Apparatus And Method For Crystallization

A multi-stage apparatus for crystallization, comprising:

• a vessel having a central axis, a lower wall, and upper wall, and a side wall extending between the lower and upper wall, the vessel further defining an interior having a lower portion and an upper portion, wherein the vessel comprises an inlet for introduction of process material into the interior, and an outlet;
• a first stage barrier wall extending perpendicularly to the central axis of the vessel, the first stage barrier wall being positioned between the lower and upper portions, wherein the first stage barrier wall separates the vessel into a first stage and a second stage, and wherein the first stage barrier wall provides at least one fluid passageway between the first stage and the second stage;
• a first draft tube positioned in the first stage of the vessel and extending between the lower portion and the first stage barrier wall, wherein the draft tube is spaced from the lower wall, first stage barrier wall, and side wall of the vessel, thereby defining an annular space between the first draft tube and the side wall of the vessel;
• a second draft tube positioned in the second stage of the vessel and extending between the first stage barrier wall and the upper portion, wherein the draft tube is spaced from the first stage barrier wall, the upper wall and the side wall of the vessel, thereby defining an annular space between the second draft tube and the side wall of the vessel;
• a rotor shaft extending along the central axis of the vessel and extending through the first and second stages of the vessel;
• a first helical screw positioned in the first stage of the vessel and within the first draft tube, the first helical screw being attached to and configured to rotate with the rotor shaft;
• and
• a second helical screw positioned in the second stage of the vessel and within the second draft tube, the second helical screw being attached to and configured to rotate with the rotor shaft.

A method for crystallization of a process material, the method comprising:

• supplying the process material into the interior of a vessel;
• moving the process material through a central portion of the vessel;
• circulating at least a portion of the process material through an annular space in the vessel;
• and
• discharging at least a portion of the process material through an outlet of the vessel.