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By D Yan, D Connelly

Beneficiation of magnetite is an integral part of the future of iron ore processing. Historically, the focus of Western Australian producers has been on exporting direct shipping ore (DSO) namely haematite. The future for new DSO resources is limited so companies are changing their emphasis into processing the very large, undeveloped magnetite ores in Western Australia (WA), using beneficiation to produce shippable magnetite concentrates. These magnetite resources require higher cost processing techniques such as fine grinding and beneficiation to produce saleable concentrates. This distinct difference, from the DSO ores, has led to the development of a number of new technologies. This paper reviews: the different techniques used for magnetite beneficiation and provides some case studies in the WA industry; the use of mineral liberation analysis (MLA) to describe the nature, grain size, occurrence and associations of the mineralisation;the consideration of coarse cobbing as a critical upgrading; the application of high pressure grinding rolls (HPGR) to save energy; how the field of magnetic separation has resulted in new machines with higher field strength (SLon Separators); ultra fine grinding requirements of magnetite concentrates; andthe application of reverse flotation to reduce silica in the concentrates.

Jan 1, 2009

By Jorge Cárdenas, Luis Huaroc, Máximo Cari, Nestor Delgado

In Peru, after four years of pandemic, some mining companies have chosen to install integrated operating centers in central offices where through network technology and video surveillance it allows them to carry out their activities remotely, this has become a disruptive strategy to promote a safer and smarter mining industry. Our fundamental value is to improve the quality of life, safety and well being of our collaborators, that is why we have created the remote blasting engineering control center " Core" that allows us to humanize mining. Core is an integration of experience, security, technology, quality of life and artificial intelligence; it has media technology connected directly to the mining operation, specialist engineers and technical assistants in team they seek to create optimal proposals of drilling and blasting designs remotely that generate added value to customers. In the planning process the team suggests drilling meshes, in the loading process there are optimized, digitized designs and efficiency in the factory trucks finally in the safety process allows us to identify inadequate pipes within the blasting project, deviation of procedures, remote inspections, identify operating conditions to prevent future risks that may arise in the blasting process. The remote communication systems allow you to monitor mining operations remotely to identify and alert any operational or security deviation that was not identified by the personnel present in the operation, as well as to store images in case investigations are required. The results obtained have allowed us to reduce the exposure of personnel to any risk of the mining operation, to optimize times in the activities of our engineers who are in the mining operations since there is the permanent support of centralized specialists to face every challenge that arises in the operation, for the engineers who are in the offices of Core can be very close to the family and do not lose it, and for our customers it is to meet their needs with engineers specialists in the drilling and blasting process, as well as in safety to be able to proactively cope with any deviation that arises.

Jan 21, 2025

By Dominic Ammon, Mark Rothbauer, Paul Landers P. E.

Across the Potomac River from the location of the DFI47 Annual Conference (October 2022), in Alexandria, VA, two large permanent anchored walls with a decorative shotcrete face were recently constructed for the North Hill project, a new multi-family and townhome development. The project was executed with a design-build approach for the Fairfax County Redevelopment and Housing Authority with review by the Fairfax County Geotechnical Review Board. The project was constructed in highly variable Potomac group sediments that include high plasticity clay/silt terrace deposits overlying coarser grained materials. The soils were over consolidated and exhibited potential for slickensides from relief of horizontal stresses from past erosion. The wall system was designed to include deep soldier piles and permanent long strand anchors considering past slope instability in the area. As the construction progressed, problematic soil conditions and water issues required modifications to drilling methods. The two permanent walls spanned 800 and 1,000 feet long with a maximum height reaching 40 feet.

Oct 1, 2022

By M. Gonçalves Peixoto da Silva, E. Rodrigo Carvalho Souza Siqueira

Mining in narrow veins is commonly applied for precious metals, generally carried out to extract gold in underground mines, due to the ore occurrence on narrow veins, mainly up to 2-meter large. The current work presents the implementation of the methodology in a zinc mine located in the state of Minas Gerais in Brazil. The Vazante Mine through the years has always carried out mining on stopes with a thickness larger than 3,5 meters, but nowadays due to the need to reduce the waste planned in its blocks, as well as increase the useful life of mine, mining has been implemented in blocks that are less than two meters. Given this, the challenge is to be able to carry out blasts that does not exceed the operational dilution required and does not generate an impact on recovery, as working with extremely heterogeneous stopes. This study seeks to correlate the main characteristics of stopes and its relationship with the results obtained in the execution of those blasts. Also, it proposes an analysis between the empirical data, and existing theoretical references, creating ideal mining parameters, such as minimum thickness, maximum height, and optimum timing in the blast plan. One of the main challenges for carrying out this mining method is the control of operational dilution, generally pointed out as the biggest difficulty for companies that adopt this methodology, due to the thickness of those stopes, any displacement can make it unfeasible, thus the technical level on carrying out the drilling and loading of these blocks must be impeccable, an understanding of the structural geology of the site is also essential for dilution control. The outcome will be a set of ideal parameters and mining methodology to guarantee the success in execution of these blocks, thus bringing a financial benefit to the company.

Jan 21, 2025

By Hollis R. G, Tuppurainen J. M I

Improved control of non-ferrous sintering operations requires the on-line measurement of sinter quality. No on-line measure of sinter quality is currently available, however, previous work has shown that the raw mix chemistry and peak sintering temperature determine the mineral phases formed and hence the resulting Blast Furnace behaviour. Control of these factors should therefore lead to improved quality control. In this paper, the development of a simplified heat and mass balance model of the Sinter Plant at Mt Isa is described. The model used available plant data to calculate raw mix composition and a simplified reaction scheme to predict sinter composition. The extent of reaction is inferred from the flue gas analyses. Off-line testing of a dynamic version demonstrated that actual plant performance could be predicted with reasonable accuracy.

Jan 1, 1989

By J. L. Bowlby

TWO years ago, at the annual meeting of this Society, the writer presented a paper dealing with various aspects of the water problems existing in the Cape Breton coal-mining area. Much of that paper was of a theoretical nature, in that an attempt was made to get at the fundamental principles underlying the problems, in order to establish a sort of background against which future results could be laid. Up to that time, only Central power plant in Glace Bay had been under observation, and, since the work had been in progress only a year, it was recognized that there were strong possibilities that certain variations in procedure might have to be introduced as w; became better acquainted with our problem. We were by no means certain that we had covered all the facts of the case. The present paper will therefore be of the nature of a progress report, rather than a formal contribution to the Society. Subjects of a theoretical or academic nature will be avoided as far as possible, attention being confined chiefly to the results obtained during the past two years. In looking over the work with low-pressure boilers, there are certain general conclusions that can apparently be safely drawn. Wherever possible, proper operating conditions will be expressed in terms of appropriate units. Absence of corrosion in boilers where the alkalinity has been maintained within the pH range 11.0 to 11.4 forces one to the conclusion that these are safe working limits. Previous experience had shown that corrosion would occur if the alkalinity were much reduced. Higher alkalinities are un-necessary, more expensive, and are said to introduce the possibility of pitting. We made no attempt to obtain quantitative data in respect to pitting. It is said to occur at pH 12.0. Consequently, conditions of alkalinity were main-tained well below this figure. In the above paragraph, the pH range 11.0 to 11.4 applies to boiler waters which have received the lime and soda treatment. The general practice, when this treatment is employed, is to use 1.0 lb. lime to 7.0 lb. washing soda. At Central power plant, soda-ash is at present substituted for washing soda, the equivalent proportions being kept the same. But not all the plants are on the lime and soda treatment. At Waterford Lake, a 1: 1 mixture of soda-ash and trisodium phosphate is satisfactorily employed, and in Sydney Mines and at No. 3 power plant in Sydney, good results are being obtained at a somewhat greater cost with a commercial phosphate treatment.

Jan 1, 1936

By Gulsen Tozsin, Ekrem Kalkan, Taskin Oztas, Elif Agirman Akturk, Ercument Koc, Ali Ihsan Arol

Marble wastes are generated by quarries (marble quarry waste-MQW) and processing plants (marble cutting waste-MCW). The large amount of marble wastes is becoming serious problem for industry and environment because of discarded into rivers and lagoons, without any treatment. Marble wastes can cause environmental problem and economic loss if the waste is not used. However, this type of wastes has a good potential to be used as an amendment for the neutralization of acid soils. In this study, MQW and MCW were applied to an acid soil at different rates and their effectiveness on neutralization was evaluated by a laboratory incubation test. The results showed that soil pH increased from 4.71 to 6.36 and 6.84 by applications of MCW and MQW, respectively. It was suggested that MQW and MCW could be used as soil amendments for the neutralization of acid soils, and thus the negative impact of marble wastes on the environment could be reduced.

Jan 1, 2014

By P. Chris Pistorius, Johannes Sono, Rossouw Sono, J. J. Kobus

Different coal properties are important in SL/RN (coal-based rotary kiln) direct reduction of iron ore, and in electrical smelting of prereduced iron ore. These differences were highlighted when a plant which processes titaniferous magnetite had to change to different coal types after decades of operation. Laboratory simulation was used to evaluate two candidate coals, which were similar in volatile content and rank, but differed in reactive maceral content. Direct reduction was evaluated by isothermal experiments using a packed bed of ore and coal, measuring the off-gas composition to determine reaction rates and departure from equilibrium. These indicated reduction to be under mixed control, and quite sensitive to temperature (confirming that the coal reactivity is of importance). An aspect of electrical smelting was assessed by determining dissolution rates of the coal in molten iron at 1550°C. Dissolution rates did correlate with differences in coal structure, as determined by X-ray diffraction, with the more ordered ("more crystalline") coal dissolving faster. The conclusion is that the coal which is more reactive during direct reduction is less reactive during dissolution. However, it is concluded that controlling the temperature during direct reduction offers a feasible method to reconcile the two process steps.

Jan 1, 2003

By Aitor Elorriaga Fernandez de Arroyabe

The purpose of Sinter plants is to heat iron ore fines along with fluxes and coke fines or coal, to produce a semi-molten mass that solidifies into porous pieces of sinter with the needed size and strength. Fluxes used in the sintering process need to have an appropriate size distribution and TI to avoid generation of fines, which could reduce the productivity of the Sinter. Besides, a homogeneous chemical composition and high absorption characteristics are necessary to control the basicity and to combine the flux with P, S, Si, etc, respectively. PASEK Dunite is an ultramaphic rock exploited in the north of Spain with a basic chemical classification, being olivine and serpentine its principal minerals. It is a very homogeneous and hard stone and its main characteristics are: high hot and cold resistance to mechanical stresses, softening and melting points of a flux not of a refractory material. In addition, due to its mechanical and chemical properties, less fines are generated in the sintering process and during the handling and transportation to the blast furnace, improving the productivity of these processes. In this way, the use of PASEK Dunite allows increasing the homogeneity structure of sinter, reducing the percentage of return fines and improving the Sinter productivity.

Oct 30, 2017

By Bruce Mathema, Steven Huynh, Terry Cheng, Gerry Gomez

"The use of PM40N, a specialty precious metals promoter in conjunction with a standard Xanthate based collector was extensively investigated in the flotation of a complex, silver-bearing, lead-zinc ore containing naturally occurring graphitic gangue. The ore, considered difficult to treat with conventional reagents, was tested at plant scale to determine the impact of the promoter on silver recovery, lead grade and also on the amount of zinc misplaced to the final lead concentrate.Initial laboratory-scale rougher flotation testing implied significant improvements in the recovery of silver and lead with a marginal amount of zinc displaced. Subsequent mini pilot flotation tests further revealed that a gain in selectivity and recovery could be achieved by adjusting PM40N promoter dosage and incorporating a cleaner flotation step, further improving rejection of sphalerite. Plant trials resulted in an improvement of 3% in Silver recovery coupled with a 2% increase in recovered lead whilst maintaining lead grade in the lead circuit.To date, the use of PM40N as a promoter has enabled the processing operation to significantly increase its plant economics. The partial replacement of the standard Xanthate based collector has also reduced the overall quantity of Xanthate required in the standard circuit by approximately 10% - which is a positive impact on the environment. It is envisaged that further optimization of plant parameters will favor stable operation and continue to boost revenues generated by subsequent improvements in silver metallurgy."

Jan 1, 2014

By Pavel A. Torres, Darwin Torres, Sandro Huaman

Given the limited efficiency of blast-induced ground vibrations prediction empirical models, due to the complex geological system from a Peruvian mine. An artificial neural network was built in order to get better results. More accurate and precise predictions allowed the generation of blasting domains for future designs and decision making.

Feb 1, 2020

By Eugene V. Cilento, R. Clark Lantz, K. A. DiGregorio

"This laboratory bas developed a sensitive electro-optical method to quantify the initial rate (R) and total amount (MAX) of superoxide (02) produced by single pulmonary alveolar macrophages (PAM). The method uses a microscope-based TV system to visualize PAM in culture, and to video record the images during the time the cells produce 02. MAX and R are calculated from measurement of temporal changes in optical density in the images due to precipitated diformazan formed by the reaction of O2-, produced by each PAM, with nitroblue tetrazolium present in the culture medium. To date, values of Rand MAX, measured due to adherence of PAM to the dish, have been compared to values obtained when quartz, coal mine dust (CMD), and kaolin . were added to the medium (in vitro). Rand MAX have also been calculated for PAM lavaged from animals exposed to quartz and CMD in the WVU Inhalation Facility. Presently, experiments are being done using which will permit PAM to be restirnulated by different dusts to help establish a dose response relation~ p and a means to study the role of lung surfactant on modifying the acute toxicity of inbaled dusts. Ultimately, this methodology should provide useful insight into establishing the role of 02 in PAM dysfunction due to inhalation of dusts, and in lung diseases such as pneumoconioses. INTRODOCTIONPAM are free cells found in the lungs which protect the lungs by removing foreign debris and bacteria. This is accomplished, in part, by the process of phagocytosis, whereby foreign matter is internalized into vesicles known as primary phagosomes. Phagocytosis also involves the chemical breakdown of inhaled dusts and the killing of microbes. Detoxification is aided by the respiratory burst, which is a metabolic response of the cell to foreign substances, that results in the production of highly reactive oxidizing agents from the partial reduction of extracellular oxygen to superoxide (02) at the surface of the plasma membrane. Superoxide undergoes either spontaneous or enzyme catalyzed dismutation reactions to form hydrogen peroxide (H202) and subsequently hydroxyl radical (OH•) and singlet oxygen (02 t ). However, while these oxygen metabolites aid in the killing of microbes they also may destroy endogenous tissue. For example, 02 has been linked to the aging process and to many diseases including emphysema, diabetes, and cancer.'' Therefore, a better understanding of the production of 02 is extremely important since an abnonnally low production could result in damage by inhaled dusts and bacteria while an abnormally high production could result in direct damage to the lung tissue by the phagocytes. Inhalation of respirable sized mineral dusts, such as quartz (silica), coal mine dusts (CMD), and asbestos, results in various pulmonary disorders. PAM are thought to play an important role since evidence suggests that the first step in fibrogenesis is an interaction of dust particles with PAM. Generally, in vivo exposure of animals to mineral dusts results in increased respiratory burst activity, migratory patterns, phagocytic behavior, and secretory potential of PAM, and for this reason these have been implicated to be pivotal events in the pathogenesis of pulmonary diseases.1 In addition to stimulation of resident PAM, an influx of monocytes into the lung and/or production of new macrophages generally occurs in response to fibrogenic dust inhalation. Further, PAM may attract and stimulate fibroblasts, which normally synthesize proteins and collagen during rep~ of tissue, by secreting chemoattractants and enzymes. Thus, PAM may be involved in pulmonary disorders through failure or partial loss of their defensive capability, or indirectly, through release of other mediators."

Jan 1, 1990

By R. Clark Lantz, Charles Stanley, David E. Hinton

Morphometric examination of lung alterations following exposure to toxic and pathogenic substances is invaluable in detecting subtle changes which might otherwise be overlooked. Results, from evaluation of initial structural alterations, support and guide subsequent nonmorphological techniques and, when coupled appropriately, can lead to a better understanding of the pathogenesis of a disease. Morphometry is a technique which can be used to determine, quantitatively, the site, extent, development, and progression of a disease state. Determination of the extent of tissue and cellular involvement in the response to inhalation of silica has been performed in order to gain a better understanding of the development of fibrosis following inhalation of this toxicant. In addition, since silica has been postulated as one of the important pathogenic minerals in coal mine dust' it is important to understand the lung tissue response to silica prior to evaluating the effects of inhaled coal mine dusts. Male Syrian golden hamsters were placed in Hazelton 1000 inhalation chambers and were exposed to either filtered air (controls, n = 24) or filtered air plus 30 mg!m3 silica (Min-U-Si110,95%ofparticles < 5 um,n =24)for16hours per day, five days per week, for two weeks. Animals were returned to the animal quarters prior to subsequent tissue processing at 1, 4, and 12 weeks following exposure. This schedule was designed to allow time for the development of fibrosis. Lungs were fixed by intratracheal perfusion of ½ strength Karnovsky's fixative at a pressure of 20 cm H20 and tissues were taken for embedment and analysis at the light level. Determination of site, extent, and development of alterations was performed using a multitiered approach. Changes in large structures (airways, blood vessels) was determined prior to evaluation of changes at the septal tissue level. Data will be presented outlining the progression of changes. Results indicate the usefulness of morphometric analysis of lungs following inhalation of toxic substances in quantitatively defining the structural alterations.

Mar 1, 1989

By Christian Trassy, Pierre Proulx

"Inductive plasmas are now commonly used in material processing: spraying, powder synthesis, densification or spheroidization. An inductive discharge presents, in the coil region, recirculation eddies due to the Lorentz forces, resulting in an axial backflow. If the central jet is strong enough to ""pierce"" the recirculation this axial backflow disappears on the centerline, but the external layer of the injection flow is skimmed by the remaining eddy, and particulates are rejected to the discharge periphery. To avoid this disadvantage, it is common to introduce the injection pipe inside the discharge, so that its outlet is positioned after the recirculation eddy. The powders remain confined in the axial zone, to the expense of shortened residence time.In order to increase the efficiency of the particle trajectories, a double flow injector has been designed. It enables the particles to travel closer to the axis, while the outer schrouding gas is skimmed and passes through the electromagnetic eddies. This injector is made up of two concentric tubes. The powders are injected with the carrier gas in the inner tube. A schrouding gas is injected in the annular space between the inner and the outer tubes. The powder is confined to the vicinity of the axis, resulting in a more homogeneous thermal treatment.Tungsten powders have been spheroidized with and without this device. Using the double flow injection, the spheroidization yield has been increased from 70 % up to 95 %.The design of such an injection device has. been studied and improved using numerical modelling. Another useful tool, a visualisation technique described elsewhere, has been used for the experimental study, that drastically simplifies the comparison between experimental and theoretical results: injecting yttrium oxide into the discharge results in a colorful display of the 4000 K isothenn: the ""cold"" zone, below 4000, appearing as red, and the ""hot"" zone as blue. Furthermore, it is of great industrial interest since it is a very cheap and efficient way to obtain a picture of an important isotherm."

Jan 1, 1999

By Gupta R. C

Direct reduction of iron ore by solid reducing agents have been studied extensively and summarised by several authors (Otsuka and Kunii, 1969; Abraham and Ghosh, 1979; Frauhan, 1977; Rao, 1971; Kawasaki, Sanscainte and Walsh, 1962; Ghosh, 1970; Rao, 1979). While studying the reduction behaviour, it is generally agreed that the reduction occurs via gaseous intermediate, generated by carbon gasification reaction which involves mass transfer, heat transfer nucleation and growth, etc through a) reduction reaction occurring at solid reductant, and b) reduction reaction occurring at solid iron oxides, thus making the overall reduction process very complex in terms of clearly defining the reduction kinetics of the system. In addition to this, practical difficulties like correctness of reaction temperature, (Seaton, Foster and Velasco, 1983) difficulties in isothermal temperature studies of reduction, difficulties in monitoring the reduction process while using gaseous reductants and separation of reduction by volatile matter from overall reduction process make the reduction kinetics more complex (Misra).

Jan 1, 1999

By J E. Moffatt, N A. Spooner, T J. de Prinse, D J. Ottaway, E Klantsataya, L d. S Teixeira, B W. Smith, T B. Payten, G Tsiminis

Single wavelength fluorescence sensing has been used in the preconcentration of ores for many years in situations where it is typically specific to the mineral of interest. Examples of fluorescence sensing include the sorting of diamonds in diamond mines and the sorting of scheelite in tungsten ores. However, the number of minerals that show useful single wavelength fluorescence properties in the visible spectrum is relatively small, so the application of fluorescence sensing is currently limited to niche application in the minerals industry. Recent developments at the University of Adelaide have focussed upon extending fluorescence signal measurements into the infrared spectrum, as well as investigating multi-wavelength fluorescence known as up-conversion fluorescence. These techniques may not only significantly increase the number of minerals that exhibit fluorescence properties suitable for both identification and sensor-based sorting, but also provide mineral-specific signatures of higher quality than previously attainable. This paper details the research work carried out by the University of Adelaide and funded by CRC ORE to develop a mineral-specific fluorescence sensor. The sensor targets two fluorine bearing minerals, fluorite and fluorapatite, that are common in many base metal ores such as porphyry copper ores and silver/lead/zinc ores. Fluorine is a known penalty element in mineral products derived from these ores, so mining companies need to monitor and control the amount of fluorine in their final product to keep it below commercially agreed specifications. Currently there is no real time sensor capable of monitoring fluorine in the ore feed so monitoring and control is carried out using time-consuming standard sampling and off-line laboratory measurements. The development and application of a real time fluorine sensor will enable the mining companies to monitor and control fluorine levels in the plant, greatly reducing the time and cost associated with producing their mineral concentrates within the prescribed specifications.

Nov 10, 2020

By P. R. Taylor

Titanium carbide and titanium diboride powders have been successfully synthesized by direct treatment of ilmenite concentrates in a non-transferred arc thermal plasma reactor. Methane gas was used as the reducing agent and boron oxide was used as the boron source in these processes. Free energy minimization plots were used to predict the behavior of each system under different molar ratios and operating conditions. Products were characterized by XRD, SEM and chemical analytical techniques. The average size of the ceramic product is in the submicron range. Metallic iron apparently is finely deposited on the surface of the titanium carbide or titanium diboride particles. Minor impurities such as silica, manganese and zircon were converted to the carbide form.

Jan 1, 1995

By James A. Clum

The shift to lower grade iron ores, e.g., magnetic taconites, resulted in a shift towards agglomeration practices which could effectively deal with the fine particle sizes generated in the liberation and concentration processes. If the iron bearing particles are not extremely fine, e.g., -1/2 in + 100 mesh, sintering is an adequate means of agglomeration.(1) For the more dispersed ores which result in fine concentrates (more than 80%,-325 mesh), the fine particles must be agglomerated by mechanical means before final hardening, e.g., pelletizing.(1) In the pelletizing process, the essentially mechanical step of balling is extremely critical since the strength of the pre-fired pellet determines the firing conditions. The ability of the proper amount of moisture to hold together a ball of the very fine ore concentrate particles has long been recognized. It is a charac¬teristic of the reaction at the interface between the ionic solid of the ore concentrate and the polar water phase which overlays the solids. The strength in such moisture laden balls, the green strength, is a strong function of the water content (Figure 1) and thus deteriorates rapidly for either a small excess or a small deficiency of moisture. For purposes of commercial practice, the control of green ball handling properties by accurate control of ball moisture is too demanding. Moreover, as the ball is heated towards its hardening tempera¬ture, e.g., 1300&apos;C, there is a substantial drying reaction which would lead to such a low dry strength of the ball that it would not support its own weight much less the weight of other balls in a firing furnace.

Jan 1, 1976

By George S. Rice

"The emission of hydrocarbon gases from coal beds and contiguous strata causes many accidents in coal—mine workings, the number of fatalities so caused being second only to those due to falls of roof. Gases tend to increase in amount with depth of coal mining, hence the danger of explosion is increased with depth. The pressure of the gas in virgin—coal areas at a distance from mine workings likewise tends to increase with depth from the surface, probably due to corresponding increase in hydraulic head and possibly, when the gas is held in nonporous formations, to greater ground pressure. The rise in gas pressure with depth under usual conditions is shown in wells drilled from the surface and in some coal fields in drill holes into the face of workings; however, under normal conditions of coal formation gas does not issue into workings under high pressure because the coal and adjacent strata have many bedding and joint planes which allow the gas to escape freely at the face of the workings. The rare occurrence of instantaneous outbursts of gas, with violent effects referred to later, constitute the exception.Variations of volume and pressure of fire-damp or methane found in different coal beds by wells at a distance from mine workings, are analogous to variations in volume and pressure of natural gas found in different gas and oil sands, although in general the pressure tends to increase with the depth. Sometimes, however, in tight sands higher in the formation the pressure of gas therein is abnormally high, and on drilling the well deeper gas in the lower strata may be found at lower pressure."

Jun 1, 1934

1. Proposals were submitted to the Western Administrative Center of the US Bureau of Mines, Denver, Colorado on 30th December, 1974 and Contract No J 0255003 was awarded, the effective date being 8th May, 1975. Dames and Moore, Denver, are associated with PD-NCB Consultants in regard to environ-mental problems, surface mining practice and legislation in US. BACKGROUND TO THE STUDY 2. Under the threefold pressures of -increased domestic fossil fuel demand -increased value of domestic energy resources -increased demand for environmental protection and safety

Jan 1, 1976