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

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

Dec 1, 1994

By J. K. Brimacombe, F. D. Richardson

Studies have been made of interfacial turbulence occurring in reactions in which indium, zinc and cadmium, dissolved in amalgams, are oxidised into aqueous phases by ferric or mercurous ions. It has been found that this turbulence occurs when the concentrations of oxidising ions in the aqueous phase become sufficiently great. These concentrations are the same as those at which the mass-transfer coefficients in the aqueous phase increase sharply when both phases are stirred by gas bubbles rising through them. The effects of gas flow rate on the mass-transfer coefficients for zinc in mercury have been established, and the oxidation of pure mercury has been investigated. The relevance of the work to processes involving liquid metals is discussed

Dec 1, 1971

By H. K. Taylor, B. Denby, L. D. Smith

Contributions by H.K. Taylor and G.A. Davis discuss the three papers published in Transactions IMM A, vols. 103 and 104, with responses by Smith and Dowd

Dec 1, 1995

By R. L. F. Kay, T. A. Fletcher, A. J. Boyce, C. M. Rice

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. The synorogenic, mafic Ordovician intrusion comprises orthopyroxene-rich xenoliths and mafic-ultramafic cumulates with low-grade pyrrhotite, chalcopyrite and pentlandite mineralisation. Despite abundant textural, mineralogical and O isotope evidence for significant assimilation of country rocks, S isotopes indicate only a modest uptake and suggest that mineralisation is dominated by magmatic sulphur. The preferred explanantion is that the magma was close to S saturation on emplacement. Uptake of elements such as Si and O led to early crystallisation of orthopyroxene, resorption of olivine and early segregation of a sulphide liquid. Post-magmatic interaction with a high-temperature, surface-derived fluid, whose movement may have been controlled by regional shear zones, reset biotite and whole-rock O isotope values but not those of orthopyroxene. This model identifies the presence of olivine-rich rocks and evidence of extensive assimilation as guides to prospectivity

Jun 19, 1905

By E. L. Evans

The historical development of South Yorkshire mining is traced and note made of the liability to generate spontaneous combustion of some of the seams which have been worked. The liability factor is analysed firstly as an inherent property in the material of a coal seam, and secondly as a circumstance of a situation in which access is provided for the air necessary to sustain oxidation. The geological settings in which incidents of heatings have been known to occur is discussed and conditions favouring a natural pre-disposition to spontaneous oxidation exposed, particularly the effect of argillaceous material overlying the seam. An extensive strata-dynamic study follows to demonstrate the situations in which stray air currents tend to impinge on readily oxidizable material. Prevention techniques are indicated as the identification of strata-dynamic situations in which air access to broken coal is induced and thereafter th operational action to seal off the voids which have been opened up so as to exclude air from the broken coal. Measures to reduce the tendency for ventilating air to short circuit across waste voids, and to obviate deflection of air into packs are outlined. The importance of face and roadway design features is demonstrated and the consequences of practices inimical to good control of spontaneous combustion are related. Discussions on means of detection and also on the sealant materials available are included.

May 23, 1905

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 R. G. Jones

Many novel projects suffer delays, cost overruns or failure because of inadequately qualified technologies. A new qualification to measure the quality of innovation is discussed.

Jul 1, 2015

By I. D. Nock, R. M. Parkin

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: Knowledge-based condition monitoring of cone crushers). A large proportion of the electricity used by the quarrying industry is consumed in the comminution and sizing process. In most cases aggregate processing plants operate with minimum control features resulting in limited operational efficiency. Improved control is required to increase operational efficiency with concomitant savings associated with reduction in re-circulating load and improved resource utilisation. Development work has suggested that a combination of adaptive control and process condition monitoring could improve control of comminution plants. Many commercial process control and condition monitoring systems are available, but none were deemed suitable due to the domain specific characteristics of the application. An assessment of the particular characteristics of cone crushing concluded that the application was best suited to the use of small domain specific process control combined with bespoke condition monitoring. The processing power of the control system for the project is a function not of the academic requirement, but rather the economic and practical constraints imposed by the application. As a result of the constraints a high-end PC system has been designed in preference to a workstation. Within the research project work packages are sub-divided into novel wear sensor development, knowledge based control/condition monitoring and the investigation and mathematical modelling of the wear mechanisms inherent in cone crushing. Numerous strategies were considered to implement the control system outlined. The system currently under development is a modular design which utilises intelligent novel sensors to provide a variety of data inputs

Apr 1, 1994

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 L. J. Cabri, J. M. D. Wilson, R Lastra

An image analysis program can search for gold minerals in polished sections by scanning about 100 x 100 back-scattered electron images at a magnification of x400, allowing gold grains as small as 1 micrometre in diameter to be detected. Typically, a c.15 h overnight search of a product smaller than 45 micrometres will scan c.1 500 000 particles, providing data that are not easily obtained through manual operation of an optical microscope. The program locates grains of the correct brightness, acquires gold X-rays from them by wavelength-dispersive spectrometry, filters the data to remove artefacts and record the images and stage locations for subsequent retrieval. At the end of the run, the program allows the operator to verify and identify the grains found. Industrial studies at Canmet have included determining the nature of gold in cyanidation tailings, checking the mineralogy and size of gold grains in samples from an Indonesian Cu-Au concentrator and locating and measuring gold liberation and grain sizes in an ore

Jun 21, 1905

By S. G. Beattie, N. Mojtabai

A study was carried out which aimed to: determine the effects of blasting on excavation perimeters and nearby slopes; establish a low-cost blast monitoring and field observation programme to determine peak particle velocities and blast damage; and to develop criteria for observable blast damage that are based on the peak particle velocity. Full-scale production blasts in a large open pit copper mine were monitored and studied to develop damage criteria for various rock types. Better blast designs can be achieved by correlating the results of blast monitoring with field observations of damage at the pit walls and on benches. Back-break and damage are related to blast-induced ground vibration. Peak particle velocity is accepted as a reliable measure for the prediction of ground vibration levels. Empirical models for the estimation of rock damage can be developed and used for blast design. The models are used to determine the zones of damage within the rock face. Rock damage models can also be used to design trim shots to achieve further reduction of back-break in more critical areas

Apr 1, 1996

By Mohammed Ali Shah, Martin Waller

The mining industry depends to a large extent on the availability of high performance equipment. For drilling this means a requirement for well engineered, reliable machines with mechanised handling and widespread utilisation of automatic control. Such machines enable performance optimisation of drilling operations and integration into a high productivity mining system. A review is presented of the current status of drilling technology as applied to the mining and minerals industry. This covers developments in: drill bit materials and design; drilling techniques; machine design; mechanisation; automation; and drilling control. It also covers the ways in which current and future mining methods and practices will influence the applications and demands placed on drilling activities. The probable impact of current research on the industry is discussed.

Jan 12, 1992

By G. S. Camm

Gwynfynydd is a small, high-grade black shale-hosted vein-gold deposit. The Chidlaw Link Zone is the only area being mined and contains 24 000 t ore grading 15.2 g/t gold. Within the Link Zone a complex vein structure occurs consisting of a mother vein up to 5 m thick and narrow (less than 0.5 m) leader veins. The former shows minor variations in dip, strike and thickness, whereas the latter show marked changes in all three. The leader veins are hosted within the footwall zone of the mother vein and both are composed of quartz with galena, sphalerite, chalcopyrite, pyrite and minor arsenopyrite. The vein system is transected by a series of cross-vein and intra-vein dip-slip faults. Pockets of gold occur at vein intersections or branches and within the complex footwall zone and are often related to variations in vein attitude and/or geometry. The Chidlaw Link Zone displays a complex, erratic distribution of gold mineralisation and a multi-stage history of structural activity, fluid flow and mineral deposition

Jun 18, 1905

By P. P. Jenkins, T. G. Ball

Paper presented at the Drillex '90 conference held in London, 5 April 1990. Two drilling techniques are employed - guided longhole drilling and reverse circulation coring - for underground longhole exploration of the coal reserves and the fault structures that affect them. These are complementary to, or replacements for, surface boreholes, underground development drivages and seismic techniques. The developments of the drilling techniques and some case histories are presented in detail.

Jan 1, 1991

By Tawsaporn Nuchanong, Ian Nichol

Investigations of the dispersion of gold in soils and stream sediments associated with three gold deposits in Thailand indicate the existence of different geochemical dispersion patterns in the three areas, demonstrating the need for the adoption of a variety of exploration techniques. The three gold deposits which were investigated were the Phu Tham Phra-Phu Thong Daeng copper-gold prospect, the Doi Tung and the Huai Hin Lab gold prospects. Overall the investigations at the three localities demonstrate clearly that the chances of exploration success can be significantly enhanced if composite soil samples are analysed to ensure a more reliable estimation of the gold content in soils and if both the 63 micrometre fraction and the field-panned concentrates of stream sediments are analysed because of the variable grain size of the gold characterising different gold deposits and surface environments.

Jan 4, 1992

By ed. comp., S. H. White, A. J. Naldrett, P. R. Simpson

Peter Simpson's introduction, Tony Naldrett's concluding remarks and discussion by Prof. White of D.M.A. Flight's report of the proceedings are presented from the conference held in Keyworth, UK, in April 1992

Apr 1, 1995

By M. K. G. Whateley, W. Hatton

Paper presented at the conference: Risk assessment in the extractive industries, held in Exeter, UK, 23-24 March 1994, and first published London: IMM, 1994, preprint volume, 20pp., 31 refs. Estimates of coal tonnage on UK open cast mining sites often vary from the recoverable tonnage. This is because the estimates depend on the geological variability of the coal measures. Geological parameters, such as thickness, quality and disturbance of the seam, have a direct control upon this variance. Risk analysis techniques have been applied using commercially available software to combine each parameter's variability into a cumulative variance, resulting in a tonnage distribution. Sensitivity modelling has also been used to identify the geological parameters which have the largest influence on the variance of the simulated tonnage distribution. An understanding of the relationship between the tonnage and geological variability has helped to focus exploration more efficiently. A cost to risk relationship can now be monitored, helping management to avoid negative consequences on site

Aug 1, 1995

By R. J. Gochin, M. A. Diaz

A modified Hallimond tube is described which allows the determination of the ultimate recovery R and the flotation rate constant k in a single, continuous experiment. The range of fine particles which can be satisfactorily floated with the modified apparatus can be extended by increasing the length of the bottom part of the tube. Findings suggest that pyrite and arsenopyrite can be separated in alkaline suspension using the so-called F series of collectors. Lime was found to act as a depressant. The collectors operate under pH and dosage control and do not require other depressants. Collectors used in the study were thio-amine (a cationic surfactant) and alkyl propionamide (a non-ionic surfactant)

Apr 1, 1995

By NA NA

RJB completes purchase of second lease-licence mine, Miller buys Wimpey Mining, Point of Ayr Colliery in North Wales closes, jobs created at Lithgow Minerals Processing Park, Australia.

Jan 9, 1996

By A. S. W. Kurny, M. Z. Huq

Bangladesh ilmenite is partially altered, containing pseudorutile, rutile and haematite as well as the predominant ilmenite phase. A typical analysis is 39.45% TiO2, 24.19% FeO and 33.0% Fe2O3. Reduction of the ilmenite by charcoal was found to involve two major reactions: conversion of pseudorutile into ilmenite and rutile, and change of ilmenite into metallic iron and rutile. The first, which was much the faster reaction, was responsible for an initial increase in ilmenite content with reduction time at lower temperatures. Apart from these two major reactions, rutile was reduced to lower oxides at 1 100 degrees C with a consequent decrease in its XRD peak height

Jun 19, 1905