Scaling up of the reaction rates for the waste rock at Antamina Mine, Peru

Multiple scales of experimentation help to better understand the processes taking place in waste rock and can be used to predict effluent water quantity and quality. The objective of this research is to evaluate if a reactive-transport model that is developed for a small-scale experiment can be up-scaled to model a larger scale experiment of similar material. Waste rock at Antamina has been studied at multiple scales, including humidity-cells, field-barrels, experimental-piles and finally full scale. Generally, full-scale modelling is highly complex, involving processes that are difficult to model, such as heat flow and gas transfer. This thesis will focus on the field-barrel and experimental-pile scale to determine if and how reaction rates from the smaller-scale experiments can be used to predict the drainage from larger-scale experiments. To develop the reactive-transport models, a large dataset from five field-barrel experiments and one experimental pile, each containing skarn waste rock, was compiled and analysed. The field-barrels are approximately 1 meter tall, with the top layer of waste rock open to atmospheric conditions, and are representative of the tipping phases used to create the experimental pile. The experimental pile is approximately 10 meters tall and is exposed to nearly identical atmospheric conditions. Both sets of experiments ran for approximately 10 years. Reactive-transport modelling of the field-barrels involved calibrating the reaction rates to best fit the observed data. These rates were then used in the modelling of the experimental piles. The model fit was analyzed using methods including least squares, mean square error and root mean square error. Overall, the results show that the small-scale rates do not account for all of the processes taking place at the larger scale, resulting in 50% error between the modelled results and the observations.