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By Xuanxue Mo, Kaihui Yang

"Abstract- The Laochang mine, located in the Sanjiang area of southwestern Yunnan Province of China, is a volcanogenic massive Pb-Zn-Cu sulfide deposit. It is hosted by a pyroclastic sequence of Barly Carboniferous age, namely the lower member of the Yiliu Group, which was intruded by syenite and rhyolite porphyry . The volcanic suite is basaltic or basaltic-andesitic in composition, has alkaline affinities, and is associated with the initial rifting along the margin of the Baoshan-Shanstate continental rnicroplate (Yang, 1989). The ores are typically Pb>Zn>Cu in composition, averaging 3.820Jo Pb, 3.51% Zn, from 0.01% to 1.85% Cu (0.107% av.), a high average content of Ag (113 g/t) and recoverable amounts of Au, Tl, Gd, Ga, Ge, In. A massive sulflde zone, in which lenticular and stratiform orebodies are localized in a sulflde-carbonate-silica shale unit or sulfldic tufflte horizon that usually overlies coarse-grained pyroclastic rocks, is underlain by a stringer sulflde zone developed in a subvolcanic intrusion or volcanic sequence. The sulfide mineral assemblages, from the top to the bottom of the deposit, are: realgar + orpiment - galena + sphalerite + pyrite- chalcopyrite + pyrite + pyrrhotite + arsenopyrite. Oxide and sulfate minerais occur rarely in the massive ores. The massive ores are generally fine-grained and banded, but coarse-grained ore, colloform and framboidal texture, and growth-zoned pyrite and sphalerite are common. Sedimentary features such as graded bedding, brecciated and deformed ore clasts, and chaotically emplaced blocks, are well preserved, indicating that the massive orebodies have undergone slumping and dis­ placement. Alteration is weak in the hanging-wall rocks, but strong in the stringer zone. Two dis­ tinctive alteration zones have been identified: the upper zone, characterized by an assemblage of quartz, carbonates, chlorite, albite, zeolite and sericite, and the lower zone containing diopside, trema­ lite, actinolite, gamet, clinozoisite, and epidote.The general features of the Laochang deposit are in accord with the descriptive mode! of VMS deposits (Lydon, 1984). However, it falls into neither the Zn-Cu group nor the Zn-Pb-Cu group chemically (Franklin et al., 1981). The depositional setting of the Laochang deposit is quite different from Cyprus or Besshi-type massive sulfide deposits. Laochang is hosted by alkaline lavas that were erupted in a submarine continental rift. Although some features of the Laochang deposit are similar to those of Kuroko-type deposits, there are remarkable differences in the alteration mineral assemblage, the proportion of ore-forming elements (lead enriched) and the amounts of oxides and sulfates. These suggest corresponding differences in ore fluid composition and the associated ore-forming environment. Thus, the authors suggest that the Laochang deposit may be a distinct type of VMS deposit."

Jan 1, 1993

By Sergio Cattalanl, Francis Chartrand

"The geology and origins of volcanogenic massive sulfide (VMS) deposits in the Abitibi belt of northwestern Quebec have been the subject of discussion since the discovery of the Horne orebodies in Noranda in 1923.The present Noranda version of the VMS model characterizes the ideal deposit as a stratabound, base-metal accumulation that is in close spatial relationship with hydrothermal alteration and stockwork zones, felsic lava domes, coarse phreatic-pyroclastic breccias, and subvolcanic intrusions that characterize vent- and proximal{acies submarine volcanic environments. Deposits tend to occur in a favorable stratigraphic interval within a mining camp, and this is well-documented in the Rouyn-Noranda and Matagami camps.However, in recent years many VMS deposits have been shown to deviate from the ideal Noranda-type. For example, the Ansi/ deposit is characterized by sulphide-bearing alteration zones that extend far above the massive sulfide lenses, and by abundant magnetite immediately underlying massive sulfide. The Horne deposit appears to lack the typical chloritic alteration pipe underlying the massive sulfide lenses, as well as laterally-equivalent exhalite horizons. The Horne and Quemont deposits, besides being the two giants of the camp, are particularly rich in gold, whereas others, such as WaiteAmulet and Millenbach, have low gold values. Finally, some deposits in the Noranda camp, such as the Ansil, Corbet and Mobrun mines, are outside the favorable stratigraphic interval. Therefore, it would appear that part of the key to renewing base metal reserves in northwestern Quebec is the use of evolving descriptive-genetic models that incorporate geological variations like those cited above."

Jan 1, 1990

By H. J. H. Pieterse

Agitation requirements in oxidation autoclaves can vary widely depending on the mineralogy of the feed material and the specific process selected. Before selecting an agitation system it is important that the client specify the desired throughput, mineralogy, chemistry, kinetics, compartments, overall retention time, and the desired oxygen utilization. In selecting the agitation system, the factors mentioned above as well as oxygen solubility, oxygen mass transfer coefficients, and specific power are evaluated. Much research effort has been directed toward open tank systems for fermentation and oxidation processes. However, for high pressure autoclave oxidation processes little information is available. In this review the author's experience in the autoclave industry and some of the available literature are utilized to compare the installed power per unit volume with some of the methods proposed for open tank oxidation. Equations that appear to give results close to that experienced in the industry have been identified. Further work is required in this area to develop a higher degree of confidence in the ability to predict the power required for any given case.

Jan 1, 2004

By J. Girard, V. Aubé, M. Barakate, S. Bellec, M. R. Eddahabi, Y. Chaik, M. Deshaies

"The activated carbon used in the carbon-in-leach (CIL) process to absorb gold is subject to breakage. This carbon breakage can be minimized, but it will always be necessary to deal with fine carbon particles, known as carbon fines. These fines contain a significant amount of gold and mining operations generally struggle with the treatment of this product. Since IAMGOLD’s Essakane mine is located in Burkina Faso, shipping carbon fines out of the country was not considered a viable solution due to the logistical burden and legal procedures in place. A benchmarking study demonstrated the complexity of treating carbon fines on site. IAMGOLD partnered with the host government to find an innovative approach to economically recover the gold locked in these fines. This paper describes the new circuits commissioned in July 2016 built to improve carbon fines collection, incinerate the carbon fines and leach the gold in the ashes produced by incineration. These new circuits successfully demonstrate that it is possible to extract more than 94% of the gold content in the carbon fines. This is profitable for the company as it improves the overall mill recovery rate by 1.0% to 1.5% and significantly decreases gold inventory build-up on site.INTRODUCTION The activated carbon used in the carbon-in-leach (CIL) to absorb gold is subject to breakage. This breakage can occur in the CIL tanks, the stripping circuit, the regeneration process or anywhere throughout the pumping and handling processes of carbon through the circuit. Fine carbon particles are invariably created and, because of their small size, present a large specific surface which favors gold absorption (Hilsher et al., 2014). At the very beginning of operations at Essakane, the carbon fines were recovered by means of a thickener and a filter press, but the circuit was undersized and inefficient. Subsequently, a decantation basin was used to settle the fines before the thickener. The settled fines were shovelled from the basin into bags. All these bags were stored in the backyard of the plant. The average tonnage of carbon fines recovered monthly was 23.5 tons with a gold grade at 1938 g/t."

Jan 1, 2017

By David Nicholls

?Overview of New Afton ?Reserves and Resources ?Geology and Mineralization ?Exploration ?Capital Project Development to Date ?Mine Development ?Processing ?Construction ?LOM ?Health, Safety, Environment and Social Responsibility Overview of New Afton ?Fully owned by New Gold Inc ?Large gold-copper porphyry deposit, amenable to block cave mining, production commencing in 2012 -1 million ounce gold reserve -1 billion pound copper reserve -Estimated 13 year mine life ?Low operating cost ?Estimated capital expenditure requirements -Spend to date ?US$200million -Remaining to be spent ?US$400milllion ?Robust economics ?Excellent location and infrastructure ?Significant cash flow contributor for the Company

May 1, 2010

By Nehad Elsafty

It is always necessary to expand existing buildings, so that they could meet the growing societal needs. Compared with demolishing them and then constructing new ones, the expansion of existing buildings could not only reduce project cost, but also save the use of energy and raw materials in projects. Therefore, it is widely adopted in most under-developed countries. However, the expansion of existing buildings is not an easy task. It has been involved with a lot of issues in defining the scope of work, planning landscape, managing construction activities, etc. This paper investigates the potential challenges in expanding existing buildings. The project of expanding the Al-Agoza Hospital, one of the biggest and oldest hospitals in Cairo, Egypt, is selected as a case study. In the case study, the project documents have been carefully reviewed. The project engineers and the health-care professionals working in the hospital have been interviewed. This way, the point of views from the owner, the architect/engineer, and the contractor have been taken into account. Several lessons are learned through the discussion with these people. The results from this paper are expected to provide pieces of useful advice and suggestion for the expansion of existing buildings in the future.

Aug 1, 2013

By Franz Xaver Spachtholz

K+S Potash Canada GP (KSPC) is part of the K+S Group, one of the world's leading suppliers of standard and speciality fertilizers and the world?s leading salt producer. Globally, the K+S Group employs more than 14,000 people. The K+S share ? the only commodities stock on the German DAX index ? is listed on all German stock exchanges. Legacy, K+S Group?s most recent project, is a greenfield solution potash mine and production plant in the south of the Canadian province of Saskatchewan. Therefore K+S will invest 4.1 billion CAD. With the expected commissioning in summer 2016 the company projects to reach the two-million-tonnesmark of production capacity at the new location at the end of 2017. The gradual extension of the annual capacity to 2.86 million tonnes of potash products will occur afterwards. The Legacy Project will be Saskatchewan?s first new potash mine in nearly 40 years. It is one of the world?s most economically attractive potash projects. The project will contribute to Saskatchewan?s growth through employment, tax revenues, utilities, and local partnerships. Located in the southern part of Saskatchewan?s potash belt, the deposit is too deep to be mined conventionally due to rock mechanics and high temperatures. Legacy will therefore be a solution mine. Proximity to the urban centers of Regina and Moose Jaw is imperative, with their workforces and economy, as well as access to highways, railway carriers and, most importantly in the prairies, water. With this unique project setting and mining technique, we are convinced that Legacy will be one of the most efficient, economic, sustainable and safe potash facilities in the world.

Aug 1, 2013

By P. S. Arthur, G. R. F. Alvear

Development of a new smelting process is risky. Many novel processes in the metals industry failed to fulfil the initial expectations of their inventors. Large sums of capital have been invested in technologies that either didn't provide a satisfactory return on investment, or didn't perform at all, and had to be replaced. One of the keys to success in process development is incremental scale up of the technology, with potential problems being identified and rectified as early as possible. In this way the cost of any rectification that is required can be minimized. The ISASMELTTM process was developed to maturity by Mount Isa Mines through the 1980's and 1990's using incremental scale up. Commercialization only occurred once the process had been proven on laboratory, pilot and demonstration scale over many years. As a result ISASMELTTM technology now operates successfully at numerous plants around the world. The methodical approach to development of the technology has allowed owners to modernise their existing operations or create new businesses with significantly reduced technical risk.

Jan 1, 2011

By Balmer Neilly

We are regularly told that before making a new investment one should seek the advice of his banker. If we were to place the subject matter of this paper before bankers. other than those who have experience in our mining camps, their reply would probably be evasive. However, if for example: a mining company asks them for a loan and offers as security certain mining investments, they are, in most cases, explosively candid. The idea is preposterous, unless, under Section 88 of the Bank Act, the mining company is able to deposit with the bank, gold or silver bullion, to an amount sufficiently in excess of the loan, to provide for what the banker describes as a reasonable margin of safety in case of contingencies. In addition the directors of the mine personally must jointly and severally guarantee payment of the loan. With any of these conditions missing the banking atmosphere becomes chilly. The local manager explains that the general situation, and particularly European conditions, are so unsettled that head office has warned him that his discretionary powers must not be exceeded under any circumstances.

Jan 1, 1924

By W. D. Freeborn

Slim-hole drilling and completion techniques were first used in the Cynthia area of the Pembina field, Alberta, by the Texaco Exploration Company in the summer of 1957. Prior to that time, eighty-eight wells had been drilled and completed in this area in a conventional manner. Subsequent to the initial four-well evaluation programme, twenty-one additional wells have been drilled using slim-hole techniques. No difficulty was encountered in the drilling and completion of slim-hole wells, or in obtaining production from them. A comparison of drilling and completion economics and practices has been made for slim-hole and conventionally completed wells. Penetration rates for both bit sizes (614 in. and 9 in.) were relatively equal. The shorter life of the smaller bits required the use of 15 per cent more bits per well, but the total trip time to change bits was similar for both hole sizes because of the higher hoisting speeds possible with the lighter drilling strings used in the slim holes and better hole conditions. Completion costs of the slim holes were reduced by 37 per cent as compared to the costs of conventional-type completions. This was made possible through the use of smaller well equipment, the elimination of tubing, and a reduction in rig time for completion operations.

Jan 1, 1958

By W. L. Falconer

"IntroductionThe very recent emphasis on the importance of the northern portions of the Alberta basin as a prospective oil province has led the oil companies northward into new and undeveloped territory. Northern Alberta is a land of continuous forest, covering a plains-type topography. The plains are only occasionally broken by sharp, broad river valleys. Tributary streams head up quickly and very soon lose themselves in large undrained areas. It is these pseudo-swamps that cause most of the troubles and headaches of the oil explorer.The rivers have served as the main transportation arteries since people first ventured into this area. The bush is being pushed back, but the advance is slow and there is very little more than trappers' trails beyond a few miles from the Northern Alberta Railway lines and the recently built Grimshaw or McKenzie Highway. Indeed, bush and muskeg flank many miles of the railways and roads within as close a distance as fifty miles of Edmonton. Northern Alberta is pioneer country in the truest sense of the word, and our greatest problems derive from this fact. In all pioneer areas, the first requirement is the development of access roads, and before active oil exploraton can get down to the job at hand these roads and trails must be an accomplished fact. There are two factors in Northern Alberta which offer discouragement to the oil explorer: the first and greatest stumbling block is presented by the numerous muskegs, large and small; the second is the fact that road building uses up so much of reservation time. Of course, the second is aggravated by, and a direct result of, the first. So we come back to the main problem facing the development of the north - the muskegs."

Jan 1, 1950

By L. C. So, S. Faucher, S. Mostaghel, A. Triwahyuono, D. Sauter, S. -Y. Oh, S. K. Lee, K. Aswin

"Molten hauling and water granulation are the commonly used slag treatment methods in the production of nickel. Water is present in these processes either to accelerate cooling of the dumped slag or in the granulation itself which creates an inherent safety risk of explosions. Even good design and operation are not sufficient to prevent explosions or injuries from occurring. Several dry methods to treat slags have been intensely studied. However, most of these technologies have never been commercialized due to numerous challenges including scalability, cost, low heat recovery efficiencies, and difficulties in heat utilization. Ecomaister-Hatch has recently developed and commercialized a reliable and simple Dry Atomization process, which eliminates water and allows for heat recovery. As part of the development towards other sectors, laboratory-scale and pilot-scale trials have been completed in a number of base metals and PGM facilities. Recently, Dry Atomization of a nickel laterite slag was successfully demonstrated at the laboratory-scale. The current paper introduces the technology and reports the test results obtained from atomization of the nickel slag.INTRODUCTION The processing of nickel laterites produces vast amounts of slag with over 90% of the feed to the furnace reporting as slag. Slag handing is therefore of critical importance to a laterite smelter. Traditionally there are two ways in which the slag is handled (1) Molten hauling, dumping, cooling and quarrying (2) Water granulation, dewatering, stockpiling. There are inherent disadvantages of both methods that will be outlined in this paper. An alternate route of Dry Atomization provides distinct advantages over the two conventional routes that are of particular interest to the nickel producer such as elimination of molten hauling, dumping and quarrying, elimination of water and improved safety. There is also the potential to convert the slag, which is typically regarded as a waste product, into a value added product and the continuous nature of slag tapping makes it amenable to heat recovery. Hatch has recently conducted laboratory-scale test work on laterite slag to demonstrate its viability for Dry Atomization. Results of this work are presented."

Jan 1, 2017

By W. B. Boggs

Part 1 Originally, the copper produced at the Noranda ?smelter was shipped in the form of blister bars to the Laurel Hill refinery of the Nichols Copper Co., New York. In 1930 a refinery was built at Montreal East for the purpose of refining Noranda copper and copper from the Hudson Bay Mining and Smelting Co., at Flin Flon. After investigation of the probable costs of making anodes at Noranda and at Montreal, it was decided to make them at Noranda rather than to continue to make blister bars there. Fuel is a major item of expense in making anodes: and since less fuel would be required in making anodes from molten copper than in making them from blister bars, a lower anode furnace cost could be expected at Noranda than at Montreal. Further, the expense connected with making blister bars at Noranda would be eliminated. The cost of treating anode and wire bar furnace slags is a serious item in a refinery, and it was found that the cheapest method would be to ship such slags back to Noranda. With the anode furnace at Noranda, much less anode furnace slag would be made at the refinery. Against these savings which would be effected by making anodes at Noranda must be set the high operating cost of an anode furnace at Montreal, using only tank-room scrap and the Flin Flon copper. This furnace would be handling a comparatively small tonnage and would have a high cost per ton. The usual equipment for making anodes from. liquid copper consists of either a stationary reverberatory furnace or a tilting Tacoma-type furnace together with an anode wheel of the Clark or Walker type. The reverberatory type of furnace has been developed from the furnace used in the old Welsh process of smelting and refining copper, while the tilting furnace is a development of the holding furnace, which is essentially a Peirce Smith converter without tuyeres and provided with burners.

Jan 1, 1932

By J. R. Levin, E. J. Schelter

"We present some of our recent efforts in the development of predictive, directed oxidation chemistry of cerium(III) complexes under non-aqueous conditions. The electrochemistry of cerium(III)- alkali metal heterobimetallic aryloxide complexes is reported and compared with cerium aryloxide complexes that are kinetically stabilized by hydrogen bonding cations that span between the complexed aryloxide ligands. Comparative electrochemical measurements reveal differences between the heterobimetallic complexes and the hydrogen-bonded complexes.INTRODUCTIONThe rare earth elements comprise the lanthanides, La–Lu, and the element yttrium (Aspinall, 2001). Rare earth ores such as monazite, LnPO4, and bastnäsite, LnFCO3, typically bear mixtures of light rare earths: La–Sm while monazite, LnPO4, contains mixtures of heavy rare earths (Eu–Lu) (Cotton, 2006). Pure rare earth elements typically are isolated using a liquid-liquid separations process.(Bautista, 1995) The hydrometallurgy of these elements is a difficult problem because the separation factors between neighboring rare earths, which are predicated on the small differences in the sizes of the trivalent ions, are quite small (Cox, 1992). The element cerium, with its 4f1 electronic configuration in the trivalent state, is unique among the rare earth elements due to a relatively accessible 4f0 electronic configuration. The accessibility of the 4f0 configuration underlies the chemistry of cerium(IV), the only rare earth ion with molecular chemistry in the tetravalent oxidation state (Cotton, 2006). Cerium is trivially separated from mixtures of light rare earths by making use of its unique oxidation chemistry. In an effort to extend separations chemistry by oxidation reactions to other rare earth elements such as terbium and praseodymium, the solution electrochemistry of well-defined cerium complexes is of interest."

Jan 1, 2012

"The ventilation-related risks from mines with elemental sulphur include dust explosions, spontaneous combustion with emission of heat and toxic sulphur dioxide or hydrogen sulphide gases, reactions with nitrates, corrosion, acid water, and pyrophoric reactions with naked iron or other metals. Elemental sulphur will form explosive mixtures in air at lower dust concentrations and at lower ignition temperatures than coal or sulphide dusts. Potential controls include primary ventilation circuit design, control of dust deposition and static discharges, enclosing steel surfaces, inert stone dusting, FRAS ducting, humidifying the air, alternate stench gas, self-contained self-rescuers with goggles, careful siting of underground infrastructure, controls on explosives formulations and procedures, mining method selection, controls on surface temperatures and protection of equipment, careful materials selection for ventilation seals and changes to worker clothing and training.INTRODUCTIONSulphur (“Brimstone” in biblical times) is one of the world’s most important industrial feedstocks and is used in a wide range of chemical processes and industries. Until the early 20th Century, most of the world’s production of sulphur came from ‘conventional’ underground mines in Sicily (Demetra produzioni, 2006; Bellia, 2006). This was a hazardous activity. The Frasch solution mining process replaced traditional underground mining of sulphur until the late 20th Century. Most of the world’s production of elemental sulphur is now as a by-product from sour gas produced in petroleum refineries and natural gas installations (Anon, 1993). As such, there is considerable experience in understanding and managing the hazards of elemental sulphur in chemical plants and surface transport.Whilst rare, underground mines with high elemental sulphur contents (as a gangue mineral) create an unusual range of mine design and operational issues, including many ventilation-related ones. The key hazards from elemental sulphur include: primary and secondary elemental sulphur dust explosions, fires and burning (with emission of heat and sulphur dioxide or hydrogen sulphide gas), reactions with nitrates used in explosives, corrosion of steel and other metals, generation of acid water (especially at higher water temperatures), and pyrophoric reactions with naked iron (e.g., ground support, ladderways or underground fixed plant) or other metals including silver and copper (e.g., used in electrical components and equipment)."

Jan 1, 2019

By Warwick Bullen

A hypothetical economic model has been developed for diamond projects in the Canadian Arctic using data from recent exploration and mining projects. The model reflects economic conditions as it applies to the diamond mining industry in the Canadian Arctic at the present time. The economic model captures pre-production expenditures, production data, and post-production costs. Before- and after-tax cash flows are derived from the data along with the relevant economic criteria. From the corporate perspective, the model provides guidance as to the minimum size and/or in-situ value per tonne requirements of targets being sought in order to ensure economic success and probable exploration and development expenditures. From the government perspective, the model provides an indication of income and mining tax revenues that can be expected from a particular diamond project. The model shows, on average, diamond projects in the Canadian Arctic are expensive to explore for and develop, but are economically robust. They generate great economic return for mining companies and significant amounts of tax revenue for governments. The fact that diamonds can be transported directly from the mine site by air makes them particularly attractive targets for mining companies that operate in the Canadian Arctic.

Apr 1, 2005

By Jean-Marc Simard, Richard Genest

"La mine Agnico-Eagle, localisée près de Joutel, a été découverte en 1962 par le forage d'anomalies électromagnétiques. Exploitée à partir de 1974, elle a déjà produit près de 30 tonnes d’or à partir de 2 puits, le puits Eagle et le puits Telbel, distants de 1,3 km.Le gisement est situé entre le sommet du complexe volcanique de Joutel, à dominante felsique, et la base de l'ensemble sédimentaire de la rivière Harricana. Ces deux unités ont une extension régionale; elles sont orientées NW-SE avec une polarité NE et des pendages subverticaux. Une faille majeure, la faille Harricana, passe de façon subconcordante au contact de ces deux ensembles.La minéralisation aurifère, de 2 à 5 m d’épaisseur moyenne, est liée a une zone carbonatée, comprise entre des tufs felsiques, argilites et sédiments chimiques (éponte inferieure) et des argilites carbonatées (éponte supérieure). Le minerai est constitué habituellement de 20% de fine pyrite disséminée. L’or est en fines particules associées directement à ces grains de pyrite de texture cataclastique.Deux modelés ont été for mules jusqu' a présent pour expliquer la genèse du gisement: une thèse syngenetique (Barnett et a/.1982) et une thèse épigénétique (Wyman et al. 1986). Cette dernière apparalt comme la plus probable du fait de la présence de la minéralisation dans les zones cisaillées a carbonates secondaires et pyrite cataclastique."

Jan 1, 1990

By Y. Nishida, Y. Nara, T. Ishida

Understanding time-dependent deformation and fracturing in rock is essential, because the information of the long-term stability of rock is required for many sub-surface structures excavated in a rock mass. Time-dependent fracture propagation has been invoked as a potential key mechanism responsible for the increase in seismicity preceding earthquake ruptures. In engineering projects and in preventing natural hazards, the study of time-dependent fracturing is necessary. Subcritical crack growth is one of the main causes of time-dependent fracturing in rock. For silicate rocks, subcritical crack growth has been investigated by various researchers. It has been clarified that surrounding environmental conditions (temperature, humidity, and existence of water) have strong influence on subcritical crack growth in silicate rocks. Therefore, the information of subcritical crack growth in silicate rocks has already been enough. On the other hand, information of subcritical crack growth in carbonate rocks is not enough. Especially, the influence of surrounding environment on subcritical crack growth in carbonate rock has not been clarified yet. In this study, we investigate subcritical crack growth in carbonate rock experimentally using a fracture mechanics testing method. Marble obtained in Skopje in Macedonia is used as a carbonate rock sample. The Double Torsion method is used to measure the crack velocity and stress intensity factor. Especially, influence of water on subcritical crack growth in Macedonian marble is investigated. It was shown that the crack velocity in water is much higher than that in air at the same temperature. Based on the results of subcritical crack growth measurements, the long-term strength is evaluated for marble. It was clarified that the long-term strength in water is lower than that in air in marble. It is concluded that water has a remarkable influence on subcritical crack growth in marble. It is also considered that the long-term stability of carbonate rock masses should be ensured in a dry environment.

Jan 1, 2015

By L. Rao, P. Carabin

"Advances in thermal plasma torches have resulted in this technology becoming a commercially viable solution for chemical and metallurgical processes. The main advantages of plasma are its ability to control process chemistry and to build small footprint reactors due to its high energy density and reactivity of the free radicals that are produced. This paper focuses on thermal plasmas produced by DC torches and their applications for waste treatment, production of high purity metals, and nanomaterials. Both transferred and non-transferred torches have been used as either a source of heat or as a reagent in various industrial processes. INTRODUCTIONPlasma technology has become an ideal solution for many industrial chemical, metallurgical and mechanical processes (Venkataramani, 2002). Thermal plasma powered systems are typical used for their unique characteristics such as high energy densities, high temperatures, small installation sizes, rapid startup and shutdown features, controlled process chemistry and use of electrical energy as a heating source resulting in decoupling the heat source from the oxygen flow rate (Heberlein et al., 2007). Depending on the nature of the main plasma forming gas used, thermal plasma systems offer a high temperature heating source coupled with a highly reactive plasma plume rich in free radicals and ions which promote otherwise hard to drive chemical reactions, as well as high heat transfer rates.Industrial plasmas can be broadly classified as thermal plasmas and non thermal plasmas. Thermal plasmas are atmospheric pressure plasmas characterized by local thermodynamic equilibrium (Boulos et al., 1994). Thermal plasmas are typically established between any two current conducting electrodes separated by an insulator. A plasma forming gas is blown between the two conducting electrodes resulting in a high temperature plasma plume. A plasma torch generates and maintains an electrically conducting gas column between the two electrodes; a cathode (negative electrode) and an anode (positive electrode) (Camacho, 1988). If both electrodes are housed in a single housing, resulting in an arc enclosed inside the plasma torch, then such plasma generating torches are termed as non-transferred (NT) plasma torches, whereas, if the second electrode is external to the torch, creating an arc transferred between the cathode and the working piece, then such plasma torches are termed as transferred (T) plasma torches. Depending on the source of the electricity which can be either direct current (DC), alternating current (AC) at main network frequency or at radio frequency (RF), the plasma torches are classified as DC, AC or RF plasma torches (Venkataramani, 2002)."

Jan 1, 2012

Mining Equipment Challenges Equipment Availability Unplanned downtime Maintenance Costs Secondary damage and catastrophic failures (T282 $750k) Emergency work is 4x the cost of planned work Inspections Troubleshooting time Incorrect repairs (parts, labor, lost production) Equipment Life Mis-operation of equipment

May 1, 2013