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By Daniel J. Kennedy, George W. Klinowski

A significant portion of each mine is ventilated with the help of auxiliary fans delivering fresh air to the faces of its developing headings via flexible or rigid ducts. Quality and volumes of air delivered to the blind working faces are essential for creation of safe and acceptable conditions for employed crews. Well designed and properly maintained delivery systems are necessary in each mine. The Cape Breton Coal Research Laboratory, part of the Canada Centre for Mineral and Energy Technology located in Sydney, Nova Scotia, Canada, developed a tracer gas based technique which provides fast and accurate evaluation of any auxiliary ventilation system performance. In addition, important information about the system's behaviour is gathered which can be used for designing a similar system in comparable conditions.

Jan 1, 1989

By T. J. Carew

INTRODUCTION The application of micro-computers to the evaluation of an advanced exploration project is illustrated by reference to a large project in the Sudbury Basin region of Canada. The deposit in question is polymetalic (Cu, Pb, Zn, Au, Ag) with a strike length of 3048m (10000ft) and has been explored to a depth of 457m (1500ft) by approximately 1350 diamond drillhole of between 9 - 305m (30-1000ft) in length. The large amount of data involved and the ability to rapidly recalculate geological reserves in response to fluctuating metal prices were key factors in the application of a micro-computer based evaluation system. The evaluation software was implemented at two levels, with data capture implemented mainly on - an entry level workstation comprising an IBM-PC compatible (PC-XT) micro-computer equipped with a 20Mb hard disc, printer and RS-232 serial communication facilities. Data analysis, display, geo- logical modelling and processing was carried out on a high-level workstation based on a Hewlett-Packard 9000 super- micro computer and peripherals, including a 40Mb hard disc, tablet digitizer and plotter. Basic drillhole data was entered either directly at the super- micro or transferred from the PC via the RS-232 link. The evaluation process proceeds once the data is edited and in a "clean" format within a master project database. The software is comprised of a suite of modular, integrated programs based on ease of use, interactive graphics and optimized for the computer workstation. Drillhole data was displayed and plotted as hard copy plots on which geological interpretations were developed. The data was copied into small manageable projects consisting of 100 to 150 drillholes, within which a sectional model was created such that all the models are interconnected along the entire strike with no overlaps. Geological reserves were derived by developing a set of function variables, including Net Smelter Return, within the database. The values of these functions can be displayed on the model sections and "ore” zones defined in accordance with pre-determined cutoff values. Interpolation of the modelled data was then carried out and geological reserves calculated and reported. DATA CAPTURE Drillhole data for the project consisted mainly of existing drillhole logs, although the system allows for the entry of new information as it becomes available. The structure and format (i.e. number and length of variable fields) is user defined. The log for this project comprises an abbreviated section for name, competency, grain size, texture, colour and alteration. Fields are defined for structural information regarding bedding and fault angles and up to seven mineral identification columns and percentages are available. Assay information consisting of the sample number, width and six determinations (Cu%, Pb%, Zn%, Fe%, Au opt., Ag opt.) along with a comments section of 25 characters completes the log. One powerful feature of the data- base is the ability to set up function variables that are mathematical and/or logical combinations of the project variables, enabling the user to develop economic variables such as Net Smelter Return. These functions include current treatment costs, deductions and penalties and can be rapidly recalculated within the database to accommodate changes in metal prices, forecast recoveries and exchange rates (Table 1).

Jan 1, 1987

By Charles A. Edwards, Kenneth D. Merrill

The Construction of the Northeast Extension of the Baltimore Metro involved soft ground, compressed air tunneling. During the tunneling, gasoline and dry cleaning fluid contamination were encountered. Innovative approaches and solutions were developed to address these problems. Special emphasis was on the problem of compressed air pushing gasoline vapors into surrounding communities, resulting in an extremely dangerous situation and a public relations nightmare. Guidelines and standards were established for working in this contaminated environment. Also, through a proactive approach by all parties, all claims and disputes have been resolved.

Jan 1, 1995

By L. F. Zeiler

In the past, health concerns in coal mines have primarily centered on those elements which have been essentially inherent to the mining environment. These would include respirable coal mine dust, respirable crystalline silica, excessive noise levels, and diesel exhaust particulates. Commercially-available chemical products are prevalent on mine property. These potentially toxic materials are chemical formulations that can degrease, clean, and lubricate metal parts, separate coal from rock in float/sink operations, and aid in roof consolidation, among other uses. As the general public has become more aware of the hazards of chemical exposures, miners have likewise become more concerned about working with an ever-expanding variety of chemical products on the job. Often, product or chemical specific hazard communication training is inadequate or ineffective, and miners do not know exactly what the ingredients are in the products they handle, or the health hazards involved with their use or misuse. Currently, the Mine Safety and Health Administration (MSHA), by law, enforces 1972 Threshold Limit Values (TLV). MSHA is making preparations to adopt new personal exposure limits for enforcement. The values given throughout the article are 1994 TLV's and are not enforcement standards, but are used for discussion purposes. They reflect the current scientific thinking regarding personal exposure to these chemical agents. An overview of these products is presented, and the potential health hazards associated with their use are discussed. Controls needed to prevent overexposures, such as proper handling procedures and personal protective equipment, are covered. Methods used to collect and identify contaminants are presented.

Jan 1, 1995

By Geoffrey Purcell

The flotation response to amine collector of quartz and the feldspars microcline and albite, of the pyroxenes augite and spodumene, and of olivine can be, explained by a physical adsorption model. Flotation decreases in the order given above, and the different behavior of the three groups is attributed to structural variations of the silicates, With sulfonate collector both chemical action and physical adsorption play their part in producing hydrophobic surfaces, and flotation increases in the order given.

Jan 1, 1966

By Timothy J. L. Haley

The population of the Rhondda underwent a spectacular rise as energy requirements increased in the mid-nineteenth century. The rapid expansion in the demand for coal transformed the population from a few hundred sheep farmers in the eighteenth century, into a thriving coal-based economy of some 168,000 inhabitants in 1924. Cochrane (1958) put forward the idea that the differential migration of more healthy men from the Rhondda Fach during the period since the peak of population in 1924, had resulted in a respiratorily-impaired residual population. This idea was used to explain the reduced survival of miners & ex-miners aged 55-64 years from this valley as compared with a similar group from Leigh in England. Using the proportional hazards regression model of Cox (1972), a comparison is presented of the exact twenty-year mortality of migrant and non-migrant miners & ex-miners and non-miners from the Rhondda Fach. The analysis makes allowance for the pattern of migration throughout the twenty-year period and adjusts for the confounding influence of variables such as age, occupation, and category of Simple Pneumoconiosis. The results indicate that contrary to expectation, any effect of migration upon mortality is manifest only at higher ages. Furthermore, for these men, the migrants have worse survival than the non-migrants. Also, contrary to expectation in the light of work by the British Coal Board (Soutar et al, 1982) there is no evidence of increased mortality amongst men with category I simple pneumoconiosis. INTRODUCTION [The Background] In September 1950, the Medical Research Council's Pneumoconiosis Research Unit at Penarth in South Wales initiated a study of lung disease in the smaller of the two Rhondda Valleys - the Rhondda Fach. At that time, the primary interest was in assessing the possible role of pulmonary tuberculosis in the aetiology of the serious (complicated) form of coal-workers' pneumoconiosis, i.e. Progressive Massive Fibrosis. The Rhondda Fach is situated in South Wales, some 25 km north-west of Cardiff. It is a narrow winding river valley about 12 km long, and approximately 1 km wide. The name means Little Rhondda; there is a corresponding Big Rhondda - the Rhondda Fawr. Together, these valleys make-up most of the Rhondda Municipal Borough. Following the initial survey in 1950-51, there have been several follow-up studies of this population. In addition, amongst numerous other investigations to unravel the aetiology of coal-workers' pneumoconiosis, Medical Research Council teams studied various other (sample) population groups, particularly in the industrial areas of the adjacent Aberdare Valley, and in Staveley and Leigh in England. The agricultural areas of the Vale of Glamorgan in South Wales, and Annandale in Scotland were also studied.

Jan 1, 1993

By F. M. Doyle, S. Duyvesteyn, K. Sreenivasarao

Toxic metals entering surface or ground water from sources such as metal finishing shop spills and abandoned mines can pose a significant threat to public health and the environment. Ion flotation and similar foam separation techniques show great promise for treating dilute, metal-contaminated solutions, and could also be used to treat effluents from many minerals and metallurgical processing operations prior to discharge. In ion flotation, an appropriate collector is added to the solution to form hydrophobic complexes with the metal ions. These metal-bearing species are then removed by flotation, usually with trace addition of a frother to stabilize the foam. In an effort to better understand the underlying scientific and engineering principles that determine the performance of ion flotation, the removal of Cu(II), Pb(II), Cd(II), Cr(II) and Cr(VI) has been studied using laboratory scale flotation columns in batch mode. The effects of the superficial air velocity, solution and froth height, nature of the collector, collector: metal-ion ratio, ionic strength and several frothers at low concentrations on the flotation kinetics are reported. Finally, results are presented on methods that might allow regeneration of collector and recovery of by-product metal from the foam product.

Jan 1, 1995

By Louis C. Just, Grahan A. Mathieson

Low cost, greater operating flexibility, and relatively simple operation are just three of the reasons for using minicomputers in the mining industry. No less than a dozen US manufacturers have sold the new generation of minicomputers to mining operations in the US and the world. Many manufacturers produce several models of minicomputers, each with excellent calculating capabilities. Prices for these "mini-giants" range from about $10,000 for a basic system to over $300,000 for a very powerful, sophisticated system with numerous peripheral devices. While the acceptance of minicomputers by the mining sector has lagged behind their penetration into other businesses, mines with minicomputer capability-especially remote mine sites-have found applications in practically all areas of operations including standard payroll processing, mineral deposit modeling and planning, surveying/mapping, production reporting, and daily production scheduling. In fact, the only limit to the further application of minicomputers in mining is the user's imagination. There are some obstacles to the accelerated use of minicomputers in the mining sector: the limited amount of software available, limited information on site-specific uses, and limited interest in the mining market by manufacturers. The latter is especially significant in light of the fact that many manufacturers queried in a recent telephone survey did not compile statistics on locations of their units in mining. The general consensus is that mining sales represent less than 1% of the total market. Many manufacturers do believe that market dynamics will increase their future research and development for the mining industry. The minicomputer was introduced in 1968, when Digital Equipment Corp. of Maynard, MA, developed a small computing device-the PDP-8 minicomputer. It is important to note that since then, it has become increasingly difficult to precisely define a minicomputer (see box, page 1582). The mini has evolved to surpass the capabilities of many of the large computers (mainframes) of 1968, and some models rival the mainframes of today.

Jan 11, 1981

By Thomas O’Neil

Part 2 of this article continues with a discussion of features that distinguish contemporary investment analysis in mining from earlier methods. Part 1 traced the evolution of evaluation methodology from the traditional and discounted cash flow methods to the present. Quantitative investment models of the past 20 years played an important role in mine evaluation, but a new integrated approach to mine investment decision-making is now developing because of growing economic, technical, and political uncertainties. One of those uncertainties -inflation-was discussed in Part 1. Increased Risk At a time when mineral production technology and analytical evaluation tools have never been more sophisticated, it may seem anomalous to claim that mining ventures are riskier. Whereas technical risk has, indeed, been notably reduced, business risk the chance of a major loss due to market factors-has increased. This has been caused by two factors: the rapidly rising capital requirements of new projects and increasingly unpredictable future economic conditions. These difficulties are compounded by the long lead times of large, new mining projects. Rising Capital Requirements A $100 million investment is no longer considered to be a large mining project in most cases. For a large metal mining project, the total cost of the concentrator alone can exceed $100 million. Amoco Minerals' Thompson Creek molybdenum mine being developed in Idaho will cost over $350 million, for a relatively modest sized (23-kt/d or 25,000-stpd) ore operation with no extraordinary features. For a major grass roots copper operation producing blis¬ter or refined copper, the capital requirements are billions of dollars, not millions. Project costs are higher for two reasons. One, the projects themselves are larger; and two, the capital cost per unit of production is rising rapidly. Projects are larger because lower grade ores, yielding smaller margins, must be mined in greater volume-particularly in view of the high fixed costs of modern technology. When analysts contemplate any capital project, an important consideration is the minimum economic size of the facility. This is the smallest size that can be built and still be competitive on a total unit production cost basis. In the conventional copper smelting business, for example, a production rate of at least 91 kt/a (100,000 stpy) of blister copper is about the absolute minimum for reducing unit fixed costs to competitive levels. Clearly, many variables affect the minimum economic size of a mining facility, but with few exceptions that size continues to grow. Unit capital costs of new mining projects also are continuing to rise. The accompanying table shows that the capital costs in primary copper production have risen faster than the cost of living. Of particular note is the capital charge of over $1.70/kg (77411b) required for a new, fully integrated facility in 1981. Thus, the mid-1982 copper price would not even cover the cost of capital for a new copper producing complex without considering the direct operating costs for such a facility. The breath-taking costs of new mining projects are caused by factors such as increasingly complex technology, the rising social costs of creating attractive living and working conditions for employ¬ees, and the expenditures re¬quired for environmental protec¬tion. For whatever reasons, how¬ever, unit capital costs in mining continue to exhibit staggering growth rates. Future Economic Conditions Risk is not only a function of the size of the potential loss-an im¬portant measure of which is the capital intensity of mining dis¬cussed above-but also of the like¬lihood of incurring the loss. It is here that the ever increasing lead times of mining projects and the glaring limitations of economic forecasting are so important. In comparison to nearly all other in¬vestments, mining has more capi¬tal at stake for a longer period of time before commercial uncer¬tainty is resolved by distant eco¬nomic conditions that are subject to high forecasting errors. A sobering example of the pre¬ceding points occurred with the Lakeshore copper mine in south¬ern Arizona that Hecla Mining Co. undertook to finance and manage in 1969. The project was a joint venture of Hecla and the El Paso Natural Gas Co. and included two mines-one producing oxide ore and a second in the sulfide zone¬and a complex processing facility producing both electrowon cop¬per cathodes and copper precipi¬tates. The project originally was

Jan 12, 1982

By J. A. Luppens

Five years ago, Phillips Coal Company decided replacing mainframe/workstation programs with a new package of PC software was clearly the best solution for computer reserve modelling. The system chosen was actually three programs distinguished by their power, cost, flexibility and integration, and ease of learning and use. Phase I involves the use of the "StratiFact" program for borehole data management and seam correlation. This phase is probably the most neglected, yet critical aspect of reserve evaluation. Phase II employs the "PC/Cores" package for modelling and volumetrics. Phase m is "PC-Cut" which provides mine planning tools including an automated cut generator.

Jan 1, 1996

By A. D. Davis, C. J. Webb, F. W. Beaver

The proposed National Underground Science Laboratory will be housed in the former Homestake Gold Mine at Lead, South Dakota. Uses will include underground neutrino experiments that must be shielded by several thousand feet of rock, as well as ground-water research in fracture-flow environments, and investigation of the microbiology of extreme environments. The Homestake Mine has about 300 miles of underground workings. Seepage of ground water into the mine openings is approximately 500 gallons per minute. Average annual precipitation in the northern Black Hills is approximately 28 inches per year. The majority of this becomes surface-water runoff or evapotranspiration, with little ground-water recharge because of the low permeability of the Precambrian rocks in the area. Dewatering of the workings over the 125 years of operation of the mine has influenced the subsurface hydrology of the 8,000-footdeep mine.

Jan 1, 2003

By James E. Friant

The technology applied to shaft sinking has lagged far behind other construction activities. While surface oriented construction and mining have made great strides with new processes and equipment, the majority of shafts sunk currently still follow a drill, blast and muck-out cycle developed in the 16th century. Today, in 1979, the shaft sinking industry is in the midst of its own private industrial revolution. Millions of dollars are being spent annually by industry and government alike to spring the art of shaft sinking into the 20th century. The objective of this paper is to review a few of the newest mechanized schemes for shaft sinking. This is not a theoretical review, however, but a practical one, and deals only with hardware and projects which are currently on jobsites. Figure 1 shows the equipment. On the left is the 241SB 184, a 24 foot diameter blind shaft borer. This machine is currently at about 200 feet, constructing a coal mine shaft in Alabama. It is built and utilized in a manner similar to a tunnel borer. In the upper center is the 1211SR, a 12 foot diameter blind shaft reamer. This machine follows a 6 foot pre-drilled blind pilot hole, and is at work in Chicago. On the upper right is the 121BR, a powerful new blind drill. Just below it is the conical drill head for the 121BR which can utilize either carbide or standard disc cutters. At the center bottom is an expandable back reaming head which can be used to enlarge a drilled shaft up to a maximum of 16 feet diameter, or can be used to produce a shaft having several diameter changes. This equipment is also in use in Chicago.

Jan 1, 1979

By Anthony G. Fonseca

About 45% to 50% of the coal mined in the United States passes through coal preparation plants. East of the Mississippi River, this number increases to about 75% to 80%. Although the cost for coal preparation is worthwhile to some, the coal industry faces the challenges of continuing downward pressure on the price of coal and the impact of new environmental regulations. Coal preparation is an effective process that achieves 75% to 80% ash reduction, 15% to 80% trace element reduction and 85% to 90% Btu recovery. It is less effective for pyrite reduction (35% to 70%) and on-line operating time (40% to 60%). It also suffers from obsolete control systems. In coal preparation, raw coal is modified to a more preferred form to enable its use. The methods used to achieve this modification must be cost-effective and appropriate to the raw coal, the scale of production and the end-user requirements.

Jan 1, 1995

By Sharon G. Roness

Powder River Basin (PRB) mines were originally built to serve power plants designed specifically for their: coal. Sulfur was the major concern. Btu content and sodium limited the market for some plants. The PRB market has now extended to plants that are converting from other coals because of the Clean Air Act. These new customers are more sensitive to constituents that affect boiler and precipitator performance. At the same time, the prospect of deregulation is forcing power companies to improve cost controls. Kerr-McGee Coal's Jacobs Ranch Mine has responded to the changing marketplace with an expanded coal quality and customer service program.

Jan 1, 1998

By G. G. O. O. Uwadiale

A number of Nigerian iron ore deposits have been upgraded to the specifications of concentrates for the blast furnace and the direct reduction iron- and steel-making plants. Depending on the mineralogy of the ore deposits, the techniques of oil agglomeration, magnetizing reduction, washing and scrubbing, gravity concentration, and reverse froth flotation have been utilized. A mode of distributive management of the deposits, in the direction of their technoeconomic utilization in the country's developing iron and steel plants, is presented.

Jan 1, 1990

By B. Towson, R. F. Dalton, G. W. Seward

This paper reviews the successful application of oxime reagents for the solvent extraction of copper and considers the role that well focussed research initiatives can play in bringing further radical change to the metallurgical industry. Particular reference is made to the Cuprex Metal Extraction Process (CMEP), for the treatment of low grade or difficult to treat sulfide concentrates, using the reagent Acorga CLX- 50 to recover the copper and the reagent Acorga ZNX-50 for the recovery of zinc from chloride solutions. Other new extractants, currently in development, are also referenced.

Jan 1, 1994

By Kenneth N. Han, Yichang Guan

The dissolution behavior of metals from Au/Ag/Cu-alloys has been studied using rotating disc electrodes in solutions containing acids, cyanide, and ammonia. Electrochemical methods as well as leaching tests were adopted in this study. The results showed that there was no galvanic effect on the dissolution of metals from homogeneous alloys. In aerated cyanide solutions, the dissolution of gold, silver, and copper from their alloys was partly controlled by surface chemical reaction, but largely by mass transfer. On the other hand, the galvanic coupling effect played a very important role in heterogeneous alloy systems.

Jan 1, 1995

By G. Kazonich, S. L. McGill, J. W. Walkiewicz

Naturally occurring minerals and reagent-grade compounds were tested to determine their receptivity to microwave heating. The maximum temperature achieved for the samples and the time required to reach temperature are reported. A description of the microwave oven and a thermocouple technique that accurately measures and continuously records the temperature of samples during irradiation are reported. Extractive applications using the generated microwave data were investigated. Stress fracturing at mineral grain boundaries in a gangue matrix was shown. This should significantly affect grinding energy requirements and liberation properties. A method to produce a magnetic phase on pyrite surfaces, a method of using microwave heating to retort cinnabar concentrate, and a roast-leaching microwave treatment of chalcopyrite ore are described.

Jan 1, 1987

By O. Fernandez, M. Vesely

Abrasive grinding, leading to ultrafine product and "critical size" material buildup inside the mill, is proposed as the cause of high power consumption and low capacity in many fully autogenous grinding processes. Addition of steel balls (hence, semiautogenous grinding) or pebble removal and separate crushing have been used, with different efficiencies, to overcome the problem. Information and data for the conceptual analysis, basic design, and operation of a pebble crusher at the Los Bronces semiautogenous grinding plant is presented along with data showing a production increase of 1000 t/d (1100 stpd) and significant operating costs savings.

Jan 1, 1987

By M. Li, J. D. Miller

It has been discovered that water insoluble alcoholic solutions of alkyl hydroxamic acids serve as selective collectors for the flotation of phosphate mineral resources (Miller et al., 2000). The effectiveness of the new collector chemistry has been demonstrated by the results from single stage bench scale flotation experiments for feed material from plants in Florida, North Carolina, and Utah. In the best case, from experiments with low grade (5% P20,) coarse feed (16 x 35 mesh), a single stage phosphate recovery of 95% was achieved with a concentrate grade of 31% P20,. Such a separation efficiency could not be achieved using the traditional fatty acid/fuel oil collectors as is evident from a comparison of the respective grade/recovery curves.

Jan 1, 2002