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By Donald C. Strimbeck

The Bureau of Mines, U.S. Department of the Interior, is conducting research and development on a coal-burning gas turbine. This work includes the development of (1) turbine blades resistant to coal ash erosion, (2) equipment to feed coal under pressure to a turbine, (3) an efficient combustion system, and (4) equipment to remove coal ash from the gases that drive the turbine. Initial emphasis is being placed on testing the first turbine ever equipped with blades designed specifically for use with coal as the fuel. Operating tests with this turbine are now in progress. This paper describes the Bureau's coal-burning gas turbine development program and progress on this operating test.

Jan 1, 1964

By Roe-Hoan Yoon

INTRODUCTION In 1960, coal accounted for 49% of the world energy consumption, an amount that was reduced to 29% in 1973 because of the availability of cheap oil. At that time, it seemed that oil would remain available for a long time in unlimited quantities. However, this situation changed drastically in 1973/74 when a series of closely spaced price increases from $3 per to $12 per bbl by mid-1974 hit both industrialized and developing countries. Another sharp price increase in 1979/80 to the $34 to $38 per bbl level also hit the world economy hard and, at the same time, set in motion powerful technology development forces for increased coal utilization. At this point, the price of coal was approximately $1.50 per MM Btu, while that of oil approached $6.00 per MM Btu. This huge price differential offered an incentive for developing new coal technologies including liquefaction, gasification, fluidized bed combustion, coal-water mixture (CWM), etc. The CWM technology was of particular interest to the utility industry, which consumes more than 80% of the coal mined in the US for power generation. In this technology, a powdered coal is mixed with water to produce a stable slurry that can be stored for an extended period of time without settling and is readily pumpable. Various reagents in the amount of approximately 1% by weight of the coal are added to inhibit sedimentation during storage and to reduce the viscosity for atomization in burners. The coal loading is in the range of 50 to 80% solids, depending on the particle size and its distribution. With very fine particles, it is difficult to increase the coal loading above 50%, and a binomial distribution helps increase the coal loading. The presence of water consumes a relatively small amount of the heating value of the coal during combustion; for a coal-water slurry containing 30% water, less than 5% of the calorific value of coal is usually consumed due to evaporation. The major advantage of burning coal as a slurry is that many of the oil-burning furnaces can be converted to coal-burning with a minimum retrofit cost. Considering the substantial price margin between coal and oil, the pay- back period for retrofit costs can be relatively short. Nevertheless, the retrofit cost can be further reduced if low-ash coals are used as feedstocks for CWM; there will be savings in the capital cost of installing bag filters or electrostatic precipitators that are designed to remove the ash from the combustion gases. Furthermore, the use of low-ash coals can minimize derating of boilers because the velocity of the combustion gases can be maximized without creating erosion

Jan 1, 1991

By Jurij Karlovšek, Wolfgang Angerer, Vojtech Ernst Gall, Jacob Grasmick

The International Tunneling Association (ITA) Working Group (WG) 22 “Information Modelling in Tunneling” has developed a guideline for the implementation of Building Information Modeling (BIM) concepts for Bored Tunneling Projects. The guideline primarily covers the use of BIM during the conceptual and delivery phases of a project. It provides Owners with an introduction to BIM, an overview of the current capabilities of BIM, and a guide for implementation for a Bored Tunnel. The document will be officially published at the World Tunnel Congress (WTC) in Copenhagen in 2022. This paper describes the need for the guideline and provides a preview of its contents.

Dec 1, 2022

By J. L. Coburn

The Huari-Huari ore body is located in Southern Bolivia, at an elevation of approximately 3,800 meters above sea level. The ore is a complex massive sulfide, slightly marmatitic sphalerite, in a fault fissure filled hypo- thermal vein in Paleozoic shales and quartzite-altered sandstone. The sphalerite has common associations with pyrite and quartz and is frequently intricately intergrown with stannite, chalcopyrite, and pyrrhotite. The sphalerite also contains numerous inclusions of pyrite, marcasite, galena, boulangerite, jamesonite, quartz, arsenopyrite, and cassiterite. A research program was undertaken to develop a flowsheet for the recovery of separate silver, zinc, and tin concentrates by selective flotation. Based on this experimental work and subsequent flowsheet development, engineering and construction of a 500 metric ton per day concentrator was undertaken. This paper describes the process that was developed for the Huari-Huari ore and the unique aspects of the Huari-Huari concentrator.

Jan 1, 1977

By Jr. Schnakenberg

In 1986 the U. S. Bureau of Mines (USBM) embarked on a major research effort to develop technology that can substantially reduce worker exposure to face hazards simply by relocating the equipment operators to an area of relative safety. This reduced exposure mining system (REMS) research effort enhances the USBM ongoing health and safety research efforts to reduce and control dust and noise and to reduce accidents through training and better mining practices. This paper reports progress of the research that is developing and will demonstrate the technologies required for the computer-assisted tele-remote operation of continuous mining machines, haulage systems, and roof bolting machines.

Jan 1, 1996

By Fan Yang, Zhiping Wen, Tiancheng Nie, Jinhe Pan, Ruibo Jia, Changchun Zhou

Rare earth elements have important strategic significance and economic value, and the rare earth elements in coal resources have considerable development potential. This study took coal refuse in the Jungar area of Inner Mongolia, China, as the research object, and investigated the occurrence modes of rare earth elements. A special sequential chemical extraction experiment was designed, and the results showed that the rare earth elements in coal refuse mainly occur in silicate and aluminosilicate form, accounting for approximately 65% of the total rare earth elements. According to the results of SEM-EDS, micro morphology of the sample belonged to the lamellar structure of clay minerals, and Al, Si, Fe, S, Y, and La were all present in the sample. Through SPSS software analysis, rare earth elements have an obvious linear positive correlation with Al, Si, and Fe elements, and a negative correlation with S elements. The rare-earth element occurrence mode in coal refuse can provide a definite theoretical basis for the later extraction and enrichment work.

Feb 18, 2022

In the late 1980s and into the 1990s, the Mountain Pass Mine in California produced about 40 percent of the world?s rare earth elements. At the height of this production, the facility produced up to 54 L/s (850 gpm) of saltwater that was piped to offshore holding ponds where the water was evaporated. In 1998, following a series of waste water pipeline breaches, separations activities were suspended, reducing the Mountain Pass site to just the openpit mine and mill. The environmental concerns were addressed and the affected areas have since been remediated. However, in the years following the breaches, 97 percent of the world?s production of rare earth elements moved to China. By 2011, Molycorp, and the Mountain Pass Mine, had rebounded from the difficult times and were once again in a position to become a significant player in the rare earth industry.

Jan 1, 2011

By T. M. Barczak, S. C. Tadolini

Reduction in the recovery time required and improvements in safety during a longwall face move have compelled coal mine operators to examine and use pre-driven longwall recovery rooms. The recovery entry is developed at the longwall stop position and supported ahead of time so that the required combinations of standing and internal sup-ports can be installed before the longwall face approaches. A calibrated three-dimensional finite element model, developed in conjunction with an underground test area, provided the critical components and design principals for a comprehensive parametric study. The study indicates that vertical, horizontal, and shear stresses concentrated on the outby abutment pillar corner of the recovery room resulting in deformations in the immediate roof above the primary roof support anchorage level. The results of the numerical model and field site observations indicated that the combination of the internal bolting system and the standing concrete supports are critical for the successful and safe extraction of the longwall equipment. Cable supports installed at and angle over the pillars can help stabilize the disturbed zone above the adjacent fender and outby pillars, however; standing supports are required in most sedimentary roof conditions to increase stability and assure a safe longwall extraction.

Jan 1, 2004

By S. Komar Kawatra, J. J. Carlson

"It is widely known that steel made from iron ore pellets high in phosphorus is brittle. Removal of phosphorus from iron ores such as hematite has proven to be difficult. The majority of research on phosphorus removal from hematite ores has been focused on flotation. The purpose of this study was to assess phosphorus distribution under current operations at an existing hematite concentrator and determine how efficient the plant is at removing phosphorus. Objectives included: (1) Perform a phosphorus balance at an operating plant to assess phosphorus distribution under current operations; (2) Determine phosphorus removal efficiency of each separating unit and (3) Perform a quantitative liberation analysis to determine max phosphorus removal by physical means. Liberation was quantitatively determined using wet high intensity magnetic separation (WHIMS) to separate iron ore from liberated apatite (and other nonmagnetic compounds).It was observed that 61.2% of the total phosphorus entering Plant F was rejected during current operations. The desliming process was the most efficient step at removing phosphorus (45.1% P removed), whereas the flotation step was much less effective (16.1% P removed). Liberation analyses indicated that the deslime thickener may have been more efficient at removing phosphorus than the flotation circuit due to the greater abundance of liberated phosphorus in the deslime thickener feed. The scavenger returns stream was identified as having a high concentration of phosphorus and a possible point of phosphorus removal. However, liberation analyses indicated that only 32.4% of the total phosphorus in the stream was liberated. Grinding the scavenger returns to 80% passing 5.2 µm increased the amount of liberated phosphorus in the stream to 70.4%."

Jan 1, 2014

By William W. Edgerton, Moussa Wone, David H. Corkum, Carlton M. Ray

"The DC Clean Rivers (DCCR) Project is a 25 year, $2.6 Billion court ordered project to reduce combined sewer overflows (CSOs) discharging into the Potomac and Anacostia Rivers and Rock Creek, and also reduce flooding in the northern areas of the District of Columbia. Like all massive infrastructure programs, DCCR faced technical challenges, management challenges, risks of cost and schedule overruns, procurement challenges, and financing challenges. While DC Water is no stranger to large capital improvement projects (CIP), this CSO Program represents a once in a lifetime event for the Owner requiring the assembly of a single purpose team to implement. Some of the DCCR Project team’s most successful accomplishments to date are attributable to its introduction of early contractor involvement (ECI) to thoroughly vet the work from the perspective of the future constructors, development of functional baselines to share risks that are difficult to price and reduce reliance on geotechnical baseline interpretation during tunnel excavation, and attainment of financing through Municipal Century Green Bonds based on using design criteria of a minimum of 100 year life for the structures to establish intergenerational equity and fairness. This paper will discuss these innovations in detail and provide some sets of recommendations for the underground industry on when and how to use different approaches to better manage projects of this magnitude. INTRODUCTION The District of Columbia Water and Sewer Authority (DC Water) is an independent multi-jurisdictional authority that was established in 1996. Its primary mission is to provide water distribution services to more than 640,000 residents in the District of Columbia (District), and sewer treatment and disposal to 1.6 million residents of the District, Montgomery and Prince George’s counties in Maryland and Fairfax and Loudoun counties in Virginia."

Jan 1, 2016

By F. Segobia, H. Lozano, M. Portal, F. Ysla, L. Goicochea

This case study evaluates the long- term physical stability of various historical mining structures remediated by the Center for Mining Environmental Research and Studies (CIEMAN) in Hualgayoc, Cajamarca, Peru. The region has a long history of mining activity, with remnants dating back to pre-Inca times. CIEMAN has assumed responsibility for remediating 286 environmental liabilities in the area, including adits, shafts, pits, tailings, and waste rock dumps. The study analyzes the methods employed to stabilize these structures, including geotechnical engineering techniques and revegetation. Long-term monitoring results are presented, assessing the effectiveness of remediation measures and predicting the future stability of the structures. This study highlights the importance of responsible remediation of mining environmental liabilities to ensure the safety and sustainability of communities and ecosystems affected by historical mining.

Feb 1, 2025

By St. E. Deák

This paper focuses on maintenance of underground salt air curative quality using environmental friendly solutions. Possible ways to preserve its curative properties, in relation with the admissible salt air quality parameters, are analyzed. In situ investigations regarding microbiological impregnation in walls and the air inside the Romanian salt sanatorium were initiated. The results of a pilot project, which is in progress at Praid salt mine, are presented. After the end of the investigation at this site, investigations will continue in other Romanian salt mines, such as Slanic Prahova, Targu Ocna and Cacica.

Jan 1, 2006

By Daniel F. Meyer, William C. Paschen

INTRODUCTION The problems involved with moving millions of tons of rock are being addressed by nationally recognized tunnel contractors who have converged in Chicago over the past 5 years. This wealth of expertise has been needed to meet the risk and challenge of constructing the world's largest network of underground tunnels which in turn has required a dramatic advance in the art and science of tunneling. These pioneers, through innovation, adaptation, and hard work, have eliminated the one major concern of The Metropolitan Sanitary District of Greater Chicago - how to move 8 million tons of rock. The Metropolitan Sanitary District of Greater Chicago (MSDGC) serves 122 municipalities covering 866 square miles in Cook County, Illinois. Of these cities, towns, and villages, 53 have combined sewer systems. On an average of once every four days, these systems overflow about 4 million gallons of combined sewage and rainwater into the area's rivers and canals. The overflows occur at approximately 640 outfall locations of which 10% are owned by the MSDGC, with the remainder of the points belonging to various other municipal bodies. All those who own these "point" sources of pollution are in violation of Illinois State and Federal regulations. To enable its member municipalities to come into compliance with State and Federal law, the MSDGC is implementing its Tunnel And Reservoir Plan (TARP). TARP is a regional solution to the problem of combined sewer overflow in the metropolitan Chicago area. TARP will greatly reduce the pollution of area waterways by intercepting the combined sewage and rainwater carried in the existing sys-

Jan 1, 1981

By Ari Glazer

"Every year the tunneling business is expanding and collaboration with the International Society of City and Regional Planners (ISOCARP) for the future design of cities and urban communities is in the making. During the last half of this century, billions of people migrated to cities, and it is estimated that by 2030 almost five billion people worldwide will reside in urban communities. Hence, “Underground development will be an important tool in reshaping our urban areas to meet the challenges of the future without destroying their heritage or worsening their surface environment” (Esaki, 2005). In 2013, the Organization for Economic Co-operation and Development (OECD) estimated life expectancy to be around 80 years, meaning that in less than a decade we will need to bury billions of people in cities and urban communities, while trying to retain the deceased’s beliefs and customs. Religion plays a major role in our lives, and many people worldwide still decline to cremate their body after their death; therefore, cemeteries are essential for city inhabitants. Rites and traditions usually call for burials to be near the place of residence, which allows the remaining family members and friends to visit the grave frequently, at least in the first years. This is a challenge that urban designers and architects must confront while trying to solve the problems of future urbanization. In recent years, population growth, the rising cost of land and the extensive preservation of green areas have made cemeteries a burden and a nuisance, particularly for large cities and communities. Many graveyards that were once on the city's outskirts have become lifeless islands in populated areas (Fig. 1), rarely visited by the second and later generations. Cities worldwide face the challenge of allocating less land to maintain current burial practices. In response, some cities have begun to bury their dead at a great distance from the community; others have started to stacked burials, one on top of the other, while still others are constructing buildings and even skyscrapers for the practice of burial (Fig. 2)."

Jan 1, 2016

By Staff

In 2012, the estimated value of mineral production increased in the United States for the third consecutive year. Production and prices increased for most industrial mineral commodities mined in the United States. While production for most metals remained relatively unchanged, with the notable exception of gold, the prices for most metals declined. Minerals remained fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels, including mining, processing and manufacturing finished products. Minerals? contribution to the GDP increased for the second consecutive year. Trends in other sectors of the domestic economy were similar to those in mineral production and consumption rates (Table 1). After continued decline following the 2008-2009 recession, the construction industry began to show signs of improvement late in 2011 and throughout 2012, with increased production and consumption of cement, construction sand and gravel, crushed stone and gypsum, mineral commodities that are used almost exclusively in construction.

May 1, 2013

By S. Kenzap, V. Kazakidis

Risk assessment is an essential component of mine feasibility studies. However, it is often challenging to identify the appropriate analysis and derive the required input data. The uniqueness of a mining project and the associated technical issues require customization of the risk assessment approach to meet both requirements and characteristics. The uncertainty driving the operating risk in mine feasibility studies and its assessment through Monte Carlo simulation as a component of a cash flow analysis are discussed in this paper. The paper introduces the use of the analytic hierarchy process for derivation of qualitative input and conducts quantification of the three main sources of operating performance delays, equipment, ground and schedule problems, in a cash flow simulation. A methodology for the assessment of operating risk in mine feasibility studies is presented.

Jan 1, 2011

By C. Heckman, M. S. Moats, A. Luyima, W. Cui

"Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and galvanodynamic and chronopotentiometric techniques were used to characterize the effects of DXG-F7®, a commercial smoothing agent, on copper electrodeposition onto 316L stainless steel from a synthetic electrolyte containing 40 g/L copper (Cu2+), 160 g/L sulfuric acid (H2SO4) and 20 mg/L chloride (Cl-) at 40oC. The findings were compared against results using HydroStar® 4208, a modified polysaccharide. The nucleation overpotential and plating potential observed in cyclic voltammetry and galvanodynamic testing showed that neither DXG-F7 nor HydroStar significantly polarized acidic copper electrodeposition. Subtle differences between the additives were found during EIS testing and modeling, but more research will be needed to fully understand these differences. Surface-roughness measurements of two-hour deposits indicate that DXG-F7 and HydroStar produced smoother deposits as their concentrations in the electrolyte increased. No difference in the surface roughness of deposits was detected between the additives. Based on the experimental evidence resulting from the laboratory testing, no significant difference was found between DXG-F7 and HydroStar at 20 mg/L Cl- concentration, with the exception that DXG-F7 dissolves more easily in water than HydroStar. Introduction Cathode deposits obtained from acidified copper sulfate electrolyte(s) without organic additives are often soft, coarsely crystalline and nodular (Sun and O’Keefe, 1992). Therefore, small amounts of organic additives are added to the electrolyte to produce level and dense cathodes during copper electrowinning. The action of organic additives is thought to be due to their adsorption on the surfaces of the newly formed copper grains. Hence, any copper grain that grows excessively fast adsorbs a layer of organic additive, which inhibits growth. The result is a smoother and harder deposit of suitable purity (Sun and O’Keefe, 1992). In part I of our four-part series on the examining of copper electrowinning smoothing agents, a review of previously published work on organic additives used during copper electrowinning was presented (Moats, Luyima and Cui, 2016). In the review, it was noted that many tankhouses had switched from guar to other saccharide-based products such as HydroStar and DXG-F7."

Jan 1, 2016

By A. Halim, J. Gustafsson, A. van Wageningen, J. Johansson, · J. Lööw, K. Kocsis

A major part of the European Union’s (EU) project Sustainable Intelligent Mining System (SIMS) is investigating the development of diesel-free/carbon–neutral underground mines in order to ensure sustainable underground mining in the future. Replacing diesel machines with electric vehicles in underground hard rock mines has been widely acknowledged by the mining industry worldwide as a critical step to improve working conditions by reducing diesel exhaust–related contaminants, to reduce mine ventilation electrical power cost by reducing mine airflow quantity, and to reduce mine greenhouse gas emissions. All of these are major requirements to achieve sustainable future underground mining practices. A field trial of Epiroc’s 2nd generation of Battery Electric Vehicles (BEVs) at Agnico Eagle Finland’s Kittilä mine was conducted during 2019–2020. Vehicles tested were MT42 mine truck, ST14 Load-Haul-Dump (LHD), and Boomer E2 jumbo drill rig. This paper outlines the improvement of the working conditions observed in the field trial, and the opinions of the mine personnel at Kittilä mine on using BEVs instead of diesel machines. Measurements of atmospheric contaminants and air temperatures taken during the field trial clearly demonstrated a significant improvement of working conditions when BEVs were operating as opposed to diesel machines. This field observation was supported by the opinion of the majority of the Kittilä mine workers. However, some remaining concerns must be addressed before BEVs can replace diesel machines.

Oct 25, 2021

By Michael Casson

With the mining industry changing rapidly due to mergers, acquisitions and fluctuating market pricing, today?s market for coal, minerals, ores and aggregates demands electrical apparatus that perform every time with maximum efficiency and with consideration for personnel safety. This is especially true in existing mining operations where every payload counts. Draglines are the workhorses of surface mining operations, and reliable and efficient operation is absolutely critical to success. However, the inherent disadvantages of using dc motors and motor-generator (MG) sets can significantly impact productivity and return on investment (ROI).

Jan 1, 2013

By Elwyn King, Donald J. Dodds

"...Unfortunately, the research activities in soil mechanics had one undesirable psychological effect. They diverted the attention of many investigators and teachers from the manifold limitations imposed by nature on the application of mathematics to problems in earthwork engineering. As a consequence, more and more emphasis has been placed on refinements in sampling and testing and on those very few problems that can be solved with accuracy. Yet accurate solutions can be obtained only if the soil strata are practically homogeneous and continuous...." This statement about soil mechanics was made by Karl Terzaghi, thirty years ago and applies to a greater degree today to the infant science of rock mechanics. More uncontrolled variables are added to the already many existing in soil mechanics. Variables, such as Macro-discontinuity and in situ stress levels. In no other field of engineering are the problems as site oriented. Presently this site dependance demands the investigator or rock mechanics engineer to get his hands dirty rooting in the muck of a tunnel floor trying to properly install or readout test apparatus in a comprehensive site investigation. This paper discusses such a site investigation designed to determine the problems and solutions inherent in the driving of the Trans Koolau Tunnel. The paper will describe the various types of tests to be performed, how the results are to be used and the interrelation of the various tests themselves.

Jan 1, 1997