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By Alesse V, Belardi G

A new class of collectors, Mercapto-Benzo-Oxazoles (MBO), exerting selective action on copper sulphides in the presence of Pb, Zn and Fe sulphides (galena, sphalerite and pyrite), has been synthesised in co-operation with Enichem's Donegani Insitute. The collectors have a mixed aliphatic-aromatic structure and contain functional groups which form chelates with copper. Some reagents of this class having hydrocarbon chains of various lengths have been laboratory tested on a complex sulphide ore containing chalcopyrite, galena and sphalerite in pyritic gangue. Comparative flotation tests have permitted selection of the best collector for chalcopyrite, namely Methyl-Mercapto- Benzoxazole (MMBO). Systematic flotation tests have been performed with this reagent, varying collector concentration, grain size of the feed, pH and flotation time. The results obtained show that the synthesised collector is much better than potassium-amylxanthate (KAX) as regards selectivity towards Pb and Zn. Moreover, it is possible to work at natural pH (6-7) and the flotation rate is higher. In fact in the rougher stage with 80 g/t of collector at natural pH, a copper grade of 7.14 per cent was obtained with a recovery of 73.87 per cent, while the grade with KAX did not exceed 2.11 per cent for a recovery of 73.54 per cent. The amount of Pb and Zn reporting in the copper concentrate was eight per cent and ten per cent respectively, while with KAX it was no lower than 24.34 per cent and 22.71 per cent in that order. After two minutes flotation a copper grade of 5.2 per cent with 52 per cent recovery could be attained, against a grade of 2.5 per cent and a recovery of 44 per cent in the case of KAX. The efficiency of this new collector has been ascertained on two samples of complex sulphide ores of diverse mineralogical composition.

Jan 1, 1993

During the 1960s chalcocite ore was mined from the Black Rock open cut. A large amount of this uneconomic material was not treated by the No 3 Concentrator at the time and as a consequence a surface stockpile was created which contained 750 000 tonnes of material at an average of 1.5 per cent copper.Laboratory trials indicated that due to oxidation, an average of 25 per cent of the copper was water soluble and the remaining copper was leachable using a sulphate/ferriclbacterial leach. On the basis of these trials it was decided to investigate the feasibility of producing copper via a leach SX-EW process. The investigation proved the process was feasible, so began the design, construction and commissioning of a 10 tpd (cathode copper) Copper Leach SX-EW Pilot Plant. CMPS Pty Limited in a joint venture with John Holland Engineering Pty Limited were awarded the turnkey contract for the design, construction and commissioning of the Pilot Plant.

Jan 1, 1993

The initially cautious approach taken towards ground support and reinforcement at the Porgera Underground Gold Mine in the Highlands of Papua New Guinea has evolved rapidly in the two years since stoping commenced. The confidence to continue the evolution process has grown from an increasing knowledge of mining conditions as stoping has progressed, to the extent that reinforcement requirements have decreased by 50 to 75 per cent depending on local circumstances. Changes to mining practices have significantly assisted and influenced this process.Empirical observations of ground behaviour, assisted by a deliberately selective extensometer monitoring program, provided the stimulus for early changes to ground support and reinforcement practices. Further optimisation of the ground support and reinforcement effort is being pursued through an active monitoring, measuring and analysis program. Ultimately, situation rather than site specific design will ensure continuing high quality ground support and reinforcement installations. However, local structural and lithological factors will continue to become more critical as the optimum position is reached.

Jan 1, 1993

By Nevolina VG, Zakharova IB

The results of a study on the flotation of baddeleyite and associate minerals are presented, together with effective flotation reagents. Detailed microcrystallomorphological analysis of the benefication products were made to find out the features of distribution of different baddeleyite generations between froth and chamber products. To reveal the dynamics of interaction of technological properties of minerals with their morphology and constitution, a method of onthogenetic analysis was used. It is well known that the difference between technological properties of the particles of the same mineral depend greatly on its genesis, but also the relation is direct - by means of constitution (habit). Thus, flotation behaviour of minerals depends on morphology microinclusions, distribution of impurities, dislocations and physical properties of individual particles. The microrelief of baddeleyite grains and crystals from froth and chamber products was studied with an electron scanning microscope. Chemical composition was determined by means of laser, microprobe and chemical analyses. The difference between baddeleyite generations, their distribution in benefication products, and the effects of grain sizes, number of inclusions and chemical compositions were valuated. Conclusions on baddeleyite flotation properties were made. Mineralogical study on eudialite grains from rough ore and eudialite concentrate was carried out. The interrelation between eudialite and associate minerals and negative effect of aegirine on technological properties of eudialite were revealed as well.

Jan 1, 1993

Martin Mining and Tunnelling Pty Ltd is a mining contractor with offices in Kalgoorlie, WA, Australia and Timmins, Ontario, Canada.Martin Mining and Tunnelling Pty Ltd offers services in mine contracting which include shaft raising, raise enlarging, excavation of rock passes and ventilating systems. It also offers the mining industry a unique mining method using the Alimak raise climber system.The Alimak raise climber system may be utilised in various types of orebodies, as the system is flexible to change. Sloping widths, drill hole patterns and changes in dip can all be accommodated with this method.This system allows for a highly productive, cost-efficient alternative to conventional longholing methods. This paper will focus on various aspects of the Alimak system which inherently make it a safe, viable method of ore extraction.

Jan 1, 1993

By Gutsche O, Kapur PC

Experimental data on the production of fines as a function of specific grinding energy consumption show that in general the energy utilisation in a choke fed high-pressure roll mill is higher than in a ball mill, but lower than in the single-particle mode of comminution under slow compressive loading. There is some evidence to suggest that the presence of water in feeds improves the energy efficiency of pressurised roll milling somewhat. Within a wide range of energy input, the size distributions of the ground product are self-similar, the logarithmic median size decreases linearly with the amount of fines produced and the inverse of the median size increases linearly with the energy spent. The production of fines as a function of energy expended follows essentially the same pattern as the one frequently encountered in media mills. The kinetics of grinding in the high-pressure roll mill can be simulated satisfactorily by modifying the standard particle population balance equation in order to account for energy dissipation in the tightly compressed bed. Common characteristics and important differences in grinding by the media mill and the high-pressure roll mill are highlighted.

Jan 1, 1993

By Krokhmai VS, Sayko OP

The paper summarises the theoretical and experimental studies which led to the development of new industrial equipment designed to recover liberated gold from placer gravity concentrates. The new technology is based on environmentally clean magnetic methods, which avoids use of mercury in the production process and obtains higher gold recoveries compared to the amalgamation technique, and which can reach 98.6 - 99.5 per cent. The complex of equipment thus developed is now commercially used at nine Russian gold mining operations. Six more such complexes are due to come on stream in 1993, some of them outside the CIS. The new technology appears to hold much promise for the recovery of precious stones (diamonds, rubies etc) semi-precious stones (pyropes, chrysolites etc) and also artificial diamonds, for which case there are encouraging laboratory results.

Jan 1, 1993

By Jin C, Shu H

The effect of operating parameters of a shaking table on the separation of mixed quartz-magnetite artificial feed has been experimentally investigated by use of laboratory-scale shaking table. Based on a great number of experimental data collected, the multi-variate non-linear model of shaking table has been developed. The model allows for the calculation of the product grade and recovery. A computer model has been programmed, for inclusion in a software package for the simulation and optimisation of shaking table if the feed characteristics and the concentrate grade are given.

Jan 1, 1993

The Mobile Miner MM130 (Figure 1) is designed to tunnel or mine in hard rock. It has a 4.1 m diameter cutterhead mounted on a horizontal axis which in turn is perpendicular to the line of the machine. The cutterhead rotates at 15 rpm and is supported on a boom which swings the cutterhead through a horizontal arc.

Jan 1, 1993

By Gonzalez-Dominguez J. A, Dreisinger D. B

At Cominco's Zinc Refinery at Trail, British Columbia impurities are removed from zinc sulphate electrolyte by a two-stage purification process using zinc dust. Copper, cadmium and thallium are removed in the first stage whereas cobalt is removed in the second stage. Cobalt removal kinetics are affected by soluble antimony and copper additions to the electrolyte. This study was focused on the kinetics of cobalt removal by zinc powder cementation. Experimental variables included copper and antimony concentrations, pH and temperature. Common organic additives employed in zinc plants were studied to determine potential interactions with the cobalt removal process. Cementation products obtained from laboratory experiments and plant practice were studied using SEM. A number of significant results were obtained: 1. Copper and antimony ions were sustantially removed from solution during the early stages of the cementation reaction (within the first 15 minutes). Cobalt cementation kinetics are slow and follow a first order kinetic regime. 2. A drop in the cobalt removal rates can be correlated with a rise in the Eh of the slurry. 3. Ligninsulphonate, Percol 351 and animal glue at levels of 2 mg/L significantly impede cobalt cementation.

Jan 1, 1993

Mining software systems have provided a basis for integration of resource, survey, and design functions. They can similarly provide a basis for incorporating ground conditions into the process.Exploration and mine geologists have a prime role to play in this process, extending their responsibilities further across the geological spectrum, into exploration of ground conditions, analyses of results, and assessments of their implications for mining. Ground conditions are as much a part of the geology of a prospect or mine as its mineralisation, and can have critical imnlicationa for mining.

Jan 1, 1993

By Basillo CI

The adsorption mechanisms of various thiol collectors can be subdivided into four classes: chemisorption, EC-mechanism, catalytic oxidation and metathetical substitution. The chemisorption mechanism occurs at potentials below the thermodynamic potentials for the metal-thiol compound formation and is reversible. The EC-mechanism occurs when the mineral is sufficiently oxidised to liberate metal ions to form metal-xanthates; therefore, it is observed with more easily oxidisable minerals and/or with collectors having large pK values. Thionocarbamates adsorb on sulphide minerals via the EC-mechanism due to their large pK values. Although the adsorption occurs at very low potentials as compared to xanthates, it is irreversible with large overpotentials. On the other hand, the adsorption of modified thiophosphates and thiophosphinates occurs near the thermodynamic potentials because of the low pK values. The metathetical substitution is believed to occur only when a mineral is highly oxidised. These classifications are useful for studying the effects of electrochemical potentials and the molecular structure on the collector adsorption Mechanisms.

Jan 1, 1993

By N E. Whitehead

An application to mine an ilmenite-rich sand deposit in Westland led to public concern about potential radioactive hazards should the ore be further processed to recover zircon or monazite. A review recommended that any material involved in the heavy mineral sand industry containing more than 0.05% thorium, uranium or their mixture should be considered a radioactive substance and, for mining purposes, a notifiable product. Safeguards for those occupationally exposed would operate via the Radiation Protection Regulations. The major safety requirement would be the minimisation of dust in certain operations.

Jan 1, 1993

By Barria J, Mencho J, Gonzalez GD

An extended Kalman Filter is used to build an on-line estimator of total ore, fine ore and water hold-ups in a SAG mill. In addition, an equivalent grinding rate from coarse to fine ore, as well as the discharge rates of solids (fines) and water are also estimated as part of the adaptation procedure of the model used for the Kalman Filter. The measurements used in the Kalman Filter estimator are the total mill weight provided by load cells, and inferred discharge flows of fines and water from flow and density measurements performed downstream. The net ore and water feed to the SAG mill are used as inputs to the estimator, and also the proportion of fine ore in the feed. As an example of how to introduce robustness in the estimation in the face of sensor bias errors, an estimation of the load cell bias error is introduced in the estimator, thus providing self calibration. The estimator presented in this paper has been tested by simulation using a detailed SAG mill mechanistic dynamic model comprising 27 size fractions well fitted to a pilot mill. The maximum error in the estimation of the operational variables - total and fine ore as well as the mill contents under different operating conditions - is about ten per cent.

Jan 1, 1993

By Behl S

Flocculation behaviour of six different dolomite samples, four from the Florida mining district, one from Perry, South Georgia and another from New Jersey was examined using polyethylene oxide (PEO) as a flocculant. The samples were similar in chemical composition, however the porosity of the samples from the Florida mining district was higher than the others. FT-IR, adsorption and surface modification by leaching revealed that flocculation was directly related to the presence of isolated hydroxyl groups on the surface. The adsorption mechanism was believed to be hydrogen bonding of the ether oxygen of PEO with isolated -OH sites on the solid.

Jan 1, 1993

The individual or company director who ignores his or her obligations under the Resource Management Act 1991 and under the proposed hazardous substances legislation, ignores them at their peril. Two recent cases in Canada and the United Kingdom concerning environmental offences under similar legislation illustrate the risks well.

Jan 1, 1993

By Mozley R

Contaminated sediments are a multinational problem. A crucial factor in solving an environmental problem is knowledge of, not only the amounts of polluted soil, the contaminants involved and their concentration, but also the historical background of the problem. Processing polluted soil is a tailor made activity based on rational decisions resulting from a detailed treatability study. Lack of information about characteristic properties of a specific sludge/pollution combination is the main obstacle in the route from first ascertaining that a particular harbour subsoil is polluted, to final identification of the full scale treatment plant. In the first instance, information must be generated regarding the distribution of pollutants in relation to the distribution of the original geophysical components. Based on this information rational decisions can be made on separation at a particular cutpoint and what sequential techniques should be involved for a certain fraction. For this purpose a `fingerprint method' is presented especially developed for investigation of polluted soil and sediments. The heart of the fingerprint method is a series of sequential hydrocyclone separations, by which a series of products is generated. The objective of the fingerprint method is to select an optimised treatment procedure in which the pollutants are concentrated in as small a volume of material as possible, leaving the bulk of the material clean. The pollutants can then readily be destroyed or isolated from the environment. The philosophy and advantages of the fingerprint method are demonstrated for a harbour sludge containing heavy metals as main pollutants. Hydrocyclone separation combined with flotation of both the coarse and fine fraction resulted in reusable and dischargeable products. Flotation of the fraction of fines was carried out by means of an experimental flotation cyclone enabling the selective recovery of mineral particles with diameters less than 10 microns. The overall conclusion is that design and engineering of treatment flow schemes for polluted dredged materials is a tailor made activity based on rational decisions resulting from the fingerprint information.

Jan 1, 1993

Mount Isa Mines' Hilton Mine was brought into large-scale production in 1990/91 at a time of sharply falling metal prices. To ensure the operation's survival and eventual prosperity there was an urgent need to reduce operating costs and increase revenue. A target of a 40 per cent increase in productivity over five years was set. Strategies to obtain the required improvements were developed on the basis of greater involvement and increased contribution from the workforce, major changes to the mining methods and the development and application of new technology. This paper describes the organisational, operational and technological changes that have been implemented at Hilton and presents the results achieved to-date.

Jan 1, 1993

By James DG, Turner JH

This paper describes laboratory testwork for the beneficiation of a medium grade iron ore, using Wet High Intensity Magnetic Separation (WHIMS). Factors leading to the selection of machine type for this method of separation are discussed and the design of the WHIMS section flowsheet of an iron ore beneficiation production plant are described including methods to achieve operational flexibility and adequate protection of the WHIMS separating chamber. The results of the commissioning and operation of the production plant over several years are described, together with experience developed in plant operation. Data on recovery of hematite over the full range of size fractions treated is presented and compared with data in the literature. Potential methods of improving plant performance are discussed. KEYWORDS: Iron ore beneficiation, plant design, wet high intensity magnetic separation.

Jan 1, 1993

By W C. Cook, S J. Mathews, A H. Purvis

The Golden Cross Gold Mine is located at the head of the Waite kauri Ri ver, 8 km northwest of Waihi near the southern end of the Coromandel Range. The mine produces gold and silver from epithermal veins hosted by Miocene andesitic flows and pyroclastics of the Coromandel Group. Golden Cross is owned in joint venture by Coeur Gold NZ Ltd (80 per cent) and Viking Mining Company Ltd (20 per cent). Mining is by open pit and underground methods. Mineralisation in a near-surface sheeted/stockworked vein zone is mined from the open pit. The deeper Empire Vein System is mined from underground where higher grade mineralisation is restricted to generally discrete veins. The open pit stockwork zone is west of and offset from the updip trend of the Empire Vein System. The Empire (hangingwall) Vein strikes generally north-northeast and dips steeply west. Dips become subvertical at greater depth. The hangingwall vein is a well developed, generally continuous structure with relatively high gold grades. A complex footwall vein system forms shallow west-dipping offshoots to the hangingwall vein. Structure and gold grades become increasingly erratic away from the hangingwall vein. The better developed footwall veins carry economic grades and high 'spot' grades over 50 g/t Au are not uncommon. Highest gold grades are associated with tightly crustiform banded sections of quartz veins and with dark fine grained siliceous breccias. The main hangingwall vein occupies a major north-northeast trending fault structure, the Empire Fault. Footwall veining forms within subordinate splinter fault zones. There has been extensive multidirectional pre-, syn- and post-mineralisation faulting. Fault manifestation is highly dependent on host rock characteristics. The central part of the hangingwall vein and surrounding silicified country rock has been shattered by a major fault structure, the West Mine Fault, forming a poorly consolidated, blocky quartz-breccia ore zone. Away from the more brittle ore zones and associated silicified envelope, wide clay-filled shears mark the major fault trends. Development of the deposit is considered to have occurred in two distinct stages related to separate episodes of dilational jog movement on the Empire Fault. The first phase reactivated the pre-existing Empire Fault as a dilational fissure with subordinate splinters on the footwall side. The Empire Vein System (hangingwall and associated footwall veining) formed during this phase. A second phase of renewed movement with further dilation resulted in more extensive fracturing of the Empire Vein and surrounding country rock and formed the sheeted/stockwork veining of the open pit. An upwards/westward migration of the hydrothermal system is assumed but fluid pathways between underground and open pit veining are unclear. Ore extraction and mining geology methods have responded to improved understanding of the grade and structural variability, and changing ground conditions inherent in the vein system. The underground mine produces ore from flatback cut and fill, post-pillar and bench stopes. Open pit and underground ores are campaign milled through a conventional CIP plant.

Jan 1, 1993