Project results
- Article
Hydrogen: The key to a more sustainable manganese production
Summary
- Manganese (Mn) is the fifth most abundant metal in the Earth’s crust, widely used in metal alloys and batteries, but difficult to produce.
- Current Mn production methods have high energy consumption and CO2 emissions.
- Professor Jafar Safarian from the Norwegian University of Science and Technology (NTNU) developed the HAlMan process: a novel, sustainable way of producing Mn, ferromanganese, and manganese–aluminum alloys.
- The HAlMan process offers a cleaner conversion of Mn oxides to Mn metal or high-value alloys in the presence of hydrogen, while recovering energy.
Author
Jafar Safarian, Dep. of Materials Technology, Norwegian University of Science and Technology, Norway
- Conference paper
Computational reacting flow models for the pre-reduction of lumpy Nchwaning manganese ore with hydrogen
Abstract
Solid-state pre-reduction of manganese ores with hydrogen presents many potential advantages that include reduction of greenhouse gas emissions and lower energy consumption of the downstream smelting step. Before designing a pre-reduction reactor, it is crucial to investigate and understand the process kinetics and their influence on the overall pre-reduction reactor performance. Computational fluid dynamics (CFD) reacting flow models are used to predict the influence of kinetics, geometry and flow field on the chemical reaction rates. The current work employs the CFD models to predict the influence of temperature, flow field and kinetics on the degree of manganese pre-reduction with hydrogen. The models allow for the determination of the optimum reduction temperature and reduction time.
Authors
Mopeli Khama, Mintek, South Africa
Quinn G Reynolds, Mintek and University of Stellenbosch, South Africa
Buhle Xakalashe, Mintek, South Africa
Alok Sarkar, PhD candidate, Norwegian University of Science and Technology
Jafar Safarian, Dep. of Materials Technology, Norwegian University of Science and Technology, Norway
- Conference paper
Presented 17 – 19 June 2024, Brisbane Australia
Flux smelting behavior of pre-reduced Mn ore by Hydrogen at elevated temperatures
Abstract
Understanding how ore interacts with flux particles at elevated temperatures to create molten slag is crucial since it governs the dynamics of a chemical reaction. This study explores the smelting behaviour of pre-reduced Nchawaning manganese ore when combined with lime, with the objective of examining the evolving interaction between pre-reduced ore particles and lime over time. The research sheds light on the interaction between solid and liquid and the phases that emerge during this process. To achieve this, a sessile drop furnace was employed to rapidly heat the materials positioned adjacent to each other on an alumina substrate and to observe the smelting process as it unfolded over time. This method allowed for the direct observation of the melting temperatures and the flux-ore reaction progression rate, and the potential disruptive events that might occur. By comparing the molten interfaces of the fluxed materials at various time intervals, this study provides insights into the relative rate of slag formation from the two materials. The results indicate that the main slag formation initiated at approximately 1400 oC and continued to advance with time, with complete mixing occurring around 1500 oC. The possible phases formed were identified using Scanning Electron Microscopy and modelled using Fact Sage thermodynamic software. In addition, the iron particles in the pre-reduced Mn ore were separated and settled from a rich MnO-containing slag.
Authors
Pankaj Kumar, PhD candidate, Department of Materials Science and Engineering, Norwegian University of Science and Technology
Jafar Safarian, Professor, Department of Materials Science and Engineering, Norwegian University of Science and Technology.
- Conference paper
62nd Conference of Metallurgists, COM 2023
The Production of Manganese and Its Alloys Through the HAlMan Process
Abstract
In a new integrated process, HAlMan process, hydrogen, and aluminum are used to produce metallic manganese, aluminum-manganese (AlMn), and ferromanganese (FeMn) alloys with low energy consumption and carbon footprint. In this process, hydrogen gas is used to pre-reduce manganese ores and obtain intermediate Fe- and MnO-containing pre-reduced ore. The MnO content of this material is further reduced at elevated temperatures by aluminum in a smelting-aluminothermic reduction process. The main product of the process is metallic Mn, Al-Mn alloy, or ferromanganese, depending on the process feed chemistry. In the present work, the experimental results on the hydrogen reduction of manganese ore are presented and the effect of process conditions such as reduction temperature is evaluated. It is shown that the microstructural properties of the reduced ore depend on the process temperature, and the rate of ore reduction is higher at elevated temperatures. In addition, the smelting-aluminothermic reduction step is discussed and it is shown that the process is flexible to produce a variety of metallic products. Mass and energy balance calculations are presented and it is shown that the energy consumption for the process is lower than the state-of-the-art technology of the submerged arc furnace. It is revealed that the process is sustainable regarding the valorization of Al-dross industrial waste. It is shown that ferromanganese production by this process will prevent the emission of about 1.5 t CO2/t metal, with less practical challenges to produce low-carbon ferromanganese. The implementation of the HAlMan process on a pilot scale through an EU project is presented and it is shown how the process products can be used to make commercial metal products, and also the process products can be valorized to establish a sustainable process for the future ferroalloy industry.
Author
Jafar Safarian, Professor, Department of Materials Science and Engineering, Norwegian University of Science and Technology
- Article
Isothermal pre-reduction behavior of Nchwaning Manganese Ore in H2 atmosphere
Abstract
The application of H2 to pre-reduce manganese ores is a sustainable approach to performing decarbonization in the ferroalloy industry. The process has been extensively studied and tested in a lab-to-pilot scale in the HAlMan EU project. This work presents the results of an experimental study that was conducted in a lab-scale vertical thermogravimetric furnace for the pre-reduction of a manganese ore by H2 under isothermal conditions at 500 °C, 600 °C, 700 °C, and 800 °C. The ore and reduced samples were characterized by XRF, XRD, BET and SEM techniques to outline the H2 reduction behavior of the ore from mineralogical, microstructural, and chemical points of view. The rate and extent of reduction were studied using the continuous mass changes during the reduction. It was found that the pre-reduction at a temperature of 700 °C and 800 °C yields metallic iron formation from Fe2O3 and MnO formation from MnO2/Mn2O3. The pre-reduction at lower temperatures did not show a complete reduction in Fe and MnO. The pore structure of the ore was affected by the pre-reduction temperature, and a significant porosity evolution was observed.
Authors
Alok Sarkar, PhD candidate, Norwegian University of Science and Technology
Trygve Lindahl Schanche, SINTEF, Norway
Jafar Safarian, Professor, Department of Materials Science and Engineering, Norwegian University of Science and Technology
- Article
Evaluating the Reaction Kinetics on the H2 Reduction of a Manganese Ore at Elevated Temperatures
Abstract
This study investigates the hydrogen reduction of Nchwaning manganese ore at elevated temperatures to enhance understanding of reaction kinetics and optimize industrial applications. Experimental investigations were conducted across temperatures ranging from 600 °C to 900 °C to observe reduction behavior and identify rate determining steps. Thermogravimetric analysis (TGA) was employed to monitor manganese ore weight loss, facilitating precise measurement of reduction rates. Various kinetic models validated experimental outcomes for H2 reduction, revealing an apparent activation energy (Ea) of 65.76 kJ/mol and an apparent pre-exponential factor (k0) of 319.66 min⁻1. The rate constant (k) exhibited a significant temperature-dependent increase, following the Arrhenius equation where rates approximately doubled every 100 °C, rising from 0.037 min⁻1 at 600 °C to 0.377 min⁻1 at 900 °C. Morphological and compositional analyses using scanning electron microscopy (SEM) and X-ray diffraction (XRD) assessed structural changes post-reduction. Results demonstrated that pre-reduction temperature critically influences the physical and microstructural properties of the ore particles, particularly above 700 °C, where a notable reduction in BET (Brunauer–Emmett–Teller) surface area and pore volume indicated sintering within the ore. The rate determining step for this reduction process is most likely the chemical reaction at the gas–solid interface between hydrogen and the manganese ore. These findings highlight advancements in efficient manganese ore reduction processes, with significant implications for metallurgical practices and the hydrogen economy.
Authors
Alok Sarkar, PhD candidate, Norwegian University of Science and Technology
Trygve Lindahl Schanche, SINTEF, Norway
Jafar Safarian, Professor, Department of Materials Science and Engineering, Norwegian University of Science and Technology
- Seminar presentations
“Mn og Si Dag” (Mn and Si Day) presentations
A seminar titled “Mn og Si Dag (Mn and Si Day)” was organized by NTNU on the 20th and 21st of February 2025. During this event, Elias Trondsen Dahl (Master student), Pankaj Kumar and Alok Sarkar (Ph.D. students) and Manish Kumar Kar (Postdoctoral researcher) from the HAlMan project (NTNU), had the opportunity to present their work.
MnO2 production from pre-reduced Mn ores for battery applications
Presenter: Elias Trondsen Dahl (Master’s Student, NTNU, Norway)
Isothermal Hydrogen Reduction of Nchwaning Manganese Ore: A Kinetics Study at Elevated Temperatures
Presenter: Alok Sarkar (Ph.D. Student, NTNU, Norway)
Effect of pre-reduction of manganese ore by hydrogen on its smelting behavior and interaction with stable oxides
Presenter: Pankaj Kumar (Ph.D. Student, NTNU, Norway)
Presentation:
Hydrogen Reduction of Dust from a Ferromanganese Submerged Arc Furnace (SAF)
Presenter: Manish Kumar Kar (Postdoctoral Researcher, NTNU, Norway)
- Article
Hydrogen reduction of lumpy Nchwaning ore in a fixed bed reactor
Abstract
The application of hydrogen gas for prereduction of manganese ore may substitute fossil carbon consumption and as such reduce CO2 emissions in manganese ferroalloy production. The pre-reduction behavior of Nchwaning manganese ore was investigated using a fixed bed reactor. Reduction rates at different temperatures and temperature programs were investigated, and particles were sieved after reduction to measure decrepitation. The reduction rate was measured by adding a tracer gas to the reducing gas and quantifying the off-gas by GC-analysis. Different particle size distributions of the input material were reduced to investigate the effect of particle size on reduction rate. Chemical analysis and XRD were used to characterize the raw and reduced material. The influence of particle size distribution and temperature on the oxygen removal rate are discussed. The manganese oxides were mostly reduced to MnO in the samples, while some iron oxide and carbonates remained. The reduction degree is improved by smaller particles and increased temperature.
Authors
- Trygve Lindahl Schanche – SINTEF As, Trondheim, Norway
- Heiko Gaertner – SINTEF As, Trondheim, Norway
- Frida Vollan – SINTEF As, Trondheim, Norway
- Alok Sarkar – PhD candidate, Norwegian University of Science and Technology
- Casper van der Eijk – SINTEF As, Trondheim, Norway
Learn more on International Journal of Minerals, Metallurgy and Materials
- Article
An Integrated, CFD-Based, Analysis of Carbonation in a Stirred Tank Reactor
Abstract
Carbonation precipitation processes have been widely used due to their numerous applications in a wide range of fields. The complexity of these processes lies within the interplay of transport phenomena, multiphase flows, chemical reactions, and solid precipitation, deeming the experimental analysis and in-depth mechanistic understanding of the process dynamics a rather challenging task. In this work, a three-dimensional CFD model is developed, focusing on the carbonation step of the carbonation precipitation process, taking into account the flow dynamics of the liquid solution in the stirred tank, the CO2 bubble flow, and the dissolution in the liquid solution, as well as its dissociation in water. The model is validated with experimental measurements, and a very good agreement is achieved. Additionally, a parametric analysis is conducted to study the effect of different process parameters, such as temperature, CO2 flow rate, and rotational speed. The analysis of the different phenomena and their interplay reveals the key mechanisms that dictate the carbonation step, resulting in an in-depth understanding of the process. The presented computational approach can potentially pave the way towards a knowledge-based process and reactor design; thus, assisting the scale-up of such processes in stirred tank reactors.
Authors
- Georgios P. Gakis – School of Chemical Engineering, National Technical University of Athens (NTUA), Zografou, Greece
- Danai Marinos – Laboratory of Metallurgy, School of Mining and Metallurgical Engineering, National Technical University of Athens (NTUA), Zografou, Greece
- Ioannis G. Aviziotis – School of Chemical Engineering, National Technical University of Athens (NTUA), Zografou, Greece
- Efthymios Balomenos – Laboratory of Metallurgy, School of Mining and Metallurgical Engineering, National Technical University of Athens (NTUA), Zografou, Greece
- Andreas G. Boudouvis – School of Chemical Engineering, National Technical University of Athens (NTUA), Zografou, Greece
- Dimitrios Panias – Laboratory of Metallurgy, School of Mining and Metallurgical Engineering, National Technical University of Athens (NTUA)
- Article
Evaluation of the Effects of Fluidization Conditions on Hydrogen Reduction in Manganese Ore Fines
Abstract
Hydrogen prereduction of two manganese ores fines was investigated under varied operating conditions in a fluidized bed. The manganese ores used in this study are the Zambian ore and the South African Nchwaneng ore from the Kalahari region. The samples were milled and sized before they were characterized with regard to sphericity, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) chemical analyses, X-ray diffraction (XRD) analyses and Scanning Electrons Microscope (SEM) analyses. Prereduction experiments were conducted in a laboratory scale fluidized bed with the parameters of interest being minimum fluidization velocity, terminal velocity, elutriation, average bed voidage, residence time, temperature, intrinsic ore properties and cohesive adhesion. Experiments for the determination of fluidization velocity and terminal velocity were conducted at both ambient temperature and elevated temperature (500 °500 °C, 550 °550 °C, 600 °600 °C, 700 °700 °C, 800 °800 °C and 900 °900 °C), and for varied sample masses (100 g, 300 g and 700 g) and varied particle-size ranges (200–300 μ300 μm, 300–425 μ425 μm, 425–500 μ500 μm and 500–600 μ600 μm). The experimentally observed minimum fluidization velocities for particles size groupings of [+106–200 μ200 μm], [+200–300 μ300 μm], [+300–425 μ425 μm], [+425–500 μ500 μm] and [+500–600 μ600 μm] as well as the mix (20 wt% of each) was comparable with the theoretical minimum fluidization velocity. The fluidized bed was heated to a desired temperature at a rate of 10 °10 °C/min under argon whilst logging the pressure drop across the bed with increasing temperature. The convectional cooling during the introduction of cold hydrogen as well as the net energy of endothermic and exothermic chemical reactions were observed to result in a temperature drop in the order of 100 to 250 °250 °C. Thermal mineral transformation under argon was observed to yield iron manganese oxide in the order of 15 to 30 wt/wt%. Prereduction was conducted using hydrogen gas at a desired temperature and terminal velocity. Reduction extent was observed to increase with the increasing temperature and residence time. Increasing reduction temperature beyond 700 °700 °C was not observed to improve reduction, whereas longer residence time (of up to 40 min) was observed to favor the formation of iron manganese oxide, iron manganese and manganosite. For hydrogen prereduction experiment conducted at 900 °900 °C, the reactor was observed to be brittle after the experiment. Cohesive adhesion was observed to be more pronounced at 900 °900 °C.
Authors
- Dursman Mchabe – Mintek, Gauteng, South Africa
- Sello Tsebe – Mintek, Gauteng, South Africa
- Elias Matinde – Mintek, Gauteng, South Africa
- Article
Kinetics study on the H2 reduction of Nchwaning manganese ore at elevated temperatures
Abstract
Replacing solid carbon with hydrogen gas in ferromanganese production presents a forward-thinking, sustainable solution to reducing the ferro-alloy industry’s carbon emissions. The HAlMan process, a groundbreaking and eco-friendly method, has been meticulously researched and scaled up from laboratory experiments to pilot tests, aiming to drastically cut CO2 emissions associated with ferromanganese production. This innovative process could potentially reduce CO2 emissions by about 1.5 tonnes for every tonne of ferromanganese produced. In this study, a lab-scale vertical thermogravimetric furnace was used to carry out the pre-reduction of Nchwaning manganese ore, where direct reduction occurred with H2 gas under controlled isothermal conditions at 700, 800, and 900°C. The results indicated that higher pre-reduction temperatures (800 and 900°C) effectively converted Fe2O3 to metallic iron and Mn2O3 to MnO. By continuously monitoring the mass changes during the reduction, both the rate and extent of reduction were assessed. A second-order reaction model was applied to validate the experimental outcomes of H2 reduction at various temperatures, showing apparent activation energies of 29.79 kJ/mol for dried ore and 61.71 kJ/mol for pre-calcined ore. The reduction kinetics displayed a strong dependence on temperature, with higher temperatures leading to quicker and more complete reductions. The kinetics analysis suggested that the chemical reaction at the gas–solid interface between hydrogen and the manganese ore is likely the rate-limiting step in this process.
Authors
- Alok Sarkar – NTNU Norwegian University of Science and Technology, Department of Materials Science and Engineering, Faculty of Natural Sciences, Resources, Energy & Environment research group.
- Trygve Lindahl Schanche – SINTEF Industry, Trondheim, Norway
- Maria Wallin – NTNU Norwegian University of Science and Technology, Department of Materials Science and Engineering, Faculty of Natural Sciences, Resources, Energy & Environment research group.
- Jafar Safarian – NTNU Norwegian University of Science and Technology, Department of Materials Science and Engineering, Faculty of Natural Sciences, Resources, Energy & Environment research group.