Dynamic Modelling and Simulation of Lactose Cooling Crystallisation: from Batch and Semi-Batch to Continuous Operations

The focus of this work is to revise for semi-batch and continuous operations, the model equations of a seeded batch cooling crystallisation of α-lactose monohydrate. A case study of evaporative semi-batch operation is also included for reference as models of cooling and heating are not much different. In order to achieve the highest yield, dynamic optimisations must be performed on these models to get optimal cooling, feeding and heating (for evaporative mode only) strategies. Applying these strategies in bench scale experiments shows that models of batch and semi-batch work well before the growth becomes slow. Semi-batch is slightly faster than batch and evaporative semi-batch is ten times faster than cooling but is more difficult to control. The performance of a cooling and seeding run in continuous mode is simulated. The system reaches steady state after seven residence times but the predicted particle size could not be stabilised and continued to increase up to one hundred hours. A plug flow reactor is being studied instead of a continuous stirred tank reactor to close the mass and population balances.