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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

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 Ren G. Dong, Jay Kim, Daniel E. Welcome, Won Joon Song, Charles Hayden

Prolonged, extensive exposure to hand-transmitted vibration could cause a series of vibration-induced disorders in the vascular, sensorineural, and musculoskeletal structures of the human hand-arm system, which have been collectively called hand-arm vibration syndrome (HAVS).1 To assess the risk of HAVS the international standard ISO 5349-1 (2001)1 recommends using the root-mean-square (rms) acceleration of the measured vibration with a frequency weighting. While a few epidemiological studies have reported results consistent with the predictions made according to the recommendation, many other studies have reported results with large discrepancies.2 This may be partially attributed to the time-averaging effect involved in calculation of the frequency components, especially for impact type tools. Because the spectral characteristics of impact tools change dramatically with time, a time-frequency (T-F) analysis can provide better characterizations of such highly transient vibrations. The analytic wavelet transform (AWT) is an ideal T-F analysis tool because it possesses the advantages of both the Fourier transform and the wavelet transform.3 The objective of this study was to explore the application of the AWT method for characterizing the impact tool vibrations and assessing their exposure risk. Methods Five tools (two chipping hammers, two riveting hammers, and one concrete cutting saw) were used in this study. The saw vibration was measured when it was used to cut a section of road pavement during a repair. The vibrations on the other tools were measured by the procedure specified in ISO 8662-2 (1992).4 A sampling rate of 16,386 Hz was used in the measurement. The AWT and Fourier analysis were applied to these signals and to identify their characteristics. Results Figure 1 compares the T-F characteristics of the accelerations measured from the relatively steady concrete saw and a riveting hammer. The frequency weighting specified in ISO 5349-11 was applied in the calculations. The comparison clearly shows that the two tools have completely different T-F characteristics.

Jan 6, 2006

By C. Dorfling, P. Albertyn

"Hydrometallurgical recovery of metals from printed circuit board waste typically involves multiple leaching stages; conventionally, base metals dissolution by mineral acids is followed by leaching of gold using cyanide or halide based lixiviants. Alternative lixiviants for gold leaching can reduce the potential hazardous nature of operation. The aim of this study was to investigate the feasibility of using thiosulfate as lixiviant for gold leaching from waste printed circuit boards. Batch leaching tests were performed to investigate the effects of thiosulfate concentration (0.1 – 0.2 M), ammonium concentration (0.2 – 0.4 M), pH (9 – 10.5), solids content (25 – 50 g/L), and copper content of the feed material on the gold leaching behavior. The concentrations of metals in liquid samples were determined by means of inductively coupled plasma atomic emission spectroscopy, and high pressure liquid chromatography was used to evaluate thiosulfate degradation/consumption. The ratio of thiosulfate to ammonia was found to have the most significant effect on the extent of gold leaching, with the best gold extraction observed at a ratio of 0.5 mole thiosulfate per mole ammonia. The lower pH range of 9 – 9.5 generally produced better Au leaching, while low copper extraction during the first stage base metal leaching stages has proven to be detrimental to gold leaching from the residue. Thiosulfate degradation/consumption increased and gold extraction decreased with higher residual copper in the feed. An optimum gold extraction of 78.5 % from base metal leach residue was achieved with 0.2 M thiosulfate, 0.4 M ammonia, and 0.02 M cupric ions at 25°C in the pH range 9 – 9.5.INTRODUCTION Background and Aim The recycling of e-waste is becoming increasingly important as it provides certain economic benefits apart from the obvious environmental benefits. Printed circuit boards (PCBs) are found in most forms of e-waste and contain especially high concentrations of base and precious metals. Hydrometallurgical processes are often considered for the recovery of valuable metals from PCBs; these processes normally implement several leaching stages to selectively recover certain metals."

Jan 1, 2018

By Yavuz Ali Topkaya

Rare earth ferrosilicide is a versatile alloy mainly used to control the detrimental effects of sulfur in steel and to modify graphite structures in cast iron. The aim of this study was to determine the optimum conditions to make rare earth ferrosilicon alloy using a preconcentrate produced from a bastnasite type of ore present in the Beylikahir-Eskisehir region of Turkey. This concentrate contained 23.5%REO, 41.37% CaF2, 10.69% BaSO4, 8.50% CaCO3, 4.18%Fe2O3, 2.83% Al2O3, 2.74% SiO2, 1.20% P2O5 and small amount of other oxides. The initial metallothermic reduction of this concentrate using ferrosilicon and aluminum in a graphite crucible placed in a muffle furnace gave very low recoveries due to the difficulties encountered in adjusting the slag composition, temperature and amount of additives. Therefore, two batches of rare earth oxide concentrate containing 61.1% and 81.7% cerium oxide, respectively, that were procured from a Turkish glass producer, were used to optimize with respect to temperature, duration, slag-making additives and amount of reducers. In these experiments, smelting and reduction was done in an induction furnace with graphite crucible, and, ferrosilicon and aluminum were added after melting the charge. As a result, there was no difficulty in obtaining a rare earth ferrosilicon alloy containing 35-55% RE, 5-25% Fe and 20-40% Si, with about 80% metal recovery. When the optimum conditions were applied to the preconcentrate, alloys of similar compositions were obtained with 70-80% recovery. Experiments were also done with mixtures of preconcentrate and rich concentrate, and, recoveries as high as 95% were obtained. Only in this case, to increase the recovery, mixtures had to be charged to the empty graphite crucible after heating the crucible to the required temperature.

Jan 1, 2006

By Walter R. Crane

PAGE I. Apparatus and Methods.......... 406 1. The Magnetic Circuit...........406 2. Apparatus Employed in the Traction-Method...... 406 a. The Coils............409 b. The Pole-Pieces..........409 3. Methods of Testing Fields Produced by Different Pole.Pices.. ..409 c. Testing with a Search.Coil........410 d. Testing with Iron-Filings and Glass Tube.. .. .410 4. General Forma of Pole-Pieces.........411 e. Flat Poles............411 f. Conical Poles........... 411 g. Spherical Poles...........411 h. Chisel-Edged (Chamfered) Poles.......412 II. Magnetic Fields...........412 5. Methods of Testinq for Magnetic Permeability...... 421 i. The Rod-Method..........423 j. Method Employed in These Experiments......424 k. Difference in the Results of the Two Methods..... 425 l. The Traction-Method.........427 m. Effect of Loosening the Charge.......430 n Corrections...........432 6. Theory.............433 o. Effect of Varying Weight on Tractive Force..... 434 p. Effect of Varying Pole-Distance.......436 q. Effect of Varying Magnetization.......436 T. Effect of Varying Size.. .......437 a. Summary,........... 441 III. The Relative Magnetic Permeability of Various Minerals,. 443 The form and strength of magnetic fields have attracted much attention. especially in connection with the designing of dynamo-electric machinery—an art which has been revolution-

Jan 1, 1902

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

By K. T. Lee, M. U. Ozbay, M. D. G. Salamon

Design of yielding chain pillars in deep coal longwall mines is not as well established due mainly to the lack of knowledge in the behavior of coal pillars in the post-peak regime. This study shows that two of the existing strain-softening models have the potential to provide an improved understanding of yielding and, therefore, could form a rational basis for yielding coal pillar design. Analytic and numerical modelings of a row of chain pillars in a two-entry development at a depth of nearly 700 m suggests that yielding pillars are feasible, but the design is very sensitive to the coal’s post-peak behavior.

Jan 1, 2001

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 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 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 K. C. Garner

The visit reported was made with support from the 1997 J.C. Boyle travelling scholarship. The management and control of hazardous gases released into the underground environment are an integral part of coal mining. The power-generations stations at Appin and Tower collieries, with a combined electrical output of 94 MW, have been operating for some time and have demonstrated a technology that is able to exploit the available gas fully. Contributory factors have been the development and introduction of directional drilling techniques, pre- and post-drainage of coal, relatively high seam permeability, a high gas content of the worked seam, high production rates and a willingness to embrace new ideas and technology

Jun 21, 1905

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

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

By A. W. Schlechten, R. P. Abendroth

Jan 1, 1960

By Gary Anderson

??Privately Held Corporation ??Incorporated in Delaware, May of 2002 ??HQ in Malvern, PA (just outside Philly) ??Approx 40 employees ?9 Field Engineers ?MSHA Certified ?10 Development/NOC Engineers ?Site Survey/Site Design ?RF Engineers ??Standards Based ?IEEE 802.11 ??Commercial Off the Shelf (COTS) ?Gateworks, Ubiquity, Atheros, Linux Based ??Technology was developed and inspired by the lack of communications during the terrorist attacks of Sept. 11, 2001

May 1, 2009

By Ross Nairn

"Tulawaka Mine is a joint venture between Pangea Minerals Limited 70% (a wholly-owned subsidiary of Barrick Gold Corporation) and Northern Mining 30%. Tulawaka Mine is located in North West of Tanzania in the Lake Victoria Goldfields. Tulawaka Mine is scheduled to process 360,000 tonnes per year at an average 11.5 g/t head grade over a 4 year mine life.The Tulawaka Process Plant uses single stage crushing, single stage SAG milling, gravity, intensive leach of gravity concentrates, CIL, Zadra desorption and cyanide detoxification to process the ore. Gold recovery exceeds (or is expected to) 95%.The Process Plant was designed and constructed under the supervision of Ausenco Engineering of Australia. Site works commenced in January 2004, Process Plant construction commenced in July 2004 and the first ore was presented to the Process Plant 26th February 2005. The first gold was poured on 15th March 2005. All construction contractors were demobilized from site 7th April 2005. Major achievements have been 3.4 million hrs LTI free during construction and operation to date, training of the Tanzanian workforce at Bulyanhulu Mine prior to commissioning, a succession plan to replace expatriate personnel with Tanzanian staff and significant over performance of the Process Plant against design.INTRODUCTIONTulawaka Mine is situated approximately 160 km south west of Mwanza in the western Lake Victoria Goldfields District of north western Tanzania. The property is held under a joint venture between Pangea Goldfields Inc (70%), a wholly owned subsidiary of Barrick Gold Corporation, and Explorations Minieres Du Nord Ltée (30%). A location map showing the position of the operation in Tanzania is shown in Figure 1.Mine site staff at Tulawaka comprises a combination of Tanzanian and Expatriate personnel. All Pangea personnel live on site and commute to their place of residence for their R&R on a 9 weeks on 4 weeks off roster."

Jan 1, 2006

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

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

By D. F. Malan

In deep level hard rock mining the rheological behaviour of the rock is important as time-dependent aseismic processes can lead to a stable dissipation of energy thus reducing violent outbursts. Underground closure measurements, observations of time-dependent fracture formation and siesmic data indicate that the rock in deep South African gold mines shows significant time-dependent behaviour. The objective of this work is to quantify the time-dependent rock behaviour for laboratory specimens and underground conditions. Laboratory experiments indicated that lava and quartzite specimens undergo measurable creep strain at stress magnitudes below the failure stress. Quartzite is however prone to more significant creep at lower stress levels. A viscoelastic analysis showed that laboratory creep results can not fully explain the behaviour observed underground. The in situ behaviour is governed mainly by the rheological behaviour of the fracture zone and the resulting time-dependent formation of new fractures. A viscoplastic discontinuity model implemented in a boundary element program is used to simulate this behaviour.

Jan 1, 1997