Search Documents

By S. Afrouz, C. Keles, W. R. Reed, E. Sarver, T. Akinseye, A. Greth, L. Pan, F. Animah

Among underground coal miners, roof bolter operators are generally considered to have some of the highest risks for hazardous respirable dust exposure. This is because bolting requires drilling into roof strata that can often be a source of silica and silicate dust, which are associated with occupational lung diseases. However, little is known about the variability of dust characteristics (e.g., mineralogy constituents, particle size) in the vicinity of the bolter—or when specific dust controls are applied. As part of a prior NIOSH study, respirable dust samples were collected during several different events in standardized locations around an active roof bolter, and personal samples were also collected from the operator during the cleanout of the bolter’s dust collection system when it was equipped with a novel wet dust box versus a traditional dry box. Those samples were made available for follow-up analysis by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), as well as direct-on-filter Fourier transform infrared spectroscopy (FTIR). Results showed variability in dust constituents and particle sizes at locations around the roof bolter, and indicated some event-to-event differences in dust sources. Additionally, compared to the dry dust box, the wet dust box appeared to reduce (by 41–82%) the relative silica and silicate content in the respirable dust to which the operator was exposed during cleanout. Furthermore, an inter-laboratory comparison demonstrated the reproducibility of a standardized direct-on-filter FTIR method for estimating quartz mass (i.e., the predominant form of crystalline silica) in respirable coal mine dust samples. However, for constituent analysis by SEM–EDX, differences observed between results from two independent labs indicate that standardization of the analytical protocol is necessary to enable comparability of results.

Jan 5, 2024

By Robert L. Major

The expanded role which coal has been assigned in the energy future of the United States has raised numerous policy questions. The very complexity of these questions makes them suitable to analysis by econometric models. However, as the Wall Street Journal indicated in its recent article, business' success with such models have been mixed. I have been asked to present my views as to how coal producers can use such models and in what ways the industry is likely to be impacted by such models. I do not presume to speak for the whole coal industry, but only to share with you the personal observations of one who has worked "both sides of the street", having been employed' both by government and a consulting firm prior to joining the coal industry. In my opinion, the use of econometric models to analyze the coal industry will impact the coal producers in two main ways. First, their use by government will have a profound impact on future government policies related to the mining, transportation and utilization of coal. Second, such models, when properly calibrated and refined, may become useful tools for the coal producers in doing market research and long-range planning. While the former has already begun to impact on the operating environment or the coal industry, the latter is still in the embryo stage.

Jan 1, 1977

By H. Wen, X. Zhai

"The Jurassic coal fields which lay in west China are the major energy base and contain half of coal resources in China. Due to the gather and degeneration rules, the spontaneous combustion characteristic of Jurassic coal is distinguished with permo-carboniferous coal, which needs to be studied deeply. Programmed heating experiments of five Jurassic coal samples and three permo-carboniferous coal samples from different primal coal fields in West China were conducted to identify the characteristic parameters in the low temperature stage of oxidation and spontaneous combustion. The experiments were carried out under non-isothermal heating conditions up to 180? at the heating rate of 0.33?/min in an air atmosphere. The result showed that oxygen consumption rate, CO gas production rate and heating intensity of all coal samples increased with the rising of the temperature, which of the Jurassic coal was higher than that of Permian-carboniferous coal. The C2H4 gas of Jurassic coal generated earlier, more than that of Permian-carboniferous coal in the process of oxidation and spontaneous combustion. It indicated that the Jurassic coal was easier to be oxidized and spontaneous combustion and the index parameters of spontaneous combustion were different between the Jurassic coal and permo-carboniferous coal.INTRODUCTION Coal was the foundation of industry development, and occupied 70% of primary energy production and consumption structure in China. According to the data of the 3rd coalfield prediction, 39.6% of the total coal resources were located in northwest Jurassic coal field in China [1], where the quality of coal was excellent. The study of northwest Jurassic coal already dated from the 80s of the 20th century, about coal rock composition, coal metamorphism [2], coal-derived hydrocarbons, coal structure [3], etc. The results of these studies showed that the composition and properties of Jurassic coal was obviously different from Permian-carboniferous coal, as well as the characteristic of spontaneous combustion [4]. As a result, the spontaneous combustion characteristic of Jurassic coal particularly needed to be studied. Now more and more methods could be conducted to test the characteristics of coal spontaneous combustion, for example, thermal analysis technology [5-7], programmed heating experiment [8-10] and coal spontaneous combustion experiment [11,12]. In these methods, programmed heating experiment could be conducted to determine the oxygen consumption rate, CO gas production rate and heating intensity quickly."

Jan 1, 2015

By Carlos Tarazaga

Progressive Design-Build (PDB) is an emerging variation of alternative delivery programs in the underground construction industry. PDB refers to the way a construction project design is developed by the Owner and the Design-Builder in a step-by-step process. According to the Design-Build Institute of America (DBIA), Progressive Design-Build allows the design and construction team to collaborate during the earliest stages of project development. This enables engagement between the three key players in a construction contract: the owner, the designer, and the contractor. Is the PDB the best alternative program delivery for large contracts? What is the perspective of the private sector? This paper will provide an overview of the different alternative delivery programs used in the underground industry, pros and cons of each of programs, and the perspective of the designers and contractors. The paper will focus on how the PDB works, reasons why owners should consider PDB for their projects, best collaboration strategies among owners, designers, and contractors to deliver a successful project, and how to manage the project risks using a PDB method.

Jun 13, 2023

To gather additional field data from the western United States, researchers from the National Institute for Occupational Safety and Health (NIOSH) installed an array of field instrumentation at a longwall coal mine in Central Utah. The purpose of this field site was to monitor ground movement and changes in pressure during mining where conditions include massive, stiff overburden and relatively deep cover. To accomplish this, field instrumentation was installed in the two-entry gate road between the fifth and sixth longwall panel in the current mining district.

Jan 7, 2020

By D. Suarez

The work of engineers responsible for the design and performance of mine facilities is often challenged by economic and practical constraints in the field. Problems have developed in implementing design criteria dictated by persons or agencies not familiar with the dynamic nature of mine engineering. Regional and site-specific conditions frequently require changes to standard designs, or the use of a completely innovative approach, which is not provided for in the regulations. The implementation of engineering design, therefore, usually requires a hard-sell approach to management and regulatory agencies that allows for a happy-medium to all parties concerned. Flexibility on the part of the regulatory agencies is needed to solve operational and environmental problems with sound engineering. Typical hydrologic issues which will be discussed fall in the following general categories: ? Design criteria for sizing water control structures (i.e., culverts, diversion and sedimentation ponds, ditches, etc.) ? Implementation (construction and operation) difficulties ? Regulatory compliance ? Reclamation planning with hydrologic considerations ? Protection of groundwater resources

Jan 1, 1986

By M. J. Gula

In the solvent extraction -electrowinning recovery of copper from oxide or sulfide ores there is a continuous transfer of iron and other impurities from the primary leach solution to the copper electrowinning electrolyte via chemical transfer or mechanical entrainment. Iron is the principal impurity that has to be controlled in the electrolyte by a "bleeding" of the electrowinning solution. This bleeding transfers copper and sulfuric acid back to the primary leach circuit along with the iron. Copper is recovered via the solvent extraction process and generally the sulfuric acid is used as a reagent in leaching. Unfortunately, cobalt, which is added to the electrowinning solution to modify the anodic process, is irreversibly lost through the bleeding operation. This cobalt loss represents a significant operating cost to SX-EW copper producers. DiphonixTM ion exchange resin contains diphosphonic acid and sulfonic acid functional groups on a polystyrene-divinyl benzene matrix. This resin has been found to strongly and selectively extract ferric ion from copper sulfate -sulfuric acid solutions containing cobalt. Thus, an ion exchange process using DiphonixTM resin for the control of iron has been developed to replace the conventional bleed stream process. The new process minimizes the loss of cobalt from the electrowinning circuit and strips the iron into a sulfate based solution suitable for leach solution makeup. In addition, this process can effect a lowering of the total iron concentration in the electrolyte circuit with an associated increase in current efficiency. In this paper, data on the loading and elution of iron are presented. Laboratory and pilot scale data will be discussed along with information on process design and comparative economics.

Jan 1, 1996

By D. W. Jahn

Road construction in the near future will require contractors to guarantee that a project will remain trouble free for years after the project has been completed. These guarantees will challenge aggregate producers to become technically proficient in judging performance of their products. Testing procedures are described that may be used to predict performance of concrete and asphalt pavements before being committed into a construction project, and may also be used as quality assurance tools during construction to monitor performance as construction proceeds.

Jan 1, 1995

By Richard Weinstein, Richard Snoby

There are many advantages to upgrading coal with dry jigging technology. The most obvious is the lack of process water, which eliminates the need for fines dewatering and slurry confinement. Dry jigging eliminates the clean coal moisture penalty associated with wet processing. Particulate emissions are virtually nonexistent due to inclusions of fabric dust collectors on all modern dry jig plants. Because of the environmentally friendly nature of dry jig plants, installation permits are often measured in days, not months. There has also been a fundamental advance in dry jigging efficiency. All of these advantages have renewed the coal industry’s interest in dry jigging. But air jigging is not right for every application. There are limitations due to particle size, particle shape, moisture and near gravity content. This article explores the evolution of dry jigging. It reviews parameters important for determining the suitability of dry jigging. It also compares historical performance data as measured by imperfection, against results from modern dry jigging technology. The article also presents data from modern dry jig installations.

Jan 1, 2007

By H. Rush Spedden

A process has been developed and piloted to reject copper, lead, iron, phosphorus, bismuth, antimony, elemental sulfur, and insol from molybdenite concentrate without decomposing the contained molybdenite and rhenium. The impure concentrate is first heated with concentrated sulfuric acid at 260 to 290°C for 1 hour. This bake not only oxidizes the contaminating sulfides, but also activates the concentrate for later rejection of insol by flotation. Two stages of leaching follow the sulfation step. The first is an acidified water leach which extracts the oxidized copper, iron, and phosphorous; the second leach rejects the lead, bismuth, and antimony into a warm concentrated solution of sodium chloride. Final upgrading is achieved by conventional froth flotation. The chemistry of the process as well as results obtained from its implementation in a 5,000 lb/day pilot plant are presented.

Jan 1, 1971

By L. S. Harris

The application of briquetting in various chemical, mineral, mining and metallurgical processes has been rapidly increasing in the past two decades. This is, in part, due to the development of new, more economical and higher performance briquetting equipment. Some of these developments, which have reduced the operating and maintenance costs,, include anti-friction bearings, hydraulically applied pressure enclosed and sealed gearing and bearings, tapered predensification feed screws, water cooling and materials of construction capable of operating at temperatures up to 18000F, and control systems capable of maintaining optimum briquette quality control. The briquets can be formed into almost any desired size and shape, To date, with present rotary briquetting presses in the 25 to 500 ton force range, briquets from 1/4" to 6" length are presently being used, some of which are illustrated in Figure No. 1. In force fed rotary briquet machines, these shapes are produced by feeding the material in between a pair of counter rotating rolls, as illustrated in Figure No. 2. The rolls have forming dies indented into their circumferential surface, as illustrated in Figure No. 3.

Jan 1, 1973

By Greg Sanders, Michael Gilbert, James G. Shaughnessy

"A new raw water intake from the South Holston River to the Kingsport water treatment plant is under construction. The exploration for the 335 meter long horseshoe shaped tunnel design took advantage of the site topography along the alignment to better define the complex geology consisting of Knox Limestone and Sevier Shale formations separated by a fault zone. To assess the geological conditions and to determine the extent of the fault zone, a 183 meter long horizontal boring and geophysical investigation was performed along a portion of the tunnel’s horizontal alignment. Explorations defined the fault zone width at approximately 5 meters and packer testing along the alignment provided a means of estimating groundwater inflows. As the tunnel excavation advances, comparisons of exploratory data versus encountered conditions will be made. This paper provides details on the geotechnical investigation, lessons learned, and the influence of the geology on the tunnel design. PROJECT OVERVIEW The Kingsport WTP is supplied with raw water via the South Holston River. The City of Kingsport (City) owns and operates the Kingsport Water Treatment Plant (WTP). The existing raw water intake system, consisting of pumps, power supply, raw water piping and appurtenant facilities has been determined to be vulnerable to failure. The original Raw Water Pump Station (RWPS) was constructed in 1928 as part of the original Kingsport WTP project. The 1928 RWPS operated until 1970 when it was replaced by the existing RWPS. This existing system still utilizes the 1928 piping and piping tunnel. Improvements to the RWPS hydraulics and capacity are required to meet the City’s future water treatment needs. The system extracts water from the South Fork of the Holsten River and coveys it via three pressure pipelines to the WTP. The conveyance piping exits the RWPS, ascends approximately 23 m up a near vertical rock outcropping then enters a 120 m long tunnel. Upon exiting the tunnel the piping continues underground to the WTP. The drill and blast tunnel is horseshoe shaped and nominally 3.3 m high by 3.3 m wide. The easternmost 62.3 m of the tunnel is without any type of support. The remainder is lined with concrete. According to the City of Kingsport, the concrete lining was installed in the 1970’s as part of upgrades to the facility. An evaluation of the current facilities concluded that the conveyance piping was in poor condition and required replacement."

Jan 1, 2016

By Richard J. Robbins

This paper is presented with particular reference to the findings of the OECD Advisory Conference on tunneling held last July in Washington D. C. A great deal has been said about the Conference in the past few months, but it may be appropriate to review briefly the background and objectives of the Conference to better understand how the mining community can relate its underground excavation problems to the results of the Conference. OBJECTIVES OF THE OECD CONFERENCE The world demand for tunneling (the term tunneling is used here loosely to include almost all forms of underground excavation) is expected to grow at an in- creasing rate. During the decade of the ?70's, the demand is expected to at least double by comparison with the previous decade. Much of this increase in demand will be due to the rapid growth of urbanization around the world. As urban populations grow larger and denser, the conservation of surface land and the quality of the environment become more important. This aspect of the increasing demand poses a difficult challenge to those who must plan and implement urban development.

Jan 1, 1970

By Leland E. Paulson

The Grand Forks Energy Research Center and Commonwealth Edison of Chicago jointly conducted tests in which 400 tons each of subbituminous coal and lignite were dried in a commercial scale dryer, oil sprayed and cooled, then shipped in open-top rail cars from Pekin, IL to Grand Forks, ND and stockpiled. Cars containing raw coal and dried coal that had not been oil sprayed were also transported for comparative purposes. The tests were conducted in August and November of 1974. The subbituminous coal was dried from 26 to 16 pct moisture and the heating value was upgraded from 8,420 to 9,650 Btu/lb. The lignite was dried from 39 to 22 pct moisture and its heating value was increased from 6,420 to 8,300 Btu/lb. Before loading subbituminous coal was cooled to 115° F and sprayed with oil at a rate of from 2 to 6 gal/ton. Similarly, lignite was cooled to 85° F and oil sprayed at rates of from 1 to 2 gal/ton. Both shipments arrived in Grand Forks with a minimum of difficulty. The subbituminous coal was subjected to 2 inches of rain during transit with no change in average moisture content. The cars containing dried and oil treated coal had less material lost to wind than either cars containing raw or untreated dried coal. With both dried lignite and subbitnminous shipments, a moderate increase in temperature was measured during transit. With the subbituminous shipments, ignition occurred near poorly fitted bottom dump doors, but was limited to a very small area. The dried lignite was shipped when ambient temperatures were below freezing, and frozen coal was noted around the edge of the car. At Grand Forks, the coal was stockpiled using proven techniques and has remained stable to this date.

Jan 1, 1975

By George W. Parker

The ever increasing costs of labor and supplies have made it imperative that operators of open pits look for some way in which to cope with these increases. One of the most logical ways to increase the efficiency of an operation is by the introduction of larger haulage equipment, as generally haulage costs are the greater portion of the over all expenses. These larger haulage units require larger shovel units. In the late 1930's and the early 1940's large mining, quarrying and heavy construction operations had more or less standardized on the 4 to 6 cubic yard shovels. During this same period the haulage units were generally 22 to 27 tons. Some ten years ago 9 - 13 cubic yard shovels along with plus 50 ton haulage units were introduced by manufacturers in an effort to enable operators to decrease costs.

Jan 1, 1962

By C. L. Lin

The image-based On-line Particle Size Analyzer (OPSA) system has been developed at the University of Utah to measure particle size distributions under plant conditions where overlapped and segregated particles are being transported on a moving belt conveyor. Evaluation of the OPSA system at several plant sites has been completed. The results show a consistent agreement between the particle size distributions obtained from the OPSA system and those obtained from laboratory screen analysis of belt samples. These results and the stable performance of the OPSA system during the field tests suggest that continuous quality control of crushed products is possible using the OPSA system.

Jan 1, 1999

By William A. Turcotte

Introduction The need for water is fundamental to every minerals processing operation. Though this may sound rather elementary, it is one area that cannot be over- looked. Frank C. Quinn in his paper entitled "Water Is Water Is Water" (1967) said, "but it isn't as simple as that. Very often research is slowed down and production is hampered because of a lack of appreciation for the behavior of water." The quantity of water needed for any operation is determined from bench and pilot plant testing. The quality required by the process for both fresh and reuse water is also established during these two testing phases. Quinn's statements are true whether the process involves the paper industry, the minerals industry, or any other industry. It is not the author's intent to cover water quality, quantity, or re- cycle in specific terms, but to provide the reader with a general outline of the topic with reference to several valuable sources of information. The first part of the chapter will cover several of the areas that have been de- tailed by others and also provide a list of reference sources. The references at the end of the chapter are not all inclusive but will provide a good starting point. In the second part of the chapter, a detailed description, with flowsheet illustrations, is pro- vided on the evolution of the reclaim (reuse) water system at the Tilden concentrator. Mineral Industry Water Needs Beresford and Edler (1978) surmnarized the minerals industry's need for water this way: "minerals are necessary to a modern complex technological society. The minerals industry, while its water needs are relatively minor compared to large users such as agriculture, nevertheless requires a large quantity of water to carry out daily operations from mining to final product refining." In 1973 total water use in the United States was estimated at 15.14 billion cubic meters (4 trillion gallons) for the minerals industry. Of this, about 69% was recirculated within the system. In 1982 Watt and Horton stated that the percent of recycled water in the minerals industry had improved to 73%, showing the minerals industry is an efficient user of water and that steady improvement in water recycling is something the minerals industry can look to with pride. The percent of water needed by the United States' minerals industry was estimated in 1962 to be about 2% of the total water required by industry

Jan 1, 1986

Mine managers need better information to locate new opportunities and then to assess the effect of their decisions. We are developing the Intelligent Decision Support System (IDSS) and its two major modules, the Pattern Recognition System (PRS) and the Knowledge Representation Subsystem (KRS) to automatically provide the information from monitoring system sensors. This paper focuses on the KRS Algorithms that extract key information from lists of time study type event sequences. Because a static system cannot operate effectively in a dynamic mining environment, we are prototyping an index based technique that allows the system to adapt itself to this dynamic environment.

Jan 1, 1990

By E. Z. Casassa

There has been a recent revival of interest in concentrated coal/water slurries as a substi¬tute for fuel oil or for coal/oil mixtures, particularly in electric power generation. The idea is not a new one. Coal/water slurries were transported by pipeline in the U.S. in the early nineteen-sixties, and the Black Mesa coal pipeline has been in operation for several years, while in Germany, coal/water slurries were being burnt for power generation in the early nineteen-seventies, as described by Merten and Höner (1972). Since coal is not a pure substance but a carbonaceous mixture, the different chemical and physical behavior of coal/water dispersions from different deposits must be understood in order to optimize the properties of the result¬ing slurry fuels. Since minerals which are minor constituents of coal may also strongly affect slurry properties, coal chemistry may vary considerably even within a single deposit. Thus it is unlikely that there will be a single formula for optimizing the slurry properties of all coals, and even the answer for coal from a single source may change with time.

Jan 1, 1983

By Wayne A. Sadik

The mine ventilation system of the Henderson Mine provides a case study of designing and maintaining high-quality respirable air in a large underground mine with over 200 units of diesel-powered equipment. This system was designed with concern for minimizing exposure to personnel of siliceous dust, diesel exhaust, smoke, and potential fire hazards while optimizing general environmental air quality throughout the multilevel/multiheading operation. As a relatively new operation, the Henderson Mine incorporates a modern ventilating plant and mine de- sign as well as state-of-the-art technology where appropriate. Two main ventilation shafts approximately 2,300 ft (701 m) in depth (one intake, one exhaust) will handle 1.8 million cfm (850 m3/s) of air circulated throughout 60 miles (97 km) of drifting, providing the ventilation requirements for more than 25,000 diesel horsepower (18,642 kw) underground.

Jan 1, 1980