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By J. Drzymala, K. L. Wolters, T. Chmielewski, T. D. Wheelock, D. H. Birlingmair

Microflotation tests were conducted with a modified Hallimond tube equipped with a fritted glass disk and magnetic stirrer to determine whether the results would support an equation that predicts a linear relationship between particle size and the reciprocal of particle density in water for a specified flotation recovery in a given time. Data obtained with the tube for either hydrophilic or hydrophobic solids fit the equation satisfactorily. It was also shown that the natural flotability of molybdenite is somewhat less than that of elemental sulphur and that sodium dithionite is a good depressant for sulphurised pyrite. In addition, it was found that the untreated pyrite and galena used in the study were hydrophilic and did not float by particle-bubble attachment.

Jan 4, 1992

By D. V. Venugopal, W. W. Gardiner

Spessartine-quartz rocks are manganiferous sedimentary rocks rich in spessartine and quartz which occur in north-central New Brunswick. They represent a recrystallised manganiferous siltstone/chert that is contained in or associated with red manganiferous siltstone (RMS) units. The spessartine-quartz rocks and RMS form part of an Ordovician volcanic and sedimentary succession within the Appalachian-Caledonian orogen which hosts numerous massive sulphides and polymetallic vein deposits. The New Brunswick spessartine-quartz rocks are spatially and temporally associated with stratiform base-metal, precious metal and hydrothermal tin-tungsten deposits. This suggests that spessartine-bearing lithologies and zones can be useful in predictive metallogeny and for the understanding of the stratigraphy and palaeographic setting of the early Palaeozoic rocks of the Appalachian-Caledonian orogen.

Jan 12, 1992

By I S. Lowndes, K. Moloney

Diesel powered equipment is currently used extensively in mining and tunnelling operations around the world due to its mobility, flexibility and through selective application to enhance productivity. However, the increased use of diesel equipment has exacerbated the pollutant load (including heat, humidity, exhaust gases and particulates) placed upon the environmental systems of many underground operations. This expansion in the use of diesel equipment has prom pted researchers to evaluate m easure ment and control technology. This paper reviews the recent research conducted in various countries.

Jan 10, 1996

By W. R. Chambers

A wide variety of mining conditions exists within the South Midlands Area and across this range of conditions more than one half of the mines are highly susceptible to spontaneous combustion. Two thick seams in which the greatest risk exists are described and illustrated. The different heatings which take place are categorized by the locations at which they occur in the mines: additional special cases not easily categorized by location are discussed separately. The discussion for each category of heating follows the pattern of: (i) the reasons why it occurs; (ii) when it arises the means by which it is fought, and (iii) the preventive measures taken in an attempt to avoid its occurrence. Relatively new factors which may affect the incidence of heatings are highlighted and suggestions are made which may assist in reducing the number of incidents in the Area. A new method of continuous sampling, analysis and recording is described and mention made of an original method of interpreting carbon monoxide results with the aid of the computer. The first results from this work show that an early warning is given of an adverse change in trend several weeks earlier than with the present methods. Lastly, suggestions are made about the direction in which research might proceed to assist in reducing the special hazards created by several features inherent in the present methods of mining.

May 23, 1905

By Tuncel M. Yegulalp, Selamet G. Ergelebi

A description is given of a method of analysing modern mining systems in terms of reliability and their effects on productivity. Non-exponential distributions, such as the Weibull and lognormal distributions, for failure and equipment repair times are also considered. The resulting non-homogeneous Markov process is solved by the method of stages. A longwall mining system is analysed as an example.

Jan 4, 1993

By I. A. Scott, T. J. Napier-Munn

Size-by-size partition curves for mineral separation in dense-medium cyclones pivot about a single characteristic point. This is defined for stable, non-segregating media by the medium density and the proportion of the medium reporting to the underflow. The pivot point departs from these values for unstable, conventional media. The phenomenon can be represented by an equation with two parameters defining pivot point coordinates and two the Ep value. On the basis of experiments in a 200 mm cyclone using ferrosilicon media, simple regression equations were developed for the separation parameters in terms of operating conditions (the coefficients were likely to be site-specific). The experiments successfully decoupled the effects of medium density and viscosity and showed that the value of Ep was independent of the former but strongly dependent on the latter. A classification model was used to predict the density of the underflow medium, a knowledge of which is required to determine the pivot parameters. The model correctly reflects the performance trends observed in dense-medium cyclone operation and has the potential to be generalised to a wide range of industrial practice.

Jan 8, 1992

By R. J. Pine

Procedures are described for the application of risk analysis or probabilistic methods to mining geomechanics. The methods are widely applicable to existing mine design models. Detailed examples are given of plane slope failure and of pillar design based on displacement-discontinuity stress modelling and empirical strength assessment. The modelling techniques assessed are the Latin hypercube sampling method, incorporated in a spreadsheet environment, and the general point estimate method (GPEM), programmed in TurboBasic. An example GPEM program listing is included. Both methods are very convenient to use. Probabilistic acceptance criteria for slope stability after Priest and Brown are examined and alternatives are proposed where output distributions of factor of safety are approximately normal or lognormal and output distributions of safety margin are normal. The reliability index is included as a useful measure of variability with proposed acceptance criteria.

Jan 12, 1992

By G. H. Blackwell

Sequences in open pit mining must be planned and regularly revised to incorporate changes in the variables which affect profitability. Interactive computer planning with colour graphic facilities is an effective tool for this purpose in the short and medium term. An interactive computer planning system for medium-size, low grade porphyry copper-molybdenum open pits is described. The planning system proved especially valuable during the critical stages of pushback mining when deep, inner pit ore was nearly depleted and the erratic grades of the next pushback provided ore and marginal material at a time of depressed metal prices.

Jan 8, 1993

By R. M. Honey

An attempt is made to summarise the mining law of England, Wales and Scotland. Attention is also drawn to the recent privatisation of the electric power and gas industries and the intention of the present Government to follow suit as regards coal mining. The subject of mining law is discussed under the headings: minerals or rights that have been nationalised or are vested in the Crown; ownership (of land and mineral rights); special customs; tracing of owners; right of support (arising from mining); ancillary rights and easements; obtaining prospecting and mining rights; planning permission; statutory aids to obtaining rights; notes on the history, law and practices of petroleum (onshore and offshore), gas, coal, prescribed substances, gold and silver; electricity; safety, health and welfare; and technical information and boreholes. A correction in the subsequent issue amends errors on p.A75 and A82 and regrets the publication of misinformation on the availability of grants

May 1, 1991

By J. Ostwald, L. T. Matthews, C. E. Loo

Australia has large reserves of pisolitic limonite. Mining recently commenced on the Yandicoogina deposit to produce a high-grade sintering ore. The ore contains about 10 wt% combined water and simulated sintering temperature profiles indicate that progressive dehydration of ore particles occurs in the temperature range 300-700 degrees C. Studies by optical microscopy show that although the dehyrdrated ore particles contain numerous cracks, there is no change in the microstructure of the ore because topotactic transformation to haematite results in the formation of compact masses of very fine-grained haematite microcrysts. When the ore is held at around 1 200 degrees C for 1 min significant recrystallisation of these microcrysts occurs, resulting in the formation of optically visible, micrometre sized haematite crystallites. Studies to simulate the behaviour of ore particles during sintering (as nuclear particles surrounded by a standard adhering fines mixture) show that the recrystallisation process occurs much earlier at temperatures of about 900 degrees C. Further studies indicate that CaO in the adhering fines mixture enhances the recrystallisation of the ore nuclei. The results of the investigation indicate that the pseudo-relict haematite in sinters produced from ore blends that contain significant levels of pisolitic limonite consists of dehydrated goethite that has undergone significant recrystallisation and grain growth, a phenomenon that is facilitated by the presence of lime derived from the sintering melt.

Jan 12, 1992

By Walshe J. M.

The slow-speed compressor is giving place to the high-speed type, with its greater economy of material and space; and, where very large units are required, the turbo-compressor is supplying the need. In the very large air-supply stations on the Rand, turbocompressor units of a capacity of 20,000 and even 50,000 cubic feet, requiring 4,000 to 13,000 horsepower, are quite a commercial proposition, and have proved a practical success. Air-compressors of this size are, however, very exceptional, and the high-speed reciprocating compressor is quite capable of dealing with the highest outputs so far required in this country and, in the hands of manufacturers experienced in the design of high-speed steam-engines, a very high standard of reliability and efficiency in operation is obtained. The so-called “high-speed” or more correctly quick-revolution type of compressor is now extensively used in mines and collieries; for the air-pressures required for power purposes in mining work, two-stage compression, with an intercooler between stages, is the design usually adopted in best practice. It is not the writer’s intention to describe a variety of high-speed air-compressors but to select as an example of this type of compressor the one with which he is most familiar, and which is probably more largely used than any other, namely, the double-acting two-cylinder two-crank type with automatic light-plate air-valves, and with the working parts lubricated on the forced-lubrication principle. Sectional drawings, efficiency curves, air-cylinder diagrams and other data accompany the descriptions and photographs of compressor design, components and mine applications

Dec 1, 1916

By R. Macleod, G. G. Bursey, T. R. C. Aston, J. E. Gale

In 1991 the problems of water inflow at the mine were addressed by a three-phase study. A three-dimensional finite-element computer code, CFEST (Coupled Fluid, Energy and Solute Transport), was used to model the system of groundwater flow around the mine, allowing assessment of the nature of the hydrological regime and of the various recharge mechanisms and sources of inflow. A regional (111 km2) model was used to simulate conditions of low to average mine inflow and provide boundary conditions for the subsequent local (16.8 km2) model. The regional model produced inflows of 0.26 m3/s and the local model 0.25 m3/s. With the use of constant head conditions to simulate a saturated flood plain along the Gays River and on doubling the rate of surface recharge, the local model produced a maximum mine inflow of 0.255 m3/s, in contrast to a measured peak mine inflow of 0.37 m3/s. The discrepancy suggests that during periods of high river level surface water gains access to features with high permeability, such as sinkholes, that may be connected directly or indirectly to the mine workings. Improved simulation of high inflow conditions can probably be achieved by determining the hydraulic conductivity of the river-bed and flood-plain sediments and modelling known sinkholes as discrete units. Possibilities for controlling the amount of inflow to the mine include sealing the flood plain with dykes, checking regularly for new sinkholes, which should be filled and capped, maintaining adequate mine drainage, and monitoring well levels and pressures on a continuous basis.

Jan 12, 1993

By Williams J. A.

"Changes proposed in 1969 to modernize legislation governing the exploitation of mineral deposits in the United Kingdom serve as the basis for a discussion of what is considered to be a desirable framework for future legislative proposals.Proposals with regard to prospecting and exploration, evaluation, and acquisition and exploitation are considered, as are suggestions relating, inter alia, to aerial surveys and land restoration.It is concluded that without legislation along the lines proposed there can be no significant revival of metal mining in Britain."

Dec 30, 1971

By NA NA

In the third of its features on the new owners of the British coal mining industry, Mining Technology reports on the newest company in the field, Midlands Mining.

Jan 2, 1997

By C R. Ferrari

Residual subsidence is generally accepted as being about 5% of the total subsidence occurring within 12 months of all mining finishing. This paper looks at five case studies from different parts of the country, in various mining settings within a depth range of 430m to 760m. From a single seam single panel working to working the eleventh seam, all are within the concealed coalfield, similar to today's mining. The monitoring of subsidence continued for many years once the mining had finished and the results obtained are at considerable variance from the accepted norm. Subsidence has been found to carry on for up to eleven years after mining has ended, within a range of 8% to 45% of total subsidence. A highly significant factor was that subsidence, as a whole, was generally much more than predicted. The residual subsidence aspect has to he viewed in this context and in order to debate the subject at length, the causes of residual subsidence have to be balanced against the apparent inability to accurately predict subsidence. The results from the case studies were similar, even though the mining settings differed considerably. Subsidence of around 10% to 20% continued for several years after mining had ceased.

Jan 7, 1997

By L. J. Barnes, R. O. Koch, J. H. Versteegh, C. J. N. Buisman, P. J. H. Scheeren

Several water treatment options have been studied and piloted. A process based on activity of sulphate reducing bacteria combines sulphate removal and heavy metal removal in one process step. The anaerobic bacteria reduce the sulphate to sulphide and consequently metal sulphides will precipitate. The final design for the commercial scale plant is described.

Jan 12, 1992

By Ruddle R. W.

The slags produced in copper smelting are largely composed of silica and ferrous oxide and may therefore be regarded as essentially ferrous silicates. A fair amount of information is available on the constitutions of the liquid slags used in copper smelting and, in this connection, the large volume of work being carried out on steelmaking slags should be helpful. Constitutional diagrams are available for most of the principal systems involved (SiO2-FeO; SiO2-FeO-Al2O 3; SiO2-FeO-CaO; SiO2-FeO- MgO; and SiO2-FeO-CaO-Al2O3) and these show that additions of Al2O3 and CaO reduce the freezing points of SiO2-FeO slags but that additions of MgO increase the freezing point. A certain amount of information is available on the thermodynamics of slags, but much further work on this subject is required. Modern theories of the constitution of liquid slags deny the existence of molecular compounds but consider that liquid slags are mixtures of various ions such as, Fe2+. O2- and SiO4(4-). Little appears to be known of the reactions between matte and minor constituents dissolved in the slag

Jan 1, 1953

By J R. Leeming

The paper describes a technique that has been developed by the Health and Safety Executive (USE) to make an assessment of the effectiveness of Health and Safety (H and S) management at complex sites. The paper then describes how the technique was adapted and used for the first time at a large coal mine. The results highlighted certain deficiencies in the safety management system, allowing directed advice to he given to management.

Jan 4, 1997

By H. L. Willett

Wrapping up the symposium, covers incidence of spontaneous combustion in British mines, assessment of liability to spontaneous combustion, precautions, rate of advance, starting a line of a coalface, local heatings at roadsides, burying packs, coal headings, retreating longwall, detection and sealant coatings.

May 23, 1905

A study of the thermodynamic properties of magnesium chloride ammines was carried out with the ultimate objective that the thermal decomposition of the hexammine MgCl2.6NH3 may prove successful on a commercial scale for the manufacture of anhydrous magnesium chloride, which is required for the efficient electrolytic production of magnesium. The experimental data are presented in the form of an equilibrium diagram that aids the understanding of the conditions associated with the thermal decomposition of ammines

Jun 13, 1905