The reprocessing of historic mine tailings
Loading...
URL
Journal Title
Journal ISSN
Volume Title
Kemian tekniikan korkeakoulu |
Master's thesis
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Authors
Date
2021-01-26
Department
Major/Subject
European Mining Course
Mcode
CHEM3052
Degree programme
European Mining, Minerals and Environmental Programme (EMMEP)
Language
en
Pages
88 + 29
Series
Abstract
Billions of tons of mine tailings are being produced every year. With the increase of demand in metals and an ever-decreasing grade in conventional mines, the volume of tailings production is only expected to increase further. Mine tailings are a major source of a wide range of risks. It is, therefore, becoming ever more important to increase the production of metals from secondary sources to reduce the production of mine tailings. Historically, mined grades had been much higher and metal recovery had been lower in comparison with today’s mining operations. This left a tremendous wealth of unrecovered metals in waste streams. Consequently, historic mine tailings are now being recognized as a viable source of responsible metals production. This thesis investigated the feasibility of the remining and reprocessing of historic mine tailings. A techno-economic case study was performed to assess the technical and economic viability of a tailings reprocessing project, following a cost-benefit approach. The research was undertaken in Nevada on a real tailings deposit owned by NovaMetallix. The exact name and location of the studied tailings cannot be disclosed, due to restrictions in given permissions. Historic operating data has been analyzed, resulting in a preliminary resource prediction. Field reconnaissance has been performed to collect samples of the tailings for assay analysis. Resource models were created from the spatial assay database, which allowed for accurate resource estimation and the validation of the preliminary resource prediction. A conceptual process flowsheet was designed for the extraction of precious metals, reflecting an earlier successful reprocessing operation. Design improvements were incorporated to increase plant efficiency and reduce potential environmental impacts. Capital and operational expenditures were estimated, which together with the projected revenues, formed the basis of a discounted cash flow analysis. This multidisciplinary series of activities demonstrated the technical and economic feasibility of the tailings reprocessing project. Preliminary resource predictions based on a historical data analysis has been proven to be a time and cost-effective method. It is an appropriate starting point for research, given that sufficient and reliable data is available. Modern resource estimation techniques can be successfully used on tailings deposits. The exploration phase for tailings reprocessing projects carry significantly lower risk due to the visibly finite deposit size. Tailings reprocessing project could benefit from modifications made to resource estimation guidelines, as man-made deposits are inherently different to sub-terranean deposits made by geological processes. The main challenges associated with the reprocessing of historic mine tailings are related to the mineralogy and grain size. Refractory or complex minerals are a common occurrence in tailings deposits because the easy recoverable metals had been extracted during initial processing. Materials with small grain size often exhibit issues related to dust emissions, high viscosities, and poor solid-liquid separation rates. This can result in an overly complex process design with potentially a poor economic outlook. Factors that make the reprocessing of historic mine tailings feasible include improved market conditions, advancements in process technologies, and a reduction in costs for exploration, excavation, and comminution. The reprocessing of historic mine tailings creates numerous value-creation opportunities, well beyond the conventional scope of mining. Land reclamation, responsible metal production, economic benefit for local communities, and smaller carbon footprints are a few examples of the wide range of benefits the reprocessing of historic mine tailings has. The results of this study show that mining companies may benefit from following a similar approach presented in this thesis. This will allow for the identification and appraisal of other historic tailings deposits, resulting in additional responsible metals production and decreased primary mining waste. This combination of environmental management and recovery of metals from secondary sources support the aspirations for a circular economy.Description
Supervisor
Serna, RodrigoThesis advisor
Cincilla, BillKeywords
historic mine tailings, feasibility, resource estimation, process design, economic evaluation