Investigation of CaO Influences on Fast Gasification Characteristics of Biomass in a Fixed-bed Reactor

Abstract

The CaO was added into the sawdust with different mass ratios of 1%, 5% and 10% respectively for biomass gasification in a fixed-bed reactor at a temperature from 600 to 900 °C, and combining the micro-characterizations with SEM and XRD, the mechanisms of CaO as tar pyrolysis catalyst and carbon absorbent during gasification process were also investigated. It was found that at 700 °C the volume fraction of H2 could reach 44% with 10% CaO added, meanwhile, the condition with 5% CaO added at 700 °C was found to be the best one due to its higher tar removal rate, lower CO2 release and higher released combustible gas amounts. Moreover, the tar yield decreased due to intense pyrolysis reaction with the increasing reaction temperature, but above 800 °C the CaCO3 produced by absorbing CO2 would undergo severe decomposition reaction, which will reduce the activity of calcium oxide, and the excess CaO could also play a role during the combustion process, and as a result lead to the decreased quality of combustible gaseous products.