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By C. Villa Diniz

It is proposed that battery grade Mn02 can be produced directly from a manganese ore from Azul Mine in Brazil, by leaching with HCI to remove heavy metals selectively. We are working to find a way of selectively separating Cu, Ni, Co, Pb and Fe from the resulting acidic manganese chloride solution, to detoxify it and produce marketable chloride solution. Chelating ion exchange resins are proving more promising for this separation than solvent extraction with commercially available reagents. Results from batch and column ion exchange tests that characterize the behavior of copper, nickel, cobalt, lead and iron are reported.

Jan 1, 1999

By P. R. Hervey

Quartz is the second most widely used electronic material, with approximately 3,000 tons of single crystals used each year. Virtually all of this material is synthetic; grown with a technique called hydrothermal growth. We will review the basics of hydrothermal growth, the feedstocks for these crystals, and the challenges to improving the growth process. We will also review the processing of these crystals, the markets and applications where they are used, and the global outlook for these markets.

Jan 1, 1999

By H. Y. Sohn, M. Pérez-Tello, P. J. Smith, K. M. Riihilahti

A three-dimensional computer model for the Kennecott-Outokumpu flash converting process for copper matte is presented. The model incorporates the transport of momentum, heat and mass, and reaction kinetics between the gas and particles in a particle-laden turbulent gas jet. The k-E model is used to describe gas-phase turbulence in an Eulerian framework. The particlephase is treated from a Lagrangian viewpoint which is coupled to the gas phase through the source terms in the Eulerian gas-phase governing equations. Matte particles were represented as Cu2S·yFeSx. Based on experimental observation, the oxidation products were assumed to be Cu2O, CuO, Fe3O4, and SO2. A reaction mechanism involving the external mass transfer of oxygen to the particle surface and diffusion of the oxygen through the oxide layers of CuzO/Fe304 and CuO/Fe3O4 is proposed. Predictions of the mathematical model were compared with the experimental data collected in a large laboratory furnace. A reasonable agreement between the model predictions and the measurements was obtained in terms of fractional conversion of the oxidation reactions and of sulfur remaining in the reacted particles. The simulation of an industrial flash converting furnace was also performed. Higher oxidation rates, more even distribution of particles, and thus a more efficient use of the reactor volume are predicted with a burner having a distributor cone, than with a single-entry burner.

Jan 1, 1999

By M. A. van Nierop

The Discrete Element Method (DEM) is a model that is used to simulate the motion of the media in a grinding mill. The sum of the energy that is lost in inter-media and media-wall collisions represents the power drawn by the mill. The fact that the DEM predicts the power drawn by grinding mills over a large range of diameters has been used to show the validity of the DEM. However, the power drawn by a mill is a function only of the sum of forces of the load on the shell liners. A more accurate and detailed validation of the DEM would be to measure these forces as a function of angular position as the liner moves under the load, and to compare these measurements with predictions generated using the DEM. An experimental mill has been developed to reproduce exactly what the 2-dimensional DEM simulates. The 0,55 m diameter mill has a length of 0,023 m, which is fractionally larger than the diameter of the media used in the mill. One of the lifters in the mill has been instrumented so that the forces on the lifter can be measured as the mill rotates. The DEM simulation will be used to predict these forces. This will give experimental evidence of the validity of the DEM for modelling load behaviour in rotating grinding mills.

Jan 1, 1999

[CURTIS M. BELDEN RMCMI PRESIDENT 1999-2000 on behalf of the RMCMI Board of Directors and Officers of The Rocky Mountain Coal Mining Institute cordially invites you and your family to attend the 96th Regular Meeting and Convention to be held June 25 thru June 27,2000 Durango, Colorado]

Jan 1, 1999

By David Rees

Tomago Aluminium, a 400,OO tonnes per annum primary aluminium smelter in Australia, has installed Ozone for biological control of its process water. The system was designed in Australia by Ionics Watertec Engineering, whilst ANCO Australia monitors the water quality and provides technical support for the project. The motivation was initially to reduce operating costs, however investigations indicated that there were substantial environmental benefits to be achieved by the elimination of a part, or all of, the chemicals being used to control the system. Also the existing chemicals appeared to be losing their ability to control biological growth in the system, in particular, the legionella bacteria. Ozone water treatment commenced in January 1998 and after a short transition period has operated without chemical addition since. There appears to be no doubt that the biological control is effective, the clarity and purity of the water has improved and initial testing indicates that the corrosion control rate is acceptable, although some chemical corrosion control may be introduced after further testing around the total circuit to guarantee protection

Jan 1, 1999

By J. L. Cupp, R. C. Ford, B. R. Romig

The Climax Molybdenum Mine, located near Leadville, Colorado, is the site of a lengthy mining history spanning more than 80 years. In the 1960’s, extraction of molybdenum from oxide ore located adjacent to the massive molybdenite sulfide deposit resulted in the construction of an earthen core dam to impound fine-grained oxide tailing in the Eagle River Valley. Through recognized value of water storage and reclamation opportunities, a tailing removal project was initiated in 1993 to convert the impoundment facilities to a post-mining beneficial land use of developed water resources. An evaluation of the effect residual materials and lake dynamics would have on in-stream water quality was performed. Eagle Park Reservoir stands as a model for future reclamation efforts that involve water delivery to highly sensitive receiving waters. This paper provides a case study on project development, the evolution of water quality assessment, and the regulatory framework that contributed to this project’s success.

Jan 1, 1999

By Yin Zhang, Xiaoyu Huang, Mi Wang, Bencheng Du, Youduo He

"Burners are important facilities for blast furnace stoves to raise hot-blast temperature up to 1200°C. Common types of two-ring ceramic burners have very long flames so that part of combustion occurs in the upper part of the chequers and will cause damage to the refractory materials. Using computer simulation to analyze the turbulent diffusion flame in the combustion chamber, some good results were obtained. A new type of ceramic burner will be installed by Anshan Steel Complex in stoves of blast furnace number 4. A pilot experiment was done on the new burner. The experimental data have shown that the mixing condition was improved and the length of flame was shorter with the new type of ceramic burner.IntroductionPulverized-coal injection can give significant operating saving, reducing coke rate in blast furnace(BF) operation. However, during high rates of coal injection, extra heat must be compensated in hearth to maintain certain raceway adiabatic flame temperature. One of the effective methods for heat compensation is to raise hot-blast (HB) temperature up to 1200°C. Nowadays, since the fuel being combusted in stoves is BF gas only, in which the calorific value is down to round 3000 kJ/m3 , to increase the combustion ability and to provide a suitable length of flame in combustion chambers of stoves becomes more important. In other words, designing a good ceramic burner which will affect to HB temperature and stove lifetime is drawing more attention."

Jan 1, 1999

By N. Can

Kinetics and mechanism of the chemical interactions between Si3N4 and TiC were investigated by isothermally reacting samples under nitrogen and argon atmospheres at temperatures between 1600°C and 1700°C? The initial composition of the powder compact contained 20, 30 and 40 volume per cent TiC? Kinetic analysis were performed by measuring mass losses and composition of the titanium carbonitride (TiC1-xNx) at predetermined time intervals? It was found that in the Si3N4-TiC system the degree and rate of the reactions increased with increasing temperature and content of TiC in both nitrogen and argon atmospheres? Si3N4 in the presence of TiC was stable in nitrogen atmosphere and the reactions were confined to Si3N4/TiC and TiC/N2 interfaces? At both interfaces interchange reaction occurs by simultaneous diffusion of nitrogen towards the centre of the particle and desoprtion of carbon in the opposite direction resulting in formation of titanium carbonitrides with various compositions? Reaction products under nitrogen atmosphere were B-SiC, TiCl1-xNx and N2? The maximum "x" value in TiC1-xNx was found to be 0?67 under nitrogen atmosphere? Si3N4 was found to be unstable in argon atmosphere in the presence of TiC and dissociated into liquid silicon and nitrogen gas within approximately four hours of reaction time, depending on temperature? The reaction mechanism in the initial stages of the interaction between Si3N4 and TiC under argon atmosphere proceeds similar to reactions under nitrogen atmosphere? However, considerable amount of Si3N4 dissociates within the first half hour? Liquid silicon aggressively attack both TiC1-xNx and unreacted or partially reacted TiC particles through cracks and pores and diffuses into interier part of the particle forming liquid solutions? After this stage, reactions under argon atmosphere proceeded according to Si-Ti-C ternary system?

Jan 1, 1999

By Vaughan R. Voller

"Solidification systems from conduction controlled freezing of a pure material through to alloy phase change that include flow and segregation processes are described. The components in a general solidification model-variables, governing transport equations, and local scale relationship-are outlined. A central focus is the presentation of an explicit procedure for coupling between macroscopic and local scale variables.IntroductionSince the seminal work of Byres et al.[!] in the 1940's there has been a steady progress in modeling solidification systems with increasing levels of complexity. The object of this paper is to track the evolution of these solidification models and present a general modeling approach that applicable to a wide range of the solidification systems of current interest.Solidification SystemsIn a broad sense the underlying physics in a solidification process occur at two distinct length scales:1. The macroscopic scale of the process over which the governing transport equations of heat, mass and momentum hold.2. The local scale at the solid-liquid interface where the solidification phenomena are operative."

Jan 1, 1999

By W Shamu

The mechanical properties of rock samples of identical lithologicalcomposition may vary significantly due to existence of materialdiscontinuities. Laboratory tests were carried out to determine the effect of material discontinuities on rock sample mechanical properties. The investigations consisted of detecting discontinuities, observing the failure mechanisms during uniaxial compressive strength tests, and analysing of the factors affecting the strength. A non-destructive testing method has been adopted to assist in thedetection of discontinuities. Laboratory testing proved that fractures leading to failures initiated on the detected discontinuities. The location, orientation, size, density and extent of the discontinuities contribute to different modes of failure and these affect the mechanical parameters of rock samples. Four modes of failure were distinguished for hard and brittlecylindrical rock samples. These modes were referred to as simple shear failure, multiple shear failure, multiple fracturing and vertical splitting. To evaluate the effect of discontinuities on mechanical parameters, the ratio of uniaxial compressive to tensile (Brazilian) strength was calculated and analysed for the different modes of failure. It was found that the value of the ratio depended on the mode of sample failure. The lowest value of the ratio was observed for shear mode of failure and the highest for vertical splitting mode of failure.

Jan 1, 1999

By S. Neven

The smelting of copper anode slimes, a material which contains mostly lead, silver, copper and selenium, has been practiced for many years with a view to recovering the silver and associated small amounts of gold. However, a theoretical understanding of the process has been lacking and this handicaps efforts to improve and intensify smelting operations. In the past few years work has been done in this area and this work will be reviewed in the paper. The underlying thermodynamics of the oxidation of silver-copper selenide mattes has been developed and used as a basis for the construction of a computational thermodynamics model which attempts to predict the composition of all condensed phases during the course of smelting. The model will be outlined and its successes in matching experimental data, as well as its current deficiencies, will be considered. Supporting work on the thermodynamics of silver solubility in slags, on activity-composition relationships in the Ag-Se system and work in progress on the oxidation state of copper in the slags will be reviewed. These projects are designed to provide further detailed data which will improve the robustness of the thermodynamic model.

Jan 1, 1999

By P. J. Cook

Comminution is one of the fundamentals of mineral processing, requiring large expenditures to be made on capital equipment, installation, power and maintenance. The trend toward lower grades and higher operating costs, mean mining operations are becoming increasingly marginal. The challenge is to improve and more importantly, utilise crushing and milling technologies that provide for reduced capital and operating costs whilst providing increased unit efficiencies. The Svedala Barmac Autogenous Crushing Mill presents such an opportunity by providing many of the cost savings and production increases required by its ability to produce a finer mill feed size and realise reduced energy consumption. This paper briefly describes the operation of the Svedala Barmac Autogenous Crushing Mill and reviews its benefits towards improving the efficiency of crushing and milling operations.

Jan 1, 1999

By L. Z. Villanueva

An investigation and evaluation has been performed to determine the potential utilization of electron beam irradiation technology for sulfur oxides removal from reduced-S02-strength metallurgical gases from copper smelters. These off-gases, though too weak to be converted to usable, concentrated: sulfuric acid by conventional means, are characterized by SO2 content higher than 2,000 ppm and a complex chemical composition, including high oxygen content and its generation occurring in a cyclical, fluctuating pattern. This work was based on information supplied by principal smelter companies in Chile. A laboratory facility with flow rate of 20 Nm3/h and equipped with an electron accelerator of beam energy 8.00 keV, has been used for testing. Influence on SO2 removal efficiency of operational parameters such as gas temperature, water vapor content, ammonia feed ratio and irradiation dose was established. The main conclusion of this work, from experimental laboratory tests as well as engineering studies, is that the Electron Beam Process (EBDS) is a cost-effective, simple and appropriate chemical process means for emission abatement. EBDS can, on a site-specific basis, adequately augment SO2 removal to upgrade overall abatement as required and in an optimal manner.

Jan 1, 1999

By S Porter, R Woodall, N Weeks

Nelsen, Porter and Wilson (1996) provided some preliminary concepts for the design of the Melbourne City Link tunnels. At that time, the City Link project was in the early design phase whereas now it is nearing completion. This paper provides details of the actual design adopted for the various sections of the tunnels as well as some commentary on the design process. The tunnels form a critical element of the project and the design of both driven and cut and cover tunnel sections is a significant factor contributing to successful project execution. Geology, hydrogeology, site constraints, traffic management and program were important design inputs. Design for the cut and cover sections in particular varied significantly in response to these differing inputs.

Jan 1, 1999

By Misra V. N

Davis tube tests were conducted on a Koolanooka magnetite iron ore sample, supplied by Kingstream Steel Ltd, to determine the optimum grind size, maximum iron recovery and the cleanness of the products from low intensity magnetic separation (LIMS). The ore sample contained 38.6 per cent iron, 37.8 per cent silica, 6.5 per cent magnesia and 0.54 per cent alumina. XRD and microscopic examination showed that the main minerals in the ore were amphibole (42 per cent), magnetite (39 per cent), and quartz (14 per cent). Amphibole, (Mg, Ca, Fe),Si8O22.2(OH), containing 50.3 per cent SiO2, 35 per cent FeO and 11.5 per cent MgO is the main gangue mineral in the ore, and about 30 per cent of the total iron in the ore is contained in the amphibole. Heavy liquid separation tests showed that it is very difficult to separate iron from silica by gravity separation to obtain a high quality iron concentrate. Three grind sizes were initially tested, ie 45, 38 and 20 ¦m. It was found that grinding to 100 per cent -38 ¦m (P80 of 29 ¦m) appeared to be the best option for liberating the magnetite from gangue minerals. The iron recovery to the LIMS magnetic product for the 100 per cent -38 ¦m sample reached 73 per cent and the iron content was 65 per cent. Further test work suggested that the optimum grind size was a Psu of 25 ¦m.

Jan 1, 1999

By G. France

The Blair Athol Coal Mine (BAC) is a large open cut operation in the Bowen Basin of Queensland, Australia. Current mine capacity is about 11 million tonnes per annum(Mtpa) of export coal. On-line analysis at BAC consists of two Coalscan 9500s installed directly on the output of the crusher plant and immediately before the product stockpiles, while a third Coalscan 9500 is installed on the transfer conveyor feeding the train loading bin. The two product Coalscans have a dual purpose. The first is to provide real time coal quality data directly back to the mining operations. The second is that of modeling the product stockpile with accurate on-line information. This modeling enables both production and coal quality personnel to accurately examine the coal quality of each stockpile with a degree of resolution which previously had never been achieved.

Jan 1, 1999

By Zhenbo Zhao

The processes and equipment for INLRFH (Isothermal Normalizing by Utilizing the Residual Forged Heat) of alloy carburizing steel products are presented. It is shown that four key parameters: namely (I) cooling rate before isothermal normalizing, (IT) the lowest cooling temperature before isothermal normalizing, (111) isothermal normalizing temperature and (IV) isothermal normalizing time, should be controlled. The prediction and calculation of these parameters can be achieved on the basis of components treated and the technical requirements of the steel parts by an on-line expert system. The cost-reductions due to the energy savings resulting from implementing this system for automotive parts heat-treatment are most promising.

Jan 1, 1999

By R. Harris

Blister copper melts of 800 g to 1000 g containing less than 1 wt % S and up to 3 wt % Ni were desulfurized at 1523 K in air or by a pure oxygen jet blown at 75,500 and 1000 cm3/min, from 1 cm above the melt. Rates of desulfurization and oxygen pickup were measured and visible surface phenomena were photographed and videotaped. It was observed that SO2 was evolved from Cu-S melts in a manner reminiscent of the effervescence seen in carbonated drinks. The effervescence lasted up to 20 minutes and resulted in the ejection of material up to a height 50 cm above the melt surface. Sporadic discharge of large bubbles was also observed in a Ni containing melt top-blown with oxygen at 1000 cm3/min. The Cu-S melts top-blown with oxygen experienced faster sulfur elimination as compared to stagnant melts exposed to air and experienced only a single period of turbulent SO2 evolution, which occurred almost immediately after oxygen injection commenced. The Cu-S melts exposed to air experienced multiple episodes of effervescence. The stagnant blister copper melt containing nickel did not exhibit effervescent behaviour and experienced a lower rate of sulfur elimination compared to Cu-S melts tested under similar conditions. The present article examines the role of surface phenomena in determining the observed behaviour.

Jan 1, 1999

By G T. Hefter, P Singh

The effect of using SO2 as an anodic depolariser in the electrowinning of copper from aqueous acid sulphate solutions has been studied using cells without/with a ceramic diaphragm. In all cases SO2-saturation of the electrolyte/anolyte decreased the anode potential by 68 to 75 per cent largely due to a change in the anode reaction from the oxidation of water to the oxidation of SO2 . However, poor quality deposits and low current efficiencies are encountered if SO2 is allowed free-access to the copper being deposited at the cathode. This situation is easily avoided by using a diaphragm to restrict SO2 to the anode compartment and for these conditions the resultant copper deposits are of a similar (high) quality to those obtained in the absence of SO2.

Jan 1, 1999