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By R. L. Guerguerian

Nowadays, most grinding mills driven by a wrap-around ring motor are operating successfully. Some of the earlier problems could be attributed to the lateral stiffness and stability of their bearings. As a result, modifications to the bearings included the rearrangement of the shoes, or the addition of more shoes, closer to the horizontal centerline. This technical paper reports a study of the effects of bearings on the lateral stiffness of grinding mills driven by a wrap-around ring motor. The discussions cover the design of the four shoe trunnion bearings and examine the effects of the angular location of the shoes.

Jan 1, 2000

By Craig Naudé

"An enhanced gravity concentrator was installed in conjunction with an Intensive Leach Reactor at the Sadiola plant in Mali last year and commissioned in Dec 2007.There has been much debate over the years as to the effect of gravity concentration on overall plant performance. The late Dr Laplante suggested that for every 10% of gold recovered by gravity, there was a corresponding 0.1% to 1% additional overall plant recovery. The results at Sadiola are consistent with this hypothesis with an overall 4% gain in plant recovery.With total gold recovery of 12% in the gravity section, grades are increased from 3.54g/t in the gravity feed to an average of 2 600g/t in the concentrator feed to the in-line reactor. The recovery of gold in the in-line reactor is in excess of 98.5%.This paper discusses the background to the project, the laboratory testwork prior to the equipment selection, the operational results of the system, as well as the benefits of the future application of high mass yield centrifugal concentrators in base metals, sulphides and industrial minerals. Bench scale, pilot scale and plant practice examples are also presented.INTRODUCTIONBesides picking nuggets off the ground or out of riverbeds, gravity concentration is arguably one of the oldest methods of recovering gold. In circa 6000BC people discovered that gold can be found behind the rocks and in depressions of creek beds. By placing rocks in a stretch of channel with the proper slope the first sluice is built, probably around 4,000 BC, and this method is still practiced today."

Jan 1, 2009

By G. J. de Korte

Dense-medium beneficiation of fine (minus 0.5 mm) coal is not a new concept and has been used in South Africa previously. The dense-medium fine coal plant at Greenside Colliery operated for almost 18 years and, despite proving a difficult plant to operate, did succeed in producing a fine coal product with a low ash content of 7%. No other beneficiation process available could achieve this. Dense-medium beneficiation of fine coal was also used in other countries, of which the plants at Homer City in the USA and Curragh in Australia were the best known. The first application of dense-medium cleaning of fine coal was, however, at the Tertre plant in Belgium1. This plant was built in 1957. About nine years later, a second fine coal dense-medium plant was built at the Winterslag Mine, also in Belgium. According to reports, this plant operated satisfactorily for a period of some 17 years.

Jan 1, 2002

By M. H. B. Nasseri

Barre granite?s samples have been tested for fracture toughness under mode I along two different directions with respect to microstructural fabrics were investigated. 3D objects counter algorithm technique is applied on micro CT images to identify physical properties such as crack induced porosity, crack density, generated total surface area and contribution of individual mineral grains within the damaged zone.The result obtained justifies very well the fracture toughness anisotropy in Barre granite, and explains the difference in the structure of the damage zone evolving as a result of test crack interacting with pre-existing microstructural fabrics. The present study has potential application in the fields of rock mass stability, oil reservoir stimulation, rock fragmentation and damage in blasting and emplacement of dykes.

May 1, 2009

By L Besra, A. R. Prasad, B. P. Singh

The role of surface-chemical phenomena and the physical processes that participate in the dewatering of a suspension of alumina trihydrate were subjected to a systematic investigation, which has increased understanding of the influence of surface tension, contact angle and adsorption in the process. The residual moisture content of the cake can be reduced significantly through the use of surface-active agents in slurry pretreatment or as wash-water additives. The effectiveness of a particular surfactant is hard to predict from any single parameter, but is dependent on its ability to reduce surface tension and possibly to modify the solid-liquid contact angle. If scaled up to industrial operation of the dewatering step of the Bayer process in India, the use of these chemical additives could substantially improve its process economics, reducing the fuel costs for thermal drying by a much as Rs 50/t

Jun 21, 1905

By T Christie, A Swain

Patterns of quartz veining in epithermal gold-silver deposits at Wharekirauponga, Neavesville and Ohui in the Hauraki Goldfield, have been analysed to determine the effects of different lithologies on vein distributions. At Wharekirauponga, quartz veins are hosted in rhyolite and minor andesite, with the andesite containing slightly higher gold grades. Local basement andesite, rhyolitic tuff and silicified black shale host gold-bearing quartz veins at Neavesville. At Ohui, quartz veins are hosted in rhyolite, rhyolitic tuff and andesite. Fractal analysis was used to quantitatively describe the distribution of veining. The fractal dimension (D) of veining in silicified tuff is 0.25, moderately silicified rhyolite has D = 0.23 - 0.26, clay-altered andesite has D = 0.3, strongly silicified rhyolite has D = 0.3 - 0.39, silicified andesite has D = 0.4, and silicified black shale has D = 0.43. The D values are related to the composition of the host rock, and appear to be controlled by its competency. Hydrothermal silicification results in increased competency and higher D values. Vein thickness frequency plots for different lithologies show that andesite at Ohui, and to a much lesser degree at Wharekirauponga, contains more thick veins than rhyolite and tuff. Gold grades show a strong to fair correlation with higher vein density in three drillholes at Wharekirauponga. The fractal dimension of veining is an important control on fluid flow and gold deposition within an active epithermal system. Vein systems with higher D have a greater density of veining which would have favoured increased fluid-rock interaction. Lower D vein systems have more clustered arrays. The increased fluid-rock interaction induced by a high D vein system, when combined with a reactive host rock, results in an environment which is highly favourable for gold deposition. This situation is seen in the andesite at Wharekirauponga.

Jan 1, 1994

By H Ulrich Leiste, Leslie Talor

This paper describes a series of small scale tests conducted to investigate the loading applied to a flat plate by the detonation of a cylindrical charge very close (between two and three charge radii from the center of the charge) to the structure. The testing used very small quantities of explosive (PETN): Two different series of tests were conducted. In the first test series, impulse loading on the target plate was investigated using three different sizes of charge. In the second series, pressure time profiles were determined. The charge size was 6 g or less. Impulse was found using high speed video of the target plate to determine its displacement as a function of time, from which initial plate velocity was obtained. Kolsky Bars, placed at the same distance from the charge as the target plate, were used to determine the free-field pressure time profile of the output of the charge at this distance. Two different types of target plates were used in the impulse study. One was just a plate while the other was a plate constrained with a steel frame.

Jan 1, 2009

By Cathy Aimone-Martin, Brent Meins

A comprehensive instrumentation program was implemented at the Howland Hook Marine Terminal on Staten Island, NY during proximate underwater rock blasting in 2014. Forty-two blasts took place over a 4-week period to deepen the 1200-ft (366 m) Berth 3 from -45 ft (-14 m) to -50 ft (-15 m) MLW to accommodate Post-Panamax vessels. Approximately 86,000 yd3 (65,752 m3) were blasted 120 to 9 ft (37 to 2.7 m) from the wharf to a total depth of -57 ft (-17.4 m). Pre-blast planning included developing and implementing a comprehensive monitoring plan and setting vibration and strain limits to protect the wharf. The plan outlined methods to measure vibrations on five corners of four concrete deck sections, on five concrete-filled pipe piles just below the pile cap near deck corners, and in bedrock adjacent to pile sockets. Water overpressures were measured near instrumented piles for 19 blasts closest to the wharf. A total of 19 geophones were secured to the wharf structure and buried 12 ft (3.7 m) in drilled holes.

Jan 1, 2016

By Lumley G, Rowlands D

The overburden slusher (OS) is proposed as a stripping tool that is expected to find application in overburden stripping operations including open cut coal and oil shale mines. OS is expected to combat the effects of increasing depth on the productivity of conventional dragline stripping.Although previously developed stripping techniques have included the use of drag scrapers the OS is sufficiently different as to constitute a new stripping method.A study undertaken at the University of Queensland during 1985 is believed to be the first major study on the use of the OS and preliminary economic results are very encouraging. It appears that the OS has the capacity to remove overburden at a cheaper unit cost than the equivalent powered dragline stripping machine at any comparable depth of overburden. The OS is not adversely affected by increasing stripping depth to the same extent as a dragline. In addition, the action of the OS machine allows for the lowering of spoil face angles, thereby reducing spoil slope stability problems encountered in deep open cut strip mines.

Jan 1, 1986

Perhaps one of the most important conferences or symposia which our Institute has conducted, was the joint Aus. LM.M./AJ.M.E. meeting held in Canberra in May 1978, with the theme International Resource Management (Woodcock, 1978).We were privileged to witness active participation in the meeting by outstanding personalities from the mining and metallurgical industries of Australia and New Zealand, the United States of America, Canada and the United Kingdom and to hear addresses on subjects of international significance to the mining and metallurgical industries.Our Institute is one concerned with professionalism.The principal objects of The Institute as described by our founders include, "promoting the arts and sciences connected with the economical production of the useful minerals and metals, and the welfare of those in the industries, by meetings for social intercourse, and the reading and discussion of professional papers, and to circulate by means of publications amongst its members and associates, the information thus obtained".Sir Maurice Mawby (1968) said in his Presidential Address to the Institite, "the most important aspect of these objects was the promotion of the arts and sciences of the mining industry".Why is it then, that a large proportion of the papers given at the meeting in Canberra dealt with world wide social aspects of the mining and metallurgical industries, rather than the technology, the arts and sciences of mining and metallurgy as principal factors in international resource management?The answer is quite simple of course, and that is that the social and political factors are the principal factors which create the demand for basic raw materials and in the long term determine the costs and prices of the commodities which our professional abilities are drawn upon to produce.

Jan 1, 1979

By H. T. Kennedy, S. M. Avasthi

An equation developed for gaseous hydrocarbon mixtures predicts molal volumes with an average absolute deviation of 0.73 percent when applied to 264 natural gas and condensate systems including 2,043 PVT points. Another equation developed for liquid hydrocarbon mixtures predicts molal volumes with an average absolute deviation of 1.12 percent when applied to 346 crude oil systems including 1,759 PVT points. Both equations require composition of the mixture to be expressed as mole fraction of methane through heptanes-plus, hydrogen sulfide, nitrogen and carbon dioxide, together with the characteristics of the heptanes-plus fraction in addition to the temperature and pressure. The equations cover wide ranges of the variables involved, and their accuracy is considerably better than that of other available methods. The equations were differentiated to allow calculation of the coefficients of isothermal compressibility and isobaric thermal expansion. (In this paper the coefficient of isothermal com-pressibility and the coefficient of isobaric thermal expansion will be expressed as compressibility and thermal expansion coefficient, respectively.) Equations to calculate these quantities are presented. INTRODUCTION Calculations of reservoir performance for petroleum reservoirs require accurate knowledge of the volumetric behavior of hydrocarbon mixtures, both liquid and gaseous. Compressibilities are required in transient fluid flow problems, and thermal expansion coefficients are important in thermal methods of production. An accurate laboratory investigation of the PVT behavior of each reservoir fluid encountered would be costly and time consuming. For this reason various correlations for predicting fluid properties have been developed and recorded in recent literature. Correlations have been presented in the form of graphs, tables and equations. Since an increasing number of studies are being conducted with the aid of electronic computers, recent efforts have been directed toward development of correla-tions suitable for computer programming. Application of computers permits the use of more complex correlations which otherwise are not feasible. Moreover, methods for predicting reservoir performance, particularly those based on the compositional material balance, depend upon the capability of accurately expressing the molal volumes and other fluid properties as functions of pressure, temperature and composition. The coefficient of isothermal compressibility c is defined by

Jan 1, 1969

By James H. Aase

Shales from 10 locations in Michigan were sampled, tested, and evaluated to determine their suitability as raw materials for producing lightweight aggregate by rotary-kiln methods. Sampling procedures and the geology of the shale units tested are discussed. Preliminary testing in a muffle furnace preceded extensive testing in a l6-inch by 14-foot rotary-kiln. Rotary-kiln products from these shales ranged in weight from 35.5 to 61.2 pounds per cubic foot (pcf). Concrete test specimens made pith selected aggregates were evaluated to determine the qualities of the concrete. Compressive strengths of the concrete ranged from 2,830 to 4,240 psi after 28 days of curing. Unit weight of the concrete ranged from 94.8 to 101.5 pcf. Lightweight aggregate suitable for use in structural concrete meeting ASTM standards was produced by the rotary-kiln method using shale samples from two locations.

Jan 1, 1967

By Hamid Maleki

In this paper, the authors present a review of data gathering programs and stress analyses for improving mine layout designs at BRL mines located near Paonia, Colorado. BRL and other companies have used both longwall and continuous miner methods for the extraction of the Upper D, Upper B, Lower B and C seams from the multiple-seam reserves in the North Fork Valley. Historic mining in the B and C seams has created stress footprints in the neighboring unmined seams compounded by stress transfer from recent longwall extraction in the Upper D Seam. Thus optimum positioning of workings in the remaining reserves requires careful collection of pertinent data and consideration of load transfer from previous workings through remnant abutment pillars. Based on long-term subsidence monitoring, underground mapping and stress analyses, we have confirmed initial load transfer analyses finding mild interactions between the UD and LB workings, and the mining conditions have proven to be good and manageable during the development stage of the LB Seam. This has been achieved through prudent mine planning, prudent positioning of the gateroads in multiple seam workings and support allocations.

Jan 1, 2007

By O A. Cottrill, G A. Oldfield, S B. Nowell

Host-rock û wallrock major and trace element geochemistry associated with epithermal gold mineralisation in the Hauraki Goldfield of New Zealand is poorly documented, even though rock geochemistry is a recognised tool in exploration. Such responses assist in recognition of the regional scale imprint of fossil hydrothermal activity, and indicate targets for detailed evaluation within these alteration zones.   Recent investigation of gold deposits in the Waihi (Gladstone), Golden Cross (Empire), Thames (Waiotahi) and Coromandel (Tokatea) areas indicate enrichments of Au, As and Sb in the andesitic wallrocks hosting mineralisation. Of the other elements examined, Si, K and Rb are enriched, and Na, Ca, and Sr are depleted at all deposits. These trends are best developed in the vicinity of veining. In deposits with clay alteration dominating (Waiotahi and Tokatea) there is also depletion of Mg, Mn, Zn and Cu. Ba and Cr are variably enriched or depleted within different styles of alteration. Base-metal enrichment in the wallrocks is not a feature of Hauraki deposits.

Jan 1, 1990

By J P. Ashby

Compared with elsewhere in the world, New Zealand quarries have tended to be mostly small. The reasons for this are a combination of the relatively high transport costs, low population density and a pioneering, self-employed attitude. The small size of the operations is reflected in low productivity, a tendency to repair and rebuild equipment rather than replace it, designed flexibility in the processing plant, minimal reserves investigation or development planning and a versatile and innovative work force who are generally not professionally trained. The Resource Management Act and the Health, Safety and Employment Act as well as a customer driven demand for higher quality and consistent products will have even greater influence upon future direction of the Industry. The trend will be towards fewer quarries operated by companies and professional managers that can adapt to the new demands.

Jan 1, 1993

THE Great Cobar Company Limited owns 1100 acres of freehold, which include the Great Cobar Oopper Mine and smelters, the Cobar Gold Mine, the Cobar-Ohesney Copper Mine, and the Great Peak Gold Mines.ORE OCCURRENCEThe ore-bodies in the first three mines-namely, Great Cobar Copper Mine, Cobar Gold Mine, and Cobar-Ohesney Oopper Mine are, speaking generally, lenticular deposits of evidently more or less complete metasomatic replacements of the country rock along a line of powerful faulting. These lenses vary from 150 ft. to 400 ft. in length, and from 20 ft. to 100 ft. in width.

Jan 1, 1919

By B. Salt, R. Sullivan, E. Roos, M. de Vries, K. McKenna, L. R. Nelson, M. J. N. Uys, P. Jacobs, E. Munnik, P. Lewarne

A review is presented of the furnace cooling system design and operating developments since the initial furnace start up in January 2001 of the Chambishi DC-arc furnace to produce ferrocobalt alloy. The furnace operating conditions present a number of challenges to the furnace designers and operators in particular to provide a sustainable lining that can withstand the highly corrosive siliceous slag (roughly 50% SiO2). This is exacerbated by the dual requirement to operate this slag in a relatively highly superheated state (?T ? 400°C when tapped at 1550°C) to ensure that the ferroalloy can be tapped (estimated 1370°C alloy liquidus temperature) prior to atomisation. The core design challenge occurs at the alloy-slag interface, where a single refractory type cannot simultaneously meet the dual requirement of both adequate alloy and slag corrosion compatibility. Progression by the fourth furnace campaign to involve a retrofit of the bath sidewall to Hatch high-intensity, water-cooled, copper Waffle coolers and tapblocks is described. This involves operation of the entire slag bath, the slag-alloy interface and a portion of the alloy within a more chemically compatible refractory/slag (and possibly at times even an alloy) freeze-lining. Due to the high furnace power density employed (up to 500 kW/m2 hearth area) coupled with the large slag superheat needed, the resulting imposed peak bath sidewall heat fluxes are substantial, especially in the alloy (typically averaging 170 kW/m2), and on occasion have exceeded 1000 kW/m2. The performance of the Hatch Copper Waffle coolers under such aggressive process pyrometallurgical conditions is described. Aspects of the design and especially operating strategies to effect sustained production at up to 38 MW power input are also discussed.

Jan 1, 2004

By Gus Van Weert, Peter Kondos

"Ore sorting has been quite successful in providing a separation means in the rock size range of 1 to 6 inches; a range where mineral dressers do not have many options. The industrial minerals and recycling worlds have embraced this technology. However, ore sorting has not found wide application in the base or precious metals mining industry. One reason for this is thought to be the reliance of most sensors on rock surface characteristics, not very useful in case of sulphides, non-existing in case of gold. Microwave heating, however, is specific for sulphides and graphite (or carbonaceous matter) embedded in the rocks; washing or even drying does not appear necessary. Separation can be done afterwards by already existing ore sorting technology using infrared sensors. Test results on six Nevada gold ore samples are presented in detail. Some simple test procedures are also presented for those wishing to explore the microwave potential of sulphide sorting in their own operations.INTRODUCTIONMineral processing in the base metals industry most often involves upgrading of the ore, concentrating the valuable mineral fraction by classic methods, such as flotation. Since the liberation of minerals in the ore occurs mostly at or below the 100 micron level, the industry has been living with fault lines, so to speak, between blast hole spacing (10,000 mm), run-of-mine ore size (100 mm) and beneficiation size (0.1 – 0.01 mm). The acceptance of ore sorting will inevitably lead to the revisiting of the following questions: “Exactly how much below ore grade rock ends up in the mill because the geologists or the miners cannot define the resource boundaries more precisely? How can the economics of dilution be improved? How many ore grade rocks are lost with the overburden?”"

Jan 1, 2007

By Jean Cayouette, Paul Blatter, Paul Cousin

"The Laronde mill was commissioned in 1988 and has been treating the Laronde Penna ore since 2000. The Laronde plant, situated in the Abitibi region of Quebec, has experienced mill expansions to accommodate 7500 mtpd and to recover gold and silver as well as important amounts of base metals (Cu, Zn, Pb). Ten sequential metallurgical and environmental processes are responsible for metals recovery and process viability. Over 200,000 ounces of gold, 4,5 million ounces of silver, 7000 tonnes of copper, and 78,000 tonnes of zinc are produced annually.In 2008, the Goldex plant began trucking high grade (35-45 g/t Au) pyrite sulphide concentrate (TCGO) for gold extraction at a newly constructed treatment plant, increasing gold output at Laronde by 40,000 ounces. In 2009, the high gold grade Lapa ore processing facilities were annexed to the Laronde plant increasing output by 120,000 ounces of gold. TCGO and Lapa productions are forecasted until 2018 and 2015 respectively, with known reserves of each mine.Today, up to 140 permanent employees run and optimise the Laronde plant operation. As a result, Laronde has intricacies intrinsic to a large and varied operation. The paper will outline the metallurgical highlights, challenges, and future outlook related to the treatment of each ore type (Laronde, TCGO, and Lapa).INTRODUCTIONFollowing the 2000 to 2003 expansions, the Laronde plant evolved into a mature milling complex with developed processing, man power, and water treatment capabilities able to accommodate the complex Laronde ore. The ore requires a series of grinding, copper/lead flotation and separation, zinc flotation, zinc tails precious metals leaching, followed by a counter-current decantation circuit and Merrill Crowe precipitation. A paste backfill and SO2-air cyanide destruction operate intermittently. The tailings area has a dedicated cyanide destruction and metals precipitation plant prior to water recycling to the mill. A biological water treatment plant was put into service in 2004 to address the build-up of thiocyanate in the tailings ponds at Laronde. This was the result of the high sulphide content of the Laronde ore and 90% recirculation of the process water. The plant uses bacteria to oxidize and destroy thiocyanate, and removes phosphate from the water before it is released to the environment."

Jan 1, 2011

By David Preece

The Thirlmere aqueduct was constructed over 110 years ago to provide water from the Lake District (in the north-west of England) to the city of Manchester some 60 miles (100 km) away. The aqueduct remains, to this day, a key piece of infrastructure in the distribution of raw water in the north-west of England. A short section of the aqueduct was identified as being in poor condition during routine inspections by the owner. Subsequent investigations attributed the conduit damage to the movement of unstable ground over the conduit. Bachy Soletanche Ltd was subsequently appointed to carry out the design and construction of the slope stabilisation works and to undertake repairs inside the damaged conduit. The works were undertaken on an existing slope which, in places stands at a gradient of up to 40º to the horizontal. Strict limitations on plant and equipment were imposed by the client (United Utilities) to ensure that slope and conduit loading and associated vibrations were kept to an absolute minimum during construction. An intensive instrumentation system was installed to monitor surface movements, ground movements at depth, conduit movement and strains across existing planes of weaknesses within the conduit. The solution comprised the installation of spaced piles up-slope and down-slope of the conduit. Restrictions were imposed on the minimum stand-off distance between the outside face of the conduit and the piling works so targeted permeation grouting was undertaken to improve the ?connection? between the conduit and the down-slope piles. The presence of existing sub conduit groundwater flows was suspected and the permeation grouting was focused in areas to minimize disruption to the groundwater regime. The paper presents the basis of the design and highlights the combined construction and instrumentation methods adopted to minimise damage to this valuable asset.

Jan 1, 2011