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Brazilian Journal of Chemical Engineering, Volume: 24, Número: 4, Publicado: 2007
  • An expendient method for the synthesis of bis(acylhydrazones) under microwave irradiation in solvent-free medium Bioprocess Engineering

    Li, J. P.; Zheng, P. Z.; Zhu, J. G.; Liu, R.J.; Qu, G. R.

    Resumo em Inglês:

    A simple, efficient and eco-friendly method for the synthesis of bis(acylhydrazones) from hexanediohydrazide aldehydes under microwave irradiation without use solvent catalyst is reported. technique solvent-free condition proved to be quite valuable in organic synthesis.
  • A mathematical model describing the kinetic of cationic liposome production from dried lipid films adsorbed in a multitubular system Bioprocess Engineering

    Torre, L. G.; Carneiro, A. L.; Rosada, R. S.; Silva, C. L.; Santana, M. H. A.

    Resumo em Inglês:

    Cationic liposomes are an alternative to DNA non-viral carrier in gene therapy, promoting higher efficiency for transport and delivery into the cells. Liposome production large scale is still a challenge. Among many processes, from dried film adsorbed inside multitubular system promising due its operational simplicity. this field, engineering contributions scarce no mathematical treatment literature describing type of process available. formulation proposed describe kinetic considering wetting disintegration lipid followed by lipids aggregation bilayers generating liposomes. model has fitted experimental data mass thickness, being useful predictions scaling up as well contributing development pharmaceutical products.
  • Effluent generation by the dairy industry: preventive attitudes and opportunities Environmental Engineering

    Brião, V. B.; Tavares, C. R. Granhen

    Resumo em Inglês:

    Work aimed to identify the effluent is generating areas in a dairy company for purpose of changing concept pollution prevention. methodology consisted measuring volumes and collecting samples effluents production sectors. analysis was conducted by sector, order those which generated excessive amounts effluents. results show that dry products (powdered milk powdered whey) are greatest generators BOD, nitrogen phosphorus, while fluid form (UHT milk, formulated UHT, pasteurized cream) butter produced large quantities oils grease. solids recovery, waste segregation water reuse can be applied with saving potential as much R$ 28,000 ($ 11,200) per month only raw materials also environmental gains in pollution prevention.
  • Effects of Aspergillus niger inoculum concentration upon the kinetics of starchy wastewater pretreatment in a tanks-in-series bioreactor under transitory conditions Environmental Engineering

    Coulibaly, L.; Agathos, S. N.

    Resumo em Inglês:

    This paper discusses the effects of three Aspergillus niger inoculum concentrations (0.12, 2.3 and 3.6 g/l) upon the kinetics of starch pretreatment under aerobic and transitory conditions using a tanks-in-series reactor. A synthetic wastewater containing starch as model polysaccharide was fed into the reactor system to study this polymer transformation by Aspergillus niger. Starch and metabolites (oligosaccharides with a molecular weight lower than 1 kDa) in the individual reactors were quantified respectively by the starch iodine complex (SIC) and anthrone methods. Enzyme activities were characterised with API ZYM kits. Starch degradation and metabolite accumulation were both influenced by both fungal inoculum and reactor HRT. Starch degradation improved from 34 to 99% with a parallel in increase inoculum concentration from 0.12 to 3.6 g/l. An overall of 400 mg/l of metabolites accumulated in the reactor system. A. niger secreted both extracellular and cell-wall-bound enzymes among which amylases.
  • Effectiveness-ntu computation with a mathematical model for cross-flow heat exchangers Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Navarro, H. A.; Cabezas-Gómez, L. C.

    Resumo em Inglês:

    Due to the wide range of design possibilities, simple manufactured, low maintenance and low cost, cross-flow heat exchangers are extensively used in the petroleum, petrochemical, air conditioning, food storage, and others industries. In this paper a mathematical model for cross-flow heat exchangers with complex flow arrangements for determining epsilon -NTU relations is presented. The model is based on the tube element approach, according to which the heat exchanger outlet temperatures are obtained by discretizing the coil along the tube fluid path. In each cross section of the element, tube-side fluid temperature is assumed to be constant because the heat capacity rate ratio C*=Cmin/Cmax tends toward zero in the element. Thus temperature is controlled by effectiveness of a local element corresponding to an evaporator or a condenser-type element. The model is validated through comparison with theoretical algebraic relations for single-pass cross-flow arrangements with one or more rows. Very small relative errors are obtained showing the accuracy of the present model. epsilon -NTU curves for several complex circuit arrangements are presented. The model developed represents a useful research tool for theoretical and experimental studies on heat exchangers performance.
  • Experiment and numerical simulation on the performance of a kw-scale molten carbonate fuel cell stack Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Yu, L. J.; Ren, G. P.; Jiang, X. M.; Yuan, J. Q.; Cao, G. Y.

    Resumo em Inglês:

    A high-temperature molten carbonate fuel cell stack was studied experimentally and computationally. Experimental data for fuel cell temperature was obtained when the stack was running under given operational conditions. A 3-D CFD numerical model was set up and used to simulate the central fuel cell in the stack. It includes the mass, momentum and energy conservation equations, the ideal gas law and an empirical equation for cell voltage. The model was used to simulate the transient behavior of the fuel cell under the same operational conditions as those of the experiment. Simulation results show that the transient temperature and current and power densities reach their maximal values at the channel outlet. A comparison of the modeling results and the experimental data shows the good agreement.
  • A study of the pneumatic conveying of non-spherical particles in a turbulent horizontal channel flow Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Laín, S.; Sommerfeld, M.

    Resumo em Inglês:

    In this work, the pneumatic conveying of non-spherical isometric particles with different degrees of non-sphericity is studied. The solids mass loading fraction is small enough in order to have a dilute flow, so inter-particle collisions can be neglected. As a first approximation, only the aerodynamic drag force acting on the particles is considered, neglecting the lift forces and the particle rotation. The drag coefficient is calculated using the correlations of Haider and Levenspiel (1989) and Ganser (1993). The numerical simulations are compared with experimental data in a narrow six meters long horizontal channel flow laden with quartz and duroplastic particles with mean diameters of 185 and 240 mu m, respectively (Kussin, 2004).
  • Predictive QSPR analysis of corrosion inhibitors for super 13% Cr steel in hydrochloric acid Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Cardoso, S. P.; Gomes, J. A. C. P.; Borges, L. E. P.; Hollauer, E.

    Resumo em Inglês:

    An experimental and theoretical study on the inhibition corrosion efficiencies of twenty three compounds in hydrochloric acid (15% w/v) on 13% Cr modified stainless steel (martensitic) has been carried out. This inhibitor set includes amines, thiourea derivatives and acetylenic alcohols. Experimental weight losses at 60ºC were correlated with group and quantum AM1 descriptors obtained from QSPR analysis. Such data, for a large set of molecules, offer a unique opportunity for searching for correlations between inhibition corrosion efficiency and molecular properties. Calculations based on three different statistical methodologies were carried out. The first method, using calibration procedures, employs an ordinary least squares (OLS) methodology with a simple descriptor selection based on R² values. From this procedure, we obtained a model, Y15, having a R² value of 0,979 and a Q² value of 0.786. The second method employs a descriptor selection based on the second-order cross-validation OLS procedure (SOCV-OLS). In this process, the variables are chosen according to their ability to predict molecular inhibition efficiencies. The best model obtained using this methodology, Q5, had R² and Q² values of 0.859 and 0.785, respectively. The third method, based on regular partial least squares (PLS), resulted in R² and Q² values of 0.859 and 0.754, respectively. All calculations were carried out for the weight isoesteric Langmuir adsorption function (WILA function), ln(thetaM/(1-theta )) or ln Kads. A careful comparison between the calibration and the cross-validation descriptor selection indicated that they had very few descriptors in common. This article presents some key equations and the most relevant descriptors. We are unaware of any similar QSPR study on super 13% Cr stainless steel in the literature.
  • Drying rates in shrinking medium: case study of banana Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Katekawa, M. E.; Silva, M. A.

    Resumo em Inglês:

    Drying of foodstuffs is used to improve product stability, but presents some potentially harmful side effects such as shrinkage. The reduction of the relative humidity of the environment was studied in this work to substitute heating during drying, also taking into account the effect on shrinkage. Drying experiments of cylindrical slices of banana were conducted in commercial equipment, with controlled temperature and relative humidity. The samples of banana, with diameter/thickness aspect ratio of approximately five, were used. Results showed the existence of a constant drying flux period is when the variation of the transfer area is taken into account, which is evidence that the shrinking is two-dimensional. Relative humidity, and not only temperature, influences the final characteristics of the product. With this, an equivalence project of drying rates is considered in different conditions for the optimization of energy costs and product quality.
  • Intermittent drying of beans in a spouted bed Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Oliveira, C. A.; Rocha, S. C. S.

    Resumo em Inglês:

    Carioca beans are a highly nutritious grain, in terms of the amount of protein, iron and potassium as well as carbohydrates and fiber and as a source of vitamins. The moisture content of recently picked beans is too high for good preservation and storage, resulting in the need for drying before packaging. In this work, the drying of Carioca beans in a laboratory scale spouted bed under intermittent conditions of the drying air was experimentally analyzed. Experiments carried out consisted of two types of intermittent regime: intermittence in the spout regime, referred to as spouted/fixed bed and intermittence of the air supply to the bed, called spouted bed/rest. The results were compared to those for bean drying in a spouted bed dryer without intermittence.
  • CFD predictions of drilling fluid velocity and pressure profiles in laminar helical flow Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Pereira, F. A. R.; Barrozo, M. A. S.; Ataíde, C. H.

    Resumo em Inglês:

    Fluid flow in annular spaces has received a lot of attention from oil industries, both in drilling operations and in petroleum artificial rising. In this work, through numerical simulation using the computational fluid dynamics (CFD) technique, the flow of non-Newtonian fluids through the annuli formed by two tubes in concentric and eccentric arrangements of a horizontal system has been investigated. The study analyzes the effects of viscosity, eccentricity, flow and shaft rotation on the tangential and axial velocity profiles and on the hydrodynamic losses. It evaluates the performance of the numerical method used, comparing the results obtained with those in other reported works, aiming to validate the simulation strategy by the interpolation routines as well as the couplings algorithms adopted.
  • Adsorption equilibrium of light hydrocarbon mixtures by monte carlo simulation Thermodynamics And Separation Processes

    Cabral, V. F.; Castier, M.; Tavares, F. W.

    Resumo em Inglês:

    The procedure presented by Cabral et al. (2003) was used to predict the adsorption of multicomponent mixtures of methane, ethane, propane, and n-butane adsorbed on Silicalite S-115 at 300 K. The methodology employed uses the algorithm of molecular simulation for the grand canonical ensemble as an equation of state for the adsorbed phase. The adsorbent surface is modeled as a two-dimensional lattice in which solid heterogeneity is represented by of two kinds of sites with different adsorption energies. In all cases presented, the simulations described well the adsorption characteristics of the systems.
  • A subdivision algorithm for phase equilibrium calculations at high pressures Thermodynamics And Separation Processes

    Corazza, M. L.; Corazza, F. C.; Cardozo Filho, L.; Dariva, C.

    Resumo em Inglês:

    Phase equilibrium calculations at high pressures have been a continuous challenge for scientists and engineers. Traditionally, this task has been performed by solving a system of nonlinear algebraic equations originating from isofugacity equations. The reliability and accuracy of the solutions are strongly dependent on the initial guess, especially due to the fact that the phase equilibrium problems frequently have multiple roots. This work is focused on the application of a subdivision algorithm for thermodynamic calculations at high pressures. The subdivision algorithm consists in the application of successive subdivisions at a given initial interval (rectangle) of variables and a systematic test to verify the existence of roots in each subinterval. If the interval checked passes in the test, then it is retained; otherwise it is discharged. The algorithm was applied for vapor-liquid, solid-fluid and solid-vapor-liquid equilibrium as well as for phase stability calculations for binary and multicomponent systems. The results show that the proposed algorithm was capable of finding all roots of all high-pressure thermodynamic problems investigated, independent of the initial guess used.
  • Dynamic simulation of the carbon-in-pulp and carbon-in-leach processes Thermodynamics And Separation Processes

    Lima, L. R. P. de Andrade

    Resumo em Inglês:

    Carbon-in-leach and carbon-in-pulp are continuous processes that use activated carbon in a cascade of large agitated tanks, which have been widely used to recover or concentrate precious metals in gold extraction plants. In the carbon-in-pulp process adsorption occurs after the leaching cascade section of the plant, and in the carbon-in-leach process leaching and adsorption occur simultaneously. In both processes the activated carbon is moved from one tank to another in countercurrent with the ore pulp until the recovery of the loaded carbon in the first tank. This paper presents a dynamic model that describes, with minor changes, the carbon-in-leach, the carbon-in-pulp, and the gold leaching processes. The model is numerically solved and calibrated with experimental data from a plant and used to perform a study of the effect of the activated carbon transfer strategy on the performance of the adsorption section of the plant. Based on the calculated values of the gold loss in the liquid and of the gold recovered in the loaded activated carbon that leaves the circuit, the results indicate that strategies in which a significant amount of activated carbon is held in the first tank and the contact time between the carbon and the pulp is longer are the best carbon transfer strategies for these processes.
  • Preliminary study of the influence of CO2 extraction conditions on the ester, aldehyde, ketone and hydrocarbon content of grape bagasses from jam production Thermodynamics And Separation Processes

    Santos, J.; Dariva, R.; Mossi, A.; Stuart, G.; Nascimento, I.

    Resumo em Inglês:

    The main objective of this work was to assess the influence of temperature and pressure on the chemical characteristics of the essential oil obtained from CO2 extraction of grape bagasses in the production of jam. The experiments were performed in a laboratory-scale unit, where the effect of temperature (290 and 303 K) and pressure (15 and 25 Mpa) was investigated in terms of liquid yield and chemical composition of the extracts. The CO2 mass flow rate was kept within a range of 2.5 to 3.0 g/min. The instrumental analysis was performed by gas chromatography with a mass spectrometer detector (GC-MS). The extraction conditions investigated in this work had no significant influence on the mass of essencial oil extracted. The main compounds identified in the extracts by the GC-MS spectra library (match quality higher tan 90%) were octadecane, dihydroxy ergostene-dione and phenylethyl n-decanoate when the temperature was increased from 290 to 303 K. Heptanal, ethyl ester of decosonoic acid and hexatriacontane were the individual compounds with the greatest increase in the chromatographic peak area when the pressure was increased from 15 to 25 Mpa. The most important class of compounds were hydrocarbons at 303 K and 15 MPa and were ketones and aldehydes at 25 Mpa and 290 K.
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