556 resultados para Cogeneration ashes
Resumo:
The mass accumulation rates (MARs) of aeolian dust in the ocean basins provide an important record of climate in the continental source regions of atmospheric dust and of the prevailing wind patterns responsible for dust transport in the geologic past. The incorporation of other terrigenous components such as volcanic ashes in seafloor sediments, however, often obscures the aeolian dust record. We describe a new approach which uses the delivery rate of crustal 4He to seafloor sediments as a proxy for the mass accumulation rate of old continental dust which is unaffected by the addition of other terrigenous components. We have determined the flux of crustal 4He delivered to the seafloor of the Ontong Java Plateau (OJP) in the western equatorial Pacific over the last 1.9 Myrs. Crustal 4He fluxes vary between 7.7 and 30 ncc/cm**2/kyr and show excellent correlation with global climate as recorded by oxygen isotopes, with high crustal 4He fluxes associated with glacial periods over the entire interval studied. Furthermore, the onset of strong 100 kyr glacial-interglacial climate cycling is clearly seen in the 4He flux record about 700 kyrs ago. These data record variations in the supply of Asian dust in response to climate driven changes in the aridity of the Asian dust sources, consistent with earlier work on Asian dust flux to the northern Pacific Ocean. However, in contrast to previous studies of sites in the central and eastern equatorial Pacific Ocean, there is no evidence that the Inter Tropical Convergence Zone (an effective rainfall barrier to the southward transport of northern hemisphere dust across the equator in the central and eastern Pacific) has influenced the delivery of Asian dust to the OJP. The most likely carrier phase for crustal helium in these sediments is zircon, which can reasonably account for all the 4He observed in the samples. As a first order estimate, these results suggest that the mass accumulation rate of Asian dust on the OJP over the last 1.9 Myrs varied from about 4 to 15 mg/ cm**2/kyr. In contrast, previous studies show that over the same interval the total MAR of terrigenous dust (i.e. Asian dust plus local volcanics) on OJP varied between about 34 and 90 mg/ cm**2/kyr.
Resumo:
A sequence of ash layers recovered from site 178 of the Deep Sea Drilling Project in the Gulf of Alaska was studied to determine the nature of highly explosive volcanic eruptions associated with the Aleutian Arc and Alaskan Peninsula during the last 8 m.y. The major-element chemistry of 25 distinct ash layers was determined. When the analyses are plotted on conventional major-element variation diagrams, the unusual, highly evolved, calc-alkalic characteristics of the ashes are apparent. Perhaps more significantly, there is a good correlation of certain indices of the degree of chemical evolution of each ash (SiO2 content and Larsen index) with sample age. Both parameters vary cyclically, with maximum values of both indices occurring at present, 2.5, and about 5.0 m.y. ago. The cause of the cyclic activity, as well as discontinuous volcanic activity reported for other areas by other investigators, is not precisely known. However, we suggest that variable rates of subduction provide a viable hypothesis for discontinuous volcanic activity associated with convergent plate boundaries.
Resumo:
The progressive depletion of fossil fuels and their high contribution to the energy supply in this modern society forces that will be soon replaced by renewable fuels. But the dispersion and alternation of renewable energy production also undertake to reduce their costs to use as energy storage and hydrogen carrier. It is necessary to develop technologies for hydrogen production from all renewable energy storage technologies and the development of energy production from hydrogen fuel cells and cogeneration and tri generation systems. In order to propel this technological development discussed where the hydrogen plays a key role as energy storage and renewable energy, the National Centre of Hydrogen and Fuel Cell Technology Experimentation in Spain equipped with installations that enable scientific and technological design, develop, verify, certify, approve, test, measure and, more importantly, the facility ensures continuous operation for 24 hours a day, 365 days year. At the same time, the system is scalable so as to allow continuous adaptation of new technologies are developed and incorporated into the assembly to verify integration at the same time it checks the validity of their development. The transformation sector can be said to be the heart of the system, because without neglecting the other sectors, this should prove the validity of hydrogen as a carrier - energy storage are important efforts that have to do to demonstrate the suitability of fuel cells or internal combustion systems to realize the energy stored in hydrogen at prices competitive with conventional systems. The multiple roles to meet the fuel cells under different conditions of operation require to cover their operating conditions, many different sizes and applications. The fourth area focuses on integration is an essential complement within the installation. We must integrate not only the electricity produced, but also hydrogen is used and the heat generated in the process of using hydrogen energy. The energy management in its three forms: hydrogen chemical, electrical and thermal integration requires complicated and require a logic and artificial intelligence extremes to ensure maximum energy efficiency at the same time optimum utilization is achieved. Verification of the development and approval in the entire production system and, ultimately, as a demonstrator set to facilitate the simultaneous evolution of production technology, storage and distribution of hydrogen fuel cells has been assessed.
Resumo:
The use of fly ash (FA) as an admixture to concrete is broadly extended for two main reasons: the reduction of costs that supposes the substitution of cement and the micro structural changes motivated by the mineral admixture. Regarding this second point, there is a consensus that considers that the ash generates a more compact concrete and a reduction in the size of the pore. However, the measure in which this contributes to the pozzolanic activity or as filler is not well defined. There is also no justification to the influence of the physical parameters, fineness of the grain and free water, in its behavior. This work studies the use of FA as a partial substitute of the cement in concretes of different workability (dry and wet) and the influence in the reactivity of the ash. The concrete of dry consistency which serves as reference uses a cement dose of 250 Kg/m 3 and the concrete of fluid consistency utilized a dose of cement of 350 Kg/m 3 . Two trademark of Portland Cement Type 1 were used. The first reached the resistant class for its fineness of grain and the second one for its composition. Moreover, three doses of FA have been used, and the water/binder ratio was constant in all the mixtures. We have studied the mechanical properties and the micro-structure of the concretes by means of compressive strength tests, mercury intrusion porosimetry (MIP) and thermal analysis (TA). The results of compressive strength tests allow us to observe that concrete mixtures with cements of the same classification and similar dosage of binder do not present the same mechanical behavior. These results show that the effective water/binder ratio has a major role in the development of the mechanical properties of concrete. The study of different dosages using TA, thermo-gravimetry and differential thermal analysis, revealed that the portlandite content is not restrictive in any of the dosages studied. Again, this proves that the rheology of the material influences the reaction rate and content of hydrated cement products. We conclude that the available free water is determinant in the efficiency of pozzolanic reaction. It is so that in accordance to the availability of free water, the ashes can react as an active admixture or simply change the porous distribution. The MIP shows concretes that do not exhibit significant changes in their mechanical behavior, but have suffered significant variation in their porous structure
Resumo:
The conceptual design of a pebble bed gas-cooled transmutation device is shown with the aim to evaluate its potential for its deployment in the context of the sustainable nuclear energy development, which considers high temperature reactors for their operation in cogeneration mode, producing electricity, heat and Hydrogen. As differential characteristics our device operates in subcritical mode, driven by a neutron source activated by an accelerator that adds clear safety advantages and fuel flexibility opening the possibility to reduce the nuclear stockpile producing energy from actual LWR irradiated fuel with an efficiency of 45?46%, either in the form of Hydrogen, electricity, or both.
Resumo:
El alcance del proyecto es describir las directrices técnicas, la definición de criterios, y la estrategia de suministro de energía (Electricidad. Calefacción y Agua Caliente Sanitaria (ACS)) a un barrio modelo situado en un entorno urbano. De inicio se estudia los diversos modelos energéticos atendiendo a la normativa y tecnología, que se pueden aplicar en un conjunto residencial, dando como resultado el modelo propuesto de abastecimiento energético, mediante calefacción de distrito, que incorporara el diseño de una planta de producción de energía termo-eléctrica o Central de Energías basada en la tecnología de condensación de baja temperatura para calefacción y A.C.S. incluyendo una cogeneración con pila de combustible. Al mismo tiempo se han calculado y diseñado una serie de chimeneas externas para dar cumplida necesidad técnica y legal al proyecto. Estos estudios nos sirven de punto de partida para analizar la amortización de la inversión y por tanto la rentabilidad y viabilidad del proyecto, comparándose con los costes económicos derivados de la generación por sistemas convencionales. Para finalizar se hace mención a las ventajas medioambientales y a los grados de seguridad en la planta de producción ABSTRACT The scope of this work is the description of an energy supply project ( Electricity, heat and hot water ) to a housing development in a urban neibourhood , including technical criteria in their different options. Initially, several solutions are studied based on available technologies and legal restrictions. The final proposal is based on the district hearing model including electricity production in cogeneration via fuel cell technology as well as heating and hot water produced by low temperature condensation boilers It includes calculations and design criteria of the exhaust gases system and chimeneys in compliance with legal requirement in urban areas. This work also includes an economical model including payback, IRR and VAN analysis and an economical comparaison with the standard solutions. Finally, environmental advantages of the preferred solution over other standards as well as safety issues are also presented.
Resumo:
En el presente proyecto se estudia la viabilidad, tanto técnica como económica, de la instalación de una planta de cogeneración, en una industria alimentaria en Aldaya (Valencia). El diseño de la central de cogeneración se basa en la demanda energética de la fábrica, atendiendo a los requisitos necesarios para acogerse al Régimen Especial de producción de energía eléctrica establecidos en el Real Decreto 661/2007, de 25 de mayo. En cuanto a la viabilidad económica, se ha elegido la alternativa de venta de electricidad a la red a tarifa, (a un precio fijo y regulado) con el fin de asegurar los ingresos en el estudio económico y reducir la sensibilidad del proyecto a las variables del mercado. Como resultado se obtienen la reducción de los costes de energía de la fábrica, mejora de la fiabilidad de suministro, reducción de emisiones globales de CO2, y una elevada rentabilidad del proyecto. ABSTRACT The aim of this project is to study the technical and economic feasibility of a cogeneration plant in a food industry in Aldaya (Valencia). The design of the cogeneration plant is based on the energetic demand of the factory, attending to the requirements specified in the Special Regime of production of electric power established in the R.D. 661/2007. The studied alternative in terms of economic viability is selling electricity to the net by tariff, which is a fixed and regulated price in order to assure the revenue in the economic study and to reduce the project sensitivity to the market variation. The results obtained are: reduction in energy costs of the fabric, improvement of reliability in the electrical supply, reduction of global CO2 emission, and high profitability of the project.