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By E. Keskinkilic

Drying, calcination, prereduction, and smelting are the main steps in conventional crude ferronickel production. Industrially, these steps are conducted using the rotary kiln-electric arc furnace (RKEF) process. In this paper, calcination characteristics of Sivrihisar laterite ores from the Central Anatolia region are investigated. The extent of elimination of chemically bound water and other volatiles was studied by experiments conducted at various temperatures in the 250?800°C range. Phase changes were examined using X-ray diffractometry. For the particle size used in the study, 300°C was determined to be almost sufficient for complete transformation of goethite to haematite, and 700°C was required for effective elimination of all volatiles in the ore.

Jan 1, 2012

By J. P. Hoffman

This paper describes the metallurgical aspects and properties of a duplex austenitic-ferritic steel SAF 2205. As well as having high yield strength and hardness, SAF 2205 combines the high resistance of ferritic stainless steels to chloride-induced stress-corrosion cracking and the excellent resistance of austenitic stainless steels to hydrogen-induced stress-corrosion cracking. Its alloying elements contribute to its mechanical and corrosion properties as follows: nitrogen increases its pitting potential and improves its strength, nickel increases its resistance to pitting and its toughness, chromium and molybdenum give improved resistance to pitting and crevice corrosion. SAF 2205 has better resistance than steel types 316 Land 317 L both to pitting corrosion and to stress-corrosion. This makes it a very good material for pipes, tanks, and pumps in harsh environments such as those in petrochemical and desalination plants.

Jan 1, 1986

By B. N. Soutar

The design and operation of a double- V compartment vertical-flow settler by B. N. SOUTAR, B.Sc. (Mech. Eng.) Wits. (Visitor) This paper describes the development of a vertical-flow settler for underground pumping installations in the mines of Gold Fields of South Africa Ltd. The recommended settler employs the principle of 'dynamic filtration': the solids that are in suspension in mine water are filtered through a stable horizontal bed of flocculated particles, a technique that was established in about 1958.

Jan 3, 1977

By D. Visser

This paper is based on the Townlands Ore Replacement Project whereby the concept of conventional sinking of one large diameter shaft was declined and replaced with three smaller raise bored shafts. A wire line geophysical survey was done and the results indicated that a single shaft larger then 4 m diameter unsupported would not be suitable. The shafts were placed 28 meters apart measured from centre to centre. To ensure that the skin to skin pillars between the shafts remained regular and to minimise any deflection, the pilot holes were drilled with the Rotary Vertical Drilling System. The different shaft sinking methodologies are discussed explaining the risk associated with each method.

Jan 1, 2009

By Y. Tanaka, H. Miki, Y. Aoki, H. Okamoto, G. P. W. Suyantar, T. Hirajima

Due to environmental limitations and the scarcity of freshwater, flotation using seawater or desalinated seawater as process water becomes more common for mining operations. On the other hand, seawater has been reported to affect the flotation behavior of sulfide minerals. Few reports are available on influence of pyrite depression, recycled seawater and lime consumption on flotation by using seawater. In this study, the flotation tests were performed using ore sample to investigate the effect of pH with seawater and process water used in plant on the flotation behavior in a laboratory-scale flotation cell and a pilot plant-scale. The results of laboratory scale flotation indicated that copper and molybdenum flotation kinetics decreased with increasing pH. Furthermore, the iron (mainly pyrite) recovery decreased with increasing pH. The pilot plant-scale flotation test showed that water with a higher concentration of magnesium and calcium (plant processes water) consumed a higher amount of lime. Because of low lime consumption and high copper and molybdenum recovery and grade, pH 8 is suitable compared with pH 8.5 for flotation. Keywords: seawater, process water, copper-molybdenum rougher flotation, pH, pilot test

Jan 1, 2020

The 87th Annual General Meeting of the South African Institute of Mining and Metallurgy was held at Kelvin House, Johannesburg, on Wednesday, 15th August, 1984. Professor R.P. King (President) was in the chair, and declared the meeting open at 16h00.

Jan 1, 1984

By M. S. Shishvan, J. R. van Duijvenbode, L. M. Cloete, M. W. N. Buxton

Geochemical and mineralogical datasets from Tropicana Gold Mine, Australia, have been used to define ore fingerprints. VNIR/SWIR spectral data were represented by four normalised wavelength regions and were clustered to form spectral classes. Sequentially, these spectral class proportions within a block and collocated XRF data were clustered to form material types (fingerprints). The material types were related to an Equotip-BWi correlation. These correlations can be used to extrapolate a hardness signature and generate a BWi proxy for different blocks. The combined fingerprints and BWi proxy can assist as a tool for enhancing the prediction of comminution behaviour. They can explain specific domain-related hardness variations. For example, one material type could be separated into a softer (~15-18 kWh/t), and harder (>20 kWh/t) material blend. This was accomplished using the commonly overlooked VNIR region at 605 nm. This outcome has significance for blending strategies.

Sep 1, 2021

By T. Watanabe, S. Hayashi, M. Hayashi, K. Nagata, H. Fukuyama

Chemical states of fluorine in CaO-SiO2-CaF2glasses in a composition range of CaO/SiO2=0.5?1.3 and 5?25 mol%CaF2have been investigated by 19F solid-state NMR with and without MAS. The isotropic chemical shifts of the glasses are close to those of cuspidine crystal (59.4 and64.3 ppm with respect to C6F6) and CaF2crystal (58.6 ppm). The fluoride ions are coordinated with four or less than four calcium ions in this composition range. The chemical shifts move to the lower frequency with an increase in the CaF2content, whereas those are not affected by theCaO/SiO2ratio. The ionic distance between calcium and fluoride ions increases with an increase in the CaF2content. The chemical state of fluorine is not disturbed by the degree of polymerization of the silicate network. Comparing the MAS and static NMR spectra, the second moment attributed to 19F-19F dipole-dipole interaction has been estimated. The values of the glasses range over 3.1?7.3107Hz2andthose are larger than the calculated value of cuspidine crystal. This indicates that fluoride ions form Ca-F clusters in the glasses and that the size of clusters increases with increasing the CaF2content. Keywords: chemical state of fluoride ion, CaO-SiO2-CaF2glass, solid state 19F NMR spectroscopy

Jan 1, 2004

By Gaspard Devos

1. A NEW CONTEXT FOR METAL INDUSTRY Producers and owners of industrial extractive sites are living hard times due to Environmental pressure and liabilities. This is valid whatever the region in the world, it is just a question of time. On one hand, the normative environmental pressure is increasing through more severe regulations and controls on all pollution sources and production materials. [ ] Furthermore, more impurities are extracted and captured, more the volume of the related wastes is increasing. But disposal costs are increasing, disposal areas for wastes are restricted, markets for wastes are limited and technologies for waste treatment are, most of the time, not available. On the other hand, for most of the extractive industries, the costs required to get access to refine primary raw material are killing the profitability of the industry. Definitively, a technological and economical breakthrough is ongoing: extractive industries have to increase their feed from secondary material and to be involved more and more with the recycling business.

Jan 1, 2005

Limestone formations in the United States can be subject to relatively high horizontal stresses due to the existence of tectonic loading of the limestone strata. Underground limestone mines use the room-and-pillar method, in which 12- to 18-m-wide rooms are typically excavated. The stability of these excavations can be compromised by the horizontal stress, resulting in a rockfall hazard. Rockfalls are the cause of 15% of all reportable injuries in underground limestone mines. Horizontal stress related damage can occur in the form of guttering along one or more sides of an excavation, roof beam buckling or oval shaped roof falls, with the long axis perpendicular to the major horizontal stress. Numerical analyses show that the pillar layout and orientation of the mine workings have an effect on the horizontal stress distribution within the roof. The effects of high horizontal stresses can be mitigated by orientating the heading development direction parallel to the maximum horizontal stress, reducing the number of cross-cuts and offsetting the cross-cuts to limit the potential lateral extent of horizontal stress related roof falls. The modeling approach described in this paper can be used as a tool to evaluate potential roof failure and optimize the stability of room and pillar layouts.

Jan 1, 2008

By J. P. G. Pretorius, T. C. Partridge

The analysis of angular atypicality of lineaments as an aid to mineral exploration by J. P. G. PRETORI USc, M.Sc. (Pret.) (Visitor) and T. C. PARTRIDGE, Ph.D. (Natal) (Visitor) In an exploration project, data pertaining to 84000 lineaments in an area of 25 000 km2 were recorded. The total length of lineaments in intervals of one degree was determined. Angular intervals with Iow length densities were regarded as atypical. The proportion (by length) of lineaments with such atypical orientation was calculated for 5 km X 5 km grid squares. This index of angular atypicality was contoured and, used in conjunction with conventional photogeological techniques, contributed in a large measure to the success of the investigation.

Jan 5, 1974

ACCUMULATED FUNDS Balance at 30 June 1990 (Loss) income over expenditure for the year (63 154)

Jan 1, 1991

Balance Sheet at 30 June 1989 ACCUMULATED FUNDS Balance at 30 June 1988. Excess of income over expenditure for the year ended 30 June 1989

Jan 1, 1989

Balance Sheet at 30 June 1988 ACCUMULATED FUNDS Balance at 30 June 1987. Excess of income over expenditure for the year ended 30 June 1988

Jan 1, 1988

Balance Sheet at 30 June 1990 ACCUMULATED FUNDS Balance at 30 June I989 . Excess of income over expenditure for the year ended 30 June 1990

Jan 1, 1990

By W. D. Grimsley, R. P. King, J. B. See

Samples (15 to 20 g) of pre-calcined Mamatwan manganese ore or pure Mn 304 smaller than 48 mesh were reacted at temperatures in the range 1000 to 1300°C with samples of spectrographically pure graphite smaller than 325 mesh. Samples (1 g) of ore or pure Mn02 smaller than 48 mesh were reacted at temperatures of 1000 and 1200°C with pure graphite fines in argon, with graphite in carbon, .'1onoxide, and with carbon monoxide alone. In each case, the loss of mass as a function of time was recorded with a hermobalance. The rate and degree of reduction were found to increase with additions of carbon and with increasing temperature up to 1300oC, when they reached their maximum. The shape of the reduction curves, together with the results obtained from examination of the products of reaction by microscopy and X-ray diffraction, were used as the basis for a postulated reduction mechanism. Some details are given of an initial kinetic model that was used to verify the proposed mechanism. It was found that the reduction of Mamatwan ore by graphite at temperatures in the range 1000 to 1300°C occurs in two stages: (i) an initial stage during which the higher oxides of manganese are rapidly reduced to MnO with concurrent formation of CaMn2O4 and (ii) a longer stage during which CaMn2O4 and MnO are reduced to carbides by carbon dissolved in the ferromanganese phase.

Jan 1, 1978

By G. L. du Plessis

This paper describes the design, installation and operation of an endless rope haulage system recently built for and commissioned at Evander Gold Mines in Mpumalanga, South Africa. The factors which lead to the choice of such a system and the advantages gained over more commonly used winding systems are outlined.

Sep 1, 2001

By A. P. I. Popoola

Aluminium AA1200 was laser alloyed with a combination of nickel and titanium diboride using different weight ratios. Chemical reactions took place with the formation of different phases. The characterization of the alloyed surfaces was carried out by x-ray diffraction (XRD), optical and scanning electron microscopes. The alloyed surfaces are composed of the initial phase of Al-Ni dendrites and eutectics of TiB2/Al and TiB2/Ni distributed on the initial phase. Experimental results obtained showed that Al-Ni intermetallics brought about a significant increase in the hardness property of Al; however, these intermetallics are highly brittle and prone to fail by brittle fracture or stress corrosion cracking when put in service. The addition of TiB2 brought about a reduction in the formation of the seintermetallic phases. A microhardness increase of over 10 times the hardness of the substrate was achieved. Keywords Dendrites, intermetallics, metal composite, Nd: YAG laser.

Jan 1, 2011

By M. Sciarone, B. Collins

The production, properties, and selection of ferrosilicon powders for heavy-medium separation by B. COLLlNS. B.Sc Eng. (Rand) (Fellow). T. J. NAPIER-MUNN. B.Sc. (Eng.). A.R.S.M. (Visitor). And M. SCIARONE. M.Se. Eng. (Delft) (Visitor). There are basically two types of ferrosilicon powder available to operators of heavy-medium plants in South Africa spherical and milled grades. The production processes are described, and the properties of the two types are examined and compared. Guidelines are given for the selection of the correct grade of ferrosilicon for any particular application.

Jan 12, 1974

By Jacolien P. Wyethe

Zincor uses a Roast-Leach-Electrowinning circuit to process zinc sulphide concentrates. It also processes zinc oxide fume, originating from a slag smelting operation in the Democratic Republic of the Congo (DRC). Zincor achieved an average zinc recovery of 90.3% during the period January 2006 to May 2007. The bulk of the losses occurred in the iron and lead silver residues, both as soluble and un-dissolved losses. The un-dissolved losses in the iron residue constituted around 33% of the total zinc lost from the circuit, and were largely attributed to the presence of zinc-ferrite in the calcine used for neutralization during iron removal. As part of Zincor?s continuous improvement programme, the un-dissolved zinc losses in the iron residue were targeted by: the partial replacement of calcine with zinc oxide fume (from the DRC); and the preferential use of ?low-ferrite content calcine? as neutralizing agents in the iron removal circuit. These initiatives, coupled with other operational factors, resulted in a marked improvement in recovery to 92.6% during June to December 2007. The zinc oxide fume, directly fed to the circuit, required investigation of the halide rejection capacity of the Zincor circuit. Rejection of chloride via the magnesium bleed operation was considered adequate. Fluoride was mainly rejected via the iron (~70%) and lead silver (~27%) residues. Fluoride rejection via the lead silver residue varied significantly, probably as a result of variations in the sparingly soluble CaF2 content in the feed. The mechanism for fluoride rejection in the iron residues is uncertain. The fluoride rejection capacity of the Zincor iron residue (comprising of mainly jarosites, schwertmannite and ferrihydrite) at 2 ? 4 mg/L F in solution, was estimated at 0.14 ? 0.19 kgF/tFe residue.

Jan 1, 2008