Characterisation of BOS steelmaking dust and techniques for reducing zinc contamination

Steer, Julian Mark; Grainger, C.; Griffiths, Anthony John; Griffiths, M.; Heinrich, Tobias; Hopkins, Andrew

doi:10.1179/1743281213y.0000000106

Cited by 19 publications

(17 citation statements)

References 17 publications

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“…Knowledge of the form in which the iron and zinc are found within the BOS dust is crucial in understanding how to best recycle the dust or how best to process it for recycling. 2,3,5) A well-known issue with steel plant by-products is their high variability. 1,2,5,6) In the case of BOS dust, the composi-…”

Section: Introductionmentioning

confidence: 99%

Self-sintering of BOS Filter Cake for Improved Recyclability

et al. 2019

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The self-sintering of BOS filter cake has been investigated by studying its oxidation in air between 100 to 1 000°C. The aim of the study was to gain an understanding of the self-sintering of the BOS filter cake in stockpiles, in terms of what reactions occurred, and how strength was developed in the filter cake during self-sintering. Upon heating, the BOS filter cake underwent a sequence of drying, oxidation and calcination events. The self-sintering process was driven by the oxidation of very fine (200-300 nm) particles of metallic iron and wüstite at low temperatures. Reactions in self-sintering were found to be the oxidation of metallic iron and wüstite to hematite and zinc ferrite, beginning at approximately 120°C and largely complete by 500-600°C. Phase analysis, thermodynamic modelling and enthalpy measurements were used to propose a probable reaction path consistent with the observed reaction products. These exothermic oxidation reactions at low temperatures provided the energy required to heat the stockpiles to drive self-sintering. Bonding within the reacted filter cake was from a network of particle-particle bonds formed between the very fine iron oxide particles in the matrix during oxidation at elevated temperatures. Exposure of the BOS filter cake to temperatures above 600°C under oxidising conditions is likely sufficient to form adequately strong material for transport and recycling in the BOS. Fluxes played little role in the development of the bonding within the filter cake.

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Section: Introductionmentioning

confidence: 99%

Self-sintering of BOS Filter Cake for Improved Recyclability

et al. 2019

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“…In this case, the high iron content and form of the zinc (possibly zinc ferrite) may be a concern for zinc producers [6,7,8]. Hence, knowledge of the form in which the iron and zinc are found within the BOS dust is crucial in understanding how to best recycle the dust or how best to process it for recycling [2,4,5,9,10].…”

Section: Introductionmentioning

confidence: 99%

“…sintering behaviour of the BOS filter cake are required if it is to be optimised. One difficulty in achieving this goal is the well-known issue of the high variability of steel plant by-products [1,2,9,10]. In the case of BOS dust, the composition, phase content and particle size can change from heat to heat, depending on the target steel grade and charge materials (hot metal and scrap composition), as well as within a single heat, depending on the blowing conditions and any additions made (fluxes and coolants).…”

Section: Introductionmentioning

confidence: 99%

Understanding the Self-Sintering Process of BOS Filter Cake for Improving Its Recyclability

Longbottom

Monaghan

Pinson³

et al. 2019

J. Sustain. Metall.

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Basic oxygen steelmaking (BOS) filter cake has been found to undergo a self-sintering process, improving its mechanical properties to allow easier recycling and utilization on plant. The aim of this study was to gain an understanding of the self-sintering of the BOS filter cake in terms of what reactions occurred, and how strength developed in the filter cake during self-sintering. The approach used was to characterize samples before reaction, and to measure the reactivity of the BOS filter cake during heating in air. Reacted samples were characterized and compared to self-sintered samples from the plant. The BOS filter cake consisted of very fine particles (200-500 nm) of metallic iron and wüstite. Upon heating in air from 100 to 1000 °C, the BOS filter cake underwent a sequence of drying, oxidation, and calcination events. The primary reactions in self-sintering were found to be the oxidation of metallic iron and wüstite to hematite and zinc ferrite, beginning at approximately 120 °C and were largely completed by 500-600 °C. These exothermic oxidation reactions at low temperatures were likely driven by the very fine particle size, and provided the energy required to heat the stockpiles and drive self-sintering. The strength required for recycling the BOS filter cake appeared to result from a network of particle-particle bonds that formed between the very fine iron oxide particles in the matrix during oxidation at elevated temperatures. Temperatures between 600 and 800 °C under oxidizing conditions are likely sufficient to form adequately strong material for transport and recycling in the BOS.

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“…As the BOF process is a batch process the Zn concentration of the dust is not constant. The concentration is usually highest shortly after the beginning of the blow and decreases with the blowing time . However, in the dust discharged from the dust‐separator, the dust is partly re‐mixed.…”

Section: Introductionmentioning

confidence: 99%

Zinc Enrichment in In‐Plant Electrostatic Precipitator Dust Recycling by Air Classification in Converter Steelmaking

Lanzerstorfer¹

2018

steel research int.

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Steelmaking in a basic oxygen furnace generates a considerable amount of dust, which is separated in a growing number of plants by dry de‐dusting systems. This dust is rich in Fe and therefore, suitable for recycling within the steel mill. Because of the elevated Zn content recycling via the sintering process is often not feasible. Therefore, several steel mills apply in‐plant dust recycling where the dust is recycled back into the furnace. Thereby, the Zn content of the dust increases steadily until the desired concentration in the dust for discharge is reached. In this procedure, the Zn atoms in the dust are circulated several times consuming energy and reduction agent for the volatilization each time. Classification experiments with basic oxygen furnace dust performed in this study show a certain dependence of the Zn concentration on the particles size. This size dependence is exploited by introducing an air classification step into the recycling process. The calculations for this novel process show that the required average number of times a Zn atom has to be volatilized and can be reduced by 35–72% depending on the underlying circumstances. Thus, the energy and reduction agent consumption required for dust recycling can be reduced substantially.

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Characterisation of BOS steelmaking dust and techniques for reducing zinc contamination

Cited by 19 publications

References 17 publications

Self-sintering of BOS Filter Cake for Improved Recyclability

Self-sintering of BOS Filter Cake for Improved Recyclability

Understanding the Self-Sintering Process of BOS Filter Cake for Improving Its Recyclability

Zinc Enrichment in In‐Plant Electrostatic Precipitator Dust Recycling by Air Classification in Converter Steelmaking

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