Heat transfer and residence time distribution in plug flow continuous oscillatory baffled crystallisers

Heat transfer coefficients in a continuous oscillatory baffled crystalliser (COBC) with a nominal internal diameter of 15 mm have been determined as a function of flow and oscillatory conditions typically used under processing conditions. Residence time distribution measurements show a near plug flow with high Peclet numbers on the order of 100s to 1000s, although there was significant oscillation damping in longer COBC setups. Very rapid heat transfer was found under typical conditions, with overall heat transfer coefficients on the order of 100s W m-2 K-1. Furthermore, poor mixing in the COBC cooling jacket was observed when lower jacket flow rates were implemented in an attempt to decrease the rate of heat transfer, in order to achieve more gradual temperature profile along the crystalliser length. Utilising the experimentally determined overall heat transfer coefficients, a theoretical case study is presented to investigate the effects of the heat transfer rate on temperature and supersaturation profiles and to highlight potential fouling issues during a continuous plug flow cooling crystallisation.