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By Michael G. Nelson, Hanguang Wu, V. Izaxon, Sukumar Bandopadhyay

The method of mine ventilation involving heated air, which is frequently used in mines in cold regions, does not correspond to the natural conditions prevailing in permafrost regions; it is not economical and leads to a series of complications which can be prevented or greatly reduced by lowering the temperature of the air stream entering the mine until it is equal to or very close to the temperature of the frozen ground This paper presents ventilation design approaches which can be engineered to provide the required micro-climate and thus en- sure the stability bf the ground for placer mines in permafrost. Specifically three ventilation design approaches are presented: 1) design based on minimum thermal impact; 2) design based on positive/negative heat accumulation in the existing mine airways; and 3) design based on heat exchanging devices such as thermosyphons placed above ground.

Jan 1, 1997

By R. J. Sweigard, T. Beckman, C. T. Justice, E. D. Thompson, T. C. Hopkins

As a means of permanent disposal, fine coal refuse is often pumped as a slurry into surface impoundments. As the available volume is filled, the embankment heights are frequently increased. The additional embankment material is often placed upon consolidated fine coal refuse. There has been concern about the long-term effect of consolidation of this material at or above the liquid limit on its shear strength. A laboratory investigation was performed using three different types of fine coal slurry taken from central Appalachian coal-preparation plants. The refuse was consolidated in 3-m (10 ft) Plexiglas columns under incremental amounts of surcharge loading. The incremental loads were designed to simulate the effect of increasing the height of a refuse embankment on top of the consolidating coal slurry. After the refuse in the columns had consolidated for several months, the columns were cut apart, and triaxial tests were performed on both the consolidated and unconsolidated material for comparison of their shear-strength parameters.

Jan 1, 1998

By D. B. Stephens

Assessing the occurrence of natural ground-water recharge at mine and mill waste disposal sites may be crucial to addressing regulatory agency concerns regarding the potential impact of waste seepage on ground-water resources. Recharge has been shown to occur even in semi-arid areas where annual lake evaporation exceeds precipitation. Permanent storage of waste seepage in the unsaturated zone is not to be expected if recharge occurs under natural conditions. Establishing the direction and rate of fluid movement in the vadose zone by field measurements is an important element that should be included in the site selection process.

Jan 1, 1987

By Wayne A. Sadik

The mine ventilation system of the Henderson Mine provides a case study of designing and maintaining high-quality respirable air in a large underground mine with over 200 units of diesel-powered equipment. This system was designed with concern for minimizing exposure to personnel of siliceous dust, diesel exhaust, smoke, and potential fire hazards while optimizing general environmental air quality throughout the multilevel/multiheading operation. As a relatively new operation, the Henderson Mine incorporates a modern ventilating plant and mine de- sign as well as state-of-the-art technology where appropriate. Two main ventilation shafts approximately 2,300 ft (701 m) in depth (one intake, one exhaust) will handle 1.8 million cfm (850 m3/s) of air circulated throughout 60 miles (97 km) of drifting, providing the ventilation requirements for more than 25,000 diesel horsepower (18,642 kw) underground.

Jan 1, 1980

By Wayne A. Ericson, Kirk S. Davis, Cornelis Winkler

BCI has developed a chemical process known as Ecophos® for the multi-industrial Pine Level Project in DeSoto County, Florida. Approximately 85 percent of the phosphogypsum at Pine Level will be converted to a very clean gypsum. The remaining 15 percent, including impurities plus some quartz tailings sand, constitutes what is termed redigestion solids. BCI has developed an alternative to the practice of disposing phosphogypsum in large above-ground impoundments. The proposed disposal method consists of mixing the redigestion solids with clays and reacting the mixture (leached tailings) with lime prior to disposal into the mine excavations as a reclamation soil material. Leachate water quality testing using lysimeter equipment indicates that the pore water associated with neutralized leached tailings meets maximum contaminant levels set for the drinking water standards of radium and selected primary metals.

Jan 1, 1992

By S. K. Kawatra, S. J. Ripke

During iron ore pellet production, bentonite clay is used as a binder. Typical pellet plants spend from $3 million to $5 million annually for the clay. If bentonite dosages could be reduced by using it more efficiently, a significant cost savings would result. If the binding mechanisms can be completely understood, procedures can be developed to use bentonite more efficiently. Classical bentonite bonding theory is based on the behavior of bentonite at low percent solids and high mixing shear rates. Under these conditions, bentonite was understood to expand, disperse into platelets, and dry into a bonding "film" or "gel." However, these are not the conditions that exist during pelletization, which is carried out at high percent solids and relatively low shear rates. In this paper SEM imaging was used to identify and explain the bonding mechanisms of bentonite on the surface of magnetite concentrate. It was determined that bentonite would form a fibrous network under the proper conditions and that the formation of these fibers corresponded with an increase in the bonding of particles by the bentonite.

Jan 1, 2000

By Michael G. Nelson, Sekhar Bhattacharyya

Between 1974 and 1977, a detailed study of coal pillar strength was conducted by the University of Utah at the Beehive mine in southeastern Utah. This study was funded by the U.S. Bureau of Mines, and included laboratory testing of coal samples, extensive field instrumentation and measurements, and finite element analyses based on the laboratory results. Recently, a similar analysis of the laboratory results and mine design geometry was completed using the LAMODEL program developed by NIOSH. The results of this analysis were close to the data collected in the field. This study allows comparison with the earlier finite-element analysis, and illustrates the utility of the LAMODEL software suite.

Jan 1, 2005

By B. C. Cornilsen, X. Shan, D. H. Carlson, J. H. Johnson

Airborne respirable Diesel Particulate (DP) presents an additional health hazard in that it has been shown to be mutagenic. This problem is of increasing concern as more coal mines introduce diesel vehicles. If the DP present in coal mine air is to be controlled it must first be measured. This paper describes development of the laser Raman spectroscopic measurement of the amount of DP in DP/coal mixtures collected on filters in the laboratory and in coal mines. The Raman technique provides a chemical measure of the carbonaceous material in each component, and is not dependent upon particle size. When this work was begun there were no known analytical methods for this measurement. Side-by-side in-mine comparisons of the results obtained from Raman, neutron activation analysis, and size selective analyses (MOUDI and personal samplers) are presented. The neutron activation and size selective analyses were obtained by the USBM Twin Cities Research Center and University of Minnesota. Good agreement has been found among these three methods.

Jan 1, 1991

By George L. Baloo, Dave Kwiatkowski, Jose G. Cañlzales

Capital project funding for a medium to large materials handling project often includes a budget for procurement of supplier-recommended spare parts, and it is the Project Team's responsibility to select these parts. With today's economic climate, limited budget, and other factors, the spare parts selection process is a difficult and arduous effort. This decision carries with it a risk to plant operations and in some cases the commodities producers. Too often the decision-making process is not documented, and the reasons for eliminating and reducing quantities are based on "best guess " Recently on the Solids Handling Phase 2 Project in Jose, Venezuela, the Project Team took a unique approach to this problem. This paper discusses the analytical approach taken by the Project Team, the database system that was developed to manage this problem, lessons learned, and their applicability to pre- project planning and preliminary design.

Jan 1, 2004

By Jan W. Oberholzer, Patrick Linzer

The globally increasing environmental awareness which has manifested itself in the past few years also encompasses problems associated with mine closures. A crucial requirement for the effective planning, management, monitoring and control of mine closures is an information system which allows the qualitative and quantitative evaluation of proposed closure strategies, not only in terms of their local influences, but also of their potential effects on areas farther a field. This paper describes some of the closure associated problems and the establishment of such an information system from existing facilities, all of which are readily available. No modifications to these facilities are necessary, which enables rapid and cost-effective implementation of the system.

Jan 1, 1996

By B. Cristol, G. Benier

Laboratory and pilot tests have shown that the grinding of some aluminas makes two populations appear : agglomerates’ and ultimate crystals’. Classical breakage functions (Size Mass Balance Method) aren't able to describe correctly this kind of grinding. So we have optimized a particular breakage matrix which takes into account the fact that the agglomerates can either be reduced in size or either be blown up to liberate the ultimate crystals. The models which were developed using this breakage matrix are in good agreement with the experimental results of the pilot tests. The industrial breakage functions were estimated from pilot breakage functions, using scale up prediction procedures and plant tests. The agreement between predicted and actual plant performance is excel1ent.A 20 % increase in capacity was predicted to be available by improving the grinding circuit classifier performances.

Jan 1, 1992

By Mark R. Stanton

Geochemical and mineralogical analyses of 46 samples from six drill cores in the Mayday mine pile near Silverton, Colorado, demonstrate wide variability in trace metal contents with spatial location. This variability results from the original geochemical composition of mined rocks, mixing of ore and non- ore rocks during emplacement of the pile, and weathering since rocks were placed in the pile. Weathering reactions are controlled by factors such as pile thickness (depth), water availability, microbial activity, and mineral dissolution and formation kinetics. These factors result in variable redistributions of trace metals from primary (ore) to secondary (weathering products) minerals within each core.

Jan 1, 2000

By T. Brasier, K. Oakes, S. Crabtree, B. Lusk

Destructive wave interference has been studied in theory for many years. In application however, limited information can be found. Recently, circumstances have enabled a multidisciplinary team to utilize electronic detonators and seismograph analysis to create destructive wave interference in an underground production blasting application. Springfield Underground, located in Springfield, MO, in conjunction with Orica, ETI, White Industrial Seismology, and the University of Missouri – Rolla has shown the ability to use destructive wave interference in underground blasting to reduce ground vibrations directly above. In order to develop additional reserves a reduction in vibration levels was necessary for tunneling under the Springfield Municipal Water Supply. The paper discusses the process by which the reduction in vibration was achieved in practice, as well as a technical explanation of the effects of destructive wave interference and sacrificial holes.

Jan 1, 2006

By G. T. Adel

The growing interest in column flotation has created a need for a fundamental scale-up procedure which is capable of meeting the necessary design and control criteria for industrial columns. Unfortunately, most of the avail able scale-up procedures deal with column diameter only and not overall column volume. Current work focuses on the effect of bubble size distribution and air hold-up on the scale- up of column volume. A series of pressure transducers has been used to measure air hold-up along the length of a bench-scale column. These measurements have been used to validate a mathematical model of the air phase. In addition to scale-up, the model appears to have the potential for use in control of air hold-up and bubble size.

Jan 1, 1990

By R. D. Kelsey

The theory, definition and practical application of cutoff grades have evolved over a long period. This evolution is reflected in the continuing flow of papers on this and other related matters though the rate has varied as new ideas and theories have become understood and applied in practice. Papers by Lane(l) in 1964 and Taylor(-2)- in 1972 provided landmarks in the understanding and general communication of cutoff grade theory and its application. The reasons for the continuing interest in cutoff grades are obvious. Too high a cutoff can reduce the mineral recovered and possibly the life of a deposit. Too low a cutoff would reduce the average grade (and hence profit) below acceptable levels. This paper provides a brief overview of existing cutoff grade theory and some particular aspects of its application.

Jan 1, 1979

By Val Ness, Leonard Harris

Mentoring is defined as close counseling by an experienced and objective advisor within the industry. It is one aspect of attracting the best candidates into the minerals industry, holding their interest, and encouraging stable career growth. By encouraging proper mentoring practices, we foster strong careers, we transmit important wisdom to the next generation, we fortify the industry with better talent, and we encourage the best possible advocates for the minerals industry. This paper illustrates the consequences of poor mentoring, offers an example of positive mentoring practice at the college or university level, reviews some guidelines for stable and fruitful mentoring, and proposes a plan to spread appropriate mentoring practices. Authors' note: The use of masculine pronouns is for convenience and simplicity only. Our best engineers and managers come from both genders, and the authors intend no slight to either one.

Jan 1, 2001

By J. C. Ransdell

A conventional paddle-type mixer and a gravity-flow mixing device were evaluated for conditioning of fine phosphate feed (- 35 + 150 mesh) with fatty acid and fuel oil, and for acid scrubbing prior to cationic flotation. Gravity-flow mixing re- quired less residence time but slightly higher reagent concentrations to achieve recovery levels similar to conventional conditioning. Grade was less sensitive to reagent concentration using the gravity-flow mixer. For acid scrubbing, the gravity-flow mixer proved equally effective. In this paper, the effect of time, pulp density, reagent concentration, and emulsification on conditioning and acid scrubbing efficiency of the two devices is discussed.

Jan 1, 1987

By M. A. Cristovici

The use of surfactants as wetting agents to suppress sulfide ore dust has been investigated. Numerous surfactants were examined to determine their characteristics and to investigate their ability to improve the wetting of the sulfide ore dust. However, the surfactants selected as suitable dust suppressors proved to have a negative effect on the flotation of ore contaminated with such reagents. A method was developed to eliminate the detrimental influence of dust-suppressing surfactants. It consisted of surfactant adsorption on activated carbon and separation of loaded carbon prior to flotation. The technique is simple and requires minimal changes in the plant flowsheet.

Jan 1, 1992

By N. Rajmohan, K. T. Jacob

Presented is a thermodynamic feasibility analysis of extracting base metal chlorides from low-grade, multi-metallic oxide ores using CaC[1]2 as a chlorinating agent in the presence of SO2 and O2. The oxides react to form corresponding chlorides, while CaC[1]2 is converted to CaSO4. The Ellingham diagram is used for comparing the standard Gibbs' free energy change for the sulfation-chlorination reaction of a large number of oxides. Except for alumina, silica and chromia, most of the other metal oxides will be converted to their respective chlorides. The volatile chlorides can be condensed, and the chlorides present in the condensed state can be leached. A process is proposed that uses a nontoxic chlorinating agent and gives an efficient separation of the metallic values from the gangue.

Jan 1, 1993

By J. W. Hawley, G. S. Austin, L. A. Brandvold, J. Renault

Soil next to a smelter abandoned about 100 years ago near Socorro, NM was found, by the US Environmental Protection Agency (EPA), to contain high Pb concentrations. Detailed characterization of the soil by the New Mexico Bureau of Mines and Mineral Resources (Bureau) shows that the highest Pb concentration is in the clay-size fraction, although this fraction accounts for only 1 to 3 wt % of the soil. The depth of contamination, determined in areas relatively undisturbed since the smelter was abandoned, is no more than 76 mm (3 in.). Because of the soil's alkalinity, the Pb mobility is dominated by the movement of Pb-bearing particles, as opposed to chemical transport in solution.

Jan 1, 1994