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Geometallurgical Variability Study of Spodumene Pegmatite Ores, Central Ostrobothnia - Finland
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This geometallurgical variability study was conducted for Keliber Oy definitive feasibility study. Itincludes the Syväjärvi, Länttä and Rapasaari lithium ore deposits located in Central Ostrobothnia –Finland. These deposits present different characteristics in terms of spodumene grade, grain size,alteration, and weathering.A geometallurgical approach was used to characterize the ore and learn about the variability withinand between the deposits in terms of mineralogy and processing response. In the project designchosen, grinding and flotation tests were performed. In addition, chemical composition ofspodumene, mineralogical and liberation studies were carried out by MLA and EDS analysis.Spodumene is the main Li mineral in the deposits and its characteristics and elemental compositiondiffer between and within these deposits, affecting mineral processing behavior. Spodumeneimpurities content as FeO and MnO are the highest in Länttä and lowest in Rapasaari. With respect tothe harmful elements, Mg is carried by amphiboles and micas and P by apatite and sicklerite.Grinding is mainly influenced by the spodumene grade of the ore. The total grinding time to reach theP80 target was similar for the average ores, around 30 minutes of two stage grinding. Pre-flotationremoved more than 50% of the apatite with on average 4.6% losses of spodumene. A cleaning stagefor the pre-flotation product is recommended to recover some of the spodumene losses.In spodumene flotation with rougher and seven cleaning stages, Syväjärvi average ore showed highrecoveries (about 90%) to final concentrate, whereas Länttä and Rapasaari presented clearly lowerrecoveries, (about 70%). In addition, Länttä presented the lowest spodumene grade in the finalconcentrate (about 70%) and Rapasaari the highest (about 75%). The flotation process, in general,turned out to be efficient in terms of concentrate grade, achieving, in most of the cases, the targetedLi2O grade of 4.5%. Although, the geometallurgical test is based on flowsheet developed for Syväjärviand it is quite expected that Länttä and Rapasaari samples show poorer performance. Therefore,flotation tests and process optimization should be done to improve the spodumene recovery of Länttäand Rapasaari deposits. Considering Syväjärvi samples, spodumene head grade and grain size hadpositive effects in flotation. In contrast, spodumene alteration had a negative effect. Länttä showslower spodumene liberation with given grind which leads to lower recovery and grade in flotation. Acombination of lower feed grade, locking association, P80 and secondary Li minerals may explainRapasaari samples performance. The weathered Rapasaari sample showed a positive effect onspodumene recovery which is possibly due to the liberation of spodumene grains from feldspars andquartz. Controlled waste dilution on ore samples promoted lower spodumene recovery and lowerfinal concentrate grades, proportional to the dilution ratio. The results indicate that flowsheet andprocessing conditions as P80 and collector dosage need to be optimized by the deposit and by the oretype. Nevertheless, the present study is a diagnostic test and the results cannot be directly correlatedto full-scale process.

Place, publisher, year, edition, pages
2017.
Keyword [en]
Lithium pegmatites; Geometallurgy; Spodumene; Kaustinen Li province; Ore Variability
National Category
Mineral and Mine Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-66536OAI: oai:DiVA.org:ltu-66536DiVA: diva2:1155927
External cooperation
Keliber Oy; FAME Project
Subject / course
Student thesis, at least 30 credits
Educational program
Geosciences, master's level (120 credits)
Supervisors
Examiners
Available from: 2017-11-17 Created: 2017-11-09 Last updated: 2017-11-17Bibliographically approved

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