Search Documents

By K Nilsson, G Cheong

Troy Resources NL acquired a 70 per cent interest in the Mina Sertpo gold project in Goißs State, Brazil, in 2001 following a successful bid for the highly competitive international tender of a tenement package put out by Western Mining Corporation (WMC). The Sertpo deposit is located on cleared grazing land 380 km west of Brasilia and is 30 per cent owned by Amazonia Mineracao Ltda, a private Brazilian company. It is a small high grade open-pittable orebody with a measured and indicated resource of 108 000 tonnes at a grade of 49.7 g/t for 172 500 ounces using a 2.0 g/t cut-off. Troy undertook the project management and development of the project while Amazonia managed the exploration activities and provided other services as required. The project development involved drilling metallurgical test holes, scouring the world to locate an available and suitable second-hand plant, and arranging shipping to andreconstruction in Brazil.

Jan 1, 2004

By P. D. Hodgson, G. L. Kelly, H. Beladi

"The formation of ultrafine ferrite by strain induced transformation is assessed using rolling and hot torsion experiments. These experiments are used to examine the impact of thermomechanical processing conditions and steel chemistry on strain induced austenite to ferrite transformation and the formation of ultrafine ferrite. The critical strain for dynamic strain induced transformation increased with increasing carbon equivalence, deformation temperature and austenite grain size. The deformation structure in the austenite grains changes with the thermomechanical processing conditions.Drawing on these results and the current literature, the important factors for the production of ultrafine ferrite are described and a mechanism proposed."

Jan 1, 2004

By A. Mainza

It is common practice in the mineral processing industry to use hydrocyclones for particle classification. However, classification in the UG2 platinum circuits using the hydrocyclone poses major challenges due to the differences in density between silica and chromite, the two major components of this ore. Silica,-the PGM carrying component, has an average density of 2.7 and the barren chromite component has an average density of 4.5. When conventional and flat bottom cyclone are used there is a misplacement of particles due to differences in density leading to inefficiencies in the classification by size. As a result of the density effect, coarse silica reports to the overflow, resulting in loss of recovery, and fine chromite reports to the underflow, resulting in loss of milling capacity and unnecessary production of fine chromite. A classifier based on a different concept was required in the classification of UG2platinum ore. The three-product cyclone, which is a hydrocyclone with two concentric vortex finders to produce three distinct products, has been tested in the UG2 ore application and indications are that misplacement of particles due to differences in the component densities can be minimized through the use of this unit. Industrial and pilot plant trials were conducted and indications are that the three-product cyclone can be installed to selectively produce a middlings stream that can be screened using Pansep screens to provide a screen oversize, which is predominantly coarse silica that can be preferentially reground to recover the PGM values contained in the coarse silica.

Jan 1, 2004

By N. Sano

The chromium oxide in stainless steel slags usually exists as Cr2O3. However, there is a possibility that it is oxidized to hazardous CrO3 after disposal or during use. Therefore, some technical developments to reduce chromium oxide by using a smelting reduction technique have been reported recently. This paper describes the fundamentals of the technique which have been applied to ferrochromium production and reviews the recent results in literature.

Jan 1, 2004

By S Smit, P J. J Strobo

ZINIFEX Century Mine is a zinc, lead and silver concentrate producer. Flotation is the primary method of minerals separation in this circuit. The flotation circuit is quite large with 79 flotation cells. The levels in each of these interconnected cells are controlled at more than 45 level control stations. Due to the multivariable interaction throughout the circuit, good level control was found to be difficult to achieve by just using normal Proportional-Integral-Derivative (PID) control. As a first step in advanced process control, the FloatStar Level Stabiliser, a multivariable controller developed specifically for flotation circuits, has been commissioned at Century mine to solve the level control problems. The first section of this paper therefore discusses and shows the results and improvements obtained by using the FloatStar level stabiliser. The results and benefits of the FloatStar Flow Optimiser are discussed in the second section of this paper.

Jan 1, 2004

By J. M. Font, R. G. Reddy

Jan 1, 2004

By K. G. Baxter, D. G. Dixon

The Sepon process plant utilises an autoclave to oxidize a flotation concentrate containing pyrite, residual copper minerals, and sulphur. The concentrate is produced from the residue of a preceding atmospheric copper leaching circuit. The function of the autoclave is to provide iron and acid for that atmospheric copper leaching circuit. The key issues in the operation of the autoclave are to maximise the production of acid and ferric ions and to avoid scaling issues related to sulphur balling in the autoclave. Scale control in the autoclave was examined using various dispersants and residue recycle without success. Operation of the autoclave at high temperature and high acidity addressed the scale issue through rapid oxidation of the sulphur and produced a ferric sulphate precipitate in the residue that could be re-leached to provide ferric iron. This paper presents the development steps followed, through batch and continuous piloting that resulted in an autoclave circuit design that addressed the above process requirements. Following definition of the process design basis, modelling of the autoclave operation was carried out to assist with engineering design. The model included thermodynamics and kinetics of oxidation of pyrite, elemental sulphur and covellite and also considered gas/liquid mixing, oxygen solubility as a function of temperature and solution composition, ferrous to ferric oxidation, gangue reactions with acid and precipitation/re-dissolution of basic ferric sulphate and alunite.

Jan 1, 2004

By J. Ekengård, H. Srinath, M. Andersson, P. Jönsson, D. S. Sarma

The present paper deals with mixing between the metal and slag phase during the ladle refining process, including vacuum degassing. Dispersion of metal drops in ladle slags has been studied. The results show a larger quantity of metal droplets in ladle slag during the alloying and stirring phase than during the subsequent vacuum degassing phase. The thermodynamic and kinetic aspects of the interaction between metal drops and the slag matrix have been considered and probable reasons for the observed distribution discussed.

Jan 1, 2004

By L. Chen, G. A. Brooks, S. A. Nightingale

The dissolution of alumina and magnesia has been investigated using laser scanning confocal microscopy (alumina) and a rotating finger apparatus (magnesia) to assess the effects of temperature, composition and forced convection on the rate of dissolution in CaO-SiO2-Al2O3based slags. The two techniques have differing strengths and limitations, and provide complementary methods for studying dissolution. Alumina dissolution was studied for temperatures from 1477 to 1577°C. Based upon the data, the rate controlling mechanism was thought to be mass transfer control in the slag. The diffusion coefficients for the alumina particles are estimated to be in the range 10-11to 10-10m2.s. MgO degradation for sample rotation speeds of 50 to 800 rpm at 1500 and 1530°C was studied for both congruent and incongruent dissolution. The results show that the rate of dissolution for this is primarily controlled by a diffusion mass transfer mechanism for congruent dissolution except at the highest rotation speed. For incongruent dissolution, the mechanism is much more complex, with the morphology and distribution of the spinel reaction product having a significant effect. At high speeds and prolonged times, mechanical forces played a major role in the degradation process. Keywords; kinetics, corrosion, refractories, dissolution rate, inclusions, mass transfer, slags, steelmaking

Jan 1, 2004

By Bob Turnbull

The dictionary definition of calibration is: to determine by measurement or comparison with a standard, the corre c t value for each scale reading on a device.1 As a consultant or blast contractor, you assess risk every day. But, have you considered the importance of, and the risks associated with the calibration of your seismograph and the accuracy that is p rovided? Can your calibration pro v i d e r back you up in times of trouble and provide documented evidence that the equipment was functioning within specification? Can their calibration pro c e d u res withstand independent scrutiny and be shown to be traceable to a National Standards for accuracy of measurement? These are important documents that in court provide tremendous support that blasting and monitoring activities are conducted professionally and competently.

Jan 1, 2004

By Yaw Boadi, Andrew McCallum, Sandy Gray, Yavuz Atasoy, Peter Wemyss

"Various full-scale test programs and installations of the InLine Pressure Jig (IPJ) have provided evidence that pre-concentration of the difficult to leach sulphide mineral through gravity can provide significant increases in economic recoveries. The continuous gravity concentrates are intensively treated either by re-grinding or Intensive Cyanidation. Data from various mine sites worldwide is presented. Treatment of complex ore bodies with this low cost methodology may render previously uneconomic ore bodies financially viable and assist in the recovery profile of transitional ore.INTRODUCTIONThe use of gravity is made extremely attractive in complex ore situations due to the low cost of operation, typically a few cents per ton operating cost and lack of chemicals.Gold mines which suffer from poor recovery due to complex mineralogy such as Stibnite, Arsenic, Carbon, Telluride, Silver and other pacifying agents such as Iron, which can form coatings, can all benefit from the process proposed in this paper. The key issue is not overall recovery as much as one of economic recovery. The key to this is maximised recovery at the lowest possible capital and operating cost. Other options such as flotation are reviewed but are not seen in many instances to be the panacea due to issues discussed in the paper. The use of the InLine Pressure Jig in the re-circulating load of the milling circuit is a cost effective means of recovering a sulphide/gold concentrate containing the complex mineral assemblages which require re-grinding and intensive leaching for optimised gold recovery.The benefits of Jig Assisted Grinding (JAG) are many and the challenge over the past years has been developing, understanding, implementing and evaluating the benefits of various flowsheet models. This has involved the reconciliation of results in plant scale trials back to the original laboratory test program. The following paper outlines the insights gained in this area through extensive work carried out by many people across both laboratories and plant sites in Australia and overseas. The examples in this paper are some of the work carried out on a few selected sites but similar work has been carried out on other sites such as Penjom, Granny Smith and Agnew. This work has eventuated in several installations which we believe have great importance in the future of the gold processing industry. They will lead the way forward to the modern all-gravity plants of the future.Compared to flotation, for the recovery of sulphides, gravity is a simple option. The simplicity generally translates to low capital and operating cost."

Jan 1, 2004

This paper provides a review of the chemical reactions occurring in the submerged arc processing of chromite ores. The excavations of industrial furnaces have shown that the charge, as it descends through the furnace, passes through a number of distinct reaction zones. Each zone is characterised by differing process conditions and reaction products. The phase equilibria, reaction steps and mechanisms occurring as the charge progresses through the furnace are examined, and the potential influences of these factors on the process outcomes are discussed.

Jan 1, 2004

By V. Mathebula

Paper written on project work carried out in partial fulfilment of B. Tech (Mining Engineering) degree The purpose of this study is to establish whether to mine the Bottom of Pit (BOP)/TOB 4 reserve before the commencement of the Block Cave or whether this should be disregarded and the reserve be extracted at the end of the life of the Cave. The primary goal of this report is to investigate and propose a practical mining method to safely extract the reserve given the set constraints. This report quantifies the additional revenue the TOB 4 will contribute to Finsch?s overall NPV thus enhancing Finsch?s business case and strategically enhancing the SBP. Several underground mining options have been investigated. The proposed mining method includes the installation of a series of extraction tunnels below the TOB 4 reserve from 53 level, with a slot access tunnel system. Ground will be loaded by LHDs from the draw points and tipped into 50-ton dump trucks at a transfer point, from there the ground will be transported to 53 level No. 1groundpass where it will join the existing ground-handling system. Primary development is scheduled to begin October 2002 and last for a period of approximately 7 months until early April 2003.The production is broken into 4 phases. Phase 1 is scheduled to begin mid-April 2003. The final production phase will be completed by November 2005. The production scheduling has been designed in order to remain ahead of the Block 4 undercut in order to ensure stability and safety. Due cognisance was taken of the health and safety of all employees concerned during the design of the mining and ground-handling processes for the Bottom of Pit. As far as is reasonably practicable, the BOP was designed and will be constructed and equipped to provide conditions for the safe operation of machinery and a healthy working environment for people underground. Relevant requirements of the Mine Health and Safety Act regulations pertaining to mining operations have been identified and adhered to during all phases of the design process.

Jan 1, 2004

By Ann Barron, Mark Abernethy

Along with the immense benefit of modern explosives seismic and acoustic effects caused by their detonation can be disruptive and alarming to many people. Claims range from affecting sexual performance to outright demolition of a residential structure. Regardless of the quality of the blast design and other precautionary measures, the inherent danger posed by the use of explosives often leaves residents searching for restitution. Consequently, many blasting companies today find themselves at the center of litigation. In the event that a blasting complaint proceeds to litigation your case will not be decided on “reasonable doubt” as in criminal trials. Instead, the jury will be instructed to decide guilt or innocence on a “preponderance of the evidence” presented. Even if you are able to present the best and most complete evidence that you have not caused the claim, the jury may rule in the favor

Jan 1, 2004

By R. W. Fedors, S. T. Green, R. A. Hart, D. B. Walter

Computational fluid dynamic (CFD) modeling of a potential nuclear waste repository drift may be an important tool to estimate moisture redistribution caused by natural convection within the drift. To refine and support CFD techniques, a small laboratory cold-trap experiment was developed. Results from numerical modeling of the laboratory experiment show the sensitivity of the bulk air flow rate and average air temperature within the drift to several key parameters, including various boundary condition assumptions and surrounding porous media properties.

Jan 1, 2004

By S. E. Olsen, K. Tang

Slag-metal and slag-metal-gas heterogeneous equilibria involving MnO-containing slags have been simulated using recently developed Mn-based alloy and IRSID oxide thermochemical databases. A large number of experimental equilibrium data have been used to verify the calculation results. The experimental slag-metal and slag-metal-gas equilibria in MnO-SiO2binary, MnO-SiO2-CaO and MnO-SiO2-Al2O3ternary, MnO-SiO2-CaO-Al2O3quaternary andMnO-SiO2-CaO-Al2O3-MgO higher-order system can be reproduced within experimental uncertainties. The influence of temperature, CO partial pressure and slag chemistry on the Mn-and Si-distribution equilibria have been quantitatively evaluated. This leads to a sound basis for optimizing the manganese ferroalloy production processes. Key words: MnO-containing slag, manganese ferroalloy, equilibrium simulation, thermochemical database

Jan 1, 2004

By B. Elevli

The aim of this paper is to demonstrate the implementation of multicriteria analysis in selection of the most suitable underground ore transport system for a chromite mine in Turkey. The related problem includes five possible ore transport systems and six criteria to evaluate them. The adopted evaluation and ranking method for this study is PROMETHEE. PROMETHEE I revealed a partial order of alternatives where incomparability exists. PROMETHEE II gave the absolute ordering of alternatives. The results have shown that the PROMETHEE method can be successfully used in solving mining engineering problems. Keywords: multi-objective, decision analysis, mining, ore transport system

Jan 1, 2004

By N. D. L. Burger, S. Thorley

In engineering design of operators? compartments, in underground mining equipment, ergonomics principles are often neglected or not given the full recognition they deserve. This paper defines ergonomics, applies it to machinery in an underground mining environment, and describes the ergonomics analysis undertaken during the design phase of an EJC extra low-profile mining loader. Encompassing the design of the operator?s compartment of this new loader, this paper illustrates the importance of ergonomic principles within the collective design process ensuring that it is fully integrated into the design approach. An ultimate aim of this study is to ensure that all future designs follow this route to guarantee not only the outcome of a highly efficient, cost effective and productive machine but that it is also takes the human factor into account, not only in maintenance but also in operation. Maximizing comfort will have the ultimate outcome of actually increasing productivity beyond expectations.

Jan 1, 2004

By M. Radwan, S. Shimada, S. Z. El-Tawil, K. A. El-Barawy, Y. Miyamoto

This study presents the results of synthesizing monolithic siliconoxynitride, Si2N2O, ceramic from a mixture composed of reclaimed silicon and natural desert sand by using the nitriding combustion synthesis method. Single-phase Si2N2O powder was prepared by the combustion of a mixture composed of silicon and pulverized sand in 3 MPa nitrogen gas. The combustion reaction completed in 2 min and the combustion temperature reached 1577°C.The as-synthesized Si2N2O powder is agglomerate of fine particles with sizes < 5 µm and has various morphologies; rod-like and irregular crystals, irregular kinking, hollow crystals and grown pseudo-hexagonal prismatic crystals. Porous Si2N2O compacts (24.5–47.1% porosities) were fabricated from the synthesized Si2N2O powder at different calcia-alumina additives (5–20 wt%) by normal sintering at 1500°C for 1 hr in N2atmosphere.They showed superior oxidation-resistance at high temperatures up to 1500°C in an oxidizing atmosphere of Ar/O2/H2O(70/20/10 kPa).Near-full dense Si2N2O compacts were also successfully fabricated from the synthesized Si2N2O powder with 5 wt% oxide additives by using the spark plasma sintering at 1600°C.DenseSi2N2O had good mechanical properties (18.7 GPa Vickers hardness, 3.3 MPa.m1/2fracture toughness and 363 MPa strength) and excellent chemical and oxidation resistance.

Jan 1, 2004

By L. Forsbacka, L. Holappa

Viscosities of quasi-ternary CaO-SiO2-CrOxmelts in contact with metallic chromium were measured by the rotating cylinder method up to 1750ºC. Twelve slag compositions were selected in the composition range 20–55 wt% SiO2, 10–45 wt% CaO and 10–60 wt% CrOx. Estimation of the amounts of CrO and Cr2O3was made by regression analysis based on the earlier data. Professor Iida’s (Osaka University) viscosity model was applied and model parameters (0CrO,CrOand Cr2O3) were evaluated. The Iida model gave good consistency with the measured viscosity values.

Jan 1, 2004