-One of the main uses of catalysts in the oil industry is in the fluidized catalytic cracking process, which generates large quantities of waste material after use and regeneration cycles and that can be treated by the electrokinetic remediation technique, in which the contaminant metals are transported by migration. In this study, deactivated FCC catalyst was characterized before and after the electrokinetic remediation process to evaluate the amount of metal removed, and assess structural modifications, in order to indicate a possible use as an adsorbent material. The analyses included pH measurement and the concentration profile of vanadium ions along the reactor, X-ray microtomography, X-ray fluorescence, BET analysis and DTA analysis. The results indicated that 40% of the surface area of the material was recovered in relation to the disabled material, showing an increase in the available area for the adsorption. The remediation process removed nearly 31% of the vanadium and 72% of the P 2 O 5 adhering to the surface of the catalyst, without causing structural or thermal stability changes.
The procedure for obtaining the particle size distribution by visual inspection of a sample involves stereological errors, given the cut of the sample. A cut particle, supposedly spherical, with radius R, will be counted as a circular particle with radius r, r≤R. The difference between r and R depends on how far from the center of the sphere the cut was performed. This introduces errors when the extrapolation of the properties from two to three dimensions during the analysis of a sample. The usual method is to correct the distribution by probabilistic functions, which have large errors. This paper presents a method to reduce the error inherent to this problem. The method is to compute a simulation of the preparation process in a sample whose structure can be described by non-penetrating spheres of various diameters which meet a known probability distribution function, for example, a log-logistic function, or even a constant function. For each distribution radius, a number of spheres is generated and virtually cut, generating a bi-dimensional (2D) distribution. The 2D curves of the spheres distribution obtained in this simulation are compared with that obtained by the experimental procedure and then the parameters of the threedimensional distribution function are adjusted until the 2D curves are similar to the experimental one using the optimization method Simulated Annealing for the curve-fitting. In future this method will be applied to the analysis of the oil reservoir rocks.
In this contribution the issue of the stochastic reconstruction of particulatemedia from 2D photomicrographic images is addressed with particular reference to pore space connectivity. The reconstruction of porous bodies in 2D or 3D space was achieved by using simulated annealing techniques. Two methods were proposed to reconstruct a well connected pore space. The first, named PSA (Pixel-based Simulated Annealing), a pixel-movement based, three constraints were found to be necessary for the successful reconstruction of well connected pore space: the two-pointcorrelation function, the d3-4 distance transform distribution and the linealpath function for the pore phase. The second, named OSA (Object-based Simulated Annealing), only constrains the two-point correlation function. Following several researches which tried to reconstruct porous media using pixel-movement based simulated techniques, we propose a new parameter to add a microstructure descriptor, but we also propose a new technique, based in moving the microstructure grains (spheres) instead of the pixels. Both methods were applied to reconstruct reservoir rocks microstructures, and the 2D and 3D results were compared with microstructures reconstructed by truncated Gaussian methods. The PSA resulted in microstructures characterized by poor pore space connectivity, and by artificial patterns, while the OSA reconstructed microstructures with good pore space connectivity. These results indicate that the OSA method can reconstruct better microstructures than the present methods.
Accurate determination of heat flux is an important task not only in the designing aspect, but also in the performance analysis of rocket engines. In this purpose, this work deals with the heat flux determination in a combustion chamber through the inverse method. In this approach, the transient heat flux is determined from the experimental temperature data measured at the outer sidewall of the rocket engine. In this work the physical phenomenon was modeled by the transient one-dimensional heat equation in cylindrical coordinates and the material properties of the chamber were considered constant. Furthermore, the model is solved using the inverse heat conduction problem with least squares modified by the addition of Tikhonov regularization term of zero-order. Moreover, the sensitivity coefficients were obtained by Duhamel’s theorem. Through the regularization parameter, it was able to generate acceptable results even when using data with considerable experimental errors.
Following a thorough time-resolved 2-D particle image velocimetry experimental investigation of the wake of a square wall-mounted finite cylinder, at Reynolds Re = 5.4 × 10 4 with aspect ratio H/d = 3, a 3-D DNS numerical investigation was performed under similar flow conditions and comparable Reynolds number (Re = 4.0 × 10 4). In this paper, the simulation results in four 2-D planes are compared to the experimental case using proper orthogonal decomposition (POD), spectral analysis and mean flow. Numerical and experimental POD modes were similar, with a few differences in mean flow values and main vortex emission frequency that can be explained by differences in boundary layer thickness. The investigated horizontal planes were z/H = 0.3, z/H = 0.5 and z/H = 1.0 planes, as well as the vertical x-z symmetry plane. While time-resolved experimental results were acquired independently for each investigated plane, numerical results were acquired concomitantly in all four planes, with full 3-D wake data available. The results in this paper confirm that the simulation is able to reproduce the main dynamic features of the flow, establishing the basis for deeper analysis of the full numerical data set in the future. Keywords Cylinder wakes • Finite cylinders • Computational fluid dynamics • Particle image velocimetry • Low speed flow List of symbols d Square cylinder side dt Time step z Cylinder height coordinate H Total cylinder height Re d Reynolds number based on the cylinder side St Strouhal number δ 99% Boundary layer thickness
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