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By B. Samoski

In late 1994, EPA and OSM acknowledged that efforts by any one agency or by the many different agencies to remedy the water quality impacts of decades of contamination from abandoned coal mine lands in Appalachia would not be successful if their disjointed efforts were not unified and if the local watershed organizations were not included. The result of the collaboration between EPA and OSM was the creation of a statement of mutual intent which was a pledge by government agencies, watershed organizations, and the industry to restore watersheds degraded by acid mine drainage from abandoned coal. The presenter will describe the evolution of this pledge from a paper promise to on-the-ground remediation projects.

Jan 1, 2002

By Graeme Lyall, Oy Leuangthong, Clayton V. Deutsch

There are many variables to consider in the evaluation of nickel laterite deposits including the concentrations of nickel, iron, silica, and magnesia. These variables show complex relationships with each other such as mineralogical constraints, non-linear correlation, and heteroscedasticity. The complex multivariate relationship between the variables cannot be reproduced by conventional Gaussian or indicator geostatistical techniques. We introduce the stepwise conditional transformation method as a pre- and post-processing multivariate transform for the stochastic simulation of a nickel laterite deposit. Transformed data are multiGaussian and independent at h = 0; thus, cosimulation can be avoided after verification that variables are independent at all lag distances. Back transformation restores the features of the input multivariate distribution to the simulated realizations. The complex multivariate correlations are reproduced and sensitivity issues are addressed.

Jan 1, 2002

By N. Abdel-Khalek, A. Youssef

The tailings from beneficiation of Florida phosphate ore contain considerable phosphate values. These tailings are currently discharged into large disposal areas. More than three million tons of P2O5 are discarded with the phosphatic slimes (clays) in Florida each year. These phosphatic clays not only create one of the most difficult disposal problems in the mining industry, but also represent a tremendous loss of P2O5. As the quality and quantity of Florida’s phosphate reserves diminish, recovery of phosphate values from these wastes becomes more vital. This will also significantly lengthen the life of these important phosphate resources. Thus, it is the goal of this study is to recover more than 80% of the phosphate values in phosphatic clays. A systematic study to characterize samples taken from inactive disposal area has been conducted. The data suggest that natural segregation takes place in the settling pond. In other words, coarser particles settle closer to the feeding point of the pond. Flotation tests were conducted using the +325 mesh fraction of samples obtained from sites close to the feeding point (sample# A) and further from that point (sample# B) and (sample# C) which is even further away from the feeding point. The results show the following: Sample# A gives the highest grade and recovery, followed by that of # B and then of # C. There is a great potential to upgrade sample# A where concentrates of high grade (68.9-70.1 % BPL or 31.5- 32.1% P2O5) and recovery (~86.6-95.4 %) can be obtained under the investigated operating conditions (1.0 – 2.0 kg/ton sodium silicate and 1.5—3.0 kg/ton collector mixture of fatty acid and fuel oil). The mineralogical and chemical analysis of all samples is presented in this paper for comparison. Only in this paper, the flotation data of (site # A) are discussed below.

Jan 1, 2002

By R. J. Snow, S. N. Bhattacharya, D. D. Patil

Electrokinetics involves the movement of charged particles or water molecules in an applied dc field. Applications in particle fluid systems include the dewatering of soils, the densification of mill tailings and the treatment of coal wastes. In this paper, a novel application of this technique is discussed, wherein an electric field is applied to a coal-water slurry flowing through a pipe, resulting in lower pressure losses in the system. A unique experimental setup was designed and built to study the effect of an electric field (dc) on the wall shear stress for the flow of coal-water slurry through the pipe. The effect of solids concentration, current strength and pH on drag reduction across the system was quantified.

Jan 1, 2002

By S. C. Lamey, P. A. Hesbach

This study evaluated the use of regionally produced coal combustion products to neutralize and remove metals from acid mine drainage (AMD). Synthetic AMD mixtures were treated with a number of fly ashes and fluidized bed combustion (FBC) ashes. All of the ashes reduced the volume of the sludge produced and gave a faster settling rate than the sludge produced by treatment with lime. Faster settling allows greater throughput rates. In addition, the FBC ashes, which generally contain alkaline components used for sulfur capture, completely neutralized the acidity and, if desired, raised the pH above 10. The fly ashes, on the other hand, reduced the final volume of sludge but required additional neutralizing agents to attain a pH >5. The pH of the AMD can be taken to above 10 to insure complete removal of manganese, or it can be taken to a more neutral pH of 7 or 8 to allow for the safe introduction of the aqueous phase into ponds or streams. The process combines two industrial waste products to reduce the disposal volume of one of the waste products and to produce an environmentally safe aqueous discharge.

Jan 1, 2002

By V. Bush, T. G. Killingsworth, E. P. Ruffel

Effective and sustained corporate energy management programs are becoming a necessity for energy users as electricity deregulation laws are enacted on a state-by-state basis across the country and environmental regulations pertaining to emissions become more prevalent. The “Total Energy Asset Management” (TEAM) approach has been developed to assist energy end users with the development and implementation of corporate energy management programs designed to reduce energy risks and increase energy cost savings. This paper highlights the ways in which this approach can be applied to the mining industry while minimizing initial program implementation costs and increasing potential program benefits. Nearly the entire mining industry has become very focused on identifying opportunities to reduce costs per unit of yield. The industry as a whole has increasingly faced pricing pressures in large part due to the effects of global competition. The result of international marketplace participation and the emergence of higher efficiency recovery techniques have resulted in flat or even decreased prices for mining products. Thus, opportunities to reduce costs are actually opportunities to gain a competitive edge over similar mining operations. Due to the energy-intensive nature of many mining operations, the costs associated with energy are often a substantial percentage of operating costs. Therefore, it becomes very important to develop the corporate mentality that energy is an asset whose use should be optimized globally. In addition to the cost benefits of the TEAM approach, other benefits may occur such as reductions in facility greenhouse gas emissions.

Jan 1, 2002

A thermomechanistic model was developed for the thermal decomposition of the enargite contained in a copper concentrate at 650° to 750°C in a fluidized bed with an inert atmosphere. At the particle level, the model permits one to predict the thermal profile inside the reacting enargite particles, as well as their thermal cycle. At the macroscopic level, a population-based model coupled to the bubbling-bed fluidized bed model allows one to predict the fractional conversion (dearsenification) of an enargite-bearing copper concentrate.

Jan 1, 2002

By K. Biswas, S. J. Jung

Health and safety of workers in mineral industry in the U.S. is still a vey important issue as Mining along with Agriculture, Forestry and Fishing and Construction industries have contributed most of the fatal occupational injuries ill between 1980 - 1995 (Worker Health Chartbook, 2000). Health and safety issues, especially for the mining or related excavation industries, arise either from exposures of the human workers to the contaminants liberated or generated by mining operations that have adverse effects on human health (for example coal dust etc.) or from the exposures of the human workers to hazardous working environment that constitutes mining operations (for example blasting etc.). One of the biggest challenges is to understand the combinatorial effect of numerous work-condition (e.g. exposure to dust) and human-factor (e.g. smoking habit) variables on a health or safety-condition variable (e.g. incidence rate of a disease). This paper uses an example dataset on Coal miners' cough problem to illustrate the applicability of Generalized Linear Modeling (GLM) in understanding the relation between cough and other response variables, such as, age, height, smoking habits, time of underground exposure etc.

Jan 1, 2002

By G. Petrakis

The selection of suitable species of plants for the rehabilitation of mining disturbed lands is one of the most crucial decisions to be made concerning the success of planting revegetation. Native plant species are best suited for use in the work of reintroducing vegetation in rehabilitated areas. By using such species an increase in the success rate of rehabilitation is attained not only as regards yield due to their better growth ability (they are adapted to local climatic conditions), but also because of a better adjustment to and better visual harmonization with the surrounding unspoiled areas.

Jan 1, 2002

By P. Riveros, A. Pratt, G. Deschênes

The effect of pyrite, pyrrhotite, chalcopyrite, realgar and arsenopyrite on gold dissolution in cyanide media was investigated. The cyanidation of synthetic gold ores, in the presence of various concentrations of sulphides, was studied under constant experimental conditions. A mineralogical analysis of the minerals was performed. The leaching kinetics were determined. The negative effect of sulphides on the gold dissolution rate varies with the sulphide mineral, and decreases according to the following order: realgar > pyrrhotite > chalcopyrite > pyrite > arsenopyrite. The chemical characterization of gold and sulphide minerals surfaces using X-ray photoelectron spectroscopy (XPS) was undertaken to identify the mechanisms involved. XPS analysis showed that a passivation layer of sulphides, arsenic or iron compounds may form on the gold surface as a result of the dissolution of the sulphide minerals.

Jan 1, 2002

By Kadri Dagdelen, M. Waqar Asad

Cement production involves the processing of raw materials that contain - Si02, A1203, Fe203, CaO, MgO, LOI (loss of ignition), S03, K20, Na2O, Ti02, P2055 and Cl- to produce the synthetic mineral mixture called "clinker". The use of other additives - sandstone, flyash, iron ore, and clay - is also mandatory in order to achieve the optimum blending requirements of cement. However, the use of these additives needs to be minimized due to their significantly higher costs ($/Ton). This paper presents a mixed integer programming (MIP)-based optimum quarry scheduling algorithm, which is used to generate quarry plans, satisfying geometric and production capacity constraints while providing minimum cost/optimum blend of raw materials mix to a cement plant. The benefits of this new methodology are demonstrated on a case study.

Jan 1, 2002

By J. Kim, H. Cho

The objective of the experiment was to investigate the efficiency of hindered-settling column in recovering carbon from anthracite. Two types of Korean anthracites were prepared for feed materials. Each sample was crushed and classified by size, and washability analyses were performed. Separation efficiency was evaluated under various operating conditions using a laboratory scale hindered settling column. Results showed that the carbon recovery was higher for the smaller sizes, but the purity of the product was better for the larger sizes. In, overall, 2-0.21mm particles of 40-45 % ash could be processed into about 20 % ash products.

Jan 1, 2002

By Steve Richards

Incorporating a bottleneck analysis into the mine plan can provide a significantly better basis to make economic decisions regarding materials handling systems. Every materials handling system has a bottleneck. The bottleneck at a mine may change over time as a function of location or time. Since a mining reserve is a finite amount and can usually only be mined once, knowing how the bottleneck changes can provide a critical backdrop to capital investment decisions, especially those affecting the materials handling system. A bottleneck analysis can better quantify the expected 'return and also indicate the optimal time to complete tile project.

Jan 1, 2002

Geopolymerization is a process by which Al-Si minerals undergo dissolution and polymerization in an alkaline solution to form a monolithic material with a high mechanical strength (Davidovits, 1991; 1994). In this study, Na-feldspar (albite) and K-feldspar (microcline) have been selected to investigate their abilities to undergo geopolymerization. The interaction between alkali metals present in the alkali-feldspars and alkali metal cations contained in alkaline solution during geopolymerization has also been studied. It has been found that both albite and microcline can be applied in geopolymerization to produce geopolymers with a high compressive strength. Although the dissolution of M-feldspar (where M = Na and/or K) in concentrated MOH solution is inhibited when the alkali metal cations of the alkaline solution differ from the alkali metals structured in M-feldspar, the resulting geopolymers are found to demonstrate a higher compressive strength. Moreover, a proper molar ratio of Si/Al in the geopolymeric gel phase and a higher average hardness of the undissolved particles remaining in the geopolymers are found to greatly increase the ultimate compressive strength of the geopolymers.

Jan 1, 2002

By E. S. Peterson, M. K. Harrup, K. A. Dolbeare, J. E. Wey

Efficient methods for removal of copper from heap leach solutions without mobile organic phases are a current mining industry need. To satisfy this need a selective, high-capacity, durable solid material is required. The INEEL has developed a set of materials based upon current solvent extraction chelates that provide selective copper concentration in the presence of high concentrations of iron. In contrast to conventional solvent extractions, our strategy anchors the chelators to a non-polymeric solid substrate through the use of a custom designed linker molecule. The fundamental synthetic routes to these materials have already been established and attachment to the solid surfaces achieved in an efficient manner. Our continuing research is focused on the optimization of the synthetic pathways to these solid materials and the evaluation of their copper capturing capabilities.

Jan 1, 2002

By K. S. E. Forssberg, S. Subramanian, Hanumantha K. Rao

The dispersion characteristics of apatite and magnetite minerals have been assessed based on zeta-potential measurements, using various inorganic and organic reagents, namely sodium silicate, sodium tripolyphosphate, sodium hexametaphosphate and lignin sulphonate. These results highlight that apatite is dispersed to a greater extent vis-à-vis magnetite. Further, the dispersion efficiency of the phosphate reagents is better than that of sodium silicate or lignin sulphonate, for both apatite and magnetite. Batch flotation tests on a high phosphate magnetite ore from Kiruna indicate that higher apatite recovery with minimum phosphorous loss to the magnetite fraction can be achieved using sodium silicate as a dispersant. Although comparable dephosphorization can be attained with lignin sulphonate dispersant, the recovery of magnetite in the non-float fraction is lower, possibly due to the adverse synergistic effect of this organic reagent with the Atrac collector, resulting in the flotation of magnetite. The high intensity conditioning of pulp for up to 30 min resulted in better apatite flotation with <0.015% phosphorous in the magnetite product.

Jan 1, 2002

By M. H. Al-Dabbagh

In this paper, the authors outline the deficiencies of PERT/CPM as a method for scheduling complex projects such as mine development. In particular, PERT/CPM networks cannot accommodate logical nodes (events) or stochastic branches (activities). The Graphical Evaluation and Review Technique (GERT), developed by Pritsker and. co-workers, is introduced as an alternative to PERT/CPM that overcomes many of the deficiencies of the latter and enables a more realistic analysis of complex projects that are subject to significant uncertainties. A brief overview of GERT network structures and network analysis is given and a PC implementation of the method is described. The technique is illustrated by application to the development of an open-pit gold mine in Saudi Arabia.

Jan 1, 2002

By Paul Grisley

Air-supported belt conveyors-conveying systems that replace troughing idlers with a film of air-were a revolutionary concept when introduced in the 1970s. But high installation and operating costs limited their application. Now, system refinements have led to successful applications, even under the challenging conditions of mines and process plants. In this presentation the author will discuss the latest developments in the engineering of these systems, including the ability to retrofit existing transfer points with modular air conveyor components. Air conveyor applications and limitations in mineral-handling operations will also be examined.

Jan 1, 2002

By H. B. Oblad

The WEMCO® SmartCell™ flotation machine is a continuously-stirred tank reactor in which solids are suspended in water and are contacted with air. The reaction is particle flotation resulting in the separation of valuable material from gangue. The effects of several operating variables on the flows of water and air and on motor power were measured. A miniature magnetic flowmeter was installed in the draft tube that allowed measurement of the water flows into the rotor. This work has led to a better understanding of machine function which will lead to improved performance and better operation. General equations for optimization, design, and scale-up were inferred.

Jan 1, 2002

By K. N. Han, K. Peri, Y. Guan

The leaching behavior of gold in ammonical solutions with iodine as an oxidant was investigated using cyclic voltammogram and Tafel polarization. The majority of the experiments were carried out at 75°C, and the results were compared with consideraton given to the equilibrium of the iodine-ammonia system. The distribution of nine iodide-containing species at various pH values in the absence and presence of ammonia were considered at three different temperatures. It was found that, with the introduction of ammonia into the system, the concentration of iodide (I-), iodine (I2) and triiodide (I3-) is increased substantially, which in turn helps the rate of gold dissolution. The apparent activation energy was found to be about 46 kJ/mole, indicating a chemical-controlled mechanism.

Jan 1, 2002