Dust barriers in open pit blasts. Multiphase Computational Fluid Dynamics (CFD) simulations

Abstract

In the framework of the Research Project CTM2005-00187/TECNO, "Prediction models and prevention systems in the particle atmospheric contamination in an industrial environment" of the Spanish National R+D Plan of the Ministry of Education and Science, 2004-2007 period, there has been developed a CFD model to simulate the dispersion of the dust generated in blasts located in limestone quarries. The possible environmental impacts created by an open pit blast are ground vibrations, air shock waves, flying rocks and dust dispersion, being this last effect the less studied one. This is a complex phenomenon that was studied in previous successful researches through the use of several digital video recordings of blasts and the dust concentration field data measured by light scattering instruments, as well as the subsequent simulation of the dust clouds dispersion using Multiphase Computational Fluid Dynamics (CFD). CFD calculations where done using state of the art commercial software, Ansys CFX 10.0, through transitory models simultaneously using 7 different dust sizes with Lagrangian particle models crossing an Eulerian air continuous phase. This paper presents results and observations obtained through repeated simulations that virtually install physical barriers in the vicinity of the blast with the aim of diminishing the dust cloud dispersion ant the associated environmental impact. There have been tested several combinations of low and high barriers installed 100 or 200 m apart from the blasting area. Assuming full trapping of the dust in the solid barrier there are scenarios where dust retention in the model could be as high as 90%, which shows the potential use of barriers to avoid dust dispersion. Models also show the barriers shadow effect in the dust deposition area, useful for the definition of protection areas where sensible equipment or installation could be located.