- Title
- Optimised burden delivery for blast furnace operations
- Creator
- Chibwe, Deside Kudzai
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- As far back in time from its first inception until modern day, the blast furnace (BF) ironmaking process route has gone through enduring evolutionary developments into a highly efficient process and thus establishing itself as the most popular and viable process of preference over other alternative routes for the production of iron hot metal (HM). The importance of this ironmaking process route cannot be over-emphasised as it is self-evidenced by the ever-increasing growth in the proportion of HM produced via the BF route for the steelmaking industry. Ferrous material (iron oxides), coke and fluxes (limestone) are the reactant materials of the process which are charged on top of the BF shaft. These materials are distributed on the burden surface via a complex charging, storage, discharging and transportation system commonly referred to as the charging system. The charging system is quite centrally important to the efficient operation of the BF because the burden distribution in the upper part of the furnace shaft is largely influenced by the history of the material flow in the preceding process unit operations. The flow of the reactant materials through the charging system is admittedly complex and often experience repetitive mixing and segregation (de-mixing) due to differences in particle size and density, which is problematic. Thus, a better understanding of the fundamental phenomena and influence of reactant materials flow characteristics and their interactions throughout the charging system is of paramount importance to ensuring reliability, performance and high efficiency of the BF operation through an established control mechanism of the flow behaviour. In this thesis, discrete element modelling (DEM), which is a well-established particle dynamics technique, was applied to obtain a deeper insight into the mixing and segregation of reactant materials. After validation of DEM with experimental results from unpublished internal company technical reports by BlueScope Steel (BSL), the model was primarily used to study the granular flow behaviour in furnace top (FT) material bins, weigh-hoppers and the overall charging system. Two major areas of focus were the mixing and segregation of mixed ferrous charge (pellets and sinter) and mixed ferrous and coke charge (nut coke and sinter). In the ferrous mixed charge, the mixing and segregation associated with the influence of highly flowable pellets mixed in sinter ore materials were studied. While mixing and segregation is an intrinsic aspect of the granular flow, the major challenge for BF ironmaking process is to have a correct inference of the granular description in the furnace shaft so as to be able to implement an appropriate blowing philosophy. An alternative methodology for evaluating the degree of mixing and segregation was developed. Utilising particle scale information obtained from DEM, a near-neighbour separation index (SI) was established in this study based on the geometrical particle distances of a particle mixture. The near-neighbour SI gives useful inferences on segregation and dispersion as it provides an unprecedented quantification of the particle-particle scale distributions of particles and fully provides a quantitative description of the particle mixture homogeneity. The work embodied in this thesis made use of the DEM, appropriate qualitative inferences and quantitative measurements to evaluate different scenarios. The effects of different parameters such as particle sizes, particle size distributions, densities, chute inclination angles, vibro-feeder frequencies were investigated. All the assumptions, validations, calibrations and observations are presented. New knowledge is obtained about the limitations of the charging system with regards to promoting reactant materials homogeneity in through the charging process chain. The funnelling flow behaviour of the unit operations such as FT material bins, WH and dynamic centring device (DCD) is concluded to be largely responsible for the mixing and segregation behaviour of reactant materials in the charging system.
- Subject
- DEM; granular flow; blast furnace; iron-making; mixing and segregation; separation index
- Identifier
- http://hdl.handle.net/1959.13/1406158
- Identifier
- uon:35599
- Rights
- Copyright 2019 Deside Kudzai Chibwe
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 9 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 931 KB | Adobe Acrobat PDF | View Details Download |