The economic viability of processing tailings to reduce environmental liability

Many mining operations produce tailings that contain sulphides. Sulphidic tailings are disposed into a tailings facility and measures are taken to control the release of deleterious seepage resulting from the oxidation of sulphide materials. Often this control needs to be maintained in the long term, which presents a long term environmental risk. This thesis examines the viability of processing tailings to reduce the long term environmental risk of tailings impoundments. A spreadsheet model was developed to calculate project life costs of two tailings disposal methods - conventional disposal and disposal of autoclaved tailings. A generic mine site in British Columbia and assumed operating parameters were used as a basis for the model. Unit operation designs for the two flowsheets were based on recently designed or constructed equipment or on accepted design methodology. Capital costs and unit operating costs were obtained from recently completed pre-feasibility studies. Monte Carlo simulations were run while varying selected parameters to derive project costs for a range of situations. The simulation results indicate that for smaller operations where the processing rate is less than 5000 tonnes per day, the mine life is less than 12 years and the sulphur content is less than 12% it may be economically viable to autoclave tailings in order to produce material that would be more geochemically stable in the long term. The combination of parameter values at which autoclaving tailings is economically viable follows a curve as sulphur content decreases in conjunction with processing rate and mine life increases. The economics of autoclaving tailings is sensitive to the amount of solids reporting to the autoclave.Applied Science, Faculty ofMining Engineering, Keevil Institute ofGraduat