Discrete element method modeling of the triboelectric charging of polyethylene particles: Can particle size distribution and segregation reduce the charging?

Electrostatics 2015

物理学;数学

Konopka, Ladislav^1 ; Kosek, Juraj^1

University of Chemistry and Technology Prague, Department of Chemical Engineering, Technicka 5, Prague 6

166 28, Czech Republic^1

关键词: Downstream-processing;    Fluidized bed polymerization reactors;    Operational problems;    Particle charge distribution;    Particle-particle interactions;    Polyethylene particles;    Reactor temperatures;    Triboelectric charging;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/646/1/012045/pdf
DOI  :  10.1088/1742-6596/646/1/012045

来源: IOP

【 摘 要 】

Polyethylene particles of various sizes are present in industrial gas-dispersion reactors and downstream processing units. The contact of the particles with a device wall as well as the mutual particle collisions cause electrons on the particle surface to redistribute in the system. The undesirable triboelectric charging results in several operational problems and safety risks in industrial systems, for example in the fluidized-bed polymerization reactor. We studied the charging of polyethylene particles caused by the particle-particle interactions in gas. Our model employs the Discrete Element Method (DEM) describing the particle dynamics and incorporates the 'Trapped Electron Approach' as the physical basis for the considered charging mechanism. The model predicts the particle charge distribution for systems with various particle size distributions and various level of segregation. Simulation results are in a qualitative agreement with experimental observations of similar particulate systems specifically in two aspects: 1) Big particles tend to gain positive charge and small particles the negative one. 2) The wider the particle size distribution is, the more pronounced is the charging process. Our results suggest that not only the size distribution, but also the effect of the spatial segregation of the polyethylene particles significantly influence the resulting charge distribution 'generated' in the system. The level of particle segregation as well as the particle size distribution of polyethylene particles can be in practice adjusted by the choice of supported catalysts, by the conditions in the fluidized-bed polymerization reactor and by the fluid dynamics. We also attempt to predict how the reactor temperature affects the triboelectric charging of particles.