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By Dianyuan Dang, Guihong Han, Wenjuan Wang, Tao Jiang, Yanfang Huang

In this study reduction kinetics and swelling behaviors in "two-step process” were investigated by weight-loss technique and visualizing physical changes of pellet. Results showed that reduction degree (r) increased with increasing temperature and time. According to the dynamic calculation, when reduction temperature was lower than 1000°C the reduction process was controlled by chemical reaction with apparent activation energy of 72.27 kJ/mol. When reduction temperature was higher than 1000 , the equation of t/[1-(1-r)1/3] against [1+2(1-r)-3(1-r)2/3]/[1-(1-r)1/3] followed straight lines, demonstrating that reduction was mixed-controlled. Swelling experiments indicated that the maximum swelling index increased with the increase of reduction temperature and CO content.

Jan 1, 2016

By Zhijing Zhang, Ramana G. Reddy

"The viscosity of molten oxides is one of the important physical properties since viscosity has a decisive influence on fluid flow. The knowledge of the viscosity of molten oxides is essential for modeling and controlling of metallurgical process. In the present study, viscosities of high basic Na2O-B2O3 and Na2O-SiO2 binary melts and viscosities of Na2O-SiO2-B2O3 ternary melts were measured as a function of temperature and composition. Experiments were carried out using rotary viscometer and graphite components. Our experimental results were compared with those in literature. Based on the current experimental data, the previously developed viscosity model was modified. The characteristic features of viscosities of these melts have been discussed. The predicted viscosity results are in excellent agreement with the present experimental data in the temperature range with molten state samples. IntroductionThe viscosity of molten oxides is one of the important physical properties since this property has a decisive influence on fluid flow, and is one of key factors to be taken into consideration in process modeling. The manufacturing operations require the viscosity of molten oxides to be within certain ranges. Although, some viscosity measurements on borosilicate systems have been carried out [1-4], the viscosity data in literature are available only for a few temperatures and cover small composition ranges. The agreement between the results of these works is not satisfactory [I-4]. Even the viscosities of binary systems Na2O-B2O 3 and Na2O-SiO2 generally are well studied, the available viscosity data in literature are only found in the composition range of O to 0.333 mole fraction ofNa2O. The aim of the present study is to provide a base with accurate experimental data for reliable model extrapolation."

Jan 1, 1999

By Suchun Zhang

The alkaline oxidation of refractory gold concentrates containing arsenopyrite and pyrite at ambient temperatures and pressures has been found to be accompanied by the simultaneous dissolution of gold without the addition of cyanide. A detailed study has been made of the kinetics of the oxidation of the pure minerals and of several concentrates. The reaction products of the oxidation of arsenic and sulphur have been monitored using chromatographic techniques. In the case of arsenopyrite, thiosulfate, monothioarsenate, arsenate and sulfite are the principal products while thiosulfate has been confirmed to be the dominant product of pyrite oxidation. Gold, either as added powder or as a constituent of the concentrates has been found to dissolve simultaneously during the alkaline oxidation of both arsenopyrite and pyrite, and this appears to be associated with the in-situ formation of thiosulfate as a lixiviant. The effects of temperature, stirring speed, oxygen partial pressure, alkalinity and pulp density on the oxidation of arsenopyrite and the dissolution of gold have also been investigated. Keywords: Gold, dissolution, arsenopyrite, pyrite, alkaline, oxidation, thiosulfate, thioarsenate

Jan 1, 2005

By Niko Hellstén

To capture efficiently the valuable trace metals from nickel slag using electric furnace, it is important to study their distributions between the slag and metallic phases in the furnace. It is impossible to calculate accurately these distributions without experimental measurements. Therefore, in this work, selected trace metal distributions and phase equilibria between K2O containing iron-silicate slags and a metallic Ni-Fe-Cu alloy in nickel slag cleaning furnace conditions were studied. The experimental method developed and applied during the work, involved a modified quenching technique that included equilibration of the samples in semi-sealed quartz ampoules in an inert atmosphere and metallic Fe saturation. The use of the semi-sealed quartz ampoule prevents the escape of volatile elements from the sample during equilibration. Chemical compositions of the phases and the trace elements were analysed by EPMA. From the measured compositions, the trace metal distribution coefficients between the molten Ni-Fe-Cu alloy and slag were calculated.

By Khandaker M. Anwar Hossain

This paper presents the development of lightweight concrete (LWC) incorporating pumice aggregate and volcanic ash (VA) based ASTM Type I blended cement (PVAC). Fresh and mechanical properties of LWC mixtures such as slump, air content, compressive strength, tensile strength, density and modulus of elasticity are described. The durability characteristics are investigated by drying shrinkage (DS) and water permeability. The investigation suggests the production of LWCs incorporating blended PVAC and VPA having satisfactory strength/durability characteristics for structural applications. The use of PVAC induces the beneficial effect of reducing drying shrinkage and water permeability. Development of such non- expensive and environmentally friendly LWCs with acceptable strength and durability characteristics is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.

Jan 1, 2010

By Leonard A. Duval

This concept employs a viable energy saving method that uses a solvent to separate oil from particle matter; it can be used in metal forming industries to deoil sludges, oxides, and particle matter that is presently committed to landfill. If oily particles are used in their oily state, severe consequences to environmental control systems such as explosions or filter blinding, occur in the air handling equipment. This is due to the presence of hydrocarbons in the stack gases resulting from the oily particles. After deoiling, the particles can be recycled and the separated oil can be used as a fuel. The process does not produce a waste of it's own and does not harm air or water. It demonstrates the dual benefits of being commercially viable and in the national interest of conserving resources.

Jan 1, 1994

By Liu Wei

In order to make clear the dissolving characteristic of the chrysocolla (CuSiO3?H2O) in the ammonia-ammonium chloride solution, a thermodynamic model of the chrysocolla (CuSiO3?H2O)-ammonia- ammonium chloride-water system is established using the exponential computation method based on both mass balance and charge balance equations. The equation group of the thermodynamic model is solved by the MATLAB Soft on PC. The condition which is favorable for dissolving high concentration of copper in solution is making out. The stable area of chrysocolla (CuSiO3?H2O) and the condition of chrysocolla (CuSiO3?H2O) converting to atacamite (Cu(OH)1.5Cl0.5) is also studied. A group of experiments are designed to validate the veracity of the results of the thermodynamic calculation.

Jan 1, 2010

By Emil B. Milosavljevic, Ljiljana Solujic

Cyanide is exceptionally reactive, and in typical gold/silver processing liquors, cyanide may be transformed into various species and forms depending on the mineralogy of the ore and chemical make-up of the process water. The exact speciation and relative concentrations depend on the Eh and pH values, as well as the free CN concentration in the system. Very good cyanide balances can be achieved by the judicious selection of the analytical techniques used. The choices an analyst has to make (which analytical methods to use and which ones to avoid) in order to gain better understanding of cyanide speciation and balances in a particular system under investigation will be discussed. Examples of cyanide balances obtained for the laboratory scale tests (agitated leach and column tests) will be presented and discussed.

Jan 1, 1999

By E. Saez, M. Bellet, T. Coupez, O. Jaouen

"The paper presents a 3D finite element solver for non-steady state fluid flow. The thermomechanical simulation package REM3D® has been initially developed to model Stokes' flow for polymer injection. The mechanical module is based on a Eulerian velocitypressure formulation. The spatial discretization uses P 1+IP1 tetrahedral elements. The front tracking module consists of the resolution of a transport equation, thanks to a space-time discontinuous Galerkin formulation. It includes mesh adaptation, which permits a dynamic refinement at the front, thus controling the numerical diffusion. The same approach is used to solve heat transfer. In this paper, we focus on the specific adaptations done to treat Navier Stokes flow. The treatment of inertia is detailed, as well as the implementation of sliding conditions at mould surface, using conservative normals. Industrial applications are presented.IntroductionThe study of the mould filling stage in casting processes requires the ability to simulate complex non steady-state three-dimensional flows. Most commercial software use the volume of fluid (VOF) method, associated with a Eulerian formulation, see for instance the series of conferences ""Modelling of Casting, Welding and Advanced Solidification Processes"" [1-3]. The VOF method [4] consists in solving the conservation equation dF / dt = 0 for a variable F - the volumic fraction of fluid - whose value is 1 in filled regions and 0 elsewhere. Two fluids are actually considered: the molten alloy and a gas in the empty regions. This method suffers generally from numerical diffusion in the resolution of the free surface tracking equation, which is of pure advective type. The precision of the computation is then strongly dependent on the mesh density. Since the mesh is fixed (Eulerian formulation) this implies that in case of complex flow the user must have a priori a fairly good idea of the flow characteristics in order to capture properly the critical features of the flow. In addition, the method can hardly handle the discontinuity of the material viscosity at the interface. To prevent this difficulty, the viscosity value is smoothed around the interfuce, adding once again some inaccuracy. Since the value F = ½ is supposed to represent the free surface, it results in a smeared fluid surface. An alternative to the fixed mesh methods are the methods in which the mesh covers the fluid domain only, as proposed by Navti and Lewis [5-6], or Gaston and Bellet [7]. Based on updated Lagrangian schemes, they must be associated with an ALE formulation (arbitrary LagrangianEulerian) in order to reduce the number of full remeshing operations."

Jan 1, 2004

By Shivendra Sinha

Total pressure oxidation (TPOX) is widely outreached leaching practice for base metals from sulfide minerals, wherein high temperature (T ∼ 200 °C) and oxygen pressure (pO2 ∼ 25 bar) are required. These aggressive conditions intensify the oxygen mass transfer, and therefore facilitate metal dissolution. However, challenging-cum-negative aspects of such practice are energy and material intensive requirements and high oxygen demand. Thus, the present study explores the novel emulsified medium for enhancement of oxygen mass transfer, which assists faster metal dissolution at significantly lower temperature and pressure condition. It is possible to achieve quantitative dissolution (>95%) of Cu, Ni and Co from mixed sulfide minerals at T ∼ 95 °C and pO2 ∼ 2 bar using an emulsion of 2.5% (v/v) n-Hexadecane in dilute sulfuric acid. In addition, n-Hexadecane was found to be inert, stable and immiscible in a pressurized leaching system, thus can be easily separated and recycled in subsequent leaching stages. Thus, this study offers an energy efficient route for low temperature-pressure leaching of sulfides.

By C. A. Silva

The kinetics of chlorination of titanium-bearing raw materials has been investigated. For comparison purposes pellets of controlled macro-porosity, made of analytical grade TiO2 and anatase concentrate (Brazil) , have been exposed to different combinations of gas composition - CO, CO2, C12 -, gas flowrate and temperature. A thermogravimetric technique and an adapted grain model have been used in order to assess the influence of the several experimental parameters upon the chlorination behavior.

Jan 1, 1997

By Y. H. Su, C. Y. A. Tsao

"The solidification behaviors and velocity of atomized droplets during flight is formulated by a mathematical model, in which the concept of transient nucleation is applied. During the flight, the droplet velocity shows a maximum, followed by an inflection phenomenon. The velocity of large droplet is lower than that of small droplet at shorter flight distance, and higher than that of small droplet at longer flight distance. The effect of the gas flow pattern is more significant at longer flight distance than at shorter flight distance at a given flight distance, large droplet has higher temperature than small droplets prior to nucleation. Large droplet has higher nucleation temperature than small droplet. Medium size droplet flies over the shortest flight distance before the nucleation starts. At the end of recalescence, large droplet has less solid fraction than small droplet has.IntroductionTraditional concept of steady state nucleation was used in all the previous models describing the solidification of molten droplets. [1-5] However, during atomization, the solidification rate of the molten metal droplets is very high, and therefore there is very little time for the nucleation event to occur. In the present work, the concept of transient nucleation [6] is considered to model such short nucleation event during solidification of the atomized droplets. The solidification behaviors and velocity of atomized droplets are modeled and the effects of the atomization gas flow pattern are also presented."

Jan 1, 1997

By V. Reiter, K. Reinharter, C. Wenzl, D. Gregurek, A. Spanring

The refractory linings in lead furnaces are exposed to several stresses rather complex in their interaction. In the present study the magnesia-chromite brick out of a lead recycling furnace suffered from a high chemical attack by the process slag. The high CaO, BaO and sulfur bearing silicate slag, as well as a high NaO2 supply from soda resulted both in a deep-reaching infiltration of the brick microstructure and a severe corrosion of the brick components. Both the sintered magnesia and chromite were attacked chemically. The FactSage calculations showed the formation of high amounts of liquid phase in the infiltrated microstructure. Further phenomena affecting the refractory performance such as iron oxide attack, redox effects, and boron attack are also discussed in the paper. The obtained information and insights serve as a basis for improving refractory materials (i.e., choice of refractories for individual process and new developments) and consequently furnace operations.

Mar 1, 2017

By A. E. M. Warner

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

Jan 1, 2003

By Elsa Olivetti

Life cycle assessment (LCA) is used increasingly as a tool to provide quantitative metrics of environmental impact and inform early stage materials selection decisions. One common challenge in LCA stems from allocation of burden when multiple adjacent products share some of the same processes. A critical example of this is the partitioning of benefit or burden at product disposition in open-loop recycling scenarios. This work reviews the challenge of allocation and investigates the various methods proposed for allocating end-of-life (EOL) burden. Specifically this work examines whether these methods lead to different results and explores the trends in allocation method bias for or against particular materials classes.

Jan 1, 2010

By Ann M. Hagni

The mineralogical, chemical, microtextural, and particle size character of electric arc furnace (EAF) dusts are being studied by reflected light microscopy, scanning electron microscope-energy dispersive spectroscopic analysis (SEM-EDS) and electron probe microanalysis (EPMA). The dusts consist predominantly of metallic iron, iron oxide, and calcium-iron-manganese silicate phases, together with smaller amounts of iron-manganese-zinc-calcium, iron-calcium-zinc-manganese, and calcium-iron-manganese silicates. The samples vary in their zinc contents. Chlorine occurs in phases containing iron, lead, zinc, manganese, and calcium. The dust particles range greatly in size from 1 to more than 300 ~m, but most particles are about 1 to 6 ~m. Larger particles. about 20-50 um across. also are present. They are predominantly spherical in shape, but some are cenospheres, and others are more angular particles, some of which are broken spheres and cenospheres. Their internal microtextures exhibit evidence of liquid immiscibility, exsolution, skeletal crystal growth, and oxidation react i on rims. Because EAF dusts have been classified by EPA as hazardous wastes, there is heightened interest in the treatment of these dusts to render them non-hazardous. The mineralogy of products of pyrometallurgical treatment of EAF dusts by flash furnace and pyrohydrolysis are currently under study.

Jan 1, 1991

By Tianming Sun, Gabriella Tranell, Ragnhild E. Aune, Mark William Kennedy

Rare Earth Elements (REEs) are critical for the production of many advanced materials and products. Mining and primary production of REEs are generally associated with significant environmental impacts. By recovery of REEs from secondary sources, through recycling or as a byproduct, the adverse environmental impacts may be partly avoided. In the present study apatite concentrate originating from iron ore beneficiation done by LKAB in Kiruna, Sweden, is explored as a possible source for REEs. The composition and distribution of the REEs within the concentrates are studied using ICP-MS, XRD and SEM-EDS/EPMA, as well as the melting point and heat of fusion using DTA-TGA-MS. The behavior of the material during melting has also been studied through wetting and slag saturation experiments. The overall aim of the study is to evaluate the implications for future smelting experiments aimed at concentration and recovery of the REEs.

Jan 1, 2015

By Chen Wen, Li Zhao-jia, Zhao Qiang, Ning Shun-ming, Tang Sanchuan, Wang Hong-qiang

"The carbon-burdened and cold-bonded pelletizing-electrosmelting process is used to dispose low-grade manganese, and the qualified rich-manganese slag is obtained. On the condition that reduction roasting temperature was 1000?, reduction time was 45min, particle-size was -1mm, reductant dosage was 1.6%, basicity was 0.3, smelting temperature was 1410?, smelting time was 60min, it had a good effect on the melting between slag and metallographic phase, the manganese content was 32.58%, manganese recovery was 92.16% in the slag; while the iron content was 94.40%, iron recovery was 95.32% in the metallographic phase. It was proved by the demonstration tests.IntroductionManganese is an important raw material for steelmaking, which is extensively utilized in modern industry, the consumption of manganese for iron and steel industry accounts for 90% to 95%. After mining over 30 years, the high-grade manganese resources drop markedly, especially with the hypergrowth of steel industry, the domestic manganese is far from the requirement, as a result, we have to buy significant quantities of manganese overseas. Besides, the property of imported manganese is more and more complex, and the high-grade and lump manganese decrease year by year, while the fines and high-crystal water manganese are on the increase. Therefore, how to make effective use of domestic low-grade manganese and intensify the manganese’s smelting is an effective approach to reduce the cost of manganese series ferroalloy and improves market competitiveness[1-4]. It has important practical meaning."

Jan 1, 2012

By Bo Björkman

Four different arsenic containing dusts from the Boliden plant, Boliden mineral AB, Sweden have been examined. A kinetic study of the As elimination was performed in a laboratory scale roasting furnace for roasting furnace ESP dust and smelting furnace ESP dust. Characterisation and thermodynamic calculations were carried out to determine the mineralogy, and the stability of compounds in the dusts studied. The characterisation methods used were chemical analysis, X-ray diffraction analysis and microprobe analysis. It was found in the experiments that a high degree of As elimination was obtained for roasting fumace ESP dust and a low degree for smelting fumace ESP dust. Derived kinetic models are given. A prediction of the As-elimation for settling furnace dust and converter ventilation dust is presented.

Jan 1, 1994

By Kazuya Kitatani, Gen Sasaki, Naoto Ohta, Hideharu Fukunaga, Makoto Yoshida, Jin Pan, Kenya Nagahisa, Toshihiro Ishikawa

"A sintered SiC (Tyranno-SA) fiber-reinforced MAS glass matrix composite was fabricated by using a slurry infiltration method and hot-pressing. The microstructure and mechanical properties were investigated: To prepare the preform, the MAS glass slurry including a dispersing agent was infiltrated into a bundle of the fibers. The preform was then hot-pressed under the conditions of 1473 K, 30 MPa, 3.6 ksec. A unidirectionally-reinforced oxide matrix composite with 50% Vf. of the fiber and a density of 2.84 g/cm3 was obtained. As the mechanical properties at room temperature, the three-point flexural strength- and quasi-static adsorbed energy were 500 MPa arid 6,000 J/m2, respectively. Without graphite or an h-BN pre-coating on the surface of the fiber, pull-out and bridging of the fibers from the matrix was found, and this leads to a high value of the adsorbed energy. By TEM observation, nano-scale crystalline products were found between the fibers and the glass matrix. The push-out test reveals that this layer causes the appropriate debonding of the interface during the fracture process of the composite.Introduction It is known that the CFCCs (continuous-fiber-reinforced ceramic matrix composites) are characterized by their non-linear fracture behavior, which is' hardly found in monolithic ceramic materials. It is inevitable for the CFCCs to exhibit a large fracture toughness so 'that debonding of the fiber/matrix interface; pull-out and bridging of the fibers then' occurs during the fracture process. This series of fracture behavior is known as the so-called ""the mechanism of toughening of the CFCCs"". Thus, different from the MMCs in which strong interfacial bonding is necessary, the interfacial strength of the CFCCs has to be controlled. As techniques for controlling the interfacial strength, it is also known that both a CVD-graphite coating and an h-BN coating are effective to induce the mechanism of toughening[1,2]. In the case, of the Si-C-O or Si-Ti-C-O fibers/glass or crystalline oxide matrix composites, it is reported that the formation of the in-situ graphite layer, which is also effective to increase the fracture toughness of the CFCCs, is often found during the fabrication process such as hot-pressing. The lower the crystallinity of the Si-C-O fibers, the higher is the tendency to form the in-situ graphite layer as found by the chemical reaction between the fibers and the glass matrices[3-12]. On the-other hand crystallized stoichiometric 'SiC fibers are attractive for high temperature service because of the higher phase stability compared to the Si¬C-O or Si-Ti-C-O fibers. However, in the previous, studies, the mechanical properties and the interfacial chemical reaction of the crystallized SiC fibers / glass matrix Composites have still been unknown. In this study, a polycrystalline 'sintered SiC fiber-reinforced MAS glass composite was fabricated. The mechanical properties and microstructure were then investigated. The slurry infiltration technique followed by hot-pressing was used to prepare the composites. The formation of the in-situ graphite layer and the relationship between microstructure and mechanical properties at room temperature were examined by the TEM observation of the fiber/matrix interface."

Jan 1, 2000