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By G. Adachi, K. Machida, T. Ozaki, K. Murase

The chlorination rate with CCl4 was unexpectedly slower than carbochlorination using chlorine under the same reaction conditions. Chlorination with CCl4 was topochemical and the amount of monazite reacted after different periods suggested that the kinetic control step was the reaction between CCl4 and the monazite core at the interface. The kinetic order of the reaction was 0.5. The presence of a complex former, AlCl3, promoted the chemical vapour transport of rare-earth chlorides as complexes

Jun 18, 1905

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 T. Ogasawara, J. P. Barbosa, A. J. Monhemius, F. T. Da Silvia

A thermodynamic analysis of the sulphation of rare-earth phosphates and the water-leaching of rare-earth sulphates was used to guide experimental work on the sulphation and leaching of concentrates from Pitinga. It was concluded that the sulphuric acid digestion of xenotime is technically feasible and could be used industrially to produce yttrium and other rare-earth oxides. Yttrium extractions of more than 90% were obtained by digestion at 503 K for 4 h at an acid:concentrate ratio of 2:1 with particle size -0.053 mm. The apparent activation energy at temperatures less than 473 K, as determined from the Arrhenius plot, was 11.0 kJ/mol, indicating that the reaction is controlled by the diffusion of the reactants or products through the sulphate layer

Jun 19, 1905

By J. C. Griffiths

There are two kinds of problems concerning the elements of a population : the first is to estimate the proportion of some specific kind of element in the population, e.g. the amount of gold in a block of ground (equals population) or the proportion of mercury in a sample; the second is to estimate the length, breadth, volume, etc., of a specific kind of element, e.g. the grain size of quartz grains in a beach sand or the size, shape and arrangement of lenses of ore in an ore deposit. Given a specific objective, a bounded population, identified elements and the element characteristics of interest, it is then necessary to select a sample of the elements from the population and the problem of sampling requires a decision on how to select the sample. It is also necessary to establish, either by heuristic analysis or empirically, based on long experience, the model frequency distribution of the desired element characteristics: in general, constant-probability models are used as models, the binomial or Poisson for count data and the normal distribution for measurements (or their transformed equivalents). The objective of sampling then becomes to obtain an appropriate statistical estimate of the desired population parameter: for example, the estimators may be the mean (X) and variance (a2): these should be unbiased sufficient estimators of their corresponding parameters (u, a2, respectively). Statistical tests are performed in order to determine that the estimators are of the appropriate kind: all statistical tests are designed to test against bias of a specific kind, although they are stated as tests against randomness. Given a random sample of some population, the estimators are usually stable and adequate to solve the sampling problem. Random samples are simple to define but exceedingly difficult to achieve in practice: in selecting a sample, if every element in the population has an equal chance of occurring, then the sample is a random sample. Interaction between the arrangement of elements in a population, i.e. its structure, and the sample selection process frequently introduces bias—that is, some elements have more chance than others of appearing in the sample and, hence, the sample is not random. An algorithm for dealing pragmatically with this aspect of the sampling problem offers one way of achieving random samples and, therefore, adequate estimators. Examples of the use of this algorithm on various kinds of geological populations, in both field and laboratory, illustrate the requirements for solving sampling problems and the achievement of appropriate estimators.

Dec 1, 1971

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 A. K. Tripathy, P. K. Pattnayak, H. S. Ray

The effects of water addition on the solid-state reaction between Cr2O3 and Na2CO3 at low temperatures (up to 873 K) were investigated to determine its possible influence on the reaction rate and the degree of conversion to soluble chromate. Experiments at high temperatures were conducted for comparison. It was found that adding water to the mixture before roasting enhanced both reaction rate and yield significantly. The reactions followed the Lesokhin-Tempelman equation at low temperature and the Ginstling-Brounshtein equation at above 973 K; the respective activation energies were 95 and 22 kJ/mol

Jun 19, 1905

By I. L. Whyte

apparent density and drag coefficient of porous ores on

Apr 1, 1995

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 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 G W. Clamp

The most traum atic event within the lUK coal industry during the last 30 years was its privatisation. Who were the relatively unknown people from RJB: white knights or robber barons? This paper highlights the strong safety and progressive engineering cultures th at existed and continues within the company. A long-term view of the business coupled with proven professionalism is amply developed. Quite dearly, to revert to private ownership is not a return to Victorian values but ‘back to the future’.

Jan 8, 1997

By Briggs H.

The illustrated device uses the principle that the lamp can burn with a smaller inlet passage if the air is rich in O2 and that the size of the inlet can be made a measure of O2 percentage. The appliance consists of an adjustable cut-off applied to the inlet of a safety lamp of the improved Gray pattern. Precision is assessed from tables of calibration tests in air contaminated with blackdamp of CO2:N2 composiiton 1:5.67 at temperatures of 40-70 degrees F. Results are presented of tests at St. Germain's colliery, of tests in air contaminated with pure CO2 and of air contaminated with both blackdamp and inflammable gas; published ranges in mine-air blackdamp compositions are tabulated as ranging from 90.06% N2 to 43.90% CO2. When firedamp is present at 1.25-2.5%, its content must first be estimated by means of the cap and a fifth of its value then deducted from the lamp reading for O2

Dec 1, 1916

By M. G. Fleming

The professional mineral engineer is an individual of personal integrity who has undergone rigorous intellectual instruction in the scientific disciplines fundamental to his vocation; he has learnt to apply these disciplines to the discovery, mining and treatment of mineral resources and, through practical training and experience, has acquired competence and judgment to fulfil his undertakings. In the course of this development he has recognised and accepted a threefold responsibility to society, to his employer and to his profession

Dec 1, 1971

By R D. Lama, A Misra

One of the major factors restricting an increase in the productivity of a longwall mine is lower productivity obtained in a development panel. There has been a significant improvement in gate road development, particularly in mines requiring high density roof and rib bolting within 2 m of the face. Advance rates have increased from an average of 3 m to 5 m per shift in 1985 up to an average of 5 m to 10 m per shift in 1991. In mines at shallow depths with reasonably good conditions the increase has not been that significant. Advance rates have increased from an average of 7 m to 12 ni per shift in 1985 to an average of 12 m to 15 m per shift in 1991. Compared to the United States' (US) development rates, these are much lower. Extensive research work has been carried out to minimise cutting, wheeling, support setting time, and to optimise pillar length to achieve maximum advance rates. Pillar optimisation is very important in order to expedite adverse rates. This paper investigates various development rate technologies, both present and future, and optimises pillars to improve these dev elupment rates. Pillar optimisation is based upon time and motion studies conducted at mines in the Illawara region of New' South Wales, Australia, and the basic tools of arithmetic.

Jan 9, 1996

The mineralogical composition of the ore was determined and the mineral phases with which nickel is associated were identified. The ore was prepared by grinding to -420 micrometres and classification into granulometric fractions. Prior to the main series of experiments the effect of agitation rate on nickel recovery was investigated. The influence of sulphuric acid concentration, temperature and particle size on the kinetics of nickel extraction was then studied, both quantitatively and qualitatively, over fixed value intervals. Application of the initial rate method enabled determination both of the order of reaction with respect to sulphuric acid concentration and the activation energy for the dissolution of nickel. The results indicate that a physical mechanism can be ruled out as the rate-determining step in the extraction of nickel from the ore and that a chemical mechanism is more likely

Dec 1, 1991

By L. T. Matthews, C. E. Loo, R. P. Williams

The behaviour of iron ores and fluxes in the high temperature zone of a sintering bed is extremely complex. Following a review of current knowledge, an attempt is made to define relevant terminology to describe the processes that occur in this part of the bed. A deformation temperature is used to quantify the initial formation of melt, which is produced predominantly by reactions between fine particles in the sinter mix. The subsequent assimilation of larger particles is considered to depend on the reactivity of the melt and the assimilation resistance of these particles. Novel laboratory experimental techniques are used to quantify these parameters. Results demonstrate that the properties of the raw materials used have an extremely important influence on the initial processes of melt formation and assimilation and also on the nature of the sintering reactions and sinter-bonding phases.

Jan 4, 1992

By Haldane J. S.

(Paper presented at the Institution of Mining Engineers' general meeting held in London on 8th June 1916.) It was shown in the last Supplement to the Registrar-General's Reports, in connection with the census of 1901, that the general death-rate among colliers was considerably lower than in the great majority of occupations but that there is an exception to this in the case of colliers above the age of 55. Examination of the statistics finds that the excessive death-rate among old colliers is to a large extent only apparent, and that the real excess of bronchitis from which they have suffered has greatly diminished. It is concluded: (1) that good ventilation is of considerable importance to the health and continued working efficiency of miners, as well as to their safety from accidents; and (2) that there is no real statistical evidence of harm resulting from the inhalation of coal-dust or shale-dust in the quantities ordinarily breathed by miners, and a strong presumption that the dust they breathe protects them against serious dangers from bacilli that are removed from the lungs by the dust-clearing cell mechanisms

Dec 1, 1916

Studies were carried out to examine the effect of introducing varying levels of a pisolitic limonite (Yandi) into an Australian iron ore blend. Compared with other ores in the blend Yandi is more porous. This structure is found to have a considerable effect on the sintering behaviour of the blends. Pilot-scale sintering studies and plant trials showed that sinter plant productivity, sinter reducibility and the low-temperature reduction degradation index altered significantly when the level of Yandi in the ore blend exceeded 15 wt%. The improvement in the reducibility is thought to be a direct result of increased porosity in the sinter and the presence of highly reducible pseudo-relict haematite. Plant trials have also shown that operational changes could be made to the sinter plant to avoid potential deterioration of productivity

Dec 1, 1991

By III, Peter J. Rogers, J. Gordon Ogden

A study is described which attempts to identify the chemical factors of common concern to environmental and exploration geochemistry as indicated by recent work in both disciplines in Nova Scotia. Cores taken in lake sediments define geochemical baselines for the modern and pre-industrialisation periods. The investigation of lake and stream drainage indicates the presence of numerous chemical and organic factors that can be attributed to man's activities, such as construction and energy consumption. Geochemical surveys of lake and stream sediments are used to locate potentially toxic, high risk areas in Nova Scotia. Rapid change occurs in most surface drainage systems with the possibility of numerous chemical reactions taking place. It is found that spatial and temporal variations in the chemistry of modern and recent sediments are of interest to exploration and environmental surveys.

Jan 4, 1992

By E. H. Baker

Vapour pressures of sulphur have been measured over the temperature range 340-1039°C by means of boiling-point measurements, an internally heated pressure vessel being employed with argon as the pressure medium. The results are expressed satisfactorily by a four-term pressure-temperature relation. At the cited critical temperature of 1040°C the calculated critical pressure is 204 atm. From the pressure-temperature relation and available thermal data for the vapour, the approximate composition of the saturated vapour in terms of the various molecular species has been derived for the critical point

Dec 1, 1971

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