Search Documents

By G. E. Agar

The energy required for dry grinding of phosphate rock in ball and roller mills has been analyzed by the method suggested by Charles and others. The findings are not wholly in agreement with Charles' predictions; but, nevertheless, the method of analysis is shown to be sound. Some of the deviation is probably attributable to the characteristics of a dry grinding system. Many laboratory and pilot plant scale experiments have been made to determine the energy requirements for size reduction. This topic was recently reviewed by Agar and Brown' and it was apparent that very little if any data exists in the literature which permits one to apply the Charles 2-Holmes3 analysis to industrial size systems. More recently, the idea has been put forward that the postulate of comminution by impact used by Charles and others was not sufficient to explain size-reduction throughout the grinding operation. The opportunity exists in the grinding operations of International Minerals and Chemical Corp. (IMC) to analyze the energy-size relationship for dry grinding phosphate rock in both ball and roller mills. This situation arises because the mills are used for custom grinding and make products from 50% to 85% minus 200 mesh. BACKGROUND A correlation of particle size in a comminuted material with the energy expended in size reduction was proposed by charles2 to be of the form

Jan 1, 1965

By M. E. Volin, F. H. Erbisch, G. M. Wenberg

Bacterial leaching of copper and uranium is practiced under acidic conditions in environments furnishing sulfur and iron. However, many mineral deposits do not have these conditions; the chalcocite and native copper deposits in Michigan's Upper Peninsula are examples. Species of bacteria and fungi isolated previously from samples taken at the White Pine Copper Co. tailings pond and mine, were screened for solubilization of copper from chalcocite ore and flotation concentrate and from native copper jig concentrate. Certain Penicillium species solubilized significant amounts of copper under neutral to slightly acidic conditions in a carbon and nitrogen-enriched medium. Leaching apparently was accomplished by release of metabolites which chelated with the copper. The copper yield was highly dependent upon the medium composition and the concentration of copper in the source material. The standardized procedures which were developed in an attempt to maximize copper yield in leaching times of three to five days are described. This preliminary research indicates a biological leaching process for copper which is different from those in use, but whether it can be applied economically remains to be determined.

Jan 1, 1972

By J. P. Norris, W. T. Pettijohn

The Mufulira Copper Mine, Ltd., is in Northern Rhodesia, ten miles from the Belgian Congo border, and is one of the group of four operating mines comprising the Northern Rhodesian Copperbelt. The ore deposits at Mufulira are on the limb of a large syncline striking NW.-SE. and dipping NE. at about 45 deg towards the Congo border. The host rocks are well-consolidated, highly-silicified, felspathic quarzites of the lower part of the pre-Cambrian Séries des Mines of the Katanga. The ore rocks are underlain, unconformably, by the older "Muva Series," in this case hard, green, metamorphosed quarzites. There are three superimposed orebodies, the first, or upper, orebody averaging 40-ft true thickness with a strike length of about 5000 ft, the second, or middle, orebody of about 50-ft true thickness with a strike length of about 6000 ft, and the third or lower orebody of around 60-ft true thickness with a strike length of 8000 ft. The orebodies are separated by varying widths of waste, or very low-grade ore, from a few feet up to 50 ft. The middle and lower orebodies are so close together for a strike length of 3000 ft that they are mined as one orebody. In all, the mineralized zone is about 200 ft in true thickness.

Jan 6, 1950

By J. J. De Witte, J. G. Cazort

The Paranam plant in Surinam (formerly Dutch Guiana) was built during 1939-40 to supply crushed and dried bauxite for the growing U.S. aluminum industry, supplementing production from the Suriname Aluminum Co.'s Moengo works, which began operation in 1922. A subsidiary of Aluminum Company of America, Suralco's total annual production from these two plants averages 2.55 million dry metric tons of various grades of bauxite. Starting in 1941 with bauxite from mines on the west side of the Suriname River, annual production at the Paranam plant has varied from a low of approximately 450,000 tons to more than 1 million tons in 1949. High production rates during World War II and the late 1940's rapidly depleted these reserves, and in 1950 plans were made to mine the known deposits on the east bank of the river, about five miles downstream from the original Paranam plant.

Jan 11, 1960

By J. C. Konopka, S. A. G. Poppen, E. K. Roesner

Many shafts have experienced stability problems during shaft sinking because the designer failed to fully appreciate the conditions he would encounter. Some shafts have failed during construction because the ground supports provided to compensate for the expected conditions were inadequate despite the most careful investigations and analyses. To design a ground support which is ultimately safe to achieve stability during shaft sinking would be too costly and impractical and, therefore, many shafts would simply not be constructed. The design of a ground support for shaft sinking based on an intimate understanding of the expected ground behaviour and stress development during excavation combines the art of mining with the science of geotechnical engineering. Where no historical design data is available, the designer of the ground support must: 1. classify the rocks and soils and assess their behavioural characteristics; 2. calculate the primary and secondary stresses; 3. design and/or select a ground support system which will ensure stability of the excavation during shaft sinking.

Jan 1, 1983

By Reamy Joyce

CONDITIONS in underground mining are so variable that in approach-ing the problem of the economies effected by the use of pressure-treated mine ties and mine timbers, it is necessary to secure specific data for each mine. Facts must first be dug out to show the service life of untreated timber and the reason for its failure. Generally speaking, decay is the usual cause of failure, but in some mines mechanical destruction is an important factor. Occasionally the two causes combine to produce fail-ures, and it is difficult to determine positively which factor is responsible. In making comparisons, it is always necessary to start with the cost in place and for this reason there must be accurate information covering the labor cost of installation and the labor cost of renewals. When treated timber is used, it is necessary to know the specifications for the treating process, whether the timber was painted, dipped, treated open tank, or impregnated under pressure according to standard specifica-tions. It is also necessary to know the preservative used and the amount of the preservative that was retained by the timber after treatment. It is also well to know whether the timber was thoroughly air-seasoned before treatment or was green at the time it was treated. The kind of timber available, both untreated and treated, must be known and all of the factors listed above must be taken into consideration in the study of any problem.

Jan 1, 1939

By S. E. Piper, E. M. Buchalter, R. P. King, E. T. Woodburn

The problems involved in an optimum decision making model for flotation circuit are, first of all, to characterize the feed material in terms of parameters which can quantitatively describe the network flotation action in terms of a feasible set of control actions. Once the characterization has been postulated, it is then necessary to devise tests relating to parameter sensitivity, in order that credibility of the model predictions can be assessed. Once a credible model is available, the optimum control set is determined by a hill climbing technique. Details will be reported as to the credibility of model predictions using the stochastic flotation model on a network and further, computational problems associated with hill climbing for a complex objective function are reviewed. Discussion is presented on use of the Rosenbrock technique with constraints and use of a modified objective function with constrained derivatives when employing Fletcher and Powell technique.

Jan 1, 1969

By L. W. Kempf

THE thermal conductivity of aluminum alloys is of considerable indus-trial importance. This is particularly true in such applications as inter-nal-combustion engines where one of the principal reasons for the use of these alloys is their relatively higher thermal conductivity. In spite of this, relatively few data are available on this property of aluminum alloys. The reason is quite apparent to anyone concerned with the experimental determination of coefficients of thermal conductivity. This determina-tion, in theory so simple, is extraordinarily difficult if any high degree of precision is desired. Fortunately, some knowledge of the relationship between thermal and electrical conductivity has permitted the use of the latter physical property in deducing the relative approximate-values of the thermal conductivities of metals. This fundamental relationship, first enunciated by Wiedemann and Franz1 as applying to metallic elements and later shown by Lorenz to be applicable to alloys within a single metallic system, has been of service in the industrial application of metals. The electrical conductivity of metals is easily determined with a high degree of precision. It is, therefore, quite desirable that the relationship between electrical and thermal characteristics be determined with the greatest possible precision. This paper presents data on the electrical and thermal conductivities of a number of aluminum alloys of industrial importance.

Jan 1, 1937

By M. N. Dunlap

Tries article summarizes the successful incorporation of a flash-flooding stream into the tailing-disposal system at the St. Joseph Lead Company's Federal Division mill, in St. Francois County, Missouri. The mill was built in 1906, by the Federal Lead Co., as its No. 3 mill for the concentration of southeastern Missouri lead ores, and damming Davis Creek was first considered in 1908. Plans were made also in 1925 and in 1937. Dam layouts varied from a reinforced concrete structure to a barrier built of tailings alone. All were abandoned because of liability that would be incurred by flashflood rupturing of an incompleted dam. By 1942 mill capacity had reached 12,000 tons daily and increasing tailing-disposal costs again focused attention on the Davis Creek basin. This time the problem of riskless dam building was solved. Moreover, most of the items that appeared in the answer were materials that normally required wasting and the major portion of labor involved performed functions that it would normally have done, without constructive benefit, elsewhere. The new layout also made possible advantageous changes in mill-water supply pumping; static head being reduced from 514 ft to 95 ft, friction head from 4900 ft to 2860 ft, and pumping can be done now at periods of low power demand. The following facts about the Davis Creek watershed explain the 36-year reluctance to reach these, and other, benefits. Size: 3600 acres. Outline: roughly pear-shaped, 2 1/2 by 3 miles at the largest dimensions. Topography: mostly hill land with steep valleys. Relief : 760 minimum to 1153 maximum. Maximum rainfall: 3.36 in. per hour. Permanent water: none natural. Now 2200 gpm discharged through 16-in. drill hole from mine pumps underground. Geology: the 17 acres near dam centerline is Bonne Terre dolomite covered with sand and gravel eroded from Pleistocene beds that cap some of the hills. The remainder of the pond basin is on Davis shale. Soil cover: mostly second-growth timber with some abandoned fields; all subject to careless burning, which reduces water-retaining ability. Flood history: flash-flooding that had taken at least one life. Downstream values: two railroad bridges before creek intersection with Flat River. Immediately below confluence, a highway bridge, a low-water crossing, a few business establishments and several blocks of residences. In July 1942 the following segments of an ingenious plan were put into operation. A ditch 270 ft long, 16 ft wide and 5 1/2 ft deep was excavated to bedrock in the gravelly soil along the proposed dam's centerline. This excavation, which exposed many gravel-filled channels, was run full of slimes drawn from a riser set in the top of an adjacent tailings-disposal

Jan 1, 1947

By D. V. Doane, G. A. Timmons, W. G. Scholz

Molybdenum of high purity can be produced by direct dissociatiott of commercial molyhdenm disulfide in vacuo at 1600° to 1700°C (2910° to 3090°F). The Product is lower in oxygen than commercially available molybdenzdm powder. Analyses of ingots arc-cast from commercial molybdenum powder, hydrogen-re-cluced from animonium molybdate, and from thermally dissociated molybdenum disulfide indicate that the levels of chemical impurities in these ingots are similar. Equipment now in operation will produce 100-lb hatches of powder product. The paper describes development of processing equipment, control of processing varzahles, handling of the product, and evaluatiotl of the melal produced. MOLYBDENITE (molybdenum disulfide) can be decomposed by heat in the absence of oxygen to produce elemental molybdenum and sulfur, which is evolved as a gas. The temperatures required for the dissociation are above 1370°C (2500°F); the sulfur must be continuously withdrawn to permit the reaction to proceed to completion. This is accomplished by continuous evacuation of the thermal dissociation chamber and condensation of the gaseous sulfur in another part of the system. Cognizance of the fact that the dissociation takes place in two steps is important in controlling the process. Basically, the molybdenite dissociation process has two potential advantages as a method of produc- ing pure molybdenum: 1) The materials entering into the process contain little or no oxygen. Since the process is carried out in vacuum at high temperature, the quantities of interstitial oxygen, nitrogen, and hydrogen in the product should be very low. 2) The process is more direct than the commercia1 method of producing high-purity molybdenum. In the conventional process, molybdenite is roasted to molybdic oxide, the oxide is purified first by sublimation, then by conversion to ammonium molybdate, and finally, the molybdate is reduced in a hydrogen atmosphere (usually in two steps) to the metal lic molybdenum powder. This paper presents a description of the stages in scaling-up of the dissociation equipment and an account of attempts to evaluate the molybdenum produced by thermal dissociation, rather than a report of a fundamental study of the dissociation reaction. Since little has been written on the subject, it is appropriate, before detailing the development of the process, to review briefly the research that has been conducted over quite a period of years. LITERATURE SURVEY The first accounts of the possibility of thermal dissociation of the mineral molybdenite were re-

Jan 1, 1962

By Arthur V. Abbott

In a few places attempts have been made to introdnce some means of delivering heat from a central station. Probably Pittsburgh, through the advantages derived from its almost inexhaustible supply of natural gas, has made a more wide-spread success in this direction than any other city. From the gas-wells in the vicinity of that town an enormous supply of natural gas can readily be obtained at a pressure sufficient to force it many miles from its source and to distribute it to all consumers. Obviously, very few places have such natural advantages, and some other means must be devised, if it is desired to furnish heat in a location not supplied with gas-wells. Several plants have been introduced to deliver heat by

Jan 1, 1888

By C. S. Barrett

Measurements of impact hardness of ß-brass are reported for a wide range of temperatures. Abrupt softening is observed when temperatures are raised above 425ºC, accompanied by abrupt widening of deformation bands in the deformed samples. Current theories of these effects, and of the lack of twinning, are discussed. HARDNESS1 and flow stress2 of a sample of ß-brass at room temperature depend upon the temperature from which the sample is quenched. It is believed that the state of order in the superlattice is responsible for this dependence—not the order within individual domains, which reaches near-perfection during the quench from any temperature, but the size of the domains which is presumed to be a minimum in the hardest samples, those quenched from temperatures near the critical disordering temperature of 468°C. Measurements of impact hardness made over a range of temperatures and microstructural studies of samples deformed both rapidly and slowly over a range of temperatures, reported herein, should be of aid in reaching a more complete understanding of the underlying factors controlling the properties of the disordered body-centered-cubic material and the ordered material. It appears that such data have not

Jan 1, 1955

By J. C. Bartlett

The following discussion was suggested by an experiment of Mr. Krom, the Manufacturer of air-jigs, to illustrate the superiority of air over water as a medium of concentration. The paper is written in the interest of no system of concentration, but simply to test the experiment, and, perchance, to add something to the general fund of information on the subject. To speak of testing an experiment by a theoretical discussion, may seem a misuse of terms, but the theories concerning falling bodies and the resistance of fluids are pretty well crystallized into laws, which may properly be used to show where experiments which seem to refute them were improperly performed, and that instead of refuting they only corroborate. It is well known that a sphere of galena & inch in diameter, and a sphere of quartz 1/2 inch in diameter, are equal falling in water ; that is, these two spheres, being placed together in a column of water at rest or in motion, will practically remain together, filling or rising together, or remaining in suspension. Mr. Krom, to show that these

Jan 1, 1879

By Paul C. Ragland, P. Geoffrey Feiss

The Piedmont province of the southern Appalachians is the focus of interest for many exploration geologists. In the past, only those deposits with significant surface exposure were exploited. Thus, few deposits have been found and relatively little exploration has been conducted in recent years. Modern geochemical and geophysical techniques can alleviate this problem of concentrating on exposed ore bodies by allowing us to "look through" the soil and saprolite to detect the presence of significant mineralization at depth. This paper will attempt to evaluate the feasibility and effectiveness of several geochemical exploration techniques in the Piedmont province of Cabarrus and Stanly counties, N.C. The area chosen for study is shown in Fig. 1, lying almost wholly within the Mt. Pleasant quadrangle, N.C. The area is on the eastern boundary between the Charlotte belt, a zone of plutonic and intermediate grade metamorphic rocks, and the Carolina Slate belt, a series of complexly interbedded volcanic and sedimentary rocks of predominantly low metamorphic grade. The area is considered to be an early Paleozoic active, continental margin. 1 As is typical of most of the piedmont, outcrop is sparse. Figure 2 is a sketch map of the general geology of the area under study, showing the Charlotte belt rocks in the north-western quadrant and slate belt rocks to the east. Within the area are a number of old mines and prospects, the most famous of which are the Furniss and Phoenix mines in Cabarrus County. All are reported to have contained Au and Cu. Ag and Pb were reported from some. A summary of the deposits is given in Table 1.

Jan 6, 1979

By George F. Becker

Complexity of Rock-Fractures.—The strains to which rocks have been subjected are manifestly very complex, and it is entirely safe to presume that every possible mode of deformation and rupture is exemplified. The most superficial inspection of any ordinary mountain region is sufficient to assure the observer that the rocks have been pressed, stretched, bent, buckled, twisted, and shorn. The study of torsional rupture cannot fail, therefore, to throw light on geological phenomena. The question is how areas which have been broken in this manner are to be distinguished from those which have yielded to other systems of forces. Phenomena of Joints.—It is well known that a large part of the more homogeneous rocks and some very heterogeneous rocks are intersected by partings often ailed joints. These partings are frequently flat surfaces even when seen in very large exposures, but are sometimes surfaces of moderate, single, or double curvature. Joint, usually occur in groups, in each of which the several partings are parallel to one another, and several such groups often intersect the same rock-mass. In such cases the different systems make large angles with one another. Nearly all students of the subject of jointing have reached the conclusion that joints are faulted surfaces, the dislocations usually being of small amplitude; and this conclusion receives abundant support from the study of thin sections under the microscope. It has thus been shown that much even of what would be regarded in hand specimens as mere slaty cleavage

Jan 1, 1895

By Gen-Hua Shi, Richard E. Goodman

In hard, discontinuous rocks, failure modes and stability are controlled to a great extent by the intersection of discontinuities with the excavated surface. We have solved the general problem of finding the shape and size of all blocks formed through the inter- section of any number of joints and excavation surfaces and will demonstrate a simple graphical method for determining which of these is the "keyblock." An example will explain this methodology applied to a simple open pit. The effects of slope curvature in plan or section, will be demonstrated. Finally, we will show how to determine the optimum orientations for the cut slopes. The methodology is based upon a powerful topologic theorem concerning the finiteness of spatial intersections. This paper is a companion to another dealing with underground openings in the Proceedings of the 22nd Symposium on Rock Mechanics (MIT) , July 1981. This paper discusses the rock blocks created by the intersection of discontinuities and excavation surfaces in a rock mass. It establishes principles and procedures by means of which those blocks that are finite and critically located can be identified and described. The main assumptions are the following: 1. The rock itself is assumed to be strong so that the only concern for stability is the movement of rock blocks them- selves.

Jan 1, 1983

By R. E. Ford, P. Tarassoff, P. H. Jennings

Copper oxide ore may be leached at all sizes from run-of-mine down to pulp, and consideration must be given to all available methods in determining the most economical one. Heap leaching was evaluated in a pilot plant at Gaspe Copper Mines, Ltd. which was designed to simultaneously leach two 1200-ton dumps of ore. The plant was operated for two years, in part under severe winter conditions. Two modes of leaching were investigated: acid leaching in which sulfuric acid was added externally to the leach solution, and pyritic leaching in which pyrite concentrate was added to the dump and acid was generated in situ by bacterial action. The pilot plant operation is described, and the results are compared with laboratory data obtained in 6-in.-diam columns. It is concluded that pyritic leaching offers certain operating advantages over acid leaching when copper is recovered by cementation in that iron buildup in the solution is prevented.

Jan 1, 1974

By R. N. Woody, S. J. Work

Crushing development at Duval Corp.'s Sierrita concentrator in Sahuarita, Ariz., has been a continuing effort since plant startup in January 1970. The original crushing system was designed to produce 65 000 t/d (72,000 stpd) of ore. However, in the summer of 1970 the Sierrita plant was averaging only 43 000 t/d (47,000 stpd) due to coarser than expected secondary crushing plant feed, lower than design crusher operating availability, and inability to achieve design tertiary crusher power draught at an acceptable hydraulic support pressure.

Jan 4, 1979

Within the last century, and largely during the latter half of it, the increase of our knowledge of the development of man, both in his search for a livelihood and for power, and in the growth of his reason and conscience, has been greater than all we had known before. The great interest in all kinds of archaeological work and the many excavations made of buried and long forgotten places has put at our disposal historical records not available, and in many cases not known before, and a study of these and other records of human progress from paleontological and geological sources has given us a much broader view of what we call "civilization" than was possible even a short time ago. The old idea that men were created with fully developed minds, speech and reason has yielded to the view that in the upward progress of the human race the development of the mind and reason has been a comparatively recent occurrence, as we think of the half million, and probably more, years that have passed since our earliest records of man were made. The traits that come to us without effort

Jan 1, 1935

By V. S. Rood, J. A. Norden

The general system of workings at the Utah-Apex is similar to that found in many of the western metalliferous mines. There is a vertical three-compartment shaft extcnding to the surface, from which the various levels have been driven to the orebodies. The 1000-ft. (305-m.) level, about 3/4 mile long, was driven as a haulage and drain adit. Geology The formation is a flat north-dipping series of alternating limestone and quartzite beds. Extensive north-south faulting and fissuring have taken place, resulting in the formation of large replacement orebodies in the crushed zones in the limestone. The orebodies are irregular in shape and size, but follow closely the trend of the mineralizing fissures. The ore consists of galena, pyrite, sphalerite and small values in silver and gold. Large masses of non-commercial pyrite are frequently found in or adjacent to the orebodies, and more or less pyrite is found for some distance in the walls of the orebodies. Lenticular bodies of a black pyritic shale also occur in the zones where extensive faulting has taken place. Mining Methods and Condition of Workings Geological conditions, mentioned before, have made the ground extremely heavy. In mining above the 1000-ft. level, square-set and filling methods were used, but not altogether successfully. The crushing of timbers extended even into the filled portions of the stopes. The filling material itself, consisting of limestone, shale, and pyrite, possessed swelling qualities which added to the difficulty of maintaining

Jan 1, 1920