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By John C. Holtz

Information on the gaseous products from the detonation of explosives has been obtained in two ways. In the first, the atmosphere in nines is analyzed after blasting, aid in the second, the gases found after detonating an explosive in a testing apparatus are analyzed. The Bureau of Mines, in

Jan 1, 1940

By Robert Stefanko

13.1-SUBSIDENCE AND GROUND MOVEMENT ROBERT STEFANKO 13.1.1-SUBSIDENCE AND FAILURE This treatment of subsidence and ground movement will be confined to subsidence control for limiting surface damage by assessing the significant parameters affecting ground movements during mining to optimize mining techniques. The material will be equally applicable to evaporite mining as well as coal but will not deal with block caving or similar systems where failure is deliberately induced and surface protection is not necessary or provided. When an underground opening is established, the original equilibrium is disturbed with resultant stress concentrations. While many factors are involved in opening stability, the span (W) undoubtedly is one of the most important factors in failure. Assuming it is relatively small, the overlying rock strata can bridge across the opening and little if any movement or convergence of top and bottom will occur. However, as the span increases, a point is reached where the stress in the overlying rock strata exceeds some strength value of the rock, and the top breaks. If the opening span is limited to some subcritical value (-We) and/or is at great depth (D), a pseudo-arch will form, achielring stability before rupture occurs to the surface. The boundary of this arch is thought to approximate an ellipse in form with the major axis vertical and equal to four times W, although there has been little field research to substantiate this theory. However, if the width of this opening is increased at this horizon to some critical value (W,) or the same span is created in a shallower seam, the overlying strata ill progressively rupture to the surface and the characteristic subsidence trough is formed (Fig. 13-1) The area of the surface affected is much greater than the area of the seam extracted, depending on the "angle of draw" (a), which is the angle between a vertical line from the edge of the opening and another line extended to a point at which subsidence tails out to zero. This angle has been found to be about 35° in Europe but is rather academic, being a function of instrument precision in detecting subsidence. Since the subsidence effect is so small at any point beyond n 25° angle, this latter may be considered the practical limit of subsidence. Further- more, indications are that the angle of draw varies with depth and nature of the strata.' In a field study over a 1,000-ft-deep potash mine in New Mexico, the maximum angle of draw was found to be 51.5°.2 So far, only a single opening has been considered. However, the width of the excavation applies to any complex mining system of entries, rooms and longwalls as long as the seam has been fully extracted and the width represents the distance from one solid rib to another. It will be noted that the amount of vertical displacement varies from point to point on the surface (s), but the maximum subsidence for a given trough occurs at the center (S). This latter value may not he equal to the maximum possible subsidence (Sm) which occurs only if a critical or super- critical (+W,) width has been exceeded (Fig. 13-1). Substantial surface damage can result when subsidence occurs. Factors affecting the amount and type of ground movement are: thickness and properties of the seam, angle of draw, width of excavation, depth and type of overburden, inclinations of strata and surface, and the amount of support left in the gob. In Europe,

Jan 1, 1973

By Robert L. Lagace

A whole-mine experiment to assess the practical feasibility and utility of the dedicated-wire technique for overcoming poor trolley carrier phone system performance at a large underground coal mine was designed, performed, and evaluated. The technique involves the use of a single, low-loss, properly terminated and branched auxiliary wire placed in the rail haulageway. This auxiliary dedicated wire allows signals to electromagnetically couple to the trolley wire/rail transmission line, and thereby significantly decrease the overall signal attenuation rate on the trolley wire/rail line. The in-mine dedicated-wire demonstration program and its results, conclusions, and recommendations are described. The dedicated-wire technique is shown to be a valid and practical one for significantly improving carrier phone system performance in coal mines.

Jan 1, 1981

By R. M. Spang

Abstract Between the German city of Dresden and the Czech capital Prague a 4-lane highway is under con-struction. At the outskirts of Dresden it will cross the narrow and deeply eroded Weißeritz Valley by a bridge. Two twin tube tunnels under oblique angles join the bridge out of the rocky valley flanks. The different geotechnical conditions of these 4 tunnel portals, their design and construction are described within this publication. The two southern portals of the tunnel Dölzschen are situated within a vertical 65 m high former quarry slope, 25 m above the valley floor. The slope proved instable due to toppling failure and exposed serious rockfall risks. Systematic anchoring, scaling, rock bolting, netting and filling under extreme access conditions eliminated these risks. Tunnel excavation started from the slope surface without any pre-cut or conventional portal construction. The opposite northern portals of the tunnel Coschütz are situated in more gentle rock slopes. After removal of debris, excavation of the eastern tunnel started in a 30° slope striking oblique to the driving direction, without any precut, too. Because of the gentle slope inclination the cross section was not earlier completely covered by rock than 30 m behind. The western tunnel started from an optimized short, narrow and steep precut. Its flanks were stabilized by reinforced shotcrete and rock bolts. Because of the small distance between the tubes rock bolts were drilled into the cross section of the neighboring tunnel. Tunnel excavation was made by drill and blast operation, preliminary support consisted of steel arches, reinforced shotcrete and radial rock bolts. Thorough survey of the bolt’s coordinates and direction prevented them from meeting each other. Rock bolts were of the permanent type to prevent the final lining from being obliquely loaded. Systematically arrayed measuring devices checked deformations of slopes and tunnels. Zusammenfassung Der Neubau der Bundesautobahn A 17 wird Dresden und Prag miteinander verbinden. Die vierspurige Autobahn quert westlich von Dresden das enge und tief eingeschnittene Tal der Wilden Weißeritz mit einer Brücke. An beide Brückenwiderlager schließen mit schiefwinkligem Anschnitt doppelröhrige Tunnel an, deren Portale in den felsigen Talflanken liegen. Die unterschiedlichen geotechnischen Verhältnisse, die Überlegungen für einen jeweils optimalen Entwurf und der Bau der portalnahen bergmännischen Tunnelabschnitte sind Gegenstand dieser Veröffentlichung. Die Südportale des Tunnels Dölzschen liegen in einer vertikalen, 65 m hohen Felswand, 25 m über dem Talgrund. Die Felswand erwies sich als global kippgefährdet, außerdem lagen flächig verteilte erhebliche Steinschlag- und Felssturzrisiken für Bau und Betrieb vor. Die Kippgefahr wurde durch ein Systemraster aus vorgespannten Felsankern, die Steinschlag- und Felssturzrisiken durch bergsteigerisches Beräumen mit dem Brecheisen, Felsnägel und Steinschlagschutznetze eliminiert. Der Tunnelausbruch begann von einer Vorschüttung direkt in der Felswand ohne Voreinschnitt im Schutz einer kurzen Luftbogenstrecke. Die gegenüberliegenden Nordportale des Tunnels Coschütz befinden sich in wesentlich flacheren Hängen. Nach dem Aushub einer mehrere Meter dicken Abraumhalde begann der Tunnelausbruch der östlichen Röhre asymmetrisch mit einer Luftbogenstrecke in einer spitzwinklig zur Vortriebsrichtung streichenden, 30° mit dem Vortrieb steigenden Felsfläche, ebenfalls ohne Voreinschnitt. Wegen der flachen Neigung der Böschung war der Tunnelquerschnitt erst nach 30 m vollständig überdeckt. Für den Vortrieb der westlichen Tunnelröhre mussten erst eine zwischen den Röhren vorhandene Felsnase teilweise abgetragen, die westlich anschließende zurückspringende Felswand vertikal gestellt und gesichert und Felsaushub in der rechten Flanke getätigt werden. Der damit entstehende Voreinschnitt wurde so kurz wie möglich und ohne seitliche Arbeitsräume ausgeführt. Die Sicherung der Böschungen erfolgte mit bewehrtem Spritzbeton und Felsnägeln. Wegen des geringen Abstands der beiden Röhren wurden die unteren Lagen der radialen Ausbruchsicherung durchgeankert. Der Tunnelvortrieb begann im Schutz eines geankerten Portalkranzes und ebenfalls von einer Luftbogenstrecke aus.

Jan 1, 2003

By Vladimiros G. Papangelakis

During the past five years, chemical modelling work at the University of Toronto has elucidated the role of soluble magnesium on the autoclave acidity and has demonstrated why feeds rich in magnesium, and other divalent metals, require more than the stoichiometric requirements in acid to produce a leaching performance comparable to that of low magnesium feeds. This understanding has allowed the calculation of acid additions to the pressure acid leach (PAL) on a less empirical basis. Optimizing acid additions to the PAL confers savings in neutralization costs, ensures high productivity and minimises corrosion problems. Hence, our picture of the solution chemistry inside the autoclave during the PAL process has been substantially improved and is reviewed here. Experimental techniques based on solubility and direct acidity measurements that support the theoretical predictions are presented. Concepts of chemical modelling of electrolyte systems at high temperature and software issues are also discussed. Finally, a better understanding of the solution chemistry at temperature has led to better kinetics models because all metal dissolution and precipitation reactions are acid driven and controlled. . Therefore, reactor modelling efforts by our group are also presented and a reactor model with very good performance, as compared to pilot-plant data, is also made here. Finally, in spite of the above success in PAL solution chemistry and reactor modelling, significant challenges lie ahead in theoretical data gaps and instrumentation; these are also discussed in this paper. Keywords: Laterites, process modelling, pressure acid leach, solution chemistry, chemical modelling, reactor simulation

Jan 1, 2004

Knowledge of true block grades is obtained from a mathematical model of an orebody, simulated with sample grades normally distributed and spatially correlated according io a spherical semi-variogram model.The superiority of kriging to the polygonal method of estimation is demonstrated on this modelled deposit by comparing the true values with the kriged and polygonal estimates obtained from sampling the deposit. Finally, selection of blocks of the deposit on the basis of the estimated values, shows that if kriging is used, what is predicted is largely mined, whilst if the polygonal method is used large biases can occur depending on the position of the cut-off grade.

Jan 1, 1978

By H. E. Powell

A laboratory investigation was conducted by the Bureau of Mines to study the magnetic characteristics and to measure the magnetic susceptibility of the mineral siderite. All susceptibility measurements were made by the method of Gouy on powdered samples and at room temperature. Specific susceptibilities of samples from 15 different locations, domestic and foreign, were determined. Values ranged from 66 to 103 (10-6) cgs electromagnetic units. The relation of susceptibility to mineral composition is discussed in this report. The specific susceptibilities of 76 minerals are tabulated in an appendix.

Jan 1, 1963

By V. A. Danielson

The Bureau of Mines examined sources, consumption, and movement of iron and steel scrap in the southeastern States--Alabama, Florida, Georgia, Kentucky, North Carolina, South Carolina, and Tennessee. Officials of the scrap-processing and scrap-consuming industries were interviewed, data was obtained from the published literature, and a canvass was made by the Bureau of scrap consumers. The Southeast generated excess scrap which was shipped to domestic and foreign consumers in about equal proportion. Total 1963 demand in the Southeast was 3,336,000 net tons, of which purchased scrap was 75 percent, foreign exports 13 percent, and domestic exports 12 percent. Alabama, with 47 percent of the purchased scrap consumption in 1963, was the most important scrap-consuming State, and Kentucky, with 34 percent, was the second most important one. Southeast demand was 4.8 per-cent of the total U.S. demand. Projected 1980 consumption is 8,340,000 tons. Scrap prices showed a slight downward trend for the period 1953-63, although gross consumption increased slightly. A significant trend in processing scrap in the Southeast is the preparation of smaller bundles or "briquettes" weighing from 75 to 150 pounds, which are easier for consumers to handle and inspect. Another significant development is the "shredding" of automobile scrap which produces a dense, clean scrap especially desirable for use in electric furnaces.

Jan 1, 1967

By A. Visnapuu

The Bureau of Mines, as a part of its goal to minimize occupational hazards associated with mining and mineral processing operations, has developed and field tested a compact exhaust air muffler for mechanized, jumbo-mounted pneumatic rock drills. The muffler is constructed of 1/8-inch sheet steel and has nominal dimensions of 1-3/4 by 9 by 13 inches. A directed air passage, flexible neoprene baffles, and an expandable slit-type outlet are incorporated to reduce drill exhaust air noise and eliminate muffler icing. Field tests in actual mining operations showed a l5-dbA reduction in exhaust noise and an 8-to 12-dbA reduction in overall drilling noise with no icing problems or decrease in drill performance. Data are presented on muffler construction, laboratory, and field test results.

Jan 1, 1979

By Karl Dufresne

Blasting in geothermally high temperature ground and/or extremely reactive ground is an increasing common challenge for surface and underground mines. Many current PETN based non-electric and electronic detonators have manufacturer published in-hole temperature limits ranging from 55°C to 65°C (131°F to 150°F) and prescribed in-hole residence times on the order of days. When confronting blasthole temperatures above the manufacturer published limits, operations may request site-specific guidance and qualification for use. The advised safe loading window for in-hole PETN based detonators is often too short to be practicable for production blasting. To overcome limitations of PETN based initiation systems, surface mines with high temperature ground and/or reactive ground are known to load blastholes with a qualified high temperature bulk emulsion that are top primed with a cartridge of temperature qualified detonator sensitive emulsion plus an RDX detonating cord downline. As there is no in-hole delay detonator in this system, blasthole timing is accomplished with surface delays. Although this system is safe, top priming and surface delaying does influence floor quality and top size fragmentation, and safe loading windows times reduce blast block size and increase blasting frequency. The DynaEnergetics IGNEO high temperature electronic initiation system is rated for in-hole use in ground up to 150°C (302°F) for 48 hours. The detonator consists of a high strength detonator with an HMX base charge and thermally resistant downline. To make up a primer, the detonator is inserted into a booster charge assembly that is fitted with a small HMX shape charge. This high energy primer is designed to be compatible and reliable for firing bulk emulsions, including those with high percentages of urea inhibition to combat reactive ground. Up to 1000 detonators may be programmed in 1ms increments up to 1500ms. The system is controlled by a digital firing panel that can be used with either a wired or wireless trigger. The system enables high temperature and/or reactive ground sites to utilize in-hole delay initiation and realize the associated performance benefits. An underground mine in Western USA has several areas in their development heading with very high temperature, in view of this, they decided to use the IGNEO detonators in order to evaluate the effectiveness and performance of the system.

Jan 21, 2025

By Jack C. Haptonstall

Abstract-Minas de San Luis, S.A. operates the old Tayoltita mine located in the Sierra Madre Occidental in Durango, Mexico. Yearly production is 55 000 kg (1.7 million troy ox) of silver and 1000 kg (31,000 troy ox) of gold from milling 165 000 t/y (181,900 stpy) obtained from fissure veins. A 4.4 km (2.75 miles) adit, to intersect the veins below existing workings, was completed in 1974. The adit and ancillary projects facilitated extensive mechanization of the mine, ramp development of it, integration of duplicate facilities and elimination of obsolete facilities. It provided a deep-level access for exploration and development of the veins, and resulted in a 25% increase in production with the same labor force. The cost of the in-house financed project was $3.4 million.

Jan 2, 1978

By A. D. Walters

"IntroductionScreens are used in coal preparation plants for four basic functions, namely:I. Scalping off large size run-of-mine coal for initial size reduction;2. Sizing of coal treatment in different process streams;3. Removal of magnetite (dense medium) from clean coal and refuse;4. Dewatering.Canadian coal preparation plants use screens extensively in the above functions. Even plants where no beneficiation takes place, screening and crushing are carried out in the size reduction process.Description of Process UnitsThe type of screen used in coal preparation plants generally falls into the following categories:Fixed Screens and Grizzlies (for large coal)Often a simple rugged construction, either set horizontally above a bin or inclined with the coal flow.Fixed Sieves (for fine coal)They are used for dewatering and/ or size separation of slurried coal or discard. The sieve bend, the Vor-Siv, the Wilmot riffle and the cross flow screen fall into this category. The most commonly used in coal preparation plants is the sieve bend, Figure 1. Coal slurry is fed tangentially onto a fixed curve wedge wire screen deck. The solids are separated at a predetermined particle size, delivering a partially dewatered overproduct and a dilute underflow. The coal slurry is initially delivered to the sieve bend via a feed box. A series of baffles spreads the feed evenly across the width of the deck. The slurry drops from the last baffle, passes through the feed spout and is fed tangentially to the screen. It is important that the feed should contact the surface immediately at the front end of the sieve bend. It is possible to lose as much as 250Jo of screening area with a poorly fitted screen box.The full stream of coal slurry flowing over the sieve bend decreases in depth, in increments of approximately •;4 the slot width each time it passes a slot. Sieve bends make a size separation at 112 to 2h the slot width. This feature virtually eliminates blinding of the screen surface. Slot sizes are normally quoted in millimetres, available standard slot sizes are from 2 mm to 0.125 mm. The sieve bend is also widely used in coal preparation for preliminary dewatering."

Jan 1, 1989

By A. P. Gize, J. F. W. Bowles, D. J. Vaughan, S. J. Norris

Paper presented at the IAGOD international symposium on mineralization related to mafic and ultramafic rocks held in Orleans, France, 1-3 September 1993. Geological evidence from tropical laterites indicates clearly that platinum group metals are taken into solution and precipitated to form grains larger than those in the source rocks. Platinum and palladium move differentially in the surface environment, with Pt partitioning into soils and eluvial or alluvial deposits while Pd remains more mobile in natural waters. Natural organic acids, particularly humic acid, can interact with platinum-group elements and concentrate them even in areas where their content in rocks is very low. Experimental work has confirmed that Pt and Pd can be taken into solution by humic acid at room temperature and in geologically short time-spans. Solubility and deposition may be controlled by physicochemical conditions, reaction kinetics or an adsorption effect, or there may be two competing reactions, solubilisation assisted by organic matter and a kinetically slower metal precipitation

Apr 1, 1994

By Ginger S. Evans

This report documents a preliminary hydrologic investigation of an area where longwall mining methods are to be used. The scope of work includes: determination of physical and chemical characteristics of major soil types in the area; determination of physical and chemical properties of surface water bodies; collection of geologic characteristics, including stratigraphy, structure, and detailed aquifer descriptions; collection of 10 years' meteorological data and installation of a weather station; and a detailed ground-water investigation that includes completion of observation wells, aquifer testing, water quality sampling, and analysis using a 3-D computer model. The Trescott model developed by USGS was used to simulate steady-state aquifer conditions. Input data from 8 multiple-completion monitor wells were used to model an area of approximately 10 square miles. Two layers, coal and overburden, were simulated, both confined. Model results showed good agreement with know piezometric data, desaturated areas, and flow from springs. The study area was found to have very low-yield bedrock aquifers with transmissivities ranging from 5 to 320 ft2/day for the coal (depths from 500 to 1,200 ft) and from 499 to 576 ft2/day and fractured sandstone units (depths less than 100 ft). Annual precipitation and recharge are very low, 10 to 11 inches and 0.25 inch respectively. The area has very high relief and large areas of rock outcrop. No perennial streams are present on the site.

Jan 1, 1983

By G. A. Beiswenger

The application of the law of supply and demand to the sale of crude oil is generally conceded, but the motives underlying the buyer's (refiner's) demands are not always obvious to the seller (producer). In some cases this obscurity has led to the conclusion that the refiner may be unnecessarily particular when he selects one crude and rejects another. This preference, however, is very largely the reflection of the refiner's product demands and the quality of the stocks obtainable from the selected crude. The purpose of this paper is to point out critical characteristics of the major classes of refined products and to show how crudes vary in their suitability for such products. With relatively few exceptions, available processing methods and addition agents make it theoretically possible to produce any type of refined product from any crude source, although it may not be economi-cally sound to do so. The widespread application of thermal cracking for converting higher boiling stocks into gasoline is well known. More recently cracking and refining in the presence of catalysts9 have been developed, as well as various processes for polymerizing lighter hydro-carbons into gasolines having desirable characteristics.6 For several years, selective solvents have been applied commercially to refining inferior quality kerosene, Diesel fuel and lubricating oil distillates .3 Improved methods for refining lubricating oils from crude residua,4 formerly suitable only for fuel, are now in use and a number of special solvent processes are available for dewaxing lubricating oils to low pour point.5 These improved refining methods have been developed not only to meet the demand for improved product quality but also to enable the refiner to obtain quality products from crude sources that would not yield such products by the older refining methods. In many cases, the utilization of these modern refining tools necessi-tates an appreciable expenditure for equipment as well as added manufac-turing costs, and their application therefore must be justified economically. Despite the availability of such tools, the added processing costs involved and yields obtainable may render their application entirely impractical. To illustrate this point, inspections of typical cuts from various crudes

Jan 1, 1940

By P. A. Rusin

Many manganiferous silver deposits remain undeveloped because standard chemical extraction methods yield poor recoveries or are ' environmentally unacceptable. Biotreatment of such ore deposits in our laboratory resulted in manganese and silver recoveries of greater than 90%. Ore and sediment samples were collected from mining sites in Colorado and Arizona. Portions of samples were incubated in a semi-solid mineral salts medium amended with 20 mM glucose mid manganese dioxide (Mn medium). The cultures were incubated at 3(fC until manganese reduction was detected by a .color change fr:om .black to clear. Bacteria from these cultures were purified on Tryptic Soy Agar and individual isolates were retested for Mn reduction by an agar overlay method. Bacteria were identified according to Bergefs Manual ?of Systematic . Bacteriology. Most of the Mn-reducing bacteria are Bacillus species. Bacterial manganese reduction kinetic experiments were performed in 52 ml mineral salts broth supplemented with manganiferous silver ore instead of manganese dioiide. These cultures were incubated with agitation for 16 d. Aliquots were removed periodically and analyzed for solubilized manganese by atoniic absorption (AA). Cyanide (1,0 M) Vias added to the remaining ore-medium mixture for a 24 h bottle roll. The supernatant was analyzed for soluble silver by AA. Similar experiments were conducted on a larger scale using 15% pulp density. After bfotreatment of the ore, standard bottle rolls were performed. The pregnant solutions and the residues were analyzed for manganese and silver?using AA or fire assay as appropriate. In sterile. controls-which received no biotreatment, manganese and silver recoveries were 0.3% and 10% respectively; During biotreatment, total manganese solubilizatiori was as high as 99.8%. The reduced manganese could . be stripped from ?the growth medium using hydrometallurgical techniques. Silver recovery vaned from 70% to 92.5%. Microbial treatment of refractory mangairlferous ores can result in high recoveries of manganese and silver. Retention time varies depending upon the relative concentrations of manganese, silver, and other metals in the ore with only two days required in some cases, The biotreatment of ore is environmentally' acceptable while the use. of chemicals such as sulfur dioxide is less so.

Jan 1, 1991

By James Weaver

During the past 16 years, the authors have successfully used high-capacity rock anchors installed inside open-ended pipe piles, driven to bedrock, to provide uplift and overturning resistance for various structures including piers, bridges, power plant components and commercial buildings. These systems were ultimately used on the projects due to a combination of high uplift forces or overturning moments on the structures and the relatively poor subsurface conditions present at the sites. Other, foundation systems such as rock-socketed drilled shafts and spin fin piles were considered but were found to be economically prohibitive or not technically feasible.

Jan 1, 2011

By Yinan Zhang, Yi Luo

The widely used R70 method is modified to measure the self-heating propensity of low-rank coals. This modified R70 method enables the introduction of controlled amount of moist oxygen into the reaction vessel. Three coal lumps were collected from three different locations in a surface mine in the Powder River Basin. The coal samples were tested in oxygen flow with controlled moisture content under adiabatic condition. By measuring the relative humidity at the exhaust exit point of the testing setup, the flux and cumulative wetting heat that is consumed by coal samples can be determined. Through a better way of determining the coal’s specific heat, the total heat, including heat of wetting and coal’s oxidation heat, required to raise coal to a given temperature can be determined. Then, the contribution of heat of wetting at the different stages of the testing is quantified. The effects of evaporative heat through a group of tests have also been quantified. From this research, a better understanding of the effect of wetting heat on inducing low-rank coal’s spontaneous combustion can be acquired.

Nov 30, 2022

By Marco Antonio Falquete

A novel spark-generating tube, containing no explosive in its composition, is evaluated and compared with conventional shock tube. The product overcomes a series of problems found in conventional shock tube technology. The technologic development had multiple aims: to avoid transport and storage costs associated with explosives, to be more environmental-friendly, to obtain a high-velocity, hightemperature spark whose thermal performance could overcome poor heat transfer to the delay charge by gas convection at shock tube end, and that could cross barriers such as tight kinks, close knots, cuts, extreme environmental conditions, and long-term hot explosive emulsion exposure. The product of this development is evaluated and compared with conventional shock tube in a series of aspects and performance tests, including spark thermal performance (ignition of tougher, low sensitive delay columns, spark gap test), propagation in critical conditions of use (kinks, knots, cuttings), extreme environmental conditions (long-term exposure to hot emulsion explosive, extremes of cold, heat, moisture, underwater exposure), safety features (ignition through flame, open fire), and security against terrorist acts. Due to the safe characteristics of the tube, a series of demonstrations will be performed during the presentation. In nearly all tests and aspects, the spark-generating tube exceeds conventional shock tube, and in the rest equals shock tube, making it a more reliable alternative.

Jan 1, 2005

By Paul Grady, Martin Froehling, Curtis Mohns, Eliab Roman

"Since the idea of processing rock to unlock the valuable minerals inside was put into practice, efforts to improve production began. Methods have been learned that allow for operation in environments and under circumstances where it would not have been possible until now. All existing operations have experienced at least some form of productivity improvement measures. The objective is simple: generate more product of better quality in less time and at lower unit cost. Since the year 2000, various modifications have been made at the Kemess Concentrator in efforts to improve productivity. The following is a discussion of these modifications and their contributions to the success of the operation.INTRODUCTIONThe Kemess South Mine, a major producer of gold and copper, is located in north-central British Columbia. Kemess was brought into production in May 1998 by Royal Oak Mines with a modern mill controlled by a fully integrated Foxboro IA DCS system and employing 134 people. On February 11, 2000 Northgate Exploration Limited (now Northgate Minerals Corporation) acquired Kemess Mine from receivership. Since acquisition in 2000, Kemess has seen many accomplishments, including the reduction of costs by 40% site wide.The mill has a nameplate capacity of approximately 56,000 tonnes per day which is processed through a Metso (Svedala) 60” x 89” Primary Gyratory Crusher and then conveyed by a 60” conveyor to a stockpile with 48 hours of total storage capacity. The nominal minus 6” rock from the stockpile is fed to two parallel grinding circuits (A & B). Each section consists of a 10.4 m F x 4.7 m SAG mill with dual drive motors (4,480 kW apiece) discharging onto a 2.4 m x 7.3 m Metso (Svedala) single deck vibrating screen to remove the coarse material for recycle to the SAG mill by a Continental 45º high angle sandwich conveyor. Screen undersize is pumped along with ball mill discharge to a cyclopac consisting of twelve Krebs 66 cm F cyclones to classify flotation feed to a size of approximately 65% minus 200 mesh. Cyclone underflow feeds a Metso (Svedala) 6.8 m F x 11.0 m ball mill, also with dual drive motors (4,480 kW apiece). The primary grinding circuit has 35,840 kW available for grinding."

Jan 1, 2005