Search Documents

By James H. Boettcher

In the second quarter of 1979, ASL Inc. inquired whether Crocker National Bank ("CNB") would provide $4 million in term loan financing to help ASL acquire the outstanding shares of the S&S Coal Company in West Virginia. ASL had, prior to approaching CNB, sought financing with the assistance of a financial advisor from a number of commercial banks without success. A summary of the initial terms requested by ASL is shown in Table I compared with the actual terms the transaction closed with. It is not difficult to note that the two sets of terms differ significantly. This is often the case when financing requests based on the expectations and vision of a mine developer are juxtaposed with more pragmatic requirements of a commercial bank. The "art" and fun of structuring financing plans for mining ventures (highly leveraged acquisitions or grass roots) comes in working with mine developers to arrive at a final financial structure that meets their objectives and constraints as well as those of the bank or other financial institution providing much of the financing. This article briefly describes the process we went through with ASL beginning with the terms they requested initially and ending with the ones on which the transaction was finally closed.

Jan 1, 1981

The concept of "classification is expanded beyond the performance of the classifying equipment to include all aspects of the fines removal system of the grinding circuit. Design and operating parameters which affect fines removal are identified and discussed, and a quantitative index for circuit fines removal effectiveness is defined. This approach lends new interpretation to certain observed phenomena, and suggests useful guidelines for circuit design and operation.

Jan 1, 1985

By R. H. King

Underground coal mining machinery utilizes portable electric sables, "trailing cables." to obtain power from load centers or distribution boxes. Cables are frequently damaged since mobile equipment, poor lighting, and restricted space are inherent to coal mining operations. Normally, the damage is repaired by splicing--the joining of one or more severed conductors and replacing insulation and jacket. Figure 1 illustrates a typical single conductor splice. Although the repair seems simple, difficulty of the splicing process is exemplified by the many safety hazards and frequent production delays that result from defective splices. Forty-two cable splice related injuries were reported to the U.S. Bureau of Mines in 1972 and 1973. Additionally, 17 splices related fires were reported in the three year period prior to December 1972. Assuming the damaged area is quickly located, an average splice time for a two conductor cable is twenty minutes. Some operators estimate this delay is incurred once per day per operating section. If one ton per minute is averaged throughout the shift, each unit could loose 4800 tons per year from splice delays. An estimated cost for materials and labor to make a splice is $20. The expenditure could result in a $4800 annual cost per section. The estimated expense does not include wages of other personnel waiting for the repair to be completed. Nevertheless, labor and materials cost is minor compared to the income lost from decreased production.

Jan 1, 1975

By Kim A. Lapakko, William W. III White

The ASTM standard method D 5744-96 was developed to provide a well-defined kinetic test protocol, conducted under controlled reaction conditions, with the intent of generating reproducible results. The US Bureau of Land Management, American Assay Laboratories, and the Minnesota Department of Natural Resources cooperated in a intralaboratory and interlaboratory testing of the protocol. Intralaboratory testing was conducted on duplicate samples of gabbro (8) and siltite-argillite (5) rocks for periods of 20 to 125 weeks. The difference between replica& intralaboratory pH readings on drainage from the gabbro for the drip-trickle leach alternative typically did not exceed 0.1 units, although differences as high as 0.4 units were observed. The difference from the mean for rates of sulfate, calcium and magnesium release was typically within 10%. Intralaboratory results for the siltite-argillite samples were generally similar, although a one unit pH difference was observed for one sample. Three different laboratories tested a gabbro sample for 125 weeks, with a maximum difference from the mean pH of 0.5 units. The percent difference from the mean for sulfate and calcium release rates was typically within lo%, although values as high as 30% were observed. Data on intralaboratory and interlaboratory agreement on the flood rinse alternative of the method were limited. Replication on the sample tested was comparable to of better than that observed for the drip-trickle method testing of the same sample.

Jan 1, 2000

By Arif Emre Dursun, Ali Aras, Hakan Özşen

Specific energy (SE) is defined as the amount of work required to cut a unit volume of rock and is used to estimate the performance of excavation machines. Generally, the SE value is produced from full-scale or small-scale rock cutting tests. However, these tests require expensive equipment and experienced personnel, and the testing procedure is time consuming and impractical. Therefore, for estimation of SE, this study aimed to find a solution to estimate SE using rock mechanics test results and Bond work index values (BWi), which can be produced in a more practical, less time-consuming manner and with inexpensive test equipment. Small-scale rock cutting, rock mechanics and Bond work index tests were carried out on seven rock samples, which can be grouped into two different type of rocks: marble and travertine. In addition, the instantaneous cutting rates (ICR) of a selected roadheader were calculated using SE values. Rock mechanics tests performed in this study were uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), ultrasonic velocity (Vp), Schmidt rebound hardness (RL), corrected point load index (Is(50)) and density (ρ). The simple regression method was used to estimate SE from rock properties and BWi. As a result of this simple regression, a significant and highest correlation was found between SE vs. UCS and Is(50). A good correlation was found between SE vs. BTS, RL and BWi values. A moderate correlation was found between SE vs. Vp and ρ.

Jul 28, 2021

By E. E. Maurer

Kerr-McGee has operated the Ambrosia Lake uranium mill since startup in 1958. Tonnage milled per day has varied from 3500-7000 tons. The mill capacity is currently rated at 7000 tons per day. The process consists of two parallel circuits following crushing and sampling, \\lhich include open circuit rod mill grinding, sulfuric acid leach, cyclone classification, and counter-current washing circuits of sand classifiers and slime thickeners. Pregnant solution is clarified and polished by precoat pressure leaf filters prior to amine solvent extraction. Yellowcake is precipitated from the pregnant strip solution with ammonia, filtered and dried.

Jan 1, 1972

By Carmel Bofinger, Maureen E. Hassall, David Cliff, Eric Stemn

Incident investigation is of utmost importance in most high-risk industries and is often used to improve organisational safety. This study was undertaken to examine the content of past incident investigation reports to determine the effectiveness of the incident investigations. The study uses a semi-quantitative method to assess the effectiveness of incident investigations in the Ghanaian mining industry by evaluating the quality of past investigation reports. The assessment tool consists of five elements with several indicators and rating scales for assessing the quality of an investigation report as a measure of the effectiveness of the investigation. The method was applied to 304 investigation reports of three Ghanaian large-scale gold mines, and the results correlated with incidence rates of the mines to determine if any relationship existed. The results showed that the mines differ significantly in the quality of their investigation reports, suggesting differences in the effectiveness of their investigations. In addition, the incidence rates of the mines negatively correlated with some elements of the assessment tool. In general, the method was found useful and revealed areas where improvement is needed.

By G. A. Doyle

The White Pine Mine is the second-largest active underground copper mine in the United States, covering an area of approximately 13 square miles in the Upper Peninsula of Michigan. The mine operator intends to initiate in-stope solution mining by circulating a solution of mine water, sulfuric acid, and ferric iron through rubblized ore and recovering copper from solution. As planned, the solution would be retired in the mined-out stopes following completion of solution mining activities. Investigations into the fate of the retired solution mining fluid indicate that the solution, through time, will change from an acidic, metal-rich solution to a near-neutral, reducing solution containing much lower concentrations of metals. Investigations include reaction path modeling (EQ3/6) and laboratory and in-mine experiments. The combination of neutralization and reduction will result in precipitation of most metals, primarily as metallic sulfates, chlorides, and sulfides.

Jan 1, 1996

By M. Moats, J. Young

Short term laboratory cell electrorefining experiments were performed to examine the impact of electrolyte composition, current density and temperature on deposit structure, roughness, and adhesion to 2B mill finished 316L stainless steel. Copper electrodeposits were produced using synthetic electrolytes with thiourea and the continuous addition of glue. Deposit structures were evaluated using X-ray diffractometry. Surface roughness was measured using profilometry and analyzed using scaling analysis. Finally, an internally developed method was used to measure the force required to remove the electrodeposited copper from stainless steel to determine adhesion strength.

Mar 2, 2022

By Simon E. Rodriguez

This paper presents sulfur isotope data obtained for the deposits and country rocks of the Bailadores and Aroa Mining District, Venezuela. The study is a part of an extensive geochemical investigation of the mineralized belts that has as their aim the elucidation of the genesis of ores. The Bailadores deposits are located at about 600 Km. west-southwest of Caracas, or about 10 Km. southeast of the Town of Bailadores, Merida State (Fig. 1). The mine concession is held by the Ministry of Mines and Hydrocarbons (De Lima I, De Lima II and La Cascade areas). In a straight distance the mine is about 90 Km. southwest of Merida, the capital of Mérida State. From Mérida to Bailadores, through La Victoria and Tovar, it takes 3 hour by car. From Bailadores to the mine site it is about 40 minutes by jeep. The Aroa deposits are located at 4 Km. east of Aroa Village, Yaracuy State, about 220 Km. west of Caracas. It is 83 Km. from San Felipe, the capital of Yaracuy State to the mine (Fig.2). The mine is about 600 m above sea level, situated on the northern foot of the E-W trending Andes. The topography of the mine are shows a mature stage and is somewhat rugged. As the climate is warm and humid, the area is thicky covered with jungle.

Jan 1, 1974

By Roger N. Kust

Because ammonia can form complex ions with certain of the transition metals, such as copper and nickel, it has long been of interest to extractive metallurgists interested in leaching or separating these metals. Although it is a relatively expensive reagent, ammonia is amenable to recycle because of its volatility. In development of processes utilizing ammoniacal leaching or separation schemes, information regarding solution vapor pressures, pH and solubility limitations is needed. There is voluminous literature on ammonia-water systems generated by the urea industry. However, frequently the systems of interest to metallurgists differ significantly in concentrations of ammonia used, the temperatures of interest. Furthermore, the differences arising from the presence of metal values in solution must be comprehended. There is surprisingly little information readily available regarding systems of practical interest to metallurgy. As a result, those interested in ammonia-based processes end up either doing expensive laboratory research to obtain necessary data or overdesigning the process. Another approach to obtaining desired information about ammoniacal systems is to attempt to calculate from first principles the various solution properties. This paper is being presented to illustrate what can be accomplished by estimating the state of equilibrium in an ammoniacal carbonate system from available thermodynamic information making simplifying assumptions when needed.

Jan 1, 1976

By M. B. Daza, B. Lattimer

"Even with modern detection and firefighting techniques, mine fires continue to be a safety concern. However, some underground mine fires can be addressed with the remote application of high expansion foam, reducing firefighter exposure to hazards. The flow of this foam can be numerically or computationally simulated in order to gain a better understanding of its behavior, but rheology parameters are needed as inputs to produce accurate simulations. For this reason, this work studies the rheology of firefighting high expansion foam using a foam generator and Poiseuille –Flow Rheometer. Rheological parameters for foams with expansion ratios between 250-1280 are represented by the consistency index (k) and the power law index (n) due to the results show a strong agreement with the Power Law model for non-Newtonian fluid viscosity. Furthermore, experimental results show that high expansion foam behaves as a shear thinning fluid with a power law index around 0.4 and viscosities in the range of s 0.1 Pa-s and 0.042 Pa-s under shear rates between 44 ??-1 and 187.3 ??-1. INTRODUCTION High expansion foams are called to foams with expansion ratio greater than 200. Expansion ratio (??) is defined as the ratio between the volume of foam produced (i.e. volume of foam solution and volume of gas) and the volume of foam solution used (NFPA 2014). Because of its high expansion ratio, one of the most important application of high expansion foams is to fill or flood large spaces such as hangars, storage facilities and underground mines for fire suppression. The foam can fill large structures using small quantities of foam solution within a short time (Sthamer 2012) (Martin 2012). Although the specific high expansion fire suppression mechanism has not been understood on a quantitative basis, a possible mechanism is fuel isolation when the foam act as a physical barrier between oxygen and the flame. Furthermore, as a consequence of this contact water is evaporated, causing cooling of fuel and surrounding air. Besides, water vapor as product of water evaporation causes a dilution of oxygen concentration available to the fire (Fleming and Sheinson 2012). High expansion foam can be applied remotely by means of conduit pipes or in situ close to the fire. In most of the underground mines scenarios, fires have to be addressed remotely to reduce miner and firefighter exposure to the hazards (Smith et al. 2005). Although high expansion foams should not be blasted and must be deposited directly on the area of application because of their low density (Harding et al. 2016) sometimes it is complicated to apply it directly to the fire due to complex access areas at underground mines. In these cases, foam has to be applied far away from the fire. Despite of this fact there is a lack of knowledge in terms of rheological behavior of high expansion foam under high shear rates (Gardiner, Dlugogorski, and Jameson 1998). Furthermore, there are a few attempts to simulate numerically the high expansion foam flow due to the ignorance of its rheological parameters and its complex behavior. (Weaire 2008)."

Jan 1, 2018

By Greg Struble

The Homestake Gold Mine is one of the deepest and most extensively developed hardrock mines in North America. The mine is divided into five divisions which produce a total of 1.7 million metric tons of ore per year. In the past, labor intensive mining methods such as open cut-and-fill, shrinkage, and timber stoping were utilized. In recent years there has been an extensive change to the more productive methods including Vertical Crater Retreat and Mechanized Cut-and-Fill. Also, the percentage of production from the lower divisions below the 4850 level is increasing while upper level reserves are beginning to decline. Combined, these factors have strained the ventilation resources to the limit. By early 1984 it became clear that future production trends would require a detailed study of future ventilation resources. By November of 1984 the Ventilation Department completed a study to project these future requirements. This paper will detail the first phase of a scheduled two phase upgrade: the installation of a new surface fan.

Jan 1, 1987

This paper presents a method for evaluating the economic feasibility of solution mining a hypothetical uranium roll-front deposit. It is assumed the wellfield will be operated in a prudent manner and that leaching tests were performed in depth in both lab and field (push-pull) prior to startup. Leach test results are reduced to two important parameters and used as the basis for solution mining a wellfield. This case study assumes a 10 mil- lion-lb uranium deposit with 40 possible small wellfields; four are kept in operation simultaneously until the deposit is depleted. The wellfields have different ore reserves and grades, lixiviant circulation rates, leach rates, and peak concentrations, and thus the daily uranium production will vary. Daily production is used to assess the profitability of a particular lixiviant and the mode of well- field operation in light of realistic market price estimates. The mathematical procedure is simple and straightforward, based on reasonable in-situ leaching relationships as well as accepted accounting practices.

Jan 1, 1985

By S. Tan

In this paper, several commonly used computer truck dispatching criteria are evaluated. A computer-oriented truck dispatching and production simulator was developed to provide data for comprehensive cross comparison among the dispatching criteria. The definitions, primary considerations, characteristics, and performances of these dispatching criteria were investigated. From the simulation results, it was concluded that, in general, no one criterion can dominate all others. All basic dispatching criteria including minimizing truck waiting time, minimizing shovel waiting time, minimizing truck saturation, maximizing truck momentary productivity, or truck routes optimization provide a local optimal solution. To obtain a direct global optimization solution for this complex stochastic process does not appear to be likely. Therefore, the search for an optimal dispatching criterion that will fit all conditions may not be realistic. However, based on the simulation results of the mine operation, several dispatching criteria which have good potential to increase performance can be selected. It may be necessary to search for the best combination of these truck dispatching criteria for a given situation. For example, a truck flow measurement such as the truck clustering factor at shovels can be used as a switch parameter to change from one criterion to another. The values for the switch parameter at which actions should be taken to change the criterion can be established through simulation programs.

Jan 1, 1992

By Fathi Habashi

SELENIUM AND tellurium are by-products of electrolytic copper refining. Copper anodes contain 0.01-0.2 % Se and up to 0.04 % Te; during electrolysis these deposit as a slime at the bottom of the cell. Such slimes contain 2-15% Se and 0.5-8 % Te, as selenides and tellurides of gold, silver, and copper. The following compounds have been identified in the slimes: (Ag, Au)Te2, Ag2Se, Ag2Te, CuAgSe, Cu2Se, Cu2Te. Anodic slimes from copper electro¬lytic refining are a grayish black powder, minus 200 mesh. When this complex mixture is decomposed in an acid medium, elemental selenium and tellurium can be obtained, while in an alkaline medium, both metals go into solution. Acid leaching The slime is charged in acid digesters of 800-900 lb capacity, heated to 260°C with 78 % H2SO4, for 8-12 hr. During digestion the following reactions take place:

Jan 1, 1970

By S. S. Peng

The generation and transportation of the airborne dust are mainly governed by the velocity and the movement pattern of the ventilation air in the longwall face. Generally speaking, the higher the air velocity, the more the airborne dust will be generated and the longer the period of the dust of certain size will be carried away from the source. In order to effectively prevent the production and the spread of the airborne dust, The airborne dust concentration distribution in the longwall face must be known in advance. Before the dust concentration distribution can he predicted theoretically with confidence, the air velocity distribution pattern of the ventilation air in the longwall face area must be determined first. However, the complicated, time-dependent and unpredictable mining conditions along and around the face area make the theoretical studies of the problem rather difficult. For instance, one of the factors commonly affecting the air velocity distribution at the longwall face is the air leakage, either into or from the gob area. The leakage quantity and the location of occurrence differ from mine to mine, face to face, and time to time. They depend not only on the compactness of the caved roof fragments in the gob, but also on the degree of obstructions in the working space and in the return entry. Another obstacle to the theoretical studies about the velocity distrbution is the complicated boundary conditions of the ventilated spnce which is very difficult to represent accurately in mathematical forms. In this paper, the air velocity distributions measured in four longwall faces are presented. A statistical model for each longwall face is also derived for prediction of air velocity distribution in the longwall face.

Jan 1, 1985

By Robert W. Row

The run-of-mine coals in the U.S. being fed to coal cleaning plants have become increasingly finer due to the adoption of modern, mechanized mining methods, and economics are dictating that finer fractions, as well as the coarser fractions, be cleaned. Traditional dewatering methods (vacuum disc filters and centrifuges) are proving inadequate for preparing fine refuse for disposal or fine coal product for downstream handling. The Electric Power Research Institute has been supporting research into the nature and limitations of mechanical dewatering, and novel ways of improving it. The efficiency of various silicone-based chemicals at aiding dewatering was investigated, and it was shown that the final moisture content of hydrophilic coals after vacuum Filtration could be reduced by 1 to 5% with up to 40% increase in filtration rate by addition of one of several of these silicones. EPRI also has an on-going program at its Coal Cleaning Test Facility to investigate the performance of the Larox pressure filter in comparison with that of the disc filter and solid bowl centrifuge. While improvements to the dewatering performance currently being obtained in existing operating plants by such means are achieveable, a fundamental study has shown that, regardless of changes in operating conditions, there may be a limit to the lowest cake moisture content attainable by mechanical dewatering of a given sample of coal fines. Determination of this limit for a specific coal would be useful in designing facilities to dry and handle it.

Jan 1, 1984

By Craig Smith

California is the nation's leading producer of diatomite products. The Lompoc Mining District in Santa Barbara County is the world's largest source of commercial marine diatomite. Grefco Inc. exploration has defined a large embayment of commercial grade freshwater diatomite in Shasta County. Exploitation of this massive deposit could substantially increase California's diatomite production.

Jan 1, 1980

By Haydn H. Murray

Kaolins and bentonites of economic importance in Australia and New Zealand are described. Clays that are used for structural clay products are not discussed. Residual, hydrothermal, and sedimentary kaolins are utilized including clays associated with coal measures. Bentonites are sedimentary and residual. Very little kaolin and no bentonite is exported presently, but this will change in the near future as transportation costs continue to escalate. Many areas of Australia, in particular, where kaolins are known to occur have not been investigated to determine the quality and quantity of the deposit.

Jan 1, 1982