Torrefaction and pelletisation of biomass feedstocks

BO2-technology
Torrefaction is the process of mild pyrolysis between 200-300°C. The Energy research Centre of the Netherlands (ECN) has developed a torrefaction-based technology for biomass upgrading into high-quality solid fuel, called BO2-technology. It consists of an innovative torrefaction technology concept in combination with densification. It enables energy-efficient and cost-effective production of 2nd generation fuel pellets with superior properties in terms of high energy density, excellent grindability and water repellant nature, enabling outdoor storage. Together with industrial partners, the technology is now in the demonstration phase, to be followed by global market introduction.

Quality of torrefaction pellets
The quality of torrefaction pellets depends on the biomass feedstock and the torrefaction and pelletisation production conditions. The quality can be tuned to the requirements set by the logistics chain and the end-user. ECN offers to produce on demand pellets from any biomass feedstock that can be processed in the reactor under well-controlled torrefaction conditions. Upon request, products can be delivered in non-pelletized form as well.

Quantities up to several kilograms per set of conditions are produced in bench-scale equipment. Production of up to several tones is performed in a 50-100 kg/hr continuous torrefaction reactor. Products can be produced under well controlled conditions for different sets of conditions. Optionally the condensable volatiles can be recovered for further investigations. 

Assessment
Over the last ten years, ECN gained extensive knowledge with respect to torrefaction and densification, including the requirements set by logistics and end-use applications like combustion and gasification. 

ECN offers to assist in the assessment of the different end-use applications and the demands that these set to the quality of torrefaction pellets. This can include the often done characterization of samples produced by third parties.

FAQ
Is there an optimal torrefaction condition?
There may not be a singular optimal torrefaction condition; each application or each feedstock may require a different product. Focus can be on heating value, but also on energy efficiency, pellet durability and density, hydrophobicity and grindability.

Is pelletisation the only densification option?
For certain types of biomass feedstocks and/or end-use applications briquetting may be more attractive. ECN is involved in the development of this option as well.

What feedstock can be torrefied?
Torrefaction can be applied to upgrade all (pre-dried) lignocellulosic biomass as well as biomass/plastic mixtures. Tests have been conducted for a wide variety of streams like bagasse, grass seed hay, road side grass, straw, beech, poplar, willow, larch, pine, spruce, forestry residues, palm oil residues, RDF and SRF.
 

More information
Together with you, ECN can discuss and put together a test programme that covers a variety of operating conditions to meet your requirements. For information about production of batches of BO2-pellets, assessment of logistics and end-use performance and about BO2-technology demonstration and market introduction, please contact Ruud van den Brink.