Search Documents

By Liangying Wen, Xuewei Lv, Yuelin Qin, Feng Zhu, Guibao Qiu, Chenguang Bai, Meilong Hu, Shengfu Zhang

"The COREX process is the first reduction ironmaking technology with coal and pure oxygen to get high quality hot metal, which consumes a lot of high quality lump coal and some coke. In order to increase the utilization of fine coal, reduce coke consumption and enhance the competitiveness of the technology, the combustion behavior of pulverized coal injection in melter gasifier is studied experimentally. The results show that the combustion rate of PCI increases with the increase of temperature. And the combustion rate increases with decreasing coal particle size. Compared bituminous coal with anthracite, the former’s burning ratio is higher than the latter in the same granularity. The combustion effect is remarkable when coal blend of bituminous coal and anthracite with the smaller particle size is pulverized in COREX process.IntroductionThe COREX process is the first reduction ironmaking technology with raw coal and pure oxygen to get high quality hot metal, which consumes a lot of high quality lump coal [1-3]. However, the proportion of lump coal in raw coal is very small, and it is avoidless to produce fine coal because of mechanical coal cutter and storage and transportation process, so it is important to resolve utilization of fine coal in COREX ironmaking process in order to energy conservation and reduce the cost of hot metal [4]. Currently, Coal briquetting technology is adopted to utilization of fine coal in COREX process [5], but coal briquetting system has high investment cost and requires feasible adhesive agent. The pulverized coal injection (PCI) into a blast furnace is being used on a global scale to improve the stability and reduce the cost of blast furnace operations [6]. The successful development of PCI in blast furnace is contributed to pulverized coal in COREX melter gasifier. However, it is different in PCI process between COREX melter gasifier and blast furnace, and the differences are as follows: firstly, The air is injected into blast furnace, which temperature is about 1200 ?, but in COREX melter gasifier the normal temperature oxygen is blasted, so PCI in blast furnace begin burning in blowpipe, but the combustion of PCI in COREX melter gasifier is only in raceway. Secondly, the racway of COREX is smaller than that of blast furnace of the same size. So, the combustion behavior of PCI is complex in COREX melter gasifier, which is not use for reference."

Jan 1, 2012

By J. Winters, L. Vos, C. Canoo

Committed to a sustainable development of zinc applications, Union Miniere is investigating processes for the minimisation of waste and residues originating from the classic hydrometallurgical zinc process. In that context, Union Miniere has developed a method for the cold inertisation and solidification of goethite, the Graveliet® process. The result is a hard and inert gravel that can be used in the building industry. During the past two years, a pilot plant for the production of Graveliet® has been built and operated. In the present paper, the Graveliet® process and the pilot plant are described after which the properties of the produced gravel are discussed, from both a mechanical and an environmental point-of-view. Graveliet fulfils the criteria for use as a secondary building material. The GravelietJ process is a viable technology to avoid stockpiling of goethite residues and it thus assures the long-term development of the hydrometallurgical zinc process.

Jan 1, 2000

By Kunibert Hanusch

Copper in recycling material is accompanied by various groups of metals: 1) Metals which are much more negative than copper, such as Fe, Al, Si, P, Be They are mainly removed by fire refining during the recovery of copper and leave the process in form of slag. 2) Metals which are more positive than copper or difficult to separate by fire refining and which are partly reduced together with the copper. These metals are for example As,. Sb, Ni, Ag, Pb, Zn, Sn. They are enriched in intermediate products and recovered from these or remain for their major part in the fire-refined copper and can be separated by electrolytic refining and recovered from the electrolyte or anode slime. This report describes the process of Hüttenwerke Kayser AG in Germany and illustrates how considerable returns of material are partly required to separate or recover associated metals. They are finally removed in saleable products.

Jan 1, 1995

By Jian Li, S. Penttilä, P. Liu, W. Zheng, C. Bibby

"The materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. The current Canadian pressure-tube supercritical water (SCW) concept design requires core outlet temperature of 650 °C at 25 MPa with peak cladding temperature reaching as high as 850 °C. Aside from oilier challenges, there is currently very limited data on candidate stainless steels' corrosion resistance under this operating condition. Austenite stainless steels that include 316L, 304H, AL6XN and 3 l0S that cover a wide range of Cr contents are promising candidates for either direct in core applications or as base coating materials. However, their corrosion resistance has not been tested systematically under this stringent condition. In this study, these types of stainless steels are tested, and their corrosion resistances are compared.IntroductionThe Canadian pressure-tube supercritical water (SCW) concept will operate at a core outlet temperature of 650 °C at a pressure of 25 MPa, with potential peak cladding temperature reaching as high as 850 °C. High-temperature corrosion resistance is one of the key design requirements for fuel cladding components. As summarized by Allen [1 ], most testing to date has been carried out at temperatures below 730 °C. To date, SCW corrosion data above 600 °C is very limited. Even at relatively low temperature exposure to SCW (e.g. 500 °C), F/M steels develop a thick oxide layer rapidly, while some austenitic stainless steels develop thinner surface oxide. Ni based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of intermetallic precipitates [2-5]. Dissolution of major alloying components from all of these alloys could also pose significant problems for downstream piping [6]. Kaneda et al. [7] suggested some modified stainless steels provide better SCW general corrosion resistance, with no sign of SCC under the slow-strain rate test.Cho [8] suggested that as the Cr content increase, general corrosion resistance improved at 510 °C and 25 MPa. However, similar to Cho's work, most of the SCW corrosion resistance assessments were based on weight change measurement. This can be unreliable due to potential exfoliation of thick oxide film. Besides, there have been no systematic SCW corrosion resistance tests for candidate stainless steels under higher temperatures. SCW corrosion rate increase dramatically for alloys tested at 600 °C [1]. It is also important to understand the role of major alloying elements under this stringent operating condition, not only for fuel cladding components' materials selection, but also for coating materials development."

Jan 1, 2013

By Z. Y. Xie

The visualization techniques were employed for the analysis of computer simulation studies of dislocation core structure in ordered alloys. Atomistic computer simulation was used for the study of the local configuration of the material in the vicinity of the dislocation. Stresses were applied in the simulation in order to study the necessary stress level for the dislocation to move and onset plastic deformation of the material. The results were analyzed in terms of the strain tensor as a function of the position (x, y) in the material with the dislocation located at (0, 0). Various visualization packages are used to plot the invariants of this strain tensor and to visualize the changes that the dislocation core undergoes under stresses until it finally moves.

Jan 1, 1993

By Linda C. White

The use of red mud, a waste product of the ?Bayer? process for bauxite refining, was investigated for its arsenic removal effectiveness from aqueous solutions under various conditions. Red mud efficiently removed As(III) between a pH range of 7.6 and 9; and As(V) in the pH range between 5.5 and 6. Pre-washing of the red mud with salt water considerably improved its arsenic adsorption capabilities. With appropriate red mud dosage, the residual arsenic in solution was decreased below the regulated acceptable arsenic limit (0.1 mg/L) from aqueous industrial wastes. The arsenic adsorption followed first-order rate kinetics and fitted the Langmuir isotherm model. Results suggest that red mud is potentially a useful adsorbent for removal of arsenic from contaminated water or industrial waste solutions.

Jan 1, 2003

By Takayuki Watanabe, Yoshiki Shimizu, Yusuke Moriyoshi

"B-C-N nanotubes prepared by a flush evaporation method using a de arc plasma were mainly characterized by transmission electron microscopy (TEM) and electron energy· loss spectroscopy (EELS). The nanotubes obtained· were divided into three types such as carbon boron nitride and carbon or carbon nanotubes surrounded with boron nitride nanotubes. These types of nanotubes were obtained at higher temperatures than about 3000 K, however, these were not formed at lower temperatures than about 3000K. On the other hand, 11anocapsules were· formed at all the experimental temperatures and nanocapsules with a homogeneous phase were obtained at lower temperatures than about 3000 K. The effect of additives on the formation of B-C-N nanotubes was not clear. Based on these experimental data depending on temperatures and corresponding microstructures, the formation mechanisms of both nanotubes and nanocapsules were briefly .discussed 1 Introduction As reported previously, nano tubes have unique electrical properties1, 3) The preparations of nallotupes have been usually carried out by flush evaporation methods using either a de arc plasma or a laser4 -5) By these methods the reaction rate is so rarid that we have no data of intermediate products between initial raw materials and. final products of nanotubes 6-9). So, the formation mechanisms of nanotubes have been mainly speculated only from the microstructures of resultant nanoiubes. In order to have more reliable formation mechanisms, it is particularly important to have the information of intermediate products at the corresponding temperatures. From the viewpoints, we have studied about the effects of temperatures on the preparation of nanolubes. Here we report mi firstly some problems on the preparation of B-C-N nanotubes 10), secondly the effects of temperatures on the preparation of B-C-N nanotubes, and finally the formation mechanisms of nanotubes."

Jan 1, 2000

By María Cristina Ruiz

Hematite precipitation is a convenient alternative for the removal of iron from leaching circuits because of its chemical stability, high density and high iron content. The precipitation of hematite from ferrous sulfate solutions was studied in a batch reactor. The precipitation occurs by two sequential steps: oxidation of the ferrous to ferric ions followed by hydrolysis of the ferric to hematite. The main objective of this study was to determine the effect of the main operating variables on the rate of two steps of hematite precipitation. The variables studied included: stirring speed (100 to 600 rpm), temperature (160 to 200 ºC), concentration of sulfuric acid (1 to 10 g/L), initial iron concentration (1 to 15 g/L), and partial pressure of oxygen (1 to 6 atm). The sulfur content and the particle size of the solids that precipitated under various conditions were also determined. The results showed that at low temperature and high acid concentration the rate of Fe3+ hydrolysis is the step that controls the overall process. The variable that affects most the rate of Fe2+ to Fe3+ oxidation and the rate of hematite precipitation is the temperature.

Jan 1, 2008

By Dirk Bergmann

During the spray forming process, a continuous molten metal stream is atomized by impinging high speed inert gas jets. In the generated spray cone, the resulting metal droplets are rapidly cooled by the huge temperature difference to the surrounding gas phase and thereby partly solidified during flight. After a certain flight and residence time inside the spray cone, the droplets impinge onto the solid substrate and form the product (deposit) by compaction. Material properties of this preform strongly depend on several process parameters and especially on the thermal and kinetic state of the deposited droplets at the point of impingement. Smaller droplets may cool very fast due to their low mass and impinge onto the product in a completely solidified state as solid metal powder particles. Larger droplets with big mass contain a higher amount of thermal energy and impact during the state of phase change or still as completely liquid. It is obvious, that a certain amount of liquid content in the droplets is needed for forming a homogeneous deposit. Therefore, the thermal history of metal droplets during flight in the spray cone is of great importance for overall process modelling and control. Modelling the effects of the impinging droplet mass on the formation and heat balance of the deposit, the thermal conditions of the droplet stream need to be temporary and spatially averaged at different locations. Averaging may be achieved in different ways, giving alternative results. A first method is averaging over the droplets total enthalpy which consists of the thermal content and the remaining latent heat of fusion within the droplets. A second method may yield the average over the heat content and the solid fraction separately. Results of these two methods depend on the application and the kind of information which one wants to achieve and show some deviations, which will be discussed in terms of consolidation and energy conservation of the deposit.

Jan 1, 1999

By Zuomei Jin

The Mineralogical form of Silver in a Ag-rich complex ore was determined. In the complex sulfide ore, acidic thiourea leaching resulted in 35% extraction of silver directly. In the same complex sulfide ore, under the effect of ultrasonic treatment, 65% of silver can be ex¬tracted. After the above ore had been roasted and acidically leached of Zn and Cu, the silver extracted from this Pb-Ag residue was 96.8%. The effets of temperature, thiourea and ferric ion concentrations and partical size were examined. The leaching rate of silver from the Pb-Ag residue was diffusion controlled. The activation energy was calculated to be 10. 49%KJ/mole. The kinetic model for the thiourea leaching of silver from Pb-Ag residue was obtained and is given by, The kinetics of silver cementation by aluminium in thiourea solutions was also investigated. The activation energy was calculated to be 65. 13KJ/mole, which is reasonable fora rate-limiting surface reaction.

Jan 1, 1995

By Andrew Shabalin, Vladimir Skorohodov, Svetlana Babaeva, ?lga Makovskaya

"At processing of some kinds of wastes (electronic scrap, secondary materials, spent nuclear fuel) in nitric acid solutions, and also in technology of silver refining, the significant amounts of palladium and platinum passes into a solution. The ion-exchange concentration of palladium and platinum in nitric acid solutions (5-500/dm3) are investigated. More than 30 various classes of ionites are tested. The most chemically resistance resins at the given conditions are identified. It is shown, that the maximum sorptive capacity to studied metals at high acidity the complexing, synthetic and inorganic sorbents possess. To definition of platinum metals sorption optimum conditions the kinetics is studied, isotherms of a sorption at various parameters from nitrate solutions are obtained. The conditions of the platinum and a palladium desorption from the pregnant sorbents and its regeneration with the subsequent reuse of materials were defined. The raw materials containing precious metals have very diverse composition and physical properties. Commonly the materials are processed by hydrometallurgical way. If gold or PGMs there are in raw materials to its opening hydrochloric acid solutions are applied. As an oxidizer nitric acid, hydrogen peroxide, gaseous chlorine, etc are used. Nevertheless, at processing of argentiferous materials and preliminary treatment of a waste including the spent nuclear fuel, nitric acid solutions are often used and the specified metals in some extent pass into solution [1]. Therefore selective extraction of PGMs from nitrate solutions is an actual problem. In the present work the ion-exchange concentrations of palladium and platinum in nitric acid solutions (5-500 g/dm3) are investigated. At the testing more than 30 various classes of ionites the most chemically resistance resins at the given conditions are identified. These resins are synthesized on the base of polyacrylate, styrene-divinylbenzene and vinylpyridine. For a selection of the most effective resin among what are made in Russia and overseas, a number of ionites with various functional groups were studied. Influence of functional groups type on a PGM sorption is shown for extraction of a palladium as an example (table 1). The presented data shows, that palladium concentration in a phase of ionites depends on sorbent type. If the increasing of solution acidity essentially reduces palladium sorption by sulfonic cation-exchange resins (KU-2×8) than its sorption by strongly basic anionites is approximately equal. Intermediate position is occupied by complexing sorbents. The latter (AN-31, SN-3, ANKB-35, Lewatit TP 207, Purolite S 930) are the most effective for extraction of PGMs from nitrate solutions from the point of view of capacity value. According to [2], solution behavior of Pt (II) and Pd (II) are similar. As is known from coordination chemistry, ligand environment of the metal ions substantially impacts to character of electronic spectra. The figure 1 shows the results of measurements of optical density of platinum bearing solutions with various concentration of nitric acid at ?=400 nanometers"

Jan 1, 2008

By H. Kung, T. R. Jervis, M. Nastasi, T. E. Mitchell

"A systematic study of the structure-mechanical properties relationship is reported for nanolayered composites of MoSh-SiC, Mo-MoSh, Mo-MoShNx, MoSi2-MoSi2Nx, and Mo-MoShMoSi2Nx (x=3-4) synthesised by sputtering techniques. These composites have been studied by nano-indentation and cross-sectional TEM as a function of annealing temperature. As-deposited layers are amorphous except for Mo. With increasing annealing temperature, first MoSh and then SiC crystallize, while the hardness progressively increases until the layers start to spheroidize and grain growth sets in at 900ºC. For the case of Mo-MoSi2, the layers react and the composite deteriorates rapidly. However, MoSi2Nx remains amorphous up to 1000ºC, suggesting that it could act as a diffusion barrier between Mo and MoSi2. In fact the Mo. MoSi2Nx, MoSi2-MoSi2Nx and Mo-MoSi2-MoSi2Nx nanolayers are found to remain stable up to such temperatures. IntroductionMolybdenum dislicide, MoSh, is a potential matrix material for high temperature structural composites due to its high melting point and good oxidation resistance at elevated temperature [1]. The two major drawbacks for structural applications are inadequate high temperature strength and poor low temperature ductility. Silicon Carbide (SiC) being hard and thermally compatible with most ceramics and intermetallic compounds, has been found to be suitable for second phase reinforcement in various structural applications and, in particular, the addition of SiC whiskers improves the high temperature yield strength of MoSi2 [2]. While most of the research in MoSb-SiC composites has been on the particulate form of SiC, laminated composites may offer unique properties. It has been shown that synthetic multilayers with alternating layers of metal and/or compounds may exhibit interesting mechanical properties [3]. Enhancement in mechanical properties by decreasing the wavelength of multilayer spacing has been studied extensively. In general, two types of strengthening have been proposed: (1) Hall-Petch strengthening [4,5], where the strength increase is inversely proportional to the square root of the layer thickness; (2) Koehler modulus strengthening [6], which increases with modulus difference and decreasing layer thickness. In the present study, we have performed a systematic study of the relationship between strength and structure in a number of different nanolayered systems based on MoSh. Layer thicknesses have been varied and their nanostructures have been varied by heat treatment. Previous work on MoSi2-SiC is summarized [7]. In an attempt to improve fracture toughness, MoSh-Mo nanolayered materials have been prepared but are found to react and deteriorate. Previous work has shown that nitrided MoSi2 (MoSi2Nx with x=3-4) is highly stable [8] and so nanolayered composites of MoSi2-MoSi2Nx and Mo-MoSi2-MoSi2Nx have been prepared to assess the' stability and mechanical properties of these composites. Preliminary results are presented."

Jan 1, 1994

By Patrick F. Mahoney

Each year in the United States over 10 million tons of metal are discarded with our municipal waste. This, includes, not only ferrous metals, aluminum and copper but gold, silver, platinum and every other precious metal. Resource recovery, as an approach to waste management, is replacing disposal and it presents great opportunities for those in the metal refining and recovery industry. Combustion of waste enriches the metal fraction left in the ash to the point where metals can be efficiently recovered. The recovery and quality of metals can be enhanced by good combustion control. Innovative technology is needed to efficiently tap this generous, and renewable mine.

Jan 1, 1995

By Yongqi Sun, Zuotai Zhang

Our study investigated the influence of P2O5 and B2O3 on the viscosity and crystallization behavior of Ti-bearing blast furnace (Ti-BF) slags for the purpose of Ti extraction. The investigation of the crystallization behaviors were carried out using a single hot thermocouple technique (SHTT) and the viscosity was obtained by rotating cylinder method. For the viscosity, the results showed that P2O5 substantially increased the slag viscosity. P2O5 is a network-forming oxide, which increased the degree of polymerization of slags and accordingly increased the slag viscosity. However, both of slag viscosity and apparent activation energy for viscous flow remarkably decreased with B2O3 addition. As a typical network forming oxide, B2O3 was introduced into the network and existed dominantly as 2-D structure, BO3 triangular, which caused a simpler structure and a decreasing slag viscosity. As for the crystallization behaviors of Ti-BF slags, both P2O5 and B2O3 enhanced the crystallization trend of rod-shape rutile and suppressed the crystallization trend of dendrite CaTiO3. Therefore the added P2O5 and B2O3 caused the primary phase change from CaTiO3 to rutile. Additionally, it was found that the rod-shape rutile showed a 1-D growth, whereas the dendrite CaTiO3 showed a 3-D growth style.

Jan 1, 2015

By Olga A. Gomon, Alexey N. Lozhko

The technology of heat treatment for metal frequently includes multiple fast heating and cooling of the products surface. If the product is heavy-weight or long-size, its moving from a zone of cooling to a zone of heating and return require a long time. Other important condition of ensuring qualitative surface at heat treatment is intensification of cooling phase. It is known that turbulization of a flow activates heat exchange and increases efficacy of cooling without increasing volume flow rate of water. Additional difficulty is to ensure the regularity of heating and cooling on length of a product. The technology of cyclic heat treatment of rolling products, at which mobile zone of turbulent heat exchange is formed on the surface of a product, was developed and realized. The submission of water occurs through to face spray systems. Each of the systems has six long-range atomizers, which are located circularly. Two flows of water move towards one another along a surface of a product. When they collide, the right zone of turbulent heat exchange creates heat transfer in this zone of 10-15 time more intensive than on other surface of a product. The effect of moving turbulent zone on length of a product is reached by changing the proportion of volume flow rate of water, which is created by face sprays. The speed of movement for turbulent zone along a surface of a product is chosen so, that the cooling takes place on a small depth only. Then after passing the turbulent zone over a determined site of a surface, its temperature recovers fast owing to hot internal layers. The parameters of process were determined by mathematical simulation of cooling in an installation. The equations for dynamics of movement of collision point of flows, which were received this way, are interesting supplementary products of research. The experiments show that frequency of movement of turbulent zone is an important technological parameter. It defines mechanical properties of a surface and should be chosen depending on a profile of product and metal grade. The results of comparison of mechanical properties of a surface of various rolling products, which were received by developed and conventional technologies, are described in this report. Dependence of regularity of mechanical properties on frequency of movement of turbulent zone is adduced.

Jan 1, 1998

By Aichun Zhao, Rui Wang, Yihong Li, Yanping Bao, Yafeng Ji, Jiansheng Liu, Xiao Hu, Qingxue Huang

The slag entrapment under different conditions of 80t blowing argon ladle furnace was investigated by physical simulation. The water was used to simulate liquid steel and liquid paraffin was for slag. The processing of slag entrapment under different blowing structures was analyzed and the critical velocity and critical droplets diameter of describing it was obtained. Based on the experiments, the relationship between the interface flow velocity and the critical blowing rate CBR was deduced. In the real process, it is suggested that the bottom blowing rate is from 40 L/min to 180L/min when the interface tension is 0.12~1.2 N/m during the soft argon blowing.

Jan 1, 2016

By Jörn E. Fischer

Cracks were observed at the top of spray formed billets for some alloys. In this paper the effect of process parameters on crack probability is discussed. After the spray run the thermal conditions at the top of the billet change rapidly. A hot spot with melt residue] can occur inside the billet and shrinkage will be suppressed due to the solidified surface of the billet. In this situation hot cracks can be initialized. The temperature history of the billet during and after the spray run is calculated. The temperature difference between core and outside diameter of the billet is taken as indicator for hot crack probability. The effect of different process parameters on the hot crack probability is discussed. The results lead to a better understanding of the process. The calculations are taken as a tool to find process parameters in order to reduce or avoid hot cracks in spray formed billets.

Jan 1, 1999

Due to problems with old technologies more and more product designers have turned to liquid crystal (LC) displays, which have consequently experienced phenomenal growth. The success of liquid crystal displays has fostered continued development, to the point where full-color video displays have been realized which can rival. The details of the lens structure and of the devices fabrication and performance are described using the Jones matrix method. Director n can change from point to point and is, in general, a function of space.. The transition can be approached by changing the impurity concentration or, indirectly, by tuning the temperature since the pinning strengths of the random and crystal potential have in general a different temperature dependence. Light from the conventional light source or laser is passed through a polarizer and then incident on the specimen. The resist profile simulation is carried out using the combined data thus obtained. The nematic liquid crystal is clear only when a long range order exists, in the whole medium. At the nematic-isotropic, transition temperature, the medium becomes isotropic and looks clear and transparent.

Jan 1, 2006

By Ilie Butnariu

Steel manufacture in VOD procedure needs a very attentive correlation and pursuit of the technological stages ,on the background of keeping the influence factors within best performances zones. For a better co-ordination of the main stages specific to this process ,this work presents a detailed study of the optimization possibilities for each stages ,beginning with the furnace charging ,going on with the pre-aftinage and aftinage stages in the electrical furnace and then with the refinement stages in the VOD installation. One has intended the effective emphasis of the main influence factors with global implications on the process and especially on the purity and quality of the stainless steel ,Among the main novelties proposed by this work , we can emphasize the following: - a computer assisted charging method ,with the possibility of using a large scale of wastage, also respecting the density proportions of the components of the charges; - the advanced recuperation of the elements of the charge by reducing the combustion of the valuable elements ; - the optimization of the oxygen blast conditions and of the aftinage stage ,by establishing some calculations concerning critical carbon content , that requires the oxidation to be continued very carefully; - the simulation of the thermic and chemical parameters by modeling the alloying process of the stainless steel in the case of some large amounts of additions.

Jan 1, 1994

By James C. Sever

Two green field magnesium reduction plants are under consideration using dolomite as the raw material. The Calix calciner was independently selected for both plants. The unique design of this calciner is detailed and the advantages defined for the specific application. The low carbon foot print of this unit combined with the ability to capture food grade carbon dioxide makes this an environmentally proactive approach to carboniferous ore calcination.

Jan 1, 2015