Effect of particle size in fluidization of polyethylene particle mixtures on the extent of bed electrification and wall coating

• Effect of Polyethylene fluidizing particle size on the degree of bed electrification and column wall coating was studied.
• Polyethylene resin as received resulted in a wall coating consisting of 400 micron particles and smaller.
• In binary mixture of small and large particles, the wall coating was dominated by small particles when higher than 10%.
• The net specific charge of the wall coating elevated with increasing the fraction of smaller particles in the mixture.
• The magnitude of wall coating declined with increasing the fraction of smaller particles in the mixture.

In this work the effects of polyethylene fluidizing particle size (smaller than 400 μm) on the degree of fluidized bed electrification and wall coating formation was studied. Experiments were conducted in a stainless steel, 0.15 m diameter column, under ambient conditions. Polyethylene resin as received (20–1500 μm) as well as mono-sized and binary mixture of large (600–710 μm) and small (212–300 & 300–425 μm) polyethylene particles were fluidized while their mass, net specific charge and size distribution in the bulk of the bed and the wall coating were measured. For the binary mixture the fraction of the small particles examined were 5%–10% and 20%. The extent of wall coating varied between different cases tested with the mono-sized large particles resulting in the most amount coating. It was found that as the fraction of the small particles in the binary mixture was increased, these particles formed majority of the wall coating. At the mass fraction of 20%, the extent of wall coating and its net specific charge were similar to that of resin as received. Overall results implied that the magnitude of the smaller sized particles within the resin played an important role in the degree of particles electrostatic charging and the extent of the particles adhesion to the column wall. Small particles were found to generate a much larger net specific charge which although resulted in them coating the column wall but prevented the coating layer growth.