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By Carlos Viramontes Aldana

Mining in Mexico is one of its post traditional activities, whose influence in the development of important cities and communications has been decisive. Precious metals and, to some extent, copper and tin were known and used before the Colonial period, but from the sixteenth century to tie end of the nineteenth century, mining and metallurgical industries were concentrated in the precious metals, mainly silver. This silver was exported to Spain and other countries under the Spanish. Rule, Mexican peso was known world wide since the end of the sixteenth century and Mexico ranked as the first silver producer since the eighteenth century.

Jan 1, 1985

By Yongqin Zhang

A single bubble released into surfactant solution first accelerates, reaching a maximum velocity then decelerates to reach a terminal velocity. Modeling this "velocity profile" is fundamental to understanding the motion of bubbles in flotation systems. This contribution considers the terminal velocity. Modeling is by a combination of the Navier-Stokes equation for flow around the bubble and the Marangoni effect induced by surfactant on the bubble surface. Numerical simulation is shown to agree with experiment for bubbles in pure water and surfactant solutions.

Jan 1, 1999

By Robert N. Evans, Delon Hampton

During construction of the Washington Metropolitan Area Transit System, the hand-mining of a mixed-face condition was anticipated on a portion of tunnel located in the downtown area of Washington, D.C. The Section, consisting of two circular tubes, extends from Station 12+80, heading in a westerly direction, traverses along a curve under Lafayette Square, and ends in a northwesterly direction at Station 37+62 (see Fig. 1a). It was near the northernmost portion of the section that the mixed-face condition was encountered. Decomposed rock was first encountered in the invert at Station 31+00. From this point the rock gradually increased in height until it intersected the springline at Station 37+62, the project limit. Summarized within this paper are measurements of the soil load on a horseshoe-shaped portion of tunnel located in the mixed face condition. These measured loads are compared to the soil load on tunnels as determined by current design methods. The paper also discusses rib and surface movements associated with the post loading process. Comments will be made on how the presence of a mixed face condition might help or hender the tunnel design and construction procedures.

Jan 1, 1974

By Gregor de Ratmiroff

Field prospecting for bauxite in Venezuela has had a long but interrupted history having till now oferred but evidence of occurrences. The Venezuelan Government, trough the Corporación Venezolana de Guayana (C.V.G.), in 1974, formalized a major effort in prospection for bauxite in the Shield area and the Orinoco Delta in orden to establish the possibility of raw material supply to an upcoming and expanding aluminium industry. The Corporation, in turn, created and delegated to the Division of Geological Stu- dies, the formulation of the necessary infrastructure and execution of work in orden to determine the existence of economically exploitable bauxite deposits.

Jan 1, 1979

By R. J. Sweigard

Differential settlement on reclaimed land presents a particular problem when the land is to be used for row crops. The poorly drained depressions caused by differential settlement restrict crop yield resulting in additional costs to alleviate the problem. Potentially more serious is the threat of failing to meet target yields due to settlement: related reductions. Because the mechanism by which the problem occurs is not well understood, a physical model study was conducted to investigate the importance of several factors. Although the importance of such factors as the relative amounts of rock and unconsolidated overburden in the undisturbed condition and the size distribution of rock fragments were considered, the analysis concentrated on the causes of settlement in the reconstructed soil layer above the rock spoil.

Jan 1, 1989

By Ann M. Gosier

Over the past 20 years, diesel-powered equipment has been introduced into the underground mining environment in increasing numbers. While the introduction began years earlier in the metal-nonmetal sector, the exponential growth in coal mining use during this time has been more pronounced. Reasons for the continued use and rapid growth of diesel equipment in underground mines are easily understood. The safety and operational advantages afforded by this equipment in production and support systems are demonstrable. As other mine operators witness the advantages enjoyed by their competitors, they too move to introduce an increasingly diverse array of such equipment into their underground mines. As with any industrial technology, the use of diesel-powered equipment entails potential safety and health concerns. Existing Mine Safety and Health Administration (MSHA)approval regulations (30 CFR Parts 31, 32 and 36) apply only to diesel locomotives and mobile diesel-powered equipment for noncoal mines. In the absence of specific regulations, MSHA has required the use of equipment approved under Part 36 (gassy noncoal mines) for areas of underground coal mines where permissible electrical equipment is required. However, a considerable amount of diesel-powered equipment without explosion-proof or fire prevention features is in use in areas of coal mines where permissible electrical equipment is not required. It is on the use of this latter class of equipment that MSHA is focusing much of its regulatory attention relative to coal. The agency also is focused on revising existing occupational exposure limits for gaseous emissions and instituting limits on diesel particulate emissions for both coal and metal-nonmetal mines.

Jan 1, 1993

By Daniel K. Dysinger

Capital resource budgeting is the way managers of publicly held companies fulfill their fiduciary responsibility to maximize the wealth of stockholders. Managers maximize shareholder wealth by allocating investment capital to the most productive of competing alternative projects. Managers do this in a manner that maximizes the net present value of the firm's future cash flow. The techniques of cash flow analysis are the primary tools available for selecting a corporate portfolio of projects that meets or exceeds the rate of return expected by shareholders. The reliability of cash flow analysis hinges on the ability of managers to forecast the future values of individual components of cash flow. The accuracy and reliabil¬ity of forecasting determine the soundness of capital investment decisions and, ultimately, determine the value of the firm.

Jan 1, 1997

Up to the middle of 19 14, when I had reached what seemed like the advanced age of 30, I had enjoyed far more than my share of success and a lot of minor adventure. But the exciting experiences in distant lands that Soldiers of Fortune had made me long for had not yet materialized. And I had not accomplished the two goals that Mrs. Hughes' geography class at Belmont had set up for me. They were to see In its tropical home the enormous yellow bill of the toucan bird and to ride on a straw "bolsa" on Lake Titicaca. These aims were gratified In the next five years that were the epitome of "romance" in its German connotation of facts seen through the rosy glasses of imagination. Dr. Louis Ricketts was to a large extent responsible for my opportunity. I had been lucky enough to do a lot of work for and with the Doctor, as he was affectionately called by the mining men of the southwest. My association was in connection with his work with John Greenway on the complex metallurgical problems at Ajo. Soon after the Ajo investigation Ricketts had been made chief consultant for the Anaconda Copper Co. When Anaconda decided to undertake a cam- paign of exploration of the west coast of South America Dr. Ricketts thought of me and arranged with Greenway to give me a leave of absence from my Calumet and Arizona job. It took three days in New York in June 1914 to arrange the expedition. Ben Thayer, executive vice president of Anaconda, did most of the planning and I was to report to him. T.H. France, a 45-year-old mining engineer who had been driven out of Mexico by the Madera Revolution, was to accompany and help me. He spoke excellent Spanish and his years of Mexican experience had taught him how to get along with Latin Americans. He went ahead to Bolivia, our first target, to get an idea of the country and the problems. This was lucky as I hardly knew where Bolivia was.

Jan 1, 1976

By R. Fraher

The control of mine roof is of vital interest in underground coal mining not only for reasons of safety, but also to avoid the high costs of cleanup, resupport and production losses that can result from roof falls. The difficulty in determining roof stability mine-wide is due in large part to the broad variation of geologic and structural conditions that typically exist throughout a mining area. To ensure a stable roof over the entire mine, support systems must be selected to minimize the possibility of failure. The magnitude and cost of the support selected is a trade off against the cost of the number of falls that can still occur after it is installed. Because of the large number of variables involved in analyzing and optimizing roof stability versus support, a digital computer simulation was selected to find a cost effective solution to roof support design. A total cost approach is used which includes the actual cost of the roof support as well as the cost of the roof fall in terms of resupport and loss of production (Fraher 1990a). A Monte Carlo simulation program called ROCSIM (Roof control Optimization Cost SIMulation) has been developed for determining the optimum roof control system and design layout for underground room-and-pillar mining.

Jan 1, 1992

By Renee Y. Allee

The Chino open pit mine, concentrator, and smelter are located in Grant county in Southwestern New Mexico. Chino Mines Company is a partnership, two- thirds owned and operated by Kennecott Santa Fe Corp., and one third owned by MC Minerals Corp. (Mitsubishi) of Japan. The concentrator, with a design capacity of 37,000 tons of copper-molybdenite ore per day, was commissioned in July, 1982. Further design modifications have resulted in an increase in throughput capacity to 42,000 tpd

Jan 1, 1986

By Ted H. Eyde

Specialty sand and bentonite are produced in the plateau province from the Bidahochi Formation near Sanders, Apache County, Arizona. It appears that deposits of both sand and bentonite formed during the Pliocene in fluvial and lacustrine environments, respectively, along the west side of the Defiance Uplift. The bentonite is an alteration product of airborne vitric ash that fell or was washed into lakes. In the Cheto district, the individual bentonite horizons, which range from less than a foot to more than 10 feet thick, are restricted to the position of the medial volcanic member. Bentonite production began at the Allentown mine in 1924 and the Chambers mine in 1926. In 1933 strip mining of the extensive deposits in the Cheto district commenced. Production increased each year to a peak of 270,000 tons in 1957. As a result of the introduction of synthetic zeolites into petroleum refining, production declined. About 40,000 tons of bentonite are currently produced from the district each year. Bentonite is shipped out of State for processing into desiccants, thickeners, and acid-activated clay products. The specialty sand was derived from Permian sandstones and deposited by streams draining the Defiance Uplift. Although stream channels are usually restricted to the upper member of the Bidahochi, stratigraphically above the bentonite horizon, a few actually cut through the bentonite. The well-sorted sand, suitable for use as a proppant in hydraulically fractured oil and gas wells, is localized in elongate lenses along the margins of the channels. These lenses range from 5 to 50 feet in thickness and often extend thousands of feet in both width and length. The sand is about 97 percent silica, has a yield of 40 percent in the minus 20 plus 40 mesh size fraction, and has a roundness of 0.6 to 0.7 on the Krumbein scale. Production of this sand began about 1961. All of the current production, which amounts to about 40,000 tons per year, is sold in the petroleum-producing area near Farmington, New Mexico.

Jan 1, 1987

By Ed Ramsay

The Hill is a cyanidation plant with flotation and roasting. The grinding and treatment have at the present time a capacity of 1400 tons of ore per day and the precipitation has a capacity of 6000 tons per day. The ore is delivered by a 36" conveyor belt and tripper to 8 mill bins having a capacity of 6000 tons. The ore from these bins is discharged onto 20" gathering conveyor belts which are regulated with p.i.v. speed changers to control the belt weight. A weightometer determines the tonnage milled. The feed enters the 8' x 12' rod mill through a rubber lined chute and the product is discharged through a launder to a 7' rake classifier in closed circuit with 10' by 6' hardinge ball mill. Lime slurry is added at the rake classifier to give a strength of .30#/ton. The classifier sand is fed into the ball mill with a scoop feeder and the mill discharge flows in a launder back to the classifier. The classifier overflow is pumped to a 24' by 12' bowl classifier in closed circuit with a 8' by 15' regrind mill. The bowl classifier sands are fed to this mill and the mill discharge is pumped back to the bowl. The bowl overflow at 8% - 200 mesh is the final product from the grinding circuit.

Jan 1, 1975

By Jim Merza

The recent heightening of environmental issues has forced more and more mining operations to focus on developing new methods to control dust problems encountered at their concentrate dryers, stock piles, tailings ponds and during the loading, transportation and unloading of their products. The development of dust control agents requires a quick reliable and most of all accurate method to evaluate the performance and to optimize the formulation of these products in the laboratory, thus avoiding expensive field trial evaluations. This paper gives an overview of the industry requirements for specialty dust control agents, application techniques and current laboratory evaluation procedures. The paper will also outline the development of a unique dust suppression testing apparatus called the "Dust Box, which is used to evaluate chemical dust suppressants at the laboratory level. Laboratory results from two test programs on different substrates are presented in the paper.

Jan 1, 1994

By J. N. Adamson

The Alcan Smelter project at Lynemouth on the Northumbrian coast draws cooling water for the power station through shafts and tunnels from the North Sea. The sea at this part of the coast is frequently very rough and even in calm weather the coastal currents are strong. The adjacent coal mine makes use of these currents to disperse colliery waste and discharges into the sea some thirty thousand tons each week. In consequence the sea bed is continuously shifting and the sea is black and turbid. Construction of sea shafts under these conditions presents difficulties as drilling from a floating vessel is hazardous and sea bed activity of divers is greatly hindered by the entire absence of visibility. After considering several alternatives a method of construction was agreed with the Consultants in which the drilling and also the lining of the shaft would be completed in sequence from an eight legged work barge (GEM 126). Each shaft would be drilled to full depth and a steel cylinder, with its ends closed temporarily, would be lowered into the hole and grouted into the formation to form a full-length permanent lining. The bell mouth for each shaft would be constructed in advance to form part of the cylindrical casing. On interception of the shaft by its appropriate tunnel the lower end of the cylindrical casing would be cut away and the internal walling of the shaft installed from below. After completion of construction the shafts and tunnels would be flooded and the bell mouth sealing covers removed by divers.

Jan 1, 1997

By G. L. Finfinger, F. E. McCall, A. A. Campoli, M. D. Zuber

Injecting pressurized water into a coalbed prior to mining reduces mining-generated respirable dust. Because of economic and geological barriers, water infusion for longwall dust control in the United States is now limited to the Pocahontas No. 3 Coalbed in Virginia. Water is pumped into the coalbed through underground boreholes that are drilled horizontally from the headgate toward the tailgate side of retreat longwall panels. This paper theorizes that the barriers to widespread utilization of water infusion for longwall dust control could be overcome by long-duration, low-pressure water infusion through vertical gob-gas boreholes. Currently, 43% of the 72 longwall mines in the United States employ vertical gob-gas boreholes. Computer coalbed-reservoir simulation suggests that one vertical surface borehole could infuse the same longwall panel area as four horizontal boreholes in the current water-infusion system for longwall dust control in the Pocahontas No. 3 Coalbed.

Jan 1, 1997

By M. J. Garcia, Howard Hallman, G. M. T. Marshall, Ken Higby, Louis Cope, Robert S. Hess, John Peters, A. G. Law, William C. Larson

After a good year in 1979-strong mineral demand, adequate prices for most metals, minimal labor problems-1980 was not so good. The US produced $24.8 billion worth of nonfuel minerals last year, up 3.5% from 1979, according to preliminary US Bureau of Mines figures. But the $800 million increase was the smallest annual gain since 1977 and reflected reduced auto and construction industry demand, strikes, and energy shortages. Preliminary figures for 68 minerals show that production of 42 decreased, 25 increased, and one was unchanged. Production of 11 of 21 US-produced minerals was up. Noteworthy mineral events in 1980 included a copper industry strike, increased gold and silver prices, troubles in the iron ore and uranium industries, discussion about a US nonfuels mineral policy, and corporate interest in mining companies as merger targets. Recessionary conditions experienced by the Western world in 1980 resulted in a slowdown in new mine development, evident in the relative scarcity of major new base metal projects. This could lead to short term supply/demand anomalies within the next few years which, in turn, could have a significant effect on metal prices, according to Mining Magazine (Jan. 1981). World Mining (Sept. 1980) noted that US mining strength is in open pit operations. A much lower tonnage is mined underground and is centralized in trona, uranium, lead, zinc, molybdenum, potash and, to a lesser extent, copper. The most notable increase in new underground mines has been in Wyoming's trona district where new mines are being developed and production will increase, the magazine said.

Jan 5, 1981

Compared to alternative ways of dealing with coal fines, oil agglomeration has always been a commercial bridesmaid and never yet a bride. Yet interest is high in the process, as shown by a number of pilot plants in operation that are funded by industry as well as government. In the past in the US, alternative ways to handle coal finer than 100 to 200 mesh included flotation, or no treatment except dewatering, or discarding the fines as waste. There are now a number of factors that tilt the economics more toward fine coal recovery. Today, the cost of mining a ton of underground coal runs from $22-30, and discarding even 10% as unrecovered fine coal is a real economic loss. A number of attempts (notably by EPRI) have been made to quantify the effect of coal cleaning on utility boiler operations. Transportation and ash handling costs, frequency of unscheduled outages, fouling and slagging problems, and boiler tube erosion are all lowered by cleaning coal. The advantage of coal cleaning on these parameters has been shown, but the dollar amount varies with many assumptions and is difficult to pin down. The message to a utility, however, has not been lost and the trend toward cleaner steam coal is accelerating. This may lead to fewer installations that only wash the coarse coal, and add back the unwashed fine coal until a maximum contractual ash limit is reached. And, as the proportion of coal fines continues to increase by continuous and longwall mining, it may become impossible to clean the coal sufficiently without cleaning the fines. Flotation and oil agglomeration are the only processes that presently deal directly with cleaning the very finest coal fractions. Flotation has proven its effectiveness in cleaning blackwater and in separating fine coal from mineral matter. It has the achievable potential for far greater pyrite rejection than is now obtained in commercial preparation plants. While flotation will continue to be the predominant method for fine coal cleaning, there are conditions and opportunities where oil agglomeration can be a

Jan 8, 1980

By Brij M. Moudgil

Lack of understanding the major process parameters and inadequate scale-up factors have led to the belief that fundamental knowledge is not important for successful flotation plant operations. Flotation of simple and easy to process ores may not require a strong fundamental knowledge base for day to day operations. However, as low grade complex ores are mined and process control is integrated into flotation schemes, it is imperative for a plant operator to acquire a strong background in the basics of the flotation process at hand and/or have access to such a knowledge base at short notice. In order to meet the challenges of unexpected changes in the feed, reagent quality, water chemistry, physical, mechanical and hydrodynamic conditions, the flotation plant superintendent/chief metallurgist must have a strong background in the flotation fundamentals.

Jan 1, 1993

By P. Somasundaran, D. R. Nagaraj, Jing Wang

Polysaccharides have been widely used as depressants in mineral processing for decades. They constituent one of the most abundant family of biopolymers. However, only a small number of them have been used by industry so far because of a general lack of understanding of interactions between these polymers and minerals. In this work, adsorption tests, electrophoretic mobility measurements, microflotation and fluorescence spectroscopic tests were performed along with computer simulation to explore the mechanistic aspects of guar gum adsorption and conformation on talc as a function of relevant variables such as ionic strength, pH, solvent composition and polymer molecular weight. From microflotation tests, it was found that talc hydrophobicity decreased markedly due to the adsorption of guar gum even at very low concentrations and reached a plateau below moximum adsorption. Guar gum adsorption on talc was found to be not affected significantly by changes in solution conditions such as pH and ionic strength, ruling out electrostatic force as controlling factor for adsorption. Fluorescence spectroscopic studies showed no evidence of the formation of hydrophobic domains at talc-aqueous interface. Also urea, a hydrogen bond breaker, reduced the adsorption of guar on talc. All of the above results suggest that one of the main driving forces for guar adsorption on talc is hydrogen bonding in preference to electrostatic or hydrophobic force. This information should help toward designing reagents of optimum molecular architecture for efficient depression, dispersion or other such surface modification of particles.

Jan 1, 2005

There are several simulators available and are being used for analysis, improvement and optimal control of the grinding process. However, these tend to be developed on informal software engineering methodologies. The informal approach is not suitable for long term development and a formal design methodology is necessary to develop efficient, error-free, and easy-to-use and to maintain software. In meeting this goal, basic concepts of a software model for describing the mineral process objects has been proposed. The software model forms the basis for software design and efficient implementation of the simulation. This paper describes the development of software models for grinding circuits. The work constitutes the theoretical foundation for the development of an advanced simulator for comminution.

Jan 1, 1995