Reduction of Electric Arc Furnace Dust (EAFD) Using Biochar Towards Sustainable Ironmaking
摘要
The current study presents a sustainable ironmaking process that recovers iron from the toxic solid waste of steel plants and the electric arc furnace dust (EAFD) and uses carbon–neutral biochar to reduce environmental risks and CO2 emissions. The reduction behaviour of an EAFD–biochar composite pellet was investigated in a tube furnace between 1000 °C and 1200 °C for a duration of 5 to 20 min, and at varying pellet carbon levels. The transverse cross section of the reduced pellets revealed three layers: an inner core that was partially reduced and powdery, a layer of slag at the top, and a layer of slag-entrapped iron underneath. As the concentration of biochar in the pellet increased above a C/O ratio of 1, the reduction level dropped, and this was associated with an increase in the partially reduced powdery core. The iron and slag layers enveloping the inner core caused gas and pressure build-up, declining char gasification, and reduction at the core. Thermocouple temperature measurement indicated that biochar reduction started 100 °C earlier than coal reduction, indicating higher reactivity of biochar. Biochar pellets, however, produced a lesser extent of reduction, attributed to quicker gasification of the biochar and a short-lived reduction period that ended at 900 °C. A higher pellet heating rate under flash heating in a muffle furnace was found to be ineffective for biochar pellets to produce iron nuggets because the pellets disintegrated. The ideal conditions for reducing the EAFD–biochar composite pellet were C/O = 1 and a slower heating rate at 1200 °C. The reduced pellets were comprehensively characterized by weight loss, FactSage analysis, SEM, EDS, and XRD examination.