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
