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.