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By K. G. Markkola

The Minera Candelaria concentrator was commissioned in August 1994, and in October 1997 it doubled its grinding capacity. The concentrator was designed to treat 56,000 metric tonnes of copper ore with a primary crusher, two grinding circuits, pebble crushing, and flotation. The grinding circuit includes two 11.2 m (36 ft) diameter by 4.6 m (15 ft) long semi-autogenous (SAG) mills, each fitted with a 12 MW motor. Throughout the history of Candelaria, different strategies have been developed to maximize the plant's operational time, strategies that include increasing the life of the SAG mill liners and reducing the time involved in changing these elements. This work describes the improvements made in the design of the liners, the change planning, and a new strategy to change the liners with the purpose of increasing their use and throughput.

Jan 1, 2007

By K. Harris, J. B. Wahl

Ni-base superalloy cast materials provide an outstanding balance of high temperature strength, fatigue resistance, oxidation resistance and coating performance and can be produced to very tight tolerances in extremely complex configurations, such as axial and centrifugal integral cast turbine wheels. As a result, cast superalloys are used in the most demanding applications of aero and industrial gas turbine engines. Use of these materials is expanding to smaller microturbine, turbojet, turbocharger and missile engine applications due to this unique combination of desirable properties. This paper will present an overview of the application of investment cast Ni-base superalloys and process capability to small turbine and missile engines.

Jan 1, 2010

To determine the optimal circuit configuration for gravity gold recovery consideration should be given to a range of factors in addition to the efficiency of the gravity circuit, including capital costs, ease of operation and impact on comminution. The most common gravity gold circuits utilise a centrifugal concentrator treating a portion of the hydrocyclone underflow. This paper will examine this option and alternative circuit configurations to illustrate the effect of various gravity circuit feed and tailings configurations on the equipment sizing, capital costs, operating costs, water balance, comminution efficiency and gravity gold recovery. The optimum circuit configuration can provide reduced capital and operating costs, maximise gravity gold recovery and improve comminution efficiency.

Jan 1, 2011

By Ausenco Engineering Canada

"This paper demonstrates the selection of grinding circuit technology for a number of recent projects including discussion of the key drivers and the role of energy efficiency. Decreasing head grades combined with a strong and sustained increase in operating costs has forced miners to examine increased project size, increased equipment capacity and efficiency improvements in order to reduce their unit operating costs and improve overall project economics. Comminution energy consumption, safety and capital cost considerations play a critical role in the success of projects. This paper presents some key guidelines for a successful and cost effective comminution circuit design and includes a case study on three projects, outlining the issues and the drivers which led to the ultimate circuit selection and the critical role that energy efficiency played.INTRODUCTIONComminution circuits for minerals processing are selected based on their suitability and efficiency in reducing run-of-mine ore to the desired feed size for the downstream process. The input material (ore) properties and downstream process requirements are the key determinants and there are standard approaches for each circumstance.The minerals processing industry has been a fast adaptor of efficiency improvements based on increasing capacity of equipment (e.g. trucks, crushers, mills, pumps) but less successful in adapting radically new technologies that disrupt incumbent flowsheets or processes.The installed power of grinding mills has increased linearly over the past 25 years (Meka & Lane, 2010) and pumps and classification equipment have kept pace. The autogenous grinding (AG) and semiautogenous grinding (SAG) mills displaced stage crushing as a dominant method of coarse rock breakage in many applications causing crusher manufactures to increase the capacity of cone crushers to meet the competitive demand.Examples of new comminution technology in the 20th and 21st centuries are the development and adoption of cyclone classification in the 1940s (Newtech, 2016), AG milling in the late 1950s, vertical grinding mills in the 1980s, high pressure grinding rolls (HPGRs) also in the 1980s and ultrafine milling technology in the 1990s (Meka & Lane, 2010)."

Jan 1, 2016

By Vladislava A. Ignatkina, Fillip O. Milovich, Vladimir A. Bocharov

"Complex research of flotation concentrates of monomineral fractions of chalcopyrite, sphalerite, galena, pyrite, pyrrhotite included methods of adsorption of collectors, surface compounds by IR ATR, and surface films of flotoreagents by TEM. They revealed that the proportion of the parts of thionocarbamate (TC) and dithiophosphate had an effect on the adsorption rate of the components of minerals, on the presence of characteristic bands, and, what is an important, visualized surface film of organic flotation reagents on the particles of concentrates by TEM. The predominance of thionocarbamate in a composition selectively increases the adsorption rate constant of the components and recovery of chalcopyrite compared with sphalerite and galena. The highest flotation rate using TC is characteristic for chalcopyrite (0.62 min- 1) in case of individual use, and it's in combination with butyl xanthate (25% butyl xanthate or 3:1) 0.89 min-1 too. We studied the ternary blend - dithiophosphate: thionocarbamates: butyl xanthate. The increase of the proportion of butyl xanthate in combination reduces the contrast of the flotation rate among all sulfides.Practice flotation of refractory sulfide copper-zinc ores of the Urals (content sulfide iron - 75- 95%) confirmed that the use of a combination of selective collectors increases selective recovery of copper sulfide minerals up to 50% at the first fraction that is the conditioned copper concentrate. New selective sulfhydryl collectors resulted in high levels of recovery of copper into a concentrate - more than 90% - against 70-72% (butyl xanthate) from copper-pyrite ore. Low floatability of iron sulfides has been obtained by selective sulfhydryl collectors. Using weak selective sulfhydryl collectors can reduce pH into collective or selective flotation from pH 10-10.5 to pH = 7.2-7.5, which improves the quality of individual concentrates of nonferrous metals and their recovery. The same is true for polymetalic sulfide ore. The volume of gold recovery also increased."

Jan 1, 2016

By Stéphane Robert

This document presents estimates of future "total cash cost per ounce" and "minesite cost per tonne" that are not recognized measures under United States generally accepted accounting principles ("US GAAP"). This data may not be comparable to data presented by other gold producers. These future estimates are based upon the total cash costs per ounce and minesite costs per tonne that the Company expects to incur to mine gold at the applicable projects and do not include production costs attributable to accretion expense and other asset retirement costs, which will vary over time as each project is developed and mined. It is therefore not practicable to reconcile these forward-looking non-GAAP financial measures to the most comparable GAAP measure. A reconciliation of the Company's total cash cost per ounce and minesite cost per tonne to the most comparable financial measures calculated and presented in accordance with US GAAP for the Company's historical results of operations is set forth in the notes to the financial statements included in the Company's Annual Information Form and Annual Report on Form 20-F, for the year ended December 31, 2009, as well as the Company's other filings with the Canadian Securities Administrators and the SEC.

May 1, 2011

By A. L. Mular

"This paper summarizes the present-day usage of computers in the mining-metallurgical industry. The industry appears to be following a path taken by other industries in improving the operation of processing plants, production schedules, grade control and haulage performance. A reduction in the cost of computers and computing has been a significant factor.An attempt is made to forecast the future of computers in our industry. Such developments as time-sharing, mini-computers, and easy-to-understand process-oriented languages will lead to wider usage. Considerable strides have been made in the use of computers for laboratory data acquisition. In general, the implementation of new methods, new techniques and new equipment will require plant personnel to develop new skills. The universities are meeting this challenge by re-structuring curricula and offering special courses. Most vendors of computers already offer special courses within their own facilities at a customer's plant."

Jan 1, 1970

By A. Warczok

Chalcocite concentrate obtained by magnetic separation and flotation of Bessemer matte is processed in the Inca top blowing bottom stirring MK reactor into semi-blister copper. The semi-blister is then converted into blister copper in the multi-purpose vessels (MPV) by oxidation of iron, nickel and sulphur. High melting point NiO and Fe30 4 are formed inside the MPV s, which together with Cu20 and smaller amount of fayalite are the major constituents of the solid mush. The accumulation of solid mush and buildup requires periodic MPV cleaning by adding reductant and copper-nickel matte, a unique process called "washout". Various reductants and their combinations, such as pig-iron, 15%Si Ferro-silicon and 50%Si Ferro-silicon, have been used for the reduction of solid mush and buildup. The possibilities of using calcium carbide as a reductant and slagging flux were examined experimentally at the crucible scale. The rate of reduction of MPV buildup was determined by continuous measurement of CO and C02 contents in the offgas and the flowrate of argon carrier gas. The rate of the buildup reduction with calcium carbide was approximately five times faster than the rate of reduction with coke. Additionally, the formation of CaO results in the melting of reduced buildup and formation of a slag at 1300°C and higher temperatures. It was found that simultaneous silica addition enhanced the melting and slag formation. The results showed the strong dependence of the reduction rate on temperature. Activation energy is approximately 225 kJ/mol. Expected benefits of using calcium carbide are related to cost saving on reductant, significant acceleration of solid mush reduction, and reduced amount iron input from reductant.

Jan 1, 2007

By B. R. Maas

Processing material at a consistent rate through the continuous countercurrent decantation (CCD) thickeners presented a major bottle neck to unlocking additional value from one of the post-flotation streams at the Kansanshi processing plant. The manual operation of the thickeners making up the CCD train resulted in frequent imbalances and process upsets across units. The automation of CCD trains is notoriously tricky as the available manipulated variables are outnumbered by the parameters requiring regulation. The implementation of an advanced, auction-based, control philosophy to manage the movement of both slurry and solution inventory through the train addressed this parameter imbalance and lead to the stabilisation of the circuit. Since the commissioning of this control strategy: an additional 7 200 dmt/day (+36% throughput) of material can reliably be processed through the train, the number of monthly downtime events has reduced, and a saving of $354 000/month in reagent cost has been achieved. INTRODUCTION CCD operation Agitated leaching is a common method used in hydrometallurgy to extract a metal from its host ore. The host ore is initially finely ground to liberate the surfaces of the valued minerals and improve the kinetics of the leaching process. The ore is then contacted in an agitated tank with a lixiviant to dissolve the desired metal into the aqueous phase. The resultant slurry from the leaching process comprises of a solution pregnant in the metal salt and a barren ore. The first purification step taken after leaching is to wash the pregnant liquor solution (PLS) from the depleted ore. On the industrial scale, a set of between two to ten thickeners arranged in a countercurrent configuration is often used to carry out this separation (Perry & Chilton, 1973). The slurry is introduced at the head of the train and a wash solution at the tail. The two streams are pumped through each thickener countercurrent to one other. At each stage the residual PLS in the slurry is mixed and diluted down with the countercurrent overflow solution from the downstream thickener. The diluted slurry is fed into the thickener where the solids separate out through gravity sedimentation. The settled solids are channelled towards the underflow of the thickener by a rake mechanism and pumped downstream to the next thickener in the train. The outcome is the recovery of a PLS from the overflow of the lead thickener and a slurry of washed solids from the underflow of the tails thickener.

Jan 1, 2019

By J. E. Hawley

"The zinc-lead deposit of the Lake Geneva Mining Company is on lot 7, con. VI, Hess township, Sudbury district, Ontario, about 10 miles northwest of the northern rim of the Sudbury Basin. Though a relatively small deposit, it shows some rather interesting relations to cross-cutting, pre-ore, quartz diabase dykes, which merit description.The deposit was discovered in October 1924 by J. H. Collins beneath iron-stained drift and oxidized sulphides. This proved to be the northwestern extremity of the orebody, the remainder of which extends southeast below swampy ground. Exploration began in 1927. In 1928 a vertical shaft was sunk to 250 feet and a level established at 235 feet. Later the shaft was deepened to 400 feet and new levels opened at 315 and 375 feet. In 1943 an inclined winze was sunk below the vein from the 315-foot level to a vertical depth of 640 feet, and two additional levels were opened at 525 and 615 feet respectively.The geology of the area has been described by T. T. Quirke (1), F. F. Osborne (2), F. J. Alcock (3), and Ralph Tuck (4). Private reports have also been made by Carl Tolman, J. E. Gill, and K. W. Fritzsche. Tuck's paper, covering the work completed to 1930, gives a detailed account of the character of the ore and enclosing rocks.Up to May 1944, when the property was closed, all ore above the 375-foot level and a small tonnage from below this elevation had been removed. Ore mined from 1941 to 1944 yielded the following:"

Jan 1, 1954

By G. Fuentes, J. Viñals

"The nature and basic kinetics of the hydrothermal reactions of bornite, covellite pyrite and enargite with copper sulfate solutions were investigated, as a previous study on the behavior of the bulk Chilean copper concentrates. The reaction of bornite produced digenite at 160 °C and djurleite above this temperature. Covellite was transformed to digenite at < 200 °C and to chalcocite (Q and M) at > 200 °C. The pyrite reaction was significant at > 200 °C and extensive at 240 °C, enargite reacts only above 240°C and produces digenite. The hydrothermal treatment of Chilean Codelco-type copper concentrates with hydrothermal reactions was similar to those obtained from pure mineral samples.INTRODUCTIONStudies on the hydrothermal enrichment of chalcopyrite concentrates were begun by MacGauley and Roberts (1951), Roberts et al. (1953) and MacGauley and Schaufelberger (1956). In the 1970's these processes were reexamined by McKay et al. (1972), and Johnson and Coltrinari (1976), but it not was until the 1990s when the kinetics, mechanisms and full engineering aspects were studied by Barlett, (1992), Jang and Wadsworth, (1994) and Peterson and Wadsworth (1994). The main objectives were to solve some important problems in the copper pyrometallurgy: The increase of the smelting capacity, the reduction of the iron slag – and associated copper losses – as well as the reduction of sulfur emissions. The present rise in copper demand and price implies the production and subsequent treatment of very impure concentrates. Thus, a significant increase of environmental problems can be expected in the copper pyrometallurgy. The previous purification of concentrates can reduce the processing of wastes containing hazardous heavy metals in the copper refineries and the hydrothermal treatment can be an alternative which combines both enrichment and purification. On the other hand, Chuquicamatatype concentrates (Viñals et al., 2004a) contains digenite (Cu1.8S), pyrite (FeS2), chalcopyrite(CuFeS2), b ornite (Cu5FeS4), covellite (CuS) and sphalerite (ZnS) as the main mineral components, with minor amounts of enargite (Cu3AsS4), galena (PbS) and molybdenite (MoS2)."

Jan 1, 2012

By Rolf Andreas Lauten, Yanhong Wang, Yongjun Peng

"In mineral flotation, bentonite as a kind of clay mineral imposes deleterious effects on the flotation of valuable minerals, possibly through its ability to increase the pulp viscosity. A higher viscosity lowers the amount of froth and affects the bubble-particle collision frequency. A previous study found that adding gypsum to a bentonite-ore mixture lowered the viscosity, possibly by inhibiting the formation of interconnected network structures. In this study, sulfate as an anion with different types of cations, Na+, K+, Mg2+ and Ca2+ were used to reduce bentonite viscosity and to improve flotation performance. It was found that at the same concentration, MgSO4 was the most effective salt in reducing bentonite suspension viscosity, while CaSO4 was not as effective likely due to the lower solubility of CaSO4. Na2SO4 and K2SO4 reduced bentonite suspension viscosity at high concentration. Flotation kinetics of ore blended with bentonite was increased with increasing the electrolytes concentration, which generally correlated with the reduction of bentonite viscosity. Meanwhile, significant discrepancies were found between flotation results and rheological measurements in the presence of monovalent ions. It is indicated that the morphology of bentonite aggregates in electrolytes solution is likely to influence the hydrodynamics in the froth zone.INTRODUCTIONClay is present in many ore bodies as a gangue mineral. Presence of clay presents several challenges in the processing of valuable minerals. They are soft compared to valuable minerals, which means that during grinding of the ore, clay particles are likely to obtain a smaller particle size than the valuable mineral. Often clay particles may be within the colloidal size domain (<20 µm). The smaller size increases the probability of entrainment in the concentrate. Another challenge is their anisotropic charge distribution, where depending upon the pH, edges (E) and faces (F) carry charges of opposite sign. This facilitates formation of aggregation structures that may impede percolation of bubbles through a froth, but also increase the viscosity more than expected from the mere change in volume fraction. In addition to lowering the froth mobility, a high slurry viscosity will have implications for the gas dispersion in the flotation column as it affects the dispersion of the suspended particles, and it modifies the bubble-particle collision rate and attachment efficiency (Bakker, Meyer, & Deglon, 2009; Shabalala, Harris, Leal Filho, & Deglon, 2011). A pragmatic approach to this problem is to blend high clay ore with ore of lower clay content, reducing the overall clay concentration. Alternatively, one may lower the solids content of the flotation slurry to counteract the viscosity-building properties of clay. While feasible, this approach has the disadvantage of increasing required flotation volume, and it also affects the properties of the froth. Thus, there are currently limited options in lowering the impact of clays and their tendencies to increase viscosity in flotation slurries."

Jan 1, 2016

By J R. M Hutcheson

Advocate Mines Limited came into initial production on June 30, 1963, with an annual capacity in excess of 60,000 tons of high-quality chrysotile asbestos fihres, thus strengthening Canada&apos;s position in world production. The history of this development is traced from discovery through initial exploration, financing, orebody delineation and evaluation, pilot-plant production and product evaluation, construction of the plant, construction of deep?-sea shipping facilities, provision for a closed shipping season, and provision for the remoteness and for the lack of services, through to realization of full production capacity. The many unique aspects of the project are given special attention, particularly in the light of the first year of full-capacity operation. The marketing of the products in a highly competitive world market is reviewed, with special emphasis on product evaluation, quality control and the shipping of high-quality products to consumers throughout the world. C ANADA&apos;S newest asbestos producer, Advocate Mines Limited, is located at the north end of the Burlington Peninsula, White Bay District, Newfound-

Jan 1, 1965

By V. G. Papangelakis, A. Dani

"Alkaline pressure oxidation, particularly in the presence of trona as additive, can be used to oxidize high carbonate refractory gold ores as it prevents the formation of CO2 in the autoclave. However, the presence of silica in the ore can lead to the encapsulation of pyrite due to the solubility of silica in alkaline solutions and its subsequent reprecipitation on the reacting pyrite surface, leading to the formation of a passive layer. This fundamental study investigates the chemical composition and thickness of the passive layer on a rotating pyrite disk using XPS and SEM, as a function of process conditions at 230°C, in an aqueous slurry containing silica sand, sodium carbonate and calcium carbonate under 100 psi of oxygen overpressure.INTRODUCTIONAlkaline pressure oxidation (POX) has been used successfully to treat high carbonate refractory gold ores, which contain carbonates in addition to sulphides, most notably at Mercur and Goldstrike mines operated by Barrick Gold. There are several advantages to using alkaline POX over its acid counterpart, especially due to high carbonate content. First, it eliminates the production of CO2 in the autoclave without resorting to pre-acidification, which allows for high oxygen utilization. Second, alkaline POX suppresses the formation of elemental sulphur and intermediate sulphur oxyanions (such as thiosulphates and dithionates), which reduce gold recovery. Third, the use of sodium hydroxide or salts prevents the formation of anhydrite scale by forming soluble sodium sulphate. Other advantages are the use of cheaper materials of construction and the formation of non-acidic residue that do not require further treatment prior to cyanidation (Thomas, 2005).Sodium carbonate in particular is a promising reagent for alkaline POX because it was shown to significantly accelerate the kinetics of pyrite oxidation by molecular oxygen, when compared to other reagents such as sodium hydroxide, sodium borate and calcium hydroxide. This has been attributed to the following factors: a) the faster oxidation kinetics of Fe2+-CO3 complexes compared to Fe2+ oxidation, b) the buffering effect of carbonate ions on the acidic pyrite surface, and c) the increased solubility of oxidizing Fe(III) species due to carbonate complexation (Caldeira, 2010)."

Jan 1, 2012

By H. Aaltonen, T. G. Robinson, M. Morimitsu

"The energy required to plate pure zinc can be the most significant operating cost for an operator in the production of electrolytic zinc. This paper reports on developments on low energy Outotec coated titanium anode process technology with fully amorphous coatings, MSA®, and its application to brownfield zinc electrowinning operations around the world. This technology aims to reduce the operating cost and increase productivity for zinc producers.INTRODUCTIONZinc electrowinning is an energy-intensive process using more than 3,000 kWh/t of electric energy [1-4], and the reduction of the energy consumption is one of the key issues. The high energy consumption is due to a high cell voltage during electrolysis, which is mainly caused by a high overpotential of oxygen evolution reaction on lead alloy anodes which have been widely used in commercial zinc electrowinning processes. The overpotential of oxygen evolution is 0.6 V or more and which is approximately 4 times higher on average than that of the cathodic reaction (zinc deposition) [3,4]. Therefore, the reduction of oxygen overpotential is significant to reduce the electric energy consumption, and this will become more significant with increasing demand in metal production and rising energy costs.Oxide coated titanium anodes have been widely investigated for the oxygen evolution anodes in order to replace the lead alloy anodes [5-9], because it is known that the oxygen overpotential strongly depends on the material and structure of the anode. The most typical example of such anodes is an IrO2-Ta2O5 coated titanium anode, which is usually prepared at thermal decomposition of a precursor solution containing metal salts at 450 oC or more and obtained mixed oxide coating consists of crystalline IrO2 and amorphous Ta2O5. On the other hand, one of the authors of this paper, Professor Morimitsu, Doshisha University in Japan, has developed a novel oxide coated titanium anode, MSA® [10-25]. The most specialized point of MSA® is that the catalytic coatings are prepared at low thermal decomposition temperature and amorphous IrO2 or RuO2 is contained as the components in the coatings. Such amorphous coatings have high catalytic activity for oxygen evolution compared to lead alloy or crystalline coatings. Outotec acquired the international specialized MSA® patent licensing rights from Doshisha University and has produced and commercialized the amorphous oxide coated titanium anodes. These anodes have already been utilized mainly in copper electrowinning plants worldwide and have demonstrated a significant voltage reduction, a cost-efficiency, and a long lifetime. This novel technology is also effective to zinc electrowinning process, thus this paper presents the characterization and performance of amorphous IrO2-Ta2O5 coated titanium anodes and amorphous RuO2-Ta2O5 coated titanium anodes for oxygen evolution in zinc electrowinning."

Jan 1, 2016

By A. Elsayed

Lightweight metals such as magnesium show potential in replacing aluminum alloy castings for engine cradles, cylinder heads and transmission cases. Unfortunately, magnesium alloys are susceptible to entrapping oxides and other impurities during casting that hinder strength and ductility. The current study examined various filter sizes and configurations with the aim of improving the mechanical properties of permanent mould cast AZ91E. The unfiltered casting had a yield strength, tensile strength and ductility of 93.3 MPa, 153.3 MPa and 2.2 % respectively and increased to 96.5 MPa, 167.0 MPa and 3.1 % with the use of a fine mesh filter within the well of the mould. The increased strength and ductility was likely due to the filtered castings containing fewer inclusions on their fracture surfaces as compared to the unfiltered castings.

Jan 1, 2011

By J. Stachulak

In recent years more emphasis has been placed on the control of nitrogen dioxide (NO2) emissions from mining diesel equipment. Worldwide, diesel engine regulations to control emission and protect the environment are also driving the development of the diesel engine technology to reduce oxides of nitrogen NOx (Nitric oxide, NO + NO2). NOx are toxic gases produced in mines during the operation of diesel equipment. Most of the diesel equipment used in underground operations are equipped with Diesel Oxidization Catalysts (DOCs) designed to reduce carbon monoxide (CO) and hydrocarbons (HC). The effects of DOCs on NO2 production from diesel powered equipment is not well understood. DOCs do not alter NOx concentration, but may promote the oxidization of engine exhaust NO to the more toxic NO2, thus increasing the undesirable NO2 exposure of workers in the mine environment. In 2012, the ACGIH reduced the NO2 TLV concentration value from 3 ppm to 0.2 ppm. Vale and CanmetMINING have been involved in several research projects to reduce diesel emissions exposure to workers. One aspect of the current program is to determine the effects of in-use DOCs on NO2 production. Several in-use DOCs taken from mining equipment were selected for testing in the laboratory using ISO 8178-C1 and mine LHD transient test cycles. The paper presents the laboratory test results and effects of DOCs on NO2 production. The results indicate significant reductions in CO concentration, by over 77%, while increases in NO2 varied from 46% to 315% based on the ISO 8178-C1 8-mode steady state test cycle. The mine LHD transient test cycle showed the same pattern, although the magnitude of CO reduction was less. Consequently, it is recommended the use of only those DOCs that have been properly evaluated and shown not to significantly increase NO2 emission in the environment be used on mine equipment.

Aug 1, 2013

By G. Ellie, D. F. Coates

"The mining of coal in thick and inclined seams is difficult, and there are only a few countries in the world that are really interested in the problems associated with their exploitation. In France a considerable amount of investment has been made in the mechanization of systems appropriate for such conditions.For seams inclined up to 50 degrees, of normal thickness, a new system was introduced in 1967. It consists of a longwall advancing to the rise with walking props, a shearer and hydraulic backfill. During the first two years the panel productivity was an average of 25 TN/MS, and they foresee the possibility of reaching an average of 30 TN/MS.A system for thick beds, both horizontal and inclined, is in p•rocess of being mechanized. In 1969 they started with a method consisting of a longwall in a footwall slice, or sub-level drifts with walking props, and caving and drawing up to a height of 20 m of coal. Recent experiments with a shearer have produced panel productivities between 9 and 11 TN /MS, and there is hope that with experience an average of 16 TN/MS will be obtained.In 1964 a method was initiated for beds inclined from 60 to 90 degrees, based on a mechanical cutter designed by the collieries in Lorraine. An overhand slice of 4.2 m in height is taken with a drum cutter mounted on the end of a boom. Hydraulic fill is placed at the completion of a slice. The face productivity, which has been from 13-20 TN /MS, can be perhaps increased to an average of 22 TN/MS. For those companies with important reserves in inclined and thick seams, these French systems may be worth the trouble of examining in some detail."

Jan 1, 1972

By Z. I. Zaki

Synthesis of TiC /A1203 Composite from TiO2, Al and graphite using combustion technique has been investigated at different initial temperatures; room, 400 and 600 °C. The effect of initial temperature on the composition of the product, wave velocity and combustion temperature of the reaction was studied. The measured combustion temperature and wave velocity were increased with increasing the initial temperature of the combustion reaction. The maximum wave velocity obtained was 5.9mms-1 when conducting the combustion reaction at initial temperature of 600 °C. Oxidation resistance of the obtained composite was also studied at the temperature range 300-800 °C. No oxidation is detected before 400 °C while it takes place effectively at 700 °C forming different titanium oxides. Wave velocity measurements method was used to calculate the activation energy of the reaction between the starting materials. It was found to be 316.34 kJ mol 1 at the temperature range that was studied.

Jan 1, 2007

By I. Yarita

Magnesium alloys have the lowest density among the metals in practical use, and have properties such high specific strength, electromagnetic interference shielding and good vibration damping. Thus, there are many applications of these materials in automotive and electric parts. However, there is a little use of the products of metal forming of these materials because of poor plastic deformability in the normal temperature range and their high cost of production. To expand the range of application of products manufactured by metal forming, rolling technology for producing thin sheets having good mechanical and surface qualities is required. In this study, hot-rolled Mg-alloy sheets are experimentally rolled with or without lubrication in the temperature range from 293 K to 523 K. Rolling force, plastic deformability and surface quality are investigated, and the grain structures and their uniformity are observed. The effect of friction between the roll and the deforming material on the uniformity of the grain structure is discussed. Moreover, rolled materials are annealed and their mechanical properties are investigated by the tensile test and compared with those of as-rolled materials. The effects of the rolling conditions on the mechanical properties are discussed.

Jan 1, 2006