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By J. M. Rios

This paper exposes the reasons that led the Empresa Nacional Minera del Sahara, S.A. (ENMINSA) to the selection of a conveyor belt system for the transport of phosphate rock over a distance of 100 kilometers. ENMINSA was created in 1962, with the main objetive of the exploitation of phosphate rock deposits in the Spanish province of Sahara, in North West Africa. Poor grade outcrops were known previously. A detailed geological research carried over the province led ENMINSA to the discovery of deposits not exposed, and of much higher grade. The sector known as Bu-Craa was chosen as the most promising, and was explored by means of drill holing and shafting. The important amount of information obtained permitted a detailed evaluation of the capacity and grade of the rich ore contained in the Bu-Craa area. Simultaneously with the systematic reconnaissance of the Bu-Craa deposits, ENMINSA developped the study of the technical and economical problems required for the beneficiation of the rock, which comprised five main groups of projects: rock exploitation; beneficiation plant; rock transport from the mine site to the Atlantic coast; storage, handling and loading facilities by the sea- side, and power plant. Once determined the location of the marine loading facilities, which to date are in an advanced stage of construction (figs. 1 and 2), the studies conductive to the selection of the best transport system from the mine to the ocean, along 100 kms. distance were undertaken.

Jan 1, 1968

By Vladimir Jindrich

This paper presents a history of a successful three year effort in locating a large, economic deposit of high purity limestone. The exploration program has been carried out by Ernest K. Lehmann & Associates, Inc., geological consultants, for Dravo Corporation, owner of the limestone property which is now under development. The permission of Mr. L. P. Struble, Jr, President of Dravo Lime Company, and Mr. M. W. Robinson, Director of Research and Development, to present this paper is gratefully acknowledged. The limestone property is on the Ohio River near Maysville in northern Kentucky, 60 miles east of Cincinnati (Fig. 1). The area lies at the eastern flank of the Cincinnati Arch, a regional structure where the Lower Paleozoic strata crop out below the adjacent younger sedimentary rocks of the Illinois and Apallachian basins. In general, the limestone formations of the Middle Ordovician High Bridge group offer the best potential for industrial limestone in Kentucky and adjacent parts of Ohio and Indiana. These formations are exposed along the axis of the Cincinnati Arch in central Kentucky. Toward the west, east and north, strata of the High Bridge group are progressively deeper, concealed beneath a succession of interbedded fossiliferous limestone and shale. The High Bridge group limestone formations are shallow-marine deposits largely of tidal flat, shallow lagoon and related environments. Principal lithologies include cryptocrystalline micritic limestone and crystalline dolomitic limestone to dolomite. Shale and bioclastic limestone are subordinate but the proportion of shale increases in the basal formations. Characteristic, is the occurrence of several thin beds of bentonite that serve as regional stratigraphic key horizons.

Jan 1, 1975

By Philip G. Meikle

The Bureau of Mines Coal Mining Technology program has developed new concepts aimed at improving the efficiency of underground coal product ion. Conceptual designs have resulted in equipment prototypes, some of which are currently undergoing proof-of-concept evaluations at Bureau and cooperator facilities. Several of these systems and concepts are described.

Jan 1, 1984

By Larry J. Hughes

Ground-based electrical geophysical techniques have be valuable for three indirect exploration strategies: "tracer" sulfide mineralization, 2) mapping structure with or controlling mineralization, and 3) mapping proven to 1) mapping? associated alteration zones. When sulfide mineralization is associated with gold, it often can be mapped using induced polarization (IP). This technique can detect pyrite in amounts as small as 0.2% by volume, and in some cases can distinguish pyrite from anomalies due to graphite and clays. A case history illustrates mapping sulfides in a shear zone. Structure and alteration mapping are often the domain of controlled source audio-frequency magnetotellurics (CSAMT) due to the superior lateral resolution and depth penetration of this technique. Typical CSAMT targets include silicified sediments and volcanics, faults, brecciated zones, argillic alteration, clay and graphite horizons, and certain lithologies. Examples of mapping silicification and mapping epithermal alteration are presented in CSAMT case histories over Cannon mine in Washington and Hishikari mine in southern Japan. In our experience, four things are needed to use geophysics effectively in precious metals exploration. First, the explorationist must correctly identify the exploration stage at which the geophysics is most useful. Second, the explorationist must clearly define the types of "tracer" mineralization, host geology, or alteration which need to be defined by the geophysics. Third, the right electrical technique needs to be applied to the problem to provide the best chance of success. Fourth, the explorationist must be willing to commit adequate finances to do the geophysics properly. With careful adherence to these principles, geophysics can greatly enhance exploration success while reducing the total cost of exploration.

Jan 1, 1989

By J. N. Albright

Both microgravimetry and crosshole seismic tomography are means by which subsurface collapse and rock failure may be observed. We show results of calculations that predict changes in gravity and gravity gradient that result from void migration, bulking, and hydrology disruption due to room and pillar mining. Crosshole seismic tomography also holds promise for detecting and mapping changes in structure during subsidence. Commercially avail- able logging tools, advances in theory, and recent field results strongly suggest tomographic surveys are now possible. Subsidence phenomena which may be located are faulting, joint separation, bed parting, water table changes, and formation outgassing.

Jan 1, 1982

By William W. Shriver

When the Henderson Project is completed in 1975, it will become one of the Free World's largest primary molybdenum producers. The Henderson Mine will be located approximately 50 miles west of Denver, Colorado, on the eastern slope of the Continental Divide. Ore reserves are currently estimated to be 303,000,000 tons with a grade of 0.49% MoS2. The mill and tailing area will be located approximately 14.5 miles from the mine in the Williams Fork Valley, which is on the western slope of the Continental Divide. Ore haulage from the mine to the mill will be by ten miles of underground railroad and 4.5 miles of surface railroad. The concentrator has been designed to mill 30,000 tons per day and will yield approximately 50,000,000 pounds of contained molybdenum per year. This paper is concerned with the tailing and water supply system for the Henderson Project and in particular the environmental considerations affecting their design.

Jan 1, 1970

By Melvin A. Jennings

Even though the title of this paper is quite long, the ideas presented herein are very simple. In fact, it occurs to me to be somewhat humble about coming before such a distinguished group with such a simple presentation. However, the application of these ideas has proven useful in at least two copper flotation plants. The purpose in presenting this paper is to inspire some interest in the great stores of data chat the Mining Industry often accumulates without making any attempt at analysis. Unfortunately, many milling engineers rely rather heavily on percent recovery as a strict measure of a concentrator's relative performance. The fallacy of this reasoning is not difficult to see since, by definition, percent recovery is a function of feed assay, tails; and concentrate grade. If copper tailing is constant, and it very nearly is for a strictly sulfide copper ore, percent recovery must fluctuate almost directly to the feed assay. The point that I wish to make here is that it is very seldom justified to compare the percent recovery figure from one period of time to another without considering the difference in feed assay. The problem of comparing results is even further complicated when the ores are of mixed oxide and sulfide mineralogy.

Jan 1, 1978

By Charles C. L. Smith

A review and comparison is made of the circuitry utilized for dc crane control systems. Anti-parallel three phase full wave thyristor bridges for dc motor reversing and speed control are compared with a single three phase full wave thyristor bridge for speed control and either contactor or static switching for reversing control to obtain complete four quadrant operation for crane material handling. In recent years the Harnischfeger Corporation has developed a solid state adjustable voltage control system to control the speed and direction of dc motors for crane applications and handling materia1.1 Shunt wound dc motors are utilized and speed is controlled in the motor base speed operating region at constant torque by a thyristor, silicon controlled rectifier (SCR), adjust- able armature voltage supply. The three phase thyristor bridge is the power controlling element of the dc adjustable voltage control. ELECTROTORQUE is the Harnischfeger Corporation registered trade name for this type of drive system. By controlling the gating signals or firing pulses to the thyristor bridge SCR's the dc output voltage can be varied over a wide range. This range is limited only by the magnitude of the ac applied voltage. To obtain operation of the motor in both directions two thristor bridges are connected in an anti-parallel arrangement. A typical schematic for two anti-parallel connected three phase SCR bridges is shown in Figure 1.

Jan 1, 1973

By D. M. Thayer

In the last decade public awareness of the need for pollution abatement has increased greatly. The concern that had been previously shared by local and state conservation groups has spread to create a national concern for preservation of our non-polluted environmental assets and regeneration of those that have been wasted. Because other current matters such as inflation, civil rights,' tax reform and the Vietnam situation have been the object of most national concern, an extremely strong national pressure base has not been brought to bear on the pollution control crisis. Yes, the word is crisis, for in many areas pollution is of critical concern. One has only to look at Lake Erie, the skies about our major urban areas and many of our major rivers and streams to see this crisis These are not situations that can be corrected overnight. We are faced with two basic problems that should be attacked simultaneously: (1) Cleaning up the present sources of pollution and (2) preventing the generation of new pollution sources. What approach should be taken? As in any engineering problem, the limits must be well defined before a final solution is attempted. Pollution must be defined on a national basis. This means that basic Federal legislation and control is necessary. This should reduce any competitive advantage that can presently be gained by movement of operations from one state or geographical area to another on the basis of differences in local legislation .and enforcement. By giving real numbers as guidelines, selective enforcement can be avoided. As a starting point, for a definition of pollution let us use the following - "Any change in the environment occurring from other than natural causes." This definition may not be satisfactory to all but surely we must be somewhat dramatic in our statements to counteract the present prevailing philosophy. Our statement of this philosophy - "At what level of pollution can we afford to operate?" On the basis of our general definition we would like to state what we feel should be the philosophical statement - "How little can we change our physical environment as a result of operations?"

Jan 1, 1970

By Alan D. Hoagland

The Flat Gap Mine is on Copper Ridge in the Appalachian Valley of East Tennessee, Large zinc orebodies occupy zones of solution and collapse breccias in lower Ordovician Kingsport limestone and dolomite, The principal ore mineral is sphalerite and the principal gangue is dolomite, The orebearing horizons are considerably more than 95% covered by thick residual clay, and geochemical prospecting under these conditions is an effective exploration technique which played an important role in the discovery and exploration of the Flat Gap Mine, The residual nature of the over-burden at Flat Gap is emphasized, Background heavy metals (mainly zinc) range from 50 to 200 ppm, and the anomalies range to 3000 ppm and more, About 80% to 9W0 of the soil zinc is in relatively insoluble form in solid solution with the hydrous iron oxides and in the crystal lattice of the clay minerals. Quite discrete zones in the soil with sharply contrasting metal value boundaries mark vestiges of bedrock mineralization, and such anomalous soil areas are often contiguous with partially weathered ore. It has not been possible on the basis of chemical criteria to distinguish between an anomaly formed from non-commercial mineralization and one formed from ore.

Jan 1, 1962

By Dennis S. Kostick

Soda ash is the common name for sodium carbonate (Na2CO3), an alkali compound that is the 11th largest inorganic chemical in terms of production of all domestic inorganic and organic chemicals, excluding petrochemical feedstocks. Despite that most people have never heard of soda ash, it is an important industrial compound used to manufacture glass, chemicals, soaps and detergents, pulp and paper, and many other familiar consumer products. Natural alkalis have been used by mankind for thousands of years; however, their industrial manufacture dates back to only the latter half of the 18th century. Natural deposits of sodium carbonate have been known as early as about 3500 BC, when the Egyptians used natural soda ash in making glass. They also mixed lime and soda ash to make sodium hydroxide (caustic soda) that was combined with silicate minerals found in the Sinai desert. This made a soluble silica, which when added to aluminum-rich silt from the Nile River, produced a silica- aluminate cement mortar with excellent bonding properties for construction. The Romans in the first century AD also used natural soda ash in glass manufacture but expanded its use medically for the treatment of colic pains and skin eruptions, and in the making of bread. Elsewhere, people used the ashes of wood to obtain their source of alkali. People learned over time that different types of wood yielded various ashes with different properties; therefore, various plants were burned specifically for their ashes. Ash from plants grown in salt-bearing soils (such as saltwort) and from kelp and other seaweeds, especially Spanish barilla, were so different from ashes obtained from other vegetation that it became known as soda ash (due to its sodium content) versus pot ash, a potassium-based alkali ash. About 13 t of barilla ashes produced 1 t of sodium carbonate and 14 kg of iodine as a byproduct. The difference between these two ashes was relatively obscure until Duhamel Dumonceau made the distinction clear in 1736. The word soda ash developed from common usage and is perhaps more well known today than its synonym sodium carbonate. One of the primary ores of soda ash is trona, a sodium carbonate-bearing mineral that's name is traced back to Arabic origin. Trona also is known internationally by other names such as urao (Venezuela), kaum (Nigeria), natron (from Greek nitron and Latin natrium), and szekso (Hungary). The beginning of the Industrial Revolution in Western Europe in the late 18th century soon put a strain on the availability of raw materials to meet consumer demands. One of these scarce materials was soda ash. Because of the Seven Years War with England and the Napoleonic wars with other parts of Europe, France could not obtain sufficient quantities of Spanish barilla or other supplies of vegetable alkali to meet the growing demand. Efforts were needed to synthesize soda ash. In 1775, the French Academy of Sciences offered a large prize of 2,400 livres to someone who could find an inexpensive method to make soda ash. In September 1791 at St. Denis, Nicolas Leblanc (1742- 1806), a French chemist, developed such a technique using salt, sulfuric acid, coal, and limestone. The French Revolution interfered with its development, and his patent and factory were confiscated with Leblanc receiving only token compensation. Napoleon returned his factory to him; however, Leblanc was not able to raise enough capital to reopen it, and he committed suicide in 1806. A small, but not particularly successful, Leblanc plant was established in England in 1814. It was not until 1823 when the process first became commercially successful in Liverpool, England. The process was introduced in Germany in 1843 and in Austria in 1851 (Harness and Coons, 1942). Soda ash production by the Leblanc process reached its peak of about 599 500 t in 1880, after which it began to decline as the Solvay process became more popular. The Leblanc process was used to a limited extent in Europe during World War I but had disappeared by World War II. The Solvay process, also known as the ammonia-soda process, was developed by Alfred and Ernest (1 838-1922) Solvay in 1861 based on a concept by Fresnel that had been known since 1811. For the next 50 years, the implementation of the idea evaded industrial chemists because no large-scale and economic means could be found to commercialize the concept. Although Ernest Solvay was unaware of the existance of an ammonia-soda concept, he solved the problems by utilizing carbonating towers. The Solvay process produced soda ash from salt, limestone, and coke, with ammonia as a catalyst. With a capital of 136,000 francs, the first plant was built by the Solvay brothers at Couillet, Belgium, in 1863 with production commencing in 1865. Synthetic soda ash production amounted to 1.5 tpd in 1866, but reached 10 tpd by 1872. They patented their use of carbonating towers in 1872 that had made ammonia-soda manufacturing a successful continuous process. Their second plant was built in 1872 at Dombasle, France. In 1874, the first Solvay plant in England was built at Northwich by Ludwig Mond, the namesake of Brunner Mond and Co. (formerly Imperial Chemical Industries), the company that currently operates the two English Solvay plants. In the United States, William B. Cogswell in February 1879 heard a presentation on the Solvay process and sailed to Europe to meet with the Solvay brothers to seek their support for using their process in New York. At first, the brothers were not interested; however, Mr. Cogswell was persistent and ultimately gained their support. The Solvay Rocess Co. was formed Sep. 2 1, 1881, and construction began immediately on the first Solvay plant at Geddes, near Syracuse, NY. The plant came onstream Jan. 10, 1884, and produced 11 180 t in its first year of operation. In 1910, rotary calciners were installed that increased capacity to 1 000 tpd. By 1930, plant capacity was up to 2 400 tpd. The facility remained in continuous operation for more than 100 years. By 1939. 10 Solvay soda ash plants were in operation in 6 States throughout the nation. The Syracuse plant was officially closed Jan. 6, 1986, with total shutdown completed by Feb. 1986. Ironically, this facility was the first Solvay plant as well as the last. Other than the first Solvay plant beginning in 1884, the majority of US soda ash supplies during the 19th century came from imports. The remainder of the US supply

Jan 1, 1994

By Walter E. Heinrichs

To many, petroleum exploration and successful geophysics , are partly synonomous, This is not because natural petroleum is usually concentrated as a liquid, nor certainly not because oil can be detected directly. The reason is Chat geophysics helps to at least better understand and sometimes, to even explain the essential geology involved. That groundwater is similarly a liquid with all but a few of its basic geologic relationships practically identical to petroleum, seems to have escaped many of those most interested and responsible for complete geo-hydrologic knowledge. The paramount need to use every means at our disposal for maintaining and expanding our crustal resources reserves are generally obvious, However, in view of the rapidly mounting requirements, continual re-emphasis is worthwhile.

Jan 1, 1963

By Wayne P. Myers

Electricity, as normally thought of by a layman's definition, is a man- made force that has no color, no odor, is not visible, cannot be heard, yet man can control it and make it perform his work for him. A person dare not cheat on it, for it then will master him. It has laws, rules, and regulations that must be strictly adhered to if it is to perform in the safest, most reliable, and economical manner. In the early days of coal mining the power source was man himself. Later man employed steam and compressed air to reduce his muscle power requirements needed in the extraction of coal. By the turn of the 20th century, electricity had become the most common source of power for the coal industry. Steam and compressed air are still found in use in isolated cases today for specific applications; however, they are rapidly being replaced by electricity. Electrical laws and regulations are quite extensive and somewhat complex for the proper generation and use of electricity. Man-made laws, rules, and regulations for the care and handling of electricity, designed for man's safety, are rigidly enforced by Mine Safety and Health Ad- ministration (MSHA), as well as the various state departments of mines.

Jan 1, 1981

By Enrique Fernandez

The success of the excavation of a sewage tunnel in a very extreme geological conditions, from river deposits and sandy layers to hard dolomite, and several meters below the estuary under the sea water influence, shows that the choice of a right equipment together with the use of chemical products like foam and polymers enable to dig tunnels in unexpected areas and give solution to the environmental problems. The paper describes the excavation and support process as well as the adopted solutions in every material and during the cross through the intermediate shafts, also under sea influence.

Jan 1, 2003

By J. M. Pachter

Property sales and acquisition are prominent features of today's coal industry. Before selling or buying a site, a company must know the property's economic net worth. Any evaluation of economic net worth would be inadequate if determinations of a property's environmental liabilities and costs were omitted. Short-term and long-term costs can result from liabilities related to reclamation, water treatment, subsidence, and hazardous waste disposal. A structured, interdisciplinary approach can aid in the delineation, summation, and scheduling of these costs and liabilities.

Jan 1, 1986

The adsorption of gold onto activated carbon in iodide solutions has been studied. The adsorption rates were determined as a function of temperature, salt concentration and pH as well as activated carbon concentration. A kinetic model was also developed for the adsorption. The adsorption rate was believed to be controlled by a mixed mechanism of film diffusion and pore diffusion, but the film diffusion had a major contribution to the overall rate. Experimental findings were in good agreement with the model developed. The apparent activation energy was found to be 14.9 kJ/mol.

Jan 1, 1993

By R. K. Mehta

An electrochemical coal oxidation model involving heterogeneous kinetics is presented. This model was tested by collecting current transient data on three coals assaying different ash content under varying operating conditions such as particle size, temperature, and % solids. In all cases, the model fitted the data very satisfactorily. Three intrinsic rate constants, namely mass transfer coefficient of Fe(II) Ions diffusing from solution to the anode (kma), mass transfer coefficient of Fe(II) Ions diffusing from solution to the coal surface (kmc), and chemical rate constant for coal oxidation with respect to Fe(III) at coal surface (k), were calculated. It was interesting to note that in this system, the mass transfer at anode was as important as the chemical reaction at the coal surface. The validity of this model was further demonstrated through a comparison of the activation energy of coal oxidation: firstly, by utilizing calculated chemical rate constant and assuming Arrhenius' type of relationship: secondly, by utilizing conventional approach using limiting current values. The comparison revealed that agreement was quite close. This kinetic analysis is useful because such a model can be used in predicting the intrinsic rate constants so that the relative importance of mass transport can be rationally analyzed.

Jan 1, 1991

By Robert A. Metz

During the past decade we have witnessed spectacular improvements in productivity of open pit mining equipment. Thousand-horsepower engines, 200-ton trucks and 15-yard electric shovels, which such a short time ago were just dreams on a drawing board, are now realities. More productive equipment and metal shortages have encouraged increased production at existing mines and the development of new larger tonnage operations. Operators and engineers have been able to employ computers and various other types of automation to "stay on top of things". The mine geologist, however, is merely faced with a bigger and more rapidly changing pit to pick in. Keeping geologic information current in these mines presents entirely new problems to mine geological staffs. To obtain adequate geologic information on the developing orebody requires enlargement of the staff to share the work load or revision of methods in keeping with the times. The former has the disadvantage of loss of the comprehensive knowledge of the pit that a chief geologist likes to have, not to mention management's usual lack of enthusiasm for force increases.

Jan 1, 1970

By S. A. Pirzada

A thermal plasma assisted laminar flow reactor has been used to evaluate the kinetics of converting alumina to sodium aluminate in flight. Free energy minimization calculations were used to determine experimental conditions. The experimental variables include: alumina particle size, alumina/sodium nitrate molar ratio, temperature and residence time. A mathematical model for the conversion was developed and validated. Experimental and mathematical results are presented.

Jan 1, 1996

By Q. Xu

The adsorption behavior of gold in ammoniacal solutions on to activated carbon has been studied. The gold loading capacity of the activated carbon used in the system and the recovery efficiency by the adsorption were examined. The parameters affecting the adsorption of gold on to activated carbon included temperature, agitation speed, concentration of 'cation and anion as well as that of ammonia. It was found that the maximum gold loading on activated carbon used was about 10 kg of gold per ton of carbon. The recovery of gold by the adsorption from ammoniacal solutions was dependent upon the initial gold concentration in the solution. A recovery of 98% of gold was obtained on to the activated carbon under experimental conditions after 120 hour adsorption. It was also found that the initial adsorption rate was relatively fast compared to the whole period of the adsorption. The apparent activation energy for the adsorption was measured to be 15.8 kJ/mol. It was believed that the kinetics of gold adsorption on activated carbon was controlled by pore diffusion.

Jan 1, 1995