Search Documents

By Allister McLeod

Coal is expected to play a major role in energy supply in the next 20 years. Oil is a convenient and still reasonably abundant fuel. However, its major sources of supply are regions where there is nervousness about political stability. Uranium is a more efficient fuel - but there is a continuing community apprehension regarding its use. What coal may lack in efficiency, it makes up in long term availability and competitive overall cost. Moreover, diversity of source ensures stable long-term supply. In this way, a major role for coal in the world energy scene is assured. Cyclical considerations aside, demand for coal will increase significantly and it will meet a substantial share of new energy demand, replacing oil and gas in major industrial and electric utility markets. By around the year 2000, coal's share of world energy could reach 30% and rival oil as the largest single source of energy.

Jan 1, 1982

By M. King Hubbert

In 1856 Henry Darcy described in an appendix to his book, Les Fontaines Publiques de la Ville de Dijon, a series of experiments on the downward flow of water through filter sands, whereby it was established that the rate of flow is given by the equation: q= - K(h2- h2)/I1 in which q is the volume of water crossing unit area in unit time, I is the thickness of the sand, h1 and h2 the heights above a reference level of the water in manometers terminated above and below the sand, respectively, and K a factor of proportionality. This relationship, appropriately, soon became known as Darcy's law. Subsequently many separate attempts have been made to give Darcy's empirical expression a more general physical fornzulation, with the result that .so many mutually inconsistent expressions of what is purported to he Darcy's law have appeared in published literature that sight has often been lost of Darcy's own work and of its significance. In the present paper, therefore, it shall be our purpose to reinform ourselves upon what Darcy himself did, and then to determine the meaning of his results when expressed explicitly in terms of the pertinent physical variables involved. This will be done first by the empirical method used by Darcy himself, and then by direct derivation from the Navier-Stokes equation of motion of viscous fluids. We find in this manner that: q = (N4(p/p)[g - (l/p) gradPI = WE, is a physical expression for Darcy's law, which is valid for liquids generally, and for gases at pressures higher than about 20 atmospheres. Here N is a shape factor and d a characteristic length of the pore structure of the solid, p and IL are the density and viscosity of the fluid, a = (Nd2)(pip) is the volume conductivity of the system, and E = [g - (l/p) grad p] is the impelling force per unit mass acting upon the fluid. It is found also that Darcy's law is valid only for flow velocities such that the inertial forces are negligible as compared with those arising from viscosity. In general, three-dimensional space there exist two superposed physical fields: a field of force of charucteristic vector E, and a field of flow of vector q. The force field is more general than the flow field since it has values in all space capable of being occupied by the fluid. So long as the fluid density is constant or is a function of the pressure only, curl E = 0, E = - grad F where F = gz + dp/p The field of flow, independently of the force field, must satisfy the conservation of mom, leading to the equation of continuity div pq = — f ap/at , where f is the porosity, und t is the time. For steady rnotion ap/at = 0. and div pq = 0 .

Jan 1, 1957

By J. Iannicelli

Spray drying is the principal drying method used in the production of over six million tons annually of beneficiated kaolin in Georgia. Thirty-three dryers in the Georgia Kaolin belt comprise the highest concentration of large tonnage spray dryers in the world. The steady growth of spray drying in the U.S. kaolin industry is paced by advances in design and development of large spray dryers which have led to large scale new applications in mining and related industries.

Jan 1, 1982

By Robert J. Willard

This chapter includes tables for 1982 that were not available in time for publication of the 1982 Minerals Yearbook, but does not include corresponding tables for 1983. The value of raw nonfuel minerals produced in the United States during 1988 was estimated at $21.1 billion, an increase of $1.5 billion over the value for 1982. This is a reversal of last year's downturn in value from that of 1981, which was the only decrease noted since 1971; hence, an overall trend of increasing values has been maintained for 12 years, except for 1982. Although the reversal is a basis for cautious economic optimism, it is tempered by continued problems in the domestic mining industry: inadequate funds for capital investment and competition with other countries that have lower production costs. Output of metal commodities in 1983 increased for 8 out of 21 metals, and metal values, in general, increased for 9 of the metals. Output of nonmetal commodities was mixed, with 24 nonmetals showing increases, 20 showing decreases, and 2 unchanged. Nonmetal values were also mixed in 1982: 25 showed increases, 20 declined, and 1 was unchanged. Improvements in the international metals market have not been forthcoming because of the continued depressed prices for major metals. Governments in foreign producing countries have been concerned with maintaining employment and continuing foreign exchange flows through mineral exports. Consequently, the excess of supply in the face of shrinking demand brought downward pressure on metal prices in general, except for the precious metals. On the domestic front, this situation means U.S. mining companies must become even more cost efficient. The major trend in the mining industry in 1983 was to cut costs further, reduce or stabilize total production, reduce outlays for major capital equipment, modify existing systems and equipment, and streamline operations. Most of the accomplishments reported herein reflect this trend.

Jan 1, 1984

By C. D. Elifrits

The required reclamation of land disturbed by surface coal mining often results in the creation of some over steepened slopes which are prone to rapid erosion and sediment production. This natural activity on such slopes is not desirable nor allowed under current regulations. Experience has indicated that novel approaches must be devised to address the problem. Research conducted on field sites in Missouri has indicated that construction, during the reclamation and grading processes, of a man-made drainage system will control the erosion. The drainage system must replicate or exceed the natural system in terms of drainage density and channel frequency. Basic design considerations will be summarized in this paper and field results shown.

Jan 1, 1986

By Patrick T, David K. Miller

Driven piles are an effective and cost-efficient deep foundation method; however, when piles are driven near existing buildings and improvements, vibrations must be controlled to non-damaging levels. Monitoring of adjacent structures is important for loss prevention, specification compliance, and public relations. The fundamentals of ground vibrations, including particle velocity, acceleration, displacement and frequency will be discussed. Types of pile driving and the ground vibrations that result will be summarized. Industry standards for safe vibration levels for various structures (residential, commercial, industrial, historic, utilities) will be reviewed. The paper/presentation will include a discussion of soil settlement from pile driving vibrations and case histories of observed settlements. Methods for calculating vibration amplitudes and frequencies will be presented. Best practices for monitoring and controlling ground vibrations, including available state-of-the art equipment, will be outlined. The paper/presentation will conclude with steps for designing and implementing a monitoring and control program.

By D. G. Purdy

Planning, as defined in Webster's New Collegiate Dictionary, is a detailed program of action designed to achieve an end. When developing a detailed plan to incorporate all the complex activities involved in a surface lignite mine, many elements must be carefully evaluated as to the individual and cumulative effects on the end result. The following elements are generally evaluated when planning a surface lignite mine: ? Reserve evaluation, including lignite quality characterization; ? Delineation of mining parameters, including lignite recovery factors, geotechnical factors, land control factors; ? Selection of mining blocks; ? Pit sequencing; ? Reclamation, including soil reconstruction design and land use planning; ? Overburden handling design; ? Selection of equipment; ? Sizing of equipment; ? Manpower requirements; and ? Other elements, including contract negotiations and execution, financing, investment return, operation economics, permitting and scheduling.

Jan 1, 1985

By K. Fair

Using an agitated column 203 mm (8") diameter by 1829 mm (72") tall with independent agitation units for the gas dispersion zone and the collection zones, respectively, permitted the independent evaluation of the attachment and the detachment mechanisms for the chalcopyrite/ silica system. Three particle size fractions were used in this study, i.e. coarse (+75 µ m), intermediate (-75 µ m + 10 µ m) and fines (-10 µ m). The optimum selection of the two agitation zones for the three particle size fractions were determined as a function of grade, recovery, residence time and air superficial gas velocity.

Jan 1, 1990

By Johnson R. Cann

Ocean floor sulfide deposits are now known from many parts of the world mid-ocean ridge system and from some seamounts. Clearly they can be expected to occur commonly on the ocean floor. However, only two or three of the known deposits appear to approach the million-ton size, and in none of the deposits has the grade been well-defined. Can knowledge of the processes that happen within the hydrothermal plumbing below deposits help define the conditions under which large, high-grade deposits form? Here I review present knowledge of ocean-floor hydrothermal processes to attempt a first answer to this question. There are three sources of information about these processes. The solutions emerging from active systems must be compatible with patterns of alteration that underlie the volcanogenic sulfide deposits of ophiolite complexes, which are slices of ocean crust thrust onto land. Both of these types of evidence can be linked by computer modelling of the exchange of heat and metals between rocks and flowing water.

Jan 1, 1988

By A. Yazadni-Chamzini

Considering the nature of open pit mines, harvest volume, it usually is required to remove a lot of waste to access to mineral planned grade. So, one of the most important part of open pit mines design, is waste dump site selection. Many factors are effective in waste dump site selection. These factors are sometimes in conflict with each other. So selecting the desired location for waste dump is a process complex and multi-criteria decision making. There are a variety of methods for decision making under complicated condition, such as fuzzy, Delphi, multi-criteria decision making and Expert system methods can be hinted. VIKOR method, which is one of the decision making multi criteria methods, is useful tool for decision-making. On the other hand with regard to uncertainty in decision-making, fuzzy approach is a useful tool for this purpose. This article has tried to select the best waste dump site in Sari Gunay Gold Mine by Fuzzy VIKOR. The results show that C position has a higher priority than other positions.

Jan 1, 2012

By F. M. Goodwin, John Campbell, W. P. Yant, G. W. Jones

"INTRODUCTION The cooperative investigation dealing with the general hazards of combustible gases and vapors in manholes owned by the Edison Electric Illuminating Co. and the New England Telephone and Telegraph Co. in Boston, Mass. and surrounding territory, was continued during 1934.The method and procedure of conducting the survey for 1934 were the same as those followed heretofore.ACKNOWLEDGMENTSThe cooperative investigation was arranged through the interest and effort of F. D. Comerford, president of the Edison Electric Illuminating Co. of Boston; E. M. Farnesworth, Jr., vice president and general manager of the Boston Consolidated Gas Co.; and A. C. Fieldner, chief engineer, Experiment Stations Division, U.S. Bureau of Mines. Thomas H. Haines, superintendent, Distribution Department, of the Edison Electric Illuminating Co., cooperated in furnishing both men and information for the work.The New England Telephone and Telegraph Co., through Chief Engineer G. K. Manson, R. F. Esterbrook, H. G. Crush, and A. J. McCarron, cooperated by assigning a telephone company employee for the test truck. The company has borne its proportionate share of the expense and has taken an active interest in the work during the year. The test crew was operated under the direct supervision of John Campbell, superintendent of the Special Service Department of the Edison Electric Illuminating Co., and 7. M. Goodwin, vice president of the Boston Consolidated Gas Co."

May 1, 1936

By E. Bonates

Dispatching systems have attracted considerable attention in the last years due to substantial gains in productivity achieved through their implementation. These systems will be extensively used in the future by mine operators as a means of optimizing productivity. This paper describes a computer simulation model designed to study the feasibility of continuously dispatching trucks in open-pit mines based on different operating procedures. The system developed is semi-automated and performs an active role by suggesting to the dispatcher the best assignment according to each specific circumstance. It is modeled based on an advance-clock increment to reduce computing time and allows the insertion of heuristic dispatching policies and equipment real-locations when breakdowns occur. Dispatching procedures taking into account long-term production objectives are considered in system development.

Jan 1, 1988

I N the introductory chapter to "Man and Metals," T. A. Rickard wrote "Five hundred thousand years ago the first footfalls of man's oncoming echoed down the corridors of time." This phrase has always appealed to me, not only for its resonance but because it seems to place in some perspective man's place in the cosmos. As we go about our daily occupations and as we meet here tonight, we must agree that we have come a long way slowly at first through the ages of change but with a quickening pace that has brought to man's know-ledge and use, within the last hundred years, more ideas, more material advantages, more opportunities and more comforts than were ever imagined or dreamed of in those long corridors of time. Looking back to the dawn of his-tory, a mere five thousand years ago, there is one aspect of the birth and growth of civilization that has particular significance for the miner and the metallurgist.

Jan 1, 1965

By K. E. Tame

The Bureau of Mines is studying possible modifications in conventional uranium ore-processing steps to confine and permit controlled disposal of radioactive wastes. A potential method of minimizing pollution from radio-active nuclides, principally radium 226, in uranium mill waste streams is to reuse the waste solutions within the mill. Such reuse of waste solution in the Kerr-McGee Shiprock-type process was investigated in the laboratory. The Shiprock mill employs a two-stage acid-leaching process for dissolution of the uranium, countercurrent decantation for liquid-solid separation and washing, and organophosphorus solvent extraction for recovery of the uranium and vanadium from solution. The simulated use of barren raffinate instead of fresh water in the mill circuit was carried through a laboratory campaign of 28 interlocked leaching, washing, and solvent extraction cycles. About 99 percent of the uranium and 91 percent of the vanadium were dissolved from the are, Washing efficiency in the thickener circuit averaged about 99.5 percent when the pulp was washed with enough barren raffinate and makeup water to recover 2.5 tons of pregnant solution per ton of ore. The only solution discarded was that contained in the washed and thickened leach residue. A buildup of salts due to recycling of solutions did not adversely affect operation of the washing circuit.

Jan 1, 1962

By T. A. Read, H. K. Birnbaum

STRESS-induced twin boundary motion in the AuCd ß'phase (52.5 at. pct Au 47.5 at. pct Cd having an orthorhombic structure (space group D h)' was discussed for the case of transformation twins.' Mechanical twinning, i.e., introduction of new twin orientations by the applied stress was sometimes observed in the ß' phase which contained two transformation twin orientations. (See Ref. 2 for experimental details.) The transformation twins terminated at the mechanical twin boundary; the two initial orientations having been twinned to the new orientation as shown in Fig. l. In a "hard" tensile instrument, formation of each mechanical twin was accompanied by a sharp drop in load (and an audible click) resulting in a typical serrated load-extension curve. The mechanical twins increased in width and additional twins were nucleated as the load increased until the entire specimen was occupied by the mechanical twin orientation. A restoring force2 caused the mechanical twin and transformation twin boundaries to return towards their initial configuration on releasing the load. In a stabilized specimen* the total strain introduced by mechanical twinning was recovered on releasing the applied stress. Initial and final microstructures were identical. After decreasing gradually to a critical width, mechanical twins suddenly disappeared accompanied by audible clicks and sharp increases in load (measured at a constant rate of crosshead motion in a "hard" machine). Mechanical twins could be stabilized in any position by maintaining the applied load for a sufficient time, indicating a decrease in restoring force with time similar to that observed for transformation twins.' Orientation relationships for mechanical and transformation twins were determined and are shown in Fig. 2. The mechanical twin, T3, was twin related to transformation twin, T,, by reflection in (1ll), and twin related to transformation twin, T2, by reflection in (111)T, . T, was related to T, by reflection in(ll1)T1 . The "average" mechanical twin composition plane lay several degrees from (1ll), . In every specimen which mechanically twinned, orientation T3 was most highly favored by the applied stress, i.e., it was the twin orientation which provided the greatest change in length compatible with the direction of applied stress

Jan 1, 1961

By C. D. Broadbent

Open pit blasting can be a low cost routine or a high cost bottleneck depending on geology, environment and the operator's ability to master site conditions. Because blasting is a repetitive operation, there should be ample opportunity to optimize the process; but ordinarily this optimization is rarely achieved and then only if conditions remain consistent and predictable. Often, however, and particularly with porphyry coppers, hidden differences in rock characteristics nullify the operator's best efforts. At a porphyry copper deposit being mined by Kennecott Copper Corporation, all of the following rock types occur; oxidized and fresh porphyry, altered and silicified limestone, explosion breccia, rhyolite, sandstone, shale and several others. The units can cover large areas or be limited to a few tens of feet in maximum dimension. They are rarely visible on the bench surface and often do not show up in the bench slope. Even though the blastability of these rocks varies substantially, a generally-uniform blasting pattern was formerly used with disappointing results. Secondary blasting was often required and high bottoms occurred frequently, overblasting wasted drilling time, and explosives caused excessive throw.

Jan 4, 1974

By Peter J. Clarke

The petroleum industry continued to be the most important mineral activity in Bahrain during 1978-79. Revenues generated by the petroleum sector increased from $378 million' in 1977 to an estimated $419 million in 1978 and approximately $522.5 million in 1979, despite decreasing production over the 2 year period. There were two oilfields that produced revenues for Bahrain, the Awali oilfield, the nation's only onshore producer, and the Abu Sa'fah oilfield, located in the Persian Gulf, north of Bahrain, The Await oilfield has been decreasing output from a high of 27,973,000 barrels in 1970 to 19,000,000 barrels in 1979. Bahrain shared the revenues from the Abu Sa'fah oilfield with Saudi Arabia, as settlement of an ownership dispute. For the first time, in 1978, revenues from the Abu Sa'fah oilfield represented over 50% of the total receipts from the petroleum sector. The years 1978-79 saw the gradual takeover of the Bahrain Petroleum Co. (Bapco), formerly a subsidiary of the California Texas Petroleum Co. (Caltex), by the Government-owned Bahrain National Oil Co. (Banoco). By yearend 1978, Banoco owned 60% of Bapco, and Caltex the remaining 40%. The Government-owned company controlled exploration concessions, managed domestic marketing of petroleum products, and controlled natural gas production and marketing. On December 15, 1979, the Bahrain Government completed full takeover of the Bapco operations. Bapco will continue to own and operate the 250,000-barrel-per-day oil refinery located near Sitrah, as well as handle foreign marketing of petroleum products.

Jan 1, 1981

By H. Dong, J. J. Valencia, L. Nastac

"A comprehensive computer model was developed to understand and optimize the centrifugal casting process for manufacturing TiC/Al-bronze friction drums. Performance of these components requires proper distribution of TiC particles, which is shown by dimensional analysis to be dominated by centrifugal buoyancy effects and solidification kinetics.The model addresses the following: (1) a rheology-viscosity model of the interference between moving particles, (2) engulfment (entrapment) or pushing of particles in the mushy region by the advancing solid/liquid interface, (3) nucleation and growth of equiaxed and eutectic phases, (4) effects of particle size, particle concentration, and cooling rate on the final grain size, and (5) the impingement effect of particles on the nucleation and growth kinetics of solidifying microstructure.Parametric studies were conducted using the computer model to investigate the effects of various process and material parameters on the distribution of TiC particles. The effects of the volume fraction, size, and morphology of the particles (including clusters and agglomerates) on the particle distribution were evaluated in detail. The complex interaction between the solidifying structure and insoluble ceramic particles in centrifugally-cast metal-matrix-composites was also investigated.The model predictions of particle distribution and microstructure were validated with experimental data for centrifugally-cast A356/SiC and TiC/Al-bronze alloys.This work was conducted by the National Center for Excellence in Metalworking Technology, operated by Concurrent Technologies Corporation under contract No. N00140-92- C-BC49 to the U.S. Navy as part of the U.S. Navy Manufacturing Technology Program."

Jan 1, 2000

By I. I. Gardescu

Rumania produced during 1936 some 62,500,000 bbl. of oil. Of this production, 99 per cent comes from an area running east and west along the southern foothills of the Carpathian Mountains just north of Bucharest. This almost rectangular area measures 20 by 40 miles and is located in the districts of Dambovita and Prahova between the cities of Targovigte to the west and Mizil to the east. The remainder of the production is about evenly divided between the oil fields north and east of Mizil in the Buzh district and those to the north on the eastern flanks of the Carpathian Mountains in the district of Baciiu. The Transylvanian Basin to the north and west of the Carpathian Mountains has produced to date only dry gas from its numerous salt domes. Bucsani Field The Bucgani oil field produced 15,600,000 bbl., or 25 per cent of the total production of Rumania in 1936. Bucgani is a deep-seated salt dome 7 miles south of the old Moreni oil field. A slight surface doming, not dissimilar to the topography observed on some of the oil fields of the Californian basin, called attention to the area. It is the southernmost oil field and, together with the deep-seated and prolific Boldesti field, points to the great oil possibilities of the deep-seated domes along the northern edge of the Rumanian plains south of the Carpathian foothills. The Government is the principal owner of the oil and gas subsurface rights in the areas south of the foothills. The acquisition of leases by the operating oil companies may be made either by application for an exploration permit, the company being assigned part of the acreage in case of successful wildcatting, or, if the area has already been declared as proven territory, through competitive bidding. A block of 164 acres was auctioned recently for $200,000, or $1200 per acre. The largest producer in the Bucgani oil field is the Steaua Romana, which produced 39.5 per cent of the total for the field. The Steaua Romana is a post-war company and 50 per cent of its shares are owned by the British Steaua and the Steaua Franpaise and the other 50 per cent by a group of Rumanian banks and by the Government. The Colombia,

Jan 1, 1937

By William Bent

MORE than twelve years were spent by Wöhler at the instance of the Prussian Government in experimenting upon the resistance of iron and steel to repeated stresses. The results of his experiments are expressed in what is known as Wöhler's law, which is given in the following words in Du Bois's translation of Weyrauch :* "Rupture may be caused not only by a steady load which exceeds the carrying strength, but also by repeated applications of stresses, none of which are equal to the carrying strength. The differences of these stresses are measures of the disturbance of continuity, in so far as by their increase the minimum stress which is still necessary for rupture diminishes." A practical illustration of the meaning of the first portion of this law may be given thus : If 50,000 pounds once applied will just break a bar of iron or steel, a stress very much less than 50,000 pounds will break it if sufficiently often repeated. This is fully confirmed by the experiments of Fairbairn and Spangenberg, us well as by those of Wöhler; and, as is remarked by Weyrauch, it may be considered as a long-known result of common experience. It partially accounts for what Mr. Holley has called the "intrinsically ridiculous factor of safety of six." Another "long-known result of experience "-although this has not, as the writer believes, been investigated by scientific experimenters-is the fact that rupture may be caused by a succession of shocks or impacts, none of which alone would be sufficient to cause it. Wrought iron will crystallize by repeated blows in service and become weaker than cast iron. Iron axles, the piston-rods of steam-hammers, and other pieces of metal subject to continuously repeated shocks invariably break after a certain length of service. They have a " life" which is limited. Iron rods in bridges sometimes crystallize and break, although the rods in most of our iron bridges * Strength and Determination of Dimensions of Structures. By Dr. J. J. Weyrauch. Translated by Du Bois, New York, 1877.

Jan 1, 1880