(86a) In-Situ Evaporation of Water within Mining Rock Piles - a Modeling and Laboratory Study

Acid rock drainage (ARD) is an environmental problem commonly faced by the mining industry. ARD occurs when sulfide-bearing rock, usually in the form of a large rock pile on the side of a mountain, is exposed to air and water and oxidizes to form sulfuric acid which can leach hazardous metal ions from various minerals. Laboratory tests are typically conducted using short columns packed with a crushed mining rock sample to determine a rock sample's potential to produce acid. The room temperature procedures that are typically involved in these tests are inherently non-isothermal because they involve a drying phase in which water evaporation occurs. We are investigating the processes that govern evaporation within a rock pile and the important parameters that describe these processes. A two-dimensional axially-symmetric model of the drying phase of the testing procedure has been developed by our research group. The model was developed using Darcy's law, heat transfer in porous media, and mass balance equations and was verified with an analytical solution under simplifying assumptions. The model was calibrated with experimental data from our laboratory for a certain rock type. Hypothetical studies of the effects of heterogeneities in the form of inclined layers were also conducted.