Resumo em Inglês:

The RPN indicates how potentially difficult it is for a given system to achieve the desired performance robustly. It reflects both the attainable performance of a system and its degree of directionality. Two new indices, RPN ratio and RPN difference are introduced to quantify how realizable a given desired performance can be. The predictions made by RPN are verified by closed-loop simulations. These indices are applied to quantify the IO-controllability of the quadruple-tank process.

Resumo em Inglês:

Interest in biomass as a clean source of fuel, chemicals and materials is growing fast. What is attractive about biomass is its renewability and that it is CO2 balanced and sulfur-free. Biomass pyrolysis produces charcoal, bio-oil and gases in different proportions, depending on the technology and raw material used. In this study biopitch, a substitute for fossil pitches in electrodes, was produced from bio-oil distillation in bench-scale equipment. Biopitch and charcoal were mixed and thermically modified to give prebaked electrodes. The physico-chemical and mechanical properties of the biopitch and final electrodes were measured and compared with those of coal tar and petroleum materials. Despite their similar application, biomaterials are structurally and chemically different from minerals. The oxygen content in biopitch is ca 20 wt% and in mineral pitches it is no more than 2 wt%. Characterization experiments for electrode samples measured electrical resistivity, Young's modulus, rupture strength, density, porosity and proximate analysis.

Resumo em Inglês:

The odoriferous species Lippia sidoides Cham. is abundant in the Brazilian Northeast. Its essential oil possesses antiseptic activity due to the presence of thymol. In this work, thermodynamic and kinetic data were experimentally determined for the CO2 + L. sidoides system. Solubility was determined using the dynamic method at pressures of 66.7 and 78.5 bar and temperatures of 283.15, 288.15, 293.15, 295.15, and 298.15 K. SFE kinetic data were obtained at 288.15 K and 66.7 bar. The composition of the multicomponent solute mixture was determined by GC-MS and compared to the composition of both the volatile oil obtained by steam distillation and the oleoresin obtained using ethanol. The SFE process yield was higher than the yield of either the steam distillation or the ethanol extraction. The solubilities were correlated using the Peng-Robinson equation of state with one binary interaction parameter for the attractive term, considering the essential oil as a pseudo-component. Sovová’s model quantitatively described the overall extraction curve.

Resumo em Inglês:

Experimental liquid-liquid equilibria of the water-acetic acid-butyl acetate system were studied at temperatures of 298.15± 0.20, 303.15± 0.20 and 308.15± 0.20 K. Complete phase diagrams were obtained by determining solubility and tie-line data. The reliability of the experimental tie-line data was ascertained by using the Othmer and Tobias correlation. The UNIFAC group contribution method was used to predict the observed ternary liquid-liquid equilibrium (LLE) data. It was found that UNIFAC group interaction parameters used for LLE did not provide a good prediction. Distribution coefficients and separation factors were evaluated for the immiscibility region.

Resumo em Inglês:

A strong metal support interaction (SMSI) effect was observed on Pd/Nb2O5 and Pd/TiO2 catalysts, and it produces small, exposed Pd ensembles. A decrease in the trans/cis 2-butene ratio was observed after reduction at 773 K. Selectivity changes were ascribed to the decoration model. Theoretical models were developed based on semi-empirical molecular-orbital calculations for 1,3-butadiene and Pd n clusters. Experimental results are in agreement with our theoretical model, which proposes a greater stabilization of the cisoid intermediate on small Pd ensembles.

Resumo em Inglês:

The NRTL (nonrandom, two-liquid) model, expressed in mass fraction instead of mole fraction, was used to correlate liquid-liquid equilibria for aqueous two-phase polymer-salt solutions. New interaction energy parameters for this model were determined using reported data on the water + poly(ethylene glycol) + salt systems, with different molecular masses for PEG and the salts potassium phosphate, sodium sulfate, sodium carbonate and magnesium sulfate. The correlation of liquid-liquid equilibrium is quite satisfactory.

Resumo em Inglês:

Of nine epiphytic isolates of the genus Bacillus, only B. subtilis R14, B. pumilus C116, B. megaterium pv. cerealis RAB7, and B. cereus C210 showed antibiotic activity when tested in vitro against the bacterium Xanthomonas campestris pv. campestris LFR-3. Aiming product a biocontrol agent for black rot in crucifers, the production of B. subtilis R14 was evaluated in a batch bioreactor. Rapid growth was observed in a medium containing molasses and yeast extract as C-source and N-source, respectively. During the exponential growth phase, the specific growth rate was 1.2 h-1. A quick sporulation was also observed in a C/N well-balanced medium. After the sporulation phase, maximum viable spore concentrations around 10(9) CFU/mL were obtained. Preliminary sedimentation tests at different pH values showed better biomass separation efficiencies at low pH values.

Resumo em Inglês:

The objective of this paper is the development and solution of nonlinear and mixed-integer (MIP) optimization models for real-world planning and scheduling problems in petroleum refineries. Firstly, we present a nonlinear planning model that represents a general refinery topology and allows implementation of nonlinear process models as well as blending relations. The optimization model is able to define new operating points, thus increasing the production of the more valuable products and simultaneously satisfying all specification constraints. The second part addresses scheduling problems in oil refineries, which are formulated as MIP optimization models and rely on both continuous and discrete time representations. Three practical applications closely related to the current refinery scenario are presented. The first one addresses the problem of crude oil inventory management of a refinery that receives several types of crude oil delivered exclusively by a single oil pipeline. Subsequently, two optimization models intended to define the optimal production policy, inventory control and distribution are proposed and solved for the fuel oil and asphalt plant. Finally, the planning model of Moro et al. (1998) is extended in order to sequence decisions at the scheduling level in the liquefied petroleum gas (LPG) area for maximization of the production of petrochemical-grade propane and product delivery.

Resumo em Inglês:

Sterilization of fermentation medium involving heat may result in undesirable chemical reactions that alter nutrient concentration and yield products, which interfere in the fermentation performance. Sterilization of heat-sensitive compounds usually involves separate sterilizations of carbon source and nutrient solution. Membrane separation processes are an alternative to thermal processes, as they have many advantages such as the possibility of continuous and modular operation and the use of moderate temperatures. In this context, the objective of this work was the preparation of hollow-fiber membranes and the design of modules suitable for continuous sterilization of fermentation medium. The membrane with the best performance had a maximum pore diameter of 0.2 mu m and a permeability of 42.9 L/m².bar.h for a glucose/peptone/yeast extract medium. A module with 0.26 m² of permeation area was built with these membranes. This module was able to provide a permeate flow rate of 2.2 L/h using a pressure difference of 0.2 bar. The collected permeate was completely sterile, thus confirming the efficiency of this process.

Resumo em Inglês:

This work studies the use of biological and combined biological/enzymatic treatments in phenol degradation. The systems studied were conventional batch aerobic biological followed or preceded by enzymatic treatment. Tyrosinase extracted from the mushroom Agaricus bispora was employed. Biological treatment efficiently degraded effluents containing up to 420 mg.L-1 of phenol, removing 97% of the COD and 99% of the phenol in 48-hour batches. Alterations in phenol concentration intake reduced treatment efficiency significantly. Enzymatic polishing of biotreated effluent removed up to 75% of the remaining phenol in a four-hour reaction with 46 U.mL-1 of tyrosinase and 50 mg.L-1 of chitosan (used as coagulant). Enzymatic pretreatment with 20 U.mL-1 of tyrosinase reduced the phenol concentration by 25 % after 2 hours of reaction, although initial COD increased up to 58%. The subsequent biological treatment of that enzymatic pretreated effluent reduced COD to 151 mgO2.L-1 and phenol concentration to 1 mg.L-1 in 24-hours batches.

Resumo em Inglês:

The potential production of rhamnolipid-type biosurfactants is assessed based on the development of a fermentative process with a strain of Pseudomonas aeruginosa PA1, which was isolated from oil production wastewater in the Northeast of Brazil. These production of molecules using different carbon (n-hexadecane, paraffinic oil, glycerol and babassu oil) and nitrogen sources (NaNO3, (NH4)2SO4 and CH4N2O) was studied. The best results were obtained when using glycerol as substrate. A C/N ratio of 60/1 and use of sodium nitrate as nitrogen source resulted in higher production of the rhamnolipid, expressed by rhamnose (3.16 g/L) and by the yield in relation to biomass (Yp/x = 0.70 g/g). Additionally, physical-chemical characteristics of the spent broth with and without cells were studied, providing a low critical micelle concentration of 19 mg/L and toxicity values of 13 and 13.8 mg/L using two test organisms, the micro crustacean Daphnia similis and the bacterium Vibrio fisheri (Microtox), respectively.

Resumo em Inglês:

The purpose of this work was to develop a continuous fermentation system operating with a tower reactor using some flocculent yeast strains isolated from an industrial process. The strain was an used in the trial of the proposed system, composed of two serial glass tower reactor. The effects of the following variables were studied on the yield and productivity of the system: total reducing sugar (TRS), concentration in feeding, recycle flow in the second reactor, residence time and diameter/height ratio of the reactors. It was observed that the TRS concentration in feeding and residence time is the variables that interfere most with the productivity of the system. Yield was not affected by any of the variables within the range of values studied. All trials were performed according to a factorial experimental design (making up a total of 19 trials) and the results were evaluated by response surface.

Resumo em Inglês:

An enzymatic extract produced by Penicillium restrictum having a high level of lipase activity (17.2 U.g-1) was obtained by solid-state fermentation using babassu cake as substrate. The enzymatic extract was used in the hydrolysis of a dairy wastewater with high fat contents (180, 450, 900 and 1,200 mg.L-1). Different hydrolysis conditions were tested, and it was determined that it should be carried out at a temperature of 35ºC, without agitation, with 10% v/v enzymatic extract and a hydrolysis time of 12 hours. Both crude and hydrolysed effluents were then submitted to an anaerobic biological treatment. It was observed that for the enzymatically pretreated effluent there was a significant improvement in the efficiency of the anaerobic treatment. For the highest fat content tested (1,200 mg.L-1), removal efficiencies of 19 and 80% were attained for crude and hydrolysed effluents, respectively. In addition, a tenfold increase in the removal rate of COD from the hydrolysed effluent (1.87 kg COD.m-3.d-1) was observed in relation to the crude effluent (0.18 kg COD.m-3.d-1). The results obtained in this study illustrate the viability of using a hybrid treatment (enzymatic-biological) for wastewaters having high fat contents.

Resumo em Inglês:

The synthesis of acetoin in YM medium and under aerobic conditions by Hanseniaspora guilliermondii was studied. Experimental design and surface response analysis were employed to evaluate the influence of glucose concentration, temperature and pH on the process. The experiments were carried out in shaking flasks under controlled temperature. Five different levels of initial concentration of glucose, temperature and pH were used with variations from 17 to 81 g/L, from 24 to 36ºC and from 4.0 to 6.0, respectively. The maximum concentration of acetoin was the response obtained. The parameters which affected acetoin production most were initial concentration of glucose and temperature. An empirical model that showed statistically significant and predictive capacity was constructed. The optimum values of glucose concentration and temperature obtained for acetoin production were 63 g/L and 28ºC, respectively.