Gas–Solid Reaction Kinetics of ZnFe2O4Formation from 907 to 1100 °C

In order to reduce the burden of electric arc furnace dust on steel recycling plants, a new technology called in-process separation (IPS) was proposed. By separating Zn vapor from the solid particles in the electric arc furnace off-gas, production of Zn-containing electric arc furnace dust may be prevented. However, the spinel formation reaction at high temperatures and its impact on the technology's feasibility still require better understanding. This paper demonstrates a model that was developed to provide this insight, based on the results of our previous work on the kinetics of the spinel formation.This model evaluates the performance of IPS based on four key process parameters: the position of the separation unit, the timetemperature profile inside the off-gas duct, the solid particle size distribution, and the initial Zn and Fe content of the off-gas. The impact on the efficiency of each parameter was demonstrated using the results of the model for a specific off-gas treatment setup.

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“…4) [7] can be accounted for. This allows the implementation of the time-temperature profile into the model.…”

Section: Calculation Methodsmentioning

confidence: 99%

“…We found that, thermodynamically, Zn vapor will react with magnetite to form franklinite (Reaction 1) [6]. In order to understand the impact of this reaction on the composition of the solid particles in the EAF off-gas, the reaction kinetics were studied and diffusion coefficients describing the reaction were found [7].…”

Section: Introductionmentioning

confidence: 99%

Zn Loss into ZnFe2O4 in an Open Type Electric Arc Furnace: An In-Process Separation Performance Model

Suetens

Guo

Acker

et al. 2015

J. Sustain. Metall.

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“…Through recycling it may be possible to create a product that may be used as an input for a zinc recovery process, through either a pyro-or hydrometallurgical route. 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%

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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“…The presence of zinc ferrite or a zinc-containing spinel within the sample has been noted in other steel plant byproducts that contain iron and zinc oxides. [21][22][23][24] It should be acknowledged that there were not enough of the zinc bearing phases (zincite and spinel, with a trace amount of zinc hydroxide detected) to account for all of the ZnO content as measured by XRF (Table 1). This "missing" zinc is most likely one of the components of the nonbulk crystalline proportion of the sample.…”

Section: Characterisation Of Unreacted Bos Filter Cakementioning

confidence: 99%

In situ Phase Analysis during Self-sintering of BOS Filter Cake for Improved Recycling

Longbottom

Monaghan

Pinson³

et al. 2020

ISIJ Int.

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The self-sintering of basic oxygen steelmaking (BOS) filter cake has been studied using in situ high temperature X-ray diffraction (XRD) during heating in air from room temperature to 1 273 K. The aim of the study was to improve the understanding of the self-sintering process, using this in situ method to identify what reactions occur at different temperature ranges.The in situ phase analysis measurements correspond well, and are consistent with, the previously reported characteristics of BOS filter cake oxidation. However, the in situ measurements have allowed a more detailed analysis of the reactions taking place over the temperature ranges studied. Wüstite was the first component of the BOS filter cake to react with air, reacting at temperatures of approximately 373 K to 773 K to form a magnetite-zinc ferrite spinel solid solution. The reaction of metallic iron began at higher temperatures than wüstite, beginning at ~633 K and finishing at ~873 K. The decomposition of fluxes (mainly CaCO 3 ) occurred at temperatures above 873 K. At temperatures higher still, at approximately 1 073 K, hematite reacted with zinc oxide to form zinc ferrite.The knowledge that wüstite reacts at the lowest temperatures is an improvement in the understanding of the self-sintering of BOS filter cake, and may give insights into the initiation of the self-sintering process. This improved understanding will aid analysis and approaches focused on process optimisation to increase the amount of filter cake that can be recycled back to the BOS.

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Gas–Solid Reaction Kinetics of ZnFe₂O₄Formation from 907 to 1100 °C

Cited by 5 publications

References 13 publications

Zn Loss into ZnFe2O4 in an Open Type Electric Arc Furnace: An In-Process Separation Performance Model

Zn Loss into ZnFe2O4 in an Open Type Electric Arc Furnace: An In-Process Separation Performance Model

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

<i>In situ</i> Phase Analysis during Self-sintering of BOS Filter Cake for Improved Recycling

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