Search Documents

By J. M. Carter, Rodney H. Sergent, L. E. Kun, J. T. Pressly

Underground mine service water in South Africa is used for dust suppression and cooling the environment as well as the pneumatic rock drills. Although the chilled water is not intended for potable use, it is often used as drinking water by mining personnel. Furthermore, droplets sprayed are liable to be inhaled. The water is recirculated on a continuous basis and is a potential source of infection by intestinal microorganisms or water-borne diseases such as cholera or typhoid. In order to protect the health of the underground workforce it is customary to disinfect the chilled service water, The bacteriological quality of the water is monitored by enumerating total aerobic bacteria (TAB), total coliforms (C C) and Escherichia coli (E Coli). E coli is an indicator of human faeca_l __ - -- contamination, The bacteriological standard specified by the Anglo American Corporation for mine service water is less than 3000 TA B per 100ml, less than 2 CC per ml and the total absence of E Coli. There are several disinfecting agents available for use. Among these are UV irradiation, ozone, chlorine dioxide and compounds that produce hypobromous and hypochlorous acids. Historically, the methods of treatment have been chlorine based and include the use of gaseous chlorine (surface installations only), calcium hypochlorite granules or tablets, chlorinated cyanurate tablets, sodium hypochlorite solutions and hypochlorite produced by electrolysis.

Jan 1, 1991

By Peijian Zhang, Yansheng Liu, Yuusaku Tominaga

The directions for ventilation control are often given in linguistic styles such as "if the airflow rate measured is small, a high value of rotation on a local fan should be chosen." In order to control the underground climate using a computer instead of a human being, both the reliability of data values measured underground and the application of human recognition of data values are required. The efficiency of data transmission is dependent on a method of checking a signal which is changed by mixing noises resulting from cases of electrical and mechanical damage to cables. In the study, fuzzy reasoning is adopted to choose a checking method for underground conditions from a normally operating state to an emergency. Fuzzy reasoning is applied to control airflow rate under the linguistic control rules given. It is shown that an effective series of linguistic control rules derived by fuzzy-sets theory is available in ventilation control when used in conjunction with an air velocity sensor, a computer and a local fan with thyristor control. Moreover, a system to make an optimum series of linguistic control rules for ventilation control is introduced.

Jan 1, 1987

By Henry T. Miller

INTRODUCTION The basic purpose of this paper is to suggest procedures and practices to insure that no employee working in a uranium milling operation receives exposure to radioactive, toxic, or other materials or agents that might produce a permanent, deleterious effect upon his physical health and well-being. This program is also designed to insure that each employee can carry out his assigned duties without risk to his health or to that of his fellow workers. The assumptions underlying this program are by necessity, conservative, with emphasis being placed upon prevention rather than correction or reaction to an undesirable situation. The limits specified-either as Threshold Limit Values (TLVs), Maximum Permissible Concentrations (MPCs), or Radiation Protection Guides (RPGs)--represent both standards of best practice and those of law and regulation. The total program is envisioned as a balanced combination of occupational hygiene and radiation monitoring. This includes surveying, air sampling, personnel dosimetry, bioassay, medical surveillance, epidemiology, and training--all backed by a thoroughly tested and evaluated set of emergency procedures. The program, as presented, is keyed to the results of monitoring, surveying, air sampling, medical surveillance, and epidemiology--it being obvious that no problem can result when no hazard can be identified. The lack of an identified hazard, however, does not negate the need for such a program and prudence suggests the need for routine surveillance programs in the best-designed facility. [The Model Mill] The model mill used in this paper is that presented by the U. S. Environmental Protection Agency in its study of the uranium fuel cycle1. The model mill processes 600,000 metric tons of ore per year into 1,140 metric tons of U308 as yellowcake per year using an acid leach process. Other characteristics of the mill such as location, tailings dam design, number of light water reactors supported, and geographical location are not pertinent to this paper. The usual remote western location of these facilities produce some difficulties in delivering the required occupational medical services and is not within the scope of this paper. The operating lifetime of most mills is commonly estimated as from 12 to 15 years in actual practice; however, the U. S. Environmental Protection Agency estimated a 20-year lifetime for its model. The principal steps in the acid leach process include :2 (a) Ore is blended and crushed to pass through a 2.5 cm (one inch) screen. The crushed ore is then wet ground in a rod or ball mill and is transferred as a slurry to leaching tanks. (b) The ore is contacted with sulfuric acid solution and an oxidizing reagent to leach uranium from the ore. The product liquor is pumped to the solvent-extraction circuit while the washed residues (tailings) are sent to the tailings pond or pile. (c) Solvent extraction is used to purify and concentrate the uranium. (d) The uranium is precipitated with ammonia and transferred as a slurry. (e) Thickening and centrifuging are used to separate the uranium concentrate from residual liquids. (f) The concentrate is calcined and pulverized. (g) The concentrate or yellowcake is packaged in 208 liter drums for shipment. This process is illustrated in Figure 1.3

Jan 1, 1981

By Michael C. Stanley

The set of discoveries for a mining district or camp is a reflection of the exploration history. In the western Abitibi greenstone belt of Ontario, future exploration can be guided by a study of statistical trends of known gold deposits. In this area simple trends indicate a strong decrease in the contained quantity of gold discovered through time. Much of this decrease is attributed not to falling mining grades but to smaller tonnages of ore. A plot of the largest discovery in each ten year time period suggests that deposit discoverability is following a size-biased sampling model. Cumulative ounces of discovered gold indicate that an asymptotic value has been reached where exploration is not expected to add significantly to known reserves. This is substantiated by a downward trend in the exploration success ratio of the number of new deposits discovered versus the number of new mineral prospects. The set of discovered deposits reflects a non-random sampling process where size- biased modeling suggests that the largest deposits will be discovered early in the exploration effort. It is the exceptionally large deposit contributing to the observed size-biased distribution. Although this pattern is observed for the western Abitibi the model is complicated by recent, large reserve additions that are attributed to the original discovery. There is present in this area a subtle learning process in exploration leading up to the largest discovery. For comparison a learning model was estimated using cumulative size of discovery per unit of time. This model yielded results consistent with the statistical trends and is thought to be a superior forecast of future discoveries in this region.

Jan 1, 1992

By Paul L. Bearden

The accumulation, handling, and utilization of sludges formed from wet process phosphoric acid is one of the major problems in the industry. The purpose of this paper is to explain some of the considerations and techniques that can be employed to provide some measure of control over the problem. An acid made from a Central Florida phosphate rock is used to illustrate the effects of one process design approach used to provide one type of control. Other approaches or techniques are discussed on a general basis. In every case, the discussion is purposely limited to conventional dihydrate processing in which phosphoric acid is produced from the filter at a strength of approximately 30% P205 and is subsequently concentrated to higher strengths such as 44 and 54% P205.

Jan 1, 1966

By T. H. Phillips

The Mission Mine is an open-pit copper mine located 18 miles south of Tucson, Arizona in the eastern foothills of the Sierrita Mountains. Mining is done on 40 foot benches using P & H 2100 shovels and 170-ton Terex trucks. Drilling is accomplished With two (2) Bucyrus-Erie 45R?s, one (1) Bucyrus-Erie 60R and two (2) Ingersoll Rand T-5?s. For secondary drilling. a Joy VCR-ISO truck mounted drill is used. The mine is currently operating 3 shifts/day, 7 days/week at 59,100 tons per day, with the mill receiving 28,500 tons per day. The management of the drilling and blasting program requires extensive record keeping in all phases of the operation. This is essential in order to evaluate different products and procedures.

Jan 1, 1988

By Frank Palkovits

All technologies move through a cycle from infancy to maturity. Thickened tailings have moved into the young adulthood phase of its development. Many mining companies like the idea of reducing their water-taking and water disposal issues. This limits the risks associated with traditional surface water-covered tailings facilities and the reduced dilution possible through underground disposal of thickened or paste tailings. Just as home theater systems advertised as ?plug and play? are rarely quite that straightforward, implementing and improving a thickened-tailings system has its challenges. However, the technology has also developed in recent years so it is more accessible. Some success factors have emerged because of the new technologies. Is thickened tailings the right solution? The first step in success with thickened tailings should be whether it is, in fact, the right solution for a particular mine. And, if so, what type of thickening is best. The answer depends on several factors, including: ? Grain size: The grain size that is optimal for maximizing mill recovery is some-times not suitable for thickening. Other mineralogical factors, such as mica content, may also influence whether the tailings are suitable. ? Water issues: Available water does not always have the purity necessary for the process. Another issue to consider is that if water is in short supply, as is increasingly often the case, thickening may be a way to reduce the need to both take and dispose of water.

Jan 1, 2008

By Shigeru Sarata

Working places in underground mines are formed by digging. The main feature of underground working places is that they are surrounded by rock. Digging through rock, which is main operation of mining, generates great reacting force. In many cases, supports are required to maintain a roof. Working places change their location with progress of mining operation. Therefore, for automate the work in such environment, a locomotive mechanism which can endure great reacting force, can support effectively the roof and floor, and has high moving performance in rough environment, might be required. In narrow underground environment which is surrounded by rock, it is possible to generate great fixing force by means of a jack which is set between the roof and floor or both side wall it is usual to apply a jack as anchor post for fixing machinery or reacting force. Self advancing supports widely used in long wall faces in coal mines could be said an example of locomotive mechanism with propping up fixing method. However it is difficult to say that ordinary self advancing supports have enough adaptability for various condition of the roof and floor. New locomotive method for underground working place 'Swing Phase Locomotion' is proposed. It is achieved by mechanism based on frame type support and synchronous control of jacks. Furthermore, to achieved high adaptability to various conditions of the roof and floor, another walking mechanism has been developed. The mechanism employs propping up jack as its legs.

Jan 1, 1989

By Bruno Mattle, Max John

For tunnels with low overburden, the shotcrete lining is the main element of ground support, which is why shotcrete behavior is of prime importance. Following its application, shotcrete not only gains strength and stiffness with time but—if loaded at an early stage—it is also subject to creep which in turn leads to stress relaxation. For two-dimensional FE calculations, a computational modulus of elasticity of shotcrete is to be used. Based on parameter studies it was found that the modulus of elasticity of shotcrete depends on both shotcrete mix and ground behavior. While the Young’s Modulus used for young shotcrete may range from 1,000 to 7,000 MPa, the Young’s Modulus used for hardened shotcrete is best represented by a value of 15,000 MPa.

Jan 1, 2003

By G. Barbery

A review is given of the present applications of random sets and integral geometry in fragmentation and liberation models of ores and minerals. Although attempts have been made in the past to apply such mathematical techniques to the comminution of solids, it is shown that it would not result in major progress. In liberation modeling, it is demonstrated that the approach can lead to fruitful results. Following a recent paper by Davy (1984), a model of liberation prediction is developed that can be calibrated for ore texture and breakage using image analyzers. The model is demonstrated for the case of a Poisson polyhedra ore texture and monodisperse fragment size. The model enables prediction of the complete composite particle distribution and thus is valuable for integration of ore breakage models with minerals separation models.

Jan 1, 1988

By L. Vandamme, J. H. Curran

A fully three-dimensional hydraulic fracture propagation model, based on the Displacement Discontinuity Technique, is briefly described. Using this model, it is shown that the geometry of a propagating fracture is dependent on several factors, among which the fluid pressure distribution within the fracture plays an important role. The containment of hydraulic fractures is found to be dependent on stress and toughness barriers in the formation. Containment is also observed to be more effective with a decrease of the viscosity, pressure or flow rate of the injected fluid. The three-dimensional layout of the fracture is shown to have a definite influence on the width and pressure distributions within the fracture. The examples considered indicate the need for fully three-dimensional models, as complements to the commonly used two-dimensional and pseudo-three-dimensional models.

Jan 1, 1986

By Gary S. Brierley, John W. Critchfield

This paper is a case history of a subsurface exploration program conducted for a system of sewer tunnels in upstate New York. The focus of the discussion is a non-technical outline of how the exploration process was organized to efficiently produce a large body of geological and geotechnical data. A brief description of the project and geological setting is provided, the scope of the exploration program is summarized, the logistics of collecting, processing and reporting subsurface data is outlined, and recommendations for management of explorations applicable to any rock tunnel are provided.

Jan 1, 1983

By D. E. Ranta, Jean-Michel Rendu

It is generally recognized that geologic input is required for the results of a geostatistical study to be meaningful. However the link between geology and geostatistics is often complex and not well understood. A geostatistical evaluation can be divided into four phases: Background discussions, computation, reserve reporting and reserve audit. Each one of these phases is described, as well as the role the geologist should play during their completion. This role will vary depending on the geology of the deposit being studied, the geostatistical method chosen and the computer hardware and software being used. The geologist's acceptance of the results is needed if the geostatistical model is to have any credibility. The most significant obstacle to a meaningful study comes from the difficulties geologists and geostatisticians often encounter when attempting to communicate with each other.

Jan 1, 1992

By Ralph J. Holmes

INTRODUCTION Although sampling techniques used by the mineral industry continue to improve, sampling is still an area which is often neglected. Frequently, sampling and sample preparation requirements are left to personnel who do not fully appreciate the significance and importance of sampling. Consequently, plant evaluations are often based on seriously biased samples, leading to mass balance problems and incorrect assessments of plant performance. The basic rule for correct sampling is that each particle of ore or concentrate must have an equal probability of being collected and becoming part of the final sample for analysis. If this is not the case, bias is easily introduced and the sample is not representative. For example, when ore is travelling on a conveyor belt, the lumps may come to the surface. Consequently, a grab sample taken from the top layers only will contain a greater proportion of lumps, i.e., the sample is biased. There seems little point in making major investments in precise analytical equipment, if the sample provided to the analytical laboratory is not representative in the first place. This paper describes the sources of plant sampling errors, reviews the methods of estimating their variance, presents some worked examples, and provides some practical advice for reducing sampling errors and their variance. SAMPLING BASICS It is generally accepted that the discharge point of an ore or concentrate stream is the most suitable sampling location. The stream can be intersected at regular intervals, and representative samples, referred to as increments, can be obtained by taking a complete cross-section of the ore stream. On the other hand, sampling devices that take part of the stream on an intermittent or continuous basis, e.g., a bleed from a pipe, may introduce serious bias, and should be avoided at all cost. Increments may be taken at completely random times or tonnages during the sampling operation, in which case it is called "random sampling". However, as shown below, random sampling results in the largest sampling variance, so it is preferable to divide the ore or concentrate stream up into strata of equal time or mass and take one increment from each stratum. This operation is called stratified sampling and may be either systematic sampling, in which increments are taken at the same point in each stratum, or stratified random sampling in which the increments are taken at random within each stratum. Systematic sampling results in the smallest sampling variance, provided periodic variations in quality or quantity are not present which may coincide with, or approximate to, any multiples of the proposed sampling interval. In such cases, it is strongly recommended that stratified random sampling within fixed time or mass intervals be carried out.

Jan 1, 1991

By K. Hanumantha Rao, K. S. E. Forssberg

The separation of feldspars from quartz has been the subject of numerous studies since 1930 and the flotation process so far proved to be the most suitable method. In the conventional process, feldspars are separated from quartz using a cationic collector and hydrofluoric acid as an activator of feldspars. There is no general agreement on the mechanism of fluoride activation of feldspar surfaces and the role of fluoride ions is briefly discussed. The use of HF is no longer acceptable due to environmental and health problems, and a few new reagents schemes have been reported. The available evidence shows that the success of these new reagent schemes is very limited. A new reagent scheme which is environmentally safe and cost effective for the separation of feldspars from quartz is yet to be resolved.

Jan 1, 1994

By Ishwar G. Mulani

In conveyor design, the first step is capacity and the second step is belt width and speed. The third step is decision on 'ff," where distinction arises between DIN/ISO and CEMA for calculating resistances. Then again, both the methods are virtually similar. This topic helps in understanding Dm design style and its comparison to CEMA. This topic is from the book Engineering Science and Application Design for Belt Conveyor wherein the issue has been analysed in detail. It presents a workable calculation model to calculate the value off in design office, based on conveyor parameters. CEMA uses Kx, Ky and 0.01 5 instead off. Thus, f is a sum effect of Kx, Ky and 0.015. Hence, knowledge on f is also applicable to Kx and Ky. This helps to understand their relationship.

Jan 1, 2004

By Anthony Edey

It is a generally accepted and widely discussed fact that the world in general, and the United States in particular, face a shortage of energy at the present time which will become worse in the future. There is, however, no sign of a similar concensus as to the actions which would prevent or overcome this expected shortage. An immense variety of solutions has, however, been put forward, ranging from the purely political to the outer fringes of sophisticated technology. One resource which surprisingly is often only cursorily included in this discussion is the immense known petroleum reserve lying within the United States. When this subject is discussed, indeed, it is usually in the context of the improvements in production or new discovery rate that could be expected to result from possible politico-economic actions that would raise the real price obtained for domestic crude. This interest in the potential for improved domestic production is undoubtedly justified, but very little attention is normally drawn to the fact that even under the most favorable policy framework the majority of the oil that has been, or will be, discovered will remain in the ground due to the inherent limitations of production through surface wells.

Jan 1, 1979

By Juan H. Rojas

The Chuquicamata mining and metallurgical complex is the main division of CODELCO-CHILE. Its comparative advantage in the world of primary copper producers had deteriorated severely and, consequently, its top management launched an extensive modernization plan. This paper shows how Chuquicamata recovered its position as a low-cost copper producer and is now well positioned to face the end of this century, as far as competitiveness is concerned. It also shows the company's vision for the )(XI century. Given the volume of its ore reserves, one possibility is expanding the sulfide production line capacity, while in the case of the oxide production line, ore reserves are limited so that there is a need to maximize the effectiveness of both organization and technology use. A final consideration has to do with the balance of supply and demand. Most observers of the copper market agree that supply is growing faster than demand. On the other hand, copper is facing severe environmental problems, especially in the piping business, plus the usual threat of substitution. Nevertheless, copper producers are making very weak efforts to defend the market and increase copper consumption through the promotion of new uses of the metal. This issue is crucial and must be considered if copper producers want to maintain a profitable market.

Jan 1, 1998

By Wen L. Chen

The steam coal quality is less stringent than metallurgical coal quality. The steam coal is prepared either by cleaning full size range of raw coal or cleaning coarse coal only, leaving the fine coal raw. The latter scheme is more cost competitive. It is particularly applicable to U.S. eastern soft coal where low ash coal is concentrated in fine sizes. For raw coal size separation, a recently developed Rotating Probability Screen, developed by the British Coal Board, may be advantageously used for easy change of raw coal separating size and to avoid screen deck plugging when handling wet and clayey raw coals.

Jan 1, 1983

By D. G. Kotlyar

Silver is an economically important component of many complex, massive sulfide ores. Current beneficiation for these ores is almost entirely by flotation. Silver recovery often is low, but little is known about the flotation behavior of the silver-bearing minerals. Floatability studies were conducted using silver-bearing tetrahedrite and lead-zinc ore. The effects of xanthate collector concentration, conditioning time, potentiostatic control of the mineral potential, and pH on mineral floatability were evaluated. The floatability of the silver-bearing minerals was shown to depend on collector concentration and mineral potential. The effect of controlling mineral potential during the flotation process is discussed.

Jan 1, 1994