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The authors provide a discussion of the paper, ?Coal workers? pneumoconiosis prevalence disparity between australia and the united States,? a peer-reviewed paper that appeared in the technical papers section of the July 2012 issue of Mining Engineering magazine. The original authors, G.J. Joy (gjoy@cdc.gov), J.F. Colinet (jcolinet@cdc.gov) and D.D. Landen (dlanden@cdc.gov), respond.

Jan 1, 2013

By A. E. Petersen

The United States Bureau of Mines conducted research on high-intensity magnetic separation methods for upgrading tantalum concentrates from Alabama. Process flow sheets were studied to maximize tin removal and minimize tantalum loss. Using laboratory-scale equipment, concentrates were produced which contained over 65% combined Ta2O5-Nb2O5. Up to 78% of the tin was recovered as a byproduct, containing about 70% SnO2. Only 1 to 5% of the tantalum reported with the tin byproduct. The producer subsequently incorporated high-intensity magnetic separation into its process flow sheet to provide concentrates for the National Defense Stockpile.

Jan 1, 1993

By S. K. Sharma

The Bureau of Mines' rapid method of dewatering fine-particulate slurries uses extremely high molecular weight polymers. These polymers form large, strong flocs which can be dewatered by sieving or sedimentation. However, sometimes these flocs deteriorate rapidly if water is not removed immediately. During field tests, clay slurries have been encountered that could have been dewatered economically if it were not for the rapid floc deterioration. A kinetics study was conducted to determine the rate of kaolin-PED floc degradation in which polymer addition, to bring the flocs back to their original condition, was used to determine the extent of floc decay. Results showed that the amount of polymer added, to replace polymer lost by spreading, was less for the lower PEO concentrations. For this clay-polymer system, floc breakage as judged by polymer additions followed first order kinetics. It was also found that the addition of fluoride ion stabilized the kaolin flocs.

Jan 1, 1992

By H Arvidson, Rondinelli Sousa, Nic Pollock, Cesar Carrasco, Boz Elloy

Global public mineral reporting codes have driven strong governance of public disclosures of minerals information. Recently, we have seen an increase in disclosure of information related to Environmental, Social and Governance (ESG) issues, and governance of ESG information in mining companies has arguably reached a similar level of governance and diligence afforded mineral reporting. We define Resource Governance as the conjunction of environmental, social and minerals governance. A modern systems approach to Resource Governance, which combines mineral and ESG information, would provide not only reporting and governance capability, but also has the potential to sense/respond, predict, and manage ESG risks.

Feb 1, 2024

By S. S. SHINDE, P. C. JIKAR, N. B. DHOKEY

Mill scale is an oxide waste product of steel mills, containing around 70 percent iron and other allied impurities. In the present context, a dynamic prototype counter-current reactor (CCR) was used for the experimentation and simulation of a particle bed using the discrete element method (DEM). Mill scale was pulverized to ASTM mesh range 140 (106 μm)/+ 270 (53 μm) and oxidized in a CCR to make a single oxide Fe2O3 phase by maintaining the required thermodynamic conditions, such as pure oxygen at 1,100 °C. This oxidized powder was then subjected to a reduction reaction in the CCR, with gas mixture (H2:N2) ratio of 1:4 at 875±5 °C for filling degree, fd , and reactor revolution, ω, ranging from 5.38 to 16.14 percent and 2 to 5 rpm, respectively. A creeping fluid flow condition (Re < 1) and natural heat convection (Gr/Re2 >> 1) were maintained during the solid–gas reaction, and the particle-bed behavior was quantified by Froude number for the optimum operating window. The simulation was validated with the experimental results of reactor reaction product by X-ray diffraction (XRD) and scanning electron microscope (SEM) images.

By HASAN SERKAN GOKCEN, SERKAN CAYIRLI

Manufacturers have improved various stirred mill types to be well adapted to fine and ultrafine grinding applications. These stirred mills, which are operated in wet or dry conditions, may be classified as horizontal — such as AHM-horizontal agitated media mill, IsaMill and Drais mill — or vertical — such as tower mill, Vertimill, Maxmill, Stirred Media Detritor and ATR vertical agitated media mill. The main difference between vertical and horizontal structures is in their operational variations. Additionally, the scaling-up of mills is also an important parameter for selecting the suitable orientation [1]. The purpose of this study was to investigate the dry grindability of calcite powders in a vertically and horizontally orientable laboratory batch-type stirred mill. The experimental results were evaluated using stress intensity analysis. The results showed that the d50 values decreased with increasing stress energy down to a certain point and then increased for both milling orientations. Even though the optimum stress energies for both vertical and horizontal orientations were in the range of 1 × 10−3 to 5 × 10−3 Nm at 750 and 1,500 kJ/kg energy consumption, the product size was finer for the horizontal orientation at the same stress energy value.

By Steven J. Van Kauwenbergh, Talaat A. B. Lawendy

Batch laboratory-scale beneficiation tests were conducted on four high-iron phosphate samples. These samples included sedimentary ores (Tilemsi Valley, Mali and Tahoua, Niger), a sample from an igneous phosphate deposit (Matongo, Burundi), and a fine-grained phosphatic iron ore processing residue from Chile. The Matongo phosphate deposit occurs as a thick (up to 80 m) residual blanket of P205-enriched soil over solid parent rock (carbonatite and associated rock types). Although the Matongo deposit is an igneous deposit, ore from the deposit can be subjected to beneficiation treatments commonly used to treat sedimentary rocks. The beneficiation flowsheets designed to process these diverse ore types involve attrition scrubbing, size classification, and flotation. At the best flotation conditions tested, phosphate concentrates assaying 32.0%-39.0% P205 and 1.0%-1.5% Fe2O3, were obtained at 64.2%-82.2% overall P2O5 recoveries from run-of-mine (ROM) ores containing 9.2%-28.6% P205 and 5.9%-16.1% F,20,. A cleaner phosphate concentrate assaying 33.1% P205, 1.8% A1203, and 3.3% Fe2O3 at 53.4% overall P205 recovery was obtained from the phosphatic iron ore residue that originally contained 4.5% P205, 8.0% A1203, and 17.6% Fe2O3.

Jan 1, 1993

By J. C. Norman

The boron review did not arrive in time for publication in the June issue. The United States was the world&apos;s largest producer and consumer of boron compounds during 1992. The US Bureau of Mines estimated that boron mineral concentrate and chemical production in the United States totaled 1Mt (1.1 million st) in 1992, yielding 521 kt (574,000 st) of B203 for a total estimated value of $333 million. That was about 20% less than 1991 revised production figures, and less in value by $107 million. The United States continues to provide essentially all of its own boron supply while maintaining a strong position as a source of sodium borate products and boric acid to foreign markets. Domestic employment in the mining and beneficiation of boron products in 1992 was about 900 people, the same as in 1991. In 1988, 1250 people worked in the boron industry. The Bureau estimated that total world production of boron in 1992 was about 3 Mt (3.3 million st), or about 1.2 Mt (1.3 million st)of B2O3. World production in 1992 was about equal to revised 1991 levels. US production Mines and processing operations in southern California were the only domestic sources of boron mineral concentrates and chemicals. US producers, in order of quantity of production, included:

Jan 1, 1993

By Douglas Ball

An underground storage field is a gas field where man, not nature, has put all or most of the gas. All but one of those in use today are in the pore spaces or "porosity" of sedimentary rocks, the most common being sandstone. The one exception, near Newcastle, England, is a gas storage in a cavern dissolved from rock salt. The tens of millions of barrels of LPG (liguified petroleum gas) now stored in salt caverns mined in shale is liquid storage, not gas storage, and in this paper I recognize the presence of these installations but do not include them in the gas storage category, Since, with the English exception, gas storages are gas fields, they can all be sorted into the categories used to describe gas fields, 95% of them once gas fields anyway, but some of the remaining 5% are the ones having the greatest effects on underground waters.

Jan 1, 1960

By A. Simon, J. Weyer, J. Brune, V. Zhiteneva

"Reiche Zeche is a lead-zinc-silver deposit in Freiberg, Germany, that was mined for over 800 years. Since 1969, Reiche Zeche has been a teaching and research mine with numerous adits for dewatering large amounts of inflowing water. Infrequent metal water quality monitoring in the 1980-1990s and flooding of the mine in 2002 led to a lack of relevant data. New measurements were taken at different level adits and ore veins for comparison to historical values, revealing pH levels as low as 1.95, conductivity as high as 22000 µS/cm, and an overall trend towards less acidic waters. INTRODUCTION Reiche Zeche is part of the Himmelfahrt Fundgrube, a former iron ore mine in Freiberg, Germany, in the Erzgebirge mining region of Saxony. The polymetallic sulfide ore found in Freiberg was mined from 1168 to 1969, and though it is no longer producing ore, Reiche Zeche remains as a teaching and research mine for the Technische Universität Bergakademie Freiberg. The most important ore minerals mined were sphalerite, galena, pyrite, chalcopyrite, and silver, and important gangue minerals include calcite, fluorite, barite, siderite, and quartz (Zänker et al 2002). Over one thousand ore loads were mined from this region during operation, which was ceased in 1969 after the lower part of the 700 meter depth was flooded, leaving only the top 200 meters under the surface open for research and teaching. Mined materials from this region can be separated into high grade ore and waste rock. High grade ore, composed of pyrite, sphalerite, galena, chalcopyrite, and arsenopyrite, was brought to surface for smelting during mine operation, and spaces were backfilled with waste rock, which is the primary site of sulfide oxidation and acid mine drainage (Haubrich and Tichomirowa 2002). The waste rock includes remnants of ore from ore loss, veins which were too small to mine, or ore minerals within host rock. Waste rock is primarily composed of biotite gneiss, with sulfides including jarosite, gypsum, minor anglesite, scorodite, and sulfur (Haubrich and Tichomirowa 2002). When weathered, the gneiss forms clay minerals such as illite and kaolinite (Haubrich and Tichomirowa 2002)."

Jan 1, 2016

By José Ricardo Lopes, Alaor Coelho, Marco Gomes, Alfredo Dacio Moraes Filho, Akira Koshima

"Very low strength alluvial peat soil was found under two old drainage galleries with just 4.3m cover above a twin tunnel due to be excavated by a 10.6m diameter EPB Shield for São Paulo Metro’s Line 5. Alignment was required to strengthen soil and drive the TBM through safely without damaging the galleries. The design included six levels of self-drilling forepoling with lengths up to 15m, using 100 mm-diameter SCH160 metal tubing and injection bulbs with estimated 0.20m diameter. Two 6m-diameter circular shafts were excavated along the shield-tunnel axis, one each side of the galleries, and forepoling fanned out under gallery foundations. Given the peculiar soil and confined working space, more data were needed for correct drilling geometry. Ground mass treatment was successfully designed and executed and galleries were fitted with instruments to enable the shield’s advance. DESCRIPTION São Paulo Metro’s Line 5 (aka Lilas or purple line) is adding 11 stations along an 11.5km extension and three EPB TBMs are being used simultaneously (three EPBs on the same job for the first time in Brazil) with one of them excavating a large cross- section twin-track tunnel. Currently the largest work-in-progress for São Paulo Metro, this project has been divided into seven lots and 9km are already operational. This study refers to Lot 6 where the 10.6m - diameter EPB shield excavation is only 4.3m below two galleries running through a 10m layer of very soft peat soil in an old alluvial riverside region ringed by major roads. After recent filling, this area (Parque das Bicicletas) was used for recreation, although temporarily it has become a construction site. This paper will describe the original basic design; precautions in relation to the structural condition of the galleries after inspection; the problem of absence of data for their foundations; subsoil bore tests; evolution of the engineering design for the galleries and conditioning and reinforcing the soft soil below the galleries to ensure safe advance of the EPB shield, and finally the successful outcome of the solution used."

Jan 1, 2016

By Claude Boisjoly, Pierre de Courval, Don Nguyen

The Sainte-Marguerite-3 (SM3) hydro project, presently under construction, requires the excavation of an underground powerhouse and large water conveyance tunnels. This paper describes the planning of the project, main features of underground structures, excavation techniques and ground support.

Jan 1, 1997

By W. O. Henderson, H. W. Seaney

The sinking and grouting methods employed at the 3C and 3D ore hoisting shafts and the No. 5 service shaft are discussed. The reasons for selecting a circular section over a rectangular one and other technical aspects are reviewed.

Jan 1, 1974

By P. Bartel

Coal cleaning can be effected by the bacterium Sulfolobus acidocaldarius, which in oxidizing sulfur and dissolving mineral matter requires carbon dioxide and oxygen; carbon dioxide as a carbon source and oxygen as an electron acceptor. The desulfurization of coal by thermophilic bacteria under elevated partial pressures of carbon dioxide and oxygen was studied at a total pressure of 1 atm. The partial pressure of carbon dioxide was varied over the range 0.00032 to 0.33 atm (0.00032, 0.007, 0.10, 0.33 atm), and the partial pressure of oxygen was varied over the range 0.14 to 0.40 atm (0.14, 0.21, 0.30, 0.40 atm). The maximum rate of coal desulfurization increased by 32%, from 9.0 to 11.9 mg S/1 hr, as air was enriched in carbon dioxide from its atmospheric level of 0.00032 atm to 0.10 atm. Enrichment with carbon dioxide up to 0.10 atm, at constant oxygen partial pressures, increased the desulfurization rate, but enrichment to 0.33 atm caused the rate to decrease. At constant carbon dioxide partial pressures, the desulfurization rate was maximum at oxygen partial pressures of 0.21 and 0.30 atm. At higher (0.40 atm) and lower (0.14 atm) oxygen partial pressures the rate decreaed by 9 to 20%. The desulfurization rate decreased by 58X, from 9.0 to 3.8 mg S/1 hr, when the air pressure was increased from 1 atm to 3 atm. The effects justify an economic analysis during design and operation of a commercial air feed in a process to desulfurize coal by microbial action.

Jan 1, 1986

By NARAYAN K. BHAGAT, ARVIND K. MISHRA, Aditya Rana, M. M. Singh

The paper presents an innovative directional controlled blasting (DCB) technique for excavating unstable slopes along the Konkan railway in India without disturbing the traffic. New empirical formulae for small geometry blasting to estimate burden and throw were developed. A unique sequence of firing and excavation with powder factor varying between 0.04 and 0.39 kg/m3, irrespective of the actual free face, was used for rock blasting. The process controlled the throw of blasted material over the track and resulted in a smooth and stable wall. The slope angle was changed from 80–82 to 45–47 degrees, and possible wedge, planar and toppling failures were eliminated. No incident of rockfall and slope failure along these slopes has been observed after the stabilization.

By Bernard L. Cohen

I.INTRODUCTION The B E I R-III Report (NAS-1980) introduces large increases in the estimated health effects of radon as compared with previous work (NAS-1972). It is the purpose of this paper to point out some important failures of these new BEIR-III estimates, to offer a general critique of the procedures used in obtaining them, and to offer more rational estimates. In Sec. II we use the BEIR-III model to calculate the risk to non-smokers from environmental radon, and show that it predicts more than twice the total lung cancer rate actually experienced by nonsmokers. In Sec. III we review the histological evidence which shows that no more than about 10% of the lung cancers among non-smokers can be due to radiation. In Sec. IV, we discuss alternative causes of lung cancer, which further reduces the fraction that can be caused by radiation, and in Sec. V we summarize and conclude that the BEIR-III model over-estimates the lung cancer rate in nonsmokers due to environmental radon by at least a factor of 40. In Sec. VT we review the evidence on risk of radon exposure to smokers, and conclude that it is probably not more than four times the risk to non-smokers; this means that the BEIR-III model over-estimates the risk of low level radon exposure to smokers by at least a factor of 10. In Sec. VII, we consider the reasons for the large over-estimates in the BEIR-III. Report. II. BEIR-III LUNG CANCER RATES DUE TO ENVIRONMENTAL RADON AND COMPARISON WITH TOTAL LUNG CANCER RATES AMONG NON-SMOKERS The BEIR-III Report gives the following estimates of the lung cancer risk from low-level radon exposure in terms of working-level-months (WLM): age 35-49, risk = 10 x 10-6 /yr-WLM 50-64, 20 >65, 50 where ages refer to age at death. For latent periods between exposure and onset of these risks it gives age 0-14, latent period = 25 years 15-34, 15-20 years (we use 17 yr) >35, 10 years where ages refer to age at exposure. This is a clear and unambiguous model which is readily usable for deriving numerical estimates. We begin by using it to calculate lung cancer rates due to environmental radon. *This is an abridged version of a paper scheduled to appear shortly in Health Physics. The first step in this process is to estimate the environmental exposures; this was done in a recent paper (Cohen-1981) which concluded that these are about 0.22 WLM/year. In Table 1, this is used to calculate the BEIR-111 predictions for radoninduced lung cancer rates in the U.S. (Col. (5)), and by combining these with population statistics, it is shown (Col.(7)), that it predicts about 24,500 fatalities per year, almost one-third of all U.S. lung cancers. The comparison between the age-specific expected rates from Col. (5) of Table 1 and observed rates among non-smokers is shown in Table 2. The recent paper by Garfinkel (1980) presents the results of a 12 year follow-up on one million Americans in a study by the American Cancer Society. The paper by Hammond (1966) gave the results of the first four years of that study. The paper by Kahn (1966) is based on the so-called "Dorn Study" of 293,000 U.S. veterans of World War II who carry government health insurance. It represents 8 and 1/2 years of follow-up. A recent update on that study (Rogot-1980) does not give absolute lung cancer rates, but the age-standardized ratio between smokers and non-smokers has remained the same which indicates that there has probably not been an important change in the rates for either. The paper by Hammond and Horn (Ha-1958) was an early study by American Cancer Society. It is immediately evident from Table 2 that the BEIR-III estimates for lung cancer induced by environmental radon exceed the [total] lung cancer rates due to [all] causes among non-smokers by about a factor of two at every age. It is only fair to point out that this does not represent a direct discrepancy with the BEIR-III Report since the latter states that its estimates for non-smokers may be too high by a factor ranging from 1 to 6, favoring a factor intermediate between these. Comparisons can also be made with total lung cancer incidence for all ages. A paper by Hammond and Seidman (Hammond-1980) gives the rate for ages above 40 to be 177 x 10-6/year for men and 124 x 10-6/year for women, whereas the rate calculated in Table 1 from BEIR-III for ages above 40 is 309 x 10-6, a factor of two higher. For all ages, the rate among women was reported as 36 x 10-6/year (Hammond 1958) as compared with 114 x 10-6/year calculated from BEIR-III in Table 1, a discrepancy of well over a factor of two. All of the data we have presented are basically from three study groups, but in all three cases the BEIR-III estimates for lung cancer induced [by environmental radon alone] are a factor of two higher than actual [tota] lung cancer rates among non-smokers. Another approach to comparing the BEIR-III pre-

Jan 1, 1981

By BHAMIDIPATI S. SASTRY, SRIVATSAN J. SRIDHARAN, ANMAYA NAIK, ASIF AHMAD, ADITYA PANDEY

Wet kata cooling power (WKCP) measured using a kata thermometer is a well-known heat stress index in mining industries. Although over the years several researchers have proposed different heat indices and indicated the limitations of the kata thermometer, it is still being used in many areas, especially in the South African gold mining industry, mainly because of its simplicity and rapidity of assessment. This paper presents a comparative analysis of the newly developed empirical expression for WKCP, and some of the more prevalent empirical expressions. The analysis presented based on a regression technique aims to assess the disagreement between model predictions and actual measurements. It is found that the WKCP expresses bioclimatic interaction quite well under the specific parameter of interaction that explains the harsh thermal environment and air condition, such as metabolic activity, the person’s clothing, and the velocity of the air in which the person is working. The statistical analysis shows that the WKCP exhibits significant estimates to thermal stress under lower air velocities, light clothing, and higher metabolic activity rates.

By L. Galarza

"INTRODUCTION Beneficiation of ores and minerals in a concentrator plant requires a significant amount of water [1] for the grinding and particle separation processes; most of it ends up being recirculated for reuse, slurry pumps are used after crushing and grinding feeding the ore to a classifier to separate fine-grained material (less than 5 mm) from coarse-grained material requiring further grinding. The lower ore grades [2] in the past couple of decades have demanded an increase on power size and efficiency of process machines to maintain a competitive plant throughput; Hydro-cyclone feed pumps to control both under and over milling or grinding are not the exception; Fig. 1 shows a conventional drive train [3] comprising an (1) asynchronous motor (also known as squirrel cage induction motor = SCIM), a high speed coupling (2), a gear reducer (3) and a low speed coupling (4) attached to the shaft of the pump (5), to accommodate the motor rated speed (typically 1800 rpm) to the process requirements (in the range of 250 rpm to 350 rpm), requiring additional components related to the gearbox: instrumentation, maintenance, disposable lubricants and filters, spare parts, thus reduces the overall system efficiency ultimately reflected into CAPEX and OPEX.WHY VARIABLE SPEED DRIVES FOR CYCLONE FEED PUMPS Hydrocyclones or commonly referred as “cyclones” are one of the most important devices in the minerals industry [4]; almost universally used in close-circuit grinding because of their high capacity and relative efficiency, the evolution of Power Electronics made affordable the use of Medium Voltage - Variable Frequency Converters (VFC) for Cyclone Feed pumps in combination with induction motors larger than 500hp (373kW) to gain multiple benefits: - Soft start with minimum electrical utility disturbance = inrush current mitigation - Full Torque available at zero speed for overload startup with pulp solidification after long still stand periods, superior to any other reduced voltage starting method. - Optimum and constant pump speed (independent of the electrical network or load condition), compared to across the line SCIM operation - Flexible Motor Voltage and Speed regardless of the power distribution Voltage and Frequency - Improved Power Factor (close to unitary), over the entire operating speed range"

Jan 1, 2015

By Michael P. Evans

Traditionally in coal processing jigs have been used to clean the coarse coal fraction, the +3/8" or +1/4" material. Today with the advent of modern fine coal jigs in the United States, its place was moved from the coarse to the inter- mediate coal circuit, the 3/8" x 100 mesh. The most economical coarse coal circuit to build and operate is a heavy media bath circuit. The following table summarizes the cost per raw coal ton processed for a coarse coal jig circuit, and a coarse coal heavy media bath circuit. The flowsheets used to compare these two circuits are shown in Figures 1 and 2.

Jan 1, 1983

By Lauren M. Roberts, Ralph R. Sacrison

The Meikle Mine uses long-hole open stoping and cut-and-fill methods with backfill as the primary ground support technique. The mine operates at 2,858 tonnes per day (3,150 tpd) and has sustained operation in excess of 3,175 tonnes per day (3,500 tpd). Consistent backfill production is critical in achieving these mining rates. The heart of the system is a 7.65 cubic meter (10-cyd) horizontal shaft ribbon mixer located 328 m (1,075 ft) underground. System control is through several PLC&apos;s, allowing for a high degree of automation and process flexibility. Aggregate feed is routed 257 m (842 A) through vertical drop pipes in the ventilation shaft, a rockbox, transfer raises, and then into either of two raisebored storage silos. The aggregate is crushed mine waste, nominally 70% 3.8 cm x 1.0 cm (1-1/2"x 3/8") and 30% -1.0 cm (- 3/8"). The binder is routed through a vertical borehole, surge bins, and transfer raises. The binder is a mixture of Type II cement and fly ash. Two primary manufactured fill designs are produced: a high strength mix for stopes which will be undercut; and a low strength mix for stopes with only rib exposure. The high strength target is 5.5 Mpa (800psi) unconfined compressive strength in test cylinders. The low strength target is 2.8 Mpa (400 psi). The systim has allowed consistent achievement of these targets, while experience has allowed reduced costs and increased efficiencies. Fill placement is through 6.1 cubic meter (8 cyd) LHD&apos;s dumping into stopes. Specific sills and cut-and-fill drifts are jammed to the back. System enhancements have included colloidal mixers for cemented waste slurry placement and transfer raises for sending manufactured fill to the lower levels of the mine.

Jan 1, 2001