Gasification characteristics of sawdust char at a high-temperature steam atmosphere

Abstract

Gasification characteristics of sawdust char at a high-temperature steam atmosphere were experimentally studied in a fixed bed reactor. The char was prepared at 600–1400 °C. The effects of temperature, steam flow rate, reaction time and char preparation temperature on conversion rate, the composition of product gas, the pore structure of char and ash, as well as kinetics were analyzed. Gas chromatography, scanning electron microscopy, and a specific surface area analyzer were utilized to measure the composition of the gas, the surface morphology, and the specific surface area of the char and ash. Results show that the carbon conversion rate increases with temperature, steam flow rate, and reaction time. At 800–1200 °C, H2 content in product gas increases from 53.08% to 60.01%, and CO increases from 15.35% to 21.87%, while both CH4 and CO2 decrease. At 0.94–2.61 g/min, H2 in the product gas rapidly increases, but since CO decreases, H2 and CO slightly decrease. The specific surface area of sawdust ash increases to 948.84 m2/g and 987.61 m2/g at 800 °C and 1000 °C, respectively, on account of the fact that new micropores are generated, but it reduces to 520.76 m2/g at 1200 °C as a result of the decrease of micropores and mesopores. The surface reaction controlled shrinking core model can describe high-temperature steam gasification reaction of sawdust char.