José Renato Baptista de Lima

Modeling classification in small-diameter hydrocyclones under variable rheological conditions

Although several mathematical models describing hydrocyclone performance exist in the literature, only a few suitably describe classification of non-Newtonian slurries in small-diameter hydrocyclones (smaller than 75 mm of diameter). In order to develop a mathematical model accounting for the effects of slurry rheology on classification, experiments have been conducted with phosphate ore slurries of variable solids concentration and chemical environment, covering a wide range of rheological conditions, both Newtonian and non-Newtonian. Semi-empirical models for estimating the hydrocyclone capacity and corrected cut size and an empirical model of water split have been proposed and/or modified from the literature in order to describe classification under such extreme rheological conditions. Of particular interest is the application of a model developed by the authors and based on the residence time theory, that is used to predict the corrected cutpoint. Experimental results demonstrated that, under the conditions studied, hydrocyclone capacity and sharpness of separation were not affected by slurry rheology. It was also found that the plastic viscosity is the most significant parameter for modeling the corrected cut size in 50 and 25 mm diameter hydrocyclones.

An Innovative Approach to Mine Blast Fragmentation Management Using Complexity Analysis: Three Case Studies

This paper introduces an innovative solution for devising a robust blasting plan that will present consistently good fragmentation performance under highly uncertain environments. The analysis will be carried out using complexity analysis tools, a model-free approach to complex systems which is particularly well suited to the problem of finding non-deterministic dependencies between multiple variables. The study is backed-up by data from over 2,000 blast records from Brazilian mines and identifies what are the critical aspects of the system and how to manage the blasting plan to reduce their impact on its performance.

Dimensionamento de espessadores: validação experimental de três técnicas convencionais

This work reviews the fundamentals of three important techniques currently used to dimension thickeners: Flux of Solids, Talmadge-Fitch, and Roberts. They were applied to validate the calculation of diameter (D) and sedimentation area (A) of a real thickener, which clarifies brine in a plant located at Cubatao-SP. The calculation of thickener dimension (A and D) was based on the sedimentation behavior of salt particles in brine on a laboratory scale. The values of D and A (D=13,9-14,1m; A=151,7-156,1m²), which were calculated by the three techniques, were compared with the diameter of the real equipment (D=20,0m). On the other hand, corrected values of D and A (D=18,1-18,3m; A=257,0-263,0m²) were obtained by using a scale factor (f=1,3). These results are 10% lower than the real equipment.

Effect of colloidal agents in iron ore pelletizing

ABSTRACT Organic binders have been used to replace bentonite in the pelletizing process of iron ore. In this research, colloidal agents were evaluated in a pelletizing process comparing their influence with the behavior of Peridur® and bentonite. Bench tests were carried out to identify the effects of binders and dispersant on the dispersion degree of mixtures, and their influence on the liberation/flocculation of fine particles. The results show that the dispersant acts on the fine particle content of the iron ore by removing ultrafine particles that are adhered to the surface of coarse particles, making the ultrafine available to the medium.

Experimento para quantificar a eficiência de aspersão de líquidos: aplicação em distribuidores espinha de peixe

This paper describes a device developed on the pilot scale and a simple approach to compare liquid distributor efficiencies. The technique consists basically of analyzing the mass of the liquid collected in 21 vertical pipes measuring 52 mm in internal diameter and 800 mm in length placed in a quadratic arrangement and positioned below the distributor. A 50 mm thick acrylic blanket that does not disperse liquids was placed between the distributor and the pipe bank to avoid splashes. Assays were carried out with ladder-type distributors equipped with 4 parallel pipes each for a column measuring 400 mm in diameter as an example of the application. The number (n) of orifices (95, 127, and 159 orifices/m2), orifice diameter (d) (2, 3, and 4 mm) and the flowrate (q) (1.2; 1.4; and 1.6 m3/h) were varied. The best spread efficiency, which presented the lowest standard deviation, was achieved with 159 orifices, 2 mm and 1.4 m3/h. The pressure (p) at the distributors inlet for this condition was only 51000 Pa (0.51 kgf/cm2), while the average velocity (v) was 6.3 m/s in each orifice. These results show some limitations of the practical rules used in distributor designs.

Influência do estado de agregação da polpa na flotação de quartzo, apatita e calcita

Many academic studies were carried out in the United States during the 1930s and 1940s, motivated by the correlation between the pulp aggregation state and the recovery at the flotation process, observed in industrial circuits. The aim of this work is to contribute to a better understanding of the phenomenon within the Brazilian reality. Microflotation and dispersion tests were carried out with quartz, apatite and calcite particles. The results strengthen the assertion by Taggart and co-workers that the aggregation occurs in the pulp as an effect of the reagents action and not as the primary cause of good flotability.