flow rate of fuel and air through pulsed parameters, and supplies fuel and air in a pulsed manner according to a set frequency and adjustable phase difference, thereby generating disturbances in the furnace.

[0043] The furnace characteristic monitoring module is used to acquire the furnace's natural frequency and internal temperature data.

[0044] The adaptive control module is used to optimize the pulsation parameters of the pulsation combustion generation and control device based on the data obtained by the furnace characteristic monitoring module. It dynamically adjusts the pulsation frequency, amplitude and phase difference through the PID neural network algorithm to achieve enhanced furnace temperature uniformity and NOx emission reduction.

[0045] The pulsed combustion generation and control device supplies fuel and air in a pulsed manner according to the optimized parameters output by the adaptive control module. The furnace characteristic monitoring module feeds back the furnace status data to the adaptive control module in real time. The adaptive control module dynamically adjusts the pulsed parameters according to the feedback data to achieve uniform temperature distribution in the furnace and reduce NOx emissions.

[0046] As can be seen, the device is the core actuator for generating controllable pulsed combustion, including a fuel supply unit, an air supply unit, and a control unit:

[0047] Actuation unit: High-speed switching valve (response time ≤10ms) is used to control the flow rate of the fuel line, and variable frequency fan is used to control the flow rate of the air line to ensure accurate transmission of pulsation signals;

[0048] Control signal: The control unit outputs a preset periodic function as a drive signal. The signal parameters include frequency 1-50Hz, amplitude (flow fluctuation amplitude) 5%-30%, and waveform can be selected as sine wave, square wave or trapezoidal wave.

[0049] Phase adjustment: The phase difference between the fuel and air pulsation signals is independently adjusted by the phase controller (adjustable from 0-180°), and optimized in real time according to combustion efficiency to ensure that the fuel and air are fully mixed within the pulsation cycle.

[0050] A frequency matching and adaptive method for furnace characteristics is proposed. This method achieves dynamic matching between pulsation parameters and furnace characteristics through monitoring and algorithm optimization, including:

[0051] Natural frequency monitoring: Arrange 3-5 acoustic sensors on the side wall of the furnace to collect sound wave signals inside the furnace. The natural frequency of the furnace is obtained by Fourier transform analysis. The control unit adjusts the combustion pulsation frequency to avoid the resonance frequency within ±5%, or adjusts the pulsation frequency to 1 / 2 or 1 / 3 times the natural frequency under non-resonance risk conditions, and uses the resonance effect to enhance airflow disturbance.

[0052] Adaptive Algorithm: Based on temperature data collected by in-furnace temperature sensors (arranged in different areas of the furnace and on the surface of the billet), billet arrangement information (through visual recognition or preset parameter input), and target temperature curve, a multi-input multi-output model is established. The PID neural network algorithm automatically adjusts the pulsation frequency and amplitude: when the temperature difference on the billet surface is >50℃, the amplitude is increased to 20%-30% and the frequency is reduced to 1-10Hz; when the temperature difference is ≤20℃, the frequency is maintained at 10-30Hz and the amplitude at 5%-15% to stabilize combustion.

[0053] To achieve precise heating by considering the segmented heating requirements of steel billets, differentiated pulsation parameters are used. The specific steps are as follows:

[0054] Preheating section (billet temperature 20-400℃): Start the high-speed switching valve and variable frequency fan, use high frequency 10-50Hz, small amplitude 5%-15% pulsation parameters, set the phase difference between fuel and air to 30-60°, enhance convective heat transfer to quickly increase the surface temperature of the billet and shorten the preheating time.

[0055] Heating section (steel billet temperature 400-1000℃): Adjust to low frequency 1-10Hz, large amplitude 15%-25%, and phase difference 60-90°. Use the eddy current generated by strong pulsation to break the stagnant gas film, promote uniform heat distribution in the furnace, and ensure that the temperature difference between the core and surface of the steel billet is ≤30℃.

[0056] The heat soaking zone (steel billet temperature 1000-1250℃): maintain a low frequency of 1-5Hz and a large amplitude of 20%-30%, and dynamically adjust the phase difference according to the analysis results of combustion products (80-120°) to avoid local high temperature, while quickly carrying the combustion products away from the reaction zone, completing the heat soaking while inhibiting NOx generation;

[0057] Stopping phase: Gradually reduce the pulsation amplitude to below 5%, maintain the frequency at 5-10Hz for 3-5 minutes, and then stop the fuel supply to avoid stress concentration in the billet caused by sudden temperature changes.

[0058] like Figure 1 A flowchart illustrating the implementation of a furnace homogenization enhancement and NOx emission reduction system based on the principle of pulsed combustion is presented. The flowchart outlines the main components of the system and their interrelationships, including a pulsed combustion generation and control device, a furnace characteristic monitoring module, and an adaptive control module. The pulsed combustion generation and control device is responsible for generating controllable pulsed combustion by periodically controlling the flow rates of fuel and air to create strong disturbances within the furnace. The furnace characteristic monitoring module acquires the furnace's natural frequency and internal temperature data, which are crucial for the adaptive control module as it optimizes the pulse parameters based on this monitoring data. The adaptive control module employs a PID neural network algorithm to dynamically adjust the pulse frequency, amplitude, and phase difference to achieve enhanced furnace temperature uniformity and reduced NOx emissions. The entire system is designed to improve heating efficiency while reducing environmental pollution through precise control of the combustion process.

[0059] The following is an optional embodiment of this application:

[0060] In this embodiment, the heating furnace has a volume of 100m³. 3 The slab heating furnace is suitable for slabs with dimensions of 1500mm × 200mm × 3000mm. The system includes:

[0061] Pulsating combustion generation and control device: The fuel pipeline adopts a DN50 high-speed electromagnetic switch valve (model ZCT-50, response time 5ms), the air pipeline adopts a variable frequency centrifugal fan (power 15kW, frequency range 10-50Hz), and the control unit adopts a PLC controller (Siemens S7-1200) equipped with a touch screen for parameter setting;

[0062] Monitoring module: Four acoustic sensors (frequency response 20Hz-20kHz) are arranged on the side wall of the furnace, eight K-type thermocouple temperature sensors are arranged inside the furnace, and three infrared temperature sensors are attached to the surface of the steel billet to achieve full-range temperature monitoring;

[0063] Adaptive control module: Based on MATLAB, a PID neural network model is established, which communicates with the control unit in real time via industrial Ethernet to complete parameter optimization calculations.

[0064] 1. System startup: Turn on the acoustic sensor and temperature sensor to collect the initial signal. The natural frequency of the furnace is obtained by Fourier transform analysis and is 12Hz. The initial value of the combustion pulsation frequency is set to 8Hz (to avoid the resonance range).

[0065] 2. Preheating of steel billet in furnace: When the steel billet temperature is 25℃, start the pulse combustion device, set the frequency to 30Hz, the amplitude to 10%, and the phase difference between fuel and air to 45°. After running for 20 minutes, the surface temperature of the steel billet rises to 400℃, with a temperature difference ≤15℃.

[0066] 3. Heating section operation: Adjust the parameters to a frequency of 5Hz, an amplitude of 20%, and a phase difference of 75°. Monitor the billet temperature in real time. When the temperature difference between the surface and the core reaches 35°C, the adaptive algorithm increases the amplitude to 25%. After running for 40 minutes, the billet temperature rises to 1000°C and the temperature difference drops to 28°C.

[0067] 4. Immersion section operation: Adjust the frequency to 3Hz and amplitude to 28%. The phase difference is dynamically adjusted (90-110°) based on feedback from the flue gas analyzer (NOx concentration monitoring). After 30 minutes of operation, the billet temperature stabilizes at 1200℃, with a temperature difference ≤20℃, and the NOx emission concentration is 85mg / m³. 3 ;

[0068] 5. Stop operation: Reduce the amplitude to 5%, maintain the frequency at 8Hz for 4 minutes, turn off the fuel supply, and stop the blower after it continues to run for 5 minutes.

[0069] In this embodiment, the slab heating cycle is shortened by 18% compared to the traditional process, energy consumption is reduced by 12%, and NOx emissions are reduced by 52% compared to the traditional heating furnace, fully meeting the temperature uniformity requirements of high-end slab heat treatment.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A heating furnace uniformity enhancement and NOx emission reduction system based on the principle of pulsed combustion, characterized in that, The system includes a pulsed combustion generation and control device, a furnace characteristic monitoring module, and an adaptive control module, wherein: The pulsed combustion generator and control device is used to generate controllable pulsed combustion. It periodically controls the flow rate of fuel and air through pulsed parameters, and supplies fuel and air in a pulsed manner according to a set frequency and adjustable phase difference, thereby generating disturbances in the furnace. The furnace characteristic monitoring module is used to acquire the furnace's natural frequency and internal temperature data. The adaptive control module is used to optimize the pulsation parameters of the pulsation combustion generation and control device based on the data obtained by the furnace characteristic monitoring module. It dynamically adjusts the pulsation frequency, amplitude and phase difference through the PID neural network algorithm to achieve enhanced furnace temperature uniformity and NOx emission reduction. The pulsed combustion generation and control device supplies fuel and air in a pulsed manner according to the optimized parameters output by the adaptive control module. The furnace characteristic monitoring module feeds back furnace state data to the adaptive control module in real time. The adaptive control module dynamically adjusts the pulsed parameters according to the feedback data to achieve uniform temperature distribution in the furnace and reduce NOx emissions.

2. The system according to claim 1, characterized in that, The pulsed combustion generation and control device includes an execution unit and a control unit, wherein: The execution unit consists of a high-speed switching valve and a variable frequency fan, which respectively control the flow pulsation of fuel and air; the control unit outputs a periodic function control signal with a frequency of 1-50Hz, an amplitude of 5%-30%, and a waveform of sine wave, square wave, or trapezoidal wave; the phase difference between the pulsation signals of fuel and air can be adjusted within the range of 0-180°.

3. The system according to claim 2, characterized in that, The response time of the high-speed switching valve is ≤10ms, and the frequency conversion range of the variable frequency fan is 10-50Hz to ensure accurate transmission of pulsating signals and flow control.

4. The system according to claim 1, characterized in that, The furnace characteristic monitoring module specifically includes: Three to five acoustic sensors are arranged on the side wall of the furnace to collect sound wave signals inside the furnace; Temperature sensors are placed in different areas of the furnace and on the surface of the steel billet to monitor temperature data in real time; The frequency matching unit obtains the furnace's natural frequency through Fourier transform analysis and adjusts the combustion pulsation frequency to avoid the natural frequency within ±5%, or to 1 / 2 or 1 / 3 times the natural frequency, in order to enhance heat transfer through resonance.

5. The system according to claim 1, characterized in that, The adaptive control module employs a PID neural network algorithm. Input parameters include the temperatures of different zones within the furnace, the surface temperature of the billet, billet arrangement information, and the target temperature curve. Output parameters are the adjustment values ​​for the pulsation frequency and amplitude. When the surface temperature difference of the billet is >50℃, the output parameters have an amplitude of 20%-30% and a frequency of 1-10Hz. When the surface temperature difference of the billet is ≤20℃, the output parameters have an amplitude of 5%-15% and a frequency of 10-30Hz.

6. The system according to claim 1, characterized in that, The system also includes a web front-end display module, which is used to visualize the operating status, temperature distribution and NOx emission data of the heating furnace through a web interface.

7. The system according to claim 6, characterized in that, The web front-end display module includes: The 3D visualization unit is used to display the temperature distribution and pulsating combustion state of the heating furnace in a three-dimensional form. The data interaction unit allows users to query data in real time, adjust parameters, and review historical data through a web interface.

8. The system according to claim 1, characterized in that, The system is suitable for volumes of 50-500m³. 3 The heat treatment furnace and slab heating furnace can be adapted to the heating requirements of steel billets of different specifications.

9. A pulsed combustion process for a heating furnace, implemented in the system described in any one of claims 1-7, characterized in that, Includes the following steps: Preheating section: billet temperature 20-400℃, using pulsating parameters of frequency 10-50Hz and amplitude 5%-15%, with a phase difference of 30-60° between fuel and air; Heating section: billet temperature 400-1000℃, using pulsating parameters with frequency 1-10Hz and amplitude 15%-25%, and fuel-air phase difference 60-90°; Soaking zone: billet temperature 1000-1250℃, using pulsating parameters of frequency 1-5Hz and amplitude 20%-30%, fuel and air phase difference 80-120° and dynamically adjusted according to NOx concentration; Stop phase: After the amplitude drops below 5%, maintain the frequency of 5-10Hz for 3-5 minutes and then stop the fuel supply.

10. The process flow according to claim 9, characterized in that, The preheating section enhances convective heat transfer through high-frequency, low-amplitude pulsations, while the heating and homogenizing sections promote temperature homogenization and suppress NOx generation through low-frequency, high-amplitude pulsations.

Images