Abstract
Replacement of fossil carbon by renewable biomass-based carbon is an effective measure to mitigate CO2 emission intensity in the blast furnace ironmaking process. Depending on the substitution rate of fossil fuels, the required amount of biomass can be substantial. This raises questions about the availability of biomass for multiple uses. At the same time, the economic competitiveness of biomass-based fuels in ironmaking applications should also be a key consideration. In this assessment, availability of energy wood, i.e., logging residues, small-diameter wood and stumps, in Finland is discussed. Since biomass must be submitted to a thermochemical process before use in a blast furnace, the paper describes the production chain, from biomass to charcoal, and economics related to each processing step. The economics of biomass-based reducing agents is compared to fossil-based ones by taking into account the effect of European Union Emissions Trading System (EU ETS). The assessment reveals that there would be sufficient amounts of energy wood available for current users as well as for ironmaking. At present, the economics of biomass-based reducing agents in ironmaking applications is unfavorable. High CO2 emission allowance prices would be required to make such a scheme competitive against fossil-based reducing agents at current fuel prices.
Highlights
Renewable energy plays an important role in the European Union’s energy policy towards attaining a carbon-lean economy
It is assumed that 1.7 t sinter is used to produce t hot metal [15]; 6 According to Norgate et al [10] not currently practiced, 5–10% of iron in blast furnace feed could be replaced with pre-reduced iron ore composite pellets [15]
Biomass-derived charcoal could substitute for a small fraction of the top-charged coke or coal in metallurgical coke production, and small amounts could be used in the injected oil in Finnish blast furnace ironmaking
Summary
Renewable energy plays an important role in the European Union’s energy policy towards attaining a carbon-lean economy. According to the Finnish plan of action, the majority of the increase in renewable energy should come from the use of wood-based biomass in heat and power production [2]. Suopajärvi and Fabritius [8] have evaluated the plant site energy and environmental effects of biomass-derived charcoal use as a reducing agent in integrated steelworks. In this paper the pathway to a bio-based reducing agent utilization scheme in Finnish ironmaking is described, from wood-based raw materials to application in the blast furnace. The paper provides an availability assessment of domestic logging residues, stumps and small-diameter wood (defined here as energy wood), with analysis of competing uses of raw materials based on the recent literature. An economic assessment of charcoal production is presented with comparison of fossil reducing agent costs at different CO2 allowance prices
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