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By Sara Swiokla Korsikas, Toren Olson, Amado Guzman, Yuri O. Zepeda P

Ore agglomeration has been used as part of the heap leaching process for the last 40 years. However, industrial experience shows that the lack of a universal agglomeration standard has limited the benefits of this, otherwise, valuable unit process. The more complex the ore, in terms of the nature and relative abundance of fines (<74 μm), the more important that the agglomeration product satisfies some minimal requirements. This paper presents an agglomeration scale that identifies the quality standards for agglomerates and documents the resulting mechanical, physical, and hydraulic (hydrodynamic) behavior associated with each level on the agglomeration scale. The hydrodynamic properties of an agglomeration product are critical for the proper design of a leaching operation and, as shown in this paper, can be used to select the optimal pretreatment method for a given ore sample. Agglomeration as a unit process not only allows better conditioning of the hydrodynamic behavior of the ore but also creates an opportunity for optimized delivery of reagents to kick-start the leaching process which may ultimately improve the economic performance of leaching. Industrial case data is used to demonstrate the shortfalls associated with low-quality agglomeration and the benefits of improved agglomeration which range from enhanced porous structure (better percolation and drainage characteristics) to better metallurgical response (faster kinetics and higher metal recovery). Proper agglomeration has been used to render otherwise untreatable ores into valuable leaching resources.

Feb 9, 2024

By MEHMET KIZIL, PETER KNIGHTS, ROYAL REA

A 1/20 scale experimental dozer push test rig was designed and constructed to quantify the expected production rates (loose cubic meters per hour) for dozers operating in hard-rock bulk push applications. The particle size distribution of the material employed in the test rig was modeled on a fragmented muckpile representative of that for a typical surface copper/gold mine overburden. Buckingham Pi theory was applied to mathematically develop factors for scaling up dozer productivity parameters, including blade loads and push times. Dozer production rates were investigated for various dozing distances and slope angles. A series of instantaneous productivity curves were produced which are applicable for use in hard-rock dozer push operations. The productivity curves produced demonstrate that dozer productivity declines rapidly over the range of 10 to 40 m.

By A. E. Foscolos

British Petroleum (BP, 2005), indicates that world reserves for oil to be 1198 billion barrels, for natural gas the equivalent of 1156 billion barrels of oil and for coal the equivalent of 3219 billion barrels of oil. If we take into consideration the mean aver-age annual increase in demand of the last three years for oil, 2.6%, for natural gas, 3.9%, and for coal, 6.6%, then their respective reserves? lifespan are calculated to be 27, 34 and 38 years. Without taking into account their annual increase in demand, lifespan increases to 38, 67 and 161 years respectively. Since zero increase or perpetual increase in energy demands on finite resources is unrealistic the selection of the most suitable energy commodity for power generation rests upon the law of supply and demand of each commodity. This defines its price hence its selection for the production of cheap electricity. When the ratio of supply to demand is less than one, peak production is achieved. Any further increase in demand results in price increase to quench its demand. The Association for Oil and Gas Peak (ASPO) has calculated that when oil demand exceeds 84 million barrels/day, Peak Oil Production will be attained thus prices will start to increase in order to even demand with supply. Correspondingly, Gas Peak Production is expected to take place when demand exceeds 9.1 or 10.2 billion cubic meters/day. Peak Oil production has been calculated to take place in the current year, 2006, while Gas Peak production is estimated to take place between 2020 and 2025 provided that gas will not cover the energy deficit created from the lack of oil otherwise Gas Peak production could arrive as early as 2010. The use of coal for power generation is considered a better alternative than oil and gas if new combustion technologies with an energy efficiency of 43%, Germany, and 47%, Denmark, are adopted. These not only extend the lifespan of coal reserves but reduce also CO2 emissions by 25% and 31%, respectively. In the very near future CO2 sequestration and fixation in deep geological strata will eliminate its emissions thus rendering the use of coal the cheapest feedstock for power generation.

Jan 1, 2006

By Wen Tao Liu, Tong Tian, Fu Sheng Niu, Xiu Man Liang

The level of automation employed in flotation production is relatively low. In an actual concentrator, operators use their judgment to adjust the production state based on the visual characteristics of the flotation froth surface. There are shortcomings, such as strong subjectivity and lagging process operation, that easily cause the waste of manpower and material resources. Machine vision technology is introduced to replace human visualization, achieving a quantitative description of the visual characteristics of the froth surface. The state variable parameters are provided for the identification of the flotation conditions.

By Pafos Busch, Martin Fischer, Johannes Jaeger

The Spitzenberg Tunnel is a 600 m (1,970 ft) long twin tube motorway tunnel on Germany’s Autobahn A44 between Kassel and Eisenach. Since flexibility was considered to be very important in the continuously changing geological conditions, NATM was chosen as the construction method. When passing an old quarry with only 1,80 m (6 ft) of overburden, the excavation works became extraordinarily challenging. This paper not only describes the special methods, like double sidewall drifts and pipe umbrellas applied in this zone but also highlights the cooperation between the parties involved, which in combination made the project a joint success.

Jun 13, 2021

By Edwin R. (Original by) Phelps

Surface mining refers to the process of removing the material (over- burden) overlying a coal seam and exposing the coal so that it can be loaded out and conveyed by trucks or other methods to the preparation plant or other facility. Surface mining has not always been important in the coal industry. In the early 1900s, almost all of the coal mined in the United States was mined by underground methods. In 1900, about 192 Mt (212 million st) of bituminous coal were mined and less than 1% was mined by surface methods. The development and use of larger equipment has allowed surface mining to gain prominence throughout the years. Table 1 shows the total production of coal by mining method in the United States for ten-year periods since 1920 and indicates the growth of surface-mined coal production. Surface mining will undoubtedly continue to account for a large percentage of the coal production in the US for many years because: 1) The capacity of surface mining excavators has continued to increase. Today, mining companies are using shovels (see Fig. 1) which are able to move up to 137.6 m3 (180 cu yd) in each bite and draglines (see Fig. 2) which move up to 168.2 m3 (220 cu yd) in each bucketful. 2) Increasing tonnage from the thick western coal seams is being produced by surface mining methods. 3) Surface mining has normally had lower costs and a better safety record than underground mining; 4) Surface mining normally recovers a- much higher percentage of the coal reserve than can be recovered by underground mining. 5) Some coal measures can best be extracted by surface mining [ ] methods because of geologic reasons such as the nature of the roof or bottom, thickness of the seam, multiple bedding, etc.

Jan 1, 1981

By Paul R. Wieber

This paper describes the U. S. Energy Research and Development Administration&apos;s (ERDA) program to develop in situ coal conversion processes, especially gasification, he potential of this technology, the technical directions being explored, and the program strategy to carry the process concepts toward commercialization are emphasized. The geographic location of the U. S. coal resources and a market analysis are described. Commercially successful in situ coal processes could add over a trillion tons of coal to the U. S. coal reserves. The economics of these processes is compared with surface gasification independent studies show this process to be 25Z cheaper than surface gasification for Western coals. The major projects are briefly described. The Linked Vertical Well process is in the lost advanced stage and shows great promise. The last test produced a low-Btu gas averaging 171 Btu per standard cubic foot for average pro¬duction rates of 5.5 million standard cubic feet per day. The other projects are Packed Bed, Longwall Generator, and Steeply Dipping Beds.

Jan 1, 1977

By Norris E. Brooks

MAPCO Inc. is an integrated energy company involved in oil, gas, gas liquids, pipelines, and coal. The Coal Segment has installed a simple incentive program based on profit, tons produced, and hours worked at each operation. The plan has two segments-production bonus and profit sharing. Each segment is described and the results, which include high productivity, good safety, and high morale are discussed.

Jan 1, 1983

By I. Mikov

Established in the 60-ies, the Zlatna Panega quarry is a cement raw materials quarry supplying 95% of the needs of the Zlatna Panega Cement Plant with limestone, marl and other silica-aluminates. The two major types of raw materials are formed by accordingly dipping strata of Upper Jurassic limestones and lower Cretaceous marls. Between them there is a ?transition-zone? or ?contact-zone? of a high-silica content layer, about 5-m thick, defined as ?flint? by investigations including spot sampling throughout the quarry. For many years this ?contact-zone? layer was neglected due its negligible thickness. Further, with the increasing demand on the quality of the raw materials feed to the Plant and the focus on variability of the chemical and mineralogical components, it was decided not to mine any of the parts of the quarry contaminated by this material, for about three years. The latter had an impact on the availability of operating benches that could result in a substantial decrease in the total recoverable re-serves of Zlatna Panega, particularly with respect to marls. There were considerations for resorting to a partial, selective excavation of the quarry pit with a reduced lifetime for the lime-stones and re-opening of an other (currently in-active) marl quarry at a distance of 6 Km from the Plant. The Quarry Team of the Zlatna Panega quarry was assigned to study the problem. The ?contact? layer was duly confirmed with systematic geological (including mineralogy) studies, statistical analysis of available data, surface sampling and shallow exploration drills, resulted into distinguishing a third type of reserves and their credible subsurface delineation by means of geological 3-D modeling and quarry design. A new quarry design was finally elaborated with a view of providing flexibility in mining, utilization of the total volume of all available reserves and maximizing the mine life of Zlatna Panega quarry. An industrial test took place in December 2005, by using the contaminated parts of the quarry (co-mining of the ?contact-zone? materials) at a contribution of 15-20% in the raw materials mix, as dictated by their contribution in the total recoverable resources of the quarry. The purpose was to investigate the viability of this solution ? in line with improved quarry planning ? without compromising the quality of cement production and the efficiency of Plant Operations. Results were overall successful.

Jan 1, 2006

By Tim Neil, O&apos

Large is the applicable adjective here. The largest hydraulic shovel in the world, the largest copper mine in the world, the largest copper producing company in the world. The O&K RH 300 hydraulic excavator has been put into service to move overburden and mine ore at the Chuquicamata open pit mine of the Chilean state copper mining company, Corporation Nacional de Corbre de Chile (Codelco). A large shovel: Equipped with a 26-m3 (34-yd&apos;) rock shovel, the RH 300 is able to fill a 170-t (187-st) truck in three passes with cycle times of 30 seconds. A large mine: At present, the Chuquicamata pit is 4 km (2.5 miles) long, 2 km (1.2 miles) wide, and 520 m (1700 ft) deep from rim to bottom bench. The current 450 kt/d (496,000 stpd) of material mined will increase to 600 kt/d (661,000 stpd) when the expanded production rate is reached in 1989. (Chuqui Expansion details, p. 20). A large mining company: Codelco&apos;s total output from its two open pit and three underground copper mines is more than 1.1 Mt/a (1.2 million stpy) of copper. This makes Codelco by far the largest copper producer in the world. It accounts for about 15% of the Western World&apos;s copper requirements. Chuquicamata is located in the hot and arid Atacama desert of northern Chile. The mine is located 240 km (150 miles) northeast of the port city of Antofagasta. Mine elevation is 2700 m (8850 ft). Chuquicamata&apos;s known reserves of oxide and sulfide ores amount to more than 450 Mt (496 million st) of contained copper. There are also reserves of more then 1.4 Mt (1.5 million st) of contained molybdenum. Originally, Chuquicamata was a rail pit. The shovels loaded rail cars hauled by locis on tracks along the benches. During the 1970s, the rail transport was replaced by truck haulage. Crushing and conveying rock waste in the pit is the latest step in the continuing evolution of more productive and economical methods of materials movement. In 1990, the in-pit crushing plant will be in operation. The waste will be mainly transported out of the pit on belt conveyors rather than trucks. The system will incorporate a 9.6-kt/h (10,600-stph) semi-portable crushing station, a 14-km (8.7-mile) conveyor using 1.8 m (6 ft) wide heavy duty belts, and a tripper-spreader to stack the waste dumps. Since Chuqui went into production in 1915, more than 2.5 Gt (2.8 billion st) of material has been excavated. This includes nearly 1.7 Gt (1.9 billion st) of ore from which some 16.4 Mt (18 million st) of copper has been recovered. The Chuquicamata porphyry type ore body is an altered and fractured intrusive granodiorite or quartz-monzonite porphyry that carries the mineralization. The action of ground water on primary sulfide minerals in geo¬logic time has created oxide ores and a zone of secondary enrich¬ment. The oxides occur above the sulfide zone and are also mixed with the upper parts of the latter. At Chuquicamata, the current grade of 1.5% copper is expected to decline to about 1% by 1995. To maintain metal production at cur¬rent levels, it will be necessary to increase ore production rates by about 50%, as mentioned, to 153

Jan 1, 1988

By James O. Glanville

Ice frozen from a dilute chemical solution is mechanically weaker than ice frozen from pure water. This phenomenon is the basis of a practical method for reducing the strength of a mass of frozen coal. If a chemical additive is applied to moist coal, prior to its shipment during freezing weather, the resulting frozen coal can be more easily broken than in the absence of the chemical additive. This greatly expedites the unloading and handling of coal during winter. There has been considerable research into the nature and mechanical strength of ice frozen from various solutions. The literature relating to this process has been reviewed as has the literature relating to the chemical treatment of coal and mineral particulates. Some important articles are discussed and speculations are made about the nature of the ice-weakening process. A laboratory evaluation of the effects of chemical additives on the mechanical strength of ice and frozen coal has been made. An apparatus designed for this purpose is described, and some results obtained with it are discussed.

Jan 1, 1980

By Earl M. Woodward

INTRODUCTION Kerckhoff-2 is a 140 MW underground hydro-electric project designed and owned by Pacific Gas and Electric Company and constructed between May, 1980 and May, 1983 by Auburn Constructors. The project is located in the western foothills of the Central Sierra Nevada Mountains, about 30 miles northeast of Fresno, California, and develops the power potential of the lower San Joaquin River and its tributaries between the existing Kerckhoff and Millerton Lakes. The Kerckhoff-2 Project consists of project roads, adits, and access tunnels, service tunnels, power tunnels, powerhouse, tailrace tunnel surge shaft, buss shaft, intake structure, discharge structure, and switchyard. In the 1920s, the Kerckhoff 1 project, consisting of a dam, reservior, tunnel, and 34 MW powerhouse, was built in the same general area as Kerckhoff-2. The tunnel was constructed by conventional methods, and was left unlined. In time, other projects were built upstream, allowing the flow of the San Joaquin River to be regulated. The Kerckhoff 2 project is designed to harness that regulated flow, providing an additional 140,000 ON of power. Kerckhoff 2 will be the primary power plant; Kerckhoff I will produce power whenever the flow rate exceeds 4,800 cubic feet. The new power tunnel is built along the east side of the San Joaquin River between Kerckhoff and Millerton Lakes, parallel to the existing tunnel but extending approximately one mile further downstream.

Jan 1, 1983

By Robert W. Carn

This paper presents the concepts which are presently being utilized in the design of coal export terminals. Criteria for selecting a viable site and establishing the terminal plan are presented. Factors affecting the design of the terminal as well as the present techniques and procedures in use today to determine the optimum use of equipment will be discussed along with the current trends in export terminal control systems. Finally capital and operating costs for a typical export terminal are reviewed.

Jan 1, 1982

By Irwan Halim, Seung Han Kim

This paper will describe design of precast segmental tunnel lining for the Pawtucket CSO Tunnel Project in Providence, Rhode Island. The tunnel is 11,700 LF long with 30-foot finished diameter to be constructed in complex sedimentary rocks. Special features of the segments include a large keystone and no connector used on radial joints. The typical segments will be steel fiber reinforced, and hybrid segments with additional steel rebars and shear bicones will be used around the adit openings without use of any structural framing. The important design considerations will be discussed, including special 3D segment to adit connection analyses performed.

Dec 1, 2022

By L. Zhou, L. Yuan, R. A. Thomas, D. Bahrami

The abstract emphasizes the importance of a calibrated ventilation network model for mine ventilation planning, optimization, and fire simulation. It highlights the impact of continuous airflow monitoring on improving model calibration. The paper discusses an experimental study at the Safety Research Coal Mine (SRCM) to understand the use of continuous airflow data for model improvement. It also addresses practical problems in calibration and tuning using this data, including analysis of air velocity sensor fluctuations and application of sensor location correction factors for accurate average air velocity.

Mar 7, 2022

By Arthur W. T. Grimley

Hydraulic coal mining is being successfully practiced in China, U.S.S.R., Japan and Canada and in each country, excepting Japan where suitable sites are not available, the system is being expanded to either existing conventional mines or new mines. Productivity levels and economics at these mines are in all cases better than the productivities achieved in conventional mines in the same general localities. In the U.S.S.R. face productivities approaching 50 tons per man shift have been reported while in Canada the latest statistics show average face area productivity levels are in the region of 200 tons per man shift production monitor. In the United States hydraulic mining has not been actively pursued to the same degree and consequently there are no full scale hydraulic coal mines in operation or construction. Because many of the coal measures in the Western U.S.A. are generally somewhat similar to those being successfully hydraulic mined in Western Canada and parts of Siberia it is realistic to believe that successful hydraulic mines can be designed and developed in the Western U.S.A. Particularly if the vast technological base that already exists is used to improve on other people&apos;s ideas, systems, methods and equipment.

Jan 1, 1983

By J. Kuti

In room and pillar mining a large number of working points are arranged to follow a mining pattern. Geological and roof control problems can be overcome or their effect minimized by varying this pattern. Longwall mining on the other hand, fixes the mining pattern for anyone panel. This aspect of longwall mining leads to constancy, so that a well-conceived organization, ventilation, dust and roof control systems lead to daily repetition and subsequent simplicity of control. All the same, a fixed mining pattern calls for a very careful consideration and selection of design parameters. (Ref. 1.)

Jan 1, 1971

By A. H. Farazi, C. Quamruzzaman

The freezing and subsequent solidifying of unstable, weak (sands, silts and clays) and/or wet soil to form a desired-shape frozen barrier around a construction area are possibly the main features of the freezing method for shaft sinking. The barrier, along with strengthening the soil, provides a dry environment to ensure sustainable subsurface construction work before placing a permanent lining. The freezing method requires the installation of freezing pipes in boreholes around the construction area and the circulation of chilled salt water through these pipes and has long been a proven technique for dry shaft sinking through unstable and water-bearing seam around the world. As removing heat from the ground is the main feature of the method, an efficient thermal design of the freezing process is mandatory to ensure success of the shaft sinking operation. This applies to both the sustainability and economy of the intended structure. The design presented in this paper is aimed at figuring out the heat-removing ability and operating time of the refrigerative equipment using some simple formulae. The authors adopted a theoretical approach to determine the quantity of heat to be removed from the ground. The amount of energy for the equipment was found to be greater than that for freezing, which proved the validity of the design. The active freezing period was calculated to be 121 days. The authors followed the structural design of the freezing process they proposed in their previous work (Farazi and Quamruzzaman, 2013). Though the first coal seam in the coalfield was encountered at a depth of approximately 352 m in the subsurface, the target depth for cooling and freezing was decided to be 162 m. The formation demands extra care to nullify its risk of the temporary structure collapsing and water rushing in (Farazi et al., 2012). Discussion on the determination of refrigerative equipment parameters was excluded from the scope of this work.

Jan 1, 2014

By David Newman

"Horizontal stress can have a profound effect on the stability of an underground limestone mine. The presence of horizontal stress is usually determined once the mine has been developed and the orientation of headers and crosscuts are well established. Multiple attempts are typically made to control roof falls without re-orienting the mine. Once the decision has been made to change the orientation, pillar centers, mine opening widths, and the question of how to determine the correct orientation must be answered.A case history is presented to illustrate how geologic structure, ground conditions and roof falls in adjacent mines, the World Stress Map (Heidbach et al., 2016), in-mine measurement of “cutter” roof orientation, the orientation of strata offset (cats eyes) within borescope holes, and the diametral deviation method of determining horizontal strain from drill core were used to establish the most likely range of horizontal stress.The main headers were re-orientated in a direction parallel to the median of the range of horizontal stress. The crosscuts were angled 60° to the headers to avoid being perpendicular to the horizontal stress direction. Pillar centers and opening widths were increased in the favorable stress direction of the mains and decreased in the less favorable crosscut orientation. The major principal horizontal stress magnitude was estimated using the strain measurements from the diametral deviation method and elastic modulus obtained through testing.INTRODUCTIONOver the past decade, there has been a significant increase in the number of underground stone mining operations in the United States. As stripping ratios at surface quarries become uneconomical and reach the extent of the mineral boundary, coupled with the encroachment of urban development on previously rural mining operations, the remaining mine reserves are best accessed through underground development.Although the majority of underground limestone mines in the Midwest are in relatively flat lying deposits with minimal geologic structure, many Appalachian mines are in folded and faulted environments. Tectonic horizontal stresses associated with multiple orogenic episodes are locked in the formation and are released as the underground mine is developed.A common misconception is that horizontal stress impacts are more prevalent at shallow depths where the ratio of horizontal to vertical stress may be high. However, field observations and academic research indicates that horizontal stress conditions may be encountered at any depth due to the tectonic compression of the limestone formation (Esterhuizen et al., 2007; Dolinar and Esterhuizen, 2007; Iannacchione et al., 2003; Slaker, Murphy, and Miller, 2017; Kuhnhein and Ramer, 2004). This paper outlines mine design and layout guidelines for the mitigation of horizontal stress impacts on underground stone mining operations through a case history example. This approach to mine planning and the ability to anticipate horizontal stress can significantly improve future production of multiple levels (Newman and Newman, 2019). As underground stone production continues at deeper depths and in more geologically and geometrically complex mining conditions, an emphasis on ground control and the anticipation of horizontal stress can provide safer and more productive single and multiple level mining operations."

Jan 1, 2019

By W. G. Pariseau

A study of coal pillar strength at the Beehive Mine in central Utah was done in the 1970s. This study was a cooperative effort by the University of Utah, RE/SPEC, Inc., and the American Coal Company and was funded by the U.S. Bureau of Mines. Mine measurements of closure at 117 points and pillar stress using 119 vibrating wire stress gauges were made during retreat mining in this room-and-pillar operation. Laboratory testing for the strength and modulus of 372 coal cylinders up 0.3 m (1 ft) in diameter and 0.6 m (2 ft) in length was also done. Two-dimensional finite element model analyses complemented the study. However, the real world of mining is three-dimensional and in consideration of the significant advances in computing power since the time of the original study, a revisit of the data seemed warranted. In this regard, a novel finite element method was used that allows for the whole-mine analysis of tabular excavations on the kilometer scale and yet enables details to be obtained at pillar walls on the meter scale. The effects of material properties variability in situ and of joints can also be taken into account. Results that compare computed two- and three-dimensional seam-level closures with mine measurements show noticeable differences; three-dimensional results are reasonable, while two-dimensional results overestimate closure by nearly a factor of two.

Jan 1, 2014