ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Fundamentals of High Temperature Processes
Self-sintering of BOS Filter Cake for Improved Recyclability
Raymond James LongbottomBrian Joseph MonaghanGuangqing ZhangDavid John PinsonSheng Jason Chew
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2019 Volume 59 Issue 3 Pages 432-441


The self-sintering of BOS filter cake has been investigated by studying its oxidation in air between 100 to 1000°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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© 2019 by The Iron and Steel Institute of Japan
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