Validation of Bench Scale Spray Dryer Numerical Analysis by rma97348


									Validation of Bench Scale Spray Dryer Numerical Analysis
K. J. Brown1, R. Schick1, W. Kalata1
  Spraying Systems Co.
Spray dryers are used for various chemical and pharmaceutical applications. Spray dry applications are complex and include
many variables that must be analyzed to obtain the desired dry particles. Full analysis of the spray characteristics and
transition from wet to dry particles is crucial to achieve the desired performance and throughput.
The spray injections were empirically acquired using Phase Doppler (TSI) and Laser Scattering (Malvern) techniques. This
information was compiled to determine injection properties of the wet particles. Air flow, temperature and pressure was
measured and monitored throughout. Numerical analysis was performed using commercial computational fluid dynamics
(CFD) software.
Dry particles from the collection vessel were measured using a Malvern instrument at the conclusion of the run. The CFD
model was setup using the wet particle properties measured in the laboratory environment. The CFD model was studied to
determine droplet drift, evaporative effects, coalescence, etc. The trajectories of the droplets was calculated by the discrete
phase model (DPM) within the gas flow field characterized by the Navier-Stokes equations. The flow field and the
calculation of the droplet trajectories are closely coupled to allow for an accurate depiction of the spray and drying process.
The particle sizes were counted as they passed through a plane into the collection vessel in the model.
The dry particle distribution was compared with empirical measurement of dry particles. A correlation between the
numerical model results and the empirical particle size distributions was drawn.

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