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By T. Fabritius, L. Hekkala, J. Härkki

The Outokumpu steel belt sintering technology is used for manufacturing chromite pellets that are charged into smelting furnace for ferrochromium production. Hot air is blown through the moving bed of raw pellets. Direct temperature and flow measurements are difficult to do in the bed of a real scale belt sintering process. Therefore, a tested and reliable mathematical model would be a valuable help for optimising operational parameters of the process and designing new constructional improvements. The aim of this work is to present a mathematical model that calculates the gas flow and temperature distribution in the bed of pellets and the atmosphere. Computational fluid dynamics program FLUENT is used to calculate the gas flow, composition and temperature of the gas in the sintering bed during processing. Energy equation for the bed, containing the effects of evaporation of water and oxidation of carbon and iron oxide, will be added to the model to obtain the temperature of the pellets. The porous media model used for pressure drop calculations in the bed is shortly discussed. A comparison between CFD-calculations and experiments with a pilot scale batch-sintering reactor are also presented. The final model can be used as an engineering tool when developing the process and the equipment further. Different designs can be easily tested with the model and the effects of the changes to the flow pattern and temperature distribution can be studied.

Jan 1, 2004

By J. B. Morrow

BITUMINOUS COAL production for 1937 up to Nov. 27, was 400,000,000 ions, an increase of 3.43 per cent over the comparative period in 1936. The in- crease in consumption, however, was not so great as the increase in production. Stocks of coal, mostly in the hands of consumers, on Nov. 1 were 57,000,000 tons, compared to 44,400,000 tons at the same periods in 1936. The prospects were that both production and consumption for December, 1937, would be lower than for the corresponding month of 1936. , Anthracite production for the period ending Nov. 20 was 43,900,000 tons, com- pared to 48,500,000 tons for the corresponding period in 1936, or a decrease of 9.5 per cent. Production of mechanically loaded coal in. 1936 was approximately 57,000,000 tons, an increase of 17.5 per cent over

Jan 1, 1938

By Bodo Peinemann

For more than 35 years Lurgi has been providing its fluid bed roasters on a world­wide basis. The current total annual capaci­ty of the 250 Lurgi roasters approaches 26 million mt of sulphide minerals, including gold-bearing flotation pyrite concentrates. While the stationary fluid bed has been uti­lized for roasting exclusively, Lurgi has now commercially introduced its Circulating Fluid Bed (CFB) technology for gold roasting in a successful effort to maximize gold re­covery.

Jan 1, 1990

By P. G. Flood

A simplified conceptual model shows how the arc flank to arc fringe areas adjacent to ignimbritic centres form a prospective zone for natural zeolites. Large alkaline lakes that serve as the repository of voluminous ash-fall tuffaceous material provide the ideal chemical setting for pervasive alteration of silicic glass to zeolites. The unusually old age of the Escott deposit demonstrates that any silicic volcanic province that contains low-temperature, unmetamorphosed sequences is a potential zeolite exploration target and that age should not be used as a criterion to exclude potential areas. It has also been demonstrated that heulandite and mordenite, formed by diagenetic alteration of silicic glass, do not always change to analcite and albite through the ageing process

Jan 1, 1991

By P G. Self, M D. Raven, R A. Eggleton

Investigation of an abandoned quarry near Rowland Flat in South Australia identified asbestiform antigorite as the fibrous serpentine mineral mined during the 1940s to 1978 for filler applications, not amphibole asbestos or chrysotile as reported in earlier investigations. Scanning and transmission electron microscopy (SEM and TEM) and selected area electron diffraction (SAED) of individual fibres were used to confirm the identification. Chrysotile is widely regarded as the only asbestos mineral in the serpentine group. Further work was done therefore, on the geology and mineralogy of the occurrence, and the health implications were reviewed. A zone of antigorite alteration, with associated talc, is traceable for 750 m along strike of recrystallised dolomitic siltstone within Woolshed Flat Shale of Neoproterozoic age. The antigorite formed, in part, by replacement of prismatic crystals of probable tremolitic amphibole. The deposit is proximal to the Williamstown Fault and the serpentine-talc alteration is possibly due to fluids expelled along the fault during late-stage deformation in the Early Palaeozoic Delamerian Orogeny. The antigorite comprises white to pale green bundles of lath-shaped fibres that occur either as randomly- arranged equant patches after amphibole or as cross-fibre veins, both intimately mixed with calcite. Highly fibrous product was mined from the weathered zone where calcite was leached during weathering. Gentle grinding releases fibres with a high aspect ratio (>10:1) that show a wide range of fibre thickness, including a significant proportion of fibres <0.25 ¦m width. Toxicological studies on fibrous antigorite from Poland and Italy indicate that the carcinogenic potential of this form of serpentine is similar to amphibole asbestos. X-ray diffraction (XRD) and fourier-transform infrared (FTIR) techniques readily distinguish antigorite from chrysotile. Determination of asbestiform habit and confirmation of antigorite mineralogy is most reliably done using electron microscopy, preferably with SAED capability.

Jan 1, 2008

By Boorder De, B. S. Panov, A. B. Westerhof, V. A. Korcemagin

Paper presented at the conference on Economic geology in Europe and beyond II, models for <mineral deposits> in sedimentary <basins>, held in Keyworth, UK, 13-14 April 1994. The Hg and Sb deposits of the Mediterranean and Circum-Pacific Belts are often found at elevated structural levels, suggesting that their preferential occurrence in young orogenic belts is not a fundamental metallogenic feature but merely reflects their chances of surviving post-orogenic peneplanation. In western Europe their emplacement appears often to be related to late orogenic extensional events accompanied by a notable increase in heat flow. Although Nikitovka and Almaden have quite different settings, both appear to be related to deep-reaching shears. Together with brittle fault zones at higher levels, these provided pathways for fluid phases that originated at least partially within the mantle. The Nikitovka deposits are located in the Donets segment of the 2 000 km Pripyat-Dniepr-Donets palaeorift in the East European Platform. Initiated in the mid-Devonian with a possible Precambrian precursor, its listric boundary faults displace the Moho from a depth of about 50 km north and south of the rift to 35 km along the axes of the Pripyat and Dniepr segments. The steep central anticline of the Donets segment, within which the main Hg-Sb district is located, is interpreted to be associated with a reactivated fault reaching into the upper mantle. The Almaden syncline, formed during the Variscan Orogeny, may be an older pull-apart basin or half-graben associated with the collapse of the Cadomian Orogenic Belt. It is situated on a major ENE-WSW-striking shear zone which may represent a Late Cadomian transfer zone reaching into the mantle

Apr 1, 1995

By S Robotham, P C. Stewart, K Maher

A data science based dilution study was conducted to identify the causes of dilution at South32’s Cannington Mine (Cannington), a large open stoping operation. In terms of industry benchmarks for unplanned dilution, Cannington is already performing very well, and so opportunities for improvement are more difficult to identify. The study is based upon back analysis of nearly 150 case studies from the mines reconciliation database, and has quantified the relative effect and significance levels for the following dilution parameters; time until paste filling, faulting and cable bolt reinforcement. Specifically, significant contributions were associated with faults and stope open duration. Quantifying the effect of faults on stability graph accuracy enabled a site specific adjustment to improve the predictive ability of the Cannington stability graph (unstable stope specificity improved from 63 per cent to 74 per cent). Despite Cannington’s already high levels of stope performance compared to industry benchmarks, data science methods have identified a complex interaction between identified dilution factors (ie stope open duration, presence of faults and cablebolting). Specifically, a third order Factorial ANOVA (Analysis of Variance) provided evidence that stope open duration reduces the effectiveness of cable bolts in faulted ground (average dilution = 2.1 m, p-value = 0.13). These results are consistent with site observations of a relationship between the stope open duration and the extent of failure when unravelling on a fault, even when cables are present.CITATION:Maher, K, Stewart, P C and Robotham, S, 2016. A data science approach to identifying and quantifying causes of dilution at Cannington Mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 491–500 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By W. A. Wood, H. M. Bendler

Cylindrical fatigue specimens of OFHC* copper were subjected to alternating torsion while under axial tension. The superimposed tension strongly influenced the fatigue life of the specimens as well as causing characteristic changes in the structure of the fissures that form and develop throughout the life of the specimen. A further effect of the superimposed tension is a continuous extension of the specimen throughout its life in a manner formally similar to creep at elevated temperatures. RECENTLY, studies of the structural changes leading to fracture of metals by fatigue have been made by a technique which reveals, in section, the lattice distortion arising from slip movements inside the metal and the disturbances built up by these slip movements at the metal surface.1&apos;2 According to this approach, fatigue develops as follows: a) fine slip movements concentrate in bands, producing little strain-hardening and thus permitting abnormal totals of plastic strain before fracture and, therefore, abnormal amounts of lattice distortion along each slip band; b) both forward and backward slip movements occur in each band which, according to their distribution across the band, may build up surface disturbances that include sharp notches; c) these notches early in the life of a specimen penetrate the distorted slip zones and transform them into deep, fine fissures; d) the fissures on continued cycling locally saturate the metal and cause local collapse in the form of a microcrack. Thus, the significant consequence of fatigue or cyclic

Jan 1, 1962

By R. Grandori, L. Pellegrini

The construction of the La Joya hydropower plant (Costa Rica) was awarded by the Spanish power company, Union Fenosa, to the Italian Joint Venture formed by the companies SELI SpA and Ghella SpA. The project, located in a mountainous region of central Costa Rica, includes a 7.9-km-long head race tunnel having an excavation diameter of 6.18 m. A double-shielded TBM was selected to perform the tunnel excavation, which involved mainly volcanic rocks in variable but generally very weak conditions. The tunnel crossed long and continuous sections in completely weathered rock masses with no residual cohesion and with high water inflows. The paper describes and analyzes: The special methods adopted to overcome these sections with the TBM includ-ing face stabilization by chemical grout and foams as well small by-pass tunnels in the crown combined with TBM advance/support The grouting design and the grouting method that was implemented to meet the waterproof design specifications and restore the original groundwater level in the mountain The additional geological investigations performed to improve the knowledge of the rock mass in front of the TBM and the outcomes of these investigations The performance of the TBM in different ground conditions and on average along the entire tunnel Finally, the author’s comment about the possibility of implementing and improving the technologies experimented with in this project in future similar applications.

Jan 1, 2007

By James A. Finch, Jason S. Doucet, Cesar O. Gomez

"Exercising control over the physical environment of flotation as a step towards process optimization is the driving force for characterizing gas dispersion in flotation cells, a subject of considerable research and still not fully understood. From an operational standpoint, however, there are just a few variables that can be manipulated to manage gas dispersion on a cell-to-cell basis, the most important being gas rate (superficial gas velocity Jg). Measurements in eight plants demonstrate there is often no strategy for distribution of gas to cells in a bank, i.e., there is no particular Jg profile. Two exercises where Jg profiles were set allowed metallurgical performance to be manipulated and an optimum Jg profile to be selected. To facilitate setting Jg profiles, a multi-unit device based on McGill Jg sensor technology is introduced. Possible directions for gas dispersion management are discussed.INTRODUCTIONThe earliest patents regarding the flotation process ignored the importance of air and in certain cases, steps were taken to eliminate bubbles from the system (Nelson and Smit, 2005). Rickard (1916) described a keen metallurgist who observed better than expected performance and hypothesized that entrained air was enhancing the process. Within a few years of this observation, the basic concept of modern froth flotation was developed whereby air is dispersed into slurry to induce bubble particle contact.As research into flotation advanced, the link between performance and the flow-rate of air entering the cell was established. In the first volume of the International Journal of Mineral Processing, Harris (1974) described the importance of airflow-rate and derived parameters such as the superficial gas velocity (then called the superficial airflow velocity) as being important parameters for cell design and scale-up. Mehrotra and Kapur (1974) presented research suggesting that the rate of flotation was strongly correlated to the aeration rate. McKee et al. (1976) continued to demonstrate the importance of airflow-rate linking it to the entrainment rate of hydrophilic gangue material."

Jan 1, 2006

By C. Kennedy, S. Jensen

Traditionally, mineral processing plants are designed to achieve the highest recovery of valuable material with limited regard for the cost of managing waste products-both solid and water components. As an industry, we are confronting ever more stringent environmental standards and lower grade deposits requiring more intensive processing. The most profitable processing route can, in fact, lead to costly issues downstream. Issues or risks associated with waste management include water treatment and handling and storage of potentially acid generating material. The capital and operating costs of dealing with these issues are significant and should be considered as a consequence of plant design and optimisation. The authors of this paper are involved with a number of projects where process operation changes offer opportunities to mitigate risks associated with water and waste management. Examples of these changes will be discussed along with the estimated benefits to the value of the project and reduction of long-term environmental risks. Process changes include 1) the application of in-plant water treatment as opposed to dealing with the entire tailings management facility and 2) the potential to reduce metal leaching and acid rock drainage through the preferential liberation of carbonate minerals in the grinding process.

Jan 1, 2014

By Blanchard R

In stopes of the 2000- and 2150-ft. levels in the North mine section of North Broken Hill Limited, whence a substantial proportion of the company&apos;s production is being drawn, and especially in stopes which involve the portion known as the Northern orebody, occurs it light-coloured friable porous material which represents average grade ore from which the lead and zinc minerals, and certain gangue constituents, have been largely or wholly removed by leaching. The 2000- and 2150-ft. levels lie, respectively, 1550 and 1700 ft. below extreme base of the pre-mine oxidized zone. Composition of the cellular product shows it to be supergene. The oxidation and leaching, therefore, must be assumed to have taken place since drainage of the affected areas was accomplished by mining operations.The matter is of more than passing interest, because the post-mine...

Jan 1, 1942

By Alexander Garcia

Roof and rib falls are the basic ground control hazards associated with underground roadways during development, stand up and, if applicable, retreat. Falls of ground can happen following the deterioration of supports or rock conditions over time, and particularly as a consequence of continuing rock deformation and/ or failure to install adequate support. Once developed, the risk of a failure is increased due to the effects of time as well as to front abutment stresses through retreat mining. The measurement of strata displacement using monitoring equipment is a form of ground control risk assessment. These monitoring systems are active, or ?live?, in a sense that risk is assessed real-time. However, there are circumstances in which falls of ground can occur without the prior recording of excessive movement. In addition, monitoring equipment is typically placed at set intervals, and strata conditions could vary between these points. Consequently, a visual assessment of other factors contributing to the risk of a fall should be made in order to complete a ground control risk assessment. Such surveys are usually one-off, thus capturing roadway conditions at one particular point in time. Ongoing deterioration is not documented through such one-time surveys, and there is a requirement for real-time or live assessment where a system is in place so that observation data can be updated on an ongoing basis, and a useful summary of prevailing roadway states produced on demand. To address the shortfalls of one-time assessments, a ?live? computerbased quantitative ground control risk assessment process has been developed. It combines visual observations processed in a quantitative manner with existing monitoring data into an interpretable output which indicates zones of roadway where there is an increased risk of a fall of ground from the roof or sides, so that remedial action can be carried out to mitigate that risk. Through improved procedures, it is now possible to generate a ground control risk assessment for each roadway, and one which can be updated frequently. This paper aims to outline and describe the assessment process.

Jan 1, 2012

By Mark DeSalvatore

Currently, at Caltrans, the Office of Structure Design is carrying out an extensive seismic retrofit program involving transportation structures throughout California. The goal of the retrofit program has been to upgrade existing transportation structures to meet the present seismic codes and anticipated loads that are generated during a seismic event Part of the retrofit program involves retrofitting existing structure foundations when required. To determine if the foundations of a specific structure need to be retrofitted, an engineering analysis of the existing foundations has to be done. If the engineering analysis of the structure foundations determines that the foundations will not meet the load carrying demands required by the structural engineer, the existing foundations are then retrofitted. The retrofit projects that require foundation modifications can be separated into two general cases. The first case comprises structures where the original designs will not meet the demands of the present seismic design code. In this case, the existing foundations are not capable of providing the load capacities the current seismic code requires. The second case consists of structures where the retrofitting of the superstructure will increase the required load carrying capacity of the existing foundations during a seismic event In this case, the anticipated load demands on the existing foundations are greater than the foundations are capable of providing. For either of the cases listed above, the present strategy for increasing the capacity of the existing structure foundation consists of installing tiedown anchors or large capacity piles to provide the required resistance to seisraically induced loads.

Jan 1, 1993

By Ott F. Heizer

The mines and the mill of the Nevada-Massachusetts Co. are on the east slope of the Eugene Mountains, in Pershing County, Nevada, 8 miles northwest of Mill City, a station on the Southern Pacific R.R. and on the Victory Highway. Fig. 1. Supplies and, concentrate are transported by truck over an automobile road of easy grade. The property is at an average elevation of 5500 ft. and climatic conditions are generally favorable for continuous operation throughout the year. The ore treated is supplied by two adjoining mines, the Stank and the Humboldt. Physical and mineral characteristics of the ores produced by these two mines are substantially similar, although variations occur in hardness and mineral distribution.&apos; The economic mineral is scheelite (CaWO4), composed, when pure, of 80.6 per cent tungstic trioxide (WO3) and 19.4 per cent lime (CaO).

Jan 1, 1935

By R. A. Welsh

The Bureau of Mines has developed a photoelectric concentrator apparatus which is capable of collecting incremental products from the discharge of wet concentrating tables. The instrument uses photoelectric cells as sensors to differentiate between two products which have differences in color or reflectivity. The photocells provide a signal that controls a mobile splitting device that separates the products. Tests conducted on a wet table demonstrated the ability of the apparatus to separate a product containing 81.5 percent pyrite from a lower-grade product containing only 68.8 percent pyrite. The photoelectric concentrator should have a broad application for collecting concentrates with visible color or reflectivity differences from wet concentrating tables.

Jan 1, 1972

By Jon C. Volkwein

In This Chapter [Instruments for measuring dust How to calculate the amount of dust from a source How to get a valid concentration measurement Sampling to assess control technology effectiveness] When there is more than one source of dust, sampling may be required to find which dust sources are most significant. Then, efforts to reduce dust can be concentrated where they will have the most impact. This chapter explains how to perform dust source sampling. It describes two kinds of instruments that are available and discusses their limitations. It explains how environmental variables such as concentration gradients, dust dilution, and production changes can impact dust measurements. It also suggests practical ways to improve the validity of dust source measurements under adverse conditions, such as high-velocity airflow or the presence of water mist in the air. [Dust source sampling at coal mine longwalls and at tunnels is more complicated. Chapters 3 and 7 have more information on sampling in those circumstances.] TWO KINDS OF INSTRUMENTS FOR MEASURING DUST Gravimetric samplers. The conventional gravimetric sampler is a good device for measuring dust because it is the instrument used for compliance measurements. This dust sampler consists of an air pump, a small cyclone that separates out the respirable size fraction of the dust cloud, and a filter to collect the respirable dust. In coal mines, the Mine Safety and Health Administration (MSHA)-approved gravimetric sampler uses a 10-mm Dorr-Oliver cyclone operating at an airflow of 2.0 L/min [30 CFR78 74 (2002)]. A correction factor of 1.38 is applied to make the results consistent with the U.K. MRE sampler, the instrument on which the 2.0 mg/m3 coal dust standard is based.

Jan 6, 2003

By Collin Stewart

Bowie Resources maintains one of the most pro-active ground control programs in the U.S. mining industry today. Its guiding philosophy is that everyone in the organization, from the miners at the face all the way through the top management, are involved in ground control. Some of the unique elements of the Bowie ground control program include: ? Roof bolt operators log the stratigraphy of test holes in nearly every cut. These ?lithgraphs? are used by section foremen to determine the need for additional roof support, and they are entered into the geologic data base for use in geologic modeling and mapping. ? Underground core drilling is conducted to obtain data for CMRR and stability maps. ? Weekly ?Quality? meetings, involving mine management and technical staff, are held to ensure that ground control information is integrated into production operations. The paper will describe the program in detail, discussing the involvement of roof bolters, section foremen, surveyors, technical staff, and production managers. It will also show how the program has contributed to the mine planning process. Case histories of successful ground control interventions will be discussed.

Jan 1, 2006

By Deepak B. Deshpande

This paper enumerates various difficulties encountered in the design and construction of deep caisson foundations for the Second Bassein Creek Bridge constructed over a creek with very difficult site conditions. The designer of the bridge had anticipated the problems associated with the construction of large diameter floating caissons and limited the maximum size of caisson to 12.5m O.D. facilitated by the means of Shock Transmission Units (STUs). This is the first road bridge in India where STUs are installed to distribute seismic horizontal loads among piers installed with fixed and unidirectional bearings. Besides the usual difficulties of tilts, shifts, and sinking in the construction of floating caissons, the paper also describes a novel methodology used to retrieve a circular 12.5m O.D. caisson which had been swept away during a storm and stuck into the creek bed.

Jan 1, 2002

By André de Jager, Henk Ludik

Navachab Mine experiences difficulties with pit wall stability in certain areas of the mine. The main reason for the instability is the fact that the geology comprises many joints and faults. Blasting, without impacting negatively on the stability of the pit walls, poses a major challenge. The mine has installed a technologically advanced seismic monitoring system with monitoring sensors positioned at various locations and depths throughout the pit. The electronic data recording system records all relevant information on a continuous basis with early warning signals in cases of potential danger. From the information recorded by this micro-seismic system it was established that the energy release into the high-wall is predominantly influenced by the mining rate, water content and mining tempo and to a lesser extent by the blasting operations. To limit the negative effects of blast vibrations, the use of Electronic Delay Detonators (EDDs) was introduced. The optimal delays were determined through signature trace analysis. The vibrations obtained during blasts initiated by means of electronic delay detonators were monitored and compared to those traditionally obtained when standard pyrotechnic delay detonators had been used. The measured vibration data indicated an improvement of 25% to 100% drop in vibration amplitude compared. The accuracy and programmability of EDDs presented huge potential for blast optimization in terms of limiting the vibrations without compromising fragmentation. The whole project was conducted over a twelve week period with some 4000 EDDs. The average size of a blast was in the order of 350 holes using about 40kg explosives per hole, which equates to 14,000 kg explosives over 12 different blasts. The paper deals in detail with the blast optimization process with regard to: - determining the rock response time; - establishing the signature traces; - analyzing the wave interference patterns; - predicting the direction of constructive and destructive wave interferences; - optimizing of the inter-hole and inter-row delay periods; - measuring the ground vibrations. The results obtained during electronic blasting are compared to those obtained during pyrotechnic blasting. Comparisons are being made with regard to the following: - ground vibration measurements; - pit wall stability measurements; - blast safety.

Jan 1, 2006