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By Thomas J. Feeley

The US Department of Energy (DOE) is supporting the engineering development of three advanced physical coal cleaning technologies: selective agglomeration, advanced flotation and advanced cycloning. Each is capable of significantly reducing the pyritic-sulfur content of US coals. The objective is to provide the coal and electric-utility industries with a cost-effective option for addressing the SO, emission reductions required by the 1990 Clean Air Act Amendments (CAA). A secondary objective is to evaluate the potential of advanced coal cleaning for removing trace elements that are precursors to the formation of hazardous air pollutants (HAS). The proposed National Energy Strategy (NEE) and the 1990 CAA lay a foundation for a more efficient and environmentally sustainable energy future (1991). The need to use energy resources in an environmentally sound manner presents critical challenges and opportunities for coal preparation during the next decade, particularly regarding the control of SOS and HAY emissions. The principal challenge is the development of cost-effective coal preparation approaches for sulfur and HAY precursor removal.

Jan 1, 1993

By Juan L. Yarmuch, Gonzalo Sepulveda

Medium- and short-term mine planning holds immense significance in optimizing production and resource utilization. It serves as a vital link between the long-term strategic plans and the day-to-day operational activities of a mine. In this context, a mathematical formulation is proposed to incorporate mining width constraints into the production scheduling process, aiming to maximize the net present value (NPV) of the schedule while ensuring enough room for the operation of mining equipment.

Jul 1, 2024

By Keivan PakIman, Maziar Pasdarpour

Transportation tunnels are highly sensitive to ground movements and are required to be stable and secure for safe operation. In urban areas, the interaction between tunnels and adjacent piles, which are widely used to support buildings and other structures, requires careful consideration. The seismic response of tunnels may vary depending on the lateral stiffness and strength of the tunnel walls, while the axial loading and seismic impact of adjacent piles may cause soil displacement and stress changes that can damage the tunnel lining. As a result, tunnel owners often impose strict limits on the design of new piles lying close to existing tunnels including maximum allowable tunnel deformation, stress change limits, and minimum tunnel to pile separation distances. This paper describes a numerical analysis of the inuence of the axial loading and seismic impact of bored pile foundations on subway tunnels, undertaen using the nite element software laxis D. ased on the results of the numerical analysis, the paper suggests a more realistic and less conservative approach for designing piles in close proximity to transportation tunnels. INTRODUCTION The interaction between tunnels and adjacent piles can cause stress changes and displacements in the soil and structures which may adversely impact structural performance and tunnel safety. It is therefore important to take account of relative load transfer and piling conguration when designing new piles in

Jun 23, 2024

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 Yutaka Mochida

OUTLINE Beginning in 1946, a careful geological survey was made of the Tsugaru Straits. In 1964, excavation of the exploratory tunnels were started to observe the characteristics of faults and rock formation directly, and to study construction methods of excavation and sealing water inflow. In March 1971, the investigation stages were over, and in April 1971, the construction project was authorized from the government. The geological features in the straits may be divided into three broad classes. One third consists of andesite on Honshu side. The other two thirds consists of tuff. The middle of the straits consists of tuff, so-called Kuromatsunai-layers. On Hokkaido side, it consists of tuff, called as Kunnui-layers. There are nine noteworthy faults on the route. Prior to the excavation of the main tunnel, the horizontal pilot tunnels and service tunnels are made. Exploratory borings are taken to confirm the geological conditions and the presence of gushing water. Groutings for sealing water inflow are carried out when necessary. In geologically bad conditioned sections such as disintegrated or fractured zones, special methods are applied. In geologically good zones, the tunnels are bored through using the same methods as for a mountain tunnel driving. The pilot tunnel being constructed at the sea bottom is under direct control of the Japan Railway Construction Public Corporation. The service tunnel and the main tunnel are being excavated by contractors.

Jan 1, 1981

By M. J. McPherson, P. Mousset-Jones, G. Danko

Ventilation and refrigeration fortune climate modification contributes significantly to the operating costs of a deep hot mine. Mine climate simulation programs can he used to minimize the impact of these costs. There are several computer codes available to assist in this work. Whichever simulation program is used, it is the mine ventilation engineer who must supply the input data. This paper raises and answers the following question, namely, what accuracy is required of the basic input parameters, in order for a certain precision to he obtained in the predicted air temperatures? In the first part of the paper a new approach is described to estimate the dry and wet bulb temperature of the airflow, either in a dry or wet roadway. The calculation procedure allows an arbitrary temperature change with time, using Duhamel&apos;s superposition solution. Matrix-vector representation is applied to simplify the computational structure. In the second part of the paper the sensitivities of the dry and wet bulb air temperatures are analyzed, to the changes of the rock thernrophysical properties, the heat transfer coefficient, and the wetness factor.

Jan 1, 1987

By Allan E. Hall, Stephen G. Hardcastle, Lucien D. Nel, Jean-Paul Saindon

A description is given of the investigation conducted at Sherritt Gordon&apos;s Ruttan Operation in Manitoba during 1986. Gas and dust concentrations were measured in the exhaust air of the major working sections to assess the potential for recirculating exhaust air into the intake air in winter to reduce heating costs. The results indicate that there is excellent potential to significantly reduce winter heating costs by controlled recirculation of exhaust air. Gas and dust concentrations vary significantly during the working shifts but have consistent trends from shift to shift and day to day. The variations in gas concentrations have similar trends but no single gas could be reliably used to predict the variation of the other gas or the dust concentrations. Dilution and the other effects which reduce pollutant levels as the exhaust air returns to surface indicate that recirculation should take place as close to surface as possible, subject to the economic constraints of the airway construction required and the extra fan energy required for the longer recirculation path. Recommendations are made for the choice and positioning of air and dust monitoring sensors and the logic of a control system. Economic analysis of the results indicates that controlled recirculation is viable at an existing mine with a pay back period of approximately two years. Incorporation of a system into a new mine at the planning stage would significantly shorten the pay back period.

Jan 1, 1987

By T. Ertekin, R. V. Ramani, W. Sung

The emission of methane in the coal mine working faces has two immediate impacts with regard to coal mine planning. Firstly, at the planning stage, the coal mine ventilation system must be designed such that airflows in the faces keep the concentrations of the gas in faces areas to below one percent. If the concentrations were greater than one percent, the production machine has to be shut down resulting in a loss of productive time. In an extreme case, concentration can reach explosibility limits which may lead to ignitions and explosions. Secondly, in excessively gassy coal seams, several alternatives can be applied to the mine layout configuration, and the mining method to be predicted for the extraction of coal, so as to insure a productive and safe operation. In this study a two-phase, two-dimensional finite-difference model was used to predict the methane emission rates into active mine working area under several methane drainage schemes. The numerical model utilizes a recently developed multi-mechanistic flow theory which describes the flow of methane in an heterogeneous and anisotropic coal seam. Transport of methane in the micropore structure of the coal is described by the Fick&apos;s law of dif- fusion under the influence of existing concentration gradient, while flow in the more permeable butt and face cleats (macropore spaces) is formulated by Dar- cy&apos;s law under the influence of existing pressure gradient. The desorption of the methane is accounted with the aid of a quasi-steady kinetic sorption model. A series of simulation studies were conducted in a systematic manner by sifting through the parameters associated with the coal seam characteristics and the degasification strategies in order to understand those which most significantly affect the methane emission rates in the face areas during mining. Along these lines, the effects of coal seam properties such as thickness, porosity, permeability, sorption characteristics and scheduling of drainage process against the mining operation have been isolated to understand the role of each individual parameter on the methane emission rates.

Jan 1, 1987

By C. I. Everson

The Elkhorn mining district is located 35 kilometers southeast of Helena, Montana, on the southeast edge of the Boulder Batholith. Geologically the district consists of a folded sequence of Paleozoic limestones and shales which have been thermally metamorphosed and altered by monzonite to diorite intrusives related to the Cretaceous Boulder Batholith. For the most part, the skarns are associated with metasomatic: replacement of calc-silicate hornfels, diorite and marble by iron rich, dark green pyroxene, garnet, sulfides, the district contains excess of 30,000 Kg.

Jan 1, 1992

By Reinhard Gnilsen

Ground pillar control in soil and weak rock often represents a critical and sometimes a determining factor for mined underground civil structures. A concept is desirable that minimizes the restrictions possibly imposed by pillar control requirements on geometrical tunnel characteristics and on the mining operation itself. Conventional concepts are discussed and an alternative concept is introduced. This concept reduces pillar control requirements to ground control measures required with "regular" tunnels. The conventional model of pillar mechanics with potential yielding of a ground body in more than one direction, is then avoided. Due to the complexity of pillar mechanics, the level of engineered design furnished to the contractor is crucial to optimizing ground pillar control. Conventional versus alternative contractual arrangements for pillar control are described and their important role is illustrated. The concept introduced relates to principles inherent to the New Austrian Tunneling Method (NATM). However, tunnel projects using other mining concepts can employ alternative ground pillar control principles as well, if certain criteria are observed. Case histories in the United States and abroad are presented and the impacts from different concepts of ground pillar control are illustrated. The paper concludes by analyzing concept characteristics that can infer monetary impacts on both the owner and the contractor.

Jan 1, 1987

By B. K. Parekh, R. H. Mehta

Handling of fine coal is an importance issue for coal as well as the utility industry. Reconstitution in form of pellet or briquet would be desirable if it could be done economically. This paper evaluates the effectiveness of three binders e.g., asphalt- emulsion, corn starch and Brewex, in forming pellets of ultra-fine clean coal. It was found that asphalt emulsion and corn starch were not effective binders for ultra-fine clean coal, however, Brewex provided excellent quality of pellets, which exceeded all the minimum quasi requirements of coal pellets. INTRODUCTION Advanced coal preparation techniques (physical or chemical) are designed to process ultra-fine (minus 200 mesh or 74 pm) coal. The average particle size of the clean coal product is about 25 pm. Currently available dewatering techniques are effective in providing a 25 to 30 percent moisture product of this size coal slurry (Parekh et al. 1989). Handling and utilization of this dewatered ultra-fine size coal is difficult. Reconstitution, which includes pelletization, briquetting, extrusion, etc., of the dewatered coal product provides an ideal answer to handling and transportation problems. However, reconstitution of fines in the coal industry has not been successful due to various reasons. The most important criterion for its unsuccessful application in the coal industry is the cost of the binder (Capes et al. 1965). Various methods of reconstitution, such as briquetting, disk pelletization, extrusion pelletization and roller and die-pelletization, have been tested for fine coal agglomeration (Conkle et al., 1991) (Richards, 1990). Conkle et al., (1992) have provided a detail analysis of each technique in terms of moisture and operating cost requirements. According to Conkle, briquetting requires a product containing very low moisture, whereas pelletization can be done with coal containing up to 30 percent moisture. Currently available dewatering technique provides about 25 percent moisture product, thus, pelletization appears to be an ideal route for reconstitution. In this paper, results are presented on the comparison of three different binders i.e., asphalt-emulsion, corn starch and Brewers condensed solids (BCS or Brewex), for fine coal pelletization.

Jan 1, 1995

By Malcolm J. McPherson

This paper describes the algorithm used in a BASIC program for an IBMXT microcomputer, to simulate the underground mine climate. The program called CLIMSIM has been developed and refined over several years as a result of considerable use at operating mines. The program has been designed to be easy to use and be understood by the practicing mine ventilation engineer. It provides predictions of the work place climate, so that the optimum ventilation/cooling system can be designed to obtain a certain air cooling power or effective temperature at the work place. An example is given of the application of the program to a mechanized cut and fill stope at the Homestake gold mine in South Dakota.

Jan 1, 1986

By V. K. Paruchuri, J. D. Miller, J. Nalaskowski

An understanding of forces responsible for the stability of dispersions of colloidal particles when interacting with each other in aqueous solutions is of great interest academically and industrially. When water-soluble polymers are adsorbed onto colloidal particles, various effects on the stability of their suspensions can be expected ranging from steric stabilization to bridging flocculation. The possibility of detailed characterization of such systems using direct measurements of interaction forces between particles can help in further improvement of existing technologies of solid-liquid separation. An atomic force microscope (AFM) colloidal probe was used to measure the interaction forces between a silica sphere and a silica substrate in the presence of water-soluble polymers. Poly(ethlene oxide) (PEO) with three different molecular weights (7,000, 43,000, and 63,000), each with a very narrow molecular weight distribution, were used in this study. The interaction forces measured with the AFM over an extended time scale are discussed in terms of the adsorption kinetics measured through in-situ FTIR/IRS measurements.

Jan 1, 2003

By Murali M. Gadde, Syd S. Peng, C. T. Holland

Cutter roof failure is one of the most common ground control problems affecting the safety and economy of an underground coal mine operation. Several attempts were made in the past to understand the processes responsible for cutter development and to devise mitigating measures. Yet, many cutter failures still happen and their advance prediction remains as elusive as before. One of the reasons for the impasse in predicting cutters lies in the limitations of the current numerical modeling technologies. The development and propagation of cutters is a progressive phenomenon and continuum models can only approximate this process. Since the discontinuum modeling is severely restricted by the lack of reliable input data, alternatives must be sought to better understand cutter failures using the continuum models. This paper proposes one approach using strain-softening material model to simulate the cutter initiation and propagation process. An attempt has also been made to provide some insights into the reasons for the change in cutter location at different parts of a development layout.

Jan 1, 2005

By Richard H. Adams

INTRODUCTION With the discovery and depletion over the years of near surface ore bodies, exploration targets are tending to be at greater depth or overlain by various types of overburden which in some cases extends to considerable depth or is heavily water bearing. Access to these types of deposits for exploration and development often requires vertical shafts. This paper discusses the concept of small shaft engineering and construction, primarily for underground exploration but also for use as a low tonnage production facility or for mine ventilation. The option of a small shaft may be attractive in a number of cases, some of which are: The underground exploration of a deposit at depth where minimal expenditure is desirable until the potential of the deposit has been determined. The exploration shaft in many cases later serves as a ventilation way and second means of egress. Production of ore in a small tonnage/high-grade operation where decline access is impractical. For ventilation where other types of openings are impractical or would delay start-up of mine operations.

Jan 1, 1987

By Y. Ooishi, Y. Matsumoto, T. Arai, H. Ohta

The multi-circular face shield (MFS) is a new type of tunnelling machine for construction of the special cross section and has been put to practical use in 1988. The MF shield has two circular faces partially overlapped in a single shield machine and can construct the cross section shaped like glasses for the double track railway. And it is possible to equip two or more cicular faces horizontally or vertically, if necessary. During the development of the MF shield the experiments have been carried out for the purpose of estimating the excavatability and the face stability of the MF shield. As a result it was confirmed that the both types of MF shield (one with double faces aligned horizontally and the other with double faces aligned vertically) has higher performance in the face stability and lower value in the cutter torque and the total thrust than the conventional circular shield.

Jan 1, 1991

By D. Krzyszton, P. Czaja

Mining explosions in rocks originate stress waves of great intensity, which crush the surrounding rocks and are then propagated as a seismic wave. Seismic waves are the cause of dynamic loading of pillars and their subsequent destruction. In calculating safe dimensions for inter-room pillars, not only the stresses conditioned by overburden pressures should be taken into consideration, but also the dynamic stresses caused by explosion. This is of particular importance for pillars with great specific acoustic impedance which have been destroyed mainly by the reflected seismic wave. It is possible to take dynamic loading into consideration in the calculation of pillars when the parameters of the propagation wave, the dynamic elastic constants of rocks, the strength properties of rocks, the strength properties of rocks subjected to dynamic loads and the parameters of the blasting charge are known. An example of the calculation for the safe width of an inter-room pillar subjected to the seismic effect of an explosion is given and the possibilities of reducing the dynamic loading of pillars are discussed.

Jan 1, 1982

By Phillip J. Maddex

During the last 10 years there have been many new developments in transport and handling equipment. Important technical and economic developments that can be used to reduce costs are; new terminal and materials handling concepts large river tows - 40,000 tons and 9000 hp towboats slurry loading and unloading of ocean vessels long distance pipelining of solids development of the shuttle train (unit train) large ocean barges ? 25,000+ tons ? pushed & towed 150,000 ton self-unloading super tankers - 300,000+ tons container shipping Some of these developments have been discussed at SME meetings in papers describing the transportation of minerals from new mines. But, only a few papers described improved transportation from older operations. Since transportation is a major part of the delivered cost for minerals, the economic benefits to be gained by putting new transportation developments to work are very substantial. Frequently good transportation planning and management makes the difference between a marginal ore body and a very profitable one.

Jan 1, 1972

By R. J. Smith

Hornestake&apos;s Mclaughlin Mine is the first commercial application of pressure oxidation pretreatment of gold prior to cyanidation. Inherent to the autoclave process are several liquid/solid separations. Flocculant consumption represents a significant portion of the consumable reagent costs at McLaughlan. This paper focuses on the efforts of the Operating, Metallurgy and Engineering groups to improve thickener operation and minimize flocculant consumption. An operating philosophy incorporating feed solids control, increasing flocculant dilution water and minimizing flocculant solution shear has resulted in a reduction in 1986 flocculant costs of $0.054/t ($0.06 st) versus 1985 costs. Additional changes are projected to result in a further cost reduction of $0.20/t ($0.22/.st) in 1987.

Jan 1, 1988

By M. C. Manderson

While the United States has been the world&apos;s largest volume producer and marketer of phosphatic fertilizers for many years, it has recently suffered heavy losses for a variety of reasons. While improved economic performance is expected, it is still at least a year or two away. But when recovery does manifest itself, it will likely yield only mediocre profits, due in part to the fact that about 50 percent of output is export-dependent. Therefore, there appears to be limited likelihood that profits will be adequate to justify the further outlay of large amounts of capital for expansion.

Jan 1, 1986