Effect of water vapour and biomass nature on the yield and quality of the pyrolysis products from biomass

Slow pyrolysis/activation of biomass in a flow of steam is studied in labor atory equipment supplied with a fixed bed reactor. Forestry and agricultura l residues of different origin are selected as raw materials (birch wood, o live stones, bagasse, pelletised straw and miscanthus). The final pyrolysis temperature is varied in the range 700-800 degreesC and the duration of th e activation is 1 or 2 h. The effect of both the nature of the investigated biomass samples and the presence of water vapour on the quality of the pyr olysis products is in the focus of interest of this work. Column chromatogr aphy is used to characterize the liquid products. The surface area and the acid-base neutralization capacity of the solid products are determined by t he adsorption capacity towards iodine and reactions with EtONa and HCl. The results are compared with those obtained in pyrolysis in inert atmosphere of nitrogen. It is shown that the presence of steam has strong effect on th e yield and properties of the products. Significant part of the liquid prod uct is found dissolved in the water phase obtained after condensation of th e volatiles. The solid products obtained in the presence of steam have the properties of activated carbons. (C) 2001 Elsevier Science B.V. All rights reserved.