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By J P. Wyethe, D P. Padayache, B R. Green

The development of an ion exchange process for the recovery of vanadium from solutions containing low concentrations of vanadium and/or slurries is discussed. The process can be used to improve overall vanadium recovery throughout the plant, and/or to reduce the vanadium concentration of waste materials prior to their disposal. The development of the process on a laboratory and miniplant scale is discussed, and includes:selection of a suitable resin with the desired loading and elution characteristics; laboratory-scale testwork to evaluate the use of the resin in both resin-in-pulp and fixed bed configurations; recovery of a high-value vanadium product from the resin eluate; and a preliminary techno-economic assessment of the financial viability of the process.

Jan 1, 2000

By E Jak

A viscosity model has been developed for both completely liquid and heterogeneous, partly crystallised slags in the Al2O3-CaO-æFeOÆ-SiO2 system in equilibrium with metallic iron. The Urbain formalism has been modified to describe the viscosities of the liquid slag phase over the complete range of compositions and a wide range of temperatures. The Roscoe equation has been used to describe the effect of presence of solid suspension (slurry effect) on the viscosity. The parameters of the viscosity model were optimised to describe large experimental data set in the low-order subsystems, as well as in the multi-component system. The computer package FACT was used for prediction of the proportion of solids and the composition of the remaining liquid phase. The model provides a good description of the experimental data (over four thousand experimental points) in liquid phase, and liquid + solid mixtures, over the complete range of compositions and a wide range of temperatures. This model can now be used for viscosity predictions in industrial slag systems. An example of the application of the new model to slag cleaning and reduction smelting processes is given in this paper.

Jan 1, 2000

In formulating its strategic plan in 1998 the New Zealand Minerals Industry identified two related critical issues facing it. These are, broadly speaking, the issues of access to minerals; and the perception the public has towards the industry and its behaviour towards the environment. This presentation will report on the Industry's response to the public perception issue. The Industry has, through the NZMIA Council, and its Communication and Website Committees, developed and implemented strategies covering: communication through the print media, and through its website www.minerals.co.nz, a long-term educational outreach programme with schools, focussing on the significance of minerals, their contribution to community wellbeing and the negligible long-term environmental effects of the Industry's activities.

Jan 1, 2000

By M Brooks, M Nelson

A fundamental study was carried out on super pit sulphidic gold ore to establish the most influential flotation characteristics which were subsequently used in the development of an optimum flowsheet to achieve best economical recovery of gold. In developing the flowsheet, consideration was given to existing operational constraints in the treatment of the Super Pit ore. The fundamental study also included an innovative diagnostic investigation to establish the location and value of gold in the major mineral assembly of the super pit ore from a metallurgical rather than a mineralogical perspective. This study mapped a metallurgical fingerprint of the major types of super pit ore in relation to the location and association of gold.

Jan 1, 2000

By S Brown

With oxygen conditioning routinely used in both the lead and zinc circuits at Pasminco Elura Mine a more sophisticated method of determining oxygen demand was required. It is known that different ore types have different oxygen consumption rates, however oxygen is added at a fixed rate regardless of ore type in the plant. Therefore, a simple laboratory test was devised to measure the oxygen demand of ores. The paper describes the technique employed, and provides an interpretation of the results. These data, together with pulp chemical measurements (Eh, pH and EDTA extraction data) were correlated against laboratory flotation performance to establish the relationship between oxygen demand and the position of the grade/recovery curve.

Jan 1, 2000

By D Craw, L C. Kerr, P Wopereis

Gold placers in the Nokomai and Nevis valleys are dominantly Quaternary in age. They occur mainly in western tributaries of the upper Nevis, eastern tributaries of the middle and upper Nokomai, and in the trunk valleys themselves. Placer gold in both valleys is dominantly a-phase Au-Ag-Hg alloy. Au-Ag alloy is absent or rare in most of the deposits, except in the lower Nokomai. Alpha-Au-Ag-Hg alloy is typically coarse-grained (up to 2 cm), angular, and rarely flattened or folded. Crystalline texture, quartz intergrowths, and psuedo-hexagonal crystal-pluck cavities are common. Fluvial transport distance predicted from the maximum Flatness Index ofAu-Ag-Hg alloy particles is typically less than 10-20 km. Coarse (up to 2 cm) cinnabar is commonly associated with the Au-Ag-Hg alloy, and both were probably derived from hydrothermal sources in western tributaries ofthe upper Nevis and eastern tributaries of the upper Nokomai. Minor secondary Au-Ag-Hg alloy occurs locally in the lower Nokomai, where it coats or cements detrital a-phase Au-Ag-Hg and Au-Ag alloy particles. Au-Ag alloy dominates over Au-Ag-Hg alloy in the lower half of the lower Nokomai alluvial plain and gravel of a raised channel incised into semischist basement adjacent to the plain. The Au-Ag alloy is rounded and commonly flattened and folded. Crystalline texture, quartz intergrowths, and pluck cavities are rare, and a fluvial transport distance of 25-40 km is estimated from maximum Flatness Index ofAu-Ag alloy particles. The Au-Ag alloy, three types of gamet, magnetite, clinozoisite and well foliated schist boulders in the abandoned channel are not found in the pumpellyite-actinolite facies bedrock in the Nokomai. These components were derived from greenschist facies schist and sedimentary sources in Otago, many tens of kilometers north of the Nokomai catchment. They were transported to the Nokomai either in Wakatipu Glacier till or fluvio-glacial outwash that entered the valley via Nokomai Saddle, the confluence with the Mataura, or both.

Jan 1, 2000

The economic viability of many Southern African massive mining operations is threatened by excessive dilution. In many operations currently in progress, some stopes are experiencing as much as 115 per cent waste ingress reporting to drawpoints. This paper examines the magnitude, causes and types of dilution and presents a set of general principles for the control of dilution in massive stoping operations.

Jan 1, 2000

An extensive study was carried out to evaluate the performance of Outokumpu OK50, OK38 and Maxwell MX14 cells at ComincoÆs Red Dog flotation concentrator in Alaska. Tests were conducted by varying operating conditions of the cells installed in different circuits in the plant. The hydrodynamic and gas dispersion properties were measured and the metallurgical performance of the cells was evaluated for each condition used in the tests. This paper highlights the importance of superficial gas velocity, bubble surface area flux, gas hold-up, power consumption, residence time distribution and froth flow behaviour in optimising cell performance. The findings of these tests provide valuable insights into selection of the best cell operating conditions to optimise circuit performance.

Jan 1, 2000

By I Mason, A Wellington, J Hargreaves

Many people are familiar with the use of marine echo sounders which are used by fishermen to monitor water depth and locate schools of fish. Similar technology has recently been used in some West Australian mines to provide detailed maps of ore contacts and other geological structures. Whilst drillhole intersections provide details of the location of a contact at a point, echo sounding can be used to obtain a continuous profile of the contact. A series of profiles together with drillhole intersection data can be used to build a more accurate geological model than can be inferred from drillhole intersections alone. The benefits of this are more complete ore extraction, less dilution and the ability to make more informed financial decisions. This paper presents a case history which demonstrates the successful application of the technology.

Jan 1, 2000

By R J. Norris, D J. MacKenzie

Gold-bearing veins have formed at a wide range of depths throughout the uplift history of the Otago Schist. The earliest gold mineralisation occurred during the later stages of Mesozoic metamorphism. This mineralisation was characterised by diffuse wall rock alteration with greenschist facies metamorphic or retrograde metamorphic mineral assemblages, and gold occurs in this altered rock. Quartz veins formed in .steeply dipping extensional fractures associated with this mineralisation type strike north to northeast. The Macraes mine exploits this deposit type. The present northwest strike of the mineralised zone at Macraes is a result of post-mineralisation deformation of the schistosity-parallel mineralised shear zone which hosts northeast striking extensional veins. This combination of schistosity-parallel shear zone and steeply dipping northeast striking veins may exist elsewhere in Otago, and this deposit type is most prospective. Steeply dipping quartz veins formed during post-metamorphic un-roofing of the Otago Schist strike northwest to west and occur as clusters of near-parallel structures in east and central Otago. These veins consist mainly of massive quartz, although some prismatic quartz occurs also. Breccia fragments in veins are common and these are generally silicified, with some gold. Wall rock alteration is negligible, and vein margins are sharp. A set of middle Tertiary veins occurs in northwest Otago. Most of these also strike northwest and dip steeply, but some strike northeast. These veins contain abundant ankeritic carbonate as well as quartz. The carbonate pervades adjacent wall rock as veinlets, but gold mineralisation is confined to veins. Quartz is commonly prismatic and vuggy, and contains gold, which is commonly coarse grained especially in silicified breccia zones. Associated veins contain stibnite. This vein type formed close to the paleosurface (>2 km). Mineralised veins in Marlborough currently strike northwest, but these have been rotated from northeast strike during Alpine Fault displacement of Marlborough from Otago. Some of these veins were formed under late metamorphic conditions and are similar to the north to northeast striking veins in Otago. As in Otago, this type should be considered to be most prospective if they have associated schistosity-parallel shears.

Jan 1, 2000

The 115-year history of the Hall-Heroult process for production of aluminium has been characterised by a sustained technology-driven improvement in costs and productivity. In the past decade the industry has effectively transferred best practice into older technology with improvements through computer control of the process, and redesign of cell linings using computer modelling . Incremental development is now at the point where diminishing returns will apply for further technical improvement effort however, until the gap between technical limits and current best practice is addressed through major process redesign. The process remains a long way short of its technical limits in energy consumption, carbon anode consumption, cell life and product purity. Investment cost in new capacity is very high, supporting the retention of older and less efficient technology and hence limiting the application of best practice in environmental performance and occupational health exposure. The industry is a major emitter of greenhouse gases yet the process has the potential to release oxygen as the primary waste. All of the above issues will be addressed in the new century, but only through commitment to the necessary long-term research and development that is required to achieve a redesign of the process.

Jan 1, 2000

By R G. Jeffrey

The Northparkes, Endeavour 26 orebody is a porphyry copperûgold deposit and comprises a moderately to well jointed rock mass characterised by gypsum veining, the intensity of which decreases with depth. The top 480 metres of the orebody is currently being mined by block caving, the undercut dimensions measuring 196 metres in length by 180 metres in width. Continuous caving was never achieved after the completion of the undercut thus cave inducement techniques were sought to maintain caving so as to safely sustain production. The use of hydraulic fracturing as a cave inducement tool was successfully trialled in December 1997 using existing exploration boreholes located midway up the current lift. Subsequent fracturing campaigns have enjoyed various degrees of success and have yielded in excess of seven million tonnes of ore at a significantly lower cost than conventional cave inducement techniques. Monitoring of both the hydraulic fracture system and the rock mass response has provided considerable insight into the geometry, growth and influence of hydraulic fracture networks above the Northparkes block cave, and has initiated additional research into the use of hydraulic fracturing in other mining methods.

Jan 1, 2000

By W J. Bruckard, M J. Vaisey

Ashton Mining Ltd (Ashton) and Lynas Corporation Ltd (Lynas) have established a joint venture partnership to develop and process rare earth oxides (REOÆs) from the Mt Weld deposit in Western Australia. The deposit is located in a deeply weathered volcanic carbonatite structure that contains approximately two million tonnes of rare earth oxides at an average grade of 20 per cent REO. As part of the 1999/2000 feasibility study currently being undertaken by Ashton and Lynas, an extensive laboratory beneficiation test program was undertaken by CSIRO Minerals on diamond drill core samples from the Mt Weld orebody. The aim was to develop a flowsheet, based primarily on flotation that could be confirmed at pilot plant scale. The target concentrate grade was 52 per cent REO with a REO recovery of at least 35 per cent. Two main ore types, nominated as CZ (limonitic siltstone) and LI (nodular limonitic ironstone) were identified for separate laboratory evaluation. The lower grade LI-type ore overlies the higher grade and more extensive CZ-type ore. The majority of the work was conducted on the CZ ore; only limited testing of the LI ore was undertaken. The latter contains a clay component that will present difficulties in processing due to its poor filtering and settling characteristics. Two processing options for treatment of CZ ore were presented for pilot plant consideration. One (Option 1) includes gravity concentration prior to flotation while the other (Option 2) includes finer grinding and four stages of open circuit cleaning. The benefits of each scheme are discussed in detail. Neither has been fully optimised and the definitive flowsheet is most likely to be a hybrid of the two schemes, incorporating the best features of each. Typical metallurgical results from each scheme were final concentrate grades of 49 per cent REO, 10-16 per cent Fe2O3 and 3.2-4.8 per cent CaO. REO recoveries were above 35 per cent in both cases. Features of the processes developed by CSIRO were the inclusion of a gravity concentration stage prior to flotation, a modified flotation reagent scheme, a change in the method of feed preparation, and incorporation of magnetic separation to upgrade final flotation concentrates. Metallurgical results obtained from flotation tests on LI ore were much poorer than those obtained for CZ ore. The best rougher/scavenger result, with the limited amount of testing so far completed, was an REO grade of 32 per cent with a recovery of 28 per cent. Further work is needed to develop a viable processing route for this ore type.

Jan 1, 2000

By R A. Medower

This paper provides a glimpse into the future of minerals processing with emphasis on æAutomation InnovationsÆ for the new millennium, particularly those involving advanced process control and innovative new applications of process control technology in 2007.

Jan 1, 2000

By J Zhiming, X Qian

All high stopes and pillars in Anqing Copper Mine were extracted by use of large-diameter longhole mining method. The height of stopes was 120 m. The forced mining was the leading concept that the safe and efficient operation was carried out in this mine, while the mining production was faced with the major technical problems on the stability of both primary ore pillars produced in the first-step stoping of stopes and the cemented fillbody on two sides of stope in the second-step stopping of pillars. Starting with mining technology, the authors emphatically describe the test results obtained in Anqing Copper Mine and make an approach to the deployment prospects and development trend of large-diameter longhole mining technology in China underground metal mines.

Jan 1, 2000

By S Dirdjosuwondo, R Plaisance, L Thoma

PT Freeport Indonesia, a subsidiary of New Orleans-based Freeport McMoran Copper and Gold of New Orleans, operates a large mining complex on the Western half of the Island of New Guinea in Tembagapura, Irian Jaya, Indonesia. The IOZ (Intermediate Ore Zone) mine, one of the underground orebodies, is mined by block caving. The area affected by the cave collects a large quantity of rain and ground waters mixing with fine rock particles. The mixture, commonly called æwet muckÆ, sometimes spills into drawpoints and makes the working environment hazardous to the loader operators. Wet muck is observed in an increasing number of drawpoints in the IOZ mine and remote LHD (Load-Haul-Dump) technology has been implemented to handle the ore. The driving force for this automation project has been the safety of the loader operators. The system has been developed mainly in-house and incorporates state-of-the-art features. Up to eight remote loaders and nine rock breakers are controlled from an underground control room located approximately 400 metres from the active extraction panels. The two underground crushers and nine conveyor feeders are also operated remotely from an adjacent control room. The development of FreeportÆs remote system has taken time and considerable effort. Not only the success of the IOZ mine was at stake but also the fulfillment of environmental commitments pertaining to the mill tailings. Approximately eight per cent of the mill feed must come from underground skarn deposits to neutralise the acid-generating tailings generated by the huge Grasberg open pit ores.

Jan 1, 2000

This paper presents a summary of tools and methods used for geotechnical assessments and monitoring systems at block caving mines. A critical review of these tools is given based on the authorÆs experience in block caving operations. The reviewed tools include cavability prediction, fragmentation evaluation, geotechnical monitoring systems, numerical stress analysis and others. Some of these tools have been developed under certain circumstances in particular mines and experience shows that their applications under different geological and mining conditions have often been difficult. Examples from block cave mines are also utilised in this paper to illustrate the importance of the further development of these tools, whilst possible improvements on these tools are also suggested.

Jan 1, 2000

The unique characteristics of the Target orebody and modernistic approach to mining present significant challenges and a concomitant high potential for new opportunities. The break-away from the traditional labour intensive mining methods improves both safety and productivity significantly. The intention of the paper is to illustrate the application of well known mining methods to the particular requirements of a complex orebody at depth. The evolutionary process followed to establish the final mining method design provides insight behind the finished product, and the modern approach to the planning and service principles equips the reader with a suite of mining engineering ideas.

Jan 1, 2000

By D Guibal, J Vann, M Harley

Many sample value distributions are highly skewed and present variograms with high relative nugget effects and/or short-range structures. In consequence, significant deskewing of the histogram and variance reduction occurs when transforming between sample and block support, where blocks are of significantly larger volume than samples. When making estimates in the mining industry we usually wish to estimate on the basis of block support rather than sample support. The selective mining unit (SMU) refers to the minimum support upon which ore/waste allocation decisions can realistically and practically be made. The SMU is usually significantly smaller than the sampling grid dimensions, in particular at exploration/feasibility stages. In a non-linear estimate, for each large block (by convention called a æpanelÆ) we estimate the proportion of SMU-sized parcels above a cut-off grade threshold. A series of proportions above cut-off defines the SMU distribution. Use of such non-linear estimates reduces distortion of grade-tonnage curves and provides a better basis for mine planning and economic decision-making. At present, Multiple Indicator Kriging (MIK) is the most widely used technique for performing estimation of recoverable resources. MIK is not the only approach available and it has some potentially serious limitations. The MIK technique is described and a number of theoretical and practical implementation issues are examined. In particular: MIKÆs assumptions about spatial distribution of grade; the behaviour of indicator variograms; application of change of support models; order relationship problems; and modelling the tail of the distribution. Some simple tests are described which allow us to determine the suitability of different estimators for a given deposit and criteria to identify a preferred estimator are also examined. Uniform Conditioning (UC), an alternative estimator which may be used instead of MIK, is described.

Jan 1, 2000

By F R. A Jorgensen, G W. Jensen

A pilot scale experimental investigation of the condensation of zinc vapour from smelter off-gases was performed in conjunction with a mathematical modelling study of the system. The work investigated the feasibility of using the high heat and mass transfer rates associated with a fluidised bed to condense zinc directly from smelter off-gases containing zinc vapour. Of particular interest was whether zinc would revert to zinc oxide during the process of condensation, and whether a zinc fog would form and be carried out of the condenser. A 0.1 m diameter fluidised bed condenser was mounted on the top of a 200 kVA DC electric arc furnace in which mixtures of vapours and gases were generated at 1150 - 1300¦C. The gas/vapour mixtures investigated included Zn/N2, Zn/N2/CO/CO2 and Zn/N2/H2/H2O. Greater than 90 per cent of the zinc was deposited on the zircon sand bed of the condenser, and there was no sign of zinc oxide formation, suggesting that the rate of heat transfer was faster than the reaction rate for zinc oxide formation. There was also no evidence that fog was being formed in the condenser. Using the methods of Kunii and Levenspeil (1991), a mathematical model was developed to predict the behaviour of the fluidised bed condenser. The model enabled the distribution of gas/vapour temperature and bed temperature to be determined as a function of distance from the condenser inlet. Similarly the partial pressure of zinc vapour in the gas mixture, and hence the mass transfer rate of zinc to the particles, was determined. Experimental data allowed validation of the predicted bed and gas/vapour temperatures.

Jan 1, 2000