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Feasibility of gravity and magnetic separation for Yxsjöberg historical tungsten ore tailings
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.ORCID iD: 0000-0003-1872-5803
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.ORCID iD: 0000-0002-2265-6321
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
2019 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Repositories of historical tailings (HT) pose environmental risks but could also become new resources for valuable metals. This is because relatively high minerals and metals content characterize them due to less efficient extraction methods and/or relatively low metal prices at the time. In this investigation, geometallurgical studies were conducted by collecting drill core samples (DCS) from the Smaltjärnen tailings repository in Yxsjöberg, Sweden. The collected DCS were from the main layers of the longest drill core, and were characterized physically (color, texture, moisture content and particle size distribution) and chemically (elemental composition and distribution, and mineralogical composition). The characterization of DCS indicated that the tailings mass distribution was high in the coarser particle size fraction of +149 μm. Tungsten (W) and Copper (Cu) were the metals of interest with highest concentrations being 0.22 %WO3 and 0.11 %Cu. Feasible physical separation methods selected were Knelson concentrator, LIMS and HIMS, based on the knowledge from literature, tailings characteristics, and assessment of processes from which the Yxsjöberg HT were produced. Using the Knelson concentrator, the recovery of scheelite, which is the main W mineral, was enhanced, with 75 wt.% tungsten recovered in the 34 wt.% of concentrate produced. In magnetic separation, sulphur (S) was mostly recovered in the ferromagnetic and paramagnetic fractions with only 1.0 wt.% in the non-magnetic fraction, meaning pyrrhotite, the main Fe-sulphide mineral in the HT responsible for AMD, was separated to the desired magnetic fractions of the LIMS and HIMS. These results are fundamental in the development of methods for separation of valuable minerals from these HT in order to produce an inert and environmentally safe residue.

Place, publisher, year, edition, pages
2019.
Keywords [en]
Historical tailings, Tungsten, Scheelite, Geometallurgy, Reprocessing, Physical separation
National Category
Engineering and Technology
Research subject
Mineral Processing; Centre - Centre for Advanced Mining & Metallurgy (CAMM)
Identifiers
URN: urn:nbn:se:ltu:diva-76407OAI: oai:DiVA.org:ltu-76407DiVA, id: diva2:1361590
Conference
Minerals Engineering International (MEI) Conference_Physical Separation ’19, Falmouth, UK, June 13-14, 2019
Projects
REMinE (Improve Resource Efficiency and Minimize Environmental Footprint)
Funder
Vinnova, 215 06 631Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-10-22
In thesis
1. Geometallurgical study of historical tailings from the Yxsjöberg tungsten mine in Sweden: Characterization and reprocessing options
Open this publication in new window or tab >>Geometallurgical study of historical tailings from the Yxsjöberg tungsten mine in Sweden: Characterization and reprocessing options
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Alternative title[sv]
Geometallurgisk studie av historisk anrikningssand från Yxsjöbergs volframgruvan i Sverige : Karaktärisering och upparbetningsalternativ
Abstract [en]

Tungsten (W) is listed among the European Union (EU) critical raw materials (CRMs) for its supply risk and economic importance. Primarily, tungsten is produced from scheelite and wolframite mineral ores with 0.08-1.5% tungsten trioxide (WO3) grade. However, as primary deposits for these resources are becoming less or lower in grade, alternative sources need to be explored. These alternative tungsten sources include scrap from end-of-life products, mine waste and rejects from the ore beneficiation processes (tailings). The latter alternative source is the focus within this thesis.

Historical tailings repositories often pose environmental risks but may also become secondary sources of CRMs. This is because of relatively high minerals and metals content due to less efficient extraction methods and/or relatively low metal prices at the time of active mining. Therefore, reprocessing of such tailings is not only a supply risk-reducing measure but also an approach to remediation that contributes to the mining industry’s aim of moving towards a circular economy.

The aim of this thesis has been to develop efficient methods for separating valuable minerals from the tailings in order to leave behind a stable and environmentally safe residue. Geometallurgical studies were conducted by collecting drill core samples from the Smaltjärnen tailings repository in Yxsjöberg, Sweden, for evaluating the potential of this repository for further processing. The tailings were originally produced from the ore that was mined by Yxsjö Mines while it was in operation from 1935 to 1963, with average ore grades of 0.3-0.4 wt.% WO3, 0.2 wt.% Cu and 5-6 wt.% fluorspar. The exploited minerals were scheelite for W, chalcopyrite for Cu and fluorspar. The tailings repository is estimated to have about 2.2 million tons of tailings covering an area of 26 hectares, with elemental concentrations of 1-2 wt.% S, 0.02-0.2 wt.% Cu, 0.02-0.3 wt.% W, 0.02-0.04 wt.% Sn and 0.02-0.03 wt.% Be.

Sampling and characterization of the historical tailings were conducted based on geometallurgical units (i.e. a distinction between different layers and locations in the repository), followed by metallurgical test work. The tailings were characterized with regard to color and granulometry, particle size distribution, chemical composition, scheelite mineral occurrence, texture and mineral liberation, as well as mineralogical composition. Based on a comprehensive literature survey, tailings characteristics, and assessment of the earlier processes from which the Yxsjöberg tailings were produced, feasible separation methods were pre-selected involving dry low-intensity magnetic separation (LIMS) and high intensity magnetic separation (HIMS), enhanced gravity separation (EGS) using a Knelson concentrator, and batch froth flotation.

The average WO3 and Cu concentration in these tailings based on the sampled locations was 0.15 % and 0.11 % respectively. Applying them to the estimated 2.2 million tons of tailings in this repository gives approximately 3300 tons of WO3 and 2512 tons of Cu. From the metallurgical test work, several feasible processing routes have been identified that need to be further assessed based on the economic and environmental criteria.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Keywords
Critical raw materials, Historical tailings, Tungsten, Scheelite, Geometallurgical approach, Characterization, Beneficiation, Reprocessing, Gravity separation, Magnetic separation, Flotation
National Category
Engineering and Technology
Research subject
Mineral Processing; Centre - Centre for Advanced Mining & Metallurgy (CAMM)
Identifiers
urn:nbn:se:ltu:diva-76416 (URN)978-91-7790-480-9 (ISBN)978-91-7790-481-6 (ISBN)
Presentation
2019-12-10, F531, Luleå University of Technology, Luleå, 10:00 (English)
Opponent
Supervisors
Projects
REMinE (Improve Resource Efficiency and Minimize Environmental Footprint)
Funder
Vinnova, 215 06 631
Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2019-11-27Bibliographically approved

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