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By S. C. Suboleski

Forecasts indicate that the acid rain bill currently before Congress is likely to cause an increase in demand of 30 to 40 million tons per year of compliance quality coal from Central Appalachia. This represents a doubling of this segment of the coal business. This paper will examine how this doubling can be met, what the likely implications for pricing are, the major uncertainties associated with these predictions, and the likely outcomes of the growth in compliance coal. Finally, some implications for fuel planners will be discussed.

Jan 1, 1993

By Colin J. Booth

Hydrogeological impacts of active longwall mining were studied at two sites in Illinois. At the site with the more transmissive sandstone aquifer, aquifer permeabilities increased an order of magnitude due to subsidence. Piezometric levels declined with subsidence due to increased porosity, and ahead of mining due to a transmitted drawdown. Levels recovered rapidly at first and fully over two years. At the site with the less transmissive aquifer, impacts were similar except that recovery has been limited. Local aquifer enhancement through increased yield can occur, but only where the aquifer is transmissive enough for recovery.

Jan 1, 1986

By I. C. Watson, J. W. Klokow, A. F. Knoetze, R. G. B. Pickering

In the late 1970s and early 1980s there were a number of attempts to use Tunnel Boring Machines in deep level gold mines. These attempts must be regarded as unsuccessful. Since then there have been comprehensive developments in tunnel boring equipment and tunnel support technology. This paper defines the problems experienced in those early trials, reviews the technology development, and concludes that tunnel boring in deep level goldmines can be justified in today’s environment.

Jan 1, 1999

Mining employment, gross output, local economic contributions and productivity are typical economic indicators. However, these economic indicators play a much bigger role in the overall capacity of the industry to be heard in decision-making on a national scale. Total mining employment in the USA has decreased significantly in the last 20 years. Gross output from most of the mining sectors has also declined, except in the case of construction aggregate. However, significant gains have been made in productivity. This paper explores these statistics and comments on their overall impact on academic institutions and political decision-making.

Jan 1, 2003

By Stanley A. Bunk, Desmond J. Bruyns

The purpose of roasting gold ores is to release for extraction, typically by cyanidation, the small particles of gold which are surrounded by refractory stone. The roasting simply opens up passages for the penetration of solution into the interior of the ore particles. This is accomplished by the removal by volatilization or formation of volatile oxides of certain constituents such as sulfur, arsenic or antimony. Temperature is an important parameter. High temperatures tend to form a dense iron particle rather than a "spongy" calcine. The dense iron particles result in lower gold recoveries. High temperature can cause melting of some components which also results in gold encapsulation. Roasting of refractory gold ore concentrates has been practiced for decades. Multiple hearth, rotary kiln and muffle reactors were first used for roasting. Fluid bed roasting provided a low capital cost, low maintenance technology with better process control and soon became the favored technology. The first fluid bed concentrate roasters were commissioned in the late 1940's. Early fluid beds were "bubbling" type. Environmental considerations did not significantly impact on the design. Feedstocks were highly exothermic and reaction rates were relatively rapid. Roasting today must compete with other technologies for treatment of refractory ores. Ore bodies which are not

Jan 1, 1993

By C. I. Huang

The mining industry is an easy target for criticism from an environmentally sensitive society. Recent researches discovered that human activities, including mining. cannot be blamed for all of the pollution observed on earth. Interdisciplinary research is providing diagnostic and remedial solutions to problems such as acid mine drainage and cyanide-polluted streams. Researchers have also found that mercury-bearing hot springs and volcanic eruptions are partly responsible for some pollution. Geochemists, mining geologists, engineers, and environmental scientists can pool their efforts to make the environment cleaner and safer. Remote sensing of the environment and the use of microbes may become much more popular in the near future in the mining-environment arena.

Jan 1, 1988

By R. W. Barbaro, R. V. Ramani, K. V. K. Prasad, P. T. Luckie

The limitation of sulfur dioxide in power plant In this study, the following quality parameters of the coal emissions dictates that sulfur in coal be reduced to the lowest possible level before combustion to not aggravate the emission control problem at the stack. For coal-fired power plants, the methods in practice to achieve low-sulfur coal include mining areas with relatively low sulfur, reducing sulfur in the mined coal through preparation techniques and blending high- and low-sulfur coals. A prerequisite to the successful implementation of any of these practices is the knowledge of the spatial distribution of sulfur and the capability to predict its value in mining blocks. In this paper, the results of a study conducted to evaluate the applicability of geostatistics for describing the short scale variability of sulfur in a coal seam are presented. Four sides of a block of coal to be mined by the longwall method were extensively sampled at closely spaced intervals. The details of the longwall sampling plan and analysis procedures are discussed. The results of the statistical and geostatistical analysis are presented. The implications of these for prediction of sulfur for control purposes are examined.

Jan 1, 1991

By F. E. Heuze, R. N. Nilson, R. J. Shaffer, R. P. Swif

As part of the Unconventional Gas Program at the Lawrence Livermore National Laboratory, we are developing a model that allows for time-dependent tracking of the fluid front and flow pressures during the quasi-static or dynamic fracturing of jointed rocks. Application of the model is directed towards both short fast fractures (as in tailored pulse loading) and long hydraulically induced fractures (massive hydraulic fracturing). The thrust of this research is to determine crack extension characteristics due to specific joint systems and fluid properties and to correlate pumping records with crack behavior in jointed systems.

Jan 1, 1986

By Paul L. Russell

Introduction As the US and world population increases, so does the problem of supplying expanding energy needs. Early requirements worldwide were mostly met by abundant forest vegetation. Man's large scale use of minerals-energy resources is a fairly recent development. It occurred only during the past 200 years. Coal was the first mineral fuel to be used extensively. It was not a large factor in US energy production until the beginning of the 19th century. Petroleum and natural gas use is about 125-years-old. Electricity generation by falling water is about a century old. Atomic energy is only about 30-years-old. Extensive use of it is still in the future. Solar energy is in its infancy. Other energy sources such as wind, peat, and geothermal energy are minor and primarily of local importance. There were three main features of the fuel supply picture during the past 125 years. By 1900 coal replaced wood as the principal energy source. Since 1900, oil and gas have captured many coal markets. And after the mid-1970s, there was a resurgence of coal usage. (Figs. 1 and 2). Wood Until the advent of mineral fuels for energy, the major global energy source was wood. But populations increased and became centered in towns and cities. The problem of a sufficient energy supply first developed as nearby, easily obtained wood was exhausted. This problem became more acute as industries such as shipbuilding, smelting, and pottery making, became more widespread. Results of wood use as an energy source and building material are starkly evident in areas of the world where civilization is oldest. Entire forests were consumed and have never been replaced. In the US, wood supplied 90% of all fuel requirements until about 1850; and more than 50% until after 1880. By 1900, wood still supplied 20% of all energy uses. In the mid-1970s, energy costs increased, due largely to the oil embargo. This increase resulted in an increased wood demand for domestic heating. While large quantities of wood were being used, its share of the total energy market was still less than 3%. By 1983, wood was becoming increasingly scarce and more costly near most large US cities. Wind Wind powered ocean vessels for many centuries. Sailing ships were still common in 1900. Windmills provided an early, cheap energy source and continue to be used today on farms. Design and development of windmills for electricity generation is being conducted. Interest in wind power is growing worldwide where availability of wind currents warrants the investment. Also, US regulation requires power companies to "buy back" electricity generated by windpower in excess of that used by the windmill owner. Coal By the 1600s, England was producing, 900 kt/a (1 million stpy) of coal for heating and other uses. The first coal-fired blast furnace for iron smelting was developed in 1621. Coke-making was developed in 1755, and Watt invented the steam engine in 1769. Illuminating gas made from coal was introduced in London in 1800. During this same 200-year period, France and Germany developed coal production, but on a smaller scale than England. US, bituminous coal was mined near Richmond, VA, as early as 1748. Major bituminous coal-producing states in the early period were Pennsylvania, Virginia, Ohio, Kentucky, Illinois, and Maryland. West Virginia replaced Virginia as a major producer, when that state was formed in 1863. As the US expanded west, new coal deposits were found and exploited. Indiana, Alabama, Tennessee, Iowa, Kansas, Missouri, Washington, Colorado, Wyoming, Arkansas, Oklahoma (Indian Territory), Montana, New Mexico, and Texas had significant coal mining operations by 1900. Today the eight major coal producing states are Kentucky, West Virginia, Pennsylvania, Illinois, Ohio, Virginia, Wyoming, and Montana. These states accounted for about 80% of all coal (lignite, bituminous, and anthracite) produced in the US during the past several years.

Jan 8, 1984

By James G. Sampson

The discarded phosphatic clays from mining operations have historically been stored behind earthen dams for long periods of time before any reclamation was accomplished. In efforts to expedite the dewatering and reclamation of the clay ponds, the phosphate industry explored alternatives to conventional clay disposal practices. One alternative, employed by CF Industries, Inc., combines the clay and the discarded sand prior to disposal behind earthen dams. The sand encourages the clays to 'give up' trapped water more readily resulting in enhanced consolidation behavior. This paper provides an overview of the sand-clay mix process including the reclamation of sand-clay disposal areas.

Jan 1, 1992

By H. Z. Kuyumcu

In order to ensure a sustainable development in the mineral industries it is very important to reduce the process water consumption in mineral processing. Based on a systems analytical approach this paper deals with the most important parameters of process water management during plant operation and indicates strategies for reducing the water consumption in mineral processing.

Jan 1, 2003

By S. Bozinis

In this paper, blast design considerations and implementation that lead to reduced vibrations will be presented. In addition, blast vibration data collected during hard and semi-hard rocks blasting in the proximity of an inhabited area will be analyzed and presented. In all cases maximum vibration levels are kept below the limits set by DIN 4150.

Jan 1, 2006

By Norbert Patzelt, Johann Knecht

INTRODUCTION Grinding mills have been used in the minerals processing industry for over 100 years. Their dimensions have grown continuously during this time. Besides increasing throughput rates of grinding plants due to the depletion of high grade ores, the lower specific in- vestment costs, as well as reduced operating and maintenance requirements are major reasons for this trend. When selecting new plant equipment one must consider that design principles which have proven their reliability on sizes of today's equipment do not automatically warrant a successful operation on the ever larger size of equipment. Modern calculation methods as for instance the Finite Element method already contribute considerably to the safe design of the huge equipment being built today and are a standard tool of the design engineers. More recently, modern computer programs are also being used in order to size the equipment to meet the process requirements. Today, two design principles are on the market - one which supports the weight of such a unit on trunnion bearings through cast conical endwalls and one which is supported through slipper pad bearings arranged at the circumference of the mill shell (Fig.1). The reason for the development of this alternative grinding mill design can be found in the past. During the sixties and seventies the growing sizes of ball mills with high LID ratios caused many mill failures due to cracked endwalls. The accuracy of the calculation methods as well as the quality standards for castings were not developed to a degree required for such kind of heavy equipment. One way to overcome these problems was the increase of the manufacturing quality standards as well as the introduction of the finite element method based on the analysis of the experience available. The biggest grinding mills being built today are large size SAG mills with cast conical endwalls and trunnion bearings (Fig.2). This is due to the fact that mill manufacturers who had come from the conventional ball mill design adopted these principles as well to their SAG mills. These grinding mills perform well without special concern to the operators. Other manufacturers overcame the problems as mentioned above by eliminating completely the heavy castings and trunnion bearings and the problems associated to it (Fig.1). This design was originally applied to ball mills for the mining and other industries. Due to the success of these shell supported ball mills, this design principle was also applied to SAG mills(Fig.3). Despite of the fact that the majority of today's grinding mills are built to the conventional design it is also interesting to have a look at this alternative. Principles which have proven their reliability on sizes of today's equipment do not automatically warrant a successful operation on the ever larger equipment if bigger mill sizes are realized only based on the pantograph principle. With growing grinding mill sizes, the mass and volume flows through the equipment increases rapidly. Thus it is very important not only to concentrate on the safe design of the structural components of the equipment but as well on the process requirements. The influence of the design on important process parameters of dry and wet grinding plants are discussed thereafter. It shall be shown how modern computer programs can assist in the optimization of the design of components in order to fulfil the operational requirements of such large size equipment. PROCESS REQUIREMENTS OF LARGE SIZE GRINDING MILLS Dry Grinding Mills The world's biggest ball mill is a dry grinding ball mill having a diameter of 6.2m and an overall length of 25,5m with a drive power of 11,200 KW or 15,000HP. This grinding mill dries and grinds gold ore at a rate of 500 tons per hour at a moisture content of up to 9,5%. As shown in Fig.4 this mill was built as a shell supported unit. In fact only this design principle allowed to meet the process requirement. This mill could hardly be built with cast conical endwalls due to the constraints of the trunnion bearings limiting the mill inlet. The following case shows how modern computer programs can help to meet the design criteria of the air system of large size dry grinding plants. For dry grinding plants, the gas flow through the SAG mill has to match the drying, as well as the material transportation require-

Jan 1, 1998

By Gemei Yang, Pierre Mousset-Jones, Felipe Calizaya, Malcolm J. McPherson

Laboratory tests on controlled airflow recirculation have shown the development of transient states in response to changes in system prevailing conditions such as those generated by a sudden start-up and stoppage of fans. Researchers in many European countries have developed various models to explain these phenomena. However, these models failed to consider some important factors such as diffusion and dispersion of gas in turbulent flows. For both in-line and cross-cut recirculation, tests have shown that after the start- up of a booster fan, the gas concentration in the system fluctuates, reaching high levels at the initial states and slowly dying out with time. These fluctuations cannot be represented adequately by simple step-wise functions but rather by smooth, albeit complex equations. In this paper, the phenomena are explained by the convection-dispersion theory, and represented by a mathematical model. Based on a few simplifications and applying Fourier's Transform Method to the differential equations of the flow recirculation model, an integral form of gas concentration function was derived. The Simpson Integration Method was used to compute numerical results for two laboratory tests. The paper also discusses the range of the dispersion coefficient to improve the accuracy of the model.

Jan 1, 1989

By D. Morin, J. Villeneuve, S. Foucher

The development of new processes has to follow "best practice" rules in order to be technically and economically as efficient as possible. However, innovations, new process routes and new rules are continuously emerging to minimize financial risk and maximize environmental compliance. Process simulation, which offers a complete overview of the flowsheet, makes it possible to cope with this new challenge-minimizing waste production and water consumption. Furthermore, simulation provides an estimate, at the early stage, of the cost of alternative technical routes. Four examples involving biotechnological circuits are presented, both at the design and commissioning stages.

Jan 1, 2000

By Alwyn Protheroe, Steve Smith, Herbert Jr. Gibson

In September of 2000, Cowin and Company, Inc., contracted with Paramont Coal Corporation to construct a large decline approximately 820 m (2,700 feet) in overall length at a grade of 8 degrees to the Lower Banner Coal Seam. This paper will discuss the methods used by the contractor and owner to overcome the unique problems required to construct this tunnel in a coal mine environment. The problems include, initial design considerations, equipment selection, ventilation, ground control, control of water in?ows, and placement of concrete.

Jan 1, 2003

By J. D. Miller, P. L. Sibrell

The nature of surface sites for the adsorption of gold from alkaline cyanide solutions has been investigated using samples of synthetic, highly-oriented pyrolytic graphite (HOPG). This HOPG material offers an idealized graphite structure enabling the independent study of the graphitic basal-plane sites and the edges, or defect sites, of the graphitic planes. Radiochemical and X-ray photoelectron spectroscopic experiments independently demonstrated that gold adsorption was much higher on the edges (defects) of the graphite planes than on the planes themselves. These results suggest that site-specific adsorption is prevalent in the adsorption of gold by graphitic carbons (including activated carbon, carbon black and graphite) and that most of the favored sites are at edge defects in the graphite crystal structure.

Jan 1, 1993

By G. Granger, D. Malhotra

The paper briefly reviews the criteria employed in the selection of chemical reagents for testing and discusses the steps involved in laboratory and plant evaluation of these reagents. An example of successful implementation of reagent change in the plant is illustrated.

Jan 1, 1986

By Pengfei Pan, Lianjun Guo, Houguang Sun, Donglin Xu, Chi Yang, Lihua Luan, Daning Zhang

"Based on the introduction of production technology of Anqian mining company, the stope ore mass distribution was analyzed in detail. The processability indexes of different grade ores were obtained with magnetic tube whereas the grinding time, concentrate grade and concentrate yield were measured. On the basis of digital ore deposit model which integrates ore natural attributes and processing attributes, two stages of ore blending optimization models were established. The first stage model sought the minimum of stope ore transportation cost under the restraints of output ore grade and stope production. The second stage was a system optional model that aimed at the furthest use of resources meeting not only the production constraints of mining field and process field but also ore beneficiability and the system output requirements of the concentrate grade. Lastly, the solving method of big M simplex algorithm was discussed and used in production. 1. Foreword China is the biggest iron ore consumption market. But most of iron ore deposits in china possess such features as low grade, complex compositions, weak magneticity and refractoriness. Under the current economic and technical conditions, rational utilization of low-grade and refractory iron ore is strongly needed to improve the utilization ratio of mineral resources and keep mine development sustainable (Lei 2011). In recent years, the domestic research institutions and mines made a lot of achievements of rational development and utilization of low grade iron ore resources in the beneficiation technology and equipment, high and low grade balance, cost and tax analysis (Wang and Zhao 2013, Zhang 2014, Zhu and Li 2014), laying the foundation for reasonable utilization of low grade iron ore. In this paper, Anqian mining company is taken as an example in which the production conditions, raw ore quality control, different grade of ore processability, and ore blending optimization mode in mining pit and processing plant were discussed to achieve the maximum utilization of low-grade refractory ores under the economical and reasonable conditions. This will ensure the stable operation of mining joint ventures and maximize the enterprise's production life and therefore, maximize the economic and social benefits in the enterprise life cycle."

Jan 1, 2017

By Robert J. Timko, R. Lincoln Derick

This report presents a Bureau of Mines evaluation which examined the extent of gas leakage from sealed areas in underground coal mines and measured the effectiveness of commonly used structures for controlling the quantity of gas exchange from these areas. Evaluations were performed on five abandoned areas in two operating underground mines within the same coal seam. Methane and oxygen levels inby the seals were monitored to determine if the gas leakage was unidirectional or bidirectional. Results from this and prior work dealing with minimizing gas leakage were then applied to a newly abandoned area. Also discussed are bulkhead site preparation, construction plans, techniques for monitoring the status of the atmosphere within the sealed volume, and a modified European method for controlling gas migration from the sealed volume to the active mine.

Jan 1, 1991