An Innovative Experimental Pilot-Plant to Investigate the Gasification Process of Biomass Impact of Raw and Torrefied Pellet on the Process Performances

In this paper the results of an experimental study on gasification process are presented. A small batch reactor, using air as gasification agent, has been suitable designed to investigate the gasification of both raw and torrefied biomass (spruce) densified in form of pellet (P). The novelty of this study consists in the continuous monitoring of the biomass lost amount (gasified biomass) by placing the reactor, appropriately instrumented, on a suitable scale. Thanks to this simple expedient, it has been possible to rework the mass and energy balances of the process as if they accord to those of a continuous steady-state updraft fixed-bed configuration. The experimental results have been processed by elaborating a dedicated procedure that has allowed to turn the quantities expressed in term of mass amount, such as the treated biomass and the char production, into mass flow rate quantities. This study highlights the role of the air flow rate ˙ Va,wb as guiding parameter through which the performance indexes of the process as cold gasification (ηC) and carbon conversion (ηCC) efficiencies, syngas (Ys) and power to biomass (Ypb) yields can be assessed. Within the selected ˙ Va,wb ranges: 15–25 Nl.min 1 for raw wood pellet (WP) and 15–30 Nl.min 1 for torrefied pellet (TP), the reactor gasification power (Pgr) sets within: 1,45-2,18 kW for WP and 1,66-3,23 kW for TP. Furthermore, the results demonstrate the fundamental role of the char layer in improving the quality of the Low Heating Value (LHV) of the produced syngas in turn also conditioned by the selected ˙ Va,wb values. As general outcome, the performances results more promising for TP than WP. Both the experimental approach and the proposed elaboration procedure provide an alternative methodology that could contribute to improve the design procedures to enhance the exploitation of this technology within the current renewable energy scenarios