Studies of fluid bed granulation in an industrial R&D context

Following a brief overview of recent developments in laundry powder processing by comparison with other areas of industrial application, and current drivers and trends, a review is presented of collaborative research between Unilever R&D and Sheffield University on fluidised bed granulation using melt binders. These fall apart into 4 areas: 1. Contact zone studies; 2. Growth similarity for non-ideal systems; 3. Growth and breakage decoupled; 4. Scale-up rules based on similarity of growth kinetics. The emphasis of the paper is on the identification and relative quantification of the dominant mechanisms, which are found in the balance of fluxes of solids and binder, together with heat transfer and conduction, not so much binder viscosity. These mechanisms allow for the control of the growth kinetics and rapid scale-up. Together, this lays the broad ground-work for fluidised bed granulation. Some concluding remarks provide pointers for the future of research in this area: • There is a strong requirement for multi-dimensional phase volume distribution based population balances. • Many processes require pre-granulation, and liquid–liquid contact in the spray-zone is scarcely investigated. • Simple combined Lagrangian–Eulerian modelling implemented in commercial code environment can be especially useful to investigate the effects of the relations between material properties and process conditions on growth kinetics.

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