Gas FGR (Flue Gas Recirculation) burners reduce nitrogen oxide (NOx) emissions by recirculating a portion of the burner’s exhaust gas back into the combustion process. This lowers peak flame temperature, helping reduce NOx formation.
When properly engineered and commissioned, the system can maintain rated heat output without a meaningful loss of overall efficiency.
Emission compliance is an important design consideration for Indian industry, alongside fuel cost and burner capacity. Plants operating near residential areas or in industrial zones with stricter emission requirements may need low-NOx combustion equipment.
Gas FGR technology reduces emissions directly at the burner, rather than relying only on downstream exhaust treatment.
What Is NOx, and Why Does It Matter?
NOx refers to nitrogen oxides formed when nitrogen and oxygen in combustion air react at high temperatures inside a flame. These pollutants contribute to smog and are associated with respiratory health effects.
Because NOx formation is strongly influenced by flame temperature, lowering the peak temperature is an effective way to reduce its formation.
How Does Flue Gas Recirculation Work?
A Gas FGR burner takes a portion of its cooled, oxygen-depleted exhaust gas and routes it back into the combustion air stream. This recirculated gas absorbs heat without contributing significantly to combustion, lowering peak flame temperature and reducing the oxygen concentration available for NOx formation.
External FGR
Exhaust gas is routed from the flue or exhaust stack back to the combustion air intake through ducting, using a fan or the burner’s draft.
Internal FGR
The fuel and air jets draw exhaust gas back into the flame zone without requiring external recirculation ducting.
Potential NOx reduction: Independent combustion research commonly reports reductions of roughly 50–80% with FGR, depending on the recirculation ratio, fuel and burner design. Actual performance must be confirmed against certified data for the specific model.
Does Reducing NOx Affect Efficiency or Heat Output?
Not necessarily. A properly engineered Gas FGR burner is designed to deliver its rated heat output while reducing emissions. The recirculation ratio is calibrated to balance NOx reduction and combustion performance.
Why Correct Commissioning Matters
Excessive or poorly tuned recirculation can reduce efficiency. Correct burner selection, combustion tuning and commissioning are therefore essential to achieving the intended emissions performance.
When Should You Choose a Gas FGR or Low-NOx Burner?
- Your plant operates in or near an industrial zone with air-quality monitoring or stricter permitted emissions.
- Your industry or state has NOx emission requirements applicable to your combustion equipment.
- You are installing new combustion equipment and want to plan for potential changes in emission requirements.
- Lower-emission operation supports your sustainability objectives or customer requirements.
For plants in Ahmedabad, Gujarat and other industrial regions of India, confirm the current applicable limits with the relevant State Pollution Control Board or the Central Pollution Control Board.
Gas FGR vs Other Low-NOx Approaches
Flue gas recirculation reduces NOx at the point where it forms — inside the flame. This differs from downstream exhaust treatment, which treats emissions after combustion.
FGR Technology
Recirculates part of the exhaust gas to lower peak flame temperature and reduce NOx formation within the burner.
Downstream Exhaust Treatment
Uses additional equipment to treat exhaust gases after combustion. The suitable approach depends on emission limits, equipment design and site requirements.
What Does a Gas FGR Burner Project Involve?
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Confirm Emission Limits
Verify applicable limits for the location, industry and equipment capacity. -
Assess the Site and Fuel
Confirm the suitability of Gas FGR technology for the existing fuel system and application. -
Select and Size the Burner
Match the burner to the required heat output and emission target. -
Install and Commission
Verify combustion and emission performance during commissioning. -
Maintain Performance
Schedule maintenance and combustion tuning to support efficiency and emissions performance over time.
Frequently Asked Questions
How much can a Gas FGR burner reduce NOx emissions?
Research commonly reports reductions of roughly 50–80%, depending on the FGR ratio, fuel and burner design. Confirm the actual reduction using certified emission test data for the selected burner.
Does FGR reduce heat output or fuel efficiency?
When correctly engineered and commissioned, a Gas FGR burner can deliver its rated output with minimal efficiency impact. Poorly calibrated recirculation may reduce efficiency.
Is a Gas FGR burner only needed in strict emission zones?
No. Some plants also choose low-NOx technology to support sustainability goals, customer requirements or future emission planning.
Can an existing gas burner be retrofitted with FGR?
It depends on the existing burner and site configuration. A purpose-built Gas FGR burner may be more reliable than a field retrofit. A site assessment can confirm the suitable approach.
The Bottom Line
Gas FGR technology helps reduce NOx emissions without necessarily sacrificing the heat output a process requires. As emission requirements become an increasingly important part of industrial burner selection, FGR is worth evaluating during the initial equipment specification.
The right solution depends on the required capacity, fuel, site conditions and applicable emission limits.
Need a Gas FGR or Low-NOx Burner?
Contact Suntec Energy Systems to discuss your plant’s combustion requirements, emission targets and suitable Riello burner options.
Contact Our Engineering Team
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