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By J. S. Pitsillos

A new furnace tapping technique involving the simulation of a control valve at the exit to a furnace is being investigated. The purpose of this new tapping technique is to regulate the flowrate of liquid furnace products( slags, metals and mattes). Numerical modelling and experimental work has been carried out on tapping of slags leaving a SIROSMELT reactor and the results found to be in good agreement. Numerical modelling has also enabled prediction of the important industrial conditions for the onset of blockage from the shape of the pressure versus flowrate curves. Slag launder experiments have been carried out and a one-dimensional heat transfer model was used to evaluate the effectiveness of launder covers and different coolants. From the experimental results and mathematical model some launder design guidelines such as inclination angle, covers and coolants have been developed.

Jan 1, 1991

By Yuhsuke Mizukami

Crude high Cr containing steel such as tool steel, heat-resistant steel or stainless steel is produced by dissolution of high carbon ferro-chromium into molten crude steel. In the refining process, decarburization is performed at the first stage, and deoxidation is followed in the next stage. Therefore, the equilibrium relation between dissolved Cr and 0 in molten Fe-Cr alloy after decarburization is very important when yield of deoxidizer is considered for the ovemll control and optimization of the process. It is well known that the yield of deoxidizer does strongly depend on the kinds of refractories of furnace in the secondary refining process. In the present work, the equilibrium relation between dissolved Cr and O in molten Fe-Cr alloy has been measured in a Cr2O3, MgO or Al2O3 crucible at steelmaking temperature. O contents at given Fe-Cr components have been lower in order of Cr2O3, Al2O3 and MgO crucible. The present results have been discussed based on the activities of the constituents in pure solid Cr2O3, and FeO-Cr2O3, MgO Cr2O3 and (AI,Cr)2O3 solid solutions.

Jan 1, 2003

By Kazuyuki Kakegawa

The sintering characteristics and the change in the compositional distribution in the PbTiO3 PbZrO3-Pb(Mgl/3Nb2/3)O3 system during the sintering process by spark plasma sintering (SPS) method were examined. They were compared with those by a normal sintering method. The densification by the normal sintering was slow even at high temperatures, When SPS method was employed, much lower temperature and shorter period resulted in sintered bodies having almost the theoretical density. As expected in normal sintering, the compositional distribution decreased as the sintered density increased. On the contrary, the change in the compositional distribution by SPS was much smaller than that in the normal sintering. This sintering characteristic of SPS suggested a possibility of fabrication of sintered material having a desired compositional distribution.-

Jan 1, 2003

By I. Hilerio

Chromium Nitride (CrN) thin films were deposited on AISI steel 316 substrates by means of the reactive magnetron sputtering method. CrN films were produced under two different conditions. In the first one, the substrate was heated by a DC source. For the second coating a negative substrate bias voltage was applied. X ray diffraction, quantitative energy dispersion and scanning electron microscope were employed to characterize the two different phases, their chemical composition as well as their microstructure. In addition, a microhardness test was carried out. The results show that a better phase formation of CrN thin films was achieved when a heating source was present (first case). Both coatings presented homogeneous surface. Their compositions show differences even when the gases flowing are the same in composition. Regarding to the hardness test results, there can be found a higher value when using a heating source.

Jan 1, 2009

By Kazuyuki Kakegawa

The sintering characteristics and the change in the compositional distribution in the PbTiO3-PbZrO3-Pb(Mg1/3Nb2/3)O3) system during the sintering process by spark plasma sintering (SPS) method were examined. They were compared with those by a normal sintering method. The densifieation by the normal sintering was slow even at high temperatures. When SPS method was employed, much lower temperature and shorter period resulted in sintered bodies having almost the theoretical density. As expected in normal sintering, the compositional distribution decreased as the sintered density increased. On the contrary, the change in the compositional distribution by SPS was much smaller than that in the normal sintering. This sintering characteristic of SPS suggested a possibility of fabrication of sintered material having a desired compositional distribution.

Jan 1, 2003

By Filippos Patsiogiannis

Laboratory size (4.5 kg) low carbon steel melts were deoxidized using Al and FeAl (33% Al), with and without synthetic fluxes, in alumina and zirconia crucibles. The dissolved oxygen, total oxygen, soluble aluminum, insoluble aluminum, silicon and carbon contents in the melt were determined as a function of refining time and temperature. It was observed that the reaction between aluminum and oxygen in solution closely follows thermodynamic equilibrium. Silica present in the alumina crucibles was found to be a source of oxygen for the melt, while this was not the case for zirconia crucibles. Reoxidation of the melt occurred through oxygen pick-up from the atmosphere. The extent of this reoxidation was found to be a function of oxygen content of the bath and the slag cover on the surface of the melt. The effectiveness of calcium-aluminate based fluxes in protecting the melt from the reoxidation and in increasing the rate of removal of inclusions was evaluated.

Jan 1, 1992

By cheng Peng-fei, TANG Hai-yan, guo Xiao-chen, LI Jing-she, Liang Yong-cang, Zhao Baojun

In the process of oxygen blast furnace, the lower coke ratio and the higher coke load make the skeleton coke more important. To understand the dissolution of coke in melting and dropping zone, the influence of FeO content, temperature and reaction time on the dissolution of coke with slag were studied by single-factor experiment. Meanwhile, the three factors and three levels orthogonal were conducted. The dissolution degrees were characterized by the weight loss ratio and diameter variation. The results showed that the weight loss ratio increased and the diameter decreased with the increase of FeO content, temperature and time. The three factors and three levels orthogonal test showed that time was the most significant factor on coke dissolution, FeO content of the second, and finally the temperature. The microstructure of coke after reaction indicated that the dissolution occurred on coke surface.

Jan 1, 2016

By Guanghui Li, Xuling Chen, Zhiyun Ji, Min Gan, Tao Jiang, Xiaohui Fan, Zhiyuan Yu

With the increase of proportion of biochar(without modified) replacing coke breeze, the physical strength of sinter decreases due to the faster burning speed of biochar. An investigation upon passivating biochar with boric acid was then conducted to strengthen sintering in this paper. A layer of thin film of B2O3 distributed in the surface of biochar was observed, which could reduce the contact between reaction gas and biochar. So the burning speed of biochar was decreased properly after passivation, and the combustion efficiency increased due to the inhibition of carbon gasification. The comprehensive effects of above changes could increase the maximum temperature of sintering bed, which facilitated to the mineralization of sintering mixtures. Eventually sintering indices got reinforced. Thus the indices of sinter as applying 40% passivated biochar were comparable with that of 100% coke breeze.

Jan 1, 2015

By Klaus-Markus Peters, Robert M. Cravens, James G. Hemrick

"Degradation of refractories in molten aluminum applications leads to energy inefficiencies, both in terms of increased energy consumption during use as well as due to frequent and premature production shutdowns. Therefore, the ability to enhance and extend the performance of refractory systems will improve the energy efficiency through out the service life. TCON_ ceramic composite materials are being produced via a collaboration between Fireline TCON, Inc. and Rex Materials Group. These materials were found to be extremely resistant to erosion and corrosion by molten aluminum alloys during an evaluation funded by the U.S. Department of Energy and it was concluded that they positively impact the performance of refractory systems. These findings were subsequently verified by field tests. Data will be presented on how TCON shapes are used to significantly improve the thermal management of molten aluminum contact applications and extend the performance of such refractory systems.IntroductionThe production of molten aluminum creates aggressive environments for processing equipment, thereby requiring refractory materials to contain the aluminum during melting, transfer, treatment, and casting operations. Degradation of these refractories not only causes issues with reduced product quality and production yields, but also increases heat losses as the insulative properties of the refractories are compromised. Furthermore, in addition to disrupting production output, refractory failures lead to further impacts upon energy efficiency as large amounts of energy are lost during the cooling and subsequent reheating of the equipment as the refractory linings are repaired or replaced.The need for improved refractory materials is recognized throughout the industry. A joint U.S. Department of Energy and industrial workshop held in 2000 on applications for advanced ceramics in aluminum production [1] noted that refractory materials used in melt processing equipment have many limitations. The workshop report noted that these issues may be addressed by using advanced ceramics, but new materials must be cost effective when compared to current refractory materials. Also, in 2005 the Canadian aluminum industry produced a technology roadmap [2] having the goal of identifying and bridging gaps between current technological resources in the industry and future requirements. One of the areas identified as being crucial to the future of the industry was the need for improved molten aluminum-resistant materials."

Jan 1, 2009

By J. P. Bellot

During the non-ferrous metal processing, the melting step under vacuum or under rarefied gas leads to volatile metal losses. It is the case of the metallurgical processing of the nickel-based, titanium-based or zirconium-based alloys where the evaporation losses don't allow a sufficient control of the alloy chemical composition. A theoretical approach has been carried out involving both a continuum description in the liquid phase and a molecular approach in the rarefied gas phase. The finite volume method is used in order to solve the coupled transport equationsin the liquid, whereas the Boltzmann equation is modelled by using a Monte Carlo method. At the liquid metal and metallic vapor interface, the volatilization and recondensation fluxes link up the two calculations. Simulation results are given for the melting and refining of reactive metals such as titanium alloys where the control of the chemical composition remains a major difficulty. The validity of the kinetic Langmuir's law is discussed for different operating conditions.

Jan 1, 1996

By P. D. Lee

The effect of strontium on porosity formation in aluminum-silicon alloys is not well understood and there is no consensus upon the cause of the effects observed. This paper describes a series of experiments where the effect of adding strontium on pore formation was observed directly with combination of a traditional temperature gradient stage and real time micro-focus radiography. These in situ observations provide a new insight into the effect of strontium on the nucleation and growth kinetics of porosity. The addition of strontium was found to have a minor effect on the growth of the pores in the mushy zone. However, strontium appeared to alter the nucleation and stability of hydrogen bubbles within the melt. The interaction of strontium with titanium-boride grain refiners produced an even stronger change in the nucleation and stability of the bubbles formed.

Jan 1, 2002

By Frame Ritzert, Dennis Keller, Vijay Vasudevan, David Arenas

"An investigation was conducted to describe topologically close packed (TCP) phase instability as' a function of composition in the advanced ·Ni-base superalloy Rene N6. TCP phases are detrimental to overfill high-temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements. Thirty-four variations of polycrystalline .Rene N6 determined from a design-of-experiments approach were cast and homogenized at 13 l5°C for 80 hours followed by exposure at 1093°C for 400 hours to promote TCP formation. The alloys had the following composition ranges in atomic percent: cobalt 10.61 to 16.73, Mo 0.32 to 1.34%, W 1.85 to 2.52%, Re 1.80 to 2.11%, Ta 2.36 to 3.02%, Al 11.90 to 14.75%, and Cr 3.57 to 6.23%. Physical and chemical characteristics of all microstructures obtained were described using various analytical techniques. From these observations, a mathematical description of TCP occurrence (s and P phase) was generated for polycrystalline Rene N6.IntroductionNi-base superalloy single crystals represent the state-of-the-art for turbine engine airfoil application as they offer the best balance of properties to allow for the high operating temperatures required: for efficient engine operation.1 Current trends in alloy design take advantage of improved creep rupture strength with the addition .of higher levels of refractory elements. 2 In .particular, the addition of significantly higher levels of Re in third generation superalloys is key for both microstructural stability and creep rupture strength. 3 While the presence of the refractories is thought to provide strength benefits from solid solution hardening, a tendency for alloy instability in the form of topologically-close-packed (TCP) phases or secondary reaction· zone (SRZ) ·phenomena accompanies the high refractory content. 3 The formation of these phases in sufficient amount is detrimental to the overall high temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements.4 The tendency for a particular composition to form TCP may not be immediately known since the precipitation of TCP phases in Ni-base superalloys is nucleation controlled, thereby requiring long times at elevated temperatures to precipitate. 5 They preferentially nucleate along the octahedral planes of the Ni-base superalloys, usually in areas of refractory metal enrichment at grain boundaries or inside dendrites.5-6 In Rene N6, two closely related TCP phases, a and P, have been observed.2"

Jan 1, 1998

By Jennifer Murphy, Brad S. Schake, Karol Holmes, John R. FitzPatrick, Mike H. West

"The separation and purification of uranium from either nitric acid or hydrochloric acid media can be accomplished by using either solvent extraction or ion-exchange. Over the past two years at Los Alamos, emerging programs are focused on recapturing the expertise required to do limited, small-quantity processing of enriched uranium. During this period of time, we have been investigating ion-exchange as a method for extraction/purification of uranium from acidic media. In addition, waste stream polishing is associated with this effort in order to achieve more complete removal of the uranium prior to recycle of the acid. Extraction chromatography has been demonstrated to further polish the uranium from both nitric and hydrochloric acid media thus allowing for a more complete recovery of the actinide material and creation of less waste during the processing steps.We will discuss contact experiments for evaluation of eleven different resins for uranium removal from nitric acid, the evaluation (again by contact experiments) of uranium elution from the ion-exchange media by various chemicals, and small-scale experiments for the removal of 235U from nitric acid. Larger-scale (1 DO-gram) flow experiments, using depleted uranium, were done after the small-scale evaluation of the selected resin. A discussion is also included concerning the shortcomings of the contact experiments and how the flow experiments were modified in order to overcome these problems. We will also discuss the application of ion-exchange for some specific process needs at Los Alamos.Contact experiments were used to evaluate some commercially available solvent-impregnated resins in addition to evaluation of several resins of this type synthesized in our laboratory. These experiments involved both nitric and hydrochloric acid media. The data from these experiments will be used to determine the column size and amount of resin required to polish the waste stream produced by the ion-exchange process described above. Small-scale flow experiments will be described and data given on the mass balances achieved using this two step process.Future work for evaluation of new ion-exchange and solvent-impregnated resins as well as the search for new eluants will be discussed. Other future experiments for both processes, including large-scale experiments, will be discussed in detail."

Jan 1, 1996

By Robert M. Leary

The Kennecott Utah Copper smelter operates two Outokumpu flash furnaces: a smelting furnace for production of high-grade matte and a converting furnace for production of blister copper. Flash furnaces typically possess several characteristic features that must be considered in process control development such as long lag times associated with settler volume, non-linear input and output responses, large process gains, and unmeasured disturbances. Additionally, the Kennecott smelter possesses certain unique characteristics which must be considered such as single mine concentrate source, limited concentrate blending capacity, and feed preparation facilities that inevitably cause significant lags between furnace control parameters and manipulated set points. In order to improve furnace control and on-line time, a process control system was developed to address these issues. The feed forward control module provides predictive control and operates in response to furnace feed input changes. The feed back control module provides responsive control and is based on furnace output deviations. To provide regular feed back information to the control room supervisors, new sampling methods were developed which provide the operators with molten metal and bulk material samples at regular intervals to provide information for control. The control system was implemented on the Flash Converting Furnace in May 1999 and on the Flash Smelting Furnace in August 1999.

Jan 1, 2000

By R. Cavanagh

Studies relating to the fixation of sulfur by reaction of 4 to 8 mm diameter cylinders of calcined limestone or dolomite with high strength sulfur dioxide in the temperature range 880°C to 1020°C were undertaken. Dolomites are far superior in sulfate capacity and reactivity than dense limestones even at high strength SO2. The sulfation reaction was first order with respect to SO2 concentration below 100 percent. Zero reaction rate at 100 percent SO2 concentration indicates that sulfate was the exclusive reaction product and that sulfite had no role in the reaction. At relatively low SO2 concentrations gaseous diffusion through the reaction product layer has a marked effect on the rate. As SO2 concentrations were increased up to 100 percent more complex rate controlling mechanisms unfold. By sectioning partially reacted dolomitic limestone pellets a moving interface was observed. Reaction ceased because of pore plugging for dense non-porous limestones at 30% conversion. With dolomitic material virtually complete sulfation of the calcium was observed. S.E.M. analysis showed that the average atom ratio Ca:S was 1.01, thus supporting the argument that little if any of the magnesium was sulfated.

Jan 1, 1996

By S. P. Mathew

The ISASMELT Lead Process is a continuous two stage process for the production of crude lead from concentrate. It is based on the use of a top entry submerged Sirosmelt lance to produce turbulent baths in which high intensity smelting or reduction reactions can occur. The process involves oxidizing the concentrates in the first stage to produce a high lead slag. This slag is tapped continuously and transferred down a launder to a second furnace where it is reduced with coal. Crude lead and discard slag are tapped continuously from this furnace through a single taphole and separated in a conventional forehearth. Process and engineering design work for a commercial scale Lead ISASKELT plant designed to produce 60000 tpa crude lead has been completed. This plant is planned to be operational in 1991.

Jan 1, 1990

By Mark H. Hashiguchi

Examination of tensile bar surfaces shortly after destructive testing was conducted to search for clues that would aid in optimization of mechanical properties, especially tensile strength, yield strength and elongation to fracture. Cu-Ni-Si-Cr alloy bars in the as-cast, forged, rolled and extruded conditions were examined. Low ductility bars (<4% Elongation) showed dramatically different features than the fracture surfaces of high strength - high ductility bars (7 to 10% Elongation). Analysis of the fracture surfaces at 15X to 2000X and use of Energy-Dispersive X-Ray Spectroscopy (EDS) identified Ni-Si and Ni-Si-Cr precipitates of varying sizes and morphologies. Thermo-mechanical processing techniques to control the size and distribution of these precipitates show promise in improving the properties and performance of this alloy system and appear to correlate with improvements in the fracture surface morphology.

Jan 1, 2008

By Edward Rosenberg

The synthesis and characterization of silica polyamine composites modified with a variety of sulfur containing ligands is described. The two most successful ligands in terms of sulfur in-corporation and mercury capture are ethylene sulfide and carbon disulfide. The ethylene sulfide forms either an amino mercaptane or a polysulfide upon reaction with amino groups on the composite. The carbon disulfide undoubtedly forms a dithiocarbamate functional group upon reaction of the amino group under basic conditions. Both materials posses excellent capture kinetics and capacities for mercury, Once captured, the mercury is extremely difficult to remove from the composite materials, even with concentrated acids, and they easily pass the TCLP test. The materials are compared with related thioether modified silica polyamine composites and appropriate potential applications are discussed.

Jan 1, 2003

By Zdzislaw Miczkowski

At KGHM Polska Miedz S.A, a direct flash smelting process is used for smelting of chalcocite concentrate for the production of blister copper. The paper presents a model of complex oxidation process of single concentrate grains smelted at KGHM. The description covers main chemical reactions, phenomena of heat and mass exchange inside the grains and between a grain and the surrounding space. In the model, two zones describing the course of process inside the grain were distinguished: ? The first one, which moves faster towards the centre of a grain, both organic and carbonate carbon are freed, The process takes place without the presence of oxygen and results in an increase of the temperature in the core of the particle. ?The second zone moves slower into the grain and the rate of the movement is determined by the presence of oxygen, In that zone the sulphur is eliminated and the oxidation of the organic compounds vapours moving from deeper layers of a grain takes place. Based on the results of laboratory tests, the coefficients that describe the oxygen transportation into the grain and decide the progress in the chemical reaction were determined, The paper contains the results of model calculations for single grains reacting in environment of various content of oxygen as well as the results of model calculations for the laboratory reactor system.

Jan 1, 2003

By B. Q. Li

A numerical study of the developing fluid flow and thermal aspects during the staning phase of aluminum continuous casting processes is presented. The deforming finite element method, coupled with a quasi-Lagrangian formulation, is used to represent the growth of an ingot and the dynamic fluid flow and thermal behavior that evolves in the growing ingot. The mathematical formulation of the problem and the numerical treatment are discussed. The algorithm solves the free moving nodes as part of total unknowns with an automatic time step control for time integration. This permits an optimal computing efficiency while still keeping the computational errors under control. A selection of the results obtained using the algorithm is presented. The results are concerned with the evolution of fluid flow, temperature and solidification phenomena during a DC round ingot casting process, as it evolves from the beginning of casting operation to a steady state. These results show that the time-varying, complex fluid flow and thermal phenomena during continuous casting processes can be very well represented by the computational algorithm. The results also illustrate that, during the casting process, ~e fluid flow and temperature fields change drastically at the initial stage but evolve slowly afterwards

Jan 1, 1993