I. Gulyurtlu

Laboratório Nacional de Energia e Geologia, Amadora, Lisbon, Portugal

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Publications (99)139.43 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: 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≈1500m(2)g(-1)). 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.
    Journal of Colloid and Interface Science 07/2014; 433C:94-103. · 3.55 Impact Factor
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    ABSTRACT: Fly ash, a residue produced from pine gasification, was used as precursor of carbon-based materials assayed in acetaminophen adsorption. Materials prepared by activation with K2CO3, presented high porosity development (ABET ≈ 1200 m2 g−1) 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 samples monolayer adsorption capacities attained values similar to those of commercial carbons. The influence of the micropore 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 surface was demonstrated. The increase of temperature lead to higher monolayer adsorption capacities, most likely due to the easier accessibility of the acetaminophen species to the narrowest micropores.
    Chemical Engineering Journal 03/2014; 240:344–351. · 3.47 Impact Factor
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    ABSTRACT: A thermodynamic model was applied to foresee the occurrence of fouling, slagging, and bed agglomeration phenomena during fluidized bed monocombustion of three different types of biomass, namely straw pellets, olive cake, and wood pellets. The cocombustion effect in reducing the occurrence of deposits and agglomerates of blends of 5, 15, and 25% (wt.) biomass with coal was also assessed. Chemical fractionation was applied to evaluate the reactive and nonreactive fraction of elements in the fuels, which was used to estimate their partition between the freeboard and bottom zone of the boiler. Qualitative and semiquantitative analytical techniques, namely, X-ray diffraction and scanning electronic microscopy − energy dispersive spectroscopy were used to compare the results from the simulation with the mineralogical and morphological composition of ash and deposits formed during combustion. The thermodynamic modeling revealed to be a powerful tool in foreseeing the formation of melt and liquids salts, depending on the temperature and chemical composition of fuels. The main discrepancies observed between the experimental and simulated data were due to particularities of the combustion process, which are not incorporated in the software, namely, kinetic limitations of the reactions, possible occurrence of secondary reactions in the ashes, and elutriation effects of ash and silica sand particles.
    Energy & Fuels 01/2014; 28:697-713. · 2.85 Impact Factor
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    ABSTRACT: It was found a strong correlation between PCDD/F formation and the sulphur and chlorine content. Our results point to an interesting empirical model which should be further tested with more experimental data. Additionally, the attained mathematical model can be used to adjust fuel mixtures with appropriate sulphur and chlorine input in order to maintain PCDD/F emissions below the legal limits.
    1st International Congree on Bioenergy Portugal; 05/2013
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    ABSTRACT: The behavior of Cynara cardunculus L. was studied during fluidized-bed (FB) combustion and gasification. The Cynara had a low moisture content and considerable lower heating value (LHV). Cynara presented significant quantities of S, Cl, and ash, which contained high levels of Na, K, P, Ca, and Si. The fuel N conversion to NO x was high because of the large release of NH 3 and HCN during pyrolysis. The conversion of the fuel S to SO 2 was low because of S retention mainly as alkali sulfates. HCl emissions were higher than the usual legal limits imposed in European Union (EU) countries, although retentions of 40− 55% fuel Cl could be estimated. The co-combustion of Cynara with eucalyptus was tested with benefits regarding process conditions, pollutant emissions, and ash behavior, but still, the HCl concentration surpassed the legal limit. The tendency for bed agglomeration was also observed during the gasification of cardoon. Two strategies were carried out to minimize this adverse effect: (1) co-gasification of cardoon with eucalyptus and (2) addition of natural minerals to the gasification bed. The results of the first strategy caused a decrease in H 2 levels, while tar, hydrocarbon, and CO amounts were found to increase. On the other hand, the addition of natural minerals did not lead to any significant change in the major gas components, although some tar and hydrocarbon abatements were observed, with olivine being the most effective. Dolomite and ZnO gave rise to a greater reduction in HCl and sulfur compounds in the gas phase, respectively.
    Energy & Fuels 01/2013; 27:6725-6737. · 2.85 Impact Factor
  • Applied Energy 01/2013; 102:272-282. · 5.26 Impact Factor
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    ABSTRACT: This paper presents the study of the combustion of char residues produced during co-gasification of coal with pine with the aim of characterizing them for their potential use for energy. These residues are generally rich in carbon with the presence of other elements, with particular concern for heavy metals and pollutant precursors, depending on the original fuel used. The evaluation of environmental toxicity of the char residues was performed through application of different leaching tests (EN12457-2, US EPA-1311 TCLP and EA NEN 7371:2004). The results showed that the residues present quite low toxicity for some of pollutants. However, depending on the fuel used, possible presence of other pollutants may bring environmental risks. The utilization of these char residues for energy was in this study evaluated, by burning them as a first step pre-treatment prior to landfilling. The thermo-gravimetric analysis and ash fusibility studies revealed an adequate thermochemical behavior, without presenting any major operational risks. Fluidized bed combustion was applied to char residues. Above 700°C, very high carbon conversion ratios were obtained and it seemed that the thermal oxidation of char residues was easier than that of the coals. It was found that the char tendency for releasing SO(2) during its oxidation was lower than for the parent coal, while for NO(X) emissions, the trend was observed to increase NO(X) formation. However, for both pollutants the same control techniques might be applied during char combustion, as for coal. Furthermore, the leachability of ashes resulting from the combustion of char residues appeared to be lower than those produced from direct coal combustion.
    Waste Management 09/2011; 32(4):769-79. · 3.16 Impact Factor
  • 1st International Conference Wastes: Solutions, Treatments and Opportunities, Guimarães; 09/2011
  • J Morais, R Barbosa, N Lapa, B Mendes, I Gulyurtlu
    Resources Conservation and Recycling 09/2011; 55(11):1109 - 1118. · 2.32 Impact Factor
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    ABSTRACT: Two combustion tests were performed in a fluidized bed combustor of a thermo-electric power plant: (1) combustion of coal; (2) co-combustion of coal (68.7% w/w), sewage sludge (9.2% w/w) and meat and bone meal (MBM) (22.1% w/w). Three samples of ashes (bottom, circulating and fly ashes) were collected in each combustion test. The ashes were submitted to the following assays: (a) evaluation of the leaching behaviour; (b) stabilization/solidification of fly ashes and evaluation of the leaching behaviour of the stabilized/solidified (s/s) materials; (c) production of concrete from bottom and circulating ashes. The eluates of all materials were submitted to chemical and ecotoxicological characterizations. The crude ashes have shown similar chemical and ecotoxicological properties. The s/s materials have presented compressive strengths between 25 and 40 MPa, low emission levels of metals through leaching and were classified as non-hazardous materials. The formulations of concrete have presented compressive strengths between 12 and 24 MPa. According to the Dutch Building Materials Decree, some concrete formulations can be used in both scenarios of limited moistening and without insulation, and with permanent moistening and with insulation.
    Waste Management 05/2011; 31(9-10):2009-19. · 3.16 Impact Factor
  • International Conference on Renewable Energy and Power Quality, Las Palmas; 04/2011
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    ABSTRACT: Syngas obtained by co-gasification of coal and wastes was hot cleaned in two catalytic reactors, which allowed destroying tar and gaseous hydrocarbons with more than one carbon atom. H2S and NH3 contents were also significantly reduced, but CH4 concentrations varying between 2% and 10% and small amounts of H2S (below 100ppmv) were still found in syngas, depending on coal type and waste composition. This paper studies the effect of experimental conditions on CH4 destruction by reforming reactions in absence and in presence of catalysts. The effect of experimental conditions (temperature, steam flow rate and syngas composition) on CH4 destruction and on CO conversion into CO2 in the absence of catalyst was studied first, using the Equilibrium Reactor model from CHEMKIN modelling software. The selected experimental conditions were then tested in a fixed bed reactor with and without catalyst and the results obtained were consistent with CHEMKIN Equilibrium Reactor model predictions. Commercial Ni-based catalysts were tested (G-90 B5 and G 56B from C&CS). These catalysts were capable of significantly reducing CH4 content, by promoting reforming reactions. At the experimental conditions used and in absence of steam, G 56B seems to be more effective in CH4 conversion, as lower CH4 contents were obtained. In presence of steam both catalysts were capable of completely destroying CH4. Both catalysts also promoted WGS (water gas shift) reaction to some extent, though they are not specific catalysts for this reaction. Thus, a high increase in H2 content was observed, due to its formation by both reforming and WGS reactions. For a complete conversion of CO into CO2 and H2 a specific catalyst for WGS reaction is still needed.
    Fuel 04/2011; 90(4):1645-1654. · 3.36 Impact Factor
  • J Morais, R Barbosa, N Lapa, B Mendes, I Gulyurtlu
    Resources Conservation and Recycling 01/2011; 55(11):1109-1118. · 2.32 Impact Factor
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    ABSTRACT: It is predictable that in the near future fossil fuels will continue to have the greatest contribution to energy production. Thus, it is necessary to develop and improve technologies that ensure low CO2 emissions. Oxy-gasification is one of such technologies, as the use of oxygen instead of air will allow solving the problem of nitrogen dilution effect in syngas and consequently will simplify the process of CO2 capture. On the other hand, the use of oxygen will increase investment costs, as an oxygen production unit will have to be added to the overall installation, and operation costs will also rise, due to the extra energy necessary for oxygen production. Apart from this, it is important to check the performance of installations initially designed to operate with air, when retrofitted to use oxygen and to analyse the effect that this change may have on syngas composition. In this work the effect of gasification agent on syngas composition, including tar content was determined during co-gasification of two types of coals (German and Polish) mixed with several wastes, like pine, olive bagasse and polyethylene (PE). Air and steam or oxygen and steam mixtures were used as gasification agent, keeping constant ER (equivalent ratio), that is to say, for each coal and wastes blend the oxygen flow was the same for both gasification agents. However, when oxygen was used, gas flows fed into the gasifier were lower than those used in presence of air, which means that residence times were higher than when air was used. Therefore, syngas presented lower hydrocarbons contents and higher CO2 concentrations, probably because there was more time for reactions to occur in presence of oxygen.
    Fuel. 01/2011;
  • Paula Teixeira, Helena Lopes, Ibrahim Gulyurtlu, Nuno Lapa
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    ABSTRACT: Three species of biomass origin (straw pellets, olive cake and wood pellets) and two coals from different countries (Coal Polish and Coal Colombian) have been studied to understand the fate of their ash forming matter during the combustion process and to investigate the influence of co-firing biomass with coal. Three different approaches to investigate the ash behaviour were employed: (1) chemical fractionation analysis to evaluate the association/reactivity of ash forming elements in the fuels as a prediction tool, (2) establishment of elements partitioning in ash streams produced in the combustion and co-combustion trials, and (3) evaluation of enrichment factors of elements in the ash streams. The chemical fractionation analysis was applied to all fuels used to evaluate how the association/reactivity of elements making up ash may influence their behaviour during combustion. Combustion tests were carried out on a pilot scale fluidized bed combustor (FBC). Four ash streams were obtained at different locations. The uncertainty of measurements was estimated allowing a critical evaluation of mass balances over the combustion system and the partitioning of elements in the ash streams. The enrichment factors of elements in the several ash streams were estimated, incorporating uncertainties associated with analytical measurements. Results obtained showed that for FBC the relation between the chemical fractionation and the experimental partitioning is strongly affected by elutriation of particles. The element enrichment factor estimated for each ash stream, using Al as a reference element, revealed better correlations with the elements reactivity obtained by chemical fractionation because it overcomes particles elutriation effects. Nevertheless, it was observed that the reactivity estimated by chemical fractionation could not be solely interpreted as tendency of the elements to volatilize on FBC system, as reaction in bed zone of boiler may also occur retaining reactive elements.
    Fuel. 01/2011;
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    ABSTRACT: Coal mixed with different types of wastes was co-gasified in a pilot-scale installation. The syngas produced was hot treated in two catalytic fixed-bed reactors. In the first one, dolomite was used and in the second reactor, a nickel-based catalyst was employed. Two different grade coals were tested, Puertollano and Colombian. Puertollano coal had high ash and sulphur contents, 42.5% and 2.4%, respectively, while ash and sulphur contents of Colombian coal were, respectively, 12.7% and 0.9%. Pine, bagasse, RDF and PE were the wastes mixed with both coals. After dolomite fixed-bed reactor, H2S and NH3 contents in syngas were much lower than those of the gas leaving the gasifier. For most coal and waste blends, NH3 reductions changed between 30% and 50% depending on feedstock nitrogen content, while H2S reductions achieved values from 68% to 74%, also depending on H2S concentration in syngas. After syngas had gone through the nickel-based catalyst, it presented H2S and NH3 contents that allowed its use in boilers and gas engines for most coal and waste blends. The overall syngas treatment led to H2S and NH3 reductions higher than 97%. For most experiments, final H2S and NH3 concentration in syngas were below 20ppmv and 30ppmv, respectively.
    Fuel 11/2010; 89(11):3340-3351. · 3.36 Impact Factor
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    ABSTRACT: It is predictable that energy demand will greatly increase in years to come, due to the continuous growth of world population, together with the quest to improve living standards. CO2 emissions are hence expected to increase significantly. Gasification is a mature technology for energy production that permits an easier separation of CO2 for its storage. As modern societies are producing everincreasing amounts of wastes with negative impact on the environment, new technologies have been developed to co-gasify these wastes either with coal or alone, thus resolving a serious problem of waste disposal. Wastes gasification reduces the dependence on fossil fuels and co-gasification with coal could provide the benefit of security in fuel supply, as the availability of wastes and biomass fuels could vary from region to region and show seasonal changes. Gasification experimental conditions and technologies and syngas cleaning methods are key issues for the production of a clean gas that could find a wide range of applications. This chapter will concentrate on syngas end-uses, focusing on new ones, like gas turbines or engines in IGCC, synthesis of methanol, ethanol and dimethyl ether, Fischer–Tropsch synthesis, and hydrogen production. The role of gasification in CO2 sequestration will also be discussed.
    10/2010: pages 151-175;
  • World Congress Congresso ISWA/APESB, Turning Waste into Ideas, Lisboa; 10/2010
  • The Second International Conference Hazardous and Industrial Waste Management, Creta; 10/2010
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    ABSTRACT: Thermal degradation was studied as a method to decompose mixtures of rubber tyre (RT) and different plastic wastes (PE, PP and PS) with the aim of producing a liquid fuel [1], as well as valuable chemical raw materials. An experimental set of runs was performed to establish the operational conditions that maximize liquid fraction production in a 1 litre batch reactor. Waste blends used were composed of 30% w/w RT and 70% w/w plastics (20% PE, 30% PP and 20% w/w PS). The complex hydrocarbon liquid mixture obtained during pyrolysis of these residues was highly dependent on experimental parameters, namely temperature, initial pressure and reaction time, which are the three most important factors affecting liquid yields. Regression analyses of experimental data were performed according to response surface methodology (RSM). As a result, experimental conditions optimized based on Factorial Design Methodology were 370 °C, 0.48 MPa for initial pressure and 15 min for reaction time. In order to validate the results obtained by the RSM model, three extra runs were conducted sequentially and average values were calculated and found to be: gas yield of 4.9% w/w, liquid yield of 81.3% w/w and solid yield of 12.7% w/w with an experimental deviation of 0.95%.
    Fuel. 09/2010;