Multi-stage crystallization apparatus and method

A crystallizer system for forming solid crystals, comprising:

• a vessel defining a cylindrical sidewall;
• a sparge device located at a bottom of the vessel, the sparge device adapted to release gas bubbles into the vessel;
• an impeller assembly including a shaft and a plurality of impellers attached to the shaft, each impeller including a plurality of blades spaced circumferentially about the shaft;
• each impeller defining blade outer edges;
• and
• a plurality of redistribution funnel assemblies vertically spaced apart, each funnel assembly positioned underneath a respective impeller of the plurality of impellers, each funnel assembly including:
• a downwardly-oriented funnel defining a topside, an underside, and a substantially circular lower edge;
• a disc attached to the shaft such that the disc rotates with the impellers, the disc oriented substantially perpendicularly to the shaft, the disc located at the lower edge of the funnel, such that gas bubbles rising to contact the disc are directed around the lower edge and onto the underside of the funnel;
• the lower edge of the funnel and the disc define a lower gap therebetween, such that solid particles falling from within the funnel are directed out of the lower gap when the disc is rotated;
• and
• a channel extending radially inward from a location near the cylindrical sidewall, the channel penetrating through the funnel to an interior of the funnel, the channel adapted to direct gas bubbles from the cylindrical sidewall to a location near the blade outer edges of the respective impeller.