Fines removal in a continuous plug flow crystallizer by optimal spatial temperature profiles with controlled dissolution

This work presents a systematic study for obtaining the optimal temperature profile in a continuous plug flow crystallizer (PFC). The proposed PFC consists of multiple segments where the temperature of each segment can be controlled individually. An optimization problem is formulated for a target crystal size distribution (without fines) with the temperature of the segments as decision variables. The results indicate that for the crystallization kinetics considered, dissolution steps are necessary for the reduction of fines due to nucleation. A systematic study on the form of growth and dissolution kinetics suggested that the key factor that determines whether the dissolution steps will be successful in reducing fines, without compromising the final size of the crystals from seed, is the size dependence of the growth and dissolution kinetics. Best fines removal is achieved when the larger crystals grow faster than the smaller ones and the smaller crystals dissolve faster than the larger ones. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4582–4594, 2013