Flue gas recirculation system of molten salt furnace and process thereof

Abstract

The invention 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. The ultra-low nitrogen combustor is used for heating the molten salt furnace; one end of the flue gas backflow channel is communicated with the molten salt furnace, and the other end of the flue gas backflow channel is communicated with the ultra-low nitrogen combustor; the exhaust pipe is communicated with the flue gas backflow channel, and the exhaust pipe is provided with a valve; the FGR circulating fan is used for circulating flue gas, and the FGR circulating fan is communicated with the flue gas backflow channel; the high-pressure air blower is used for feeding air into the ultra-low nitrogen combustor, and the high-pressure air blower is communicated with the ultra-low nitrogen combustor; the adjusting valve is arranged at the flue gas backflow channel; and the adjusting valve, the ultra-low nitrogen combustor, the high-pressure air blower and the FGR circulating fan are electrically connected with the DCS. According to the scheme, the problem that precise temperature control is difficult to achieve due to manual adjustment of the fuel and air volume ratio is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical production equipment, and in particular relates to a molten salt furnace flue gas recirculation system and a process thereof. Background Art

[0002] The concentrations of pollutants such as particulate matter, SO2, and NOx in the flue gas from coal-fired molten salt furnaces exceed standards, making it difficult to meet the special emission limits of the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015). Low thermal efficiency: After long-term operation, coal-fired molten salt furnaces suffer from severe furnace ash accumulation, reducing thermal efficiency and leading to energy waste.

[0003] Currently, the existing molten salt coal-fired boiler with a flue gas generator, listed as CN117073226A, comprises a two-pass flue with a molten salt delivery pipeline installed on its inner wall, one side of the lower portion connected to the precombustion chamber outlet, a three-stage molten salt heat exchanger installed in the upper portion, the side away from the precombustion chamber connected to the inlet of the three-pass flue; a burner installed at the top of the precombustion chamber; a two-stage molten salt heat exchanger installed in the three-pass flue, with the outlet of the molten salt delivery pipeline connected to the inlet of the second molten salt heat exchanger; and a flue gas recirculation duct with one end connected to the three-pass flue and the other end connected to the precombustion chamber. The flue gas recirculation duct is equipped with a flue gas circulation fan, which is used to introduce the gas in the three-pass flue, after heat exchange with the second molten salt heat exchanger, into the precombustion chamber. It is mainly used for coal combustion.

[0004] However, there is a problem: low automation. Traditional coal-fired molten salt furnaces rely on manual adjustments to the fuel and air flow ratio, making precise temperature control difficult. Existing gas-fired molten salt furnaces, while capable of reducing some pollutants, lack effective control measures for high nitrogen oxide (NOx) emissions. Furthermore, their low system integration makes them incompatible with 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 solve the problem of manual adjustment of the fuel and air volume ratio and difficulty in achieving precise temperature control.

[0006] This solution provides a molten salt furnace flue gas recirculation system, including: molten salt furnace; Ultra-low nitrogen burner: used to heat the molten salt furnace; Flue gas reflow channel: one end of the flue gas reflow 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 smoke return channel and is provided with a valve; FGR circulation fan: used for circulating flue gas, the FGR circulation fan is connected to the flue gas return channel; High-pressure blower: used to supply air to the ultra-low nitrogen burner, the high-pressure blower is connected to the ultra-low nitrogen burner; Also includes: Regulating valve: The regulating valve is set at the flue gas return channel. DCS control system: the regulating valve, ultra-low nitrogen burner, high-pressure blower and FGR circulation fan are all electrically connected to the DCS control system.

[0007] The principle of this solution is that some high-temperature flue gas from the molten salt furnace is drawn back into the ultra-low nitrogen burner through the flue gas recirculation channel by the FGR circulation fan, while the excess flue gas is discharged through the exhaust pipe. The recirculated flue gas mixes with fresh air and enters the burner, reducing the oxygen concentration and temperature in the combustion zone, thereby reducing NOx generation.

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

[0009] The DCS control system uses sensors to collect real-time data on key parameters within the molten salt furnace, such as temperature and oxygen concentration, 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 minimize pollutant emissions.

[0010] The benefits of this solution are: 1. Through precise adjustment of the DCS control system, the temperature in the molten salt furnace can be precisely controlled, avoiding the errors and instabilities caused by traditional manual adjustment. The automated adjustment mechanism can dynamically adjust the combustion parameters according to actual operating conditions to ensure that the temperature is always within the set range.

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

[0012] Furthermore, it also includes a heating layer, which is arranged inside the molten salt furnace. The flue gas recirculation channel is connected to the ultra-low nitrogen burner through the heating layer, and the heating layer is made of heat-conductive material. The heating layer is arranged inside the molten salt furnace, between the flue gas recirculation channel and the ultra-low nitrogen 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 plays a secondary heating role, using the waste heat in the flue gas to preheat the fresh air or other medium 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 nitrogen burner through the heating layer, so that some high-temperature flue gas can pass through the heating layer before entering the burner. This design allows the heat in the flue gas to be further utilized, improving the energy utilization rate of the entire system.

[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, the stirring rod is fixedly connected to the rotating shaft, and the stirring rod is located inside the molten salt furnace.

[0014] After the motor starts, it transmits power to the shaft, causing it to begin rotating. The shaft then rotates synchronously with the attached stirring rod, stirring the molten salt. As the stirring rod rotates, it pushes the molten salt into motion, disrupting the laminar flow and creating turbulence. This increases the contact area and flow rate of the molten salt. This turbulence helps evenly distribute heat, preventing localized overheating or uneven cooling. Continuous stirring minimizes temperature differences within the molten salt, ensuring a relatively uniform temperature throughout the system. This uniform temperature distribution improves heating efficiency, reduces energy waste, and extends equipment life. If the molten salt contains additives or other substances, the stirring mechanism helps disperse these substances more evenly throughout 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 collecting box. The filter plate is arranged in the flue gas return channel. The dust collecting box is provided with an ash inlet, which is connected to the flue gas return channel. The dust collecting box cooperates with the filter plate.

[0016] As flue gas passes through the flue gas recirculation channel, it first passes through the filter plates. These plates effectively capture fine particles in the flue gas, such as dust, fly ash, and other solid impurities. The pore size and material of the filter plates determine their filtration efficiency, typically achieving high filtration accuracies (e.g., PM10 and PM2.5 levels). Dust captured by the filter plates gradually accumulates on their surfaces. Gravity forces the dust off the filter plates and into the dust collection box through the ash inlet.

[0017] Dust in the dust box can be regularly cleaned or automatically discharged to prevent excessive dust accumulation that could impact system operation. Dust containing hazardous substances must also be properly handled with appropriate environmental protection measures. This mechanism removes particulate matter from flue gas, reducing wear on downstream equipment (such as ultra-low nitrogen burners and FGR circulation fans), thereby extending equipment life. It also prevents dust accumulation in critical areas such as pipes and heat exchangers, preventing system blockage and ensuring long-term stable operation.

[0018] Furthermore, the filter plate includes a second baffle, a transparent plate, and a spring. The filter plate is tilted, the second baffle is fixedly connected to the filter plate, and the second baffle is engaged with the ash inlet. The transparent plate is fixedly connected to the smoke return channel. One end of the spring is fixedly connected to the second baffle, and the other end is fixedly connected to the transparent plate. The filter plate is slidably connected to the smoke return channel. During normal operation, the second baffle blocks the ash inlet to prevent dust from escaping.

[0019] To prevent dust in the dust box from flowing back into the flue gas reflux channel, this mechanism prevents gas from passing through the filter plates when too much dust accumulates on them. The exhaust flow rate from the exhaust pipe is restricted by the valve, increasing the air pressure in the flue gas reflux channel. This causes the filter plate compression spring to move downward, which in turn drives the second baffle downward, opening the ash inlet. Dust on the filter plates falls into the dust box, allowing the filter plates to resume function. This mechanism controls the opening and closing of the ash inlet by moving the filter plates up and down, reducing the possibility of dust escaping.

[0020] Furthermore, it also includes absorbent cotton, a first baffle, a water collecting box 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, and the water collecting box is connected to the exhaust pipe.

[0021] Under normal operation, the first baffle blocks the exhaust pipe, forcing 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 air pressure increases, causing the filter plate to move downward. This movement of the filter plate drives the first baffle and pressure plate downward, opening the exhaust pipe and allowing the absorbent cotton to resume its water absorption function. Gas enters the exhaust pipe and is absorbed by the absorbent cotton, which absorbs moisture and toxic liquids from the gas, ensuring that flue gas must pass through the absorbent cotton before being discharged from the system. When the air pressure returns to normal, the first baffle returns to its original position, and the pressure plate squeezes the absorbent cotton, forcing 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 strict environmental standards.

[0022] Furthermore, it also includes a cleaning rod, wherein a plurality of cleaning rods are provided, and the plurality of cleaning rods cooperate with the filter plate, and the cleaning rods are fixedly connected to the transparent plate.

[0023] Normal operation: When flue gas passes through the flue gas recirculation channel, it first passes through the inclined filter plates. The filter plates capture particulate matter in the flue gas, and dust gradually accumulates on their surfaces. Multiple cleaning rods are fixed to the permeable plates. When dust accumulates to a certain level on the filter plates, the resistance to gas passing through the plates increases, causing the air pressure in the flue gas recirculation channel to rise. The exhaust flow rate is restricted by the valve in the exhaust pipe, further increasing the pressure in the flue gas recirculation channel.

[0024] As air pressure increases, the filter plates are pushed downward, causing the compression spring to move downward. This movement of the filter plates simultaneously moves the second baffle downward, opening the ash inlet. Dust on the filter plates then falls through the inlet into the dust collection box. During this process, multiple cleaning rods are inserted into the filter plates' pores, removing dust adhering to the surface and ensuring it remains clean.

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

[0026] The spring's restoring force 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 blockage 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 nitrogen burner through the connecting pipe. The temperature sensor and the cooler are arranged inside the connecting pipe. The temperature sensor and the cooler are both electrically connected to the DCS control system.

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

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

[0030] When the temperature sensor detects that the gas temperature has dropped to within 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 mechanism achieves precise control of the temperature of the gas entering the ultra-low nitrogen burner through the cooperation of the temperature sensor and the cooler, ensuring the optimization of the combustion conditions and improving the combustion efficiency.

[0032] This solution also provides a molten salt furnace flue gas recycling process, including the following steps: Step S10: Start the ultra-low nitrogen 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 and blast volume; Step S20: controlling the flue gas recirculation ratio through the FGR fan to suppress NOx generation; Step S30: When the flue gas temperature exceeds 150°C or the natural gas pressure is abnormal, the cooler is triggered or the gas supply is cut off.

[0033] This solution monitors changes in molten salt temperature in real time and dynamically adjusts the gas and air flow ratio based on deviations, helping to maintain a stable molten salt temperature and avoid overheating or underheating. Furthermore, by controlling the flue gas recirculation ratio through the FGR blower, NOx generation is significantly reduced, meeting strict environmental standards and helping to reduce environmental pollution.

[0034] Furthermore, the ultra-low-NOx burner uses a staged injection method for gas and air, with the combustion zone temperature maintained at ≤1100°C. NOx generation primarily relies on high temperatures (thermal NOx), and NOx generation increases significantly when the combustion zone temperature exceeds 1200°C. By injecting gas and air in stages, the local temperature of the combustion zone can be effectively lowered, while the overall combustion zone temperature is controlled at ≤1100°C, significantly reducing NOx generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a structural diagram of a molten salt furnace with 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 state diagram of the normal operation of the dust removal mechanism of the flue gas recirculation system of a molten salt furnace. 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 figure marks in the specification include: 1. furnace body; 2. furnace cover; 3. motor; 4. flue gas recirculation channel; 5. exhaust pipe; 6. recirculation pipe; 7. heating layer; 8. regulating valve; 9. connecting pipe; 10. high-pressure blower; 11. ultra-low nitrogen 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 collecting box; 23. cleaning rod; 24. spring; 25. transparent plate; 26. water collecting box. DETAILED DESCRIPTION

[0037] Basically as attached 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 nitrogen burner 11, a flue gas recirculation channel 4, an exhaust pipe 5, an FGR circulation fan, a high-pressure blower 10, a regulating valve 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°C to 550°C (adjustable according to specific process requirements). The molten salt furnace consists of a furnace body 1 and a furnace cover 2, which are fixedly connected by bolts.

[0038] The ultra-low nitrogen burner 11 heats the molten salt furnace, using staged injection of gas and air to maintain a combustion zone temperature of ≤1100°C. Combustion efficiency: ≥98%. NOx emissions: ≤30mg / m³ (meets ultra-low nitrogen emission standards). Gas pressure range: 2kPa to 10kPa. Air flow adjustment range: 100Nm³ / h to 500Nm³ / h.

[0039] Flue gas recirculation channel 4 returns some of the high-temperature flue gas from the molten salt furnace to the ultra-low nitrogen burner 11, reducing the temperature and oxygen concentration in the combustion zone. The recirculation ratio is 10% to 30% (dynamically adjustable via the DCS control system).

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

[0041] The FGR circulation fan is used to circulate flue gas. Parameters: Air volume range: 200 Nm³ / h to 1000 Nm³ / h. Maximum temperature resistance: 400°C.

[0042] The high-pressure blower 10 delivers fresh air to the ultra-low-NOx burner 11. Parameters: Air volume range: 300 Nm³ / h to 1500 Nm³ / h. Pressure range: 5 kPa to 20 kPa. Control valve 8: Function: Located in the flue gas recirculation channel 4, it regulates the amount of flue gas recirculated. Adjustment range: 0% to 100% opening. The ultra-low-NOx burner 11 and high-pressure blower 10 are both located within the working chamber 14, which is located below the furnace body 1.

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

[0044] Heating layer 7 is located inside the molten salt furnace, between the flue gas recirculation channel 4 and the ultra-low nitrogen burner 11. It uses the waste heat from the flue gas to preheat the fresh air entering the burner. Materials: Copper, aluminum, or a specific alloy (thermal conductivity ≥ 200 W / m•K). Preheating efficiency: ≥ 70%. One end of heating layer 7 is connected to the flue gas recirculation channel 4 via a recirculation pipe 6, and the other end is connected to the ultra-low nitrogen burner 11 via a connecting pipe 9.

[0045] The stirring mechanism includes a motor 3, a rotating shaft 12, and a stirring rod 13. Motor 3 is fixedly connected to the molten salt furnace, and its shaft is fixedly connected to the rotating shaft 12. Stirring rod 13 is also fixedly connected to the rotating shaft 12 and is located inside the molten salt furnace. The stirring mechanism drives rotating shaft 12 and stirring rod 13 through motor 3, stirring the molten salt and promoting even heat distribution. Specifications: Motor 3 power: 2.2 kW to 5.5 kW. Speed range: 30 rpm to 60 rpm. The length of stirring rod 13 is customized according to the size of the molten salt furnace.

[0046] The dust removal mechanism 15 removes particulate matter from the flue gas to protect downstream equipment. The filter plate 19 is arranged in the flue gas return channel 4, and the dust 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 box 22 cooperates with the filter plate 19. The filtration accuracy of the filter plate 19 is PM10 and PM2.5 level, and the temperature resistance is 400°C. The capacity of the dust box 22: 50L~200L. The second baffle 20 cooperates with the ash inlet 21 to prevent dust backflow. The compression force of the spring 24 is 50N~100N. Absorbent cotton 16 and related components: Function: Absorb moisture and toxic liquids in the flue gas.

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

[0048] Cleaning rods 23 remove dust accumulated on the surface of filter plate 19. There are 40 to 80 cleaning rods 23 (configured based on the area of filter plate 19). They are located below filter plate 19 and are fixed to a transparent plate 25, which allows air to pass through.

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

[0050] During operation, high-temperature flue gas is drawn from the molten salt furnace through the flue gas return channel 4 and is drawn back into the ultra-low nitrogen burner 11 by the FGR circulation fan. The returned flue gas mixes with fresh air and enters the burner, reducing the oxygen concentration and temperature in the combustion zone, thereby reducing the generation of NOx.

[0051] The DCS control system monitors and adjusts the opening of valve 8 in real time based on preset parameters (such as temperature and oxygen concentration), controlling the amount of flue gas reflux. Simultaneously, the DCS system monitors and adjusts the operating status of the ultra-low nitrogen burner 11 and the air supply of the high-pressure blower 10 to ensure the stability and efficiency of the combustion process.

[0052] The temperature sensor monitors the temperature of the gas in the connecting pipe 9 in real time and transmits this data to the DCS control system. Based on the set target temperature range, the DCS system determines whether to activate the cooler to adjust the temperature. If the temperature sensor detects that the gas temperature is too high, exceeding the set safety range, the DCS control system automatically activates the cooler. The cooler cools the gas using dry nitrogen, ensuring that the gas temperature entering the ultra-low nitrogen burner 11 is within the optimal range.

[0053] The DCS control system uses sensors to collect real-time data on key parameters within the molten salt furnace, such as temperature and oxygen concentration, 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 minimize pollutant emissions.

[0054] When there is too much gas in the heating layer 7 or the filter plate 19 is clogged, the air pressure in the flue gas return channel 4 increases, causing the filter plate 19 to compress the spring 24 and move downward. The downward movement of the filter plate 19 drives the second baffle 20 downward, opening the ash inlet 21, and the dust on the filter plate 19 falls 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 away 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 drive the first baffle 18 and the pressure plate 17 to move downward, the exhaust pipe 5 will be opened, the exhaust pipe 5 will be exhausted, 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 being discharged out of the system.

[0056] When the air pressure returns to normal, the first baffle 18 returns to its original position, and the pressure plate 17 squeezes the absorbent cotton 16, allowing the moisture in the absorbent cotton 16 to flow into the water collection tank 26. Simultaneously, the second baffle 20 returns to its original position, blocking the ash inlet 21 to prevent dust from escaping. Simultaneously, the cleaning rod 23 emerges from the filter holes of the filter plate 19, allowing the filter plate 19 to function normally.

[0057] The beneficial effects of this solution are as follows: 1. Through precise adjustment of the DCS control system, the temperature in the molten salt furnace can be accurately controlled, avoiding the errors and instability caused by traditional manual adjustment. The automated adjustment mechanism can dynamically adjust the combustion parameters according to the actual operating conditions to ensure that the temperature is always within the set range. 2. Flue gas recirculation technology effectively reduces the temperature and oxygen concentration in the combustion zone, reducing the generation of NOx. The application of ultra-low nitrogen burners 11 further enhances this effect, significantly reducing the NOx emissions of the entire system. 3. The heating layer 7 not only serves as part of the physical connection channel, but also plays a secondary heating role, using the waste heat in the flue gas to preheat the fresh air or other media entering the burner, saving energy. 4. Dust deposition in key areas such as pipes and heat exchangers is avoided, preventing system blockage and ensuring long-term stable operation. 5. The absorbent cotton 16 absorbs moisture and toxic liquids in the flue gas, significantly reducing the emission of these substances, meeting strict environmental protection standards. 6. Regularly removing dust from the surface of the filter plate 19 reduces the risk of local blockage and ensures stable operation of the system.

[0058] This solution also provides a molten salt furnace flue gas recycling process, including the following steps: Step S10: Start the ultra-low nitrogen 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 and blast volume; Step S20: controlling the flue gas recirculation ratio through the FGR fan to suppress NOx generation; Step S30: When the flue gas temperature exceeds 150°C or the natural gas pressure is abnormal, the cooler is triggered or the gas supply is cut off.

[0059] The fuel gas and air of the ultra-low nitrogen burner 11 are injected in stages, and the temperature of the combustion zone is ≤1100°C.

[0060] This solution monitors changes in molten salt temperature in real time and dynamically adjusts the gas and air flow ratio based on deviations, helping to maintain a stable molten salt temperature and avoid overheating or underheating. Furthermore, by controlling the flue gas recirculation ratio through the FGR blower, NOx generation is significantly reduced, meeting strict environmental standards and helping to reduce environmental pollution.

[0061] NOx generation primarily relies on high temperatures (thermal NOx). When the combustion zone temperature exceeds 1200°C, NOx generation increases significantly. By injecting fuel gas and air in stages, we can effectively lower the local temperature in the combustion zone and control the overall combustion zone temperature to ≤1100°C, significantly reducing NOx generation.

[0062] The above are only embodiments of the present invention. Common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be considered as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records 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 nitrogen burner (11): used to heat the 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 smoke return channel (4), and the exhaust pipe (5) is provided with a valve; FGR circulation fan: used for circulating flue gas, the FGR circulation fan is connected to the flue gas return channel (4); A high-pressure blower (10) is used to supply air to the ultra-low nitrogen burner (11), wherein the high-pressure blower (10) is in communication with the ultra-low nitrogen burner (11); It is characterized by further comprising: Regulating valve (8): The regulating valve (8) is arranged at the flue gas return channel (4). DCS control system: the regulating valve (8), ultra-low nitrogen burner (11), high-pressure blower (10) and FGR circulation fan are all electrically connected to the DCS control system.

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 arranged inside the molten salt furnace. The flue gas reflow channel (4) is connected to the ultra-low nitrogen burner (11) through the heating layer (7), and the heating layer (7) is made of a heat-conducting material.

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

4. The molten salt furnace flue gas recirculation system according to claim 1, characterized in that: The dust collecting box (22) further comprises a dust removal mechanism (15), wherein the dust removal mechanism (15) comprises a filter plate (19) and a dust collecting box (22), wherein the filter plate (19) is arranged in the flue gas return channel (4), and the dust collecting box (22) is provided with an ash inlet (21), wherein the ash inlet (21) is communicated with the flue gas return channel (4), and the dust collecting box (22) cooperates with the filter plate (19).

5. The molten salt furnace flue gas recirculation system according to claim 4, characterized in that: It also includes a second baffle (20), a transparent plate (25) and a spring (24), the filter plate (19) is tilted, the second baffle (20) is fixedly connected to the filter plate (19), the second baffle (20) is matched with the ash inlet (21), the transparent plate (25) is fixedly connected to the smoke 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 transparent plate (25), and the filter plate (19) is slidably connected to the smoke return channel (4).

6. The molten salt furnace flue gas recirculation system according to claim 5, characterized in that: It also includes absorbent cotton (16), a first baffle (18), a water collecting box (26) and a pressure plate (17), wherein 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 the first baffle (18) cooperates with the exhaust pipe (5), and the water collecting box (26) is communicated with the exhaust pipe (5).

7. The molten salt furnace flue gas recirculation system according to claim 6, characterized in that: It also includes a cleaning rod (23), a plurality of the cleaning rods (23) are provided, and the plurality of cleaning rods (23) cooperate with the filter plate (19), and the cleaning rods (23) are fixedly connected to the transparent plate (25).

8. The molten salt furnace flue gas recirculation system according to claim 1, 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 arranged inside the connecting pipe (9). The temperature sensor and the cooler are both electrically connected to the DCS control system.

9. A molten salt furnace flue gas recycling process, characterized in that: The following steps are involved: Step S10: Start the ultra-low nitrogen 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 and blast volume; Step S20: controlling the flue gas recirculation ratio through the FGR fan to suppress NOx generation; Step S30: When the flue gas temperature exceeds 150°C or the natural gas pressure is abnormal, the cooler is triggered or the gas supply is cut off.

10. The molten salt furnace flue gas recycling process according to claim 9, characterized in that: The fuel gas and air of the ultra-low nitrogen burner (11) are injected in stages, and the temperature of the combustion zone is ≤1100°C.

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