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By O Ostrovski

Iron ore reduction and iron cementation by CH4-H2-Ar gas was investigated in a laboratory isothermal fixed bed reactor. Iron ore was first reduced to metallic iron by hydrogen, then carburised to cementite by methane. Increasing temperature and hydrogen content accelerated the reduction process. Methane had almost no effect on the reduction process. Meanwhile, higher temperatures increased the rate of cementation and also the rate of free carbon deposition. The optimal temperature for cementite formation was found to be 750¦C. At this temperature, reduction of iron ore to cementite by gas containing 55 vol per cent hydrogen, 35 vol per cent methane and 10 vol per cent argon was completed in about 15 minutes. Addition of sulphur into the reducing/carburising gas strongly retarded the process of cementite formation and free carbon deposition. Cementite is an unstable phase which decomposes to iron and carbon. The rate of cementite decomposition increased with temperature up to 600¦C and above 750¦C . In the temperature range from 600¦C to 750¦C the rate of cementite decomposition decreased with temperature. Cementite was the most stable at 750¦C and least stable at 600¦C. The two-interface grain model was used to describe the process of iron ore reduction and the volume reaction model was employed to model the iron cementation process. The simulated results for both reduction and cementation are consistent with the experimental data.

Jan 1, 2000

The sole reason for a mine to exist is to extract the finite mineral resource. Accurate grade control is critical to the economics of any mine. If grade control is not optimised, then no matter how good the downstream processes are, the full potential of the operation will not be realised. The detailed implementation of grade control varies but typically consists of sampling and assaying to determine the location of the ore zones. A lot of time, money and effort are spent defining the location of the ore as accurately as possible à but then it is blown up! The effect that blasting has on grade control is rarely adequately accounted for when the rock is excavated because there has never been an accurate and practical method for measuring blast movement. This paper draws on over six years of research into measuring and understanding blast movement, which started at the Julius Kruttschnitt Mineral Research Centre (JKMRC) of the University of Queensland. The research has made a unique contribution to open pit blasting by helping to develop a practical tool for measuring blast movement, which was then used to improve the understanding of three-dimensional blast movement dynamics. However, these achievements would be of largely academic interest without taking the final step of using this technology and knowledge to account for blast movement by translating the ore polygons in response to the measured movement vectors. This paper provides an overview of blast movement but focuses on one site where blast movement was measured during three separate periods, with significantly different orientation of the mineralisation on each occasion. The theoretical ore loss varied from nine per cent to 24 per cent. The differences are primarily due to the orientation of the ore polygons relative to the direction of movement. The optimum grade control solution is a combination of accurately accounting for blast movement and designing appropriate blasts.

Jan 1, 2009

By W R. Hancock

Control of complex machinery through the internet is investigated through the construction of a vehicle prototype developed using off-the- shelf hardware. The vehicle was able to be controlled remotely through the use of a client side interface connected to a steering wheel and foot pedals. By attaching sensors to the vehicle, data could be collected from which one could infer the effectiveness of such a control system. The effect of latency on control was monitored by the introduction of an artificial latency, simulating a wide variety of internet-related issues, such as unstable connections and dropouts. Sensor data could then be used to gain an understanding of how the system could be improved though either control or interface design. A path tracking experiment was conducted to gather controllability data and it was found that such a system is plausible within a reasonable range of latencies. It is expected an area of future research would be an extension of this current project, applying the information gained to real world control systems.

Jan 1, 2008

This paper summarises the performance of the gold exploration industry in the Western World since 1970, with particular emphasis on the period 1985 - 2003. It identifies the number and size of major (ie >1 million ounce) primary gold discoveries made over this period by location and type of company. Estimates are also made of the likely contribution from smaller discoveries down to 0.1 million ounces. It also assesses the overall trend in the percentage of grassroot discoveries that are converted into mines, and the time taken to get them into production. By comparing the discovery data against total exploration expenditures it is possible to determine the average unit cost of finding a major gold deposit. It is significant to note that the average unit cost per discovery and per ounce of resource has tripled over the last 30 years. An attempt is made to determine the overall economic value generated by the industry. This is based on a detailed analysis of the rates of return and the Net Present Values (NPVs) of 109 major gold projects. After including an adjustment for discoveries not modelled, the NPVs are compared against the total amount of money spent on exploration to determine the value-to-cost ratio for the industry. Based on historical spot gold prices and tax rules, it is found that the return on investment for gold exploration in the Western World over the period 1985 - 2003 was around five per cent real after-tax. The returns achieved in the US and Australia was significantly higher than that for Canada. The returns also appear to have declined in recent years. With regard to the relative performance of junior versus major companies, the paper estimates that the junior sector accounted for 30 - 40 per cent of the total exploration expenditure, and were was associated with 34 per cent of the total number of major deposits, 27 per cent of the contained ounces and 25 per cent of the economic value found.

Jan 1, 2004

By Lockyer PC, Reed MR Bartlett PM

Difficult ground conditions have plagued the underground operations at Mount Windarra since mining started in 1974.The ore at Mount Windarra consists of seven vertically dipping, sub vertically plunging ore shoots. The ore zone in which the shoots lie is characterised by moderate to heavy cleavage and the presence of serpentanite. The ore is known to extend to 1100 metres below surface.Long hole open stoping under cover of backfill has been used as the primary mining method at the mine, but its poor performance brought the mine near to closure in 1984. The mine had been closed from 1979 to 1980.

Jan 1, 1985

By Mercer JK

This paper gives a description of the research undertaken by an explosives manufacturer to give better technical advice to the Mineral Industry. Blasting Physics is defined as giving a systematic and coherent account of the initiation and subsequent effects of high explosives upon the surrounding medium. As a result of this work a mathematical model based on the gener- ally accepted mechanism of blasting has been developed. The mechanism and the resulting model are briefly outlined. IFrom'this model the effects of burden, spacing, blasthole diameter, rock and explosive properties upon fragmentation and heave can be calculated. Using these calculations it is then possible to see how variations in frag Imentation and heave can affect the overall production costs of a mine whether it is surface or underground. The overall costs are made up of a number of individual costs - drilling, blasting, loading, hauling and crushing. ach of these operations influences or is influenced by fragmentation and heave s these costs are inter-related, the

Jan 1, 1975

The Golden Valley Volcanic Centre has been recently interpreted as being a combination diatreme breccia pipe and rhyo-dacite flow dome complex of Permo-Carboniferous age that intrudes basement granitoids and sediments of Ordovician-Devonian age. Exceptionally good exposure at the Centre has enabled the relationships between different lithologies to be determined. This, along with petrological studies, has led to a detailed understanding of the geological environment in which the complex formed. Gold, silver and base metal mineralisation have been recently shown to be associated with the Marginal Breccia at the perimeter of the diatreme. Comparisons have been made between the geology and mineralisation in this system and several similar diatremes which also contain gold-base metal sulphide mineralisation.

Jan 1, 1990

The facilities used and techniques employed in the manufacture of steel and iron rolls at the Steel Foundry, B.H.P., Iron & Steel Works, Newcastle are described.

Jan 1, 1972

The fragmentation of whole rock by blasting has an influence on the subsequent loading, hauling and crushing operations. However, no method of calculating the frag- mentation has yet been developed. This paper gives a method of calculating the fragmen- tation for the simplest form of blasting, i.e. cratering. Cratering consists of the detonation of a spherical charge of explosive in a blasthole breaking to one free surface. This paper gives a method of calculating the extent of the system of radial cracks generated by the explosive in the rock. This system of radial cracks is then used to calculate the fragment size distribution curve from blasting. The calculated curves are shown to be in good agreement with experiment.

Jan 1, 1977

A large scale distributed process con-trol system has been successfully applied to the automatic control of aluminium reduction cells at Boyne Smelters. A three stage hierarchy of minicomputers and microcomputers is used to continuously monitor and control conditions in each cell and to manage the data generated during the process.The automation hardware was purchased on the basis of low cost, high reliability, prior use in the aluminium industry and a high level of backup under failure conditions. The hardware has met performance criteria to date.The process control strategies have continually been updated to minimise the energy and raw material consumptions in each cell. A major change to systems software has recently been made to decrease the development time for-future changes. Various low energy potline retrofit alterations are currently being investigated requiring significant changes to the process control strategies.

Jan 1, 1985

DR. WARK, said: I have not come to Broken Hill to tell you how to conduct flotation operations; indeed, during my short stay here I have already learned much concerning the process, of the many difficulties which have been overcome, and of those still awaiting solution. My purpose to-night is rather different. All who have been concerned with the operation...

Jan 1, 1933

By Kaji S

The Tsugaru Tunnel, located on the Honshu island approach to the Seikan Tunnel, is 5,880 m long and has a "Shinkansen" cross section of 90 m2 area. The geological formation through which the tunnel passes consists of very soft rock most of which is unsolidified sandstone belonging to the Neogen. The permeability coefficient is in the range of 10-2 to 10-4 cm/s and being water bearing with a high ground water level, the ground is unstable and subject to soil outflow phenomenon. Kajima Corporation, undertaking the Futamata Construction Section (1,420 m long), excavated the tunnel by the upper half heading method with side pilots employing the following countermeasures to cope with these severe conditions.

Jan 1, 1987

With the recent wider introduction of friction hoists of the Koepe type. for winding from depths of more than 3000 feet it has been found that failure by fatigue is the most common form of rope deterioration. Large numbers of wire breaks occur near the centre of the rope cross-section and it is difficult to detect these with certainty using the preferred d.c. magnetic test. For best results with conventional search coils their dimen- sions should be related to the typical wire break field pattern surrounding the longitudionally magnetised rope. The field of a broken wire was experimentally determined, using a Polish type MD6 Defectograph wire rope testing magnet and a short prepared length of rope with a movable simulated broken wire. The external field distortion perpendicular to the rope was measured by means of a gaussmeter and Hall probe. The advantages of this method are that terrestial magnetism and inherent rope "noise" have no effect on the results.

Jan 1, 1971

Spatial data processing using geographic information systems produces qualitative results which are superior to those from other existing software tools. However, the answers to various quantitative questions in mining operations is often limited by the capacity of the GIS to process appropriate spatial data. The efficient operation of a large underground mine demands that an adequate GIS be put in place.

Jan 1, 1995

An increase in the silver to gold ratio with increase in depth in the main ore shoot of the Crown- Crescent lode in the Emperor gold mine, Fiji, was found to be due mainly to vertical zoning of gold-silver tellurides. The zoning resulted from

Jan 1, 1980

Examples are given of the different management approaches used to improve a mine's profitability and the view is put that attention to mine design is very important but easily overlooked. The need for humans to use graphics to ccanprehend and develop strategies to exploit ore deposits is discussed. The use of two and three dimensional representations for geology, mine design and survey data is reviewed. The current use of computers in mining is discussed and reasons for the limited use of ccanputer graphis are proposed. Suggestions are made as to how more extensive use may be made of catputer graphics in mining by using recent and possibly forthcoming advances in computer hardware and by adopting certain software approaches.

Jan 1, 1983

By D P. Telionis, P P. Vlachos, R-H Yoon

Industrial processes involving multi-phase flows such as flotation require understanding of the relationships between bubbles, solid particles and the flow. Modern experimental tools are employed in this effort to measure with great accuracy the basic features of the motion of all three phases in turbulent flow. We employed a unique digital particle image velocimeter (DPIV) that can record with great accuracy and kHz temporal resolution, velocity vectors of all three phases, namely the fluid, the solid particles and the air bubbles. The interaction of these three phases was studied in homogeneous isotropic turbulence generated by cylindrical grids. Particles and bubbles were released into the turbulence and the motions of the three phases were monitored. The experimental results obtained in the present work were compared with the predictions of the models published in the literature.

Jan 1, 2005

By Yamamoto Y, Ohyama H

In case of NATM, mechanical cutting is desirable in view of the original purpose of not spoiling natural ground. As typical tunnelling machines, there are two (2) kinds available: one is "Full Face Excavator" known as TBM (tunnel boring machine), and the other is "Roadheader" known as Part Face Excavator. By the use of the former, accurate profile cut is made possible, but there is a limit in the shape of a cutting section. By the use of the latter, cutting of various sections is made possible, but in order to cut a section economically and accurately, operators are required to have a high level of skill. In this text, we introduce Automatic Controlled Profile Cutting System (hereafter "ACPC" System) developed as a roadheader.

Jan 1, 1987

By Boehme PW, Gregory OR

The results presented here show quite definitely that in the system investigated the intensity of dispersion is enhanced by switching the flow entry from bottom to sides of the packed trough. Since there is no reason to suppose that this would not be true generally then it is not surprising that the blast furnace dispersion data of Standish and Polthier lie above the data for packed columns with bottom fluid entry. In fact, on the basis of the present results, blast furnace dispersion results can never equal standard packed column behaviour but must always be above these. The result that the intensity of dispersion in the trough model is higher closer to the side ports than away from them is at variance with that of Standish and Polthier blast furnace results. Aside from the obvious structural differences between these two systems, it is thought that the presence of raceways and the tortuous path of the gas flow in the furnace may provide an answer. Clearly this is an important difference in the behaviour of the two systems and further investigations designed to clarify the position would have significant practical value. This would also give an indication of how the furnace D/ud values may be decreased along the whole height - assuming of course that this result gives the best overall performance of the furnace. However, there is to date no knowledge whatsoever about this aspect of blast furnace Technology.

Jan 1, 1975

Gravity concentration of tin at Renison Limited uses tables and spirals to treat the various coarser fractions produced from sulphide flotation tailing. An acceptable final tailing cannot be made from one pass over the tables and spirals and therefore the tailing from these separators is reground and combined with the sulphide flotation tailing as the feed to the classification section. The gravity section became increasingly overloaded in the years preceding 1976 due to efforts to maximize tin recovery to the gravity concentrate. In April, 1976, two 2DSV Reichert cone concentrators in series were installed to treat the table and spiral tail- ing stream, prior to regrind, to scavenge a small tonnage of hard, coarse low tin grade material for rejection to final tailing. Gravity section loadings were decreased markedly, allowing operator attention to be directed more to table performance than to spillage collection. An increase in mill throughput of approximately 15% was possible following the commissioning of the Reichert cones. The cones are currently operated to make the minimum tonnage of tailing consistent with reasonable- gravity section loadings.

Jan 1, 1978