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By D. F. Liub, Z. Y. Liu, W. Y. Xue, Y. F. Shenb, Y. D. Wang

"The microstructure characteristics and deformation behavior of ultrafme grained (UFO) 304SS fabricated by accumulative rolling and armealing have been investigated by means of tensile tests, electron-backscatter-diffraction (EBSD) and transmission electron microscopy (TEM) techniques. The volume fraction of martensite phase decreases with increasing armealing temperature. In the grain sizes ranging from 300 nm to 10 µm, the strength held Hall-Petch relationship. The sample with an average grain size of 300 nm exhibited extra high yield strength of 1700 MPa and a tensile strength of 1780 MPa, while the elongation retains 12%. The limited uniform elongation in the UFO materials could be explained in terms of plastic instability. Very interestingly, for the bulk material with an average grain size of 1.200 µm, the high yield strength and uniform elongation were simultaneously achieved to be as 1000 MPa and 18%, respectively.IntroductionUltra-high strengths have been achieved in elemental metals by employing heavy plastic deformation, or by creating ultra-fine-grained (UFO) structure. Here UFO materials are defined as polycrystalline solids with property-controlling microstructural features below the 1 µm level. Typical processing routes include severe plastic deformation (SPD) [1, 2], which decomposes the grains through dislocation accumulation and reorganization (polygonization). Several different kinds of SPD process for bulk materials are typically as equal-charmel angular pressing (ECAP) [3], high-pressure torsion (HPT) [4] and accumulative roll-bonding (ARB) [5]. One of the main motivations for such a push for the very small grain sizes stems from the expectation of unprecedented mechanical strength, as predicted by the well-known Hall-Petch relationship that projects a continuous rise of strength with decreasing grain size [6]. However, these ultra-high strength metals no longer have the high ductility typical of their conventional coarse-grained counterparts, because the undesirable inhomogeneous deformation on the microstructure level can lead to the early onset of failure, severely limiting the useful ductility [2]. Recently, the interesting strategies have been performed to increasing simultaneously the ductility and strength ofUFG pure copper and nanostructured alloys by Zhao et al [7, 8]. In a pure copper, a high ductility has been achieved without sacrificing strength by introducing a high density of pre-existing twins and a large fraction of high-angle grain boundaries. Their encouraging results trigger our motivation to obtain high strength and ductility from the commercially bulk material."

Jan 1, 2013

By Nathaniel Arbiter, Brij M. Moudgil

Separating oil shale from waste material or into high- and low-grade fractions can have a major economic influence on the surface retorting process. Different shale rock components vary significantly in physical and surface chemical properties, such as specific gravity, color, and water wettability. Various techniques that use the differences in one or more of these properties have been proposed to preconcentrate oil shale before retorting. This article discusses some proposed techniques, such as gravity separation, sorting, and froth flotation. Retorting oil shale is the most common method for recovering oil from the rock. This process is accomplished either underground (in situ) or above ground (ex-situ or surface retorting). Both techniques have serious limitations, such as low recoveries in the underground method and the ability to process rich shales only in the above ground retorting method. Also, environmental problems are associated with both techniques. Some of these limitations could be overcome if feed to the retorts is of consistent grade. This could be achieved by selecting appropriate sites for in situ retorting and selective mining for surface oil shale retorting. Both of these, however, would have a serious economic impact on shale oil recovery. Obviously, little control can be exercised over preparing feed material in the in situ retorting process, but beneficiation of oil shale could definitely be advantageous in surface retorting, and should have positive influence on the overall economics of recovering oil from the shales. For example, preconcentration of mined shale could result not only in reduced costs for materials handling, but also in waste disposal costs, since waste characteristics before and after the retorting process are significantly different. Upgrading the oil shale might also allow substitution of alternate technology for retorting as well as extend the process to recover oil from marginal deposits. Also, the separated material may become a potential source for recovering other values from shale deposits. Overall, the incentives for preconcentration are to reduce costs and improve thermal efficiency of the recovery process. Oil Shale Properties Important to Preconcentration Oil shale is a carbonaceous rock assaying 5-30% organic material (kerogen) and 70-95% ash-forming minerals. Kerogen is soft, nonbrit¬tle or semi-brittle material, and generally forms a matrix between irregularly distributed mineral grains. Inorganic mineral mat¬ter-quartz, feldspar, dolomite, kaolinite, dawsonite, and nahco-

Jan 9, 1982

By Maria Kuttig, Christian Ruback, Gerhard Tober, Petra Maier

"It has been demonstrated that there is a strong relationship between work hardening with various post heat treatment and cyclic deformation behavior of structural steel S275. This study contributes to a project developing a process for the complex forming of steel, which combines rolling and bending. Due to the complex geometry of the final work piece, the deformation degree varies greatly. The forming temperature, as well as post heat treatruent, influences recrystallization processes in dependence of the local deformation degree, resulting in inhomogeneous microstructure of the work piece, which affects the quasi-static and dynamic properties. Cyclic creep and hardening or softening has been monitored during constant amplitude loading at stresses near fatigue strength in normalized condition. Work hardening, stress relief or recrystallization influence the cyclic deformation behavior and produces cyclic creep effects. Cyclic softening or hardening and creep were observed to occur in parallel. To what extent these properties are noted depends on the deformation degree.IntroductionThis work is part of a research project developing a new process for the three dimensional forming of steel. For the final product the fatigue strength influenced by the forming parameters is very important. Due to its complex geometry, the formed final plate has different deformation degrees. This leads to different recrystallization behavior and heat treatruent will have different effects on the microstructure. The peak deformation degree cp of the plate will be around -0.5 what leads to the analysis using rolling from 22 mm to 13 mm of thickness. The quasi-static material properties are very important for calculating the preliminary design. However, work pieces which are cyclic loaded need fatigue tests to describe the in-service material behavior. [l] For the prediction and to guarantee the wanted life-time of the part cyclic deformation tests are important. [2, p.23-32] When it is assumed that the work piece will only loaded in cyclic tension, fatigue testing will be done from zero to a maximum force value. In preliminary tests this value is the tensile fatigue strength from a Smith diagram. During processing, here forming, work hardening takes place resulting in strengthening. Therefore, in further tests maximum load can be increased to monitor cyclic deformation mechanism in more detail. However, to study cyclic creep and hardening and softening data should be evaluate over sufficient life time and should not fracture too soon."

Jan 1, 2013

By R. W. Nesbitt

The TAG and Broken Spur hydrothermal mounds are located on the Mid Atlantic Ridge (MAR) at 260N and 290N (respectively). Both were initially discovered by exploratory work from surface vessels and both have since been investigated by submersibles. The discovery of TAG resulted from a NOAA Trans-Atlantic Geotraverse (Rona et al. 1975) which fortuitously sampled low temperature materials on the east wall of the MAR rift valley and follow up operations (Rona et al. 1986) located the high temperature (365°C) mound some 5km to the west. In 1994, ODP deep sea drilling (Leg 158) at over 3,500 metres of water recovered core to a depth of 150 m below surface (Herzig et al. 1998) and for the first time allowed a geological interpretation of an active mound. The Broken Spur mound was accidentally discovered in 1993 when sulphide fragments were observed on a deep-sea towed camera system (Murton 1993). Later that year, exploratory submersible dives by Alvin located the hydrothermal field and the area was again explored by submersible in 1994 and 1997. Despite the amount of work carried out, our geological understanding of the MAR mounds is limited. Much effort has gone into measuring fluid chemistry whilst practical difficulties have inhibited good geological mapping of the sulphide areas. It is clear from both TAG and Broken Spur that the mounds are not necessarily located in the areas of highest heat potential. Indeed, TAG is some 2 km from the rift valley axis and has been operational for several tens of thousands of years. Hence, heat availability is not a major consideration and the most obvious control is a structural one. Mapping on Broken Spur indicates a series of isolated vent-sulphide areas, concentrated around a minor graben. Their distribution, size and nature all indicate that they are residual parts of a much larger sulphide body which was at least the size of the present TAG field. The evidence is for a cyclical pattern of mound growth -mass wasting? rejuvenation and the Broken Spur mound appears to be in the rejuvenation stage of the cycle. Mound cyclicity must be related to the supply of hot water which itself is a function of the connectivity of fracture systems. Hence, we return to the theme that the major controls in mound development are structural ones.

Jan 1, 1998

The Malvern Hills coal project is now in an advanced stage of development with the stripping of overburden from above former underground workings in which a 3 m seam of subbituminous C coal with very low ash and sulphur was previously mined. The main seam dips at 45¦ to the south-east, along with other adjacent potentially recoverable thinner seams, and the strike extent of past coal mining in the Malvern Hills approaches 10 km with most extraction by underground methods. Overburden and interburden is predominantly weak mudstone, with only very minor sandstone, whilst a 1 - 2 m thick veneer of Last Glaciation loess covers the area. The coal product from the present mine site will supply the local industrial market, with production planned to peak at about 20 000 tpa. Settling pond design has been based on several different approaches, including an estimate of likely inflows from the contributing catchment of about 5 ha under predicted storms having a ten year recurrence interval. A pond of about 1000 m2 in area has been constructed with its invert in mudstone bedrock, and soil slopes have been lined with lime-stabilised clayey loess silt incorporating a gravel armour layer. The pond outflow takes place via a 2 m high 1.8 m diameter concrete dewatering tower, with a skimmer arrangement to lower the pond by approximately 500 mm between storm events. The overflow water discharges to the main stream above a natural wetland, which will act as a secondary polishing pond, and this is to be enhanced in conjunction with the neighbouring forestry company. Discharge consents specify turbidity and pH as the controlling criteria, and both will be monitored at the settling pond discharge point as well as at the entry to the main stream. Investigations to date indicate that the pH of water exiting from previous underground workings is in the range 6.8 to 7.2, and that acidic drainage will not be an issue with this mine site. No dispersive clays have been identified in assessing the overburden and batter materials, although erosion during storm events is expected and all drains will ultimately be routed through the main settling pond to ensure adequate control of runoff-generated sediment. Reestablishment of vegetation on cut and fill batters remains a priority, and ongoing monitoring will ensure satisfactory long-term performance of the pond system.

Jan 1, 2003

By V 7. 0 / 300 dpi

WHEN the copper smelters were built, in Montana, all of the refractory products which were used in their construction were shipped in from Eastern factories. It was apparent that if a material suitable for the manufacture of these products could be found within the State, a saving of freight could be effected and a new industry built up. Prospecting for such materials was started and experiments were made with samples from numerous deposits. Considerable effort and funds were expended in an attempt to manufacture silica brick from Dillon quartz, a light colored sandstone that is found near Dillon, Mont., on the Oregon Shortline railroad. As a brick material the Dillon quartz was a failure, but it has proved very satisfactory as a silica cement. It is now being used in laying silica brick and for reverberatory furnace bottoms. A bed of quartzite that is particularly suited to the manufacture of high-grade silica brick -was finally discovered at Browns Spur, 6 miles west of Anaconda. The material from this deposit is now being used in the manufacture of the Anaconda silica brick, which have gained a wide reputation for heat-resisting and lasting qualities. The analysis of all average sample of this quartz is: SiO2,, 96.7; Fe203, 0.3; Al203, 2.5; CaO, 0.3 per cent. The very low percentage of fluxing ingredients makes this a most refractory material. All of the Anaconda silica brick are hand molded. Various types of brick machines have been tried, but the hand-mold process proved the best suited to the manufacture of silica brick from this material. The silica is first put through a jaw crusher and is then clumped into wet pans, where 4 per cent. of lime paste is added, to produce a bond. Without the lime the. material would not be plastic enough to mold. After a few minutes' grinding in the wet pans the material is conveyed to the molder, who forces it into the molds by hand. The brick are then dumped on pallets and placed in the drier, where they are left until dry enough to be set in the kilns. Some of the brick are re-pressed before being dried. They are burned about five days, in round down-draft kilns. It is not necessary to have as much heat in the kilns as the brick will be subjected

Jan 9, 1913

By Reuben John Mathew

"Oxygen evolution is the main anode reaction in industrial copper electrowinning. The oxygen bubbles do not conduct electricity, thus increasing the electrolyte resistance. The oxygen bubbles formed at the anode rise to the surface, occupying a larger volume of the electrolyte at the top of the cell than at the bottom. This oxygen bubble concentration gradient contributes to a gradient in electrolyte resistance and consequently a tendency toward uneven current distribution. This phenomenon increases the chance for uneven growth on the cathode and/or short-circuits, particularly on the lower portions of the cathode. This issue may be ameliorated by increasing the charge transfer resistance for oxygen evolution down the height of the anode. This concept was studied by solving the current distribution for a 2-D model of a copper electrowinning cell using COMSOL.IntroductionA copper electrowinning tankhouse aims to operate at the highest current density that will deposit on the cathode a layer of copper metal possessing the desired physical and chemical characteristics. The operating current density is directly related to the physical nature of the copper deposit on the cathode (Figure 1), limiting a copper electrowinning tankhouse to some operating current density that produces acceptable copper deposits.[!] The ratio of the operating current density to the limiting current density is typically around 0.3.[2] If the limiting current density for a cell could be raised, the operating current density could also be raised and thus result in savings in capital cost for a tankhouse. [3]The average operating current density in a copper electrowinning plant is 270A·m- 2 .[4] The value for average current density, however, obscures the fact that the face of a cathode does not experience this value equally. Indeed, the current density varies along the height of an electrode and is independent of the height of the electrode.[5] This phenomenon partly explains why the lower portions of a cathode tend to display a rougher copper deposit.In order to utilize a higher operating current density but still remain at 30% of the limiting current density, the limiting current density must be raised, but it is affected by the mass transfer regime at the electrodes. The mass transfer regime is currently poorest at the lower portions of the cathode and this is part of the reason for the tendency for poor cathode deposits to occur at the lower portion of the cathode.[6]"

Jan 1, 2012

By J. O. Nomland

Bahrein 'Island.—In 1936 the Bahrein Petroleum Co. continued drilling additional wells to further increase production. In all, 39 flowing wells have now been finished and five others are drilling. A second well has been deepened for prospecting the deeper horizons but has not been successfully completed as a commercial producer. In addition, a well has recently been drilled near the eastern limit of the producing area for edge-water observation. The present system places wells 3000 ft. apart in a rhombic grid, or about one well to 179 acres. The total production for the year was 4,644,635 barrels. It is expected that refinery capacity of 20,000 bbl. per day will have been completed by July, 1937. A new permanent and enlarged camp with office buildings is being built. A new hospital has been constructed and two additional medical men have been added to the staff. Saudi Arabia.—In eastern Saudi Arabia, the California Arabian Standard Oil Co. has continued with the program of prospect drilling started in 1935. After the gas encountered in Dammam well No. 1 had been successfully shut off, it was completed as a small flowing well of 51" gravity oil. Dammam No. 2, which had been started in 1935, tested 3840 bbl. of approximately 50" gravity oil from a depth of 2175 ft. Dammam No. 5, before being deepened for prospecting lower productive horizons, encountered a gas zone producing 30 million feet. Five other wells on the Dammam dome are in various stages of drilling or completion. Most of these have been located principally to outline the productive area and the various producing horizons of the structure. An extensive program of geological work is being continued. In June, 1936, a well was started on the El 'Alat structure about 25 miles northwest of the Dammam development. Although various tar showings have been reported, the well has not yet, at 2518 ft., reached the depth at which it has been thought that productive horizons might be encountered. A prospect well is being drilled by the Kuwait Oil Co. (jointly owned by Gulf and Anglo-Iranian Oil Companies) in the Sheikdom of Kuwait. The well is near Bahra, a few miles north of Kuwait Bay and about 240 miles northwest of El 'Alat. To date no favorable results at depth of about 6000 ft. have been reported.

Jan 1, 1937

By Jamil M. Khalifeh, Shadia J. Ikhmayies, Bothina A. Hamad

"We computed the optical properties of the cubic niobium nitride (o-NbN) compound using the full potential linearized augmented plane wave (FL-LAPW) method within density functional theory (DFT). The complex dielectric function and optical constants, such as optical absorption coefficient, refractive index, extinction coefficient, energy-loss spectrum, and reflectivity, are all calculated and compared with experimental results. The behavior of the computed quantities is similar to that obtained experimentally, but the optical positions are shifted to lower energies. This shift was related to the strong interband transitions, which are located at energies higher than 5 eV for NbN- as they are for IV B transition-metal mononitrides- and they appear in the computed spectra and not in the experimental spectra. These interband transitions simply shift the position of the reflectivity edge or the screened plasma frequency to the longer wavelength side.IntroductionIn recent years, NbN, as a transition metal nitride, has become a very popular material due to its high hardness, melting point, wear resistance, chemical inertness and temperature stability, which makes it suitable for use as emission cathodes in microelectronics and sensors, optical films and micro-mechanics etc [l]. Niobium nitride has long been known as highly polymorphic material, for which several crystalline structures have been reported in the literature [2]. These structures include the well known super-conducting rock-salt (Fm-3m, or Bl) structure (o-NbN), the hexagonal structure with space group p63/mmc and prototype Fe2N (18fuN), the hexagonalstructure with space group p63/mmc and prototype NiAs ~-NbN) and others.There has been a lot of computational studies for the structural and electronic properties ofNbN [3, 4-7], but according to our knowledge there is not any computational work that has been devoted to study the optical properties of this transition metal compound. At the same time a number of authors had performed experimental work in this direction. For example, Xin-kang et. al [l] studied the microstructure and optical properties of magnetron sputtered NbN thin films. Torche et. al [8] studied the composition, structure, electrical and optical properties of nonstoichiometric niobium nitrides. Newport et. al [9] investigated the reflection and transmission spectra of cubic niobium nitride films, and Tanabe et. al [10] had investigated the optical parameters and reflectivity of reactively sputtered NbN thin films by using in situ ellipsometry."

Jan 1, 2013

By Arthur F. Wendt

The hot-blast oven of which the accompanying plate gives complete details, was designed by the writer for the spiegel-furnace of the Lehigh Zinc and Iron Co., at Bethlehem, Pa. Members of the Institute who visit these works will have occasion to notice the large amount of zinc-dust in the gases, and the consequent dirtiness of both the hot-blast and the boilers. The zinc collects in a crust on the iron hot-blast pipes and leads to the frequent burning of them. A large vertical standing-pipe stove, a modification of the "Pleyer," thus gave considerable trouble by the burning of pipes and, on one occasion, the toppling over of a whole row. These inconveniences are avoided in the hanging-pipe stove under consideration, and less heating-surface has been found to be required to heat the blast to a given temperature. The construction of the stove is so simple and so plainly shown in the plate that it is needless to enlarge upon it. Each pipe rests in a box and is connected by U-branches with the next adjoining pipes. An iron sleeve is placed around the joint and tightened, as usual, with iron filings. In case of a pipe burning out, that particular section is cut off by the valves and the sleeves are broken. The pipe is then readily lifted out of the box and a new one is substituted. The whole operation requires only a short time and the section can then be at once put into use. The boxes supporting the pipes cover the whole surface of the hot-blast and are closed by iron covers rammed with fire-clay. Owing to the air-space around the U-pipes there is little loss of heat in the upper part of the stove. Each section as built has 280 square feet of heating-surface. The furnace is blown by a horizontal engine with 46-inch stroke and 48-inch diameter of blowing-tube. At 28 to 30 revolutions, the engine delivers 3000 cubic feet of air per minute, at a pressure of 5 pounds. When five sections of stove are in use, the blast enters the furnace at a temperature of 850" F. That is, there are over two cubic feet of air per square foot of heating-surface heated to that temperature per minute.

Jan 1, 1887

By W. L. Zeigler

THE tailing from the gravity concentration plant of the Hecla Mining Co., Gem, Idaho, was former-ly loaded into railroad cars to be used for ballast, highway surfacing material, or concrete work, or dis-posed of by an aerial tramway, which dumped it into another gulch. The tailing averages about 1.2 per cent lead and 0.8 oz. silver to the ton. Further treatment for the recovery of the valuable metals had been investigat-ed several times with results that did not warrant the construction of a retreatment plant; but early in 1925 experimental work was again started with small tests, and later with a 10 tons per day flotation test plant. This showed that the tailing could be ground and treat-ed by flotation at a profit. It was decided to make the new flotation plant an addition to, rather than incor-porate it in the old concentrator, the original capacity of which had been increased many times, the present arrangement being by no means ideal. The old mill buildings were of timber and board contruction, creat-ing more or less fire hazard, so all new construction was made fireproof. Construction work on the new plant was started in the middle of July, 1925, and the plant was placed in operation early in December. The building is of concrete and steel with hollow tile walls, steel sash and corrugated asbestos roofing. The ball-mill floor has for its foundation a cellular reinforced concrete block about 14 ft. deep, extending to cemented river gravel, and the cells filled with tailing to give weight to the block. Overhead, built into the steel frame, is a 5-ton hand-operated traveling crane. With both ball-mills running fully loaded, there is not the slightest trace of vibra-tion in the foundation or building. The flotation floor is of reinforced concrete beam construction and spans Canyon Creek. Adjustable plunger feeders are arranged under the the tailing-bin, which feed by gravity to a 14-in. eleva-tor, discharging to a short 18-in. conveyor. From the conveyor the tailing is discharged into a dividing hop-per, from which point the plant is arranged in three separate units. Each unit consists of a ball-mill in closed circuit with a classifier, and an 8-cell flotation machine and has an approximate capacity of 300 tons per 24 hours.

Jan 8, 1927

By Charles Himrod

IN presenting this paper it is not intended to enter into any discussion of the theory of the blast-furnace, but simply to give the results of a number of determinations of CO and CO2 in furnace gases, and some conclusions arrived at, and the result of an experiment made in hopes of increasing the production of CO2. In the first table, on page 198, is given the averages of a number of analyses of gases of different furnaces, and in the second, of two stacks of different sizes under varying circumstances. The conclusions arrived at as to what influences the production of CO2 are as follows: 1st. Kind of fuel. Bituminous coal not permitting the formation of as much CO2 as coke. 2d. Kind of ores. Rolling-mill cinder being much less favorable to formation of CO2 than hematite ores, magnetites probably less than hematites, but more than cinder. 3d. Length of time of contact of gases with ore. Small furnaces and too rapid driving both waste fuel by not allowing enough time for conversion of CO into CO2. 4th. The temperature of blast. The hotter the greater the quantity of CO2. 5th. Regularity of passage of stock through the furnace. The hanging and dropping of the stock, however slight, seems to pack it more solidly in the hearth, increases the resistance to the blast, and decreases the quantity of CO,. These are the most common causes noticed which influence the production of CO2, unless we except the one that might be considered the greatest of all, the one that has spoiled so many tons of iron, and the amiability of so many furnacemen, the one most dreaded, the great unknown. It would seem a self-evident proposition that the better the contact of the gases with the ore and the less with the fuel, the greater would be the amount of CO2 produced. To prolong the contact of gas with the ore furnaces are enlarged with advantage, and pains are taken to charge the stock in such a, manner as will best promote it. Still, with furnaces of most approved construction and most skilful manipulation, the gases leave the furnace so rich in CO, that not half the heating power of the fuel is obtained, and the highest

Jan 1, 1877

By E. E. Barker

Although flotation was known to be a successful process prior to 1312, Utah Copper Co.'s ores were not entirely treated by this process until 1923. Experiments had been conducted, of course, prior to that time, and in February, 1917, the first unit of the Arthur plant was changed over from gravity concentration to flotation. On May 16, 1918, the entire Arthur plant was on flotation, excepting the coarse concentrate which was tabled prior to fine grinding. The reasons for the delay in adopting flotation at these plants were, first, that it was decided to await the outcome of the litigation with the Butte & Superior Mining Co., which began with an injunction served on Oct. 3, 1911. This litigation continued for years. Then the demands on the plants in the war years 1916, 1917 and 1918, really precluded any further drastic changes during that period, as all efforts were bent on maximum tonnage, and the cry of tonnage, rather than of recovery, was the major issue. The postwar depression followed these years of intensive production, so that it was not until 1922 that the Magna plant was equipped to use this process. Excepting, then, the amount of coarse concentrate that was tabled, 1923 was the first year when the Utah Copper Co.'s ores were on a full flotation basis. Effect of Flotation on Ore Reserves The object of this paper is to point out the effect that flotation has had on the operations of the Utah Copper Co. In 1905, when D. C. Jackling began making history in copper, the ore reserves were 34,000,000 tons, with a grade of 2 per cent. copper and a mill capacity of 700 tons daily. The point of cut-off between nonprofitable and profitable grades was 1.2 per cent. A few years later the capacity was increased to 6000 tons, when 1.1 per cent. became the point of cut-off. Ore reserves had climbed to 80,000,000 tons, having a grade of 1.9 per cent. In 1911 there was an ore reserve of 300,000,000 tons, with a grade of 1.5 per cent. and a cut-off of 1 per cent.; in 1918 the ore reserve was approximately 400,000,000 tons, and a grade of 1.38 per cent., and point of cut-off 0.95 per cent., based on normal costs and prices. Up to this

Jan 1, 1928

By Michael Drozd

Introduction Flotation is a recovery process that utilizes natural or chemically-introduced hydrophobicity of minerals to separate ore from gangue by attaching the ore particles to bubbles. Flotation has been known since 1906, when it was patented by E. L. Sulman, H. G. K. Pickard and John Ballot. Flotation's first documented plant use was in 1911, when it was used on gravity tailings from a zinc plant. Cyanide leaching was first patented in 1887. Most early precious metals flotation was linked to lead or copper concentrates. Most precious metal flotation is linked to sulfide recovery and utilizes such reagents as xanthates, dithiophosphates and thiocarbanilides. But the involvement of flotation in precious metals recovery does not have to be limited to active flotation of the gold and silver bearing minerals. Flotation can be used to remove interfering minerals, such as carbon, or cyanicides, such as copper, arsenic bearing minerals or other cyanide complexing minerals. Cyanide Leaching The use of cyanide to recover precious metals is the backbone of the industry. The various recovery processes that use cyanide are: 1. Leaching-Counter Current Decantation(CCD) Merrill-Crowe 2. Carbon-in-pulp (CIP) 3. Carbon-in-leach (CIL) 4. Vat leaching 5. Heap leaching These processes are selected depending on ore grade, ore leaching characteristics, reserve size and capital limitations. Ore grade is used as the first criteria to determine the type of cyanide plant required. However, the reserve size can determine whether a ground ore alternative is used. The ore leaching characteristics may indicate that the higher recovery, associated with a process that employs grinding, is the only economic recovery alternative. There are some extremely large leaching plants with grades that would be non-economic for some existing heap leach plants. Many factors, such as strip ratios, metal recovery and reserve size, determine what the ultimate plant design will be. The exact processing scheme that is used, is a multifaceted decision matrix, which gives the process metallurgist some job security. Precious Metal Recovery Using Flotation Flotation recovery can conceivably be used on any ore that has been ground. Many operations utilize gravity separation on the ore to remove native gold from the ore prior to sending it to cyanide leaching. On certain ores, where the gold is in visible nuggets or particles, this processing alternative is advantageous because the native gold cyanide recovery is

Jan 1, 1993

By J. J. Bodmer

The substances or materials employed in this manufacture, are the same as those used in the preparation of mortar and concrete, viz., the different kinds of lime and sand. Instead of, or in conjunction with, sand there may be used calcined clay, blast-furnace slag, clinkers or ashes from furnaces, natural puzzolana, powdered chippings from stone quarries, etc. Of the different kinds of sand, pitsand—siliceous sand, as it commonly occurs mixed with gravel—and the sand found on the seashore, where the salt has been washed out by long exposure, whilst out of reach of the tide, may be used. The purer the above-named materials are from admixtures of clay, earth, or organic substances, the more complete will be their combination with the lime, the quicker will the manufactured brick or block set, and the more satisfactory will be the quality which it ultimately attains. For this reason, subdivided blast-furnace slag is preferable in most cases to sand, and the only sand which, in reference to setting capacity, is analogous to blast-furnace slag, is the volcanic sand occurring in different localities in North and South Wales, as an almost pure calcined silica. The lime used for the manufacture may be either slaked or unslaked. In the first case, (slaked), in order. to obtain satisfactory results, the lime must be strongly hydraulic. The use of unslaked lime, however, is by far preferable. A process for using fresh or unslaked lime has been patented in England by Major-General Scott. Lime thus prepared is called " selenitic lime," and consists of a mixture of fresh (unslaked) lime with sulphate of lime, or plaster of Paris. The graystone lime, for instance, found by the Medway, is mixed with from 5 to 7 per cent. of plaster, which has the effect of keeping the lime from slaking when water is added. This mixture also partakes of the nature of cement, and when used for mortar, or concrete, attains in a shorter time a greater degree of hardness than the same lime would ever have obtained after being slaked. Bodmer's process for the manufacture of artificial stone bricks consists chiefly in the use of automatic measuring, forwarding, and mixing apparatus, by means of which the materials are supplied and unite in a continuous stream, and are accurately measured. They

By Ross Gilders, Leo Cheung, C. David Desjardins

"For the past twenty years significant progress has been made in bacterial leaching. In fact, a recent article in the Northern Miner has cited that nearly all new copper production is based on bioleaching. The bacteria that play the predominant role in bioleaching is an obligate chemolithoautotroph called thiobacillus ferrooxidans. These bacteria thrive in areas rich in sulphide and prefer low acid media. In the simplest sense, they metabolize sulphide converting it to sulphate either as acid or as soluble metal sulphates. This process is well known because these bacteria generate acid mine water. Over the last five( 5) years, we have been carrying out development work on creating optimum bioleach conditions for the extraction of metals from sulphide rich ores and concentrates. Recently, a study was carried out on a byproduct sulphide concentrate produced in a tin flowsheet developed for the Mt. Pleasant Mine of ADEX Mining Corp. The objective was to determine whether a bioleach process might successfully leach this sulphide material which contains copper, zinc, iron and, what is more important, trace metals such as Indium, Gallium, and Bismuth. The current work describes the successful recovery of these metals achieving extractions of more than 80% by applying bioleaching techniques. An overview of this technical program forms the basis of this paper.IntroductionBio-Oxidation of metal sulphides has emerged to be one of the leading edge hydrometallurgical processes for the economic extraction of metals from ore and concentrates. The fundamental process involves the bacterial assisted oxidation of sulphide to sulphate yielding metal sulphates which can be subsequently leached by conventional means. The bacteria that play the predominate role is an obligate chemolithoautotroph named thiobacillus ferrooxidans (TF). These bacteria thrive in areas rich in sulphide and occur naturally worldwide. In fact, TF is responsible for generating acid in water (acid mine water) from exposed sulphide surfaces primarily through the oxidation of pyrite. TF bacteria thrive under the proper conditions of temperature and oxygen supply in the presence of sulphides and populations in excess of a million per millilitre (ml) of solution are achievable. Typically, at room temperature, the bacteria will bio-oxidize in a pH range of 1.0 to 3.0. Today, bio-oxidation has been applied commercially with great success for the extraction of uranium, copper, and gold."

Jan 1, 1996

Consolidated Gold Fields Limited published annually an excellent reference, GOLD 1978, GOLD 1979, giving the Supply and Demand for Gold, Recent Developments and Prospects, Soviet Gold Production, etc. This outstanding reference is authored by Christopher Glynn, Investment Department, London, Great Britain. The 1978 Report marked the tenth anniversary of Gold Field's review of world gold market developments; and from it and the 1979 report, the following information was derived. The recovery of gold is widespread in the Soviet Union. Originally, gold was mined principally in the Urals, but in the last few years several major deposits have been discovered in the southwestern areas of the Soviet Union. One of the most dramatic discoveries has been the Muruntau deposit in Western Uzbekestan. This deposit, discovered in 1958, is reported to be the largest and among the lowest cost producers in the Soviet Union. It is located in Armenia, approximately 750 km (465 miles) northeast of the Iran-Afghanistan border, lying in the center of the Kyzylkurn (Red Sands) desert at the foot of Muruntau Mountain. Free gold occurs in both fine and coarse size in quartz veins up to 20 m (66 ft) thick associated with a small percentage of sulfides, mainly arsenopyrite. The ore zone constitutes a large gold-enriched stock work of about 4 sq krn (1.5 sq miles). The development of Muruntau was a major undertaking with open -pit development and construction of the mill and refinery complex started early in 1967, and the first gold bar poured in mid-1969. At the end of the first construction stage in 1970, the mill building was an imposing structure about 38 m (125 ft) high and 330 (1,080 ft) in length housing, probably, 11 parallel milling circuits. The first construction stage also included six 50 m (165 ft) diameter thickeners and 30 Pachuca tanks. The original mill complex was tripled in size after large additional gold reserves were discovered at a depth of 600 m (1,970 ft); and the deposit is now being exploited by both open- pit and underground workings. Ore is ground in semi-autogenous mills with the free gold being recovered into a high-grade concentrate on shaking tables. Table tailings are purnped to duplex spiral classifiers in closed circuit with the grinding mills. Classifier overflow is then thickened before being transferred to the Pachuca building where cyanidation takes place. An ion exchange resin is then added in a countercurrent

Jan 1, 1981

By Peter P. Harvey

The Nonel Primadet is a non-electric blasting initiation device. The system incorporates the safety advantages of a cap and fuse system with the precision blasting afforded by electrical blasting caps. Each unit is made up of a delay blasting cap factory-crimped to a Nonel® shock tube lead line. The delay elements in the blasting caps are manufactured in both millisecond and long period series. There are 16 periods available in both series - period 0 through period 15. The units are manufactured in 12', 16', and 20' lead lengths. The hollow shock tube is made of surlyn plastic and it is coated on the inside with a reactive material. The powder train has a density of only 1/10 grain per linear foot of tube. A typical blast round is timed precisely the same way it would be with electrical caps. After the round has been timed and loaded, the tube leads are gathered in convenient bunches and tied into a detonating cord trunkline. The Nonel® tube bunches are initiated by the output of an 18 grain per foot detonating cord trunkline. Once initiated, the Nonel® shock tube will reliably propagate at 1800 meters per second. The energy from this shock front initiates the delay elements in each delay cap. The shock tube is inert to electrical energies, including; stray current from AC/DC power sources, as well as, electrostatic discharges. The tube is also inert to initiation by impact. The system has proven to be particularly advantageous in both tunnel and shaft blasting applications. The major advantages in using the Nonel® system in this type of work are: 1) faster and easier tie-in techniques through the use of bunch-blasting. 2) electrical power can be left on during loading and tying-in. a. electrical lights can be turned on at the working face - better lighting facilitates loading and tying-in. b. electrical pumps can continue to function throughout loading and priming procedures (this is particularly advantageous in shaft work with water problems). 3) down-time due to approaching electrical storms is minimized. 4) increased overall efficiency in the blasting cycle: a. it is easier to train a man in the proper use of the system. b. fewer missed holes per round. c. less time required for tie-in. 5) safety-advantage--The system is not susceptible to involuntary initiation from extraneous electrical energies.

Jan 1, 1979

By Francis Donaldson

The direct injection of cement grout into water-bearing fissures as a means of checking or stopping the flow of water into shafts and tunnels has been experimented with for a decade or longer and seems to have been first attempted in Europe. The earliest application of which the writer has found a record was at a shaft sunk by the Mining Society of Lens; this is described by C. Dinoire in the Transactions of the Institution of Mining Engineers.1 It is only lately, however, that the process has been entirely successful. This success has been accomplished on the Catskill Aqueduct, now under construction by the city of New York. This aqueduct includes a number of deep pressure tunnels, reached by shafts for both waterway and construction purposes. In portions of these shafts and tunnels considerable underground water was met. The contract for the first of these deep pressure tunnels was let to the T. A. Gillespie Co.; this section is known as the Rondout Siphon. It leads under the Rondout valley at a depth of from 400 to 800 ft. and is about 5 miles long. The engineers expected that considerable water would be encountered, but fortunately this was not the case except at one shaft, known as No. 4, which penetrated the rock at a junction between limestone and conglomerate. Water-bearing fissures were encountered almost immediately. At a depth of about 200 ft. a flow of 1,500 gal. per minute was struck. The. shaft then contained as many pumps as could be used, and it seemed impossible to sink it further. After vain efforts had been made to proceed, John P. Hogan, a division engineer of the Board of Water Supply, suggested that cementation of the fissures be tried. The process was attempted for the first time in this country. Since the shaft was partly full of water it was necessary to drill grout holes with a diamond drill. Platforms were placed on the timbers at the water level, the diamond drill was installed and six 90-ft. holes were drilled in the bottom of the shaft. Several car loads of cement were pumped through these holes into the fissures, the drill casings being used for grout pipes. This largely cut off the flow of water from, the bottom and sinking could then

Jan 1, 1915

By K S. Smith, B P. Jackson, P J. Lamothe

The upper Arkansas River south of Leadville, Colorado, USA, contains deposits of fluvial tailings from historical mining operations in the Leadville area. These deposits are possible non-point sources of acid and metal contamination to surface- and ground-water systems. We used stable-metal isotopes to help ascertain metal retention and release mechanisms that influence metal transport from the deposits to shallow ground-water systems. To accomplish this, we excavated an intact core from a small fluvial tailings deposit and performed laboratory column experiments to examine the amount of metals leaching through the core. Deionised water was continuously applied to the top of the core, and effluent was collected from the bottom of the core for a period of about two months. Three saturation conditions were used, including unsaturated, partially saturated, and fully saturated. Reducing conditions developed upon partial and complete saturation of the core. During the unsaturated leaching phase, core effluents were acidic (pH 2.8 - 3.5) and contained elevated metal concentrations. During a portion of the unsaturated leaching phase, stable-metal isotope spikes and conservative tracers were simultaneously applied to the top of the core. The isotopes provide a means to delineate metal behaviour within the core. During the unsaturated leaching phase, the isotope spikes did not exhibit breakthrough with simultaneously added conservative tracers. However, some of the stable-metal isotope spikes did break through when reducing conditions occurred in the core (during the partial- and completesaturation conditions). In this paper, we use Cd as an example of the utility of stable-metal isotopes in geochemical studies. In the case of Cd, after the core was partially saturated, the 111Cd spike was released as evidenced by a change in the Cd isotope ratios in the effluent. This release continued during the fully saturated leaching phase, however, the total Cd concentration did not increase. These results suggest that the 111Cd spike was retained inside the core during the unsaturated leaching phase, and only partially released as reducing conditions developed. Results from this core-leaching experiment indicate there is a large reservoir of water-soluble material within the fluvial tailings deposit, which yields elevated metal concentrations and high acidity, and which may degrade adjacent ground- and surface-water quality. Use of stable metal isotopes in this study facilitated the determination of different metal-retention processes, metal-release processes, and metal sources in the fluvial tailings deposit in response to changing geochemical conditions.

Jan 1, 2003