Fast torrefaction of large biomass particles by superheated steam: Enhanced solid products for multipurpose production

Conventional torrefaction technology upgrade biomass for improved storage or as pretreatment prior to combustion or pyrolysis, and are generally performed on small-scale particles. Superheated steam (SHS) as the carrier gas and sole heat source was proposed to heat biomass rapidly and evenly while generating intensively torrefied biomass. This work revealed the potential of SHS torrefaction to upgrade large wood particles (Phi = 30 mm, H = 60 mm), to improve the feedstock suitability and expand products diversity in torrefaction technology. The effects of SHS torrefaction at different depths in large particles were investigated. A torrefaction time of 30 min was deemed capable of upgrading even the inner sections of large particle to have appropriate fuel properties. The HHV of the torrefied biomass enhanced by 50% reaching 28.76 MJ kg(-1). Combustion and pyrolysis behaviour of torrefied biomass demonstrated their properties as benign fuel and pyrolysis feedstock, respectively. Moisture absorption (from 13.52 to 3.42 wt%) and grindability results (386.96-10.52 kWh ton(-1)) indicated that large particles from SHS torrefaction were easy for handling, transportation, and storage. The investigation of physicochemical properties at different depths of the torrefied biomass helped to understand SHS torrefaction behaviour in large biomass particles, hence, to control the reaction extent in the desired end product. (C) 2021 Elsevier Ltd. All rights reserved.