Author:
Kar Manish Kumar,Hassanzadeh Ahmad,van der Eijk Casper,Safarian Jafar
Abstract
AbstractTo minimize the carbon footprint in the industrial valourization of bauxite residue, hydrogen was used as a reducing agent. The current study experimentally investigated hydrogen reduction of bauxite residue-CaO sintered and self-hardened pellets at 1000 °C, along with magnetic separation of these reduced pellets for iron recovery. Calcium was introduced to bauxite residue to form leachable calcium aluminate phases with the existing alumina in bauxite residue. This involved the addition of either CaCO3 or a mixture of CaO and CaCO3 while maintaining the fixed Ca content during pelletization. The former underwent sintering at 1150 °C, while the latter was self-hardened through the cementing effect of CaO in exposure to moisture and air. Both types of pellets were reduced in a thermogravimetry furnace at an elevated temperature under similar conditions. The pellets were characterized by the X-ray diffraction (XRD) method and scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS), and their physical and mechanical properties were measured via standard techniques. During hydrogen reduction, a negligible amount of gehlenite (Ca2Al2SiO7) was formed in the self-hardened pellets, while this phase dominated in the sintered pellets. Alumina in the bauxite residue converted to mayenite phases during reduction in both the pellet types; however, reduced self-hardened pellets had a higher amount of alumina containing mayenite leachable phase. The two pellets showed similar reduction behaviour, while different chemical, physical, and mechanical properties were observed. The magnetic properties of milled reduced pellets were examined through a Davis Tube magnetic separator in a wet environment under a constant magnetic field of 800 G. Higher iron recovery was observed for the self-hardened reduced (41%) pellets than for the sintered pellets (27%).
Funder
H2020 European Research Council
NTNU Norwegian University of Science and Technology
Publisher
Springer Science and Business Media LLC
Subject
Materials Chemistry,Metals and Alloys,Mechanical Engineering,Geotechnical Engineering and Engineering Geology,General Chemistry,Control and Systems Engineering
Reference18 articles.
1. Safarian J, Kolbeinsen L (2016) Sustainability in alumina production from bauxite. Sustain Ind Process Summit:75–82. https://www.academia.edu/63547300/Sustainability_in_alumina_production_from_bauxite. Accessed 15 Nov 2023
2. Lazou A, van der Eijk C, Balomenos E, Kolbeinsen L, Safarian J (2020) On the direct reduction phenomena of bauxite ore using H 2 gas in a fixed bed reactor. J Sustain Metall 6:227–238. https://link.springer.com/article/10.1007/s40831-020-00268-5. Accessed 15 Nov 2023
3. Rukini A, Rhamdhani M A, Brooks GA, Van den Bulck A (2022) Metals production and metal oxides reduction using hydrogen: a review. J Sustain Metall 8:1–24. https://link.springer.com/article/10.1007/s40831-021-00486-5. Accessed 15 Nov 2023
4. Baolin H, Zhang H, Hongzhong LI, Qingshan ZHU (2012) Study on kinetics of iron oxide reduction by hydrogen. Chinese J Chem Eng 20:10–17. https://www.sciencedirect.com/science/article/pii/S1004954112603577. Accessed 15 Nov 2023
5. Elshkaki A, Graedel TE, Ciacci L, Reck BK (2018) Resource demand scenarios for the major metals. Environ Sci Technol 52:2491–2497. https://pubs.acs.org/doi/full/10.1021/acs.est.7b05154. Accessed 15 Nov 2023