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By H. Hahn, B. H. Kear, K. Kan, S. C. Danforth, G. Skandan, W. Chang

"A new chemical synthetic process for the production of non-agglomeratednano structured ceramic (n-ceramic) powders, starting from metalorganic precursors, is described. The process combines rapid thermal decomposition of a precursor/carrier gas stream in a hot tubular reactor with rapid condensation of the product particle species on a cold substrate. Critical to the success of this Chemical Vapor Condensation (CVC) process are (1) a low concentration of precursor compound in the carrier gas, (2) rapid expansion of the gas stream through an uniformly heated tubular reactor under a reduced inert gas pressure of 1-35 mbar, and (3) rapid quenching of the gas phase nucleated clusters or nanoparticles as they exit from the reactor tube. A wide variety of metal organic precursors is available commercially, all of which can be utilized in the CVC process to produce n-ceramic powders, including single phase, multiphase and multicomponent systems.The CVC process has been used to synthesize non-agglomerated n-SiCxNy and n-ZrOxCy powders, with controlled particle size in the range 2-20 nm. Heat treatment of the assynthesized n-powders in various high purity gas streams causes compositional and structural modifications, including particle purification and crystallization, as well as transformation to a whisker-like morphology. Thus, as-synthesized amorphous n-SiCxNy particles transform to (1) cubic n-SiC particles, when heated in flowing argon at temperatures> 1350 °C, (2) hexagonal n-Si3N4 whiskers, when heated in flowing NH3IH2 at 1400 °C, and (3) cubic nSiC whiskers, when heated in flowing H2 at 1400 °C.Non-agglomerated n-ceramic powders form uniformly dense powder compacts by cold pressing, which can be sintered to theoretical density at temperatures as low as 0.5 Tm' For example, full densification ofn-Zr02 powder compacts under free sintering conditions can be achieved at 1125 °C."

Jan 1, 1994

By A. Mezei

Samples of cobalt and bismuth concentrates produced from the NICO deposit in Northwest Territories were subjected to a comprehensive metallurgical testwork consisting of: pressure oxidation, ferric chloride leach and carbon in leach, to recover the cobalt, bismuth and gold, respectively. A specific testwork program was designed to allow for the optimization of process parameters under multiple restrictive criteria. The overall objective was to establish leaching sequences that could produce acceptable recoveries while generating environmentally disposable residues as well as solutions suitable for further processing. The recoveries for the leaching stage, under the optimum conditions, were 97% for cobalt and 95% for gold, in the case of the cobalt concentrate. The bismuth concentrate produced recoveries of 99% for bismuth, 99% for cobalt and 97% for gold, respectively

Jan 1, 1999

By Bradley C. Bockrath

Some thirty coals were evaluated for liquefaction activity under a mixture of CO and H2 at 425° C. The viscosity of the liquid products was taken as an indicator of the degree of liquefaction. It was found that the direct liquefaction of a particular coal may be beneficially influenced by the presence of pyrite. Active pyrites are often found in the native mineral matter of the coal itself. For example, subbituminous and bituminous coals and lignites of relatively high pyrite content were found to liquefy more readily than similar coals or lignites which were poor in pyrite. The reactivity of inactive coals could be improved by using blends with active, pyrite-rich coals. In addition, pyrite was effective when added separately as pyrite concentrates obtained from coal beneficiation operations. Various other iron- and sulfur-bearing additives were also effective when used in combination as added slurry-phase catalysts, including iron oxides and mineral residues derived from liquefaction of active coals. Under liquefaction conditions, pyrrhotite ( Fe I- x5) is formed from pyrite or from the iron oxides and many sulfur containing species. Pyrrhotite was shown to be a hydrogenation/dehydrogenation catalyst for tetralin but is not active for initiating a variety of free radical reactions that do occur when pyrite is heated with tetralin. The role of pyrite in coal liquefaction is complex and still not well understood.

Jan 1, 1981

By S. Seetharaman

The present paper presents. the concept of micro-models and illustrates the application of the same in the simulations metallurgical processes. Development of micromodels requires access to accurate thermodynamic, thermophysicaland kinetic information for the relevant systems with suitable models to extrapolate the data as functions of temperature and composition. Experimental measurements and modelling of the thermodynamic properties, sulphide capacities and viscosities of oxide melts carried out in the department are presented. The incorporation of these models in process models, with special reference to ladle refining of steel is illustrated. Typical example of micro-modelling of solid-gas reactions is also presented.

Jan 1, 1999

By John Hanna

The University of Alabama Mineral Resources Institute (MRI) has developed a unique process for selective fatty acid flotation of carbonate gangue from sedimentary apatites (francolite) in the pH range of 4-6, without collector conditioning of the pulp. The process, which does not require an apatite depressant, was modified to beneficiate a high MgO siliceous phosphate matrix from South Florida. The modified process includes two flotation stages, one for carbonate removal, as mentioned above, and the other for phosphate recovery from the siliceous gangue. The selective flotation separation of the carbonate and phosphate from siliceous constituents of the matrix at various pH levels and collector dosages are discussed. In the carbonate flotation stage, about 70% of the MgO was rejected in the froth, and the phosphate flotation stage produced concentrates analyzing about 31% P20S' 0.7% MgO and 4% acid insolubles. The overall P20S recovery in the two stages is about 85%.

Jan 1, 1989

By Agnes Y. Lee

he U.S. Bureau of Mines developed a method to treat lead-contaminated soil and ebonite battery casing wastes to produce a nonhazardous material. The cleanup procedure involves wet screening to separate a minus 18-mesh soil fraction; removal of metal1ic lead, rocks, wood, etc. ; carbonation to change lead sulfate to acid-soluble lead carbonate; size reduction; acid leaching; and rinsing. The casing wastes undergo size reduction and washing to remove the lead sulfate sludge before carbonation. Similarly, the minus 18-mesh soil is carbonated, then acid leached and rinsed. In leaching, fluosilicic acid (H SiF,) and hydrogen peroxide (H20,) are used to dissolve lead compounds. An electrowinning method is employed to strip lead from the lead-rich leachate. The acid content in the leachate is replenished with fresh H,SiF, acid prior to recycling. Treated casing wastes and soils pass the Toxicity Characteristic Leaching Procedure (TCLP) test and can be reclassified as nonhazardous materia1s. Based on this process, a conceptual pilot plant has been designed which will be demonstrated on wastes from two Superfund sites.

Jan 1, 1993

By James Vaughan

Ionic liquids are solvents of interest for applications such as electro- plating, winning and refining of metals. Of particular interest is the possibility of processing reactive metals such as aluminium, magnesium and titanium that cannot be deposited from aqueous solutions. Aluminium has been electro deposited from AlCl3 : ionic liquid mixtures at low temperatures relative to conventional Hall-Héroult smelting. Imidazolium ionic liquids are have been used in the past due to their relatively high ionic conductivity and cation stability. The less studied and less expensive phosphonium ionic liquids systems may provide a viable alternative to imidazolium ionic liquids for certain applications. New information regarding the physical properties and electrochemical behaviour of phosphonium ionic liquid systems is presented.

Jan 1, 2006

By Isrun Bohlinger

Resources recovery of brasses for semifinished products often results in the formation of hard spots impairing the quality of following abrasive and/or surface finishing processes. A short survey is given on the recycling processes, followed by the actual knowlegde of genesis, composition, and possibilities of avoidance of hard spots. Informations on genesis and composition of hard spots are completed by data from recent experiments.

Jan 1, 1998

By E. Maziar Sauber

In order to prepare a more desirable feedstock for a rare earth elements separation refinery, cerium, a penalty element in the refinery feedstock, should be removed from the mixed rare earth elements oxide or carbonate feedstock. In this study, cerium (III) to cerium (IV) oxidation by calcium hypochlorite and subsequent precipitation was used to remove cerium from a mixed rare earth elements chloride solution. A factorial design of experiments was used to determine the effect of process variables such as temperature, pH, and oxidizer addition on the oxidation of cerium (III) using synthetic solutions. Under certain test conditions, all of the cerium was successfully removed from the chloride solution, and some REE accompanied cerium and reported to the precipitate. This proposed technology can allow for low cost removal of cerium from mixed rare earth elements chlorides.

By Milton Blander

A review of concepts and theories for predicting thermodynamic solution properties of multi- component high temperature liquid solutions is reviewed. During the last 50 years the ability to predict :such properties for molten salts, silicates and metals based on the generally known properties of the lower order (often binary) systems has been developed and shown to provide predictions which are quite useful in science and technology. There are many gaps in our understanding of these high temperature solutions, especially for metals, and considerably more work is needed.

Jan 1, 1996

By I. Goy D. Gaballah

Decontamination of synthetic K2Cr2O 7 solutions containing 10 to 1000 ppm of hexavalent chromium using chemically treated barks have been studied at a laboratory scale. Metal removal from solutions depends on the pH, the initial concentration and the bark species. The use of a pulp density of 2 % in an agitated flask at the optimum pH for 2 hours leads to a percentage chromium removal of about 95 of the initial metallic ions content. Other trials conducted by column percolation permit the determination of the maximum retention capacity of the treated bark. Depending on the bark species, oak or pine, the rate of saturation is 110 and 215 mg of Cr per gram of bark respectively. The incineration of the metal charged barks gives recyclable, ashes containing 36 and 54 % of chromium metal for the oak and pine barks respectively. Experiments, of Cr6+ removal from industrial effluents containing up to 1800 ppm have been carried out on the semi-pilot plant scale. They have lead to the elimination of about 90 % of hexavalent chromium from this industrial waste solution. Further studies are conducted in order to define the hexavalent chromium binding mechanisms on bark constituents.

Jan 1, 1992

By H. Shang

The materials science and metallurgical engineering communities have expended enonnous resources in developing high fidelity process models. Exploiting these Models for Predictive Optimization (MPO) and Control (MPC) is a new frontier in Materials Process Engineering that will lead to exceptional process perfonnance. This paper will begin with a short survey of the development of high quality process models available in the literature and a discussion of how these could be used to improve process operation. A summary of the current "state-of-the-art" in process automation technologies and the traditional framework in which these technologies are deployed will be presented. An illustration of the use of MPO in process design and operations will be presented for the continuous casting of steel. In addition, a simple run-out table simulation will be used to demonstrate the power of the MPC technique.

Jan 1, 2003

By Duan Xin-hui, Wang Xin, Peng Jin-hui, C. Srinivasakannan, Zhang Li-bo

The work attempts to optimize the process of preparation of modified semi-coke from semi-coke using phosphoric acid (H3P04) as the activating agent using the response surface methodology (RSM). The influences of three major dependent variables, the impregnation ratio, activation time, and activation temperature were assessed on the independent variables yield and the iodine number. The empirical relationship between the dependent and the independent variables were established using the quadratic response surface models, which were utilized to optimize the process parameters. The significance of each of the parameters and interaction among the parameters on the independent variable was assessed based on analysis of variance (ANOVA). The process variables were varied within the range of impregnation ratio (IR) from 1.5 to 4, activation time from 30 to 90 min and activation temperature from 550 'C to 650 'C. The optimized process conditions were estimated to be an IR of 2.29, activation time of 32 min, and an activation temperature of 605°C respectively using the process optimization tool. The BET surface area of modified semi-coke of the optimized sample was estimated to be 915m2/g, with the pore volume of0.71cm3/g, with an average pore diameter of 3.09 nm, with micropore volume fraction being 52.36%. The scanning electron microscope (SEM) images were utilized to visualize the surface pore structure.

Jan 1, 2013

By Xinhua Wang, Xuefeng Liu, Die Yang, Lifeng Zhang, Wen Yang

"CSP thin slab continuous casters are well used in recent years. The control of heat transfer in the mold is very important because it is correlated with several slab defects. The mean heat flux of CSP mold was studied based on the plant production data of LCAK steel and weathering steel. The effect of various operation conditions on the heat flux was analyzed and discussed. The results showed that the heat flux was 2.1-2.6 MW/m2 on the wide face and 1.2-2.2 MW/m2 on the narrow face for the casting of LCAK steels. During the casting of weathering steel, the heat flus was mostly 2.05-2.5 MW/m2 on the wide face and was 1.1-1.8 MW/m2 on the narrow face. The heat flux depended largely on the casting speed. The heat flux on the wide face increased obviously with increasing casting speed when the casting speed was relatively low; however, at high speed, the heat flux increased slowly or kept constant. At low casting speed, the heat flux depended little on the superheat of the molten steel. The mean heat flux depended little on the level fluctuation at continuous casting mold.IntroductionCSP thin slab continuous casters are used more frequently in recent years for its low cost of construction and manufacturing. The structure of CSP mold is very different from that of conventional thick slab casting mold, inducing the difference of heat flux between them. There have been some studies about the heat flux of thick and medium slab casters [l, 2]. Heat transfer in the mold is very important for the solidification of molten steel because it is correlated with several slab defects such as slab break-out, longitudinal crack, and surface depression. Moreover, higher casting speed is desired to improve the productivity. The control of solidified shell is extremely important. The heat flux is largely influenced by several casting parameters such as the cooling intensity of the mold, the casting speed[3], the mold flux powder [3, 4] and the carbon content of steel as well [5]. The investigation on the heat flux and affecting parameters can help to understand the solidification of molten steel in the mold."

Jan 1, 2013

By F. Garcia-Carcedo

This research aimed to develop a clean technology for the production of ZnO from residues generated by the steel making industry. Scientific and technologic parameters were both investigated in order to define an industrial methodology allowing the integral recycling of EAF dusts. A reengineering of the Waelz process was perform,~d, aiming to produce a clean fraction of ZnO, fluorine free, as well as a slag enriched in metallic iron, which can be recycled in electric arc furnaces. The technical conditions used to produce the ultra pure fraction of ZnO are described. The magnetic separation of the EAF dust allowing the production of a phase high in iron and recyclable to the electric arc furnace is also discussed. Thermodynamic of the volatilization of all the elements contained in the EAF dust was performed in order to better control the thermal process in the rotary kiln. Tests were run using different reducing agents, weakly or highly reactive, aiming to determine their specific efficiency.

Jan 1, 2000

By A. E. M. Warner

Inco Limited has long and extensive experience in converting nickel-copper primary smelting mattes over a broad range of nickel/copper weight ratios and combined nickel-copper-cobalt contents. At the Copper Cliff Smelter, the composition of the converter product matte has to meet the requirements of the matte separation process; at the Thompson Smelter, converter matte of a different composition is cast into anodes for nickel electrorefining; and in Soroako, Indonesia, a very low copper product matte is granulated for the Japanese market. Recently, Inco has conducted pilot plant testing of three possible nickel-copper matte continuous converting routes, namely flash converting, oxygen top blowing-nitrogen bottom stirring, and tuyere blowing. This test work has generated substantial new information on nickel-copper matte converting chemistry. This overview paper reviews the metallurgy of nickel-copper matte converting, in particular the behaviour of cobalt and the operating conditions required to meet the iron and sulfur specifications of the product matte. The relevant thermodynamic information is used to discuss the industrial data.

Jan 1, 2003

Cospidie (3CaO*2SiO2*CaFe2) is one of the most important compounds crystallized in mold flux films during casting in the continuous casting process of steel, The primary crystallization field of cuspidine has been experimentally developed in the CaO-SiO2-CaF2-SiF4 system. The cuspidine-NaF binary and cuspidine-CaF2-NaF ternary systems have been also experimentally determined to study effects of addition of NaF on the primary field of cuspidine. In order to discuss its thermodynamic stability the standard Gibbs energy of formation of cuspidine has been deterimed by an electromotive force methods using CaF2 as solid electrolyte and a transpiration method as follows: ^fG° (cuspidine) /kjmol-1 = 5198 + 0.825T (+12) (1313<T/K<1329): EMF method ^fG° (cuspidine) /kjmol-1 = 5178 + 0.813T (+8) (1221<T/K<1469): Transpiration method The chemical potential diagram and constituent activities for the CaO-SiO2-CaF2 System have been evaluated based on the obtained thermodynamic data.

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 N. J. Themelis

In the last two decades, the Outokumpu flash smelting process has become the dominant new technology for copper smelting and has? also been applied to the smelting of other metal sulfides. The application of oxygen enrichment and improvements in concentrate burner and furnace design have resulted in ever increasing smelting rates per unit volume of the reaction shaft. This paper examines the. rate phenomena taking place in the reaction shaft of the Outokumpu furnace and compares information obtained from a mathematical model of heat and mass transfer rates to results obtained in pi1ot tests conducted at Pori, Finland, and to actual performance of a number of flash smelters around the world. 2?

Jan 1, 1985

By S. Agatzini-Leonardou

The objective of this work was to prove repeated loading capacities and investigate the selectivity of physically stabilized algal biomass from Spirulina platensis and Chlorella sp. for the removal and recovery of cobalt, nickel and chromium from laterite heap leach liquors. The testwork was carried out on a bench scale in small glass columns and proved that it was possible to immobilize the biomass on the highly porous surface of pumice stone (kissiris). Nickel and cobalt could be removed from pure aqueous solutions of each metal by the immobilized cyanobacterial biomass. Nickel and also cobalt biosorption was sensitive to the initial solution pH. Cobalt recoveries up to 80% were achieved after 5 loading cycles, from low concentration solutions, at pH 6.0. Nickel removal was complete under the same conditions, whereas chromium sorption was ineffective. Desorption of the metal loaded columns was effected by dilute sulfuric acid. The algal species giving the best adsorption capacities for the metals under consideration was selected for further experimental work with real laterite heap leach solution produced by column leaching. A statistical analysis of all obtained results was conducted using the fraction of metal removed as response. The ratio "mass of metal removed to mass of protein contained in the immobilized cells" was determined as well. The described method might be applicable for recovery of cobalt and nickel from diluted laterite heap leach solutions, such as heap wash waters, or for their removal from waste streams of a hydrometallurgical extraction process.

Jan 1, 1997