A low-nitrogen combustion system and low-nitrogen combustion method suitable for carbon baking

Abstract

This invention relates to a low-NOx combustion system and method suitable for carbon roasting, including a roasting furnace and a flame system. The flame system includes an atomizing swirl low-NOx burner and an exhaust pipe. The atomizing swirl low-NOx burner includes a base, a gas pipe, a lower gas guide pipe, and a support rod installed at the lower end of the base. The lower gas guide pipe is sleeved over the gas pipe, and the gas pipe is sleeved over the support rod. A nozzle is installed at the lower end of the support rod, with the lower end face of the nozzle higher than the lower end face of the gas pipe. An annular gap is left between the nozzle and the gas pipe, and multiple inclined grooves are provided on the outer circumference of the nozzle. The furnace chamber includes a preheating zone and a roasting zone. The temperature in the roasting zone is controlled at 1200℃-1400℃ to reduce the generation of thermal NOx. The exhaust pipe promptly discharges the flue gas from the preheating zone, shortening the residence time of the high-temperature flue gas in the preheating zone and reducing the generation of transient NOx. The hollow swirl gas ejected from the nozzle mixes rapidly with the surrounding air, achieving energy saving and NOx reduction effects.

Description

Technical Field

[0001] This invention relates to the field of roasting furnace equipment technology, and in particular to a low-NOx combustion system and method suitable for carbon roasting. Background Technology

[0002] Carbon materials are a general term for substances and solid materials that are primarily composed of carbon (generally, the carbon-to-hydrogen atomic ratio is greater than 10). Currently, carbon materials are widely used in metallurgy, chemical industry, electronics, electrical appliances, machinery, as well as nuclear energy and aerospace industries. Carbon materials have become indispensable structural and functional materials in modern industry. Calcination is the process of heating carbon raw materials with specific shapes, sizes, densities, and mechanical properties at a controlled rate under conditions of isolation from air and a protective medium to obtain finished carbon products.

[0003] The carbon roasting furnace, a key piece of equipment in the carbon production process, plays a crucial role in the calcination and heat treatment of carbon materials, primarily for removing volatile components and improving material strength. It typically uses gaseous fuels such as natural gas for heating, with natural gas being the preferred choice due to its high calorific value, combustion stability, and relatively low impurity content. The roasting temperature range needs to be strictly controlled between 800 and 1300 degrees Celsius; this range helps optimize carbonization reaction efficiency and ensures uniform product quality. The flue gas directly emitted from the roasting furnace contains various pollutants such as dust, sulfur dioxide, and nitrogen oxides, mainly originating from the fuel combustion process and impurities in the raw materials, posing a potential pollution risk to the atmospheric environment.

[0004] In existing roasting furnace control systems, the energy consumption level of the burners is significantly high, resulting in nitrogen oxide emission concentrations exceeding 100 mg / m³. 3 This figure far exceeds the emission limits stipulated by national environmental protection regulations, failing to meet stringent environmental standards. Therefore, a specialized denitrification process is necessary to effectively reduce pollutant emissions and achieve compliance. However, the current denitrification equipment in roasting furnaces consumes a huge amount of energy during operation and incurs high maintenance costs, including frequent equipment repairs, spare parts replacements, and additional energy expenditures. This significantly increases the operational burden and economic pressure on enterprises. Given these challenges, there is an urgent need to develop a new, low-cost, and high-efficiency denitrification device to address cost issues and improve system sustainability, thereby achieving the dual benefits of energy conservation, emission reduction, and environmental protection. Summary of the Invention

[0005] The purpose of this invention is to provide a low-NOx combustion system suitable for carbon roasting to solve the technical problems of high energy consumption and high nitrogen oxide content in the exhaust gas of the roasting furnace in the prior art; the purpose of this invention is also to provide a low-NOx combustion method suitable for carbon roasting.

[0006] Therefore, the present invention provides a low-NOx combustion system suitable for carbon roasting, which adopts the following technical solution: A low-NOx combustion system suitable for carbon roasting includes a roasting furnace and a flame system. The roasting furnace includes a furnace cavity, which is divided into a preheating zone and a roasting zone from top to bottom. The flame system is used to inject flames into the roasting zone to increase the temperature inside the furnace cavity. The flame system includes an atomizing swirl low-NOx burner and an exhaust pipe. The atomizing swirl low-NOx burner is arranged at a density of 4-6 burners / square meter in the roasting zone. The atomizing swirl low-NOx burner includes a base, with a gas pipe, a lower gas guide pipe, and a support rod installed at the lower end of the base. The lower gas guide pipe is sleeved outside the gas pipe, and the gas pipe is sleeved outside the support rod. A nozzle is provided at the lower end of the support rod. The lower end face of the nozzle is higher than the lower end face of the gas pipe. An annular gap is left between the nozzle and the gas pipe to allow gas flow. Multiple inclined grooves are provided on the outer circumference of the nozzle, and the inclined grooves are inclined at 5-15 degrees relative to the axis of the nozzle. The exhaust pipe has multiple gas inlets on the portion arranged in the preheating zone to extract the flue gas in time under negative pressure.

[0007] Furthermore, multiple inclined grooves are evenly distributed on the outer peripheral surface of the nozzle.

[0008] Furthermore, the inclination angles of the multiple inclined grooves are consistent.

[0009] Furthermore, the nozzle is cylindrical, with an outer diameter larger than that of the support rod, and a shoulder tapered transition between the nozzle and the support rod.

[0010] Furthermore, the nozzle, gas pipe, and lower gas guide pipe are arranged concentrically.

[0011] Furthermore, the inner diameter of the gas pipe is d, the outer diameter of the nozzle is d1=[0.8d,0.9d], the height of the nozzle is h1=[3d,4d], the depth of the inclined groove is h2=[0.01d,0.05d], the width of the inclined groove is w2=[0.02d,0.1d], and the inner diameter of the lower gas guide pipe is [1.5d,2d].

[0012] Furthermore, the flame system also includes a pressure regulator for adjusting the gas pressure fed into the atomizing swirl low-NOx burner and a solenoid valve for controlling the gas flow interruption. The low-NOx combustion system also includes a detection system for detecting the temperature and gas pressure at different points in the furnace cavity and a control system for controlling the solenoid valve and the pressure regulator. The detection system is electrically connected to the input port of the control system to transmit the detected temperature and pressure signals to it. The pressure regulator and the control valve are electrically connected to different output ports of the control system for controlled operation.

[0013] Furthermore, it also includes an alarm system electrically connected to the output of the control system to issue alarm signals under control.

[0014] Furthermore, the height of the preheating zone accounts for 1 / 2 to 1 / 3 of the total height of the furnace cavity.

[0015] The present invention provides a low-nitrogen method for carbon roasting, which adopts the following technical solution: When heating the furnace cavity, a segmented heating method is adopted. The lower the temperature and the faster the heating rate, the greater the pressure and duty cycle of the gas injected by the atomizing swirl low-NOx burner. The higher the temperature and the slower the heating rate, the lower the pressure and duty cycle of the gas injected by the atomizing swirl low-NOx burner. The duty cycle and pressure of the gas injected by each atomizing swirl low-NOx burner are controlled independently.

[0016] The beneficial effects of this invention are as follows: The formation mechanisms of nitrogen oxides in the roasting furnace mainly include the following three types: (1) Thermal NOx: It is generated by the oxidation reaction of nitrogen (N2) and oxygen (O2) in the air in the local high-temperature zone (usually above 1400 degrees Celsius) of the roasting furnace. This reaction follows the Zeldovich mechanism and is extremely sensitive to temperature. (2) Fuel NOx: mainly derived from the fixed nitrogen element contained in the fuel itself. When organic nitrogen compounds in fuels (such as coal, heavy oil, biomass, etc.) are decomposed by heat during combustion, the nitrogen-containing intermediates (such as HCN, NH3, etc.) released react with oxygen to form nitrogen oxides. (3) Prompt NOx: In the relatively low temperature flame front region (usually 600-900 degrees Celsius), carbon-containing free radicals (such as CH, CH2) generated by the combustion of hydrocarbons react with nitrogen (N2) to generate intermediate products such as HCN, which are then rapidly oxidized to form NOx.

[0017] In conventional combustion processes, thermal nitrogen oxides are usually the main source of formation. Their formation is significantly affected by furnace temperature: when the furnace temperature is below 1500 degrees Celsius, the formation rate of thermal nitrogen oxides is low and the formation amount is small; while when the furnace temperature is above 1500 degrees Celsius (especially above 1600 degrees Celsius), the reaction rate increases exponentially with temperature, and the formation amount increases significantly. For thermal nitrogen oxides, their generation is also closely related to the residence time of flue gas in the high-temperature region. The longer the residence time, the more complete the high-temperature reaction between nitrogen and oxygen, and the greater the amount of nitrogen oxides generated.

[0018] In this invention, the furnace cavity includes a preheating zone and a calcination zone. The temperature in the calcination zone is controlled at 1200℃-1400℃, thereby controlling the carbon calcination temperature within the range of 800℃-1300℃, minimizing the generation of thermal nitrogen oxides. The preheating zone has a lower temperature, but the flue gas from the preheating zone is promptly discharged through the exhaust pipe, shortening the residence time of the high-temperature flue gas in the preheating zone and minimizing the generation of transient nitrogen oxides. Therefore, it achieves the effect of low-NOx combustion.

[0019] Meanwhile, the gas ejected by the atomizing swirl low-NOx burner in this invention is a hollow swirl centered on the nozzle. The air outside disperses the gas ejected in this hollow swirl form, achieving rapid mixing of gas and air. After ignition, the gas can greatly improve combustion efficiency, achieving rapid and stable combustion and thus energy saving. Furthermore, uniform mixing can reduce the local high-temperature zone of the flame, further reducing the generation of thermal nitrogen oxides and achieving the goal of low-NOx combustion.

[0020] Furthermore, the total amount of nitrogen oxides (NOx) generated is roughly proportional to fuel consumption. Oxygen concentration is also a key factor; as oxygen concentration (or oxygen partial pressure) increases, the amount of NOx generated usually increases proportionally. However, the effect of the excess air coefficient (α) is non-monotonic: when the excess air coefficient is close to 1 (i.e., close to the theoretical air volume), the NOx generation rate reaches its peak; once the excess air coefficient deviates significantly from 1 (whether in rich fuel or strong lean combustion conditions), the NOx generation rate will drop sharply. This is mainly because insufficient oxygen under rich fuel conditions limits the oxidation reaction, while the reduced combustion temperature under strong lean combustion conditions inhibits the thermodynamic reaction. In this invention, by controlling the duty cycle and injection pressure of the injected gas, the heating rate is controlled in stages; the higher the temperature, the slower the heating rate, resulting in a more uniform temperature distribution within the furnace cavity and further reducing the amount of NOx generated.

[0021] The low-NOx combustion system of this invention can effectively assist existing denitrification equipment. By optimizing combustion efficiency and reducing the generation of nitrogen oxides, it ensures that the concentration of pollutants in the roasting flue gas remains within the environmental protection standard limits, while significantly reducing the consumption of natural gas, thereby achieving energy saving and nitrogen reduction effects.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of an embodiment of an atomizing swirl low-NOx burner suitable for carbon roasting according to the present invention; Figure 2 This is a schematic diagram of the hardware connection structure; Figure 3This is a schematic diagram of the structure of an atomizing swirl low-NOx burner; Among them: 100, roasting furnace; 200, flame system; 300, detection system; 400, control system; 500, alarm system; 21, atomizing swirl low-NOx burner; 22, pressure regulator; 23, exhaust pipe; 1. Base; 2. Gas pipe; 3. Lower gas pipe; 4. Nozzle; 5. Support rod; 6. Upper gas pipe; 7. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] Example 1 of an atomizing swirl low-NOx burner suitable for carbon roasting according to the present invention: A low-NOx combustion system suitable for carbon roasting includes a roasting furnace 100, a flame system 200, a detection system 300, a control system 400, and an alarm system 500. The roasting furnace 100 has a furnace cavity, which is divided into a preheating zone and a roasting zone from top to bottom. The raw carbon to be roasted is placed in the roasting zone at the bottom of the cavity. The flame system 200 provides heat energy by injecting combustion gas downwards to continuously heat the roasting zone. Since the flame is located in the roasting zone, the gaps within the roasting zone form fire channels. The detection system 300 detects the pressure of the injected combustion gas and the temperature at different locations within the furnace cavity. The control system 400 controls the amount and pressure of the injected combustion gas based on the detection results to adjust the temperature and pressure within the furnace cavity. The alarm system 500 issues an alarm signal when the detected values ​​exceed a set threshold.

[0027] The flame system 200 includes an atomizing swirl low-NOx burner 21 and a pressure regulator 22. The atomizing swirl low-NOx burner 21 includes a base 1, with a gas pipe 2 and a lower air guide pipe 3 installed at the lower end of the base 1. The lower air guide pipe 3 is fitted over the gas pipe 2, with the gas pipe 2 serving as a gas passage and the lower air guide pipe 3 serving as an air supply passage. A nozzle 4 is inserted inside the gas pipe 2, and the end of the nozzle 4 is connected to the base 1 via a support rod 5. The atomizing swirl low-NOx burners 21 are evenly distributed within the roasting zone, with a density of 6 burners per square meter. In other embodiments, when the nozzle size of the atomizing swirl low-NOx burner 21 varies, the number of atomizing swirl low-NOx burners 21 arranged per square meter of roasting zone can be any number between 4 and 16.

[0028] The nozzle 4 is cylindrical, with an outer diameter larger than that of the support rod 5. The nozzle 4 and support rod 5 are connected by a conical transition. The nozzle 4 is concentrically installed in the gas pipe 2, with an annular gap between the nozzle 4 and the inner wall of the gas pipe 2. The lower end face of the nozzle 4 is higher than the lower end face of the gas pipe 2, which in turn is higher than the lower end face of the lower gas guide pipe 3. Three inclined grooves 41 are evenly distributed on the outer wall of the nozzle 4, all running in the same direction. The inclination angle between the inclined grooves 41 and the axis of the nozzle 4 is 5 degrees. In other embodiments, the inclination angle between the inclined grooves 41 and the axis of the nozzle 4 can be any angle between 5 and 15 degrees. When the distance between the lower gas guide pipe 3 and the gas pipe 2 is large, the inclination angle between the inclined grooves 41 and the axis of the nozzle 4 can be increased to increase the tangential velocity of the ejected gas flow.

[0029] The natural gas, which is transported downward along the gas pipe 2, is guided to the downward slope by the inclined groove 41 when it flows through the nozzle 4. Then, affected by the reaction force of the inner wall of the gas pipe 2 below the nozzle 4, the gas flow that is finally ejected from the lower end of the gas pipe 2 presents a swirling airflow centered on the nozzle 4. The gas is evenly dispersed in the swirling airflow and can burn more completely.

[0030] In this embodiment, the inner diameter d of the gas pipe 2 is 2cm, the outer diameter D is 2.2cm, the outer diameter d1 of the nozzle 4 is 1.8cm, the height h1 of the nozzle 4 is 8cm, the depth h2 of the inclined groove 41 is 0.1cm, the width w2 of the inclined groove 41 is 0.2cm, and the inner diameter d3 of the lower gas guide pipe 3 is 3cm. When the gas is ejected at a pressure of 8000KPa, the tangential velocity of the swirling flow formed after being ejected through the nozzle 4 can reach more than 0.6m / s, forming a uniform gas-air mixture. The CO concentration after combustion is less than 50ppm, which is far lower than the CO concentration after combustion when using a conventional burner. The concentrations of other pollutants also meet the environmental protection standard limits and can be discharged without further post-treatment.

[0031] Verification has shown that the outer diameter d1 of nozzle 4 = [0.8d, 0.9d], the height h1 of nozzle 4 = [3d, 4d], the depth h2 of inclined groove 41 = [0.01d, 0.05d], the width w2 of inclined groove 41 = [0.02d, 0.1d], and the inner diameter of lower air guide pipe 3 = [1.5d, 2d] can all achieve high energy saving and nitrogen reduction effects.

[0032] An upper gas duct 6 is installed above the base 1. The upper end of the upper gas duct 6 is connected to a gas inlet connector 7. The gas inlet connector 7 is a standard connector that can be connected to the municipal gas supply pipeline. The upper gas duct 6 is connected to the lower gas duct 3. Therefore, the gas supplied by the municipal gas supply pipeline can be directly sent into the lower gas duct 3 through the upper gas duct 6 and sprayed out from the middle.

[0033] In this embodiment, the gas supplied by the municipal gas pipeline is processed by the pressure regulator 22 and then sent into the atomizing swirl low-NOx burner 21. The outlet of the pressure regulator 22 is connected to a solenoid valve, which is opened and closed under control.

[0034] The preheating zone occupies half the total height of the furnace cavity. The lower end face of the nozzle 4 is located at the interface between the preheating zone and the roasting zone to ensure the flame is directed entirely towards the roasting zone, preventing excessively high temperatures in the preheating zone. The flame system 200 also includes an exhaust pipe 23. The portion of the exhaust pipe 23 located within the preheating zone has multiple flue gas inlets spaced vertically. The exhaust pipe 23 is under negative pressure, specifically controlled between 0 and -4000 Pa, to promptly expel the flue gas and reduce its residence time in the preheating zone. Furthermore, the exhaust pipe 23 is only located in the lower-temperature preheating zone, minimizing deformation. Simultaneously, it concentrates the flame in the roasting zone, resulting in higher temperatures in that zone.

[0035] When heating the furnace cavity, a segmented heating method is adopted. The lower the temperature and the faster the heating rate, the greater the pressure and duty cycle of the gas injected by the atomizing swirl low-NOx burner. The higher the temperature and the slower the heating rate, the lower the pressure and duty cycle of the gas injected by the atomizing swirl low-NOx burner. The duty cycle and pressure of the gas injected by each atomizing swirl low-NOx burner are controlled independently.

[0036] Specifically, in this embodiment, the temperature inside the furnace cavity rises from room temperature to 550°C in 8 hours, and the allowable error of the temperature detected by the detection system during this stage is 1–10°C; from 550°C to 650°C in 8 hours, the allowable error of the temperature detected by the detection system during this stage is 1–10°C; from 650°C to 750°C in 8 hours, the allowable error of the temperature detected by the detection system during this stage is 1–10°C; from 750°C to 800°C in 8 hours, the allowable error of the temperature detected by the detection system during this stage is ±1–3°C; from 800°C to 1200°C in 72 hours, the allowable error of the temperature detected by the detection system during this stage is ±1–3°C; after the temperature rises to 1200°C, the allowable error of the temperature detected by the detection system is ±1°C.

[0037] The detection system 300 detects the actual temperature at the corresponding point in the fire channel and compares this value with the set temperature to obtain the temperature difference. The larger the temperature difference, the larger the duty cycle (the ratio of the opening time to the closing time) of the gas injected through the solenoid valve, and the higher the set pressure of the pressure regulator 22; the smaller the temperature difference, the smaller the duty cycle (the ratio of the opening time to the closing time) of the solenoid valve, and the lower the set pressure of the pressure regulator 22.

[0038] In this embodiment, the duty cycle and pressure of the gas injected by the multiple sets of atomizing swirl low-NOx burners 21 can be controlled independently.

[0039] An embodiment of the present invention, an atomized swirl low-NOx combustion method adapted to carbon roasting: A low-NOx combustion method using atomized swirl combustion adapted for carbon roasting employs a segmented heating method when heating the furnace cavity. The lower the temperature and the faster the heating rate, the greater the pressure and duty cycle of the gas ejected by the atomized swirl low-NOx burner. Conversely, the higher the temperature and the slower the heating rate, the lower the pressure and duty cycle of the gas ejected by the atomized swirl low-NOx burner. The duty cycle and pressure of the gas ejected by each atomized swirl low-NOx burner are independently controlled.

[0040] Specifically, in this embodiment, the temperature inside the furnace cavity rises from room temperature to 550°C in 8 hours, and the allowable error of the temperature detected by the detection system during this stage is 1–10°C; from 550°C to 650°C in 8 hours, the allowable error of the temperature detected by the detection system during this stage is 1–10°C; from 650°C to 750°C in 8 hours, the allowable error of the temperature detected by the detection system during this stage is 1–10°C; from 750°C to 800°C in 8 hours, the allowable error of the temperature detected by the detection system during this stage is ±1–3°C; from 800°C to 1200°C in 72 hours, the allowable error of the temperature detected by the detection system during this stage is ±1–3°C; after the temperature rises to 1200°C, the allowable error of the temperature detected by the detection system is ±1°C.

[0041] The detection system 300 detects the actual temperature at the corresponding point in the fire channel and compares this value with the set temperature to obtain the temperature difference. The larger the temperature difference, the larger the duty cycle (the ratio of the opening time to the closing time) of the gas injected through the solenoid valve, and the higher the set pressure of the pressure regulator 22; the smaller the temperature difference, the smaller the duty cycle (the ratio of the opening time to the closing time) of the solenoid valve, and the lower the set pressure of the pressure regulator 22.

Claims

1. A low-nitrogen combustion system suitable for carbon baking, characterized by: The system includes a roasting furnace and a flame system. The roasting furnace includes a furnace cavity, which is divided into a preheating zone and a roasting zone from top to bottom. The flame system is used to spray flames into the roasting zone to increase the temperature inside the furnace cavity. The flame system includes an atomizing swirl low-NOx burner and an exhaust pipe. The atomizing swirl low-NOx burner is arranged at a density of 4-6 burners / square meter in the roasting zone. The atomizing swirl low-NOx burner includes a base, with a gas pipe, a lower gas guide pipe, and a support rod installed at the lower end of the base. The lower gas guide pipe is sleeved outside the gas pipe, and the gas pipe is sleeved outside the support rod. A nozzle is provided at the lower end of the support rod. The lower end face of the nozzle is higher than the lower end face of the gas pipe. An annular gap is left between the nozzle and the gas pipe to allow gas flow. Multiple inclined grooves are provided on the outer circumference of the nozzle, and the inclined grooves are inclined at 5-15 degrees relative to the axis of the nozzle. The exhaust pipe has multiple gas inlets on the portion arranged in the preheating zone to extract the flue gas in time under negative pressure.

2. A low-nitrogen combustion system suitable for carbon baking according to claim 1, characterized in that: Multiple inclined grooves are evenly distributed on the outer circumferential surface of the nozzle.

3. A low NOx combustion system suitable for use in carbon baking according to claim 2, characterized in that: The inclination angles of the multiple inclined grooves are consistent.

4. A low-NOx combustion system suitable for carbon roasting according to claim 1, characterized in that: The nozzle is cylindrical, with an outer diameter larger than that of the support rod, and there is a shoulder tapered transition between the nozzle and the support rod.

5. A low NOx combustion system suitable for use in carbon baking according to claim 4, characterized in that: The nozzle, gas pipe, and lower gas guide pipe are arranged concentrically.

6. A low NOx combustion system suitable for use in carbon baking according to claim 2, characterized in that: The inner diameter of the gas pipe is d, the outer diameter of the nozzle is d1=[0.8d,0.9d], the height of the nozzle is h1=[3d,4d], the depth of the inclined groove is h2=[0.01d,0.05d], the width of the inclined groove is w2=[0.02d,0.1d], and the inner diameter of the lower gas guide pipe is [1.5d,2d].

7. A low-nitrogen combustion system suitable for carbon baking according to any one of claims 1 to 6, characterized in that: The flame system also includes a pressure regulator for adjusting the gas pressure fed into the atomizing swirl low-NOx burner and a solenoid valve for controlling the gas flow interruption. The low-NOx combustion system also includes a detection system for detecting the temperature and gas pressure at different points in the furnace cavity and a control system for controlling the solenoid valve and the pressure regulator. The detection system is electrically connected to the input port of the control system to transmit the detected temperature and pressure signals to it. The pressure regulator and the control valve are electrically connected to different output ports of the control system for controlled operation.

8. A low NOx combustion system suitable for use in carbon baking according to claim 7, characterized in that: It also includes an alarm system, which is electrically connected to the output of the control system to issue alarm signals under control.

9. A low NOx combustion system suitable for use in carbon baking according to claim 2, characterized in that: The height of the preheating zone accounts for 1 / 2 to 1 / 3 of the total height of the furnace cavity.

10. A low-nitrogen combustion method using a low-nitrogen combustion system for carbon roasting according to any one of claims 1 to 9, characterized by: When heating the furnace cavity, a segmented heating method is adopted. The lower the temperature and the faster the heating rate, the greater the pressure and duty cycle of the gas injected by the atomizing swirl low-NOx burner. The higher the temperature and the slower the heating rate, the lower the pressure and duty cycle of the gas injected by the atomizing swirl low-NOx burner. The duty cycle and pressure of the gas injected by each atomizing swirl low-NOx burner are controlled independently.

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