Torrefaction of Biomass Upgrading

ABSTRACT: Torrefaction is a mild pre-treatment of biomass at a temperature between 200-300 °C. During torrefaction the biomass its properties are changed to obtain a much better fuel quality for combustion and gasification applications. In combination with pelletisation, torrefaction also aids the logistic issues that exist for untreated biomass. This paper treats the principles of torrefaction and production technology that is under development at ECN (TOP technology for the production of TOP pellets from biomass). Attention is also paid to the process its economics and its influence on the economics of a biomass-to-energy production chain. Torrefaction of biomass is an effective method to improve the grindability of biomass to enable more efficient co-firing in existing power stations or entrained-flow gasification for the production of chemicals and transportation fuels. Torrefaction by means of the TOP process leads to a very energy dense fuel pellet of 15-18.5 GJ/m3. Typically, the process has a thermal efficiency of 96 % and the total production costs amount 40-50 €/ton of TOP pellets. The logistic costs amount 50%-66% the costs involved with wood pellets