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By R. W. Smith, S. A. Davis, A. M. Raichur, M. Misra

The flocculation of coal is typically accomplished by the addition of commercially available polymeric flocculants. Recently it was shown that biopolymers derived from microorganisms can also be used. The biopolymers flocculate coal efficiently and make the coal more hydrophobic. This increase in hydrophobicity can be utilized to separate coal flocs and can be used for reducing the moisture content of the flocculated coal. In this regard, flocculation and settling tests using biopolymers and synthetic flocculants were performed on fine coal. The experimental results are discussed and a transport model is presented for the time-dependent settling of fine coal.

Jan 1, 1998

By R. W. Raymond

Jan 1, 1911

By R. H. T. Garnett

Recovery performance may be measured in absolute terms or in relative ones that relate the actual mining outcome to what was expected. Consideration is possible in terms of the control exercised by the operator. The eventual mineral output is the only figure known with complete certainty. The paradox is that, while performance is judged against the sampling, the reverse also applies. The R/Efactor and its four component factors are the best overall measures of performance. The choice of equipment for sampling and mining is very important. The sampling process may introduce errors and the sample density may lead to poor mining block selection. The resulting recovery performance is most visible on a regression curve. Changes in the cutoff grade must also be taken into account to avoid unrealistic production targets. Estimation methods incorporating different mathematical assumptions and techniques may cause over-or underestimation of the grade and volume. If the selective ability of the mining equipment does not match the size of the reserve blocks, the performance will be compromised. The treatment plant efficiency, the throughput rate and the degree of bedrock clean-up also affect performance. The maximization of throughput does not yield the optimum results. Marine conditions, which are outside the operator's control, affect not only operational availability but also performance. Examples are provided from actual operations for various commodities, showing the relative magnitude of the different effects upon performance.

Jan 1, 1999

By I. R. Kramer, L. J. Demer

T. H. Alden and R. L. Fleischer (General Electric Research Laboratory)— The authors' results indicate clearly and, we believe, significantly that during tensile deformation the surface layers of an aluminum crystal are hardened more severely than the interior of the crystal. A probable explanation of this effect, as the authors indicate, is that dislocations in the primary slip system may be obstructed at the surface or, it should be added, near the surface. The intent of this discussion is to show that the oxide film on aluminum is not likely to be responsible for this effect, but that the results can be understood if it is assumed the secondary slip is more active in the surface layers than in the interior. Prior study has shown that the principal mechanical effect of an oxide film on a single crystal is to raise the yield stress while leaving the rate of strain hardening during the initial deformation relatively unaffected.33 Since the yield stress is unchanged during polishing in the present case, we conclude that continual removal of the oxide film exerts a small effect on the plastic hardening.* It appears that the hardening interactions are occurring not only at the immediate surface, but to an appreciable depth below it, although with decreasing severity. For example, Kramer and Demer found that with removal of 0.004 in. from a specimen, the easy glide region was extended somewhat; but the yield stress did not decrease. The initial yield stress was recovered only after 0.041 in. was removed. Since a very brief polish would permit dislocations trapped behind a surface film to run out,34 extra dislocations must, instead, be trapped to a considerable depth below the surface. The same conclusion is drawn from the observation of decreasing hardening slope with increasing surface removal rates. If the hardening interactions were only at the immediate surface, a full softening effect would be observed at some small removal rate. The view is taken here that strain hardening is principally caused by small amounts of secondary slip.35 The secondary dislocations will interact in various ways with the primaries, interfering with their motion and causing them to accumulate in the crystal. Prior studies of easy glide have shown Diehl's model of hardening to be qualitatively consistent with the effects of impurities,36 of temperature,36 and of crystal size.37 On this basis the enhanced hardening of the surface layers in aluminum arises from increased secondary slip at and to some depth below the surface. Selective removal of this hardened layer is expected to decrease the measurable "bulk" hardening, the effect increasing with the removal rate and decreasing with the applied strain rate. We suggest that the stress on secondary systems is raised by the bending moments arising from interactions with the grips during the deformation. This stress from the grips has been shown to be a maximum37 near the surface, and hence, increased secondary slip should result. Prior investigations of grip effect:; indicate that as the grip stresses are raised by changing the crystal shape, the easy glide slope increases while the extent of easy glide decreases.38-40 It has been shown also that bending moments superimposed during tensile testing may either decrease easy glide, when supporting the moments caused by gripping, or increase it, when cancelling the gripping moments.38 This interpretation of the authors' results, emphasizing the special importance of secondary slip near the surface, is also consistent with the earlier results of Rosi.41 Copper crystals alloyed with silver in the surface layer show greatly increased easy glide compared with pure copper. In addition, the easy glide slope is reduced. The effect of bulk alloying in extending easy glide has been well established and has been interpreted as indicating the relative difficulty of secondary slip in alloy crystals. Since non-basal glide is difficult in zinc crystals, the effects of surface removal during deformation may be less important. Experiments to test this idea are in progress. I. R. Kramer and L. J. Demer (authors' reply)—The authors wish to thank Dr. Alden and Dr. Fleischer for their discussion. Our interpretation of the data in the paper is that dislocation motion is obstructed by "debris" which starts to form at the surface and extends towards the interior of the crystal with further plastic deformation. The fact that we did not find a reversion from Stage II to Stage I by surface removal shows that in Stage II the "debris" fills the entire cross-section of the specimen. Drs. Alden and Fleischer take the view that bending stresses due to the grips are responsible for the

Jan 1, 1962

By J. Mackintosh Bell

In the numerous districts subsidiary to Cobalt, and carrying mineral deposits similar in character to that world-famous mining camp, the most interesting recent developments have occurred in South Lorrain. The district, the center of which lies about 16 miles southeast of Cobalt, was the scene of a rush in 1907 but, in spite of the success of the Wett-lauffer mine, the locality soon lost its popularity, largely on account of the unsavory early history of the Keeley mine. In recent years, following the successful development of this property by the London operators, who acquired it from the liquidator of the original company, and the later conspicuous progress made on the properties of the Mining Corporation contiguous to the Keeley on the north, the district has again come into prominence and, at present, is doing much toward maintaining the gradually declining production of Cobalt itself. Apart from the Mining Corporation of Canada and the Keeley Silver Mines Limited, the principal concerns now operating in South Lorrain are the Lorrain Consolidated, the Trout Lake Mines (operated by English interests associated with the Mining Corporation) and the Canadian Lorrain Silver Mines (operated by the Huronian Belt Co., of London). A number of minor prospects are also active. The Wettlaufer and Currie, on both of which considerable work was done some years ago, are now closed. TOPOGRAPHY AND GENERAL GEOLOGY The topography of the South Lorrain area is rather more rugged than that of the vicinity of Cobalt, but the local relief, relatively speaking, is not great. Numerous lakes and streams lend a certain picturesqueness to a landscape, which is not entirely marred by the absence, from the valleys and hillsides, of the splendid bush that formerly clothed them but which has been swept away by forest fires. The geology of the locality is simple, in a lithological sense, but rather complicated structurally. The oldest rocks are Keewatin greenstones

Jan 1, 1924

By G. Bhat, J. F. Libsch

lsoembrittlement curves depicting the influence of time and temperature in the range 800' to 1260°F (425' to 680°C) on the development of embrittlement in a commercial chromium alloy steel and a commercial molybdenum alloy steel are presented. Two distinct regions of embrittlement occur in the chromium alloy steel: I—at 800' to 1000°F (425' to 540°C) and 2—in the region just below the lower critical temperature. Embrittlement is most pronounced at 800' to 1000°F, decreasing very rapidly with increasing temperature above this region, only to increase again as the lower critical temperature is approached. The data suggest two distinct modes of embrittlement with possible superposition of the two modes at extended embrittling times in the temperature range 1100° to 1150°F (590' to 620°C). While the molybdenum alloy steel shows little susceptibility to embrittlement at 800' to 1000°F (425' to 540°C), considerable embrittlement may occur just below the lower critical temperature. THE subject of temper embrittlement in alloy steels has received considerable attention in the last few years. Points of view on the mechanism of embrittlement differ, however, resulting in part from the incompleteness of the data developed and in part from the speculation regarding the susceptibility of plain carbon steel to temper embrittlement. Libsch, Powers, and Bhat1 carried out short-time embrittling treatments on an AISI 1050 steel and demonstrated that hardened plain carbon steels are quite susceptible to embrittlement when tempered in the range from 850°F (455°C) to the lower critical temperature. The isoembrittlement diagram,' representing the embrittling characteristics of this steel, is reproduced in Fig. 1. It is evident from the shape of the curves shown that embrittlement in plain carbon steel increases progressively with both temperature and time in the embrittling range. A comparison of the isoembrittlement diagram for AISI 1050 steel with that presented by Jaffe and Buffum' for an SAE 3140 steel shows that up to 930°F (500°C) the isoembrittlement characteristics of the plain carbon steel are similar to those of SAE 3140 steel, although the embrittlement is much more severe in the latter steel. Above 930°F (500°C), the rate of embrittlement in the plain carbon steel increases continuously with increasing temperature; whereas, in the SAE 3140 steel, the embrittlement rapidly decreases. The influence of alloying elements upon embrittlement during tempering thus appears to cause a decrease in embrittlement above the region of maximum embrittlement, i.e., 850" to 1000°F. The question naturally arises as to what effect individual alloying elements have upon the embrittling characteristics of the plain carbon steel. Current knowledge on the influence of alloying elements on temper brittleness may be found in the review papers of Hollomon" and Woodfine. Hollo-mon," from the results of other investigators, has shown that, in general, the amount of embrittlement increases with increasing alloy content (except for molybdenum and possibly tungsten and columbium). Jaffe and Buffum," by a comparison of the embrittlement in a plain carbon steel with that of a SAE 3140 steel postulated that the presence of alloying elements in moderate amounts tends to retard the development of temper brittleness. It is difficult to determine what effect chromium has upon temper brittleness, since most of the information available has been based on the combined effect of other elements with chromium, particularly nickel and manganese. However, Wilten, and recently Jolivet and Vidal,' Vida1, and Woodfine have reported that chromium steels are temper brittle, that the embrittlement is reversible with a maximum rate of embrittlement at approximately 975°F (525"C)," and that the susceptibility increases with increasing amounts of chromium. Taber, Thorlin, and Wallacel" have found a large embrittling effect with increasing chromium content in a medium C-Mn-Ni steel. But Hultgren and Chang," from their experiments conducted on synthetically prepared ternary Fe-C-Cr alloys, could not conclude that these alloys are susceptible to temper embrittlement. However, on addition of manganese or phosphorus, these Fe-C-Cr alloys became susceptible, from which fact they concluded that the embrittlement developed in chromium-bearing Fe-C alloys is due chiefly to the presence of these elements. Considerable data are available to show that molybdenum decreases the susceptibility of steel to temper embrittlement. However, its effectiveness in preventing or decreasing embrittlement appears limited to its presence in small amounts. Vidal" has shown that a plain 2 pct Mo steel was susceptible. Hultgren and Chang" also have shown that molybdenum additions in excess of 2 pct to synthetically prepared Ni-Cr steels did not prevent embrittlement. Jolivet and Vidal' and Lea and Arnold found that molybdenum reduced temper brittleness. Lea and Arnold further stated that molybdenum decreased the rate of embrittlement rather than the total amount of embrittlement, whereas Preece and Carter" have shown that the presence of molybdenum greatly reduces the equilibrium extent of the change at a given temperature but does not appear to influence the rate of embrittlement. There appears to be very little information as to how molybdenum by itself affects the temper brittleness susceptibility of a plain carbon steel.

Jan 1, 1956

By Henry A. Pohs

It is a rare work of art that attains the proportions of a major construction project. One instance of such a phenomenon is Bartholdi's Miss Liberty, which was designed and built section by section in Paris and then erected in New York Harbor. Another is Borglum's massive presidential quartet hewn from the granite of Mount Rushmore. Now, however, there is a new monument in the making which will completely dwarf all others. The sculptor of this supercolossus is Korczak Ziolkowski, a colorful, bearded genius who assisted Borglum on Mount Rushmore and is now carving his own granite masterpiece from Thunderhead Mountain near Custer, S. D., just ten crow-flight miles away from Rushmore.

Jan 11, 1966

COUNCIL OF SECTION DELEGATES Jack A. Criehton. Chairman Allen T. Cole. Vice Chairman M I. Signer, Secretary EXECUTIVE COMMITTEE W. C. Leonard, North Pacific W. K. Beck, Cleveland W. W. Leonard, Southwest Texas

Jan 1, 1952

By E. A. Noble

In the Western Coal Region, successful reclamation of surface-mined areas includes the protection of groundwater sources. To accomplish this, a complete understanding of the geohydrology of the affected area is imperative. Successful mine design also calls for careful attention to geohydrology. Because the Western Coal Region is semi-arid land used mainly for farming and grazing, groundwater is a particularly sensitive topic. It is especially sensitive where the lignite scheduled for mining is itself the aquifer supplying the farms and ranches. Such is the case throughout much of the Western Coal Region, particularly where there are no near-surface sand and gravel aquifers that are commonly found in the glaciated portions of the Region. Just as mining can adversely affect groundwater supply, so can groundwater adversely affect mining. Mine flooding and highwall instability are examples of this. But, mine operators must realize that procedures they use to remedy geohydrologically-related mining problems can have a dramatic effect upon ground- water conditions in areas adjacent to the mine. A logical precaution is to require the acquisition of complete baseline data prior to making the first cut. We recommend that the mining plan not only incorporate the reclamation plan, but that they be developed as one plan.

Jan 1, 1976

By F. D. Ford, Z. Dai, A. Byers

Manitoba Mining and Milling operations consist of three underground mines (Thompson T1, T3 and Birchtree), feeding the Thompson Mill. Three years ago, a collaborative effort involving Mines Exploration, Mines Project Development Group, Mill Technical Services and Vale Base Metals Technical Excellence Center was initiated to establish and verify the cause of high variability in concentrate quality and Ni recovery at the Thompson Mill. One outcome of this work was a program to systematically characterize the mineralogy and metallurgical performance of current and future orebodies feeding the mill. Mineralogy results show that high value enabling ores typically have a high pentlandite to pyrrhotite ratio and benign silicate mineralogy (mostly quartz and feldspar from sedimentary host rocks), while metallurgically challenging ores contain some combination of pyrite and/or hexagonal (non-magnetic) pyrrhotite and/or elevated quantities of talc (with associated carbonates) derived from altered ultramafic host rocks. The metallurgical performance of these two ore types has been simulated by an Excel particle flotation model, which calculates the relative floatability of particles based on the particle’s mineral composition and mineral locking determined from MLA images. The relationship between these mineral properties measured by MLA and metallurgical performance was established using 13 monthly composite samples from Thompson Mill. The model was then validated with results of laboratory flotation experiments on individual orebodies submitted for evaluation. The validated model can be used to predict plant metallurgical performance based on individual ore bodies feeding the mill. Individual orebody’s grade-recovery curves are assumed to be additive, and can be weighted in proportion to the mill feed to predict mill recovery over the same time period. The ore mixing can be done with a simple Excel spreadsheet and comes with a graphical output for easy visualization of the resulting grade-recovery curve.

Jan 1, 2015

By Malcolm Arnesen

Mineral Resource Management (MRM) is a business concept with the purpose of increasing throughput by management of key process variables to optimize ore utilization. To achieve a MRM process focus there are four principles that need to be applied to the business. In this sense, the paper define these principles and describe how they are applied to the mining business using Thabazimbi iron ore mine as an example. Also the article deals with the generic approach to Mineral Resource Management and the second part with the application and success of MRM at Thabazimbi Iron Ore Mine.

Jul 17, 2000

By A. R. Elsea, C. C. McBride

HIGH-TEMPERATURE alloys, that is, alloys that are strong at high temperatures, have become increasingly important with the development of modern aircraft engines. Many alloys of this type are available. However, metallurgists do not have a clear understanding of the phases or structures which are responsible for these high-temperature properties. If these basic factors were understood, it might be possible to make better or cheaper alloys for service at high temperatures. For this reason, an investigation of the fundamental factors promoting high-temperature strength in alloys was started at Battelle Memorial Institute. This was to have included a study of the relationship between the structure and properties of cobalt-chromium base alloys of the vitallium type. It soon became clear that the structure of vitallium is quite complex and that the equilibrium diagrams which should explain these structures were unreliable. As a result, the cobalt-chromium binary diagram was determined as the first phase of this investigation1. This diagram is shown in fig. 1. During the study of the cobalt-chromium binary system, it was learned that these alloys may pick up considerable nitrogen when melted and heat treated in air. The extent to which nitrogen affects the various reactions in cobalt-chromium base alloys was not known, but there were indications that this impurity might be responsible for some of the erratic test results obtained for vitallium. Consequently, nitrogen was the first ternary addition studied. Thereafter the work was extended to ternary additions of iron and of nickel. This paper describes the investigation of the effects of nitrogen, iron, and nickel upon the reactions in cobalt-chromium alloys with 80:20 and 68:32 cobalt-chromium ratios. Experimental Work Alloy Preparation: A series of cobalt-chromium base alloys containing various amounts of the third element being studied were made for both the 80:20 and the 68:32 cobalt-chromium ratios. Electrolytic chromium, cobalt, and iron, and reagent-grade nickel powder were used as melting stock. Table I contains the chemical analyses of these materials. The charges were melted in alun-dum thimble crucibles which absorbed chromium oxide and effectively deoxidized the melts. These crucibles were supported by close-fitting graphite sleeves so that if they cracked during melting the metal would not be lost. Carbon increases, during

Jan 1, 1951

Stripping of Fe (III) from D2EHPA Using Different Reagents The common way to extract Fe(III) from an organic solvent is by using concentrated acidic solutions. The stripping of Fe(III) from organic solvent Di-2-ethylhexyl phosphoric acid (D2EHPA) by hydrochloric acid (HCl) solutions has been found to increase with increasing the acid concentration. However, the use of a concentrated acidic solution such as 6 M HCl can degrade the organic molecules. In this research, to increase the efficiency of Fe(III) stripping from D2EHPA, effect of some acids, salts and buffer solutions was studied. Influence of Tri-butyl phosphate (TBP) as modifier on the Fe(III) stripping operation was also investigated. According to the results, the best Fe stripping recovery was achieved in the presence of low acid concentration and the salts which was 72.4 per cent oxalic acid, 70 per cent ammonium oxalate and 75 per cent buffer of oxalic acid and ammonium oxalate. The results also showed a better recovery in the presence of the buffer rather than the salt. Finally, increasing the concentration of TBP, HCl and H2SO4 resulted in a higher stripping efficiency of Fe(III). However, in the presence of oxalic acid and its salts increasing the reagent concentration did not increase the stripping efficiency and at this condition, the recovery of iron remained constant.

Sep 13, 2010

By D. R. Mash

A strong yield point with attendant enhanced mechanical properties was found in commercially pure beryllium under certain conditions of heat treatment. Beryllium specimens also responded to both quench and strain aging treatments. Based on these results, a possible means of obtaining increased normal temperature mechanical properties is suggested. COMMERCIALLY pure beryllium has been found to exhibit the yield point phenomenon and several other aging manifestations under certain conditions of heat treatment. This behavior is not surprising in view of the present accumulation of experience regarding such effects in numerous metals; but in addition to extending this experience to include beryllium, the present study is of interest because aging effects are generally associated with the presence of small amounts of solute elements. The well known lack of tensile ductility in beryllium at normal temperatures is also considered to be due to impurities in some way. In the present investigation, the view was taken that beryllium of commercial purity (greater than 98 pct) should be considered as a dilute alloy and that precipitation phenomena may well exist which could lead to enhanced mechanical properties. In connection with this possibility, published data on the variation of mechanical properties with temperature are of interest. For example, Fig. 1 illustrates the variation of ductility (percentage of elongation) and ultimate strength as a function of temperature for beryllium of various histories.* Although these curves are somewhat schematic in nature, they clearly indicate the possibility that precipitation of an unstable phase and/or aging effects occur during tests in the region 400" to 700°C. The existence of such behavior should be recognized as affecting the properties of the commercial material and perhaps can be employed advantageously. Experimental Method All testing was done at room temperature using a Baldwin universal testing machine. A microformer extensometer was used in conjunction with a micro-former-type stress-strain recorder. All tests were conducted at constant loading rate, the slowest rates being used. This corresponded to 120 lb per min in the 1200 lb full scale range and 300 lb per min in the 6000 lb full scale range. After the rate of loading was set in the elastic range of the material during the early part of the test, no further adjustments were made, allowing the test to proceed at that setting. In the plastic region of the curve above the yield region, strain rates of from 0.002 to 0.006 in. per min were regularly obtained. All experimentation was carried out on specimens machined from the same lot of beryllium, lot No. Y5036BP. Table I shows the chemical analysis as furnished by the supplier, Brush Beryllium Co., as well as the standard specifications to which commercial beryllium is produced. Both 1/4 in. thick hot pressed plate and ½ in. round hot pressed and warm extruded rods were obtained. The history of the material is reported to be as follows: 1—Beryllium metal plates, produced from a standard hot pressed QMV beryllium metal block 4x15x40 in., were cut off and finished machined to 1/4x6x12 in. flat plates. The original hot pressed block was made by hot pressing —200 mesh vacuum cast attri-tioned powder at about 1050°C under vacuum. 2—Beryllium rod was hot pressed and warm extruded. Extrusion billets were machined from the regular hot pressed blocks followed by extrusion at 425°C. The extrusion was done without jacketing, and graphite was used as a lubricant. The rods were then straightened at 720 °C, after which they were annealed at 800°C for 15 min. Both flat tensile specimens and round tensile specimens were tested. The former were machined from the plate stock into standard specimens according to specifications shown in ASTM E8-52T. The nominal cross-section was 0.25x0.500 in. and the gage length was 2 in. The round specimens were

Jan 1, 1956

By L. Y. Zhang

The metallic sulphides in Jinchuan Mine are relative friable and the gangue minerals suffer of wide secondary change, the overgrinding of metallic sulphides and sliming of gangue minerals are the main cause that makes the mineral separation indexes difficult to improve. So changing the process of grinding, and classification, and optimizing the particle size distribution of grinding product is the key improving the separation performance of Jinchuan nickel and copper ore.

Jan 1, 2014

By B Murphy

Traditionally comminution optimisation has been focused on energy minimisation, whereas flotation optimisation has been focused on recovery improvement. One of the largest, if not the largest, operating cost over the life of a flotation circuit is electrical energy. With increasing pressure on operators to lower production costs and the cost of energy increasing, reducing the energy consumption of the flotation circuit can be beneficial to site economics. This paper reviews the use of energy by mechanically agitated flotation machines and discusses the measurement and benchmarking of energy consumption in modern flotation concentrators. Opportunities for improving flotation energy efficiency are also identified.CITATION:Murphy, B, 2013. Flotation energy consumption and opportunities for improvement, in Proceedings MetPlant 2013 , pp 399-412 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By Roberts T, Firth B. A

A series of flotation experiments was carried out to study the interaction between the parameters of pulp density (mass per cent of solids in feed slurry) and frother addition (on the basis of solid mass feed rate). It was found that certain combinations of pulp density and frother additions caused large losses in yield. The interactive effect of these parameters can be primarily attributed to the total amount of frother added per unit of water. Consequently it is suggested that frother additions be made on the basis of water flow rate. As frother addition increased, in terms of the amount of frother per unit of water, yield increased rapidly but above an addition rate of about 10 g/tone it reached a plateau. Such results correlated well with qualitative visual observations of changes in bubble size and dispersion, with increasing levels of frother addition.

Jan 1, 1984

By G. Balletto, C. Furcas

"The mineral raw materials industry is a key-component of the Gross Domestic Product of industrialised economies, closely related to both the building and the industrial sectors. Despite this, at local level mining and quarrying are associated with both irreversible environmental damage and several visual alterations affecting the natural landscape. In this sense, SIA (Social Impact Assessment) has become a strategic tool that can not only improve the prediction but also the assessment of the social impact by involving the local communities in a participatory process. Taking into account the SIA experience, together with the examination of some relevant international case studies, it is possible to draw up a list of good practices for mining project management, from exploration through to closure and beyond, with quarry restoration. Such good practices will complement the existing studies, focusing on environmental issues, with the social issues arisen considered in SIA application."

Jan 1, 2011

Jan 1, 1921

By Arthur C. Spencer

The object of the following paper is a description of the Treadwell gold-deposits in their geological aspects. quite apart from any consideration of the economical methods of mining and milling which have been developed and successfully applied

Jan 1, 1905