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The effect of the chemical composition of pulverized bituminous coal particles on their physical transformation during the initial stages of combustion has been investigated. The results suggested that cenosphere formation does not require extensive thermal decomposition of the coal particles. The vitrinites in the bituminous coal softened earlier and developed larger cenospheres than the othe macerals. The coal particles swell to a higher extent during combustion than in pyrolysis; however, the cenospheres formed in the former process experienced a higher extent of fragmentation. The development of microporosity occurred predominantly after the resolidification of the swelled char particles. The type of macerals originally in the coal did not significantly affect the microporosity of the chars. Conversely, the morphology and anisotropy of the chars were strongly dependent on the maceral composition of the coal.

Jan 1, 1986

By H. C. Siebert

According to the "Survey of Energy Resources 1980" (1)*, which was prepared by the Federal Institute for Geosciences and Raw Materials in Hannover (FRG)for the World Energy Conference 1980 in Munich, the world coal deposits are assessed at 775 billion tce proven reserves 448 billion tce of them recoverable and 6 161 billion tce additional resources. If one ignores growth rates, the current world coal output of 2,8 billion tpy gives our recoverable reserves a static life expectancy of 175 years. With an average increase in world output of 3,2 % like between 1973 and 1980 this range would be further shortened to an alarming degree. Furthermore, the criteria used to distinguish between workable and unworkable resources give rise to the suspicion that deposit characteristics are not always taken into account to a sufficient degree. For example, little attention is paid to major ?Bonitaet" - factors such as dip and seam thickness. There have been wide-ranging scientific discussions on the lower limit for workable coal resources, but no such limits have been set at the other end of the scale. Otherwise it is well known that performance and costs are badly affected den in level and moderately inclined seams the seam thickness is more than 4 to 5 m, because special mining methods have to be used beyond this limit. These are associated with significantly higher costs than with the winning of seams of ?normal? thickness.

Jan 1, 1985

By Ken Pill, Jennifer Nyman, Liz Moran, Keaton Belli, Chelsea Bokman

The Moab Uranium Mill Tailings Remedial Action (UMTRA) Project Site (Site) is a former uranium-ore processing facility near Moab, Utah, where production ended in 1984. The United States Department of Energy Office of Environmental Management (DOE-EM) is responsible for remediating the site to meet 40 Code of Federal Regulations (CFR) 192 standards promulgated by the United States Environmental Protection Agency under the authority of the Nuclear Regulatory Commission (NRC). Tailings from the former mill were stored in an unlined impoundment (tailings pile), totaling 16 million tons of waste material. Surface cleanup has been ongoing since 2009 and consists of removal and transport of tailings via rail to an off-site disposal facility in Crescent Junction, Utah, with an estimated completion date around 2029. Gravity-driven migration of tailings fluids and recharge through the tailings pile and former on-site ore storage areas in the northeastern part of the site led to contamination of site soil and groundwater. The primary contaminant of concern is ammonia, which was present in fluids used in the milling process (DOE 2003). Uranium is a contaminant of potential concern. An interim groundwater remedy is currently in place that utilizes a system of extraction and injection wells to limit discharge of contaminated groundwater into the nearby Colorado River. Exceedance of surface water standards for ammonia are a principal concern due to potential endangered species fish habitat areas along the Colorado River adjacent to the Site. When necessary, surface water diversion is used to lower surface water ammonia concentrations when suitable habitats develop for endangered young-of-year fish. Once surface cleanup concludes and the tailings pile is removed, a formal groundwater remedy must be selected and documented in a Groundwater Compliance Action Plan (GCAP). Under Title 1 of the Uranium Mill Tailings Radiation Control Act, natural flushing (i.e., monitored natural attenuation), may be selected as the groundwater remedy if it can be demonstrated that the remedy will achieve groundwater standards within 100 years. The 40 CFR 192 groundwater standard for uranium is 44 micrograms per liter (μg/L), and the target groundwater concentration of ammonia based on adverse effects on local fish species is 3 milligrams per liter (mg/L). A collaboration with Geosyntec Consultants, Inc. (Geosyntec), the Moab UMTRA Project team, the DOE Office of Legacy Management, the DOE-EM, and the Network of National Laboratories for Environmental Management and Stewardship was held in 2022 with the goal to generate actionable recommendations to develop a GCAP for the Site. The primary recommendation was development of a groundwater fate and transport model to predict the remedial timeframe under various groundwater remedies. This paper presents the results of soil and groundwater sampling, geochemical modelling, and laboratory column and batch reactor testing that will be used to parameterize a numerical model for estimating the remedial timeframe under various scenarios, including natural flushing.

Feb 1, 2025

By Peter Johnson, David Barber, Lachlan Henderson

"The traditional approach to rail tunnel fire safety design is to follow NFPA 130, which assumes a major tunnel fire could occur and requires bi-directional emergency ventilation. There is no regard to the impact of ventilation on fire growth and smoke production. In Europe and other parts of the world, the need for tunnel ventilation systems to provide smoke management in the event of fire is being questioned. The European Commission’s Safety in Railway Tunnels TSI is based on a philosophy that improved running capability (preventing fires and other events stopping the train in the tunnel) and elevated fire performance of materials means the chances of a major fire in a tunnel is highly unlikely, with only small fires expected, and no tunnel ventilation required. This approach is reinforced by the International Tunneling Association which has recently published an Engineering Methodology for Performance Based Fire Safety Design on Underground Rail Systems, which includes a methodology that does not require assessment of tenability in tunnels, but requires a scenario based risk assessment to be undertaken to determine overall fire safety measures. Recent research by the University of Edinburgh has shown that forced airflow from a mechanical ventilation system may promote fire growth and increase smoke volumes much more than with natural ventilation. Whilst the concept of no mechanical ventilation (i.e. natural ventilation) is a new concept for some, for many rail tunnels it is worthy of serious further consideration. RAIL TUNNEL SMOKE MANAGEMENT AND STANDARDS Smoke management using mechanical bi-directional ventilation systems has been a central part of the fire safety design solution under NFPA 130 for rail tunnels since 1982. The current version of the standard, NFPA 130: 2014, states that mechanical ventilation should be fitted to rail tunnels of length greater than 305 meters and an engineering analysis should be undertaken for tunnels of length 61 to 305 meters to determine whether mechanical ventilation should be fitted. However, this approach is not necessarily reflected elsewhere in the world. In Europe in particular, mechanical ventilation systems for smoke control within rail tunnels have taken a much less central role within the standards framework."

Jan 1, 2016

By Richard Campbell, Claire Pirona, MEHMET KIZIL, Ismet Canbulat, Stephen Giese, Ravindu Goonawardene, Edward Steed, Serkan Saydam

The Australian longwall mining industry spends millions of dollars per year on proactive and reactive ground consolidation applications across most of the operations currently in production. The design and effectiveness of the applications and products vary widely and are based predominantly on-site precedence or what were considered successful applications at other sites in similar situations. In the continual improve the effectiveness of how consolidation products are used and when by enhancing our knowledge of the mechanical properties of products used in underground coal applications and applying this increased understanding to geotechnical design. One of the current challenges to further developing more appropriate and accurate geotechnical design methods for consolidation activities is the lack of standardised materials testing and knowledge of rock mechanics data on in situ performance. The lack of industry standardisadesign of consolidation programs, with a reliance on experience-based guidance for rockmass consolidation design. consolidation products. The program was designed to provide the industry with a set of geomechanical property index tests and a data set that can be utilised by rock mechanics engineers as baseline information for product evaluation and engineering design. The laboratory work undertaken is critical to understanding the exact small-scale mechanical properties of these products and testing was carried out at Monash University for various states of curing of each product. Recognising that the speed at which a mixed product develops its desired properties to act as a support element in underground coal mines is critical to its serviceability. This paper presents the testing rationale proposed, the testing results, and a framework for how the data set can be used to improve the engineering basis for ground consolidation design, in terms of expected rockmass performance under various mining conditions and application parameters.

Jun 25, 2024

By E. D. Sehnke

The refractory materials industry provides the largest commercial market for nonmetallurgical grade bauxite. Refractory grade bauxite is prepared from bauxites having low iron, titania, and alkali content by calcining at temperatures near 1,650° C. Although there are substantial bauxite reserves in the world, premium grade bauxite ores suitable for use in refractory applications are limited to only a few specific sources, primarily in Guyana and the People's Republic of China. Consumption of bauxite for refractory use is closely associated with the production and consumption of primary metals, in particular iron and steel. Barring major disruptions within the principal producer nations, sufficient supplies of refractory bauxite will be available to meet world demand well into the next century, and raw material costs will continue to determine the availability of markets for bauxite-based refractory products.

Jan 1, 1992

By M. Laliberte

"Gold-mine effluents are often characterized by high concentrations of copper, ammonia and cyanide derivatives (mostly cyanates and thiocyanates). While not acutely toxic to birds, this water can be acutely toxic to fishes and invertebrates. In many jurisdictions, the effluent requires further treatment in order to pass a mandatory requirement to be nonlethal to species like the rainbow trout (Oncorhynchus mykiss) or Daphnia magna. Using actual mine water, it has been demonstrated that aerated moving bed biofilm reactors will biodegrade the ammonia, cyanides, cyanates and thiocyanates, thereby removing the toxicity associated with these components. By removing copper by precipitation the water can be made to pass acute toxicity tests. Tests have demonstrated that the process is stable between 4 and 25°C, with no significant changes in the treated water composition. Once the biomass is acclimatized, the process is resistant to upsets and requires very little inputs except for phosphorus and air. Furthermore, it has been demonstrated that an anoxic reactor can be added downstream of the aerated reactors to remove nitrates if required.IntroductionThis paper will demonstrate that gold-mine effluents, which are toxic to fishes and invertebrates, can be made nontoxic by using a combination of chemical precipitation and biological oxidation.The typical composition of gold-mine effluents will first be described. The applicable legislation will then be introduced, with its requirement that the treated effluent be nontoxic. The toxicity of a typical untreated effluent will then be confirmed, and the sources of the toxicity identified. After that, a number of toxicity reduction treatment methods will be presented, and the selected method will be described.The lab tests that confirmed the efficiency of the treatment method will be presented, with three phases of testing as the understanding of the process gradually improved. Toxicity test results showing that the water is nontoxic after treatment through the temperature range will be presented."

Jan 1, 2015

By Karoly (Charles) Kocsis, Jeff Johnson, Felipe Calizaya, Tulio Dias, Natanna Nunes

Two pressure balancing chambers were constructed at a Colorado coal mine to reduce the risk of spontaneous combustion. Each chamber was established by installing a Kennedy stopping at about 10 ft (3 m) in front of an isolation seal, and equipped with two safety doors, a nitrogen injection system, and a set of environmental monitors. Several pressure balancing tests for different ventilation conditions were conducted in these chambers. During each test, pressurized nitrogen was injected into the chamber and the pressure differentials across the stoppings and seals monitored. This study presents a summary of the results achieved, lessons learned, and the basic requirements to operate a pressure chamber effectively.

Feb 1, 2024

By R. B. Massy-Greene

Project engineering and development is a process of optimisation of capital, operating and financial costs, and extraction rates in the light of current and forecast economic conditions for the sale of the product. The aim of the process is to maximize financial returns to the sponsors (project owners) within many often conflicting constraints. Thus, the sponsor's engineering and financial staff have a common goal, with performance measured in financial terms. Consequently, each group must be aware of, and responsive to, the constraints imposed upon the other. For financial staff, the increasing size and complexity, and escalating capital costs of new ventures have required them to seek finance in larger amounts, and by non-traditional methods. In addition, senior management are requiring indications of the availability of finance as a pre-requisite to a decision to commence project development activities.

Jan 1, 1982

By F. J. Sotillo

Mineral processing requires good classification of particles to attain an adequate separation of minerals. This is of utmost importance in the case of sulfide minerals. An ideal classification is obtained when particles are separated at a given mesh, which is fixed according to the characteristics of each sulfide ore. Under these ideal conditions, particles coarser than the mesh of separation are recovered in the underflow, whereas particles finer than the mesh of separation are recovered in the overflow. This paper presents the results of pilot plant tests that were performed on Ag-Pb-Zn and on Ag-Au Peruvian sulfide ores using a Density Separator, and the comparison of these results with those obtained using hydrocyclones, under similar operating conditions. The results show that the ratio of circulating load is reduced by 50% by using a Density Separator with respect to that obtained by using hydrocyclones. Moreover, the effect of the improvement in the separation efficiency obtained by using the Density Separator on the kinetics of flotation is also shown. Silver recovery of the Ag-Pb-Zn ore increased by 18% whereas gold grade in the concentrate of the Ag-Au ore is doubled.

Jan 1, 1998

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 J. Weyer

"A lot of incorrect, dangerous and misleading statements about the effect of CO2 on the human body can still be found in the internet, the media and in books. It is a fact that already low concentrations can lead to critical reactions, higher concentrations cause a narcosis. The real effect is not a lack of oxygen but an inner suffocation. The breathing reflex is decreased and the transport of oxygen in the blood is reduced due to a low pH value of the blood. Furthermore a reduced oxygen content in the air can also lead to the failure of diesel engines. MOTIVE Different gases can appear in active mines as well in abandoned mines, adits and caves. The most dangerous gases are CO, NO/NO2, H2S, SO2, CH4 and CO2. Although the general danger arising from these gases is mostly known some aspects are underestimated. Furthermore misleading or wrong statements exist about the detection and the effect of gases on the human body. This is especially true for CO2. In the last years a couple of accidents happened with a great number of injured persons and unfortunately also some fatalities. As a result wrong information and comments about the effect of CO2 have been published in the media. A huge unexpected CO2 outburst in a potash mine showed again some additional problems and limits for rescue troops. ORIGIN OF CO2 AND MISLEADING STATEMENTS ABOUT THE EFFECT ON THE HUMAN BODYCarbon dioxide can appear as free gas in the earth crust. It is especially known in significant concentrations in some potash deposits, in hard coal mines and some caves. Furthermore it can be formed due to complete oxidation of carbon. It can appear in technical processes. It is also used for or in technical processes, as fire extinguishing agent, as cooling agent, it is contained (added) in sparkling water or other soft drinks and it is formed by fermentation processes. Up to today a lot of wrong information about the effect of CO2 on the human body is published or is still in the mind of many people and unfortunately even in the mind of members or leaders of rescue troops. On August 16th 2008 a faulty CO2 extinguishing installation in the city of Mönchengladbach/Germany caused the injury of 107 people and the evacuation of further 150 people /1/. People on the streets became unconsciousness and felt down. Fortunately all could be rescued due to the immediate rescue operation of local fire fighters. Furthermore the CO2 concentration on the ground was diminished by help of a helicopter. What could have happen with the engine will be discussed later. After 6 days a second similar accident took place /2/. In the news members of the rescue teams explained that CO2 leads to suffocation due to a lack of oxygen. This is wrong! Also cave explorers often say that a burning candle can detect a low oxygen and/or high Carbon dioxide content in the air. This is also wrong and deadly dangerous! Similar statements we find nowadays in the internet /3, 4 and many other/. In a forum “science and mathematics > chemistry” several people say that winegrowers go with a candle into the vine-cellar to detect CO2 /5/. Again: this can be deadly! Another dangerous statement is that CO2 in higher concentrations leads to headaches so people should leave such areas. A last example found in the literature is that at 3 % the breathing volume is doubled and at a concentration of 20 % one can felt some warmth on the skin. Both is not wrong but can lead to false conclusions. /6/"

Jan 1, 2015

By Rainer Antretter

While respirable crystalline silica (RCS) dust that arises in industrial production mostly emanates from point sources and can be well mitigated, the extraction of dust is much more difficult in underground construction, since locally generated dust spreads widely. Analysis of dust measurements shows that RCS values are difficult to predict, and effective dedusting systems are required to comply with permissible exposure limits (PEL) in breathed air. Dedusting systems are effective near the tunnel face, while dedusting of working areas away from the tunnel face is difficult or even impossible. In general, there is little temporal influence on the tunnelling work—except for drill and blast excavation—which makes it necessary to remove the deduster and ductwork from the face area. Concurrent work in the tunnel is affected by the backflowing air mass of ventilation and therefore the quality of this air mass must be considered. The use of personal protective equipment (PPE), e.g., dust filter masks, is considered the least-desirable safety measure available. However, for certain individual operations in the tunnelling process, the use of PPE cannot be avoided, especially if other technical mitigation measures are not possible. In tunnels with small cross sections for example, dedusting systems often cannot be accommodated and PPE must be used instead. This raises the question of whether the use of PPE can be avoided by designing appropriate excavation cross sections and allowing for the implementation of technically engineered mitigation measures. The paper highlights problems with dedusting measures and shows possible ways to achieve OSHA compliance.

Jun 13, 2021

By Joan Carles Casado Ortega, Mitchell Gerdtau, Sandeep Pyakurel, Eric Crocker, Frank Perrone

The Parallel Thimble Shoal Tunnel (PTST) project is a part of the Chesapeake Bay Bridge- Tunnel (CBBT) complex. The project involves the construction of a two-lane bored tunnel under the Thimble Shoal Channel between Portal Island #1 (the southernmost island) and Portal Island #2. The new PTST will be the rst transportation tunnel constructed in the Mid-Atlantic region by a tunnel boring machine (TBM). This paper describes the design and construction of the tunnel approach structure in an open marine environment with the strategies employed to overcome the various construction challenges. The project is unique since the entire tunnel approach structure is built on a very limited area within an open marine environment without any reclamation of the existing island.

Jun 23, 2024

By Lukas Erkurt, Wolfgang Holzer, Stefan Auderer, Richard Gradnik

SEM/ NATM Tunnelling contracts in Austria and Germany are usually tendered applying unit price contracts. The purpose of this paper is to show how contractual problems are resolved in these countries. The focus will be put on describing the theoretical approach, several case studies will show how contractual problems were dealt with on site.

Jun 23, 2024

By Peter Zhang, Daniel Su, Mark Alexander Van Dyke, Heather Dougherty, Bo Hyun Kim

The National Institute for Occupational Safety and Health (NIOSH) has been evaluating longwall mining-induced strata fractures and their impacts on casing stability of Marcellus shale gas wells located in longwall pillars. To understand the extent of overburden fractures after longwall mining, NIOSH researchers drilled a post-mining corehole into the fractured strata above the Pittsburgh coal seam longwall gob. Knowing the extent of the fracture zone height will help gas operators minimize the hazards of drilling into longwall gobs. The core was retrieved from the surface down to the top of the gob void. Various fractures were encountered varying from 35 to 64°, depending on lithologic type and relative closeness to the gob. The longwall panel dimension was 457-m wide and 3657-m long, in which the total fracture zone height was found to be at 141 m and the hydraulic connected fracture zone at 87.7 m above the top of the Pittsburgh seam. In addition to core drilling through the gob, FLAC3D modeling was also used to simulate the formation of fracture zone and the orientations of longwall-induced fractures. This study provides much-needed evidence on the fracture zone of Pittsburgh seam longwall gobs to help gas operators avoid potential hazards associated with drilling through highly fractured zones in longwall gobs.

Jun 9, 2022

By R. Gray, B. Hebblewhite

Experience from Australia had identified what is referred to as nonconventional surface subsidence behavior. This occurs under irregular surface topography, resulting in valley closure, valley floor uplift or “upsidence,” and far-field horizontal movements, occurring even beyond conventional “angle of draw” limits. This paper discusses such behavior recently observed in Pennsylvania and focuses on the 2005 case of Duke Lake Dam in Ryerson Station State Park. In July 2005, there was a significant increase in water leakage through a number of growing cracks in the dam, leading to the dam being breached to avoid an uncontrolled failure. An underground longwall mine was located approximately 900 ft to the north, mining at depths of 330 to 720 ft. Investigations, including a subsequent ground movement monitoring program, found a range of evidence in the vicinity suggesting that valley closure and farfield horizontal movements may have occurred, resulting from the adjacent mining. Besides discussing the phenomenon of nonconventional subsidence behavior and the Ryerson State Park case study, this paper includes an assessment of the mining, geology and subsidence impacts and suggested ground behavioral mechanisms.

Jan 1, 2015

By T. Cantwell

Techniques useful in operations, analysis are applied to the problem of planning an exploration program. The model used treats mineral exploration as a Markov process, and maximization of gain is the criteria determining the optimum program. The mathematical description of the model and the optimization are first worked out. Application of the mathematics to several simple examples is given. Finally, comparison of the data necessary to use this operations analysis with the available data shows that the method can only be a guide to planning an exploration program.

Jan 1, 1962

By James W. Mitchell

On December 2, 1942, a scientific team lead by Nobel Prize winner Enrico Fermi first initiated and controlled a self-sustaining nuclear chain reaction. This historic event occurring beneath the stands of the University of Chicago football stadium instantly created an entirely new and tremendously broad area of technology. Indeed, the event probably changed the course of world history and considering the curret energy shortage, it probably came none too soon. Following many technological breakthroughs in the ensuing years, this event led to the first full scale nuclear fueled electric generating plant. In December, 1957, the Shippingport Nuclear Power Plant became operational and the United States had entered the era of the nuclear fueled electric generating station. Today, only fifteen years later, there are some thirty-five operating nuclear power plants in the United States with another 56 under construction and 116 on order. Still, we are only scratching the surface of this tremendous energy source. In 1970, less than one-percent of the total electric generating capacity in the United States was nuclear fueled. By 1985, it is projected that 45% of our generating capacity will result from nuclear power plants. These projections are based upoa statistics of six months to a year ago and considering the current energy shortage and recent attempts by the United States Atomic Energy Commission (USAEC) to speed the licensing process and encourage standardized plants, the contribution of nuclear power to our total generating capacity may be even greater. In summary, it is obvious that nuclear power is now, and will continue, playing an important role in our future. Those factions of government, industry and the professional community charged with fully developing this tremendous energy source must deal with it rationally, logically and expediently. The various environmental considerations in nuclear plant siting play an important role in the overall plan.

Jan 1, 1974

By C. B. Manula

The application of computers to materials handling problems has recently been investigated by various mining groups. This approach has been found, especially useful where a large amount of alternatives must be investigated prior to arriving at a final decision. These alternatives may be expressed in terms of man hours, units and types of equipment such as trucks or conveyors, or the allocation and operation of proposed or existing haulage facilities. The decision problem becomes especially evident when we consider the mechanical revolution which has flooded the mining industry in recent years. The industry has become highly competitive, with the need to keep low profit materials away from high cost production faces ever increasing. The capital investment required for the highly sophisticated equipment that is necessary to perform this function is generally great, and management is faced with decisions which must all too often be made without sufficient data.

Jan 1, 1967