Resumo em Inglês:

The use of electroflotation in emulsified oil wastes was studied. A rectangular electroflotation cell was designed and constructed in acrylic with stainless steel cathode and DSA® anode with a nominal composition of Ti/Ru0.34Ti0.66O2. The variables studied in the present work were current density and oil, flocculant and electrolyte (NaCl) concentrations. The experiments were carried out in accordance with 2(4) full factorial experimental designs with two center points. The STATISTICA 5.5 software was used for calculations in order to relate experimental data to a statistical model. The best results, yielded 99.71% oil removal were obtained from 1050ppm of emulsified oil feed.

Resumo em Inglês:

The anaerobic treatment of wastewater from the household and personal products industry was studied using a 16.3 L hybrid reactor (UASB and biofilter). The top of the UASB reactor was filled with coconut shells to act as the support material for the biofilter. The wastewater was characterized in terms of pH (1.0 - 12.0), COD (1,000 - 5,000 mg/L), BOD5 (700 - 1,500 mg/L), chloride (55 - 850 mg/L), ammonia nitrogen (0.4 - 0.9 mg/L), total Kjeldahl nitrogen (22.1 - 34.0 mg/L), phosphorus (2.0 - 2.5 mg/L), anionic surfactants (100 - 600 mg/L), turbidity (115 - 300 NTU) and total suspended solids (450 - 1,440 mg/L). The bioreactor was operated continuously for 120 days at room temperature (26 ± 5ºC) with hydraulic retention times of 50, 40 and 60 h. COD and BOD removals and biogas production were evaluated in order to analyze process efficiency. The average removal efficiencies for COD (77%, 72% and 80%) and BOD5 (approximately 90%) were obtained with HRTs of 50, 40 and 60 h, respectively. The average specific biogas production was 0.32 L/g COD (at standard temperature and pressure) for the three experimental runs. These data indicate good reactor efficiency and suggest the possibility of using this system to treat wastewater generated by the household and personal products industry.

Resumo em Inglês:

In this paper, a comparative study of the treatment of raw and biotreated (upflow anaerobic sludge blanket, UASB) textile dye bath effluent using advanced oxidation processes (AOPs) is presented. The AOPs applied on raw and biotreated textile dye bath effluent, after characterization in terms of COD, colour, BOD and pH, were ozone, UV, UV/H2O2 and photo-Fenton. The decolorization of raw dye bath effluent was 58% in the case of ozonation. However it was 98% in the case of biotreated dye bath effluent when exposed to UV/H2O2. It is, therefore, suggested that a combination of biotreatment and AOPs be adopted to decolorize dye bath effluent in order to make the process more viable and effective. Biodegradability was also improved by applying AOPs after biotreatment of dye bath effluent.

Resumo em Inglês:

Inulin is a polysaccharide frequently used as a sugar or fat replacer in the food industry, which offers the advantage of a functional effect similar to those of dietary fibers. By cooling or freezing an inulin concentrated solution, a more concentrated solution precipitates as a paste-like substance, while the liquid phase forms a diluted solution. In this work, the effect of storage temperature of inulin concentrated solution as well as temperature on the rheological behavior of liquid and precipitated phases obtained from a process of phase separation were evaluated. The precipitated phase of inulin was evaluated under two conditions: pure and formulated with encapsulating agents. It was observed that a reduction in storage temperature resulted in a higher inulin precipitation, which produced higher apparent viscosity values for the precipitated phase. All the samples analyzed had a shear-thinning rheological behavior.

Resumo em Inglês:

The volumetric overall mass transfer coefficients in a pilot plant Hanson mixer-settler extraction column of seven stages have been measured using toluene-acetone-water system. The effects of agitation speed and dispersed and continuous phases flow rates on volumetric overall mass transfer coefficients have been investigated. The results show that the volumetric overall mass transfer coefficient increases with increase in agitation speed and reaches a maximum. After having reached its maximum, it falls with further increase in agitation speed. It was found that the volumetric overall mass transfer coefficient increases with increase in dispersed phase flow rate, while it decreases with increase in continuous phase flow rate. By using interfacial area, the overall mass transfer coefficients for continuous and dispersed phases are determined from volumetric coefficients. An empirical correlation for prediction of the continuous phase overall mass transfer coefficient is proposed in terms of Sherwood and Reynolds numbers. Also the experimental data of the column investigated are compared with data for various extraction columns. Comparison between theoretical models and experimental results for the dispersed phase mass transfer coefficient shows that these models do not have enough accuracy for column design. Using effective diffusivity in the Gröber equation results in more accurate prediction of overall mass transfer coefficient. The prediction of overall mass transfer coefficients from the presented equations is in good agreement with experimental results.

Resumo em Inglês:

Experimental studies were conducted in a spiral plate heat exchanger with hot water as the service fluid and the two-phase system of water – palm oil in different mass fractions and flow rates as the cold process fluid. The two phase heat transfer coefficients were correlated with Reynolds numbers (Re) in the form h = a Re m, adopting an approach available in literature for two phase fluid flow. The heat transfer coefficients were also related to the mass fraction of palm oil for identical Reynolds numbers. The two-phase multiplier (ratio of the heat transfer coefficient of the two phase fluid and that of the single phase fluid) was correlated with the Lockhart Martinelli parameter in a polynomial form. This enables prediction of the two-phase coefficients using single-phase data. The predicted coefficients showed a spread of ± 10 % in the laminar range.

Resumo em Inglês:

Microwave (MW) drying is a rapid dehydration technique that can be applied to specific foods. Increasing concerns over product quality and production costs have motivated the researchers to investigate and the industry to adopt microwave drying technology. The advantages of microwave drying include the following: shorter drying time, improved product quality, and flexibility in producing a wide variety of dried products. Drying is influenced by heat and mass transfer between drying airflow and product, as well as the complex moisture transport processes which take place in the product.. This paper presents an analytical approach for the drying of potato. The laws of moisture content change in the food product as a function of mass transfer are used for the theoretical approach. The study gives a brief description of efforts made to obtain basic drying parameters under different microwave drying conditions. This computational method can be used as a tool for microwave drying of potato slabs more efficiency.

Resumo em Inglês:

A mathematical model is developed to describe the coupling between heat, mass, and momentum transfers and is applied to simulate the drying of saturated and shrinking media. This model is called "the Darcy-flow model", which is based on the fact that the liquid flow is induced by a pressure gradient. The main novelties of the model are that firstly no phenomenological law need be introduced by keeping solid mass conservation and solid volume conservation together and secondly we use the effective stresses notion strongly coupling mechanical behaviour with mass transport. The analysis is limited to the preheating and the constant rate drying periods because shrinkage occurs during these two periods for most materials. Our purpose is to simulate the drying process and to compare the results of the simulations and the experiments done on clay material to demonstrate the consistency of the model developed. One of the important conclusions is that is no correlation between moisture flow and moisture gradient.

Resumo em Inglês:

A suitable method is needed to solve the nonquality problem in the grated coconut industry due to the poor control of product humidity during the process. In this study the possibility of using an artificial neural network (ANN), precisely a Multilayer Perceptron, for modeling the drying step of the production of grated coconut process is highlighted. Drying must confer to the product a final moisture of 3%. Unfortunately, under industrial conditions, this moisture varies from 1.9 to 4.8 %. In order to control this parameter and consequently reduce the proportion of the product that does not meet the humidity specification, a 9-4-1 neural network architecture was established using data gathered from an industrial plant. This Multilayer Perceptron can satisfactorily model the process with less bias, ranging from -0.35 to 0.34%, and can reduce the rate of rejected products from 92% to 3% during the first cycle of drying.

Resumo em Inglês:

Here asphaltene precipitation in petroleum reservoirs during natural depletion and miscible gas injection is modeled via two distinct and new methods (polymer solution and lattice theories). The first model is based on the polymer solution theory, which is a combination of Miller's combinatorial term with a modified residual term of the original Flory-Huggins theory. The second one is the application of the well-known Sanchez-Lacombe equation of state (SL EOS) to describe the phase behavior of asphaltene compounds in crude oil. The results of both models show an acceptable and good agreement between the real data (field and experimental) and these two models. As it can be seen from the obtained results of these two models, it seems application of the lattice or polymer solution theories (based on The Miller's combinatorial term) could give the better and more close to real data.

Resumo em Inglês:

Garlic (Allium sativum L.) and garlic extracts have therapeutical properties that stem from their sulfur-containing compounds, mainly allicin. The main objective of this work was to compare conventional and "premium" garlic extracts in terms of yield and quality, with the latter being obtained using supercritical carbon dioxide (SC-CO2) as the solvent. Yield ranged between 0.65 and 1.0% and increased with extraction pressure (150-400 bar) at a constant temperature of 50°C. Extraction temperature (35-60°C), on the other hand, had little effect at a constant pressure of 300 bar. Based on yield and quality considerations, the best extraction conditions using SC-CO2 were 35-50°C and 300-400 bar. A yield of 5.5% was obtained by conventional extraction using ethanol as the solvent, but ethanol appeared to be less selective for valuable components than SC-CO2. The use of fresh garlic resulted in extracts that more closely resembled commercial products, possibly because of thermal and oxidative degradation of valuable microconstituents during drying.

Resumo em Inglês:

The paper reports on experimental data on the extraction of caffeine, coffee oil and chlorogenic acids from green coffee beans using pure supercritical CO2 and supercritical CO2 modified with ethanol (5% w/w) and isopropyl alcohol (5% w/w) at 50 and 60ºC and 15.2 24.8 e 35.2 MPa. In this study extraction kinetics were obtained for all assays i.e. samples were collected at several time intervals for each solvent and mixed solvent. When pure CO2 and CO2-ethanol mixed solvent were used, an increase in pressure resulted in an increase in the amount of oil extracted. When CO2 was modified with isopropyl alcohol, the amount of coffee oil extracted also increased with pressure. Caffeine extraction initially increased and subsequently decreased with pressure. Chlorogenic acids were only extracted when isopropyl alcohol was used as a co-solvent. An increase in extraction temperature resulted in a decrease of caffeine and oil extraction (retrograde condensation) when only CO2 was used as solvent. With the use of co-solvent this retrograde behavior was no longer observed and the increase in temperature resulted in the increase in the extracted amounts of caffeine, coffee oil and chlorogenic acids.

Resumo em Inglês:

Studies on the extraction of citric acid by TOMAC (trioctyl methyl ammonium chloride) dissolved in 2-propanol and 2-octanol (active solvents) and their mixture (1 : 1 volume ratio) are reported. Experimental results of batch extraction experiments are calculated and reported for partitioning coefficients (D), loading factors (Z), and extraction efficiency (E). All measurements were carried out at 298.15 K. The results of the liquid-liquid equilibrium measurements were correlated with a linear solvation energy relationship (LSER) model which takes into account physical interactions. Solvatochromic parameters of the model were obtained from the literature. The remaining parameters were fitted to the experimental results. Experimental results for the liquid-liquid equilibrium were compared to the model.

Resumo em Inglês:

This work reports high-pressure cloud point data for the quaternary system glycerol + olive oil + n-butane + AOT surfactant. The static synthetic method, using a variable-volume view cell, was employed for obtaining the experimental data at pressures up to 27 MPa. The effects of glycerol/olive oil concentration and surfactant addition on the pressure transition values were evaluated in the temperature range from 303 K to 343 K. For the system investigated, vapor-liquid (VLE), liquid-liquid (LLE) and vapor-liquid-liquid (VLLE) equilibrium were recorded. It was experimentally observed that, at a given temperature and surfactant content, an increase in the concentration of glycerol/oil ratio led to a pronounced increase in the slope of the liquid-liquid coexistence curve. A comparison with results reported for the same system but using propane as solvent showed that much lower pressure transition values are obtained when using n-butane.

Resumo em Inglês:

Minimization of Gibbs free energy using activity coefficient models and nonlinear equation solution techniques is commonly applied to phase stability problems. However, when conventional techniques, such as the Newton-Raphson method, are employed, serious convergence problems may arise. Due to the existence of multiple solutions, several problems can be found in modeling liquid-liquid equilibrium of multicomponent systems, which are highly dependent on the initial guess. In this work phase stability analysis of liquid-liquid equilibrium is investigated using the NRTL model. For this purpose, two distinct stochastic numerical algorithms are employed to minimize the tangent plane distance of Gibbs free energy: a subdivision algorithm that can find all roots of nonlinear equations for liquid-liquid stability analysis and the Simulated Annealing method. Results obtained in this work for the two stochastic algorithms are compared with those of the Interval Newton method from the literature. Several different binary and multicomponent systems from the literature were successfully investigated.

Resumo em Inglês:

Cashew nut shell, a waste product obtained during deshelling of cashew kernels, had in the past been deemed unfit as a fuel for gasification owing to its high occluded oil content. The oil, a source of natural phenol, oozes upon gasification, thereby clogging the gasifier throat, downstream equipment and associated utilities with oil, resulting in ineffective gasification and premature failure of utilities due to its corrosive characteristics. To overcome this drawback, the cashew shells were de-oiled by charring in closed chambers and were subsequently gasified in an autothermal downdraft gasifier. Equilibrium modeling was carried out to predict the producer gas composition under varying performance influencing parameters, viz., equivalence ratio (ER), reaction temperature (RT) and moisture content (MC). The results were compared with the experimental output and are presented in this paper. The model is quite satisfactory with the experimental outcome at the ER applicable to gasification systems, i.e., 0.15 to 0.30. The results show that the mole fraction of (i) H2, CO and CH4 decreases while (N2 + H2O) and CO2 increases with ER, (ii) H2 and CO increases while CH4, (N2 + H2O) and CO2 decreases with reaction temperature, (iii) H2, CH4, CO2 and (N2 + H2O) increases while CO decreases with moisture content. However at an equivalence ratio less than 0.15, the model predicts an unrealistic composition and is observed to be non valid below this ER.

Resumo em Inglês:

The reduction efficiency is an important variable during the black liquor burning process in the Kraft recovery boiler. This variable value is obtained by slow experimental routines and the delay of this measure disturbs the pulp and paper industry customary control. This paper describes an optimization approach for the reduction efficiency determination in the furnace bottom of the recovery boiler based on the minimization of the Gibbs free energy. The industrial data used in this study were directly obtained from CENIBRA's data acquisition system. The resulting approach is able to predict the steady state behavior of the chemical composition of the furnace recovery boiler, - especially the reduction efficiency when different operational conditions are used. This result confirms the potential of this approach in the analysis of the daily operation of the recovery boiler.