Waste Epoxy Modified Iron Oxide-Polymer Composite Pellets: Green Strength Development and Oxide Reactivity in Ironmaking Technology

The effect of waste epoxy blending with iron oxide-polymer composite pellets on mechanical compressive strength (crushing strength), nature of crushed pellets and extent of reduction of iron oxide in iron oxide-polymer composite pellet has been investigated in the laboratory. The mechanical compressive strength (crushing strength) of self-reduced pellets modified with and without waste epoxy was determined using a universal mechanical test equipment INSTRON 3369 operating at load cell 50 KN and crosshead speed 2mm/min. Gas analysis of the offgas was conducted on thermal decomposition products at 1600 °C using a continuous infrared gas analyser, followed by reduction studies at 1200 and 1600 °C. It was observed that incorporating waste epoxy into the green pellets results in significant improvement in the crushing strength from around 0.2 kN to over 4.0 kN. Additionally, green pellets with waste epoxy did not suffer from catastrophic pulverisation that was observed for pellets without epoxy. Gas measurements by continuous infrared gas analyser revealed significant amounts of the gaseous reducing agents CO and CH4 and minor amounts of CO2 as the major gaseous products from thermal decomposition at 1600 °C. Finally, the presence of waste epoxy in the pellet resulted in significant improvement in the extent of reduction of Fe2O3 by raw palm nut shell (PNS) and charred palm nut shell (CPNS), with measured extent of reduction increasing from 43.6% to 92.7% and from 63.3% to 96.9% at 35% replacement of PNS and CPS, respectively. Keywords: Waste Epoxy, Palm Nut Shells, Composite Pellets, Compressive Strength, Extent of Reductio

Production of Metallic Iron from the Pudo Magnetite Ore using End-of-Life Rubber Tyre as Reductant: The Role of an Underlying Ankerite Ore as a Fluxing Agent on Productivity

This research work investigated the nature of a nonmagnetic ore from Pudo in the Upper West Region of Ghana and its fluxing effect on the extent of reduction of the Pudo titaniferous magnetite ore using pulverised samples of charred carbonaceous materials generated from end-of-life vehicle tyres (ELT) as reductants. Reduction studies were conducted on composite pellets of the Pudo titaniferous magnetite iron ore containing fixed amounts of charred ELT and varying amounts (0%, 10%, 15%, 20%, 30%, 40% and 50%) of the nonmagnetic fluxing material in a domestic microwave oven and the extent of reduction was calculated after microwave irradiation for 40 minutes. Analyses by XRF, SEM/EDS and XRD of the nonmagnetic ore revealed an Ankerite type of ore of the form Ca0.95Fe0.95Mn0.1 (CO3)2. From the microwave reduction studies it was observed that premium grade metallic iron could be produced from appropriate blends of the Pudo iron ores using ELT as reductant, with a measured extent of reduction up to 103.8%. Further, the extent of reduction was observed to increase with an increase in the amount of the nonmagnetic fluxing material (Ankerite) that was added as fluxing agent.   Keywords: Ankerite, End-of-life Rubber Tyres, Fluxing Agent, Extent of Reductio

Production of Iron Nuggets from the Akpafu-Todzi Iron Ore and Artisanal Ferrous Slag using Post Consumer Thermosets (Waste Electrical Sockets) as Reductants

AbstractPost-consumer thermosets are difficult to recycle because, unlike thermoplastics, they cannot be remoulded to create other items as a result of the extensive cross-linkages in their structure. The increased production of thermoset blends and composites in recent years has greatly increased the amount of waste materials. However, higher levels of carbon and hydrogen present in thermosets make them a potential reductant in the iron extractive industries. In this research work, postconsumer thermoset was transformed into carbon resource through a charring process. The resulting carbonaceous material from the thermoset was used as reductant in the production of metallic iron from the Akpafu-Todzi iron ore and artisanal slag using the microwave technology through the composite pellet approach at varying firing times. Analyses by XRF, XRD and SEM/EDS showed that the Akpafu Todzi iron ore is comprised of the iron oxides hematite (Fe2O3) and wustite (Fe0.942O), while the artisanal slag was predominantly fayalite (Fe2SiO4). Complete reduction of the ore was attained after 120 min reduction but the maximum extent of reduction was 78.84% for the slag, demonstrating the potential of postconsumer thermosets to function effectively as a reductant in the iron extractive industry. Keywords: Reduction; Akpafu-Todzi Iron Ore; Post Consumer Thermosets; Waste Electrical Socket

Recycling Mixed Plastics Waste as Reductant in Ironmaking

One of the major obstacles to the implementation of an appropriate plastics recycling scheme is the inhomogeneity of many plastics waste. Accordingly, most of the existing recycling schemes require a feedstock that is reasonably pure and contains only items made from a single polymer type. However, in reality, waste plastics contain a mixture of plastic types, and are often contaminated with non-plastic items. This demands sorting out, which is expensive and highly labour intensive. In this work, the reduction of reagent grade iron oxide by mixed plastic waste (MPW) has been investigated through experiments conducted in a laboratory scale horizontal tube furnace. Composite pellets of reagent grade iron oxide (97 % Fe2O3) with MPW [consisting of 50 wt % high density polyethylene (HDPE), 30% polypropylene (PP), 10% low density polyethylene (LDPE) and 10% polyethylene terephthalate (PET)] were rapidly heated at 1520°C under high purity argon gas and the off gas was continuously analysed for CO, CO2 and CH4 using an online infrared gas analyser (IR). The extent of reduction after ten minutes was determined for each carbonaceous reductant and the results were compared with the extent of reduction by conventional metallurgical coke under the same experimental conditions. The results show that iron oxide can be effectively reduced to produce metallic iron using MPW as reductant. An improvement in extent of reduction was observed over metallurgical coke and the individual polymers when MPW was used as reductant. This eliminates the need to sort out individual plastics from municipal solid waste for their effective utilisation as reductants in ironmaking.Keywords: Reduction, Metallurgical coke, Mixed plastics waste, Extent of reductio

Sorption of Heavy Metals from Mine Wastewater by Activated Carbons Prepared from Coconut Husk

A study on sorption of heavy metal ions: Lead (Pb2+), Copper (Cu2+) and Cadmium (Cd2+) from mine wastewater by activated carbons prepared from coconut husk was conducted.  The activated carbons were prepared by carbonisation of the husk at 900 ºC pyrolysis temperature, followed by steam activation of the pyrolysis derived char. Activation was also performed at 900 ºC for various durations at steam addition rate of 0.2 mol/h/g in a Gas Fired Static Bed Pyrolysis-Activation Reactor. The derived activated carbons were contacted with mine wastewater containing heavy metal ions to assess their heavy metal ions adsorption potential. The results show that the activated carbons efficiently adsorbed the heavy metal ions from solution, reducing concentrations of  Pb2+, Cu2+ and Cd2+ from 1.56 mg/L, 1.87 mg/L and 0.69 mg/L respectively to below Ghana Environmental Protection Agency (GEPA) standards of  0.10 mg/L, 1.30 mg/L and 0.03 mg/L for Pb2+, Cu2+ and Cd2+ respectively. The significances of this study are that, the conversion of the coconut husk to activated carbons provides a solution to environmental problems associated with dumping of the waste and also provides valuable products capable of reducing the effects of heavy metals in wastewater.  Keywords: Coconut Husk, Activated Carbon, Heavy Metal, Adsorptio

Production of Gypsum from Clamshells and Waste Acid Recovered from End-of-Life Lead Acid Batteries

Gypsum exists in the Dihydrate (CaSO4 2H2O), Hemihydrate (CaSO4. ½H2O) and the Anhydrite (CaSO4) forms. The exploitation of the natural rock form deposit of gypsum is on the increase, necessitating the need to find alternative and efficient sources of gypsum so as to sustain all the industries dependent on gypsum as raw material. This work investigates the production of gypsum from clamshells and waste sulphuric acid from end-of-life car batteries. Clamshells obtained from the Volta Region of Ghana were calcined at a temperature of about 1000 ˚C with a view of producing CaO which was pulverised to particle size of 96 % passing 106 μm. Samples of the Pulverised Clam Shells (PCS) were then reacted with five different concentrations of the Waste Battery Acid (WBA). The reaction was observed to be very exothermic; a temperature of 101 ˚C was obtained for the 6.5 M concentration of WBA. The resulting mixture was filtered and an XRD analysis was performed on the oven dried residue to ascertain its composition. The findings from the work revealed that 100 g of pulverised clam shells produced an average of 58.08 g of calcined product and 134 g of gypsum. Peaks of SiO2 and CaCO3 in the XRD diffractogram of the gypsum indicated that the reaction between PCS and WBA was incomplete. Conclusively, the results from the XRD analysis showed peaks of the three forms of gypsum that was successfully produced. Keywords: Net Present Value; Internal Rate of Return; Sensitivity Analysis; Risk Analysi

Recycling of End-of-Life Polycarbonate as a Carbon Resource in Ironmaking

Globally, millions of end-of-life Polycarbonates (PC) are generated annually. Landfill disposal is one of the primary options for handling end-of-life PCs. There is a possible potential release of Bisphenol-A (BPA) from PC via hydrolysis or leaching when disposed at landfill sites. In this work the use of end-of-life PC as reductant for the production of metallic iron from Mbalam iron oxide was investigated in a horizontal tube furnace through the composite pellet approach. Elemental analysis of the charred PC shows a carbon content of (78.92 wt %) and hydrogen content of (7.07 wt %) which are reasonably above those of various forms of coals and can be recovered for use as reductant in metal extraction processes. Composite pellets of high-grade Mbalam iron ore (assaying ~97 % Fe2O3) with charred end-of-life PC were heated from room temperature to 800 °C and then between 800-1300 °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. Gas emission studies revealed the emission of large volumes of the reductant gas CO along with CO2. It is further demonstrated that end-of-life PC is effective in reducing iron oxide to produce metallic iron with reduction in oxygen content from 30.99 wt % to 0.0372 wt % corresponding to 99.88 % in less than 2400 s

Recycling Waste Polyurethane as a Carbon Resource in Ironmaking

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 Analyse

Recycling Waste Electrical Socket as a Carbon Resource in Ironmaking

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 % Fe2O3) 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. Keywords: Waste Electrical Sockets, Thermosetting Polymer, Agbaja Iron Ore; Municipal Solid Waste

Carbothermal Upgrading of the Awaso Bauxite Ore using Sawdust and Coconut Shells as Reductant

Ghana’s bauxite is exported in the raw state with no value addition. One way to achieve value addition is to carbothermally upgrade the ore into magnetic and nonmagnetic fractions, followed by separation using a magnet. This work investigates the carbothermal upgrading of the Awaso bauxite ore using reductant generated from locally available saw dust (SD) and coconut shells (CNS). Composite pellets of bauxite-reductant were prepared, air-dried and cured for 72 hours. The cured pellets were placed in a fire-clay crucible and heated in a custom-made gas-fired furnace for 30 minutes. The fired composite pellets were separated into magnetic and non-magnetic portions using a low intensity hand-held magnet. The various portions were then characterised using XRD, XRF and SEM analyses. XRD results showed magnetite as the predominant species present in the magnetic fraction whilst the non-magnetic fraction showed alumina as the predominant peaks along with some traces of unreduced hematite, silica, carbon and titania but no hercynite.  Keywords: Bauxite, Palm Nut Shells, Gas-Fired Furnace, Hercynite, Cha