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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.
- Benefits and drawbacks of energetic valorisation of Eucalyptus Globulus stumps by thermochemical processesPublication . Pinto, Filomena; Andre, Rui N.; Lopes, Helena; Neves, Diogo; Varela, Francisco; Santos, João Navalho; Miranda, Migueln the pulp and paper industry in Iberian Peninsula there is an intensive use of eucalyptus globulus that has a fast growth and a high productivity. There are large areas of forest dedicated to its growth. After 9 to 12 year rotation cycles trees are cut and the stumps are left in the fields. After 2 or 3 harvesting cycles these tree stumps are removed from the fields and considered low value biomass wastes. This corresponds to depletion on organic matter and of valuable minerals related to soil fertility. The use of these biomass wastes in thermochemical conversion processes like gasification or combustion may be a valuable alternative solution as it allows taking profit of these wastes energetic content. The solid by-products obtained by thermal conversion (ashes) may be incorporated in soils to return the valuable minerals and to ensure a good forest management system. Stumps removed from eucalyptus stands were used in combustion trials to improve the burning conditions and in gasification tests with different experimental conditions to obtain syngas suitable to be used in furnaces (chemical recover) of pulp industries. Stumps combustion and gasification processes were compared in terms of stumps energetic valorisation, gaseous emissions and gasification gas utilisation.
- Comparison of a pilot scale gasification installation performance when air or oxygen is used as gasificatio mediumPublication . Pinto, Filomena; Gulyurtlu, Ibrahim; Andre, Rui N.; Lopes, Helena; Franco, Carlos
- Comparison of co-gasification of wastes mixtures obtained from rice production wastes using air or oxygenPublication . Pinto, Filomena; Andre, Rui N.; Lopes, Helena; Neves, Diogo; Varela, Francisco; Santos, João Navalho; Miranda, MiguelThe world annual production of rice is higher than 700.7 million tons, which generates rice husk and straw wastes. Rice culture also produces big amounts of polyethylene (PE) bags used in rice packs and for seeds and fertilizer storage that usually end up in landfills, due to their degree of contamination. The energetic valorisation of these wastes may be accomplished by different processes, co-gasification is one of the most viable, as it leads to the production of a synthetic gaseous mixture (bio-syngas) that can be used for energy production to be used during rice milling processes. Gasification of rice husks has some challenges, due to these wastes high content of silica and alkali metals that lead to the formation of solids with lower melting point, thus, leading to bed agglomeration that causes reactor erosion and serious damage. PE has lower ash content and much higher energetic content than rice husks. However, PE polymeric structure may lead to the formation of higher tar contents, which compromise most gasification gas utilisations. Co-gasification of PE and rice husks allows taking advantages of each waste favourable characteristic, diluting the unsuitable features. Co-gasification of these wastes was done in presence of steam blended with air or oxygen. Steam promoted the gasification reactions and favoured H2 production. Air or oxygen promoted the partial oxidation of the feedstocks to be co-gasified and supplied the energy necessary for the endothermic gasification reactions. The use of air has a low cost, but has the great disadvantage of diluting the bio-syngas produced, thus lowering its energetic content. On the other hand, the use of oxygen solves the problems related to gas dilution with nitrogen, but increases the operating cost. Bio-syngas composition obtained by co-gasification trials done with air enriched with different oxygen contents was compared with those obtained with air or pure oxygen to determine the best approach considering both the technical and economical sustainability.
- Prediction of H2S and HCl formation during RDF and co-gasification in fluidized bedPublication . Gulyurtlu, Ibrahim; Pinto, Filomena; Lopes, Helena; Andre, Rui N.; Dias, Mário; Cabrita, IsabelMost solid fuels contain S and Cl and during their gasification, the formation of pollutants such as H2S and HCl becomes inevitable, however, a better understanding of the mechanism involved in their formation and subsequent destruction during the process could help to define operating conditions and to achieve synergy during co-gasification to minimize their emissions. The formation of these pollutants along with the partitioning of S and Cl in the gas and solid phases can be predicted using theoretical models in software packages like FactSage. If the tendency of H2S and HCl emissions predicted by the model corresponds to what has been observed, then an overall mechanism could be derived at using the thermochemical stability data. In this paper a comparison between numerical and experimental results is presented. The results obtained seem to suggest a relationship between the levels of sulphur in the fuels and the concentration of H2S in the gas phase, although the presence of K, Na and Ca may minimize the release of H2S. The formation of HCl seemed to be greatly affected by the inorganic matter of the fuels.