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By Russell Barr

Operational excellence is generally known as a management system integrated across critical functions that is geared towards continually improving operational performance. Functional areas such as health, environment and safety, quality and human resources are the focus of many corporate-wide operational excellence programs. Operational excellence also focuses on improving areas such as customer orientation, employee empowerment as well as process, and systems optimization. It is widely viewed as critical to sustaining business performance improvement. Although it is difficult to find a universally accepted definition, or even common foundation in many respects, operational excellence remains a popular term in the business world. Many organizations have developed their own version of organization excellence, influenced by such individual factors, other similar institutions or even third-party service providers. A mining organization is no different from other organizations in that adopting and implementing effective operational excellence programs can dramatically improve business execution and performance across regional or global interests. This paper brings together various perspectives of operational excellence and reconciles them for a useful composite for the mining industry. While most agree that operational excellence should include normal functions in a manufacturing operation such as production, maintenance and engineering and processes such as quality, environmental and continuous improvement, many other factors for operational excellence seem to vary from perspective to perspective. Thus, programs that manufacturers engage in may seem the same, but may, in fact, be different in key areas. This may affect organizational performance in tangible ways. Management must buy into the company?s definition of operational excellence and be dedicated to achieving it. A review of many of the existing definitions of operational excellence, explicit or embedded as part of a program, seems to yield the following common factors: ? It should help organizations better execute their processes and services. ? It should be geared towards improving quality ? It requires that the various operations should be aligned with the overall enterprise strategy. ? It should be geared towards continuous improvement. A composite of operational excellence definitions suggest that it is: ? Geared towards helping the organization achieve sustained profitability; ? tied to strategic alignment and business objectives; ? tied to solid investment strategies; ? integrated as part of the culture, process, time plan and performance; ? a relevant performance measurement system; ? extended to include all aspects of the supply chain (including external suppliers); ? integrated with health, safety and environmental (HSE) aspects. And, while the pursuit of operational excellence intuitively suggests that businesses should improve, it is very difficult to achieve given the difficult challenges facing companies today. Mining businesses face numerous pressures to perform in a global marketplace such as demand, energy cost, variable cost and pricing fluctuations as well as infrastructure challenges to further confound the environment. Companies generally must look to the following:

Jan 1, 2009

By R. H. Lambeth

Disposal of mine tailings in "waters of the United States" is presently prohibited even though case studies indicate that the practice may be environmentally viable. To simulate disposal in the natural environment, nine containers of tailings and sediment were instrumented and placed on the ocean floor near Juneau, AK as were ninety-six biosample containers. Pore water concentrations of five metals were determined, and biota populations were characterized for both materials. After 500 days of exposure there were no statistical macro scale differences between tailings and sediment biota populations or Cu, Pb, and Zn pore water concentrations. Tailings released slightly more Fe than sediment, but sediment released significantly more Mn than tailings. Disposal of mine tailings in marine waters may be environmentally safe.

Jan 1, 1998

By D. D. Faulkner

Cable bolts anchored with traditional two component polyester resin cartridges have successfully supported difficult roof conditions in underground mines. Resin cartridges provide a cost-effective cable bolt anchoring system with consistent anchorage performance characteristics when properly installed. The most commonly used cable bolts in the U.S. mining industry are 270 ksi (1,862 MPa), 0.7 and 0.6 inch (18 and 15 mm), seven-strand smooth cable with resin mixing bulbs (also known as bird cages), and 40- and 30-ton nominal capacity, respectively. However, there are other types of cable bolt anchoring systems aside from bird cages. Recently, many questions have been raised regarding the anchorage characteristics of various types of cable bolts. Keystone Mining Services, LLC (KMS), the affiliated engineering company of Jennmar Corporation, conducted a variety of controlled tests developed to closely model actual underground installations. These tests compared the performance of three commonly used cable bolt varieties, including plain, bird caged and indented seven-strand cable. Details of the laboratory testing and comparative analysis of the results are provided.

Feb 23, 2014

By J. A. Ober

"In 2016, the estimated value of total nonfuel mineral production in the United States was $74.6 billion, a slight increase from the revised total of $73.4 billion in 2015 (Table 1). Increased construction activity spurred increased production of industrial minerals, especially those used in infrastructure and residential construction. Although starting the year relatively low, prices for several metals, especially for some of the precious metals, began to trend upward. Decreased production of most metals produced in the United States, however, contributed to an overall decline in the value of metal production.Several U.S. metal mines and processing facilities were idled or closed permanently in 2016, including iron ore mines in Michigan and Minnesota; three primary aluminum smelters in Indiana, Missouri and Washington; one secondary zinc smelter in North Carolina; a titanium sponge facility in Utah and titanium mineral operations in Virginia. In addition, in May, the weekly average rig count for oil and gas drilling reached its lowest level since the 1940s when that measurement was first recorded. The reduced drilling activity resulted in decreased production of some industrial mineral products used in the drilling sector. Trends in mineral-related sectors of the domestic economy declined or held steady, except in the manufacturing of nonmetallic mineral products and nonferrous metals excluding aluminum, which increased. Overall, mining trended downward as the result of significant declines in coal mining, oil and gas extraction and metal mining (Table 2). Discussion of mine production is frequently segmented according to the type of materials produced within the broad categories of metals and industrial minerals (also known as nonmetallic minerals). Industrial minerals can be further subdivided as construction aggregates and other industrial minerals. Metals tend to have higher unit values but very low production quantities compared with those of industrial minerals, which have higher production quantities but are lower-valued materials, such as crushed stone or construction sand and gravel. Therefore, for discussion and analysis of the performance of the nonfuel minerals industry, the value of production is used rather than the tonnage produced. Tonnages of construction aggregates are orders of magnitude larger than those for most other mineral commodities thus making direct compar"

Jan 5, 2017

By D. McElhinney, J. Winfield, G. Buchan, B. Slaker, A. Iannacchione, T. Minoski, G. Rashed, M. Van Dyke, M. Murphy

"The National Institute for Occupational Safety and Health (NIOSH) has previously established pillar design guidelines for the underground stone mining industry. These guidelines were created from an empirical database of pillar observations and were largely drawn from shallow, flat-lying mining operations. Current trends forecast a great amount of underground stone mines developing under deeper cover, higher seam dips, and more frequent multiple-seam mining configurations than in the past. The complex loading conditions and limited experience in these environments presents a substantial increased risk of ground failure. To investigate these loading conditions, NIOSH has installed a pillar and roof monitoring system at an underground limestone mine in central Pennsylvania. The mine is operating in a seam with dips ranging from 13 to 18 degrees and overburdens ranging from 275 m (900 ft) to 425 m (1,400 ft). Instrumentation installed in an undeveloped pillar and in surrounding strata is currently measuring pillar and roof behavior in response to stress redistribution during excavation. Laser scans are being used to measure ground displacement and changes in conditions associated with local mining conditions and significant geological features. Initial stress measurements show a gradual increase in stress in response to mining, and stress changes that correspond with blasts. The seismic system is operational, with calibration events signaling on each of the 18 sensors. INTRODUCTION Improving mine-wide ground control stability can help reduce the potential for catastrophic failure of underground structures. The National Institute for Occupational Safety and Health (NIOSH) has conducted prior research in stone pillar design and has established fundamental pillar design guidelines for the underground stone mining industry, which resulted in the development of the S-Pillar program (Esterhuizen et al., 2011; Esterhuizen and Murphy, 2015). The data that constitute the S-Pillar program were derived from past mining experience that was almost exclusively drawn from shallow, flat-lying, single-level mining operations1. Stakeholder interactions with NIOSH researchers have indicated that increased numbers of underground stone operations are expected to mine under significantly deeper cover, with greater seam dips, and under multi-level operating conditions (Slaker and Murphy, 2016). The complex loading conditions and limited experience in these challenging environments present a substantial increased risk of ground failure. Inadequate pillar design in these new and challenging environments could result in catastrophic wide-area pillar collapses and an increased safety burden to miners working in the U.S. limestone mining industry. To develop design guidelines and prevent inadequate pillar designs for these challenging environments, NIOSH is currently conducting detailed pillar response investigations at case-study mine sites operating in challenging environments."

Jan 1, 2018

By U. S. Geological Survey Staff

"In 2017, the total estimated value of nonfuel mineral production in the United States increased by 6 percent from 2016 (Table 1). The value of metals produced domestically increased by 12 percent and the value of industrial minerals produced domestically increased by 3 percent. Some metal commodity values (cobalt, magnesium metal and palladium) increased by more than 35 percent in 2017 from 2016 owing to higher prices.Some U.S. metal mines and processing facilities remained idle in 2017, including three primary aluminum smelters in Indiana, Missouri and Washington; a titanium sponge facility in Utah and a byproduct vanadium production facility in Utah. In contrast, new gold mines opened in late 2016 and 2017 in Nevada and South Carolina, respectively, and iron ore mines in Michigan and Minnesota restarted or operated for the full year. In addition, increased oil and natural gas drilling activity led to increased production of some industrial mineral commodities that are used for oil and gas drilling. Production of some industrial minerals, especially those used in infrastructure and residential construction, remained essentially unchanged in 2017, a reflection of the limited growth in construction activity. The production of some metals, including iron and steel, aluminum and other nonferrous metals and nonmetallic mineral products increased. Overall, mining activity trended upward as the result of increases in coal mining, oil and gas extraction and metal mining (Table 2).Discussion of mine production is commonly segmented according to the type of materials produced within the broad categories of metals and industrial minerals (also known as nonmetallic minerals). Industrial minerals can be further subdivided as construction aggregates and other industrial minerals. Metals tend to have higher unit values but very low production quantities compared with those of industrial minerals, such as crushed stone or construction sand and gravel, which have higher production quantities but are lower-valued materials. Therefore, for discussion and analysis of the performance of the nonfuel minerals industry, the value of production is used rather than the tonnage produced. Tonnages of natural aggregates are orders of magnitude larger than those for most other mineral commodities, thus making direct comparisons based on weight meaningless (Fig. 1)."

Jan 5, 2018

By J. M. Wood

Green algae have been found to be much more resistant to heavy metals than blue-green algae. Several mechanisms for resistance to toxicity have been recognized in laboratory strains of Cyanidium, Chlorella and Chlamycomonas. Cyanidium and Chlorella both grow at low pH in acid mine water. Cyanidium removes metal ions from solution by precipitation as metal sulfides whereas Chlorella complexes metal ions to the cell surface i.e. cell wall) and therefore functions as an efficient ion exchange vehicle. We have shown that Ca2+, Mg2+, K+ and Na+ are of critical importance in both the resistance and bioaccumulation of toxic heavy metals.

Jan 1, 1986

By H. Sevim

Three transportation systems in surface coal mines: 1-Truck Haulage, 2-Belt Conveying, and 3-Coarse-Coal Slurry Transportation are compared from the operations and cost point of Views. Computerized design and cost models were developed and cost data banks were compiled for each system. These models can be used to evaluate transportation systems and layouts that are practiced in most of the U.S. surface coal mines. A typical midwestern area strip mine was considered for illustration purposes. Sensitivity analysis on critical parameters such as production rate, transportation, distance, etc. was conducted and the outcomes are presented.

Jan 1, 1990

By J. B. Knaebel

I have been asked to discuss the "Development of the Twin Buttes Mine for Production." This property, which is a large low-grade open pit copper mine about 25 miles south of Tucson, Arizona, was recently brought into production by The Anaconda Company under a long-term lease agreement with the Banner Mining Company. Since the scope of this paper is limited to the subject broadly indicated by its title I will confine discussion of historical, environmental and other general matters to a brief summary sufficient, I hope, to establish a background of those conditions which influenced our approach to the technical and economic problems that faced us at Twin Buttes. The paper deals primarily with our studies and activities related to the solution of these problems and with the resulting engineering and business decisions that were taken - decisions which culminated last September in the initial commercial operation of another major open pit copper producer unique and interesting in several respects.

Jan 1, 1970

By J. G. Groppo

Lowering of filter cake moisture of ultra-fine coal to a 20 percent level using conventional vacuum filtration could be achieved using a combination of metal ion and surfactants. Pretreating coal slurry with about 0.2 Kg/ton of a surfactant and 50 ppm of copper or 10 ppm of aluminum ions provided filter cake containing 22.8 percent moisture. The lowering of moisture is explained due to formation of hydrophobic micro-agglomerates which facilitates dewatering.

Jan 1, 1994

By V. T. McLemore

"Lindgren (1933) defined a belt of alkaline-igneous rocks associated with large quantities of gold and rare earth elements (REE) that extends from Alaska and British Columbia southward into New Mexico, Texas and eastern Mexico. The North American Cordilleran alkaline-igneous belt since has been exploited for numerous types of mineral deposits. In New Mexico, Mid-Tertiary alkaline to calc-alkaline rocks are found with seven types of deposits in these districts: (1) polymetallic epithermal/mesothermal veins, (2) gold-bearing breccias/quartz veins, (3) Cu-Au, Au and Mo porphyry deposits, (4) skarns and carbonate-hosted deposits, (5) iron skarns and replacement bodies (with some gold), (6) gold placers, and (7) Th-REE (with some U, Nb) epithermal veins. Some of New Mexico’s largest gold and REE deposits are found within this belt. Their origin is not well understood, but a compilation of new data (age dates, isotopic and chemical analyses) allows for a better understanding. The diversity of igneous rocks and associated mineral deposits along this belt suggests that this region is characterized by highly fractionated and differentiated; multiple pulses of magmas and involves both upper mantle and lower crustal sources. Once magmas and metal-rich fluids reached shallow levels, local structures and wall rock compositions determined distribution of and final style of intrusions and resulting mineral deposits. INTRODUCTION Lindgren (1933) was one of the first geologists who noted that a belt of alkaline-igneous rocks extends from Alaska and British Columbia southward into New Mexico, Trans-Pecos Texas, and eastern Mexico (Fig. 1) and that these rocks contain relatively large quantities of gold, fluorine, zirconium, rare earth elements (REE), and other elements. Since then, the North American Cordilleran alkaline-igneous belt has been explored and exploited for numerous types of mineral deposits, especially gold. The North American Cordilleran alkaline belt is a north-south belt of alkaline igneous rocks and crustal thickening, roughly coinciding with the Great Plains physiographic margin with the Basin and Range (Rio Grande rift) and Rocky Mountains physiographic provinces (Mutschler et al., 1985, 1991; Bonham, 1988; Thompson, 1991a; Richards, 1995; McLemore, 1996; Jensen and Barton, 2000; Kelley and Luddington, 2002). Deposits within this belt have produced significant amounts of gold in the United States and Canada and include Cripple Creek, Colorado (702 metric tons of gold production), Black Hills, South Dakota (235 metric tons gold production) and Landsky-Zortman, Montana. In New Mexico, the North American Cordilleran alkaline belt extends from the Sangre de Cristo Mountains near Raton, southward to the Cornudas Mountains, in the northern Trans-Pecos alkaline belt (Fig. 2). The alkaline-igneous related mineral deposits in New Mexico have been referred to as Great Plains Margin (GPM) deposits by North and McLemore (1986, 1988) and McLemore (1996, 2001). Alternative classifications by other workers include Au-Ag-Te veins (Cox and Bagby, 1986; Bliss et al., 1992; Kelley et al., 1998), alkalic-gold or alkaline-igneous related gold deposits (Fulp and Woodward, 1991a; Thompson, 1991a, b; Bonham, 1988; Mutschler et al., 1985, 1991; Richards, 1995), porphyry gold deposits, and the North American Cordilleran belt of alkaline igneous rocks (Woolley, 1987; Mutschler et al., 1991)."

Jan 1, 2015

By Virgil L. Barr

National income originating compared to physical production for an enterprise or an industry reflects its ability to strengthen the national economy. For a single industrial sector or for an industry this comparison can be useful to reflect changes that may occur in this ability to contribute because of changing supply-demand-income-investment equilibria. A favorable relationship can be postulated by specified economic incentive, and the accompanying technologic input required can be shown. The new index proposes the use of the Federal Reserve Board indexes of production divided by the constant dollar income originating in the petroleum industry which reflects increases or decreases in performance. When compared with other mineral industries and with, total industry, an approximation of relative strength is evident. By constructing three different hypothetical conditions for future petroleum imports, assuming a constant excess capacity requirement for domestic production, and providing an estimate for future domestic demand for petroleum, the impact on the performance index can be shown. Thus, a strong position for the petroleum and natural gas industry can be stated. If this is done, it becomes evident that because of restrictions on cost-price relationships, a drilling program that would provide enough domestic oil to meet demand may not be practicable. By difference, the amount of improvement in methods of production and processing through technologic advancements can be stated explicitly.

Jan 1, 1960

By Subhash Bhagwat

The definition of high sulfur coal varies from plant to plant and is subject to changes over time as the environmental regulations change. In plants constructed after September 1978 hardly any domestic coal can currently be burned without the use of Flue Gas Desulfurization (FGD) because a 70 percent reduction in potential S02 emission is mandatory even when the potential emission is less than 0.6 lbs. S02/106 Btu heat input. On the other hand older power plants may in many cases be legally emitting up to 6 lbs. S02/106 Btu or more under some State Implementation Plans (SIP). The Clean Air Act requires, however, that in the long run all stationary sources of S02 pollution must abide by the ceiling of 1.2 lbs S02/10 Btu heat input.. Coals with a potential to exceed this limit must, therefore, be considered as high sulfur coals. Such a definition would be unrealistic because many SIP's aim at an emission level of 1.8 to 2.0 lbs. SO2/106 Btu for existing plants and a stricter limit does not appear to be enforceable in the next 5 to 10 years. As a result, coals with an emission potential of greater than 2.0 lbs of S02 per 10 Btu heat input are considered high sulfur coals for the purpose of this investigation. Based on this definition and the 1984 actual consumption of coals by U.S. electric utilities (table 1) only 7 out of the 24 coal producing states could be categorized as low sulfur states. The actual S02 pollution, however, depends on total tonnage of a type of coal as well as the sulfur content of the coal. Table 1 also indicates that only 6 states--Kentucky, Illinois, West Virginia, Ohio, Pennsylvania and Indiana-account for nearly 77 percent of S02 pollution potential in the United States. These 6 states have therefore been chosen for this investigation.

Jan 1, 1986

By A. E. Foscolos

British Petroleum (BP, 2005), indicates that world reserves for oil to be 1198 billion barrels, for natural gas the equivalent of 1156 billion barrels of oil and for coal the equivalent of 3219 billion barrels of oil. If we take into consideration the mean aver-age annual increase in demand of the last three years for oil, 2.6%, for natural gas, 3.9%, and for coal, 6.6%, then their respective reserves? lifespan are calculated to be 27, 34 and 38 years. Without taking into account their annual increase in demand, lifespan increases to 38, 67 and 161 years respectively. Since zero increase or perpetual increase in energy demands on finite resources is unrealistic the selection of the most suitable energy commodity for power generation rests upon the law of supply and demand of each commodity. This defines its price hence its selection for the production of cheap electricity. When the ratio of supply to demand is less than one, peak production is achieved. Any further increase in demand results in price increase to quench its demand. The Association for Oil and Gas Peak (ASPO) has calculated that when oil demand exceeds 84 million barrels/day, Peak Oil Production will be attained thus prices will start to increase in order to even demand with supply. Correspondingly, Gas Peak Production is expected to take place when demand exceeds 9.1 or 10.2 billion cubic meters/day. Peak Oil production has been calculated to take place in the current year, 2006, while Gas Peak production is estimated to take place between 2020 and 2025 provided that gas will not cover the energy deficit created from the lack of oil otherwise Gas Peak production could arrive as early as 2010. The use of coal for power generation is considered a better alternative than oil and gas if new combustion technologies with an energy efficiency of 43%, Germany, and 47%, Denmark, are adopted. These not only extend the lifespan of coal reserves but reduce also CO2 emissions by 25% and 31%, respectively. In the very near future CO2 sequestration and fixation in deep geological strata will eliminate its emissions thus rendering the use of coal the cheapest feedstock for power generation.

Jan 1, 2006

By Ali Ekrem Aritan

Exposure to hand-arm vibration (HAV) among the labor force in the mining industry can result in permanent vibration diseases such as behavioral disorders, visual impairment, osteoporosis, pain (mostly in the hands, wrists, and shoulders), circulatory system disorders, and malnutrition. In this study, the vibration exposure of excavator operators working regularly in 25 different natural stone quarries was measured. In addition, the relationship between vibration exposure and rock properties was investigated. Gloved and ungloved vibration measurements were performed and revealed that antivibration gloves reduce excavator operators’ vibration exposure by 7.10–25.95%. Samples from each quarry were characterized with rock mechanics tests. The correlations between the hand-arm vibration measurements and the natural stone physical–mechanical properties (uniaxial compressive strength, Shore hardness, Knoop hardness, apparent density and total porosity) were determined to be over 70%. One finding of the study was that the health risk in excavators cannot be reduced sufficiently by the sole use of antivibration gloves. Furthermore, the excavation of any rock with a Knoop hardness above 121 is associated with an 81% risk of HAV. To increase awareness of the danger of vibration exposure for natural stone miners, training programs should be provided, and technical and operational changes should be implemented.

By M. Z. Rashad

The purpose of this paper was to compare the covariance and multiquadric functions in same mining and geological applications. The basic principals of the two techniques are covered briefly. Similarities and dissimilarities of the covariance and multiquadric functions are discussed geometrically, mathematically and practically. A 14 by 16 kilometer square area in Baharia Oasis, Western Desert of Egypt, was selected for a detailed comparative test. The gravity anomalies of forty-eight test stations were computed by using the data of sixty-three control stations. The results indicated that the covariance function is quite better than the multiquadric one. On the other hand, the multiquadric function more simple in computation than the other one, which needs to precalculations such as semivariogram and covariogram. Moreover, multiquadric equations are based on geometrical and physical considerations rather than covariance functions.

Jan 1, 1990

By Dolf W. Fieldman

Most recently the geologic setting of the mineral deposits in the Silver Cliff district is described by William M. Sharp in ?Geologic Map of the Silver Cliff and Rosita Volcanic Centers, Custer County, Colorado?, (U. S. G. S. Map I- 1081). The discussion will relate only to the southern half of the Silver Cliff volcanic center and differences in geologic interpretation, which are largely structural, will be pointed out as they arise. Only the manganese/silver zone of the Kate Area will be discussed in detail.

Jan 1, 1980

By Kevin Lofftus

The rest potentials of molybdenite electrodes are measured as a function of pH in absence and presence of flotation reagents. The chemicals used include sodium ethyl xanthate, kerosene, dextrin,sodium hydrosulfide, hydrated sodium molybdate, sodium sulfate, and hydrated sodium thiosulfate. The effect of dissolved oxygen is also noted. The obtained data are correlated with the results of micro-flotation tests obtained under similar chemical conditions.

Jan 1, 1984

By Dan Nilsson

INTRODUCTION A company must have an objective, and that usually is to earn money. In some countries an objective can also be to reduce unemployment in an area or to develop nonindustrialized areas. Government-owned companies can also have as an objective that of serving the com¬munity. This discussion is limited to the consideration of normal companies wanting to earn money. Such an objective, however, has to be defined in more detail. It is not satisfactory only to maximize the total annual profit from, for example, a mining project. In comparison with most other branches, the mining in¬dustry is very capital intensive. When starting a new project, the mining company must invest a lot of money in mines, ore treatment plants, etc. It is normally many years before any income is received from the ore. Fig. 14 illustrates the payments for a new mining proj¬ect with an expected lifetime of 10 years. Whether this project is a profitable one depends on a lot of things. If the company has a shortage of money, it can be impossible to finance the project. Even if the company has enough money, the management may think that perhaps the project may not return the money fast enough. Such limitations will not be discussed here. Suppose that the company has internal funds from its own operation or can borrow them. Since the mining company must invest the money in advance, it is not satisfactory only to add all of the costs during the mine's lifetime and compare them with the total income during the lifetime. The company must include the time value of the capital. In this appendix, the basic investment theory neces¬sary to judge the profitability and costs of mining proj¬ects will be discussed. INVESTMENT THEORY Time Value of Money If a private person has a dollar and puts it into a bank, he or she will receive interest. If the interest rate is r%, the value after one year will be $(1 + r), after 2 years $(I + r)2 , etc. The interest rate represents the time value of money. If the same person wants to have $1 in the bank af¬ter one year, he or she has to put $(1 + r)-1 in the bank today. If the person wants $1 after 2 years, it is neces¬sary to put $(1 + r)-2 into the bank today, etc. So one dollar today is worth more than one dollar tomorrow. It is, of course, not correct to compare money at differ¬ent times since each dollar has a different value. It is necessary to transform all payments to the same point in time. That is called the calculation of the capital value of a cash flow, and to do this an interest rate is used. In the same way, the cash flow from a project like that shown in Fig. 14 can be translated to any other point in time. Most common is to translate all payments to the beginning of the mining period. That capital value is often called the present capital value. Interest Rate What interest rate will the company use? A com¬pany, just like an individual, has the basic alternatives of keeping its money in the bank and receiving interest, or borrowing money from a bank and paying an interest rate. The interest rate represents the time value of money for the company. If the company has a shortage of money, or many good potential investment projects, it has to use a higher interest rate than if it has a lot of money available. Most companies also increase their interest rate as a hedge against the risk involved by using money for uncertain investments, because of taxes, etc. Capital Value When the interest rate has been decided, it is possi¬ble to estimate the capital value of a project. Here the discussion will be limited to the estimation of present capital values. Suppose that one wants to know the present capital value of $1 (Fig. 15), which will be received after n years. To transform it n years back in time, one must multiply it by the factor (1 + r)-, where r is the inter¬est rate the company uses. Table 1 gives these factors for different years and interest rates. Example: At the end of year 5 a mining company has to invest $50 million in a new mine. What is the present capital value at the end of year 0? The company uses an interest rate of 15%a.

Jan 1, 1982

By G. Van Weert

Separation of minerals by shape has received little attention, since minerals normally do not break into different shapes during crushing and grinding. However, comminution of consumer wastes generates opportunities for novel separations based on particle shape. For instance, ductile plastics are broken into longer curved shapes, whereas brittle plastics yield angular particles. Using spouting beds for particle separation in water requires controlling the spout's instability. The preferred geometry for such redesigned spouting beds is reported. Plastic cylinders, discs and spheres were separated as a function of rising water velocity and amount of particles in the system. By using 5 mm particles, differences in settling behavior could be video recorded.

Jan 1, 1999