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By W. Kint

More than 10 years ago, one of MECS?s current partners KVT developed the so called SULFOX process for cleaning waste gases containing sulfuric compounds. In this Wet Acid Process (WAP) compounds such as SO2 and H2S, CS2, COS are oxidized over catalyst bed(s) to SO3 and finally sulfuric acid is formed. The individual plants are designed according the feed gas concentrations and customers requirements to keep the investment and operating costs as low as possible. MECS strongly believes the technology we propose will meet all your expectations. Thanks to our vast experience in the construction of sulfuric acid plants (MECS built over 800 sulfuric acid plants worldwide) we were able to design you a very reliable installation. MECS is offering the metallurgical industry, besides our conventional acid plant technology (for strong SO2) and our DynaWave? scrubbing technology (for very low SO2), a SULFOX wet acid plant (for the mid range SO2 concentrations) including an optional upstream DynaWave gas cleaning plant if required. See the figure below. Besides providing advanced technology, MECS is the only company who designs and manufactures its own key critical equipment. We manufacture our own catalyst, mist eliminators, acid distributors and coolers. Because of our in-depth technology knowledge, we understand the critical aspects necessary for making optimum equipment designs. With this combined supply of technology and key critical equipment, we can make a single overall guarantee second to none other in the world.

Jan 1, 2009

By W Dodson, S Dogramaci

Isotopes and hydrochemistry were used to define groundwater flow systems and better understand the hydrogeological setting of the Karijini National Park, which is in the Central Pilbara region adjacent to the Marandoo iron ore mine. Based on the stable isotope composition of the water samples, the data can be divided into two main groups. Groundwater is characterised by depleted dD and d18O, suggesting no significant evaporation effect. Surface water on the other hand is more enriched in dD and d18O due to evaporation. The relatively high concentration of Cl- compared to rainfall and depleted dD and d18O values of groundwater indicate that recharge of the aquifers is occurring during intense rainfall events when rapid infiltration occurs. Evapotranspiration then acts to concentrate ionic species prior to recharge. Relationships between the major ion concentration and catchment area, surficial Tertiary cover and distance between recharge and discharge were identified. The results show that these catchment variables combine to determine unique water chemistry for each sub catchment in Karijini National Park. The TDS concentration of the groundwater in the Marra Mamba Iron Formation that hosts the Marandoo ore body is higher than most of the water bodies surrounding the mining area suggesting significant modification or different recharge mechanisms to that of the Karijini groundwater.

Jan 1, 2009

By E. F. Perry

Simulated weathering tests are used to estimate leachate quality of rocks containing varying concentrations of pyrite and carbonates at mines. This study reports the inter-laboratory results from the third phase of a three part effort to develop a standardized, reproducible simulated weathering test for coal mine overburden. Initial development in phases I and II included evaluation of different test apparatus, effects of particle size, gas composition, leaching frequency and other variables. Phases I and II results are reported by Brady et al (2004) and Hornberger et al (2004). In Phase III, a standard column leaching protocol was used by eight commercial, government and university labs to test five rocks of different lithology, pyrite and carbonate content. Ideally, a simulated weathering test should have three characteristics to be useful in mine drainage studies. These include the capability to produce repeatable results, accuracy in simulating field conditions, and a concise test protocol of weeks to a few months. Simulated weathering, or kinetic testing, produces an effluent that simulates mine drainage composition. This can be beneficial for predicting mine drainage quality in comparison to whole rock analyses. The effluent may be tested for the same water quality parameters as the drainage produced during mining, such as pH, acidity, alkalinity, sulfate, iron, manganese, aluminum or other parameters. If the physical, chemical, and biological conditions of the kinetic tests are representative of those found in the mine environment, leachate composition may be used to estimate the water quality parameter concentrations produced during mining. Hornberger and Brady (1998), and Geidel et al (2000), compiled comprehensive chapters on kinetic tests for mine drainage prediction. These sources included: (1) a chronology and synopsis of scientific literature on these kinetic tests as they have developed over approximately 50 years, (2) discussion of the influence of physical, chemical, and biological processes, and (3) general guidelines for test procedures, data interpretation, and recommendations for further research to develop standard methods. Most of the kinetic test methods in use today were substantially developed and applied more than 40 or 50 years ago, including leaching columns (Braley, 1949), humidity cells (Hanna and Brant, 1962), Soxhlet reactors (Pedro, 1961), and field scale tests (Glover and Kenyon, 1962). . The most commonly used kinetic tests for mine drainage prediction are leaching columns and humidity cells. While these kinetic test methods and others have been used in hundreds of mine drainage studies as shown in Hornberger and Brady (1998) and other references (e.g. Sorini, 1997), they have rarely been used in coal mine permitting by either regulatory agencies or the mining industry. The major impediment to routine use of kinetic test methods is the variation in the design and operation of these kinetic tests, and lack of a standardized, accepted (e.g. by EPA or ASTM) test method. Interpretation and data comparison from different studies can be difficult. METHODS Five rocks of varying lithology, mineralogy, carbonate and pyrite content were collected in bulk from Pennsylvanian age coal measures in Pennsylvania, West Virginia and Indiana. Mineralogical composition of the samples was characterized in detail by Hammerstrom et al (in press) using optical, X-ray diffraction, scanning electron microscopy and electron microprobe methods. Acid Base Accounting (Sobek et al 1978; Skousen et al, 1997, Kania, 1998) was performed on bulk samples for % total sulfur (%S) as a measure of pyrite and potential acid generation, and Neutralization Potential (NP) as an index of carbonate content. A modified NP test, following the procedure suggested by Skousen et al, 1997 was also conducted for four of the five samples. The modified NP test accounts for initial acid consumption, Fe oxidation, and subsequent Fe hydrolysis by the iron carbonate mineral siderite. Siderite, even though it is a carbonate gives zero net alkalinity. Lithologic, Acid Base Accounting and general mineral composition data for the five rocks are shown in table 1 (see Appendix). Whole rock elemental analysis for major and trace elements was conducted on a sub-sample of each rock type. One laboratory was contracted to mix, homogenize, and size the bulk samples and prepare sub-samples for all the participating labs. Splits were sent to eight labs, and each organization was provided a detailed set of instructions for column assembly and leaching procedure. The protocol was developed based on results from phases 1and 2 of this study. The principal features of the column assembly are: a specific composition of particle size by weight (table 2), weekly leaching cycles, and incubation under humidified air containing 10% CO2. Figure 1 shows the column construction. [ ] The particle size distribution of the crushed rock sample is largely an artifact of the crushing process, rather than a natural systems process like the particle size distribution of a soil or an unconsolidated sedimentary deposit. The standardized particle size distribution, shown in Table 2, promotes operational consistency of the weathering test procedure, and provides better control over reaction kinetics. Large amounts of fine particles within specific zones of the leaching columns have been found to impede uniform fluid flow and/or gas flow (Hornberger and Brady, 1998). Regarding reaction kinetics, the importance of surface area to volume ratios has been described in a previous phase of this study (Brady et al., 2004), and significant differences in crushed particle size distributions and effective surface areas were found among the lithologic units. Standardizing the particle

Jan 1, 2009

By C. Pritchard

John Marks said in his acceptance of the Hartman Award in 2008 ? ?I guess that without the occasional complaint, your mine is probably over-ventilated? (Marks, 2008). Miners are seldom in this situation and often spend much of the time trying to find enough air to keep the operation running. With examination there are some things that can be done to make the best use of ventilation systems. Should there be surplus air, in which some of these options may result - financial and other benefits can be obtained. Some of the issues mine operators have needed to address recently are increased airflow requirements to dilute diesel particulates in metal and non-metal mines. Also, operations are faced with demands from reserves that are deeper, hotter and further away from fans and shafts, not to mention increased production demands. Mine ventilation air is a costly commodity, especially by the time it has been heated or cooled and moved to the bottom of the shaft and through the mine airways. Most of the options presented in this paper are useful for metal non-metal operations but some may be applicable to coal too. OPTIONS FOR IMPROVEMENT Some of the areas to be addressed are shop ventilation methods, auxiliary equipment areas, dedicated intakes and returns, optimizing development, examination of mine airway utilization and alternative ventilation methods. UNDERGROUND SHOPS First, examine what is being done with the underground shop air. If it is being coursed directly to the returns there may be some potential to better utilize this, in most cases, relatively contaminant free air. Research the legal options for ventilating mine shops. MSHA regulations in 30CFR 57.4761 (1) allow the following options: To confine or prevent the spread of toxic gases from a fire originating in an underground shop where maintenance work is routinely done on mobile equipment, one of the following measures shall be taken: use of control doors or bulkheads, routing of the mine shop air directly to an exhaust system, reversal of mechanical ventilation, or use of an automatic fire suppression system in conjunction with an alternate escape route. The alternative used shall at all times provide at least the same degree of safety as control doors or bulkheads. Discussion This regulation gives some operators flexibility in ventilating underground shop facilities. If shop air is to be coursed through the work area, and then directly to the mine return, the question should be asked ? is the quality of air good enough to be reused in the mine, and if so, what are the risks? Can the risks be accommodated and managed to accomplish the change? If so, a considerable increase in mine level airflow could be attained by reusing shop air. Clearly, regulations are a minimum standard, and can be exceeded. Metal non-metal mine regulations are not as specific as coal due to the multitude of different mining methods and conditions utilized. Risks must be thoroughly examined and addressed to assure a safe environment. Issues Determine what contaminants are being produced in the work area ? welding fumes, diesel exhaust, paint fumes, chemicals and solvents, etc. Survey the area and determine exposures. MSHA requires exposure monitoring in 30 CFR 57.5002 (1) of dust, gasses mists and fumes to assure air quality is being met. Perform surveys and examine existing data to quantify personal and area concentrations of contaminants. Often there is adequate circulation such that exposure levels in shop work areas are low. After sending shop air back into the system any contaminants would be further lowered by dilution with other mine intake air downstream. Look at the shop work schedule. If only on day shift, the other two shifts and possibly weekends have no activity or source of contamination to affect the ventilation system. The worst case planning scenario would be a shop fire. Study and simulate how this would affect the mine and shop area. MSHA regulations require an escape route and a fire suppression system be installed and maintained as follows in 30 CFR 57.4671 (1): (d) Automatic fire suppression system and escape route. If used as an alternative, the automatic fire suppression system and alternate escape route shall meet the following requirements: (1) The suppression system shall be? (d)(1)(i) Located in the shop area; (d)(1)(ii) The appropriate size and type for the particular fire hazards involved; and (d)(1)(iii) Inspected at weekly intervals and properly maintained. (2) The escape route shall bypass the shop area so that the route will not be affected by a fire in the shop area. Case Study In an underground room and pillar mine, active mine workings were advancing further away from the mine shaft with deteriorated returns and leakage having a negative effect on ventilation airflows to the face. Mine level airflows were 236 m3/s (500,000 cfm) and shop airflows were 24 m3/s (50,000 cfm) (see Figure 1A). No additional capacity was available at the main surface fan. A solution was to utilize the shop air then send it to the mine areas instead of directly to the return. Considerable information on shop air quality and exposures from many years of operation was examined and no negative data was discovered. A risk analysis determined that moving forward with a shop air reuse program was desirable. A plan was developed, analyzed and decision to proceed approved by mine management. The change was simulated on the computer with the USBM/MTU MFire program before being implemented. This included utilizing fire scenarios to examine potential exposures to inby mining sections and plan escape routes. A monitoring system was designed and installed in cooperation with the US Bureau of Mines to monitor carbon monoxide

Jan 1, 2009

By G E. Ho, M Anda, S Dallas

Water auditing and water conservation measures are fast becoming the quantitative tools for water balance reporting in the mining and minerals processing sector. Therefore, this paper was written to describe the process of water auditing in a goldmining environment and to contribute towards building an appropriate water management framework for The Cooperative Research Centre (CRC) for sustainable resource processing (CSRP). The research will assist with the assessment of water balances in mining and hydrometallurgical processes and ongoing probabilistic modelling for Newmont Mining Corporation, its wholly owned gold mines, and its joint venture operation of Kalgoorlie Consolidated Gold Mines (KCGM). Kalgold or KCGM are the managers of a joint venture project between Barrick Australia (50 per cent) and Newmont Mining Corporation (50 per cent) at Kalgoorlie, Western Australia (WA). Boddington Gold Mine (BGM), Western Australia, will commence operations this year and manage the new goldmine expansion project. BGM is 100 per cent Newmont owned and will operate to continue mining gold and copper from the existing (BGM) site that was decommissioned in 2001.

Jan 1, 2009

By Larry DeGraff

With the increase of new mine development in the past several years, many coal mines have decided to self- perform the design and construction for their slope development projects. The development process of determining the proper configuration is challenging, and a major economical consideration. Greenbrier Smokeless Minerals engineering staff and consultants, along with DSI/American Commercial, developed a support configuration that was best suited for their slope. The developmental process took into consideration the length of slope, depth of slope at the high-wall transition, economics of a single or multiple entries, waterproofing, stresses on the steel supports and lagging during the backfilling operation. This paper describes the developmental concept of using a single entry, side by side configuration, using steel ?Banjo String? supports with steel plank lagging, to develop a long term permanent installation in a cut and cover application.

Jan 1, 2009

By S. Janisko

Studies have linked long-term inhalation of diesel exhaust with adverse health effects such as cardiovascular disease, cardiopulmonary disease, and lung cancer. Diesel exhaust levels in underground mines can approach 100 times the environmental level and are therefore monitored closely in the mining industry. Elemental carbon (EC) (a product of diesel combustion commonly referred to as ?soot?) has proven to be a good indicator of diesel exhaust levels. The current procedure for measuring EC levels involves taking personal samples from a mine worker?s breathing zone and/or stationary samples in various parts of the mine and subsequently sending these samples to a lab for analysis by NIOSH 5040 method. Unfortunately, the whole process can take up to several weeks to complete. To address the problem of waiting weeks for results, NIOSH?s Pittsburgh Research Laboratory is developing a portable device for measuring levels of elemental carbon. This optical device takes a continuous sample of air in the surrounding environment and measures the absorbance of light passing through a filter that collects diesel exhaust particulates within the instrument. This technology can provide a near real time measurement of EC with accuracy within 10% error. The ability to take near real time measurements, combined with the instrument?s portability (currently small enough to be worn on a miner?s belt), makes this device extremely useful in the mining industry.

Jan 1, 2009

By Dave Bulled, Jim Thompson, Tim Leriche, Mark Blake, Troy Wilkie

"A commitment to a core testing, plant modeling and reconciling technique has shown substantial economic benefits to IOC in terms of accurate production forecasting, smoother operation of the mill, improved expectations of throughput and co-operation across production departments from geology, planning, mining, and processing, to shipping of concentrate to market.This paper describes a successful seven year program of forecasting throughput of the autogenous milling circuit at the Carol Lake concentrator of IOC. Work started with audits of the grinding circuit in 2001 and benchmarking of the data collected from samples of mill feed and plant operation to the CEET mill design and throughput forecasting model.Initially 390 drill core samples were tested for SAG Power Index (SPI) to measure the energy required in milling, and the data distributed using a geostatistical technique across the two operating pits, so that hardness was estimated in each of the 40,000 blocks (or 1500 million tons) of potential ore. In 2004 a forecast of energy requirement, i.e. forecast of throughput for a given power availability at the mill, was produced for each ore block using the CEET model and used for mine planning to smooth plant throughput. The forecast for blocks mined on a monthly basis was reconciled with plant results over the next 2 years and minor changes made to the CEET model. The forecasting exercise was repeated in 2006 and in 2008 with the latest model based on the testing of almost 1300 samples of drill core at closer spacing.INTRODUCTIONThe contracting of sales to clients and the timely supply of products to meet those contracts is a cornerstone of good business practice. Ensuring the correct scheduling of production is a major concern of mining companies where the supply and qualities of the raw material is uncertain and production facilities are not flexible. This is particularly challenging when the product is of high volume and produced far from the customer, such as iron ore.Apart from the metal content of the ore being mined, the greatest impact on production scheduling is the throughput of the comminution section of the extraction plant; most notably when size reduction is achieved by autogenous grinding. The response of the mills to variability in the hardness of the ore can change throughput by as much as 50% from day to day at some plants."

Jan 1, 2009

By J. Schenck

Goldcorp Inc. has mining operations and exploration projects throughout Canada, the United States, Mexico, Guatemala and Honduras; as well as partnerships in Argentina and the Dominican Republic. In rural areas of developing countries it is very common to have mining operations surrounded by diverse communities consisting of people with limited, or no formal education. This is fertile ground for anti-mining NGOs to cultivate. The limited educational backgrounds of the people, coupled with a company desire to maintain a low profile can lead to a problematic lack of trust between the local communities and the mining company. As part of its commitment to environmental stewardship and sustainable development, Goldcorp has implemented various programs to build trust at these operations, as well as incorporating this policy into any new projects prior to commencement of operations. This paper is intended to describe two initiatives that have shown positive results for both the communities and the Marlin Mine.

Jan 1, 2009

By F Palkovitz, S Wilson, F Felipe

The management of waste from mining operations is a significant aspect of bringing a mineral commodity to final market. The ore beneficiation process and transport/disposal of waste involves significant consumption of costly resources. A number of options exist to dispose of mill waste on surface and as a backfill material. These range in complexity, risk, capital cost, operating cost and ultimately business performance. This paper discusses the value delivered to a business in using dewatering systems including paste as opposed to conventional slurry tailings disposals. This is illustrated through various case studies and serves to demonstrate how paste can add value and reduce risk to a successful business.

Jan 1, 2009

By Arthur D. Silber

The economic success and growth of any metropolitan region depends on mobility. Today, mobility between New Jersey and New York is threatened by a transportation system that cannot meet 21st century travel demands. The transportation bottleneck created by the Hudson River threatens the viability of one of the world?s great centers of commerce and culture. Fortunately, there is a solution: The Access to the Region?s Core Mass Transit Tunnel. The US$8.7-billion Mass Tran-sit Tunnel?s (MTT) new two-track line will double commuter rail capacity under the Hudson and create a new, state-of-the-art cavern station in Midtown Manhattan, with wide platforms, high-speed escalators and other features to improve riders? travel experience. The capacity and other benefits of the MTT project will launch a new era of prosperity for the region, just as the Pennsylvania Railroad did almost 100 years ago when it built the existing two, single-track rail tunnels that now form the sole commuter rail link between New Jersey and New York. The existing tunnels run from North Bergen, NJ, under the Hudson River to Pennsylvania Station at 33rd Street in Manhattan. Construction on the MTT, the largest public works project in the United States, is scheduled to start this year and continue through 2017. The MTT is ready to go to construction thanks to a major commitment of financial, engineering, project management and other resources from NJ TRAN-SIT, New Jersey?s statewide mass transit agency, and the Port Authority of New York and New Jersey, a bistate agency that operates the Holland and Lincoln tunnels, the George Washington Bridge and other major transportation facilities in New York and New Jersey. The project is also strongly supported by the state governments of New York and New Jersey, as well as that of New York City. The MTT is New Jersey Governor Jon Corzine?s number one transportation priority.

Jan 1, 2009

Talvivaara deposits, Kuusilampi and Kolmisoppi, comprise one of the largest sulfide nickel resources in the world with 642 Mt in Measured and Indicated Resource categories. TalvivaaraÆs preferred extraction technology is bioheapleaching, which is already widely used for other metals, notably copper and gold. The company has demonstrated the viability of bioheapleaching technology for the extraction of nickel using the Talvivaara ore. The leaching process is heat generating and therefore suitable for the subarctic climatic conditions. The planned annual metal production is 33 000 t of nickel, 60 000 t of zinc, 10 000 t of copper and 1200 t of cobalt. Talvivaara deposits are well-suited for open pit mining due to a thin overburden, favourable resource geometry and a low waste to ore ratio. The ore is relatively low-grade, but well suited to bioheapleaching due to its high sulfide content. Bioheapleaching is a process whereby metals are leached from ore as a result of bacterial action. The bacteria used in the Talvivaara bioheapleaching process are endemic to the area and therefore well adjusted to the prevailing environmental conditions. The solution is collected at the bottom of the heaps and either re-circulated through the heap or fed to metal recovery. In metal recovery, nickel, copper, zinc and cobalt are precipitated from the pregnant leach solution and filtered to produce saleable metal products. After the metals are removed, the solution is further purified and returned to irrigate the heaps. Mining, bioheapleaching and metal recovery techniques for the Talvivaara mine have been tested in a 17 000 t on-site demonstration trial during 2005 and 2006. Subsequent construction of the mine started in 2007 and commercial production in the fourth quarter of 2008.

Jan 1, 2009

By L. Hansen

Sulphuric acid plants now and then see unexpected increases in SO2 emissions. Our experience is that it is not always easy for the acid plants to pinpoint the exact reason for the SO2 increase. Sometimes a catalyst bed is sacrificed even though reliable temperature readings and gas analyses could have verified satisfactory activity. Hence the leaking heat exchanger is never discovered and after the shutdown the SO2 emissions are still too high. This paper will look into some basic catalyst management tools: good record keeping is a necessity for collection of representative catalyst samples; reliable operating data is an inevitable starting point for all analysis; and trending of operating data is a must for plant optimization and troubleshooting. In addition, these catalyst management tools will give continuous updated knowledge of the catalyst status in each bed, providing the basis for a more effective replacement strategy. The most typical reasons for increasing SO2 emissions will be presented together with easy guidelines for cross-checking operating data, temperature optimization and good record keeping.

Jan 1, 2009

By Robert L. Parsons

This paper describes the results of a detailed analysis of a loess deposit at the deep foundations test site established by the Kansas Department of Transportation. Multiple CPT, SPT, and pressuremeter tests were conducted as part of the investigation. This paper includes an evaluation of the effectiveness of common correlations used with the CPT, SPT when used for classification of loess and estimating its properties. Results show that common correlations must be used with caution as significant errors in estimation may result from using methods developed for other soil types. Laboratory testing included direct shear, triaxial, collapse, and consolidation testing, with many of the tests conducted on both vertically and horizontally oriented samples to evaluate anisotropic behavior. The results showed that strength properties could be considered to be isotropic.

Jan 1, 2009

By D. McBride

Representative samples are required from process streams in order to accurately measure chemical and physical characteristics. This information can then be used by process operators and metallurgists to evaluate the process and effect control actions for the operation. The capture and presentation of representative samples can be critical to measuring values, such as elemental analysis and particle size, with on-line or near-stream analyzers. A comprehensive multi-physics model has been developed and used to better understand the effects of slurry flow and particle segregation under certain operating parameters. An algebraic slip model coupled with a free surface algorithm is used to track motion and position of particles and phases within a specified geometry.

Jan 1, 2009

The use of belt air in underground coal mines has been a continuous discussion since it was first introduced in the Federal Coal Mine Health and Safety Act (Coal Act) of 1969. Although the Coal Act prohibits the use of belt air to ventilate active workings, there were two exceptions prior to the 2004 Final Rule. There have been several major studies/rule-proposals by MSHA since 1985 and the most recent of which is the Technical Study Panel (TSP) established by the Mine Improvement and New Emergency Response (MINER) Act of 2006 to study the use of belt air and related issues. This paper reviews the history of belt air use, its associated controver-sies, and more specifically, the 20 recommendations unanimously approved by the TSP.

Jan 1, 2009

By G. Adderley, A. Wetherelt

The problems of poor drilling in underground operations have been highlighted on many occasions. Incorrect collaring and poor angular deviation can all lead to an increased block size, dilution, over-break adding to both cost and time, while in a tunnelling operation sidewall damage and a poor percentage pull from a blasted round has similar consequences. This paper sets out to further investigate the ability of the laser scanner method of obtaining drill hole deviations and collaring errors at the face as described by Wetherelt and Williams (2006). Tests were carried out to compare measured inter-hole burdens from this method in comparison to that obtained using a total station survey. To investigate the ability of these methods to accurately determine drilling errors, a field test was carried out through an analysis of a series of pre-drilled blast holes of known inclination and direction. A time-motion study was also conducted for a varied number of holes to assess the usability of each method. In line with current research into blast vibration being undertaken at the Camborne School of Mines, 6 cut blasts were carried out to establish the effect of poor drilling on a blasts success to see whether an increased burden at the toe of a hole had an influence on vibration.

Jan 1, 2009

By Don Langlois, Udo Weber

"The effect of grinding media performance on milling and operational behaviour was demonstrated under different selected milling conditions of calcium carbonate. A variety of grinding media material and bead sizes, along with 2 different stirrer tip speeds, were used in the grinding process to generate a particle size reduction of the calcium carbonate (CaCO3). To determine the optimum milling parameters the collected test data was used to calculate and evaluate specific energy as well as stress intensity under different milling conditions.INTRODUCTIONAs a result of increasing energy costs and raw material prices it is important to look at the efficiency of the manufacturing process. Wet grinding and ultrafine wet grinding in stirred media mills are now a possible cost-effective production step for the processing of industrial minerals and precious metals. The generation of smaller particle sizes (down to micrometer scale) can be advantageous for further production steps – i.e. better liberation of precious metals or improved industrial mineral qualities.In the following, the wet grinding process is investigated under different milling conditions of calcium carbonate. Different grinding media materials varying in specific weight, bead size and stirrer tip speeds are used to determine optimal energy consumption for the milling process.DESCRIPTION OF TEST CONDITIONS AND PARAMETERSMill ParametersTests were performed in a Drais Laboratory Perl Mill PML H/V with an installed electrical motor power of 3 kW. The mill chamber is silicon carbide where as the stirrer and discs are made of yttria stabilised zirconia. The mill working volume is 0.9 l. A screen cartridge with a screen size of 0.2 mm is used to separate the beads and slurry at the outlet of the mill. All tests were performed with a grinding media filling grade of 80% (Mill working volume). The stirrer tip speed was set at 6 m/s and 10 m/s."

Jan 1, 2009

By S. Lim, G. Walsh, V. Romero

The cable television show, Mythbusters, contacted the New Mexico Institute of Mining and Technology requesting a pressure gauge to be used in underwater testing. The requirements for the gauge were: it must be passive (i.e. require no power to function), it must indicate when a certain, pre-determined pressure was reached, and that indication was to be visual. A pressure gauge was developed, using standard, commercially available rupture discs, set to burst at 500 psi. Underwater testing was conducted using a 400 lb Pentolite charge. Test devices were set out at ranges from 50 to 200 feet from the seat of the blast. The rupture discs showed a lethal range up to 100 feet, but not at 150 feet. This result matched well with the behavior predicted through modeling and simple shock physics calculations. Additionally, the geometry between the incoming shock and the pressure gauge did not seem to have a strong effect on gauge performance.

Jan 1, 2009

By W. P. Arnott

This paper presents real time photoacoustic measurements of diesel-soot black-carbon (BC or EC) and Dusttrak nephelometer total carbon (TC) concentrations in a Nevada gold mine. Comparisons with time-integrated filter-based measurements of EC and TC accomplished using the NIOSH 5040 method were found to be 50% smaller than the integrated real time measurements. This work was initiated primarily as a demonstration project for the usefulness of photoacoustic instruments in measuring BC in the mine environment. Real time black carbon measurements are very useful for determining miner exposure, for providing feedback in mine ventilation systems, and for quantifying machine specific emission rates to understand the operating conditions for specific machines that produce greatest black carbon concentrations. This paper reports real time measurements of DPM from a loaded and empty hauler as it is operated in a drift with a 12% grade. The photoacoustic instruments were demonstrated to be satisfactory for BC measurements in the mine environment.

Jan 1, 2009