Browsing by Author "Gulyurtlu, Ibrahim"
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- Carbon-based materials prepared from pine gasification residues for acetaminophen adsorptionPublication . Galhetas, M.; Mestre, A. S.; Pinto, Moisés L.; Gulyurtlu, Ibrahim; Lopes, Helena; Carvalho, A. P.Fly ash, a residue produced frompine gasification,was used as precursor of carbon-basedmaterials assayed in acetaminophen adsorption. Materials prepared by activation with K2CO3, presented high porosity development (ABET 1200m2 g1) and samples calcined at 900 C presented high volumes of large micropores and mesopores. Kinetic and equilibrium acetaminophen adsorption data showed that the process obeys to the pseudo-second order kinetic equation and Langmuir model, respectively. The rate of acetaminophen adsorption depends of the presence of larger micropores. For the lab-made samplesmonolayer adsorption capacities attained values similar to those of commercial carbons. The influence of themicropore size distribution of the carbons in the acetaminophen adsorption process justified the lower adsorption affinities of the lab-made carbons. The importance of pores of a specific dimension (0.7 nm) to enhance the affinity of the molecule towards the carbon surfacewas demonstrated. The increase of temperature lead to highermonolayer adsorption capacities, most likely due to the easier accessibility of the acetaminophen species to the narrowest micropores.
- Chars from gasification of coal and pine activated with K2CO3: Acetaminophen and caffeine adsorption from aqueous solutionsPublication . Galhetas, M.; Mestre, A. S.; Pinto, Moisés L.; Gulyurtlu, Ibrahim; Lopes, Helena; Carvalho, A. P.The high carbon contents and low toxicity levels of chars from coal and pine gasification provide an incentive to consider their use as precursors of porous carbons obtained by chemical activation with K2CO3. Given the chars characteristics, previous demineralization and thermal treatments were made, but no improvement on the solids properties was observed. The highest porosity development was obtained with the biomass derived char (Pi). This char sample produced porous materials with preparation yields near 50% along with high porosity development (ABET 1500 m2 g1). For calcinations at 800 C, the control of the experimental conditions allowed the preparation of samples with a micropore system formed almost exclusively by larger micropores. A mesopore network was developed only for samples calcined at 900 C. Kinetic and equilibrium acetaminophen and caffeine adsorption data, showed that the processes obey to a pseudo-second order kinetic equation and to the Langmuir model, respectively. The results of sample Pi/1:3/800/2 outperformed those of the commercial carbons. Acetaminophen adsorption process was ruled by the micropore size distribution of the carbons. The caffeine monolayer capacities suggest a very efficient packing of this molecule in samples presenting monomodal micropore size distribution. The surface chemistry seems to be the determinant factor that controls the affinity of caffeine towards the carbons.
- Chemical and ecotoxicological properties of ashes produced in the co-combustion of coal and sewage sludgePublication . Barbosa, Rui; Lapa, Nuno; Boavida, Dulce; Lopes, Helena; Mendes, Benilde; Gulyurtlu, Ibrahim
- CO2 and NOx reduction in combustion systemsPublication . Cabrita, Isabel; Azevedo, Pedro; Gulyurtlu, Ibrahim
- 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
- Development of advanced characterisation tools for the prediction of reburn performance in PF combustors: 3rd annual reportPublication . Carapau, Nuno; Bent, Raquel; Azevedo, Pedro; Gulyurtlu, Ibrahim; Boavida, Dulce
- Effect of syngas composition on hydrogen permeation through a Pd–Ag membranePublication . Pinto, Filomena; Andre, Rui N.; Franco, Carlos; Carolino, Carlos; Gulyurtlu, IbrahimHydrogen separation from a syngas mixture with different compositions was studied by using a Pd–Ag membrane. The effect of temperature (from 300 C to 600 C) and of relative pressure (from 0.2 MPa to 0.5 MPa) was studied. In general, rises of both these parameters allowed increasing H2 permeate flux. The Pd–Ag membrane showed to have a great selectivity, as when inlet gas mixture contained different compositions of CO2, CO or CH4, these gases were never detected in membrane permeate side. However, when hydrogen content in inlet gas decreased, a significant reduction in H2 permeate flux was observed, especially when CO was present, probably due to the deposition of solid carbon in membrane surface by Boudouard reaction. It was also observed the formation of hydrocarbons, due to CO and H2 reactions. H2 permeances were calculated by application of Sieverts’ law and values between 4.9 10 4 and 1.5 10 3 mol m 2 s 1 Pa 0.5 were obtained. The highest value was obtained at 600 C. H2 permeances at different temperature followed Arrhenius’ equation. Thus, activation energies values between 11.5 kJ mol 1 and 14.0 kJ mol 1 were calculated.
- 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.
- Evaluation of the environmental hazard of char residues produced in the co-pyrolysis of different wastes :chemical and ecotoxicological characterizationPublication . Bernardo, Maria; Lapa, Nuno; Gonçalves, Maria Margarida; Barbosa, Rui; Mendes, Benilde; Pinto, Filomena; Gulyurtlu, IbrahimChar residues produced in co-pyrolysis of different wastes were characterized through chemical and toxicity tests. A fraction of the solid chars was treated by extraction with dichloromethane. Different volatilit fractions present in the extracted and non extrated char were evaluated. A selected group of heavy metals was determined in both chars. Chars were subjected to the leaching test ISO/TS 21268-2 and resulting eluates were further characterized by determining a group of inorganic parameters and concentrations of several organic contaminants. An ecotoxicological characterization was performed by using the bio-indicator Vibrio fischeri. The chemical and ecotoxicological characterization led to a classification on the chars as ecotoxic
- Fluidised bed combustion of two species of energy cropsPublication . Abelha, Pedro; Franco, Carlos; Lopes, Helena; Gulyurtlu, Ibrahim; Cabrita, IsabelThe use of biomass fuels for energy production through combustion has a growing application worldwide mainly for two reasons: first, the utilization of biomass for energy contributes to mitigate emission of green house gases; second, its use decreases the dependence of imported fossil fuels in Europe. The objective of this work was to study the combustion behaviour of two endogenous biomass species: cardoon (cynara cardunculus) and arundo (arundo donax), which were specially produced in energy crops plantations. Mixtures of cardoon and a forestry biomass specie (eucalyptus) were also studied to evaluate potential benefits from synergies between both biomass fuel types. The results showed that the utilization of cardoon, in pelletized form, and loose arundo as feedstock, did not give rise to any operational problems related with the feeding system. It was verified that the mono combustion of cardoon could pose problems at industrial scale in fluidised bed systems, considering the high levels of HCl and NOX emissions obtained and tendency to sinter the bed sand material. The addition of the forestry biomass to cardoon appeared to prevent the bed agglomeration problem. Furthermore, both the NOX and SO2 emissions were found to decrease at the same time suggesting potential synergy of blending different types of biomass regarding pollutant emissions and in bed agglomeration problems.
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