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By Robert C. Bates

Published information on costs of radon-daughter control in uranium mines was analyzed to develop estimates of the cost per ton for any level of radiation exposure control. All data were converted to 1967 cost of living index to provide a common analysis base. Results of the analysis show that the cost per ton increases exponentially as the radiation level is lowered. A linear relationship with the cost of living index is assumed, and equations and graphs are provided to estimate control cost per ton for any exposure control level and cost of living index.

Jan 1, 1981

By Joachim H. Schubert, David G. Hulbert, Ian K. Craig, Roger G. D. Henning

This paper presents a stabilizing controller for flotation plants which uses a quasi-multivariable technique. The controller monitors all the levels in the plant, and by anticipating interactions between various parts of the plant, is able to stabilize the plant far more successfully than the normal plant control. Once stabilizing control has been achieved, optimization of the process becomes easier and more sustainable. An estimate of the improvement in metallurgical performance is made and a singular value analysis was conducted to verify that the multivariable algorithm will theoretically control better than a collection of individual PID loops. Metallurgical results are presented to show that the improvements are attainable in practice. Control by the Mintek algorithm was alternated with normal plant control, to show that the improvements are statistically significant.

Jan 1, 1995

By R. V. Ramani, R. Bhaskar

While the National Academy of Sciences has stated that gravimetric sampling technology for compliance purposes is adequate, research into various aspects of respirable dust control require data on many other parameters of airborne dust. These, in turn, have created the need to use many instruments, other than personal gravimetric samplers, in mine environments for dust measurement. There is a need to evaluate the performance of these instruments under conditions of potential use. As part of research in the Generic Technology Center for Respirable Dust, cascade impactors, gravimetric personal samplers and gravimetric samplers collecting dust using isokinetic sampling principles were employed for dust measurements under identical conditions in a mine airway. During the course of the experiments, 8-stage cascade impactors and gravimetric samplers drawing air isokinetically were located in the center of a mine airway at various stations. Two types of data were examined - concentration of dust and size distribution of the dust collected in the samplers. The data show that the amount of dust collected by an impactor is less than half the amount collected isokinetically. The size distributions of the dusts collected from the two instruments, though comparable, show a consistent difference in median diameters. The cause for this bias is examined. The paper presents and discusses the results of the tests, including the concentrations and size distributions obtained from the two instruments for different experimental conditions. There is a need to document the performance of various dust measuring devices in mine airflow conditions.

Jan 1, 1987

By J. M. Dean, R. L. Grayson, N. P. Reddy, Y. J. Wang

This 1988 survey provided a cross section of computer software use by the US coal industry. From 1250 mailed questionnaires, 171 responses were received, representing a 4.9% sampling of the 3496 US coal mines. Since the distribution of responses by regional stratum matched well with the distribution of mines by stratum, the survey was given statistical validity. A statistical description details the computer use by region, mining type, organizational size, the level of application within the organization, the type of software application used, the variety of computers on which the software was used and the percent of users within engineering, management and general applications categories. Overall, 63.5% of the respondents use computers at some level in their organizations. All of the mines producing more than 454 kt/a (500,000 stpy) used computers. However, for those producing more than 9 kt/a (10,000 stpy) but less than 91 kt/a (100,000stpy), only 44% used computers. Generally, the software applications were still data-processing oriented. The application sophistication grew with increasing mine size. Computer system models and configurations for different sized organizations are recommended based on the configurations used in the industry at the time of the survey.

Jan 1, 1994

By Michael Gauna, William J. Gray, Joseph C. Zelanko

Mechanized mining in the underground coal industry has continued to evolve since the introduction of the remote control mining machine. Remote control continuous mining machines without an onboard operator’s compartment are now the norm in the industry. Extended cuts in excess of 30 ft (9.1 m) are commonplace. Unfortunately, machine operator positioning has become an often unrecognized safety concern, particularly when remote control continuous mining machines excavate a turn (turn a crosscut). From January 2001 through July 2004, remote control continuous mining machine operators or helpers have been involved in ten roof fall fatalities and eight machinery crushing fatalities. The machinery crushing incidents occurred when machines were being repositioned or moved to another place. Of the ten roof fall fatalities, three occurred while a crosscut was being turned and a fourth fatality occurred while mining was being conducted adjacent to the crosscut. The operating time associated with turning crosscuts is a relatively small part of the mining cycle. In recent years, however, a disproportionate number of fatal incidents appear to have been associated with this activity. Procedures for reducing the incidence of operator fatalities while turning crosscuts are discussed. These techniques include: minimizing the number of turn cuts, limiting turn cut depth, establishing no work zones and using visual warning devices to designate them, installing more roof/rib support in the vicinity of the turn cut, using notch cuts prior to initiating a full turn cut, and positioning the remote control miner operator in nontraditional locations.

Jan 1, 2005

By Richard A. Williams

The design, modelling and simulation of solid-liquid mixers remains one of the least advanced aspects of minerals processing, due to difficulties in quantifying complex slurry hydrodynamics from first principles, and in acquiring reliable experimental data for model verification and development. This contribution describes the application of electrical resistance tomography (ERT) for three dimensional imaging of the concentration of mineral particulates in a slurry mixer as a function of key process variables (particle size, impeller type, agitation speed). It is demonstrated how ERT can provide a wealth of detailed data to allow model development, which ultimately will lead to much improved design capabilities and the generation of mixing models which could reside within Particle Process Simulators. This principle is illustrated using descriptions of mixer behaviour based on an empirical approach, although the measurement methodology described is equally suited to development of computational fluid dynamics models, cellular models or design approaches based on artificial intelligence. The experimental data can be built into a visualisation data bank, which acts as a "process toolkit" by allowing a library of process responses to be catalogued. Hence these data can be accessed for the purposes of model development, equipment selection, optimisation of operating conditions or testing on-line control strategies.

Jan 1, 1995

By G. Olson, T. Mudder, T. Clark

An evaluation was made of an innovative chemical approach for controlling the biotic portion of sulfide oxidation of tailing and waste rock using thiocyanate. This lipophilic anion is selectively toxic toward acidophilic bacteria, including those that oxidize metal sulfides. Sulfidic materials from precious metal and base metal mining operations were treated with thiocyanate solutions and subjected to accelerated laboratory weathering at 1 to 50 kg scale in humidity cells, trays, and columns. Initial field trials were conducted at 13.6 t and 100 t scale. Thiocyanate at relatively low concentrations reduced ARD from 50% to over 99%, depending on the sample and specific ARD parameter measured. Test work also was done with phosphate as an agent to coat reactive sulfides, further reducing their oxidation by biological and chemical reactions. The combination of phosphate and thiocyanate treatment is the basis for a potentially comprehensive approach to ARD prevention and control. Additional research and pilot testing are underway.

Jan 1, 2004

By Harold D. Taylor

Cone fitting is a procedure which can be used to estimate the short range, linear portion of a variogram. Rather than combining data over windows In different directions and fitting by hand, cone fitting estimates the variogram in all directions at once using a multiple regression approach. The method automatically provides estimates of nugget effect, anisotropy, and initial slope of the variogram. This paper presents the results of simulation studies which have been carried out. These studies Indicate that the method works well and that it may be particularly useful for small data sets. The simulation studies also indicate that the local variogram may differ greatly from the theoretical variogram.

Jan 1, 1986

By Jeffrey D. Swanson, Martin L. Smith

Smelterville Flats in Idaho's Silver Valley has been designated as a Superfund site due to metals contamination resulting from the use of the South Fork of the Coeur d'Alene river as a tailings impoundment earlier in this century. Tailings average in excess of 4% lead and zinc. Selective mining of highly contaminated zones is being studied as one of several possible remediation strategies. The first step towards remediation is the examination of the stratigraphic, geochemical and spatial characteristics of the site. These characteristics are related to appropriate sampling protocols and exploratory sample grid design. Special problems involved in the geostatistical analysis of tailings are emphasized.

Jan 1, 1992

By K. Biswas

A finite-element algorithm was developed for an axisymmetric heat-transfer problem involving phase change. The finite-element treatment of the phase-change problem was dealt with by using the enthalpy method. The finite-element algorithm was subsequently applied to model the heat exchange between mine ventilation air and frozen ground in the presence of roof bolts in an underground mine with permafrost. This paper analyzes a single bolt in the problem domain with the convection boundaries at the roof level of the mine airway. A short-term study, comprising the evaluation of roof bolting (friction-anchored type), was conducted, and recommendations were made regarding the applicability of roof bolts as a support system for a given thermal condition.

Jan 1, 1996

By E. Topuz, M. J. McPherson, I. M. Konduri

This paper describes experiments conducted to evaluate the effectiveness of jet fans for ventilating blind headings in under- ground mines. A laboratory model of a mine heading was built by using dynamic similarity criteria, and water as the fluid medium. In order to verify laboratory test results, field experiments were designed and carried out in a full scale mine model and in a coal mine in West Virginia. Using CO, as the tracer gas and in combination with a computerized gas monitoring system, tests were conducted to evaluate jet fan performance. The results highlight the flexibility and versatility of jet fans for ventilating blind headings. Numerical modeling of a jet fan in a typical coal mine heading was carried out to evaluate the potential of computational fluid dynamics.

Jan 1, 1997

By S. D. F. Rocha

The influence of surfactants on the crystallization of calcium sulfate was investigated in both hatch and continuous systems. The investigation was per formed at the following conditions. 343 °K, 28% P205 and with a sulfate level of 2.0%. At concentrations of 5 and 200 µgig, respectively, dodecylbenzene sulfonic acid (DBSH) and sodium diisooctil sulosuccinate (SSNa) promoted both an increase in the size and a reduction in the length/width (L/W) ratio of the calcium sulfate hydrates produced in the hatch and continuous crystallizers. Unique effects were observed in the batch system at higher DBSH concentrations. At 10 µg/g, the precipitation of hemihydrate crystals with a distinct morphology and texture occurred under conditions where dihydrate precipitation was expected. Above 50 µg/g, the precipitation of calcium sulfate hydrates was completely inhibited.

Jan 1, 1996

By Vas Choudhry, Randhir Sehgal

Conventional clean coal technologies which consist of coarse coal cleaning by gravity methods and treatment of natural fines by flotation can only remove a portion of the pyritic sulfur and ash in the coal. Higher (+90%) pyritic sulfur rejection is attainable when coals are ground to ultrafine sizes to enhance liberation of the mineral matter and then cleaned. However, cleaning of coal at very fine sizes poses a number of unsolved problems, the chief one being the loss of cleaning efficiency. This, of course, means that liberation of pyrites does not always equal its rejection. In addition, the dewatering of fine- cleaned coal, and its handling, transportation, and acceptability to the utility industry a1 so pose considerable technical and economic problems, especially when compared to the FGD alternative. This paper addresses some of the critical issues involved in the cleaning of ultrafine coal s.

Jan 1, 1989

By A. Peppas

Perlite is a naturally occurring siliceous rock, which can be expanded from four to twenty times its original volume when heated at a temperature close to its softening point. The expanded perlite is characterized by increased sound and thermal insulating properties. However, the conventionally expanded perlite products have high porosity and low mechanical properties that limit the range of their applications in the construction and chemical industry. The present work aims at the development of new closed porous microcellular material from perlite with enhanced mechanical and physical properties to be applied in new applications, like joint compounds, functional fillers for special paint types, special blasters and mortars, artificial marble. For the production of these new materials a vertical electrically heated furnace with six different heating zones and controlled gradient temperature profile was used. The effect of major process parameters, like temperature and air flow, on the quality of the produced materials was studied using Greek perlite from Milos Island. The quality of the new products was evaluated in terms of their bulk density, compression strength, water and oil absorption, surface area and pore volume. The experimental results show that the produced materials are characterised by improved mechanical and physical properties compared to the conventionally expanded perlite products.

Jan 1, 2006

By F. Grandjacques

INTRODUCTION Selective Reduction of Nickel in Oxidized Ores Oxidized nickel ores, either garnieritic or lateritic, contain much more iron than nickel. The regular carbon reduction in an electric furnace is operated in such a manner that the greater part of iron oxides is reduced simultaneously with nickel oxide, resulting in a low nickel content ferronickel. In order that the nickel content of residual slag may be suitably low, -excess carbon must be fed so that the carbon content of the ferronickel thus obtained is that of casting iron. The metal also contains other impurities such as silicon, chrome, etc. In order to convert the casting iron into slightly carburized ferronickel with high nickel content, the greater part of the carbon and more than half the iron contained therein must be oxidized by means of oxygen. Energy is thus consumed as carbon, and power to reduce iron oxides, and more energy is consumed as oxygen to re-oxidize the iron contained. This method can be economically adopted for nickel ores with grades ranging around 2. 5 to 370, but it gets excessively costly when nickel grade falls below these values. This is why, for nickel ores with low nickel grades and high iron content, studies were conducted to develop a selective reduction process which, while reducing only a small part of the iron oxide, would provide efficient reduction of nickel oxide. Rich ferronickel is thereby obtained, with nickel content ranging around 30 to 50%. Due to the presence of slag with a high iron oxide content, the metal thus

Jan 1, 1979

By Jerome F. Machamer

Ninety percent of manganese is used as an alloying element in steel. Smaller amounts are used in dry-cell batteries, in aluminum and bronze alloys, and many other uses. The element has several oxidation states, and oxidation-reduction reactions control its chemical behavior. Manganese, in primary minerals such as rhodochrosite, rhodonite, and braunite, is in a divalent oxidation state, and manganese in secondary minerals, such as pyrolusite and cryptomelane, is in a quadrivalent state. Virtually all manganese ore production comes from three types of sedimentary manganese deposits. First, lenticular beds of manganese carbonate or carbonate-silicate rock in Early Precambrian volcano-sedimentary complexes in South America and Africa have been major sources of manganese ore. Second, laterally extensive beds of mangano-silicate and manganiferous carbonate minerals in certain banded iron formations are major sources of commercial ore and constitute the largest resource of manganese. Finally, manganese accumulations deposited in marginal to epicontinental basins are the largest source of current manganese ore production. Residual deposits resulting from the destructive weathering of rocks with a low manganese content have been, but are no longer, important sources of manganese ore. Most deposits have been altered to some extent by super- gene oxidative processes, and are economic because of that alteration. Outcrops of manganese ores are invariably oxidized and can be very deceiving as to the character of the underlying material. Nearshore facies of epicontinental basins, and nearshore age-equivalents of metalliferous black shales are among the targets for new manganese exploration. Very high-grade manganese occurs in sedimentary deposits altered by metamorphic and metasomatic processes.

Jan 1, 2001

By J. C. Yingling, J. Sottile

This paper addresses detailed models of the temporal pattern of material flows produced by longwall mining units and procedures for inferring the parameters of these models from field data. First, a model is established that predicts material flows referred to shearer position and cutting element. This model is comprised of trend and fluctuation components. The trend component, which is invariant between repetitions of the cut cycle, accounts for deterministic effects on the flow pattern, such as web depth variation as a function of the cutting operation, systematic tendencies for seam height and cutting speed variations along the face, changes in the relative velocity between the shearer and face conveyor, etc. The fluctuation component models random effects on material flow and employs time series approaches. Subsequently, a method is given for converting the positionally-referenced flows to temporally-referenced flows. The model serves as a basis for generating detailed, accurate computer simulations of material flows from longwall units. As such, it provides a more rigorous foundation for analysis of cutting procedures and outby materials handling systems in longwall mines.

Jan 1, 1994

By John A. Shuster

INTRODUCTION Controlled ground freezing for mining and construction applications has been in use for over a century. Despite the great technological evolution which has occurred during this period, ground freezing is still used on projects today with much the same basic technology as that used originally over 100 years ago. Major developments have occurred in the separate fields of frozen soil mechanics, refrigeration, and heat transfer analysis. However, except for a few projects in Europe and Asia, these developments have not been combined to upgrade ground freezing techniques to their potential level. In view of this situation, it is believed desirable to examine the art of ground freezing in light of recent technical developments, together with highlights on some of the apparent advantages, disadvantages and economics of the various alternative approaches. The purpose of this paper is to attempt such an examination, with particular emphasis on the practical application of presently available technology. GENERAL ADVANTAGES AND DISADVANTAGES Ground freezing may be used in any soil or rock formation, regardless of structure, grain size or permeability; however, it is best suited to soft ground rather than rock conditions. Freezing may be used for any size, shape or depth of excavation and the same physical plant can be used from job to job despite wide variation in these factors.

Jan 1, 1997

By Y. Zimmels, C. Feldman

Closed-circuit grinding processes are considered in the context of a reactor-separator circuit that involves multifraction streams and products. Because grinding circuits are low-efficiency, capital-intensive operations, modeling to maximize their economic return is appropriate. An attempt to develop and test such a model is presented in this work. The model relies on process simulation for both the mill and the separator, in conjunction with constraints imposed by product specifications. The grinding process was simulated using breakage functions, which provided complete data on the feed and product of the mill. A cyclone bank used as the separator was also simulated using known models. The overall process model provided a complete simulation of the multistream grinding and separation process. The process model was then incorporated into an economic model that predicts grinding cost, subject to process constraints, for a given set of operating variables. The model facilitates economic optimization of the grinding process as it relates to process variables and process hardware.

Jan 1, 1993

By Kenneth L. Rubow, Virgil A. Marple, Ye Tao

Techniques are being developed for measuring the mass concentration of respirable diesel exhaust particles found in underground coal mines. Studies have been conducted over the past five years to investigate size selective sampling techniques to measure the respirable mass concentrations of diesel exhaust and mine dust aerosol particles in underground coal mines. Results from these studies have been used to develop design and performance criteria for a personal diesel exhaust aerosol sampler. Three personal diesel exhaust aerosol samplers have subsequently been designed and evaluated in both laboratory and field settings. These samplers use size selective classifiers for the determination of the respirable mass concentrations of mineral dust and diesel exhaust particles. Their designs are based on the premise that diesel exhaust particles are predominantly less than 0.8µm while mineral dust is greater than 0.8 µm. One design, selected for field evaluation, consists of a 10 mm nylon respirable dust cyclone followed by a 0.8 µm cutpoint impactor and afterfilter. The cyclone removes the large nonrespirable particles while the inertial impactor stage, collects the mineral dust on an impaction plate and allows the diesel particles to penetrate to an afterfilter. The two sample fractions of the respirable particles (<0.8 µm and >0.8 µm) are gravimetrically analyzed to determine the concentrations of the diesel and mineral dust portions in the respirable coal mine aerosol.

Jan 1, 1991