A novel technique for measuring the kinetics of high-temperature gasification of biomass char with steam

Solar thermal gasification of biomass is a promising technology that allows for operation at high temperature without burning a large portion of the biomass feedstock. Additionally, the process allows for solar energy to be stored and transported in chemical form. In order to design efficient solar reactors, a kinetic rate expression for high-temperature steam gasification is needed. Various methods have been used to measure the steam gasification rate of coal and biomass char at temperatures up to 1000 degrees C. These conventional techniques often fail to collect accurate kinetic data at temperatures above 1000 degrees C due to heat and mass transfer resistance, and the time constants associated with the analysis system. In this paper we discuss a novel kinetics measurement technique based on a modified fixed bed and data collected solely from a gas flow meter. The technique was used to collect kinetic rate data for switchgrass char over a range of reaction conditions between 1000 degrees C and 1150 degrees C. An empirical expression to predict the kinetic rate as a function of the degree of conversion, temperature, steam concentration, and hydrogen concentration was developed. The random pore model was used to predict the reaction rate as a function of conversion, and the initial kinetic rate was fit using a Langmuir-Hinshelwood type expression. (C) 2012 Published by Elsevier Ltd.