Abstract
The first part of the current reported work presents experimental results of brewers’ spent grains gasification in a pilot-scale downdraft gasifier. The gasification procedure is assessed through various process characteristics such as gas yield, lower heating value, carbon conversion efficiency, and cold gas efficiency. Power production was varied from 3.0 to 5.0 kWh during the gasification experiments. The produced gas was supplied to an internal combustion engine coupled to a synchronous generator to produce electricity. Here, 1.0 kWh of electricity was obtained for about 1.3 kg of brewers’ spent grains pellets gasified, with an average electrical efficiency of 16.5%. The second part of the current reported work is dedicated to the development of a modified thermodynamic equilibrium model of the downdraft gasification to assess the potential applications of the main Portuguese biomasses through produced gas quality indices. The Portuguese biomasses selected are the main representative forest residues (pine, eucalyptus, and cork) and agricultural residues (vine prunings and olive bagasse). A conclusion can be drawn that, using air as a gasifying agent, the biomass gasification provides a produced gas with enough quality to be used for energy production in boilers or turbines.
Highlights
Population and incomes rising will continue to push up the global energy demand, according to the International Energy Agency (IEA) [1]
The results suggest a good potential of brewer’s spent grains (BSG) for bio-oil production due to their high heating value and high volatile matter content
The equivalence ratio was computed as the ratio between the actual oxygen added to the gasifier and the stoichiometric oxygen needed for the complete combustion of the biomass
Summary
Population and incomes rising will continue to push up the global energy demand, according to the International Energy Agency (IEA) [1]. Spent grain is generated in the beer-brewing process, which begins with the production of the wort. Ulbricha et al [11] studied the influence of temperature and residence time on the hydrothermal carbonization and carbon dioxide gasification of brewers’ spent grains. The temperature increase leads to increased CO and H2 contents and decreased CH4 and CO2 contents Another possible route of valorization for BSG is downdraft gasification, which is a proven technology and a low-cost process with the additional advantage of generating very low tar levels [19]. The second part of this work is dedicated to the development of a modified thermodynamic equilibrium model of the downdraft gasification to assess the potential application of the main Portuguese biomasses through produced gas quality indices
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