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By E. M. Yates, H. M. Hamilton

"For the assent of any new mining project it is essential to determine a realistic value of revenue from the sale of concentrates.A description of the market factors influencing the concentrate terms will be presented along with a detailed review of historical terms of a smelter contract for zinc concentrates. OverviewFor the assessment of any new mining project it is essential todetermine a realistic value of revenue from the sale of concentrates.This applies at all stages of assessment through to the final feasibilitystudy. In forecasting revenue for a zinc mine the followingfactors must be considered:(a) mill recovery and zinc concentrate grade;(b) metal price forecast for all payable metals;(c) smelter terms; and(d) other selling costs.Normally, data from test work are used to determine mill recovery and concentrate grade.Market forecasting, and indeed all economic prediction is an inexact science and probably will always remain so. We have our econometric models our input/output models and a lot of other tools. But they are of no help in predicting the unpredictable. OPEC's huge increase in the price of oil was certainly the most dramatic example of this. It had a tremendous effect on the cost of producing most products world wide and on the price of these products. Any forecasts made prior to the OPEC action were obviously proven wrong."

Jan 1, 1994

By Charles D. Haynes

Outside air for ventilating coal mines in Alabama varies considerably in both temperature and moisture content during the year. Alternate condensation and evaporation of the moisture on mine roofs may result in stresses detrimental to the strength of mine roof. It is well known that the clays in shales absorb moisture, and many investigations have noted the weakening of shales by absorption of moisture. Parker (1970) concluded that there is an annual cycle of rock deterioration in mine roof rock caused by the annual temperature-humidity cycle at the surface. He further noted that moisture reduces the strength of dry rock by one-half, that moisture added to dry rock can cause failure in compression, and that drying of wet rock causes tensile stress buildups by shrinkage. His recommendations for alleviating the moisture-temperature problem was to seal the rock in critical areas and to control ventilation so that air temperature will be lower than rock temperature. The latter recommendation will avoid condensation on the rock surfaces. Hartmann and Greenwald (1941) published the results of a very comprehensive experimental project to determine the effect of temperature and humidity changes on the behavior of mine roof. Their general conclusions included statements that roof rocks were very sensitive to moisture changes, but had low coefficients of thermal expansion. The coefficients were twice in the direction normal to the bedding plane as compared to the parallel

Jan 1, 1975

By A. D. Randolph

Comminution represents one of the major costs of mineral recovery from low-grade ores. Efficient mineral recovery in a typical low-grade ore grinding-flo¬tation process depends on grinding the ore small enough to liberate mineralization without producing excessive slimes, which would result in higher power and flotation reagent costs. Size criteria for efficient grinding should be stated in terms of the distribution of mineralization sizes, but as the mineralization-size distribution is difficult to determine, less desirable criteria of absolute particle-size distribution (PSD) are used in practice. Thus, there is considerable incentive to be able to analyze and predict the PSD performance of grinding circuits for control and optimization of the process. Any realistic model of a grinding circuit must account for recycle of oversize material; such oversize recycle adds to the total mill load and limits total production rate. Simulation of such closed-circuit operation to study grind factors affecting total throughput can be done in a straightforward fashion provided recycle calculations can be added to an accurate input-output model of PSD in the grinding mill itself. Such a total simulation of mill performance is of obvious practical value in assessing the practicality and benefits of various over-all mill control schemes and/or modes of operation. For example, considerable interest has been shown in the development of continuous on-line particle-size sensors and such instruments should be an operating reality in a few years. A total closed-circuit PSD model of this type would be invaluable in the utilization of, and in predicting the pay-out from, such an on-line particle-size sensor. The purpose of this paper is to present a new approach to the development of an input-output PSD model of a grinding mill. The model is continuous in the par¬ticle size coordinate, L, and is based on the principle of a particle population balance along the particle size coordinate. Most previous studies of the grinding unit operation attempt to relate power

Jan 1, 1971

By Songsong Wang

Recently, replacing Pierce-Smith converting process with the oxygen bottom-blowing continuous converting technology has become a new research focus. Based on the principle of Gibbs free energy minimization, the thermodynamic model of oxygen bottom-blowing continuous converting multiphase equilibrium system has been established. The elements distribution behavior is calculated at the same burden composition and operation parameters as the industrial production. The results show that the absolute errors of the mass fraction (wt%) of Cu, Fe, S, Pb, Zn, As, Sb, Bi in crude copper are 0.06, 0.0030, 0.070, 0.38, 0.39, 0.020, 0.017, 0.034, 0.010, respectively, and the absolute errors of the mass fraction (wt%) of Cu, Fe, S, Pb, Zn, As, Sb, Bi in slag are 0.53, 0.81, 0.020, 0.23, 2.5, 0.0048, 0.0010, 0.0030, 1.49, respectively. The calculated results agree well with the actual industrial production data, indicating that the model can be well applied in the oxygen bottom-blowing continuous converting practice.

By F. H. Abd EL-Rahiem

A selective dispersion process is presented and the work carried out to find optimum process conditions to minimise the colouring material in ground calcium carbonate (GCC) is described. The feed material is the overflow product from a hydrocyclone which results from using a Denver Attritioning machine with semi-autogenous grinding for one hour and a 1:1 ore/water ratio. By using sodium silicate (SS), with pH 9 and pulp density 5%, the iron content (as colouring impurities) is decreased from 0.21% in the original concentrate to 0.12% in the final concentrate. The degree of whiteness reached is improved to 85% from 63% in the original material. However, by using hexametaphosphate (SHMP) at pH 10 at the same pulp density, the iron content decreased to about 0.073% and hence the whiteness degree increased to about 96%.

Jan 1, 2004

By R. E. Heithecker, D. B. Taliaferro

"INTRODUCTION Recovery of core specimens from subsurface formations and their subsequent analysis are important aids in efficient development and operation of oil and gas fields. Gore specimens first were obtained mainly for the geologic information they revealed; now they are analyzed to determine many of the physical characteristics and conditions of the subsurface formations as well. Cores recovered from the producing formations may be analyzed for porosity, permeability, oil content, ""connate"" water content, and other physical and chemical properties of the formation, all to the end of furnishing enough data for making reliable estimates of the quantity and avail¬ability of oil and as within a reservoir and in devising efficient means for their withdrawal.Examination of bottom-hole samples of oil gives valuable information concerning the amount of gas in solution in the oil within the reservoir and the resultant shrinkage of the oil when the gas is released. Producing characteristics of reservoirs nay be determined by means of subsurface pressure and temperature gages and measurements male at the wellhead; however, unless reliable core analyses are available, these data have only limited use in any quantitative study of reserves. In such a study the quantity of oil, gas, and water contained in a unit volume of the reservoir formation is extremely important. Although reliable methods of analyzing cores have been developed and the data thus obtained are valuable, their applications become more limited or reservoirs at higher temperatures and pressures are discovered. This condition results almost entirely from the fact that in recovering a core from a formation of high pressure and temperature by present methods a large part of the fluid content of the core is lost or contaminated to an unknown extent. For a number of years most petroleum engineers have held that if this loss and contamination of the fluid content of a core were eliminated, the value of core analyses would be increased greatly."

Nov 1, 1939

The purpose of this paper is to outline some aspects of the experimental worlr that has been carried out in the mineral dressing laboratory at M'ount. Morgan during recent years.The subject matter has been dealt with under the following headings:1. Comminution of various mill products.2. The application of sulphur dioxide as a flotation reagent.3. Heavy-media separation.4. Bulk flotation of sulphide ores.COMMINUTION OF VARIOUS MILL PRODUCTSThe following data were cbtained by processing fractions of reserve grade ore.Granular TailingIn Table 1 are shown the results of tests on material representative of average grade tailing. In the first test (H1 ) the granular tailing was floated as received and in the second test (Ha) the tailing was ground prior to flotation.

Jan 1, 1952

By R. P. Adams, R. A. Beall

The Bureau of Mines developed a method to melt and cast specimens of hafnium- carbon alloy and studied their properties . A rotating - ladle vacuum or inert atmosphere arc furnace was designed , special electrodes and molds were developed , and operating procedures were worked out for casting small shapes . The cast specimens were evaluated according to their carbon content for melting point , density , microhardness , electrical resistivity , and oxidation resistance . Lattice dimensions were determined , and metallographic specimens were prepared . Photomicrographs were taken of specimens containing 2.72 , 5.50 , 6.47 , 9.97 , 12.8 , and 15.7 weight - percent carbon , and their grain structures were compared .

Jan 1, 1963

By E. J. Kloos

The Bureau of Mines evaluated all previously approved gas masks to determine their ability to provide respiratory protection against each of the following six selected amines: ethylenediamine, diethylamine, n-butylamine, ethylamine, methylamine, and hydrazine. Minimum requirements were a 24-minute service life at a flow rate of 64 liters per minute (32 liters per minute for hydrazine) and an amine concentration of 1.0 volume-percent (0.5 volume-percent for hydrazine). The three masks meeting these requirements were the LG4, Willson Products Division, The Electric Storage Battery Co.; the GMD-SS, Mine Safety Appliances Co.; and the 084-PHOV-R, Acme Protection Equipment Co.

Jan 1, 1966

By Elisa Alonso

Manufacturing firms that rely on finite resources have a stake in ensuring sustainable materials use. Higher material prices and uncertain material supply, consequences associated with scarcity, can be damaging to firms. Firms have a number of options to improve material sustainability including dematerialization, material substitution and recycling. However, these options require technological capability, capital investments and supply-chain infrastructure; firms may decide to make such investments only if material prices increase. Once decisions are made, the barriers and delays to implementing changes may harm firms. The impact of not reacting to changes in material supply on firms was examined for the case of different platinum-using industries. It was found that taking action is particularly important for firms when limited material availability leads to volatile market conditions. Industries can benefit especially if they ensure process flexibility and have options for changing their material use patterns.

Jan 1, 2010

By R. Krog, M. Valente, R. Ochsner, W. Marchewka, R. Jensen, R. K. Zipf

A tube bundle system (TBS) is a mechanical system for continuously drawing gas samples through tubes from multiple monitoring points located in an underground coal mine for analysis and display on the surface. The U.S. National Institute for Occupational Safety and Health (NIOSH), in collaboration with Signal Peak Energy (SPE), LLC, Bull Mountains No. 1 Mine, operated a TBS during mining of two bleederless, longwall panels. This paper describes the gas analysis data and its interpretation. As verified by the TBS, coal at the SPE mine tends to oxidize slowly. It was known that a reservoir of low-oxygen concentration atmosphere developed about 610 m (2,000 ft) behind the longwall face. A bleederless ventilation system facilitates formation of an inert atmosphere in this longwall gob and decreases the likelihood of spontaneous combustion. Connections of the mine atmosphere to the surface through subsidence cracks could allow airflow into the longwall gob, revive coal oxidation and increase spontaneous combustion risk. The atmospheric composition of the sealed areas was homogeneous, except in the immediate vicinity of suspected ingassing points. The TBS verified that gases within the partially sealed, bleederless longwall gob expanded into the longwall tailgate area when barometric pressure decreased. The concentration of carbon dioxide in the back return airflow at the longwall tailgate was observed to increase by a factor of three and possibly up to 10 times the typical background concentration of 0.5 to 1.0%, depending on the size of the longwall gob and the magnitude of barometric pressure decrease. TBS have the inherent disadvantage of slow response time due to travel time of the gas samples and sequential gas analyses. A TBS or similar continuous monitoring system could be beneficial in detecting and providing warning of potentially hazardous gas concentrations, if the slow response time of the system is always understood.

Jan 1, 2013

When a thin film of volatile matter is deposited under vacuum on a polished coal surface, and the coated surface is examined microscopically in plane-polarized reflected light, colour changes are observed which are characteristic of the various macerals present. The colour changes appear to be mainly due to interference between light reflected at the upper surface of the film and at the film!coal interface. A variety of source materials for the volatile matter required have been tested, including powdered bituminous coal, coal tars, boron oxide, and certain resins. Bituminous coal gave the best results.

Jan 1, 1970

By Barry Hope, Javier Rico

"Goldcorp’s Hoyle Pond mine has recently completed several projects which have impacted the overall ventilation system. The project includes extending the Fresh Air Raise (FAR) to depth, development of a new Return Air Raise (RAR), and the installation of new sensors and ventilation controls throughout the mine. Two years after the completion of #2 Winze, the mine is ramping up its ore production to 1,300 tpd (up from 1,100). To ensure safe and profitable production, a reliance upon technology has been needed to provide the required ventilation to the work areas according to the mine plan. To systematically assess the mine’s ventilation in real-time, a significant increase in remote monitoring was required. This included installing additional flow, pressure, temperature and gas sensors. The first step in upgrading the existing monitoring was to purchase airflow and differential pressure monitors and install them in key areas of the mine. This paper presents the process of expanding the monitoring capability at Hoyle Pond mine, the selected equipment and the results of the implementation. The intended goal was to improve safety while minimizing capital and operation costs. The monitors were installed in strategic locations to provide immediate feedback on the impact of changes to the primary ventilation airflows. Comparing the available sensor technologies, installing them and systematically monitoring the ventilation served as a first step towards developing a mine wide Ventilation Control System. In addition, the initial state of the monitoring and control system, with final results and the chosen solution for the mine site, are presented. INTRODUCTION The Hoyle Pond mine is located in the City of Timmins, within the Porcupine mining district, Ontario, which has produced more than 70 million ounces of gold since 1910. Currently, approximately 60% of Porcupine Gold Mines gold production comes from the Hoyle Pond underground mine. Mechanized cut and fill and long-hole mining methods are used to extract the ore. The remainder of the ore comes from the Hollinger Open Pit mine. The Dome Underground mine ceased operations in 2017. Hoyle Pond is currently mining at 1820 meters below the surface and plans to go deeper. The average dry-bulb as wet-bulb temperature underground varies according to the depth and surface conditions which has extremes of –40°C in winter to +30°C in summer. The total airflow volume pushed down from surface is 240 m3/s to accommodate the diesel-powered equipment needed for normal operations. In order to improve the quality of air underground a program has been implemented to use diesel particulate filters, starting with the truck fleet and 6-yard scoops, followed by the intention to implement the rest of the functional diesel-powered equipment and eventually move to electric equipment."

Jan 1, 2019

By Wilson G. L, Lord J. H

A detailed analysis of faulting indicatcs that blocks of "greenstone" have been thrust beneath the southern end of the Mt. Isa orebodies.This "greenstone" basement is considered to be a major structural control in the localization of these orebodies.INTRODUCTIONThis paper is based on exploration carried out by Mining Corporation (Aust.) N.L. from 1956 to 1960 in the area immediately south of Mt. Isa, Queensland. During this period over 20,000 ft of diamond drilling was completed together with costeaning and geochemical exploration.Early in 1959, it became apparent that diamond drill information could not be correlated with the current geological concepts of this area and a detailed geological appraisal became necessary. In all, sixty square miles were mapped at a scale of 1 in. to 500 ft, using enlarged aerial photographs. All drill core was logged and sections re-interpreted.Professor K. C. Dunham of the University of Durham consulted on this project and contributed through valuable discussion. Dr. A. Day of the University of Sydney carried out a gravity survey in February 1960 and Dr. H. Wilshire of the same University undertook microscopic examination of rocks from the area. Certain sections of the area were investigated geochemically by Mr. K. K. Hughes of New Consolidated Gold Fields (Asia) Pty. Limited in 1960.In outlining a theory of ore genesis in the area the writers have drawn heavily on the invaluable data published by many previous workers on the Mt. Isa field, in particular...

Jan 1, 1963

By Shamsher Prakash

Equivalent spring constants for analysis of footings is a function of Young's modulus of pile material (Ep), shear modulus of soil (Gs), and geometry of the footing and/or piles. Shear modulus is strongly strain dependent in soils. Therefore, the spring constants are strain dependent, which is acceptable to the Geotechnical engineers. However, structural engineers prefer to use spring constants as a function of displacement, rather than strain. In order to develop these relationships, appropriate relationships between strain and displacement are needed. Also, modulus degradation with strain needs be built into these relationships. Description of spring constants kx , ky, and kz in x, y, and z direction and k?, k?, k?, about x, y, and z directions are relatively simple. However, description of kxø and ky?, the cross-coupling spring constants depend on 2 - components of displacement and rotation. Thus, there are 8 spring constants and likewise there are 8 damping constants. Approximate strain-displacement relationships on which displacement dependant k's and c's are based are presented with appropriate equations, and a numerical example is included illustrating k's and c's as functions of displacement.

Jan 1, 2002

By Mohammad Irshad, Klaus Mussger, Harald Wagner

Despite the fact that the New Austrian Tunneling Method; NATM, has been used in the United States for the past 23 years or so, still considerable misconceptions exist in the industry about the nature of the method and its implementation. In the authors’ view its implications are usually not well understood. The paper provides an overview of the highlights of NATM usage over the past two decades to illustrate the point that NATM is now a well-established tunneling method in the U.S.A. Accordingly the thrust of this paper is on the more pragmatic aspects of the NATM technology usage as it concerns the Owners, Designers and the Contractors. Prior to examining the implications of NATM usage from the viewpoints of various stakeholders, it should be helpful to first briefly provide an overview of the history of the method as it was introduced and implemented on several key tunneling projects in the US, over the last 2 plus decades.

Jan 1, 2005

By Stephen A. Gasiorowski, Frank J. Hrach, James D. Bittner

Separation Technologies, LLC (ST) has developed a processing system based on triboelectric charging and electrostatic separation that provides the mineral processing industry a means to beneficiate fine materials with an entirely dry technology. The environmentally friendly process can eliminate wet processing and required drying of the final material. The process requires little if any pre-treatment of the material other than grinding and operates at high capacity - up to 40 tonnes per hour by a compact machine. Energy consumption is low, approximately 1 kWh/tonne of material processed. Since the only potential emission of the process is dust, permitting is typically relatively easy. In contrast to the other available electrostatic separation processes that are typically limited to particles greater than 75 µm in size, the ST belt separator is ideally suited for separation of very fine (<1 µm) to moderately coarse (500 µm) materials with very high throughputs. The triboelectric particle charging is effective for a wide range of materials and only requires particle-particle contact. The small gap, high electric field, counter-current flow, vigorous particle-particle agitation and self-cleaning action of the belt on the electrodes are the critical features of the ST separator. The high efficiency multi-stage separation through charging / recharging and internal recycle results in far superior separations and is effective on fine materials that cannot be separated at all by the conventional electrostatic techniques. Since 1995, this triboelectric process has been extensively used for the beneficiation of coal fly ash with eighteen separators in place and over 100 machine-years of operation at locations in North America and Europe. The technology has been also successfully applied to the beneficiation of a variety of minerals including calcium carbonates, talc, and potash.

Jan 1, 2012

By Leon Maday, Robert Robinson, Judy Cochran, Don Davis

Over the past 20 years, several soft-ground tunnels have been successfully completed in the Seattle area. These tunnels were built using design-bid-build contracting methods, and have benefited from advancing technologies in exploration, design and construction methods. Owners have utilized various contractual means to share some of the risks that are inherent to tunneling projects. This has helped to foster a competitive bidding environment and to resolve issues related to unanticipated underground conditions in a fair manner. This paper presents case histories of tunnels constructed by King County and the Washington Dept. of Transportation that illustrate a common approach to design and construction issues. The common thread is successful project completion with minor cost changes under the design-bid-build contracting method. Lessons learned from these projects are being applied to the upcoming King County Brightwater Project tunnels, Sound Transit’s Light “Link” Rail tunnels and other tunnel projects.

Jan 1, 2005

By C. R. Fast, George C. Howard

Laboratory and field testing of various squeeze cementing techniques and materials revealed that many improvements could be made in squeeze cementing operations. The use of a slow-pumping squeeze cementing procedure permitted the control of the quantity of cement displaced into a formation and aided in obtaining a high final squeeze pressure. Field testing indicated the desirability of obtaining high final squeeze pressures, the need for improved formation breakdown fluids, and the necessity of controlling the pressure differential during testing after a squeeze job. INTRODUCTION During the past few years, squeeze cementing operations have been investigated, both from the theoretical as well as the practical point of view, in an effort to arrive at some solution to the many and varied problems that arise with this type of operation. A review of well files indicated that in many instances, wells were being squeeze cemented four and five times before a satisfactory pressure buildup was obtained. There seemed to be considerable variation in opinion as to the proper method of squeeze cementing, as well as disagreement as to the proper breakdown agent, the quantity of cement that should be used, type retainer and length of WOC* time that was necessary. Consequently, it was deemed advisable to approach this problem theoretically, field testing each idea developed in hopes of eventually arriving at a squeeze cementing procedure that would give reasonable assurance of a successful job after one squeeze cementing operation. This investigation was. therefore, divided into two broad headings: (1) Preliminary studies, which include both theoretical and laboratory studies, and (2) Field investigations to determine the proper squeeze cementing methods. PRELIMINARY STUDIES Overburden Pressure Studies Squeeze cementing problems are so intimately related to the earth&apos;s overburden pressure that solutions to them are very difficult, if not impossible, without an understanding of the nature and magnitude of the overburden pressures encountered at the depths of producing wells. It was thus felt that the first approach to research on squeeze cementing should be made through a study of these pressures. Since there has been rather loose usage of a number of the terms related to overburden preasure by different writers, the terms to be subsequently used are defined here. Theoretical overburden pressure is the calculated pressure at any given depth exerted by the theoretical weight of overlying formations as calculated from the average rock density. Fluid displacement pressure is that pressure at which fluid can be injected into a formation after it has been broken down. It may be more or less than the theoretical overburden pressure. Formation breakdown pressure is that pressure at which a formation parts or breaks and is usually thought of as fluid displacement pressure plus rock strength. Breakdown agent is that fluid with which the formation is fractured. The first step in the study of the earth&apos;s overburden pressures involved a review of pertinent technical literature. The general opinion expressed was that the overburden pressure gradient of the earth&apos;s formations is roughly 1.0 psi per foot of depth, and that application of sufficient pressure to stratified formations. will cause them to part at or parallel to the bedding planes. The second step in the study of overburden pressures involved a study of available well data in an effort to obtain some definite information as to the actual values experienced in the field for the above mentioned terms. Data from 115 cement squeeze jobs in the Gulf Coast area and 46 cement squeeze jobs and acid jobs in the West Texas-New Mexico area were closely analyzed. The analysis of these data showed that the average formation breakdown

Jan 1, 1950

By B. G. Klugh

(New York Meeting, February, 1912). IN a paper before the Institute at Wilkes-Barre, Pa., June 1911,1 Mr. James Gayley discussed the application of this process to iron-bearing materials. The same author2 described the results of operations at the plant at Birdsboro, Pa. The purpose of the present paper is to present further discussion of some technical details involved in the operation of this plant, and of the theoretical and practical relations of this product to blast-furnace practice. Since Oct. 1, 1911, the Birdsboro plant has been in operation at the blast-furnace of the E. & G. Brooke Iron Co. The results have been highly satisfactory, although the material treated, being chiefly the flue-dust currently made by the furnace or taken from the accumulated stock-pile, was excessively high, and yet not uniform, in carbon, so that the desirable control or regularity of the amount of fuel in the mixture treated could not be maintained. Nothing could more forcibly demonstrate the flexibility of the process than the fact that, under these conditions, the sinter produced was, in all cases, of excellent quality. The Dwight & Lloyd process, as such, and its present highly-developed mechanical appliances were described by Mr. Gayley in the paper above mentioned. While the repetition of some particulars will be unavoidable in this paper, it will be confined to features bearing upon the metallurgical principles involved. According to the principle of the process, the finely-divided iron-bearing material to be sintered is intimately mixed with

May 1, 1912