Resumo em Inglês:

The textile industries are distinguished by the use of dyes that are applied to textiles. Dyes are pollutant materials that are difficult to decompose by microbiological treatment. An alternative way to prevent contamination of the environment by dyes is the oxidation of these materials through photocatalysis, a process by which illumination of an oxide semiconductor produces photoexcited electrons and cations that migrate over the surface of the oxide, effectively participating in the chemical reaction. The purpose of this work is to synthesize catalysts and study their performance in the photocatalytic degradation of dyes. Niobium pentoxide and silver oxide supported on niobium pentoxide (Ag/Nb2O5), prepared by the impregnation method, were used as catalysts. Prior to use the catalysts were submitted to thermal treatment for drying and calcination. Drying was carried out at 150°C for 12 hours and then the solids were calcined at 500°C for 5 hours. After that the catalysts were applied in the photocatalytic degradation of different types of dyes from textile industries. Discoloration tests were carried out in a photocatalytic reaction unit during a period of 24 hours under different operational conditions in the presence and absence of ultraviolet light (UV). The results, evaluated by spectrophotometry, show that photodegradation of the dyes occurs, which allows evaluation of the influence of the silver on photocatalytic degradation.

Resumo em Inglês:

This work presents a way to predict the biochemical oxygen demand (BOD) of the output stream of the biological wastewater treatment plant at RIPASA S/A Celulose e Papel, one of the major pulp and paper plants in Brazil. The best prediction performance is achieved when the data are preprocessed using principal components analysis (PCA) before they are fed to a backpropagated neural network. The influence of input variables is analyzed and satisfactory prediction results are obtained for an optimized situation.

Resumo em Inglês:

The ligninolytic fungus Pleurotus ostreatoroseus (synonymy of Pleurotus ëous) was used to treat the first alkali extraction stage (E1) effluent of a kraft bleach plant. It was pelletized and used for two continuous experiments in a two-liter turbulent-flow bioreactor. In the first experiment, the average removal of color and of total phenols was 18.6 and 11.6%, respectively, after the addition of glucose. During the second experiment, which was developed with the addition of several quantities of glucose, the maximum removal of color, of total phenols and of lignin/chlorolignin was 19.4, 9.4 and 44.5%. For both experiments, the best results were obtained when the effluent was diluted and enriched with glucose. This indicated the need for an extra carbon source for the fungal treatment. Using the mycelial mass in suspension, three experiments were carried out. The best results were obtained with 20% fungus and shaking of the effluent. During the last three days of the experiment the average removal of color, of total phenols and of lignin/chlorolignin was 84.4± 6.1, 82.1± 5.7 and 72.4± 8.9, respectively. The results indicate the potential of Pleurotus ostreatoroseus for use in the treatment of E1 effluent.

Resumo em Inglês:

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.

Resumo em Inglês:

Fresh-cut vegetables are an important and rapidly developing class of convenience foods. Their storage life may be greatly reduced due to their high rates of respiration and transpiration and the possibility of enzymatic and microbiological deterioration. Consequently, the objective of this work was to determine the shelf life and the failure attribute that conditioned the shelf life of fresh-cut spinach treated with chemical solutions and packaged in bags with different permeabilities. The shelf life of fresh-cut vegetables was defined as the time of refrigerated storage at which any one of the sensory attributes scored below 7 or when the microbiological counts exceeded 5.10(7) CFU/g. Fresh-cut spinach was treated with citric acid and ascorbic acid solutions and packaged in mono-oriented polypropylene (OPP) bags or low-density polyethylene (LDPE) bags. Sensory attributes and total microbial counts were evaluated throughout refrigerated storage. Response surface methodology (RSM) was used to study the simultaneous effect of chemical treatment and refrigerated storage time on sensory and microbiological quality of fresh-cut spinach. A quadratic polynomial regression model was assumed for predicting off-odor, general appearance, wilting, browning, color, and mesophilic aerobic population. Type of packaging film only influenced development of off-odor (p<FONT FACE=Symbol>£</FONT>0.001) and had no effect on visual sensory attributes or microbiological counts (p>0.05). Development of off-odor was the attribute that limited shelf life of fresh-cut spinach packaged in OPP bags. On the other hand, shelf life of samples packaged in LDPE bags was dependent on a decrease in general appearance or an increase in microbiological counts, depending on the chemical treatment used.

Resumo em Inglês:

The effects of popping and extrusion processes on some of the hydration properties of Amarantus cruentus, which had already been degermed and dehulled, are discussed. Response surface methodology was used to analyse the effect of process variables (temperature and moisture) on hydration properties, evaluated by water solubility (S) and by amylographic retrogradation (R) . Results show that precooked flours obtained by popping have a very high suspension consistency with low or intermediate S, while those obtained by extrusion have very high S but a much lower suspension consistency. The high S values for extruded samples are even higher than those for extruded waxy types of cereals. The effects of the variables on each response depend on each case. S increases as temperature (T) and moisture (M) increase in both processes, although in extrusion, a maximum value was observed at 200 ºC and about 15% M. On the other hand, an inverse variable effect is observed for R; a minimum value is observed with extruded samples at about 14% M and for the whole T range, while a typical saddle-shaped surface is obtained for popped samples, with maximum values found at about 14 % and 18 % M for the two extreme T values, the highest and lowest, respectively. Another interesting effect is that the S-R pair values corresponding to popped samples do not fit the correlation between S and R, normally found with extruded samples. We can conclude that with the application of both processes it is possible to obtain precooked flours that have a wide range of hydration properties.

Resumo em Inglês:

Ten strains of lactobacillus from the CNRZ collection were tested as adjunct culture in miniature washed curd cheeses manufactured under controlled bacteriological conditions with two different starters, Lactococcus lactis subsp. lactis IL 416 and Lactococcus lactis subsp. cremoris AM2. Lactobacilli growth seemed to be dependent on the Lactobacillus strain but was not influenced by the starter strain or counts. Lactococci counts were higher in the miniature cheeses with AM2 starter and added lactobacilli than in the control cheeses without lactobacilli. Gross composition and hydrolysis of s1 casein were similar for miniature cheeses with and without lactobacilli. In the miniature cheeses manufactured with IL416 starter, the lactobacilli adjunct slightly increased the soluble nitrogen content, but that was not verified in the AM2 miniature cheeses. Phosphotungstic acid nitrogen content increased in miniature cheeses manufactured with IL416 when Lactobacillus plantarum 1572 and 1310 adjunct cultures were added. That was also verified for several Lactobacillus strains, specially Lactobacillus casei 1227, for miniature cheeses manufactured with AM2 starter. Free fatty acid content increased in miniature cheeses made with lactobacilli adjuncts 1310, 1308 and 1219 with IL416 starter, and with strains 1218, 1244 and 1308 for miniature cheeses with AM2 starter. These results indicate that production of soluble nitrogen compounds as well as free fatty acid content could be influenced by the lactobacilli adjunct, depending on the starter strain.

Resumo em Inglês:

The stress-strain of samples deformed until failure and the relaxation response after 50% deformation of the initial height under constant stress were obtained. Uniaxial compression and stress-relaxation tests enabled satisfactory differentiation of the mechanical resistance of gels with different alginate and carrageenan concentrations. Higher values for initial force at the beginning of the relaxation test were associated with higher calcium uptake by the gels. An increment of failure stress during the uniaxial compression tests for higher concentration of calcium in the gel structure was also observed. The maximum amount of cation uptake was higher than the theoretical value for saturation of all the carboxylic groups available in alginate molecules due to structural rearrangements. Stress-relaxation tests indicated that the residual stress of the gel increased with kappa-carrageenan concentration.

Resumo em Inglês:

The effect of polysaccharide content on the stability of an oil-in-water emulsion (20% oil, droplet diameter 6.5 mum, pH = 7) containing soy protein (5 mg/ml) as the emulsifying agent was studied. Flocculation occurs by addition of two depletion flocculants: xanthan (0.01- 0.4%) and lambda-carrageenan (0.001- 2%). We report that in both cases the onset of flocculation occurs below the overlap polymer concentration (c* = 0.15 % for xanthan and c* = 0.58% for lambda-carrageenan). The strength of depletion interaction is dependent on such factors as polymer concentration, molecular weight and also the presence of other macromolecules. Profiles of the creaming behaviour of the sample emulsions were obtained by measuring the height of the boundary between the cream phase and the serum as a function of time for each emulsion. The result indicates that creaming kinetics is dependent on polymer concentration in a complex way. The turbidity of the serum gave an indication of whether the system was fully flocculated or contained flocks together with unflocculated droplets. At very low polymer concentrations the droplets cream individually or in small aggregates at the top of the container. At higher concentrations the droplets appear to cream as a single entity, with a sharp lower boundary separating the cream phase from a clear serum. In these emulsions and in some of the coexistent ones, there is a delay before creaming starts. The presence of the polymers at higher concentrations resulted in a stable emulsion with a very high apparent viscosity for the continuous phase and/or a strong emulsion gel network. The length of the delay phase increased with increasing concentration of both polymers.

Resumo em Inglês:

"Surimi" itself is not a food; it is an intermediate phase of the production of "kamaboko"(a gel formed by the addition of salt to the surimi and direct heating to 80-90ºC) and a series of high-priced shellfish analogs. The protective effect that two cryoprotectant mixtures exerted during freezing and frozen storage of frozen surimi of surubí (Pseudoplatystoma coruscans) on the functional quality of the gels prepared was studied. The selected washing conditions selected to obtain an acceptable functional quality of gels prepared from frozen surimi (25% extracted proteins and of final moisture) using the response surface methodology were wash temperature, 18ºC; washing time for each of the three washing cycles, 4.62 min. and water-mince ratio, 3.5:1. Cryoprotectant mixtures used were sucrose/sorbitol (1:1) and maltodextrin/sorbitol (1:1) and they were added (8%) to the washed and drained minced fish before freezing. To evaluate the functionality of the frozen surimi during six months of storage, the penetration test to measure the gel strength was chosen; samples were assessed at 4, 45, 90 and 180 days of frozen storage. Results showed that even with the cryoprotectants freezing decreased gel strength, since it produced a decrease of almost 32% in the strength of the gel prepared with fresh surimi. However, the two cryoprotectant mixtures tested showed very good behaviour throughout frozen storage; specially at 45 and 90 days of storage the surimi gels with the sucrose/sorbitol mixture had a greater resistance than those with maltodextrin/sorbitol.

Resumo em Inglês:

A new reactor, the pulsed sieve plate column (PSPC), was developed to perform continuous emulsion polymerization reactions. This reactor combines the enhanced flexibility of tubular reactors with the mixing behavior provided by sieved plates and by the introduction of pulses that is important to prevent emulsion destabilization. The main objective of this work is to study the kinetics of vinyl acetate (VA) emulsion polymerization reactions performed in this PSPC. Therefore, both experimental studies and reaction simulations were performed. Results showed that it is possible to obtain high conversions with rather low residence times in the PSPC.

Resumo em Inglês:

An optimization method for determining the best configuration(s) of gasketed plate heat exchangers is presented. The objective is to select the configuration(s) with the minimum heat transfer area that still satisfies constraints on the number of channels, the pressure drop of both fluids, the channel flow velocities and the exchanger thermal effectiveness. The configuration of the exchanger is defined by six parameters, which are as follows: the number of channels, the numbers of passes on each side, the fluid locations, the feed positions and the type of flow in the channels. The resulting configuration optimization problem is formulated as the minimization of the exchanger heat transfer area and a screening procedure is proposed for its solution. In this procedure, subsets of constraints are successively applied to eliminate infeasible and nonoptimal solutions. Examples show that the optimization method is able to successfully determine a set of optimal configurations with a minimum number of exchanger evaluations. Approximately 5 % of the pressure drop and channel velocity calculations and 1 % of the thermal simulations are required for the solution.

Resumo em Inglês:

The design of the main control system of the CAREM nuclear power plant is presented. This plant is an inherently safe low-power nuclear reactor with natural convection on the primary coolant circuit and is self-pressurized with a steam dome on the top of the pressure vessel (PV). It is an integrated reactor as the whole primary coolant circuit is within the PV. The primary circuit transports the heat to the secondary circuit through once-through steam generators (SG). There is a feedwater valve at the inlet of the SG and a turbine valve at the outlet of the SG. The manipulated variables are the aperture of these valves and the reactivity of the control rods. The control target is to regulate the primary and secondary pressures and to monitor steam flow reference ramps on a range of nominal flow from 100% to 40%. The requirements for the control system are robust stability, low-order simple controllers and transient/permanent error bounding. The controller design is based on a detailed RETRAN plant model, from which linear perturbed open-loop dynamic models at different powers are identified. Two low-order nominal models with their associated uncertainties are chosen for two different power ranges. Robust controllers with acceptable performances are designed for each range. Numerical optimization based on the loop-shaping method is used for the controller design. The designed controllers are implemented in the RETRAN model and tested in simulations achieving successful results.

Resumo em Inglês:

It is known that the optimal control may introduce significant economical benefits into production processes, thus being an important and challenging research area with practical relevance. The modeling and optimization of biotechnological processes has been object of research and their related results have generated improvements in operating conditions and strategies, however, the inherent features of dynamical bioprocesses prevent the application of conventional optimization algorithms, hence making necessary the development of tailored methods and strategies. The objective of this work is to develop mathematical programming strategies for simultaneous optimization of dynamic systems and evaluate their computational performance. Simultaneous optimization with orthogonal collocation is applied to a simplified model for biosynthesis of penicillin from glucose, which was studied by Cuthrell and Biegler (1989). The results show that discretization of differential equations systems (DAE) by orthogonal collocation in finite elements efficiently transforms dynamic optimization problems into nonlinear programming (NLP) problems, enabling to solve complex problems with several control variables and minimizing the approximation error.

Resumo em Inglês:

This paper addresses the problem of integrating in a single model operational optimization and cyclic scheduling of continuous plants. Considered are multiproduct, multistage plants with finite intermediate storage capacity (FIS). A combined optimization approach introduces synergic effects for more effective scheduling and plant operation (Alle and Pinto, 2001a,b). The representation proposed for this problem results in an MINLP model with a nonconvex feasible region and nonconvex objective function. In order to deal with nonconvexity, a spatial branch-and-bound global optimization algorithm is applied. Results show that the global approach is effectively able to yield more profitable solutions than those obtained by local optimization methods.

Resumo em Inglês:

Pipelines provide an economic mode of fluid transportation for petroleum systems, specially when large amounts of these products have to be pumped for large distances. The system discussed in this paper is composed of a petroleum refinery, a multiproduct pipeline connected to several depots and the corresponding consumer markets that receive large amounts of gasoline, diesel, LPG and aviation fuel. An MILP optimization model that is based on a convex-hull formulation is proposed for the scheduling system. The model must satisfy all the operational constraints, such as mass balances, distribution constraints and product demands. Results generated include the inventory levels at all locations, the distribution of products between the depots and the best ordering of products in the pipeline.

Resumo em Inglês:

This paper addresses the development of an efficient numerical output feedback robust model predictive controller for open-loop stable systems. Stability of the closed loop is guaranteed by using an infinite horizon predictive controller and a stable state observer. The performance and the computational burden of this approach are compared to a robust predictive controller from the literature. The case used for this study is based on an industrial gasoline debutanizer column.

Resumo em Inglês:

This article describes the application of a three-layer feed-forward neural network to analyze industrial plant data. To adjust mathematical models (for control or optimization purposes) from plant data, it is necessary to analyze and detect outliers and systematic errors and to remove them. The system studied is the feed preparation of an isoprene production unit and represents a multivariable problem. To detect outliers in a multivariable system is not an easy task. The technique used in this paper is able to identify this kind of error. The methodology employed involves construction of a reliable neural network model to represent the process and its training with a few iterations (a few thousand). Thus, the points at which errors between the experimental and calculated data appear to be scattered far from the majority of the values are probably outliers. In some cases, outlier points can be easily detected, but in others, they are not so obvious. In these cases, they are separated and a cluster with other similar data is built. After analyzing these clusters based on the similarity principle or by hypothesis tests for means, it is then decided whether or not these points can be excluded. At the same time the process is checked for any abnormalities recorded during the specific period. Three year's worth of process data were analyzed and about 30% of the data were excluded.

Resumo em Inglês:

In recent years, many process industries have been forced to drastically increase their product variety and adopt mass customization production strategies. Many of them have found that traditional bill of material (BOM) processing systems do not sufficiently support the maintenance of the very large amounts of data (concerned with product structure) demanded by these new production policies. Due to the use of BOM technology within the framework of integrated information systems, there is a demand for both (i) a new representation of BOMs, able to deal efficiently with product variants and to handle decomposition-based production strategies, and (ii) its corresponding BOM information processing system. This paper describes a conceptual representation that integrates elements of semantic relationships with object-oriented concepts to develop a data model for a hybrid bill of materials. The proposed semantic relationships include composed-of, decomposed-into, variant-of, restriction-of, and their corresponding reverse relationships. The conceptual model has been implemented using object-oriented data-based management system (OODBMS) technology that allows creation of persistent Java objects. Preliminary tests show a remarkable reduction in the number of relationships when compared with former approaches.