Experimental and numerical study of wall layer development in a tribocharged fluidized bed

Abstract

The effects of triboelectricity in a small-scale fluidized bed of polyethylene particles were investigated by imaging the particle layer in the vicinity of the column wall and by measuring the pressure drop across the bed. The average charge on the particles was altered by changing the relative humidity of the gas. A triboelectric charging model coupled with a computational fluid dynamics-discrete element method (CFD-DEM) model was utilized to simulate gas-particle flow in the bed. The electrostatic forces were evaluated based on a particle-particle particle-mesh method, accounting for the surface charge on the insulating walls. It was found that simulations with fixed and uniform charge distribution among the particles capture remarkably well both the agglomeration of the particles on the wall and the associated decrease in the pressure drop across the bed. With a dynamic tribocharging model, the charging rate had to be accelerated to render the computations affordable. Such simulations with an artificial acceleration significantly over-predict charge segregation and the wall becomes rapidly sheeted with a single layer of strongly charged particles.

Discrete element method–computational fluid dynamics analyses of flexible fibre fluidization

“…2002; Liu & Hrenya 2018; Sippola et al. 2018); however, particle shape is known to have a significant impact on particle packing (Wouterse, Williams & Philipse 2007), particle flow (Guo et al. 2012) and fluid–particle interaction (Hölzer & Sommerfeld 2008).…”

“…Extensive studies on fluidization have been conducted experimentally and computationally. Particles are assumed to be spherical in most of these studies, particularly computational studies (Pan et al 2002;Liu & Hrenya 2018;Sippola et al 2018); however, particle shape is known to have a significant impact on particle packing (Wouterse, Williams & Philipse 2007), particle flow (Guo et al 2012) and fluid-particle interaction (Hölzer & Sommerfeld 2008). Thus, fluidization behaviour is also affected by particle shape.…”

Charge transport equation for bidisperse collisional granular flows with non-equipartitioned fluctuating kinetic energy

“…The charge accumulation on particles is modelled by an effective-work-function-based model (Laurentie, Traoré & Dascalescu 2013). The effective work function is a lumped parameter that can be used to quantify charging rates and extents observed in specific experimental studies (Laurentie et al 2013;Naik et al 2015Naik et al , 2016Kolehmainen et al 2017b;Sippola et al 2018) or quantum calculations (Naik et al 2015). Similar CFD-DEM approaches were also developed by Pei, Wu & Adams (2016) and Grosshans & Papalexandris (2017).…”

The effect of electrostatic charges on particle-laden duct flows

“…For example, due to particle–wall adhesion the charged particles can coat vessel walls, which requires frequent cleaning (Sippola et al. 2018). Also, the dynamics of fluidized beds is greatly influenced by electrostatic interactions (Jalalinejad, Bi & Grace 2012, 2015).…”

“…However, in some other powder-handling facilities, such as fluidized beds, it occurs incidentally and leads to operational problems (Fotovat, Bi & Grace 2017. For example, due to particle-wall adhesion the charged particles can coat vessel walls, which requires frequent cleaning (Sippola et al 2018). Also, the dynamics of fluidized beds is greatly influenced by electrostatic interactions (Jalalinejad, Bi & Grace 2012.…”