Effects of warm water washing on the fast pyrolysis of Arundo Donax

Abstract

This work reports how warm water washing of biomass affects fast pyrolysis. Specifically, we applied this concept to Arundo donax, a common herbaceous biomass, and studied the washing effects on fast pyrolysis yields in a Py-GC/MS and a fluidized bed reactor. We stir-washed samples in water at 20 °C, 40 °C and 60 °C, and found that water at 60 °C led to an 18% increase in the removal of ash and an 11% increase in the removal of potassium compared to a room temperature wash. We pyrolyzed these samples via Py-GC/MS-FID and found that the reduction in ash increased the pyrolysis yields of acetol, furanone and levoglucosan relative to the unwashed samples. Additionally, we pyrolyzed washed A. donax in a fluidized bed reactor and compared the results to those of unwashed A. donax. We found that A. donax washed at 60 °C produced 9.7 wt% more bio-oil than unwashed, with increases in glycolaldehyde and levoglucosan yields of 0.78 wt% and 1.24 wt%, respectively. The yield of olefinic gases increased by 0.22 wt% and yields of carbon dioxide and alkane gases decreased 2.40 wt% and 0.11 wt% respectively. Char and water yields decreased 4.32 wt% and 10.08 wt% respectively. The gas produced from pyrolysis of washed A. donax has a greater HHV than that from unwashed A. donax (7.77 MJ/kg vs. 6.81 MJ/kg). We believe these results are a consequence of differences in the extent of secondary reactions catalyzed by the inorganic species present in herbaceous biomass.