(255b) CFD Modeling of Droplet Formation from High Pressure Nozzles Used in Spray Drying of Pharmaceuticals

Spray drying (SD) of pharmaceuticals is a process often used to stabilize amorphous active pharmaceutical ingredients (APIs) in order to increase their solubility and bioavailability. The process typically involves atomization of a polymeric/API solution into fine droplets, followed by their immediate drying to obtain solid particles. The main properties of the spray dried intermediates (SDIs), which include shape, flowability, compressibility and stability, can be greatly affected by the SD process. A great effort needs to be invested to ensure these properties are maintained upon scale up. The main parameters that need to be maintained consistently during scale up involve droplet size distribution and overall droplet drying rate. The aim of this study was to develop a computational fluid dynamics (CFD) modeling strategy that can predict the performance of high-pressure atomization nozzles, which are typically used for large scale SD processes. These nozzles are operated at very high pressures and their performance currently can only be assessed through at-scale experiments and measurements. This work was able to successfully demonstrate that by using CFD modeling techniques it is possible to predict nozzle performance and obtain the following: liquid flow rate, spray angle, liquid velocity and droplet size distributions as a function of operating pressures. The CFD modeling was successfully demonstrated using Newtonian and non-Newtonian (shear sensitive) liquids. Results obtained from the CFD simulations showed a very good agreement with experimental data. Additional information is presented regarding viscosity measurements of shear-thinning liquids and some new considerations for successful scale-up of SD processes.