Search Documents

By David G. Dixon

A general, unsteady-state model for leaching of one or more solid reactant species from a non- reactive, porous, spherical pellet is derived in dimensionless form for the interpretation of leaching data, and for use in the design of coarse-ore leaching processes. The effects of diffusion rate, chemical reaction rate, variable reaction order, and competition between multiple solid reactants are examined using the concept of the effectiveness factor. It is shown that the model is capable of simulating both "reaction-zone" and "heterogeneous" kinetics, depending on the choice of three dimensionless parameters. Results of batch leaching tests of artificial ore pellets are presented, and their relationship to the model is discussed.

Jan 1, 1993

By Long Meng, Yaodong Yi, Kuiyuan Chen, Zhancheng Guo, Yu Li

Blast furnace slag is the main by-product discharged in the iron and steel industry and contains considerable waste heat at dischargeing temperature between 1450 and 1550 °C. To fully utilize waste heat and slag, this study directly converted high temperature liquid Ti-bearing blast furnace slag into glass-ceramics via the “Petrurgic” method. Samples at different crystallization temperature were prepared and its influence on crystal phases, pore structure, and compressive strength were investigated via SEM, XRD techniques, and compressive strength measurements. Results showed that all glass-ceramic samples contained main crystals of perovskite, diopside and gehlenite and had a qualified mechanical performance with compressive strength above 100 Mpa, which meets the requirement of Chinese national standard for natural granite stone. With increasing crystallization temperature, pore size decreased, while the size of the perovskite phase firstly decreased and then increased with decreasing crystallization temperature. Samples had an optimum crystallization temperature of 1215 °C, maximum grain size and a densified structure with minimal pore defect.

Mar 1, 2018

By O. Forsén

In the first part of this paper is studied the behaviour of small amounts of impurity elements? in the solidification of copper anodes. In the second part the dissolution of these impure anodes in sulphate based electrolysis is discussed. The first part is introduced with practical examples, the .model of solidification of impurities during the solidification of anode copper. According to this model the solidification structures of anode copper are strongly influenced by both thermodynamic and kinetic factors. Thermodynamics determine the microstructure of anode copper, but kinetics can alter the composition of melt to such that there is formed unequilibrium structures during the solidification, especially when the residual melt is solidified. The electrolysis experiments have clarified the behaviour of impuririties in the electrochemical dissolution in sulphate. Based copper electrolysis. In this study it is widely investigated to what extent any impurity elements or oxides will dissolve. In copper electrorefining. With the aid of the electrochemtcal experiments it was possible to fulfil quantitatively the qualitative results accomplished by microstructure studies.

Jan 1, 1985

By Reinhard Bott

The Companhia Mineira de Metais (Brazil) runs a Zn-recovery plant in Tres Marias, federal state Minas Gerais, Brazil. The Zn-production is about 65,000 t/a, This corresponds to a concentrate throughput of about 255,000 t/a with a Zncontent of about 29.5 % at an output of 85 %, The plant is run continuously 360 d/a and 24 h/d, respectively. From this it can be concluded that: Input: approx. 650 - 700 t/d ore-concentrate and approx. 29 t/h ore-concentrate, respectively.

Jan 1, 1990

By Carlos M. Fontes Vieira, Ruben J. Sanchez Rodriguez, Carlos E. Gomes Ribeiro

"In this study we attempted to model a response surface for the apparent dry density of ternary blends of calcitic marble particles. The crushed marble was divided into three granulometric ranges. Simplex network methodology was used to determine the mathematical relation between granulometric ranges and apparent dry density (ADD) of particle mixtures. A highly significant regression was obtained and the simplex network methodology proved to be able to predict high packing particle compositions.IntroductionProblems with packing and expected porosity of particles are common and widely recognized to be important in terms of both fundamental physics and engineering applications. For example, densification of a powder mass is important in the shaping of solids in ceramics, powder metallurgy or composite synthesis; chemical processes such as solid-liquid separation (sedimentation, thickening and filtration), raw material handling (stockpiling, blending, drying, storage and transportation) and pyrometallurgical processes (agglomeration, coke making, ore sintering, blast furnace iron making and new iron making processes) [1,2].Many factors can affect particle packing, but in practice, there are three main factors: (dimensionless) particle size distribution, particle shape and absolute particle size [2].Geometrical and practical methods were developed to predict properties in mixtures. Zou, Gan and Yu [2] present a paper treating a prediction of the porosity of multi-component mixtures of cohesive (fine) and non-cohesive (coarse) particles. Bahiense et al. [3,4] used a simplex network to determine a mathematical model for obtain the optimal compositions between aggregates to a greater packing of a ternary particles mixture. Despite these techniques for predicting particle packing, some studies in particulate composites production don't present clear criteria for choice of particle distribution [5,6]. As the best particle packaging depends on the size, distribution and shape of these particles, individual models can be constructed for specific combinations of these factors."

Jan 1, 2014

By Rejane Tubino Geyer

The volume of electric arc furnace (EAF) plus oxygen (BOF) slag produced yearly in the world is about 84 million ton. Because of this, the study of recycling processes as a way to solve the storage problem of these slags rise in importance. There are, however, some inconvenients on using this byproduct: lime, which takes part of the process of steel production, remains as a non-reactive raw product in the slag. Since lime reacts in presence of humidity, forming expansive compounds, slag use is strongly limited. There are some utilizations for the electric arc furnace and oxygen slag in the Civil Construction Industry, mainly as base, subbase and asphalt covering in highways. However, independently of the type of recycling, a period of "cure" of about six months is necessary. Because of this slow cure process this byproduct may turn non-competitive in some regions if compared, for example, with the natural aggregate. The objective of this work is to present the flowsheet of the slags production as a residue both at the electric and oxygen steel plants and, through a bibliographic review, to analize the possibilities and limiting factors for the use of steelmaking slags in the Civil Construction Industry.

Jan 1, 1996

By Dinesh P. Amalnerkar, Nagegownivari Munirathnam, Tirthalli Prakash, Katia Vutova, Vania Vassileva, Veliko Donchev

"A time-dependent model for electron beam melting and refining (EBMR) of different metals and alloys is developed. The model is 3D axi-symmetrical and an adapted numerical scheme of Pismen-Rekftord type is applied. The developed computer program computes the thermal fields in the metal ingots during EBMR process as well as the dynamics of the thermal streams and the geometry of the molten metal pools. Calculated results for different regimes of EBMR of titanium are obtained and discussed in the paper. Experiments are performed and impurities' concentration data are presented. Simulation results are compared with experimental data and are used for optimization of the EBMR process in the case of Ti.IntroductionElectron beam melting and refining (EBMR) has an important role in the special electrometallurgy[ 1-6] and it is approved for obtaining of pure titanium [7]. EBMR of metals and alloys is being recognized as a competitive and even the single method for obtaining new materials for all areas of human activity.The principal scheme of the EBMR drip process is shown in Fig.1. A thin layer of molten metal is formed on the front part of the feeding rod during the e-beam processing and generated droplets fall into the molten pool in the crucible where the ingot is formed. The refining is mainly realized at the boundary liquid metal - vacuum. There are three zones in EBMR (Fig.1) - on the front part of the feeding rod (zone I in Fig.1 ), on the surface of the generated droplets (zone II in Fig.1) and the surface of the molten pool in the water-cooled copper crucible (zone III in Fig.1)."

Jan 1, 2013

By D. S. Barr

Mineralogical, lithological, and metallurgical studies were conducted on various gold ore deposits currently controlled by Freeport-McMoRan Gold Company. Ore samples were first lithologically and mineralogically categorized, then subjected to chlorination, roasting, and autoclaving pretreatments to determine their effects on gold recovery in a subsequent alkaline cyanide carbon-in-leach extraction. The studies indicate that, while organic carbon and sulfide sulfur are the primary refractory components, their effect on process response must be interpreted with respect to the deposit's geology and mineralogy. This approach has proven to be an effective method for evaluating metallurgical alternatives and fore-casting future mill performance.

Jan 1, 1987

By Peiye Yan, Huiqing Tang

To reduce coke consumption in blast furnace ironmaking, this study proposed a new method of applying iron-coke briquette prepared using hematite powder and pulverized coal to protect coke in BF iron making. Results showed that, with a ratio of hematite to coal of 2.0, the iron-coke briquette could obtain a satisfying compressive strength of more than 1500 N both before gasification and after being gasified by CO2 for 1 h. The activation energy of the iron-coke briquette was 93–135 kJ/mol, which is lower than the coke and therefore could protect the coke in BF. The agglomeration and stratification of iron particles occur in the course of iron-coke briquette gasi fication and is bene ficial to the improvement of the iron-coke briquette strength.

Mar 1, 2018

By Christoph Czettl, Christian Storf, Gregor Kücher, Stefan Luidold

The purpose of this investigation is to provide a basis for the semidirect recycling of hard metals. The present investigation focuses on revealing the fundamental chemical kinetic aspects during cemented carbide leaching in hydrochloric acid media. The kinetic relations of cobalt binder leaching from WC-Co cemented carbide are studied using a central composite face-centered design of experiments with temperature, acid concentration, and hydrogen peroxide as variables.

Mar 1, 2017

By M. G. Silva-Valenzuela, A. T. Machado, F. M. S. Carvalho, J. R. Matos, A. A. S. Araujo

Electric arc furnace steel dust is a by-product of the steelmaking process and contains high amounts of iron and zinc and significant amounts of lead, chromium, and cadmium and others chemical compounds in minor proportion. However, the material recycling is very complex, mainly due to their mineralogical composition. In this study the characterization and application of this material is presented. Ceramics were produced with clay and variable amounts of steel dust. Th bulk material was fired between 800 and 1000 °C. The influence to insertion of this material on the ceramic composition on the mechanical strength, linear shrinkage, water absorption, apparent density and bending strength of the ceramic samples was investigated. A blend of clay with 5% dus presents potential for use in structural ceramics production.

Mar 1, 2017

By D. Tait, M. A. Halim, V. I. Lakshmanan, R. Sridhar

Rare earth elements (REEs), nickel and cobalt find their use in developing strategic materials and their demand is consistently increasing in the world while the extractable ores of these metals are gradually depleting. Process Research ORTECH Inc. (PRO) has developed innovative mixed chloride leaching processes for the recovery of REEs from alumino-silicate ores, and nickel and cobalt from laterite ores. The addition of magnesium chloride in hydrochloric acid enhances the activity of the hydrogen ion by orders of magnitude, which permit rapid leaching rates at moderate temperature and atmospheric pressure, along with high metal recovery. Innovative solvent extraction process steps are used for the separation of these metals from pregnant leach solutions. PRO’s processes also produce value added by-product of high purity iron oxide and recycle chloride lixiviant to the leaching stage. This paper describes the leaching and separation reaction mechanisms and potential process flowsheets.

Mar 1, 2017

By Fábio O. Braga, Sergio Monteiro, Artur C. Pereira, Foluke S. de Assis

The jute fiber is one of the most investigated natural lignocellulosic fibers due to its easy processing and extensive occurrence. However, the studies with some varieties of jute fiber such as the Corchorus capsularis are rare, so this wor kinvestigated the toughness behavior of polyester matrix composites reinforced with up to 30% in volume of a fabric made of jute fiber by means of Charpy impact tests. It was found that the addition of jute fabric results in a marked increase in the absorbed energy by the composites. Macroscopic observation of the post-impact specimens and SEM fracture analysis showed that transversal rupture through the jute fabric interface with the polyester matrix is the main mechanism for the remarkable toughness of these composites.

Mar 1, 2017

By Thamyres C. Carvalho, Edemarino A. Hildebrando, Roberto F. Neves, Francisco R. Valenzuela-Diaz

Synthetic clays are an option of materials that can be modified to obtain better and specific properties when compared with natural clays. Although clays are found in nature, they have many disadvantages that limit the use of them, such as existence of impurities, and variations in composition. Therefore, the objective of this work was to obtain synthetic clay/polyester resin nanocomposites. To characterize the clay, we used X-ray Diffraction (XRD), Total Attenuated Reflection Spectroscopy in the Fourier Transform Infrared Region (ATR-FTIR) and Scanning Electron Microscope with Field Emission (FEG-SEM) methods and the nanocomposites were characterized by XRD and mechanical resistance to compression. The results show the purity of the clay and the time of synthesis is an important parameter for its crystallization process. The clay/polyester nanocomposites were obtained and showed an increase in the ductility.

Mar 1, 2018

By Gregor Kücher

Lack of basic knowledge on the semi-direct recycling methods for hard metals hinders the application on an industrial scale. However, advantages like reduced expenses and lower environmental impact draw interest at future potentials. Consequently, this report aims to offer insight into the influence of varying bulky hard metal substrates during their lixiviation in acidic media with an oxidant. The statistical software Modde 11 assisted in the development of a design of experiments (DOE) for evaluation of the impact of average grain size, binder and tantalum carbide (TaC) content on the leaching characteristics. The other experimental parameters were constant. Among them were temperature, solution concentration and quantity, duration and substrate surface exposed to liquid volume. Eventually, prediction plots and factors of the computed model equation describe the effects of varying substrate qualities on leached binder metal and selectivity.

By C. G. Bastos Andrade, F. R. Valenzuela Diaz, S. M. Toffoli

The modification of structural clays by chemical processes is a common method. It usually uses strong inorganic acid attacks, aiming at improving the clay’s properties and applications. Among the applications are its use in clay-polymer nanocomposites, cosmetics, medicines, and bleaching clays. Tests using acid attack to modified Brazilian bentonites were successfully performed and, resulted in significant improvement in the clay properties. This paper discusses the use of a Brazilian bentonite modified by acid attack as bleaching clay. The treated bentonite samples were characterized by XRF, specific surface area (BET) and SEM/EDS. The treated clay exhibited improved bleaching capacity for Brazilian nut oil and other Amazonian oils.

Mar 1, 2018

By Chen Tian, Sen Zhang, Qinghai Pang, Junhong Zhang, Wenlong Zhan, Zhijun He

Alkali metal is one of the key critical factors that determine the coke degradation. Previous studies on the influence of alkali metal on coke structure were mostly focus on the catalysis of alkali carbonates for coke gasification reaction. Besides, the difference of alkali metal and coke gasification effects on coke degradation was still not clear. Highly reactive coke developed by Nippon Steel was proved to increase the reaction efficiency and to decrease CO2 emission effectively. Therefore, conventional coke and highly reactive coke adsorbed 5% sodium were studied in this paper. Coke degradation tests were undertaken in atmosphere of N2 and CO2. SEM, EDS and XRD were employed to analyze samples. Results showed that the degradation of conventional coke strength by sodium was stronger than highly reactive coke in the atmosphere of N2. The effect of CaO catalyst on the coke reactivity has been interpreted as a change in highly reactive coke microstructure and strength.

Mar 1, 2017

By S. Gupta, M. Fuka

This paper reports for the first time the synthesis of deintercalated MoAlB particulates which belongs to a family of novel ternary borides called MAB phases by selected etching of Al from these particulates by treating them with a solution of LiF and HCl. The FESEM analysis showed that these particulates hada stacked 2D-particles like morphology reminiscent of multilayered MXenes, but unlike MXenes, the 2D layers were interconnected with anisotropic porosity between them with an average length and width of pores being 257 ± 126 nm and 35 ± 10 nm, respectively. The EDS analysis of particulates showed that a typical particulate had a chemistry of (Mo Al )B{O F } which indicate partial 0.67 0.33 0.19 0.02 deintercalation of Al from the particulates. These novel particulates were also referred to as MABenes due to their microstructural similarity with multilayered MXenes.

Mar 1, 2018

By Afshin Sadri

Acousto Ultrasonic-Echo (AU-E) is a technique developed to provide accurate measurements of the refractory lining wear in operating smelters based on the principles of stress wave propagation. The objective of the system is to provide feedback for the continuous optimization of the overall smelter operation. In some cases, the AU-E refractory lining measurements have allowed clients to extend their smelter campaigns and operate safely for several years beyond their planned reline schedule. In other cases, AU-E results inform clients of serious issues within their furnace allowing them to shut down their smelters ahead of predicted failures and possible disasters. This paper presents the results of several smelter AU-E inspections of the hearth and sidewall. These case studies demonstrate how the AU-E results were used to positively affect the smelter operation.

By Cheng Fang, Zhou Lie-xing, Peng Jin-hui, Guo Sheng-hui

This article discusses the behavior of temperature and microwave thermo gravimetric analysis characteristic of ammonium paratungstate in a microwave field. Experimental results show that when 12g of material is place in a microwave with 900W of power, paratungstate’s temperature rises at 70°C/min. This results in paratungstate’s temperature being 980°C after 14 minutes. Compared with thermo gravimetric analysis characteristic, former two-step process of paratungstate microwave calcined completed ahead of schedule, after two-step process reaction is more intense,Paratungstate warming is more rapidly, the reaction time is much shorter; According to XRD and SEM, the product is high purity, the crystal particle size is uniform, and the grain size is fine.

Jan 1, 2015