TY - JOUR
TI - Combined organic acid leaching and torrefaction as pine wood pretreatment before fast pyrolysis
AU - Westerhof Roel
AU - Oudenhoven Stijn
AU - Hu Xun
AU - Van Swaaij Wim
AU - Kersten Sascha
JN - Thermal Science
PY - 2019
VL - 23
IS - 15
SP - 1403
EP - 1411
PT - Article
AB - Reducing pine wood particle size is beneficial for acid leaching (shorter  leaching time, smaller equipment size) and also for pyrolysis (low pyrolysis  time, high oil and sugar yields). Torrefaction helps to improve the energy  efficiency of grinding. However, it is not well established whether Alkali  and Alkaline Earth Metals (AAEM’s) can still be removed effectively, after  torrefaction, by leaching with an acetic acid solution, while keeping high  oil and sugar yields. To investigate this, an experimental study was carried  out combining torrefaction (290°C, 20 minutes) and subsequently acid  leaching of pine wood as pretreatment step before fast pyrolysis of the  feedstock at 530°C. The oil, char, gas, water, pyrolytic lignin, light  oxygenates and levoglucosan yields were compared with the results obtained  from fast pyrolysis of untreated pine wood and acid leached pine wood at  530°C. In addition, pyrolysis vapors were condensed step-wise into two  distinguished fractions (condensation T=80oC) to increase the levoglucosan  concentration up to 45 wt% with or without applying torrefaction as  pretreatment. Intra-particle reactions during torrefaction are more  profound in the presence of AAEM’s. Cellulose and Lignin derived products  (e.g. levolucosan (~0.2 kg/kg pine wood) and pyrolytic lignin (~0.11 kg/kg  pine wood) were not affected by the torrefaction pre-treatment of acid  leached pine wood. In general, torrefaction of acid leached pine wood  followed by fast pyrolysis showed similar total organics, char, gas, light  oxygenates and produced water yields compared to fast pyrolysis of acid  leached pine wood. Contrary, when acid leaching is applied after  torrefaction the organics (dry bio-oil) and light oxygenates yields are  quite comparable to the results of untreated pine wood fast pyrolysis.