High solidity counterflow impeller system

Abstract

A mixing apparatus has a tank for holding a material to be mixed, a drive shaft rotatable in the tank, a radially inner impeller on the drive shaft with blades pitched to produce axial flow of the material in a first direction, and a radially outer impeller with blades pitched to produce axial flow in an opposite direction. The radially inner impeller can be a high solidity impeller disposed in a preferably-stationary flow shield occupying a portion of a circumference between the inner and outer impellers, and providing a barrier between the material flowing axially in opposite directions while leaving spaces for recirculation of material by radial flow at the ends of the opposite axial flows. The outer impeller can be coupled to the drive shaft by connecting members protruding radially through axial spaces provided in or around the flow shield. Baffles are fixed in the tank and support the flow shield. The baffles have inclined inner and outer sections that extend axially and are pitched to intercept circumferential flow produced by the inner and outer impellers, respectively, redirecting the flow axially in the appropriate direction. A number of axially spaced impeller stages are provided, each having an inner impeller in a section of the flow shield and an outer impeller on connecting members that extend through axial gaps between sections of flow tube supported on the baffles.

Dependencies are inferred from the claim text.