Effects of different pretreatment methods on the grindability of pitch pine sawdust biomass and its blends with coal

Abstract

Using biomass to produce energy is becoming a more desirable approach to environmentally sustainable energy production. However, there are currently several obstacles to efficient exploitation of this fuel source. In this study, the effects of torrefaction and ash reduction on the grindability of pitch pine sawdust (PSD) and its blends with coal were investigated. The particle size distributions after grinding, Hardgrove grindability index (HGI), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) results of the fuels treated by the different methods were compared. The results indicated that ash reduction improved the grindability of raw PSD better than torrefaction, whereas torrefaction improved the grindability of ash-reduced PSD. Biomass particles produced by ash reduction generated high electrostatic forces and were relatively small. The SEM and BET results showed that the particles pretreated by ash reduction and torrefaction lost their characteristic fibrous structure and had a higher pore volume and surface area after grinding. The particle size distributions of the coal- PSD blends were between those of coal and biomass. Both the 10 wt.% raw and ash-reduced PSD-coal blends exhibited similar grinding behaviors to pure coal after torrefaction. Therefore, ash reduction and torrefaction improved the grindability of single biomass fuels and coal-PSD blends.