Search Documents

By R. O. Ifill

Alternating current electrocoagulation (AC/EC) may be an alternative to chemical coagulation in the thickening of tailings in the mineral, coal and petroleum industries. In the current study, ground silica (d50 as received, 20 µm) served as the model tailings solid with characteristically poor settling behavior. Its natural initial settling rate was 1.6 x 10-3 cm/min. This paper discusses the indirect application of AC/EC via aluminum electrodes to the enhancement of the settling behavior of the silica. ?Indirect AC/EC? means that the silica was coagulated upon dispersion in water that had been treated by AC/EC. The effect of AC/EC retention time on settling behavior is examined and the water chemistry is analyzed. Test results show that the initial settling rate of silica was enhanced by a factor of 4,000 at its maximum of 6.4 cm/min, under the conditions employed. Settling enhancement was achieved upon contact between the AC/EC-treated water and the silica, and the enhanced initial settling rate was dictated by the floc size. The aluminum dosage increased with AC/EC retention time, reaching a maximum concentration that was equivalent to 13.1% of that predicted by Faraday?s law. Complex aluminum ions are considered to have adsorbed onto the silica surface and an adsorption mass ratio of 0.3 mg Al/g silica was the most effective in enhancing settling behavior. Owing to pH change or slow kinetics, aluminum hydroxide precipitation did not lower the ion product ([Al3+][OH-]3) below the KSP of 6.3 x 10-32.

Jan 1, 2011

By J. C. Willett, J. R. Sanfilipo, P. D. Warwick

The U.S. Geological Survey has conducted an assessment of the Nation’s coal deposits that potentially could be mined during the next 30 or more years. For the Gulf Coastal Plain region, the assessment includes reviews of the stratigraphy, coal quality and resources, and coalbed methane potential of the Cretaceous, Paleocene, and Eocene coal deposits in the region. The results of these efforts are a series of digital maps, text, and tables published in CD-ROM format. Although abundant coal resources are available in the Gulf Coast region, coal quality issues may limit large-scale development in the future. Additional data are required to better evaluate the coalbed methane resource potential for the Gulf Coast region.

Jan 1, 2001

By W. K. Callaway

The need to increase ore recovery and pillar stability caused the Magmont Mine staff to investigate the use of sandfill to accomplish both tasks. The use of hydraulically stowed classified mill tailings as a subsidence preventative will be discussed as well as the use of sandfill in pillar recovery and as a part of the regular mining cycle.

Jan 1, 1986

By K. E. Kolm, W. H. Langer

Developing natural aggregate resources (sand, gravel, and stone) creates environmental impacts. A systems analysis method has been designed to characterize the components of the environmental system, identify potential impacts to those systems, and evaluate the extent of those impacts. The step-wise method consists of problem definition, data collection, preliminary conceptualization and characterization, additional data collection, data analysis, and refinement. The method requires analyzes of various systems making up the environment, including land surface, geomorphic, subsurface, and groundwater systems. After system characterization is complete, the method focuses on identifying and evaluating potential environmental impacts to determine acceptable mining strategies.

Jan 1, 2001

By Lane White

In mid-April 1992, MINING ENGINEERING mailed a survey questionnaire relating to mining shovels and hydraulic excavators to 125 SME members working at surface mines or at the headquarters of companies that operate surface mines. The mailing was directed to individuals whose titles indicate that they have management or mine planning responsibilities for surface mining operations. A total of 56 usable surveys returned by June 17 are the basis of this report. Precious metals mines Eighteen precious metals mines or mining companies returned completed surveys in time to be included in this report. Of these, 14 use hydraulic shovels only for both ore and waste, I uses both hydraulic and rope shovels, and 2 use Caterpillar 988 front-end loaders for both ore and waste. (Of the latter 2, neither expects to be in the market for a shovel in the next three years. I of these 2 placed Harnischfeger P&H number one and O&K number two in response to the question, "Based on your current knowledge of their machines, which manufacturer would you likely chose to supply new shovels or excavators to a mine or mines operating under your responsibility, if you were in the market?") Another uses front-end loaders, make not designated. The latter does not expect to be in the market for mining shovels or excavators within the next three years. Of the final total of 14 precious metals mines using only hydraulic excavators to load ore and waste, 8 use Hitachi excavators only, 1 uses Demag excavators only, 1 uses Liebherr excavators only, 1 uses O&K excavators only, 1 uses Harnischfeger P&H and O&K excavators, 1 uses Harnischfeger P&H and Hitachi excavators, and 1 uses Hitachi and Demag excavators. Of the 14 precious metals mines using only hydraulic excavators, 7 use excavators in the 7.6 to 11.5 m; (10 to 15 cu yd) size range. Of these 7, 5 use only excavators in this size range, and they are used to load both ore and waste. 1 of the 7 also uses 11.5 to 17 m' (15 to 22 cu yd) excavators, and I also uses a 17 to 23 m3 (22 to 30 cu yd) excavator. Of the 7 remaining of these 14 precious metals mines that use only hydraulic excavators, 3 use 11.5 to 17 m' (15 to 22 cu yd), 2 use 17 to 23 m3 (22 to 30 cu yd), and 2 use less than 7.6 m' (10 cu yd) units.

Jan 1, 1992

By Giorgio De Tomi, Ricardo Tichauer

Mineral exploration is a critical step for success in mining. However, small-scale mining often ignores exploration best practices. This paper introduces the Tichauer-DeTomi Matrix, a tool for assessment of geological uncertainty in small-scale mining. This matrix, which measures the level of compliance of exploration programs in small deposits with industry best practices, has been applied to three small mining projects in Brazil: an artisanal gold mine in the Amazon, a small-scale manganese mining venture in the Northeast, and a small manganese deposit in the Southeast. The application of the matrix resulted in indexes that reflect the actual level of maturity of the mineral exploration program in each project. Therefore, the matrix has shown potential to be an effective tool for assessment of the geological uncertainty remaining in small-scale mineral projects, as well as to identify priority exploration activities for reduction of risks associated with the geological uncertainty. As a risk assessment tool, the TichauerDeTomi Matrix may be helpful in promoting investment and sustained development in and around small mines.

By P. Dhar, H. R. Kota, M. Thornhill

Precipitated calcium carbonate is used as a filler and coating material in the manufacturing of paper because of its high brightness and light scattering characteristics. However, beneficiated calcite has similar potential, given the fact that the industrial specifications are already achieved. For paper industries, the requirement is that the desired product should be pure and have a brightness of 93 to 95 percent. A very-high-grade calcite deposit of around 92 percent is located in the north of Norway, which is used as the raw material for ground calcium carbonate (GCC) feed for the paper industries. There is a substantial amount of calcite resource, which has pyrite and pyrrhotite as major impurities. These sulfides, even when present in minor concentrations, impart color to the end product (paper). Removing these minerals is estimated to increase utilization of the deposit by 10  percent, which represents several million tonnes of calcite marble. Due to the requirement for environmentally friendly reagents and chemicals by the mineral industry, fatty di-amines are being tested for pyrite and pyrrhotite flotation. The interaction mechanism of diamine with the main components of the ore were studied and optimum conditions for removal of sulfide impurities are outlined.

By Douglas B. Silver

Traditional cycle theory would postulate that if you have a supply shortage relative to demand, the price will increase because buyers will incrementally increase the price they are willing to pay to ensure that their needs are fulfilled. As prices rise, more supply will be brought on and will eventually exceed demand. This supply excess will cause the price to decline as producers have to lower their prices to sell their goods. What is interesting is that cycles are simply volatility over time. Without the time factor, volatility simply goes up and down. When we add the time element, a cycle is created. This cycle can be big or small. In mining?s case, we are talking about a Super Cycle ? a big cycle. But a Su-per Cycle can be formed in two ways. It can form by either increasing the wavelength or the volatility. If these two elements are combined, a Super Cycle is formed. It is bigger than the normal cycle in terms of time duration and extent of volatility. A recent study (Fig. 1) conducted by Cuddington and Jarrett showed an interesting proof of Super Cycles and suggests that these cycles last between 15 and 30 years. So, what causes a Su-per Cycle? Is it a convergence of unrelated events or a consequence of related events? In a global community everything is related. Equilibrium theory would also take the position that a Super Cycle is a consequence of events.

Jan 1, 2008

By Bruce Clements

The Bagdad mill, located near Bagdad, AZ, was built in 1977 with a designed mill capacity of 36.3 kt/d (40,000 stpd). An autogenous mill-ball mill crusher (ABC) grinding circuit was chosen. The original mill contained three independent grinding circuits. Each contained one 9.75m-diam x 4-m-long (32-ft-diam x 13-ft-long) fixed-speed autogenous mill, a4.7-m-diam x 6.7-m- long (15.5ft-diam x 22-ft-long) ball mill and one 2. 1-m-diam (7-ft-diam) short head cone crusher. Total installed power per grinding circuit was about 8.4 MW (11,350 hp), with 5.9 MW (8000 hp) in the autogenous mill, 2.2 MW (3000 hp) in the ball mill and 261 kW (350 hp) in the crusher (Fig. 1). The autogenous mills were designed to be able to operate semi-autogenously. However, they were never converted to semiautogenous grinding (SAG) mills. As a result of this design, only about 4.1 MW (5450 hp) of the designed power is used in the autogenous mills. The grinding circuits are closed, with 2.4 x 6 m (8 x 20 ft) double-deck vibrating screens. A series of conveyors re- turn screen oversize underneath the mill coarse ore stockpile to feed the crushers. Variable speed belts feed the crushers and control power draw. Crusher product reports directly to the tail end of the autogenous mill feed belt (Fig. 2). A magnetic sensor detects tramp iron in the autogenous mill-crusher circuit.

Jan 1, 1992

By M. A. Reyes, L. Yan

Heat and humidity buildup withn refuge alternatives (RAs) may expose occupants to physiological hazards such as heat stress. The Mine Safety and Health Administration (MSHA) regulations require RAs in underground coal mines to provide a lifesustaining environment for miners trapped underground when escape is impossible. RAs are required to sustain life for 96 h while maintaining an apparent temperature (AT) below 95 °F (35 °C). The National Institute for Occupational Safety and Health (NIOSH) tested a 10-person tent-type RA, a 23-person tent-type RA, and a 6-person metal-type RA in its underground coal mine facilities to investigate the thermal environment over a 96-h period. The test results showed that mine air and mine strata temperatures surrounding an RA occupied by simulated miners (SMs) increased over the 96-h test period. The test results suggest that RA manufacturers should consider this increase in temperatures when calculating and evaluating RA components during surface and laboratory tests. The findings can equip stakeholders with additional considerations for calculating the interior heat and humidity temperature profiles for occupied RAs not tested in situ.

While the United States and the rest of the world struggles with record-setting oil prices Canadian oil sands producers are ramping up production to meet demand for oil while also fighting against a host of negative images. In recent months, the price of oil has skyrocketed. Most of that oil comes from Saudi Arabia. In Alberta, Canada there are unconventional oil reserves that rival those in Saudi Arabia in the vast Canadian oil sands, sometimes called the tar sands. Proponents of the oil sands say that Alberta?s oil sands can be a secure source of oil and energy for the United States for many years to come. With new mining and drilling projects, the industry has said that it could quadruple its production to nearly 4 million bbl/day by 2020. Time magazine once called the oil sands, ?Canada?s greatest buried treasure that could satisfy the world?s demand for petroleum for the next century.? So why hasn?t the United States embraced this close, politically secure source of energy? Because, getting usable fuel from the oil sands can be a dirty business, say opponents. The oil sands are a combination of clay, sand, water and bitumen. It is a heavy, black, thick oil. Oil sands can be mined and processed to extract the oil-rich bitumen, which is then refined into oil. The bitumen cannot be pumped from the ground in its natural state. Instead, tar sand deposits are mined, usually using strip mining or openpit techniques, or the oil is extracted by underground heating with additional upgrading. These methods require a huge amount of energy and water and produce a large amount of carbon emissions. Environmental groups that have long spoken out against the oil sands projects got some political backing in the United States in June when a group of mayors from large U.S. cities spoke out against the oil sands, as did presumptive Democratic candidate for U.S. president Barack Obama?s senior energy advisor. During a convention of large-city mayors in Miami, FL, Alberta?s oil sands were singled out in a nonbinding resolution calling for national guidelines to track the lifecycle impact of different types of fossil fuels. The resolution urges cities not to use unconventional sources of energy with a large carbon footprint, such as liquid coal and oil shale and oil sands.

Jan 1, 2008

By D. W. Partridge, W. Lamb, A. E. Lamb, S. Bird

Due to the constant need to improve SAG mill performance and efficiency, extensive research into all aspects of SAG mill optimization has been performed. This paper will review the current evolution of SAG mill shell liner design and their performance at the Copperton Concentrator. The effect of these liner design changes will be discussed with respect to: • Liner configurations • Mill operating performance, i.e., throughput, power draw, mill control • Mill mechanical performance, i.e., liner wear profiles, liner life, liner breakage, liner hardness • Foundry manufacturing considerations • Economic evaluation of throughput versus liner life This paper will discuss the results of Kennecott Utah Copper’s (KUC) and ME International’s (MEI) test work, providing an insight into the past, present and potential future opportunities of SAG mill liner design.

Jan 1, 2002

By Ren Xiangwen, Shi Xuefa, Shao Mingjuan, Ye Jun, Yang Yaomin, Li Bing

"The Mid-Atlantic Ridge (MAR), one of the archetypes of slow spreading ocean ridges, extends from the Arctic Mid-Ocean Ridge southward to the Bouvet triple junction making up a significant proportion (~ 40%) of the global oceanic ridge system. During the past few decades, many hydrothermal fields like TAG, Logatchev, Ashasze were discovered along the northern part of the MAR, whereas the southern part, which makes up one third of the ridge (6000km), shows little documentation of hydrothermal mineralization, except for three sites: Site 4°48! the Nibelungen Field, and Lilliput. During March to May 2011, following discovery of three new hydrothermal fields during the 2nd Leg of COMRA's 22 Cruise of the R/V DayangYihao, the 3rd and 4th Legs found another two high temperature hydrothermal fields (SMAR15°S, SMAR26°S), one low temperature field, and several fields with strong turbidity and temperature anomalies in the water column. In this study, we present a preliminarily study of the mineralogy and isotopic geochemistry of the sulfides from SMAR 15°S and SMAR26°S.SMAR 15°S is situated in a SE-NW offset depression of an axial neovolcanic ridge in the median valley, with water depth of about 2793m. In the water column around this field, strong turbidity and temperature anomalies were detected. Ten-meter tall venting chimneys, hydrothermal mounds, as well as a large amount of hydrothermal vent shrimp were also observed and recorded by ROV and deep-tow camera surveys. The samples collected from this field include sulfide chimney fragments, massive sulfides and basaltic rocks. Based on the major metal and the mineral assemblages, three types of sulfides have been identified: 1) Zn-Fe rich sulfides with abundant wurtzite and pyrite zoned fragments, 2) Cu-Fe rich sulfides with much isocubanite and pyrite assemblage, 3) Fe-rich sulfide with massive pyrite fragments. These indicate that this field has undergone at least three phases of mineralization during the venting history."

Sep 1, 2014

By C. Özgen Karacan

The formation of the gas emission zone in longwall mining and the potential amount of gas in this zone are factors of local geology and spatial variability within this geology. Therefore, geostatistical methods can be used for modeling and prediction of gas amounts and for assessing its uncertainty in the gas emission zone of longwall mines. This study used core data obtained from 64 exploration boreholes drilled from the surface to the bottom of the Pittsburgh coal seam in a mining district in the Northern Appalachian basin. After identifying important coal layers for the gas emission zone, semivariogram modeling was conducted for different coal seams to define the distribution and continuity of various attributes. Sequential simulations were performed for stochastic assessment of these attributes to calculate gas-in-place (GIP) in each coal seam. GIP calculations for coals of various gas emissions zones were combined and ranked for their cumulative distribution function to find GIP in the caved zone and in the fractured zone at the 5%, 50%, and 95% quantiles. Fifty percent quantile results were later used to isolate a panel from the whole area and create a mosaic representation corresponding to the daily advance rate of the longwall face. This approach helped to estimate the daily emissions of this panel from the caved zone and from the fractured zone. Results showed that gas-in-place in the Pittsburgh coal seam, in the caved zone, and in the fractured zone showed spatial correlations that could be modeled and estimated using geostatistical methods. This study showed that gas-in- place volumes in the study area may be as high as 12.3 Bscf and as much as 3.5 MMscf per acre of mining.

Jan 1, 2012

By Libby R. Ricafort, Victorio V. Pato, R. S. Pizarro

Introduction Atlas Consolidated Mining and Development Corp. (ACMDC) started gold production at its Masbate gold mine early in 1980. This involved an open-pit mine and a 3.5-k/d (3850-stpd) carbon-in-pulp processing facility (Pizzaro and Antonio, 1981). When this operation started, the mine began stockpiling sub-grade milling material averaging 1 g/t (0.029 oz per st) gold. Furthermore, geologists estimated that there were additional low grade reserves within the ultimate pit limits. These amounted to 2.4 Mt (2.6 million st) with an average grade of 1.1 g/t (0.03 oz per st) gold. The success of low cost heap leaching prompted an investigation to determine if this tech¬nique would be applicable for the low grade Masbate ore. The findings were favorable and a series of laboratory tests were undertaken. These tests indicated the amenability of this subgrade milling ore to heap leaching. Depending on ore size, gold extractions of more than 60% were obtained. To further define operating parameters for a commercial heap leaching plant, a 400-t (440-st) batch pilot plant was built and operated. These test results were used to design the first commercial heap leaching plant in the Philippines. One design concern was the control of solutions during the rainy season. Due to the material's low grade, every effort was made to minimize capital and operating costs. To this end, surplus mining equipment from the copper operations of ACMDC and used machinery in the crushing circuit were considered. Location: The Masbate gold heap leaching operations are located on the northeastern part of Masbate Island, Philippines. This is about 480 km (300 miles) south-east of Manila. Climate: The climate is moderate with two distinct periods. The dry season runs from January through June, and the rainy season extends from July through December. During the wet season, the rainfall at the mine site averages 300 mm/m (11.8 in. per month) for a total of about 2000 mm/year (78 in. per year). However, heavy downpours in excess of 100 mm/h (4 in. per hour) can occur. Geology: Four distinct rock types have been identified in the pit area. They are tuffaceous agglomerates, andesitic agglomerates, metasedimentary rocks, and hornblende augite andesitic porphyry. The tuffaceous agglomerate occupies the northern and western flanks of the mine. Andesitic agglomerates are localized distinctly in the central portion of the volcanic plug within the mine site. The eastern boundary of the mine is occupied by metasedimentary rocks, whereas, the hornblende augite andesitic porphyry occurs as an intrusive within the andesitic agglomerate and tuffaceous agglomerate. Some areas of the pit contain high proportions of clay minerals, requiring an agglomeration step in the flowsheet. This ensures satisfactory percolation through the heaps. Ore characteristics: Gold and silver are microscopically dis-

Jan 9, 1987

By Joseph J. Diehl, Brian B. Khalighi

This paper discusses the Queens Water Tunnel, No. 3, Stage 2, being driven by a new Robbins High Performance (HP) Tunnel Boring Machine (TBM).The paper is divided into four sections. In the INTRODUCTION section, a short overview of the scope of the project is presented. In the GEOLOGY section, the geological condition along the tunnel drive is briefly introduced. The TBM DESIGN section discusses the various design criteria and the resulting machine specifications. The paper concludes, in the TBM OPERATION section, with a case history describing the tunneling operation from start-up to the time of the writing of this paper.

Jan 1, 1997

By N. Chow

The recovery of manganese from lower grade resources has been studied for a number of years. Of key importance of prior work, was the discovery that higher valent manganese resource can be readily leached with sulfurous acid. This eliminates the need for high temperature reduction roasting that is conventionally used in processing high grade material. High temperature roasting is energy intensive, emits a large amount of carbon dioxide, and would not be economical for processing lower grade material. While the prior work provides important information to extract manganese from lower grade resources, the production of unwanted by-products, and high water and energy usage has limited its commercial use. This paper describes the results from laboratory work that demonstrate solutions to problems, which to this point preclude commercial development. Preliminary mass and energy balances show that a significant opportunity exists in producing manganese with this hydrometallurgical scheme in a low cost, environmentally friendly manner. Emphasis of the work is on low water use, low overall energy use and economic destruction of unwanted by-products.

Jan 1, 2011

By John J. Sammarco

Mining has one of the highest annual average fatality rates among major US industries. Health and safety dangers have been inherent to mining since the early days of picks and shovels. Even though miners’ health and safety has improved over the years, mining is still one of the most dangerous occupations. Mining was traditionally a low tech industry. It is now driven by competitive pressures to go high-tech by using programmable electronics (PE) for machine control, atmospheric monitoring and material processing. The industry’s experience with the functional safety of PE is limited compared with other industries. Thus, PE is an emerging technology for mining that can potentially create or worsen hazards.

Jan 1, 1999

By Y. P. Chugh, J. Ma

Higher production, better safety standard, and potential for automation are some of the benefits of longwall mining. Today, longwall face advances at a faster rate exposing many diversified rock layers in a short period of time. It is now a serious challenge to cope with ground control problems such as roof falls, face and floor failure, and excessive shield loading as fast as possible to minimize production and monetary losses. In Illinois coal mines, the existence of weak floor strata blow the coal seam may pose additional problems related to floor heaving, shield base punching, and associated roof and face falls. In this study, the effects of weak floor on longwall ground control are analyzed using two-dimensional finite element models. A two-leg 635.6-ton (700-short-ton) yielding capacity shield is included in the models to evaluate the effects of different thickness and material properties of the weak floor. The study indicates that the thickness and material properties of weak floor have significant effects on shield loading, the distribution and intensity of front abutment stress, failure zones in the surrounding strata, roof-to-floor convergence, and floor punching by the shield base.

Jan 1, 2000

By F. Warnaars

Historically, this area produced gold and silver from many well-known vein deposits, like Tayoltita, Topia, and San Jose de Gracia. Modern exploration identified three categories of deposits: 1) low grade porphyry golds in shallow level dacite porphyries; 2) batholith-related deposits; and 3) those formed in volcanic sequences of Late Cretaceous to Late Tertiary. At least four porphyry golds have been identified, of which Metates is best known. These are formed by and within daciteporphyries, associated hydrothermal breccias and sometimes within surrounding meta sediments. Their ages are from mid-Cretaceous to Early Tertiary. Precious metal deposits associated with batholiths occur as veins, contact haloes in meta sediments or volcanics, skarns, tectonic breccias, hydrothermal tourmaline breccias, dacite dikes or as disseminated or stockwork deposits such as La Fortuna.Several new gold discoveries were made in older EarlyTertiary Volcanic Sequences and in the younger Tertiary volcanics within prominent structures exceeding 3 to 5 km in lengths. Some of these are open-pittable but most have to be mined by underground methods.

Jan 1, 1999