NAGY, Z.K., 2009. Model based robust control approach for batch crystallization product design. Computers and Chemical Engineering, 33 (10), pp.1685-1691.
The paper presents a novel control approach for crystallization processes, which can be used for
designing the shape of the crystal size distribution to robustly achieve desired product properties. The
approach is based on a robust optimal control scheme, which takes parametric uncertainties into
account to provide decreased batch-to-batch variability of the shape of the crystal size distribution.
Both open-loop and closed loop robust control schemes are evaluated. The open-loop approach is
based on a robust end-point nonlinear model predictive control (NMPC) scheme which is
implemented in a hierarchical structure. On the lower level a supersaturation control approach is used
that drives the system in the phase diagram according to a concentration versus temperature trajectory.
On the higher level a robust model-based optimization algorithm adapts the setpoint of the
supersaturation controller to counteract the effects of changing operating conditions. The process is
modelled using the population balance equation (PBE), which is solved using a novel efficient
approach that combines the quadrature method of moment (QMOM) and method of characteristics
(MOC). The proposed robust model based control approach is corroborated for the case of various
desired shapes of the target distribution.