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Brazilian Journal of Chemical Engineering, Volume: 15, Número: 1, Publicado: 1998
  • Taking Variable Correlation into Consideration during Parameter Estimation

    Santos, T.J.; Pinto, J.C.

    Resumo em Inglês:

    Variable correlations are usually neglected during parameter estimation. Very frequently these are gross assumptions and may potentially lead to inadequate interpretation of final estimation results. For this reason, variable correlation and model parameters are sometimes estimated simultaneously in certain parameter estimation procedures. It is shown, however, that usually taking variable correlation into consideration during parameter estimation may be inadequate and unnecessary, unless independent experimental analysis of measurement procedures is carried out.
  • Adsorption of textile dyes on alumina. equilibrium studies and contact time effects

    MOREIRA, R.F.P.M.; PERUCH, M.G.; KUHNEN, N. C.

    Resumo em Inglês:

    The use of nonconventional adsorbents, particularly those that can be easily regenerated, to replace activated carbon in the removal of color from dye wastewaters has been recently proposed. This work shows a thermodynamic and kinetic study of the adsorption of reactive dyes (yellow monochlorotriazine and yellow dichlorotriazine), in liquid phase, on commercial alumina. The basic thermodynamic data were obtained using the static method, with a thermostatic bath at four different temperatures (30, 40, 50 and 60oC) and different pH values. The kinetic data were obtained by adding a known quantity of adsorbent to a dye solution at a constant temperature and under controlled stirring conditions. It was possible to draw the uptake curves, using the effects of the stirring on the adsorption rate. The intraparticle effective diffusivity was estimated using the film and pore diffusion model. The results were compared with the data obtained using a commercial activated carbon.
  • FLOODING IN PULSED SIEVE PLATE EXTRACTION COLUMNS WITH MASS TRANSFER EFFECTS

    TRIBESS, A.; BRUNELLO, G.

    Resumo em Inglês:

    Measurements of flooding in a pulsed sieve plate extraction column were carried out using toluene - water and toluene - acetone - water systems. The influence of plate spacing and initial acetone mass fraction in toluene (in the case of the three-component system) on flooding curves was studied and empirical correlations for the maximum of these curves are presented. In the ternary system, acetone goes from toluene drops to water: the descending phase. An experimental pulsed column, with an internal diameter of 39.6 x 10-3 m and an operational height of 2,670 m, and with stainless steel perforated plates, thickness of 1.5 x 10-3 m, with a hole diameter of 3 x 10-3 m and a free fractional area of 23%, was used. It was verified that the plate spacing and initial acetone mass fraction in the toluene have a great influence on throughput and frequency at the maximum; this influence depends on the phase ratio.
  • SIMULATION INVESTIGATIONS TOWARDS THE DEVELOPMENT OF A BACTERIAL BIOPESTICIDE FED-BATCH REACTOR

    Cunha, C.C.F. da; Souto Maior, A.M.; Souza Júnior, M.B. de

    Resumo em Inglês:

    In this work, the growth of Bacillus thuringiensis var. israelensis, a bioinsecticide producer, is investigated. Experiments were carried out in batch mode in order to obtain kinetic model parameters that were further applied to simulate fed-batch processes. The fed-batch mode allows more flexibility in the control of the substrate concentration in the culture medium. Different techniques, such as constant feeding, "bang-bang" control and model based control (exponential feeding and singular control), were compared. For the techniques based on a model, combinations of models with and without a substrate inhibition parameter were used to represent the simulated process and the internal model of the feeding controller. Singular control based on the model with an inhibition parameter proved to be the most robust controller.
  • A STATISTICAL EVALUATION OF THE EFFECTS OF PROCESS VARIABLES DURING CATALYTIC HYDROGENATION OF PASSION FRUIT (passiflora edulis) SEED OIL

    ANDRADE, G.M.S.; da ROCHA FILHO, G.N.; TAQUEDA, M.E.S.

    Resumo em Inglês:

    Hydrogenation of passion fruit (passiflora edulis) seed oil was carried out with a commercial nickel/silica catalyst under different experimental conditions. The influence of reaction parameters (reaction temperature, hydrogen pressure, amount of catalyst, agitation rate and reaction time) on the response variable (iodine value) was studied using a central composite rotatable design and six center points for replication. Under the experimental conditions used, the model response equations for the iodine value showed good agreement with the experimental results.
  • A METHOD FOR EXERGY ANALYSIS OF SUGARCANE BAGASSE BOILERS

    Resumo em Inglês:

    This work presents a method to conduct a thermodynamic analysis of sugarcane bagasse boilers. The method is based on the standard and actual reactions which allows the calculation of the enthalpies of each process subequation and the exergies of each of the main flowrates participating in the combustion. The method is presented using an example with real data from a sugarcane bagasse boiler. A summary of the results obtained is also presented together based on the 1st Law of Thermodynamics analysis, the exergetic efficiencies, and the irreversibility rates. The method presented is very rigorous with respect to data consistency, particularly for the flue gas composition.
  • HYDRODYNAMIC CHARACTERISTICS OF FLUIDIZED BEDS CONTAINING LARGE POLYDISPERSED PARTICLES

    Resumo em Inglês:

    This paper presents a hydrodynamic study of fluidized beds containing large polydispersed particles (B and D categories of Geldart’s classification). The experiments have been carried out with particle samples characterized by the Rosin-Rammler-Sperling (RRS) size distribution. The parameters analyzed in this study are the dispersion index and the average particle diameter obtained from the RRS size distribution model. Correlations to estimate the initial and complete fluidization velocities and the segregation velocity as a function of these two size distribution parameters have been established.
  • INTEGRAL TRANSFORM SOLUTION FOR THE FORCED CONVECTION OF HERSCHEL-BULKLEY FLUIDS IN CIRCULAR TUBES AND PARALLEL-PLATES DUCTS

    Resumo em Inglês:

    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.
  • Effects of Electrodiffusion on the Pb-Sn Eutectic Growth

    Resumo em Inglês:

    In the growth of a binary eutectic alloy, the formation of two new solid phases results in an unusual solute segregation process. In order for growth to happen, one of the solid phases must experience a decrease in the initial melt concentration of one of the alloy constituents and an increase in the amount of the other element. An analogous phenomenon occurs with respect to the other phase. The lateral composition gradient gives rise to mass transport parallel to the growth direction and across the solid/liquid interface, which controls the liquid interfacial composition field. The presence of an electric field during solidification can change the interfacial liquid composition distribution and thereby the growth condition. In this work, the Pb-Sn eutectic alloy was directionally solidified under the influence of an electric field normal to the growth direction. The results obtained show that electrodiffusion due to the electric field can change the eutectic lamellar spacing, the lamellar growth orientation and the eutectic microstructure regularity.
  • CARNAUBA WAX USED AS AN HYDROPHOBIC AGENT FOR EXPANDED VERMICULITE

    Resumo em Inglês:

    This work deals with the use of carnauba wax as an expansion and hydrophobicity agent for vermiculite, to be utilized in the sorption process of oil in water. Evaluation of the system (oil-water-hydrophobic vermiculite) submersion percentage was considered in assessing the performance of vermiculite in comparison to a Mexican turf. Carnauba wax seems to be more efficient in both fresh and salt waters.
  • EXCESS MOLAR ENTHALPIES OF 1-OCTENE + DIMETHYLCARBONATE OR DIETHYLCARBONATE OR 1,2-PROPYLCARBONATE AT 363.15 K AND 413.15 K

    KRÄHENBÜHL, M. A.; BOELTS, R.; GMEHLING, J.

    Resumo em Inglês:

    The excess molar enthalpies of 1-octene + dimethylcarbonate or diethylcarbonate or 1,2-propylcarbonate have been measured at two high temperatures 363.15 K and 413.15 K and for pressures varying from 18 to 20 bar with an isothermal flow-calorimeter. All these mixtures have exhibited positive HEm.
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