Device for generating and distributing microwaves in rotary heat application systems, comprising: - an essentially cylindrical rotating drum which in turn comprises: - a side wall with at least one group of through slots ; - annular extensions projecting from an external face of the side wall ; - a front closure ; and - a rear closure ; which delimit an internal housing intended to house an element to be heated, and where each group of slots is located between two consecutive annular extensions ; - at least one microwave emitter ; - at least one fixed microwave filter , without direct contact with the rotating drum , made up of a cylindrical body of metallic material, for outer covering of a sector of the side wall of the rotating drum in which a group of slots is located; and - a fixed external structure that supports the above elements; the device being characterized in that the microwave filter comprises: - at least one through hole for insertion of the microwave emitter ; - an external face, for fixing the microwave emitter ; and - an internal face, opposable to the external face of the side wall for covering the group of slots , comprising at least one band-eliminating filter ; so that in the device a partially mobile slotted waveguide is formed, delimited by: - the external face of the side wall of the rotating drum , with the slots ; - the internal face of the microwave filter , with the band-eliminating filter ; and - two opposing faces of two consecutive annular extensions . - an essentially cylindrical rotating drum which in turn comprises: - a side wall with at least one group of through slots ; - annular extensions projecting from an external face of the side wall ; - a front closure ; and - a rear closure ; which delimit an internal housing intended to house an element to be heated, and where each group of slots is located between two consecutive annular extensions ; - a side wall with at least one group of through slots ; - annular extensions projecting from an external face of the side wall ; - a front closure ; and - a rear closure ; - at least one microwave emitter ; - at least one fixed microwave filter , without direct contact with the rotating drum , made up of a cylindrical body of metallic material, for outer covering of a sector of the side wall of the rotating drum in which a group of slots is located; and - a fixed external structure that supports the above elements; the device being characterized in that the microwave filter comprises: - at least one through hole for insertion of the microwave emitter ; - an external face, for fixing the microwave emitter ; and - an internal face, opposable to the external face of the side wall for covering the group of slots , comprising at least one band-eliminating filter ; - at least one through hole for insertion of the microwave emitter ; - an external face, for fixing the microwave emitter ; and - an internal face, opposable to the external face of the side wall for covering the group of slots , comprising at least one band-eliminating filter ; so that in the device a partially mobile slotted waveguide is formed, delimited by: - the external face of the side wall of the rotating drum , with the slots ; - the internal face of the microwave filter , with the band-eliminating filter ; and - two opposing faces of two consecutive annular extensions . - the external face of the side wall of the rotating drum , with the slots ; - the internal face of the microwave filter , with the band-eliminating filter ; and - two opposing faces of two consecutive annular extensions . <EOS>