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By A. L. Mackie

Mine water from base metal mines is generally characterized as having high concentrations of heavy metals and low pH, resulting in the need for treatment prior to discharge to receiving waters. In this study, two high-rate clarification processes were evaluated at bench-scale: the high density sludge (HDS) process and sand-ballasted flocculation. High-rate clarification processes generate larger, denser flocs which settle more quickly than those formed in conventional flocculation processes. The HDS process uses recirculated sludge in order to seed floc formation, whereas ballasted flocculation uses microsand. Both of these high-rate processes require the addition of quicklime or hydrated lime to increase pH and allow for the formation of insoluble metal hydroxides, which can then be removed in the clarification stage. Previous research has shown that cement kiln dust (CKD) can effectively replace quicklime in conventional sedimentation processes for metals and acidity reduction to meet discharge guidelines (Mackie & Walsh 2012). CKD is an alkaline by-product of cement manufacture that has fine particle sizes and varying free lime concentrations depending on the manufacturing process. The lower solubility (i.e., free lime content) of CKD requires larger doses of material to be added to reach treatment pH targets for metals precipitation. The purpose of this study was to evaluate the treatment efficacy of high-rate clarification processes for mine water treatment, compared with conventional sedimentation, at bench-scale with conventional (i.e., lime) and novel (i.e., CKD) pH adjustment additives. Results of the study showed that all treatment processes (i.e., HDS, ballasted flocculation, and conventional sedimentation) were able to reduce target metal concentrations to well below Canadian guidelines (i.e., total zinc and total nickel < 0.5 mg/L, total copper < 0.3 mg/L) using either CKD or lime. Additionally, mine water samples treated with CKD generated lower sludge volumes than those treated with lime (i.e., 50 versus 100 mL for conventional sedimentation and 100 versus 200 mL for HDS) even with increased concentrations of solids introduced during treatment. This is most likely due to slower neutralization rates when using CKD, due to its lower solubility, as well as finer particle size. The sand-ballasted flocculation process was able to reduce final turbidity in CKD-treated samples while the HDS process did not when compared to conventional sedimentation, making the ballasted flocculation process preferable for reducing final solids concentrations in CKD-treated mine water.

Aug 1, 2013

By J. P. Germiquet

"Rock properties have a material impact on mining processes, including drilling performance. An investigation using point loaded index (PLI) data converted to uniaxial compressive strength (UCS) has revealed that a direct relationship between grain size and UCS exists at Mogalakwena Mine. This correlation is best seen in unaltered rock, with lower correlations for altered rock types. Measurements from the new RockMa system installed on drill rigs can be used to obtain rock strength data to validate the current rock strength domains and create additional data for the next benches below. An investigation of penetration rates in different lithologies shows that rock composition plays an important role in determining drill performance. Additionally, there is an inverse relationship between rock strength and drilling penetration rate – a measure of how efficiently a hole is drilled.The domaining of grain-size-adjusted UCS at Mogalakwena Mine will allow more accurate scheduling of drill rigs through increased knowledge of rock strength in various areas. Successful rock strength domaining has the potential to be incorporated into blast indexing and predicting crushing/milling performance.IntroductionThe optimization of mining and processing through geometallurgical characterization of ore are key drivers of value realization (Deutch, 2013). Rock strength is one such property and is affected by, among other variables, composition, texture, and grain size (Ozturk, Nasuf, and Kahraman, 2014). Mogalakwena Mine is exploiting the intrusive Platreef PGE (platinum group element)-bearing orebody which forms part of the northern limb of the Bushveld Complex. This complex orebody exhibits areas of metasomatic alteration, metamorphism, and sporadic mineralization of the footwall and hangingwall (Nex et al., 2006). Understanding this variability is paramount due to the implications for rock strength and hardness, which in turn affect crushing, milling, and liberation efficiency. These variables must be known prior to blasting in order to optimize mine and plant processes using in-situ variables. This necessitates predictive modelling (Deutch, 2013). Geological and geotechnical data was sourced from the Overysel (OY) exploration database for the study. Point load testing was done for each borehole and the results converted to uniaxial compressive strength (UCS) (Akram and Bakar, 2007). The relationship of lithology, texture, and grain size with UCS revealed an inverse relationship between grain size and UCS in unaltered rock. The relationship was not present in altered rock types. A comparison of mean strength and hardness results indicated that Bond work index and UCS may be related. Drilling performance is affected by UCS (Bourgoyne et al., 1986), and this was proven using recent measurements obtained during drilling. Lastly, grain-sizeadjusted UCS values were applied to a 3D model for the OY property."

Jan 1, 2016

By David J. T. Carson

"The metalliferous deposits of Vancouver Island have generally been assigned to the Mesozoic ""Coast Range Orogeny."" However, a metallogenic study by the writer has revealed that several important classes are early or middle Tertiary. Included are porphyry coppers, and gold-quartz, arsenic and copper-arsenic veins.The porphyry coppers and many gold-quartz veins are within and adjacent to Oligocene-Eocene quartz diorite intrusive complexes. Arsenic and copper-arsenic veins have a close spatial relationship to sills and laccoliths of Oligocene dacite porphyry which intrude the late Cretaceous Nanaimo Group.Other deposits of demonstrable Tertiary age include a molybdenum stockwork related to a relatively potassic Eocene plug and a few small copper-skarn occurrences. Some copper stockworks and a mercury deposit are probably also Tertiary.The copper deposits of previously recognized Tertiary age are those of the Sooke area that occur in Eocene basalts and Oligocene gabbros."

Jan 1, 1969

By Maurício Covcevich Bagatini, Maycon Athayde

Water consumption reduction in pellet feed operation is of paramount importance. Compared with traditional ball mills, high-pressure grinding rolls (HPGR) play an important role in Blaine surface area (BSA) generation to improve agglomeration properties, although stability is still a challenge. Grindability improvement of existing operation has a direct impact on the performance of the filtering and pelletizing operation. The results of this study, as a pregrinding operation, can be applied not only in new operations but also in existing ones, helping the operator control process variation in a more effective way while ore hardness increases. 

By Cary Hirner, David Stacey, William A. Rochford

Design considerations and construction techniques were implemented to address groundwater infiltration from a confined aquifer during the excavation and lining of the Cady Marsh Flood Relief Tunnel. This 3-m finished diameter, 2-km long tunnel was successfully completed cost-effectively in an urban setting near East Chicago, Indiana. The soft ground was mined using a conventional tunnel boring machine with hydraulically actuated flood doors and supported with steel ribs and timber lagging. The tunnel was lined with cast-in-place concrete. Dewatering was implemented in settlement prone, boulder-laden ground in residential neighborhoods during construction to depressurize and partially dewater the aquifer at the tunnel horizon. This paper describes the design decisions and construction methods utilized to mitigate and limit infiltration into the tunnel during construction and operation, as well as manage ground settlement.

Jan 1, 2007

By C. Bailey Williams

Aragonite "sand," an oolitic lime-stone, is distributed throughout the Bahamas on the Grand Bahama Bank, adjacent to Southeast Florida. Bahamian deposits hold 75-100 billion tons of recoverable Aragonite. Aragonite&apos;s precipitation from seawater over 700 years ago assures low contaminates, making it a pure material for such industries as cement, glass, etc. A 90-acre, man-made production island was built south of Bimini, adjacent to ocean shipping channels mining is by cutterhead, suction dredge, dewatering, and stockpiling for further drainage and shipping. Aragonite is transferred to the U. S. East and Gulf Coasts via bulk carriers to points of sale.

Jan 1, 1978

By J. C. Franklin

A data-acquisition system was designed by the Bureau of Mines to monitor five detectors with radon continuously flowing through each. These detectors could be monitored up to 12 times an hour, but were only monitored according to a preset time, thus allowing radon to be monitored continuously in a uranium mine. The counter can be set to monitor each detector for any period of time up to 16.5 minutes. This allows very low concentrations to be monitored longer to reduce statistical error. There would be no upper limit in radon concentration that could be monitored, but there would be a lower limit of 50 picocuries per liter (pCi/l). Each detector was cylibrated in the laboratory by the Lucas flask method. Multiple samples were taken at two different concentrations, and the correction factor for each detector was determined by a least squares fit of the data. To verify the calibrations, a series of measurements at several concentrations were made against a constant source. Our agreement at low radon concentrations (300 pCi/i) with the two-filter method as within 3 percent; thus, the total error would be this difference plus the two-filter error. At high concentrations the coefficient of variation ranged between 2.1 and 9.8 percent for the five different detector units.

Jan 1, 1976

By Iain M. Mason

Linear meridional zones of bad roof conditions have been frequently encountered in producing collieries working the Permian age Lithgow seam in the western coalfield of New South Wales. The prediction of such zones ahead of mining is desirable for reasons of both safety and economics. In March, 1981, we carried out an experimental, three-component in-seam seismic survey at Invincible Colliery to discover whether such zones have any unambiguous seismic effect. The underground survey was the first of its kind to be attempted in an Australian mine. The data quality was excellent with the spectra broadband and clear. Polarisation analysis disclosed two modes: one compressional; the other shear horizontal. The SH model was clearly dispersive and well gound to the plane of the seam. Modal velocities decreased by up to 15% at the fracture-swarm site. There is a strong suggestion on the RLS maps obtained here that the distributed fault zone is acting as a composite scatterer of channel waves. The P-SV and SH wave tomograms obtained show, in a general way, the distribution of stress in the coal panel.

Jan 1, 1982

By J. P. D. Strydom

The transmission of excessive vibration to the human body can cause physical stress that may result in crippling pain or permanent disability. Rock drills are known to transmit high levels of vibration that are difficult to attenuate through conventional approaches to vibration isolation. However, it can be shown that once the ISO frequency weighting has been applied, most of the vibratory effect of the rock drill?s motion is concentrated at the drill?s operating frequency. This observation opens the way for utilizing a concept known as vibration absorption, aimed at attenuating the rock drill?s vibration. In essence this entails using the inertia of a secondary vibratory system to counteract the motion of the handle. This article documents an investigation into the use of such an absorber for attenuating rock drill vibration and demonstrates the feasibility of such an approach. A mathematical model of such an absorbing handle was developed and used for design studies. Based on these investigations an experimental prototype model was manufactured and tested. A significant reduction in vibration levels could be achieved.

Jan 1, 2002

By Henry H. Roos

NTRODUCTION In the mining industry, a "drill jumbo" is a drilling unit equipped with one or more rock drills and mounted on a mechanical conveyance. Jumbos range from single¬drill ring drills mounted on simple steel skids to sophisti¬cated multiple-drill units mounted on diesel engine powered carriers and equipped with automatic controls and sound-abatement cabs. Individual types of jumbos usually are designed for specific tasks such as fan drilling in sublevel caving operations. Some units, such as development jumbos, can be utilized for several functions in addition to their normal applications, e.g., for production drilling in room-and-pillar operations, stoping in cut-and-fill mining, etc. Mine operators can purchase individual components from manufacturers, assembling these components into a jumbo suitable for specific conditions. However, this requires that mine personnel have good engineering and mechanical abilities. Although manufacturers of jumbos maintain facilities for designing machines to meet con¬ditions created by new mining methods and unusual ap¬plications, the cost of the engineering and experimental work for new types of jumbos should be evaluated in terms of both costs and benefits; it may be advantageous to plan the mining operation so that existing and proven units can be utilized. GENERAL SELECTION CRITERIA Since the operating conditions vary in underground mines, the design of a jumbo must be selected to cope with the individual characteristics of the mine. The necessary considerations include access space into the working areas, grades expected to be encountered, radii of the curves, ambient temperatures, the characteristics of the rock, the acidity or alkalinity (pH rating) of the mine water, etc. Access to Mine Workings The mine workings must be accessible to the selected jumbo. Frequently, a jumbo must be disassembled at least partially to pass through the mine shafts. There¬fore, a bolted construction allowing disassembly into pieces of suitable size and weight is desirable in most applications. Type of Undercarriage Generally, a crawler-type undercarriage should not be used in trackless mines having acidic mine water. The acidic water causes an electrolytic action between the individual crawler parts and causes rapid corrosion and early failures. Propulsion A two-wheel drive on a pneumatic-tired jumbo is marginal for grades exceeding 12%. A four-wheel drive unit with good weight distribution is capable of operat¬ing on grades of up to 35%. At least 30% of the gross vehicle weight (GVW) should be carried on the steering axle; otherwise, the steering tires may not have sufficient traction on loose road surfaces and may "plow" instead of steer. To assure stable operation in mines with steep grades, the height of the center of gravity of the jumbo should be considered. It should not make the unit prone to rolling over on the steep grades that may be encoun¬tered. Turning Ability In confined working areas, a skid-steering or crawler unit has the best maneuverability. An articulated carrier is preferable when base-rotated parallel booms are being utilized. A rigid-frame jumbo with automotive steering is compact and economical, having lower maintenance requirements than the other two types. However, the turning radius of a rigid-frame unit is wider than either the skid-steering or articulated units, and this wider turning radius may be detrimental in mines with narrow drifts. JUMBO COMPONENTS Rail Undercarriages A mine with a rail-transportation system generally utilizes drill jumbos that are mounted on rail-type under¬carriages. With a light load and good weight distribu¬tion, this carrier may consist of a simple two-axle four-wheel platform onto which the boom-mounting brackets are attached. As the depth of the round and the penetration rates increase, the weight of the equip¬ment installed on the chassis also increases. The greatest problem with a heavy overhung load is balancing the carrier; a three-boom unit may require a substantial amount of counterweighting to maintain an acceptable 70% to 30% axle-load balance. Although lengthening the wheelbase helps balance the unit, a long wheelbase increases the turning radius, often creating problems on curves and sometimes requiring a swivel truck-type chassis. A good rule of thumb for a simple four-wheel undercarriage is to maintain a wheelbase length to track gage-width ratio that does not exceed 2.5 to 1.0. For a larger ratio, a swivel truck should be utilized. Swing-out outriggers or roof jacks help keep a jumbo in place during the drilling cycle. Usually, a rail-mounted jumbo is not self-propelled. Instead, it is maneuvered into place by a locomotive. Occasionally, several headings are being advanced in close proximity, and a self-propelled jumbo is con¬venient. In electrified mines, such a jumbo utilizes conventional battery-powered traction gear; in dieselized mines, hydrostatic drive components offer good flexi¬bility. The tractive power requirements of a typical rail jumbo may be calculated from the formula: HP = [(RR + GR) X Sl/[33,000 X Em X Eh]

Jan 1, 1982

By E Topal

Stopes are used in several underground mining methods. Boundary determination of these stopes is generally based on simple rules of thumb. While several stope boundary optimisation techniques are available, they fail to guarantee true optimum results. The first part of this paper reviews some important stope boundary optimisation studies and proposes a new algorithm to optimise stope boundaries and layouts for underground operations. The second part applies the proposed algorithm to a block model to test its ability to produce optimum results and demonstrate its applicability in a number of different scenarios. The results demonstrate that the proposed algorithm can find optimum stope boundaries and layouts in three dimensions for different stope sizes and economic conditions.

Jan 1, 2009

By Terry R. Neumann

During 1984, at the request of the U. S. Bureau of Land Management, U.S. Bureau of Mines personnel conducted a mineral survey of the 28,600-acre South Pahroc Range Wilderness Study Area (NV-050-0132). The Wit derness Study Area is located in Lincoln County, NV, about 900 miles north of Las Vegas. Five mineral properties and two mineralized zones were examined during this study; of these, one mineralized zone, two small prospect pits, and part of two claims are within Wilderness Study Area boundaries. Perlite resources were identified in the study area; however, no significant metallic mineral values were noted at any of the sites. The Wilderness Study Area is dominated by a Tertiary volcanic sequence consisting of an interlayered series of tuffs containing thin beds of volcanic pebble gravel, sandstone, and perlite. At the base of the exposed volcanic section, perlite occurs along a 2.4-mile-long zone that parallel s the study area&apos;s northeastern boundary. The perlite is suitable for filtration, insulation, and soil conditioning purposes, Because of prohibitive operation and transportation costs, the estimated 6 million tons of perlite occurring inside the South Pahroc Range Wilderness Study Area are classified as an indicated subeconomic resource.

Jan 1, 1986

By M. J. Hordon

Measurements of the 103 yield stress of ordered and disordered poly crystalline Cu ,Au were related to the ordered antiphase domain size determined by resistivity measurements. For undeformed material, a yield stress maximum wa obtained at a critical domain diameter of about 40A. Plastic deformation resulted in a marked increase in the yield stress and electrical resistivity of the ordered alloy compared to the disordered, the strain hardening rate increasing regularly with initial antiphase domain size. Order hardening was accompanied by a sharp reduction in size of the initially large domains. It has been observed that the yield stress of ordered and partially ordered Cu3Au alloy varies sensitively with antiphase domain size aid degree of order.ly2 In addition, ordering of the lattice leads to a marked increase in the strain hardening rate (order hardening) as compared to the rate for the disordered alloy. In the present investigation, changes in the electrical resistivity and yield stress of ordered polycrystalline Cudu with varying initial domain diameters were measured after tensile plastic deformation in order to examine the effect of cold work on the antiphase domain size. EXPERIMENTAL PROCEDURE Au-Cu alloy of 99.99 pct purity analyzing 50.85 wt pct Au-balance copper was obtained from the Handy-Harmon Co., N. Y., in the form of 0.061 in. diam drawn wire. Wire specimens 3 in. in length were given the following annealing treatment in nitrogen: 500" for 72 hr, 820" for 15 hr, and 450" for 5 hr, followed by a water quench. The annealing sequence resulted in a completely disordered structure with a grain size of about 0.2 mm. The disordered specimens were then reannealed at 360&apos; in nitrogen for periods varying from 10 min to 150 hr followed by quenching to produce ordered structures with varying domain sizes. The degree of ordering and variation of domain size was followed by electrical resistivity measurements made at room temperature using a low resistance precision Kelvin double bridge apparatus. The specimen resistance was determined over a length of 4.0 cm between two brass knife-edge contacts while the specimen was immersed in an oil bath to minimize temperature variations. In addition, the current flow in the circuit was minimized by a current pulse technique in balancing the bridge in order to avoid heating the specimen. Using a sensitive galvanometer to detect the bridge null, the accuracy of the resistance measurement Wire specimens were plastically strained in tension with an Instron tensile unit at strain rates in the range 5 x 10"5 sec-&apos; to 2 x 10"4 sec-&apos;. Stress and extension data were fed into the Instron chart drive amplifier to obtain the actual stress-elongation curve from which the yield stress at 10"3 strain was determined. The maximum resolution of the apparatus was approximately 50 psi stress and 3 x 104 strain. At various plastic strain levels, deformation was interrupted and the electrical resistivity determined after removing the stress. RESULTS AND DISCUSSION 1) Yield Strength of Ordered Cudu. In order to determine the effect of the ordered antiphase domains on the initial yield stress, specimens were prepared with varying domain sizes ranging from zero for 5 completely disordered structure to about lo5A for a completely ordered structure by suitable annealing treatment. Domain sizes were estimated by comparing room temperature electrical resistivity data with the original data of Jones and sykes3 as modified by rdle.&apos; In agreement with previous work, the resistivity varied sensitively with domain diameter and degree of order, decreasing from approximately 11.6 x l0- ohm-cm for the disordered structure to about 5.9 x l0- ohm-cm for ordered domains above 10"3 cm in diameter. Fig. 1 shows the change of the 103 yield stress with ordered domain size. It is evident that the maximum

Jan 1, 1963

By John B. Cocanour

The U.S. Bureau of Mines (USBM) has developed a laboratory-scale on-line analysis and process control system for a decopperization electrolytic circuit. This system is software driven, running on a 486DX-33 personal computer (PC) utilizing a portable energy- dispersive x-ray fluorescence (XRF) spectrometer as the sample analyzer. The XRF copper reading obtained was used as the control variable through an RS-232 serial interface to the PC for software-based control of feed flowrates. When the copper concentration in the electrolytic cell (as measured by the XRF) deviated from the set point, the feed flowrate to the cell was automatically altered using software-based proportional-integral-differential (PID) computer control to yield the desired copper concentration at the electrolytic cell outlet.

Jan 1, 1994

By R. Abela

In over ninety per cent of mineral sand plants, the most commonly used equipment is the spiral concentrator. The tonnage treated over typical spiral plants can range from as low as 200 ton per hour up to 6 000 tons per hour. Due to the limited capacity of each spiral, plants consist of multiple spirals assembled into banks. The mixture of minerals present in the sand feed requires several spiral stages to achieve the desired mineral recovery. Due to the complexity of the spiral circuits, there are always some design and operating problems that present themselves in plants. These range from slurry distribution, spirals operating at incorrect design parameters and feed variations. The material being treated is difficult to maintain in suspension due to its high density, resulting in segregation and preferential flow in pipelines, distributors and sumps. The objective of this paper is to highlight common problems associated with spiral installations to designers and operators of plants. Practical solutions are recommended in order to prevent and minimize these mistakes in the design. These solutions may be used to improve performance on operating plants.

Jan 1, 2003

By S. N. Monteiro, C. M. F. Vieira, M. M. Ribeiro

"This work has as its objective to evaluate the effect of incorporation of the powder waste retained in the eletrostatic precipitator of the sintering stage from an integrated steel making plant on the physical and mechanical properties of a red ceramic. Formulations were prepared with incorporation of the waste in amounts up to 20 wt.% into a kaolinitic clay. Rectangular specimens were prepared by uniaxial mold-press at 20 MPa and then fired at 750, 900 and 1050°C. The evaluated physical and mechanical properties were: linear shrinkage, water absorption and flexural rupture strength. The results showed that the waste has a potential to be used into red ceramics. The incorporation of the waste enhanced the properties of the ceramic, decreasing the water absorption and increasing the mechanical strength at all investigated temperatures.IntroductionThe sintering stage of an integrated steel-making plant is dedicated to the agglomeration of a mixture of iron ore, coke or coal, fluxes and water [1]. It is a common practice in this stage to use of solid wastes with great amounts of iron in the form of sludge and powder. One of the atmospheric pollutants generated during the sintering process is the particulate material, which is normally retained in an equipment denote as electrostatic precipitator. This equipment retains very small particulates, present in the gaseous emissions by application of an electrical potential difference in between the plates that the fluid is forced to go through. [2]."

Jan 1, 2011

By Jorge Alberto Soares Tenório, Victor Bridi Telles, Denise Crocce Romano Espinosa, Felipe Fardin Grillo, Vicente de Paulo Ferreira Marques Sobrinho, José Roberto de Oliveira

"This research aims to study the process of incorporation of the metal iron in electric arc furnace dust (EAFD), from a steel mill producing long steel by liquid iron in addition to the changing temperature of 1400 degree Celsius altering experimental conditions such as how to add the EAFD (as received and in the form of briquettes), the percentage of EAFD to be added (10, 20 and 30% of initial weight of sample pig iron) and the time of withdrawal of the sample of pig iron and slag (30 minutes after the addition of EAFD). Previously, the EAFD will be characterized using the following techniques: chemical analysis, particle size analysis, X-ray diffraction, scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) microanalysis. After characterization, the eletric arc furnace dust to be added to the bath of liquid iron, will be divided into 2 types: the first order of addition will be in the form ""as received"" from the plant and the second is through the agglomeration of EAFD in the form of briquettes. The achievement of fusion experiments in laboratory scale, will take place in a vertical tubular furnace with temperature control. The fusion experiments to assess the incorporation of the metal iron will use graphite crucibles. A flow of inert gas (argon) will be maintained inside the furnace during the experiments. It is expected that the results obtained at the end of the research allow the evaluation of the iron metal incorporation of eletric arc furnace dust in hot metal bath.IntroductionThe steel industry generates a variety of solid wastes, liquid effluents and gaseous emissions at various stages of processing. The electric furnace dust (EAFD), generated in electric arc furnaces, represents a major problem for their content of chemical elements such as zinc, iron, chromium, cadmium, among others, issued to the atmosphere during the manufacture of steel[1]."

Jan 1, 2012

By T. Braun, J. Parker

On June 25, 1999, BHP Billiton (BHPB) announced the suspension of operations at the BHP Copper Inc.(BHP) San Manuel copper mine in Pinal County, Arizona. Subsequent to this announcement, BHPB aggressively pursued a number of alternatives for the underground mine and open pit facilities, including continued curtailed operations, sale to a qualified mining operator and closure of the property. After consideration of these various alternatives over a 2.5-year period, BHPB announced final closure of the mine site on January 15, 2002.This paper describes how the BHPB charter and HSEC policy apply during the closure process.

Jan 1, 2004

By O. C. Blade

This report on the properties of motor fuels sold through service stations in the United States was made in accordance with a cooperative agreement between the American Petroleum Institute and the Bureau of Mines of the United States Department of the Interior. By agreement with the American Petroleum Institute, identification of the items is confidential. It presents analytical data for 4,954 samples, representing the products of 93 companies. The samples were collected during December 1955, January and February 1956. As in previous surveys, the gasolines covered by this survey include those from both large and small suppliers. The data were obtained by laboratories of various refiners, motor manufacturers, and chemical companies and submitted to the Bureau of Mines for compilation. A list of the National Motor Gasoline Survey reports published during the post 10 years is given on page 5.

Jan 1, 1956

By Chris Brown

"The Island Copper plant was designed and built by Fluor Utah Ltd, in conjunction with Utah design staff, Originally designed to treat 33,000 tons/day (t/d) of ore, the current average milling capability is 38,000 t/d (Nov'74). The first of six semi-autogenous grinding lines was brought on line in October 1971, startup of the remainder being governed by equipment delivery schedules.The summer of 1973 saw the start-up of an additional three ball mills, and attainment of the present production level. The current process flowsheet is shown in simplified form.CRUSHINGThe crushing circuit is relatively simple, comprising single stage crushing of the ore followed by screening to fine and coarse fractions.The crusher is a 54 x 74in. Allis Chalmers Superior Gyratory with a setting of 9-lOin., driven by a 500-hp motor. Trucks dump on three sides of a rectangular dump pocket. An 84in. x 20ft. link belt apron feeder draws crushed ore from a 250-ton surge bin below the crusher, discharging onto a 72in. wide inclined steel cord conveyor belt. A fixed splitter box at the conveyor discharge separates feed to two parallel Jeffreys 6 x 20ft. vibrating grizzlies for screening into +4in. and -4in. fractions. The fractions are collected on short reversible conveyors which feed the coarse and fine ore stacker conveyors. Trippers distribute ore to outside stockpiles adjacent to, and above, the concentrator grinding 'floor."

Jan 1, 1975