Experimental and CFD investigation of inert bed materials effects in a high-temperature conical cavity-type reactor for continuous solar-driven steam gasification of biomass

Abstract

Solar biomass gasification was performed in a high-temperature conical bed reactor for thermochemical syngas production, which represents an efficient route to promote biomass valorization while storing intermittent solar energy into carbon–neutral solar fuels. The developed solar reactor is based on a conical cavity-type receiver enabling continuous biomass feedstock injection under real concentrated solar irradiation. In this study, the use of inert bed materials is considered to directly absorb a portion of the entering solar power and to transmit thermal energy to the gas and reactive particulate phase by radiation, convection and particle-to-particle interactions, with the aim of homogenizing the reactor temperature. A fluid dynamics study of the gas/particle flow was first performed to provide insights into the reactor hydrodynamics in the case of empty cavity and cavity containing inert particles in the forms of packed-bed and spouted-bed. The beneficial effect of the inert particles bed was emphasized. The spouted bed particles play a role in retaining the reacting biomass particles longer inside the reaction zone and promote phase mixing, as also confirmed by cold tests on a replicated transparent mockup cavity. Different inert particle bed materials were then considered and experimentally tested to unravel their impact on the biomass conversion, syngas composition and yield, and gasification performance in the solar-heated reactor operated at 1200 °C and 1300 °C.