Flow behavior of polypropylene reactor powder in horizontal stirred bed reactors characterized by X-ray imaging

Horizontal stirred bed reactors (HSBRs) are widely used in the commercial production of polypropylene (PP). Despite their commercial significance, a comprehensive understanding of the flow behavior in HSBRs remains elusive, primarily due to the lack of detailed experimental data. This study investigates the influence of operating parameters on the particle flow behavior of two types of PP reactor powder in a laboratory-scale HSBR using X-ray imaging. Our results indicate that the overall flow behavior and phase holdup in the HSBR are dominated by agitation. Moreover, gas injection through the inlet points at the bottom of the HSBR results in spouting behavior, which can lead to reduced gas–solid contacting and, in extreme cases, complete bypass. Finally, the presence of liquid (in this study, isopropyl alcohol) adversely affects the flow behavior of the PP reactor powder due to liquid bridging at the contact points of particles. Powders that comprise particles with relatively small sizes and dense surface morphology are particularly prone to reduced flow behavior when exposed to liquid. • The flow behavior of polypropylene powder in an HSBR is studied by X-ray imaging. • The overall flow behavior is dominated by agitation. • Gas injection results in spouting behavior, reducing gas–solid contact. • Liquid presence reduces flow, especially for powders with smaller, denser particles. • Findings aid in optimizing and scaling HSBR systems for improved production.