A device for reducing the concentration of nitrogen oxides in the flue gas at the kiln tail of a shaft kiln

Abstract

The utility model relates to the field of sleeve kiln tail flue gas treatment technology, concretely to a device for reducing the concentration of nitrogen oxides in the flue gas of the kiln tail of a sleeve kiln, comprising a flue gas extraction unit, a pressurized conveying unit, a flue gas distribution unit and a safety control unit, wherein the flue gas extraction unit comprises an air extraction pipe arranged in front of the chimney of the kiln tail of the sleeve kiln, a first manual butterfly valve is arranged on the air extraction pipe to extract low-temperature flue gas from the kiln tail; a filtering component is installed at one end of the air extraction pipe close to the chimney, the filtering component is a metal filter screen or a ceramic filter core, and is used to filter dust and impurities in the flue gas. The device for reducing the concentration of nitrogen oxides in the flue gas of the kiln tail of a sleeve kiln can effectively reduce the concentration of nitrogen oxides in the flue gas of the kiln tail of a sleeve kiln. In actual application scenarios, the flue gas treated by the device has a nitrogen oxide emission concentration that is lower than that before the transformation.

Description

Technical Field

[0001] This utility model relates to the field of flue gas treatment technology for kiln tail gas in sleeve kilns, and more specifically, to a device for reducing the concentration of nitrogen oxides in the flue gas at the tail of sleeve kilns. Background Technology

[0002] In industrial production, the sleeve kiln, as a widely used calcination equipment, plays a crucial role in processes such as lime production. It boasts significant advantages such as high thermal efficiency and stable product quality, making it highly favored by industry. However, with increasing global environmental awareness and increasingly stringent environmental regulations, the exhaust emissions generated during the operation of sleeve kilns, especially nitrogen oxides (NOx), have gradually become a focus of industry attention. Nitrogen oxides (NOx) are a class of pollutants that pose serious threats to the environment and human health. Environmentally, their emissions lead to acid rain, photochemical smog, and other problems, causing significant damage to ecosystems. From a health perspective, NOx irritates the respiratory tract, triggering a range of respiratory diseases and seriously threatening human health. During the combustion process in a kiln, due to the high-temperature environment and the involvement of air in combustion, large amounts of NOx are inevitably generated. Effectively reducing its emission concentration has become a pressing technical challenge. Utility Model Content

[0003] The purpose of this invention is to provide a device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln, in order to solve the problem mentioned in the background art that, during the combustion process in a sleeve kiln, a large amount of NOx is inevitably generated due to factors such as high temperature environment and air participation in combustion, and how to effectively reduce its emission concentration has become an urgent technical problem to be solved.

[0004] To achieve the above objectives, this utility model provides a device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln, comprising a flue gas extraction unit, a pressurized conveying unit, a flue gas distribution unit, and a safety control unit. The flue gas extraction unit includes an extraction pipe installed in front of the chimney at the tail of the sleeve kiln, and the extraction pipe is equipped with a first manual butterfly valve for extracting low-temperature flue gas at the tail of the kiln. A filter element is installed at the end of the exhaust pipe near the chimney. The filter element is a metal filter screen or a ceramic filter element, which is used to filter dust and impurities in the flue gas. The pressurized conveying unit includes a high-temperature fan and a conveying main pipe. The air inlet of the high-temperature fan is connected to the exhaust pipe, and the air outlet of the high-temperature fan is connected to one end of the conveying main pipe. The high-temperature fan is used to pressurize the extracted low-temperature flue gas to 20 kPa. The flue gas distribution unit includes a flue gas ring pipe and several branch pipes. The flue gas ring pipe is located near the combustion chamber of the sleeve kiln and is connected to the other end of the main conveying pipe.

[0005] This setup achieves nitrogen oxide concentration reduction through a "extraction-purification-pressurization-distribution" process. First, an extraction pipe located before the chimney at the kiln tail extracts the cooler flue gas from the kiln tail (low-temperature flue gas contains more active substances that readily participate in subsequent reactions and cause less damage to equipment). A metal or ceramic filter near the chimney end of the extraction pipe filters out dust and impurities from the flue gas, preventing dust blockage of subsequent pipes and equipment and ensuring smooth flue gas delivery. Then, a high-temperature fan pressurizes the filtered low-temperature flue gas to 20 kPa, ensuring sufficient power to deliver the flue gas to the vicinity of the combustion chamber. Finally, a main delivery pipe connected to the high-temperature fan outlet delivers the pressurized flue gas to a flue gas ring pipe located near the combustion chamber of the kiln, and then distributes the flue gas to the periphery of the combustion chamber through several branch pipes, allowing the extracted low-temperature flue gas to mix with the combustion products in the high-temperature zone of the combustion chamber. After mixing, the inert gases (such as nitrogen and carbon dioxide) in the low-temperature flue gas can dilute the oxygen concentration in the combustion zone and reduce the combustion temperature. At the same time, some components in the low-temperature flue gas (such as water vapor and carbon monoxide) can undergo reduction reactions with nitrogen oxides, thereby inhibiting the formation of nitrogen oxides or promoting their conversion into harmless substances.

[0006] Preferably, the main conveying pipe is equipped with a second manual butterfly valve and an electric regulating butterfly valve in sequence.

[0007] This device is equipped with a second manual butterfly valve and an electric regulating butterfly valve sequentially installed on the main conveying pipe. The second manual butterfly valve, as a manual control component, can manually control the opening and closing of the main conveying pipe during device startup, maintenance, or when the electric regulating butterfly valve fails, playing an emergency and auxiliary control role. The electric regulating butterfly valve, by adjusting its own opening, changes the flow cross-sectional area of ​​the flue gas in the main conveying pipe, thereby controlling the amount of flue gas conveyed, and works with the subsequent control unit to achieve precise adjustment.

[0008] Preferably, the number of branch pipes is consistent with the total number of burners and injection pipes in the upper and lower combustion chambers of the sleeve kiln. Each burner and injection pipe is connected to the flue gas ring pipe through an independent branch pipe. A manual ball valve is provided on the branch pipes connected to the burners in the upper and lower combustion chambers.

[0009] This setup ensures that the number of branch pipes matches the total number of burners and injection pipes in the upper and lower combustion chambers of the kiln. Each burner and injection pipe is connected to the flue gas ring pipe via an independent branch pipe, allowing the flue gas to be accurately and evenly delivered to each burner and injection pipe for thorough mixing with fuel and air. The manual ball valves installed on the branch pipes connected to the burners in the upper and lower combustion chambers allow for manual adjustment of the flue gas supply at the corresponding burner. Based on the different combustion conditions in the upper and lower combustion chambers (such as differences in temperature and oxygen concentration), the flue gas distribution can be flexibly adjusted to ensure that each combustion zone achieves the best denitrification effect.

[0010] Preferably, the outlet end of the high-temperature fan is provided with a pressure buffer section, which is an arc-shaped pipe with an inner diameter larger than that of the main conveying pipe, used to stabilize the pressure fluctuation of the flue gas after pressurization.

[0011] The pressure buffer section at the outlet of the high-temperature fan is an arc-shaped pipe with an inner diameter larger than that of the main conveying pipe. When the pressurized flue gas enters the pressure buffer section, the increased pipe diameter expands the flue gas flow space and reduces the flow velocity, which can effectively alleviate pressure fluctuations caused by fan operation fluctuations or flue gas flow rate changes. The arc-shaped pipe design can reduce the resistance and eddies of the flue gas during the flow process, avoid sudden increases and decreases in local pressure, and allow the flue gas pressure to gradually stabilize before entering the main conveying pipe.

[0012] Preferably, the safety control unit includes a pressure sensor and a vent valve. The pressure sensor is arranged in a ring at equal intervals on the flue gas ring pipe to detect the pressure inside the flue gas ring pipe. The vent valve is installed on the flue gas ring pipe and is electrically connected to the pressure sensor. When the pressure sensor detects that the pressure in the flue gas ring pipe exceeds a preset threshold, the vent valve automatically opens to reduce the pressure.

[0013] In this safety control unit, pressure sensors arranged in a ring at equal intervals on the flue gas loop can comprehensively and accurately detect the pressure at various locations within the flue gas loop, avoiding inaccurate pressure detection caused by single-point detection. The pressure sensors are electrically connected to the vent valve. When the pressure sensor detects that the pressure inside the flue gas loop exceeds a preset threshold, it sends a signal to the vent valve, causing the vent valve to open automatically, discharging excess flue gas from the loop and reducing the pressure inside the loop. Once the pressure drops to a safe range, the vent valve automatically closes.

[0014] Preferably, the system also includes a flow metering unit, which is a flow meter installed on the main conveying pipe or the extraction pipe for real-time measurement of flue gas flow.

[0015] The flow meter of this flow metering unit is installed on the main conveying pipe or the extraction pipe. Through the detection elements inside the flow meter (such as turbine, orifice plate, etc.), the flow rate of the flue gas is calculated and displayed in real time based on the physical changes generated during the flow of flue gas (such as turbine speed, differential pressure, etc.). The staff can understand the current amount of flue gas extracted or delivered by reading the data from the flow meter.

[0016] Preferably, the system also includes an automatic adjustment unit, which includes a nitrogen oxide concentration sensor and a control system. The nitrogen oxide concentration sensor is installed on the chimney and is used to detect the nitrogen oxide concentration in the kiln tail flue gas. The control system is electrically connected to the nitrogen oxide concentration sensor and the electric regulating butterfly valve, and is used to control the opening degree of the electric regulating butterfly valve according to the detected nitrogen oxide concentration value.

[0017] This automatic adjustment unit achieves precise regulation of nitrogen oxide concentration through closed-loop control. A nitrogen oxide concentration sensor installed on the chimney monitors the nitrogen oxide concentration in the kiln tail flue gas in real time and transmits the data to the control system. Upon receiving the data, the control system compares it with a preset control strategy. If the nitrogen oxide concentration is higher than the target value, it sends a signal to the electrically controlled butterfly valve to increase its opening, thereby increasing the flue gas flow and enhancing the denitrification effect. If the nitrogen oxide concentration is lower than the target value, it controls the electrically controlled butterfly valve to decrease its opening, reducing the flue gas flow and avoiding energy waste.

[0018] Preferably, the control system has a preset nitrogen oxide concentration threshold range. When the kiln tail flue gas detection device detects a concentration higher than the upper limit of the threshold, the control system controls the electric regulating butterfly valve to increase its opening. When the detected concentration is lower than the lower limit of the threshold, the control system controls the electric regulating butterfly valve to decrease its opening.

[0019] This setting controls the preset nitrogen oxide concentration threshold range within the control system. When the nitrogen oxide concentration sensor detects that the nitrogen oxide concentration in the kiln tail flue gas is higher than the upper threshold, the control system determines that the current denitrification effect is not good and that the flue gas flow needs to be increased to enhance the denitrification effect. Therefore, it sends a signal to the electric regulating butterfly valve to increase the opening. When the concentration is detected to be lower than the lower threshold, the control system determines that the current flue gas flow is too large and may cause energy waste. Therefore, it sends a signal to the electric regulating butterfly valve to decrease the opening, reduce the flue gas flow, and keep the nitrogen oxide concentration within the preset threshold range.

[0020] Compared with the prior art, the beneficial effects of this utility model are as follows: This device for reducing nitrogen oxide concentration in the flue gas from a sleeve kiln effectively and significantly reduces the concentration of nitrogen oxides in the flue gas. In practical applications, the nitrogen oxide emission concentration of the flue gas treated by this device can be stably reduced from a relatively high level before the modification to a level far below the value stipulated in the "Emission Standard of Air Pollutants for Building Materials Industry," demonstrating a significant emission reduction effect. This achievement not only helps enterprises meet increasingly stringent environmental regulations but also greatly reduces pollution to the surrounding environment and mitigates the potential harm of nitrogen oxide emissions to ecosystems and human health. Precise control of flue gas flow: The flow metering unit in the device, i.e., the flow meter installed on the main conveying pipe or the extraction pipe, can measure the flue gas flow in real time and accurately. The nitrogen oxide concentration sensor and control system in the automatic adjustment unit can automatically and intelligently control the opening of the electric regulating butterfly valve based on the nitrogen oxide concentration in the kiln tail flue gas detected by the nitrogen oxide concentration sensor on the chimney. When the kiln tail flue gas detection device detects that the nitrogen oxide concentration is higher than the preset upper threshold, the control system will automatically control the electric regulating butterfly valve to increase its opening, allowing more low-temperature flue gas from the kiln tail to be extracted and sent into the kiln for combustion, thereby further suppressing the formation of nitrogen oxides in the combustion zone. Conversely, when the detected concentration is lower than the lower threshold, the control system controls the electric regulating butterfly valve to decrease its opening, ensuring that the entire system is always in a highly efficient, stable, and energy-saving operating state, achieving precise control of nitrogen oxide emission concentration. The pressure buffer section at the outlet of the high-temperature blower, an arc-shaped pipe with an inner diameter larger than the main conveying pipe, effectively stabilizes the pressure fluctuations of the flue gas after pressurization, reducing the adverse effects of pressure instability on the entire conveying system and the combustion process within the kiln, and ensuring the continuity and stability of flue gas delivery. Simultaneously, pressure sensors in the safety control unit are evenly distributed in a ring along the flue gas ring pipe, monitoring the pressure within the pipe in real time. Once the pressure sensors detect that the flue gas ring pipe pressure exceeds a preset threshold, the vent valve automatically opens to reduce pressure, preventing equipment failures or even safety accidents caused by excessive pipeline pressure. This significantly improves the operational safety and stability of the entire unit, reducing equipment maintenance costs and operational risks for the enterprise. With a significant reduction in nitrogen oxide emissions, enterprises can not only meet environmental protection requirements and reduce pollution, but also obtain considerable economic benefits. Because the equipment can precisely control flue gas flow and the combustion process, combustion within the kiln is more complete and efficient, thereby reducing fuel consumption and saving production costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the flue gas ring pipe in this utility model; Figure 3 This is a schematic diagram of the structure of the high-temperature fan of this utility model; The meanings of the labels in the diagram are as follows: 1. Chimney; 11. Nitrogen oxide concentration sensor; 2. Exhaust pipe; 21. Manual butterfly valve; 22. Filter components; 3. High-temperature fan; 31. Air inlet; 32. Air outlet; 4. Main conveying pipe; 41. Manual butterfly valve; 42. Electric regulating butterfly valve; 43. Flow meter; 5. Flue gas loop pipe; 51. Branch pipe; 52. Pressure sensor; 53. Vent valve; 6. Control system. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] This utility model provides a device for reducing the concentration of nitrogen oxides in the flue gas from the tail gas of a sleeve kiln, such as... Figure 1 , Figure 2 , Figure 3 As shown, it includes a flue gas extraction unit, a pressurized conveying unit, a flue gas distribution unit, and a safety control unit. The flue gas extraction unit includes an extraction pipe 2 installed in front of the kiln tail chimney 1 of the sleeve kiln. The extraction pipe 2 is equipped with a first manual butterfly valve 21 for extracting low-temperature flue gas from the kiln tail. A filter element 22 is installed at the end of the exhaust pipe 2 near the chimney 1. The filter element 22 is a metal filter screen or a ceramic filter core, which is used to filter dust and impurities in the flue gas. The pressurized conveying unit includes a high-temperature fan 3 and a conveying main pipe 4. The air inlet 32 ​​of the high-temperature fan 3 is connected to the exhaust pipe 2, and the air outlet of the high-temperature fan 3 is connected to one end of the conveying main pipe 4. The high-temperature fan 3 is used to pressurize the extracted low-temperature flue gas to 20 kPa. The flue gas distribution unit includes a flue gas ring pipe 5 and several branch pipes 51. The flue gas ring pipe 5 is located near the combustion chamber of the sleeve kiln and is connected to the other end of the conveying main pipe 4.

[0024] The nitrogen oxide concentration is reduced through a "extraction-purification-pressurization-distribution" process. The core structure operates in a coordinated manner as follows: First, the extraction pipe 2, located in front of the chimney 1 at the tail of the kiln, extracts the active substances from the low-temperature flue gas at the kiln tail. These substances are more likely to participate in the reaction and cause less damage to the equipment. The first manual butterfly valve 21 on the extraction pipe 2 can manually control the start and stop of the extraction and the basic flow rate. The filter component 22, a metal filter or ceramic filter element, located near the chimney 1 on the extraction pipe 2, can filter dust and impurities in the flue gas, preventing blockage of subsequent pipes and equipment. Subsequently, the air inlet 32 ​​of the high-temperature fan 3 is connected to the extraction pipe 2, pressurizing the filtered low-temperature flue gas to 20 kPa. This pressure ensures that the flue gas has sufficient power to be transported. The air outlet of the high-temperature fan 3 is connected to the main conveying pipe 4, which transports the pressurized flue gas to the flue gas ring pipe 5 located near the combustion chamber of the kiln. The flue gas is then distributed to the periphery of the combustion chamber through several branch pipes 51. After mixing, the inert gases nitrogen and carbon dioxide in the low-temperature flue gas dilute the oxygen concentration in the combustion zone and lower the combustion temperature. Components such as water vapor and carbon monoxide undergo reduction reactions with nitrogen oxides, inhibiting their formation or converting them into harmless substances. The exhaust pipe 2 works in conjunction with the high-temperature fan 3 to achieve the recovery and reuse of low-temperature flue gas at the kiln tail, eliminating the need for additional denitrification agents and reducing costs. Filter component 22 prevents dust from abrading the high-temperature fan 3 and clogging the conveying main pipe 4 and flue gas ring pipe 5, extending equipment life and ensuring stable operation of the device; The high-temperature fan's pressurization effect of 320kPa ensures that the flue gas smoothly reaches the flue gas ring pipe 5 through the main conveying pipe 4, meeting the subsequent distribution requirements; The annular + multi-branch design of flue gas ring pipe 5 and branch pipe 51 ensures that the flue gas is evenly distributed to the periphery of the combustion chamber, guaranteeing that oxygen dilution and nitrogen oxide reduction can be achieved in all parts of the combustion zone, and initially reducing the nitrogen oxide concentration of the flue gas discharged from chimney 1.

[0025] In this embodiment, the conveying main pipe 4 is provided with a second manual butterfly valve 41 and an electric regulating butterfly valve 42 in sequence.

[0026] The second manual butterfly valve 41 and the electric regulating butterfly valve 42 are sequentially installed on the main conveying pipe 4, forming a "manual + electric" dual control logic: the second manual butterfly valve 41 serves as an emergency and auxiliary component, manually controlling the opening and closing of the main conveying pipe 4 when the device is started, under maintenance, or when the electric regulating butterfly valve 42 fails; the electric regulating butterfly valve 42 adjusts the cross-sectional area of ​​flue gas flow in the main conveying pipe 4 by changing its own opening degree, thereby controlling the flue gas conveying volume and providing an execution basis for subsequent automatic adjustment. The second manual butterfly valve 41 provides redundant control for the device. When the electric regulating butterfly valve 42 fails, the conveying main pipe 4 can be manually maintained to avoid device shutdown and improve reliability. The electric regulating butterfly valve 42 can flexibly adjust the amount of flue gas in the main conveying pipe 4, and work with the subsequent control unit to achieve precise adjustment, avoiding incomplete denitrification or energy waste caused by a fixed amount of flue gas, and ensuring stable denitrification effect.

[0027] Specifically, such as Figure 1 , Figure 2 , Figure 3 The number of branch pipes 51 is consistent with the total number of burners and injection pipes in the upper and lower combustion chambers of the sleeve kiln. Each burner and injection pipe is connected to the flue gas ring pipe 5 through an independent branch pipe 51. A manual ball valve is provided on the branch pipes 51 connected to the burners in the upper and lower combustion chambers.

[0028] The number of branch pipes 51 is consistent with the total number of burners and injection pipes in the upper and lower combustion chambers of the sleeve kiln. Each burner and injection pipe is connected to the flue gas ring pipe 5 through an independent branch pipe 51 to ensure that the flue gas can be accurately delivered to each combustion point and fully mixed with fuel and air. The manual ball valves on the branch pipes 51 connected to the burners in the upper and lower combustion chambers can manually adjust the flue gas supply of the corresponding branch pipe 51 according to the temperature and oxygen concentration differences in the upper and lower combustion chambers to achieve differentiated distribution. The independent branch pipe 51 design avoids uneven distribution of flue gas during the delivery process from the flue gas ring pipe 5 to the burner / injector pipe, ensuring that all combustion points receive sufficient and appropriate amounts of flue gas, thereby improving the overall denitrification efficiency. The manual ball valve can adjust the flue gas volume of the branch pipe 51 according to different combustion chamber conditions to meet complex combustion requirements. When a branch pipe 51 fails, the corresponding ball valve can be closed for maintenance without affecting the operation of other branch pipes 51, thus improving the flexibility and maintainability of the device.

[0029] Furthermore, such as Figure 1 , Figure 2 , Figure 3 As shown, the outlet end 31 of the high-temperature fan 3 is provided with a pressure buffer section. The pressure buffer section is an arc-shaped pipe with an inner diameter larger than that of the main conveying pipe 4, which is used to stabilize the pressure fluctuation of the flue gas after pressurization.

[0030] The pressure buffer section 31 at the outlet of the high-temperature fan 3 has an inner diameter larger than the arc-shaped pipe of the main conveying pipe 4, which can alleviate pressure fluctuations: when the flue gas pressurized by the high-temperature fan 3 enters the buffer section, the expanded flow space reduces the flue gas velocity and offsets the pressure fluctuations caused by fan operation fluctuations or flow changes; the arc-shaped pipe design reduces the flow resistance and eddies of the flue gas, avoids sudden changes in local pressure, and allows the flue gas pressure to stabilize before entering the main conveying pipe 4. The pressure buffer section stabilizes the flue gas pressure at the outlet 31 of the high-temperature fan 3, avoiding fluctuations that could affect the pressure inside the flue gas ring pipe 5 and branch pipe 51, ensuring a stable flue gas supply to each branch pipe 51 and guaranteeing consistent denitrification performance. Reduce the impact of pressure fluctuations on the main conveying pipe 4, flue gas ring pipe 5 and connecting components, reduce pipeline fatigue damage, extend the service life of the main conveying pipe 4 and flue gas ring pipe 5, and avoid pipeline leakage hazards caused by excessive pressure.

[0031] Furthermore, such as Figure 1 , Figure 2 As shown, the safety control unit includes a pressure sensor 52 and a relief valve 53. The pressure sensor 52 is arranged in a ring at equal intervals on the flue gas ring pipe 5 to detect the pressure inside the flue gas ring pipe 5. The relief valve 53 is installed on the flue gas ring pipe 5 and is electrically connected to the pressure sensor 52. When the pressure sensor 52 detects that the pressure in the flue gas ring pipe 5 exceeds a preset threshold, the relief valve 53 automatically opens to reduce the pressure.

[0032] In the safety control unit, pressure sensors 52 are arranged in a ring at equal intervals on the flue gas ring pipe 5. They can comprehensively detect the pressure at each position of the flue gas ring pipe 5, avoiding the limitations of single-point detection. The pressure sensors 52 are electrically connected to the vent valve 53 on the flue gas ring pipe 5. When the pressure sensors 52 detect that the pressure in the flue gas ring pipe 5 exceeds the preset threshold, the vent valve 53 is triggered to open automatically, discharge excess flue gas and reduce pressure. After the pressure drops to a safe range, the vent valve 53 closes automatically. Pressure sensor 52 monitors the pressure of flue gas ring pipe 5 in real time, and relief valve 53 automatically reduces pressure, effectively preventing pipe rupture and damage to connecting parts due to excessive pressure in flue gas ring pipe 5, and ensuring safe operation of the device. The pressure sensors 52 arranged in a ring at equal intervals ensure comprehensive detection and avoid the risk of undetected local high pressure in the flue gas ring pipe 5. The venting valve 53 is automatically controlled without manual intervention, improving the automation and safety of the device.

[0033] Furthermore, such as Figure 1 As shown, it also includes a flow metering unit, which is a flow meter 43. The flow meter 43 is installed on the main conveying pipe 4 or the extraction pipe 2 and is used to measure the flue gas flow in real time.

[0034] The flow meter 43 of the flow metering unit is installed on the main conveying pipe 4 or the extraction pipe 2. Through internal detection elements such as turbine and orifice plate, the flow rate of flue gas is calculated and displayed in real time based on the physical changes in the flow of flue gas, such as turbine speed and differential pressure. The staff can use the data from the flow meter 43 to know the extraction volume of the extraction pipe 2 or the conveying volume of the main conveying pipe 4. The flow meter 43 provides real-time flow data for staff, making it easy to detect abnormal flow in the exhaust pipe 2 or the main delivery pipe 4, quickly troubleshoot problems such as pipe blockage and high-temperature fan 3 failure, and ensure stable operation of the device. Flow data can be used to optimize the denitrification process. For example, by combining the nitrogen oxide concentration at the outlet of chimney 1, the optimal flue gas flow range of the extraction pipe 2 or the main conveying pipe 4 can be determined, thereby improving denitrification efficiency and avoiding energy waste or incomplete denitrification.

[0035] Furthermore, such as Figure 1 As shown, it also includes an automatic adjustment unit, which includes a nitrogen oxide concentration sensor 11 and a control system 6. The nitrogen oxide concentration sensor 11 is installed on the chimney 1 and is used to detect the nitrogen oxide concentration in the kiln tail flue gas. The control system 6 is electrically connected to the nitrogen oxide concentration sensor 11 and the electric regulating butterfly valve 42 respectively, and is used to control the opening degree of the electric regulating butterfly valve 42 according to the nitrogen oxide concentration detection value.

[0036] The automatic adjustment unit achieves precise adjustment through closed-loop control: the nitrogen oxide concentration sensor 11 installed on the chimney 1 detects the nitrogen oxide concentration in the kiln tail flue gas in real time and transmits the data to the control system 6; the control system 6 is electrically connected to the nitrogen oxide concentration sensor 11 and the electric regulating butterfly valve 42 respectively, compares the detected value with the preset strategy, if the concentration is higher than the target value, controls the electric regulating butterfly valve 42 to increase the opening degree, increasing the flue gas volume of the conveying main pipe 4; if the concentration is lower than the target value, controls the electric regulating butterfly valve 42 to decrease the opening degree, reducing the flue gas volume. The nitrogen oxide concentration sensor 11 works in conjunction with the control system 6 to achieve automatic monitoring of nitrogen oxide concentration, eliminating the need for frequent manual checks; the control system 6 automatically controls the electric regulating butterfly valve 42, reducing the labor intensity of workers and improving the automation level of the equipment. Closed-loop control can quickly respond to changes in nitrogen oxide concentration at the outlet of chimney 1. By adjusting the flue gas volume of the main conveying pipe 4 through the electrically adjustable butterfly valve 42, the concentration is kept stable within the target range, avoiding excessive concentrations or energy waste caused by untimely manual adjustments, and improving the stability and accuracy of denitrification.

[0037] Furthermore, such as Figure 1 As shown, the control system 6 has a preset nitrogen oxide concentration threshold range. When the kiln tail flue gas detection device detects that the concentration is higher than the upper limit of the threshold, the control system 6 controls the electric regulating butterfly valve 42 to increase the opening degree; when the detected concentration is lower than the lower limit of the threshold, the control system 6 controls the electric regulating butterfly valve 42 to decrease the opening degree.

[0038] The control system 6 has a preset nitrogen oxide concentration threshold range, forming a clear adjustment logic: when the nitrogen oxide concentration sensor 11 detects that the flue gas concentration at the outlet of the chimney 1 is higher than the upper limit of the threshold, the control system 6 determines that the denitrification is insufficient and sends an increase opening signal to the electric regulating butterfly valve 42 to increase the flue gas volume of the conveying main pipe 4; when the concentration is lower than the lower limit of the threshold, it determines that the flue gas volume is too large and sends a decrease opening signal to the electric regulating butterfly valve 42 to reduce the flue gas volume of the conveying main pipe 4 and maintain the concentration within the threshold range. The preset threshold provides a clear adjustment basis for the control system 6, making the action logic of the electric regulating butterfly valve 42 more scientific and avoiding blind adjustment. To ensure that the concentration of nitrogen oxides in the flue gas emitted from chimney 1 remains stable within the preset range, thus meeting environmental protection standards while avoiding excessive energy consumption of the high-temperature fan 3 due to excessive opening of the electric regulating butterfly valve 42, thereby achieving a balance between environmental protection and energy conservation and optimizing the operating performance of the device.

[0039] This utility model's device for reducing nitrogen oxide concentration in the flue gas from a sleeve kiln operates on the core principle of "internal circulation denitrification." It extracts components from the low-temperature flue gas at the kiln tail, including inert gases and water vapor, that can participate in the denitrification reaction. After purification, pressurization, and precise distribution, this gas is returned to the periphery of the combustion chamber. The low-temperature flue gas dilutes the oxygen concentration in the combustion zone, lowers the combustion temperature, and inhibits nitrogen oxide formation through component reactions. Simultaneously, real-time monitoring and automatic adjustment ensure stable denitrification performance that meets environmental protection requirements. The specific principle can be broken down into three parts: Physical dilution and temperature control: Inert gases such as nitrogen and carbon dioxide in low-temperature flue gas can reduce the local oxygen concentration in the combustion chamber and avoid the large-scale generation of thermal nitrogen oxides (NOx) under high-temperature oxygen-rich conditions; at the same time, the low temperature of the flue gas itself can directly reduce the temperature of the combustion zone and further inhibit the synthesis of nitrogen oxides. Chemical reduction reaction: Water vapor, carbon monoxide and other components in low-temperature flue gas can undergo reduction reactions with nitrogen oxides generated during combustion, such as CO + NO → N2 + CO2, converting harmful nitrogen oxides into harmless nitrogen and carbon dioxide. Closed-loop intelligent control: Real-time data is acquired through detection elements such as nitrogen oxide concentration sensors, pressure sensors, and flow meters. The control system automatically adjusts the flue gas delivery volume and pipeline pressure according to preset thresholds to achieve closed-loop control of "detection-judgment-adjustment", ensuring stable denitrification effect and avoiding energy waste. Based on the device structure shown in Figures 1, 2, and 3, the overall working process unfolds according to the following flow: "Flue gas extraction → purification and filtration → pressurization and transportation → flow metering → pressure stabilization → loop distribution → combustion denitrification → real-time monitoring → automatic adjustment → safety protection". The specific operations of each stage are as follows: During normal operation of the sleeve kiln, the nitrogen oxide-containing flue gas generated at the kiln tail flows towards the chimney 1. At this time, the first manual butterfly valve 21 on the extraction pipe 2 is opened, and the negative pressure generated by the subsequent pressurized conveying unit is used to extract the low-temperature flue gas in front of the chimney 1 through the extraction pipe 2 to avoid damage to the equipment caused by the high-temperature flue gas, and the components of the low-temperature flue gas are more likely to participate in the denitrification reaction. The metal or ceramic filter element of the filter component 22 at the end of the exhaust pipe 2 near the chimney 1 is activated simultaneously to filter the dust in the extracted low-temperature flue gas, remove particulate impurities from the flue gas, prevent wear of the impeller of the subsequent high-temperature fan 3 and blockage of the main conveying pipe 4 and the flue gas ring pipe 5, and ensure stable operation of the equipment. The filtered low-temperature flue gas enters the inlet 32 ​​of the high-temperature fan 3. The high-temperature fan 3 starts and pressurizes the flue gas to 20 kPa—this pressure ensures that the flue gas has sufficient power to overcome pipeline resistance and be smoothly transported to the vicinity of the combustion chamber. The pressurized flue gas enters the conveying main pipe 4 from the outlet 31 of the high-temperature fan 3. The second manual butterfly valve 41 on the conveying main pipe 4 is opened, and the flue gas is conveyed forward along the conveying main pipe 4. The flow meter 43 installed on the main conveying pipe 4 or the extraction pipe 2 measures the flue gas flow in real time and feeds the flow data back to the staff or control system 6, so as to facilitate real-time monitoring of the flue gas delivery volume. If the flow is abnormal, such as too low, it may be due to blockage of the filter component 22, or too high, it may be due to pipeline leakage, and the fault can be investigated in time. The pressure buffer section 31 at the outlet of the high-temperature fan 3, with an inner diameter larger than that of the main conveying pipe 4, plays a role in the following: when the pressurized flue gas enters the buffer section, the expanded flow space reduces the flue gas velocity and offsets the pressure fluctuations caused by the operation fluctuations or flow changes of the high-temperature fan 3; the arc design reduces flue gas eddies and resistance, avoids sudden changes in local pressure, and allows the flue gas pressure to stabilize before entering the main conveying pipe 4, laying the foundation for subsequent uniform distribution. After the flue gas pressure stabilizes, it enters the flue gas ring pipe 5, located near the combustion chamber of the sleeve kiln, through the main conveying pipe 4. Since the number of branch pipes 51 matches the total number of burners and injection pipes in the upper and lower combustion chambers of the sleeve kiln, and each burner and injection pipe is connected to the flue gas ring pipe 5 via an independent branch pipe 51, the flue gas is evenly distributed to each branch pipe 51 within the flue gas ring pipe 5. Operators can adjust the flue gas supply to the corresponding branch pipe 51 by adjusting the manual ball valves on the branch pipes 51, based on differences in operating conditions between the upper and lower combustion chambers, such as temperature and oxygen concentration, thus achieving differentiated distribution. Each branch pipe 51 transports the low-temperature flue gas to the periphery of the combustion chamber, where it is fully mixed with the high-temperature flue gas, fuel, and air generated during combustion. On the one hand, the inert gas in the low-temperature flue gas dilutes the oxygen concentration in the combustion zone, reduces the combustion temperature, and inhibits the generation of nitrogen oxides. On the other hand, the water vapor, carbon monoxide, and other components in the low-temperature flue gas undergo a reduction reaction with the generated nitrogen oxides, converting them into harmless substances. Finally, the treated flue gas is discharged into the chimney 1 along with the main flue gas at the kiln tail. A nitrogen oxide concentration sensor 11 installed on chimney 1 detects the nitrogen oxide concentration in the exhaust gas in real time and transmits the detection data to control system 6. Control system 6 has a preset nitrogen oxide concentration threshold range and judges the detected values ​​accordingly. If the concentration is higher than the upper limit of the threshold: it is determined that the denitrification is insufficient. The control system 6 sends a signal to the electric regulating butterfly valve 42 on the main conveying pipe 4 to control it to increase the opening degree, increase the flue gas conveying volume, and enhance the denitrification effect. If the concentration is below the lower threshold: it is determined that the amount of flue gas is too large. The control system 6 controls the electric regulating butterfly valve 42 to reduce the opening, reduce the amount of flue gas transported, and avoid energy waste of the high-temperature fan 3. Pressure sensors 52, arranged in a ring at equal intervals on the flue gas ring pipe 5, detect the pressure at various locations within the flue gas ring pipe 5 in real time and transmit the data to the vent valve 53. When the pressure exceeds the preset threshold, such as when the pressure in the ring pipe rises suddenly due to blockage of the branch pipe 51, the vent valve 53 will automatically open to discharge excess flue gas in the flue gas ring pipe 5 and reduce the pressure. When the pressure drops to a safe range, the vent valve 53 automatically closes to prevent excessively low pressure from affecting flue gas distribution and to ensure the overall safe operation of the unit.

[0040] Finally, it should be noted that the electronic components in the above-mentioned components, such as the electric regulating butterfly valve 42 in this embodiment, are all general standard parts or parts known to those skilled in the art. Their structure and principle can be learned by those skilled in the art through technical manuals or conventional experimental methods. In the idle part of this device, all the above-mentioned electrical components are connected by wires. The specific connection method should refer to the working order between each electrical component in the above working principle to complete the electrical connection. All of these are technologies known in the art.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln, comprising a flue gas extraction unit, a pressurized conveying unit, a flue gas distribution unit, and a safety control unit, characterized in that: The flue gas extraction unit includes an extraction pipe (2) installed in front of the chimney (1) at the tail of the sleeve kiln. The extraction pipe (2) is equipped with a first manual butterfly valve (21) for extracting low-temperature flue gas at the tail of the kiln. The exhaust pipe (2) is equipped with a filter element (22) at one end near the chimney (1). The filter element (22) is a metal filter or a ceramic filter core, used to filter dust impurities in the flue gas. The pressurized conveying unit includes a high-temperature fan (3) and a conveying main pipe (4). The air inlet (32) of the high-temperature fan (3) is connected to the exhaust pipe (2), and the air outlet of the high-temperature fan (3) is connected to one end of the conveying main pipe (4). The high-temperature fan (3) is used to pressurize the extracted low-temperature flue gas to 20 kPa. The flue gas distribution unit includes a flue gas ring pipe (5) and several branch pipes (51). The flue gas ring pipe (5) is located near the combustion chamber of the sleeve kiln and is connected to the other end of the conveying main pipe (4).

2. The device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln according to claim 1, characterized in that: The main conveying pipe (4) is equipped with a second manual butterfly valve (41) and an electric regulating butterfly valve (42) in sequence.

3. The device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln according to claim 1, characterized in that: The number of branch pipes (51) is consistent with the total number of burners and injection pipes in the upper and lower combustion chambers of the sleeve kiln. Each burner and injection pipe is connected to the flue gas ring pipe (5) through an independent branch pipe (51). A manual ball valve is provided on the branch pipe (51) connected to the burners in the upper and lower combustion chambers.

4. The device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln according to claim 1, characterized in that: The outlet end (31) of the high-temperature fan (3) is provided with a pressure buffer section, which is an arc-shaped pipe with an inner diameter larger than that of the conveying main pipe (4) to stabilize the pressure fluctuation of the flue gas after pressurization.

5. The device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln according to claim 1, characterized in that: The safety control unit includes a pressure sensor (52) and a relief valve (53). The pressure sensor (52) is arranged in a ring at equal intervals on the flue gas ring pipe (5) to detect the pressure inside the flue gas ring pipe (5). The relief valve (53) is installed on the flue gas ring pipe (5) and is electrically connected to the pressure sensor (52). When the pressure sensor (52) detects that the pressure in the flue gas ring pipe (5) exceeds a preset threshold, the relief valve (53) automatically opens to reduce the pressure.

6. The device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln according to claim 1, characterized in that: It also includes a flow metering unit, which is a flow meter (43). The flow meter (43) is installed on the main conveying pipe (4) or the extraction pipe (2) and is used to measure the flue gas flow in real time.

7. The device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln according to claim 1, characterized in that: It also includes an automatic adjustment unit, which includes a nitrogen oxide concentration sensor (11) and a control system (6). The nitrogen oxide concentration sensor (11) is installed on the chimney (1) and is used to detect the nitrogen oxide concentration in the flue gas at the kiln tail. The control system (6) is electrically connected to the nitrogen oxide concentration sensor (11) and the electric regulating butterfly valve (42) respectively, and is used to control the opening degree of the electric regulating butterfly valve (42) according to the nitrogen oxide concentration detection value.

8. The device for reducing the concentration of nitrogen oxides in the flue gas from a sleeve kiln according to claim 7, characterized in that: The control system (6) has a preset nitrogen oxide concentration threshold range. When the kiln tail flue gas detection device detects that the concentration is higher than the upper limit of the threshold, the control system (6) controls the electric regulating butterfly valve (42) to increase the opening degree; when the concentration is detected to be lower than the lower limit of the threshold, the control system (6) controls the electric regulating butterfly valve (42) to decrease the opening degree.

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