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By K. N. Han, Q. Xu

The adsorption behavior of gold in ammoniacal solutions on activated carbon was studied. The gold adsorption capacity of the activated carbon and the recovery efficiency were examined. The parameters affecting the adsorption of gold on the activated carbon included temperature, agitation speed, the concentration of cation and anion and the concentration of ammonia. It was found that the maximum gold adsorption was about 10 kg/t of carbon. The recovery of gold by the adsorption, from ammoniacal solutions was found to be dependent upon the initial gold concentration. Under experimental conditions, a gold recovery of 98% was obtained after 120 hrs of adsorption. It was also found that the initial adsorption rate was relatively fast, when compared to the entire adsorption period. The apparent activation energy for the adsorption was determined to be 15.8 kJ/mol. It was believed that the kinetics of gold adsorption on the activated carbon was controlled by pore diffusion.

Jan 1, 1997

By W. P. Blacutt

A financial-economic model incorporating physical, market and policy variables has been developed for mining investment in Bolivia. Additional risk criteria emanating from political instability, new mining legislation, recent environmental regulations and a new minerals taxation system are accounted for and are integrated into the investment decision model. Results of the model indicate that geologic and market variables have the dominant effect on the investment-worth function. Among policy variables, exchange rate and taxation policies have the most significant influence. Depreciation allowance for infrastructure development has negligible weight in the investment-worth function. The business structure of the firm considering investing in the Bolivian Polymetallic Project, is found to be an instrumental factor in the investment-worth outcome.

Jan 1, 1995

By E. F. ‘Pat’ Nelson, Richard Broom

Our portion of this afternoon’s session is dedicated to the operation of automatic process control associated with small to medium size primary or SAG milling circuits. In recognition of the subject matter of this symposium, specifically precious metals, our historical reference is Rosario Dominicanna in the Dominican Republic, one of the largest gold producers in the Western Hemisphere. Plus a backward glance to review very briefly the initial performance of the big primary mills at Island Copper in British Columbia and Pima IV in Arizona. We will then get to the subject at hand with a discussion of a retrofit control logic recently installed on a 5000 hp primary mill. The focus of this review is the simple, inexpensive, and cost effective character of this retrofit installation.

Jan 1, 1984

By J. W. Wilson, S. Nakajima, B. D. Singh

According to the Project Independence blueprint, a 270 percent increase in coal production is expected from western coal fields compared to an increase of 100 percent for the nation as a whole. Furthermore, 30 percent of the total United States coal reserves lie in the western states, which are classified as beyond the strippable limits and can be recovered only by underground methods. In view of the fact that the majority of the seams in the West are thicker than those presently mined in other parts of the country, it is important to consider the parameters that relate to mining thick seams and the factors that affect such mining systems. Apart from thick seams, a common feature of many western coal fields is the occurrence of multiple seams that lie in close proximity to one another. These multiple seam deposits present difficult mining problems that have not been encountered to any degree in other U.S. coal fields; for example, ground pressure changes in one mine level caused by mining in the other, sudden water or gas influx from the adjacent levels, the danger of spontaneous combustion in gobs and large and complex subsidence displacements on the surface. Perhaps equally important is the fact that the country can ill afford the present systems of underground mining that attain only 50 to 60 percent coal recovery. With the probability of increased thick seam mining, conservation shall be a focal point in future mine design systems. It is possible that in the future it will be forbidden to adopt the present day wasteful mining methods to ensure that coal can be conserved for future generations.

Jan 1, 1977

By Gary S. Brierley, James R. Lambrechts, Andrew F. McKown

Various innovative Ground Improvement techniques have been proposed and applied to facilitate construction of the Central Artery/Tunnel Project in Boston. Given in this paper are discussions of the extensive use of deep soil mixing and jet grouting, and passive construction dewatering applications that are associated with the Design Sections D009A, D007A, and D019E.

Jan 1, 1999

By Robert J. Neubauer

I was asked here today to discuss the first long-term freight rate contract ever signed by a U.S. railroad and shipper. That was ICG's contract with the hoosier energy company to haul coal from southern Illinois to an Indiana power plant. I?ll also talk about why you can expect to see more such contracts in the future But first, let me tell you a little bit about the Illinois central gulf railroad and why coal contracts are so important to us. ICG is a principal mid-American freight carrier. We are one of the ten largest railroads in the united states and one of the ten largest coal-hauling railroads. ICG links the industrial great lakes region with the warm weather ports of the gulf coast. Some of the major points on our route map are Chicago; Indianapolis; Omaha; Kansas City; Memphis; St. Louis; and, of course, baton rouge and new Orleans.

Jan 1, 1981

By Ralf Vergeiner

The most famous landmark of the city of Graz (Austria) is the clock tower on the castle hill. An underground chamber was built as a multifunctional structure beneath this landmark. The required structure was designed as cavern. The overburden to the clock tower in the north side of the cavern was only 30 m. To allow access from the city to the chamber and the clock tower, a vertical shaft was built near the cavern. Rock excavation was by drill and blast method. The pilot shaft was made by the raise-boring method. Because the location of the building site was in the center of Graz, special care was taken to minimize deformations and vibrations so as to protect surrounding buildings.

Jan 1, 2001

By Robert W. Gordon

The art of excavating tunnels with continuous, full-face boring machines began almost 90 years ago, in the early 1880's. At this time, Colonel Beaumont designed and manufactured a seven-foot diameter tunneler for boring under the English Channel, Despite the absence of modern materials and manufacturing techniques, Beaumont's tunneler, powered by compressed air piped in from the surface, was quite successful. During its short, but impressive existence, this machine set a record of advancing in chalk 50 feet per day for 53 days - which is impressive even by today's standards. Despite the apparent success of this early tunneler, almost 80 years passed before any further significant development was accomplished in this field. Demands from the construction and mining industry and society itself have motivated the development of the modern tunneling machine. Our rapidly growing civilization needs faster, less expensive and safer means of excavating tunnels. Space age technology and materials have played a major role in making hardrock tunneling machines possible.

Jan 1, 1970

By F. L. Wilke

Truck haulage costs form a major part of the total mining costs in hard rock open pit, mining operations. In order to minimize these costs one has to - determine the optimal truck fleet (type, size and number of trucks), and. simultaneously - determine the optimal organization of running the haulage system, i.e. especially select the optimal dispatching strategy in order to ensure maximal utilization of the trucks, and simultaneously - establish a reliable maintenance and servicing system to guarantee maximal availability.

Jan 1, 1982

By A. M. Laird

Endako Mines' molybdenum operation is located near the geographic center of the province of British Columbia, Canada. The property is six miles south of the Northern Transprovincial Highway and the northern main line of the Canadian National Railway. The area is broken by high hills covered with dense stands of spruce and pine with vast areas of the valley floors covered with aspen and poplar. The climate is moderate with precipitation averaging 22 inches per year. Approximately four feet of snow accumulates in the winter, and temperatures range from 900 F. in summer to -40° F. in winter. The orebody, a lowgrade porphyry type deposit, occurs in a widespread granitic intrusive which has been locally weakened at the intersection of two regional faults. In this vicinity the quartz monzonite has been further shattered to permit the entry of mineralizing solutions and local dykes. Two types of mineralization occur within the orebody. The most prom¬inent is the six inch to four foot wide continuous quartz veins with characteristic ribbons of molybdenite and frequently finely-divided grains of molybdenite within the quartz. The second type occurs as fine fractures filled with quartz molybdenite in the form of a stockwork halo radiating out from 20 to 200 feet from the quartz veins. Minor hematite, magnetite and chalcopyrite are also present. Mineralization is roughly proportional to the extent of kaolinization in the quartz monzonite, kaolinization being one of three distinct forms of hydrothermal alteration. Pyrite is commonly associated with molybdenum mineralization within the orebody and a pyrite halo is recognized on the south side of the orebody.

Jan 1, 1968

By Joseph M. Denk, Gary J. Wirth

This paper summarizes a three phase face ventilation study which was conducted from September 1989 through March 1990 to determine face area methane liberation patterns on two extended longwall sections. The coal seam being mined was considered gassy and the mine liberated an average of 14.4 million cubic feet per day (cfd) or 0.41 million cubic meters per day (cmd) of methane through the mine fans. The mine also used an extensive underground degasification program to recover up to 13.4 million cfd (0.38 million cmd) of methane. Data was collected while the longwall sections were mining from the beginning, middle and end of panel extraction to determine the relationship between the methane liberation and extent of longwall retreat. As expected, methane concentrations did increase from the headgate (intake) to the tailgate (return) side of the longwall face and peak concentrations were detected above the shearer as it passed a methanometer location during mining. There were significant differences in the methane liberations due to the location of the active face within the longwall panel. Results from this study could be used to determine a minimum design face air quantity for an extended longwall section operating under similar conditions.

Jan 1, 1991

By S. A. Moffatt, S. K. Kawatra, T. C. Eisele

This paper describes the decomposition of bulk samples to fine particles using alkali metal vapors. Basalt, pyrite, alumina, pyrex and quartz glass samples were exposed to sodium vapors at elevated temperatures for different time periods up to 30 hours. Examination of the particles showed that fragmentation occurred preferentially along grain boundaries. Emphasis of this paper is on the theory of the degradation mechanism and the size distribution of the particles produced.

Jan 1, 1992

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 C. Alan Tapp

Introduction Mine sampling determines the practicality of any mining operation. Improper sampling can result in an incorrect appraisal of present production and future potential. Therefore, the mine department in charge of ore-reserve calculations and mine sampling should be overseen by competent and experienced professionals with technical backgrounds qualifying them to produce accurate results. Sampling is a process by which portions of an ore body are collected and analyzed to estimate the average mineral content of the entire ore body. It is incorrect to assume that a large number of samples eliminates any errors in the sampling method. To obtain unbiased samples, proper sample location with respect to rock type and mineralization is just as important. The sampling procedure must yield correct results for the type of mineral deposit, and careful consideration should be given to whether or not the sampling technique has been developed to an extent sufficient to eliminate as much human error and bias as possible. Only after the ore has been mined and milled is the sampling accuracy known. Sampling also provides information about the bulk composition of the ore for mineralogical and metallurgical tests that determine the economic ore-waste boundaries and the geologic trends for exploration. Actual mining plans can be developed from this information to maximize profits. Accurate sampling is critical, and thus must be approached in a scientific manner. Sampling Techniques Sampling practices and techniques are as varied as the mines in which they are used. The method(s) chosen must be tailored to suit the company and mining needs. For instance, tabular uranium deposits, vein gold deposits, and porphyry copper deposits pose special problems in conducting unbiased sampling. The mine geologist or engineer in charge must develop a sampling method, test it in a sample area, and then critically evaluate the results. If the results from the test area are accurate within the economic limits established by the company, they then may be adopted for general use in the mine. Four routine sampling methods are suitable for specific sampling objectives in the daily mine routine: (1) channel sampling, (2) chip sampling, (3) grab sampling, and (4) bulk sampling. The final sampling results depend upon how the four methods are combined to accurately determine the grade of the ore body. When used in conjunction with each other during different stages of mine development, the channel, chip, grab, and bulk sampling methods provide an in-house check or a comparison by which mining methods and sampling procedures can be evaluated. However, the most valid check is based upon the daily mill production. Channel Sampling Channel samples consist of cuttings collected from a groove cut into the rock about 102 mm (4 in.) wide and 19 mm (0.75 in.) deep. Various tools ranging from a 1.8-kg (4-lb) hammer and moil to a pneumatic chisel can be used to cut the sample. Accessibility and rock hardness determine the applicable sampling tools. Before attempting to take a sample, the rock surface must be cleaned thoroughly; the method of cleaning depends upon the amount of mine dust accumulated on the surface or the degree of alteration of the rock surface. Typical cleaning methods 'employ a wire brush, water, or chipping a fresh surface. Next, the sample outline is marked on the prepared surface, taking care to choose appropriate sample loca- tions. After determining the proper sample outline and length, the sample can be chiseled out, catching the rock fragments on a canvas tarpaulin on the floor, in a powder box, in a canvas bag to avoid contamination, or by some other suitable means to capture all of the sample. Vertical veins present a special problem because the drift's back usually is arched, not square. For example, Fig. 1 shows that if sample intervals are measured from A' to D', the length of the sample interval is greater than the true vein width, resulting in an incorrect calculation of the ore reserves. The correct method would collect three samples at A'-B', B'-C', and C'-D', using either actual measurements in the mine represented by A-B, B-C, and C-D or trigonometric calculations to determine the true ore thickness. Then, each sample can be weighted by grade and true thickness for the vein. Channel lengths usually are a maximum of 1.5 m (5 ft), and it is good practice to divide longer samples into smaller intervals according to structures, changes in rock types, or differences in rock hardnesses. The influence of those features on the mineralization then can be determined. Chip Sampling Chip sampling is a variation of channel sampling used when the rock is too hard to channel sample economically or when little variation in the mineral content indicates that this sampling method will yield results similar to those of channel sampling. Rather than cutting a channel in the rock, small chips are flaked off at regular intervals over the entire face or area being the mine. sampled. Care must be taken to assure that the sample is representative of variations in the rock hardness and type. hi^ method is fast and useful in preliminary evaluations, but it should not be used for quantitative ore-reserve calculations. Grab Sampling Grab sampling is a fast method for double checking either channel or chip-sampling procedures, and, in some instances, mine production can be estimated from carefully taken grab samples. Grab sampling takes equal amounts of material at selected intervals over a mine dump, a muck pile, or from an ore car to estimate its Channel Sampling mineral content. Generally, this method is not considered reliable. Many independent variables can affect this type of sampling process. Thus, if the ore occurs in the softer fraction and a proportional amount of the result-

Jan 1, 1982

By Jim Jonas

The Berkeley pit-lake was sampled during two seasons, fall 1997 and spring 1998, from the surface to the bottom. Various parameters were measured to determine what effect the seasons had on the water column. It was determined that a seasonal turnover did occur between the fall and the spring sampling; however, the depth of mixing due to turnover could not be established. Trends were observed which suggested that microbial activity was altering the iron speciation at depth, and subsequently masking the extent of mixing. Various trace metals were removed from the surface water by either co-precipitation with schwertmannite or adsorption.

Jan 1, 2000

By Floyd L. Prestridge

A test of a solvent extraction (SX) pilot plant featuring electrostatic coalescence has been performed by C-E Natco at the United Nuclear uranium mill in Church Rock, New Mexico. Operating in parallel with the United Nuclear SX system, the C-E Natco electrostatic SX pilot plant exhibited comparable extraction efficiency to the United Nuclear system which utilizes conventional mixer-settlers. The C-E Natco pilot, however, operated at much higher liquid loading rates and exhibited less communication between the aqueous phases of the extraction and stripping circuits.

Jan 1, 1983

By Jon C. Yingling

Techniques for optimization of mineral processing flowsheets are reviewed. Though not yet widely used in the minerals industry, approaches for chemical process optimization based on successive quadratic programming (SQP) algorithms may be employed to determine optimum unit design and control settings for a mineral processing flowsheet. Moreover, in certain mineral processing flowsheet applications, specialized techniques can be applied because of the nature of the system relations. These techniques offer advanta es in efficiency. Moreover, their capability exceeds that o f the SQP approaches since simultaneous optimization of circuit configuration and unit controls can be addressed.

Jan 1, 1990

By H. Lyn Bourne

Daily everyone depends on the great variety of glass products, so much so that glass is often taken for granted. In fact most people do not realize how versatile glass has become. Consider the various uses and then try to imagine a day in which we are not influenced by glass. Common uses include container ware, table ware, window glass, lead crystal, automobile glass, and fiber glass. Several less common, but important, uses include laboratory ware, pharmaceutical, TV bulbs, light bulbs, glass ceramics, optical glass, fiber optics, and laser glass. Corning, Inc., a leader in specialty products, uses nearly 1 000 different compositions to manufacture about 60 000 different products (Edwards and Copley, 1977). Glass is such a complex product that-definitions vary and exceptions can be found for most definitions. Glass is an inorganic amorphous (non-crystalline) solid. Most glasses are produced by melting of a mixture of oxide raw materials, and then cooled to room temperature. Soda-lime-silica composition.s account for about 90% of all glasses melted (Anon, 1973). The properties of the glass product come mainly from its chemical composition. All of the different glasses require melting a combination of raw materials and forming the molten material into the desired shape. Both the melting and the forming processes use sophisticated technology and these technologies require experts to manage these production systems. The manufacturing process is continuous and takes place in tonnage quantities, so adjustments in the batch to achieve the desired finished product requires a great deal of expertise. Raw materials are fed to the batch mixing area in very large quantities (tons in most cases). As a result, impurities in the range of 0.1% result in addition of that impurity within the molten glass in kilogram amounts. More than twenty different industrial minerals are consumed in the manufacture of various kinds of glass (O'Driscoll, 1990). This chapter describes the major and minor ingredients of the various glass batches. It discusses the roles of the various oxides in the glass batch and most importantly considers the mineral raw materials which supply the glass industry. Each of the raw materials is described in detail in other chapters so the geology and mineralogy sections are kept brief here. Container glass, by far, accounts for the most production; followed by flat glass, fiber glass, and specialty glass of which table ware accounts for the greatest tonnage. [Table 1] shows the general production data for 1987 through 1990. Statistics for many of the uses do not appear because production volumes are small compared to the major uses. The glass industry is organized in four categories: containers, flat glass, fiber glass and specialty glass. The US Department of Commerce, Bureau of Census, publishes production data about the glass industry in three different categories: 1) glass containers, 2) consumer, scientific, technical and industrial glassware, and 3) flat glass. The Bureau has very complete statistics about the glass industry in these three categories but they report production data in different units according to industry standards. Therefore, [Table 1] gives the production data in dissimilar units. The production of most glass articles follows similar steps. The raw materials are mixed and the resulting batch is fed into the furnace. In soda-lime-silica glasses melting begins between 600 and 900°C. At these temperatures CO, and other gasses are released which create bubbles in the molten glass. To remove the bubbles and insure complete melting the temperature is raised to between 1 500 and 1 600°C. This is the melting-refining stage during which the refining agents in the glass batch serve to aid in the release of gas bubbles, homogenize the melt, and prevent the formation of scum on the surface of the molten liquid. At the conclusion of the melting-refining stage the glass is too fluid for working and the melt is cooled to about 1 100°C to attain the proper viscosity for working and forming to begin. After the glass article has been made, it must undergo annealing (slowly and uniformly reheated and cooled) to remove thermal stresses that were created during the forming process.

Jan 1, 1994

By D. R. Taylor, R. G. Goss

The use of clay-based granules as carriers for pesticides dates back to the early 1940s. It now represents a business conservatively estimated at between 180 and 270 kt/a (200,000 and 300,000 stpy) in the United States alone. Prices for these materials typically range from $110 to $165/t ($100 to $150/st). Aside from economic and specific target pest efficacy advantages, the use of clay granules as pesticide carriers also delivers a number of environmental benefits, which are reviewed. Topics discussed include drift control (vs. liquid sprays), mobility (in the environment), worker safety and transportation (spill) safety.

Jan 1, 2000

By M. A. Mahtab, N. M. Cruickshank, M. T. Wane

Gas outbursts occur as sudden eruptions of gas and minerals from the face of a mine heading as the heading approaches potentially burst prone (or anomalous) zones of rock. Such outbursts have resulted in considerable damage to equipment, and in some cases lives have been lost. Characterizing these anomalous zones and detecting their presence is therefore vital to safe mining. Certain significant characteristics associated with the outburst-prone zones are: (1) the presence of fluid inclusions, (2) unstable stress conditions, (3) characteristic geologic structures, (4) certain physical properties of the rock, and (5) microseismic activity. Geophysical and engineering methods for detecting these characteristics are discussed and are considered with respect to their past success and future potential for predicting gas outbursts.

Jan 1, 1987