Constitutive modelling of compression and stress relaxation in pine pellets

Simon Klinge Nielsen, Hamid Rezaei, Matthias Mandø, Shahab Sokhansanj

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The increasing pellet production and a demand for making high quality biofuel pellets call for tools that can facilitate producers to meet these requirements and help understanding the effect feedstock and process parameters. In this study, mechanical and rheological properties of pine pellets made of different particle sizes and compression speeds were studied via pelleting tests and numerical simulations. Single pelleting tests were performed with six different particle size samples, ranging between 0.25 and 2.8 mm, and pelleted at compression speeds of 1, 5, and 10 mm min−1. The experimental results of specific compression and extrusion energy showed a positively linear correlation between particle size and energy consumption. The highest pellet durability was observed for pellets produced from small and mixed particle sizes. Eight different constitutive models were evaluated on their ability to simulate compression and stress relaxation, and their level of complexity. A non-linear Maxwell representation of the Standard Linear Solid (SLS) model was setup and fitted to the experimental compression data. The model coefficient of spring 1 composes the asymptotic stress level of the relaxed pellet, and the coefficient of spring 2 was found to be positively correlated with particle size. The viscosity of the dashpot is also found to be positively correlated with particle size, likewise it depends on the compression speed, where higher compression speed resulted in lower viscosities. The results of the study elucidate new insight into mechanical behavior of biomass particle compression, and the resultant simulations have utility for predicting the pressure requirements to produce pellets.
Original languageEnglish
Article number105370
JournalBiomass & Bioenergy
Volume130
Number of pages10
ISSN0961-9534
DOIs
Publication statusPublished - Nov 2019

Fingerprint

stress relaxation
Stress relaxation
pellets
Pinus
Particle size
compression
particle size
modeling
Pelletizing
Compaction
Viscosity
viscosity
Data compression
Biofuels
Constitutive models
energy use and consumption
Feedstocks
durability
Extrusion
feedstocks

Keywords

  • Compression
  • Pelleting
  • Biomass
  • Biofuel
  • Constitutive modelling
  • Energy

Cite this

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title = "Constitutive modelling of compression and stress relaxation in pine pellets",
abstract = "The increasing pellet production and a demand for making high quality biofuel pellets call for tools that can facilitate producers to meet these requirements and help understanding the effect feedstock and process parameters. In this study, mechanical and rheological properties of pine pellets made of different particle sizes and compression speeds were studied via pelleting tests and numerical simulations. Single pelleting tests were performed with six different particle size samples, ranging between 0.25 and 2.8 mm, and pelleted at compression speeds of 1, 5, and 10 mm min−1. The experimental results of specific compression and extrusion energy showed a positively linear correlation between particle size and energy consumption. The highest pellet durability was observed for pellets produced from small and mixed particle sizes. Eight different constitutive models were evaluated on their ability to simulate compression and stress relaxation, and their level of complexity. A non-linear Maxwell representation of the Standard Linear Solid (SLS) model was setup and fitted to the experimental compression data. The model coefficient of spring 1 composes the asymptotic stress level of the relaxed pellet, and the coefficient of spring 2 was found to be positively correlated with particle size. The viscosity of the dashpot is also found to be positively correlated with particle size, likewise it depends on the compression speed, where higher compression speed resulted in lower viscosities. The results of the study elucidate new insight into mechanical behavior of biomass particle compression, and the resultant simulations have utility for predicting the pressure requirements to produce pellets.",
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Constitutive modelling of compression and stress relaxation in pine pellets. / Nielsen, Simon Klinge; Rezaei, Hamid ; Mandø, Matthias; Sokhansanj, Shahab.

In: Biomass & Bioenergy, Vol. 130, 105370, 11.2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

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AU - Rezaei, Hamid

AU - Mandø, Matthias

AU - Sokhansanj, Shahab

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N2 - The increasing pellet production and a demand for making high quality biofuel pellets call for tools that can facilitate producers to meet these requirements and help understanding the effect feedstock and process parameters. In this study, mechanical and rheological properties of pine pellets made of different particle sizes and compression speeds were studied via pelleting tests and numerical simulations. Single pelleting tests were performed with six different particle size samples, ranging between 0.25 and 2.8 mm, and pelleted at compression speeds of 1, 5, and 10 mm min−1. The experimental results of specific compression and extrusion energy showed a positively linear correlation between particle size and energy consumption. The highest pellet durability was observed for pellets produced from small and mixed particle sizes. Eight different constitutive models were evaluated on their ability to simulate compression and stress relaxation, and their level of complexity. A non-linear Maxwell representation of the Standard Linear Solid (SLS) model was setup and fitted to the experimental compression data. The model coefficient of spring 1 composes the asymptotic stress level of the relaxed pellet, and the coefficient of spring 2 was found to be positively correlated with particle size. The viscosity of the dashpot is also found to be positively correlated with particle size, likewise it depends on the compression speed, where higher compression speed resulted in lower viscosities. The results of the study elucidate new insight into mechanical behavior of biomass particle compression, and the resultant simulations have utility for predicting the pressure requirements to produce pellets.

AB - The increasing pellet production and a demand for making high quality biofuel pellets call for tools that can facilitate producers to meet these requirements and help understanding the effect feedstock and process parameters. In this study, mechanical and rheological properties of pine pellets made of different particle sizes and compression speeds were studied via pelleting tests and numerical simulations. Single pelleting tests were performed with six different particle size samples, ranging between 0.25 and 2.8 mm, and pelleted at compression speeds of 1, 5, and 10 mm min−1. The experimental results of specific compression and extrusion energy showed a positively linear correlation between particle size and energy consumption. The highest pellet durability was observed for pellets produced from small and mixed particle sizes. Eight different constitutive models were evaluated on their ability to simulate compression and stress relaxation, and their level of complexity. A non-linear Maxwell representation of the Standard Linear Solid (SLS) model was setup and fitted to the experimental compression data. The model coefficient of spring 1 composes the asymptotic stress level of the relaxed pellet, and the coefficient of spring 2 was found to be positively correlated with particle size. The viscosity of the dashpot is also found to be positively correlated with particle size, likewise it depends on the compression speed, where higher compression speed resulted in lower viscosities. The results of the study elucidate new insight into mechanical behavior of biomass particle compression, and the resultant simulations have utility for predicting the pressure requirements to produce pellets.

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