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By Hustwick I

New Zealand Steel Mining Limited operates two independent sand mining operations on the West Coast of the North Island of New Zealand. (Fig. 1)Waikato North Head 30km south of Auckland supplies ironsand concentrate as the raw feed for New Zealand Steel's works at Glenbrook, and Taharoa 70km further south, exports ironsand concentrate to Japan. Taharoa uses two sets of six low pressure Warman centrifugal pumps in series to load bulk ore carriers 3km off shore through two underwater pipelines.Waikato North Head delivers the ironsand to Glenbrook l8kms through a 200mm ID buried pipeline using two stages of high pressure positive displacement (HPPD) pumping.A high level of operating and maintenance expertise has been developed since commissioning the two systems which are proving to be reliable, efficient and of minimal impact environmentally.

Jan 1, 1990

By Jamsa-Jouneia SL, Lahteenmaki S

Sophisticated control systems require sufficient and reliable information from the process to be controlled. At the Pyhasalmi concentrator two novel measurements, a particle size indicator (PSI) and a mill level monitor (MLM), have led to significant progress in the control of the grinding circuit. The PSI and the MLM measurements have brought additional information from the process. The PSI has been an absolute prerequisite for determining the overall grinding circuit efficiency and the design of the integrated grinding and flotation control system. The MLM measurement has enabled studies on the volumetric filling of a mill to be utilised for maximising the mill throughput. The paper describes the operation principles of the PSI and MLM devices and the additional process information received. The results of a metallurgical pre-control audit are discussed and finally the design of the integrated control system is outlined.

Jan 1, 1993

The need for formalised geotechnical reporting has not been fully explored at many operations. With the continuing need to provide safer and more efficient workplaces, the requirement for good geotechnical reporting systems (as with other reporting systems) has become of greater importance.Historically, the risk from rockfalls has been the largest cause of fatal injuries in the underground mining industry. The response of the ground to mining is generally poorly documented at many mines. At Olympic Dam, it was found that the existing corporate hazard and incident reporting (HIR) procedure did not record enough specifics about geotechnical issues. A separate and more specific geotechnical reporting process was set up to address this problem.This paper examines the role that geotechnical reporting plays at the WMC Resources Olympic Dam Mine; from reporting and rectifying day-to-day geotechnical issues that affect the operation to documenting and analysing longer term trends.

Jan 1, 2004

By C J. McKenzie, D F. S Natusch

The lignite deposits of Southland and Central Otago are a potentially significant energy resource for New Zealand. Current estimates put the technically mineable lignite reserves at 5.3 billion tonnes, which is more than ten times the energy content of the Maui gas field. Thus, the strategic importance of the lignite as a basis for maintaining current levels of self-sufficiency in transport fuels, or as a possible feedstock for electricity generation, deserves full investigation. The full extent of the lignite deposits was only recently established as the result of a scout drilling programme undertaken between 1976 and 1979 by the Mines Division of the Ministry of Energy, and from companion studies conducted by the New Zealand Geological Survey. These discoveries of large quantities of lignite coupled, at the time, with rising oil prices, raised the prospect of their development for production of transport fuels.

Jan 1, 1983

By Anylmore M, Walker A, Fletcher A

Roasting of sulphide and sulph-arsenide gold ores produces unwanted emission of sulphur and arsenic oxides, and a less than complete recovery of gold. Pyrite loses sulphur and arsenopyrite loses arsenic at a useful rate at temperatures of 600¦C and above in an inert atmosphere. Sulphur and arsenic driven off can be condensed before entering the atmosphere. During the process, solid-solution gold redistributes itself on internal surfaces of the resulting iron sulphide. Two subsequent processing options may be used; direct cyanidation of the porous sulphide resulting from the anoxic pyrolysis, or a second-stage roast to oxidise the remaining iron sulphide. The first option may be viable under certain conditions of pyrolysis. The two-stage option has an environmental advantage over the traditional roast because it reduces oxide vapour emissions by 50 per cent. The second stage may provide nearly enough energy to sustain the entire process.

Jan 1, 1992

By Rivers CJ

The Brolga deposit is a Ni-Co enriched laterite, formed over intensly serpentinised peridotites of the Marlborough Block. Basement lithologies at Brolga consist predominantly of serpentinised dunite, with lesser massive serpentinite shear, gabbro and harzburgite. Investigation of the deposit has defined 17 different varieties of saprolite, ferralite (limonite), and ferricrete. Different combinations of these varieties form three distinct lateritic associations, the Hard, Soft and Dyke Associations. Recognition of key textural and mineralogical features in each association, an understanding of basement geology, and an awareness of current climatic conditions, suggest that: 1. both the Hard and Soft Associations have formed under relatively dry climatic conditions; 2. the Soft Association reflects much poorer groundwater drainage than the Hard Association; and 3. the Dyke Association has formed from a gabbroic basement, and has also been affected by restricted groundwater drainage, caused by poorly permeable marginal serpentinite shears.

Jan 1, 1996

By W Whiten

The determination of mineral composition is necessary in the mineral sands industry. Tiwest has developed a procedure for safe and convenient determination of the mineral composition using a magnetic separation followed by chemical analysis using X-ray fluorescence spectroscopy. This then requires the conversion of the elemental assays to mineral compositions. A project at the Julius Kruttschnitt Mineral Research Centre has developed a convenient analysis method for this conversion. This analysis is based on a reconciliation of the of the assays of the sample with the standard mineral assays by making minimal adjustments based on the assay accuracies to both sets of assays. As well as providing the mineral composition it to be tested for other applications and variations of the procedure to be evaluated. Given a range of samples, testing for the accuracy of the assays of the standard minerals, has been demonstrated.

Jan 1, 2001

Stereological transformation relies on knowledge of the textural characteristic that governs the relationship between the one-, two- and three-dimensional liberation spectrum. Transformation functions can be built from fractionation of real mineralogical particles. Alternatively, transformation functions can be built from simulated textures, geometrical textures or artificial textures. These transformation functions can be useful when the texture of an ore has not yet been characterised for the preliminary assessment of liberation. Recently, Lin et al (1995) developed a methodology for generating such an artificial texture. The artificial texture can be used to produce broken particles of known volumetric composition. Data from image analysis on several artificially generated samples is readily available, and can be used to build the associated stereological transformation function. In this work, the methodology for calculating the transformation function from LinÆs artificial texture is presented. The new texture is implemented for stereological transformation applications.

Jan 1, 2008

By Y Gu, W McCallum

Mathematically sophisticated methods are now in common use for metal balancing of complex separation flow sheets at many concentrators. These balances usually entail minimisation of the sum of weighted squares of data adjustments subject to flow sheet constraints. The adjusted data provides numerical consistency across the complete flow sheet to facilitate performance calculations. A mine with multiple ore sources can be considered as a flow sheet with the end node comprising the concentrator and its products concentrate(s) and tailings. If the mass transfer and grade estimates for each ore source are sufficiently reliable, a similar metal balancing approach can be used for combined mine and concentrator data. Comparison of balanced and measured assays and mass movements provides useful guidance to security of marginal grade ore and possible dilution problems. This paper includes a summary of results from a case study based on a mine with multiple ore sources.

Jan 1, 2002

The processes most likely to be adopted for beneficiating ores or concentrator streams containing a large proportion of particles finer than 10 um are froth flotation, selective flocculation, wet magnetic separation and selective leaching. Flotation will be made more efficient for very fine particles if ways can be found to selectively flocculate the valuable mineral beforehand (floc-flotation), to produce smaller bubbles and to reduce entrainment of ultrafine gangue. Schemes for selective flocculation have proved difficult to implement because of the delicate balance between surface forces (electrostatic, dispersion, hydrophobic) and hydrodynamic forces, that determines flocculation, and the changes which occur to particle surfaces through hydrolysis, oxidation-reduction and cross-contamination between minerals in aqueous suspensions. The search for a better understanding of selective adsorption of flotation collectors and flocculants continues and will be particularly important for the practical success of selective flocculation and selective magnetic coating.

Jan 1, 1986

Open pit planning and scheduling play a significant role in establishing, maintaining and improving the economics of open pit mining ventures.The development of an open pit plan and schedule involves consideration of the following elements:ò the market for the mineral, ò the mineral deposit,ò the treatment process, ò the external factors,ò the mining method,ò the scale of operations, ò the open pit design,ò the open pit schedule,ò the calculation of economic performance, andò the implementation of the open pit plan and schedule.The above factors are described and discussed. Open pit planning and scheduling is the linkage which enables a mineral deposit amenable to open pit mining to meet a market requirement for the particular mineral. To effect this linkage the open pit planner should have a good detailed appreciation of both the mineral deposit and the market.

Jan 1, 1992

A cry that is often heard from front-line employees, particularly as a mine grows or circumstances change is "We used to be one big team but now they have set up teams for different functions - we don't know what's going on and we don't share resources any more. We used to just get in and do what had to be done, now we can't.". It usually occurs after management decides that, with the increasing mine complexity, functions and accountabilities of a manageable size need to be identified and defined for individuals and teams to facilitate optimum performance. However, as the statement indicates, these changes have often not delivered all the intended benefits. This paper will explore the reasons why the full benefits have not been realised and will identify actions which can be taken to improve the likelihood of optimal outcomes.

Jan 1, 1998

Most Geologists have a well rounded knowledge of the exploration phase and those who have worked as mine geologists have an understanding of the production phase. Few have had exposure to the development and the construction phases. Even fewer have had the experience of closing a mine, disposing of the plant and equipment, carrying out the final cleanup and making the area safe and environmentally acceptable.During the various phases of exploration, the geoscientist gains a wealth of non-geological information which can be of considerable value to engineers and technicians in the feasibili-ty, development, operation phases and finally the closure of a project. Such basic controls as surveys, adopted assay sample lengths and the location of items of infrastructure during exploration, may continue to affect the project through its entire life. Thus the geologist's responsibilities extend well beyond the explo-ration phase of a project.

Jan 1, 1990

Exploration of a coal deposit provides the data on which a range of mine plans can be developed during project feasibility. The stages of exploration use methods and procedures which initially outline the deposit with more detailed data gathering and analysis of the specific site complexities. The in situ coal resource and reserves are calculated. The mine plan is a function of the mining method chosen and can have significant impact on the recoverable reserves. Other factors which can impact on the recovery of the reserves and the ability to maintain planned production levels are those which were either undetected during exploration or were misinterpreted. Exploration programs should be detailed enough to minimise to an acceptable standard the recognised and potential risks. Past programs which explored to achieve a minimum exploration density required to satisfy measured reserve status have generally proven to be inadequate, placing reserves and production at risk.

Jan 1, 1997

By Brenchley R

Partitioning behaviour studies for -particles in the 250 to 1,000 micron size range at. the Curragh coal preparation plant are presented. Plant surveys were conducted to compare the partitioning efficiencies of dense medium cyclones and froth flotation. The aim was to assess the potential for improving yield of coal by directing more of the top size of flotation feed material to dense medium cyclones. ovel mass balancing and model fitting NI procedures were used. While flotation offers high yield of low ash particles smaller than 500 microns, dense medium cyclone rejection .of high ash particles larger than 250 microns is superior. These strengths of the two processes are turned to good advantage by the use or desliming sieve bends which tend to perform some density separation on the'size fractions of interest, directing lower ash material to froth flotation than to the dense medium cyclones.

Jan 1, 1987

By S H. Marshall, H Hutcheson

Conventional batch cell and FASTFLOT pilot plant studies of reverse flotation of coarse marcasite and pyrite (100 - 400 μm) to reduce the sulphidic sulphur content of a rutile concentrate, were undertaken. The batch cell experiments found no significant improvement in sulphur removal with acid wash and copper activation of marcasite and pyrite. Batch cell trials also identified potential difficulties of conventional mechanical cell plants operated at 40 per cent w/w solids. The FASTFLOT 250 B-2 pilot plant trials indicated that with a 0.6 - 0.7 per cent w/w feed sulphur content, target product grade can be met on a routine basis by a three-stage FASTFLOT plant floating coarse marcasite and pyrite. The trials found that 150 g/t PAX dosage and 15 minutes conditioning time are adequate reagentisation for 40 per cent w/w solids feed to the FASTFLOT plant.

Jan 1, 1998

By D M. Weedon

This paper introduces a novel roll crusher design, which incorporates non-cylindrical crushing rolls. The use of non-cylindrical rolls enables the crusher to achieve a greater reduction ratio than is possible with conventional roll crushers. Referred to as the NCRC (non-cylindrical roll crusher), the new crusher incorporates two rolls comprised of an alternating arrangement of plane and convex or concave surfaces. The two rolls are complementary and arranged so that when they rotate the convex and concave surfaces of each roll are substantially opposed. With the rolls rotating in opposite directions at the same speed, this arrangement produces a gap between the rolls that remains approximately constant. Discontinuities on the roll surfaces provide improved angles of nip, which increase the probability of larger particles being drawn into the crusher. Initial tests on a scale prototype of the NCRC have indicated that reduction ratios exceeding 10:1 are achievable.

Jan 1, 2000

By Strickland R. E J

Heap leaching is establishing itself as an efficient method for the extraction of gold from low grade ore. It has the advantage of low capital costs, low operating costs and rapid startup. However, not all ores are amenable to heap leaching. It is only applicable to well oxidized ores that have reasonable permeability characteristics. Ore with excess fines or clay often display low permeability and are unsuitable for heap leaching.In this study, an attempt has been made to increase the rate of cyanide leach solution percolation by flocculating clay particles or reducing the surface tension of the leach solution. A wetting agent was found to decrease the rate of gold dissolution, possibly by presenting a hydrophobic surface to the gold particle. Flocculation of the clay increased the solution flow rate. The flocculation agent had no affect on the total gold leached but decreased the leaching rate.

Jan 1, 1992

By F Pothitos, S Hewson

The geological and geotechnical conditions at the Cadia Hill Open Pit are very complex. This complexity coupled with high mining rates has required significant technical input into the design and optimisations of the pit slopes, accesses, cutbacks and scheduling. A multi-discipline team of NML engineers, geologists and external consultants has been conducting comprehensive geological and geotechnical programs in order to achieve an optimum design of the pit slopes. Extensive data collection, analysis and interpretation has led to the formation of working geotechnical models of large structures, rock masses, and back-analysed slope performance charts. The current Cadia Pit Optimisation Project focuses on the risk-and-return principle for pit design and on the integration of geotechnical, hydrogeological, mining engineering and scheduling. The risk management for pit design has also been incorporated into the short term and long-term operation of the pit mining to ensure safety and production.

Jan 1, 2003

By Sorokin M. L, Komkov A. A

Flash smelting of nickel sulphide concentrate has been practiced at WMC's Kalgoorlie Nickel Smelter for 20 years. The mineralogy of the concentrate from the original mines was particularly suited to this process. However, taking a strategic view, potential new processing routes should be fully evaluated as possible replacements for the current technology. The Vanyukov process has been under development in Russia for the past 40 years and has been successfully applied on a large scale to the smelting of copper concentrates, at two locations - Norilsk and Balkhash. The potential for the application of the Vanyukov process to the smelting of nickel concentrates offers a number of processing advantages, including smaller reactor and decreased dependence on fuel oil. This paper reports on preliminary investigations into the application of the Vanyukov process to the smelting of nickel concentrates. At this stage the investigations are limited to semi-quantitative comparisons and modelling studies.

Jan 1, 1992