With environmental regulations becoming increasingly stringent, low-nitrogen emission technology for gas boilers has become the focus of industry attention. Among them, FIR (flue gas internal circulation combustion technology) and FGR (flue gas recirculation technology) are two mainstream low-nitrogen combustion technologies, each with unique advantages and application scenarios. This article will combine the arguments of authoritative institutions and experts to conduct a detailed comparative analysis of the two technologies to help industry professionals make a more informed choice.
I. Technical Principles and Advantages
(1) FIR (flue gas internal circulation combustion technology)
FIR technology forms a negative pressure reflow zone at the burner head, causing part of the burned flue gas to be sucked back to the burner head to form secondary combustion. This design helps to quickly disperse the intermediate heat to the surrounding area and exchange heat with the furnace, thereby reducing the combustion speed and the intermediate temperature of the flame, and effectively reducing the generation of NOx. According to the "China Low-nitrogen Burner Industry Status Analysis and Development Trend Research Report (2024 Edition)", FIR technology is expected to become the mainstream direction of low-nitrogen technology development due to its advantages such as high efficiency, energy saving, safety, and wide adaptability.
(2) FGR (Flue Gas Recirculation Technology)
FGR technology is to reintroduce part of the flue gas after combustion into the burner or furnace through the return flue gas duct, mix it with fresh air and then participate in combustion again. By reducing the combustion temperature and oxygen concentration, FGR technology suppresses the generation of NOx. "Economic Analysis of Low Nitrogen Emissions from Gas Boilers" mentioned that FGR technology is a mature technology for achieving low nitrogen emissions from gas boilers, but the problems encountered in actual application, such as combustion stability, boiler stability, and boiler efficiency reduction, cannot be ignored.
II. Performance Comparison
(1) Safety and Combustion Efficiency
FIR: Flame stability, high safety, high combustion efficiency (O<3%CO=10ppm).
FGR: Easy to flame out, high condensate water, average safety, and low combustion efficiency (CO>50ppm).
(2) Boiler Efficiency and Equipment Power Consumption
FIR: Boiler efficiency remains unchanged, and equipment power consumption is not affected.
FGR: Boiler efficiency decreases by 4%, and equipment power consumption increases by 15-20%. (3) Operating cost and maintenance cycle
FIR: Low operating cost, maintenance cycle is annual.
FGR: High operating cost, maintenance cycle is monthly.
(4) Heating furnace output and scope of application
FIR: No impact on heating furnace output, wide scope of application (boiler/oilfield heating furnace).
FGR: Reduced heating furnace output (15%), limited scope of application (indoor boilers).
III. Industry Outlook
According to the discussion at the First National Combustion Industry Technology and Industry Development Forum in 2019, industry experts unanimously agreed that the staged combustion + FGR model is only temporary and is a transitional technology for the development of low-nitrogen combustion. In the future, staged combustion + FIR technology will become the mainstream direction of low-nitrogen technology development due to its advantages such as energy saving, low nitrogen, safety, and wide adaptability. This view has been supported by many industry leaders.
In summary, FIR technology and FGR technology each have their own advantages, but FIR technology performs better in terms of combustion efficiency, boiler efficiency, equipment power consumption, operating cost, maintenance cycle and heating furnace output, and has a wider scope of application. Currently, FIR technology has relatively high requirements for furnace size, making it suitable for not every boiler. For businesses and applications seeking high efficiency and low cost, FIR technology is undoubtedly a better choice, but careful consideration must be given to boiler compatibility. However, the choice of technology depends on a comprehensive consideration of factors such as the specific boiler type, operating environment, and budget.
With environmental regulations becoming increasingly stringent, low-nitrogen emission technology for gas boilers has become the focus of industry attention. Among them, FIR (flue gas internal circulation combustion technology) and FGR (flue gas recirculation technology) are two mainstream low-nitrogen combustion technologies, each with unique advantages and application scenarios. This article will combine the arguments of authoritative institutions and experts to conduct a detailed comparative analysis of the two technologies to help industry professionals make a more informed choice.
I. Technical Principles and Advantages
(1) FIR (flue gas internal circulation combustion technology)
FIR technology forms a negative pressure reflow zone at the burner head, causing part of the burned flue gas to be sucked back to the burner head to form secondary combustion. This design helps to quickly disperse the intermediate heat to the surrounding area and exchange heat with the furnace, thereby reducing the combustion speed and the intermediate temperature of the flame, and effectively reducing the generation of NOx. According to the "China Low-nitrogen Burner Industry Status Analysis and Development Trend Research Report (2024 Edition)", FIR technology is expected to become the mainstream direction of low-nitrogen technology development due to its advantages such as high efficiency, energy saving, safety, and wide adaptability.
(2) FGR (Flue Gas Recirculation Technology)
FGR technology is to reintroduce part of the flue gas after combustion into the burner or furnace through the return flue gas duct, mix it with fresh air and then participate in combustion again. By reducing the combustion temperature and oxygen concentration, FGR technology suppresses the generation of NOx. "Economic Analysis of Low Nitrogen Emissions from Gas Boilers" mentioned that FGR technology is a mature technology for achieving low nitrogen emissions from gas boilers, but the problems encountered in actual application, such as combustion stability, boiler stability, and boiler efficiency reduction, cannot be ignored.
II. Performance Comparison
(1) Safety and Combustion Efficiency
FIR: Flame stability, high safety, high combustion efficiency (O<3%CO=10ppm).
FGR: Easy to flame out, high condensate water, average safety, and low combustion efficiency (CO>50ppm).
(2) Boiler Efficiency and Equipment Power Consumption
FIR: Boiler efficiency remains unchanged, and equipment power consumption is not affected.
FGR: Boiler efficiency decreases by 4%, and equipment power consumption increases by 15-20%. (3) Operating cost and maintenance cycle
FIR: Low operating cost, maintenance cycle is annual.
FGR: High operating cost, maintenance cycle is monthly.
(4) Heating furnace output and scope of application
FIR: No impact on heating furnace output, wide scope of application (boiler/oilfield heating furnace).
FGR: Reduced heating furnace output (15%), limited scope of application (indoor boilers).
III. Industry Outlook
According to the discussion at the First National Combustion Industry Technology and Industry Development Forum in 2019, industry experts unanimously agreed that the staged combustion + FGR model is only temporary and is a transitional technology for the development of low-nitrogen combustion. In the future, staged combustion + FIR technology will become the mainstream direction of low-nitrogen technology development due to its advantages such as energy saving, low nitrogen, safety, and wide adaptability. This view has been supported by many industry leaders.
In summary, FIR technology and FGR technology each have their own advantages, but FIR technology performs better in terms of combustion efficiency, boiler efficiency, equipment power consumption, operating cost, maintenance cycle and heating furnace output, and has a wider scope of application. Currently, FIR technology has relatively high requirements for furnace size, making it suitable for not every boiler. For businesses and applications seeking high efficiency and low cost, FIR technology is undoubtedly a better choice, but careful consideration must be given to boiler compatibility. However, the choice of technology depends on a comprehensive consideration of factors such as the specific boiler type, operating environment, and budget.