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By R. Ciccu, P. P. Manca, A. Bortolussi, G. Massacci

Tool performance and the unit cost of cutting depend on a number of operational variables (peripheral velocity, pull-back force, water injection rate, angles of the sections of wire outside the rock) as well as on the geometric features of the cut itself (area and shape). Cutting rate and wire productivity are also influenced by the type and number of diamond beads per unit length of wire and by the characteristics of the rock (granite or marble). A computer program aimed at handling a problem of this complexity has been developed and tested with the use of available field and laboratory data and has been found acceptably reliable. Discrepancies between current industrial data and some of the results suggest future lines of research, while the simulation should also be extended to include different types of rock and tool and a variety of bench face geometries

Aug 1, 1994

By K. D. Russ, A. J. Beer

Non-contact systems for measuring underground voids have used theodolites, reflective or non-reflective laser methods and sonar techniques. An effective but cheaper alternative is based on use of a Wild T1000 electronic theodolite coupled to a Leica Data DISTO and a Wild GRE3 data logger. The software used to process the theodolite data is a spreadsheet and macro combination, while Surpac, Datamine and AutoCAD modelling packages have been investigated for viewing the tunnel profiles. The main limitations were found to be blinding, when irregularities in the stope obstructed the line of sight, and the 30 m range of the Data DISTO model used in the study, although more powerful models are available. All three modelling packages proved suitable, with Surpac providing the best-quality printed images of the voids surveyed and AutoCad by far the cheapest alternative

Jun 21, 1905

By J. E. Misiewicz, A Rozendaal

Paper presented at Geofluids '93, held in Torquay, UK, 4-7 May 1993. The tin field consists of a fragment of Lower Proterozoic volcanosedimentary rocks surrounded by granitoids. Almost all the significant deposits are hosted by arkoses and are classified as replacement and space-filling types, with particular styles of mineralisation dominating at different mines. Petrological and geochemical investigation of borehole cores from four centres indicated the presence of a stratified zone 500-600 m thick and continuous over at least 20 km along strike, consisting of pervasively altered clastic arenitic sediments. The alteration is zoned into a grey-green sodic albitised footwall, an 80 m thick sericitised-tourmalinised sulphidic tin zone and a red haematitic potassic hanging-wall. The zoning and the localisation of three cassiterite phases are consistent with the tectonic history and with multiple pulses of stanniferous hydrothermal fluids derived from late differentiates of the granites over a prolonged period. Areas of high fracture density acted as conduits for the fluids, whose initially rapid ascent was retarded by decreasing pressure contrast, limited development of fracturing and/or impermeable shaly arkose to cause lateral spreading and pervasive alteration over a broad, stratified front. Lateral overlapping of local fronts at the various centres suggests a continuous zone, while the many petrological and geochemical similarities point to a shared fluid composition

Aug 1, 1995

By J A. Hacked

This paper explores the potential to exploit controls over the outputs of the primary blasting operation, arising from the performance consistency benefits gained in using modern bulk emulsion explosives technology. The former, allied with the latest powerful blast predictive software and measuring tools, offers the user the opportunity to apply control over both cost and performance, which has not been possible in the past.

Jan 12, 1997

By B. Sonmez, B. Aksanl, S. Ersaym, I. F. Erkal, S. L. Ergun

The comminution circuit at the plant has experienced severe problems arising from a feed containing much larger amounts of clay and having a higher moisture content than expected. Three solutions were proposed: replacement of the crushing circuit by tooth roll-type crushers; using washing drums; and introducing primary autogenous/semi-autogenous millling instead of crushing. Computer simulations studied the effects of the first two solutions on the circuit capacity. Laboratory and industrial scale ball mill batch grinding tests were carried out. The parameters of a kinetic model were determined. The ball mill circuit was sampled and operating model parameters were calculated. The ability of batch grinding parameters to represent the operating conditions was studied. Tests failed to find acceptable model parameters, but parameters from an industrial size batch mill were found to be suitable for simulation studies. The simulations indicated that a continuous feed of -12 mm provided by tooth roll crushers would maintain the desired capacity. Increasing the feed size to -25 mm would reduce the capacity by 8-15%. The use of washing drums could also solve the capacity problem, but small fluctuations in water flow rates might result in problems of excess water in the grinding circuit.

Jan 4, 1993

By F. T. Da Silva

Concentrates of titaniferous minerals containing around 30 wt% Ta2O5 are processed hydrometallurgically by hydrofluoric acid leaching and solvent extraction, followed by the precipitation of hydrated potassium heptafluorotantalate. A fundamental study of the thermodynamics of this precipitation and recrystallisation was undertaken to increase understanding of the conditions most conducive to the production of pure, well-crystallised K2TaF7. Activity-pH diagrams for the Ta-K-F-H2O system explained the dissolution of Ta2O5 in fluoride solutions quite well and also the precipitation-recrystallisation of K2TaF7.H2O. X-ray diffraction and scanning electron microscopy confirmed the thermodynamic observations. It was concluded that the best precipitating agent for K2TaF7 from fluoride solutions is KF but a recrystallisation step in a HF environment produces purer, well-crystallised K2TaF7.H2O, eliminating oxy-salts and other impurities

Jun 21, 1905

By Qing Wang

In this method the state of an open-pit mine is represented by the number of benches that are mined in each predesigned mining phase (or pushback). Consequently, a specific mining schedule can be represented by a sequence of states which starts with the topography of the mine site and ends with the ultimate pit. For a given set of mining phases all feasible states are first generated and sequences of states are then evaluated for technical and economical feasibility. The best sequence, which gives the maximum net present value (NPV), is found by applying a dynamic programming optimisation algorithm. The algorithm also optimises the cut-off grade which satisfies the mill feed requirement for each planning period. It was found that the algorithm can be used not only for scheduling but also as an effective tool for analysing the effects of mining and milling capacities and cut-off constraints on the mining schedule and the total NPV. The algorithm, which was programmed in C, was successfully applied to a large Au-Cu deposit

Jul 1, 1996

By Y. L. Ding, N. A. Warner

Cylindrical pellets made from graphite and chromite mixtures were reduced in high-carbon ferrochromium melts at 1 600-1 695 degrees C, under an atmosphere of almost pure CO. The reduction rate, as measured by gas evolution, increased with increasing melt temperature and graphite addition and with decreasing pellet diameter or height, although reductant particle size had a very limited effect on kinetics. At a pellet size, heat and mass transfer were significant in controlling the early stages of reduction of large pellets while at chromite grain size, gas diffusion was probably a rate-controlling step. The time required for dissolution of unfluxed pellets into the melts was significantly longer than that for reduction. This indicates that pellet dissolution may be the limiting factor in determining the operating parameters for a proposed new process to produce high-carbon ferrochromium using melt circulation

Jun 19, 1905

By S. P. Mishra, G. R. Chaudhury

The adsorption of Cu2+ ions by Penicillium sp. displayed a dual rate, with an initial faster phase followed by a slower one. The adsorption rate increased with increasing pH due to chemical and biochemical reactions. The Cu-loading capacity of the biomass increased at higher initial Cu2+ concentrations. Above 40 degrees C the adsorption rate decreased which may be due to partial hydrolysis of biopolymers which are essential constituents of the cell wall. Adsorption kinetics followed the Freundlich isotherm and the equilibrium concentration that was calculated on the basis of the isotherm matched the observed value well. A series of theoretical adsorption curves were produced using mathematical correlations between the mass transfer coefficient, the Cu2+ ion concentration at equilibrium and at time t. The correlation between the theoretical and observed adsorption rates for different experimental conditions was good. It was concluded that the results from the study were best explained using a mass-transfer adsorption model

Aug 1, 1995

By Xuejing Xie, Tianxiang Ren

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Standardised stream-sediment sampling procedures have been used in mountainous and hilly terrains. Special sampling procedures were developed for application in remote environments, such as high mountains, desert, semi-desert, karst and loess-covered regions. The diversified analytical methods used in more than 20 analytical laboratories participating in the project have been unified into two multi-element, multi-method analytical systems. A unified data monitoring procedure was developed based on primary and secondary standard samples. To date the project has covered about 4 000 000 km2 and the aim is to complete the coverage within the present decade

May 1, 1991

By Eric Forssberg, Vigen Zeng

During mechanical grinding high intensity vibration is emitted that contains information on the mill's operating state. Tests, using a laboratory ball mill, studied the influence of operating parameters on the vibration signature. The parameters studied were: mill speed; powder filling; pulp density; grinding period; and pulp temperature. Vibration signals were detected by an accelerometer, amplified by a vibrometer and recorded onto digital audio tape. A digital oscilloscope converted the signals into IBM-compatible data format. Digital signal processing and multivariate data analysis were carried out with specially developed software. The power spectral density was estimated from the time-domain vibration signal. Four new latent variables were used to describe changes in the vibration spectra. A relationship was established between operating parameters and latent variables which could form the basis of a quick and automatic method of monitoring operating parameters in ball mill grinding.

Jan 4, 1993

By C. J. V. Wheatley

Recent studies of the mineralisation at Avoca in southeast Ireland, Parys Mountain in Anglesey, and Coniston in the Lake District result in the proposal of a new metallogenetic model for mineral deposits in the Southern Caledonides. A regional pattern of metal zoning exists, an axial belt, including the major copper deposits, being bordered by areas with lead-zinc deposits. Conformable lenticular pyritic zones occur in the central belt, closely associated with acid volcanic sequences and, often, post-dating them. These zones are thought to have been formed in a marine environment, mineral growth taking place below the sediment-water interface, whereas magnetite-rich zones developed under different Eh and pH conditions. Stockworks containing appreciable copper and, in some cases, lead and zinc were developed at a later date, stratigraphically below the pyritic zones, by migrating hydrothermal chloride and metal-rich fluids. Complex lead-zinc-pyrite mineralisation resulted from the reaction between pyritic zones and the final fraction of the hydrothermal fluids. Crosscutting vein-type fissure infilling mineralisation occurs in every mineral field. These deposits apparently comprise a pulsatory metasomatic sequence, closely related to tectono-stratigraphic controls, ore localisation being influenced by the coincidence of suitable structures and pyritic shale horizons. The implications for mineral exploration are considered and it is concluded that the model offers an explanation for the existing pattern of metal zoning; and it may have wide applicability to mineral deposition in geosynclinal sequences.

Dec 1, 1971

By R. Patel, J. Ephraim

The production of titanium dioxide (TiO2) from its minerals such as ilmenite is challenging, and subsequent isolation of titanium from TiO2 is even more difficult because of the metal-oxygen bond strength. Currently, titanium sponge is mainly produced via the Kroll process, which is energy intensive and generates large quantities of waste. A number of international research groups have come up with technologies for the production of titanium metal. However, none of them have been commercialised, because of engineering or economic issues. The team at Bradford have confirmed that ultra-pure titanium powders can be separated from TiO2 powder through metallothermic reduction and are working to scale up the process.

May 1, 2015

By H. K. Taylor

Ore reserves are inadequately defined. Geological reconnaissance and pre-feasibility mining work generate a broad range of valid tonnage estimates, many published for the benefit of various interests, who may view all figures as reserves. This work reviews the regular estimation of tonnages, grades and relevant factors for single deposits. A consistent framework of definition is suggested which, by conforming to the known structures of feasibility studies and long-range plans, avoids the pitfalls of over-categorisation and of unrealistic promises. Applications are based on North American experience but are intended for general use

Sep 1, 1991

By A. D. Mukherjee, H. N. Bhattacharya

Middle Proterozoic sulphide ore mineralisation occurs in isolated blocks of the NE-SW trending Delhi fold belt composed of Delhi Supergroup rocks. The Ajari-Basantgarh-Pipela belt forms part of the longest, widest and westernmost tectonic unit of the Delhi fold belt and consists of amphibolites, metapelites, quartzites and carbonates. The metapelite lenses and associated amphibolites host pyritic copper mineralisation. Mineralisation takes the form of sheet-like bodies consisting of ore lenses of various sizes interlayered with host or associated rocks. Massive, banded and disseminated varieties of ore are found. Pyrite is dominant with subordinate chalcopyrite and sphalerite. Pyrrhotite, galena, cubanite, mackinawite, marcasite and freibergite constitute the minor minerals. The characteristic features of the ores suggest a possible correlation with Besshi-type deposits, and the closely associated amphibolites are interpreted as low-K tholeiites of a fore-arc setting

Jun 19, 1905

By J. Laskowski, J. Lekki

"The mechanism of joint action of a frother (alpha-terpineol) and a collector (ethyl xanthate) in the flotation of chalcocite has been examined. In order to study the dynamic effects of frother and collector in bubble-particle collisions, the following aspects were investigated : determination of zeta-potential. Measurements of the thickness of fluid film on the surface of chalcocite and adsorption of xanthate, as influenced by alpha-terpineol, induction time and flotation versus concentration of alpha-terpineol and ethyl xanthate.The mechanism of the adsorption-desorption phenomenon on chalcocite with regard to non-ionic molecules, e.g. a-terpineol, has been considered, and the influence of this on the stage and thickness of the intervening wet layer between a bubble and a particle, changing the probability of collision and attachment, is suggested."

Dec 1, 1971

By M. C. Ruiz, M. E. Godoy, J. B. Rivarola, M. W. Ojeda

The amount of Pd recovered from an exhausted olefin hydrogenation catalyst was found to depend on mixing technique, particle size, carbon percentage, chlorine flow, reaction time and temperature. Pd extraction was total when a sample in the 125-175 micrometre particle size range was chlorinated for 60 min at 723 K with 20 cm3 Cl2/min, for 60 min at 748 K with 30 cm3 Cl2/min and for 30 min at 773 K with 30 cm3 Cl2/min. No C addition was needed; the initial C content of the catalyst was sufficient for total recovery. Pd extraction was also affected by heat treatment in different atmospheres before chlorination. Treatment with O2, N2 and N2 with traces of O2 led to different degrees of oxidation of C and permitted the formation of oxidised Pd species. Thermal pretreatment in N2 with traces of O2 was most conducive to Pd extraction

Jun 21, 1905

The paper, presented at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 8th April 1916, presents experimental work undertaken to observe the quenching effect of different substances, to find the most efficient of these substances, and to arrive at a possible explanation of their preventive action. The coal-dusts experimented with were such as passed through a 100-mesh sieve (10,000 holes to the square inch), and were obtained by grinding the coals. The quenching substances, used in as fine a state of division as possible, included gypsum, dried Chance mud, quicklime, magnesia, magnesia alba (levis), anhydrous sodium carbonate, sodium bicarbonate, soda-crystals, Glauber salts, ground shale and boiler-ashes

Dec 1, 1916

By T. Bennett

Geothermal energy has the potential to provide 20% of the UK's annual average electricity generation capacity requirement. This article discusses the costs and potential benefits.

Jun 1, 2015

By Fearnsides W. G.

Discussion at the The Midland Institute of Mining, Civil and Mechanical Engineers' general meeting held in Doncaster on 27th May 1916, on the paper published in Trans. I.Min.E., vol.LI, 1916, p.409-448, included oral contributions by Lupton A. on the mechanisms of subsidence and water egress and by Kendall P.F. on the validity and accuracy of the contour extrapolation technique and the effect of major faults, together with the author's response

Dec 1, 1916