Studies of Biochars Generated from Pilot-Scale Downdraft Gasification

Abstract

<abstract><title><italic>Abstract.</italic></title> Biochars were generated with a pilot-scale downdraft gasifier using wood chips as the raw material. Biochars were collected from the bottom of the gasifier (coarse char) and from the filter (fine char). They were characterized by scanning electron microscopy (SEM), elemental analysis, thermogravimetric analysis (TGA), and higher heating value (HHV) and compared with the raw material and commercial activated carbon. Coarse char showed a larger average particle size than fine char. Coarse char also had higher carbon content (47.2%) than fine char (32.4%). Both biochars had much lower carbon content but higher mineral content than commercial activated carbon (Filtersorb 200; 88.1%). Both coarse char and fine char retained considerable HHV (14.5 and 10.0 MJ kg^-1 respectively), but their HHVs were lower than that of wood chips (17.7 MJ kg^-1) and much lower than that of Filtersorb 200 (30.7 MJ kg^-1). Fine char showed higher thermal stability than coarse char. Both biochars were more thermally stable than wood chips but less stable than activated carbon.