Surface Paste Disposal of High-Sulfide Tailings at Neves-Corvo - Evaluation of Environmental Stability and Operational Experience

摘要

The Neves-Corvo mine is a world-class underground copper-zinc mine located in the semi-arid south of Portugal. The mine has been operated since 1988 by Somincor (Sociedade Mineira de Neves-Corvo, SA), a subsidiary of Lundin Mining.Pyritic tailings produced in the copper and zinc plants have a high acid generation potential and have historically been placed subaqueously since the startup of the mine. This disposal system at Somincor has provided safe and reliable storage of tailings. However, the tailings facility was predicted to reach full capacity in 2011 and alternatives for provision of sufficient tailings storage capacity were studied by Somincor. Surface disposal of paste was selected as the preferred alternative.The feasibility of changing the tailings deposition method to sub-aerial placement of paste has been investigated since 2001. Work completed includes a laboratory screening program, a field cell monitoring program, a large-scale field trial, a feasibility study, basic engineering, detailed engineering, and commissioning of the paste plant, culminating in operational placement of paste commencing in late 2010. Co-placement of acid-generating waste rock occurs in the form of berms and dikes that contain the paste.This paper summarizes the geochemical work conducted to evaluate the environmental stability of the paste. In addition, operational learnings and observations are presented.Operational experience to date indicates that the environmental behavior of the paste is consistent with the predictions resulting from the field and laboratory geochemical testing programs, demonstrating the value of these extensive efforts. Despite the high acid generation potential of the paste, its surficial placement under controlled conditions results in responsible and reliable management of both tailings and waste rock.