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By Mukesh Jain

The liquor from potroom wet scrubbers is treated with lime to precipitate the soluble fluorides. The solids after filtration, referred to as scrubber mud, contain in addition to calcium fluoride, alumina, carbon, tars including polyaromatic hydrocarbons (PAH), cryolite and pachnolite and are considered hazardous. This communication deals with the pilot plant scale calcination of scrubber mud with a rotary kiln to obtain non-hazardous fluoride raw materials. Air classification was performed to separate the mudinto aluminarich andcalcium fluoride rich fractions which were then calcined. With proper control of calcination parameters and addition of lime, the carbon and tars were destroyed and hydrogen fluoride emissions were controlled. The calcined products could be used in the steel indusny as a fluxing agent or as a substitute for fluorspar in the production of aluminum fluoride.

Jan 1, 1994

By C. Lupi

In 1996 the Italian Agency for Environmental Protection (ANPA) has initiated a study of the environmental impact of the industrial sector of steel produced by Electric Arc Furnace (EAF). Within the framework of this study a hydrometallurgical process to treat EAF dusts was considered and developed. The paper describes the zinc and lead recovery from fumes coming from carbon steel production. The zinc extraction consists in acidic leaching followed by SX-EW steps. The leaching sludge containing lead sulfates was treated to obtain pure lead salt and inert solid residue. The whole process, that minimizes effluents by recycling the main liquid streams, has been developed to obtain marketable products. The solid waste, containing spinels, was subjected to elution tests in order to verify its compatibility with environmental regulation. The process, that has been set-up and tested in the laboratories of the University of Rome, will be transferred and studied on a pilot plant in order to assess its industrial and economical feasibility.

Jan 1, 1999

By M. Misra

The bacterium?Mvcobacterium Phlei has a demonstrated potential to be used for the flocculation of a variety of finely divided minerals. The microorganism possesses both hydrophobic surface and high negatively electrostatic charge. It can adhere to many mineral surfaces ?if the charge and hydrophobic interaction? between the microorganism and the minerals are favorable to adhesion. Experimental results showed that the dolomitic phosphate slime from Florida and fine hematite can be :readily flocculated from dilute suspension.. In the case of dolomitic phosphate slime, a consolidated sediment containing 24'-25 weight% :solids can be obtained from .a dilute slurry .in a short time. Sediments obtained from hematite flocculation are rather massive and more .consolidated than phosphate slime. Mycobacterium Phlei has a specificity for selective flocculation of hydrophobic fine coal particles from pyrite and ash containing minerals. Because of mutual hydrophobic interaction of coal and Mycobacterium Phlei, it was noticed that coal particles appear to be strongly held in the aggregate by adhesion or bridging of bacteria. However, Mycobacterium Phlei is not a good flocculant for either associated pyrite or ash present in coal.

Jan 1, 1991

By S. N. Ashrafizadeh

Nowadays, hard carbides have found various industrial application in the manufacture of cutting and drilling tools as well as metal forming devices. About 60% of the world tungsten production is consumed in the manufacture of hard carbide pieces. Regarding the high economic value of hard carbide components, i.e., Ni, Co, TaC, TiC, and WC, their recovery from scrap species is attracting much interest. In the current research, the cobalt and tungsten content were recovered from scrap cemented carbide pieces through the application of high voltage electrolysis in nitric acid media. By this method, cobalt and tungsten were initially recovered as cobalt nitrate and tungstic acid, respectively. The precipitate of tungstic acid was calcined at 800ºC after being washed twice with distilled water. A pure tungstic oxide was obtained. The effects of current density, electrolyte concentration, speed of agitation, and the surface area of the anode on the efficiency of the electrolysis process were investigated. The optimum conditions of current density of 1500 A/m2, an acid concentration of 1.5 M, and a cell temperature in the vicinity of 60 to 80ºC were obtained. At the optimum conditions, an acceptable rate of collapse for the anodic carbide pieces of about 3.1 g/h was achieved, which remained constant up to the completion of the recovery process without any passivation .

Jan 1, 2003

By Baozhong Zhao

The direct smelting of copper concentrates to copper metal in a single furnace offers environmental and energy advantages over conventional two-stage copper smelting processes. However, the direct copper making results in unacceptably high level impurities (As, Sb and Bi) in the anode copper. Experimental studies have shown that it is possible to remove these impurities from molten copper by injection of sulfur-hexafluoride. This paper discusses the experimental findings on the influence of various factors on the rate of removal of impurities, such as the impurity inter-effects, initial oxygen content in the metal and injection rate of SF6.

Jan 1, 1995

By M. C. Ruiz

The conventional pyrometallurgical methods to treat copper sulfide concentrates include generally, one or more oxidizing steps where the formation of SO2 gas can not be prevented. From the economical point of view and the nature of some of the processes in which SO2 is produced, its complete capture is not feasible; therefore an important fraction is released to the atmosphere as fugitive emissions. In this research, the reduction of chalcocite was studied in the presence of lime as an alternative method, which overcomes the pollution problems related to SO2 emissions. The effect of temperature, time, concentration of carbon and CaO on the reduction rate were studied. Among these variables, temperature affects most the reduction rate. Conversions over 95 % can be obtained in less that 20 minutes at temperatures over 1000 ° C. The measured partial pressures of the gaseous components indicated that the chalcocite reduction proceeded through the gaseous intermediate species CO, C02, and the overall kinetics was controlled by the Boudouard reaction. The kinetic model In(1-X)= kt fits well the experimental data. Apparent activation energy of 3 14 kJ/mol was calculated for the temperature range of 900 0C-1050 °C.

Jan 1, 1999

By Huang Kai

Uniform needle-like and spherical nickel oxalate particles were prepared by the chelating precipitation process, which was based on the reaction of oxalate acid and the solution of ammonia nickel chloride. The molar ratio of ammonia to nickel ion in the mixed solution is essential to determine whether the spherical or needle-like particles are formed, which means actually the concentration of ammonia is the key to determine the growth mechanism. When oxalate acid is added in the form of solid, it may act as the nucleation interface for the eariy-precipitated substance and so induce the formation of spherical particles. The PVP agent can improve the dispersing degree of the needle-like particles and higher reacting temperature leads to larger particles. The composition of the needle-like particle consists of ammonium and nickel oxalate instead of the pure nickel oxalate.

Jan 1, 2003

By P. A. Davidson

"We discuss the influence of a static magnetic field on jets, vortices and turbulence. This is particularly relevant to D.C. braking in slab casting. Our main conclusion is that, typically, the magnetic field destroys mechanical energy, via joule dissipation, but is unable to destroy momentum. Rather, it continually rearranges the momentum in such a way that the energy falls.IntroductionIt is well-known that a static magnetic field can suppress motion of a liquid metal. That is to say, movement of the liquid across the magnetic field lines induces a current. This leads to Joule dissipation and the resultant rise in thermal energy is accompanied by a corresponding fall in kinetic energy.This phenomenon has been exploited in a range of metallurgical processes. For example, in the continuous casting of large steel slabs, an intense, static magnetic field is commonly used to suppress motion within the mould. The objective is to keep the free surface of the liquid quiescent, thus avoiding the entrainment of surface debris. In other solidification processes, such as techniques for growing semi-conductor crystals, it is widely believed that natural convection has a detrimental effect on the metallurgical structure of the solid. Again, the imposition of a static magnetic field is seen as one means of suppressing these unwanted motions. Finally, magnetic damping is used in the laboratory measurements of chemical and thermal diffusivities, particularly where solutal or thermal buoyancy can disrupt the measurement technique.In this paper we shall look at the damping of jets, vortices and turbulence. Our aim is to present a unified theoretical framework from which the many published studies may be viewed."

Jan 1, 1999

By E. Allaine

Carbochlorination kinetics of pure MoO3, Nb2O5, Ta2O5 and V2O5, by Cl2+CO+N2 gas mixtures was investigated between 380 and 1000 °C. Standard free energy of carhochlorination reactions and phase stability diagrams of these refractory metal compounds were calculated. The influence of total gas flow rate, temperature, reactants partial pressures on the reactivity of these oxides were investigated. The apparent activation energies were found to be about 83, 75, 110 and 100 kJ/mole below 650°C for MoO3, Nb2O5, Ta2O5 and V2O5, respectively. Above this temperature, the Arrhenius plots exhibit a rate anomaly attributed to thermal decomposition of COCl2 and/or structural changes of these refractory metal oxides. The apparent reaction order of carbochlorination of these oxides with respect to Cl2+CO was determined. For these refractory metal oxides, the reaction rate was maximum for a Cl2/CO ratio of about 1 in the chlorinating gas mixture. Results of carbochlorination of these oxides are compared and discussed.

Jan 1, 1995

By Annette Revet

Aluminum fluxes have been used for the remelting of secondary aluminum since the beginning of the recycling industry. During the last sixty years, a number of fluxes have been designed, researched and tested at the laboratory and plant scale. Fluxes are primarily a mixture of potassium chloride and sodium chloride with the addition of some other chloride and fluoride containing salts. The conventional Mining methods of potassium chloride and sodium chloride yield products that are not high in purity without costly reprocessing or additional refining. In 1993, Kalium Chemicals, Ltd. began supplying flux mixtures to the aluminum industry. Kalium produces potassium chloride and sodium chloride which are mined and refined by a patented solution-mining process. The salts produced by this process are high in purity with lower concentrations of iron oxide, sulfates, and other impurities. This paper will present the different mining methods used in the production of sodium chloride and potassium chloride. The paper Will address how these mining methods affect the purity of the final product as well as the effect of purity on the performance of the fluxing salt.

Jan 1, 1995

By A. Kar

A mathematical model is presented for pure titaqium deposition from titanium tetrabromide on a stainless-steel (SS 304) substrate. Five three-dimensional, transient, and nonlinear partial differential equations are used to account for the diffusion of various species inside the deposition chamber and the thermal decomposition of titanium tetrabromide, titanium dibromide, and titanium monobromide at the surface of the substrate in order to determine the thickness of the titanium film deposited on the substrate. The effects of various process parameters on the deposition and shape of titanium films are examined, and under certain conditions, the deposited titanium films are found to have volcanic profiles.

Jan 1, 1992

By Norihiko Fukatsu, Takashi Iwamoto, Noriaki Kurita, Koji Katahira, Kunihiro Koide, Teruo Ohashi

"The galvanic cell-type hydrogen sensor employing CaZro.9Ino.t03-a. as the solid electrolyte was designed for the measurement of hydrogen activities in molten copper under industrial .conditions. The sensor probe consists of the cap-shaped solid electrolyte with porous platinum electrode on the inside and alumina refractory tube. The gas mixture of the composition 4%H2-0.5%02-Ar was made to flow on the inside electrode. The hydrogen sensor probe was inserted directly into molten copper and the melt was used as the outer electrode. The effect of oxygen activity gradient to EMF was eliminated theoretically by measuring the oxygen activity in the melt simultaneously with an oxygen sensor. The high stability of output and excellent response to the change of hydrogen activity were obtained over the wide range of industrial copper melting conditions.IntroductionIn the metal casting process, hydrogen easily dissolves in molten metals from water vapor in the surrounding atmosphere. Owing to the large difference in hydrogen solubility between liquid and solid metal, dissolved hydrogen becomes a cause of the defects of blowholes in castings or ingots. It is necessary to control the hydrogen content in the molten metals [l]. Using proton-conducting ceramics as a solid electrolyte, high temperature-type hydrogen sensor can be constructed [2]. SrCe03- and BaCe03-based perovskite-type oxides exhibit appreciable proton conduction under hydrogen containing atmosphere at high temperature [3-5]. A hydrogen sensor for molten aluminum using CaZro.91no.103-a. has been developed and widely used in the ·process control in the aluminum melting industry [6,7]. The same type of hydrogen sensor has also been expected in the copper melting industry. .. However, CaZro.91no.103-a shows ·not only proton but also oxide ion conduction in the high temperature and at low oxygen activies like the copper melting· conditions. Then we studied the oxide ion conduction in CaZro.91no.103-a. iit · detail [8]. From the consideration on the EMF of the galvanic cell employing this material as electrolyte, it was shown that the unknown hydrogen activity may be precisely determined from cell potential which is corrected for the effect of oxygen potential gradient And the hydrogen sensor based in this principle was constructed and tested in laboratory-scale [9,10]. We repeated the similar tests in factory-scale and developed the sensor system for practical uses [11, 12]. In this report, the structure and system of the hydrogen sensor for molten copper will be introduced first. The reliability of the sensor will then be demonstrated from the results of experiments for sensor probes carried out in TYK's laboratory."

Jan 1, 2000

By H. H. Law

Large amounts of waste material in the form of flue dust are generated in the operation of copper smelter furnaces. As a result of increasingly stringent disposal, it has become important to develop methods for treating such metallurgical wastes to extract metals and convert them into salable products. A two-step closed-loop hydrometallurgical process, has been developed: (1) extraction with sulfuric acid removes about 90% of zinc and decreases the dust volume by 50%; (2) extraction with hydrochloric acid dissolves the lead and further decrease the dust volume by 75%. A process scheme for generating salable products is proposed.

Jan 1, 1992

By Jing Zhan, Gui Li, Wei-feng Li, Li-Hua Jiang, Chuan-fu Zhang, Jian-yang Hwang

Thermodynamics analysis for processing the charge with lead concentrate and lead sulfate-containing materials in bottom blowing smelting furnace was conducted. The results show that the technology of large-scale processing PbSO4- containing materials with PbS concentrate in bottom blowing furnace under the condition of using high-iron slag type, batch heat supplement, high temperature and rich oxygen is thermodynamically feasible. The exploration test and industrial experiment confirm the results. When S content in mixed ore is 16~17% with coke foam content of about 5%, the lead paste amount can be increased up to 40%.

Jan 1, 2015

By John H. Schloen

Copper refineries are constantly looking for methods to upgrade their plants to reduce refining costs and to improve the purity of their electrolytic cathodes at the same time that the purity of the anodes they refine is being lowered by the rehabilitation of reverberatory furnace smelters to one of the direct smelting processes. The comments given below are based on the answers to the questionnaire returned bf the 36 copper refineries that represent 66% of the western world s refining capacity. Eleven refineries employ some form of uniform weight anade casting, e.g., Outokumpu, Contilanode, Mitsubishi, Lurgi, or Hazelett. This type of anode casting presents the best possibility for improving cathode purity. The cathode press of Phelps Dadge can improve current efficiencies and cathode quality. The press is used on first-run cathodes, after 48-60 hours, on half-cells at a time without interruption of the cell current. One refinery interrupts current for sever.al hours to allow the anode slime to settle before the, cathode pressing. The cathode press is now used at eight refineries. Apart from periodic reverse current (PRC), it is not expected that current densities will be increased. Thirty refineries, using direct current, average 231 amps/M, with a low of 178 and a high of 350. Five refineries use PRC at an average of 338 amps/M, with a low of 290 and a high of 380. Current efficiencies are good at an average of 94%, with a low of 88% and a high of 99% for the 34 refineries that reported. It must be remembered that the cycle efficiency with PRC is about 93%., so that the effective current efficiency with PRC would be only .94 X .93 or 87% However, PRC should be considered seriously for refinery expansions because it can save about 25% on capital costs.

Jan 1, 1987

By Tapio Ahokainen

Commercial modeling software and increasingly efficient computers enable today computational fluid dynamics (CFD) to be used as a tool for a more comprehensive understanding of the flash smelting and flash converting processes. CFD modeling can be used for design purposes in many technological areas, but some relevant physical and chemical phenomena are still missing in the commercial CFD solver packages. Therefore, Outokumpu has developed several subroutines for solvers to describe analytically the phenomena in the flash smelting environment. CFD sub-models of the copper concentrate and matte combustion, the particle-particle-wall interactions and for more accurate radiation properties of the gas-particle suspension are needed to ensure reliability of numerical simulations on the flash smelting and converting vessels. Several basic combustion phenomena can be modeled with a number of commercial solver packages, but own models for combustion must be included in the case of sulfides as the feed. Mathematical models for copper concentrate and solid matte combustion have been developed during the last decade. They calculate compositions of the particles and temperature, based on extensive experimental research work in laboratory scale furnaces with validated kinetic parameters and temperature measurements of reacting particles. Inside and near the concentrate burner, the standard particle tracking methods do not include the particle-particle interactions and the particle-wall interaction is too much simplified to describe properly the particle collisions with the distribution cone. Therefore, additional models for the particle-particle as well as particle-wall interactions have been written and implemented. For thermal radiation, models for the emissivity of a gas mixture and for calculating the particle absorption and scattering coefficients have been developed and tested. In addition, the advanced radiation model can be used i.e. in the enhanced simulation of off-gas cooling in the heat recovery boiler area of the flash smelter.

Jan 1, 2006

By L. J. Lutz

The U.S. Bureau of Mines has developed an electrorefining process to recover Ni, Co, Cr, and other metals from mixed and contaminated superalloy scrap. The superalloy scrap is cleaned then directly electrodeposited as a Ni -Co deposit. The process recovers approximately 90 pct of the Ni-Co available from the scrap as a 99t pct pure Ni-Co alloy. During electrorefining the electrolyte undergoes a purification process which results in Cr and other refractory metals reporting to the purification residue. Operating data is given for a 3-L compartmented electrolytic cell. Techniques for the removal of Fe, Cr, and trace impurities from the recycled electrolyte are outlined. The economics of a facility producing 15 mt/d of a Ni-Co alloy are also discussed.

Jan 1, 1993

By Taegong Ryu

The thermal plasma process has been applied to the preparation of nanosized tungsten carbide (WC1-x). The reduction and carburization of the vaporized chloride by methane-hydrogen mixtures produced nanosized WC1-x powder, with a small amount of WC or W2C phase. The products were characterized using XRD, carbon analyzer, and TEM. The effects of plasma torch power, the flow rate of primary plasma gas (Ar) to generate plasma flame, and the addition of secondary plasma gas (H2) on the product composition were investigated. The tungsten carbide (WC1-x) powder had a particle size less than 30 nm. The powder was treated under hydrogen atmosphere to fully carburize the WC1-x, and W2C phases to WC as well as remove excess carbon in the product. Finally, WC powder with a grain size less than 40 nm was obtained.

Jan 1, 2008

By J. N. Hryn

This paper describes some of the work done in Phase 1 of a multi-year, five-phase program aimed at demonstrating the economic feasibility of producing commercial-scale quantities of commodity materials derived from salt cake residue-oxide. The amount of salt cake generated annually in the U. S. is estimated to be 510,000 tons, including 340,000 tons of residue-oxide. Used beverage can (UBC) processing accounts for the majority of residue-oxiae that could be made available for further processing into commercial products. To characterize the composition of residue-oxide. eight residue-oxide samples from various secondary processors were obtained and analyzed. Surprisingly, the composition of residue-oxide was found to be independent of source or alloy family being processed, with? the exception of slightly elevated silicon levels in 3XXand UBC residue-oxide samples. Major phases detected in the residue- oxide were? alumina, spinel, and aluminum hydroxides. Preliminary economic analyses indicated that the refractory market appears to be the best choice for high value-added products produced from residue-oxide with minimum processing. Bench-scale tests indicated that low silicon containing residue-oxide is ready to enter this market, but the elevated silicon content of UBC and 3XX residue-oxide preclude this possibility. A separation technology should 'be developed to remove silicon-containing . species from the alumina and spinel values Present in residue-oxide. This technology would then allow UBC and 3XX residue-oxides to be converted to significantly higher value-added products.

Jan 1, 1995

By H. Y. Sohn, Haitao Wang, Moo Eob Choi

"A novel ironmaking technology is under development at the University of Utah. This technology produces iron directly from iron ore concentrate by gas-solid suspension reduction. Hydrogen is the main reducing agent for high reactivity and for the elimination of carbon dioxide release in this ironmaking process. The direct use of concentrates allows bypassing the problematic pelletization/sintering and cokemaking steps in the steel industry.Intrinsic kinetics of the suspension reduction of magnetite concentrate particles by hydrogen has been measured. Experiments were carried out in the temperature range of 1423-1673 K, other experimental variable being hydrogen partial pressure, the amount of excess hydrogen and particle size. Under most experimental conditions, 95% reduction was attained within several seconds, which presents sufficiently rapid kinetics for a suspension reduction process. The reaction kinetics followed the nucleation-and-growth equation, and a rate equation that contains all the effects of the experimental parameters has been obtained.IntroductionWith the rapid increase in steel production, it is critical to control CO2 emissions which is the main greenhouse gas. It is inevitable to release a huge amount of CO2 when coke and/or coal are used as the main reducing agent in producing iron. As one of the methods to reduce the CO2 emission from ironmaking, the utilization of the gaseous reducing agents and fuels, including hydrogen, has been investigated [1-6]. The use of such gases forms the basis for a new ironmaking technology under development for producing iron directly from fine concentrates by a gas-solid suspension technology. This technology would reduce energy consumption by about 40% of the amount required by the blast furnace and drastically lower environmental pollution, especially CO2 emission, from the steel industry [4]. This is accomplished by adopting H2-based reductant and bypassing pelletization/sintering and cokemaking steps. Unlike other gas-based alternative ironmaking processes using shaft furnaces or fluidized-bed reactors, the suspension reduction technology is a high-intensity process because it will not suffer from the problems that other processes do when operated at high temperatures mainly from the sticking and fusion of particles."

Jan 1, 2011