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By T. T. Chen

A mineralogical study of copper anodes and copper anode slimes was carried out to elucidate the silver phases present and the behaviour of silver during copper electrorefining. Most of the silver in the anodes is in metastable solid solution in the copper metal. As the copper dissolves, silver also dissolves, but is rapidly removed from solution by a variety of reactions. Some of the silver is precipitated as Ag by cuprous ions and some is precipitated as a complex CU-Ag-Pb-As-Se oxidate phase. Much of the silver, however, reacts with copper selenides to form, progressively, (CU,Ag) 2se, AgCuSe and Ag2se. The reaction commences at the periphery of the selenide grains and progresses inward; the result is commonly a silver-rich species on the outside of a silver-deficient core. Slimes collected periodically throughout the electrorefining cycle show a progressive silver enrichment of the selenides. Traces of Ag2Te also may be present, but the telluride seems to J:ie a rare constituent of most raw anode slimes.

Jan 1, 1989

By Willy Persson

A common feature of the kinds and amounts of impurities present most pyrometallurgical, processes is injection of oxygen to, remove various in the feed. The degree of success of a specific process step relies critically on control of the instantaneous oxygen potential/oxidation stage, throughout the step as well as upon termination of the step. This will, for instance, determine the distribution of impurities between metal and slag. As long as the operation is perturbation free -detailed analysis of all additions and application of advanced models often yield satisfactory control means However, a pyrometallurgical process is seldom free from disturbances, which reduces the accuracy of the static models and leads to inconsistencies in scheduled route might be uncontrollable changes in quality and quantity of feed, operator interventions and shift changes, timing of cranes, lining wear and accretions etc. The implementation of dynamic, control to correct for disturbances and, more generally for process optimization, requires continuous on-line information on, the actual status of the process. The implementation of sensors for continuous process monitoring, e.g., as regards the instantaneously prevailing oxygen potential or oxidation stage, has been hampered by the highly aggressive environment in smelters; This is. where remote-sensing techniques based on optics and spectroscopy, have proven to form invaluable, tools towards the realization of dynamic production control. Since about 15 years Semtch has developed and industrialized a remote-sensing technology, based on ,optics and spectroscopy, for continuous on-line process monitoring and production control of various pyrometallurgical processes. The presentation will discuss applicability aspects with examples and experiences from installations and tests in ferrous and non-ferrous industry. Keywords: Applied spectroscopy, Metallurgy, Process monitoring, Production. Control

Jan 1, 2003

Microstructural investigation has shown that grain splitting or deformation banding ( DB ) develops progressively with increasing strains during cold rolling. Of particular significance to simulating texture development in cold rolled BCC polycrystals is the operation of higher order slip systems other than 110 and, the occurrence of DB in the rolling plane since the latter allows a new relaxation of the shears. Deformation banding ( DB ) model includes grain subdivision in the rolling plane and applies the Relaxed Constraints ( RC ) mechanism for the other shears. An energy criterion for deciding whether deformation banding occurs or not has been postulated, referred to as Deformation Banding Criterion ( DBC ). This paper reports the results of the investigations into the effects of different slip systems, i.e., those based on 110, 112 and 123 slip planes and their combinations using RC, DB and DBC models, in developing simulated BCC rolling textures.

Jan 1, 1999

By Jochen Petersen

Design and operation of heap leach processes are still largely based on,operator experience and rule of thumb. Although considered a low-cost, low-tech route for mineral extraction, the underlying physical, chemical and biological processes are actually rather complex. Numerous heap leach models have been devised over time, but the majority of these tend to simplify the true process and are of limited use in practise. The modelling approach presented here combines the more conventional reaction-diffusion model with models accounting for equilibrium reactions in solution, bacterial growth kinetics, complex reactions schemes, gas flow, heat conservation, etc. One particular model application is discussed in the context of developing a novel high temperature heap leach processes using thermophile micro-organisms. The complexity of processes such as this can only be appreciated with the aid of a systematic model. For the designing engineer an accessible, personal computer based model should be an indispensable tool for the design and optimisation of efficient heap leach operations.

Jan 1, 2002

By Zhigang Zak Fang, Michael L. Free, Jaehun Cho, Syamantak Roy, Amarchand Sathyapalan

Leaching characteristics of impurity removal from the Upgraded Titania Slag (UGS) using hydrochloric and boric acids has been investigated. Specifically, this study has focused on removal of iron oxides from the UGS that has been reduced by hydrogen gas and magnesium at 750oC for 5 hours. Reduced UGS is mainly composed of titanium hydride and impurities like iron oxides, silicon oxide, aluminum oxide, and magnesium oxide. The concentration of hydrochloric and boric acids and the leaching temperature have been chosen as the prime variables to identify the optimum conditions and leaching characteristics for removal of iron oxides. It was observed that under the constraint that 1 wt % of titanium hydride loss is the maximum amount tolerable, 0.1M HCl with 1M boric acid and 90oC are the most effective parameters for iron removal from the reduced UGS. Also, the overall rate of reaction seems to follow interfacial reaction controlled kinetics. The calculated activation energy of the reaction is 73.90kJ/mol.

Jan 1, 2016

By Norbert Patzeh

The demand for nickel is growing and will continue to do so for the foreseeable, future. This will make the construction of new leaching and smelting plants necessary. This paper described a number of possible alternative processes. The first projects with new technology are currently undergoing trials and feasibility studies. Experience from other industrial sectors and from existing plants is being incorporated into these investigations. The question is, to what extent the old nickel producing concepts will continue to be applied in the future. Keywords: Latcritc, rotary kiln, cyclonc rcactor, dust processing

Jan 1, 2004

By B. C. Tripathy

The effects of alkali metal ions Li+, Na+, K+and transition metal ions Cr3+ and Mo6+ on the cathodic current efficiency, deposit quality, crystallographic orientations, deposit morphology and polarisation behaviour of the cathode during nickel electrocrystallisation on stainless steel substrate from aqueous sulphate solutions containing boric acid were investigated. The alkali metal ions had virtually no effect on the cathodic current efficiency, deposit quality, crystallographic orientations, deposit morphology and cathodic polarisation. On the other hand, there were significant variations in the current efficiency and deposit characteristics when Cr3+or Mo6+ were present in the electrolyte. Current efficiency decreased by more than 10% even at lower concentrations (> 100 mg/L). Similarly purity of the deposits was affected by the presence of either of the metal ions. In the presence of Cr3+, there was progressive shifting of the nucleation potential of nickel towards more negative values, whereas, in the case of Mo6+the nucleation potential shifted initially towards positive values in the concentration range 2-40 mg/L, but then towards negative values when its concentration exceeded 40 mg/L.

Jan 1, 2003

By Sridhar Komarneni

"Microwave-hydrothermal processing is a novel technique which combines the conventional hydrothermal processing with microwave field and we previously showed for the first time, that ceramic powders can be rapidly produced by this technique. This review paper deals with the synthesis of unary oxides such as Fe203, Ti02, Zr02, etc., binary oxides such as BaTiO3, SrTiO 3, PbTiO 3, SrZrO 3, KNbO3, etc., and ternary oxides such as NaTi2 (PO4)3 and pyrochlore phases of Pb(Mg1/3Nb2/3)O3, Pb(Zn1/3Nb2/3)O3 etc. and metal powders such as Cu, Ni, etc. below 195°C. This method can be adopted to the synthesis of a large variety of powders by the appropriate control of pH, Eh, temperature/pressure and concentration of chemical species. The main advantages of this method compared to conventional hydrothermal processing are (a) it increases the kinetics of reaction by one to two orders of magnitude, and (b) it can lead to novel phases especially those with layered structures.IntroductionConventional hydrothermal processing is a well-established synthesis technique which has been extensively used in the preparation of fine ceramic powders [1-5], large single crystals [6-8] and massive cement blocks [9]. Technologically important ceramic powders such as BaTiO 3, Al203 etc. made by the hydrothermal process are now commercially available. Although there are numerous methods for materials synthesis, hydrothermal method is truly a low temperature and environmentally benign process. For example, ZrSi04 (Zircon) which is extensively used in ceramic industry can be prepared hydrothermally at 150·C [10] compared to sol-gel or solid-state method [11,12] which require a temperature of about 1000·C. The hydrothermal method is environmentally benign because hydrothermal reactions are carried out in closed systems at low temperatures and the contents can be recovered and recycled after cooling to the ambient conditions. One of the disadvantages with any low temperature processing method is slow kinetics. For this reason we have combined the hydrothermal method with microwaves to enhance kinetics and we named this method as ""Microwave-hydrothermal"" processing [13- 16]. Although the combination of microwave and hydrothermal techniques has been used in the past few years to dissolve all kinds of inorganic (e.g. alumino silicate rocks) and organic materials rapidly for chemical analysis, we were the first to show its potential value for the synthesis of various ceramic powders [13-16]. In this paper, I show that this novel method is applicable to the synthesis of all unary, binary and multinary oxides by the appropriate control of pH, Eh, temperature, pressure and concentration of chemical species. In addition, this method is also found to be useful for the preparation of metal powders."

Jan 1, 1994

By Qian Li, Haiyan Leng, Kuo-Chih Chou, Haoyuan Xiao, Zhigang Yu

Magnesium borohydride and Magnesium alanate were synthesized by mechanochemical metathesis reaction. The thermal decomposition behaviors of Mg(BH4)2-nMg(AlH4)2(n=0.5,1) systems were investigated as potential hydrogen storage materials. The results showed that the systems started to desorb H2 at 120 ℃ and desorbed 3.9 wt. and 4.9 wt.% H2 below 300 ℃ when n equals 0.5 and 1, respectively, while individual Mg(BH4)2 started to desorb H2 at 250 ℃ and desorbed only 0.82 wt.% H2. Because of the exist of the Mg(AlH4)2, the isothermal desorption kinetics of Mg(BH4)2 in the Mg(BH4)2-0.5Mg(AlH4)2 systems was 50% faster than that of pristine Mg(BH4)2. In addition, the re-hydrogenation rates also increased 49.4% and 37.9%.

Jan 1, 2015

By Chai Liyuan

This paper focused on the preparation of porous ceramic pellets for microorganism carriers. A new method for the process was developed using simple gel-casting and bubble-in-water-in-oil type of multiphase double emulsion. The globules, consisting of a foamed sepiolite slurry suspension, were dispersed and consolidated in spherical shape in liquid paraffin as gelation progressed. The green pellets were sintered at 1100°C. The influence of surfactants, extension ratio and impeller revolution rate on the process and characteristics of the pellets was investigated. The pellet size was in the range of 1~4mm and determined directly by impeller revolution rate. The fine cell diameter of porous ceramic was in the range of 100~500m and the micropore diameter was less than 5m. The inner macropores were interconnected and extend to the external surface. It is impossible to analyze a result by SEM micrographs and digital camera.

Jan 1, 2006

By Leonard J. Friedman

The contact process for the production of sulfuric acid has been used commercially since before the turn of the century (1880?s), and rapidly replaced the chamber process after the development of vanadium catalysts in the early 1900's (1910's - 1920's). Plant size has increased from a few tons per week to single train units in excess of 4,000 tons per day. Much of the history of the contact process is in the minds of the few remaining early process pioneers that started in the industry in the 1920's and 1930?s, and in sulfuric acid industry books published in 1921, 1925, 1936, and the last Deucker and West in 1959. Since those not familiar with history are doomed to repeat the failures and mistakes of the past, this paper includes a brief history of the contact process along with the history and development of equipment and materials in each equipment area of the process. The main focus of the paper is to present the development and analysis of equipment and materials in the contact section of the sulfuric acid plant - from the dry tower to stack.

Jan 1, 1999

By Jens Kristen Laursen

In 1999, Molymex S.A. de C.V. (Molymex), Mexico. (a company wholly owned by Molibdenos y Metales S.A. (Molymet), Chile) decided to install the Haldor Topsrae Wet gas Sulphuric Aicd (WSA) process for cleaning of the 4-5% SO2 off-gas from their molybdenum sulphide master in Cumpas, Mexico to produce sulphuric acid. The decision to install a WSA plant was based on the successful operation of a WSA plant at Molymet's molybdenum sulphide roaster in Santiago, Chile since 1993. This paper describes the process layout of the Cumpas plant, the operating experience of the Santiago plant, and the, differences in. process design between the two plants. It will furthermore summarise the applications of the WSA process for other roasting plants and smelters within the non-ferrous. metals industry producing metals such as copper, lead, and molybdenum.

Jan 1, 2002

By Sheng-hai Yang

The electrochemical synthesis was conducted in anhydrous ethanol solvent mixed with conductive reagent when tantalum plate was used as anode and stainless steel plate as cathode. The effects of different conductive reagents (such as NH4Br, (CH3)4NCl, (C4H9)4NCl), conductive reagent concentration and the space on the cell voltage and the current density were investigated. The current efficiency of electrosynthesis was more than 95%. The electrolyte, a mixed solution was then undergone air distillation and vacuum distillation to get the final product which was characterized by Fourier Transform Infrared(FTIR) spectroscopy, Raman spectra, 1H-Neclear Magnetic Resonance(1H-NMR) spectroscopy. Carbon and hydrogen contents in the product were determined by elemental analysis instrument. Results consistently show that the product was tantalum penta-ethoxide.

Jan 1, 2006

By Wei Liu

A new process for extracting cadmium from the electric precipitated dust produced by ISP process was studied. A leaching rate of 89.1% of cadmium was attained by leaching the dust with NH3?H2O-(NH4)2SO4 system under the best leaching conditions: ratio of liquid to solid(l:s)=2.5, c(NH3):c(NH4+)=3:5, total concentration of ammonium and ammonia=8 mol?L-1, leaching time= 1.5h, temperature=35. The most troublesome impurity of lead could be deposited from the leached out solution automatically after put it static more than 15h when the total concentration of zinc and cadmium was up to 45gL-1 , and the final concentration of lead was 0.0047 gL-1, which meant 99% of it was removed. Metallic cadmium which contained cadmium more than 99% was prepared by electrowinning under the conditions: current density=750Am-2, total concentration of Cd2+ and Zn2+>25gL-1. The current efficiency was about 87% and the energy consumption for every ton of cadmium was about 548KWht-1. Main impurities of the metallic cadmium were copper and zinc and all of they could be got rid of in the following pyrometallurgical refining step.

Jan 1, 2006

By Teruo Tanabe

The hydrogen-absorbing materials are expected to have the following properties at moderate conditions, (a) a large capacity of hydrogen absorption, (b) the absorption rate of hydrogen is large and (c) hydrogen-absorbed materials can easily desorb hydrogen. Thus the three concepts of capacity, rate and reversibility seem to be indispensable to clarify the mechanism of hydrogen absorption by the materials. In this work, the amount of absorbed hydrogen, the absorption rate and the reversibility of hydrogen absorption- desorption reaction were measured for binary R-M systems (R = Y, La, Ce; M = Co, Ni). These experimental results were discussed by the following three physical properties that were calculated by the extended Hückel method, i.e. the density of states unoccupied by electrons, the cohesive energy and the energy fluctuation. The major results are as follows: (a) the amount of absorbed hydrogen increases with the density of states in the energy range between -9 and -4 eV, (b) the R-M compounds of which energy fluctuations are large show a large value of rate of hydrogen absorption, and (c) when the cohesive energy is large, the compound has a tendency not to easily desorb hydrogen, i.e. its reversibility is poor.

Jan 1, 2006

By Dachun Liu, Yifu Li, Baoqiang Xu, Yongnian Dai, Bin Yang

"The removal of impurity arsenic from crude tin is one of the major problems in the process of tin refining. Through a thermodynamic analysis on vacuum refining process of crude tin, the vapor pressure of impurity arsenic under different temperatures can be obtained, which demonstrates that it is possible to separate tin and arsenic by the vacuum refining process. This paper attempts to verify the behaviors of impurity arsenic. The experiment result shows that through vacuum distillation, crude tin with 0.16% arsenic can be refined from crude tin with 0.96% arsenic, and about 50% impurity arsenic can be collected in the form of metallic arsenic.PrefaceThe crude tin obtained by the reduction process is insufficiently pure for most applications, even smelting from tin concentrate. Arsenic is a common impurity in crude tin and also one of the predominant elements to affect tin performance. Arsenic is a poisonous metal that has long been linked to an increased risk of cancers, diabetes, thickening of the skin, diseases of the liver and digestive complications, so there is a mandatory limit on the amount of arsenic (<0.015%) in tinfoil wrapper and tin layers for food packaging. Arsenic causes a poor appearance and plasticity, and increases viscosity. The impurities content of crude tin fluctuate over a wide range; a lot depends on composition of tin ore concentrate, treatment method and technological process before reduction smelting. And the content range of arsenic is usually 0.5~4%, but it is higher in some factories."

Jan 1, 2012

By Ahmad Umar

A variety of ZnO nanostructures such as sea-urchin-like structures composed of nanowires and nanorods, nanocombs, nano/micro spheres and cages, star-shaped ZnO nanostructures, flower-shaped nanostructures, needle-like nanostructures etc. have been synthesized applying two different fabrication techniques i.e. thermal evaporation and cyclic feeding chemical vapor deposition techniques at different reaction parameters such as reaction temperature, growth period, reactant concentrations, types of source material and substrates etc. It was observed from the experiments that the morphologies of the grown structures were highly influenced by the reaction parameters and fabrication techniques and specific morphology can be obtained at particular reaction parameters in a specific synthetic procedure. Extensive morphological investigations of the obtained products demonstrate that the grown structures are single crystalline and having a wurtzite hexagonal phase. Room-temperature photoluminescence spectra of all the deposited products exhibited good optical properties. Finally, the growth process of the fabricated structures were proposed and discussed in detail.

Jan 1, 2006

By Harold R. Kokal

Lisakovsky is a 3-billion ton oolitic iron ore deposit in north-central Kazakhstan operated by Orken LLP, a subsidiary of Ispat Karmet and the LNM Group. The iron oxide minerals are goethite and limonite. The gangue occurs as discrete quartz grains and an unidentified form of colloidal silica-alumina. The concentrate produced contains about 49.5 percent iron (Fe) and 0.6-0.8 percent phosphorus (P) or 10-20 times the acceptable phosphorus level. The phosphorus is intimately associated with the iron oxide and colloidal gangue, no discrete phosphorus minerals are found, and beneficiation is not possible. Therefore, to reduce the phosphorus, a hydrometallurgical process that includes roasting followed by leaching in dilute sulfuric acid has been developed. Phosphorus extraction is 70-90 percent, with only a minor loss of iron. The process has been tested in the laboratory and in a pilot plant at 50-300 kg/h. Construction of a 900,000 t/y demonstration plant is underway.

Jan 1, 2003

By Hiroyuki Matsuura, Fumitaka Tsukihashi

"Emission of CO2 gas from steelmaking industry covers more than 12 % of total CO2 emission in Japan. Though many efforts have been made to curtail energy consumption and high energy efficiency of Japanese steel production process has been achieved so far, further reduction of CO2 emission is strongly requested to develop sustainable steel production process and produce “green material”. Recently, authors have proposed the innovative hydrogen production process, in which water vapor is reacted with discharged steelmaking slag to produce hydrogen gas. This reaction can be achieved without any external energy source and operated by huge thermal energy associated with steelmaking slag and FeO or unrecovered Fe droplets that are relatively rich in the slag. In this paper, thermodynamic calculation results with various initial conditions in terms of hydrogen productivity were presented. Laboratory-scale experiments were also conducted to clarify the validity of thermodynamic calculation and the reaction rate in realistic conditions.IntroductionIronmaking and steelmaking process from iron ore through blast furnace and BOF is an essential steel production route for Japanese steel industries to supply high quality steel products in large quantity to society stably. Blast furnace – BOF process requires huge amount of fossil fuels such as mainly coal, resulting the emission of considerable amount of CO2 gas. Since the emission of CO2 gas from steel industries, about 147 Mt (FY2011), accounts for approximately 12 % of domestic CO2 gas emission in Japan (FY2011),[1] it is an urgent issue for steel industries to develop environmental-friendly ironmaking and steelmaking process and reduce CO2 emission. Various kinds of gases and by-products generated from ironmaking and steelmaking processes have been recycled as much as possible at present. Enormous thermal energy is also generated from processes and released to surrounding atmosphere as various forms such as sensible heats of gases, molten steels or by-products, and as heat losses. However, these energies are not utilized before final dissipation to atmosphere. Although various technologies to utilize thermal energy from ironmaking and steelmaking processes have been attempted to develop, practical application of these technologies has not been achieved because the thermal energy is not always useful as an energy source. In steelmaking process by BOF, fluxing agent such as CaO is added during reefing and thus about 100 kg/t-steel of steelmaking slag are generated. Since the steelmaking slag is discharged at temperature range between 1873 and 1923 K after discharge of refined molten steel, it also has large thermal energy. Amount of generated BOF slag is 11.0 Mt/y (FY2012) in Japan.[2] Assuming the amount of steelmaking slag is 10 Mt/y and its average heat capacity from room temperature to 1923 K is 1 kJ/kg·K,[3] unutilized heat is estimated to be 16 PJ/y, which is equal to annual energy consumption of 420 thousand families in Japan.[4]"

Jan 1, 2014

By Tangstadm Merete, Eli Ringdalen

"This paper presents an overview of results from The Norwegian Research Institution SINTEF and the Norwegian University of Science and Technology, NTNU regarding new and ongoing research in silicon production. The main studies are related to condensation of SiO gas and cavity formation. If SiO gas condensation is increased at the top of the furnace resulting in SiO content in the off-gas closer to equilibrium, the Si yield will be increased significantly. Experimental work, simulating a cavity under industrial conditions, has shown that the cavity grows downwards from one layer. Physical appearance of zones in industrial furnaces, and selected reactions in these, are discussed based on results from excavation of industrial furnaces and results from laboratory experiments. Experimental studies of reaction rates for the formation of SiO are presented. Quartz properties are demonstrated to vary between differing quartz types and the effect of this is discussed.Introduction Both the theoretical and industrial issues associated with the production of silicon are described in detail in the textbook written by Schei et al [1]. This book covers the knowledge of silicon production process up to 1998. Together with the work by Myrhaug [1] and by Aasly[2], this is the main basis for this paper. Recent and ongoing research at SINTEF and NTNU focusing on production of Si and SiO in the high temperature zone, dissociation of SiO and condensate and cavity formation will be discussed."

Jan 1, 2012