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Brazilian Journal of Chemical Engineering, Volume: 19, Número: 3, Publicado: 2002
  • Treatment of low-strength wastewater using immobilized biomass in a sequencing batch external loop reactor: influence of the medium superficial velocity on the stability and performance Biotechnology

    Camargo, E.F.M.; Ratusznei, S.M.; Rodrigues, J.A.D.; Zaiat, M.; Borzani, W.

    Resumo em Inglês:

    An anaerobic sequencing batch bioreactor with external circulation of the liquid phase wherein the biomass was immobilized on a polyurethane foam matrix was analyzed, focussing on the influence of the liquid superficial velocity on the reactor's stability and efficiency. Eight-hour cycles were carried out at 30ºC treating glucose-based synthetic wastewater around 500 mgDQO/L. The performance of the reactor was assessed without circulation and with circulating liquid superficial velocity between 0.034 and 0.188 cm/s. The reactor attained operating stability and a high organic matter removal was achieved when liquid was circulated. A first order model was used to evaluate the influence of the liquid superficial velocity (vS), resulting in an increase in the apparent first order parameter when vS increased from 0.034 to 0.094 cm/s. The parameter value remained unchangeable when 0.188 cm/s was applied, indicating that beyond this value no improvement on liquid mass transfer was observed. Moreover, the necessary time to reach the final removal efficiency decreased when liquid circulation was applied, indicating that a 3-hour cycle could be enough.
  • Development of a bioprocess for the production of actinomycin-D Biotechnology

    Sousa, M.F.V.Q.; Lopes, C.E.; Pereira Jr., N.

    Resumo em Inglês:

    S. parvulus was selected from three species of Streptomyces that produce actinomycins, as it has the greatest antibiotic activity (152 mg/L) and produces only actinomycin-D. Aiming at improving the antibiotic production in shaken flasks, the substitution of glucose by fructose in concentrations of 20, 30 and 40 g/L was investigated. In all cases this replacement led to an increase in the antibiotic production, reaching a maximum concentration of 635 mg/L for an initial fructose concentration of 30 g/L. In experiments conducted in a bioreactor at different degrees of aeration (0.5, 1.0 and 1.5 vvm) and stirring speeds (300 and 500 rpm), it was found that the greatest antibiotic production (1530 mg/L) occurred with a aeration of 1.5 vvm and a stirring speed of 500 rpm. The fermented medium showed the rheological behavior of a pseudoplastic fluid.
  • Morphological observation and microbial population dynamics in anaerobic polyurethane foam biofilm degrading gelatin Biotechnology

    Tommaso, G.; Varesche, M.B.; Zaiat, M.; Vazoller, R.F.; Foresti, E.

    Resumo em Inglês:

    This work reports on a preliminary study of anaerobic degradation of gelatin with emphasis on the development of the proteolytic biofilm in polyurethane foam matrices in differential reactors. The evolution of the biofilm was observed during 22 days by optical and scanning electron microscopy (SEM) analyses. Three distinct immobilization patterns could be observed in the polyurethane foam: cell aggregates entrapped in matrix pores, thin biofilms attached to inner polyurethane foam surfaces and individual cells that have adhered to the support. Rods, cocci and vibrios were observed as the predominant morphologies of bacterial cells. Methane was produced mainly by hydrogenothrophic reactions during the operation of the reactors.
  • A simplified approach to the drying of solids in a batch fluidised bed Particulated Systems

    Srinivasakannan, C.; Balasubramanian, N.

    Resumo em Inglês:

    A simplified model for drying solids in the constant rate period in a batch fluidised bed was developed.It assumes the bed to be divided into dense and bubble phases with heat and mass transfer between the phases.The model predicts the constant-rate drying period, provided the fluid bed shape and material characteristics are known.The model is compared with experimental data reported in the literature covering a wide range of materials, gas flow rates, column diameters, material hold-ups, air temperatures and humidities.Model predictions compare satisfactorily with the experimental data.
  • Analysis and optimization of gas-centrifugal separation of uranium isotopes by neural networks Particulated Systems

    Migliavacca, S.C.P.; Rodrigues, C.; Nascimento, C.A.O.

    Resumo em Inglês:

    Neural networks are an attractive alternative for modeling complex problems with too many difficulties to be solved by a phenomenological model. A feed-forward neural network was used to model a gas-centrifugal separation of uranium isotopes. The prediction showed good agreement with the experimental data. An optimization study was carried out. The optimal operational condition was tested by a new experiment and a difference of less than 1% was found.
  • Nonlinear dynamic modeling of multicomponent batch distillation: a case study Process Systems Engineering - Control System

    Jiménez, L.; Basualdo, M.S.; Gómez, J.C.; Toselli, L.; Rosa, M.

    Resumo em Inglês:

    The aim of this work is to compare several of the commercial dynamic models for batch distillation available worldwide. In this context, BATCHFRAC™, CHEMCAD™ BATCH, and HYSYS.Plant® software performances are compared to experimental data. The software can be used as soft sensors, playing the roll of ad-hoc observers or estimators for control objectives. Rigorous models were used as an alternative to predict the concentration profile and to specify the optimal switching time from products to slop cuts. The performance of a nonlinear model obtained using a novel identification algorithm was also studied. In addition, the strategy for continuous separation was revised with residue curve map analysis using Aspen SPLIT™.
  • Modeling and simulation of a pseudo-two-phase gas-liquid column reactor for thermal hydrocracking of petroleum heavy fractions Reactors Engineering And Catalysis

    Matos, E.M.; Guirardello, R.

    Resumo em Inglês:

    This work presents a model to predict the behavior of velocity, gas holdup and local concentration fields in a pseudo-two-phase gas-liquid column reactor applied for thermal hydrocracking of petroleum heavy fractions. The model is based on the momentum and mass balances for the system, using an Eulerian-Eulerian approach. Using the k-epsilon model,fluid dynamics accounts for both laminar and turbulent flows, with discrete small bubbles (hydrogen) flowing in a continuous pseudohomogeneous liquid phase (oil and catalyst particles). The petroleum is assumed to be a mixture of pseudocomponents, grouped by similar chemical structural properties, and the thermal hydrocracking is taken into account using a kinetic network based on these pseudocomponents.
  • Conversion of n-Butane to iso-Butene on Gallium/HZSM-5 Catalysts Reactors Engineering And Catalysis

    Gheno, S.M.; Urquieta-González, E.A.

    Resumo em Inglês:

    The conversion of n-butane to iso-butene on gallium/HZSM-5 catalysts at 350ºC and WHSV=2.5h8-1 was studied. The catalysts were prepared by ion exchange from a Ga(NO3)2 solution and further submitted to calcination in air at 530ºC. TEM analysis with an EDAX detector and TPR-H2 data showed that after calcination the Ga species were present mainly as Ga2O3, which are reduced to Ga2O at temperatures near 610ºC. The specific acid activity (SAA) of the catalysts increased with the increase in aluminum content in the zeolite, and for a fixed Si/Al ratio, the SAA increased with Ga content. Values for specific hydro/dehydrogenation activity (SH/DHA) were significantly higher than those for SAA, indicating that the catalytic process is controlled by the kinetics on acid sites. Moreover, the production of iso-butene with a selectivity higher than 25% was a evidence that in gallium/HZSM-5-based catalysts the rate of the hydrogenation reaction is lower than that of the dehydrogenation reaction; this behavior confirmed the dehydrogenation nature of gallium species, thereby showing great promise for iso-butene production.
  • An empirical method to correlate and predict solute distribution in ternary liquid-liquid systems Thermodynamics

    Zamaro, J.M.; Campanella, E.A.

    Resumo em Inglês:

    This paper presents a method that combines activity coefficient models with Hand's equation for tie lines. The proposed method calculates solute distribution in liquid-liquid ternary systems. The combination improves the calculated solute distributions using activity coefficient models while Hand's equation gives a good correlation of the experimental tie lines. The method could be used to extrapolate experimental information.
  • The drying of solids in a modified fluidized bed Short Communication

    Ambrosio, M.C.B.; Taranto, O.P.

    Resumo em Inglês:

    When fine and cohesive particles are the subject of study, fluid beds are of concern of due to the formation of channeling. This work presents a study that was carried out on the drying of fine particles, in this case a crystalline organic acid, in a mechanically stirred fluidized bed. The drying kinetics curves were determined by evaluating the influences of initial moisture content and temperature of the drying gas at the entrance of the bed. This study shows the suitability of the stirred fluidized bed for the drying of solids of low-quality fluidization.
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