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By M. Moinpour, Y. K. Rao

The catalysed direct reduction of copper sulphide with carbon and lime was investigated in the range 850-1000 degrees C using Cu2S-CaO-C and Cu2S-4CaO-4C reaction mixtures. The effects of the catalytic additives K2CO3, Li2CO3, Na2CO3, NaF, Na2SO3 and the ternary eutectic (K,Li,Na)2CO3 were determined. Potassium carbonate, sodium fluoride and the ternary appear to be the most effective catalysts for the direct reduction process. The rate enhancement of the catalysed carbothermic reduction of copper sulphide in the presence of lime was explained in terms of the catalysis of the Boudouard reaction

Jul 1, 1991

By R. O. Suominen, P. A. Taskinen, K. R. Lilius, A. T. Jokilaakso

Chalcopyrite concentrate was flash-oxidised in a laminar-flow furnace in oxygen-nitrogen atmospheres that ranged in composition from N2 to N2 + 50 vol% O2. Gas pre-heating temperatures were 500-1100 degrees C and four particle-size fractions were studied: 28-38, 38-44, 44-62 and 62-74 micrometres. The effect of the residence time of the particles on sulphur removal was studied in the range 0.1-0.35 s. Scanning-electron microscopy combined with energy-dispersive analysis and back-scattered electron analysis was used to determine the morphology and mineralogy of the reacted particles. Total desulphurisation was achieved under the most oxidising conditions. Particles were observed to undergo fragmentation during oxidation, the violence of this depending on the iron and sulphur contents and the original particle-size fraction. The melting and/or reaction stages of the particles under different conditions were studied in powder samples. Polished sections were examined to follow the development of porosity and the mineralogy of the particles. A model for the fragmentation process is described

Jul 1, 1991

By D. C. Goldring

Many high-grade iron ores are considered to result from the supergene enrichment of banded iron formations. The secondary processes may be related to either present-day or ancient erosion cycles and may reach a considerable depth. Other high-grade ores hosted by banded iron formations are regarded as either sedimentary or metamorphic in origin although often also subjected to the secondary processes. The evidence for this multiplicity of origins is reviewed with descriptions of selected deposits: Kedia d'Idjil and M'Haoudat in Mauritania, Bomi Hills and the Nimba Range in Liberia, the Itabira district in Minas Gerais, Brazil, and El Pao in eastern Venezuela. Emphasis is placed on the recognition of textures that show that some ores are tectonites, the precursor materials having undergone pervasive deformation accompanied by metamorphism. The question whether such ores are pre- or syntectonic is difficult to resolve, the evidence being inconclusive, but a diagenetic/early deformation origin is preferred. The possible range of origins has to be taken into account in exploration, particularly as regards the depth of drilling, and in the characterisation of ores for metallurgical use

Jul 1, 1991

By J. D. Appleton, J. Ridgway, K. B. Greally

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). The results suggest that meaningful geochemical maps can be produced from very low-density surveys, and that existing data sets could perhaps be incorporated into such a map series with the use of a system such as Uniras software. There are still many problems to be resolved, however, including the compatibility of data derived from different analytical methods, and the precise methods to be employed will necessarily require international agreement. Sampling densities should be chosen on the basis of the scale of the geochemical and geological features to be distinguished and will vary from region to region. Reanalysis of selected samples from archives to increase the range of elements determined or to unify analytical methods is only likely to be effective if the original survey was at quite a low density

Jul 1, 1991

By R. G. Garrett, A. J. S. Geddes

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). The 1986 geochemical survey was successful in recognising all the previously known mineral occurrences of significance in Jamaica, in outlining areas not previously believed to have mineral potential and in stimulating fresh appraisals of old occurrences in terms of their potential for new commodities. This has resulted in a very significant increase in mineral exploration activity in Jamaica

Jul 1, 1991

By Xuejing Xie, Tianxiang Ren

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Standardised stream-sediment sampling procedures have been used in mountainous and hilly terrains. Special sampling procedures were developed for application in remote environments, such as high mountains, desert, semi-desert, karst and loess-covered regions. The diversified analytical methods used in more than 20 analytical laboratories participating in the project have been unified into two multi-element, multi-method analytical systems. A unified data monitoring procedure was developed based on primary and secondary standard samples. To date the project has covered about 4 000 000 km2 and the aim is to complete the coverage within the present decade

May 1, 1991

By P. Mousset-Jones, G. Danko

Variations of the temperature and steam/moisture content of the air with distance and time are modelled for a single airway. The input for the simulation is an air temperature that varies with time, together with the moisture/steam content that results, for example, from a fire with a given distribution of heat and of fume concentrations at the beginning of the airway. The transport of heat and moisture to the surface of the wallrock is assumed to be simultaneous. Such multiphase convection may result in evaporation from the moist wall close to the fire and recondensation downstream. The modelling of this non-linear effect is a unique feature of the new simulation. A new analytical solution is used to calculate the conduction of transient heat within the rock mantle, which, in the event of a fire, is typically a short-term process. This allows for an arbitrary variation of surface temperature with time - unlike that permitted by the age function solution, which is limited to stepped temperature changes. An iterative numerical scheme that has recently been developed to simulate mine climate is used to calculate the coupled transient heat conduction and multiphase surface heat transport in successive length increments along the airway. To demonstrate the simulation procedure a numerical example is presented in which a fire with a given distribution of heat and fume concentrations with time is located at the beginning of an airway

May 1, 1991

By R. Sankey, L. Gatty, F. Bizzozero, G. F. Shannon, F. Savaglio, L. McDonald

State mining regulations in Queensland stipulate that a mine be provided with an earth installed on surface and that all underground equipment that needs to be earthed should be connected via a copper conductor to this surface grounding point. The regulations further require that all exposed metal surfaces in underground substations be connected to an earth. In a study of earthing conditions at Mount Isa mine it was found that the physical anchoring of metal work at substations (with rockbolts and associated steel mesh) also provides an excellent electrical connection to the country rock. It was established that not only is the mine's earthing system grounded at numerous underground locations but also that such anchor points offer, in general, a path to ground with lower resistance than does the legally required grounding point on the surface. It is recommended that metalliferous mines should utilise a multiple-earth system and not a run earth connected to a single, above-ground earth point

May 1, 1991

By L. T. Isaacs, W. H. Traves

A numerical model for analysing the drainage of fill in mine stopes has been described. The model can be used to analyse the process of fill drainage in existing and proposed mine stopes. The validity and potential value of the model have been established by experience with a simpler, 2-dimensional numerical model and by testing the new model against the earlier model. The new model is more useful than the 2-dimensional model because it allows for heterogeneity of fill material within the stope - a factor that has been demonstrated to affect drainage characteristics significantly. The 3-dimensional model is also capable of predicting pore pressures and drainage rates at specific locations in the stope without the need to resort to 2-dimensional generalisations. Such information, integrated with relevant field data as they become available, will provide valuable mine planning information for the scheduling of filling operations and design of fill mixes

May 1, 1991

By Oscar Marreros D

Luego de que Centromin realizara los estudios de los taludes del tajo Raúl Rojas a través de los métodos Janbu y Bishop, se recomendó que el talud final del lado oeste se mantuviera con el diseño planeado a 45° puesto que así lo requerían las instalaciones de la concentradora al límite del tajo. Posteriormente, este diseño se eliminó porque se comprobó la estabilidad del talud estudiado. En ese sentido, el presente texto señala los nuevos análisis de mecánica de rocas para la estabilidad en cuña, donde se eliminan los riesgos de seguridad de la concentradora y se disminuye la cantidad de desmonte.

Apr 1, 1991

By W. R. Paterson, W. Morton, D. B. Cameron

The Massbal II computer simulation program has been used to develop a general framework for the building of thermochemical models of metallurgical processes. The framework allows the rapid, simple construction of complex models of process equipment for use in flowsheet design, planning and plant operation. Application of the program to model the iron-making blast furnace and a flash smelting process is described

Apr 1, 1991

By Pedro Hugo Tumialán

El presente texto describe el proceso de mineralización de la mina Farallón, la cual está ubicada en la provincia de Huarochirí, Lima. Este yacimiento polimetálico produce principalmente zinc, cobre, plomo, plata, oro, donde la longitud total inclinada de mineralización es de 600 m. Asimismo, la silificación se da en toda la roca con rasgos de caolinización, sericitización y propilitización de menor temperatura y la mayor área mineralizada se encuentra en el intrusivo, en menor proporción por el lado volcánico.

Apr 1, 1991

By S. Haggarty

"Wholly owned by Corona Corporation, the Nickel Plate Mine is an open pit, gold mining operation located near Hedley, 50 km west of Penticton, in Southern British Columbia.Milling capacity is 3,400 SDT /Day with an average feed grade of 0.080 Oz Au/Ton. Gold processing involves three stage grinding including tertiary pebble milling, two stage cyanide leaching and filtering and Merrill-Crowe zinc precipitation.A summary of process improvements required to increase milling capacity above the initial design tonnage of 2, 700 SDT /Day are described -Installation of a 42"" x 65"" Allis Chalmers Gyratory crusher replacing a 42"" x 48"" Traylor jaw crusher.Installation of polyurethane screen panels replacing woven wire cloths on an 8' x 20 ft triple deck screen.Installation of a hopper clarifier to reduce filtrate turbidity.Automated control of solution balancing and effluent treatment circuits.INTRODUCTIONThis paper describes mining and milling practices at the Nickel Plate Mine and details post start-up process modifications which were required to attain design tonnage.Wholly owned by Corona Corporation, the Nickel Plate Mine is an open pit, gold mining operation located near Hedley, 50 km west of Penticton, in Southern British Columbia.Mining capacity from the open pit is approximately 32,000 TPD with an average waste/ore ratio of 8.4:1.Milling capacity is 3,400 SOT/Day, above initial design tonnage of 2,700 SOT/Day. Feed grade averages 0.08 Oz Au per ton yielding 85,000 troy ounces of gold per year."

Jan 1, 1991

By Zhang Baoshan

In this paper, the forced features and dynamic behaviors of stone-column composite foundation are concisely related. The characteristics of Rayleigh wave method is summarised. This method is proposed in which, the stress ratio of the stone-column to the surrounding soil and the bear­ing capacity of the composite foundation are determined. Through the engineering cases, it is shown that, checking and evaluating the composite foundation in this method, is feasible, with high speed and low cost.

Jan 1, 1991

By Wilfred G. Comeao

Close-in blasting occurs every time the use o f explosives for excavation or demolition requires the surpassing of the commonly accepted cosmetic damage criteriain order to arrive at reasonable and practical explosive weights per delay. One of the many effective blast design procedures consists in establishing a reasonable charge weight per delay with respect to scale, geometry, costs, requirements and constraints of the project. Once this reasonable charge weight per delay is determined, it’s environmental effects have to be estimated with respect to the surroundings.

Jan 1, 1991

By Wayne A. Charlie

An experimental test program being conducted at Colorado State University and involves the study of the behavior of water saturated sands under shock and explosive loadings. The study is being conducted to evaluate potential blast induced changes in dynamic soil properties, soil shear strength loss (liquefaction) and densification of water saturated sands under single and multishock loadings. This paper presents testing and measurement objectives, and the equipment and instrumentation developed to load, measure, record and analyze the transient and long term soil behavior. The laboratory shock facility is capable of generating multi-shock pulses with milli-second rise time, peak stress amplitudes of up to 35,000 KPa (5000 psi), peak particle velocity of 5000 cm/set and peak acceleration of 10,000 g. The field explosive facility subjects saturated soil to controlled explosive loadings. Of major interest is the soil strain and water pressure, both during and after the passage of the stress wave, as a function of peak particle velocity, peak strain, loading rate, soil density, initial confining stress and the number of loadings. Based on data obtained to date, soil densification is due to consolidation following liquefaction.

Jan 1, 1991

By J. M. Goris

The U.S. Bureau of Mines is conducting research on cable bolt ground supports to assess their material and support properties, to provide design criteria for using cable bolt supports as roof control systems under various types of underground mining conditions, and to develop a mathematical model of cable bolt support systems. Part 1 described laboratory studies of the support properties of conventional steel cable bolts. Part 2 describes the strength characteristics of conventional cables with steel buttons, single and double birdcage cables, and epoxy-coated cables.

Jan 1, 1991

By B. K. Loveday

The South African Institute of Mining and Metallurgy hosted a School on 'The Practical Design of Comminution Processes' at Megawatt Park (near Johannesburg) on 14th to 16th May, 1991 Derek Barratt, a Senior Consultant of Wright Engineers, Canada, and the main speaker, provided a good insight into how Wright Engineers design milling circuits, particularly large semi-autogenous mills. He was ably assisted by Jens Lichterof Allis Mineral Systems, who described some interesting examples of pilot-plant testwork and summarized South African milling practice. Mike Moys of the Witwatersrand University spoke on the influence of pulp viscosity on mill performance, and Johan Engelbrecht and Jeremy Bosman of Multotech

Jan 1, 1991

The following is based on two examples of emission control with coal fired power stations as practised in Germany at Heilbronn Block 7 power station and the Rheinbraun coal combined power station with integrated high-temperature Winkler system (HTW). Heilbronn Block 7 demonstrates the successful emission control of sulphur and nitrogen oxides and the (HTW) system the reduction of the specific carbon dioxide emission. Both were sparked off by legislation which demanded certain emission control standards. Since the early eighties environment protection has been a matter of heated public debate in the European Community. A recent survey in Germany showed unemployment as being the only subject matter more frequently in the minds of people than environment protection. A new kind of forest devastation in areas away from industry has caused investigations by several government departments and private enterprise. Because of lack of conclusive evidence so far, the principle of PRECAUTION has replaced the CONCLUSIVE evidence as a base for new legislation concerning the environment. The new legislative standards for nitrogen oxide emissions in Germany for example have reduced NOx emissions of power stations from 1000 mg NOx per cubic metre of flue gas in the beginning of 1983 to 200 mg NOx per cubic metre of flue gas in April 1984. These new standards were enshrined in legislation when research provided some evidence linking nitrogen oxide emissions through photo-chemical reactions with forest devastation. Thirty European countries signed a treaty in 1983 expressing their concern about air pollution and their willingness to co-operate with each other in controlling large scale emissions.

Jan 1, 1991

This paper outlines the advances made in vacuum filtration as developed by Outomec Process Filters and details the results obtained at a number of Australian installations. The first section of the paper details the technical advances made by the use of ceramic media in vacuum filtration and explains the reasons for the use of the technology. The second part of the paper discusses a number of Australian installations of the ceramic vacuum filter and where possible compares the actual experiences with those predicted from the test work which preceded the installations. The Ceramec Capillary Vacuum Filter is a vacuum disc filter which combines the proven mechanical attributes of a disc filter with exciting new ceramic vacuum technology from Outomec of Finland.

Jan 1, 1991