Elucidation of Char Combustion Behaviors for Various Types of Biomass by Reaction Kinetic Analysis

Abstract

Although the fixed carbon content in biomass is generally lower than that of volatile matter, the combustion duration of the fixed carbon occupies a longer portion of the overall combustion process, compared to the release and combustion of volatile matter. Therefore, this study elucidated the combustion behaviors of biomass char experimentally and from kinetically. The combustion characteristics of various types of biomass char in air were quantitatively examined, using thermogravimetric analysis. The biomass char samples were produced under a nitrogen atmosphere at 1173 K, after which the atmosphere was switched to air to observe the char combustion behavior. The biomass samples employed in this study included softwood, hardwood, parts of palm and sorghum. Additionally, the content of major biomass components like lignin, hemicellulose and cellulose was analyzed. The crystal structure of the produced char was also analyzed to discuss their influence on the combustion behavior of the char. As a result, biomass with a higher lignin content in the biomass raw material tended to have longer char combustion durations. Additionally, biomass char containing a graphitic structure showed a tendency for prolonged combustion times. The pore structure parameters obtained from kinetic analysis showed little variation among the biomass chars employed. Those findings quantitatively clarified that lignin content and crystalline structure influenced the combustion behaviors of biomass char.