O.C. Nocera

Universidad Nacional de San Luis, San Luis, San Luis, Argentina

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Publications (3)4.06 Total impact

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    ABSTRACT: We present here experimental results on the flow and stability conditions for a granular system as a function of the moisture percentage present inside the sample. The granular material used in all the experiments was a pozzolanic ash frequently used in cement production. Water was added to the sample in order to obtain different moisture percentages measured in water weight over dry sample weight. We studied values up to 6%. Firstly, different stability angles were measured as a function of the moisture of the material. Secondly, we related these angles to some parameters of the flow of the material through a silo with different geometries and obtain a basic phase diagram for the flow. This phase diagram is of great help to set appropriate funnel and hopper conditions in silo devices often used in cement industries. Finally, some of our results are compared with basic theories and with our own simulation models in order to understand the behavior of wet granular systems. KeywordsStability angles–Flow–Granular piles–Cement production
    No preview · Article · Oct 2011 · Materials and Structures
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    ABSTRACT: Raw granular materials used in cement manufacturing are limestone grains displaying a broad size distribution, ranging from microns to a couple of inches. They are stored as pyramidal heaps and, although empirical homogenization techniques are used with good results, there are important factors like segregation and grinding conditions that produce mixtures with different poorly controlled size. For this reason, the stability of the heaps strongly depends on these factors and it is important to study the influence of the respective amounts of particles of different sizes on the properties of the mixture. In this work, we report experiments analyzing the relationship between the characteristic angles of equilibrium of the heaps and the geometry, size and chemical composition of the grains. We also look for correlations between the values of the characteristic angles and the relative amounts of grains of different sizes that make up the materials.We demonstrate that the chemical composition is correlated with the geometry of the grains and that their aspect ratio does not influence the critical angles. We also show that the critical angles mostly depend on the relative amount of fine grains in the granular mixture and on the dispersion of the sizes. The results obtained allow one to draw conclusions that may be relevant to the treatment and storage of raw materials in the cement industry.
    No preview · Article · Apr 2006 · Powder Technology
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    ABSTRACT: One of the stages in cement production is grinding and storage of rocks from the quarry. Basically, this material consists in limestone grains of different diameters. Different mining sources cause that chemical composition of limestone grains varies substantially. An adequate mixing of different species is crucial for a good final quality. In this work, we present experiments in order to analyze the relationship among the characteristic angles of equilibrium for the piles and the geometry, size and chemical composition of their granular components. Grains from four different sources were gathered and their chemical compositions were obtained from fluorescence spectroscopy. Critical angles as well geometrical parameters were measured for each sample. Our results show that critical angles are mainly affected by the ratio of fine grains present in the granular mixture and by the dispersion in the size of the grains. We also found that chemical composition is correlated with geometry of grains and aspect ratios do not influence critical angles.
    No preview · Article · Jan 2005