Flameless combustion applied to a semi-industrial boiler

Contacts : Danielle MAKAIRE, P.Ngendakumana


The aim of this study is to perform diluted combustion into a semi-industrial boiler supplied by natural gas. Diluted combustion, which is also called "Flameless combustion", is a technique leading to very-low NOx emission levels and currently used in high temperature furnaces using preheated air.

This technique requires separate injections of natural gas and air. The burner design (high flow speed) and the combustion geometry induce large internal recirculation of the combustion products and heats up the reactants. Under certain conditions, combustion takes place without any visible or audible flame, that is why it is called flameless oxidation.

The conditions to be met to have flameless combustion are mainly a high recirculation rate and a temperature of the reactants above the auto-ignition temperature. Boilers are different from furnaces because they are cooled by water and considered as "cold combustion chambers" and also, because their combustion chambers do not have the same geometric containment as the ones of furnaces.


The burner sizing, injection design and the numerical simulation have been performed by the thermal engineering and combustion team at University of Mons.

The experimental part is performed in our laboratory:
The first part is a characterization of the temperature field of the combustion chamber when the burner works in conventional combustion mode.
The second part is the change from classical combustion mode to flameless combustion mode according to the procedure determined by numerical simulation.

Test rig

The burner has been installed on the 400kW semi-industrial boiler in the laboratory. The configuration permits to inject air through the burner and natural gas through a separate injector below the burner.
The boiler is provided with windows in order to analyze the flame spectroscopy.



Département d'aérospatiale et mécanique / Thermotechnique
Adress: ULg - Bât. B49 Thermotechnique
chemin des Chevreuils 7
4000 Liège 1 Belgique
Tel. : +32 4 3664803
Fax : +32 4 3664812
email: pngendakumana@ulg.ac.be


This project is performed in the frame of IEA implementing agreement with the financial support of the SPW-DGO4.

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