A two-zone solar-driven gasifier concept: Reactor design and experimental evaluation with bagasse particles

A two-zone solar reactor concept for the steam-based gasification of biomass particles using concentrated solar energy has been developed and experimentally evaluated with particles of sugarcane bagasse at a 1.5 kW solar input scale. The gasifier has been designed with the objective to provide pyrolysis and gasification conditions yielding high carbon conversion into syngas and suppressing the formation of tars and gaseous hydrocarbons. It consists of two zones. In the upper drop-tube zone, a high radiative heat flux to the dispersed particles induces their fast pyrolysis. In the lower trickle bed zone, a structured packing provides the residence time and temperature required for the char gasification and the decomposition of the other pyrolysis products. A series of 20 min gasification experiments comparing the two-zone reactor vs. a drop-tube reactor were performed in a high-flux solar simulator with a maximum particle flux of 16 g/s m(2). It has been demonstrated that the former allows for more efficient decomposition of CH4 and C-2 hydrocarbons at comparable reactor temperatures. The LHV of the product gas leaving the two-zone gasifier was significantly higher than those typically obtained in conventional autothermal gasifiers. Solar energy was chemically stored in the product gas, resulting in energetic upgrade of the biomass by 5% and a maximum energy conversion efficiency of 21%. (C) 2013 Elsevier Ltd. All rights reserved.