Large-scale transportation and storage of wood pellets: Investigation of the change in physical properties

Hamid Gilvari,Coen H.H Van Battum,Simon A Van Dijk,Wiebren De Jong,Dingena L Schott

doi:10.1016/j.partic.2020.12.006

Hamid Gilvari, Coen H.H Van Battum + Show 3 more

Open Access

https://doi.org/10.1016/j.partic.2020.12.006

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Journal: China Particuology	Publication Date: Jan 21, 2021
Citations: 12	License type: cc-by

Affiliation: Delft University of Technology

Abstract

The change in physical properties of wood pellets, with a focus on particle size distributions due to pellet breakage and attrition, was studied in a large-scale (∼450ton/h) transportation system. Critical locations with a high probability of breakage through the whole transportation system were chosen and sampled to study the effect of transportation system design and operation on the mechanical properties of pellets. Bulk density, mechanical durability, moisture content, and particle size distribution of pellets were characterized for each sample. Analysis of variance showed that there were significant differences between the percentages of small particles (< 5.6mm) in the samples taken at different locations, especially at one with a vertical free fall of 7.8m. On average, this relatively long drop increased the proportion of particles < 5.6mm in the samples from 8.73% to 14.09%, and that of particles < 3.15mm from 4.82% to 9.01%. Moreover, the measurements showed a wide deviation in the mechanical durability values, between a minimum of 90.8% and a maximum of 98.7%, which were not correlated to the sampling points but related to pellet properties. It can be concluded that pellet transportation systems require more dedicated design strategies to prevent breakage and attrition.

Highlights

Worldwide use of wood pellets as a renewable energy carrier has increased sharply, from ∼12 million metric tons in 2008 to 56 million metric tons in 2018 (Calderón, Gauthier, & Jossart, 2019)
Analysis of variance (ANOVA) of all 77 samples revealed that there was no bias in the results for pellet properties at different locations or on different days ( ̨ = 0.05, i.e. 95% confidence interval)
The mechanical durability varied between 90.8% and 98.7% in all locations, and this exceeded the 2% repeatability limit set by the standard (ISO, 2015)

Summary

Introduction

Worldwide use of wood pellets as a renewable energy carrier has increased sharply, from ∼12 million metric tons in 2008 to 56 million metric tons in 2018 (Calderón, Gauthier, & Jossart, 2019). More than 27 million metric tons of wood pellets were consumed in Europe in 2018, more than 45% of them for industrial purposes. Not all pellets consumed in Europe are produced by European countries. Pellets are normally produced under high temperature and pressure conditions in a so-called pelletization process, which involves the elastic and plastic deformation of particles and the softening of natural binders such as starch, protein, lignin, fat, and fibers to help agglomerate particles (de Souza et al, 2020; Kaliyan & Vance Morey, 2009; Mani, Tabil, & Sokhansanj, 2008; Nanou, Huijgen, Carbo, & Kiel, 2018)

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