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By Pedro H. Tumialán de la Cruz

La Cordillera Negra está constituída por rocas volcánicas que han sido intruídas por stocks porfiríticos de composición intermedia en el Terciario Superior con mayor afloramiento en las partes altas. De acuerdo a la metalogenética, las vetas polimetálicas se encuentran las partes altas cercanas a los stocks de los intrusivos y en los mismos stocks de dicha cordillera, En este sentido, algunos yacimientos polimetálicos contienen plata en zonas de mayor temperatura respecto al plomo y zinc, mientras que los yacimientos tipo estratos se encuentra ligado son singenéticos y se observan en las rocas estratificadas del Cretáceo. Por ello, el presente texto señala que la Cordillera Negra ofrece las condiciones idóneas metalogenéticas de yacimientos tipo filoniano hidrotermal en el departamento de Ancash.

Nov 8, 1984

By Jens Gutzmer, Helmut Mischo, George Barakos

"It has been nearly eight years since rare-earth elements (REE) became the subject of frontpage headlines. It was when the controversial Chinese export policy for these critical commodities was epitomized in a maritime border dispute with Japan in September 2010 that resulted in the big REE crisis and price spike of 2011 (Barakos et al., 2016c; Mancheri, 2015).The world was dismayed, especially in REE-importing countries such as the United States that was, and still is, totally dependent on Chinese production and exports (Barakos et al, 2016c; Kennedy, 2015). The short-lived alarm initiated a treasure hunt by way of exploration for REE deposits all over the world. The continuously growing demand on the one hand, and the Chinese sovereignty of the REEmarket on the other, led the rest of the world to explore their own REE resources. In just a few years, more than 400 projects were initiated to explore REE deposits outside of China (ERECON, 2015; Goodenough, 2016).The prices of REE, however, dropped rapidly in late 2017 and were in six-year lows, before the 2011 crisis (Barakos, 2017). The viability of even major established producers is being challenged, not to mention the development prospects of potential REEmarket entrants (Barakos et al., 2016b; Rollat et al., 2016). Production cutbacks and industry consolidation in China have impelled REE market experts to forecast that prices have already reached their lowest point and have nowhere to go but up (Adamas, 2015; Roskill 2015). Yet, expectations for increased REE prices are limited and drastic changes are unlikely to happen in the near future, as there is still excess supply in the overall REE market (Barakos, 2017). Nevertheless, the low prices of rare earths are not the only reason that potential producers are struggling to enter the global REE market. Among other parameters, the separation process of the individual elements seems to be the most important factor, as it is technically challenging and expensive to build and to operate."

Jan 8, 2018

By D. J. A. Chambers, J. M. Wempen, K. D. Koper, M. K. McCarter, K. L. Pankow

"The EarthScope Transportable Array (TA) of broadband seismometers (www.usarray.org) was deployed across southwest Wyoming from November 2007 through May 2009. During this time period the Array Network Facility (ANF, anf.ucsd.edu) detected and located a total of six seismic events near the trona-mining district. This lack of seismicity is atypical compared to coal mines employing similar mining methods. In this study, eighteen months of continuous seismic data from several nearby TA stations are reexamined using conventional and correlation-based methods to detect seismic events. Waveform cluster analysis and epicentral locations are used to discriminate between mining induced seismicity (MIS) and seismic energy generated from surface blasts at nearby coal mines. The locations and magnitudes of the 143 newly detected MIS events are compared to regional subsidence as measured by Differential Interferometric Synthetic Aperture Radar (DInSAR). INTRODUCTION An abundance of natural resources and a favorable political climate have made southwest Wyoming home to multiple large mining operations. Among these operations are five underground trona mines located approximately 50 km west of Rock Springs, Wyoming. The trona mines employ room and pillar, longwall, and solution mining methods over an area roughly 900 km2, and produce a sizable portion of the world’s soda ash (Brown 1995). Historically, in the Rock Springs mining district, several relatively large magnitude seismic events have occurred. These events are thought to have been related to mining activity and have caused notable subsidence (Case 1997). The largest event in the region recorded by seismometers, ML 5.1, has been confirmed as the 1995 Solvay Trona Mine collapse (Pechmann et al. 1995). In addition, blasting at surface coal mines near Rock Springs produces significant amounts of seismicity; approximately 50% of all daytime seismic events in the Mountain time zone from 2007 to 2009 locate near an active surface mine in this region (Astiz et al. 2014). Much of the current research related to surface subsidence and induced seismicity focuses on wastewater impoundment (Ellsworth 2013) and hydraulic fracturing. The observable seismicity in geological injection environments is widely variable and McGarr (2014) has argued that, in such environments, the maximum amount of seismic energy that can be released is proportional to the injected volumes. Like injection environments, in extraction (mining) environments seismicity is highly variable depending on many geological and operational variables (Boltz et al. 2012; Carnec and Delacourt 2000; Fritschen 2010; Iannacchione et al. 2005; Sen 2013) and does not always correlate well spatially with subsidence, a surface expression of extraction at depth."

Jan 1, 2015

By W. M. Zeng

A mixed culture of moderately thermophilic microorganisms was enriched from Acid Mine Drainage (AMD) samples collected from several chalcopyrite mines in China,which can leach copper from chalcopyrite effectively. Its tolerance to chalcopyrite was brought up to 80 g/L after being adapted to gradually increased concentrations of chalcopyrite. The effects of several leaching variables on copper recovery in Stirred Tank Reactor had been investigated. The ore contained chalcopyrite (62.2%) and galena (25.6%) as the main sulfide minerals. The results of the tests show that it is possible, operating at 8% of pulp density to attain copper extraction of 75% in 44 days. The leaching rate of chalcopyrite tends to increase with the dissolution of total iron. Microscopic counts of microorganisms in the solution tend to be higher at low pH range. Furthermore, the analyses of leached residues indicate that the passivation of this chalcopyrite is mainly due to the formation of a mass of jarosite and anglesite (about 48.3% and 21.7% in residue respectively), other than elemental sulphur layer. The bacterial community composition was analyzed by using amplified ribosomal DNA restriction analysis (ARDRA). Two moderately thermophilic bacteria species were identified as Leptospi-rillum ferriphilum and Acidithiobacillus caldus, with different proportion in the bio-pulp, 67% and 33%, respectively.

Jan 1, 2014

By Lijun Xu, Jan M. Mutmansky

"Mutmansky, J.M. and· Lijun Xu, 1989. Some observations on particulates collected in underground coal mines using diesel and non-diesel equipment. Min. Sci. Technol., 9: 207-218.The results obtained when sampling twenty underground coal mine sections, each in a different mine, are outlined. The sampling effort was oriented toward a detailed characterization of coal mine dusts and thus eight-stage Anderson Model 298 impactors were used as the primary collection instrument. This instrument allowed a fairly detailed size distribution for each of the particulates sampled. Because four of the mines used diesel outby equipment and/or diesel shuttle cars at the face, it is possible to make some comparisons of the particulate distributions in diesel versus non-diesel mines.One of the more interesting results is the pattern that exists in mines lising diesels only for outby utility haulage. Particulates in these mines seem to be consistently heavy in the fine size ranges, perhaps being of significant concern to the industry. While no definite conclusions can be drawn from the limited data, a more detailed study of particulates may provide a better picture of particulate loadings.IntroductionThe subject of particulate emiss1ons from underground diesel equipment is currently a very important topic as health concerns and regulation of diesel particulate emissions have created new environmental problems for mine operators. The amount of particulate matter originating from diesels has not been extensively measured and problems of differentiating coal and mineral dust from diesel particulates make existing data questionable.However, it is necessary to make an assessment of the problem in order to solve it. It is known that particulates from diesel engines are solid aerosols formed in the combustion process. Technically, this places the particles in the category of fumes. It is also known from tests where no mineral dust could be a factor in the measurements that about 90% of diesel particles are less than 1 µm in aerodynamic diameter [3]. To measure the diesel component of a coal/diesel particulate to measure, Johnson et al. [2] have developed procedures for utilizing laser Raman spectroscopy. The determination of diesel content in a coal/diesel mixture is difficult due to the chemical similarity of the two organic materials. However, laser Raman spectroscopy, which is often used for identification of organic materials, has potential if the Raman spectra for the two materials are different and unique. The study concluded that an accuracy of ±~% could be achieved for mixtures containing up to 55% diesel particulate. The method is relatively complex and would need further development for routine application."

Jan 1, 1990

By William G. Pariseau

Elastic-plastic finite-element simulation of cut-and-fill stoping in deep, narrow veins shows substantial quantitative agreement with field measurements of stope closure and fill pressure made at two mines in the Coeur d'Alene mining district of northern Idaho. The simulation procedure, validated by field data, was used in an analytical study of vein-wall closure and sill-pillar stress as influenced by fill modulus, rock modulus, and premining stress. Ratios of closure and pillar stress in the filled stopes to closure and pillar stress in the unfilled stopes are used as prediction indices for fill performance. In general, the support capability of fill increases dramatically as the ratio of fill modulus to rock modulus approaches 1. A significant reduction in closure .from the open stope--up to 75 percent--occurs with a relatively low-quality 10-ksi-modulus fill (rock modulus of 1,000 ksi). However, a higher quality fill is needed to achieve a substantial reduction in pillar stress from that of the open stope. A 100-ksi-modulus fill reduces pillar stress in both the 36-foot and l6-foot pillars (vein width is 10 feet) by about 50 percent relative to the open stope.

Jan 1, 1976

By Linda D. Raedeke

The main platinum-group metal (PGM) deposit in the Stillwater Complex is associated with a stratiform zone formed by magma mixing. In general, the intrusion is a large, layered body of Archean age which formed by repeated magmatic injections in- to a single, large, hypabyssal magma chamber. The Complex is broadly divided into the lower Ultramafic series of olivine ± orthopyroxene rocks (1000-2000 m thick) and the upper Banded series of predominantly plagioclase-rich rocks (24500 m thick). The latter is further divided into Lower, Middle, and Up- per Banded zones. The Ultramafic series, plus most of the Lower and Upper Banded zones formed from repeated injections of an olivine-saturated magma, the rocks accumulating from the floor upward with a crystallization order of olivine, or- thopyroxene, plagioclase, clinopyroxene. The olivine-bearing subzones of the Middle Banded zone formed predominantly from a magma which crystallized in the sequence plagioclase, olivine, clinopyroxene. Olivine-bearing subzone I, with which the PGM mineralization is associated, occurs generally -400 m above the Ultramafic series-Banded series contact. Ore grade mineralization is usually found in plagioclase or plagioclase-olivine cumulates. The platinum-group elements are associated with disseminated base-metal sulfides dominated by the assemblage, pyrrhotite-chalcopyrite-pentlandite. Olivine-bearing subzone I marks an interruption in the crystallization sequence of the Lower Banded zone, with the reappearance of cumulus olivine and an associated change of the crystallization sequence. These changes indicate the addition and mixing of a secondary magma of the same composition as that which later dominated in the formation of the Middle Banded zone. Characteristics associated with mixing include laterally discontinuous but well-developed layers, xenoliths of ultramafic rocks, and sedimentary-type structures such as slum- ping and graded layering. The influx of new magma caused sulfide saturation by one or more of several chemical changes including addition of sulfur, decrease in oxygen fugacity, decrease in FeO, or increase in SiO2. Once an immiscible sulfide liquid was formed, platinum-group elements were scavenged from the magma by the sulfide liquid and segregated.

Jan 1, 2013

By Jardine G, Woodall C

The Henty Gold Mine, located in Western lasiuania use, uuiusatise solutions to effectively manage a mining operation in an environmentally sensitive setting and has been presented with several environmental awards. Fill is required as part of the mining method to provide passive ground support, minimise rock exposure and ensure maximum recovery of the small but high-grade orebody. The use of the whole portion of leach residue in the backfill reduces the surface tailing disposal requirements. Therefore, High Density Paste Fill (HDPF) has been selected as the most appropriate fill method to meet these objectives. Additional benefits include the minimisation of excess water from fill and the subsequent need for the collection and treatment of water and slimes. There are minimal equipment requirements during placement, thereby optimising mine resources for production. The initial paste fill design was based on the Bad Grund and Ranunelsberg Mines paste fill systems of Preussag in Germany and comprised pumping filtered tailings paste some 1.2 kin uphill from the mill to the mine portal, where cement was to be added before being distributed underground. The system was designed following initial testwork that was undertaken on a bulk sample of ore mined from the scar surface Sill Zone. Subsequently, during the mining of the Zone 96 orehody, it was found that there were significant mineralogical variations in the composition of the ore mined. Following processing, the resultant Icach residue caused significant changes in the paste rheology and therefore the pump and flow characteristics. An alternative solution was implemented that involved the use of agitator trucks to transport the cemented paste to the portal. This required modifications to the fill preparation system and also the underground distribution system. Laboratory strength tests of the HDPF using actual gold plant leach residue showed low early strengths were attained with HDPF containing only filtered leach residue. Therefore, high binder addition rates or an increase in the fill cycle time would be required to allow the fill to gain sufficient strength. A considerable amount of potentially acid generating waste rock also requires underground disposal. By blending the waste rock with the HDPF, the strengths were improved and the required cement addition rate reduced by about one-half. The potentially acid funning waste rock is encapsulated in the highly alkaline cemented paste, minimising the potential for acid generation.

Jan 1, 1998

By K. A. Johnson

Marshall and Bird have published the results of a cooperative investigation by the Bureau of Mines in which they developed a procedure for measuring the agglutinating value of coal.4 As stated in their paper, the procedure outlined was suggested by the early worn of Richters5 and Campredon,6 whose procedures were hurriedly modified to meet the need of an investigation then in progress. Since the publicatien of that paper, further work has been done in an attempt to show how the variables involved affect the concordance of the results, in order that such results may be obtained in different laboratories. Briefly, Marshall and Bird's method for determining the agglutinating value of coal consists in carbonizing an intimate mixture of 10 parts by weight of sand and 1 part by weight of coal in a porcelain crucible at a uniform temperature of 950° C. in a, vertical, cylindrical, electrically-heated furnace. After carbonization, the resultant buttons are crushed in a testing machine and the breaking strengths recorded in grams. The agglutinating value reported is the average breaking strength of 10 buttons. The coal for the test is prepared by crushing to pass a 100-mesh screen. The sand used as a diluent is sized between 40 and 50 mesh sieves with openings of 0.381 icon and 0.279 millimeters, respectively.

Jan 1, 1930

By W. Hitchcock

To enable the analysis of stability for a mine feasibility study a variety of geotechnical engineering parameters need to be obtained. At the early stage of a project it is usual for those responsible for the study to require a wide spatial distribution of RC holes in order to define a resource at the lowest possible cost. By the time a geotechnical study has commenced drilling priorities have usually switched to improving the definition of a resource, by drilling with diamond coring methods in the central area of the main orebody. The usual timing for geotechnical data collection is therefore after a wide distribution of holes have been drilled but which contain little geotechnical information. Conventional methods employed usually involve estimation methods, including book values and examination of disturbed core, or expensive additional drilling. With downhole geophysical methods we can economically take advantage of existing holes to obtain continuous values for density, defect orientation and ranking, elastic modulus values, unconfined compressive strength estimates and fracture frequency. This paper presents the results of a geophysical study and discusses the advantages and potential pitfalls of the method as compared to conventional methods of data collection.

Jan 1, 1999

By M. Rehor

The importance of brown coal as a raw material is currently given by growing energy needs of Czech Republic. More than 70% of mined brown coal comes from North Bohemian Basin these days. Mining of brown coal is run in four mining locations. They are geologically different and the parameters of mining coal are quite different too. This requires a little bit different methodology of both extraction and reclamation. Methods of reclamation works in the region are given mainly by the characteristics of overburden rocks appearing in the upper horizon of recuperated localities. The difficulties of the North Bohemian mine dumps reclamation works are caused by extremely unfavourable properties of rocks poured down to the majority of mine dumps. These are mainly rocks of the overlaying strata and the rocks strata of brown coal bed. Main materials poured down to the mine dumps are sands, clayey sands and kaolin ? illitic clays. Admixtures in filled rocks consist of organic (coal) mass, siderite and pyrite. These rocks are mechanically instable with respect to the wind and water erosion and during weathering they are getting unfavourable, acid (phytotoxic) nature, due to the influence of SO3 and Al ions. External and internal dumps of open pit mines are significant part of the North ? Bohemian landscape sustained by excavation. Their as fast as possible preparation and gradual integration into ecosystem of the area is interest of both citizens of region and mining companies. The paper briefly summarizes the methodology of restoration of the largest dumps of the North Bohemian Brown Coal Basin and the results of analyses and evaluation of samples taken on restored localities Rado-vesice dump, Strimice dump, Ru?odol dum pand internal dump of Bilina mine. An example of modern non-tradicional restoration methods is the restoration of internal dump of Bilina mine (application of power plant stabilizer). According to observations and results of sample analyses the methods of restoration were selected to limit the erosion influence, adjust the chemical and physical composition of surface of Radovesice and Strimice dumps. The application of marlites and bentonite prevent the unfavourable weathering processes on dump surface. Compensation of Quaternary sediments was artifically formed here. The need of marlite ploughing in, application of organical substrates and vegetation preparation was proved on Radovesice dump. The conception of landscape reclamation of the largest dumps after finishing of mining, methodology of technical reclamation and well considered using of fertilizable soils are main results presented in this article.

Jan 1, 2014

"Developing markets for western metallurgical coal have continued to stimulate considerable exploration activity in the Rocky Mountain foothills and to influence major segments of a wide-ranging carbonization R&D pro-gram. Adjunct studies have included expanded petrographie investigations.Coal preparation has• been principally directed toward utilization of prepared small coal and was, like much of the year's combustion work, strongly influenced by concern over atmospheric pollution. Particular attention has been given to desulphurization and to the suppression of pollutants in combustion systems.In the area of non-fuel utilization of coal, interest has centered on plant nutrients and on a series of coal-based carbons which, inter alia, possess utility as filtration media.Other projects included the development of improved sampling and analytical methods, investigations into the effect of storage on coal proper-ties and R&D in solids pipelining. In addition, a significant volume of basic 'uncommitted' research has been maintained."

Jan 1, 1968

By B Olsson, R Norman, M Volz

Australia has seen unprecedented demand for coal exports in the last ten years and this demand is set to expand further still according to many analysts. This rapid increase in demand has placed pressure on multi-user coal chains to guarantee the capability to meet the required demand, in terms of both current operations and capacity expansion.The projects required to deliver these forecast tonnages take place in an increasingly complex commercial and technical environment. These challenges include brownfield and greenfield projects, multiple rail and terminal service providers as well as a myriad of mine operators, all needing to operate in an increasingly integrated manner to get the most out of expensive shared assets.Increasing complexity and integration drives the need for more holistic and sophisticated analysis tools. The capacity of coal chain subsystems, such as mine, rail and port, can no longer be determined effectively in isolation. Understanding the nature of the interactions between these subsystems and the resultant capacity of the integrated system is the key to maximising value. TSG advocates the use of a total integrated system approach to understand the behaviour and performance of complex coal chains.Recently, TSG has worked in conjunction with the Integrated Logistics Company and a number of stakeholders in the Dalrymple Bay Coal Chain to deliver the first independent system master plan. This master plan has provided a quantitative and rational assessment of coal chain capacity in its current state and a prediction of its capacity once a pipeline of committed capacity improvements is in place. It is underpinned by a highly detailed discrete-event simulation model of the complete coal chain as an integrated system, including mine load-outs, rail, terminal and port operations.This paper provides an overview of the study and describes the differences between subsystem and total integrated system model performance.

Sep 26, 2011

By S. K. Kawatra, H. J. Haselhuhn

"Thickening is used during two primary mineral processing operations: water removal and desliming. During water removal, the pulp density is increased through the injection of flocculants. These flocs settle and create a dense pulp while clarified water is removed through the overflow. During desliming, fine particles are removed through the overflow. Desliming can also be used as a mineral separation process known as selective flocculation-dispersion, where valuable minerals are flocculated and gangue minerals remain dispersed and exit through the overflow.There are many ways to analyze thickener performance on a laboratory scale, but these analyses often do not correlate well with full-scale performance. Some pilot-scale systems have been designed using a semicontinuous approach, but the amount of material required to perform their tests can make semicontinuous pilot thickeners impractical for most applications. This paper focuses on the design and optimization of a continuous pilot-scale deslime thickener that requires minimal material to operate. The design, optimization strategy, and an example study of reagent selection are demonstrated. IntroductionMany laboratory methods have been employed to size and optimize thickener performance. The most common of these include the Coe and Clevenger method and methods derived from the Kynch theory of sedimentation. The Coe and Clevenger method was developed in 1916 and was proven for slurries that do not require flocculation to settle. This method proposed that the settling rate of the pulp is only a function of the solids concentration. It is executed by creating slurries of several different concentrations of solids and performing bench-scale settling tests in graduated cylinders. For each concentration, a thickener unit area can be determined using the following equation (Coe and Clevenger, 1916; Laros, Slottee and Baczek, 2002):"

Jan 1, 2017

By G. R. Hopkins

According to reports received by the United States Bureau of Mines, Department of Commerce, as of January 1, 1929, there were 2,205 cracking units completed or being built in the United States, with a total daily charging capacity of 1,476,874 barrels. A similar survey of a year ago showed 2,334 units of 1,288,000 barrels total capacity. This indicates that despite a decrease in. number of units, there was a material increase in capacity. The year 1928 was, in general, an important one for the cracking branch of the industry. Gasoline consumption reached record levels, prices were higher than in 1927, and it is probable that in the late months of the year the cracking plants were operating very close to capacity.

Jan 1, 1929

By J. A. Organiscak

The Bureau of Mines recently investigated dust generation and methane liberation during half-and full-web cutting at a double-drum shearer longwall face. This study was conducted to ascertain the health and safety aspects of wider web shearing at longwalls. Results from these underground tests showed that deeper web cutting reduced dust generation and methane liberation per ton of coal mined, while significantly improving shearer production rates. When cutting with the airflow (head-to-tail cut pass) full-web cutting decreased dust generation per ton by 16 pct at the shearer and 6 pct at the tailgate, with an increase in shearer production rate of 72 pct. Methane liberation per short ton also deere~sed by 36 pet at the shearer and 22 pct at the tailgate. Full-web cutting against the airflow (tail-to-head cut pass) decreased dust generation per ton by 41 pct at the shearer and 37 pct at the tail-gate over half-web cutting, with an increase in shearer production rate of 61 pct. Methane liberation per ton also decreased by 35 pct at the shearer and 41 pct at the tailgate. These improvements for full-web cutting are a reflection of improved cutting efficiency (less dust and methane produced from cutting) and less new face area exposed per ton of coal mined (less methane liberated from face per short ton of coal mined).

Jan 1, 1988

By R. V. Kumar, C. Schwandt, S. Subramanian, S. Sampath, S. Vimalnath

Waste waters and industrial effluents containing toxic heavy metals such as Pb, Hg, As and Cr, beyond permissible limits (0.1 ppm, 0.01 ppm, 0.02 ppm and 0.05 ppm, respectively) (WHO, 2011), pose serious threats to the ecosystem, when discharged into the environment. It thus becomes imperative to monitor the concentration of the toxic heavy metals and treat them before discharging. In this study with the above objective in mind, a microbial sensor has been developed using P. aeruginosa cells drop coated onto a carbon paste electrode (CPE) for the detection of Pb(II) ions in aqueous solutions. Detailed biosorption experiments confirmed that complete bioremoval of lead could be achieved using P. aeruginosa cells under optimum conditions of pH and biomass loading. For the electro-analytical determination, the Pb(II) ions were initially preconcentrated on the P. aeruginosa modified CPE, reduced and then anodically detected with oxidation of Pb0 using differential pulse anodic stripping voltammetry (DPASV) technique. All the experiments were carried out in the presence of 0.1 M sodium acetate buffer and KNO3 as background electrolyte. The parameters namely pH, scan rate, biomass loading, deposition potential, deposition time and concentration of Pb(II) ions were optimized for the biomass modified CPE, to obtain maximum voltammetric response. Under the optimized conditions of pH 5.6, scan rate of 0.008 V/s, biomass content of 1.7–1.8×109 cells/mL, deposition potential of –1.2 V, and deposition time of 500 s, the developed microbial sensor showed a linear response for the peak current between 0.5×10-5 M and 1×10-8 M of Pb(II) ions with the R2 value of 0.9979. The lowest limit of detection (LLOD) was determined as 2.4×10-7M of Pb(II) ions (0.05 ppm). The redox mechanisms of Pb(II) ions on the P. aeruginosa modified CPE surface are discussed.

Jan 1, 2016

By P. Dinham, G. C. Summerton, N. McCulloch, S. Dowling, D. C. Craig

"Development of a process for the treatment of a nickel copper matte rich in the minerals heazlewoodite, chalcocite and bornite has demonstrated significant base metal recoveries and metal separation efficiencies. The determination of chemical and mineralogical changes occurring in the individual leaching stages in laboratory experiments has enabled a better understanding of the complex leaching chemistry. The chemistry and mineralogy of the piloting and laboratory processes are discussed.INTRODUCTIONThe nickel-copper sulfide ores of the South African Bushveld Complex are among the most important Platinum Group Metal (PGM) bearing ores, and contain the world’s largest reserves of platinum. The treatment used in the recovery of PGMs from these ores includes three types of processes, namely ore concentration using physical techniques such as flotation and gravity separation, concentration by pyrometallurgical means, hydrometallurgical extraction of the base metals followed by the PGMs. Following milling of the ore, flotation involves the separation of high value minerals from gangue by taking advantage of the differences in their hydrophobicity. These differences are generally maximized through the use of a surfactant or wetting agent. Concentrates are then thermally treated and melted which brings about physical and chemical changes that enable the recovery of base metals and PGMs. The main aim of the smelting and converting process is to separate and eliminate the valuable metals from the bulk of the unwanted gangue and essentially all of the iron and to concentrate the metal VALUES (into a high grade converter matte. The matte can be further enriched by magnetic separation, producing a PGM-rich magnetic fraction and a base metal-rich non-magnetic fraction. The magnetic fraction is treated by hydrometallurgical processes to produce a PGM concentrate which is further refined to separate and purify the individual metals. The non-magnetic fraction is treated to produce marketable metal VALUES (such as nickel, copper, cobalt and to a lesser extent PGMs. The principal objective of any hydrometallurgical extractive process is to leach the desired elements selectively into an aqueous phase so as to separate them from the bulk of the material. (Crundwell, Moats, Ramachandran, Robinson and Davenport, 2011; Hundermark, Mncwango, de Villiers and Nelson, 2011)."

Jan 1, 2012

By A. M. Strachan

The application of submerged electric arc furnace smelting techniques to tin concentrates at the Capper Pass tin smelter in England is discussed. Some experimental data from earlier small scale 50 KVA electric smelting testwork on various low and medium grade tin concentrates is presented. Design considerations for the construction of a 3 MVA electric furnace to treat tin concentrates from the East Kemptville mine in Canada are considered, together with necessary precautions peculiar to the construction of a high grade smelter in close proximity to an existing low grade, complex non-ferrous metal smelting operation<. Slag composition modifications to optimise operational smelting conditions for various concentrates treated are discussed, together with refractory selection. The effect of concentrate impurity levels on the permissible degree of recycle to produce a satisfactory metal product is highlighted.

Jan 1, 1990

By R D. Fleming

A single-cylinder research engine was operated on pure hydrocarbons and simple (two-component) mixtures of pure hydrocarbons to study the effect of fuel composition on exhaust emissions from a spark-ignition engine. Used as fuels were three pure hydrocarbons that represented the primary hydrocarbon types present in commercial motor fuels: A paraffin (2,2,4-trimethylpentane), an olefin (2,4,4-trimethylpentene-2), and an aromatic (meta-xylene). The engine was operated at the same equivalence ratio for all of the fuels used in the experiment. Exhaust gas samples were collected and quantitatively analyzed for carbon monoxide, carbon dioxide, hydrogen, nitrogen oxides, aldehydes, and hydrocarbons. Exhaust hydrocarbons were separated and quantitatively measured with a chromatographic system employing a flame-ionization detector. Unknown hydrocarbons and oxygenated materials in the exhaust were identified with a Time-of-Flight mass spectrometer coupled to a chromatographic system. The results of the exhaust gas analyses showed that ethylbenzene, l-methyl-3-ethylbenzene, and l-methyl-3-vinylbenzene were more abundant in the exhausts from either 2,2,4-trimethylpentane--m-xylene or 2,4,4-trimethylpentene-2--m-xylene fuel mixtures than in exhaust produced from m-xylene. Also, the pure 2,4,4-trimethylpentene-2 fuel produced smaller amounts of C2 to C7 olefins in the exhaust than that produced by the pure 2,2,4-trimethylpentane fuel. The exhaust from pure m-xylene fuel contained aromatic hydrocarbons of higher molecular weight than the parent fuel. The amount of total hydrocarbon (moles of exhaust hydrocarbon per mole of fuel used) in the exhaust from the three pure fuels decreased in the following order: 2,2,4-trimethylpentane > 2,4,4-trimethylpentene-2 > m-xylene. The hydrocarbon mole-fractions of unreacted fuel in the exhausts produced from each of the pure fuels were 0.20 for 2,2,4-trimethylpentane, 0.13 for 2,4,4-trimethylpentene-2, and 0.66 for m-xylene.

Jan 1, 1970