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"Above ground, elevated belt conveyors that span more than 200 m (656 ft) between support points can cross valleys, rivers, forests and buildings with a minimal footprint. The cable bridge conveyor (CBC) is a new type of suspension bridge based belt conveyor system that has long spans between support points. It combines a typical belt conveyor and an improved simple suspension bridge to form a conveyor bridge. The improved simple suspension bridge places a widened bridge deck directly on suspended cables, without the need for high truss towers. The benefits include reduced cost and increase aerodynamic stability compared to conventional suspension bridges. The CBC’s compatibility with current belt conveyors allows versatility in application.A belt conveyor is a ubiquitous material handling system. Conveyors can be placed directly on ground or elevated above ground by support structures. Considerations of cost, design, environment, civil work, safety and process requirements are all factors in choosing the ground-based or elevated conveyors (Zhang, 2014). The ground-based conveyor has the lowest structural cost when the conveyor is placed on an existing road. Maintenance access is easy and straightforward. Compared to the groundbased conveyor, the elevated conveyor can cross existing buildings and structures, give passage to traffic beneath the conveyor, has a smaller footprint and requires less civil work to pass mountainous areas. The drawback of the elevated conveyor is higher structural cost, which can be compared with savings in civil work and other benefits. Conventional elevated conveyors are supported by rigid truss-type structures, with a typical span of 15 to 25 m (50 to 82 ft) between concrete support bents or steel trestles. Triangular truss, using steel pipes instead of hot rolled steel sections, is more efficient. The typical span of a triangular truss-supported conveyor is around 30 to 40 m (100 to 130 ft), while the weight is about 10 percent less than conventional box truss with a shorter span (Jennings, 2013).Long-span elevated structures based on suspension bridge is another step forward in increasing the distance between support bents, reaching 100 to 400 m (330 to 1,312 ft) and beyond. The wide distance between the support points of an elevated conveyor offers unique benefits. The conveyor can cross rivers, valleys, highways, forests and other obstacles with minimal footprint and reduced civil work. The versatility from long-span conveyors makes bulk material transportation over previously impossible terrains now a feasible option."

Jan 1, 2014

By J. J. Harrington

The pH control system at Kennecott Copper Corporation's Nevada Mines Division concentrator consists of two independent systems, lime dilution and lime addition. Lime dilution is accomplished in a mixing tank where slaked lime and water are introduced proportionately. The desired dilution of the milk of lime is determined by the electrical inputs provided by eight pH probes, one per grinding section. The inputs are averaged and applied to a time base generator. The summation output of the time base generator determines the proportion of lime and water that are to be mixed and applies this input to a voltage sensitive switching device. The switching device provides a signal to one of two relays which will add either slaked lime or water, dependent upon the summation output. The entire cycle is based on a two-minute repetition rate to allow for sufficient mix time. Responsivity is controlled by maintaining a limited maxi- mum solution level in the mix tank. Lime addition is controlled independently within each grinding section. The electrical input from the pH probe in a given section controls the solenoid valves which provide lime to each of the ball mills. The valves remain open within a time range capable of maintaining the pH of flotation feed at a given set point.

Jan 1, 1975

By David S. Young

All pigments and extenders or fillers whether organic or inorganic fall into the following broad general classes: I. Colored II.-White III. Black IV. Metallic A pigment- is any particulate matter that is essentially insoluble and chemically unaffected by the media into which it is dispersed. According to this very broad definition, colored pigments, white pigments, fillers, extenders, and functional pigments would all be included. The particulate size range would also be quite broad ranging from very fine colloidal particles (~0.01µ) to relatively coarse particles (~100.0µ). This broad definition is usually subdivided into more practical divisions which tend to relate the classification of the pigment to its primary function in the system in which it is used. Hence, the word extender implies that its major purpose may be to extend the system.

Jan 1, 1985

By G. E. Viens

The electric arc furnace has characteristics which make it attractive for a number of metallurgical applications. Some of these characteristics are: high thermal efficiency, the possibility of attaining very high temperatures, low off-gas volume compared to fuel-fired furnaces, no impurities are introduced by the heat source, and impurities in only minor amounts are introduced by the electrodes. It also has disadvantages, the chief ones being the relatively high cost of electrical energy compared to fossil-fuel energy and the fact that, when oxide ores are smelted using carbon as reductant, the off-gases emitted are rich in carbon monoxide. As in many other pyrometallurgical processes, fumes and dust are emitted from melting or smelting operations. In many installations, some or all of the off-gases are flared, thereby wasting their energy and contributing to atmospheric pollution. During the last eight years, a shaft-electric furnace has been under development at the Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada. This project was initiated to try to overcome, or at least minimize, the disadvantages of the electric furnace. Experience on other projects, prior to the beginning of this program, had indicated that preparation of the charge materials, for example by sizing raw ore, sintering concentrates and crushing and sizing the sinter, or agglomerating concentrates into uniform-sized pellets, could make a substantial contribution towards achieving success in arc-furnace smelting projects; This entire

Jan 1, 1971

By V. Shchukin

According to the scientific views formed by the middle of nineteen seventies there should be no possibility of commercial diamondiferous kimberlites in the north of the west European platform. However a later analysis of the geological data gave rise to the concept that diamond bearing kimberlites would be present in the north but on the mineralogical level they would differ from kimberlites of South Africa and Yakutia. Further investigations resulted in the confirmation of these conclusions and with discovery at the beginning of 1980 of diamond bearing kimberlite pipes in the Arkhangelsk region.

Jan 1, 1995

By N. B. Aughenbaugh

Compacted clays are used as permeability barriers in many mineral engineering projects such as heap leaching, containment ponds, tailings disposal and earth dams. Source materials used for clay liners include a wide variety of sand, silt and clay admixtures that exhibit dramatically different engineering properties when densified. The permeability and plastic properties of fine-grained soils are reviewed with respect to the state of compaction as the water content varies. Be-cause they are weak in tension, compacted clays are susceptible to cracking when subjected to differential flexural movements. Designs of compacted clay liners must include an evaluation of their flexibility which is the ability of a fine-grain soil to bend plastically without cracking. This paper will also discuss the importance of flexibility with respect to soil types, compaction effort, failure mechanism and testing evaluation to the performance of clay liners in preventing seepage of pollutants from a containment site.

Jan 1, 1990

By S. Pastor, S. Hahn

"As the concept of autonomous haulage systems (AHS) moves from proto-types to production-ready applications, the operating performance of the haul road will become ‘mission critical’ to the overall success of autonomy in mining. Deterioration in road performance will require remediation, human intervention and significant, albeit temporary, changes to operating procedures, to accommodate road maintenance. With autonomous trucks comes the opportunity to reduce road formation and operating width, and therefore generating potentially significantly reductions in stripping ratios and improvements to mine economics, but only if the design of the road, and it’s associated deterioration rate, is predictable and manageable, based both on the materials used to construct the road and the maintenance interventions to be carried out on the road. This paper presents the assessment of a digital photogrammetric approach to the characterization of a mine haul road surfacing, or wearing course material. Design and maintenance parameters for these roads are currently determined from physical particle size distribution (PSD) assessments of ‘in-road’ material. However, this approach does not accommodate the need, nor leverage the benefits from, AHS. The digital imaging approach is assessed in this paper, using two standard digital analysis software tools, together with in-service mine haul road wearing course samples and images which are assessed to determine the applicability and reliability of the approach to deliver a real-time assessment of haul road surfacing conditions and thus to identify the road maintenance interventions required to address deterioration. INTRODUCTION Enhancements in mine road design, construction and management for the past 20 or more years has largely been focused on short-term tactical needs. These improvements have not been matched by advances in the fundamental technologies that underpin mine road design and management, and although the quality of mine roads have probably increased, many of fundamental and longer-term issues have yet to be addressed. With AHS’s evolving from prototype to production applications, any decision to implement these systems in a mine requires a thorough evaluation of impacts, not only operational improvements, but the inter-connectivity of this autonomy technology to other organizational processes. In developing an understanding, the full interactions that may affect autonomous truck behaviour due to changes in various sub-systems or external environments, haul road conditions and operating performance is a key consideration. This is as true in autonomous as well as in conventional mine truck-based hauling systems where the mine haul road network is a critical and vital component of the production process."

Jan 1, 2015

By Dan Ifrim

Soft ground tunneling poses major challenges to the underground industry. Most of soft ground tunnels are in highly urbanized areas, often include limited cover, and include a strong trend of increasing diameters. Therefore, soft ground tunneling works can sometimes cause inevitable ground movements and settlements that may lead to damages to adjacent buildings, roads, structures or utilities; many of these being “lifeline” infrastructure assets. Tunneling operations, Tunnel Boring Machine (TBM) advance rates, and face pressure control can significantly increase or decrease such risks, depending on how well the TBM and operational parameters are applied to the ground conditions. Additionally, the risks of impacting existing infrastructure are heightened in many parts of North America because of cobbles and boulders. To date there is no standardized guideline that determines appropriate tunneling rates nor operator’s guidelines, to ensure safe tunnelling in soft ground. The paper analyzes tunneling records from completed soft ground tunnels to determine a relation between ground conditions, tunnel cover, TBM cutters maintenance and TBM advance rates. The records are discussed to draw several mitigation measures to be adopted during tunnelling, to reduce risks of settlements, over excavation or sinkholes.

Jun 13, 2021

By S. A. Suhler

The detection of hazardous geological anomalies through remote sensing techniques is the subject of current research efforts sponsored by the U.S. Bureau of Mines. In this review, hazardous geological anomalies are discussed with respect to the "view" presented along with potential operational concepts for each technique. The design and development of a borehole radar is described with emphasis on the potential range and resolution capability of the system under realistic underground conditions. Results of field tests at two coal mines and at a hard rock future subway location are presented.

Jan 1, 1978

By J. Bilant, B. Carlson, N. Gow

"High-pressure grinding roll (HPGR) technology was evaluated to replace tertiary cone crushing at Coeur Rochester operations (Coeur Rochester Inc.) as an opportunity to improve silver recovery. In 2016 and 2017, onsite and third-party pilot programs were initiated to evaluate the impact on metallurgical recovery and heap leach performance of crushed product generated by an HPGR. In 2018, Forte Dynamics evaluated the HPGR laboratory metallurgical data from Coeur Rochester and all third parties to develop field-scale leach curves based on new crushing scenarios. The laboratory recovery test work data were consolidated and scaled to field conditions to determine projected heap leach performance. Based on the metallurgical testing conducted, the replacement of current tertiary cone crushers with HPGR technology has the potential to increase Coeur Rochester’s silver recovery rate by 8 percentage points, from 61 percent to 69 percent, and shorten the overall timing of silver recoveries from 20 years to just more than two years.The Rochester Mine, and associated valley fill heap leach facilities is an openpit silver and gold mine located in Pershing County, NV, approximately 42 km (26 miles) northeast of the city of Lovelock. In 2017, Rochester produced approximately 4.7 million oz silver (Ag) and 51,000 troy oz gold (Au). Ore mined at Rochester is either fed directly to the primary X-Pit crusher, crushed at an in-pit crusher system, or placed directly onto a heap leach pad as run-of-mine (ROM). Both crushing circuits are comprised of three stages of crushing to produce a nominal 3/8 in. ore. Primary crushing consists of jaw crushing while secondary and tertiary crushing are composed of varying cone crushers.Historical recovery rates of crushed Rochester ore averaged 61.4 percent Ag and 95.9 percent Au over a period of 20 years (Robinson et al., 2018). These rates were derived from third-party verification of in-house metallurgical test results, crusher production and heap leach production results from 1986 through 2004 in a private report for Rochester produced by KD Engineering Co., Inc. Recovery rates are regularly verified by compositing daily samples of ore delivered to each leach pad from the X-pit crusher, in-pit crusher and/ or ROM. A proportionate split of each sample is used to generate monthly composites for metallurgical analysis utilizing column leaching and bottle roll leaching. These tests are run in a manner analogous with production conditions and deliver test results that provide expected heap leach performance. As the Rochester oxide deposit has been mineralogically and metallurgically consistent, the gold and silver recovery trends have also been consistent over the life of the project."

Sep 1, 2019

By Robert M. Matyas, P. E. Sperry, Robert J. Smith, A. A. Mathews

INTRODUCTION The first Dispute Review Board (DRB) was utilized on a tunnel project 20 years ago. Increasingly utilized on a wide range of construction projects, DRB's are becoming the norm on tunnel and underground projects. This paper summarizes the growth in this usage, uses observations and experience to establish that barriers to the utilization of DRB's are more perceived than real and that many arguments against the DRB concept are not valid, and notes some of the salient elements that should be considered in practice to optimize DRB effectiveness. The purpose of the paper is to provide an annotated checklist for current and prospective users. The basic concept, structure, and operation of DRB's are described elsewhere and will not be repeated here (ASCE, 1991). DISPUTE REVIEW BOARD USAGE A compilation of Dispute Review Board usage for tunnel and underground projects to January 1994 indicated use on 63 contracts with a cumulative construction value of $3.8 billion and a total of 60 disputes settled. As of that same date, DRB's were planned for another 63 contracts with an estimated construction value of $4.7 billion. (A listing of these 126 projects is available from the authors.) This success and popularity have spread to other civil projects as well as process and building construction. The increase in DRB usage has been exponential. See Figure 1.

Jan 1, 1995

To generate a most profitable ultimate pit limit is generally the first step in mine design. This paper presents a new graph theory oriented, optimum ultimate pit limit design algorithm which will maximize the total undiscounted net profit. This algorithm performs much better than the well known Lerchs-Grossmann algorithm, in terms of the reduction in computation time and computer memory requirements. This algorithm operates on many directed trees in a graph, where each vertex in a tree represents a block in the mine model. The formation of each directed tree is based more on the ore-waste support concept than the geometry constraints alone. The general procedures of the algorithm, programming considerations and two case study results are discussed in the paper.

Jan 1, 1990

By Ralph van Rijswick, Erik Vlot

"Anglo American operates 18 Weir GEHO piston diaphragm pumps (PD) in the two pump stations of the 52-km (32-mile) long Minas Rio iron ore concentrate pipeline. The pipeline is designed to transport 26.5 Mt/a (29.2 million stpy) of concentrate from the mine to the export terminal at the coast.During the commissioning of the pipeline in the fall of 2014, high pressure pulsation levels were experienced, with peak-to-peak levels as high as 20 bar. Based on pressure readings it was concluded that hydraulic resonances were present in the system, which were excited by the third and sixth harmonic of the flow pulsation generated by the pumps.Based on this observation, Weir Minerals Netherlands, manufacturer of GEHO PD slurry pumps, recommended installing a phase shift controller that controls the phase shift between the crankshafts of the individual pumps, thereby minimizing the effect of the hydraulic resonances.GEHO piston diaphragm pumps and pressure pulsation analysisPiston diaphragm pumps are used worldwide to transport abrasive and/or aggressive slurries against high discharge pressures in the mining, mineral processing and power industries. The basic operating principle of a piston diaphragm pump is shown in Fig. 1.A crankshaft is driven by an external electric motor via a gearbox. The crank mechanism transfers the rotating motion of the crankshaft into a reciprocating motion of the piston. The piston displaces a hydraulic fluid, called the propeling liquid, which displaces an elastic rubber diaphragm. When the piston moves to the right, the pressure in the pump chamber drops below the suction pressure and the nonreturn valve on the suction side will open, allowing the pumped fluid to flow into the pump chamber. When the piston moves to the left, the fluid is compressed, and when the pump chamber pressure rises above the pipeline pressure, the nonreturn valve on the discharge side will open allowing a displacement of fluid into the discharge line. The main objective of the diaphragm is to isolate the piston and the drive mechanism from the abrasive and/or aggressive fluid and create a hermetic seal between the pumped fluid and the ambient environment. Piston diaphragm pumps as shown in Fig. 1 are among the largest positive displacement pumps in the world and have been produced with stroke volumes of up to 100 L (26 gal) per pump chamber for flow rates up to 800 m3/h, discharge pressures up to 250 bar and hydraulic outputs over 2 MW per unit (van Rijswick et al., 2010)."

Jan 9, 2017

By H. Shafick Hanna

The major problems are identified the high phosphorus content and the fine dissemination or encapsulation of mineral impurities, in, ,the iron bearing minerals, A process which combined extreme fine grinding techniques with magnetizing roasting or flotation separation methods, is suggested. By these methods concentrates assaying 60-61 percent Fe exceeding the widely accepted upper limit of 56 percent Fe set for these ores, were produced with 75-90 percent iron recovery. Moreover it was shown that the phosphorus content of these concentrates could be reduced from 0.25 to 0.03 percent phosphorus by acid leaching. A brief discussion on production costs based on current and future developments in iron ore processing is given.

Jan 1, 1980

By J. Paraszczak

Metal mining at great depths presents a number of serious challenges for mine operators. Among them is the high demand for fresh air required to cool down mine openings, evacuate noxious gases and contaminants and provide sufficient amounts of oxygen for miners. At the same time, modern mechanized mines extensively use diesel-powered load-haul-dump (LHD) machines, trucks and other mobile equipment. These vehicles not only emit exhaust gases and diesel particulate matter (DPM), but constitute an additional source of heat. As mine regulations get steadily more stringent with regard to air quality, the use of diesel engines has an additional adverse impact on ventilation costs. In this context, the present paper examines possible alternatives for diesel power trains, both those commercially available and those in development. They are reviewed with regard to their principles, required infrastructure, stage of technology development and progress. The questions of their flexibility, practicality and economic viability are also addressed. Finally, their possible benefits and potential for implementation in the conditions of deep metal mines are discussed. The paper concludes with short- to medium-term predictions concerning promising drive alternatives for vehicles destined to operate in deep metal mines.

Jan 1, 2009

By O. M. Arafat, J. A. Finch

Since its development, the functional performance equation for ball milling (McIvor, 1988) has facilitated a new understanding of industrial circuit cause and effect relationships, leading to significant strides in operational performance. Success stories of this approach to plant circuit performance improvement are now too numerous to list. Finch and McIvor (circa 1986) also discovered that the functional performance mill grinding rate at the size of interest was the same cumulative grinding rate that is calculated from mill feed and discharge size distributions using a first-order rate equation. By calculating these cumulative grinding rates for all screen sizes, a complete ball mill model is generated (as used by Finch and Ramirez, 1981). Others in industry, Hinde and Kalala (2009), for example, have noted the same. Lacking the complexity needed to maintain their interest, most researchers have ignored this model, broadly opting instead for Epstein’s (1948) characterization of grinding as a chemical reaction, combining selection rate and breakage size distribution functions. The much simpler ball mill model has previously been incorporated into a proprietary circuit modeling program (McIvor, 2005) and used for plant improvement work (for example, see McIvor and Finch, 2007, and McIvor, 2014). Now, by combining this business-friendly ball mill model with optimization criteria from functional performance analysis, a circuit modeling system (including the needed supplementary steps to assure successful plant implementation of circuit design changes) is at the disposal of every plant metallurgist, grinding equipment/ material provider and circuit designer.

Jan 11, 2017

By M. SIDDARAJU, Rameshwar Sah, Satendra Kumar, Arvind Jaiswal

The study explores a novel process to sinter porous iron ore with improved productivity and quality. The iron ore is pre-processed with calcined lime to temporarily close pores, preventing water absorption during granulation. This enhances reaction kinetics and early slag formation during sintering, resulting in significant improvements in sinter productivity, product yield, and cold strength property.

Feb 28, 2022

By D. Washington

The US economy and the demand for nonfuel minerals grew at lower rates in 1995 than in 1994. Demand for major metals, such as aluminum, copper and steel, was mixed but relatively stable. The building industry, including highway construction, helped to support modest overall growth in demand for industrial minerals. The value of processed materials of nonfuel mineral origin produced in the United States during 1995 was estimated to be $395 billion, an increase of almost 10%compared with 1994 (Fig. 1). The estimated value of US raw nonfuel minerals production during 1995 was $38billion, about 7% more than in 1994. The value of US minerals production has increased in 30 of the last 35years.

Jan 1, 1996

By M. Li, J. D. Miller

During the past decade, considerable effort has been made to develop improved flotation strategies for the sedimentary phosphate resources from Florida, particularly the dolomitic phosphate resources. New flotation equipment and alternate flotation strategies have been evaluated. These developments are reviewed for both traditional siliceous resources and future dolomitic resources. Most process strategies involve variation in the reagent sequence and/or the use of depressants/dispersants. Further research and development efforts in flotation technology are needed to increase flotation plant capacity by elimination of the conventional double float process, to improve the recovery of coarse phosphate, and to achieve the desired selectivity with respect to carbonate minerals, particularly dolomite.

Jan 1, 2000

By Kazem Oraee

In underground coal mining, particularly room-and-pillar methods, the coal pillars play a significant role in roof stability. If the pillar dimensions are increased, the pillar bearing capacity also increases, but more coal remains in the pillar and therefore the recovery of mining operation decreases. Therefore, determining the optimum pillar dimension based on technical, economical and performance parameters is important. In this paper, the coal pillar is designed by using the concept of ground reaction curve (GRC). For this purpose, the GRC for coal pillars is drawn and then the elastic and plastic zone of coal pillar behavior is determined. Based on elastic and plastic zone, different equations are presented to draw a pillar reaction curve and the process of coal pillar design based on GRC is explained. As a case study, this new technique is applied to study the coal pillar state in Tabas coal mine of Iran. The results show that the presented new approach is successfully used in the design of the optimum coal pillar dimensions, and also determines the elastic and plastic behavior limit, which is important especially for the logical design of yield pillars.

Jan 1, 2009