Abstract: A steam generator gas burner for burning gases of low calorific value comprises a core air tube, a gas tube arranged coaxially around the core air tube to form a gas flow cross section, at least one further tube element arranged coaxially around the gas tube to form a secondary air flow cross section and first swirlers being arranged in the gas flow cross section. The first swirlers are adjustably arranged to allow for the steam generator gas burner to adjust to varying properties of the combustible gas, in particular a fluctuating calorific value, while taking into consideration the respective ignition intensity.