The device comprises a liquid flow conduit (12), a rotating nozzle (14), which is mounted on a liquid discharge opening (20) of the flow conduit (12) so as to rotate, the rotating nozzle (14) being penetrated by at least one opening (32, 33, 34) for spraying a liquid, a wall (48) for distributing the liquid extending transversely in the flow conduit (12) over the entire cross-section of flow, the wall (48) for distributing the liquid being penetrated by a central conduit (56) for generating a central jet, and at least one tangential conduit (60) for generating at least one tangential jet in the direction of a drive axis, and a wall (50) for driving the nozzle (14), which extends opposite the wall (48) for distributing the liquid and is penetrated by at least one conduit (64) for receiving the or each tangential jet in order to rotationally drive the nozzle.The drive wall (50) is rotationally engaged with the nozzle (14).