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By Gordon Kidd

Inflation and burgeoning costs are two among many factors which have generated a new surge of interest in "fringe benefits" (sometimes referred to as "supplementary remuneration" or "supplementary compensation"). Other specialized forms of compensation ("perks", in the vernacular) such as company cars, windowed offices, etc., which also are the subjects of current study, are outside the scope of this paper. For businesses, interest in fringe benefits is based on concern for employees? welfare, compliance with government requirements, and an increasingly burdensome impact on bottom lines. In 1980, according to Fred D. Lindsey in the October 1980 issue of Nation's Business, employee benefits will cost American employers an estimated $420 billion. To paraphrase Winston Churchill, "some fringes!" Indeed, few if any administrators consider employee benefits as fringes. Employee benefits impact other major areas of a company's operations as well. As listed by Beadle (1980), these areas include employee relations, collective bargaining, short-term costs, long-range funding, manpower planning, compliance with legislation, taxation for the company and for the employee, corporate image in the community, competitiveness for staff, communications, administration, claims cost containment, etc., etc.

Jan 1, 1980

By Michael J. Mujadin

Since the late 60's, planners at American Natural have known that natural gas supplies from traditional sources will be insufficient to maintain a consistently high level of service in the near future. This dwindling of traditional gas reserves will force American Natural and other gas companies to seek new and more exotic sources of supply. In recent years a number of alternative supply sources were considered, including arctic gas, LNG, and SNG based on naptha, LPG and coal feedstocks. Several combinations, all of which included SNG from coal were selected as the most suitable alternative sources of gas supply for American Natural, and thus our company embarked on the formation of a coal gasification project in the early 70's. Work began with the evaluation of available coal supplies in the United States in late 1970. Western North Dakota was selected for several reasons: large contiguous reserves of lignite were available near the surface, similar to German brown coal for which the Lurgi gasification process was originally developed; the conditions for land reclamation in the area are favorable; and the people in the area have a positive attitude toward well ordered development.

Jan 1, 1977

In early 1970, General Mills Chemicals, Inc. announced the availability of en improved liquid ion exchange reagent, LIX® 64N, for the recovery of copper from various solutions, such as dump leach liquors. LIX 64N has been shown to be a considerable advance over LIX 64, and is presently in use in three commercial plants. Results have been very gratifying. For example, one of the plants was designed for operational production of 40,000 pounds copper per day, and in fact reached this output within the third week following startup of the plant. In addition to the operating plants, another is scheduled to come on stream this month with L D( 64N being used to extract and recover both copper and nickel. The chemical properties and operating characteristics of this reagent have been fully described in a previous paper. 1 LIX 64N is quite an effective and selective extractint for copper, even with copper contents as high as 15 g/l, but the reagent is somewhat limited in pH range, and loses some of its extraction efficiency as the pH drops below 0.8. Liquors derived from vat leaching, electrolytic tankhouae bleed streams, or some of the new leach schemes derived to solubilize copper from sulfide concentrates are examples of the liquors that present major problems when treated via liquid ion exchange. LIX 64N could extract some of the copper from such streams, but recovery was limited to about 75 percent. Also, in some parts of the world there are streams which are relatively low in copper (-5 g/l) but which are very high in acid (25-50 g/1 H2SO4). Again, LIX 64N can attain only about 75 percent recovery from such streams. For effective treatment, these streams require a reagent which will maintain the excellent selectivity of LIX 64N, and will

Jan 1, 1971

By N. Moelans, I. Bellemans, K. Verbeken

Metallic droplets can remain attached to solid particles within liquid slags, resulting in production losses in several movement of solid particles in the liquid slag in a system, considering the attachment of liquid metal droplets to solid slag and on the resulting microstructures is investigated as a function of the velocity of the particles. For all wetting For the amount of metal attached to the particle, a clear trade-off was found between the speed of motion of the solid particle and the wetting regime.

By Bobby G. Cahoon

The ( ) Tayaaja ( ) . The deposit ( ) 130 kilometers due east of the continental divide and approximately 290 kilometers east-southeast of Lima (Figure 1). Relief in the immediate vicinity of the mine, which lies or the west side of the Mantaro river, is in excess of 2,000 meters, and the elevation varies from a low of 2,000 meters above sea level on the Mantaro River to a high of 4,386 meters at point T-27 (Figure 2). Although the Cobriza deposit was first reported by the Italian Geographer Antonio Raimondi in 1866, only three reports have been published on the deposit, which began production in 1966 (Duefias, 1908; Fernandez Concha and Garcia y Garcia, 1961; Petersen. 1965). Many private reports have, however, been written by geologists employed by the Cerro de Pasco Corporation. These reports and the author's observations, while employed as the Cobriza Division Mine Geologists form the basis of the present paper, which describes the relations between-the ore controls in the Cobriza mine and the regional and local structure.

Jan 1, 1971

By Morgan M. Sears, Gamal Rashed, Michael M. Murphy, Brent Slaker

A parametric study was conducted using FLAC3D numerical models to examine the impact of oblique loading on the strength and yield pattern of a stone pillar using two simplified geometry types. In type-1 the side walls of the pillars were assumed to be perpendicular to the roof and the floor, while in type-2 the side walls were assumed to be vertical. These two geometries are frequently used to simplify/model the creation of pillars in dipping mines. Results from the numerical modeling indicate that dipping pillars have reduced strength compared to horizontal pillars, and they are at an elevated risk of failure. Also, an asymmetric failure propagation pattern could be obtained depending on the interaction between the pillar width/height (W/H) ratio, seam dip, in situ stresses and pillar geometry.

By V. Herman, B. Knorr, D. Whalen

"Edge effect is a condition widely observed in High Pressure Grinding Roll (HPGR) operations that gives rise to reduced comminution at the edges of the roll surfaces. This effect is caused by a reduction in the local crushing pressure at the edges of the rolls resulting from the sliding friction between the static cheek plates and HPGR feed material. Practically, this has an impact on equipment sizing, as the edge effect leads to coarser particles reporting to downstream equipment in open-circuit operations and increased circulating load and diminished HPGR circuit capacity in closed-circuit operations.To address this, Metso's HRC™ HPGR incorporates an Arch-frame to maintain a parallel relationship between the rolls and allow for the use of a flanged roll design. We conducted a series of pilot-plant tests with a 750 mm by 400 mm HRC HPGR to compare the performance of the flanged roll design against that of a traditional cheek plate arrangement under similar operating conditions. The edge effect was found to be significantly reduced with the flanged roll design. Based on the pilot-plant results, the implications for circuit design, energy efficiency and overall plant performance in a full-scale application were investigated and discussed.IntroductionGlobal trends such as lower ore grades and rising operating costs are driving the market toward more energy-efficient mineral processing solutions, most notably in comminution circuit design. High pressure grinding rolls (HPGRs) have been recognized as an energy-efficient solution relative to more conventional circuit designs. The basic operating principle of HPGRs, in which a fairly uniform pressure is applied to a bed of material in the compression zone, lends itself to this improved energy efficiency (Morley, 2006). Studies have estimated that savings of 10-15 percent are possible when comparing an HPGR circuit with a traditional SABC circuit (Rosario and Hall, 2008). While HPGRs offer a more energy-efficient solution than tumbling mills, there is still room for improvement in many aspects of the design. Edge effect, in particular, is one such aspect that limits the effectiveness of the machines. Edge effect is the impaired performance at the edge of the rolls due to a reduction in crushing pressure (Morley, 2010; van der Meer, 2010). As described in our prior work (Knorr, Herman and Whalen, 2013), edge effect is caused by the interaction between the ore entering the crusher and the relatively static cheek plates positioned at the edges of the rolls. As the material is drawn into the crushing zone, the sliding friction between the ore and the cheek plates inhibits the ability of material to be effectively drawn into the compression zone at the edges of the rolls. This reduces the crushing force in those edge regions relative to the center of the roll where material is being drawn into the compression zone at a higher rate. In addition, the cheek plates of a traditional HPGR design are held in place by spring-loaded brackets that are adjustable to manage the clearance. This spring-loaded cheek plate design prevents full compression of the material in the edge regions of the roll as there is relief at the outer edges."

Jan 1, 2016

By J. B. Malcolm

The discovery of tungsten-bearing quartz outcroppings in Vance County, N. C., by the Hamme brothers in 1942, made international news in the mining industry and was, in fact, one of the major ore discoveries made in the U.S. during the last 25 years. Operations began at the Hamme mine in 1942, but after 16 years of successful operation, the mine was closed down in 1958 under adverse market conditions. By that time, it had produced nearly 20 million lbs of metallic tungsten. Because of the square-set timber mining method then in use, mine operating expenses were high, actually representing 78% of the total operating expenses at the property. In timber work alone, 160 men were employed. Approximately 500,000 bd ft of timber were placed monthly at a direct supply cost of $1.00 per ton of ore mined. Late in 1959, following a slightly improved position in the tungsten market, company management decided that, by changing the mining method, the operation could be economically feasible. The major premise in this decision was that a reduction of from 25 to 30% of the mining costs could be achieved by the conversion of the mining method from square-sets to horizontal cut and fill. Reopening of the mine began in February 1960, Full production has now been reached and overall mine productivity has been doubled.

Jan 1, 1962

By N. Arbiter

Fracture under low velocity free-fall and double impact, and under slow compression have been-investigated. The pattern of breakage and the size distribution of resulting fragments for sand-cement and glass spheres have been determined. Photoelasticity methods were used to simulate the stress distributions in free-fall impact in order to explain the observed patterns of breakage. Oblique fracture planes, occurring only in free-fall impact, develop along lines which coincide with the trajectories of principal compression as determined by mathematical analysis Breakage efficiencies for different modes of fracture were compared for both types of spheres. For the same specimen and loading system, static loading and low velocity dynamic loading induce geometrically similar stress fields resulting in reasonably similar fracture patterns and shapes of fragments.

Jan 1, 1968

By David B. Brooks, Roger L. Williams

Control of the environment is as old as mining. Engineers have always had to consider how best to deal with the surface, and the character of the surface environment always affects mining method in some way. However, if the relationship of the mine to the environment is old, today's approach is new. For one thing, land, air and water formerly could be viewed simply as obstacles to be overcome or resources to be utilized to win ore at the lowest possible cost. Now we have come to realize that these nonmineral components of the environment also are highly valuable. For another thing, environ- mental protection has become a public policy issue. Again, a special public interest in land and land use is old. From the firs(, the crown claimed extra rights in valuable minerals, and to this day a multitude of laws and regulations control-and tax-land use in every country. What is new is the detailed public attention bring given to waste management practices, whether these wastes be in the form of solids, liquids or gases, and regardless of where in the environment they appear. (It is convenient to lump all mining environmental problems, including hank fires and subsidence, together under the term "waste management," for in effect that is what they are.) As a result of these changes, the mining engineer must consider that lie is dealing with two productive resources the minerals and the remainder of the environment-and he must expect that lie will be judged not only on his efficiency in recovering the one but also on his effectiveness in protecting the other. Further, in seeking to protect the environment, the modern mining-environmental engineer has a dual role. First, there is the obvious task of finding better ways for industry to cope with waste-management problems in actual operations. Second, there is the less obvious but equally important task of helping formulate appropriate public policy objectives for the environment. Throughout; the section it is assumed that mining is an acceptable land use for the tracts under consideration. The question of whether mining will be permitted at all on these tracts is a further public-policy issue, ultimately to be resolved politically and thus, since it is beyond the scope of engineering, is not a subject that can be usefully discussed in a mining handbook. Finally, none of the statements in the section are predicated on the assumption that required waste-management measures will be privately profitable in the conventional sense. Indeed, the reverse is more likely to be the case-at least if accounts are kept so as to include all appreciable costs and a normal rate of return on investment in waste-disposal and reclamation equipment.',',' However, it is clear that improved waste management will be required of mining firms and that, to a considerable although undetermined degree, this expenditure is in the best long-run interest of both public and industry. The several studies that have attempted to quantify the impact of mining on the environment are admittedly rough but still provide enough information to indicate that there is a big job to be done. For example, something approaching 7,000 mi of stream in Appalachia alone are continuously or significantly affected

Jan 1, 1973

By David L. Kuck

Siderophyle platinum-group metals and sane gold are a thousand times more abundant in metal and chondritic meteorites than in terrestrial or lunar rocks. Type I and II carbonaceous chondrites contain granules of the high boiling point metals W, Re, Mo, Ir and Os. Metal meteorites and the metal fractions of other chondrites contain siderophyle Pt, Pd, Ru, Rh, Os, Ir and Au. Spectra of sunlight reflected from asteroids, when compared with those of meteorites and specific minerals, provide a rough classification and guide to sources of precious platin-group metals.

Jan 1, 1982

By Jalal Vakili

In designing very large excavated slopes which are becoming increasingly common in both mining and civil engineering projects, the most important decision of the engineer is the selection of a slope angle. The purpose of the geotechnical study of the slope is to ensure reasonable stability of the slope in the most economical way. Because the rock mass composing each slope is unique, there are no standard solutions for slope stability analysis. A practical solution is formulated from the basic geologic data, engineering properties of the rock, geometry of the slope, and ground water observations. Stability analysis consists of analyzing the forces causing and resisting slope failure. There are several methods of slope stability analysis. The limit equilibrium method evaluates the overall stability of the sliding mass just on the verge of slip, using some or all of the three equations of static equilibrium of a plane problem. The stress-strain relationships of the rock mass are not considered. Method of analysis include the assumption of the shape of the slip surface. Peterson (10) introduced the Swedish method of analysis in 1916, which is based on cylindrical sliding surfaces. Fellenius (4) in 1926 extended this method and introduced the method of slices. This method was refined by Bishop (I) in 1955 and later used by Morgenstern and Price (8) in 1965. In many cases layers of extremely soft strata or strata weakened by neutral stress cause failure to take place by translation along plane of weakness instead of by rotation on a circular surface. In this paper, a slope with a horizontal layer of weak meterial is selected for analysis. This is a usual case for open pit lignite mines where lignite seam may be non-cohesive and 'weaker than the overburden rock or a soft clay layer underlies the seam. It is also a common case of rock fill dams supported on a foundation stratum of clay where the strength of the clay layer is less than that of the rock fill. It is shown that utilizing this method, the location of potential failure surface and the value of the minimum factor of safety can be calculated directly and the trial computations of factors of safety for a number of assumed failure surfaces are not necessary.

Jan 1, 1982

By Robert Hochscheid

A patent issued to J.N.J. Leeman (1957) described the change in performance that takes place when a cyclone is installed in the horizontal position rather than the vertical position. Although this patent was directed more toward improvements that could be realized in the heavy medium cleaning of coal, it contained specific references to reducing the quantity of fine solids that would report in the underflow, and an example for fine sand classification is also included. The three cyclone installations for which data is given in this paper demonstrate that horizontal mounting of large cyclones can improve classification efficiency, eliminate some operational difficulties, and reduce cyclone maintenance requirements in closed circuit grinding installations. Cyclone Experience at Serrana S.A. Each of four grinding circuits at the Serrana S.A. de Mineracao Apatite flotation plant in Brazil have a 2.7 X 4.6 meter (9 X 15 foot) rod mill and each originally operated in closed circuit with two vertically mounted Model D20B (500m nominal diameter) Krebs Cyclones. New feed size is 25mm. The Apatite is liberated at a relatively coarse 35 to 28 mesh grind, but the 500mm cyclones had to be fed at 66 pct. solids in order to obtain an overflow analyzing 12 pct. coarser than 42 mesh. Because dilution water in the cyclone feed had to be limited, classification was inefficient, and there were other significant circuit difficulties as summarized in a recent article by C. A. Busnardo (1984):

Jan 1, 1985

By Ali Nazem, Rennie Kaunda, Zoheir Khademian, Fei Wang, Raymond Henn, Alex Peretiatkol

"The field demonstration portion of the Underground Grouting and Ground Improvement (UG&GI) short course offered by the Colorado School of Mines was held on May 18, 2016 at Baski Inc.’s Yard in Denver, CO.Numerous full field scale demonstrations of grouting methods and equipment were conducted under various field conditions. As part of these field tests, permeation grouting testing and demonstrations were also conducted. Various cement grout mixes were injected into 1.5-m (60-in.) tall transparent sand columns under controlled conditions (Fig. 1). The objective of the sand column permeation grouting demonstrations in the study was to show students the effects of ordinary Portland cement versus ultrafine cement on the engineering properties of the grout, and the permeation height through various types of soil stratigraphic layers in the sand columns. Similar previous demonstrations have had a specific focus on various brands of Type I-II Portland cements and ultrafine cements with a range of water cement ratios and injection pressures. More detailed information about these previous studies can be found in published proceedings (e.g. Henn et al., 2009 -2011).Equipment and material usedThe five clear plastic sand columns were 191 mm (7.5 in.) inside diameter and 1,524 mm (60 in.) tall. Each sand column had a 19 mm (0.75 in.) diameter hole drilled at the base (bottom) of the blind flange for injection of the grout. A perforated plate and/or screen at the base of the sand columns helped to prevent sand from plugging injection port. A ChemGrout grout plant was used for the demonstration consisting of 0.36 m3 (97 gal) high shear (colloidal) tank mixer, a 0.36 m3 (97 gal) agitator tank and a progressive helical cavity pump with maximum output capacity of 77 L/min (20 gpm) at a maximum discharge pressure of 265 psi (18 bar) (Fig. 2). A simple grout header arrangement consisting of control valves, pressure gauges, flow meter, grout delivery and return line, and a short injection line was also custom built. Also used were infra-red thermometers to measure the temperatures of the grout mix batches, CRD and marsh funnels to measure viscosity, baroid mud balance to measure specific gravity, and a digital scale to measure weights. The grout materials used were Holkim Portand cement (Type I-II), Nippon Steel Sumikin superfine cement and U.S. grout ultrafine cement."

Mar 1, 2017

By W. D. Hausel

The Wyoming craton in the western United States is a favorable terrane for diamond deposits. The craton hosts a variety of ultramafic, ultrabasic, and ultrapotassic rocks. Additionally, a few hundred 'kimberlitic' heavy mineral anomalies and some geophysical and remote sensing anomalies indicate the presence of undiscovered, mantle-derived, pipes in the craton. The Wyoming craton is separated into a Wyoming 'archon' known as the Wyoming Province, and the Colorado 'proton' known as the Colorado Province. The 'archon' underlies much of Montana and Wyoming and continues north into Alberta and Saskatchewan; the Colorado 'proton' underlies much of Colorado and a small portion of Wyoming. Although most exploration geologists would consider the 'archon' the most favorable terrane for commercial diamond deposits, the 'proton' has produced more than 120,000 diamonds, while the 'archon' has not been very productive.

Jan 1, 1996

By Ranajit Kumar Sahoo, Shatrughan Soren, Surendra Kumar Biswal, Soumya Sahoo, Sachida Nanda Sahu

The presence of appreciable quantity of clay mineral in Indian hematite ore needs an attrition technique using screw scrubber in the beneficiation circuit to remove the ultrafine clays and avoid downstream operational problems. Spectroscopic analysis revealed that iron ore samples obtained from the Barbil region of Odisha contain a high amount of silica and alumina in the form of clay minerals (e.g., kaolinite) contributed as a loss on ignition (LOI) in the iron-making process. Iron ore fines of below 10 mm size were subjected to a laboratory-scale screw scrubber, and the effectiveness of scrubbing as well as the pelletization of the scrubbed product was investigated. The screw scrubber in the beneficiation circuit helps to remove the clay minerals, causes an increase in iron values from 63.65% Fe(T) to 66.18%Fe(T), with improved physical (CCS of 325 kg/pellet) and metallurgical (RDI of 2.24%) pellet properties.

Aug 31, 2020

By S. S. Pathak, S. Mishra, M. H. Tyeb, A. K. Majumder

Roping in hydrocyclones is a well-known phenomenon in mining and mineral industries which put serious restrictions on their continuous and maintenance free operation. Roping is mostly observed in association with high underflow solid concentrations which can be attributed to higher fraction of solids reporting to the underflow or the feed solid concentration itself being higher. This paper proposes a newly designed spigot with a truncated conical geometry which can allow for a rope-free discharge at higher feed solid concentrations. The experimental observations revealed that in the operation of a 50.8-mm-diameter hydrocyclone, roping ensued at 10% to 12.5% (wt%) feed solid concentration depending on feed inlet pressure for the cylindrical spigot, whereas with the modified spigot, rope free discharge was attained even at 25% (wt%) feed solid concentration.

Jan 8, 2022

By J. P. McCluskey

The effects of air quality regulations passed in the last few years have been felt in a more pervasive way by the electric utility industry than by perhaps any other industry. I'm referring especially to those regulations dealing with the control of air emissions from stationary sources, and those specifying the quality of fuel used. Particularly, I would like to describe some of the effects that these regulations have had on the Commonwealth Edison Company. To put the subject into perspective, a brief descrip¬tion of the company will be presented first. Then, a historical outline of some of the efforts at control of electric generating station emissions will be described. Following this will be an indication of the Company's response to early State and local regulations prompted by the growing pressure for stringent envi¬ronmental control. Finally, the Company's plans to achieve com¬pliance with the most recent, Federally approved, State of Illinois regulations will be summarized.

Jan 1, 1973

By J. K. Ahlness

The Bureau of Mines investigated technologies for determining the integrity of in situ leach mining wells. A self-contained trailer-mounted well integrity testing system (WITS) was designed and built to enable rapid testing of well casings for leaks as required by environmental regulations. The WITS utilizes two inflatable packers to seal off the entire casing length or any portion thereof. Water pressure is built between the packers to the desired test pressure, and the presence or absence of casing leaks is determined by monitoring the pressure drop between the packers. A winch and steel cable are used to run the packers in and out of the well. The WITS underwent an industry field test at the Irigaray in situ uranium leaching mine near Buffalo, WY. A total of 37 wells with an average depth of 225 ft (69 m) were tested at an average rate of four wells per 8-h shift with a two-person operating crew. This represents a 75-pct time savings and an 83-pct labor savings compared to the rigid-pipe method previously used at the mine, with which a three-person crew tested an average of one well per shift.

Jan 1, 1986

By J. Richard Kyle

The Pb-Zn ore bodies in the Pine Point district are localized in paleo-solution structures that developed as the result of post-middle Givetian subaerial exposure of the carbonate barrier complex. Sulfides are concentrated in transgressive pale-solution structures that acted as natural bypasses between aquifers and loci for mixing of fluids of different character, one of which contained metals and the other reduced sulfur. Complex ore textures indicate rapid early sulfide precipitation followed by slower sulfide growth. Evidence for both sulfide-carbonate equilibrium and disequilibrium conditions suggest fluctuations in ore fluid composition. District and ore body metal distribution patterns may reflect the nature and movement of mineralizing fluids.

Jan 1, 1979