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By M. Pötsch, W. Schubert

"The kinematic analysis of rock blocks is one part of a block stability assessment. It provides information about a block’s movability, i.e. if a block can detach from the adjacent rock mass and move towards the free space. This paper introduces an analytical method for the analysis of pure rotations of arbitrary finite polyhedral blocks. It enables the engineer to judge a block’s rotatability about a corner or an edge. The method is presented using a graphical and computational method. The application of the method is illustrated with an example. INTRODUCTIONThe kinematic analysis of rock blocks deals with the determination of the movability of blocks. Established methods typically cover: (a) translational motion (John 1968, Markland 1972, Londe et al. 1969, 1970, Goodman & Shi 1985, Warburton 1981) and (b) the specific rotational cases Toppling (Goodman & Bray 1977) and Slumping (Kieffer 1998). Mauldon & Goodman (1990, 1996) and Tonon (1998) introduced rotational kinematic analyses for three-joint pyramids and tetrahedral blocks extending Goodman & Shi’s block theory.All mentioned methods are subject to assumptions that limit the applicability to engineering problems. For example, the kinematic test of daylighting joints or intersections inherently assumes a finite block, which only can be proved by the finiteness theorem (Goodman & Shi 1985). Daylighting of an intersection or plane is not a sufficient condition for removability. Goodman & Shi’s and Warburton’s methods are limited to translational block motion. The methods for block rotations so far address tetrahedral blocks only. They also address only pure rotational modes and neglect the general motion of a rigid body. This paper introduces an analytical method for the analysis of the kinematic rotatability of finite rock blocks. It extends Mauldon's and Tonon's theory of rotatability of tetrahedra to arbitrary polyhedral blocks. A graphical method using the stereographic projection and a computational method are presented."

Jan 1, 2015

By K. J. Aglias, M. Jeffery, J. V. Simmons, J. A. Johnston, S. G. Fityus

"Shales and mudrocks undergo weathering in the near-surface geological environment, and degradation when directly exposed at the surface. Despite having superficially similar appearances, many shales have very different degradation behaviours. For example, some shales break down readily upon exposure whilst others remain more or less intact. Further, for those shales which break down, the style of degradation can vary greatly. A phenomenon is described where fresh shale blocks that are exposed at the surface undergo rapid breakdown to a fragmented texture which then persists for relatively long times, without further breakdown to finer soil particles. This is illustrated for some coal mine waste rocks. Furthermore, this metastable fragmented texture seems to be particular to each particular type of shale. The paper presents a conceptual model for this physical breakdown of shales which accounts for the differences in fragmental texture that are observed. The importance of several factors including strength, permeability and expansive clay content are identified for their contribution to the degradation behaviour of different shales.INTRODUCTIONShales and MudrocksThe term shale is applied widely to a class of mudrocks having a range of distinctive but gradational appearances and mechanical behaviours. Mudrocks are sedimentary rocks primarily composed of silt and clay sized particles (Tucker 1982). Mudrocks form in low to very low energy environments such as flood plains, lakes and deltaic environments, where the finest detrital particles are able to settle out of suspension (Reeves et al., 2006; Stow, 2005; Tucker, 2001).Unlike coarser siliciclastic sedimentary rocks, mudrocks do not present with a wide variety of sedimentary structures and textures. The most common texture is a preferred orientation of clays and micas parallel to the bedding plane. This textural component is related to the property of fissility or the ability for such textured mudrocks to split along smooth planes that are parallel to the bedding. Another common structure is lamination, formed by variations of grain sizes and types during deposition, Massive texture describes the situation where no sedimentary structures or textures are apparent (Boggs Jr., 2009; Tucker, 2001). The term shale varies between sources and contexts, with Reeves et al. (2006) stating that a shale is a fissile mudrock, where “fissility is a property that has developed at a certain stage of weathering”."

Jan 1, 2015

By Laxman M. Amaratunga, David N. Yaschyshyn

"In the mining industry several types of fills are used for backfill operations. They are broadly categorized into three basic types: rock fill, hydraulic/slurry fill, and paste fill. Recently, paste fill has become the popular alternative for backfilling because of its many environmental and operational advantages including its ability to use total tailings, both fine and coarse fractions.Amaratunga and Annor (1989) first presented the concept of agglomeration of fine tailings, which are otherwise excluded from backfilling, for utilization in backfill as a readily available supplementary fill material. Previous experimental work investigated the use of agglomerated fine gold mill tailings in low density slurry fills (60 -70% pulp density), consisting of varying agglomerate and tailings compositions.This paper presents the ongoing research into utilizing these agglomerates in a high density paste fill (70 -85% pulp density). Various binder dosages, curing period and combinations of pellet to tailings ratios were studied. Slump of the raw fill and compressive strength of the cured fill were examined. Results from the above study indicate that agglomerated tailings paste fill (ATPF) has superior strength characteristics when compared to total tailings paste fills.IntroductionThe Canadian mining industry produces more than 500 million tonnes of tailings and waste rock annually. These tailings consist of a coarse fraction and a fine fraction and can be either reactive (acid generating) or non-reactive. Most mining operations utilize the coarse fraction for backfilling while the fines have been traditionally disposed of in surface tailings ponds. Recently, paste fill has been developed which uses a fraction of the fine tailings (10 - 30% w/w of >45 µ,m) in the fill. This development allows a mining company to use a portion of the fines for backfill, but still requires surface impoundment of the unused portion of fine tailings. Reactive tailings have the added problem of generating acid after being oxidized in the presence of air and water. Treating acid mine drainage (AMD) seepage from these ponds has proven to be a costly environmental problem and long term liabilty.One practical method to reduce the environmental impacts associated with the tailings pond and to modify the physical and chemical properties of the fine mill tailings so that they can be utilized and disposed of in an environmentally safe manner through surface or underground applications is through agglomeration using the Cold-Bond Tailings Agglomeration technology (CBTA). Amaratunga and Annor (1989) first presented the concept of agglomeration of fine tailings for use as coarse aggregates for underground backfill, gravel or surface covering material. CBT A reduces the necessity of impounding tailings on surface while providing a suitable coarse aggregate resource material for practical use. Although the CBT A technology has been mainly limited to pelletization agglomeration alone, other forms of agglomeration like pressure agglomeration which include the techniques of briquetting and extrusion have also proven successful (Amaratunga, 1995)."

Jan 1, 1996

By Jean-Francois Magnan

"The old conventional process to produce lithium raw material dates from 1954 (CA patent #504477A). This process produces low purity lithium carbonate (Li2CO3) only. To obtain battery-grade carbonate, another polishing process is needed. To further obtain lithium hydroxide, another chemical conversion process is needed. That is why historically, the value of lithium hydroxide has always been higher than that of the lithium carbonate precursor. With the old conventional process, the low quality lithium carbonate is precipitated from a lithium sulfate solution (Li2SO4) by adding soda ash (sodium carbonate and its impurities). The resulting reaction produces significant quantities of sodium sulfate (salt cake) as a by-product with amounts larger than the impure Li2CO3 recovered with part of the soda impurities. When this conventional process was invented, the salt cake by-product was not an issue: it was discarded in a river near the plant. This practice cannot be done today in North America. While looking to find a solution for salt cake, electrolytic salt splitting of Na2SO4 into NaOH and dilute sulfuric acid appears as a technically feasible solution to get a rid of the salt cake. However, the sodium sulfate salt splitting process has difficulties to economically compete with the chlor-alkali process, which produces millions of tons of NaOH from sodium chloride (NaCl) every year.In contrast, the process developed by Nemaska to directly produce LiOH by Li2SO4 salt splitting not only solves the environmental problems related to the conventional process to produce lithium carbonate raw material, it also produces very high purity lithium hydroxide monohydrate directly at very competitive OPEX cost in comparison with industry peers (Figure 1). It also drastically reduces the amount of reagent and the direct greenhouse gas emissions."

Jan 1, 2016

By P. Erskine

"Hyperaccumulator plants can be utilized as ‘metal crops’ in agromining operations. This emerging technology produces ‘bio-ore’ by growing ‘metal crops’ on sub-economic ore materials, such as natural ultramafic soils. In a typical application plant material is periodically harvested, followed by air-drying and incineration to produce the bio-ore intermediate. The bio-ore is of very high grade (>15 wt. % nickel), and of high purity, and may be processed into a number of different products (including nickel metal, nickelbased catalysts and pure nickel salts). Current research efforts from our team focus on Mediterranean climate field trials (Albania, Spain) and tropical climate field trials (Malaysia, Indonesia). Field-scale demonstrations are required to provide evidence of real-life performance and of economic viability. If the trials are successful, agromining may in the near future support local livelihoods with income opportunities as an alternative type of agriculture: to farm nickel.INTRODUCTION AND BACKGROUNDHyperaccumulators, plants with the exceptional ability to uptake and concentrate trace elements in their shoots, can be utilized as ‘metal crops’ in agromining operations (Van der Ent et al., 2013a; Chaney et al., 1998; 2007; Baker et al., 2010). Agromining produces ‘bio-ore’ from harvested ‘metal crops’ grown on unconventional resources such as natural ultramafic soils (Van der Ent et al., 2015a). The bio-ore is a high purity and very high-grade (>15 wt. % nickel) product intermediate that may be turned into a range of different nickel products (nickel metal, nickel-based catalysts and pure nickel salts). The potential for agromining is greatest in tropical regions (Asia-Pacific Region: Indonesia, Malaysia, Philippines, Papua New Guinea and New Caledonia) where very large expanses of ultramafic soils exist (Van der Ent et al., 2013b). Agromine operations may replace existing marginal agriculture on poor ultramafic soils, for example oil palm plantations that require high fertilizer inputs to be profitable, or take place under a cocropping regime. The ability of ‘metal crops’ to achieve high nickel concentrations in biomass (and hence in harvested bio-ore) from soils with just <0.5 wt. % nickel, makes it possible to access non-conventional resources, not accessible by traditional mining techniques. For example, agromining could be implemented both on the large ‘halo’ around the mine leases, and as part of the progressive rehabilitation process after conventional resource extraction. As with all methods for resource extraction, agromining will be finite due to the diminishing concentrations of nickel in the zone accessible by plant roots (Chaney et al., 2014). Nevertheless, considering soil materials with 0.2 wt. % nickel and ‘metal crops’ with a yield of 100 kg nickel ha-1 the agromining venture may be sustainable for decades (Van der Ent et al., 2015a)."

Jan 1, 2016

By I. Ueda, S. Ishikawa, T. Nagata

“O-SR process” in which the S-Furnace of the Mitsubishi process is followed by existing reverberatory furnaces (RFs) and Peirce Smith (PS) converters has been operated since December 2007. The S-Furnace smelts copper concentrates to produce molten matte containing 58-62%Cu which is then settled in the RFs and converted to blister copper in the PS converters. The SO2 gas generated from the S-Furnace and PS converters is converted to sulfuric acid in the acid plants. In addition to the smelting copper concentrates, the O-SR process has advantages in terms of recycling various waste/secondary materials. Automotive Shredder Residue (ASR) has been treated in the RF to reduce fossil-fuel consumption in RFs, and to recover various metals included in ASR as well, since 1993. Electronic circuit boards (E-scrap) has also been processed in order to recover not only copper but also rare resources such as gold, silver and PGMs since 2013. Strategic modifications have enabled expansion of the processing volume of E-scrap. Enhancing recycling of wastes and scraps from urban mines while reducing the consumption of natural resources in the “O-SR” process will be demonstrated and discussed in the present paper. INTRODUCTION Onahama smelter and refinery has been operating as a custom smelter since 1965. Smelting facilities were subsequently expanded to two green-charged RF furnaces and five PS converters in 1973. Since RF is a conventional old-fashioned smelting furnace that necessarily consumes a huge amount of fuel to smelt copper concentrates, saving fuel cost has been an important objective. In early 1980’s the fuel was changed from bunker oil to pulverized coal, while utilizing the combustion heat of waste tires. Furthermore, treatment of combustible waste such as shredder residue (SR) was initiated in order to save fossil fuel for smelting concentrates in the RFs. Since enhancing of the treatment of SR requires a reduction in concentrate smelted in the RFs, most concentrates were dried and injected through tuyeres into the PS.converters. These modifications enabled to reduce the amount of the pulverized coal combustion and to increase SR treatment in the RFs. SR treatment capacity has increased to 12,000mt/month because the SR market has grown after the enforcement of the Vehicles Recycling Law. Such business environment has been attributed to establish the thermal-materials recycling system of SR in which the RFs have changed their role from copper concentrates smelting furnaces to waste materials combustion furnaces.

Jan 1, 2019

By Liu Yulin, Zhao Yi, Tan Qi, Liu Lei

"Hydrotalcite is one kind of layered double hydroxides, and has special crystal chemical characteristics. Due to its good thermal stability, hydrotalcite used as the PVC heat stablier has attracted scientists’ attention. In this study, nano-hydrotalcite was synthesized by the method of mechanochemistry/crystallization, using brucite, Al(OH)3 and Na2CO3 as raw materials, and added into PVC to investigate the effect of hydrotalcite on thermal stability of composites. The synthesis mechanism was suggested by virtue of XRD, FE-SEM, FT-IR. It has been indicated that at the first of dry milling process, the parical sizes of brucite and Al(OH)3 decrease, while specific surface areas of them increase by the action of mechanical force, until produced amorphous particles. In the process of wet milling, metal ions in the amorphous body, which has high surface energy, can easily react with H2O, and produce the precursor of Mg6Al2(OH)18•4.5H2O, which has the same crystal structure as hydrotalcite. Under the hydrothermal condition, anions of OH- in the interlamination of precursor are exchanged by CO32- in the solution and nano-hydrotalcite is generated at last. The thermal stability was characterized by Congo red method. The results have revealed that hydrotalcite is one kind of long-term heat stabilizer, and residual stability time increase with the rise of added hydrotalcite amounts.INTRODUCTIONHydrotalcite, one kind of anionic clays, has been attracted a great interest for researchers because of their unexpected physical and chemical properties. The general formula is Mg6Al2(OH)16CO3·4H2O, where Mg2+ and Al3+ occupy octahedral positions in the brucite-like layers, and CO32- is an interlayer anion (Hoyo, 2007). Hydrotalcite is widely used in the fields of chemical engineering, materials engineering, environmental protection, medicine, and so forth, owing to its unique capability of adsorbability, ion exchange and thermal stability (Rozov, Berner, & Taviot-Gueho, 2010; Iwasaki, Yoshii, & Nakamura, 2012; Ay, Zümreoglu-Karan, & Temel, 2011; Cavani, Trifiro, & Vaccari, 1991; Li & Duan, 2005; Lin, Wang, & Evans, 2006). As a result, the study on synthesis and application of hydrotalcite has received considerable attentions."

Jan 1, 2016

By Bahri Öteyaka, Ali Uçar, Oktay Sahbaz

"A Jet Diffuser Flotation Column (JDFC) is a newcomer flotation device whose operation principles similar with Jameson cell but it has an essential change in downcomer. By taking into account the hydrodynamic and fluid mechanic principles (Sahbaz et al. 2013) downcomer was changed as a diffuser, therefore turbulence at the end of the downcomer was reduced to provide better aggregate stability and homogenous dissipation of the bubbles in the separation tank. Thus the performance increase has been aimed for the coarse particles.According to theoretical results, obtained by the formula of Oteyaka (1993) showing the relationship between velocity gradient and maximum floatable size for the various contact angles, the d50 of quartz flotation of JFDC is about 240 µm and 310 µm for the contact angle of 50° and 60°, respectively. This result was verified by the experiments. According to the experimental results; d50 which was accepted the maximum floatable particle size of quartz flotation of JFDC was about 256 µm and 300 µm for the contact angle of 50° and 60°, respectively.INTRODUCTIONFlotation is a kinetic process used for separation of hydrophobic particles from hydrophilic particles. There are many different parameters affects the success of the flotation and particle size is one of them. While the flotation is very efficient for intermediate size, the efficiency of the process starts to decrease for both fine and coarse sizes (Trahar, 1981; Muganda et al., 2011). Therefore; researchers have tried to find a solution for the efficiency decrease in fine and coarse sizes by modifying the chemical condition and designing the new devices. For example, Jameson cell is a unique device for the fine particle flotation due to the suitable design and fine bubble producing (Jameson, 1988; Evans et al., 1995; Sahbaz, 2010). Because of this success operation the Jameson cell is applied more than 200 flotation plants in worldwide. On the contrary, the efficiency of the cell decreases for coarse particle flotation due to the turbulence occurred in the separation tank (Sahbaz, 2010; Cowburn et al., 2007). That’s why, new flotation device was designed in loboratory scale by Sahbaz, Oteyaka and Ucar in 2010s and it has been called as Jet Diffuser Flotation Column (JDFC) recently."

Jan 1, 2016

By David Minson

On many occasions, operators have seen that high density and paste thickener performance does not meet the initial design expectations, and the installed equipment produces lower than expected thickener underflow solids content. This lower-density tailings slurry leads to more water and lower beaching angles being seen at the tailings storage facility (TSF). This not only reduces storage capacity, but also increases the risks of non-compliance with environmental permit constraints. Reasons for the shortfall in performance can be many, but perhaps the main problem is inadequate understanding of the critical components of thickener design and operation, with too much reliance placed on standardised design terminology; such as tph/m2. This paper discusses additional factors that influence high-density thickener operation and presents test work that defines “Dynamic Slurry Fluidity”, “Bed Compaction Rates”, and “Natural Slump Angles” for these high yield stress/viscosity slurries. Finally, the paper uses this data to define thickener geometry, drive torque, floor slope(s), rake blade configuration and how this can be used to provide engineers with more tools for in depth evaluation of a High-Density thickener design. INTRODUCTION Generally copper mines are high tonnage operations, with copper flotation concentrators producing high volumes of tailings slurries of milled solids and water. As a result, Tailings Storage Facilities (TSF) become very large and this, along with potential scarcity of water, favours a design that maximises storage space. In theory, the use of filtration equipment that achieves immediate water recovery, high TSF in-situ densities and high stacking angles are preferred for this duty. However, large tailings filter units are uncommon, and have high operating and capital costs that favour the use of thickeners. The use of high-density thickeners to produce a thick or near-paste like slurry with high un- sheared yield stress values above 100 Pascals, is becoming more common. The higher thickener underflow is required to not only maximise water recirculation within the mill, but to also increase beaching angles, maximise tailings storage capacity and minimise evaporation losses arising from large areas of superficial water. However, the reliability of this equipment is also under scrutiny and there is perhaps a need to better define these designs.

Jan 1, 2019

By S. Heusermann, S. Fahland, J. Behlau, A. Schäfers, J. Hammer

In the course of the deep subsurface use, the Federal Institute for Geosciences and Natural Resources has been carrying out extensive geological and geomechanical research and practical project work on domal salt structures, to prove their suitability e.g. for the disposal of radioactive wastes. Recent work on disposal sites has been taking into account the 3-D geological and geomechanical modelling of the underground structures. The geological models are generated using the special-construction openGEOTM code to improve the visualisation and interpretation of the geological data basis, e.g. borehole, mine, and geophysical data. For the geomechanical analysis of underground structures the JIFE finite-element tool has being developed to analyze large 3-D structures and to consider coupled THMC processes. The results of finite-element calculations, i.e. stresses, strains, displacements, and dilatant zones, are basic values for the evaluation of the stability of the structures and the long-term integrity of the geological barrier. As an example, the results of geological and geomechanical investigations of the Morsleben repository are presented including three-dimensional modelling of the entire geological structure of the central part of the mine as well as three-dimensional geomechanical model calculations to provide the necessary results for a long-term safety prediction.

Jan 1, 2015

By J. Dupre, A. Gontcharov, H. Pepin

Produced by the conventional TIG welding CMSX-4 welds had been studied. It was demostrated that microstructure of welds depended on filler materials, welding parameters and joint design. Epitaxial solidification of CMSX-4 clad deposits produced a directionally solidified structure while welding with the similar filler material. Defects free clad welds were obtained by TIG welding without preheating using similar and dissimilar filler materials.

Jan 1, 2006

By A. Zarei-Hanzaki, O. Golmahalleh, S. M. H. Hosseini, H. Azizi-Alizamini

The main importance of acicular ferrite microstructures arises from their desired combination of mechanical properties in comparison with the bainite and ferrite-pearlite microstructures. Several factors affect the microstructural transition from bainite microstructure into the acicular ferrite one. As is well established any factor corrupting the prior austenitc grain boundaries nucleation potential, such as the thin layer of allotriomorph ferrite and the austenitc deformation inhomogenities may promote the acicular ferrite formation instead of bainite. Accordingly, this study deals with the effects of the aforementioned features on the acicular ferrite formation in low carbon microalloyed steel. The results indicate that the formation of strain-induced ferrite at the prior austenite grain boundaries accompanied by deformation inhomogenities in the austenite grains change the effectiveness of allotriomorph ferrite on acicular ferrite formation from active to inert one.

Jan 1, 2004

By C. Blawert

In spite of various corrosion studies on HPDC AZ91, there is no clear indication which microstructure gives the best corrosion performance. The skin with its fine microstructure is sometimes reported to have the best corrosion resistance, but there is no clear definition of the skin. If the skin is the outermost part of the casting and nothing is removed from it, then it is contaminated and the corrosion resistance is low. If the outermost skin is removed (about 25 µm) then a better corrosion resistance can be obtained. However this does not automatically mean that there is no other region in the bulk of the casting which could have a similar or even better corrosion resistance. Indeed, the corrosion measurements including potentiodynamic polarization and long term electrochemical impedance spectroscopy (EIS) revealed a lower corrosion resistance of the original as-cast skin about 100 pm thick. The thickness of this region is more or less independent from the thickness of the casting section. The surface region is free from any dendritic grain growth which influences the amount and distribution of the 13-phase and therefore the distribution of the most important alloying element Al. This could explain the different corrosion behavior. Further reason can be found in the enrichment of some impurities such as Fe in the near surface.

Jan 1, 2006

By Frank Ebbutt

Introduction The property of the Britannia Mining and Smelting Company, Limited, is situated on the east side of Howe sound, about six miles from its head. It is roughly thirty miles by water from Vancouver, one of the important ports of the Pacific and the industrial and financial centre of British Columbia. Howe sound is navigable for ocean-going vessels and Britannia Beach is a daily port of call for the commodious boats of the Union Steam-ship Company, sailing from Vancouver. Few mines are so ideally situated or have so many or varied natural advantages. Copper was first found on Britannia mountain in 1888, by Forbes, but it was not until 1898 that five claims were staked here by Oliver Furry, a trapper. It is from these claims that the major production during the past thirty years has come. In 1900 the Britannia Copper Syndicate was formed and development of the property was commenced. In 1903 the late Grant B. Schley obtained control, and through his efforts the Britannia Mining and Smelting Company was organized in 1908 as a subsidiary of the Howe Sound Company. Since that time, a persistent and progressive policy has been followed, which has resulted in a prolonged and profitable operation. The country in the immediate vicinity of the mine is marked by strong relief, with mountains rising abruptly from tide-water to elevations of 5,000 feet and more. Two broad transverse valleys deeply dissect the area. These are the valleys of Britannia creek and Furry creek. The region has under-gone prolonged and relatively recent glaciation. Over much of the surface there is deep overburden and dense vegetation. The geology of the mine and vicinity has been described in reports by S. J. Schofield (1), H. T. James (2), J. G. Barry, and others (3). The present writer is in accord with much of this literature on Britannia, but during recent years, extended observations made underground have shown that the &apos;quartz porphyry&apos;, or &apos;mine porphyry&apos;, of several of the earlier writers is not the host rock to the commercial mineralization; and he contends that the mineralization occurs in highly altered phases of a complex series of ruffs, flows, and pyroclastics and their autoclastic metamorphosed products.

Jan 1, 1935

By P. Fleming, W. Pascheto

"Rod mills processing nickel and copper ore experienced recurring failures of liner bolts. In some cases failures became very frequent, requiring constant mill intervention and consequently impacting process stability and operating costs. Investigation related to the causes of bolt failures involved a multidisciplinary approach with the participation of engineering, maintenance and operation. It included the determination of bolt failure mechanisms as well as the assessment of mechanical properties, fabrication quality and handling and installation procedures. In addition, other parameters affecting bolt performance such as mill and liner design, operating parameters and maintenance practices were studied. This paper reports the failure investigation results and proposed solutions for failure prevention. INTRODUCTIONOccasional liner bolt failures are common in rod mills. However, chronic bolt failures developed in rod mills processing nickel and copper ore caused frequent shutdowns for bolt replacement to an extent that affected process stability. At first, it was thought that the cause of recurring failures was related to bolt quality. The operation then submitted several failed bolts to failure analysis. However, it became apparent that bolt quality was unlikely to be the main cause of failures. The determination of root cause (s) then became more complex, requiring a multi-disciplinary approach to failure investigation, requiring the assessment of bolt installation methods, mill design, operating conditions and maintenance practices. The results of the metallurgical failure analysis and investigation of other possible causes of failures are reported here."

Jan 1, 2016

By Kremena Dedelyanova

The paper presents research of mechanism for the creation of air bubbles in vibratory a column flotation machine. Factors are discussed that influence the increase in the duration of the bubble in the area of contact with the mineral particles. Formulas are derived for the parameter effect of vibrations, applicable to the design of flotation machine. The collision efficiency of the bubbles in a vibratory column flotation machine is determined.

Aug 1, 2013

By E. Ghali, C. Su, G. Houlachi

"The influence of lead ions on zinc electrowinning process was investigated by means of electrochemical noise measurements (ENMs) and cyclic voltammetry in conjunction with scanning electron microscopy and X-ray diffraction. All electrochemical experiments were performed in sulphuric acid electrolyte containing different lead ion concentrations as impurity. Lead was added in six trace levels between 0.05–0.8 mg/L in the bath. The lead content of the zinc deposits was dependent on the introduced lead concentrations. The overpotential associated with zinc electrodeposition shifted to higher values with the increase of lead concentration in the solution. An appropriate correlation was found between the different concentrations of lead in the electrolyte and the morphology of zinc deposit by ENM. The results showed that the increase of lead ion concentrations is generally accompanied with the decrease of skew and increase of kurtosis values that could be related to the morphology of zinc deposit. Effectively, the morphology changes from well-defined hexagonal platelets to large hexagonal, layered platelets and finally to non-symmetric refined crystalline structure, respectively.INTRODUCTION In commercial zinc electrowinning, zinc oxide is leached from the roasted calcine with an aqueous acid sulfate electrolyte. Then the zinc-rich solution is purified and transferred into an electrolytic cell. During electrolysis, zinc is deposited on aluminum cathode where lead-silver or pure lead is served as anode. Electrodeposition of zinc could be influenced by several parameters such as bath acidity, temperature, current density, the nature and concentration of impurities as well as additives in electrolyte. Metallic impurities play a complex role during zinc electrowinning and they can adversely"

Jan 1, 2016

By T. Rahimzadeh, C. W. Trueman, S. Farzaneh, S. V. Hoa, I. Abdalla

This paper presents the shielding effectiveness (SE) of woven continuous carbon/epoxy composite materials. The theoretical and physical concepts behind the experimental results are demonstrated in details. The influence of frequency, the overlapping angle between overlapped layers and the number of overlapped layers upon the EMI shielding of composite sheets are discussed. In this work, in particular, the epoxy layers are considered as dielectric apertures of the conducting carbon fiber slab for the interpretation of the experimental results. The experimental results, using ASTM standard D4935-89, indicate that the SE can reach values greater than 90 dB above 500 MHz.

Jan 1, 2006

By S. Gößling-Reisemann

Most copper ores contain valuable co-products such as molybdenum, gold, silver, nickel, etc. Sulphuric acid and steam are valuable by-products, which are generated dur¬ing copper production. The environmental impacts from mining and refining therefore need to be shared between these by-products and co-products, an issue in Life Cycle As¬sessment (LCA) referred to as allocation. There are different, recognised methodologies for doing so: burdens can be allocated based on the market values of these commodities, they can be allocated by mass, volume, molar amount, functionality, or other physical, technical or economic factors. All of these methodologies have their respective merits and restrictions, and the choice is usually case specific. Nevertheless, the choice between alternative methodologies can have dramatic effects on the LCA results. Recycling in LCA has to be handled in a similar way, as it essentially constitutes a special case of co¬production. The existing standards (ISO 14040 ff.) allow different methods for imple¬menting recycling and allocation into metal LCAs (open loop, closed loop, value cor-rected substitution, etc.), which are still a subject of discussion in the scientific community. However, the methodology used can significantly influence the ecological profile of copper and copper products. We will present an overview of the different methodologies available for including recycling and allocation and give an analysis of how the meth¬odological choice affects the final LCA results. This work will be followed up by quantitative case studies.

Jan 1, 2007

By P. Patnaik, F. Cuneo, D. M. Wang

Microwave (MW) energy has been used widely for several decades for communications, food processing, wood drying, vulcanization of rubber and medical therapy. Recently, this technology was found to be capable of successfully sintering ceramic and metallic powder materials, with the advantages of reducing soaking times and sintering temperatures. Unlike conventional heating, MW radiation works through the absorption of the microwave energy by a material placed in an electromagnetic field within the microwave cavity. A far more efficient heating process is produced due to the unique ability of microwaves in selectively heating a pecific part of the material with desirable dielectrical properties. This exploratory research was initiated with the objective of locally sintering the thermal barrier coating of gas turbine components using MW radiation. This novel technique may allow repairing of the component without subjecting the entire piece to unnecessary elevated temperatures and reduction of process time and cost. Y ttria stabilized zirconia was used in this study and sintering was conducted using a multimodal 1.2 kW microwave facility. Three configurations of heating setup were experimented and the preliminary results will be discussed in this paper.

Jan 1, 2006