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By K. A. Natarajan, Abha Kumari

"The effect of applied DC potentials on the bioleaching of a chalcopyrite concentrate in the presence of Acidithiobacillus ferrooxidans is discussed. Copper dissolution was the highest at an applied potential of +600mV (SCE), while all the dissolved copper got cathodically deposited at a negative potential of -600mV (SCE). Electrobioleaching at an applied potential of +600mV (SCE) was established at different pulp densities as a function of time. The effect of applied potentials and electrolytic currents on the activity and growth of bacterial cells was assessed. Preadaptation of bacterial cells to the concentrate slurry and electrolytic growth conditions significantly enhanced copper dissolution. Electrochemical and biochemical mechanisms involved in electrobioleaching are illustrated with respect to oxidative dissolution and biocatalysis of anodic oxidation. IntroductionIn recent years, the bioleaching of low-grade chalcopyrite ores as well as their flotation concentrates has been receiving increased attention. Use of mesophilic bacteria such as Acidithiobacillus ferrooxidans in the bioleaching of chalcopyrite does not yield desirable copper extraction rates due to its easy passivation.Bioleaching of chalcopyrite using A. ferrooxidans has been reported to be very inefficient, and use of thermophilic bacteria at higher temperatures is recommended to improve its bioleaching rates. Bioleaching under imposed applied DC potentials or currents has been shown to enhance not only bioleaching kinetics but also to confer selectivity in mineral dissolution (Abhakumari, 1996; Chirpa Selvi and Natarajan, 1998; Natarajan, 1992a, b,c). Electrochemical principles governing electrobioleaching have been earlier illustrated (Jyothi et.al, 1989). The role of applied potentials on the activity and growth of A. ferrooxidans has also been studied (Natarajan, 1992b). Also, the electrochemical aspects of bioleaching of several sulfide minerals when present alone or in binary and ternary combinations have been reported (Jyothi et al., 1989). The electroleaching of copper-nickel concentrate (Natarajan et al., 1985) and electrobioleaching of sphalerite concentrates have already been studied (Selvi et al.,1998). However, it is possible to enhance the bioleaching rate of chalcopyrite in the presence of A. ferrooxidans under galvanic conditions in the presence of nobler minerals such as pyrite (Jyothi et al.,1989). Also, dissolution of chalcopyrite can be significantly enhanced under applied potential conditions. Ali Ahmadi and his coworkers recently studied the electrochemical bioleaching of chalcopyrite concentrates using moderate thermophiles (Ahmadi et al., 2010, 2011)."

Jan 1, 2015

By Iain M. Mason

Linear meridional zones of bad roof conditions have been frequently encountered in producing collieries working the Permian age Lithgow seam in the western coalfield of New South Wales. The prediction of such zones ahead of mining is desirable for reasons of both safety and economics. In March, 1981, we carried out an experimental, three-component in-seam seismic survey at Invincible Colliery to discover whether such zones have any unambiguous seismic effect. The underground survey was the first of its kind to be attempted in an Australian mine. The data quality was excellent with the spectra broadband and clear. Polarisation analysis disclosed two modes: one compressional; the other shear horizontal. The SH model was clearly dispersive and well gound to the plane of the seam. Modal velocities decreased by up to 15% at the fracture-swarm site. There is a strong suggestion on the RLS maps obtained here that the distributed fault zone is acting as a composite scatterer of channel waves. The P-SV and SH wave tomograms obtained show, in a general way, the distribution of stress in the coal panel.

Jan 1, 1982

By X. F. Wang, K. B. Fu

"We investigated experimentally and theoretically the adhesion behavior of Acidithiobacillus ferrooxidans (At.f6) to different copper sulfides. The adsorption experiment showed cell densities of 10.74 × 106, 8.06 × 106, 3 × 106, 4.24 × 106 and 2.35 × 106 cells/cm2, respectively, on the surfaces of djurleite, bornite, covellite and chalcopyrite. The order was: djurleite > bornite > covellite > chalcopyrite. The results indicate that A. ferrooxidans has high affinity to adhering to the surfaces of djurleite and bornite in the acidic region. But the thermodynamic approach predicts that there will be no attachment of At.f6 to the surfaces of bornite, covellite and chalcopyrite. This discrepancy is due to the inadequate description of electrostatic interactions. The DLVO approach shows attachment of At.f6 to the surfaces of djurleite, bornite and covellite, and repulsion between At.f6 and chalcopyrite. The DLVO approach can explain the differences of the adhesion of At.f6 to different copper sulfides.IntroductionThe bioleaching of low-grade copper sulfides is a developing technology, and has been applied successfully to the extraction of copper from secondary sulfide minerals (Watling, 2006; Pradhan et al., 2008; Akcil and Deveci, 2010). The bioleaching of chalcopyrite is still a major challenge (Bosecker, 1997; Brierley and Brierley, 2001; Ehrlich, 2004). A study conducted at Billiton Process Research showed the following preferential order of sulfide minerals leached by mesophilic cultures: chalcocite > bornite > cubanite > covellite > pyrite > enargite > carrolite >> chalcopyrite (Dew et al., 1999). The bacteria can solubilize the valuable metals from the orebodies by the oxidation of minerals. Bacterial adhesion plays a critical role in the bioleaching processes (Chen et al., 2008; Harneit et al., 2006). Generally, bacterial adhesion can be explained by surface thermodynamics and the extended DLVO theory, in which the adhesion energy between the bacteria and mineral is calculated as a function of the separation distance (Sharma, 1999; Bos et al., 1999; Sharma and Hanumantha Rao, 2002). These methods take into account Lifshitz-van der Waals interactions, electrostatic interactions and acid-base interactions (Busscher et al., 2010). These interactions are very well understood and formulated in mathematical equations. The most important inputs in these calculations are surface energy, surface charge, electron donation and electron acceptance on the bacterial cell surface and mineral."

Jan 1, 2015

By L. Adler

A systematic, balanced and inclusive formulation of the vast input data for mine design is presented. Since the quality of this statement severely influences subsquent design it is extremely important to senior mining engineers and the profession-at-large. If unfocussed, chaos can result along with serious ommisions. The basic categories, each a traditional one are: 1) Natural Conditions (geology and geography), 2) Company Capabilities (monetary and managerial), 3) Public Domain (regulations, contracts, good will, etc.) and 4) State of Art (mining engineering professionalism). To further reduce the data additional organizing principles were used: the distinctions of mining (vs. civil) engineering, proceeding from the general to particular, the basic engineering dimensions, and separating dependent from independent variables. The results are a unique and unified corpus, which anticipates the mine design procedure.

Jan 1, 1987

By R. C. Burtan

Long before the dawn of recorded history, man began to dig into the earth's crust in a never ending search for useful materials. It has been well established that prehistoric man discovered flint. "The Flintstones" were aptly named. The flintknappers of southern England and Wales still exist today in ever dwindling numbers as they seek out chunks of flint. It is a well known fact that more than half of the earth's crust is composed of silicon dioxide (SiO2), also known as silica. Silica and silica containing materials have a great many uses in modern society. However, this material is potentially extremely hazardous to our health. Centuries before the Christian Era, Hippocrates wrote of a lung disease common to those who mined in hard rock. It is obvious to us that he was describing silicosis. It is also apparent from ancient writings, that the Egyptians were aware of this malady. Dioscorides also wrote on this subject in the fifth century, B.C. It is undoubtedly the oldest and best studied of the occupational lung diseases. It was certainly described by Agricola in his "De Re Metallica" published in 1556, in which he described lung disease among hard rock miners. This publication, I'm sure, is of special interest and perhaps known to many of you in the mining community. The original document was written in Latin and was translated in 1912 by two gentlemen, Hoover and Hoover. One of these translators was Herbert L. Hoover, a former president of the United States, who made his living before his presidency as a mining engineer.

Jan 1, 1984

By Dan Nilsson

The Luossavaara "Research Mine" is the First large, offensive effort in mining research conducted by the Swedish state. Over a 5-year period, 1981-1985, the Swedish Mining Research Foundation works in the "Research Mine" on the development of mining systems and equipment. The purpose is to bolster the competitive strength of the Swedish mining and mining equipment industry. The previosly abandoned Luossavaara mine in Kiruna, in northern Sweden, has been reopened especially For the project. Ore is mined and sold during the course of the research project. The income from the sales covers a large portion of the costs for teh research.

Jan 1, 1985

By G. E. Rouse

Anomalies of sulfur dioxide and other gases have been defined, by direct measurement, around various sulfide bodies. These readings were made (1) in soil gas and (2) in the atmosphere, from both ground vehicles and, to a limited extent, from helicopters. Test areas included porphyry copper and molybdenum deposits, sulfide bearing vein systems, pyrite zones associated with sandstone uranium accumulations, and pyrite-bearing mine dumps. Some of the deposits are covered by as much as several hundred feet of overburden or barren rock, while others outcrop, or have been exposed by mining operations. Depending on local conditions, background values of sulfur dioxide in soil gas and the atmosphere range from 1 to 15 parts per billion. Using present techniques, anomalous readings are recognized at approximately two times background. Apparent "depth penetration? on known deposits has ranged to several hundred feet. Readings have been made over known deposits from a helicopter and ground vehicle moving at up to 40 mph. The rate at which the survey may be carried out depends largely on the size and extent of the anomaly. The existence and magnitude of sulfur dioxide anomalies around sulfide-bearing deposits is a function of geology, target size, soil moisture, and climatic conditions such as temperature and temperature changes, barometric pressure, wind velocity, and precipitation. Industrial S02 pollution can effectively mask the presence of the anomalies sought.

Jan 1, 1971

By C. Jack Powell

TVA's involvement in air quality programs is perhaps a bit unique. The Tennessee Valley Authority was established in 1933 as a regional resource development agency and therefore must view clean air and clean water as essential resources for the overall development of the Tennessee Valley region. TVA operates certain resource development and production facilities, including power-generating facilities, which are potential air pollution sources. The remarks in this paper will be restricted to air pollution control technology at power-generating stations. Perspectives of Air Pollution Control The art of pollution control must be viewed from several perspectives: 1. It must be viewed in a time perspective--what is available now for air pollution control, what might be available in the near future, what are the likely technologies for the more distant future, and what the future trends in availability of resources might be. 2. Each air pollution abatement scheme must be viewed in the perspective of its total environmental consequences--not just its ability to clean up the air. The generation of electricity from coal produces waste gases, waste particulates, and waste heat. These wastes must be disposed of either in water, in air, or on land. If the polluting wastes are removed from the gas streams going into the air, then they must be disposed of either on land or in water or, hopefully, converted into a product which has some beneficial use. As an example, removal of S02 from stack gases could be more readily accomplished if one could dump waste sulfur products in water. He would solve an air pollution problem by creating a water pollution problem. 3. Techniques for air pollution control must be viewed in the perspective of regional, national, and world resources with their national security and economic implications. The power industry might reduce air pollution by switching generating plants to burning desulfurized fuel oil or natural gas.

Jan 1, 1972

By W. D. Bullock

The King-Beaver mine of Asbestos Corporation Limited operates an open pit in the city of Thetford Mines, Quebec. The approximate loca-tion of the open pit is at Latitude 46° 02' North and Longitude 71° 20' West. The general topography is 1020 feet above sea level. Thirty-six percent of the company's scheduled asbestos ore production, for the Thetford Mines area, comes from the King-Beaver pit. The pit operates 24 hours a day, six days a week. Normal production is 10,500 tons of ore per day at a waste to ore ratio of 2 to 1. The remaining ore requirements are mined from the King-Beaver underground mine and the British-Canadian mine.

Jan 1, 1980

By David N. Hedges

This paper discusses the actual recovery and installation of a longwall in a bituminous coal mine in Western Pennsylvania. The coal bed mined is in the Lower Freeport seam which averages 42 inches (1.07m) in height locally. Drainage from the mine is approximately 3.5 million gallons of water per day (13.25 million liters per day). This water deteriorates the mines predominately fire clay bottom making it extremely difficult to move equipment. Support removal is accomplished by pulling the 6 ton (5443 kg) shields out under their own hydraulic power and transporting them by track over four miles (6437m) co the next longwall panel. This paper also discusses the changes that will be made to aid in the succeeding longwall recoveries and installations.

Jan 1, 1984

By W. D. Elston, A. E. McLaughlin, G. B. Hampton, W. L. Barham, J. F. Murphy, W. H. Cundiff, J. W. Mulloy, R. G. Breuer, J. W. Shaffer

Introduction Alumina (aluminum oxide) is the material from which all the world's aluminum is produced. In the Western World, all the alumina is made from bauxite by the Bayer process. In the nearly 150 years since aluminum was first isolated by Oersted, the metal has grown from a laboratory curiosity to a position of major importance in the world's commerce. In terms of annual production rates aluminum is first among nonferrous metals. Oersted's discovery-reduction of aluminum chloride with potas¬sium amalgam-was improved on by Ste. Claire Deville, whose so¬dium amalgam reduction of aluminum chloride led to the commercial production of aluminum in France in 1855. Ste. Claire Deville's method prevailed until 1886 when Charles Martin Hall and Paul T. Heroult each invented a process for the production of aluminum by the electrolysis of alumina dissolved in molten cryolite. The inven¬tion by Karl Josef Bayer in 1888 of an economical process for making very pure aluminum oxide (alumina) from bauxite established the necessary link between known ores and the Hall-Heroult reduction process. Bayer's work completed the scientific base-the ore bauxite refined to alumina by the Bayer process (U.S. Patent No. 515,895), the alumina reduced to aluminum in the Hall-Heroult cell (U.S. Patent No. 400,766--upon which today's aluminum industry is founded. Small-scale production of aluminum in the U.S. began in 1888 utilizing the Hall cell. By 1903, bauxite properties and a Bayer process refining step had been incorporated into the production activities. On this base the aluminum industry in the U.S. has grown at an annual compounded rate of 15%. Since 1946 the annual growth rate has been 10%.1 The rapid growth of the industry is the result of many factors among which are the existence of widespread bauxite ore deposits; a sound and economic production technology; and the properties of the metal-lightness, strength, ductility, good electrical and heat con¬ductivity, and pleasing appearance, which lead to ever greater de¬mands for aluminum in an industrializing society. At the inception of the industry, the only market that could be found for aluminum was in the production of cooking utensils. How¬ ever, the rapidly accelerating industrial and technological development of the Western World soon created new needs for aluminum, and today aluminum is marketed in a broad range of industrial, commer¬cial, and consumer applications. The principal uses for aluminum are:' building and construction, 22%; transportation, 18%; electrical, 13%; packaging, 11%; consumer durables, 10%; machinery and equipment, 7%; other, 19%. The 1974 production of primary alumi¬num in the world was 14.5 million short tons, which at an approximate ingot price of 40¢ per lb puts a value of $11.6 billion on the industry product prior to fabrication. While aluminum is widely distributed in the earth's crust and is a major constituent of many rocks and soils, to date no method of extraction of aluminum from such nonbauxite material has been brought to commercial practice in the Western World. In the USSR alumina is produced by the complex processing of nepheline syenite, but elsewhere all commercial production of alumina is from bauxite. A brief discussion of recent developments and other processes for alumina is included in the subsection "Other Processes for Alumina," page 19-15. In early 1973, a major U.S. aluminum producer announced the successful development of processes for the production of aluminum from aluminum chloride. This achievement promises to exert a major influence on the future of the aluminum industry. In the initial com¬mercial application of this new technology, Bayer alumina will be chlorinated, and the aluminum chloride then reduced by electrolysis. Important claims for the new processes are lower energy requirements (one-third less than obtainable in Hall cells) and reduced labor costs. Capital costs are said to be no greater than for conventional plants. While the announced intention is to produce the aluminum chlo¬ride from Bayer process alumina, the new chloride reduction process will eliminate the other raw materials, carbon and fluorides, required by the conventional Hall cells. The electrodes in the chloride cell will not be consumed on the reduction process and the electrolyte will have, as the name indicates, a chloride rather than a fluoride base. 2. Bauxite Definition and Origin. Bauxite is a naturally occurring raw material composed principally of a mixture of one or more of the hy¬drated aluminum oxide minerals gibbsite (Al2O2 3H2O), boehmite (Al2O3 H2O), and diaspore (Al2O, - H2O), and impurities of silica, iron oxide, titania, and other various elements in trace amounts. It is an end or near-end product of chemical weathering. Depending on the amount of iron impurities, the color of bauxite varies from dark red and brown to pink to white. Some bauxite is finely divided, free digging earthy material, while other forms are dense and rocky, requiring explosives in mining. Many gradational forms exist. It is one of the most variable of mineral raw materials in chemical composition and physical appearance. It is generally believed that bauxite deposits resulted from intense chemical weathering of aluminum-bearing rocks or formations under tropical or subtropical conditions with alternating wet and dry sea¬sons. Topographic conditions were favorable for drainage and the in-situ accumulation of aluminum, iron, and titanium oxides. There was low to moderate topographic relief with a minimum of erosion during long quiet periods in earth history.2 The occurrence of bauxite is widespread and it has been found on all continents except Antarctica. Production was reported from 27 countries in 1974, at which time total world production was over 79 million metric tons. Of this production 76% was from seven coun¬tries-Australia, Jamaica, Surinam, Guinea, USSR, Guyana, and Greece-which ranked in that order of production. In Table 1 are shown typical compositions of bauxite from some

Jan 1, 1985

By D. Chakravarty, G. Samanta, B. Samanta

The present study highlights the planning and design aspects of a well-known openpit copper deposit in India. The mine has been operational since 1982 and presently reaches a depth of 168 m below the surface. The present planning effort has been given due consideration in view of the recent upsurge of copper prices in the global market. The prime focus of the study has been directed towards examining the possible extent of final pit beyond the current pit outline and generating an extraction sequence of future mining operations. To this end, an orebody model of the deposit has been developed and the optimized pit has been derived using L-G 3D algorithm. A sensitivity analysis has also been performed to scrutinize the possible effects of the changing economic scenarios on the ultimate pit configuration. It has been observed that with the current production rate, mine life can be extended another 40 years. With a five-year production plan, these materials can be extracted in eight push-back schemes. The extraction sequence of these push-backs has been outlined in this paper.

Jan 1, 2011

By T. E. Masoner

The struggle to get the minerals industry seriously interested in high intensity wet magnetic separation* has been difficult. The high capital cost of the equipment, the lack of basic research, the lack of operating information, and the diverse characteristics associated with different minerals and ores have prevented the development and use of HIMS-W on a wide scale. The Climax Molybdenum Company, a Division of American Metal Climax, Inc., located at Climax, Colorado, was among the first companies in the Americas in recent years to support the development of HIMS-W to recover weakly magnetic minerals on a large scale. The Climax Molybdenum Company, one of the world's largest underground mines, processes about 40,000 tons per day of ore, from which about fifty million pounds of molybdenum disulfide are produced each year. By-products include tungsten, iron pyrite, tin, and some monazite.

Jan 1, 1968

By L. G. Austin

Introduction My first contact with industrial milling was during the time I worked in the electricity generating industry in the United Kingdom. In visits to power stations to investigate either deposits in the boiler furnaces or polluting deposits settling around the stacks. I had to check the performance of the vertical coal pulverizers, since poor pulverization aggravated both problems. Naturally, then, when I came to the USA in 1957 to take a PhD in fuel technology at Penn State, I was put to work to review the science of coal pulverization. After this reviewing, I was completely confused. On one hand, there was a well-developed understanding of stress-strain equations, and a rap- idly developing knowledge of how stressed, brittle solids fractured, based on the Griffith crack theory. On the other hand, reading in the grinding literature gave me: • Kick's Law, which was clearly not correct in the light of modern fracture theory; • Rittinger's Law, which was also clearly not correct; • Bond's Third Law of Comminution, which was claimed to have something to do with the Griffith crack theory, but where the connection between the two was made by intuitive pseudo- scientific reasoning I could not accept; • the choice of mill motor power for the most common type of coal mill, the Raymond pulverizer, was calculated from the fan power required to move air through the mill. Although I could accept the empirical connection between the two, it made no sense from the point of view of fracture energy. Even today, most books or review chapters on size reduction start from these laws. incorrect statements abound in the literature, such as “the Hardgrove Index is based on Rittinger's Law," which it is not, "The Bond theory states that work input is proportional to new crack tip length produced in particle breakage," which is not true, etc. My own test work showed that these "laws" did not fit the data for grinding of coal. At about this time, Epstein (1 948) and Broadbent and Callcott (1 956), following the original work by R.L. Brown (1941) at the British Coal Utilization Research Association, proposed describing breakage as a series of fracture stages. I took their concepts and developed the basic differential equation for a batch grinding process continuous in time, analogous to a batch chemical reactor. Robin Gardner then joined the project and did his PhD on treating batch grinding in the same way as a batch chemical reactor. He found that the basic equation had already been partially derived by Sedlatschek and Bass (1 953) in Germany. We confirmed experimentally the validity of the equations for describing batch grinding (1 962) and formulated the equation describing steady-state continuous grinding in a fully-mixed mill. At about the time this work was published, Gaudin and Meloy (1962) and Filippov (1961) independently published essentially the same equations, but without experimental proof of the validity of the concepts. I will give a brief overview of what these beginnings had led to in the design of mills for size and power, and show some of the results of this more detailed understanding of grinding processes. Concepts of Fracture Mills such as tumbling ball, rod, pebble and autogenous mills and vertical mills such as the Raymond, and E-type apply compressive stress to lumps or particles relatively slowly. Compressive stress applied to a particle of an elastic brittle solid imparts overall strain energy to the solid and produces local regions of tensile stress, (Fig. 1) (Berenbaum and Brodie, 1959). Irwin (1949) showed from solution of the stress-strain solutions that a small hole in a region of tensile stress reduces stress concentration at the hole, that is, the tensile stress at the tip of a crack or flaw in a solid is much higher than the general tensile stress in the region. The longer the crack, the higher the stress concentration. Griffith (1920) hypothesized that when the regional tensile stress is large enough, then the chemical bonds at a preexisting crack tip are stretched to breaking point, as illustrated in Fig. 2. When the bonds break, the crack becomes longer, the tensile stress concentration increases, the situation is unstable and a crack opens up (propagates) a surface of tensile stress, creating its own tensile stress at the leading edge. Stored strain energy is converted to the kinetic energy of the moving stress field, which is analogous to sound propagation through the solid, so the crack tip accelerates to velocities approaching those of sound. The moving crack will pass through regions that were previously under regional compressive stress. The equations for "ideal" and "Griffith" strengths are where a is the intermolecular distance, y is Young's modulus, g is the energy

Jan 1, 1998

By Justin Kolster, Donald Benjamin, Kyle White

Expansion of the Plum Island Wastewater Treatment Plant requires interconnection of three operating pump stations using only two existing 10-ft diameter shafts for access. These two existing shafts require additional support to allow access 130 feet below grade. Interconnection requires rehabilitation of an existing tunnel, excavation of two new tunnels, and abandonment of additional existing tunnels. Construction has discovered unexpected conditions at all three connection points. The CMAR contracting method has effectively accommodated project team discussion, value engineering decisions, and allocation of risk during preconstruction and construction phase services.

Dec 1, 2022

By Roy A. Grancher

CYCLING WITH CEMENT "THE WHEEL IS COME FULL CIRCLE" Shakespeare's King Lear Act V, Scene 3, Line 176 The time clock of the cement industry has been turned back to the early 1950s. After the trials and tribulations of the decade of the Sixties, the hands now stand where they did just over twenty years ago. Cement shipments have steadily increased, with a record 419 million barrel level (78.8 million tons) being reached last year. Plants are operating at average utilization rates in excess of 85 percent of rated capacity. The spread between supply and demand has narrowed to where a definite shortage of cement now exists within the industry. The notable and unfortunate difference between the two periods however is that, back then, cement's returns were a respectable 14 to 18 percent, whereas today they stand at less than half those levels. Insufficient return forms the present foundation of the U.S. cement industry. This lack is destined to have a cumulative effect. Just as the industry's balance between supply and demand is returning to favorable proportions, promising a period that has historically and now should generate those profit levels required to modernize and provide for capacity addition, cement instead finds itself frozen by federal price controls into the semi-depressed condition that has existed for over a decade and from which it was just starting to emerge. Capital is not attracted to continued low returns, and increasingly restrictive pollution control measures are necessitating great non-productive expenditures be made as definite costs to stay in business. Even a clouded crystal ball would reveal that additional cement plant closings can be expected.

Jan 1, 1972

By J. R. Boldt, C. M. Kleemann, V. N. Mackiw, B. Meddings, J. A. MacLellan, E. J. Maney, D. E. Halter, D. J. I. Evans, J. Honkasalo, M. F. Dufour

The technology employed in the processing of nickel- and cobalt¬bearing ores is a continually developing process for utilizing the natu¬ral resources available at a given time. Most of the nickel-bearing ores of commercial importance fall under the category of sulfide or lateritic ores. While the occurrences of both types of ore have been known for over a century, until 1960 sulfide ores largely from Cana¬dian mines have constituted the chief source of production for com¬mercial nickel in the Free World. Sulfide ores are readily amenable to some physical means of concentration, but the lateritic ores are not readily concentrated, and to compete economically with the sulfide ores only the high-grade garnierite ores (a type of lateritic ore) found in New Caledonia were processed to any great extent up to the time of World War II. Around 1960, a gradual shift in emphasis towards latetitic ores as a commercial source of nickel became evident. See Fig. 1. New discoveries of sulfide ores, usually located underground, had not kept pace with the steadily increasing demand for nickel. The lateritic ores, found near the surface of the earth, could be readily surveyed and mined. Lower cost processes were being developed for the extrac¬tion of nickel from lateritic ores and for a time it appeared that, based on pre-OPEC economics, the lower grade lateritic ores-down to 1.2% nickel-could satisfy an increasing share of the world demand for nickel. The sharp increase in the price of crude oil in the 1970s, however, slapped an economic damper on the lateritic ores. Processes for treat¬ing lateritic ores consume large amounts of energy; as the nickel industry entered its deep recessionary period in 1981-83, nickel pro¬duction from lateritic ores became less and less profitable than from sulfide ores. At the same time, new sulfide ores were discovered and brought into production, notably in Australia and South Africa. The chapters in Section 17 were prepared in 1973. Recent improvements in mineral dressing techniques since then include Inco's pyrrhotite separation process which can remove additional pyrrhotite from nickel concentrates, resulting in reduced sulfur dioxide emission from the Sudbury smelter, by some 25%. The chapters in this section dealing with nickel are grouped in line with the two broad categories of nickel ores. Starting with the description of nickel and cobalt ores in Chapter 2, Chapter 3 deals with the processing of sulfide ores, and Chapter 4 deals largely with lateritic ores. The intermediate steps to produce a suitable feed for extraction plants and refineries are similar in principle within the same categories, although dissimilar between sulfide and lateritic ores. Thus Inco in Canada employs flotation and so does Western Mining Corp. in Australia, although Inco's plants were started before World War II, and that of Western Mining only recently in the late 1960s. Treatment subsequent to the ore dressing step, however, shows some interesting differences. The earlier parts deal mostly with established and conventional practices, leaning heavily on pyrometallurgy in both

Jan 1, 1985

By Roy A. Grancher

HAPPY BIRTHDAY Not only is 1971 the Centennial Year of the AIME, but it also marks the One Hundredth Anniversary of the United States Portland Cement Industry. On September 26th in 1871 David O. Saylor of Allentown, Pennsylvania, received his patent Numbered 119,413 for the manufacture of portland cement. "Cement" had been used in the United States before that. This was, however, natural cement - a direct product of rocks as found in nature, usually burned at low temperatures in open kilns. During the early 1800s this natural cement played an important role in such projects as the building of the Erie Canal. It was only after the Civil War that small amounts of high priced portland cement was imported from Europe. The successful use of this material in construction led to Saylor's experiments and subsequent patent for the manufacture of a scientifically controlled product in this country. These one hundred years have witnessed four major "ages" of cement . . . three of them occurring in the last quarter century since World War Two. The first age was the "Age of Development", a seventy-year period which saw the growth of cement and its concrete end uses as major construction materials. Next followed a period called the "Age of Demand" when, after the war, cement became in short supply relative to large building requirements. In effect a cement shortage existed. The decade of the Sixties proved to be the "Age of Reaction", with its courses of action coming in response to the problems that arose when the industry's expansion programs provided too much capacity. Today cement, and the concrete industries, find themselves entering the "Age of Reason". Overcapacity, low price, rising costs, and poor returns are several of the reasons behind that name, As these industries face the construction challenge of the Seventies, and beyond, the application of basic management principles (otherwise known

Jan 1, 1971

By V. Voller

A relatively simple model of grinding which incorporates both the Bond grindability equations and the population balance equations has been extended to form a comprehensive simulation package that can describe most kinds of conventional grinding circuits. The package has two programs, with the first consisting of an input program which helps the user to specify the prescribed circuit, while the second program performs the actual simulation. The package serves two main purposes - i) as a check on mill design, with the output providing not only predictions for the product passing size but also of the full product size distribution, and ii) as a means to assess the likely effects on the product size distribution of operating under different sets of conditions.

Jan 1, 1981

By Felicia F. Peng

An economic analysis for evaluating coal preparation plants in the Appalachian Region is presented. A complete coal preparation plant which includes multi-streams and/or multi-stages coal cleaning circuits, complete closed water circuits, environmentally acceptable refuse disposal and reclamation systems is used to determine the capital and operating costs. The plant is capable of producing metallurgical grade clean coal or deep cleaned steam grade coal for future power generating plants use. Utilizing a profit maximization as a decision criterion, an optimal yield, and optimal coal clean¬ing circuits, closed water circuits, and disposal and reclamation systems for a given coal characteristic may be selected among the process alternatives by using a process simulation-economic model of the coal preparation plant. A deterministic analysis is used to calculate the discounted-cash-flow interest rate of return (DCFIROR) and project the selling prices, and determine the Return on Investment (ROI) for the cases of 32.65% and 52.74% plant utilization with producing two cleaned products. Sensitivity analyses are performed to quantify the effect of total capital investment, operating cost, run-of-mine cost and yield on an economic criterion-ROI and selling prices. A probabilistic evaluation using the Monte Carlo simulation technique is further made to quantify the risk involved in obtaining the desired profit levels. The results of the economic analysis for a given coal preparation plant configuration and characteristics of raw coal indicates that the selling prices of producing two cleaned products are greatly affected by the change in percent of plant utilization (production schedule), yield, and run-of-mine cost, and total capital cost. The sensitivity analysis also shows that the total capital investments has a three times greater effect on required selling prices than operating costs. The risk analysis shown that the overall economics look very attractive with current coal sale prices and 52.74% plant utilization.

Jan 1, 1979