Apparatuses and methods are provided for crystallization. An apparatus includes a vessel defining an interior, a draft tube positioned in the interior of the vessel and defining an annular space between the draft tube and a side wall of the vessel, a rotor shaft extending along a central axis of the vessel, and a helical screw attached to and configured to rotate with the rotor shaft. A multi-stage apparatus further includes a stage barrier wall separating the vessel into two stages, with a draft tube and helical screw positioned in each of the stages. A method for crystallization includes supplying process material to be crystallized into a vessel, moving the process material through a central portion of the vessel, circulating a portion of the material through an annular space in the vessel, and discharging a portion of the material through an outlet.
