Search Documents

By Leiting Yue, Peng Ren, Yu Shen, Zhihong Liu, Haibao Shao, Longgong Xia, Feng Yu

The Kennecott-Outotec Flash Converting technology has been proven as an advanced and mature process in 5 individual plants during the past 2 decades. High grade copper matte (65–72%) produced in the flash smelting, or other smelting technologies is granulated to 3-5mm granules in a water torrent, and further crushed to fine powder (≈50µm) and dried to contain less than 0.3% H2O. Oxygen enriched air, together with fine copper matte powder and lime flux are injected into the reaction shaft by a matte burner. The copper making and slag making reactions will happen in very short time and distance during the particle falling and settling. However, industrial practice has found negative effects caused by sodium contamination. Na is introduced in the copper matte granulating process, and appears as Na2SO4 on particle surface. When Na content was high, scaling problems in the boiler will be worse, and the processing air will be blocked by the growing accretion around the matte burner, and as-produced blister copper is always high in S and O. In this present study, an industrial matte sample was used in the experimental work. Na was introduced into the matte powder by Na2SO4 solution soaking. The burning behaviour of the doped copper matte powder has been investigated as a function of the impurity concentration and processing temperature. Morphology and composition of these samples explained how Na2SO4 converts and reacts in the oxidizing atmosphere, and how they or their converting species influence the burning behaviour of matte particles. Cross-sections of as-prepared samples were analyzed with SEM-EDS, and the reaction mechanism has been carefully interpreted. Results from the present study can benefit both academic and industrial people. INTRODUCTION "Flash Converting" technology was developed jointly by Kennecott Utah Copper Smelter and Outotec (Finland) OY in 1992. The first industrialization of the technology was in Utah Smelter in 1995. Since 2006, it has been successfully applied in Xiangguang Copper, Tongling Jinguan Copper Branch, Fangchengang Jinchuan Copper, and Ningde Southeast Copper. The technology has also been further developed in those smelters. At present, roughly 2 million tons blister copper is produced annually through the Kennecott-Outotec Flash Converting technology, accounting for more than 10% of global primary copper production. The technology has advantages of high efficiency, high sulfur capture rate, good in environmental issues, mature equipment supporting, high automatic control level, low comprehensive energy consumption and flexible connection with the smelting unit, which make the technology to be one of the best choices in investing a new large-scale copper smelter or updating an old copper project in the world.

Jan 1, 2019

By S. Papanakli, Th. Rondoyanni, N. Sabatakakis, K. Kavoura, G. Tsiambaos

"A representative composite fault-related landslide of the Corinth Gulf graben named “Panagopoula” is reported that considered to be one of the most prone to slope instability sites along the main motorway and railway connecting Athens with the city of Patras. The presence of tectonically highly sheared and weathered geological formations, including Alpine basement (mainly flysch) contributes to the site instability, triggered/reactivated by seismic activity and heavy rainfalls. Although a series of remedial measures have been already constructed, the inclinometer readings during the last twenty years time period show a continuous very slow movement which indicates that the landslide is still ""active"". This fact has resulted to divert the axes of the new motorway and railway through twin tunnels which are under construction. INTRODUCTIONThe spatial and temporal evolution of landslides in the case of structurally complex slopes is lithologically and often structurally controlled while their type and frequency are mainly related to tectonic and lithological anisotropy (Baron et al. 2005; Hradecky et al. 2007). The triggering mechanisms mainly include: (a) excessive rainfall generating high pore pressure and (b) strong earthquakes resulting in dynamic loading conditions at the failure surface. Data such as past earthquakes or the precipitation records are useful to be gathered when a landslide model is examined since they could act as a landslide triggering mechanism. Recording of the movement through surface and inclinometer measurements as well as combination of the above information with historical records of failure could lead to a more accurate estimation of the location of the failure surface and understanding of the landslide mechanism.Slope instability in the southern segment of the Gulf of Corinth, Northern Peloponnesus, Greece, is ubiquitous and ranges from deep-seated bedrock failure to secondary earth flows in recent deposits. In this part of Greece, the periodically induced landslide events triggered by heavy rainfall, earthquake and anthropogenic activity are closely related to active fault tectonics. The Gulf of Corinth is considered as a typical example of a relatively simple asymmetric half-graben with major border faults to the south and a flexure of the northern shore. Panagopoula landslide is located along the trace of a WNW trending normal fault (dipping northwards) (Figure 1). The area is considered to be one of those most prone to slope instability along the E95 motorway and railway connecting Athens with the city of Patras."

Jan 1, 2015

By Jr. Fackler

The ionization potentials of gaseous Group 11elements are similar, with Au(0) being 1.5 eV greater than the next highest member of the group, Cu(0). The ionization potentials are all very much greater than the alkali metals, making these ?coinage? elements rather unreactive to chemical oxidation. Ionization from the first oxidation state shows a different pattern, with Ag(I) being the most difficult of the Group 11 ions to lose an electron. Gold(I) is noble and only normally oxidized in the presence of strongly coordinating ligands such as thiols or cyanide. Gold(I) compounds are 2-, 3- and 4- coordinate, with 3-coordinate species generally showing visible photoluminescence under UV excitation. Dinuclear Au(I) compounds with strongly coordinating S or C ligands can be oxidized to form isolable metal-metal bonded Au(II) compounds which are often readily isolable. Many have been structurally characterized. T he ease with which electrons are lost from closed shell dinuclear sp ecies (with anti-bonding M-M interactions) increases when metalmetal bonded compounds are formed. T his observation was made by our group with oxidative-addition studies of dinuclear gold(I) ylide complexes. It was superbly demonstrated recently by Cotton?s group who reported the isolation and characterization of a dinuclear closed shell transition metal species which is more readily oxidized than cesium. Trinuclear Au(I) pyrazolates, TR(pz), carb eniates, TR(carb), and benzylimidazolates, TR(bz), are well known and undergo electron loss through oxidative addition forming Au(I,III) mixed valence species and ultimately trinuclear Au(III) species. Au(II) species are absent from isolation in these oxidations. These carbeniates and benzylimidazolates also are excellent bases for metals ions such as Tl(I) and Ag(I). The acidic, neutral trinuclear compound [Hg(C6F4)3]3 also interacts with these bases. We have also shown that the neutral organic pi acids C6F6 and TCNQ form stacked pi-acid pi-base products with the trinuclear Au(I) compounds. In this paper, the structure of the octafluoronaphthalene acid-base product will be described. It displays a feature not observed previously in that the product is photoluminescent with a bright yellow emission. The 3.5 ms lifetime is very long and reminiscent of the long lifetimes observed by Balch for the stacked methyl,methoxy Au(carb). The electrochemical oxidation of tetragold(I) clusters, [Au4(form)4] have been studied in 0.1 M Bu4NPF6/CH2Cl2 at Pt working electrode at different scan rates. Three waves are obtained at 0.75, 0.95, and 1.09 V vs Ag/AgCl at scan rate 500 mV/s. The potential of the three reversible waves is independent of the scan rate in the range 50 mV/s to 3 V/s. The current at the third wave is larger than those at the first two waves. These tetranuclear species app ear to be effec tive catalyst precursors for the oxidation in air of CO. Introduction. The electronic structural relationships of the coinage elements and the alkali metals are similar in the sense that each have a [closed shell]ns1 configuration, yet their ionization energies (Table) and chemistries are clearly vastly different. The Group 11coinage elements have an underlying nd10 level immediately below the ns1 level. Unlike the alkali elements, ionization leaves the filled d electron shell the next accessible for further ionization. The coinage elements are all relatively ?noble?, much less reactive to environm ental conditions than the alkali metals. With the coinage elements, oxidation becomes very much dependent upon the types of ligand s availab le to bo nd to the ionized state.

Oct 1, 2003

By J. Lu, D. B. Dreisinger, G. Houlachi

"Zinc metal is primarily produced by electrowinning from sulfate solution. Zinc electrowinning is very sensitive to impurities such as Co and Ni. These impurities have to be removed to produce high-quality zinc and maintain a high zinc current efficiency. Zinc dusts are used to remove these impurities by cementation. However cobalt cementation is extremely slow and it is typically activated by the addition of Cu and Sb. Even with the use of Cu-Sb activation, cobalt is still difficult to remove. The zinc dust used for cobalt cementation is negligible compared to that consumed for hydrogen evolution. In some plants up to 6-7% of electrolytic zinc is used for cementation. This is a great waste of energy. Cu-Sb activation is not well understood. The objective of this study was to further understand the Cu-Sb activation and then find a way to reduce hydrogen evolution and promote cobalt cementation. The investigation reveals how hydrogen evolution (or zinc dissolution) and cobalt cementation and re-dissolution change with temperature, zinc dust dosage, the concentrations of copper and antimony and time. In the Cu-Sb activation, copper is deposited on a zinc particle to produce a porous shell. The zinc particle as an anode dissolves while the shell as a cathode provides a place where cobalt cementation and hydrogen evolution occur and they are catalyzed by antimony. A certain level of antimony (around 0.1 mg/L) is a key to maintain the catalytic effect of the shell. At a higher antimony concentration, cobalt cementation is accelerated slightly while hydrogen evolution is increased greatly. When a zinc particle dissolves to a certain degree, cobalt loses its cathodic protection and starts to re-dissolve. The change in cobalt concentration is determined by the rates of cobalt cementation and re-dissolution. The operation conditions can be optimized to maximize the cobalt removal and minimize the zinc dust dosage.INTRODUCTIONMost of the world’s zinc metal is produced by electrowinning from sulfate media. Many impurities such as iron, copper, cobalt and nickel are co-extracted into solution with zinc. Iron, mercury, indium, lead and tin are removed by co-precipitation as hydroxides. Copper, nickel, cobalt, aluminum, arsenic and germanium are partially co-precipitated with iron while cadmium, magnesium and chloride remain in solution. Cobalt, copper, cadmium, nickel and etc. are subsequently removed by cementation with zinc dust to achieve an acceptable current efficiency and high purity metal product for the economical production of zinc. Zinc provides a strong thermodynamic driving force for the cobalt cementation:"

Jan 1, 2016

By John Smith

"The RTZ Corporation PLCFrom a company's point-of-view, a good investment decision is one which results in the purchase of an asset that is worth more than it costs. Thus, in order to judge the merit of an investment opportunity, it is necessary to estimate the value of the assets to be acquired.Discounted cash flow (DCF) analysis has become widely adopted by companies in assessing potential new investments. The principle is a simple one: invest in projects which have a positive net present value, and reject those which do not. However, perhaps because of its apparent simplicity, DCF analysis is frequently misused. Good practice in the use of the technique is discussed, together with several common misconceptions.Sound analysis requires sound data; thus, the valuation process relies heavily upon a wide range of specialists to provide the basic input from which cash flow forecasts can be built up. The analyst must maintain close liaison with these specialists from the outset in order to ensure that the data provided is indeed relevant and complete.IntroductionBefore turning to the main subject of this paper ""How Companies Value Properties"", it is of interest to consider first a slightly different question ""Why do Companies value Properties""? In other words, for what purposes are such valuations prepared? Certainly the commonest, and probably the most important circumstance in which a valuation is required is when the company is considering an investment opportunity. This may be the direct purchase of a property or group of properties from a third party, but could also be the opportunity to develop a new operation or expand an existing one.A very simple objective in making any kind of investment is to make our shareholders richer than they would otherwise have been. That is, to make investments whose value to shareholders exceeds the consideration required to acquire them. Thus the investment decision focusses on the difference between an asset's value and its cost.This distinction between ""value"" and ""cost"" is an important one. Study of a company's balance sheet may tell a lot about the cost of this company's assets, but very little about their value. Then again, it is sometimes argued that a business should be bought because this will result in assets being acquired for less than their replacement cost. This merely compares one cost with another, it says nothing about value."

Jan 1, 1991

By E. Yan, M. Mankosa, E. B. Wasmund

Mechanical cells are the dominant unit operation in base metal rougher flotation applications worldwide. As economic demand for metals increase, and as the feasible ore grades decrease, the installed capacity of mechanical flotation units worldwide has greatly increased, adding significant capital and operating cost. One opportunity to improve this situation is to use fundamental knowledge to make the industrial flotation process more efficient. A key insight is that the flotation process can be optimized by dividing the processing of the pulp into two distinct fluidic environments; a collection cell where air and pulp mix in a highly energetic compartment, and a low energy gravity separation cell. This is the basis of the “2-stage flotation device” that has been patented by Eriez and marketed under the tradename StackCell™. Two industrial case studies will be presented to highlight the potential metallurgical and commercial advantages of the StackCell. In the first, a train consisting of three pilot scale StackCells (each 0.6 metre diameter) was run in parallel with a train of conventional mechanical cells in a major copper concentrator and benchmarked against a batch Denver test. In the second, the performance of a 3 metre diameter StackCell in a nickel sulfide cleaning application was benchmarked against a batch Denver test. The flotation kinetics observed in the StackCells were 2.4 to 2.9 times faster when compared with the lab Denver test. In the first case study, the kinetics of the StackCell was about six times faster than conventional mechanical cells. It is hypothesized that the efficiency improvement in kinetics is because of reduced “drop-back” during the froth recovery phase, which is reduced because of the reduction in the shear that is present in a conventional mechanical tank cell. This result suggests that a 2-stage flotation system can be used to reduce the working volume of flotation units by five to six times. This would allow operators to significantly reduce the size of their flotation lines for a comparable flotation objective. Some discussion will follow about the scale-up criteria, maintenance and operability issues, comparisons of layout, and possible cost savings. INTRODUCTION The solution that most equipment suppliers have offered to reduce the cost of mechanical flotation equipment over the last 30 years has been to increase the size of the flotation unit cell (Mankosa, 2017). For example, three 100 m3 machines with three smaller motors, mechanisms and control valves could be replaced with a geometrically similar 300 m3 with a larger version of each ancillary component. While there are some efficiencies and cost improvements to be gained by this approach, it does not take advantage of fundamental insights into the flotation process, and it does not represent a step-change in terms of process design or economic benefit for the customer. The advantage of the “bigger is better” approach is that there is past experience of incremental improvements by making cells larger and there is a well-established scale-up method, which allows practitioners to estimate equipment capital costs based on very simple laboratory test- work. A different paradigm, which is gaining interest rapidly is to use a unit operation in which it is easier to optimize the flotation process, which will be described in this paper. This approach is often referred to “2- stage flotation”. Because this approach is new, it is important to benchmark it against existing conventional technology and to demonstrate a robust methodology for sizing equipment and flowsheets. This paper aims to address these issues with two case studies.

Jan 1, 2019

By E. Bratygin, G. Gazaleeva

"The article describes the analysis of methods and criteria of selectivity of optimal ore preparation schemes. Traditional criteria based on study of physical-mechanical properties of ores give the comparison of obtained figures with a reference standard or statistic data and the selection of the ore preparation scheme is made on a basis of a similar scheme from the existing production.Further on estimation is given to different criteria of the crushing selectivity, the new criterion is offered, the definition of which is done by results of an optical microscopy– the estimation of a valuable mineral release degree. The final estimation of the crushing process selectivity L? is performed by a calculation of a ratio of the valuable mineral free grains quantity in a desired size grade of a crushed material to the valuable mineral free grains quantity in a desired size grade of a raw product.Besides, optimality assessment of using the specific crushing unit is preliminary performed according to a maximum crushing degree of a material, however, the priority is given to the maximum selectivity criterion. The check of the proposed criterion was done when comparing the crushing of niobium bearing ores of the Vishnevogorskoye deposit in cone inertial and centrifugal impact crushers. Different operation modes of crushers were also checked. The comparison of the crushing selectivity criterion L? showed that the centrifugal impact crusher (CC) has the value of the selectivity criterion lower than the cone inertial crusher (CIC). For the crusher CC the criterion L? is 0.82 – 0.87 units, whereas for the crusher CIC – 1.43-1.755 units. The best crushing mode for the crusher CIC-300? is as follows: turning angle of debalance is 120°, peripheral speed of a cone rotation – 1,420 rpm, specific energy consumption – 6.99 kW?t/t.INTRODUCTIONIt has been shown that the most efficient techniques of mineral raw materials disintegration are selective crushing enabling to produce liberation of particles at maximum use of destruction techniques by borders of minerals cleavage. These days, such techniques are usually called special disintegration techniques (Jankovic & Valery, 2015), and they are used in 3–4 crushing stages. The selection of optimal crushing techniques is performed based on the following main parameters:- degrees of crushing, calculated based on granulometric features of raw and crushed products;- selectivity criterion defined according to useful mineral release and slime ability degree; and- traditional criteria (Gazaleeva et al., 2015) of choice based on study of physical-mechanicalproperties of ores gives the comparison of obtained figures with a reference standard or statistic data and the selection of the ore preparation scheme is made on a basis of a similar scheme from the existing production."

Jan 1, 2016

By Rachel S. Prudhomme, Michael L. Jeremic

"The consolidation of mine backfill by free zing is a concept which has been under study in the mining engineering laboratories at Laurentian University during the past three years. The proposed underground application of freezing involves the artificial freezing of in-situ backfill by means of a refrigerated brine solution which would be circulated through a circuit off freeze pipes. The most interesting findings to date are: (I) The uniaxial compressive strength off frozen fill is considerably higher than that of cemented fill in a ratio of 20:1 (aggregate to cement), and (2) load deformation characteristics of the frozen fill suggest that a higher ice content results in more brittle failure and that samples which have initially failed can still support up 10 one-half the ultimate load without additional failure.Although at this early stage a derailed economic analysis of the procedure has not been possible, a general evaluation of the costs involved suggests that the method could be competitive with the hydraulic placement of cemented backfill. Results obtained from laboratory investigations indicate that the freezing of backfill is a structurally feasible option .IntroductionGround consolidation by freezing is based on the principle of transformation o f water contained in an aggregate-slurry into ice, which act s as a binding agent between the bulk particles, and which results in the transformation of a granular soil into a ""rock -type"" material. The abrasive nature of the particles enhance s the strength o f the ice by providing internal friction. As a result of this internal friction, the chances of plastic flow of the frozen mass when in a loaded condition are reduced(1). T he strength of a frozen aggregate is al so dependent on the grain shape of the aggregate particles which may or may not promote particle interlocking(2) and on the temperature since, below the freezing point of the water/aggregate mixture, the strength of the frozen mass increase s with decreasing temperatures.In the shaft sinking industry, artificial freezing of loose , unconsolidated soils has been in practice for several decades. Shafts for Saskatchewan 's potash industry have been sun k to depths of 3000 feet by employing artificial freezing to stabilize the Blairmore Formation(3). The common procedure for freezing ground for shaft sinking is summarized as follows(4,5): I) 150 mm diameter bore holes spaced on 1.5 m centres are drilled in a circular pattern with a radius of 1.5 m outside the periphery of the proposed shaft."

Jan 1, 1985

By F. J. Macias, A. Bruland, F. E. Dahl

"Tunnelling by use of Tunnel Boring Machine (TBM) is gaining a greater presence as a suitable excavation method. Disc cutter consumption has a strong influence on performance and cost when using TBMs and the influence becomes even more relevant in hard rock. Furthermore, good predictions of TBM performance and cost facilitate the control of risk as well as avoiding delays and budget overruns. Since abrasive wear is the most common process affecting cutter consumption, good laboratory assessments are needed. A new abrasivity test method called Rolling Indentation Abrasion Test was developed. The goal of the new test design and procedure is to reproduce wear behaviour on hard rock tunnel boring in a more realistic way than traditionally used methods by introducing wear by rolling contact on intact rock samples. INTRODUCTIONHigh investments are involved in the tunnelling industry, especially in Tunnel Boring Machines (TBMs) projects. Performance predictions and cost estimations are crucial for planning and risk management of TBM projects. Cutter consumption has a large influence in terms of time and cost, and an even greater effect in case of hard rock projects. Many factors are influencing the amount of cutters consumed in hard rock TBMs. Normal TBM operation results mainly in abrasive wear on the cutters and appropriate methods for abrasivity assessment are needed. Rock abrasiveness cannot be considered as an intrinsic property and the complete tribological system should be considered in addition to the geological properties of the rock.In the present paper, a new test method for abrasivity assessment in tunnel boring called Rolling Indentation Abrasion Test (RIAT) is presented. The traditionally used test methods for determination of rock abrasiveness uses sliding or impact contact in order to cause wear while the RIAT introduces rolling contact on intact rock samples. The ambition of the new test device is to have a reliable method to evaluate the cutter wear in hard rock tunnel boring by reproducing wear behaviour on rolling disc cutters in a more realistic way. It has been established by many authors that the abrasion of a cutter ring is proportional to its rolling distance (Rostami, 1997; Bruland, 1998). In the present work, the weight loss of a mini-cutter ring is measured subsequent to testing in order to evaluate wear in the rolling process and could hence be related to cutter ring wear. Indentation of the tools in the intact rock sample is considered as an indication of the surface hardness of the rock or the resistance to indentation by rolling."

Jan 1, 2015

By P. I. Laforest, M. S. Moats

"Antimony in smelted copper anodes has been shown to cause problems in electrorefining including brittleness of starter sheets. In order to improve deposit properties, a study was conducted examining the effect of anode chemistry on cathode ductility and electrolyte chemistry. Two industrial anodes with different molar ratios of As/(Sb+Bi) were used in laboratory electrorefining experiments with commercial electrolyte, and the addition of commercial glue and Avitone. The ductility of 21-hr copper deposits was evaluated by a 180° bend test. X-ray diffraction (XRD) and metallography were performed on unbent specimens to characterize the deposit structure. Increasing the anode As/(Sb+Bi) molar ratio from 0.54 to 3.8 resulted in an increase, on average, from four to eight bends to failure in cathode material produced. Significantly lower concentration of antimony (V) in the electrolyte was detected when operating with the higher molar ratio anode. The presence of (111) and (200) planes was noted in cathode material produced from the higher molar ratio anode suggesting that mixed growth character could be responsible for the observed increase in bend test results. The ductility of the starter sheet materials was improved by a higher anode molar ratio.INTRODUCTIONThe presence of antimony in copper electrorefining electrolyte has been reported to cause problems in cathode production (Hiskey, 2012; Peng, Zheng & Chen, 2012; Wang, Chen, Zhou-Lan & Lian-Sheng, 2006; Wang, Chen, Zhou-Lan, Wang, Xiao & Zhang, 2010; Wang, Chen, Zhou-Lan, Wang, Xiao & Tang, 2011; Wesstrom, 2014). To better understand the impact of antimony, laboratory scale electrorefining experiments were conducted using industrial inputs (anodes, cathodes and electrolyte). The influences of anode chemistry on the valences of antimony and arsenic in the electrolyte were monitored and correlated to physical cathode characteristics, such as a bend test to failure and crystallographic orientation.Commercially, starter sheets are produced by electrorefining impure cast copper anodes onto titanium blanks. The starter sheets are then hung in an electrorefining or electrowinning cell using loops of bent starter sheet material. These loops, in the absence of sufficient ductility, fail resulting in cathodes falling into the electrolysis cells. It is thought that the reduction in ductility can be related to anode composition; in particular, the molar ratio of arsenic to antimony plus bismuth As/(Sb+Bi). It has been stated that maintaining this ratio above 2:1 results in numerous improvements to electrorefining operations (Baltazar, Claessens & Thiriar, 1987; Kamath, Mitra, Radhakrishnan & Shetty, 2003; Krusmark, Young & Faro, 1995; Noguchi, Itoh & Nakamura, 1995; Wenzl, 2008)."

Jan 1, 2016

By A. Mcdonald

"An X-Met Analyzer was purchased from Outokumpu in late 1983for use in the Hudson Bay Mining and Smelting smelter. Its first use was in the fuming plant to give zinc assays of each charge of slag tapped from the fuming furnaces. This quickly told the operators exactly when each charge had reached its economic tap-out point, and gave supervision a fool-proof method of identifying good operation. These and other factors led to major improvements in coal utilization in the fumers and to major increases in zinc oxide production. A second unit was later purchased for the reverberatory furnace to give silica and iron assays of the slag, and these were used to make adjustments in the feed composition to maintain the desired SiO2:Fe ratio in the slag. Since purchasing the units for the furnace, the oil consumption and copper content of the slag have dropped significantly. IntroductionSmelters have lagged far behind concentrators in process control by mean s of rapid product analysis. The on-stream X-ray analyzer was developed about seventeen years ago, and soon concentrators around the world were getting assays of the incoming ore, .concentrates and tailings every fifteen minutes, and using these to control reagent additions and other process variables. Almost always, the concentrate grade and recovery improved.In smelters, product streams are solids or molten materials, not the more easily handled slurries, and until seven years ago no inexpensive equipment was available to provide rapid analysis of this type of material. In approximately 1980, several companies developed instruments based on irradiating solid samples with low-intensity gamma rays from radio-isotope sources, and measuring the secondary X-rays emitted from different elements in the sample to provide an analysis of the elements desired.The smelter staff had a close look at what was needed and listed the following points as being critical:1. ability to provide Zn assays of a sample of slag within 15 minutes of taking it, in order to achieve optimum fuming times (zinc fuming , being a batch process, had the greatest potential benefit from rapid slag analysis);2. ability to give Cu and Fe assays on the slag, and on other smelter products, such as matte and converter slag;3. ability to give Si02 assays since the SiO2 content of the slag has a strong effect on fuming rate; and4. ability to stand up to an industrial atmosphere such as exists in the fuming plant."

Jan 1, 1987

By Bhawani Singh, Mahendra Singh, N. K. C Samadhiya

"Inherently anisotropic rocks occur in abundance at many rock engineering project sites in Himalayan region. These rocks pose difficulty in analysis and design due to their direction dependent strength behaviour. Moreover the strength varies in a non-linear manner with confining pressure. Mohr- Coulomb strength criterion is widely used by geotechnical engineers for defining strength of rocks subjected to given confining pressure. However, the conventional Mohr-Coulomb (MC) criterion suffers from the limitation that the strength is treated to be linearly dependent on confining pressure. In the present article, the MC criterion has been modified by incorporating non-linear term while retaining the original parameters c and ?. The non-linearity with confining stress level has been imbibed through critical state concept (Barton, 1976). The criterion has been applied to a triaxial test data base comprising of more than 1140 triaxial tests conducted world-wide on anisotropic rocks. Statistical evaluation of the goodness of fit of the proposed criterion to the data-base has been carried out. Further the predictive capabilities have been evaluated by determining the error in estimation of triaxial strength if only few triaxial test data are available for determining the criterion parameters. The data base has also been back-analysed to assess the critical confining pressure for anisotropic rocks. Statistically the critical confining pressure, for the present criterion, may be taken nearly equal to 1.25?cmax, where ?cmax is the maximum value of the UCS out of all orientations of planes of anisotropy. It is concluded that reasonably good estimates of the anisotropic strength are possible through the proposed criterion.INTRODUCTIONMany rocks encountered in Himalayan region like shale, slate, schist and phyllite are inherently anisotropic and exhibit direction dependency in their strength behaviour. In addition, the strength of the rock also depends on the confining pressure and, the strength response is non-linear especially when the confining pressure may vary over large range. Conventionally, Mohr-Coulomb criterion is the most widely used criterion for rocks. However, the limitation of this criterion in its present form is that the strength is treated to be linearly dependent on the confining pressure. The present study attempts to address the following two main objectives: i) Include nonlinear response in the Mohr-Coulomb criterion while retaining parameters c and In their original form; and ii) consider anisotropic response of the rock for a given confining pressure. A nonlinear strength criterion, which uses shear strength parameters c and as per Mohr-Coulomb criterion, has been suggested based on critical state concept for rocks."

Jan 1, 2015

"Cambior now holds a 49% interest in the Valdez Creek Placer, having acquired American Barrick's 23.125% interest in May 1990. At the same time, the company assumed the management of the operation and received environmental permits to divert the river. Plans are underway to divert the Valdez River in order to continue mining the deposit upstream, and to construct a new, higher capacity wash plant (by 60%) closer to the operations. Mining operations, which were suspended in October 1989 pending higher gold prices, resumed in August 1990. The mine is expected to produce 10000 ounces of gold in 1990and more than 80 000 ounces in 1991.IntroductionThe Valdez Creek Placer is located in the Valdez Creek mining district of Alaska on the western flank of the Clearwater mountain range, about 150 miles northeast of Anchorage by air (Fig. I) . The mine is accessible by air or by road.The mine is situated at an elevation of about 3000 ft and is isolated from towns and villages. Consequently, the mine site contains the facilities necessary to house and feed 135 people at any given time. The Valdez Creek Placer has 159 employees, including 130hourly and 29 salaried employees. The hourly employees are divided into three rotating teams. The daily schedule consists of two shifts of 12 hours, and each team works 14 days followed by seven days off, resulting in a weekly rotation of teams.The salaried employees work normal hours for ten consecutive days followed by four days off. A weekly rotation ensures continuity of services and management.Gold was first discovered at Valdez Creek in 1903, when a team of four men led by Peter Monahan left the village of Valdez to explore the area up the Susitna River, to the east of Mount McKinley. They discovered gold at the mouth of a creek that they immediately named Valdez Creek, in honour of their native town. In 1904, they discovered the Tammany Channel to the right of Valdez Creek. This was the beginning of a long period of mining in the area which continued until the beginning of World War II .In 1980, the Denali Mining Co. was formed. Geophysical work and drilling carried out through 1980 and 1981 led to the discovery of Channel A, a second channel which is older than the Tammany Channel. In 1983, Denali Mining optioned its claims to Camindex to explore, develop and mine the Valdez Creek property. A joint venture agreement was signed among Camindex, Talcorp, BCP Alaska (Barrick), Sum Resources (Cambior), Norfran and WGM to form Valdez Creek Mining Co., Inc., and production began in 1984. Valdez Creek Mining Co., Inc. (VCMC) was subsequently restructured and in 1989 was held by the following three companies: Camindex Mines Ltd. - 51070; Cambior Inc. - 25.875%; and American Barrick - 23.125%.VCMC is managed by a committee of the partners. Decisions made by the committee are subject to a 70% majority vote. Cambior receives its share of production in kind, and contributes in the same proportion to the expenses of the joint venture (VCMC)."

Jan 1, 1990

By R. J. Mitchell

"High narrow backfills of significant strike length approach the stress conditions associated with a free standing wall but this lower bound design approach is not considered efficient for earth structures. This paper considers the design of high narrow backfills using upper bound limit analysis, retaining wall theory with backfill arching and centrifuge model tests. Complex toe support situations pertaining to operational factors at Falconbridge's Lockerby Mine are investigated. It is shown that the susceptibility of high narrow fills to toppling is much lower than anticipated from the retaining wall analysis and that toppling can be avoided by a suitable toe support. It is also concluded that adhesion between the fill and an adjacent pillar can markedly increase the stability of the fill. INTRODUCTIONFalconbridge's Lockerby Mine pillar projects will expose cemented tailings backfills to heights (H) up to 55 m. The exposed backfills may have strike lengths (L) greater than the heights but are relatively narrow, having widths (w) of up to 12 m. The bulk cement content of the fills varies from 8.3% (12.1 T:C) to 3.0% (33.1 T:C). Exposed faces may have up to a metre of overhang due to stope overblasting, as shown in Figure 1. These fills have a solids specific gravity of close to 3.0 and were placed at a pulp density of about 68%. The tailings have a fairly uniform grain size with 32% less than 0.075 mm (200 sieve) and about 12% slimes (less than 0.02 mm sizes). The fill exposed by early pillar removal will be backed by adjacent, near vertical, ore pillars. Future pillar removal may expose similar fills which are not supported by an adjacent ore pillar but which will be backed by either an open void or by uncemented backfill. Furthermore, these fills may be undercut when the pillar slot is driven, further reducing stability (case 3, Fig. I) or a wedge could be left to help support the fill (case 2, Fig . 1). This paper presents limit equilibrium analyses for these various backfill conditions in a 22: 1 T:C fill and com- pares the results to data from centrifuge model studies at a scale factor of A= 157 as indicated in Figure I. Prototype fills have a 6 m deep cone plug of 16:1 T:C which is accounted for in the comparison of centrifuge model test with analytical results."

Jan 1, 1989

By A. A. Ruitenberg, C. J. Morrissy

"The Lake George antimony deposit comprises a system of stibnite-bearing quartz veins that cut Silurian greywacke and slate. The stibnite-bearing ore zone is in part enveloped by a uraniferous zone.The ore-bearing quartz vein system occupies an easterly striking, gently north-dipping fracture system that cuts across north-northeasterly trending gently southwest-plunging, tight Acadian (early Middle Devonian) folds. This vein system continues at depth into a siliceous skarn zone intruded by altered granite porphyry dykes, which constitute probably a late phase of the Hawkshaw granitoid intrusion to the north.Most of the ore occurs in a northeast-plunging, trough shaped vein structure that formed where the vein system (gently north-dipping) intersects the axial surf ace zone (steeply northwest-dipping) of an Acadian synform. The trough shaped structure resulted from deflection of the fracture zone (containing the vein system) by competent beds.Emplacement of the quartz-stibnite veins was preceded by, and is in part penecontemporaneous with, the formation ofa micaceous-argillaceous alteration halo, which in turn intersects a patchy biotite alteration zone.The hypabyssal intrusions associated with the Lake George deposit probably represent a late phase (early Carboniferousr) of the nearby Hawkshaw intrusive granitoid complex. IntroductionThe Lake George Antimony Mine is situated 40 km southwest of Fredericton and 2.5 kin north of Lake George, New Brunswick (Fig. 1). The mine is owned by Consolidated Durham Mines and Resources Ltd.Shaw (1940) described the early history and development of the mine. In subsequent years, available drill cores were relogged by several geologists. Much new information became available when an extensive diamond drilling program (Kidd , 1970) was started by Consolidated Durham Mines and Resources Ltd. in 1970. A study of the geology and economic potential of the deposit was made by Glover (1973). Abbott and Watson (1975) made a study of the ore mineralogy. Available drill cores were relogged and a preliminary study of the fracture system in the mine was made by G.A. Pierce and A.A. Ruitenberg during 1976. Outcrops in the area sur rounding the mine are extremely sparse.Between 1976 and 1979 the present authors made a detailed study of the mine workings, available drill core and regional structure in the vicinity of the mine, with results set forth in this paper. The regional geologic setting of the deposit, the geometry and structural controls of the ore zones, and the mineral zonation and rock alteration are emphasized."

Jan 1, 1980

By D. R. Nagaraj, Napoleon Tercero, Raymond Farinato

"Several studies conducted recently have shown that molybdenite flotation from Cu-Mo ores is adversely impacted in sea water at pH >~ 10.0 irrespective of the pH modifier; under the same conditions Cu sulfide flotation is relatively unaffected. This has been attributed to the presence of Mg2+ ions and their hydrolysis products in the sea water which adsorb and precipitate on molybdenite surfaces as Mg(OH)2. However, why and how Mg(OH)2 impacts only molybdenite flotation in the complex flotation pulps containing a multitude of minerals is not understood. The work presented in this paper probes the interface and interphase regions near the edge and basal planes of natural molybdenite (MoS2) in aqueous solutions and flotation pulps, particularly in the presence of copper ore pulp and added Mg2+. Differences in interaction of metal ions and their hydrolysis products (Mg2+, Mg(OH)+) were measured on the two faces of this anisotropic mineral. How those differences relate to molybdenite floatability and the impact of aqueous solution chemistry are discussed.INTRODUCTIONWater resource management is an important sustainability challenge in mineral processing. In view of the shortage of fresh water in many parts of the world, mineral processing plants are evaluating alternative sources. Seawater flotation has received much attention recently and there have been several important studies reported in the literature, particularly for the processing of Cu-Mo ores (S. Castro, 2012; S. Castro, Rioseco & Laskowski, 2012; S. Castro et al., 2012; Laskowski & Castro, 2012; Ramos, Castro & Laskowski, 2013; S. Castro & Laskowski, 2013; Laskowski, Castro & Ramos, 2013; Nagaraj & Farinato, 2014; S. Castro, Uribe, & Laskowski, 2014; Veki, 2013). The main conclusions from these studies on Cu-Mo ores in seawater at elevated pH were: a) flotation recovery of Cu sulfides is either unaffected or only marginally reduced, b) molybdenite recovery is adversely affected in seawater at pH values necessary for rejecting pyrite (i.e. pH > 10 to 10.8 depending upon particular system), and c) the precipitation of Mg2+ in seawater as Mg(OH)2 is responsible for the adverse effect on Mo flotation. In order to further investigate the individual effects of Mg2+ and Ca2+ on molybdenite depression in Cu-Mo ore flotation, Nagaraj & Farinato (2014) conducted flotation tests wherein individual metal ions were spiked into tap water during grinding of Cu-Mo ores. They showed the strong adverse effect of Mg2+ addition on Mo recovery and, to a lesser extent, on Cu recovery when pH > 9.5. Under similar conditions, Ca2+ had virtually no effect on either Cu or Mo sulfide flotation. Figure 1 below shows the previous results for Cu- Mo ores in tap water and the effect of addition of Ca2+ and Mg2+ ions. Note that in seawater the adverse effect of Mg2+ on Cu recovery was much smaller than that in tap water (Nagaraj & Farinato, 2014; Figure 4a and 4b and Table 4 therein)."

Jan 1, 2016

By G. Girard, A. Larouche, J. Colbert, G. Doyer

"The Direct Chill (DC) casting process uses water to extract heat from molten aluminium and helps to control the solidification process. Many factors such as the water flowrate, water distribution around the mould and water impingement angle have significant impacts on the solidification process. It has been noted that the chemistry variation of the cooling water is also an important factor that has a major impact on the presence of defects on the ingot. A significant change in the water quality can produce defects on the ingots such as cracks, bleedouts, or runouts. Understanding the impact of water quality variation on ingots is therefore essential to ensure good ingot production and reduce defects. This paper aims at describing a new approach to follow the variations of process water quality over time. It is an original and innovative method, which is still under progress. A water quality and stability index (WQSI) is under development to evaluate changes in the water composition based on water physico-chemical parameters. The index is calculated by comparing each of the actual parameters with historical values previously modeled by a statistical law. It is a dimensionless number having an adjustable weight factor for each parameter. The positive or negative contribution of each parameter, with respect to the water cooling capacity, is taken into account to calculate the WQSI. The current selection of parameters is based on knowledge from the literature as well as on empirical experience. When the developed tool will be mature, it could be used to track water variations upon time and anticipate problems, enabling proactive actions to ensure good ingot production.INTRODUCTIONFor many years, the impact of water chemistry on heat transfer, during DC casting, has been of great interest in the aluminum industry. Several papers have been published to demonstrate the correlation between water chemistry and heat transfer (Yu, 1985), (Gildemeister, 2014). Although numerous studies do present the effects of water parameters (i. e. hardness, conductivity, oil, and grease…) on cooling capacity under controlled experimental conditions, they do not reflect the strong interactions between the parameters and variations present in a casting center. Wells and Cockcroft also demonstrated that laboratory based studies are not fully representative of real heat transfer in an industrial casthouse, there are too many factors involved (Wells, Li, & Cockcroft, 2001). In this context, it becomes very difficult to obtain a quantifiable relationship between the capacity of water to cool the ingot and ultimately the performance of the cast."

Jan 1, 2016

By L. A. Wolff

"Second only to profitability (but not always), productivity is the most sought after measurement for any operation. Whether it is in mining, manufacturing, construction, etc. managers always strive to know how productive various plants are. Even the Federal Government publishes, on a monthly basis, the nation's factory productivity.Just what is productivity and how is it measured? This is an important topic that needs definition. There could be as many definitions as there are people who use it. In the mining industry, the problems of defining productivity would be analogous to the definition of equipment availability. Each mine uses its own definition to suit its needs. Webster's Dictionary primary definition for productivity is ""the quality or state of being productive,"" with productive defined as ""yielding or furnishing results"". This is a definition open to a broad spectrum of interpretation. A discussion of how productivity is currently used in the mining industry and an introduction to a potentially different approach to its measurement and meaning is outlined in this paper.Defining ProductivityTypically, mining companies track several productivity measurements. These are partial measurements and can include the following: tons per specific equipment class per hour, tons per man-hour, and tons per shift. None of these, however, track the over -all performance of an operation, that is, a unit of output per unit of input.For a mining operation, output can be defined as the ore for mill processing. Input includes the required components of production to get to the first step of processing.The Wesbter's Dictionary definition exposes a major fault with the popular conception of productivity. The critical issue of accountability is not addressed. Anyone can produce, but how effectively and efficiently are resources used? Quantifying an inclusive measurement is difficult. Statistics referring to an increase in productivity are often published. For example, the statement, ""gold productivity has increased by 10%"" has many potentially dangerous interpretations. One must ask, what does this statistic really mean? Did gold companies produce 10%” more gold? Were less manpower or equipment required to produce an equivalent amount of gold? Did ore grades increase resulting in more ounces of gold produced, etc. Obviously, production and productivity can have similar implied applications and meanings, but also two different, distinct meanings.To mitigate a problem like this, a standard needs to be developed within the mining industry. Because of varying ore grade, changing waste to ore ratios, different mining methods, etc. all of which have a direct impact on mining, development of a standard is difficult. Kendrick(1) discusses the use of Total Factor Productivity as a productivity measurement. Summarized, the total factor productivity measure is an indication of the change in efficiency in the use of basic labour and capital factors associated with an operation.This measurement has little meaning when calculated at a given point in time. It should be an on-going calculation, tracking an operation over a period of time, to evaluate trends. These trends can be used to determine if an operation's productivity is what it should be, and alert management to potential problems before they become major and adversely affect an operation."

Jan 1, 1990

By G. Mucsi, J. Faitli, K. Bohács

"The authors developed an online tube rheometer to supplement a Netzsch MiniCer (Netzsch GmbH, Germany) stirred media mill in order to monitor online the rheological characteristics of the suspension and therefore the result of grinding during the process. Previously it was demonstrated that the above measuring system was working appropriately based on the preliminary tests. The product related stress model was applied for the evaluation of the grinding results. It was found that the suspension concentration and the change of the material properties during grinding, consequently the rheology strongly affects the grinding result, i.e. specific surface area, median particle size as well as specific grinding energy. The tested model limestone – water suspensions behaved Newtonian initially, then after a given grinding time their properties had changed and they become Bingham plastic. INTRODUCTIONStirred media milling now is a common practice to produce fine and ultrafine granular materials for different purposes. With an increasing demand of ultrafine powders for industries (Kwade, 1999), wet and dry ultrafine grinding has been increasingly used in various fields, such as minerals (Mucsi, Rácz, & Mádai, 2013)(Rácz, 2014), ceramic materials (Becker & Schwedes, 1999), pigments (Ohenoja, Illikainen, & Niinimäki, 2013), chemical products (Baláž et al., 2013), microorganisms (Kwade & Schwedes, 2002) and pharmaceutics (Afolabi, Akinlabi, & Bilgili, 2014). It is well known that suspension rheology affects the wet comminution of materials (He, Wang, & Forssberg, 2006a). The rheological behaviour of the suspension containing the ground particles might indicate the level of interparticle interaction or aggregation and therefore it is an important variable factor of the process control (Muster & Prestidge, 1995). The influence of the rheological behaviour of mineral suspensions on their grindability has attracted more and more interests and attention, especially on ultrafine grinding performance (He, Wang, & Forssberg, 2006b) (Bernhardt et al., 1999). However, there are still many issues concerning the machine and the process for the different applications. When grinding is effective and the particle size range decreases significantly, the circulating suspension is becoming typically non-Newtonian. The changed rheological behaviour and the increasing rheological material parameters can negatively affect the grinding efficiency; therefore it is an important issue. Ultrafine stirred media milling as well as solid-liquid two phase flow have been studied for a long time at the Institute of Raw Materials Preparation and Environmental Processing of the University of Miskolc. Regarding ultrafine grinding the research is focusing on the description of materials’ grindability (energetic aspects) both in wet and dry circumstances (Mucsi et al., 2013; Rácz, 2014). Concerning rheology, the three measuring pipes tube rheometer was developed decades ago (Faitli & Gombköto, 2015). So far many different solid materials from all over the world had been tested in this rheometer (Faitli & Gombköto, 2015). Main aim of these tests was to gain basic data for large scale hydraulic transport applications. Among the many stirred media mills there is a Netzsch MiniCer mill at the Institute. It was reasonable to combine the two fields together, and the goal of the research presented in this paper is to develop an online tube rheometer for the Netzsch mill and to carry out grinding and rheological testing simultaneously."

Jan 1, 2016

By Jacques H. Nantel, James F. Archibald

"Frozen tailings material may be required, in the future, to perform the support functions of underground backfill in mines located in zones of permafrost, notably in the high Arctic. To date, no knowledge of physical support parameters of such materials has been obtained in Canada due to the limited mining activity in permafrost regions. It is therefore judged essential that the important physical and mechanical properties relating to frozen tailings material be assessed.Innovative mining methods will be required to cope with the harsh environmental conditions that exist at mining sites in the Canadian Arctic. A preliminary laboratory study, in the absence of field trials at limited Arctic mining sites, has been completed in which the physical and mechanical properties of several types of representative mill tailings mixtures have been investigated. A variety of tests, to determine frozen slurry and pelletized tailings strength properties, moduli of compression, optimum water contents, deformation characteristics and the like, have been conducted.The results of this study will be used to establish guidelines for the suitability of tailings use in such northern mining environments. IntroductionFrozen tailings material has never been used to backfill underground openings in Canadian mines. At present only one Canadian mine, the Polaris Mine situated on Little Cornwallis Island, is investigating the use of frozen backfill. However, the Canadian North covers a large territory and potentially contains a large number of mineral deposits. The understanding of concepts related to mining activities in sub-zero frozen ground is therefore important.The implications of using frozen tailings as underground backfill material are far reaching both from the point of view of mine stability and disposal of tailings in the arctic regions.The strength of frozen materials (soil, backfill, etc.) may take on different meaning depending on the engineering situation. Both the concepts of rupture and excessive deformation need to be considered.The functions usually required to be performed by the backfill material in underground mines may be summarized asfollows:a) working floors; such as in cut-and-fill stopesb) stope wall support; for cut-and-fill and delayed fill stope~c) self-support when backfill is exposed on one face; during pillar recovery phases.For fill functions such as working floors, the short-term response of the frozen fill is the dominant concern. For the other fill functions, the long-term deformation response of the frozen fill, or creep, is of interest."

Jan 1, 1986