Modeling and experimental study of a Wurster type fluidized-bed reactor coupled with an atmospheric pressure plasma jet (APPJ) for the treatment of polypropylene (PP) powders
Résumé
Polypropylene (PP) powders are used for various purposes. However, its good
mechanical properties are accompanied by poor wettability. The PP powder was therefore
modified by a pulsed arc atmospheric pressure plasma jet (APPJ) in a homemade Wurster
fluidized bed reactor (Wurster-FBR). The physical and chemical modifications of the
treated PP powders as compared to the non-treated ones were determined by water contact
angle (WCA) measurements, X-ray photoelectron spectroscopy (XPS), attenuated total
reflection Fourier transform infrared spectroscopy (ATR-FTIR) and SEM for morphology
observations.
The average diameter of our PP powders being determined to be 700 µm, they can be
classified as particles of category B according to Geldart classification which can be easily
fluidized. PP powders are basically hydrophobic but after plasma treatment with our handmade reactor they became strongly hydrophilic, because of increase the atomic
concentration of oxygen on the surface of particles.
The plasma torch was introduced into transparent glass reactor with 118mm inside
diameter, placed in the middle of a bronze gas distributor (Fig.1). An internal Wurster tube
was added to control the residence time of particles in the plasma jet, and therefore the
homogeneity of the treatments. The innovative design of wurster tube improved the
powders treatment process by increasing the interaction between plasma torch and the
particles, therefor the efficiency of system increased.
A 2D CFD model was developed using Comsol Multiphysics 5.2 along with this
experimental study. The multiphase flow was calculated by using the k-ε turbulent EulerEuler model which solves one set of Navier-Stokes equations per phase to accurately
describe the particles velocity and volume fraction inside the reactor.