Search

Mud-rush mechanisms during ore extraction have not been fully studied. In this study, a new experimental setup was created to analyse mud-rush events under controlled conditions. A block caving drawbell was scaled and filled with wet granular material to be extracted. The material drawn was then classified based on its consistency index. The results showed that the yield stress and the material consistency are good predictors of mud events in the experimental results. Finally, mud-rush events occurred mainly when material consistency was classified as plastic, soft, or fluid – with soft and fluid being the most significant. [ABSTRACT FROM AUTHOR]

Highlights • Present hydrodynamic behavior in five hydraulic reactors for ultra-flocculation. • Estimate agitation using a new mean shear rate based on hydraulic variables. • Shear rate production depends on the pressure drop, vorticy and confinement level of reactor designs. Abstract The efficient use of water has become an important issue in the mining industry, especially in countries where it is located in desert areas with low water reserves, as is the case in Chile. In addition, low ore grades necessitate efforts to recover the maximum amount of minerals in solid–liquid separation processes. Fine particle flocculation is a preliminary stage in various solid–liquid separation processes. The conventional flocculation process is done at low shear rates, ensuring that large flocs remain unbroken. However, it has been seen that the application of high shear rates at the beginning of the process for a short period of time significantly improves the solid removal efficiency, reducing the flocculant dosage and the duration and cost of the process, which is known as ultra-flocculation. This work presents a numerical CFD study of the hydrodynamic behavior in five hydraulic reactors for ultra-flocculation, analyzing the shear rate curve over treatment time, dissipation efficiency and average shear rates. A new mean shear rate, which uses hydraulic variables to estimate the average agitation, is also defined. It was shown that the hydraulic shear rate can be useful for developing better hydraulic designs because it provides a second view, which, added to the shear rate curve over treatment time and effective shear rate, allows a more complete judgment of the performance of the designs. [ABSTRACT FROM AUTHOR]

To date, 17 circumbinary planets have been discovered. In this paper, we focus our attention on the stability of the Kepler circumbinary planetary systems with only one planet, i.e. Kepler-16, Kepler-34, Kepler-35, Kepler-38, Kepler-64 and Kepler-413. In addition to their intrinsic interest, the study of such systems is an opportunity to test our understanding of planetary system formation and evolution around binaries. The investigation is done by means of numerical simulations. We perform numerical integrations of the full equations of motion of each system with the aim of checking the stability of the planetary orbit. The investigation of the stability of the above systems consists of three numerical experiments. In the first one, we perform a long-term (1 Gyr) numerical integration of the nominal solution of the six Kepler systems under investigation. In the second experiment, we look for the critical semimajor axis of the six planetary orbits, and finally, in the third experiment, we construct two-dimensional stability maps on the eccentricity-pericentre distance plane. Additionally, using numerical integrations of the nominal solutions we checked if these solutions were close to the exact resonance. [ABSTRACT FROM AUTHOR]

• The effect over roping of inlet pressure and particle size distribution is addressed. • Inlet particle size distribution has a direct impact on underflow hydrodynamics. • When operates with coarser material the hydrocyclone has a tendency to roping. Hydrocyclones are used for classification purposes in the mining and mineral processing industries. According to their geometry and under certain operating conditions, hydrocyclones may present roping, which is a defective operation. Studies have related the roping phenomena to many variables such as hydrocyclone geometry and operating conditions. Some authors established a connection between the solids concentration of the feed and the discharge as one of the factors that generate roping. Other authors presented factors such as the apex and the vortex finder diameters, inlet pressure and the relationship between roping generation and the air core. This research aims to study the effect of inlet pressure and particle size distribution in the feed on roping in hydrocyclones. We develop a model using computational fluid dynamics (CFD) in order to study a 75-mm hydrocyclone operating with a variable flowrate and fed with two different materials. Each material is characterized by five granular phases interacting with each other and the model is validated by comparison with experimental data. The turbulence is treated using the Reynolds Stress Model (RSM) and the Eulerian Multiphase Model is used for the interactions between phases. The granular phases are described by the kinetic theory of granular flows (KTGF). The characteristics studied were: (i) air core and material distribution inside the hydrocyclone, (ii) underflow shape and spray angle, (iii) flow and solid concentrations, (iv) efficiency curve and separation size and (v) particle size distribution in the underflow and the cut sizes. According to the results, the particle size distribution of material in the feed has a direct impact on underflow behavior; when operating with coarser material the device tends to rope as the spray angle decreases. The same happens with an increase in the feed pressure. The roping condition generated by the coarse material directly affects the efficiency of the hydrocyclone, triggering an increase in separation size. The underflow particle size distribution tends to be coarser with an increase in the inlet pressure. When the inlet pressure decreases, the overflow particle distribution tends to be finer. [ABSTRACT FROM AUTHOR]