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By A. F. Barsotti

Apart from jewelry, holistic apparel, and special collections of color and sometimes rare crystal specimens, the average layperson has little or no appreciation of the omnipresence of minerals or mineral derived products in the home. From concrete in the driveway to aspirins in the medicine cabinet, minerals, especially industrial minerals, play a major role in day to day living. For a better appreciation of this let's look into the a day of the life of a fellow named John, and see how much we depend on industrial minerals. The sounds of soft violins nudged John from his sleep. The melodic sounds of Beethoven's Pastoral coming from his radio alarm clock brought him out of his dreams. He reached for the reading light switch, then checked his watch--6:30 a.m., and another day of work. As he got up, the darkness outside reminding him of winter coincided with the soft voice of the all night disk jockey forecasting the fall of four inches of snow. Warm beads of water beating on his face removed all remnants of sleep and, like a stimulant, the morning shower brought thoughts of yesterday and plans for a new day. These carried over as he looked himself in the mirror while shaving and brushing his teeth.

Jan 1, 1993

By D. W. Mitchell

Never increase, reduce, or remove ventilation without unquestionable, compelling reasons. This rule applies every day as well as when fighting fire, attempting to find survivors, or recovering the mine. Right now in some mine a miner is adjusting a regulator in one place to get more air into another. The chances are the desired result will be achieved. Has the miner done a good thing? NO! Solving the immediate problem reinforces the belief he or she can do it again. That "again" might be, to give but one of many examples, the explosion in Greenwich No. 1 Mine. Robbing the proverbial Peter can be the prelude to disaster in a mine. Reducing the airflow is a common practice when fighting a mine fire. In fact, some people have been taught to do that at MSHA's academy. People who believe that to be proper must be people who never experienced a fire. To fight most fires you have to scramble to get enough air. An explosion demands totally different "thinking". If people are soon to go into the mine, DON'T adjust the ventilation. If teams are in the mine, each affected area must be explored or sealed before making any ventilation change.

Jan 1, 1993

By R. A. Winters

At the operations level, productivity is a principle key to profitability. If you are competing with other mines that are paying roughly the same wage rate and the same prices for capital, materials, and energy, the only way your profit can be greater is by producing more output per unit of input. Mines with higher productivity have higher profit margins. Higher profit margins lead to greater operating cash flow, and cash flow is what distinguishes a dog from a cash cow. The turnaround in U.S. metals during the 1980s was in large part due to incredible improvements in productivity. According to statistics compiled by Kaufmann, 1991, labor productivity, measured as tonnes of primary production/manhour, increased 64% in steel, 94% in copper, 75% in lead, 143% in zinc, 132% in molybdenum, and 75% in gold. These improvements were hard won. However, with most modernization programs now complete, measuring and monitoring productivity becomes even more important as producers strive to maintain the gains they have achieved.

Jan 1, 1993

By M. C. Williams, T. P. Meloy

With the increasing power of computers to simulate and control processes in the mineral industry, predicting the potential use of computers in the minerals field is not a hazardous enterprise, but predicting the timing of their use is. Like the railroad industry, technology invades the mineral industry, rather than being an industry like electronics that creates technology. Because of this invasive nature of computer technology in the minerals field, this paper predicts what will be possible to do effectively and economically with computers in the mineral industry. Moreover, this paper explores the problems of using the emerging computer technology in the mineral industry. For example, if not now, it soon will be possible to control the output of a mineral processing circuit - high grade, high flow or a mixture of it - to meet the daily market conditions and to sell each day that daily "mill" output as "mill" futures on the commodity market. Finally, suggestions are made which may be done to prepare the industry for the computer revolution in the mineral industry.

Jan 1, 1993

This report presents production and delivered costs for coal exports from the five major Western coal-exporting countries: Australia, Canada. Colombia, South Africa, and the United States. Cost data were compiled from visits to 43 mines by U.S. Bureau of Mines engineers between 1985 and 1990. All report costs are in January 1989 U.S. dollars per short ton. Production costs for raw coal are divided into mining and regulatory categories. Costs are broken down by type of cost, type of mine. and country. Scheduled operating and capital costs for raw coal were processed by the Bureau's MINSIM discounted cash flow program to determine total production costs calculated at 0% and 15% discounted cash flow rates of return (DCFROR). Delivered costs are for salable coal delivered to various markets. Costs are broken down by supply country, market, and type of cost. Scheduled operating and capital costs for salable coal were processed by the Bureau's MINSIM discounted cash-flow program to determine total salable coal costs at 0% DCFROR. Added to total salable coal costs were transportation and port costs to get delivered costs. Comparative overview information on the coal industries of the five study countries are appended. This appendix includes information on industry economics and exports, production and reserves, and coal industry issues.

Jan 1, 1993

By J. E. Feddock

To succeed in today's competitive coal market, coal companies must continuously improve production and lower cost. However, the coal industry's historical management practices must change to remain viable? The practices of the current day efficient coal mine manager are reviewed and examined using W. Edwards Deming's definition of management. The statistical tools, including Pareto Charts, Control Charts and Scatter Diagrams, which identify the problems management must approach differently to increase productivity at a coal mine, are discussed.

Jan 1, 1993

By Alfredo P. Vargas

Industrial flotation of sulfide ores is 80 years old. It has gone through many advances to date. However most flotation operations are still struggling to improve performance, which as a worldwide average is at the 90% level. What can be done to push the ceiling to 95% or better without performing finer primary grind, nor without duplicating flotation plant capacity? Such "unique task" can be performed by the low volume high capacity new flotation equipment known as the JAMESON CELL, when used as, "post-scavenger" of final plant tails. Improved efficiencies are obtained mainly from two cases: -Particles which never contacted a bubble. -Particles sheared-off by cell turbulence due to reduced number of hydrophobic sites. The application reverses conventional trend of using large volume mechanical cells by trade-in with smaller efficient equipment: resulting in reduced capital expenditures and operating costs. Outstanding "pre-rougher" applications are also presented.

Jan 1, 1993

By Kenneth N. Han

Thermodynamic and kinetic aspects of nickel and cobalt leaching from metals. minerals and ores in various media have been reviewed and discussed in this paper. A kinetic model developed to delineate the leaching mechanisms for these metals has been discussed in view of experimental observations. The current review also includes the dissolution behavior of nickel and cobalt from various minerals such as oxides, sulrides. ocean floor manganese nodules, and laterites. A particular emphasis has been extended to similarities and differences of the dissolution behavior of these two metals in various media. The leaching of nickel as well as cobalt metal in acidic solutions and arnmoniacal solutions exhibits in most part mass transfer controlling. although at some pH's, chemical controlling or mixed controlling mechanisms seem to prevail. The leaching of nickel and cobalt from oxides in acids and ammoniacal solutions. on the other hand, can be described best by chemical controlling mechanisms.

Jan 1, 1993

The last decade has seen a very rapid development in TBM tunnelling. Some trends are purely technical or economical and others relate more to preferences of different interests. Power levels have more than doubled and thrust levels too. Shield machines are developed to be able to handle harder rock and the open TBMs are made more feasible for `difficult' rock. What is right and what is wrong is more a matter of opinion, but one thing is certain: TBMs now are a useful tool and no longer an experimental work-shop for the enthusiasts.This paper highlights some recent developments and indicates some probable future ones. A few features that have increased the open TBMs' ability to cope with ever harder rock and also to overcome problems with poor rock are discussed in detail, using the Atlas Copco JARVA Mk 27 -the most powerful TBM built so far - as a reference.

Jan 1, 1993

By G. B. Harris

Much has been written over the past decade concerning the disposal of arsenic from metallurgical processes. In Canada, there are proposed regulations which would classify arsenic in the Primary Group of twenty one persistent, toxic pollutants to be banned or phased out. Since many nickel and cobalt ores, not to mention those of copper, gold and uranium, contain significant amounts of arsenic, it is pertinent to assess the current state-of-the-art of its disposal. The literature is reviewed, and it is demonstrated that from a purely chemical point of view, the family of ferric arsenates largely immobilize arsenic. There is clear evidence from laboratory studies that both crystalline ferric arsenate (scorodite) and amorphous ferric arsenates in which the molar Fe/As ratio is at least three (Fe/As = 3) have very low arsenic solubility; plant data are given to support this. The debate over the long term stability of these compounds continues however; the evidence presented for long term stability and for compound breakdown is critically reviewed in the light? of the recent structural studies, and the role of base metals in these compounds evaluated. Finally, conclusions are drawn as to the viability of a purely chemical process for the long term disposal of arsenic from metallurgical processes.

Jan 1, 1993

By R. R. Klimpel

This paper demonstrates, using the results of an unusually complete industrial test sequence, what the various interactions are between grind size, collector dosage, and frother type. While particle size is universally acknowledged to be important in optimizing industrial copper sulfide rougher flotation circuits, many of the various interactions that do occur at the industrial level with particle size are still being identified and/or quantified. This study also presents, in a consistent manner, the changes in flotation kinetics that occur as a function of particle size, in a typical industrial circuit along with some insights as to how flotation operators can optimize rougher circuit performance.

Jan 1, 1993

By D. de la Villa

From 1989 to 1992 Rio Tinto Minera has developed and implemented a productivity program in its Huelva Plant, including Smelter, Acid Plant and Electrorefinery. This Plan was designed in order to increase productivity, reduce emissions and produce a better quality of cathodes. This paper describes investments and operating improvements involved in this project, focusing on Smelter and Acid Plants, and comments the results obtained so far.

Jan 1, 1993

By J. P. Coughlin

The U.S. Bureau of Mines has developed a monitoring system that acquires and analyzes data for use in determining the conditions that may precede mountain bumps in coal mines. Based on a UNIX workstation linked to an array of geophones in a working longwall operation, the system captures complete waveforms of microseismic events and simultaneously obtains continuous samples of the voltage levels of each geophone. Event rates and locations are calculated and displayed in real time on the UNIX workstation, which is situated in an underground instrumentation room. These results also are transmitted from the workstation to a display computer near the longwall face. The system runs continuously and has the capability to acquire, analyze, display, and archive microseismic (transient) data and single point data, such as closure and pressure changes, simultaneously.

Jan 1, 1993

By B. Q. Li

A numerical study of the developing fluid flow and thermal aspects during the staning phase of aluminum continuous casting processes is presented. The deforming finite element method, coupled with a quasi-Lagrangian formulation, is used to represent the growth of an ingot and the dynamic fluid flow and thermal behavior that evolves in the growing ingot. The mathematical formulation of the problem and the numerical treatment are discussed. The algorithm solves the free moving nodes as part of total unknowns with an automatic time step control for time integration. This permits an optimal computing efficiency while still keeping the computational errors under control. A selection of the results obtained using the algorithm is presented. The results are concerned with the evolution of fluid flow, temperature and solidification phenomena during a DC round ingot casting process, as it evolves from the beginning of casting operation to a steady state. These results show that the time-varying, complex fluid flow and thermal phenomena during continuous casting processes can be very well represented by the computational algorithm. The results also illustrate that, during the casting process, ~e fluid flow and temperature fields change drastically at the initial stage but evolve slowly afterwards

Jan 1, 1993

By Jon C. Volkwein

The U. S. Bureau of Mines investigated a method of using inert gas to prevent the formation of explosive gas mixtures in auger highwall mining of coal. A combination of gasoline and diesel engine exhaust gases was introduced into the auger drill hole using a short section of pipe located at the collar. Gas samples were taken and analyzed on site with infrared detectors for oxygen, carbon dioxide, methane, and carbon monoxide. Evacuated bottle samples were also taken and analyzed by gas chromatography at the Pittsburgh Research Center. These gas results were analyzed for explosibility. Personal exposure to carbon monoxide was also monitored. The highest methane level observed was 9.55 pct. The Inert gas levels, (carbon dioxide and nitrogen) were sufficiently high to prevent any ignition of the methane. Results showed that for all conditions during mining, gas concentrations were non-explosive. The maximum personal time weighted average sample for carbon monoxide was 20 ppm. This system provides a safe, inexpensive, simple method for preventing explosions during auger mining. INTRODUCTION The auger highwall mining method is an effective method to recover coal from a reserve when removal of the overburden by surface mining equipment becomes uneconomical. In this method of mining, a horizontal auger enters the coal seam from the surface mine bench under the highwall and the coal is drilled in a series of parallel holes. Historically, coal mined from the surface is relatively shallow, and over time, methane associated with the coal has dissipated through the surface. In most circumstances, little methane has been found associated with auger mining. However, mining technology has enabled surface mining of deeper reserves of coal. Furthermore, environmental constraints have forced the highwall extraction method to be used to remove coal under wetlands, further increasing the chances of encountering methane. Recently incidents of methane explosions at a few auger mining operations have resulted in injuries and increased testing for methane at the collars of auger holes. The fuel source of the reported explosions was not necessarily limited to methane, but may also have involved coal dust. The Mine Safety and Health Administration (MSHA) met with the Bureau to discuss what technology might be available to enable the safe resumption of mining. The discussion included the difficulty of ventilating through the solid shafts of the augers, that steel bits probably created the ignition source, and that perhaps inerting the holes with low oxygen and high carbon dioxide concentrations from the machine's diesel exhaust was a potential solution. Considering the ventilation aspects of the problem, it was not clear If ventilation could be reliably established. If some degree of ventilation to the front of the mining head is achieved, it may combine with methane to bring the hole atmosphere from a rich, nonexplosive mixture to an explosive mixture. Furthermore, it may not prevent a dust explosion in such a mining configuration. Lack of access through the shafts of auger type mining machines further limits the ability to add water or air to cool bits to prevent an ignition source from developing. Either of these approaches would also be expensive. The process of mining coal In an inert atmosphere has been considered in the past, but to our knowledge, never implemented (Department of Interior, 1970). Clearly, implementation in underground mining would be more complicated. On a mine bench open to the atmosphere, however, adding inert gas to the mining head could provide a quick, feasible method to prevent explosions at auger highwall mining operations. Also the problem of how to move the inert gas to the cutting head of the machine had to be considered. Preventing explosions on auger mining machines using inert gas requires three primary considerations: first is the source of inert gas; second, placing the inert gas at the cutter head; and third, monitoring the hole atmosphere. Any gas source having an effective inert gas concentration of 34 volume pct or greater will prevent methane from Igniting (Zabetakis, 1965). Sources of inert gas considered for this application included liquid nitrogen, modified shipboard inert gas generators (for hydrocarbon shipping and transfer), jet turbine engine (Paczkowski, et. al., 1982), the auger's diesel engine and a gasoline engine. Operation cost, purchase cost and availability limited our testing to the diesel and gasoline engines. This work tested each engine, separately and combined. To ensure effectiveness, both company and enforcement personnel need to know how to monitor the condition of the inerted hole. Measurements at depth inside the hole are possible by remote sampling through rigid tubing, but this method is Impractical for routine monitoring. Continuous monitoring of the exhaust gas stream is an alternative. The U. S. Bureau of Mines evaluated an inert gas system at an auger mining operation at a surface mine near Owensboro, KY. Coal was mined from the Number 9 Coalbed in Henderson Co. KY. Tests were conducted in January and March of 1992.

Jan 1, 1993

By Yu AB, Azahari HL

Indonesia has the largest coal reserves in the south-east Asian region. According to estimates from the World Energy Confer- ence, it has reserves of 18 billion mt lignite, 4.4 billion mt sub-bituminous coal and 774 million mt bituminous coal (Wyllie,1988). In recent years, substitution of coal for oil in power plants has been the goal of the Indonesian government since proven deposits of coal are about five times as large as national hydrocarbon reserves and most of Indonesia's power stations are still oil fired. Recently a coal fired power plant has been built in Java Barat, which will have a full capacity of about 3000 MW. It is intended to supply coal for this power plant from Bukit Asam mining area (South Sumatra). Coals from Bukit Asam - which are of the lignite or brown coal type - usually contain considerable moisture . It should be noted that reference to moisture in coal pertains to the total moisture content. This is comprised of what is commonly termed as equilibrium moisture and surface moisture. Surface moisture typically affects combustion process as well as pulveriser performance since it possibly influences the relative ease with which coal may be ground. In practice, the surface moisture produces agglomeration of the fines in the pulverising zone and reduces pulveriser drying capacity because of the inability to remove the fines as quickly as they are produced. This agglomeration has also the same effect as coarse coal during the combustion process because the surface area available for the chemical reaction is reduced, hence the combustion efficiency is also reduced. The influence of the moisture of some coals on their grindability (Hardgrove Grindability Index) has been previously correlated by several authors; some of them will be mentioned later. Those correlations, however, could not be immediately applied to any coal since it is still believed that there are other factors which influence the grindability of the coal, such as type and rank of the coal. The relationship between coal moisture content and its grindability has been investigated by Ellmann and Belter (1955). It was found that, for North Dakota lignites, the grindability varied as the moisture content changed. In Britain, Fitton, Hughes and Hurley (1957) stated that, for Bilsthorpe coal, over a wide range of free moisture content (from air-dried to about 30 per cent moisture), the Hardgrove Grindability Index (HGI) remains virtually unchanged. In addition to that, it was suggested that it would be slightly advantageous to dry the coal below its air-dried moisture content (at temperature ¦ 100¦C) to increase the ease with which coal could be ground, especially for low-volatile coal and high-volatile non-caking coal. Furthermore, it was also concluded that a broad relationship appeared between coal rank and Grindability.

Jan 1, 1993

Modern coal cleaning technologies have allowed coal preparation facilities to become quite efficient at removing sulfur compounds, waste rock and low grade coals from run of mine coal. Up to 50% of the raw mined coal stream may end up as refuse, particularly when the coal originates from longwall mining operations, or is high in partings, rock and impurities. The refuse materials vary from coarse materials removed by physical screening to very fine materials removed by floatation and density separation processes. Coal refuse piles are also known by a variety of other names including "waste dumps", "gob piles" and "slate dumps". The potential hazards of improperly reclaimed refuse include contamination of surface and groundwaters by acidic leachates and runoff, erosion and sedimentation into nearby watersheds, spontaneous combustion, disturbance of topsoil borrow areas, and damage from landslides should large slope failures occur. Many of these problems have been particularly acute for abandoned refuse piles, and modern regulations attempt to minimize the environmental impact of coal refuse disposal operations.

Jan 1, 1993

The adsorption of gold onto activated carbon in iodide solutions has been studied. The adsorption rates were determined as a function of temperature, salt concentration and pH as well as activated carbon concentration. A kinetic model was also developed for the adsorption. The adsorption rate was believed to be controlled by a mixed mechanism of film diffusion and pore diffusion, but the film diffusion had a major contribution to the overall rate. Experimental findings were in good agreement with the model developed. The apparent activation energy was found to be 14.9 kJ/mol.

Jan 1, 1993

By Raja V. Ramani

The importance of adequate mine ventilation for good health and safety conditions has been recognized since miners first ventured underground. All over the world, governmental actions on mine health and safety are directly connected with mine atmospheric environments, their assessment and control. These governmental actions have been, and continue to be, motivated by the repeated experience that potential threats from inadequate control can evolve, either suddenly or in the long-term, into unpleasant reality, with catastrophic health and safety consequences. These governmental actions are also an indication of the remarkable professional progress being made in the field of mine ventilation. Surely, no developed country allows underground mines to operate without strong measures for the control of ventilation under legislation specific to the mining industry. In the United States, the federal government's responsibility for mine safety has evolved over the years through a series of legislative actions beginning in 1865 and continuing through 1910, 1941, 1947 and 1952. The passage of the Federal Metal and Nonmetallic Mine Safety Act of 1966 (the 1966 Metal Act), the Federal Coal Mine Health and Safety Act of 1969 (the 1969 Coal Act) and the Federal Mine Safety and Health Amendments Act of 1977 (the 1977 Mine Act) are the most important milestones in this long legislative history. The 1977 Mine Act adopted many of the stronger features of the Occupational Health and Safety Act of 1970, perhaps the most significant piece of legislation on workers' occupational health and safety in US history. It is worthwhile to ask, "How far has the United States come in mine ventilation since the enactment of the 1969 Coal Mine Health and Safety Act?" This Act and its associated regulations defined in great specificity many standards for healthful and safe operation of a mine and, in some cases, what constitutes good ventilation practice. Since 1969, the frequency and severity of disaster-type events in US coal mines has decreased markedly. A primary reason for this achievement is the strength of the Coal Mine Health and Safety Act's regulatory features in such areas as methane concentration control, dust control, intrinsic safety and explosion-proof enclosures, minimum air quantity and quality standards and air distribution and escapeway provisions. These requirements greatly influenced mine ventilation planning, engineering and practice, leading to increasingly safe working conditions.

Jan 1, 1993

By Tom W. Gonzales

Magma Metals Company commissioned a 3000 tpd Outokumpu flash smelting furnace in July 1988. Through September 1992 the PSP has smelted a first campaign record 4.1 million tons of concentrate. This paper discusses modifications made to the original process equipment to overcome design flaws as well as future design changes currently under consideration.

Jan 1, 1993