Dynamics and control of continuous crystallizers

Graduation date: 1982The theoretical analysis of an unseeded, isothermal mixed-suspension\ud mixed-product-removal (MSMPR) crystallizer with a fines trap is developed.\ud The lumped parameter system equations are presented for a homogeneous\ud nucleation and a number-dependent secondary-nucleation model. Linear\ud stability analysis and system simulations are used to investigate the\ud system's dynamic behavior.\ud Modal control algorithms for the above systems are developed using\ud throughput rate or fines-recirculation rate or both as the manipulated\ud variables. The system performance is significantly improved when modal\ud control is applied whether the system is stable or unstable.\ud The characteristic equation for size-dependent growth rate in an\ud MSMPR crystallizer is found by linear stability analysis. The case in\ud which the growth rate is size-dependent for small crystals and size-independent\ud for large crystals; and the case in which the growth rate\ud is given by the Abegg - Stevens - Larson (ASL) equation are solved to illustrate\ud the effect of size-dependent growth rate on stability.\ud A new on-line probe was developed to measure the particle size\ud distribution. Its theory, limitations (it is useful for large particles)\ud and applicability are discussed