Search Documents

By Cui Wang, Qian Li, Kexin Jiao, Haibin Zuo, Jianliang Zhang

Abstract：A rational cooling water system is the assurance for long campaign life of blast furnace．In the paper, the heat transfer of different furnace period and different furnace condition based on the water quality characteristics were analysed, and the reason of the heat flux over the normal from the hydrodynamics was analysed. The results showed that, the vapour-film and scale existence significantly influenced the hearth heat transfer, which accelerated the brick lining erosion. The water dynamic characteristics of the parallel inner pipe or among the pipes were the main reason for the abnormal heat flux and film boiling. As to the reasonable cooling water flow, the gas film and the scale should be controlled and the energy saving should be considered.

Jan 1, 2015

By V. Baltazar

The behaviour of arsenic and antimony during copper electrorefining was studied in order to identify the conditions under which good quality copper cathodes could be produced from anodes with high levels of these impurities. Examination of the effect of current density over the range 21 to 37 mA/cm2 indicated that the relative amounts of As and Sb entering the electrolyte affected the onset of passivation. When the ratio of As/Sb entering the electrolyte was greater than 2, the anodes showed no sign of passivation even at the highest current density; when the ratio was less than 2, the anodes passivated at 37 mA/cm2. Cathode analyses showed that anodes with an As/Sb dissolution ratio less than 2.0 tend to produce cathodes of inferior quality even at normal current densities (25.7 mA/cm2). The criterion of a minimum As/Sb dissolution ratio of 2.0, and mathematical correlations for the distribution of As and Sb between the electrolyte and slime developed in a previous study, allow the calculation of the maximum allowable Sb level in en anode for a given As concentration. Analyses of plant data at the CCR Division of Noranda Inc. for the last four years of operation have demonstrated that the use of this as a quality control tool has allowed the quality of copper cathodes to be maintained despite a significant increase in the average Sb levels in anode receipts.

Jan 1, 1987

By M. Jennings

In 1987, Echo Bay discovered a major silver/gold ore body at their McCoy property in Nevada, and quickly made a decision to build a 5000 tpd mill which was expanded during the design to 7500 tpd. Since the ore reserves consisted of cyanide leachable oxide as well as sulfide, the plant flow sheet involved an oxide leach, a gravity circuit, and lead sulfide and a pyrite sulfide recovery by flotation. The paper describes the process development, equipment selection, plant design and the startup of the oxide treatment.

Jan 1, 1990

By Munyaradzi Kwatara, Ron Schonewille, Edgar Peek, Juzer Tayabally

"The potential recovery of nickel from a South-American saprolitic laterite ore using the segregation roasting technique was investigated. The ore was heated to temperatures that ranged between 900 and 1 000°C in a rotary kiln. In all the tests, the laterite ore was first mixed with a predetermined amount of calcium chloride and either coal or coke. By varying the temperature, calcium chloride and reductant in the different tests, a preliminary set of optimal conditions was established for the specific laterite ore that was tested. A combination of chemical analysis and electron-probe-micro-analysis (EPMA) were used to determine and evaluate the effectiveness of segregation roasting on the recovery of nickel. The present paper describes the test procedure and the results that were obtained.IntroductionIt is known that laterite ore resources account for an estimated 72% of the world's nickel resources, with sulfide sources accounting for the remaining 28%. Yet sulfide resources account for 58% of the world's primary nickel production while laterite resources account for the remaining 42% [I]. There are numerous reasons for this discrepancy, but the most important one is the mineralogical and compositional complexity that is associated with laterite ore deposits. For example, this complexity currently offers only limited opportunities for upgrading, thereby creating capital intensive whole ore processing facilities. It then follows logically that the identification and application of a low-cost processing option for the treatment of laterites could potentially open up an opportunity for exploiting these vast untapped laterite resources.To this end, a preliminary screening investigation was initiated by Xstrata Process Support to evaluate the potential application of the so-called (nickel) segregation process as a unit operation that could potentially be integrated into a laterite processing flow sheet. Laboratory bench tests were performed on this segregation process and this paper details some of the findings from this preliminary investigation."

Jan 1, 2011

Novel techniques were developed to obtain samples from and make measurements in the shaft of the flash furnace at the Kalgoorlie Nickel Smelter. The data obtained was used to validate mathematical models of the burners and the reaction shaft. Particle, gas and wall temperatures were measured along with the oxygen potential of the molten particles. Collected particles were characterised by sizing, chemical analysis and optical microscopy. The region of the shaft immediately beneath the burner where the rate of change was most rapid received special attention.

Jan 1, 1993

By Richard D. Hagni

Reflected light microscopy is routinely applied to the study of ore minerals and textures in polished sections prepared from a wide variety of ore specimens. With the increasing interest in environmental problems, the important role of the reflected light microscope in the precise phase identifications and the determination of the textural relationships between those phases needs to be recognized. Among other environmental applications, the microscope has been applied to the recognition of lead smelter particles from remote collect sites in Missouri and those particles have been compared to dust particles from specific localities at the nearby lead sinter plant and lead blast furnace. Dust from a secondary copper refinery has been studied for its mineralogy. Soils in the vicinity of a Missouri lead smelter have been studied for their mineralogy in preparation to the clean up of those soils. Electric arc furnace (EAF) dusts, recently classified as hazardous waste by the EPA, have been examined for their mineralogy and textural intergrowth in order to better evaluate proposed metallurgical treatment procedures to render the dust non-hazardous. The initial products from experimental metallurgical treatment of EAF dusts also have been studied to aid in determining the effectiveness of those treatment procedures. Refractory gold sulfides that have been roasted in the presence of lime to retain environmental objectionable sulfur and arsenic while recovering the gold have been studied by RLM to determine their mineralogy, porosity, and permeability for cyanide leach solutions. These case histories illustrate the applicability of ore microscopy to the study of problems related to environmental concerns.

Jan 1, 1995

By Frank M. Kimmerle

Spent Potlining (SPL) contains recoverable chemical elements (C, F, Na and Al) which are lost in stabilization or immobilization processes primarily aimed at eliminating cyanides and reducing leach rates of soluble fluorides prior to landfiling. They can be recovered in a variety of mineral forms for recycling in the aluminum industry and elsewhere. Alcan has developed a cost-effective hydrometallurgical route, combining a number of proven unit processes to destroy cyanides, recycle the chemical values and provide a zero-discharge process. Pilot plant studies of this Low Caustic Leach and Liming (LCL&L) Process prove that the fluoride scan be converted to acid grade fluorspar, while the sodium and aluminum are recovered as a sodium aluminate and caustic feed to the Bayer Plant operations. The remaining brick and carbon fraction constitutes a high ash solid fuel which meets TCLP leach criteria and whose reduced sodium content enhances its value as a chemical reducing agent.

Jan 1, 1994

By Chi-Ming Chang

Alloy powders are commonly used in the purification of zinc sulfate solutions for use in standard electrowinning practice. The primary goal of this research was to study the use of zinc-lead alloys for similar reactions in the galvanic stripping of impurities from organic solutions. The effects of various parameters on the electrochemical behavior of commercially produced zinc-lead alloy powders were determined. A qualitative evaluation and summary of the influence of the more pertinent parameters on iron removal from di-(2-ethylhexyl) phosphoric acid (D2EHPA) by galvanic stripping is given. Water concentration, oxygen content and reaction temperature were the principal factors affecting the reaction rate and process efficiency. Activation energies were also calculated and indicated that the reaction changes from chemical to diffusion control .with increasing temperature in the range of 35" to 45°C. The results showed that zinc-lead alloy gave faster reaction rates with less sensitivity to process variables than SHG zinc as a reducing agent for galvanic stripping. The role of lead could be as cathodic sites for the reaction which enhances the zinc dissolution or anodic half reaction. The morphology of the zinc-lead alloy surfaces, before and after the reactions, supports this assumption.

Jan 1, 1998

By D. R. Spink

A partial desulfurization roasting (PDR) technique has been developed for use on zinc concentrates whereby the sulfide sulfur associated with the iron content is selectively removed over a very short residence ?time in the roaster. The resulting PDR product is then leached for the selective removal of the iron. The resulting leach restdite is an upgraded zinc sulfide concentrate which has a very low iron content. The up-graded zinc concentrate can be subjected to a conventional dead roast without formation of deleterious zinc ferrite so that hot acid leaching and jarosite (or other) iron precipitation steps are obviated. Examples are presented for the treatment of three very different types of zinc concentrates.

Jan 1, 1990

By N. Can

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

Jan 1, 1999

By William J. Pardee, Michael A. Shaff

"Deeper materials science knowledge from mathematical models and in situ material property sensors will be exploited in next generation factory process controllers to improve productivity and quality. These intelligent control systems will accelerate productivity growth and materials science application through the ease with which they can be modified to accept new materials knowledge and sensors. Carbonization of resin matrix carbon fiber composites, specifically, is a violent solid state chemical reaction with large stresses due to gas pressure, matrix shrinkage, and differences in thermal expansion. The matrix strength falls sharply, then rises again during the process. At least two competing reaction paths are important; the first cleaves methylene bonds, reduces toughness, density and stiffness; the second reforms those bonds, ultimately resulting in aromatic ring condensation that increases density, strength, and modulus. Since these reactions have different temperature dependencies, one can expect to shift the process towards the second path by changing the heating rate, but that change must be accomplished without producing macroscopic interlaminar crack growth. To accomplish this, we employ gas sensors to infer matrix chemical state and acoustic emission to identify microstructural changes and to recognize brittle fracture. The latter does not prevent delamination, but is important in testing models for the causes of delamination and in improving the processing cycle. This paper describes a control strategy to accelerate the process while still lowering the risk of failure.IntroductionDeeper materials science knowledge from mathematical models and in situ material property sensors will be exploited in next generation factory process controllers to improve productivity and quality. These intelligent control systems will be more easily modified to accept new materials knowledge and sensors, thus accelerating productivity growth. Such a control strategy for carbonization control is described below.Carbon-carbon composites are time consuming and costly to manufacture. Processing methods have been developed empirically and are usually very conservative because the process often fails when any change is made. Apparently minor changes in materials or geometry can produce failures that are difficult to diagnose and correct. We will describe below several essentially unavoidable sources of variability. These are best dealt with by applying materials science to adapt (i.e., closed loop control on materials properties) the process in real time to reduce the effect of unavoidable model idealizations, material variability and environmental noise. The most critical issue in control of the carbonization process control is avoiding catastrophic delamination. The strategy developed below makes use of a priori materials knowledge and real time sensors to accelerate the now very slow process without destroying the material, and without requiring unreasonable resources to determine the statistical properties of the material."

Jan 1, 1988

By Georgette Smits

The gun-sprayed refractory lining of electrothermal furnaces used for the manufacture of carbon disulphide from liquid sulphur and charcoal at between 800 and l000°C are severely attacked during the process. A mineralogical study of samples of eroded refractory material disclosed that carbon disulphide had penetrated the lining, causing the precipitation of sulphides and carbon, and the decomposition of mullite, a major constituent of the lining, to corundum and amorphous silica. Calcium, iron, titanium, and chromium are undesirable cations in a refractory that is used in furnaces for the production of carbon disulphide, since they react readily with this substance. A series of tests, in which samples were exposed to different amounts of carbon disulphide for various residence times and at different temperatures, was carried out with eight types of aluminosilicate-based castable and brick refractory materials, to compare their resistance to attack by carbon disulphide. Mineralogical investigation of the test cores showed that castable refractory materials are unsuitable for this type of process because of the presence of calcium aluminates and other impurities in the cement. Of all the refractories that were tested, a mullite brick of low porosity, containing a minimum amount of impurities, appeared to be the most suitable for use in this type of operation.

Jan 1, 1989

By Garry W. Warren

The brass foundry industry produces a significant amount of waste sand containing Cu, Zn and Pb which is often classified as a hazardous waste due to Pb content. The potential application of a hydrometallurgical process to treat the sand by extracting metal values and thus detoxifying the material has been investigated. The process involves leaching of metal values followed by cementation. The emphasis of this investigation was on the leaching step, although some preliminary cementation experiments have been performed. In order for any alternative treatment scheme to be successful, the smaller size fractions of the sand must be addressed. Experiments have been performed on five individual size fractions using various lixiviants HCI, acetic acid and HCI/NaCI. Cu extraction was found to be slower than either Zn or Pb. Results obtained in this investigation indicate that copper is present in two forms, an oxide form which dissolves rapidly and is insensitive to the level of oxygen, and a less soluble form, probably metallic which dissolves more slowly and requires an oxidizing agent. The presence or absence of oxygen had no influence on the rate of Zn dissolution indicating that zinc is present mostly in oxide form. Toxicity Characteristic Leaching Procedure (TCLP) tests showed that residues could be produced which meet the toxicity limit for lead. Preliminary cementation experiments have also demonstrated the feasibility of Cu and Pb recovery.

Jan 1, 1991

By Jerome Feinman, Sven O. Santen

"The principles involved in the generation and application of plasma energy are reviewed briefly and the major developments in commercial and semi-commercial primary metal and alloy production are described and discussed in broad outline, with emphasis on present performance and future potential. New concepts in the application of plasma energy in primary operations are described with emphasis on the expected advantages over conventional technology and the problems that have to be solved to enable effective implementation.IntroductionThe use of plasma energy in industrial processes is generally considered to have started in 1905 with the operation of the Birkeland process for nitrogen fixation for fertilizer production. Although it seems logical to apply plasma energy to metallurgical processes, which also usually require considerable energy at high temperature levels, serious development work along these lines did not begin until the early 1970's. The reasons for this hiatus are associated in part with recognized difficulties in applying plasma energy in processes involving tonnage quantities of solids in severe industrial environments and the delicate nature of the earlier plasma generators. Another, and perhaps overriding factor, is the fairly steady improvement in efficiency and economy of most primary metal producing processes by conventional developments and modifications through the 1950's and 60's. Examples of these evolutionary changes include burden preparation and fuel injection in blast furnace applications and prereduction treatments in ferroalloy operations. By the end of the 1970's most primary metal producing processes had been optimized close to the limit, at least in terms of those operations that were able and willing to implement the developed improvements. In this context, plasma energy offered the possibility to achieve further significant improvements in primary operations where conventional means were exhausted."

Jan 1, 1988

By Patrick Clark

As part of the Mine Waste Technology Program (MWTP), a large-scale column test using bacteria and a sulfide ore was conducted at McClelland Laboratories, Inc., in Sparks, Nevada. Four technology providers participated in this demonstration. A mining company in Nevada provided the sulfide ore, process effluent and make-up water. A process effluent column, a chemical oxidation column, and the four biological treatment columns were set side by side on a test pad outside the laboratory building. The process effluent and chemical oxidation columns were used for experimental control. The goal of this project was to evaluate the viability and feasibility of using these biodegradation technologies to reduce the cyanide to the regulatory level of 0.2 parts per million (ppm) within an acceptable timeframe and with low operational costs. The column testing began on December 3, 1998 and operated until May 17, 1999. One technology provider reached the regulatory level within the 158 days. The remaining three biotechnology columns were approaching the regulatory limit at completion of the demonstration. The MWTP is funded by the U.S. Environmental Protection Agency (EPA) and is jointly administered through an interagency agreement with the U.S. Department of Energy (DOE).

Jan 1, 1998

Direct electrowinning is an electrochemical process which has been developed for the extractive recovery of copper from dilute, acidic leach solutions. In passing through a thin particulate coke cathode. copper is reduced and electrodeposited in a thin layer forming a solid copper-coke sheet. The product is melted in a furnace to separate the coke, then the molten copper is fire refined to produce a salable product. A description is given of a prototype unit which is designed to treat 20 gpm leach liquor and recover over 100 pounds of copper per day. Economic analyses show that in a commercial facility producing about 25.000 TPY copper.*the direct electrowinning process has lower overall cost than either conventional iron-cementation or the newer liquid ion exchange-electrowinning when the leach liquors contain less than 2 grams per liter of copper.

Jan 1, 1976

By Vanessa M. Torres

Cia. Vale do Rio Doce is currently developing Niquel do Vermelho Project. The laterite deposit is located at Carajas Mineral Province at less than 15 km from Sossego Copper Project, scheduled for start-up in 2004. The available infrastructure, includes paved roads, large capacity railroad and port complex owned by CVRD, power supply and good quality water. The project was evaluated in the past for ferronickel production. In the late 1990s, CVRD switched its attention to investigating the usage of pressure acid leaching. The combination of good metallurgical behaviour for pressure acid leach (PAL) process route with reasonable mineable grades, and existing infrastructure justified the start of engineering studies in 2002. The project approach at the engineering phase is based on the dual objective of minimizing risks while maximizing project profitability and value. CVRD is currently completing the Niquel do Vermelho prefeasibility study. This paper outlines the main outcomes of the study and future perspectives for the project.

Jan 1, 2004

By Ted H. Eyde

Natural Zeolites are a less expensive and in certain applications a superior alternative to organic ion exchange resins. Mining and metallurgical waste streams are difficult to treat because the effluents which contain potentially valuable heavy metals such as copper, lead, and silver are often highly acidic and contain significant quantities of suspended solids. Under rigorous operational conditions, certain natural zeolites can remove the metals, which if desired can be recovered by either elution or conventional smelting techniques. There are significant differences in cation exchange rate, selectivity and capacity as well as resistance to either high or low pH, blocking cations and tolerance to elevated or depressed temperature and pressure not only between different zeolite minerals but between the same mineral from different deposits. Applying natural zeolites to the treatment of mining and metallurgical waste streams depends on matching the specific zeolite to the effluent by characterization of the zeolite minerals.

Jan 1, 1993

By Daniel C. McLean

Extraction data for Cu, Zn and Fe were obtained from 4.5" and 10" columns using massive sulfide ore and natural acid mine water. The purpose was to determine if recycling of solution through the column would produce leach liquors of 4 g/l Cu and Zn at extraction rates of 1 g/l per pass at typical flow rates of 0.002 to 0.006 gpm/sq.ft. Test results exceeded expectations. Cu and Zn concentrations of 4 g/l were obtrained within 4 to 6 cycles. Concentrations greater than 6 g/l Cu and 8 g/l Zn were reached within 10 cycles. Concentrations of greater than 40 g/l of Fe and free sulfuric acid were obtained with no decrease in biological activity being observed. No reagents were used.

Jan 1, 1995

By John J. Mahoney, George P. Demopoulos, Matthew T. Bohan

In recent times processing of arsenic-laden complex ores and heightened awareness of the detrimental health effects of arsenic has put an increasing burden on metallurgical operations to remove arsenic from processes for disposal in an environmentally stable form. At present, arsenic is removed and prepared for storage by precipitation of insoluble secondary arsenic-bearing minerals. It has been suggested that Ca(II)-Fe(III)-As(V) phases resembling the natural mineral yukonite, under certain conditions, may have a role in controlling arsenic pore water concentrations in arsenical waste storage facilities. In this study, a previous synthesis method of yukonite (Ca3Fe5(AsO4)4(OH)9⋅4H2O) is revisited and new solubility/stability data is presented based on a modified method.

Jan 1, 2014