Scielo RSS <![CDATA[Brazilian Journal of Chemical Engineering]]> http://www.scielo.br/rss.php?pid=0104-663220150002&lang=en vol. 32 num. 2 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[EFFECTS OF CULTIVATION MEDIA COMPONENTS ON BIOSURFACTANT AND PIGMENT PRODUCTION FROM <em>Pseudomonas aeruginosa</em> PAO1]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200317&lng=en&nrm=iso&tlng=en Abstract Biosurfactant and pigment production by P. aeruginosa have been known to be associated with its selfish growth and colonization. However, according to recent studies these products can be exploited for human benefits. In the present work the effects of culture media components on yield of these two products from P. aeruginosa PAO1 have been studied with statistical screening design experiments. Biosurfactant yield was found to be increased by two times in a modified medium. This study will help in further modifying the media composition for cheaper media development, kinetic modelling and fermentation strategy development. <![CDATA[ETHANOL PRECIPITATION OF GLYCOSYL HYDROLASES PRODUCED BY <em>Trichoderma harzianum</em> P49P11]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200325&lng=en&nrm=iso&tlng=en Abstract This study aimed to concentrate glycosyl hydrolases produced by Trichoderma harzianum P49P11 by ethanol precipitation. The variables tested besides ethanol concentration were temperature and pH. The precipitation with 90% (v/v) ethanol at pH 5.0 recovered more than 98% of the xylanase activity, regard less of the temperature (5.0, 15.0, or 25.0 °C). The maximum recovery of cellulase activity as FPase was 77% by precipitation carried out at this same pH and ethanol concentration but at 5.0 °C. Therefore, ethanol precipitation can be considered to be an efficient technique for xylanase concentration and, to a certain extent, also for the cellulase complex. <![CDATA[A MULTISTAGE GRADUAL NITROGENREDUCTION STRATEGY FOR INCREASED LIPID PRODUCTIVITY AND NITROGEN REMOVAL IN WASTEWATER USING <em>Chlorella vulgaris </em> AND <em>Scenedesmus obliquus</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200335&lng=en&nrm=iso&tlng=en Abstract Chlorella vulgaris and Scenedesmus obliquus were grown in artificial-wastewater using a new nitrogen-limitation strategy aimed at increasing lipid productivity. This strategy consisted in a multi-stage process with sequential reduction of N-NH4 concentration (from 90 to 60, 40, and 20 mg.L-1) to promote a balance between cell growth and lipid accumulation. Lipid productivity was compared against a reference process consisting of nitrogen reduction in two stages, where the nitrogen concentration was suddenly reduced from 90 mg.L-1 to three different concentrations (10, 20, and 30 mg.L-1). In the multi-stage mode, only C. vulgaris exhibited a net lipid-productivity increase. Lipid content of S. obliquus did not present a significant increase, thus decreasing lipid productivity. The highest lipid productivities were observed in the two-stage mode for both S. obliquus and C. vulgaris (194.9 and 133.5 mg.L-1.d-1, respectively), and these values are among the highest reported in the literature to date. <![CDATA[GROWTH AND COMPOSITION OF <em>Arthrospira (Spirulina) platensis</em> IN A TUBULAR PHOTOBIOREACTOR USING AMMONIUM NITRATE AS THE NITROGEN SOURCE IN A FED-BATCH PROCESS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200347&lng=en&nrm=iso&tlng=en Abstract NH4NO3 simultaneously provides a readily assimilable nitrogen source (ammonia) and a reserve of nitrogen (nitrate), allowing for an increase in Arthrospira platensis biomass production while reducing the cost of the cultivation medium. In this study, a 22 plus star central composite experimental design combined with response surface methodology was employed to analyze the influence of light intensity (I) and the total amount of added NH4NO3 (Mt) on a bench-scale tubular photobioreactor for fed-batch cultures. The maximum cell concentration (Xm), cell productivity (PX) and biomass yield on nitrogen (YX/N) were evaluated, as were the protein and lipid contents. Under optimized conditions (I = 148 μmol·photons·m-2·s-1 and Mt = 9.7 mM NH4NO3), Xm = 4710 ±34.4 mg·L-1, PX = 478.9 ±3.8 mg·L-1·d-1 and YX/N = 15.87 ±0.13 mg·mg-1 were obtained. The best conditions for protein content in the biomass (63.2%) were not the same as those that maximized cell growth (I = 180 μmol·photons·m-2·s-1 and Mt = 22.5 mM NH4NO3). Based on these results, it is possible to conclude that ammonium nitrate is an interesting alternate nitrogen source for the cultivation of A. platensis in a fed-batch process and could be used for other photosynthetic microorganisms. <![CDATA[OPTIMIZATION OF THE OPERATING CONDITIONS FOR RHAMNOLIPID PRODUCTION USING SLAUGHTERHOUSE-GENERATED INDUSTRIAL FLOAT AS SUBSTRATE]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200357&lng=en&nrm=iso&tlng=en Abstract Biosurfactants have a wide range of applications in emulsions, separations, and solubilization because these chemicals reduce the surface tension and viscosity of solutions. This work studied rhamnolipid production using a batch bioreactor with a working volume of 1.5 liters, Pseudomonas aeruginosa ATCC (American Type Culture Collection) 10145 strain, and the greasy effluent from the slaughter of poultry and pigs as the substrate. The main goal of this research was to evaluate the level of aeration, agitation speed and inoculum concentration using a Central Composite Design (CCD). Experimental conditions were selected using the surface response technique obtained from the CCD, and the results were validated to test the reproducibility. The following operating conditions were selected: 1.2 vvm level of aeration, 600 rpm agitation speed, and 1.0 g/L biomass inoculum concentration. Under these conditions, the following results were obtained: the rhamnose production, surface tension and emulsifying index were 5.37 g/L, 25.6 dyne/cm and 100%, respectively. <![CDATA[PERFORMANCE OF LOOFA-IMMOBILIZED <em>Rhizopus oryzae</em> IN THE ENZYMATIC PRODUCTION OF BIODIESEL WITH USE OF OLEIC ACID IN <em>n</em>-HEXANE MEDIUM]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200367&lng=en&nrm=iso&tlng=en Abstract The performance of loofa-immobilized Rhizopus oryzae (as a whole-cell biocatalyst) in the synthesis of methyl oleate was evaluated using oleic acid as a model substrate. The activities of the cell-bound lipase in terms of the esterification and hydrolysis reactions were found to be higher for the immobilized cells as compared with those of the free cells. The time to reach equilibrium for methyl oleate synthesis was 12 h in the presence of n-hexane (hexane:oleic acid ratio 9:1(v/v)), and the yield was 80%. In the absence of solvent, equilibrium was reached after 48 h and the yield was only 30%. The moisture repellency and the hydrophilic properties of loofa sponge make this natural fiber a good candidate for cell-enzyme immobilization, especially for lipases as the interfacial enzyme. <![CDATA[INFLUENCE OF SOLID MOISTURE AND BED HEIGHT ON CULTIVATION OF <em>Aspergillus niger</em> FROM SUGARCANE BAGASSE WITH VINASSE]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200377&lng=en&nrm=iso&tlng=en Abstract Solid-state cultivation (SSC) may be defined as growth of microorganisms on a solid support impregnated or not with a nutrient solution in near absence of free-water conditions. The use of sugarcane bagasse as a support for SSC usually demands that the particles are impregnated and moistened with nutrient solution. Vinasse is the main wastewater of ethanol fermentation-distillation. As there are no reports of the use of wastewater for moistening solid supports in SSC, the proposal is the development of an innovative process, with valuation of these by-products. Thus, the aim of this research was to evaluate SSC of Aspergillus niger using sugarcane bagasse and vinasse for citric acid production. The results indicate that citric acid production and glucose consumption are dependent on oxygen availability, which can be modulated by selection of bed height and air-flow in packed-bed bioreactors. <![CDATA[EFFECT OF SULFATE LOADING RATE AND ORGANIC LOADING RATE ON ANAEROBIC BAFFLED REACTORS USED FOR TREATMENT OF SANITARY LANDFILL LEACHATES]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200385&lng=en&nrm=iso&tlng=en Abstract This study investigated the effect of organic loading rate (OLR) and sulfate loading rate (SLR) on landfill leachate treatment by a lab-scale anaerobic baffled reactor (ABR). Landfill leachate contained a concentration of organic matter between 3966 and 5090 mg COD.L-1 and no detectable amounts of sulfate. Reactors were started-up by feeding them with iron-sulfate at a SLR of 0.05 g SO42-.L-1.day-1 (4 weeks). Factorial design and response surface techniques were used to evaluate and optimize the effects of these operating variables on COD removal. ABRs were operated at OLRs ranging from 0.30 up to 6.84 g COD.L-1.day-1 by changes in influent volumetric flow. SO42- was added to the influent at a SRL from 0.06 to 0.13 g SO42-.L-1.day-1. The highest value of COD removal (66%) was reached at an OLR of 3.58 g COD.L-1.day-1 and SLR of 0.09 g SO4-2.L-1.day-1 with a COD/SO4-2 ratio of 40. Under these conditions sulfate is mainly used for molecular hydrogen consumption while organic matter is preferentially degraded via methanogesis. <![CDATA[BIOHYDROGEN FROM CHEESE WHEY TREATMENT IN AN AnSBBR: ACHIEVING PROCESS STABILITY]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200397&lng=en&nrm=iso&tlng=en Abstract An AnSBBR (anaerobic sequencing batch reactor containing biomass immobilized on an inert support) with liquid phase recirculation, containing a 3.5 L working volume, treated 1.5 L of cheese whey wastewater in 3 and 4 h cycles at 30 ºC to produce biohydrogen. From startup the bioreactor presented process instability. To overcome this problem the following measures were taken, however without success: adaptation of the biomass with uncontaminated easily degradable substrates, pH control at very low levels, and a different form of inoculation (natural fermentation of the feed medium). The problem was solved by cooling the feed medium to 4 ºC to prevent acidification in the storage container, by eliminating nutrient supplementation to prevent possible formation of H2S by sulfate-reducing bacteria and by periodic washing of the support material to improve the food/microorganism ratio. Hence, stable hydrogen production could be achieved with minimal presence of methane (36% H2; 62% CO2; 2% CH4) and the AnSBBR fed with cheese whey (influent concentration of 4070 mgCOD.L-1 and 3240 mgCarbohydrate.L-1 and applied volumetric organic loading of 14.6 gCOD.L-1.d-1) presented improved productivity and yield indicators compared to pure lactose and other reactor configurations, reaching values of 420 NmLH2.L-1.d-1 and 0.60 molH2.molCarbohydrate-1 in the steady-state phase (conversions of carbohydrates and COD were 98% and 30%, respectively). <![CDATA[EVALUATING ARSENIC AND MANGANESE REMOVAL FROM WATER BY CHLORINE OXIDATION FOLLOWED BY CLARIFICATION]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200409&lng=en&nrm=iso&tlng=en Abstract This paper investigates the simultaneous removal of arsenic [As(V) or As(III)] and manganese [Mn(II)] from natural waters of low and high turbidity by clarification (with polyaluminum chloride and aluminum sulfate as primary coagulants) associated or not with chlorine pre-oxidation. The results showed that the clarification process exhibited low Mn(II) removal, that varied from 6% to 18% and from 19% to 27% for natural waters of low and high turbidity, respectively. The use of chlorine as pre-oxidant increased Mn(II) removal up to 77% and was associated with the formation of birnessite. Regarding As(V) removal by clarification, particularly for high turbidity water, a concentration lower than that established by the National Drinking Water Quality Standards (10 μg.L-1) was achieved in almost all tests. Oxidation preceding the clarification led to AsIII removal efficiencies from 80% to 90% for both coagulants and types of water. <![CDATA[REMOVAL OF ESTROGENS BY ACTIVATED SLUDGE UNDER DIFFERENT CONDITIONS USING BATCH EXPERIMENTS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200421&lng=en&nrm=iso&tlng=en Abstract Wastewater treatment by deactivated and activated sludge was investigated to evaluate the removal of estrogens [estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2)] via adsorption and degradation. Different treatment conditions were used, including three mixed liquor volatile suspended solid (MLVSS) concentrations, three methanol concentrations (carbon source) and three types of aqueous media (water, synthetic solution, and supernatant). The E2 was degraded the fastest by the bacterial community. In all cases the removal rate increased when the initial MLVSS and methanol concentrations increased and when the macro- and micronutrients were present in the solution. In the experiments with deactivated sludge, the synthetic compound EE2 was more easily removed via sorption. The bacterial communities of the activated sludge were studied, which indicated a similarity of more than 75% between the different samples. A similarity of only 50% was found between the activated and deactivated sludges. <![CDATA[MODELING AND SIMULATION OF THE EFFECT OF THE FIRING CURVE ON THE LINEAR SHRINKAGE OF CERAMIC MATERIALS: LABORATORY SCALE AND INDUSTRIAL SCALE]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200433&lng=en&nrm=iso&tlng=en Abstract Single-cycle firing is currently the most widespread method used for the production of ceramic tile. The productivity is directly related to the performance of the constituent materials of the ceramic piece during thermal cycling. Numerical tools which allow the prediction of the material behavior may be of great help in the optimization of this stage. This study addressed the mathematical modeling of the temperature profile within a ceramic tile, together with the sintering kinetics, to simulate the effect of the thermal cycle on the final size. On the laboratory scale, 80 mm x 20 mm specimens with thicknesses of 2.3 mm and 7.8 mm were prepared in order to determine the kinetic constants and validate the model. The application was carried out on an industrial scale, with 450 mm x 450 mm pieces that were 8.0 mm thick. These results show that the model was capable of predicting the experimental results satisfactorily. <![CDATA[DETERMINATION OF THE EFFECTIVE RADIAL THERMAL DIFFUSIVITY FOR EVALUATING ENHANCED HEAT TRANSFER IN TUBES UNDER NON-NEWTONIAN LAMINAR FLOW]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200445&lng=en&nrm=iso&tlng=en Abstract Enhanced heat transfer in tubes under laminar flow conditions can be found in coils or corrugated tubes or in the presence of high wall relative roughness, curves, pipe fittings or mechanical vibration. Modeling these cases can be complex because of the induced secondary flow. A modification of the Graetz problem for non-Newtonian power-law flow is proposed to take into account the augmented heat transfer by the introduction of an effective radial thermal diffusivity. The induced mixing was modeled as an increased radial heat transfer in a straight tube. Three experiments using a coiled tube and a tubular heat exchanger with high relative wall roughness are presented in order to show how this parameter can be obtained. Results were successfully correlated with Reynolds number. This approach can be useful for modeling laminar flow reactors (LFR) and tubular heat exchangers available in the chemical and food industries. <![CDATA[EFFECT OF WATER CONTENT, TEMPERATURE AND AVERAGE DROPLET SIZE ON THE SETTLING VELOCITY OF WATER-IN-OIL EMULSIONS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200455&lng=en&nrm=iso&tlng=en Abstract Water-in-oil (W/O) emulsions are complex mixtures generally found in crude oil production in reservoirs and processing equipment. Sedimentation studies of water-oil emulsions enable the analysis of the fluid dynamic behavior concerning separation of this system composed of two immiscible liquids. Gravitational settling was evaluated in this article for a model emulsion system consisting of water and a Brazilian crude oil diluted in a clear mineral oil as organic phase. The effects of water content and temperature were considered in the study of sedimentation velocity of water-oil emulsions. Water contents between 10% and 50 % and temperatures of 25, 40 and 60 ºC were evaluated, and a Richardson-Zaki type correlation was obtained to calculate settling velocities as a function of the process variables investigated. Water contents and average droplet sizes were monitored at different levels in the settling equipment, thus enabling identification of the effect of these variables on the phenomena of sedimentation and coalescence of the emulsions studied. The results showed that the emulsion stability during sedimentation was governed by the emulsion water content, which yielded high settling velocities at low water contents, even when very small droplets were present. A quantitative analysis of the combined effects of drop size and droplet concentration supports the conclusion that a stronger effect is produced by the higher concentration of particles, compared with the relatively smaller effect of increasing the size of the droplets. <![CDATA[ACIDIC REMOVAL OF METALS FROM FLUIDIZED CATALYTIC CRACKING CATALYST WASTE ASSISTED BY ELECTROKINETIC TREATMENT]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200465&lng=en&nrm=iso&tlng=en Abstract One of the main uses of catalysts in the oil industry is in the fluidized catalytic cracking process, which generates large quantities of waste material after use and regeneration cycles and that can be treated by the electrokinetic remediation technique, in which the contaminant metals are transported by migration. In this study, deactivated FCC catalyst was characterized before and after the electrokinetic remediation process to evaluate the amount of metal removed, and assess structural modifications, in order to indicate a possible use as an adsorbent material. The analyses included pH measurement and the concentration profile of vanadium ions along the reactor, X-ray microtomography, X-ray fluorescence, BET analysis and DTA analysis. The results indicated that 40% of the surface area of the material was recovered in relation to the disabled material, showing an increase in the available area for the adsorption. The remediation process removed nearly 31% of the vanadium and 72% of the P2O5 adhering to the surface of the catalyst, without causing structural or thermal stability changes. <![CDATA[SELF-SIMILARITY OF VERTICAL BUBBLY JETS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200475&lng=en&nrm=iso&tlng=en Abstract An integral model for vertical bubbly jets with nearly monodisperse bubble sizes is presented. The model is based on the Gaussian type self-similarity of mean liquid velocity, bubble velocity and void fraction, as well as on functional relationships for initial liquid jet velocity and radius, bubble diameter and relative velocity. Adjusting the model to experimental data available in the literature for a wide range of densimetric Froude numbers provide constant values for the entrainment coefficient, momentum amplification factor, and spreading ratio of the bubble core for different flow conditions. Consistency and sensitivity of key model parameters are also verified. Overall, the deviations between model predictions and axial/radial profiles of mean liquid velocity, bubble velocity and void fraction are lower than about 20%, which suggests that bubbly jets tend to behave as self-preserving shear flows, similarly to single-phase jets and plumes. Furthermore, model simulations indicate a behavior similar to those of single-phase buoyant jets and slurry jets, but some differences with respect to confined bubbly jets are highlighted. This article provides not only a contribution to the problem of self-similarity in two-phase jets, but also a comprehensive model that can be used for analysis of artificial aeration/mixing systems involving bubbly jets. <![CDATA[VAPOR-PHASE CATALYTIC CONVERSION OF ETHANOL INTO 1,3-BUTADIENE ON Cr-Ba/MCM-41 CATALYSTS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200489&lng=en&nrm=iso&tlng=en Abstract Al-MCM-41, 16%Ba/Al-MCM-41 and 1.4%Cr-16%Ba/Al-MCM-41 were used as catalysts in the vapor-phase catalytic conversion of ethanol. Physical-chemical properties of the catalysts and the effect of barium and chromium on the Al-MCM-41 activity and 1,3-butadiene yield were studied. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption (BET method), CO2 chemisorption and Fourier transform infrared spectroscopy (FT-IR). When ethanol was completely converted on Al-MCM-41 and 16%Ba/Al-MCM-41, the reaction products showed a high selectivity for ethylene (90-98%). However, on the 1.4%Cr-16%Ba/Al-MCM-41 catalyst, a greater number of reaction products were obtained such as ethylene, acetaldehyde, diethyl ether and 1,3-butadiene. The maximum 1,3-butadiene yield obtained from ethanol reaction was 25% at 723 K and W/FEtOH = 15 g h mol-1. The latter result was obtained in a single step and without addition of reaction promoters (e.g., acetaldehyde, crotonaldehyde, hydrogen) in the feed stream to the reactor. <![CDATA[OPTIMIZATION OF PRODUCTION OF 5-HYDROXYMETHYLFURFURAL FROM GLUCOSE IN A WATER: ACETONE BIPHASIC SYSTEM]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200501&lng=en&nrm=iso&tlng=en Abstract 5-Hydroxymethylfurfural (HMF) is considered to be an important building block for biorefineries and has a high potential for the production of chemicals and fuels. Production of HMF from glucose was studied using phosphoric acid as catalyst, in a water:acetone system with volume ratio of 1:2 and NaCl. An experimental design was applied to examine the influence of temperature, time and concentration of catalyst on the HMF yield. HMF yields of more than 50 % were obtained when using 200 ºC, 8.4 min and 0.8% of catalyst. The temperature is the main factor influencing the HMF yield. <![CDATA[SYNTHESIS AND CHARACTERIZATION OF COPOLYMERIC AND TERPOLYMERIC HYDROGEL-SILVER NANOCOMPOSITES BASED ON ACRYLIC ACID, ACRYLAMIDE AND ITACONIC ACID: INVESTIGATION OF THEIR ANTIBACTERIAL ACTIVITY AGAINST GRAM-NEGATIVE BACTERIA]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200509&lng=en&nrm=iso&tlng=en Abstract In this study, copolymeric and terpolymeric hydrogel-silver nanocomposites based on poly(acrylamideco-itaconic acid), poly(acrylic acid-co-itaconic acid) and poly(acrylic acid-co-acrylamide-co-itaconic acid) were synthesized by free-radical polymerization. These nanocomposites were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), UV-Visible Spectrophotometry (UV-Vis) and X-Ray Diffraction (XRD) analysis, as well as their swelling behaviors. In addition, antibacterial properties of these hydrogel-silver nanocomposites were investigated against Pseudomonas aeruginosa. Acrylic-based hydrogel-silver nanocomposites demonstrated antibacterial activity against Gram-negative bacteria. These hydrogel-silver nanocomposites can be used as antibacterial material in the medical field. <![CDATA[EFFECT OF ROTATION RATES ON THE LAMINAR FLOW AND HEAT TRANSFER PAST A CIRCULAR CYLINDER]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200519&lng=en&nrm=iso&tlng=en Abstract In this work, forced convection heat transfer past a rotating circular cylinder with a constant non-dimensional rotation rate α varying from 0 to 6 was investigated for Reynolds numbers of 20-200 and a Prandtl number of 0.7. The numerical calculations are carried out by using a finite-volume method based commercial computational fluid dynamics solver FLUENT. The successive changes in the flow pattern are studied as a function of the rotation rate. Suppression of vortex shedding occurs as the rotation rate increases (α &gt; 2). A second kind of instability appears for higher rotation speed where a series of counter-clockwise vortices is shed in the upper shear layer. The rotation attenuates the secondary instability and increases the critical Reynolds number for the appearance of this instability. In addition, time-averaged (lift and drag coefficients and Nusselt number) results were obtained and compared with the literature data. A good agreement was obtained for both the local and averaged values. <![CDATA[INFLUENCE OF INTERFACIAL FORCES ON THE MIXTURE PREDICTION OF AN ANAEROBIC SEQUENCING BATCH REACTOR (ASBR)]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200531&lng=en&nrm=iso&tlng=en Abstract In the operation of bioreactors, the fluid movement promotes mixing between sludge and substrate. The dynamics of this system are complex, and the interaction between the phases is difficult to evaluate accurately. In this work, Computational Fluid Dynamics is applied to simulate a pilot-scale anaerobic sequencing batch reactor, using a three-dimensional, transient and multiphase modeling. Several correlations were applied to estimate the interfacial forces. Results indicate that the use of different coefficients for the drag and lift forces strongly affects the predicted turbulent kinetic energy, and thus the mixture estimation in the bioreactor. The use of the drag as the only interfacial force provided an average turbulent kinetic energy close to the value found using a more complete model. However, the absence of lift and virtual mass forces had a significant impact on the resulting turbulence distribution. <![CDATA[OPTIMIZATION OF A PULTRUSION PROCESS USING FINITE DIFFERENCE AND PARTICLE SWARM ALGORITHMS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200543&lng=en&nrm=iso&tlng=en Abstract Pultrusion is one of several manufacturing processes for reinforced polymer composites. In this process fibers are continuously pulled through a resin bath and, after impregnation, the fiber-resin assembly is cured in a heated forming die. In order to obtain a polymeric composite with good properties (high and uniform degree of cure) and a process with a minimum of wasted energy, an optimization procedure is necessary to calculate the optimal temperature profile. The present work suggests a new strategy to minimize the energy rate taking into account the final quality of the product. For this purpose the particle swarm optimization (PSO) algorithm and the computer code DASSL were used to solve the differential algebraic equation that represents the mathematical model. The results of the optimization procedure were compared with results reported in the literature and showed that this strategy may be a good alternative to find the best operational point and to test other heat policies in order to improve the material quality and minimize the energy cost. In addition, the robustness and fast convergence of the algorithm encourage industrial implementation for the inference of the degree of cure and optimization. <![CDATA[NEWTONIAN HEATING, THERMAL-DIFFUSION AND DIFFUSION-THERMO EFFECTS IN AN AXISYMMETRIC FLOW OF A JEFFERY FLUID OVER A STRETCHING SURFACE]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200555&lng=en&nrm=iso&tlng=en Abstract In this communication we have investigated the phenomenon of Newtonian heating under the application of a uniform magnetic field when thermal-diffusion "Soret" and diffusion-thermo "Dufour" effects appear in the energy and concentration equations in a flow of a Jeffery fluid. The flow is induced by the stretching of a disk in the radial direction. The solutions of the nonlinear equations governing the velocity, temperature and concentration profiles are solved analytically "using HAM" and graphical results for the resulting parameters are displayed and discussed. Numerical values of local Nusselt and Sherwood numbers for different values of physical parameters are computed and shown. It is shown that the magnetic field retards the flow, whereas Newtonian heating acts as a boosting agent which enhances the flow. It is also noted that the combined Soret and Dufour effects on the temperature and concentration profiles are opposite. <![CDATA[MODELLING OF DISPLACEMENT WASHING OF PULP FIBERS USING THE HERMITE COLLOCATION METHOD]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200563&lng=en&nrm=iso&tlng=en Abstract A non-linear mathematical model for displacement washing of pulp fibers with suitable boundary conditions is presented. Model equations are divided into two phases: particle phase and external fluid phase. The Hermite collocation method (HCM) is employed to solve the non-linear model equations. The validity and efficiency of the proposed model is demonstrated by comparing the numerical results with the experimental ones. Stability of the proposed method is checked by evaluating L2 and L? norms at different time intervals. Industrial parameters such as displacement ratio and wash yield have been calculated to check the validity of the model. Numerical values obtained from the model equations are presented in terms of 2D graphs. <![CDATA[ADSORPTION OF MANGANESE FROM ACID MINE DRAINAGE EFFLUENTS USING BONE CHAR: CONTINUOUS FIXED BED COLUMN AND BATCH DESORPTION STUDIES]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200577&lng=en&nrm=iso&tlng=en Abstract In the present study, continuous fixed bed column runs were carried out in an attempt to evaluate the feasibility of using bone char for the removal of manganese from acid mine drainage (AMD). Tests using a laboratory solution of pure manganese at typical concentration levels were also performed for comparison purposes. The following operating variables were evaluated: column height, flow rate, and initial pH. Significant variations in resistance to the mass transfer of manganese into the bone char were identified using the Thomas model. A significant effect of the bed height could only be observed in tests using the laboratory solution. No significant change in the breakthrough volume could be observed with different flow rates. By increasing the initial pH from 2.96 to 5.50, the breakthrough volume was also increased. The maximum manganese loading capacity in continuous tests using bone char for AMD effluents was 6.03 mg g-1, as compared to 26.74 mg g-1 when using the laboratory solution. The present study also performed desorption tests, using solutions of HCl, H2SO4, and water, aimed at the reuse of the adsorbent; however, no promising results were obtained due to low desorption levels associated with a relatively high mass loss. Despite the desorption results, the removal of manganese from AMD effluents using bone char as an adsorbent is technically feasible and attends to environmental legislation. It is interesting to note that the use of bone char for manganese removal may avoid the need for pH corrections of effluents after treatment. Moreover, bone char can also serve to remove fluoride ions and other metals, thus representing an interesting alternative material for the treatment of AMD effluents. <![CDATA[INFLUENCE OF FUSEL OIL COMPONENTS ON THE DISTILLATION OF HYDROUS ETHANOL FUEL (HEF) IN A BENCH COLUMN]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200585&lng=en&nrm=iso&tlng=en Abstract The components of fusel oil form azeotropes with water, resulting in challenges in obtaining hydrous ethanol fuel (HEF) and increasing investment and operating costs. The aim of this study was to evaluate how the presence of fusel oil affected HEF distillation. Mixtures of ethanol (6.0 to 6.5 % w/w) and water (93.0 to 94 % w/w) containing different concentrations (zero to 0.5 % w/w) of 3-methyl-1-butanol, 2-methyl-1-propanol, propan-1-ol and propan-2-ol were distilled in a laboratory apparatus. Under total reflux conditions, HEF concentrations in compliance with Brazilian legislation specifications were obtained, but the desired concentration could not be attained under continuous operation. All of the experiments resulted in a high loss of ethanol in the bottom product under multiple operating conditions. The results demonstrated that fusel oil affects HEF distillation, but that HEF concentrations can still be obtained in compliance with Brazilian legislation. <![CDATA[PERFORMANCE INDICES TO DESIGN A MULTICOMPONENT BATCH DISTILLATION COLUMN USING A SHORTCUT METHOD]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200595&lng=en&nrm=iso&tlng=en Abstract In this paper, three quality or performance indices (Luyben's capacity factor, total annual costs, and annual profit) were applied for the design of a batch distillation column working at variable reflux. This work used the Fenske-Underwood-Gilliland short-cut method to solve a problem of four components (benzene, toluene, ethyl-benzene, and ortho-xylene) that needed to be separated and purified to a mole fraction of 0.97 or better. The performance of the system was evaluated using distillation columns with 10, 20, 30, 40 and 50 theoretical stages with a boil-up vapor flow set at 100 kmol/h. It was found that the annual profit was the best quality index, while the best case for variable reflux was the column with 50 stages. It was confirmed that the best case always required a reflux ratio close to the minimum. <![CDATA[APPLICATION OF A SURFACE-RENEWAL MODEL TO PERMEATE-FLUX DATA FOR CONSTANTPRESSURE CROSS-FLOW MICROFILTRATION WITH DEAN VORTICES]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000200609&lng=en&nrm=iso&tlng=en Abstract The introduction of flow instabilities into a microfiltration process can dramatically change several elements such as the surface-renewal rate, permeate flux, specific cake resistance, and cake buildup on the membrane in a positive way. A recently developed surface-renewal model for constant-pressure, cross-flow microfiltration (Hasan et al., 2013) is applied to the permeate-flux data reported by Mallubhotla and Belfort (1997), one set of which included flow instabilities (Dean vortices) while the other set did not. The surface-renewal model has two forms - the complete model and an approximate model. For the complete model, the introduction of vortices leads to a 53% increase in the surface-renewal rate, which increases the limiting (i.e., steady-state) permeate flux by 30%, decreases the specific cake resistance by 14.5% and decreases the limiting cake mass by 15.5% compared to operation without vortices. For the approximate model, a 50% increase in the value of surface renewal rate is shown due to vortices, which increases the limiting permeate flux by 30%, decreases the specific cake resistance by 10.5% and decreases the limiting cake mass by 13.7%. The cake-filtration version of the critical-flux model of microfiltration (Field et al., 1995) is also compared against the experimental permeate-flux data of Mallubhotla and Belfort (1997). Although this model can represent the data, the quality of its fit is inferior compared to that of the surface-renewal model.