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By O. Ozdemir

Soda ash, an essential raw material for major industries, such as the glass, chemicals, soap and detergents, pulp and paper, mining and water treatment industries, is traditionally produced by chemical and thermal treatment of trona ore. The treatment processes for trona ore are not only chemically expensive but also energy intensive. Hence, the production of a high-purity trona concentrate at a lower energy and operating cost is of considerable interest to the trona industry. In this study, we describe a possible two-stage process for concentrating trona ore, involving dry magnetic separation followed by flotation, to remove insoluble impurities from the trona ore. The results showed that a trona concentrate of 91.7% purity with a recovery 91.1% can be obtained by two-stage magnetic separation, which could be further improved to 98.1% purity at a recovery of 83.8% by subsequent flotation of the non-magnetic trona product. The purity of trona concentrate is limited by the particle size and impurity content of the trona ore. The operating parameters for magnetic separation and flotation have been identified to obtain an acceptable quality concentrate.

Jan 1, 2011

By Dale K. Nash

The authors have developed a com¬puter-assisted critical path planning and scheduling model to help reduce time required to move longwall mining units. The model includes time constraints and limited resource constraints, such as manpower, machinery, supplies, work space, and transportation routes. Outstanding results were achieved on the first move to which the computer-model pas applied; e.g., downtime due to the move was cut by 50%. The model and the schedules developed using it provide an excellent blueprint for future moves and have led to significant savings in time and costs for Emery Mining Corporation, Huntington, Utah.

Jan 1, 1983

By G. A. Kordosky

There are a number of reasons why the solvent extraction of molybdenum deserves attention: 1. The solvent extraction chemistry of molybdenum is interesting and complex, 2. The price of molybdenum is predicted to average about US$ 20.00 / pound in 2010 and, as China, India and other countries develop, the demand for specialty steels will increase putting long term demands on molybdenum supply, 3. Uranium ores often contain significant concentrations of molybdenum[1] and typically yellow cake will have a moly specification which when exceeded brings penalties, and 4. The valuable metal rhenium is a byproduct of molybdenum recovery circuits.

Jan 1, 2010

By T. McDonald

Test work indicated and plant operation has since confirmed that SAG milling is a viable option for INCO's Sudbury Operation milling rationalization project only if pebble crushing is included in the SAG/ball mill circuit. Throughput increases more than fifty percent with pebble crushing incorporated into the comminution process. The finer product of high speed pebble crushing provides further energy savings. The unconventional approach of pumping the pebble crusher product, while simplifying plant layout, has produced challenging wear problems.

Jan 1, 1992

By C. W. Fitzgerald

INTRODUCTION Continuous mining machines are used in regular flat ore beds having uniform thickness. Since coal is the most common type of material occurring in such beds, most continuous miners are used for the extraction of coal from underground mines. The first continuous mining machine for under¬ground coal mining was introduced in 1948. In one machine, the continuous miner combines the functions performed by a conventional face drill, a cutting ma¬chine, and a loading machine. It breaks or digs the material out of the surrounding solid and transfers the material back through the machine chassis by means of a chain conveyor. The conveyor carries the material to a haulage system, usually a rubber-tired vehicle known as a shuttle car. Generally, continuous miners are used in seam heights from 890 to 3660 mm (35 to 144 in.). For seam heights of 1070 mm (42 in.) or less, the haulage system may be a multiple-bridge conveyor or battery-powered tractors that haul low-bed trailers. Proj¬ects are being undertaken by private industry and through government contracts to develop a continuous haulage system for all seam heights. As of 1976, the majority of continuous miners were of two types. The first type is the drum miner, which mounts the cutting elements on a series of drums across the cutting head of the machine, sometimes using a cutting chain to cut clearance for the gear drive. In the drum-type machines, the cutting head rotates parallel to the material face. The second type is the auger miner, which utilizes cutting elements mounted on two auger-type cutting heads. One head is located on each side of the machine, with the heads mounted per¬pendicular to the material face. Chain-head ripper-type miners/miners having rotary cutting elements with oscillating motion and twin-head boring-type miners have all been popular within the last 15 years. Although these are considered obsolete, some machines are still being supplied for specialized applications. GENERAL DESCRIPTION This chapter describes only continuous mining ma¬chines available as manufacturers' production models as of September 1976. Figs. 1 through 11 illustrate some typical machines currently in use. Cutting Elements The cutting elements are the interface between the machine and the material being mined. In describing the cutting elements, consideration must be given to the differences between the drum- and auger-type machines, the bit-tip speeds, and the bit types. Drum-Type Continuous Mining Machines: Three of the four principal manufacturers of drum-type miners use multi-motor designs that provide separate a-c motors for driving the cutting elements. Gear trains are used to reduce the speeds of the motors to the rotational speeds of the cutting elements. One of the three suppliers drives the cutting elements of its low-seam models with a heavy-duty drive chain that is equipped with cutting bits; all other functions of this machine have separate motor drives that are either electrical or hydraulic. The fourth principal manufacturer generally provides two a-c electric motors, utilizing gear reducers, drive shafts, and hydraulically operated engaging clutches to power all of the operating functions, including the cut¬ting elements. Some drum-type miners use trim chains, equipped with cutting bits, to cut clearance for the gear drives. These trim chains vary from two 305-mm (12-in.) chains to one 760-mm (30-in.) chain per machine, de¬pending upon the manufacturer's design concept. In all machines other than the low-seam models that use chains to drive the heads, the trim chains are driven by sprockets on the drive shaft of the final cutterhead drum; therefore, the trim chains are not used for power trans¬mission to the cutting elements. In addition to cutting clearance for the gear drives, the trim chains provide uniform bit spacing all the way across the head and assist in moving the cut material to an area where it is either loaded directly into the miner's conveyor or is easier to load into the conveyor. On a drum-type mining machine, the cutting ele¬ments all rotate from the top to the bottom. Therefore, the recommended procedure is to raise the cutterhead to the maximum seam height, sump the entire machine forward to maximum depth by means of a crawler drive, and then shear downward until the cutter elements reach the floor level. The maximum sump depth varies ac¬cording to the drum diameter, the type of material, the floor conditions, and the operator's abilities. It normally varies an average of 460 to 760 mm (18 to 30 in.). Cutter drums are supplied with two types of cutting bit holders. Weld-on holders are attached permanently. Pin-on holders are replaceable at the face. Cutter-drum diameters over the bit tips vary from 660 to 965 mm (26 to 38 in.), depending upon the chassis height of the machine and the range of cutting heights. Auger-Type Continuous Mining Machines: As cut-

Jan 1, 1982

By A. Noble

For the past 30 years, process flowsheet design has been accomplished largely through modeling and simulation. This approach provides circuit designers the freedom to test various separation approaches while minimizing physical and human resource requirements. The Limn® software provides a unique approach to process simulation, through a Microsoft Excel interface. While the software comes with standard process models for numerous unit operations, the Excel calculation environment and the accompanying VBA platform provide a convenient interface for custom model integration, even for non-experienced programmers. This feature is especially useful for university students in introductory process modeling and simulation-assisted flowsheet design courses as well as experienced practitioners with proprietary process models. This paper shows how the Limn® software may be used to solve basic process engineering problems as well as more comprehensive circuit design challenges. Industrial examples as well as opportunities for training and education are presented.

Feb 23, 2014

By A. R. Rule

As part of the Federal effort to help maintain an adequate supply of fertilizer minerals, the Bureau of Mines is conducting research to characterize complex, low-grade western phosphate rock and to develop methods for economic recovery of phosphate. The rock varies from soft, friable, altered phosphatic shale to hard, tightly cemented, unaltered phosphate rock. To supplement current beneficiation by sizing, a flotation procedure was devised that included depression of phosphate minerals with H2SiF6 and anionic flotation of carbonate minerals, followed immediately by cationic flotation of silicate minerals. Application of the procedure to several different ores resulted in phosphate concentrates that ranged from 28 to 31 pct P20S in grade and from 60 to 70 pct in phosphate recovery.

Jan 1, 1977

By Armine F. Banfield

Selection of a plant site is becoming increasingly more difficult and important, mainly due to advances in technology, antipollution laws and changing economic, social and community conditions. Discussion falls naturally under three headings: economic considerations, terrain considerations and environmental considerations. Aside from acquisition of surface rights, problems having to do with terrain, or topography, usually can be dealt with by management alone. Economic considerations largely involve decision-making by management plus negotiations with government regulatory agencies acting under set rules. Environmental considerations, such as air and water pollution, townsites, housing, schools, noise abatement, appearance, surface rehabilitation and the like usually are under the control of federal, state or municipal bodies with a large degree of decision-making. Successful solution of environmental problems often requires lengthy negotiations, during which public relations by the mining company play an important part. Existing union regulations or customs may confine decision- making and the establishment of wage rates, working conditions and regulations. These usually require considerable planning and negotiation. Initial production often is delayed by formal negotiations involving environmental considerations. Surface facilities usually can be divided into two broad categories: those for concentrating ores--such as gold, silver, base metals, low-grade iron ore and potash-which should be close to the mine to reduce ore-transportation costs to a minimum, and those where the ore is shipped elsewhere for treatment, such as direct-shipping iron ores, complex high-value ores requiring specialized treatment and ores from which special products are derived for local markets. The long-term aspects of plant-site selection too often are given no or insufficient consideration because of immediate financial limitations. As a result, additional capital expenditures may be required later for relocation of townsites, roads, railroads and plants to provide additional room for extension of open-pit operations, tailings disposal, storage, or danger to foundations through underground subsidence or open-pit mining. In the past, hillside sites for concentrating plants were preferred to take advantage of gravity-feed methods The modern trend, however, is to place as much equipment as possible on approximately the same level. Some costs relating to plant sites are included in this section. They are ranges as of the year 1970, and are offered only as general guides. Such costs will vary widely with geographical location and, of course, are subject to escalation due to increases in wage rates and cost of materials. Items in the bibliography contain more detailed and comprehensive data on specific subjects. Most contain bibliographies of their own.

Jan 1, 1973

By Roshan B. Bhappu

Stimulated by current $0.80 to $1.20 per pound price tag of copper, considerable interest and activity have been generated in the copper mining camps throughout the world, and especially in the Southwestern United States and Northern Mexico copper belt. Under these economically favorable conditions, many of the marginal oxide-copper deposits, as well as newly discovered prospects, are under scrutiny for possible exploitation. For both the known deposits and new prospects, the big question facing the mine operator is the selection of the best method for processing these economically attractive oxide-copper deposits. Several variations of the hydrometallurgical processes are currently available for treating oxide-copper ores which can be mined by the open-pit method. Basically, these processes involve preparing the ore for application of an acid solution, applying the solution to the ore, and recovery of the metal from the pregnant solution. Dump leaching, heap leaching, vat leaching, agitation leaching and, in more recent times, in situ leaching or solution mining in combination with well established cementation process or the newly developed solvent extraction-electrowinning system have all been employed or have been investigated for the recovery of copper from oxide ores. Of these processes, dump, heap and vat leaching have been successfully practiced for treating oxide-copper ores. Agitation leaching is a relatively newcomer and has been adopted from the experiences of uranium and gold processing. Finally, the inplace leaching technique is the latest process to be suggested for possible treatment of oxide-copper ores.

Jan 1, 1974

By R. F. Yap

Although laboratory studies of tin flotation have been reported as far back as the 1920`s(1), the commercial application has only been realized within the past few years(2,3). The principal technical difficulty in the application of the process to tin ores has not been in the flotation of cassiterite itself, this mineral being readily recoverable with the common collectors, including xanthates with heavy metal ion activation(2). The difficulty has been with the depression of the gangue minerals commonly associated with tin ores, and to a lesser extent with the problems of collector consuming semi-colloidal minerals which are in some cases present. The application of sulfosuccinamate collectors to flotation of cassiterite from the Catavi, Bolivia, slime tailings has recently been described(3). The investigation which led to this successful process development included studies of other samples of gravity plant tailings as well as of lode tin ores. A common flowsheet with few significant variations was applied to most of these ore samples with acceptable results. In the following the process is described and the results of its application to samples from Bolivia and elsewhere given. Among the factors considered are: gangue depression, particle size and slime effects, and reagent and pulp density levels.

Jan 1, 1971

By S. Mathur

Oxide particles are commonly used as fillers in plastics, paper, rubber, etc. (particulate composites). The successful fabrication of such composites is dependent upon the adhesive strength of the filler particles to the matrix. The compatibility of the matrix and the filler particles is generally enhanced by the adsorption of surface modifiers such as surfactants and polymers at the particle-matrix interface. To develop a scientific basis for the selection of the appropriate modifiers it is necessary to understand their adsorption mechanisms. specifically, the adsorption of polymeric additives is attributed to a combination of chemical and electrostatic interactions, hydrogen bonding and van der Waals forces. Hydrogen bonding has been suggested to be the primary adsorption mechanism for nonionic polymers. However, a literature survey of the Poly(ethylene oxide) (PEO)-oxide system suggested that PEO, a nonionic polymer, was substrate specific. A systematic study was undertaken to investigate the adsorption mechanisms of PEO on oxide particles. It was determined that strong Bronsted acid sites on the surface interact with the ether oxygen, a Lewis base, of PEO to induce adsorption. In this work, characterization of PEO binding sites on oxides is reported and the mechanisms of PEO adsorption are discussed.

Jan 1, 1999

By R. P. Aldis

A wide range of mineral-derived products are required by the electronics industry for it to function. In one form or another, almost all the known elements have been experimented with and tested for various electrical applications. The two major areas for which minerals are used in electronics are as conductors and semiconductors. Conductors provide the means to transport and distribute electricity, while the main application of semiconductors has been to manipulate electricity. Silicon is the most widely recognized semiconductor material, but gallium, indium, and germanium are rated as the most important metals to the semiconductor industry for future and near future technologies.

Jan 1, 1991

By J. M. Avasthi

Gulf Research & Development Company conducted the nation's first underground coal gasification test in steeply dipping beds near Rawlins, Wyoming. The geotechnical considerations played a major role in the initial site selection. The test plan included a detailed geotechnical program for site evaluation, test design, permitting, and environmental studies before the burn. During burn, the geotechnical activity continued in the form of monitoring surface subsidence and acoustic emission. The postburn evaluation included studies of the drill cores obtained from the burn zone and effects on the surrounding rock mass.

Jan 1, 1981

By M. L. Harris

Explosions in underground mines and surface facilities such as processing plants are caused by confined accumulations of combustible dust and/or flammable gas mixed with air in the presence of an ignition source. Underground explosions can be prevented by minimizing methane concentrations through methane drainage and ventilation, by adding sufficient rock dust to inert the coal dust, and by eliminating ignition sources. The effectiveness of rock dust in arresting explosion propagation was proven by experiment and practice (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11). The precise mechanism by which rock dust (generally pulverized limestone dust) quenches flame has not been fully explained, but is believed to be absorption of thermal energy from the heated gases and absorption of radiant energy, which reduces the preheating of unburned coal particles ahead of the flame front. One measurable aspect of explosibility is incombustible content. In order to determine whether enough rock dust is applied, 30 CFR1 § 75.403, Maintenance of Incombustible Content of Rock Dust, requires at least 80% incombustible content on the roof, ribs, and floor of underground coal mines. 30 CFR § 75.403-1 further defines the incombustible content as follows: ?Moisture contained in the combined coal dust, rock dust and other dusts shall be considered as a part of the incombustible content of such mixture.? In order to determine the incombustible content of the mine dust, samples of deposited dust from specified areas in a mine must be collected, analyzed, and then compared with the minimum standard of 80%. The traditional low temperature ashing (LTA) approach to determine if a coal and rock dust mixture is compliant with the inerting requirement consumes the coal dust and considers the remaining material to be inert. Compliance with the law is then determined by comparing the measured percentage of inert material of the representative band sample with the pre-established requirement of 80%. The incombustible content of the sample includes rock dust, the amount of moisture as received at the lab, and the inherent ash in the coal. The LTA method is not itself a direct measure of explosibility but is a surrogate that calculates a single parameter associated with large-scale Bruceton Experimental Mine (BEM) explosion test results conducted with dry rock dust. This method assumes a homogenous mixture with no layering of rock dust and coal dust. Float coal dust is a serious explosion hazard if it accumulates on top of the rock dust and is not mixed with the rock dust (12). Mitchell and Nagy (13) studied the effectiveness of water as an inerting agent for the coal dust explosion hazard. The study emphasized that surface water evaporates readily from dusts. Thus, in a passageway where the dust is wet, changes in weather or the ventilation system could dry the dust and make it unsafe in a relatively short period of time. Where adequate rock dust has been applied, this drying effect is not a factor. However, if the mine depends upon the moisture content as part of the incombustible content, fluctuations in the dust surface moisture within a mine can render moisture content an ineffective and inconsistent measure of safety. Additionally, if sufficient moisture is absorbed and subsequently relinquished by rock dust, a cake can form and render the rock dust ineffectual. The trend has long been recognized that mine explosions occur primarily during the winter season when the humidity is low for long periods of time (14, 15, 16). In light of this trend and due to the potential variability of the moisture content of the dust, it may not be prudent to include variable surface moisture in the total incombustible content of the sample. Instead, surface moisture should be viewed as an additional safety measure as long as the rock dust is dispersible. However, moisture limits the ability of the rock dust to disperse and can significantly reduce its capacity to effectively inert propagating explosions (2, 13, 17, 18, 19, 20, 21, 22). Given the methods by which the as-received moisture and incombustible content are determined, dust samples from the 2010 MSHA database were assessed to determine the variability of the moisture content throughout a year and how often the measured as-received moisture might have affected the dust explosibility determination if removed. The findings were then verified by observation in laboratory studies and within the NIOSH OMSHR Safety Research Coal Mine (SRCM).

Feb 23, 2014

By Thomas A. Mekelburg

Due to a tight ash constraint on the clean coal product and difficult middlings washability characteristics, a considerable amount of coal was being lost in the jig middlings at the Monterey No. 2 Mine. An investigation was conducted into circuitry to recover this lost coal with minimal effect on the total clean coal ash. A reverse two-stage hydrocyclone system cleaning at low specific gravities was selected. This system is currently recovering approximately 5.8 kg/s (23 tph) of 11.5% to 12.5% ash coal. The specific gravity of separation for the system is about 1.5 and the probable error is 0.13.

Jan 1, 1984

By C. G. Anderson

Extraction of valuable resources from complex orebodies will become more common. This is obvious for two reasons. First, the cleaner and more readily processed ores have continually been depleted through centuries of mining. Second, new technologies have evolved for effectively handling complex ores. One of these new processes has been in place at Sunshine since 1984. Based on sulfuric acid oxygen pressure leaching with nitric acid as an oxidizer, this patented technology allows silver and copper to be efficiently recovered from a complex sulfide concentrate. As efficient as it is, this process represents novel technology found nowhere else on an industrial scale. As such, a research program was undertaken in 1989 to optimize this leach process and to better understand it. From this study, several potential plant improvements were found and recommended. As a result, two of these options, nitric acid replacement by sodium nitrite and concentrate regrind are now used in day to day operation at Sunshine. Patenting of these changes was recently accomplished (1). Thus, the development, perceived mechanisms, plant integration and potential applicability of this technology will be covered in this paper.

Jan 1, 1994

By J. T. Carlson

Dolomite is an objectionable impurity in phosphate ores, due to its MgO content. Even though dolomite and apatite liberate at a coarse size, the very similar densities of dolomite and apatite makes density separations difficult. However, if operated correctly, jigging can be a very efficient process. This has led to the development of a unique laboratory scale jig that allows for easy alteration of effective jigging properties. Key jigging parameters have been investigated for the separation of dolomite from phosphate ores. It was found that a pulsation rate of approximately 200 pulses/minute worked best for separating dolomite from apatite.

Jan 1, 2010

By A. D. Hammond

Until recently, the volumes delivered and unloaded from heap-leaching pads have been estimated by manual methods at Wharf Resources' South Dakota operation. In August 1989, the Engineering Department acquired the MINE-SURVEY software developed by GEM COM Services, Inc. of Vancouver, Canada, as part of a mine planning/grade control software package. The implementation of MINE-SURVEY for pad control resulted in a cost-effective tool to provide accurate and prompt estimates of ore delivered or unloaded from the pads. Volumes can be calculated in a matter of minutes as opposed to hours or days. Another benefit is the ease of comparison of as-build and designed volumes, plotting cross-section in any orientation, importing into AUTOCAD, validation of ore densities and truck factors. This paper describes the application of the MINE-SURVEY systems in heap leaching pad volumetrics.

Jan 1, 1991

By James S. Browning

In 1975 bituminous coal and lignite production in the United States reached an all-time high of 637 million tons, an increase of 6 percent over production in 1974. The output, valued at $11.9 billion f.o.b. mines, was produced at 5,100 mines in 24 states (6). Coal mining is the largest mining industry in Alabama. Production from Alabama's mines in 1975 was over 21 million tons, and present projections forecast a steady increase in production, with tonnages almost doubling by 1985 (5). Of the total quantity of coal produced, about 16 million tons were consumed in electric power generation and the remainder was used for metallurgical coke production, extraction of chemicals and petroleum based products, and power for industry. The fact that 75 percent of Alabama's power is generated by burning coal attests to the importance of this fossil fuel to the State. Approximately 14 million tons of coal were produced by strip-mining methods in Alabama during 1975 and about 7 million tons were produced by underground mining during the same period. Surface mining is expected to continue at about 14 million tons per year, but by 1980 underground coal mining is expected to increase to about 25 million tons (3). About 7 million tons of surface-mined coal in Alabama is subjected to some means of washing or cleaning. The methods used are screening accompanied by heavy media separation, jigging, tabling and flotation. Some of the simpler approaches employ screening and jigging, or tabling. Except where flotation is used, the screen undersize fraction (finer than 0.25 inch) is rejected, with the result that 10 to 15 percent of the coal is lost. Thus, in the State of Alabama an aggregate of about 1 million tons of coal is wasted annually in the fines which are impounded from treatment of surface-mined coal. The use of the Humphreys spiral to concentrate fine coal was practiced as early as 1947. At that time the Hudson Coal Company (1) used Humphreys spirals to concentrate anthracite fines. In 1950, the use of spirals to treat fine-size

Jan 1, 1977

By John W. Rozelle, David S. Bolin

INTRODUCTION During the normal course of a mining project, a feasibility study will be prepared that addresses all the aspects of the project including geology and mineral inventories, mining and geo- technical, metallurgical processing, infrastructure, environmental considerations and economic analyses. These studies are prepared for various reasons. Occasionally, a feasibility study will be prepared solely for use within a company as justification for development expenditures, however, these documents are frequently submitted outside the company either to raise funds from financial institutions or from public financing on one of the various securities exchanges. Mineral industry consultants are often called upon to participate in the preparation of feasibility studies or to conduct an independent audit and review of an internally prepared study. As the recoverable mineral resources form the foundation upon which the balance of a feasibility study is based, including the economic analysis of the project, the resource aspect of the study is examined very carefully by financial and securities organizations. The balance of this discussion is directed toward the various geological and resource estimation aspects of feasibility studies that experience has shown to be of particular importance. Much of this discussion will be directed toward open pit gold operations, although the principles are applicable to any type of deposit. 2.0 GEOLOGIC RESPONSIBILITIES IN FEASIBILITY STUDIES The principal geological effort in the preparation of a feasibility study is generally dedicated to the following areas: - Preparation of Geologic Reserve/Resource Estimates - Condemnation of Sites for Facilities, Access Roads, Leach Pads, Waste Dumps and Tailings Disposal - Collection of Geotechnical Data - Provision of Mineralogical and Petrological Data Pertinent to Metallurgical Processing - Selection of Appropriate Bulk Sampling Sites for Collection of Metallurgical Samples Each of these items will be addressed in detail in the following sections. 3.0 RESERVE/RESOURCE ESTIMATION An ore reserve estimate consists of the determination of a volume, or tonnage, and a grade for the deposit. There are numerous cases in the mining industry of projects that have experienced severe difficulties when operational ore grade, tonnage or metallurgical amenability have proven to be deficient compared to predicted estimates. An error in estimation of tonnage generally leads to more long term problems affecting mine life and production schedules. However, a significant error in the estimation of grade, particularly if mined grade is lower than anticipated, can have an immediate, and often disastrous, effect upon a project. The geologic preparation leading to an ore reserve estimate generally follows a logical sequence familiar to

Jan 1, 1987