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.

The reduction of FeO-containing slag by blends of metallurgical coke and end-of-life tyres (RT) have been investigated through experiments conducted in a laboratory-scale horizontal tube furnace. Composite pellets of EAF slag (47.1% FeO) with coke, RT, and blends of coke/RT (in four different proportions) were rapidly heated at 15508C under high purity argon gas and the off gas was continuously analyzed for CO and CO 2 using an online infrared (IR) gas analyzer. The extent of reduction after 10 min, level of carburization and desulfurization, and the total amount of CO 2 emissions were determined for each carbonaceous reductant. The results indicate that the extent of reduction, level of carburization and desulfurization of the reduced metal are significantly improved when coke is blended with RT. Blending of coke with RT resulted in a decrease in direct CO 2 emissions from the reduction reactions.

The reduction of MnO in slag by blends of coke with high density polyethylene (HDPE) was investigated by the sessile drop method at 1 500°C in this study. The results show improved wettability and extents of reduction are realised with the use of an HDPE/coke blend in this system by comparison to reduction by pure coke, whereby increasing HDPE content resulted in further improvement in extent of reduction and increased wettability. The extensive devolatilisation from HDPE samples is the primary cause for these improvements, whereby the gasified HDPE created both CH4 and H2 reducing gases. Additionally, increased sample porosity allowed for improved wetting, and thus improved reduction capabilities. The dynamic contact angle between the carbon substrate and the slag varied, with HDPE samples ranging between 140°-60°, whilst the coke samples ranged between 160°-120°. The addition of HDPE allowed for the near complete reduction of MnO and partial reduction of SiO2 from the slag with distinct metallic regions of Mn-Si formed in the sample; regions containing pure Si were also found.

The reduction of FeO containing slag by blends of metallurgical coke and end-of-life polyethylene terephthalate (PET) has been investigated through experiments conducted in a laboratory scale horizontal tube furnace. Composite pellets of EAF slag (47?1%FeO) with coke, PET and blends of coke/PET (in four different proportions) were rapidly heated at 1550uC under high purity argon gas and the off gas was continuously analysed for CH 4 , CO and CO 2 using an online infrared gas analyser (IR). The extent of reduction after ten minutes, level of carburisation and desulphurisation were determined for each carbonaceous reductant. The results show significant improvement in extent of reduction, level of carburisation and desulphurisation of the reduced metal when coke is blended with PET.

Globally, major avenues available for dealing with waste Poly-Urethane (PU) are disposal at landfill sites and incineration. However, PU contains high levels of carbon and hydrogen that can be recovered for use as reductant in metal extraction processes. In this work the use of post-consumer PU as reductant for the production of metallic iron from iron oxide was investigated in a horizontal tube furnace through the composite pellet approach. Composite pellets were formed from mixtures of iron oxide and post-consumer PU. The iron oxide-PU composites were heated from room temperature to 1200 °C and then between 1200-1600 °C in a continuous stream of pure argon and the off gas was analysed continuously using an infrared (IR) gas analyser. Elemental analyses of samples of the reduced metal were performed chemically for its oxygen content using a LECO oxygen/nitrogen analyser. The extent of reduction was then determined at two temperatures 1200 °C and 1550 °C. Gas emission studies revealed the emission of large volumes of the reductant gas CO along with CO2. It is further demonstrated that post-consumer PU is effective at reducing iron oxide to produce metallic iron with complete reduction achieved in less than 4 min at 1550 °C. Keywords: Polyurethane, Composite Pellets, Infrared gas Analyser, LECO Carbon/Sulphur Analyser

Globally, millions of waste electrical sockets (WES) are generated annually. This category of waste material is difficult to recycle because they are thermosetting polymers which cannot be remoulded after setting. In this work, the reduction of medium grade Agbaja iron ore from Nigeria, by carbonaceous materials generated from WES was investigated through experiments conducted in a domestic microwave oven. Composite pellets of medium grade Agbaja iron ore (assaying ~74 % Fe 2 O 3 ) with WES were irradiated in a domestic microwave oven (Pioneer, Model PM-25 L, 2450 MHz and 1000 W). The reduced mass was characterised by XRD and SEM/EDS analyses and the extent of reduction after 40 min was determined. SEM/EDS analysis revealed a highly reduced mass with distinct peaks of elemental iron and this was corroborated by XRD analyses that confirmed the formation of metallic iron. The extent of reduction obtained after using WES as reductant was over 80%. Accordingly, carbonaceous materials generated from waste electrical sockets are effective reductants for producing metallic iron from the Agbaja iron ore.

The reduction of FeO-containing slag by blends of metallurgical coke and waste polypropylene (PP) has been investigated through experiments conducted in a laboratory scale horizontal tube furnace. Composite pellets of EAF slag (47.1% FeO) with coke, PP and blends of coke/PP (in three different proportions) were rapidly heated at 1500 °C under high purity argon gas and the off gas was continuously analysed for CO and CO2 using an online infrared gas analyser (IR). The extent of reduction after fifteen minutes, level of carburisation and desulphurization were determined for each carbonaceous reductant. The results show that FeO can be effectively reduced from EAF slag to produce metallic iron using waste PP and its blends with coke as reductants; improvements in the extent of reduction and levels of carburisation and desulphurisation of the reduced metal were observed when coke was blended with PP.

The pre-reduction of higher manganese oxides with post-consumer plastics as reductants has been investigated through experiments conducted in a laboratory scale horizontal tube furnace coupled with an off gas analysis through an online infrared (IR) gas analyser. Composite pellets of calcined manganese oxide (Mn 3 O 4 ) with high density polyethylene (HDPE) (at C/O molar ratios of 1?5, 2?0 and 3?0) were heated rapidly to 1150uC under pure argon and the off gas was measured continuously by an IR analyser for CO, CO 2 and CH 4 . The extent of reduction of Mn 3 O 4 to MnO was calculated from a mass balance for removable oxygen. Solid reaction products were characterised by scanning electron microscopy and X-ray diffraction analysis was used to confirm the presence of MnO. The results indicate that Mn 3 O 4 can be successfully pre-reduced to MnO using HDPE as a reductant. Gas analysis studies indicated that the polymer is first converted to CH 4 which cracked partially or reformed to H 2 , C and/or CO. Reduction of Mn 3 O 4 to MnO was subsequently effected by C, CO, H 2 and the residual CH 4 .