Towards a Rigorous Solution of Population Balance Equations for the Gas Antisolvent Crystallization (GAS) Process

The utilization of SCFs for the processing of several products has attracted considerable interest in recent years as an emerging “green” technology. Particle formation using SCFs can be carried out according to several different techniques, including antisolvent techniques such as the gas-antisolvent (GAS) process. The potential advantages of the GAS crystallization process lies in the possibility of obtaining solvent free, micron and submicron particles with a narrow size distribution. By varying the process parameters, the particle size, size distribution and morphology can be “tuned” to produce a product with desirable qualities. However, depending on the considered particle formation mechanism, population balance model of GAS process may include phenomena such as primary nucleation, secondary nucleation, crystal growth, as well as agglomeration and/or breakage (attrition) of crystals. The resulting equation is often of the integropartial differential form. A powerful numerical algorithm for the treatment of the implemented population balance model structures was applied in this work. Algorithm simulations were performed for changes in the main GAS process operating parameters, i.e., the antisolvent addition rate and saturation level.