Supercritical water gasification of wheat straw: Composition of reaction products and kinetic study

Supercritical water gasification (SCWG) technology is a potential technology to convert solid wastes to hydrogen rich gas products. But the gasification mechanism of real biomass in SCW is unclear due to its complicated composition and unique properties of SCW. In this paper, the gasification experiment of wheat straw in SCW was conducted in a quartz tube batch reactor, and the gasification properties was analyzed through researching the variation of gas yield, composition, liquid products and surface morphology of biochar to help understand the gasification mechanism. Besides, the reaction kinetic model of wheat straw was established to provide guidance for the acceleration of its gasification. The results illustrated that the increase of reaction time can enhance the gasification obviously (CGE increased by 37% as time extended from 1 min to 15 min) and temperature became the limitation factor after 15min. Higher temperature can increase the hydrogen yield obviously, which was raised by 7.2 mol/kg within 100 °C temperature increment, and the highest hydrogen yield was 12.88 mol/kg at 700 °C, 30 min. Kinetic study illustrated that the decomposition of PAHs was the rate-controlling step of wheat straw, activation energy of which was the highest, 427.13 kJ mol⁻¹.