Studies into the nature of Akpafu-Todzi iron ore and its response to reduction using waste polymers.

Abstract

This work is to study the nature of Akpafu-Todzi iron ore and how it responds to carbothermal reduction using waste polymers under microwave irradiation and gas heating. Physical analyses such as particle size distribution, tumble and abrasive index, porosity, bulk density and Bond work index were performed on the as-received sample. Pulverised samples of the ore were then characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopic (SEM) analyses. Reduction studies were conducted on the ore using waste polymers (High density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and their various blends biomass (saw dust (SD), palm nut shells (PNS), coconut shells (CNS)) as reducing agents. The results from the XRF, XRD and SEM analyses of the representative sample showed that the Akpafu-Todzi iron ore is of a low-grade hematite with an average Fe content of about 43.91 wt%, high gangue material (SiO2+Al2O3) and no deleterious elements (sulphur and phosphorus). The values obtained from the bulk density and porosity test showed a strong negative correlation between the two with average values of 3.3 tonnes/m3 and 12.2% respectively. The mechanical test showed that Akpafu-Todzi iron ore has Tumble Index value > 93.97 wt% and Abrasion Index value < 4.0 wt%. These values indicate that Akpafu-Todzi iron ore will produce little or no fine particles when it goes through the various processing stages. Results from the reduction studies showed that iron ore samples responded very well to the carbothermal reduction using various waste polymers under the various energy sources utilised. The highest extent of reduction recorded was approximately 98%; it occurred after 20 mins with saw dust as reducing agent and microwave irradiation as the mode of heating. Rate of reduction for microwave and “Sika Bukyia” gas heating sources were 0.00948 g.s-1 and 0.00427 g.s-1 respectively. This implies that the reduction process of Akpafu-Todzi iron ore can record high productivity within a short period of time. Akpafu-Todzi iron ore was found to satisfy the commercial physical requirement but did not satisfy the chemical requirements for the Corex, blast furnace and the major direct reduction processes (Midrex, HYL III and SL/RN). The ore was found to be suitable for composite pellet formation which could be used as feedstock for smelting reduction, microwave reduction and locally design furnaces