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By D. G. Feuerbacher

Maximizing production of oil from sandstone petroleum reservoirs is aided by use of non-damaging drilling and workover/completion fluids. Various tests, such as X-ray diffraction, scanning electron microsccpy, petrographic microscopy, porosity and permeability are conducted on core samples. Several fluids are selected, on the basis of these results, for return permeability tests. A report is then written giving the results of all tests, potential reservoir problems, and recommended practices for exploiting the reservoir.

Jan 1, 1983

By G. Ferrara

To obtain a reliable comparison between conical and cylindrical separatory vessels used in dynamic dense medium separation systems, the following studies were made: (1) study of the swirling flow in conical and cylindrical vessels using laser-Doppler velocimetry (LDV); (2) study of the behaviour of suspensions of magnetite and ferrosilicon in water in both separators. It was found that: (a) the tangential velocity profiles differ in conical and cylindrical vessels: in a conical cyclone free vortex conditions affect the largest part of the vessel, while in a cylindrical vessel, the motion approaches that of a forced vortex, i.e. that of a centrifuge; (b) the conical vessel manifests higher centrifugal acceleration and very strong densifying; the density differential, and hence the density gradient inside the vessel is large; (c) the cylindrical vessel manifests lower centrifugal acceleration and low densifying, i.e. low density differentials, and hence, the density gradient inside the vessel is small; (c) due to greater densifying, the density cut-point in cyclones is higher than the operating medium density, while in cylindrical vessels the density cut-point is closer to the medium density. The results provide an interesting description of the differing behaviour of conical and cylindrical vessels and help explain the differences in performance between the two types of separators.

Jan 1, 1998

By Seanley C. Suboleski

This paper examines the likely productivity improvements that have resulted from the introduction of technological advances in underground coal mining during the decade from 1977 to 1987. Included in these advances are the changes in longwall mining; the introduction of larger, more reliable, more repairable continuous miners and shuttle cars; the introduction of remote control and flooded-bed scrubbers; supersections; and other improvements. Procedural improvements are also examined and quantified, the unexplained gains in productivity are attributed to??other factors", among them an increasing maturity of the work force, stabilization of the mining laws, increased labor-management co-operation, and economic urgency.

Jan 1, 1990

By Ernest B. Snyder

The word "line" has been used loosely for many forms of the common steel plant flux. For example, many people use the word "lime" for nigh calcium and dolomitic limestone, for high calcium and dolomitic quicklime (also called caustic lime, calcined lime; burnt lime, pulverized and pebble lime) and ;van for clinkered dolomite. Calcium hydroxide, also called slaked lime and hydrated lime, is called "lime" but is seldom used as a flux except when the quicklime air slakes in open boxes or bins. All of the above forms of "lime" are used in the steel plant. Calcium hydroxide is used for water treatment, acid neutralizing, and as a lubricant for wire drawing. All the other limes are used as fluxes in the sintering plant, blast furnace or steel producing furnaces. In the production of self-flux or super-flux sinter, high calcium and dolomitic limestone fines are used. Where quicklime fines are available, they may be added to the sinter mix also. The blast furnace uses both high calcium and/or dolomitic limestone. A few trials have been made using iron oxide stabilized dolomitic lime in an attempt to reduce coke consumption and to increase the production rate. The trials were very successful but would' not be economical, except in periods of coke shortages, with resulting extremely high coke cost and exceptionally high hot metal demand.

Jan 1, 1979

By S. K. Nicol

Flotation, water-washing cyclones (hydrocyclones) and spiral concentrators are the three process units most commonly utilised in fine coal preparation. The results of testwork conducted on these three units will be presented and their performance and separation characteristics examined in detail. In particular, the dependence of the separation characteristics of each unit on particle size and the constraint this places on product quality (ash and sulphur levels) will be discussed. This dependence will be shown to be a critical criterion in the selection of fine coal circuits.

Jan 1, 1986

By J. P. McKinney

Benchtop experiments were performed, in which an electric field was used to enhance separation of water from phosphatic clay suspensions from a central Florida mine. A constitutive relationship was established that relates the increase in solids content to operating time and the applied electric field. An upper limit to the degree of separation was found to be a function of electric field, and the time required to achieve this limiting value was also a function of electric field. The energy requirement for removal of water ranged from 1.25 to 175 Wh/kg water removed as a function of the electric field. A mathematical model was developed that provided good agreement to the experimental values and served to validate the constitutive relationship.

Jan 1, 2011

By Richard J. Fantel

The U.S. Bureau of Mines performed engineering and economic analyses on 130 domestic phosphate mines and deposits, all containing demonstrated resources, of which 73 are in the Southeastern states of Florida and North Carolina, to determine the domestic availability of phosphate rock. Of the total domestic resources studied (6.4 billion tons of recoverable rock) over 60 percent is found in these two Southeastern states. At an estimated cost of $30 per ton, in January 1981 dollars, approximately 1 billion tons of rock is potentially recoverable from Southeastern deposits, increasing to 3 billion tons at $45. In addition, there is nearly 6 billion tons of recoverable rock at the inferred level (some presently unmineable) in Florida and Georgia.

Jan 1, 1983

By J. Fuchs

This paper describes the mechanized narrow vein cut-and-fill approach used for the Deep Copper orebody at Falconbridge Limited's Strathcona Mine. Strategies for achieving high productivity while maintaining ground stability at depth and controlling dilution are discussed, including the use of mini-electrohydraulic drilling equipment, containerized truck haulage, consolidated rockfill placement techniques, and a miners' incentive system.

Jan 1, 1992

By D. W. Park

A vast majority of longwall operations in the United States use shield-type hydraulic supports to provide ground control along the longwall face. The three-dimensional finite-element technique combined with a progressive failure approach was utilized to simulate interaction between shields and surrounding strata and determine various loading conditions. In addition, a separate finite element model of the shield structure was made to study responses of each long wall shield to the different loading conditions. Shield responses under various loading conditions and the shield characteristics, such as shield stiffness, the ability of resisting horizontal forces, and the effect of shield height, were studied based on the results from finite-element analyses. The results can provide the basis of effective shield design and be used for evaluation of the shield performance. It is suggested to develop a technique incorporating the finite-element method to evaluate the real-time shield performance for the purpose of effective ground control.

Jan 1, 1992

By Richard L. Gordon, William A. Vogely

In this chapter, the principles that determine the procedures selected to transform minerals in the ground into usable commodities are re¬viewed.a I argue here that straightforward mod¬ification of the modern general economic theory of production suffices to meet the practical needs of a mineral economist. Therefore, the chapter is largely a review of the general economic theory of production to which is added discussion of the special prob¬lems of the exhaustibility of mineral resources and the economics of finding and developing economically recoverable minerals. In many cases, propositions applicable to all industries are reviewed because they are not treated ade¬quately in prior texts. In the discussion, use is frequently made of basic concepts of differential calculus widely used in economics. However, this is supple¬mented by simpler verbal and graphical treat¬ments, so that those either untrained in the calculus or, as is often the case, whose skills have grown rusty, can still follow the discus¬sion. Where the argument depends critically on the mathematics, this is noted and the justifi¬cation for including the material is provided. In addition, an appendix outlines the critical mathematics and reviews some of the numerous books published that provide the most readable available introduction to the subject. Further¬more, mineral industries examples are used to suggest the relevance of the theory. THE RELEVANCE OF THE ECONOMICS OF PRODUCTION Three basic steps are involved in establishing the relevance of economic analysis to mineral ¬industries decision making. First, the general theory of production must be defined, and its relationship to the simpler models of production stressed in economics textbooks must be noted. Second, the critical modification-considera¬tion of the problems of discovering and devel¬oping mineral deposits-must be developed. It turns out this too involves a special case of the general theory of production. Third, the concept of an economics of exhaustible resources must be explored sufficiently to suggest why its practical relevance is doubtful (or at least far smaller than the numerous writers on the subject seem to believe). The present approach is heavily influenced by post-1945 developments in economic anal¬ysis. Particularly since World War II, economic theory has drastically changed its scope. First, stress has increased greatly upon viewing the economy as a network of intertwined markets known technically as the general equilibrium system.b In this view, not only is the economy viewed as an integrated system, but critical con¬cepts are viewed somewhat differently than was previously fashionable. Specifically, in general equilibrium models, the concepts of supply and demand are rejected as central concepts in favor of a distinction be-

Jan 1, 1985

By-products are of greater importance in lead and zinc mining than in any of the other major base metals. While I think most mining people would accept that statement, you would probably get some widely varying estimates when attempting to quantify the value of by-products in lead and zinc mining. We are now able to do this with our lead-zinc mine cost model. This model was originally developed as a zinc mine cost model to help us forecast long-term zinc supply and price as part of a study we completed in late 1979 entitled "Zinc - The Next Decade". Before demonstrating the importance of by-product revenue to lead- zinc mines, let me first explain how the cost model was constructed. I will discuss the model as it was originally constructed - as a zinc mine cost model. It has subsequently been expanded to include lead only mines and now can Be run either as a zinc or a lead mine cost model.

Jan 1, 1980

Because the Environmental Protection Agency has identified methane as a greenhouse gas, the importance of de gasification through gob wells has become more critical. It has been observed that the degree of methane emission is closely related to the geomechanical characteristics of coal bearing strata, roof, floor, and surrounding coal seams. Monthly production data from 250 gob wells were collected from the Warrior Basin in Alabama, and many interesting correlations were observed between methane production with longwall face width, face advancement rate, number of gob wells in a panel, and geologic columns. Extensive finite element analyses were performed to estimate the characteristics of the emission zone in an attempt to corroborate these findings. This paper describes an investigation for developing correlations between the geomechanical behavior of the methane emission zone with methane production.

Jan 1, 1996

By Clarence O. Babcock

A simple robust rock bolt load gage was tested in the laboratory to define its characteristic behavior and to obtain a measure of its performance. The gage uses three vibrating wire sensors crimped 120 degrees apart into the outer surface of a hollow cylindrical steel tube. The resonant frequencies of the wires change as the gage is loaded. This change is read with a Creare meter developed for the Bureau on a previous contract to read borehole stress gage results. A statistical analysis of data obtained defines the variables influencing results. A U. S. patent (3,914,992) assigned by the author to the Department of the Interior was granted October 28, 1975.

Jan 1, 1976

By T. Yukimasa

Hachinohe smelter, a zinc-lead blast furnace complex with the annual capacity of zinc plus lead of 100,000 tons, had originally treated normal zinc and lead sulfide concentrates. However, it is currently handling a great variety of raw feeds ranging from complex sulfides to oxidic recycled materials in view of resource economy, most of which are unsuitable for zinc electrolysis. This paper reports on some significant efforts recently carried out on improving sintering operation, i.e., the increasing use of secondaries against harmful ingredients like halogens, and the substantial reduction in energy use as the results of various modifications and improvements.

Jan 1, 1982

By A. J. Lynch, M. J. Lees

Introduction The design of wet grinding circuits may vary considerably according to the duty which is to be performed. Grinding machines which are commonly used in these circuits are rod mills, ball mills, autoge¬nous mills, and pebble mills while size separation machines commonly used are vibrating and wedge-wire screens, hydrocyclones, and rake classifiers. In some circuits, such as those producing feed to cement kilns, all the ore entering the circuit is discharged in a single product stream. In others, such as those operating on magnetite-taconite ores, the feed entering the circuit leaves in two or more streams. Grinding circuits in flotation plants normally include sections in which either the concentrate or the tailings from the primary flotation circuit is reground and these additional sections should be regarded as an inte¬gral part of the grinding circuit. A typical circuit is shown in Fig. 18. Problems in achieving maximum efficiency may occur at three stages: 1) At the design stage when the optimum size reduction flow¬sheet must be selected with respect to the types, numbers, and sizes of processing units. 2) At the operating stage when the correct selection of values must be made for those variables which may be altered while the circuit is off-line but which are constant while the circuit is on-line, for instance the vortex finder diameter of the cyclones. 3) Under conditions of continuous operation when changes in the circuit feed or in the mechanical operation of the circuit may cause undesirable changes in the circuit product. The first two prob¬lems are concerned with optimization, that is, with making the best choice from many possibilities, and the last with control. Optimization Problems. The main purpose of a wet grinding circuit is to produce particles with a sizing distribution which will ensure optimum performance of the later chemical reaction or physical concentration circuits, because it is on the efficiency of these later circuits that the economics of the total mineral treatment process depend. The size distribution of the product from a grinding circuit may be affected by many variables, some concerned with the arrange¬ment and operation of the machines and some concerned with the ore characteristics, and it is important that these should be recognized in the design and operation of the circuit. For instance, in a simple ball mill-cyclone circuit the variables which affect the product size even for constant feed characteristics are shown in Fig. 19. In addition, the rate, size, hardness, and mineralogical composition of the feed will affect the performance of the circuit and the product size. When the circuit contains more than one mill, both the number of choices available and the complexity of the problem are increased consider¬ably. Consequently, one type of problem which is to be solved if an optimum product is to be obtained from an existing grinding circuit is that of circuit design, and this includes arrangement of processing units and selection of those operating conditions which cannot be altered when the circuit is operating, such as mill speed and cyclone inlet and outlet dimensions. The other major problem in optimization is encountered at the design stage when a choice must be made about the type, number, and size of processing units. For instance, for a typical high-capacity size reduction operation, should two circuits each containing one rod mill and two ball mills or three circuits each containing one rod mill and one ball mill be used? Alternatively, should ball mills only be used and if so, how many, what size, and what arrangement?

Jan 1, 1985

By Britta Schoesser, Zdenek Zizka, Markus Thewes

"The support pressure of a slurry shield corresponds to the in situ earth and groundwater pressure to ensure the stability of the tunnel face. The support fluid (bentonite suspension) penetrates from the excavation chamber into the pore space and transfers the support pressure to the granular structure of the soil within this zone. At the same time, the cutting tools rotate periodically with the cutting wheel and remove the penetrated soil up to a certain cutting depth at the face. Shortly after the tool passing, the penetration process starts again. Both, the support pressure and the soil excavation, act in the same direction at the tunnel face, but they are subject to different cyclic intervals. This relationship between the time needed for the transient penetration process and the interval of the cyclic passage of the cutting tools at a local point at the face is examined and the impact onto the global face stability is discussed. INTRODUCTION Slurry shields are usually deployed for excavations in soft ground. The main application range is in non-cohesive soils (DAUB Recommendations 2010). In non-cohesive granular soils, the tunnel face stability is one of the key design issues. The slurry shields make use of pressurized bentonite suspension (slurry) to support the unstable tunnel face. To support the tunnel face effectively, the slurry pressure has not only to counter the groundwater pressure, but also has to be transferred into an effective stress to support the soil grains. In general, the pressure transfer can be achieved in two ways: (1) with a thin flexible membrane or (2) a penetration zone. The membrane (1), called filter cake, creates a thin impermeable layer from bentonite particles directly on the tunnel face, and enables a transformation of excess slurry pressure into effective stress. In case of penetration zone formation (2), the excess slurry pressure is transferred onto the soil skeleton along the entire penetration depth by shear stresses between slurry and soil grains. These theories, presently applied to assess the pressure transfer on the grains within slurry shield tunnelling, are originating from diaphragm wall technology, e.g. Müller-Kirchenbauer (1977), Kilchert and Karstedt (1984). They assume that the support pressure transfer mechanism is built-up instantaneously on the whole tunnel face and is not damaged or influenced by the interaction with excavation tools. These assumptions are valid for conditions during the excavation of diaphragm wall trenches whose bottom is excavated and the walls of the trench are supported. At the tunnel face of a slurry shield, the support suspension acts on the same area as the soil excavation. Hence, the conditions on the tunnel face are transient (time dependent) due to the time period needed for the penetration process of the slurry and the periodical damage of the pressure transfer mechanism by excavation tools (Fig. 1a)."

Jan 1, 2016

By Henk L. C. Meuzelaar

Most of us are aware of the relationship between the golden-yellow resin spots on Upper Cretaceous Wasatch Plateau coals and fossil tree resins (?amber?). Nevertheless, confusion remains about the exact chemical composition and structure of commercial coal resin preparations as well as their observed heterogeneity. In order to arrive at a more detailed chemical description we need to distinguish between micropetrographic, organic geochemical and process technological definitions of coal resins, which may include substantial quantities of constituents unrelated to fossil tree resins. New information on composition and origin obtained by Curie-point pyrolysis/evaporation in combination with isobutane chemical ionization mass spectrometry, as presented in this paper, points to the presence of four more or less distinct resin components: (1) a sesquiterpenoid polymer; (2) sesqui-and triterpenoid monomers and dimers; (3) a suite of triterpenoid alcohols, ketones and acids; and (4) a series of increasingly aromatized hydrocarbons with naphthalene and picene type skeletons. Moreover, a strong similarity is found between the composition of recent Dammar resin and fossil Wasatch Plateau coal resins. Some of the technological implications of these findings and the consequent need for a more precise chemical definition and nomenclature are discussed.

Jan 1, 1990

By W. J. McDonough

Rapid growth and acceptance of engineered materials have changed the way we live. We have come to expect improved performance at less cost. At the same time, our awareness of societal and environmental issues created by these materials during and after their lifetime has been heightened. As a result, material lifecycle analysis is receiving considerable attention. Material lifecycle analysis evaluates the cost/effective tradeoffs at each stage of a material's life: feedstock, fabrication, performance, recycle, and disposal. The U.S. Bureau of Mines investigates a material's lifecycle using technical cost models augmented with decision and impact analyses. Results of these studies are useful in gaining a better understanding of current material selections and illustrating the multifaceted issues associated with engineered materials in today's society.

Jan 1, 1992

By J. M. Mutmansky

The usual method employed to determine the direction of flow in a connecting airway in advance is to conduct a survey between the two existing nodes being connected by means of the new airway. It is then assumed that airflow will take place from the node with higher pressure to the node with lower pressure. The purpose of this paper is to examine this direction-of-flow problem --using properties of the system characteristic curve for a two-terminal network --and specify some conditions that ensure that flow will take from the higher-pressure node to the lower-pressure node. It is concluded that the only requirement is that all characteristic curves of fans in the network should be strictly decreasing. Five numerical examples illustrate some important properties of the direction-of-flow problem.

Jan 1, 1999

By Richard A. Brown

The direct precipitation of uranium with hydrogen peroxide has been known since 1877. Commercial use of the process began in the 1960's. During 1967 the Bureau of Mines assisted the Climax Uranium Co., Grand Junction, Colorado in the development of a uranyl peroxide precipitation process to control a molybdenum impurity problem (1). Atlas Minerals, Moab, Utah has used hydrogen peroxide to control vanadium and sodium levels in their uranium concentrates since 1969 (2). Recently, the use of hydrogen peroxide by the uranium industry has grown, particularly since the increased demand for uranium has led to the processing of low grade ores. Impurities present in low grade ores can be concentrated with the uranium during milling and will substantially complicate the refining of uranium yellowcake concentrates. Consequently, commercial nuclear fuel processors have imposed stringent specifications and penalties to control these impurities. The ability to produce a pure uranium yellowcake can eliminate penalty or reprocessing costs. Hydrogen peroxide precipitation of uranium is specific and quantitative, producing a very high purity product.

Jan 1, 1980