Volume 92, Issue 11 2100210
Research Article
Open Access

Use of Bentonite and Organic Binders in the Briquetting of Particulate Residues from the Midrex Process for Improving the Thermal Stability and Reducibility of the Briquettes

Laura Lohmeier

Corresponding Author

Laura Lohmeier

Institute of Thermal-, Environmental- and Resources’ Process Engineering (ITUN), Technische Universität Bergakademie Freiberg (TUBAF), Leipziger Straße 28, 09599 Freiberg, Germany

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Christoph Thaler

Christoph Thaler

voestalpine Stahl GmbH, voestalpine-Straße 3, 4020 Linz, Austria

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Christopher Harris

Christopher Harris

voestalpine Stahl GmbH, voestalpine-Straße 3, 4020 Linz, Austria

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Ralf Wollenberg

Ralf Wollenberg

ATNA Industrial Solutions GmbH, Zschortauer Straße 76, 04129 Leipzig, Germany

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Hans-Werner Schröder

Hans-Werner Schröder

Institute of Thermal-, Environmental- and Resources’ Process Engineering (ITUN), Technische Universität Bergakademie Freiberg (TUBAF), Leipziger Straße 28, 09599 Freiberg, Germany

Center for Efficient High Temperature Processes and Materials Conversion (ZeHS), Technische Universität Bergakademie Freiberg (TUBAF), Winklerstraße 5, 09599 Freiberg, Germany

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Andreas Siegfried Braeuer

Andreas Siegfried Braeuer

Institute of Thermal-, Environmental- and Resources’ Process Engineering (ITUN), Technische Universität Bergakademie Freiberg (TUBAF), Leipziger Straße 28, 09599 Freiberg, Germany

Center for Efficient High Temperature Processes and Materials Conversion (ZeHS), Technische Universität Bergakademie Freiberg (TUBAF), Winklerstraße 5, 09599 Freiberg, Germany

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First published: 05 August 2021
Citations: 4
Research data are not shared.

Abstract

With the aim of achieving sufficient reducibility and thermal stability of briquettes for reuse as feedstock in the Midrex direct reduction process, a defined mixture of residues from the Midrex process is briquetted with an organic binder and bentonite. In the first step, briquetting tests are conducted to investigate the influence of water and binder content on the mechanical properties of the briquettes. Suitable briquettes are then used for reduction tests, where mechanical properties under Midrex-relevant conditions are considered. The tests show that briquettes with an organic binder (with and without bentonite) are not stable under Midrex-relevant conditions, whereas briquettes with a mixture composition with 5 wt% bentonite and 5 wt% water are. This can be justified on the basis of microscopic images. Bentonite favors the sintering mechanisms occurring between the particles. The organic binders decompose thermally and carbon remains, which prevents sintering. The reduction tests show that oxygen release from the briquettes occurs more slowly than for iron oxide pellets. However, the residual mixture already contains reduced material (Femet of briquettes with bentonite 28.1 wt%), so less oxygen has to be removed. Furthermore, a small briquette format (volume 10 cm3) shows better reduction behavior compared to bigger briquettes.

Conflict of Interest

The authors declare no conflict of interest.

Data Availability Statement

Research data are not shared.

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