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Research article - Peer-reviewed, 2021

Pelleting torrefied biomass at pilot-scale – Quality and implications for co-firing

Agar, David; Rudolfsson, Magnus; Lavergne, Simon; Melkior, Thierry; Da Silva Perez, Denilson; Dupont, Capucine; Campargue, Matthieu; Kalen, Gunnar; Larsson, Sylvia;

Abstract

The co-firing of solid biofuels in coal plants is an attractive and fast-track means of cutting emissions but its potential is linked to biomass densification. For torrefied materials this topic is under-represented in literature. This pilot-scale (121–203 kg h−1) pelleting study generated detailed knowledge on the densification of torrefied biomass compared to untreated biomass. Four feedstock with high supply availability (beech, poplar, wheat straw and corn cob) were studied in their untreated and torrefied forms. Systematic methods were used to produce 180 batches of 8 mm dia. pellets using press channel length (PCL) and moisture content (MC) ranges of 30–60 mm and 7.3–16.6% (wet basis) respectively. Analysis showed that moderate degrees of torrefaction (250–280 °C, 20–75 min) strongly affected pelleting behaviour. The highest quality black pellets had a mechanical durability and bulk density range of 87.5–98.7% and 662–697 kg m−3 respectively. Pelleting energy using torrefied feedstock varied from −15 to +53 kWh t−1 from untreated with increases in production fines. Optimal pelleting MC and PCL were reduced significantly for torrefied feedstock and pellet quality was characterised by a decrease in mechanical durability and an increase in bulk density. Energy densities of 11.9–13.2 GJ m−3 (as received) were obtained.

Keywords

Torrefaction; Durability; Energy density; Densification; Pelletization; Bio-coal

Published in

Renewable Energy

2021, volume: 178, pages: 766-774

Authors' information

Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology
Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology
Lavergne, Simon
RAGT Energie
Melkior, Thierry
Université Grenoble Alpes
Da Silva Perez, Denilson
Institut technologique FCBA
Dupont, Capucine
IHE Delft Institute for Water Education
Campargue, Matthieu
RAGT Energie
Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology
Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology

Sustainable Development Goals

SDG7 Affordable and clean energy
SDG13 Climate action

UKÄ Subject classification

Renewable Bioenergy Research
Chemical Process Engineering

Publication Identifiers

DOI: https://doi.org/10.1016/j.renene.2021.06.094

URI (permanent link to this page)

https://res.slu.se/id/publ/112634