Unintentional Flow of Alloying Elements in Steel during Recycling of End‐of‐Life Vehicles

Abstract

SummaryAlloying elements in steel add a wide range of valuable properties to steel materials that are indispensable for the global economy. However, they are likely to be effectively irretrievably blended into the steel when recycled because of (among other issues) the lack of information about the composition of the scrap. This results in the alloying elements dissipating in slag during steelmaking and/or becoming contaminants in secondary steel. We used the waste input-output material flow analysis model to quantify the unintentional flows of alloying elements (i.e., chromium, nickel, and molybdenum) that occur in steel materials and that result from mixing during end-of-life (EOL) processes. The model can be used to predict in detail the flows of ferrous materials in various phases, including the recycling phase by extending steel, alloying element source, and iron and steel scrap sectors. Application of the model to Japanese data indicates the critical importance of the recycling of EOL vehicles (ELVs) in Japan because passenger cars are the final destination of the largest share of these alloying elements. However, the contents of alloying elements are rarely considered in current ELV recycling. Consequently, the present study demonstrates that considerable amounts of alloying elements, which correspond to 7% to 8% of the annual consumption in electric arc furnace (EAF) steelmaking, are unintentionally introduced into EAFs. This result suggests the importance of quality-based scrap recycling for efficient management of alloying elements.

Recycling of Rolling Stocks

“…Around 50% of the light shredder residue contains a combustible portion that can be thermally treated. Although there are new technologies that enable sorting and using up to two-thirds of the mass of the shredder residue, in practice, approximately 67% of the remains, after the shredding process, are landfilled [20][21][22][23][24]. It is noted that the materials derived from shredding process cannot be classified as reusable.…”

Matching global cobalt demand under different scenarios for co-production and mining attractiveness

“…Second, the critical materials are commonly aggregated together into the non-ferrous metal sector, or to even higher levels. Disaggregation of individual metal sectors in IO tables, as shown by Hawkins et al (2007), Nakamura et al (2008), Nakajima et al (2013), Ohno et al (2014), has been done at the country level, but requires very detailed data that are usually not available for critical metals on the global scale. Moreover, MRIO tables represent oneyear snapshots of the world economy or short historic time series only, and there is no standard procedure for how to extrapolate these tables into the future.…”

Material Flow Analysis and Waste Management

“…For example, Ohno et al ( 2014 ) showed that considerable amounts of alloying elements, which correspond to 7-8 % of the annual consumption in electric arc furnace (EAF) steelmaking, are unintentionally introduced into EAFs. This type of analysis is an interesting application of MFA to help development of more appropriate recycling systems.…”

“…Some studies discuss alloying elements in metal recycling (Nakajima et al 2011(Nakajima et al , 2013Nakamura et al 2012 ;Ohno et al 2014 ). For example, Ohno et al ( 2014 ) showed that considerable amounts of alloying elements, which correspond to 7-8 % of the annual consumption in electric arc furnace (EAF) steelmaking, are unintentionally introduced into EAFs.…”