Search Documents

By J. du Plooy

Mintek has implemented a training scheme that provides students with the experiential training requirement for the National Diplomas in Chemical Engineering and Extraction Metallurgy. This note describes the main features of the scheme and the course content, and our view of future developments in this area.

Jan 1, 1998

To provide operators of large-opening mines with a ventilation planning tool that will help them develop a healthier, safer, and more efficient ventilation system in the underground workplace.

Jan 3, 2006

By C. C. Hwang

The Bureau of Mines made time-dependent calculations to determine the size of a stationary source fire within a ventilated duct (or passage-way) necessary to ignite a combustible duct liner. The objective of this work was to gain more understanding of what occurs in duct fires and to determine critical conditions for ignition and propagation of mine fires. Heat transfer to the combustible surface includes both convective and radiated components, while the heat is conducted into the combustible and reradiated to the surroundings. The combustible is assumed to ignite when the net heat transfer to its surface is sufficient to raise the surface temperature to some minimum temperature, defined as the ignition temperature. A nondimensional parameter, which characterizes the source-fire intensity in the presence of ventilation flow, emerges as a parameter for a criterion of the critical conditions. The results of these calculations indicated that the minimum fire size necessary for ignition increases with the ventilation rate and duct cross section. These results are compared with experimental results obtained from fires in a 0.8-by 0.8-by Il-m-long duct and a full-scale gallery (2.4-by 2.4-by 65-m). Agreement between the theory and the experiment is good.

Jan 1, 1988

By Walter E. Duncan

The ores treated at the concentrating plant of the Mahoning Mining Co. at Rosiclare, III., come largely from the blanket replacement deposits of the northeastern part of Hardin County, Illinois, and consist of complex mixtures of galena, sphalerite and fluorspar in a gangue of quartz, limestone and sandstone. The several minerals are so intimately inter-grown that they are not liberated at the sizes usually treated by gravity concentration in the usual fluorspar plant. For this reason, an all-flotation method of concentration was developed in cooperation with the station of the U. S. Bureau of Mines at Rolla, Mo.1 This flotation separation made possible the commercial production of four concentrates: (I) lead, (2) zinc, (3) acid-grade fluorspar and (4) metallurgical-grade fluorspar.2,3 Although fluorspar had been floated in Canada in 1921 and a plant at Rosiclare had been floating fluorspar since March 1929, fluorspar flotation was given considerable impetus by the Mahoning developments, since some features of the separation were quickly adopted by other fluorspar companies. The Bureau of Mines6 reports that in the 10 years preceding 1938 only 50,552 tons of fluorspar flotation concentrates were produced in the United States. The rise from this almost nominal figure to 153,750 tons (largely acid grade) in one year (1944)6 is indicative of the activity in fluorspar flotation occasioned by the war. The industry thus proved to be in a position to expand and keep up reasonably well with the requirements imposed upon it by such developments as occurred in high octane aviation gasoline alkylation, in the use of Freon as a refrigerant and as carrier in the Aerosol "bug bomb," and in the atomic bomb project as well as in the expansion of other activities requiring hydrofluoric acid; for example, the aluminum industry. Despite the fact that the greater portion of acid-grade fluorspar produced in the last few years went directly into war uses, the future of the acid-grade field still appears bright. As a result of the activity in fluorine chemistry during the war, it seems likely that in the relatively near future almost every phase of human endeavor will find some fluorine compound involved. The other three concentrates produced deserve some attention in these introductory remarks. The lead concentrates first produced contained both zinc and fluorspar but these did not interfere with their marketing. As will be pointed out later, the quality has steadily improved until today it is a relatively high-grade product. Although some zinc smelters accept concentrates containing limited quantities of fluorspar, it is a very objectionable impurity. Since flotation methods fail in the complete removal of the fluorspar, chemical methods were developed for

Jan 1, 1947

By Walter E. Duncan

The ores treated at the concentrating plant of the Mahoning Mining Co. at Rosiclare, III., come largely from the blanket replacement deposits of the northeastern part of Hardin County, Illinois, and consist of complex mixtures of galena, sphalerite and fluorspar in a gangue of quartz, limestone and sandstone. The several minerals are so intimately inter-grown that they are not liberated at the sizes usually treated by gravity concentration in the usual fluorspar plant. For this reason, an all-flotation method of concentration was developed in cooperation with the station of the U. S. Bureau of Mines at Rolla, Mo.1 This flotation separation made possible the commercial production of four concentrates: (I) lead, (2) zinc, (3) acid-grade fluorspar and (4) metallurgical-grade fluorspar.2,3 Although fluorspar had been floated in Canada in 1921 and a plant at Rosiclare had been floating fluorspar since March 1929, fluorspar flotation was given considerable impetus by the Mahoning developments, since some features of the separation were quickly adopted by other fluorspar companies. The Bureau of Mines6 reports that in the 10 years preceding 1938 only 50,552 tons of fluorspar flotation concentrates were produced in the United States. The rise from this almost nominal figure to 153,750 tons (largely acid grade) in one year (1944)6 is indicative of the activity in fluorspar flotation occasioned by the war. The industry thus proved to be in a position to expand and keep up reasonably well with the requirements imposed upon it by such developments as occurred in high octane aviation gasoline alkylation, in the use of Freon as a refrigerant and as carrier in the Aerosol "bug bomb," and in the atomic bomb project as well as in the expansion of other activities requiring hydrofluoric acid; for example, the aluminum industry. Despite the fact that the greater portion of acid-grade fluorspar produced in the last few years went directly into war uses, the future of the acid-grade field still appears bright. As a result of the activity in fluorine chemistry during the war, it seems likely that in the relatively near future almost every phase of human endeavor will find some fluorine compound involved. The other three concentrates produced deserve some attention in these introductory remarks. The lead concentrates first produced contained both zinc and fluorspar but these did not interfere with their marketing. As will be pointed out later, the quality has steadily improved until today it is a relatively high-grade product. Although some zinc smelters accept concentrates containing limited quantities of fluorspar, it is a very objectionable impurity. Since flotation methods fail in the complete removal of the fluorspar, chemical methods were developed for

Jan 1, 1947

By R. E. de Barrio, M. E. Lanfranchini, R. O. Etcheverry

"The El Abuelo Ca-Fe-magnetite skarn and related hydrothermal quartz veins are located at Cerro Pepita Hill, in southwestern Chubut province of southern Argentina, 1700 km southwest of Buenos Aires. These deposits are developed in a continental magmatic arc environment linked to the Andean orogeny. Iron skarn mineralization is mainly hosted by an Upper Jurassic to Early Cretaceous sedimentary sequence interbedded with Upper Jurassic basaltic andesite, and is spatially associated with Early Cretaceous calc-alkaline dikes. Ore grades vary between 40 and 63 wt.% Fe. In addition, anomalous metal contents (>10 000 ppm Cu and up to 81 g/t Ag) are present in the hydrothermal quartz veins.At least three paragenetic mineral assemblages have been identified in the El Abuelo exoskarn: (1) amphibole > epidote ± chlorite ± quartz, formed by isochemical contact metamorphism; (2) Fe-clinopyroxene ± Ca-garnet, formed during prograde metasomatic anhydrous exoskarn formation; and (3) actinolite ± epidote ± chlorite ± quartz ± magnetite > titanite, resulting from hydrous retrograde alteration of exoskarn. Endoskarn alteration involved an early Mg-Fe-clinopyroxene ± Fe-garnet assemblage followed by retrograde actinolite replacement of pyroxene. Lower temperature hydrothermal alteration related to quartz veins was superimposed on the skarn assemblages, showing an innermost sericite ± adularia ± pyrite ± chalcopyrite assemblage and an external propylitic halo.Some metallogenic characteristics of the mineralization and the geological setting resemble those in several iron oxide copper-gold deposits elsewhere in the world."

Jan 1, 2007

By Michael A. Trevits

Since the promulgation of the MINER Act and the follow-up changes to the regulations governing mine seal construction and maintenance, mine operators must be acutely aware of the atmosphere in sealed mine areas and prepared to deploy control technologies when the conditions are warranted. On Site Gas Systems1 in Newington, Connecticut was awarded a contract by the National Institute for Occupational Safety and Health (NIOSH) to construct a novel in-mine nitrogen (N2) generation plant using pressure swing adsorption (PSA) technology. PSA technology utilizes carbon molecular sieve material and pressure to adsorb oxygen (O2) molecules while allowing N2 molecules to pass through the sieve material. The prototype PSA unit was tested at the NIOSH Safety Research Coal Mine (SRCM) where a 62,000 ft3 area of the mine was rendered inert during a series of two tests. The resultant data were then used to construct a CFD simulation of both injection tests. In addition, O2 depletion and gas leakage rates were quantified in the model and were compared to actual values. Once the model was calibrated, the sealed mine area was doubled and simulations were made with various injection rates and injection site locations to determine the impact on the time needed to render this area inert. This paper presents an overview of the PSA plant, the details of the gas injection tests and CFD modeling work.

Jan 1, 2010

By Sudhir Kumar Kashyap

In underground activities ground control is a challenging problem. It affects safety, production, and efficiency. As per statistics of accident data, ?fall of roof/sides? is one of the major causes of mine accidents. In many cases, our experiences and understanding of soil and rock behavior still fall short of being able to predict how the ground will behave. Presently, empirical approaches to design are widely used in estimating mine support parameters. Under these circumstances, expert judgment plays an important role, and such accidents can be obviated with accurate measurement and optimization of data and analysis using the neuro-fuzzy technique of artificial intelligence. Recently, a neuro-fuzzy hybrid approach has become one of the major areas of interest in engineering fields because it gets the benefits of neural networks as well as those of fuzzy logic systems, and it removes the individual disadvantages by combining them on the common features. Neural network and fuzzy logic technologies have common features, such as a distributed representation of knowledge, the ability to handle data with uncertainty and imprecision, etc., like in ground control. Fuzzy logic technique has tolerance for imprecision of data, while neural networks have tolerance for noisy data. In this paper we have focused an intelligent technique, i.e., neuro-fuzzy technique, to approximate the setting load given to the standing support (props) erected for the purpose of supporting freshly exposed roof during underground mining. We have used twelve input variables of rock parameters, and after having trained using a neural network with a sigmoidal function as an activation function, simulation was done to find the output parameter, i.e., the pre-load (setting load)to be applied on props. Outputs of the neural network were again fed to the fuzzy system together with the twelve parameters, incorporating five triangular membership functions for each parameter. Final optimum output was approximated using the MATLAB program, which was found to be satisfactory. Neuro-fuzzy technique has better performance over individual neural networks or fuzzy logic technique.

Jan 1, 2012

By Russell Frith

For many years, underground rock mechanics and in particular, roadway/tunnel roof stability has been underpinned by the often unchallenged assumption that roof strength (as defined by the UCS) and stiffness (E) are key stability controls. This has logically led to the proliferation of laboratory testing of rock specimens and the development of indirect geophysical methods to gain estimates of these two rock parameters. Furthermore, many design methods are significantly focussed on replicating rock mass behaviour through either intact or failed constitutive models. Demonstrably the strength and stiffness of the host rock material is commonly used as one of the key indicators of excavation roof stability and it finds either direct or indirect use in just about every rock mass rating system in use today. In more recent times there has been a common move to consider and apply (even if only conceptually at the current time) structural engineering type principles (e.g. buckling) to coal mine roadway roof (and rib) stability. Similarly our knowledge of the in situ stress environment and its likely origins has improved significantly, largely through stress measurements and subsequent analysis. This paper combines knowledge in both of these fundamental areas through a deterministic model for roadway roof stability and in combination with field examples, reaches the almost certainly controversial conclusion that UCS and E are commonly irrelevant, albeit that the former may provide an indication of other relevant geotechnical parameters (e.g. bedding cohesion). As with all hypotheses or rules, there are naturally exceptions and in this case, the most obvious is the tailgate of the longwall panel (with adjacent goaf). Due to the significant change in the strata loading environment of a longwall tailgate as compared to first workings for example, the stability equation materially changes so that UCS and E become critical controls. The point of the paper is to present a different perspective on a traditional mining problem and to challenge geotechnical professionals to keep thinking ?outside of the square? in the never-ending endeavour to improve our understanding of the engineering problems we regularly face. Such an understanding impacts upon such issues as geotechnical data collection from borecore, support hardware requirements and design capabilities. Therefore making the assumption that our understanding is always fundamentally correct could in fact be limiting the development of new and improved engineering in the future.

Jan 1, 2006

By William Hustrulid

Pre-split blasting is a primary technique for creating slopes with a minimum amount of unwanted damage to the remaining rock mass. Rock slopes created in such a way have both safety-related and economic advantages. The applications extend from road cuts to rock quarries to large open pit mines. For example, as deep open pit mines approach the end of their operating lives, slope steepening is one option to be considered. To be able to safely achieve and maintain steepened final slopes, good blast design techniques must be available and applied together with close operational control. Pre-split blasting is an important element in this slope creation process.

Jan 1, 2007

It is well known that the electrochemical precipitation of metals from aqueous solutions is conducted by the electrochemical standard potential scale. This scale indicates the order of nobility of different metals. Consequently, the standard potential scale shows the nocivity of metals when they are present as impurities in aqueous solutions containing metals. In the hydrometallurgy of cobalt, nickel and zinc are co-deposited during cobalt electrodeposition. Nickel has almost the same chemical, physical and electro-chemical properties as cobalt. Furthermore, the electrochemical potential of nickel is relatively higher than that of cobalt. For this reason nickel is preferentially reduced at the cathode in the presence of cobalt. The presence of small amounts of zinc in solution leads to contamination of cobalt electrowon. In spite of its lower electrochemical potential in comparison to cobalt, zinc is reduced on the cathode because of its higher hydrogen-overvoltage. But, in the hydrometallurgy of zinc, small amounts of cobalt present solution will contaminate the zinc reduced at the cathode. This is easily explained by the fact that cobalt is more electropositive than zinc. The co-deposition mechanism of sulphur at the cathode is not yet well understood. Great attention has to be paid to the mechanism of co-deposition of sulphur during cobalt electrolysis. This work aimed to investigate the influence of some parameters on the co-deposition of nickel, zinc and sulphur during cobalt electrowinning. The following parameters have been investigated: Co2+concentration in the electrolyte, current density and ammonium sulphate (NH4)2SO4additions. It has been established that important nickel, zinc and sulphur co-deposition takes place at relatively low Co2+ concentration in solution. The behaviour of these elements with regard to the cathodic phenomena has been established.

Jan 1, 2005

By N. H. J. Freire, D. Majuste

In this paper, the effects of some organic compounds on the current efficiency, cell voltage and specific energy consumption during nickel electrowinning, and on the deposit features (morphology, crystallographic orientation and nanohardness) were described. The organics tested here (extractant, diluent, flocculant, lubricating oil and acid mist suppressant) are currently used in industrial plants. The results indicated that only the flocculant and acid mist suppressant exhibit relevant negative impacts on the current efficiency and energy consumption. The current efficiency dropped from 93.6 % (organic-free solutions) to 86.0 % and to 92.8% in electrolytes containing 100 mg.L-1 of acid mist suppressant and flocculant, respectively. At this concentration, their addition to the electrolyte led to increases of the specific energy consumption in the order of 18 % (acid mist supressant) and 2 % (flocculant). Cyclic voltammetry showed that Ni nucleation occurs at more negative potentials at 50 and 100 mg.L-1 of these organics in the electrolyte, thus indicating an inhibition of the deposition process. The deposit quality decreased at the higher concentration of all organics, when more hydrogen pitting was observed. The acid mist suppressant caused delamination of the Ni deposit at 50 and 100 mg.L-1. The addition of 100 mg.L-1 of flocculant and acid mist suppressant to the electrolyte increased the nanohardness of the deposit around 31 and 72%, respectively. The increase in Ni deposit hardness may lead to a decrease in the material ductility, thereby affecting the stripping and cutting of Ni sheets. Our findings may be helpful since strong adverse effect of some organics that may be present in the electrolyte were identified, thus the industry can control and optimize the organic´s dosage in the corresponding operations.

Jan 1, 2016

By Juan Rassmuss

El presente artículo señala el valor del azufre y la influencia del método de beneficio en lsu explotación. Asimismo, se describe los yacimientos de Piura y los de Báyovar, como del extremo norte está Ticsani, Tutupaca, Yucamani, Cano y en el Sur, Paucarany. La formación de estos yacimientos se debe a lla oxidación parcial de sulfuro de hidrógeno de origen volcánico, a excepción de los yacimientos de Bayovar y Piura, considerados como productos resuidual de petróleo.

Jul 1, 1956

By P. W. Godbehere, B. W. Brooks

"This paper deals with the milling of slags from the Noranda Continuous Process, in the Horne Concentrator at Noranda, Quebec. The milling of copper slags, although novel in Canada, has been practiced in Japan, Finland and elsewhere for several years.In March 1973, the prototype Noranda Continuous Process furnace or ""reactor'' came on-stream, In this pyrometallurgical process (see Fig. 1), copper concentrates mixed with flux are smelted in a single furnace to form copper or a high grade copper matte, and slag. The conventional smelting processes of roasting, reverberatory smelting and converting have been incorporated in a single 17 ft. diameter by 70 ft. long steel cylindrical vessel (l, 2). The copper or matte is tapped from the bottom of the reactor into ladles and transferred to an anode furnace or to a converter. The slag is tapped into 40 ton capacity ladles, cooled, crushed, and conveyed to the concentrator. At the present time, the reactor is operated to produce matte. The matte slag* containing 4 - 6 per cent copper is milled using conventional ore dressing grinding and flotation equipment. A flotation concentrate assaying 35 - 40 per cent copper is recycled to the reactor. Crushing, conveying, grinding, flotation and tailing disposal equipment previously used for over 40 years for ore treatment has been modified to suit the requirements of slag milling. Slag milling is essentially the scavenger circuit of a pyrometallurgical process."

Jan 1, 1977

By R. O. Williams

A recent article by Chernock, Singer, Mueller, and Beck 1 which supports the use of the integral of I sin $ d$ for comparing fiber texture data does not settle what happens to I sin ø as ø approaches zero, where I is the diffraction intensity for poles oriented 0 deg from the fiber axis. They indicate that they believe that it should approach some constant value (that is, I increases without bound) and the fact that in reality it does not was a result of the diffraction

Jan 1, 1960

The slags produced by the Imperial Smelting Process (ISP) are based on the system ZnO-?FeO?-Al2O3-CaO-SiO2. The slag chemistry is important to the process since it determines the fluxing practice and the operating temperature of the furnace required to produce fluid slag. The paper presents the results of the first systematic experimental investigation of these ZnO-containing slags in equilibrium with metallic iron, and provides information on the primary phase fields and liquidus temperatures in these slags over the range of compositions used in ISP practice. A feature of the slags is the presence of alumina, which has a major influence instabilizing the spinel phase. This information presented in the form of pseudo-ternary sections ZnO-?FeO?-(Al2O3+CaO+SiO2) enabling the data to be readily used by plant engineers. Keywords: liquidus temperature, ISP, EPMA, ZnO-?FeO?-Al2O3-CaO-SiO2, phase equilibria.

Jan 1, 2004

By Carlos Avalos Casillas, Saul Ortiz Landeros

The current work shows metallurgical results obtained at the Centro de Investigación y Desarrollo Tecnológico (Peñoles CIDT), as a continuation of the work first published in February 2012. With the aim of optimizing the economic values of the products, ores from San Julian (Fresnillo) were selectively floated to produce a lead concentrate and a zinc concentrate containing high silver values. In the laboratory, this included regrinding of the rougher and scavenger lead concentrate to increase the liberation of mineralogical species and thus lower zinc recovery. Cyanide leaching bottle tests were conducted to improve the value of the silver. It is proposed to leach the silver contained in the zinc concentrate and then recover the silver using the Merrill Crowe process. The results show a reduction of zinc recovery in the lead concentrate from 11.3% to 2.0% after regrinding to a P80 of 10 microns, improving the metallurgical quality and economic value of the lead and zinc concentrates. Also laboratory and pilot scale cyanidation tests showed that about 65 to 80% of silver will be leached from the zinc concentrate, after regrinding to a P80 of 10 microns. The proposed processing increases the economic recovery of silver from 72.7% to 78.8%.

Jan 1, 2014

By P. J. Brereton-Stiles, C. J. Hockaday, I. J. Barker, M. S. Rennie

This paper reports on studies that have been done on the electrical conduction in silicon, ferro silicon, and charge chrome furnaces. A system has been developed that can distinguish between normal resistive conduction and arcing, and this was used to quantify in particular the relative amount of arcing that takes place in these furnaces. It was found that silicon and ferro silicon behave similarly and exhibit a relatively large amount of arcing. Charge chrome on the other hand exhibits considerably less arcing, and the extent of this arcing is highly correlated with the tapping of the furnace. The arcing measurements can also be used online in the control of the furnace, both for the electrodes and electrical circuit, and for the raw materials.

Jan 1, 2007

By R. Raghavaraju

Estimation of the dynamic stress field in terms of its amplitude and decay around a blast hole is a key input parameter in all numerical modeling and blast prediction exercises. However, there is very limited information available in literature on these critical parameters, which would be considered essential in any blast modeling exercise. A laboratory-scale experimental study has been carried out in two different rock types to study at very close range the stress wave decay from a blast hole at distances ranging from 3 to 10 borehole radii. The single–hole blasting experiments employed a centrally located detonating cord (5.3 g/m) in 6 mm(1/4 inch) and 10 mm (3/8 inch) boreholes. The coupling medium employed was air and water, in addition to using a thin-walled copper tube in intimate contact with borehole wall to prevent of penetration of explosion gases into the emerging cracks. The paper describes the nature (amplitude and decay) of the transmitted shock pressure and their evolution in the two rock types for these various experimental conditions, which are present to varying degrees in all blasting operations.

Jan 1, 2014

By J. D. Morgan

In the first half of the year, lessening of cold war tensions was welcome. But Iraq's invasion of Kuwait in the second half led to the Persian Gulf War in January and February 1991. This caused an oil shock that dampened the economy. So the US gross national product rose only 0.9% to $5,463 billion (US billion = 109). The buildup of military forces in the Persian Gulf area focused greater attention not only on petroleum but also on other strategic materials. The Department of Defense continued to review stockpile goals and to upgrade several mineral materials. In addition, the Bureau of Mines continued to maintain the standby Emergency Minerals Administration. The Defense Production Act, which authorizes priorities, alloca¬tions and supply expansion, lapsed on Oct. 20. So the Selective Service Act of 1967 became the authority for assuring that orders of the armed forces and defense atomic-energy programs were given priority treatment. Consumer demand strongly affects mining worldwide. US citizens carry significant debt, and large stocks of housing and consumer goods are already in place. Some 250 million persons have 188 million licensed motor vehicles and 100 million dwelling units. Consequently, new car production fell 11 %, to 6.1 million units. Truck and bus production fell 8%, to 3.7 million units and new private housing starts fell 13% to 1.2 million units.

Jan 1, 1991