Search Documents

By D. Harrington

Insofar as prevention of mine explosions is concerned, it is apparent that the coal-mining industry has profited but little from experiences during the past 15 years. The fact that explosions can be prevented if well-known preventive measures are adopted and conscientiously carried out appears to warrant the conclusion that many coal-mining people are indifferent to the hazards that may result in explosions. Although the principal burden of preventing explosions is upon the management, and much of the evident carelessness in failing to place in effect and to enforce suitable precautions, is assessable directly against management, the worker also has a very definite responsibility, and numerous explosions have resulted because of his failure to carry out his part in accepted principles of safety. The record of fatalities from mine explosions during the past 5 fiscal years has been anything but encouraging or about which coal-mining people can take pride; more men were killed by explosions (673) than were killed from the same cause during the preceding eight years combined (577). During each of the fiscal years 1942 and 1943, 152 fatalities resulted from explosions, compared to 163 during the fiscal year 1941, 206 in 1940, and only 16 in 1939.

Jan 1, 1944

By Feng Yongxuan

Anchored sheep pile is normally used in deep excavations, many of which only require stability in accordance with Terzaghi theory. In this paper, based on the experience, new lateral earth pressure method is adopted taking account into interaction among soil, anchors and sheet piles so that a group for the project under very difficult conditions and very severe requirments, especially, for the displacements are determined according to that mentioned above. During and after construction, displacements monitoring were carried out for about four months, which was proved that there was a little difference between calculation and practice.

Jan 1, 1991

By J. Härkki, R. Hiltunen

The Akanvaara intrusion (surface area 50-55 km2) in Savukoski, Northern Finland, hosts 23 distinct monocumulate layers of small euhedral chromite crystals enclosed in a silicate matrix. These chromitite layers have been divided into four groups; UC (upper chromitite), ULC (uppermost lower chromitite) LC (lower chromitite) and LLC (lowermost lower chromitite). The driving force for investigating the Akanvaara chromites and their reduction behaviour originated from their very low MgO content and relatively low Al2O3 content, giving them a unique quality which based on thermodynamics should facilitate the reduction. Another interesting feature is the high amount of V2O3 present especially in the upper chromitite. The chromites included in this study are from the UC and ULC layers (24.9 and 22.7 per cent Cr2O3 respectively). To obtain a better understanding of the reduction behaviour of Akanvaara samples in comparison to MgO-bearing chromitites, Kemi chromite from the ferrochrome works in Tornio, Finland, was included in the study as a reference sample. The reduction experiments were isothermal in a temperature range of 1000-1400°C in CO atmosphere. Experiments were also conducted with coke addition in pellets and briquettes in CO/Ar/H2 atmospheres. The results of the reduction experiments complemented with microanalytical research indicate that the Akanvaara chromites do reduce to a higher degree than the Kemi chromite. Although the aim was to characterize the mechanisms of reduction focusing on gas-solid reactions, the nature and amount of the gangue minerals was such that a considerable amount of slag phase was formed, which affected the reduction mechanisms extensively. The structural features together with low MgO and high FeO content in both Akanvaara chromites are important factors resulting in better reducibility than in the Kemi chromite.

Jan 1, 2004

By Marcel Vanpee

Eight extinguishing powders KCI, were tested on five types of diffusion flames. The effect of flame temperature on the inhibition efficiency was investigated by varying the oxygen index of the flame supporting atmosphere. Inn addition a spectrographic investigation of powder flame dissociation products was carried out on the methane/air/ABC (NH4H2PO4) flame. Dissociation products for this flame included P0, PH, NH, and Na. It is concluded that the main factor to be considered in the efficiency of tie powder is the flame temperature Purple K (KHC03) was typically inefficient in low temperature flames and very efficient in high temperature flames. On the other hand, ABC (NH4H2PO4) was found to lose its efficiency at high temperature but to be quite efficient in the low temperature flames. The effect of temperature is offered as an explanation of the poor efficiency of Purple K (KHC03), against coal dust explosions as contrasted to the high efficiency of phosphate salts against coal dust explosions.

Jan 1, 1982

By Wellington Pereira Inácio

This work investigated the toughness behavior of polyester matrix composites reinforced with up to 30% in volume of long, continuous and aligned sisal fibers by means of Charpy impact tests. It was found that the addition of sisal fibers results in a marked increase in the absorbed impact energy of the composites. Macroscopic observation of the post-impact specimens and SEM fracture analysis showed that longitudinal rupture through the sisal fiber interface with the polyester matrix is the main mechanism for the remarkable toughness of these composites.

Jan 1, 2010

By K. E. Tame

Pollution from radioactive nuclides, principally Ra226, in liquid waste from uranium mills can be minimized by reusing the waste solution within the mill. Such reuse of waste solution in the Vitro Chemical Co.-type process was investigated in the laboratory. Vitro employs an acid leaching process for dissolution of the uranium, countercurrent decantation for liquid-solid separation and washing, and amine solvent extraction for recovery of the uranium from solution. The simulated reuse of barren raffinate in the mill circuit was carried through two separate laboratory campaigns of 29 and 31 cycles. Conventional chloride stripping of the amine was employed in the first campaign, whereas nitrate stripping was used in the second campaign. Dissolution of uranium from the are in the acid leaching circuit averaged 96 percent. Washing efficiencies of 98 to 99 percent were attained by using 4 volume tons of combined raffinate and makeup water per ton of ore. Uranium recovery from the pregnant solution using a 5-percent solution of amine LA-1 in kerosine ranged from 99.3 to 99.9 percent.

Jan 1, 1962

By J. R. Thoenen

This circular is part 5 of the third paper (entitled "Excavation") of a series summarizing the technical problems involved in the production and preparation of sand and gravel. Part 1 discussed the use of power shovels, draglines, and excavator cranes; part 2, power scrapers, slackline cable-way excavators, and hydraulic monitors; part 3, hydraulic, clamshell, ladder, and dipper dredges; and part 4, haulage systems in general, with particular reference to locomotive and car, hoist and car, and remote-control systems. This circular discusses the use of motor trucks, conveyor belts, pumps end pipe lines, barges and towboats, and aerial trams. MOTOR-TRUCK HAULAGE During recent years motor trucks have gained considerable ground as a successful competitor of locomotive haulage for quarries and gravel pits. Often where trucks have displaced locomotives and cars the operators readily admit an increase in both labor and total haulage operating costs but point to some other advantage as offsetting the extra expense. In other instances haulage costs have beep reduced by the use of trucks. In still others operators, having replaced locomotive haul with trucks, have again returned to the earlier method. Obviously gasoline-driven motor trucks cannot successfully compete with other types of haulage under all conditions. The apparent' growth in the number of advocates of truck haulage, however, indicates that it has passed the experimental stage and become a permanent competitor to other tyres.

Jan 1, 1936

By G Liu

Seventy-nine gold deposits and prospects have been discovered in theJiamusi region of northeast China, and constitute one of the most important gold metallogenic belts in China. All these endogenic gold occurrences can be subdivided into three main deposit types: 1. porphyry related; 2. metamorphic-intrusive hosted, and 3. sediment-hosted deposit.   The first two types of gold deposit are spatially and temporally related to Mesozoic Yanshanian granitoid intrusions with hydrothermal activity channelled along crustal-scale fissures. The ultimate cause of the Yanshanian magmatism is considered to be the subduction of Pacific oceanic lithosphere beneath the Eurasian continent. In contrast, the chemical sediment-hosted deposit is typified by the Dongfengshan gold deposit, and genetically related to Proterozoic sedimentation and Mesozoic igneous activities.

Jan 1, 1995

By N. Romani, R. Provost

"Commissioning of a circulating dry scrubber (CDS) plant was recently completed at an existing facility in Québec, Canada. The CDS plant treats the sulphur dioxide off-gas emitted from rotary kilns in order to meet increasingly stringent environmental requirements. This installation enables the existing facility to reduce their sulphur emissions by over 90%.Proper planning of the different commissioning stages and staffing an integrated team are the most important factors required for a successful plant start-up. A strong Operational Readiness plan must be in place as early as the start of construction in order to ensure a smooth transition from commissioning to operations. Plant performance can meet or exceed performance criteria within the required timeframe if the proper group dynamic and good communication is established between construction, commissioning and operations teams.The road blocks encountered are often from systems that one assumes will operate without trouble such as air-conditioning, or design assumptions that were taken years earlier in feasibility process stages, namely the capacity of existing systems that will connect the new plant to the existing facilities. The challenges associated with rectifying these issues in addition to the requirements to properly start-up and operate a new plant without impacting production are great, and it is imperative to have the necessary resources to react quickly to any problems.IntroductionCommissioning of a circulating dry scrubber (CDS) plant was recently completed at an existing facility in Québec, Canada. The CDS plant treats the sulphur dioxide off-gas emitted from rotary kilns in order to meet increasingly stringent environmental requirements. This installation enables the existing facility to reduce their sulphur emissions by over 90%.The CDS ProcessA general overview of the CDS process is presented in Figure 1 below. The combined, de-dusted off-gas from multiple kilns is sent to the CDS, which acts as an entrained fluid bed, where the gas is contacted with a water mist, re-circulated solids and hydrated lime. The SO2 from the gas stream and the available calcium hydroxide (Ca(OH)2) from the hydrated lime dissolve in the water and react to ultimately form calcium sulphites and gypsum. The solid residue (referred to as CDS residue), is the primary by-product of the process."

Jan 1, 2016

By W. G. Dallas

The social and environmental problems presented by the location of a large zinc/ lead ore body within one mile of a thriving town are described. The development problems are social, involving the education of the in habitants , and environmental, requiring the development of a planning strategy and the evolution of a baseline and post -operational monitoring system. The necessity for an environmental-impact assessment and a thorough baseline study is emphasized. The continuing psycho-social consideration of community reaction is advocated.

Jan 1, 1977

By O. A. Lima

Effective solids suspension is a necessary precondition for particle collection, and solids suspension is largely dependent on the hydrodynamics of the flotation cell. This study attempted to correlate the status of the suspension of apatite particles of different sizes in a Denver laboratory flotation cell versus the impeller rotational speed (N) adopted to operate the machine. The latter variable (N) influences the impeller capacity to lift the particles from the bottom of the tank and also to disperse them throughout the volume of the vessel. Such an impeller capacity can be characterized by the critical impeller speed for the accomplishment of solids off-bottom suspension (Nz) and also by the velocity of the radial water flow discharged by the impeller (U) divided by the particle terminal settling velocity (Us). This way, the status of the suspension of apatite particles inside the flotation cell can be characterized by one of three categories: ?segregation? (N/N2 < 0.60 and Us/U > 0.08); ?suspension? (0.60 = N/N2 < 1 and 0.06 < Us/U < 0.10); and ?dragging? (N/N2 = 1 and Us/U = 0.03). The range of impeller rotational speed (N), which was able to suspend the finest particles (Dp = 90 µm), was unable to suspend the coarsest particles (Dp = 254 µm). Conversely, the high value of N (N > 1,300 rpm), which is adequate to suspend the coarsest particles, may promote the entrainment of the finest particles to the froth layer.

Jan 1, 2009

Flotation of Phosphate Gangue from Magnetite Fines - Non-Ionic Surfactant as Atrac Collector Modifier

Sep 13, 2010

By I. Bock

Selective Blast Mining (SBM) makes use of milli-second sequential blasting technology to separate the valuable reef material from waste rock in the blasting operation at stope faces in the mining of tabular ore bodies such as exist in the gold and platinum mines in South Africa. The waste rock is cast blast to the back of the stoping area, and the reef material is fractured and deposited close to the stope face. Only the reef material is transported to the surface. A simplified economic model is presented to evaluate the economic benefits of SBM. Although premature, in that adequate experimental demonstration of the validity of the model has not yet been possible, the model is presented since it indicates substantial benefits in the case of narrow reef gold mines. It is suggested that many marginal mines should seriously consider SBM. Benefits can also be realised in platinum mines, but a lot more experimental work is necessary to establish cost parameters more reliably. Some practical experience in the use of SBM in the mining of the UG2 reef is presented.

Jan 1, 1998

By D. K. Chibwe, P. Taskinen

"This investigation consists of a numerical and physical modelling exercise on flow patterns, mixing, solid-liquid mass transfer, and slag-matte phase distribution in a 0.2-scale cold model of an industrial Peirce-Smith converter (PSC). Water, kerosene, air, and sintered benzoic acid compacts were used to simulate matte, slag, injected gas, and solid additions into the PSC. The 2D and 3D numerical simulations were carried out using volume of fluid (VOF) and realizable k-e (RKE) turbulence models to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using the commercial computational fluid dynamics numerical code FLUENT.Numerical and physical simulations were able to predict, in agreement, the mixing and dispersion characteristics of the system in relation to various blowing conditions. Measurement of mass transfer indicated that fluid flow in the PSC is stratified. Blowing configurations and slag volume both had significant effects on mixing propagation, wave formation, and splashing.As a potential process alternative to increase conversion efficiency, we propose a combined blowing configuration using top lance and lateral nozzles. The numerical simulations were conducted on combined as well as lateral blowing conditions, and the results of the combined concept are encouraging."

Jan 1, 2015

By Tracy Brettmann

? Hollow Stem Auger ? Drill Bits ? Leads/Torque Arm ? Hydraulic Gearbox ? Hydraulic Power Unit ? Grout Pump ? Crawler Crane

Jan 1, 2001

By Robert Stefanko

The growing demand for energy during the post World War I and World War II periods has prompted underground coal production to increase rapidly. This has been met primarily by mine mechanization, resulting in the development and application of new mining machine types. Correspondingly, the total connected horsepower of each machine as well as the number employed has enlarged rapidly since 1950. (2,3,9,14,16,17) Electrical consumption for each mine has also grown. In the early years of mining electrical applications, only d-c power was utilized underground. Yet, d-c machine limitations were soon realized, and many a-c systems were substituted to permit economic and efficient utilization of a-c distribution and motors. Due to the attractive torque characteristics, ease of distribution and speed control, several traction applications have continued to be powered by d-c motors. The result has been the now prevalent use of mixed a-c/d-c mine power. However, augmented electrical power employment seems to have added to underground coal mining electrical accidents.

Jan 1, 1974

By S. P. Pearton

"Pumpable emulsion explosives have been available to surface and underground massive mining operations for decades, and their unique properties offer significant advantages in terms of improved safety, reliability, and performance. However, the benefits of pumpable emulsions have been unavailable to narrow-reef mining operations due to the lack of technology necessary for their successful implementation in this challenging environment. Despite efforts to promote and enhance the safety and performance of bulk emulsions for narrow-reef stoping, little research has been undertaken to advance the pump technologies required for their implementation. This has resulted in a gap in knowledge and technology, and as a consequence the successful implementation of a pumpable emulsion system has consistently eluded the narrow-reef environment.The purpose of the following investigation was to evaluate the viability of pumpable emulsion explosives for use in South African narrow-reef mining operations. By approaching the problem from multiple perspectives, this research aimed firstly to propose a theoretical framework and suite of equipment suitable for the implementation of pumpable emulsions within the narrow-reef environment. Through the development of this suite of pumpable emulsion technology, tests could be undertaken on the proposed narrow-reef emulsion formulation and pumpable emulsion technology to obtain the necessary understanding of the performance of the system under controlled operating conditions prior to its implementation in the broader mining industry."

Jan 1, 2015

By Glen Mc Gavigan

The roof of the Sishen cave is being mined in order to exploit 6.8Mt of high grade ore. The cavity is filled with quartzite backfill in order to support the roof in the event of collapse. The cave dips at approximately 37o, is 260m along dip and 70m along strike and has a total volume of 261,391m3. GPS and optical monitoring techniques were attempted to detect subsidence but proved to be impractical. The GroundProbe Slope Stability Radar (SSR) uses differential interferometry to measure sub millimetre movement in a rock face. The SSR was applied in a non production situation and detected subsidences of 38mm/day before visual signs of instability were detected. The rate of deformation detected was slowing as a result of the roof coming to rest on underlying backfill. Monitoring during production drilling detected a sudden subsidence of 18.6mm/hour which resulted in the evacuation of personnel from the area. Further inspection of data showed that the rate of deformation was slowing and production was allowed to continue without further incident. The SSR has helped dispel the fears of workers and has proven that subsidence can be accurately measured and delineated with the SSR.

Jan 1, 2006

By W. M. Shaver, W. R. Dengler, F. A. Edwards

INTRODUCTION The Macassa Division of Lac Minerals Ltd. is a high grade gold mine that has been operating in Kirkland Lake, Ontario for the past 51 years. It produces approximately 120,000 tonnes of ore per year, averaging approximately 18.7 grams per tonne (0.45 ounzes per ton) of gold. Over the years, the ore body has been developed to a point where mining takes place below the 1,220 m (4,000 feet) elevation and 1,830 m (6,000 feet) west of the original shaft. The mine is currently serviced by two surface and two winze shafts. (Figure 1). The ore body extends below the 1,930 m (6,400 feet) Level which is the bottom of the existing mining operation. An ambitious underground exploration program has substantially increased these reserves. Concurrent with the discovery of greater reserves, has been rapidly escalating mining costs, particularly labour which constituted 66% of the total cost in 1981. These costs continued to escalate as the major proportion of mining was carried out to the west, far away from the existing hoisting systems. This required three lift hoisting for men, materials and ore. I n addition to the increased travel time and ore handling expense, increased humidity and temperature and ventilation and compressed air losses have added to the inefficiency of the operations. As a result, studies were initiated in 1980 to assess the future of the Macassa operation.

Jan 1, 1985

By L. Echeverri

Research studies have shown that the flow within feedwells displays a vortical structure and high velocities at the locations where standard tangential inlets force its way into the feedwell swirling flow, producing high local shear rates and flow non-uniformities. These hydraulic deficiencies can be attributed to the discrete feeding through a few entrances, usually one or no more than a few tangential feedpipes, which practically project jets into the vortex within the feedwell. The main consequences are unequal flocculation with aggregates subjected to different amounts of shear and a non-uniform discharge from the feedwell. This paper presents results on the application of CFD and small-scale models to develop a new design that overcomes these problems by using an involute shaped inlet that converges around the feedwell. The result is a new feedwell with enhanced hydraulics that perfectly couples with the FLSmidth E-Duc® Feed Dilution system by protecting the flocculated aggregates that have been carefully produced upstream, and that favors uniform sedimentation conditions within the thickener thanks to a uniform discharge, while maintaining a practical and trouble-free geometry with excellent turndown.

Jan 1, 2012