Search Documents

By Glastras M. V

The presence of arsenic in solutions which result from the processing of many sulphide minerals leads to a need to understand its speciation in aqueous systems and the reactions of those various species. This paper deals in particular with the precipitation of arsenic from aqueous solution in the form of insoluble inorganic compounds in order to remove arsenic from various hydrometallurgical process streams. The solubility and stability of the precipitates is examined. It has been found that many of the arsenic compounds presently used are more soluble than previously accepted and unstable in disposal sites such as tailings ponds.

Jan 1, 1987

By K Brown, J Webster-Brown

Coal mining activity first began on the West Coast in 1864 and has since led to the exposure of large areas of coal and host rock to chemical weathering. These exposed abandoned workings have led to the formation of acid mine drainage, which flows into selected rivers and streams impacting on the natural environment. A previous study conducted for the West Coast Regional Council identified four catchments receiving mine drainage which had elevated arsenic concentrations. The aim of this research is to expand on this initial study by determining the spatial distribution and attenuation of the arsenic within the sediment and water column in each stream of concern. Cannel Creek is influenced from drainage from the Bellevue coal mine adit and exhibits a low pH of ~3, elevated sulfate concentrations and high arsenic and iron concentrations in the sediments. This pattern is repeated in the Rapid Stream and Soldiers Creek catchments, which are also affected by adit inflows from the Sullivan and Blackball coal mines respectively. Soldiers Creek also has significantly high arsenic in the waters, with an accompanying pH of ~5.5. Snowy River exhibits a similar trait with a pH also of ~5.5, but with very low sulfate concentrations. Arsenic concentrations in the waters are consistently around 30 ppb, with sediment concentrations up to 900 ppm. These sediment values might be partially attributable to the operation of the Snowy battery gold ore production facility, but the consistently high As concentrations in the water column and in the sediment upstream of the battery have an as yet unconfirmed source.

Jan 1, 2002

By Wright J

Large scale cut and fill mining in narrow silver-lead-zinc orebodies began at Mount Isa in 1964. Initially each orebody was one stope and access was via raises from the level above. Upholing was the principal mining method, although flatbacking was employed where ground conditions were more difficult. Developments since have included access via footwall inclines and connection of all stopes with major crosscuts. Flatbacking is the principal method. The most recent cut and fill operation is now fully mechanised using drilling jumbos, rockbolting jumbos and load-haul-dump units. Improved ground support and drilling and blasting practices have enhanced safety, recovery and productivity in all cut and fill operations.

Jan 1, 1988

By Isokangas T. A

With some two-thirds of the production exported, coal mining prac- tices of the last few years in Australia have been much influenced by the decline in the price received. It became essential to improve efficiency and rationalise operations. Trends in underground practice vary. On the one hand many additional longwalls have been installed and most recently the results achieved by them have shown a significant up-turn; this may be correlated more with increases in equipment capacity than with utilisation which has altered little during the past six years. Varied constraints remain affecting cur- rent and future longwall operations. On the other hand a number of mines have been closed whilst others have sought to improve results by various installations including miniwalls, shortwalls, and use of continuous haulage and mobile breaker line sup- ports. All mines continue to review working practices.

Jan 1, 1988

By Vilela A. C F

In the present work, the process of dephosphorisation of stainless steel was developed in laboratory scale by adopting a high frequence induction furnace, using BaCO3 base flux. By using BaCO3 - CaO - BaC12 - Fe2O3 Flux of about 110 g/Kg-metal, 30 per cent dephosphorisation degree was obtained a stainless steel containing 18,8 per cent Cr and carbon between 0,08 and 2,0 per cent. In addition, a dessulfurisation degree of 89 per cent was achieved too.

Jan 1, 1991

By Liu X

The solubility of cobalt oxide in iron silicate slags has been measured at 1573 K by equilibration of silica and alumina saturated slags with liquid Co-Au-Fe alloys, and by equilibration of silica unsaturated slag with solid Co-Fe alloys, at oxygen pressures of either 10-9 or 10-10 atm (1 atm = 1.013 x 105 Pa). The activity coefficient of cobalt oxide has been calculated and compared with previous studies.

Jan 1, 1991

By Misk A

Several logging methods are presently available to the oil industry for the evaluation of formation porosity: the Sonic and Neutron logs are already widely used, the Gamma-Ganmia log is being progressively introduced. The readings of these instruments are primarily a function of the rack-porosity, hence the general term of "porosity tools". Apart from porosity, however, other variables such as type of fluid in the pores, nature of matrix and degree of shaliness have an important influence.The response of each device is a different function of such parameters: therefore, a cci bination of porosity tools can lead to information on these variables in addition to the evaluation of effective porosity.For example, the presence of gas; rather than water or oil, in a formation which is not deeply invaded, will tend to give Neutron derived porosity values which are too 'low; on the other hand, the Sonic derived porosity: value will be too high in such- a case. For the same porosity, the Sonic gives a longer transit time in sandstone than limestone, whereas in the low porosity range, the Neutron will read more counts per second in a sandstone than in a limestone of the same porosity. The presence of shale also affects the readings of the various porosity tools in different ways so that the combination of two or more methods may lead, in some cases; to an evaluation of both the-effective porosity and the shale, content.In conclusion, it may be said that the various porosity tools pre-sently available, are, to a large extent, complementary, and that in many problems the use of two porosity tools, instead of one, is very likely to bring valuable additional information.

Jan 1, 1962

By N Slade, D Kennedy

Optimal throughput is a key objective for the successful operation of any manufacturing or processing business. In the mining industry in particular, in order to obtain maximum return on the significant capital investment in the physical assets involved, ensuring continuous throughput is a major focus for the complete leadership team. Failure to meet throughput objectives becomes a major source of distraction for management which too often attempts to solve shortfalls by æforcingÆ and æenforcingÆ production targets. This focus on the short term and the lack of attention to addressing root causes frustrates operators who attempt to satisfy unattainable short-term targets and lose sight of the long-term goal. Mount Isa Copper Operations, Xstrata Copper, North Queensland, had ambitious plans to increase throughput volume by ten per cent within a four month period to allow budgets to be achieved within the financial year. To achieve this, the process had to overcome the interplay of a multi-node (æsiloedÆ) production system and its associated inventories, each node, of which on the face of it at least, had more than enough ænameplateÆ capacity to meet these plans. However, the actual volume achieved at the end point of the system was well below this nameplate capacity and the system operated with an extraordinarily high standard deviation. The key issues in terms of making or exceeding plan were: how to substantially reduce the variability of the system and managing the inventories between nodes, how to synchronise throughput between the production nodes, and how to improve the decision-making ability within the process. In this paper, the implementation team has shown that a revolutionary process view of the operation together with appropriate planning decisions allowed increased throughput to be achieved without further capital investment.

Jan 1, 2006

By Whiten WJ

A method that allows data to be mass balanced and screen models to be fitted in a single step is described. The inclusion of several variables to describe the feed data in the fitting procedure allows a mass balance to be conducted at the same time as the fitting of the screen model. Analysis of Groote Eylandt Mining Company screening data has demonstrated that this method is ideally suited to applications where complete stream data are not available. Also, certain random fluctuations in screen model parameters arising from the fitting of consecutive mass balances and screening models are significantly reduced. A cubic spline function with fixed knot positions corresponding to particle sizes and variable (fitted) cumulative percent passing values is used to describe the feed size distribution. When the spline function is interpolated at the experimental feed particle sizes a fitted feed size distribution is obtained. This feed size distribution is then used as input to the screen model calculations from which product size distributions are generated. Since both feed and product size distribution data are used to minimise the residual errors between the observed and fitted stream size distributions, a mass balance is Conducted simultaneously with the screen model parameter fitting.

Jan 1, 1984

Esso Australia Ltd. operates a large natural gas producing system in the Gippsland Basin, supplying gas to the Gas and Fuel Corporation of Victoria, the State Electricity Commission of Victoria and several industrial customers. Gas reaches the Longford processing plants from three offshore platforms via a network of large diameter pipelines, which must be protected against the formation of ice-like hydrates. When gas production commenced in 1969, methanol was used to inhibit hydrate formation in the offshore pipelines. However, later investigations showed that the methanol was causing excessive degradation of molecular sieve in the onshore gas-processing plants. (Molecular sieve is used to remove water and H2S from the gas prior to further processing to remove heavy hydrocarbons.)

Jan 1, 1982

It is important to prevent the overload ing of mills being operated near maximum tonnage. Changes occurring during overload differ in their usefulness as guides to control action. The Primary Ball Mills of Bougainville Copper Ltd. provide an example of some of the problems and progess in avoiding overload.

Jan 1, 1978

Stope control information at the C.S.A. mine is obtained by diamond drilling inclined holes from within the stapes. Practical mining outlines are determined from complicated ore contours by a joint mining engineering and geological study. Production holes to achieve this outline are individually marked up and checked. Stope control also extends to selective mucking of ore mixtures for metallurgical reasons and to marginal ore and waste mixtures for economic reasons.

Jan 1, 1969

The results of iron ore exploration in Western Australia between '1961 and 1964 are outlined, with particular.reference to the Hamersley Iron Province. Exploration during: these three years has increased the known resources of the-,Statle from 275 million tons to almost 9,000 million tons of high- grade hematite ore. In addition, reserves of lower-grade .pisolitic limonite ore are-estimated to amount to 6,000 million tons. The origin and characteristics of the different types of ore is discussed,

Jan 1, 1964

By D Michaelsen, S Miller

The Grasberg Mine is a copper and gold open pit mine operated by PT Freeport Indonesia (PTFI) and located in the high equatorial mountains of the Indonesian province of Papua. The climate is alpine/subalpine with little seasonal variation in temperature or rainfall. The daily average temperature ranges from about 2¦C to 14¦C and the annual rainfall in the vicinity of the mine and overburden stockpiles is about 4000 mm to 5000 mm. Mining of the Grasberg open pit will continue until 2014 at which time approximately 2750 Mt of overburden will have been produced. Current overburden production rates are 200 Mt per annum. The current mill rate is 230 000 t/day from the Grasberg pit (190 000 t/day) and the underground operations (40 000 t/day). The acid rock drainage (ARD) issues associated with overburden from the Grasberg operations were identified early in the mining operation. Almost all overburden placed to date has been Potentially Acid Forming (PAF). Laboratory testing has identified four main overburden types: limestone and non-acid forming (Green waste), PAF low capacity (Blue waste) and PAF high capacity (Red waste), and Heavy Sulfide Zone (HSZ), which contains greater than 20 per cent pyrite. Waste type block modelling indicates that at least 30 per cent of the overburden production from 2003 to the end of Grasberg pit operations will be limestone. Strategies are being developed to maximise the beneficial use of limestone through strategic blending and placement for ARD mitigation and control.

Jan 1, 2003

Mining regulatory authorities worldwide mandate frequent inspection of winder ropes used in shaft-equipped underground mines and ski lifts. Visual inspections are effective in identifying and assessing the type and severity of damage found in the exterior of the rope. In addition, electromagnetic or permanent magnet-based methods are used to identify broken wires, corrosion damage and other anomalies that occur anywhere within the core of wire ropes made of steel, which is a ferromagnetic material. The magnetic methods yield the loss of metallic area due to wire breaks and other damage in the ropeÆs section as well as local flaws that give rise to discontinuities in the magnetic field. The quantitative measurement of the loss of metallic area is indirectly related to the loss of breaking strength that is commonly used as a rope discard criterion. The ropes used in a mine winder in the Goldfields of Western Australia are inspected using Meraster 120B permanent magnet-based rope tester and their condition is assessed against published discard criteria.

Jan 1, 2003

Following GyÆs earlier proposals for the use of StudentÆs t-test, a simplified, effective method and philosophy are proposed to test for maximum tolerable bias in data sets as well as in sampling devices. The philosophy of testing is particularly emphasised to derive important practical implications in terms of decision-making and risk control. Conclusions are offered which should equally matter to manufacturers and users of sampling equipment.

Jan 1, 2005

The importance of orebody definition and optimisation in project development cannot be overstated. Inappropriate orebody definition is the single most important reason for project under performance and/or failure. Without the firm foundation of good orebody definition, the structure of a project cannot be assembled reliably. Many factors need to be considered in the process of orebody definition. These factors are well summed up in paragraph 123 of The Institute's Code and Guidelines for Assessment and Valuation of Mineral Assets and Mineral Securities (Valmin Code). The factors range from the initial geological data through assaying, geotechnical and hydrogeological factors to mining and metallurgical considerations. There are other factors which also need to be considered including marketing and environmental factors. This paper briefly reviews some of these factors and their impact on project development. Three examples are presented where one or more of these factors have had significant impact on the development of the Project.

Jan 1, 1997

In presenting the paper, Mr. Davey quoted subsequent work which yielded k, at miscibility gap composition, of about 50.We can confirm the authors' findings for k j 300 for nearly pure tin to k 2 about 50 (average 47) from our own experience and from repeat experiments on materials described by the authors, at 1150°C.During laboratory-scale trials we also found confirmation of the authors' view that it is more difficult to reach equilibrium from the high-iron (in slag) side than from the low-iron (high-tin) side. Working from the high-iron side tends to yield results that point to a high k, leading to optimistic values of iron/tin ratio in final slags. In practice the smelting of a tin concentrate, unless it is exceptionally low in tin and high in iron, must yield initially a tin-rich slag and therefore equilibrium can only be reached from the "tinny" side.

Jan 1, 1967

The Plant Control and Data Logging System for the Loy Yang Open Cut (LYOC) is part of a control and communications network designed to provide a high level of surveillance of open cut plant and facilitate the efficient co- ordination of operations and plant maintenance. The computer system selected utilises a central dual mini-computer and multiple microcomputer data transmission network ,linked to the plant controllers using distributed, microcomputer based remote data collectors or outstations. Several aspects of the computer system are outlined.

Jan 1, 1982

It is a well known fact that the best method of rock reinforcement is to avoid physical ground support. This goal can be achieved by means of: - Increasing the rock structural strength - Geological definition and forecasting. - Sequencing the excavation - Smooth blasting In many cases however, extra ground support is needed in order to maintain safe working conditions. In an open pit, the structural strength of rock cannot be increased by lowering the pit walls due to economical reasons. Economy demands steeper walls and less waste to be hauled to the dump. The geological conditions can also often be extremely poor and unpredictable. For excavation sequencing and smooth blasting there are good possi- bilities, such as cleaning of the pit walls after the main excavation, arul- ing of long small diameter straight inclined holes, use of smooth blasting techniques and lightened explosives.

Jan 1, 1989