A burner that includes a primary air or gas duct delimited by an exterior wall and a concentric interior wall of axis X and ducts for radial primary air or gas injection is described. The air or gas duct includes a ring that is rotationally mobile and has axial protrusions constituting distributors which collaborate with the radial primary air ducts arranged on the interior wall and form two passages of different angles in each duct. Rotating the ring making it possible to vary the angle of injection of the radial primary air. Thus, the regulation is situated just at the tip of the burner, in the region of the outlet of the primary air into the kiln, by modifying the outlet angle of the radial component for fixed section, thereby greatly simplifying the regulating of the burner.