Method of operating a rotary furnace (10) for the production of hydraulic binder so as to reduce ring formation therein, whereby the longitudinal temperature profile in the furnace (10) is varied during furnace operation by injecting at least one fluid (61) other than the main fuel(s) (31, 311, 312) the primary oxidizer (32) and hot air (22) from the material cooler (20) with at least one continuously or discontinuously varying injection parameter.