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By D. C. Crothers

"What is new in air compressors? A good deal - the designers have been keeping pace with technical developments in related fields and also contributing new techniques of their own. Plant reliability no longer requires bulky slow-speed machines. Even the reciprocating machines, which still provide the most efficient method of compressing air, have been greatly reduced in size and installation cost for a given capacity rating. New materials and fabrication techniques are being used, by most manufacturers, to produce less costly plants in total. Many packaged plants are available, which generally means a more complete assembly for shipment. This type of construction offers savings in handling and erection costs at the site. A warning is in order, however - the extent of packaging in any given plant should be investigated carefully to determine what is included and just what field costs can be realized. A suggested specification has been offered for consideration when studying comparative costs. Rotating machines intrigue many because of their potential as regard fewer wearing parts, higher speeds and hence smaller units, utilizing less expensive drivers, and lack of contamination of the compressed air by lubricants. The inherent shortcomings of these machines - lower •efficiency and capacity control - have been much improved lately, and this type of plant is now becoming quite popular. Noise control, of much concern to everyone, is another development that has received considerable attention.Systems for efficient capacity control and continuous monitoring of compressor operation offer additional reliability and low-cost operation of the modern compressed air plant. Accessory equipment and its effect on over-all plant operation is also considered."

Jan 1, 1972

By R. S. Fowkes

A study was made by the Bureau of Mines of the penetration of selected granular materials in an unconfined state by wedge-shaped tools having dimensions comparable with the dimensions of the particles composing the materials. The output force for larger particles fluctuated radically. A custom-designed integrator was used to obtain work as a function of depth of penetration in the form of smooth curves. The influence of wedge angle, depth of penetration, penetration rate, entry angle, compaction state, and particle size on the force required and the work performed was ascertained. Empirical equations describing force and work as a function of penetration were obtained for each set of experiments.

Jan 1, 1973

By Umay Cinarli, Ahmet Turan

High-energy consumption in primary aluminum production (from bauxite ores) makes secondary aluminum production (from metallic raw materials such as scrap and dross) very critical. Aluminum dross, as a waste, arises in pyrometallurgical processes, and it is the mixture of metallic Al, Al2O3, other metal oxides, metal halides, and some other compounds like AlN. Aluminum dross has two subgroups (white and black) with respect to its metallic aluminum content. White dross is a secondary aluminum resource because of its high metallic aluminum content, whereas black dross, having low metallic aluminum content, is generally disposed in dumping areas. In the present study, it was aimed to develop a simple technique to valorize aluminum black dross in the form of alumina-based ceramic materials through pyrometallurgical (calcination) and hydrometallurgical (leaching) operations. Moreover, thermochemical simulations were conducted by using HSC Chemistry 6.12 software to simulate calcination conditions. After leaching experiments, an alumina-based ceramic containing approximately 36.8% Al2O3, 61.4% MgAl2O4 with 1.8% Na2FeO4, which might be available to use as a spinel refractory in steel smelting furnaces, was obtained in the experiment carried out in a solution containing 10 mLH2SO4 and 40 mL distilled water (3.5 M). Moreover, the sinterability of the alumina-based ceramic was investigated at the temperatures from 1350 to 1550 °C. In the sample which was sintered at 1550 °C, a density value of 3.15 g cm−3 and a hardness value of 69.58 HV were measured.

Oct 26, 2020

By Jian-guang Yang, Lei Jie, Si-yao Peng, Jian-ying Yang

A new membrane electrolysis process for bismuth recovery from bismuthinite concentrate was introduced. Under the conditions of temperature 70 degrees C, acidity 3 mol/L, solid liquid ratio 1:4 and 1.1 times stoichiometry sodium chlorate dosage for 1.5 h oxidation leaching, more than 98.5% bismuth can be leached from bismuthinite concentrate. The resultant leach solution was subjected to membrane electrolysis. Under the conditions of NaCl concentration 300 g/L and pH 7 in anolyte, bismuth ions concentration 80 g/L and HCl concentration 3 mol/L in catholyte, heteropole distance 6 cm, temperature 40 degrees C and current density 200 A/m2, a flat deposited bismuth plate can be obtained after 24 h electrolysis, and the bismuth purity was more than 99%. The current efficiency of cathode was 97.88%. Chemical component analysis results showed that the average convert efficiency of the sodium chlorate was 52.77% and the average oxidizing efficiency of chloride ion was 69.78%, and the resultant anolyte generated in anode compartment could be fully reused as oxidant for leaching bismuthinite concentrate again.

Mar 1, 2017

By Larry Rayburn

Augercast piles evolved in the late forties from the process of pressure grouting open holes backfilled with stone. In 1956, a patent was issued for a cast in situ pile by pumping high pressure grout through hollow-stem, continuous flight auger as the auger is gradually withdrawn from the ground. The patent rights expired in 1973 and the use of auger-cast piles greatly expanded with most large deep foundation contractors now installing augercast piles. At one time augercast piles had a bad reputation, partly because of not having a blow count to give some engineers a confidence factor and there were some quality issues. Over the years the quality issues have been eliminated and I am sure the augercast is the most installed pile in private industry and is now being used by some State Agencies.

Jan 1, 2005

By A D. Strand

The Coeur dÆAlene mining district in northern Idaho, USA is the second largest producer of silver in the world. The Proterozoic Revett Formation hosts most of the mesothermal Ag-Pb-Zn vein ore in the district; it consists of informally designated lower, middle, and upper members. All three members show up to an order of magnitude of southward thickening across the regionally significant Osburn fault. Changes in thickness of the Revett Formation across the Osburn fault reflect a major, down-to-the-south, crustal-scale fault that:was active during sedimentation, was periodically reactivated during the structural and metallogenic history of the district, and likely provided first-order control over regional fluid flow during mineralization events. Where vein structures intersect favourable strata, they produce rich ore; where vein structures cross unfavourable strata, they are poorly mineralised or barren. The most favourable host rock in the district is quartzite, which accounts for the large production from the quartzite-rich Revett Formation.The district has five main types of hydrothermal alteration:feldspar destruction, hydrothermal bleaching, carbonatisation, sulfidation, and silicification. Feldspar destruction is the most extensive and pervasive type of alteration, involving the district-wide absence of feldspar from Belt Supergroup rocks. Hydrothermal bleaching results from the destruction of hematite; it forms alteration envelopes that extend for tens to hundreds of metres into the wall rocks around many of the mineralised veins. Siderite alteration is most diagnostic of mineralisation, forming alteration envelopes that extend for tens to hundreds of metres into the wall rocks around all mineralised veins. Fine-grained arsenopyrite and/or fine-grained pyrite commonly form alteration zones adjacent to high-grade ore shoots that extend for metres to tens of metres into the wall rocks. Widespread silicification is most easily recognised by the presence of numerous quartz veins.

Jan 1, 2002

By Niles E. Grosvenor

One of the most important considerations in the efficient operation of an under¬ground mine is the haulage system. Often the determining factor between profit or loss is the quick removal of ore and waste from the working places to secondary and main-line haulage areas, and so on to the outside. Important, too, is moving supplies from the surface to the working faces so that the loading process can continue with little interruption. Men must he transported in a rapid but safe manner. It has been through the efficient use and generally the combination of mine cars, track, belt conveyors and rubber-tired haulage equipment that underground operations have been able to compete with the more popular strip or surface mining. As near-surface ore bodies are exhausted, underground haulage will play an expanding part in economically furnishing the world's needs for all types of minerals. The choice of underground haulage equipment, wherever possible, should be one that will give the smallest overall cost of ore removal during the life of the mine while meeting necessary safety requirements. The reader is referred to Sec. 12 for equipment such as scrapers and load-dump-¬haul units that perform loading as well as haulage duties. 14.1-MINE CARS AND TRACK NILES E. GROSVENOR Main-Line and Secondary Haulage-Many mines today use a combination of belt and rail haulage. Even if a- belt system is used to carry the product from the face to the surface, track is used to transport workmen and supplies. A track system, when properly installed, will provide interruption-free and safe haulage. Schrecengost 2 lists the following as major advantages of track haulage: 1. Safety in transporting men in and out of the mine in personnel cars. 2. Easy and rapid transportation of supervisory personnel. 3. A temporary shutdown occasioned by a roof fall or power failure along the haulage system will not shut down the production areas. 4. Quick availability of repair parts and supplies. 5. Large pieces of coal or rock can be handled without damage to the haulage equipment. 6. In areas where quality fluctuates noticeably, different cars may be separated out for special preparation. 7. Rock or equipment may be loaded and moved out of the mine without interference with the production or preparation of the coal. 14.1.1-MINE CARS Mine cars with steel bodies are used in all types of present-day mining. Wooden cars usually are more bulky and less resistant to wear and damage, but are more easily repaired. Regardless of the type of mine car selected, it is most practical to standardize on one type or make to simplify repairs and limit the amount of spare parts necessary to stock. Rigid-body flat-bottomed cars are simpler and usually lower than others of equal capacity. Advantages are: ease of loading because of the low sides, simplicity, cheapness and high ratio of capacity to weight. The disadvantages include the

Jan 1, 1973

By Allen D. Look

Underground fires often prove difficult to control , and a small fire can quickly grow into a large one , endangering life and causing large property damage . Even a small underground fire may produce enough noxious gases to cause suffocation ; therefore , every precaution should be taken to prevent and control such fires . It is ironic that mine fires should be caused when utilizing materials that are in themselves fire - resistant ; yet , cutting and welding of iron and steel are proving to be common causes of underground fires in metal mines . This paper includes 19 examples of underground fires of this nature , and undoubtedly this is only a fraction of the number of similar fires that have occurred in the last few years . This paper will review some metal - mine fires caused by cutting or welding and point out precautions to be taken to prevent other fires from this cause .

Apr 1, 1948

By F. F. Aplan

"The material known as coal has a highly variable composition. As a consequence, coals show a great variation in their physical and chemical properties as a function of coal rank. The situation is further complicated because the preparation engineer must deal with raw coal, as mined. This is an assemblage of coal, upwards of 30% mineral matter and, typically, several percent pyrite. The kind and amount of the mineral constituents is also highly variable from source to source. A knowledge of coal rank and source location, and the kind and amount of associated impurities, is the first step in evaluating the response of a raw coal to preparation procedures. The raw coal must first be characterized before information from one source can be extrapolated to that of another.INTRODUCTIONCoal is a black or brownish-black combustible solid, derived from a heterogeneous mixture of plant remains and associated mineral matter that have undergone chemical and physical metamorphic changes by biological and geological processes without free access to air. It is composed principally of carbon, hydrogen and oxygen with lesser amounts of nitrogen and sulfur. 'Its exact chemical and physical nature has remained poorly defined, because the term 'coal' refers to a broad range of coalified solids ranging in rank from anthracite to a variety of bituminous coals of differing volatile matter content, sub-bituminous coals, and ending with lignite and brown coals. The variation in chemical and physical properties through these ranks is massive. In summary, Luckie's (1988) assertion is apropos: ""There is no such thing as coal; there are coals"". The coal preparation engineer, and, most especially, those scientists and engineers from other disciplines wishing to work with coal, must constantly keep this admonition in mind because what is true for one coal seam is often not directly applicable to another."

Jan 1, 1989

The plans for the activities of the Petroleum Division for the coming year do not differ materially from those of the past several years. The fall meeting is scheduled for Oct. 12 and 13 and is to be held at Tulsa, Oklahoma. The Division, of course, will take part in the annual meeting of the Institute at New York. A fall meeting will also be held in California at approximately the same time as the meeting at Tulsa. A number of papers are to be presented at the two meetings simultaneously. The various committees are at work arranging the programs. The Division will continue to be active in its various fields of endeavor, such as stabilization, production reviews, and economics, but special stress is to be laid on the engineering and research fields. In the past the Division has served as a forum for open and frank discussion of problems confronting the engineers in the oil industry. It is hoped that it will continue to function in this capacity. Papers presenting original ideas and extending the boundaries of knowledge and understanding in the field of petroleum production will be welcomed. Members who have interesting information to contribute should not wait until called upon by one of the Committees, but should offer a paper at the earliest opportunity. The past year has seen a decided strengthening of the control over production, with prospects of even more rigid control in the future. It is essential that production programs under such control be carefully planned and it is highly desirable that petroleum engineers take an active part in the planning, to insure efficient production of oil and minimize the waste of this natural resource. At a time like this, when it is difficult to keep the production of oil within reasonable limits, it may seem unnecessary to improve the efficiency of production methods, but, as has been aptly said, the trouble is not that we have too great a reserve of oil but that we are producing tomorrow's oil today. Therefore it behooves those who are entrusted with the engineering and scientific phases of production to learn how to get the greatest yield economically possible from the present and future fields in order that we may enjoy the advantages of petroleum products for a long time to come.

Jan 1, 1934

By John Hughes

1. De Beers, Diamonds and Canada 1.1. De Beers was founded long ago (1888, the same time that Canada became a country) in a rural mining village in South Africa. Today, we employ 22,000 people across 19 countries and have 14 mines including open pits, shafts, beach-sands and seabed. 1.2. Last year our sales were US$5.7 billion and our total production amounted to 47 million carats which means a 40% global market share. For the Kyoto buffs in the audience, the company consumes 66 million cubic metres of water per annum, 210 million litres of hydrocarbon fuel and 1,600 GWh of electricity. Stats are good, but aren?t as expressive as a movie. This one is 2 minutes long, which is quicker than I could elaborate. (Video 1 - 2 minutes) 2. De Beers in Botswana is the leading source of diamonds 2.1 Today Botswana is the Jewell in the Crown. There are three big open pits that enjoy economies of scale that make them the lowest cost producers. Last year 60 million tonnes of overburden and 30 million tonnes of ore were moved in Botswana alone. Botswana produced 31 million carats, compared to 14 million carats in South Africa and 2 million very high quality carats inn Namibia. 3. Diamond Mines provide feedstock? ?.to jewellery stores

Apr 1, 2005

By J. R. Klaehn, M. Shi, T. E. Lister, L. A. Diaz, J. S. McNally

Since 2019, approximately two dozen international battery recycling companies have been operating at the commercial or pilot scale [1]. However, current process capacity does not exceed 100,000 tons of end-of-life (EOL) lithium-ion batteries (LIB) per year, and the current recycling rate is only about 5% in North America [2-3]. Recycling metals from EOL LIBs is not only essential to waste minimization and environmental stewardship, but also a source of critical materials, which can contribute towards supply chain stabilization. LIB recycling can be roughly divided into three categories: direct recycling, pyrometallurgy, and hydrometallurgy. Direct recycling seeks to retain as much of the manufactured effort with minimum chemical processing [4]. The evolution of battery designs and chemical compositions are challenges to this approach [5-6]. Pyrometallurgical processes are robust and flexible allowing a broad spectrum of batteries with minimum pre-processing requirements. Some of the matrix issues are solved through combustion of some constituents. Smelting is strongly tied to fossil energy and air emissions are a concern. In addition, pyrometallurgical processes are not stand alone, as hydrometallurgical refining normally required to separate and recover the metals of interest (Co, Ni, and Cu) from the produced alloy and Li from the slag [7]. Hydrometallurgical processes can be highly selective and efficient in recovering high purity materials [8]. In general, hydrometallurgical processes are considered cleaner and less costly than high temperature processes [4,9-10]. Extensive chemical consumption and waste generation significantly increase the operating costs and overall environmental impact of the hydrometallurgical processes [11]. Leaching of metals from LIBs is dominated by the mixture of sulfuric acid (1 to 4 M H2SO4) and hydrogen peroxide (1 to 15 wt.% H2O2) [10]. Although organic acids have been tested as lower environmental impact alternatives, the reported pulp density operations are low < 60 g/L [10-11]. For the H2SO4/H2O2 leachates, high leaching efficiencies >90% are reported for Co, Ni, Mn, and Li from cathode materials at temperatures over 40 ⁰C and pulp densities between 30 to 200 g/L [9-10]. H2O2 acts as reducing agent to convert Co+3 and Mn+4 into their soluble forms, Co+2 and Mn+2 [12]. Despite the claims of H2O2 being a clean reducing agent [13], production of H2O2 has significant environmental impacts as determined by life-cycle analyses [13-14]. Moreover, the costs and risks associated with H2O2 transportation and storage cannot be ignored [15].

Mar 2, 2022

IN this paper an attempt is made to describe the sluicing operations on the tin fields of north-eastern Tasmania. No claim is made to completeness, for much of the ground has already been covered, and nothing is to be gained by needless repetition. On this account some portions of the subject have obviously received but scanty attention in order that others may be rather more fully dealt with; for instance, figures referring to the accuracy of various methods of valuing alluvial deposits, particulars of efficiencies, and water duties on both overburden and drift; also, the system of recording water distribution, &amp;c.The plans of the tin-streaming shed, sluice and feed&#183;race, and overburden tail-race represent types of the most modern design.The principal alluvial deposits being worked at the present time are situated either in the ancient or modern bed of the Ringarooma river or its tributaries. This river flowed in a north-easterly direction, receiving numerous tributaries on either bank, and finally emptying into Boobyalla harbour. The most important of these tributaries, from a mining point of view, are the Cascade, Main creek, Weld and Frome rivers (which unite just before joining the modern Ringarooma), Wyniford river, and Bradshaw&apos;s...

Jan 1, 1911

By S. T. Wlodek

The scale md subscale reaction products were identified and their rates of formation were studied in air over the range 1600" to 2000°F (871 " to 1149°C) for periods of up to 400 hr and for hoth the solution-annealed and aged conditions. The effect of prior sltrface preparation on suhscale oxidation was also studied The general oxidation behavior of both Ni-Cr-Mo-Al-Ti type alloys was similar. A surface film of a, Al2O3, forms immediately on exposure Subsequent oxidation continued at a linear rate (QL = 55 * 5 kcal per mole) as colonies of Cr2O3 nucleated at the A12O3/gas interface Further oxidation proceeded at a paraholic rate zvhiclz could he fitted to two successive rate constants. During paraholic oxidation, and depending on temperature, the scale consisted of Cr2O3, NiCr2O4 , and TiO2 with traces of NiO. In the case of Rene 41, the activation energy of both paraholic processes was 66 * 3 kcal per mole suggesting that diffusion of cations tlzrozrgh Cr2O3 was the rate -determining process. An unusual decrease in the oxidation of Udimet 700 at 1900°F where a spinel of Ni(A1,Crh0, zuas the predominant reaction product prevented the accurate assignment of activation energies for this composition. In both alloys internal oxidation of Al2O3 commenced shortly after parabolic scaling was observed. Prolonged exposure prod7tced intemal oxidation of TiN, and in Udimet 700 a complex Mo-Ni nitride was also found. At 1900oF, the subscale reactions in Udimet 700 undergo an inversion which parallels the decrease in surface oxidation; internal oxidation ceases hut is replaced by the formation of "spherodized" 3.&apos; colonies. Surface-preparation techniqtles which introduce appreciable working, such as coarse surface grinding or grit blasting. increase the amount of alloy depletion and internal oxidation in Reni 41. The reverse is true of Udimet 700 for which electropolished or mechanically polished specimens show much more subscale oxidation than strongly worked stirfaces. The strongest commercial nickel-base alloys presently available are generic to the Ni-Cr-Mo-A1-Ti base which exploits the precipitation of Ni3(A1,Ti) as the main strengthening mechanism, while relying on solid-solution strengthening by molybdenum and chromium reinforced by the pre- cipitation of carbides to attain maximum properties. This study characterizes the oxidation behavior of Rene 41, the strongest alloy of the Ni-Cr-A1-Ti type commercially available in sheet form, and Udimet 700, whose higher aluminum and titanium content allows it to exhibit one of the more attractive combinations of high-temperature properties available in a wrought product. The scaling processes of complex, type nickel-base alloys have received relatively little attention. Malamand and vidal as well as Poulignier et al.2&apos;3 have determined the composition gradients across the metal/oxide interface produced by high-temperature oxidation and considered the effect of surface perature, Limited weight-gain data has also been published by Fere 5 for alloys of this type and Radavich6 has identified the reaction products on Udimet 500 and Inco 702 after oxidation at 1832°F. Reference can, of course, be made to the excellent reviews of Kubaschewski and Hopkins7 or Ignatov and Shamgunova8 for a summary of the data available on the oxidation of binary and ternary alloy systems which are related to the more complex alloys considered here. EXPERIMENTAL The analyses of the different commercial heats studied are given in Table I. Using the experimental procedures previously established,9 continuous weight-gain data were obtained on both heats of Rene 41 sheet (A and B) and 150-mil-thick slices of cast Udimet 700. Subscale oxidation reactions were followed by static exposure of cylindrical specimens obtained from swaged Rene 41 (Heat C) and Udimet 700 (Heats E and F). In brief, continuous weight-gain tests were performed on specimens with a surface area of 10 to 12 sq cm. These were abraded through 600 grit Sic paper, electropolished to 2p rms in an electrolyte of 10 pct H2So4 in ethanol, and lightly etched in 10 pct HCl in ethanol before final washing and rinsing in ethanol. All continuous weight-gain data were obtained in dried (-70°F dew point) flowing (1 liter per min) air to an accuracy of +0.1 mg. Subscale oxidation processes were followed by the metallographic examination of 0.5-in-diam by 1.0-in.-long specimens. After an initial center-less grinding, various additional surface treatments were employed to determine the effect of surface preparation on subscale oxidation processes. Before exposure in zirconia crucibles, all samples were lightly etched in 10 pct HCl-ethanol, washed in ethanol, and dried. The depth of internal oxidation was measured to ±0.00025 in. on unetched specimens mounted so as to provide a taper mag-

Jan 1, 1964

By Michael S. Miller

In 1985, at the request of the Bureau of Land Management, the Bureau of Mines studied a 50,57U-acre portion of the 90,345-acre Twin Peaks Wilderness Study Area (CA-020-619A) in order to evaluate its identified resources. The area studied is located about 45 miles northeast of Susanville, CA, in Lassen County, CA, and Washoe County, NV. The area is underlain by Tertiary volcanic, volcaniclastic, and intrusive rocks. Quaternary stream, lake, and landslide deposits overlie the older rock. There are no mines or mining claims in the study area. One mineral resource, pozzolan, was identified. Mining claims, inactive in 1985, have been staked adjacent to or near the northwest corner of, and also southeast of, the study area. Examination and sampling of 17 mineralized sites, delineated mostly by prior geochemical surveys, showed at least 30 million tons of subeconomic pozzolan resources and small or low-grade occurrences of gold, silver, copper, lead, zinc, nickel, molybdenum, zeolites and clay.

Jan 1, 1986

By H J. Ross, R K. Beatson, T J, W R. Fright

Traditional method of explicitly defining three-dimensional (3D) ore-waste and geological boundaries relies heavily on a time-consuming process of manual digitisation. This method of modelling can be best described as surface modelling, as complex surface geometry is built up by digitising points that lie on the surface. With the advent of fast 3D interpolation methods, however, construction of geological surfaces using volume functions is now a practical alternative to explicit modelling of surfaces. Unlike explicit modelling, surfaces contained in volume functions are not explicitly defined or digitised. Instead the existence of surfaces in the volume function is implicit, thus the process of modelling surfaces from volume function is called æimplicit modellingÆ. Based on recent advances in fast scattered data interpolation methods, implicit modelling first defines a continuous three-dimensional function that describes the grade or rock distribution. This volumetric function is interrogated for a grade value, or a geological surface, thus allowing the extraction of the 3D object to be automated and eliminating the need to manually digitise surfaces. Since the function is continuous throughout space and does not depend on a mesh or grid for its definition, the extracted geological or grade wireframes can be constructed at any desired resolution in the specific volume of interest. The volume modelling method can work on scattered drillhole data of any data density, including processing combined information from dense grade control data as well as sparse resource drilling. It offers distinct advantages over surface modelling, including: being able to wireframe geological objects that may take days to digitise in tens of minutes; substantial improvement in modelling accuracy; and the ability to generate conditional models rapidly allowing mining risks inherent in geological modelling to be examined.

Jan 1, 2003

By Arthur. H. Winckers, Stephan L. Chryssoulis

"The deportment of gold in residue samples of cyanide leach tests of David Bell ore from level 6A block 13 was established using a comprehensive quantitative mineralogical approach. In every test the feed was first pre-aerated for 4 hours, followed by 48h cyanidation. Test no. 2 was done without lead nitrate and yielded a residue assaying 3.03g Au/t. In test nos. 4 and 9 lead nitrate was added before pre-aeration at 0.03kg/t and 0.3kg/t respectively yielding residues of 1.04 and 0.81 g Au/t.The mineralogical approach employed to establish the deportment of gold involved superpanning, to preconcentrate the free gold and assaying of the tailing fraction to determine the gold associated with quartz. It was thus determined that without lead nitrate added 47.2% of the lost gold is in the form of residual free gold particles less than 20 µm in size. It is this form of gold which is under represented in the residues of leach tests with lead nitrate added.Having eliminated coarseness of gold particles as a factor for lower recovery, it was determined that the residual gold particles have extensively contaminated surfaces. Amongst the deleterious surface contaminants identified: S, As, Ag, Sb and Hg, the two most harmful are S and Hg because of their concentration on the surface and rate of accumulation.Mercury and Ag are minor constituents of native gold at David Bell (average composition Au: 78.9 wt%, Hg: 18.5 wt% and Ag: 2.6 wt%) and they become enriched on the surface of residual gold particles because of their slower rate of dissolution in cyanide. The other elements absorb onto the gold particles from solution.The beneficial effect of lead nitrate was documented by comparative surface analysis of gold from residue samples of 48 hour leach testing with and without lead nitrate added and from time dependent (0-2 hour) leach tests in the presence and absence of lead nitrate. Lead nitrate accelerates the dissolution of gold by performing the following functions: (i) catalytic effect on the cyanidation of gold by accepting electrons; (ii) reaction with surface sulphur to form PbS which is then removed by oxidation; (iii) catalytic reaction on amalgam and Ag facilitating the cyanidation of Hg and Ag thus slowing down their build up onto the dissolving gold particles and (iv) the precipitation of sulphide sulphur from solution thus minimizing its build up on the surface of dissolving gold particles which is believed to facilitate the access of cyanide ions."

Jan 1, 1996

By W. M. Weigel

Economic deposits of barite occur in Missouri in two main districts. The most important, the Southeastern or Washington County district, is in the southeastern part of the state, mostly in Washington County with a small extension into the northeastern part of St. Francois County. Roughly, it embraces nine townships or about 200,000 acres and accounts for from 80 to 90 per cent. of the state production. The Central district, is in the central part of the state, includes most of Morgan and Miller counties, and parts of Camden; Benton, Moniteau and Cole counties. The area embraced is much larger than the Washington County district, but the deposits are more infrequent. The location and general area covered by the two districts is shown in Fig. 1. There is another small area in southern Franklin County but so far its production has been of small consequence. It might be considered as a northward extension of the Washington County field. An, area in the central part of Hickory County has also produced a small amount. The outline of the districts as shown indicates the general area in which deposits have been found. The total area covered by deposits of barite is only a small part of this, as, in the Central district especially, there may be miles of supposedly barren areas between ore-bearing areas of an acre or two in extent. The date when barite was first mined in Missouri cannot be definit stated, but the industry probably dates back to about 1860. The occurrence of barite was known long before this, as it was encountered in the lead mines in Washington County and mentioned by several earlier writers." Missouri is reported as producing 8000 tons in 1882 so it is evident the industry was well under way in the seventies in order to have arrived at this substantial production. By 1893 Missouri production had increased so that it ranked with that of Virginia, then the largest producer it increased until in 1914 Missouri accounted for about 65 per cent. of the total United States output.

Jan 1, 1929

By M. Pelegrin Rodríguez, J. Castellanos Suarez, R. Causse Miyares, A. Mosqueda Martínez, Rubén Aja

"This paper will describe the methods and the results of studies to integrate polymetallic nodule extractive metallurgy methods into existing and operating technologies or plants with the aim of reducing the capital cost of deep-sea mining challenges and to streamline the supply chain of raw materials where such opportunities exist (Moa Bay and others). It will also assess the possibility to carry out pre-industrial processing operations with productivity corresponding to pilot mining operation in the Clarion Clipperton Fracture Zone (5–10% of assumed annual production) with the use of existing facilities. The present study shows the results of high pressure acid leaching of polymetallic nodules (PN) mixed with laterite non-commercial ore. It also presents PN processing in the presence of ammoniacal tailings obtained from the Caron process. The experiments were carried out according to 24 full factorial design. The regression equations were determined for extractions of Ni, Co, Cu, Zn, Fe and Mn. The obtained results show that increasing temperature, the acid/ mineral ratio and the leaching time have a positive and significant effect on extraction of all the studied metals. However, increasing the tailings addition favors the extraction of the Co, Zn and Mn. The extraction of Fe diminishes, while the extraction of Ni is not affected. In the following conditions; 180 min, 260°C, 0.5 kg acid /kg minerals and 2.5 kg PN/kg tailing; the following extractions were achieved; 96% Ni, 90% Co, 97% Cu, 99.9% Zn, 43% Mn and 26% Fe."

Jan 1, 2017

By E. O. Wagner, V. F. Parry

This paper summarizes investigations during 1949 on three pilot plants for drying low-rank fine cool by entrainment in hot gases. Detailed operating results on processing seven coals having moisture ranging from 24 to 62 pct, formulas and data for calculating performance of large units, and general conclusions on the problem of drying fine coal are presented.

Jan 1, 1950