Combustion kinetics and particle fragmentation of raw and torrified pine shells and olive stones in a drop tube furnace

This study focuses on the combustion kinetics and particle fragmentation of raw and torrified pine shells and olive stones in a drop tube furnace (DTF). The two biomass fuels studied have been torrified in a nitrogen inert atmosphere at 280-300 degrees C. Both raw and torrified biomass fuels were then burned in the DTF. The data reported includes gas temperature and particle burnout measured along the DTF for five furnace temperatures (900, 950, 1000, 1050 and 1100 degrees C). In addition, measurements of particulate matter (PM) concentrations and size distributions were made for all the biomass fuels at 1100 degrees C in the middle and near the exit of the DTF. The results showed that: (1) The high heating value of the torrified biomass fuels are higher than those of the raw biomass fuels; specifically, for pine shells it increased by 25% and for olive stones by 18%; (2) in contrast with the torrefied olive stones, the torrified pine shells require similar residence times to attain overall burnout values comparable to those of the untreated material; (3) the kinetic data for both fuels, raw and torrified, indicates that the torrefaction reduces the activation energy of the present biomass chars; and (4) torrefaction does not promote particle fragmentation even for biomass fuels that present high tendency for it. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.