N. Saha-Chaudhury

Recycling Waste Plastics in EAF Steelmaking: Carbon/Slag Interactions of HDPE‐Coke Blends

Due to the inherent limitations of current methods of plastic waste disposal, there have been concerted efforts worldwide towards developing alternative, environment friendly and economic recycling processes. With an aim to recycle waste plastics in EAF steelmaking, carbon/slag interactions for a number of blends made of metallurgical coke and HDPE (high density polyethylene) and an EAF slag (34.8 mass-% Fe2O3) have been investigated at 1550°C using a sessile drop arrangement. The rate of gas generation showed an increase with increasing HDPE concentration, reaching a maximum for blend #3 (with appr. 30 % HDPE) and decreasing thereafter. Among all the blends investigated, blend #3 showed significantly higher levels of slag foaming as compared to metallurgical coke. HDPE-coke blends also showed better wetting compared to metallurgical coke with contact angles in some cases improving from 140° to 70° after 10 minutes of contact. These results have been discussed in terms of ash and sulphur contents of carbonaceous residues and dynamic changes in slag composition. Industrial trials on blend #3 showed a good agreement with laboratory results. This work opens novel avenues for the utilisation of plastics wastes as a valuable carbon resource in EAF steelmaking.

Recycling of Rubber Tyres in Electric Arc Furnace Steelmaking: Carbon/Slag Reactions of Coke/Rubber Blends

Synopsis End of life tyres are discarded at an alarming rate reflecting the strength of developing countries economy and the intensity of trade and transportation. Conversely, environmental concerns are increasing the need for alternative materials in steelmaking industries. The solution to this problem involves the development of environmentally-friendly technologies that would utilize these waste products. The present study investigates carbon/slag reactions, including slag foaming and FeO reduction, for a range of coke/rubber blends. Off-gas emissions (CO and CO2) were monitored and correlated with dynamic changes in volume as a result of iron oxide rich EAF slag and carbon. The gaseous emissions from metallurgical coke showed lower concentrations in comparison to the emissions from the coke-rubber blends. With an increase of rubber in the blend, gaseous emissions were enhanced. Significant carbon/slag interactions occurred when coke/rubber blends were used, with associated iron oxide reductions within the slag phase. The quantitative estimation of the slag droplet volume was performed by using the Vt/Vo ratio as a measure of slag foaming. These results indicate that partial replacement of coke with rubber is not only viable, but efficient leading to improved interactions with EAF slag.