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One of the major objectives of cost analysis is to enable the manager to predict the financial outcomes of decisions. To accomplish this, the future costs and benefits of alternative courses of action must be determined. If care- fully used, information about past financial performance can be helpful in this analysis despite the fact that, by definition, financial reporting information is historical. In many cases, both revenues and costs need to be estimated for decision- making. For the production manager, additional revenue is a result of increased throughput or recovery of valuable material from the stream of mined material. A reduction in operating cost, although similar to a revenue increase in its financial impact, is estimated using slightly different techniques. Generally, the estimation of cost is more difficult than the estimation of revenue. Most cost estimates have two components: an estimate of fixed costs and an estimate of variable costs. As discussed in chapter 5, the total cost of an activity during a specified period can be expressed as: Total cost = (Variable cost per unit of activity) x (Units of activity) + Fixed cost or TC = VX+F

Jan 1, 1999

By R. D. Cook, J. L. Johnson

"Measuring mud bed level in a sedimentation device is an important control variable. Methods used to date for this purpose have had limited success providing continuous, consistent measurements at a reasonable price. This paper describes a new instrument for detecting the mud bed / liquor interface as well as bed density profiles. The state of the bed is measured directly with sensors located in the thickener. Data from bench-scale and full-scale tests show that the bed level is well defined and easily detected. In addition, full-scale testing revealed unprecedented information about thickener beds. Variation in bed density gave new insight into thickener bed dynamics, providing design and control opportunities never before possible. This novel instrument can significantly improve thickener control by providing reliable and consistent bed level measurements. It is also capable of measuring bed density profiles that can potentially identify significant operating problems early enough to take corrective action before experiencing costly shut downs. INTRODUCTION Numerous studies and papers have been devoted to the subject of thickener design and operation to achieve specified throughput and discharge densities. Mathematical models have been developed that present methods for sizing thickeners and predicting performance under varying process conditions. The compression effect of deeper beds on dewatering performance is a recognized phenomenon (Wilhelm and Naide 1981). This is one variable of many that are inter-related and influence thickener performance. For example in the steady-state, continuous operation of a thickener, if the solids feed rate increases and the bed level remains the same, the underflow discharge rate must increase with the result of solids concentration being lower. The interactions of these parameters are at the heart of thickener models. One such model (Burger and Narvaez 2007), predicts solids concentration profiles increasing downward and discontinuities between settling zones. This model uses sediment height (bed level) as a parameter that influences capacity calculations to achieve the specified solids concentration of the underflow. Knowing the bed depth is critical to maintaining stable thickener operation. Implicit in these modeling strategies are some basic assumptions such as homogeneous distribution of solids in the different settling zones, plug flow of solids through the settling zones and steady state operation of the thickener. The accuracy of these assumptions has not been verified because there has been little visibility inside the bed of full size operating thickeners. Testing of the instrument presented in this paper demonstrates that it provides a degree of visibility of the dynamics in a thickener not previously possible and indicates that the basic assumptions of the modeling strategies may not be completely accurate."

Jan 1, 2015

By J. W. III Leonard, T. E. Wilson

In addition to coalbed thickness and basic coal quality data, coal drill cores can produce design data for coal beneficiation processes. To generate design data, a coal drill core should be reduced from its original cylindrical form to a particle size distribution and composition that represents (with the possible exception of top size) a raw coal process stream. Reducing a coal core with a crushing machine rarely accomplishes this representation. This investigation employs drop-shatter impact breakage followed by dry batch tumbling in a steel cylinder rotated about its transverse axis to characterize the core in terms of first-order and zeroth-order break- age rate constants, which are indices of the propensity of the coal to degrade during handling. To reduce composition variables and conserve difficult-to-obtain coal cores, the initial drop-shatter and dry-tumbling tests were done with synthetic cores. Then, cores from three coal beds, Illinois No. 6, Upper Freeport and Pocahontas No. 5, were tested. Comparison of a crushed drill core and a drill core prepared by drop-shatter and tumbling indicated that the size distribution and size fraction composition of the drop-shattered/tumbled core more closely resembled the plant feed.

Jan 1, 2000

By W. Addy Majewski, Kenneth L. Bickel

The U.S. Bureau of Mines (USBM) and Diesel Controls Limited evaluated a new diesel emission control system on an underground mine vehicle. The system was a catalyzed ceramic wall-flow diesel particulate filter (CDPF) combined with an catalytic converter, or diesel oxidation catalyst (DOC). This paper describes the design and installation of the system on a load-haul-dump (LHD). The results of screening tests conducted by the USBM are also given. The screening tests were conducted to determine if the device's particulate collection efficiency, regeneration temperature, and effect on gaseous hydrocarbon (HC) and carbon monoxide (CO) emissions changed over the period it was being used. The system was removed from the LHD and evaluated in the laboratory after operating for 308 and 1200 hours. After 308 hours of operation, laboratory testing revealed its particulate collection efficiency varied from 41.0 to 93.5 percent, depending on engine operating conditions. Its regeneration temperature was about 415° C. It reduced HC emissions by up to 97.6 percent, and CO by up to 95.0 percent. When tested in the laboratory after operating for 1200 hours on the vehicle, no significant change in performance was observed.

Jan 1, 1995

By W. E. L. Minter

The most important witwatersrand gold placers occur on extensive unconformity paleosurfaces that were produced during protracted periods of fluvial degradation. The erosional etches on what was generally unlithified substrate indicate that low sinuosity erosion patterns prevailed. The transport systems were dominantly braided fluvial with a minor debris-flow component. The placer sediments were non-cohesive sands and gravels which were evidently transported by fluctuating, yet perennial, discharges across extensive, low relief, bra1dplains, not far from littoral environments. Progress made in understanding heavy-mineral transport processes now emphasizes the importance that selective entrainment probably had in producing concentrations. Cognizance that these characteristics are not unique to the Witwatersrand should be taken into account when designing exploration models.

Jan 1, 1988

By Michael Traylor, Michael Jatczak, Brett Robinson

The Detroit River Outfall No. 2. is an effluent water conveyance system linking the Detroit Metropolitan Wastewater Treatment Plant to the Detroit River. The 6.4m (21ft) finished diameter tunnel extends 1,890m (6,200ft) east from the bottom of a 91m(300ft) deep, 9.2m (30ft) diameter drop shaft. At the eastern terminus of the tunnel, six Riser Shafts connect the tunnel to diffuser heads on the riverbed. The tunnel runs through a highly fractured Limestone formation capable of producing high levels of groundwater in?ows and Hydrogen Sul?de gas. Control of this water and gas was a theme which ran through the entire Project’s design and construction. This paper will provide an overview of each portion of the Project’s construction, including the Entrance Shaft, Precast Concrete Segments, TBM Tunnel, Pre-Excavation Grouting Methods, and the Riser Shafts.

Jan 1, 2003

By Gerald G. Griswold, James O. Greenslade, Cherie Tilley, Richard Reseigh

INTRODUCTION The Harrison Western Corporation, a leading Denver based mine contracting and engineering concern, is presently engaged in sinking two 1,006 m (3,300 ft) shafts for the Phillips Uranium Corporation at their Nose Rock Project, approximately 13 miles northeast of the small community of Crownpoint in McKinley County, New Mexico. The Nose Rock Project is the first attempt by the Phillips Uranium Corporation to tap the deep uranium reserves in what has become known as the Grants Mineral Belt. (See Figure 1) Project Description Phillips Uranium Corporation's plan for the large 2700 metric ton per day (2950 tons/day) mining facility calls for a series of deep access and ventilation shafts ranging from 4.27 m (14 ft) to 5.49 m (18 ft) in diameter to approximate depths of 1,006 m (3,300 ft). The initial pair of shafts consists of one production shaft and one ventilation shaft separated by a distance of 91 m (300 ft). The interbedded layers of sedimentary sandstones and shales to be penetrated by the shafts contain several major water producing aquifers, the deepest being the mineralized zone called the Westwater Canyon Member of the Morrison Formation.

Jan 1, 1981

By Lennart Malmqvist

Decision-making in exploration deals with experience, knowledge, and sometimes faith, but very often financing and profit, mineral resource aspects, employment, and general political ambitions are parts of the scene. At one end of this spectrum, there is the prospector and his decision on the actual project. The exploration business now expands from its pioneering phase for the benefit of a single company to a wider spectrum which includes the benefit of the large mining consortium and a national development program. Its objectives are also to maintain employment and to favor long-term stability in a mining district or a mining company. The prospector then has new aspects and questions to consider such as, what to do in mining districts where there is a shortage of ore resources but there are still useful investments in mines, processing plants, etc. To analyze the exploration process, therefore, seems to be of great importance in a time of rapidly changing conditions. As in other areas of complex decision-making, for example, in the fields of investments, of production, and of the armed forces, computers most certainly have an important role to play in future exploration decision-making systems. However, we must first analyze our own business as closely as possible to find out what kind of information we need, i.e., why we recommend an exploration program as a good or a poor one. An important part of the debate about exploration is the case study. Case studies on exploration are few and most of those written are only about successful exploration programs. Where are the case studies of the failures and the not so successful programs? Every prospector knows that the majority of exploration projects fail. Consequently, the most important experience seems to be hidden in the failures.

Jan 1, 1979

By John Mastoris, Kostis Dragasakis, Kostas Kouklidis, Shkurtë Gashi, Halil Berisha, Jenuz Bulica

Titan Group’s environmental policy and Sharrcem’s Corporate Social Responsibility (CSR) are the driving forces behind the development and implementation of a comprehensive Rehabilitation Plan at Dimce Quarry, which is the main raw material source for Sharrcem Cement Plant since the 1970’s, located in the municipality of Hani i Elezit in Kosovo. Based on an Environmental Impact Assessment Study and the approved Mining Plan and also on the principles prescribed in the Guidelines on Quarry Rehabilitation, released by the Cement Sustainability Initiative of the World Business Council for Sustainable Development (WBCSD-CSI), Sharrcem has adopted a quarry operation and rehabilitation process in line with the best practices in the mining and cement sector. This paper discusses the background for the development of the rehabilitation plan and the results of rehabilitation activities, as have been implemented over the last few years. The main objective of the progressive rehabilitation plan at Dimce Quarry is to restore the depleted pit and return it back to the original land owners for resettlement. To date approx. 3,4Ha of former mining area has been restored by backfilling and levelling of the depleted closed pit and returned back to owners, who have built their houses and turned it into a living area again. This Quarry has turned out to be a real composition and practical example of preserving and returning back the natural resources in a state compatible with the surrounding environment and with respect to the needs of the local stakeholders. The motivation for business to engage in rehabilitation activities in the first place lies in the belief that the development and implementation of a progressive and practical Quarry rehabilitation plan and restitution of the land will deliver significant environmental and social benefits that outweigh the long-term rehabilitation costs, while maintaining the company’s reputation.

Jan 1, 2017

By H. E. Bonner

The recovery of fine coal has historically had limited success due to the intimate clay association on the surfaces of the coal particles. This clay presence has detrimentally affected conventional beneficiation techniques resulting in a recovered product containing unacceptably high concentrations of ash and moisture. An ultrasonically activated tray that operates in a continuous fashion has been developed that separates the clay film from each particle's surfaces. This separation is of sufficient duration to allow conventional beneficiation techniques to be utilized more efficiently.

Jan 1, 1989

By David J. Dunn

Materials related problems at mines can be big ones - like a newly completed 1 -m (3.5ft) water pipeline burst during initial filling, grinding ball consumption at double the typical norms on startup of a new semiautogenous grinding (SAG) mill circuit or 30 open-pit haul trucks in the shop for new bed liners after less than a year’s service. Materials engineering provides solutions to these kinds of equipment problems by selecting good materials and designs, by trouble-shooting service failures and by maintaining high quality in vendor-furnished materials and components. Materials with good properties, correctly made and fabricated, correctly installed in mining and processing equipment, produce ore and final products reliably and efficiently. Materials engineering, applied during design phases, specification writing, and receipt and installation of materials, ensures that equipment will have the best possible shot at performing up to expectations. Good calls on materials properties - specifying state-of-art materials produced by competent manufacturers - help mine managers to reduce downtime and mining and processing costs. Materials that are improperly made or specified can make a mining operation less efficient or, possibly, uneconomical.

Jan 1, 1992

By S. G. Hardcastle, K. C. Butler, M. G. Grenier

The most common method of determining airflow employed by mine ventilation engineers is the product of i) the average air velocity as measured by a vane anemometer and stopwatch through a continuous traversing technique, with ii) the cross-sectional area of the roadway. This method requires the vane anemometer to accumulate the total flow over the duration of the traverse. Historically, this has been facilitated by a mechanical analog instrument that has either a counter or set of dials that display the flow. Common instruments of this type are Airflow Development's AM5000, Davis's, or Taylor's Biram type anemometer. The AM5000 is widely used in the Canadian mining industry but is no longer available. Therefore, regulatory authorities have seen fit to evaluate presently available commercial instruments to replace the AM5000. This paper describes an instrument evaluation contracted by the Atomic Energy Control Board of Canada which regulates the uranium industry. Over the last two decades there have been numerous advances in the development of electronic air velocity meters. Currently available units have the following features: a) battery operation; b) are compact and can be hand-held; c) employ LCD's, and microelectronic circuitry; and d) provide a time integration for the duration of a traverse. These features make such instruments a possible replacement to the analog units and stopwatch determinations. This paper details five of the new generation of vane anemometers plus a vortex air meter, and it explores their limitations in comparison to analog units. Specific consideration is given to linear response, the effects of yaw, traversing speeds and ergonomics relating to both handling and use. The paper concludes with some features that are attractive and should be considered when purchasing a new anemometer.

Jan 1, 1991

By Richard I. Grass

The White Pine Mine is located 4- 1 /2 miles south of Lake Superior in the western part of Michigan's Upper Peninsula. The orebody occurs in tabular, gently dipping Keweenawan sediments. GEOLOGY The orebody outcrops beneath 30-50 feet of Pleistocene clays and dips to the east and northeast to a depth of 3, 000 feet in five miles. It lies midway between the Porcupine Mountains and the Bergland Hills, both of which are steeply dipping felsite and coarse porphyry intrusives, extrusives and sediments (Figures 1 and 2). The orebody sediments were deposited in the Keweenawan basin during mid- and upper Keweenawan times. Mineralization occurs in the basal 20 to 25 feet of the Nonesuch formation, which is made up primarily of laminated siltstone s. Native copper, chalcocite, and silver are the ore minerals. The ore is mined by trackless room-and-pillar methods.

Jan 1, 1967

By A. D. Paul, Yoon R. H., C. I. Basilio

Considerable amounts of Fe3+ ions are released into solution when coal is exposed to 1-3 M acid solutions. These ions superficially oxidize the coal surface, and are reduced to Fe2+ ions. When provisions are made to generate the Fe3+ ions in solution, e.g., by inserting an anode whose potential is above the reversible potential for the Fe3+/Fe2+ couple, considerable amounts of mineral matter are liberated from the coal matrix. With many eastern U.S. bituminous coals, this mineral liberation is achieved selectively without significant breakage of the coal. It is believed that this process is induced by the osmotic pressure set-up in the crevices between the mineral matter and coal that are exposed to the solution. A theoretical model predicting the osmotic pressure is presented in this work, along with some results obtained with different coal samples.

Jan 1, 1992

By Robert M. St. Louis, Janet M. Edgecombe

The Mercur Mine's autoclave is an alkaline pressure oxidation system, operating at 220°(428°F) and 3061 kPa (444 psig) (total). Up to 725 metric tons (800 st) of ore, grading 2.02 g per mt (0.059 oz/st) Au and containing 1 to 2% sulfide sulfur, are treated daily in this circuit. A mineralogical and chemical investigation was initiated to locate the cause of lower than anticipated gold recoveries. Greater than 70 wt. % of reduced sulfur is oxidized; therefore, the autoclave is operating at specification. The low recoveries were attributed to increased concentrations of organic carbon in refractory ore. Activated carbon concentration in the attached CIL circuit was increased from 15 to 40 g per 1, leach temperature held below 21°C (70°F), and carbon flow changed to counterflow. These measures resulted in gold recovery improving from 75 to 82%.

Jan 1, 1990

By John Chapman, Daryl Hockley, Michael Paul, Silvia Jahn

As part of the waste characterisation program to address site reclamation, WISMUT GmbH initiated 56 columns operated as large-scale humidity cell tests. The columns were initiated to assess the acid generation characteristics of waste rock from 14 waste rock piles distributed around the site. Of the 56 tests, 11 are ongoing and have been operational in excess of 160 weeks. The results to date from these long-term tests are surnrnarised. In particular, the methods for, and importance of, establishing the availability of the carbonate neutralisation potential and acid generation potential respectively, are discussed. Geochemical controls on uranium, and the conformity between the geochemical models MINTEQA2 and EQ3/6 in assessing these controls are discussed. Testing indicates that waste rock with an MS-NP:AP ratio in excess of about 2.7 should result in net neutral pH conditions.

Jan 1, 2000

By J. J. K. Daemen, C. Fairhurst

Two aspects of tunnel support design are considered, and for both particular attention is paid to the influence of rock failure around the tunnel on the loads developed on the supports. 1) In general it has not been possible to extend analytical methods for the study of rock failure around tunnels to three dimensions. As a consequence it was not possible to calculate either the influence of the face or the actual sequence of support loading as the face advanced. The finite element method made this extension possible. A simplified analysis of the influence of the face and of the sequence of support installation has been made. The influence of the original stress field and of the rock behaviour on the length of tunnel which can be left unsupported (related to the stand-up time) is shown. The degree to which a 2-dimensional analysis can be used to approximate the final support load is shown to be dependent upon the post-failure behaviour of the rock. 2) Tunnel support design requires a knowledge of the forces and of the -rock displacements which cause stressing and deformation of the support system. A 2-dimensional model incorporating a detailed representation of several support systems, of the rock behaviour in the broken zone and of the interaction between rock and support is given. The model allows the calculation of the stress distribution in the support. The significance of the relative stiffness of support and rock on the stresses developed in the support is shown.

Jan 1, 1997

By D. D. Harbuck, G. K. Green

The Bokan Mountain area on Prince of Wales Island, AK, contains vast quantities of heavy rare earth minerals. To lessen the US dependence on foreign sources, the US Bureau of Mines (USBM) investigated yttrium recovery from this ore. By sulfating the ore at 250 ° C for 1 hr at an H2S04:ore ratio of 1:1 and then water leaching the sulfated material for 1 hr at 20% solids and 25ºC, over 74% of the yttrium, cerium, and lanthanum were solubilized. Solvent extraction (SX), using a synergistic combination of OPAP and DEHPA, selectively loaded 100% of the yttrium. Yttrium was stripped directly as a solid using a 2M, 35 ° C NaOH liquor. When the OPAP/DEHPA mixture was tested in a continuous SX circuit, yttrium loading and stripping were 100% and 96%, respectively. The organic showed excellent recyclability properties with minimal solvent loss.

Jan 1, 1996

By R. F. Hüttl

The restoration of surface mining landscapes requires the (re)creation of ecosystems. In Lusatia (eastern Germany), large-scale open-cast lignite mining operations generated spoil dumps widely consisting of acidified, phytotoxic substrates. Amelioration and rehabilitation measures have been developed and applied to these substrates since the 1950s. However, it is still not clear whether these approaches are sustainable. This paper reports on collaborative research work into the ecological potential of forest ecosystem development on typical minesites in the Lusatian lignite district. At first sight, pine stands on minesites along a chronosequence comprising about 35 years did not show differences when compared with stands on non-mined sites of the general region. Furthermore, with some modification, conceptual models for flora and fauna succession in forest stands on non-mined sites seem to be applicable, at least for the early stages of forest ecosystem development. For example, soil organism abundance and activity at minesites had already reached levels typical of non-mined sites after about 20-30 years. In contrast, mine soils are very different from non-mined soils of the test region. Chemically, mine soil development is dominated by processes originating from pyrite oxidation. Geogenic, i.e. lignitic, soil organic carbon was shown to substitute for some functions of pedogenic soil organic matter. Rooting was hampered but not completely impeded in strongly acidified soil compartments. Roots and mycorrhizae are apparently able to make use of the characteristic heterogeneity of young mine soils. Considering these recent results and the knowledge accumulated during more than 30 years of research on minesite rehabilitation internationally, it can be stated that minesite restoration might be used as an ideal case study for forest ecosystem development starting at "point zero" on "terra nova".

Jan 1, 2002

By J. Slivnik, A. Stergarsek

[The site] [Z]irovski vrh uranium ore deposit is located in the extreme north-western part of Yugoslavia, some fourthy kilometers from the capital of Socialist Republic of Slovenia, Ljubljana, not far from the Italian and Austrian border. The sandstone type deposit of uranium ore with medium grade is located in a foothill of Julian Alps. The site shows some typical conditions for this region, which demand special attention in respect to the incorporation of an uranium treatment facility into environment. Among these specific conditions the following site characteristics should be mentioned: - populated area of agricultural and recreational value, - unconvenient climatic conditions with excessive rainfall and long lasting temperature inversions in the winter time, - very pure surface and underground waters which supply the drinking water reservate for large area including the capital of Slovenia, - sharp relief, - unconvenient geological structure. The choise of technology The intention to produce uranium and at the same time respecting the natural characteristics and existing uses of the site made the design of the ore treatment facility relatively difficult one. In general, there were two basic alternatives available perform the task. First alternative was to adopt the usual technological flowsheet with wet tailings disposal and with discharge of used water i.e. liquid effluents into the river. In order to prevent the negative impact of such technology on the sourrounding area sophisticated water purification installation and costly measures in wet tailings disposal e.g. impermeabilisation of large areas by concrete injections, large dam constructions, uncertain capturing of the water sources should be employed. Second alternative was to modify the usual flowsheet by employing the maximal recycling of liquid effluents to the process and to dispose the solid

Jan 1, 1980