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By J. Gartelmann, B. Zaslavsky, Y. Vojta, D. J. Chaiko, W. Mego, A. N. Rollins

"Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that we have studied are generated by combining an aqueous salt solution with an aqueous polymer solution.We have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. We have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this chapter we review the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.IntroductionAqueous biphasic extraction (ABE) is a highly adaptable separation technique that can be used in a wide range of applications. We have been evaluating various types of ABE systems for possible applications in the treatment of solid radioactive wastes (1,2), liquid nuclear wastes (3,4), and contaminated soils (5-7), and in the removal of organics from aqueous salt solutions (8). We have also conducted fundamental studies of the solution microstructure of ABE systems using small angle neutron scattering (SANS) (9).The extraction systems are generated by combining an aqueous salt solution and an aqueous polymer solution. This produces two distinct liquid layers that are as immiscible as oil and water, yet each liquid layer contains at least 70 to 80 wt % water. The biphasic systems that we have been working with consist of immiscible polyethylene glycol (PEG) and salt solutions. Some inorganic salts that promote biphase formation with PEG solutions include the sodium/potassium salts of sulfate, carbonate, phosphate, and hydroxide (10)."

Jan 1, 1996

By Nickolas J. Themelis

The role of copper in the economy will not diminish in the 21st century. Following the tenets of industrial ecology, production and use of copper must take into account both human needs and also how to minimize "collateral" effects on the environment. Dispersive uses will be phased out and post-use recovery of copper will increase. This will result into an advantage for smelting processes that can accommodate mixed metal scrap and waste streams. The bath smelting processes of Noranda and Mitsubishi will continue to make progress but the dominance of the Outokumpu flash smelting will not be challenged until the Noranda reactor overcomes the obstacles to the direct production of copper, thus eliminating the need for a converter.

Jan 1, 1999

By I. Gaballah

About forty percent of the SOx emissions are generated during the processing of metal sulfides of Cu, Pb, Zn, Ni, etc. Although new technologies for metal sulfide's smelting allow the production of H2S04 with a reasonable cost and decrease the emissions of sulfur oxides, the generated quantity of SOx is considered as a serious threat to environment. This paper suggests alternatives for low temperature processing of complex sulfide ores or concentrates 'CSO or CSC' under neutral, reducing and chlorinating atmospheres or their combination. At T > 400 "C, The neutral and reducing treatments allow the decomposition of pyrite and the partial recovery of sulfur as So and H2S. At 300 "C, the chlorinating treatment of CSC is fast, exothermic and allows the separation of FeC13 from the valuable elements' chlorides. It also generates SyCIx that can be either reduced by H2 or hydrolyzed in presence of sodium sulfide. The recovery rate of elemental sulfur with respect to the sulfur input exceeds 90 %.

Jan 1, 1999

By G. C. Gullo, H. Wabusseg, P. J. Uggowitzer, H. Kaufmann

"The basic concept of New Rheocasting (NRC) is described and the application of wrought alloys with this process is discussed. Practical experiments with the aluminium alloy AIMgSi I are explained. For this alloy the proper NRC - casting temperature was determined by using Thermo Cale - computer software and DT A and the essential processing conditions are shown. In the experiments the melt was taken from an aluminium holding furnace and cast into NRC steel cups. After controlled cooling the resulting slurries were cast into a 4-step die on an UBE HVSC 350 Squeeze Casting machine. The characteristic microstructural values such as grain size and shape factor were measured and compared with classical casting alloys. The influence of the wall thickness of the step part (6 mm, 10 mm and 14 mm) on the microstructure is described. Tensile properties in different heat treatment states are compared with characteristic prope1ties of the same alloys in forged condition. The ew Rheocasting - process CNRC)The NRC process is a recently developed new semi-solid processing method which allows the production of pore-free, pressure tight components.In the NRC process a fu lly liquid, but only slightly superheated melt is taken from a holding furnace and poured into specially designed steel crucibles, which are placed on a carousel next to the Vertical Squeeze Casting machine. In this ,NULL,slurry maker'· globul ar a-Al grains grow, following forced homogeneous nucleation at the cup wall [ 1, 2]. In the few minutes during which the melt is cooled to sem i-so lid processing temperature, a stable ske leton of a-Al phase forms. The resulting slug keeps a cylindrical shape during its slide into the sleeve of the Vertical Squeeze Casting machine, where it is cast into shape."

Jan 1, 2000

By A. J. Paul, K. O. Yu

"Today, foundries are moving towards the use of models and design tools to gain a competitive advantage in producing castings of high desired quality. This leads to a growing alliance between foundries, software developers and researchers seeking to model, visualize and understand the phenomena taking place during the casting process. In addition, there is a need to develop affordable techniques to produce parts in small lot sizes. This leads to the development of a Flexible Manufacturing System consisting of: (1) up-front computer-aided engineering; (2) computer integrated proto typing with solid freeform fabrication; and (3) fabrication of the actual mold and related equipment to cast the part.This paper discusses some of the developments that are taking place today in the areas of modeling the physical phenomena during the casting process as well as towards developing a Flexible Manufacturing System for producing cast parts. Areas that require most work involve prediction of defects and mechanical properties using simplified analyses. In addition, electronic data sharing for collaborative engineering between geographically dispersed team members is also discussed. Case studies are presented showing successes as well as failures.IntroductionCasting, one of the oldest forms of metalworking, has recently seen a flurry of developments in the area of solidification modeling. These developments have come about after the realization that, in order to stay competitive, foundries need to reduce their scrap rate and production costs, and increase casting quality. Even though this is not new knowledge for foundry engineers, the tools to help them achieve this goal are just being developed and put in place for use by foundries. Several state-of-the-art software packages are currently available to analyze the solidification behavior in complex shaped castings. These packages make use of several different approaches for solving the various problems associated with casting processes. The overall architecture of a comprehensive solidification modeling system is shown in Figure 1."

Jan 1, 1994

By Lamar S. Todd

The direct production of metal from a sphalerite concentrate is an attractive route for primary zinc. A series of operations and conditions have been selected to efficiently cause the following overall exothermic reaction. The process uses a continuous circulation of molten copper for material and energy transfer between the unit operations. Sulfide concentrate is reduced with an excess of superheated copper to make a copper alloy and white metal. The alloy is stripped of volatile metals under vacuum and some metals can be separately condensed. The residual copper and the white metal are fed into a copper converter to be blown with oxygen for desulfurizing and the superheated copper is recycled. The paper will include a detailed material flow sheet for the process, discussion of the operating conditions of the individual units, behavior of minor elements, and zinc quality.

Jan 1, 1999

By Chao Li, Lim Hongxu, Yuyue Wang, Xie Yang

"A intergrated process of sulfuric acid leaching, sodium chloride leaching, lead chloride crystallization, lead hydroxide synthesis and roasting was carried out for the recovery of lead, cadmium, copper and zinc from lead smelting dust containing various metals. The results showed that the separation of cadmium, zinc and copper from dust could be obtained after sulfuric acid leaching and corresponding leaching rate were 92.12%, 90.25% and 88.26% respectively. The subsequent sodium chloride leaching carried out for lead with optimized parameters as: sodium chloride concentration 250g/L, leaching temperature 90°C, leaching time 2h, pulp density 33g/L, 0.12mol/L CaCh; The lead compounds crystallization rate reached 86.67%, and then transferred into mPbO·nH2O, the product of 98.66% ß-PbO could be obtained through roasting under 502°C. In the end, a feasible method of ß-PbO preparation from lead containing dust was put forward.IntroductionThe pyro-metallurgy flue dust from smelting lead activities are often stockpiled and pose potential environmental risks due to the heavy toxic elements, such as Pb, Cd, As, Cu, Cl, and Zn which are contained in the dust. With the rapid depletion of rich ore resources in recent years, it has become increasingly more financially attractive to recover valuable metals from previously stockpiled dust, while simultaneously reducing the potential of environmental pollution from toxic elements contained in the dust. Nowadays, pyro-metallurgical and hydrometallurgical routes or both combined methods can be developed to treat secondary materials such as lead ash, leach residues etc. By comparison the hydrometallurgical processes are often considered more eco-friendly.Some chloride leaching processes for recovering lead have been employed using either NaCl, or MgC2 and CaCl2, or FeCl3 [1] The effectiveness of the brine leaching method is based on the formation of complex metal chlorides in concentrated chloride solutions [2] Similarly, Other metals such as zinc, cadmium and copper contained in the flue dust are often treated with sulfuric acid, hydrochloric acid, ammonium solution and sodium hydroxide etc. as lixiviants [3] The metals from leach solutions thus has been obtained by precipitation, ion exchange, solvent extraction or replacement [4]"

Jan 1, 2014

By P. Rooney

In due course, new smelters will have to be installed in order to meet the increasing worldwide demand for copper. This paper presents the results of a study made for the purpose of identifying the most desirable countries in the world in which to locate a new smelter. Both sociopolitical and economic factors were taken into account. Criteria developed and methods used to assess each possible location are described. The study indicated that the most interesting potential locations are Canada, -Chile, Portugal and the USA for new copper smelting complexes.

Jan 1, 1983

By R. E. Sundell, S. M. Correa

"A mathematical model is developed for the fluid flow in tungsten-inert gas weld pools. The fluid is taken to be incompressible, viscous, electrically conducting, and confined within a pool of specified shape. The flow is driven by surface-tension gradient (thermocapillary), electromagnetic, and buoyancy forces generally in this order of importance. Analysis indicates that the electromagnetic field may be calculated a priori and so decoupled from the nonlinear fluid mechanics and heat-transfer problem. The resulting set of equations is solved numerically by a line relaxation process. Computational errors caused by truncation in finite-difference schemes and by inadequate grid distributions are considered. The model is used to study several cases of differing heat and current input to the pool with and without surfactant-induced thermocapillary forces. The principal conclusions are that the thermocapillary flow, when present, is dominant with surface velocities on the order of 1 m/s. The heat transfer, as deduced from isotherms within the pool, is crucially dependent on the flow. Also, flow velocities and weld-pool surface temperatures were measuredand agree well with the model.2. IntroductionThe requirements of improved control and of automation in the TIG (tungsten-inert gas) welding process have led to the development of mathematical models for the heat transfer to the workpiece. It is now widely recognized that the fluid flow in weld pools sufficiently distorts the conduction heat transfer pattern to warrant inclusion in a process model. The experiments of Woods and Milner (1), among others, demonstrated that TIG weld pools could be driven by the electromagnetic J x B body forces present, J being the current distribution and B the induced magnetic field. Atthey (2) calculated that in typical pools the buoyancy force was about an order of magnitude less important - despite the large temperature gradients present - and neglected it in a computational study of the magnetohydrodynamic (MHD) flow. This work also reviewed many earlier studies of MHD flow caused by a source of current at a fluid surface, including analytical studies by Shercliffe (3), Sozou (4), and Sozou and Pickering (5), and a numerical study by Andrews and Craine (6). These works establish the importance of the electromagnetic force in the weld-pool flow."

Jan 1, 1986

By A. Christlo

Short circuit detection in 1984 involved nine inspectors for production rates of 43,000 tpa. Trials indicated the feasibility of applying cell voltage monitoring to short circuit detection and improving operational efficiency. A computerised cell voltage monitoring system was commissioned in February 1986, to read voltages from 648 cells. The system incorporates 16 evenly distributed work face units which communicate with a central computer system. Provision has been made in the computer program for the automatic adjustment of cell reference voltages. This allows for the effect of polarization and other process variables which might other wise interfere with short circuit detection. The work face units can continue to work independently for several days should this become necssary. Current efficiencies have been maintained and the number of inspectors reduced from nine to five.

Jan 1, 1987

By Gus Van Weert

Solvent extraction of iron from zinc refinery liquors has been investigated before, mainly on the MEHPA / HC1 stripping combination. Leakage of chloride into the zinc electrolyte and the costs of handling the ferric chloride eluate have prevented this option from being adopted. This work explores the stripping of the ferric loaded organic phase with nitric acid to take advantage of the possibility of regenerating up to 6N nitric acid, and clean spheroidal hematite production by autoclave treatment of ferric nitrate solution. The work was carried out with DEHPA (di 2-ethyl-hexyl phosphoric acid) in kerosine. Degradation testing proved the DEHPA to be very stable, when exposed to nitric acid solutions up to 6N and temperatures up to 70" C over a period of five days. Ferric iron was removed completely froma synthetic hot acid leach liquor, irrespective of the DEHPA concentration. Stripping the ferric turned out to be the problematic step. Although the stripping efficiency was considerable better at 50 than at 20° C, it decreased with increasing DEHPA/Fe ration in the organic phase. Eluates of no more than 5-10 g/l ferric nitrate were produced. surprisingly, nitric acid was found to be a less efficient stripping agent than sulphuric at equivalent normality and its efficacy levelled off above 4N. It was concluded that DEHPA does not appear to be the S.X. reagent to take advantage of the low cost autoclave decomposition of ferric nitrate opportunity in zinc hydrometallurgy and that another S.X. reagent, also resistant to nitric acid, but based on weaker compound formation is needed.

Jan 1, 1998

By Dean Ilievski

Mathematical modelling of the precipitation process requires that the kinetics of crystal growth, nucleation and agglomeration be known: This paper reviews the current state of knowledge on these precipitation sub-processes (ie. growth, nucleation and agglomeration) and describes a number of experimental techniques for estimating their kinetics. The experimental methods used to generate the precipitation data and the data analysis techniques used to extract the kinetics information from the data are discussed separately. There is no universal "best" technique for determining the kinetics. However, studies on multi-crystal systems are more reliable for modelling purposes than are single crystal studies. The selection of a technique will depend on which sub-processes are present. A problem with all kinetics studies is that there is generally a large uncertainty in the estimated kinetic parameters. This stems from the scatter in the experimental data being further propagated by the mathematical techniques used to extract the kinetic parameters.

Jan 1, 1996

By Andrew Case

The Port Nickel facility in Braithwaite, Louisiana, is known for pioneering hydrometallurgical processes for the 'separation and recovery of nickel, cobalt and copper. Ten years ago, in 1985, a new CRI-MET process for the recovery of molybdenum, vanadium, nickel, cobalt and alumina from spent catalysts was developed and implemented. Spent- catalysts from the petroleum industry consietute the majority of feed. These are not only a valuable-source of metals, but due to EPA regulations are frequently classified as hazardous under RCRA. Molybdenum and vanadium are selectively leached in an oxidative hydrothermal step. Alumina is then extracted in a caustic digestive leach. The unique technology produces four primary commercial products l molybdenum trioxide, vanadium oxide, aluminum trihydrate and nickel-cobalt concentrate. This paper discusses the process, modifications. during ten years of operation, and the relationship of these modifications to the future of the catalyst recycling business.

Jan 1, 1995

By C. A. Young, J. D. Miller

Adsorption isotherms previously determined by in-situ Fourier transform infrared/internal reflection spectroscopy (FT-IR/IRS) for oleate adsorption at calcite and fluorite surfaces near pH 9 and at various temperatures are compared. Results indicate that, at both mineral surfaces, chemisorption occurs at equilibrium concentrations below approximately l x l0-5 M oleate while calcium dioleate surface precipitation occurs at higher equilibrium oleate concentrations. The extent of chemisorption at the calcite surface is 3 to 5 times less than that at the fluorite surface while the extent of calcium dioleate surface precipitation on calcite is nearly a magnitude larger than that on fluorite. However, for both minerals, surface precipitation decreases with increasing chemisorption. Contact angle measurements and flotation recoveries show the hydrophobicity of fluorite to be greater than that of calcite at each of the temperatures and oleate concentrations studied. Significant differences are noted only in the chemisorption region. Unlike calcite, the hydrophobicity of fluorite was sensitive to the presence of oxygen in the system. Multichannel Laser Raman Spectroscopy (MLRS) showed this behavior was caused by the double-bond reactivity of adjacent chemisorbed oleate molecules and subsequent formation of an epoxide/polyether complex at the fluorite surface. Such a reaction product could not be detected at the calcite surface. These differences in adsorption density, hydrophobicity, and polymerization behavior are discussed in terms of the intrinsic surface properties of the minerals.

Jan 1, 1999

By E. T. White, Dean Ilievski

"Mathematical modelling of the precipitation process requires that the kinetics of crystal growth, nucleation and agglomeration be known. This paper reviews the current state of knowledge on these precipitation sub-processes (ie. growth, nucleation and agglomeration) and describes a number of experimental techniques for estimating their kinetics. The experimental methods used to generate the precipitation data and the data analysis techniques used to extract the kinetics information from the data are discussed separately. There is no universal ""best"" technique for determining the kinetics. However, studies on multi-crystal systems are more reliable for modelling purposes than are single crystal studies. The selection of a technique will depend on which sub-processes are present. A problem with all kinetics studies is that there is generally a large uncertainty in the estimated kinetic parameters. This stems from the scatter in the experimental data being further propagated by the mathematical techniques used to extract the kinetic parameters.IntroductionCrystallisation operations, including precipitation, are widely used in a number of hydrometallurgical processes to recover a desired component or to remove an undesired impurity. The goals of industrial precipitation processes are to maximise the recovery while maintaining product quality (generally product crystal size distribution, purity and morphology and product handling properties). Knowledge of the precipitation mechanisms and kinetics is invaluable for designing new precipitators or for improving existing units. The mechanistic and kinetic information is generally incorporated into mathematical precipitator models, which are then used for process design and optimisation."

Jan 1, 1996

By J. V. Atwood

The U.S. Bureau of Mines has developed a novel Double Membrane Electrolytic Cell (DMEC) that exhibits unique features for recycling contaminated metals and metal alloys. The DMEC incorporates two anionic ion exchange membranes, separating anodic and cathodic regions of the cell. The ion exchange membranes prevent significant transport of unwanted cationic impurities to the catholyte from the impure anolyte while the anion/cation balance in cell compartments is maintained through the free movement of anions between compartments. The membrane barrier makes it possible to electro refine highly contaminated materials or to electrowin from solution while utilizing alternate anode reactions. Sinceanolyte and catholyte cross contamination has been eliminated, premium cathode products are produced. The DMEC has been tested at bench, pilot, and commercial scales. Configuration of the DMEC, cell operation, scale, up efforts, and significant design factors are discussed. Two separate recycling investigations utilizing DMEC technology are presented. The first investigation examines recovery of high purity cobalt and nickel from severely contaminated super aIloy scrap. The second involves? upgrading contaminated cobalt in the U.S. Government's National Defense Stockpile. Capital and operating costs for both potential applications are presented.

Jan 1, 1995

By Jorge Gibson, P. Chris Pistorius, Megha Jampani

"The main reason for the significant carbon intensity of integrated steelmaking (approximately 1.8 tons of CO2 per ton of steel) is the use of carbon-based reductants in blast furnace ironmaking. Several changes to blast furnace ironmaking have been proposed as ways to reduce carbon intensity and cost. A conceptually simple two-zone blast furnace mass and energy balance can be used to quantify the expected impact of such process changes on coke rate, carbon intensity, and productivity. Examples to be discussed include top gas recycling, combining lower blast temperatures with increased coal injection to produce a rich top gas, using prereduced feed, and tuyère injection of natural gas. The use of the operating window – which illustrates how allowable flame temperatures and top-gas temperatures constrain feasible oxygen enrichment levels – is illustrated. Increased use of natural gas would lower the carbon intensity of blast furnace ironmaking.IntroductionBecause of the significant carbon intensity of steelmaking (approximately 1.8 tons of CO2 emitted per ton of steel produced) and the high production rate of steel (more than 1.4 billion tonnes per annum), steelmaking is responsible for a large percentage, approximately 6.7%, of world anthropogenic CO2 emissions [1]. By far the largest input of the carbon into conventional steelmaking is as coke, which is essential to blast furnace ironmaking. A typical fuel rate for blast furnace ironmaking is 450 kg of fuel per tonne of hot metal (THM). (""Fuel"" includes coke and injectants which partially replace coke; pulverized coal and natural gas are typical injectants.) Assuming the fuels to contain 90% carbon on average, and since nearly all of this carbon exits the steel plant as CO2, a fuel rate of 450 kg is equivalent to a CO2 intensity of 1485 kg/THM – by far the largest part of the total CO2 intensity of steelmaking.Blast furnace ironmaking is expected to remain the main source of new iron units; this paper gives some estimates of the extents to which further reductions in carbon intensity from blast furnace ironmaking is possible. A recent European assessment suggested that blast furnace process intensification options such as increased pulverized-coal injection or natural gas injection would yield only modest energy savings [2]. However, if the focus is on CO2 emissions rather than on total energy use, there would be an advantage to using fuels – such as natural gas – which have lower carbon contents relative to energy content."

Jan 1, 2014

By Derek J. Fray

"In order to extend the application of fused salts in\the electrowinning and electrorefining of metals, it is necessary to maximise the current density, minimise the voltage drop and greatly increase the area of electrode surface so as to compete with the space-time yield of pyrometallurgical reactions. The various designs of electrowinning cell are reviewed and it is shown that by the application of a modest centrifugal field it is possible to reduce the anode to cathode interelectrode spacing to 4 mm whilst still maintaining a current efficiency of 85-90%.The thermodynamic potential for electrorefining is far less than for electrowinning yet fused salt electrorefining is only applied in limited cases. The reasons for this are discussed and the important design parameters evaluated. It is concluded that by using packed bed electrodes, separated by a diaphragm, the possibility of electrorefining with very low energy consumption can be achieved. Carbothermically-produced metals are always cheaper than those produced by electrolysis but suffer from the disadvantage of low purity. It is proposed that fused salt electrorefining may offer an energy efficient way of upgrading the metal. IntroductionThe majority of metals can be deposited from fused salts (1,2) but as commercial production is restricted to the more reactive elements, it is worthwhile considering the advantages and disadvantages of fused salt electrolysis as' compared to smelting and aqueous electrolysis. The advantages over aqueous extraction are as follows:1) the much higher conductivities and diffusivities result in much lower IR losses and higher current densities can be achieved at modest voltages;2) the elevated temperatures of operation result in larger exchange currents which give rapid kinetics and lower activation polarisation for the electrode reactions;3) the absence of water as a solvent means that it is not necessary to consider the evolution of hydrogen as a competing cathodic reaction. Furthermore, alkali halide salts, often used as solvents in fused salt electrolytes, have high deposition potentials;4) molten salts generally are mutually soluble and, therefore, concentration polarisation effects are minimised."

Jan 1, 1988

By B. Mishra, W. A. Averill

"The application of various hydrometallurgical, pyrometallurgical and electrochemical processes in the extraction, purification and production of radioactive metals as well as the use of various materials, ego metals and alloys, ceramics, polymers, etc. in the process, construction and handling equipment in the nuclear industry has generated a large stockpile of radioactively contaminated waste material and scrap metal which can not be directly discarded, recycled or considered for long-term storage due to its volume and potential hazards, without the separation of radionuclides. This paper reviews the emerging methods that have been investigated and suggested for dealing with some of these wastes and scrap material.The separation technologies studied for the recovery of radioactive components from the pyrometallurgical and electrochemical processing wastes have been discussed in details with results from some of the recent theoretical and physical modeling work as well as the data obtained from the actual waste treatment. Specific processes shall be described in terms of its advantages and limitations. These emerging separation technologies are being considered by the US Department of Energy as alternatives for dealing with the issues of environmental management [EM] and decontamination and decommissioning [D&D].IntroductionThe high temperature carbothermic or metallothermic smelting reduction methods for metal production are associated with the generation of significant quantity of waste as slags, flue dusts, sludges, residues, effluent salts etc. Certain hydrometallurgical processes also generate lots of aqueous waste due to the inherent nature of the technique. Also, the gas-based reduction processes are not applicable to many stable metal compounds, such as alumina, titania, beryllia, lanthanide and actinide oxides, etc. due to thermodynamic considerations. All these methods cause substantial environmental hazard. There is a need to develop alternative processes which have low waste or ideally a ""zero-waste"" generation.Pyrochemical processes using molten salts provide a unique opportunity for the extraction and refining of many reactive and valuable metals either directly from the beneficiated ore (aluminum, beryllium, neodymium, plutonium, uranium, etc.) or from other process effluent that contain reactive metal compounds. The processes reduce metal compounds electrolytically (A12O 3 and BeCI2) on a carbon anode or by calciothermic reduction (Po, Nd). The by-product, in the latter case, is a calcium oxide saturated halide salt. The waste-treatment to recycle the halide has to be done as a separate step or stored as a contaminated waste. A successful separation technology can provide a new insight to the waste minimization strategy for the nuclear industry."

Jan 1, 1996

By Qingchun Yu, Baoqiang Xu, Yongnian Dai, Bin Yang, Fulong Zhu

"In this paper, the mechanism of the carbothermic reduction-chlorination process to extract aluminum from alumina in vacuum was investigated. The carbon monoxide (CO) content of the gas, phases of the reduction slag, surface morphology of the reduction slag and the product aluminum were measured by means of gas chromatography (GC), XRD, and SEM. The experimental results indicated that the content of CO in the gas decreased, but Al4C3 increased with time at 1773K during the carbothermic reduction process of alumina. AlCl(g) and graphite (C) were produced by the reaction between Al4C3 and AlCh(g) at 1773K, and then aluminum beads generated after the decomposition of AlCl(g). It implied the mechanism of alumina carbothermic reduction-chlorination process in vacuum involves three steps as follows: the carbothermic reduction of A}z03 to produce Al4C3, the chlorination of Al4C3 by AlCh(g) to produce AlCl(g), and the decomposition of AlCl(g) to produce Al(l).IntroductionAluminum is the basic raw material for many industries [1], and it is used extensively because of various excellent properties such as light weight, good malleability, high strength, excellent thermal conduction, high corrosion resistance and so on [2]. Industrial production of aluminum currently includes refining alumina and electrolytic aluminum processes. However, its development has been effected by some factors such as high energy consumption and heavy environmental burdens [3]. In the past several decades, there had been numerous attempts to produce aluminum by new methods. Extracting aluminum from alumina or bauxite directly by carbothermic reduction-chlorination process had been studied [ 4-6]. Although the alumina carbothermic reduction process [7~9] had been studied, the mechanism of the carbothermic reduction-chlorination process had not been systematically elucidated.In order to investigate the mechanism of the carbothermic reduction-chlorination process in vacuum, GC, XRD and SEM techniques will be used to determine the CO content and to characterize the surface morphology and composition of the slags at various temperatures."

Jan 1, 2011