CFD modeling of pollution transport in open pit mines under arctic air inversion (original) (raw)

14th United States/North American Mine Ventilation Symposium, 2012

Abstract

As open pit mines continue to grow deeper and productivity continues to increase, the management of air pollution can become challenging. The natural wind flow in open pit mines is generally recirculatory. This recirculation can trap harmful aerosols and gases in open pit mines. This problem is exacerbated as the depth of the pit increases. Maintaining a safe and healthy atmosphere in open pit mines can present a particular challenge at high latitudes due to atmospheric inversion. Air inversions are common during the winter months in arctic regions. Arctic winters are characterized by extremely short days. During winter months, a deficit of solar radiation incident upon the bottom of the pit can result in a negative surface energy balance. This results in heat flow from the air to the pit surfaces. Under these conditions, the convection currents that normally keep the atmosphere in the pit well mixed do not exist, resulting in stagnant and polluted air. Developing predictive models for air quality in open pit mines under conditions of arctic inversion is complex. The quality of air in the pit is determined by a coupled relationship among mesoscale meteorological processes, topography, the air inversion process, and the sources and extent of pollution. The influence of pit geometry on wind flow patterns within open pit mines under neutral atmospheric conditions and the effects of Earth's diurnal cycle significantly influence the stability and height of the boundary layer, and, thus, impact the retention of contaminants in an open pit mine. Two-dimensional models were created for several different pit geometries to analyze the transport of contaminants in the pit under arctic air inversion. This paper will present the effects of pit depth, wind speed, and inversion strength on the contaminant concentrations within the pit. The results of this study indicate that the concentration of air pollutants in open pit mines will increase with increasing pit depth and inversion strength. Natural ventilation alone is not sufficient to mitigate the inversion problem.

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