| Power plant upgrade
CFD studies for ZETES 2 unit 3 project
Single burner geometry isothermal CFD model CFD study 1:
The single burner model looked at what effects different TA (tertiary air) damper settings had on air mass flow and swirl, both of which affected flame shape and stability. The RJM upgrade removed the need to adjust these TA damper settings once properly set up during commissioning.
The single burner CFD modelling confirmed different airflow behaviour at different TA damper settings (below)
Windbox isothermal CFD model CFD study 2:
This model evaluated how the air was distributed to each windbox as well as the burner and OFA port within each one. The modelling also showed
that some burners were receiving air in the opposite swirl direction to the burner swirl configuration. Reconfiguring the windbox dampers to operate in an opposed blade configuration resolved this problem.
Single burner combustion CFD study 3:
The CFD models confirmed that different tertiary air damper settings produced different flame profiles (numbers = % open) and that at certain settings (eg, 50% and 100% open) the burners were subject to damage due to excessive heat. To resolve all of these issues, RJM applied its tried and tested burner, which is designed as a multiple layer, air & fuel staged low NOx
burner.
Full furnace CFD model CFD study 4:
Having established the desired combustion characteristics in the single burner model, RJM then applied these parameters to the full furnace model.
This 10 000 ppm CO isosurface model indicates flame extent. The baseline study (below left) shows damaging flame extent into the top of the boiler, whereas following the RJM upgrade, the flames are fully retained within the furnace (below right).
The benefits of the multiple layer staged burner (below, left) are extremely low NOx
and controlled carbon in ash. Also, the strong
internal recirculation zone (IRZ) ensures the flame is controlled by the burner and will remain stable across the load range for all coal types. The right hand image shows CFD modelling of burner prior to modification.
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