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By M. Wason

An Ore bed magnetic liner element is made of permanent ceramic magnets embedded in a rubber molding. (See figure 1) They are difficult and expensive to manufacture correctly. Therefore, the lining for a complete mill is expensive, as high as 400% more than conventional rubber liners. The magnets are not very resistant to impact as they are very brittle. Mills of 12 feet or more can use only I inch balls; mills under 12 feet can use balls of 1-1/2 inches. These liners are therefore used in regrind applications with small balls or in secondary pebble mills. Rubber liners for these applications last a long time, so if life was the only consideration, the pay back for these liners would be longer than the life of the mine. The Ore bed liner and its bed of ball chips or magnetic ore is relatively thin and the surface of this bed has a high coefficient of friction. The liners are made so that opposing poles are situated next to each other and that the mill shell and the bed of ore or ball chips completes the magnetic circuit. (See figure 2) The combinations of these properties results in a very efficient liner. Due to the low profile of this bed, there is no material that is lifted too high, so we have a very compact charge with very high attrition, good for fine grinding. These liners have shown a 10% ball consumption reduction and a 10% lower power draw for the same capacity. Due to the magnetic orientation, the bed is formed in a wave shape along the lines of magnetic force. Tests conducted at a copper mine in the southwest United States have confirmed these findings. The mills where the liners were tested are 10.5 feet by 16 feet Hardinge regrind mills operating as overflow ball mills.

Jan 1, 1999

By G. H. Lewis, C. L. Krcil, N. S. Harding, D. E. Havekotte

INTRODUCTION Limestone injection work was completed in a 440-kW (1.5-million Btu per hour) pilot-scale combustor in preparation for a 50,000-kg/h (110,000-lb per hour) industrial steam boiler limestone injection test program. The main objectives were to: (1) identify the important variables that affect sulfur capture, (2) determine the maximum SO2 removal, and (3) determine the effect of limestone addition on furnace operability and heat transfer. A more detailed report is given by Lewis et al. (1985). The test program was divided into two phases. The objectives of Phase I were to determine the important variables that affect SO2 reduction and to investigate the effect of limestone addition on combustor operation and heat transfer surfaces. The objective of Phase II was to determine, using only the important variables identified during Phase I, the conditions that resulted in the greatest sulfur dioxide reduction. Phase I Test program Using one limestone, five variables were identified as having an effect on SO2 reduction. These are noted with their respective ranges: heat release rate [103 to 166 kW/m3 (10,000 to 16,000 Btu per hour-cu ft)], Ca/S molar ratio (0 to 3), flue gas oxygen concentration (3% to 5%), additive particle size [90% -150 µm (-100 mesh) and 90% -45 µm (-325 mesh)], and burner stoichiometry (SR = 0.75 and >1.15). A 2.3% sulfur northern West Virginia coal, pulverized to a nominal grind of 70% -75 µm (-200 mesh), was burned for the tests. The limestone used was obtained from a Maysville, KY, quarry and contained 51.75% (wt) CaO. An 11-run statistically designed program (plus three duplicates) was used to screen the five variables. The effect of limestone injection on the combustor heat transfer surfaces was determined by comparing the heat transfer rates through a slag panel and fouling probes during periods with and without limestone injection. Combustor operation was determined by noting any operating problems that occurred during the tests. Test procedure After furnace wall temperatures had stabilized at operating conditions, heat transfer surfaces (slag panel and fouling probes) and the convection section were blown clean, and a four-hour test was begun. The

Jan 1, 1987

By B. Lin, C. Tang, Z. Chen

Earthquakes, underground impact pressures and rock bursts all produce acoustic emissions. The rate of these emissions can be used to describe rock instability. In this study, it was found that acoustic-emission rates obtained by simulating a twin sample (rock-rock) model could be used to indicate the acoustic-emission-rate characteristics during rock instability. A computer simulation and two case studies support this conclusion.

Jan 1, 1997

By D. H. Davidson

In situ leaching (ISL) of copper has the potential of reducing both capital and operating costs for copper production. The ISL process combines surface facility (SX/EW) and wellfield operations, each of which must process the same total flow rate and pregnant liquor copper concentration. Commercial cost data are only available for SX/EW facilities. This paper discusses: the interaction between the principal wellfield costs associated with well modules, and wellfield start?up with SX/EW costs; how to estimate what the level of wellfield costs must be to optimize DCF/ROR; and how to relate these wellfield costs to orebody geologic and mineralogic characteristics.

Jan 1, 1988

By S. T. Krukowski

Traditionally the lime industry is governed by market, location, and transportation. These factors also may act as obstacles to global market access. Lime manufacture responds to market opportunities by first focusing on location. Lime markets are diverse and widespread, and ubiquitous occurrences of limestone make development of a widespread industry possible. Lime’s low to moderate unit value restricts transporting it long distances. Other factors (including lime reactivity, dedicated container use and other liabilities) limit shipping lime far. In the past many small to medium size companies made lime for local use. Today the global aspect of the industry is ownership by few large companies producing lime for local consumption.

Jan 1, 2003

By Fu Lizhu, Qiu Tingsheng

An application of water-system magnetizing technology for the mineral processing and hydrometallurgy is introduced in this paper. The water-system magnetizing technique flotation and cyanidation leaching test of vein-ore of gold-bearing and conventional technique flotation and cyanidation leaching of gold-bearing vein-ore was carried out. The best condition of water-system magnetizing was determined by orthogonal test. The results have shown that the water-system magnetizing technology may increase the efficiency of flotation and cyanidation leaching for gold. The industry-scale test results also show that it can increase flotation recovery by 1-3% and leaching extraction by 3-5% of a gold-bearing vein- ore. The interaction of magnetizing water-system with minerals was carried out and initially investigated.

Jan 1, 1995

By Robert L. Bonomi

One of the major operating costs for any labor-intensive operation is that of its employees' wage and benefits package. Today's packages are extremely complex, with multiple pay rates for different grades and shifts, intricate bonus criteria, and expansive benefit packages that include all sorts of medical, dental, pension and other costs that can be "hidden" from direct examination and consideration. The problems of estimating the total cost of such a package to a company becomes even more acute at negotiation time, when pressure from both sides to settle intensify and changes to package offers come rapidly. A comprehensive system is needed that can evaluate these costs and perform sensitivity analyses, on the various components of an agreement so as to aid in the solving of major labor deadlocks, productivity problems, and cost impacts created by those agreements.

Jan 1, 1982

By H. Ankara

Determining the identicalness levels of the same model trucks working in open pit mine transportation system by means of statistical analysis methods is very significant in terms of availability analysis. In this study, the identicalness levels of two trucks picked randomly from the 170-short-tonne truck fleet working in open pit coal mine over one-year period were examined through a non-parametric test, Mann-Whitney U test for two samples. Time to failures (TTFs) and Time to Repairs (TTRs) of the trucks were analyzed with this test technique and then whether they were identical or not was determined. In order to determine whether the trucks identified to be identical at the end of this test displayed the same mining performances within the same open pit transportation system, the availability analysis of the identical trucks was carried out. As a result of the availability analysis, it was observed that the trucks had availability values that were very close to each other. It was also determined that Mann-Whitney U test could be employed together with availability analysis. Finally, it was observed that Mann-Whitney U test for two samples could yield rapid results in the performance analysis of complex systems like open pit mines.

Jan 1, 2010

By G. A. Dawe, E. G. Kelly

Because of the nature of the breakage in the Barmac vertical spindle impactor, the 80% reduction ratio is very small, so that when an energy efficiency is calculated from Bond's method, it appears to be very low. However, the product size distribution contains a high proportion of fines. It is argued that the production of these fines accounts for the high energy consumption, and Bond's method is modified to account for this, by considering the crusher to be, effectively, a number of smaller crushers in parallel, each having a different reduction ratio.

Jan 1, 1990

By J. W. Leonard

Since the interpolation of exploratory data 1 can be no better than sampling procedures, a series of field experiments were conducted in an effort to determine whether hand-cut channel or core washability determinations best represent continuous miner produced run of mine coal. By obtaining a core drilled to within a few feet of channels taken from an underground face and then overmining both locations; core, channels and run-of-mine coal allocations were obtained from a common sample and all allocations were subjected to identical washability determinations. In order to compare results, basic rules2,3 previously anticipated and later published by the writer were employed. The first rule states that "For any full seam washability determination, the sulfur versus ash function for increasing cumulative specific gravity float coal fractions is linear". The second rule states that "For any full seam washability determination, the recovery versus ash function for increasing cumulative specific gravity float coal fractions is logarithmic".

Jan 1, 1988

In early March 2011, a 6.2 m (20.3 ft) diameter Rob-bins Double Shield tunnel boring machine (TBM) crossed the finish line in Sochi, Russia. The machine completed a 4.5-km- (2.8-mile-) long section of tunnel that will ultimately become part of the transportation infrastructure for the 2014 Winter Olympic Games. The TBM advanced through difficult ground at aver-age rates of 100 to 120 m/week (330 to 390 ftpw) for contractor OJSC Bamtonnelstroy, a division of the SK Most Company. The section of tunnel will ultimately become a service tunnel for Complex #3 - a section of Sochi?s transportation infrastructure under construction, which includes road and rail tunnels. A second, 10 m (32.8 ft) diameter Robbins Double Shield TBM is currently excavating the parallel 4.6-km- (2.9-mile-) long main railway tunnel using a continuous conveyor system for efficient muck removal. A 13.2 m (43.3 ft) diameter highway tunnel is also under construction. The 6.2 m (20.3 ft) Robbins TBM achieved high rates despite difficult conditions. The tunnels run through mixed ground including massive to completely fractured limestone with clay seams. Some sedimentary rock including sandstone and siltstone is present, along with fault zones consisting of breccias and conglomerates. In May 2010, the machine was stopped after encountering a significant fault zone consisting of broken rock and running soft ground. Field service personnel and crew successfully freed the machine by excavating a bypass tunnel around the TBM, freeing the cutterhead. Following the restart, a combination of continuous probe drilling and ground treatment with cement silicate and foam kept the machine moving forward.

Jan 1, 2011

By J. W. Merks

At mineral processing plants the accuracy and precision characteristics of assays in mill feed, tailings and concentrate largely determine the reliability of the metallurgical balance. The accuracy of measurements is ensured by selecting effective sampling methods and efficient sample preparation procedures, and by effecting each phase without introducing a systematic error while the precision of measurements is determined by the sampling regime. Sampling systems and components, sampling methods and regimes, and sample preparation procedures will be reviewed. Different techniques to determine variance components for sampling, preparation and analysis, and to detect systematic errors in assays at mineral processing plants, will be discussed.

Jan 1, 1986

By George M. Leonard

Mineral commodities on National Forest System lands contribute to the nation's well being. Access to these commodities is dependent on public perceptions of the effects of mineral operations on other resources. An outlook is described which the Forest Service believes is essential to the minerals industry if it plans to continue seeking minerals on National Forest and Grasslands.

Jan 1, 1991

By K. Johnson, B. Schiffer

Demonstrating aquifer restoration is an essential component of regulatory approval needed to mine uranium, copper, and other minerals by in-situ recovery (ISR). A PHREEQC geochemical model provided a useful means of forecasting the time for restoration and predicting future groundwater quality following low pH mining at Strata Energy’s Ross ISR Project in northeast Wyoming. The model simulated groundwater quality at three phases of the process: at the end of mining; during restoration; and post- restoration. The model utilized the one-dimensional reactive transport and dual porosity features of PHREEQC. Mineral surface ion-exchange, dissolution/precipitation reactions, and adsorption processes were simulated to estimate water quality as the pH was shifted from circumneutral to acidic during mining and back to neutral during restoration. The model results showed that cost-effective management of mine water could meet regulatory requirements. Additionally, the model was used to interpret results from a field trial and inform operational decisions. The predictive approach and geochemical understanding developed have application in assessing aquifer restoration for other ISR projects.

Mar 2, 2022

By J. E. Shearer

The state of Arizona produced 253,276.2 metric tons (279,000 st) of crude gypsum during 1986. This represents approximately 1.7% of the total U.S. production. Four mines provided Arizona's gypsum, three of these mines are in the San Pedro Valley. The uses of the gypsum produced in Arizona are for manufacture of cement, agricultural uses, and wallboard manufacture. The gypsum is used as a retarder in the manufacture of Portland cement. The use in agriculture is treatment of alkali soils to allow water penetration. Other deposits in the San Pedro Valley have production potential, providing there is sufficient market for additional wallboard. The author completed an evaluation of one property earlier this year.

Jan 1, 1988

By J. E. Lees

Advanced remote sensing can be a powerful new information tool to help private and public entities make better environmental and resource management decisions. However, some regulated entities are reluctant to develop or use this tool because of their concerns that it will lead to increased risks and costs of environmental legal liability. They fear that new ways of monitoring the environment will increase liability, undermine existing enforcement agreements, reopen compliance agreements, and generally provide a competitive disadvantage to early adopters by accelerating environmental cleanup costs. Others counter that the increased risks are marginal, and that several advantages outweigh these risks, including the opportunity to more effectively manage environmental operations, target and set priorities, measure and track management and compliance effectiveness, provide more defensible environmental assessments and baseline conditions, make and defend optimal siting decisions, and avoid or resolve environmental disputes. This paper offers strategic advice on ways regulated entities can enjoy the benefits of these powerful new information tools while mitigating down-side legal and compliance risks as much as possible.

Jan 1, 1999

By Peter Erlynne

Rising costs have affected the cost of operating and install­ing crushing circuits, just as they have affected every other area and there is little possibility that the cost cycle is about to be reversed - power costs, wear materials costs and labour costs continue to increase but a basically stable gold price makes little allowance for these cost increases. Additionally, lower grades of ores being worked, and harder feed materials have a significant effect on the potential for higher processing costs. There are, of course, options for size reduction - some of them newer than others - some are suitable for certain types of ores and less suitable for others and it can sometimes be difficult to ascertain the accuracy of anticipated results before plant design and con­struction are completed - by which time the capital outlayed will preclude a change to another method ofreduction. Nordberg's patented WaterFlush Technology has the potential to change the way that Ball Mill Feed production is viewed: Some of the elements that must be considered are: • Capital Cost • Operating Cost • Efficiency • Flexibility • Availability • Control • Support Efficiency • Expertise • Spares availability • Environmental considerations

Jan 1, 1995

By A. Griffiths

The? use of hydrogen peroxide to detoxify gold mill waste waters containing cyanide and other toxic substances is already an established technology. Recent advances have extended the range of application of hydrogen peroxide treatment to include the removal of complex iron cyanides, the simultaneous removal of cyanide and toxic metals down to very low levels and treatment of barren bleeds, CIP' pulps and tailings pond discharges. Three treatment plants are described here. Each was installed at a gold mine in North America in 1987 and each illustrates a different application of hydrogen peroxide. The need for individual design of the detoxification plant to fit particular requirements is shown by the examples chosen.

Jan 1, 1988

By Stefano Colombelli, Nicola Bona, Gabriele Eccher, Luca Schiavinato, Paolo Cucino, Domenico Nave

"BIM technologies provide tools and processes to effectively support the entire life of an infrastructure, from strategic planning to maintenance. As a consequence, infrastructure design processes currently make frequent use of BIM tools. This paper describes the BIM oriented design of the underground railway extension in the metropolitan area of Catania. The paper highlights the design process and the chosen BIM tools considering the boundary conditions characterizing the project, i.e. basic information missing in the final design project, need of coordination between different design disciplines and designer companies, and, finally, need for a flexible design approach able to adapt to changes occurring during design development. INTRODUCTION The underground railway extension in the metropolitan area of Catania is composed of two lots of approximately two km each, namely “Stesicoro-Aeroporto” and “Nesima –Misterbianco”. Works to be realized are: •,Main tunnel: mechanized tunneling using a TBM-EPB machine, for the entire length of the lot; •,Underground stations: San Domenico, Vittorio Emanuele and Palestro, conventionally excavated as enlargement of the TBM tunnel after the partial demolition of precast segments; •,Ventilation and emergency shafts: connecting seven tunnel levels to road level on Stesicoro-Areaposto lot, six on Nesima-Misterbianco lot; •,Additional structures such as technical rooms and parking lot; •,Electric Substation at Monte Po' stop; •,Temporary works: TBM launching and arrival pit to be dismantled at the end of the works."

Jan 1, 2016

By K. N. Santini

The evaporite deposit at Searles Lake consists of alternating brine-saturated saline beds and saline-bearing mud beds. Three major subsurface brine-saturated saline horizons have been identified by private companies and the U.S. Geological Survey. They have been termed, from bottom to top, the Mixed Layer, Lower Salt, and Upper Salt. The important water-soluble components (Na, K, Mg, CO3, HCO3 , SO4, Cl, and B407) are either in brines or have combined to form the following minerals: halite, hanksite, trona, nahcolite, burkeite, borax, thenardite, northupite, sulfohalite, glaserite, etc. Kerr-McGee Chemical Corp., the current operator at the lake, selectively pumps interstitial brines from each of the major horizons to feed its three chemical plants. As the pumping continues, brines are continuously replenished within the deposit by dissolution of the minerals through natural recharge or artificial fluid injection (solution mining). The brines are processed to produce a variety of chemical products, which include sodium carbonate and sulfate, potassium chloride and sulfate, sodium borate, and boric acid. The Anaconda Minerals Co. has been evalua¬ting potential domestic trona acquisition since 1981. We have evaluated various properties in the Green River, Wyoming trona district, and Owens Lake and Searles Lake in southern California. In 1983, we purchased with our joint-venture partner, Leslie Salt Co., the southern portion of Searles Lake from Occidental Petroleum Corp. Since mid-1983, Anaconda has been conduct¬ing a small exploration-drilling program at the property. The initial core holes were drilled along and adjacent to the existing access road. In 1984 we used an all-terrain drill rig to gain access to drill sites on the playa where no roads exist. The use of this equipment proved to be highly successful. The drill program consists of coring to an average depth of 450 feet and collecting brine samples from potentially commercial horizons. The brine samples are collected by setting a packer and swabbing the hole. The core is logged and split lengthwise; one-half is submitted to our Tucson Geoanalytical Laboratory for semi-quantitative mineralogy by X-ray diffraction and the following suite of chemical analyses: Na, K, Mg, C03, HCO3, SO4, Cl, B407, Li, H20 insolubles, and acid insolubles. Additional test work for selected core samples will include effective porosity and horizontal permeability determinations. The brine samples are subjected to the same suite of chemical analyses (minus insolubles) as the core samples. In addition, specific gravity is also determined. Both cross sections and isopach maps are being constructed. The hydrological characteristics of the potentially commercial horizons are also being investigated.

Jan 1, 1987