Search Documents

By J. Rastas

The recovery of lead, silver and gold from existing and potential zinc process residues using a sulfidization-flotation method was investigated on a laboratory scale. The following residues were tested: neutral leach residue, high acid leach residue, and hematite residues. The sulfidization of lead and silver is carried out at low pH by the addition of a stoichiometric amount of sulfide at a controlled rate. To increase the particle size of the sulfides, seeding with synthetic lead and silver sulfides -is employed. The flotation is carried out at pH 2-4 using low pH-collectors such as dithiophosphates and dithiophosphinates. Special attention must be paid to the role of oxygen in the conditioning stage. The effect of different parameters on both the sulfidization and the flotation has been evaluated. Recoveries of 85-90, 90-95 and about 80 % were obtained for lead, silver and gold, respectively. Typically, concentrates containing 50-60 % lead, 3-5 kg/t silver and 10-15 git gold were produced.

Jan 1, 1990

By Shinroku Matsuzaki

Data the measurement sensor installed with spatial distribution on the blast furnace were successively accumulated online from the process computer to the database system over a long period. This is a new system that accurately considers the relation with the installation position of each sensor, and picture computerization of the measurement data was developed. The overall operation state of a blast furnace, which skilled operators can see in their mind?s eye, was objectively visualized as pictorial information.

Jan 1, 2006

By E. V. Verhoef

The proposed EU directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment promotes the substitution of lead in consumer electronics to reduce emissions from lead in the end of life phase. In this paper, the consequences of substituting lead in solders is assessed using the Eco-lndicator-99 method for the examples. The base metal production system is considered as an interconnected network modeled dynamically in Simulink 4 and Matlab 6 (Mathworks Inc 2000), where the recovery and production of metal components of the assessed product partially overlap. This approach requires global modeling of metal production processes and mass balances and resulting allocation choices. It also reveals the susceptibility of LeA scores to different choices in the modeling and data availability and uncertainty. Besides the comparison between lead-free and lead-containing solders, other side effects are revealed. Lead is carrier material for the recycling and production of many co-elements in the interconnected production and recovery system. Substitution may have adverse effects such as temporary shortages of other connected metals that are often not considered in normal LeA assessments, thus leading to erroneous results. The suggested approach provides directions for including these external effects and for further assessment of the environmental effects of substituting lead. This paper shows that in order to assess the environmental aspects of metallurgy, dynamic modeling of the total system is required based on the fundamental thermodynamics in each metallurgical reactor, the basis of this dynamic model. With this the true environmental impact of metallurgy can be explained. In the case of lead free solder, it is shown that the mining of substitutes has a very much larger impact.

Jan 1, 2003

Carbon injection into metallurgical slag is important in electric arc furnace (EAF) steelmaking for foamy slag practices and in nonferrous slag cleaning operations. The current publication presents kinetic data for coal injection into EAF slag to understand the interaction between injected carbon and metallurgical slag. Coal particles were injected into EAF slag and the kinetics were followed by gas and slag analysis. The results were analyzed, in terms of fundamental rate equations for each possible reaction step, as a function of temperature and slag composition.

Jan 1, 2003

By Forsén. O.

In this ?paper practical solidification of anodes containing nickel, arsenic, antimony and bismuth is compared with the equilibrium? diagrams and kinetic ?factors. In order to clarify the distribution of the impurity elements in the anode the structures were studied after the solidification and also after the electrolysis of anodes. This examination was carried out with optical microscope, scanning electron microscope and electrochemical measurements. All the nickel is remaining metallic in the copper matrix during the solidification and therefore nickel is dissolved in the electrolysis at all oxygen contents, when the nickel content is 0.25 wt-% or less in the anode. The practical .solidification mechanism of the anodes, when the nickel content exceeds 0.25 wt-%, proceeds by the crystallization of nickel oxides. In oxygen containing copper anodes nickel oxide is verified to crystallize together with antimony in certain conditions and to form a micaceous compound (3Cu2O?4NiO?Sb2O5), which may build up a very harmful floating slime in the electrolyte. Arsenic is strongly enriched along the phase boundaries in oxygen free copper anodes. An intermetallic compound Cu3As is formed when the amount of arsenic in the anode. exceeds 0.7 wt-%. This compound is more noble than the copper matrix. This means 'that a selective dissolution of copper-arsenic compounds takes place. The copper matrix dissolves more strongly than the grain boundaries. The solidification structures of oxygen free bismuth containing copper anodes show clearly the influence of bismuth. Thin bismuth films which are less .noble than the metallic copper matrix, are formed during the solid1ficatton process. As a result of this the?grain boundaries are dissolved faster than the copper matrix.

Jan 1, 1987

By D. D. Rodier

Most zinc concentrates contain some silver and varying amounts of such valuable trace elements as gold, indium, germanium and gallium. With increasing similarities in plant installations, the predominance of electrolyte process and the increasing environmental constraints on iron disposal, it is essential that zinc smelters optimize the recovery of any valuable elements in their feed stocks. The process options, to date, of smelting, flotation or leaching of silver-rich leach residues cannot be applied economically to all installations. It is therefore necessary that new innovative processes, to recover silver and other valuable metals from relatively low grade feeds, be developed. This paper attempts to place this strategy in the context of today's constraints and will also provide a simple evaluation tool for any process alternatives.

Jan 1, 1990

By Carlos M. Fontes Vieira, Ruben J. Sanchez Rodriguez, Carlos E. Gomes Ribeiro

"In this study we attempted to model a response surface for the apparent dry density of ternary blends of calcitic marble particles. The crushed marble was divided into three granulometric ranges. Simplex network methodology was used to determine the mathematical relation between granulometric ranges and apparent dry density (ADD) of particle mixtures. A highly significant regression was obtained and the simplex network methodology proved to be able to predict high packing particle compositions.IntroductionProblems with packing and expected porosity of particles are common and widely recognized to be important in terms of both fundamental physics and engineering applications. For example, densification of a powder mass is important in the shaping of solids in ceramics, powder metallurgy or composite synthesis; chemical processes such as solid-liquid separation (sedimentation, thickening and filtration), raw material handling (stockpiling, blending, drying, storage and transportation) and pyrometallurgical processes (agglomeration, coke making, ore sintering, blast furnace iron making and new iron making processes) [1,2].Many factors can affect particle packing, but in practice, there are three main factors: (dimensionless) particle size distribution, particle shape and absolute particle size [2].Geometrical and practical methods were developed to predict properties in mixtures. Zou, Gan and Yu [2] present a paper treating a prediction of the porosity of multi-component mixtures of cohesive (fine) and non-cohesive (coarse) particles. Bahiense et al. [3,4] used a simplex network to determine a mathematical model for obtain the optimal compositions between aggregates to a greater packing of a ternary particles mixture. Despite these techniques for predicting particle packing, some studies in particulate composites production don't present clear criteria for choice of particle distribution [5,6]. As the best particle packaging depends on the size, distribution and shape of these particles, individual models can be constructed for specific combinations of these factors."

Jan 1, 2014

By Greg Andrews, David Dreisinger

The Foxtrot deposit of Search Minerals contains a range of rare earth element containing minerals including allanite, fergusonite and bastnasite. The Search Minerals Direct Extraction Process for treating these minerals involves coarse crushing of the ore to -6 mesh (3.45 mm), acid treatment at 200 °C in a novel reactor configuration, water leaching, various purification steps to reject iron, aluminum and uranium/thorium (present in small amounts) and finally precipitation of rare earths as an oxalate and calcination to form a mixed rare earth oxide product for refining. The economics of the process are presented.

Mar 1, 2017

By C. J. Newman

In January 1999, a redesign of the Kennecott Flash Converting furnace settler was initiated to enhance furnace integrity and extend furnace life. This furnace uses Kennecott-Outokumpu Flash Converting technology to produce copper directly from copper matte. A detailed assessment was made of all technology available around the world before making a decision on the design features to be incorporated in the new design. The new design includes the following: redesign of all sidewall cooling elements to include the latest cooling element technology; redesign of the furnace hearth to include a stadium hearth at the reaction shaft end of the furnace; redesign of the furnace hearth to include a stepped hearth design adjacent to the furnace sidewalls; addition of flat settler roof cooling elements .around the reaction shaft; replacement of reaction shaft transition elements with an improved design and improvements to the furnace cooling element monitoring systems. The Flash Converting furnace was shut down on a planned basis in July 2001 to implement these improvements after 29 months of operation, converting more than 1,000,000 tonnes of matte. During the 30 day shut down, the improvements were successfully completed, with furnace start up in August 2001

Jan 1, 2002

By Toshiaki Akahoshi

Keywords: Wasted catalyst, Hydrodesulfurization, Ammonium vanadate, Ammonium molyb-date, Hydrometallurgical process. The fundamental reactions have been investigated in order to develop a hydrometallurgical process for recovery of molybdenum and vanadium from wasted catalysts generated in the hy-drotreating desulfurization of heavy oil. The principal steps of the process are a mild oxidation roasting of the waste catalysts at temperature around 500°C, leaching of the target metal components with dilute ammoniacal aqueous leachates, selective precipitation of vanadic acid, and ammonium molybdate precipitation. The selective recovery of vanadium as vanadic acid is successfully performed using ammonium sulfate as a salting-out agent. Recovery of ammonium molybdate is based on large dependence of solubility of ammonium molybdate in ammoniacal solutions upon temperature and ammonium salt concentration. In this process, the solution after recovery of vanadium and molybdenum is recycled to the leaching stage of the roasted materials, and the ammonium salts in the process liquor is in the repeated use. Employment of am-moniacal system makes it possible to operate the roasting at much lower temperature than that for the currently operating process.

Jan 1, 2005

By N. Kanari

The kinetics of oxychlorination of MgO by Cl2+O2 was studied in the temperature range of 850 °C - 1025 °C, using thermogravimetric analysis. The effects of C12/02 ratio, gas velocity, temperature and partial pressure of reactive gases on the reaction rate were investigated. The oxychlorination process was characterized by an apparent activation energy of about 214 kJ/mol. The reaction orders with respect to C12+O2. C12 and O2 at 950 °C were about 0.65.0.98, and -0.37, respectively. Some data about oxychlorination kinetics of MgO, Cr2O3, and MgCr2O4 contained in chromite were compared. Efficiency of using oxychlorination for the removal of iron oxides contained in magnesia was demonstrated.

Jan 1, 1999

By S. V. Ketov, V. P. Menushenkov, V. S. Shubakov

"The glass samples were obtained by melting of the oxides mixture SrO-Fe2O3-B2O3(Al2O3) at 1200-1250°C with subsequent quenching of the melt on quickly rotating steel roller. Submicronsized Sr(Fe,Al)12O19 particles were formed in glass-ceramic matrix during the crystallization aging of glass. The aging temperature Tag varied in the range 650-950°C. The submicron-sized hexaferrite powder was obtained by removing of the matrix phases using etching. The samples were characterized by X-ray diffraction, scamiing electron microscopy and magnetization measurements. The glass-ceramic material exhibits very high coercivity value up to 10 kOe. The samples of magnets were obtained by pressing of the hexaferrite powder at RT and subsequent aging in the range 900-1200°C. The aged samples exhibit coercivity value up to 8 kOe.IntroductionStrontium M-type hexaferrites have been widely used in technology and industry mainly for production of permanent magnets owing to their appropriate magnetic properties, chemical stability and low cost [1,2]. The SrFe12019-based compounds are characterized by high magnetocrystalline anisotropy and single easy magnetization axis. The highest coercivity is received for monodomain, defect-free single crystal particles with size D - 100 mn. Finely grained strontium hexaferrite prepared by chemical methods such as sol-gel pyrolysis and oxide glass crystallization exhibits high coercivity up to 6-8 kOe [3-5]. Owing to the partial substitution of Al for Fe in the strontium hexaferrite leading to the increase in the magnetic anisotropy field Ha=2Ki/M,, the increase in the coercivity may be received [6]. The notable results were achieved using the SrO-Fe2O3-AlzO3-B2O3 glass crystallization and formation of perfect submicron crystals of alumina-doped hexaferrite [ 6, 7]. The coercive force of glassceramics reached values of up to 10 kOe. Hexaferrite particles are well faceted and have the shape ofhexagonal bipyramids with truncated vertexes [7].In the present paper, we report results of our investigation into the SrO-Fe2O3-B2O3(Al2O3) glass crystallization, hexaferrite powders and permanent magnets, which were prepared by pressing submicron-sized hexaferrite powders at RT and subsequent sintering at 900-1200°C."

Jan 1, 2012

By Nickolas J. Themelis

The flash oxidation and smelting of mineral sulfides is a very prominent metallurgical achievement of the second part of this century. Its initial industrial implementation owes much to the work of Petri Bryk, in Finland, and Paul Queneau, in Canada. However, attempts to develop flash reduction pro- cesses, such as the reduction of iron oxide concentrates with hydrogen, have not yet been successful. The author, on the basis of experimental studies on both kinds of flash reaction systems, examines the respective rate controlling phenomena and the relative rates of flash oxidation and flash reduction.

Jan 1, 1993

By Omid Marzoughi

Chromium has a wide range of applications, including as an alloy addition in various steels and also as a corrosion resistance coating. Carbothermal reduction of chromite ore (FeCr2O4) in a submerged arc furnace is an important industrial process for extracting chromium, but the energy consumption is excessive. It is suggested that one area for future research is the low temperature carbothermic solid state reduction of chromite to produce an intermediate product, which can subsequently be upgraded to ferrochromium. In this regard, a thermodynamic model has been developed to investigate this process and the effects of temperature, carbon additions and ore composition on the recovery of chromium and the grade of the ferrochromium, have been studied. Further development of the model may allow it to be applied to the simulation of other processes for the recovery of chromium from chromite ores.

By Nobuo Takahashi

Effective solvent extraction media have been investigated for purification of rare earths. At first, a quaternary ammonium compound was studied. The counter anions of rare earths and organic dielectric substances were tested to improve separation factors,. And second, crown ethers were selected for extractant. Several diluents of crown-adducts were tested to improve solubility and distribution coefficient as well as the counter anions of rare earths. Especially, in the presence of strong reducing agents, highly selective extraction of europium from other rare earths was observed. The third extactnts were ß -diketones. Presence of organic dielectric substances was very effective to improve separation factors. Though those. three groups of extractants were suitable for mutual separation of light rare earths, alkyl esters of alkyl-phosphonic acids were suitable for mutual separation of heavy rare earths because of their high separation factors. To keep proper pH value was necessary for acidic extractants, so control method of the solution pH was studied with high molecule insoluble amines or salts of those.

Jan 1, 1995

By Kenneth McGowan

"The aluminum industry is the 5th largest consumer of energy and the largest consumer of energy on a per-weight basis. Process heating accounts for 25% of the energy consumed to manufacture aluminum. Consequently, the generation of this energy results in the production of a significant amount of CO2 (over 3.75 million metric tons in 2003)1. As a result, the Aluminum Industry Technology Roadmap of 2003 listed the development of improved refractory materials as a goal to reduce energy use and decrease greenhouse gas creation. The result of a R&D effort addressing this desire is the development of patented microporous refractory materials for metal contact applications in all furnace areas including the belly band. It has been demonstrated that this material can reduce energy consumption up to 38% in furnaces and significantly reduce heat loss in launder and trough systems. Furthermore the material developed is non-wetting and remains un-penetrated by metal throughout its lifetime. The material does not contribute to the formation of corundum. As a result, the energy efficiency of an older lining remains intact compared to standard refractory materials which may have an initial high insulating value (such as lightweights and board) or standard dense refractory (even with penetration inhibitors) both of which show a rapid increase in thermal conductivity as the refractory is penetrated with aluminum and formed corundumIntroductionThe aluminum industry is the second largest producer of metal in the United States, behind the iron and steel industry. It is the 5th largest consumer of energy and the largest consumer of energy on a per-weight basis. Process heating is required to melt, hold, purify, alloy, and heat treat the metal and accounts for 25% of the energy consumed to manufacture aluminum. As such, process heating is the second largest energy consuming operation. Smelting, which utilizes an electrolytic reduction process is the largest energy consuming operation1.Most process heating is accomplished through the use of fossil fuels, either directly or indirectly. The choice of fuel is dependent on a plant’s location and fossil fuel availability. Table I shows the processes impacted by refractories and the calculated BTU’s generated by usage of the respective fuels as well as the Metric Tons (MT) of metal passed through each process in 20001."

Jan 1, 2009

By Dominik Hofer

A broad spectrum of tantalum containing input materials can be processed for the production of synthetic tantalum concentrate (“SynCon”). The use of these low grade substances offers a secure alternative to mining of coltan in Central Africa. SynCon is produced in a multi-stage pyrometallurgical process, wherefore the melting behaviour of slags presents an important factor especially regarding the energy consumption and its optimisation. The characteristics of a slag comprising mostly Al2O3, CaO, SiO2 and MgO are influenced by the amount of other oxidic constituents which enfolds the main focus of this study. A hot stage microscope serves for the investigation of the slag behaviour in a temperature range from 1000 to 1600 °C under reducing atmosphere (CO/CO2 gas). The experimental results are compared with thermodynamic calculations (FactSage) to get a better understanding of the process.

By Bryce Clark

An outline of the current world's known sources and resources of cobalt, looking at both land and possible undersea deposits, is given as a prelude to an examination of current and historical actual world production on geographic/company basis. These production figures will be compared to apparent consumption by segments, both geopraghically and end-use based. Consumption of cobalt has been regarded as price sensitive and a historical look at prices against all other figures will be considered. Included in this scenario will be a brief overview of cobalt's uses and a comment on future trends. Tables will include: Resources, Production, Consumption, Prices, Markets.

Jan 1, 1993

By Yuezhen Zhou, Zewei Liu, Dachun Liu, Chongfang Yang, Wenlong Jiang, Fansong Liu

A novel process that the combination of vacuum decomposition and acid leaching was proposed. The influence of distillation times, diameter and thickness of the feeding material on the mass fraction of Molybdenum (Mo) and sulphur (S) in residual was investigated. The influence of leaching temperature, leaching time, concentration of hydrochloric acid solution, and ratio of liquid to solid on leaching rates of Mo and S in acid leaching process was also investigated. Due to the fact that SO2 emission happening in the long process of traditional molybdenum metallurgy could be avoided in this novel method, this combination process was environmentally-friendly. Molybdenum powder was obtained through handling molybdenite concentrate under the optimal condition parameters, and the mass fraction of Mo reached 98.29 wt%. So it's feasible to produce molybdenum powder from molybdenite concentrate by using this new method.

Mar 1, 2017

By Timothy W. Ellis

This paper presents the basic theory of operation, physical chemistry and phase equilibria which allow the development of liquid-liquid extraction circuits based on metallic solvents. The incorporation of reduction and reduction/diffusion processes into the process 'scheme is discussed and a detailed description of ,several liquid-liquid extraction schemes are developed. A synopsis of experimental results obtained using this: method to separate rare earth and other metal based materials will be given.

Jan 1, 1996