Abstract A three dimensional gas-solid reactive flow model based on the Eulerian-Eulerian approach was used to study the effects of different nozzle designs with internal parts inside the FCC riser. The simulations were solved using Computational Fluid Dynamics (CFD) with CFX version 14.0 as tool. The results showed that the nozzle designs have a significant influence on the gas-solid behavior, resulting in an important role in the hydrodynamics and thermal behavior of the riser. Furthermore, the simulations show it is possible to improve the catalyst-gas distribution with an appropriate nozzle design.

In this work the air flow in a furnace was computationally investigated. The furnace, for which experimental test data are available, is composed of a movable block burner connected to a cylindrical combustion chamber by a conical quarl. The apertures between the movable and the fixed blocks of the burner determine the ratio of the tangential to the radial air streams supplied to the furnace. Three different positions of the movable blocks were studied at this time. A three-dimensional investigation was performed by means of the finite volume method. The numerical grid was developed by the multiblock technique. The turbulence phenomenon was addressed by the RNG k-epsilon model. Profiles of the axial, tangential and radial velocities in the combustion chamber were outlined. The map of the predicted axial velocity in the combustion chamber was compared with a map of the experimental axial velocity. The internal space of the furnace was found to be partially filled with a reverse flow that extended around the longitudinal axis. A swirl number profile along the furnace length is presented and shows an unexpected increase in the swirl in the combustion chamber.

Human, bovine and swine teeth were analyzed by Proton Induced X-ray Emission (PIXE). The aim of this work was to determine the concentration of trace elements in enamel and dentine of different animal species. PIXE analysis was carried out at the Laboratório de Análise de Materiais por Feixes Iônicos da USP (LAMFI) using a 2.4 MeV proton beam to probe the samples. Healthy teeth from São Paulo region were analyzed. Thirteen elements were measured and quantified in the samples: P, S, Cl, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Sr and Ba. The measured ratio of Ca:P in dentine and enamel teeth is the same expected for hydroxyapatite: 2.13, for all three types. Trace element concentrations were found to be very similar between the three species, except for S, Cl, Fe, Cu and Sr. Ni and Cu concentrations were found to be close to 1 ppm, which is also close to the detection limits of the SP-PIXE system.

In this work a new mechanical device to improve the gas flow in cyclones by pressure drop reduction is presented and discussed. This behavior occurs due to the effects of introducing swirling breakdown phenomenon at the inlet of the vortex finder tube. The device consists of a tube with two gas inlets in an appositive spiral flux that produces a sudden reduction in the tangential velocity peak responsible for practically 80 % of the pressure drop in cyclones. In turn, peak reduction causes a decrease in pressure drop by a breakdown of the swirling, and because of this the solid particles tend to move faster toward the wall , increasing collection efficiency. As a result of this phenomenon the overall performance of cyclones is improved. Numerical simulations with 3-D, transient, asymmetric and anisotropic turbulence closure by differential Reynolds stress for Lapple and Stairmand standard geometries of 0.3 m in diameter, show a reduction in pressure drop of 20 % and a shift of the tangential velocity peak toward the wall. All numerical experiments were carried out with a commercial CFD code showing numerical stability and good convergence rates with high-order interpolation schemes, SIMPLEC pressure-velocity coupling and other numerical features.

Computational fluid-dynamics techniques were employed to study the aerodynamics of a movable block swirl burner, developed by the International Flame Research Foundation, IFRF, which is characterized by the ability to adjust continuously and dynamically the intensity of the swirl by means of the simultaneous rotation of eight movable blocks, inserted between eight fixed blocks. Five three-dimensional grids were constructed for the burner, corresponding to five positions of the movable blocks. Both the k-e and RNG k-e isotropic turbulence models were applied. Only the latter described the existence of a central reverse flow along the annular duct. The employment of first-order and second-order interpolation schemes provided distinct results. The later provided results closer to the experimental tests. The swirl number decayed in the annular duct. The predicted swirl numbers for this movable block swirl burner were lower than the corresponding IFRF's experimental data, as was also observed by other researchers. This gave rise to the suspicion of some possible measurement error in the IFRF's experiments. On the other hand, the lack of agreement between the experimental data and the predictions regarding swirling flows could be attributed to the possible inadequate performance of the k-e model, as a consequence of its isotropic approximation. Still another possible explanation could be a phenomenon called bifurcation, in which one given swirl number can be associated with two distinct conditions of steady state flow. In addition, this complex flows requires a scrupulous development of the grids for the boundary condition and the employment of adequate interpolation schemes.

This work presents a way to predict the biochemical oxygen demand (BOD) of the output stream of the biological wastewater treatment plant at RIPASA S/A Celulose e Papel, one of the major pulp and paper plants in Brazil. The best prediction performance is achieved when the data are preprocessed using principal components analysis (PCA) before they are fed to a backpropagated neural network. The influence of input variables is analyzed and satisfactory prediction results are obtained for an optimized situation.