Agglomeration of wet particles in dense granular flows.

Thanh Trung Vo,Patrick Mutabaruka,Jean-Yves Delenne,Edouard Izard,Saeid Nezamabadi,Farhang Radjai,Roland Pellenq

doi:10.1140/epje/i2019-11892-9

Abstract

In order to get insight into the wet agglomeration process, we numerically investigate the growth of a single granule inside a dense flow of an initially homogeneous distribution of wet and dry particles. The simulations are performed by means of the discrete element method and the binding liquid is assumed to be transported by the wet particles, which interact via capillary and viscous force laws. The granule size is found to be an exponential function of time, reflecting the conservation of the amount of liquid and the decrease of the number of available wet particles inside the flow during agglomeration. We analyze this behavior in terms of the accretion and erosion rates of wet particles for a range of different values of material parameters such as mean particle size, size polydispersity, friction coefficient and liquid viscosity. In particular, we propose a phase diagram of the granule growth as a function of the mean primary particle diameter and particle size span, which separates the parametric domain in which the granule grows from the domain in which the granule does not survive.

Highlights

Given the large number of parameters involved in the agglomeration process, its detailed physical mechanisms and their relative importance for the resulting properties of are complex
The material parameters are the properties of the binding liquid and raw material such as liquid viscosity, primary particle size distribution, mean particle size and friction coefficient of primary particles [19,28,29]
In the work presented in this paper, we consider idealized particles, and drum rotation is used only as a means to sustain a dense continuous flow while we investigate the influence of mean particles size, size ratio, liquid viscosity and friction coefficient on the granule growth

Summary

Introduction

Given the large number of parameters involved in the agglomeration process, its detailed physical mechanisms and their relative importance for the resulting properties of are complex. The agglomeration process is easier to model and control when particle dynamics is governed by binary collisions, as in granulators based on fluidized bed or high shearing by impellers. Such processes have been extensively investigated in application to the pharmaceutical industry [10]. The DEM allows for direct quantification of particlescale kinetics and accretion/erosion events This method has already been applied to investigate agglomeration in granular shear flows. In the work presented in this paper, we consider idealized particles, and drum rotation is used only as a means to sustain a dense continuous flow while we investigate the influence of mean particles size, size ratio, liquid viscosity and friction coefficient on the granule growth. We briefly present the numerical algorithm with its input parameters and main calculation steps

Physical assumptions

Numerical method

Drum flow

Conclusions