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During the construction of storage caverns, and during their lifetime if the use to which they are put so requires, it is necessary to provide adequate ventilation to ensure the safety and comfort of the underground workforce. An analysis of likely contaminants during construction has indicated that where a large facility is situated in a rock mass of even moderate temperature climatic conditions are likely to be the limiting factor during most of the mining operation and atmospheric pollution when blasting is undertaken. Possible options for improvement are increased air flow, cooling of intake air and reduction of the heat source by altering the number and type of haulage units employed in the cavern. Local solutions are an alternative approach where heat problems are confined to a few specific locations

Aug 1, 1994

By J. L. Robson, C. M. Bristow

mass flow rates of particles and air (the loading ratio).

Dec 1, 1994

By M. W. Robotham, H Wang

removal efficiency is analysed from a stochastic

Apr 1, 1995

By T. Yalcin

In the Box-Wilson method, the correlation between dependent and independent variables is represented by a polynomial response function, whose constant and coefficients are determined by applying regression analysis to the experimental data collected. The five levels used for each variable consist of a minimum, a maximum and three intermediate values. A study was carried out using Ni-Cu ore from Sudbury, Ontario, in which 15 experiments designed according to the Box-Wilson method were carried out in random order and in duplicate. The two sets of replicate data showed close similarity, with an overall variance of 0.311 for the five parameters studied. The response functions were used to optimise frother dosage, collector concentration and air flow rate and an experiment was then carried out under the optimised conditions; the results agreed closely with those predicted by the response functions

Jun 21, 1905

By P. Varona, L. Lorig, M. Board, E. Chacon

Geomechanical factors at the mine are important and will become even more relevant as the pit expands and deepens. To address these demands a team was assembled to collect geomechanical information and perform numerical analysis. The west wall is the largest and flattest of all the design sectors in the pit and rigorous studies were carried out on this wall. The wall behaviour is controlled mainly by a set of steeply dipping joints within the slope in the Fortuna Granodiorite and a weak zone, the Zona Plastica, that extends vertically near the pit bottom. These features lead to large toppling displacements in the upper portions of the wall. Two numerical models were used to reproduce the general features of failure observed in the wall. The modelling indicated that a toppling mode of failure results from shear on the steeply dipping joints. The toppling leads to slumping or landslides whereby the west wall flows slowly downslope as the Zona Plastica compresses

Apr 1, 1996

By V. Krupa, E. Lazarova

A method is proposed for the continuous calulation of a rock mass in real time while tunnelling with a TBM. Rock properties are investigated through models of the fracture stress under the disc cutters, the quasi-shear stress between the disc cutters and the specific energy of cutting under the disc cutters. Comparison of theoretical and monitored data of cutting specific energy can be used to determine theoretically the prevailing shape and size of the bulk debris. The shape and size of the chips from a given rock vary with the boring parameters. Introducing shape and volume corrections into the models of the evaluated stresses suppresses the influence of the boring regime and allows the rock properties to become dominant

Dec 1, 1996

By J. A. Finch, D. Lin

The robustness of the large-sections correction procedure, Hill's fast approximation, Barbery's correction and the PARGEN correction was examined by comparing their ability to reconstruct the true liberation distribution using sectioning data from computer-generated spheres. The results indicate that the flexibility of a correction procedure is related to the assumptions it makes about the continuity of the liberation distribution, locked-particle characteristics and ore texture. Overall, the large-sections procedure appeared to be the most generally applicable. The Hill fast approximation performed well, but this was probably because it partially incorporates the sphere model; the performance of the PARGEN and Barbery corrections varied from case to case.

Dec 1, 1995

By D. Newman

Mineral production in the Highlands and Islands of Scotland during the last ten years has been confined to the sporadic production of industrial minerals—for example marble, anorthosite, limestone, talc and silica. From 1962 onwards there has been an upsurge in mineral exploration in the Highlands, increasing in tempo from 1966 onwards due to the efforts of the Institute of Geological Sciences, the Highlands and Islands Development Board, and private and public companies. Geological, chemical and economic aspects of some of the more interesting mineral prospects are discussed: these include anorthosite, feldspar, magnetite, quartzite and brucite marble. Reference is made to a geochemical survey undertaken in the Rosehall district of Sutherland, the results obtained being summarised. Problems that affect the future of mineral exploration in the Highlands are stated.

Dec 1, 1971

By F. Tailoka

Bi was electrorefined from alloys containing 10-90 wt% Pb, together with Cu and Ag as minor impurities, in a basic cell and in a recessed-channel cell with 27.5:72.5 NaCl-PbCl electrolyte at 450-470 degrees C and 10 000-20 000 A/m2. The voltage in the basic cell was as high as 9 V, with some carryover of Bi to the cathode observed, whereas in the recessed-channel cell it was as low as 285-635 mV. Flow patterns observed in a room-temperature model indicated that the recesses provide both static liquid hold-up and good mixing of the alloy, enhancing cell performance in combination with the reduced anode-cathode distance of 0.90 mm. The purity of the resulting anode product is as high as 99.9%

Aug 1, 1995

By T. C. Alex, S Srikanth, Premchand

It has been suggested that reduction of the iron and manganese phases as far as FeO and MnO is preferred for the complete liberation and selective reduction of the copper, nickel and cobalt oxides in manganese nodules. The oxygen partial pressure/temperature regime suitable for this purpose has been delineated. Free-energy minimisation and thermogravimetric results indicate that the requisite conditions can be achieved if more than 10% of neutral oil is used at temperatures greater than 923 degrees C. Neutral oil content, temperature and roasting time have been optimised to maximise leaching recoveries of Cu, Ni and Co: up to 96% of Cu and Ni and up to 85% of Co can be recovered if 15% of neutral oil is used as a reductant at 973 K for 90 min

Jun 21, 1905

By G. G. Barbante

Anode slimes produced during copper electrorefining are a valuable source of silver, gold, selenium and tellurium. The conventional pyrometallurgical process for treating slimes involves preliminary leaching in sulphuric acid followed by smelting in a reverberatory furnace with fluxes, but it is slow and has many recycle streams. The chemistry of the phases and the reactions that occur in slimes smelting are poorly understood and and this prevents major improvements to the process. Laboratory-scale experiments were conducted using unleached slimes, with and without the addition of fluxes and under neutral, oxidising and reducing conditions. Results show that selenium is readily removed as gaseous selenium dioxide and that molten Cu-Ag-Se-O phases form when fluxes are added. Oxidation-refining of these phases by air injection and flux addition can result in the formation of silver suitable for further electrorefining

Aug 1, 1995

By W. P. C. Duyvesteyn, B. J. Sabacky

Reprinted with revisions from Extractive metallurgy of copper, nickel and cobalt, volume I: Fundamental aspects. ed. Reddy R.G., Weizenbach R.N. Warrendale, Pennsylvania: The Minerals, Metals and Materials Society, 1993. Development work on the Escondida process, concluding with the successful operation of an integrated leach-SX-EW pilot plant and a pilot flotation plant for the upgrading of leach residues, demonstrated that all major process objectives could be achieved. Extraction of 40% of copper in concentrates containing monovalent copper was achieved with essentially no oxidation of sulphide sulphur. The Cu contents of leach residues from four different types of concentrate were successfully upgraded to the original feed grades, giving a product that has potential as a high-quality concentrate for the smelter market. A compact solvent extraction section effectively recovered the ammonia lixiviant for recycling to leaching and selectively transferred Cu into a conventional acid sulphate electrowinning system. High-quality "six-nines" copper cathode was produced on commercial-scale stainless steel blanks, demonstrating that the process will be able to compete effectively in the premium cathode market

Dec 1, 1995

By D. C. Yates, G. V. Jolliffe

In the five coalfields of Staffordshire, there have been some 43 incidents of spontaneous fires and heatings which have required special attention in the past ten years. This total excludes incidents in the Thick Coal Seam of South Staffordshire, which was worked until 1967, and which was subject to an almost continuous series of heatings. The incidents have been classified to show the sites of occurrence, the contributory factors which may have caused them and the treatments applied to them. The remedial techniques, as practised in Staffordshire, are dealt with in detail, with particular reference to standard methods of stopping-off. Precautionary measures taken are described, including a "liability to spontaneous combustion" classification of all seams, and the setting up of an emergency organization with emergency stocks of materials and equipment. The paper is concluded by a few words on the organization and control at the time of an incident.

May 23, 1905

By L. J. Cabri

Although no complete mineralogical balances have been published, the background knowledge and proven, highly sensitive analytical techniques to produce them already exist. For PGE-Cu-Ni sulphide ores a combination of ore microscopy, image analysis and electron microprobe analysis with proton microprobe analysis of sulphides for Pd, Rh and Ru and ion microprobe analysis for Pt, Ir and Rh (in some minerals) should provide the necessary data when combined with reliable assays. Other sulphide ores, such as the Cu-Ni-(PGE) ores of Sudbury, Ontario, require a similar approach except that the ion microprobe would be more suitable for the analysis of Pd, Pt and Rh because of its greater sensitivity. Oxide-silicate ores may be harder to deal with quantitatively, although the potential to confirm the presence of trace PGE within silicates and oxides may be greater than in PGE sulphide and Cu-Ni-(PGE) sulphide ores. However, solid solution of PGE in oxides and silicates still requires thorough documentation and evaluation in terms of their significance for the overall metallurgical balance

Apr 1, 1994

By Xiao Min You, D. R. Swonbourne

Smelting of Cu anode slimes involves the use of a slag to hold the oxidised Cu, but some Ag is also inevitably oxidised to the slag. The solubility of Ag in sodium silicate slags at 1 100 and 1 150 degrees C has now been determined over a very wide range of oxygen partial pressures. Silver was found to be present in the slags both as neutral atoms and as AgO(0.5). The activity coefficient for atomic Ag was a very strong function of slag composition and temperature, whereas that for AgO(0.5) was much less affected by slag composition and was almost independent of temperature over the limited range examined. The results reveal that the dissolved Ag cannot be fully recovered by reduction of the slag with very reducing gases

Jun 21, 1905

By G. G. Barbante

An understanding of the thermodynamics of smelting copper anode slimes is a prerequisite for improvements to the process. During slimes smelting, a silver-copper selenide matte is formed and subsequently oxidised to silver metal. As part of a series of investigations, molten silver selenide matte was oxidised at 1 100 degrees C with pure oxygen. The chemical potential diagram for the system was developed and used for qualitative prediction of the results of the experiments. A simple, computational thermodynamic model of converting is presented, the adjustable parameters of which were determined by matching the model with the experimental results. The practical usefulness of the model was demonstrated by predicting the effect on silver recovery of smelting temperature and of using either oxygen or air as the smelting gas

Jun 21, 1905

By J. A. Hudson, D. L. Millar

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: Rock engineering system performance monitoring using neural networks.) Synthetic and analytical approaches to objective-based design of rock engineering projects are discussed. Rock masses are considered as complex dynamic systems with components that concurrently interact with each other and their environment. The existence of a rock engineering system canon (i.e. a set of systems governing rules) is proposed. Its possible components are highlighted and an application is demonstrated using a "rock mass automaton" designed to simulate dynamic heat distribution in rock. In the example given, the canon implements the basic result from probability theory applied to the thermodynamics of solids. Rock engineering system performance is reduced to the mapping of the output of a rockmass to varying input (design) options, within the state space of the systems model. The Kohonen Self-Organising Map provides an extremely useful analytical tool to reduce the hyper-dimensionality of rock engineering system behaviour. Further, the hyper-dimensional state vector is mapped "quasiconformally" such that the neural map tends to spatially organise similar input state vectors, facilitating interpretation of rock engineering system behaviour (performance monitoring). Work is reported on the development and validation of the automation as a basis for an internal representation of the rock mass bahaviour. The results are reported of simulations compensating for the uncertainty of the exact mechanisms operating within the rock mass, using additive noise with the input state vector in the training stages of the self-organising map implementation. Initial work on adopting Grossberg's Adaptive Resonance Theory neural network architecture for classification of rock engineering systems behaviour is also presented

Apr 1, 1994

By S. P. Mishra, G. R. Chaudhury

The adsorption of Cu2+ ions by Penicillium sp. displayed a dual rate, with an initial faster phase followed by a slower one. The adsorption rate increased with increasing pH due to chemical and biochemical reactions. The Cu-loading capacity of the biomass increased at higher initial Cu2+ concentrations. Above 40 degrees C the adsorption rate decreased which may be due to partial hydrolysis of biopolymers which are essential constituents of the cell wall. Adsorption kinetics followed the Freundlich isotherm and the equilibrium concentration that was calculated on the basis of the isotherm matched the observed value well. A series of theoretical adsorption curves were produced using mathematical correlations between the mass transfer coefficient, the Cu2+ ion concentration at equilibrium and at time t. The correlation between the theoretical and observed adsorption rates for different experimental conditions was good. It was concluded that the results from the study were best explained using a mass-transfer adsorption model

Aug 1, 1995

By S. G. Ozkan

An investigation was carried out into the effect of physical parameters, such as particle size of the sample, residence time, solid/liquid ratio and impeller speed in the flotation cell, on the solubility in soft tap-water of colemanite (calcium-bearing borate) from Emet, in Turkey. Solubility increased steadily with residence time from 5 to 20 min but only minimally thereafter. There was a similar increase with impeller speed from 500 to 1 500 rev/min, beyond which a solubility of around 1.05 g/l was again established. There was a slight decline in solubility as the solid/liquid ratio was increased from 1 to 30%, with stable values around 1.05 g/l at a 20% ratio, while a sharp decrease was observed with decrease in size down to the -20 micrometre fraction. The effect of solubility should be taken into account if the application of a wet-processing method is being considered for the ore, while it can also result in losses of material during handling and storage

Jun 21, 1905

By F. T. Da Silva

Concentrates of titaniferous minerals containing around 30 wt% Ta2O5 are processed hydrometallurgically by hydrofluoric acid leaching and solvent extraction, followed by the precipitation of hydrated potassium heptafluorotantalate. A fundamental study of the thermodynamics of this precipitation and recrystallisation was undertaken to increase understanding of the conditions most conducive to the production of pure, well-crystallised K2TaF7. Activity-pH diagrams for the Ta-K-F-H2O system explained the dissolution of Ta2O5 in fluoride solutions quite well and also the precipitation-recrystallisation of K2TaF7.H2O. X-ray diffraction and scanning electron microscopy confirmed the thermodynamic observations. It was concluded that the best precipitating agent for K2TaF7 from fluoride solutions is KF but a recrystallisation step in a HF environment produces purer, well-crystallised K2TaF7.H2O, eliminating oxy-salts and other impurities

Jun 21, 1905