Search Documents

By R. L. Eppley

The Blacklick Creek Watershed Association was awarded a $158,000 Growing Greener grant from the Pennsylvania Department of Environmental Protection in 2002 for the design and construction of a sulfate reducing bioreactor (SRBR) cell to treat acidic discharge from the Judy 14 abandoned underground coal mine near Indiana, PA. The vertical flow SRBR was designed to treat 38 liters per minute of MIW containing elevated concentrations of aluminum and iron. Other treatment systems at this site plugged due to aluminum precipitates; this problem did not occur in the SRBR. The bioreactor has been periodically overloaded with flows up to six times the design rate. To date, the only maintenance performed on the unit has been the addition of hay to the surface of the unit in response to less than expected performance. The periodic hay additions appear to have restored the SRBR to nearly post-construction levels. Since construction, the SRBR has treated about 136,000 cubic meters (36 million US gallons) of MIW.

Jan 1, 2010

By S. K. Kawatra

In order to meet federal air pollution guidelines, it is necessary to remove a considerable quantity of sulfur from many North American coals. This may be accomplished by oxidizing the sulfur to water soluble forms, followed by washing the coal. Selective oxidation of the various sulfur forms can be accomplished through the use of a variety of types of bacteria. In this paper, the various bacteria and their requirements are described, and processes using bacteria to remove coal sulfur are discussed.

Jan 1, 1987

By C. Garcia, A. Potulska, J. J. Opazo, T. Comi

"The Sierra Gorda SCM sulfide ore processing plant began commissioning in the third quarter of 2014. Located in the Atacama Desert in northern Chile, the project is an open pit mine and Copper-Molybdenum processing plant is one of the most highly-instrumented operations in the world. It is the first hard rock operation in Chile and the second in South America to utilize HPGR technology. It is a significant Molybdenum resource especially in the first five years and the Molybdenum separation plant is complex. Designed to process up to 60 million lbs. of fine Molybdenum per year, it uses the latest technology and equipment to ensure superior recovery and product quality. It also has gas handling and alarm systems to fulfil the Company’s vision of “Zero Harm”. This paper discusses the overall operation and issues relating to the concentrator start-up. These include a review of the mineral processing design, the unified process control center and management information systems, and the correlation of geological and metallurgical performance data (mine-to-mill) for use in anticipating and preparing for treatment of diverse ore deliveries. INTRODUCTION Sierra Gorda SCM is a joint venture partnership with KGHM International (owned by KGHM SA, Poland), Sumitomo Metal Mining, and Sumitomo Corporation (Japan) operating in northern Chile. The Sierra Gorda open pit mine and Copper-Molybdenum processing plant will become one of the largest mines in the world. The need for optimum production efficiency and sustainability has driven the creation of the most modern, well-instrumented mine in Chile. This paper contains a general review of the project including geology and history. This was a very fast-track project going from greenfield site acquisition to mill start-up in 10 years. Highly-experienced and motivated engineers and technical staff have overcome many significant challenges resulting in a rapid ramp-up of production capacity. A potential expansion to double the production rate in the fourth year of operation has also been intensely studied. The Sierra Gorda property is located in the Atacama Desert of northern Chile, in the District of Sierra Gorda, Region II of Antofagasta, Chile (see Figure 1). There is almost no precipitation in this area. The mine site is generally flat with some rolling hills. The project is located about 5 km from the village of Sierra Gorda at an elevation of approximately 1,700 m above mean sea level. The village is near a highway and railway line. The city of Calama, home of the famous Chuquicamata Mine, is located about 60 km northeast of Sierra Gorda. In addition, the SG mine is in the midst of numerous other mines including Spence, Esperanza, Mantos Blancos, El Tesoro, Lomas Bayas, Gabriela Mistral, El Abra, Radomiro Tomic, and Escondida, to name a few."

Jan 1, 2015

By C. Sun

The Leeville underground mine has been in operation since 2006 and currently produces 3,300 tons of ore per day with an average gold grade of 0.4 opt. The mine has a large horizontal extent of 2,500 feet by 500 feet and a vertical extent of 20 to 200 feet. Based on the characteristics of the ore bodies, the deposits are divided into several mining zones. The geotechnical properties of mining zones are also different from one zone to another. A successful geotechnical collection system is very important for the mining designs and operations in the Leeville underground mine.

Jan 1, 2010

By T. J. Jr. Corwin

This paper will cover the problems confronting an owner when planning and estimating the cost of a proposed tunnel. Three factors are known: the length, size and the time allocated for the completion of the work. In general the difficulties encountered when driving a tunnel in California are the greatest at the lower elevations and in the Coast Range and are minimal in the Sierra Nevada mountains particularly in granitic formation. The writer will discuss the experience gained from observing the driving of about 120 miles of tunnel in California as well as the repairs of some tunnels. SIZE OF TUNNELS It is known that a small tunnel may be more costly to drive than one of somewhat larger dimensions. This fact was found to be true when a tunnel about 4,000 feet long was constructed to eliminate 7 miles of canal. The formation was lava so it was anticipated the ground would be self supporting because of the small bore. Actually the tunnel required support for most of its length and working conditions were poor. It became apparent that a larger size could have been driven at no additional cost and probably in less time. On another unlined tunnel, to be driven in granitic formation, the contractor was given the option of using

Jan 1, 1974

By J. C. Edwards, C. C. Hwang

A computational fluid dynamics (CFD) program was applied to fire spread along combustibles in a ventilated mine entry. The rate of flame spread was evaluated for the ribs and roof of a coal mine entry; timber sets; and a conveyor belt. The CFD program models char forming materials with temperature dependent thermal properties. The program solves three dimensional time dependent flow equations with a mixture fraction model for the gas phase reactions. Radiant heat exchange is evaluated for non-scattering gas. The CFD program predicted a flame spread rate of 0.0145 m / s for an actual coal mine fire in which the estimated flame spread rate was 0.0086 m / s. This overestimated flame spread rate was a possible consequence of the presence of inert materials in the mine entry’s roof and ribs. CFD fire spread rate predictions of 0.043 m / s and 0.73 m / s bounded the measured value of 0.27 m / s for fire spread along Douglas Fir timber sets in a tunnel.

Jan 1, 2006

By J. Platt

Debate over acid rain legislation has presented a moving target for coal and utility company planners attempting to figure out how legislation will affect their business environment. In spite of disagreement among experts, the prospect for continued change, and persistent --perhaps even growing --uncertainty, a great deal has been learned about coal market dynamics. This paper reviews progress and describes some of the major problems and controversies.

Jan 1, 1990

By J. D. Grace

[Screening by centrifugal force is an unique, subject, for with the exception of only one vibrating screen presently on the market, all vibrating screens depend upon, gravity to pass material through a sizing mesh or screen cloth. This one screen that sizes by centrifugal force and utilizes gravity only to convey materiel along the screen, is the SYMONS V-Screen. This screen was designed by Loren Symons, a member of the family that has contributed so much to the metallic and non-metallic mineral processing industries. Among Symons' other outstanding contribution to these industries are the original Cone Crusher which revolutionized reduction crushing practice, the first high-speed horizontal vibrating screen, the original Rod Deck Screen, and one of the earliest vibrating Bar Grizzlies.]

Jan 1, 1965

By Lim Thi Duong, Du Duy Bui, Thuat Ngoc Pham, Chuc Ngoc Pham, Que Anh Nguyen, Hoa Anh Bui, Chi Thi Ha Nguyen, Hoan Thanh Nguyen, Bac Quang Nguyen, Kien Trung Nguyen, Dung Trung Doan, Nhiem Ngoc Dao

The microstructures and kinetics of a rich iron ore ( TFe = 65.84%) of Na Rua mine, Vietnam, used for the iron production were investigated in this study. Thermal behaviors of iron ores were well-examined by heating microscopy, thermogravimetric analysis, and differential thermal analysis. After being pelletized and then oxidatively fired at 500–1200 °C for 2 h, the pellets fired at 1200 °C (P1200) displayed a hard and dense structure with a decent compressive strength of 317.9 kg/pellet whereas those fired at 500 °C (P500) had a soft and spongy structure. The reduction of iron pellets conducted in a flow of a 60–100% CO2/ Ar gas mixture at 900–1100 °C showed significantly higher efficiency than the reduction using coal. The spongy pellets showed superior performance for the reduction in the CO/Ar gas mixture compared to the dense ones, compatible with the production of sponge iron. When mixed with an amount of coal, P1200 designed for iron production in the blast furnace demonstrated an impressive reduction activity compared to P500 and previous studies. The kinetics of pellet reduction was determined by the diffusion of substances through the solid product layers having the mathematical model of 1 − 2 3 f − (1 − f )2∕3 = kt . The microstructures of pellets during the oxidative firing and reduction were also examined by X-ray diffractometry; scanning electronic microscopy; energy-dispersive X-ray spectroscopy; and Brunauer, Emmet, and Teller method.

Jun 7, 2022

By Yinan Zhang, Yi Luo

The widely used R70 method is modified to measure the self-heating propensity of low-rank coals. This modified R70 method enables the introduction of controlled amount of moist oxygen into the reaction vessel. Three coal lumps were collected from three different locations in a surface mine in the Powder River Basin. The coal samples were tested in oxygen flow with controlled moisture content under adiabatic condition. By measuring the relative humidity at the exhaust exit point of the testing setup, the flux and cumulative wetting heat that is consumed by coal samples can be determined. Through a better way of determining the coal’s specific heat, the total heat, including heat of wetting and coal’s oxidation heat, required to raise coal to a given temperature can be determined. Then, the contribution of heat of wetting at the different stages of the testing is quantified. The effects of evaporative heat through a group of tests have also been quantified. From this research, a better understanding of the effect of wetting heat on inducing low-rank coal’s spontaneous combustion can be acquired.

Nov 30, 2022

By Michael J. Miller

The demand and supply of wollastonite has gone through a dynamic period in the 1990's. A 10% -15% growth rate of demand stimulated interest in evaluating new projects. However, the mid-1990's brought declining prices for commodity applications and natural barriers to entry for technical applications, making many of these potential projects uneconomic. Successful projects that were brought to market were done so by incumbent producers. This work examines the competitive structure of the wollastonite market by evaluating the strategic decisions of the industry leader, NYCO Minerals Inc., and a new market entrant, Orleans Resources, in an attempt to identify the environmental threats and opportunities of this industry. Results suggest new entrants like Orleans Resources face significant entry barriers for technical applications, while NYCO Minerals could improve its profitability by having less exposure to commodity applications.

Jan 1, 1999

By M. Yekich, W. R. Reed, G. Ross, M. Shahan

"Canopy air curtains on roof bolting machines have been proven to protect miners from respirable dust, preventing their overexposure to dust. Another desired application for canopy air curtains is in the compartments of shuttle cars. The challenges faced in developing the design of canopy air curtains for shuttle cars include mine ventilation rates in tandem with the shuttle car tram speeds. The resulting cab airspeeds may exceed 182 m/min (600 fpm), as found in the present study conducted in a central Appalachian underground coal mine by U.S. National Institute for Occupational Safety and Health (NIOSH) researchers. Prior research and laboratory testing had indicated that successfully protecting a miner in high air velocities is difficult, because the clean air from the canopy air curtain is unable to penetrate through the high-velocity mine air. In this study, the dust concentrations to which a shuttle car operator was exposed were measured, and air velocities experienced by the operator were measured as well using a recording vane anemometer. The results indicate that the highest exposure to respirable dust, 2.22 mg/m3, occurred when the shuttle car was loading at the continuous miner, where the average airspeed was 48 m/min (157 fpm). While tramming, the operator was exposed to 0.77 mg/m3 of respirable dust with an average airspeed of 62 m/min (203 fpm). This study indicates that a canopy air curtain system can be designed to greatly reduce an operator’s exposure to respirable dust by providing clean air to the operator, as the majority of the operator’s dust exposure occurs in air velocities slower than 61 m/min (200 fpm). IntroductionThe U.S. National Institute for Occupational Safety and Health (NIOSH) issued contract #200-2015-63485 to develop a canopy air curtain for coal mine shuttle cars with Marshall University and J.H. Fletcher & Co. (Salem, Begley and Ross, 2016). The proposed design maintains a design similar to that of a roof bolter canopy air curtain by providing filtered air through a blower over the operator. The plenum, which will provide uniform airflow over the operator, is anticipated to be built into the shuttle car canopy. One of the main interferences with a canopy air curtain is ventilation airflow perpendicular to the plenum airflow (Engel, Johnson and Raether, 1987). This ventilation airflow can shear the downward flow from the plenum, and this shear can reduce the effectiveness of the canopy air curtain by either disrupting the downward flow or allowing contaminated mine air into the canopy air curtain zone of protection."

Jan 11, 2018

By Benjamin Grunauer, Anthony Iannacchione, Taylor DaCanal

"In Pennsylvania’s rich mining history, various forms of room-and-pillar mining have been in use for over 150 years. Longwall mining, introduced in the late 1960s, occupies only the last 60 of those 150 years and now represents the dominant method of extracting coal in the Pittsburgh coalbed. The introduction of longwall mining allowed larger quantities of coal to be extracted in safer and more efficient manners than room-and-pillar mining. However, the associated formation of subsidence basins have elevated both the number and intensity of watersource and surface structure impacts. When these first longwall panels were mined the factors responsible for these impacts were poorly understood and regulations were focused only on surface structures. Today, with over 600 panels mined under a wide range of conditions, these factors are known and regulations have developed to help mitigate water supply and surface structure impacts.The cause and severity of surface effects are thought to be dependent on multiple factors, including the location within the subsidence basin, overburden, panel width, and orientation of the panel. The changing characteristics of over 600 longwall panels mined in the last 60 years are analyzed to determine factors important in subsidence related surface impacts. This study compares the location of the surface impacts with the longwall panel size, overburden, and maximum predicted vertical subsidence. The data shows that changing these characteristics are impacting surface features in a significant manner as measured by the number of company liable reported effects.INTRODUCTIONLongwall mining has occurred in Pennsylvania for over 60 years, and at the current mining rates, longwall mining is expected to continue in the Pennsylvania Pittsburgh Coalbed until the reserves are exhausted. Figure 1 shows all mining that has occurred in the Pittsburgh Coalbed, as well as the area that is left to mine. It is predicted that there are 40 years left of longwall mining on the Pittsburgh Coalbed, under the assumption that 50% of the total 280,000 acres will be mined at the current rate of 3500 acres/year."

Jan 1, 2019

By M. A. Evanto

Since the late 1970's, the Roof Control Division (RCD) of MSHA's Technical Support has been performing linear analyses for the enhancement of miners' safety. This remote sensing process uses Landsat data to predict areas of potentially hazardous ground conditions in underground mines. To date approximately 700 analyses have been completed by the RCD, with nearly 75 being performed with the current equipment, software and methodology which was updated in early 1995. While success is difficult to measure, requests for linear analyses continue to come from large and small mining companies which suggests the industry's acceptance of the process.

Jan 1, 1998

By H. L. Holden

The single line grinding circuit at Bond Gold's Colosseum mine consists of variable speed drive semi-autogenous (SAG) milling and secondary grinding with a fixed speed ball mill. There are several advantages and disadvantages of operating SAG mills with variable speed drives. Discussion in this paper will focus on the effects of variable speed SAG milling in relation to mill liner wear, grinding media consumption, and mill operating availability. Operating experiences, corresponding mill data, and pertinent design changes are also presented.

Jan 1, 1991

By L. Yuan, J. H. Rowland III

"In 1995 and 2003, the Mine Safety Health Administration (MSHA) conducted surveys to determine the number of atmospheric monitoring systems (AMS) being used in underground coal mines in the United States. The survey reports showed data for the different AMS manufacturers, the different types of equipment monitored, and the different type of gas sensors and their locations. Since the last survey in 2003, MSHA has changed the regulation requirements for early fire detection along the belt haulage entries. As of December 31, 2009, point-type heat sensors were prohibited for use for an early fire detection system; instead carbon monoxide (CO) sensors are now required. This report will examine the number of AMS currently used in underground mines in the United States to see if there is a change in their use. The locations and parameters monitored by AMS are also discussed. INTRODUCTION The last survey conducted by the Mine Safety and Health Administration (MSHA) on atmospheric monitoring systems (AMS) used in underground coal mines in the United States (US) was in 2003 [1]. The survey report states that since 1995 there had been a steady increase in the use of AMS in underground coal mines as the technology of CO sensors was improved by manufacturers. AMS had become more reliable and some CO sensors could be purchased with the capability to discriminate between the CO produced from a fire versus CO produced from diesel equipment. This increase in reliability had reduced the number of false alarms and the response time. The faster response time to a developing fire allowed for the miners to take the necessary action to put out the fire or exit the mine. It should also be noted that at the time of last MSHA survey, some mines still used point-type heat sensors to detect the presence of a fire on conveyor belts. This detection method works by measuring the temperature of the air around the sensor. As a fire starts to develop, smoke and hot gases are produced from the combustion process, and the air is heated up. Once the air and gases reach a designated temperature detected by the point-type heat sensor, a fire alarm signal is generated. Studies have shown that the response times for detecting the presence of a fire using CO sensors are much shorter than using point-type heat sensors [2]. Finally, since the last MSHA survey, regulations have changed on the type of automatic fire detection systems permitted to be used in conveyor belt entries. As of December 31, 2009, point-type heat sensors are not permitted to be used for fire detection in underground coal mines in the US; instead CO sensors are required as a replacement (30 CFR 75.1103-4). This study will examine how the changing of the above regulations has impacted the use of CO sensors in underground coal mines in the US compared to their use based on the last MSHA survey. Importantly, in the previous MSHA survey, the data was recorded for producing and non-producing coal mines. In this study, only the data from the producing coal mines was recorded. Data was collected from a total of 235 coal mines for this study with the help of the MSHA district offices."

Jan 1, 2017

By Marko Oosthuizen, Charl P. Botha, Lidia Auret, Annelette Malan, Marthie de Leeuw

Flotation performance is affected by upstream disturbances (e.g., mineralogy, water quality, flow rate) and controlled variables (e.g., pulp level and air addition). Process disruptions can lead to undesired conditions, such as pulp overflowing flotation cells (with insignificant/absent froth, and thus no valuable mineral concentration). Early detection and appropriate intervention of pulping events improves concentrator performance. An approach to real time flotation pulping event detection by means of convolutional neural networks is presented, including a case study of the industrial application of this technology on three flotation banks.

Feb 22, 2026

By M. S. Klima

Coal gasification solid residue (slag) contains unconverted carbon (char), which is considered an impurity for utilization applications of slag. Under this study, table concentration was used to process approximately 24,000 pounds of a nominal-3.4 mm gasifier slag (-85% ash) to separate high (-100%) ash slag from low (-50%) ash char. The results indicated a nearly ideal separation of the slag from the char for sizes coarser than about 1 mm. An overall slag yield of 71 % was obtained. The slag was sufficiently clean to be used as feed material for the production of expanded lightweight aggregate. The recovered char had an ash content of about 47% and was a nominal -1mm in size.

Jan 1, 1997

By M. V. Chari

A prime objective of physical coal cleaning is the separation of raw coal into a clean coal product with the required low ash and pyritic sulfur content and a high ash refuse. The refuse should also contain a minimum amount of combustible matter. In order to be effective, cleaning processes require that the mineral matter in the feed, including pyrite, be largely discrete and free particles, liberated so that the particles are not attached or embedded in coal. Liberation of mineral matter from coal, particularly pyrite, was investigated by Bechtel as part of two fine coal cleaning research programs sponsored by the Department Of Energy (DOE), Pittsburgh Energy Technology Center (PETC). Two proof-of-concept (POC) plants, each with a capacity of 900 kg per hour, were installed and tested to evaluate production of ultra-clean coal using microbubble flotation and spherical agglomeration technologies. The plants were designed to produce clean coal with 2 percent ash and pyrite content lower than that achievable by conventional methods. Also, the quality targets were to be attained at energy recoveries above 80 percent. Bench-scale flotation and agglomeration tests indicated that it would be practical to grind the 6 mm top size feed coal to a mean particle size (050) of 10 micrometers in the POC test plant. In this part of the paper, the steps taken in the grinding circuit to maximize liberation of mineral matter are described.

Jan 1, 1991

By M. S. Enders

The McDonald deposit is a volcanic-hosted epithermal gold resource that is estimated to contain 251,000 kg of gold in 375 Mt of ore at an average grade of 0.7 g/t gold. Phelps Dodge exploration geologists, working for the Seven-Up Pete Joint Venture, discovered the deposit in 1989. By the end of 1992, 494 drill holes for over 113,000 m of drilling, bulk sampling, soil geochemistry, geophysics, metallurgical testing, engineering, and environmental studies had been completed to support feasibility studies. The discovery of McDonald required vision, persistence, and commitment of everyone from the geologist on the drill rig to the senior management of the company.

Jan 1, 1995