Method of operating a rotary furnace for the production of a hydraulic binder, whereby: • the furnace has a substantially cylindrical shape with a longitudinal axis which is inclined with respect to the horizontal, an upper end , a lower end and a substantially cylindrical wall, the length of the furnace being at least 9 times the diameter of the furnace , and preferably from 9 to 40 times the diameter of the furnace, • the furnace rotates around the longitudinal axis, • material to be pyroprocessed is fed to the furnace at its upper end , travels downwards through the furnace under the effect of gravity, is pyroprocessed in the furnace by heat generated by combustion of a main fuel in the furnace and leaves the furnace at its lower end as pyroprocessed material, • the pyroprocessed material is transferred from the furnace to an air-cooled material cooler , to produce cooled pyroprocessed material and hot air , • the furnace comprises a burner assembly at its lower end for injecting the main fuel and primary combustion oxidizer into the furnace so as to generate partial combustion of the main fuel with the primary combustion oxidizer, • hot air from the material cooler is fed to the furnace at its lower end as secondary oxidizer to provide substantially complete combustion of the main fuel , • the flame generated by combustion of the main fuel with the primary and secondary oxidizer is directed substantially parallel to the longitudinal axis of the furnace , • flue gas is evacuated from the furnace at its upper end , characterized in that : • the longitudinal temperature profile within the furnace is varied during furnace operation by means of injection into the furnace of at least one fluid other than the main fuel , the primary oxidizer and the secondary oxidizer , whereby the variation of the longitudinal temperature profile is achieved by continuously or discontinuously varying at least one injection parameter of the injection of said fluid into the furnace . • the furnace has a substantially cylindrical shape with a longitudinal axis which is inclined with respect to the horizontal, an upper end , a lower end and a substantially cylindrical wall, the length of the furnace being at least 9 times the diameter of the furnace , and preferably from 9 to 40 times the diameter of the furnace, • the furnace rotates around the longitudinal axis, • material to be pyroprocessed is fed to the furnace at its upper end , travels downwards through the furnace under the effect of gravity, is pyroprocessed in the furnace by heat generated by combustion of a main fuel in the furnace and leaves the furnace at its lower end as pyroprocessed material, • the pyroprocessed material is transferred from the furnace to an air-cooled material cooler , to produce cooled pyroprocessed material and hot air , • the furnace comprises a burner assembly at its lower end for injecting the main fuel and primary combustion oxidizer into the furnace so as to generate partial combustion of the main fuel with the primary combustion oxidizer, • hot air from the material cooler is fed to the furnace at its lower end as secondary oxidizer to provide substantially complete combustion of the main fuel , • the flame generated by combustion of the main fuel with the primary and secondary oxidizer is directed substantially parallel to the longitudinal axis of the furnace , • flue gas is evacuated from the furnace at its upper end , characterized in that : • the longitudinal temperature profile within the furnace is varied during furnace operation by means of injection into the furnace of at least one fluid other than the main fuel , the primary oxidizer and the secondary oxidizer , whereby the variation of the longitudinal temperature profile is achieved by continuously or discontinuously varying at least one injection parameter of the injection of said fluid into the furnace . <EOS>