ITEC - Instituto de Tecnologia

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/25

Navegar

Agora exibindo 1 - 20 de 191

Acesso aberto (Open Access)
Alumina para utilização cerâmica, obtida a partir do rejeito de beneficiamento de caulim
(1997-12) FLORES, Silvia Maria Pereira; NEVES, Roberto de Freitas
The kaolin processing for paper covering produces a great volume of residues formed primarily by kaolinite claymineral, here the starting material for the synthesis of ammonium alumen aiming to obtain free sodium alumina with fine grade for ceramic manufacturing. The synthesis process to obtain ammonium alumen consisted of the following procedures: residues calcination and sulphuric leaching of metakaolinite followed by neutralization/crystallisation of aluminum sulphate solution with ammonium hydroxide concentrated solution. The effect of calcination temperature (650 °C, 700 °C and 750 °C), calcination time of residues (30 min, 60 min and 120 min), sulphuric acid concentration as well as leaching temperature (70 °C, 80 °C and 90 °C) on the kinetics of aluminum leaching were studied. The influence of pH on ammonium alumen crystallization was also studied. Data on chemical analysis, XRD, DTA, TGA and granulometry of the material utilized and synthesized are presented and discussed.
Acesso aberto (Open Access)
High pressure vapor-liquid equilibria of palm fatty acids distillates-carbon dioxide system
(1997-12) MACHADO, Nélio Teixeira de; BRUNNER, Gerd
Vapor-Liquid equilibria of palm fatty acids distillates/carbon dioxide system has been investigated experimentally at temperatures of 333, 353, and 373 K and pressures of 20, 23, 26, and 29 MPa using the static method. Experimental data for the quasi-binary system palm fatty acids distillates/carbon dioxide has been correlated with Redlich-Kwong-Aspen equation of state. Modeling shows good agreement with experimental data. Selectivity obtained indicates that supercritical carbon dioxide is a reasonable solvent for separating saturated (palmitic acid) and unsaturated (oleic+linoleic acids) fatty acids from palm fatty acids distillates in a continuous multistage countercurrent column.
Acesso aberto (Open Access)
Separation of satured and unsaturated fatty acids from palm fatty acids distillates in continuous multistage countercurrent columns with supercritical carbon dioxide as solvent: a process design methodology
(1997-12) MACHADO, Nélio Teixeira de; BRUNNER, Gerd
In this work the separation of multicomponent mixtures in counter-current columns with supercritical carbon dioxide has been investigated using a process design methodology. First the separation task must be defined, then phase equilibria experiments are carried out, and the data obtained are correlated with thermodynamic models or empirical functions. Mutual solubilities, Ki-values, and separation factors aij are determined. Based on this data possible operating conditions for further extraction experiments can be determined. Separation analysis using graphical methods are performed to optimize the process parameters. Hydrodynamic experiments are carried out to determine the flow capacity diagram. Extraction experiments in laboratory scale are planned and carried out in order to determine HETP values, to validate the simulation results, and to provide new materials for additional phase equilibria experiments, needed to determine the dependence of separation factors on concetration. Numerical simulation of the separation process and auxiliary systems is carried out to optimize the number of stages, solvent-to-feed ratio, product purity, yield, and energy consumption. Scale-up and cost analysis close the process design. The separation of palmitic acid and (oleic+linoleic) acids from PFAD-Palm Fatty Acids Distillates was used as a case study.
Acesso aberto (Open Access)
Extração de oleoresina de Cúrcuma (Curcuma longa l) com CO2 supercrítico
(1997-12) CHASSAGNEZ MÉNDEZ, Angel Luis; CORRÊA, Nádia Cristina Fernandes; MEIRELES, Maria Angela de Almeida
Turmeric (Curcuma longa L) is one of the most used source of natural color in the food industry. Curcuminoids can be obtained from the roots of this plant. These pigments impact a yellow color and they might be able to substitute synthetic dyes. Turmeric oleoresin extraction experiments have been carried out with supercritical CO2 to investigate the influences of the pretreatment of the rhizomes on oleoresin. The extractions were conducted at the Department of Chemical Engineering of the Federal University of Pará (Universidade Federal do Pará). Turmeric was dried at 70ºC and 105ºC. Extractions have been carried out at pressures of 200, 250 and 300 bar and a temperature of 45ºC. Results shown the total yield and the content of curcumin present in the oleoresin. Amount of oleoresin extracted from the material dried at 70ºC was larger while most of the curcuminoids remained in the solid material.
Acesso aberto (Open Access)
Influência da temperatura nos parâmetros de modelos bi-paramétricos que predizem isotermas de adsorção de umidade do guaraná (Paullinia cupana) em pó
(1997-12) PENA, Rosinelson da Silva; RIBEIRO, Claudio Cavalcanti; GRANDI, José Glauco
Eight biparametric mathematic models of the literature and widely applied in the prediction of moisture adsorption isoterms were analised. The guarana (Paullinia cupana) powder used in this study, was obtained in spray dryer from a hidroalcoholic extract. The experimental points of the moisture adsorption isotherms of the product at 15°C, 25°C and 35°C were fitted by non-linear regression analysis. To study temperature effect in the parameters of the models were used linear, exponential, logarithmic and inverse regressions. They were also used to fit the software STATGRAPHICS 5.1. The Handerson, Oswin and Mizrahi equations presented the best results among tested models.
Acesso aberto (Open Access)
Extraction of oil from pressed palm oil (Elaes guineensis) fibers using supercritical CO2
(1997-12) FRANÇA, Luiz Ferreira de; MEIRELES, Maria Angela de Almeida
Residual fibers from palm oil production are a good source of carotene, since they contain more than 5% of the original oil, with about 5000 ppm of carotenoids. As carotenoids are thermosensitive molecules, supercritical CO2 can be used for oil recovery, because this technique employs low temperatures. In this work results of oil extraction experiments from pressed palm oil fibers are shown. Fibers were from AGROPALMA, an industry which is located in Tailândia (Pará, Brazil). Extractions were carried out at 200, 250 and 300 bar and at temperatures of 45 and 55oC. Oil was analyzed by UV/vis spectrophotometry for total carotene determination. Results showed a large increase in extraction rate from 200 to 250 bar and a small variation from 250 to 300 bar. The total amount of carotenes did not increase in the course of extraction at 300 bar, but it showed a large increase at 200 and at 250 bar. Free fatty acids are present in amounts larger than those found in commercial oils.
Acesso aberto (Open Access)
Integral transform solution for the forced convection of herschel-bulkley fluids in circular tubes and parallel-plates ducts
(1998-03) QUARESMA, João Nazareno Nonato; MACÊDO, Emanuel Negrão
The thermal entry region in laminar forced convection of Herschel-Bulkley fluids is solved analytically through the integral transform technique, for both circular and parallel-plates ducts, which are maintained at a prescribed wall temperature or at a prescribed wall heat flux. The local Nusselt numbers are obtained with high accuracy in both developing and fully-developed thermal regions, and critical comparisons with previously reported numerical results are performed.
Acesso aberto (Open Access)
A Law of the Wall Formulation for Recirculating Flows
(2000) CRUZ, Daniel Onofre de Almeida; BORTOLUS, Marcos Vinicius
This work presents a new law of the wall formulation for recirculating turbulent flows. An alternative expression for the internal length which can be applied in the separated region is also presented. The formulation is implemented in a numerical code which solves the k-e model through a finite volume method. The theoretical results are compared with the experimental data of Vogel and Eaton (J. of Heat Transfer, Transactions of ASME, vol.107, pp. 922-929, 1985). The paper shows that the present formulation furnishes better results than the standard k-e formulation.
Acesso aberto (Open Access)
Aplicação de modelos matemáticos bi e tri-paramétricos na predição de isotermas de adsorção de umidade do guaraná (Paullinia cupana) em pó
(2000-04) PENA, Rosinelson da Silva; RIBEIRO, Claudio Cavalcanti; GRANDI, José Glauco
In this study, twelve mathematic models (six biparametrics and six triparametrics), applied in the prediction of isotherms, were studied on prediction of moisture adsorption isoterms of guarana (Paullinia cupana) powder obtained in spray dryer. The moisture adsorption isotherms of the product were fitted at 15° C, 25° C and 35° C, by nonlinear regression analysis, using the software STATGRAPHICS 5.1. The best results among studied models on prediction of moisture adsorption isotherms were GAB, modified BET and Anderson equations (triparametric), Handerson and Oswin equations (biparametric).
Acesso aberto (Open Access)
A mass transfer model applied to the supercritical extraction with CO2 of curcumins from turmeric rhizomes (Curcuma longa L)
(2000-09) CHASSAGNEZ MÉNDEZ, Angel Luis; CORRÊA, Nádia Cristina Fernandes; FRANÇA, Luiz Ferreira de; MACHADO, Nélio Teixeira de; ARAÚJO, Marilena Emmi
Increasing restrictions on the use of artificial pigments in the food industry, imposed by the international market, have increased the importance of raw materials containing natural pigments. Of those natural substances with potential applications turmeric rhizomes (Curcuma longa L), are one of the most important natural sources of yellow coloring. Three different pigments (curcumin, desmetoxycurcumin, and bis-desmetoxycurcumin) constitute the curcuminoids. These pigments are largely used in the food industry as substitutes for synthetic dyes like tartrazin. Extraction of curcuminoids from tumeric rhizomes with supercritical CO2 can be applied as an alternative method to obtain curcuminoids, as natural pigments are in general unstable, and hence degrade when submitted to extraction with organic solvents at high temperatures. Extraction experiments were carried out in a supercritical extraction pilot plant at pressures between 25 and 30 MPa and a temperature of 318 K. The influence of drying pretreatment on extraction yield was evaluated by analyzing the mass transfer kinetics and the content of curcuminoids in the extracts during the course of extraction. The chemical identification of curcuminoids in both the extract and the residual solid was performed by spectrophotometry. Mass transfer within the solid matrix was described by a linear first-order desorption model, while that in the gas phase was described by a convective mass transfer model. Experimental results showed that the concentration profile for curcuminoids during the supercritical extraction process was higher when the turmeric rhizomes were submitted to a drying pretreatment at 343 K.
Acesso aberto (Open Access)
Supercritical extraction of pupunha (Guilielma speciosa) oil in a fixed bed using carbon dioxide
(2000-09) ARAÚJO, Marilena Emmi; MACHADO, Nélio Teixeira de; FRANÇA, Luiz Ferreira de; MEIRELES, Maria Angela de Almeida
The pupunha (Guilielma speciosa) is the fruit of a palm tree typical of the Brazilian Northern region, whose stem is used as a source of heart of palm. The fruit, which is about 65% pulp, is a source of oil and carotenes. In the present work, an analysis of the kinetics of supercritical extraction of oil from the pupunha pulp is presented. Carbon dioxide was used as solvent. The extractions were carried out at 25 MPa and 323 K and 30 MPa and 318 K. The chemical composition of the extracts in terms of fatty acids was determined by gas chromatography. The amount of oleic acid, a saturated fatty acid, in the CO2 extracts was larger than that in the extract obtained with hexane. The overall extraction curves were modeled using the single-parameter model proposed in the literature to describe the desorption of toluene from activated coal.
Acesso aberto (Open Access)
Optimization of annatto (Bixa orellana L.) drying in fixed bed
(2000-12) FARIA, Lênio José Guerreiro de; ROCHA, Sandra Cristina dos Santos
The drying of annatto seeds (Bixa orellana L.), red piave cultivate, was studied in a fixed bed dryer. The best conditions were estimated to minimize the loss of coloring and to obtain final moisture of the seeds in appropriate levels to its conservation and maintenance of quality. The quantification of the influence of entrance variables in the final contents of bixin and moisture seeds and the identification of the optimal point was performed through the techniques of factorial design, response surfaces methodology, canonical analysis and desirability function. It was verified that the final moisture of the seeds may be estimated by a second-order polynomial model and that the final content of bixin is only significantly influenced by the time of drying being described properly by a linear model, for the seeds used in this study.
Acesso aberto (Open Access)
Integral transform method for laminar heat transfer convection of herschel-bulkley fluids within concentric annular ducts
(2001-12) VIANA, Marcos Jose Gomes; NASCIMENTO, Udilma da Conceição Serrão; QUARESMA, João Nazareno Nonato; MACÊDO, Emanuel Negrão
Related momentum and energy equations describing the heat and fluid flow of Herschel-Bulkley fluids within concentric annular ducts are analytically solved using the classical integral transform technique, which permits accurate determination of parameters of practical interest in engineering such as friction factors and Nusselt numbers for the duct length. In analyzing the problem, thermally developing flow is assumed and the duct walls are subjected to boundary conditions of first kind. Results are computed for the velocity and temperature fields as well as for the parameters cited above with different power-law indices, yield numbers and aspect ratios. Comparisons are also made with previous work available in the literature, providing direct validation of the results and showing that they are consistent.
Acesso aberto (Open Access)
Preliminary risk analysis applied to the handling of health-care waste
(2002-12) CARVALHO, Samira Maria Leão de; SILVA, Meuris Gurgel Carlos da
Between 75% and 90% of the waste produced by health-care providers no risk or is "general" health-care waste, comparable to domestic waste. The remaining 10-25% of health-care waste is regarded as hazardous due to one or more of the following characteristics: it may contain infectious agents, sharps, toxic or hazardous chemicals or it may be radioactive. Infectious health-care waste, particularly sharps, has been responsible for most of the accidents reported in the literature. In this work the preliminary risks analysis (PRA) technique was used to evaluate practices in the handling of infectious health-care waste. Currently the PRA technique is being used to identify and to evaluate the potential for hazard of the activities, products, and services from facilities and industries. The system studied was a health-care establishment which has handling practices for infectious waste. Thirty-six procedures related to segregation, containment, internal collection, and storage operation were analyzed. The severity of the consequences of the failure (risk) that can occur from careless management of infectious health-care waste was classified into four categories: negligible, marginal, critical, and catastrophic. The results obtained in this study showed that events with critics consequences, about 80%, may occur during the implementation of the containment operation, suggesting the need to prioritize this operation. As a result of the methodology applied in this work, a flowchart the risk series was also obtained. In the flowchart the events that can occur as a consequence of a improper handling of infectious health-care waste, which can cause critical risks such as injuries from sharps and contamination (infection) from pathogenic microorganisms, are shown.
Acesso aberto (Open Access)
Comportamento higroscópico da farinha de pupunha (Bactris gasipaes)
(2003-08) FERREIRA, Cristiane Damasceno; PENA, Rosinelson da Silva
It was studied the hygroscopic behavior of the pupunha flour obtained by drying in the oven at 70°C. It was collected data of moisture adsorption for two temperatures (15°C and 35°C), using the static method, where the recipients with the capacity of 500mL, having saturated salt solutions, it was used as environment generators of constant relative humidity, ranging from 11% to 97%, which were submitted the samples of the product. From the equilibrium data, it was built isotherms of moisture adsorption, being observed type III isotherms, but even that the equilibrium moisture for the product decreases with the temperature increase. It was determined the isosteric heat of adsorption for different levels of equilibrium moisture and the equivalent moisture to the monolayer, which were inferior of 5g H2O/100 g s.s. It was verified the application of the GAB model in the equilibrium data prediction for the product. According to the results obtained, the pupunha flour shows low hygroscopicity, low affinity for water molecule.
Acesso aberto (Open Access)
Alkaloids and volatile constituents from the stem of Fusaea longifolia (Aubl.) Saff. (Annonaceae)
(2005-06) TAVARES, Josean Fechine; BARBOSA FILHO, José Maria; SILVA, Marcelo Sobral da; MAIA, José Guilherme Soares; CUNHA, Emidio Vasconcelos Leitão da
A phytochemical study of the ethanol extract and an extraction of the volatile compounds, performed by means of Clevenger apparatus were carried out with the stem of Fusaea longifolia (Aubl.) Saff. (Annonaceae). The ethanol extract yielded O-methylmoschatoline, isolated for the first time in this species, and stepholidine, reported for the first time in genus Fusaea. The structural identification of the alkaloids was made based on the analysis of their NMR spectra. Through the use of GC and GC-MS, two sesquiterpenoids, a-cadinol (12.5%) and spatulenol (12.0%) were identified as the major constituents of the essential oil.
Acesso aberto (Open Access)
Controle Fuzzy aplicado à melhoria da estabilidade dinâmica em sistemas elétricos de potência
(2005-06) BARRA JUNIOR, Walter; BARREIROS, José Augusto Lima; COSTA JÚNIOR, Carlos Tavares da; FERREIRA, André Maurício Damasceno
This work presents a fuzzy control strategy which can be applied to improve the dynamic stability of electric power systems. The gains of fuzzy controller are smoothly adjusted by using interpolation among the gains of a set of previously designed local controllers, according to the current plant operating condition. In this way, the parameters of the fuzzy controller are automatically adjusted on-line, in order to cope with changes in the power system operating conditions. The performance of the fuzzy strategy was assessed by simulation studies, using a nonlinear machine infinite bus bar dynamic model. The results show that it is possible to improve the power system dynamic performance under time-variable operating conditions.in english. Please notice that the abstract in english comes first.
Acesso aberto (Open Access)
Caracterização e processamento de leite bubalino em pó em secador por nebulização
(2005-09) GUERRA, Roberta Batista; NEVES, Elisa Cristina Andrade; PENA, Rosinelson da Silva
This work aims to show the process development based on the spray dryer for the obtaining of powdered buffalo milk. For that, physiochemical analyses were made in the milk in natura and later in the powdered product, which was also submitted to microbiological analysis to be sure that it could be consumed by humans; and to sensorial analysis for obtaining information about the product's acceptance. Sorption isotherms for the powdered product were obtained at 25ºC with the purpose of perceiving the hygroscopic behavior. The buffalo's powdered milk presented the following characteristics: 3,4 % moisture content, 23,2% proteins, 46,1% fat, 4,2% ash, 0,5% soybean lecithin and 22,6% of total carbohydrates. The product was characterized as whole powdered buffalo milk, because it didn't suffer any standardization. Nutrient losses, during the process, were less then 5%, and just for proteins the variation was more than 15%. It can be justified by the desnaturation of the casein due to high temperatures (>80ºC). The powdered product presented type III sorption isotherms and the same behavior was observed for the whole powdered milk. Through sorption isotherms, the moisture content value, referent to the monolayer, was on an average of 4,4g H2O/100g dry solids, which confirms the process efficiency. The hysteresis behavior presented by the powdered product was similar of the whole powdered milk. The product acceptance was of 74%, close to the commercial powdered milk acceptance.
Acesso aberto (Open Access)
Considerações sobre a pobreza no Brasil e suas manifestações nas cidades da Amazônia
(2006) CARDOSO, Ana Cláudia Duarte; NEGRÃO, Marcília Regina Gama
This paper offers information about poverty to non-specialists, contextualising its manifestations on Brazilian and particularly on Amazonian cities, under economic liberalism. Its first section discusses different approaches to poverty, according to developing countries perspectives. Afterwards structural causes to poverty in Brazil and evolution of official understanding to the problem are presented. These are followed by liberal policies to fight poverty recommended by World Bank, and their impacts on public policies inherited from Welfare State, and by the information related to recent approaches of Brazilian government to the problem. At last, liberal strategies applied to cities during the last decades are presented, highlighting their echoes on Amazonian cities.
Acesso aberto (Open Access)
Generalized integral transform solution for hydrodynamically developing non-Newtonian flows in circular tubes
(2006-03) NASCIMENTO, Shirley Cristina Cabral; MACÊDO, Emanuel Negrão; QUARESMA, João Nazareno Nonato
The Generalized Integral Transform Technique (GITT) is applied to the solution of the momentum equations in a hydrodynamically developing laminar flow of a non-Newtonian power-law fluid inside a circular duct. A primitive variables formulation is adopted in order to avoid the singularity of the auxiliary eigenvalue problem in terms of Bessel functions at the centerline of the duct when the GITT approach is applied. Results for the velocity field and friction factor-Reynolds number product are computed for different power-law indices, which are tabulated and graphically presented as functions of the dimensionless coordinates. Critical comparisons with previous results in the literature are also performed, in order to validate the numerical codes developed in the present work and to demonstrate the consistency of the final results.