CYANIDE RECOVERY AND DETOXIFICATION STUDY ON SEABRIDGE GOLD'S KSM PROJECT

摘要

This paper presents results from the proposed cyanide detoxification circuit for Seabridge Gold's KSM project. The proposed flowsheet uses a two-stage CCD (counter-current washing/decantation) circuit to transfer the flotation products CIL(carbon-in-leach) barren solution to a SART process (Sulphidization, Acidification, Recycling of precipitate, and Thickening of precipitate) to recover copper and free cyanide from the copper cyanide complex. The SART barren solution is then treated by an AVR process (Acidification, Volatilization of HCN gas, and Reneutralization) to concentrate the cyanide that was liberated in SART for recycling to leach. The washed CIL barren pulp (the CCD underflow) is treated with the SO_2/Air process to oxidize residual cyanide.The goal of this complex flowsheet is to recover and recycle as much cyanide as possible and produce a final effluent containing less than 0.5 mg/L copper and CN_(WAD) at the lowest cost. The SO_2/air process is capable of achieving low residual CN_(WAD) (<1 mg/L) in the final product, but the persistence of aqueous copper above the target level has been detected in the treated solution in some instances. The expected high concentrations of copper and cyanide in the KSM CIL barren ( >200 mg/L each species) and the difficulties this might create for the SO_2/air process was a key factor in the decision to consider including the washing, SART and AVR steps in the project flowsheet.The target concentrations of CN_(WAD) and Cu were readily achieved after aging the SO_2/air treated pulp, as would occur in a tailing or polishing pond. This suggests no additional treatment will be required to sustain low levels of these species in the final plant effluent.