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With constantly rising energy costs it is ever more important that we look at ways of im- proving comminution efficiency both in terms of power consumed as well as capital costs required for purchasing and installing equipment. I intend to show that commonly used appli- cation criteria, which is presently accepted for designing crushing and screening plants, need drastic revision if it is to be used to accura- tely design, predict and refine performance in new and existing facilities. Unless we can calculate performance accurately, we cannot minimise capital investment and maximize Profitability.

Jan 1, 1978

By K Matsui, T Sasaoka, S Kubota, Y Yosh

A large amount of wastes from the preparation plant is produced. The properties of these wastes vary depending on the mineralogical contents of the mother rock in which the coal is embedded. The waste quality depends on the method of mining and cleaning. The waste mainly consists of clays, quartz, carbonaceous materials, mica, pyrites and so on. About 55 per cent of coal-ash is now utilised and the remains are disposed of at the disposal sites, however, the life of the disposal site is limited. Moreover, it is difficult to find new disposal sites. Therefore, it is requested that the percentage of the utilisation of the coal-ash be increased in every field in Japan. So, it is very much available if the injection material for natural/artificial openings can be applied on the cement that is added to flyash. Among the man-made pozzolans, a flyash is probably the most successful component used in grout injection. When flyash is added to Portland cement concrete, the same kinds of oxides as those of the cement are being added. As an injection component, flyash acts, in part, as a fine aggregate and, in part, as a binding component. However, there is not a substantial alteration of the properties of the original component. From these points of view, in order to clarify to what degree the flyash content affects the properties of the injected grout mixture; different combinations of flyash, Portland cement and water were considered by means of several experiments.

Jan 1, 2003

In a previous paper in these Proceedings(l) it was shown from a study of the bore'logs and analyses then available, that the brown coal seams of the Latrobe Valley areas show progressive changes in composition with increase of stratigraphic depth, equivalent to a rise in rank: These changes appear as:(i) An increase in ultimate carbon and hydrogen, calculated on a dry, ash-free basis, and(ii) An increase in calorific value, calculated on the, same basis, each of the order of 1% per 100 ft. of depth, and(iii) A decrease in moisture content of the order of 0.5% to 1.0% per 100 ft. of depth. The decrease in moisture content was found to be less regular than the other changes. In some bores the moisture content remained more or less constant throughout a single seam, or fluctuated slightly, decreasing stepwise on passage to the seam below.It was noted that individual analyses within a bore showed irregular fluctuations, tending to mask the general trend in composition change. This was particularly so for the moisture content, which had been determined for 10 ft. lengths of core, whereas the other components were determined for 50 ft. lengths of core. Averaging of the moisture contents over 50 ft. lengths reduced the masking effects of these irregularities. The suggestion was made that these irregularities arose from variations in the relative proportions of pollen, resin, wood (lignite) and woody attritus composing the core. Such variation in the coal seams has since been established in some detail for the...

Jan 1, 1948

The optimisation of capital in the total planning context has broadly two components: ò maximising the efficient utilisation of capital against competing capital demands; and ò maximising the efficiency with which the industry's capital requirements are sourced. This paper focuses on the latter of these two concepts, as I wish to highlight that within the coal industry the inefficient sourcing of capital has resulted in the inefficient utilisation of capital. In discussing the optimisation of capital within the coal industry I would like to outline three fundamental issues which currently impact the industry and its application of capital: Initially, from the perspective of an independent investor, the perceived risk associated with investing in a volatile industry cycle has not permitted appropriate funding structures to be created thus leading to an inefficient utilisation of capital. Secondly, investors seeking out a windfall gain have established a practice of trading in the assets rather than encouraging recapitalisation. And lastly the mismatch of supply and demand leading to the establishment of new projects which include a percentage of offshore investment has fostered an environment of lower returns and subsequently a dilution of capital.

Jan 1, 1991

By Jaczkowski B. M, Cox T. J, Domfeh I. A, Stalker I

Mining and treatment of gold ore in the Ashanti region at Obuasi, Ghana has been continuous for more than 100 years. Earlier production from this world class deposit can be traced far into the history of West Africa's gold trade. As part of a general development and expansion program, Ashanti Goldfields Corporation (Ghana) recently undertook a program to heap leach oxidized near surface ore. Kappes, Cassiday & Associates was given a major role in the design, equipment supply, installation and start-up management of the 3000 tonne/day heap leach. Unusual conditions included a high annual rainfall and an ore which could be characterized as a soft, decomposed, water saturated schist. Production began in March 1990. Startup problems and their solutions are discussed.

Jan 1, 1991

By J J. Cilliers, K Hadler

The potential of air rate profiling to significantly improve the flotation performance of a bank of cells has been shown by numerous studies. To date many profiles have been evaluated; balanced, increasing, decreasing and combinations of these. An increasing air rate profile, where the air rates are increased proportionally to each cell down the bank, has been typically found to yield improved flotation performance compared to other profiles. Air rate profiling has two distinct components; determining the correct total air rate for the bank, and determining the correct distribution of that air. This can be done simultaneously by finding the optimal air rate to each cell in the bank in turn through air recovery optimisation. Air recovery is the fraction of the inlet air which overflows the weir of a cell as unburst bubbles. The peak in air recovery (PAR) is a robust measurement of optimal performance for the operating conditions in the cell, and sets the PAR air rate. In this study, plant trials of different air rate profiles and profiling based on PAR, were evaluated. The total air rates to the bank for all profiles tested were approximately equal, allowing direct comparison. The highest cumulative mineral recovery was achieved by operating at the PAR air rates for each cell down the bank. Different distributions of the same total air rate to the bank gave the same cumulative upgrade ratio, but lower cumulative recoveries. In this work the upgrade ratio is defined as the ratio of the concentrate grade to the feed grade. The increase in cumulative mineral recovery, at the same upgrade ratio, in this study was greater than 33 per cent. Air recovery based optimisation of air rates to banks of cells significantly improves flotation performance as it simultaneously determines the optimal air rate to the bank, and the optimal distribution of that air.

Jan 1, 2009

By P J. A Lever

This paper presents details of CRC MiningÆs work with waterjet assisted blasthole drilling. The objective of this work was to investigate techniques that reduce the cost and increase the productivity of blasthole drilling. The focus is on a technology that uses a high pressure waterjet to assist the conventional rotary rock cutting action of a tricone drill bit. The potential benefits of this technique are increased productivity, reduced drill bit wear and reduced hole deviation and hence improved quality of drilling. This paper describes the results of a laboratory based experimental program comparing conventional tri-cone drilling performance to the proposed waterjet assisted approach. Additionally, work has been completed looking at the more practical issues around the collection and sampling of drill cuttings and water recovery (recycling) when drilling with a waterjet. These studies have demonstrated that waterjet assisted drilling can significantly increase the rate of penetration over conventional rotary drilling. For the best-case experimental result, the relative improvement was over 40 per cent. More importantly, it is a starting point for examining alternative uses of the additional drill productivity obtained from waterjet assisted drilling. For example, increased drill productivity could be used to improve rock fragmentation by drilling a tighter blasthole pattern in the same time period. an existing drill fleet, then the drill fleet size could be reduced, or improved rock fragmentation could be achieved by drilling a tighter blasthole pattern within the same time period.

Jan 1, 2004

Builders have been very familiar with iron since ancient times, but because of its weathering characteristics it was relegated to use as a fastening material in unexposed places and bronze became the popular metal for exposed applications. It is of interest that iron nails buried deeply about A.D. 87 at a Roman fortress and carefully covered with clean beaten earth under conditions practically excluding oxygen were found to be almost unrusted 1870 years later. (1) Today, weathering steels, which contain less than 2% of alloying additions, can be used in exposed situations without protection and without experiencing continuous wastage. As we all know the steady access of atmospheric oxygen to the surface of plain steel causes continuous corrosion. Weathering steels, on the other hand, due to their alloying additions develop their own impervious surface layer which limits the access of atmospheric oxygen and effectively limits corrosion. Table 1 shows the chemical composition of a plain carbon steel and a typical weathering steel. Fig. 1 shows what we refer to as direct corrosion - time curves in which corrosion loss is plotted against time of exposure in an strial environment. The weathering steel has a high rate initially which then decreases steadily for about three years, as the stable rust film builds up. This is followed by a practically linear relation where the very low corrosion rate, according to one school (2), is due to a blocking of the rust pores by insoluble complex salts formed from interaction of the oxidation products of the separate alloying elements. The start of the linear region represents a total corrosion loss of only about 2 thousandths of an inch.

Jan 1, 1970

The paper gives details of the performance of a 6-ft. by 6-ft. grate discharge ball mill which was converted into a rod mill of the overflow type and then into a grate discharge rod mill. Proposals for further alterations are outlined.INTRODUCTIONThe mill of King Island Scheelite (1947) Limited recovers scheelite by gravity methods.Crushed ore at the rate of 34 tons per hour is divided between two mills. (6 ft. by 6 ft. and 8 ft. by 6 ft. respectively), the mill discharges being pumped to a common distributor which feeds seven Hummer Screens. Each screen has three 4-ft. by 2-ft. Ton-cap sections and repulping compartments are provided. The screen oversize is returned to the mills whilst the screen undersize is finished grinding section product. A third (6 ft. by 6 ft.) mill regrinding the coarser table tailings also discharges into the common Hummer Screen Distributor.The screen undersize is pumped to a bowl classifier which separates at 200 mesh. The bowl classifier sands are treated on tables whilst the bowl classifier overflow, after thickening, is treated in the slime plant by flotation. The flotation concentrate is further concentrated on vanners and slime tables.A recovery of 80 per cent. is possible by tabling whereas only 50 per cent can be recovered in the slime section. The object of comminution is, therefore, to reduce all the new feed to less than a certain mesh (22 mesh Tyler) with the production of a minimum quantity of minus 200 mesh material. cheelite is, a very friable heavy mineral (Sp.Gr. 6'0) and is therefore susceptible to overgrinding. For the evaluation of grinding performance it is hence advisable...

Jan 1, 1955

By Thomson S, Eisenstein Z

Field instrumentation was installed to monitor ground and lining behaviour during and after construction of the Mount Shaughnessy Tunnel (Rogers Pass Short Tunnel) in Canada. The instrumentation was placed in a soft ground section of the tunnel at its crossing with the Trans Canada Highway. The tunnel was excavated through a dense bouldery soil. Presentation of the field data and inter- pretation of the tunnel performance from a geological-geotechnical point of view form the basis of this paper. The loss of ground due to the tunnel excavation was found to be exceptionally small. This has been attributed to the unusually high strength and stiffness of the host soil. Evaluation using the Boundary Element Method, together with a simplified analytical technique, were applied to assess the relevant soil parameters and their influence on the tunnel performance.

Jan 1, 1987

By Weir D. R, Doyle B. N

The Sherritt Zinc Pressure Leaching Process is based upon the direct pressure leaching of zinc sulphide or lead-zinc bulk sulphide concentrates to produce zinc sulphate in solution and elemental sulphur in the leach residues. The zinc sulphate solution is compatible with conventional purification and electrowinning technology. The pressure leach residues can be treated for the recovery of elemental sulphur, lead and silver. With the conversion of sulphur to the elemental form, zinc pressure leaching allows zinc winning to be independent of sulphuric acid production. Direct pressure leaching of zinc sulphide concentrates was started commercially in October 1980. Continuing research and development studies have defined various pressure leaching configurations for integration with existing roast-leach operations, for grass roots plants, or for plants which are to have the roast-leach section completely replaced. These studies have included the treatment of zinc concentrates from various Australian producers and the development of process flowsheets for potential applications in Australia.

Jan 1, 1989

By R Lau

In recently completed road tunnel projects in Queensland, such as the Airport Link and the Clem7 tunnels, there is a smoke duct running along the roof of the carriageways to extract smoke in case of fire. In New South Wales, no road tunnels have a smoke duct. In the Melbourne City Link tunnels, there is a small smoke duct running along the roof. All of the tunnels are safe as claimed by the designers and authorities. However, there is significant cost associated with providing a full size smoke duct compared with no smoke duct. This paper is going to present a comparison of the road tunnel safety with a smoke duct and those without one from a risk perspective. It further discusses the cost-effectiveness of such provisions and whether similar levels of safety could be achieved without a smoke duct.CITATION:Lau, R, 2014. Smoke duct or no smoke duct for road tunnels, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 83–86 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

Aluminium in Australia, and in fact all round the world, is made virtually exclusively by the Hall-Heroult process, whereby the metal is derived from the electrolysis of alumina dissolved in an electrolyte comprising fluoride salts. It is the distribution and control of these inorganic fluorides during and after the reduction process which go to make up the bulk of environmental problems associated with aluminium reduction smelters. The emission characteristics of fluorides from the process, the occurrence and effects of fluorides in the environment, and the control techniques wnich are applied in industry, all need to be taken into account in assessing the overall environmental aspects of aluminium Production.

Jan 1, 1977

Based on a principle developed at a South African Mine, the CSIR developed a device with which the alignment of guide rails in mine shafts could be measured. Originally the technique could only be used to obtain guide misalignment values at the bunton sets. At the time this was considered adequate since it was assumed that guide realignment could only be done at the support points anyway. The technology was developed further and now it is possible to obtain æcontinuousÆ guide profiles from the measurements. Software was developed with which a guide realignment schedule can be drafted and the shape of the realigned guides can be predicted. A measuring system based on this technology is being used to conduct guide alignment measurements in shafts. The data is then analysed and a realignment schedule is recommended in consultation with the mine. Such a schedule may be prioritised so that the worst sections in the shaft are dealt with first. The measurement hardware and analysis software are described. Examples are presented that illustrate the principles and highlight measurement errors. A case study illustrates measurements recorded in a newly equipped shaft. A repeat measurement, 18 months later, shows the effect of recommended realignment as well as the change in guide alignment over this period.

Jan 1, 2005

By Lu S, Zhou S

The flash smelting technology employed in Jinchuan demands a better mineral processing concentrate with an MgO content below 6.5 per cent. Two ways for MgO removal have been investigated in detail based on properties and process mineralogical characteristics of the rich ores in the number one mining area in Jinchuan. The key to the first way is the use of a new flowsheet which has two-stage grinding and separation followed by single-stage regrinding and multi-stage cleaning for the rougher concentrate. The second approach utilises two novel reagents, AT-131 and AT-202, which have been developed recently. Excellent metallurgical performance has been obtained in a commercial test and a batch test, respectively. The MgO content of flotation concentrate can be reduced to about six per cent.

Jan 1, 1996

By Carlson BL, Overton DD

This paper compares the designs of heap leach facilities for four precious metal mining projects in the southwestern United States. These four proposed projects are of small-to medium-size relative to other operating mines in the United States, and are either permitted or in the final stages of permitting. The differences and similarities in the heap leach facility designs are compared with respect to site conditions, operating conditions and regulatory requirements. This comparison provides a summary of the state-of-practice for heap leach facility design in the southwestern United States and identifies current issues in project development and process material containment.

Jan 1, 1997

By Regan R

Appin Colliery mines the Bulli Seam with a gas composition of 98.5% methane and 1.5% carbon dioxide. Relaxation of the strata generally occurs to below the base of the Wongawilli Seam, some 40 m below the Bulli Seam, and approxim- ately 125 m above the Bulli Seam, for longwall face widths of 135 m or more. Previous exper- ience showed that when longwall faces were mined for a distance approximately equal to the face width, the mine ventilation could not provide sufficient dilution due to methane emissions from the underlying measures. Postdraining downholes were drilled to intersect the Wongawilli Seam below the operat- ng longwall. These holes were connected to an underground to surface gas range and various suction levels were applied to improve gas drainage. The resulting gas flow rates and purity from all the downholes were regularly monitored and peak flows in some holes exceeded 160 1/sec. The surface plant drained almost 20 million m3 of gas for the period July 1981 to January 1982 at an average methane purity of approximately 70%. Distinct patterns emerged for different downholes from curves illustrat- ing their variations in flow rate with distance subsequent to passage of the longwall face. The difference between free flow characteristics and those obtained with the application of

Jan 1, 1982

By Streichfuss M, KeBler H-W, Burgwinkel P

This paper describes the design of an expert system used as a part of a diagnostic system for diesel hydraulic drives. A PC-based diagnostic system ruDi (KeBler and Burgwinkel, 1993) was developed to minimise the time for diagnosis and repair work of vehicles with diesel hydraulic drives used in the mining industry. One part of ruDi is an expert system that helps to locate errors in any of a vehicle's subsystems, and supports technicians in removing the cause of a malfunction. Apart from the standard knowledge of diesel engines and hydraulic transmissions, the expert system supports the interpretation of the data obtained during sophisticated engine analysis tests such as high-resolution speed analysis or high-pressure analysis of the diesel injection system. The expert system is designed to diagnose various vehicles of the same type. Data for each vehicle is stored separately allowing checks to be carried out individually for each machine. An additional feature of this system is a database interface to a Maintenance Planning and Control System (MPCS) that allows an automatic generation of work orders for the defects found during the expert system sessions.

Jan 1, 1995

By Richmond AJ, Allan J

The use of long-hole in-seam drilling techniques for seam gas drainage ahead of mining was introduced to the Australian coal industry by ACIRL in mid-1981. ACIRL's research program has involved the development and demonstration of drilling and borehole survey technology in addition to evaluating the gas drainage potential of long-hole in- seam boreholes. This paper presents the results of the long-hole drilling carried out to date in the Illawarra District of the New South Wales coal fields. Drilling experience in relation to both vertical and horizontal directional control of the drill string, drill performance and borehole survey techniques are discussed. In addition, results of gas drainage effected by the long boreholes are presented. Future potential and requirements for further development of this technology are Reviewed.

Jan 1, 1982

A study of the effect of nickel on the cupellation process has shown that a very low "nickel limit" must be imposed for cupellation (0·08 grams nickel or 0·05 grams when copper is present). In the presence of slightly greater amounts of nickel, lead tends to spreadon the cupel with detachment of drops from the main lead pool. In crucible fusions nickel contaminates the lead button to a small extent, and this contamination is increased.in the presence of either iron or copper. Nickel also causes "shotting" of the lead, this effect being more apparent in the presence of iron.Both the spreading during cupellation and the shotting during crucible fusion are considered to be caused by adsorption of insoluble NiO at the Pb-PbO interface, lowering the interfacial tension.Excess litharge crucible charges are' fused at 116boC. to eliminate shotting. A brief· soaking in molten basic litharge slag effectively reduces the nickel content of lead buttons. The solubility of silver in litharge slags is considerably decreased in the presence of nickel. Corrections can be applied for silver losses in slags but these corrections are not as accurate as with copper ores.INTRODUCTIONThis paper on the effects of nickel on fire assays for silver is the second of an intended series describing investigations into the fire assaying method.In the first paper, discussing the effect of copper on fire assaying processes (Guerin, 1957), it was shown that certain elements, because of their relatively low affinities for oxygen, will tend to contaminate the lead button during crucible fusion and scorification. Nickel, having a slightly greater affinity for oxygen than has lead, would be expected to be oxidized and slagged readily, and would not be expected to appear in the metal phase (lead button) to any appreciable extent. Thus, judged solely on this basis of...

Jan 1, 1960