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Fluxing behaviour : reactions between iron ore and fluxing agents in the cyclone converter furnace of Hlsarna
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Whiston, James (2021) Fluxing behaviour : reactions between iron ore and fluxing agents in the cyclone converter furnace of Hlsarna. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3821709
Abstract
Steel is under increasing pressure from governments and environmental groups to cut CO2 emissions. To fight this, a number of alternative ironmaking processes have been devised to replace the blast furnace (BF) ironmaking process in modern integrated steel plants. The blast furnace has been targeted, as it is the highest producer of greenhouse gases in the steel plant. This is due to the high use of coal as an active ingredient and the energy intensive processing of raw materials for use in the furnace such as coking ovens and sintering. Tata Steel Europe have been developing an alternative iron making plant called HIsarna that is a combination of two technologies: cyclone converter furnace and HIsmelt smelting reduction vessel. The trials have shown that the process can cut CO2 emissions drastically compared to the current BF ironmaking and has greater flexibility in the raw materials and energy used for the process.
With the development of new processes, the issues that arise from new reactions means that new fundamental knowledge is needed to understand the certain phenomena in the. In this thesis, the interaction between iron ore and Ca-based materials (lime, limestone, and basic oxygen steelmaking slag) will be studied with an interest of these reactions occurring in the CCF. The process has seen issues of accretions building up in the region between the CCF and SRV, and requires a solution to dissuade the agglomeration of such accretions.
The accretions found in the process were taken from the IJmuiden HIsarna pilot plant and analysed by examining the structure, composition, and thermal properties. The structure and porosity were examined with XCT and microscopy. The sample had two defined sections (dense and porous) with some microstructural aspects. The composition was detected by electron dispersal spectroscopy (EDS) and was used to study the chemistry of the accretion against the iron ore used in HIsarna. The thermal properties indicated the temperature at what temperature the material will be molten to understand and stop the accretion forming. The results allowed for the orientation of the accretion to be determined and theories on how the formation of the accretion. It shows that how the classic formation via alkalis of accretions found in a BF do not seem feasible due to the higher temperatures in the HIsarna.
The interactions between iron ore and Ca-based materials were then conducted with the aim to show the benefits of doping the CCF with CaO to reduce the melting point of the ore to increase uidity. To increase HIsarna's flexibility of raw materials, three Ca-based fluxes (lime, limestone and BOF slag) were compared to show how they work in terms of reactivity and effectiveness in increasing the molten material. This was done with in situ experimentation and post experimental analysis of the flux-iron ore interface. The finding showed that limestone was the most reactive from the test with a high molten fraction and evidenced from SEM imaging. The BOF slag was also showed to be a potential source of fluxing material in the HIsarna process. Using BOF slag would help increase the environmental benefits to the process and industry as this promotes recycling of BOF slag produced in an integrated plant.
Finally, the study progresses from small scale bulk reactions to a single particle reaction with a Ca based pellet (lime and limestone) to test likelihood of how the particles react in the CCF. This allowed for a more varied compositions of iron ore due to the heterogeneous nature of particles to be studies with higher content of impurities such as SiO2, Al2O3 and MgO. The test used a unique method implementing a sessile drop camera (SDC) with the high temperature confocal scanning laser microscope (HT-CSLM) to obtain a two-plane in situ view of a particle interacting at high temperatures. The test showed that a high SiO2 content in the particle increased the melting point of a CaO-FeOx system. Al2O3/MgO also efxix effected the interaction negatively but by a smaller degree. The visualisation from two angles allowed the particle to be measured over a period of 60 s and allowed for a kinetic study of the interaction. This found that the composition of each particle had a greater effect on the rate of reaction rather than the shape, size, and temperature. It also provided further evidence of the increased activity of newly formed CaO from calcination of limestone.
Item Type: | Thesis (PhD) | ||||
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Subjects: | T Technology > TN Mining engineering. Metallurgy T Technology > TS Manufactures |
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Library of Congress Subject Headings (LCSH): | Cyclone furnaces, Smelting furnaces, Iron and steel industry, Carbon dioxide mitigation, Flux (Metallurgy) Steel -- Metallurgy | ||||
Official Date: | 2021 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Warwick Manufacturing Group | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Li, Zushu | ||||
Sponsors: | Tata Iron and Steel Company ; Engineering and Physical Sciences Research Council | ||||
Format of File: | |||||
Extent: | xx, 143 leaves : illustrations, charts, photographs | ||||
Language: | eng |
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