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By L. Widdifield, R. Riggle

"In today’s challenging mining environment the “Big Picture” (Caterpillar, 2013) approach to mining is often neglected. With haulage costs approaching up to 45 % of the overall mining costs, all too often the load-haul-dump- return cycle is not investigated in its completeness. This paper will discuss the aspects of taking the time to observe an operation from the “Big Picture” approach. In today’s mining business miners, engineers, trainers, supervisors, and managers have ever increasing roles and responsibilities as never seen before in the past decade. The endless human resource, safety, environmental, cost control issues and performance initiatives, detracts from precious time that may have been dedicated to examining the day to day operation. Having examined numerous mining operations over the past several years, one common denominator is lack of time to properly observe operating practices in the field and recognize both positive and negative observations. The old fashioned vocation of observing the operation to assess the haulage, loading and maintenance processes to adjust, maximize or enhance operations have sometimes vanished. Four areas to be discussed in this paper: (1) Look at the “Big Picture”(Caterpillar, 2013), (2) Use common sense, (3) Areas identified for biggest improvements in the operations, (4) Observation of small details for big impacts to lower cost per ton and increased production. The objective of this paper is to provide low cost recommendations to lower cost per ton and increase production. INTRODUCTION Whether miners claim to have been around and experienced it all or the “rookie” on the mine site, miners are expected to execute the mine plan at the lowest cost possible. So why is it so difficult to execute this task? Shouldn’t supervisors just have to man the equipment, tell operators to have a safe day and tally up the numbers at the end of the shift? And let the technology system do the rest? So what could go wrong? Lots. Mining companies seek help from consultants, training departments, performance reporting systems and an arsenal of resources. Armed with all this information, the supervisors just hop in the pick-up and tell the shovel operator to speed up. Sounds simple enough. When the improvements don’t happen, what could have gone wrong? It comes down to people, the simple things that were not executed over the months previously and as a result today the mines performance is not where it should be. A mine is built by people. Managers who have the vision to develop the ore body in a manner that follows sound engineering practices. The infrastructure to mill the ore and support the equipment needed to move the material. Along the way equipment is procured and operators trained to run the gear. Engineers and geologists set up the design, the material movement, and haulage routes. Sounds easy to this point. So, why mine after mine is there this constant struggle to move more with less and get the costs down? Understanding how to make “Great Miners” out of these people is critical to lowering your cost per ton."

Jan 1, 2016

By R. Cooper, K. De Wet, A. Janwong

"Horsehead Metal Products is a zinc refinery in Mooresboro NC treating crude Waelz Oxide (WOX) to produce Special High Grade Zinc by a hydrometallurgical process, comprising leaching, zinc solvent extraction/electrowinning (SX/EW), melting and casting and bleed treatment. Cadmium removal by zinc dust cementation plays an essential role in the bleed treatment circuit to prevent a build-up of cadmium in the circuit. Silica, although not present at significant levels in the WOX feed material (approximately 0.3%), had a significant impact on the efficiency of cadmium cementation with zinc dust, most likely due to the passivation of zinc dust particles with silica gel. Solid/liquid separation efficiency by filter press was also impacted. The silica levels were mapped throughout the circuit in an attempt to identify the source of the silica issues. Adjustments including using PLS as feed to cementation, pH control in WOX leaching and neutralization have been introduced to mitigate the issues created by silica gel in the circuit. INTRODUCTION Located in North Carolina, Horsehead Metal Products Inc. is a hydrometallurgical zinc refinery processing Waelz Oxide (WOX) to produce Special High Grade (SHG) zinc. The flowsheet, known as the Modified Zincex® process, consists of leaching, solvent extraction, electrowinning, melting and casting and bleed treatment as illustrated in Figure 1. Cadmium cementation, part of the bleed treatment process, provides an essential bleed of cadmium from the circuit, as metallic cement. The Cadmium cementation circuit consists of agitated cementation reactors, a zinc dust addition system, filter presses, agitated purification (releach) reactors and a cadmium concentrate filter press Silica can be found in several forms in acid leaching. The first form is fine silicate particles. The size of the particles can vary from one to twenty microns (1). Fine silicate particles can lead to the formation of crud in solvent extraction circuits (2, 3). At Mooresboro, crud has been observed in Depletion, which is part of the solvent extraction circuit. Silica content in the solution in this section is high. The second form of silica is monosilicic acid Si(OH)4, which begins to polymerize almost immediately upon being leached into solution. Monosilicic acid polymerizes to silica gel or a silica precipitate dependent primarily on supersaturation (5). Factors that influence the rate of polymerization include temperature, sulfuric acid concentration / pH, hydrofluoric acid concentration, seeding, and dissolved salts concentration such as zinc and aluminum in the solution (4, 5, 6). In sulfate systems, silica solubility is reported in the range of 150 to 450 ppm of SiO2 (3, 5, 7)."

Jan 1, 2016

By Ralph J. Anctil, James E. Palmer

According to relatively recent estimates by the US Geological Survey and the US Bureau of Mines, there are more than 0.9 Tt (one trillion tons) of remaining identified coal resources in the seven major western US coal-producing states and about 200 Gt (220 billion tons) in the demonstrated reserve base. Considering coal's current national production level of 0.7 Gt/a (0.8 billion tpy), these US reserve and resource figures are reassuring. Given here is a preliminary analysis of geologic constraints and an estimate of their effects on mining and recoverability of western coal. Mining Constraints USGS and USBM coal figures incorporate only thickness and depth, and are "blind" to many other major geologic constraints on mining and recoverability. The most important of these geologic constraints include: • coal seams too thin or too thick for conventional mining methods; • coal seams that cannot be mined due to insufficient separation from underlying or overlying previously-mined beds; • unstable or otherwise unfavorable roof strata; • soft or heaving floor strata; • coal seams that are too lenticular or discontinuous for conventional mining methods; • coal seams in intensely faulted areas; • coal seams having high angles of dip precluding the use of conventional coal mining methods; • coal seams that cannot be mined due to proximity of water-bearing strata; and • coal quality problems such as excessive ash, sulfur, chlorine, or sodium. Coal Thickness Present USGS-USBM classification for reserve base includes bituminous coal beds more than 0.7 m (28 in.) thick and subbituminous beds more than 5 m (60 in.) thick to depths of 305 m (1,000 ft). Both of these thicknesses are less than the thicknesses now considered mineable in the western US. The lower limit for bituminous steam coal in deep mines is about 1.5 m (5 ft). For subbituminous coal, a thickness of at least 2.4 m (8 ft) is generally required. Accordingly, the Bureau of Mines reserve base includes many thinner coal seams that will not be mined in the foreseeable future. Within the Powder River Basin of Wyoming and Montana many seams-Wall, Upper Pawnee, Lower Pawnee, Cache, Manning-range in thickness from 7.6 m (25 ft) to more than 30 m (100 ft) and occur at depths to 305 m (1,000 ft). These have been included in the Bureau of Mines reserve base. However, the mining technology required to mine these thick seams does not now exist. It will require many years for development. The ultimate recoverability from these thick seams is unknown, but could be as low as 25%.

Jan 8, 1982

By Mritunjoy Sengupta

The Green River formations in the Western U.S.A. contains vast amounts of petroleum reserves in oil shale deposits. Exploitation of this petroleum reserve calls for large scale mining of the oil shale. Applicable mining methods include conventional underground mining using roan and pillar, sub-level caving and block caving; underground insitu retorting of oil shale and open pit mining. Roam and pillar mining offers one of the most economic methods of underground mining of oil shale. A 2.4 x l09 litre per year (50,000 barrels per day) of crude oil production would require a daily oil shale production of 100,000 tomes per day from underground operations. For this large production, a highly mechanized room and pillar mining muld utilize large capacity diesel equipment such as 85 tonne trucks and 8m front end loaders. The total air requirements of an oil shale mining operations can. be as high as 28443/s. Ventilation planning for such a large scale underground mining operation presents a formidable task. The major objectives of providing ventilation air to underground workings are to dilute airborne .dust and diesel fumes to harmless levels, and to insure that the mine environment is compatible with the health and safety of mine personnel. Regulation of air velocities and air temperatures is a major factor in mine environmental control. Colorado State law requires that a minimum of 0.047m3/s of fresh air be supplied for each kW of diesel power operating underground. Additionally, 0.047m3/s of fresh air must be supplied for each underground employee, and a minimum air velocity of 0.15m/s must be maintained in all working places. It is desirable to exceed this minimum velocity in order to prevent stratification of ventilation air. Moreover, Colorado law also stipulates the maximum allowable concentration of noxious gases mine air, below: ? C02 - 0.5% by volume, 5,000 ppm. ? CO - 0.005% by volume, 50 ppm. ? Oxides of Nitrogen - 0.0025% by volume, 25ppm. ? Nitrogen Dioxide 0.005% by volume, 5 ppm. This paper examines ventilation requirements for the underground mine, with respect to air quality requirements and distribution of air in mine workings in light of the above regulations. Analyses were made for sane typical mining plans to determine airflow resistance or pressure drops and fan horsepower requirements. In addition, the possible occurrence of high concentrations of toxic gases, was examined. Expected temperature levels in mine workings were approximated.

Jan 1, 1980

By Lars A. Stålberg

"This paper will touch several of the topics covered by SDIMI 2005, including,• Sustainability indicators for the minerals industry, • Best practice of sustainable development in the minerals industry, • Social contributions,The complex issues of a company’s "sphere of influence" and "complicity" are important to every discussion of business and Human Rights. The paper will argue that to protect and promote Human Rights needs to be regarded as an integral part of sustainable development policies for the minerals industry. This implies a need for explicit inclusion of Human Rights indicators among the indicators to be applied by the minerals industry."

Jan 1, 2005

By J. S. Walstrom

Debate on an appropriate, acceptable method of regulating mine and mineral processing wastes has been ongoing since Congress passed the Resource Conservation and Recovery Act (RCRA) on October 21. 1976. Final regulatory determination on which mineral processing wastes are excluded from the RCRA hazardous waste regulations under the Bevill amendment was made by the U.S. Environmental Protection Agency on June 13, 1991. Regardless of whether a mining or mineral processing facility?s waste stream(s) lost or maintained its exclusion status under the Bevill amendment, that facility can expect more stringent regulation of affected waste streams. These more stringent regulations will be added to an already complex regulatory maze, which includes the Clean Air Act (CAA), Clean Water Act (CWA), Safe Drinking Water Act (SDWA), Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), Superfund Amendments and Reauthorization Act (SARA), and Toxic Substances Control Act (TSCA), as well as state and municipal environmental regulations.

Jan 1, 1992

By T. A. Moss

The installation of equipment and structures at mines often requires the evaluation of unique loading and operating conditions. Consideration of these unusual features is required throughout design and construction and into operation. The necessity for employing sound civil, structural and mechanical engineering techniques to the design of structures and equipment is well understood. However, the influence of geotechnical factors on the overall behavior during construction and operation of these facilities is less appreciated. Mine operators routinely perform exploratory drilling for the purposes of defining ore deposits. These exploration activities can be extensive and often include provisions for assessment of subsurface conditions as they relate to the mining operation, i.e., requirements for ground support. All of these factors are important to the economics of the mine and are well justified. Surface facilities are provided to access and service the mine and they play an important role in the successful development and operation of a project. Headframes, hoist foundations and shaft collars, in particular, are examples of unique installations encountered at underground mine sites. The design and above surface behavior of these facilities can be analyzed with the usual fundamental engineering practices employed throughout the engineering professions. This requirement during the project development is understood and adopted. Unfortunately, near surface exploration for the purposes of assessing soil and rock conditions for foundations are often given a reduced priority and less consideration. This paper is aimed at providing an outline into the benefits and importance of performing such explorations and to provide a brief discussion of the merits of such an approach. References in the paper relate particularly to shaft headframes, hoists and shaft collars but the issues raised apply equally well to other installations of a similar nature, e.g. milling equipment.

Jan 1, 1992

The objective of this paper is, firstly, to summarize several field developments utilizing the art of hydraulic fracturing as it has been extended into various mining applications. Secondly, to summarize the understanding of the hydraulic fracturing processes; and lastly to discuss researchable areas and possible future applications. Hydraulic fracturing was developed as a method of stimulating production of oil from oil producing formations. The primary paper by Clark (1) in 1949, describes the process of placing a hydrostatic pressure of sufficient strength on the producing formation of an oil well that the rock apparently cracked, and then, on allowing the well to flow back, a higher rate of recovery of oil was enjoyed. The interpretation of the process mechanism was that the formation rock was cracked to a considerable distance from the well bore, increasing the drainage area; thus, the productivity of the well was measurably improved. Figure 1 is illustrative of this process. This development was of major significance to the oil producing community and considerable research and development ensued. Improvements in method, engineering development of equipment, and research to ascertain the optimum application of fracturing practice led to a highly sophisticated, but specialized technology. The Production Research Division, Continental Oil Company, vigorously pursued research in this area in the 1950's with a resulting number of process improve¬ments. The research group, published a significant number of technical papers on these various researches. One of the developments was the process aimed at controlled orientation of the fractures, either in the vertical (2) or horizontal (3) orientation.

Jan 1, 1969

By William J. Bronkala

One of the oldest tools used in mineral concentrating is the magnetic separator. Virtually every mineral handling system has need for some type of magnetic equipment in two types of basic usage. 1. Equipment protection through tramp iron removal. 2. Mineral concentration based on magnetic properties of the minerals contained in the ore.

Jan 1, 1969

By Lee W. Saperstein

P.L. 95-87 contains explicit demands for land-use planning in its reclamation and designation sections. Both sections require recognition of local land-use plans; however, the sections are not well integrated. Accommodations to these planning requirements may be found in suggestions based on British mineral planning practice. Better links can be created among local land-use planners, the state's permitting authority and designation office, and mine designers. Mining companies should take more interest in local land-use plans and in resource inventories; states should consider devolving to local government responsibility for accepting mine permit applications and designation of unsuitability petitions.

Jan 1, 1982

By R. J. Smith

Tar sand deposits in Utah represent more than 25 billion barrels of in-place bitumen, 96% of the known U.S. reserves. The technological development of a hot water processing strategy for the Canadian tar sands and the commercial Production of synthetic crude oil from this natural resource suggest that similar success may be possible for the utilization of Utah tar sands to provide our country with a new domestic source of synthetic crude oil. In this regard an active research program to develop a hot water processing strategy for Utah tar sands has been sustained at the University of Utah for the past five years. The hot water process for Utah tar sands differs significantly from that used for Canadian, tar sands due to the inherent differences in the respective bitumen viscosities and the nature of the bitumen-sand association. These differences have led to the identification of certain design criteria necessary to achieve satisfactory phase disengagement during digestion. (8,9) Subsequent flotation of the digested tar sand is a subject of current attention and is considered in this contribution for the Asphalt Ridge tar sand deposit. Although contact angle measurements of pure Asphalt Ridge bitumen indicate moderate hydrophobicity, air bubble attachment to the bitumen concentrate taken from a 37 liter flotation cell is not possible. This surprising result suggests that the flotation separation is dependent on air bubble entrapment rather than on attachment due to surface hydrophobicity. The occlusion of air bubbles in the bitumen is apparent from visual examination of the concentrate, especially at lower temperatures. It seems that a bitumen bubble agglomerate forms in the impeller region of the flotation cell, the effective density of which is such to allow the agglomerate to float to the surface. A factorial design of the major operating variables in the flotation separation indicated that the quality of separation was significantly dependent on the flotation temperature and to a lesser extent on the degree of agitation. For a flotation temperature of 77C recovery of 96.7 percent was realized at a grade of 61.0 percent bitumen. The improved separation at higher flotation temperatures was found to be due to the decrease in bitumen viscosity resulting in more effective rejection of coarse sand from the concentrate.

Jan 1, 1980

By Robert L. Cheek, Sid McIlveen

Sodium sulfate is an important industrial chemical. As recently as ten years ago it was produced and consumed in the United States in quantities exceeding 1 Mtpy. Since then, both its production and use have declined; however, approximately half the production still comes from natural sources. [Fig. 1] illustrates the history of production of natural sodium sulfate in the United States. Production of natural sodium sulfate from various types of deposits is the main source of this chemical in Canada and Mexico, and probably in Argentina, Chile, Iran, Spain, and the Russian Republics. MINERALOGY AND PHYSICAL PROPERTIES Sodium sulfate is widespread in occurrence and is a common constituent of many mineral waters, as well as seawater. Atmospheric precipitation contains sulfate; it is one of the major dissolved constituents of rain and snow (Davis and Dewiest, 1966). Many of the saline lakes throughout the world contain varying amounts of sodium sulfate. Because sodium is usually the dominant cation, some workers make an anionic distinction, referring to lakes containing predominantly sulfate as bitter lakes and those containing predominantly carbonate as alkali or soda lakes (Bateman, 1950). Sodium sulfate in its natural form is found in two principal minerals, mirabilite and thenardite. Mirabilite, the hydrous form, is commonly called Glauber's salt. It was discovered by the German chemist, J.R. Glauber (1603-1668), who derived its name from the Latin, sal mirabile, meaning wonderful salt. Thenardite, the anhydrous variety, was named for the French chemist, Louis Jacques Thenard (1777-1857) of the University of Paris (Mitchell, 1979). The largest quantities occur in the form of mirabilite. Sodium sulfate is found in varying degrees of purity, from theoretically pure efflorescent crystals of mirabilite to combinations and admixtures of other salts and impurities. It is a common constituent of some brines; from this source much is extracted commercially. Sodium sulfate also is found in compounds, such as the minerals glauberite, the double salt of anhydrous sodium and calcium sulfate, bloedite, the hydrous double-salt of sodium sulfate and magnesium sulfate, and burkeite, the anhydrous double-salt of sodium carbonate and sodium sulfate. Over 40 minerals contain sodium sulfate in varying proportions; many are of special interest because of their frequent occurrence. Table 1 lists some sodium-sulfate bearing minerals. The reader is referred to other publications (Cole, 1926, Dana, 1932, Grabau, 1920, and Dietrich, 1969) for descriptions of these minerals. Only mirabilite and thenardite will be described herein. Mirabilite Na$04.10H20, contains 55.9% water of crystallization. It is noted for its efflorescence or spontaneous loss of water. On dehydration it changes to the anhydrous form, Na2S0,. Mirabilite is an opaque to colorless, water-soluble mineral that tastes first cool, then slightly bitter. It has a specific gravity of 1.48. It frequently forms as efflorescent, needlelike monoclinic crystals, but generally is found in the massive form. Thenardite, the anhydrous mineral, Na2S04, contains 43.68% Na20 and 56.32% SO3. It ranges from colorless to white and may be tinted shades of gray or brown. It is a water soluble mineral with a slightly salty taste. Its specific gravity (2.67) and hardness (2.5 to 3) exceed those of mirabilite. It commonly occurs in the massive form without visible crystals. Its crystals are frequently tabular pyramids of the orthorhombic system. Sodium sulfate also occurs as a heptahydrate, containing seven molecules of water, but this is unstable and has not been found in the natural environment. The solubility of sodium sulfate has an important effect on the crystallization of the salt in nature, as well as in its production. Its solubility in water generally increases as a nonlinear function of temperature. Below 1.2°C, ice and mirabilite form. As the temperature is increased above O°C, increasing amounts of sodium sulfate become soluble. At 32.4°C, a transition point on the solubility curve is reached, as the decahydrate melts in its own water of crystallization and the anhydrous form crystallizes. With in- creasing temperatures, solubility decreases somewhat. The presence of other dissolved salts changes the transition temperature and solubility characteristics of sodium sulfate.

Jan 1, 1994

By Robert C. Freas

Lime, the versatile chemical is, generally speaking, a calcined or burned form of limestone commonly known as quicklime, calcium oxide or, when water is added, calcium hydroxide or slaked lime. Almost 40 different lime products are available, a fact which has contributed to the rather loose use of the term lime as well as to confusion and misunderstanding. The term is frequently, albeit erroneously, used to denote almost any kind of calcareous material or finely ground form of limestone or dolomite. Lime is made from high calcium or high magnesium limestone, generally having a minimum of 97% combined carbonate content. Normally, high calcium lime has less than 5% MgO. When the lime is produced from a high magnesium limestone, the product is referred to as dolomitic lime. Calcination/Hydration Calcination, or the production of lime, has its origins in the earliest days of alchemy, with the general reaction class having been identified in an Arabic text printed in 1000 AD. It was much later, however, in the mid-1700s to the mid-1800s before this basic reaction became understood from scientific perspective. The pro- duction of lime has been so basic and simple that its underlying scientific principles have over the years received only intermittent investigation. Rather, much of the thought and inquiry has been directed toward the development of kilns. Thus, it has only been in the last 25 to 30 years that lime has received any concentrated scientific investigation relative to the thermodynamics and kinetics of the calcination and hydration reactions. Particular emphasis has been focused upon energy consumption and fuel efficiency. Calcination refers to a broad class of reactions, of which the limeflimestone reaction is just one, wherein a substance is heated to less than its melting point, resulting is a weight gain or weight loss. In the calcination of limestone to produce lime, the basic chemical reaction is as follows: [ ] While there is nearly universal agreement bout the equilibrium conditions related to the limestone/lime reaction above, there have been numerous and varied calcination models developed for the reaction. Recent investigations have resulted in the development of the model shown in [Fig. 1]. From this model it can be seen that calcination is a function of both temperature and CO, pressure. It does not, however, provide any indication of the rate at which the reaction takes place. Calcination is strongly time variant with different limestones. In a very broad sense this relates to the fact that the calcination reaction starts on the exterior surface of the limestone and then proceeds toward the center. As the calcination reaction takes place, the CO2 released at the interface must make its way through the lime to the exterior surface. Since calcination is limited by gas diffusion to the surface of the partially calcined limestone, the natural impurities in the stone, differences in crystallinity, grain boundary chemistry, density variations, and imperfections in the atomic lattice all play a significant role in calcination rate. Therefore, the suitability of a given limestone as a source material for lime production can be determined only after completion of adequate burn tests designed to evaluate the various limiting factors. When a coal-fired kiln system is considered, the entire process of calcination is made even more complex by the introduction of additional chemical constituents into the calcination environment. The reader is referred to the references for a more detailed description of the complete calcination reaction and the differences inherent between differing kiln systems. In the foregoing discussion it was noted that CO2 is released during the reaction. This release results in a 44% weight loss during the complete calcination of a high calcium limestone, or a 48% weight loss for a highly dolomitic limestone. The trade term for this weight percent loss is loss on ignition, or LOI. This weight loss is frequently used as a measure of the completeness of calcination. Because the calcination reaction is chemically reversible, quicklime or burned lime is frequently referred to a being highly reactive, or unstable. The more stable form of lime, hydrated lime, is commonly preferred and generally specified by the user. Hydrated lime is obtained by adding water to quicklime to produce a dry, fine powder. Quicklime's affinity for moisture is then satisfied, although it still retains a strong affinity for CO2.

Jan 1, 1994

By Haydn H. Murray, Fred G. Heivilin

The "Hormite Group" was proposed for palygorskite (attapulgite) and sepiolite for their complex magnesium silicate composition and elongate crystals (Martin-Vivaldi and Robertson, 1971). These minerals occur in close association with each other and more complex structural variations may exist (Bailey, 1972). In 1862 Savchenkov used the name palygorskite to describe a mineral from the Palygorsk locality (Hay, 1975), near the Ural Mountains. Ovecharenko and Kukovsky (1984) mention that when mountain leather deposits were prospected in the Palygorsk Division mine it was assumed this unusual mineral was a variety of asbestos. Early mineralogists used the terms "mountain cork" or "mountain leather" when referring to palygorskite. Robertson (1986) mentions that it appears palygorskite was known since Theophrastus&apos; time, ca. 314 BC. J. de Lapparent used "attapulgite" for clays from Attapulgus, GA, and Mormoiron, France, because he thought them different from palygorskite, but the two types were proved to be the same (Bailey et al., 1971). The name attapulgite is still used for the Florida and Georgia deposits when the crystal length to diameter ratio does not exceed 10:1(Merkl, 1989). Georgia palygorskite clays are of much shorter length compared to classic palygorskite. In 1847 Glocker first used the name sepiolite which was called "Meerschaum" by Werner (1788) and Hauy (1801) namedit "Ecume de Mer." Brochant (1802) described low density and white magnesium silicates adding the name Talcum Plasticum and Ecume de Mer. In the Meigs-Attapulgus-Quincy district palygorskite (attapulgite) commonly occurs in two distinct forms referred to as short length palygorskite (Meigs Member) and long length palygorskite (Dogtown Member) (Merkl, 1989). Long length palygorskite crystals (> 10 pm) are rarely observed in the Meigs and Dogtown Members, but when present are in association with dolomite crystals. The short length form is usually less than 2 pm in length and has a low magnesium content whereas the long length form has a high magnesium content and a length greater than 2 pm. The distinctions in morphology are not only important because of the relationship to the origin of the deposits, but also in relation to activity in causing membranolytic activity related to data on palygorskite samples from 9 locations ranging from relatively inert to active in work reported by Nolan et al. (1989). The > 10 pm lengths amounted to only 51 of 17,401 fibers sized. The shortest lengths (< 0.5 pm) were relatively inert. This study pointed out that surface activity, morphology, and chemical differences may be distinctly different within the definition of palygorskite, or for that matter for any individual mineral so that health and other properties must be measured because the name alone does not necessarily indicate uniformity. Palygorskite (attapulgite) fuller&apos;s earth was first sold for drilling mud in 1941. The market for this use expanded slowly and has maintained a level of 7 to 10% of the total US production during the last few years. Most of the fuller&apos;s earth sold for drilling mud comes from the southern part of the Meigs-Attapulgus-Quincy district of Georgia and Florida. Palygorskite clays produced in this area are superior to most other fuller&apos;s earth for mud used in drilling salt formations, but because of high water loss, they are inferior to bentonite where the rocks drilled contain no saltwater. According to Oulton (1965), more than 90 different grades of fuller&apos;s earth are produced. Some of these grades are used for pharmaceuticals designed to absorb toxins, bacteria, and alkaloids; for treatment of dysentery; for purifying water and dry cleaning fluids, dry cleaning powders and granules; for the manufacture of NCR (no carbon required) multiple copy paper; for the manufacture of wallpaper; and as extenders or fillers for plastic, paint, and putty. Fuller&apos;s earth mined near Ellenton, FL, was used for making lightweight aggregates for the construction of concrete barges during World War I1 (Calver, 1957). Still other uses of fuller&apos;s earth and its suitability for uses in new products are outlined by Haden, Jr., and Schwint (1967), Haden, Jr., (1972), and Haas (1970). One special use of fuller&apos;s earth is as a carrier of platinum catalysts that are made in the United Kingdom from sepiolite clays mined in Spain. Other uses of sepiolite fuller&apos;s earth (Chambers, 1959) are similar to those of the palygorskite (attapulgite) type mined in the United States.

Jan 1, 1994

By R. Edward Williams

The Spa1lation Process Because of the low thermal conductivity of many hard rocks, rapid heating of these rocks produces a thin surface layer in which the temperatures attain high values. Thermal expansion of this surface layer is constrained by the reminder of the still cool rock, and when stresses within the surface rock become high enough, the surface rock breaks away from the cooler rock behind it and flies or falls off as a thin flake called a spall. Then the next, newly exposed surface is heated, and the process continues. This process is the basis of spallation drilling. The hot gases from a jet burner provide the heat for spallation to occur, and their high velocity provides a scouring action that transfers heat to the rock and removes the spalls as rapidly as they form. Spallation is a process which works in very hard rock. It is dependent upon the thermal expansion coefficient and the thermal diffusivity of the rock but is also affected by any discontinuities in the rock. To date the efforts which have been made to evaluate the various rock according to their spallability has been minimal. As the success of this process is dependent upon the characteristics of rock it is expected that the study of rock mechanics will prove to be of greater value to this program than to the other mechanism for drilling and excavating rock. Commercial Uses of SPALLATION In the 19408s, the Linde Air Products Division of Union Carbide (UC 1 began developing spallation for use in mining taconite ore, which is presently the chief source of iron in the United States. In this work UC developed a jet-piercing tool that burned fuel oil with oxygen to produce spallation and contained mechanical cutters to remove rock that was not amenable to spallation. The UC jet-piercing machines have since produced about 40 million feet of shallow blast holes used for emplacing explosives in the taconite mines. During this work it was found that hole diameters could be increased by merely reducing the advance rate of the burners and that existing holes could be enlarged by making another pass through the hole with the same burner. The Browning Engineering Go. of Hanover, N.H., has developed a hand-held spallation burner to cut slots in granite. It has been used for a quarter of a century and is now standard equipment for quarrying granite throughout the world. This burner, which resembles a small jet engine oriented with its exhaust pointed downward, is the forerunner of a flame jet burner used to spall experimental holes in granite at maximum rates in excess of 100 ft/hr when operating in hard, competent granite. It uses No. 2 fuel oil, which is burned with compressed air. The system uses water to cool the burner and the exhaust gases. These gases, along with the steam produced from the cooling water, blow the spalls from the hole. Experimental Work Theoretical and experimental work has been accomplished by the Massachusetts Institute of Technology and the Los Alamos National Laboratory. This work is reported in Refs. (3) and (4). To verify the experimental results of this work laboratory scaled down field tests were conducted using two we1 1 characterized granites from quarries in Barre, VT and Westerby, RI, under defined heating conditions. In the laboratory tests a propane - oxygen heating torch was used to direct a flame at the granite surface and the spal 1 ing process was examined at various heating rates with a high-speed video taping system operated at 200 frame per second. This produced a time-lapse sequence where the onset of the spallation process was easily distinguished. Also the heat flux from the torch to a flat surface at various stand off distances and flows was measured. A similar set of tests was conducted using the more easily quantified and uniform heat source of a 1.5 kw GO2 laser. This allowed accurate

Jan 1, 1986

By Duport. P. J.

INTRODUCTION In February 1981, the Canadian Institute for Radiation Safety (CAIRS) initiated a routine Personal Alpha Dosimetry service for personnel of the Canadian uranium mining industry. This service is based on the use of the [Personal Alpha Dosimeter] developed by the French Atomic Energy Commission (CEA). The origins of personal alpha dosimetry and its rational are briefly described. Technical and organizational aspects of a routine personal alpha dosimetry service are outlined in this paper. HISTORICAL BACKGROUND International recommendations (1) and Canadian regulations have established Maximum Permissible Exposures (MPE) for each source of radiation exposure. Uranium workers in mines and mills are exposed to external radiation ( [y] rays) and to internal radiations ( [B] and [a] particles) which are delivered to the respiratory track by airborne alpha emitters (Rn and Th daughters and Long Lived Dust). To date, dosimetry for uranium workers has been performed by area monitoring/collective dosimetry. In North America the concentration of radon daughters is routinely measured by grab samples taken at the work place and by on-site gross alpha counting. The concentration of potential alpha energy is then calculated (usually by Kusnetz method) and expressed in Working Levels (WL). The time spent by each worker at a given work place is determined from his time sheets and used to calculate the individual monthly exposures to airborne alpha emitters, which is then expressed in Working Level Months (WLM). The uncertainties attached to such a procedure are obvious even in the case of frequent grab samplings and can be expected to lead to an underestimation of individual doses. Among fifteen possible sources identified in a mine situation, (2) four may stretch the standard deviation of the measurements&apos; distribution, nine may lead to an underestimation and two may lead to either an underestimation or to an overestimation. To improve this situation, in 1971 the Atomic Energy Commission began studying the use of personal alpha dosimeters to determine individual exposures from the airborne alpha emitters encountered in the uranium industry environments. Criteria for a Personal Alpha Dosimeter In order to minimize the difficulties encountered in determining exposures received by uranium workers, the CEA in co-operation with the Atomic Energy Control Board of Canada (AECB), has developed a set of criteria for personal alpha dosimeters. Exposures may be determined easily and accurately using this criteria. Autonomy The dosimeter must operate for at least 10 to 12 hours. Excess time spent in the mine or in the facility may possibly be related to an accidental situation causing unusual levels of radioactivity. Since the dosimeter may be needed in non-underground settings where a cap lamp is not used, full autonomy is desirable. Maintenance, Periodicity of Reading In order to complement other dosimetry systems, the personal alpha dosimeter should be read monthly when the filter should also be changed. Routine air flow checks can be made according to local conditions (e.g. diesel loading). Radioisotopes Identification Since the exposure unit (WLM) is based on the concentration of potential alpha energy in the air, the personal alpha dosimeter should be capable of identifying each short lived alpha emitter included in the calculation of the WI, and WLM. Permanent Exposure Record Three points may be considered here: 1. In many countries, lung cancer in uranium workers is a compensable occupational disease. In some instances, compensation is awarded when it can be proven that the worker has received an exposure above a certain limit. The present uncertainty of the individual exposure makes the compensation procedure difficult. 2. By design, a personal alpha dosimeter must representatively sample all airborne particles, ranging in size from the unattached fraction to the upper limit of respirable aerosols (0.001 to 5 µm). The dosimeter must offer minimal resistance to the penetration of these aerosols. While the mining/ milling environment presents harsh conditions which may accidentally contaminate the dosimeter, it is important to be able to distinguish these cases of contamination and still obtain accurate readings. 3. A dependable dose register is most valuable for further epidimiological studies. The dependability of such a data base increases with the possibility of a second assessment of the dosimeters&apos; reading (filter, film).

Jan 1, 1981

By Fred T. Towne

Recent developments in fine grinding by the means of mechanical impaction are the result of continuing improvements in modern machine construction. This is especially true when related to the bearings and mechanically operated parts of impact mills. These improvements allow manufacturers to increase the speeds of the impacting members Most of the more common forms of size reductions, such as percussion, pressure, friction and sectioning, or cutting were at one time accomplished by human hands. These actions were transferred to machinery. Originally of limited application, their use widened as industrial materials and construction became more sophisticated.

Jan 1, 1965

By Jack D. Melin

The commercial development of the Liwell Screen is a result of a thorough search for a non-blinding and highly efficient screening device capable of handling even the most difficult-to- screen feed materials. A proprietary development of Hein, Lehmann A.G. of Duesseldorf, West Germany, the Liwell Screen utilizes a unique flexible deck motion for sizing a variety of sticky, high surface moisture feed materials including raw coal and lignite at separations ranging from 3/4-inches (19mm) down to 10 mesh (1.5 mm).

Jan 1, 1983

By Jonathan Ludlow, Robert A. Jankowksi

Introduction A longwall operator can make few changes to increase output, significantly reduce respirable dust, and decrease power consumption. Reducing drum speed, and thereby cutting with increased pick penetration, is one. This article defines the benefits of deep cutting in terms of reduced dust production and power consumption. It also identifies the practical aspects of high pick penetration in terms of shearer performance and coal loading. Before examining some practical aspects of reducing drum speed and looking at the theoretical background, it is worthwhile to summarize what is meant by high penetration and deep cutting, and what potential benefits and pitfalls may be expected. Deep cutting (in the sense of high penetration rather than wide web) can be defined in one or more of the following ways: • Cutting with an average pick penetration distance higher than that used in the past. • Cutting with a pick penetration higher than the longwall operator would have used if the advantages of deep and slow cutting were not considered. • Cutting with a well-designed shearer drum below 40 rpm. All these definitions are slightly arbitrary. They are given to provide a basis for discussion and to make the point that any move towards deeper, more efficient cutting can result in operational benefits. The benefits of deep cutting appear in many different areas. The most noticeable benefit, provided suitable instruments are available, is the reduction of airborne respirable dust. During an experiment on a longwall in the Pittsburgh seam, a nearly four to one reduction in dust levels was seen when drum speed was halved. Not all studies have shown such a big reduction, but it seems that some benefit is almost always obtained when drum speed is reduced. Production rate and specific power consumption are also affected (in a positive sense) by reducing drum speed or increasing pick penetration. Although these changes may not be as spectacular as those in dust level, they contribute to the economic return of the longwall operation. Similarly, improved washability through fines reduction may have a beneficial economic effect. Cutting with shearer drums operating at lower speeds does have some possible deleterious impacts that an operator should be aware of. For example, cutting reactions - loads imposed on the picks by the coal being cut - will be increased as a deeper cut is used. Steps must, therefore, be taken to ensure the stability of the shearer and provide an adequate haulage effort. These increased cutting reactions also result in higher loads on the power transmission system (gearboxes, ranging arms, pick boxes, etc.) from the shearer motor(s) to the pick tip. These higher loads must be anticipated and provided for with the necessary hardware. In particular, extra haulage power must be provided with low drum speeds, since haulage effort required increases roughly in proportion with pick penetration. Because the drum will be rotating more slowly or will have fewer picks, the load on shearer components will also be more variable. If suitable, robust equipment is not used, this increased vibration will decrease reliability. Benefits of Deep Cutting Lower dust levels, decreased specific power consumption, and improved product washability are the most noticeable benefits of reduced drum speeds. Although the benefits will vary greatly with mining conditions and the type of coal, some examples of what can be expected are described below. Reduced Dust Levels Figure 1 shows principal results of a study on the effects of reduced drum speed conducted on a longwall in the Pittsburgh seam (Ludlow, 1981). This figure shows that average dust production was reduced by about 70% when drum speed was halved. By making some assumptions about such quantities as coal density, it is possible to apply this proportional reduction to the quantity of respirable dust liberated per ton of coal mined. When this is done, two kinds of results are obtained: • At 70 rpm, about 1 g (15 gr) of airborne respirable dust is created for every ton mined (roughly one part per million). At 35 rpm, only 0.28-0.37 g/t (3.9-5.1 gr per st) of coal mined become airborne respirable dust. • At 35 rpm, nearly four times the amount of coal may be mined before the compliance level is exceeded, compared with 70 rpm.

Jan 3, 1984

By A. E. Hall

The authors are to be commended for their attempt to provide a convenient piece of software for preliminary drum hoist specification. This field has received little attention in recent years and is eminently suited to calculation by computer. Unfortunately, there appears to be an error in the calculation of the required rope diameter. The 66-mm (2 5/8-in.) rope selected is oversized for this application. Wire rope weight and breaking strength are related to the rope diameter. For a round strand rope

Jan 1, 1988