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.

Laboratory evaluation of young ovines inoculated with natural or 60Co-irradiated Crotalus durissus terrificus venom during hyperimmunization process

Laboratory profile of young ovines was studied in order to evaluate and compare their antiserum production from natural and Cobalt-60 irradiated Crotalus durissus terrificus (C.d.t.) venoms. The parameters analyzed included complete blood count, and urea, creatinine, aspartate aminotransferase, total proteins, albumin and globulin serum measurements. Three groups of six animals each were used. Group 1 (G1) received natural C.d.t. venom; Group 2 (G2) received irradiated C.d.t. venom; and Group 3 (G3) was used as control and did not receive venom, only adjuvants, using seven venom inoculations. During the experimental period, animals were fortnightly weighed. According to clinical and weight evaluation, sheep in post-weaning phase showed no changes in their physiological profiles but had excellent weight gain. The parameters analyzed were not statistically different (p<5%) among the groups tested. The hyperimmunization process was successfully accomplished with the production of specific antibodies against Crotalus durissus terrificus venom. Results bring a new possibility of utilizing ovines in the commercial production of anticrotalic serum, which may be used to treat human and animal envenomation. Its production cost may be reduced by subsequent use of hyperimmunized sheep for human consumption.

Economical analysis of ethanol steam reformer for hydrogen production associated with a sugarcane industry

An expressive amount of produced hydrogen is generated by customers in-situ such as petrochemical, fertilizer and sugarcane industries. However, the most utilized feedstock is natural gas, a non-renewable and fossil fuel. The introduction of biohydrogen production process associated in a sugarcane industry is an alternative to diminish emissions and contribute to create a CO2 cycle, where the plants capture this gas by photosynthesis process and produces sucrose for ethanol production. The cost of production of ethanol has dramatically decreased (from about US$ 700/m3 in 1970s to US$ 200/m3 today), becoming this a good option at near term, inclusively for its utilization by customers localized in main regions (localized especially in regions such as Southeastern Brazil) Also in near future, it will possible the utilization of fuel cells as form of distributed generation. Its utilization could occur specially in peak hours, diminishing the cost of investments in newer transmission systems. A technical and economic analysis of steam reformer of ethanol to hydrogen production associated with sugarcane industry was recently performed. This technique will also allow the use of ethanol when its price is relatively low. This study was based on a previous R&D study (sponsored by CEMIG - State of Minas Gerais Electricity Company) where thermodynamic and economic analyses were developed, based in the development of two ethanol steam reformers prototypes.x In this study an analysis was performed considering the use of bagasse as source of heat in the steam reforming process. Its use could to diminish the costs of hydrogen production, especially at large scale, obtaining cost-competitive production and permitting that sugarcane industry produces hydrogen in large scale beyond ethylic alcohol, anhydrous alcohol (or ethanol) and sugar.

Influence of alcohol consumption on alveolar bone level associated with ligature-induced periodontitis in rats

Alcohol consumption is a risk indicator for periodontal disease. The purpose of this study was to morphometrically evaluate the influence of alcohol consumption on alveolar bone level associated with ligature-induced periodontitis in rats. Thirty-six female rats (Wistar, 120 days-old) were randomly divided into three groups that received a daily administration of a water diet (control, n = 12), a 10% alcohol diet (10% ethanol, n = 12) or a 20% alcohol diet (20% ethanol, n = 12). Four weeks after the onset of the experiment, cotton ligatures were placed around the cervix of the upper right second molar in six rats. The other 6 rats in each group remained unligated. The rats were sacrificed four weeks after ligature placement. The maxillary bones were removed and alveolar bone loss was analyzed by measuring the distance between the cementoenamel junction and the alveolar bone crest at 2 buccal and 2 palatal sites on the upper right second molar. Analyses between the ligated and unligated groups showed that the presence of ligature induced alveolar bone loss (p < 0.05). Unligated groups showed no significant differences between each other (p > 0.05). In the ligated groups, rats receiving 20% ethanol showed significantly greater bone loss compared to control rats or rats receiving 10% ethanol. These results demonstrate that alcohol consumption may increase alveolar bone loss in female rats in a dosedependent manner.

Glycerol: Production, consumption, prices, characterization and new trends in combustion

The demand for petroleum has been rising rapidly due to increasing industrialization and modernization. This economic development has led to a huge demand for energy, most of which is derived from fossil fuel. However, the limited reserve of fossil fuel has led many researchers to look for alternative fuels which can be produced from renewable feedstock. Increasing fossil fuel prices have prompted the global oil industry to look at biodiesel, which is from renewable energy sources. Biodiesel is produced from animal fats and vegetable oils and has become more attractive because it is more environmentally friendly and is obtained from renewable sources. Glycerol is the main by-product of biodiesel production; about 10% of the weight of biodiesel is generated in glycerol. The large amount of glycerol generated may become an environmental problem, since it cannot be disposed of in the environment. In this paper, an attempt has been made to review the different approaches and techniques used to produce glycerol (hydrolysis, transesterification, refining crude glycerol). The world biodiesel/glycerol production and consumption market, the current world glycerin and glycerol prices as well as the news trends for the use of glycerol mainly in Brazil market are analyzed. The technological production and physicochemical properties of glycerol are described, as is the characterization of crude glycerol obtained from different seed oil feedstock. Finally, a simple way to use glycerol in large amounts is combustion, which is an advantageous method as it does not require any purification. However, the combustion process of crude glycerol is not easy and there are technological difficulties. The news and mainly research about the combustion of glycerol was also addressed in this review. © 2013 Elsevier Ltd.

Hydrogen production by biogas steam reforming: A technical, economic and ecological analysis

Fuel cells are electrochemical energy conversion devices that convert fuel and oxidant electrochemically into electrical energy, water and heat. Compared to traditional electricity generation technologies that use combustion processes to convert fuel into heat, and then into mechanical energy, fuel cells convert the hydrogen and oxygen chemical energy into electrical energy, without intermediate conversion processes, and with higher efficiency. In order to make the fuel cells an achievable and useful technology, it is firstly necessary to develop an economic and efficient way for hydrogen production. Molecular hydrogen is always found combined with other chemical compounds in nature, so it must be isolated. In this paper, the technical, economical and ecological aspects of hydrogen production by biogas steam reforming are presented. The economic feasibility calculation was performed to evaluate how interesting the process is by analyzing the investment, operation and maintenance costs of the biogas steam reformer and the hydrogen production cost achieved the value of 0.27 US$/kWh with a payback period of 8 years. An ecological efficiency of 94.95%, which is a good ecological value, was obtained. The results obtained by these analyses showed that this type of hydrogen production is an environmentally attractive route. © 2013 Elsevier Ltd.

Análise termodinâmica, termoeconômica e econômica de uma usina sucroalcooleira com processo de extração por difusão

Pós-graduação em Engenharia Mecânica - FEIS

Análise do aproveitamento energético do biogás produzido numa estação de tratamento de esgoto

Pós-graduação em Engenharia Mecânica - FEIS

Alterações nutricionais em hortaliças decorrentes de diferentes métodos de cozimento

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Uso da avaliação do ciclo de vida para a determinação na redução de emissões de gases do efeito estufa e do consumo de energia associados a reciclagem de EPS

Pós-graduação em Engenharia Mecânica - FEG

Mathematical modeling of a continuous alcoholic fermentation process in a two-stage tower reactor cascade with flocculating yeast recycle

Experiments of continuous alcoholic fermentation of sugarcane juice with flocculating yeast recycle were conducted in a system of two 0.22-L tower bioreactors in series, operated at a range of dilution rates (D (1) = D (2) = 0.27-0.95 h(-1)), constant recycle ratio (alpha = F (R) /F = 4.0) and a sugar concentration in the feed stream (S (0)) around 150 g/L. The data obtained in these experimental conditions were used to adjust the parameters of a mathematical model previously developed for the single-stage process. This model considers each of the tower bioreactors as a perfectly mixed continuous reactor and the kinetics of cell growth and product formation takes into account the limitation by substrate and the inhibition by ethanol and biomass, as well as the substrate consumption for cellular maintenance. The model predictions agreed satisfactorily with the measurements taken in both stages of the cascade. The major differences with respect to the kinetic parameters previously estimated for a single-stage system were observed for the maximum specific growth rate, for the inhibition constants of cell growth and for the specific rate of substrate consumption for cell maintenance. Mathematical models were validated and used to simulate alternative operating conditions as well as to analyze the performance of the two-stage process against that of the single-stage process.

Chemical weathering rate, denudation rate, and atmospheric and soil CO2 consumption of Parana flood basalts in Sao Paulo State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aproveitamento energético de uma planta de sulfatação

Pós-graduação em Engenharia Mecânica - FEG