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 °C. These conventional techniques often fail to collect accurate kinetic data at temperatures above 1000 °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 °C and 1150 °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.