Skip to content

Project results

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

Read more on Research Features

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

Learn more on Researchgate

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

 

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

Learn more on Springer

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

Read the article on MDPI