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By C. Siyasiya

One of the problems that is occasionally encountered during the continuous casting of DIN 1.4003 stainless steel (hereafter referred to as 1.4003) is the side bulging effect, a problem that is generally prevalent in ferritic stainless steels. This occurs because the unconstrained narrow sides of the solidification shell are not able to withstand the ferrostatic pressure once the strand has emerged from the mould. Coupled with side bulging, there is strand width variation at high temperatures, i.e. when the steel is in the ferrite-austenite dual phase region. Both of these dimensional changes to the slab profile create some processing problems in subsequent hot rolling operations when unacceptable width variations are encountered. The strength of the solidification shell and its ability to withstand the ferrostatic pressure during continuous casting is dependent on its thickness and phase composition when exiting from the mould up to a few metres downstream. From the study of the high temperature metallurgical behaviour of this steel, it was observed that a thicker solidification shell when exiting from the mould and a higher austenite volume fraction in the steel would be favourable for the reduction of the side bulging effect during continuous casting. It was also found that as long as the d-ferrite to austenite phase ratio keeps fluctuating due to variations in chemical composition and process control in the dual phase region from cast to cast, the strand width variation problem would probably persist. The remedy to this effect lies in more strict chemical composition and process control during continuous casting of this steel. The hot ductility experiments revealed that 1.4003 exhibits good hot ductility in the strand straightening temperature range with a minimum of 75 per cent reduction in area and this was attributed to the high volume fraction of ferrite (0.2 to 0.4) in the steel. This would provide a remedy to side bulging by increasing the secondary cooling rate of the strand in order to form a thicker solidification shell without necessarily risking transverse cracking and other surface defects during unbending. Keywords: side wall bulging, resistance bending moment, applied bending moment, ferrostatic pressure.

Jan 1, 2005

By M. T. Shehata, R. W. Revie, M. Elboujdaini

Environmentally assisted cracks in linepipe steels are initiated either as a result of stresses in combination with environmental effects, as in stress corrosion cracking (SCC), or as a result of trapped hydrogen in the steel, as in hydrogen-induced cracking (HIC). To understand better the mechanism of the crack initiation process, key metallurgical and environmental elements that can affect the cracking phenomena were investigated and are reviewed in this paper. The complexity of both cracking phenomena results from the dependence of SCC and HIC on multiple metallurgical, mechanical, and environmental parameters that may all influence both crack initiation and propagation; e.g., composition, microstructure and non-metallic inclusions in the steel, applied stress, water chemistry in the field, and ionic concentrations in the groundwater near the pipe surface to name a few for SCC. In addition, for HIC phenomena, one can add the concentration of H2S in the fluids transported in the pipe as well as concentration of CO2, pH, etc. In this paper, cracking of linepipe steels is analyzed critically, with particular attention to the crack initiation process. The paper is divided into two parts: The first part covers SCC and the second covers HIC.

Jan 1, 2005

Start with your assessment of the minerals business —domestic mining as well as operational and consulting perspectives. As a third generation miner, I have been living the mining business for as long as I can remember. I have watched commodity prices produce boom and bust cycles in places like Price, Utah (coal), Douglas, Arizona (copper) and Eureka, Nevada (gold). It is unsettling to see how our industry has fluctuated, but it always seems to rebound if you can stick out the down cycles. However, our most recent dip in the cycle was, in my opinion, characteristically and permanently different. In the past, when prices went south, people hunkered down and waited out the cycle until things came back, much the same as they had every other time. Not this time. This time, we saw a consolidation of the industry in proportions never seen before. Mega-mergers like Exxon-Mobil, Phelps Dodge-Cyprus and Newmont-Normandy have changed the complexion of our industry forever. And that is true not just of the mining companies; it happened across the supporting business lines as well. As a midsized niche engineering and environmental service provider to the mining industry, companies like mine are few and far between these days. The lean cycle saw many of the small and midsized providers get gobbled up by consulting giants like URS and TetraTech. The mentality of a mega-company, whether a commodity producer or a goods or service provider, is different than that of their small- and medium-sized counterparts.

Jan 1, 2005

By S Sims, A Stradl, G Hope, B Lacouture

Column flotation cells have been installed in numerous base metal operations around the world. The majority of these cells utilise conventional air-only spargers to introduce air into the bottom of the column. The recent development of instruments to measure the bubble characteristics in these columns has provided a renewed understanding of column behaviour. These new tools provided insight into why the columns at Red Dog Mine had never performed up to expectations. After efforts to optimise the spargers failed to substantially change the bubble size and air efficiency, alternate sparger systems were investigated. The Metso Minerals CISA Microcel sparger system appeared promising and was selected for a full-scale plant trial. The Microcel sparger system was originally developed for the coal industry at the Virginia Centre for Coal and Minerals Processing. In October 2003, a Microcel was retrofitted into one of two 3.66 m diameter flotation columns in the zinc retreat circuit at Red Dog Mine. The operation of the two different sparger systems in parallel allowed a detailed comparison. This paper discusses the performance of the Microcel based on the data collected during several detailed surveys. Bubble size measurements carried out in the pulp zone using the McGill University bubble viewer showed a significant difference in bubble size. The mean Sauter diameter of the bubbles decreased from 3.4 mm for the jetting-type sparger to 1.9 mm for the Microcel sparger. The overall recovery and the recovery by size fraction for both valuable and gangue minerals were compared. Paired t-tests demonstrated that the Microcel column produced a higher concentrate grade (0.6 per cent zinc absolute) and a higher unit recovery (2.8 per cent zinc absolute) than the existing Canadian Process Technologies Inc (CPT) SlamJet column. These improvements provided a payback period of 1.5 months for the $109 000 investment.

Jan 1, 2005

By J. W. Coetzee, H. E. Deist

Carbon-in-pulp (CIP) and Carbon-in-leach (CIL) processes are used extensively in the gold mining sector to recover aurocyanide from solution. This paper discusses the modelling of these operations, using various simplifying assumptions, in order to simulate the effect of changing operating conditions on the dynamics of the system. It is assumed that the adsorption and leaching rates are a function of concentration difference between the source phase and recipient phase. The simulation was set up using Matlab's Simulink interface. Plant variables are solved using a medium scale Newtonian search algorithm in Matlab, where the differences between the actual and predicted plant outputs are minimized on a continuous time-line.

Jan 1, 2005

By Andrey V. Tarasov

To carry out a physicochemical substantiation of a transition to ?soft? modes of reduction of calcine obtained by desulfurizing roasting of nickel concentrate produced as a result of copper-nickel converter matte separation in a nickel anode production circuit, an analysis has been conducted of the macrokinetic behavior of actual calcine samples in the presence of gaseous H2-CO mixtures and solid reductant additives. Within a temperature range of 900°C to 1100°C the main regularities typical of the calcine reduction process with individual gases (H2, CO) also take place when using a gaseous mixture. Under the conditions of low-temperature (900°C to 1000°C) nickel oxide reduction with products of fuel oil conversion in the presence of coke, the role of the latter is insignificant from the technological viewpoint. As a result of the present investigations, we have obtained analytical expressions of macrokinetic parameters of the reaction interaction within the [NiO] calcine-H2-CO-C-CO2-H2O-O2-N2 system.

Jan 1, 2005

It is well known that the electrochemical precipitation of metals from aqueous solutions is conducted by the electrochemical standard potential scale. This scale indicates the order of nobility of different metals. Consequently, the standard potential scale shows the nocivity of metals when they are present as impurities in aqueous solutions containing metals. In the hydrometallurgy of cobalt, nickel and zinc are co-deposited during cobalt electrodeposition. Nickel has almost the same chemical, physical and electro-chemical properties as cobalt. Furthermore, the electrochemical potential of nickel is relatively higher than that of cobalt. For this reason nickel is preferentially reduced at the cathode in the presence of cobalt. The presence of small amounts of zinc in solution leads to contamination of cobalt electrowon. In spite of its lower electrochemical potential in comparison to cobalt, zinc is reduced on the cathode because of its higher hydrogen-overvoltage. But, in the hydrometallurgy of zinc, small amounts of cobalt present solution will contaminate the zinc reduced at the cathode. This is easily explained by the fact that cobalt is more electropositive than zinc. The co-deposition mechanism of sulphur at the cathode is not yet well understood. Great attention has to be paid to the mechanism of co-deposition of sulphur during cobalt electrolysis. This work aimed to investigate the influence of some parameters on the co-deposition of nickel, zinc and sulphur during cobalt electrowinning. The following parameters have been investigated: Co2+concentration in the electrolyte, current density and ammonium sulphate (NH4)2SO4additions. It has been established that important nickel, zinc and sulphur co-deposition takes place at relatively low Co2+ concentration in solution. The behaviour of these elements with regard to the cathodic phenomena has been established.

Jan 1, 2005

"The link between ore texture and mineral liberation has previously been established at a microscopic scale. To construct ore texture models that can be used in mining applications requires this relationship to be retained at a significantly larger scale. This is initially dealt with by finding a basic set of microtextures that form the elements of the ore textures at the next larger mesoscopic scale, simulating these mesotextures at a fine scale, then changing the support of the mesotexture simulations to generate the expected mining block/stope mesotexture distributions. Thus, a mutually exclusive and exhaustive set of spatially locatable mesotextures can be used to fully characterize the metallurgical properties of in situ material.A method that generates expected distributions of mesotextures for any mining block size or shape is proposed, and includes: (1) characterizing the spatial correlation of the set of mesotextures with a single covariance function; (2) generating multiple simulations of mesotextures at a fine scale; and (3) using the simulations at a fine scale to generate the expected mining block/stope mesotexture distributions. A case study, using the George Fisher sediment-hosted base metal deposit in Queensland Queensland, Australia, is developed to demonstrate the proposed methodology as well as show the inadequacy of off-the-shelf approaches.Mining-scale texture models can be used to improve the in situ discrimination of ore from waste by exploiting the joint spatial variability of grades and textures to quantify the expected metal recovery of in situ material, then calculate local marginal cut-off grades. An artificial case study is presented to demonstrate the changes in ore/waste selection when considering ore texture models compared to constant metal recoveries."

Jan 1, 2005

By Wen-Ming Chien

Keywords: AN-KN Phase Transition, Lattice Parameters of AN-KN, X-ray Diffraction The lattice parameters of the low and high temperature phase of KNO3-rich (in NH4NO3) solid solutions have been determined by the X-ray diffraction method. The low temperature single KNO3 phase (KN II) are from 92%-100% KNO3 in NH4NO3 composition range and from room temperature to 393 K showing in X-ray diffraction patterns. The high temperature KNO3 phase (KN I) showed very broad composition range between 20% to 100% KNO3. The lattice parameters of KNO3-rich (KN II and KN I) solid solutions have been calculated at different temperature range. The volumes of orthorhombic KN II phase decrease from 0.3208(3) to 0.3195(3) nm³ at the room temperature as the compositions increase from 95% to 100% KNO3. The lattice constants of the hexagonal KN I phase show that there is no significant change in a-direction when the temperature increases. Details X-ray results and lattice expansion equations during heating will be presented.

Jan 1, 2005

By Robert S. Thomas, Bernard M. Tarralle, Nasser Massoudi

"The Commonwealth of Virginia is restoring and expanding its Capitol of great historic significance. Designed by Thomas Jefferson in 1785, it is the second oldest Capitol building in the United States. The building expansion required excavations immediately adjacent to its South Portico. The building, which rests on shallow brick footings, is very sensitive to any disturbance caused by construction and excavation. A comprehensive and secure plan of operations was devised by the design team to ensure that this national monument remains unharmed by the new construction. Various construction techniques were implemented to satisfy the strict movement goal of 0.25 inch and distortion of U2000. They consisted of jet grout columns to stabilize the upper soils, compensation grouting for future foundation leveling, a tied-back reinforced concrete diaphragm wall for excavation retention and foundations, and realtime instrumentation for monitoring. This paper describes the design approach for the retention system, providing information on the various construction phases and techn iques, and reports on the movements recorded by the real-time monitoring system during the course of the project. At the time of this manuscript preparation, and the deep excavation complete to final grade, the results indicate that the extremely restrictive building movement criteria have been met. The success can be credited to detailed design, close cooperation among the project team, prudent construction methods, and real-time monitoring. INTRODUCTIONThe Commonwealth of Virginia is undertaking a comprehensive renovation and expansion of the Virginia Capitol building located in Richmond, Virginia. The Capitol building was designed by Thomas Jefferson in 1785, with construction of the original building starting the same year. The Capitol building was designated a National Historic Landmark in 1960 and was listed on the National Register of Historic Places in 1966.A part of the comprehensive renovation and expansion of the Capitol is a 25,000-square foot, two-level subterranean extension on the south side of the Capitol building, which will serve as a new Visitor Center and public entrance for the Capitol. Deep excavations were required for the construction of the new Visitor Center. The excavation required a permanent retention system to accommodate an approximately 40- foot deep excavation."

Jan 1, 2005

By Mary Ann Bennett, Val Nichols, Colleen Proctor

"In 1997 when Royal Oak Mines Inc. went into receivership, the mineral processing technicians (mill operators) who had been working at Giant Mine in Yellowknife, Northwest Territories for most of their career walked out with no credentials to serve as testimony of their knowledge and skills.As a result of new diamond mining activity and the establishment of socio-economic agreements, mining industry representatives approached the Department of Education, Culture and Employment (ECE), Government of the Northwest Territories, in 1999. They requested support and direction to promote training and recognition for mineral processing technicians at BHP’s (BHP Diamonds Inc.) Ekati mine. ECE recommended the development of occupational standards and certification.This paper describes the development process and end products that resulted from this collaborative project between industry, government and education. In addition, industry representatives involved in the project share their views on the development process and the benefits of standards and certification.The conclusion invites industry members to support national occupational standards and certification with their associated benefits: standardized training in the workplace and institutions, proof of competence for hiring, recognition of prior learning, and a nationally and internationally recognized credential.INTRODUCTIONSwiftly changing labour market demands are nothing new in the North. The fur trade and mineral discoveries have brought employment to workers in a feast and famine cycle for decades. In the late 1990s, the Giant, Con, Lupin, Polaris and Nanasivik mines were nearing the end of productive runs. Many experienced workers found that without credentials, they had no proof of their abilities to offer prospective employers."

Jan 1, 2005

By Q Liu

Open stoping is one of the widely adopted methods in underground bulk mining. In this method, fanned or parallel holes are often drilled from a top sill down to a sublevel in the ore zone and blasted ring by ring into a stope for excavation. A mass stope blast may involve blasting rock from multi-level drift rounds and displacing the muck to specific locations in order to allow safe and easy access for ore removal. This paper presents a strategic mass stope blast that took place at a large lead and zinc underground mine in eastern Canada. The blast consisted of more than 800 holes drilled in six blocks from three different sublevels. The challenge lay in the control of ground vibration and muck movement using precise timing to complete the blasting within 6.5 seconds. During this time span, sufficient voids were created in each level to allow the muck to move from the upper to the lower levels in sequential order across the six mining blocks without bridging. This paper describes stope blast simulations using a discrete element computer code for modeling blast-induced rock displacement as well as the application of electronic detonators. These detonators provided the means to accomplish the desired firing sequence including a drop raise blast at the start of the mass blast. The modelling concept is also described in the paper.

Jan 1, 2005

Coal mining legislation makes frequent reference to æSafety Management SystemsÆ but there is a chronic shortage of useful guidance material as to how these might be applied to hazardous exposures. Several studies have indicated that for each death that is reported as a result of an industrial æaccidentÆ, there are five deaths that caused by occupational exposures. Because the deaths from occupational exposures do not occur on site and often well after employment has ceased, they are generally unreported. Improved access to mortality data from coroners, the Australian Institute of Health and Welfare and superannuation service providers (early claims from death and total permanent disability), has given rise to some analysis of death and disability data that provides evidence that there are emerging opportunities to develop and improve safety management systems for hazardous occupational exposures. Issues explored include how safety management systems might be developed in relation to dusts and chemicals and other hazardous exposures to ensure the risk of disorders with long latency periods are reliably assessed and the exposures effectively managed. The current standards and guidelines which refer to safety management systems in general or to management of exposure related hazards are examined. Many standards are based on dose-response studies that provide for an acceptable percentage of workers to suffer adverse health outcomes. An alternative management system might be to apply dose-response relations to health surveillance to identify æat riskÆ individuals and effectively manage health and related safety risk at an early stage.

Jan 1, 2005

Conditional simulation can be used to determine the probabilities of block iron-grades being above selected cut-offs. However, there are much faster alternatives that can produce acceptable results. In this paper blasthole data from a selected area of Joffre Member hosted ore of the Brockman Iron Formation at the Mt Whaleback orebody is used as the basis of a case study to assess alternatives to simulation. Iron grade, in per cent, is interpolated from a blasthole dataset into a block model using ordinary kriging. Samples are then removed from this blasthole dataset to produce data subsets. A complete distribution of iron grades for points or blocks is obtained utilising the data subsets and the following techniques: conditional simulation, median indicator kriging, the probability from conditional expectation and confidence intervals attached to the estimation of blocks in the framework of the discrete Gaussian model. The complete blasthole dataset is considered to represent the true iron grades at sample point support while the ordinary kriging estimate derived from these samples is considered to represent the true block grades. The distributions obtained from point estimates, block estimates and simulations are compared to each other and to the true estimates of iron grades using graphs and statistics. The conditional expectation technique reproduced the results obtained from conditional simulation extremely well and it is a viable alternative to simulation at point support. At block support the confidence intervals technique reproduced the results of the conditional simulation more closely than the median indicator kriging and in the data subsets tested the confidence intervals technique actually reproduced the true grade distribution more closely than the conditional simulation.

Jan 1, 2005

By J P. Moodie

Recent trends in flotation technology are briefly reviewed. These show that considerable development has been made as the operators, suppliers and technologists have responded to the challenges of the industry. Most of these advances have been based on empirical and phenomenological methods. There is a considerable opportunity to make further advances through a more fundamental, scientific approach. Some of this work is discussed and, although progress is being made on this front, industrial uptake has been somewhat slow. A number of specific issues facing the industry are discussed.

Jan 1, 2005

By H. Tan

The effect of carbonaceous matter on gold extraction was investigated in cyanide systems with pure gold as well as pre-robbing sulfide gold ores. Auger studies demonstrated that the carbonaceous matter preferentially smeared on iron sulfide rather than aluminosilicate surfaces during wet or dry grinding. During mechanically mixed leaching, coating of sulfides and silicates and stripping of carbonaceous matter occurred simultaneously. TEM and XPS studies indicated preferential coating in the form of elemental (graphitic) carbon at the edges and the defect sites of particles. Interestingly, carbonaceous matter extracted from the gold ore was predominantly graphite and not preg-robbing in a solution with a high KCN concentration. However, the carbonaceous coating had a significantly detrimental effect on gold dissolution when gold was pre-ground with the gold ore. Artificial coating on gold surfaces with the natural carbonaceous matter from the ore was also found to substantially retard gold dissolution. With the addition of the natural carbonaceous matter from the gold ore, gold extraction from two non preg-robbing sulfide gold ores was inhibited owing to carbonaceous coating. The presence of carbonaceous matter significantly reduced the current density for gold oxidation and increased the current density for pyrite oxidation. This could explain the fact that carbonaceous coating hindered gold dissolution while enhanced sulfide preg-robbing.

Jan 1, 2005

By Günter Huber, Bruno Mattle, Helmut Westermayr, Daniel Spöndlin, Max John, Nejad Ayaydin

PROJECT DESCRIPTION Alignment The Strenger Tunnel forms part of the S16 four-lane expressway between Landeckand Bludenz. The construction of this important East-West connection started in 1973with the Arlberg Road Tunnel as its key constituent. Beginning in 1992, solutions for the section between Pians and Flirsch were investigated. Efforts to conserve nature and to avoid potential avalanche and landslide areas led to a solution detouring the villages in the Stanz valley. The starting points were predetermind by the intersections at Pians in the East and at Flirsch in the West. As a result of the expected traffic load and the comparatively high gradient of 2.9%, both one-way, two-lane tubes were constructed at once. The north tube is 5.851 m long, the south tube 5.775 m, see Figure 1. Layout of Tunnel Cross-Section The tunnel cross-section was determined by 2 × 3.75 m wide, 4.70 m high roadways, two sidewalks and sufficient space for two fans above the clearance

Jan 1, 2005

By D. Berkley

"Economic and environmental constraints drive more and more industrial organizations in using energy management as one of the means for addressing these issues. The recent increase in energy price could even make energy management a matter of “survival” in some cases.Experience shows that energy management is successful when the energy is managed like a resource, i.e. continuously, systematically, and in an organized manner, not like an expense, paying the bills once a month. This requires the development and implementation of an energy management program (EMP).This paper outlines some of the barriers, keys to success, components, and approaches to a successful energy management program, plant- or corporation-wide."

Jan 1, 2005

As students progress further into a degree, the decision of vocation selection, and even more importantly û securing employment in a particular industry sector, can become quite daunting. However, with a little initiative, students can overcome these issues by not only researching what employment opportunities exist, but by applying for summer vacation employment. Undergraduate vacation employment, especially with a world-leading hydrometallurgy research organisation such as the Parker Centre, can dramatically alter a studentÆs perspective of particular industries and possibly even alter their selection of vocation pursuits upon graduating. Students can also use vacation employment to enhance their networking capabilities, technical skills and knowledge by dealing with challenging new topics such as sulfur dioxide leaching, which is also discussed in this article.

Jan 1, 2005

By William H. Walton, Clyde N. Baker Jr., Darren S. Diehm

"A 51-story concrete core and steel frame commercial office tower was recently constructed on the site of the former US Gypsum building in downtown Chicago, Illinois, USA The structure foundation reused several caissons from the demolished US Gypsum building supplemented with new belled caissons bearing on silty clay hardpan. Extensive in-situ pressuremeter testing was performed during the geotechnical investigation to determine allowable bearing capacity and better estimate building settlements. Problems during foundation construction along the south side of the building frame required remediation of two caissons. One caisson was supplemented with micropiles, while the second caisson was abandoned and replaced with a straight-shaft rock socketed caisson. To determine the effectiveness of the repairs, the building foundation settlements were monitored during construction.IntroductionIn 2001, The John Buck Company began development of a new office tower at the southeast corner of West Monroe Street and South Wacker Drive in Chicago, Illinois. The site was formerly occupied by the 18-story US Gypsum (USG) building. Mr. Clyde N. Baker, Jr. (Senior Principal at STS Consultants, Ltd .) served as the foundation engineer for USG which was completed in 1962. The building was founded on a forest of belled caissons bearing at elevation -56 Chicago City Datum (CCD). For reference, the ground surface at Upper Wacker Drive is approximately elevation +20 CCD. The bearing material was a hard silty clay, locally described as Chicago Hardpan. The foundation caissons were designed using an allowable bearing pressure of 16 ksf (766 kPa). In 1996, the USG superstructure was razed, and the three-level basement was converted to an underground parking ramp.South Wacker DevelopmentThe 51-story high-rise building was completed in 2005 with a structural height of 681 feet (208 m), and an internal space of more than 1,000,000 square feet (93 ,000 square meter). The typical floor size is 27, 700 square feet (2, 570 square meter). Renderings of the building are provided in Figures 1 and 2. The largest single tenant is the accounting firm of Deloitte & Touche, which occupies roughly 45% of the building space with over 3,000 employees."

Jan 1, 2005