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- Gasification study of cynara cardunculus to produce hydrogen rich gasPublication . Franco, Carlos; Lopes, Helena; Pinto, Filomena; Andre, Rui N.; Gulyurtlu, Ibrahim; Cabrita, IsabelThe need to substitute fossil fuel feedstocks with endogeneous biomass to produce energy with lower environmental impact makes necessary to develop innovative and technologically more advanced processes for energy production. Gasification of Cynara cardunculus L. (cardoon) alone and mixed with Eucalyptus was carried out in a bench scale fluidized bed gasifier to study the influence of operating parameters that could lead to a gas rich in hydrogen. The gasification tests were carried out using a mixture of oxygen and steam, as gasifying agent, to avoid the dilution effect of nitrogen that exists in air. The effect of catalysts addition to the bed on gas composition was analyzed as well as the influence in the level of contaminants like H2S, HCl, NH3 and tars in the gas produced. Steam and temperature had a positive effect by promoting the hydrogen production. The higher heating value of the gas produced was determined to be in the range 12 – 15 kJ/nm3 in a dry-nitrogen-free basis. Cardoon contains N, S and Cl which may give rise to problems during the gasification process and to the eventual use of the syngas produced. The results obtained showed that the presence of contaminants could be decreased through retention in the solid phase and by employing a condensation system to separate out pollutants in the liquid phase. This paper will fully present and discuss the results obtained with the gasification of cynara cardunculus and eucalyptus in a fluidized bed gasifier.
- Evaluation of slagging and fouling tendency during biomass co-firing with coal in a fluidized bedPublication . Teixeira, P. Alexandra; Lopes, Helena; Gulyurtlu, Ibrahim; Lapa, Nuno; Abelha, PedroOver the last decades, several indices based on ash chemistry and ash fusibility have been used to predict the ash behaviour during coal combustion, namely, its tendency for slagging and fouling. However, due to the physicalechemical differences between coals and biomass, in this work only the applicability of an ash fusibility index (AFI) to the combustion and co-combustion of three types of biomass (straw pellets, olive cake and wood pellets) with coals was evaluated. The AFI values were compared with the behaviour of ash during combustion in a pilot fluidized bed and a close agreement was observed between them. For a better understanding of the mechanisms associated with bed ash sintering, they were evaluated by SEM/EDS and the elements present on the melted ash were identified. Evidences of different sintering mechanisms were found out for the fruit biomass and herbaceous biomass tested, depending on the relative proportions of problematic elements. The particles deposited on a fouling probe inserted in the FBC were analyzed by XRD and the differences between the compounds identified allowed concluding that the studied biomasses present different tendencies for fouling. Identification of KCl and K2SO4 in the deposits confirmed the higher tendency for fouling of fruit biomass tested rather than wood pellets.