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By G. W. Norval, V. G. Papangelakis, G. A. Moldoveanu

Smelting has been the primary method of treatment for refractory copper sulfide concentrates such as enargite (Cu3AsS4), but the pyrometallurgical processing generates elevated levels of volatile arsenic. The present research investigates a novel hydrometallurgical process of oxidative dissolution of enargite at ambient conditions in the presence of chlorine dioxide (ClO2), a very powerful oxidant generated in solution by the reaction between a strong acid (HCl or H2SO4) and sodium chlorite (NaClO2). The effects of initial oxidant concentration, particle size, agitation speed and temperature on dissolution kinetics and copper extraction were investigated. It was found that a stoichiometric ratio of ClO2:Cu3AsS4 = 9:1 were needed to completely and congruently dissolve the mineral with fast kinetics (<15 minutes) under ambient temperature. The dissolution extent (metal extraction) increases with increasing ClO2 concentration and decreasing particle size of solids, but is not influenced by temperature or agitation speed.

Jan 1, 2014

By A. G. Eccles

Western Mines&apos; milling circuit produces three concentrates (copper, lead and zinc), with the tailings being disposed of at the bottom of Buttle Lake. In view of the mine&apos;s location and the method of tailing disposal, a comprehensive pollution control program has been in effect since start-up. Changes -in the ore over the past few years have required the use of increasing quantities of sodium cyanide in order to effect a good copper-lead separation. This led to the use of alkaline chlorination for destruction of ?residual cyanide and precipitation of dissolved copper contained in the tailing effluent. The development of Western Mines&apos; alkaline chlorination plant is discussed in detail, including initial test work and the evolution of procedures leading to the present operation. The current monitoring program is also reviewed.

Jan 1, 1977

By Christopher Andreae

Years before iron and steel works were established at Sydney, several thriving although short-lived iron works operated in Nova Scotia. These furnaces reflected the general nineteenth-century North American experience with iron works. At the beginning of the century, small furnaces struggled to supply local needs. Charcoal was the principal fuel and water powered most furnace equipment. By the end of the century, a few huge primary iron and steel works dominated production for Nova Scotia and the rest of Canada. Two sites achieved prominence in the nineteenthcentury Nova Scotia iron industry: Londonderry and Ferrona (Fig. 1). Londonderry, the larger and longerlasting of the two sites, is today a small village on the south flank of the Cobequid Mountains, about 30 km west of Truro. Prior to the establishment of an iron works in 1849, no community existed. At the peak of operation in the 1880s, however, over 2600 people were located there. The second site, Ferrona, today is a mere crossroads on the map, about 10 km south of New Glasgow. Following the construction of a blast furnace there in 1892, a small village grew up around the furnace. But once the furnace was blown out in 1904, the population gradually drifted away.

Jan 1, 1999

By Hulbert A. Lee

"A REVIEW OF MINERAL DISCOVERIES IN CANADA, and in particular the Canadian Shield, using the physical aspects of overburden reveals a trend in the art of exploration. At an early time of exploration (1847-1954), float and heavy clasts were used successfully to find ore deposits with little knowledge of Quaternary environments. At a later time (1955 to present) , use of Quaternary rock-units for sampling have made possible tracing indicator trains of float, heavy clasts and other ore-type clasts to the source bedrock. The basal till of retreat ice is now recognized as a1l favourable sampling environment and as such has been used to successfully discover hidden orebodies. The esker massive gravel is beginning to be recognized as a favourable environment and use of it has met with technical success. An understanding of those changes that have taken place during the transportation of the material and after its deposition is essential to proper sampling and treatment of the samples from the basal till and the esker massive gravel. Use of float and heavy clasts in search of orebodies is continuing in present-day exploration on the Shield. Lessons learned from it are being incorporated into exploration using favourable Quaternary rock-units for sampling. Hence, both subjects have a need for review and are discussed in this paper."

Jan 1, 1971

By Thomas M. Ware

"MR. Chairman, our Honourable Minister, Mayor Cole, it is a pleasure for me to come here, and join with you in one of the largest industrial shows ever held in Saskatchewan.It is an honour to be asked to keynote your meeting, to help mark an early chapter of this new industry for Saskatchewan. God has placed in our hands a new resource for His man on earth. This store of potash, 350 million years in the making, offers a vital resource to help man support his advanced intellect for thousands of years. It is a gift so large we must all wonder at its purpose and our responsibilities in serving our fellow man with it.We who are here to plan and implement the development of this essential mineral resource enjoy a great -privilege; and we share a great responsibility -to see that the billions of tons of potash which have waited beneath these prairies for millions of years are widely and wisely used to nourish the earth through future millenniums.To know the true value of potash, to be able to bring forth this re-source from over 3,000 feet deep in the earth, to establish markets and develop its potential worldwide is all part of our great heritage from generations past. So I think it is fitting on this occasion that we reflect for a moment on this heritage, to help us assess the responsibilities of its future development."

Jan 1, 1966

By D. P. Ziegler

Formulas relating economic optimum busbar cross sectional areas to busbar cost, electric price and financial parameters are reviewed and revised. Application of the formulas is illustrated with discussion of the appropriate choice of parameter values and the sensitivity of the optimum to the parameters. The extension of the single busbar concept to optimization of more complicated arrangements of bus for smelting pots is complicated by the constraint of obtaining a specified current distribution. An example problem illustrates the optimization of a section of a bus network containing a fork, with the imposed limitation of achieving a specified uniformity in the current. In cases where the current in the individual conductors may vary, Kelvin&apos;s law does not apply. Further extension of the technique to a full pot set of conductors poses additional problems which are discussed, but whose solution has not yet been accomplished. Aluminium 2006 45th Annual Conference of Metallurgists ofCIM Montreal, Quebec, Canada Edited by

Jan 1, 2006

By M. R. Hudec, M. A. Nikolinakou, P. B. Flemings

"We model the shale response to the large deformations associated with salt bodies, and we identify the implications of the stress changes for hydrocarbon exploration. We employ both the static and evolutionary approach, and show that while the static one can model actual geologic geometries, only the evolutionary approach can provide a detailed description of the stress history of shales, which is essential for predicting stress, porosity, and pore pressure and, more generally, for understanding Earth processes related to salt-hydrocarbon systems.INTRODUCTIONDuring the last two decades, understanding the stress, material behavior, and pore pressure in shales around salt bodies has become increasingly important. The energy industry routinely drills near salt (Beltrão, Sombra, Lage, Fagundes Netto, & Henriques, 2009; Meyer, Zarra, Rains, Meltz, & Hall, 2005; Seymour, Rae, Peden, & Ormston, 1993), because a significant number of hydrocarbon reservoirs around the world are found in layers dipping away from salt diapirs.Salt is a viscous material that cannot sustain deviatoric stresses. Under differential loading it flows, changes shape, and eventually relaxes to an isostatic stress state (Urai & Spiers, 2007). Therefore, emplacement of a salt body and its viscous relaxation process may cause significant deformation of the surrounding sediments, perturb their state of stress and create local overpressures (Dusseault, Maury, Sanfilippo, & Santarelli, 2004; Seymour et al., 1993). As a result, drilling near salt is particularly challenging, and problems leading to additional expense or even abandonment are common (Bradley, 1978; Dusseault et al., 2004; Meyer et al., 2005; Seymour et al., 1993; Willson et al., 2003).Historically, salt and the evolution of its cross section to the present day geometry have been studied using kinematic restorations (Rowan & Ratliff, 2012). This approach aims to explain the present geologic section through a sequence of plausible past sections; however, it does not model the constitutive response of the wall rocks, hence it cannot provide any prediction on their state of stress. Similarly, largestrain numerical studies (Albertz & Beaumont, 2010; Chemia, Schmeling, & Koyi, 2009; Goteti, Ings, & Beaumont, 2012; Gradmann, Beaumont, & Albertz, 2009) have focused on the rheological evolution of salt systems without modeling the geomechanical response of the sediments."

Jan 1, 2015

By Curtin University Western Australian School Mines

"Curtin University’s Gold Technology Group has developed an online CIP/CIL simulation model called SIMCIL which has been used since 1999 to model and simulate industrial leach-adsorption circuits. Recently the model has been upgraded to include an integrated liberation-leach modelling (ILLM) approach which can be used to evaluate the impact of various process parameters (such as grind size, bleed to gravity etc.) and circuit configurations on leach-adsorption circuit behaviour and overall plant gold recovery. A new time-efficient ore characterisation methodology has been researched and developed to provide the required liberation-leach data used in the ILLM approach, which is implemented online for the modelling of gold operations. The model structure, modelling approach, and some scenarios are discussed.INTRODUCTIONCurtin University’s Gold Technology Group has developed an online CIP/CIL simulation model called SIMCIL which has been used since 1999 to model and simulate industrial leach-adsorption circuits. The model has recently been upgraded to include an integrated liberation-leach modelling (ILLM) approach. The ILLM approach provides the means to evaluate the impact of the gravity recoverable gold (GRG) characteristics of the ore (GRG content and liberation behaviour), various process parameters (such as grind size, bleed to gravity, etc.) and circuit configurations on the gravity gold recovery, leachadsorption circuit behaviour and overall plant gold recovery.A new time-efficient ore characterisation methodology has been researched and developed to provide the required liberation-leach data used in the ILLM approach. The data required for the ILLM calibration can be obtained directly from the 3 stage GRG test, leach tests and size-by-assay analysis of the 3 stage GRG test products, and leach test products.This paper describes the ore characterisation methodology, model structure, modelling approach, and the application of the ILLM."

Jan 1, 2016

By T. W. Wlodek

"AbstractIn this paper a new type of durable 'spiral-rolled' drill set is introduced and its performance discussed. Efficient and economical mine drilling-depends to a great extent on durability of the drill-set employed. Premature failure of this element damages the drill bit and is costly when tungsten carbide bits are used.Time of drilling of 'spiral-rolled' drill sets introduced at present in Canada is considerably larger than for the presently used drill steel, but laboratory simulated service tests and practical field tests show that the 'drilling life' of the spiral-rolled drill set is several times that of ordinary drill steel.Some features of differential plastic deformation and differential surface rolling, so called 'spiral-rolling', are given.Relations between the drilling machine drill set and characteristics of the ore are discussed. The effect of shims on conical drill rod attachments, the mechanism of failure of drill steel, .and stresses during mine drilling, are analysed.IntroductionIN MINE DRILLING operations, the main interests are: the drilling machines as a source of working energy, the drill set as the tool transferring the working energy to the cutting edges of the bit, and, finally, the drilling characteristic of the .ore or waste rock.This paper includes a review of the possibilities of metallurgical and mechanical improvements in the drill set, with particular attention to drill steel and the attachments.For economical and efficient mine drilling operations, a durable drill rod, attachment, and drill bit are essential. Premature failure of any of these parts interferes with mining operations and is costly."

Jan 1, 1955

By S. Luidold, A. Poscher, H. Antrekowitsch

"The rare earth elements (REE) are nowadays mainly used for permanent magnets, catalysts, hydrogen storage alloys in rechargeable batteries, for glasses, ceramics, and polishing agents. Other important areas of application are phosphors in different types of lamps (fluorescent tubes, energy-saving lamps, etc.). These lamps are often collected and treated at their end of life by disintegration and sorting. However, the obtained fine fractions comprise not only REE-containing phosphors but also small amounts of mercury and are therefore disposed till today in special landfills. Due to the enormous price increase of the rare earths during the last two years, a lot of activities started for extracting these elements from secondary resources such as for example phosphors. All recycling concepts for this task mainly work with hydrometallurgical methods. The large number of different compounds in phosphors with sometimes very different behaviors with respect to their solubility in aqueous phases forms a major challenge to achieve good yields as well as acceptable purities of the produced rare earth concentrates by a process with a reasonable number of operation steps. Therefore, this paper gives at first a brief overview about the compounds, used as phosphors and about existing concepts or investigations. It further describes our own process design and the results, obtained on laboratory scale. INTRODUCTIONThe rare earth elements (REE) have a central position in the industrialised world despite their marginal production volume in comparison to common metals such as aluminium, copper, zinc etc., because they are essential for many applications. They often cannot be substituted without a considerable loss on functionality and quality. This group of metals comprise the lanthanoids (f–block elements, lanthanum–lutetium) as well as scandium and yttrium.The estimated world mine production of REE amounted to 133,000 t rare earth oxide equivalent in 2010, whereat China accounted for 130,000 t or 98 % (Cordier, 2012). The European Union (EU-27) imported 23,013 t in 2008 to cover its demand. The figure 1 shows the fraction of the European member states in terms of the total imports of rare earth compounds from outside the EU-27 (Schüler, Buchert, Liu, Dittrich, & Merz, 2011)."

Jan 1, 2012

By David R. Lentz

Abstract -At True Hill in southwestern New Brunswick, low-grade porphyry-style Bi-Sn-Mo greisen mineralization is associated with the cupola of an epizonal granite porphyry (granite) that also exhibits three episodes of brecciation. The first episode of brecciation is an in situ, 8 m to 10 m wide transitional zone of net-veined to coarse-grained "blocky" endogranitic mesobreccia that is chloritized and greisenized and hosts weak disseminated mineralization. ln a zone doser to the host rock­ granite contact, angular fine- to coarse-grained endogranitic mesobreccia with greisenized matrix is superimposed on the earlier transitional breccia. The latest episode is fault-controlled and consists of quartz- and chalcedony-hosted subangular to rounded fine-grained "pebble" mesobreccias that crosscut and brecciate the other breccia types, as well as the adjacent altered metasedimentary country rocks. The first two episodes of brecciation are magrnatic-hydrothermal in origin related to hydrofracturing of the granite carapace and are accompanied by greisenization and mineralization, whereas the post-mineralization, silica-hosted, "pebble" mesobreccias related to hydromagrnatic, low­ temperature fluid circulation and/or boiling along faults near the contact. These magmatic­ hydrothermal and hydromagmatic mesobreccias are similar to those associated with W-Mo-Bi porphyry-greisen mineralization at the Mount Pleasant deposit.

Jan 1, 1994

By R. E. Whitehead, G. J. Prior

"Abstract -Biotite from aplite that appears to have crystallized simultaneously with disseminated Cu-Mo mineralization at MacLeod Lake in northern Quebec yields K-Ar dates in the range 2032 ± 44 Ma to &apos;2f1:)1 ± 47 Ma. The mean value, 2065 Ma, is some 400 Ma younger than the 2485 ± 64 Ma date obtained from a hornblende concentrate separated from a granodiorite sill that is spatially, but apparently not genetically, associated with the disseminated Cu-Mo deposit. The mean biotite date of 2065 Ma at MacLeod Lake, a K-Ar date of 2055 Ma reported from an area 50 km east of MacLeod Lake and published dates of about 2000 Ma for galenas from the Chibougamau Cu-Au ores, suggest a widespread thermal and mineralization event, in that part of the Superior Province east of James Bay, that differs from the common late Archean mineralization that is related to volcanism and metamorphic-intrusive activity.Sommaire - Les datations au K-Ar sur des biotites qui auraient cristallisé en même temps que la minéralisation disséminée en Cu et Mo dans une aplite mise en place au Lac MacLeod, au nord du Québec, s&apos;échalonnent entre 2032 ± 44 Ma et &apos;2f1:)1 ± 47 Ma. La datation moyenne, soit 2065 Ma, est d&apos;environ 400 Ma plus récente que la datation obtenue pour un concentré de hornblende extrait d&apos;un fùon-couche de granodiorite qui est spatialement mais ne serait pas génétiquement as­ sociée à la minéralisation disséminée en Cu et Mo. La datation moyenne de la minéralisation au Lac MacLeod, soit 2065 Ma, la dataion au K-Ar à 2055 Ma citée pour une région à 50 km à l&apos;est du Lac MacLeod, de même que les datations d&apos;environ 2000 Ma établies pour des galènes qui se trouvent dans le minerai aurifère et cuprifère à Chibougamau, suggèrent un phénomène thermique répandu qui aurait produit la minéralisation dans cette région à l&apos;est de la Baie James, dans la province du lac Supérieur. Ce phénomene serait différent de celui qui aurait produit la minéralisation répan­ due d&apos;âge archéen tardif qui elle serait associée à l&apos;activité volcanique et à l&apos;activité intrusive accompagnée de métamorphisme."

Jan 1, 1992

By H. C. Gunning

Introduction Considerable attention has of late been attracted to the area surrounding Nimpkish lake, on northern Vancouver island, by the discovery of important rich copper deposits. In less than two years some 200 mineral claims have been staked in a small area, and at least two groups have very promising surface showings. During the summer of 1929, the writer spent one month investigating the general geology and mineral deposits of the region, and, although no detailed work has as yet been done in the field or in the laboratory, the importance of the mineral discoveries and the lack of geological information available to the public warrants a preliminary paper on the district. The district is, from a mining viewpoint, very accessible. Boats from Vancouver call at Englewood, in Beaver cove, four times a week. From Englewood, a first-class logging railway, operated by the Wood, .English Company, extends to the northeast corner of Nimpkish lake. The fifteen-mile trip from the north to the south end of the lake is made by boat, two tugs being maintained by the logging company. The whole trip from Englewood can easily be made in one day. The known mineral deposits lie immediately east of the southern part of the lake, four miles or less from the shore. A fair trail, four miles ? long, leads from the lake to the Nimpkish Copper group. Apart from this trail and an old logging railway grade which follows the east side of Klaanch river for several miles, no trails exist on the southeast side of the lake.

Jan 1, 1930

By M. Kunst

The creep behavior of three AJ62 alloys was investigated in a wide range of stresses and temperatures. Multi-level tensile creep tests revealed a distinct primary creep stage and a high stress exponent up to a value of 10. The threshold stress concept which is commonly used in combination with high stress exponents was utilized in the analysis of creep behaviour. This resulted in an effective stress exponent for the AJ alloys indi¬cating dislocation climb as the dominating creep mechanism. In addition, microstructural observations of the lamellar eutectic and of the a-Mg-matrix were carried out using opti¬cal microscopy, SEM and TEM. The creep properties of the alloys are discussed in the context of microstructural parameters such as phase volume-fraction, stability and solute supersaturation.

Jan 1, 2006

By P. S. Arthur, G. R. F. Alvear

Development of a new smelting process is risky. Many novel processes in the metals industry failed to fulfil the initial expectations of their inventors. Large sums of capital have been invested in technologies that either didn&apos;t provide a satisfactory return on investment, or didn&apos;t perform at all, and had to be replaced. One of the keys to success in process development is incremental scale up of the technology, with potential problems being identified and rectified as early as possible. In this way the cost of any rectification that is required can be minimized. The ISASMELTTM process was developed to maturity by Mount Isa Mines through the 1980&apos;s and 1990&apos;s using incremental scale up. Commercialization only occurred once the process had been proven on laboratory, pilot and demonstration scale over many years. As a result ISASMELTTM technology now operates successfully at numerous plants around the world. The methodical approach to development of the technology has allowed owners to modernise their existing operations or create new businesses with significantly reduced technical risk.

Jan 1, 2011

Roasting of molybdenite concentrate is an important stage in the production of commercial molybdenum trioxide. The oxidation kinetic and mechanism of molybdenum sulfide concentrates from two plants were investigated at temperatures from 444 °C to 640°C. The rate of reaction was determined for thin layer samples in a muffle furnace at controlled temperatures, oxygen excess and removal of sulfur dioxide. For both concentrates the rate of reaction is fairly slow at temperatures below 500°C and remains fairly constant from 540 to 600 °C. It was observed that the concentrate from the first plant presents a tendency for sintering or glazing at temperatures above 620°C, whereas the same phenomena was observed at 20 or 30 °C higher temperature for the second concentrate. A kinetic model of two reactions, involving the formation of Mo02 as intermediate oxide for the production of Mo03 is proposed and activation energies of 23.0 and 20.8 kJ/mol for the first and second reaction were calculated for temperatures between 520 °C to 600 °C. These low values of activation energies indicate that the overall rate of oxidation is controlled by mass transfer, particularly in a porous layer of oxides. Therefore, the renewal of the surface by mixing and motion of the concentrate layer is of great importance. Sublimation of Mo03 becomes significant for temperatures above 650 °C.

Jan 1, 2007

By A. S. Robb

SAMPLING of an ore-body is one of the fundamentals in its exploration, development, and exploitation. It is carried out to determine the gold value per ton of an ore-shoot and the probable gold output of the refinery. Sampling also places any broken ground in one of two classes, ore or waste. The value and importance of correct sampling has been shown repeatedly in the past. On the other hand, instances could be given where those in charge of mines have not believed in sampling, and the result has been the same in every case-disaster. This has in all probability been due to assuming that good-looking, well-mineralized rock was ore. Sampling in some form might have averted this misfortune. In this essay, only the method of sampling and the estimation of ore reserves is treated. All titles, figures, and values are fictitious. None of the illustrations can be directly applied to any portion of the Hollinger mine, except Figures 1 and 2, which are included with the special permission of the Canadian Mining Journal. METHODS OF SAMPLING Hollinger Consolidated Gold Mines, Limited, has, from the very beginning of operations, carried out an extensive system of sampling, and the results of this sampling have completely governed the whole mining programme. The Hollinger discovery was made in 1909 and prospecting and exploration of &apos;the surface began at once. Four men were given jobs as samplers and they sampled thoroughly all the outcrops and all bed-rock which could be exposed to view by removing the overburden. When shaft sinking began, samples were taken at two-foot intervals. In 1912, an underground gang of six samplers was organized, and the number was increased at a rate of about two men per year as the size and extent of the workings grew. No permanent record of sampling was kept until 1919, in which year an average of 11.6 men took 28,458 samples, cutting 113,894 feet of sample. From that time until the end of 1934, the average number of samplers varied, but the total number of samples cut, and the total footage sampled, increased.

Jan 1, 1937

By Guangdong Institute of Resources Comprehensive Utilization, Y. H. Tang, H. X. Hu, T. S. Dong, Z. H. Zhang

"A world class rare metals ore deposit in Africa belongs to a massive granite type poly-metallic pyrochlore-niobium resource. Successful project development in realizing the resource is vital to Africa’s economy and pyrochlore processing technology.The ore properties are quite complex due to the presence of varieties of valuable minerals, fine dissemination and intimate association of minerals and the relative abundance of easy-floatable minerals. The separation of pyrochlore from zircon, calcite and mica is generally considered difficult. Whilst studies have previously been conducted by several independent institutions overseas, no satisfactory process has yet been developed to date for the ore deposit—possibly due to the process designed being too complex; high cost of regents; lower performance.Based on process mineralogy study and extensive testwork, the authors have in recent years developed a new technology—“De-slime—Iron-rejection—Zircon (with calcite) and Calcite reverse flotation—Pyrochlore flotation”. The flow-sheet is characterized by ?1prior removal of slimes and iron minerals; ?2 Zircon (with calcite) and Calcite reverse flotation; and ?3Pyrochlore flotation applying new type of chelating collector GYX3 developed by GZRINM in conjunction with selected regulators and depressants.The process involved in the new technology is simple to implement and facilitates stable operation; the flotation reagent regime is easily adaptable; the cost of main reagent is lower largely because it is easy to manufacture and is environmental friendly. Laboratory test results demonstrated that, for raw ore assaying 0.35% Nb2O5, 0.03% Ta2O5 and 0.45% ZrO2, pyrochlore concentrate grade of >35% Nb2O5 could be obtained with >74% recovery. Meanwhile, the Ta2O5 content in pyrochlore concentrate could be recycled, and ZrO2 recovery >50% could be achieved in zircon concentrate assaying ZrO2>63%—significantly improving the technical-economic indicator. These results were verified in pilot trials of 1.44t/d throughput. The paper presents the new technology in whole, summarizes the key factors affecting its performance and discusses in simple terms the mechanism of separation."

Jan 1, 2016

By R. C. Gilmore, J. F. Brune

"Pulverized limestone rock dust used in United States underground coal mines to prevent and suppress coal dust explosions must easily disperse by forces of a methane or coal dust explosion. Moisture in the mine environment causes caking of the dust. Colorado School of Mines researchers performed dispersibility tests in a full-size explosion test drift. Tests included conventional, hydrophobized, and rock dust approved for German mines. Conventional and German standard rock dust products partially agglomerate, which may not be effective in suppressing a coal dust explosion, while hydrophobic rock dust retains better dispersibility.INTRODUCTIONA coal dust explosion devastated the Upper Big Branch mine in 2010 resulting in the death of 29 miners, the worst mining accident in the United States since 1972. The explosion propagated through approximately 65 km of active mine workings, but was extinguished in areas that had been properly rock dusted (Page, 2011). Researchers have long studied and established the ability of inert limestone rock dust to suppress coal dust explosions, see Richmond et al. (1975), Cybulski (1975), and Sapko et al. (2000).To be effective, rock dust must contribute to a total inert content of > 80% by weight and 100% of rock dust particles must pass through an 850 µm sieve, while 70% of the rock dust must be finer than 74 µm. This is established in US regulations 30 CFR §75.2. Dry rock dust is a nuisance that prevents mining work downwind from rock dusting activities. To overcome this problem, dust manufacturers have proposed applying the rock dust as a wet slurry or foam. After drying, manufacturers expected the slurry or foam-applied dust to have the same explosion suppression capabilities as dry-applied rock dust.Researchers at the Colorado School of Mines (CSM) designed and built a full-scale, underground Explosion Test Facility (ETF) at the CSM Edgar Experimental Mine in Idaho Springs, Colorado about 20 miles west of the CSM Golden, Colorado campus. To disperse the different rock dust products, researchers produced an air pressure pulse using a mesh array of PETN detonation cord. This method is simpler, more reproducible and safer than other methods considered, including methane-air explosions and a compressed air cannon. The detonation cord blasts produce a wind velocity of 30 to 50 m/s, the minimum velocity at which coal dust explosions can propagate, based on research by Nagy (1981) and Cybulski (1975)."

Jan 1, 2019

By Mahmood Alemrajabi, Ake Rasmuson, Kerstin Forsberg, Kivanc Korkmaz

"In the present study, the recovery of rare earth elements (REE) in the nitrophosphate process of fertilizer production is investigated. The apatite has been recovered from iron ore tailings by flotation. After digestion of apatite in concentrated nitric acid, Ca(NO3)2.4H2O is first separated by cooling crystallization and then the REEs are recovered by precipitation. Optimum conditions in these steps have been determined in a previous study. The precipitate mainly consists of CaHPO4.2H2O and REE phosphates.In the present study, selective dissolution and re-precipitation have been studied in order to obtain a precipitate that is more concentrated in REEs. The precipitate was selectively dissolved in nitric and phosphoric acid at different acidities (pH 6 to 0) with the liquid /solid ratio of 100 mL/g. It is shown that most of the CaHPO4.2H2O and other calcium containing compounds will be dissolved at pH 2 while the REE phosphates are not dissolved above a pH of approximately 2. Thus, by partial dissolution of the REE precipitate at pH 2.5 most of the solid calcium phosphates will be dissolved and the remaining solid phase, which is more concentrated in REEs, can be filtered off as a fairly concentrated REE solid mass and the liquor can be recycled back to recover more P nutrients. Alternatively, the REE enriched precipitate was dissolved completely in nitric acid and re-precipitated again by addition of ammonium hydroxide to pH 1.2. A chemical equilibrium software, MEDUSA (Puigdomenech, 2013) has been used to evaluate the experimental results and to estimate the optimum conditions for selectively dissolving the precipitate."

Jan 1, 2016