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The Low NOx burner developed by ATS4i (Aerothermal Solutions) in partnership with Samarco received the Aço Verde do Brasil Award (Brazilian Green Steel Award), Sustainability category, part of the ABM 2026 Technical Recognition. The award was presented during ABM Week, held in São Paulo from September 8 to 10, 2026, and recognized the paper “Strategies for NOx Reduction in Pelletizing Through New Burner Technology”.
Cover photo: ABM (ABM Brasil on Flickr).
What makes the project special is the path to the result: the burner was designed entirely in CFD, a single prototype was built, and in one week of testing in Samarco’s pelletizing furnace in Ubu (ES, Brazil) it reduced NOx emissions by 15% to 37%. The paper and the award came afterwards, as a natural consequence of a well-executed engineering product.
Project summary
- Award: Aço Verde do Brasil Award (Sustainability theme), ABM 2026 Technical Recognition.
- Technology: Low NOx burner operating on natural gas, water and air, for pelletizing furnaces.
- Method: CFD++ design coupled with chemical kinetics models and a single physical prototype.
- Field result: NOx reduction of 15% to 37% at the same thermal power, across 42 industrial tests in Samarco’s furnace in Ubu (ES).
- Technical paper: ABM Proceedings, DOI 10.5151/2594-5327-41876 (in Portuguese).
What is the Aço Verde do Brasil Award at ABM Week?
The Aço Verde do Brasil Award is part of the Technical Recognition granted by ABM (the Brazilian Association of Metallurgy, Materials and Mining) to technical papers. The awarded paper was presented at the 2nd Seminar on Maintenance and Project Engineering in Metallurgy and Mining, within the 9th ABM Week (September 9 to 11, 2025), and the recognition was delivered in 2026, during the 10th edition of the event.
The paper was written by Raphael Dias de Medeiros, Sérgio F. Nunes and Maurício C. Fonseca (Samarco); Pedro Castro Souza Villela, Diogo M. Pio and Guilherme A. Lima da Silva (ATS4i); and Pedro H. F. Gonçalves (IPT).
The challenge: reducing thermal NOx in pelletizing furnaces
Pelletizing furnaces combine an oxidizing atmosphere with high operating temperatures, which favors the formation of NOx. The dominant route is thermal NOx, described by the Zeldovich reactions: nitrogen and oxygen from the combustion air react at high temperature, and formation rises sharply as the temperature increases. The paper uses a conservative reference of about 1,370 °C; in the ATS4i Cantera equilibrium calculation with the full gri30 mechanism (chart below), the accelerated growth starts at around 1,380 K. The range depends on operating conditions and on the chemical combustion model. Reducing the flame peak temperature is therefore the most direct way to cut it.
Most NOx control methods work either before combustion (pollution prevention) or after it (corrective technologies), as summarized in Table 1.
| Method principle | Technology | Type |
|---|---|---|
| Flame temperature reduction | Flue gas recirculation | Preventive |
| Excess air reduction | Preventive | |
| Catalytic combustion | Preventive | |
| Air and fuel staging in the burner | Preventive | |
| Chemical reduction of NOx | Selective catalytic reduction (SCR) | Corrective |
| Selective non-catalytic reduction (SNCR) | Corrective | |
| NOx oxidation with subsequent absorption | Oxidant injection (ozone) | Corrective |
Table 1. NOx control methods, according to the technical paper.
How the Low NOx burner works
The burner runs on natural gas, water and air. The water, injected through small holes at different angles in a dedicated jacket, vaporizes in the flame and lowers the peak temperature, the main driver of thermal NOx. The original burner’s air jacket was kept, which preserves compatibility with the burner block. To deliver the same power to the furnace, natural gas flow must be increased slightly, which creates a fuel consumption penalty.
CFD++ design: from model to prototype
The design used CFD++ (Metacomp) for the flow and combustion simulation, with geometry prepared in SolidWorks, meshing in Ennova Meshing and post-processing in Tecplot 360 EX. NASA-CEA and Kintech Lab supported the thermodynamic and chemical kinetics studies used to choose the combustion mechanism. The NOx model of the paper uses a simplified 15-reaction mechanism, chosen to keep the run time low with a refined mesh, so the analysis focused on relative results (original burner versus Low NOx burner) rather than absolute NOx values. This is the difference from the NOx formation curve shown above: an equilibrium calculation can use the full gri30 mechanism, with over 300 reactions, but in CFD the computational cost requires a reduced kinetic mechanism.
Both cases were simulated at the same thermal power of 3.01 MW, as shown in Table 2.
| Parameter | Value | Unit |
|---|---|---|
| Downcomer air inlet | ||
| Flow rate | 19,000 | Nm³/h |
| Temperature | 1,266.15 | K |
| Pressure differential at the air outlet | -300 | Pa |
| Original burner, 3.01 MW | ||
| Natural gas inlet | 280 | Nm³/h |
| Air inlet | 330 | Nm³/h |
| Natural gas and air temperature | 303.15 | K |
| Low NOx burner, 3.01 MW | ||
| Natural gas inlet | 305 | Nm³/h |
| Liquid water inlet | 250 | L/h |
| Natural gas and water temperature | 303.15 | K |
Table 2. Boundary and operating conditions of the CFD simulation.
The CFD model predicted a NOx reduction of 29% at 250 L/h of water. After the awarded paper, ATS4i evolved the model: its CFD work now uses a reduced 51-reaction mechanism for methane and natural gas, built with Cantera and Python models, that predicts absolute NOx concentration at the stack.
Industrial tests in Samarco’s furnace in Ubu (ES)
The prototype was tested for one week by Samarco and ATS4i, with support from IPT-SP, using an auxiliary skid to meter natural gas and water. Using a single prototype and a minimal number of test days was only possible because CFD was used intensively during the design phase. The test campaign took place at the end of 2022.
In total, 42 tests were run in a specific chamber of the pelletizing furnace, covering three natural gas flow levels (minimum, intermediate and maximum) with water flows from 150 to 650 L/h. The main findings:
- NOx reduction of 15% to 37% with the Low NOx burner delivering the same power, for natural gas flows between 120 and 297 Nm³/h.
- The largest reductions occurred at high natural gas flows; at the lowest water flow (150 L/h) the reduction was around 15%.
- At 250 L/h of water, the measured reduction was 22% to 27%, close to the 29% predicted by CFD++.
- The natural gas consumption penalty measured at 250 L/h was 4% to 6%, below the theoretical 8.9%.
- At maximum gas flow, tests with 450 L/h of water showed no flame extinction and no methane in the flue gas; methane (200 to 800 ppm) appeared only at 550 L/h, at a gas flow of 252 Nm³/h.
- Chamber temperature remained stable and followed the natural adjustments of the furnace, so the water did not harm its operation.
The paper’s recommendation is to use water flows between 250 and 450 L/h for medium and high gas flows. The tests were run on a single burner, with the three other burners of the chamber operating conventionally, so the reduction with all burners converted is expected to be higher than the one measured.
Team and partners
The project was led by Raphael Dias de Medeiros (Samarco) and brought together ATS4i (design, CFD, test planning and execution), IPT – Institute for Technological Research (testing, sampling and instrumentation), Durag Siena do Brasil (prototype manufacturing) and Clesse do Brasil (measurement skid manufacturing). Samarco made the design decisions jointly with ATS4i and prioritized the test schedule.
From research to industrial application
According to Revista Mineração & Sustentabilidade (in Portuguese), the technology already operates in 16 burners installed in Samarco’s Plants 3 and 4. ATS4i has kept evolving the topic: it now works with a reduced 51-reaction mechanism for methane and natural gas, built in Cantera with Python models, that predicts absolute NOx concentration at the stack, and with reduced kinetic mechanisms for several liquid and gaseous fuels.
The project was also featured in Revista Minérios & Minerales (in Portuguese).
Read more
- Full technical paper: “Strategies for NOx Reduction in Pelletizing Through New Burner Technology” (ABM Proceedings, DOI 10.5151/2594-5327-41876, in Portuguese)
- Low NOx burner: project development (2023 post)
- Versão em português deste artigo
- Service: Analysis of Pelletizing Furnaces
- Service: Burner Design, Combustion Analysis and Emissions
Frequently asked questions
What is thermal NOx?
Thermal NOx is formed when nitrogen and oxygen in the combustion air react at high temperature through the Zeldovich reactions. Formation grows sharply at high flame temperatures (the paper uses about 1,370 °C as a conservative reference), which is why lowering the flame peak temperature reduces it.
How does the Low NOx burner reduce NOx emissions?
Water is injected into the flame through a dedicated jacket and vaporizes, lowering the peak temperature. The burner needs a little more natural gas to keep the same power, but in the field tests NOx fell by 15% to 37%.
How does CFD shorten the development time of a burner?
CFD lets the team compare burner geometries and operating conditions virtually before manufacturing. In this project it allowed a single prototype and only one week of industrial testing.
Do you need to reduce emissions or improve the performance of your burners and furnaces? Talk to the ATS4i team.
