RESUMO A disposição inadequada de areia de processos de moldagem após vazamento do metal fundido aumenta os custos de logística e impacto ambiental por causa da presença da resina fenólica na sua composição. O processo de regeneração de resíduos areia fenólica de fundição (RAFF) objetiva a reciclagem deste material. Como os métodos de regeneração mecânica não são eficientes para garantir 100% de limpeza dos grãos de areia e sua utilização novamente no processo de moldagem, este trabalho investigou a eficiência de um método de regeneração térmica deste tipo de resíduo que pode operar de forma complementar. Um reator de leito fluidizado em escala de laboratório foi projetado e construído para regenerar RAFF que foi tratada anteriormente por um método mecânico. A metodologia utilizada para projetar e construir o protótipo de leito fluidizado é descrita, assim como a caracterização do resíduo, da areia limpa padrão e da areia regenerada. Os resultados da regeneração térmica no leito fluidizado foram muito satisfatórios no que concerne a eficiência de regeneração. Para as nove condições de processos testadas, os valores de perda ao fogo foram reduzidos quando comparados a areia limpa padrão. Este estudo apresenta as vantagens de uma combinação de dois processos, regeneração mecânica e térmica, que permite reduzir o tempo e eventualmente a temperatura de remoção da resina, devido à remoção parcial da camada de resina ou seu enfraquecimento durante o processo de regeneração mecânica. Das nove condições de processo testadas, seis tiveram perda em valores de ignição abaixo da CSS. Desta forma, a regeneração térmica nos resultados do leito fluidizado foi bastante satisfatória em relação à eficiência de regeneração.

ABSTRACT Improper disposal of sand used in molding processes after casting increases logistical costs and environmental impact because of the presence of the phenolic resin in its composition. The regeneration process of waste foundry phenolic sand (WFPS) aims to recycle this material. As mechanical regeneration methods are not efficient to guarantee 100% cleaning of the sand grains and their use again in the molding process, this work investigated the efficiency of a method of thermal regeneration of this type of residue that can be employed as a complementary procedure. A laboratory-scale fluidized bed reactor was designed and built to regenerate WFPS that was previously treated by a mechanical method. The methodology used to design and construct the fluidized bed prototype is described, as well as the characterization of the residual, the standard clean sand and the regenerated sand. The results of the thermal regeneration in the fluidized bed were very satisfactory with respect to the regeneration efficiency. For the nine process conditions tested, loss on ignition values were reduced when compared to standard clean sand. This study presents the advantages of a combination of two processes, mechanical and thermal regeneration, which allows to reduce the time and eventual temperature of resin removal due to the partial removal of the resin layer or its weakening during the mechanical regeneration process. Of the nine process conditions tested, six had loss on ignition values below the CSS. Thus, the thermal regeneration in the fluidized bed results was quite satisfactory in relation to the regeneration efficiency.

This paper aims to present Galerkin Least-Squares approximations for flows of Bingham plastic fluids. These fluids are modeled using the Generalized Newtonian Liquid (GNL) constitutive equation. Their viscoplastic behavior is predicted by the viscosity function, which employs the Papanastasiou's regularization in order to predict a highly viscous behavior when the applied stress lies under the material's yield stress. The mechanical modeling for this type of flow is based on the conservation equations of mass and momentum, coupled to the GNL constitutive equation for the extra-stress tensor. The finite element methodology concerned herein, the well-known Galerkin Least-Squares (GLS) method, overcomes the two greatest Galerkin shortcomings for mixed problems. There is no need to satisfy Babuška-Brezzi condition for velocity and pressure subspaces, and spurious numerical oscillations, due to the asymmetric nature of advective operator, are eliminated. Some numerical simulations are presented: first, the lid-driven cavity flow of shear-thinning and shear-thickening fluids, for the purpose of code validation; second, the flow of shear-thinning fluids with no yield stress limit, and finally, Bingham plastic creeping flows through 2:1 planar and axisymmetric expansions, for Bingham numbers between 0.2 and 133. The numerical results illustrate the arising of two distinct unyielded regions: one near the expansion corner and another along the flow centerline. For those regions, velocity and pressure fields are investigated for the various Bingham numbers tested.