Search Documents

By J. E. Allison

As part of a Bureau of Mines research program to conserve critical and strategic metals, an aqueous electrodeposition method for preparing stainless-steel-type coatings was studied. Chromium powder (averaging 3 J1.m diam) was suspended in a ferrous-nickelous sulfate electroplating bath and occluded in the electrodeposited Fe-Ni alloy matrix. Subsequent heat treatment of the resulting composite coating formed the ternary alloy. The occlusion process was affected by the quantity of Cr powder suspended in the electrolyte and by the microstructure and composition of the electrodeposited matrix. Coatings containing up to 21 wt pct Cr were deposited from an electrolyte containing 20 vol pct suspended Cr powder. Heat treatment at 1,100° C for 8 h homogenized the composite coating. Deposition of 44Fe36Ni20Cr alloy coatings (250 J1.m thick) on AISI 1020 carbon steel rods, followed by heat treatment, provided complete protection of the carbon steel during exposure to a boiling 65-pct-HN03 solution. Corrosion rates of 0.6±OA mm/yr for the coating in the boiling HN03 approximate that of 304 stainless steel. Practically shaped electroforms have been prepared by the coating method.

Jan 1, 1989

By Phillip Cancilla, Daniel Roy, Frank Rosenblum

"The manual moisture determination methods employed today by mineral processing plants falls short in providing timely information required for automation control. The costs associated with transporting and handling concentrates still represent a major portion of the overall treatment price. When considering the cash flow of a mining operation, that is governed by both the smelter contract, with moisture penalties and the quantity and quality of the concentrates shipped, an efficient method of on-line moisture content would be a welcome tool.A novel on-line determination system for ore concentrate moisture content would replace the normally tedious classic manual procedure. Since the introduction of microelectronic-based control systems, operators have strived to reduce the treatment costs to the minimum therefore a representative and timely determination of on-line moisture content becomes vital for control set points and timely feedback. Reliable sensors have long been on the “wish list” of mineral processors since the problem has always been that you can only control what you can measure. Today, the task of moisture determination is still done in the classical technique of loss in weight by uncontrolled procedures. These same methods were introduced in the earliest base metal concentrators. Generally, it is acceptable to have ore concentrate moisture content vary within a range of 7 to 9%. Many times, delays in manually achieving reliable feedback on the moisture content results in the moisture varying from 5 to 12% before corrective actions can be made.This paper first reviews the traditional and widely available methods for determining moisture content in granular materials by applying physical principals and properties to measure moisture content. All methods are in some form affected when employed on mineral ore concentrates. This paper describes a unique and promising on-line moisture sensor in two mineral processing applications, which not only automates the tedious tasks but also results in reliable moisture feedback that can be used in the optimization of the de-watering process equipment such as pressure or vacuum filters and fuel-fired driers. Finally, two measurement applications will be presented to indicate the usefulness and to summarize the measurement requirements for the proposed method of employing drag force and mechanical properties of the material itself to determine the moisture content."

Jan 1, 2001

By V N. Rudashevsky, F Melcher, J Lodziak, D Klosa, N S. Rudashevsky, M Sitnikova, L Gast

A combination of novel and æclassicÆ methods, namely electric pulse disaggregation (EPD), hydroseparation (HS), preparation of monolayer polished sections, and mineral liberation analysis (MLA) was employed to study ores from platinum pipes (Bushveld Complex, South Africa), pristine PGE mineralisation of the Main Sulfide Zone (Great Dyke, Zimbabwe), as well as ancient and modern gold/PGM placer deposits. It is shown here that the EPD technique liberates mineral grains of interest without any visible destruction allowing the study and analysis of individual rock-forming and ore minerals, in our case especially platinum-group minerals. The HS method is an effective tool in concentrating heavy minerals by factors up to 10 000 fold. As near-total recovery of grains >10 ¦m is achieved, the nugget effect can be overcome also in case of limited availability of samples (drill core, museum specimens). The MLA technique is a fast tool to detect and characterise mineral phases in ores and ore processing products. Many mineralogical parameters of individual grains and mineral assemblages can be deducted and documented. The results show that the techniques employed, either on their own or in combination, provide a wide range of additional information especially on platinum ores which is beneficial to both the researcher and the metallurgist.

Jan 1, 2008

By P González, J Videla, E Córdova, I Gottreux

Currently, underground mining of deeper massive deposits with lower grades, harder rock conditions in high strength environments, entails difficulties in caving, fragmentation and seismicity of the orebody.So far, the use of preconditioning (PC) with hydraulic fracturing (HF) has shown positive results in terms of seismic response and caving performance, while PC combined with explosives aims to weaken the rock mass, causing an additional effect on fragmentation.In particular, mines commonly referred to as ‘supercaves’, operated by caving methods, have the need to integrate mine to plant processes, where rock fragmentation appears as a key tool. In fact, it implies making mining and comminution processes more efficient to the plant and for mines, it justifies the search of innovative solutions in drilling and blasting techniques to precondition the rock mass. The following paper aims to show the feasibility of numerical blast modelling to weaken the rock mass using explosives, mainly through sensitivity analysis applied to designs to minimise bias and uncertainty in the results. It is shown how the presence of structures, their geometry and in situ stresses influence or interfere with the PC method being used.From the work, it is concluded that better knowledge on the application of explosives weakening allows specialists to strengthen numerical models associated with every design and therefore previously validate their applicability, helping to understand complex phenomena such as the propagation of mechanical waves in non-elastic heterogeneous media. In this sense, it is understood that while there are studies (Sanchidrián, Segarra and López, 2006) showing that the transfer of energy in the rock mass could be even greater in a confined environment, the more competent rock mass and higher in situ stresses interfere mostly on the effectiveness of a technique using explosives.CITATION:Gottreux, I, Córdova, E, González, P and Videla, J, 2016. Preconditioning modelling and explosives effectiveness in block caving, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 683–688 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Sanjay Kumar Singh

The mechanics of load transfer in bord-and-pillar mining is not well understood despite the evolution of the art of pillar extraction over the last 20 years via trial and error (empirical) or Rock Mass Rating (RMR), simple monitoring and pillar extraction experiences at neighboring mines. Variations in geologic conditions and pillar extraction methods, along with a lack of comprehensive instrumentation programs for monitoring ground behavior during pillar recovery, are among the factors that make it difficult to predict how strata will respond to pillar extraction. Efficient and safe use of roof supports depends on the interaction between the designed support and coal strata. Of particular interest in this study is the mechanics of strata deformation as influenced by geologic conditions, pillar extraction methods and optimum support with load-bearing capabilities in strata control during mass exploitation of underground coal deposits required detailed investigation,?. To provide a better understanding of the mechanics of strata deformation, as researchers, we have collected data and reviewed measurements of convergence and stress in one mine of South Eastern Coalfields Limited (S.E.C.L.), i. e., in North Chirimiri Pondary Hills (NCPH) and have completed numerical modeling with FLAC software for (Fast Lagrangian Analysis of Continua modeling, Itasca India Consulting Pvt. Ltd.) for two typical pillar extraction plans. Stress distribution in the mine roof above pairs of roof supports was calculated to demonstrate how Resin roof bolt support installed support contributed to roof block movement control. It was shown that overall stress and roof-floor convergence patterns were most influenced by the stiffness of coal measure rocks and by pillar extraction sequences and layouts. Also, resin roof bolts and other support systems play a critical role in controlling stability of both the immediate roof and the main roof for a distance of up to 18 meters (i.e., working coal seam height X three times) above the seam. Installed supports provide unique strata control advantages over other types of secondary support by significantly reducing the time between mining and installation of the secondary support. Although resin roof bolts are similar to posts in stiffness and capacity, they are more effective than posts under static loads because they can yield and still maintain loads at nearpeak capacity(Singh, et al., 2006), whereas posts fail and lose their ability to limit mine roof deformation.

Jan 1, 2012

The Government signalled its intention in the Economic Statement on 17 December 1987 to improve the fairness of the taxation system and to facilitate the process of economic adjustment by: removing tax concessions that benefit some taxpayers at the expense of other taxpayers,ensuring that those who can afford it shoulder their fair share of the tax burden,securing a revenue base which will provide sufficient resources to maintain effective social services,reducing artificial protection and concessions that discriminate against some sectors, and encouraging confidence through an economic environment with a medium-term orientation. The Government has clearly stated to all sectors that tax preferences will be phased out and businesses need to look inwardly to their investment policies if they are to survive in an open economy. This paper will address the effect of these Government objectives on the taxation structure for all forms of mineral exploration in New Zealand. The present tax structure will firstly be analysed, in particular setting out the tax advantages available to the industry. The effect of changes to the tax system within the recent past which relate to mineral exploration will then be examined. Finally the paper will address the question of possible future changes, particularly in the light of Government's intention to move towards a tax system which does not provide an advantage for any one sector of the economy.

Jan 1, 1988

By T. Bajpayee, L. Prosser, A. Iannacchione

Reducing the number of roof fall injuries is a goal of the NIOSH mine safety research program. Central to this effort is the development of assessment techniques that will help to identify the nature of the risks associated with working under potentially hazardous roof conditions. This paper discusses a method to determine the roof fall risk using a qualitative risk analysis technique. The ability to determine roof fall risk has been a long-standing goal of safety professionals and can provide the kind of information, needed by on-site personnel responsible for worker safety, to mitigate roof fall injuries.

Jan 1, 2007

By C. J. Badenhorst

The scope of this project was to research, develop and eventually produce a personal occupational hygiene and safety exposure monitor system to assist in recording and analysing various stress factors that could affect the health, wellness and safety of employees, i.e. that could result in injury or ill health of workers, create stress build-up within individual workers that could negatively affect worker alertness and safety, and, may even result in permanent disability or death. Utilized systems at the time were all reactive, whereas the DOHEMS (Proactive Digital Occupational Hygiene and Safety Exposure Monitoring) System enabled the measurement of exposure (and associated risk) in a proactive manner via real-time exposure and digitized recordings. The idea of the development was to create a unit that is so cost effective, small and light that every worker can use a system on a daily basis. The development will eventually replace current, bulky and expensive monitoring equipment. The device must be a portable battery operated device and monitor the immediate working environment by periodic sampling for vibration, noise, toxic gasses (NO/NOX/CO/VOC, etc.), body temperature and heart rate. The samples must be time and date stamped, utilizing a real-time clock (RTC) synchronized with the closest regional secondary time source and related to synchronized real-time video captured samples. These samples are then recorded onto a rugged non volatile storage device with the capacity to store a vast number of samples covering the entire working shift of eight (8) hours plus. The system has been fitted with a clear visual local alarm indication system, indicating any excessive exposures or stresses, for the worker?s supervisor to respond to. This system allows for a pro-active approach. The system is also a wireless system (to the external environment) so as to not affect the mobility of an employee and flameproof to allow for use in explosive environments. Keywords: safety, digital, exposure, monitoring, proactive.

Jan 1, 2010

High Pressure Grinding Rolls Scale-Up and Experiences

Sep 13, 2010

By L. B. Clarke

The optimal maintenance and control of the air flow and pressure distribution in a mine network are achieved by the correct positioning of the mine fans and regulators within the mine ventilation circuit. The principal considerations are the location of the main and underground fans or regulators and the attendant control of mine leakage. Air flow control is achieved by either passive or active regulation. Passive regulation adds resistance, usually in the form of a regulating door. Active regulation adds pressure sources in the form of underground booster fans. Ventilation engineers are increasingly turning to analytical tools to assist them in the design and operation of ventilation systems. The application of computer methods, formal optimisation methods and numerical solution methods is outlined

Jul 1, 1996

By M. Götze, P. Eysel

Over the last years, the importance of the assessment of environmental and social aspects as well as of issues of good governance has increased significantly in mining finance. For this, international standards as well as internal guidelines of the banks and other involved institutions have been established and continuously improved. Considering these standards and regulations, the banks can influence the sustainability of mining projects - and they have done so in the past -, mainly by implementing certain provisions and covenants in the loan documentation, binding the financing to the mining company’s adherence to the agreed sustainability standards. However, there are limits to the banks’ influence due to the competitive environment with other available means of financing. Nevertheless, the experience of the last years has shown that the standards and regulations bound to the financing by the banks help to lead the mining industry towards more sustainable projects.

Jan 1, 2011

New developments in the non-invasive and real-time measurement of the velocity profile of slurry flow in horizontal pipes will be described. This information can be used to determine the approach and onset of solid deposition on the bottom of the pipe. Having this information in real time can enable operation at lower velocities or higher solids concentration or both while avoiding solids deposition or plugging and their associated operational costs. In addition, advances have been made in the measurement and trending of pipewear on slurry lines. In contrast to manual methods, CiDRA?s system uses a permanently or semi-permanently installed ring of conformable ultrasonic transducers clamped onto the outside of the pipe. These transducers are used to measure the thickness of the pipe under their respective locations. This results in better repeatability, accuracy, and failure prediction, along with reduced labor costs. The benefit is significantly improved pipe wear monitoring in pipelines with abrasive solids. This provides an improvement in the ability to insure safe operation and avoidance of costly operational and environmental damage due to leaks caused by pipe wear.

Jan 1, 2009

By William J. Campbell

This report describes a Bureau of Mines study undertaken to determine the applications and limitations of solution techniques as a general method of fluorescent X-ray spectrographic analysis. Systematic errors due to variations in particle size, surface preparation, and sample inhomogeneity are eliminated by the use of solutions. The range of applicability of fluorescent X-ray spectrography is increased in two ways: (1) Samples in the form of wire, filings, turnings, etc., can be analyzed as solutions, and (2) samples submitted as solutions can be analyzed as received 0 The lower limit of detectability varies from 0.14 gram per liter for sulfur, atomic number 16, to 0.0015 gram per liter for strontium, atomic number 38. Most elements have limits of detectability between 0.02 and 0.002 gram per liter.

Jan 1, 1959

By J E. Nethery

At the Red Dome and Mungana deposits in north Queensland, Australia, it is proposed that mineralisation and alteration developed as a 'telescoped' overprinting continuum, ranging in style from hypothermal to epithermal, reflecting the major changes that developed in the regional setting over the period circa 325 - 290 Ma. Regional assessment suggests that this also applies to many other precious and base metal deposits within a 40 km length of the host Siluro-Devonian Chillagoe Formation.   A ten stage paragenetic sequence of structural preparation, multi phase intrusion and associated mineralisation, alteration and brecciation is postulated for the Chillagoe district.

Jan 1, 1995

The theme of this conference is æRediscover OtagoÆ. In order to ensure the development and exploitation of mineral discoveries in New Zealand, considerable capital will be required, particularly from overseas. This paper briefly reviews the Government's foreign investment policies and procedures and highlights some trends.

Jan 1, 1992

ignitions caused by cutting tools have occurred at a rate of some 14 per year in UK coal mines since 1965, mostly on the coalface. The rate has held steady despite reducing output and number of collieries. Investigations were carried out over this period into factors affecting both the concentration of firedamp in the cutting zone and the igniting source. A study into detecting and suppressing ignitions on shearers has been undertaken and it is feasible to prevent certain ignitions from spreading outside the cutting zone. Practical measures have been adopted by British Coal to identify frictional ignition sites and to lay down working procedures to minimise risk.

Jan 1, 1988

Concentration of Phosphate Ore by Flotation With/Without Desliming

Sep 13, 2010

By S. Nagamatsu

Alumina supported gold catalyst prepared by spray reaction method (spr) provides gold particle with about 20 nm of diameter. The gold particle size is larger than conventional gold catalysts. However, the spr catalyst shows higher catalytic activity for NO-CO reaction. In the present paper, we have discussed the local structures of spr-Au/Al2O3 catalyst by using Au L3-edge XANES spectra. In order to investigate the local structures of Au-sites, multiple scattering approach to XANES analysis was applied. Calculated Au L3-edge XANES spectra for fcc-Au and Au2O3 were in good agreement with the observed spectra. XANES spectra for spr-Au/Al2O3 were characterized by 4 types of Au sites (bulk, interface, surface and peripheral). In this case, almost all gold sites (> 90 %) are bulk site. The other sites are less than 10 % of gold particle. However, the experimental and the calculated results of Au L3-edge XANES spectra for spr-Au/Al2O3 require about 30 % of gold oxide or hydroxide. Bulk of Al2O3 contains a certain number of gold nano-particles, which was incorporated in the bulk Al2O3 support. In the interface area, gold oxide forms a few layers. This result was also supported by DV-Xa electronic structure calculations. The comparison of the catalytic activities of the spray catalysts and the impregnation catalyst for the NO-CO reactions imply synergy effects between gold nano-particles and alumina support.

Oct 1, 2003

By W. L. Garrison

Improvements continue to be made in rapid excavation and tunneling technology. There are several ways to examine the impacts of such improvements. The most common procedure is to monitor current developments and to evaluate prospects for expansion of present types of uses. Other approaches are called for, however, if the technology might be used in ways not now imagined, if the search is for information for managers of technology development, and if the issue is that of the wise use of the technology by society. The first section of the paper will pose these matters as questions. These questions will be examined from the point of view of the processes of technology development and utilization, and then further examined against the backdrop of processes at work within the urban area. Such an examination will provide insight into the way technology developments should proceed. The final section will present some comments that may be useful to those guiding the development of the technology and to those who might provide leadership for its wise utilization. THE QUESTIONS Three questions are posed: 1. Are there uses for the technology beyond further penetrations of its present markets? 2. Can information be supplied to managers of technology development so that they may improve the assignment of priorities among development choices? 3. How can society make wiser use of the technology?

Jan 1, 1974

By K. Lim, J. Sobil, L. Galarza Castillo, F. Tozlu

"For mining operations globally, the scale and criticality of the grinding mill drive has meant that selection of the correct mill drive technology is paramount. With so much depending on the successful implementation of the electrical drive system— safety operation, timely installation, availability, energy efficiency, minimum maintenance and extend its use as tool to assist during mill liner exchange—customers are justified in their scrutiny and slow adoption of new drive technology. From the first installation of low, fixed speed synchronous motors to the introduction of the current source and further voltage source variable frequency drive, innovations require long periods of time and mining customers willing to push the industry forward. In recent years, the variable frequency drive has been the stepping stone for a new generation of mill drive technology. In use for decades in other heavy industrial applications, the drives allow for system optimization in a myriad of ways. The most dramatic of changes is in the design of the motor. Where in the past motor design was bound by line frequency, today the designer can optimize machine size and, more importantly, eliminate the need entirely for the synchronous motor. Induction motor design has now progressed to the point where low speed operation is possible at efficiency levels nearing those of the synchronous design. Moreover, the simplicity of the squirrel cage design means that availability, reliability and spare part requirements are greatly improved. As the next step in the evolution of large pinion driven grinding mills, the low speed induction drive offers a new reliable and robust system to the market.IntroductionAs deposit grades continue to decline, new ways of processing ever greater concentrator throughputs have been required to maintain throughput efficient and profitable operations. Furthermore, the high risk nature of mining developments requires a constant search for safer, higher availability and more efficient equipment design. Limitation of downtime is a key factor in ensuring mining operations can be sustained through volatile market conditions. Often processing the entire mine throughput through just 1 or 2 lines, the crushing and grinding circuits are of particular criticality to the uptime and, thus, profitability of any mining operation."

Jan 1, 2016