Improved Sinter Mix Preparation Using Challenging Raw Materials
Scenery
Responsible person: Maxime EVRARD (Geologist, Researcher, ULg)
Partners: CRM Group, ArceloMittal, Tata Steel, Voest Alpine, BFI
Supervisor: Pr. E. Pirard (ULg)
Sponsors: European commission (RFCS): 2.5 M€
Context
Since 1950’s, the main iron ore deposits are the Banded Iron Formation and are exploited in precambrian shield of Brazil, Mauritania, Australia, China, etc. To be reduced and transformed into steel, iron ores have to be sent to the blast furnace where the temperature reaches 1600°C. However, the finest particles (<6,3 mm) tend to decrease the permeability of the blast furnace, which reduces its effectiveness. So, these particles have to be sintered. This technique consists of forming small pellets (balls) from a mixture of iron ores, coke, flux (limestone, olivine,…) and water. This mixture is heated and gives a semi-molten mass that solidifies into porous pieces of sinter with the size and strength characteristics necessary for feeding into the blast furnace.
Iron ores show a downward trend of their quality (finer particles, broader size distribution, lower grades and higher fluctuation of properties). To ensure its competitiveness and sustainability, the European steel industry must use such ores together with recycled materials at the sinter plant, while improving sinter quality and productivity at lowest possible environmental impact and energy consumption. The objective of the IMSIMI project is to allow an optimal use of challenging input materials in such a difficult context, by an advanced control of all preparation phases (mixing, granulation, etc.) and a better understanding of their impact on the sintering process.16:40:26
Objectives
The processing of iron ores often requires a modification of particle size by granulation in order to improve further processability. The granulation process is partly influenced by the characteristic of the feed and partly by the action of cohesive force inside the drum granulator (Newitt et al. 1958). The main goal of this investigation is to determine which parameters are the most powerful on the granulation process and to know the factors which determine the texture, shape, porosity and mechanical strength of the microgranules. The granulation behaviour of recycling materials such as sinter return fines is also a priority
Equipement
Ore mineralogy
In this investigation, four commercial grade iron ore concentrates (Goethite, Magnetite, Hematite B and Hematite S) plus sinter return fines are used as feed material for the making of iron microgranule. These primary particles have been characterized before being granulate: 2D shape analysis, qualitative and quantitative mineralogy, chemical composition, pycnometry Hg…
Indeed Iron ore are very heterogeneous, even if their mineralogy is extremely simple, involving only 3 major
Hematite (Fe2O3), Magnetite (Fe3O4) and Goethite (FeOOH). The traditional trading of iron ores is based on chemical specifications and size distribution requirements. However, studies on iron ores and their behaviour in steelmaking processes show the importance of the microtexture of iron ores. iron-bearing mineral species:
Laboratory experiments were carried out in a stainless steel batch granulation drum 8.5 cm in diameter and 4.25 cm long. In order to evaluate the iron ore granulation processes and the influence of different parameters, several tests have been carried out to set up the methodology to obtain suitable granules for the kinetics study of granules by asymptotic analysis.
The resulting granules have been characterized with X-ray microtomography in order to quantify the number of nuclei, the porosity after an image processing and have informations about the texture.