Discrete Phase Modeling of Atmospheric Particulate Transport From Mine Tailings

Arid regions such as Arizona are susceptible to dust storms. Metal and metalloids contained in the tailings dust can travel long distances and deposit in vegetated areas, soil and water.  An approximate geometry of a tailing in Dewey-Humboldt has been constructed and meshed using ANSYS mesh generator.  This tailing is massive in size and it is close in proximity to near-by residents which can be affected by coarse particles that can deposit in the lung airways. 

Particulate transport was investigated using the discrete phase model (DPM) available in the computational fluid dynamics (CFD) software ANSYS FLUENT.  The wind flow field was simulated using the k-epsilon turbulent model and appropriate equations and constants that solve a simple logarithmic and unidirectional wind profile that resembles the atmospheric boundary layer.  North-west winds at a reference height of 10 m ranged from 1 to 15 m/s.  Qualitative and quantitative information was obtained from the trajectories of particles with densities comparable to that of dust (about 1000-2500 kg/m³). Particles 3-100 mm in diameter were released from various locations of the tailing with the objective of investigating how particles dispersed and how they compare to ideal cases where topography is not included. 

Results suggest that the vertical drag exerted on the particle can have less or no effect on particles greater than 15 mm during the initial stage of injection, therefore gravitational force is dominant causing these particles to reach the same maximum heights.  As particle motion progresses, horizontal drag becomes more important for smaller particles causing them to settle first.  Variables such as angle of injection, velocity of injection, and height of injection were also investigated.