TY - JOUR
T1 - Particle Breakage
T2 - Limiting Conditions for Crystal-Crystallizer Collisions
AU - Tyrrell, Rory
AU - De Souza, Brian
AU - Frawley, Patrick J.
N1 - Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/2/7
Y1 - 2018/2/7
N2 - Two prominent theories surround the origin of secondary nuclei in batch crystallization experiments. Traditionally, the generation of secondary nuclei has been attributed to attrition breeding, resulting from collisions between crystals, impeller, and vessel geometry. Mechanistically, it is assumed that the collision of crystals leads to the generation of fine particles and nucleation sites. More recently, an alternative mechanism has received considerable attention, namely, cluster breeding secondary nucleation whereby the source of fine particles is attributed to clusters in solution. In the present work, a detailed experimental investigation of particle wall collisions of active pharmaceutical ingredient crystals is conducted. A pressurized test rig was developed whereby crystals in suspension were fired through a nozzle perpendicular to a stainless steel target. Using shadowgraphy, direct imaging particle-plane collisions are captured for crystals between 100-400 μm as they approach a target surface with initial velocities of up to 10 m/s. Crystals approaching a target surface are seen to be cushioned by a squeeze film boundary layer, greatly reducing their impact velocities. Furthermore, below a critical freestream particle Reynolds number, complete particle arrest was observed, preventing contact with the target surface entirely. This work provides further evidence to suggest that indeed secondary nucleation cannot be accounted for through particle-impeller breakage events. The alternative crystal breeding ideology is therefore further supported.
AB - Two prominent theories surround the origin of secondary nuclei in batch crystallization experiments. Traditionally, the generation of secondary nuclei has been attributed to attrition breeding, resulting from collisions between crystals, impeller, and vessel geometry. Mechanistically, it is assumed that the collision of crystals leads to the generation of fine particles and nucleation sites. More recently, an alternative mechanism has received considerable attention, namely, cluster breeding secondary nucleation whereby the source of fine particles is attributed to clusters in solution. In the present work, a detailed experimental investigation of particle wall collisions of active pharmaceutical ingredient crystals is conducted. A pressurized test rig was developed whereby crystals in suspension were fired through a nozzle perpendicular to a stainless steel target. Using shadowgraphy, direct imaging particle-plane collisions are captured for crystals between 100-400 μm as they approach a target surface with initial velocities of up to 10 m/s. Crystals approaching a target surface are seen to be cushioned by a squeeze film boundary layer, greatly reducing their impact velocities. Furthermore, below a critical freestream particle Reynolds number, complete particle arrest was observed, preventing contact with the target surface entirely. This work provides further evidence to suggest that indeed secondary nucleation cannot be accounted for through particle-impeller breakage events. The alternative crystal breeding ideology is therefore further supported.
UR - http://www.scopus.com/inward/record.url?scp=85041892451&partnerID=8YFLogxK
U2 - 10.1021/acs.cgd.7b00125
DO - 10.1021/acs.cgd.7b00125
M3 - Article
AN - SCOPUS:85041892451
SN - 1528-7483
VL - 18
SP - 617
EP - 622
JO - Crystal Growth and Design
JF - Crystal Growth and Design
IS - 2
ER -