Next Article in Journal
Solar Access Assessment in Dense Urban Environments: The Effect of Intersections in an Urban Canyon
Next Article in Special Issue
Effects of Syngas Cooling and Biomass Filter Medium on Tar Removal
Previous Article in Journal
Sensitivity-Based Model of Low Voltage Distribution Systems with Distributed Energy Resources
Article Menu
Issue 10 (October) cover image

Export Article

Open AccessEditor’s ChoiceArticle
Energies 2016, 9(10), 794;

Torrefied Biomass Pellets—Comparing Grindability in Different Laboratory Mills

Deutsches Biomasseforschungszentrum gemeinnützige GmbH, Leipzig 04347, Germany
School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK
Author to whom correspondence should be addressed.
Received: 17 August 2016 / Accepted: 26 September 2016 / Published: 4 October 2016
(This article belongs to the Special Issue Woody Biomass for Bioenergy Production)
PDF [1498 KB, uploaded 4 October 2016]


The firing and co-firing of biomass in pulverized coal fired power plants around the world is expected to increase in the coming years. Torrefaction may prove to be a suitable way of upgrading biomass for such an application. For transport and storage purposes, the torrefied biomass will tend to be in pellet form. Whilst standard methods for the assessment of the milling characteristics of coal exist, this is not the case for torrefied materials—whether in pellet form or not. The grindability of the fuel directly impacts the overall efficiency of the combustion process and as such it is an important parameter. In the present study, the grindability of different torrefied biomass pellets was tested in three different laboratory mill types; cutting mill (CM), hammer mill (HM) and impact mill (IM). The specific grinding energy (SGE) required for a defined mass throughput of pellets in each mill was measured and results were compared to other pellet characterization methods (e.g., durability, and hardness) as well as the modified Hardgrove Index. Seven different torrefied biomass pellets including willow, pine, beech, poplar, spruce, forest residue and straw were used as feedstock. On average, the particle-size distribution width (across all feedstock) was narrowest for the IM (0.41 mm), followed by the HM (0.51 mm) and widest for the CM (0.62 mm). Regarding the SGE, the IM consumed on average 8.23 Wh/kg while CM and HM consumed 5.15 and 5.24 Wh/kg, respectively. From the three mills compared in this study, the IM seems better fit for being used in a standardized method that could be developed in the future, e.g., as an ISO standard. View Full-Text
Keywords: grindability; torrefied biomass; pellet; energy consumption; co-firing grindability; torrefied biomass; pellet; energy consumption; co-firing

Graphical abstract

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Supplementary material


Share & Cite This Article

MDPI and ACS Style

Khalsa, J.H.A.; Leistner, D.; Weller, N.; Darvell, L.I.; Dooley, B. Torrefied Biomass Pellets—Comparing Grindability in Different Laboratory Mills. Energies 2016, 9, 794.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Energies EISSN 1996-1073 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top