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By Frank Marotta, Louis B. Lesem, Frank Greytok, John J. McKetta

Although one of the primary variables in the calculation of the flowing bottom-hole pressure in gas wells from surface measurements is the temperature at any point and its distribution in the flow-string, only few experimental data are available in the literature and little attention has been given to analysis of the problem. Virtually all of the recently published methods of calculating flowing bottom-hole pressures depend on the assumption that either the temperature is constant at some average value or that the variation is linear with depth. The purposes of this work are to analyze the problem theoretically and to verify the analysis by comparison with experimental data so that practical problems in the analysis of the behavior of gas wells can be solved with greater accuracy, reliability, and ease. MATHEMATICAL OUTLINE OF PROBLEM Assuming that: 1. The mass velocity and chemical composition of the gas stream are constant and in normal gas well operations, the change in linear velocity in the entire flow-string is trivial, 2. The product of the density and heat capacity of the gas is constant, 3. No horizontal temperature gradient exists in the gas stream, 4. Net flow of heat by conduction within the formation and in the gas stream in the vertical direction is trivial in magnitude and can be neglected, 5. The regional vertical geothermal gradient is constant, and 6. The temperature of the gas entering the borehole is constant, and equal to that of the reservoir, a set of two simultaneous, linear partial differential equations with appropriate boundary conditions was derived to describe the temperature distribution in the gas stream and the surrounding formation. These equations were solved by operational techniques for the distribution of temperature in the gas stream. The resulting integrals were evaluated numerically on an IBM 604 at the Machine Accounting Div. of the Railroad Commission of Texas. DERIVATION OF FUNCTIONS FOR THE DISTRIBUTION OF TEMPERATURE The physical system is a circular hole of radius a in an infinite medium with thermal conductivity K, density p8, and heat capacity c,. Under shut-in conditions the well is in thermal equilibrium with the surroundings and the increment in temperature is given by - ?T3/L x. Gas of density pg and heat capacity c.. flows upwardly through this hole in the direction of increasing x with a linear velocity W. Writing a heat balance on an element of gas ?x in thickness, convective heat transfer + conductive heat transfer + energy required to lift a unit mass of fluid = change in energy content. pa2W po Co To - pa2Wpo Co To x+xx - 2apK?x ?T8/?r r=a - Wpa2 po?x/778 = CoPopa2?x?To/?t... Dividing by (copopa2?x) and taking the limit as ?x tends to zero, -W (?To/?x + 1/778Co) + 2 K/a Po Co ?T3/?r r=u = ?To/?t

Jan 1, 1958

By P. B. Crawford, W. L. Huskey

A study has been made to determine the effects of random vertical fractures existing in a reservoir matrix on the effective matrix properties and producing characteristics of a well. The study indicated that short vertical fractures may distort the isopotentials by 1 percent in the vicinity of the fracture. A correlation was developed which showed the effect of fracture density on the producing capacity of a well. The correlation indicated that fracture shape had little effect on producing capacity, but that total fracture length was closely correlated with the producing capacity. Effective values of reservoir permeability were found to correlate closely with fracture density when measured parallel to the direction of flow. INTRODUCTION In reviewing the petroleum literature, it is found that in most analytical solutions of hydrocarbon reservoir behavior the assumption is made that the rock is uniform throughout although core analysis and well logging surveys indicate that substantially all reservoirs are heterogeneous and some are fractured. Only in recent years have investigators studied the effects of reservoir hetrogeneity. Russell1 discussed the effect of fractures in reservoirs. The literature indicates that fractures greatly affect the exploitation of man reservoirs. This is described by Elkins and Skov2 and Little-field et al. 3 Several types of reservoir heterogeneity have been studied by unsteady-state methods. In 1959, Landrum et al. 4 showed that transient phenomena in hydrocarbon reservoirs could be studied by thermal models. pickering5 studied the flow of heat in stratified linear reservoirs consisting of plates of different metals separated by sheets of rubber which were suddenly exposed to a low-temperature source at one end. Cotman6 studied both laterally and vertically heterogeneous thermal model reservoirs with special reference to cross flow. Another type of reservoir heterogeneity involves the presence of highly permeable, circular lenses around or near the wellbore which was studied by Miesch7 using a thermal and a steady-state model. Many studies have been made of the effects of induced hydraulic fractures on well performance. 8-10 Work regarding vertical fractures that exist initially in the reservoir was reported by Givens, et al.11 Since there appears to be little published work on the importance and influence on reservoir performance of fractures that exist out in the rock matrix, this study was conducted to determine the effects of vertical fractures on pressure distribution, producing capacity and the effective permeability of the reservoir rock. The analogy between the flow of electrical current through a conducting body and the flow of fluid in a porous medium provides a convenient method of studying various aspects of petroleum reservoirs. For electrical radial steady-state flow,12 For steady-state fluid flow, With the above analogy, it is only necessary to establish the ratio of the values of the electrical units in terms of the corresponding flow units to make the analogy quantitative. The ratios are shown below.

By John W. Bell

IN the introduction to an excellent pamphlet, John Gross1 makes the following statements: Although marked progress has been made along mechanical lines, the theory and conception of underlying principles have not advanced so rapidly. This lack of advance in theory may be attributed to the unfortunate situation resulting from the controversy as to whether the Rittinger or Kick law is applicable to crushing. Many pages of the technical literature are burdened with theoretical discussions in favor of one or the other of these laws, which have tended to cloud rather than to clear the atmosphere. Realizing the situation, the Milling Committee of the American Institute of Mining and Metallurgical Engineers, through its secretary, E. A. Hersam, studied the milling industry and, because of the apparently hopeless lack of agreement in the Kick versus Rittinger dispute (5, 13, 14, 16, 18, 19, 21, 22, 23, 24, 30. 34), concluded that a foundation for the theory of crushing was of primary importance. The numbers in the paragraph quoted refer to papers listed by Mr. Gross in his Bibliography on Crushing and Grinding.1 One is obliged to infer that these papers show "hopeless lack of agreement in the Kick versus Rittinger dispute." No. 22 is a paper by Arthur O. Gates2 and No. 23 is one by the writer.3 Employing the subject matter contained in papers Nos. 22 and 2323 the writer will show that their authors formulated identical conclusions, based solely on experimental evidence. Exactly the same defect in the Stadler hypothesis was described in each of the two papers, although entirely different experimental methods were employed in uncovering it. Both of the authors, independently, formulated the conclusion that Rittinger's was a. true hypothesis and Stadler's false. The evidence in a third paper4 will be employed to prove that Stadler's hypothesis, when examined experimentally, is worthless. STADLER'S HYPOTHESIS WORTHLESS It is the writer's opinion that the evidence available in 1915 and the corroborating evidence in 1916 was amply sufficient to eliminate the need for any further consideration of Stadler's hypothesis. Certainly the evidence produced in 1918 dealt this hypothesis its coup de grace. It follows, therefore, that in the year 1918 there was only one credible hypothesis left-the Rittinger hypothesis. Gates' Opinion What information is available in Mr. Gates' paper?2 His conclusions are not consecutively summarized, none the less they are perfectly clear. On page 876, Gates says, and it is a very significant utterance: But my results show, among other things, that many more of Stadler's energy units are obtained per foot-pound-applied in coarse than in fine crushing. This suggests a doubt as to the correctness of his unit, since one would expect a foot-pound-applied to produce the same number of "energy units," whether the feed and resulting product were coarse or fine. When Rittinger's theory is applied, the number of mesh-tons (my unit of surface produced) is

Jan 1, 1942

By H. W. Schadler

Single crystals of tungsten, which were grown by electron bombardment floating zone refining, were strained 2 pet in tension and bending at 298°, 77°, and 20°K to determine the modes and crystallography of the plastic deformation of these temperatures. At 77° and 20°K plastic deformation occurs by slip on systems of the type (011) [111] and by twinning on (112)-type planes. For crystals strained at 298°K, deformation occurs by slip in [111] directions on either (Oil)- or (112)-type planes. CURRENT models for the initiation of brittle fracture in crystalline materials are based on a knowledge of the details of their plastic deformation.1 Body-centered cubic tungsten exhibits brittle failure at temperatures below about 500 °K yet the modes and crystallography of its plastic deformation have not been studied below 1000°K. In 1924, Goucher2 reported that tungsten single crystals with a total impurity content of less than 0.01 wt pet deformed by slip on the (112) [111] system in the temperature range 1000° to 3000°K. He also observed (001) [010] slip in one crystal which was constrained by the presence of a large fissure. According to Barrett3 tungsten also deforms by twinning on the (112) plane in the [111] direction, but he gives no details on the tendency for twin formation or the temperature range in which twinning occurs. Therefore, as a necessary part of a study of the factors influencing the brittle fracture of tungsten, the modes and crystallography of the plastic deformation were determined at 298°, 77°, and 20°K. Tungsten single crystals, grown using the electron-bombardment zone-refining technique first described by Calverly,4 were deformed to between 1 and 2 pet plastic strain in tension and bending. The surface offset resulting from slip or twinning was observed with an optical microscope to determine the crystallography of the deformation. The existence of twins was proven by the standard polishing and etching technique; and the crystallography of dislocation motion was followed using the dislocation etchant described by Wolff.5 Some observations on the fracture characteristics of tungsten single crystals are included. EXPERIMENTAL TECHNIQUES Growth, Purity, and Perfection of the Crystals-Several years ago Calverly, Davis, and Lever4 dem-onstrated the feasibility of growing tungsten single crystals by the electron-bombardment floating zone-refining technique, and Carlson6 showed that crystals produced in this way had a high degree of purity and were ductile at room temperature. Tungsten single crystals produced by this technique in equipment similar to that described by Carlson were used in this study. The starting material, a powder metallurgy product, was obtained in the form of a swaged 1/8-in. rod from the General Electric Wire Plant in Cleveland, Ohio. The crystals were grown from this material in a vacuum of 10"4 mm of Hg by passing a molten zone 1/8 in. long down the rod twice at a speed of 3 mm per min. At this zone speed

Jan 1, 1961

By S. Budavari, F. M. C. C. Vieira

For several decades, the deep, gold-bearing reefs of the Witwatersrand basin have been mined predominantly according to layouts characterised by longwalls with strike pillars to provide regional support. During the past few years, a new generation of mining layouts has been introduced. These layouts are based on the concept of grid-type, scattered mining with dip pillars for regional support. As the extraction of the gold reefs extends to depths below 3500 m, the hazards associated with mining at these ultra-depths are expected to increase to unacceptable levels. Therefore, the question arises as to, which of the currently applied mining layouts is most acceptable for the economic and safe extraction of an ultra-deep orebody. The purpose of this paper is to describe a research investigation carried out to evaluate the degree of acceptability, from the rock engineering view point, of four currently used mining layouts for application at a depth-range of between 3500 and 5000 m. Pendant plusieurs décades, les filons d’or profonds du bassin du Witwatersrand ont été exploités d’une manière prédominante selon des dispositions caractérisées par des longues tailles avec des piliers directionnels pour donner un support local. Les dernières années ont vu la naissance d’une nouvelle génération de dispositions de mine. Ces dispositions sont basées sur le concept d’extraction type grille, éparpillée, avec des piliers au pendage pour le support local. Comme l’extraction des filons d’or va à des profondeurs en dessous de 3500m, il faut s’attendre à ce que les risques associés à l’exploitation à ces profondeurs extrêmes atteignent des niveaux inacceptables. Par conséquent, la question se pose de savoir laquelle des dispositions de mine couramment utilisées est la plus acceptable pour l’extraction rentable et sans danger d’un gisement ultra profond. Le but de l’étude présente est de décrire les recherches exécutées pour évaluer le degré d’acceptabilité, du point de vue d’ingénierie de roche, de quatre dispositions de mine couramment utilisées pour application à un rayon de profondeur entre 3500 et 5000m. Die tiefen, goldträchtigen Riffs des Witwatersrandbeckens wurden über einige Jahrzehnte hindurch vorwiegend nach jenen Layouts abgebaut, die von Langfrontstreben mit Schlagpfeilern charakterisiert waren, um regionale Unterstützung zu gewährleisten. Während der letzten Jahre wurde eine neue Generation von Grubenlayouts eingeführt. Diese Layouts basieren auf dem Konzept der Rasterfeld-Art, gestreuter Bergbau mit Neigungspfeilern für regionale Unterstützung. Es kann erwartet werden, daß auf Grund der Tatsache, daß sich die Extraktion der Goldriffs auf Tiefen unterhalb 3500 m verlagert, die Gefahren, die mit dem Bergbau an diesen Ultratiefen verbunden sind, sich auf ein nicht annehmbares Niveau erhöhen. Folglich erhebt sich die Frage, welche der gegenwärtig angewendete Abbaulayouts für die ökonomische und sichere Extraktion eines ultra-tiefen Erzkörpers am annehmbarsten ist. Zweck dieser Arbeit ist es, eine durchgeführte Untersuchung zu beschreiben, die vom Gesichtspunkt der Gesteinstechnik gesehen, vier gegenwärtig angewandte Abbaulayouts für den Einsatz in einem Tiefenbereich zwischen 3.500 und 5.000 m evaluiert.

Jan 1, 2003

By Chen Bing Ching

Hsikwangshan mine is located at Lengshuijiang city of Hunan Province. It is a stibnite deposit. The orebody is gently inclined; its ore run is about 3 km in length and extends about 1.2 km along the direction of dip. The thickness of the ore body is non-uniform and varies from 1.5 to 20 m. The orebody is mined by room and pillar and cementation filling. The nine levels at the ore top have been mined out. At present, the mining operations are at the eleventh level. The mine ventilation system consist of three main fans which are installed in different shafts and are ventilated in parallel. The main fans can be connected to each other through comprehensive return air drifts. Two of the fans are located underground and the other on the surface. The general configuration of the ventilation system is shown in Figure 1. Because the operating areas are scattered and vary frequently as well, it is difficult to bring about air flow control. If the air flow cannot be varied with the variation of production in time, the air quantities are not sufficient in some areas and are excessive in others. However, it is also a problem to coordinate the three main fans with one another to obtain the optimum economic cost of operation. In order to make the air delivery fit the variation of production continuously to satisfy the ventilation requirement of the working faces and to reduce power consumption, we have made a great effort over five years to install an automatic control system for mine ventilation at the Hsikawangshan mine. The key part of this system is a microcomputer. The whole system consists of a console, which is located at the surface; the circuit network that is provided for signal transmission; air doors and ventilators at the working face; the scale air doors which are installed at the main branch airways; main fans and their speed regulating devices, as well as the sensors used for observing pressure, air quantities, temperature and the concentration of carbon monoxide, etc. This system can continuously telemeter the air quantities and carbon monoxide concentration in the main branch airways, air pressure, air quantities, electric current, the temperature of the bearings of the main fans, etc. According to the production air requirements, the system controls the ventilators or air doors which are located at the working faces and regulates the air quantity in the main branch airways. It can also choose the optimum mode of operation automatically, and regulate the rotating speed of the main fans to guarantee the least total power consumption while satisfying the total air quantity requirements. If abnormality of the observed results is discovered, the audible and flashing light alarm signal starts up automatically. The operating mode of ventilation equipment also feeds back to the control room and displays on the console. The configuration of control the system is shown in Figure 2.

Jan 1, 1987

By A. V. Deforest, C. W. Macgregor, A. R. Anderson

One of the important problems in the design of structures and machine parts subjected to rapidly applied loads is the determination of the strength and ductility of the material itself under such conditions. Realizing the need for such information, many investigations have been carried out in the past. Most of these experiments have been made using notched bars in bending either with the Charpy or Izod impact machine. While yielding valuable data on the effect of notches in the energy absorption of the material and on the condition of heat-treatment, this form of test does not lend itself readily to a determination of fundamental stress-strain relations. For this and other reasons, more attention has been paid recently to the tension impact test. An extensive literature already exists on the subject and only those investigations somewhat closely related to the present paper will be mentioned. For a more comprehensive list, the reader is referred to the Symposium on Impact Testing or the A.S.T.M., 1938. The work of Mann.' Clark and Dätwyler,2 Nádai and Manjoine,3 Winlock and Leiter,4 Deutler,5 and Brinkmann,6 however, deserves especial mention. In most of the previous investigations on the subject, when stress-strain relations were obtained under high rates of loading, it was the common procedure to determine stresses based on the original area and strains based on the original length. Stress-strain curves were then constructed by P ALo plotting So = 1/A0 as a function of eo = ALr,o where A0 and Lo refer to the original area and gauge length, respectively. At present there exists a paucity of true stress-strain data in the impact problem. The advantages of constructing so-called true stress-strain curves in order to reveal the fundamental physical properties of the material for the tension test were discussed recently by one of the authors.7'8 It was shown that the true physical behavior of the material in the tension test could best be represented P by plotting the average true stress, S = 2P as a function of 6 = q' = log —r = log ~9L where P, A, L, S, E, and q' refer to the load, the cross-sectioned area while the load P is applied, the actual gauge length, the average true stress, the true strain and true reduction in area, respectively. Besides giving a better physical representation, the method has certain additional advantages in that the stress-strain curve so plotted becomes a straight line from the maximin load point to fracture. The construction of such curves, however, while comparatively simple for the slow rates of loading customarily used in the tension test, presents certain dificulties for tensile impact in that both loads and diameters are required throughout the test. The continuous measurement of test-piece diameters to fracture under impact conditions offers considerable experimental difficulty. In order to make it feasible to

Jan 1, 1942

By A. V. Deforest, A. R. Anderson, C. W. MacGregor

One of the important problems in the design of structures and machine parts subjected to rapidly applied loads is the determination of the strength and ductility of the material itself under such conditions. Realizing the need for such information, many investigations have been carried out in the past. Most of these experiments have been made using notched bars in bending either with the Charpy or Izod impact machine. While yielding valuable data on the effect of notches in the energy absorption of the material and on the condition of heat-treatment, this form of test does not lend itself readily to a determination of fundamental stress-strain relations. For this and other reasons, more attention has been paid recently to the tension impact test. An extensive literature already exists on the subject and only those investigations somewhat closely related to the present paper will be mentioned. For a more comprehensive list, the reader is referred to the Symposium on Impact Testing or the A.S.T.M., 1938. The work of Mann.' Clark and Dätwyler,2 Nádai and Manjoine,3 Winlock and Leiter,4 Deutler,5 and Brinkmann,6 however, deserves especial mention. In most of the previous investigations on the subject, when stress-strain relations were obtained under high rates of loading, it was the common procedure to determine stresses based on the original area and strains based on the original length. Stress-strain curves were then constructed by P ALo plotting So = 1/A0 as a function of eo = ALr,o where A0 and Lo refer to the original area and gauge length, respectively. At present there exists a paucity of true stress-strain data in the impact problem. The advantages of constructing so-called true stress-strain curves in order to reveal the fundamental physical properties of the material for the tension test were discussed recently by one of the authors.7'8 It was shown that the true physical behavior of the material in the tension test could best be represented P by plotting the average true stress, S = 2P as a function of 6 = q' = log —r = log ~9L where P, A, L, S, E, and q' refer to the load, the cross-sectioned area while the load P is applied, the actual gauge length, the average true stress, the true strain and true reduction in area, respectively. Besides giving a better physical representation, the method has certain additional advantages in that the stress-strain curve so plotted becomes a straight line from the maximin load point to fracture. The construction of such curves, however, while comparatively simple for the slow rates of loading customarily used in the tension test, presents certain dificulties for tensile impact in that both loads and diameters are required throughout the test. The continuous measurement of test-piece diameters to fracture under impact conditions offers considerable experimental difficulty. In order to make it feasible to

Jan 1, 1942

By Hongmin Zhu, Kai Huang, Shuqiang Jiao

"Garlic peel was used as the raw material to synthesize the biosorbent for the selective recovery of precious metals from the acid chloride solution. Garlic peel is rich in carboxyl-, amino- and thiol-groups, has the potential of exhibiting high affinity to Au(III) when appropriate chemical modification process was employed. Here in the present study, the biosorbent was prepared by cross-linking garlic peel particles with concentrated sulfuric acid. Adsorption tests for mixing different metal ions such as Au(III), Fe(III), Cu(II), Ni(II) and Zn(II) from various concentrations of hydrochloric acid media indicated that Au(III) was selectively adsorbed on the cross-linked garlic peel gel over the other coexisting base metal ions investigated. The crosslinking mechanism and selective adsorption of Au(III) were also investigated briefly.IntroductionPrecious metals are quite popularly applied in the modern industries such as jewelry, electronics and electrical devices, catalysts in chemical industry, etc. While their high values, limited deposit and quite large demand in industry makes its recovery from the industrial wastes, typically e-wastes, quite necessary. Actually, many techniques have been developed to recycle and recover the precious metals from various industrial wastes effectively in last decades, but the cleaning and ecofriendly processes are still seriously scarce [1]. Taking into account of the typical recovery processes using cyanide lixiviant in the alkaline media, or aqua regia, followed by the further recovery process using activated carbon adsorption or cementation with zinc, iron or aluminum plate or powder, though they both are quite effective recovery processes, if considering the special requirements on safety and ecofriendliness for the modern hydrometallurgical processes, various improved or novel extraction processes are greatly demanded [2]. Recently, the biosorption technology applied to the recover precious metals in the hydrometallurgical process has become a concern [3,4]. Inoue’s research group made great progress in the recovery of precious metals such as gold, palladium and platinum from the e-wastes such as spent mobile phone by using biosorption from the hydrochloric acid media [5,6]. This new hydrometallurgical process exhibits the prominent advantages of being cost-effective for its short process, easy operation and near-zero emission. In the above recycling process for e-wastes treatment, the preparation of biosorbents is the key and backbone of the whole recovery process. For this purpose, they developed a series of suitable sorbents for precious metals recovery by using the tanning-based or cellulose-based biomass such as persimmon peel, grape peel, orange juicing residue, waste cotton, waste paper through the crosslinking process with concentrated sulfuric acid and relative chemical modification processes [7-10]. In the present study, we also applied this technique to prepare the biosorbent of precious metal uptaking by using garlic peels as the raw materials, and investigated the adsorption properties of such-obtained gel in the hydrochloric acid media."

Jan 1, 2012

By C. E. Birchenall, M. H. Davis

The rate of oxidation of titanium in the temperature range 650° to 950°C has been measured. 'The linear rate law obtained is explained by interface reaction control of the process. Tracer experiments indicate the oxygen diffuses in at least one phase of the scale. THE kinetics of oxidation of titanium, principally at low temperatures and under varying oxygen pressures, have been reported.¹,² In the present investigation the rates of oxidation of titanium have been determined by the gravimetric method in the temperature range 650" to 1000°C under 1 atm of oxygen. Some of the scales formed were powdered and an endeavor was made to identify the phases present by X-ray diffraction. Alexander and Pigeon1 ascribe a logarithmic rate law to the growth of thick films formed at temperatures up to 565"C, and Gulbransen and Andrew' suggest that the parabolic rate law holds up to 600°C. In both cases large initial deviations from those relationships are apparent and no explanation is offered. In the present experiments it is shown that a linear rate law holds in the temperature range 650" to 1000°C, and it is suggested that the initial deviations observed are due in part to a spurious surface area effect and also to the high solubility of oxygen in titanium metal. Positive information on the mechanism of oxidation is not available, but oxygen ion diffusion through the lattice is inferred from the re- sults of trace experiments. X-ray analysis of the scale confirms Gulbransen and Hickman's' observation on the presence of rutile TiO². Experimental Details The titanium used in these experiments was prepared by the reduction of titanium tetrachloride with magnesium and was used in the form of rolled sheet. Samples approximately 0.040x0.5x0.75 in. were cut and polished to a fineness of 4/0 on metal-lographic polishing papers. Individual samples, suspended on a platinum wire, were lowered into the hot zone of a furnace, in vacuo, by means of a winch, and oxygen was admitted after the desired temperature was attained. The increase of weight of single samples oxidized for fixed times at certain temperatures was determined by weighing the sample before and after oxidation on a chemical balance. In these instances the sample was used for only one time at one temperature. In some cases the course of oxidation was followed by attaching the sample to a sensitive spring balance and noting periodically the extension of the spring with time of oxidation. Kirkendall type experiments were carried out by marking the surface of the titanium prior to oxidation with a solution containing radioactive silver. After drying, the specimen was heated in vacuo to decompose the silver nitrate used, leaving a small amount of metallic radioactive silver on the surface. Following oxidation, these samples were mounted, ground, and then placed in intimate contact with

Jan 1, 1952

By S. A. Saki, J. F. Brune

"INTRODUCTION Longwall coal mining leaves large areas where the coal has been made removed and the roof rock strata collapse, forming a zone of broken rock rubble called the gob. Figure 1 shows a typical longwall gob area along with the gate roads. The ventilation pattern for progressively sealed longwall panels follows a simple “U” pattern where fresh air is coursed inby to the headgate, flows along the face and exhausts through the outby tailgate as shown in figure 1(a). An important variation of this pattern is the back return (BR) arrangement where the exhaust air from the face is drawn inby and around the nearest open cross cut before it turns in the outby direction towards the exhaust fan. Figure 1(b) illustrates the use of back return. This arrangement moves the point of low pressure from the tailgate corner up to 60 m inby and thus maintains fresh air in the tailgate region that could otherwise be contaminated with gob air.The gob area may contain remnants of unmined coal or parts of overlying coal beds that continue to release methane, eventually filling the gob area with methane in concentrations far above the explosive range of about 4.5 to 15%. Many gob areas must be equipped with gob ventilation boreholes (GVBs) to extract methane, and GVBs often exhaust methane at concentrations from 50% to 90% (Saki, 2016). Due to oxidation processes occurring in the gob, the oxygen content is reduced to a low level, with nitrogen and CO2 making up the major remaining components of the gob atmosphere. FORMATION OF EXPLOSIVE GAS ZONES IN GOBS Since the longwall face area is ventilated with fresh air below 1% methane and the face and gob areas are not separated, an explosive fringe will form where the methane content lies within the explosive range and oxygen content remains above 12%. Figure 2 shows a typical development of such an EGZ. This figure is based on a computational fluid dynamics (CFD) model developed by CSM researchers to analyze gas concentrations and flow patterns in longwall mining. Figure 2(a) shows the formation of EGZ in the gob with a U type ventilation scheme, where EGZ lies right behind the shields in the tailgate corner. Figure 2(b) shows the formation of EGZ in the gob combining U type ventilation scheme with BR, where EGZ is pushed away from the face deep into the gob. The CFD modeling parameters and boundary conditions have been verified with field data from two cooperating, active longwall mines (see Worrall 2012, Marts 2015, Gilmore 2015 and Saki 2016). Other mine geometries, methane inflow rates and gob permeability distributions can be modeled to establish representative gob atmospheric conditions. Two GVBs were operating in the model, extracting 0.165 m3/sec each. The methane in the working areas and returns was kept below 1%. Methane flowing into the model from a rider coal bed above the mined seam was at the rate of 0.55 m3/sec."

Jan 1, 2017

By Torsten Zeller

Due to the increasing worldwide demand for raw materials and the resulting rise in commodity prices more expensive processing that is able to utilize complex ores becomes economically viable. This and increasing ecological awareness is why the interest in recycling and urban mining is steadily growing in Germany. In addition to that; landfills do also contain elements, which were not targeted over the period, when they were being accumulated. Examples are rare earths, indium, gallium, cadmium, arsenic, selenium and tellurium. Also copper, zinc and lead, the target components of ancient mining, can be obtained due to more effective processing and smelting technologies. Funding by the German Federal Ministry for Education and Research, entitled "r³ ? Strategic Metals and Minerals ? Innovative Technologies for Resource Efficiency" also indicates the high level of strategic interest. It is against this background that the research project "Exploitation of the Raw Material Potential of Mining and Metallurgical Tips in Respect of Sustainability as Exemplified in the West Harz Mountains (ROBEHA)" has been implemented. A major concern of this project is the possible transfer of results to landfills in other areas. Therefore the development of an expert system based on the innovative processing methods and a method manual for urban mining are the central components of the investigation. This will provide an important contribution to the cost optimization of ensuing urban mining projects. To ensure the success of landfill mining projects it is necessary to record the composition and quality of the deposits accurately. Also the environmental impact caused by landfill mining and changes in the natural and cultural landscape will be considered in a multicriteria evaluation method. Depending on their origin the tips are divided into the categories mining, processing, and smelting. The content of a landfill and thus the economic potential in terms of urban mining is dependent on the type and composition of the deposits (host rock, gangue, and ore mineral), the available processing and smelting technology, and the target components at the time of mining. Zinc, for example, was not been processed until the 19th century, when it gained attention as being material of economic importance. After such knowledge about a landfill is obtained the decision for further investigations can be made. For a total of 158 landfills in the Harz Mountains, both the volume and the approximate contents of copper, zinc, and lead has been estimated for the different types of tips within past research projects. Based on the prices of the London Metal Exchange (LME) and a euro/dollar exchange rate of 0.76 (as of 03/05/2012) and assuming a minimum density of ? ? 1.5 t/m³ a average value of 1.6 billion ? in copper, zinc, and lead can be obtained. Although only these three metals are considered in this first estimate, it demonstrates the potential of landfill mining and the need for further research. KEYWORDS Urban Mining,

Aug 1, 2013

By W. T. Isbell

In the Parkes process of lead refining, after desilverization has been completed by means of the addition of zinc, there remains in the lead from 0.5 to 0.6 pct zinc. At this stage in the refining operations virtually all impurities are reduced to refined lead specifications except zinc and antimony. All excess copper, nickel and cobalt have been removed by the zinc additions. The silver remaining should not exceed 0.1 oz per ton. It then remains only to remove the zinc and antimony in order to produce refined lead. At the Herculaneum plant of the St. Joseph Lead Co., practice formerly was to complete the refining by means of oxidation in a reverberatory furnace. This process consisted of heating the lead to 1400O to 1500OF and allowing it to come in contact with excess air passing over the surface of the lead and periodically agitating the bath of lead with air. This procedure not only resulted in the loss of zinc but of a considerable quantity of lead converted to the oxide in the form of dross and fume. The fume, collected in the baghouse, together with the dross was returned to the blast furnace, thus adding appreciably to the circulating load on the blast furnace and refinery. In addition, operation and maintenance of the reverberatory furnace were expensive and required the performance of disagreeably hot and somewhat hazardous work. The process of dezincing with high vacuum was developed at this plant as a substitute for the oxidation process and finally led to lower operating costs, the practical elimination of dross and fume and the direct production of metallic zinc, which is very suitable for re-use in the desilverization process. Essentially this process consists of subjecting the lead to high vacuum, in a kettle provided with means for heating, a bell-shaped member open at the lower end so constructed that it can be immersed in the molten lead, and means for evacuating the interior of the bell and for sealing an agitator. Metallic zinc is thus produced and collects on the upper cooled part of the bell member. This metallic zinc is periodically removed and re-used in the desilverization process. The process is quite simple. It is conducted at a low temperature, thus permitting the use of iron equipment, and shows a material saving in refining costs over the old method. Equipment and Its Uses Degincing Machine.—The equipment employed in this process consists of a dezincing machine, a steel kettle of 120 tons capacity, a vacuum system and equipment for handling the dezincing machine (Fig 1). The dezincing machine consists of a compact assembly, suitable for handling with an overhead crane, consisting of a treating chamber and the agitating mechanism. Treating Chamber.—The treating chamber is a bell-shaped shell (4), similar in shape to a hemispherical kettle with a lid

Jan 1, 1949

By J. B. Chatelain, M. F. Dufour

FLUID jet mills, employing a compressible fluid to grind materials to the subsieve range, was developed in the early 1930's, and the subsequent acceptance of these units was the result of their ability to pulverize solids that, because of physical properties, could not be processed by other attrition methods, such as ball, pebble, and hammer mills. Also, the fluid energy pulverizer is the only grinding device that will discharge continuously a 5-micron or smaller product. Simultaneous ultra-fine grinding and classification is the widest application of this unit. Jet mills may be used to advantage to reduce particle size of solids suspended in liquids, for coating one material with another, and effecting chemical reactions and changes in physical characteristics other than a reduction in size. Materials that can be processed by this grinding method include nonmetallic and metallic minerals, ores, metals, pigments, insecticides, fungicides, pharmaceuticals, plastics, dyes, and numerous other organic and inorganic products. Grinding principles utilized in the fluid mills available on the market are basically the same, the major difference being in the shape of the, grinding and classification chamber. Grinding in fluid jet pulverizers is accomplished by collisions between particles of the material being ground with the energy being supplied by compressed fluids entering the grinding chamber at high velocities. The "Micronizer" is a fluid energy mill employing a relatively flat cylindrical grinding chamber. Fig. 1 shows general construction details. The mill shown is equipped with a venturi type feeder using a compressed fluid to inject the feed into the grinding chamber. The energy consumed in forcing the feed into the grinding chamber against the mill pressure is, in some cases, as much as 40 pct of the total required for processing. Recent improvements, using a compression screw feeder as shown in Fig. 2, can reduce this to 1 or 2 pct of the total energy requirements. Grinding Grinding, as carried out in the. Micronizer involves the action of gaseous jets emerging from nozzles located in the peripheral wall of the grinding chamber. The axes, of the jets are tangential to a circle of smaller diameter than the grinding chamber as is shown in Fig. 1, and the gases entering the chamber maintain a high rotational velocity. The feed introduced into the mill is accelerated by the rotating gases and is thrown to the outside where a portion, coming in the zone of action of a nozzle, is further accelerated tangentially and inward. Violent collisions occur between the particles so accelerated and other particles circulating at a slower rate in a thin band near the periphery. It is estimated over 90 pct of the reduction in Micronizers occur as a result of impact within a fraction of an inch of the orifice. Observations also indicate that size reduction is independent of any interaction with the walls of the

Jan 1, 1952

By G. H. Matheson, J. M. W. Mackenzie

The coal concentrates studied contained clay slimes which would not flocculate on the addition of a polymer flocculent alone. The mechanism of the flocculation process is interpreted on the basis of the flocculation of lyophobic colloids. The filtration rate characteristics are shown to deviate slightly from certain basic filtration equations. Cake moisture was shown to decrease with cake drying time and vacuum, and increase with cake thickness. Filtration is a commonly accepted method of dewa-tering the fine coal concentrates produced in coal cleaning operations. Dewatering of these concentrates, using drum or disc vacuum filters, usually presents few technical difficulties and will result in the production of a filter cake containing some 20 to 25 pct moisture. In many coal cleaning operations it is common practice to add flocculants to the coal concentrates prior to filtration to increase the filtration rate. The mechanism whereby flocculation increases filtration rate has been summarized by Gaudin,4 while Geer, et a15 have compared the effectiveness of starch and synthetic flocculants as filter aids for a variety of coal concentrates. Coal concentrates, containing appreciable quantities of expanding lattice clays of the montmorillonite-illite group, sometimes prove impossible to filter without flocculation of the pulp prior to filtration. The fine coal concentrates produced at the Newcastle washery of The Broken Hill Proprietary Co. Ltd. fall into this group. Coals mined in this district contain appreciable quantities of expanding lattice clays which break down in the washery circuit waters and, by processes of mechanical inclusion, contaminate the coal concentrate thickener feed. Despite the classifying action of this thickener, the underflow which is pumped to the filters contains sufficient clay slimes to render filtration of the unflocculated pulp impossible. Filtration leaf and plant tests were carried out to develop effective and economic flocculant combinations and to determine the filtration characteristics of the flocculated coal concentrates. The determination, by leaf testing, of the filtration characteristics, and the analysis of these characteristics in the light of the equations of Brown2 resulted in the successful trial operation of the filters in the Newcastle washq. Although the filtration characteristics are not entirely in agreement with the theoretical treatment of Brown, the equations developed made it possible to predict, from leaf tests, the effect in the plant filters of pulp density, form vacuum, and form time on filtration rate and filtrate volume. EXPERIMENTAL PROCEDURES The sample used for leaf testing was the coal concentrate thickener underflow, which in plant operations would form the feed to the two 12-disk Dorr-Oliver filters. The feed to the coal concentrate thickener comprises the undersize produced by dewatering the Diester table concentrate on 5-mm dewatering screens and the overflow produced by cycloning of the froth flotation concentrate. At the time of testing these filters were inoperative because of the difficulties in filtration, arising from contamination of the

Jan 1, 1962

By R. A. Nadler and

Specimens of Ti-155A (Ti-5Al-1.3Fe-1.3Cr-1.2Mo), Ti-6Al-4V and Ti-4Al-3Mo-1V were hydrogenated, aged to high strength levels, and subjected to notched stress-rupture tests and tensile tests at two strain rates. Both Ti-6Al-4V and Ti-155A were relatively unaffected by hydrogen in amounts exceeding those found in commercially -produced material. Inconsistencies in the data and a relatively low initial level of ductility prevented an accurate determination of the hydrogen tolerance for aged Ti-4Al-3Mo-1V, but there was no evidence that this alloy was any more susceptible to hydrogen embrittlement than Ti-155A and Ti-6A1-4V. THE metallurgical literature has been considerably enriched in the past five years by the publication of the results of many investigations which were concerned with the effects of hydrogen on titanium and its alloys. Although it is not the authors' intention to provide a complete literature survey of this vast field, it is worthwhile to summarize briefly some of the important factors which influence the embrittling phenomenon in a - B alloys. Some of the influencing factors are those of strain rate, temperature, and composition. Hydrogen embrittlement in a - B titanium alloys is now believed to be a strain-induced phenomenon, and whether or not embrittlement occurs at high hydrogen levels depends largely upon whether sufficient time is available for hydride precipitation. This condition is fulfilled by tensile testing at very slow strain rates or by rupture testing smooth or, preferably, notched specimens over relatively long periods. Conveniently, maximum embrittlement occurs at or near room temperature. The presence B - stabilizing elements, in amounts sufficiently small to prevent an all -B or nearly all -P condition, promotes hydrogen embrittlement and this tendency is believed to be related to the amount of a - B interfacial area present. Aluminum, by increasing the solubility of hydrogen in A titanium, greatly reduces the danger of hydrogen embrittlement, while oxygen has been shown to have detrimental effects.' The preceding discussion is based on experimental work performed on annealed a - P alloys. This early work has shown that annealed Ti-6A1-4V and Ti-155A are relatively insensitive to the embrittling effects of hydrogen.' Although no work has been reported on annealed Ti-4A1-3Mo-lV, the alloy would be expected to exhibit somewhat the same insensitiv-ity as Ti-155A. In sharp contrast to the voluminous literature on annealed titanium alloys is the paucity of reported investigations on materials receiving commercial heat-treatment cycles. To date, the most notable contributions in this field have arisen from two separate investigations on Ti-3Mn-1Fe-1Cr-1V-lMo, the so-called 3Mn comple~. These investigations

Jan 1, 1961

By Xian Jian Guo, Lei Li, Hua Wang

The distribution and behavior of As, Pb and Zn elements in the copper smelting process were investigated using thermodynamics. The differences between thermodynamics evaluation and practical smelting processes were analyzed. The main factors affecting the distribution of the elements are oxygen enrichment in blowing, copper matte grade and smelting temperature. In general, the distribution ratio of As, Pb and Zn to off gas increases with the smelting temperature and decreases with oxygen enrichment in blowing. Meanwhile, their distributions in matte decreases and that in slag increases with the increase of copper matte grade. There is some gap in distributions between thermodynamics evaluation and practical smelting processes. INTRODUCTION The copper concentrates usually contain a number of minor elements, the control of which in copper smelting processes is often a key to the quality of the anode copper produced and may also have a bearing on the overall economics of the process (Yang et al., 2017). Knowledge of the thermodynamic properties of the minor elements in slag is very important in the control of the slagging reactions (Takeda Y, Ishiwata & Yazawa, 2007). In addition, the environmental contamination caused by the minor elements associated with copper-bearing ores, such as As, Pb and Zn, has become more and more important (Wang, 2004). Arsenic, lead and antimony, which are all carcinogenic metalloid elements, are usually contained in iron-rich wastes, and theirs emissions are considered to be one of the foremost environmental concerns (Wang, 2004). It is important to elucidate the elements distribution of them in the reducing-matte smelting process. The distributions of As, Pb and Zn elements in the copper smelting process are dependent on many factors, including the temperature, raw material composition, reduction atmosphere, concentration level, and slag chemistry etc. (Chen L Z, Xu X, 2016). Generally, these minor elements mainly distribute in phases of gas, copper matte and slag in the smelting process (Shu, Wang, & Qu, 2016). The arsenic exists mainly in the form of sulfo-arsenides in the copper concentrate, and it will decompose and be oxidized in the smelting process (Chen & Lu, 2016). Part of the products, including AsS, AsO, As2 and As2O3, evaporates into the gaseous state, and some other part enters into slag phase in the form of As2O3 and As2O5 (Wang, Guo, & Tian, 2017). Meanwhile, the As2O3 in the slag phase can also be reduced to metallic As and combine with Cu, S, Fe forming Cu3As2, As2S3 and Fe3As2, and then enter into copper matte. During the copper smelting process, about 50% of zinc enters into slag phase in the form of ZnO and 45% exists in the copper matte in the form of ZnS. Little volatizes into the gas phase. Most lead exists in forms of PbS and PbO in the copper concentrate, and it is mainly distributed in copper matte in the smelting process (Zheng & Lin, 2015).

Jan 1, 2019

By H. Furman Byars

INTRODUCTION of bottom dump hauling units into the Ray, Ariz., stripping operation of the Isbell Construction Co., was motivated by several reasons, with what appears to be debatable results. The accepted theory of truck design for use in open-pit holds that end dump vehicles are the most adaptable for the work. But, because operations of the bottom dump, under certain construction and haulage conditions, proved economically feasible, the unit was put to work in the Ray copper pit. The decision to try bottom dump was reached after considerable observation of the unit in action on construction of earth filled dams, levees, airport construction and several other similar tasks. Basic tire design also motivated the choice. All things being equal, a vehicle running on low pressure single tires will outperform another operating on dual high pressure tires, providing load carrying capacities are the same. The investment required to equip a vehicle with four single tires to handle the same load as one with dual tires mounted on two axles and single front axles is about 60 pct greater. Thus, in order to reach the break even point on tire costs, single tires must operate 60 pct longer. Comparison is made with a truck outfitted with 10 16:00x25 tires. Two other factors were considered in selecting bottom dump trucks. It was felt the bottom dump principle would work well in dumping ore into a hopper where gate design fits this particular method. Also, with the absence of hydraulic dumping, ore pollution with oil is reduced. The mechanical simplicity of the unit also lent weight to its choice. Ordinary reasoning indicated maintenance costs would be low compared with other units carrying similar loads. The bottom dumping principle is not new. It dates back to the days when horses were used to haul the same kind of rig. The unit employed at Ray holds 25 cu yd struck measure, or approximately 42 short tons. Dumping is accomplished by releasing an air cylinder opening a dog holding the doors. Doors are closed by a cable system operating off a wheel wind deriving power by friction with the trailer tire. The unit is mounted on four 27.00x33 and two 14.00x24 tires on the front axle. The power unit is a 300 hp Cummins engine. Hydraulic power boosts the steering. A straight mechanical drive and friction clutch with 10 speeds is used. Conditions Not Ideal Top performance of the truck can be expected only under the conditions for which it was designed, in particular grades under 5 pct, handling fine material, and dumping where one thin layer can be placed on top of another. The machine will handle 42 tons per haul, operating at high speed, with only seconds used for dumping. On a 2 or 3 pct grade over a one mile haul,

Jan 1, 1952

By R. L. Rickett, W. C. Leslie

The influence of deoxidation practice, prior thermal history, and aging time and temperature on the strain-aging behavior of low-carbon open-hearth steels was investigated. The criterion of aging employed was the increase in yield strength in the tensile test, after straining and aging. Composition, prior heat treatment, and aging conditions were all found to be important in governing the strain-aging characteristics of these steels. THAT deoxidation changes the strain-aging propensities of low-carbon steels has been known for a long time, but there has been little agreement, and even contradiction, between results obtained by different investigators and between results obtained in the laboratory and in the mill. This investigation was begun in the hope that some of the uncertainties connected with the strain aging of commercial steels could be eliminated. In considering this problem, it was necessary to define strain aging and to examine the methods used to measure this property. Strain aging can be defined as the changes in properties of a metal or alloy with time, after cold working. The rate at which these changes occur increases as the temperature is raised above atmospheric. The requisite plastic strain is the principal distinction between strain aging and quench aging, the latter being due to precipitation from supersaturated solid solution. Strain aging is also characterized by rapid attainment of maximum hardness at high aging temperatures and lack of softening (overaging) at low aging temperatures. Several possible criteria of strain aging have been listed by Sachsl and by Davenport and Bain.' Because changes in mechanical properties are the most easily measured and the most commonly used, consideration of methods to be used in this investigation was confined to three tests: tensile, notch-impact, and hardness. Hardness tests are the most economical and easiest to perform, but produce only one measure of strain aging. Also, as pointed out by Felmly, Hartbower, and Pellini,³ hardness changes due to aging are not pronounced for steels containing more than 0.15 pct C. Notch-impact tests require careful preparation of large numbers of specimens. Above and below the transition temperature the test lacks sensitivity; furthermore, it is extremely difficult to impart a uniform strain to the specimens, followed quickly by aging and final testing; machining must generally take place after straining. For these reasons, the tensile test was selected for use. Although this test requires a considerable expenditure of time, labor, and money in preparation of the specimens and performance of the test, more information can be gained than from any other single mechanical test, information which includes upper and lower yield points, yield-point elongation, tensile strength, strain-hardening exponent, reduction of area, and elongation. Low and Gensamer' and Schwartzbart and Low5 lso used the tensile test, taking the increase in flow stress after straining in tension and aging as a measure of strain aging. In our work, as in theirs, each specimen was strained an arbitrary amount, sufficient to pass through the

Jan 1, 1954

By E. McCarthy

"INTRODUCTION Talc is a hydrous magnesium silicate with the approximate elemental composition 4MgO.3SiO2.H2O. It is one of the layered phyllosilicates (like kaolin and mica) but it differs from these in that it is relatively hydrophobic. This is due to its unique crystalline structure whereby a brucite inner layer is sandwiched between silica layers and the adjacent silica layers have no interlayer bonding other than van der Waals forces. This allows talc to be sheared easily along this basal plane, and the surface is covalent not ionic. Talc occurs both as a relatively pure material (>90% talc content) and in conjunction with many other minerals in proportions all the way from 1% to 90%. At lower concentrations, it is often considered a nuisance mineral when it occurs with base metals like copper, molybdenum or nickel or with precious metals like platinum or palladium. It floats readily with these materials and often is suppressed using guar gum or carboxy methyl cellulose which will absorb along the basal surface and make it hydrophilic. Alternately if the reduced ore is hydrophobic, like MoS2, then a partial oxidation of the sulfide will convert the surface to a hydrophilic oxide and the talc can be floated away in a separate step. Talc in grades from 20 to 90% has been commercially exploited in a wide range of pigment (paint and paper), material (ceramic, construction and cosmetic), reinforcing (polymers and composites) and functional (pitch adsorbent, lubricating agent) applications. Initially these tended to be local or regional markets, but eventually with certain higher purity grades, cosmetic, polymer and ceramic applications became valuable enough to be national and trans ocean markets. TALC FLOATATION PLANTS This drove the need for higher purity grades of talc and initially this need was met primarily by ore sorting. This works well for certain deposits with well crystallized talc lenses, but for ores, such as those from widely available ultramafic deposits, where the liberation size is closer to 100 microns, sorting is not effective. That drove the need for floatation and the first investigations were published by Clemmer and Cooke of the US Bureau of Mines in 19362. The first commercial floatation plant was installed in Johnson, VT by the Eastern Magnesia Talc Co in 1937. The circuit is shown in the schematic (Figure 1). The ore was an ultramafic, serpentine derived talc; mineralogy was about 55% talc, 40% ferroan magnesite and 5% oxides, sulfides and other silicates. The oxides include hematite and chromite, sulfides pyrite and gerstorffite and silicates chlorite, serpentine and mica. After crushing, the ore was dry ball milled and then air classified to remove minus 325 mesh fines. The coarse fraction was further classified to cut at about 100 mesh and the fines from this were the feed to floatation. The -325 mesh (about 15% of the ore) was sold as a paint grade and the plus 100 mesh (about 25% of the ore) was screened to make an asphalt backsurfacing grade."

Jan 1, 2018