A calcination unit able to decarbonate raw materials intended for clinker production, the unit including: a main duct in which the raw materials circulate according to a first movement direction, the raw materials being calcined in the main duct; a solid fuel supply duct opening onto the main duct via a fuel outlet, the solid fuel moving according to a second movement direction; a retaining device located in the main duct and arranged opposite the solid fuel outlet so that the solid fuel arriving in the main duct via the fuel outlet passes through the retaining device.