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By J. Fixter, P. Prangnell, Z. Pinter, E. Eimer, B. Chehab

"High deposition rate Wire and Arc Additive Manufacture (WAAM) can provide benefits to the aerospace industry, including a reduction in lead time, reduced material waste and, through higher solidification rates, refinement of the as-built microstructure relative to a cast material. However, candidate 2xxx series high strength alloys for this process normally require a solution treatment, which is problematic for large near-net-shape components, and age hardening to achieve maximum mechanical properties. With each layer being subject to multiple thermal cycles, exploiting the thermal conditions in the WAAM process to avoid post-build solution treatment is therefore of interest. A solutionisation model has been developed for the WAAM process, based on diffusion controlled dissolution using DICTRA, which was validated through thermal simulations combined with 2D and 3D image analysis. The model has subsequently been used to simulate the solutionisation behavior during a typical WAAM thermal cycle and to explore what could theoretically be achieved by, for example, refining the starting microstructure.INTRODUCTION There is currently great interest in exploiting additive manufacturing (AM) in the aerospace sector due to several benefits it can potentially provide; including reduced material waste, shorter product lead times and greater design freedom (Herzog, Seyda, Wycisk, & Emmelmann, 2016). However, with aluminium alloys the material properties obtained are generally inferior to those of conventional high-strength wrought products; therefore more research is required to explore the potential for exploiting the unique process conditions in AM to improve the as-deposited microstructure. A range of AM techniques are now available (Debroy et al., 2018), which differ in terms of the feedstock type and power source and it is necessary to match the appropriate technology to a particular application. This generally requires a compromise between the build rate and shape resolution. Wire and plasma-arc additive manufacturing involves using an electric arc to melt wire onto a substrate, and fabricates a part by building up overlapping layers of deposited weld beads (Addison et al., 2015; Williams et al., 2015). The benefits of this process over other AM methods are the much higher deposition rates (e.g. kg’s/hour) achievable and lower capital equipment costs relative to powder bed techniques, which makes it suitable for large scale applications. However, limitations include a lower part complexity, lower solidification rates and a greater need for post-process machining (Frazier, 2014)."

Jan 1, 2018

By Wayne F. Luinstra, Frédérique Vincent, André R. Laplante

"A test to determine the amount of gravity recoverable gold (GRG) in an ore is described. Typical GRG results are given; possible uses are discussed. A case study of how the technology was used at Hemlo Gold Mines is presented.IntroductionUsing gravity to supplement either flotation or cyanidation is a well established practice in the gold industry. It differs from most recovery circuits in that most of the gold recovered by gravity would be recovered in any case by the circuit downstream, be it flotation or cyanidation. The economic justification of gravity is therefore based on small margins (for example. a net smelter return of gravity gold of 99%, as opposed to 94% by flotation). It was easily demonstrated when either flotation or cyanidation were relatively inefficient processes, and labour costs low (as gravity can be labour intensive). Over the past thirty years, the advent of better flotation machines (flash, column, high capacity), more effective collectors, and better control systems has increased flotation's metallurgical performance, thereby decreasing the incentive for gravity recovery. Cyanidation technology has undergone similar changes, with the advent of activated carbon, oxygen and lead nitrate addition, and improved impeller design.Today, gravity could remain an attractive option only inasmuch as it can be implemented with very low capital and operating costs. This has resulted in a relative shift away from gold gravity recovery (except for alluvial deposits), in the seventies and eighties. For example, as of the early nineties, gold gravity recovery has disappeared from the typical South African flow sheet. The advent of the Knelson Concentrator, at the beginning of the eighties, foreshadowed a resurgence of gravity recovery, as gold's grinding and classification behaviour (Banisi, Laplante and Marois, 1991) makes it possible to achieve adequate gold recoveries with very simple, Knelson based, gravity circuits (Laplante et al., 1994).Consider for example the Hemlo recovery circuit, made of a single 61 cm x 122 cm (2' x 4') screen, an automated 76 cm (30"") Knelson feeding a Gemeni table, to produce a 70-80% Au concentrate which accounts for approximately one fourth of the gold production (about 3 million grams per year). The low capital and operating costs make it possible to justify the gravity circuit on the basis of savings in other operating costs (e.g. fewer carbon stripping and reactivation cycles). Any improvements in recovery, which would at Hemlo be difficult to measure, would be additional benefits. Such a circuit is rapidly becoming a standard in Canadian and Australian operations.The justification for installing a gravity circuit must be first based on an estimate of how much gold it will recover (irrespective of what the potential benefits are). This is a function of the nature of the gravity circuit to be installed; however, Knelson circuits, by their very simplicity and efficiency, limit the options. This leaves the amenability of the ore to gravity recovery as the single most important parameter. Various approaches can be used to characterize this response (Woodcock, 1993). The present work sought a route which would fulfil the following criteria:"

Jan 1, 1996

It?s a pleasure to be with you in Vancouver today to reinforce the good work you and your companies do to develop and operationalize new technology as a lever to improve operational performance and reduce our impact on the environment in absolute terms. Although I will use the work we do at Shell to reinforce this perspective, the principles apply to all of us in this industry regardless of whether you are a producer or supplier. I?d like to help demystify the future of Canada?s oil sands based on Shell?s view of global energy developments, including forecasted demand. One of the incontrovertible truths of this era of global energy defines change as an unchangeable law of progress. Another tells us that the art of progress is to preserve order amid change and to preserve change amid order. These axioms help frame the increasingly public debate about the future of Canada?s oil sands. I hope to illustrate how Shell?s commitment and investments create positive progress that embraces change amid order in the oil sands. I?m going to spend a little time today to focus the spotlight on the future of the oil sands to help demystify Canada?s hydrocarbon energy future. To do that, I?ll identify the features of our future energy security, including three hard truths about global energy that drive Shell?s business imperatives. Then, it?s instructive to examine Canadians? current consciousness about oil sands sustainability.

Oct 1, 2009

By Dale Coffin

Definition Of A Crisis Crisis \kri-ses:\ An unstable or crucial time or state of affairs whose outcome will make a decisive difference for better or worse (Webster's New Collegiate dictionary) An event or set of circumstances that could significantly affect a company?s ability to carry out its business, damage a company?s reputation and/or threatens the health, safety and well-being of employees, the community or the public at large You?re Having A Crisis When... . The emergency poses a significant threat to the public or employees . The emergency situation provokes government scrutiny . The company no longer has full control of the situation . The situation has created significant regional, national or international media interest . The corporation?s reputation may be damaged or there is a threat to the bottom line or share value

May 1, 2004

By G. E. Agar

"The distribution of gold in the grinding-classification circuit of an operating gold plant was determined by assaying the size fractions of samples from each of the streams. This analysis identified the streams with the maximum potential for gravity recovery of gold and revealed that there was up 110 seventy-five times as much gold in the primary cyclone underflow as in the concentrator feed.Laboratory jigging and tabling tests were done on samples from two of the streams to determine what the recovery might be with a gravity circuit and to show that a high grade concentrate could be produced. A numerical simulation procedure was used to calculate a material balance for a circuit that included gravity separation on the primary cyclone underflow. The numerical simulation optimistically indicated that as much as 84% of the gold might be recovered in a reasonable grade of concentrate even though the recovery in batch bench scale tests was only 14%.Incorporation of a gravity separation device would reduce the inventory of gold in the grinding-classification circuit.INTRODUCTIONMany gold concentrating plants include a gravity concentration operation while others do not and the reasons that some do and some do not is not clear. Some of the advantages and disadvantages of gravity circuits are discussed by Penman (Penman 1987) without clear cut resolution. Penman's comments elicited an interesting response from Lloyd (1989) who produced a simple way to determine if the addition of a gravity concentration circuit would enhance the recovery of gold. Lloyd's method does not consider the cost of running the circuit so it only partially answers the question. There are reports in the literature (Wells and Patel 1991, Matwijenko 1988) that as much as 60% of the entire production comes from a gravity circuit when it is used, and that the grade of the concentrate produced often exceeds 65% gold, an assay that far exceeds most Merrill-Crowe precipitates that are sent to refining. In at least one instance (Hood 1984) a range of recovery from 40-50% was indicated from laboratory test work and the plant subsequently realized recoveries in the range of 26-40%. Despite these favorable numbers other plants use gravity separation when as little as 20% of the gold is recovered in the gravity concentrate (Carter 1992)."

Jan 1, 1993

By Lex L. Udy

External-detonation-generated plasmas, highly ionized zones of reacting material ejected from the surface of detonating explosive charges, are shown to be the cause of channel desensitization, i.e., the self-quenching of a detonating explosive column loaded in a borehole with an air annulus between the explosive and the borehole wall. The effects of this phenomenon on several explosive compositions and types are demonstrated and discussed. The explosives tested include aluminum-sensitized and explosive-sensitized slurries, ANFO, liquid explosives and dynamites. Various techniques are described that can be used to reduce or eliminate the plasma effect.

Jan 1, 1979

By Steve R. McCutcheon, Cees R. Van Staal, John P. Langton, Leslie R. Fyffe

The volcanic-dominated Tetagouche Group in northern New Brunswick contains numerous massive-sulfide deposits and intimately associated metalliferous sediments. The massive sulfides are generally hosted by Llanvirnian-Llandeilian volcaniclastic sedimentary rocks of the Nepisiguit Falls, Patrick Brook, and Boucher Brook formations. These formations are intercalated or closely associated with rhyolitic-dacitic flows and/or domes, and minor continental tholeiites of the Flat Landing Brook Formation. Pyroclastic rocks are relatively scarce in the silicic volcanic complex. Tuffites and epiclastic sandstones, of the Nepisiguit Falls and Patrick Brook formations, respectively, generally occur along the fringes of the silicic volcanic complex. The flows and tuffites are intruded by quartz- and feldspar-phyric rhyolite (porphyry) dykes, sills, and domes. Although the volume of the silicic volcanic complex is large, evidence for a previously proposed collapsed-caldera model is lacking. On the basis of host-rock type and stratigraphic position, the sediment-hosted massive sulfides have been divided into three groups: the Brunswick-, Caribou- and Halfmile Lake-type deposits. Syngenetic feeder pipes and asociated alteration zones are generally not present beneath the Caribou- and the Halfmile Lake-type deposits and, if present at all, are poorly developed underneath the Brunswick-type.

Jan 1, 1992

By L. Chunpongtong

ABSTRACT The mining limit in oil sands is regulated by the ratio of total mining volume (ore, interburden, and overburden) one has to mine per volume of bitumen in place (TV/BIP). This paper presents a mathematical solution for creating the most economical pit outline where the TV/BIP ratio upper limit is 12, by combining mining economic theory and the Lerchs-Grossmann (LG) algorithm.

Jan 1, 2014

By Z. Z. Öztürk, N. Sarica, A. H. Üçisik, C. Bindal

"Titanium oxide films were fabricated on commercially pure titanium surfaces via anodization procedure. Anodization parameters, anodization time and voltage were altered, whereas temperature and chemical composition of anodization bath were kept constant. The main idea in this study is to obtain rough titanium-oxide surfaces. The type and feature of titanium oxide formed were observed via SEM and EDX analyses. What was revealed from SEM and EDX analyses were combined with Ti-O phase diagram in order to make judgment on the type of phases obtained, e.g. solid solution and/or compounds. Studies on the different regions of each sample showed that surfaces consist of different titanium oxide compounds with various O/Ti ratios in nano level and solid solutions varying in terms of chemistry on the same sample. Thus together rough surfaces and inhomogeneous distribution of "titanium oxides" were obtained. It was also found that when anodization time and voltage were increased, more granular surface with higher O/Ti atomic ratio was obtained."

Jan 1, 2015

By L. Chunpongtong

The mining limit in oil sands is regulated by the ratio of total mining volume (ore, interburden, and overburden) one has to mine per volume of bitumen in place (TV/BIP). This paper presents a mathematical solution for creating the most economical pit outline where the TV/BIP ratio upper limit is 12, by combining mining economic theory and the Lerchs-Grossmann (LG) algorithm.

Jan 1, 2014

By Pierre C. Vieillescazes

MIGA: Unique Multilateral Risk Mitigator ?A World Bank Group agency established in 1988 to promote and facilitate sustainable foreign direct investment in emerging coufacilitate countries ntries (north(north--south and southsouth south--south) ?Guarantees equity and debt and many other types of investments against non-commercial risk. ?Can cover the following type of risks: ?Expropriation ?Breach of Contract ?Currency Transfer and Inconvertibility ?War and Civil Disturbance ?Non-Honoring of Sovereign Financial Obligations

May 1, 2010

By P. J. Lunder, R. C. Pakalnis

This paper presents the results of research that has been undertaken in order to develop an improved method of determining the strength of hard-rock mine pillars. Pillars are found in various shapes and sizes in all underground mining operations. Prudent engineering design requires that if pillars are to perform as desired, both the pillar strength and the pillar stress must be determined. A detailed pillar stability study has been combined with an extensive database of published pillar case histories (178)resulting in a new “hybrid” pillar strength formula, “The Confinement Formula”, that utilizes classic strength of rock methods combined with empirical methods. “The Confinement Formula” utilizes a “mine pillar friction term” calculated from the average minor/major stress ratio with-in the pillar core. Statistically, the new formula provides better results at predicting pillar strength for the combined database than the best empirically ft pillar methods that currently exist. “The Confinement Formula” allows for the determination of the strength of mine pillars with an increased level of confidence over previously applied methods.

Jan 1, 1997

By P. Mageau-Béland, È. -M. Proulx, M. -C. Patoine

Over the past six decades, Hatch has helped several industrial processing facilities in debottlenecking their operations, allowing them to produce more with the same equipment, to reduce and even eliminate expenditure investments, or to increase the return value of their expansion projects. These successes result from the application of a proven analysis approach that can be applied to any industrial facility. A five-stage methodology is discussed and demonstrated with a specific example of a nickel concentrator optimization study. The first stage is an observation stage which allows to meet key actors at the plant, develop mutual understanding of problems, understand operating philosophy, and efficiently collect large amounts of operating and maintenance data. Following is a data compilation stage during which data is analyzed over a representative time period to identify parameters that significantly affect the production, to evaluate data reliability and to define the focus of the upcoming analysis. Quantitative metrics are defined using statistical tools such as pivot tables, histograms, percentiles and MDR (Maximum demonstrated production rate during 3 to 7 consecutive days). Then, the production bottlenecks are identified by a thorough analysis of the facility’s control philosophy, process throughput, equipment capacity, availability, downtime causes, and interaction between components of each circuit. Understanding the maintenance practices and frequency of planned shutdown is also critical to this analysis. Opportunities for improvement are identified in collaboration with the operation, maintenance and engineering teams, ranked as a function of their impact on the bottlenecks and prioritized. The final and most critical stage involves engagement with the plant stakeholders, namely the operators and the maintenance staff members, to present the results of the analysis and obtain their participation in the implementation of the solutions. The benefits of the case study translated into: 10% production capacity gain, improved maintenance planning and avoidance of several million dollars of investment.

Jan 1, 2016

By Mitchell Gordon

"In almost all thickener applications the highest possible solid/liquid separation efficiency is what is desired by the user. There is a trend in the industry due to monetary restraints and environmental pressures to look at ways to extract this maximum performance by either retrofitting existing thickeners or installing the most cost effective new thickener. This paper looks at some of the common problem areas and presents a range of solutions developed by Outokumpu Mintec in North America and outokumpu's subsidiary Supaflo Technologies Pty. Ltd.The Emerging PictureAfter many hours of discussions with a large number of plant personnel over the last two years a picture began to emerge regarding current thickening operations in the industry. Initially, it seemed that everybody had their own unique process problems and therefore needed a correspondingly unique solution. Looking more closely at all the cases and the ideas that we had either implemented or suggested, it gradually became apparent that the majority of operators all had one and the same process need ....""Better Separation Efficiency""The range of operational problems that were uncovered in the survey were much more varied than expected and often were not even considered initially to be thickener problems. Often, it was only after the rejection of many solutions to the problem, generally due to capital cost, that the actual cause of the problem was looked at and found to be a thick-ener.A summary of the problems that have so far been identified is presented in Table 1. They are subdivided under three major categories of environmental, process and paste fill to highlight the wide range of mining activities that can be affected by poor thickener performance. These seem to be the major areas where the need for better separation efficiency is rooted."

Jan 1, 1995

By A. Galibois, H. Monette, J. L. Collins

This paper deals with the problem of caving, which occurs in varying degrees in blast holes before loading. It is shown that the distribution of the amount of caving in materials may be described by a gamma density function. A decision model to determine the optimal depth of over-drilling 'in order to minimize the expected additional cost per hole is described. Two different policies are discussed. In addition, charts which permit the mine operator to realize significant savings have been drawn for different actual situations.

Jan 1, 1971

By Kousuke Takahata, Hirofumi Yoshimura, Jun Nakahigashi

Studies of a protium treatment for grain refinement of a + ß type titanium alloy are reviewed and recent experimental results are introduced. Protium treatment consists of the following three processes: (1) protium absorption, (2) martensitic transformation and hot working, and (3) final treatment for protium desorption and recrystallization. A combination of these processes results in the ultra-fine grains of 0.3 to 0.5 µm in diameter with high angle boundaries. The ultra-fine-grained material exhibits superplastic elongation of over 9000%. Superplastic forming was successfully used to fabricate a denture base. These materials may be widely applicable as biomaterials in various medical industries.

Jan 1, 2004

By Thomas. L. O.

Apart from a few sketches and incomplete maps, mainly topographical, and one or two detailed maps of placer-creeks, there is little information on the topography and geology of most of the country adjacent to the sections of the Alaska Highway in the Liard River area, particularly that part east of Kechika river. In 1943, the Geological Survey of Canada made a recon-naissance from Fort Nelson clown the river of that name to the Liard, thence up the latter to Hell Gate, and also up Beaver river for a distance of fifty miles. The whole of the area covered was found to be underlain by sedimentary rocks, not a single igneous dyke being seen. The British Columbia Department of Mines began reconnaissances near the highway both in and north of the drainage basin of Prophet and Muskwa rivers with a view to finding structures favourable for the accumulation of oil. In Liard River valley near the mouth of Smith river and at intervals from there clown to Devil' s Portage occur warm springs whose character and origin are not definitely' known, since they have not been investigated (21, p. 38A). Similar springs are said to occur at several localities over a broad belt extending from Muskwa river across the Liard to the Nahanni River country (26, p. 11). On Liard river below the mouth of Dease river, stratified sands, gravels, and clays of Pleistocene (?) age are constantly met with and in one or two places are underlain by sandy clays. The distribution of the latter, however, is very limited in the section cut by the river west of the Rocky mountains. The only range of these mountains that reaches the Liard is the high limestone ridge which approaches the mouth of Vents river from the southeast and then almost vanishes a few miles to the northwest of it (27, pp. 43-45). In general, the ranges of the Rockies in the area under consideration have been but little explored, but they are undoubtedly very largely sedimentary and, with the exception of some volcanics and intrusives on their western flanks, are probably almost entirely so. Unlike the high, deeply incised ranges in southern British Columbia, they dwindle in elevation north of Terminus mountain to low-wooded ridges separated by wide swampy valleys, and practically lose their identity between it and the Liard. The foothills, which, along the Liard, have a width of 38 miles (from near the mouth of Trout river to Hell Gate) are composed of a great series of alternating shales and sandstones, with some limestones, all folded closely together, which resemble those found in the foothills farther south (27, pp. 50, 19-20).

Jan 1, 1944

By M. Hashemzadeh

The efficiency of water use is a top priority for the global minerals industry, especially in regions with limited freshwater supplies. In these areas, the freshwater shortage has prompted mining companies to search for alternatives to freshwater sources. Seawater has been proven to be a potential water source for mineral beneficiation and metal extraction processes. This study compares chalcocite leaching behavior with ferric chloride to that with cupric chloride. We carried out leaching tests with a highly pure chalcocite sample in jacketed reactors under fully controlled pH and solution potential. The effect of chloride concentration, oxidant concentration, and temperature on copper extraction was quantified in both cupric and ferric chloride systems. In the ferric chloride system, increasing ferric concentration showed a positive effect on the first stage of chalcocite leaching. In the second stage, increasing temperature markedly enhanced copper extraction. In the cupric chloride system, chloride concentration presented a considerable effect on both the first and second stages of leaching, while temperature had a remarkable effect only on the second stage. The findings of this study would be beneficial to mine operations aiming to replace fresh water with seawater for heap leaching of chalcocite. INTRODUCTION Mineral processing operations/plants are normally operated adjacent to mines which are often located in remote and arid area, such as northern Chile, southern Peru and Australia with limited access to fresh water (Liu, Moran, & Vink, 2011, 2013). Water scarcity in these areas has prompted mining companies to invest in sustainable technologies to reduce the water use and/or increase the water use efficiency. One of the current sustainable approaches in mineral processing operations is to replace fresh water with seawater. Seawater is now being increasingly used for mineral beneficiation and metal extraction processes (Hernández et al., 2015). Another application of seawater could be for heap leaching of copper secondary sulfides, mainly chalcocite. However, the high concentration of chloride ion in seawater may significantly affect leaching kinetics of copper sulfide concentrates and ores (Watling et al., 2014). Therefore, it is essential to develop a fundamental understanding of the leaching of chalcocite in chloride media.

Jan 1, 2019

By Z. Y. Liu

A local additional potential model (LAPM) was developed to illustrate the role of strain rate in stress corrosion cracking (SCC) of pipelines. According to LAPM, both density and mobility of the local active spots on the steel surface, i.e., dislocation emergence points, increase linearly with strain rate. Generation of such active spots introduces an additional negative potential locally, affecting the electrochemical reaction and, consequently, the susceptibility of the steel to SCC. Electrochemical corrosion measurements, slow strain rate tests and electrochemical hydrogen permeation test were combined to demonstrate the validity of LAPM to illustrate pipeline SCC in an acidic soil solution. It is found that a maximum of the SCC susceptibility occurs at strain rate of 10-6 s1, which is associated with an enhanced hydrogen evolution due to the local additional potential (LAP) effect.

Jan 1, 2010

By Habib Zughbi, Paul Zulli

"A key step towards sustainability in iron and steelmaking is to optimise the use of raw materials and energy consumption, and consequently minimise CO2 emissions. Models based on a Process Integration (PI) approach play a key role in evaluating various scenarios and the impact of introducing changes in raw materials and operational conditions on the overall energy consumption and CO2 emissions. BlueScope uses a PI based comprehensive model for its Port Kembla Steelworks (PKSW), called the Integrated Steelworks Energy and Emissions Model (ISEEM). ISEEM is tightly coupled to the configuration of PKSW. It is based on mass and energy balances as well as thermodynamic relationships. ISEEM is a steady-state model and is used to predict overall and detailed unit-by-unit energy consumptions and CO2 emissions. It is also used for plant-based scenario modelling. This paper investigates the impact of major changes to PKSW configuration, including the shutting down of a blast furnace and cokemaking battery, on the energy consumption and CO2 emissions of the plant. It discusses some of the issues involved in updating the model and some identified opportunities."

Jan 1, 2015