Hélio Carlos Miranda de Oliveira

Analysis of the Compressibility of Sediments in Batch Settling Tests Using Newtonian and Non-Newtonian Fluids

The study of compressibility in deformable porous media is of interest in many industrial processes, such as, filtration, thickening and during oil well drilling processes in the petrochemical sector. In this work the compressibility of porous media was evaluated by the comparison of solid concentration profiles in sediments using fluids with Newtonian and non-Newtonian behavior. For this, consolidation tests in distillated water, solutions of xanthan and glycerol were performed in a vertical column from the gravitational settling of suspensions. The porosity distribution in the formed sediment was obtained after the complete settling of particulate material. The local porosity measurements were performed using the ionizing radiation emitted by americium-241. The gamma-ray attenuation technique used in this study allowed the realization of nondestructive measurements for achieving local concentration of solids. The results showed that the rheological behavior of the fluid does not change significantly the compressibility of the porous matrix.

Obtaining Constitutive Equations for Thickening and Filtration Non-Newtonian Fluids

The study of filtration and thickening of particulate systems are used in many industrial processes involving processes of solid-liquid separation, such as in sedimentation ponds, filters, the drilling of oil wells, among others. This paper aims to advance the empirical mechanisms involved in the processes of solid-liquid separation and obtain constitutive equations relating the pressure in solids and porous media permeability from non-Newtonian fluids. In the experiments used aqueous solutions of xanthan gum concentration of 0.1% in weight basis in order to ensure non-newtonian means. For the preparation of suspensions, was used calcium carbonate as particulate material in the separation process involved an initial concentration of 12% by volume. The concentrated sediment was maintained between 30 and 48% by volume. Settling tests were carried to term and sediments resulting from each test were evaluated by making use of the Gamma Rays Attenuation Technique (GRAT). The results show that GRAT is effective in determining sediment concentration distributions formed from non-Newtonian solutions, allowing the constitutive equations to obtain pressure and the solid porous medium permeability, very important for simulations of solid-liquid separation processes.