Crystallization

Claim 1

A PROCESS FOR CRYSTALLIZING A MATERIAL CHARACTERIZED BY RAPID RATE OF CRYSTAL GROWTH WHICH COMPRISES WHITHDRAWING SOLUTION OF SUCH MATERIAL FROM THE TOP OF SUCH SOLUTION CONTAINED IN A CRYSTALLIZING VESSEL; CIRCULATING THE WITHDRAWN SOLUTION THROUGH AN EVAPORATOR; THEREIN CONCENTRATING THE SOLUTION TO A SELECTED DEGREE OF SUPERSATURATION; CONTINUOUSLY INTRODUCING A STREAM OF THE RESULTING SUPERSATURATED SOLUTION INTO A LOWER PART OF SAID CRYSTALLIZING VESSEL CONTAINING A SUSPENSION OF CRYSTALS OF SAID MATERIAL IN SUPERSATURATED SOLUTION THEREOF; DIRECTING SAID STREAM AND CONTROLLING ITS VELOCITY TO MAINTAIN TWO ZONES IN THE RESULTING RISING SUSPENSION OF CRYSTALS, NAMELY, A LOWER ZONE OF CRYSTAL GROWTH WHEREIN A SUSPENSION OF RELATIELY COARSER GROWING CRYSTALS IN MAINTAINED IN CONTINUOUS RAPID, SUBSTANTIALLY VERTICAL STREAMLINED ROTATION BY KINETIC ENERGY IMPARTED BY SAID STREAM, AND AN UPPER, RELATIVELY QUIESCENT ZONE CONTAINING A SUSPENSION OF FINER CRYSTAL; TRANSFERRING FINE CRYSTALS FROM SAID LOWER ZONE TO SAID UPPER ZONE BY UPWARD FLOW OF SOLUTION; CONTINUOUSLY INTRODUCING A CONTROLLED STREAM OF SUPERSATURATED SOLUTION OF SAID MATERIAL INTO SAID UPPER ZONE; THEREIN CONTACTING SAID FINE CRYSTALS WITH RESULTING SUPERSATURATED SOLUTION OF SAID MATERIAL OF A CONTROLLED DEGREE OF SUPERSATURATION UNTIL THEIR SIZE IS SUBSTANTIALLY INCREASED; INTRODUCING THE RESULTING CRYSTALS OF INCREASED SIZE INTO SAID LOWER ZONE AS SEED CRYSTALS; AND WITHDRAWING STRONG MATURE CRYSTALS FROM A LOWER PORTION OF SAID LOWER ZONE.