Search Documents

By G. Michael Lloyd

The term phosphate beneficiation often conjures up visions of processing technologies that physically separate the phosphate rock from some impurity and do not result in a change in the chemical nature of the phosphate rock. However, when we consider hydrometallurgical processing as a phos¬phate beneficiation technique we have to include all chemical treatments that convert phosphate rock into a more useful product. With most of the phosphate rock mined being used for fertilizer pro¬duction, the best known and most widely employed hydrometallurgical process is wet process phospho¬ric acid manufacture. In general, all phosphate rocks are so insoluble that there is no physical treat¬ment that will allow the phosphate content to be used by vegetation in a timely manner. However, after chemical treatment, 100% of the phosphate is readily available for vegetation nutrition. If there is a chemical beneficiation process that could be considered the standard method of treat¬ing phosphate rock it would have to be the wet pro¬cess for phosphoric acid production. In this process finely ground phosphate is reacted with sulfuric acid to give phosphoric acid and phosphogypsum. The phosphogypsum crystals are removed from the phosphoric acid solution and discarded; the phos¬phoric acid is further processed to give the finished fertilizer product. The primary reason that this pro¬cess was adopted so widely is because the phosphogypsum solid that is formed can be easily separated from the phosphoric acid, thereby removing the calcium portion of the phosphate rock and the sul¬fate portion of the sulfuric acid. Other acids have been used to treat phosphate rock but nitric acid is the only other acid used commercially. Nitric acid gives a mixture of phos¬phoric acid and nitrates that can be further pro¬cessed into N-P fertilizers, but the range of N/P grades that can be produced is limited. Hydrochlo¬ric acid has been used to react with phosphate rock, and it can be used to generate a pure phos¬phoric acid but only after solvent extraction to separate the calcium chloride from the phosphoric acid. And then there is the problem of what to do with the calcium chloride. The acid that has received the most attention as a substitute for sulfuric acid is phosphoric acid. In this process, the phosphoric acid reacts with the phosphate rock to give a mono-calcium phosphate solution. This process does not dissolve all the impurities in the phosphate rock, and these solids can be removed from the solution before sulfuric acid is added to convert the soluble calcium to insoluble phosphogypsum. Despite all the claimed advantages, this process has not found favor. A suc¬cessful application of this process to treat some of the lower grade phosphate rocks being used today would seem to have some distinct advantages. Other beneficiation schemes have been pro¬posed or practiced on specific phosphate rocks on a limited scale. These include calcination followed by water leaching to remove lime, weak acid

Jan 1, 1999

By Andy Cole, Stanley Bunk, Steve Dunn, Thom McCord

In 1994, Goldstrike initiated a research program to investigate processing options for treating what was then the small amount of carbonaceous ore identified in the reserves. The focus of the research was on developing a process which incorporated the autoclave technology already utilized at Goldstrike. Over the next two years, Barrick pursued the development of an ammonium thiosulfate leaching (ATS) process. During the period in which the ATS research was being conducted the amount of carbonaceous ore in Goldstrike's reserves increased substantially and continued growth was projected. By 1996, significant advancement was made on the development of the ATS process. The work culminated in a series of integrated pilot plant runs incorporating autoclaving, ATS leaching, resin in leach, stripping and cementation. Several questions about the process chemistry remained unanswered, preventing commercial development. Barrick was committed to producing gold from the carbonaceous ore reserves by 2000. A due diligence review of carbonaceous ore processing options was initiated during the second half of 1996. Processes considered in addition to ATS were fine grinding/autoclaving, as practiced then by Santa Fe, and whole ore roasting as practiced by Independence Mining and Newmont. The objective by year-end was to recommend the most robust and economical process for Goldstrike's carbonaceous resources. In the fall of 1996, a detailed review of roasting as a processing alternative for Goldstrike was initiated. Throughout the ATS development period, whole ore roasting was used as the benchmark. All the ATS metallurgical and financial results were compared to roasting bench top test results. It was clear this data was too imprecise for use in due diligence study, a more definitive recovery value was needed to complete the carbonaceous ore review. The primary goal of the roasting review was to conduct pilot plant roast tests to gain a more thorough understanding of Goldstrike's carbonaceous ore's response to roasting and its effects on gold recovery. Using the test facility at Hazen Research, four pilot plant campaigns were conducted to determine optimum roast conditions and further define metallurgical design parameters. Conventional two-stage fluid bed technology based on Freeport­McMoRan's roasting patent was the specific process basis for testing. The ore's response to roasting exceeded expectations. In January 1997, a preliminary economic evaluation comparing ATS and roasting was presented, and the outcome was approval to proceed with a roasting prefeasibility study. In July 1997, approval for Goldstrike's Roaster facility was received and basic engineering started immediately thereafter. Detailed engineering _began in January 1998 and plant construction commenced in October 1998,t, Goldstrike's Roaster facility is designed to treat 12,000 tpd of a refractory gold ore, which contains both pyrite and organic carbon. Circuits in the facility include primary and secondary crushing, dry grinding, roasting, gas handling, neutralization, thickening and standard CIL. Gold desorbtion and recovery is carried out at Goldstrike's existing refinery. Plant start-up of the first dry grinding and roasting train is scheduled for March 2000, with the second train coming online in May 2000.

Jan 1, 1999

By R. J. Lutton

The U. S. Army Corps of Engineers is seeking empirical slope data from mining companies and other organizations to help establish guides for engineering Judgment in crater excavation for canals and other civil works. Slopes from about 100 open pits and other excavations range in heights to greater than 1000 ft. Factors known or expected to affect stability (and optimum slope inclination) are: geological structural orientation, geological structural ordering, method and technique of blasting, design life of slope, groundwater conditions, depth of excavation, climate, and height. These and other more subtle factors appear to combine and produce an overall effect brought out best on a family of empirical curves relating slope height and inclination.

Jan 1, 1968

By Richard B. Muter

In determining the layout or combination of unit operations to be utilized in a modem preparation plant, several factors must be taken into account. Among these are the washability data, size consist data, the particular market or markets for the coal, the mining method used, the degree to which the coal must be prepared, expected fluctuations in raw coal and markets, and the overall economics of the process. In addition, there are the health and safety aspects of coal utilization and preparation. Chapter 1 of this book discusses the characteristics of coal and coal markets, while Chapter 2 deals with the design of preparation plants. Once the unit operations for a particular plant have been decided upon, these arrangement may be depicted by using a flowsheet. A coal preparation plant flowsheet is a two-dimensional graphical representation of the sequence of operations, the arrangement of machinery, and the flow of materials for a particular coal cleaning operation. The flowsheet is usually qualitative in nature, becoming more quantitative as material balances, water balances, numbers and sizes of various pieces of equipment, etc. are added. The usual convention in preparing a flowsheet is to show the feed flowing from left to right, starting at the top left and working down as in an all-gravity process. Various symbols are used for each unit operation as depicted on a flowsheet, and Fig. 14-37 is a compilation of the commonly accepted international standard symbols for each unit operation. Fig. 14-38 through Fig. 14-40 are flowsheets of various coal cleaning processes as published in the January 1976 issue of Coal Age. Each process has its own unique features which, among others, depend upon the coal being cleaned, the coal market, and the mining operation. Fig. 14-38, for example, is a flow diagram for a jig plant preparing steam coal from two strip mines located a few miles apart. In addition to the jig washer, cyclones are used to treat the finer size coal. Fig. 14-39 is a flowsheet of a heavy media plant using a heavy media washer for + %-in. (+6.3-mm) coal, froth flotation for -28 Tyler mesh (-0.6 mm) material, and dewatering phase units (dwp) for Y, in. x 28 Tyler mesh (6.3 x 0.6-mm) cleaning of steam coal. In addition, thermal drying, centrifuge drying, and the use of vacuum disk filters and thickeners for dewatering are depicted. Fig. 14-40 is a flowsheet of a plant producing metallurgical coal. In addition to the heavy media and froth flotation circuits, a tabling circuit is also employed. These flowsheets are intended to give the reader an example of how the various unit operations for coal cleaning may be linked together. Figs. 14-41 and 14-42 illustrate the conversion of block diagrams into an IS0 prescribed set of symbols.

Jan 1, 1991

By R. M. Rowe, A. K. Bhasin, D. Malhotra

Introduction Most primary molybdenite producers use a selective flotation process in which molybdenite is floated from the ore while other sulfide and nonsulfide gangue minerals are depressed in the same step. The process was developed at the Climax mill. Reagents used in the rougher flotation stage include vapor oil (collector), syntex (surfactant), pine oil (frother), and occasionally sodium cyanide and Nokes reagent (depressant). Rougher concentrate is upgraded by cleaner flotation to produce market-grade molybdenite concentrates. Reagents used in the cleaner flotation stage are Dowfroth 250, vapor oil, sodium cyanide, and Nokes reagent. The development of the flotation reagent scheme at Climax and the role of the reagents have been well described by Born et al. (1976) and Malhotra et al. (1976, 1977a, 1977b, 1977c, 1980). The hydrocarbon collector, vapor oil, accounts for approximately 50% of the total molybdenite flotation reagent cost. Because vapor oil sources are limited, and the cost of vapor oil has increased significantly over the last decade, several studies have been done to evaluate alternate oil-based collectors and/or blends of collectors that would produce similar metallurgical results at a reduced cost, or increase the overall molybdenite recovery at the same cost (Smit and Bhasin, 1983; Hahn, 1969; Smith and Bhappu, 1971). The approach taken in the present study was to evaluate alternate nonoil-based collectors and collector systems that are less expensive than vapor oil. A series of potential nonoil-based collector classes were identified and evaluated in the laboratory against the current collector system. The metallurgical performance of these collector classes was related to their chemical structures. The results of this study are discussed. Collector classes A survey of sulfide mineral collectors was performed with the objective of identifying and selecting potential collectors for molybdenite flotation. The available reagents were categorized into 10 general classes. Table 1 summarizes these collector classes, their chemical formulas, the manufacturers, and selected commercial collectors in each class that were evaluated in the present study. Experimental procedure A Climax ore sample, assaying 0.3% MoS2, 2.2% FeS2, 0.007% Cu, 0.003% Pb, and 0.03 oz per ton Ag, was used for this study. Standard laboratory rougher flotation test procedure involved grinding a 2-kg ore charge in a rod mill at 60% solids. Reagents were added to the rod mill including a collector, syntex (0.005 kg/t), pine oil (0.03 kg/t), lime (to adjust pH to 8), and sodium silicate (0.15 kg/t). The ground pulp was transferred to a 1000-g cell, and flotation was performed at 35% solids and 1800 rpm using a Denver D-1 flotation machine. Concentrate was collected for a flotation time of six minutes. The general approach used in the present study was to substitute the nonoil-based collectors at two to three different dosage levels (0.01 to 0.15 kg/t) for vapor oil in the bench-scale, open-circuit rougher flotation tests

Jan 1, 1987

By Gordon M. Pugh, David G. Rasmussen

INTRODUCTION This method is a variation of cut-and-fill mining where either the wall rock or the vein is too unconsolidated to permit safe mining by conventional cut-and-fill methods. Basic development consists of driving a 2.4 x 2.7-m (8 x 9-ft) haulage heading laterally in the footwall side of the vein. Crosscuts are driven over to the vein at 91-m (300-ft) intervals. Then the vein, at each inter¬section, is mined out to a distance of about 9 m (30 ft ) above the track level. After the installation of an ore chute, scrams or intermediate drifts are driven in both directions along the vein. Mining then starts imme¬diately below the level bounding the upper limit of the stope. A cut varying between 3 and 4.2 m (10 and 14 ft) in depth and mined for a distance of 45.7 m (150 ft )along the strike is taken from the orepass in each direction (Fig. 1). In this mined-out void, the floor of the cut is equipped with 203 x 203-mm (8 x 8-in.) caps hitched into the wall with steel saddle hitches installed on 1.5-m (5-ft) centers. Double wood stringers, 152.4 x 152.4 mm (6 x 6 in.), are then installed on 1.2-m (4-ft) centers longitudinally down the length of the stope. Reinforc¬ing wire mesh is also placed, overlying each mat of timber. Directly above the stringers, stulls are installed from hanging wall to footwall to hold the timber in place during the sand-filling operation. Then a cement¬sand mixture in a ratio of about 1:10 weight is poured to a depth of about 2.4 m (8 ft). The entire cycle is then repeated down to the scram drift. Another variation of timbering is illustrated in Fig. 2. There is a vein width of approximately 5.5 m (18 ft) with the same unconsolidated ground conditions. The primary difference between handling this situation and the previously described undercut-and-fill method is that standard timbered sets are installed in each excavated stoping void rather than stulls. Once again the basic method is to work down the ore block from an upper timbered drift to a lower timbered drift. Cuts are taken from a timbered raise with a chute on the stope side. Each piece of ground excavated is essentially two sets high, 5.5 m (18 ft), by two sets wide, 5.5 m (18 ft), by the length of the cut along the strike of the vein. The timbered sets are 2.4 x 2.4 x 2.4 m (8 x 8 x 8 ft). The net result is, therefore, two sets of timber on a top floor separated by doubled-up 76-mm (3-in.) lagging from

Jan 1, 1982

By Norman L. Weiss

The full importance of tailings disposal is yet to be realized by the mining industry, but our awareness of its present and future implications is growing faster, perhaps, than any single phase of ore processing. Few engineers can look very far into the future because of the complexity of the problems that may confront us if we project from the general indifference of past years through what we are already being expected to correct in existing operations, to confrontations with new statutes and an awakened public in any new plants hence- forth. The mistakes of the past have not been limited to the United States nor even to other countries of the Western Hemisphere. Indeed, all continents and subcontinents have suffered from myopia in releasing the tailings without retaining responsibility. However, the US as one of the world's great leaders in technology has a particularly unimpressive record. It may be safely generalized that the degree of control applied to the tailings of a milling operation has depended upon several factors more important than national boundaries. Thus in arid and semiarid climates no incentive was needed other than the scarcity of water to create a permanent and stable lodgment for mill tailings. On the other hand. where water has been plentiful. the temptation to let the tailings run into a river or lake or ocean (at least at certain times of the year) was often irresistible. So we find that modem tailings disposal in the southwest deserts of this country, with one or two notable exceptions where very serious breaks seem to occur at regular intervals, is satisfactory according to the standards of the 195QF and 1960s. while in various operations in Idaho, Michigan, western Colorado. Newfoundland, and elsewhere the record has been less praiseworthy. In the same way, cyanide plants which did not concern themselves about leakage, seepage, spillage, or wastage of tailings pulps with solutions containing toxic levels of free or combined cyanide soon heard a demand for better control. In consequence the industry has seen a growing use of cyanide regeneration of tailings or wash solutions, elimination of leakage, and careful structuring of tailing dams. The chemical and thermal qualities of tailing waters have occasionally been a spur to good tailings management. Some tailings disposal problems for example, the southeastern Florida phosphate clays and the Bayer red muds-have been given the intensive study they merited, but not always with much success.

Jan 1, 1985

By Gabriel de Almeida

INTRODUCTION The widespread use of desktop computers by an ever increasing number of people, both for personal and for business and government uses, has brought public attention to surprising stories about computer abuse. Before the advent of microcomputers in the information processing environment, hundreds of amazing misdeeds involving large computers had already been reported, most of them perpetrated by highly skilled professionals. The undreamed enlarging of microcomputer potential has steadily posed a major threat to complex mainframe computing systems, as joyful teenagers become familiar with the habit of hacking around someone else's large processing system, by means of makeshift phone communication networks, based on their intended homework for personal computers -- for the sheer fun of it. Now, the never ending capacity and speed improvement of commercially available micros has given rise to a brand new concern for society: the hazards of processing sensitive information in the powerful, but still unsafe microcomputer itself, whether or not linked to other micros or mainframe networks. This paper deals with some aspects of the problems and presents some practical hints as to enhance protection and minimize risks to sensitive and secretive information when processed on microcomputers. The physical considerations of computer security and pertinent safety precautions will not be discussed, because while essentially relevant to information protection, recommendations are well defined by processing resources suppliers and their importance is more widely recognized by users in general. Definitions and Classifications. The following definitions and classifications will be considered in this report: Information Assets: Any knowledge or information processing, storing or conveying device displayed in one's environment. It consists of two main categories: INFORMATION RESOURCES: End user's application data wherever recorded. PROCESSING RESOURCES: EDP skilled user's hardware, software, peripherals, magnetic media, communication devices, auxiliary equipment, supplies and related operational procedures. Information Protection: In a broad sense this is the set of necessary procedures to assure to the legitimate user the effective control of the operation and allow modifications of information assets, so that their physical or cognitive integrity be preserved or any unexpected loss minimized inspite of accidental occurrences or intentional actions. Classification Processes: Commonly two classification processes are used to define key terms in information protection: SENSITIVE CLASSIFICATION: Pre-defined standards for assessing the vulnerability to losses due to lack of proper processing continuity if information is destroyed, disclosed, secluded, or misused. SECRECY CLASSIFICATION: A spectrum of degrees as to the expectancy of holding exclusiveness of unique information whose destruction, disclosure, seclusion or misuse will cause a negative impact on the legitimate holder environment. Sensitive Information: Any knowledge whose destruction. disclosure. seclusion or misuse - - - implies losses to its legitimate holder. It may be classified as: VITAL INFORMATION: An essential knowledge whose lack of proper availability implies total loss or termination of p

Jan 1, 1987

With the rapidly growing use of hydraulics in mining equipment, maintenance personnel should be familiar with the various components in hydraulic systems. Hydraulic systems do wear out - the fluids they transport are hot and turbulent, the equipment they power often imposes tremendous pressure pulsations and bending stresses, and the working environment is harsh. Therefore, even though hydraulic hoses are made of remarkably trouble-free components, they do need to be replaced periodically. There must be coupling methods that allow hoses to be replaced without disturbing other components. Couplings must also provide a variety of leak-resistant connections between hoses and other components in the hydraulic circuitry. Threaded Connection and Seals Hydraulic coupling thread ends and sealing arrangements are standardized, with many types available. Their outward appearance varies, but coupling configurations are recognizable by examining threads and seals and comparing them to the examples provided here. Iron Pipe Thread There are two kinds of iron pipe threads normally used in mining equipment circuitry - National Pipe Tapered Thread for Fuels (NPTF) and National Pipe Straight Thread Mechanical Joint (NPSM). The NPTF seal is the engagement of the coupling threads, called thread interference. When tightened, the tapered thread of the male fitting binds into that tapered thread of the female fitting to form a relatively leakproof seal (Fig. 1). In the NPSM seal, there is a 30° angle seat machined into the end of the male NPTF fitting. This seat engages with a mating 30° angle cone on the inside of the female fitting. Female NPSM fittings have straight threads, as opposed to the tapered threads of the NPTF fittings. However, most NPTF solid male fittings also have a 30° angle seat enabling them to be used with NPSM female fittings (Fig. 2). JIC and SAE Fittings Joint Industry Conference (JIC) and Society of Automotive Engineers (SAE) seals are formed by joining two mating, conical metal surfaces. The coupling threads are used to bring and hold these surfaces together to form a leak-resistant seal. A JIC connection is a solid male threaded end, with a 37° machined male nose, mating with a 37° female flare seat. When connected, the mating surfaces are held together by the threads, but the threads do not form the seal. The female seat is created by flaring a tube end or machining the interior surface of a stem to 37°. A female JIC has a swivel nut, allowing the sealing surfaces to be joined together without twisting a hose or twisting the seats against each other (Fig. 3). JIC couplings are frequently used on low, medium, or high pressure hydraulic circuits on mining equipment and machinery. The SAE connection is similar in appearance and sealing characteristics to the JIC system, except the angle of the machined male nose and female flare seat is 45° (Fig. 4). "O" Ring Fittings Seals for "O" ring fittings are formed by compressing an "O" ring against an exposed machined surface on a mounting block or hydraulic component part. The "O" ring must be compatible with the type of hydraulic fluid used (Fig. 5). An "O" ring boss connection is made of a male straight thread

Jan 10, 1983

By D. W. Gentry

Introduction Until recently, there were many jobs for mineral engineering graduates. Traditionally, minerals-related career paths available to university graduates stem from rather standard offerings in the disciplines of mining, metallurgy, petroleum, geology, geophysical engineering, and mineral economics. Within each discipline, there exists many career opportunities. In fact, until fairly recently, the most difficult decision for most graduates was choosing among all the available alternatives. Unfortunately, this relative state of euphoria changed quickly and dramatically within the minerals sector. Within two or three years, graduates from minerals-related engineering disciplines found it exceedingly difficult - and then almost impossible - to secure employment in the minerals sector upon graduation. At the same time, there were dramatic reductions in production requirements and, ultimately, mine closings. This resulted in massive layoffs and often termination of professional personnel possessing significant and valuable industrial experience. Obviously, this worsened an already bad employment picture for those hoping to begin a career in minerals. Certainly, there is no universal agreement on what the future offers for the US minerals industry or the career opportunities associated with it. However, there are a number of considerations that deserve study by students, faculty, administrators, and industrial personnel before minerals-related career paths are chosen. Where Will the Jobs Be and How Many? Everyone is aware that the minerals industry is very cyclic. It is not surprising then that job opportunities for new graduates also fluctuate. Typically, there is a two-to-four year lag between industry's engineering manpower needs and the academic community's ability to produce this talent. Due to the response lag, there will necessarily be years when supply and demand do not match. Employment Projections It is extremely difficult to anticipate what the key career paths might be within the next few years. Considerable speculation remains with respect to whether activity in the US minerals sector over the short-, intermediate-, and long-term will improve, remain status quo, or further deteriorate. However, some information pertaining to the prospects for career opportunities in mining engineering was offered by Tingley and Ghose (ME, Sept. 1983, p. 1274) from a study performed by Fenvessy and Schwab. Results from this industry-sponsored survey suggest that the US will experience 700 more mining engineers than needed in 1985, 1300 in 1990, and 1800 in the year 2000. These conclusions were based on the assumptions that future graduate levels remain flat and demand increases 3.6% annually. Educators quickly argued that depressed job markets, coupled with university student mobility, would negate the assumption of flat mining graduate levels in the immediate future. Student Mobility Student mobility from one engineering discipline to another is high. This is perhaps best demonstrated by the tremendous growth in programs such as computer engineering and computer science at the expense of enrollments in the more traditional engineering programs. The ability and willingness of students to quickly change engineering disciplines in response to existing and perceived job market demands have created significant student, faculty, and resource dislocations within universities nationwide. This has resulted in problems for university faculty and administrators responsible for effective use of

Jan 2, 1985

By John D. Morgan

Introduction The US Bureau of Mines' (USBM) world reserve/consumption ratios (Table 1) indicate that, if the world is relatively peaceful in the next two decades, there should be ample world supplies of minerals to permit rising standards of living for increasing world population. But it must be remembered that most mineral reserve estimates are conservative and that normal mining practice is to develop a ton of ore reserve for every ton mined. It should be noted that "reserve," as used in this paper follows the definition given in US Geological Survey (USGS) Circular 831, 1980; "that part of the reserve base which could be economically extracted or produced at the time of the determination." In addition to accurately determining the geologic parameters of mineral deposits, a judgment as to whether that deposit is a "reserve" per se involves consideration of many other factors. These factors were recognized nearly a century ago by a well-known mining engineer and later President, Herbert Hoover. In "Principles of Mining," 1909, Hoover wrote: "Unfortunately for the mining engineer, not only has he to weigh the amount of risk inherent in calculations involved in the mine itself, but also that due to fluctuations in the value of metals. If the ore is shipped to custom works, he has to contemplate also variations in freights and smelting charges ...In a free market, the law of supply and demand governs the values of metals as it does that of all other commodities. So far, except for tariff walls and smelting rings, there is a free market in the metals under discussion. The demand for metals varies with the unequal fluctuations of the industrial tides. The sea of commercial activity is subject to heavy storms, and the mine valuer is compelled to serve as weather prophet on this ocean of trouble. High prices, which are the result of industrial booms, bring about overproduction, and the collapse of these begets a shrinkage of demand, wherein consequently the tide of price turns back." Current supplies and use There have been ample supplies of most mineral materials to permit several-fold increases of world production of common major mineral based minerals (steel, aluminum, copper, and cement) over the past three decades. Motor vehicle production is a major consumer of mineral materials. However, in the last decade, down-sizing to facilitate improved fuel efficiency and reduce harmful emissions has reduced the weight of the average US-made automobile 15%, to 1.5 t (3200 lbs). Also in the US, there are 92 million dwelling units, or on average, fewer than three persons per dwelling unit. Construction is another major consumer of materials in the industrialized developed countries. It will also be a major consumer of materials worldwide as less developed nations seek to improve their infrastructures by adding roads, bridges, railroads, airfields, ports, and housing. Fortunately, a large number of traditional common materials, many of mineral origin and also many of agricultural origin, are readily available for construction. Traditional construction materials such as steel, aluminum, copper, and cement, are being replaced in many applications by engineered plastic and ceramic

Jan 4, 1986

By Walter R. Jr. Hibbard, William A. Vogely

INTRODUCTION Volatile markets and pricing, increasing imports, constraining but effective laws related to the environment, health and safety and price controls lead to concerns which generated pious laws stating non-fuel policy and authorizing studies but resulting in ineffective implementation. Several commissions, reports by the Secretary of Interior and even the President have led to many recommendations but little or no action. No single comprehensive policy could solve problems which are diverse, commodity specific and not categorizable (Landsberg 1982, 1983). Thirteen laws administered by 27 agencies regulate or affect minerals and materials. Political instability created by communist regimes in Southern and Central Africa jeopardized sources of critical imported materials. This situation led to a Resource War mentality. It was feared that the U.S.S.R. was seeking to control this area and exclude the United States from resources (Vogely, 1980). The success of the Organization of Petroleum Exporting Countries with a petroleum cartel led to fears of an Organization of Minerals Exporting Countries which might create more cartels and/or make the existing ones more effective. Economic needs of developing countries required export to maintain employment and balance of payments have led to world surpluses, weak markets, low prices, and large loans from the World Bank which have under- mined U.S. industry (Landsberg, 1982a). Un- cooperative environmental laws, obsolete facilities and non-competitive costs have led to shipping U .S. ores to other countries for processing into ingot and bars which are imported back to the United States. Yet massive internal turmoil has interrupted supplies, and led to un- certain availability and higher prices. This situation could happen again. Included in this category of critical materials with uncertain sources are metals required in the manufacture of military aircraft, which has led to concern regarding the defense industry base (Morgan 1983). Remedies have been proposed which include: updated stock piles, material substitution, international cooperation and coordination, foreign policy aimed at resolving racial and national stresses in South and Central Africa, relaxing U.S. environmental and public land regulations and action under the Defense Production Act (Goth 1982). The President's report (1983) to Congress has stated a national materials policy which recognizes: that materials play a critical role in our economy, defense, and standard of living; that public lands contain a vast untapped mineral wealth; that the role of government is to identify mineral issues and act on them; and that there is a need for long term high potential pay off research (Bureau of Mines 1983). There is a serious question as to whether or not a comprehensive national mining, minerals, and materials policy is feasible let alone necessary. One solution is to abandon the attempt at comprehensiveness and to target specific is- sues with realistic policies (Comptroller General 1979). In the following sections, the major studies of the 1970s will be reviewed, major issues yet to be faced will be identified, the principles involved in these resolutions will be reviewed,

Jan 1, 1985

By Robert A. Jankowski, George E. Niewiadomski

INTRODUCTION The utilization of longwall mining technology in the United States has steadily increased since the first longwall plow system was installed in 1952. At the errs of FY 1992, some 76 coal mines were employing longwall mining systems for coal extraction, and approximately 78 shearer and 3 plow faces are operating nationwide at any given time. Although the number of operating longwalls has remained relatively constant over the last five years, longwall production levels have increased significantly during this period. During the same timeframe, the number of continuous miner sections has decreased by 13 pct., from approximately 1438 in FY 1988 to less than 1250 in FY 1992. According to Mine Safety and Health Administration (MSHA) data, the average production of longwall sections increased from approximately 2400 tons per shift (tps) in FY 1988 to more than 3100 tps FY 1992. In fact, the average production has more than tripled since 1978, when it was only 850 tps. Approximately 25 pct. of operating longwalls are capable of producing in excess of 4000 tps. Longwall production currently accounts for nearly 36 percent of U.S. underground coal production, compared to 4 pct. in 1978. These improvements are attributed to improved longwall equipment and increased availability, larger longwall panels and automation. While longwalls are highly productive and offer other advantages, operations employing this method of mining continue to experience dust compliance problems more frequently than other mining system. Although dust levels have remained relatively unchanged over the past five years, averaging 1.6 mg/m3 and 1.9 mg/m3 based on results of operator and inspector sampling, respectively, during FY 1992, approximately 25 pct. of the operating longwalls were in noncompliance during any given bimonthly sampling cycle. Although modest gains in longwall dust control technology have been made, these have been overshadowed by significant increases in production rates. As more coal is mined, more dust is generated (Figure 1). Therefore, the increase in longwall productivity has meant that far more dust is being produced which must be controlled. [ ] In view of the current compliance record, any efforts to further increase longwall output, as has been forecasted, must be accompanied by: (1) the reduction of dust levels at existing operations through the proper installation and maintenance of suitable engineering dust controls; and (2) the advancement of dust control technology for today's and future longwalls that will enable all face personnel o work in an environment that is free of excessive levels of respirable coal mine dust. MSHA'S RESPIRABLE DUST CONTROL PROGRAM Since 1972, federal regulations have required each coal mine operator to continuously maintain the average concentration of respirable dust in the mine atmosphere during each shift in the active workings at or below 2.0 mg/m3 through the application of environmental dust control methods. The regulations provide for further reduction in the dust standard whenever the

Jan 1, 1993

By Dale R. Ralston, Roy E. Williams, Gerry V. Winter, George L. Bloomsburg

Aquifer. A formation, group of formations, or part of a formation that contains sufficient satu rated permeable material to yield significant quan tities of water to wells and springs. Artesian. Synonymous with confined; see ground water, confined. Capillary fringe. The zone immediately above the water table in which all or some of the interstices are filled with water that is under less than atmospheric pressure and that is continuous with the water below the water table. Conceptual model. A conceptualization of a field hydrogeologic framework that facilitates the development of analytical field testing procedures. The results of the test(s) may force changes in the initial conceptual model. Conductivity, hydraulic. Replaces the term "field coefficient of permeability." The volume of water at the existing kinematic viscosity that will move in unit time under a unit hydraulic gradient through a unit area measured at right angles to the direction of flow, if the porous medium is isotropic and the fluid homogeneous. Confining bed. A body of "impermeable" material stratigraphically adjacent to one or more aquifers; its hydraulic conductivity may range from nearly zero to some value distinctly lower than that of the aquifer. Flow, steady. Any point where the magnitude and direction of the specific discharge are constant in time. Flow, uniform. At every point the specific discharge has the same magnitude and direction. Flow, unsteady. At any point the magnitude or direction of the specific discharge changes with time. Fluid potential. The mechanical energy per unit mass of a fluid at any given point in space and time with respect to an arbitrary state and datum; the fluid potential is proportional to the head. Ground water, confined. Ground water under pressure significantly greater than atmospheric; its upper limit is the bottom of a bed of distinctly lower hydraulic conductivity than that of the material in which the confined water occurs. Ground water, perched. Unconfined ground water separated from an underlying body of ground water by an unsaturated zone. Ground water, unconfined. Water in an aquifer that has a water table. Head, static. Height above a standard datum of the surface of a column of water (or other liquid) that can be supported by the static pressure at a given point. Homogeneity. Hydrogeologic properties are identical everywhere. Hydraulic gradient. Change in static head per unit of distance in a given direction. Hydrostratigraphic unit. A body of material having considerable lateral extent and comprising a geologic framework for a reasonably distinct hydrogeologic system. Isotropy. Condition in which all significant properties are independent of direction. Porosity. Property of containing interstices or voids; may be expressed quantitatively as the ratio of the volume of its interstices to its total volume. Porosity, effective. Interconnected pore space available for fluid transmission; expressed as a percentage of the total volume occupied by the interconnecting interstices. Potentiometric surface. A surface that represents the static head along a particular specified surface or stratum. Specific retention. Ratio of the volume of water that the rock or soil, after being saturated, will retain against the pull of gravity to the volume of the rock or soil. Specific yield. Ratio of the volume of water that the rock or soil, after being saturated, will yield by gravity to the volume of the rock or soil. Storage, specific. The volume of water released from or taken into storage per unit volume of the porous medium per unit change in head.

Jan 1, 1986

By Graham J. Morgan

The following material is excerpted from a presentation Mr. Morgan gave recently to representatives of the financial community. Introduction 1982 was a period of challenge for United States Gypsum Company because of reduced market opportunity. Housing starts for the first 10 months averaged a seasonally adjusted annual rate of 1 million units, 9% below the comparable 1981 period when housing starts were the lowest in 35 years. Industry gypsum board shipments declined 9% from the already low levels of the same period in 1981. US Gypsum met the challenge with stringent cost reduction programs and aggressive action in the marketplace. In late 1981, anticipating market deterioration, the company's management adopted strategies to focus on two shortterm objectives: • Adjust operations to perform profitably in view of limited opportunities through more efficient operations and asset management. • Continue to strengthen U.S.G.'s resources and ability to take advantage of important market opportunities as the economy improves through selective expansion of production capacity in key growth markets. Concentration on these two objectives resulted in a nine month performance in 1982 that, while certainly not satisfactory by company standards, compared very favorably with that of principal competitors in terms of net earnings, margin on sales, and return on average stockholders' equity. To counteract limited market opportunities, U.S.G. focused on productivity improvement, cost reduction, expense control, and maximization of market penetration. Energy Use Improving performance encompassed all segments of operations. For example, efficient use of energy was a significant factor despite lower operating rates at most plants. Overall, in the third quarter of 1982 versus 1972, the company used 27% less energy per unit of production, a savings of $15 million in that quarter alone. These continuing improvements helped to partially offset constantly rising energy costs. A number of operations achieved superior results in the first nine months of the year compared with the same period in 1981. For example, gypsum board plants in Jacksonville, FL, and Sweetwater, TX, recorded 8% and 7% reductions, respectively, in energy use per unit of production. Paper mills in Oakfield, NY, Galena Park, TX, and Kansas City, MO, each reduced energy use more than 12%, while the Greenville, MS, ceiling products facility achieved a 16%o reduction. Safety Safety is another important element that received increased attention. U.S.G.'s safety performance over the past five years has consistently improved. In 1981 it was five times better than that of the gypsum industry; nearly 10 times better than all industry as measured by the National Safety Council; and almost 20 times better than all US manufacturing as recorded by the Bureau of Labor Statistics. In addition to human concerns, this excellent record results in significant dollar savings that directly affect company results. In 1981, U.S.G.'s pre-tax savings in claims, premiums, and related expenses were about $20 million compared to the industries in which it competes. For the first half of 1982 performance improved further, with a cumulative lost workday incidence rate per 200,000 man-hours worked of only 0.27, an all-time record. Expense Control Careful control of inventories and receivables also received special attention. As of Sept. 30, 1982, inventories were 29%, or $44 million, below the level of Sept. 30,

Jan 2, 1983

By Adrian J. Mathias

For many years excavations were made in rock exclusively by conventional blasting methods, and without concern for damage to the rock surfaces which remained after the excavation was completed. Recently, however, there is an increasing awareness for the importance of making rock excavations with as little damage as possible to the remaining rock surfaces; consequently, several revolutionary new precision blasting techniques have been developed during the past few years. These techniques, variously known as cushion, smooth- wall, perimeter, pre-shear, and pre-split blasting, basically involve the creation of a fracture plane in the rock between a series of blasted holes. The variations in each of these techniques are largely due to the differences in hole diameters, hole spacings, methods of charging, and sequence of blasting used to achieve certain specific results. The development of these precision blasting techniques was initiated by Canadian Industries Limited in 1953 at the time the Sir Adam Beck No. 2 Hydro-electric Project was under construction by the Hydro-Electric Power Commission of Ontario. Since then, these techniques have been somewhat advanced, and they have been applied with varying degrees of success to a number of projects. These projects include railroad and high- way cuts, dam spillway channel excavations, canal excavations, tunnel driving, shaft sinking, and other underground applications.

Jan 1, 1965

By Z. T. Mathe, M. A. Vera, M. C. Harris

This contribution presents a methodology how to quantify froth zone recovery in a continuously operated laboratory mechanical flotation cell. The methodology consists of relating the overall flotation rate constant to the froth depth of the flotation cell. As a result, a froth zone recovery factor (Rf) can be extracted. This froth performance parameter has been studied as a function of the flotation cell operating variables. By understanding the effect of these operating variables on Rf, an integrated methodology for modelling froth zone performance in batch and continuously operated laboratory flotation cells has been proposed. The Rf modelling is based on a semi-empirical approach which considers a number of parameters to be used. Some of these parameters may have physical significance, i. e. they may be easily and physically measured. The modelling approach consists of taking into account the interaction between the pulp and froth zones. This interaction allows froth zone recovery (Rf) to be predicted. The whole modelling exercise process lies on auxiliaries relationships which indicate the dependence of the parameters with the operating conditions of the flotation cell. This contribution is part of a larger project that deals with the modelling and optimisation of flotation plants (Project P9L, 2000).

Jan 1, 2001

By Catherine C. Kilgore

The Bureau of Mines investigated the availability of fluorspar from 35 domestic and 50 foreign, mines and deposits in 13 countries. Only 6 domestic properties are considered to be economic reserves, as 29 domestic deposits were found to have an average total cost of production that was uneconomical at a breakeven (0 pct) DCFROR. The 50 foreign properties evaluated were selected to represent at least 85 pct of the known demonstrated fluorspar resources located in market economy countries and China. All evaluated foreign operations were found to be economic to marginally economic in January 1984 dollars. World demonstrated ore reserves of 344 million metric tons (mt) containing 123 million mt of CaF2 were evaluated for the 56 operations. Average total costs needed to cover all costs over the life of each operation were determined for all recoverable fluorspar products. Comparisons of mining, beneficiation, and transportation costs per mt of fluorspar concentrate illustrate advantages between countries. Of the three largest producing countries, China, with its high-grade, low-cost operations had the lowest weighted average total cost of production ($38/mt concentrate). Mexico was next at $54/mt concentrate, and South Africa needed an average of $90/mt of concentrate to cover all costs of production for its low grade deposits.

Jan 1, 1985

By L. A. Bakhvalov

According to the practice of mining management in the system of industrial complexes, the Kazakhstan gold mines are part of the mine processing industrial concerns providing ore-mining and ore-dressing. The cycle technology of winning operations used at the mining of vein deposits in the mines of the industrial concern is mainly provided by the systems of scrapping, scipping and electric locomotion. At present the information and computer system, elaborated on the basis of the Maikain underground mine is intended for creation of the system of automatic operation for the industrial complex mines. The information and computer system includes: - parametres characterising the accepted technology of works; - the main parametres characterising the technical devices of operation and control ; - information about the material, technical and personnel resources available at the mine; - mining and geological conditions of the deposit; - the facilities of the subsidiary units, of the mine; - the direct parametres and technico-economical indices in which the mine efficacy and activity is estimated. The suggested structure of the automatic operation system can be sensibly realized with the application of the microprocessor on the first level, the personal computer IBM PC/XT or PC/AT on the second level. For the complete realization of the project each mine will need 4-5 computers (as PC/XT), one IBM PC/AT and each mine complex - one super IBM for creation of the distributed information bank and its including in the integral world communication system.

Jan 1, 1992

By Alok Garg, Rajeev Kumar Dayal

The Himalayan ranges have complex geological formation induced with locked up tectonic stresses and squeezing ground conditions. High overburden, steep slopes, perennial snow, and forest cover restricts accurate prediction of geological features, resulting in surprises during excavation. The tunnel planning under high altitude, extreme climatic, and unfavorable approachability conditions requires elaborate detailing. The construction technique and working faces for excavation are influenced by site accessibility/high overburden conditions, restricting the provision of access tunnel or shaft. The paper discusses site constraints influencing construction method and working faces for 8.9 km long highway tunnel at elevation 3,000 m under 1,900 mover burden through quartz-mica-schist formation.

Jan 1, 2001