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By Charles Pretorius

Electronic Delay Detonators (EDDs) with remote wireless programming and initiation capabilities have been successfully used for almost two years now. This system has been used in blasts mainly in South Africa, but also in South America and other countries in Africa. Initially the industry was slow to accept the idea of remote programming and blasting. The advantages were not fully understood and there were some safety concerns. With close to 200 successful blasts as a reference, a much better understanding exists. The advantage of such a system becomes even more significant when the programming of the detonators is digitally integrated with the blast design software as used by the Blast Engineer. It is now possible to import a survey file into the blast design software, to do the blast design using actual hole positions and to then export the designed firing times directly to the detonators down the hole via remote wireless communication. Mines that have been exposed to this technology favour it to the extent that wireless centralised programming is becoming the norm against which other electronic delay detonator technologies are measured.

Jan 1, 2005

By Ramiro da Conceição do Nascimento Júnior

O uso de minérios lateríticos na metalurgia extrativa do níquel tem demandado investimentos em pesquisa e acordos de cooperação técnica para o desenvolvimento de tecnologias mais econômicas e produtivas. Devido às características de difícil processamento do minério e pelo decréscimo da sua quantidade e qualidade, ressalta-se a necessidade de se determinar técnicas efetivas de concentração, que possibilitem o aproveitamento de minérios marginais finos. Estabelece-se então, dentro de uma rota de processamento proposta, a estratégia de se produzir aglomerados (pelotas e/ou briquetes) a partir de concentrado de níquel. Além da fabricação dos aglomerados, faz-se necessária a sua caracterização em uma série de ensaios, para servir de base para a certificação desse produto e sua aplicação em processos de obtenção de ferro níquel ou gusa enriquecido com níquel. Um dos ensaios realizados envolve a caracterização física desses aglomerados. O ensaio foi realizado em máquina universal de ensaios, observando-se a resistência à compressão de amostras de aglomerados que passaram por diferentes tipos de rotas de processamento, e de diferentes etapas do processo de pelotização. Os resultados mostram que os aglomerados submetidos ao ensaio possuem resistência à compressão de pelotas verdes e secas de minério de ferro, conforme o esperado.

Aug 17, 2017

By M. Massinaei, S. Abasi, M. Oliazadeh

Reliable measurement and control of the pulp-froth interface (froth depth) in the flotation columns is critical to achieve the desired metallurgical performance. Shallow froths result in a reduction of grade because of particle entrainment and deep froths reduce recovery because of the drop back of entrained and weak hydrophobic particles to the pulp zone. The cleaner circuit at Miduk copper concentrator consists of three parallel MicrocelTM flotation columns 4 m in diameter and 12 m in height. The interface level of the flotation columns is measured by two pressure sensors located at 1.4 and 2.4 m from the cell lip (in the collection zone). In this study the performance of the level detection system at different operating conditions was evaluated. A calibrated float-ultrasonic location system was used for measuring the actual froth depth. The results indicated that the existing level control system was subject to considerable error. The absolute error was found to be 33.27 cm. This was mainly attributed to the constant set-point value assigned to the froth density (ρf=0.3 g/cm3), which actually varies with the operating conditions. The actual froth density at different conditions was calculated and its average value (ρf=0.12 g/cm3) was re-set in the control system. This resulted in substantial reduction in the level-detecting error. Recommendations for more accurate measurement of the interface level were presented. INTRODUCTION Froth flotation is a complicated process because of many involved variables. One of the most significant controlled variables in the flotation process is the pulp-froth interface (froth depth). The froth depth has a profound influence on the metallurgical performance parameters (i.e. grade and recovery). Shallow froths result in grade reduction because of particle entrainment and deep froths reduce recovery resulted from the drop back of entrained and weak hydrophobic particles to the pulp zone (Finch and Dobby, 1990). Various techniques have been developed for measuring the interface level of the flotation cells in the last few decades. These techniques can be classified as: Techniques based on hydrostatic pressure measurements (Finch & Dobby, 1990), Techniques based on the density gradient (float) (Moys & Finch, 1988), Techniques based on conductivity measurements (Uribe-Salas, 1991), Techniques based on temperature measurements (Moys & Finch, 1989).

Jan 1, 2019

By Ernie Doell, Trung Nguyen

"In early 1995 Cluff Mining commissioned a newly constructed high density tailings thickener at its Cluff Lake uranium mill. The 85 ft diameter high density thickener is one of the first of its kind in North America, and incorporates the novel paste technology in its design to produce densified (in the range of 60 -65% solids) mill tailings suitable for stable deposition in the tailings management area. This paper discusses the impetus behind the installation of such an unconventional thickener, and the many trying experiences in making it operational.IntroductionCluff Mining, a wholly owned subsidiary of Cogema Resources Inc., is the operator of a uranium mine and mill complex at Cluff Lake which is located in northern Saskatchewan. Since 1980, the company has developed and mined out several different ore bodies within the Cluff Lake region for the production of uranium concentrates, commonly known as yellow cake. Based on the known ore reserves, the Cluff Lake operations are projected to last till the early 2000's.Tailings from the Cluff Lake mill have been discharged to a tailings management area consisting of a tailings pond and two facilities for primary and secondary treatment systems. The tailings pond has an impervious bentonite lined dam, and it is divided into a solids and a liquids holding areas. Until the beginning of 1995, the mill tailings were discharged in two separate lines to the solids pond; one line carried the slurry residue of 45-50% solids (w/w) from the CCD circuit, and the other discharged raffinate tails containing less than 1 % (w/w) gypsum precipitate. Supernatant in the solids pond is treated in the primary treatment system prior to discharging to the liquids pond. Figure 1 shows the site plan of Cluff Lake tailings management area.It has been estimated that by the end of 1995 the solids pond would be filled to about 60% of its design capacity, and probably would be full before the year 2000. Therefore, Cluff Mining had to consider a more efficient tailings disposal method that could extend the service life of the existing Cluff Lake tailings management area. A high density tailings thickener was believed to be the most practical and economical system for tailings disposal at Cluff Lake mine."

Jan 1, 1996

With a price slowly rising above US$35 per ounce gold became a mineral worthy of prospecting and mining endeavour in the early to mid 1970s. Fortune therefore appeared to smile onNew Zealand with its favourable geological environment for gold and past record of major gold production from both hard rock and placer deposits. This was a particularly welcome development as the post war years, including both the base metal exploration boom of 1967/1971 (which produced major nickel, iron and bauxite mines in Australia) and the earlier period of uranium exploration failed to produce any mines in New Zealand with the exception of the small Tui Mine and iron sand mining. Whilst hard rock mining now appears imminent it is 15 years further along the track since the 1967/1971 exploration boom and eight years since the upsurge in prospecting for gold in 1978. New Zealand still has no hard rock base or precious metal mining. This is not for want of proven or potential gold mining situations for these clearly exist at Waihi, Monowai Reef, Golden Cross, MacRaes Flat and elsewhere.

Jan 1, 1986

By Cristian Rodriguez, Tom BoBo, Maria Rocha, John Kemeny

Blast fragmentation depends on many factors. First of all, it depends on the specific blast design, which includes the amount and type of explosive, the blasting pattern, the timing and sequencing, and other parameters. Secondly, it depends on the properties of the rock mass, including the uniaxial compressive strength (UCS), the rock mass elastic modulus (E), the rock discontinuity characteristics (as reflected in the GSI or RMR), and the rock density. Several fragmentation models have been proposed to predict blast fragmentation based on the blast design and the properties of the rock. These models include the Kuz-Ram model and variations of this model, as well as recent models by Kim and Kemeny (2011) and others. Fragmentation models are validated and calibrated by comparing the predicted fragmentation with actual post-blast fragmentation from image processing monitoring systems.

Jan 1, 2014

By H. E. Cline

Solidification of Pb-Sn alloys ranging in composition from 1.2 to 56 at. pct Pb ws observed with polarized light. Lamellar structures were observed over a larger range of compositions in alloys containing excess tin than excess lead, as expected from constitutional supercooling. The occurrence of pools of supercooled liquid surrounded by lead is explained by the difficulty in nucleating tin. Cells and dendrites weve observed in tin-rich alloys. Evidence was found that the degenerate structure formed at low growth rates, the formation of faults, and abrupt changes in composition and structure can be attributed to non-steady-state growth. The apparent interface shape was observed to have deep grooves at the interphase boundaries. HUNT and Jackson have observed the shape of the interface during growth of organic eutectics. They observed the formation of lamellar faults and shape instabilities upon changes in growth rate. The lamellar structure in these organic eutectics was not restricted to the eutectic composition. Recent work by Mollard and Flemings2 indicated that Pb-Sn alloys from 12 to 26 at. pct Pb could be solidified with a lamellar or rodlike structure if a sufficiently steep temperature gradient was used at a slow growth rate. Observations of the solid liquid interface of the Pb-Sn eutectic were made by Davies3 using polarized light. Photographs were at too low a magnification to determine the interface shape, but he has concluded that tin was the leading phase. In the following experiments, solidification of a range of Pb-Sn alloys from 1.2 to 56 at. pct Pb was observed using polarized light, to determine the factors controlling stability of the lamellar structure. EXPERIMENTAL Procedure. One hundred-gram ingots of alloys prepared from 99.999 pct pure Pb and Sn were cast into graphite molds under argon. The compositions of the alloys were 1.2, 6, 12, 26, 36, 46, and 56 at. pct Pb. Two-gram pieces were melted between two cover glass slides which were squeezed into a 1-mm separation. Samples were then observed under polarized light in a hot stage shown in Fig. 1. A long working distance objective designed for viewing at 500 times was used. Photography was made difficult by the lack of illumination and contrast at these high magnifications. By using an elliptical polarization compensator, as suggested by A. Holik, the contrast and illumination could be optimized. Photographs could be taken only at slow growth rates to avoid excessive interface motion during the 15-sec exposure used. The solidification rate was varied by increasing or decreasing the power to the heater. It was found that insulation was necessary to avoid undesired growth rate fluctuations. The temperature gradient, as measured with two thermocouples 1 cm apart, was 80" ± 20°C per cm during all the experiments reported here. The advantage of this procedure is in being able to observe solidification while it is occurring. However, the observations are restricted to the glass-metal surface and may be influenced by this surface. Also, one has no knowledge of the interior of the sample, in contrast to studies of the freezing of transparent organic eutectics.' Observations. The alloy near the eutectic composition (26 at. pct Pb) solidified in a lamellar structure when the growth rate was uniform. If the growth

Jan 1, 1968

By W. Dziurzynski

Transient states of the air parameters in mine workings occur as the effects of natural and technological disturbances, and in particular as a result of changes in ventilation conditions, caused by alteration of the mine workings geometry, state of fans performance or emission of gases. Particularly significant are those transient states caused by disturbances resulted from catastrophes, since they are frequently associated with violent phenomena that may be a danger for life and health of the staff working underground. The paper presents a number of examples of transient states of the air parameters in mine workings after a catastrophe, like the bump in the ZABRZE-BIELSZOWICE coal mine. Registration of air disturbances by the monitoring systems of ventilation in mine workings in the area of disaster both at the moment of a catastrophe occurrence and later during the rescue operation, enabled to track out the incident and identify the circumstances and reasons of those tragic events which caused death of 18 miners during last two years. Furthermore, computer simulations of processes occurring in mine ventilation network make effective research tools to be applied in practice, among others for the study of accidents and disasters.

Jan 1, 2003

By Carlos Espinoza Zegarra

El presente trabajo describe el método de mecanización del sublevel caving realizado en la mina Yauricocha, donde se aplica a cuerpos que varían de de pequeños a medianos, irregulares o angostos a través del uso de Scoops. Así también el método puede ser usado en roca competente, así como en cuerpos que ya han sido parcialmente explotados como es el caso del cuerpo Cuye. Finalmente no es requisito fundamental que el mineral sea de resistencia muy mala, ya que al descubrir una superficie relativamente grande a través de varios bolsillos, el mineral cae con facilidad debido a la presión del techo aún sin usar explosivos.

Sep 12, 2005

By T. Schmidt, J. Merza

"This study considers two lead/zinc/silver orebodies which have historically had a problem with pyrite, pyrrhotite and sphalerite contamination in the lead circuit. The problem was previously addressed with high dosages of sodium cyanide as the primary depressant. However, large amounts of cyanide led to environmental problems in the effluent, especially during winter months. The objective was to reduce cyanide consumption while maintaining or improving overall lead grade and recovery via the reduction of the undesirable sulphides.Extensive laboratory and mill testing was necessary to determine the optimal operating parameters for continuous plant application. Evaluation of data received from this testing has shown that selective addition and optimization of the dosage of Unimax SD100 to specific areas of the flotation and grinding circuits has resulted in improved Pb grade and recovery. Parameters such as pH control, regrind operation, the cyanide/Unimax ratio and sulphide mineral content may also affect the performance of the depressant. Each factor is discussed and optimal operating conditions were determined based on the testing.Results are presented for two case studies. Both indicate that Unimax SD100 improves the lead grade/recovery curve by increasing iron and zinc rejection while reducing cyanide consumption and the resulting environmental concerns. 1. Hart"

Jan 1, 1992

By E. Lampard

Mines must manage variability from within their operations as well as those imposed upon them by external forces. This paper provides a framework to manage both internal and external variability through the review and adjustment of the mine plan where applicable to minimize lost production and maintain operational safety. KEYWORDS Mine plan, mine schedule, variability, safety, lost production, float days, update, adjustment, operations, Maintenance

May 1, 2011

By P M. Bradbury

The nature of aggressive process chemical requirements typically in the Platinum Refinery Industries, lend themselves to the use of Polymer Composite Glass Reinforced plastics for pipework and other associated equipment in these types of Plants. This paper discusses the basic characteristics of a Polymer Composite glass reinforced piping system and gives sample examples of applications in current present day use.

Jan 1, 2006

By Laszlo Toth

A feeder is used to control the gravity flow of bulk solids from storage areas, like a bin or a stockpile. For this type of application, it is important to select a proper drive that can fulfill all of the demands put on it. High starting torque capacity, variable speed and the ability to handle frequent starts and stops are some of the demands that the drive must be able to meet. The following is a comparison of the most common type of drives used today for feeder applications. When a feeder is started, the breakaway torque may reach as high as200% of the running torque. The accelerating torque usually is set to protect the carrying element of the feeder, like the belt for the belt feeder and the carrying chain of the apron feeder (Fig. 1).

Jan 1, 2003

By Yunnen Chen

In the present study, waste materials like pine sawdust and spent grains were investigated to assess their potential for removal of cobalt ion from water by the process of biosorption. The effects of solution pH, reaction time and initial concentration were studied in batch experiments. The removal efficiency of Co(? ) by spent grains was higher than that of pine sawdust. The initial removal was rapid and equilibrium was established in less than 90 min. Equilibrium data all agreed well with both Langmuir and Freundlich isotherm models for the two metal-biomass sorption processes. Good correlation coefficients were obtained for the pseudo second-order kinetic model. Pine sawdust and spent grains were shown to be promising biosorbents for Co(? ) removal from aqueous solutions.

Jan 1, 2010

By Elizma Ford, Vincent Sithole

"Two shortened test procedures for estimating the Bond ball work index are compared for suitability of use on Zambian/DRC-type copper–cobalt ores. The first procedure is based on a batch milling test while the second procedure is based on a limited locked-cycle test. Both procedures were conducted using a standard Bond test mill. INTRODUCTION The Bond ball work index is widely used in the field of minerals processing as an indicator of ore grindability. The work index is determined by means of a locked-cycle test procedure that typically requires seven to eight cycles to stabilise at a re-circulating load of 250%. A typical test requires between three to four kilogram of ore sample and around eight hours of operator time. For geometallurgical test work applications, where a large number of variability samples are to be tested, it would be highly beneficial to use a test procedure that requires less sample mass and operator time. Certain test work laboratories, for example SGS and JK Tech, are already offering various types of shortened test procedures for estimating the Bond ball work index. This paper discusses a comparison of two shortened test procedures that were evaluated for suitability of use on Zambian/DRC-type copper–cobalt ores. EXPERIMENTAL Test Procedure 1 – Batch Milling The first test procedure is derived from a batch milling approach proposed by the University of Hacettepe (Aksani, 2000). Some modifications were, however, made to the data analysis method from that originally proposed. During this test procedure, a 700 mL volume of sample is milled in a standard Bond test mill for a pre-determined number of revolutions. The feed and product particle size distributions are measured for each test. These results are then used to back-calculate a cumulative breakage rate parameter (k) for each particle size, according to the following formula:"

Jan 1, 2015

By P. J. Doig

The LCLS project at SLAC will allow new insights into material properties, chemical reactions and biological processes. The project includes half a mile of new underground construction. Excavation in weathered rock is by NATM, using AM 50 roadheaders. Construction began in 2006 and is expected to be completed in 2008. This paper details the construction of the tunnels and cavern on the project.

Jan 1, 2008

By Li Chen

A new process, i.e. Ball milling--Neural leaching--Oxidation calcinations--Chloridizing distillation--Hydrolysis, was designed to recover germanium from the vacuum furnace slag produced in Shaoguan smelter. The suitable process and operational parameters were determined for the practical production.

Jan 1, 2005

By NORMAN EBBLEY

NUMEROUS references have been made recently to "Alaska's oil reserves," and in view of the wartime petroleum situation sober thinking demands a dispassionate and scientific study and investigation of these reserves or supposed reserves. The question naturally arises, "Is there actually oil in Alaska, or are the reserves there a supposition?" True, in 1923 President Harding established Naval Petroleum Reserve No. 4 in Alaska, certainly implying that oil was there. This reserve, embracing about 35,000 sq. mi., was set aside on the advice of the Bureau of Engineering of the Navy Department and was based upon the existence of known petroleum seepages at Cape Simpson on the Arctic coast. The Cape Simpson seepages have been known for more than fifty years, but in spite of persistent rumors of other seepages in northern Alaska no definite evidence of their existence has been available.

Jan 1, 1944

By Forrest T. Moyer

THIS CHAPTER of the Minerals Yearbook contains injury experience and related employment information for the coal-mining, coking, oil and gas, peat, and native asphalt industries in the United States for 1963. No attempt has been made to combine these data and present injury-frequency rates reflecting the mineral-fuel industries because the hazards of the separate industries are not comparable. Tabulations showing the trend of injuries and employment for all mineral industries are presented in Volume III of the Minerals Yearbook. COAL Injury experience of the coal-mining industry was improved slightly in 1963, as measured by the 2-percent decline in the Injury-frequency rate. Although the total number of fatal and nonfatal injuries increased 1 percent, the greater proportional increase of 3 percent in man-hours worked accounted for the improved frequency rate. Employment and injury data for 1963 are based on final data for anthracite mines and preliminary data for bituminous coal and lignite mines.

Jan 1, 1964

By C A. Feebrey, R A. Duncan

The Ebor Volcano in north eastern New South Wales is an eroded example of a central-type intraplate volcanic-intrusive complex. It is of Miocene age (19 - 20 Ma) and has similarities to other central-type volcanoes in eastern Australia which may represent manifestations of sub-lithospheric hotspot activity. Thick lava flows are exposed around the Great Escarpment and are dominated by a tholeiitic basaltic suite, ranging from ol-tholeiite to qz-tholeiite to icelandite with ages of 19.2 - 19.6 Ma. On its western edge, the tholeiitic lava suite probably overlies remnants of basanite flows belonging to the Eocene (~48 Ma) Doughboy province, but elsewhere, minor alkaline basaltic lavas may be coeval with the tholeiitic suite. Several felsic bodies were emplaced into the volcano at ~19.0 - 19.2 Ma and include subalkaline and peralkaline types. The Crescent Complex is a Miocene-age, strongly differentiated mafic to felsic intrusion in basement rocks and centrally located in pre-erosion reconstructions of the Ebor Volcano. It is interpreted to be a major feeder for the tholeiitic lavas based on age and composition. Evolution of the dominant tholeiitic suite proceeded from a parental ol-tholeiite magma, through qz-tholeiite, icelandite and small volumes of felsic rocks by fractionation of plagioclase, olivine, clinopyroxene and titanomagnetite, accompanied by enrichmentof SiO2, SFeOlMgO, alkalies and HFSE.

Jan 1, 1995