Improving charging system availability in a blast furnace
- Authors: Hendricks, Osrick Morne
- Date: 2012-06-08
- Subjects: Blast furnaces , Charging system
- Type: Thesis
- Identifier: uj:8751 , http://hdl.handle.net/10210/5102
- Description: M.Ing. , Steel products can be produced by either following the blast furnace with oxygen steel making route or the electric arc steel making route. The blast furnace with oxygen route requires liquid iron to produce steel and the electric arc route requires scrap metal as a major input. This in essence implies that for the blast furnace route if no liquid iron is produced, no steel products will be produced and similarly so for the electric arc route. ArcelorMittal Vanderbijlpark Works produces its liquid iron from two furnaces namely blast furnace C and blast furnace D. However the reliability of these furnaces is in question as their daily operations are plagued with random failures of equipment and machinery. The main consequence of these failures is the unavailability of the furnaces to produce liquid iron. This is undesirable from a business perspective due to the inherent production losses, loss of potential earnings as well as the high costs incurred to restore the furnaces back into operation.This research dissertation will focus on the operation of these blast furnaces. The fundamental success criteria for this research document will be to identify opportunities to improve the reliable operation of these furnaces. The scope of the work will however be limited to blast furnace C and particularly at improving its charging system’s availability. The availability of the charging system can be improved by knowing what type of failures to expect and how to mitigate their effects. A starting point would then be to examine past failure data. Thus data from 2008 has been collected and analyzed making use of statistical methods, design analysis methods and research methodologies. The results suggest that the availability of the system has a direct correlation between its reliability and maintainability. The results obtained were then subjected to a risk analysis to identify measures that could be employed to improve the charging system’s availability.
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Simple criteria for evaluating sulphate attack in concrete
- Authors: Ekolu, Stephen
- Date: 2014
- Subjects: Concrete - Mixing , Blast furnaces , Slag cement , Concrete
- Type: Article
- Identifier: uj:5082 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13653
- Description: This paper attempts to analyse results from the standard test methods employed for sulphate attack and evaluates their correlations, consistency and contrasts, as well as physical observations. Data from expansions and mass change of 25 x25 x 285 mm mortar prisms and 75 x 75 x 285 mm concrete prisms were used. Mortar mixtures consisted of 1: 2.25: 0.5 cement to sand to water while concrete mixtures were of water-cementitious ratio (w/cm) of 0.45, 0.50, 0.65. Mixtures were made using CEM I 42.5N with or without 30, 50, 70% ground granulated blast furnace slag (GGBS) and stored in sodium sulphate solutions of 28 g/L and 50 g/L as SO4. Results show that ASTM C 1012 mortar expansion criteria of 0.10% corresponds to 1.2% mass gain. Similarly, concrete prism expansion criteria of 0.05% is equivalent to 0.75% mass gain. It is proposed that in the absence of expansion monitoring, the use of mass gain criteria of 1.2% mass in mortar prisms or 0.75% in concrete prisms may be sufficient for evaluating sulphate attack.
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Sulphate resistance of concrete made with moderately high alumina slag
- Authors: Ekolu, Stephen O. , Ngwenya, Adam
- Date: 2014
- Subjects: Blast furnaces , Slag cement - South Africa , Mortar - Congresses
- Type: Article
- Identifier: uj:5062 , ISBN 978-1-61499-466-4 , ISSN 9781614994657 , http://hdl.handle.net/10210/13625
- Description: This paper reports findings of ongoing investigation into the effect of high alumina ground granulated blast furnace slag (GGBS) on sulphate resistance of concrete. Slags used in most countries contain low alumina contents and provide high resistance to sulphate attack among other durability improvements. It is however known that slags of high alumina contents do not necessarily improve sulphate resistance but may otherwise adversely influence concrete performance. South African slags have moderately high alumina contents but hardly any studies have been conducted to determine its influence on sulphate resistance of concretes. In this investigation, commercially available slag widely used in South Africa was used. Mortar prisms 25 x 25 x 285 mm of 0.5 water-binder ratio incorporating 30%, 50%, 70% GGBS were prepared and immersed in sodium sulphate solutions of different concentrations of 28 g/L and 50 g/L as SO4. Expansion and mass change of the cementitious systems were monitored. Variables examined were compressive strengths prior to immersion in Na2SO4 solution, slag replacement levels, concentrations of sulphate solutions. It was found that the moderately high alumina slag improved resistance to sulphate attack in correspondence with increase in the replacement levels of the extender. Mixtures that were not cured to develop 20 MPa initial strength prior to exposure in Na2SO4 solution, showed elevated early age expansion while their cured counterparts did not expand. The long-term expansions of mixtures that had not been cured were much higher than expansions of the respective cured mixes. Interestingly, the use of GGBS in proportions exceeding 50% mitigated the adverse effects of early age expansions giving no long-term expansions in any of the mixtures containing the extender.
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