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By D. Mills, G. B. Craig

The defortnaliotz of zirconicltt single crystals conlaining osygen in the range 740 to 6800 atom parts per nilllion was esanined oc7er the range 77" to 950°K. An anctlsis of the dqfarmaliotz parameters leads to the cotcllsiotr that the rale -cotzfrolling thermally activated dqivr,irrtion process oe-r /he range 77" to 560°K is oc.crco,ling osvgen alotns. A thermally actitaled defor,ilntion process is not found between 600" and 800", but does occur aboz%e 800°K. THE present investigation was undertaken to measure the effects of controlled amounts of oxygen on the deformation parameters of a zirconium single crystals over the temperature range 77" to 950°K and to determine the rate-controlling mechanisms. Although there is no doubt that the mechanical properties of the group IV metals, titanium, zirconium, and hafnium, are strongly influenced by the interstitial impurities oxygen, nitrogen, carbon, and hydrogen, there are many conflicting theories as to the role played by the interstitials during the deformation proess.'- There is general agreement that the mechanisms which control plastic flow in a metal impose characteristic values on such parameters as the flow stress and its temperature dependence, the activation volume, and the activation energies. These parameters will be used to analyze the deformation mechanisms. eltham,' Sargent,16 and ibbs' have shown that the stress relaxation technique allows the activation volume characteristic of the deformation process to be found during the course of a simple tension test. In many cases it is found that the relaxation of stress is logarithmic with time and obeys a relationship of the following form: T-T = AT =S logl0(qt + C) [I] where t, is the shear stress at the start of the relaxation test, t is the shear stress at time t, and S. q, and C are experimental constants, and S is the strain rate sensitivity of the stress t as shown in the appendix. The slope found from a semilogarithmic plot of At vs time is approximately equal to S. The activation volume u, association with the deformation process, is found from the following relationship: The theoretical treatment of thermally activated plastic flow due to schoeck18 shows that the activation volume when combined with the temperature dependence of the flow stress gives the activation energy for the process according to equations: seegerZ3 considers that the flow stress at lower temperatures ld is composed of two parts such that Tapplied = tinternal + Teffective , where Teffective 3 ff , is the stress necessary to overcome the local obstacles to deformation and Tinternal, ri, is the stress necessary to overcome the long-range elastic stress field of dislocations on other planes. ri is considered to be largely elastic in origin and can be estimated from the stress value at the temperature independent portion of the flow stress-temperature curve. EXPERIMENTAL The crystal bar zirconium used in this investigation was supplied by Wah Chang Corp. whose certified analysis gave the following impurity contents in parts per million by weight: oxygen, 150; nitrogen, 10; iron, 180. All others were less than 100 ppm. The oxygen and iron contents were confirmed by neutron activation and chemical analyses, respectively. Single crystals were grown in an electron beam furnace according to the method of Wilson and Pickle-simer'' and ills.'' The orientation of the crystals was such that the specimen axes were located in the lower third of the standard section of the basal plane stereographic projection for zirconium. This orienta-

Jan 1, 1969

By C. W. Chiaretta

Utah Power and Light Company's Deer Creek Mine had been developed to a point where mine ventilation efficiency had declined to an unacceptable level. Problems identified were ventilation of inactive areas, excessive leakage, and restrictions in the return and intake air ways. Mine management implemented an intensive mine ventilation improvement program to alleviate future problems with respirable dust in the working sections and diesel equipment emissions. Program objectives included sealing of inactive areas of the mine, rehabilitation of high resistance areas, and construction of additional intake and return aircourses. Applications of computer modeling techniques are used to predict the effects of ventilation changes and improvements. Improvements are then prioritized to achieve the largest efficiency increases first. Actual real time assessment of the mine environment and ventilation changes are accomplished with a mine wide monitoring computer system. The Deer Creek ventilation improvement program has more than doubled the ventilating efficiency of the mine.

Jan 1, 1990

By Marcie A. Greenberg

The Fence Lake Project is located in the Salt Lake coal field, an extension of the San Juan Basin. Geologic formations exposed in the Project area range in age from late Cretaceous to Quaternary. Coal is encountered in the Moreno Hill Formation (upper Cretaceous). Salt River Project (SRP) followed the basic textbook approach for the exploration, regional appraisal, detailed reconnaissance, detailed surface appraisal and three dimensional sampling (physical exploration). SRP is exploring this property as a potential fuel source for the Coronado Generating Station. Therefore, for the physical exploration stage, the quality sampling program was designed from a utility company viewpoint to determine possible impacts to the Station. Exploration drilling was completed in spring, 1982; September, 1982, and summer, 1984. Engineering, environmental, and land acquisition studies were added in the Summer, 1984 Program to more closely evaluate the potential Fence Lake Project coal supply option for the Coronado Generating Station. Studies, including drilling, are ongoing-at this time.

Jan 1, 1984

By K C. Corin, C T. O’Connor

In recent years it has been shown that the concept of using partial molar excess Gibbs energy (G̅ex) to explain the behaviour of collectors in the recovery of minerals can be usefully applied to explain flotation performance. Fundamentally this is because hydrophobicity of a mineral particle on which a collector is adsorbed may be strongly related to the fact that the alkyl chain associated with the collector behaves in the same way as any hydrocarbon would in an aqueous medium. This hydrocarbon-water system represents a classical non-ideal mixture, and such mixtures are quantified thermodynamically by determining the activity coefficient of the hydrocarbon moiety of the collector and hence its G̅ex in the mixture. It has been shown that G̅ex is a more rigorous indicator of the contributions of various alkyl groups of a collector than HLB (Corin and O’Connor, 2014) and was also able to explain aspects of froth behaviour (Harris and O’Connor, 2017) and hydrophobicity (O’Connor, 2021). The present paper is aimed at extending the above concepts in two different ways. Firstly, a study is undertaken of a range of results previously reported in which various reagents containing different alkyl groups were analysed in terms of their effect on contact angle and their performance as flotation reagents in terms of recovery. These results sustain the previous observations that there is a robust positive relationship between hydrophobicity as indicated by flotation recovery and contact angle and G̅ex of the alkyl group associated with the collector. Secondly, on the basis of the observation that increases in G̅ex are indicative of increases in the hydrophobicity of the mineral particle-collector aggregate, a study was undertaken to examine the effect of ions typical of electrolytes in water as well as the effect of the presence of alcohols and of pH on G̅ex of the collector alkyl group. In the former two instances the absence of any correlation between G̅ex and recoveries supported the proposition of the respective authors of these studies that the major effect of these electrolytes and added alcohols may be on particle–bubble attachment rather than on the hydrophobicity of the mineral/collector in the aqueous system. On the other hand, the effect of pH on G̅ex correlated reasonably well with changes reported in the literature on the effect of pH on recovery and contact angle.

Aug 24, 2022

By J. M. Tranquilla

EMR Microwave has developed several unique processes for the pretreatment of refractory gold and copper ores. This report describes a recent large scale pilot project involving a carbonaceous gold-bearing whole ore. Pilot plant testwork conducted jointly by EMR and Bateman Engineering Inc. has shown that 90+% cyanide soluble gold recovery is obtainable from refractory (sulphide and carbonaceous) Carlin, Nevada gold ores. Typical cyanide soluble gold recoveries for untreated material is 20%. AC energy consumption was found to be between 58.l kWh/ton and 15.5 kWh/t for an assumed heat recovery of 50% and 80% respectively. The plant was operated at reduced temperatures ( 400°C) from previous testwork on similar ore at 600°-700°C.

Jan 1, 2000

By J. B. Littlefield

[Ata. meeting of the Subcommi ttce on Chemical _ et.lOds of Air Ant:..1ysis of-the American Public Health Ascociation in October 1937, the llse of the impinger for collectinG lcs.d fu.l1e wa:., discussed. The Bureau of Mnes de-cided to obtain infornw.tion on the efficiency of the lerge and midget im-pingers for this purpose y using the electric recipitator as a reference method. 'I'ests ~ ere made aJ,so to aScer ain the effici ency of the recently developed midget i;npi gerS..! for collac ing lead dust. For comparative pur-poses, samples collected by tte large impinger wore included.]

Jan 1, 1938

By Donald L. Gaughenbaugh

Under the terms of the 1970 amendments to the Clean Air Act, the EPA established national ambient air quality standards for a number of pollutants. Sulfur dioxide (SO2) was one of these pollutants. These ambient air quality standards have had perhaps their biggest impact on the power utilities. In an effort to meet the air quality standards set forth by the EPA, utilities using high sulfur fuels have been forced to install flue gas desulfurization (FGD) systems. The majority of FGD systems in operation today are nonregenerable systems, that is the by-product of the system is disposed of, usually into settling ponds. Limestone slurry is the most common reagent used to remove SO from the flue gases. The calcium carbonate (limestone) slurry interacts with the flue gas, absorbing the SO2 and forming a by-product of calcium sulfate/sulfite which is disposed of.

Jan 1, 1986

By S. J. Bluhm

INTRODUCTION Lesotho is a mountainous area of southern Africa from which water is to be exported in an extensive tunnel system, to industrial regions inland. The related tunnelling project has involved a num- ber of drives using tunnel boring machines [TBMs] to excavate about 100 km of 5 m diameter water tunnels [von Glehn and Bluhm, 1995). This paper describes the ventilation and cooling of some of the tunnel drives from both the operational and design points-of-view with a particular focus on heat generation. There were many common features in all of the drives but this paper is focused mainly on the Hlotse drive which was 18,4 km long. The drives were ventilated using forced ventilation systems to provide appropriate air flow throughout the tunnels and face zones. In addition, the Hlotse drive required refrigeration equip- ment which provided chilled water to the tunnel. While the sec- ondary ventilation systems play an important role in gas and dust handling, the paper concentrates on the primary ventilation and cooling issues. The ventilation of these tunnels was an exacting exercise be- cause: • Rock temperatures and geothermal heat flow were high. • TBMs with relatively high power ratings were used. • Diesel locomotives were used. • Drives were relatively long. • High altitude meant a low air density. An important feature was the simulation and monitoring of the ventilation and heat flow components and the project was characterised by analysis, monitoring and ongoing tactical decision-making throughout the progress. The thermodynamics of the systems were complex because there were many interactive effects and analyses were carried out using special computer pro- grams. The monitoring confirmed the accuracy of the models, and in this manner it was possible to confidently ensure healthy and safe working conditions and still minimise costs. Local ambient climate conditions range from temperatures higher than 35 "C in summer to below -10 OC in winter. Based on available statistical data and the thermal storage/damping effects in the system, design summer ambient conditions were taken as 15 OC/25 "C wet-bulb/dry-bulb. The barometric pressure was 80 kPa and due to the altitude, the ambient air density was only 0,9 kg/m3. The local Authority specified a maximum in-tunnel wet- bulb temperature [at any point] of 32,O OC and a mean wet-bulb temperature [from all locations] of 27,5 OC maximum. The maxi- mum height of ground cover above the tunnel was 1 200 m and the maximum virgin rock temperature was 41 OC; see Figure 1. Diesel dilution criteria specified by the local Authority was a minimum of 0.1 m3/s per rated kW of diesel engine. Other requirements related to gases such as CO, CO2, NOx and CH4 [and the need for intrinsically safe equipment] but these are not of direct relevance to this paper. The actual average face advance was about 30 m/d with good days achieving 60 m/d and good months achieving 1 000 m [23 working days]. The original design tunnelling rate was 50 m/d. DESCRIPTION OF HLOTSE DRIVE VENTILATION AND COOLING SYSTEM The ventilation requirements in the tunnels were dictated by heat and diesel dilution needs. The best ventilation and cooling policy is generally a balance between using increased quantities of fresh air or refrigeration [or both]. In this particular scenario it turned out that, since the diesel emission criteria required large quantities of air, the refrigeration needs were modest. The drive was ventilated using a ducted, forced ventilation system from fans located at the portal. The maximum ventilation requirement was 51 m3/s when the drive was at 18.4 km. From a heat flow point of view, the worst scenario was a heat load of 3.5 MW when the drive was at 7 km. This was cooled by the ventilation air and a supply of chilled water to the tunnel. Refrigeration and chilled water system In the design phase, a detailed comparison was carried out between two general alternatives for providing refrigeration. First, was a system in which refrigeration sets and air coolers are installed on the TBM train; the refrigeration sets are cooled by condenser water piped to and from cooling towers at the portal. Second, was a system in which refrigeration water chillers are in- stalled at the portal and chilled water is piped into the tunnel. The detailed comparison indicated that the capital and running costs of the second system were at least 60 % lower than the in-tunnel plant. There were also many obvious practical benefits for favouring the portal system. The refrigeration plant supplied 23 11s of cold water at a temperature of 10 OC. After providing the cooling effect in the drive, the water returned to the portal where it was initially cooled in open-circuit evaporative pre-cooling towers, chilled in the refrigeration plant and then returned to the tunnel. The cold water flowed into the tunnel in an insulated supply pipe and returned in an uninsulated pipe; the water was simply circulated to the end of the pipe and returned. The cooling effect in the tunnel was achieved entirely through heat transfer from the pipe [long linear heat exchanger] and no air coils or other heat exchangers were required. The cooling requirements were satisfied by the heat transfer to the returns chilled water steel pipe [200 mm]. The pipes were eventually installed to a maximum distance of 10,8 km in what was considered a very practical and cost effective solution.

Jan 1, 1997

By T. T. Tomimatsu

This? Bureau of Mines paper discusses the corporate structure dynamics, methods of financing, and financial assessment approaches that should be utilized to evaluate the economic health of the coal industry. It suggests rates of return and other measures of corporate economies necessary to attract capital required to finance emerging coal demand, plus impact of coal sales to total revenues. The study illuminates the activities of 30 selected coal-producing companies, including their subsidiaries or affiliates, that were responsible for approximately 60 percent of the total U.S. production in 1974. The selected firms are not all primary coal producers; many of the larger producer's are classified by the financial institutions as petroleum, metal, and steel producers, public utilities, or chemical industries. The bituminous coal industry is highly competitive as to price, service, and quality of pronuct and is subject to competition from other noncoal energy sources. The top 15 bituminous coal-producing companies mined about 46.6 per-cent of the Nation's total production in 1974, and the balance of approximately 3,885 companies were responsible for the rest of the production. Thus, the U.S. bituminous coal industry is not an oligopoly. Today, about 65 percent of the Nation's total coal production is consumed by electric power utilities and 26 percent by steel, space heating, and other industries; the balance of 9 percent is exported.

Jan 1, 1976

By W E. vanSteenburgh

The Polar Continental Shelf Project was initiated in 1959 to provide an administrative and logistic vehicle for research in the physical sciences of the land, sea and channel area of the Arctic Archipelago. Most of the scientists are supplied on secondment from the professional branches of the Department. The yearly expeditions number some eighty scientists and sub-professional staff, and they are supported by a fleet of fixed-winged aircraft and helicopters. Accurate positioning is obtained by the use of a Decca Lambda navigational system which is moved as the area of interest is shifted. The Project is designed to accommodate not only physical scientists, but to provide facilities for other scientist who may have an interest in the area under study. The main research scope of the Project includes topographical surveys, hydrography, oceanography, geology, including marine sedimentary studies, gravity, magnetics, seismology, glaciology and geography. The Polar Continental Shelf Project was initiated and recommended by the Committee on Northern Development in 1958.

Jan 1, 1963

By R. J. Wasilewski

Elastic constants have been determined on single crystals of maximum-melting-temperature NiAl compound (50.6 at. pct Al) at 25°C. Temperature variations of Young&apos;s modulus in the three principal crystal directions between -150°C and +800°C exhibit no anomalies similar to those repovted for the isomor-phous compounds brass and AuCd. It is concluded that the ordered CsCl structure is stable throughout the temperuture range investigated NICKEL aluminide is a congruently melting inter-metallic compound of CsCl (B2) structure, stable over a rather wide composition range (40 to 54 pct Al). It exhibits a lattice-parameter maximum of a. = 2.883A at 50.6 pct 1,&apos; at which composition the excess aluminum atoms are randomly distributed on the vacant nickel sites;&apos; at higher nickel compositions the excess nickel atoms replace substitutionally in aluminum sites, while at higher aluminum compositions vacancies are present in the nickel sublattice.&apos; For compositions close to NiAl no significant variation in order has been observed at temperatures up to 900°C.3 At high nickel (65 pct) compositions the existence of a martensitic structural transformation has been reported.4 NiAl is isomorphous with the ordered B-brass structure and with the high-temperature structures of AuCd and TiNi alloys close to equiatomic composition. All of these exhibit anomalous elastic behavior as the temperature of their diffusionless transformation to lower-symmetry structures is approached.&apos;-&apos; This behavior has been explained as indicative of low stability of the CsCl structure in these compounds.8 The present paper reports the experimental determination of the elastic compliances of single-crystal NiA1. EXPERIMENTAL METHOD 1) Specimens. Polycrystalline NiAl was prepared by induction melting of carbonyl nickel and high-purity aluminum and casting into solid copper molds in gettered helium atmosphere. The castings thus produced were canned in mild steel and impact-extruded at 1100 to 1200°C to 38-in.diam rod. After the steel sheath was pickled off, the rods were converted to single crystals by repeated high-frequency satisfactorily produced the desired orientations in the form of crystals 38 in. diam by 8-12 in. long. These were subsequently center less-ground to 7 to 8 mm diam by 12 cm long, electropolished (in 80 pct methanol, 20 pct HzSO, at 25°C and 15 v), and their axial orientation determined to 1 deg by the Laue back-reflection technique. The rod dimensions were determined to 0.01 mm and the densities determined from geometrical dimensions and the weight of every specimen. The average density was 5.905 0.005 g per cu cm. 2) Elastic Data Measurements. Room-temperature elastic compliances Sii were obtained by determining to 0.1 cps the fundameGtal resonance frequencies in the longitudinal and torsional vibration modes. At these frequencies the following relations hold: E =p(2lfif =pvl= Sn- 2r[Sll- S12- -£„«] g -P(2iftf = pvf = (s<« - fr(sii - sw - ±s»y where vl and vt are the velocities, and f andft the resonance frequencies of the longitudinal and torsional waves, respectively; 1 is the length of the specimen, and r is the direction cosine factor—{cos2 a • cos2 0 + cos2 a . cos2 y + cos2 0 ¦ cos2 Y}. Given three crystals of orientations (loo), (110), and (111)) i.e., F = 0, 14, and 13, we can obtain six equations for the three unknown compliances, thus providing adequate internal check. Mode mixing can readily occur in the relatively long wavelength resonance utilized here. This could cause a significant error in the torsion wave velocities calculated from the apparent resonance frequenies. Therefore, throughout the present work, a method, described previosl,&apos; was used to ensure that no significant mode mixing took place at resonance. The apparatus used was originally designed for the Elastomat, Magnaflux Corp.. Chicago, 111. determination of flexural vibration resonance frequencies. At room temperature torsional vibration mode could be established by suitable positioning of the thin wires from the input and pick-up transducers, and longitudinal mode by cementing thin magnetic foils at the ends of the specimen, and inducing the vibration by means of electromagnetic transducers. Only flex-ural resonance frequencies could, however, be obtained reproducibly over the temperature range of -150 to 800°C. These data are considerably less accurate, the error in the modulus being estimated at -0.6 pct from the specimen dimensions and the room-temperature Poisson&apos;s ratio. The reproducibility of the resonance frequencies in repeat runs was, however, to better than l in 15,000, hence the relative elastic modulus error less than 0.02 pct. Therefore, the temperature variation of the principal Young&apos;s moduli obtained by flexural resonance, relative to room-temperature values, is believed to be satisfactorily accurate.

Jan 1, 1967

By L. Muhr, Y. -T. Tang, M. -O. Simonnot, B. Laubie, R. -L. Qui, Z. Chour

"Agromining aims at recovering metals from different secondary resources with hyperaccumulating plants. These natural plants can selectively concentrate metals at very high level and can be transformed to produce commercial compounds. The classical strategy to recover metals from hyperaccumulator plants is based on hydrometallurgy. It consists of: i) burning the plant to obtain ash, which is a very rich bio-ore without organic matter, ii) transferring the target element(s) into aqueous solution by acid leaching and iii) purifying the leach liquor to obtain the target element(s) in the desired form. This method has enabled us to obtain nickel salts, nickel oxide, zinc and cadmium from different plants. However, it is not possible to apply this approach to recover rare earth elements (REEs) from the fern D. dichotoma, growing on mine tailings in South China. Actually, this plant is very rich in silicon: plant burning gives an amorphous ash, very stable despite severe leaching conditions. Therefore, the strategy has been changed and processes are currently developed to extract REEs by direct leaching of the biomass, without burning the plant. Several conditions (i.e. leaching solutions) have been investigated, showing that a good extraction yield was obtained with HNO3 0.5 N (around 84%). This yield was increased to 99% by adding a complexing resin into the leaching solution. After two-steps of elution, results have shown that is possible to recover 75% of the REEs at 81% purity.INTRODUCTION The demand of rare earth elements (REEs) (including 15 lanthanides, yttrium and scandium) has been growing sharply over the past years, because of their industrial applications. REEs are essential elements for emerging technologies, and are used for example in permanent magnets, lamp phosphors or rechargeable batteries. China is the main producer, and the market supply became tense in 2010 when this country decided to limit exports of these elements. Exploitable mineral resources, as well as REE separation capacity are concentrated in a few countries (e.g. USA, Australia, Malaysia, France), which increases the supply risk. Therefore, these elements are considered as critical raw materials (CRM) for many countries and especially for EU (Fortier and Gambogi, 2017)."

Jan 1, 2018

By J. C. van Dyk, F. B. Waanders, J. Brand, C. A. Strydom

"Underground coal gasification (UCG) is a fast-emerging, in situ mining technology that provides access to low-cost energy through the utilization of coal reserves that are currently not technically or economically exploitable by conventional mining methods.Groundwater monitoring for conventional coal mining in South Africa is well established, with SANS, ASTM, and ISO standards for the specific environment, location, and purposes. South Africa’s groundwater is a critical resource that provides environmental benefits and contributes to the well-being of the citizens and economic growth. Groundwater supplies the drinking water needs of large portions of the population, and in some rural areas it represents the only source of water for domestic use. Implementation of, and adherence to, groundwater monitoring standards are thus non-negotiable.The groundwater quality management mission, according to the Department of Water and Sanitation in South Africa, is set in the context of the water resources mission and reads as follows:‘To manage groundwater quality in an integrated and sustainable manner within the context of the NationalWater Resource Strategy and thereby to provide anadequate level of protection to groundwater resources and secure the supply of water of acceptable quality.’ (SABS, 2016).In this paper we propose fit-for-purpose groundwater monitoring standards for a commercial UCG operation. It is important to proactively prevent or minimize potential impacts on groundwater through long-term protection and monitoring plans. Scope of study / standard proposal The purpose of this paper is to set out a National Standard Proposal to emphasize groundwater monitoring as one of the five strategies of the ‘Policy and Strategy for Groundwater Quality Management in South Africa’ (Department of Water Affairs and Forestry, 2000) and to align it with the National Water Act, Act no. 36 of 1998 (Republic of South Africa, 1998).The focus of this standard is directed solely towards groundwater monitoring during underground coal gasification (UCG). Groundwater in this context refers to water as sampled from dedicated monitoring wells around the targeted site, which will include the shallow aquifer referred to as groundwater, and water flow at the level of the underground gasifier, referred to as ‘coal water’."

Oct 1, 2018

By H. Herbert Hughes

Iceland spar is a variety of calcite ( calcium carbonate ) characterized by its purity , transparency , and perfection of crystalline structure . It takes its name from the country in which it was discovered . The actual demand for it is small , but the supplies of high - grade optical spar are so meager that the search for it has become international in its scope . Iceland spar is a scientific necessity , for without it research precision and technology would be hampered considerably . The earliest students of mineralogy were familiar with calcite , but the transparent variety was not discovered until early in the seventeenth century , when crystals of it were found in the bed of a stream in Iceland . It received little attention until 1669 , when Erasmus Bartholinus first recognized its powers of double refraction . The results of his investigation were published in a book , " Experimenta Crystalli Islandici , " which appeared in 1670. The law governing the action of the rerracted rays was discovered by Christian Huygens eight years later . The polarization of light rays in passing through Iceland spar was discovered in 1809 by Etienne Louis Malus , a French physicist , who published a paper describing the phenomenon . His work was closely followed by that of William Nicol , who in 1828 designed the Nicol prism which is still used as the source of polarized light in most optical instruments .

Jul 1, 1931

By M Edwards

The paper outlines the successful application of some of the on-belt technologies available from Scantech International Pty Ltd and how these have provided benefits in a number of mining and mineral processing operations. Effective process control requires real time analysis so quality can be fed back to the previous process and fed forward to a subsequent process. A range of on-belt analysers that allows for full stream, continuous, non-contact analysis of conveyed materials is available to achieve this. Real time results can provide timely information for effective process control. Benefits of on-belt analysis systems become more evident once the true variability of material quality and moisture content in conveyed flows is measured. To obtain economies of scale in mineral processing operations large material flows are achieved using conveyors. The cost and effort to sample representatively increases as conveyor flows increase. One sample may represent a few tonnes or up to 10 000 tonnes of material. The turnaround time between sampling and availability of sample analysis data does not allow real time process control. Tonnage flow rate, moisture content and elemental or mineralogical composition are required to perform effective process control of most conveyed streams. Tonnages can be effectively measured using belt weighers. The analyses derived from small samples supplied by conveyor-based sampling systems contain high variability. On-belt, continuous analysers see all the material and, through short term compositing of analyses, supply less variable results. Real time analysis helps operators develop a better understanding of material variability. Analysers can be effectively utilised to improve the consistency of product quality through bulk sorting and blending control. Many existing users of the technologies have gained competitive advantages through their ability to supply a more consistent quality product to the market.

Jan 1, 2008

By Gilbert Soler

PRODUCERS of alloy steels recognize the importance of chemical composition in rela-tion to the hot-working properties and the typical surface defects found in their prod-uct. Each analysis of steel has its own peculiar characteristics. Under conditions of standard mill practice each analysis is susceptible to certain types of defects. Mill practice must be varied to obtain the best combination of surface and internal quality in the product. Chemical composition influences the cast structure and crystallization character-istics of the ingot. It also determines the rate of heating and cooling, the plastic hot-working range, and the phase structure of the steel at various temperatures as well as the tendency toward scale formation and decarburization, This paper endeavors to emphasize the manner in which chemical composition affects the various properties of steel, and to indicate the relative impor-tance of these factors in relation to the hot-working properties and surface charac-teristics of killed steel. The influence of chemical composition may be outlined as follows: I. Effect on the cast structure of steel, including: A. State of deoxidation, and type of inclusions. B. Gas content of steel. C. Freezing point and melting point of steel.

Jan 1, 1940

By C. Dorfling

Experimental work was performed using a bench scale autoclave to evaluate the effects that leaching temperature, pressure, initial acid concentration, and the solid to liquid ratio have on the behaviour of base metals and platinum group metals in a high-pressure sulphuric acid oxygen leaching system. The concentrations of metals in the leach solution were measured over time at different leaching conditions. At the conditions investigated, the initial acid concentration had the largest influence on the copper leaching kinetics, while the leaching rates of the other precious metals (OPMs: rhodium, ruthenium, and iridium) were highly dependent on the leaching temperature. A set of chemical reactions that can be used to describe the leaching chemistry was proposed, and the associated reaction kinetics were quantified. As a first estimation, the rate expressions were considered first order, and the rate constants were determined using the method of least squares, considering the experimental and predicted concentrations obtained for the different leaching conditions. Of the OPM compounds, the sulphides showed the fastest dissolution rate, followed by OPM alloys, and finally the OPM oxides. During the initial leaching stages, base metals and OPMs competed for the available dissolved oxygen, with oxygen being preferentially used for copper leaching. Precipitation of OPMs during the initial leaching stages can be ascribed to copper and nickel dissolution according to exchange reactions between dissolved OPMs and copper present as digenite or nickel present as polydymite. Control of the autoclave residence time is of particular importance to enhance the selectivity of this leaching step, given the dependence of the PGM leaching rates on the extent of copper dissolution.

Sep 1, 2012

By Valery Kaplan

Sulfur emission in the form of SO2 in flue gases is one of the most serious atmospheric pollutants associated with coal combustion and non-ferrous metals production. The carbonate eutectic method for removing SO2 from flue gases at 723–923 K was initially proposed in the 1970s but despite its great efficiency (SO2 concentration in the flue gas after purification reached 0.003 volume %), it could not be implemented by industry due to the complexity of the carbonate melt regeneration stage. Earlier we proposed a method suited to coal-firing power stations where the melt was regenerated using CO as a reducing agent. However, most metallurgical plants do not use coal and therefore lack a large source of CO. Here we propose a method for removing sulfur from the carbonate eutectic melt by purging it with natural gas or a natural gas/air mixture, which are available in the vast majority of metallurgical plants. This reaction leads to the reduction of sulfate to H2S gas that leaves the melt. The experiments we conducted show that nearly complete sulfur removal from the melt is possible at 823 K and that the reaction rate is sufficiently high for a large scale process. One can foresee that this carbonate melt-based SO2 removal technique may become a practical and economically attractive method for limiting sulfur emission to the atmosphere from non-ferrous metallurgical processing plants.

By Sylvan Cromer

The need for a clear understanding of the physical nature of the flow of gas-liquid mixtures in vertical pipes is ever becoming more apparent. This type of flow is encountered when gas and oil are produced from a well; when water is removed from gas wells with siphon lines and when liquids are elevated by means of air or gas lift. Although a number of investigator1-7 have published data on the flow of gas-liquid mixtures, in only a few cases has the experimental setup been devised to permit visual study. In the fields of heat transmission, such as the boiling of liquids and the study of the critical phenomena of the hydrocarbons, researchers have been able to throw additional light on heretofore unexplainable happenings through actual observation in glass apparatus. This investigation was therefore undertaken in order to obtain qualitative as well as quantitative results for air-water flow. Experimental Apparatus and Procedure The flow column used in these tests was made of standard 2-in. pipe and was approximately 98 ft. in height. Pyrex observation sections 2 ft. long having the same internal diameter as the wrought-iron pipe were placed at 14-ft. intervals in the column. The bottom of the tube was cut off square and terminated in the mixing chamber. No perforated nipple or footpiece of any kind was used. To the top of the column was fastened a semicircular return bend having a 4-ft. radius. The flow column was supported by a standard cable-tool drilling derrick (Fig. 1) into which were built observation platforms at each Pyrex section.

Jan 1, 1940

By Sylvan Cromer

The need for a clear understanding of the physical nature of the flow of gas-liquid mixtures in vertical pipes is ever becoming more apparent. This type of flow is encountered when gas and oil are produced from a well; when water is removed from gas wells with siphon lines and when liquids are elevated by means of air or gas lift. Although a number of investigator1-7 have published data on the flow of gas-liquid mixtures, in only a few cases has the experimental setup been devised to permit visual study. In the fields of heat transmission, such as the boiling of liquids and the study of the critical phenomena of the hydrocarbons, researchers have been able to throw additional light on heretofore unexplainable happenings through actual observation in glass apparatus. This investigation was therefore undertaken in order to obtain qualitative as well as quantitative results for air-water flow. Experimental Apparatus and Procedure The flow column used in these tests was made of standard 2-in. pipe and was approximately 98 ft. in height. Pyrex observation sections 2 ft. long having the same internal diameter as the wrought-iron pipe were placed at 14-ft. intervals in the column. The bottom of the tube was cut off square and terminated in the mixing chamber. No perforated nipple or footpiece of any kind was used. To the top of the column was fastened a semicircular return bend having a 4-ft. radius. The flow column was supported by a standard cable-tool drilling derrick (Fig. 1) into which were built observation platforms at each Pyrex section.

Jan 1, 1940