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By H. E. Rojas, G. T. Adel

The primary objective of most comminution operations is liberation; however, mill performance is generally quantified in terms of particle size. Only recently has the use of image analysis equipment made it possible to quantify mill performance on the basis of liberation. In this investigation, a series of tests were carried out to study the effect of mill operating parameters on the liberation of sphalerite from a sphalerite/dolomite ore. The parameters studied included mill rotational speed, mill loading and ball size. The results of this work appear to indicate that sphalerite liberation is improved under conditions that promote impact breakage, while dolomite breakage is enhanced under attrition conditions.

Jan 1, 1992

By B. Pregerson, M. Gaft, J. Rabinowitz

The main phosphate minerals, apatite and francolite, are characterized by intensive selective photoluminescence, connected with impurities of Eu2+, Ce3+, V4+, Mn2+ and (UO22+ ). The non-uniform distribution of phosphate minerals in lumps makes photoluminescence sorting possible. As result, an intermediate product is recovered which is enriched by P205 and has relatively small amounts of chert, dolomite, calcite, fluorite, etc. In the case of Zin Phosphate Plant coarse rejects, for example, it is possible to separate a product enriched by francolite, practically free of chert and with a lowered calcite content. This material is suitable for flotation, with a potential 6-7 % increase yield of concentrate.

Jan 1, 1993

By Stuart R. Cotterill, Jack D. Nelmark

Introduction Opencast surface mining requires blasthole drilling to achieve mine planning. No single method of mining is right for all conditions. Occasionally, mine planners introduce a project with little regard to drilling and blasting. These costs are usually a significant percentage of total mine overhead. One drilling and blasting method that can be used to reduce overall mine expense is inclined or angle hole drilling. But inclined-hole drilling will not cut costs unless a set of required circumstances is met. Several conditions of mine design indicate the use of angle drilling. Geotechnical problems must first be analyzed. Primary considerations are safety, fragmentation, production, and maintenance. Secondary considerations are, in some instances, reduction in amount of explosives, which lowers blasting costs; reduction of practical fragmentation beyond blasting pattern limits; and reductions in overall costs due to reduced volume of excavation. Future trends in blasthole drilling may include incorporation of drill equipment designed to allow rapid change from vertical to inclined drilling. This will allow the operator to adapt to changing hole requirements with minimal production loss. Another improvement may be the ability to chamber holes at any elevation throughout the hole depth. This will allow more charge to be placed at strategic locations to improve fragmentation. Merits of Drilling Inclined Holes Drilling is performed to create voids for explosives. It is done either to recover minerals or to excavate a volume of earth. The manner of mining or excavation can greatly affect the economics of the overall project. Many innovations and methods have been tried, but the most practical and economical is still drilling holes and using explosives to fragment the material. To break up the material, the practice has been to place charges within the mass. This is done by drilling holes of a specific diameter and depth into the material. The holes are of such magnitude as to develop sufficient energy to break or loosen this material, providing for easier removal. In general, more open or exposed faces must exist to aid material breakage when blasting. Inclined drilling can be advantageous in open-cut mining with highwall depths of at least 24 m (80 ft). A minimum of two faces are open in open-cut mining and the material can be thrown outward to cover pre-mined volume. This cuts cost by eliminating the need to remove or relocate a large portion of material. Sometimes the material is of such a mass that more energy per unit is required to loosen it than can easily be done by blasting vertically. Inclined holes allow a more uniform loading of drilled holes. The unit of energy is raised, so little or no secondary blasting is required. This usually comes about only if the main plan calls for drilling holes deeper than 24 m (80 ft). For shallow holes, spacing and burden can be made closer to allow sufficient energy to blast the toe. If the open face is in only one

Jan 9, 1984

By A. B. Cortes

This research work discusses the development of a two-dimensional model that represents the flow that occurs in the inlet section of hydrocyclones. The governing equations are the two-dimensional, unsteady, incompressible Navier-Stokes equations in cylindrical polar coordinates with primitive variable formulations. In this approach, no assumptions have been made other than independence in the axial direction. The full two-dimensional Navier-Stokes equation in the r-a plane is used. The commonly used simplifying assumption of axisymmetry is not used. A numerical technique based on a newly developed spectral-difference method is used to solve the equations. The spectral-difference method is a multi-domain, and multi-dimensional extension of the Jacobi polynomial collocation technique. The computational grid for the inlet section is composed of 25 sub-domains which result from five partitions in the angular direction and five partitions in the radial direction. Several test cases are used to validate the appropriateness of the numerical model.

Jan 1, 1995

By J. C. Motz

The advantages of producing a fine mill feed have been recognized for many years. The extent to which fine crushing can be carried out will vary and depends on the ore characteristics, plant and crusher design. Unfortunately, the ore characteristics are generally beyond our control, so the concentration of effort lies primarily on the plant arrangement, equipment design and operation Where fine crushing should stop and grinding begin is controversial and is influenced greatly by personal opinions and experiences. Often, this break point will be different if consideration is being given to a new plant in comparison to a modest expansion. Most new plant designs employ the largest and most efficient equipment. The modification of existing plants becomes more complex because of the space requirements and the related equipment already in operation. Fine crushing is, of course, a relative term. Obtaining a final crusher product of minus 3/4" is commonplace today and can occasionally be obtained in an open circuit final crushing stage.

Jan 1, 1980

By M. M. Fine

Development of a process for winning copper from pelletized chalcocite concentrate without matte smelting and converting is underway at the Twin Cities Metallurgy Research Center, Bureau of Mines. The new route from concentrate to metal includes 2-stage fluid-bed treatment; pelletized concentrate (33 percent Cu, 7 percent S) is first desulfurized (to about 0.5 percent S) in an oxidizing atmosphere, and in the second stage the calcine is metallized by reduction with hydrogen. Thereafter, the reduced product plus 10 percent CaO is routed to a smelting furnace to separate metallic copper from the gangue. Recovery and the Cu content of the product at this point are in the 97-98 percent range. The metal must be refined to remove sulfur and iron to make wirebar copper. An important feature of the process is the pelletizing of the fine concentrate into mini-pellets prior to fluid-bed treatment, which has permitted shorter reaction time, decreased dusting, and facilitated subsequent processing.

Jan 1, 1970

By William J. Wasko

Maintenance of mining equipment has become so complex and important from a cost and product ion standpoint that the organization must be set up in an engineering fashion to be successful. Production costs are greatly affected by proper maintenance. Tonnages can only be met when operating time is at its maximum and breakdown time is at its minimum. Last, but equally important, large capital expenditures must be protected and improved The effectiveness of the maintenance program will, in many respects, be a direct, result of the effort put torch in developing the overall program. Once the need of maintenance is realized, the next step is to determine what the organization should be and what it should accomplish. Follow through is then most vital. Preventing machine breakdowns and reducing maintenance costs are the primary goals of all maintenance organizations. Good preventive maintenance, a system for inspecting equipment and a complete record of inspections will help attain these goals.

Jan 1, 1966

By John B. Squyres

The purpose of this paper is to describe certain features of the uranium deposits of the South San Juan Basin, and to suggest a mode of origin for the deposits which is consistent with the data. A series of photographs is included at the end of the paper to illustrate the nature of the ore bodies. Since the general geology of the Grants Region is well described in the literature, it will be only briefly reviewed, and the time will be spent instead on the morphology, spatial relations, and geochemistry of the ore deposits. Part of this material is original, but data and ideas have been taken from a variety of sources, including the literature and the personnel of the USGS, the AEC, and many of the operating companies of the South San Juan Basin. I gratefully acknowledge these sources. The accuracy of the data and the conclusions presented here are my own responsibility, however.

Jan 1, 1974

By James E. Gingrich

The new Track Etch* technique for uranium exploration has been utilized in several survey programs conducted during the last few years. The results from these programs have been very encouraging, and new uranium ore bodies have been discovered by using this new technique. The Track Etch method is being used in several exploration programs in various locations around the world. The Track Etch exploration technique utilizes small pieces of special radiation-sensitive plastic film to detect the presence of radon gas which is released by uranium ore bodies. Because of the selectivity and sensitivity of the technique, ore bodies not normally detected with other surface or airborne monitoring methods are found. Since no large equipment or special training of personnel is needed, the Track Etch technique is easily used in field operations. The basis for the Track Etch method, its application in field exploration programs, and the results obtained to date in locating uranium ore bodies is discussed.

Jan 1, 1974

By D. L. Stevens

Following an in-depth scenario and strategic planning exercise in 1997, Noranda's mine production goal was set at 500,000 tonnes per year of both copper and zinc metal within five years. There had been no recent discoveries, reserves were shrinking and things had to be done differently and quickly. Change is now continual in our program but here is what we did first: Combined the exploration and business development groups Formed teams to search for and respond to opportunity Made our geologists more business minded and our engineers more optimistic Went global Set clear thresholds, farmed out the marginal properties, fast tracked the others Focused reconnaissance exploration where we had a clear competitive advantage Became a "flexible" partner to both juniors and seniors Is it working? A number of successes, near successes, and outright failures are discussed. The main result is a much higher rate of opportunity flux which is essential for success in the mining industry.

Jan 1, 1999

By Fred C. Wrobbel

Two counties in Illinois, Ope and Hardin, and three counties in Kentucky, Crittenden, Livingston and Caldwell comprise the entire Kentucky-Illinois fluorspar district. The output from these five counties, however, makes up over 60 percent of our domestic fluorspar production, amounting to some 175,000 tons of finished product in 1956, The area is rough and hilly. It is bisected by the Ohio River, and has numerous smaller rivers and creeks. Add to this a generous average annual rainfall, in excess of forty inches, and it is understandable that the-area-can boast of an ample water supply. An abundance of water, however, is unfortunately not always conducive to ideal mining conditions. The faulted structure of the area and the soluble Mississippian limestones make the subsurface sediments' willing hosts to the surface water. Limestone cavers and sinkhole topography also compound the occurrence of underground water. It is little wonder, then, that water frequently presents an economic problem in the area, particularly in vein-type mining.

Jan 1, 1958

By C. W. Matthews

Introduction Screening is an art, one of the oldest in the process field today, and one of the most widely used in our present age. Screening is being applied to an ever-increasing number of assignments, in an ever-expanding circle of industries. Screening is defined precisely as a mechanical process which accomplishes a separation of particles on the basis of size and their acceptance or rejection by a screening surface. Particles are presented to apertures in a screening surface and rejected if larger than the opening, or accepted and passed through if smaller. Screens are machines with screening surfaces used to classify materials by size. The screening surface is the medium containing the apertures for the passage of the undersize material. Screens are put to many uses - size separation, dewatering, desliming, media recovery, scalping, trash removal, washing, dedusting, conveying, concentration, and many combinations of these functions. It is interesting to note that screens are used for handling commodities

Jan 1, 1985

By J. E. Moyle

Introduction In October 1983, Rio Algom Ltd. decided to develop the East Kemptville tin deposit. This decision was the result of intensive geological and metallurgical evaluation work, as well as careful studies of environmental and marketing aspects. The property is located about 54 km (34 miles) northeast of Yarmouth, Nova Scotia, near the village of East Kemptville. Geology The geological setting is a granitic intrusive at the contact with metasediment. The tin mineralization is in the form of cassiterite (SnO2), which is about 80% tin. Sulfides are associated with the deposit containing silver, copper, and zinc, which are recoverable as byproducts. The mineralization is associated with quartz veins and greisen alteration. In the center of the deposit, the zones are so close together they have the appearance of a massive or porphyry type deposit. Ore Reserves The mine plan is based on 56 Mt (62 million st) at 0.165% tin. Up to the ninth year, mill feed will average about 0.2% and lower grade material will be stockpiled. In later years, the average grade will be 0.16% tin. A 0.08% cutoff grade is planned for the entire 17 years of production. East Kemptville is a relatively low grade tin deposit, and only a combination of favorable circumstances has made it economic. • The ore body is situated at, or very close to the surface, permitting mining by open-pit methods at a very low stripping ratio. • The tin occurs in relatively large crystals that allow for good recovery by gravity techniques. • It is ideally located in a well-settled area, with all essential infrastructural requirements already in place. • The positive and cooperative response from various governmental agencies involved are encouraging. Mine Plan The mine plan incorporates an initial pit, followed by three expansions to the ultimate pit. Mining will be at 14 kt/d (15,000 stpd) and will include 9 kt (10,000 st) of ore plus 5 kt (5,500 st) of waste and low grade. After five years, the mining rate will increase to 21 kt/d (27,500 stpd). It is planned to drill vertical 165-mm (6.5-in.) blast holes on a 6-x 6-m (20- x 20-ft) pattern. Bulk slurry explosives will be used to break the rock. Loading will be with hydraulic shovels into 70 t (77 st) haulage trucks. The trucks will deliver the ore to a 13 x 20 m (42 x 65 ft) gyratory crusher, where it will be crushed to 150 mm (6 in.). Secondary and tertiary cone crushers will be used to further crush the ore to 13 mm (0.5 in.). Process Design Tin extraction technology is practically unknown in North America, but Rio Tinto Zinc, which has a 53% ownership in Rio Algom, is involved in tin production in the UK. Rio Algom has used this experience and expertise in metallurgical evaluation work and in tin-related aspects of plant design. Mineralogical and metallurgical test work have been performed, both on laboratory and pilot plant scales. Mineralogical work was done largely in the UK, the laboratory test program was carried out at the Lakefield research facility in Ontario, and pilot plant work was conducted in Australia. This program has resulted in significant improvements in recovery and concentrate grades, over best projections that could be made before this work was carried out. Concentrating Process The concentrator is being designed to process about 9 kt/d (10,000 stpd). The first step is to reduce the size of the ore to -700 µm (-24 mesh) in a rod mill/ball mill grinding circuit. The ball mill will operate in closed circuit with high capacity banana-type screens. The screened product will be deslimed to 30 µm (560 mesh) with cyclones, then passed over the pri-

Jan 4, 1984

By A. Ardiant, C. E. F. Mumbunan, I. Irawan

As a part of mine operation’s success key, Community Development nowadays seems to be a rule of thumb. Not only is for a short term need of the company during their operation but also for the national public opinion on the presence of the mining industry to a certain region. Nanggung region which is only a 2-hour drive from Jakarta, brings the challenges to Antam’s gold mine business in the areas such as illegal miner presence, easy access to the mine area as it is very close to the community, and national political sensitivity considering its proximity to Jakarta. The company allocates about 3%of its total operational cost annually for Community Development pro-gram. The program is derived through SWOT analysis and broad involvement of all community components to assure that the allocated fund is addressed to the right place. In the year of 2002, the company has successfully established a conducive-relation with the community.

Jan 1, 2004

By T. C. Canter

Technological change is continually affecting the mining industry and the many papers being presented at this meeting reflect this fact. I fully agree that miners must remain fully cognizant of technology that can change mining costs and therefore your competitive marketplace. Despite the embrace of new technology and effective mine management techniques, the mining enterprise may not realize increased net income if the structure of the minerals marketplace is not understood. An important segment of the marketing structure for minerals is transportation. Transportation costs per ton can be much greater than the mining costs per ton and may accordingly overshadow hard earned gains in productivity. Change is greatly affecting the transportation industry but the change is driven more by governmental policy than technology. Although some technological advances are occurring in the bulk transportation business, the changes I want to address arise from policy. Policy changes have come from legislation in the 1970's culminating with the Staggers Act of 1980 and ensuing Interstate Commerce Commission decisions.

Jan 1, 1985

By B. J. Arnold, C. D. Harrison, R. A. Lohnes

More than 544 Mt (600 million st) of coal are handled annually for use by this country's coal fired power plants. Coal is transported in various ways: overland conveyors, railcars, trucks and barges. It can travel short distances or thousands of miles, picking up moisture, freezing or drying. When the coal is received at the power plant, environmental problems with fugitive dust and further handling problems can arise. To ensure that power plant availability is not jeopardized by coal handling problems, the Electric Power Research Institute's (EPRI) Coal Quality Development Center (CQDC) developed a research program aimed at addressing utility coal handling problems. The program has identified key areas, and is investigating the cost and cause of coal handling problems as well as the solutions to these problems. The ultimate goal of the program is to develop a "handleability index" that utilities can use in their coal specifications or hardware for a utility's sampling system to predict handleability and determine if a coal shipment should be accepted.

Jan 1, 1993

By Fernando de Oliveira Durão

A complete computer package for the steady-state simulation, either in analysis or in design mode, of mineral processing flowsheets is described. The main features of the simulation package are: modular architecture, flexible structure and sequential solution strategy. Different detail levels of mathematical models of several mineral processing unit operations have been developed and implemented as unit modules (FORTRAN routines). Unit operations currently modelled are: coarse/fine crushing, grinding, screening, hydrocyclone classification, gravity separation, heavy media separation, froth flotation, high gradient magnetic separation and solid-liquid separation. In design mode, a simulation study is stated as a general non linear optimization problem. The objective function is a weighted sum of square deviations between the design specification set points and the calculated values, subject to non linear equality and inequality constraints. The optimization problem solution is obtained solving successive Quadratic Programming subproblems followed by inexact line search of an exact penalty function (Powell algorithm). One non trivial example is discussed, illustrating the design capabilities of the simulation package.

Jan 1, 1992

By R. Bhima Rao

Performing a magnetizing roast in a furnace or kiln is a well-established technology. However, the use of microwave heat for the magnetization of hematite in the beneficiation of ferruginous bauxite is a new approach. This paper reports on an investigation of this procedure, which is followed by comminution and magnetic separation. The results of this investigation indicate that a nonmagnetic product containing 80% A1203 and 2.5% Fe203 with a recovery of 80% can be made from a crude bauxite ore containing 55.9% A1203 and 5.6% Fe203. This product is suitable for refractory use. The mechanism is explained by the ability of the microwave radiation to heat specific points within the bauxite. These heat-specific points are at the location of iron minerals. In a reduced atmosphere, the microwaves promote faster conversion of the iron minerals to a magnetic phase, which improves the magnetic-separation process.

Jan 1, 1997

By L. Henry Smith, David C. Arthur

The Williams Mine is Canada's largest gold producer, with annual production of 14,000 Kg (450,000 ounces) from 2,300,000 tonnes of ore. Highly mechanized and automated underground mining practices are employed in order to achieve and maintain high levels of productivity and minimize costs. The Mine Ventilation System is modified to include a new Vent Raise and Variable Pitch Vane-Axial Fan. This addition allows several fan installations underground to be decommissioned. A substantial net savings in installed horse power is achieved. Heating costs associated with underground ventilation air are a significant portion of mine operating costs. Air heating costs are substantially reduced by recovering heat from upcast exhaust air, mine water and compressor cooling circuits. This waste heat is used to supplement propane fired air heating systems for underground ventilation air. An additional benefit is the availability of a heat sink for summer cooling of the compressors. System design, energy savings data and payback calculations are presented.

Jan 1, 1997

By Samuel M. Cassidy

The exact date of man's first use of coal is lost in antiquity. The discovery that certain black rock would burn was undoubtedly accidental and probably occurred independently and many times in the world over thousands of years. It is quite likely that these independent discoveries were made when primitive man chanced to build camp fires on exposed ledges of a black rock, then was amazed when it caught fire. The Chinese recorded the use of coal 1100 years before the Christian Era and from the Bible we learn that King Solomon was familiar with coal in what is now Syria. In Wales, there .is evidence that the Bronze Age people used coal for funeral pyres, and it is known that the Romans used this fuel. There are other ancient references. So the knowledge that coal would burn, and even some uses of that knowledge, go back thousands of years. However, practical and consistent use of coal seems to date to England in the Middle Ages.

Jan 1, 1981