Materials Science Forum Vols. 727-728

Abstract: The developing of nanosystems has been intensely studied because of their efficiency when applied to pharmaceutical excipients, frequently called as drugs delivery systems. Sol-gel obtained pseudoboehmite, a fine synthetic ceramic precursor of alumina, shows itself as very promising due to its adsorption/desorption properties with pharmaceutical molecules. The use of factorial planning of two levels is very effective in preliminary studies about the possible influence of specific factors in the reagent conversion to a product. A method of pseudoboehmite obtainment was adopted, that has been already reported. The factorial planning 2³ used for the pseudoboehmite synthesis involved three variables of synthesis: temperature (A), the aluminum nitrate (Al (NO3)3·9H2O) concentration (B) and the ageing time (C). The X-ray diffraction data shows that the aging time has influence in the crystalinity of the synthesis product.

Abstract: The development of nanocomposites polymer matrix with clay from Brazil has been naturally abundant and low cost alternative. In this study, we obtained nanocomposites polyamide66 (PA66) with 1% and 5% of bentonite clay from Brazil, to be used as microporous organic/inorganic hybrid membranes. The clay was treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared using the technique of immersion-precipitation of solution from the nanocomposites. Treated clay and untreated clay were characterized by X-ray diffraction (XRD) and Thermogravimetry (TG). The membranes were characterized by TG and XRD. The result of XRD showed the presence of quaternary ammonium salt in the structure of clay, after organophilization. For TG, we observed that the treated clay showed higher thermal stability when compared to untreated clay. For TG, we observed that in general the membranes of PA66 with treated clay, present decomposition temperature higher when compared with untreated clay, thus revealing a greater thermal stability of membranes PA66 with treated clay. Through the X-rays patterns, it was found that membranes with 1% of nanoclay present exfoliated structure and can therefore be applied as microporous membranes.

Abstract: Membranes can be defined as polymer film that acts as a semipermeable barrier to filtration in a molecular scale, separating two phases. In this work, microporous membranes were obtained from hybrid organic/inorganic polyamide66 (PA66) and clay mineral from Paraíba State, treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared by immersion-precipitation technique from the nanocomposites obtained by solution, with a pre-determined reaction time of 2 h, with characteristics suitable to be used in microfiltration process for separation of the oil present in water. Samples of natural and organophilic clay were characterized by X-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR). Meanwhile, the membranes were characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results of FRX and FTIR confirmed the presence of quaternary ammonium salt in the clay structure after treatment with organic salt. Through DSC analysis it was observed almost no change in the melting temperature of the pure polyamide66 membranes. By SEM, it was revealed an asymmetric morphology consisting of a skin layer and a porous sublayer, showing the pore size distribution appropriated to water-oil separation.

Abstract: Mathematical models for thickeners can be used for equipment design, to simulate the process operation, and to develop control strategies for a continuous operation. In this work, numerical simulation to obtain the final height of the sediment when operating at steady state conditions were performed using two mathematical models: the model introduced by Tiller and Chen (1988) and the one proposed by Arouca (2007). The simulated results were compared to experimental data obtained when the thickener was operated with and without the use of flocculent agent. The equipment used to obtain experimental data was a conventional thickener, built in acrylic. Aluminum sulfate was used in the experiments for the production of flocculated suspensions. The results showed that the Tiller and Chen (1988) model produced a deviation of 39.0% for kaolin suspensions and 14.3% when aluminum sulfate was added to the system. The Arouca (2007) model resulted in values much closer to those obtained experimentally, with deviations of less than 3% for kaolin suspensions regardless of the use of flocculent agent.

Abstract: Several applications in chemical industry use randomly packed bed of particles, such as particulate separation systems, chemical reactors or fixed bed drying. Fluid dynamic behavior, heat and mass transfer, in addition to structural properties of the bed are fundamental issues to design of these processes. Several studies about heat transfer in packed beds aiming drying application have been performed in order to contribute with the process. Seeds drying temperature is especially important for the seeds quality indices and must be carefully controlled in drying process. In this paper temperature profiles experimentally obtained in a packed bed composed by soybean seeds are presented and discussed. Axial profiles of temperature were applied for obtaining effective thermal conductivity following previous studies from literature. The results indicate that thermal homogeneity can be achieved inside the bed for controlled air flow conditions. Axial effective thermal conductivity presented results in agreement with previous studies from literature.

Abstract: The numerical simulation in fluid mechanics has large application in chemical engineering. The objective of the present work is the analyze of a computational model for the fluid dynamics behaviour of a bubble column of the geometry cylindrical non regular with multiphase mixture. Experimental data and CFD results of the hydrodynamics of gaseous and liquid phases have been compared. Five different diameters of bubbles have been used in the CFD simulations. The comparisons between CFD simulations and experimental data show that the Eulerian-Eulerian approach provides a computational model that represents the process satisfactorily.

Abstract: This paper presents a kinetic study of pyrolysis of sugarcane bagasse from dynamic thermogravimetric experiments (TG). The methods of Kissinger, Ozawa, Starink, Kissinger-Akahira-Sunose and Friedman were used to estimate the activation energy. These methods consider the temperature shifts with increase of heating rate for a given conversion in dynamic TG tests. The activation energy values obtained by the isoconversional methods were in a range 182.8 192.4 kJ·mol^-1, values very close to the other biomasses presented by literature.

Abstract: The permeability is a physical property related to porous structures. It is a physical quantity that quantifies the resistance that a permeable matrix has to the flow of a particular fluid. Knowledge of the permeability of a filter media is important for the design, optimization and operation of various equipment, such as fabric filters, sedimentary, filtering hydrocyclones and others. There is the routine that the experimental determination of permeability of a filter medium is not made during the operation of industrial equipment, because they require a specific instrumentation or because it not presents a flat filtration. Therefore the experimental determination of permeability occurs out the industrial, in testing of laboratory by flat filtration. The two different times (industrial and laboratory) increase operation costs for the user by requiring uninstalling or fragmentation of the equipment to take it the laboratory. This work aimed to present a methodology (experiments combined with CFD techniques) in which it is possible to determine the permeability of a filter media (non-flat geometry) in their own manufacturing plant. According to the main results achieved, the proposed methodology was satisfactory, eliminating the need for characterization of filter media in the laboratory.

Abstract: Average particle velocity measurements were carried out in a conical-cylindrical spouted bed made of acrylic. In this study an intrusive fiber optical technique which is based on a cross-correlation function between signals from its two channels was used. For a non-intrusive measurement in order to compare with the intrusive technique, images of particle movement were recorded using a high-speed video camera. The experiments were conducted in differents air velocity conditions above the minimum spouting velocity. The latter method was limited in velocity measurement only near the spouted beds wall inasmuch as the spouted bed used was a three dimensions one. On the other hand, the fiber optical is a promising technique for measuring particle velocity distributions in a three dimensions spouted bed. To predict the minimum spouting velocity in order to use this result in the measurement techniques investigation, simulations were carried out using the Eulerian-Eulerian multiphase model.

Abstract: The use of hydrocyclones for particles separation is widespread due to advantages such as low cost, simple structure, large capacity and low volume. The shape and size of a hydrocyclone has a decisive effect on the internal flow structure of the continuous phase, and therefore, the separation or classification of the dispersed phase [1]. Therefore, in order to improve the equipments performance, several geometrical changes have been studied in the literature for hydrocyclones of different families [2-13].