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By E. Ferguson

In evaluating refractory designs for cast house applications, thermal calculations are frequently performed to determine cold face shell temperatures, temperature profiles and metal freeze plane locations within the refractory layer, and heat loss in the steady state condition. A problem arises when looking at molten metal transport crucible designs in that these structures are usually operating under non-steady state conditions throughout their production cycle. Because the molten metal temperature varies with time, and material properties such as thermal conductivity are temperature dependant, mathematical solutions are at best... complicated. This paper presents a relatively simple, iterative solution, that can be set up on a standard computer spreadsheet program, to calculate heat transfer in non-steady state conditions. These calculations can provide curves for (1) molten metal temperature vs time and (2) cumulative heat loss vs time, given variable starting conditions, to aid in the evaluation of molten metal transfer crucible refractory designs.

Jan 1, 2004

By Noel W. Kirshenbaum

Difficulties and costs of transport markedly affect Canadian mineral producers because of distance from markets, weather conditions and rugged terrain. The chemical and physical nature of sulphide concentrates presents additional difficulties in handling and transport, resulting in higher costs which are ultimately borne by the mineowner. Troublesome properties include the thixo-tropic character of wet concentrates, freezing, susceptibility to autogenous heating, and fine particle size causing spillage and dusting losses. Canadian mineowners and shippers must contend with these problems and with stringent regulations governing the maritime shipping of concentrates. A "systems approach," in which complementary techniques in materials preparation, handling and transport are integrated, could reduce freight costs and losses for those selling concentrates, facilitate operations for those carrying and handling them and, in some cases, improve metallurgical processes in smelters receiving them.

Jan 1, 1969

By M. R. Khalesi, S. Bellec, C. Bazin, D. Hodouin

Batch grinding tests conducted on a gold ore indicated that gold is not randomly distributed within the size fractions of the ground ore. Since gold leaching performances were found to be dependent of the size of the gold carrying particles an integrated gold ore grinding-leaching simulator should incorporate a method to predict the gold size distribution of a ground ore. The paper describes the results obtained from batch grinding tests showing the non random distribution of gold within the size intervals of a ground ore and the initial developments of a grinding model to predict the gold size distribution in a batch grinding product.

Jan 1, 2011

By E. J. Marcotte

"BRIEF DESCRIPTION OF GRINDING CIRCUITCrushed ore at -5/ 16 in. is delivered by a conveyor system from the crushing plant to two 1250 ton fine ore bins. The ore is transferred from each bin by a 30 in. feeder conveyor belt, operated by a Link Belt P.I. V. (variable speed) drive, to a 24 in. conveyor that feeds the 8 x 10 Allis Chalmers rod mill.The rod mill discharges to a common mill discharge pump box. Three 6 x 6 SRL pumps are employed to pump the combined mill discharge pulp to a common distributor box which distributes the feed to two of the three Kreb D lSB cyclones in each of the two banks at a hydraulic pressure of 6 psi.The cyclone overflow at a specific gravity of 1. 25 (i.e. 32% solids) is transferred by gravity to two revolving chip screens for wood chip removal and from there to a pump box. Two 5 x 5 SRL pumps feed the pulp to the thickeners. The underflow from the cyclones is fed to two 8 x 8 Allis Chalmers ball mills which discharge to the common mill discharge pump box. Thus, a closed circuit is formed between the ball mills and their respective bank of cyclones. The circulating load as most recently calculated is 262%."

Jan 1, 1966

By J. L. Nebreda, Z. Fan, J. B. Patel

"A380 alloy has been widely employed to produce thin-wall components via high pressure die casting (HPDC). During HPDC processing, there is a significant problem of property variation even with the very stable and precision automated casting procedure. The enlarged variation lowers the component performance and affects the steady and uniform property distribution along the whole component. In this study, high shear melt conditioning technology was developed and applied to the melt prior to pouring into the shot sleeve. Experimental results show that with application of intensive melt shearing, the variation of elongation was decreased from 21.8to 13.9%, and yield strength variation was reduced from5.5to 3.6%. The improved property variation is attributed to enhanced nucleation both in shot sleeve and the die-cavity, and to the improved distribution of porosity and secondary phases as a benefit of high shear induced grain refinement. With application of high shear, large number of the Spinel phase (MgAl2O4) particles with double size distribution in average diameter of 80and 300nm were formed. Due to the good orientation relationship and small misfit between alpha Al and MgAl2O4, the particles act as the effective nuclei in shot sleeve and die cavity, respectively.INTRODUCTIONA380 alloy had been widely used for produce automotive components by cold chamber high pressure die casting(HPDC) processing, due to its relative good mechanical properties and cast ability performance, and more important most of A380 ingots were produced by recycled Al alloys. Therefore, to promote utility of A380 will contribute to reducing emission of CO2and to the lightweight of automotive industry as well. When cold chamber HPDC was employed to produce the components, the mechanical properties of A380 alloy always have a distribution range (named variation herein), or in other words the properties were not stable. The reason was ascribed to the typical solidification characteristics occurred in HPDC processing. During HPDC processing, there are three steps of melt movement. The first step is that the melt was poured into shot sleeve at temperature of about 680°C, in which shot sleeve was preheated by few shots of melt filling, or by heater. During step one, the first solidification of melt was happened in shot sleeve and about 20% solid made of coarse a-Al grains was formed(Li, Xiong, & Guo, 2016).Such kind of grains will retain in the final products and deteriorate the properties variation. The second step is that the melt was forced moving forward slowly by plunger at about 0.2–0.3m/s until the liquid melt front to the inner gate of mold. The third step is that the melt moved very fast to complete the filling of die cavity and refilling the solidification shrinkage by fast movement of plunger about 2–3m/s. The second solidification was occurred in die cavity and fine a-Al grains will be formed by high cooling rate at about 500–1000°C/s. From the solidification point of view, the grain size was dominated by nucleation and growth. When HPDC was employed to produce components, the melt quality becomes the priority factor to control the solidification process as the other casting parameters were kept at the same."

Jan 1, 2018

By J. A. Drozdiak, W. Tse, P. P. Rosario

"In a recent publication (SAG 2015), we presented a non-conventional high pressure grinding roll (HPGR)-ball mill circuit as a lower capital cost alternative to the “standard” HPGR circuit. The circuit was designed for the treatment of a hard ore and relatively high tonnage (50,000 t/d). That paper provided details such as flowsheets, layouts, and equipment lists for the two options and compared their calculated capital costs demonstrating significant savings for the proposed circuit. This paper extends the analysis to a third option, a traditional semi-autogenous ball crushing circuit, giving the same level of details and now including the operating cost estimates for all three options for a more comprehensive analysis. Moreover, this work also provides information about the strengths and weaknesses of the non-conventional HPGR circuit when compared to the “standard” HPGR option.This study demonstrates that the proposed non-conventional HPGR-based circuit not only provides a lower overall capital costs for the project if compared to a “standard” HPGR circuit but also brings the capital cost to the level of the traditional semi-autogenous grinding (SAG)-ball mill circuits. In addition, the innovative HPGR circuit provides similar operational cost savings of the “standard” HPGR and thus a significant advantage when compared to the SAG option. With the current capital cost sensitivity for most greenfield projects, the proposed alternative circuit should help make HPGR-based circuits more competitive and thus promote the utilization of a technology that enables higher energy efficiency and reduced greenhouse gas emissions. INTRODUCTIONThe application of high pressure grinding roll (HPGR) technology in comminution circuits is well established for the processing of cement, diamonds and iron ore (Broeckmann & Gardula, 2005), and over the past 10–15 years, this technology has slowly been applied to hard ores in high-tonnage precious and base metal operations. Unfortunately, under the current economic climate, the ability to finance large capital projects has become very difficult and companies tend to have an easier time securing funding if the capital expenditures (CAPEX) are low with a proven process method. The traditional semi-autogenous grinding (SAG) mill / ball mill circuits easily fit into this mould, having been installed in countless plants around the world over the past 30 years with relatively low capital requirements. In contrast, it has been well-documented that HPGR-based circuits are capital intensive with complex material handling systems (Seidel, Logan, LeVier, & Veillette, 2006). Although these circuits benefit from reduced operating costs with the increase in energy efficiency and the elimination of steel grinding media (Rosario, Boyd, & Grundy, 2009), if the company is unable to secure financing to build the plant, these advantages remain out of reach. With the current trend to retrofit existing SAG circuits with a secondary crushing circuit to achieve design throughput, the opportunity to circumvent this gross inefficiency by making HPGR-based circuits more capital friendly would greatly benefit the industry."

Jan 1, 2016

By C. R. Edwards, D. R. G. Watt

"Equity Silver Mines Ltd. a member of the Placer Development group of companies operates Canada's largest silver mine near Houston in north-central British Columbia. Initially, the silver-gold-copper flotation concentrate contained excessive levels of antimony and arsenic, so a leach process was installed to remove undesirable metals and provide improved smelter terms for the leached concentrate. The leach plant which has been fully described elsewhere (1, 2, 3), was forced by deteriorating process economics to shut down in April 1984. Equipment was mothballed and alternate uses sought.The Endako Mines Division of Placer Development Limited, located some 150 kilometres east of the Equity mine site, shut down its molybdenite mining and milling facilities in the spring of 1982. Endako has continued to produce molybdic oxide (molybdenum trioxide or MTO) via intermittent roaster runs, and also a high purity, lubricant grade molybdenum disulfide in the Ultrapure Plant. With the steel industry in the doldrums, molybdenum chemicals present an alternate and growing potential for molybdenum sales. In 1982 Placer Development began testing this market. Molybdenum chemicals were produced in the United States on a toll basis using Endako MTO as process feed. The transfer of this production to Canada was being considered when Equity's leach plant shut down, and it was noted that most of the equipment and skills necessary could be provided by the leach plant. See Figure 1.A careful investigation of process requirements was completed by engineering and production staff at Equity and Endako. A provisional capital and operating cost estimate was made, and it was decided to perform a test run during July 1984. There were strong reasons to proceed with this project. A positive cash flow was expected for both Endako and Equity. Endako would have product to continue to expand in the molybdenum chemicals market with the added selling point that now the complete production process would be under direct control of Placer Development companies. Equity would further benefit since a portion of the leach plant would continue in operation thus maintaining and exercising our hydrometallurgical engineering and operating skills. Finally, Equity would have a base from which to search out other processes adaptable to the idled leach plant equipment."

Jan 1, 1986

By F. Liu, H. A. Meier, D. M. Valiveti, P. A. Gordon

Hydraulic fracture is a frequently used technique in the Oil and Gas industry to create high permeability pathways for extraction of hydrocarbons. Numerical simulation of this method poses challenges such as representation of 3D fractures, propagation of randomly oriented fractures in 3D media, enabling fluid leak-off from fracture to poro-elastic medium. We have developed a numerical model using the Generalized Finite Element Method (GFEM) to simulate fluid driven fracture in a poro-elastic medium that addresses these challenges. In the GFEM framework, special enrichment functions are used to augment the solution space in the displacement and pore-pressure fields in order to accurately capture the response in the vicinity of the fracture. Adaptive refinement of the finite element mesh is also employed to facilitate accurate and efficient solution of the model. Our model fully couples fluid flow in the fracture, represented with the lubrication approximation, to the geo-mechanical behavior of the bulk poroelastic rock, comprised of an elastic rock skeleton saturated with fluid. Fracturing fluid exerts traction on the fracture surface and is also allowed to leak-off into the poroelastic medium using a transfer function approach. Stress intensity factors (SIFs) are evaluated based on the Contour Integral Method, accounting for the fluid pressure on the fracture surface. The SIFs are used to govern a full 3-D evolution of the fracture. Verification of the model is performed for known behaviors for the poroelastic response and fluid flow in the fracture.

Jan 1, 2015

By L. W. Krahenbil

The programmable Logic Controller (PLC), at its present stage of evolution, is now considered as a mature control system. The PLC combines the solid-state reliability of hardwired logic and computer control systems with the simplicity of a relay ladder logic. Relay symbolic programming through a function-oriented keyboard provides a means which plant personnel can easily become accustomed to work with. In a large coal facility, it is shown that the control engineer can provide improved control flexibility with the advanced capabilities of the PLC.

Jan 1, 1979

By T. E. Morimoto

Summary The Research Council of Alberta has made a series of tests with the cyclone washer to investigate the influence of the following operating variables: underflow apex diameter, .specific gravity of medium, pulp ratio, density distribution of the feed, and size analysis of the feed. The results obtained for all the variables studied, except size analysis of the feed, are included in this paper. The tests were made with smaller underflow apex diameters and lower specific gravity .suspensions than have been recommended by Cerchar for the sharpest separations. However, what is considered to be sufficiently good cleaning was accomplished with a suspension of 1.30 specific gravity and an underflow to overflow diameter ratio of 0.56. It was found that the sharpness of separation was not affected appreciably by variations in specific gravity of suspension or underflow apex diameter provided that the density of separation was within the normal range of washery operation. Cyclone performance was not too adversely affected by decreasing the pulp ratio. The minimum figure which gave reasonable separation was 4 to 1. The tests with various density distributions of feed revealed .that the degree of washing difficulty had no detrimental effect on the .sharpness of separation given by the cyclone. Introduction A major problem of the bituminous coal industry today is that of reducing the ash content of the finer sizes (minus 1/4-inch) of coal. This problem is particularly acute in Alberta, where, because of tectonic movement subsequent to deposition, the coals have been rendered friable, and bands of impurities have been intimately mixed with the clean material. As a consequence, most Alberta coals, as mined, contain a large proportion of fines and have a high inherent mineral-matter content. The advent of mechanized mining and stripping operations ?has further aggravated this problem.

Jan 1, 1952

By S. Dominguez, E. Gebrehiwot, S. Richardson, S. Sandoval

Copper electrowinning/electrorefining (EW/ER) is powered by direct current (DC) rectifiers that typically generate 30,000 to 70,000 amps and a bus-bus voltage of 200 to 500 volts DC. Tankhouses are designed so that DC current flows through “cell lines” which contain individual EW/ER cells electrically connected in series. Electrolyte composed of copper sulfate and sulfuric acid in water forms the “liquid conductor” that connects the metallic conductors in this circuit. In this setting, stray current is a DC current that strays from and therefore bypasses the tankhouse circuit by finding a path to ground, often through the electrolyte in pipelines that feed into and discharge from the cells, or through dried electrolyte (i.e. sulfate), which is also electrically conductive. Tankhouse workers can be exposed to shock hazards if they become part of a stray current path to ground. This presentation details examples of stray current shock hazards in electrolytic tankhouses and provides voltage and amperage measurements associated with stray current in these examples. A review of critical safety controls in EW/ER tankhouses that will mitigate the risk of employee shock from stray current is also provided. INTRODUCTION Electrolytic tankhouses are designed to deliver relatively large amperages of DC current to a series of electrolytic cells in which copper is plated out of solution using the classic anode-cathode pair geometry within each cell. Electrolyte is the “liquid conductor” that transfers current in between the metallic conductors of the cell. The metallic conductors include inter-cell copper bus bars and the anodes and cathodes themselves. It is sometimes forgotten that electrolyte as a conductor is capable of delivering DC current outside the designed circuit of a tankhouse. Stray current is a DC current that strays from the tankhouse electrical circuit by finding a path to follow other than the designed path. Safety becomes a concern when there is a risk of an employee becoming part of an accidental stray current path, thereby suffering an electrical shock. In 2016, Freeport-McMoRan (FMI) suffered a fatality at one of its copper electrowinning tankhouses. The forensic analysis concluded that stray current from the tankhouse rectifier contributed to the fatality. An employee accidentally fell into contact with a metal flange at the end of an HDPE pipe that was collecting cell overflow electrolyte from the tankhouse. DC current passed through the employee to ground, creating a shock that was judged to contribute to his death. The situation was exasperated because the employee was unconscious, and therefore was exposed to the stray current for several minutes before being found. In addition, the employee’s clothing was saturated with liquid, and the employee was found kneeling in puddled liquid on the ground. FMI immediately began an investigation into the root cause of the stray current that was measured at the scene. Sufficient electrolyte had accumulated in the HDPE pipe such that a continuous path was formed between it and electrolyte that was continuously overflowing from energized electrowinning cells. The metal flange on the pipe was the metallic conductor that carried the current to the employee from the electrolyte inside the pipe. Current then flowed through the employee to ground. Because of this incident, FMI undertook an extensive review of the hazards of stray current in EW/ER. FMI’s tankhouse workforce received a Tankhouse Electrical Safety training course developed in- house to insure worker understanding of stray current hazards. Tankhouse design changes were implemented to better insulate workers from stray current. Personal protective equipment (PPE) standards were also reviewed and changes made.

Jan 1, 2019

By R Chandramohan

Comminution is the science of size reduction of brittle materials. It is integral to mineral extraction and is one of the most energy intensive processes in the mining industry. There are a number of tests used to quantify the strength of ore, which are then used to size the AG / SAG mill in circuit design. The calculated energy utilized for breakage in these devices is based on the assumptions that the materials treated are of average shape and that the processing equipment is designed to break the ore as efficiently as possible under the given operating conditions. In drop weight tests, it was found that shape significantly influences the measured rock strength. Controlled experiments with variations in blends of rock shape show that mill throughput increases with the addition of weaker shaped rocks.

Jan 1, 2012

By H. Tetu, F. Pells

"The copper-molybdenum property of Brenda Mines Limited is located in the Okanagan district of British Columbia, approximately 25 miles west of Kelowna. The Okanagan Valley is a resort and fruit-growing area, and therefore pollution control measures are more stringent than in some remote areas.The Brenda plant began production in April 1970 and is operated at a rate of 24,000 tons per day. The plant site is located at an elevation of 4,800 feet, which is approximately 3,600 feet above the level of Okanagan Lake. The site is in the Okanagan drainage basin.The major consideration in the design of the system was the prohibition of any downstream discharge. It was therefore necessary to redaim as much water as possible and to minimize the addition of fresh water to the system. The maintenance of a water balance is of critical importance.This paper will outline the major design criteria for the systems and the site investigations which were carried out. The design and construction of the facilities will be de-scribed and current operating experience will be outlined."

Jan 1, 1971

By Raj Rajamani

In general, many past works examine mill load, mill power, shell lifter design etc with a view to improving the mill capacity. On the contrary, only a handful of papers have addressed the transport of fine slurry through the pulp lifters. We present the flow dynamics of pulp lifters via laboratory scale experiments, high speed photography and modeling with computational fluid dynamics. Next, the flow behaviour in ArcelorMittal?s Mont-Wright autogenous mill discharge flow is examined. In an effort to improve mill throughput, a comprehensive simulation and plant scale study of the mill was taken up with a focus on the shell and pulp lifter design. The shell lifter was found to be at its optimum limit for breakage of ore particles given the constraints of wear life and occupied volume. Next, the pulp lifter study was taken up with computational fluid flow code and discrete element code. The simulations directly showed that there was considerable carry-over of slurry. This effect was traced to the area restriction in the pulp lifter channels. Further, crash-stop studies confirmed slurry pooling within the mill. Thus it was readily apparent that mill throughput can be increased if the pulp-lifter could be redesigned. Consequently, the discharger section of the pulp-lifter was redesigned. First, this paper outlines the modeling in laboratory scale studies and plant scale studies leading up to the discharger design. Next, the discharge flow in seven different published mill surveys is predicted with computational fluid dynamics (CFD) methodology shown here. Finally, Mont-Wright mill circuit performance before and after the discharger redesign is described. The usefulness of fluid flow simulations in the design of pulp-lifters is emphasized.

Jan 1, 2012

By A. Pearson, F. A. Auld, S. O. Colbeck

"""The theory of buckling of shafts and Steel tunnel-linings"" was published by E. Amstutz in 1970 and commented on by S. Jacobsen in 1974. The authors have revised and enhanced Amstutz’s work to address Jacobsen's comments on its limitations and to extend its validity over a wider range of pipe/shaft geometries, including those commonly found in deep mine access shafts. The author has looked at Amstutz’s assessment of strengthening with flexible shear anchorages and adapted the theory of non-linear shear deformation response of bolts to develop a method of assessing increased buckling capacity utilising the full plastic shear capacity of studs. INTRODUCTION “Amstutz Buckling” refers to the buckling of pipe embedded in concrete under external uniform pressure. In terms of a mining environment, this relates directly to the design of a watertight shaft. This load case will commonly occur where a main shaft is cast against a geostatically stable primary liner and the only load applied to the final shaft is that of a uniform ground water load. Ernst Amstutz wrote his first paper on buckling of pressure-shaft steel linings in 1950 and subsequently improved his theory (Amstutz, 1970), which was then widely adopted for use within the industry. Years later, an alternative approach (Jacobsen, 1974) was proposed. Within his paper Jacobsen critiques Amstutz work, identifying some mathematical inconsistencies and highlighting limitations of the theory imposed by approximations adopted by Amstutz. Despite these limitations Amstutz work has still been used as the favoured design theory for use in the mining industry. In reviewing this body of work the author realised that with the advent of readily available computing software it was possible to adopt an iterative approach using Amstutz approximate formulae to find a solution to the original precise formulae, thus eliminating the limitations highlighted by Jacobsen The shear deformation to load characteristics of bolts has long been established (Crawford & Kulak 1968) and used for the plastic design of bolted connections in shear. This relationship is directly transferable to the design of shear studs, typical properties are well known, and actual values easily established in simple lab tests. The author has taken this relationship and modified Amstutz theory (Amstutz, 1970) for shear anchored strengthened liner buckling, to give a more efficient solution, using readily available material properties."

Jan 1, 2019

By L. I. Kiss, A. Larouche, V. Dassylva-Raymond

Control of the quenching capacity of the cooling water is of primary importance for maintaining the quality and recovery rate of ingots produced by direct chill casting. Industrially, this can be done using a cylindrical metallic probe undergoing rapid quenching by direct immersion in a reservoir filled with casting water. Such a test rig originally developed at Alcan Arvida Research and development Centre was modified and used to assess the role of key parameters affecting the boiling heat transfer. During the tests, the probe of the instrument undergoes the effects of different heat transfer mechanisms. An experimental study was performed in order to clarify the details of the probe-water heat transfer during rapid quenching. The heat flux along the surface was determined by mathematical modeling using the measured temperature signals, while the corresponding heat transfer regimes like stable and unstable film boiling, nucleate boiling and natural convection were identified by the analysis of high-speed video recordings. Aluminium

Jan 1, 2006

By Dan Miners

"This presentation will provide an overview and understanding of Mine Safety and Health Administration (MSHA) and Ontario Regulations for Mines and Mining Plants. It includes discussions on the history and practical development of the standards and an overview of engineering best practices from a construction, maintenance and operational viewpoint. INTRODUCTION Ontario is one of the safest mining jurisdictions in the world and has some of the most comprehensive regulations for the construction, operation and maintenance of a mine. In the USA, several operators have adopted some or all of the practices prescribed by the Ontario Regulations as an internal procedure. Experience has demonstrated that these plants are indicating less unplanned downtime and fewer issues with MSHA inspectors in their hoist plants. HISTORY AND THE REGULATIONS Both Canada and the USA have had some form of laws governing the operation of mines since the late 1890s. The paths of legislation have run in reasonably parallel lines, continually improving the health and safety conditions in the mining industry. Ontario Mine Health and Safety In the 1970s the accident rates in mining were higher than any other industrial sector; this prompted a Royal Commission on the Health and Safety of Workers in Mines (the Ham Report). The recommendations of this report, published in 1976, generated several changes in the regulations regarding worker safety in mines. Following the release of the Ham report, the Occupational Health and Safety Act (OHS) was passed by the Legislature in 1978. The Act is a set of comprehensive laws governing almost all Ontario workplaces, and it replaced separate laws governing different industrial sectors. OHS is enforced by the Ministry of Labour (MOL), and this discussion will focus specifically on Ontario’s Occupational Health and Safety Act, R.R.O. 1990, Regulation 854, Mines and Mining Plants, Part X Mine Hoisting Plant (Ontario Regulations). USA Mine Health and Safety A coal mine explosion in West Virginia and medical studies on occupational disease led to the 1969 Federal Coal Mine Health and Safety Act (Coal Act). The Coal Act was the most comprehensive and stringent Federal legislation governing the mining industry to date. The Mining Enforcement and Safety Administration (MESA) was formed, following the 1973 Act, as a new departmental agency to assume the enforcement of safety and health in mines. The Federal Mine Safety and Health Act of 1977 (Mine Act) transferred enforcement responsibilities from the Department of the Interior to the Department of Labor and named the new agency the Mine Safety and Health Administration (MSHA). This agency enforces the Code of Federal Regulations (CFR), and this discussion refers to CFR Title 30 Mineral Resources, Chapter I Mine Safety and Health Administration, Department of Labor, Subchapter K—Metal and Non-metal Mine Safety and Health (MSHA)."

Jan 1, 2019

The principles and utility of in-situ coal gasification are discussed, and a first field test conducted by the Alberta Research Council in 1976 near Forestburg, Alberta, is described. The test was carried out in a 12-ft subbituminous coal seam under 60 feet of cover. Within this seam, a 30 by 60-foot block , containing approximately 650 tons of coal, was delineated by four injection/production holes which were oriented to take advantage of the natural fracture system in the coal. Linkage between holes was established by reverse combustion and gasification was accomplished by injecting air into the ignited coal. No steam was injected but operating pressures were adjusted to utilize formation waters for partial carbon -steam gasification. The coal gasification runs lasted six weeks and gasified an estimated 900 tons of coal ,' during sustained periods of gasification, a fuel gas with heating values of between 110 and 150 Btu/scf was obtained. Plans are now being developed for excavating the test site and inspecting the subsurface cavities created by gasification.

Jan 1, 1977

By Norman A. Jull

"IntroductionThe scope of this paper is intended to deal mainly with cyclones in grinding circuits. However, the section on Cyclone Equipment, contains more general descriptions, to cover most of the cyclones used in mineral separation plants.Cyclones as heavy media separation vessels are discussed by Mark Freberg (this volume). Their use in tailings deslirning is discussed by P.C. Lighthall, eta/. (this volume).Cyclone EquipmentCyclone TerminologyApexObviously, the apex of a cone is the smallest end. However, with cyclones the term is usually used for the fitting which is attached there to control discharge of the underflow stream.Note that the cyclone need not be so mounted that the apex is the lowest point, although that is the most common method. Keeping the apex below the rest of the cyclone helps avoid plugging when the underflow contains very large particles and the tonnage of underflow solids can fluctuate.Various devices for adjusting apex diameter or otherwise controlling the underflow are discussed later under ""Cyclone Construction"".BypassingThe transport of a portion of feed slurry directly to underflow so that classification is bypassed by that portion of feed.This action is fundamental in any hydraulic classification, whether gravity or centrifugal, because the large particles going to underflow have some void volume between them, which remains filled with feed slurry.D50By definition, D50 is that particle size which has an equal probability of going to overflow or to underflow.It is calculated by drawing a curve of recovery vs particle size and noting the size at which 500Jo recovery occurs.This may be done equally with corrected or with gross recovery (see below) and the resulting value should therefore be identified as d50c (corrected d50) or as d500 (gross d50).Note also that it is common in industry practice to plot size analysis data on the retained size rather than on the average of passing and retained (the middle of the size band). To portray sizing alone it makes no difference, but to read a D50 value off a curve of corrected or gross recoveries, it is essential to plot those values on the average size of each band."

Jan 1, 1989

By D. V. Dorling, J. T. Bowker, J. A. Gianetto

Over the last few years, interest in the development and construction of large diameter, high pressure pipelines from the Mackenzie Delta in northern Canada and Alaska's North Slope has steadily increased as a result of the projected decline in recoverable natural gas from existing reserves in western Canada. The success of such enormous pipeline projects, which will require utilization of a strain-based design approach, is largely based on successful application of high strength line pipe steels, such as X80 and X100. To fully realize the economic benefits of high strength steels, welding processes and procedures must be developed to ensure that the requirements for high strength and good low temperature toughness are confidently obtainable in field girth welds used in the construction of such pipelines. This study aims to provide a better understanding of the factors that control weld metal strength and toughness for a series of mechanized X100 girth welds produced using a range of narrow-gap gas-metal arc welding procedures. The attainment of high yield strength (> 810 MPa) is considered to be an important target to ensure overmatching strength relative to the longitudinal property distribution of X100 line pipe steel. Some factors that have been considered in this evaluation include influences of gas-metal arc welding process variants (single and multi-wire) and changes in welding procedure specifications, including joint preparation. Key components of this work relate to the reliable measurement of weld metal strength variation through-thickness and as a function of position around the circumference of a given girth weld.

Jan 1, 2005