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By S-J. Park

When evaluating mining investment opportunities, one should consider the risks associated with mineral exploration and development. These are commonly classified as technical, economic, and political risks, and are accounted for in the investment decision by changing the discount rate. Thus, a company may use different discount rates associated with varying risks in order to compensate for the variability of success. The discount rate has a tremendous effect on the economic evaluation of mineral projects. Even when all other factors used as inputs for calculating the NPV (net present value) are equal, the project under consideration may be accepted or rejected depending upon the discount rate. Determining a realistic discount rate for a given project is therefore the most difficult and important aspect of cash flow analysis. It should be determined with the consideration of proper technical, economic, and political conditions surrounding the specific project undergoing economic evaluation. One key problem for determining the appropriate discount rate is that it typically depends more on subjective perception of the degree of risk or other experience factors than on a systematic approach. Thus, this study aims to identify, analyse, and document the type, role, and impact of risk factors influencing the determination of discount rates, and then to determine discount rate by using the aforementioned factors.

Jan 1, 2011

By I. Filzwieser, S. Konetschnik, A. Filzwieser, A. Anzinger

Production in copper electrorefining tankhouses mainly depend on two factors: The deposition area, which is a result of the amount of installed cells and cathodes, as well as the current density - the amperage per square meter of deposition area. The present paper shows, that the most economical way of achieving a certain production is to maximize current density by using the METTOP-BRX-Technology - as building and infrastructure can be kept more compact. This industrial proven technology applies a parallel electrolyte flow in each electrolysis cell. In 2011, the first fully industrial applications started up: At the secondary smelter Montanwerke Brixlegg AG, 156 cells are equipped with the METTOP-BRX-Technology; this allows a current density of 390 A/m². Xiangguang Copper Co., Ltd. - a primary smelter and refinery - operates its new tankhouse (720 cells) at 420 A/m²; this stands for an production increase of 50% compared to the same sized ISA tankhouse which is limited to 280 A/m². The first part of the present paper gives a cost comparison between a conventional copper electrorefining tankhouse and a high current density tankhouse when assuming a Greenfield project. The second part describes the cost savings when installing the METTOP-BRXTechnology in an already operating tankhouse.

Jan 1, 2014

By K. L. Williams

The Bureau of Mines tested a prototype tapered-element oscillating microbalance (TEOM) dust monitor for measuring respirable coal mine dust. The monitor uses the inertial behavior of a vibrating element to measure the mass of sampled dust. Tests were performed to determine variability, drift, the effect of humidity, placement of collection filter, and element orientation during analysis, and comparability with gravimetric measurements of respirable coal dust. Variability was about 1.6 µg. Over about 26 h at 46 pct relative humidity, drift was very slightly negative. When the relative humidity was increased to 78 pct, all units showed a total positive change less then 40 µg over about 70h. Filter placement variation on the tapered element resulting from in- consistent sizing of the filter mounting bases caused significant error (up to 0.2 mg). In practice, calibration of the system for each new filter will eliminate that error. Orientation of the element during analysis did not introduce significant error, but care is necessary when mounting the canister that houses the element to avoid damping oscillation of the element. Dust tests were performed in an aerosol chamber using coal dust. Measurements made by the TEOM dust monitor agreed to within 10 pct of simultaneous measurements by gravimetric personal samplers.

Jan 1, 1986

By J. J. Montoro

The influence of blasting on the excavators’ efficiency, defined as mucking rate (amount of rock mucked per unit time) and mean bucket load (amount of rock loaded in each bucket operation), is investigated. Rock characteristics, blasting parameters (drill pattern, explosive energy, and charging), and the excavator’s performance (truck loading time and number of buckets to fill a truck) were monitored in eleven blasts in an open pit iron ore mine. ANFO, ANFO/emulsion blend, and watergel were used in the blasts and the powder factor was varied between 0.98 and 1.45 kg/m3. The mean bucket load is mainly affected by the bucket size, which is independent of the blasting parameters. Besides the relation with the mean bucket load, the mucking rate was found to be positively correlated with the explosive energy, whereas no significant correlation with the rock properties was found. The analysis of the data, together with other published works, suggests a non-monotonic relation of the mucking rate with the powder factor, with a maximum mucking rate at a certain powder factor. This is especially true when the useful work of the explosive per unit rock volume is used rather than the classical mass powder factor and when only the amount of explosive above grade is considered.

Jan 1, 2007

By L. A. Neumeier

The Bureau of Mines evaluated the properties and anisotropy in properties of rolled Zn-Cu and Zn-0.12 pct Ti-Cu alloys with various copper additions to 1.25 pct. The alloys were rolled cold and at various hot-rolling temperatures to reductions as high as 92 pct after breakdown rolling. The properties are extremely sensitive to various combinations of composition, rolling temperature, and rolling reduction, Zn-Cu alloys can develop good creep resistance, but they are inferior in that respect to Zn-Ti-Cu alloys. For alloys either with or without the titanium addition, cold-rolling results in recrystallization of the matrix and rejection of copper from solution, causing poor hardness, tensile, and creep properties, but high ductility. Peak tensile strengths develop when the alloys are rolled in the range 320° to 400° F, Best creep resistance for Zn-Cu alloys requires higher rolling temperatures when copper content is increased. Creep resistance is best for Zn-Ti-Cu alloys with about 0.75 to 1.0 pct CU rolled near 480° F. Some copper is soluble in the TiZn15 phase, which forms into "stringers" during rolling. The possible contributions to creep behavior of factors such as distribution of second-phase particles, grain size, and preferred orientation are discussed.

Jan 1, 1970

By Dianne M. Lapierre

Mining firms in Canada are increasingly incorporating the social and environmental interests of their stakeholders into their projects in an effort to become more sustainable. Such initiatives have included negotiating Impact and Benefit Agreements (IBAs) directly with would-be impacted, often aboriginal, communities near resource developments in the Canadian north. Why does a mining firm take on this extra time-and cost-intensive initiative when governments and regulatory measures are in place to address social and environmental issues? Past research has paid little attention to the corporate rationales for IBAs. Based on document review and interviews with mining executives, this study investigates the rationales of mining firms that ?over-comply? with legislative requirements by negotiating IBAs or similar types of agreements with communities. The results indicate that mining firms increasingly recognize IBAs as an intrinsic part of the permitting process. When queried, executives regularly identified the negotiation of agreements as ?the right thing to do?. While this response could be read in ethical terms, a commercial rationale is also clearly present. By building strong relationships with nearby communities, addressing community concerns, and directing benefits to local people, all of which are explicitly achieved with an IBA, mining firms are maintaining their long-term financial viability, thus their sustainability, within an evolving industry.

May 1, 2008

By G. Griffiths

"P. WitteWitteck DevelopmentThe implications of using a tower mill for fine grainding in the ore processing of tailings are significant. What can those of us who are in a research and development situation do when we recommend this equipment to a client? When this prototype is placed on stream next to a conventional grinding mill as you suggest how do we estimate the power requirements and the grind which will be achieved?ReplyLet me explain the Macassa circuit. The tower mill here was running in parallel with one of the ball mills. The feed entering the tertiary system is scalped in a primary cyclone. The finial cut is made in a secondary cyclone. The actual feed to the tower mill is the underflow from the two cyclones and was split to the ball mill and tower mill. During the testing we were unable to isolate the tower mill to determine its contribution to the overall system. We then started to look at the amount of material produced across the mill. We entered the mill at between 17% and 20% finished material and exiting at between 36% and 40% finished material. We were able to project, with a high efficiency classification system, and arrived at 6 Kwh/ton or better."

Jan 1, 1984

By Joel T. Werner

Tire costs represent one of the highest controllable costs in open-pit mining, accounting for approximately 10% of mining costs. Tire monitoring technology has evolved rapidly in recent years and is emerging as a viable tool for extending tire life and reducing costs. The majority of the major tire manufacturers and several independent companies are in various stages of developing monitoring systems that capture and store vital tire data. Previously this information had only been accessible when the vehicle passed a fixed point in the mine, or when mine personnel manually downloaded the data. Integrating this technology with a mine management system enables remote collection and management of trend and alarm data. Mine personnel can now monitor a tire?s health parameters at any time, anywhere on site, regardless of the vehicle?s location. Anomalous tire conditions can be detected early and corrective actions taken. This information can then be integrated with other major onboard systems, operating conditions, and geographical information. Tire monitoring no longer exists as a stand-alone technology, but has evolved into an important integrated tool for mine operators. This paper will review the current status and benefits of integrating this emerging technology with a real-time mine management system.

May 1, 2002

By Paul Kunze

For some of us, the most disagreeable part of being the blaster- in - charge is doing the required paperwork. Cost coding on time cards, drilling reports, magazine inventory logs, and blast records all eat into our time. When all goes well, which I suppose is 98% of the time, the blast records are submitted and filed, probably never to be seen again. Sometimes a progressive operation will use the information documented in the blast reports to evaluate blasting effectiveness and improve results. When the report is consistently used in this fashion, costs can be reduced and other efficiencies will be realized. A blast report in times past was a simple form that mainly was used to keep track of the drill footage and of the powder used in the shot. However, as the population and consequences of careless blasting increase, multiple levels of blast documentation are now being required nearly everywhere, during all phases of the drill and blast process. We are now compelled to create preliminary blast designs prior to commencing work. We are required to submit pre-blast plans before each shot, and we need to generate post-blast reports that document the details and results of each shot.

Jan 1, 2004

Mine planning includes equipment selection as a subprocess because aging equipment must be replaced to maintain or improve productivity levels. The criteria used for decision-making in mine planning and equipment selection are often inextricably linked and inherently contradictory. For example, financial wisdom demands that development, which is an expense and locks up capital, be deferred as far into the future as possible yet on the contrary technical knowledge suggests that developing well ahead of stoping is practically desirable because it generates additional geological information required to improve planning of the unmined portion of the orebody and create better operating flexibility. Consequently, mine planning professionals have to delicately balance all decision criteria when executing mine planning in order to achieve optimal mineral extraction or when selecting equipment, so that capital is optimally deployed. These two processes can therefore be characterised as belonging to the multi-criteria decision analysis (MCDA) type of problems. MCDA problems are alternatively referred to as multiple attribute decision-making (MADM) problems and belong to a broader group of problems called multi-criteria decision-making (MCDM). There is now a gradual recognition and application of MCDA techniques in the minerals industry. This paper explores the theory, current and potential application of these techniques in decision-making in the minerals industry.

Dec 6, 2010

By J. Matos e Silva

"Abstract Although one can think that it is very low the probability of a seism occurrence during the execution of an excavation in an urban lot protected by a diaphragm wall curtain, reality shows that whenever a seism occurs in an urban area several diaphragm walls will be affected by it. So it is advisable to consider the seismic action when designing a diaphragm wall curtain. The paper refers the main information about the seismic design of diaphragm walls according to the Eurocodes 7 and 8 and to the Portuguese Norms related to them (respectively NP EN 1997-1 2010 and NP EN 1998-5 2010), as the Eurocodes consider the possibility of each European country to adopt their own seismic parameters as the seismic risk is different in each country. Thus the so-called National Document of Application (in our case the Portuguese Norms) prescribes the seismic local parameters.1 - EUROCODES AND PORTUGUESE NORMS PRESCRIPTIONSAccording to Eurocode 8 - Part 5 and to the related Portuguese Norm NP EN 1998-5 2010, seismic actions on soils should be quantified adopting the Mononobe-Okabe method that gives goodapproaches when compared with reality.From paragraph 7.3.2.2 of the referred Norm, the horizontal seismic coefficient kh will be:"

Jan 1, 2014

Fine Gravity Separation in the Reflux Classifier, Exploiting a High Shear Rate, Laminar Flow Mechanism The Reflux Classifier is used in the gravity separation of particles over a broad range of particle sizes. The device consists of a fluidised bed zone, with a system of parallel inclined channels above. The inclined channels provide a significant hydraulic advantage over conventional fluidised beds via the so-called Boycott Effect (Boycott, 1920). This paper describes a new advance in fine gravity separation based on the high shear rate and laminar flow profile that arises when closely spaced inclined channels are deployed. As reported recently (Galvin et al, 2009a), a powerful density based separation mechanism develops from this arrangement, suppressing the effects of particle size. In this paper we focus on two areas, firstly the application of the separator in the laboratory for batch fractionation of particles of varying size and density to determine the grade recovery curve and hence the liberation, and secondly the step change in separation performance achieved on a continuous steady state basis when closely spaced inclined channels are used. The variation in the separation density with particle size decreases significantly, and the Ecarte Probable Error (Ep) remains at low levels over a broad size range.

Sep 13, 2010

By M. Suzuki, T. Shiomi, M. Nakada, K. Tsutsumi

Mold powder plays an important role in the continuous casting process for high quality steel production. It is well known that mold powder entrapment causes surface defects in steel sheet and the high viscosity of mold powder prevents the entrapment of mold powder in molten steel in ultra low carbon steel. This paper deals with the entrapment of mold powder caused by suction by Karman?s vortex in a laboratory experiment. At first the effect of the viscosity of oil and interfacial tension between water and oil was investigated in a water model experiment. Then hot model experiments were carried out by mold powder and molten steel. The amount of mold powder entrapment was affected by the viscosity and the interfacial tension between molten steel and mold powder. As a result, the following equation of the mold powder entrapment was obtained. m=1.06*107?-0.255?m-s-2.18 The amount of mold powder entrapment decreased when the viscosity and interfacial tension increased. But the effect of viscosity was larger than that of interfacial tension in the case of the industrial mold powder when the viscosity was under 0.5 Pa.s, interfacial tension was from 1200to 1300 mN/m.

Jan 1, 2004

By J. B. Gwiazda

S.S. Peng The highlights of this paper are : • The shield supports with lemniscate links will exert a tangential force on the roof strata, causing unnecessary and harmful roof movements, thus damaging the roof structure. The principal source of the tangential force is the horizontal movement of the point O, the pivotal joint between the canopy and the caving shield. When the support height is changed during setting, the point O will move along a curve upward and rearward toward the gob. As a result, it produces a vertical movement, causing the roof to move up a distance of ?d, and a horizontal movement toward the gob, creating vertical fractures in the roof. • The major purpose for employing the lemniscate-link system is to protect the hydraulic legs against the action of the bending moments induced by the tangential force that causes deformation or destruction of the legs. • Based on these two points, the author suggested that, in order to eliminate the harmful effects of the lemniscate-link system and strengthen its advantageous features, a shield support with a new design of that mechanism has been developed. With the new design, the conventional rigid lemniscate links are replaced by hydraulic rams. When the pressure inside the rams reaches a certain level, the ram will yield.

Jan 12, 1986

By K. Hanson

When done properly, benchmarking is an extremely effective tool for assessing ones performance, finding areas for improvement, and identifying strengths. However, when done improperly it can be an exercise in futility and result in incorrect observations and conclusions. A primary pitfall of benchmarking is collecting too much unreliable information. Surprisingly, the evolution of data storage and the ease of data collection are not helping with better data collection. Instead, it is just allowing one to collect more information, while at the same time inundating one with too much data. Additionally, the process of data collection can be tedious and is often times delegated to the least experienced individual resulting in unreliable and incorrect data collection and entry. Another primary pitfall of benchmarking is metrics that are cost based or poorly designed. Cost based metrics typically involve comparing unit mining costs ($/tonne). Between mines, unit mining costs are not very well correlated and have become further complicated by significant regional cost variations and mining inflation in the last years. Likewise, poorly designed metrics lead to poor benchmarking results. Examples of poorly defined metrics include: metrics that rely on information that is difficult to collect, metrics that are poorly defined, metrics which are too site focused, and metrics that measure low consequence practices.

Jan 1, 2011

The following paper deals with a method for the" Proximate Analysis" of Chloridized Ores, which are free from arsenic, antimony and lime. When these are present the analysis is rendered far more complicated, and many of the methods which I am about to describe could not be applied. Sufficient scope is therefore offered for discussing the analysis, when these metals are present, in a separate paper, which I hope to contribute at a future date.I am fully aware that this method is far from being perfect. No doubt many, modifications and improvements will suggest themselves to my readers, and I trust that this paper will be the means of giving a certain impetus to the study of Proximate Analysis which at the present time is practically dormant. For the benefit of my readers who are not initiated into the details of ordinary estimations, I have briefly described well known methods, which, however, will be found fully described in most text-books of analysis. Assuming that the ore contains. sulphates and chlorides of soda and magnesia, sulphates, sulphides, chlorides and oxides of copper, lead, iron, zinc, manganese and silver chloride, the analysis would be conducted as follows. The first compounds to estimate are the chlorides and sulphates of soda and magnesia.

Jan 1, 1901

By Wu Xueling

9K medium was used to isolate iron-oxidizing bacteria from 27 sump water samples collected from Dexing Cop-per Mine, Chengmen Mountain Mine and Yin Mountain Mine, Jiangxi Province, China. Lead acetate and silver nitrate were used to enrich metal-resistant iron-oxidizing bacteria from the above water samples. Isolate 16 was isolated from the sample taken at Dexing Copper Mine. Growth experiments indicated that when incubated under lead acetate (3,500 mg/L), isolate 16 still carried out ferrous ion oxidation, while isolate H1, a less resistant strain taken at Yin Mountain Mine, had a tolerance level of only 400 mg/L. When assayed with other metals, i.e., Ag+ (240 mg/L), Hg2+ (0.9 mg/L), Cu2+ (32,000 mg/L) and Mg2+ (22,500 mg/L), isolate 16 still carried out ferrous ion oxidation while, on the other hand, isolate H1 exhibited much lower tolerance levels, i.e., Ag+ (60 mg/L), Hg2+ (0.1 mg/L), Cu2+ (19,000 mg/L) and Mg2+ (13,500 mg/L). Based on 16S rDNA sequence data, isolate 16 and H1 were both identified as Acidithiobacillus ferrooxidans.

Jan 1, 2007

By Robert Hopler

Some few years ago, when the cruiser “Brooklyn” was passing through the fairway to the southwest of the Battery, the ship being fully equipped with stores, etc., and therefore at her maximum draft, she grounded quite heavily upon some obstruction, and received injuries which necessitated her docking at the Brooklyn navy yard, where extensive repairs had to be made on her damaged bottom.

Jan 1, 2007

By B. M. Loftus

An investigation into the use of impinging stream (jet) reactors for the leaching of a free milling ore produced an increase in gold recovery by 10% while decreasing leaching time by up to 90%.Tests on refractory ores demonstrate no apparent improvement in recovery. However, leaching kinetics are dramatically increased when these ores are subjected to jet reaction prior to agitation.

Jan 1, 1997

By Mani Manimaran, Inna Dymov, Mariam Melashvili, Chris Fleming, Joe O’Day

This paper presents experimental evidence that supports the use of bromine/bromide as a potential alternative to conventional cyanidation for gold leaching. The study evaluated a brominebased lixiviant, Stabilized Bromine, with considerably lower vapour pressure than liquid bromine. Using a rotating device, the rate of gold dissolution was determined at various concentrations of this reagent. The reactivity of pure pyrite, arsenopyrite and chalcopyrite minerals was also evaluated in stabilized bromine reagent. Furthermore, bromine leaching of gold in a number of gold bearing ores was undertaken. Results showed that significantly higher gold recovery can be achieved with bromine than with cyanide when leaching gold encapsulated in sulphides, but bromine consumption was high owing to simultaneous oxidation of the sulphides. The greatest promise for the bromine leach process was with oxidized gold ores. The recovery of gold from oxide ores with bromine was comparable to that achievable with cyanide and bromine consumption was reasonable when leaching was conducted at a near neutral pH of ~6. In the case of oxidized gold ores containing copper mineralization, it is possible that bromine consumption may be lower than cyanide consumption, since there is evidence to suggest that bromine is less reactive than cyanide with copper minerals.

Jan 1, 2014