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By H. A. Baumann

Experimental data are presented showing the influence of size consist and firing rate upon the performance of bituminous coal-fired, single-retort, industrial underfeed stokers. Size segregation, degradation, and distributor data are also included. The conclusion is reached that size consist of the fuel as fired, is a critical factor in its performance on this class of equipment.

Jan 1, 1950

Prior to World War I, zinc was universally made by the distillation process. Small plants were operated at Cockle Creek, N.S.W., and Port Pirie, S.A. Then the electrolytic process was developed at Great Falls, Mont., in 1915 and at Trail. B.C. encouraging the Broken Hill companies to investigate the process. England's war-time need for zinc gave impetus to the development, and the site at Risdon, Tasmania, coincided with the developing hydro-electric power there. Experimental work was begun in 1917 by a proprietary company formed and owned by Broken Hill interests. Then in 1920, the principal features of the process having been established, a public company. Electrolytic Zinc Company of Australasia Ltd. was formed, now known as E.Z. Industries Ltd.

Jan 10, 1964

By AIME AIME

EVEN though most of the program of the joint meeting at Easton, Pa., on Oct. 30 to Nov. 1. was devoted to the interests of combustion engineers rather than to coal-mining engineers, nevertheless the A.I.M.E. Coal Division was well represented, with 83, or close to one third of those in attendance giving this as their affiliation. The fuels division of the American Society of Mechanical Engineers had 108 representatives, and an equal number reported no society affiliation. Added to the men's total registration was that of some twenty ladies so the total attendance was in the neighborhood of 325, exceeding that of the last two joint meetings, at Birmingham and Columbus, and equaling the 1938 crowd at Chicago.

Jan 1, 1941

By R. S. Silo

A new process for leaching oxidized copper ore (CuO) is presented. Its principle advantage is that it requires low cost raw materials. For large operations the only materials used are sodium chloride (NaCl) and calcium carbonate (CaCO3). In those operations of medium size, sulfur, which is abundant in the North of Chile, is used. However the process may also be applied to small copper plants provided low cost sulfuric acid is available as a substitute for sulfur. That is, it may be applied to those small capacity plants where large additional installations for the regeneration of the leaching solution are not needed. The method is comprised of six stages, namely: Crushing, Leaching, Washing of the Solution, Precipitation, Regeneration of the Leaching Solution, and Fusion. A flow diagram for this process in a large or medium-sized plant is given. LEACHING This process requires hydrochloric acid as the leaching solution for treating copper ores. This is easily produced from sulfuric acid and sodium chloride as follows: A small excess of NaCl is advisable to avoid the presence of free sulfuric acid. The experiments reported here were performed with 36 grams of HC1 per liter of solution to obtain a free acidity equivalent to 50 gpl of H2SO4 (the usual leaching solution concentration). Hydrochloric acid leaching may be done by either of the usual methods; i.e. percolation or agitation. The method selected depends on the characteristics of the ore. No matter which method is chosen, low pressure air can be used either as an air lift for circulation of the solution, or for agitation of the pulp with "Pachuca" tanks. In either case, there are no problems with respect to oxidation. Leaching by agitation produces good recovery; but at times, the problem of high consumption of leaching solution or the overproduction of grinding slimes which interfere with contact between phases negates this advantage. The percolation method was used in this study. Percolation took place in four 15-liter containers, 11 1/2 in. diam. by 12 in. height, having hemispheric bottoms. Each container was fitted with a wooden bottom having 1/4 in- holes. The air lift was a 3/4 in. plastic tube 10 in. high. Air at 6 psi was supplied from a rotating laboratory compressor. 10 kg of ore were charged to the container and counter-current leaching was used. The leaching solutions were fed through the center pipe in order to use the ascending solutions to reject the air in the charge. The solution circulated through the air lift in order to facilitate the movement according to the increase in density produced by the reaction between the phases present. Specific observations made in this report cannot be generalized because the leaching characteristics are dependent on the nature of the ore used, the method of leaching, and the production of primary or secondary slimes while crushing or leaching.

Jan 1, 1967

By S. A. Mersol, C. T. Lynch, F. W. Vahldiek

The microhardness of single crystals of tungsten disilicide has been investigated by the Knoop method. The average random room-temperature hardness of the WSi, matrix was 1350 kg per sq mm. Hardness crnisotropy was noted with respect to plane and indenter orientation as determined by single-crq.stal X-rny studies. Annealing at 1600" and 1800°C decreased the average hardness to 1310 and 1230 kg per sq tnm, respectively, and produced a second phase identified by X-ray diffraction and electron-microprobe analysis to be wSio.7. Ball-impact experiwzents produced rosettes at 850°C. Optical and electron microscopy showed evidence of slip and cross slip and twinning produced by microhardness indentations. Prismatic (100), [001] slip was found and cor~elated with hardness data. THE present study was undertaken to investigate the hardness anisotropy of as-grown and annealed single crystals of tungsten disilicide. The existence of the silicide WSiz in the W-Si system has been well-established and its structure thoroughly investigated zachariasen2 found WSi, to have a tetragonal C type of structure, similar to that of MoSi, with lattice parameters a = 3.212A, Kieffer et al. studied the W-Si system and measured the density and microhardness (at a 100-g load) of both polycrystalline WSi, and WSi,.,. The values found were 9.25 g per cu cm and 1090 kg per sq mm for WSi,, and 12.21 per cu cm and 770 kg per sq mm for WSi0.7, respectively. According to Samsonov et a1.5 the microhardness of polycrystalline WSi2 is 1430 kg per sq mm (at a 120-g load). EXPERIMENTAL The WSi, single-crystal boules investigated in this paper were grown by a Verneuil-type process using an electric arc by the Linde Division of the Union Carbide Corp.6 The largest specimens were 8 mm in diameter by 16 mm long. The crystals had an average density of 9.01 g per cu cm with a tungsten • silicon content of 99.9 wt pct. The major impurities were: 87 ppm O, 41 ppm N. 54 pprn C, 500 ppm Zr, 50 ppm Na, and 50 ppm Mn. The crystals were silicon-poor, the average silicon content being 22.20 pct (stoichiometric value is 23.40 pct), and tungsten-rich, the average tungsten content being 77.70 pct (stoichiometric value is 76.60 pct). As-received single crystals were ground and analyzed by powder X-ray diffraction technique using Cu Ka radiation. Laue and layer line rotation patterns were obtained on cleaved sections of WSi, single crystals. Electron-microprobe traverses of representative crystals were done using a Phillips-AMR electron microanalyzer. Carbon replicas were used to prepare electron micrographs. This work was done with a JEM-6A electron microscope. Prior to the metallographic examination, the specimens were mounted in Lucite and then polished for short times on polishing wheels using 9-, 3-, and 1-p diamond-grade pastes. Finally they were fine-polished with Linde A powder for 24 hr on a Syntron vibratory polisher. The samples were etched with 4H 2 O:1HF:2HNO3, which is a medium fast-acting etchant. The combination 1HF:2HNO3:5 lactic acid is also a satisfactory etchant. Annealing runs for selected specimens were made at 1600" and 1800°C for 3 hr at 1.0 to 3.0 x 10-5 mm Hg. A Brew tantalum resistance furnace with WSi2 powder for setters was used. The WSi2 powder was the same as that used for the crystal growth. Temperatures were measured with a calibrated W, W-26 pct Re thermocouple and a microoptical pyrometer. Powder X-ray diffraction, emission spectrographic, and electron-microprobe analyses were done after the annealing runs. For microhardness measurements a Tukon Microhardness Tester Type FB with a Knoop indenter was used. Although measurements were taken at loads ranging from 25 to 1000 g, the 100-g load was chosen as the standard load. All measurements were taken at room temperature. Only indentations of cracking classes 1 and 2 were considered.' DISCUSSION OF RESULTS Powder X-ray diffraction analysis showed the as-received crystals to be single-phase WSi2. Laue and layer line rotation patterns obtained on cleaved sections of WSi2 single crystals proved them to be tetragonal WS 2 2 The results also indicated that the c axis of the crystal was oriented parallel to the boule or growth axis. Electron-microprobe traverses across the matrix of the as-grown crystals showed them to be homogeneous WSi,. Optical and electron microscopy of etched crystals, however, revealed that they contained minute amounts of the "golden" and the "blue" second phases as opposed to the "white" or WSi2 phase. These two second phases were concentrated in inclusion and etch-pit

Jan 1, 1965

By Roland Blanchard

Recent discovery at Mount Isa of copper mineralization in commercial amount at a depth of 1000 ft., coinciding with downward termination of ore at about the same depth within the larger silver-lead-zinc lenses that have been the standby of Mount Isa's production to date, has been cited as an example in support of mineral zoning. A previous paper by the author and Graham Hall1 furnished a detailed description of the geology of the ore at Mount Isa as exposed up to that time, but necessarily dealt mainly with the silver-lead-zinc mineralization. Most of the geologic facts that constitute the first half of the present paper were set forth in the previous one in much greater detail, with full supporting evidence for the facts cited. The large amount of underground development (approximately 20 miles) and the extensive exploration carried out by diamond drilling (100,000 ft.) at Mount Isa, added to extensive microscope work conducted over a period of years, both by the company's staff and by others, had made possible the calculation within fairly close limits of mineralogical composition of the principal mineralized block of ground down to 1000-ft. depth, and had established closely the mineral succession, with reasons for deposition of the various minerals in the patterns now occupied by them. The geologic facts as outlined in the previous paper remain as stated; but because substantial development within the new copper ore body and further exploratory diamond drilling within the new silver-lead-zinc area (Racecourse) have taken place since that paper was written, statements and figures relating to those two areas in the present paper supersede those furnished in the previous one. The recent work likewise has established more clearly the paragenetic relationship between the chalco-pyrite and galena. Evidence confirming the relationship is furnished in the present paper. The facts of ore occurrence at Mount Isa show Accepted Zonal Succession Silver sulphantimonides Galena Sphalerite Tetrahedrite Arsenical sulphides Chalcopyrite Pyrrhotite Mount Isa Succession I In the main but prob- Silver sulphantimonides ably not wholly Tetrahedrite I contemporaneous Galena Pyrrhotite Sphalerite Arsenical sulphides They show further: (I) that instead of the silver-lead minerals yielding to increased zinc in depth, the zinc yields to increased silver-lead; (2) no dovetailing of the silver-lead-zinc sulphides into chalcopyrite takes place; (3) despite the large amount of pyrrhotite deposited in the district (estimated at upward of 100,000,000 tons), its deposition took place under moderately low temperature conditions; (4) no evidence has been found for increase in temperature of deposition, with depth, to deepest exploration in ore (1475 ft.). The anomalous condition at Mount Jsa, both as to the unorthodox mineral succession and the largely unorthodox patteru of mineral distribution, is explained in the present paper,

Jan 1, 1949

By Roland Blanchard

Recent discovery at Mount Isa of copper mineralization in commercial amount at a depth of 1000 ft., coinciding with downward termination of ore at about the same depth within the larger silver-lead-zinc lenses that have been the standby of Mount Isa's production to date, has been cited as an example in support of mineral zoning. A previous paper by the author and Graham Hall1 furnished a detailed description of the geology of the ore at Mount Isa as exposed up to that time, but necessarily dealt mainly with the silver-lead-zinc mineralization. Most of the geologic facts that constitute the first half of the present paper were set forth in the previous one in much greater detail, with full supporting evidence for the facts cited. The large amount of underground development (approximately 20 miles) and the extensive exploration carried out by diamond drilling (100,000 ft.) at Mount Isa, added to extensive microscope work conducted over a period of years, both by the company's staff and by others, had made possible the calculation within fairly close limits of mineralogical composition of the principal mineralized block of ground down to 1000-ft. depth, and had established closely the mineral succession, with reasons for deposition of the various minerals in the patterns now occupied by them. The geologic facts as outlined in the previous paper remain as stated; but because substantial development within the new copper ore body and further exploratory diamond drilling within the new silver-lead-zinc area (Racecourse) have taken place since that paper was written, statements and figures relating to those two areas in the present paper supersede those furnished in the previous one. The recent work likewise has established more clearly the paragenetic relationship between the chalco-pyrite and galena. Evidence confirming the relationship is furnished in the present paper. The facts of ore occurrence at Mount Isa show Accepted Zonal Succession Silver sulphantimonides Galena Sphalerite Tetrahedrite Arsenical sulphides Chalcopyrite Pyrrhotite Mount Isa Succession I In the main but prob- Silver sulphantimonides ably not wholly Tetrahedrite I contemporaneous Galena Pyrrhotite Sphalerite Arsenical sulphides They show further: (I) that instead of the silver-lead minerals yielding to increased zinc in depth, the zinc yields to increased silver-lead; (2) no dovetailing of the silver-lead-zinc sulphides into chalcopyrite takes place; (3) despite the large amount of pyrrhotite deposited in the district (estimated at upward of 100,000,000 tons), its deposition took place under moderately low temperature conditions; (4) no evidence has been found for increase in temperature of deposition, with depth, to deepest exploration in ore (1475 ft.). The anomalous condition at Mount Jsa, both as to the unorthodox mineral succession and the largely unorthodox patteru of mineral distribution, is explained in the present paper,

Jan 1, 1949

By E. A. Gulbransen, K. F. Andrew

In a recent communication14 we have reported on the kinetics of the reactions of zirconium with O2, N2 and H2 as a function of the time, temperature and pressure variables. A systematic study was made and the results correlated with fundamental theories of gas-metal reactions. This paper will present a similar study for titanium. Titanium and zirconium are members of the IV group of the periodic table and possess many similar physical and chemical properties as a result of their similar electronic configuration for the outer electrons. The two metals are relatively inert to both gas and liquid phase corrosion at room temperature. However, at moderate temperatures the metals become active and react readily with the common gases including O2, N2 and H2 which are of interest in this study. A study of the kinetics of these gas-metal reactions is of interest for three reasons: (1) to understand the rate of reaction of titanium and its role in the behavior of high temperature alloys; (2) to understand the practical difficulties of the reduction, refining and working of titanium; and (3) to correlate the data with fundamental theories of gas-metal reactions and crystal structure predictions. Literature Survey Several review papers8 and books4243 exist on the preparation and properties of titanium and its alloys. THE METAL Titanium has, at room temperature, a hexagonal lattice of the zinc type. Hagg19 gives a value of 2.953A for the (a) axis, a value of 4.729 for the (c) axis and a density of 4.427 at 20°C. Burgers and Jacobs6 have observed the transformation of the hexagonal to the body-centered cubic structure at 880°C and have established a value of 3.31 for the cube edge and a density of 4.31. TITANIUM-OXYGEN Carpenter and Reavell6 using a pressure change method have studied the reaction at temperatures of 742° and 1000°C and for a pressure of one-fifth of an atmosphere. The probabilities for reaction are calculated from kinetic theory and they report a value of 10-5 for O2 at 1000°C and 10-6 at 740°C. The titanium-oxygen system has been investigated by Ehrlich.10,11 Five phases are observed. Between (TiO2 and TiO1.90) an alpha-phase, consisting ofarutile lattice, is found. A beta-phase is observed between (TiO1.80 and TiO1.70). A gamma-phase is homogeneous between (TiO1.56 and TiO1.46) and has a structure of the corundum type. The delta-phase exists between TiO1.25 and TiO0.6 and has a sodium chloride structure. From TiO0.42 to Ti the metal structure is observed. The surface oxide films have been studied by Hickman and Gulbransen.20 The rutile structure is observed in the temperature range studied, 300 to 700°C. Three crystalline modifications of TiO2 exist: rutile and anatase which are tetragonal and brookite which has an orthorhombic structure. Anatase is reported36 to exist in two forms: I and II. Anatase II changes to anatase I at 642°C. Anatase I is stable up to 915°C where rutile becomes the stable modification. At 1300°C rutile transforms to brookite which melts at 1900°C. The monoxide, TiO, may be prepared from the dioxide by high temperature reduction with carbon or magnesium. Its melting point is 1750°C. TITANIUM-NITROGEN Carpenter and Reavell6 report that at 1000°C a linear rate law is observed. The probability of reaction is given as 10-8 at 1000°C. Fast12 has studied the solubility of nitrogen and its effect on the mechanical properties of the metal. The crystal structure of TiN has been shown by several workers2'21'44 to follow the sodium chloride structure. However, the calculated density is found to differ from the pycnometric value. This is studied by Brager3,4 in detail. He has suggested that the titanium sites in the lattice are only partially filled at low temperatures. As the temperature of preparation is raised the vacant sites become occupied which expands the lattice and increases the hardness and density. An (a) value of 4.22Å is given for room temperature. TITANIUM-HYDROGEN The solubility and the crystal structures observed in this system have been reviewed in a recent book by Smith.40

Jan 1, 1950

By Bernard Kopelman

THE particle size of tungsten metal powder used to make tungsten wire for use in radio tubes and incandescent lamps must be closely controlled if the highly desirable feature of nonsagging is to be achieved. Our knowledge of factors affecting the particle size of tungsten powder has been limited by lack of any extensive literature on the subject. There are no publications in the English language discussing this problem in any but the most general terms. In this paper the published experimental information on this subject is reviewed. Based on the published data and some experimental data obtained by the author, a general theory of factors affecting the particle size of tungsten metal powder obtained by reduction of the oxides in hydrogen is offered. The various forms of the tungsten oxides and tungsten metal used in the experiments described were those prepared by com¬mercial processes, so that the experimental results obtained on a laboratory scale would be more directly applicable to actual commercial reduction conditions. The effects of time of reduction, temperature, and concentration of water vapor in the hydrogen were observed by counting microscopically the particle distribution obtained. Such a method is very time-consuming, but the data obtained by this method are more reliable and more fundamental than those obtained by any of the several instruments available for measurement of particle size. REVIEW OF THE LITERATURE Until the year 1912, tungsten powder was prepared commercially by reducing tungstic oxide in the presence of carbon or one of its compounds (such as glycerin or ethylene glycol), usually by firing the mixture in a closed fire-clay crucible. The resultant powder contained about 95 per cent tungsten.1 When reduction of tungsten oxides by H2 was introduced commercially, 2.1 several investigators became concerned with the equilibria between tungsten metal and its several oxides in an atmosphere of hydrogen and water vapor.4-13 While these many investigations were in fair agreement on the equilibria there arose considerable controversy as to the chemical composition of the oxide between W03 and W02, because of very poor agreement on the equilibrium constant of this intermediate oxide reduction reaction. The controversy on this intermediate oxide has been in progress for more than 10o years. Thus Malguti,14 in 1835, decided it was W02.56. In 1857, Riche" proposed the formula W308. Usler,16 in 1865, confirmed the existence of W308 and further proposed W4O11. In 1897, Desi17 agreed upon W308 but also found W5014.

Jan 1, 1946

By I. Tamura, J. O. Brittain, T. Mura

Plain carbon steel in the cold worked or marten-sitic conditions has an internal friction peak at about 250 oC at a frequency of I cps. The influence of substitutional alloying elements on this peak was examined experimentally. The alloys were vacuum melted Co-, Cr-, Mo-, Ni-, and Si-iron (about 3 pct alloying elements), and carburized Si-iron. The internal friction of the alloys in the temperature range 30o to 500 OC was determined by means of a torsion pendulum. The 250 oC peak of the cold-worked alloys was lower in height than that observed in plain C-iron and steel. Carburized Si-iron in the quenched condition had a peak which occurred at a slightly lower temperature than in quenched plain C-steel, but the height of the peak was substantially greater than that found for the same alloy in the cold-worked condition. The activation energy of this peak for martensitic Si-steel was about 35 kcal per mol. ANNEALED a iron has two internal friction peaks due to nitrogen and carbon at 20o and 40o C respectively, at a frequency of 1 cps. If a iron is cold worked, these diffusion peaks become smaller and a new peak appears at about 250o C. The activation energy for the 250o C peak is in the range of 32 to 44 kcal per mol and has an average value of 38 kcal per mo1. It has been experimentally verified that both interstitial solute atoms and dislocations are necessary for the 250o C peak. 3 Wert has also shown that an incubation period precedes the appearance of the 250 C peak.4 With regard to quenched martensitic steel, Ke et al.596 observed two peaks at around 130o and 250o C. They conjectured that the 250o C peak in martensite was due to the same mechanism as the 250°C peak in cold worked a iron, and the 130°C peak was due to the nature of tempered martensite. They did not report the activation energy for these peaks. Chernikova7 found only one peak at about 200° C in tempered martensite. In a previous paperS we reported an activation energy of approximately 40 kcal per mol for the 250° C peak in plain carbon martensitic steels. Ichiyama8 found the activation energy to be about 36 kcal per mol for the 250° C internal friction peak in steels in the martensitic condition. The present authors proposed a theory for the 250°C peak for cold worked and quenched iron and steel.= The theory for the peak is based upon the addition of a strain-energy term to the free energy for the formation of a carbide precipitate due to the presence of a disclocation. The model employed for the relaxation process consists of the growth and solution of a carbide precipitate of critical size as a consequence of an oscillating dislocation. In this report, the influence of substitutional alloy ing elements on the 250° C peak is examined and the experimental results are discussed in terms of our theory for the peak. Most of the experimental work on the alloy steels was confined to the Fe-Si-C alloys.

Jan 1, 1962

By Eugene Coste

Although some of the observers who first paid especial attention to the occurrences of oil and gas in the strata (such as Hunt in 1859, Andrews in 1861; Winchell in 1865, Mendelejeff in 1876, Höfer in 1876, Minshall in 1881, and I. C. White in 1883) seem to have been impressed with the fact that oil and gas deposits were connected with the disturbances in the rocks caused by their upheavalll yet, with the exception of Mendelejeff, and possibly Andrews, these observers do not appear to have understood what is really the one essential factor in the occurrence of oil and gas in the strata: viz., the faulting, uplifting, fracturing, fis-suring, and jointing always accompanying even slight rock disturbances, and in certain districts (petroliferous provinces)2 allowing solfataric hydrocarbon emanations to force their way up from the interior and to reach and impregnate the porous portions of sediments subjected to the disturbances. Instead of this simple explanation to account -for the observed connection between petroleum deposits and rock disturbances, most of the observers mentioned above, and many others who have foliowed them on the same lines since, have entirely reversed the problem. To them, instead of the dissemination of gases from fissures into the sediments, it presented the accumulation and concentration, according to anticlinal or other geologic structures, of oil and gas originally present throughout the whole mass of the strata where they were produced by the decomposition or distillation of organic remains. Whether this important problem involves accumulation from sources within the strata themselves, or infiltration and dissemination from outside sources, may be easily determined if all preconceived ideas are put aside and the established facts only are considered. Physical Facts Sedimentary strata are composed of alternate beds of shales, sandstones, and limestones, most of which are sufficiently close-grained to

Jan 1, 1915

By A. H. Geisler

The correlation of property changes during precipitation with structure has progressed, sometimes rapidly but other times more slowly, since the fundamental discovery of Merica, waltenberg and Scott.1 The predominent factor that hampered the progress has been limitations imposed by the various detection methods. Refiments in x ray diffraction tech-niques and in metallographic methods, which have been extended by the electron microscope, have contributed new information within the last few years. These permit an extension of the theory as proposed by Mehl and Jetter in 1940'2 Now that a sufficient number of alloys has been investigated to establish a general mechanism of the precipitation process, a correlation of the facts into a generally applicable theory of age-hardening is both warranted and desirable. The purpose of the paper is to provide an orderly correlation of the phenomenological facts of precipitation hardening. Speculation 011 mechanism of hardening will be confined to that consistent with existing theories of hardening, Age-hardening accompanies the formation of a new structure, the precipitate, as provided by a11 alloy system ill which solid solubility decreases with decreasing temperature. Upon this premise alone all such systems would be expected to include age-hardenable alloys. Alas, this is not always the case. Few attempts have been made to explain the variable degree of age-hardening among different alloys or to explain the influence of small alloying additions upon the hardening. Dispersion hardening as originally postulated3 is not adequate.* Coherency hardening—the term that will be used to distinguish the properties of a two-phase mixture in the unique and unstable transition state at which the phases are strained into precise atomic registry (continuity or coherency) in planes

Jan 1, 1949

By John Birkinbine

Secretary's Note.—In printing this paper in the present volume, the figures given in the pamphlet edition have been brought more nearly up to date, the product of 1899 being in many instances inserted. Iron-Ore Resources. In a paper presented to the Institute in 1897,* I discussed the iron-resources of the United States as then developed, calling attention to some principal sources upon which other countries depended. The following statement will give a general idea of the amounts, as compiled from the latest official records, of ores won, and metal produced, in the nations which are important contributors to the world's output. Unfortunately these are not all contemporaneous, since in some countries the statistics do not appear until after one or more years. The statement covers not only pig-iron and iron-ore, but also manganese-ore —the manganese mined being principally used in the production of spiegeleisen or ferro-manganese, and these alloys being generally included in the pig-iron output. Table I, which epitomizes the present situation, shows respectively the countries and the quantities of iron-ore and man-

Jan 1, 1901

By R. F. Yap, N. Arbiter, C. C. Harris

A fully-instrumented driving mechanism has been constructed to study the power, aerating and solid suspension characteristics of several laboratory flotation machines. Machines operating over normal flotation speed ranges give substantially constant power numbers in liquid systems indicating that they operate close to fully baffled turbulent flow conditions. Owing to lack of geometrical scaling, power numbers for different sizes of cells of the same make are different. Even larger differences occur between cells of different manufacturers. For a given impeller, varying the tank size did not significantly affect the power consumption. Tank geometry and baffling has a slight effect on power consumption with shrouded impellers. For a given impeller speed, suspension height decreases while power increases with increasing mass of solids in suspension. While power consumption is hardly affected by particle size and clearance between the impeller and tank bottom, the suspension height significantly increases as clearance increases and as particle size decreases. Aeration was found to affect not only power but also the suspension characteristics of the machine. For closely sized particles, drastic sedimentation occurred when a critical value of the air flow number was exceeded. The critical air flow number decreased with increasing particle size. This effect was less marked with a wide particle size range. The self-aerating capacity of flotation machines increases with cell size at a given speed for the same impeller-shroud system, but decreases in the presence of frother and solids. Equations have been established for correlating all of the studied variables. Data taken from the literature were also correlated with these equations. The modern mechanical flotation machine has, over a period of 60 years, displaced other designs to become the dominant type. Once the correct chemical environmental conditions have been established, the major requirement, selective mineral-air adherence, is essentially a function of two operating variables — impeller speed and air rate. The special nature of this dependence is such that in the same apparatus, but under different operating conditions, adherence can be either prevented or destroyed. Another aspect of this observation is that flotation machines though differing in detail to a considerable extent can produce similar metallurgical results. It must be concluded that having determined the correct reagent levels, establishing the correct operating conditions are at least as important as machine design. Since about 1960, after 30 years of fairly stable circumstances, manufacturers have been developing new types of machines whose major feature is emphasis on pulp flow characteristics by virtue of new im-peller-stator designs. As far as can be ascertained, these new designs necessitate radical departures from accepted impeller speed-air rate values. Performance data are still awaited. Flotation machine development has been empirical, as is selection of operating conditions. The purpose of the work at Columbia University has been to elucidate the fundamentals of the subject so that the purely mechanical aspects of the flotation process can be understood in hydrodynamic terms.1-6 Hopefully, this might lead to intelligent selection of a particular machine and its operating conditions for a specific ore based on a minimum of testing, or even to new types of flotation machines. The present investigation is the most comprehensive to date.7,8 Earlier work, which was largely exploratory, has been repeated and extended and employes the most accurate measuring techniques available. Additionally, sufficient hydrodynamic data were obtained under flotation conditions to delineate the relevant operating ranges. Attention has been given to scaling in that several geometrically scaled tanks and impellers have been constructed and tested; it has been pointed out elsewhere that undistorted geometrical scaling rarely pertains in flotation machine design.5 This paper is divided into sections dealing with relevant combinations of the three phases: liquid, air and solid. Summaries of the literature have been given in previous publications2-4 and will not be repeated here. Recently, several reviews of mixing have appeared, which can be usefully referenced.9-11 It is of interest to note that flotation is not included

Jan 1, 1970

By Evan Evans

IT is appropriate to evaluate 1947 in review as a year of a peacetime record production of about 676,000,000 tons of coal (anthracite and bituminous), closely approaching the extraordinary wartime output in 1944. Considering the general price-wage inflation, it is in point to note that the coal industry sustained the highest wages paid to workers in any major industry, but that coal prices at wholesale levels have risen much less percentage wise than the average for all commodities. The sellers' market continues to prevail. In addition to serving our own country's enormous needs, our coal industry is exporting extraordinary tonnages overseas. This unusual export demand is likely to continue for a while. Moreover, the demand in Europe for American coal mining machinery is a real tribute to the management efficiency of our modern mechanized coal industry. Competitively, the petroleum industry is concerned over its long-term supply, and already a synthetic fuels industry is being publicly advocated. In due time coal and lignite are bound to be

Jan 1, 1948

By D. C. Seidel, M. C. Fuerstenau, R. J. Roman

The existence of a surface charge on the alkali halide salts is shown, and a flotation mechanism involving surface charge and collector solubility is developed. Data suggest that KC1 is positively charged and that NaCl is negatively charged in saturated brines, and that the neutral molecule RNH,Cl is the collector in the amine-KC1 system, RSO, is the collector in the sulfonate-KC1 system, and RCOONa) is the collector in the fatty acid-NaCl system. A number of hypotheses have been advanced to explain the mechanism of soluble salt flotation; one of these involves exchange between collector ions and surface cations. With this mechanism Gaudin1 suggested that the differences in flotability of halite and sylvite with primary amines are due to the ionic size of the RNH;, Kt, and Na t ions. Fuerstenau and Fuerstenau expanded this hypothesis to include many other alkali halide salts. Several exceptions to this hypothesis are known. That is, this model does not explain why salts containing the same cation, or why salts of different degrees of hydration, respond differently to flotation. For example, why NaI is floated with an amine whereas NaI .2H,O is not. Further, no correlation between ionic size and flotation response can be made with sulfonate or car-boxylate as collectors. In addition, this hypothesis does not explain the effect of magnesium or lead activation, nor does it offer any explanation of the role of temperature in salt flotation. Rogers and Schulman3 realized some of the inadequacies of the ion exchange mechanism and proposed another mechanism based on the heat of solution of the salts. They concluded that weakly hydrated salts can be floated with alkyl amines and sulfonates, that strongly hydrated salts can be floated with fatty acids, and that excessively hydrated salts cannot be floated at all. Their work was not limited to the al-

Jan 1, 1969

By AIME AIME

THE second meeting of 'the Open-Hearth Committee, 'sub-division of the Iron and Steel Committee of this Institute, was held at the Hotel Cleveland, Cleveland, Ohio; on Oct. 13-15. On Oct: 12, the Open-Hearth Superintendents visited the plants of the Youngstown Sheet and Tube Co. and. the Republic Iron and Steel Co. These men were courteously entertailled by the two companies and every facility for a thorough inspection was furnished. Luncheon was severed at the plant bf the Youngstown Sheet and Tube Co. The meeting was opened Tuesday morning with addresses by J. V. W. Reynders, President of the Institute, and Herbert M. Boylston, Chairman of the Ohio Section of the Institute. E. A. Whitworth, of the Gathmann Engineering Co., presided at the meeting and L. B. Lindeinuth was secretary.

Jan 1, 1925

By Pradeep K. Rohatgi, Clyde M. Adams

An analysis of heal conduction in the freezing of a solution has been performed. The case considered is the semi-infinite mass of solution, bounded by a con-stant-temperature plane with one-dimensional heat flow, Numerical cooling rate and freezing rate distributions hare been calcutated for the particular case of unidirectional freezing of aqueous solutions against. a cold copper chill. The solution at each level parallel to the chill surface is subjected to a spectra of frcezing rates; the freezing rate is inilially lour., passes through a maximum, and then decreases until solidification is camplete. Arange and maximum freeeing rates are inversely proportional to the square of distance from the chill surface. The temperature of the chill surface in contact with the solution remains constant during solidification. Experimentally, it is observed that deudrite sparing increases linearly with distance from the chill surface; in the light of heat -flow analysis this means that the dendrile spacing is imersely proportional to the square root of the maximum freezing rate. SOLIDIFICATION of liquids is accompanied by rejection of latent heat at the solid-liquid interface. The over-all rate of liquid to solid transformation is governed by the rate of heat extraction. Analysis of the heat transfer in the liquid during freezing is important since it determines the freezing rate and resulting structure. A considerable amount of work has been done on metallic systems since solidification is frequently a major step in processing metals. Unidirectional freezing from heat sinks has been treated by several investigators.1-4 Much of the work has been limited to the simpler case of substances such as pure metals which freeze isothermally at a unique transformation temperature. In this case the thickness of the solid zone y, next to a chill surface. is a parabolic function of the time. 8. where a and b are constants. Eq. |1| is a close approximation giving the progress of solidification for the case in which there is a small but finite thermal contact resistance at the interface between the freezing liquid and the chill.' It has been used with some success in connection with large steel ingots4 when the therma1 contact resistance is negligibly small (as is the case when water is brought into contact with the metal chill). The constant, b. becomes zero and Eq. [l] is then exact. even when the thermal properties of the chill and the freezing liquid depend on temperature. Analysis of unidirectional solidification of solutions is more complicated since the latent heat is evolved over a range of temperatures. Next to the all-solid zone in contact with the chill surface there is a solid plus liquid zone in which solidification takes place. Although the equations presented are considered quite general the numerical and experimental results are for freezing of aqueous solutions from a copper chill. I) EXPERIMENTAL PROCEDURE Solutions of potassium chloride, sodium chloride. and lithium chloride have been used. These solutions form a eutectic: a typical phase diagram is shown in Fig. 1. A solution at its liquid us temperature is poured into a tygon tube mounted on a relatively large copper chill. The chill is immersed in a freezing mixture of dry ice and acetone at -70°C. A thermocouple connected to a high-speed recorder was mounted near the top of the chill to measure the fluctuation in the temperature of chill surface in contact with the solution. In this system the progress of solidification can be visually observed through the tygon tube. After the specimens freeze to a desired height they are removed from the copper chill and stripped from the tygon tube. Longitudinal and transverse sections are cut from the specimen for micrographic examination. Specimens in the form of a thin slice are mounted on a transparent glass slide by freezing small drops of water around the periphery. They are then polished on a series of emery papers; the final finishing is done on a soft tissue paper. A Leitz Biological microscope was used for structural observations; photography was

Jan 1, 1968

By Thomas V. Falkie

Mining and exploration, in the year 1971, can be characterized as a year of politics and the beginning of an era of legislation. Certainly the activities of our state and federal lawmakers and international politicians over-shadowed technical developments, which are outlined in the following pages. The nationalization of the Chilean copper industry was the most far-reaching event of the year. Not only will it have an effect on international metal trade, but the nationalization will also affect the major mining companies in such a way as to cause strategic, managerial and technical adjustments in metal mining and exploration efforts in other parts of the world.

Jan 2, 1972

By R. F. Sheldon

The discovery of the Carlin deposit was the result of discriminating geologic research and prospecting devoted to the objective of finding a gold deposit that could be mined by open pit methods. By the late 1950s, Newmont Mining Corp. was becoming increasingly concerned about the trend of rapidly rising underground mining costs unless bulk mining methods could be applied. The desirability of finding an open-pittable gold deposit was apparent. The attention of Newmont geologists was directed to Nevada by the publication of two papers: "Paleozoic rocks in North-central Nevada" (1958) and "Alinements of Mining Districts in North-central Nevada" (1960), both authored or co-authored by Ralph J. Roberts of the United States Geological Survey. John Livermore, geologist of Newmont Exploration Ltd., attended a talk given by Roberts in Ely, Nevada in the summer of 1961. These papers and the address by Roberts gave details concerning the Roberts Mountain overthrust, a 483 km (300-mile) long, shallowdipping fault which pushed clastic and volcanic rocks of early and middle Paleozoic age eastward over younger marine formations. Subsequent uplift and doming with consequent erosion had locally removed the upper plate strata exposing windows of lower plate carbonate rocks. Roberts noted that the principal mineral deposits of the region, including gold, were associated with these windows which exhibited a preferred alinement. In the summer and fall of 1961 Newmont's exploration geologists John Livermore and J. Alan Coope began a systematic examination of gold occurrences associated with these windows, aided by further discussion with geologists of the US Geological Survey. Attention was directed to the Lynn and Carlin windows, particularly to those formations lying immediately above and below the Roberts Mountain fault. It was appreciated at the time that many of the gold occurrences in the region were unusual in that no colours were obtained even when panning high grade samples. A large number of rock samples were collected and analysed using fire assaying procedures, and background values for gold were established. This systematic rock sampling resulted in the identification of a distinct area of anomalous gold values, and a block of claims was staked in late October, 1961. These claims, plus an adjoining optioned 32.4 ha (80 acres) of ground, cover the main area of the present Carlin gold mine. Prior to snowfall that winter, one of the bulldozed assessment pits required to establish a claim's discovery exposed 24 m (80 ft) of mineralization assaying 0.007 kg/t (0.22 oz per st) gold. In the spring of 1962 a program of trenching, sampling, and geological mapping followed by rotary drilling was underway. Other properties in the area were acquired. The generally undistinguished nature of the dolomitic siltstones and silty dolomitic limestones hosting the micron-sized gold particles, coupled with the lack of visually associated guide minerals, made identification of the gold bearing areas very difficult. The entire drill column had to be assayed to ensure that values were not overlooked, as very often sections that might be assumed to be waste turned out to be high grade. On September 10, 1962 a high grade intersection of 24 m (80 ft) assaying over 0.03 kg/t (1 oz per st) gold was encountered in the third hole drilled. An expanded program of both rotary and diamond drilling led to the further delineation of the ore body. By December 1963, the exploration program had established an initial reserve of 10 Mt (11 million st) grading 0.01 kg/t (0.32 oz per st) gold. A 1.8 kt/d (2,000 stpd) processing plant was constructed and the first gold bullion was poured in May, 1965, just two years and eight months after the discovery hole was drilled. REFERENCES Roberts, R.J., Holz, P.E., Gilluly, J., and Ferguson, H.G., 1958, "Paleozoic Rocks in North-central Nevada," Bulletin American Association of Petroleum Geologists, Vol. 42, No. 12. Roberts, R.J., 1960, "Alinements of Mining Districts in North-central Nevada," Professional Paper 400-B, US Geological Survey, Article 9.

Jan 1, 1985