The burner (1) has a primary tube (3), where a core tube (2) is arranged in the primary tube. The primary tube and the core tube form a primary tube gap (4). The primary tube gap is designed for guiding a flow of particulate fuel and gaseous oxidizer from an inlet end to an outlet end opening of the primary tube. A flow centering medium is provided for centering the flow within the primary tube in the region of outlet side end of the primary tube.
