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By Yoon R-H, Luttrell GH

A theoretical model has been developed to predict the probability of particle collection by air bubbles in a quiescent flotation pulp. The model considers the effects of both hydrodynamic and surface chemistry forces acting during the bubble-particle interaction. Hydrodynamic forces considered include the gravitational, buoyancy, streamline and film thinning resistance forces. The surface chemistry forces considered include the electrostatic, dispersion and hydrophobic forces. The hydrophobic force has been estimated from extended DLVO theory. The model is capable of predicting hydrodynamic and surface chemistry conditions under which bubble-particle adhesion is possible. Validity of the model has been verified experimentally.

Jan 1, 1993

The 250 metric tonnes of gold and 360 000 metric tonnes of copper recovered from the Mt Morgan Mine in Central Queensland justify its fame. The mine ceased operation before the advent of three-dimensional computer graphical modelling of orebodies became common practice in mine planning. The Mount Morgan Mine records however remain and are the database for this study. The Mount Morgan project takes ore deposit modelling one step further by examining the relationship between grade distribution within the orebody and key geological features, as a tool for exploration and development.The Mount Morgan gold and copper mineralisation is shown to be strongly lognormally distributed. The deposit has been split into three areas, using geological boundaries, each with different geostatistical characteristics. Important features include: the spatial relationship of near-vertical, high grade shoots with a ring dyke thought to be related to the North Dyke; separation of the high grade eastern stopes from the others along the Andesite Dyke; and lack of concentrated mineralisation along the Slide Fault.Recognition of these features is useful to those currently exploring the Mount Morgan district for similar style deposits, by stressing the importance, or lack thereof, of the geological features.

Jan 1, 1993

A major high grade zinc deposit, Dugald River has fine-grained and complex mineral associations which provide considerable metallurgical challenges for both mineral dressers and downstream processors. A long history of metallurgical testing focusing on mineralogy and flotation concentrate production has shown that while separate lead and zinc concentrates can be produced at saleable grades, high levels of iron, and particularly manganese, are likely to place constraints on the marketing of zinc concentrate produced from deeper zones where coincidentally lode development is at its maximum. Testwork has focused on characterising the flotation response of ore types ranging from banded and stringer sulphides to brecciated ores in a variety of sulphide matrices. A high level of variability with lower than expected metal recoveries has been indicated across some of the higher grade brecciated ores. However, the dominant slatey breccia has generally provided the best results. Heavy media preconcentration testwork has been moderately encouraging and at this stage, although value adding downstream of concentrate production on-site is not seen as an economic option processing developments are being monitored on a broad front. Providing satisfactory means can be developed for handling manganese during downstream processing of the concentrate, it is not difficult to see a world-class operation emerging from the resource in the medium-term Future.

Jan 1, 1993

Studying the ore textures in a discrete orebody is a novel approach to estimating liberation potential of the ore minerals present. As part of a PhD thesis, this project aims at classifying and quantifying the textures of the Hilton North orebodies, and at estimating their liberation characteristics.

Jan 1, 1993

By Edmonds W, Giles C. W, Webb R. J, Gum J. C

Gold production from The Granites - Tanami Goldfield during 1993 is expected to exceed 8 t, eclipsing that of the traditional Northern Territory gold mining districts of Tennant Creek and Pine Creek. This is the result of dedicated and successful exploration, and the consequent discovery of new orebodies such as those at Dead Bullock Soak.Following granting of access to regional exploration areas in 1988 and identification of favourable host rocks in the Schist Hills area, North Flinders Mines (NFM) began a methodical exploration program of detailed geological mapping, rock chip sampling, costeaning and various types of drilling. The first resource of 600 000 t of 3.3 g/t gold was announced in mid-1989. This has grown progressively with systematic exploration to the currently published resource inventory of 6.6 mT @ 5.4 g/t, (as at 31.12.92) contained in six separate orebodies within the Dead Bullock Soak Mineral Lease at Schist Hills.

Jan 1, 1993

By Soldenhoff K, Levins D, Collier D, Day A, Secomb R, Brown S, Tapsell G, Bellingham A, Quan C

Bench and pilot plant studies were carried out at ANSTO to develop a process for rare earth recovery from the Mt Weld deposit near Laverton, Western Australia. This paper describes the development of the flowsheet, which is similar to conventional monazite processing, but with the introduction of several innovative steps to account for the complex rare earth mineralisation and the presence of specific gangue minerals. A unique feature of the flowsheet is the recovery of cerium by solvent extraction from a sulphate leach liquor. The process was tested continuously by the operation of a pilot plant at ANSTO's Lucas Heights Research Laboratories, Sydney in the first half of 1992. The plant, designed to treat 100 kg per day of beneficiated ore, confirmed the viability of the process, with rare earth products from the operation satisfying stringent buyer specifications.

Jan 1, 1993

The Mobile Miner MM130 was delivered to Broken Hill in February 1992. During March the machine was extensively trialled on the surface to test manoeuvrability, climbing ability and muck handling prior to being trammed underground in April. The first cutting test on 30 April 1992 provided promising results. The machine has undergone continual development since it arrived in Broken Hill with aims of ensuring reliability and achieving performance goals. The paper gives a detailed account of recent performance comparing this with the predicted Performance.

Jan 1, 1993

In process industries, time-dependent random fluctuations of raw material characteristics and mass flow rates in bulk material or pulp flows cannot be always prevented for different reasons, eg because of the geological situation (no uniform formation of the deposit) or/and because of technological reasons (segregation in bunkers or on stockpiles). Since a long time, there has been practical experiences that such fluctuations can have negative consequences, eg: ò fluctuations of the final products characteristics, ò higher expenditure for process control, and ò worsening of technological characteristics (recovery, sharpness of separation etc). In the literature, there can be found a lot of details as to, eg the improvement of the sharpness of separation in a jig in dependence on the raw material blending (Kubitza, 1981; Gathen, 1983) or the decreasing flotation recovery with increasing raw material characteristics fluctuations in iron and potash ore processing plants (Bubnova, 1978). Up to now, however, these consequences of random fluctuations, eg on the separation efficiency were not predictable theoretically. It could be shown by means of the general model for mechanical macroprocesses (Graichen, 1989), that the reduction of input fluctuations passing a blending facility can be calculated in this way. In this example, the steady state of the process is the wanted one, but, in general, the model is able to describe also non-steady states of the process regarded. On the other hand, the general model of mechanical macroprocesses has been used successfully for modelling separation processes, eg cross-flow and air classification (Molerus, 1969; Neesse, 1991; Senden, 1979; Tichonov, 1973). That is why it was tried to model the influence of input fluctuations on the separation efficiency, that means, the impact of non-steady states - as a consequence of random fluctuations - on a separation process. The models discussed in the literature are related nearly exclusive to the steady state of the process. The reasons for that lie in the (relative) simplicity of the models and the fact that the steady state is aimed at by means of blending processes under practical conditions - because of the advantages mentioned above. These models cited have proved to be superior to other models, since the basic general model for mechanical macropocesses makes possible the consideration of turbulence acting in the process unit and influencing the separation process essentially. This is valid also for modelling the turbulent cross flow classification, applied to mechanical classifiers and hydrocyclones, where the correspondence between the separation characteristics (cut size, separation sharpness) calculated and determined experimentally is much better than for other models.

Jan 1, 1993

Potential hlghwaJl mining reserves in Australia are large, but geotechnical and operating conditions are quite different from those where highwall mining has evolved in the USA. In order to achieve safe and effective resource recovery, equipment and procedures should be developed to penetrate 250 m in the Australian mining environment. This paper identifies key auributes to be incorporated in such machinery and methodology. These suggestions are intended to promote discussion on innovations to satisfy Australian requirements for highly productive, safe and environmentally acceptable techniques.

Jan 1, 1993

Traditionally, the Lead Lode at Broken Hill has been represented on presentation plans, cross sections and diagrams in scientific papers as a solid black mass, around which the more 'interesting' and 'structurally useful', wall rocks appear to wrap. Structural analysis of the Broken Hill orebodies has usually turned to these wall rocks to determine the structural history of the mineralisation.This tendency to represent the orebody as a massive single entity is incorrect and the aim of this paper is to illustrate that sulphide orebodies (in this case Lead Lode), are a dynamic part of the mine stratigraphy. They can preserve a great deal of useful structural information that can be recorded with detailed internal mapping.Three main categories of ore type are recognised in Lead Lode; Stratiform ores, Mobilised ores and Metasomatically altered ore. The ore types in these categories occupy or have formed in distinct structural and stratigraphic positions and have clearly recognisable inter-relationships.

Jan 1, 1993

By M Surtees

The Limpopo region in southern Africa is considered to be a favourable target for the discovery of base and precious metal mineral deposits. The integration of gravity, geomagnetic, LANDSAT data and geotectonic history is used to formulate an ore deposit model which can be used in the implementation of mineral exploration programmes. Field work was carried out to test and refine the model.

Jan 1, 1993

This paper addresses the role of mine geology in mining geotechnics. The role is assessed and discussed in terms of five main elements; geotechnical complexity, geological complexity, mine scale, percentage sampling and geological uncertainty. Lastly, the overall objectives and mine geology requirements are listed in terms of the various mine development stages; exploration, feasibility-design and operating.

Jan 1, 1993

By Wencai X

The conversion relationship between the Bond Work Index W1, specific output of mill and the energy efficiency of grinding were developed using dimensional analysis. These relationships were validated and the value of the conversion coefficient ~ was also obtained using a new installed device for measuring grindability of ores. With the new simulating algorithm the mill specifications, output and size distribution of grinding products of industrial mills can be calculated based on laboratory measured results. This algorithm is more accurate and simpler than any of the other empirical relationships. KEYWORDS: Conversion coefficient method, grindability, grinding Constant.

Jan 1, 1993

By Chen B

In recent years great efforts have been made in the optimisation of ball mill operation. This paper describes a methodology developed for modelling and optimising the steady-state grinding process. Thirteen basic similarity numbers of the process are derived. Based on these similarity numbers, we build a group of mathematical models which give a full description of the relation between dependent and independent variables. The parameter estimation and multi-objective optimisation of the grinding process have been done using these models, and validated with experiments in a continuous laboratory-scale ball mill.

Jan 1, 1993

The disadvantages of the present zinc producing methods, RLE and ISP, are high energy consumption and environmental problems. Therefore, efforts have been directed in Outokumpu Zinc towards the development of alternate routes. One interesting pyrometallurgical process to produce zinc is to inject zinc calcine together with a solid reductant into molten iron, saturated with carbon. This process has been studied by thermodynamic calculations, laboratory tests and mini-pilot test runs at Outokumpu Research Oy, Pori, Finland. The results of these tests are presented and discussed in this paper. The mini-pilot tests demonstrated that over 97 per cent evaporation of the zinc was possible using a reactive coal dust as the reducing agent. The recovery of zinc in the metal phase was at best 88 per cent of input zinc, but only part reported in molten lead in the splash condenser. The final metallic zinc contained at best 98 per cent Zn, the main impurities being dissolved lead and coal carried along with the flue dusts.

Jan 1, 1993

Over the 20 years to 1990 the Australian mining industry, presently worth some $A60 billion, generated a negative real rate of return (McDonald, 1992); not surprisingly under-performing the returns from bonds and industrial equities. Over this same period more than $A70 billion was invested in expanding the Australian mineral industry.

Jan 1, 1993

By Fuerstenau MC

Zinc cementation and carbon adsorption are both presently used for precious metals recovery from cyanide leach solutions. Each of these techniques exhibits unique processing features which renders them suitable to treat solutions with different properties and in different applications. In this study, the two processes are reviewed and compared. Operating data from a number of Merrill-Crowe precipitation and carbon adsorption plants in North America have been obtained and used in this analysis. The relative capital and operating costs for the two processes have also been considered.

Jan 1, 1993

By Buisman C. J N, Koch R. O

Soil and groundwater beneath the Budelco zinc production plant at Budel-Dorplein (The Netherlands) are contaminated with metals and sulphate. To avoid contamination of nearby drinking water aquifers in the very distant future, a geohydrological containment system (GCS) and a microbial treatment plant for extracted contaminated groundwater have been developed. As a first step in the design of the system groundwater data from over 150 wells and geological profiles were used to model geohydrological conditions beneath the site. Several configurations of water-extraction wells were deduced from the model. Data gathered during additional fieldwork were then used to improve the model. Finally results that were calculated for the various configurations were used to select an optimal groundwater containment system. Currently some 5000 m3/day groundwater are extracted from a combination of 12 shallow and deep wells. Heavy metals and sulphate have to be removed from the extracted water before it can be discharged into the river system or used as process water. Several water treatment methods have been studied and pilot-tested at the site. The preferred and selected process is based on the activity of sulphate reducing bacteria (SRB) and combines sulphate removal and heavy metal removal in one single step. The anaerobic bacteria reduce the sulphate to sulphide resulting in the precipitation of metal sulphides. A pilot plant gave promising results and a commercial-scale plant has been designed. The proposed design has been tested in a demonstration plant which included all main process units. Test results for all process units are presented. The collected information was then used to optimise the design of the commercial-scale plant. Special attention was paid to automation and safety items. Construction of the plant was finished in May 1992. Start-up, commissioning and operational experience are reported. The concentrations of metals and sulphate in the effluent of the SRB water treatment plant are well within the limits set by the authorities for discharge to public waters.

Jan 1, 1993

The availability of three-dimensional computer hardware and software makes the solid modelling of geological entities a realistic and logical alternative to previous sectional and plan 'models'.The success of underground mining operations depends largely on the ability to accurately predict the three-dimensional location and grade of mineralisation in order to maximise the extraction of resources and minimise mining dilution. The integration of lithological, geotechnical and grade models into three-dimensional solid models provides an excellent basis for underground mine planning and operation

Jan 1, 1993

By Leach T

The Tolukuma Gold Deposit is hosted by metamorphic and volcanic rocks, and igneous intrusions. Dilatant structures for the main veining appear to be provided by post-metamorphic flexure/faulting; syn-mineralisation tectonics is recognised from the en-echelon patterns of much of the veining. A SSE trending structure containing high grade mineralisation has acted as a major dilational zone within or at the contacts of porphyry intrusions. An ESE trend has controlled numerous dilational structures splaying eastward from the SSE vein structure and containing medium grade mineralisation.Early hydrothermal activity (Stage I) is represented by unmineralised, pyrite-rich brecciation and fracturing. Associated chloritic veining is indicative of single phase neutral-chloride fluids upwelling in relatively low fracture controlled nenneahility

Jan 1, 1993