Natural gas burners utilizing advanced technology can achieve NOx levels as low as approximately 15 mg/m³ to 30 mg/m³ (calculated at 3% O₂ content on a dry basis). In terms of volumetric concentration, this corresponds to extremely low levels of roughly 7 ppm to 15 ppm.
The limits for NOx reduction in burners are primarily determined by the core technology employed and the type of fuel used:
Fully premixed surface combustion technology: By thoroughly mixing fuel gas and air prior to combustion and utilizing metal fibers or ceramic plates for flameless combustion, the flame temperature is distributed evenly. This suppresses the formation of thermal NOx at the source, allowing emissions to be easily controlled below 30 mg/m³.
Flue Gas Recirculation (FGR) technology: A portion of low-temperature flue gas is reintroduced into the combustion zone to lower local oxygen concentration and peak combustion temperatures. When combined with staged combustion, this can achieve ultra-low NOx emissions approaching 15–20 mg/m³.
Practical factors influencing ultra-low NOx levels:
Fuel type: Natural gas is the easiest fuel for achieving low NOx levels (or even flameless combustion), whereas liquid fuels or industrial waste gases with high calorific values contain chemically bound nitrogen, making NOx reduction significantly more difficult.
Equipment cost and efficiency: Lower NOx levels are not always better. When NOx emissions drop below 30 mg/m³, burners often require a higher excess air coefficient to control temperatures; this can lead to increased heat loss through the exhaust, thereby reducing overall thermal efficiency to some extent.
Natural gas burners utilizing advanced technology can achieve NOx levels as low as approximately 15 mg/m³ to 30 mg/m³ (calculated at 3% O₂ content on a dry basis). In terms of volumetric concentration, this corresponds to extremely low levels of roughly 7 ppm to 15 ppm.
The limits for NOx reduction in burners are primarily determined by the core technology employed and the type of fuel used:
Fully premixed surface combustion technology: By thoroughly mixing fuel gas and air prior to combustion and utilizing metal fibers or ceramic plates for flameless combustion, the flame temperature is distributed evenly. This suppresses the formation of thermal NOx at the source, allowing emissions to be easily controlled below 30 mg/m³.
Flue Gas Recirculation (FGR) technology: A portion of low-temperature flue gas is reintroduced into the combustion zone to lower local oxygen concentration and peak combustion temperatures. When combined with staged combustion, this can achieve ultra-low NOx emissions approaching 15–20 mg/m³.
Practical factors influencing ultra-low NOx levels:
Fuel type: Natural gas is the easiest fuel for achieving low NOx levels (or even flameless combustion), whereas liquid fuels or industrial waste gases with high calorific values contain chemically bound nitrogen, making NOx reduction significantly more difficult.
Equipment cost and efficiency: Lower NOx levels are not always better. When NOx emissions drop below 30 mg/m³, burners often require a higher excess air coefficient to control temperatures; this can lead to increased heat loss through the exhaust, thereby reducing overall thermal efficiency to some extent.