Dynamic mixer

A stepped conical geometry dynamic mixer comprising:

• two mixing parts which are rotatable relative to each other about a predetermined axis of rotation,
• each of said mixing parts having a generally conical mixing face, between which is defined a flow path which extends between an inlet for material to be mixed and an outlet,
• each of said generally conical mixing faces comprising a series of annular steps centred on the predetermined axis of rotation and defining said generally conical mixing faces, said series of annular steps having a plurality of cavities formed therein, said cavities defining flow passages bridging adjacent steps on each of the two mixing parts, each of said generally conical mixing faces being mutually positionable such that the steps of one mixing part extend towards recesses formed between the steps of the other mixing part, whereby cavities present in one generally conical mixing face are offset relative to, and overlap with, cavities present in the other generally conical mixing face in an axial direction or a transverse direction, such that material moving between the generally conical mixing faces of the two mixing parts from the inlet to the outlet is transferrable between overlapping cavities,
• wherein at least one step of one of the mixing parts and at least one adjacent step of the other of the mixing parts extends further in the axial direction than in the transverse direction, or vice versa, such that at least one annular mixing zone of substantially uniform volume is provided in between non-overlapping cavities of the two mixing parts, wherein each step is defined by a first surface which is cylindrical and centered on said predetermined axis of rotation and a second surface which is planar and perpendicular to said predetermined axis of rotation, wherein a respective one of said recesses is formed where said first surface meets the second surface of an adjacent step, wherein said first surface extends further in the axial direction than the second surface in the transverse direction or vice versa.