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By P. Peczak

A Monte Carlo simulation technique has been used to study dynamic recrystallization in polycrystals. A continuum microstructure of the polycrystal is modeled employing a discrete lattice. The response of the material to hot deformation is simulated by adding stored energy and recrystallization nuclei continuously with time. The experimentally observed nonuniform character of deformation substructures is modeled by employing a phenomenological expression for inhomogeneous distribution of the stored energy. All simulations were performed on HP-Apollo 9000 Series 700 workstations. A program written in FORTRAN with use of PHIGS graphics library calls was used to interactively monitor the current state of the matrix and all relevant parameters: deformation stress, average grain size and effective nucleation rate. Visual analysis of the simulated microstructure allows a better understanding of the data developed by averaging over a number of very long Monte Carlo runs. Since the essential features of dynamic recrystallization are accurately reproduced by the model, it is used to discuss the role of the controlling mechanisms of the dynamic recrystallization in real polycrystal.

Jan 1, 1993

By Suswnu Makino

Sumitomo Metal Mining developed a new nickel refining process ( Matte Chlorine Leach Electrowinning process) based on chlorine leach and electrowinning technologies. After the pilot plant study, the commercial plant with design capacity of 24,000 tonnes per year was constructed and has been successfully operated since August, 1992. During the practice of the past three years, great deals of improvement have been achieved. Through these operations the MCLE process has been demonstrated to be one of the most superior processes in the world with nickel recovery, productivity, cathode quality and working environment. Today the refinery product capacity is increased to 30,000 tonnes per year. This paper describes the equipments and operation of the Sumitomo MCLE process.

Jan 1, 1996

By Kongfang Feng, Fei Ruan, Zhiyu Liu, Jieyu Zhang, Xin Hong, Shaobo Zheng, Jixu Wang, Jinyin Xie

"Mixing phenomena in smelting reduction furnaces with asymmetric side blowing were studied in this paper. Mixing phenomena in a smelting reduction furnace was represented as the mixing time by electrical conductivity measurements. Experiments were performed in a water model under various operating conditions to determine the effects of horizontal angle, radial angle, inserting depth, flow rate of the upper and the lower side nozzle, the included angle between the upper side nozzle, and the lower side nozzle on mixing phenomena in smelting reduction furnace. Comparing mixing time and mixing phenomena, the optimal conditions were obtained for an asymmetric side blowing process.IntroductionIn recent years, many countries have put forward development strategies for saving resources and environment-friendly, the development of various industries had to face its influence for resources and the environment .As we all know, the steel industry is a pillar industry of the global economy, in which ironmaking is an important part of it. In the modern ironmaking process, the blast furnace is regarded as the most important equipment and tool. But with the increasing scarcity of metallurgical coke resources and considering the environmental impact of such processes, metallurgists proposed the concept of smelting reduction. Smelting reduction processes to produce hot metal from iron ore and coal were being developed as a possible alternative to the traditional blast furnace. At present, a number of smelting reduction processes had been developed all over the world, they were mainly included COREX, HISMELT, FINEX, DIOS, etc."

Jan 1, 2012

By A. Dadgar

Extraction of gold and silver from two refractory concentrates using cyanide and bromine reagents was reported at the 12th International Precious Metal Conference (1). The objective of this paper is to present the gold extraction, recovery, and economics for two refractory concentrates using cyanide and bromine reagents. Gold extractions for cyanide leaching (24- 48 hours) and bromine leaching (6 hours) were the same and ranged from 94% to 96%. Gold recoveries from bromine pregnant solutions using carbon adsorption, ion exchange, solvent extraction, and zinc and aluminum precipitation methods, were better than 99.9%. A preliminary economic analysis indicates that chemical costs? for cyanidation and bromine process are $9.50 and $10.50, respectively per ton of calcine processed.

Jan 1, 1989

By Dorothée Proffit

Characterization of solids containing cyanides is carried out according to recommendations and standard guidelines. Most of these procedures are based on the analysis of leachates collected either on site or after leaching in the laboratory of samples. Unfortunately, these sole results are often insufficient to identify the source of the pollution. To provide 'a more complete characterization of polluted solids, optical and electron microscopy, XRD, Mossbauer spectroscopy, and transmission infrared spectroscopy were combined to analyze leachates and raw or ground samples. This combination of techniques allows the determination of the kind of cyanoferrate complexes are present in the solid state, different from insoluble Prussian Blue, since they do not have the same extraction' behavior. The use of all these techniques to characterize solid samples combined ,to the usual analysis of solutions gives a better understanding of ' the cyanide behavior.

Jan 1, 1998

By N. Verbaan, E. Bourricaudy, M. Dry

"Starfield Resources is developing a novel circuit for the recovery of nickel, copper, cobalt, iron oxide, sulphuric acid and precious metals from the Ferguson Lake deposit in Nunavut, Canada. In this deposit, pentlandite is too finely disseminated in pyrrhotite for the production of a smelter-grade nickel concentrate at an acceptable nickel recovery, so established technology is not applicable and a novel chloride-based circuit is under development. The enabling aspect of this circuit is the hydrolysis of ferric chloride to hematite, releasing gaseous hydrochloric acid that is recycled. Conventional steps are used for separating and recovering the valuable metals from the chloride solution generated. This paper briefly outlines the circuit and presents the results of experimental work on the enabling steps, viz. the oxidation and hydrolysis of iron chloride to hematite and gaseous hydrochloric acid.IntroductionThe Ferguson Lake bulk sulphide ore body in Nunavut, Canada, owned by Starfield Resources Inc., contains significant amounts of base and precious metals but its mineralogy is such that it is not amenable to conventional processing. Pentlandite, for example, is too finely disseminated in pyrhhotite for even modem techniques such as fine grinding and improved flotation reagents to be effective [ 1] and extracting the value requires processing the entire bulk sulphide, including the pyrrhotite. To give the project a total green footprint, in terms of both carbon emissions and acid rock drainage, Starfield imposed the following requirements:• No reactive tailings to generate acid rock drainage.• No gaseous emissions other than normal atmospheric constituents.• No liquid effluents.• No regular consumption of fossil fuel.• High recoveries of all the valuable metals."

Jan 1, 2011

By K. R. Robilliard

Ausmelt Technology has been developed to process copper concentrates containing significant levels of lead, arsenic and antimony. A process was developed aimed at smelting these concentrate materials to remove the contaminants to fume and produce a clean copper product. The production of clean copper and the potential economic benefits of this process step over the sale of impure concentrates is discussed.

Jan 1, 1995

By M. Patel, G. Djambazov, J. Shrimpton

"Removing zinc by distillation can leave the lead bullion virtually free of zinc and also produces pure zinc crystals. Batch distillation is considered in a hemispherical kettle with water-cooled lid, under high vacuum (50 Pa or less). Sufficient zinc concentration at the evaporating surface is achieved by means of a mechanical stirrer.The numerical model is based on the multi-physics simulation package PHYSICA. The fluid flow module of the code is used to simulate the action of the stirring impeller and to determine the temperature and concentration fields throughout the liquid volume including the evaporating surface. The rate of zinc evaporation and condensation is then modelled using Langmuir's equations. Diffusion of the zinc vapour through the residual air in the vacuum gap is also taken into account.Computed results show that the mixing is sufficient and the rate-limiting step of the process is the surface evaporation driven by the difference of the equilibrium vapour pressure and the actual partial pressure of zinc vapour. However, at higher zinc concentrations, the heat transfer through the growing zinc crystal crust towards the cold steel lid may become the limiting factor because the crystallization front may reach the melting point.The computational model can be very useful in optimising the process within its safe limits.IntroductionLead bullion is commonly refined by removing various impurities (e.g. copper, silver, bismuth, antimony, etc) sequentially. This in normally achieved by the addition of reagents which selectively react with the impurities and the resulting compounds removed by various means. To aid efficient mixing (ensure uniform reactions), batch mixing of materials via the aid of impellers is common practice in a number of industrial sectors. Excess zinc, added during the desilvering process can be removed by one of three methods: (1) Vacuum dezincing - During vacuum dezincing, a vacuum is drawn on the agitated molten lead within a hemispherical vessel (Figure 1). Vaporized zinc condenses on the inner top surface of the vessel. The temperature at which zinc commences to vaporize lowers owing to heating under a vacuum. This enables vaporized zinc to be recovered in the form of high purity crystals without oxidation. The zinc crystals are recovered once the vessel lid is removed and the vacuum is broken. (2) Chlorine dezincing - In chlorine dezincing, molten desilvered lead is reacted with chlorine gas, forming a surface layer of zinc chloride contaminated with small amounts of lead chloride."

Jan 1, 2004

By F. Chabchoub

A mathematical model has been developed to study the influence of process variables on the horizontal Ohno continuous casting process. The model simulates the heat transfer and fluid flow in a wide plate ingot of pure tin. A two dimensional numerical analysis based on a control-volume finite difference approach, the Semi-Implicit Method for Pressure-Linked Equations algorithm (SIMPLER), and an Enthalpy Transforming Model was used. The shape and position of the solid-liquid interface were calculated at different casting speeds, ingot thicknesses, and cooling device characteristics, as well as various mould temperatures. Results of the mathematical model were compared with

Jan 1, 1992

By S. S. Chabot, S. E. James

A recent survey of CEOs from major steel companies worldwide revealed the importance of recycling zinc units from EAF dust, mill scale, blast furnace dust, and other zinc containing streams in their plants. Many processes were developed and installed in response to this challenge. The most successful approach involves the production of a crude zinc oxide and selling it to primary zinc producers to recover the metal value. The problem with this process is the high concentration of halides in the crude oxide. This type of material cannot be processed directly in an electrolytic zinc plant because of corrosion problems it will cause in electrolysis. In 1999, BRZ installed a zinc oxide receiving and washing plant to minimize the impact of halides to its circuit. A description of the washing plant and initial operating results are included.

Jan 1, 2000

By Kent D. Peaslee

When supersonic oxygen jetting is used in electric furnace steelmaking, the lance jet axis is typically inclined at larger angles to the vertical than is used in basic oxygen steelmaking. The supersonic jet is important not only for refining the steel, but for sustaining the foamy slag in the electric furnace. Physical modeling was carried out using a room temperature, two-dimensional slice apparatus in which mercury represented the metal and water-glycerol the slag. High speed video photography with image analysis was used to study the effects of the angle of inclination on the slag/metal bath. Mathematical modeling using FLUENT provided a method of predicting flow patterns and the trajectories of drops injected at various points in the flowfield. A one-half scale water model of the system, in which lance heights, angles, and flowrates simulated those encountered in steelmaking operations, was used to provide a better understanding of some aspects of the oxygen blowing process in electric furnace steelmaking.

Jan 1, 1994

By Corby G. Anderson

In the majority of industrial operations recovering gold and silver by hydrometallurgical means, cyanide is the predominant lixiviant. However, as an economic alternative, production of massive quantifies of silver chloride was done on an industrial scale in the nitrous-sulfuric acid pressure leaching of a refractory precious metals concentrate. This proven process required no cyanide. Thus, because of the large volumes encountered during day-to-day plant operation, the need for efficient and low cost methods of silver chloride precipitation, reduction and materials handling was mandatory. As such, this paper covers the evolution of plant scale precipitation, filtration, washing, reduction and control of silver chloride processing. As well, an in-depth description of the unique leaching system is included.

Jan 1, 1998

By Xiang-dong XING, Zhen-yang wang, Xing-le LIU, Jian-Liang Zhang

Experiments were carried out by adding CaF2 as catalyst in a Ar atmosphere to study the isothermal reduction kinetics of vanadium titano-magnetite carbon composite pellets under high temperature in the range from1473 to 1673K. By analyzing reduction mechanism, it was found that the rate controlling step was gas diffusion, and the activation energy was 178.39kJ•mol-1 without adding any catalysts. Adding CaF2 of 3% to vanadium titano-magnetite carbon composite pellets can decrease the apparent activation energy of reduction, and the decrease extent was 14.95kJ•mol-1. In addition, temperature is an important factor influencing on reaction rate.

Jan 1, 2015

By John B. Cocanour

The U.S. Bureau of Mines (USBM) has developed a laboratory-scale on-line analysis and process control system for a decopperization electrolytic circuit. This system is software driven, running on a 486DX-33 personal computer (PC) utilizing a portable energy- dispersive x-ray fluorescence (XRF) spectrometer as the sample analyzer. The XRF copper reading obtained was used as the control variable through an RS-232 serial interface to the PC for software-based control of feed flowrates. When the copper concentration in the electrolytic cell (as measured by the XRF) deviated from the set point, the feed flowrate to the cell was automatically altered using software-based proportional-integral-differential (PID) computer control to yield the desired copper concentration at the electrolytic cell outlet.

Jan 1, 1994

By W. G. Davenport

This chapter shows how flash furnace industrial oxygen and oil requirements are affected by different: (a) product temperatures (b) conductive, convective and radiative heat losses (c) electrical energy inputs (d) hydrocarbon fuels. The calculations of the chapter are all for production of 65% Cu matte from pure CuFeS2 concentrate. Blast temperature is? 298 K throughout.

Jan 1, 2001

By J. M. Khodadadi

"A computational study of the effect of thermocapillary convection on melting of a droplet under the influence of an incident uniform heat flux is presented. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables, whereby the time-dependent continuity, momentum and energy equations in the spherical coordinate system are solved. During the early periods of the melting process, conduction mode of heat transfer is dominant. As the thermocapillary convection is strengthened due to the growth of the melt zone, melting on the side of the droplet is observed to be much faster in comparison to the conduction-only case. Due to the skewedness of the temperature field, a new recirculating vortex is created which promotes melting within the droplet. The effects of the change in the sign of the surface-tension temperature coefficient on the melting pattern are also investigated.1. IntroductionMelting and solidification of materials are important processes which are encountered in nature and numerous industrial applications. Due to the recent upsurge of interest in such processes as spray casting, space radiators, rapid solidification, purification of materials, containerless processing, etc., there is a need to analyze the transport phenomena of melting and solidification in spherical configurations. Specifically, the effect of thermocapillary convection on the melting of metallic droplets has not been addressed at all. Only a few authors have studied the transport phenomena without phase change in spherical droplets. Oliver and DeWitt [l] worked out a series solution for the thermal and surface-tension-driven flow fields for a droplet experiencing an irradiant energy flux in the microgravity environment. Kudo et al. [2] solved the coupled momentum and energy equations numerically for the same problem without dropping the convective terms. Due to the nonexistence of any previous work on transport phenomena during the thermocapillary-assisted melting of metal droplets, this study was initiated to elucidate the features of the phenomenon."

Jan 1, 1999

By A. Warczok

The oxidation and smelting of chalcopyrite, bomite, chalcozine and pyrite has been studied under simulated flash smelting conditions. The results of copper sulphide oxidation show that under constant oxidation conditions, the degree of oxidation drops sharply when the particle size is increased above a given range. This critical size range varies typically between 200 and 500 pm depending on the oxygen content in the gas phase. For bomite, chalcopyrite and pyrite, the critical size range increases with increasing iron content in the mineral and with increasing oxygen content in the gas phase. The extreme case is observed for pyrite in pure oxygen, where there is no effect of the particle size on the degree of oxidization. Microscopical observations of the oxidized products show the influence of different factors on the mechanism of oxidation and fragmentation of the sulphide particles. Based on microscopical analysis and phase identification of the oxidized products, a model has been proposed for the oxidation and smelting of copper sulphide particles in suspended state. The mathematical model describing the sulphide particle oxidation is supported by the obtained results. Using this model, it is possible to describe the role of particular factors in the sulphide minerals oxidation.

Jan 1, 1992

By Karen Tempel

Newmont's Lone Tree Mine is located 30, miles east of Winnemucca in Humboldt County, Nevada. Starting in February 1994 a pressure oxidation circuit was commissioned to treat refractory gold ores. Gold is leached and recovered from the oxidized slurry in a six-stage carbon-in-leach (CIL) circuit. Lone Tree has been able to maintain tighter control' of cyanide addition and reduce cyanide consumption its CIL circuit through the installation of Degussa's Cyplus® CCS Cyanide Control System in the spring of 2000. 'The Cyplus® CCS, along with additional inputs' from plant sensors, has allowed tor a more efficient and effective control strategy over the manual control method used ,in the past. This paper documents the key aspects of the Cyplus® CCS installation; the development of the control strategy, and the benefits achieved from enhanced control.

Jan 1, 1998

By Michael K. Rhodes

A 120 tonne per day BacTech bacterial oxidation plant treating refractory gold concentrates for Gold Mines of Australia's Youanmi project in Western Australia commenced operation September 1994. This was the first commercial application of the BacTech process. A pilot plant trial on concentrates produced from Youanmi ore was carried out at BacTech's laboratory in Perth. Results and measurements from this trial were used by Signet Engineering Pty Ltd to design the commercial plant. This paper cover the results obtained from the piloting, their implementation in the plant design and the initial commissioning of the full scale plant.

Jan 1, 1995

By Derek J. Fray

The need for on-line sensors is outlined and it is demonstrated that the control of many processes is prevented by the availability of these devices. The use of solid electrolytes is described for the sensing of elements in molten pyrometallurgical phases. In the cases where there is no suitable electrolyte, the addition of a second phase of a compound containing both the element to be measured and the element whose ion is mobile in the electrolyte can be used. For the measurement of high concentrations of an element a method based on current measurement is proposed.

Jan 1, 1994