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By M. K. Gangal, E. D. Dainty, G. Kunchur

This paper presents a validation of C02 as a single surrogate measurement for other diesel-emitted pollutants in multi-diesel-machine operations typical of small underground mines. This means that the simple measurement of C02 alone can be used to estimate the concentrations of other components of diesel exhaust in the mine environment. The linear relationship of C02 concentration with other diesel-emitted pollutants was indicated by the results of simultaneous real-time monitoring of C02 with CO, NO, NO2, SO2, Respirable Combustible Dust (RCD), and Air Quality Index (AQI) in several small underground mines. The SO2 was not directly measured but calculated from the measured C02 concentration and diesel fuel analysis for carbon, hydrogen and sulphur. The measurements were made in the return air drift under various mining conditions involving a number of diesel LHDs and haulage trucks. The statistical analysis and mathematical representation of the several components of diesel pollutants with C02 are presented. Regression analysis shows that at the 1 percent level of significance there is a strong linear relationship of these diesel pollutants with C02. This relationship is discussed in detail, concluding that C02 measurement alone is a good indicator of overall mine air quality and can be used as a control parameter.

Jan 1, 1991

By A. J. Jeffery

Heat transfer to a fluid flowing through a rough duct has been shown by many researchers to be a function of surface roughness. The effect of roughness asperities on the duct surface is to turbulate the fluid as it flows through the duct, increasing frictional pressure losses and convective heat transfer rates, and also increasing the surface area per unit length available for heat transfer. These factors combine to increase the total costs to the mine in terms of refrigeration and fan power requirements. A measurement system designed to automate the collection of tunnel roughness information and based on an infra-red timed pulse laser has been developed at the Royal School of Mines in London. The system allows accurate, high resolution digital recordings of tunnel surfaces to be made in two or three dimensions. Software for analysing the data has been written, and the description of a complex surface via single numerical term has been explored. A relationship between the numerically measured surface roughness and the pressure loss of the ventilating air is being investigated with a view to establishing an alternative method of describing tunnel roughness. The paper describes the roughness measuring technique developed and the analytical techniques explored so far.

Jan 1, 1993

By P. J. M. van Heteren

The flotation system is usually distinguished from other physical chemical systems by the importance of interactions at the solid-liquid and solid-gas interfaces. In recent years, numerous quantitative studies have been made of the distribution of common collectors between the solid and aqueous solution phase. Although in flotation the main emphasis is placed on the adsorption process, chemical reactions will also take place in the bulk solution phase, These side reactions are often undesirable and will contribute towards the complex behavior of many a flotation system In sulfide flotation, the precipitation of insoluble base metal xanthates is a well-known phenomenon although the conditions under which the precipitation reaction will proceed and the magnitude of the solubility products are not known with accuracy. A knowledge of the solubility of these xanthate salts will not only be of value in flotation research, but the mill operator might be interested in knowing whether precipitation of metal xanthate can be controlled or completely prevented in the flotation circuit thereby reducing reagent consumption, For these various reasons the solubility of lead, copper, zinc, and silver ethyl xanthate was determined. The experimental techniques and results will be discussed in this paper.

Jan 1, 1958

By Gregg J. Hodges

The Stillwater Mining Company, a partnership of The Pittsburg & Midway Coal Mining Co. and Manville Corporation, began commercial production of flotation concentrates from the western hemispheres' only primary platinum palladium deposit at Nye, Montana in March 1937. In the fall of 1987 an integrated pilot plant testing campaign of electric furnace smelling and oxygen? blown converting confirmed the feasibility of further upgrading to semi? refined matte or 'white metal". In the summer of 1990 the production smelter was brought on-line at Columbus, Montana. This paper describes the technology transfer from the pilot to the production smelter. Emphasis is placed on flowsheet development and the scale factors between the test and production furnaces and gas cleaning plants. The metallurgical results of the pilot plant and of the early months of production of the commercial works are also compared.

Jan 1, 1991

By G. S. Dobby

Particle collection is considered to occur by particle collision with the bubble followed by the particle sliding over the bubble during which attachment may occur. Collision is quantified by a collision efficiency, EC. The existing model for EC is extended by including particle inertia. Attachment is quantified by an attachment efficiency, EA calculated as the fraction of particles which reside on the bubble for a time greater than the induction time. These calculations use recent data on the liquid velocity distribution over the upper half of rigid spheres. Collection efficiency, EK is given by EK = EC ? EA. Detachment is not considered. The mode is examined and shown to agree with much experimental data. For example the maximum observed in recovery vs particle size (d) can be explained as E increases with increasing d , while EA decreases. The decrease in selectivity at fine sizes is in accord with the model result that for dp < 5µm, EA ? 100% (i.e. EK ? EC) almost regardless of induction time. A decrease in bubble size does increase EK but does not improve selectivity. A high particle density (> 5g/cm3) is shown to cause a sharp peak in recovery vs size and a decreased maximum size of floatability. Finally, the possible effects of bubble and particle concentration are explored.

Jan 1, 1985

By J. J. Pavlica

Grinding in steel mills adversely affects the flotation removal of pyrrhotite from magnetite ores. To elucidate the effect of grinding media on the floatability of pyrrhotite, rest potential and short-circuit current measurements were made on electrode combinations of pyrrhotite-mild steel and pyrrhotite-stainless steel. Galvanic contact of pyrrhotite with mild steel increased the rate of surface reactions on pyrrhotite in air-exposed and oxygenated solutions. It was postulated that the formation of &apos; an iron hydroxide coating on the pyrrhotite adversely affected its floatability. Its formation was minimal when pyrrhotite was contacted with stainless steel. Fine magnetite particles caused slime coating on pyrrhotite surfaces by magnetic interaction and impaired the flotation of pyrrhotite.

Jan 1, 1982

By K. Kim, T. M. Yegulalp

A new explanation of the scale dependency of rock strength is presented based on the theory of extremes. A brief review of past work on specimen size and strength relationship is followed by an introduction to the fundamentals of the underlying theory of extremes and its relationship to the scale effect. It is shown that the weakest link theory is directly related to extremal statistics and that parameters of strength distributions of rock can be derived as a function of the specimen size. Three sets of Brazilian test data are used to demonstrate the use of this approach.

Jan 1, 1994

By David C. Sanders, Rodney H. Sergent, Victor C. Storhok, Batric Pesic

In the past, considerable work has been done on the applica­bility of bromine chemistry in the extractive metallurgy of gold. While the research in this area spanned from the understanding of fundamental dissolution chemistry to the demonstration on a pilot plant scale, no work was done on the fate of discarded leach residues with respect to the stability of accompanied heavy met­als. Because the leach residues were the discharge products of halide/halogen systems, the general perception was that the con­tained heavy metals would be more susceptible to dissolution than in typical sulfate systems, thus causing increased environ­mental problems. A long-term study was performed to obtain the information on the stability of heavy metals contained in the leaching residues after bromination. The study involved the leach residues of three different ores, as well the precipitates prepared from the synthetic solutions (not presented here). The conclusion of this study is that the stability of solid residues produced by bromination leaching was same as the sta­bility of leach residues produced by leaching in the sulfate sys­tems. Also, contrary to the past expectations, the presence of bromide ions in the test solutions (up to 1 g/L NaBr) did not enhance the solubility of heavy metals (Cu, Zn, Pb, As) beyond the solubilities found in the sulfate systems.

Jan 1, 1998

By Maurice Deul

Certain health and safety hazards occur entirely unexpectedly in some subterranean excavations. Although ground support is not the subject of this paper, ground failure can result in large and often uncontrolled flow of fluids into an excavation. Even when there is no ground failure, the disturbance of nature&apos;s equilibrium between rock or unconsolidated alluvium or rubble and the contained fluids poses severe problems to a well planned operation. Optimum conditions for safe operation cannot be the sole criterion for site selection. Some mineral deposits form in zones of structural weakness, others form where hydrothermal alteration substantially weakens the enclosing rock, and tabular deposits such as coal and evaporites inevitably undermine large areas. Excavation to acquire mineral values cannot be relocated. The same is often true for tunnels driven to connect distant points by the most direct route. Rivers and mountains cannot he avoided, and the cost of lengthening a tunnel--by even a fraction of a percent--must be strongly justified. No responsible engineer will knowingly select a dangerous route for excavation, but to what extent do engineers attempt to assess the health and safety hazards that may be reasonably expected? How, specifically, can methane explosions, water and sand flooding, dangerous dusts, toxic gases, thermal shock and radar poisoning be eliminated or minimized through systematic advance planning?

Jan 1, 1974

By S. R. LaBrooy, M. C. Costello, A. C. Bax

Nickel is present in a number of gold ores in Australia, Africa and the United States. The effects and behaviour of the nickel during the cyanidation and adsorption processes, and also during the elution and electrowinning processes have been examined by a number of researchers, usually as a part of a larger investigation. This paper examines the available data on the behaviour and effect of nickel during cyanidation and its associated unit processes. The presence of nickel is often not considered to be particu­larly important as it does not cause the same degree of problems across the circuit as those experienced in the presence of copper. It can however lead to increased cyanide consumption during leaching, and reduced adsorption of gold onto carbon. A proportion of nickel cyanide may be removed from carbon prior to elution by carrying out a hot (90° C) acid wash. The nickel which remains on the carbon will be partially eluted during the main elution step, and, dependent on its concentration in the pregnant solution, part of it may be deposited during electrowinning. There is always a risk that any nickel remaining on the carbon after the elution step will be reduced to metallic nickel during the regeneration step. This may ultimately result in an increasing base level of nickel on the carbon, as metallic nickel is insoluble in both cyanide and hydrochloric acid.

Jan 1, 1995

By Graham J. Morgan

The following material is excerpted from a presentation Mr. Morgan gave recently to representatives of the financial community. Introduction 1982 was a period of challenge for United States Gypsum Company because of reduced market opportunity. Housing starts for the first 10 months averaged a seasonally adjusted annual rate of 1 million units, 9% below the comparable 1981 period when housing starts were the lowest in 35 years. Industry gypsum board shipments declined 9% from the already low levels of the same period in 1981. US Gypsum met the challenge with stringent cost reduction programs and aggressive action in the marketplace. In late 1981, anticipating market deterioration, the company&apos;s management adopted strategies to focus on two shortterm objectives: • Adjust operations to perform profitably in view of limited opportunities through more efficient operations and asset management. • Continue to strengthen U.S.G.&apos;s resources and ability to take advantage of important market opportunities as the economy improves through selective expansion of production capacity in key growth markets. Concentration on these two objectives resulted in a nine month performance in 1982 that, while certainly not satisfactory by company standards, compared very favorably with that of principal competitors in terms of net earnings, margin on sales, and return on average stockholders&apos; equity. To counteract limited market opportunities, U.S.G. focused on productivity improvement, cost reduction, expense control, and maximization of market penetration. Energy Use Improving performance encompassed all segments of operations. For example, efficient use of energy was a significant factor despite lower operating rates at most plants. Overall, in the third quarter of 1982 versus 1972, the company used 27% less energy per unit of production, a savings of $15 million in that quarter alone. These continuing improvements helped to partially offset constantly rising energy costs. A number of operations achieved superior results in the first nine months of the year compared with the same period in 1981. For example, gypsum board plants in Jacksonville, FL, and Sweetwater, TX, recorded 8% and 7% reductions, respectively, in energy use per unit of production. Paper mills in Oakfield, NY, Galena Park, TX, and Kansas City, MO, each reduced energy use more than 12%, while the Greenville, MS, ceiling products facility achieved a 16%o reduction. Safety Safety is another important element that received increased attention. U.S.G.&apos;s safety performance over the past five years has consistently improved. In 1981 it was five times better than that of the gypsum industry; nearly 10 times better than all industry as measured by the National Safety Council; and almost 20 times better than all US manufacturing as recorded by the Bureau of Labor Statistics. In addition to human concerns, this excellent record results in significant dollar savings that directly affect company results. In 1981, U.S.G.&apos;s pre-tax savings in claims, premiums, and related expenses were about $20 million compared to the industries in which it competes. For the first half of 1982 performance improved further, with a cumulative lost workday incidence rate per 200,000 man-hours worked of only 0.27, an all-time record. Expense Control Careful control of inventories and receivables also received special attention. As of Sept. 30, 1982, inventories were 29%, or $44 million, below the level of Sept. 30,

Jan 2, 1983

By P. Crouse, J. Obermeyer

"INTRODUCTION Site location and history The Holden Mine is a former underground copper mine that was developed and operated by the Howe Sound Mining Company (Howe Sound) from 1938 to 1957. The mine is located in north-central Washington State, U.S., near Lake Chelan in the area shown as Holden Village in Figure 1. Although Rio Tinto never owned or operated the mine, they are managing and funding a several hundred million dollar clean-up to prevent future water and soil contamination and to reclaim the former mine site under the United States Environmental Protection Agency (USEPA) Superfund process. The former mine included an onsite mill and a nearby housing complex for the miners. Howe Sound developed the mine as a series of near-horizontal drifts and tunnels, interspersed with stopes and shafts that connect different mine levels underground. The tunnels that were excavated to develop the mine total nearly 100 km in length.During development of the underground workings, Howe Sound removed more than 230,000 cubic meters (m3) of waste rock from the tunnels and deposited this material in two waste rock piles. Ore was processed from the mine in the onsite mill to produce a copper concentrate that was shipped off site for smelting. Roughly 10 million tonnes of tailings were produced as a by-product of the milling operation, most of which were deposited in three large impoundments (Tailings Piles 1, 2 and 3) directly south of and adjacent to Railroad Creek. Howe Sound closed the mine in 1957. In 1961, the property was transferred to Holden Village, Inc. (Holden Village), a not-for-profit corporation that maintains a year-round community and operates an interdenominational religious retreat in the former miners’ town. With the exception of the patented private land, the remainder of the Site is on National Forest lands and is administered by the U.S. Forest Service. The mine is remote. It is only accessible by boat or float plane from Chelan, Washington, up Lake Chelan to Lucerne, nearly 40 km. Vehicle access from Lucerne to the mine is provided through a 17.5-km-long winding gravel road that climbs 640 meters in elevation. The general site features are shown in Figure 2. Physical setting The Holden Mine is located on the eastern slopes of the Cascade Mountain Range at an elevation between 975 and 1,050 m above mean sea level. Holden Mine was developed adjacent to Railroad Creek, which lies in a glacial U-shaped valley carved into the igneous and metamorphic bedrock with steep-sided slopes (Figure 2)."

Jan 1, 2017

By J. A. Organiscak

Water spray applications are one of the principal means of controlling airborne respirable dust in coal mines. Since many coals are hydrophobic and not easily wetted by water, wetting agents can be added to the spray water in an effort to improve coal wetting and assist with dust capture. In order to study wetting agent effects on coal dust capture, laboratory experiments were conducted with three wetting agents used by the coal industry on -325 mesh sized Pocahontas No. 3 coal dust. Significant differences in coal dust sink times were observed among the three wetting agents at water mixture concentrations of 0.05%, 0.1% and 0.2%. The best wetting agent as identified by the coal dust sink test was only tested at the lowest 0.05% water mixture concentration and was found to have a negligible effect on spray airborne dust capture. Water spray airborne dust capture results for all three wetting agents tested at a 0.2% water mixture concentration showed that all three wetting agents exhibit similar but small improvements in dust capture efficiency as compared with water. These results indicate that the coal dust sink test may not be a good predictor for the capture of airborne dust. Additional research is needed to examine if the coal dust sink test is a better predictor of wetting agent dust suppression effects during cutting, loading, conveying and dumping of coal products by comparison to airborne dust capture from sprays.

Jan 1, 2013

By Paul Schmidt, John Barber

This paper discusses the determination of cutoff grade (COG), including all revenue and cost factors and how to apply the COG in the world of engineering studies and mine planning for underground mines. It provides the engineer with important considerations and practical methods to establish COG and methods of using the COG in the work of mine planning, including the application of Mineable Stope Optimizer (MSO) software which is available on several 3D mine planning packages.

Feb 1, 2024

By R. M. Kakwani

The filtration and dewatering results of -32 mesh Pittsburgh seam coal are discussed with reference to the microscopic structure parameters, i.e., particle segregation in the cake and particle and pore size distributions at different layers. At low solid concentration of 0.33 kg coal/kg water, a non-uniform cake structure is observed in which the particle and pore sizes increase from the top to bottom layers in the filter cake. An increase in the solid concentration in slurry produces more uniform cake structure and higher filtration and dewatering rates. Air bubble entrapment in the coal filter cakes is also discussed.

Jan 1, 1984

By Klaus Schönert

Theories are proposed to explain consistently a class of phenomena and are established with experiences, hypotheses, and laws. Not all concepts need to be presented in a mathematical format. A comminution theory must incorporate fracture physics, particle breakage, stressing events in crushers and mills, material transport, comminution kinetics and models, etc. In this paper the state of knowledge of some of these aspects is discussed. An attempt has been made to show the benefit of theory in comminution practice.

Jan 1, 1995

By J. C. Stankus, S. Guo, S. S. Peng

In this paper, a model is developed for a resin anchor bolt system in which the smooth bar is modeled by using one-dimensional truss elements, and the resin annulus is modeled by using axisymmetric elements. These two submodels are combined and then incorporated into an existing computer code called Roofbolt. After this development, all of the components in the resin anchor bolt system, including smooth bar, bearing plate and resin annulus, can be correctly modeled.

Jan 1, 1997

A number of factors affecting the properties of cemented aggregate fill (CAF), particularly its strength development have been studied through a series of laboratory investigations carried out at the Western Australian School of Mines in the Western Australia in recent years. The outcomes of these investigations indicate that apart from cement dosage, aggregate particle size distribution, aggregate quality, additional fine materials, water salinity, admixture dosage and sample scaling all contribute significantly to the development of cemented aggregate fill strength.

Jan 1, 2001

By K. E. Hjelmstad, W. H. Pomroy

In the event of fire underground, it is essential that all miners be warned as quickly as possible. With mine air rapidly depleted of oxygen and contaminated with smoke and toxic fire gases, any delay in the warning signal could have disastrous consequences. Unfortunately, present mine fire warning systems, such as stench, audible or visual alarms, telephones, and messengers, are often slow, unreliable, and limited in coverage. Recent research by the US Bureau of Mines has established the feasibility of ultralow frequency electromagnetic signaling for underground mine fire warning. Infield testing completed thus far at five mines, signals of from 630 Hz to 2000 Hz were transmitted through rock up to distances of 1645 m (5400 ft) to a pencil-sized ferrite-core receiving antenna and intrinsically safe receiver circuit. Theoretical analysis indicates a capability to transmit effectively for distances in excess of the maximum depths of most American mines, which is about 900 to 1000 m (2950 to 3280 ft) . The prototype system uses off-the-shelf components and state-of-the-art technology to ensure high reliability and low cost. This technology would enable simultaneous and instantaneous warning of all underground personnel, thereby in- creasing the likelihood of successfully evacuating a mine during a disaster. This report discusses the theoretical basis for through-the-rock ultralow frequency electromagnetic transmission, design of the prototype transmitter and receiver, and the results of in-mine tests of the prototype system.

Jan 1, 1991

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