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.

A better understanding of the microscale meteorology of deep, open pit mines is important for mineral exploitation in arctic and subarctic regions. During strong temperature inversions in the atmospheric boundary layer--which are common in arctic regions during the winter--the concentrations of gaseous pollutants in open pit mines can reach dangerous levels. In this research, a two dimensional computational fluid dynamics (CFD) model was used to study the atmosphere of an open pit mine. The natural airflow patterns in an open pit mine are strongly dependent on the geometry of the mine. Generally, mechanical turbulence created by the mine topography results in a recirculatory region at the bottom of the mine that is detached from the freestream. The presence of a temperature inversion further inhibits natural ventilation in open pit mines, and the air can quickly become contaminated if a source of pollution is present. Several different exhaust fan configurations were modeled to see if the pollution problem could be mitigated. The two dimensional model suggests that mitigation is possible, but the large quantity of ventilating air required would most likely beimpractical in an industrial setting.

Diagnostic models of wind field and pollutant dispersion face difficulty when applied to complex terrain. Open-pit mines are an example of this difficult environment. To elucidate such difficulties, two models are developed and compared with one another. The first model is based on the prognostic Computational Fluid Dynamics-Lagrangian Stochastic (CFD-LS) paradigm, while the second model is based on the diagnostic CALifornia PUFF (CALPUFF) software. Two mine depths (100 [m] and 500 [m]) and three thermal stability conditions (unstable, neutral, and stable) are investigated using the two models. The CFD results showed that the skimming flow is only predicted under the neutral case, while more complex flow patterns emerge otherwise. Under the unstable case, the shallow and deep mines induce enhanced mixing downstream of the mine, resulting in substantial vertical plume transport and dilution of the pollutants released from the mine. Under the stable case, the plume from the shallow mine is restricted to the surface layer downstream of the mine. However, under the stable case, the plume from the deep mine rises into the substantial portion of the boundary layer due to the formation of a standing wave over and inside the mine. The results suggest that the CFD model can predict transport phenomena over open-pit mines reliably, so that the meteorological fields may be incorporated in operational models to improve the accuracy of their predictions. On the other hand, the CALPUFF model generally deviates from CFD-LS predictions, and the disagreement between the two models is the greatest when modelling the deep mine, under neutral/stable conditions, or when its solutions are considered close to the mine edge. Among many reasons, the variances appear to be related to the internal algorithms of the CALPUFF model to predict the wind eld structure appropriately. The results should caution practitioners considering diagnostic models for application over complex terrain, with opportunities to investigate such discrepancies at greater detail in follow up research.

This report presents the significant dust dispersion models that are pertinent to the mining industry in an effort to highlight past and current dust modeling exercises.

In this study, a hypothetical surface mine model was considered for simulating temperature inversion conditions and evaluating the ability of various artificial temperature inversion mitigation techniques using computational fluid dynamics (CFD). Several researchers have published recommendations of various mitigation techniques including helicopters, fans, and heaters. From this study, we find that the helicopter technique was able to effectively disperse the temperature inversions locally among all other recommended mitigation techniques.