| Evaluating Kumba Lump Ore Performance in a Blast Furnace Burden Jacques Muller1; Kobus Vreugdenburg1; 1ANGLO AMERICAN, Pretoria, South Africa; PAPER: 73/Iron/Regular (Oral) SCHEDULED: 15:15/Tue. 29 Nov. 2022/Arcadia 1 ABSTRACT: <p>The blast furnace operation and economics are significantly influenced by the performance of burden materials descending in the furnace shaft. Changes in burden permeability and reducibility relates to the degree of indirect reduction, and therefore reductant requirement and iron productivity. Chemical composition, and physical and metallurgical properties of burden materials are determined using standard (ISO) test procedures. Tests are performed on specific material size distributions, and mostly at constant temperatures and gas compositions representative of typical blast furnace zones. <br />Materials are directly compared on qualities derived from standard tests. However, the marginal impacts on economic and emissions performance when substituting burden materials are not easily determined from standard material qualities. Contributing to inaccuracies are the transient nature of temperature and gas composition in actual processes, differences in material size distribution, and effects of other material properties.<br />The softening, melting, and dripping behaviour of materials at transient conditions, typical for blast furnaces, are determined in high-temperature tests [1]. In this investigation, such tests are performed on iron ore sinters, pellets, and lump ores using the test procedure developed by Ritz et al. 1998 [2]. A material sample, normally -12.5+10 mm, is placed under load and electrically heated while varying gas mixtures are injected over time to resemble the changing conditions down the blast furnace shaft.<br />Sample temperature, pressure drop, compaction, and the outlet gas composition are continuously measured during tests. Results derived include the location of the expected softening and melting points in the blast furnace in terms of temperature and time (i.e. location and thickness of the cohesive zone), and the degree of reduction over time. These tests are believed to more accurately indicate the amount of indirect reduction to be expected in the blast furnace and therefore the impact on the reductant requirement when comparing burden materials.<br />In this work, the material qualities determined in standard (ISO) tests were related to the actual performance in the blast furnace derived from high-temperature tests by using reaction kinetics and thermodynamic modelling. The purpose of this being to more accurately estimate blast furnace performance from more readily available burden material qualities. <br />Aspects investigated include: (1) softening and melting behaviour in relation to the degree of reduction and chemical composition during processing, (2) the amount of indirect reduction achieved at the softening point (start of cohesive zone) relative to a reducibility index value for a material with size distribution of interest, and (3) the impact that percentages of different materials in the burden has on the overall blast furnace performance.</p> References: <p>[1] X. Liu, T. Honeyands, G. Evans, P. Zulli, D. O'Dea, Ironmaking & Steelmaking April (2018) 1-15.<br />[2] V.J. Ritz, H.A. Kortman, 2nd International Congress on the Science and Technology of Ironmaking and 57th Ironmaking Conference (1998).</p> |
