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By E. L. Smith

The development of larger size flotation machines, which started in the 1950's and 19601s, is still proceeding. The largest mechanical flotation machines available today have unit volumes in the range of 38 to 42 m3 (1,350 to 1,500 cft). In fact, the motivating forces of increasing capital and energy costs and decreasing ore grades, which created the need for large flotation cells, not only still exist, but are becoming more critical. This paper reports the development of an improved mechanism for these large flotation machines. The starting point in the development of a new mechanism was the identification of design and performance features of existing machines where improvements were desirable. The result of this work was a mechanism which is an improvement over existing designs. This new design is characterized by an efficient overhung stator and a vortex profile rotor. The overhung design of the stator removes unnecessary and undesirable baffling in the lowest parts of the tank, while maintaining a quiescent froth layer. This results in lower power consumption and better pulp circulation and solids suspension. The vortex profile rotor acts as an efficient pump, with higher pulp recirculation rates as evidenced by the increased air dispersion capabilities, good solids suspension, and low power consumption.

Jan 1, 1982

By D. Kang

The adsorption behavior of silver in ammoniacal solutions on to activated carbon has been studied. The parameters affecting the adsorption of silver on to activated carbon included temperature, agitation speed, concentration of cations and anions as well as that of ammonia. It was found that the adsorption of silver from ammoniacal solutions was dependent upon the initial silver concentration in the solution and other factors. The recovery of silver from ammoniacal solutions was found to be not so effective as the case with gold reported earlier. The adsorption rate was relatively slow overall, despite a rather fast initial adsorption. The apparent activation energy for the adsorption was measured to be 30.2 kJ/mol. It was believed that the kinetics of the silver adsorption on activated carbon was limited by a mixed control mechanism.

Jan 1, 1998

By Stephen L. Chryssoulis

The detection and quantification of invisible gold by microbeam techniques is discussed. Ion probe microanalysis is used to quantify the gold content of individual sulphide, sulpharsenide and oxide particles with a detection limit of 0.2 ppmw (g/t). The proton microprobe is used to determine the gold concentration of gangue minerals with a detection limit of 2 - 4 ppm. Using these techniques complete mineralogical balances for gold are obtained to assist in the process selection and optimization. A total of twenty gold and gold-bearing ores have been examined. Selected examples are presented.

Jan 1, 1990

By Andrew Chegwidden, Tara Wilk

Shaft 18B-1 is the second shaft to be constructed as a part of contract C547A along the New York City water supply system Tunnel No. 3. More complex than Shaft 17B-1, this site has an additional 30 m (100 ft) of overburden for a total excavation depth of approximately 78 m (256 ft) through water-bearing overburden soil and 145 m (475 feet) of gneiss bedrock to connect to the underlying Water Tunnel No. 3. round freeing was specied as the method to provide temporary earth support and ground water control for the overburden material. An extensive supplemental geotechnical investigation (SGI) and frozen soil testing program was performed to develop the design of a temporary ground freezing system, consisting of over 7,315 m (24,000 ft or 4.5 miles) of drilling for the installation of 95 freeze pipes. At the start of shaft excavation, the upper sandy silts strata was found to have an unprecedented low thermal conductivity, leaving the frozen soil face approximately 0.6 to 1 m (2–3 ft) behind the cutline. The ground freezing earth support needed to be augmented with ring beams and liner plates to support this soil face and allow for the excavation to proceed and be completed safely.

Jun 23, 2024

By Wan-Kyu Choi, Arpad E. Torma

The electrochemical reactions involved in a zinc sulfide flotation concentrate leaching with sulfuric acid in presence and absence of Thiobacillus ferrooxidans, as well as with ferric chloride - hydrochloric acid containing media, have been investigated. The cyclic voltammetric measurements revealed that many intermediate electrochemical reactions are involved in the zinc sulfide leaching. Using chronoamperometric and chronopotentiometric techniques, it was found that the leaching process is controlled by solid - state diffusion. The activation energy of solid - state diffusion process was determined by the Price's approach to be 21.3 kJ. The leaching mechanism is discussed in terms of solid - state properties (energy bondings) of the high energy gap solid zinc sulfide semiconductor and energy density states of redox systems of acidic leach media. A generalized model for the mechanism of zinc sulfide oxidation is present.

Jan 1, 1990

By William Harrison, Robert H. Trent

GENERAL DESCRIPTION History The most striking feature of mining in the United States has been the infrequent use of longwall systems. This system, which accounts for the majority of coal production in Europe, Japan, and other countries, is only recently growing out of its infancy in the mining of normal coal seams and is still untried in the mining of thick coal seams in the US. Its use in the mining of metal and nonmetal ore bodies has been virtually ig¬nored, except for isolated instances in trona, copper, and uranium. Longwall mining is believed to have originated in Shropshire, England, towards the end of the 17th cen¬tury (Laird, 1973). Although the method used would be considered primitive by today's standards, many of the basic concepts have remained unchanged. Longwall mining of coal in the US was first introduced before the turn of the century, but it never gained acceptance as it did in Europe. Historically, longwalling was a cyclic method where a single cut of coal was removed from the face on the producing shift each day, and the work of building stone packs in the gob and manually moving roof support was completed on the off shifts. Due to the amount of dead work, productivity was extremely low. In Europe, however, longwall methods were required despite the high costs involved, because only by this method could coal under heavy depth be mined with any reasonable degree of recovery. Reserves of coal lying under shallow cover, and therefore minable by room¬and-pillar methods, were long ago inadequate to supply most of Europe's coal requirements. In the US coal min¬ing has historically proceeded laterally with the new mines in virgin areas to replace old mines; in Great Britain, Germany, Japan, and many other countries, mining must proceed downward to greater depths. The depth of cover for most coal operations in the US is shallow, i.e., 61 to 305 m (200 to 1000 ft). This, combined with large reserves, has made room-and-pillar methods almost universally applicable. However, longwall systems were tried around the turn of the century. Whenever used, it was frequently noted that the opera¬tion was under the direction of men with foreign ex¬perience and was tried under ideal conditions. Some of the mines that were using longwall or had tried longwall prior to 1910 were the Radiant mine, CO; Vinton Coal Co., PA; Cambria Steel Co., Johnstown, PA; Grundy County and Spring Valley, IL; and unnamed mines in Washington, West Virginia, Kentucky, Iowa, and Kansas. As late as 1961, there was one circular longwall in operation at Centerville, IA. The first modern-day op¬eration to take advantage of European technology and longwall methods was Kaiser Steel Corp. at its Sunnyside mine near Price, UT. Due to deep cover and extremely poor roof conditions, combined with a need for in¬creased production, Kaiser management decided a new method was required and turned to longwall in 1961. The first longwall consisted of an Anderson Mavor shearer loader, British Jeffrey-Diamond conveying equip¬ment, and Dowty roof supports with a capacity made up of two and three 27-t (30-st) capacity props. After nor¬mal start-up problems, this unit averaged over 454 t (500 st) per shift (White and Palacios, 1976). During and after World War II, technology in hy¬draulics and controls had advanced to the point that self-advancing supports and hydraulic props were being developed. In 1960 only I % of West German produc¬tion was from mechanized longwall faces. This in¬creased to 37% in 1970 and 63% in 1973 (Kohlgruber, 1974). In 1976 there were 246 coal mines operating in the United Kingdom. Although this is only 50% of those operating ten years ago, the production has increased 42%, mainly through improvements in longwall equipment and methods (Hunter, 1976). In France and other European countries, the devel¬opment of longwall mechanization has been similar in seams up to 2.44 m (8 ft) thick. In seams that exceed 9.14 m (30 ft), a variety of longwall caving has been developed for coal seams with dips of 0 to 1.6 rad (0 to 90°). Those with the greatest success will be discussed later. As noted, the development of longwall mining to its present state of the art has mainly taken place since World War II with substantial gains in the last ten years. Mechanized longwall has been the result of several re¬lated major innovations (Jackson, 1975) 1) Development of the flexible armored face con¬veyor which can be installed along the face and moved forward without disassembly. 2) Development of face machines such as single and double drum shearer and coal plows which operate in conjunction with the armored conveyors. 3) Development of self-advancing hydraulic roof supports which now include chocks, chock shields, and shields. 4) Reliance of caving of the immediate roof based on proper planning and development. 5) Use of pneumatic slowing to enable extraction below overbuilt areas. The most recent developments in the mining of coal by longwall in the US include the introduction of shield supports at Kaiser's York Canyon mine in New Mexico, single-entry longwall development at Kaiser's Sunnyside mine, and Mid-Continent's advancing longwall system in Colorado. Metal and nonmetal longwall systems in the US have included the mining of copper at White Pine, MI; uranium in Utah and New Mexico, and trona in Wyoming.

Jan 1, 1982

By David E. Lindorff

The impact of surface coal mining on the geologic materials and ground water in different geologic settings is being investigated by the Illinois State. Geological Survey at three abandoned surface mines in Illinois. At a site near Ottawa in La Salle County, the overburden prior to mining consisted largely of pyritic shale; sand was the major component of the overburden and spoil at a mine near Coal City, Grundy County. Clays, lacustrine silts, and some shale and limestone were the dominant premining overburden materials at a mine near Harrisburg, in Saline County. Ground-water elevations at Coal City and Harrisburg are approximately at premining levels, whereas at Ottawa they are near the base of the spoil. Ground-water quality has deteriorated at all three sites, especially at Ottawa and Harrisburg.

Jan 1, 1981

By Peter G. Chamberlain

The Bureau of Mines is conducting research to boost domestic production of manganese. Virtually no mining exists in the low grade and/or small deposits that occur in this Country. One large, low-grade manganese deposit located in westcentral Arizona--The Artillery Peak district--was extensively studied and sporadically mined during the 1940's and 1950's. Although manganese mining in the district has been long dormant, recent studies indicate that the deposits may be amenable to economical production by heap and/or in situ leaching methods. A conceptual design for an in situ leaching system features undercutting and blasting a block of ore, leaching with SO2, and extracting the manganese as a sulfate or oxide. Possible applications to other manganese deposits depend upon formation permeability and specific manganese mineralogy.

Jan 1, 1981

By Earl L. Rau

Although the Sagasca deposit has been known for 76 years, the property was never put into successful operation because of various adverse factors including low market price for copper, legal entanglements, unsuccessful financial arrangements, and an inadequate metallurgical process. Late in 1963, Continental Copper & Steel Industries, Inc., obtained legal control of this property. Since that time there has been a concentrated effort to complete the necessary mine appraisal, process development, and engineering design, and to solve the legal and financial problems to bring this property into production.

Jan 1, 1970

By T. M. Yegulalp

Geometric programming is a mathematical optimization technique, first formulated by Zener [1], for dealing with certain types of functions which typically arise in engineering design problems. The theory provides algorithms for finding the optimal solution, existence theorems by which one can show that a particular design is possible or not; and characterization theorems that especially make possible to obtain the relationships among the optimal design parameters at optimum. It has been demonstrated [2] that this technique can be applied to several design problems in chemical, electrical and mechanical engineering. Design problems in mining, metallurgical and mineral engineering have many aspects similar to that of other engineering problems. Thus it is only natural to consider geometric programming as a potential tool for solving certain optimization problems in mineral industries.

Jan 1, 1974

By F. P. Schwarz

Even in an otherwise care-fully done sampling procedure, reducing subsample weight, or splitting, when the grain size of material is too large commonly generates significant error. Such error can be estimated from the standard deviation of differences between values of PAIRED ASSAYS. Samples from split-ting steps immediately before comminution, and showing a restricted range of grade, generate paired assays. Splitting steps characterized by relative standard deviations exceeding 16% generate nonrepresentative data. Such steps should be redesigned to optimize reliability of assay-dependent studies. A sampling scheme can be graphically characterized, and then redesigned as appropriate, using a SAMPLING NOMOGRAPH. Use of the nomograph avoids continued replication of assays. Generally at a splitting step, excessive error can be reduced by comminuting more material. Unnecessary effort can be mitigated by comminuting less finely and/or by splitting to a smaller weight.

Jan 1, 1992

By William R. Bush

This paper is a presentation of findings based upon an econometric model of the world zinc industry. The model was developed as a simple but useful aid for long-run forecasting and planning purposes. A structure was developed for both simulating real zinc price effects on production and consumption, and for forecasting long-run annual zinc prices and supply/ demand levels. Moreover, a methodology is provided to incorporate the effects of: (1) historic technological advances in zinc supply, and (2) the development of the competitive plastics industry. Finally, reduced form equations are used to generate ex post forecasts to evaluate the model's performance.

Jan 1, 1979

By Robert Sturk, Knut O. Halvorsen

"INTRODUCTION AND BACKGROUND The world needs visionary people to break new ground and bring development forward. The human race has an inherent power and lust to explore and push borders, but also to connect and bring people together. Transport of people and goods has through history been a key factor to develop societies and increase collaboration between people and regions. Today, in the era of globalization, efficient transport systems are still vital for further development. Often, ideas of bold projects, like long bridges or tunnels, have been raised long before those projects are realized and actually built. This shows that visions must gradually be transformed into feasible business cases and sustainable political solutions. In some cases also technological development is necessary to make visions come true. Isambard Kingdom Brunel, indeed a visionary engineer, completed the oldest underwater tunnel in the world when the Thames Tunnel in London was opened in 1843. This tunnel is still in operation and now part of London’s rail transport system. Another milestone for the tunnelling industry was passed when the 54 km long Seikan tunnel in Japan was opened in 1988 after more than 15 years of construction. This tunnel is presently the world’s longest railway tunnel. Together with the 50.5 km long Channel tunnel between the UK and France, which has the longest undersea portion 37.9 km, they constitute examples of pioneering engineering projects that bring the industry forward. In 2016, the Gotthard Base Tunnel will be opened and then becomes the longest railway tunnel in the world with its 57.1 km. The trend is obvious that tunnels throughout the world are getting longer and longer. The Brenner Basis Tunnel presently under construction will yet again break the record being 64 km long. Presently, a number of even longer tunnels are planned and under design, some of these also have very long subsea portions, e.g. Bohai Straight Tunnel (123 km), Irish Sea Tunnel (around 100 km) and the Helsinki – Tallin fixed link (approximately 90 km). Northern Europe sees an increasing demand on efficient transport corridors to meet the growth of freight transportation between the Scandinavian Peninsula and central-Eastern Europe. Sustainable solutions will be required, and a shift from road/maritime transports to rail is imperative. Consequently, this paper describes yet another visionary project, a fixed railway link between Sweden and Germany, the Shortcut, to enhance traffic between these regions and to make it greener. It is true that this project still requires some work from politicians, economists and engineers to be realized, however, building a 100 km long tunnel under the Baltic Sea may become reality sooner than we think."

Jan 1, 2016

By James R. Jones

It has been 2-1/2 years since the Congress passed the Surface Mining Control and Reclamation Act of 1977 (PL95-87) the Office of Surface Mining every deadline specified in the Act. Hopefully the Congress will begin to realize that specifying unrealistic deadlines does not accomplish the end desire of legislation any sooner -- it only adds to the confusion, and actually hinders orderly, efficient progress. OSM has been sued by all categories of involved parties -- environmental activitist organizations, the states, and the coal operators. This situation has resulted for two reasons: (1) insufficient time was allotted by the Congress to properly develop the regulations and program, and (2) OSM?s philosophy that it must dictate every detail of reclamation operations from Washington, even though many of its people are inexperienced with coal mining. These law- suits are now demonstrating their value. OSM is showing signs of "pulling-in-its horns" and, hopefully, will approach the revised regulations in a more realistic fasion.

Jan 1, 1980

By Steven E. Mischler, Jay F. Colinet

The Mine Safety and Health Administration (MSHA) promulgated a rule in 2014 that required numerous changes in compliance dust sampling requirements for coal mine operators. Two key parts of this rule were the lowering of the respirable coal mine dust standard from 2.0 mg/m3 to 1.5 mg/m3 and requiring operators of underground coal mines to use a continuous personal dust monitor (CPDM) for compliance sampling. The CPDM currently approved for compliance sampling is equipped with a display that provides miners with in-shift information on their respirable dust exposure. The goal was to provide an indication of a potential overexposure and empower the miner and mine operator to implement changes in controls and/or operating practices to prevent an overexposure from occurring.

By Jeff Easton, J Johnson, D. Foot

The Mina Santa Rosa mine in Panama was the victim of a mine closure 24 years ago that left the community in dire straits. The mine showed the potential resources of greater than 1M ounces of gold and 4.5M ounces of silver. Veragold Mining Company decided to reopen the mine and address all the issues that were involved in the startup of an historic mine. This paper provides methods to restore the community trust, provide a transparent process, and develop an environmentally sound flowsheet. Immense scrutiny surrounded the Tailings Storage Facility, and the company developed a plan focused on paste thickening and surface stacking to eliminate the need for a conventional tailings’ facility. Paste thickener principles and benefits are also provided.

Feb 1, 2024

By E. Wm. Heinrich

Glass sands fall into that extremely select category of mineral deposits that requires a fantastic degree of natural concentration (95% +) of a single component before they can even be considered as ores suitable for further refinement. The combination of geological factors that has produced such an environment of "mineralogical single-mindedness" has appeared only rarely. Factors that require consideration in the economic evaluation of a potential glass-sand deposit can be grouped into three categories: 1) geological (e.g., size, shape, structure); 2) petrographic (e.g., grain size, accessory minerals, nature of iron contaminants); 3) geographic - political (e.g., proximity to consumer, size of market, zoning restrictions). Of particular con ern is the nature of the iron contamination. Iron-bearing species appear as 1) accessory mineral grains, either detrital or authigenic, 2) cements, 3) grain coatings, and 4) quartz-grain inclusions. Selection of the cheapest form of beneficiation requires precise information on the mineralogy of the iron species and their detailed petrography. Because of the antipathetic relationships, in many parts of the United States and Canada between the geographical locations of glass plants and the geological distribution of glass sands, the selection of ac suitable source for a particular glass plant may be dichotomous. One may seek either an exceedingly pure "classic" type glass sand that is relatively distant and whose cost includes a major transportation charge or a relatively proximate and somewhat "impure" source whose cost includes a substantial fee for beneficiation.

Jan 1, 1974

By Taner Aydogmus

The A$29 billion Chevron-operated Wheatstone Project is one of Australia’s largest resource projects. Located at Ashburton North, 12 kilometers west of Onslow in Western Australia, the project will consist of two Liquefied Natural Gas (LNG) trains with a combined capacity of 8.9 million tons per annum and a domestic gas plant. The LNG Plant will serve the offshore gas fields, which are situated some 250 km off the coast of Onslow in Western Australia. Once operational and on-stream, the Wheatstone Project will contribute to Australia becoming the world’s second largest exporter of LNG. For crossing the environmentally sensitive shore area, a micro-tunnel with an internal diameter of 2 m and approx. 1,242 m in length has been constructed by means of the pipe-jacking method. The micro-tunnel will accommodate a 1.1 m diameter pipeline (trunkline) to deliver gas from the offshore fields LNG Plant. The Wheatstone shore crossing design involves a number of unique challenges owing to its coastal location, where the alignment crosses through a shore area and terminates in a marine environment. This paper provides an overview of the Wheatstone Shore Crossing Project, presents the key features, and discusses the main aspects of the micro-tunneling design.

Jun 13, 2021

By Samuel Rigert, Marco Bettelini

"INTRODUCTION AND OBJECTIVES Long rail tunnels require in most cases powerful mechanical ventilations. Besides requirements related to normal operation and maintenance, operational safety always requires a high level of smoke management. Identifying the optimum ventilation concept is essential for achieving proper performance and safety while keeping investment and operational cost at a reasonable level. For the purpose of the present paper, long tunnels have a length of typically 20 km or more. This is related to the European classification of trains (TSI 1303/2014), where the maximum distance from the portals to a firefighting point and between firefighting points is limited to 20 km (only category B passenger rolling stock allowed) or 5 km (general case). From TSI 1303/2014 it can be concluded, that tunnels over 20 km require in any case emergency stations with complex mechanical ventilations. Based on the experience arising from a number of recent projects in the European area, including in particular Gotthard (GBT), Lötschberg, Lyon-Tourin (LTF), Brenner (BBT) and Gibraltar, safety-relevant issues related to the ventilation of long railways tunnels are reviewed in this paper. Amberg Engineering is directly involved in these challenging design tasks and can provide first-hand experience and know-how. As a particular highlight, special attention is devoted to the longest tunnel worldwide, the 57 km long Gotthard Base Tunnel, which will be commissioned in 2016. THE GOTTHARD BASE TUNNEL Overview The Gotthard Base Tunnel will be commissioned in 2016 (official inauguration on the 1st of June and beginning of regular operation on the 11th of December) and will be the worldwide longest tunnel. Its complex and powerful ventilation system is very representative for many other long tunnels and is used as reference in this paper. Therefore, a few key characteristics of the Gotthard Base Tunnel and its ventilation system will be described in some detail in this initial chapter. The Gotthard Base Tunnel (GBT) consists of two single-track tunnel tubes with connecting galleries every 312 meters. Two so-called multi-functional stations (MFS), located at roughly 1/3 and 2/3 of the tunnel length, host the key equipment for normal and for emergency operation. At these locations, double crossovers allow trains to switch from one tunnel tube to the other. An emergency station is located in each multifunctional station, allowing trains to stop in case of emergency. The general layout of the GBT is presented in Figure 1."

Jan 1, 2016

By Irwan Halim, Bhoshaga Mitrran Ravi Chandran, Kevin Huynh

Tunnel segmental lining design constitutes a significant iterative process where modeling and numerical analysis are factors in deciding the number of segments, their dimensions, gasket placements, as well as the locations of dowels and bolts. Consequently, these modifications lead to revisions in the final drawing details. However, the current tunnel engineering practices lack systematic solutions that effectively bridge the gap between the iterative design process and efficient visualization of completed drawings due to the time- consuming nature of redrawing. This paper presents a pioneering application of AI-driven solutions including using Autodesk's API, for the Northside Interceptor Tunnel (NSIT) Project. It showcases the automation of drawing design and the real-time visualization of modifications, thereby streamlining the drawing process.

Jun 23, 2024