Utilization of polymeric wastes in steel refining process: Carbon dissolution into liquid steel at high temperature

High amount of polymeric food packaging wastes had been increasing during the Covid-19 epidemic, especially polystyrene (PS) and polypropylene (PP) packaging. This paper investigates the utilization of polymeric wastes as a liquid steel recarburizer in ladle refining process. PP was blended with PS into the ratios of up to 60 wt%, namely Blend#1 – Blend#6. The blends were pyrolyzed at 1550 °C for 15 min under argon atmosphere. The chars had high carbon content ranges between 86 and 91.47 wt%, and the crystallite size ranges between 0.27 and 2.45 nm. The chars were brought into contact with an electrolytic pure iron at 1550 °C under argon atmosphere for carbon dissolution experiment. It was found that overall carbon dissolution rates (K) for the chars were 1.46 × 10(−3) - 8.4 × 10(−3) s(−1), which occurred within the first 4–10 min and then keep pace with the maximum carbon content of 4.08–4.97 wt%. Sulphur transfer into liquid steel was slow for all cases with the content was in between 0.01 and 0.025 wt%. The rate controlling mechanism for carbon dissolution from polymeric chars was the dissociation of carbon atom from its host lattice. CaH(2)O(2) is a filler in the PS, was found to retard the carbon dissolution, however it can be decomposed at steelmaking temperature. The chars produced from PS and PP can be replaced a commercial recarburizer without negative effect on steel quality.