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By Allen V. Reicks, Thomas J. Rudolphi

Computerization has allowed practical design of complicated and optimized belt conveyors for bulk materials from prediction of belt tensions around the belt circuit for a wide range of belt loadings and conveyance paths. These design methods are based on a knowledge of component operating characteristics and sources of tension change. As compared to generalized 'f' methods, CEMA's historical Kx and Ky has provided nonlinear and more specific predictions of belt tension as affected by various components and operating conditions. These empirical values were developed in a different age and generalizations made in their development are now a constraint to additional conveyor improvements. This paper discusses the potential from improved and standardized ‘friction’ predictions and presents the results of sensitivity evaluations as affected by calculation method

Jan 1, 2004

By Muhammad I. Kabir

The streamline method of recovery prediction reduces a two-dimensional problem to a bundle of one-dimensional ones. This paper presents the development and application of a novel scaling technique which, when used with a streamline model, causes s bundle of one-dimensional problems to further reduce to a single one-dimensional calculation. The one-dimensional calculation accounts for chemical-rock interactions and the streamline model for areal sweep. The scaling technique significantly reduces computation time, is readily modified to desk-top calculations, and can be applied to both absorbing and reacting species. The work was sponsored by the Interior Department's Bureau of Mines.

Jan 1, 1984

By A. B. Cook

The South African socio-economic history started with pastoral and agrarian communities which had low levels of industrialization and small needs for energy. The discovery of diamonds (in the Northern Cape in 1867) and of gold (in the Transvaal in 1886) heralded economic and industrial development, with a concomitant demand for energy. The energy needs of the fledgling mines, and mining towns, were met by the combustion of wood, cut locally, or by coal, hauled laboriously from the primitive collieries, and sold to the mining companies and townships at high prices.

Jan 1, 1994

By Will Foreman, Douglas D. McLearie, Edwin K. H. Tong, William H. Hansmire

Hong Kong’s Strategic Sewage Disposal Scheme (SSDS) Stage I involves the provision of a system of deep tunnels for transporting to a central treatment works wastewater collected from a number of catchments around Victoria Harbour. For the SSDS Stage I works, about 24 km of tunnels have been excavated in hard rock at depths ranging from about 80 to 150 m below Victoria Harbour and the surrounding heavily developed areas of Kowloon and Hong Kong. Five tunnel boring machines(TBMs) with diameters ranging from 3.2 m to 4.3 m were used to excavate the tunnels. Tunnel excavation has been completed and tunnel linings are in progress. Major tunnelling issues such as ground stabilisation and water control encountered in the project are summarised. An overview of one of the possible future tunnel systems that might be adopted in subsequent stages of SSDS is also presented.

Jan 1, 2001

By Lu Yang

In the last two decades, acid iron ore pellets have established their predominant position as the iron-bearing burden material for blast furnace ironmaking in North America. It is a general practice that pelletization plants are asked to produce pellets of certain chemical composition and in a narrow range of sizes. A minimum amount of fines created during handling and transportation is desirable. Such a requirement is often expressed indirectly by the minimum compression load causing a pellet to break. The behavior of pellets inside a blast furnace, of course, is very important for a smooth and efficient operation. Before its melting in the lower part of a blast furnace during this period of several hours the behavior of pellets depends on their properties after induration as well as conditions inside each furnace. Among properties of indurated pellets, the ability to maintain their physical integrity in the burden and to be reducible are most important. To maintain the integrity of pellets (i.e., minimal low temperature breakdown, swelling and softening) so that there will be adequate overall permeability for certain wind rate and local permeability for gas/solid contact for reduction. A higher reducibility will moderate the adverse effects of swelling and softening and contribute to a smooth operation and efficient use of heat and reductants in a blast furnace. An article devoted to the relationships between the quality of iron ore pellets and blast furnace practice has been published elsewhere(1); therefore, no further discussion is needed here. The mechanism of strengthening of iron ore pellets during firing has been the subject of investigation of many authors(2). There is no doubt that the bridging of the growing hematite grains, particularly starting with magnetite concentrates, is very significant in the production of strong pellets. Recently, there are many reports from blast furnace operators that they have noticed the adverse effect of LTB in their plants. It is obvious that the strength derived from bridged hematite grains may disappear when hematite is converted to magnetite with thorough breakdown of grain structures. It is suggested that some other strengthening mechanism may be required in order to improve the LTB index of acid pellets. The influence of porosity on both compression strength and reducibility follows regular patterns. It has been suggested(1) that the amount of liquid slag in pellets during firing determines to a large extent the porosity, hence, indirectly, strength and reducibility.

Jan 1, 1983

By W. J. Van Den Berg, J. G. Taylor

The paper discusses the introduction of blindhole boring on the South African gold mines of Anglo American Corporation. It covers the boring trials conducted, and outlines the progress made in the development of blindhole borers. The operating costs, and performances, of the latest 1,52 m diameter borer are given. Future trends and requirements In the application and design of blindhole borers are discussed, as well as factors that are of importance in the design of future machines.

Jan 1, 1978

By A. C. Rice

This report describes a chemical process for preparing solutions of trivalent rare-earth chlorides from sulfate solutions obtained by treating bastnasite concentrate. The chief impurity in the final solution is cerium, and this element is less than 1 percent of the rare-earth oxides. The solution is used directly in the separation of rare-earth elements by ion-exchange methods. The attractive features of the process are that the chemicals are inexpensive and the steps few. The process starts with precipitating the rare-earth hydroxides from sulfate solutions with caustic soda. After the hydroxides are dried to oxidize the cerium, they are treated with dilute hydrochloric acid to dissolve away the trivalent rare-earth elements, leaving the tetravalent cerium. Details for controlling the leaching step are described. The process shortens older procedures by omitting the usual oxalate or double-sulfate-precipitation step.

Jan 1, 1959

The common approach of designing blasts on a trial and error basis is quickly coming to an end. When utilizing the full scale blast environment, trial and error can quickly become cost prohibitive and leaves much to be desired in terms of true blast diagnostics. In these situations testing is usually only continued until a perceived improvement is achieved and when the gross undesirables in blast results are removed. This does does not preclude, however, that further improvements of up to 100% or more can not be obtained.

Jan 1, 1991

By Ian Bell

This paper investigates fragmentation in an aggregate quarry using the fragmentation-energy fan concept. Six blasts were monitored, located one behind the other in the same quarry area. The rock structure was blocky, the water level and the usage of explosives were variable within and between the blasts. The powder factor above grade was between 0.28 and 0.44 kg/m3 (0.47 and 0.74 lb/yd3). Fragmentation of the plant feed was measured using an online digital image analysis system and three belt scales. The oversize material that was not directly fed to the plant after the blast corresponds to 3‒9.3 % of the total. Data from image analysis was used to build the size distribution in the coarse range (fragments above 120 mm), and the passing fractions at 120 and 25 mm (4.72 and 0.98 in) obtained from belt scales data were used in the range 120‒25 mm (4.72 ‒ 0.98 in) . The non-dimensional percentile sizes between 10 and 90 % for each blast are described through power functions of the powder factor above grade; the model coefficients are statistically significant. From them, using the principles of the fragmentation-energy fan and the Swebrec distribution properties, the fragmentation can be expressed in terms of the powder factor by means of five parameters: the fan focus coordinates and the three parameters of a function of the exponents vs. the percentage passing. The model shows a good capability to describe fragmentation.

Jan 1, 2019

By P. Heald-Wetlaufer

Doubly polished sections (i.e., sections polished on both sides) allow insights into complex paragenetic relationships, the interpretation of which is essential to understanding ore-forming processes. Alternate viewing of these optically superior sections in transmitted and. reflected light facilitates the recognition and definition of growth zones in ore and gangue minerals and the interpretation of postdepositional changes, such as hydrothermal leaching and replacement. Many such observations would escape detection by conventional petrographic methods. Our procedure for preparing doubly polished sections has evolved during the past 20 years and incorporates many standard procedures. Studies from such diverse districts as Creede, Colorado, Hokuroku, Japan, and the Upper Mississippi Valley zinc-lead district, southwestern Wisconsin, demonstrate the value of observations from doubly polished sections in constructing genetic models. The advent of doubly polished sections represents a major advance in the study of ore deposits and they should be a standard tool in every ore petrology laboratory.

Jan 1, 1982

By Charles H. Buclmam

"Environmental regulatory requirements for discharge of solutions and closure of operations for the gold mineral processing industry have been gradually lowered and in certain instances have been targeted to USEP A inorganic drinking water standards for dissolved ions in solution. The use of jar tests for water treatment process development is suitable for preliminary scoping work to be conducted in the research laboratory, as well as for optimization studies at the site of the treatment requirement. This paper will describe experimental methods which were performed using standard jar test equipment in efforts to produce solutions which meet USEP A inorganic drinking water standards after chemical treatment of cyanide solutions. The materials tested included gold bearing pregnant solutions from heap leaching operations, gold plant barren solutions from the Merrill-Crowe zinc cementation gold recovery process and gold heap leach wash solutions after carbon-in-column gold recovery. Experiments included cyanide destruction with sodium hypochlorite and arsenic and selenium co-precipitation coupled with mercury precipitation.IntroductionCyanide leaching solutions are used to selectively dissolve metallic gold from commercially viable mineral deposits. The heap leaching process involves stacking of gold bearing ores on specially designed solution containment pads and percolating alkaline cyanide solutions through the ore to dissolve the gold. Pregnant solutions containing the dissolved gold are collected and sent through a gold recovery process. After selective recovery of the gold, the barren solutions are recycled to the gold extraction process after adjustment of the solution alkalinity and available cyanide concentrations."

Jan 1, 1997

By Ekkehart Mertins, Hans-Dieter Wasmuth

During the last years many new concepts have been presented for magnetic separation of feebly magnetic minerals by using the new high-duty permanent magnetic material especially in Open Gradient Magnet Systems (OGMS). In this respect KHD Humboldt Wedag AG developed an improved version of a drum-type magnetic separator called PERMOS® with a special magnetic field configuration for the NdFeB permanent magnets, which gives a magnetic field strength of at least 0.7 Tesla and a wide working zone outside the drum. The magnet system within the PERMOS® unit is no longer made of relatively large magnet blocks of alternating radial magnetisation; the system is now made up of a multitude of small NdFeB bars with a specially oriented magnetisation. This PERMOS® Open Gradient Magnetic Separator can be used for dry magnetic separations in "top-feed" and 'free-fall" feed configuration as well as in the conventional wet "drum-type" feed mode. It allows high throughput rates of up to 40 metric tons of solids per hour and meter of drum length without any clogging problems, even when strongly magnetic com-pounds are present in the feed material. The important design features and the actual machine characteristics of the improved PERMOS® units for dry and wet magnetic separation are described and typical examples for their commercial application for industrial minerals and for martitic iron ores are presented.

Jan 1, 1995

By Hemendra N. Kalia

A method is proposed for the preliminary design of coal mine openings and pillars using existing design formulas. The suggested method incorporates geophysical and core logging techniques, as well as the structural properties of the rock. Some of the existing design equations have been simplified and are included. It is anticipated that the additional cost of rock mechanics tests and logging work will be more than offset by the increased coal recovery that does not jeopardize the safety of miners,

Jan 1, 1977

By Albert L. Toenges

C. P. HEINER*—I would like to ask Mr. Toenges about the highest rank coal. I did not get that clearly. What kind of coal is that? A. L. TOENGES (author's reply)— The coal in the Matanuska field ranges from high volatile "B" bituminus to anthracite. It all depends on which direction you go in the Matanuska field. C. P. HEINER—Is it a large reserve. A. L. TOENGES—That is what we hope. That is what we are trying to find out. B. W. DYER*—In those strip beds, I wonder how far back the coal would weather ? A. L. TOENGES—I never noticed particularly. B. W. DYER—The weathering does not extend back like it does in this country ? A. L. TOENGES—No, it does not. B. W. DYER—Is that due to the freezing ? A. L. TOENGES—Probably so. B. W. DYER—In this country, you would expect nothing but weathered coal. R. H. SWALLOW*—Along that line, you mentioned some of the seams were on fire. Did you ever know how far back they burned, or was it hard to tell ? A. L. TOENGES—The fires occurred in the mine. That one you refer to was from an inside fire.

Jan 1, 1950

Each spring most secondary schools select their best student science exhibits, prepared during the preceding academic year, and send them to regional "Science Fairs", which now number over 220. Winner-finalists of these regional contests are then sent to the annual National Science Fair, conducted by Science Service, a non- profit institution for the popularization of science, for final judging. (The Fair is now known as the "National Science Fair-International" because of participation by finalists from Japan, Thailand, Germany, France, Sweden and Canada.) For the first time since the Fair was started in 1950, AIME participated in the awards presentation. Held this year in Baltimore, Md., from May 5 to 9, five members of AIME's Washington, D.C., Section consented to represent the Institute as judges. They were: Marlin J. Ankeny-Director, Bureau of Mines, U.S. Department of the Interior. Kenneth N. Weaver-Director, Maryland Department of Geology, Mines, and Water Resources. William Harper-American Petroleum Institute. Vice-Chairman, Washington Section, AIME.

Jan 7, 1964

By E. O. Strahl

In the search for economic mineral deposits, the need for efficient mineral or chemical assays is of prime importance. Costly analytical methods and long delays in obtaining assay results severely limit the effectiveness of an exploration program. The assay problem becomes acute once a potential ore body is located and large numbers of samples are generated in close interval drilling programs. In order to avoid the delays and high costs of extensive assays, the exploration geologist or mining engineer is likely to be required to curtail his drilling program, composite samples, or restrict the required analyses to a limited number of critical elements. As a result, the definition of the potential ore body may be less than needed for final economic evaluation. The assay requirements for bauxite exploration usually involve a considerable number of total elemental and empirical analysis. Since the Bayer process for extracting alumina from bauxite involves the selective dissolution and reaction of specific minerals from the bauxite, a direct chemical analysis for elemental composition yields only a portion of the data required to effectively describe the potential economic value of ore body or deposit. To fully characterize the economic value of a bauxite requires digestion, mud separation and mud settling tests under conditions approximating a commercial Bayer plant. A close approximation of the process behavior of a bauxite also can be calculated from a combination of the chemical and mineralogical analyses. By determining the elemental chemistry, mineralogy, and Bayer plant processing characteristics of a few samples of a given bauxite, correlations can be derived that permit defining a bauxite in terms of a given set of process conditions.

Jan 1, 1977

By Peter A. Rona

The recent discovery of the first black smoker-type hydrothermal venting and massive sulfide mineral deposits at a site in the rift valley of the slow-spreading Mid-Atlantic Ridge near latitude 26°N, longitude 45°W (Rona et al., 1986, Nature, 321: 33-37), demonstrates that a complete series of hydrothermal mineral deposit types exists at slow-spreading oceanic ridges (half-rate = 2 cm/y), similar to the series previously known at faster-spreading oceanic ridges (half-rate > 2 cm/y). The largest hydrothermal mineral deposit known at a seafloor spreading center is a stratiform massive sulfide body with bulk dry weight of about 100 x 106 metric tons in the Atlantis II Deep at the slow-spreading axis of the Red Sea. This observation invalidates the concept that size of a hydrothermal deposit is directly proportional to rate of seafloor spreading. Instead, the occurrence, grade and size of a hydrothermal deposit formed at a seafloor spreading center is controlled by anomalous chemical and physical conditions which may occur at extremely localized sites at the full range of spreading rates. The basic hydrothermal process involving subseafloor hydrothermal convection driven by magmatic heat sources appears to be similar at slow- and faster-spreading centers. However, differences exist in the periodicity of magmatic cycles that energize hydrothermal circulation (104 y at slow-spreading centers; 103 y at faster-spreading centers); in the distribution of hydrothermal sites along a spreading axis (estimated 100 km along slow-spreading centers; 10 km along faster-spreading centers); and in residence time

Jan 1, 1986

By Christiana Mystrioti

Greece is the only EU country with extensive nickel laterite deposits. Since the 1960s, the Greek laterites are treated for ferronickel production via a pyrometallurgical route, which involves pre-reduction of the ore in rotary kilns and reduction smelting in electric arc furnaces. Due to the rising cost of energy and the decreasing grade of mined laterites, the pyrometallurgical treatment is economically marginal. For this reason, alternative treatment processes are currently under investigation. Potential applicability of hydrometallurgical treatment, using either H2SO4 or HCl, under atmospheric pressure conditions, for Ni and Co extraction from two low grade laterite ores, was examined in the present work. The two samples were selected to represent the different mineralogical composition of the saprolitic and limonitic ore deposits of the Greek laterites. The investigated parameters were temperature (65–90 °C), acid concentration (1–4 N) and solid to liquid ratio (10–30% w/v). The results indicated that HCl was more efficient than H2SO4 for the treatment of the saprolitic ore; Ni and Co extractions were very high for both elements, up to 98% and 96% respectively, while H2SO4 could leach efficiently Ni, up to 100%, but extracted only 34% of Co. Hydrochloric acid was also more efficient for the treatment of the limonitic ore, with Ni and Co extractions up to 98.3% and 87.6% respectively. With H2SO4 the maximum extractions were 71.3% for Ni and 52.1% for Co.

By P. H. Carr, G. G. Marino, K. A. Patel

Extensions to a correctional institution at Wabash Valley, Indiana, required development over abandoned coal-mine workings, at 90 m depth, where subsidence was possible at surface. Backfilling of the flooded mine in critical areas was determined to be the most cost-effective method of limiting the risk of damage to the buildings. Containment grout was first placed in selected entries and cross-cuts of each mine area; the remaining volume was then filled with a readily flowing infill grout. Where a high proportion of an area was taken up by rubble, calcium lignosulphonate was used as a retarder and plasticiser to increase penetration. Grout movement was monitored from adjacent boreholes with an electrical resistivity probe during grouting, while after the work was finished core samples were obtained from verification holes drilled in the backfilled areas

Jun 19, 1905

By Edmonds W, Giles C. W, Webb R. J, Gum J. C

Gold production from The Granites - Tanami Goldfield during 1993 is expected to exceed 8 t, eclipsing that of the traditional Northern Territory gold mining districts of Tennant Creek and Pine Creek. This is the result of dedicated and successful exploration, and the consequent discovery of new orebodies such as those at Dead Bullock Soak.Following granting of access to regional exploration areas in 1988 and identification of favourable host rocks in the Schist Hills area, North Flinders Mines (NFM) began a methodical exploration program of detailed geological mapping, rock chip sampling, costeaning and various types of drilling. The first resource of 600 000 t of 3.3 g/t gold was announced in mid-1989. This has grown progressively with systematic exploration to the currently published resource inventory of 6.6 mT @ 5.4 g/t, (as at 31.12.92) contained in six separate orebodies within the Dead Bullock Soak Mineral Lease at Schist Hills.

Jan 1, 1993