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By A. K. Mukhopadhyay, B. Sikdar, V. P. Arora

Introduction During the past several years, persistent concerns about an economic slowdown in India have tempered capital-expan¬sion plans. This has encouraged companies to find methods of increasing the capacity of existing production equipment. One of the more cost-effective methods of increasing produc¬tion capacity without major capital investment is to improve equipment maintenance to prevent needless machine down¬time. This can have a significant financial impact because of reduced maintenance costs and increased machine availabil¬ity. The maintenance program employs different techniques, but the analysis of the vibration behavior of machine compo¬nents to assess their condition was found to be the most accurate technique for monitoring various machine disorders. A dragline that handles overburden in open pit mines is one of the more capital-intensive pieces of production equip¬ment. It is imperative that the machine be run at its optimum capacity under the prevailing environmental conditions. Condition monitoring of the various components of the dragline through vibration analysis not only improves the machines availability but also ensures a long operation time free from sudden failure. This paper describes the application of vibration monitor¬ing and analysis techniques to assess the components of a W2000 dragline. The paper reveals that condition monitoring through vibration analysis can be as valuable in failure prevention as it is in failure analysis. Finally, the paper presents an approach to a knowledge-based expert system to the quick and correct diagnosis of mechanical faults in a dragline. Equipment A dragline is an intermittent-discharge-type excavator having a long boom at one end. Unlike other excavators, the bucket is not rigidly held by the frame structure. In favorable geomining conditions, the intensive operation of these exca¬vators is the least-expensive means of overburden removal. The basic working elements of this equipment are the hoist system, the crowd and retract system, the wing mechanism and the propel mechanism. The walking dragline is accepted as the most economical machine for stripping overburden at depths of up to 60 m (200 ft). They are electrically powered and the various motions are effected by individual drives. The Ward-Leonard system is used to provide the optimum flexibility in controlling different dc-drive motors. To mini¬mize the cost of mineral extraction, the largest such machine in India has a 24-m3 (850-cu ft) bucket with a boom length of 96 m (315 ft). Draglines are very costly, and considerable financial penal¬ties may arise from sudden stoppages due to component fail¬ures. Thus, operational reliability is of the greatest importance. Active measures are now being taken to minimize downtime by adopting condition-based maintenance techniques. Though a number of techniques come under this scheme, it has been observed that assessing the health of the dragline by measuring vibration is the best method of determining the dynamic behavior of its various rotating components to avoid any catastrophic failure. Based on criticality, the vibration-behav¬ior of the following components are studied: • motor-generator unit, • exciter unit, • hoist motor-gearbox unit, • hoist drum-gearbox unit, • drag motor-gearbox unit, • drag drum-gearbox unit and • swing motor unit The approach Increases in the vibration levels in different subsystems of the dragline were observed due to the presence of faults such as unbalance, misalignment, looseness and bad bearings. A vibration behavior study included the measurement of vibra¬tion level, trend analysis of time-domain vibration signals and vibration frequency analysis at bearing points of the components. A vibration meter, a vibration analyzer and a data collector are used. Vibration-level measurement. When the dragline was assembled and put into operation for the first time, vibration data were collected to generate baseline data for the equip¬ment (based on International Standard ISO 2372). After¬wards, the vibration levels were recorded regularly using a vibration meter. The measurements were taken at all bearing

Jan 1, 2000

By Gary F. Meenan

Continuous pi lot scale dewatering tests compared the performance of the vacuum disc filter with that of the screen bowl and the solid bowl centrifuges. The test results allow the a priori prediction of plant product moisture based on the feed particle size. This information is useful for selecting the best dewatering device for a given size material and for optimizing the dewatering performance of existing plant installations. Quantitative information was gathered on the ability of filter aids to improve the filtration rate of fine coal slurries. A polymeric flocculant and oil were added to the disc filter feed material at various dosage levels. Both filter aids increased the disc filter output. For the coal tested, the flocculant filter aid achieved higher filtration rates at a lower cost.

Jan 1, 1988

By J. A. Finch

The use of pneumatic methods for measuring interface level in flotation columns is analysed. It is shown that errors can vary over a wide range (e.g. 40 cm. in one industrial application) depending on bubble size, particle size, bubble loading, liquid hold-up and bulk slurry density. Accurate measurements (+ 5 cm) can be obtained by measuring intensive properties of the froth near the interface. Methods based on the measurement of temperature and conductivity are described and analysed. Control of the interface level using these measurements subject to various disturbances is demonstrated.

Jan 1, 1988

By R. Benito, J. Lopez, H. Gamarra

This article describes three practical applications of the Hill of Value (HoV) methodology within different stages of strategic planning for open-pit mining operations and projects. In the pursuit of optimal mine planning, this study establishes a comprehensive case study during the (i)design phase, by refining key parameters for efficient decisionmaking. (ii)production planning, where the HoV is used to define achievable production rates, enhancing operational effectiveness through a nuanced consideration of mining and processing capacities. (iii)Additionally, the study introduces a conceptual framework for orchestrating the optimal sequence of multiple pits during the planning phase, with a focus on maximizing project value.

Feb 1, 2024

By Pradip

The selection, testing, and commercial utilization of flotation reagents is best carried out in stages through microflotation tests on pure minerals and their synthetic mixtures followed by bench-scale batch flotation tests on the ore. A systematic approach to quantitatively evaluate different reagents, in particular, through the analysis of batch flotation data, has been presented in this paper. It is recommended that the reagents are compared both in terms of their performance with respect to the recovery-time as well as the recovery-grade plots. While the former describes the kinetic aspects of reagent interaction, the latter is a measure of its selectivity for a particular separation problem.

Jan 1, 1987

By P. Somasundaran, Bruno Lartiges

Two different groups of mechanisms have been considered in the past to explain the effects of chemical additives on grinding. While one group of explanations is based upon alterations of surface and mechanical properties of the individual particles, the other group depends mainly on the arrangement of particles and their flow in suspensions. In this paper some of the past work on grinding aids is reviewed and attrition grinding of a commercially important ceramic material, zirconia (stabilized with yttria) with polyaaylic acid as grinding aid, is studied in order to determine the effect of the aid on the ground product itself. It was observed that even though polyaaylic acid did cause a drastic decrease in the viscosity of the pulp, it did not have any major effect on the grinding of zirconia at least up to 2000 ppm and only minor detrimental effect above it. Importantly, complexation by the polymer was found to cause extraction of yttrium into solution with possibly significant changes in the surface chemical composition of the product.

Jan 1, 1992

By L. Adler

Determining whether a railroad locomotive will skid under varying conditions is a fairly routine, pervasive problem. However, some of the equations provided are wrong, others are at best murky. All require correction or clarification. Skidding during heavy braking is a crucial safety problem, possibly resulting in loss of control and collision. It can also be an economic detriment, ruining wheels and tracks and, by inhibiting acceleration, causing reduced full-speed times. While skidding is less likely for rubber-tired equipment, a comparable problem exists for tractor-trailers operating on poor surfaces. The primary reference is to the SME Mining Engineering Handbook (pp. 14-11, Eqs. 7 and 8), which is taken as authoritative and normative (Brantner, 1973). Fundamentally, the physical weight of the locomotive can never be negative (-). However, based on this reference it can be negative on adverse grades, during braking (Eq. 7), and on favorable grades, whether accelerating or braking (Eq. 8). Additionally, it should be noted that the term rW should be Rw. To avoid having the locomotive weight turn out negative, "absolute value" brackets must enclose the right-hand expression of both equations. Also, the weight of locomotive can be greater than the right-hand side value introducing the common "greater than or equal to" symbol (>_). While these alterations are easy to make, the use of the algebraic sign associated with each term is still confusing, as

Jan 1, 1991

By Randolph E. Scheffel, David C. Fitch, David K. Hogan, Mark R. Welsh

In Oct. 1981, Ranchers Exploration and Development Corp. began producing silver bullion from the Escalante mine and mill complex, located in southwestern Utah. Current in-place reserves are estimated at 2.42 Mt (2.67 million st) of ore, containing about 936 t (33 million oz) of silver at an average grade of 428.5 g/t (12.5 oz/st). The vein-type deposit is being mined underground through a decline that is currently 864 m (2,835 ft) in length, but will ultimately be at least 1.5 km (5,100 ft) long. The mine is completely mechanized with rubber-tired equipment, and is producing 680 t/d (750 stpd) of ore, five days a week, or 177 kt/a (195,000 stpy). Additional capacity is available. The cyanide leach mill and associated refinery are presently producing 4.35 t/month (140,000 oz/month) of silver bullion-an an¬nual rate of about 52.25 t (1.68 million oz). With minor modifications, the mill can produce up to about 70 t/a (2.25 million oz/year), and expansion is currently underway. History The Escalante property is located 68 km (42 miles) west of Cedar City, UT, on the west side of the Escalante Valley, where the vein forms a gentle ridge in an area of low, rolling hills. For years, the vein has been the object of considerable exploration, but never became more than a sporadic producer, primarily due to low silver prices. Heber Holt of Enterprise, UT, staked the original four claims in 1896; they were patented in 1910. During the next 48 years, limited exploration and mining activity was conducted on the property. Systematic evaluation and development did not, however, begin until March 1958, when Samuel S. Arentz, a prominent mining engineer and consultant, formed several joint ventures with mining and oil companies that conducted drilling, drifting, mining, and water drawdown tests on the property. However, it remained uneconomic, principally because of low silver prices and costs for pumping large flows of underground water. In 1975, Ranchers obtained an option on the property and in 1979 began a drilling program. As of May 1982, the company had drilled 70 core holes, bringing the number of exploratory holes drilled on the property to 138. Test mining began in 1979 as silver prices increased, and full mine development began in 1980. Mill construction began in Sept. 1980, and on Aug 29, 1981, the first ore was fed to the mill.

Jan 9, 1982

By Geoff C. Knight

Longwall mining using the shearer is acknowledged internationally as the most economically successful method of high volume production from underground coal mines. Since its introduction in the 1950s, a great deal has been achieved in developing the capability and reliability of the shearer - and the associated face conveyors and powered roof supports - to produce the competent systems now widely deployed. Equipment will continue to improve as knowledge and experience are gained and through the influence of market forces on the international equipment suppliers. However, current systems are so successful that further improvements are likely to be incremental rather than radical unless a high level of system automation is introduced. The automation concept is not new to the shearer-based longwall system. The opportunity and the need were recognized soon after the shearer and powered support were introduced in the 1950s. In the early 1960s, the British Coal Corp. (BCC; then the National Coal Board) attempted remotely operate longwall systems. Those imaginative early schemes were seen as failures at the time. But, with hindsight, a great deal was learned from the experience that stimulated automation research in several European countries. One of the most fundamental lessons learned was that coalface system automation is not possible until there is a high level of competence in automatically controlling the operation of the production machine itself within the coal seam. Once that is achieved, the rest of the system will follow with comparative ease.

Jan 1, 1991

By Alena Conrads, Markus König, Markus Scheffer, Markus Thewes, Hannah Mattern

"INTRODUCTION In recent years, the development of tunnel boring machines has revolutionized the tunneling industry. The general structure of a tunnel boring machine (TBM) can be described as a multi-component system. To achieve high performance rates, machine elements have to perform reliably. Performance losses and interruptions of the construction process should be prevented or at least, reduced to a minimum. In order to achieve high advancing rates, cutting tools must be in good condition at any time. Furthermore, failure of individual tools might result in increased and faster wear of remaining structural components. For this reason, maintaining and replacing cutting tools is crucial to prevent project delays due to insufficient boring performance. Precise prognoses concerning the prevailing geology are infeasible and thus, efficient scheduling of maintenance actions is challenging. The intention of this work is to analyze different approaches of TBM maintenance in soft ground. Different strategies are analyzed by the use of a simulation approach. Cutting tool condition is regarded as performance limiting factor. The maximum operation time of the cutting tools is determined using the “Soil Abrasivity Index”. A case study serves to show the effects of different maintenance strategies on total project duration. SCHEDULING OF MAINTENANCE ACTIONS Scheduling maintenance actions of single and multi-component systems concerns numerous fields of industrial production. Concentrating on mechanized tunneling in soft ground, cutting tool maintenance represents the most common reason for intermission of advance (Köppl 2014). In literature, time-based and condition-based maintaining techniques are widely discussed. The following section outlines the principles of time- and condition-based policies. Furthermore, examples for their applications in recent research are given. Time-Based Maintenance In general, the time-based maintenance approach assumes that the failure behavior of the system components is predictable. Maintenance actions are scheduled according to predefined intervals (e.g., hours, days, weeks). A detailed analysis of preventive repair times or interval forms the basis for maintenance decisions. For this approach, an adequate quantity and quality of data is fundamental. Numerous studies deal with the analysis of time-based maintenance for production equipment. In fields of mechanized tunneling, unplanned machine downtimes restrict the applicability of time-based maintenance approaches. Thus, this paper mainly focuses on condition-based maintenance."

Jan 1, 2016

By Maribeth Amyot, Y. J. Wang, S. S. Peng

Introduction The impact of computers on individuals and businesses increases each day. And the mining industry is no exception. The growing number of short courses, symposia, and feature articles in journals on the subject of computers is indicative of the developments and interest in their application to mining. Given this interest and the growing importance of computers, a legitimate concern is the computing background of graduating mining engineers. Based on a sample survey, this paper presents the current status of computer education in Accreditation Board for Engineering Technology (ABET)-accredited mining engineering programs in the US. Specific topics addressed include hardware and software available to students, integration of computers into curricula, concerns of mining educators, and historical and anticipated trends in computing education. Methodology Nine of the 19 ABET accredited mining engineering schools (as published in the SME-AIME Guide to Minerals Schools) were surveyed. Interviews consisting of open-ended questions were conducted with a knowledgeable faculty member from each of these schools. This was done to obtain an overall view of computing in mining engineering programs. The intent was not to evaluate nor compare individual schools, so a complete census was deemed unnecessary. The minimal deviations between the responses to the subjective questions reinforces the credibility of the sample as being representative. Results Hardware Most of the mining engineering schools polled had access to hardware on three scales - mainframe computers available university wide, minicomputers available in the college or department, and microcomputers available at all three levels. Without exception, each school had access to mainframe and microcomputers. Minicomputers, however, were not available at every school. The mainframe computers have been in place the longest. The predominant mainframe currently on campuses is the IBM model. Mainframes were once the essence of all applications. But the improved availability and capabilities of smaller machines have afforded users a viable alternative. The increasing practice in education of assessing charges for time used on the mainframe - as opposed to no charge for time on the mini- and microcomputers - makes use of the smaller machines attractive. Conversely, much of the mining engineering software is only operational on mainframes. Sometimes this restriction exists because the requisite speed or storage inherent in the software can only be met by the mainframe. More often, however, it is because the software was developed when mainframes were the only machines available, and it has not yet been adapted to run on a smaller machine. At the schools polled, many mining engineering problems that are well suited to microcomputers are being solved on mainframes simply because microcomputer software is not available. Minicomputers are available at the department or college level in many mining programs. DEC is the most popular make. Often, the minicomputers were installed to alleviate the inconveniences of attempting to access and use an overcrowded mainframe, to avoid being charged for time used on the mainframe, and to meet the needs of a specific research project. The minicomputers are currently used much more for research than for teaching applications. Therefore, minis are seldom used by undergraduate students. Microcomputers have become extremely popular at mining schools within the last five years. Generally, some form of computing policy or strategy was established near the time the first microcomputers were purchased. This was formulated in part to ensure consistency, or at least compatibility, in the type of machines acquired. Microcomputers were subsequently selected based on the established computing policies; ma-

Jan 7, 1985

By G. Mbuyi Kamba

Literature is rather abundant on the topic of steady-state network analysis programs. Many versions exist, some of them have real extended facilities such as full graphical manipulation, fire simulation in motion, etc. These programs are certainly of great help to any ventilation planning and often assist the ventilation engineer in his operational decision making. However, what ever the efficiency of the calculation algorithms might be, their weak point still is the overall validity of the model. This numerical model, apart from maybe the questionable application of some physical laws, depends directly on the quality of the data used to identify its most influencing parameters such as the passive (resistance) or active (fan) characteristic of each of the branches in the network. Considering the non-linear character of the problem and the great number of variables involved, finding the closest numerical model of a real mine ventilation network is without any doubt a very difficult problem. This problem, often referred to as the parameter adjustment problem, is in almost every practical case solved on an experimental and "feeling" basis. Only a few papers put forward a mathematical solution based on a least square approach as the best fit criterion. The aim of this paper is to examine the possibility to apply the well-known simplex method to this problem. The performance of this method and its capability to reach the global optimum which corresponds to the best fit is discussed and compared to that of other methods.

Jan 1, 1995

By B. P. Boisen

INTRODUCTION Application Measurement of rock deformation is essential to stability and behavioral monitoring of underground openings. The difficulties of obtaining adequate sample distribution, density, and orientation can frequently be overcome by the use of single and multiple position borehole extensometers. In its simplest form, a borehole extensometer consists of an instrument head, usually anchored in the collar of a borehole, and a number of in-hole anchors, each of which is fixed in place at a known distance from the collar. As rock adjacent to the borehole deforms, the component parallel to the borehole direction causes a distance change between adjacent in-hole anchors, as well as a distance change between individual anchors and the instrument head. These changes are measured by means of a mechanical link (usually wire or rod) extending to the instrument head from each anchor. The resulting data can be used to compute the distribution, magnitude, rate, and acceleration of deformation in the material intersected by the extensometer's borehole. Wire Vs. Rod Extensometers Since the early 1960s myriad varieties of borehole extensometers have become available through the combination of various special features of two basic instruments, the wire and rod versions of borehole extensometers. Recent publications have recommended shallow depth limitations for wire extensometers, and favor rod extensometers for a broad range of borehole inclinations and depths. There are three main reasons for using a deep wire system: its cost effectiveness; the fact that tremendous depth means tremendous rod weight which will cause the rod to buckle or rub against the borehole or casing wall; and users' attitude and proper understanding of how to install and apply a wire-type extensometer. Here experience plays a big role. Over the years, many have learned the hard way that untensioned rod extensometers are simple and inherently inexpensive, but limited to vertical up holes where sensitivity is not influenced by friction between the rod elements and the borehole wall or protective conduit, the inertia of the rod elements, or the direction of the movement to be measured. In deep, horizontal, or inclined holes, and in instances where compressive as well as tensile strains or displacements are anticipated, tensioned rod or wire systems are preferred. System Components Borehole extensometers are made up of at least the following five principal components: the instrument head; the collar anchor assembly; the downhole system of anchors and rods or wires; the signal cable if the head is equipped for electronic readout; and the readout apparatus, whether mechanical or electronic. These components are shown in Fig. 1. Borehole Requirements Most extensometers are designed for installation in nominal 75 to 57-mm (3.0 to 2.25-in.) diam drill holes. Either a diamond drill or a percussion drill hole is satisfactory, provided the variation in drill-hole diameter is within the tolerance of the standard anchor design. The basic system may be modified for other hole diameters by changing the dimensions of the collar anchor and downhole anchor assemblies. Some instrument heads and collar anchor assemblies require enlarged borehole collars, though usually not over 150 mm (6 in.) for a depth of 1 m (3 ft). It is desirable, although not essential, that holes be free-draining. Holes must be clean and free of debris before installation. Depth/Orientation of Extensometer Boreholes Extensometers are designed to measure axial strain components in the instrumented drill hole. As the drill hole is axially deformed, the distances between individual downhole anchors and the instrument head change, as do the distances between adjacent anchors. The distance changes measured by a multiple position borehole extensometer, for example, are reduced to functions of time, hole depth, anchor position, or other parameters of significance in terms of the structure under investigation.

Jan 1, 1982

By R. L. Frederking

Geological remote sensing is, "....the study of the Earth utilizing electro-magnetic radiation (EMR) which is either reflected or emitted from the land surface in wavelengths ranging from ultra-violet (0.3 micrometre) to microwave (3 metre)."1 Selected examples which illustrate a variety of successful geologic applications include lithologic mapping, 2 engineering soils mapping,3 tectonic interpretation,4 and mineral and petroleum exploration.5 This report examines the applicability of remote sensing for bauxite exploration in northeastern Mississippi. Specific objectives were to map lithologies of northeastern Mississippi from LANDSAT imagery, to determine the utility of LANDSAT imagery for delineating and mapping known deposits of bauxite, and to discover and map new bauxite deposits.

Jan 1, 1977

By Steve Kral

The power industry throughout the world is in the midst of a significant transition that will result in a major restructuring. Deregulation of utilities in the United States is continuing, resulting in increased competition among power providers. The traditional ways that electric power is globally bought, sold and delivered will also change. However, according to the Department of Energy's (DOE) Pat Godley, one thing is clear: "Those who provide the power during the 21 st century will be those who are willing to change - those who are willing to accept new ways of doing business and willing to employ new technologies." Godley is assistant secretary of fossil energy with DOE. Her comments came during the opening remarks at the Fourth Annual Clean Coal Technology Conference, held in Denver, CO, Sept. 5-8, 1995. The conference was sponsored by DOE and the Center of Energy and Economic Development. Under the theme "Global Opportunity," more than 300 coal and utility executives spent three days discussing the new face of the electric-power industry throughout the world and the new, mostly clean coal technologies (CCT) that will be available to power providers.

Jan 1, 1995

By W. M. Shaver, W. R. Dengler

INTRODUCTION In Canada, most of the rock being broken in underground metal mines is being carried out using traditional drilling and blasting methods. Despite advances being made in hard rock boring and other, more exotic techniques, it is Dynatec's belief that the traditional methods will continue to prevail for many years to come. It is also our belief that modest research efforts expended on the traditional methods will result in substantial financial benefits to the mining and rock tunnelling businesses. Dynatec has pursued productivity improvements through the use of long rounds in both shaft sinking and lateral development. The concept of longer rounds was developed by Dynatec on the Craig Shaft Sinking Project (RETC 1991). This paper reviews the Craig Shaft Long Round success. This technology was subsequently utilized to sink the two shafts at Aur Resources with great success. The development of a Long Round Jumbo for tunnelling is a natural progression of the long round technology developed for the Craig Shaft. RECENT HISTORY OF SHAFT SINKING Shaft sinking is one of the oldest and most difficult mining methods. Due to the relatively small amount of shaft sinking in proportion to tunnelling and

Jan 1, 1993

By F. Dudouit, M. M. Mohkam, F. Renault

The Pannerdensch Kanaal Tunnel is part of Holland’s Betuweroute high speed freight railway project linking Rotterdam to inland of Europe. It comprises of twin tunnels, 1620 m long each, with 8.6 m inner diameter. The Tunnel alignment is situated mainly in sandy formations and under high hydrostatique pressure. The over burden cover varies from relatively high to very low, sometimes much smaller than the diameter. One of the special features of the Pannerdensch Kanaal Tunnel is that, over some 250 m, the twin tunnels are to be bored in a back?lled sandpit. Some 490 000cubic meter of sand has been placed and compacted by vibro-?otation to refill the sandpit. The tunneling machine is a 9.8 m slurry shield manufactured by Herrenknecht. Tunnel lining is precast concrete consisting of seven plus one key universal segments. Other than the special feature of boring through re?lled sand, constraints such a slow overburden while crossing under Pannerdensch Kanaal and some lagoons, as well as high liquifaction potential of sandy formations, render this job very unique of the type. Fine studies were conducted in heading’s stability. And, confinement pressures were determined considering different risks of liquefaction and blowout problems. Both tubes have been successfully bored. Several sections have been monitored. The results are quite interesting and in accordance with contract technical conditions.

Jan 1, 2003

By D. A. Smith

The successful integration of overburden casting techniques into the mine production cycle can be an extremely cost effective use of explosives. The entire mining cycle revolves around the cast blasting and to be successful requires a great deal of planning and cooperation. Several operations of Cyprus Coal Company in the Appalachian coal fields have successfully integrated blast casting into their mine plan. This paper will detail the parameters and necessary controls to integrate an overburden casting program into a surface coal operation.

Jan 1, 1993

By J. W. Danni

Today's mining industry faces many challenges. Perhaps none is more important than the challenge of improving our industry's public image. Opinion polls document public concern for a clean and safe environment. As part of that public, the mining industry must share that goal. The public is now the most powerful environmental group in society. And the public wants the environment to be protected. In May 1989, Edgar S. Woolard, chairman of DuPont, spoke to the American Chamber of Commerce. He said that industry's continued existence "requires that we excel in environmental performance and that we enjoy the non-objection - indeed even the support of the people and governments in the societies where we operate." In effect, Woolard called for "corporate environmentalism." He defined it as an "attitude and a performance commitment that places environmental stewardship fully in line with public desires and expectations." Environmentalism is no longer a fringe activity, but rather is now clearly in the mainstream. How can we meet public expectations and improve our image as an industry? One of the best ways is to plan, design and operate our mine facilities with environmental responsibility and social concern. The Mineral Hill Mine provides a good case study of a facility that has made this commitment. The project used an inter-disciplinary, multiagency task force, citizen advisory groups and engineering and design considerations. As a result, Mineral Hill achieved cost-effective permitting. At the same time, the operation demonstrated effective "corporate environmentalism."

Jan 1, 1992

By D. M. Bodily, M. D. Deo, E. M. Whitney

Field data from coalbed methane wells indicate a significant variation in composition as a function of flow rate and time. In particular, San Juan Basin wells have displayed an increase in C02 concentration over time. Prediction of gas quality is critical to the economic evaluation of any coalbed project. Previous models have forecast only pressure and production profiles, ignoring compositional variations. In this study a multicomponent model that incorporates binary isotherms for methane and carbon dioxide has been developed. An extended Langmuir isotherm is used for the adsorption representation and a constant separation factor (similar to relative volatilities in distillation) describes the phase distribution of the species. This separation factor depends both on the surface characteristics of the coal and on the adsorbing species. The chromatographic separation equations have been superimposed on Darcy's law flow. The formulation allows decoupling of the pressure and compositional partial differential equations. The equations have been cast in dimensionless form and solved for pressures and compositions. It is observed that the composition of the preferentially adsorbed C02 increases at the wellbore as a function of dimensionless time. The dimensionless time is directly proportional to the real time and coalbed permeability and is inversely proportional to the gas viscosity, coal porosity and the square of the length of the reservoir. As the separation factor increases, the compositional variation increases. This variation in produced C02 concentration is also greater when the initial C02 concentration in the reservoir is higher. A sensitivity study has been performed to identify the effects of important parameters such as isotherm variables and reservoir characteristics on pressure and composition profiles.

Jan 1, 1993