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By G. M. Zhao

The gasification of lump coke with CO2 was studied in a fixed-bed reactor. The effective diffusivity of the gas was evaluated from measurements of the reactivity of the lump coke, produced by BHP Steel in New South Wales, and from kinetic parameters that were determined from the reactivity of fine grains. The grain model of effective diffusion in porous media was adopted to express the gasification rate of the lump coke and was found to fit the experimental data well. The relationship between reactivity and textural characteristics of the coke was examined

Jun 18, 1905

By R. K. Rath

Adsorption, electrokinetic and flotation studies were carried out. The maximum density of adsorption of guar gum was obtained at pH 7.5 on sphalerite and at pH 11.5 on galena. Flotation recovery of sphalerite was reduced only marginally by the presence of guar gum in the pH range investigated, whereas recovery of galena was reduced to about 20% at pH 12. Differential flotation tests on binary mixtures indicated that 10 ppm of guar gum can depress galena and separate it from sphalerite at around pH 12.1. Co-precipitation tests confirmed the formation of a metal ion-guar gum complex in the bulk solution, suggesting that this is the precursor to adsorption. The adsorption isotherms for both minerals followed Langmuirian behaviour, but adsorption of guar gum on galena was significantly higher than on sphalerite and dissolution tests indicated that the concentration of Pb ions released from galena was an order of magnitude greater than that of Zn ions dissolved from sphalerite

Jun 21, 1905

By F. J. Tavera, J. A. Finch

A probe suitable for on-line measurements of gas hold-up in industrial flotation systems has been developed. It is based on an open cell for measurement of slurry-gas conductivity and a novel syphon cell for measurement of slurry-only conductivity. The desired behaviour of the two cells was demonstrated and estimates of gas hold-up were shown to be in good agreement with independent measurements. The gas hold-up probe was used as a diagnostic tool to assess the operation of flotation columns. Differences in gas hold-up between baffled sections in two industrial columns were detected

Jun 18, 1905

By S. L. Gay

The conventional mass-balance equations used as constraints can lead to flow estimate values of zero even though the flow estimates should be some positive number. This is because many of the constraint equations are satisfied if the flow rates are zero. The way to overcome the problem is to use a slightly different form of the equations. For example, rather than use the conservation of flow of solids as a constraint it is better to use the constraint that the percentage of solids going into a unit equals the percentage of solids coming out of the unit. Examples are given using mineral processing data sets from Mount Isa, Queensland, and Red Dog, Alaska

Jun 21, 1905

By I. J. Brown

Paper prepared for presentation at Industrial minerals and the environment, held in Leeds, 24-35 September 1990. The need to submit an environmental statement (EIS) has certainly increased the workload of those concerned with both its production and assessment. However, there is now good evidence that the system is enhancing public confidence in the minerals industry in particular and improving relationships between the developer, planning authority and those consulted such as statutory bodies, parish councils, civic societies, nature conservation interests and ramblers

Jan 1, 1991

By I. D. Nock, R. M. Parkin

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: Knowledge-based condition monitoring of cone crushers). A large proportion of the electricity used by the quarrying industry is consumed in the comminution and sizing process. In most cases aggregate processing plants operate with minimum control features resulting in limited operational efficiency. Improved control is required to increase operational efficiency with concomitant savings associated with reduction in re-circulating load and improved resource utilisation. Development work has suggested that a combination of adaptive control and process condition monitoring could improve control of comminution plants. Many commercial process control and condition monitoring systems are available, but none were deemed suitable due to the domain specific characteristics of the application. An assessment of the particular characteristics of cone crushing concluded that the application was best suited to the use of small domain specific process control combined with bespoke condition monitoring. The processing power of the control system for the project is a function not of the academic requirement, but rather the economic and practical constraints imposed by the application. As a result of the constraints a high-end PC system has been designed in preference to a workstation. Within the research project work packages are sub-divided into novel wear sensor development, knowledge based control/condition monitoring and the investigation and mathematical modelling of the wear mechanisms inherent in cone crushing. Numerous strategies were considered to implement the control system outlined. The system currently under development is a modular design which utilises intelligent novel sensors to provide a variety of data inputs

Apr 1, 1994

By R. L. F. Kay, T. A. Fletcher, A. J. Boyce, C. M. Rice

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. The synorogenic, mafic Ordovician intrusion comprises orthopyroxene-rich xenoliths and mafic-ultramafic cumulates with low-grade pyrrhotite, chalcopyrite and pentlandite mineralisation. Despite abundant textural, mineralogical and O isotope evidence for significant assimilation of country rocks, S isotopes indicate only a modest uptake and suggest that mineralisation is dominated by magmatic sulphur. The preferred explanantion is that the magma was close to S saturation on emplacement. Uptake of elements such as Si and O led to early crystallisation of orthopyroxene, resorption of olivine and early segregation of a sulphide liquid. Post-magmatic interaction with a high-temperature, surface-derived fluid, whose movement may have been controlled by regional shear zones, reset biotite and whole-rock O isotope values but not those of orthopyroxene. This model identifies the presence of olivine-rich rocks and evidence of extensive assimilation as guides to prospectivity

Jun 19, 1905

By Qing Wang, H. Sevim

Belt network simulators are the most widely used models in the design of belt networks. The simulators developed in the past two decades are reviewed and their limitations are discussed. To overcome these limitations and to provide a design model that can be used efficiently in real-life applications, a comprehensive non-simulation model has been developed. The features of this model are briefly discussed. A real example is used to demonstrate the model's superiority over belt simulators

Sep 1, 1991

By H. S. Sichel, W. J. Kleingeld, C. E. Dohm

A model of ore value distributions is presented that is the culmination of a statistical approach rather than simply a model that has been successfully applied to the evaluation of ore reserves. Detailed geological and physical observations based on large sampling data sets have been used to support the statistical modelling. Fundamental to the modelling process is the concept that the occurrence of a given grade value in space is a function not only of the presence of the mineral but also of the fact that it is associated with a specific trapping mechanism. The concepts have been specifically applied to gold mineralisation

Aug 1, 1995

By A. G. Pasamehmetoglu, N. Celebi, K. Erarslan

A deposit evaluation system has been developed for a proposed new mine in the basin around Collolar in Turkey. It includes compositing, gridding and reserve estimation facilities and takes account of the economic value of the pit and the pit bottom elevation

Sep 1, 1991

By M. L. Leblanc, J. F. Burzynski, D. J. Mossman

A strong heterogeneity in the distribution of Sb+/-Au deposits exists within the North Atlantic Acadian-Hercynian domain. This is reflected in the regional disparity in Sb production among the various producing countries. This work focuses on the nature and distribution of Sb+/-Au occurrences in the Acadian-Hercynian domain. A summary listing of the general features of Sb-Au deposits found in this area is given

Dec 1, 1991

By L Besra, A. R. Prasad, B. P. Singh

The role of surface-chemical phenomena and the physical processes that participate in the dewatering of a suspension of alumina trihydrate were subjected to a systematic investigation, which has increased understanding of the influence of surface tension, contact angle and adsorption in the process. The residual moisture content of the cake can be reduced significantly through the use of surface-active agents in slurry pretreatment or as wash-water additives. The effectiveness of a particular surfactant is hard to predict from any single parameter, but is dependent on its ability to reduce surface tension and possibly to modify the solid-liquid contact angle. If scaled up to industrial operation of the dewatering step of the Bayer process in India, the use of these chemical additives could substantially improve its process economics, reducing the fuel costs for thermal drying by a much as Rs 50/t

Jun 21, 1905

By W. R. Paterson, W. Morton, D. B. Cameron

The Massbal II computer simulation program has been used to develop a general framework for the building of thermochemical models of metallurgical processes. The framework allows the rapid, simple construction of complex models of process equipment for use in flowsheet design, planning and plant operation. Application of the program to model the iron-making blast furnace and a flash smelting process is described

Apr 1, 1991

By A. F. Neil, A. S. Bahaj, P. Watkins, P. M. Hyslop, C. E. Kirby, P. A. B. James

The results of initial work indicate that for 3 of the 5 quarry sands bioleaching reduces the iron oxide content to a commercially acceptable 0.035 wt% Fe20 3, although the time taken to achieve this is 14-22 days against a target leach time of 7 day. Subsequent work has identified strains of Aspergillus niger that are more efficient at producing the array of complexing agents for iron and is yielding excellent and rapid reductions in Fe levels. Potentially, bioleaching offers a more environmentally friendly and energy-efficient process for the removal of Fe from glass-making sands than conventional routes but the production of organic acids by fermentation must be achievable with low-cost substrates such as sugar-beet molasses and lactose permeates for bioleaching to offer a commercially viable alternative to treatment with hot mineral acids. Silica sands usually contain three groups of Fe minerals: iron oxyhydroxides, which comprise crystalline types such as goethite and limonite tending to occur as thin, discontinuous coatings and in cracks and crevices on the surface of the quartz; the assemblage of heavy trace minerals, which include ilmenite, rutile, leucoxene, chromite and haematite, commonly present at levels of 0.1 wt% or less as discrete grains or sometimes cemented to the quartz; and clay minerals cemented in pits on the surface of the quartz and in association with weathered, discrete feldspars. The response of the assemblage of iron minerals to short periods of exposure to hot inorganic acids is broadly related to which group they belong to, those that form coatings being accessible to acid and tending to react rapidly whereas the trace minerals are usually resistant and react very slowly, if at all, and the clays are probably digested. The note reports on a preliminary study of the use of microorganisms to develop an alternative clean technology that will give results comparable to those achievable with hot inorganic mineral acids but with more environmentally acceptable procedures. Various fungi and bacteria produce organic acids when grown in certain media. When these acids come into contact with Fe-stained sand grains the iron is removed as soluble complexes. Several strains of Aspergillus niger have been found to produce organic acids from sugar, predominantly citric, gluconic and oxalic acids, their relative yields depending on cultivation medium and conditions. Sand samples were prepared from five quarries in the UK: Levenseat, Lothian; Redhill, Surrey; King's Lynn, Norfolk; Chelford, Cheshire; and Oakamoor, Staffordshire; ranging in iron oxide content from 0.035 to 0.153 wt% Fe203

Jun 18, 1905

By G. Adachi, K. Machida, T. Ozaki, K. Murase

The chlorination rate with CCl4 was unexpectedly slower than carbochlorination using chlorine under the same reaction conditions. Chlorination with CCl4 was topochemical and the amount of monazite reacted after different periods suggested that the kinetic control step was the reaction between CCl4 and the monazite core at the interface. The kinetic order of the reaction was 0.5. The presence of a complex former, AlCl3, promoted the chemical vapour transport of rare-earth chlorides as complexes

Jun 18, 1905

By S. A. Sayed, M. N. M. Ahmed, M. A. Doheim

The performance of a 12.7 cm hydrocyclone was investigated by considering the effect of design variables (diameters of the vortex finder and apex) and operating variables (pressure drop and solids content of the feed) at a medium feed solids concentration of mixed minerals. Cut-size was found to be the most important parameter in hydrocyclone design and operation. The effect of feed pressure in reducing hydrocyclone cut-size is less pronounced at medium feed solids concentration with a mixed mineral feed. The choice of vortex finder diameter and apex diameter becomes more sensitive at medium feed solids concentrations. The effect of feed solids concentration in increasing the cut-size becomes less marked at higher concentrations. Predictions of an empirical model were found to be in good agreement with experimental data. Comparison of results obtained from the model with those predicted by theoretically derived models showed the latter to be more promising, with the turbulent two-phase model giving closer agreement with the experimental data

Apr 1, 1995

By M. W. Robotham, H Wang

removal efficiency is analysed from a stochastic

Apr 1, 1995

By M. J. Beus, B. Stewart, S. Iverson

Ore-pass hazards are a significant safety problem in US underground metal mines. From 1975 to 1995, nearly 75% of injuries during pulling or freeing of ore-pass chutes were related to falls of broken rock or the use of hand tools. Risk assessment methods are being used to identify the most probable causes of ore-pass failures and analyse the factors that result in malfunctioning or safety reduction. Static and dynamic loads are being measured in the laboratory and by field testing, with data from test ore passes compared with mine data to characterise true system behaviour. Computer modelling using closed-form solutions, finite element analysis and a newly developed particle flow code are being use to predict loads from ore and waste flow and impact. Preliminary results indicate that dynamic impacts may be much less than expected, as a result of damping factors, normal and shear stiffness and mass frictional characteristics

Jun 19, 1905

By S a m u e l D e a n

The author's written response to previous discussion was presented at the North of England Institute of Mining and Mechanical Engineers general meeting held in Newcastle-upon-Tyne, 8 April 1916, followed by further comments by Hare S. in support of his view that the conditions in English mines were the reason for less satisfactory results being obtained with heading machines and brief comments by Greener T.Y., President

Dec 1, 1916

By L Zhang

The Chinese coal industry is the largest coal producer in the world. The total production in I995 was 1.28 bnt. On the way towards introducing a market economic system, this mature industry is facing major challenges. The main problems are a large surplus of manpower, shortage of current assets and capital, low productivity, high casualties and a huge deficit. This paper discusses the present situation and the future developments in the Chinese coal industry. The current policy can be stated as ‘rapidly developing the state collieries and improving the village and private mines; integrated development to achieve an economic operating scale and encouraging a diversified economy; rapidly exploiting and developing in the North west and South west; promoting productivity and efficiency; welcoming multi-sources and types of investment; setting up coal exchange markets; and the careful control of resources and the environment'.

Jan 11, 1996