Abstract
Small-scale gasification of woody biomass is a technology that has had a rapid development in the last years, mainly driven by favorable subsidization regimes. Biomass gasification process produces a minor fraction of solid carbonaceous by-product, known as char. Even though char presents chemical and physical characteristics that make it a potentially interesting and valuable product in the view of pushing gasification from a co-generative process to a poly-generative platform, economically viable solutions are not available yet and the disposal of char still represents a non-negligible cost in the plant management. For this reason, most of the recent developments in the small-scale gasification technology available in the market aim at reducing as much as possible the amount of material to be disposed, integrating into the plant an additional oxidizing section, i.e. afterburner, in order to have an outlet material stream mainly composed by ashes. The aim of the present work is to investigate an alternative solution for reducing the amount of generated char and at the same time increasing the efficiency of the whole conversion process. The proposed solution, investigated in a small-scale open-top gasifier installed at the Free University of Bolzano, is to recirculate the char inside the gasifier in order to increase the residence time and the conversion yields. © 2019 ETA-Florence Renewable Energies.