Particle size distribution in a multi-zone circulating fluidized bed polymerization reactor--颗粒学报PARTICUOLOGY

Hadadiyan, M., Mostoufi, N., & Marandi, R. (2024). Particle size distribution in a multi-zone circulating fluidized bed polymerization reactor. Particuology, 93, 291-299. https://doi.org/10.1016/j.partic.2024.07.005

Particle size distribution in a multi-zone circulating fluidized bed polymerization reactor

Mohammadhossein Hadadiyan^a, Navid Mostoufi^a *, Reza Marandi^b

a Process Design and Simulation Research Centre, School of Chemical Engineering, College of Engineering, University of Tehran, P. O. Box 11155-4563, Tehran, Iran
b Polymer Research Group, Petrochemical Research and Technology Company, National Petrochemical Company, P.O. Box 14358/84711, Tehran, Iran

10.1016/j.partic.2024.07.005

Volume 93, October 2024, Pages 291-299

Received 17 April 2024, Revised 26 June 2024, Accepted 8 July 2024, Available online 16 July 2024, Version of Record 27 July 2024.

E-mail: mostoufi@ut.ac.ir

Highlights

• Modeling multi-zone polymerization reactor by coupling hydrodynamic and population balance equations.

• Utilization of two-fluid model to simulate the hydrodynamics.

• Investigating impact of operating conditions and design parameters on reactor performance.

• Effect of hydrodynamic conditions on particle size distribution is shown.

Abstract

This research focuses on modeling a multi-zone circulating reactor (MZCR) in the polypropylene production process. In these reactors, designed for polyolefin production, small catalyst particles (20–300 μm) initiate polymerization in the presence of monomer gas. The reactor consists of two main regions: the riser and the downer. The riser operates in the fast fluidization and the downer is in the moving bed regime. Employing the two-fluid model with the Eulerian-Eulerian approach, the dynamics of both solid and gas phases were modeled by applying Newton's laws of motion and assuming spherical particles. The population balance of particles within the reactor was also coupled with the equations of motion. The simultaneous solution of these equations provides valuable insights into particle and fluid behavior, revealing trends such as the growth of polymer particles. Furthermore, the impact of various operating conditions was explored. This study also examined the effects of design parameters (gas inlet velocity, average inlet diameter, and temperature) on the system performance. For instance, it was shown that in the case where the solid circulation flux is 30 kg/(m² s) the velocity of particles in the bed increases from 0.4 at the inlet to 1.1 m/s in the fully developed zone, when it is 43 kg/(m² s) the velocity of particles increases from 0.3 to 1.4 m/s, and when it is 55 kg/(m² s), it is increased from 0.22 to 1.5 m/s. Additionally, trends in particle size distribution based on temperature adjustments were revealed. This study showed that higher temperatures accelerate the polymerization reaction rate, promoting faster growth kinetics and the formation of larger particles.

Graphical abstract

Keywords

Fluidization; Polymerization; Gas-solid flow; Multi-zone circulating reactor (MZCR); CFD-PBM; Two-fluid model

文章导读