Search Documents

By Simon Pelletier, Jose Delgadillo, Dave Page, Pramod Kumar, Raj Rajamani, Dilek Alkac, Martin Fillion

"In general, many past works examine mill load, mill power, shell lifter design etc with a view to improving the mill capacity. On the contrary, only a handful of papers have addressed the transport of fine slurry through the pulp lifters. We present the flow dynamics of pulp lifters via laboratory scale experiments, high speed photography and modeling with computational fluid dynamics. Next, the flow behaviour in ArcelorMittal’s Mont-Wright autogenous mill discharge flow is examined. In an effort to improve mill throughput, a comprehensive simulation and plant scale study of the mill was taken up with a focus on the shell and pulp lifter design. The shell lifter was found to be at its optimum limit for breakage of ore particles given the constraints of wear life and occupied volume. Next, the pulp lifter study was taken up with computational fluid flow code and discrete element code. The simulations directly showed that there was considerable carry-over of slurry. This effect was traced to the area restriction in the pulp lifter channels. Further, crash-stop studies confirmed slurry pooling within the mill. Thus it was readily apparent that mill throughput can be increased if the pulp-lifter could be redesigned. Consequently, the discharger section of the pulp-lifter was redesigned.First, this paper outlines the modeling in laboratory scale studies and plant scale studies leading up to the discharger design. Next, the discharge flow in seven different published mill surveys is predicted with computational fluid dynamics (CFD) methodology shown here. Finally, Mont-Wright mill circuit performance before and after the discharger redesign is described. The usefulness of fluid flow simulations in the design of pulp-lifters is emphasized."

Jan 1, 2012

By Roy Greenfield

During the detection phase, several procedures can be used to improve the signal-to-noise ratio (SIN) . • Subarrays of up to 10 seismometers should be used. The apparent failure to obtain improvement in SIN in the Westinghouse subarrav work is probably due to excessive noise in the electronics. The spacings needed for sensors in the subarray must still be established. • The sensors should be buried. Even burial to a few feet will probably give appreciable reduction of noise. A deeper burial will probably further reduce the noise; and, if the seismometers can be put below the weathered layer, the signal level will probably be increased. The reduction in noise by burial will be especially effective during high noise periods due to wind or rain. • Before attempting detection, the waveforms should be bandpass filtered. The bandpass should go from 25 Hz to an upper frequency of 100 to 200 Hz. Further measurements with a low noise system must be done before the signal-to-noise ratio can be determined for the 100 to 200 Hz range. Any narrow band noise should be removed by notch filters. • If noise levels differ among seismometers of a subarray, weights inversely proportional to the noise power should be applied to the seismometers. • Automatic methods of screening data for possible signal arrivals should be developed, but the final determination that the signal on a subarray output appears to be from a miner should be made by an analyst. Detection of "signal" on several subarrays should be required for positive identification. In the location phase, after detection: • If repeated signals are received, they should be coherently added (stacked) to give as good a SIN as possible for use in determining signal arrival times, to be used in location computations. The miner should, if possible, repeat the signal 25 to 50 times.

Jan 1, 1974

By A. J. Lyon, J. B. Johnson, Samuel Daniels

The wrought alloys of aluminum with small amounts of copper and of magnesium have, with the development of the automotive and aircraft industries, sprung into prominence through the medium of duralumin; but the cast alloys remained in the background because their possibilities in the heat-treated condition were either not recognized or not fully investigated. In 1919, the Bureau of Standards published a preliminary survey1 of this field, which pointed out that, in general, the ultimate strength and the percentage of elongation of the alloys of aluminum with and without magnesium could be improved by so simple a treatment as heating at 932' F. (500" C.) for 2 hr., cooling in air, and aging at room temperature for several days. British investigators, too, working with chill-cast material, found that" considerable improvement in the mechanical properties of copper-aluminum alloys may be obtained from suitable heat treatment applied to castings."' Jeffries and Gibson8 made the first contribution to the literature dealing exclusively with the heat treatment of sand-cast aluminum-base alloys, describing the effect of small additions or of combinations of copper, magnesium, and iron on the response to a short heat treatment comprising heating at 932" F. in a nitrate bath for 1 hr., quenching in fish oil, and reheating at 300' F. for for 1 hr. Their results disclosed the facts that the ultimate strength and the percentage of elongation of sound alloys were usually, and quite uniformly, improved by heat treatment; that with the iron content ranging between 0.36 and 0.88 per cent. and the silicon content between 0.24 and 0.60 per cent. the effect of increasing the copper content (Tables 10

Jan 1, 1925

By J. J. Jakosky

THE fundamental hydrodynamic principles governing the production of oil from wells have been carefully studied and evaluated by many investigators. These prior studies are quite complete and cover virtually the entire field of oil production and recovery.1 One of the most impor-tant measurements in production studies is that of the bottom-hole pressure at various rates of production.2 It is the purpose of this paper to outline the technique and economics of fluid-level measurements as applied to pumping wells and to review briefly other methods for obtain-ing bottom-hole data. The applications of bottom-hole pressure or fluid-level measure-ments are based on simple hydrodynamic principles. Under equilib-rium conditions, pbh = hd + pg + pch [ l] when pbh = bottom-hole pressure, lb. per sq. in. absolute, h = height of fluid in well, ft., d = average fluid density, lb. per sq. in. per foot, pg = weight of section of gas column 1 in. square from fluid level to casing head, pch = casing-head pressure, lb. per sq. in. absolute. In words, equation 1 states that the bottom-hole pressure is equal to the weight hd of the column of fluid plus the weight of the column of gas between the fluid and the casing head plus the casing-head pressure. At moderate rates of flow, the rate of production is approximately proportional to the difference between the reservoir, or static bottom-hole, pressure and the flowing or producing pressure; i.e.: Q = c(pr - pbh) [2] pr = the reservoir pressure, c = the constant of proportionality. However, at production rates approaching zero and also at high rates the proportionality may break down. By combining equations 1 and 2 the

Jan 1, 1939

By Arthur F. Taggart, G. R. M. Del Giudice, M. Hassialis, A. M. Saddler

Flotation of sulphide minerals and native metals is no longer a practical difficulty. The underlying scientific principles of the method, although not explored in anything like complete detail, have been formulated with sufficient breadth so that the direction of attack on any specific case is clearly indicated. It has been known since the earliest days of flotation that certain of the nonsulphide nonmetal minerals—e.g., sulphur and graphite—would respond to flotation by oils as sulphides do; therefore they have been grouped with sulphides in many patents. But since the development of the chemical theory of collection,1,2,3 this similarity in action has been one of the facts cited in disproof of the theory by opponents of the hypothesis.4,5,6 Air levitation† of certain oxidized minerals, both metalliferous‡ and nonmetalliferous, and separation thereby from other oxidized minerals, is a recent development in practice, although the discovery of the method dates back 17 years7 This paper presents evidence that the principles underlying the air levita-tion of the nonsulphide nonmetal minerals are the same as those utilized in the flotation of the sulphides and native metals. It will be apparent immediately to anyone with knowledge of mineral concentration that separation of air-levitated minerals in water from minerals not so levitated is a simple matter of water-gravity concentration, the separating device employed depending solely upon the size of the particles treated and the buoyancy differences effected by the levita-tion. The usual separating means employed are: (1) a flotation machine for fine, slimy and for well aerated granular material; (2) shaking tables for granular less aerated material. By using large quantities of oil, it is possible to form substantially air-free oil-bound masses or granules of nonsiliceous minerals and to

Jan 1, 1939

By C. H. Mathewson, M. R. Pickus

The study of the plastic deformation and recrystallization of metals has been the subject of many investigations. In regard to the simple deformational processes, such as tension and compression, the early knowledge gained from studies of polycrystalline material has been supplemented by many significant researches on the behavior of single crystals. Unfortunately, this has not been true for more complicated deformational processes. As far back as 1927, G. I. Taylor1 wrote: It is impossible in the present state of knowledge to do more than give a possible reason why (face-centered cubic) crystals set themselves with a (110) direction in the plane of rolling, and at right angles to the direction of rolling. The explanation of why the orientation of the crystal axes round the transverse direction is what it is, must be left till the distortion of metals, and particularly single crystals of metals in the process of rolling, has been studied in greater detail. That this gap in the systematic study of deformation and recrystallization has not yet been filled was indicated by C. H. Samans, who wrote in 1934 that "only four investigations upon cold-rolled single crystals of any of the face-centered cubic metals have been reported in the literature." Of these four studies, only those of S. Tanaka3 and T. Sakaoj4 both of whom worked with aluminum crystals, had quantitative significance. The other two, carried out by F. Wever5 and W. G. Burgers16 were of a qualitative nature. It is our hope that the present investigation may contribute something to the knowledge necessary for a rationalization of the origin of rolling textures in terms of the known behavior of single crystals, and may add pertinent information concerning the recrystallization characteristics of deformed single crystals.

Jan 1, 1939

By H. Weissenbaeck, B. Nowak, M. Oesterreicher, R. Stastny

The producers of certain metals like nickel and cobalt increasingly face a shortage of easy-to-mine and easy-to-process ore bodies. Their focus is shifting towards alternative raw materials which in turn demand new, different extraction techniques. One potential route for processing a ferrous ore with a non-ferrous target metal is atmospheric leaching with hydrochloric acid followed by purification of the pregnant leach solution (PLS). For the separation of iron from the PLS, and, in turn, the extraction of the non-ferrous compounds, the following flow sheet is proposed. Pre-concentration of the PLS, oxidation of ferrous (if present) to ferric chloride, hydrolysis of ferric chloride leading to the precipitation of hematite and the evaporation of hydrochloric acid, followed by crystallization of non-hydrolysable metal chlorides by means of sparging hydrogen chloride into the solution. Hydrogen chloride required in the latter step is produced internally by super-azeotropic distillation of regenerated hydrochloric acid. The liquid filtrate from the crystallization step is recycled to hydrolysis. Depending on the specific composition of the PLS, the hematite produced contains only traces of other impurities, whereas the crystallized mix of non-hydrolysable metal chlorides – containing also the target metal in enriched form – contains ferric chloride only in an amount referring to the filter cake moisture. These crystals can then undergo further hydrometallurgical separation and extraction processes. As an example, this flow sheet is proposed for treating nickel laterite ores. Experiments related to the demonstration of crucial assumptions in the flow sheet are presented. Based on those experiments a mass and energy balance of the flow sheet was calculated and is presented here together with a table of the major consumables in order to provide a basis for an operating cost estimate and other process economics.

Jan 1, 2016

By M. R. Pickus, C. H. Mathewson

The study of the plastic deformation and recrystallization of metals has been the subject of many investigations. In regard to the simple deformational processes, such as tension and compression, the early knowledge gained from studies of polycrystalline material has been supplemented by many significant researches on the behavior of single crystals. Unfortunately, this has not been true for more complicated deformational processes. As far back as 1927, G. I. Taylor1 wrote: It is impossible in the present state of knowledge to do more than give a possible reason why (face-centered cubic) crystals set themselves with a (110) direction in the plane of rolling, and at right angles to the direction of rolling. The explanation of why the orientation of the crystal axes round the transverse direction is what it is, must be left till the distortion of metals, and particularly single crystals of metals in the process of rolling, has been studied in greater detail. That this gap in the systematic study of deformation and recrystallization has not yet been filled was indicated by C. H. Samans, who wrote in 1934 that "only four investigations upon cold-rolled single crystals of any of the face-centered cubic metals have been reported in the literature." Of these four studies, only those of S. Tanaka3 and T. Sakaoj4 both of whom worked with aluminum crystals, had quantitative significance. The other two, carried out by F. Wever5 and W. G. Burgers16 were of a qualitative nature. It is our hope that the present investigation may contribute something to the knowledge necessary for a rationalization of the origin of rolling textures in terms of the known behavior of single crystals, and may add pertinent information concerning the recrystallization characteristics of deformed single crystals.

Jan 1, 1939

By Edward P. Chapman

IN the Leadville district toward the close of the "intermediate mesothermal period" of mineralization, there occurred a stage of ore deposition marked by a rather complex mineral association. As bismuth minerals formed in many places during this period, it is here called the "bismuth stage" for convenience of description. The minerals so far identified with this stage, listed roughly in the order of prominence, are: chalcopyrite; several varieties of galena, differing slightly from one another in their small contents of silver, bismuth and tellurium; altaite; hessite; galenobismutite; alaskaite; aikinite; ,gold; tennantite; argentite; and perhaps sphalerite and arsenopyrite. With the exception of gold, the age relations of these minerals are difficult to determine. As shown in their descriptions, they all appear contemporaneous and hypogene. Gold may be in part contemporaneous, but most of it is distinctly later. Where minerals of this stage occur so that they can be mined alone, as at the Tucson mine, they constitute high-grade ore. Elsewhere their presence in small amounts has served to increase greatly the value of what otherwise would be low- grade pyritic or zinc-lead sulphide ore. The distribution of the bismuth ores corresponds closely to the distribution of gold ores, though not so general. It seems probable that most of the gold in the district was deposited during the "bismuth stage." These ores occur relatively near the supposed centers of mineralization in Breece and Printer Boy Hills or deep down along the Tucson-Maid fault, which is one of the well recognized channels of mineralization in the Iron Hill and Graham Park areas. Consideration of the high-grade nature of this mineralization and the fact that it appears to be found relatively close to the source of mineralization suggests that prospecting along some of the known channels, even deeper than they have yet been prospected, may offer hope of commercial success.

Jan 1, 1939

By M. R. Pickus, C. H. Mathewson

THE study of the plastic deformation and recrystallization of metals has been the subject of many investigations. In regard to the simple deformational processes, such as tension and compression, the early knowledge gained from studies of polycrystalline material has been supplemented by many significant researches on the behavior of single crystals. Unfortunately, this has not been true for more complicated deformational processes. As far back as 1927, G. I. Taylor1 wrote: It is impossible in the present state of knowledge to do more than give a possible reason why (face-centcred cubic) crystals set themselves with a (110) direction in the plane of rolling, and at right angles to the direction of rolling. The explanation of why the orientation of the crystal axes round the transverse direction is what it is, must be left till the distortion of metals, and particularly single crystals of metals in the process of rolling, has been studied in greater detail. That this gap in the systematic study of deformation and recrystallization has not yet been filled was indicated by C. H. Samans,2 who wrote in 1934 that "only four investigations upon cold-rolled single crystals of any of the face-centered cubic metals have been reported in the literature." Of these four studies, only those of S. Tanaka3 and T. Sakao,4 both of whom worked with aluminum crystals, had quantitative significance. The other two, carried out by F. Wever5 and W. G. Burgers," were of a qualitative nature. It is our hope that the present investigation may contribute something to the knowledge necessary for a rationalization of the origin of rolling textures in terms of the known behavior of single crystals, and may add pertinent information concerning the recrystallization characteristics of deformed single crystals.

Jan 1, 1938

By James A. Deeks

"Motor failures and equipment bearing failures are responsible for reduced productivity.With the introduction of computers and data acquisition systems, users are now able to monitor, report and trend deteriorating conditions and take corrective action before a critical shutdown occurs.This paper discusses the monitoring and trend analysis of' motors, and motor and equipment bearings. With today's digital electronics technology users are now able to monitor their equipment, detect deteriorating or abnormal conditions quickly, alarm the condition locally and or remotely, and decide if immediate corrective action is necessary or if it can be delayed until the end of a work Shift. All of this can be done long before any damage is done to the equipment.Monitoring Trend AnalysisIt is no longer necessary to compromise in selecting products, since state-of-the-art designs allow the adjustment in such small increments that the users are able to detect minute changes in a system's performance.Monitoring and trending of motors and equipment bearings is now available in economical packages which can be expanded as a system grows. Simply select the information you need, set the parameters, choose the scan time, and decide on the degree of reporting.Buffer storage of short-term monitoring of a number of analogue channels permit the user to view the recent history of motor data such as: motor average load, unbalance, motor current, ground fault, reserve thermal capacity, plus all of the settings of the protective device.A decision can be made to freeze the stored information after the motor stops or after the motor starts. Then the user is able to recall the conditions and diagnose the performance and the cause of the abnormal condition. Typical scan times range from ¼ second to 5 seconds ."

Jan 1, 1992

By A. W. Cochardt

THERE are a number of effects that can cause material damping or internal friction. Some of these are frequency dependent, such as the thermo-elastic effect' and the stress-induced ordering.' Others depend on the amplitude of vibration, i.e., the damping related to the motion of dislocations3 and that due to magneto-mechanical hysteresis.' While many of these effects have been studied, only the magneto-mechanical effect has found extensive practical application. It is the principal source of damping in the current blade material in steam turbines.A magneto-mechanical hysteresis loop is seen in Fig. 1. If an unmagnetized, polycrystalline wire of a material exhibiting magneto-mechanical hysteresis, such as an Fe-14 pct A1 alloy, is twisted in torsion, a relation between shear stress and shear strain y is observed as indicated. The stress-strain curve does not follow Hooke's law -dashed line. Instead, the strain y increases nonlinearly and partly irreversibly, due to the motion of ferromagnetic domain walls,* until a critical stress is reached, which in this case is about 3,500 psi. If the applied stress is raised further, the strain appears to increase linearly and reversibly in accordance with Hooke's law, since all domains are now aligned in easy directions of magnetization nearest to the direction of the applied stress, and plastic flow has not yet started noticeably. On removing the applied stress, a remanent shear strain y, is observed, which is related to the irreversible magnetostriction of the material.' The energy dissipated in the material during a stress-strain cycle is proportional to the critical stress t, and the remanent magnetostrictive shear strain 7,. The purpose of this investigation was to make a survey of the magneto-mechanical damping of ferro-

Jan 1, 1957

By E. A. Kaarsberg

The electron photomicrographs shown in this paper are of samples of the A.P.I. Reference Clay Minerals Montmorillonite No. 27 and Kaolinite No. 4 and of a shale from Spraberry Oilfield in Texas. These samples are part of a larger collection whose physical properties, composition and internal structure were previously studied by ultra-sonic and X-ray methods. ' Elastic anistropy was indicated in the montmorillonite and shale samples by sound velocity measurements parallel and perpendicular to the bedding. In the montmorillonite the velocities parallel and perpendicular to the bedding were 2.12 and 1.92 km/sec respectively, a difference of about 11%; in the shale the same velocity measurements were 4.18 and 3.75 km/sec, a difference again of about 11%. Within the bedding plane the sound velocity was also found to be independent of direction. The electron photomicrographs of the montmorillonite sample, which are shown in Fig. l(a) and (b), clearly indicate the preferred orientation of the mica-like clay particles parallel to the bedding. In Fig. 2(a) and (b) similar orientation in the shale sample can be seen although not quite as clearly. This is probably because, in addition to the clays illite and chlorite, the shale sample contains grains of quartz, calcite and dolomite which do not as readily show an alignment pattern as the clays do. This suggests that the elastic anisotropy of these two samples is derived from a preferred alignment of component mineral grains which are themselves elastically anisotropic. The bulk elastic properties of these two samples therefore appear to be much like those of mica. Velocity measurements were made on the kaolinite sample in three directions at right angles because no bedding could be discerned in it. The values ob-

Jan 1, 1967

By N McKenzie, F Brodbeck

The North-South Bypass Tunnel is the first project to get underway as part of BrisbaneÆs transport plan, which aims to improve the urban road network. The total length to be excavated is 6.8 km, which includes 4.8 km of driven tunnel and associated road connections. Construction commenced in August 2006 with project completion targeted well before the contractual completion date of October 2010. Due to the local geology, in particular the hard Brisbane tuff and neranleigh-fernvale formation, a combination of tunnel excavation methods are used. The majority of the tunnel is excavated by two tunnel boring machines which have a rate of progress of 16 - 20 m per day in rock having a compressive strength of between 80 and 150 MPa. Ten roadheaders operate at a rate of up to 2 m per day excavating the remaining tunnels, such as ramps, access tunnels, cross passages and merges. The tunnel team are managing the challenges and complexities associated with tunnelling through the hard Brisbane rock. A major challenge arose during the planning of the initial mainline excavation underneath the Royal National Association Showground in Bowen Hills. This section contains low rock cover and historical maps indicate that the showground is located within a former topographic depression (alluvial valley), which a creek once flowed through.Due to traffic merge design requirements, both tunnel boring machine (TBM) and roadheader excavation methods were required to be used in this challenging geological profile. The answer was to stabilise the alluvium above both TBM section tunnels from the surface prior to excavation and to operate the TBM in single shield mode with immediate grouting of annular void from the tail shield. In addition, the roadheader section of tunnel required additional support by spiles and canopy tubes installed from the tunnel face.

Jan 1, 2008

By Lawrence Addicks

THrough the courtesy of Dr. James Douglas I am permitted to give a summary of some of the results obtained in leaching slimes tailings in a series of experiments conducted under my direction at Douglas, Ariz., during the past year. While the test run for which the data are given deals with a particular case, much of the work is general in its application and may therefore be of interest. This work was done upon the ores of the Burro Mountain Copper CO. A description of the geology of the district will be found in the paper by R. E. Somers published in this volume, p. 604. The mineral is pyrite and chalcocite very finely disseminated throughout the gangue and a characteristic of all the ores is the large amount of alumina present. A representative analysis of the particular ore under consideration would be about as follows: Cu, per cent..................... 2.35 S, per cent...................... 3.0 Ag, ounces per ton.............. 0.05 CaO, per cent.................. 0.5 Au............................ None K2O, per cent.................... 4.0 Fe, per cent..................... 1.50 SiO², per cent.................... 70.0 Alz²O³, per cent....................13.OO The leaching of the ore direct was early dismissed from consideration for the following reasons: 1. The ore would have to be quite finely crushed to liberate the mineral for leaching; concentrating after crushing would cost but a few cents a ton; and a higher total reeovery would result from leaching tailings rather than ore. 2. Rough concentration would yield a suitable material for roasting to make sulphur dioxide or sulphuric acid in connection with the leaching scheme. 3. Such a program put the question of cost vs. recovery on a basis where flotation and discarding of tailings were directly comparable. Concentrating experiments already available indicated that the tail-

Jan 1, 1916

By A. M. Saddler, G. R. M. Del Giudice, Arthur F. Taggart, M. Hassialis

Flotation of sulphide minerals and native metals is no longer a practical difficulty. The underlying scientific principles of the method, although not explored in anything like complete detail, have been formulated with sufficient breadth so that the direction of attack on any specific case is clearly indicated. It has been known since the earliest days of flotation that certain of the nonsulphide nonmetal minerals—e.g., sulphur and graphite—would respond to flotation by oils as sulphides do; therefore they have been grouped with sulphides in many patents. But since the development of the chemical theory of collection,1,2,3 this similarity in action has been one of the facts cited in disproof of the theory by opponents of the hypothesis.4,5,6 Air levitation† of certain oxidized minerals, both metalliferous‡ and nonmetalliferous, and separation thereby from other oxidized minerals, is a recent development in practice, although the discovery of the method dates back 17 years7 This paper presents evidence that the principles underlying the air levita-tion of the nonsulphide nonmetal minerals are the same as those utilized in the flotation of the sulphides and native metals. It will be apparent immediately to anyone with knowledge of mineral concentration that separation of air-levitated minerals in water from minerals not so levitated is a simple matter of water-gravity concentration, the separating device employed depending solely upon the size of the particles treated and the buoyancy differences effected by the levita-tion. The usual separating means employed are: (1) a flotation machine for fine, slimy and for well aerated granular material; (2) shaking tables for granular less aerated material. By using large quantities of oil, it is possible to form substantially air-free oil-bound masses or granules of nonsiliceous minerals and to

Jan 1, 1939

By C. C. Harris

An analytical solution of the integro-differential equation of batch grinding is proposed as a first appoximation to the xYt surface. The size distribution equation (xY plane) is a three parameter equation previously suggested. Possible refinements are outlined. Comminution kinetics research is presently following several related courses. Some are equivalent, in that they represent different ways of viewing the same facet of the problem, though the entire endeavor cannot be described as being completely integrated. The purpose of this note is to propose and discuss a framework into which the various approaches might be fitted. This must clearly be founded upon an analysis of the xYt surface.' (See also Fig. 1 of Reference 26.) The investigations referred to above comprise mainly researches into the following: (1) The kinetics of the creation of the finer sizes during relatively small grinding times. This is the Fahrenwald-Arbiter-Bhrany 2-3 approach which leads to equations equivalent to a special case of the charles4 relationship. It emerges that initial production of fines follow essentially zero order* kinetics. (2) Disappearance kinetics of the coarser fractions. This appears to be a first order relationship.5-6 (3) Prediction of the xYt surface via the selection and breakage functions utilizing computer-programmed or approximate solutions of the integro-differential equation of batch grinding.5,8-17 A recent discussion by Mika et al.5 references the relevant literature up to about 1966. In addition to these main-stream researches there is some work on the minor topic of extremely long grinding time considered as a limiting case.18-19 The field is supported by investigations into the size distribution of fragments produced by breakage processes, some of this work being most valuably statistical-mechanical in nature.20-25 Better fitting equations, however, are obtained by statistical and curve-fitting methods.26 This

Jan 1, 1969

By L. L. Wyman

THE resultant embrittlement caused by the exposure of oxygen-bearing copper when hot and exposed to reducing gases has been the subject of many studies.1 Little attention, however, has been given to the possible embrittling effects due to atmospheres or conditions that under some circumstances might be the source of a reducing gas. At rather infrequent intervals there occur reports of copper becoming embrittled during normal annealing cycles in commercial steam-atmos-hered furnaces such as customarily are used for this operation. As might be expected, several other factors exist-such as oil, dirt on the wire, or in the furnace, or metallic surface contacts that might produce reducing gases and be the source of the trouble. However, in consider-ation of the statement made by Ruder,2 it would seem that under some conditions steam itself might prove to be the source of trouble. A consideration of the amount of the dissociation of water vapor up to temperatures of the melting point of copper shows that' the amount of hydrogen that could come from this source is far too minute to account for any embrittlement. What such information does not tell is what will happen at the surface of copper when subjected to steam at elevated temperatures, for entirely different conditions may persist, which would account for Ruder's observation. Furthermore, there are no data as to what might happen at the surfaces of other materials present, the result-ant of which might affect the condition of the copper present. For this reason, it was decided to make a series of experiments com-parable to those previously conducted by the writer,1 which would clarify the effect of the steam on copper, and in copper in the presence of steel.

Jan 1, 1940

By W. H. Schacht

IN THE Lake Superior District, the air indoors must be heated continuously during eight months of the year and occasionally during the remaining months. Incident with mining in this district, therefore, there is need for heating many of the buildings connected with these operations. In addition to the mine buildings, that is, shops, engine, houses, offices, change houses, etc., such public buildings as schools, library, and theater, when close to the mines, are often supplied from the mine heating mains. At the Copper Range Company's mines, Champion, Trimountain and Baltic, the heating surface thus supplied from the mine mains is over 50,000 sq. ft. (4645 sq. m.) which requires a steam consumption, at times, of 18,000 lb. (8165 kg.) per hour, or the equivalent of a rate of over 50 tons of coal per day (were live steam used). This figure is based on a consumption of 1/3 lb. per square foot of heating surface during the coldest weather, and provided the system is not wasting steam by blowing it to the atmosphere or into the return line on account of leaky traps, which so often is the case. Under the latter conditions, steam consumptions of three to four times the above rate are not uncommon. This shows that the cost of heating is of enough importance to be given serious consideration, especially at this time of rising prices of fuel. The power and heating value of exhaust steam are appreciated by most engineers, and its application for such purposes is general. At our stamp mills, the exhaust from the stamps is used to operate low-pressure turbines, thus reducing the former water rate per horsepower developed by more than 50 per cent.

Jan 8, 1920

By T. Könighofer

Processing of copper-cobalt orebodies in Africa?s Copper Belt has received much recent attention with various flowsheet options being developed specifically for the refining of cobalt. The upfront leach and copper refining routes are well understood whereas the refining of cobalt is more complex, requiring numerous impurity removal steps to produce high purity metal. This paper describes an investigation into one of the possible processing steps in the refining of cobalt, namely, cobalt solvent extraction. The paper emphasizes the importance of upstream impurity removal to achieve the required cobalt solvent extraction feed composition. 18% (v/v) Cyanex 272 in an aliphatic diluents is used as the organic phase. The pH profiles in the various stages are evaluated in order to obtain a raffinate containing <10mg/l cobalt and with a low magnesium content reporting to the stripping section. The pH profile is also used to minimize the impurity deportment to the cobalt electrolyte. The effect of adding a pre-neutralization stage before feeding the organic phase to the extraction circuit is investigated. Zinc build-up in the stripping stages is also looked at. It is recommended for the purpose of this study that four extraction stages at an O:A ratio of 1 with a pH profile from 4.9 to 5.7 be employed. The pH is controlled with 40g/l NaOH. A pre-neutralization stage is required, where the organic phase is contacted with 10 M NaOH. Two scrubbing stages are recommended at an O:A ratio of 40, using the cobalt electrowinning advance electrolyte as the scrub liquor. Three strip stages are to be employed at an O:A ratio of 0.67.

Jan 1, 2009