Abstract: A propeller for stirring solid-in-liquid suspensions inside a treatment tank is disclosed, comprising a generally axial element consisting of at least a blade with helical development and a generally radial element consisting of a plurality of vanes with generally radial development. Said elements belong to a single central shaft defining a longitudinal rotation axis along which said elements are coaxially arranged one after the other.

Abstract: The present invention provides a reactor adapted to simultaneously accomplish chemical reactions and operations of size reduction of the solid materials in suspension and particularly for treatment in the cellulose and/or paper pulp industry. The reactor provides an essentially closed working environment and is provided in the lower part with a rotor which creates turbulence with flows over essentially the whole volume of the closed environment and is adapted to realize said conditions of the size reduction of solid materials with intimate mixing of same with the suspending liquid.