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By Gordon R. Wicker, John A. Cole

Although the evaluation of autoclave oxidation for Getchell ore was begun nearly 40 years ago, its ultimate implementation in 1989 represents the first substantial improvement in the economics of processing this refractory ore. Sulfide ores at Getchell were previously roasted prior to leaching (in the 30's and 60's), resulting in somewhat lower recoveries than are currently realized by autoclave oxidation. Recoveries on the order of 90% are expected from the high-arsenic sulfide ore over the expected 10-year mine life.

Jan 1, 1990

By R. K. Mehta, C. W. Schultz, R. R. Mallepali

Stirred ball mill feeds used for ultrafine grinding applications require a fine size separation step to avoid overgrinding. This paper presents the selectivity curves obtained for oil shale and complex sulfide ore using a 460-mesh (30-µm) Derrick vibrating screen. The selectivity curves generated from the experimental data show increasing selectivity with larger size for the oil shale but not for the sulfide ore. These unusual selectivity curves are similar to the mechanical air separator, fishhook selectivity curves described by Luckie and Austin. A two-stage, in series, classification model describing the fishhook selectivity curve has been used in proposing the classification mechanism for fine vibrating screens when a heterogeneous, multicomponent sulfide ore undergoes size separation.

Jan 1, 1994

By D. D. Harbuck

Previous studies at the US Bureau of Mines (USBM) have shown that only 70% to 80% of the germanium in domestic zinc process residues can be extracted during H2S04 leaching. To increase germanium extraction, the USBM developed and researched the hypothesis that minor amounts of germanium and zinc silicate, present in zinc calcine, dissolve during the leaching stages of zinc processing, forming soluble germanium and silica gel. This silica gel then selectively adsorbs germanium from solution, rendering the germanium insoluble. Testing showed that as the amount of formed silica gel increased, the amount of insoluble germanium in the zinc residue increased. Several processing alternatives are presented for overcoming this problem.

Jan 1, 1994

By Raimondo Ciccu, Francesco Satta, Marcello Ghiani, Piero Carbini

Nonpolar oils are utilized as collectors in low-rank coals flotation processes. The analysis of the mechanism of the hydrophobic film formation on coal particles permits the identification of the main characteristics that these reagents should exhibit in order to render the process technically and economically efficient. Such requirements - low repulsive energy developed in the interaction with coal particles; limited interfacial tension at the coal-oil boundary; relatively low viscosity and, at the sake time, poor ability to absorb into the coal pores - are found in some binary mixtures of oils having different volumic mass. The features of such mixtures as well as the advantages deriving from their use for the flotation of a Sulcis coal sample and experimentally proven, are described.

Jan 1, 1989

By S. K. Kawatra, A. K. Bakshi

An on-line rheometer was developed to monitor the slurry rheology of a thickener underflow. The thickener processed a chalcopyrite flotation concentrate having a top particle size of 125 µm and a solids content of 30% to 60% (by weight). The slurry also contained residual flotation reagents, resulting in hydrophobic particles. Polymeric flocculants and lime were added to the thickener to flocculate the particles. Using the on-line rheometer, the slurry was found to exhibit pseudoplastic behavior with no yield value. It was also determined that factors other than the percent solids were responsible for changes in the slurry rheology.

Jan 1, 1999

By R. J. Matetic, Peter G. Kovalchik, Jeffrey Shawn Peterson

The National Institute for Occupational Safety and Health (NIOSH) has initiated a study of a roof bolter to reduce noise exposure to mine roof bolter operators. An important segment of this research entails determining the affect of various drilling configurations on the performance (penetration rate) and sound power emissions when drilling into granite. Test conditions included various combinations of rotational speeds and thrusts; hex and round drill steels of one inch (1.) and one and three-eighths inch (1 3/8.) diameters; vacuum and wet conditions; and using drill media of differing compressive strengths. This paper will detail the affects of each of these on the performance and sound power level emission. When drilling into granite, it was found that wet drilling generated lower sound power levels and performed better than vacuum drilling.

Jan 1, 2005

By G. Belardi, N. Sheau, P. Plescia, F. Veglio

A study was conducted to assess a new wet gravity-separation machine, identified as the Multi-Gravity Separator(MGS). Chromite fines, obained from an Albanian chromite and olivine ore and containing 23% Cr2O3 and 18% SiO2, were used in the study. The first step was to determine the influence of various operating parameters. The study indicated that the most important variables for the MGS are rotational speed, tilt angle and shake amplitude. The best treatment conditions for the ore were then identified by investigating a series of circuits designed to produce a marketable product. In open circuit, a concentrate containing 50% CI-203 was obtained with a recovery of 72%.

Jan 1, 1996

By Feng Dingwu, Chen Jin, Sun Zhongyuan, Peng Shiying

The recent development of rare-earth permanent magnets has impacted the field of magnetic separation. The permanent magnets technology led to the advent of various magnetic separators particularly designed for application in mineral processing. In this paper, a new type of rare-earth PHGMS possessing a higher magnetic field strength in the working zone was developed using finite element analysis techniques. The NdFeB permanent magnets used had properties of 38 MGOe stored energy, and magnetic material flux levels exceed 1.2 T, The combination of scientific and engineering design and suitable matrices can offer an effective separation of industrial minerals, such as kaolin, feldspar, etc. Compared with conventional high intensity electromagnetic separators, the equipment can reduce electrical energy over 80% with lower operation and maintenance costs, and less installation space.

Jan 1, 1995

By Colin C. Harris, Jie Zheng, P. Sornasundaran

Powder surface and polymer structural changes during stirred milling have been studied as a function of grinding time, solid concentration and polymer molecular weight. It was found that specific surface area of limestone particles can be increased over 100% by using polymer additives. Particle surface and polymer structure were also found to change during grinding. Powder surface and polymer properties have been determined using Surface Tension, Fluorescence, TOC and HPLC/GPC analysis, and surface and polymer properties are correlated with operating variables and the mechanisms involved are explored. Particularly, the fragmentation of the polymer molecules was found to occur during long term grinding and this was beneficial for ultrafine grinding.

Jan 1, 1998

By Y. David

In 1990, the United States became only the second country (after China) to produce more than 900 Mt (1 billion st) of coal in a single year. US production of bituminous and subbituminous coal, lignite and anthracite totaled 933.5 Mt (1.029 billion st) in 1990, 5% more than in 1989. The production gains were largely due to the rebuilding of depleted coal stockpiles by electric utilities and a surge in US coal exports. Domestic coal consumption essentially remained at its 1989 level. A slight increase in electric utility coal consumption was partly offset by a decline in metallurgical coal use. The use of coal in other industries and in the residential-commercial sector remained virtually flat.

Jan 1, 1991

By Lawrence A. Ph. D. Hansen, J. David Deatherage

Laboratory testing programs were conducted to investigate the performance under compression loading of several types of geomembranes and geotextiles proposed for use in heap and dump leach projects. Synthetic liners of several thicknesses were sandwiched between representative subgrade soils and cover materials, thus modeling in the laboratory the actual installation conditions expected. Performance was evaluated by visual inspection and vacuum testing. Several testing procedures and equipment were used to investigate the effect of these testing parameters on the predicted performance.

Jan 1, 1987

By Michel Grenier, David A. Young, Brent Rubeli, Mahe Gangal

This work forms part of a study being conducted into the feasibility of constructing a prototype Load Haul Dump (LHD) vehicle for operation in underground Canadian mines. A series of in-laboratory assessments were performed to determine the relative contributions of a Deutz F4L912W (54 HP- conventional vehicle engine) and a Deutz F2L 2011 (31 HP hybrid vehicle engine) to diesel emissions concentration during mine transient duty cycles and steady-state operating modes respectively. Results indicate significant reductions in the quantity of gaseous and particulate emissions with the application of the hybrid system and a high-efficiency ceramic element filter. This paper describes the engine test protocols and the results of this laboratory study.

Jan 1, 2006

By D. I. Phillips, P. J. Bethell

This paper focuses on the -1/2 mm cleaning at Elk Run Coal. The original circuitry incorporated desliming cyclones. Problems with slimes entrainment in the cyclone underflow (froth cell feed) resulted in poor froth cell selectivity. Laboratory test work led to the installation of high frequency desliming screens. Consequently, great improvement in cell performance was brought about by enhanced desliming with the ability to use split flotation. The modifications resulted in significant improvement in total plant performance and overall yield while maintaining clean coal quality.

Jan 1, 1987

By J. Patrick Powers, Arthur B. Corwin

Modern improvements in hydrogeology make it possible to predict with good reliability the performance and cost of ground water pumping systems in many tunneling situations. The testing and analysis techniques are presented. Data from the Buffalo NY LRRTS (1978-1980) illustrate the successful application of the technique for tunneling in rock. Data from the Red Hook Interceptor Tunnel in Brooklyn NY (1978) illustrate the application in soft ground. The Red Hook project also illustrates concerns for the side effects from dewatering, such as ground settlement and damage to timber structures. At Red Hook protective measures included compressed air, artificial recharge and controlled dewatering. Given the uncertainties of the underground, the possibility of unexpected situations must be considered. A hard rock sewer tunnel in Atlanta, Georgia (1982) illustrates an unexpected problem, and the emergency measures used to solve it.

Jan 1, 1985

By P. L. Webster, S. D. Thompson

The Coal Mine Belt Capacity Simulator (CMBCS) was originally developed to provide an improved belt capacity simulation through more detailed, flexible and realistic modeling of belt loading. While this model offered improved capacity design for conveyor belts and surge bins, it lacked the capability to simulate some key protection and segregation applications for bunkers. Recently, CMBCS was extended so that these latter bunker applications could be considered. In addition, a fear minor extensions were made to improve the model's flexibility and of efficiency. These various extensions and the steps taken to verify and validate them are described. The associated modifications in the model's input and output as well as the model's current requirements and availability are also discussed.

Jan 1, 1992

By Burt Ensley, Viatcheslav Dushenkov, Ilya Raskin, David E. Salt

Roots of many hydroponically grown terrestrial plants, including sunflower (Helianthus annuus L.) effectively remove toxic metals such as Cu+2, Cd+2, Cr+6, Ni+2, Pb+2 and Zn+2 2 from aqueous solutions. It should be possible to scale up this process such that plant roots can be used to treat large volume aqueous waste streams. It can be extrapolated from laboratory results that to reduce the Cd concentration in a waste stream, from 1 ppm to below 4 ppb, with a flow rate of 4000 L/min, would require 3500 sq. m of plant roots with a density 5 kg fresh weight per sq. m. These results suggest that the roots of hydroponically grown terrestrial plants may provide an attractive alternative to the accepted water treatment technologies.

Jan 1, 1995

By K. L. Kasperski, M. T. Ityokumbul

The effect of reaction conditions on the desulfurization of oil-sand coke residues was studied. The variables investigated were temperature, reaction time, heat transfer resistance and mode of caustic soda addition. The results show that oil-sand coke desulfurization increases with temperature, reaction time and heat-transfer rate. In an oxidative environment, coke combustion during molten-caustic leaching (MCL) commences at temperatures above 500 °C. The mode of caustic addition has no effect on coke desulfurization.

Jan 1, 1996

By K. N. Han

The dissolution kinetics of cobalt in iodine/ iodide solutions were investigated using a rotating-disc technique. Variables studied included temperature, rotating speed, concentration of lixiviants and the pH of the solution. The overall dissolution reaction appeared to be limited by the mass transfer of tri-iodide through the diffusion boundary layer with an Arrhenius activation energy of <16.2 kJ/mol (4 kcal/mol) over the temperature range of 2 to 42ºC. The pH of the solution had little effect, as long as the pH of the solution was <8. However, when the pH of the solution became >8, the dissolution rate decreased dramatically, due to passivation. The rate of dissolution was in good agreement with the dissolution model developed by the authors earlier.

Jan 1, 1995

By J. A. Muñoz, A. Ballester, C. Gómez, M. E. Sevillano, M. Figueroa

The electrochemical behavior of massive chalcopyrite (CuFeS2) electrodes has been studied in the absence and-in the presence of mesophilic microorganisms, using cyclic voltametry as analytical technique. The culture was principally formed for Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans. The results showed that the reactivity of the chalcopyrite gradually increased with the bacterial treatment. The anodic dissolution process of the chalcopyrite treated with microorganisms was related to the breaking of passive layers when the applied potential increased. The analysis of the surface products showed that the chalcopyrite was covered with a superficial film avoided its dissolution during the bioleaching test. So, the rest potential of the bioleached samples increased possibly as consequence of its superficial transformation.

Jan 1, 1995

By Wojciech Klecan, John H. Raymer

Baseline quantities of difficult ground and support types were estimated for the Chattahoochee Tunnel using the Rock Mass Rating system. RMR classifies the ground into five categories, ranging from “very good” to “very poor,” based on five main parameters: intact rock strength, RQD, joint spacing, joint condition, and groundwater inflow. For the Chattahoochee Tunnel, these parameters were independently measured in the cores and shown graphically on the boring logs. A 55 matrix was calculated to obtain the statistical distribution of RMR for the project. Three baseline ground types were defined based on the RMR. Geologic mapping inside the tunnel during construction has verified the accuracy of this method.

Jan 1, 2003