Influence of operating conditions on the steam gasification of biomass in a conical spouted bed reactor

Abstract

Pinewood sawdust has been gasified by using steam as gasifying agent in a conical spouted bed reactor operating in continuous regime. A study has been made of the effect of temperature (in the 800–900°C range), steam/biomass ratio (between 0 and 2) and sawdust particle size (0.3–1, 1–2 and 2–4mm ranges) on the distribution of products (gas, tar and char) and their composition has been studied. Temperature has a positive effect on the gas composition by increasing H2 content and reducing that of CO. Furthermore, the tar and char yields are reduced as gasification temperature is higher. An increase in steam/biomass ratio from 0 to 1 has a positive effect on hydrogen concentration, char gasification and tar reforming, and a further increase in this parameter from 1 to 2 gives way to only a limited improvement in the results. Sawdust particle diameter plays a minor role in the gasification process in the temperature range studied, which must be attributed to the high heat transfer rate in the bed. Thus, this technology allows operating with coarse sawdust particles without reducing the syngas yield. However, the reduced gas residence time gives way to a high tar yield.