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By Paul R. Wieber

This paper describes the U. S. Energy Research and Development Administration's (ERDA) program to develop in situ coal conversion processes, especially gasification, he potential of this technology, the technical directions being explored, and the program strategy to carry the process concepts toward commercialization are emphasized. The geographic location of the U. S. coal resources and a market analysis are described. Commercially successful in situ coal processes could add over a trillion tons of coal to the U. S. coal reserves. The economics of these processes is compared with surface gasification independent studies show this process to be 25Z cheaper than surface gasification for Western coals. The major projects are briefly described. The Linked Vertical Well process is in the lost advanced stage and shows great promise. The last test produced a low-Btu gas averaging 171 Btu per standard cubic foot for average pro¬duction rates of 5.5 million standard cubic feet per day. The other projects are Packed Bed, Longwall Generator, and Steeply Dipping Beds.

Jan 1, 1977

This study was conducted to evaluate the effects of a diesel particulate filter (DPF) regeneration process on the concentrations and size distributions of aerosols in an underground mine. Two active regeneration strategies were examined for an electrically regenerated sintered metal fiber filtration system, and the effects were compared with those observed for a muffler and the same system operated in a passive configuration. The effects were assessed for three steady-state engine operating conditions. The number and mass concentrations and size distributions of aerosols in mine air were found to be strongly affected by the exhaust configuration, engine operating conditions and the regeneration process. When the system was operated in active configurations, the concentrations exhibited a transient and cyclic nature. At light load conditions, the distributions of aerosols in mine air were dominated by accumulation mode aerosols for all exhaust configurations and regeneration strategies. High concentrations of nucleation aerosols were observed when the DPF system was used and the engine was operated at high load conditions. A positive correlation between accumulation of particulate matter in the filter and the efficiency of the filter in removing accumulation mode aerosols was observed for all conditions. In the case of high engine load, reductions in accumulation mode aerosol concentrations were linked to a substantial increase in number concentrations of nucleation mode aerosol. Overall, the filtration system was found to be very effective in reducing total aerosol mass and elemental carbon concentrations for all engine operating conditions. However, the system was substantially more effective in passive than in active regeneration configurations.

Jan 1, 2012

By J. P. Wilson

The Tessenderlo-Kerley Leach process has been shown to be effective in the removal of residual copper from molybdenite concentrates. Concentrates of varying mineralogy, including those containing relatively large amounts of chalcopyrite, have been successfully leached on laboratory and pilot plant scales. The lixiviant system is ammonia and ammonium bisulfite with air / oxygen addition. An abrasive is added which greatly enhances the kinetics, and it is subsequently screened out and reused. The dissolved copper is easily recovered using existing technology. Extraction profiles, reagent consumptions, and mineralogical data are presented.

Jan 1, 1999

By K. Ananthpadmanabhan

Hydrolyzable surfactants such as fatty acids and amines undergo, in addition to micellisation and precipitation, various associative interactions in aqueous solutions to form ion molecular complexes such as acid-soap, dimers etc. depending upon the solution conditions such as pH. The interaction of these collector species with the mineral surface and with other dissolved species in solution will play a significant role in determining the interfacial processes such as adsorption and flotation. Marked differences in the hydrophobicity imparted to the mineral surface depending upon the solution conditions such as Ph can be attributed to possible differences in surface activities of the above complexes. This aspect of solution chemistry of flotation systems is discussed here for two widely used collectors namely, oleic acid and dodecylamine. Equilibrium species distribution diagrams based on the available literature .data and on estimates of energy of interactions between molecules, have been obtained for oleic acid and dodecylamine solutions.

Jan 1, 1978

By Ralph E. Magnuson

The quality of our environment is of great importance to all of us. Today, there is a great public concern about the degradation of our air, land, and water and the resultant slow death of our planet Earth. The miner has always been concerned with his environment. Historically, mining has been a part of the frontier. As a result, the miner has pioneered and developed many parts of the world. In the beginning, he had to hack out a place for his mine, himself, and his family. He was given accolades and praise for his accomplishments. Now, however, he is attacked as a ravager of the landscape. It was and is no different on the Marquette Iron Range in Marquette County, located in the Upper Peninsula of Michigan. Iron ore was discovered in 1845 and mining was begun by 1848. Over nearly 1 ¼ centuries, a total of 379,197,000 tons have been shipped to market. Ports, docks, railroads, and towns all had to be built in order to get that tonnage out to iron and steel makers. In those early days the environment had to be mastered, not pampered.

Jan 1, 1970

By Anna Gustafson, Sohail Manzoor, Håkan Schunnesson

Sublevel caving operation relies on the estimation of ore grade at drawpoints, as the mine management uses grade to decide whether the material at a certain ring should be loaded or abandoned. Grade is estimated in various ways, including visual estimation, density-based calculation, and sampling and assay methods. The grade estimation at the world’s two largest underground iron ore mines owned by LKAB in northern Sweden is based on the density difference between ore and waste. The calculations assume a constant swell factor, a theoretical fill of 100%, and a linear relationship between bucket weight and material grade. This study evaluated these assumptions in detail based on the loading data for 12,237 buckets and concluded that the method has some shortcomings which render the assumptions invalid. Further research is required to deal with these shortcomings to improve estimation of the material grade.

Oct 17, 2022

The mining industry is one of the three pillars of the Namibian economic development, besides tourism and the fishing industry. Generating 20 % of the GDP and more than 50 % of the export income, half of this amount derives from the diamond mining industry. In 2008, the annual production of 2.2 mio carat achieved an income higher than 1.44 billion Namibian Dollars (more than 750 mio Euro). After the global recession in early 2009, which also caused a significant downcrease in production to only 0.93 mio Carat, the diamond mining industry easily restored itself and the production figures for 2010 are expected to be even higher than those achieved in 2008. Compared to other diamond producing countries, Namibia is mainly producing diamonds of highest quality (jewellery quality), with less than 10 % of the mined diamonds not falling into this category. This high quality stands also for the worldwide highest prize achieved per carat. With 370 $US per carat it is more than four times higher than that of the average South African stone. In 1908 the finding of the first diamonds in the Namib desert close to the coastal town of Lüderitz was reported by a Mr Stauch, railway inspector for the then German colonial railway company. This event immediately triggered a Diamond Rush and subsequently the set-up of the restricted diamond mining area ?Sperrgebiet? through the German colonial administration. In 1913, only five years after the first mining operations had started, the steadily increasing production allowed for more than 20 % of the diamond production worldwide. After the First World War, the new South African government concentrated all mining activities in one organization, CDM (Consolidated Diamond Mines of South West Africa) which in following decades conducted an extensive and detailed exploration of the whole Sperrgebiet and started numerous new diamond mining operations.

Jan 1, 2011

By S. Koro

The current economic climate of low commodity prices and increasing costs has put a lot of pressure on mining companies to ensure their operations will survive through the current economic downturn. While history tells us that the cycle will turn around and prices will go back up again, how many mining companies will be left to take advantage of the next upturn? On average in Australia, the maintenance of mining equipment accounts for up to 50% of operating costs; which equates to nearly $15bn per year. In addition to trying to boost productivity, mining companies are also putting a lot of pressure on reducing costs; all with the intention of maintaining/increasing profit margins and thereby keeping shareholders ?happy?. The whole premise of our economy is based on ?growth? and ?profits?. Movements in the market place force mine owners to ?react? to short term fluctuations. And if that movement is downward; operations people at the sites are forced to start reducing costs. Is this cost reduction done in a logical, systematic way where all risks (short-, medium- and long term) are considered? Invariably, the answer is no! Short term ?fixes? are normally implemented with little, or no, regard for medium- and long-term impact. And the reason for this is that management is not fully focused on the long term; focus is mainly on survival. Decision making is driven by shareholder sentiment and history tells us that this is largely short-term. So given these paramteres to work within, what role can ?Asset Management? play in assisting management to meet shareholder and market requirements whilst still maintaining long-term viability of their operations (to the long-term benefit of shareholders dare I say). As maintenance costs account for nearly half the operating costs of mining companies; the ?smart? management of assets is not only crucial; it is essential for survival in today?s economic climate. What is asset management? Asset Management, according to the UK-based Institute of Asset Management (IAM) is ?the systematic and coordinated activities and practices through which an organization optimally and sustainably manages its assets and asset systems, their associated performance, risks and expenditures over their life cycles for the purpose of achieving its organizational strategic plan.? How important is asset management in today?s mining companies? IAM goes on to say: ?This definition of asset management represents a significantly greater scope than just the maintenance or care of physical assets, and is closer to the central purpose of an organization. Good asset management considers and optimizes the conflicting priorities of asset utilization and asset care, of short-term performance opportunities and long-term sustainability, and between capital investments and subsequent operating costs, risks and performance. ?Life cycle? asset management is also more than simply the consideration of capital costs and operating costs over pre-determined asset ?life? assumptions. Truly optimized, whole life asset management includes risk exposures and performance attributes, and considers the asset?s economic life as the result of an optimization process (depending upon the design, utilization, maintenance, obsolescence and other factors).?

Feb 23, 2014

By Colin Irwin, Adrian Naranjo-Castillo, Christopher Petta, Eric Zarobila

The Shoreline Consolidation Sewer is a CSO control project in Cleveland, Ohio that requires the installation of 5,000 feet of 72-inch inside diameter pipe using microtunneling methods. After award, the contractor submitted a value engineering proposal to eliminate two deep shafts and install the tunnel in two drives instead of four. In an example of successful collaboration, owner, contractor, and engineer worked together during the initial construction stages to modify the design and update the contract documents. This paper examines the importance of exible requirements in contract documents and a collaborative environment between all parties to successfully deliver a project.

Jun 23, 2024

By S. Bentley

"Everyone has a general idea what mixing means, but describing the mixing process is not so simple. The objective of any mixing process is to distribute and blend the materials with different characteristics, different quantities as evenly as possible resulting in a homogenous mixture. Introducing proportional movement with the optimal intensity into the materials achieves effective homogeneous mixing results. A simple one directional movement with inadequate acceleration of the materials would obviously not achieve the same mixing results. This would be more like stirring than mixing. The amount of relative movement that is introduced is a decisive factor. Circumstances for successful mixing involve distribution of all materials, and achieving the highest probability that all recipe particles located in a specific position at the beginning can be found at any random location in the mixing chamber at the end of the process. This is the only way to ensure that a consistent result is achieved every time mixing is repeated.THREE-PART CYCLE The mixing cycle occurs in three phases; charging the mixer, the mixing process, and discharging. The sequence in which the individual materials to be mixed are filled into the mixer can have a huge impact on the efficiency of the mixing cycle. The mixing cycle overlaps the charging process and the discharge cycle follows the mixing cycle. To achieve optimum results, effective discharging methods should be taken into consideration to avoid risks of segregation. Costs for energy and wear should be as low as possible and finally, it is very important that the mixing cycle takes place as quickly as possible. In concrete or paste backfill production, selecting the best mixing technology is crucial for both the quality of the final product to be blended and the efficiency of the production process. The optimum mixing system is one that rapidly disperses all ingredients evenly throughout the mixing trough and completely surrounds all the course or fine aggregate particles with the slurry cement particles. Specific for paste production it’s the mixers job to also break-down unconditioned tailings to achieve consistent paste viscosity or measured spread. Many paste and concrete formulas also involve small quantities of chemical additives which also must be evenly distributed effectively. The time required per mixing cycle as well as the costs of energy, wear and maintenance will determine the economy of the concrete production."

Jan 1, 2015

By Ping Zhang, Xu Ma

Perturbations arising from mining operations significantly affect the stability of rock masses, and the influences aggerates with the rapid increase of mining-operation depths during recent years. The subsurface structures with major discontinuities subject to seismic hazards resulted from the shear-slip behaviors of rock masses. In order to identify the shear-slip regime of discontinuities and calculate seismic moment and seismic energy involved with shear-slip behaviors, we use discrete element modeling to study the shear slip failure along discontinuities in an underground mine. The recorded characteristic and properties of sub-contacts in DEM provide a basis for computing and visualizing the temporal and spatial distribution of seismic moment and seismic energy with mining operations. We computed the seismic energy and seismic moment using the numerical modeling method and the analytic method. We compared the result of summing seismic energy and seismic moment from the subcontacts of numerical models and the result of the analytic method. We confirmed that this tool can be used in comparative analyses. We also found that seismic moment and seismic energy, associated with shear stress drop and shear displacement increase, accumulate in the vicinity of major discontinuities. Mining operations at a greater depth cause greater changes of seismic moment and seismic energy, leading to a higher risk of inducing seismic hazards. Quantifying seismic potential using discrete element modeling can greatly facilitate the investigation of instability of geological discontinuities and thereby can help estimate the potential of seismic hazards.

Jan 21, 2023

By A. L. Hornbaker

Management of mineral resources through land-use planning procedures is not a new concept, particularly at the local level of government. Colorado may well be one of the first states, however, to vigorously attempt to evaluate on both the state-wide and regional basis, mineral resource potential and to make certain that potential for mineral resources is included as one of the primary factors considered in the local land-use decision-making process. Less than a decade ago the only consideration given to mineral resource extraction, particularly aggregate resources, was whether or not they could be produced at the particular time they were needed. This attitude has now shifted to the other extreme, not only in Colorado, but other states as well, so that other interests, especially housing projects, mountain subdivisions, recreational and wilderness areas are gaining prime consideration in land-use decisions. Ideally, in a more acceptable median position, mineral resource potential would receive definite consideration at the local level.

Jan 1, 1977

By Don Runge, John T. Zeni

Cuprex Limited is currently developing a small gold mining operation in Central Australia in the Tennant Creek field. In February 1984, the company undertook a feasibility study on the project and operations commenced in August 1984. Ore reserves are located between 230 and 280 metres (755 ft and 919 ft) below surface and ore extraction required the establishment of a shaft network for access, ore hoisting and ventilation. Zeni Drilling Company from West Virginia, U.S.A. was contracted to blind drill two shafts for the project. Blind drilling was selected for various reasons, including timing which related to cost efficiency. The blind drill shaft technique has proved successful in this application and with enthusiastic and innovative support from the mining industry, will prove an efficient and cost effective means of accessing and operating underground mining projects of all sizes in the future.

Jan 1, 1987

By A. W. Khair

Surface subsidence is a phenomenon mainly associated with longwall mining, although it can also occur if the coal pillar left to protect the surface deteriorates with time and results in the collapse of the room and pillar system. A method has been developed that utilizes physical mine models and laser holographic interferometry. This method is capable of measuring displacements as small as 5 micro- inches by means of generating displacement contours on a surface, even that of granular materials. Analysis of subsidence in room and pillar mining using models of various extraction ratios ad overburden depths along with two different types of overburden model material (sand and gelatin) has been made. The sand represented the extreme brittle conditions of geologic material while the gelatin represented visco-elastic behavior of geologic material. This paper deals with the analysis of data which has been gathered up to date, and mainly associated with the use of sand as an overburden model material. The analysis included the effect of variation of geometric parameters on surface subsidence. Among these parameters are: variation in seam depth and thickness, surface and seam inclination, and extraction ratio.

Jan 1, 1984

By R. Sellaro, E. Sarver

It has long been understood that extended occupational exposures to respirable mine dusts can lead to chronic lung disease. In underground coal mines, coal workers pneumoconiosis (CWP) and silicosis are major concerns. While many efforts have been made with the aim of understanding the mass-based concentrations and silica contents of respirable dusts under a variety of mining conditions, little research has been completed in characterizing dust at the individual particle level (by composition, size and shape). This study employed scanning electron microscopy with energy dispersive x-ray (SEM-EDX) to analyze dust samples collected from an underground coal mine in Central Appalachia. The results indicated that particle characteristics can vary widely between locations, though many trends might be explained based on knowledge of mining conditions. A continuous personal dust monitor (CPDM) was also used during the collection of some samples to determine respirable dust concentrations, which were compared against estimated concentrations based on the particle-level analysis.

Jan 1, 2014

By Michael Prince

"Managing slurry is a constant challenge for mining operations. Since slurries are not uniform, the challenge is complicated by varying rheology, velocity, temperature and pressure, all of which affect how the slurry moves through the pipeline and how destructive it is to the system it is flowing through. Picking the right equipment from the outset — the right size pipe, the right size pump and the proper valves for the application — allows mines to operate more efficiently. Better valve designs deliver multiple benefits — they can lower the cost of operations, reduce the amount of maintenance and associated downtime required and are better for the environment. Historically, modulating systems have used ball, plug and pinch valves to manage the flow of slurry, but each of these alternatives has limitations. Ball valves require ceramic lining in order to delay wear, and once a ball valve does wear, the entire valve must be replaced. Similarly, plugs in plug valves should be coated to perform in control systems, and whole valves must be swapped out upon wear. Pinch valves are expensive and only require replacement of the sleeve. However, sleeve replacement involves an extremely arduous process in which the valve is completely taken apart.Traditionally, designers have avoided using knife gate valves (KGV) in modulating systems because KGVs have not been able to hold up under the harsh operating conditions. The throttling that is required in some of these processes rapidly fatigues conventional KGVs, rendering them useless and in need of replacement. Fortunately, innovative design changes have the potential to change established views.Breaking new groundRecognizing the need for improved components, Victaulic took on the challenge of designing a valve that could withstand abrasive slurry systems for a much longer period of time. The first step in this process was to talk to miners, maintenance personnel, process engineers and operators in the field about the limitations of current offerings and then determine design specifications for an ideal replacement.Many of the responses to these inquiries were very similar and reflected challenges with current operations; the primary objective was to find a valve that would be lighter and cheaper than the valves currently in use. In theory, a lighter valve would be easier to replace, and since replacements need to be performed frequently, a cheaper valve seemed like the right idea."

Feb 1, 2019

Not quite a year ago, during a speech to a group of mining professionals in Washington, DC, the subject centered around the long-range importance of conducting research projects and how much that research needs to specifically apply to health and safety matters in our industry. The point was made about the critical need to work together with government, private industry, labor organizations and academia speaking with a unified voice as we all march into the future together. The fundamental benefits of competitive research were mentioned --to improve our quality of life, to develop our energy resources, to achieve a safe and healthy environment and to ensure long-term economic growth. Very importantly, emphasis was given to the natural link that makes my agency, the Mine Safety and Health Administration, and the National Institute for Occupational Safety and Health --NIOSH --the beneficiaries of each other's findings. Unquestionably, there are lines of separation. The main responsibility of the agency I represent, MSHA, is enforcement of the nation's mine safety and health laws. But we also have an additional responsibility and that is to coordinate and give priority to research in a never-ending hunt for answers.

Jan 1, 1999

By Yi Luo, Jian Yang, YUJIA LIAN

Scale physical models, constructed according to the principle of similarity theory, are widely used to simulate the mining disturbances to surrounding strata and to evaluate the effectiveness of implemented ground-control techniques. This technique has also been used for studying mining-induced surface and subsurface subsidence. The movements of the observation points installed on the physical model at different mining stages are currently measured using a total station, which is time consuming and inaccurate, especially on small-scale models.

By Emily Sing, Ashim Gajurel, Thomas Pennington, William Brown

The Pardee Chemical Feed Shaft Project involves construction of two new chemical feed shafts to improve raw water treatment capabilities at the East Bay Municipal Utility District’s (EBMUD) Pardee Reservoir in Valley Springs, California. The project includes construction of two 250-foot deep, 16-inch diameter stainless steel chemical feed shafts that penetrate an existing 8-foot diameter concrete lined conveyance tunnel. The design approach required the shafts be installed using top-down drilling methods and within a strict verticality tolerance (0.1%). Innovative precision drilling techniques ensured that the shafts penetrated the tunnel in their planned locations and the installed chemical feed lines would function as designed. Challenges included extremely limited access to the tunnel because of a requirement to maintain the tunnel in service during construction. This paper discusses the overall project’s design and construction approach, including unanticipated conditions that the project team faced and how these conditions were managed and overcome through collaboration between the contractor, designer, and owner.

Dec 1, 2022

By Z. Henderson, J. Saylor, L. R. Mendoza

"Diesel particulate Matter (DPM) is a byproduct of fuel combustion in diesel engines. It is classified as a carcinogen, with associated respiratory and cardiovascular health effects. The composition, size, and concentration of DPM is dependent on factors such as engine type, loading and fuel composition. Though a number of DPM abatement and control strategies currently exist, particularly in underground mining environments, occupational exposures remain a serious health concern. As a novel abatement approach, DPM scavenging by fine water or “fog” droplets has been proposed and a laboratory set-up has been built to test the efficacy on engine exhaust. Here, we describe a series of tests that varied engine load, system flow rate and fog drop number density. While none of these factors had overwhelming effects on the results within the ranges tested, the improvement in DPM mass removal attributed to the fog treatment was about 45% on average in comparison to no treatment. INTRODUCTION Diesel engines have seen widespread use for well over a century due to their relatively high thermal efficiency and fuel economy1. More recently, however, adverse health risks of diesel exhaust have become increasingly clear. Many of these risks are associated with the physical and chemical properties of exhaust components1–3. The term diesel particulate matter (DPM) is used to refer to the solid components of diesel exhaust, which are a mixture of elemental and organic carbon (EC and OC) and minor constituents including sulfates and metal ash3. The OC fraction of DPM results from unburned fuel and lube oil, whereas EC or soot is formed during the combustion of locally rich regions within the fuel. DPM is classified as a carcinogen6,7 and epidemiological studies have demonstrated a positive correlation between long-term exposure to DPM and other combustion-related fine particulate and increased cardiovascular and pulmonary diseases8,9. Diesel engines operate in relative fuel rich/oxygen lean conditions and are characterized by relatively high emissions of particulate as compared to spark-ignition engines2,3,10. Typically, these emissions range from 107 – 109 particles/cc and cover two primary size ranges: the nuclei mode where particles have diameters less than about <50 nm, and the accumulation mode where diameters are from about 50-10,000 nm. Most OC resides in the nuclei mode as semi-volatile compounds, while most EC is in the accumulation mode3. The physical and chemical properties of DPM vary with the type of engine, fuel (e.g., petro- vs. bio-diesel) and operating conditions such as loading (i.e., a function of torque and rotational speed)2,3,9,11,12. Loading is a particularly important factor with respect to DPM toxicity9,13,14, and on the effectiveness of after-treatment technologies2,3,15. Engine load alone can affect the EC/OC ratio, and the size distribution and number density of DPM. For diesel engines, the load is roughly proportional to the equivalence ratio3, defined as the actual fuel/air ratio over the stoichiometric fuel/air ratio for complete combustion. Light loads generally favor the formation of OC and small particles. As load is increased the volatiles are oxidized leading to larger soot particles (i.e., EC), but lower total number density of DPM. With further loading, the formation of soot offsets the decrease in volatiles, resulting in increased DPM mean size and number density3."

Jan 1, 2017