A Methodology for Systemic Plant Research: An Industrial Case Study Investigating the Effects of Water Quality on Pentlandite Flotation Recovery

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School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2024-03-15
Degree programme
92 + app. 92
Aalto University publication series DOCTORAL THESES, 50/2024
The dynamicity and complexity of the recycled process water quality present mineral recovery challenges to the mining industry. Concentrator plant operations are usually optimized using an engineering-centric optimization approach. However, the impact of climate change on the recycled process water quality and pulp chemistry is overlooked. The Kevitsa concentrator plant has shown a cyclic nickel recovery pattern that coincides with the summer seasons. This thesis aims to show how process optimization and related methodologies need to evolve from an engineering-centric approach towards systemic thinking to enable the step change toward a more resilient conversion of mineral resources. This study is structured around the case of the Kevitsa concentrator plant's poor pentlandite recovery during the summer months and is divided into three main parts (a) reviewing the impact of flowsheet modifications and equipment installation, and showing the limitation of the engineering-centric approach, (b) studying the impact of process water quality on electrochemical reactivity of sulphide ore using artificially generated process water from D-loop protocol, and highlighting the gap between laboratory-based studies and plant-based studies, and (c) defining and applying the methods, techniques, and protocols for systemic plant based research on Kevitsa concentrator plant. This study demonstrates the inadequacy of the widely adopted engineering-centric optimization approach. Flowsheet reconfiguration and equipment installation alone are not sufficient to address process water quality effects on valuable mineral recovery. Systemic optimization approach is needed to encompass the effects of climate change on process water quality. The laboratory study has shown that the electrochemistry of the pulp strongly depends on the quality of the recycled process water and the residence time of the ore in the process. Such laboratory studies are not representative enough to mimic real process plant conditions, and as a result, are not able to predict water properties that arise due to process water connecting with the hydrological and climatic setting of the tailing storage facility (TSF). Protocols containing analytical and measurement methods to study the electrochemistry of pulp in the context of an operating concentrator plant are defined in this study. Such protocols allow for a systemic investigation at a plant scale and help to relate the dynamic water property matrix to changes in the mineral surface reactivity and further to plant recovery values. The study has shown that the cyclic variation in ore reactivity is driven by seasonal changes in the physicochemistry of recycled process water which consequently influences the extent of ore oxidation during milling and mineral surface passivation during flotation, resulting in a 20% loss in nickel recovery. The study shows that the process water recycled through the TSF differs significantly from the process waters within the flotation circuits. The knowledge acquired from this dissertation presents protocols and methods that can be used to carry out plant-based studies in optimising the process.
Supervising professor
Dahl, Olli, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
Thesis advisor
Heiskanen, Kari, Prof. Emer., Aalto University, Minerals Engineering, Finland
Saari, Eija, PhD, Ecosystem & Innovation Lead Metso, Finland
process optimization, process water quality, flotation, oxidation, pentlandite
Other note
  • [Publication 1]: Musuku Benjamin; Muzinda Ishmael; Lumsden Barry: Cu-Ni processing improvements at First Quantum’s Kevitsa mine. Minerals Engineering, 2016, 88, 9–17.
    DOI: 10.1016/j.mineng.2015.08.005 View at publisher
  • [Publication 2]: Musuku Benjamin; Schreithofer Nora; Dahl Olli: Review of step changes taken to improve recovery of fine pentlandite at Kevitsa mine. IMPC 2020. XXX International Mineral Processing Congress, Cape Town, 18 – 22 October 2020.
    DOI: 10.1016/j.mineng.2015.08.005 View at publisher
  • [Publication 3]: Musuku Benjamin; Olli Dahl: Impact of Recycled Process Water on Electrochemical Reactivity of Sulphide Ore. Minerals, 2022, 12(11), 1455, issue: Water within Mineral Processing.
    DOI: 10.3390/min12111455 View at publisher
  • [Publication 4]: Musuku Benjamin; Saari Eija; Olli Dahl: Oxidative Dissolution of Low-Grade Ni-Cu Ore and Impact on Flotation of Pentlandite. Minerals, 2022, 12(11), 1406, issue: Water within Mineral Processing.
    DOI: 10.3390/min12111406 View at publisher
  • [Publication 5]: Musuku Benjamin; Kasymova Diana; Saari Eija, Dahl Olli: Influence of Water Quality on Sulphide Ore Oxidation and Speciation of Sulphur Anions during Autogenous Milling. Minerals, 2023, 13(2), 277, issue: Water within Minerals Processing.
    DOI: 10.3390/min13020277 View at publisher