Recycling of waste polymers in electric arc furnace steelmaking: slag/carbon and steel/carbon interactions

This project is focused on utilizing polymer/coke blends as carbon resource in EAF steelmaking process. In-depth investigations were carried out on slag/carbon and steel/carbon interactions steel at 1550ºC using the sessile drop technique. Interactions between PET/Coke and PU/Coke blends with EAF slag (30.5% FeO) were investigated. PET/Coke blend showed sustained slag foaming with the volume ratio stabilizing at 1.2 over the reaction time, while PU/Coke showed a fluctuating slag foaming behaviour with the volume ratio ranging between 0.75-1.2. These ratios are greater than that for coke where the volume ratio was ~1 initially and then decreased with time to reach approximately 0.75. The levels of CO and CO2 generated from slag/carbon interactions for PET/Coke and PU/Coke was somewhat lower than that for coke, which allowed a better gas entrapment in the slag sample and sustained slag foaming. H2 and CH4 from the polymer/coke blends also participated in the reduction of FeO in the slag. For steel/carbon interactions, Bakelite, HDPE and PET were blended with metallurgical coke in three different ratios. Bakelite/coke blend (BK1) showed a decrease in contact angles compared to coke, but contact angles were seen to increase slightly with increasing bakelite concentration (BK2 and BK3). CaO from the bakelite caused desulphurization of steel and formed CaS at the metal/carbon interface. A small improvement in carbon transfer was observed compared to coke. HDPE/Coke and PET/Coke blends exhibited slightly better wetting behaviour with liquid steel compared to coke, and contact angles increased marginally with increasing polymers content. Volatiles from HDPE/Coke and PET/Coke slowed down the coverage of interfacial region by reaction products; oxygen from PET/Coke blends helped form FeO at the interface. A marginal improvement in carbon transfer was observed for HDPE/Coke and PET/Coke blends. Similar trends of sulphur transfer into liquid steel were observed for all polymer/coke blends