A double-effect distillation system allows a significant reduction in energy consumption, since the condensers and reboilers of different columns can be integrated thermally. To achieve this goal, some columns operate under a vacuum,... more
A double-effect distillation system allows a significant reduction in energy consumption, since the condensers and reboilers of different columns can be integrated thermally. To achieve this goal, some columns operate under a vacuum, while others operate close to atmospheric pressure. These pressure levels bring about different temperature levels, allowing energy recovery. Thus, the aim of this study is to assess the incorporation of double-effect distillation in ethanol production, and its impact on energy consumption and electricity surplus production in the cogeneration system. Moreover, because doubleeffect distillation and thermal integration involve an increase in equipment costs, an economic assessment was done. Several cases were evaluated and a thermal integration technique was applied, in order to integrate the overall process. The thermal integration study showed that it is possible to integrate the juice concentration step (multiple effect evaporation system) in the overall process without additional
thermal consumption, through the selection of a suitable set of pressures in the evaporation system. The results showed a reduction in steam consumption of between 17% and 54%, in comparison with the Base Case. Regarding the electricity surplus, this increased by up to 22% when extraction e condensing steam turbines were adopted.
thermal consumption, through the selection of a suitable set of pressures in the evaporation system. The results showed a reduction in steam consumption of between 17% and 54%, in comparison with the Base Case. Regarding the electricity surplus, this increased by up to 22% when extraction e condensing steam turbines were adopted.
Research Interests:
The sugar and ethanol production is one of the most important economical activities in Brazil, mainly due its high efficiency and competitiveness. The ethanol production is done by several steps: juice extraction, treatment, fermentation... more
The sugar and ethanol production is one of the most important economical activities in Brazil, mainly due
its high efficiency and competitiveness. The ethanol production is done by several steps: juice extraction,
treatment, fermentation and distillation. The juice extraction and treatment is a common operation of both
industries sugar and alcohol. The process begins with the sugar cane juice extraction, usually done by
devices namely mills, where the cane is compressed between big cylinders for the separation of the juice
from the bagasse. Recently, another juice extraction system named diffuser was introduced in some sugar
and alcohol factories. On diffusers, after sugar cane preparation stage, done with knives and shredders, it
passes through a bed, where the juice is separated from bagasse by the addition of imbibition water and
steam, in a lixiviation process. This study evaluates these two juice extraction systems, performing an
exergetic cost analysis. The total production plant is treated, considering the most important process
sections: cogeneration, extraction and distillation and their products: electric energy, cane juice and
hydrated ethanol, respectively. The results of exergetic efficiency, irreversibility generation and unitary
exergetic cost of products are analyzed and compared.
Keywords: sugar cane juice, extraction system, exergetic cost analysis
its high efficiency and competitiveness. The ethanol production is done by several steps: juice extraction,
treatment, fermentation and distillation. The juice extraction and treatment is a common operation of both
industries sugar and alcohol. The process begins with the sugar cane juice extraction, usually done by
devices namely mills, where the cane is compressed between big cylinders for the separation of the juice
from the bagasse. Recently, another juice extraction system named diffuser was introduced in some sugar
and alcohol factories. On diffusers, after sugar cane preparation stage, done with knives and shredders, it
passes through a bed, where the juice is separated from bagasse by the addition of imbibition water and
steam, in a lixiviation process. This study evaluates these two juice extraction systems, performing an
exergetic cost analysis. The total production plant is treated, considering the most important process
sections: cogeneration, extraction and distillation and their products: electric energy, cane juice and
hydrated ethanol, respectively. The results of exergetic efficiency, irreversibility generation and unitary
exergetic cost of products are analyzed and compared.
Keywords: sugar cane juice, extraction system, exergetic cost analysis
Research Interests:
Brazil has an increasing production of municipal solid waste that, allied to the current waste management system, makes that the search for alternatives becomes needed. In this aspect, the waste incineration aiming the electricity... more
Brazil has an increasing production of municipal solid waste that, allied
to the current waste management system, makes that the search for
alternatives becomes needed. In this aspect, the waste incineration
aiming the electricity production in steam cycles presents several
advantages so it is presented as a good alternative that can be adopted.
However, its application needs studies in order to apply it in the most
appropriate way. Thus, this work aims to study the incineration of MSW
and the electricity production through steam cycle evaluating the
influence of MSW composition. Several scenarios were studied in which
some fractions of MSW are removed previously. The MSW generated in
Santo André city was adopted for this study. Simulations results showed
that the removal of metals, organic matter and inert components
impacts in a good way on the cycle performance improving or remaining
these parameters; moreover there is the re-use possibility of the
separated fractions. The separation of recyclables showed disadvantages
by the reduction in electricity generation potential due to the high
calorific value of plastics. Despite the high energy content of plastics, it
should not be noticed as the main reason for burning waste since some
plastics have a better recovery potential by recycling. Regarding the
facilities costs agreements between close cities are necessaries in order
to achieve economies of scale.
Keywords: Waste, Municipal Solid Waste, incineration, rankine,
boiler, efficiency, net power
to the current waste management system, makes that the search for
alternatives becomes needed. In this aspect, the waste incineration
aiming the electricity production in steam cycles presents several
advantages so it is presented as a good alternative that can be adopted.
However, its application needs studies in order to apply it in the most
appropriate way. Thus, this work aims to study the incineration of MSW
and the electricity production through steam cycle evaluating the
influence of MSW composition. Several scenarios were studied in which
some fractions of MSW are removed previously. The MSW generated in
Santo André city was adopted for this study. Simulations results showed
that the removal of metals, organic matter and inert components
impacts in a good way on the cycle performance improving or remaining
these parameters; moreover there is the re-use possibility of the
separated fractions. The separation of recyclables showed disadvantages
by the reduction in electricity generation potential due to the high
calorific value of plastics. Despite the high energy content of plastics, it
should not be noticed as the main reason for burning waste since some
plastics have a better recovery potential by recycling. Regarding the
facilities costs agreements between close cities are necessaries in order
to achieve economies of scale.
Keywords: Waste, Municipal Solid Waste, incineration, rankine,
boiler, efficiency, net power
Research Interests:
The objective of the extraction process in the ethanol production from sugarcane is to separate the sucrose-containing juice from the remainder of the cane, mainly fibre. The two currents, products of this process, are the juice and the... more
The objective of the extraction process in the ethanol production from sugarcane is to separate the sucrose-containing juice from the remainder of the cane, mainly fibre. The two currents, products of this process, are the juice and the bagasse. The juice is used to produce ethanol and the bagasse is the fuel for the boilers. Two types of devices are employed to perform this operation: mills and diffusers. Each one of them consumes different types of energy: mills consume mechanical energy, diffusers consume basically thermal energy. As both devices utilize an important quantity of energy, their effect in the energy balance of the factory needs to be taken into account. Aiming to discuss and characterize these effects, simulations of the complete ethanol production process, including the cogeneration system, were carried out using the Aspen Plus software, considering both devices. Process integration was also performed targeting to reduce the energy consumption. These results are presented and compared. Considering the integrated ethanol production process, with extraction -condensing steam turbines in cogeneration system, working with mills, it can produce an electricity surplus of 83.4 kWh/t of sugarcane, however, for the same conditions, working with the diffusion extraction process a production of 91.3 kwh/t of cane can be obtained, including also a small increase of 2 % in the ethanol production.
Keywords: ethanol, sugarcane, energy, process integration, extraction.
Keywords: ethanol, sugarcane, energy, process integration, extraction.
Research Interests:
The exergy analysis is a powerful tool which has been widely applied to assess economic, environmental and social issues of energy systems. Sometimes, the exergy of a mass flow is split into their physical and chemical components to... more
The exergy analysis is a powerful tool which has been widely applied to assess economic, environmental and social issues of energy systems. Sometimes, the exergy of a mass flow is split into their physical and chemical components to obtain refined results from the analysis. Moreover, the physical component is also split into thermal and mechanical ones. In this paper, another point of view is proposed, regarding the splitting of the physical exergy of a flow into the here called enthalpic and entropic terms. By means of the application of the first and the second law of thermodynamics to a set of idealized devices, whose processes are represented in the h-s diagram, it is shown that those terms can be considered components of the physical exergy of a matter stream. It is also shown that the values of the obtained terms are independent of the chosen thermodynamic path.
Keywords:
Exergy Components, Exergy Splitting, Physical Exergy.
Keywords:
Exergy Components, Exergy Splitting, Physical Exergy.
Research Interests:
An alternative thermoeconomic approach is applied to a two-stage vapour compression refrigeration cascade cycle. This approach, called the UFS Model, is based on the splitting of the physical exergy into three terms, namely, internal... more
An alternative thermoeconomic approach is
applied to a two-stage vapour compression refrigeration
cascade cycle. This approach, called the UFS Model, is
based on the splitting of the physical exergy into three
terms, namely, internal energy term, flow work term and
entropic term. Application of the UFS Model allows the
isolation of both valves and condensers in the productive
structure. The goal is to obtain the exergetic unit cost of
each internal flow and plant product. This alternative
approach yields consistent results, because exergetic unit
costs are greater than or equal to 1 and the product-fuel
ratio of each productive unit is less than or equal to 1.
Besides the allocation of the external power cost of the
plant, analyses on the irreversibilities of each cycle unit are
carried out. Thus, it is shown that the UFS Model can also
be used to quantify irreversibilities as well as the conventional
exergy analysis.
Keywords Refrigeration cycle Thermoeconomics
applied to a two-stage vapour compression refrigeration
cascade cycle. This approach, called the UFS Model, is
based on the splitting of the physical exergy into three
terms, namely, internal energy term, flow work term and
entropic term. Application of the UFS Model allows the
isolation of both valves and condensers in the productive
structure. The goal is to obtain the exergetic unit cost of
each internal flow and plant product. This alternative
approach yields consistent results, because exergetic unit
costs are greater than or equal to 1 and the product-fuel
ratio of each productive unit is less than or equal to 1.
Besides the allocation of the external power cost of the
plant, analyses on the irreversibilities of each cycle unit are
carried out. Thus, it is shown that the UFS Model can also
be used to quantify irreversibilities as well as the conventional
exergy analysis.
Keywords Refrigeration cycle Thermoeconomics
Research Interests:
This study aimed to determine the physical and chemical properties of sugar cane bagasse, the residue of sugarcane sector, with the purpose of using it in boilers, and analyze the influence of moisture content on the compaction process.... more
This study aimed to determine the physical and chemical properties of sugar cane bagasse, the residue of sugarcane sector, with the purpose of using it in boilers, and analyze the influence of moisture content on the compaction process. Thus, analyzes of apparent density, moisture content, major elements content, ultimate composition, particle size, ash content and heating value were performed. From the results it was observed that the bagasse briquette with 15.85% moisture content showed better properties after compacting including mechanical strength when compared to briquettes with 6.19 and 10.68% moisture content.
Research Interests:
Current trends of policies and markets in the energy sector are promoting renewable energy sources as a response to the depletion of fossil fuels, the demand for energy diversification, in addition to minimize the greenhouse gas and other... more
Current trends of policies and markets in the energy sector are promoting renewable energy sources as a response to the depletion of fossil fuels, the demand for energy diversification, in addition to minimize the greenhouse gas and other emissions. In this context biomass has an important role in the conversion for power, heat and fuels, specifically the residual biomass that avoids the competition for land use with food crops. Briquetting is a densification technology that helps to overcome some disadvantages of residual biomass as an energy feedstock, as low energy density and low bulk density, which complicate the storage, transport, distribution and use in conversion processes.
This study aimed to analyze the influence of moisture content on the compaction process of sugarcane bagasse, an extensive industrial residue produced in sugar and ethanol factories. Thus, analyzes of volumetric expansion, mass variation, density, and mechanical strength were performed on sugarcane briquettes with three different moisture contents: 6.19%, 10.68% and 15.85%. From the results it was observed that the bagasse briquette with 15.85% moisture content showed better properties after compacting including mechanical strength when compared to briquettes with 6.19 and 10.68% moisture content, caused by the behavior of the sugarcane bagasse fibers.
Keywords: Biomass, briquetting, sugarcane bagasse, bioenergy, densification.
This study aimed to analyze the influence of moisture content on the compaction process of sugarcane bagasse, an extensive industrial residue produced in sugar and ethanol factories. Thus, analyzes of volumetric expansion, mass variation, density, and mechanical strength were performed on sugarcane briquettes with three different moisture contents: 6.19%, 10.68% and 15.85%. From the results it was observed that the bagasse briquette with 15.85% moisture content showed better properties after compacting including mechanical strength when compared to briquettes with 6.19 and 10.68% moisture content, caused by the behavior of the sugarcane bagasse fibers.
Keywords: Biomass, briquetting, sugarcane bagasse, bioenergy, densification.
Research Interests:
The increasing waste production on Brazil has motivated the rising of waste management policies on the country. The absence of waste characterizations on every location generates a need for search the acknowledgement on the lower heating... more
The increasing waste production on Brazil has motivated the rising of waste management policies on the country. The absence of waste characterizations on every location generates a need for search the acknowledgement on the lower heating value of this waste. To overcome these problems, the use of empirical models for its predictions is a common alternative. This paper aims to draw a comparison between models and characterizations available in the literature. The results of the study shown a small error on the most used models, but this doesn’t make the use of the others prohibitive since the errors are not bigger than the normal variation caused by the change of time and location. The important factor observed on the choosing of characterizations is the moisture and ash content of the sample, which is a simpler than the ultimate analysis. Regarding the cycle simulations, the errors encountered on the heating values was
sustained, that can be found as a problem for the impact that it would cause in future contracts. The studied models were a good alternative on cases where the value is an approximation on the true value; in other cases a bomb calorimeter analysis is necessary.
sustained, that can be found as a problem for the impact that it would cause in future contracts. The studied models were a good alternative on cases where the value is an approximation on the true value; in other cases a bomb calorimeter analysis is necessary.
Research Interests:
The sugarcane industry represents one of the most important economic activities in Brazil producing sugar and ethanol for the internal and external markets. Most of the sugarcane plants in Brazil have been projected to produce both sugar... more
The sugarcane industry represents one of the most important economic activities in Brazil producing sugar and ethanol for the internal and external markets. Most of the sugarcane plants in Brazil have been projected to produce both sugar and ethanol, prioritizing one over the other according to market prices. There are also plants dedicated only to ethanol production. Nevertheless, this change in the production pattern affects parameters in their production such as water consumption, steam demands, bagasse surplus and electricity production. Thus, the aim of this study is to evaluate the production parameters for different configurations of sugarcane plant: (a) all sugarcane juice is destined to produce ethanol without sugar production and (b) distribution of 50 %/50 % of total recoverable sugars in sugar and ethanol production. Simulations in ASPEN PLUS® software were performed in order to evaluate the mass and energy balances and thermal integration using the Pinch Method was applied in order to minimize the utilities consumption.
Research Interests:
Vapour recompression is a means of upgrading energy by the compressing of a lower pressure vapour up to a higher pressure, thus making the energy more available to do useful work. There are two types of vapour recompression:... more
Vapour recompression is a means of upgrading energy by the compressing of a lower pressure vapour up to a higher pressure, thus making the energy more available to do useful work. There are two types of vapour recompression: thermo-compression and mechanical recompression. Thermo-compression uses high pressure steam through a nozzle to compress a lower pressure vapour to an intermediate pressure. On the other hand, in mechanical recompression “mechanical” means that the compression task is done through the expenditure of mechanical energy for instance a steam turbine driven a compressor. Other means of driving could be also include an electric motor or an internal combustion engine. In both of cases the main advantage of vapour recompression is that it is not necessary to supply the latent heat of vaporization to the vapour being compressed. The aim of this study is to evaluate the possibilities of the incorporation of mechanical vapour recompression in the ethanol production process from the energy point of view. Thus mechanical vapour recompression is integrated to the juice evaporation system which is composed by a multiple effect evaporator. Simulations in Aspen Plus were accomplished to perform the mass and energy balances. Results showed that the introduction of vapour recompression promoted a reduction in steam consumption of approximately 10 % in evaporation system and 4% in overall process. In order to further reduce the steam consumption of the plant, Pinch Analysis was applied to integrate the vapour recompression process coupled to evaporation system to all available streams in ethanol production process.
Research Interests:
Ethanol is produced in large scale from sugarcane in Brazil by fermentation of sugars and distillation. This is currently considered as an efficient biofuel technology, leading to significant reduction on greenhouse gases emissions.... more
Ethanol is produced in large scale from sugarcane in Brazil by fermentation of sugars and distillation. This is currently considered as an efficient biofuel technology, leading to significant reduction on greenhouse gases emissions. However, some improvements in the process can be introduced in order to improve the use of energy. In current distilleries, a significant fraction of the energy consumption occurs in the purification step e distillation and dehydration e since conventional fermentation systems employed in the industry require low substrate concentration, which must be distilled, consequently with high energy consumption. In this study, alternatives to the conventional fermentation processes are assessed, through computer simulation: low temperature fermentation and vacuum extractive fermentation. The aim of
this study is to assess the incorporation of these alternative fermentation processes in ethanol production, energy consumption and electricity surplus produced in the cogeneration system. Several cases were evaluated. Thermal integration technique was applied. Results shown that the ethanol production
increases between 3.3% and 4.8% and a reduction in steam consumption happens of up to 36%. About the electricity surplus, a value of 85 kWh/t of cane can be achieved when condensing e extracting steam turbines are used.
this study is to assess the incorporation of these alternative fermentation processes in ethanol production, energy consumption and electricity surplus produced in the cogeneration system. Several cases were evaluated. Thermal integration technique was applied. Results shown that the ethanol production
increases between 3.3% and 4.8% and a reduction in steam consumption happens of up to 36%. About the electricity surplus, a value of 85 kWh/t of cane can be achieved when condensing e extracting steam turbines are used.
Research Interests:
This study carried out an exergetic analysis of a proposed ethanol production scheme in which a new process e enzymatic hydrolysis of sugarcane bagasse e is integrated into the conventional process. Seven cases were evaluated, among them... more
This study carried out an exergetic analysis of a proposed ethanol production scheme in which a new process e enzymatic hydrolysis of sugarcane bagasse e is integrated into the conventional process. Seven cases were evaluated, among them a conventional ethanol production plant without hydrolysis, a
conventional plant combined with hydrolysis and hydrolysate concentration by evaporation, and a conventional plant combined with hydrolysis and hydrolysate concentration by the membrane system. Process simulations were performed to evaluate mass and energy balances, adopting the pre-treatment
of sugarcane bagasse by steam explosion, and including an integrated cogeneration system. It was assumed that sugarcane trash and lignin cake, a hydrolysis residue, are available as supplementary fuel.
The exergies of streams involved in the process were calculated, along with their exergetic cost. For the conventional process, in which ethanol and surplus electricity are the major products, a second-law efficiency of 28% was found. In the integrated process, with biogas as an additional product, a higher performance in resources management was achieved, with values in the range of 35 -37%.
conventional plant combined with hydrolysis and hydrolysate concentration by evaporation, and a conventional plant combined with hydrolysis and hydrolysate concentration by the membrane system. Process simulations were performed to evaluate mass and energy balances, adopting the pre-treatment
of sugarcane bagasse by steam explosion, and including an integrated cogeneration system. It was assumed that sugarcane trash and lignin cake, a hydrolysis residue, are available as supplementary fuel.
The exergies of streams involved in the process were calculated, along with their exergetic cost. For the conventional process, in which ethanol and surplus electricity are the major products, a second-law efficiency of 28% was found. In the integrated process, with biogas as an additional product, a higher performance in resources management was achieved, with values in the range of 35 -37%.
Research Interests:
Neste trabalho, foi realizada a avaliação econômica da produção de banana-passa de uma agroindústria localizada no município de Guaraqueçaba - PR. Foi avaliado o processamento da banana-passa convencional e da banana orgânica produzida... more
Neste trabalho, foi realizada a avaliação econômica da produção de banana-passa de uma
agroindústria localizada no município de Guaraqueçaba - PR. Foi avaliado o processamento da
banana-passa convencional e da banana orgânica produzida na região, comparando-se os indicadores
de viabilidade econômica. A banana-passa orgânica é exportada para a Europa e a banana-passa
convencional é comercializada na região de Curitiba - PR. Ambos os processamentos apresentaram
viabilidade econômica positiva, apresentando a banana-passa orgânica os melhores índices (TIR 94%,
VPL R$ 486.009,39 e relação benefício-custo de 2,11) do que a banana-passa convencional (TIR 14%,
VPL R$ 34.668,00 e relação benefício-custo de 1,17). A banana-passa orgânica apresentou um custo
de produção de R$ 3,64, sendo 50,1% desse valor relativo ao gasto com insumos e 27% com mão-deobra.
A banana-passa convencional apresentou um custo de R$ 3,21, sendo 45,3% para insumos e
31,2% para mão-de-obra.
agroindústria localizada no município de Guaraqueçaba - PR. Foi avaliado o processamento da
banana-passa convencional e da banana orgânica produzida na região, comparando-se os indicadores
de viabilidade econômica. A banana-passa orgânica é exportada para a Europa e a banana-passa
convencional é comercializada na região de Curitiba - PR. Ambos os processamentos apresentaram
viabilidade econômica positiva, apresentando a banana-passa orgânica os melhores índices (TIR 94%,
VPL R$ 486.009,39 e relação benefício-custo de 2,11) do que a banana-passa convencional (TIR 14%,
VPL R$ 34.668,00 e relação benefício-custo de 1,17). A banana-passa orgânica apresentou um custo
de produção de R$ 3,64, sendo 50,1% desse valor relativo ao gasto com insumos e 27% com mão-deobra.
A banana-passa convencional apresentou um custo de R$ 3,21, sendo 45,3% para insumos e
31,2% para mão-de-obra.
O objetivo deste trabalho é realizar uma avaliação termoeconômica de um sistema de refrigeração por absorção de simples efeito que utiliza como fluido de trabalho a solução H2O/LiBr. A metodologia do análise funcional com neguentropia é... more
O objetivo deste trabalho é realizar uma avaliação termoeconômica de um sistema de refrigeração por absorção de
simples efeito que utiliza como fluido de trabalho a solução H2O/LiBr. A metodologia do análise funcional com
neguentropia é aplicada para os cálculos.
O custo exergético do produto principal, o fluxo de resfriamento, foi calculado em função da exergia da fonte quente,
a qual pode ser um calor de rejeito por exemplo de um motor de combustão interna, ou o calor de combustão do gás
natural no caso de sistemas de refrigeração por absorção de queima direta.
Na estrutura produtiva para a análise funcional foram adotados 4 volumes de controle e duas unidades virtuais. Foi
introduzido também o conceito de compressor térmico. Nos resultados foi observado que o custo exergético do
produto (fluxo de resfriamento) é maior no caso do sistema de queima direta.
simples efeito que utiliza como fluido de trabalho a solução H2O/LiBr. A metodologia do análise funcional com
neguentropia é aplicada para os cálculos.
O custo exergético do produto principal, o fluxo de resfriamento, foi calculado em função da exergia da fonte quente,
a qual pode ser um calor de rejeito por exemplo de um motor de combustão interna, ou o calor de combustão do gás
natural no caso de sistemas de refrigeração por absorção de queima direta.
Na estrutura produtiva para a análise funcional foram adotados 4 volumes de controle e duas unidades virtuais. Foi
introduzido também o conceito de compressor térmico. Nos resultados foi observado que o custo exergético do
produto (fluxo de resfriamento) é maior no caso do sistema de queima direta.
Abstract. The aim of this study is to evaluate the potential of ethanol production increase, and the impacts in electricity surplus of the cogeneration plant due to the introduction of enzymatic hydrolysis of bagasse in a conventional... more
Abstract. The aim of this study is to evaluate the potential of ethanol production increase, and the impacts in electricity surplus of the cogeneration plant due to the introduction of enzymatic hydrolysis of bagasse in a conventional distillery. Moreover a comparison of these results is performed with another scenario, where all available bagasse and trash are used in the distillery cogeneration system, in order to maximize electricity surplus, considering a steam cycle provided with extraction-condensing turbines. Simulations in ASPEN PLUS® software were performed, in order to evaluate the mass and energy balances, for the studied processes. For the case of enzymatic hydrolysis, it was assumed that sugarcane trash and lignin cake, which is a residue of the hydrolysis process, are available as fuel in the cogeneration system in order to achieve a significant ethanol production increase. In the electricity surplus study, an adequate higher pressure in the boiler and turbine has been considered. Ethanol production increase resulted 12.3% and 15.1% for the hydrolysis cases evaluated, while surplus electricity increase was 236.5% and 267.5% for the cases where condensing-extraction steam turbines were adopted without enzymatic hydrolysis.
Research Interests:
Resumo Os modelos concentrados descrevem as taxas de transferência de calor e/ou massa em um sólido, admitindo que a grandeza de interesse (temperatura ou massa) dentro do sólido seja espacialmente uniforme em qualquer instante durante o... more
Resumo Os modelos concentrados descrevem as taxas de transferência de calor e/ou massa em um sólido, admitindo que a grandeza de interesse (temperatura ou massa) dentro do sólido seja espacialmente uniforme em qualquer instante durante o processo transiente, portanto considera-se desprezível os gradientes térmicos e/ou de massa no interior do corpo.
ABSTRACT This research had, as its principal objective, the application of the methodology to evaluate psychometric processes through the use of theory which combines the First and Second Principles of Thermodynamics into an adapted... more
ABSTRACT This research had, as its principal objective, the application of the methodology to evaluate psychometric processes through the use of theory which combines the First and Second Principles of Thermodynamics into an adapted system of generating psychometric processes. With the Psychometric Processes System Generator (SIGEP) and other appropriate equipment, where air flow and electrical power from different systems of air conditioning were the most important variables.
In recent years there have been several discussions on a greater use of natural gas nationwide.Moreover, there have been several announcements by the private and public sectors regarding the construction of new pipelines to supply natural... more
In recent years there have been several discussions on a greater use of natural gas nationwide.Moreover, there have been several announcements by the private and public sectors regarding the construction of new pipelines to supply natural gas to the Peruvian southern and central-north markets. This paper presents future scenarios for the use of natural gas in the large-sized industrial and commercial sectors of the country based on different hypotheses on developments in the natural gas industry, national economic growth, energy prices, technological changes and investment decisions.
First, the paper estimates the market potential and characterizes the energy consumption. Then it makes a selection of technological alternatives for the use of natural gas, and it makes an energetic and economic analysis and economic feasibility. Finally, the potential use of natural gas is calculated
through nine different scenarios. The natural gas use in cogeneration systems is presented as an alternative to contribute to the installed power capacity of the country. Considering the introduction of the cogeneration in the optimistic–advanced scenario and assuming that all of their conditions would be put into practice, in 2020, the share of the cogeneration in electricity production in Peru would be 9.9 %.
First, the paper estimates the market potential and characterizes the energy consumption. Then it makes a selection of technological alternatives for the use of natural gas, and it makes an energetic and economic analysis and economic feasibility. Finally, the potential use of natural gas is calculated
through nine different scenarios. The natural gas use in cogeneration systems is presented as an alternative to contribute to the installed power capacity of the country. Considering the introduction of the cogeneration in the optimistic–advanced scenario and assuming that all of their conditions would be put into practice, in 2020, the share of the cogeneration in electricity production in Peru would be 9.9 %.
Research Interests:
ABSTRACT This work presents a complete improved mathematical model of drying in cyclone. The slip condition of the particles on the wall, the heat transfer wall-panicle and the shrinkage of the panicles during the drying process were... more
ABSTRACT This work presents a complete improved mathematical model of drying in cyclone. The slip condition of the particles on the wall, the heat transfer wall-panicle and the shrinkage of the panicles during the drying process were considered. The mathematical model considers a two-dimensional turbulent gas-particle flow where the panicle phase is treated as a continuum. The momentum equations of both particle and gas phases were written in cylindrical coordinates. The discretized equations were solved by the SIMPLE ...
Research Interests:
The rational use of energy became a priority for all industries in Brazil after the energetic rationing in 2001. The aim of this work is to assess a proposal of a power generation system for Companhia Siderúrgica Tubarão, a steel mill... more
The rational use of energy became a priority for all industries in Brazil after the energetic rationing in 2001. The aim of this work is to assess a proposal of a power generation system for Companhia Siderúrgica Tubarão, a steel mill plant. The current system is based on a regenerative Rankine cycle using two gases from steel production—blast furnace gas (BFG) and coke oven gas (COG)—to generate electric power and occasionally steam for the process. The proposed system is a combined cycle comprising two gas turbines, two heat recovery steam generators (HRSGs), and a steam turbine. The fuel for the gas turbines is BFG, and the supplementary firing of HRSG uses COG. The proposed HRSGs work at three pressure levels. The system was assessed by means of two thermoeconomic methodologies, Theory of Exergetic Cost and Thermoeconomic Functional Analysis; exergetic and monetary costs of power production were calculated and compared to the respective values of the current system.
Research Interests:
Sugarcane is one of the most important industries of the Brazilian economy, and its main products are sugar and ethanol. Most of the industrial plants produce both products in an integrated process, in which the sugarcane bagasse is a... more
Sugarcane is one of the most important industries of the Brazilian economy, and its main products are sugar and ethanol. Most of the industrial plants produce both products in an integrated process, in which the sugarcane bagasse is a by-product that can be used as a fuel in the cogeneration system. The bagasse is used as the only fuel of the plant, supplying all energy required for the process, and also producing electricity surplus that may be sold to the grid. In this paper, exergy analysis is used to assess an integrated sugar and ethanol plant with its cogeneration system. The plant was divided into eight sub-systems to evaluate the irreversibility generation in each separately. Data from typical sugarcane factories in Brazil, which produce sugar and ethanol, were used in the process simulation. The analysis has shown that the sub-systems with the highest contribution for the total irreversibility generation of the plant were co-generation, juice extraction and fermentation. Some improvements are proposed, including process thermal integration and the introduction of more efficient equipments for prime mover and steam and electricity generation. The analysis indicated that the total irreversibility could be reduced by 10% should those changes be implemented.
Research Interests:
ABSTRACT A numerical solution of the diffusion equation to describe solute transport inside ellipsoids, assuming a constant difiusion coefficient and a corrective boundary condition, is presented. The difiusion equation in a prolate... more
ABSTRACT A numerical solution of the diffusion equation to describe solute transport inside ellipsoids, assuming a constant difiusion coefficient and a corrective boundary condition, is presented. The difiusion equation in a prolate spheroidal coordinate system was used for a hidimensional case. The finite volume method was employed to discretize the basic equation, utilizing a uniform grid size. The equation was solved irteratively using the Gauss-Seidel method. The effect of Biot number and the aspect ratio of the body on diffusion rate ...
Research Interests:
Vyazovkin's model-free kinetic algorithms were applied to determine conversion, isoconversion and apparent activation energy to both dehydration and combustion of sugarcane bagasse. Three different steps were detected with apparent... more
Vyazovkin's model-free kinetic algorithms were applied to determine conversion, isoconversion and apparent activation energy to both dehydration and combustion of sugarcane bagasse. Three different steps were detected with apparent activation energies of 76.1 ± 1.7, 333.3 ± 15.0 and 220.1 ± 4.0 kJ/mol in the conversion range of 2–5%, 15–60% and 70–90%, respectively. The first step is associated with the endothermic process of drying and release of water. The others correspond to the combustion (and carbonization) of organic matter (mainly cellulose, hemicellulose and lignin) and the combustion of the products of pyrolysis.
Research Interests:
The aim of this study is to make an exergetic analysis of the ethanol production process, by enzymatic hydrolysis of sugarcane bagasse, integrated to the conventional process of ethanol production. Three cases were evaluated, which... more
The aim of this study is to make an exergetic analysis of the ethanol production process, by enzymatic hydrolysis of sugarcane bagasse, integrated to the conventional process of ethanol production. Three cases were evaluated, which include the conventional ethanol production plant without hydrolysis (Case I), the conventional plant joint with hydrolysis process considering the concentration of hydrolysate by evaporation system (Case II), and the conventional plant joint with hydrolysis process and concentration of hydrolysate by membrane system (Case III). Simulations of the process were performed in ASPEN PLUS® software, in order to evaluate the mass and energy balances considering the pre-treatment of sugarcane bagasse by steam explosion and with a cogeneration system that was also modelled and integrated with the ethanol production process. The use of sugarcane trash was considered in order to accomplish the energetic needs of the overall process. The exergy of streams involved in the process was calculated from studies of the literature along with the exergetic and exergetic cost analysis.
Research Interests:
The aim of this study is to make an evaluation of the possibilities of ethanol production increase through the introduction of bagasse hydrolysis process in conventional distilleries, considering the limiting situation of bagasse use: it... more
The aim of this study is to make an evaluation of the possibilities of ethanol production increase through the introduction of bagasse hydrolysis process in conventional distilleries, considering the limiting situation of bagasse use: it is the major by-product in sugar and ethanol production and is burnt in boilers to satisfy the steam and power requirements of the process. Simulations in ASPEN PLUS® software were performed, in order to evaluate the mass and energy balances, for the integrated process, considering the pre-treatment of sugarcane bagasse by steam explosion. The cogeneration system was also modelled and integrated with the ethanol production process. It consists of a steam cycle with backpressure steam turbines and
parameters of live steam of 67 bar and 480°C. In all the cases studied it was considered that the steam flow used in the system was just that necessary to fulfil the process thermal needs, so, it was assumed that the surplus of bagasse was used to produce ethanol. The use of sugarcane trash was considered in order to accomplish the energetic needs of the overall process as well as lignin cake, which is a hydrolysis process residue. Several cases were evaluated, which include: the conventional ethanol production plant without hydrolysis (Case I), the conventional plant joint with hydrolysis process without thermal integration considering different solid contents in the hydrolysis reactor (Cases II, III and IV), and the conventional plant joint with the hydrolysis process considering thermal integration through Pinch method (Case V). The results shown a modest ethanol production increase of 9.7% for the situation without thermal integration and low solid content in the hydrolysis reactor, on the other hand, the case where thermal integration was applied presented an ethanol production increase of 17.4%.
Keywords:
Ethanol, sugarcane, enzymatic hydrolysis, thermal integration.
parameters of live steam of 67 bar and 480°C. In all the cases studied it was considered that the steam flow used in the system was just that necessary to fulfil the process thermal needs, so, it was assumed that the surplus of bagasse was used to produce ethanol. The use of sugarcane trash was considered in order to accomplish the energetic needs of the overall process as well as lignin cake, which is a hydrolysis process residue. Several cases were evaluated, which include: the conventional ethanol production plant without hydrolysis (Case I), the conventional plant joint with hydrolysis process without thermal integration considering different solid contents in the hydrolysis reactor (Cases II, III and IV), and the conventional plant joint with the hydrolysis process considering thermal integration through Pinch method (Case V). The results shown a modest ethanol production increase of 9.7% for the situation without thermal integration and low solid content in the hydrolysis reactor, on the other hand, the case where thermal integration was applied presented an ethanol production increase of 17.4%.
Keywords:
Ethanol, sugarcane, enzymatic hydrolysis, thermal integration.
Research Interests:
A cogeneration system based on a reciprocating natural gas engine, a heat recovery steam generator (HRSG), an absorption refrigeration system (ARS) and a cooling tower (CT) is presented as an alternative to the current UNICAMP University... more
A cogeneration system based on a reciprocating natural gas engine, a heat recovery steam generator (HRSG), an absorption refrigeration system (ARS) and a cooling tower (CT) is presented as an alternative to the current UNICAMP University Hospital (HC) utility plant. The objective of this work is to do a thermoeconomic analysis of a cogeneration system proposed for
HC. Three thermoeconomic methodologies were applied to the cogeneration system. Three methodologies were based in the Theory of the Exergetic Cost, Functional Analysis and
Functional Analysis using negentropy. The results show that there are differences in the costs of power, steam and refrigeration (cold) production which result from application of the
methodologies.
Keywords: Cogeneration, thermoeconomics
HC. Three thermoeconomic methodologies were applied to the cogeneration system. Three methodologies were based in the Theory of the Exergetic Cost, Functional Analysis and
Functional Analysis using negentropy. The results show that there are differences in the costs of power, steam and refrigeration (cold) production which result from application of the
methodologies.
Keywords: Cogeneration, thermoeconomics
This work performs an exergoeconomic analysis in the catalytic autothermal reforming of methane process to produce hydrogen with a gas turbine coupled to produce electric energy to the process. Autothermal reforming is the combination of... more
This work performs an exergoeconomic analysis in the catalytic autothermal reforming of methane process to produce hydrogen with a gas turbine coupled to produce electric energy to the process. Autothermal reforming is the combination of reforming and partial reforming, where steam reforming is carried out in presence of oxygen. The net condition in the reformer can be endothermic, exothermic or thermo-neutral depending on the ratio of CH4-H2OO2. The first step of ATR is the reforming where synthesis gas, containing H2, H2O, CO2, CO and residual CH4 is formed. Thermodynamic chemical equilibrium is assumed in all reactions of process. After reforming, Shift reactions
produce more H2 reacting CO and H2O. After Shift Reactions the synthesis gas is purified by absorption and adsorption. The absorption is made in Diethanolamine, DEA, and produce CO2 as by product. The adsorption is made in fixed beds of molecular sieves. This procedure can produce highly pure H2 (99.999 %, wt) proper to be used in fuel cells. The exergetic analysis identifies the sources of irreversibility of the process. The exergoeconomic analysis was done applying the Functional Analysis. It was employed the Fuel-Product concept where the Control Volumes, CV, may present exergetic (electric, physical and chemical) fuel/product. The desegregation of the exergy into physical and chemical is essential to evaluate the CVs performance and how the chemical exergy flows along the process. The results show that the main source of irreversibility is the Reformer. The exergoeconomic analysis shows that the cost of products is low sensitive to CO2 exergy been determined by Hydrogen cost. The results are discussed.
produce more H2 reacting CO and H2O. After Shift Reactions the synthesis gas is purified by absorption and adsorption. The absorption is made in Diethanolamine, DEA, and produce CO2 as by product. The adsorption is made in fixed beds of molecular sieves. This procedure can produce highly pure H2 (99.999 %, wt) proper to be used in fuel cells. The exergetic analysis identifies the sources of irreversibility of the process. The exergoeconomic analysis was done applying the Functional Analysis. It was employed the Fuel-Product concept where the Control Volumes, CV, may present exergetic (electric, physical and chemical) fuel/product. The desegregation of the exergy into physical and chemical is essential to evaluate the CVs performance and how the chemical exergy flows along the process. The results show that the main source of irreversibility is the Reformer. The exergoeconomic analysis shows that the cost of products is low sensitive to CO2 exergy been determined by Hydrogen cost. The results are discussed.
thermoeconomic analysis of a cogeneration system. This system is composed of an internal combustion engine, a heat recovery steam generator (HRSG), an absorption refrigeration system (ARS) and a cooling tower (CT). With the use of the... more
thermoeconomic analysis of a cogeneration system. This
system is composed of an internal combustion engine, a heat
recovery steam generator (HRSG), an absorption refrigeration
system (ARS) and a cooling tower (CT). With the use of the
mass and energy balances, several parameters of efficiency
based in the First Law of Thermodynamics were calculated for
the cogeneration system. With the use of the exergy balance,
the exergetic efficiencies for the engine, HRSG, ARS, CT and
the total system were calculated. Also, the irreversibility
contribution of each system component was shown. An
optimization was done, having as functional objective the
maximization of the difference of the operational incomes and
expenses. An exergetic cost analysis was made using the
Theory of the Cost Exergetic (TCE). The system in study gets
to save up to 28,5% of fuel in comparison with the divided
production of heat and electric energy. The largest
irreversibility that happened in the cycle is due to the engine,
which participates in the average with 78% of the total. The
analysis with the TCE showed that the product of the ARS is
more expensive in comparison with the process heat and
electricity.
system is composed of an internal combustion engine, a heat
recovery steam generator (HRSG), an absorption refrigeration
system (ARS) and a cooling tower (CT). With the use of the
mass and energy balances, several parameters of efficiency
based in the First Law of Thermodynamics were calculated for
the cogeneration system. With the use of the exergy balance,
the exergetic efficiencies for the engine, HRSG, ARS, CT and
the total system were calculated. Also, the irreversibility
contribution of each system component was shown. An
optimization was done, having as functional objective the
maximization of the difference of the operational incomes and
expenses. An exergetic cost analysis was made using the
Theory of the Cost Exergetic (TCE). The system in study gets
to save up to 28,5% of fuel in comparison with the divided
production of heat and electric energy. The largest
irreversibility that happened in the cycle is due to the engine,
which participates in the average with 78% of the total. The
analysis with the TCE showed that the product of the ARS is
more expensive in comparison with the process heat and
electricity.
This paper reports a simple technique to perform simulations of Diesel engines, taking into account the discrete variation of engine power load under constant speed. This simulation technique was developed to be used in cogeneration... more
This paper reports a simple technique to perform simulations of Diesel engines, taking into account the discrete variation of engine power load under constant speed. This simulation technique was developed to be used in cogeneration systems simulation. To perform the model, some assumptions
were made: the combustion reaction was supposed to have only four combustion products and the heat loss were treated through a bulk simple modeling. Some technical information introduced was taken from manufacturer’s data spreadsheet.
Key-words: Engine simulation, Diesel engines, partial load.
were made: the combustion reaction was supposed to have only four combustion products and the heat loss were treated through a bulk simple modeling. Some technical information introduced was taken from manufacturer’s data spreadsheet.
Key-words: Engine simulation, Diesel engines, partial load.
The present paper discusses a calculation method for the sucrose – water solution exergy. To perform this calculation, correlations are presented to obtain some properties: density, solubility, specific heat, boiling point elevation,... more
The present paper discusses a calculation method for the sucrose – water solution exergy.
To perform this calculation, correlations are presented to obtain some properties: density, solubility, specific heat, boiling point elevation, enthalpy and entropy. These properties permit to
calculate the solution physical exergy. Moreover, a correlation for the water activity coefficient in the solution was obtained from the literature and an equation to calculate the sucrose activity
coefficient is proposed. Both coefficients are used to determine the mixture exergy. Finally, a discussion of the reference system is performed, to complete the calculation of the chemical
exergy.
To perform this calculation, correlations are presented to obtain some properties: density, solubility, specific heat, boiling point elevation, enthalpy and entropy. These properties permit to
calculate the solution physical exergy. Moreover, a correlation for the water activity coefficient in the solution was obtained from the literature and an equation to calculate the sucrose activity
coefficient is proposed. Both coefficients are used to determine the mixture exergy. Finally, a discussion of the reference system is performed, to complete the calculation of the chemical
exergy.
Este trabalho tem como objetivo estudar e analisar a evolução das políticas de cogeração e seus resultados da Espanha, assim como também no Brasil. Para isto, estudam-se as principais legislações e os resultados das políticas de fomento... more
Este trabalho tem como objetivo estudar e analisar a evolução das políticas de cogeração e seus resultados da Espanha, assim como também no Brasil. Para isto, estudam-se as principais legislações e os resultados das políticas de fomento aplicados à cogeração na Espanha, estudam-se também as legislações em temas de cogeração no Brasil. A partir da década de 1980, os paises da Europa apostaram pela utilização da cogeração, devido a que se justificava seu uso por sua maior eficiência energética com respeito as centrais termelétricas existentes. A partir de 1986, iniciou-se uma etapa de expansão da cogeração, devida basicamente ao desenvolvimento de gasodutos na Espanha. Na Espanha a liberação dos mercados de energia prejudicou o desenvolvimento da cogeração, porque causou a diminuição do preço da eletricidade. Somada à crise do petróleo de 1999, que encareceu enormemente preço do gás natural e às centrais antigas de geração que teoricamente estavam amortizadas, terminou por fazer entrar em crise o setor a partir de 1999. O crescimento abrupto da cogeração trouxe como beneficio na Espanha o Investimento no setor elétrico, a melhora da competitividade industrial e poupança de importações de combustível, já que só no ano 2000, a Espanha evitou um gasto de 532 milhões de euros por conta dela.
Research Interests:
This work reports a theoretical and experimental study on the drying kinetics of bananas, under different air drying conditions. The experimental data of moisture content during drying were treated according to a diffusional model... more
This work reports a theoretical and experimental study on the drying kinetics of bananas, under different air drying conditions.
The experimental data of moisture content during drying were treated according to a diffusional model considering constant diffusion coefficient and including successively, through different models, the effects of shrinkage of the fruit and convective mass
transfer on its surface. The diffusion and convective coefficients were determined by fitting the model with experimental data,
minimising the sum of square residuals, in successive trials. The numerical results, relative to each one of the ffects introduced, are compared with experimental data, giving interesting conclusions about the in¯uence of each one of the phenomena considered. The best fitting was obtained when only the convective boundary condition was included in the diffusional model with a constant diffusion coefficient, although this model did not describe the physical phenomena well. Bananas shrink by about 43±47% their original diameter during drying. Therefore, the shrinkage assumption in the model provides greater reliability on the calculated diffusion and convective coefficients.
The experimental data of moisture content during drying were treated according to a diffusional model considering constant diffusion coefficient and including successively, through different models, the effects of shrinkage of the fruit and convective mass
transfer on its surface. The diffusion and convective coefficients were determined by fitting the model with experimental data,
minimising the sum of square residuals, in successive trials. The numerical results, relative to each one of the ffects introduced, are compared with experimental data, giving interesting conclusions about the in¯uence of each one of the phenomena considered. The best fitting was obtained when only the convective boundary condition was included in the diffusional model with a constant diffusion coefficient, although this model did not describe the physical phenomena well. Bananas shrink by about 43±47% their original diameter during drying. Therefore, the shrinkage assumption in the model provides greater reliability on the calculated diffusion and convective coefficients.
Research Interests:
This work presents a two-dimensional diffusional model to predict the simultaneous mass transfer and shrinkage during drying of solids with prolate spheroidal shape, considering that the changes in volume of solid are equal to the volume... more
This work presents a two-dimensional diffusional model to predict the simultaneous mass transfer and shrinkage during drying of solids with prolate spheroidal shape, considering that the changes in volume of solid are equal to the volume of evaporated water. The resulting equations are numerically solved, using the finite-volume method. This model was used to study numerically the effect of the air-drying conditions and shrinkage on the drying kinetic of banana peel for six experiments, considering the natural shape of this fruit. Here, it was treated as an ellipsoid of revolution. Several results are shown and analyzed such as the comparison between numerical and experimental data; the dimensionless shrinkage parameters; the relationships of length, superficial area and volume; the moisture content distribution and finally the mass transfer and diffusion coefficients.
In the last four years, the ethanol using as a fuel, back to be a feasible alternative in the Brazil, mainly due to a increase of a petroleum price, a concern with reduction of atmospheric emission levels and exportation possibilities to... more
In the last four years, the ethanol using as a fuel, back to be a feasible alternative in the Brazil, mainly due to a increase of a petroleum price, a concern with reduction of atmospheric emission levels and exportation possibilities to other countries (US, Japan and European Union). In Brazil, ethanol is produced from sugar cane, following some production steps as extraction of sugar cane juice, fermentation and distillation. From the energetic point view, the distillation is the most important step because needs high energy quantity. In the columns of distillation, the solution ethanol-water from fermentation process is separated, producing distillated (ethanol) and water, with steam consumption in the reboiler and condenser. The application of the Exergoeconomic analysis in the comparison between different configurations is used to find the better way to improve the global efficiency of the distillation process. But, to complete Exergoeconomic analysis, the correct determination of exergy values of ethanol-water mixtures has been done. Commercial softwares that work with simulation of chemical systems, like distillation columns, do not bring enough information about the calculation of the enthalpy and entropy and consequently exergy determination. The ethanol-water solution is highly non ideal, therefore, to calculate correctly, the values of enthalpy and entropy must include the sum of the pure component and excess properties, the Gibbs free energy and activity coefficients must be considered. The procedure to calculate these properties is developed, the activity coefficients, Gibbs free energy, enthalpy and entropy excess and correct exergy values are determined for ethanol-water mixtures. Finally, the application of exergoeconomic analysis is shown, to improve the global efficiency of distillation systems.
Keywords: excess properties, exergy, ethanol-water solution, biomass characteristics, bio-ethanol, bio-fuel standardization.
Keywords: excess properties, exergy, ethanol-water solution, biomass characteristics, bio-ethanol, bio-fuel standardization.
Research Interests:
The rational use of energy has become a priority for all industries in Brazil, mainly after the energy rationing in 2001. Methodologies to quantify and improve the performance of plants that consume and generate electricity and thermal... more
The rational use of energy has become a priority for all industries in Brazil, mainly after the energy rationing
in 2001. Methodologies to quantify and improve the performance of plants that consume and generate electricity and thermal energy are being used to reach this goal. Exergoeconomic analysis provides a complete diagnosis of a plant, both in exergetic and in monetary values. This study shows the methodology used to assess the power generation system of the Companhia Siderúrgica Tubarão (CST). The current system is based on a regenerative Rankine cycle using two gases from steel production – blast furnace gas (BFG) and coke oven gas (COG) – to generate electric power and occasionally steam for the process. Use of the Theory of Exergetic Cost allowed determination of monetary and exergetic costs. Moreover, indicators such as cost variation, relative cost variation, and exergoeconomic factors were calculated to determine the influence of each component in the make-up of plant costs and to find the best way of decreasing generation costs of energy and process steam.
Keywords:
Blast furnace gas
Coke oven gas
Power generation
Steel mills
Exergoeconomic analysis
in 2001. Methodologies to quantify and improve the performance of plants that consume and generate electricity and thermal energy are being used to reach this goal. Exergoeconomic analysis provides a complete diagnosis of a plant, both in exergetic and in monetary values. This study shows the methodology used to assess the power generation system of the Companhia Siderúrgica Tubarão (CST). The current system is based on a regenerative Rankine cycle using two gases from steel production – blast furnace gas (BFG) and coke oven gas (COG) – to generate electric power and occasionally steam for the process. Use of the Theory of Exergetic Cost allowed determination of monetary and exergetic costs. Moreover, indicators such as cost variation, relative cost variation, and exergoeconomic factors were calculated to determine the influence of each component in the make-up of plant costs and to find the best way of decreasing generation costs of energy and process steam.
Keywords:
Blast furnace gas
Coke oven gas
Power generation
Steel mills
Exergoeconomic analysis
Research Interests:
Este trabalho tem por objetivo analisar a viabilidade econômica e financeira para sistemas de cogeração estudando-se o caso do Hospital das Clinicas (HC) da Universidade Estadual de Campinas (UNICAMP). Para isto, estudam-se diferentes... more
Este trabalho tem por objetivo analisar a viabilidade econômica e financeira para sistemas de cogeração estudando-se o caso do Hospital das Clinicas (HC) da Universidade Estadual de
Campinas (UNICAMP). Para isto, estudam-se diferentes alternativas de cogeração, como também a metodologia de seleção dos sistemas e a análise econômica e financeira. Para a análise de viabilidade econômica são comparados os custos operacionais sem cogeração com as alternativas de cogeração, para todas as propostas das empresas. Foram feitos cálculos com os custos atuais do gás natural e com uma taxa de atratividade de 10 %, observou-se que as alternativas apresentadas pelas empresas não podiam ser viáveis economicamente. Realizaram-se estudos econômicos procurando diferentes cenários com a variação do custo de gás natural. Sob as condições atuais o projeto é inviável economicamente. O alto custo de gás natural inviabiliza o projeto. As soluções com motores de combustão interna (MCI) são as que têm maior desempenho econômico.
Palavras chaves: Cogeração, viabilidade econômica e financeira
Campinas (UNICAMP). Para isto, estudam-se diferentes alternativas de cogeração, como também a metodologia de seleção dos sistemas e a análise econômica e financeira. Para a análise de viabilidade econômica são comparados os custos operacionais sem cogeração com as alternativas de cogeração, para todas as propostas das empresas. Foram feitos cálculos com os custos atuais do gás natural e com uma taxa de atratividade de 10 %, observou-se que as alternativas apresentadas pelas empresas não podiam ser viáveis economicamente. Realizaram-se estudos econômicos procurando diferentes cenários com a variação do custo de gás natural. Sob as condições atuais o projeto é inviável economicamente. O alto custo de gás natural inviabiliza o projeto. As soluções com motores de combustão interna (MCI) são as que têm maior desempenho econômico.
Palavras chaves: Cogeração, viabilidade econômica e financeira
Research Interests:
Particle residence time is an extremely important variable in a cyclonic dryer project. With the goal of obtaining a device that conduces to a long particle residence time, the influence of cyclone dimensions on particle residence time... more
Particle residence time is an extremely important variable in a cyclonic dryer project. With the goal of obtaining a device that conduces to a long particle residence time, the influence of cyclone dimensions on particle residence time and on the type of flow is discussed here. The research was based on a device with a very high ratio of cyclone diameter to other dimensions. Simulations were developed with computational fluid dynamics techniques by the use of the commercial code CFX 4.4 of AEA Technology. Particles were treated individually. The fit of a turbulence model was also discussed. Theoretical and experimental results showed that the dimensions of the conical part of the cyclone had a very important influence on flow and consequently on particle residence time. The influences of volumetric concentration and particle diameter on particle residence time were also observed.
Keywords: cyclone, CFD, drying, particle residence time.
Keywords: cyclone, CFD, drying, particle residence time.
The aim of this study is to present a methodology to calculate the exergy of lithium bromide–water solution (LiBr/H2O) widely used in absorption refrigeration systems, absorption heat pumps and absorption heat transformers. As the... more
The aim of this study is to present a methodology to calculate the exergy of lithium bromide–water solution (LiBr/H2O) widely used in absorption refrigeration systems, absorption heat pumps and absorption heat transformers. As the LiBr/H2O solution is not ideal, it is necessary to take into account the activity of the
constituents in the chemical exergy calculation. Adopting the reference environment proposed by Szargut et al., the chemical exergy of pure LiBr was obtained as well as the chemical and physical exergy of the LiBr/H2O solution. Results are reported in the temperature range between 5 and 1801C. In the literature, exergy values for LiBr/H2O solution are widely varied. This fact is due to different reference systems adopted to calculate exergy. Some cases in the literature are compared with that obtained with the methodology proposed in this study and
with the approaches of Koehler, Ibele, Soltes and Winter and Oliveira and Le Goff.
KEY WORDS
absorption system; exergy; lithium bromide; chemical exergy; reference system
constituents in the chemical exergy calculation. Adopting the reference environment proposed by Szargut et al., the chemical exergy of pure LiBr was obtained as well as the chemical and physical exergy of the LiBr/H2O solution. Results are reported in the temperature range between 5 and 1801C. In the literature, exergy values for LiBr/H2O solution are widely varied. This fact is due to different reference systems adopted to calculate exergy. Some cases in the literature are compared with that obtained with the methodology proposed in this study and
with the approaches of Koehler, Ibele, Soltes and Winter and Oliveira and Le Goff.
KEY WORDS
absorption system; exergy; lithium bromide; chemical exergy; reference system
AbstractÐThe objective of this paper is to discuss the use of coffee grounds in the Brazilian soluble coffee industry. This residue is used as a fuel in the boilers of the same industry; so, data about their utilization are presented and... more
AbstractÐThe objective of this paper is to discuss the use of coffee grounds in the Brazilian soluble coffee industry. This residue is used as a fuel in the boilers of the same industry; so, data about their utilization are presented and analysed, discussing the actual technology and the advantages of improving the drying of the biomass with the exhaust combustion gases. After that, an experimental study is reported
on the characteristics of this material, which are important for the combustion process, including the transport, storage and drying, the mean diameter of the particles, talus angle, apparent and real density, sphericity, surface area, terminal velocity, spontaneous ignition temperature and heat of combustion.
Keywords: Residues; burning; coffeee grounds; terminal velocity; spontaneous ignition; combustion heat.
on the characteristics of this material, which are important for the combustion process, including the transport, storage and drying, the mean diameter of the particles, talus angle, apparent and real density, sphericity, surface area, terminal velocity, spontaneous ignition temperature and heat of combustion.
Keywords: Residues; burning; coffeee grounds; terminal velocity; spontaneous ignition; combustion heat.
ABSTRACT: The majority of sugar cane industries in Brazil can produce sugar and ethanol simultaneously in integrated plants. Ethanol can be produced using molasses generated on sugar process or with a mix of extracted cane juice and... more
ABSTRACT: The majority of sugar cane industries in Brazil can produce sugar and ethanol simultaneously in integrated plants. Ethanol can be produced using molasses generated on sugar process or with a mix of extracted cane juice and molasses. The ethanol production is increasing in the last few years, with the introduction of flex fuel cars in the Brazilian market and the possibility to export ethanol. At the same time, the sugar production continues to be attractive for the internal and external markets. The electricity is another product of this industry, once the cogeneration systems of the plants consume the bagasse generated at the juice extraction system as fuel, attending the plant steam and electricity demands and generating electricity surplus that can be sold to the grid. This study aim to assess four different extraction systems: mills and diffusers using direct drive steam turbines or electrical engines, evaluating their influence on electricity generation and exergetic cost of the sugar and ethanol produced in an integrated plant.
Key words: cane sugar and ethanol industry, extraction system, exergetic cost, biomass energy.
Key words: cane sugar and ethanol industry, extraction system, exergetic cost, biomass energy.
The performance of sugar cane bagasse boilers is commonly analyzed through the first law of thermodynamics, using the energy balance method and the fuel lower heating value as calculation base. This work presents a first law analysis... more
The performance of sugar cane bagasse boilers is commonly analyzed through the first law of thermodynamics, using the energy balance method and the fuel lower heating value as calculation base. This work presents a first law analysis using two different methods: the input/output and the energy balance. The employment of the fuel higher and lower heating values as calculation base are presented and discussed. Moreover, a second law analysis is showed, based on two methods: input/output and exergy balance. The methods based on exergy concept permits to observe the main irreversibilities that happen during the steam production in a bagasse boiler.
Keywords: Boiler; efficiency; exergy; bagasse.
Keywords: Boiler; efficiency; exergy; bagasse.
The design and operation analysis and optimization of complex thermal plants, in terms of both thermal and economical variables, is the subject of Thermoeconomics. Several different thermoeconomical methodologies are presented in the... more
The design and operation analysis and optimization of complex thermal plants, in terms of both thermal and economical variables, is the subject of Thermoeconomics. Several different
thermoeconomical methodologies are presented in the literature, each one based upon different principles and therefore presenting somewhat different results. In this article, four methodologies developed by diverse authors are applied to a simple gas turbine cogeneration system. The results are compared: the importance of the division of exergy into mechanical and thermal components and the allocation of the cost of external irreversibility are discussed.
Keywords: Thermoeconomy; Second law analysis; Economic analysis
thermoeconomical methodologies are presented in the literature, each one based upon different principles and therefore presenting somewhat different results. In this article, four methodologies developed by diverse authors are applied to a simple gas turbine cogeneration system. The results are compared: the importance of the division of exergy into mechanical and thermal components and the allocation of the cost of external irreversibility are discussed.
Keywords: Thermoeconomy; Second law analysis; Economic analysis
Research Interests:
Abstract The main purpose of this work is to apply thermoeconomics concepts to a projected steam injected gas turbine cogeneration system, which aims at providing the thermal and electrical demands of an industrial district sited in Cabo... more
Abstract
The main purpose of this work is to apply thermoeconomics concepts to a projected steam injected gas turbine cogeneration system, which aims at providing the thermal and electrical demands of an industrial district sited in Cabo (Pernambuco, Brazil). The power plant is evaluated on the basis of the First and Second Laws of Thermodynamics. A thermoeconomic analysis, using the Theory of Exergetic Cost, was performed in order to determine the production costs of electricity and steam. Two hypothetical operational conditions, as regards the level of electric power generation, were considered.
Keywords: Thermoeconomics; Exergy; STIG cycle; Irreversibility; Efficiency
The main purpose of this work is to apply thermoeconomics concepts to a projected steam injected gas turbine cogeneration system, which aims at providing the thermal and electrical demands of an industrial district sited in Cabo (Pernambuco, Brazil). The power plant is evaluated on the basis of the First and Second Laws of Thermodynamics. A thermoeconomic analysis, using the Theory of Exergetic Cost, was performed in order to determine the production costs of electricity and steam. Two hypothetical operational conditions, as regards the level of electric power generation, were considered.
Keywords: Thermoeconomics; Exergy; STIG cycle; Irreversibility; Efficiency
Research Interests:
The sugarcane industry represents one of the most important economic activities in Brazil, producing sugar and ethanol for the internal and external markets. Moreover, thermal and electric energy is produced for self-consumption, using... more
The sugarcane industry represents one of the most important economic activities in Brazil, producing sugar and ethanol for the internal and external markets. Moreover, thermal and electric energy is produced for self-consumption, using sugarcane bagasse as fuel in cogeneration plants. Almost all the sugarcane plants in Brazil are self-sufficient in terms of energy supply and in the last few years some of them have been selling their surplus electricity for the grid. The reduction of process steam requirements and the use of more efficient cogeneration systems are new alternatives to increase the surplus electricity generation. The purpose of this paper is to analyze the steam
demand reduction on sugar and ethanol process and alternatives for cogeneration systems in sugarcane plants, aiming at the surplus electricity generation increase.
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demand reduction on sugar and ethanol process and alternatives for cogeneration systems in sugarcane plants, aiming at the surplus electricity generation increase.
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Research Interests:
The consumption of natural resources has been increasing continuously during recent decades, due to the growing demand caused by both the economic and the demographic rise of global population. Environmental overloads that endanger the... more
The consumption of natural resources has been increasing continuously during recent decades, due to the growing demand caused by both the economic and the demographic rise of global population. Environmental overloads that endanger the survival of our civilization and the sustainability of current life support systems are caused by the increased consumption of natural resources—particularly water and energy—which are essential for life and for the socio-economic development of societies. While not yet well utilized, process integration and polygeneration are promising tools which reach the double
objective of increasing the efficiency of natural resources, and also minimizing the environmental impact. This paper discusses the concepts of polygeneration and energy integration and various examples of polygeneration systems: (i) sugar and energy production in a sugarcane factory; (ii) district heating and cooling with natural gas cogeneration engines and (iii) combined production of water and energy. It is clearly evident that polygeneration systems which include appropriate process integration
significantly increase the efficient use of natural resources.
objective of increasing the efficiency of natural resources, and also minimizing the environmental impact. This paper discusses the concepts of polygeneration and energy integration and various examples of polygeneration systems: (i) sugar and energy production in a sugarcane factory; (ii) district heating and cooling with natural gas cogeneration engines and (iii) combined production of water and energy. It is clearly evident that polygeneration systems which include appropriate process integration
significantly increase the efficient use of natural resources.
Research Interests: Engineering, Environmental Engineering, Mechanical Engineering, Chemical Engineering, Civil Engineering, and 21 moreBiochemical Engineering, Water quality, Energy, Bioenergy, Water Treatment, Wastewater Treatment, Economic Development, Biofuels, Process Integration, Natural Gas, Environmental Impact, District Heating, Energy Production, Bioprocessing, Energy efficient, Interdisciplinary Engineering, Natural Resource, Water Quality, Bioproducts, Biomass Processing, and Support System
Cogeneration is usual practice in sugar-cane mills. In this work, thermoeconomic analysis is applied to the cogeneration system of a typical Cuban sugar-cane mill. Two different cost attribution methods, the extraction method and the... more
Cogeneration is usual practice in sugar-cane mills. In this work, thermoeconomic analysis is applied to the cogeneration system of a typical Cuban sugar-cane mill. Two different cost attribution
methods, the extraction method and the equality method are used to evaluate the exergetic and monetary (operational) costs of each ¯ux within the system, especially the steam and generated power. The methodology indicates the equipment responsible for the greatest irreversibility and for the increase in
the costs of the products of the system.
methods, the extraction method and the equality method are used to evaluate the exergetic and monetary (operational) costs of each ¯ux within the system, especially the steam and generated power. The methodology indicates the equipment responsible for the greatest irreversibility and for the increase in
the costs of the products of the system.
Research Interests:
The sugar cane industry represents one of the most important economic sectors in Brazil. It produces sugar and ethanol for the internal and external markets. Also, thermal and electric energy are produced for the own factory consumption,... more
The sugar cane industry represents one of the most important economic sectors in Brazil. It produces sugar and ethanol for the internal and external markets. Also, thermal and electric energy are produced for the own factory consumption, using sugar cane bagasse as fuel in cogeneration plants. Almost
all the sugar cane factories in Brazil are self-sufficient in terms of energy supply and in the last few years some of them have been selling their surplus for the grid. The introduction of steam power plants operating at higher pressure and temperature levels or even Biomass Gasification Systems operating in combined
cycles are new alternatives for increasing the efficiency of these systems. The purpose of this paper is to analyze different options of cogeneration systems in sugar cane factories in order to evaluate the possibilities of increasing electricity generation. The analysis of the power plant is performed together with
the steam demand reduction of sugar production process once the two systems are interlinked.
Keywords: sugar production, cogeneration, biomass energy.
all the sugar cane factories in Brazil are self-sufficient in terms of energy supply and in the last few years some of them have been selling their surplus for the grid. The introduction of steam power plants operating at higher pressure and temperature levels or even Biomass Gasification Systems operating in combined
cycles are new alternatives for increasing the efficiency of these systems. The purpose of this paper is to analyze different options of cogeneration systems in sugar cane factories in order to evaluate the possibilities of increasing electricity generation. The analysis of the power plant is performed together with
the steam demand reduction of sugar production process once the two systems are interlinked.
Keywords: sugar production, cogeneration, biomass energy.
Ethanol may be produced using sugarcane bagasse as raw material through the Organosolv process with dilute acid hydrolysis, thus increasing ethanol production with the same cultivated sugarcane area. In this work simulations of bioethanol... more
Ethanol may be produced using sugarcane bagasse as raw material through the Organosolv process with dilute acid
hydrolysis, thus increasing ethanol production with the same cultivated sugarcane area. In this work simulations of bioethanol production from sugarcane juice and bagasse are carried out using software UniSim Design. A typical large scale production plant is considered: 1000m3/day of ethanol is produced using sugarcane juice as rawmaterial. A three-step hydrolysis process (pre-hydrolysis of hemicellulose, Organosolv delignification and cellulose hydrolysis) of surplus sugarcane bagasse is considered. Pinch analysis is used to determine the minimum hot utility obtained with thermal integration of the plant, in order to find out the maximum availability of bagasse that can be used in the hydrolysis process, taking into consideration the use of 50% of generated sugarcane trash as fuel for electricity and steam production. Two different cases were analyzed for the product purification step: conventional and doubleeffect distillation systems. It was found that the double-effect distillation system allows 90% of generated bagasse to be used as raw material in the hydrolysis plant, which accounts for an increase of 26% in bioethanol production, considering exclusively the fermentation of hexoses obtained from the cellulosic fraction.
Keywords: Bioethanol; Sugarcane; Distillation; Acid hydrolysis; Simulation
hydrolysis, thus increasing ethanol production with the same cultivated sugarcane area. In this work simulations of bioethanol production from sugarcane juice and bagasse are carried out using software UniSim Design. A typical large scale production plant is considered: 1000m3/day of ethanol is produced using sugarcane juice as rawmaterial. A three-step hydrolysis process (pre-hydrolysis of hemicellulose, Organosolv delignification and cellulose hydrolysis) of surplus sugarcane bagasse is considered. Pinch analysis is used to determine the minimum hot utility obtained with thermal integration of the plant, in order to find out the maximum availability of bagasse that can be used in the hydrolysis process, taking into consideration the use of 50% of generated sugarcane trash as fuel for electricity and steam production. Two different cases were analyzed for the product purification step: conventional and doubleeffect distillation systems. It was found that the double-effect distillation system allows 90% of generated bagasse to be used as raw material in the hydrolysis plant, which accounts for an increase of 26% in bioethanol production, considering exclusively the fermentation of hexoses obtained from the cellulosic fraction.
Keywords: Bioethanol; Sugarcane; Distillation; Acid hydrolysis; Simulation