Analysis on copper, lead and tin removal in steel scrap sorting : Technologies involved, environmental considerations and economic aspects

Abstract: With the urgency of cutting down CO2 emissions to reach climate neutrality by 2050, decarbonization of the steel industry is on the European Commission's agenda. Steelmaking accounts for 10 % of anthropogenic CO2 emissions and it is one of the most challenging sectors to decarbonize. A solution that could support this progressive shift is to put more trust into the electric arc furnace (EAF) process, which relies on steel scrap as the main feedstock, but currently it is only responsible for 40% of the EU steelmaking. The almost remaining percentage is taken by the blast furnace route. Multiple European blast furnaces are currently closing due to low demands, high competition on imports and extremely high energy prices for production due to the Russian invasion of Ukraine situation. This particular moment could the proper time for increasing the employment of the EAF process. Moreover, the latter could help to improve resource efficiency and circularity of steel scrap thanks to the usage of higher shares of it, creating a “closed loop” for the steel industry. The reality of using more steel scrap is not actually very far from where we are, however, this will not be easy to reach. In fact, to ensure that the steel scrap is recycled "infinite" times it must contain very low quantities of impurities, such as copper (Cu}, tin (Sn) and lead (Pb}. Most of the times, this does not happen. Thus scrap is diluted with virgin iron to disperse those unwanted elements. This practice leads to a gradual decline of steel scrap quality, which is not in accordance with what it has just stated above. To worsen this situation even more, forecast is predicting increasing quantities of Cu that will accumulate into the steel scrap streams, due to the expected rising electric vehicles production. The aim of the following thesis work is to set a model to design a potential sorting solution to provide a higher copper (the most annoying cause of concern) removal rate in steel scrap, considering the economic and environmental implications of its implementation in the industry. Nonetheless, the presence of even lead and tin will also be taken into account. Results showcases that it is possible to get better impurities removal compared to what it has been done in many EU steel scrapyards, with ballistic separation as an additional refining separation step. Moreover, it is also an economically convenient and easy implementable solution that would assure higher quality steel scrap downstream of the process and that would also bring substantial economic and environmental benefits.