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By H. Rush Spedden

A process has been developed and piloted to reject copper, lead, iron, phosphorus, bismuth, antimony, elemental sulfur, and insol from molybdenite concentrate without decomposing the contained molybdenite and rhenium. The impure concentrate is first heated with concentrated sulfuric acid at 260 to 290°C for 1 hour. This bake not only oxidizes the contaminating sulfides, but also activates the concentrate for later rejection of insol by flotation. Two stages of leaching follow the sulfation step. The first is an acidified water leach which extracts the oxidized copper, iron, and phosphorous; the second leach rejects the lead, bismuth, and antimony into a warm concentrated solution of sodium chloride. Final upgrading is achieved by conventional froth flotation. The chemistry of the process as well as results obtained from its implementation in a 5,000 lb/day pilot plant are presented.

Jan 1, 1971

By R. R. Klimpel

The use of chemical reagents in flotation has been studied in great detail, e.g. (1, 2, 3, 4). Important progress has been made on the understanding of surface chemistry concepts involved in flotation. However, such scientific studies are often very complex even for rather simple idealized systems. Therefore, the deve- lopment of predictive or quantitative tools for plant engineering evaluation is still in the evolutionary stages. Until further progress in fundamental work is achieved, the operating engineer is faced with semi-empirical physical testing of reagent changes on several sizes of the actual equipment under study to be confident of the economic viability of any change.

Jan 1, 1980

By Alfred L. Anderson

Thorite and rare earth deposits in the Lemhi Pass area of southeastern Lemhi County, Idaho, are contained along complex shear and fracture zones and in reopened gold-quartz veins and copper lodes in quartzitic and phyllitic rocks of the Pre-cambrian belt series. Some of the shear and fracture zones are several tons of feet across and comprise broad zones of irregularly mineralized rock. These lodes contain a notable concentration of thorium and rare earth elements along with considerable amounts of barium, .potassium, calcium, iron, aluminum, phosphorus, sulfur, and silicon. The principal minerals are thorite, locally allanite, monazite, xenotime (?), apatite, specular hematite, barite, potash feldspar, occasionally calcite and quartz. Exept for some of 'the specular hematite, barite, reddish feldspar, calcite and quartz, the minerals are not distinguishable without the microscope. The thorite and locally allanite were deposited first, then the monazite and other phosphates, which were in turn followed successively by barite, potash, feldspar, calcite, and quartz. In exceptional cases, deposition of thorite and specular hematite was repeated after the feldspar. Some of the deposits contain several percent thoria, but the average os generally under one percent. The rare earth content is comparable with that of the thoria. The deposits appear to be of hydrothermal origin and are probably related genetically to late Cretaceous or early Tertiary igneous activity, manifested locally by a few dioritie and lamprophyric dikes.

Jan 1, 1959

By Richard C. Neavel

Among the many compositional parameters used to judge the quality of a steam coal is the fouling factor of Attig and Duzy1 [% base in ash % acid in ash X % Na20] in ash. The higher the fouling factor, the more likely the heat transfer surfaces of the boiler will acquire a deleterious deposit of sintered ash. While examining the elemental composition of ash from various size and gravity fractions of coals from Illinois, we noticed that variations in the fouling factor were attributable mostly to variations in the sodium content. Further, sodium content was essentially the same in all sink-float fractions from a given coal. In other words, sodium was related neither to the ash nor to the organic material. We therefore concluded that the sodium was most likely in the pore water, which was approximately a constant proportion of all fractions. This led to the supposition that the sodium might be removable through water extraction. This supposition tended to confirm the observations of Daybell,2 Daybell and Gillham,3 and Gluskoter and Ruch4 that much of the sodium in coals existed as water soluble sodium ions. In passing, it should be noted that most sodium in Western U.S. coals (i.e., Wyoming, North Dakota, Montana) is not water soluble, but rather is fairly strongly held in association with the organic material (ion-exchanged).5 Because data reported in the literature were not very conclusive about the typical proportions of sodium that might be removed by water extraction, and because there were few data indicating extraction rates, and finally, because our calculations showed a favorable economic incentive to lower sodium contents, we initiated an experimental program to investigate water extraction of sodium from Illinois coals.

Jan 1, 1976

By Raúl Castro, René Gómez

In underground mining, rock fragment size is a key variable for productivity because it impacts equipment selection and mining structure design. This study characterizes granular material fragmentation during its flow to understand its characteristics and mechanisms. Tests were conducted using a laboratory setup to emulate various heights where material is drawn. The fragment-size distribution was measured before and after tests for clay, concrete fragments, and gravel. Results showed that fragmentation mainly occurs in minor sizes, with significant increases in fine material as travel distance increases.

Jan 10, 2022

By Jacob L. Brinkman, Catherine E. Johnson

Unmanned aerial vehicles (UAVs) are being explored by researchers to measure concentrations of gas emissions in situations where such measurements are otherwise extremely difficult to obtain, such as NO and NO2 (NOx) emissions from surface mine blasting. Recently, countries have imposed or are planning to impose surface blasting gas pollution regulations, which creates a need for an improved understanding of UAV-based gas measuring systems. The experiments detailed in this paper were performed to determine if airflow generated by the rotors, also known as downwash, unnaturally alters concentration measurements. Downwash turbulence could create locations of varying pressure, which could affect concentration. A UAV fitted with gas sensors was attached to a stand in a controlled environment containing a mixture of NOx. The gas sensor measuring points were placed at various distances on and from the UAV body to evaluate downwash effects on gas concentration. Results show that the presence of downwash turbulence causes no statistically significant changes to concentration measurements at any distance or direction from the UAV. Based on these results, it is possible to use a UAV-mounted gas monitor to measure concentrations without concern for downwash interference, provided the UAV and measuring point are entirely contained within the gas cloud.

May 20, 2021

By T. J. Lutz, D. S. Yantek, L. Yan, J. R. Srednicki, J. A. Yonkey, G. T. Homce

Federal regulations require the installation of refuge alternatives in underground coal mines. Of the inuse refuge alternatives, more than 95 percent are mobile refuge alternatives, with the remainder being built-in-place (BIP) refuge alternatives. Heat/humidity buildup has been one of the major concerns with mobile refuge alternatives. For BIP refuge alternatives, however, there is a lack of in-mine heat/humidity test data to determine the extent of heat and humidity buildup. To quantify heat/humidity buildup in BIP refuge alternatives, the U.S. National Institute for Occupational Safety and Health (NIOSH) performed a series of heat/humidity tests on a 60-person BIP refuge alternative with and without a borehole air supply. At various times during the year, tests were performed with cooled, heated or unconditioned borehole air to examine how various outdoor temperatures may affect the thermal conditions inside a BIP refuge alternative. The results show that the air supplied to a BIP refuge alternative may require heating or cooling, depending on the outside air temperatures and the temperature of the mine. For example, during tests with an external ambient temperature above 21 °C (70 °F) and a relative humidity of 90 percent, providing 13 °C (55 °F) dew point air at 775 scfm, which is slightly higher than the mandated flow rate of 12.5 scfm per person, kept the internal apparent temperature below the mandated 35 °C (95 °F). Results for each test case are presented.

Jan 1, 2018

By Lixue Wen, Jun Xiao, Dongping Shi, Yan Xue, Jinmiao Wang

Mine ventilation energy consumption is one of the main sources of energy consumption in mining production, accounting for about one-third to one-half of the total energy consumption. Therefore, reducing the energy consumption of the mine ventilation system is crucial for mining production. With the premise of meeting the airflow requirements of the underground work areas and achieving sustainable development of mining production, this paper establishes a nonlinear optimization mathematical model for the mine ventilation network with the objective of minimizing the total power. Regarding the model, optimization of the decision variables was carried out using the method of minimum spanning tree. The constraints for air flow balance, wind pressure balance, and fan operating conditions were optimized using the exterior penalty function method, thereby transforming the model into a nonlinear unconstrained model. Based on this model, a modified sooty tern optimization algorithm (mSTOA) was proposed to achieve optimization. Improved the sooty tern optimization algorithm (STOA) by using the uniform reverse strategy, fitness value-distance balance selection strategy, and mutation strategy. The STOA, mSTOA, and three other classical optimization algorithms were applied to the optimization of a ventilation system of an actual mine. The experimental results show that after using mSTOA to optimize the ventilation network airflow distribution in the mine, the total energy consumption can be reduced by about 35.06% while meeting the constraints and demands of the ventilation network regulation and usage. This is of great value to mine roadway operation environment safety and clean production.

Dec 20, 2023

By Robert C. Bates

Published information discussing uranium mine radon daughter controls and related costs was examined and used to develop an estimated (projected) cost per ton for any level of control. Results show a clear power function increase of cost for conventional dilution ventilation as the annual exposure limit is lowered. Projections can be made using any assumed changes in consumer price index (CPI) and radon daughter working level months exposure limit. Bounds on the estimated costs are provided, and applicability of the final equation is discussed.

Jan 1, 1983

By K. V. K. Prasad

Stochastic simulation has been routinely used for performing risk and sensitivity analyses in a variety of fields. The commonly used means of generating the simulations has been the Monte Carlo approach which usually employs a Simple Random Sampling (SRS) scheme of the variable distributions. This method is prone to sample clustering and requires a large number of samples to represent the distribution faith-fully. This can become problematic for simulating complex processes where it is impossible to run an arbitrarily large number of replicate simulations. The Latin Hypercube Sampling (LHS) method uses a stratified sampling approach which assures representation of the input distributions for any given number of samples. In this paper the LHS and SRS approaches are compared using a petroleum resource estimation example.

Jan 1, 1993

By G. Castillo, J. Mortensen

"INTRODUCTION Molybdenite is typically produced as a co-product in the copper ore flotation process. At the Rio Tinto Kennecott Concentrator (RTKC) in Copperton, Utah, the molybdenite is initially floated with copper sulfides and other value minerals producing a Cu-Mo concentrate. This is then separated in the molybdenum plant by depressing copper sulfides and pyrite and floating only molybdenite. The molybdenum plant in RTKC comprises the rougher circuit and several stages of cleaning to achieve a certain grade requirement of Mo. The rougher circuit is where the first stage of separation occurs. Cu sulfides and pyrite are depressed in the rougher circuit by adding NaSH under nitrogen and in the cleaner circuit by adding NaSH under air. The depression of Cu sulfides (and pyrite) by NaSH is related to the redox activity1. It is important therefore to maintain a reducing potential in the circuit in order to achieve effective Cu-Mo separation. If the rougher circuit is under air, like RTKC’s molybdenum cleaner circuits, it is harder to maintain the target redox potential because NaSH oxidizes rapidly in the presence of air thereby increasing NaSH consumption significantly. CU-MO SEPARATION AND ROLE OF PULP POTENTIAL The collector adsorption on copper sulfide minerals is through an electrochemical mechanism2. The collector changes the surface chemistry of the Cu mineral allowing it to float. Molybdenite, or MoS2, on the other hand, floats readily in the presence of a frother as it is naturally hydrophobic. Usually, hydrocarbon oil extenders such as diesel or burner oil are added to enhance Mo recovery. In order to effectively separate Cu from Mo, the collector complex on the copper surface needs to be destabilized or desorbed using a reducing agent such as NaSH or Nokes. As long as the circuit is under highly reducing conditions, the collector remains detached from the sulfide mineral surface allowing Cu sulfide depression. Therefore, it is important to measure the oxidation-reduction potential (ORP) continually and maintain the reducing condition with addition of NaSH. For a given collector each mineral will have a characteristic potential or electrochemical window for flotation to occur3, therefore, it is necessary to reduce the potential outside of this window in order to effectively separate Cu and Fe sulfides from MoS2 minerals2. In RTKC plant, the target reducing condition is between -450 to -550 mV to effectively destabilize the collector and depress Cu and Fe minerals. Typically the dosage of NaSH used in the molybdenum plant could range from 6 to 30 gallons/min (gpm). The high dosage of NaSH could pose risk of H2S exposure. RTKC wanted to evaluate alternatives to NaSH in order to reduce its consumption and minimize risk of H2S gas generation."

Jan 1, 2016

By W. L. Price

The intelligent selection of wire cloth and perforated plate for screening surfaces seems a rather confusing subject to the newcomer in aggregate processing. The proper application of various screening surfaces is a complicated one and one could consider himself an expert only after many years of working with all applications. However, part of the subject matter could be simplified considerably for, the average screen user. In this paper an attempt will be made to do this, by presenting some comparative specification data along with cost figures Unfortunately, it is impossible in the limited scope of this paper to give actual service comparison records between different cloths or cloth and plate. Anyone who has considered making actual service comparisons for competing screening media is well aware of the almost insurmountable problems Their solution would form the basis for a separate paper on that subject alone. Therefore, this paper will be limited to comparative data up to the point of installation.

Jan 1, 1961

By M. Akser

Ilmenite, rutile, and zircon deposits of commercial importance have not been reported to-date from Turkey. However, information from recent reconnaissance activities indicates the possibility of an economically viable heavy-mineral deposit along the Black Sea coast of Turkey in the vicinity of Ormanli, northwest of Istanbul. Consequently beach and sand dune samples were collected from that area for additional analysis. Laboratory methodologies, designed to simulate standard industrial heavy-mineral plant practices, were used to analyze and evaluate the samples. Based on the analyses, and current market needs, none of the deposits in the Ormanli area qualify as a commercial heavy-mineral deposit.

Jan 1, 1995

By P. R. Pereira

This paper presents a comparison between the simulations of a semi-empirical model and a theoretical model for the prediction of radial stress in rock. The results of the simulations were compared to the results of a field test. The comparison of the radial stress predictions shows that in the semi-empirical model use of the plane wave approximation as the basis for the prediction of the radial stress provides a much better result than the theoretical model. The theoretical model includes the correct elastic wave geometry and theory but fails twice, firstly by considering the charge as a point (unit) energy source therefore; and secondly by using a Delta function with a very sharp rise and decay time to simulate, with no distinction between non-linear and linear zones, the attenuation of the energy per unit volume at the shock wave front as the wave moves away from the borehole. The results of the semi-empirical model were within the same order of magnitude as the results from the field test whereas only one result from the theoretical model came close to the result of the field test. However, even this closer result for the theoretical should be taken with caution as there was no measurement in the field test made at this distance from the borehole. Finally, because of its potential portability, convenience, and cost-effectiveness the theoretical model can be a most valuable tool for mining and civil construction operators in the early design of blasting rounds and of the mining operation itself.

Jan 1, 1993

By Jun Yuan

Kaolin clays from five different commercial deposits in Georgia were studied to understand the variations of zeta potential and related fundamental properties. The results suggest that higher negative zeta potential is related to exchangeable or soluble calcium ions in the clays.

Jan 1, 1997

By James S. Falcone

Soluble sodium silicate materials have well known applications in flotation for desliming, selective depression and corrosion control. Recent advances in the understanding of the complex polymeric nature of silicate solutions using NMR spectroscopy, combined with our studies of the effects of polymeric silicate anions on metal ion activities in solution, oxide mineral surface charges and surfactant adsorption on clays are related to beneficiation processes. The results of these studies indicate the sodium silicates can be used to cause a solution chemistry and particle surface charge characteristics favorable to enhanced effectiveness in typical ore beneficiation systems.

Jan 1, 1981

By Q. Xiao, R. Naidu, W. Li, S. Song

Acid mine drainage (AMD) derives from the oxidation of sulfide minerals, primarily pyrite (FeS2), and is the most severe environmental issue facing the minerals industry. The most common short-term approach to AMD treatment is migration control, such as acid neutralization and metal/metalloid and sulfate removal, through the addition of alkaline materials, including lime (Ca (OH)2), limestone (Ca CO3), gangue minerals and industrial wastes. This requires the continuous input of materials and may result in the production of a vast amount of secondary sludge requiring further treatment and disposal. Addition of chemicals is usually more important in metal/metalloid removal than in sulfate removal unless the sulfate is present in very high concentrations. A more promising long-term strategy for AMD prevention is source control through the complete removal of pyritic minerals and encapsulation of potential risk minerals by coating with impermeable surface layers. This is regarded as the most cost-effective approach, although the mechanisms underpinning this and the implementation procedures are yet to be fully elucidated. It is likely that long- and short-term practices can be combined to optimize the remediation of contaminated mining sites. Some factors such as differing geological and mineralogical characteristics and transportation costs must also be considered for the successful implementation of AMD prevention and remediation strategies. This review also considers some implications for AMD remediation, but the promising bioremediation of AMD is not discussed as it has been extensively reviewed.

By Erika Moonin, Jim Nickerson, Claudio Cimiotti, Roberto Bono

"In response to the severe drought on the Colorado River basin and in order to preserve existing water capacity to the Las Vegas Valley, the Southern Nevada Water Authority contracted a new deep-water intake (Intake No. 3) located in Lake Mead. The current project (Contract No. 070F-01-C1) includes 5 km (3 miles) of tunnel with very difficult geological conditions and a 200- m (650-ft) deep shaft and marine works. This paper will present the current status of the design-build contract being constructed by Vegas Tunnel Constructors and the challenges and problems faced and the innovative solutions developed to handle the difficult conditions encountered during tunneling with up to 15 bars of pressure.ProjectbackgroundThe Las Vegas Valley receives the majority of its water from Lake Mead, which is located approximately 30 km (20 miles) east of the Las Vegas, NV metropolitan area. Due to the severe drought that has hit the southwest region of the United States, the water level in Lake Mead has receded from its high water level of 372 m (1,221 ft) above mean sea level (amsl) to a low of 330 m (1,076 ft) amsl in June 2015. Should the lake level continue to fall, at elevation 320 m (1,050 ft) amsl, the current water intakes will not be able to draw enough water to meet the needs of the local area. The risk of losing water capacity has prompted the construction of a new deeper intake. Not only is the new Intake No. 3 situated at a lower elevation in the lake at 262 m (860 ft) amsl, the new Intake No. 3 is also located to draw better quality (Fig. 1).Project challengesThe project has had several difficult challenges to overcome:• The work consisted of a 1.2 kt (1,300 st) structure constructed on a barge and lowered 100 m (330 ft) into Lake Mead anchored with 9,200 m3 (12,200 cu yd) of tremie concrete.• The drill-and-blast starter tunnel was impacted by three inflow events, resulting in a one-year project delay.• One of the main challenges was selecting the tunnel boring machine (TBM) and excavating the tunnel with expected hydraulic head pressure of as much as 17 bar (16 bar was the highest pressure recorded during the drive), crossing faulted areas, low rock cover and the risk of tunnel instability due to direct connection with the lake.• Extensive pre-excavation grouting with a constant head pressure ranging from 12 bar to 15 bar.• Structural repair of the cutterhead in difficult hydrogeological conditions [water inflow of approx. 800 m3/hr (4,000 gpm)].• Complete repair of the cascade sealing system for the main bearing and two replacements of the pinion bearings.• The TBM approach to the intake structure."

Jan 1, 2015

By R. R. Klimpel

Over the last six years, several new commercial families of sulfide mineral collectors have been developed. This paper summarizes some plant data and use experiences gained with each of these product families. The first is a series of products (F-series) based on a chelation mechanism of attachment. The second of these families is a series of products (S-series) based on an electrochemically controlled mechanism of attachment. The major advantage of the F-series collectors is the very high metal recovery capability in complex ores involving Au, Pt, Zn, Ni, and mixed Cu minerals. The major advantages of the S-series collectors are the very high pyrite rejection capability along with reduced lime requirements in Cu/Mo plants.

Jan 1, 1995

By B. R. Benner

Progressive improvements in crusher design, screening efficiency, and operating experience along with the downsizing of many taconite operations has resulted in the abilitv of some crushing plants to produce a substantially finer product. This finer product opens the possibility of replacing the rods in the rod mill with balls as is the current practice at Sydvaranger, Norway. If this replacement could be accomplished substantial savings associated with metal wear and the elimination of rod charging may be realized. The purpose of this study was to compare the performance of a mill charged with rods with the performance of the same mill charged with balls at the pilot scale. The first objective was to establish whether we could achieve the same throughput rate at the same mesh-of-grind in a mill in which the rod media has been replaced by balls. The second point was to determine whether the ball media would create a significant tramp oversize problem.

Jan 1, 1990