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By G Gopinath, R Balachander, H S. Venkatesh

This paper describes in detail the controlled blasting adopted and the measurements undertaken for the successful excavation of large twin tunnels under a shallow cover for a six-lane highway project in India. The tunnels are D-shaped, each 15 m in diameter, and the cover between the tunnels and the existing railway track was about 14 m. These twin tunnel tubes were characterised by two separate three-lane carriageways for each direction of traffic, and were planned with about 25 m of reinforced cement concrete (RCC) portals at the entrance and exit of the tunnels. The major challenge of the project was the blasting of tunnels in rock below an operating railway line. As the tunnels approached the area below the railway line, the ground vibrations were monitored vertically above the blasting faces and on the railway track sleepers. Vibration intensities between those generated from tunnel blasting and those from the movement of the trains were compared, and it was found that the vibrations from blasting were lower than those from the moving trains. Though the permissible level of ground vibration based on the Indian Standard (IS) code happens to be 70 mm/s, the maximum charge per delay was calculated restricting this limit to 50 mm/s. This ensured that the vibrations in the vicinity of the railway tracks never exceeded the prescribed limit of 70 mm/s. The surface ground settlement before and after the blasts were also measured using an optical levelling instrument, which confirmed that there was no significant impact on the surface movements due to blasting. Extensometer readings inside the tunnels showed that there was no deformation in the tunnel. These twin tunnels are now operational and are providing faster connectivity with safety.CITATION:Gopinath, G, Venkatesh, H S and Balachander, R, 2015. Controlled blasting for twin tunnels with a shallow cover under an operating railway line, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 801–808 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Y. Jeong, K. Kim

Excess water can lead to instability and even failure in tailings storage facilities (TSFs). Simply reducing the amount of water in TSFs could be the best way to ensure the safety of nearby communities. In this case study we investigated the effects of reducing the water content in tailings slurry at a copper-cobalt-zinc mine in Mexico. An environmentally friendly polymer was used as a drag reduction agent (DRA) to offset the increase in solids percentage. The potential effects of the increased solids concentration on the tailings transportation system were also assessed. A series of ‘what if’ studies was conducted to assess whether adding the polymer would allow the solids concentration to be increased without changing the pressure loss in the tailings pipeline. The studies entailed conducting pipe loop tests to investigate these changes under various solids/ polymer concentrations and then constructing a computational fluid dynamics (CFD) simulation model using the test results. The validated model was used to determine the optimal polymer percentages needed to maintain the same pressure loss under baseline (30% solids) conditions, and to assess the potential risks (clogging, increased erosion rates) to the pipelines. The potential water savings were found to be significant, varying from about 1.852 Mm3/a at 35% solids to 3.915 Mm3/a at 45% solids.

Dec 13, 2023

By M. Abouhamad

According to the Canadian Urban Transit Association (CUTA), 140 Billion CAD is required to maintain, rehabilitate, and replace subway infrastructure between 2010 and 2014. The current practice adopted by transit authorities for prioritizing subway stations for rehabilitation is based on the station structural needs. While this classification is reflective of station condition, other factors, such as station size, location and passenger capacity, play an important role. The criticality of a station is an index that represents the functional importance of a station depending upon a set of identified factors. The system criticality is based on several attributes, such as station location, size, and nature of use. This paper presents a novel method of clustering subway stations for rehabilitation priority based on their criticality level. The different stations in a subway network are rated according to their relative importance against predefined attributes. The weights and scores of the attributes are computed with the help of experts and current subway network data. The analysis is done using the Fuzzy Analytic Network Process (FANP) to accommodate the subjectivity of human judgment as being expressed in natural language which entails ?fuzziness? in real-life problems and account for the interdependency between the selected attributes. The output of the model is a criticality based clustering of subway stations. The proposed framework helps authorities prioritize stations for rehabilitation and highlight stations with more criticality for a more robust asset analysis.

Aug 1, 2013

By Asa Weber

With continuing pressure from stockholders not only to maintain but to increase mineral revenues, producers have increased plant capacity. Depressed mineral prices have accentuated the trend toward higher production rates to maintain consistent cash flow, and these same trends have promoted the development of large-scale processing equipment. In addition to the need to handle increased throughput, larger flotation equipment can result in decreased capital-equipment and operating costs. The development of larger column and conventional flotation equipment relies, in part, on suitable scale-up procedures. To properly scale-up large flotation cells and columns, certain constraints and design parameters must be taken into consideration, including velocities in the vessel, residence time, solids suspension, and lip loading. This paper will review the design constraints and scale-up criteria for WEMCO® flotation cells. Scale-up criteria are augmented with computational-fluid- dynamics analyses and high-speed imaging techniques, as well as multiple regresesion analysis of in-plant operational data.

Jan 1, 1999

By Allen L. Hatch

A survey of all phases of the world's lead and zinc production in 1968 from ore through to refined metal was conducted by sending questionnaires to individual companies ad the results of this survey are tabulated at the end of the paper. The paper goes on to review changes in the geographical distribution of the world's lead and zinc mine and metal production and in the trading patterns of raw materials, present and future utilization of metal production capacity, developments in metal smelting and refining processes and the growing importance of marketing, product development and research in the 1950's and 1960's.

Jan 1, 1970

By M. Tangstad, J. D. Steenkamp

In April 2013 a 48 MVA submerged arc furnace producing silicomanganese was excavated in South Africa. Since the high shell temperatures recorded in the tap-hole area resulted in the furnace being switched out for relining, the tap-hole area was excavated systematically. A refractory wear profile of the tap-hole area with affected hearth and sidewall refractory was obtained in elevation. The carbon ramming paste in front of, above, andbelow the tap-hole was worn, as was the SiC with which the tap-hole was built. A clay mushroom formed but was detached from the refractories. Thermodynamic and mass-transfer calculations were conducted to quantify the potential for wear by chemical reaction between refractory and slag and refractory and metal in the tap-hole area. It was found that chemical reaction between refractory and slag or metal could offer only a partial explanation for the wear observed; erosion is expected to contribute significantly to wear.

Jan 1, 2015

By Arthur E. Bruszak, Marcel Vanpée

In many practical combustion systems ignition may occur through contact with hot burned gases . Such a process plays a vital role in flame stabilization on bluff bodies . It is also of importance in the ignition of firedamp by the hot spent gases of explosives used in mines . Also , in the communication of flames through narrow channels , a problem of practical importance in flameproofing electrical equipment , the propagation of the flame is essentially a reignition process in which hot burned gases are the agent of ignition . In the actual ignition problem a great variety of conditions may be visualized . Ignition may occur where pockets of hot gases are surrounded by cold explosive mixtures or where pockets of cold mixture may be surrounded by hot gases . Alternately , a flowing stream of combustible mixture may be initially in contact with another stream of hot combustion products , or a jet of hot gases may flow into a cold quiescent mixture ; the jet may be laminar or turbulent , continuous or discontinuous . The hot gas may also consist of the oxidant ( air for instance ) and the cold combustible pure fuel . This study by the Bureau of Mines is concerned only with ignition produced by a continuous jet of gas ( hot ) flowing into a practically quiescent cold mix- The investigation of ignition by bursts of hot gases or by turbulent jets is outside the scope of this report , and work performed on this phase of the problem has been published elsewhere

Jan 1, 1963

By Mehmet F. Taner

"Abstract - The East Sullivan Stock (ESS) is a small, composite felsic alkaline pluton of presumed late Archean age in the Val d’Or mining district. Three main facies have been distinguished: monzonite sensu stricto, porphyritic monzonite, and green trachytic porphyry. This monzonitic group of rocks is of relatively homogeneous composition with high abundances of Na2O, K2O, Ba, Sr, Rb, Zr, Mo and LREE. The alkaline ESS is distinguished from other igneous units in the Val d’Or mining district, such as the Bourlamaque Batholith, by relatively high concentrations of Ba, Sr, Rb, Mo, Cu and Au. The ESS hosts many base (Cu, Mo) and precious (Au) metal occurrences, including: (1) porphyry style Cu-Au-Mo disseminated sulfide deposits, (2) Cu-Au deposits in volcanic rocks near the ESS contact, and (3) pyritic gold mineralization in east-west trending shear zones. The ESS is well defined by concentrical zoning on the aeromagnetic vertical gradient color map, and displays four linear trends, which are assumed to be structural lineaments, at 035°-055°, 320°-300°, eastwest, and north-south. The main mineral occurrences related to the stock display a preferred spatial association with the east-west linear magnetic trends.The ESS is preferentially located along a major structure and was emplaced late in the evolution of the Abitibi subprovince like other felsic alkaline plutons. This stock is similar to late-tectonic mineralized felsic alkaline intrusions of the Kirkland Lake and Larder Lake mining districts in Ontario, and to the Allard stock in the U.S.A. which is associated with gold and base metal mineralization. Similarities also exist with younger alkaline plutons associated with Cu-Mo-Au porphyry deposits in the Canadian Cordillera, which formed in tensional tectonic environments. The felsic alkaline magma may have formed by partial melting of deeply buried supracrustal rocks, concomitant with the development of deep fractures such as the Cadillac Fault. In such an environment, hydrothermal solutions carrying remobilized metals from deep supracrustal rocks may have deposited gold and base metals in structural traps. Plutons similar to the ESS should be good targets for mineral exploration. Résumé - Le Stock de East Sullivan (SES) est une intrusion composite alcaline d’âge tardiarchéen, situé dans le camp minier de Val d’Or. Trois principaux faciès ont été identifiés: une monzonite sensu stricto, une monzonite porphyrique et un porphyre trachytique vert. Les données chimiques montrent que ce groupe des roches monzonitiques est relativement homogène en composition avec des concentrations élevées de Na2O, K2O, Ba, Sr, Rb, Zr, Mo et ETRL, définissant une suite alcaline typique. Cet alkalin stock peut être facilement distingué des autres unités géologiques de la région de Val d’Or, tel le batholite de Bourlamaque, par une concentration élevée de Ba, Sr, Rb, Mo, Cu et d’Au. Le SES contient plusieurs importants prospects de métal précieux (Au) et de métaux de base (Cu, Mo), incluant: (1) une minéralisation disséminée de type porphyre Cu-Mo-Au, (2) une minéralisation de Cu-Au dans les roches volcaniques encaissantes hôtesses près du contact et (3) une minéralisation d’or pyritique dans une zone de cisaillement de direction est-nordest. Le SES est bien défini sur la carte aéromagnétique en couleurs du gradient vertical par des zonages concentriques, où quatre linéaments structuraux ont été reconnus: 035°-55°, 320°-300°, est-ouest, et nord-sud. Les principales zones minéralisées spatialement associées au stock sont généralement situées soit près des linéaments magnétiques est-ouest, soit le long de ceux-ci.Le SES semble s’être mis en place le long d’une structure majeure, développée tardivement dans l’évolution de la Sous-province abitibienne, comme les autres plutons alcalins felsiques. Ce stock est similaire à la suite tardi-tectonique d’intrusions alcalines minéralisées des camps miniers de Kirkland Lake et de Larder Lake en Ontario, ou"

Jan 1, 1996

By Sevket Acar, Tim Acton

"Zarafshan/Newmont is a 50/25/25 joint venture between Newmont Gold and the State Committee for Geology and Mineral Resources, and Navoi Mining and Metallurgical Combinat, two entities of the Republic of Uzbekistan. The Zarafshan/Newmont joint venture consists of a heap leaching operation which will process 220 million metric tonnes of existing low-grade oxide ore stockpiles (averaging 0.036 oz Au/t) from the Muruntau mine. Net recovery over the 17-year life of the project is expected to be 4.8 million ounces of gold.The plant construction started in October 1993 and operations commenced on May 25, 1995. The crushing plant consists of four stages of crushing and screening to produce a 95% passing 3.35 mm product, followed by heap leaching and gold recovery by the Merrill-Crowe process. The dore metal is refined at the Muruntau refinery. All gold produced by the joint venture is sold on the world market. IntroductionThe Muruntau mine and nearby town of Zarafshan are located in the center of the Kyzylkum desert, 250 miles west of Tashkent, capital of Uzbekistan. Following a mining conference in Moscow in 1990, a Newmont geologist was among the first team of westerners to visit the Muruntau Mine, the second largest gold producer in the former Soviet Union. At Muruntau, they found 220 million tonnes of low grade gold ore that had been stockpiled during the previous 25 years. In February, 1992, six months after Uzbekistan's independence, Newmont signed a 50/50 joint venture agreement with the Uzbek government to use heap leach technology to process the ore. The feasibility study was completed in November of 1992. Plant construction started in October, 1993 and operations commenced on May 25, 1995.Newmont Metallurgical Services performed metallurgical studies to obtain heap leach process design criteria parameters. The initial metallurgical study on 20 grab samples is the subject of this paper."

Jan 1, 1997

By Gerard Matthes

ONLY in recent years has any practical headway been made in the application of aerial photography to geological problems, and up to the present time its principal value to the geologist and mining engineer has been in "areal geology;" i. e., the study of formations as revealed at the surface. The object of this paper is to set forth briefly the principal advantages that may be derived from aerial photographic data in geological work and to serve in a measure as a guide to those who may be con-templating its use. Geophysical prospecting has for object the locating of mineral under the surface. Inasmuch as the geologist's chief complaint in life is a dual one-inability to see under the surface and inability to visualize comprehensively what he does see on top of the ground-geophysical prospecting coupled with aerial photography should do much to lessen his burdens. To what extent aerial photography can be made a useful adjunct to geophysical prospecting remains to be proved, but the inference drawn here is that it holds many alluring possibilities. To avoid disappointments, it should be stated at the outset that to the :geologist or mining engineer an aerial photograph or mosaic is only a tool, the effecient use of which he must set out to master. Upon his skill and ingenuity in applying it to particular problems will depend largely the value of the results that he will obtain. Under the most favorable conditions an aerial mosaic or even a few loose photographs, because of the exceptionally comprehensive oversight which they afford of field data, such as dips and strike observations at isolated outcrops, local indications of faulting, mineral and fossil finds, greatly facilitate study and correlation, save much tedious foot work, and may repay their cost many times. Even so, types of country may be found where the most, skillful use of the best of pictures will produce results so meager as to render the cost of aerial photography entirely unwarranted.

Jan 1, 1928

By V. L. Elliott, C. L. Meyette

The conditioning of semifinished steel products such as billets, blooms, and slabs to remove surface defects before further processing to finished products is a necessary accompaniment to steel mill rolling operations. A knowledge of the kinds of defects which occur and of the conditions in melting, teeming, and rolling that may lead to their occurrence is favorable to the production of quality products. Surface defects may be classed as either of mechanical origin such as those that occur in the heating and rolling operations and include breaks, tears, guide marks, mechanical laps and the like, or they may have been in the ingot before heating and rolling. Examples of the latter are ingot cracks, blow-holes, scabs, and inclusions which lead to the numerous known types of seams and surface flaws. Most of the common types of surface defects and methods for their identification by visual examination or by the aid of macro-etch tests are well known. The conditions which caused their formation are also appreciably understood and this knowledge has been instrumental in the establishment of methods for metallurgical control. There are, however, defects of doubtful origin. In any endeavor to trace the causes for their occurrence, the question of first concern is: I. Whether they were formed in the rolling procedure. 2. Whether they existed in the ingot prior to rolling. In the case of semifinished products which are rerolled to finished products there is also the question of whether they were formed in the primary or in the secondary rolling. In metallurgical laboratories where numerous or routine examinations of the quality of rolled products are made over the course of time, there will doubtless be many puzzling cases of defect origin. Microscopic examination of the defects may, however, reveal a characterizing condition that can be used to classify them broadly with respect to their origin. Such a condition has been observed and, after detailed investigation, is described here with the thought that it may offer a usable and relatively simple solution to a bothersome problem. Basis For Classifying In this discussion the term "mechanical type defects" will be used to designate those that have occurred as a result of the rolling operations such as in rolling from the ingot to billets, blooms, or slabs or in rerolling to finished products. The term "steel type defects" will be used to designate those that were present in the ingot prior to primary rolling or that were in the semifinished product prior to secondary rolling to finished product. The basis for distinguishing between the two types of defects lies in the relative degree of subscale formation surrounding them. Subscale is defined1 as a zone of

Jan 1, 1949

By V. L. Elliott, C. L. Meyette

The conditioning of semifinished steel products such as billets, blooms, and slabs to remove surface defects before further processing to finished products is a necessary accompaniment to steel mill rolling operations. A knowledge of the kinds of defects which occur and of the conditions in melting, teeming, and rolling that may lead to their occurrence is favorable to the production of quality products. Surface defects may be classed as either of mechanical origin such as those that occur in the heating and rolling operations and include breaks, tears, guide marks, mechanical laps and the like, or they may have been in the ingot before heating and rolling. Examples of the latter are ingot cracks, blow-holes, scabs, and inclusions which lead to the numerous known types of seams and surface flaws. Most of the common types of surface defects and methods for their identification by visual examination or by the aid of macro-etch tests are well known. The conditions which caused their formation are also appreciably understood and this knowledge has been instrumental in the establishment of methods for metallurgical control. There are, however, defects of doubtful origin. In any endeavor to trace the causes for their occurrence, the question of first concern is: I. Whether they were formed in the rolling procedure. 2. Whether they existed in the ingot prior to rolling. In the case of semifinished products which are rerolled to finished products there is also the question of whether they were formed in the primary or in the secondary rolling. In metallurgical laboratories where numerous or routine examinations of the quality of rolled products are made over the course of time, there will doubtless be many puzzling cases of defect origin. Microscopic examination of the defects may, however, reveal a characterizing condition that can be used to classify them broadly with respect to their origin. Such a condition has been observed and, after detailed investigation, is described here with the thought that it may offer a usable and relatively simple solution to a bothersome problem. Basis For Classifying In this discussion the term "mechanical type defects" will be used to designate those that have occurred as a result of the rolling operations such as in rolling from the ingot to billets, blooms, or slabs or in rerolling to finished products. The term "steel type defects" will be used to designate those that were present in the ingot prior to primary rolling or that were in the semifinished product prior to secondary rolling to finished product. The basis for distinguishing between the two types of defects lies in the relative degree of subscale formation surrounding them. Subscale is defined1 as a zone of

Jan 1, 1949

By J. T. Liu, G. H. Han, W. C. Chai, Y. F. Huang

"In beneficiation process, metal ions could adsorb onto clay mineral surfaces or interact with flotation chemicals, and then result in the flotation behavior changing of desired minerals. Al(III) is the dominating ion existing in the bauxite flotation system. In this research, the adsorption behaviors of Al(III) on two silicate clay minerals (including bentonite and kaolin) were investigated by means of UV-Vis spectra, zeta potential testing and scanning electron micrograph analysis. The adsorption experiment results show that the adsorption capacity of clays for Al(III) ions increases with the initial Al(III) concentration, contact time and solution pH. There are some different adsorption behaviours for two clays. Increasing the clay concentration decreases the adsorption capacity of bentonite, while increases first then decreases for kaolin. Higher temperature favours the adsorption of Al(III) on bentonite but goes against for kaolin. The adsorption capacities of bentonite and kaolin for Al(III) respectively reach 12.48 and 0.875 mg/g at initial solution pH 5. Zeta potential results show that the adsorption of Al(III) on two clays is characterized by electrostatic attraction mechanism.INTRODUCTIONIn beneficiation process, there is inevitably a wide variety of metal ions generated from mineral crushing, mineral dissolution and water chemistry conditions. Metal ions adsorb on the mineral surfaces or interact with the beneficiation agents, affecting the flotation efficiency of desired minerals (DiFeo et al., 2001; Parolis et al., 2008; Shackleton et al., 2012; Shengo et al., 2014). Therefore, it is necessary to have a detailed investigation on the adsorption behaviour of metal ions on clay minerals.Having good ion exchange capacity and negative surface charge, the clay minerals could take up various metal ions from the mineral-water system. Bentonite and kaolin are very common aluminosilicate clays in the mineral processing system. These two clays both hold a permanent negative charge, =X- on the basal surfaces, and a smaller variable charge, =SiOH on the mineral edges (Gu & Evans, 2008; (Gu et al., 2010). Adsorption experiments are usually used to study the adsorption affinity of metal ions for clay minerals (Sen & Bhattacharyya, 2012). The adsorption of Zn(II), Cu(II) and Pb(II) onto natural bentonite showed that the adsorption amounts of metal ions increase with contact time, solution pH and metal ion concentration, but decreases with adsorbent concentration and system temperature (Sen & Gomez, 2011; Melichova & Hromada, 2013). Cr(III) adsorption on bentonite was significantly pH dependent. The adsorption process followed pseudo-second-order model and the equilibrium adsorption was consistent with Freundlich isotherm (Lollino et al., 2015). The adsorption behaviours of Pb(II), Cd(II), Ni(II) and Cu(II) onto kaolin indicated that increasing pH favoured the adsorption of metal ions (Jiang et al., 2010). The adsorption of Cd(II), Cu(II), Pb(II) and Zn(II) onto kaolin showed that an ion-exchange reaction occurred at pH<7.0 and inner-sphere surface complexes were prone to form at higher pH (Srivastava et al., 2005)."

Jan 1, 2016

By Ulf S. Landergren

Diffusion coefficients and marker movements have been determined in brass using welded couples. Three different concentration ranges were employed at 750°C, while a fourth concentration range was measured at 500°, 600°, 700°, and 800°C. Marker displacements toward and porosity development in the high zinc side of the couple were observed in all cases. The results were interpreted as favoring a vacancy diffusion mechanism. IN the large amount of diffusion literature which has accumulated during the past half century, very few experimental data have been presented on body-centered-cubic metallic phases. The impressive combination of experimental and theoretical studies which has given the vacancy mechanism a fairly secure position as the preferred mechanism for most face-centered-cubic metals has no counterpart for body-centered-cubic phases, although the theoretical picture seems to be in a better state than the experimental work. The attempts to select diffusion mechanisms by the theoretical calculation of the activation energy for the various conceivable unit diffusion processes and the energy of formation of the type of lattice defect required have been based on models of two kinds. The first kind utilizes potential functions fitted for certain properties of pure crystalline copper; the second kind is fitted for sodium. The latter is an example of an open metal in which the metallic ion is small compared with interatomic distance,&apos; while the former is characteristic of the larger class of metals in which the ions have diameters about as large as the interatomic distance. brass should resemble copper in this fundamental property. It should be evident that results on the mechanism of diffusion obtained for one of these classes need not necessarily apply to the other. Huntington and Seitz, using a model of the copper type, showed that the activation energies to be expected for interstitial migration or a two-atom direct interchange were much higher than that for vacancy diffusion. Zener pointed out that a four-atom ring rotation would involve an activation energy considerably lower than the two unlikely mechanisms although still higher than the vacancy mechanism in the face-centered-cubic structure. Furthermore, he argued, the four-atom rotation would be relatively easier in a body-centered-cubic lattice and might be competitive with the vacancy mechanism. Paneth showed that a body-centered-cubic crystal-like sodium could form interstitial defects of special type, called a crowdion, by crowding an extra atom into < 111 > directions where the defects would affect a line of about eight atoms. The defect was constrained to move along the defining line. Unlike the face-centered-cubic case, therefore, the theoretical calculations for the body-centered-cubic mechanism do not provide a very clear-cut answer, and the absence of adequate experimental studies is the more serious. This investigation was undertaken for the purpose of obtaining useful information on diffusion in body-centered-cubic phases. brass was chosen for several reasons: 1—the phase field is sufficiently wide at high temperatures to permit the use of diffusion couples with adequate concentration ranges for satisfactory chemical analysis, 2-—thermodynamic activity data are available for the calculation of mobilities from diffusion coefficients, 3—the phase is as close to the theoretical model of the copper -type on which the calculations have been done as any body-centered-cubic metallic phase is likely to be. Measurements of the movements (if found) of inert markers during the diffusion process would indicate that a vacancy or Or mechanism played a major role in diffusion in brass. If no marker movement should be found, a ring mechanism would be indicated but not assured. Experimental Procedure The alloys used in these experiments, listed in Table I with analyses, were supplied by the Naval Research Laboratory. They were from ingots of 3x3 in. cross-section, heated to 760°C, reduced under a

Jan 1, 1957

By Daniels E. J, Morgan W. A

In response to the increase in consumption of galvanised steel for automobiles in the last decade and the problems associated with remelting larger quantities of galvanised steel scrap, a process is being developed to separate and recover the steel and zinc from galvanised ferrous scrap. The zinc is dissolved from the scrap in hot caustic using anodic assistance and is recovered electrolytically as dendritic powder. The dezinced ferrous scrap is rinsed and used directly. The process is effective for zinc, lead, and aluminum removal on loose and baled scrap and on all types of galvanised steel. The process has been pilot tested for batch treatment of 900 tonnes of mostly baled scrap. A pilot plant to treat continuously loose scrap, with a design capacity of 48 000 tonnes annually, has been in operation in East Chicago, Indiana since early in 1993. The first 450 t of scrap degalvanised in the pilot plant have residual zinc below 0.01 per cent and sodium dragout below 0.01 per cent. Use of degalvanised steel scrap decreases raw materials, environmental compliance costs, and opportunity costs to steel- and iron-makers. Availability of clean degalvanised scrap may enable integrated steel producers to recycle furnace dusts to the sinter plant and EAF shops to produce flat products without the use of high quality scrap alternatives such as DRI, pig iron, or iron carbide. Recycling the components of galvanised steel scrap saves primary energy, decreases zinc imports, and adds value to the scrap. The quantities of zinc available by the year 2000 from prompt and obsolete automotive scrap will approach 25 per cent of zinc consumed in the major automotive production centres of the world. Zinc recycling from galvanised steel scrap, either before or after scrap melting, will have to be Implemented.

Jan 1, 1993

By Lloyd A. Morley, Robert Stefanko

Before going directly to the analysis, it would be good to summar¬ize explosion-proof container approval methods. Both Magison (52) and Short (84) state that in general practice, the systems are certified for: 1. a rugged enclosure able to withstand an internal explosion but not allow explosively hot gases to escape, and 2. maximum surface temperature, with equipment operating inside, that will not ignite the surrounding atmosphere. Also, testing insures that any material in contact with the container surface will not be ignited by a hot spot. Associated with the first practice, the enclosures are inspected for: 1. a safe flange gap width, 2. a pressure increase during ignition, and 3. an hydrostatic pressure withstand level. The hydrostatic pressure level is almost always determined by a meas¬ured ignition-pressure test and is usually applied to prove the mechan¬ical design to some safety factor. Consequently, explosion-proof enclosure testing includes temper¬ature, permissible flame gap, and pressure. Specifications and prev¬ious research also can be similarly separated even though some interre¬lation exists between the flame gap size and internal enclosure pressure during an explosion. The Schedule 2G Sections applicable to these subjects are: 1. 18.2 Definitions; 2. 18.6 Applications;

Jan 1, 1974

During the period January 1, 1977 through July 31, 1977, 5 percent (264,000 tons) of U.S. capacity was closed due to power curtailments in the Pacific Northwest because of the shortage of water. During July, one plant in Tennessee cut production by 50,000 tons annually due to a power reduction by the Tennessee Valley Authority. Full capacity production was resumed at a West Virginia smelter during September. If demand for aluminum is strong it seems likely that aluminum supply during the remainder of 1977 and in 1978 will be tight. The price was increased 3¢ per pound to 51¢ per pound effective March 28, 1977, and by an additional 2¢ per pound to 53¢ per pound, effective July 5, 1977. New projects and expansion of existing facilities are planned by Australian aluminum companies over the next 2 to 3 years. The companies listed have committed themselves to spending approximately A$801 million: Alcoa of Australia Ltd. -New alumina plant at Wagerup, south of Perth. Darling Ranges bauxite is located near the proposed project. A$650 million. Coma 1 co Industries Pty. Ltd. -Increase bauxite mining capacity and upgrade or replace other facilities at its Weipa mines on Cape York Peninsula region of Northern Queensland. A$81 million. Alcan Australia Ltd. -Expansion program that will increase capacity of the Kurri Kurri aluminum smelter north of Sydney about 50 percent, and improvement of other facilities at the plant. A$70 million.

Jan 1, 1977

By Cheung L. C C, Maconochie A. P

SIROFRAG is a computer-based imaging system that quantifies the post-blast rock fragment size distribution in a muckpile in a mine environment. Improvements in blast performance and blast modelling are being hampered by a lack of a quick and objective method to evaluate the major result of the blast: the fragment size distribution. This is usually done by hand digitising muckpile photographs: a labour intensive and tedious process. SIROFRAG is being developed to quickly, cheaply and objectively provide this information. SIROFRAG is based on active stereo image analysis. It uses a light stripe to illuminate a muckpile and a pair of video cameras to determine the 3D nature of the scanned objects. The imaging system is based on a novel prototype scanning projector that allows images to he captured in full daylight. The Microsoft Windows based software controls the projector and interprets the captured images to provide a size distribution of exposed rock fragments.

Jan 1, 1995

By H. D. Hess

This report presents the results of laboratory mineral evaluations conducted by the federal Bureau of Mines under the joint sponsorship of the U.S. Atomic Energy Commission (AEC) and the Bureau a! Ships, U. S. Department of the Navy. The major purpose of this investigation was to examine and evaluate zirconium minerals representing sizeable deposits in an effort to locate com¬mercial sources of high-hafnium ores. Although determination of the hafnium content was the principal objective, each of the zirconium minerals also was analyzed for combined zirconium-hafnium oxide, silica, uranium, thorium, yttrium, and cerium. The general laboratory procedure involved microscopic examination of the test samples, concentration of the hafnium-bearing zirconium mineral by standard laboratory techniques, and analysis of the derived concentrate by quantitative microscopic, chemical, and X-ray spectrographic methods. Of the several hundred samples tested under this program, 147 are discussed in this report, including 94 from domestic occurrences and 53 from widespread foreign sources.

Jan 1, 1962

By Stephen L. Bolivar

The Prairie Creek intrusion, near Murfreesboro, Arkansas, is the site of the only commercial diamond mine in North America. Three major lithologies are associated with the intrusion, a hypabyssal peridotite, a volcanic breccia in .which the majority of diamonds occur, and associated tuff. Previous studies, including mining history, geological, geophysical, petrological and whole-rock and mineral chemistry are reviewed. The recent suggestion, by other workers, that this intrusion may be more correctly called a lamproite is examined and supported. This has serious implications for diamond exploration in Arkansas and elsewhere in the U.S.

Jan 1, 1984