Inclined guide vanes (6) for the combustion air are mounted between a mouth cone (4) tapering towards the mouth of a burner tube (1) and an inner guide body enclosing the burner lance (2). The body comprises an internal cone (5) aligned with the mouth cone. This protrudes in the axial direction beyond the vanes. An outlet widening at the end (9) joins onto the mouth cone. The angle of the internal cone to the tube axis can be equal to or less than that of the mouth cone. Within the mouth of the inner cone are located additional openings for combustion air. A directly or indirectly controllable screen is located to control the air flow through the openings.
