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By S. Dixon

The Peñasquito deposit in Mexico is one of the largest grassroots precious metal discoveries to be developed in recent years Minera Peñasquito, S.A. de C.V., a wholly owned subsidiary of Goldcorp Inc. has developed the Peñasquito property to produce an average annual production of 120 kilo tonnes of lead containing 0.5 million oz gold and 30 million oz silver and 250 kilo tonnes of zinc containing 20 thousand oz gold and 1.5 million oz silver.. The Peñasquito property covers a 39,000 hectare area in the western half of the Concepción del Oro district in the northeast corner of Zacatecas State, Mexico, approximately 24°45'N latitude/101°30'W longitude. The sulfide reserves are 1,009 million tonnes containing 3.33 million tonnes of lead, 7.26 million tonnes of zinc, 16.5 million ounces of gold and 1,000 million ounces of silver. This paper describes the work to justify the installation of HPGR to process the crushed SAG mill pebbles. The SAG mill-Ball mill and Cone crusher (SABC) grinding circuit is an accepted grinding circuit to optimize power consumption relative to throughput. The installation of a HPGR to process the Cone crusher product is the next step in optimizing the power consumption relative to throughput. The concern expressed by some on not moving on this change in grinding circuit was the capital and operating cost of a HPGR. The pebbles from the SAG mill can be the more abrasive and are the harder particles of the ore. Goldcorp investigated the wear and processing costs of installing a HPGR to treat the crushed pebbles. The conclusion was the installation would be a very positive economic factor in the operation of Peñasquito. This is the first application of the use of HPGR to process crushed pebbles. Minera Peñasquito and M3 Engineering selected Polysius to provide a Polycom 2417 with twin 3,000 kW drives. A comprehensive test program at Polysius has shown for 7% higher circuit power it is possible to get approx 23% higher tonnage. This coupled with full utilization of the SAG and Ball Mill available energies and with proper control of the transfer size from the SAG to Ball mill circuit there is the potential to achieve 65,000 mtpd per line or a 30% total capacity increase. The cost of power for this increase in grinding capacity is 4.8 kWh/tonne.

Jan 1, 2010

By Jens Classen

"GENERAL PROJECT DATA The Sparvo Tunnel belongs to “Variante di Valico” project, a new 65 km highway link between Bologna and Florence, designed to renew the existing A1 route and to connect in a faster way Bologna and Flor-ence. It is composed of a 2,5 km twin tunnel excavated in a complex geological context, characterized by the presence of a series of surface landslides and methane gas. The gradient is 2.6 % and the minimum radius is 1’400 m. The internal diameter of the precast seg-ment lining, equivalent to the final section of the tunnel, is 13.6 m. MAIN TBM SPECIFICATIONS TBM Earth Pressure Balanced S-574 “Martina”, manufactured by Herrenknecht, has a theoretical excava-tion diameter of 15’615 mm. It is equipped with a conical shield 12.2 m long and four back-up gantries. The total length of the machine is approximately 130 m, weighing approximately 4’500 tons. The total installed power is 16’800 kW. The main drive has a diameter of 8’700 mm and has a triple axis roller type bearing equipped with a labyrinth system including 4 sealing lips. TIME SCHEDULE OF INITIAL TBM DRIVE A time schedule of the initial TBM drive is presented in the following list: •,August 25, 2011: start of the excavation of the 1st drive of the Sparvo tunnel •,October 29,2011: stop of the advance of the TBM for gear oil contamination and clogging •,October 29 to December 20, 2011: repair works on the main drive system and modifications on the conditioning system •,December 20,2011 to July 25, 2012: restart excavation of the 1st drive (north tunnel) and its breakthrough •,July 25 to November 29, 2012: 180° turning of the TBM, detailed check of the main drive seal-ing system and fixing problems on gear boxes, race ring, clamping ring and cutting wheel •,November 29,2012 to July 24, 2013: excavation of the 2nd drive (south tunnel) and its break-through •,August 2013 to July 31, 2014: disassembly of the TBM (first 4 months) and standstill of the jobsite for structural issues on precast concrete lining of the tunnel •,July 31, 2014 to March 10, 2015: inspection, dismantling and packaging of each part of the main drive (flange ring, gear box housing and main bearing). The various phases are described hereafter in detail."

Jan 1, 2016

By J. O. Marsden, C. Green

In 2003, a high-temperature pressure leaching circuit to treat copper sulfide concentrates was commissioned at the copper/molybdenum operation at Bagdad, AZ. In late 2007, a medium-temperature pressure leaching circuit was commissioned at the Morenci mine in Arizona. The Morenci circuit was shut down in mid-2008, following a fire in the autoclave circuit. The onset of the global financial crisis in late 2008 resulted in significant changes to the operating profile in the Southwestern United States with respect to concentrates production, concentrates treatment, acid production and acid consumption. As a result of these changes, the Morenci concentrator was shut down, and the pressure leaching circuit remained offline. In late 2014, the increasing acid requirements in the Southwestern United States prompted a reevaluation of the Morenci concentrate leaching facilities. As a result, the pressure leaching circuit was restarted in high-temperature (200 °C) mode in May 2015 and has operated successfully for three years since recommissioning. This paper describes the current pressure leaching circuit configuration and the factors leading to the successful application of copper sulfide concentrate leaching at this location.

By Richard L. Bullock

Believe it or not, mine evaluation and feasibility studies are as old as the industry itself. In the first recorded writing on mining by Agricola (1556), he gave several clues as what to look for in evaluating a mine, to determine if it was economically feasible. Below is the guidance from Agricola, with my interpretation of what he would include today. Now a miner, before he begins to mine the orebodies must consider seven things, namely: ? The situation (the geography/topography). ? The conditions (the geologic/mineralogic and mining conditions). ? The water (availability, hydrology and ownership). ? The roads (plus the railroads, power lines, all other infrastructure). ? The climate (the weather-rainfall/environment). ? The right of ownership (the land and legal entitlement). ? The neighbors (the social environmental concerns of the area). It is amazing how much of his guidance has not changed in 455 years. Yet Agricola gives no guidance on determining the correct cost, or determining the correct commodity pricing. But he does give a few words of caution on the related ethics involved on buying mineral properties: ?A prudent owner, before he buys shares, ought to go to the mine and carefully examine the nature of the vein, for it is very important that he should be on his guard lest fraudulent sellers of shares should deceive him.? Three hundred years later (1866), to further amplify this point, in the most famous thing that Mark Twain never said, as an introduction to a lecturer to an audience of gold-miners at Red Dog, CA, the famed author/humorist allegedly described a mine as ?a hole in the ground owned by a liar? (Farrar & Rinehart, 1935). So, one might conclude that between these two dates, the mining industry did little to improve its reputation. Unfortunately, since Mark Twain allegedly made those remarks, we have not done near enough to gain accountability for the mineral industry.

Jan 1, 2011

By J. C. Draper

This subject was introduced last April in a paper presented in Birmingham, Alabama, by James E. Elkin, General Superintendent of Duquesne's Coal Department. This paper will cover some of the same data and in addition it will update and further describe our experience. Our Portal No. 3 was started in June 1965 with battery tractor-trailer face haulage. This mine is operating in the Sewickley seam in Dunkard Township, Greene County, in Southwestern Pennsylvania as shown on Fig. 1. The Warwick group of mines fronts on the Monongahela River and extends westward for some ten miles as shown on Fig. 2.

Jan 1, 1968

By Janet A. Johnson, T. B. Borak, K. J. Schiager

INTRODUCTION In the USA regulatory agencies have adopted standards which limit the allowable concentration of ore dust in underground uranium mines. The American Conference of Governmental Industrial Hygienists has recommended a threshold limit value for silica which has been incorporated by reference in federal regulations (30 CFR 57, 1980). The Nuclear Regulatory Commission (NRC) imposes a limit for unprocessed uranium ore dust for reducing the exposure to radioactive materials from inhalation (10 CFR 20, 1980). We have been unable to trace the origin of the NRC standard. Recently the ICRP has published recommendations concerning limits for intakes of radionuclides by workers (ICRP, 1979). We have used the ICRP methodology to compute the dose equivalent commitment to lung and bone from inhalation of insoluble ore dust particles. These values were used to derive air concentrations which would provide an acceptable risk for induction of cancer from occupational exposure. Results indicate that the new ICRP recommendations are more restrictive than the present NRC standard for radioactivity. The maximum allowable dust load in a uranium mine will depend on both the concentration of silica (% Si02) and the amount of radioactivity (% U308). We have combined these standards assuming complete independence of biological hazard to establish boundary conditions for which either silica or radioactivity is the dominating factor. Based on these results we present suggestions for analysis of ore dust to insure compliance with regulatory agencies. SILICA STANDARDS Silicosis, fibrotic lung disease produced by crystalline silica, was one of the earliest forms of occupational disease to be recognized. The pulmonary lesions caused by silica, silicotic nodules, consist of concentrically arranged bundles of collagen fibers. Fusion of these nodules results in progressive massive fibrosis causing alveolar changes which decrease ventillation and blood flow in the lungs. The current Threshold Limit Value (TLV) for mineral dusts is based on the concentration of free silica. The standard is expressed in three forms: (1) Particle count standard: TLV (mppcf) = 300/(% Si02 + 10) (mppcf = million particles per cubic foot) (2) Respirable dust mass standard: TLV (mg/m3 ) = 10/(% respirable Si02 + 2) (3) Total dust standard: TLV (mg/m3 ) = 30/(% Si02 + 3) The most commonly used form is the respirable mass standard. These curent values for silica are based primarily on epidemilogical studies of Vermont granite workers and other occupationally exposed workers. In the Vermont study no cases of silicosis were seen in individuals employed after dust control measures were initiated and whose subsequent exposure averaged less than 5 mppcf. The free silica concentration in the airborne dust to which these workers were exposed averaged 25%. A concentration of 10 mppcf of granite dust is considered equivalent to 0.1 mg/m3 quartz. The current respirable mass standard allows a maximum silica concentration of 0.1 mg/m3. NIOSH (1974) has recommended a reduction in the current TLV for respirable silica to 0.05 mg/m3 Si02. As with radiation standards, the TLV for mineral dusts is an upper limit for time weighted average exposure. It is recommended that dust concentrations be maintained as far below the TLV as current practices permit. RADIATION STANDARDS The present concentration limit for airborne natural uranium in ore dust prior to chemical separation is 75 µg of uranium per m3 of air ( 10 CFR 20, 1980) . This corresponds to 1.85 Bq/m3 (50 pCi/m3 ) of natural uranium, U-238, U-235 and U-234 and is equivalent to 3.7 Bq/m3 (100 pCi/m3 ) of gross alpha activity with radioactive equilibrium between the long-lived alpha progeny through Ra-226. The origin or basis for this standard is not known, but it presumably includes both chemical toxicity and risk from somatic radiation injury. Recently the International Commission on Radiological Protection (ICRP, 1977) has published recommendations concerning the objectives and criteria for limiting radiation exposures. This was followed b y a revision of the limits for intake of radionuclides by workers (ICRP, 1979; ICRP, 1980). The previous compilation of limits for internal emitters was published by ICRP Committee II in 1959 (ICRP, 1959). The latest version includes new methodlogy outlined in ICRP Publication 26 (ICRP, 1977) as well as extensive metabolic information

Jan 1, 1981

By R. A. Limons

Natural ores, sinters, and pellets were subjected to a carbon monoxide reduction-disintegration test under laboratory conditions including a simulated blast furnace gas and a 1000°F temperature. The most significant findings were that: 1. Self-fluxed pellets broke down to a greater extent than either the acid pellets or the acid or self -fluxed sinter. 2. When pre-reduced, both the acid and self-fluxed pellets had very good resistance to breakdown.

Jan 1, 1964

By Emily Wortman-Wunder

Attendees at December?s Arizona SME Section Conference at the Hilton El Conquistador Resort outside of Tucson, AZ were feeling optimistic and ready to get to work after a year of steady growth and recovery in the mining industry. During the two-day event (Dec. 5-6, 2010) and the preceding American Mining Hall of Fame banquet and awards ceremony, the focus was on copper, worldwide population growth and regulatory pressures, with several smart new projects featured alongside updates to traditional large-scale copper development projects. Keynote speaker Timothy Snider, chair of the University of Arizona?s Lowell Institute for Mineral Resources, hit the mood of cautious optimism when he analyzed the global demand for resources, using the case example of copper. Over the next 20 years, he said, the world?s population is expected to grow to 9.2 billion and the average annual per capita copper use is expected to rise from 2.2 to 4.5 kg (5 to 10 lb). The increase in demand will provide tremendous opportunity for mining companies, he said, but cautioned that the opportunities are balanced by negative influences on demand and pressures on supply. While demand for copper is currently growing, Snider noted that there were significant downward pressures on demand as well. These included a western world that is overbuilt, in-creasing use of substitute materials in new construction and the rise of wireless devices. He also noted new regulatory pressures, and pointed out that resource development now had to occur within a context of sustainability on several levels.

Jan 1, 2011

By W. A. Haley

As far back as 1939 state laws have required reclamation of mined lands. Reclamation has been the topic of many discussions and presentations, especially since the late 1960's. In the past ten years many states have added legislation concerning the reclamation of coal-mined lands. In the near future, it seems certain that some federal regulations will be passed that will set minimum guidelines for the states to regulate. Besides the requirement of returning the land to the approximate original contour, future regulations will more than likely demand replacing topsoil from one to five feet thick. As regulations become more stringent, costs will rise accordingly. Since no one has developed a machine that can do all reclamation work by itself, it is necessary to review in detail the tools available and to select the most economical means.

Jan 1, 1976

By Edward A. Vitunac

The emerging importance of pneumatic conveying systems for bulk materials is becoming recognized by more persons responsible for materials management as consultants, at the corporate level and at the plant level. They have learned that the economic advantages of a pneumatic system are frequently decisive when compared to alternate methods. Included in these advantages are relative simplicity, ease of installation, flexibility, ease of maintenance, cleanliness, safety and ease of automation to the degree desired. In general, installed costs favor a pneumatic system when compared to competing mechanical systems if the transporting distances are long or to and from many points. In addition, supplemental use such as cooling, heating, or drying may supply the incremental value required to justify its selection. (1). The main disadvantages of a pneumatic system is the greater horsepower required per unit weight of material conveyed and material limits in abrasiveness and density. In addition, there is a tendency to increase material breakage at changes of direction and at any obstruction such as the imperfect butting of one, piece of pipe to another in the conveying line. Classification of the material at the discharge may also cause problems in dusting and segregation. Materials weighing less than 4 pounds per cubic foot tend to cause feeding and collecting problems although they can be conveyed easily. Material between 4 and 20 pounds per cubic foot can be handled with less problems but flow rate is hard to predict. The 20 to 60 pounds per cubic foot range offers best results; whereas, over 60 pounds per cubic foot, materials tend to drop out of the air stream and settle in the pipe line unless careful provisions are made to prevent it. (2).

Jan 1, 1967

Introduction Agrico Mining Co.'s Florida mining division has three surface mines and employs nearly 700 workers. The division produces some 6.3 Mt (7 million st) of phosphate rock annually. It is a good business. And Agrico has made it better by making it safer through a new approach to mine safety. In one year, Agrico - the second largest phosphate mining company in the US - recorded a stretch of one million manhours without an accident. That same year, the direct cost of accidents dropped to $9137 from a previous five-year average of about $50,000. Together with Don Roe, division manager of safety and security, Division General Manager Don Morrow made 1981 a watershed year for safety at Agrico. Morrow called on consultants from Safety Management Services of Du Pont's Specialty Services division to strengthen a safety program that was already better than average. From the late 1970s and into 1981, lost-workday cases (LWCs) were costing Agrico an estimated average of $22,000 each. And they were occurring with alarming frequency. In 1977, the company recorded six LWCs at an incidence rate of 0.64. This was followed by a jump to nine cases in 1978. In 1979, both occurrences and the rate increased - 10 LWCs at a 1.19 rate. The number of LWCs decreased to seven in 1980, with a rate of 0.71. Agrico instituted a far-reaching safety program in 1981, which began to take full effect in 1982. LWCs dropped from five in 1981, to three in 1982. And the direct cost plummeted from $110,346 to $28,828. In 1983, the mines recorded only one LWC. Its $9137 cost represented a reduction of $101,209 since the Safety Management Services of Du Pont had been called in. Through early 1984, the LWC incidence rate at the facility's three mines, phosphate drying plant, and transportation department was down to 0.26. This is 84% lower than the 1982 mining industry average, making it the safety leader among all Agrico companies, including its chemical plants. New Approach Agrico had the basics of a safety program in place when the Du Pont consultants arrived. But Du Pont suggested changes in responsibilities and company philosophy that formed the foundation of

Jan 1, 1985

By Ken Deter

I have some general comments on optimizing profitability based on working in heap leach operations in tropical environments. Many of my planned comments this morning have been stated earlier in the Conference. I get the opportunity to say only a few words, and follow up on some specific comments and concerns. In normal operations, stack the ore higher, where possible. The surface area of the stacked ore controls the total solution volume that can be sprayed on the pad at a specific time period. With higher lifts, solution will contact more ore particles as it percolate through the lift, and therefore the solution grade flowing through the base will be increased, whether it is freshly stacked or almost completely leached ore. This also allows more tonnage to be stacked per lift on the pad, decreasing conveyor movement and downtime. Increasing from 6 to 8 meter (20 to 26 feet) lifts have worked successfully, and some mines are using 10 meter (33 feet) lifts in 10,000-15,000 dmtpd plants. The same concept will work with smaller plants, but initial 6 meter lifts should be used until the start-up period has shown the leaching is working as planned. As the stacked ore lifts get higher, the solution flowing through the highest lift is diluted by solution retained in the lower ones. Eventually no real increase is noted from putting fresh ore in service, and gold production rate suffers. To address the dilution problem, an HDPE liner should be installed between each 2 to 4 lifts, depending on each site specific lift height, recovery, % slump in the lift, recovery rates, and grade treated, among others. The surface of the previous lift should be leveled and sloped to control the effluent draining from the planned lift, then the liner is placed, including berms and discharge pipes. The intermediate HDPE liner does not need to be completely sealed as would be the case with the base liner, and can accept some solution penetrating into the lower lifts. A one-mm (40-mil) thickness liner can be used. This intermediate liner allows the upper lift(s) higher-grade effluent to report to the pad discharge point. This will maintain higher gold solution grades going to the ponds. The slopes of the previous lifts should not be covered with HDPE in this concept, and precipitation falling on the lower lift slopes and benches can be directed to barren or surge ponds.

Jan 1, 1999

The National Mining Hall of Fame and Museum in Leadville, CO seized the opportunity to show off during its 10th anniversary induction banquet on Sept. 6. "We wanted to make people more aware of the mining hall of fame and museum," said Carl Miller, its executive director. The annual event honors inductees into the Mining Hall of Fame. This year, the inductees included Paul Wheeler Allen, Joseph Rosenblatt, Arthur Fay Taggart, Joseph Toy, Joseph Wharton and John Benjamin Zadra (ME, August, pp. 60-63). Allen, of Pasadena, CA and Rosenblatt, of Salt Lake City, are both living. Only Allen was able to attend. This year's induction banquet was the first held in Leadville, North America's highest incorporated city, at 3,094 m (10,152 ft) above sea level. The banquet gave attendees an opportunity to see the museum in its century-old 6,500-m2 (70,000-sq ft) Victorian schoolhouse. Many of the 350 guests came in 1890s dress to the black-tie affair. The evening included a cocktail reception and an open house along with a catered, prime rib dinner. During the open house, attendees had the opportunity to tour the museum's 12 rooms of exhibits and displays. Among items of interest, it was noted that a framed directory of inductees now enhances the entrance to the hall of fame. The directory is organized by the inductees' names and the location of their plaques, allowing visitors to quickly find hall of fame members. Noted mining historian and author Duane Smith delivered the keynote address at the banquet. After the induction of the six honorees, attendees danced to the big-band era music of the Leadville 17-piece band BandAge. Karl Elers was the master ceremonies for the evening's program. He is a member of the hall of fame's board of directors and is chairman of Battle Mountain Gold Co. Allen was honored by the presence of 26 former colleagues and associates. He told the audience that he originally thought the museum should have been located in Denver. "But I have been proven wrong," he said. For many years, Allen was the operational executive of Cyprus Mines Corp. and a key participant in the company's growth. Allen received a replica of his mining hall of fame plaque from Thomas Falkie, chairman of the hall of fame's board of governors and president of Berwind Natural Resources Co.

Jan 1, 1997

By Güldane Atesoglu, İsmail Atilgan

The changes in the elemental contents and the structural properties of chalcopyrite concentrate when roasted were studied, and the main reactions contributing to the leaching process revisited. Firstly, TG/DTA measurements were performed to identify the roasting temperatures that influenced the type of species reacting with sulphuric acid leaching liquor. The temperatures of main reactions, whose output may affect the subsequent leaching process, were analysed for the concentrate at hand, and concluded to be generally lower than those reported in literature. Secondly, the obtained results were confirmed by images and XRD measurements on the roasted concentrate at temperatures in between 350 and 600 °C with increments of 50 °C. Finally, the leaching behaviour of the roasted specimens in a stirred sulphuric acid solution examined and the Cu/ Fe selectivity investigated that the maximum Cu/Fe ratio in the pregnant solution would nearly be achieved for the roasting temperatures lower than 500 °C, since the oxidation temperature of iron sulphate is found lower than that of copper sulphate.

Aug 11, 2022

By Pierre Filiatreault, Brian Straight, Stephanie Thibeault, Devin Castendyk, Londie Cameron

"Working on or near water at active, closed or abandoned mine sites is inherently dangerous. Between 1996 and 1999, the U.S. Mine Safety and Health Administration (MSHA) reported 17 fatalities involving drowning at U.S. metal, non metal and coal mines (MSHA, 2000). Openpit mines which fill with water following mine closure, called pit lakes, present numerous risks to environmental monitoring teams including: a) drowning, b) hypothermia, c) falls to the ground from the top of high walls, d) collapse of unstable access roads, e) rock falls and avalanches from pit walls, f) avalanchegenerated tsunamis traveling across the lake surface and g) rapid degassing events.Some pit lakes are simply not safely or easily accessible for ongoing monitoring. However, the routine collection of water samples from the entire water column on a regular basis is needed to monitor the evolution of water quality over time, verify the accuracy of numerical predictions and, ultimately, manage lake water chemistry and ecological risks. For pit lakes with surface water discharge, regular monitoring is used to appropriately design and adjust water treatment plants in order to produce acceptable site discharge water quality.As a product of these risks and the need for water samples, mining companies spend considerable expense on pit lake safety as part of monitoring programs. This includes training personnel for on water duties and hazards, purchasing or hiring specialized equipment and personnel (such as boats, boat operators, personal floatation devices and cold-water clothing called mustang suits), stabilizing pit walls and maintaining safe access roads to the lake surface and employing spotters who can directly communicate with emergency medical services to watch sampling activities because cell phones and radio signals can be blocked by pit walls. Some sites utilize redundancy to prepare for unexpected incidents and accidents. For example, one Canadian mining company requires two boats on the water during pit lake sampling events, with a third boat on the shoreline, gassed and ready to go. In addition, water samplers are required to hold Marine Emergency Duties training to ensure the entire boat crew is sufficient and competent for the safe operation of the vessel in the event of an accident."

Jan 7, 2017

By D. H. Lynch

Prompted by the need to conserve energy and reduce operating costs, Agrico Mining Company has made two significant improvements in the transportation of phosphate ore from the mine to the beneficiation plant. One improvement involves a change in a slurry pipeline system which substantially reduced pumping energy, and the other improvement is a major innovation for the phosphate mining industry which involves the transportation of the ore by railroad. This paper briefly describes these two projects.

Jan 1, 1981

By Ralph H. Light

The recent surge in demand for uranium in the United States, accompanied by a significant increase in price, has resulted in exploration, mining, and milling of lower grade ores than have been exploited in the past. To sustain production levels of uranium with lower grades of feed requires larger tonnage mill operations. Also, because of recent environmental regulations, mill operations must be prepared to properly contain large tonnages of tailings, and recycle, treat and discharge, or evaporate mill effluents. Thus, the advent of lower grade ores, larger tonnage mills, and environmental considerations has made the cost of milling a critical factor in today's uranium production economics in the United States. Three basic milling methods are employed for extracting uranium from ores: 1. Acid leach, countercurrent decantation, and solvent extraction. 2. Acid leach, resin-in-pulp, and Eluex. 3. Alkaline leach, solid-liquor separation, and precipitation. Vanadium often occurs as a valuable by-product in ore deposits located in the Uravan mineral belt in Western Colorado. Also, lesser amounts of vanadium may occur in ores from South Dakota, New Mexico, and Utah. Vanadium is usually extracted in the acid leach solution with uranium and recovered by solvent extraction after recovery of the uranium. By-product recovery of uranium from phosphoric acid and porphyry copper dump leach solutions is now receiving considerable attention. Pilot plant studies are under way and construction of commercial plants is in progress.

Jan 1, 1977

By D. A. Rice

In pelletizing magnetic iron ore concentrates, about 6 to 18 lb of bentonite binder are added per ton of concentrate during balling to give green and dry strengths to the unfired pellets. The dry bentonite is mixed into the filtercake following the magnetic concentration circuit of the plant. The filtercake contains about 10% moisture, and the water may be of highly variable composition, depending on the particular concentration circuit, its source, and the ore being treated. A knowledge of the parameters that influence the balling operation is essential for optimal efficiency in producing balls strong enough to survive the treatment during transportation from the balling device to the furnace and during the firing operation. Furthermore, very weak unfired pellets probably contribute to high dust losses and poor furnace control. The factors that determine the strength of unfired pellets have received considerable study (1,2,3,4). Tigerschiold and Ilmoni(l) pointed out the significance of the surface area of the particles being pelletized. Merklin and Childs(2) reported on the effect of material size consist, chemical additives such as soda ash, lime, balling time, ball size, and the moisture content of green balls. Iwasaki and Zetterstrom(3) examined the detrimental effects of fatty acids on the pelletizing process. Stone(4) correlated the zeta potential of bentonites with the strength of unfired pellets. He found that, in general, a high negative charge on the bentonite is conducive to good balling. Although studies of pelletizing in the iron ore industry deal with a complex multicomponent system consisting mainly of the iron mineral, bentonite, and water, the last of these has received little attention, particularly with regard to the possible effects of mill water chemistry on the pelletizing process and the strength of unfired pellets. It is widely known that the composition of mill process water is an important variable in unit operations such as flotation, thickening, and filtering and that impure water can lead to poor metallurgical results. The results of the present study indicate that the chemistry of the mill water may be an important variable in the balling operation as well. Knowledge about this variable should contribute to lowering bentonite and oil consumption and to improving furnace performance. Such knowledge can also assist those who use balling in evaluating commercial bentonites for plant use as well as those investigating balling from a more fundamental point of view In this study we have examined 1) the effects of replacing mill process water in the magnetic concentrate filtercake with pure water, and 2) the effects of several chemical impurities that are commonly found in mill process waters upon the strength of unfired pellets. The results are interpreted in terms of the zeta potential of the bentonite and magnetite particles. The data lend support to a suggested mechanism whereby the electrostatic attraction of oppositely charged particle surfaces causes bentonite-bentonite and magnetite-bentonite bonding. This mechanism would also explain why several chemical additives e.g., sodium carbonates and phosphates, have such marked effects on increasing the strength of unfired pellets.

Jan 1, 1971

By F. Habashi

Chile is at present the largest copper and rhenium producer and was before World War I the largest nitrate producer. She is also an important producer of lithium carbonate and molybdenum oxide. An important event in the history of the country is the Pacific War of 1879-1883 in which she acquired the northern provinces initially belonged to Bolivia and Peru. In 1888 Chile annexed Easter Island. The Chilean mineral and cultural history is briefly reviewed together with the people who contributed to her development. The present report is the result of a number of academic and industrial visits to Chile during the period 1992 to 2009.

Jan 1, 2011

By Roy A. Koski

This paper describes variations in feed characteristics, preparation techniques, response to induration and product quality in pelletizing magnetite concentrates, earthy hematite ore fines, and specular hematite concentrates in grate kiln systems. The Cleveland-Cliffs Iron Company manages plants processing these various materials on the Marquette Iron Range in northern Michigan. The operations include the Humboldt Mining Company, Marquette Iron Mining Company, Empire Iron Mining Company and the Pioneer Pellet Plant. The combined output of the operations is approximately 9,000,000 long tons per year. The Humboldt Mining Company, owned by Ford Motor Company and Cliffs, produces pellets from a specular hematite concentrate. The Empire operation, which processes magnetite ore, is owned by Inland Steel Company, McLouth Steel Corporation, International Harvester and Cliffs. The Pioneer operation, which processes earthy hematite ores, is a joint venture of Republic Steel Corporation, McLouth Steel Corporation, Bethlehem Steel Corporation and Cliffs. The Marquette Iron Mining Company, owned by hones and Laughlin Steel Corporation, International Harvester, Wheeling-Pittsburgh Steel Corporation and Cliffs, produces pellets from specular hematite concentrate at the Republic Mine and Eagle Mills Pellet Plant. With the exception of the Eagle Mills plant, the operations employ the grate-kiln pelletizing system. Descriptions of the Empire, Pioneer and Republic operations, which have a combined capacity of 7,200,000 tons per year, are given in the paper.

Jan 1, 1969