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

Fosu, Allen Yushark; Fosu, N.; Owusu, Kingsley Bediako; Dankwah, James Ransford

doi:10.4314/gm.v16i2.8

2016

DOI: 10.4314/gm.v16i2.8

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

Allen Yushark Fosu

N. Fosu

Kingsley Bediako Owusu

et al.

Abstract: 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-cla… Show more

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Cited by 3 publications

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On the Direct Reduction Phenomena of Bauxite Ore Using H2 Gas in a Fixed Bed Reactor

Lazou¹,

Eijk²,

Balomenos³

et al. 2020

J. Sustain. Metall.

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The Bayer Process is the dominant industrial method to produce alumina from bauxite ore. Due to the generation of large amounts of Bauxite Residue (red mud), an alternative method, called the Pedersen Process, is of our interest. This process makes use of a combination of pyrometallurgical and hydrometallurgical techniques in order to prevent the Bauxite Residue generation. In the conventional Pedersen Process, iron in the bauxite is separated in the form of pig iron through a carbothermic smelting-reduction step which has a CO 2 emission similar to that during conventional iron production. In order to eliminate the CO 2 emission of this step, the focus of the present work is to reduce the iron oxides of bauxite ore by hydrogen gas (H 2) prior to smelting and minimizing the use of solid carbon materials for the reduction. The thermochemistry and the kinetics of reactions during calcination and direct reduction of a bauxite ore were studied by a thermogravimetric technique and in situ analysis of the gaseous products. The onset temperatures for the decomposition of bauxite components during calcination were determined. The kinetics of the reduction of hematite to metallic iron was studied and it is shown that the reduction of iron oxides to metallic iron starts at temperatures below 560 °C and it accelerates at higher temperatures. Moreover, it is indicated that the formation of hercynite (FeAl 2 O 4) phase retards the complete reduction at temperatures higher than 760 °C.

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On the Direct Reduction Phenomena of Bauxite Ore Using H2 Gas in a Fixed Bed Reactor

Lazou¹,

Eijk²,

Balomenos³

et al. 2020

J. Sustain. Metall.

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Enhancing Gold Assaying Crucibles in Ghana: Optimizing Fosu Clay Grog with Sintered Mullite for Improved Performance

Hou,

Gbologah,

Asante

et al. 2024

JERA

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Due to material and structural issues, fire-assaying crucibles used for analyzing precious metals in ores have encountered challenges related to poor thermal cycling in Ghana’s sub-Saharan region. This study aimed to enhance the crucibles by analyzing aluminosilicate minerals' multiphase development using X-ray diffraction and understanding the effects of composition determined by X-ray fluorescence on thermal behavior and water absorption observed through optical microscopy. The improved crucible design exhibited enhanced thermal cycling stability and lower permeability to the assay charge. Analysis showed that Fosu Clay (FC) demonstrated promise with a favorable Al2O3:SiO2 ratio and low impurities; mullite was identified as the primary phase formed at high temperatures, with quartz and cristobalite also present. Introducing 6% CSM dopant to FC increased the mullite content while supporting the transformation from quartz to cristobalite. The optimal crucible sample included coarse and fine-doped grog with an FC-clay binder, demonstrating excellent thermal stability, adequate porosity, and water absorption. Adjusting the percentage of doped grog further increased mullite content while reducing silica content; this suggests that locally produced improved crucibles are feasible through sintering commercial clay with mullite doping and precise composition adjustments.

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Compositional and Structural Deficiencies Causing Failure of Local Fire Assaying Crucibles in Ghana

Hou¹,

Gbologah²,

Asante³

et al. 2020

JERA

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Locally produced crucibles in Ghana experience dimensional failures during fire assaying of ores, therefore, even with a higher cost, imported crucibles are still the most preferred choice by laboratories in Ghana because of the stable performance of up to three cycles. Assay crucibles of locally manufactured, imported and theoretically composed were sampled and analysed via reverse engineering to identify factors that are attributed to the failure during use. Field investigation and compositional, physical and structural investigations were carried out using XRD, water boiling and SEM-EDS analyses, respectively. The results indicated that failure of the local crucible can be attributed to low mullite phase in both content and planes, which could ease the crack development and enhance the thermal stability of the crucible; non converted quartz into cristobalite, which stabilises the volume expansion coefficient during the fire assaying cycles; excess quartz content and absence of alumina content weakened the corrosion resistance against attack from the basic flux of litharge; and high porosity, allowed penetration of molten charge into the structure of crucible, leading to the dissolution of free silica content into the charge and causing structural failure. To overcome such deficiencies, higher firing temperature (~1240 °C), extra soaking time, and blending of high alumina contained clay/minerals were suggested.

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

Cited by 3 publications

References 12 publications

On the Direct Reduction Phenomena of Bauxite Ore Using H2 Gas in a Fixed Bed Reactor

On the Direct Reduction Phenomena of Bauxite Ore Using H2 Gas in a Fixed Bed Reactor

Enhancing Gold Assaying Crucibles in Ghana: Optimizing Fosu Clay Grog with Sintered Mullite for Improved Performance

Compositional and Structural Deficiencies Causing Failure of Local Fire Assaying Crucibles in Ghana

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