Three dimensional computational fluid dynamics models of fugitive dust dispersion in high-latitude open-pit mines

Abstract

The Arctic region contains vast mineral resources and mining of these resources is a major activity in several countries, including the United States. With the advancement of open-pit mining technology, the depth to which minerals can be profitably mined has increased, resulting in deeper pits than ever before. This increase in depth has several inherent challenges for mining operations. The ventilation of an open-pit mine is mostly dependent on natural airflow patterns. The dispersion behavior of the pollutants generated in a mine is also dependent on the atmospheric conditions. The control of fugitive dust in high-latitude open-pit mines is challenging due to unique atmospheric phenomena resulting in complicated flow regimes as well as atmospheric inversion due to the lack of adequate insolation during prolonged winter seasons. The development of a computational fluid dynamics (CFD) model of an open-pit mine is challenging due to the presence of several sharp and irregular features at the pit surface. A good quality mesh of the model domain is a prerequisite for convergence in solution. Besides good quality meshing, choices of various simulation setup parameters have significant impact in convergence or divergence of the simulation. Appropriate choices of simulation type, boundary and initial conditions, time stepping and various convergence criteria are important for realistic simulation of a model domain. Environmental conditions in the mine vary from season to season; hence, fugitive dust dispersion simulations using a commercial CFD software are conducted for various seasonal conditions along with several cloud conditions. Clear sky and cloudy sky conditions result in different radiative and turbulent energy fluxes. In each scenario, fugitive dust particles varying in size (PM₀.₁ to PM₁₀) and concentrations are generated at various locations of the selected mine. The simulation results predict a speedy removal of fugitive dust in summer. However, during winter, the presence of an inversion layer in the open-pit results in extensive retention of fugitive dust. For removal of the atmospheric inversion during winter, it is observed that the presence of cloud cover and convective wind are the most important factors.