Reduction of FeO in EAF Steelmaking Slag by Metallurgical Coke and Waste Plastics Blends

Abstract

In Australia, the use of plastics has increased tremendously over the last few decades, but less than 20 % of the waste plastics are recycled. The rest is usually landfilled, which poses major environmental problems. The solution to this problem involves the development of novel environmentally-benign technologies that would utilise these waste materials. This work investigates the reduction of EAF slags (47 % FeO) by blends of metallurgical coke with High-Density Polyethylene (HDPE) plastics at 1 550°C. The experiments were conducted in a laboratory-scale horizontal tube furnace, and were coupled with off-gas analysis using an infrared gas analyser and a multiple gas chromatographic analyser. The results indicate that the rate of FeO reduction in slags is significantly higher when the coke/plastics blends were used compared to pure coke, with the maximum rate of reduction (Blend 4) being over twice that of coke. Moreover, the CO 2 content in the off-gas was observed to decrease (by ϳ75 %) with increase in the polymer content of the blend. Additionally, the degree of carburisation and the removal of sulphur from the metal improved considerably when the coke was blended with plastics. The observed improvements in the rates of reduction, carburisation and desulphurisation are attributed to the reactions of hydrogen evolved from the waste plastics at these high temperatures.

Interfacial Reactions between Coke/HDPE Blends and High Carbon Ferromanganese Slag

“…Unlike in the case of reduction by coke, CO2 is no longer the dominant component as only minor amounts are detected in the off-gas. The significant decrease in CO2 emission coupled with the massive amounts of both CO and CH4 is an indication that the polymer undergoes thermal decomposition to liberate significant amounts of CH4, as was observed by Nishioka et al 20) and Dankwah et al 21) At this stage it is valid to speculate that part of the extra CO observed in the reduction by the blends could be attributed to reduction of MnxOy by CH4, as shown in Eq. (9) Gas generation from the reduction of the slag by the blends appears to be more significant than from the reduction of the slag by coke.…”

Novel Recycling to Transform Automotive Waste Glass and Plastics into SiC-Bearing Resource by Silica Reduction

“…Initial CO 2 release was negligible compared to CO generation, and almost zero for the rest of the reaction time. CH 4 release coming from Bakelite was also low, though the gas helped silica reduction and iron oxide reduction [11,20]. In contrast, CO which is the evolved gas for silica as well as iron oxide reduction reactions showed three humps.…”

“…7), and carbon analysis showed carbon content of 73.16 wt% in residual char. The rate of formation of SiO (reaction 5, 6) is enhanced by CO/ CH 4 for silica/silicate slags [20,22], and iron oxide reduction by CH 4 is also established [11]. Therefore, CO and CH 4 from Bakelite as reducing gas and produced char as a solid carbon source along with graphite blend should enhance the reduction reactions.…”

“…Studies have been carried out in our group to investigate the use of plastics as carbon sources in steelmaking [11,12]. Recently, we reported the use of waste CD as carbon source to produce SiC nanoparticles.…”

Recycling Waste Electrical Socket as a Carbon Resource in Ironmaking

“…For countries like Ghana where commercial quantities of iron ores are available, but without the relevant source of carbonaceous materials, waste polymers offer a readily available alternative to high grade metallurgical coke as reductant for iron making. In the metallurgical field, the use of postconsumer plastics as reductants or as a source of energy is currently gaining the attention of various researchers (Matsuda et al, 2006;Nishioka et al, 2007;Matsuda et al, 2008;Ueki et al, 2008;Dankwah et al, 2011;Kongkarat et al, 2011;Murakami et al, 2009;Murakami and Kasai, 2011;Dankwah et al, 2012;Dankwah et al, 2013;Dankwah and Koshy, 2014;Dankwah et al, 2015a;Dankwah et al, 2015b). However, most of the existing research in this area involves the use of thermoplastic polymers and or their blends with metallurgical coke, graphite, or biomass as reductants for the production of metallic iron from reagent grade iron oxides or electric arc furnace (EAF) slags containing iron oxide.…”