Biomass samples (pine, black poplar and chestnut woodchips) were torrefied to improve their grindability before being combusted in blends with coal. Torrefaction temperatures between 240 and 300 °C and residence times between 11 and 43 min were studied. The grindability of the torrefied biomass, evaluated from the particle size distribution of the ground sample, significantly improved compared to raw biomass. Higher temperatures increased the proportion of smaller-sized particles after grinding. Torrefied chestnut woodchips (280 °C, 22 min) showed the best grinding properties. This sample was blended with coal (5–55 wt.% biomass). The addition of torrefied biomass to coal up to 15 wt.% did not significantly increase the proportion of large-sized particles after grinding. No relevant differences in the burnout value were detected between the coal and coal/torrefied biomass blends due to the high reactivity of the coal. NO and SO2 emissions decreased as the percentage of torrefied biomass in the blend with coal increased.This work was part of the subcontracted contribution of INCAR to a project carried out by EDP Spain with the financial support from the European Regional Development Fund (ERDF) and acting IDEPA (Economic Development Agency of the Principality of Asturias) as research funding agency (Ref.: IDE/2013/000233). The authors thank A. J. Martín, member of the PrEM group at INCAR-CSIC, for his contribution.Peer reviewe
