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Canada is one of the largest mining nations providing a variety of jobs at all levels, but in an industry dominated by men, mining and mineral processing has the least amount of women employed worldwide. Women in Mining Canada (WiM) is looking to change the mining community and promote women in the industry.
From the early 1960s until the mid 1980s, dense medium cyclone circuitry design technology did not change appreciably. The basic design, which was both highly flexible and highly efficient, was consistent with technology developed by the Dutch State Mines (DSM) in the mid 1940s. During this period, the typical dense medium cyclone circuit was designed to process raw coal in the 9.5 mm x 0.6 mm size range. Coarser coal was processed in dense medium vessels or jigs, and the fines were processed in spirals, water-only cyclones, or flotation.
The past years have witnessed a significant extension in state-of-the-art dense medium cyclone circuitry design. Dense medium cyclones are rapidly becoming a common choice for cleaning a much broader size range of raw coal than considered economically feasible just a few years ago. From a nominal top size of 63.5 mm to 76.2 mm down to 0.15 mm dense medium cyclones have been shown to be capable of operating economically and over a narrow range of efficiencies. This remarkable extension of the feed size range considered appropriate for dense medium cyclone cleaning is primarily a function of the following:
Recent improvements in equipment design, coupled with innovative approaches to the control of the specific gravity of the medium in dense medium cyclone circuits, have made possible all of the following:
The impact of cyclone configuration on separating efficiency has become more clearly understood as a result of test work conducted at the Homer City Coal Cleaning Plant in Pennsylvania, as well as research undertaken at coal cleaning facilities in Australia, South Africa, and elsewhere. Cyclone configuration includes the diameter of the cyclone, apex diameter, vortex finder length and diameter, and the ratio between apex diameter and vortex finder diameter. Until quite recently, the largest dense medium cyclones provided diameters of about 710 mm with a maximum raw feed top size of 50 mm. With the exception of the so-called washing to zero plants with capacities generally in the range of 100 to 300 STPH, most cleaning plants continued to be designed with dense medium cyclones processing only a rather narrow size range, as depicted in Figure 1 (pre-1985). A typical dense medium type coal preparation plant included dense medium vessel circuitry for the coarse raw coal, dense medium cyclone circuitry for the intermediate size fraction with a spiral (or water-only cyclone) circuit for raw coal down to about 0.15 mm Ultra-fines (0.15 mm x 0) were either discarded to refuse or processed in froth flotation circuits. Such a typical plant looked something like the schematic shown in Figure 2.
Beginning in about 1995, however, U.S. equipment manufacturers began to offer much larger cyclones to the coal industry. Units with diameters in excess of 900 mm capable of handling a top size in the range of 76 to 102 mm have been successfully installed in a number of coal preparation plants with excellent results. Table 1 illustrates the large capacity increases that can be achieved by using this new generation of dense medium cyclones.
In addition to greater throughput, with obvious advantages in reducing the number of units required to handle a given quantity of raw coal, these large cyclones make it feasible in some cases to eliminate the dense medium vessel circuit entirely. The result is a simplified flowsheet with savings in space requirements and piping. Figure 3 illustrates a typical cleaning plant in which dense medium cyclones are used to process raw coal from a top size of 50 mm down to 1.0 mm
To be cost-effective, it is critical that the operating parameters in a dense medium cyclone circuit such as the one shown in Figure 3 be closely monitored and controlled. The parameters of most concern include the following:
In most cases, the appropriate medium-to-coal ratio is determined by the coal preparation plant builder during the conceptual design phase of the project. Most dense medium cyclone circuits in the United States are operated with medium-to-coal ratios of 3:1 to 4:1, by volume. Coal preparation plant designers often use the lowest medium-to-coal ratio consistent with an acceptable level of cleaning efficiency. Generally, medium-to-coal ratios should be increased as the percentage of near-gravity material increases, i.e., in middlings circuits or in applications where a low specific gravity of separation (1.45 or below) is required to produce a product meeting customer specifications. The writers believe a 4:1 ratio is most appropriate for separations where near-gravity material is less than 30% and a 5:1 ratio (or higher) should be used when the near- gravity exceeds 30%.
Contamination of the recirculating medium can be a problem in any dense medium cyclone circuit, and the adverse impact of even relatively small amounts of non-magnetic contamination in the medium is understood.
As non-magnetics (including ultra-fine coal, clays, and other ultra-fine non-bituminous particles) replace magnetite particles in the recirculating medium, the viscosity of the medium increases and cyclone performance suffers. It is especially important that ultra-fine magnetite particles (<10.0 ) be retained in the medium since a finer magnetite particle size distribution results in a more stable cyclone operation and improved cyclone efficiency. In one set of tests intended to quantify the impact of size distribution on efficiency, the percentage of ultra-fine (>5.0 ) particles was increased incrementally from 10% to 20% and probable error values were determined for each increment. The probable error value was 0.08 when the percentage of ultra-fines was 10%. This value decreased in a straight- line relationship to a value of 0.03 when the percentage of ultra-fines reached 20%, the upper limit of the test. Systems have been developed to minimize medium contamination while maintaining an acceptable grain size distribution.
Cyclone inlet feed pressure determines the volumetric flow rate through the dense medium cyclone, and higher pressures result in higher flows through a cyclone of given geometry. This relationship is shown in Table 2 for a 350 mm diameter cyclone.
Just as the volumetric flow rate increases with elevated inlet feed pressure, so, too, does the classification effect occurring within the cyclone. This classification effect can have an appreciably negative impact on dense medium cyclone performance. This deterioration in performance becomes more pronounced as the separating gravity decreases. In at least one instance, where feed pressure was held constant, relatively large diameter cyclones produced better separations than smaller units at a specific gravity of separation of about 1.30. For example, a cyclone 500 mm in diameter achieved a probable error of about 0.05 while the probable error produced by a much smaller cyclone (200 mm) was significantly higher (approximately 0.09).
In the plant where the 800mm diameter cyclone was tested, 500 STPH of 50mm x 0 raw coal was pulped in a heavy medium tank and pumped originally to four 700mm heavy medium cyclones. For the test one of these units was replaced by an 800mm diameter cyclone with the subsequent feed pressure for both units sets at approximately 15.0 psi.
With the exception of the finest size fraction, this table also shows that the coarsest fraction in both cyclone feeds was separated at a higher separating gravity than those of successively finer sizes as well as the overall composite. This has been observed in some instances where the size range of the feed to the cyclone becomes broad.
The size distribution of the raw feed plays an important part in the overall cleaning performance of any cyclone. As the feed becomes finer, performance will deteriorate for a given diameter of cyclone. This situation is particularly enhanced for cyclones of larger diameters. As such, an increase in pumping rates to these larger cyclones to provide added centrifugal force to restore their sharpness of separation (cleaning efficiency) may create excessive wear in these units.
The Detroit Copper Company started mining at Morenci, 16km south of Silver City, Arizona, in 1872. Copper Queen Consolidated Mining bought the property in 1885, with the company name changed to Phelps Dodge in 1917.
Ninety years later in March 2007, Phelps Dodge merged with Freeport McMoRan Copper & Gold, whose principal asset is the massive Grasberg copper-gold mine in Indonesia, in an agreed $25.9bn takeover by Freeport, the smaller of the two companies.
Morenci is the largest copper producer in North America and remains a major contributor to Phelpss copper output, which is second only to that of Chiles Codelco. In 1986, Phelps Dodge Morenci was established as a partnership between Phelps Dodge Mining Company (72%) and Sumitomo Metal Mining Arizona Inc. The latter belongs to Sumitomo Corp. (15%) and Sumitomo Metal Mining (13%).
For many years as an integrated mine-concentrator-smelter operation, Morenci pioneered the large-scale hydrometallurgical treatment of mined copper ore by dump leaching, solvent extraction (SX) and electrowinning (EW) during 1985, in parallel with conventional treatment.
In 1999, Phelps Dodge started a $220m mine-for-leach (MFL) conversion project, and from mid-2001 until 2006 produced all its copper this way. However, in 2005, the company announced the go-ahead for a $210m project to create the worlds first commercial copper-concentrate leaching / direct electrowinning operation at Morenci, a proprietary technology that allows primary sulphide ore treatment by leaching in combination with secondary ore processing.
As well as new leach-electrowin capacity, the project required reopening the mothballed Morenci concentrator. This programme was accelerated in 2006 to provide copper-in-concentrate for treatment at Phelpss Miami smelter, also in Arizona, before completion of the hydrometallurgical facilities at Morenci.
A feasibility study was conducted for an expansion project to raise the current milling rate from 50,000tpd to 115,000tpd. The Morenci mill expansion project began operations in in May 2014 and achieved full milling rates in the second quarter of 2015.
Copper mineralisation, identified by a regiment of California Volunteers in 1865, turned out to be part of a major porphyry copper ore body extending across a dissected mountain terrain. Both sulphide and oxide ores occur, pyrite and chalcocite being the main sulphide minerals, and chrysocolla and malachite the predominant oxides. Molybdenite, galena and sphalerite are also present.
Phelps mined underground until the 1930s depression, converting to an open-cut operation with rail haulage in 1937. The topography prevented development as a single pit: today the working area extends across 2.5km x 2.2km but is worked as three pits: the Metcalf (within the original Morenci pit), the NWX (Northwest Extension) and the Coronado.
Electric rotary rigs, mainly made by Bucyrus, drill blast holes and P&H 4100 and 2800 series electric rope shovels load the truck fleet. This includes more than 60 Caterpillar units, both 793 (218t capacity) and 797 (272t) models.
When hydrometallurgical processing started, these two mills worked in parallel with two leaching / solvent extraction operations and one electrowinning tankhouse. The MFL conversion required an expansion of the hydrometallurgical facilities to yield 365,000t/y of cathode copper, but led to the Metcalf concentrator being closed and the Morenci unit placed on care-and-maintenance until 2006.
While high-graded ore is conveyed to leach pads within the pit, the bulk of the primary crusher output (63,500t/d of ore) is secondary crushed and conveyed to the Stargo dump-leaching site. This ore is agglomerated for spreading by two Rahco mobile stacking units. Leaching is bacterially assisted, with air blown into alternate lifts.
The total heap and dump leach-liquor yield is 16,500m/h, copper recovery was 58.5% in 2003. Four SX plants, namely Central, Metcalfe, Stargo and Modoc, feed three tankhouses (Central, Southside and Stargo). The new leaching-electrowinning capacity was incorporated into the existing complex, which is already the worlds largest.
The Agnigundala Copper-Lead Mine is in Andhra Pradesh, India. The Agnigundala Copper-Lead Mine is a underground mining operation. The ore mined is composed of pyrite, chalcopyrite and sphalerite. The ore is found in veins of unknown dimensions. The host rock in this area is quartzite.
1 World-class significance is determined by total endowment of the contained commodity. This includes all past production and remaining reserves. Each commodity is considered separately and commodities cannot be combined to arrive at a significant size. The tonnage thresholds are from the mine model grade-tonnage studies. As of June 2008, many entries were classified as significant under less strict rules.
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The Roy Hill Iron Ore Project, in which Marubeni holds a 15% stake, is a large-scale project featuring the largest annual production capacity as a single iron mine in the Western Australias Pilbara region. With integrated infrastructure including mine, railway and port facilities, and having a capacity of producing 55 million tons per year, the Roy Hill iron ore mine achieves high cost competitiveness. The majority of the high-quality iron ores production volume, are sold to steelmakers in Japan and throughout Asia through long-term sales contracts. Marubeni will contribute to steel industries in Asia by ensuring stable supply of high-quality iron ores.
Marubeni invests in coking coal mines in Australia. The Jellinbah East coal mine and the Lake Vermont coal mine have high cost competitiveness, and shape the core of our coal business. As the largest stakeholder of both mines, we will continue to improve the cost competitiveness of our coal project and realize sustainable profit.
Marubeni holds a 30% stake in the Centinela, and the Antucoya copper mine, and 9.21% in Los Pelambres copper mine in Chile. Marubeni operates the mines with one of the world's leading copper producers, Antofagasta PLC. The equity volume of copper ingot from Marubenis interest is 150 thousand tons a year (payable copper equivalent), which is a leading amount worth among Japanese companies. Marubeni aims to further improve the asset values by expanding the capacity of the Los Pelambres copper mine, and developing copper deposits surrounding the Centinela copper mine.
Marubeni holds a 13.3% stake of the Alouette Aluminum Smelter in Canada, which has the largest production capacity in North America. The aluminum smelter runs on hydro power and operates with minimal environmental impact, and also succeeds in achieving high cost competitiveness. Plans are under way to expand the annual production capacity and produce high-value-added products. Marubeni will contribute to the aluminum industry, which is essential for global economic growth.
Marubeni stations employees around the world, which creates a global network that enables trading in various regions. By leveraging our network and sales and marketing abilities, which boast world class handling volume, we are stepping up efforts in environmental and circular businesses. We will also reinforce initiatives in markets with good prospects for demand growth to capitalize on changes in society such as wider uptake of EVs.
Through our investment in Marubeni-Itochu Steel Inc. and Marubeni Construction Material Lease Co., Ltd., Marubeni promotes steel products businesses related to every industry. By collaborating with each of Marubeni's divisions (including their domestic / overseas group companies), and utilizing Marubeni Group's comprehensive strength, we have been expanding our steel products business.
Panta rei, everything flows. Like the water in Tuscany, from the sea to the mountain springs. In Tuscany, you can visit historic villages, great cities of art or let yourself be enchanted by an invisible current as you discover waterfalls, mills and thousands of stories. Follow me on this exploration of four unusual trails.
This place is home to three (read: many) stories. The Giamba Mill rumbles to life after the year chestnut harvest in October and needs the water to clean them and transform them into sweet flour. The mill is part of the Montagna Pistoiese EcoMuseum, which has created a series of trails that introduce visitors to the co-existence of man and nature on the slopes of these mountains. Traveling down the nearby trail and following the river, visitors come across stories of coalmen, whose lodges were in this area, where they carried out their hard word of collecting wood and transforming it into coal. It is still possible to see the grass-covered huts and tip-toe through this historic world thats been preserved for future generations. The water continues to flow through these mountains and merges with the river cited by Tiziano Terzani, who lived in this area and left traces of his very self in Orsigna, including CAI trail n. 5, which leads to his beloved tree with eyes.
Nestled between the peaks of the Apuan Alps, the Malbacco Waterfalls are natural springs a stones throw from the municipality of Seravezza. To reach them, visitors must go by car to the namesake town of Malbacco and from there, hike along a road closed to traffic until Scesa n 4. From this point, continue right and, after coming to a ruin, the waterfalls will suddenly appear from behind the leaves. Take a dive in the waters surrounded by the sounds of nature and for the more adventurous climb the rockface to get to the natural slide created by the River Serra, splashing into the crystal-clear waters below. The springs have captivated more than a few hikers in search of a place to swim and recharge, but be warned: the water is very cold.
Legend says that many farmers have been tricked by the letters carved on a bridge on the slopes of Monte Serra. They seem made of gold as they shine in the sun, but they are simply bronze. This story inspired the name of the town: Parole dOro (Golden Words, in English). Le Parole dOro and their bridge are part of a trail that leads visitors on a discovery of the splendid and monumental aqueduct designed by Lorenzo Nottolini at the behest of Duchess of Lucca Maria Luisa of Spain in 1822. To reach it, visitors must take the trail that, following the imposing arches, leads to the Guamo Temple, where the water is collected. Its only another 20 minutes to get to the aqueducts winding canals.
For an even more fairy-tale-like atmosphere and to be immersed in the history of an 18th-century aqueduct surrounded by the forest, head to the hills around Livorno to look for the Acquedotto Leopoldino, located near Colognole. Designed in the 1700s to satisfy the need to providing water to a city whose population had tripled in less than 100 years, the aqueduct vaunts some impressive stats: 18 kilometres long and a gradient of 250 metres, the structure runs between the springs of the Morra stream and the centre of Livorno, ending at the Gran Conserva di Riseccoli, better known as the Cisternone. Following CAI trail n. 125, visitors can walk by bridges, arches, stairs and inspection huts that have been transformed into splendid Neoclassical temples. These places seem like secret landscapes nestled in a forest of centuries-old oak trees. The Acquedotto Leopoldino served the city of Livorno until the early 20th century, and still today it is used to supply small hamlets nearby. The trail is a blend between nature and architecture only a few kilometres from Livorno, home to other Tuscan water treasures, like the Terrazza Mascagni, the Fossi Medicei and the majestic boardwalk, where the smell of the sea permeates the air.Get in Touch with Mechanic