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By S. J. Gerdemann

The U.S. Bureau of Mines is studying the kinetics of wet oxidation of sphalerite concen- trate (ZnS) as a possible process for a gravity-pressurized reactor (GPR). At tempera- tures in excess of 200' C, a sphalerite water slurry will react with 0, to form zinc sul- fate (ZnSO,). However, the pressure required to keep the water from boiling at these temperatures has kept this reaction from becoming a viable continuous process. The GPR can easily obtain the high pressures required for this reaction. The reaction rate is complicated by the solubility of 0, in water and the further oxidation of ZnSO, to insoluble zinc oxysulfate (Zn4(OH),S04.4H20). The effects of pressure, temperature, and particle size on the rate of reaction were investigated. Reaction rate was found to be limited by the amount of oxygen in solution. However, at 250" C and 1500 psia, over 90 pct of the zinc was solubilized in less than an hour. The conditions for maxi- mizing the Zn++ in solution, while minimizing oxysulfate formation, are discussed.

Jan 1, 1993

By Kunibert Hanusch

Copper in recycling material is accompanied by various groups of metals: 1) Metals which are much more negative than copper, such as Fe, Al, Si, P, Be They are mainly removed by fire refining during the recovery of copper and leave the process in form of slag. 2) Metals which are more positive than copper or difficult to separate by fire refining and which are partly reduced together with the copper. These metals are for example As,. Sb, Ni, Ag, Pb, Zn, Sn. They are enriched in intermediate products and recovered from these or remain for their major part in the fire-refined copper and can be separated by electrolytic refining and recovered from the electrolyte or anode slime. This report describes the process of Hüttenwerke Kayser AG in Germany and illustrates how considerable returns of material are partly required to separate or recover associated metals. They are finally removed in saleable products.

Jan 1, 1995

By Leonel Contreras

The gas treatment system, MALIGAS (in Spanish MAnejo y Llmpieza de GASes which means handling and cleaning of gas), is part of the Codelco-Chile Potrerillos Smelter decontamination plan; which includes the newly designed system for the cooling and cleaning of the gas generated from a Teniente Converter and four Peirce Smith Converters. The gas generated in the process is captured by water cooled hoods and mixed with air. Then the gas enters a cooling pre-chamber which utilizes a water cooled screen to capture and remove the coarse and semi-fused particles. At this stage; the gas loses a portion of its heat with temperature falling below 608°C which is a necessary condition to avoid damage to the pipes, ducts and other metallic structure of the gas handling system. The gas is further cooled at the Radiation Cooler to a temperature ranging between 315 and 380°C. The gas is conditioned to avoid damage to the electrostatic precipitators that are designed to clean the gas by removing significant amount of dusts from the: gas stream. This gas stream is currently discharged to the stack, however, it will be treated in a sulfuric acid plant that is currently under construction and is scheduled for commissioning during the second half of 1999. The gas handing and cleaning system has been operated without any significant interruptions. Minimal emissions of SO2 and dusts in the work place are noted. The system requires minimum maintenance. The key to the high availability of the system is due to the good, performance of he Radiation Cooler, which efficiently cools the gas before entering the electrostatic precipitators (ESPs). This enables the ESPs to remove the dusts efficiently.

Jan 1, 1999

By Ricardo Ponce

In recent years, ENAMI implemented modernisation plans at its two smelters in order to meet the government's environmental regulations introduced in the early 1990s. The modernisation plans defined the new SO2 and particulates emission targets, deadlines for compliance, and the revised treatment capacities of the smelters. At Las Ventanas smelter, the principal process change consisted of eliminating the reverberatory furnace. All the smelter feed is currently processed in a 4m diameter, 14m long Teniente Converter, using up to 34% oxygen enriched air. Dry concentrate is injected into the bath through tuyeres. A fuel oil burner compensates for any process heat deficiency. The Teniente Converter high copper content slag is cleaned in an electric furnace. This furnace is also used to melt internal reverts. This paper will discuss the successful operation of the slag cleaning electric furnace.

Jan 1, 1999

By D. M. Jones

In May 1999 the first campaign of the BHP San Manuel flash smelting furnace (FSF) will be concluded after having set world records for both campaign length and tonnage smelted for an Outokumpu copper flash smelting furnace. This paper reviews planned process and equipment modifications including: The installation of a new 36,000 mt concentrate storage facility; replacement of the existing dryer electrostatic precipitator with a baghouse; modification of the FSF dry charge bin and feed system to achieve mass flow and uniform feed to the concentrate burner; modifications to the FSF and its ancillary cooling systems; modifications to the waste heat boiler and offgas handling system to increase gas handling capacity and improve process efficiency;- and improvements to the FSF fugitive gas collection system. A brief review of the planning and execution of the scheduled 45 day shutdown is also given.

Jan 1, 1999

By Petrus Christiaan Pistorius, Ming Tang

Magnetite concentrate is pelletized and then hardened by elevated-temperature oxidation to hematite, to produce pellets for ironmaking. Previous work showed that the rate of oxidation is under mixed control of gaseous mass transfer of molecular oxygen through the pellet pores, and solid-state diffusion into the oxidizing grains. Because of the partially limiting role of solid-state diffusion, concentrate size distribution strongly affects pellet oxidation. Previously, a simple mixed-control model was formulated to describe isothermal oxidation. In that model, the main effect of concentrate size distribution was on the plateau level of oxidation which is reached at a given temperature. However, the extent of plateau oxidation increases with increased temperature, requiring a more complex model for non-isothermal oxidation. In this paper, predictions of the non-isothermal model confirm the strong effects of concentrate size distribution and oxygen enrichment. In particular, a greater fraction of coarse magnetite particles would be beneficial, decreasing the size of the macroscopic unoxidized pellet core.

Jan 1, 2015

By Felipe Daroch, Maria C. Ruiz, Rafael Padilla

Copper concentrates with high arsenic contents must be pretreated before conventional smelting to prevent environmental pollution with arsenic compounds. In this work, experimental results concerning the selective removal of arsenic and antimony from copper concentrates are presented. The process consists of an alkaline digestion using concentrated NaHS-NaOH solutions to transform the arsenic and antimony sulfides into soluble compounds. A water leaching follows the digestion to dissolve the arsenic and antimony, leaving clean copper sulfide solid residues. The laboratory scale tests were carried out using a copper–arsenic concentrate with 15.05% As and 1.42% Sb. The results showed that the most important digestion variables were temperature and concentrations of NaHS and NaOH. Over 97% of arsenic and 92% of antimony could be removed in 10 min of digestion using 8.9 M NaOH and 100% excess of NaHS at 80 °C. The subsequent water leaching was performed at 80°C for 20 min.

Jan 1, 2015

By Luiz A. Teixeira

A process is described whereby worn, deffective or crystallized photoconductive Se-As layers can be stripped off from aluminium photocopier drums, using hydrogen peroxide solutions in conditions such that the aluminium substrate is preserved from chemical attack. The process allows the stripped drum to be recoated with a new photoconductive layer, and to be put again in use.

Jan 1, 1990

By Andre Thess, Jurij Kolesnikov, Christian Karcher

"During the motion of molten metal under external non-homogeneous magnetic field the induced electric currents produce Lorentz body forces in the opposite direction to the flow, causing deformation of velocity profile, vortical structures, and adding a pressure drop across the magnetic field. The same Lorentz force acts on the magnet system. We analyse these phenomena in metallurgy, namely, at molten metal pumping, stirring, continuous casting, and in contactless Lorentz force flowmeter (LFF). Experiments with liquid metal alloy, including direct measurements of Lorentz forces, velocities, and flow structure visualization were conducted. Based on this study the industrial prototypes of LFF systems were designed, built, and tested in a secondary aluminium production. A molten metal flow at high temperature (700°C-850°C) can be effectively measured. The LFF technique method allows measuring precisely the volumetric and mass flow rates linked with Lorentz force, and the mass accumulated within production process.IntroductionThe present work demonstrates the development of a non-contact electromagnetic system for measurement of a liquid metal flow. Our approach embodies the Lorentz force velocimetry [1-6] technique which is physically based on a measurement of the force acting on an external magnet system the field of which interacts with the flow. This force is exactly equal to the braking Lorentz force induced in a flowing conducting fluid. In what follows a measurement system based on the Lorentz force velocimetry principle. For monitoring and controlling the production process it is desirable to measure continuously the mean velocity of the liquid metal in order to deduce the mass-flux and volume-flux from it. The form and dimensions of the magnet system are in agreement with geometry of the operating channel. We consider here a version of magnet systems in a composition of permanent magnets.The LFF possesses a number of advantages which make it attractive for the measurement of flows in hot and aggressive melts. The relation between the measured force and the desired volumetric flow rate is often linear (for closed channel or at a constant liquid metal level in open channel). For the converting of the measured force into volumetric and mass flow rate we should know the calibration factor. The calibration factor is independent of the viscosity and density of the liquid metal and depends only on the magnetic field magnitude, the electrical conductivity of the liquid metal and the geometry of the channel in which the liquid metal flows. In aluminium production, for instance, there exists a number of standard alloy compositions having welldefined conductivities for which the calibration factors can thus be tabulated. We consider below consistently effects in liquid metals arising under influencing magnetic field, construction principle of LFF and measurements of metal flows at industrial conditions."

Jan 1, 2011

By Sylwia Zymankowska-Kumon, Rafal Danko, Józef Danko, Mariusz Holtzer

"Burning of ceramic materials is carried out at temperatures 900+ 1300°C, in dependence of the required functional properties. The Faculty of Foundry Engineering together with the Faculty of Material Engineering and Ceramics developed the technology of production of burned ceramic materials with using spent moulding and core sands. The mentioned above waste materials of the foundry industry fulfilled -in plastic masses intended for obtaining ceramic materials -the role of the addition weakening clay raw materials. The laboratory investigations were fully verified by the results of industrial tests. It should be pointed out that none negative effects were observed at the stage of mixing raw materials and preparation of plastic masses. The measurements of exhaust gases emissions performed during burning the products containing spent moulding sands as well as during the normal production did not exhibit any significant differences, which could have indicated the harmful impact on the natural environment.IntroductionSands are used by the foundry industry to make metal casting molds and are a mixture of silica sand, bentonite clay and carbonaceous additives or resins. During the casting process, the molten metal cause thermal decomposition of carbonaceous additives or resins, which results in the formation of potentially hazardous organics, that are emitted to the atmosphere and condense in the molding sand. Each year the U.S. foundry industry landfills about 10 million tones of sand because it is no longer suitable to make metal casting molds. A large high-silica sand content in spent foundry sands (SFSs) generates rational premises for their reuse in other than foundry practice fields. Efforts to divert the SFSs from landfills and encourage their beneficial use in manufactured soils, geotechnical applications, the construction industry (road construction, highway construction), the building materials industry (cement, bricks, limestone manufacture), in the filling of mining cavities or in landfill construction (roads on landfills, permanent covers) are make [1-7]."

Jan 1, 2013

By M. E. Reed

Clyde Materials Handling (CMH) and WorleyParsons have developed a concept for a flash furnace feed system using the specialist pneumatic conveying equipment expertise of CMH and the flash furnace process experience of WorleyParsons. CMH has developed a proprietary volumetric feeder (called a Rotofeed) which is extremely accurate and overcomes many of the problems inherent with loss-in-weight screw feeders and drag chain conveyors, previously regarded as state-of-the-art. Initial indications are that the Clyde-WorleyParsons Feed System could deliver the following benefits to Flash Furnace operation: ? Accurate pulse-less delivery of feed material to the head of the burner leading to improved combustion performance and process stability; ? Highly accurate split to the individual quadrants of a conventional burner tube, or provision of a smooth hollow curtain to a burner without guide vanes; ? Decreased pressure pulsation in the furnace due to improved combustion control and performance; ? Decreased temperature fluctuations in the furnace due to improved combustion characteristics and hence reductions in refractory thermal stress and wear; Plant measurements have indicated a correlation between the discharge of concentrate from the drag chain conveyor and high speed pressure fluctuations in the flash furnace settler. Pilot scale test have been conducted to illustrate that the system delivers pulse-less feed to the burner with even feed distribution axially.

Jan 1, 2006

By Katsutoshi Inoue, Shafiq Alam

Several novel types of chemically modified chitosan were prepared by immobilizing functional groups of EDTA and DTPA onto polymer matrices of chitosan in order to investigate their potential for mutual adsorptive separation among rare earths. Following the batch wise adsorption tests to elucidate their basic adsorption characteristics for rare earths, mutual separation was carried out using a column packed with the chemically modified chitosan. The separation between Sm(III) and Y(III) was tested using a column packed with EDTA-type chitosan while mutual separation among 4 light rare earths, La(III), Ce(III), Pr(III) and Nd(III) was tested using a column packed with DTPA-type chitosan. In both cases, satisfactory mutual separation was achieved by the chromatographic operation using these chemically modified chitosan.

Jan 1, 2014

By C. Gasparrini

Mineralogy may be applied to the selection of appropriate separation techniques, as well as to assist in the evaluation of problems causing loss of metals and other economically important elements during plant processing. Mineralogic studies may thus help develop techniques to optimize metal recoveries. The present paper describes how such factors as the minerals in which the elements of interest are concentrated, their chemistry, the chemistry of the associated minerals, grain size and textural associations with other minerals in the ore, may affect decisions on separation techniques for the recovery of economic elements. A number of case studies are described in which the mineralogical observation of ore samples has revealed the cause of problems experienced in the extraction of select precious and base metals, or has been decisive in the choice of appropriate techniques for recovery.

Jan 1, 1981

By Keizo Uematsu, Satoshi Tanaka, Nozomu Uchida, Yutaka Saito

"Effect of moisture content must be fully understood for controlling the granule compaction of ceramics. It changes the mechanical behavior of spray-dried granules applied for compaction process, and governs the structure and properties of .ceramics. To understand the time-dependent change in processing, the kinetics was examined for change of moisture content for granules placed in a die and the pressed compacts also. The results were explained in terms of apparent moisture diffusion coefficients. They varied non-linearly with the PVA content in the granules. The results were explained through the non-uniform PVA distribution in the granules.IntroductionMoisture must be controlled in compaction process to produce the green compacts having uniform structure. It affects glass transition temperature of binder and thus the deformation behavior of powder granules under an applied stress. Several studies [1-7] have clarified the effect of moisture content on the compaction behavior of granules and the structure of resultant compacts for both die pressing and cold isostatic pressing (CIP) of pre-formed compacts. In these studies, the moisture contents in the system were equilibrated with the humidity in the atmosphere before compaction. In practice, however, the moisture content in the system may vary with time if the relative humidity of surrounding atmosphere is different from what the granules were equilibrated previously. This is very likely case in real production processes. However, the kinetics of moisture change in the granules as well as in the pre-formed powder compacts have not been well studied. For controlling the microstructure in a system, it is necessary to fully understand the kinetics of moisture change and its relevance to packing structure of powders."

Jan 1, 2000

By M. K. Yelloji Roa

Effect of conditioning with Thiobacillus ferrooxidans on the floatability of sphaierite and galena has been determined in this work. The flotation behavior of the conditioned minerals clearly shows that such bacterial conditioning does produce marked modification of their surfaces. The variables affecting the surface modification and thereby the flotation response of the minerals were found to be cell concentration used for bacterial conditioning, the period of biotreatment and the pulp density. Importantly, while the enhancement in flotation obtained due to sulphuric acid treatment was retarded by biotreatment in the case of galena at all cell concentrations due to electrochemical effects, such decrease occurred in the case of sphalerite only at cell concentration sufficiently high for their attachment to the mineral surface. The effect of bacterial conditioning has significant implications to the differential flotation of sphalerite and galena. Mechanisms responsible for the modification of the surface properties of these sulphides due, to bacterial conditioning are discussed.

Jan 1, 1991

By Stober, Frank Allan

The paper describes the development of components in an lntegrated Furnace Control system for shielded-arc smelting focusing on operation and crucible integrity enhancement. The paper reviews the mechanisms of power, feed and energy input and losses into the shielded-arc smelting process and describes the furnace control system module development and integration to tailor the process. The ultimate success of a furnace control system application is transfer of knowledge, training, and operational support during furnace start-up and ramp-up phases and a model for how this has been achieved is discussed. The control modules of a shielded-arc laterite smelting furnace are described in detail including measured results and screen captures from application in a laterite smelting furnace. This paper focuses on developments in Integrated Furnace Controls tailored to shielded-arc laterite smelting but development of common furnace control modules for improved crucible and tapping operation integrity applied to other furnace processes, including immersed-arc smelting, is also covered. Keywords: IFC, Power, Feed, Supervisory, Control

Jan 1, 2004

By Halvor Dalaker, Pål Tetlie

The decomposition of methane has been studied experimentally in contact with various oxides at elevated temperatures. For each oxide, the temperature at which the cracking starts has been determined. No correlation was found to exist between the temperature for the onset of cracking for a given oxide and the affinity for carbon of the oxide's metallic component. In terms of potential for using methane as a reducing agent, calculations are presented that indicate that the suitability of an oxide for such reduction depends on the desired methane+oxide reaction being more energetically favourable than the methane+methane=ethylene/acetylene reactions.

Jan 1, 2014

By H. A. F. de Souza, Dana S. Mills, P. E. Burgener

"ICP-MS has moved from a laboratory curiosity to a functional analytical tool. This paper discusses how ICP-MS has been used to solve difficult analytical problems encountered when analyzing various mine materials. Comparisons between analytical techniques applied to the analysis of gold and the platinum group metals illustrate the advantages and problems of ICPMS when. applied to trace levels of some metals iri the presence of ore grade metals. Interferences and matrix effects are compared to ICP, AA and Neutron Activation. The necessity to select chemical extractions which are compatible with ICP-MS are also discussed.The ICP-MS techniques explained in the examples on Au and precious group elements (PGE) have validity in analytical problems encountered in testing of trace metals in the presence of major elements found in mine materials. Exploration and environmental testing are other areas that require the same analytical approach to quantify trace levels in the presence of major interfering elements normally associated with mining environments."

Jan 1, 1999

By Michael F. Kitto

The production of sulphuric acid at base metals smelters is predominantly an involuntary activity and now comprises approximately 17% of all-forms sulphur supply in world terms. The majority of elemental sulphur is also produced involuntarily in response to environmental regulations regarding emissions from hydrocarbon processing plants. The paper examines the points of similarity and difference in the sulphur and smelter acid markets, and reviews their interactions. The reasons for the merchant acid market collapse of 1993 are analyzed, and the prospects of a recurrence are considered.

Jan 1, 1996

By Kampe. S. L., Baker. Andrew H., Tony Zahrah

"Experimental heats of reaction for the formation of several Al3Ti + TiB2 intermetallic composite formulations have been determined utilizing bomb calorimetry. To overcome the kinetic constraints and achieve ignition in these formulations, a boron (B)/potassium nitrate (KNO3) initiation aid was incorporated within the blended reactant compact. The heat contribution from the initiation aid was regressed to provide estimates of the heat of reaction of the nominal formulations. Powder x-ray diffraction was utilized to identify the products of the reaction and discern any differences between the predicted equilibrium products of the formulation and the actual products.IntroductionReaction synthesis is a technique for the creation of ceramics, intermetallics, and in-situ composite materials [1]. Reaction synthesis is defined by its self, propagating mechanism, where the energy liberated from a localized reaction within a green powder compact is enough to carry the bulk reaction to completion. Achieving a self, propagating state can be achieved in variations of two primary methods of initiation: uniform volumetric heating and directional propagation [2].Uniform volumetric heating involves subjecting a green compact of the unreacted formulation to uniform heating in a furnace to encourage diffusion to initiate the reaction (Figure 1a) throughout the bulk material. Directional propagation utilizes a point heat source at one section of a green compact of unreacted formulation (Figure 1b). The localized exothermic reaction at one point in the compact then initiates the reaction in the section of the compact adjacent to it and fully propagates throughout the entire compact until completion. Initiation of the localized reaction is generally associated with the melting of the constituent with the lowest melting point, with instantaneous initiation of the reaction usually occurring close to that melting point [1]. This melting point can be high in some systems of interest, such as the titanium (Ti) and boron (B) system in equation 1:"

Jan 1, 2011