Abstract
Metal production, and especially iron ore-based steel production, is characterized by high fossil CO2 emissions due of the use of coal and coke in the blast furnace. Steel companies around the world are striving to reduce the CO2 emissions in different ways, e.g., by use of hydrogen in the blast furnace or by production of iron via direct reduction. To partially replace fossil coal and coke with climate neutral bio-coal products that are adapted for use in the metal industry, e.g., at the blast furnace, is a real and important opportunity to significantly lower the climate impact in a short-term perspective. Top-charging of bio-coal directly to the blast furnace is difficult due to its low strength but can be facilitated if bio-coal is added as an ingredient in coke or to the mix when producing residue briquettes. Bio-coal can also be injected into the lower part of the blast furnace and thereby replace a substantial part of the injected pulverized coal. Based on research work within Swerim, where the authors have been involved, this paper will describe the opportunities and limitations of using bio-coal as a replacement for fossil coal as part of coke, as a constituent in residue briquettes, or as replacement of part of the injected pulverized coal. Results from several projects studying these opportunities via technical scale, as well as pilot and industrial scale experiments and modelling will be presented.
Highlights
The steel industry faces great challenges adapting to changed raw material quality and the need to lower the CO2 emissions, which is especially important for coal- and coke-based production of hot metal via the blast furnace (BF) route that still dominates in steelmaking
Bio-Coal Top-Charged into the Blast Furnace as Bio-Coke or Bio-Briquettes
Addition of torrefied sawdust (TSD) revealed the lowest dilatation and fluidity compared to the reference coke, and generally these parameters are lowered with increasing amounts of any bio-coal added
Summary
The steel industry faces great challenges adapting to changed raw material quality and the need to lower the CO2 emissions, which is especially important for coal- and coke-based production of hot metal via the blast furnace (BF) route that still dominates in steelmaking. To partially replace fossil coal and coke with climate neutral pre-treated biomass products that are adapted for use in the metal industry, e.g., at the BF, is a real and important opportunity to significantly lower the climate impact. Woody biomass can be upgraded into bio-coal via thermochemical slow pyrolysis in the absence of oxygen, as in torrefaction or pyrolysis processes [6,7,8,9,10,11]. Torrefaction is performed at temperatures around 200 to 300 ◦ C, and pyrolysis at temperatures from 300 to 600 ◦ C, or even higher
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