US 5,454,986 AGranted

Down-flow batch mixing system

OwnerMartin Lesseninventor

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Abstract

Improved mixing effectiveness in the mixing of a gas with a liquid suspension is achieved in a batch mixing system having a mixing tank with a hemi-toroidal tank bottom which extends between a radially inner neck portion of the tank to a radially outer cylindrical wall portion of the tank. The hemi-toroidal profile of the tank bottom has a monotonically increasing toroidal radius between the neck and wall portions. Disposed within the tank is an assembly including an axial flow impeller with pitched impeller blades, a stator adjacent to the impeller and having stationary stator blades of a pitch opposite to the pitch of the impeller blades, a shroud surrounding the radial periphery of both the impeller and the stator and a gas sparging means supported by the shroud. The arrangement of the assembly provides in conjunction with the hemi-toroidal tank bottom a substantially swirl-free laminar flow of the liquid suspension directed downwardly along the neck portion and along the tank bottom when the impeller is rotatably driven by a drive shaft.

Claims12

Dependent claims

A down-flow batch mixing system for mixing a liquid under conditions of substantially swirl-free laminar liquid flow, the system comprising:

a mixing tank in which the liquid suspension is mixed, the tank having about a central axis a hemi-toroidal tank bottom extending with a monotonically increasing toroidal radius from a cylindrically shaped neck portion with an end face and formed by tank walls proximate said central axis to a cylindrically shaped and concentric upper portion of a tank wall formed radially outwardly from said neck portion;
an impeller hub radially coextensive with said end face of said neck portion and rotatably disposed adjacent thereto, said hub attached to and rotatably driven by a drive shaft concentric with said axis;
an axial flow impeller mounted to said hub, said impeller having pitched impeller blades extending radially outwardly from said hub and directing said substantially laminar flow of said liquid suspension downwardly along said neck portion and along said hemi-toroidal tank bottom;
a pitched blade assembly disposed adjacent to and radially coextensive with said impeller, said assembly having blades with a pitch relating to the pitch of said impeller blades such that the flow leaving said impeller and assembly is essentially axial;
and
a shroud extending around the periphery of said impeller and said pitched blade assembly.

3 more elements

Dependencies are inferred from the claim text.