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971.
Isabel Martínez Ramon Murillo Gemma Grasa Jose R. Fernández Juan Carlos Abanades 《American Institute of Chemical Engineers》2013,59(8):2780-2794
The integration in a natural gas combined cycle (NGCC) of a novel process for H2 production using a chemical Ca–Cu loop was proposed. This process is based on the sorption‐enhanced reforming process for H2 production from natural gas with a CaO/CaCO3 chemical loop, but including a second Cu/CuO loop to regenerate the Ca‐sorbent. An integration of this system into a NGCC was proposed and a full process simulation exercise of different cases was carried out. Optimizing the operating conditions in the Ca–Cu looping process, 8.1% points of efficiency penalty with respect to a state‐of‐the‐art NGCC are obtained with a CO2 capture efficiency of 90%. It was demonstrated that the new process can yield power generation efficiencies as high as any other emerging and commercial concepts for power generation from NGCC with CO2 capture, but maintaining competing advantages of process simplification and compact pressurized reactor design inherent to the Ca–Cu looping system. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2780–2794, 2013 相似文献
972.
A. de Pablos‐Martín D. Ristic S. Bhattacharyya Th. Höche G.C. Mather M. O Ramírez S. Soria M. Ferrari G.C. Righini L.E. Bausá A. Durán M.J. Pascual 《Journal of the American Ceramic Society》2013,96(2):447-457
The influence of the addition of 1 mol% Tm2O3 on the nanocrystallization of LaF3 in a glass of composition 55SiO2–20Al2O3–15Na2O–10LaF3 (mol%) has been studied. Tm2O3 affects the phase separation in the glass and delays the onset of crystallization with respect to the undoped glass. Additionally, the maximum LaF3 crystal size is slightly greater than that in the undoped glass–ceramics. The microstructural and compositional changes in the glass matrix have been studied using several techniques, including viscosity, dilatometry, X‐ray and neutron diffraction (XRD, ND), quantitative Rietveld refinement, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Raman spectroscopy. Photoluminescence measurements indicate that the Tm3+ ions are distributed between the glassy matrix and LaF3 crystals. Eu2O3 has been used as structure probe and part of the Eu3+ ions are reduced to Eu2+ when incorporated in the LaF3 nano‐crystals. Up‐conversion spectra under IR‐excitation show a higher intensity of the blue emission in the Tm‐doped glass–ceramic compared with that in the glass. 相似文献
973.
Moisés Frías Sagrario Martínez‐Ramírez Teresa Blasco María Frías Rodríguez 《Journal of the American Ceramic Society》2013,96(7):2306-2310
The evolution of the metastable phases in metakaolin/Ca(OH)2 systems cured at high temperatures, remains mostly unknown, newer techniques may now help to establish both the kinetic mechanism of the pozzolanic reaction and the thermodynamic stability of the main hydrated hexagonal phases: Stratlingite (C2ASH8) and tetra calcium aluminate hydrate (C4AH13). For this reason this work examines the kinetics of the pozzolanic reaction in the MK/Ca(OH)2 system over 123 d at 60°C using nuclear magnetic resonance spectroscopy (27Al and 29Si NMR). The results obtained by 27Al and 29Si NMR show that during the first 30 h, the metastable phases C2ASH8 and C4AH13, coexist with the cubic phase (C3ASH6) obtained directly from the pozzolanic reaction. The gel C–S–H is clearly identified after 21 h of reaction, whereas at shorter times the C–S–H bands overlap those with the unreacted metakaolin ones. After 123 d of pozzolanic reaction, the first signs of the cubic phase are detected, a consequence of the conversion reaction of the metastable phases, and a phenomenon not previously identified. 相似文献
974.
Isabel F. Sáez del Bosque Manuel Martín‐Pastor Sagrario Martínez‐Ramírez María Teresa Blanco‐Varela 《Journal of the American Ceramic Society》2013,96(3):957-965
This study aimed to monitor the effect of temperature and the addition of nanosilica on the nanostructure of the C–S–H gel forming during tricalcium silicate (C3S) hydration. Two types of paste were prepared from a synthesized T1 C3S. The first consisted of a blend of deionized water and C3S at a water/solid ratio of 0.425. In the second, a 90 wt% C3S + 10 wt% of nanosilica blend was mixed with water at a water/solid ratio of 0.7. The pastes were stored in closed containers at 100% RH and 25°C, 40°C, or 65°C. The hydration reaction was detained after 1, 14, 28, or 62 d with acetone, and then pastes were studied by 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR).The main conclusion was that adding nSA expedites C3S hydration at any age or temperature and modifies the structure of the C–S–H gel formed, two types of C–S–H gel appear. At 25°C and 40°C, more orderly, longer chain gels are initially (1 d) obtained as a result of the pozzolanic reaction between nSA and portlandite (CH) (C–S–HII gel formation). Subsequently, ongoing C3S hydration and the concomitant flow of dimers shorten the mean chain length in the gel. 相似文献
975.
Julián Jiménez Reinosa David Martín y Marero Adolfo del Campo Miguel Ángel de la Rubia José Francisco Fernández 《Journal of the American Ceramic Society》2013,96(6):1783-1788
Copper and iron in glasses constitute classical aims of study because of the optical effects that they produce. Structured materials are also interesting due to the incorporated functionalities derived from their spatial organization. Here, CuO and Fe2O3 were incorporated into a standard glass, from which glass coatings with different thicknesses were studied. Whereas iron cations dissolved in the glassy matrix, copper cations saturated it and crystallized at the surface, forming a hierarchical microstructure. The surface microstructure consisted of crystallizations of Tenorite (CuO) forming interconnected walls. The walls surrounding areas of glassy matrix gave rise to a cells microstructure. Rutherford Backscattering Spectrometry provided the composition of the samples with high depth resolution, and Raman Confocal Microscopy determined the phases location and their distribution forming the microstructure. The joint information from both techniques allowed high chemical and spatial resolution of the main cations location for the hierarchical surface microstructure. 相似文献
976.
Itziar Martínez de Alegría Mancisidor Pablo Díaz de Basurto Uraga Iñigo Martínez de Alegría Mancisidor Patxi Ruiz de Arbulo López 《Renewable & Sustainable Energy Reviews》2009,13(1):100-114
The European Union's (EU) energy objectives, legislation and programmes are determinant for the current strategy for the promotion of renewable energy sources (RES) and energy efficiency (EE) in Spain, which is becoming a key element for its international competitiveness.Firstly, this article explores the evolution of the EU's energy strategy, focusing on the adopted legislations and programmes to promote RES and EE. It concludes with an analysis of the impact of those measures in Spain. 相似文献
977.
Francesco Ciabuschi Oscar Martín Martín Benjamin Ståhl 《Management International Review》2010,50(4):471-491
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This paper investigates headquarters’ value-adding role in knowledge transfer. Transfer performance is considered in terms
of both efficiency and effectiveness, and a model that includes headquarters’ distribution of decision-making rights, resource
allocation, and direct intervention is tested on 141 innovation transfer projects. 相似文献
978.
Eva García Flavio Ferrari Tomás García Mercedes Martínez José Aracil 《Journal of surfactants and detergents》2001,4(3):257-262
In recent years, a number of industrial applications for lipases in biotransformation of fatty acids and lipids have been
developed. One of the main reasons for this growing interest is the reduced overall catalyst cost owing to the development
of commercially available immobilized enzymes, using polymeric carriers that facilitate recovery and reuse of the catalyst.
Additional benefits for industrial applications include the specificity of the enzyme and the mild processing conditions.
Diglycerol resulting from the dimerization of glycerol may replace molecules such as propylene glycol as the hydrophilic moiety
of surfactants. Also, diglycerol fatty acid esters are useful as biodegradable nonionic surfactants for food, cosmetics, and
pharmaceuticals. In this study, the enzymatic esterification of diglycerol and lauric acid has been optimized in a solvent-free
system. The reaction was carried out in a stirred batch reactor with a vacuum pump in order to shift the equilibrium toward
the products. The commercial lipase Novozym-435 was chosen as the most suitable catalyst, and the initial acid/alcohol ratio
was always 1∶1. The reaction of lauric acid and diglycerol leveled off at equilibrium conversion after approximately 1 h of
reaction. Previous work indicated that only temperature and catalyst concentration had significant effects on the conversion,
and a full two-factorial design has proved effective in the study of the influence of these two variables on the process.
The temperature range studied was 63–77°C, and the range of the catalyst concentration was 0.2–5.8 wt%. Both catalyst concentration
and temperature were found to be significant factors in the esterification process, and their influences are positive. The
effect of the interaction between temperature and catalyst concentration was small. A first-order approach could not fit the
data adequately, and a model that included quadratic effects was required. A second-order model was developed to predict the
yield of ester as a function of the variables. Analysis of residuals showed that the model predicted accurately the acid conversion
over the experimental range considered. This model is useful to determine the optimal operating conditions for the industrial
process.
Presented in part at the 91st Annual Meeting of the AOCS in San Diego, April 2000. 相似文献
979.
J. G. Chacón-Nava A. Martínez-Villafañe F. M. Almeraya-Calderón F. H. Stott J. G. González-Rodríguez 《Journal of Materials Engineering and Performance》2001,10(6):699-704
The erosion-corrosion (E-C) behavior of SA213-T22 steel has been studied in a laboratory fluidized-bed (FB) facility in the
temperature range from 100 to 600 °C. Tests were carried out on pin specimens in air using alumina particles of 560 μm average size at impact velocities from 1.5 to 4.5 m/s. The trends of wear with temperature showed small weight gains at
velocities up to 1.5 m/s. Erodent deposition was a dominant process at temperatures below about 300 °C and velocities below
about 2 m/s. At higher velocities, a peak wastage temperature was observed at about 350 °C. The wastage/temperature curves
observed in both cases suggested four temperature regions. In each region, a different E-C regime operates. Scanning electron
microscopy (SEM) revealed various wastage mechanisms, i.e., (a) oxide chipping, (b) development of a compact and adherent oxide scale, (c) oxide and metal removal, and (d) fracture
and spalling within the oxide layer and at the scale/metal interface. In the present study, the latter mechanism was responsible
for the high wastage rates observed at temperatures above about 450 °C and impact velocities above 3.5 m/s. 相似文献
980.
A. Molero G mez E. Mart nez de la Ossa 《Journal of the American Oil Chemists' Society》2000,77(9):969-974
The extraction of wheat germ oil by liquid and supercritical CO2 is described from the point of view of both operative method and pretreatment of raw material. The best conditions for wheat
germ oil extraction are: pressure, 150 bar; temperature, 40°C; and solvent flow rate, 1.5 L/min at standard temperature and
pressure. The yields and fatty acid compositions obtained are very similar to those resulting from the conventional extraction
process using hexane as solvent (8.0 wt%), although a higher-quality oil is obtained by using CO2 as solvent (free fatty acids, 12.4%; tocopherol content, 416.7 mg tocopherol/g wheat germ oil). These factors lead to the
conclusion that the extraction process using CO2 could be economically competitive with the conventional process, since it considerably simplifies the oil refinement stages
and completely eliminates the solvent distillation stage, which are the most costly processing steps in terms of energy consumption. 相似文献
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