Search Documents

By M. L. Chapman

When originally accepting the assignment, the Client had described the property as vacant land. A prior appraisal was later discovered and revealed that the property included a mineral rights appraisal. Further research disclosed an old dispute with a court ruling based on testimony by AIMA-certified experts. The present appraisal was therefore based on data from findings of the court with a fresh look at discount rate, absorption period, and residual land value. Fortuitously, the property subsequently sold on the market, while meeting all criteria for Fair Market Value. This provided insight into a market-based discount rate. Also, the absorption period could be adjusted in accordance with the current market conditions. The residual land value was minimal (based on comparable sales and projecting trends in market) as the property was affected by a flood zone and the surrounding development was sparse. PROPERTY HISTORY: A GREAT INVESTMENT Briefly, the subject property is located in the floodplain region of the San Jacinto River, a short river in southeastern Texas that flows into Galveston Bay, filled with sand and gravel. This location is on the north side of Houston, north of Beltway 8 on the east side of I-59.

Jan 1, 2012

By F. Calizaya

A booster fan is an underground fan installed in series with a main surface fan and used to boost the air pressure of the ventilation air passing through it. To accomplish this objective, the fan is installed in a permanent stopping and equipped with airlock doors, a monitoring system, and interlocking devices between main and booster fan controls. The stopping and doors are used to prevent flow recirculation, and the monitors to ensure safe operation of the fan. A booster fan, properly sized and sited, can be used to create safe work conditions and allow the extraction of minerals from areas that would otherwise be uneconomic to mine. In deep and large mines with heavy emissions of air contaminants, the required quantities of air can only be supplied by using high pressure fans. These fans will inevitably induce significant losses of fresh airflow through the stoppings and doors. For well defined ventilation circuits, booster fans can be used to decrease the main fan pressures and reduce the leakage flows. However, this will require a good understanding of the correct ventilation practice, from planning to operation and maintenance of booster fans. The objective of this study is to investigate the conditions under which booster fans can be used safely and efficiently in underground coal mines. Specifically, the study is directed at (1) collecting reliable information on airway resistances and flow requirements from two large U.S coal mines, (2) collecting fan performance data from one or more existing coal mine where booster fans are used regularly, (3) monitoring the performance of booster fans in a laboratory model and an experimental mine, (4) developing a booster fan selection method to assist the ventilation engineer at the planning stage, and (5) training six M.S. or Ph.D. graduate students in advanced mine ventilation.

Jan 1, 2010

By James S. Browning

This article describes research conducted by the University of Alabama's Mineral Resources Institute on removing sulfur from coal using a combination of gravity concentration and flotation methods. The research used the gravity and centrifugal force capabilities of Humphrey's spiral to remove part of the pyritic sulfur and ash. Flotation of the Humphrey's spiral coal concentrate removed additional sulfur and ash. In addition to obtaining good recoveries of high quality coal, the tests demonstrated that pyrite in the wastes could be isolated as enriched flotation products by the combined gravity-flotation approach. Domestic coal production in 1980 reached a record 757 Mt (835 million st). Forecasts are that coal production and use will approach 907 Mt (1 billion st) by 1985, with much of the increased production being used for electrical generation. Of current production, it is estimated that about 454 Mt (500 million st) of coal nationwide are subjected to some degree of cleaning, ranging from crushing and screening to gravity concentration and flotation. With expanded coal production and more rigid controls placed on coal combustion, it is reasonable to assume that the tonnage subjected to some form of preparation will increase, with time, thereby adding to the burden of coal rejects being generated. A major problem associated with increased coal use for electricity generation is the need for utilities to conform to emerging federal air quality standards for sulfur oxide emissions from power plants. To a lesser extent, other industrial operations burning coal face a similar situation. Controlling sulfur oxide emissions by using low-sulfur coal or resorting to stack gas desulfurization are two recognized approaches, but removing sulfur from the coal, if possible, by physical beneficiation before combustion is preferred because of its simplicity and lower cost. Reducing the inorganic sulfur in coal to tolerable limits by physical beneficiation, including flotation, as now practiced, is still relatively inefficient and has not kept pace with the more sophisticated physical beneficiation approaches generally employed by the nonfuel minerals industry. As one phase of a broad program conducted by the Mineral Resources Institute at the University of Alabama on sampling and evaluating impounded fine size waste coal, tests were made using samples from two impoundments to determine the quality of coal recoverable by a combination of Humphrey's spiral concentration and flotation. Particular attention was given to organic and inorganic sulfur deportment and distribution in the various products. Another objective was to determine if pyrite in the waste could be recovered for possible marketing. The use of Humphrey's spirals to concentrate fine coal was practiced as early as 1947. At that time, the Hudson Coal Co. used spirals to concentrate anthracite fines. In 1950, spirals were used to treat fine-size bituminous coal and later, in 1976, spirals were reportedly used for removing pyrite from fine-size coal. More recent investigations have discussed the use of Humphrey's spirals for treating fine-size waste coal in Alabama. Samples Description Washer waste samples were obtained from two impoundments. One sample was representative of waste generated during washing steam coal from the American, Pratt, and Nickel plate seams in Alabama. The other sample represented metallurgical coal washer waste from processing coal from the Carter, Johnson, and Milldale seams. Partial samples analyses are shown in Table 1, and screen analyses of the samples are given in Tables 2 and 3. Screen ana¬lyses showed that one sample contained about 4% of material coarser than 2 mm (10 mesh) and the other contained about 13% of plus 2 mm (10 mesh) material. Also, the analyses indicated that ash and sulfur increased as the material's particle size decreased. Experimental Laboratory Tests Sink and float tests using a heavy liquid (1.4 specific gravity) were made on the different screen sizes shown in Tables 2 and 3 to determine the effectiveness of gravity concentration for separating coal from pyrite and other gangue constituents. Tests indicated that gravity separation, under optimum conditions, could be expected to yield coal products containing 10-12% ash, and 0.2-0.3% pyritic sulfur. Good coal recoveries could also be expected. Using sink-float tests as a guide, tests were made in a Humphrey's spiral by a procedure in which a 90-135 kg (200-300 lb) portion of the

Jan 8, 1982

By Jasinder S. Jaspal

The United States has very large coal reserves in seams that are less than 1065 mm (42 in.) thick. These reserves are often not mined because of the difficulty of working in low heights and, in most cases, the seams are beyond the technical or economical limits. It is estimated that the remaining reserves in 355 to 710 mm (14 to 28 in.) thick seams that are not faulted or intruded, dip less than 15° and under a cover of 610 m (2000 ft) or less are nearly 910 Gt (1 trillion st). This is a very large percentage of coal reserves in the United States (Unrug, 1985; DuCarme et al., 1990). The US Bureau of Mines is attempting to develop new techniques for mining 150 to 1065 mm (6 to 42 in.) thick coal seams. Research has focused on existing thin seam mining techniques, testing of small- and full-scale physical models of the Bureau's slot mining concept and computer modeling of the full-scale process. In 1986, only 21 % of the total US coal production came from -1065 mm (-42 in.) thick seams. Of that, 355 to 710 mm (14 to 28 in.) thick seams share of production was minimal, probably 5% or less (Mayercheck et al., 1990). This shows that the thin seams, particularly the seams 355 to 710 mm (14 to 28 in.) thick, have not been mined to the extent of the available reserves. Thin seam coal, generally, is of premium quality. As thicker seams are depleted, the mining of thin seams could become more important. Thus, there is a need to develop technology to mine these seams (J. Farinelli et al., 1987). A successfully applied technology could change reserve categorization. In the Appalachian Plateau there are 417 Gt (460 billion st) in 355 to 1065 mm (14 to 42 in.) seams. This represents nearly 9.2% of the US remaining reserves (Unrug, 1985). At depths of 152 m (500 ft) or less, the Appalachian Plateau has about 214 Gt (236 billion st) of reserves in 355 to 1065 mm (14 to 42 in.) thick seams. Other mining areas also have substantial coal reserves in this seam thickness category. Those, however, are not as attractive for mining as the Appalachian Plateau. In the past, most of the reserves of the Appalachian Plateau region were partially worked by contour and highwall auger mining. It is estimated that these mining systems had left some 40,230 km (25,000 miles) (Readers Digest, 1987) of unreclaimed highwalls. The Bureau recognized this situation. In FY1987, the agency initiated a research project to develop anew technology for mining thin seams of the Appalachian Plateau.

Jan 1, 1992

By K. L. Wiley

In-situ leaching, initiated in 1986 at San manual, was economically developed in 1989. The primary reason for this lag time between startup and viable production was the time required for technical development. The technical development pursued comprised detailed design, development, and implementation of in-situ well construction methods, formulation of suitable well pattern arrays, and the development of extensive hydrogeologic and geochemical knowledge of the mineral deposit. Since 1989, the in-situ leaching program has become a viable and cost effective method to extract copper from the supergene mineralized zone of the San Manuel deposit. The in-situ leaching methods that are currently utilized have been progressively expanded and continually developed and will became the cornerstone of copper production from the San Manuel oxide mineral deposit. This paper presents an overview of the supergene hydrogeology, current design techniques, drilling methods and well completion, pump determination and setting, solution management, and future plans for the increased extraction of copper by in-situ leaching methods at the San Manuel mine.

Jan 1, 1993

By Hun-Joon Sohn

Chemical metathesis and electrochemical reductive conversion of chalcopyrite in the presence of cupric ions were studied in sulfuric acid solutions for temperatures up to 90°C. The process results in the displacement of iron in the chalcopyrite lattice by copper ions with rejection of ferrous ions to the aqueous phase. The rate of reaction was found to be very slow, requiring subsieve-sized particles for extensive reaction to occur. The reaction was insensitive to copper ion concentration. Stirred ball milling of chalcopyrite introduces lattice strain. The reaction rate with strained particles was markedly higher than with annealed chalcopyrite. The reaction rate was found to be diffusion-limited, showing two distinct reaction stages corresponding to the formation of CuS (covellite) followed by Cu1.8S (digenite). The experimental activation energy for the first stage was 102 J (24.4 kcal) and the second stage 123 3 (29.4 -kcal) per mole. The rate-controlling process is diffusion of lattice ions, probably iron. The enhanced rate after milling is attributed to a recrystallization process which provides new paths for diffusion along dislocations and grain boundaries.

Jan 1, 1984

By Randal J. Barnes

The January 1988 issue of Engineering and Mining Journal includes two short articles on blasting practices in surface gold mines (Anon., 1988 ; Carr , 1988). A reader of these articles learns, among other things, that a "12 x 13 ft" blasting pattern is used at the Carson Hill Mine, and a "17-ft burden and 18-ft spacing" is used at Echo Bay Mineral's Borealis operation, while at Mascot's Nickel Plate Gold Mine "ore shots are on a 10 x 10 ft" pattern. Like a new edition of the World Book Almanac, these articles are overflowing with useful tidbits of technical data; but, they never mention why the particular blasting patterns were selected. A survey carried out during the Winter of 1988 at six surface gold mines in the western United States also failed to produce a satisfactory answer. The responses from mine planning engineers to the question "why is your blasting pattern X by Y", reduced to "we use X by Y here because we used X by Y at our last operation, and it worked ok." Certainly, with the available decades of experience and professional practice in blast holes design, rock fragmentation in surface mines has been thoroughly investigated. However, and this is the central issue, fragmentation of the rock is not the primary purpose of most rotary drill holes in surface gold mines. Quoting senior mine engineers from companies operating, three of the richest surface gold mines in the world (AMAX Gold, Homestake Mining, and Gold Fields Mining)

Jan 1, 1989

By T. S. Golosinski

This paper identifies the components of belt conveyor shifting force as a vertical force. Pv, horizontal force, Ph, and longitudinal force, P1. A method for estimation of these forces is proposed, which relates their value to the properties of the conveyor structure and rails, shifting operation parameters, and other site-specific conditions. The effect of this force on shifter behaviour is analysed and guidelines are developed for selection of a suitable shifter. Also discussed are the requirements of the shifting operation for other equipment.

Jan 1, 1986

NIOSH is conducting research to reduce the silica dust exposure of workers at surface coal mines. One goal of this research is to evaluate the relationship between drilling parameters, rock strata and silica dust generation. This study involved measuring blast hole emission dust from a rotary drill rig which required sampling high concentration dust (>400 mg/m3) for silica content in a high velocity airstream. To measure dust initially, traditional sampling methods using personal sampling instruments were attempted in and around the shroud area of the drill with no success. Variations in the dust cloud concentrations under the shroud, the condition of the shroud and its orientation over the hole, and ambient air conditions prevented consistent and accurate dust measurements from being obtained. Amore consistent dust cloud is necessary for accurate measurements. An area of the drill’s dust collector system that consistently draws the emitted airborne dust from the hole is the collector tube. This tube connects the drill collector’s vacuum and dust filtration system to the shroud area. Assuming the collector system is working as designed, sampling from the collector tube would enable more consistent and accurate samples to be taken. However, current personal samplers are unable to sample in the concentrations and velocities experienced in the collector tube, so another method had to be devised. To achieve the desired results, an in-stack cascade cyclone was used. Preliminary field testing shows positive results.

Jan 1, 2003

By Cal D. Iles

Decreasing ore grades and increasing labor and material costs have seriously eroded the economic vitality of many mining operations. Coupled with global economic stagnation and recession in the early 1980's, these conditions have forced reevaluation of operating strategies and methodologies with the objective of remaining competitive in a world marketplace. A concept offering large potential benefits is hardrock portable crushing and conveying. Implementation of this system at Duval Corporation's Sierrita open pit copper-molybdenum mine (Figure 1) has significantly reduced mining costs, becoming a major part of Sierrita's cost reduction strategy. Located 48 km south of Tucson, Arizona, the 209 000 t/d property has one portable 60x89 gyratory ore-crusher in operation with tentative plans for two additional units.

Jan 1, 1985

By Nader Shahcheraghi, Verya Nasri, Mehdi Bakhshi, Ali Haghighat

An accidental fire load is one of the major loads considered in design of segmental linings in transit tunnel. Typically, a two-dimensional coupled thermo-mechanical finite element analysis (FEA) is conducted. The conventional approach involves using standard fire curves (temperature-time curves) which can lead to a significant overestimation of fire load and tunnel lining thickness in metro tunnels. The focus of this paper is on the cutting-edge approach, using 3D computational fluid dynamics (CFD) analysis of real train fires in metro tunnels and coupled thermo-mechanical finite element analysis (FEA) to accurately and cost-effectively design fiber-reinforced concrete (FRC) segmental tunnel linings for large-scale metro projects.

Jun 23, 2024

A number of factors affecting the properties of cemented aggregate fill (CAF), particularly its strength development have been studied through a series of laboratory investigations carried out at the Western Australian School of Mines in the Western Australia in recent years. The outcomes of these investigations indicate that apart from cement dosage, aggregate particle size distribution, aggregate quality, additional fine materials, water salinity, admixture dosage and sample scaling all contribute significantly to the development of cemented aggregate fill strength.

Jan 1, 2001

By Richard E. Steffens

The underground portion of Duke Power Company's Bad Creek Pumped Storage Project in northwestern South Carolina consists of a powerhouse cavern (132 m. long, 23 m. wide, 50 m. high), 407 meters of shafts and approximately 3615 meters of tunnel, both lined and unlined, with diameters varying from 4.2 meters to 9.0 meters. A case history is presented, including the early pilot tunnel exploratory work and how this affected design, the design of the project, and the excavation, rock support and tunnel lining work. Problems and experiences encountered during the construction are given. The effects of high horizontal insitu stresses in the granitic gneiss are discussed along with solution taken.

Jan 1, 1989

By A. Fiszer

One of the major problems with deep Polish hard coal mines are deformations of close-to-wall galleries since they are necessary and must he kept open for emergency situations and are largely responsible for work disturbances. In order to ensure safe and effective working operations, it is necessary to often rebuild galleries which, apart from the inevitable stoppage of operations, is greatly disadvantageous for the operation of a mine. The largest problems with maintaining the galleries open occur in Lower Silesian Coal Field mines where sometimes it is necessary to reconstruct the galleries several times [(Fig. 1)]. In light of what has been said above, the aim of this article is to present the reader with methods and ways of determining deformations occurring in close-to-wall galleries. Squeezing or convergence of headings is only a portion of the entire process of ground movement caused by ground disturbance due to workings. The term "squeezing of headings" is to be understood as a shortening of the distance between a point set on the roof of a heading and the corresponding one on the floor. It is very important to know the rules governing the process of squeezing in a particular mining system since it affords possibilities to define changes of the process and its parameters at any moment for a given system. This is of utmost importance because convergence of a heading is one of the most significant manifestations of ground pressure which has already been proved by studies performed by Everling (1). On the basis of those studies it has been observed that there exists an almost linear relation between the rate of convergence and loading [(Fig. 2)]. This, in turn, means that the deformations of the already exploited portion of heading are proportional to the pressure changes.

Jan 1, 1982

By C. Sun

The Leeville underground mine has been in operation since 2006 and currently produces 2,903 t (3,200 st) of ore per day, with an average gold grade of 0.4 opt. The mine’s horizontal extent is large, 762 by 152 m (2,500 by 500 ft), while its vertical extent is 6 to 61 m (20 to 200 ft). A high density of joints occurs within the host rock. Based on rock mass rating and field observation, the ground conditions at Leeville can be characterized as poor to very poor. As such, heavy ground support is required for its mining operation. Ore zones with a height in excess of 10 m (35 ft) are considered for longhole stoping. A typical stope measures 6 m (20 ft) wide, 30 to 55 m (100 to 180 ft) long, depending on the ground conditions, and 10 to 30 m (35 to 100 ft) high, depending the thickness of the ore body, yielding 9,100 to 18,000 t (10,000 to 20,000 st) when completed. Narrow ore zones, less than 10 m (35 ft), are mined using cut and fill. Drifts at the Leeville Mine are 4.6 m (15 ft) wide by 4.6 m (15 ft) high. Because of poor ground conditions at this mine, the establishment of a ground control monitoring system is key to operating both safely and successfully. This monitoring system is composed of comprehensive instrument design and installation. Instruments include multi-point borehole extensometers (MPBX) and “stretch measurement to assess reinforcement tension” (SMART) cables. The monitoring system covers the mining zones and infrastructure openings. After about two years’ application and measurement, useful data has been collected and continues to be collected; this information will be used to design future stopes and infrastructure. The system makes engineering and operation teams able to do their job with more confidence and efficiency.

Jan 1, 2009

By Richard E. Otoo, Evan J. Owen, Virginia T. McLemore

Disruption in critical minerals supply chains has resulted in the evaluation of various types of mineral deposits for critical minerals potential. Much of the study on critical minerals focuses on occurrence and characterization, but little research has addressed what concentrations of critical minerals in a mineral deposit are required to make an exploration target into an operating mine. Understanding the cut-off grades of ore deposits being actively mined is one criterion to determine if concentrations in an exploration target are high enough. Cut-off grade is defined as the minimum amount of mineral contained in a ton of ore that is sent to the processing plant. Among many factors, cut-off grade depends upon the size and type of the deposit and mining operation, the processing technique, and market prices. This research does not aim to define cut-offs for determining if a mineral deposit is economic. Rather, it defines estimates of concentrations of critical minerals that could be considered good enough for further exploration. For example, ~2% total rare earth oxide (TREO) is the cut-off grade for Mt. Pass carbonatite, but 500 ppm TREO could be an exploration target for coals.

Feb 1, 2025

By Robert C. Freas

Over the past twenty years people throughout the world, but particularly in the United States, have been taking an increasing interest in the environment, sources and causes of pollution, and pollution abatement. Air quality in the United States has been and continues to be an area of primary emphasis. In 1970, the US Congress passed the Clean Air Act and subsequently revised and strengthened it in 1977 with the issuance of the New Source Performance Standards. The Act has been further strengthened with the passage of the 1990 Amendments. By far the largest single source of sulfur dioxide (SO,) pollutants are coal fued electric generating power stations. Hence, a substantial portion of the flue gas desulfurization (FGD) research and equipment installation has been geared to the utility industry. Several competing FGD technologies were touted during the period 1970 to 1990 with varying degrees of success. Subsequently, the more successful technologies have been accepted, revised, and improved to the point that by 1991 third and fourth generation technology is available. A second area of emphasis for FGD has been coal fired industrial boilers. While individually they are much smaller than any electric utility generating station, they do represent a significant source of sulfur pollution. However, due to the size of industrial boilers and their location within industrial and educational complexes, the wet scrubber technology being employed by the utilities is not appropriate for these applications. Hence, fluidized bed combustion (FBC) technology has been developed for the industrial boilers. Since the installation of the first full scale test unit at Georgetown University, several equipment vendors have come forward with an increasing array of more sophisticated FBC units. Currently, FBC technology has matured to the point that the Tennessee Valley Authority (TVA), in cooperation with the Electric Power Research Institute (EPRI), has installed an FBC system on a 250 MW test unit at the Shawnee Power Station in Kentucky.

Jan 1, 1994

By Poltak Sinaga

PT Kaltim Prima Coal's 13.1 km overland conveyor was commissioned in 1991. It is of conventional 3 roller 350 troughed belt type. Cost and performance optimisation during initial design ended up with 5.4m/s belt speed, 1,000mm belt width to convey 1,350tph, and 7mtpa of coal. Despite high initial figure, the belt speed was lifted to 6.5 mps in 1996 to accommodate mine throughput increase. In 2002, new low loss ST2100 1,100mm wide belt replaced the old ST2250 due for change-out. An upgrade project was initiated at the end of 2003 to further increase the belt speed to 8.5 mps, hence to increase the OLC capacity to 30mtpa. Performance data, experience of site personnel, site observation and tests, benchmarking, and information from equipment manufacturers were major inputs to the design review. The project fast track was another challenge in addition to executing modifications on a production lifeline. The project was completed within fifteen months and the OLC was successfully commissioned at 8.5 mps belt speed in February 2005. The OLC has been to date conveying 4200tph satisfactorily.

Jan 1, 2008

By Sun Guangzhong, Liang Jinhuo

Adverse geological condition is a major factor which makes construction difficulty in tunneling. But if it is predicted and tunnel support is made efficiently in time, the above difficulty can be reduced. It is necessary to develop one or several effective and economical geological methods for prediction of tunnel geology while expensive and time-consuming instruments are used. This paper reviews and proposes several geological methods for prediction of fault, seam, contact zone, and groundwater inrush. These methods have been proved to be effective and economical in tunneling practice in China.

Jan 1, 1987

By D. M. Wyslouzil

Conditioning, in the conventional sense, means providing sufficient agitation and contact time for the reagents to react with the minerals in the ground ore. High intensity conditioning (HIC) on the other hand, as described in this paper, recognizes the need to exceed this minimum power input over a suitable length of time to induce aggregation of the finest size fraction. Time alone is not sufficient to achieve aggregation. The threshold minimum power input, kW/m3, depends on many surface properties of the fine particles and can vary considerably. In addition, the mechanical aspects and the chemical conditions must be matched to achieve good aggregation. Treatment of complex sulphide ores, requiring fine grinding for liberation, offers a large field for the application of HIC. Improved flotation rates and enhanced selectivity are some of the benefits that can be expected. This unit operation has now reached the level of commercial application. Lakefield Research considered HIC not from a fundamental point of view but as a means of solving difficult mineral processing situations arising in actual operating plants. This paper summarizes the effects of the various chemical reagent combinations that had been applied to promote faster, more selective flotation, higher mineral recoveries and cleaner separations, using HIC.

Jan 1, 1995