Discrete Element Method Modelling of the Diametral Compression of Starch Agglomerates.

Józef Horabik,Rafał Kobyłka,Marek Molenda,Mateusz Stasiak,Piotr Parafiniuk,Maciej Bańda,Joanna Wiącek

doi:10.3390/ma13040932

Abstract

Starch agglomerates are widely applied in the pharmaceutical, agricultural, and food industries. The formation of potato starch tablets and their diametral compression were simulated numerically and verified in a laboratory experiment to analyse the microscopic mechanisms of the compaction and the origins of their breakage strength. Discrete element method (DEM) simulations were performed using EDEM software. Samples comprised of 120,000 spherical particles with radii normally distributed in the range of 5–36 μm were compacted in a cylindrical die with a diameter of 2.5 cm. The linear elastic–plastic constitutive contact model with a parallel bonded-particle model (BPM) was used to model the diametral compression. DEM simulations indicated that the BPM, together with the linear elastic–plastic contact model, could describe the brittle, semi-brittle, or ductile breakage mode, depending on the ratio of the strength to Young’s modulus of the bond and the bond-to-contact elasticity ratio. Experiments confirmed the findings of the DEM simulations and indicated that potato starch (PS) agglomerates can behave as a brittle, semi-brittle, or ductile material, depending on the applied binder. The PS agglomerates without any additives behaved as a semi-brittle material. The addition of 5% of ground sugar resulted in the brittle breakage mode. The addition of 5% gluten resulted in the ductile breakage mode.

Highlights

Agglomeration of powders is one of the unit operations for improving the characteristics and functionality of the final product
The objective of this study was to investigate the possibility of numerically reproducing the brittle, semi-brittle, and ductile breakage modes of agglomerates by using the discrete element method (DEM) together with a parallel bonded-particle model (BPM)
To adjustprocess the bond and particletest parameters to the best-fitpreliminary experimental data of theand compaction compaction and thethe strength of the agglomerates, simulations analyses process and the strength test of the agglomerates, preliminary simulations and analyses of the effects of of the effects of different parameters on the relationship between the tension stress σ1 and the different parameters on the relationship between the tension stress σ and the diametral deformation diametral deformation ΔL/D, the tensile strength of the agglomerates σf during diametral

Summary

Introduction

Agglomeration of powders is one of the unit operations for improving the characteristics and functionality of the final product. It is widely applied in the pharmaceutical, agricultural, food, mineral, metallurgy, and fuel biomass industries [1]. Depending on the amount of plastic deformation needed to cause failure and shape of the force–displacement response, agglomerates can be classified as brittle, semi-brittle, or ductile. Brittle materials, such as rock, glass, and monolithic ceramics, exhibit no detectable plastic strain prior to failure and a sharp peak of the force–displacement response [5,6]. Brittle mechanical behaviour involves localised cracks [7]

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