Search Documents

By W. K. Collins, C. L. Dahlin, D. C. Dahlin, W. K. O’Connor, G. E. Rush

Direct mineral carbonation was investigated as a process to convert gaseous CO2, into a geologically stable final form. The process utilizes a slurry of water, with bicarbonate and salt additions, mixed with a mineral reactant, such as olivine (Mg2SiO4) or serpentine [Mg3Si2O5(OH)4]. Carbon dioxide is dissolved into this slurry, resulting in dissolution of the mineral and precipitation of magnesium carbonate (MgCO3). Optimum results were achieved using heat-pretreated serpentine feed material and a high partial pressure of CO2 (Pc02). Specific conditions include 155°C, PC02 = 185 atm and 15% solids. Under these conditions, a 78% conversion of the silicate to the carbonate was achieved in 30 minutes. Process mineralogy was utilized to investigate the appropriate feed characteristics, identify the process products and interpret the mineral dissolution and carbonate precipitation reaction paths. Key words: Mineral carbonation, Carbon dioxide sequestration, Carbonates

Jan 1, 2003

By Christopher Haycocks

Successful ground control is an essential part of all viable underground mining operations. To a large extent ground conditions influence the choice of mining methods, percentage and cost of extraction, and often the degree of safety that can be achieved. Utilizing the computer for ground-control planning offers great potential under many diverse conditions as not only are computations facilitated, but also details of the often complex geologic and structural framework of the mine can be readily stored and retrieved. Two basic approaches have been developed for applying the computer in solving ground-control problems. The first uses an analytical method, such as the finite element technique, for solving a specific problem. The second is more general and involves storage of geologic data and application of general design equations. The latter has found wide application in stratified deposits. It is the purpose of this chapter to describe both approaches as they are used for improving the ground-control aspects of mine planning.

Jan 1, 1979

By J. Felipe Costa, Andrew H. White, Marcot T. M. B. Vilhena

Ordinary kriiing (OK) is an interpolation algorithm mostly used in earth sciences applications where it provides satisfactory results. Robust kriging (RK) is an alternative algorithm which at- tempts to minimise the problems caused by the existence of outlier values within a given data set. Robust kriging essentially consists of an editing step prior to running the traditional OK method. This study compares the interpolation results obtained by OK and RK. Two data sets were used. The first data set consists of 140 samples mimicking a drilling survey named cluster.dat. An additional feature of this sample data is that its parent population, the reference data set, is available, thus permitting direct quantitative assessment of the effectiveness of a given estimation technique. The second data set consists of a grid sampled at 1x1 m. The estimates obtained by OK and RK using cluster.dat were compared to the reference data set. RK provided better results in terms of quality of the estimates than OK

Jan 1, 1996

By M. Balakrishnan, K. A. Natarajan, J. M. Modak, J. S. Gururaj Naik

The ability of various fungal species isolated from gold mines to uptake gold and base metals such as zinc, copper, iron and lead from gold-process cyanide effluents was investigated. Under identical treatment conditions, different strains showed wide variations in their ability to take up gold and other base metals. Aspergillus terreus exhibited as high as a 60% gold uptake. Almost complete removal of zinc was possible with various fungi and with the yeast Saccharomyces cerevisiae. Studies at various metal concentrations showed a higher gold uptake from dilute solutions, and studies with Aspergillus niger showed that gold uptake by living cells increased gradually as the contact time increased. Metal uptake capacities between living and nonliving cells were also compared. A waste biomass (ABM- I), obtained from a fermentation industry, wasalso identified as having a high gold uptake capacity. At 5% (W/v) solids, ABM-I could efficiently remove up to 83% of the gold contained in an effluent solution within 24 hrs.

Jan 1, 1995

By Judith M. Ballantyne

Carlin-type. disseminated, sediment-hosted gold deposits can be better described as hydrocarbon-associated gold deposits. A new genetic model for these deposits involves the intrusion of one or more small bodies of magma into a shallow hydrocarbon reservoir or ma of hydrocarbonenriched rocks, imposing a convecting geothermal system on the local groundwater. Pyrite, commonly associated with the organic material, provides a substrate for deposition of gold and other trace elements in an environment rich in dissolved sulfide. Both diagenetic and hydrothermal pyrite may act as gold depositional sites. Thermal cracking of hydrocarbons, catalyzed by illite, subsequently generates an oxidizing environment by depleting hydrogen. As oxidation increases, arsenic sulfide minerals and barite m stabiied at first. Increasing hydrogen depletion converts sulfide to sulfate, generating acid oxidizing conditions which: alter pyrite to hematite; continue the deposition of sulfates; and ultimately develop late stage acid-sulfate assemblages containing minerals such as kaolinite. alunite. and jarosite. Gold released from the oxidizing pyrite is redeposited as free gold, and pehaps remobilized.

Jan 1, 1988

By Robert Dimock

The successful management of large dispersed mineral operations is dependent upon accurate and timely decision making. The plant locations providing the data to support the decision making process are generally separated by distances which elongate the time required to accumulate the data at a central focus. The need exists to examine operational data in context with total mining operations, and in relation to target projections and historical trends. The use of microcomputers for local information tasks is an established capability. Grouping microcomputers into local-area networks is rapidly becoming established. Interconnecting multiple local-area networks to provide a free flowing stream of information between all operational locations of a mining enterprise is possible with use of some emerging technologies. The benefit of the potential interconnections and rapid transfer of information can readily be seen from a production reporting perspective. Numerous other advantages exist' by providing routing to enable a workgroup to be established between separated work functions.

Jan 1, 1989

By C. M. Chang, H Gu, J. A. Barrera-Godínez, T. J. O’Keefe

The inability to economically separate Fe3+(aq) from a variety of liquid effluents is a major Concern for the primary metals industry. A unique solvent extraction process, galvanic stripping, has been developed to address this problem. The galvanic stripping of iron from D2EHPA using only a 5~10 g/L H2SO4 solution is achieved after Fe3+ is directly reduced to Fee, in the organic phase using zinc metal additions. To date, the primary focus of the laboratory research has been on optimizing the parameters that control iron removal. The results from these studies have now been, used to make a preliminary design for a continuous flow process that is envisioned for zinc industrial applications. Specific quantitative data are shown for the use of a Zn-Ph cellos° in the iron-reams al process. Some introductory results on electrochemical potential measurements and impurity distribution with solution cycling are also giiven.

Jan 1, 2000

By Michael J. Sapko, Robert A. Cortese

A flame powered trigger device has been developed to explosively activate suppression barriers to quench gas and coal dust explosions. The important feature of the device is a silicon solar panel, which collects 0.3 p to 1.1 D wavelength radiation from the developing explosion, and generates electrical energy to initiate a detonator, which in turn causes the rapid explosive release of an extinguishing agent into the advancing flame front. Solar panels that are rated to produce 20 w of electrical power when exposed to the sun light are producing about 200 w when exposed to full-scale dust explosion propagating in the U.S. Bureau of Mines' Lake Lynn Experimental Mine. The solar panel is electrically isolated from the detonator by a pressure sensitive switch until the arrival of the precursor pressure pulse, which always precedes a deflagration. This combination of pressure arming and flame powered photo generator prevents false barrier activation and requires no external power supply.

Jan 1, 1991

By R. A. Jankowski

Laboratory tests were conducted to evaluate the silica collection efficiency of flooded-bed scrubbers using six different filter panel designs at two operating velocities. Test results indicated that reductions in filter density negatively impacted respirable dust collection. Silica collection efficiency for the least-dense filter was as much as 33 % lower than the collection efficiency of the most-dense filter. At the low operating velocity, the least-dense filter allowed more than 40% of the respirable silica dust in the scrubber intake air to pass through the unit and back into the mine environment. Operation of the scrubber at the higher test air velocity increased silica collection efficiency regardless of the filter panel tested The density of the filter panels also impacted the quantity of air moved through the scrubber, with higher-density filters reducing scrubber airflow. For each filter, the relationship between dust-collection efficiency and air-moving capacity must be considered to determine the overall effectiveness for each mine application.

Jan 1, 2000

By G. M. Wilemon, Swanton. R. G.

The Bureau of Mines is investigating the leaching of phosphate values from Florida phosphatic clay wastes using sulfuric acid (H2SO4) as the leaching agent and methanol as the solvent. Acid-alcohol leaching studies were done using research-grade apatite to investigate potential causes of flow extractions. It was found that a barrier layer formed on the surface of the apatite. Initial discovery of the barrier layer was made by analyzing pure apatite samples before and after leaching using an optical microscope. Subsequent Fourier Transform Infrared (FT-IR) analyses proved the coating was calcium sulfate hemihydrate (CaSO4•1/2H2O) and that unreacted apatite existed beneath the coating. Scanning electron microscope (SEM) photographs depict the CaSO4• 1 /2H20 morphology as long slender crystals adhering to the apatite surface. It was also shown that grinding the leached tailings and leaching again in the H2SO4-methanol system resulted in additional phosphate extraction.

Jan 1, 1992

Surface characterization techniques, i.e. contact angle measurement, atomic force microscopy (AFM) surface force and surface imaging measurement, were applied to investigate the molybdenite surface in aqueous solution. It was shown that the cleaved basal surface of molybdenite was very hydrophobic with a 92 degree water contact angle. The non-polar component of the solid surface free energy is 50.52 mJ/m2 while the polar components are almost zero. The solid surface was not reactive and was only weakly charged at the pH 6. When the aqueous media changes from water to 1×10-4 M KEX solution, the measured contact angle, adhesion force and surface roughness all increase slightly. However, ethanol rinsing made the surface change back to the bare substrate. It was suggested that the hydrophobic chemical, i.e. dixanthogen, which was shown in the morphology of patches by the AFM image, physically adsorbed on the hydrophobic molybdenite surface through the hydrophobic interaction.

Jan 1, 2009

By J. E. Hoffman, S. P. Sandoval, T. J. Keefe, K. P. V. Lei, O&apos

The U.S. Bureau of Mines investigated the use of the Fe2+/Fe3+-SO2 (FFS) anode reaction in the copper leaching-solvent extraction-electrowinning circuit. The investigation revealed that six process variables, including anode type, Fe 21 concentration, current density, electrolyte temperature, degree of agitation, and manifold injection point were found to influence cell voltage and cell current efficiency. A 47% voltage reduction (0.8 versus 1.5 V) compared to conventional electrowinning with activated lead (ALE) anodes was achieved at a current density of 258 A/m2 (24 A/ft2) with an industrial electrolyte. Current efficiency was maintained above 90%, and S02 above the cell measured less than 1 ppm when activated carbon was used to assist the reduction of Fe" by S02 in the copper electrolyte. Solvent extraction tests showed that Alamine 336 is a stronger H2SO4 extractant than is needed to extract the excess acid produced by the FFS anode reaction.

Jan 1, 1993

By Janusz S. Laskowski

The most important type of potash ores, sylvinite, contains sylvite, halite and a small percentage of insoluble gangue [sulfates (anhydrite), carbonates (dolomite), and clay minerals]. Primary normal long-chain amines are exlusively utilized to float sylvite from halite, but since mines are also adsorbed by insoluble slimes, the process requires prior desliming. This is carried out either by mechanical means, or by flotation of slimes and blocking off the adsorption centers on clays with the use of polyelectrolytes. Fractional crystallization is employed to produce fertilizer grade KC1 from disseminated ores with a high content of slimes. An extender oil is needed in addition to mine to float coarse sylvite fractions. The process is carried out in a saturated brine at mine concentrations exceeding the solubility limit and is strongly affected by temperature fluctuations. All these important features, which make this process differ from a conventional flotation, result from a high electrolyte concentration.

Jan 1, 1994

By Steven A. Tesdahl

Maintenance means keeping equipment running or restoring it to operating condition. However, the 21st century will usher in a broader need for equipment management, a cradle-to-grave strategy to preserve equipment functions, avoid the consequences of failure and ensure the productive capacity of equipment. Profitable future mining operations will have reduced the 35% of operating costs typically spent on maintenance and the unfavorable impact of downtime that often multiplied these costs by 300%. They will survive those operations that tried to carry outdated "maintenance" thinking beyond the year 2000. These surviving operations will have applied modern management techniques, technology and information to align the efforts of people with the needs of equipment. Future managers will use equipment management as an integral part of an overall production strategy. They will see it as a means of raising productivity, improving performance and minimizing downtime to maximize profitability. This global thinking will characterize all operations planning to survive in the competitive world of mining of the next century.

Jan 1, 1998

By Rob McIvor, Joe Keating, Gary Simmons

As more complex ores are processed, finer grinding becomes more necessary. A cross section of several industries will be presented with discussions not only of find grinding issues but also the classification of fine particles. JOHN MANSANTI: Our next topic will be fine grinding. Again, the intent is to present a topic that is generic enough to apply to multiple industries. Our first speaker is Gary Simmons. Gary is filling in for Phil Walker from Twin Creeks. Phil was not able to join us this week, because of some issues they're having with the autoclave. Gary, being involved in the development phase, is very familiar with the topic. Gary spent about three years with American Cyanamid and another four years with Noranda. He also spent some time with Meridian Gold, then became the director of metallurgy with Santa Fe Pacific Gold. He spent seven years there and is presently the director of process technology with Newmont Gold.

Jan 1, 1998

By R. L. Grayson

The Office for Mine Safety and Health Research, National Institute for Occupational Safety and Health is responsible for providing research leadership in the prevention of mining work-related illness, injury and death. Planning of the NIOSH FY99 research program focused on the comprehensive collection and risk analysis of fatality, injury and illness data according to commodity and mine type. This data, coupled with the mapping of information obtained from stakeholder meetings over several years, provided the basis for prioritizing research needs. Results of the combined analysis were compared to the FY98 program to identify surveillance and research gap areas. The FY98 research program was then assessed according to commodity and mine type and compared with exposure assessments, traumatic fatality rates, injury rates and employment trends in each commodity-mine type combination to gain insight into the potential balance of the future research program. This paper presents the methods, data and results of this planning process.

Jan 1, 2002

By R. L. Pariani, R. R. Moskalyk

Justifying refinery material handling equipment jointly involves economics and indirect benefits. The simple evaluation method is applicable when either retrofitting facilities or costing new metal refineries. The text includes points of interest regarding equipment selection as an additional guide. Although the copper industry was used as a basis, it is recognized that similarities in material handling may exist within the parallel electrolytic refining and winning of metals such as copper, nickel, lead, zinc, tin, and cobalt. The analysis of four major automatic systems, typically implemented in many tank houses, includes tabulated data plus a detailed description of additional benefits. General information regarding auxiliary material handling equipment and an overview are included for subject completeness. It is suggested that the quantitative and qualitative aspects presented may contribute to the basis for justification of automated material handling. The labor-oriented economics plus related intangible benefits described herein should provide incentives to modernize or replace manual operations where practical.

Jan 1, 1987

By Scott G. Britton

Up to now, the hands-on approach to construction has been stressed. This chapter reviews the basic tools available for construction design and monitoring of a construction project. It is divided into three discussions, all under the general title of computer aids, since the trend for using these tools-is via the computer. In the context of our discussions, the focus for computer aids will be on the use of evaluation and analysis techniques for coal mine construction applications, including mainframe programs, CPM techniques, as well as mini and microcomputer applications. Although the presentation of material in this chapter may be detailed at times, by no means does it cover the entire field of computer applications for design or project scheduling and monitoring. It is only an attempt to illustrate the possibilities that are available to construction and mine engineers. Interested persons can pursue computer applications for coal mining by reviewing Computer Methods for the 80's. by Alfred Weiss, editor, published by SME-AIME.

Jan 1, 1983

By Winfield G. Wright, Philip L. Verplanck, Philip L. Hageman, Douglas B. Yager, Dana J. Bove, M. Alisa Mast

Geological, hydrological, and geochemical information synthesized in a Geographical Information System (GIS) for water and rock surrounding South and Middle Forks of Mineral Creek, northwest of Silverton Colorado, was analyzed to distinguish between the natural and the mining-related sources of metals to dace waters in the watershed An important natural source of metals to surface water emanates from a porphyry molybdenum deposit south and upslope from the Middle Fork of Mineral Creek. Interaction of surface and ground water with fractured, altered rocks and permeable, Quatemay-age surficial deposits produces downstream water quality that does not meet current State of Colorado water quality standards for metals and pH. GIS site characterization and three-dimensional modeling distinguish surficial deposits as volumetrically substantial, significant sources of naturally occurring metals that strongly influence water quality and complicate ongoing mine-site mitigation efforts. Our findings indicate that regional hydrologic and geologic information needs to be evaluated before realistic water quality guidelines are established and mitigation recommendations are confidently implemented.

Jan 1, 2000

By Nikhil Dhawan, Veeranjaneyulu Rayapudi, Singh Rahulkumar Sunil

The ever-increasing demand for steel and the subsequent depletion of high-grade ores requires the massive utilization of low-grade iron ores. In the present study, an iron ore slime sample containing 56.1% Fe was investigated using physical beneficiation, carbothermal reduction, and a microwave-assisted process; however, physical beneficiation and microwave exposure were found to be inefficient as they yielded lower iron recovery. Using coconut shell as an alternative reductant was found to be promising and does not lead to the formation of higher iron oxides, such as fayalite and wustite phases. The microwave-assisted carbothermal reduction was found at par with conventional reduction, saving time and heating. The optimum magnetic concentrate obtained in both carbothermal reduction routes (microwave and muffle furnace: Fe grade, Fe recovery, and yield of 64.3, 97, and 84%, and 67, 99, and 83%, respectively) are suitable for alternative iron-making or blast furnace units.