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The decisive parameters: temperature and exhaust gas recirculation
© Nach Erdgas.report 1/03 VNG – Verbundnetz Gas
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Fire without flame

In 1989, experiments with a recuperative burner lead to a surprising discovery: at furnace temperatures of 1,000 °C, and with air preheating of 650 °C, the monitoring device for the burner flame ceased to indicate a signal, and no flame could be heard. Nevertheless, the fuel burnt completely. The carbon monoxide content of the exhaust gas was below 1ppm, and the NOx emissions were so low, that it was initially assumed that the measuring device was malfunctioning. However, the combustion was stable and uniform, without a flame having formed. The phenomenon was named "flameless oxidation", or FLOX for short.

In further experiments in the research project sponsored by BMWi, the researchers were able to determine the conditions under which flameless combustion is possible (fig. 4). It soon became evident that the process enabled considerable energy savings. Low emission values were also achieved when using exhaust gas heat for intensive combustion air preheating. Thus, BMWi approved a multitude of follow-on projects. The discovery ultimately led to a combustion process, patented worldwide, with numerous possibilities for implementation.

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