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Brazilian Journal of Chemical Engineering, Volume: 29, Número: 2, Publicado: 2012
  • Diauxic growth of Geotrichum candidum and Penicillium camembertii on amino acids and glucose Bioprocess Engineering

    Aziza, M.; Amrane, A.

    Resumo em Inglês:

    The purpose of this work was to examine physiological differences between the yeast Geotrichum candidum and the mould Penicillium camembertii, organisms involved in the industrial process of cheese ripening. Three groups of amino acids had previously been characterized, based on their carbon assimilation and dissimilation by the two fungal species. For both of them, a diauxic growth phase had been shown for a group of amino acids, which however had not been examined in light of physiological differences between the two microorganisms. In this work, the higher level of enzymatic activities of P. camembertii if compared to G. candidum was confirmed since a continuous and sequential use of both carbon substrates, glucose and arginine, was recorded during P. camembertii culture; while after glucose depletion, a clear stationary phase was recorded before the assimilation of the considered amino acid as both carbon and nitrogen sources by G. candidum. This behaviour was confirmed for the three amino acids tested, i.e., arginine, proline and glutamic acid. Contrarily, during the two growth phases, on glucose and the test amino acid, respectively, higher growth rates were recorded for G. candidum compared to P. camembertii, showing higher substrate utilisation efficiency by G. candidum. Improving the knowledge regarding the metabolization of amino acids might be helpful in designing strategies aiming at improving processes such as cheese ripening. The work should be followed up by similar works using small peptides.
  • Nitrogen removal from landfill leachate via the nitrite route Environmental Engineering

    Kulikowska, D.

    Resumo em Inglês:

    The feasibility of removing nitrogen from mature landfill leachate using the nitrite route was investigated in a two-stage SBR system - (1º first stage, short-cut nitrification; second stage, denitrification via nitrite. With a volumetric exchange rate (n) of 0.3 d-1 and an oxygen concentration of between 1.2 and 1.3 mg/L, the nitrite accumulation ratio - (NO2-N)×100/(NOx-N)% - was between 32% and 37%. For the same hydraulic retention time, but lower oxygen concentration - between 0.8 and 0.9 mg/L - nitrite accumulation averaged 96%, indicating that ammonia was removed completely via the nitrite pathway. In the second step, an external carbon source was added to promote denitrification. Complete removal of nitrite was obtained for a carbon dose of 2.4 mg COD/mg NO2-N using acetic acid and 3.8 mg COD/mg NO2-N for butyric acid. Also, a higher denitrification rate - 14.6 mg NO2-N/g VSS∙h - was observed with butyric acid as compared with acetic acid - 9.12 mg NO2-N/g VSS∙h.
  • [RETRACTED ARTICLE]Use of a sonocatalytic process to improve the biodegradability of landfill leachate Environmental Engineering

    Roodbari, A.; Nodehi, R. Nabizadeh; Mahvi, A. H.; Nasseri, S.; Dehghani, M. H.; Alimohammadi, M.
  • Theoretical and experimental drying of a cylindrical sample by applying hot air and infrared radiation in an inert medium fluidized bed Fluid Dynamics; Heat And Mass Transfer; And Other Topics

    Honarvar, B.; Mowla, D.

    Resumo em Inglês:

    Drying of a cylindrical sample in a fluidized bed dryer containing inert particles was studied. For this purpose, a pilot-scaled fluidized bed dryer was constructed in which two different heat sources, hot air and infrared radiation were applied, and pieces of carrot were chosen as test samples. The heat transfer coefficient for cylindrical objects in a fluidized bed was also measured. The heat absorption coefficient for carrot was studied. The absorption coefficient can be computed by dividing the absorbed heat by the carrot to the heat absorbed for the water and black ink. In this regard, absorbed heat values by the carrot, water and black ink were used A mathematical model was proposed based on the mass and heat transfer phenomena within the drying sample. The results obtained by the proposed model were in favorable agreement with the experimental data.
  • Supercritical CO2 extraction of raw propolis and its dry ethanolic extract Fluid Dynamics; Heat And Mass Transfer; And Other Topics

    Paviani, L. C.; Saito, E.; Dariva, C.; Marcucci, M. C.; Sánchez-Camargo, A. P.; Cabral, F. A.

    Resumo em Inglês:

    Three types of propolis extract were prepared and analyzed with respect to their global extraction yields and with respect to the concentration of the following markers: 3,5-diprenyl-4-hydroxycinnamic acid; 3-prenyl-4-hydroxycinnamic acid; 4-hydroxycinnamic acid and 4-methoxy-3,5,7-trihydroxyflavone. The extract EEP (ethanolic extract of propolis) was obtained by the conventional method from raw propolis using ethanol as solvent. The extracts (SFE) were obtained by supercritical solvent extraction from the raw propolis using supercritical carbon dioxide (sc-CO2), with and without the addition of ethanol as a co-solvent. The fractionated supercritical extracts (FSCE) were obtained by fractionation (extract and raffinate) of the dry EEP with sc-CO2. EEP yields of 39.5% were obtained and maximum global extraction yields were 7.3% for SFE with no co-solvent, 51% for SFE with 15% ethanol and 18% for the FSCE extract fraction. The concentrations of the markers in the different extracts differed as a function of the operational parameters, indicating that the addition of co-solvent and the selectivity of sc-CO2 could be manipulated so as to obtain extracts with the yields and concentrations of interest.
  • Wall effects on the cross-buoyancy around a square cylinder in the steady regime Fluid Dynamics; Heat And Mass Transfer; And Other Topics

    Dhiman, A. K.; Sharma, N.; Kumar, S.

    Resumo em Inglês:

    The effects of blockage ratio on the combined free and forced convection from a long heated square obstacle confined in a horizontal channel are investigated in this work. The numerical computations are performed in the steady regime for Reynolds number = 1 - 30, Richardson number = 0 - 1 for blockage ratios of 0.125 and 0.25 for the fixed Prandtl number of 0.7 (air). The governing equations, along with appropriate boundary conditions, are solved by using a semi-explicit finite volume method implemented on the collocated grid arrangement. The total drag and lift coefficients, local and average Nusselt numbers and the representative streamline, vorticity and isotherm patterns are presented to elucidate the role of blockage ratio on the cross-buoyancy across a confined square cylinder. The asymmetry in the flow and temperature fields decreases with increasing value of the blockage ratio. Similar to forced convection, the total drag coefficient increases with increasing value of the blockage ratio for the fixed values of the Reynolds and Richardson numbers.
  • The viscosity distribution around a rising bubble in shear-thinning non-newtonian fluids Fluid Dynamics; Heat And Mass Transfer; And Other Topics

    Li, Shaobai; Ma, Youguang; Fu, Taotao; Zhu, Chunying; Li, Huaizhi

    Resumo em Inglês:

    The viscosity distribution of the liquid around a rising bubble in carboxymethyl cellulose (CMC) aqueous solutions was measured experimentally by particle image velocimetry (PIV). The effect of the concentration of CMC solutions on the viscosity distribution around a bubble and the coupling relations between the viscosity field, flow field and shear stress field were also studied. Results indicated that the specific viscosity (non-dimensionalized by η0) decreases with the increase in CMC solution concentration due to a shear thinning effect. Within the experimental range, similar viscosity distributions of liquids around a rising bubble were found: a hollow cylindrical low viscosity region around the bubble wake and a high viscosity region in the central bubble wake.
  • Two-phase experimental heat transfer studies on a water-diesel system in a shell and tube heat exchanger Fluid Dynamics; Heat And Mass Transfer; And Other Topics

    Alagesan, V.; Sundaram, S.

    Resumo em Inglês:

    Two-phase heat transfer involving two immiscible systems is gaining importance in petrochemical and allied industries. Varying compositions of diesel and water were experimentally studied in a 1:2 shell and tube heat exchanger. The data on pure water and diesel were fitted to an equation of the form. h1φ = a NmRe.The two-phase multiplier, Φ L, was related to the Lockhart Martinelli (L-M) parameter, χtt², using the two-phase data and a correlation Φ L = b+c(χtt²)+d/(χtt²)² was established. The two-phase heat transfer coefficient was calculated based on the coefficients 'a' and 'm' for pure diesel and pure water along with ФL and the L-M parameter. The calculated values of the two-phase heat transfer coefficient h2φ based on pure diesel and pure water suggest that diesel is a better reference fluid since the average error is much smaller compared to pure water as reference.
  • Nitroxide mediated and atom transfer radical graft polymerization of atactic polymers onto syndiotactic polystyrene Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Abbasian, M.; Shoja, S. Esmaeily

    Resumo em Inglês:

    'Living' radical graft polymerization was employed to prepare graft copolymers with nitroxide-mediated arylated syndiotactic polystyrene as the backbone and polystyrene (PS), poly(p-methylstyrene) (PMS) and poly(methylmethacrylate) (PMMA) as branches. A two-stage process has been developed to synthesize the macroinitiator. First, syndiotactic polystyrene (sPS) was modified by the Friedel-Crafts reaction to introduce chlorine; second, the chlorine groups were converted to nitroxide mediated groups by coupling with 1-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-OH). The resulting macroinitiator (sPS-TEMPO) for 'living' free radical polymerization was then heated in the presence of styrene and p-methylstyrene to form graft and block copolymers. We used the obtained copolymer and N-bromosuccinimide as brominating agent to achieve polymers with bromine groups. This brominated copolymer was used as a macroinitiator for polymerizing methyl methacrylate in the presence of the CuBr/bpy catalyst system. The formation of the graft and block copolymers was confirmed by DSC, ¹H NMR and FTIR spectroscopy. This approach using macroinitiators is an effective method for the preparation of new materials.
  • Synthesis of a biocopolymer carrageenan-g-poly(AAm-co-IA)/ montmorilonite superabsorbent hydrogel composite Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Sadeghi, M.

    Resumo em Inglês:

    A novel superabsorbent hydrogel composite based on kappa-carrageenan (κC) has been prepared via graft copolymerization of acrylamide (AAm) and itaconic acid (IA) monomers in the presence of montmorolonite clay powder, methylenebisacrylamide (MBA) as the crosslinking agent and ammonium persulfate (APS) as initiator. Evidence of grafting and montmorolonite interaction was obtained by comparison of FTIR and TGA spectra of the initial substrates and the superabsorbent composite. A new absorption band at 1722 cm-1 in the composite spectrum confirmed montmorolonite-organic polymer linkages. Moreover, the morphology of the samples was examined by scanning electron microscopy (SEM). The swelling of the superabsorbing hydrogels was also examined in solutions with pH values ranging between 1.0 and 13.0. Finally, the swelling behavior of these composite polymers was investigated in various salt solutions. Results indicated that the swelling capacity decreased with an increase in the ionic strength of the swelling medium. This behavior can be attributed to the charge screening effect of monovalent cations, as well as ionic crosslinking for multivalent cations.
  • Polymeric membranes containing silver salts for propylene/propane separation Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Pollo, L. D.; Duarte, L. T.; Anacleto, M.; Habert, A. C.; Borges, C. P.

    Resumo em Inglês:

    The separation of olefin/paraffin mixtures is one of the most important processes of the chemical industry. This separation is typically carried out by distillation, which is an energy and capital intensive process. One promising alternative is the use of facilitated transport membranes, which contain specific carrier agents in the polymer matrix that interact reversibly with the double bond in the olefin molecule, promoting the simultaneous increase of its permeability and selectivity. In this study, polyurethane (PU) membranes were prepared using two different silver salts (triflate and hexafluorantimonate). The membranes were structurally characterized and their performance for the separation of propylene/propane mixtures was evaluated. The results of the characterization analyses indicated that the triflate salt was the most efficient carrier agent. The membranes containing this salt showed the best performance, reaching an ideal selectivity of 10 and propylene permeability of 188 Barrer.
  • Alkali-free method of hide preparation for tanning Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Valeika, V.; Beleska, K.; Sirvaityte, J.

    Resumo em Inglês:

    Usually, beamhouse processes are carried out by varying a medium from strongly alkaline (unhairing-liming) up to strongly acid (pickling). This study is designed to develop a preparation of hide for tanning via processes that avoid a sharp change of hide pH. Enzymes active in acid medium are employed for hide unhairing in a buffer system containing 2.5% acetic acid and 0.3% sodium acetate. An oxidative treatment with peracetic acid then allows the complete removal of residual hair and scud. During both processes, unhairing and oxidative treatment, the opening of the derma structure occurs: 13.3-14.6g of non-collagen proteins are removed and amount of dermatan sulphate decreases by 35%. The hide obtained can be chromed directly after the above processes and subsequent treatment with sodium chloride solution omitted conventional pickling. The pH of the hide varies in the range of 8.3-3.7 during the processes of preparation for tanning.
  • Characterization of lyophilized liposomes produced with non-purified soy lecithin: a case study of casein hydrolysate microencapsulation Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Yokota, D.; Moraes, M.; Pinho, S. C.

    Resumo em Inglês:

    A commercial casein hydrolysate was microencapsulated in liposomes produced with non-purified soy lecithin, cryoprotected with two different disaccharides and lyophilized. The encapsulation efficiency of casein hydrolysate ranged from 30 to 40%. The powders were analyzed by differential scanning calorimetry (DSC), scanning electron micrography (SEM), infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). DSC data revealed the presence of an exothermal transition in empty lyophilized liposomes, which was ascribed to the presence of a quasicrystalline lamellar phase (intermediary characteristics between the Lβ and Lc phases). The addition of peptides to the liposomal system caused the disappearance of this exothermic phenomenon, as they were located in the polar headgroup portion of the bilayer, causing disorder and preventing the formation of the quasicrystalline phase. Infrared data indicated the presence of the peptides in the lyophilized formulations and showed that the cryoprotectants interacted effectively with the polar heads of phospholipids in the bilayer.
  • Production of hydrogen in the reaction between aluminum and water in the presence of NaOH and KOH Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Porciúncula, C. B.; Marcilio, N. R.; Tessaro, I. C.; Gerchmann, M.

    Resumo em Inglês:

    The objective of this work is to investigate the production of hydrogen as an energy source by means of the reaction of aluminum with water. This reaction only occurs in the presence of NaOH and KOH, which behave as catalysts. The main advantages of using aluminum for indirect energy storage are: recyclability, non-toxicity and easiness to shape. Alkali concentrations varying from 1 to 3 mol.L-1 were applied to different metallic samples, either foil (0.02 mm thick) or plates (0.5 and 1 mm thick), and reaction temperatures between 295 and 345 K were tested. The results show that the reaction is strongly influenced by temperature, alkali concentration and metal shape. NaOH commonly promotes faster reactions and higher real yields than KOH.
  • Mixing in shear thinning fluids Process Systems Engineering

    Ameur, H.; Bouzit, M.

    Resumo em Inglês:

    In the present study, a CFD characterization of the flow generated by curved-blade impellers in a cylindrical unbaffled vessel was carried out. The tank diameter was 300 mm, with a flat bottom. The liquid height was equal to the vessel diameter. The fluids simulated have a shear thinning behavior. Analyses concern the effect of the impeller speed, the fluid rheology and the number of impeller blades on the induced flow patterns and the power consumption. The predictions were compared with literature data and a satisfactory agreement was found.
  • Modelling of fertilizer drying in a rotary dryer: parametric sensitivity analysis Process Systems Engineering

    Silva, M. G.; Lira, T. S.; Arruda, E. B.; Murata, V. V.; Barrozo, M. A. S.

    Resumo em Inglês:

    This study analyzed the influence of the following parameters: overall volumetric heat transfer coefficient, coefficient of heat loss, drying rate, specific heat of the solid and specific heat of dry air on the prediction of a model for the fertilizer drying in rotary dryers. The method of parametric sensitivity using an experimental design was employed in this study. All parameters studied significantly affected the responses of the drying model. In general, the model showed greater sensitivity to the parameters drying rate and overall volumetric heat transfer coefficient.
  • Refinery production planning and scheduling: the refining core business Process Systems Engineering

    Joly, M.

    Resumo em Inglês:

    Intelligent production planning and scheduling are of paramount importance to ensure refinery profitability, logistic reliability and safety at the local and corporate levels. In Brazil, such activities play a particularly critical role, since the Brazilian downstream model is moving towards a demand-driven model rather than a supply-driven one. Moreover, new and specialized non-linear constraints are continuously being incorporated into these large-scale problems: increases in oil prices implying the need for processing poor quality crudes, increasing demand and new demand patterns for petroleum products, new stringent environmental regulations related to clean fuels and start-up of new production technologies embedded into more complex refining schemes. This paper aims at clarifying the central role of refinery planning and scheduling activities in the Petrobras refining business. Major past and present results are outlined and corporate long-term strategies to deal with present and future challenges are presented.
  • Determination of the maximum retention of cobalt by ion exchange in h-zeolites Separation Processes

    Zola, A. S.; Barros, M. A. S. D.; Sousa-Aguiar, E. F.; Arroyo, P. A.

    Resumo em Inglês:

    This work aimed to determine the maximum content of cobalt that can be incorporated by ion exchange in zeolites H-USY, H-Beta, H-Mordenite, and H-ZSM-5. To reach this goal, batch isotherms at 75ºC were constructed after addition of zeolite samples in flasks filled with cobalt nitrate solution. The equilibrium data were fitted to Langmuir, Freundlich, and Tóth adsorption isotherm models. Langmuir was the best model for zeolites H-Beta, H-Mordenite, and H-ZSM-5, whereas experimental data for H-USY were better fitted to the Freundlich isotherm model. From the isotherms, it was possible to determine the maximum cobalt exchange level (q max) that can be incorporated in each zeolite through ion exchange. In this sense, H-USY presented the highest q max value (2.40 meq/g zeol), while H-ZSM-5 showed the lowest one (0.64 meq/g zeol). These results also show the influence of the zeolite framework related to the channel system, pore opening, presence of cavities and secondary porosity and SiO2/Al2O3 ratio (SAR) on the maximum capacity and behavior of cobalt ion exchange in protonic zeolites.
  • Pore blocking mechanism for the recovery of milk solids from dairy wastewater by ultrafiltration Separation Processes

    Brião, V. B.; Tavares, C. R. G.

    Resumo em Inglês:

    This paper evaluates the pore blocking mechanism of two ultrafiltration membranes with different geometries (tubular and spiral wound) when dairy wash water is filtered. The work evaluated the effect of transmembrane pressure and the cross-flow velocity with a 3² experimental design using classical Hermia's models and the resistance-in-series model. The resistance-in-series analysis identified external fouling on the surface of both membranes, but the tubular membrane showed higher reversible fouling, while the reversible and irreversible resistances of the spiral wound membrane averaged 41% and 45%, respectively. Cake formation is the model that best represents ultrafiltration in the spiral wound membrane at all transmembrane pressures and cross-flow velocities. In the tubular membrane, at the lowest cross-flow velocity (0.79 m.s-1), the cake formation model fitted the experimental data best. However, at higher cross-flow velocities (1.42 and 2.23 m.s-1), the best fit of flux data was obtained with the complete pore blocking model. In addition, the tubular membrane apparently had a two-step pore blocking: "pore blocking" as the initial governing mechanism followed by "cake formation".
  • Extraction, fatty acid profile and antioxidant activity of sesame extract (Sesamum Indicum L.) Separation Processes

    Carvalho, R. H. R.; Galvão, E. L.; Barros, J. Â. C.; Conceição, M. M.; Sousa, E. M. B. D.

    Resumo em Inglês:

    This article carried out the extraction of sesame oil by using three extraction techniques: supercritical fluid extraction (SFE), Soxhlet and sequential extraction. The SFE was performed using supercritical carbon dioxide (SC-CO2) as solvent and ethanol as cosolvent. Tests were performed at 20 MPa, 35ºC and a flow rate of 2.5 g CO2/min with a total extraction time of 210 minutes. The Soxhlet extraction was performed for 8 hours, using petroleum ether and ethanol as solvents, until the exhaustion of the oil contained in the seeds. The sequential extraction used ethyl ether, ethanol and water as solvents. The Soxhlet extraction was the most effective (58.93%), while the SFE technique obtained 26.47% as the best result. The antioxidant activity (AA) was determined by the β-carotene/linoleic acid system, with good oxidation inhibition percentages (29.32-83.49%) for all the extracts. The main fatty acids (FA) in sesame oil were oleic and linoleic acids.
  • Deep removal of 4,6-dimethyldibenzothiophene from model transportation diesel fuels over reactive adsorbent Separation Processes

    Wang, Shengqiang; Wang, Ruicong; Yu, Hongbing

    Resumo em Inglês:

    This paper presents a new reactive adsorbent used to effectively remove 4,6-dimethyldibenzothiophene (4,6-DMDBT) from model transportation diesel fuels. This reactive adsorbent was composed of formaldehyde, phosphotungstic acid and mesoporous silica gel. The experiment was based on an assumed condensation reaction of 4,6-DMDBT with formaldehyde using phosphotungstic acid as catalyst in pore spaces. The effect of temperature and the amount of formaldehyde and phosphotungstic acid loaded on the substrate were investigated in a batch system. In the breakthrough experiment, three different model diesel fuels containing 1000 mg/kg 4,6-DMDBT were pumped through a fixed-bed reactor packed with reactive adsorbent at constant temperature and atmospheric pressure, respectively. The experimental results showed that sulfur-free model fuel was obtained at 80ºC despite the presence of aromatics. The sulfur capacity of regenerated reactive adsorbent was almost totally recovered.
  • Cachaça distillation investigated on the basis of model systems Thermodynamics

    Scanavini, H. F. A.; Ceriani, R.; Meirelles, A. J. A.

    Resumo em Inglês:

    This work reports experimental tests using commercial spirits that were diluted and had their initial composition modified in order to better measure the distillation behavior of selected minor compounds of importance for the quality of alcoholic beverages. Such compounds were added to the commercial cachaça and the corresponding model wine, obtained after the spirits' dilution, was distilled. In this way a more precise distillation profile could be determined for those minor compounds. The alembic heating was performed by electrical resistance and the corresponding heat transfer coefficient was determined by analyzing the thermal behavior of the still during the distillations. A simulation algorithm was developed, including the mass and enthalpy balances as well as the heat transfer flux to the boiling wine. Good agreement between experimental and simulated results was obtained for the distillate rate, alcoholic graduation, temperature and most minor component profiles.
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