Search Documents

By Manzoori AR

From a detailed combustion testing program and earlier experience with Leigh Creek coal, the Electricity Trust of South Australia (ETSA) gained a wide insight into the use of low rank coal fired boiler plant. This work is fundamental for the selection of boiler design parameters and other details which in turn determine the correct coal deposit selection for future power station development. In addition it gives boiler designers a good indication of the measures required to give reliable plant operation. Extrapolation from experience with existing plant, the designers main source of information, was not considered appropriate because of the lack of experience with similar coals. Brown coal beneficiation is also being assessed by ETSA in an attempt to improve the coal quality by the pretreatment of the raw coal prior to combustion in future coal.fired boilers. ETSA is also involved in the development of circulating fluid bed and gasification processes to determine whether these alternative processes are a more viable method of utilising the South Australian coals than pulverised fuel firing.

Jan 1, 1987

By Muir D

A review of the various methods of degrad- ing cyanide either from gold processing liquors or electroplating baths is presented with some discussion on their relative merits or problems. Whilst alkaline chlorination is common practice in many U.S. and Canadian plants it poses particular problems for certain plants. Alter- native methods include electrolysis, hydrolysis and air oxidation with activated carbon as catalyst which are also integral steps in the carbon-in-pulp process. A basic study of the degradation of cyanide ion has been carried out therefore to determine the effect of temperature, oxygen and carbon. It is shown that carbon is an excellent catalyst for degradation by air and likely to lead to higher losses of cyanide in a C.I.L. circuit. Degradation by hydrolysis is important at high temperatures and high pH such as employed in the Pressure Zadra or Anglo elution processes. Carbon catalysed degradation of cyanide by oxygen in effluent streams may be an environmentally acceptable alternative to conventional chlorine degradation.

Jan 1, 1987

By Sakai S, Suga S, Bisque RE

Soil gases were collected on activated charcoal, analyzed by computerized mass spectrometry and treated with multivariate statistical pattern recognition to determine the diagnostic geochemical signature associated with the Okuaizu Geothermal Field in Japan. From this a geothermal model was developed and compare to 175 "unknown" samples in a 250 m spaced grid over 30 1Qn2 mapping the areas with a matching geochemical character. Faults and fractures were generally located by the presence of high molecular weight components. Following the initial survey, the faults in two specific areas were precisely located by a second survey with samples at 10-30m spacing. Where earlier geochemical surveys had placed anomalies 1-2 Km northeast of the geothermal center, the fingerprint survey accurately mapped the system and detected several faulted zones. It was not misled by hot springs located away from the geothermal System.

Jan 1, 1987

An extensive railway construction prog- ram in the People's Republic of China has required the excavation of many tunnels in difficult ground, particularly in mountainous regions. Conclusions drawn from case histories permit guidelines to be formulated as to the optimum location of tunnel alignments in faulted and folded terrains, and also in karst regions. Geological factors adversely affecting durability of tunnel linings can be minimised by adoption of appropriate construc- tion practices.

Jan 1, 1987

By Yu-Jun Z

According to site measurement and labora- tory experiment, the authors suggest a new mathematical model of grouted rock bolts. The rock bolt is taken as an elastic bar, and the grout is substituted by a set of springs the rigidity of which is given as K. Based on certain assumptions, a simplified formula is deduced. When the category of rock, depth of tunnel, the spacing of rock bolts and the rigidity of springs K values are given, so that we can calculate the radius of plastic zone, and subsequently the convergence of rock at the tunnel inner surface u, and the resis- tance exerted by the rock bolt p. Finally, the length of rock bolt can be determined.

Jan 1, 1987

Pulverised coal firing was pioneered in the cement industry prior to the turn of the century. Ash from the coal is absorbed into the mix in the kiln and replaces secondary materials. With high purity limestone coal with high ash content can be used. Fuel cost is a major part of the total manufacturing cost. Cement plants are thus quick to respond to fuel price changes and will use low grade fuels if there is a price advantage. Combustion conditions in a cement kiln differ markedly from a boiler. Flame length is determined by air/fuel mixing but because of fixed secondary air conditions this depends on primary air momentum. Volatile content has some effect on flame length but this can be offset by coal fineness. Much of the heat for cement production is for limestone calcination which is a low grade energy requirement. By allowing long residence time in separate direct fired vessels which then feed the high temperature kiln the energy of materials such as oil shale, tyres and lump lignite can be utilised.

Jan 1, 1987

The Proterozoic Pb-Zn deposits of the Gulf of Carpentaria, Australia, include HYC (McArthur River), Mt. Isa, Dugald River, Lady Loretta and Hilton. Two seamingly incom- patible depositional models have been proposed to account for their origin. Finlow-Bates (1980), Large (1983) and Russell(1983) classify these-deposits as sediment-hosted submarine exhalative deposits. This class includes Rammelsberg, Meggen, Silvermines, Sullivan and others. In contrast, a lacus- trine, shallow-water origin has been advocated by Williams and Logan (1981), Logan and Williams (1984), Muir (1983) and Eugster (1985). The discrepancies between these two models can be removed by creating a separate class, that of continental sediment-hosted exhalative deposits.. HYC., Mt. Isa and Dugald belong to this class and their sediments were deposited in shallow, alkaline lakes. Metal- rich, hot, Na-Ca-Cl brines entered the basins along boundary faults and interacted with pore fluids and sediments, depositing-Cu-Zn-Pb sul- fides. Similar brines entered the Lady Loretta basin after marine flooding, depositing sulfi- des and barite, placing Lady Loretta into the class of marine Sedex deposits.

Jan 1, 1987

Brief summary of results obtained by a French-Japanese cooperative study on the bottom of trenches around Japan. The geophysical prospection, multi beam echo sounding and direct observation with submersible dives of the trench bottom clarified the details of the subduction of oceanic plates. It may be noted, among many new facts found: 1. The subduction and geologic structure resulted from the process is different according to the nature of subducting oceanic plate, and the geology of the land behind the trench. Thus the Nankai trough characterized by the developpement of accretionary prisms is contrasted to that of the Japan Trench where the basement rocks are exposed on the land side cliff of the trench wall. 2. The compressional tectonic situation prevailing in the trench bottom provokes the venting, along the fissures on the bottom, of water contained in sediments. Hydrocarbons contained in the sediments are comming out with water and give nutrients for bacteria. Clams, tube warms, sea slugs and shrimps are taking these bacteria as their food and biological communities with exceptionally dense population for the deep sea of more than 3000 meters in depth are formed on the field of accretionary prism and wall of the land side cliff. 3. An intense compressional tectonic field resulted from the subduction is inducing the transition from the subduction of oceanic plate to the collision of a part of the plate to the continental plate.

Jan 1, 1987

The accuracy of an ore reserve is only as good as the geologist's understanding of the deposit. The methods that are applied to resource and reserve estimation reflect that understanding. At the Olympic Dam copper-uranium-gold deposit in South Australia, evolution in the understanding of the controls on mineralisation coupled with the changing demands of the project have led to changes in the approach to reserve estimation. The project has moved into a phase where detailed stope mining reserves are now required as distinct from global ore reserves. The complex nature of the mineralisation and the large amount of data demand that all available information be readily accessible in a flexible format. To enable the selective manipulation of geological and assay information and its characterisation, a relational database has been developed. For reserve calculations themselves, initial computations were based on a system derived from that used for the Kambalda nickel orebodies. The Olympic Dam system differed mainly in the use of statistical analyses in the estimation of grade instead of the previous polygonal area of influence weighting method, Three dimensional weighting techniques are now being used for local reserve estimates. Flexible facilities for raw data handling combined with grade estimation techniques which are commensurate with the mine geologist's understanding, produce detailed gridded and contoured ore zone models suitable for reserve calculations and stope designs.

Jan 1, 1987

By Nagai K, Moriyama K

Toyo smelter has been making s veral efforts to reduce and diversify energy for dealing successfully with such :n:;rgy problems as the first and second oil crises. ::,specially it is one of th:; most important subjects to substitute oil by alternative: energy source, because oil is expensive and unstable with respect to its supply. t _'hercfore i was decided to propel tnC ezhstitution of coal *jr oil. in the first place, the supple- mental fuel oil in the reaction shaft was replaced by oil to coal in 1981, and then th, fuel substitution of pulverized coal was achieved in the steam superheater in 1984. 3y these fuel substitutions about 7u,' of the total fuel energy at 2oyo smelter has been replaced by coal. in this paper the fuel substitu- tions at loyo smelter are described in detail.

Jan 1, 1987

Operation of a pilot heavy medium separation plant allows flexibility of operation not normally possible in an operating plant. Much useful data can be obtained, although some limitations apply. Projects carried out at AMDEL have included HMC separations at 1.5 to 3.6 specific gravity, comparative operation of HMC and DWP separators and the use of fine feed and product screens. Investigations of this type have provided a considerable amount of information on HMS plant performance and characteristics under a wide range of operating conditions.

Jan 1, 1987

By Ushakov S

New geological and geophysical in vestigation including our detailed field observation in different regions of the Koryak upland testify that Nor- theastern Eurasia margin eastward of the Ochotsk-Chukotka belt is composed of a collage of allochtonous terranes arcs and sedimentary filling of back- arc basins, which bordered North East Siberia and Chukotka (1)1). Ancient island are assemblages are the most tipical for this region (2-4; shown by heavy line). They are marked by long (500-1000 km) volcanic belts which become younger towards the Pacific up the Latest Jurassic-Neocomi- an (2) to Late Cretaceous (3) and Pale- Gene (4).

Jan 1, 1987

A computer programming language known as GPSS is described and possible applications for the mining engineer are presented. The language is continually being upgraded with improved versions appearing about every three years. The tremendous power of the language is considered by comparing it with standard engineering programming languages, such as Fortran or Basic. Sample problems that can be solved using the language are indicated. The advantages and disadvantages of the languages are also discussed.

Jan 1, 1987

The Antarctic Peninsula consists of accretion complex sedimentary and volcanic rocks, talc-alkaline magmatic are rocks, marginal basin sediments and extension-related alkali basalts, dominantly of Mesozoic to Cenozoic age. Metallic minerals have been recorded at "250 localities but two thirds of these are innocuous occurrences of Fe+Cu accessory minerals. The remaining -70 localities are related to hydrothermal mineralization processes. Metallogenetic associations identified are: vein and breccia-hosted Fe+Cu+Zn+Pb+Mo or Fe+Cu+Mo+Mn, shear-hosted Fe+Cu, volcanogenic Fe+Cu and pegmatite-hosted Fe+Cu+Mo+Mn. Anomalous Au, Ag, As, W and Sb also occur but are not of economic interest. Metallogenic zoning is unproven and genetic models are uncertain, possibly involving volcanogenic, epithermal to hypothermal vein and porphyry-type systems. Substantial field and laboratory studies are required to understand distribution and Genesis.

Jan 1, 1987

In the last several years we have seen the demise of the Department of Mining and Metallurgy at the University of Melbourne, the removal of extraction metallurgy from the Department of Metallurgy and incorporation of it within a School of Mines at the University of New South Wales, and the joining of a small Department of Metallurgy with a Department of Chemical Engineering to form a Department of Chemical and Materials Engineering at the University of Newcastle. Most of these changes have been forced by the logical application of the principles of accounting, the currency for such accounting being the Whole Student Unit (WSU). It is not my intent to address the problem of attracting young people into courses in metallurgy (including extraction metallurgy) which, at present, is the only way to introduce black ink into the WSU accounting ledger. Rather, I wish to express my disquiet over the trends, illustrated by some of the above occurrences, of separating out extractive metallurgy from METALLURGY by suggesting in broad terms how a course in metallurgy should be structured. I firmly believe that the mechanical metallurgist and materials engineer need an exposure to chemical and extractive metallurgy; similarly, the extractive and process metallurgist should, in my view, have a good grounding in the interrelationships between composition, structure, and properties, this topic being the core of the basic subject physical metallurgy.

Jan 1, 1987

To gain further understanding of the operating efficiency of the BHP Slab and Plate Products Division (SPPD) RH vacuum degasser, physical and mathematical model studies of the process have been undertaken. The purpose was to investigate how the various process parameters affect the liquid circulation rate, to visualise the flow patterns, and to identify and eliminate the cause of localised wear in the downleg. In the physical model mixing times were measured using an acid tracer technique. The results were applied to predicting trends in times required to obtain homogenous melt composition under varying conditions. A 2-dimensional mathematical model describing the liquid metal flow has been developed using the PHOENICS fluid-flow package. The physical model results were simulated and incorporated into the mathematical treatment and an improved design for vessel geometry is proposed. The effect of rounding the downleg entrance or installing a baffle between the legs is discussed.

Jan 1, 1987

By Scott IA, Jefferson C, Dipasquale S

This paper describes the use of modelling and simulation techniques in the analysis of the heavy medium plant at the Lead/Zinc Concentrator of Mount Isa Mines Limited. The objective of the study is to determine how to increase heavy medium plant recovery at a higher than current rejection rate in order to achieve the desired throughput through the grinding and flotation sections of the concentrator. Three options were considered: 1. Install smaller aperture preparation on screen to enable the cyclones to be fed finer materials. Install smaller diameter cyclones. 3. Maintain low viscosity medium.

Jan 1, 1987

With mining development on hold and other underground works in a slowdown, the develop- ment of nuclear waste repositories takes center stage on the American rock engineering scene. Three repositories for commercial spent fuel -- in salt, tuff, and basalt -- are in the phase of site characterization and conceptual design, and one pilot project for defense high-level waste in salt is under construction. A repository design for crystal line rock has recently been postponed. Because of strict quality assurance requirements throughout design and construc- tion, and because of the need to predict and ascertain in advance the satisfactory perfor- mance of the underground openings, much intellectual energy has been expended to analyze underground openings in the unusual circumstances of the repository environment. In the long term, these efforts will lead to an improved understanding of rock behavior and improved methods of underground analysis and design. For the shorter term, a formalized ground control plan was developed, the princi- ples of which may be applied to other types of projects. This paper summarizes the status of underground design and construction for nuclear waste repositories and presents some details of the ground control plan and its individual elements.

Jan 1, 1987

By Pinter R

Several major routes connecting Northern and Southern Europe or Asia run through Austria. These highways have to surmount the alpine range which traverses Austria from west to east. In order to ensure safe driving conditions even in winter, tunnels, at times quite long ones, are necessary. Austria now has tunnels totalling 160 km in length. These tunnels are either already in use or just about completed. The Plabutsch tunnel near Graz will be one of the longest tunnels in the world: approximately 10 kilometers in length. It will be put into operation in the summer of 1987. Before construction could begin, soil and rock conditions had to be investigated by means of a test tunnel. Afterwards, excavation was begun to the full 100 m' cross section. The new Austrian tunnelling method with conventional blasting was used for the major part of the tunnel. It was necessary to have such a large tunnel cross section because a fully transverse ventilation system is installed for environmental reasons. In order to avoid air pollution from the tunnel, exhaust fumes are not allowed to escape from the tunnel portals but from two shafts, each with a diameter of 8.5 m. In this way, exhaust fumes must rise 90 meters or 240 meters before they reach the open air and will thus not affect the city. The ventilation system influences the size of the excavation, and especially the size of the ventilation caverns and the air shafts. All these factors directly influence construction and maintenance costs, and an economical optimisation leads to the appropriate dimensions for the excavation.

Jan 1, 1987

By Smitham J. B, Keast-Jones R

Six Australian coals were selected to determine their potential to produce, ultra low ash (less than 2 per cent) coal by progressive size reduction followed by density separation and/or froth flotation. Density separation in organic liquids is effective in the absence of contaminating liberated mineral matter which can be removed by froth flotation with several cleaning stages. The limit of cleaning of these coals was an ash value of 1 per cent while commercially attractive yields were obtained at 2 - 3 per cent ash depending on the coal.

Jan 1, 1987