Crystallisation

Supersaturation

solution not hold molecule = force to crystallise

metastable region

unstable nucleation and saturation

crystallisation kinetics

supersaturation »nucleation » crystallisation

above solu curve

supersaturated

below solu curve

unsaturated

metastable limit

labile point of nucleation/not

to promote supersatueration

low temp (cooling), antisolvent

measure of supersaturation

vary, but ultimately [super-sat]/[EQ]

Aim rate for crystal growth

slow

Quick crystal growth

increases impurities

determination of nucleation

empirical formula1

1º nucleation emp.formula

nuclei/time/vol

2º nucleation emp.formula

evolved from Power Law

Growth vs Nucleation control

controlling growth is more logical than nucleation
nucleation = sensitive/

main crystal-operation

batch cooling

DISAd of batch

hydrodynamics, stirrer, mtf (can break crystals)

AD of batch

best for slow growth rate

Reason to avoid CSTR

break crys, slurries raises more process concerns

Basis of MB and Operation

solid/volume fraction ~ 15-20% negates the slurry formation

MSMPR crystalliser

crys lab practice to determine Rgrowth/nucleation/birth

Population balance

crystal size distribution

Principle of pop.blance

1. MSMPR crys + defined parameter

2. analysis of crystals formed - shape size

3. det. the nucleation rate

Key for batch-cool operation

Metastable zone

Cool - THEN seed
Stairway approach, one step at a time

Key of crystallisation

Lab > Operation

crystal size and Rformation

good crystal size = easy SEP process