Exploration of supercritical water gasification of biomass using batch reactor

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The focus of this study is on gasification of a biomass in supercritical water. Vapor mass yield in a batch reactor after 20 minutes in a 700°C furnace in air and supercritical water for a wide variety of biomass samples showed that the supercritical water enhanced the gasification efficiency, as it participates as both a solvent and a reactant. The heat of combustion and the heat of gasification had good correlation with the oxidation state of the carbon atom in each biomass sample and proved that thermodynamic changes of state are functions of elemental composition (oxidation state of the carbon atom). The gasification efficiency did not correlate with the oxidation state, concluding that biomass gasification efficiencies are similar for all types of biomass. The temperature and residence time are important operating parameters for supercritical water gasification. The vapor yield, gas composition, the carbon and hydrogen balance of supercritical water gasification were functions of gasification temperature, residence time and biomass load (concentration). Nano particle coating of sawdust enhances the vapor yield of sawdust. Supercritical water gasification of biomass at different heating rates showed that the vapor yield was found to depend on the time of heating during the initial period and later the heating rate played the major role. Modeling of thermochemical reactions in a batch reactor was described and used to estimate reaction order and activation energy for supercritical water gasification of ethanol, butanol and algae.