A Comprehensive Review of Secondary Carbon Bio-Carriers for Application in Metallurgical Processes: Utilization of Torrefied Biomass in Steel Production

Abstract

This review aims to show the significance of the use of secondary carbon bio-carriers for iron and steel production. The term ‘secondary carbon bio-carriers’ in this review paper refers to biomass, torrefied biomass, biochar, charcoal, or biocoke. The main focus is on torrefied biomass, which can act as a carbon source for partial or complete replacement of fossil fuel in various metallurgical processes. The material requirements for the use of secondary carbon bio-carriers in different metallurgical processes are systematized, and pathways for the use of secondary carbon bio-carriers in four main routes of steel production are described; namely, blast furnace/basic oxygen furnace (BF/BOF), melting of scrap in electric arc furnace (scrap/EAF), direct reduced iron/electric arc furnace (DRI/EAF), and smelting reduction/basic oxygen furnace (SR/BOF). In addition, there is also a focus on the use of secondary carbon bio-carriers in a submerged arc furnace (SAF) for ferroalloy production. The issue of using secondary carbon bio-carriers is specific and individual, depending on the chosen process. However, the most promising ways to use secondary carbon bio-carriers are determined in scrap/EAF, DRI/EAF, SR/BOF, and SAF. Finally, the main priority of future research is the establishment of optimal parameters, material quantities, and qualities for using secondary carbon bio-carriers in metallurgical processes.

The Materials Science behind Sustainable Metals and Alloys

“…128,397 Also biomass can be used�instead of coal or methane gas�as additional reductant feedstock. 462 One has to note that this overview diagram places focus on synthesis pathways with high TRL level (TRL, technology readiness level). It does not yet contain the recently matured liquid oxide smelting reduction methods which can be realized through hydrogenbased plasma operations in electric arc furnaces (plasma-winning of iron) and it does also not include the fused salt electrolysis process (electrowinning of iron).…”

“…In the first scenario biomass is used in the same way as waste polymer; i.e., it can be for instance charged into blast furnaces by using high injection rates and thereby reduce the amount of coke required. ,,− This process is pertinent but to some extend limited on the one hand because the internal structure and percolation in a blast furnace only work if a certain structural framework of coke is maintained. On the other hand, it must be taken into account that there is simply not enough renewable or sustainable biomass available for the replacement of all the coke in the operation of blast furnaces. ,,,, This means that the extensive use of biomass and biogas as a carbon-based reductant is limited by the availability of regional cropland. In addition, their energy and industrial utilization is in competition with other industries.…”

“…During the gas release process at the upper end of the blast furnace, the remaining reduction gas escapes as so-called blast furnace gas, being essentially a type of exhaust gas. One approach to make existing blast furnaces at least moderately more sustainable is to replace some of the fossil reductants by injected natural gas, , polymer waste shredder, ,, biomass ,, and/or hydrogen …”

“…Overview over the different principles and process pathways for conventional shaft furnace reduction, smelting reduction, direct reduction and scrap-based synthesis routes . The currently mainly pursued process variants for a fossil-free iron production in industry are the direct reduction of sintered pellets in shaft reactors where hydrogen can be used instead or together with methane and fluidized bed reactors in which the less costly iron ore fines can be used as oxide feedstock. , Also biomass can be usedinstead of coal or methane gasas additional reductant feedstock . One has to note that this overview diagram places focus on synthesis pathways with high TRL level (TRL, technology readiness level).…”

“…On the other hand, it must be taken into account that there is simply not enough renewable or sustainable biomass available for the replacement of all the coke in the operation of blast furnaces. 49,164,459,461,462 This means that the extensive use of biomass and biogas as a carbon-based reductant is limited by the availability of regional cropland. In addition, their energy and industrial utilization is in competition with other industries.…”