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Rubio B.,Institute Carboquimica CSIC | Izquierdo M.T.,Institute Carboquimica CSIC
Waste Management | Year: 2010

Two different coal fly ashes coming from the burning of two coals of different rank have been used as a precursor for the preparation of steam activated carbons. The performance of these activated carbons in the SO2 removal was evaluated at flue gas conditions (100°C, 1000ppmv SO2, 5% O2, 6% H2O). Different techniques were used to determine the physical and chemical characteristics of the samples in order to explain the differences found in their behaviour. A superior SO2 removal capacity was shown by the activated carbon obtained using the fly ash coming from a subbituminous-lignite blend. Experimental results indicated that the presence of higher amount of certain metallic oxides (Ca, Fe) in the carbon-rich fraction of this fly ash probably has promoted a deeper gasification in the activation with steam. A more suitable surface chemistry and textural properties have been obtained in this case which explains the higher efficiency shown by this sample in the SO2 removal. © 2010 Elsevier Ltd.

Martinez-Morlanes M.J.,University of Zaragoza | Castell P.,Institute Carboquimica CSIC | Alonso P.J.,University of Zaragoza | Martinez M.T.,Institute Carboquimica CSIC | Puertolas J.A.,University of Zaragoza
Carbon | Year: 2012

Multi-walled carbon nanotubes (MWCNTs) were incorporated in ultrahigh molecular weight polyethylene (UHMWPE), which is a polymer used in industrial and orthopedic applications. The composites were prepared by ball milling and thermo-compression processes at concentrations up to 3 wt.% and subsequently gamma irradiated at 90 kGy. Electrical conductivity measurements showed a low percolation threshold of 0.5 wt.%. Electron spin resonance detection of the radiation-induced radicals proved the radical scavenger behavior of MWCNTs: when the nanotube concentration increased, the number of radicals generated by the gamma irradiation process decreased. Allyl radicals seem to be the radicals most affected by the presence of nanotubes in this polymeric matrix. Fourier transformed infrared spectroscopy measurements and an accelerated ageing protocol were performed to ascertain the influence of the irradiation on the oxidation index. The results pointed to the positive contribution of the MWCNTs in increasing the oxidative stability of the composite compared to pure UHMWPE. Crosslinking density induced by gamma irradiation was obtained by swelling measurements. The findings showed that, despite the radical scavenger performance, MWCNTs are capable of maintaining the efficiency of the crosslinking density, unlike the other antioxidants, which inhibit radiation crosslinking. © 2012 Elsevier Ltd. All rights reserved.

Callen M.S.,Institute Carboquimica CSIC | Lopez J.M.,Institute Carboquimica CSIC | Mastral A.M.,Institute Carboquimica CSIC
Journal of Hazardous Materials | Year: 2010

The estimation of benzo(a)pyrene (BaP) concentrations in ambient air is very important from an environmental point of view especially with the introduction of the Directive 2004/107/EC and due to the carcinogenic character of this pollutant. A sampling campaign of particulate matter less or equal than 10 microns (PM10) carried out during 2008-2009 in four locations of Spain was collected to determine experimentally BaP concentrations by gas chromatography mass-spectrometry mass-spectrometry (GC-MS-MS).Multivariate linear regression models (MLRM) were used to predict BaP air concentrations in two sampling places, taking PM10 and meteorological variables as possible predictors. The model obtained with data from two sampling sites (all sites model) (R2=0.817, PRESS/SSY=0.183) included the significant variables like PM10, temperature, solar radiation and wind speed and was internally and externally validated. The first validation was performed by cross validation and the last one by BaP concentrations from previous campaigns carried out in Zaragoza from 2001-2004. The proposed model constitutes a first approximation to estimate BaP concentrations in urban atmospheres with very good internal prediction (QCV2=0.813, PRESS/SSY=0.187) and with the maximal external prediction for the 2001-2002 campaign (Qext 2.=0.679 and PRESS/SSY=0.321) versus the 2001-2004 campaign (Qext 2=0.551, PRESS/SSY=0.449). © 2010 Elsevier B.V.

Callen M.S.,Institute Carboquimica CSIC | Lopez J.M.,Institute Carboquimica CSIC | Mastral A.M.,Institute Carboquimica CSIC
Journal of Environmental Monitoring | Year: 2011

Urban areas constitute major pollution sources due to anthropogenic activities located in these areas. Among the legislated air pollutants, the particulate matter with an aerodynamic diameter less than or equal to 10 microns (PM10) and polycyclic aromatic hydrocarbons (PAH) are controlled under Directive 2008/50/EC and Directive 2004/107/EC, respectively due to their adverse health effects. A study was carried out at four urban and rural Spanish areas during the warm and cold seasons in 2008-2009 to quantify 19 PAH associated with the atmospheric PM10 by gas chromatography-mass spectrometry-mass spectrometry detection (GC-MS-MS) with the internal standard method. The particle-bound composition of the analysed PAH was 5 and 10 times greater in industrial and urban areas, respectively when compared to those measured in rural areas. The highest PAH concentrations during the cold period were possibly due to the additional contribution of domestic heating sources and meteorological conditions such as low temperature and solar irradiation. The use of molecular diagnostic ratios indicated that the possible, major PAH pollution sources in the most polluted areas were pyrogenic sources, mainly attributed to petroleum combustion sources (motor vehicle emissions and crude oil combustion). Petrogenic sources related to evaporative emissions also seemed to contribute in the most polluted area during the warm period. Those dates with high carcinogenic character according to the benzo(a)pyrene equivalent (BaP-eq) were also possibly attributed to petroleum combustion sources. © The Royal Society of Chemistry 2011.

Linderholm C.,Chalmers University of Technology | Cuadrat A.,Institute Carboquimica CSIC | Lyngfelt A.,Chalmers University of Technology
Energy Procedia | Year: 2011

Chemical-looping combustion (CLC) is a combustion concept with inherent separation of CO2. The process uses a solid oxygen carrier, which consists of metal oxide, to transfer the oxygen from air to fuel. This paper presents findings from batch tests performed in a 10 kWth CLC pilot for solid fuels. The pilot, which is the world's first chemical-looping combustor for solid fuels, is based on interconnected fluidized-bed technology and features a fuel reactor (FR) and an air reactor (AR) as the principal reaction chambers. In the FR, fuel is gasified with steam whereupon gasification products react with the oxygen carrier to form, ideally, CO2, H2O and SO 2. Oxygen-carrier particles exit the FR through a weir and are led to the AR, where they are regenerated to their oxidized state. The pilot has been operated using a natural iron-titanium ore called ilmenite as oxygen carrier. Previous continuous tests have demonstrated a need for batch tests in order to obtain complementary information on system performance. In this study, five fuels were fed to the fuel reactor in batches of 20-25 g at four temperatures; 940 °C, 970 °C, 1000 °C and 1030 °C. By using devolatilized fuel, it was possible to determine (a) oxygen demand associated with syngas from char gasification as well as (b) kinetics of char conversion to gas. Rates of char conversion were found to be temperature dependent, as expected, whereas no temperature dependence was found for the oxygen demand. Activation energies for conversion of char to gas were calculated using Arrhenius plots. The minimum oxygen demand for char was found to be around 5%. © 2011 Published by Elsevier Ltd.

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