Ricardo C. Santana

Flotation Selectivity of Phosphate Ore: Effects of Particle Size and Reagent Concentration

The flotation selectivity of apatite particles from a carbonatite complex was investigated in a flotation column as a function of particle size and reagent concentrations. Experiments were performed according to a factorial experimental design. Fine and coarse particles showed different sensitivities to variations in the concentration of the reagent. Coarser particles showed a higher selectivity ratio and greater sensitivity to the addition of different reagent dosages, providing a more selective separation and a better quality product. Finer particles presented lower selectivity ratios, reflecting the difficulty involved in the concentration process with this particle size.

Influence of the Water Composition on the Selectivity of Apatite Flotation

The effect of ionic species on the flotation selectivity of apatite was evaluated. Water containing fluoride, calcium, magnesium, and phosphate was used in the flotation experiments carried out in a flotation column for coarse and fine phosphate ore. The selectivity of apatite over ferrous and siliceous gangue was investigated. Coarse and fine ores showed different sensitivities according to the ion concentration. The results clearly showed the harmful effect of the ionic species under study on apatite selectivity. The contaminants responsible for the lowest selectivity ratios for ferrous and silicate gangue were calcium and magnesium, regardless of particle size.

Looking for an Ideal Particle Size for Apatite Flotation

Today, the phosphate rock processed in the world represents around some 20 billion dollars per year. Some exploitable deposits are characterizing by low grade phosphate rocks, composed of the apatite group in association with a wide assortment of accessory minerals. Usually a combination of beneficiation techniques is used to process a phosphate rock since run of mine, and then a flotation is applied to recovery apatite. This work proposes an evaluation of particle size for apatite recovery by column flotation in bench-scale. The variables collector dosage and depressant dosage were investigated experimentally applying a factorial design. According to the experimental results, the particle size range between 37&m and 105&m is an optimum size used to obtain simultaneously a product with the industry demand grade (at least 33%) and phosphorus recovery, upper than 60%.

CFD Simulation of Spouted Bed Working with a Size Distribution of Sand Particles: Segregation Aspects

Spouted bed simulations are usually performed using only one granular phase with a mean particle diameter representing the entire particle mixture, instead of a particle size distribution. In this study, the effect of the particle size distribution is accounted through the simulation of a mixture with five granular phases. The results showed that the particle segregation occurs. Larger particles are more concentrated in the upper region, while the smaller particles are preferably positioned in the lower region of the bed. Computational simulation using CFD method reproduced well the segregation experiments with different participle sizes of sand.

SIMULAÇÃO DO ÂNGULO DE REPOUSO ESTÁTICO DE RESÍDUO DE ACEROLA EMPREGANDO O MÉTODO DE ELEMENTOS DISCRETOS

RESUMO O ângulo de repouso estatico e uma caracteristica propria do material particulado e e uma funcao da densidade da particula, area superficial e forma, alem do coeficiente de atrito do material. Neste trabalho, o ângulo de repouso estatico de sementes de acerola foram obtidos experimentalmente e por simulacao simulados empregando o Metodo de Elementos Discretos, atraves do software EDEM. As forcas de contato entre as particulas foram representadas pelo Modelo Hertz-Mindlin. A fim de verificar como os parâmetros do modelo de forca de contato influenciavam o valor do ângulo de repouso, a tecnica de planejamento composto central foi empregada para delinear as simulacoes. Os resultados mostraram que quais os parâmetros que mais influenciam o comportamento granular da acerola. Tambem foi possivel encontrar um conjunto de valores para os parâmetros que produziram um resultado simulado muito proximo ao valor experimental.

Study of the Use of an Anionic Collector in the Mineral Wastewater Treatment by Dissolved Air Flotation

The use of recycled water in the apatite flotation may result in losses to the process performance due to the presence of ions, residual reagents, finely particulate material, etc. The dissolved air flotation (DAF) has been shown an efficient technique in the wastewater treatment in the removal of these pollutants. The use of anionic collector in DAF process is based on the reaction that occurs between the soybean oil soap (apatite collector) with the calcium present in the apatite lattice making its surface hydrophobic. Therefore, the collector can be an auxiliary in the water softening besides improving the hydrophobicity of the particles to be collected. Thus, this study was aimed at evaluating the effect of an anionic collector used as an auxiliary in the dissolved air flotation process. A central composite design (CCD) was proposed to evaluate the concentration of collector and the effect of pH value on the removal efficiency of calcium, magnesium, fluoride, phosphorous and turbidity present in a wastewater from a fertilizer industry. The results showed a good removal of the contaminants which guaranteed a better quality of water to the process of phosphate rock concentration.

Granulometric Characterization of Flotation Products

This work aimed on the granulometric characterization of flotation products and to analyze the effect of the variables (that were investigated in a flotation work) on the particle size distribution parameters. Besides to compare the parameter values of the granulometric analysis for the concentrate and tailing both results were compared with the parameter values of the flotation feed samples. The analyzed parameters showed lower values for the concentrate products as compared with the parameters for tailing and feed samples. For coarse and fine particle size fractions the column height was the variable that more influenced on the parameter values.

Evaluation of the Influence of Process Variables on Flotation of Phosphate

Froth flotation is an adsorptive-bubble separation method based on the selective attachment of particles on the surfaces of gas bubbles passing through a suspension. Reagents as collectors, frothers and pH modifiers are added to perform specific roles to facilitate and to improve the separation. In the present work the process of apatite flotation in column has been investigated experimentally. The influence of the reagents (collector and frother dosages and interactions), percentage of solids and pH value on the column flotation of coarse particles of apatitic ore was analyzed. Percentage of solids was the variable that more influenced on the apatite recovery and the P2O5 grade was more affected by varying pH. The best results were achieved by using lower pH values and lower pulp density. Frother addition only had significant effect for lower collector dosage.