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By G. M. Zhao

The gasification of lump coke with CO2 was studied in a fixed-bed reactor. The effective diffusivity of the gas was evaluated from measurements of the reactivity of the lump coke, produced by BHP Steel in New South Wales, and from kinetic parameters that were determined from the reactivity of fine grains. The grain model of effective diffusion in porous media was adopted to express the gasification rate of the lump coke and was found to fit the experimental data well. The relationship between reactivity and textural characteristics of the coke was examined

Jun 18, 1905

By S Colak, M Tunc, C Celik, M. M. Kocakerim

The most important parameters affecting the solubility of ulexite (sodium calcium borate) in H2SO4 were found to be reaction temperature and solid:liquid ratio, in that order. Dissolution increased with increase in temperature and stirring speed and with decrease in solid:liquid ratio, particle size and acid concentration, the last effect as a result of decreased precipitation of CaSO4 on unreacted particles. Optimum conditions, in which around 99.5% of the ulexite could be dissolved, were a reaction temperature of 60 degrees C, a solid:liquid ratio of 1:8 g/ml, an acid concentration of 8 mol/l, particle size smaller than 425 micrometres, a stirring speed of 52.33/s, a reaction time of 1 800 s, a calcining time of 3 600 s and a calcining temperature of 170 degrees C. These conditions, determined by the Taguchi method, are reproducible in a commercial production environment

Jun 21, 1905

By A. Ludkin

The paper presents the history of the occurrence of spontaneous combustion in the north area, together with the associated problems. These are examined and a description is given of the methods used to combat the danger, including the use of modern scientific instrumentation. Detailed reference is made to the underground trials with pack injection and sealant coatings which were carried out at Seafield Colliery following the formation of a working group to assess the performance, in the same underground conditions, of (1) sandbagging, (2) pack injection, (3) surface coating. Based on these trials, an improved and more economical method of prevention has been established. There is, however, still scope for further improvement in techniques which would take into account the problems of gradient, transport, manpower and cost.

May 23, 1905

By R. J. Howarth, P. L. Llowenstein

The errors resulting from field sampling, sample preparation and analysis are investigated for drainage sediments derived from homogeneous sandstone, shale, limestone, basic igneous and granite lithologies as a background to a primary reconnaissance survey of England and Wales. Emission spectrographic analyses of approximately 350 samples for Al, Ca, Fe, K, Si, Ba, Co, Cr, Cu, Ga, Li, Mn, Ni, Pb, Sc, Sn, Sr and V and atomic absorption analyses for Cu, Ni, Mn, Co, Zn and Pb have been treated statistically. For routine broad-scale surveys analysis of the unground -80-mesh sediment fraction proves satisfactory. Sampling error between localities in a stream is shown to be less than spectrographic analytical error for many of the elements considered here, except where mineralisation (contamination) occurs, but exceeds the atomic absorption analytical errors in most cases. Unless it it critical to reduce the amount of between-site variability (having regard to analytical errors) in the regional survey, there appears to be no advantage in the use of a more sophisticated sampling technique. The utility of moving-average maps in reducing the width of the confidence belt around the regional 'geochemical surface', and thus compensating to some extent for the sampling errors, is also demonstrated.

Dec 1, 1971

By R. W. Schultz

Mineral exploration carried out in Ireland since the mid-1950s has resulted in the discovery of ore deposits that are now in production atTynagh (Pb-Zn-Cu-Ag), Silvermines (Zn-Pb) and nearby Ballynoe (barite), and Gortdrum (Cu-Ag-Hg); a major Zn-Pb deposit at Navan that is now being drilled prior to development; potentially productive deposits at Keel (Zn-Cd-Pb), Ballinalack (Zn-Pb) and Aherlow (Cu-Ag); and a number of interesting prospects, including one of spodumene. Underground exploration of a formerly extensively mined copper deposit at Allihies has outlined new, albeit currently uneconomic, reserves at depth. The copper and pyrite deposits at Avoca have in recent years been re-explored and are now again being worked. Most Irish ore deposits are in the lower half of the Lower Carboniferous succession of limestones and subordinate shales and sandstones, and this stratigraphic zone is being most intensively explored at present. Other geological units under active exploration are Ordovician sediments-volcanics belts, Caledonian granites, and parts of the Old Red Sandstone and Dalradian series. Surface prospecting is made difficult in many places by glacial and other superficial deposits, including peat and alluvium. Geochemical prospecting methods have been outstandingly successful and primarily responsible for most new discoveries. Boulder hunting and outcrop prospecting have proved effective in detailed investigations of geochemically anomalous areas. Some parts of the country have been covered by three separate airborne geophysical surveys, albeit without success so far. The induced polarisation technique, the most widely used ground geophysical method, has contributed to several discoveries. The scope of application of electromagnetic surveys is more restricted than that of induced polarisation, but the method has been effective in a few cases and has contributed to the Tynagh discovery. To date, the resistivity and self-potential methods have found little application. Magnetic surveys are not applicable directly in the search for ore deposits of the various known types, but can be helpful in outlining geological structures in some areas. The gravity method has been used successfully in a survey over the Zn—Pb deposit at Navan ; it has also proved effective in trials over a blind sulphide deposit at Tynagh that cannot be detected with geoelectrical methods. An appendix lists summary descriptions of 15 Irish deposits and occurrences

Dec 1, 1971

By J. H. Chesters

The main, though rarely mentioned advantage, is likely to be the standardisation of best practice and product. In a batch process conditions vary cyclically, but with a continuous process they would, at least ideally, remain the same for long periods of time. The other main advantages of continuous over batch processes are likely to be reduced operating and capital costs, the improved possibilities for automatic control, and more consistent product quality. Recent developments are surveyed for ironmaking and steelmaking with reference to blast furnaces; solid-product and molten-product direct reduction; the trough-type processes of Thring, Worner, the Japanese National Research Institute for Metals and Glinkov; basic-oxygen furnace (LD) variants; spray steelmaking; continuous casting and vacuum degassing; rolling; and coating. Encouragement in the devleopment of continuous processes may be drawn from the way unexpected difficulties, such as trouble with sulphur and refractories, were tackled and overcome to achieve the float glass process

Dec 1, 1971

By M. J. Beus, B. Stewart, S. Iverson

Ore-pass hazards are a significant safety problem in US underground metal mines. From 1975 to 1995, nearly 75% of injuries during pulling or freeing of ore-pass chutes were related to falls of broken rock or the use of hand tools. Risk assessment methods are being used to identify the most probable causes of ore-pass failures and analyse the factors that result in malfunctioning or safety reduction. Static and dynamic loads are being measured in the laboratory and by field testing, with data from test ore passes compared with mine data to characterise true system behaviour. Computer modelling using closed-form solutions, finite element analysis and a newly developed particle flow code are being use to predict loads from ore and waste flow and impact. Preliminary results indicate that dynamic impacts may be much less than expected, as a result of damping factors, normal and shear stiffness and mass frictional characteristics

Jun 19, 1905

By A. F. Neil, A. S. Bahaj, P. Watkins, P. M. Hyslop, C. E. Kirby, P. A. B. James

The results of initial work indicate that for 3 of the 5 quarry sands bioleaching reduces the iron oxide content to a commercially acceptable 0.035 wt% Fe20 3, although the time taken to achieve this is 14-22 days against a target leach time of 7 day. Subsequent work has identified strains of Aspergillus niger that are more efficient at producing the array of complexing agents for iron and is yielding excellent and rapid reductions in Fe levels. Potentially, bioleaching offers a more environmentally friendly and energy-efficient process for the removal of Fe from glass-making sands than conventional routes but the production of organic acids by fermentation must be achievable with low-cost substrates such as sugar-beet molasses and lactose permeates for bioleaching to offer a commercially viable alternative to treatment with hot mineral acids. Silica sands usually contain three groups of Fe minerals: iron oxyhydroxides, which comprise crystalline types such as goethite and limonite tending to occur as thin, discontinuous coatings and in cracks and crevices on the surface of the quartz; the assemblage of heavy trace minerals, which include ilmenite, rutile, leucoxene, chromite and haematite, commonly present at levels of 0.1 wt% or less as discrete grains or sometimes cemented to the quartz; and clay minerals cemented in pits on the surface of the quartz and in association with weathered, discrete feldspars. The response of the assemblage of iron minerals to short periods of exposure to hot inorganic acids is broadly related to which group they belong to, those that form coatings being accessible to acid and tending to react rapidly whereas the trace minerals are usually resistant and react very slowly, if at all, and the clays are probably digested. The note reports on a preliminary study of the use of microorganisms to develop an alternative clean technology that will give results comparable to those achievable with hot inorganic mineral acids but with more environmentally acceptable procedures. Various fungi and bacteria produce organic acids when grown in certain media. When these acids come into contact with Fe-stained sand grains the iron is removed as soluble complexes. Several strains of Aspergillus niger have been found to produce organic acids from sugar, predominantly citric, gluconic and oxalic acids, their relative yields depending on cultivation medium and conditions. Sand samples were prepared from five quarries in the UK: Levenseat, Lothian; Redhill, Surrey; King's Lynn, Norfolk; Chelford, Cheshire; and Oakamoor, Staffordshire; ranging in iron oxide content from 0.035 to 0.153 wt% Fe203

Jun 18, 1905

By E. A. C. Chamberlain

New techniques for the continuous sampling and analysis of mine air are expected to replace traditional methods used for the early detection of spontaneous combustion. It has been established that the rate of evolution of carbon monoxide is the earliest indicator of incipient spontaneous combustion. Two methods of continuous monitoring of this gas are available and are now in use in the UK collieries. The first is the UNOR infra-red gas analyser, which is flameproof and may be used underground; the second is a system of tube bundles, which permits air to be drawn from any critical point in a colliery and analysed on the surface. Each system has its advantages and disadvantages but both provide the colliery manager with far more information on the condition of his pit than could previously be obtained by spot sampling and laboratory analysis. This paper describes the two systems presently in use and assesses likely future developments.

May 23, 1905

By Mavor S.

Further discussion at the Mining Institute of Scotland's general meeting held in Edinburgh, 12 February 1916, with D.W. Mowat, president, in the chair, of a paper published in Trans. Inst. Min. Engrs., 1915, vol. L, p.625 and discussed vol. L, pp.92, 433, 468, and 704 included comments by Mowat D.W. and the author's reply

Dec 1, 1916

By W. R. Donaghue, R. L. Robinson, C. Scott

Whilst spontaneous combustion has never been considered a major problem in south Durham, certain collieries in the area have a history of heatings and precautions are essential. Three collieries are affected - Shotton, Vane Tempest and Seaham - and in the case of the last two, there are huge areas of high quality coal to work under conditions where spontaneous combustion is a real hazard. The seam being extracted has an immediate roof in goaf left by the incomplete extraction of a contiguous seam worked before the turn of the century. The presence of residual coal stocks and old roadways and cavities adds to the difficulty of preventing unwanted air movement. The main preventive measures adopted are the construction of airtight gateside packs and the use of sprayed surface coatings in the gate. Sampling systems and sampling points are described and, in particular the field of continuous monitoring from the surface is examined. The resulting possibility of a quantitative as well as qualitative assessment of the preventative measures required is discussed.

May 23, 1905

By S. Vardy

The paper notes that the extraction of 22% of the remaining workable reserves in the north western area involves a risk of spontaneous combustion higher than is normal in Britain. Mining systems have been tailor made in order to minimize the risk of spontaneous heatings, and these systems are described. Well-proved methods of combating spontaneous combustion are referred to, as well as the limitations which now apply to them as the result of the introduction of modern mining techniques. A substantial part of the paper is devoted to the circumstances in which spontaneous combustion occurs underground in the north western area. Several actual incidents which have occurred in the last few years, along with the practical application of the lessons learned, are described. Of particular note are: a) the procedure adopted in the north western area to equalize pressure differences across stoppings using pressure chambers, and b) a retreat mining system, primarily designed to deal with high methane emission and steep gradients, which also affords some protection against spontaneous combustion.

May 23, 1905

By W. H. McAllister

The paper considers the geology and the coalfields that comprise the Scottish south area. It traces the history of known sources of spontaneous combustion and indicates the collieries concerned, with the position of the seams in the geological series where heatings have occurred. The methods of work over the years are described. It relates in detail the circumstances surrounding a fire at Bilston Glen Colliery in the Lothian Coalfield, and the heating at Killoch Colliery in the Ayrshire Coalfield, and the steps taken to deal with them. It also describes some of the difficulties in steep seam working. Methods adopted to prevent spontaneous combustion throughout the area are discussed, and some detail of the UNOR gas analyser is given. Finally, it comments on the present techniques in use in the area, particularly at Bilston Glen Colliery, to prevent spontaneous combustion.

May 23, 1905

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 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 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 R. I. Jeffery, J. W. Summers

An account is given of the verification and calibration of a numerical modelling technique that has been developed for the prediction of subsurface strata deformation following the extraction of coal by longwall mining methods.

Jan 4, 1992

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 S K. Das

An intensive investigation into modern roof support technology, including hy draulic and control systems, has been carried out against the perspective of global development and support behaviour on longwall faces across the Indian sub-continent. The wide ranging study examined various types and designs of modern supports used in seams of varying thickness and inclination where caving and stowing were practised. Consideration has been given to structural analysis, support resistance, the various forces acting over and on the powered supports and to support compatibility. The examination of the phy sical parameters has been allied to field experience and, together, have led to the formulation of standard designs for both the powered support structure and structural systems. A realistic mathematical model has been formulated for calculating the capacity of roof support requirements resulting from the actual behaviour of the immediate roof stratum. As a result of the work, it should be possible to readily select the most appropriate type of support sy stem for the conditions and longwall mining method that is to be employed.

Jan 4, 1997

By F. Reich, S. L. Chryssoulis, K. G. Stowe

The surface chemistry of particulates from mineral processing streams can be determined by laser-probe microanalysis. The small area of analysis (2-30 micrometres) enables the surfaces of individual grains to be characterised. Conclusions are based on data acquired from a statistically significant number of grains of a given type. Maps showing the distribution of elements on the surface of mineral particulates can be obtained by time-of-flight secondary ion mass spectrometry. The importance of such analyses in understanding the response of minerals to beneficiation practices is discussed with reference to three examples. The first relates to the loss of selectivity in the differential flotation of a base-metal ore, the second to the different flotabilities of coarse- and fine-grained pentlandite from a Cu-Ni ore and the third concerns the preg-robbing effects of organic matter in a carbonaceous gold ore.

Jan 4, 1992