Search Documents

By S. P. Mathew

The ISASMELT Lead Process is a continuous two stage process for the production of crude lead from concentrate. It is based on the use of a top entry submerged Sirosmelt lance to produce turbulent baths in which high intensity smelting or reduction reactions can occur. The process involves oxidizing the concentrates in the first stage to produce a high lead slag. This slag is tapped continuously and transferred down a launder to a second furnace where it is reduced with coal. Crude lead and discard slag are tapped continuously from this furnace through a single taphole and separated in a conventional forehearth. Process and engineering design work for a commercial scale Lead ISASKELT plant designed to produce 60000 tpa crude lead has been completed. This plant is planned to be operational in 1991.

Jan 1, 1990

By L. A. Bertram, F. J. Zanner

"The goal of this paper is to present a tool to simulate transient melting of the electrode tip. This capability is needed to develop and test furnace control algorithms since experimental determination is difficult and expensive. Simulation incorporates parameters (including arc voltage, arc current, electrode gap and furnace pressure) from previous quasi steady experiments with 460 mm diameter Inconel 718 electrodes.Cathode heating rates (determined by classical as well as experimental arc models) are linked to these independent variables. After radiative loss adjustments to the heating, transient one dimensional melting is computed. IntroductionThe vacuum arc remelting (VAR) process attempts to improve the physical and chemical homogeneity of a static-cast electrode by remelting and solidification in a quasisteady manner. To achieve steadiness of furnace operation requires automatic controls based on inputs measuring physically relevant state variables of the process. Previous industrial scale VAR studies (1,2,3) involving stainless steels, superalloys, and other alloys have provided a basis on which control strategies of some generality can be proposed (4). Of these measurements, the data for Inconel 718 is the most complete, so discussion in this paper is restricted to this alloy.Studies of the In 718 alloy subjected to the VAR process have established that melt rate M (kg/hr) depends not only on the melt current 1m (kA) supplied to the furnace, but also on ambient gas pressure of CO, PCO (micron), and electrode gap ge (mm) as well (1):"

Jan 1, 1986

By F. Shahbazian

attempt to systematize the knowledge on slag viscosities, the present work was carried out. The Among the physical properties of slags, viscosity is very important in understanding the mass out in the temperature range 1438-1762 Q The rotating cylinder method was used in the viscosity measurements. Crucibles and spindles made out of pure iron were employed. The transfer phenomena in metallurgical processes. The viscosities of fayalitic slags are of great interest in the non-ferrous metal industry, with special reference to copper production. In an slags were prefused before the measurements. In order to take into account the vaporization reactions involving CaF2, pre- and post measurement samples of the slags were chemically analysed and the compositions were ascertained. The results show that in the case of the CaO-SiO2 system, CaF2 additions tend to decrease the viscosity, in accordance with the expectations. In the case of the "FeO"-SiO2 system, at higher "FeO" / SiO2 ratios in the slags, a reverse trend was observed. The results are discussed on the basis of a viscosity model for silicate melts developed in the present laboratory as well as the structural considerations of silicates.

Jan 1, 2000

Korea has about 68 hundreds million tons of limestone's reserves. Still, high-Ca2+ limestone containing more than 52% calcium oxide makes up for about 12% only; hence the need for securing and effectively developing limestone. The best solution is to manufacture precipitated calcium carbonate (PCC). The synthesis of PCC using high-Ca2+ limestone has several advantages including the efficient development of resources and easing the import dependence on PCC. The first step is the selection of suitable limestone for the synthesis of PCC. In this study, formation age was decided as the primary key point, with its effect on calcination, hydration, and synthesis of aragonite investigated. Results showed that the yield of aragonite increased when newer limestone was used. On the other hand, neither the activity and bulk density of quicklime nor the particle size of aragonite was affected by the formation age, although special values were registered following each formation age. Moreover, the bulk density of quicklime and particle size of aragonite tended to increase with decreasing activity. This result is different from that of the other experiment. Therefore, a suitable method for measuring the activity of quicklime for use in the manufacture of PCC must be established.

Jan 1, 2006

By N. Krishna

The utilization of Electrochemical Impedance Spectroscopy (EIS) in conjunction with Atomic Force Microscopy (AFM) is a powerful surface characterization technique to study the role of sulfur formation during acidic oxidation of chalcopyrite. It has been established that the chalcopyrite dissolution kinetics is controlled by the formation of passive sulfur layer during leaching. The objective of the study was to characterize the intermediate sulfur layer formation at different oxidation conditions in acidic solution. The chalcopyrite samples were subjected to anodic oxidation and the oxidation process was analyzed using impedance spectroscopy. The sulfur growth on the chalcopyrite surface during oxidation was further analyzed using Atomic Force Microscope for sulfur roughness and grain size, peak height and sulfur growth.

Jan 1, 1999

By Jan Pan, Deqing Zhu, Xianlin Zhou, Yanhong Luo, Zixing Xue

"Magnetic roasting process, aiming at obtaining magnetite concentrate, is the principle method of exploiting siderite as a raw material in iron and steel industry. Study on preparing DRI from siderite through coal based reduction technology is sporadic. To make the process of how siderite is reduced to iron clear, roasted ore reduced from siderite by lignite under different time periods were analyzed. The results indicated that: at the temperature of 1050°C, siderite was rapidly decomposed into magnetite, and further reduced as Fe30r?FeO?Fe, the later step was slower than the previous one. A fracture of particles was found during the process of thermal decomposition and the reduction of newly formed magnetite. As the reduction proceeded, metallization rate of products increased, and the iron grain grew along with time.IntroductionWith the rapid development of economy, China demands more and more iron ores for the iron and steel industry. China has rich iron ore resources, but 97% of them are below 30% in iron grade, many are refractory and unutilized [1], therefore large quantities of imported iron ores are in a desperate need. China imported 686 million tons of iron ore in 2011 (data from the China Customs), accounting for nearly 60% of the total consumption. To guarantee the healthy development of iron and steel industry, domestic refractory iron ores have to be utilized both economically and environmentally."

Jan 1, 2013

By Ross R. Bhappu

Anticipating a major power cost increase in 1990, Cyprus Copper Company decided to modernize the Miami Smelter at a cost of $92.5 million. The modernization project included the addition of an Isasmelt vessel for use as the primary copper smelter and the modification of the existing electric furnace to a slaglmatte separating vessel. The project was completed in June of 1992 and is currently operating at close to its design capacity. This paper provides a summary of the decision making process, a description of the project, a summary of start-up problems and solutions and the current status of the smelter operation.

Jan 1, 1994

By Kenneth P. Michalek, James E. Kelly, Jonathan A. Dantzig

"Many investigations have been reported regarding the simulation of continuous casting with emphasis on in-mold heat transfer. These analyses have been limited, however, because they require either estimation or measurement of the characteristic heat transfer between the ingot and the mold. In this paper, a self-consistent model 'is presented for calculating the heat transfer between a solidifying continuous casting and the mold, in the context of the continuous casting of steel. Using both thermal and stress analyses, the air gap formed during continuous casting is calculated and used to compute the heat transfer coefficients. Iteration between the thermal and stress analyses is used to determine a self-consistent solution. IntroductionThe continuous casting process for steel is illustrated schematically in Fig. 1. Molten steel is tapped into a tundish from which it flows at a controlled rate into the continuous casting mold. The initial shell of the casting forms in the mold by transfer of heat from the metal through the mold wall to the cooling water. The remainder of the casting is solidified by application of water sprays, and/or radiation cooling below the mold.Heat transfer in the mold portion of the process is important because it controls the formation of various defects which are deleterious to subsequent processing. Examples of defects formed in this region are surface irregularities, such as cold folding and oscillation marks, and more serious defects, such as longitudinal or transverse cracks. A more catastrophic problem which may occur is a breakout, in which the shell ruptures and molten steel is discharged in an uncontrolled way."

Jan 1, 1986

By A. C. Mollison

In November of 1983 a fire inside the autoclave caused the curtailment of operation of the Kidd Creek pressure leaching facility. Subsequent repairs and recommissioning of the autoclave in 1984 allowed Kidd Creek to increase its production of zinc as originally planned. This paper describes the operation of this process from 1984 to 1988 and details major mechanical work carried out on the vessel in 1.988:

Jan 1, 1990

By Amy Nelson

In the electrolytic production of zinc, cobalt is removed from the zinc electrolyte by cementation with zinc dust prior to electrowinning. Although the thermodynamics for this reaction are favourable, kinetic barriers to cobalt reduction render the method almost useless in practice unless activators such as copper and antimony or arsenic are added. There is a large body of work studying the effect of these additives, yet the mechanism by which they act is still poorly understood. Even when the target conditions are met, zinc dust consumption is excessively high: satisfactory operation requires up to 300 times the stoichiometric amount of zinc dust. The objective of this work is three-fold: (1) to examine the effects of activators and elucidate the characteristics that make a good activator; (2) to identify new additives that could lead to a more efficient purification process; and (3) to test the new additives with synthetic and real electrolyte solutions. The present paper gives a status report on this project.

Jan 1, 1998

By Sheng Dai, Yuan Lee, Haiming Xiao, J. P. Young

"There are numerous analytical applications of scatter-emission and/or absorption spectroscopy applied to liquids and solids in the temperature range of 0 to 350°C. In this paper an all-silica fiberoptic probe is described which is useful for spectral analyses from 0 to 1600 K and can be used in harsh chemical environments. The probe has been used for Raman spectral analyses of many molten salt and solid material systems to 1000°C. It has applications for such studies at higher temperature ranges. The instrumentation required along with the demonstrated and proposed applications of the all-silica probe are presented and discussed.IntroductionThere are many kinds of scatter-emission spectroscopies that are of value for analytical measurements. Fluorescence, reflectance, arc or spark emission are descriptors for some of these. Raman scatter spectroscopy is also quite a useful technique for analytical measurements.In Figure 1, we give a simplified explanation of the Raman effect. If one shines monochromatic light into a sample, light may be absorbed, exciting the sample to some virtual state. We know from experience that almost all of the light is re-emitted in the same wavelength range. This is called Rayleigh or Mei scattering and is designated in the figure by the arrows in both examples that point up and down from the same lower energy state. A very small percentage (the order of 10-4%) of the monochromatic light is re-emitted leaving the sample at a vibrationally-excited state. Thus, this light is at a distinctly lower energy compared to the exciting radiation. This is called a Stokes shift and is represented in the left-hand example by an arrow descending to a more energetic vibrational state. If the sample is not at a temperature of absolute zero, some of this vibrationally excited state will be thermally populated. That portion of the sample still absorbs and re-emits exciting radiation as Rayleigh scattered light, but a small percentage of the exciting light is re-emitted as the sample relaxes to the lower vibrational state. The energy of this light is of higher energy and is called an anti-Stokes shift, depicted in the example to the right. Notice that the energy separation of the Stokes or anti-Stokes shifted emission from that of the exciting radiation is the same, and expressed in ~cm-I. The intensity of either shifted emission is a function of the population of the vibrational energy states; therefore, the ratio of the intensity of Stokes to anti-Stokes signal varies with absolute temperature. We will come back to this point later."

Jan 1, 1997

By E. A. van Dijk

Dusts from steel-making processes contain substantial amounts of zinc. Such dusts are also a hazardous waste and dumping them becomes unacceptable from environmental point of view. Therefore processes that can recover zinc and possibly other metals from steel-making dusts are being investigated. The aim of this paper is a contribution to the more fundamental kinetic aspects of zinc reduction from silica free calcium ferrite slags. The effects of alumina, lime and magnesium oxide contents of the slag, the COICO, ratio and the effect of initial Fe2O3/CaO ratio were studied experimentally at 1400°C The results indicated that the reduction of zinc from molten slag was possibly a first order reaction. As expected higher COICO, ratios increased both the extent and the rate of reduction. It was also observed that a higher iron content of slag improved the reduction of zinc from calcium ferrite slags. This fact seems to support the proposed mechanism that zinc is partly reduced by ferrous iron to zinc vapour and that ferric iron is reduced by carbon monoxide. The reduction rate of zinc in these slags was decreased by increasing alumina content of the slag. Alumina decreased the calculated optical basicity of the slag showing the fact that reduction of zinc oxide was more favorable in more basic slags. Probably the formation of complex ions by alumina and zinc oxide such as ZnAl2O32+ lowers the activity of Zn2+ ions in the slag and hence render them more difficult to reduce.

Jan 1, 1999

By Adam Powell

A Cahn-Hilliard phase field model is formulated to describe transport-limited electrochemical reactions coupled with fluid flow in a metal reduction cell. When the reaction is limited by mass transfer of metal ions from the electrolyte to the cathode, the metal-electrolyte interface at the cathode exhibits a Mullins-Sekerka instability, leading to the growth of dendrite-like "streamers" of liquid metal into the electrolyte, which in turn significantly enhance the apparent mass transfer coefficient there. Model results for iron reduction from ferrous oxide in slag show formation of these streamers. Although the double-layer is not included in this model, the related phenomenon of electrocapillarity can be represented by a gradient penalty term which includes the electric potential gradient, such that interfacial energy is a function of the electric field normal to the interface.

Jan 1, 2003

By David G. Dixon

A mathematical model is derived in dimensionless form which simulates the effluent concentration response of reagents from spent heaps under both fresh and recycled water rinsing. The model is based on dispersion from isochoric pathways distributed in length and cross-section, oriented normal to convection channels in ideal plug flow. The effects of heap height, rinsate flow, and initial reagent concentration are examined. It is shown that the rinsing cycle undergoes a distinct shift between fast and slow rinsing at a certain time depending on the amount of stagnant solution in the heap, and the distribution of dispersion pathways. Results of preliminary column rinsing tests on both agglomerated and unagglomerated ores are presented which partially validate the model.

Jan 1, 1994

By G. E. Lagos

This paper analyses the scope and instruments employed by the Basel Convention for regulating the transboundary movement of hazardous wastes, the present and projected hazardous waste regulations of Chile, reviews the Chilean import/export trade of wastes of the period 1985-1995, and discusses, the influence that the Basel Convention has had on mining trade, its perceived benefits and costs, and possible effects on Chile's trade of the application of the Convention's Decision III/l. There is no quantitative estimation as to the effect of the Convention on the general volume of imported or exported materials destined for recovery, recycling, reclamation, or reuse. All recycling imports, with the possible exception of residues of petroleum oil, which occurred during the decade 1985-1995, can be classified tentatively as non hazardous. The entry into force of the Convention has had several effects on Chile's trade. It has brought home the need to have a comprehensive hazardous waste legislation, it has been a base for applying import restrictions, which in all likelihood, would .have otherwise not been applied, The benefits and costs of this import restriction, as well as those of the multilateral export ban are analyzed.

Jan 1, 1999

By M. Giralico

Optimized mixer settler designs will now handle flows of over 25,000 GPM. The size and expense of the equipment hamper experimental settler optimization efforts. Computational Fluid Dynamics (CFD) is a timely and predictable tool for settler design development. In the past, CFD has been used to evaluate only the flow field in pumped and auxiliary tanks. A similar numerical analysis is used to evaluate settler flow and phase separation. Phase separation is analyzed using multiple species for the aqueous and organic phase. Experimental validation shows good agreement between the computational and experimental solutions in both flow field and phase separation. The computational model is used to show performance differences between various choices of settler geometry, liquid depth, with variable flow rates. Understanding the differences allows the development of optimized settler designs. System improvements are predicted to lower entrainment levels further and/or allow new smaller footprint designs. This paper focuses on the major design components of the settler and how future technological advances will lead to further improvements in their design. LIGHTNIN?s new designs will handle tomorrow?s production requirements, while maximizing profits.

Jan 1, 2003

By W. Gutmannsbauer

Thin films of TiO2 nanoparticles have been prepared by different reactive deposition methods, such as electron evaporation, ion plating and ion beam sputtering. Many properties especially the optical properties, are strongly related to the film morphology and surface roughness. Scanning force microscopy was employed to obtain information on the surface structure of as-deposited Ti(h thin films. The influence of the deposition conditions and the film thickness on the optical and structural properties has been investigated. The as-deposited films were found to be amorphous or polycrystalline with anatase structure.

Jan 1, 1995

By Bo Björkman

Four different arsenic containing dusts from the Boliden plant, Boliden mineral AB, Sweden have been examined. A kinetic study of the As elimination was performed in a laboratory scale roasting furnace for roasting furnace ESP dust and smelting furnace ESP dust. Characterisation and thermodynamic calculations were carried out to determine the mineralogy, and the stability of compounds in the dusts studied. The characterisation methods used were chemical analysis, X-ray diffraction analysis and microprobe analysis. It was found in the experiments that a high degree of As elimination was obtained for roasting fumace ESP dust and a low degree for smelting fumace ESP dust. Derived kinetic models are given. A prediction of the As-elimation for settling furnace dust and converter ventilation dust is presented.

Jan 1, 1994

By A. Galvan

High rate compressible media filter (CMF) tests produced exceptional total suspended solids (TSS) removal at hydraulic loading rates ranging from 97.8 to 122.2 m/h. The compressible media is manufactured from a robust resin fiber that can withstand low pH and temperatures up to 149 °C. The media porosity can be varied by applying compression onto the media. At 40% compression, the CMF can remove particles greater than 4 μ. Three synthetic test-samples were generated by Hazen Research Inc., (Golden, Colorado) to simulate the copper Pregnant Leach Solution (PLS), Raffinate and Electrolyte solutions used for the testwork conducted at their facility. The preliminary results showed that the CMF was very effective in removing TSS without the use of chemical conditioning from the above test-solutions with efficiencies of 98%, 97%, and 96%, respectively. Given the remarkably high hydraulic loading rates, the industrial equipment footprint would be minimized appreciably over conventional clarification and alternative filtration systems.

By Shengfan Zhou, XUEWEN WANG, Bianfang Chen, Mingyu Wang

Vanadium was leached from roasted stone coal by NaOH solution, and the effect of leaching temperature, leaching time, addition of NaOH, liquid to solid ratio, the grinding fineness of stone coal, and stirring speed on the vanadium leaching rate was studied. The kinetics analysis for the process is presented by the shrinking core model. The results show that the vanadium leaching ratio of roasted stone coal can be beyond 75% at the 6% NaOH addition, leaching temperature of 95°C, leaching time of 7h, liquid to solid ratio of 1.2mL/g, and grinding fineness of 0.111mm. The leaching process is controlled by interfacial reaction kinetics and the apparent activation energy was 59.36kJ/mol.

Jan 1, 2016