Thermodynamic analysis of direct steam reforming of ethanol in molten carbonate fuel cell

Fuel cell as molten carbonate fuel cell (MCFC) operates at high temperatures. Thus, cogeneration processes may be performed, generating heat for its own process or for other purposes of steam generation in the industry. The use of ethanol is one of the best options because this is a renewable and less environmentally offensive fuel, and is cheaper than oil-derived hydrocarbons, as in the case of Brazil. In that country, because of technical, environmental, and economic advantages, the use of ethanol by steam reforming process has been the most investigated process. The objective of this study is to show a thermodynamic analysis of steam reforming of ethanol, to determine the best thermodynamic conditions where the highest volumes of products are produced, making possible a higher production of energy, that is, a more efficient use of resources. To attain this objective, mass and energy balances were performed. Equilibrium constants and advance degrees were calculated to get the best thermodynamic conditions to attain higher reforming efficiency and, hence, higher electric efficiency, using the Nernst equation. The advance degree (according to Castellan 1986, Fundamentos da Fisica/Quimica, Editora LTC, Rio de Janeiro, p. 529, in Portuguese) is a coefficient that indicates the evolution of a reaction, achieving a maximum value when all the reactants' content is used of reforming increases when the operation temperature also increases and when the operation pressure decreases. However, at atmospheric pressure (1 atm), the advance degree tends to stabilize in temperatures above 700 degrees C; that is, the volume of supplemental production of reforming products is very small with respect to high use of energy resources necessary. The use of unused ethanol is also suggested for heating of reactants before reforming. The results show the behavior of MCFC. The current density, at the same tension, is higher at 700 degrees C than other studied temperatures such as 600 and 650 degrees C. This fact occurs due to smaller use of hydrogen at lower temperatures that varies between 46.8% and 58.9% in temperatures between 600 and 700 degrees C. The higher calculated current density is 280 mA/cm(2). The power density increases when the volume of ethanol to be used also increases due to higher production of hydrogen. The highest produced powers at 190 mA/cm(2) are 99.8, 109.8, and 113.7 mW/cm(2) for 873, 923, and 973 K, respectively. The thermodynamic efficiency has the objective to show the connection among operational conditions and energetic factors, which are some parameters that describe a process of internal steam reforming of ethanol.

Knowledge Representation and Orthophemism: A Reflection Aiming to a Concept

Characteristics of speech, especially figures of speech, are used by specific communities or domains, and, in this way, reflect their identities through their choice of vocabulary. This topic should be an object of study in the context of knowledge representation once it deals with different contexts of production of documents. This study aims to explore the dimensions of the concepts of euphemism, dysphemism, and orthophemism, focusing on the latter with the goal of extracting a concept which can be included in discussions about subject analysis and indexing. Euphemism is used as an alternative to a non-preferred expression or as an alternative to an offensive attribution-to avoid potential offense taken by the listener or by other persons, for instance, pass away. Dysphemism, on the other hand, is used by speakers to talk about people and things that frustrate and annoy them-their choice of language indicates disapproval and the topic is therefore denigrated, humiliated, or degraded, for instance, kick the bucket. While euphemism tries to make something sound better, dysphemism tries to make something sound worse. Orthophemism (Allan and Burridge 2006) is also used as an alternative to expressions, but it is a preferred, formal, and direct language of expression when representing an object or a situation, for instance, die. This paper suggests that the comprehension and use of such concepts could support the following issues: possible contributions from linguistics and terminology to subject analysis as demonstrated by Talamo et al. (1992); decrease of polysemy and ambiguity of terms used to represent certain topics of documents; and construction and evaluation of indexing languages. The concept of orthophemism can also serves to support associative relationships in the context of subject analysis, indexing, and even information retrieval related to more specific requests.

Thermodynamic analysis of direct steam reforming of ethanol in molten carbonate fuel cell

Fuel cell as MCFC (molten carbonate fuel cell) operate at high temperatures, and due to this issue, cogeneration processes may be performed, sending heat for own process or other purposes as steam generation in an industry. The use of ethanol for this purpose is one of the best options because this is a renewable and less environmentally offensive fuel, and cheaper than oil-derived hydrocarbons (in the case of Brazil). In the same country, because of technical, environmental and economic advantages, the use of ethanol by steam reforming process have been the most investigated process. The objective of this study is to show a thermodynamic analysis of steam reforming of ethanol, to determine the best thermodynamic conditions where are produced the highest volumes of products, making possible a higher production of energy, that is, a most-efficient use of resources. To attain this objective, mass and energy balances are performed. Equilibrium constants and advance degrees are calculated to get the best thermodynamic conditions to attain higher reforming efficiency and, hence, higher electric efficiency, using the Nernst equation. The advance degree of reforming increases when the operation temperature also increases and when the operation pressure decreases. But at atmospheric pressure (1 atm), the advance degree tends to the stability in temperatures above 700°C, that is, the volume of supplemental production of reforming products is very small for the high use of energy resources necessary. Reactants and products of the steam-reforming of ethanol that weren't used may be used for the reforming. The use of non-used ethanol is also suggested for heating of reactants before reforming. The results show the behavior of MCFC. The current density, at same tension, is higher at 700°C than other studied temperatures as 600 and 650°C. This fact occurs due to smaller use of hydrogen at lower temperatures that varies between 46.8 and 58.9% in temperatures between 600 and 700°C. The higher calculated current density is 280 mA/cm 2. The power density increases when the volume of ethanol to be used also increases due to higher production of hydrogen. The highest produced power at 190 mW/cm 2 is 99.8, 109.8 and 113.7 mW/cm2 for 873, 923 and 973K, respectively. The thermodynamic efficiency has the objective to show the connection among operational conditions and energetic factors, which are some parameters that describes a process of internal steam reforming of ethanol.

Physical-chemical and thermodynamic analyses of steam reforming of ethanol to hydrogen production

The steam reforming is one of most utilized process of hydrogen production because of its high production efficiencies and its technological maturity. The use of ethanol for this purpose is a interesting option because this is a renewable and less environmentally offensive fuel. The objective of this study is evaluate the physical-chemical, thermodynamic and environmental analyses of steam reforming of ethanol. whose objective is to produce 0.7 Nm3/h of hydrogen to be used by a PEMFC of l kW. In this physical-chemical analysis, a global reaction of ethanol was considered. That is, the superheated ethanol and steam, at high temperatures, react to produce hydrogen and carbon dioxide. Beyond it's the simplest form to study the steam reforming of ethanol to hydrogen production, it's the case where occurs the highest production of hydrogen (the product to be used by fuel cells) and carbon dioxide, to be eliminated. But this reaction isn't real and depends greatly on the thermodynamic conditions of reforming, technical features of reformer system and catalysts. Other products generally formed (but not investigated in this study) are methane, carbon monoxide, among others. It was observed that the products is commonly produced in the moment when the reaction attains temperatures about 206°C (below this temperature, the reaction trend to the reaetants, that is, from hydrogen and carbon dioxide to steam and ethanol) and the advance degree of this reaction increases when the temperature of reaction also increases and when its pressure decreases. It's suggested reactions at about 600°C or higher. However, when the temperature attains 700°C, the stability of this reaction is occurred, that is, the production of reaction productions attains to the limit, that is the highest possible production. In temperatures above 700°C, the use of energy is very high for produce more products, having higher costs of production that the suggested temperature. The indicated pressure is 1 atm., a value that allows a desirable economy of energy that would also be used for pressurization or depressurization of steam reformer. In exergetic analysis, it's seem that the lower irreversibililies occur when the pressure of reactions are lower. However, the temperature changes don't affect significantly the irreversibilites. Utilizing the obtained results from this analysis, it was concluded that the best thermodynamic conditions for steam reforming of ethanol is the same conditions suggested in the physical-chemical analysis. The exergetic and first law efficiencies are high on the thermodynamie conditions studied.

Duas formas da recepção das idéias de Lukács no Brasil: estética e ontologia

Pós-graduação em Ciências Sociais - FFC

Da transformação ao gerencialismo: as metamorfoses da concepção de participação popular no Partido dos Trabalhadores (1988-2004)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O tipo penal de disparo de arma de fogo como espécie dos delitos contra a incolumidade pública: uma antecipação de tutela penal legitimável

Pós-graduação em Direito - FCHS

Renovação Carismática Católica: continuidades e rupturas no catolicismo brasileiro (1969-2005)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Privatização e política neoliberal: a resistência da categoria bancária no processo de privatização do Banespa (1995-2000)

Pós-graduação em Ciências Sociais - FFC

O neocontratualismo de Norberto Bobbio e John Rawls em cum contexto de neoliberalismo e crise estrutural do capital

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A ideologia da nova educação profissional no contexto da estruturação produtiva

Pós-graduação em Ciências Sociais - FFC

Uma nova ofensiva do capital?: impactos do neoliberalismo e da reestruturação produtiva na ação sindical e no setor calçadista de Franca - SP

Pós-graduação em História - FCHS

As pimentas Capsicum L. no cotidiano de uma comunidade de várzea (rio Amazonas), Santarém, Pará, Brasil

Pós-graduação em Agronomia (Horticultura) - FCA

Liberdade de expressão e discurso do ódio: um exame sobre as possíveis limitações à liberdade de expressão

In a view to determining the outlines of the Freedom of Speech and to specify its contents, we face hate speech as an offensive and repulsive manifestation, particularly directed to minority groups in contemporary society. Thus, the study sought to promote, in the foreground, a study of the Freedom of Speech, in the liberal molds. Considered this way, Freedom of Speech will tend to accept hate speech as a legitimate manifestation, albeit at the injury of the victims. On the other hand, when we are dealing with the exhaustion of the liberal paradigm and the affirmation of the Welfare State, we note the recognition by the social state of the asymmetries and commitment to redistributive justice. The Freedom of Speech, warded by welfare state will tend to suffer major restrictions on its self-determination power, rejecting hate speech.

Relação entre materiais dentários e o complexo dentino-pulpar

Despite the strong valorization of the esthetics and its relationship with restorative materials, the biological principles of any clinical procedure are extremely important to maintain the vitality of the dentin-pulp complex. Dentin and pulp tissue are susceptible to different kinds of irritants such as toxins from microorganisms, traumatic procedures of cavity preparation, as well as toxic components released by restorative materials applied in non recommended clinical situations. Initially, the pulp responds to irritation by starting an inflammatory reaction which involves outward movement of dentinal fluid and intratubular deposition of immunoglobulins, upregulation of odontoblast activities, presence of immune cells and their cytokines as well as local expression of neuropeptides and chemokines. After these initial events, the inflammation process can be resolved associated or not to sclerotic dentin formation and reactionary dentin deposition. If high intensity offensive stimuli are applied to the dentin-pulp complex, death of odontoblasts takes place and consequently pulp ageing or even partial necrosis of this tissue may occurs. Thereby, clinicians need to be aware about the physiological and pathological features of the dentin-pulp complex as well as the possible biological consequences of different clinical procedures. In this way, the dentists should be able to carry out minimally aggressive operative techniques and to select the more appropriate restorative materials for each specific clinical situation in order to obtain excellent clinical results associated to the maintenance of pulp vitality.