Search Documents

By S. S. Rahman, A. Gholami, M. A. Aghighi

"This paper provides a foundation for studying the growth of fractures in presence of other discontinuities and different anisotropies of low permeable hydrocarbon formations and helps to improve the design strategies for multistage fracturing.The multistage fracturing technology has recently been used to exploit low permeable hydrocarbon reservoirs. However, the mechanism of hydraulic fractures interaction and the impact of local heterogeneities on ultimate trajectory of the growing hydraulic fractures are not yet understood in depth. A fully coupled poroelastic Finite Element based model is developed to investigate the mixed mode propagation behaviour of growing hydraulic fractures. This model takes advantage of an explicit representation of the fracture which enables us to take the effects of rock and fluid related parameters into account. Moreover, impact of fracture geometry and leak-off phenomenon is investigated. The refined mesh around the crack provides the added advantage of more detailed stress distribution, pore pressure change and back stress in the vicinity of the fracture and in particular at the fracture tip. The potential deviation propensity of the fractures is evaluated based on the fundamental rule that fractures propagate perpendicular to the direction of the minimum horizontal stress.This study shows that pressurization of transverse hydraulic fractures results in the reorientation of local principal stresses, particularly in vicinity of fracture tips. Variation of flow patterns clearly influences the evolution of shear stress around the fracture tips which will potentially lead to mixed-mode I and II fracturing and consequently, fracture deviation. The presence of local heterogeneities such as preexisting fissures and/or fractures is a main source of such pore pressure induced stress redistribution and reorientation and potential deviation of hydraulic fractures.Most existing models ignore or simplify the effect of pore pressure/stress coupling as well as the fracture geometry and fluid flow within the fracture. Also, the fluid leak-off from the hydraulic fracture into the formation, which is a controlling factor in fracture growth, is often considered using analytical models. Taking advantage of a fully coupled porelastic model along with an explicitly discretized fracture, this study provides a more realistic insight into the complex fracture propagation processes of multistage fracturing operations particularly in presence of reservoir geo-mechanical complexities."

Jan 1, 2015

By N. E. Chaouai, M. Lavigne

"Indicator kriging is one of the non-parametric geostatistical techniques, ideal for estimating the reserves of irregular mineralizations (e.g. gold, uranium, platinum, diamonds, etc.). Such mineralizations are characterized by variograms which are very sensitive to extreme values (outliers) and very difficult to model.The classical approach to this problem in the industry is to trim off these high grades using arbitrary empirical upper limits established either from practice or subjectively. Contrary to this simplistic approach, indicator kriging discretizes the histogram of the grades (usually log normal) in several classes and carries out interpolation separately for each class. This paper gives an overview of the differences between ordinary and indicator kriging along with the steps required to carry out indicator kriging. The paper concludes with a case study involving a gold deposit estimation.IntroductionParametric geostatistics (ordinary kriging) has given us satisfactory results over the years in estimating the reserves of well behaved deposits with coefficients of variation close to 1 (e.g. sedimentary and porphyry type deposits). However, numerous problems have been encountered in estimating irregular mineralizations (e.g. small vein deposits of precious metals) with high coefficients of variation in the range of 2 to 5. Such deposits are characterized by a very small proportion of extreme values (outliers) which create distortions on the variograms (pure nugget effect) and render them useless(1,2).The solution often followed by the mining industry today is to trim off these values based on empirical limits. These limits are derived either by comparison with production results (or bulk samples) or by geological interpretations. Needless to say that such manipulations can lead to serious errors in estimating ore reserves (usually underestimation of total metal quantity), especially when production results or bulk samples are absent.On the other hand, the solution followed by the geostatisticians in the past was to smooth out the data using transforms (e.g. normal-score or natural logarithms). Such transforms are nonlinear and they required non-linear estimation techniques such as disjunctive kriging (DK) or multivariate gaussian kriging (MG) which require normal related hypotheses, not necessarily true in geology.Nonparametric geostatistics (indicator and probability kriging) have been -developed in order to handle these problems related to highly skewed distributions."

Jan 1, 1990

By B. Jena, M. Rigaud, S. C. Panigrahy

"The influence of flux addition on the structure and properties of pellets produced from low silica specularite with peat moss and bentonite as binders was investigated. Specific pellets basicities in the range of 0.4 to 3.2 were obtained by the addition of limestone or a combination of dolomite and limestone as flux. A t basicities < 1.6, the bonding in the pellets was provided by a glassy silicate phase. At basicities =1.6, calcium ferrites were the predominant bonding phase. When dolomite was added as a flux, presence of magnesia-ferrite was noted. The reduction behaviour of pellets at different basicities was found to be influenced by the type of flux and binder. The pellet compression strength and swelling characteristics were improved with increased basicity.IntroductionThe properties of iron ore pellets are influenced by the type and nature of the ore or concentrate, additives and their subsequent treatment to produce pellets. The interaction between various constituents of the concentrate and additives, i.e. iron oxides, gangue and fluxes etc. result in the formation of various mineralogical phases which affect the degree and nature of bonding achieved in the pellet and the structure and distribution of pores. The pellet properties such as pellet strength and reducibility are influenced by the extent and type of bonding achieved between the ore particles. In view of the present emphasis on the production of high quality pellets to meet progressively stringent quality control requirements, it is essential to investigate the effect of additives on the bonding mechanism and properties of the pellets.In the past, the effects of additives on the bonding mechanism of pellets have been investigated. It is important to note that the conditions and parameters to be controlled are typical of a given concentrate/ore. In this paper, the results of the investigation on characterization of fluxed pellets produced from a low silica specularite concentrate are reported.This investigation was also aimed at assessing the suitability of peat moss for use as a binder for the production of low silica fluxed pellets. Peat moss is abundantly available in the vicinity of iron ore mines in Quebec and encouraging results have been obtained du ring the production of high silica acid and fluxed pellets."

Jan 1, 1992

By H. Craig Boyle, Craig H. B. Leitch

"The Trout Lake stockwork molybdenum deposit is located in the Selkirk Mountains of British Columbia, 50 km southeast of Revelstoke. The property is being explored by a joint venture between Newmont Exploration of Canada and Esso Minerals Canada.The deposit is associated with a small granodiorite stock of Upper Cretaceous age (76 Ma) which has variably altered the surrounding schists, argillites and marbles of the lower Paleozoic Lardeau Group to hornjelsic biotite schists and skarn. The intrusive is composed of a small stock and an intersecting network of northeast- and northwest-trending dykes at surface that coalesce downward into a larger stock. There are two main phases of intrusion, with an earlier quartz porphyritic granodiorite cut by an intra-mineral ""quartz diorite"" porphyry. A strong sub-vertical north-trending fault controls the distribution of the mineralized stock work and displays post-mineral movement.Molybdenite, accompanied by pyrite and pyrrhotite, is mainly present along the margins of veins in a well-developed quartz stock work, but occasionally is strongly disseminated in microfractured intrusives. The stock work is strongest in and around the contacts of the intrusive and its apophyses, and occurs over a vertical range of more than 1,000 m. As defined by the 0.10% MoS] contour, the main mineralized zone is up to 300 m long by 200m wide. Preliminary drill-indicated reserves, currently being revised, are approximately 50 million tonnes of 0.23% MoS2, within which are several zones of higher-grade material. Hydrothermal alteration, as defined by quantitative X-ray diffraction studies on composite core sections, is composed of a central quartz/K-feldspar/albite/minor biotite zone coincident with molybdenum mineralization, which is overlapped by a slightly later, antipathetic quartz/ sericite/pyrite zone. Ankeritic carbonate is also a common alteration mineral, but only traces of fluorite, and no topaz or sulfosalts, have been observed. Analysis for trace elements such as Sn, W, Bi, Sb, As, Hg, U, Ag, Au, Mn, Cu, Pb, Zn and F has been limited except for Sn and W, which appear to be zoned inside and outside the Mo zone respectively; the other elements do not show detectable patterns thus far."

Jan 1, 1983

By M. H. Moys, C. Bhondayi, Eric Tshibwabwa

"The relationship between froth bubble size as represented by intra-bubble impact distances (IID) and flotation performance is investigated. Experiments using an artificial ore comprising of limestone as the floatable component and silica as the gangue material were carried out in pseudo-steady-state circuit. A method to measure IIDs developed by Bhondayi and Moys (2014) was then used to measure froth bubble sizes as a function of froth height, superficial gas velocity and feed rate (pulp residence time). Samples for flotation performance evaluation were also taken. Results indicate that as froth height increases, the average IID values increase resulting in a decrease in limestone recovery while the grade increases. Increasing gas rate results in lower IID values that are accompanied by high recovery and low limestone grade. The effect of feed rate on both flotation performance and average IID values depended on froth depth and gas rate. Average IIDs largely remained the same at the two feed rates investigated.INTRODUCTIONIt is regarded as obvious that froth bubble size distribution (FBSD) will have an effect on plant grade and recovery. As the average FBSD decreases, the bubble surface area flux will increase making possible an increase in recovery and a decrease in grade. The opposite trend will be involved if average FBSD is increased. However: no method for measuring FBSD has been available, so these trends have not been studied in any detail. Bhondayi and Moys (2014) developed a novel technique to measure or estimate froth bubble sizes. Although they established a potential to use this method in understanding froth performance, no data have been presented to assess the correlation between the estimates of bubble sizes and actual flotation performance. In this work experiments are done to establish how the change in froth phase bubble sizes affect flotation performance. Flotation performance will be evaluated using recovery and grade. How water recovery to the concentrate changes with changes in bubble sizes will also be evaluated. It is known that water recovery is approximately inversely proportional to the square of the overflowing bubbles sizes. It will be interesting to establish how the rate of change of bubble sizes changes with water recovery."

Jan 1, 2016

By Matthew S. Bingham, David H. Searle

"One of the most significant developments in environmental law has been the development of mandatory project review processes, at both the federal and provincial levels.FederalWhile, in the past, project review processes have, f or the most part, been spelled out in guidelines, the guidelines have not had the force of law. All that has changed, particularly at the federal level, with the Federal Court decisions commonly referred to as the Old Man River and Alameda and Rafferty Dam cases. These decisions, taken as a whole, are authority for the proposition that the Environmental Assessment and Review Process Guidelines Order, SOR 82-487 is a law of general application, not a mere guideline which may or may not be applied. This federal environmental assessment process first provides for a screening, and, depending upon the results of the screening process, the possibility of a public review. This federal process only applies, however, when the proposal is being undertaken by a federal department, or where the Government of Canada makes a financial contribution, or where federal lands are involved, or where a federal licence or permit is required.Bill C-78, the Canadian Environmental Assessment Act, will replace the Federal Environmental Assessment and Review Process Guidelines Order once it has been passed by Parliament. Currently the bill is being widely discussed, both between governments as well as public interest groups.ProvincialOn the provincial scene, there are three project review processes, one concerned with new mines, the second with energy projects and the third with all other major projects. The most recent initiatives taken by British Columbia are twofold. First, the Mine Development Review Process which was in the form of a guideline, has been replaced by the Mine Development Assessment Act. Second, the Major Project Review Process has been formulated and is to apply to four main categories of major projects:1. Pulp and paper production;2. Mineral smelting and refining;3. Chemical products; and4. Major ports and marinas.Energy projects are governed by the Energy Project Review Process which is legislatively mandated under the Utilities Commission Act."

Jan 1, 1991

By Yongbao Zhu

The Ag2O-mediated reactions of cycloaurated compounds with a general formula Au(L)Cl2 (L = bi-dentate C?N ligand) with thiosalicylic acid, N-acetyl cysteine or 1,2-benzenedithiol in DMF proceeds via ligand substitution of the Au?Cl bonds to afford the S-O and S?S adducts all in good yields. The reactivity of the dichloro, S-O and S-S adducts towards thiols were examined by reacting with cysteine in an aqueous medium, revealing that all of Au-Cl, Au-O and Au-N are labile for thiol displacement. The measurement of the inhibitive activities of these compounds against human cathepsins B and K showed that the dichloro and S-O adducts are effective inhibitors with IC50 values ranging from 0.1 to 2.6 -M, and that the S-S adducts are inactive.

Oct 1, 2003

By H. Nouranian, M. Askari

GOLGOHAR Mining & Industrial Co., with annual production of 16 million tons, is one of the largest pelletizing and iron ore supplier in Iran that recently this year, because of using mineral processing techniques and extraction of ore body positioning between the metamorphic rocks, about 150 million tons of dry tailings has been created as a result of concentrate production. On the other hand, many environmental issues such as groundwater pollution have been developed by sulfide and silicate gangue minerals, which containing heavy metals such as mercury and arsenic. In this study, a new product with high added value has been introduced for the company by identification and extraction of industrial minerals in dry tailings. Also, by removing large masses of dry tailings, environmental pollution sources were gradually eliminated. This method can be used as a modern waste management approach in the world.

Jan 1, 2017

By M. X. Yao, C. D. Opris, P. C. Patnaik, R. Liu, X. J. Wu

Two cobalt-based superalloys, Stellite 694 and Stellite 712, were functionally graded with reinforcement of titanium-carbide particle for high-temperature wear/corrosion applications. The designed composite specimens were fabricated using powder metallurgy (P/M) technique, combined with hot isostatic pressing (HIP). Calorimetric effects of the alloy powders were investigated using the differential scanning calorimetry (DSC) technique, which provided the basis of the sintering cycles designed. The phases present in the microstructures of the materials were analyzed using SEM and X-ray diffraction. The wear resistance of the materials was evaluated on a pin-on-disc tribometer. It was demonstrated that adding titanium-carbide particles to the alloys has increased significantly their wear resistance. It was also found that the HIP process had improved the density of the sintered specimens and thus enhanced their wear resistance.

Jan 1, 2004

By Paul D. Young, Michael J. Allan

"The Con Mine has been producing gold continuously since 1938. In 1990 laboratory and pilot plant investigations began into the use of pressure oxidation for treatment of an arsenic trioxide waste product from two previous roaster operations on the property. This led to the construction in 1992 of a 96 ton/day plant to treat a mixture of arsenic waste and flotation concentrate from the existing mill. The plant was commissioned in the fall of 1992.This paper describes experience gained in the commissioning and initial operation of the plant. The unique aspects of treating a hazardous waste product are described including special operating procedures to satisfy environmental and employee safety concerns. The paper further describes modifications made to the process flowsheet, to operating procedures and to materials of construction in the early months of operation."

Jan 1, 1994

By J. L. Rodrigues Bravo

The aim of this paper is to show the results of the study that relate the variations of the bismuth content in the Caraíba Metais&apos; electrolytic copper with the main electrolysis&apos; process variables as electrolyte flow rate and temperature, anode&apos;s impurities content, electrolyte composition, current density, etc and their combinations and factors like cathode washing, blend of materials entering rod plant&apos;s furnace, analytical methods, shot-circuit inspection, etc. Also, the methodology considered arsenic, bismuth and antimony mass balance in the electrolysis and their electrolyte&apos;s molar ratio relations as well as bibliographic references of refineries that operate in similar conditions. The results showed the circumstances with the major probability of causing bismuth content increasing in the electrolytic copper and the main operating conditions that have to be fixed for having less bismuth variation and lower content in the electrolytic copper.

Jan 1, 2007

By F. Golestani-Fard, A. A. Nourbakhsh

In this paper microstructural development of nitride-Bonded SIC refractories is reported in presence of Al203, Mg() and Urea additives .The samples were prepared by mixing, shaping and firing at 1400-1500°c in a controlled atmosphere furnace. Phase analysis, microscopic observation and mechanical evaluation were taken for microstructural investigations. The strength of samples doped with Al203 was first increased and then decreased at higher amount of Al2O3 additions. The addition of MgO decreased the strength while the urea showed an improving effect on strength. These phenomena could be attributed to microstructural evolution and mainly to liquid phase formation and grain morphology. It was found that the additives such as Al203, MO and urea could modify the microstructure in terms of phase formation and texture modification, which in terms influences the mechanical behavior.

Jan 1, 2004

By Fengxiang He, T. Meadowcroft, Yanjun Zhang

Slag from the zinc fuming furnaces contains about 3 percent zinc and 0.1 percent lead. The paper outlines several experimental techniques for recovering these components from liquid fumer slag. The simplest method, remelting followed by a hold period, indicated that a substantial fraction of the metal values was recoverable as a result of fuming into the gas phase, presumable by reduction of the metal ions by divalent iron ions. Following on from this, slag samples were equilibrated with copper, chosen because the activity coefficients of zinc and lead in copper are very low. This improved metal recovery, with substantial amounts of lead and zinc reporting to the liquid copper as well as to the fume. Application of an electrical emf across the slag-metal interface, using a graphite anode and a liquid copper cathode, resulted in further gains in metal recovery.

Jan 1, 2004

By M. A. N. Rosa, L. C. R. Machado, R. A. Fonseca, A. M. Mendonça

"Sossego Mine was the first Vale SAG mill operation to process copper-gold ore. It is located in the state of Para, in the south-eastern Amazon region of Brazil. In the first six years of continuous operation, Vale investigated different alternatives for improving circuit performance by investigating operating conditions, mainly focusing on the SAG mill.Today, after a steady increase over five years the annual production rate seems to have stabilized. It is hoped this work will show how the SAG operating practice have been perfected with time and as new data are collected. Historical data of mill grind-outs and crash stops helped create operation curves depending on the ball charge volume and total charge volume. Also noted were impacts on throughput due to the effect of reducing liner weight and the ore type characteristics."

Jan 1, 2012

By M. Bueno

Between 1993 and 2003, a series of AG and SAG mill pilot plant trials were conducted using Hardinge Ical pilot plant scale SAG mills on numerous ore samples and ranging across a wide variety of operating conditions. The data from these tests were used to evaluate the design of SAG and AG mill circuits for over a dozen projects, of which about half were eventually constructed and commissioned. The data were also used in the development of SAG mill modelling, scale-up and simulation procedures by several consultants who had access to part of the data set. Recently, we have had the opportunity to bring this data together and further analyse the consolidated dataset. This paper reports on the outcomes of this analysis that has identified the impacts of different AG/SAG circuit flowsheets and operating conditions on energy efficiency and operating cost.

Jan 1, 2012

By Robert Lamarre

In today?s environment, the availability of production equipment is a must to increase throughput and profits. For a number of mining organizations around the world, spare parts availability is key to achieving this goal. Fortunately, having less production equipment immobilized by a lack of spare parts does not equate to increases in inventory levels or in carrying costs. Advance operations research has shown a number of avenues to increase equipment availability while reducing total investment in stock. The presentation will explore these avenues by focusing on key inventory management changes that can be implemented by organizations to optimize their service and stocking levels. We have successfully applied our approaches in start-up mining projects, in mature projects and in end of life mining operations. We will illustrate our methodology using examples from our work with > 30 mining sites around the world.

Aug 1, 2013

By H. Wilhelm, W. I. van Drunick

The Anglogold Ashanti (AGA) Navachab single stage SAG mill has provided an excellent setting for incremental optimization. Over the past decades, several interventions have resulted in marked improvements in specific performance; including steel ball scat removal, re-design of the mill lifters, replacement the pebble crusher and cyclone cluster, as well as the use of a vibrating screen in place of a discharge trommel. Recent initiatives now include an operating fine DMS circuit, studies on pre-crushing of the ROM feed and also fine-screening as an alternative to hydrocyclone classification. The current optimized state of the Navachab mill allows it to operate at approximately 20% higher efficiency when compared to mills of similar shell dimensions in gold mining, treating similar ore. This paper describes the systematic improvement of the SAG circuit to its current state.

Jan 1, 2012

By G. E. Agar, R. Stratton-Crawley

"The applicability of a hydrocyclone model to simulation of the cyclone banks in a multi-stage sandplant circuit producing mine back fill has been demonstrated. The model ha~; been used in conjunction with a modular computer program for circuit simulation in order to study the effect of changes in the operating conditions. It has been shown that weight recovery to sand fill increases as feed percent solids decreases, and, to a lesser extent as pressure drop across the banks increases. An increase in apex diameter also causes an increase in weight recovery. Increased weight recovery must, however, be balanced against sump an1l cyclone capacity and dilution of sand fill by fines. The predicted results from circuit simulation were in good agreement with plant data.The model has been found to be applicable to widely different ores."

Jan 1, 1979

In terms of throughput, product size and power draw, grindcurves provide a measure of the response of the mill performance to changes in mill operating parameters – usually mill filling. Since presenting the principle in 2006, grindcurves have been applied to a wide variety of AG and SAG mills. Mill response has been carefully measured for variations in: mill fillings from 15% to 40%; throughput by a factor of two; power by 50%; feed blends; liner profile; and mill speed from 65% to 80%. The outcomes of this extensive program of work are presented as the measured grindcurves. How they have enhanced our understanding of mill operation and how they may be applied to practical daily mill control is discussed. It is proposed that this technique provides a viable and valuable mill control tool that may find extensive application in the industry.

Jan 1, 2012

By N. Aydogan, H. Dundar, Å. Partapuoli, A. Fredriksson, P. Wikström, K. Tano, G. Adolfsson

The Autogenous milling of ores holds an increasing attraction as the focus moves towards reducing energy usage, both direct and embodied in grinding media. However, most of the early AG mills were converted to SAG for improved stability and increased throughput. This imposes a huge penalty in steel grinding media consumption. The LKAB iron ore operations in Sweden process highgrade magnetite through fully-autogenous milling lines to a final product P80 of about 45µm. The outcomes of P9O AMIRA research surveys, covering a wide range of mill fillings and throughputs and with different feed blends, are presented. Insights are provided on operational strategies, opportunities, the influence of feed size control and balancing the blend of competent gangue and softer magnetite. Areas of importance in the successful operation and control of energy-efficient autogenous circuits are highlighted.

Jan 1, 2012