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By R-H Yoon

A turbulent flotation model has been developed by considering the subprocesses of collision, attachment, detachment, and froth recovery. AbrahamsonÆs model (1975) of infinite Stokes number is used to model collision, while the attachment and detachment subprocesses are modelled by considering the kinetic energies required to overcome the energy barriers and the work of adhesion, respectively. The energy barriers are determined by considering various surface forces, including electrostatic, dispersion and hydrophobic forces, while the kinetic energies are determined from the particle velocities at close separation distances from air bubbles. The latter has been determined by modifying the turbulent root-mean-square (RMS) velocities of Liepe and Moeckel (1976) and Schubert (1999) in view of a lubrication theory. In calculating the RMS velocities, it is assumed that a flotation cell is subdivided into low and high energy dissipation zones. The model predictions made by varying various hydrodynamic and surface chemistry parameters are consistent with flotation practice.

Jan 1, 2005

By V. F. Zackay, J. F. Carlson

CURRENT experimental work on the development of gas turbine engines in the automobile industry has emphasized the need for a relatively low cost nonstrategic castable alloy for service in the 1200" to 1400°F temperature range. Ferritic steels

Jan 1, 1956

By Arnulf P. Hagen

This project was designed to explore the suitability of using fluorinated inorganic materials as solvents for the in situ mining of thin seamed, heavily overburdened coal; to build a data base for the selection of an inorganic solvent for use for coal cleaning; to determine if fluorinated solvents will reduce the organic and inorganic sulfur contents of the coal, as well as to lower the ash content. The coal samples have been combined with pure solvent, as well as with aqueous solutions at atmospheric pressure and at increased pressure. The increased pressure experiments are important since they duplicate the conditions anticipated for an in situ cleaning and mining operation. Trifluoroacetic, difluorphosphoric (phosphorodifluoroidic), and trifluoromethanesulfonic acids have been found to be effective for the cleaning of high sulfur, high ash coal at 300°C and at atmospheric pressure. At pressures up to 20,000 psi the effectiveness of these reagents is not decreased.

Jan 1, 1983

By Jamie Delgado, Marco Arelano

The changes of bench angles in an Open pit mine has a strong economical impact in the “mining business”, particularly in its cash flow related both to the decrease as well as to the increase of the global bench angle or the inter-ramp angle. The global vision of bench optimization process currently developed by Compafila Minera Zaldivar (CMZ), includes the interconnection of different processes driving to the completion of the designs. Thus five very influential areas are recognised such as: (1) The physical Surrounding terrain, (2) the strength parameters, (3) the observational model, (4) the acceptability criteria and (5) the operational considerations. One of the important variables affecting this process is Drilling and Blasting (D&B). Increasing the bench angle requires to optimisation of D&B. To achieve this efficiently controlled sub processes must be defined. Three (3) steps can be defined: (a) design parameters, (b) explosive energy distribution and (c) operation results. To control and improve said steps quantitative evaluations of D&B must be performed. One valid evaluation is the “near field vibration monitoring technique” (at bench level). With the application of damage criteria, measurements and modelling of particle velocity a proper definition and optimisation of stages (a), (b) and (c) was achieved, The use of this methodology has enabled to CMZ to successfully increase the inter-ramp angle in three degrees thus obtaining a saving of US$ 36 million in the waste material removed. Also, the efficient control of the bench slopes has resulted in the improvement of the fragmentation operational results. This has resulted in a 26Oh increase in the ore processing by saving energy in the primary crusher due to its performance improvement.

Jan 1, 2001

By A. S. Richardson

AIR conditioning, or air cooling, for the improvement of ventilation in the Butte mines has come into increasing use during the past 10 years. In part, the methods practiced have been described in previous publications of the Institute, but some improvements on earlier methods have been made and a number of new features have been developed. This paper is presented as a record of progress made, and for the sake of completeness describes all general features of the work. The need for air conditioning in the ventilation of mines in the district arises from the fact that the temperature of the ground and mine water has shown a very great increase with increase in mining depth, and has now reached a maximum of slightly over 130°F. The most difficult part of the ventilation problem is the maintenance of temperature and humidity of a satisfactory standard in the working places, especially on the lower levels. Although ordinary ventilation is adequate to maintain good conditions in most of the working places it is subject to a number of limitations at great depth. Most important among these limitations is that with increase in depth the air becomes heated before it reaches the working places, both by compression from increase in atmospheric Pressure and by heat transferred to it from rock at high temPerature, so that its capacity for lowering temperatures is greatly reduced before it reaches the operating zone. Increasing depth of mining also increases the distance traveled by the air in its passage through the mine, and this causes a corresponding increase in resistance to air flow, so that there is greater difficulty in maintaining even the same volume in circulation. Thus, in the face of a demand that the ventilating system have a very much greater capacity to remove heat from the mine, the tendency is for that capacity to diminish. The only evident alternatives were (I) the opening of additional air shafts to increase the volume of air in circulation, (2) an extension of the existing system that would be subject to the same limitations, or (3) the adoption of an entirely different method such as air cooling. Fortunately for an economic solution of the problem, the mean annual temperature of the surface atmosphere at Butte is about 40°F., with very low relative humidity in summer, so that there is unlimited natural cooling power at a temperature range adaptable to air-conditioning methods. Methods Two similar methods of air conditioning are used, as necessitated by service requirements and dependent upon the equipment available. In one, which is the more important and has the greater cooling capacity, water is circulated in a closed circuit, and, alternately, first absorbs heat from warm mine air and then dissipates it in the surface atmosphere by cooling at a cooling tower. The second

Jan 1, 1943

By Joseph Renk, David Akers, Glenn Shirey

Each year, US coal cleaning plants landfill or impound millions of tons of high-quality, fine-sized coal. This coal is not only difficult and expensive to capture during cleaning, but, if captured, can pose serious materials handling problems. The GranuFlow. Technology was developed and patented by the U.S. Department of Energy (DOE) to address these problems. GranuFlow involves the addition of a coal binding agent such as an asphalt or heavy oil emulsion to coal to reduce moisture, dusting, and freezing and to improve the flow properties of the coal in bins and chutes (1, 2, and 3). When the emulsion is added before mechanical dewatering, the binding agent causes the formation of fine-sized coal agglomerates that dewater better than untreated coal. In addition, the binding agent increases the capture of ultra-fine coal in screen-bowl centrifuges. Previous work by DOE has also demonstrated that such treatment results in a significant reduction in dustiness and a reduced potential to freeze. To address concerns about the handling and combustion characteristics of GranuFlow treated coal, DOE performed a pilot-scale pulverization and combustion test (4). No problems were encountered during pulverization or combustion, and use of this fuel in a p.c. boiler was found to be feasible from a technical perspective. CQ Inc. has an exclusive license from DOE to market this technology and is currently performing a series of commercial demonstrations to determine if GranuFlow is both technically and economically viable.

Jan 1, 2005

Jan 1, 1883

ABSTRACT' The first references to gold in New Guinea were by the Portuguese in 1525. The first significant discovery and gold rush was on Sudest Island in 1888 and was a natural extension of the rush that surged up Australia's eastern coast and ended at cook- town. Prospectors made a series of minor discoveries in coastal regions before the first large discovery at Wau/Edie Creek/Bulolo in 1925. Major post war gold discoveries were made at Bougainville, Frieda River, Porgera and Ok Tedi. On Misima Island a large bulk low grade deposit has been recognised surrounding old gold workings. Gold exploration has increased drama- tically since the lifting of a 3 year moritorium on new exploration areas in Noverrber 1982. A new bulk low grade gold discovery has been made on Lihir Island, north of Bougainville and a number of other promising areas are being drilled. Gold production is also expanding dramatically from current levels of 600,000 ounces to an anticipated 1.3 million ounces in 1985 with the opening of Ok Tedi. Other potential developments are likely to increase output above 2 million ounces by 1990. Papua New Guinea's world ranking as a producer is likely to move from 9th to 7th in 1985 reflecting the favourable geological potential, stable political environment and attractive development terms offered by the Government.

Jan 1, 1984

By P. Gonzalez, C. Ariyo, L. Holappa

Oxidation state of titanium was determined in CaO-SiO2-TiOxslags in the composition range25–53 per cent CaO, 27–46 per cent SiO2, 10–55 per cent TiOxat 1873K using gas equilibration method. In the experiments, slags with different titanium oxide contents were equilibrated with a known carbon monoxide and carbon dioxide ratio. The results were used to determine the Ti3+and Ti4+contents as well as the activity coefficient ratio of corresponding oxides in the slag. The dependency of the activity coefficient ratio as a function of oxygen partial pressure was determined. Keywords: titanium, titanium oxide, activity, activity coefficient, slag iron, carbon monoxide,carbon doixide, gas, equilibrium.

Jan 1, 2004

By Michael Poole, Joseph M. Chelini

Most earthmoving operations using off-road, rubber tired production equipment have abnormally high total tire costs. Achieving informational control over 7 direct and 2 indirect tire cost centers can reduce tire costs more than 50 percent; a 20 percent savings is often guaranteed. This is achieved by utilizing available computer software and implementing tire information management through the engineering deparatment.

Jan 1, 1983

By Don Thompson

The Minntac Mine drills and blasts approximately 75 million long tons of taconite per year. This requires drilling one million feet of 1 6-inch diameter holes. We are in the process of replacing our old generation rotary blasthole drills (Gardner-Denver 120's and Bucyrus-Erie 61R's) with new generation rotary blasthole drills (Bucyrus-Erie 59R's and P&H 120A's).

Jan 1, 1998

By Leon Maday, Robert Robinson, Judy Cochran, Don Davis

Over the past 20 years, several soft-ground tunnels have been successfully completed in the Seattle area. These tunnels were built using design-bid-build contracting methods, and have benefited from advancing technologies in exploration, design and construction methods. Owners have utilized various contractual means to share some of the risks that are inherent to tunneling projects. This has helped to foster a competitive bidding environment and to resolve issues related to unanticipated underground conditions in a fair manner. This paper presents case histories of tunnels constructed by King County and the Washington Dept. of Transportation that illustrate a common approach to design and construction issues. The common thread is successful project completion with minor cost changes under the design-bid-build contracting method. Lessons learned from these projects are being applied to the upcoming King County Brightwater Project tunnels, Sound Transit’s Light “Link” Rail tunnels and other tunnel projects.

Jan 1, 2005

By M. F. van der Merwe

Anglogold Ashanti?s Kopanang Gold Plant (previously No. 9 Gold Plant) treats ore from Kopanang and Tau Lekoa shafts. The plant is twin streamed and has dedicated treatment circuits, from milling to final product, for each shaft. Waste rock material is used to compensate for the mill gap on both streams. Each stream consists of three 4.85 m x9.15 m ROM mills in closed circuit with a single stage hydrocyclone, milling an average of 7 000 t per day. The liner configuration in each mill consists of six rows of 30 grid liners along with rectangular lifter bars. The topic of gold lock-up is not new and has been investigated and reported on many times, both within Anglogold Ashanti and the broader mining industry. Although the lock-up mechanism is understood, its measurement is neither practical nor precise. The initial lock-up in a new liner and the release as the liner wears down cannot be accurately quantified. Previous test work carried out on Kopanang Gold Plant (with a ?gold scanner?) measured the natural gamma radiation emitted by uranium. This radiation is in proportion to the mass of concentrate locked up in the grid liner pockets, as well as between the cast-on backing plate and the shell. The ratio of concentrate lock-up was estimated as 35% behind the liners and65% in the pockets. Mill gravity concentrates are recovered during routine relining operations from behind the grid liners at Kopanang Gold Plant. Prior to relining, the liners tend to release the concentrate from the pockets as the liners wear. Historical Kopanang data from actual ?mill gold? smelted indicates that an average of 29 kg gold is recovered from behind each row. This indicates a total lock-up of 250kg gold per mill. This locked-up gold should preferably be minimizedor eliminated for the following reasons: ?The cyclic build-up and release of gold in mills complicates accounting ?Gold concentrate arising from liners is a security risk and creates a major mechanism for gold theft ?Loss of interest on the value of 250 kg fine gold is significant and was a major driver for the project. These factors led to the need to develop techniques to eliminate or at least minimize the gold lock-up in the mills. Wave liners, with rubber inserts, have been successful in eliminating lock-up, and were tested at Kopanang Gold Plant in November 2000. However, due to increased load-slip and high wear rates associated with these liners, this option proved less economical in terms of liner wear. Grid liners, with rubber-filled pockets, demonstrated a very high wear life and eliminated pocket lock-up. This system was successfully trialed in January 2003, but unfortunately did not prevent lock-up behind the liners. Current developments have resulted in a system that eliminates both pocket and backing plate lock-up. The conventional grid liner design has been modified to remove its steel backing plate. Rubber inserts that are integrated onto a rubber backing plate, have been designed to be used with the newly modified grid. The backing plate and grid pockets are now completely occupied by rubber, thus completely eliminating concentrate build-up around the new grid liner system installed in November 2003. Results to date are promising and liner life is expected to exceed conventional performance.

Jan 1, 2005

By C. H. Mathewson

COPPER and the copper-base solid solutions readily form twin crystals when plastically deformed at a suitably elevated temperature or annealed after cold deformation. In fact, no feature of the microstructure of these materials is more prominent or characteristic than these straight-sided bands or simple lines of division which sometimes come from groups of thin polysynthetic lamellae, penetrating part way or wholly through the parent grain substance, but often divide the grain into a few or perhaps only two crystallographically related parts. Nearly always the bands as seen in the usual microscopic examination of a specimen come into vivid contrast with the adjacent crystalline material owing to the inherent difference in orientation. Bands which under special conditions of orientation cannot be seen with vertically incident light are often visible under oblique illumination and, when this fails, contrasting effects usually may be obtained by using polarized light. There is no longer any doubt that these synthetic banded structures obtained in the ordinary course of working and annealing are due to twinning of the spinel type which was observed long ago in a number of metals crystallizing in the isometric system.1 It has been customary in metallurgical literature to designate these synthetic twins, which grow into prominence during an annealing process, as "annealing twins" without regard to the actual mode of their formation, which is, indeed, obscure and with scant recognition of the fact that prior deformation is essential, no twins having been observed in metal of known unstrained history. This is questionable; especially in view of. the fact that in a number of metals and minerals, reorientation into the twin configuration is known to occur as a result of a simple shearing mechanism along the recognized twinning planes and the

Jan 1, 1930

By Meagan S. Boltz

From October 2000 to April 2001 a local array of fourteen seismograph stations was deployed at the Trail Mountain Mine (TMM), an underground coal mine in Emery County, Utah, to locate mining-induced seismicity (MIS). Original analysis of the data provided epicentral locations that coincided closely with the active longwall panel. The original analysis yielded poor quality hypocenters, however, preventing a useful relation from being made between mining activity and the event depths. For the original analysis, only stations at elevations above mine level were used for locating MIS. As a result, P- and S-arrival times from four of the stations in the local array were not used: an inmine station and three stations at elevations below mine level. This study compares mine workings and active mining to a revised TMM dataset that included P- and S-arrival times from the lower elevation stations that were not used in the previous study. In the revised locations, a modified master event methodology was used to calculate station delays. These station delays correct for errors in the shallow layers of the velocity model. The resulting hypocentral locations have improved depth resolution, determined by a lower root mean square (RMS) for the locations, compared to the original study. Most of the events occur in the roof of the mine and follow the longwall panel. When located using the velocity model determined in the original study, the elevations of the events increase as the longwall panel progresses. One possible explanation for the elevation increase is that it may be related to geology or the caving process. As presented here, a 10% decrease in the shallow velocity structure results in a more plausible location for the hypocenters. Consequently, it is hypothesized that progressive development of the TMM longwall panel(s) may have resulted in a progressive change in the velocity model.

Jan 1, 2012

By C. S. Trewin

ZINC, in its wrought form, is produced commercially in rolled strip, sheet, wire, rod and tubing. Wire has been made periodically, but due to the fact that slight drafts are necessary, the cost of production is greater than for the more common non-ferrous metals which are made into wire. Notwithstanding the cost, zinc wire has certain special uses for which it is particularly adaptable. Rod has been made both by rolling and extrusion, the product, however, has not indicated great commercial value. Tubing has been made from strip from time to time by forming a strip around a mandrel and either electrically or gas-welding a longitudinal joint. Recently a tube manufacturer has succeeded in making a fair quantity of this material. Its commercial adaptability is still to be determined but anyone who desires it can obtain quantities of the smaller sizes. Inasmuch as strip and sheet are commercially the most important, this paper will be devoted to these products. In the broader sense, zinc is not alloyed. That is, there are no combinations comparable to the various copper, aluminum and nickel alloys. It has been recognized,, for some time, that the lead and cadmium occurring with commercial zinc have some effect on its properties and such alloys as may be said to exist are those made from zincs containing varying amounts of lead and cadmium with a relatively low iron content. The foreign rolled zinc will analyze higher in lead than the domestic grades. A representative foreign analysis will run 1.1 per cent. lead, 0.07 per cent. cadmium and 0.02 per cent. iron. The American grades vary from zinc approximating high grade. and analyzing 0.08 per cent. lead, 0.002 per cent. cadmium and 0.015 per cent. iron, to the lower grades in which the lead will vary from 0.3 to 1.0 per cent., cadmium from 0.10 to 0.5 per cent. and the iron in the neighborhood of 0.02 percent.

Jan 1, 1927

By G. Van Weert

In the spring of 2010 double refractory ores from historical stockpiles were processed through Barrick's Goldstrike pressure oxidation facility, thereby providing preg robbing feeds for a variety of metallurgical testwork. This paper describes the effects of amount, type, place and time of addition of activated carbons on CIL gold recovery and shows that native carbon in plant PDX'ed discharge solids can still preg rob gold loaded activated carbon.

Jan 1, 2011

By P. Barnes

The subdivisions of this account are numbered 27, 28, 29, 30, 31, 32, and 33, in the general series of construction accounts, and give the details of cost of the various items of the work, as noted below: Accounts 32 and 33 relate to hand-tools and to heaters, and, being quite small in total amount, are omitted in this statement.

Jan 1, 1879

By K. S. Whiting

Elevated concentrations of copper, cobalt, and arsenic within the Panther Creek Basin sediments in north central Idaho prompted an evaluation of the sources of the metals. Potential tailings and waste rock source samples collected at the head of Blackbird Creek were compared to sediment samples in the Panther Creek Basin using electron microprobe techniques. The mineral types, degree of alteration, and the morphology of the metal-bearing sediment grains within Blackbird and Panther Creeks were found to consist of copper-, cobalt-, and arsenic-bearing sulfide minerals.

Jan 1, 1997

By Harry M. Edenborn, Richard W. Hammack

Experiments were done to determine if a mushroom compost-based sulfate reduction system could be used to treat nickel-contaminated mine waters. Sulfate reduction systems were established in columns containing acid-washed mushroom compost. Simulated mine waters containing 2000 mg/L sulfate and 50 to 1000 mg/L nickel were adjusted to pH 4.5 and pumped through the columns at flow rates between 15 and 25 mL/hr. During the first nine days of operation, virtually all influent nickel was removed in the columns by sorption and ion exchange mechanisms. The nickel removal rate then dropped to 18 to 30 mg Ni/day (7.8 to 12.8 nmol/ g-substrate/day), probably due to low sulfate reduction rates. When sodium lactate was added to the inflow, a sustained and seven-fold increase in the nickel removal rate was observed. Bacterial sulfate reduction rates measured in mushroom compost-based wetlands exposed to coal mine drainage are 2 to 20 times faster than the rates observed in this study. Low sulfate reduction rates in the columns may have been due to the inhibition of microbial activity by high nickel concentrations and the removal of labile organic compounds from the mushroom compost substrate during acid-washing. Results of this study indicate that bacterial sulfate reduction can effectively treat nickel concentrations up to 500 mg/L if labile carbon is nonlimiting.

Jan 1, 1992