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By M Wimmer

LKAB operates two underground iron ore mines located in the northern part of Sweden, both using sublevel caving (SLC) as the mining method. Knowledge of the mechanisms of gravity flow is important since it affects both ore recovery and waste dilution. This paper describes results from a large-scale field test carried out at the Kiruna mine with a focus on gravity flow. It is part of Work Package 2 in the I2Mine project financed by the EU. A total of ten rings were blasted. Smart Markers based on radio frequency identification technology were used to monitor the gravity flow. An accurate delineation of the isolated extraction zone requires reliable detection of all recovered Smart Markers and precise knowledge of the 3D position of the markers within the burden. It was therefore necessary to carry out borehole deviation measurements (collar, alignment and trajectory). The blast performance was monitored by high-speed filming, near-field vibration monitoring and velocity of detonation measurements. Three-dimensional stereo images were taken from the drawpoint and the loaded bucket after each mucking cycle. Based upon that, fragmentation was assessed both in 2D and 3D. Furthermore, volumetric differences were determined at the drawpoint, which reflects the mobility of loaded material. For draw control, the Fe content is estimated by measuring weight and assuming a full bucket. The measured volume of rock in each bucket further improves this estimate. Possible flow disturbances occurring at the drawpoint were revealed by video recording. Two-dimensional laser scanning was carried out during mucking to track the position of the bucket and estimate the position and slope of the muck pile.The results from this test clearly show that the gravity flow in the large-scale sublevel cave in Kiruna mine is often of disturbed character. Standard draw occurred only in three rings and shallow draw in the remaining seven rings. In five cases, shallow draw developed towards standard draw, but occurred at rather late stages during extraction (70–125 per cent). The maximum width of the draw varied between 10 m and 13 m except for one ring (6 m). The draw reaches the cave rather early (5–25 per cent extraction) in shallow draw situations and much later (about 50 per cent) during standard draw. Waste originates from above in most cases, while more significant portions often occur at about 20–45 per cent extraction.All the results from this extensive field test are not yet fully analysed, and further field tests are planned. A more detailed insight into gravity flow in large-scale SLC and possible influence by drilling, blasting and the mucking procedure is expected in the future.CITATION:Nordqvist, A and Wimmer, M, 2016. Holistic approach to study gravity flow at the Kiruna sublevel caving mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 401–414 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By D. Xie

An in situ gravimetric technique based on wetting and capillary action principles has been used to investigate the wetting and penetration of synthesized alumina samples and commercial magnesia spinel refractories by CaO-SiO2-Al2O3-Fe2O3slags. Synthetic slags of 40CaO-40SiO2-20Al2O3 (in weight per cent) with 0 to 9 weight per cent Fe2O3were used and the experiments were conducted at temperatures 1370 to 1470ºC under argon. The contact time between the sample and the slag was 30 minutes. The results show that the wetting and penetration are enhanced by the iron oxide addition in the slags. Addition of Fe2O3from 0 to 9 weight per cent resulted in a significant increase in the slag penetration into the magnesia spinel refractory by a factor of about 7 and a moderate increase in the synthesized alumina by about 60 per cent. The addition of Fe2O3enhanced the wetting (??cos?, where ? is the surface tension of the slag and the contact angle between the slag and the refractory) by 5 to 18 per cent. An increase in temperature from 1370ºC to 1470ºC resulted in a significant increase in the penetration of a 6 weight per cent Fe2O3slag in the alumina and magnesia samples by a factor of4 to 5 and a decrease in wetting by approximately 30 per cent. Keywords: refractories, slag penetration, wetting.

Jan 1, 2004

By Theo Lehner

"The Boliden Rönnskär Smelter operates in the European Context of tight EH&S limits, with ever increasing regulations and tribulations. The near future promises to bring new burdens in the form of C02 trading, miners and pre-treaters increased appetite for a larger share of contained values, and changing compositions and competition in raw materials. On the other hand, European Smelters such as Rönnskär, Harjavalta have demonstrated an astonishing power of survival. This presentation lists and comments on current challenges but opportunities for increased survival power are also presented. One example of the latter is the ongoing investment into increased treatment capacity for e-scrap.UPDATE ON RÖNNSKÄR OPERATIONSThe Rönnskär Smelter has achieved 80 years of age with no signs of retirement. The smelter is most active in spite of its age! And it has undergone some face lift operations to maintain its attractiveness.Raw material, processing facilities and a market for the products are some essential prerequisites for a viable operation. To justify long term survival, economic terms such as return on investments and positive cash flow need to be considered. Below, we illustrate how the Rönnskär Smelter complies with these terms. To update the reader on current operations, our current flow sheet is depicted in Figure 1. The figure summarizes our current input and output."

Jan 1, 2012

By F Linares, B De Waele, K Bischoff, M Lacorde, G Loveday

Recent exploration has identified the presence of detrital iron deposits (DIDs) associated with banded iron formation (BIF) units in the north-west of the Congo Craton, Gabon. The regional geology comprises a complex of granitoids and gneisses assigned to the Archaean Chaillu Complex, within which older slivers of lower amphibolite-grade greenstones are preserved including muscovite-biotite-garnet-bearing felsic schist, amphibolite and BIF. These units are typically overlain by several metres of residuum comprising colluvium, eluvium and duricrust. The residuum is overlain by a regionally extensive loess cover from 2 m to 10 m thick.The DIDs occur within the weathered residuum as mostly unconsolidated gravels with lesser canga (CAN) duricrust draped over deeply weathered hematite. Head grades are in the range of 45 to 52 per cent Fe. Fresh BIF, located from 30 to 50 m below surface, is comprised of magnetite-quartz±amphibole. The detrital iron gravels are comprised of rod- and plate-shaped clasts of hematite (martite)-maghemite-goethite composition, in a ferruginous sand to clay-sized matrix. The DID form ridges and plateaus that coincide with magnetic highs defined using high-resolution ground magnetic surveys.The field relations and petrography indicate that the detrital iron accumulations are the result of weathering (including enrichment) and erosion of primary BIF. This includes removal of quartz, further oxidation and re-cementation of BIF to form ferruginous caprock. This cap and the in situ oxidised BIF were subsequently disaggregated and liberated, and further weathered to form the detrital iron accumulations.Metallurgical test work on bulk detrital iron samples has shown this material can be upgraded to lump and fines iron ore products with grades of 62 to 65 per cent Fe using simple scrubbing and wet screening, followed by dense media separation of the -1 mm fraction, with overall mass yields from 75 to 85 per cent. The test work indicates a high ratio of lump to fines products, sometimes exceeding 50:50.CITATION:De Waele, B, Lacorde, M, Bischoff, K, Loveday, G and Linares, F, 2017. Geological and metallurgical characteristics of banded iron formation associated detrital iron mineralisation in Central West Africa, in Proceedings Iron Ore 2017, pp 259–268 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By C J. N Wilson

The central Taupo Volcanic Zone is a region of intense Quaternary silicic volcanism accompanying rapid crustal extension. Modem central TVZ is the most frequently active and productive silicic volcanic system on Earth, erupting rhyolite at c.0.28 m3 s-1. The rhyolites show no major compositional changes with time, but the total extent of magma chamber zonation has changed with the advent of rifting and crustal extension at c.0.7 Ma. At least 34 caldera-forming ignimbrite eruptions have formed a complex sequence of relatively short-lived, nested and/or overlapping volcanic centres in central TVZ. Taupo contrasts with other large silicic magmatic systems in the exceptionally high frequency, but small size, of caldera forming eruptions. This contrast reflects the thin, rifted nature of the TVZ crust that precludes the development of long term magmatic cycles at Taupo. Within central TVZ, non-rhyolitic compositions have been erupted apparently irregularly in time and space; in particular there is no evidence for a geographic separation of basalts from andesites. TVZ is a rifted arc, but its segmented nature, high thermal flux and voluminous rhyolitic volcanism make it unique on Earth.

Jan 1, 1995

By Daniel Hack

A few progressive mining software companies have recognized the benefit of broadening their capabilities to the sand and gravel (aggregate) industry. The most promising new developments have been designed for use with Surpac Vision, one of the world’s leading geological modeling, mine design, and production management systems. Surpac’s broad user-base, who have always had a propensity for customization, are now focusing on development of solutions in the Tool Command Language (Tcl), an interpreted scripting language. Surpac Software International made changes to TCL to add Surpac specific extensions, thus creating the Surpac Command Language (Scl). The Tcl interpreter, including Scl extensions, is bound into the Vision executable to provide a seamless interface to the data objects used internally by Vision, the GUI, and the 3D rendering system. Custom solutions can be incorporated as Vision extensions, or as stand alone-modules used in correlation with modeling, design, and planning functions.

Aug 25, 2002

By E. H. Jr. Dix

THE use of magnesium as an alloying element in aluminum alloys has been limited, in general, to comparatively small quantities. In duralumin-type, strong-aluminum alloys, magnesium is present to the extent of ½ to ¾ per cent. and various grades of Magnalite and the "Y" alloy of the National Physical Laboratory of England contain up to 1 1/2 per cent. In this country small quantities of aluminum alloy sheet containing 4 per cent. magnesium are produced commercially. All commercial aluminum contains sufficient silicon to convert a portion of the magnesium added to the compound Mg2Si. It is well known that the solubility of both magnesium and magnesium-silicide decrease with decrease in temperature. It is, therefore, impossible to separate the age-hardening effect of the magnesium-silicide from that of magnesium, except by the use of aluminum of such high purity that the silicon content is negligible. The present paper is the fifth1, 2,3,4 of a series from the laboratories of the Aluminum Co. of America reporting the results of investigations of the equilibrium relations in aluminum-rich alloys made from the high purity aluminum manufactured by this company .5

Jan 1, 1929

IN December, 1905, a Forwood down-wheeler grinding pan (5 ft dialmter), and similar in design to those in use on the Kalgoorlie goldfields, was installed for experimental work in connection with fine grinding jig tailings.The galena remaining in this product is very finely (closely) mechanically disseminated throughout the blende and gangue, rendering fine crushing imperative for its liberation. A reswne of the milling process in vogue at the old mill will enable the series of operations to be more closely followed. The ore at the South Mine assays, on the average-lead...

Jan 1, 1909

Conventional hand drawn isopach maps of the cover of the Bulli Seam are too eomplex for use in the delineation of large domains of similar cover. Isopach maps prepared from trend surfaces fitted to the cover data are much simpler in form and so provide a convenient method of delineating broad domains of similar cover.

Jan 1, 1968

By Francis D. Leathers

Four friction pile load test programs, including 23 tension tests and 9 compression tests, have been performed as part of the Central Artery/Tunnel Project in Boston, Massachusetts. The tests, performed on both precast, prestressed concrete (PPC) piles and steel piles, yielded the following adhesion values: [Soil Type Clay Clay Glacial Till Interbedded Sand and Clay Interbedded Sand and Clay Pile Type PPC Steel Steel Steel PPC Adhesion (psf) 610 to 1,200 230 to 900 220 to 550 680 1,280 ] The adhesion appears to be affected by differences in pile material type, with PPC piles having higher adhesion than steel piles. However, part of the apparent difference for the clay may be due to differences in time between driving and testing. The significant range of test data means that the need for site specific testing to determine or verify design values of adhesion should be considered during design. Creep rates at loads near failure ranged from about 0.02 to 0.18 inches per log cycle of time, with most values in the range of about 0.04 to 0.08 inches per log cycle of time.

Jan 1, 1994

By Andy Cole

Barrick Gold recently implemented an oxygen roasting process to treat carbonaceous ore from its Goldstrike property in Nevada. One of the key project challenges was the design of the roaster gas cleaning system, which was driven by the requirements of a strict air permit and the need to achieve very high reliability. The roaster gas systems include multiple stages of wet particulate collection, a dual-alkali SO2 scrubber, mercury scrubbing, CO oxidation and NOx reduction. This paper describes the gas system, the influence of regulations on project implementation, and performance of the system.

May 1, 2002

This paper describes the past, normal and advanced practice of optimisation in mining. It then discusses what needs to happen for the mining industry to make full use of what is now available.

Dec 6, 2010

By L. J. Leach

Quench and tempered Cr-Mo plate steel was found not to contain a fully martensitic structure as a result of either slow slack quenching or insufficient hardenability at the cooling rates used. The resulting microstructure contains bainite in combination with martensite. It is necessary to examine the implications of bainite for the toughness of the final product. Loss of toughness arises primarily from the inter-lath carbides that typically form in upper bainite. An investigation into the effect of upper bainite in a martensitic matrix of a steel grade containing 0.17% C, 0.1% Cr, 0.54% Mo, and 20 ppm Bindicated lower toughness than in a fully martensitic structure.

Jan 1, 2013

By Patrick M. Y. Waye

As mines utilise more automation in mining operations to improve efficiency and safety, a corresponding increasing demand is placed on the transport of information. Some of the recent technological advances in underground telecommunications are described for various data, voice and video applications. In particular, two new innovative underground communication systems are described, one with high speed data at 30 Mbps and the other for mine wide evacuation and safety applications. The high speed data system incorporates stateof- the-art data networking technologies and the existing leaky cable narrow band radio channels. The new system provides over the same basic infrastructure the high speed data network at 30 Mbps TCP/IP Ethernet with 100 Base-T interconnection, plus 32 narrow band radio channels. The second system is a system for mine wide evacuation with "through the earth" communication infrastructure. Emergency situation can be communicated to and from all the miners within seconds through a central control location. The technology involved does not require leaky cable or any other similar transmission media installation. Many applications are possible, including warning miners of emergency situations, mine rescue operation to communicate with trapped miners, regular reporting from miners working alone.

May 1, 2001

The roasting of sulphide ores and concentrates is often the first step in the production of metals or chemicals. In many processes, the production of sulphuric acid is viewed as a by-product, whereas in some plants production is an important economic factor. Regardless of the purpose, a pyrite roasting plant consists of mainly three plant sections: roasting, gas cleaning and sulphuric acid. With the addition of air, the pyrite concentrates are transformed into solid oxides and gaseous sulphur dioxide at temperatures of 600?1000°C. After cleaning and cooling, the sulphur dioxide in the roasting gas is further processed to sulphuric acid. Two types of reactors are used depending on the application: stationary or circulating fluid bed. For over 60 years, Outotec has progressively been developing the principle of fluidized bed technology in several different reactor types for a multitude of process applications. The versatility of the fluidized bed reactor system has manifested itself in the treatment of minerals, including solid fuels, and for metallurgical processes both in the ferrous and non-ferrous fields. Process applications have included roasting, calcining, combustion and charring of coals, as well as off-gas treatment. This paper provides a summary of the pyrite roasting technology currently used along with a simple cost comparison of pyrite roasting and sulphur burning processes.

Jan 1, 2009

The Mahakipawa gold deposit is located 21 km northwest of Blenheim. It became the site of a small hardrock gold rush in 1889 following nearby alluvial gold discoveries in 1888. The study investigates the geology of the area of hard rock mining in the vicinity between Cullens and Waikakaho Creeks. The Marlborough Schist which hosts the gold depos, it consists of polydeformed greenschist facies quartzofeldspathic psammitic, pelitic and volcanigenic schist.

Jan 1, 1993

This paper provides a review of the chemical reactions occurring in the submerged arc processing of chromite ores. The excavations of industrial furnaces have shown that the charge, as it descends through the furnace, passes through a number of distinct reaction zones. Each zone is characterised by differing process conditions and reaction products. The phase equilibria, reaction steps and mechanisms occurring as the charge progresses through the furnace are examined, and the potential influences of these factors on the process outcomes are discussed.

Jan 1, 2004

The 1967 Lignite Symposium was held at Grand Forks, N. Dak., on April 27-28, 1967. This was the fifth of these technical meetings and the fourth which was cosponsored by the University of North Dakota and the Bureau of Mines. These symposia have provided a meeting place where current developments concerning technology and utilization of solid fuels (lignite) are presented. There was a registration of 255 persons from 24 States, the District of Columbia, six Canadian Provinces, Germany, and India. Many segments of coal or energy oriented organizations at many levels were represented. During the meeting, 18 presentations were made covering developments in electrical power generation, mining, estimation of reserves, combustion, gasification, and chemical and speciality uses of low-rank coals; these are com-piled in this Information Circular to provide a record of the symposium and to permit wider dissemination of the information. Proceedings of the other meetings have also been published.3

Jan 1, 1968

By Joel Darmstadter

The position of the coal industry in America’s fuel and power picture remains one of prime importance. Measured in Btu terms, the industry is the country’s leading energy producer and an important exporter. Foreign coal sales yield annual proceeds of about $4 billion. Coal’s one-fifth share of the nation’s energy consumption is nearly as high as that of natural gas. Coal is the electric utility sector’s principal fuel supplier. It accounts for about55% of the electricity generated at power stations.

Jan 1, 1999

By T. McKeon, G. Luttrell

Spiral separators are commonly used to upgrade sand-sized particles in both the coal and mineral processing industries. Many plants utilize multiple stages of cleaning and/or scavenging spirals to improve recovery and/or final product grade. Field studies suggest, however, that the layout of industrial spiral circuits is often less than optimal. This oversight can usually be attributed to a failure by plant designers to consider fundamental process engineering rules that govern the layout of complex separation circuits. This article reviews some of these important rules as specifically applied to multistage spiral circuit design. Two industrial case studies, one involving the upgrading of heavy mineral sands and a second involving the cleaning of fine coal, are presented to illustrate the impact of good design protocols on spiral circuit performance.

Jan 1, 2007