International audienceTorrefaction is a thermal pretreatment of lignocellulosic biomass before gazification. This mild form of pyrolysis, carried out at temperatures between 200 and 300 °C, changes the physical and chemical properties of the material. In particular, it improves the feedstocks homogenization, enhances the fluidization ability and makes the grinding easier. Our project deals with the study of the effects of the combined torrefaction and grinding processes on (i) the main particle behavior: anhydrous weight loss (AWL), grindability, particle size distribution (ii) and the main powder behavior: bulk densities, flowability and compressibility. The studied parameters are (i) the species of the biomass (spruce and beech) (ii) the torrefaction temperature (iii) and the sieving grid size of the used knife mill (0.12 and 0.5 mm). The characterization of the particles and powders is performed using the following techniques: optical microscope and powder rheometer. The rheological behaviours of spruce torrefied at different temperatures and ground at different grid sizes are compared. It is shown that spruce torrefied at 240 °C and ground at 0.5 mm (S240/0.5) has rheological properties not as good as S240/0.12 and S300/0.5 that seem to have similar characteristics. Finally, further experiments are necessary to obtain a better morphological and rheological particle characterization
