A molten salt furnace flue gas recirculation system and process thereof

Abstract

The present application belongs to the technical field of chemical production equipment, and particularly relates to a molten salt furnace flue gas recirculation system and a process thereof, which comprises: a molten salt furnace; an ultra-low nitrogen burner for heating the molten salt furnace; a flue gas backflow channel, one end of which is in communication with the molten salt furnace and the other end of which is in communication with the ultra-low nitrogen burner; an exhaust pipe, which is in communication with the flue gas backflow channel and is provided with a valve; an FGR circulating fan for circulating flue gas, which is in communication with the flue gas backflow channel; a high-pressure air blower for feeding air into the ultra-low nitrogen burner, which is in communication with the ultra-low nitrogen burner; and further comprising: an adjusting valve, which is arranged at the flue gas backflow channel; and a DCS control system, which is electrically connected with the adjusting valve, the ultra-low nitrogen burner, the high-pressure air blower and the FGR circulating fan. The present application solves the problem of manual adjustment of the fuel and air volume ratio and the difficulty in precise temperature control.

Description

Technical Field

[0001] This invention belongs to the field of chemical production equipment technology, specifically relating to a molten salt furnace flue gas recirculation system and its process. Background Technology

[0002] The flue gas from coal-fired molten salt furnaces contains excessive concentrations of pollutants such as particulate matter, SO2, and NOx, failing to meet the special emission limits stipulated in the "Emission Standard of Pollutants for Petrochemical Industry" (GB 31571-2015). Low thermal efficiency: Long-term operation of coal-fired molten salt furnaces results in severe ash accumulation in the furnace chamber, leading to decreased thermal efficiency and energy waste.

[0003] Currently, an existing molten salt coal-fired boiler with a flue gas generating chamber, announced under CN117073226A, includes a two-pass flue, with a molten salt conveying pipeline installed on the inner wall. One side of the pipeline connects to the outlet of the pre-combustion chamber, and a three-stage molten salt heat exchanger is installed in the upper part, with the side furthest from the pre-combustion chamber connecting to the inlet of the third-pass flue. A burner is located at the top of the pre-combustion chamber. A second-stage molten salt heat exchanger is located within the third-pass flue, with the outlet of the molten salt conveying pipeline connected to the inlet of the second-stage molten salt heat exchanger. A flue gas recirculation pipeline connects to the third-pass flue at one end and to the pre-combustion chamber at the other. A flue gas recirculation fan is installed on the recirculation pipeline to introduce the gas from the third-pass flue, after heat exchange with the second-stage molten salt heat exchanger, into the pre-combustion chamber. It is primarily used for coal combustion.

[0004] However, a problem exists: low level of automation. Traditional coal-fired molten salt furnaces rely on manual adjustment of the fuel and air volume ratio, making it difficult to achieve precise temperature control. In existing technologies, although gas-fired molten salt furnaces can reduce some pollutants, they lack effective control measures for high nitrogen oxide (NOx) emissions, and have low system integration, making them unsuitable for existing molten salt furnace flues and heat exchange equipment. Summary of the Invention

[0005] This solution provides a molten salt furnace flue gas recirculation system to address the problem of difficulty in achieving precise temperature control when manually adjusting the fuel and air volume ratio.

[0006] This solution provides a molten salt furnace flue gas recirculation system, including: Molten salt furnace; Ultra-low NOx burner: used for heating molten salt furnaces; Flue gas recirculation channel: One end of the flue gas recirculation channel is connected to the molten salt furnace, and the other end is connected to the ultra-low nitrogen burner; Exhaust pipe: The exhaust pipe is connected to the flue gas return channel, and the exhaust pipe is equipped with a valve; FGR circulating fan: used to circulate flue gas, the FGR circulating fan is connected to the flue gas return channel; High-pressure blower: used to supply air to the ultra-low NOx burner, and the high-pressure blower is connected to the ultra-low NOx burner; Also includes: Regulating valve: The regulating valve is located in the flue gas return channel. DCS control system: The regulating valve, ultra-low NOx burner, high-pressure blower and FGR circulating fan are all electrically connected to the DCS control system.

[0007] The principle behind this scheme is as follows: a portion of the high-temperature flue gas from the molten salt furnace is drawn back to the ultra-low NOx burner through the flue gas recirculation channel by the FGR circulating fan, while excess flue gas is discharged from the exhaust pipe. The recirculated flue gas mixes with fresh air before entering the burner, reducing the oxygen concentration and temperature in the combustion zone, thereby reducing NOx formation.

[0008] The DCS control system monitors and adjusts the opening of regulating valves in real time based on preset parameters (such as temperature and oxygen concentration) to control the flue gas return flow. Simultaneously, the DCS control system also monitors and adjusts the operating status of the ultra-low NOx burner and the gas supply of the high-pressure blower to ensure the stability and efficiency of the combustion process.

[0009] The DCS control system collects key parameters such as temperature and oxygen concentration inside the molten salt furnace in real time through sensors, and feeds this data back to the control system for analysis and decision-making. Based on the data analysis results, the system automatically adjusts the operating status of each component to achieve optimal combustion efficiency and minimum pollutant emissions.

[0010] The beneficial effects of this solution are as follows: 1. Through precise adjustment by the DCS control system, accurate temperature control within the molten salt furnace can be achieved, avoiding the errors and instability caused by traditional manual adjustment. The automated adjustment mechanism can dynamically adjust combustion parameters according to actual working conditions, ensuring that the temperature remains within the set range.

[0011] 2. Flue gas recirculation technology effectively reduces the temperature and oxygen concentration in the combustion zone, thereby reducing NOx formation. The application of ultra-low NOx burners further enhances this effect, resulting in a significant reduction in NOx emissions from the entire system.

[0012] Furthermore, a heating layer is included, which is disposed inside the molten salt furnace. The flue gas recirculation channel is connected to the ultra-low NOx burner through the heating layer, which is made of a heat-conducting material. The heating layer is located inside the molten salt furnace, between the flue gas recirculation channel and the ultra-low NOx burner. Materials with good thermal conductivity (such as copper, aluminum, or specific alloys) are used to ensure efficient heat transfer. The heating layer not only serves as part of the physical connection channel but also acts as a secondary heating element, utilizing the residual heat in the flue gas to preheat the fresh air or other media entering the burner. One end of the flue gas recirculation channel is connected to the molten salt furnace, and the other end is connected to the ultra-low NOx burner through the heating layer, allowing some high-temperature flue gas to pass through the heating layer before entering the burner. This design allows for further utilization of the heat in the flue gas, improving the overall system's energy efficiency.

[0013] Furthermore, it also includes a stirring mechanism, which includes a motor, a rotating shaft, and a stirring rod. The motor is fixedly connected to the molten salt furnace, the shaft of the motor is fixedly connected to the rotating shaft, and the stirring rod is fixedly connected to the rotating shaft. The stirring rod is located inside the molten salt furnace.

[0014] After the motor starts, it transmits power to the rotating shaft, causing it to rotate. The shaft then drives the fixed stirring rod to rotate synchronously, thus agitating the molten salt. During rotation, the stirring rod pushes the molten salt, breaking its laminar flow and creating turbulence, increasing the contact area and flow velocity. This turbulence helps to distribute heat evenly, preventing localized overheating or uneven cooling. Through continuous agitation, temperature differences within the molten salt are reduced, ensuring a relatively uniform state throughout the system. This uniform temperature distribution helps improve heating efficiency, reduce energy waste, and extend equipment life. If the molten salt contains additives or other substances, the stirring mechanism helps to disperse these substances more evenly within the molten salt, improving the efficiency and consistency of the chemical reaction.

[0015] Furthermore, it also includes a dust removal mechanism, which includes a filter plate and a dust collection box. The filter plate is disposed in the flue gas return channel, and the dust collection box is provided with an ash inlet that is connected to the flue gas return channel. The dust collection box cooperates with the filter plate.

[0016] When flue gas passes through the flue gas recirculation channel, it first encounters a filter plate. The filter plate effectively captures fine particulate matter in the flue gas, such as dust, fly ash, and other solid impurities. The pore size and material of the filter plate determine its filtration efficiency, typically achieving high filtration precision (e.g., PM10, PM2.5 levels). The dust captured by the filter plate gradually accumulates on its surface. Due to gravity, the dust falls off the filter plate surface and into the dust collection box through the ash inlet.

[0017] Dust in the dust collection box can be treated through regular cleaning or an automatic discharge system to prevent excessive dust accumulation from affecting system operation. For dust containing hazardous substances, appropriate environmental protection measures must be taken for proper handling. By removing particulate matter from flue gas, our organization reduces wear on downstream equipment (such as ultra-low NOx burners and FGR circulating fans), extending their service life. It also prevents dust accumulation in critical components such as pipes and heat exchangers, preventing system blockage and ensuring long-term stable operation.

[0018] Furthermore, it also includes a second baffle, a permeable plate, and a spring. The filter plate is inclined, the second baffle is fixedly connected to the filter plate and cooperates with the ash inlet, the permeable plate is fixedly connected to the flue gas return channel, one end of the spring is fixedly connected to the second baffle and the other end is fixedly connected to the permeable plate, and the filter plate is slidably connected to the flue gas return channel. Under normal operation, the second baffle will block the ash inlet to prevent dust from escaping.

[0019] To prevent dust from the dust collection box from flowing back into the flue gas return channel, this mechanism prevents gas from passing through the filter plates when excessive dust accumulates. The exhaust flow rate is also restricted by a valve, increasing the air pressure in the flue gas return channel. This causes the filter plate compression spring to move downwards, which in turn moves the second baffle, opening the ash inlet. Dust on the filter plate then falls into the dust collection box, restoring the filter plate's functionality. This mechanism controls the opening and closing of the ash inlet by the up-and-down movement of the filter plates, reducing the possibility of dust escaping.

[0020] Furthermore, it also includes absorbent cotton, a first baffle, a water collection tank, and a pressure plate. The absorbent cotton is fixedly connected to the exhaust pipe, the pressure plate cooperates with the absorbent cotton, the pressure plate is fixedly connected to the first baffle, the first baffle is fixedly connected to the filter plate, and the first baffle cooperates with the exhaust pipe. The water collection tank is connected to the exhaust pipe.

[0021] Under normal operation, the first baffle blocks the exhaust pipe, allowing gas to enter only the flue gas return channel, and the pressure plate squeezes the absorbent cotton. When there is too much gas in the heating layer, the pressure increases, causing the filter plate to move downwards. This downward movement of the filter plate causes the first baffle and pressure plate to move downwards as well, opening the exhaust pipe. The absorbent cotton then resumes its water-absorbing function, allowing gas to enter the exhaust pipe. The absorbent cotton absorbs moisture and toxic liquids from the gas, ensuring that the flue gas must pass through the absorbent cotton before being discharged from the system. When the pressure returns to normal, the first baffle returns to its original position, and the pressure plate squeezes the absorbent cotton again, causing the moisture in the absorbent cotton to flow into the water collection tank. By absorbing moisture and toxic liquids from the flue gas through the absorbent cotton, the emission of these substances is significantly reduced, meeting stringent environmental standards.

[0022] Furthermore, it also includes cleaning rods, of which multiple cleaning rods are provided, and the multiple cleaning rods cooperate with the filter plate, and the cleaning rods are fixedly connected to the filter plate.

[0023] Normal operating conditions: When flue gas passes through the flue gas recirculation channel, it first passes through an inclined filter plate. The filter plate captures particulate matter in the flue gas, and dust gradually accumulates on its surface. Multiple cleaning rods are fixed to the filter plate. When the dust on the filter plate accumulates to a certain level, the resistance to gas passage through the filter plate increases, causing the air pressure in the flue gas recirculation channel to rise. The exhaust flow rate of the exhaust pipe is restricted by a valve, further exacerbating the increase in air pressure in the flue gas recirculation channel.

[0024] As the air pressure increases, the filter plate experiences a downward thrust, causing the compression spring to move downwards. This downward movement of the filter plate causes the second baffle to move downwards simultaneously, opening the ash inlet and allowing dust on the filter plate to fall into the dust collection box. During this process, multiple cleaning rods are inserted into the filter holes of the filter plate, removing dust adhering to its surface and ensuring the filter plate remains clean.

[0025] At the same time, the downward movement of the filter plate will cause the first baffle and the pressure plate to move downward, the exhaust pipe will open, the absorbent cotton will also resume its water absorption function, the gas will enter the exhaust pipe, and the air pressure will gradually return to normal.

[0026] The restoring force of the spring returns the filter plate and second baffle to their initial positions, closing the ash inlet and resuming normal filtration. The cleaning rod remains fixed to the filter plate, ready for the next cleaning operation. Regularly removing dust from the filter plate surface reduces the risk of localized clogging and ensures stable system operation.

[0027] Furthermore, it also includes a connecting pipe, a temperature sensor, and a cooler. The heating layer is connected to the ultra-low NOx burner through the connecting pipe. The temperature sensor and the cooler are disposed inside the connecting pipe, and both the temperature sensor and the cooler are electrically connected to the DCS control system.

[0028] High-temperature flue gas enters the heating layer from the molten salt furnace through the flue gas recirculation channel, where it preheats the fresh air or other media entering the ultra-low NOx burner. The preheated gas then flows to the ultra-low NOx burner through a connecting pipe.

[0029] A temperature sensor monitors the gas temperature inside the connecting pipe in real time and transmits the data to the DCS control system. The DCS control system determines whether to activate the cooler for temperature regulation based on the set target temperature range. If the temperature sensor detects that the gas temperature is too high, exceeding the set safety range, the DCS control system will automatically activate the cooler. The cooler uses a cooling medium (such as water or air) to cool the gas, ensuring that the gas temperature entering the ultra-low NOx burner is within the optimal range.

[0030] Once the temperature sensor detects that the gas temperature has dropped to the target range, the DCS control system will stop the cooler and restore normal gas flow. The system continuously monitors the gas temperature to ensure the stability and safety of the entire process.

[0031] This device achieves precise control of the gas temperature entering the ultra-low NOx burner through the cooperation of temperature sensors and coolers, ensuring optimal combustion conditions and improving combustion efficiency.

[0032] This solution also provides a molten salt furnace flue gas recirculation process, including the following steps: Step S10: Start the ultra-low NOx burner, set the target value of the molten salt outlet temperature through the DCS system, monitor the molten salt temperature deviation in real time, and dynamically adjust the ratio of gas volume to air volume. Step S20: Control the flue gas recirculation ratio using the FGR fan to suppress NOx formation; Step S30: When the flue gas temperature exceeds 150°C or the natural gas pressure is abnormal, trigger the cooler or cut off the gas supply.

[0033] This solution monitors the molten salt temperature in real time and dynamically adjusts the ratio of fuel gas to blower volume based on deviations, helping to maintain a stable molten salt temperature and preventing overheating or underheating. Furthermore, by controlling the flue gas recirculation ratio through the FGR fan, NOx generation is significantly reduced, meeting stringent environmental standards and contributing to reduced environmental pollution.

[0034] Furthermore, the ultra-low NOx burner employs a segmented injection method for the fuel gas and air, maintaining a combustion zone temperature of ≤1100℃. NOx formation primarily depends on a high-temperature environment (thermal NOx), and the amount of NOx generated increases significantly when the combustion zone temperature exceeds 1200℃. By segmenting the injection of fuel gas and air, the local temperature of the combustion zone can be effectively reduced, and the overall combustion zone temperature can be controlled at ≤1100℃, thereby significantly reducing NOx formation. Attached Figure Description

[0035] Figure 1 This is a structural diagram of a molten salt furnace in a flue gas recirculation system. Figure 2 This is a cross-sectional view of a molten salt furnace flue gas recirculation system. Figure 3 This is a diagram showing the normal operation of a dust removal mechanism in a molten salt furnace flue gas recirculation system. Figure 4 This is a state diagram of a molten salt furnace flue gas recirculation system when the gas pressure is too high.

[0036] The reference numerals in the accompanying drawings include: 1. Furnace body; 2. Furnace cover; 3. Motor; 4. Flue gas return channel; 5. Exhaust pipe; 6. Return pipe; 7. Heating layer; 8. Regulating valve; 9. Connecting pipe; 10. High-pressure blower; 11. Ultra-low NOx burner; 12. Rotating shaft; 13. Stirring rod; 14. Working chamber; 15. Dust removal mechanism; 16. Absorbent cotton; 17. Pressure plate; 18. First baffle; 19. Filter plate; 20. Second baffle; 21. Ash inlet; 22. Dust collection box; 23. Cleaning rod; 24. Spring; 25. Permeable plate; 26. Water collection box. Detailed Implementation

[0037] The basics are as follows: Figure 1 , Figure 2 As shown: This solution provides a molten salt furnace flue gas recirculation system, including a molten salt furnace, an ultra-low NOx burner 11, a flue gas recirculation channel 4, an exhaust pipe 5, an FGR circulating fan, a high-pressure blower 10, regulating valves 8, and a DCS control system. The molten salt furnace is used to add melamine hot molten salt as a heat source in industrial processes. The operating temperature range is 300℃~550℃ (adjustable according to specific process requirements). The molten salt furnace includes a furnace body 1 and a furnace cover 2, which are fixedly connected by bolts.

[0038] The ultra-low NOx burner 11 is used to heat molten salt furnaces, employing a segmented injection of fuel gas and air to ensure a combustion zone temperature ≤1100℃. Combustion efficiency: ≥98%. NOx emissions: ≤30mg / m³ (compliant with ultra-low NOx emission standards). Fuel gas pressure range: 2kPa~10kPa. Air flow rate adjustment range: 100Nm³ / h~500Nm³ / h.

[0039] The flue gas recirculation channel 4 returns a portion of the high-temperature flue gas from the molten salt furnace to the ultra-low NOx burner 11, reducing the temperature and oxygen concentration in the combustion zone. Recirculation ratio: 10%~30% (can be dynamically adjusted via the DCS control system).

[0040] Exhaust pipe 5 discharges excess smoke. Valve parameters: exhaust flow rate adjustment range is 50 Nm³ / h to 300 Nm³ / h, maximum temperature resistance: 600℃.

[0041] FGR circulating fans are used for circulating flue gas. Parameters: Air volume range: 200Nm³ / h~1000Nm³ / h. Maximum temperature resistance: 400℃.

[0042] High-pressure blower 10 supplies fresh air to ultra-low NOx burner 11. Parameters: Airflow range: 300 Nm³ / h ~ 1500 Nm³ / h. Pressure range: 5 kPa ~ 20 kPa. Regulating valve 8: Function: Located at flue gas return channel 4, used to regulate the flue gas return flow. Adjustment range: 0% ~ 100% opening. Both ultra-low NOx burner 11 and high-pressure blower 10 are located within working chamber 14, which is positioned below furnace body 1.

[0043] The DCS control system monitors and automatically adjusts the operating status of each component in real time. Monitoring parameters: Molten salt temperature deviation: ±5℃; Oxygen concentration: 2%~6% (adjustable); Flue gas temperature: ≤400℃.

[0044] The heating layer 7 is located inside the molten salt furnace, between the flue gas return channel 4 and the ultra-low NOx burner 11, and is used to preheat the fresh air entering the burner using the waste heat of the flue gas. Material: copper, aluminum, or a specific alloy (thermal conductivity ≥200W / m•K). Preheating efficiency: ≥70%. One end of the heating layer 7 is connected to the flue gas return channel 4 through the return pipe 6, and the other end is connected to the ultra-low NOx burner 11 through the connecting pipe 9.

[0045] The stirring mechanism includes a motor 3, a rotating shaft 12, and a stirring rod 13. The motor 3 is fixedly connected to the molten salt furnace, and its shaft is fixedly connected to the rotating shaft 12. The stirring rod 13 is fixedly connected to the rotating shaft 12 and is located inside the molten salt furnace. The stirring mechanism drives the rotating shaft 12 and stirring rod 13 via the motor 3 to stir the molten salt, promoting uniform heat distribution. Parameters: Motor 3 power: 2.2kW~5.5kW; Speed ​​range: 30rpm~60rpm; The length of the stirring rod 13 is customized according to the dimensions of the molten salt furnace.

[0046] The dust removal mechanism 15 removes particulate matter from the flue gas, protecting downstream equipment. Filter plates 19 are installed within the flue gas return channel 4. The dust collection box 22 has an inlet 21 connected to the flue gas return channel 4, and the dust collection box 22 works in conjunction with the filter plates 19. The filter plates 19 have a filtration accuracy of PM10 and PM2.5 levels and a temperature resistance of 400℃. The dust collection box 22 has a capacity of 50L~200L. A second baffle 20 works in conjunction with the inlet 21 to prevent dust backflow. The spring 24 has a compression force of 50N~100N. Absorbent cotton 16 and related components: Function: Absorbs moisture and toxic liquids from the flue gas.

[0047] The absorbent cotton 16 is fixedly connected to the exhaust pipe 5. The pressure plate 17 is located below the absorbent cotton 16 and is fixedly connected to the first baffle 18. The first baffle 18 is fixedly connected to the filter plate 19 and cooperates with the exhaust pipe 5. The water collection tank 26 is connected to the exhaust pipe 5. The absorbent cotton 16 has a water absorption rate ≥500%. The water collection tank 26 has a capacity of 30L~100L. The first baffle 18 cooperates with the exhaust pipe 5 to control the gas flow direction. The pressure force of the pressure plate 17 is 20N~50N.

[0048] Cleaning rods 23 remove dust accumulated on the surface of filter plate 19. The number of rods is 40 to 80 (depending on the area of ​​filter plate 19). Cleaning rods 23 are located below filter plate 19 and are fixed to a permeable plate 25, which allows gas to pass through.

[0049] The connecting pipe 9 connects the heating layer 7 to the ultra-low NOx burner 11, monitoring and regulating the gas temperature. The temperature sensor has a measurement range of 0℃ to 600℃ and an accuracy of ±1℃. The cooling medium of the cooler is dry nitrogen.

[0050] In operation, high-temperature flue gas from the molten salt furnace is drawn back to the ultra-low NOx burner 11 through the flue gas return channel 4 by the FGR circulating fan. The returned flue gas mixes with fresh air before entering the burner, reducing the oxygen concentration and temperature in the combustion zone, thereby reducing NOx formation.

[0051] The DCS control system monitors and adjusts the opening of regulating valve 8 in real time based on preset parameters (such as temperature and oxygen concentration) to control the flue gas return flow. At the same time, the DCS control system also monitors and adjusts the working status of ultra-low NOx burner 11 and the gas supply of high-pressure blower 10 to ensure the stability and efficiency of the combustion process.

[0052] A temperature sensor monitors the gas temperature within the connecting pipe 9 in real time and transmits the data to the DCS control system. The DCS control system determines whether to activate the cooler for temperature regulation based on the set target temperature range. If the temperature sensor detects that the gas temperature is too high, exceeding the set safety range, the DCS control system will automatically activate the cooler. The cooler uses dry, cold nitrogen to cool the gas, ensuring that the gas temperature entering the ultra-low nitrogen burner 11 is within the optimal range.

[0053] The DCS control system collects key parameters such as temperature and oxygen concentration inside the molten salt furnace in real time through sensors, and feeds this data back to the control system for analysis and decision-making. Based on the data analysis results, the system automatically adjusts the operating status of each component to achieve optimal combustion efficiency and minimum pollutant emissions.

[0054] When there is excessive gas in the heating layer 7 or the filter plate 19 is blocked, the air pressure in the flue gas return channel 4 will increase, causing the filter plate 19 compression spring 24 to move downward. When the filter plate 19 moves downward, it will drive the second baffle 20 downward, causing the ash inlet 21 to open, and the dust on the filter plate 19 will fall into the dust collection box 22. When the filter plate 19 moves downward, multiple cleaning rods 23 are inserted into the filter holes of the filter plate 19 to poke off the dust attached to the surface of the filter plate 19, ensuring that the surface of the filter plate 19 remains clean.

[0055] At the same time, the downward movement of the filter plate 19 will cause the first baffle 18 and the pressure plate 17 to move downward, the exhaust pipe 5 will open, the exhaust pipe 5 will exhaust, and the absorbent cotton 16 will also resume its water absorption function. The gas enters the exhaust pipe 5 and passes through the absorbent cotton 16 to absorb the moisture and toxic liquid on the gas, ensuring that the flue gas must pass through the absorbent cotton 16 before it can be discharged from the system.

[0056] When the air pressure returns to normal, the first baffle 18 will return to its original position, and the pressure plate 17 will also squeeze the absorbent cotton 16, causing the water in the absorbent cotton 16 to flow into the water collection tank 26. At the same time, the second baffle 20 will also return to its original position, blocking the dust inlet 21 to prevent dust from coming out. At the same time, the cleaning rod 23 will also come out from the filter holes of the filter plate 19, allowing the filter plate 19 to work normally.

[0057] The beneficial effects of this solution are as follows: 1. Precise temperature control within the molten salt furnace is achieved through the DCS control system, avoiding the errors and instability caused by traditional manual adjustment. The automated adjustment mechanism can dynamically adjust combustion parameters according to actual working conditions, ensuring that the temperature remains within the set range. 2. Flue gas recirculation technology effectively reduces the temperature and oxygen concentration in the combustion zone, reducing NOx generation. The application of the ultra-low NOx burner 11 further enhances this effect, significantly reducing NOx emissions from the entire system. 3. The heating layer 7 not only serves as part of the physical connection channel but also acts as a secondary heating element, utilizing the residual heat in the flue gas to preheat the fresh air or other media entering the burner, saving energy. 4. Dust deposition in critical parts such as pipes and heat exchangers is prevented, preventing system blockage and ensuring long-term stable operation. 5. Absorbent cotton 16 absorbs moisture and toxic liquids from the flue gas, significantly reducing the emission of these substances and meeting stringent environmental standards. 6. Regularly cleaning dust from the filter plate 19 reduces the risk of local blockage and ensures stable system operation.

[0058] This solution also provides a molten salt furnace flue gas recirculation process, including the following steps: Step S10: Start the ultra-low NOx burner 11, set the target value of the molten salt outlet temperature through the DCS system, monitor the molten salt temperature deviation in real time, and dynamically adjust the ratio of gas volume to air volume. Step S20: Control the flue gas recirculation ratio using the FGR fan to suppress NOx formation; Step S30: When the flue gas temperature exceeds 150°C or the natural gas pressure is abnormal, trigger the cooler or cut off the gas supply.

[0059] The ultra-low NOx burner 11 uses a segmented injection method for the gas and air, and the combustion zone temperature is ≤1100℃.

[0060] This solution monitors the molten salt temperature in real time and dynamically adjusts the ratio of fuel gas to blower volume based on deviations, helping to maintain a stable molten salt temperature and preventing overheating or underheating. Furthermore, by controlling the flue gas recirculation ratio through the FGR fan, NOx generation is significantly reduced, meeting stringent environmental standards and contributing to reduced environmental pollution.

[0061] NOx formation primarily depends on high-temperature environments (thermal NOx). When the combustion zone temperature exceeds 1200℃, NOx formation increases significantly. By injecting fuel gas and air in stages, the local temperature of the combustion zone can be effectively reduced, and the overall combustion zone temperature can be controlled at ≤1100℃, thereby significantly reducing NOx formation.

[0062] The above are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A molten salt furnace flue gas recirculation system, comprising: Molten salt furnace; Ultra-low NOx burner (11): used for heating molten salt furnace; Flue gas recirculation channel (4): One end of the flue gas recirculation channel (4) is connected to the molten salt furnace, and the other end is connected to the ultra-low nitrogen burner (11); Exhaust pipe (5): The exhaust pipe (5) is connected to the flue gas return channel (4), and the exhaust pipe (5) is equipped with a valve; FGR circulating fan: used for circulating flue gas, the FGR circulating fan is connected to the flue gas return channel (4); High-pressure blower (10): used to supply air to the ultra-low NOx burner (11), the high-pressure blower (10) being connected to the ultra-low NOx burner (11); Its characteristic is that it further includes: Regulating valve (8): The regulating valve (8) is located at the flue gas return channel (4). DCS control system: The regulating valve (8), ultra-low NOx burner (11), high-pressure blower (10) and FGR circulating fan are all electrically connected to the DCS control system. It also includes a dust removal mechanism (15), which includes a filter plate (19) and a dust collection box (22). The filter plate (19) is disposed in the flue gas return channel (4), and the dust collection box (22) is provided with an ash inlet (21). The ash inlet (21) is connected to the flue gas return channel (4), and the dust collection box (22) cooperates with the filter plate (19). It also includes a second baffle (20), a through plate (25) and a spring (24). The filter plate (19) is inclined. The second baffle (20) is fixedly connected to the filter plate (19). The second baffle (20) cooperates with the ash inlet (21). The through plate (25) is fixedly connected to the flue gas return channel (4). One end of the spring (24) is fixedly connected to the second baffle (20) and the other end is fixedly connected to the through plate (25). The filter plate (19) is slidably connected to the flue gas return channel (4). It also includes cleaning rods (23), multiple cleaning rods (23) are provided, and multiple cleaning rods (23) cooperate with filter plates (19), and the cleaning rods (23) are fixedly connected to the permeable plate (25); It also includes absorbent cotton (16), a first baffle (18), a water collection tank (26) and a pressure plate (17). The absorbent cotton (16) is fixedly connected to the exhaust pipe (5). The pressure plate (17) cooperates with the absorbent cotton (16). The pressure plate (17) is fixedly connected to the first baffle (18). The first baffle (18) is fixedly connected to the filter plate (19) and cooperates with the exhaust pipe (5). The water collection tank (26) is connected to the exhaust pipe (5).

2. The molten salt furnace flue gas recirculation system according to claim 1, characterized in that, It also includes a heating layer (7), which is located inside the molten salt furnace. The flue gas return channel (4) is connected to the ultra-low nitrogen burner (11) through the heating layer (7). The heating layer (7) is a heating layer (7) made of heat-conducting material.

3. The molten salt furnace flue gas recirculation system according to claim 1, characterized in that, It also includes a stirring mechanism, which includes a motor (3), a rotating shaft (12) and a stirring rod (13). The motor (3) is fixedly connected to the molten salt furnace, the shaft of the motor (3) is fixedly connected to the rotating shaft (12), and the stirring rod (13) is fixedly connected to the rotating shaft (12). The stirring rod (13) is located inside the molten salt furnace.

4. The molten salt furnace flue gas recirculation system according to claim 2, characterized in that, It also includes a connecting pipe (9), a temperature sensor and a cooler. The heating layer (7) is connected to the ultra-low nitrogen burner (11) through the connecting pipe (9). The temperature sensor and the cooler are located inside the connecting pipe (9). The temperature sensor and the cooler are both electrically connected to the DCS control system.

5. A molten salt furnace flue gas recirculation process, comprising applying a molten salt furnace flue gas recirculation system as described in any one of claims 1-4, characterized in that, Includes the following steps: Step S10: Start the ultra-low NOx burner (11), set the target value of the molten salt outlet temperature through the DCS system, monitor the molten salt temperature deviation in real time, and dynamically adjust the ratio of gas volume to air volume; Step S20: Control the flue gas recirculation ratio using the FGR fan to suppress NOx formation; Step S30: When the flue gas temperature exceeds 150°C or the natural gas pressure is abnormal, trigger the cooler or cut off the gas supply.

6. The molten salt furnace flue gas recirculation process according to claim 5, characterized in that, The ultra-low nitrogen burner (11) uses a segmented injection method for the gas and air, and the combustion zone temperature is ≤1100℃.

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