Search Documents

By D. A. Hayman, J. D. Steenkamp, G. M. Denton

Design of furnace containment systems can be based on one of two design philosophies: Insulating or conductive lining designs. In insulating lining designs, management of the compatibility between refractory materials and process materials (typically liquid metal and/or slag) is an important criterion for furnace design, and an important process parameter to control during furnace operation. In conductive lining designs, management of the integrity of the layer of frozen material (freeze lining) on the interface between the liquid process material, and the refractory lining, is important. For example in ferrochromium production, both lining design philosophies are applied. The work presented here discusses the significance of lining design philosophy in the context of ferrochromium production.

Mar 1, 2017

By C. Pichler, A. Ressler, D. Gregurek, A. Spanring

In order to improve the refractory lining life at one of the RHI key customer test procedures were developed within a two years collaboration project. In the first year of cooperation detailed refractory corrosion work in the rotary kiln with Ca-ferritic slag was performed. The main results of the second year of cooperation, reported in this article, involve a detailed testing work with nickel matte and pre-selected refractory brands which was performed in TBRC. A first part of this work was a complete chemical and mineralogical characterization as well as FactSage calculations carried out on provided matte samples. According to these results testing in the TBRC was realized at different process temperatures with several magnesia-chromite bricks. Based on the mineralogical investigation a high chemothermal load caused by sulfidic matte resulted in a deep reaching infiltration of the brick microstructure and partly corrosion of main brick components.

Jan 1, 2015

By V. I. Lakshmanan, R. Roy

"TiO2 is used in paints, plastics, rubber, paper, inks, textiles and other miscellaneous applications. The demand for the pigment grade Ti02 is growing at 3.0%/year on average and this invites the development of innovative and cost effective processes. The current processes are not designed to recycle the reagents and thereby discharge the effluents into the environment, causing an environmental concern.During this study, synthesis of TiO2 from an ilmenite concentrate was investigated using an innovative atmospheric mixed-chloride leach process. The solution purification was carried out using solvent extraction in two stages. In the first stage iron removal was carried out and in the second stage titanium was extracted. The strip solution obtained from the second stage solvent extraction contained the purified titanium and from this stream pigment grade Ti02 was recovered. The barren solution was used for reagent recovery and the regenerated leach liquor was recycled."

Jan 1, 2011

By Susumu Okabe

The Mitsubishi Continuous Copper Smelting/Converting Process employs an electric furnace for settling the slag/matte mixture formed in the smelting furnace. In order to improve the separation of slag and matte and to minimize power consumption, the design and the operating conditions of the electric furnace should be optimized. As the first step, numerical heat and fluid flow analysis of the melts was carried out based on the distribution of current density and Joule?'s heat obtained by the electric field calculation. For these calculations, 3-D body fitted coordinate system and a finite volume method were applied. Using the developed numerical model, the flow pattern analysis by pulse input of a tracer element was simulated. It was found that a strong thermal convection of the molten slag exists around the electrodes due to the concentrated Joule's heat generation in a small area just under the electrodes, and this strongly affects the flow pattern in the furnace. The calculation results were compared with the data obtained from 'a plant test.

Jan 1, 1998

By Xin Li, Hai-Xing Fang, Bing Xie, Hong-Yi Li

Chromium-containing vanadium slag (V-Cr slag) was obtained by an industrial smelting process of Hongge Ore, which is valuable vanadium-titanium magnetite to extract V and Cr in China. Sodium roasting thermodynamics of V-Cr slag in presence of oxygen were calculated to evaluate the reactivity of chemical compounds. Results showed that the oxidation of FeV2O4 was intensified in presence of Na2CO3 while the oxidation tendency of FeCr2O4 was far lower than that of FeV2O4. It was probably that reactions of impurities including Al2O3, SiO2 and Fe2O3 with Na2CO3 happened and the products can promote the oxidation of vanadium or chromium compounds in lower valence. Based on thermodynamic analysis, a two-step selective extraction process of vanadium and chromium was proposed. Extraction rate of vanadium was 88.6% while 7.0% for chromium in the first extraction step; extraction rate of 90.7% and 95.4% for vanadium and chromium, respectively, were obtained in the second step.

Jan 1, 2014

By M. A. Gimenes

The utilization of chlorination in extractive metallurgy and advanced ceramics areas has been widely investigated as a preparative route in order to obtain intermetallic compounds, which are used as precursors in the development of new materials and process. The major processes of decomposition of rare-earth ores use sulfuric acid and sodium hydroxide at high temperatures, however there is not much work concerning chlorination. In this work, a systematic study of the reaction between xenotime (REPO4), chlorine and carbon has been performed. Particular emphasis was on kinetic studies to establish optimized conditions for the reaction. The kinetics of chlorination of xenotime raw material by rare-earth elements/compounds has been studied over a temperature range from 600°C to 950°C. The influence on the rate of conversion of xenotime to RECl3 on temperature, partial pressure of chlorine, carbon content, and particle size were investigated. A global rate equation that includes these parameters has been developed. The results show that the process follows the unreacted core-shrinking model with a formation of a porous product layer. The powder X ray-diffraction technique corroborated this model showing clearly the patterns related to the formation of yttrium oxychloride (YOCl), indicating that the reaction mechanism involves the presence ofan intermediate step before the formation of lanthanide chloride.

Jan 1, 2000

By Elisa Alonso

Manufacturing firms that rely on finite resources have a stake in ensuring sustainable materials use. Higher material prices and uncertain material supply, consequences associated with scarcity, can be damaging to firms. Firms have a number of options to improve material sustainability including dematerialization, material substitution and recycling. However, these options require technological capability, capital investments and supply-chain infrastructure; firms may decide to make such investments only if material prices increase. Once decisions are made, the barriers and delays to implementing changes may harm firms. The impact of not reacting to changes in material supply on firms was examined for the case of different platinum-using industries. It was found that taking action is particularly important for firms when limited material availability leads to volatile market conditions. Industries can benefit especially if they ensure process flexibility and have options for changing their material use patterns.

Jan 1, 2010

By Thomas A. Post

The methodology of determining the optimum SX pumper-mixer system based on bench top, pilot, or small-scale solvent extraction systems, is demonstrated. The design of small-scale SX-plants is different than a full-scale plant. The difference is explained here. The use of dimensionless parameters Nh, Nq, and Np that describe the head, flow and power of the pumper is shown and how to use them for the scale-up. Additional data is required to determine the optimum operating range. Applications of this methodology were used to design well known currently operating SX plants. The emphasis on the optimization of hydraulic efficiency will be shown on examples, including how the hydraulic efficiency is affected when the throughput of the system goes beyond the design. Designs of all sizes of equipment will be shown which optimize the hydraulic efficiency.

Jan 1, 2003

By Adrian C. Deneys, David G. C. Robertson

"Fluid flow phenomena on the surface of a molten slag have been documented using video photography in a laboratory scale D.C. arc furnace. The flow on the surface of the slag appeared to be electromagnetically influenced. This was confirmed by varying the position of the anode, which changed the direction of flow on the surface of the slag. Temperature measurements in the bath also confirmed the change in the directional nature of the fluid flow induced by the arc.During some periods, solids were fed into the arc attachment zone (AAZ) down the center of the hollow graphite electrode. Significant movement of the arc around the basal annular surface of the hollow electrode takes place. The point of attachment of an arc on a hollow electrode was more variable than an arc attached to a solid graphite electrode. Video images showed that the solids were rapidly incorporated into the bulk of the slag. Temperature measurements confirmed the existence of a superheated slag layer at the slag-gas interface, which allowed the solids to be rapidly incorporated into the melt.This work has been conducted to study fluid flow, temperatures, and solid behavior during feeding, in the arc attachment zone of a D.C. arc furnace. The work also has relevance to optimizing furnace design for pyrometallurgical slag cleaning processes."

Jan 1, 1999

By Osarnu Inoue

In Mitsubishi Continuous Copper Smelting and Converting Process, smelting, slag-matte separation and matte converting are continuously carried out in series in three furnaces connected by launders. As a result of this operational configuration of the furnaces, influence of the change in operating condition in upper stream, such as variation of feeds in the smelting furnace, propagates to down stream with some delay. In order to achieve stabler operation, process control algorithm based on the dynamic characteristics of each furnace would be very effective. In this study, the dynamic process simulation model was developed for the smelting furnace. The model consists of two mathematical modules, i.e. the thermodynamic module and the mixing module. The calculation results using operating data obtained at Naoshima Smelter showed good agreement with the actually observed change in temperature, composition and flow rate of matte and slag at the outlet of the furnace. In addition, operation parameters such as reaction efficiency of oxygen and coal, dead volume of melts were estimated.

Jan 1, 1999

By Jacques J. Eksteen

Metallurgical accounting around toll treatment smelters pose a number of challenges. This paper reviews the requirements for good sampling practice, and how conflicting requirements for good furnace operation and design often makes reliable closure of the metallurgical balance tenuous at best. Typical physical causes of variance and bias will be identified. The propagation of error (in the form of variance) will be discussed for a copper smelter.

Jan 1, 2006

By Xiang Sun

Microwave heating has been used in numerous industrial processes due to its great advantages when compared with conventional heating methods. However, microwave heated products can be affected by non-uniform temperature distribution resulting from the mechanisms of microwave heating. To overcome this problem, a critical step is to have a temperature-time profile. In order to characterize and evaluate microwave heating effects, an accurate temperature measurement is needed. This paper discusses the possibility of applying several temperature measurement techniques in microwave processing. Both contact and non-contact methods are introduced and compared.

Jan 1, 2006

By Xingye Guo, Yeon-Gil Jung, James Knapp, Zhe Lu, Jing Zhang, Li Li

La2Zr2O7 is a promising thermal barrier coating material due to its low thermal conductivity and superior high temperature stability. In this work, Bilayer La2Zr2O7 and conventional 8 wt% yttria stabilized zirconia (8YSZ) coatings were deposited using plasma spray technique. Both singlelayer La2Zr2O7 and double-layer 8YSZ/La2Zr2O7 coating architectures were designed. Thermal cycling and thermal shock tests were used to evaluate coatings’ thermomechanical properties. All La2Zr2O7 coats were delaminated in the furnace cycle test in less than 20 cycles. This is because residual thermal stresses accumulated during thermal cycling. In the jet engine thermal shock (JETS) tests, the SCL La2Zr2O7 and DCL dense 8YSZ/La2Zr2O7 coatings were fully delaminated. In contrast, the DCL porous 8YSZ/La2Zr2O7 coating sample only partially delaminated on the edge. This is because of the porous 8YSZ layer provides strain compliance. The findings will help to propose efficient thermal barrier coating systems.

Jan 1, 2016

By Keizo Uematsu, Satoshi Tanaka, Nozomu Uchida, Anze Shui, Joaquin Lira, Cyril Lavelle, Midori Saito, Thierry Poirier

"Dispersed and flocculated alumina (non-spherical particles) slurries were prepared by pH controlling with HCL Spray-drying of these resulted in dimpled granules with a smooth surface and high density, and spherical granules with rough surface and low-density, respectively. Detailed characterization on granules and their compacts includes: SEM observation, density measuring (mercury porosimetry and Archimedes's Principle) and liquid immersion optical microscopy. Compaction of these granules originated a larger particles rearrangement in the samples made with the spherical granules than with the dimpled granules. This was verified through the orientation of alumina particles, which was pronounced in the compact made with the former granules.IntroductionOn immersing a ceramic powder in water, the surface usually acquires a charge by interaction with ionic species in solution. The charge is affected by pH and the electrolyte concentration of the water. 1 The dispersion in a slurry is achieved through the interaction of charges on the particle surface with the media. In the ceramic processing, especially in the process of casting, the dispersion of slurry has been one of the most important topics studied for many years. Recently the attention is paid on its role in the pressing. The granule characteristics are governed by the dispersion state of slurry. Takahashi et al2 , Tsubaki et al3 and Walker et al4 showed that the granules from dispersed slurry were dimpled and of high density, while granules from flocculated slurry were spherical and of low density. This variation in the granules characteristics should have a marked effect on the structure of compact.This paper presents the influence of the dispersion state of alumina slurry on the granules characteristics and also on the internal structure of compacts. Different dispersion states were elaborated by adjusting pH of the slurry. In this method, the particles are dispersed or flocculated only by the effect of surface charging, and thus some secondary effect such as the steric hindrance from an electrolyte dispersant is avoided. The characteristics of granules and compacts are examined with SEM, density measurements by mercury porosimetry and by Archimedes's Principle and liquid immersion optical microscopy. This novel microscopy provides various important information on packing structure of particles, such as their orientation. 5"

Jan 1, 2000

By John Jiang, Yeonuk Choi, Olivia Wang, Gus Van Weert

"As part of a general review of processing double refractory ores through Barrick Gold's autoclaves/CIL facility at Goldstrike, Nevada, blanking the gold cyanide adsorbing native carbon in the ore with hard (m.p. >55°C) paraffin wax was proposed. To avoid interference from other ore constituents in the exploratory testwork, commercial activated carbon was substituted for native carbon in the ore to establish the best conditions for de-activation of carbon with molten wax.IntroductionDouble refractory gold ores present two barriers to gold extraction. The first is generally a physical barrier: the gold is encapsulated or dispersed in a matrix which is impervious to the gold lixiviant. In most cases, including the Goldstrike deposit, this involves a pyrite or arsenopyrite matrix, although minor gold may also be dispersed in competent silica (quartz) or iron oxides. Gold can be rendered accessible by oxidative destruction of such sulphide matrices. At Goldstrike this is practised by roasting and autoclave oxidation (POX). It is the latter route to which this paper refers.The second barrier refers more correctly to gold recovery. Gold may be extracted from the autoclave oxidized solids with cyanide, forming a gold cyanide complex. One characteristic of this complex is that it adsorbs on graphitic surfaces. This behaviour is used advantageously on a large scale by gold millers, who use man made activated carbon particles to remove the gold from solution during leaching: the Carbon-In-Leach, or CIL process. The gold bearing carbon particles are larger than the ore solids and can be separately recovered by screening. Goldstrike uses the CIL technology to recover gold after autoclave oxidation."

Jan 1, 2012

By Miller, Geoffrey W.

The Ravensthorpe Nickel Project (RNP) flow sheet provides for the upgrading of Ni & Co in a size based beneficiation process prior to leaching. The upgrading effect on Ni and Co makes the beneticiation process a powerful addition to the flow sheet. Multiple linear regression (MLR) analysis based on 351 individual batch tests, 52 large scale composites and 21 pilot plant tests has been used to successfully model beneticiation product grade, recovery, upgrade and mass recovery. Statistically, 83% and 96% of the variability in nickel recovery and nickel product grade respectively was accounted for. Algorithms have been developed for Ni, Co, Mg, Al and Fe, which represents the revenue and operating cost factors for the process. The algorithms have subsequently been applied to the resource model, allowing prediction of elemental grade and recovery for the development of the mine schedules based upon these parameters and not head grades alone. This has allowed optimisation of the mine schedule for improvement to the project's NPV. Keywords: Ni Laterite, Prediction, Multiple Linear Regression, Beneficiation

Jan 1, 2004

By Autumn Fjeld

The filling and solidification of an industrial scale composite casting has been simulated to investigate the re-melting of the outer shell material during casting. Production of a composite requires a two-step casting process which includes centrifugal casting of a hard outer shell material and subsequent conventional ingot casting of a tough core material into the shell-mold assembly. During casting of the core, a thin layer of the shell material re-melts and mixes with the core material producing a bonding layer of intermediate composition. The present numerical model employs the volume of fluid method and an enthalpy-porosity technique to couple the filling of the core material and re-melting of the shell material. The interface between the two materials is tracked and can be used as a guide to examine the extent of melting and, to some degree, mixing of the two fluids and species diffusion.

Jan 1, 2008

By Ahmad Ghahreman, James McNeice

Separation of rare earth elements (REE) is often achieved by acid leaching of mineral concentrates followed by subsequent solvent extraction (SX), to purify individual rare earth metals (REM). Cerium, the most abundant REE, is usually the largest component of these ores. Demand for less prevalent REE, such as praseodymium and dysprosium; have led to a market saturation and price collapse of cerium. One method of improving the economics of REE separation is to remove cerium from solution prior to SX. This is accomplished via the oxidation of cerium (III) to cerium (IV), which precipitates as cerium hydroxides. This study probes the efficacy of four oxidants; hydrogen peroxide, sodium hypochlorite, potassium permanganate, and Caro’s Acid with the goal of improving cerium removal whilst minimizing REE and reagent losses. The effect of oxidant type and dosage, pH, cerium concentration, and temperature on the kinetics of the process will be discussed.

Mar 1, 2018

By L. M. Abrantes, A. P. Paiva

"A brief review of some innovative methods for the direct recovery of metals from loaded organic phases is presented; emphasis is given to electroreductive stripping and cementation, which are described and illustrated by examples: of current research. The recovery of silver using a two-phase electrolysis - by direct application of an electrical potential to a mixture of a metal loaded organic phase· containing Cyanex 471X, obtained by solvent extraction, and a stabilized sodium thiosulfate solution - is more extensively discussed. The overall efficiencies are analyzed and compared with data obtained by conventional stripping procedures. Some preliminary results achieved for the recovery of the precious metal using galvanic stripping, applied directly to similar organic solutions and involving zinc and iron powders as reducing agents, are also evaluated.Introductory ReviewThe application of hydrometallurgical methods to the recovery of metal values from ores and concentrates has been receiving a growing interest, either from researchers or from the mining industry [1].For the concentration / purification of the relatively low concentrated metallic solutions resulting from the leaching of those raw materials, solvent extraction (SX) is a well established technique [2]; the loaded organic solvent is then conventionally contacted with a suitable aqueous solution, the metal in its final form being usually recovered from this solution by electrowinning.As an efficient and / or selective stripping is sometimes difficult to achieve, depending on the specific characteristics of the system under consideration, some alternative procedures have been analyzed in order to overcome this problem. One of the chosen routes, mainly developed by Hirai and Komasawa, is to promote the reduction of the desired metal species in the organic phase, in such a way that the stripping stage becomes feasible; for the selective stripping of vanadium from a solvent containing a mixture of vanadium and molybdenum, the authors successfully used reductive [3], electro-reductive [4,5] and photo-reductive [6] techniques. The two latter methodologies have also been applied to the recovery of europium from a solvent containing europium, samarium and gadolinium [7,8].However, further processing is necessary to recover the metal in its solid state; therefore, methods causing the direct reduction of the metal species in the organic phase to their fmal metallic form would be of interest, as an intermediate step would be avoided"

Jan 1, 1997

By Vinay Kumar

The present investigation describes R & D studies carried out for recovery of copper from the sulfate solution expected from the leaching of e-wastes in presence of minor constituents such as cadmium, zinc and nickel using solvent extraction process. In order to extract copper in continuous mode in mixer settler unit (MSU), basic studies have been made to optimize the experimental condition using 5%LIX84 in kerosene. Subsequently, the solvent extraction of copper was made in MSU maintaining leach solution flow rate 4.0 L/h and A/O ratio 1. The results showed complete extraction (~97%) of copper in three stages at A/O ratio 1 from the aqueous solution containing 1.98g/L Cu at pH 1.91 in presence of impurities. Loaded metal was completely stripped after scrubbing with 10% sulfuric acid in two stages. The stripped solution could be used for metal/ salt recovery by electrolysis/ crystallization.

Jan 1, 2010