Burner for reducing NOx emissions and method for operating the burner

A method for operating a burner for heating a heating space with a reduction of NOx emissions, the burner comprising:

• a mixing and combustion chamber;
• a mixer-igniter disposed in the mixing and combustion chamber;
• a fuel feed connected to the mixer-igniter mixing and igniting device and adapted to feed fuel to the mixer-igniter;
• an air feed adapted to feed at least one partial air flow to the mixing and combustion chamber;
• a combustion chamber opening adapted to open the mixing and combustion chamber towards a heating space to be heated;
• a controller adapted to control a fuel flow via the fuel feed and for controlling at least one partial air flow via the air feed, wherein the burner and the controller operate the burner with a stable flame extending from the mixer-igniter through the combustion chamber opening into the heating space;
• and
• a cross-section of the combustion chamber opening relative to the burner output is in a range of between 1.5 mm2/kW and 10 mm2/kW,
• the method comprising:
• subsequent to a parameter value reaching a prescribed value, increasing, by the controller, the fuel flow via the fuel feed while maintaining the air flow via the air feed substantially the same as prior to increasing the fuel flow so that a ratio of the fuel flow to the airflow is changed from 1:20 to 1:10 without extinguishing the stable flame.