Abstract: One or more mixing impellers is carried on a driving shaft received in a mixing vessel. Impeller blades are angularly and/or axially distributed on the shaft and can be single staggered axially-spaced blades or groups of two or more placed angularly around the shaft, e.g., diametrically opposite. Each blade has a radially inner flat plate sloped to produce axial flow, preferably at about 15° from parallel to the rotation axis. An outer plate is joined to the inner plate at a bend line with an angle of about 20° located at about 70% of the outside diameter of the impeller path.