Metallurgical properties of iron burden materials using alternative feed in a blast furnace. By-product briquettes, biocarbon, and hydrogen injection

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

University of Oulu, L2 (Linnanmaa)

Topic of the dissertation

Metallurgical properties of iron burden materials using alternative feed in a blast furnace. By-product briquettes, biocarbon, and hydrogen injection

Doctoral candidate

Master of Science (Technology) Olli Vitikka

Faculty and unit

University of Oulu Graduate School, Faculty of Technology, Process Metallurgy

Subject of study

Process and Environmental Engineering

Opponent

Associate Professor Davide Mombelli, Polytechnic University of Milan

Custos

Professor Timo Fabritius, University of Oulu

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Metallurgical properties of iron burden materials using alternative feed in a blast furnace. By-product briquettes, biocarbon, and hydrogen injection

Despite the growing interest in hydrogen-based steelmaking, blast furnaces will remain a dominant production method for the foreseeable future due to the substantial existing capacity and the current limitations in renewable energy needed for industrial-scale hydrogen production. Considering climate goals, it is necessary to examine methods for mitigating the environmental impact of blast furnace-based ironmaking. This dissertation investigates three of them.

This study examined self-reducing auger pressing briquettes made from by-products, hydrogen injection into the blast furnace, and the use of biocarbon as a reducing agent in briquettes. Each method was evaluated using one or more of the following approaches: (1) preventing disintegration of the iron burden material, which can lead to reduced energy efficiency and operational issues, (2) saving natural resources by avoiding landfilling, and (3) replacing fossil feed.

In this study, the blast furnace process was simulated in laboratory experiments at temperatures up to 1100 °C using three different pieces of equipment, which enabled investigating the high-temperature properties of test briquettes and commercial iron ore pellets through dynamic and isothermal computer-controlled programs. The tests examined weight loss using thermogravimetric analysis, along with reducibility, swelling, cracking, and changes in porosity. In addition, mechanical strength tests were conducted, and samples were simultaneously subjected to reducing conditions and physical load to simulate the behavior of the ferrous burden in the actual blast furnace process.

No standardized tests exist for briquettes, but based on the results presented in the dissertation, auger pressing briquettes are usable, and a third of the carbon used in them can be replaced with biocarbon. Nevertheless, using briquettes in blast furnaces requires conscientious optimization between mechanical strength and self-reducing effect to maximize productivity and avoid operational issues. It can also be stated that the dynamic test programs used provide information on the pellet’s compressive strength during reduction that standardized tests cannot capture. While hydrogen injection significantly accelerates pellet reduction at elevated temperatures (900–1100 °C), the water vapor generated at lower temperatures – around 700 °C – may exert an oxidizing effect on the material surface, thereby considerably hindering the reduction process.
Last updated: 15.10.2025