Resumo em Inglês:

Abstract In Chile, the most important economic activity is mining, concentrated in the north of the country. This is a desert region with limited water resources; therefore, the mining sector requires research and identification of alternative sources of water. One alternative is seawater, which can be a substitute of the limited fresh water resources in the region. This work determines the influence of seawater on the solid-liquid equilibrium for acid solutions of copper sulfate at different temperatures (293.15 to 318.15 K), and its effect on physical properties (density, viscosity, and solubility). Knowledge of these properties and solubility data are useful in the leaching process and in the design of copper sulfate pentahydrate crystallization plants from the leaching process using seawater by means of the addition of sulfuric acid.

Resumo em Inglês:

Abstract The correlation of thermodynamic properties of nonaqueous electrolyte solutions is relevant to design and operation of many chemical processes, as in fertilizer production and the pharmaceutical industry. In this work, the Q-electrolattice equation of state (EOS) is used to model vapor pressure, mean ionic activity coefficient, osmotic coefficient, and liquid density of sixteen methanol and ten ethanol solutions containing single strong 1:1 and 2:1 salts. The Q-electrolattice comprises the lattice-based Mattedi-Tavares-Castier (MTC) EOS, the Born term and the explicit MSA term. The model requires two adjustable parameters per ion, namely the ionic diameter and the solvent-ion interaction energy. Predictions of osmotic coefficient at 298.15 K and liquid density at different temperatures are also presented.

Resumo em Inglês:

Abstract The objective of this paper was to use a thermodynamic analysis to find operational conditions that favor the production of hydrogen from steam and oxidative reforming of liquefied petroleum gas (LPG). We also analyzed the performance of a catalyst precursor, LaNiO3, in order to compare the performance of the obtained catalyst with the thermodynamic equilibrium predictions. The results showed that it is possible to produce high concentrations of hydrogen from LPG reforming. The gradual increase of temperature and the use of high water concentrations decrease the production of coke and increase the formation of H2. The reaction of oxidative reforming of LPG was more suitable for the production of hydrogen and lower coke formation. Furthermore the use of an excess of water (H2O/LPG =7.0) and intermediate temperatures (973 K) are the most suitable conditions for the process.

Resumo em Inglês:

Abstract Many efforts have been made to develop amine-based solid adsorbents for capture of CO2 by adsorption. Compared with the traditional process of absorption in aqueous solutions of amines, the adsorbents with amine immobilized in solids generally result in processes with lower capital and energy costs. The literature contains some experimental studies of CO2 adsorption in impregnated materials; however, few studies are devoted to the theoretical interpretation of this system in terms of CO2 capture for post-combustion (N2 mixture with a low partial pressure of CO2). Therefore, this study investigates the adsorption of a CO2:N2 mixture on zeolite NaX impregnated with monoethanolamine (MEA), using molecular simulation. A model of NaX impregnated with MEA was proposed and the adsorption of a 15:85 (CO2:N2) mixture was investigated based on the Monte Carlo method. The simulation of the MEA impregnated zeolite at 25 ˚C predicted higher CO2 selectivity and significant improvement in the heat of adsorption. Unfortunately, the adsorption heat improvement did not translate into corresponding increases in the amount of adsorbed CO2. Moreover, MEA concentrations higher than 12 wt% hindered the adsorption of CO2 molecules. An explanation for the results in terms of occupied volumes and interaction energies is presented.

Resumo em Inglês:

Abstract Densities and refractive index of binay mixtures of water with four protic ionic liquids, based on ammonium and fatty acids, were measured at 298.15 and 323.15 K, under atmospheric pressure. Apparent and excess molar volumes were obtained by experiments and fitting data to the Redlich-Meyer (RM), Redlich-Kister (RK) and Prigogine-Flory-Patterson (PFP) equations. The molar volume values were high, suggesting strong ion-solvent interaction. The same interaction also became stronger as the temperature increased. Excess volume values were negative, indicating that packing efficiency ability or attractive interactions occurred in mixtures of ionic liquid + water. The errors (AARD) for the properties in excess were in the range of 1.8% to 7.2%. The PFP error for the apparent volume was in the range of 0.34% to 0.06%, lower than the RM error for the same property, which was in the range of 0.70 to 1.55%. The Gladstone-Dale model was applied to correlate the refractive index of the binary mixture with the density from the values of both pure components.

Resumo em Inglês:

Abstract The Boundary Driven Non-Equilibrium Molecular Dynamics (BD-NEMD) method is employed to evaluate Soret coefficients of binary mixtures. Using a n-decane/n-pentane mixture at 298 K, we study several parameters and conditions of the simulation procedure such as system size, time step size, frequency of perturbation, and the undesired warming up of the system during the simulation. The Soret coefficients obtained here deviated around 20% when comparing with experimental data and with simulated results from the literature. We showed that fluctuations in composition gradients and the consequent deviations of the Soret coefficient may be due to characteristic fluctuations of the composition gradient. Best results were obtained with the smallest time steps and without using a thermostat, which shows that there is room for improvement and/or development of new BD-NEMD algorithms.

Resumo em Inglês:

Abstract Phase equilibria of the reaction components are essential data for the design and process operations of biodiesel production. Despite their importance for the production of ethylic biodiesel, the reaction mixture, reactant (oil and ethanol) and the product (fatty acid ethyl esters) up to now have received less attention than the corresponding systems formed during the separation and purification phases of biodiesel production using ethanol. In this work, new experimental measurements were performed for the liquid-liquid equilibrium (LLE) of the system containing vegetable oil (sunflower oil and canola oil) + ethylic biodiesel of refined vegetable oil + anhydrous ethanol at 303.15 and at 323.15 K and the system containing refined palm oil + ethylic biodiesel of refined palm oil + ethanol at 318.15 K. The experimental data were successfully correlated by the nonrandom two-liquid (NRTL) model; the average deviations between calculated and experimental data were smaller than 1.00%.

Resumo em Inglês:

Abstract Since the phase out of Halon extinguishers in the 1980s, hot aerosol fire suppression technology has gained much attention. Unlike traditional inert gas, foam, water mist and Halon fire suppression agents, hot aerosol fire extinguishing agents do not need to be driven out by pressurized gases and can extinguish class A, B, C, D and K fires at 30 to 200 g/m3. Generally, hot aerosol fire extinguishing technology has developed from a generation I oil tank suppression system to a generation III strontium salt based S-type system. S-type hot aerosol fire extinguishing technology greatly solves the corrosion problem of electrical devices and electronics compared to potassium salt based generation I & II hot aerosol fire extinguishing technology. As substitutes for Halon agents, the ODP and GWP values of hot fire extinguishing aerosols are nearly zero, but those fine aerosol particles can cause adverse health effects once inhaled by human. As for configurations of hot aerosol fire extinguishing devices, fixed or portable cylindrical canisters are the most common among generation II & III hot aerosol fire extinguishers across the world, while generation I hot aerosol fire suppression systems are integrated with the oil tank as a whole. Some countries like the U.S., Australia, Russia and China, etc. have already developed standards for manufacturing and quality control of hot aerosol fire extinguishing agents and norms for hot aerosol fire extinguishing system design under different fire protection scenarios. Coolants in hot aerosol fire suppression systems, which are responsible for reducing hot aerosol temperature to avoid secondary fire risk are reviewed for the first time. Cooling effects are generally achieved through vaporization and endothermic chemical decomposition of coolants. Finally, this review discussed areas applying generation I, II or III hot aerosol fire suppression technologies. The generation III hot aerosol fire extinguishing system is most applicable, especially in areas involving delicate electrical and electronic equipments. Nonetheless, developing a much cleaner, non-corrosive and highly efficient hot aerosol fire suppression system is still needed.

Resumo em Inglês:

Abstract In the present study a preliminary neural network modelling to improve our understanding of Recombinant Human Erythropoietin purification process in a plant was explored. A three layer feed-forward back propagation neural network was constructed for predicting the efficiency of the purification section comprising four chromatographic steps as a function of eleven operational variables. The neural network model performed very well in the training and validation phases. Using the connection weight method the predictor variables were ranked based on their estimated explanatory importance in the neural network and five input variables were found to be predominant over the others. These results provided useful information showing that the first chromatographic step and the third chromatographic step are decisive to achieve high efficiencies in the purification section, thus enriching the control strategy of the plant.

Resumo em Inglês:

Abstract This study evaluated the technical and economic feasibility of membrane bioreactors (MBR) followed by nanofiltration (NF) for dairy wastewater treatment in order to reuse the treated effluent. It was observed that the MBR efficiently removed the organic matter and color of the feed effluent; however, due to the high concentration of dissolved solids in the permeate, it was necessary to use nanofiltration as a polishing step. The final treated effluent could be reused in the industry for cooling, steam generation and cleaning of external areas. A preliminary economic analysis showed the feasibility of the proposed system. The internal rate of return was greater than or equal to 32% when membrane lifespan was at least 2 years and the depreciation time was 15 years. The total cost of the proposed treatment system ranged from R$ 9.99/m3 to R$ 6.82/m3, depending on membrane lifespan.

Resumo em Inglês:

Abstract The production of lactic acid from glycerol by means of the alkaline hydrothermal process was evaluated using high concentrations of glycerol. The operating conditions that influence the hydrothermal process were studied. Temperature (250 - 280 ºC), catalyst to glycerol molar ratio (0.05 to 0.15), and water to glycerol volumetric ratio (0.8 to 1.5) were evaluated, as well as the use of NaOH and KOH as catalysts. A concentration of lactic acid of 122 g/L was obtained at 260 ºC, 0.04 NaOH to glycerol molar ratio, 1.0 water to glycerol volumetric ratio and 3 h of reaction using crude glycerol as raw material. The results showed higher lactic acid concentration and productivity than the fermentative process and the hydrothermal process carried out using low initial glycerol concentration.

Resumo em Inglês:

Abstract Our study investigates the influence of sintering temperature on the microstructure (grain size distribution, grain boundary length), electrical conductivity, and oxygen permeation properties of permeation membranes. For this purpose, SrSc0.1Co0.9O3-δ samples with different microstructures were prepared by varying the sintering temperature from 1100 to 1250 ˚C. The average grain sizes were gradually increased, thus the grain boundary lengths decreased with increased sintering temperatures. The influence of the ceramic microstructure on total electrical conductivity was found to be negligible. The oxygen transport properties of the samples were characterized by permeation measurements as a function of temperature in an air/helium oxygen partial pressure gradient. The decrease of the sintering temperature, meaning a decrease of grain size and thus the increase of grain boundary length, leads to an enhanced oxygen permeation flux and a reduced activation energy. This implies that oxygen exchange and transport in the SrSc0.1Co0.9O3-δ membranes occur more rapidly along grain boundaries than in the grain bulk.

Resumo em Inglês:

Abstract In this work, we present a highly-accurate technique of model order reduction applied to staged processes. The proposed method reduces the dimension of the original system based on null values of moment-weighted sums of heat and mass balance residuals on real stages. To compute these sums of weighted residuals, a discrete form of Gauss-Lobatto quadrature was developed, allowing a high degree of accuracy in these calculations. The locations where the residuals are cancelled vary with time and operating conditions, characterizing a desirable adaptive nature of this technique. Balances related to upstream and downstream devices (such as condenser, reboiler, and feed tray of a distillation column) are considered as boundary conditions of the corresponding difference-differential equations system. The chosen number of moments is the dimension of the reduced model being much lower than the dimension of the complete model and does not depend on the size of the original model. Scaling of the discrete independent variable related with the stages was crucial for the computational implementation of the proposed method, avoiding accumulation of round-off errors present even in low-degree polynomial approximations in the original discrete variable. Dynamical simulations of distillation columns were carried out to check the performance of the proposed model order reduction technique. The obtained results show the superiority of the proposed procedure in comparison with the orthogonal collocation method.

Resumo em Inglês:

Abstract Dissolved gas analysis (DGA) has been applied for decades as the main predictive maintenance technique for diagnosing incipient faults in power transformers since the decomposition of the mineral insulating oil (MIO) produces gases that remain dissolved in the liquid phase. Nevertheless, the most known diagnostic methods are based on findings of simplified thermodynamic and compositional models for the thermal decomposition of MIO, in addition to empirical data. The simulation results obtained from these models do not satisfactorily reproduce the empirical data. This paper proposes a flexible thermodynamic model enhanced with a kinetic approach and selects, among four compositional models, the one offering the best performance for the simulation of thermal decomposition of MIO. The simulation results obtained from the proposed model showed better adequacy to reported data than the results obtained from the classical models. The proposed models may be applied in the development of a phenomenologically-based diagnostic method.

Resumo em Inglês:

Abstract Attention has been given to reduce the cost of surfactant by using castor oil as an alternative natural source of feedstock. A new surfactant, sodium methyl ester sulfonate (SMES) was synthesised using ricinoleic acid methyl ester, which is obtained from castor oil, for enhanced oil recovery in petroleum industries. The performance of SMES was studied by measuring the surface tension with and without sodium chloride and its thermal stability at reservoir temperature. SMES exhibited good surface activity, reducing the surface tension of surfactant solution up to 38.4 mN/m and 27.6 mN/m without and with NaCl, respectively. During the thermal analysis of SMES, a 31.2% mass loss was observed from 70 ˚C to 500 ˚C. The phase behavior of the cosurfactant/SMES-oil-water system plays a key role in interpreting the performance of enhanced oil recovery by microemulsion techniques. Flooding experiments were performed using a 0.5 pore volume of synthesized SMES solutions at three different concentrations. In each case chase water was used to maintain the pressure gradient. The additional recoveries in surfactant flooding were found to be 24.53%, 26.04% and 27.31% for 0.5, 0.6 and 0.7 mass% of surfactant solutions, respectively.