Search Documents

By J. Brent Hiskey

Recently basic concepts of semiconductor electrochemistry and solid-state electronic structure theory have been applied to the dissolution of mineral electrodes. In this paper, fundamental aspects of semiconductor electro- chemistry and interfacial charge-transfer processes are reviewed. Information regarding the electronic and semiconductor properties of chalcopyrite is summarized. The electrochemical response of chalcopyrite in acidic solution is analyzed in terms of initial dissolution processes. The initial charge- transfer reaction involves the consumption of holes. It has been shorn that Fermi level pinning is consistent with observed electrochemical and dissolution behavior. Semiconductor electrochemistry has proved helpful in explaining the formation of intermediate surface films produced during the initial stages of chalcopyrite dissolution

Jan 1, 1993

By J. K. Brimacombe

Plant trials have been conducted at the Tacoma Smelter of ASARCO to assess the effect on tuyere blockage and refractory erosion at the tuyere line, of increasing the injection pressure of air into a Peirce-Smith con¬verter. Four tuyeres each having an ID of 19.1 mm (3/4 in) were installed toward one end of the tuyere line of the No. 4 Converter. Air and oxygen-enriched air were injected at 414 kPag (60 psig) through these tuyeres and at the usual 83 kPag (12 psig) through the remainder of the tuyeres in an otherwise normal converter campaign. The test campaign consisted of 88 charges and lasted for 89 days. During this period, punching of the high-pressure tuyeres was found to-be unnecessary; and when, as a precaution, the tuyeres were cleaned by hand at the end of a charge, they were always open. Also it was observed that the flow of high-pressure air remained constant. Accretion formation around the tip of the high-pressure tuyeres varied from charge to charge and was influenced by the matte grade and the level of oxygen enrichment.

Jan 1, 1983

By J. W. Perez

A simple exponential model has been developed (Perez and Aplan. Process Mineralogy, VI, 1986) to describe the fractional yield of a given species out of a locked assemblage: Fractional Yield of Species A = a e X/U where 'X' is particle size and 'a' and 'U' are constants. In the present study, the general validity of this model has been further demonstrated. experimentally, for the liberation of coal and pyrite out of various raw coals and beneficiated fractions using a variety of crushing devices. Using data from the literature, the model is also shown to be applicable to the liberation of sulfide minerals out of ores.

Jan 1, 1987

By G. Laird, N. B. Gray, N. Lawson

"Photographic, video, laser, hot film and conductivity methods are used in the experimental study of gas-liquid flows. A discussion of their capabilities and limitations are given in this paper illustrating the wide range of phenomena that can be studied. Most of these methods are limited to physical models at room temperature with transparent fluids, although they can be extended for use with opaque and hot fluids. A number of these techniques have been used by the GKW CRC in studies on industrial plants and their usage is increasing although a number of technical difficulties still need to be overcome. An in-depth discussion of the laser doppler anemometry (LDA) and particle image velocimetry (PIV) methods is given with experimental results on the flow field of an air plume in water based on advanced development of the techniques and studies carried out at the GKW CRC. The LDA method provides high resolution data on the velocity profiles, while the PIV method provides an overall view of the complex flow structure occurring at the gas-liquid regions. These two methods complement each other in providing experimental data for validating numerical models and exploring the complexities of multi phase flows.IntroductionThe injection of gases into melts is an important operation in the metallurgical industry. It is used in converters, anode furnaces, blast furnaces, ladles, bath smelters, zinc fumers and many other smelting processes. In many of these processes, the gas is injected into a molten bath resulting in the formation of bubbles that promote reaction, mixing, alloying and heat transfer. The study of gas-liquid systems presents enormous challenges to the researcher due to the complexity of the mathematical and physical modelling which require innovative numerical and experimental skills."

Jan 1, 1996

By Bradley C. Bockrath

Some thirty coals were evaluated for liquefaction activity under a mixture of CO and H2 at 425° C. The viscosity of the liquid products was taken as an indicator of the degree of liquefaction. It was found that the direct liquefaction of a particular coal may be beneficially influenced by the presence of pyrite. Active pyrites are often found in the native mineral matter of the coal itself. For example, subbituminous and bituminous coals and lignites of relatively high pyrite content were found to liquefy more readily than similar coals or lignites which were poor in pyrite. The reactivity of inactive coals could be improved by using blends with active, pyrite-rich coals. In addition, pyrite was effective when added separately as pyrite concentrates obtained from coal beneficiation operations. Various other iron- and sulfur-bearing additives were also effective when used in combination as added slurry-phase catalysts, including iron oxides and mineral residues derived from liquefaction of active coals. Under liquefaction conditions, pyrrhotite ( Fe I- x5) is formed from pyrite or from the iron oxides and many sulfur containing species. Pyrrhotite was shown to be a hydrogenation/dehydrogenation catalyst for tetralin but is not active for initiating a variety of free radical reactions that do occur when pyrite is heated with tetralin. The role of pyrite in coal liquefaction is complex and still not well understood.

Jan 1, 1981

By F. R. A. Jorgenson

The ignition of chalcopyrite and pyrite was studied using laminar flow furnace and thermal analysis techniques which were supported by XRD and optical microscopic examination of the products. In air, chalcopyrite and pyrite ignited at temperatures of 400-500'C and 500-600?C respectively. The phase assemblages predicted from thermodynamic analyses were compared with those found by experiment, and the onset of ignition was correlated against changes in the phase compositions. Pyrite and chalcopyrite ignited when pyrrhotite and intermediate solid solution formed thus opening up the structure and allowing ready access of oxygen.

Jan 1, 1989

By Gregory A. Knapp

Treatment of industrial wastewaters generally advances with specific chemical concentration and mass-flow targets, established by National Pollutant Discharge Elimination System (NPDES) permits. Treated discharges must also address toxicity to test and receiving water organisms. Various parameters might need consideration during treatment design and planning, such as the known toxicants, hardness, alkalinity, solids, nutrients, metals in both the dissolved and particulate state, and even flow. Since toxicity is used as a "catch all" regulatory monitoring tool, design of treatment systems should focus on the various factors contributing to toxicity.

Jan 1, 1996

By I. Gaballah

Spent hydrorefining catalysts may contain 4 to 6 % of COO and/or NiO, 8 to 16 % of Moo3 and up to 10 % V205 generally supported by alumina. Raw samples are roasted in order to eliminate carbon, sulfur and hydrocarbons contained in the spent catalysts. The roasting optimum temperature and time are 500 "C and 7 hours. Selective chlorination of roasted samples with Cl2 + air, Cl2 + N2 and Cl2 + CO is investigated in order to recover the valuable metals. Depending on the chlorination it is possible to recover more than 80 % of the Ni and Co about 95 % of the Mo and up to 80 % of vanadium compounds. Cobalt and nickel chlorides are obtained by leaching the chlorination residues' by acidified water. Molybdenum and vanadium chlorides and/or oxychlorides are obtained by selective condensation from the vapor phase. The chlorination of the catalyst support, Al2O3, can be limited to less than about 5 %. Besides the reaction temperature and time, the oxygen partial pressure of the chlorinating gas mixture appears to be the key factor for the reactions' selectivity.

Jan 1, 1993

By Lauri Holappa

Copper converting is mostly performed in Peirce-Smith converters. The process is still very similar to the original one developed in the early 20th century. It is a batch process in a horizontal cylindrical reactor with air blowing via tuyeres along the length of the reactor side. The Peirce-Smith converter has its roots in Bessemer's inventions in the 1850's as he tested both horizontal and vertical vessels for steel converting. However, for steel making a vertical pear-shaped converter with air bottom-blowing was established. In the course of time, there was a distinct necessity for oxygen usage instead of air due to harmful effects of nitrogen to steel properties and its cooling effect. In-bath blowing of oxygen did not succeed, however, and top-blown oxygen converter with oxygen lance (LD or BOF) was first developed in he 1950's and emerged rapidly to a dominating position. Somewhat later oxygen bottom-blowing via special shrouded tuyeres was developed (OBM or Q-BOP) but has attained only fractional share. Bottom-blowing technique had, however, impact on the current combined blown converters which adopted the benefits of both top and bottom blowing. In copper converting Peirce-Smith type converters have kept their position until today although new processes have been introduced and at least few of them seem to be emerging. In one respect copper converting has a clear leading position i.e. in the progress of continuous converting processes (Mitsubishi, Ausmelt). These processes utilise top-blowing lances instead of in-bath blowing tuyeres. A different principle for continuous converting is flash converting by Kennecott Outokumpu, which makes smelting and converting independent of each others. Solid ground matte is used as a feed for flash converting in a reactor shaft similar to Outokumpu matte flash smelting. A comparable process has been presented by Inco too. The paper discusses principal physico-chemical and process technical similarities and differences in copper and steel converting. Although these processes are metallurgically quite different it seems that during the modem history of ferrous and non-ferrous metallurgy, starting from the 1850's, the exchange of knowledge between these disciplines has been quite intensive. In long-term perspective, many similarities in the development can be found but also divergences due to different ambient circumstances.

Jan 1, 2003

By Thomas P. Battle

Ilmenite (iron titanate) is the source of over 90% of all the titanium produced in the world today. At some point during production of titanium dioxide or titanium metal the iron impurity must be removed. Too often it becomes a waste instead of a product. DuPont and MINPRO have developed a solid-state process which separates the iron and titanium components of ilmenite into different high-purity powders, which can be separated using conventional mineral processing techniques. The main reactor in this process is a unique high-temperature ball mill, where the iron segregates from the ilmenite lattice with the assistance of catalytic quantities of He\. The results of lab, pilot plant, theoretical, and scale-up studies are presented and discussed.

Jan 1, 1996

By Patrick R. Taylor

Ilmenite concentrate and methane are fed to a non-transferred arc thermal plasma reactor to produce a powder that is primarily TiC and Fe. This material has promising characteristics for powder metallurgy applications. Free energy minimization plots were used to predict the feasibility of the reaction. An estimate of the optimum molar ratio between the ilmenite concentrate and methane was made based on the mineral composition. Argon-helium mixtures were used as plasma gases. The effects of power input level, carrier gas flow rate, powder feeding rate, and methane-ilmenite molar ratio were studied and the behavior of the system characterized. Two different powder injection angles were tried. A mathematical model to describe the temperature profiles in the reactor was formulated and solved. The product has been characterized by x-ray diffraction and atomic absorption. A conversion of 97 % of Ti to TiC was achieved. It was found that minor amounts of titanium oxides, iron carbide and free carbon are also present. TEM and SEM were used to study the morphology.

Jan 1, 1996

By K. Fagerlund

Methods for simulation of settler reactions, matte-slag separation and matte settling in copper flash smelting have been examined. The reaction, separation and settling phenomena of slightly oxidized chalcopyrite samples and cuprous sulfide-magnetite mixtures in fayalite type slags were examined at about 1300°C under inert atmosphere. Two methods based on introduction of molten samples of oxidized chalcopyrite concentrates or synthetic matte-magnetite mixtures onto the surface of molten iron silicate slag were tested. In the first method the samples were water quenched and polished specimens were studied and analysed using light optical microscope, scanning electron microscope, energy dispersive spectrometer. In the second method processes taking place after the introduction of samples onto the slag are followed "in situ" using X-ray transmission image monitoring. Great differences were observed in separation and settling behaviour of low and high grade copper mattes produced as a results of interaction of initial samples and slag.

Jan 1, 1997

By Zhi-yong Liu

A novel process, which includes hydrochloric acid leaching, iron powder cementation, sulphide precipitation and spray pyrolysis, was proposed to treat iron concentrate recovered from zinc kiln slag for comprehensive utilization. Treated by two-stage hydrochloric acid leaching, the leaching extents of Ag, Pb, Cu, Fe and Zn are 96.78%, 95.14%, 97.72%, 94.51% and 87.74%, respectively. More than 99% Cu and Ag are recovered from the leach liquor when iron powder is 25% higher than the stoichiometric requirement. More than 96% Pb and Zn is removed with three times of theoretical consumption of FeS, and the concentration of impurities of the final solution is less than 500 mg/L. Fe2O3 powder, which is spherical with a mean size of 12 μm and purity of 99%, is prepared with final solution at 700 °C. In this process, not only the metal values can be recovered effectively, but also the iron resources of zinc kiln slag can be converted into high purity Fe2O3, thus, the comprehensive utilization of iron concentrate recovered from zinc kiln slag can be realized.

By E. T. de Groot, D. L. Verhelst

With the successful start-up of Cominco's new KIVCET smelter, the final key component is now in place for Trail Operations to operate efficiently as a modern integrated zinc-lead facility. Unique metallurgical, operational, planning and management issues apply to this operation. Along with presenting the current flowsheet for Trail Operations, this paper discusses issues such as the impact of recycles, operational re-stabilization following significant process changes, plant operation with just-in-time inventories, real-time process optimization, and management philosophy.

Jan 1, 2000

By K. A. Dudley

Basic solvent extraction theory indicates that pH initiates the basis of an oxime's metal complex formation and therefore its selectivity toward certain metal species. The recommended optimum pH for some of the commercial copper reagents is in a range that should maximise copper loading of the oxime. However, this pH range also tends to maximise iron(III) loading under certain operational conditions resulting in low selectivity values. Recent operational parameters at Girilambone Copper Company have highlighted some of these conditions that have a major influence on the oxime's selectivity for copper over iron(III) in the leach solutions. The result is that the pH for maximum copper extraction is no longer within the optimum range to maximise oxime selectivity. Therefore, specific copper and iron(III) pH isotherms have been determined on-site for the changing leach solutions that are fed to the solvent extraction plant in order to optimise oxime selectivity. The influences of solvent extraction plant configurations are also discussed as a controlling parameter.

Jan 1, 1999

By J. S. Pitsillos

A new furnace tapping technique involving the simulation of a control valve at the exit to a furnace is being investigated. The purpose of this new tapping technique is to regulate the flowrate of liquid furnace products( slags, metals and mattes). Numerical modelling and experimental work has been carried out on tapping of slags leaving a SIROSMELT reactor and the results found to be in good agreement. Numerical modelling has also enabled prediction of the important industrial conditions for the onset of blockage from the shape of the pressure versus flowrate curves. Slag launder experiments have been carried out and a one-dimensional heat transfer model was used to evaluate the effectiveness of launder covers and different coolants. From the experimental results and mathematical model some launder design guidelines such as inclination angle, covers and coolants have been developed.

Jan 1, 1991

By K. Fagerlund

In this work, the rate of dissolution, melting behaviour and phase separation of silica flux with molten slag and matte were investigated. Mutual dissolution between high-grade matte and silica was chemically determined. Silica dissolution rates ,in various iron silicate slags was determined using the rotating rod method. The reaction and separation phenomena of slightly oxidised chalcopyrite samples and cuprous sulphide-magnetite mixtures with silica sand were examined all about 1350°C. The samples were water quenched, and polished specimens were studied and analysed using a light optical microscope ,and a scanning electron microscope with energy dispersive spectrometer. The silica dissolution rate in slag was found to increase with decreasing silica content and increasing ferric iron content. The reaction rate of silica sand' with matte was found to increase with increasing oxidation degree and magnetite content of matte:

Jan 1, 1998

By Charles L. Richman

The effect of the addition of Silver Sulfide on the rate of Chalcopyrite (CP) of Sulfuric acid (H2SD4 leaching is discussed, Although Ag2S in an expensive addition, a theoretical explanation of it's use will aid in the development of a economic substitution. We have used cyclic voltammography to show the presence reaction species at different potentials. Cyclic Voltammography maps the surface reaction current peaks on CP, to regions on the CP Phorbaix diagram. AC Electro-lmpedance spectroscopy (EIS) models the surface impedance properties, which control the rate of electron and ion transfer, and the surface kinetic reactions, with and with out light. EIS and other measurements show that AgCuS u Photo-reactive material- The EIS results are compared with the SEM and EDXA results to show the presence of diffusion pores, and diffusion controlled reactions during CP leaching without the addition of silver sulfate. We hypothesize that AgCuS is an ionic conductor like Ag2S. EIS shows an imposed negative leaching rate greatly. Our theory shows how the formation of Silver Copper (1) sulfide layer at open circuit potential gives an effect similar to negative potential, that is enhanced with illumination. We verify that AgCuAS is an N-type semiconductor that forms a diode type junction with the electrolyte with the Mott-Schoottly relation.

Jan 1, 2001

By Sui Xue

A process has been developed from laboratory-scale experiments for the aqueous processing of various lead-bearing wastes. The process exploits the limited solubility of lead in sulfate-rich solutions to effectively separate lead from other metals. The lead sulfate is then completely converted to lead carbonate using sodium carbonate and ammonium carbonate. The effectiveness of this conversion was observed to be sensitive to the solution pH and carbonate concentration. The final stage of the process uses low temperature calcination of the lead carbonate to form PbO. Yellow lead oxide (massicot) is readily formed if calcination is conducted at a temperature at or iibove 50G°C, wlule red iead oxide (iitharge) is formed at temperatures near 450°?C. A complete economical analysis of the process will be discussed.

Jan 1, 1996

By Richard D. Hangi

Process mineralogy techniques are uniquely applicable to industrial problems related to the extractive metallurgy of nickel, cobalt, and associated metals. Reflected 1ight microscopy, together with selected determinations by scanning electron microscopy-energy dispersive spectrographic analysis and electron probe microanalysis, provides the means to identify the ore minerals cobalt and nickel ores, determine the abundance of each ore mineral, assess the extent of intergrowth between the cobalt and nickel minerals and other ore and gangue minerals in the ores and concentrates, and predict the potential success of cobalt and nickel extraction by grinding, flotation, pyrometallurgical, and hydrometallurgical treatments. In addition, the extent of locking of the cobalt and nickel minerals with each other and with the gangue minerals can be directly observed by reflected light microscopy. Where ores have been treated by hydrometallurgical procedures, reflected light microscopy can serve to determine the causes of excessive leach consumption. Finally, the partitioning of cobalt and nickel between high-temperature synthetic phases produced by pyrometallurgical treatment can be precisely determined by process mineralogy techniques. Case histories from cobalt and nickel deposits illustrate the value of applied mineralogical techniques in the study of cobalt and nickel ores, beneficiation, hydrometallurgial, and pyrometallurgical products.

Jan 1, 1993