Investigation of the Dynamic Behaviour of the Spray Granulation in Continuously Operated Horizontal Fluidised Beds

In continuous spray granulation processes
very often horizontally constructed fluidised beds with rectangular cross
sections are used, which are divided by a variable number of plates (weirs)
into several chambers of different functionalities. Commonly an external
product processing, consisting of pneumatic conveying, screening, grinding of
the oversize granules and recycling of grinded oversize and undersize granular
material into the fluidised bed granulator is applied. The resulting internal
and external networks of solids process unit operations as well as gas, liquid
and solid flows lead to a complex and dynamic process behaviour.

This work focuses on the dynamic behaviour
of spray granulation processes in horizontal fluidised beds that affect the
process conditions, as well as the product properties. Studying the dynamic
effects of this process, on the one hand a holistic view on
the macroscopic process is considered to characterize the process behaviour
with respect to the stability and time constants of the rate processes. On the
other hand the process is divided into local compartments to analyse several
sub-processes and their effects within the granulation individually, such as
the spraying process within the spray zone and the solids residence time and
transport through the multi-staged process chamber under different weir
configurations.

Figure: Simplified process flow diagram
with schematic representation of the internal zone formation and external
process chain (left); Influence of the process conditions onto the
morphological structure (SEM pictures) of the product granules (right).

The financial support of the German
Research Foundation (“Deutsche Forschungsgemeinschaft”) within
the priority program SPP1679 is gratefully acknowledged.