Search Documents

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 Huaming Yang

The vanadium-doped SnO2 nanoparticle was synthesized by the co-precipitation reaction and subsequent calcination from the vanadium(III) chloride and tin(IV) chloride. The crystal size, pore size distribution, micrograph and properties of the nanocrystalline powders were examined by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), desorption isotherm (Barrett-Joyner-Halenda method) and transmission electron microscopy(TEM). Thermal treatment of the precipitate powder at 600°C led to the formation of V -SnO2 nanoparticle of -10mm in crystal size. Most of the pores in the nanoparticle are about 5~15nm in diameter. Effect of doped vanadium on the crystal size of the nanopartic1e was discussed.

Jan 1, 2003

By Andreas H. Vassiliou

Organic materials are major constituents of the ore in several uranium deposits. Some of these deposits have been described as "urano-organic" because, the organic materials are believed to have provided the dominant control for the accumulation and deposition of uranium and are directly and intimately intermingled with the uranium. The nature of these urano-organic deposits has been problematic in terms of (a) the origin of the associated organic materials and (b) the specific form of' occurrence of uranium. The organic materials in urano-organic deposits have been genetically related to both coal and petroleum or their progenitors or deriva-tives. Analytical data presented here (infrared, chemical. D.T.A.) suggest that coaliferous materials or related plant derivatives represent the main source of the organic fractions in practically all major urano-organic ores analyzed from the Colorado Plateau and other areas. Recognition of the specific form of occurrence of uranium in urano-organic deposits has been problematic mainly because the uranium is usually in an extremely fine-grained and disseminated state in the organic matrix. Electron microprobe and X-ray diffraction analyses presented here show that fine-grained uranium minerals, specifically uraninite or coffinite. are disseminated in the organic matrix as the predominant form of uranium in most major deposits; however. the presence of true organo-uranium compounds is also suggested for some deposits.

Jan 1, 1981

By Munyaradzi Kwatara, Ron Schonewille, Edgar Peek, Juzer Tayabally

"The potential recovery of nickel from a South-American saprolitic laterite ore using the segregation roasting technique was investigated. The ore was heated to temperatures that ranged between 900 and 1 000°C in a rotary kiln. In all the tests, the laterite ore was first mixed with a predetermined amount of calcium chloride and either coal or coke. By varying the temperature, calcium chloride and reductant in the different tests, a preliminary set of optimal conditions was established for the specific laterite ore that was tested. A combination of chemical analysis and electron-probe-micro-analysis (EPMA) were used to determine and evaluate the effectiveness of segregation roasting on the recovery of nickel. The present paper describes the test procedure and the results that were obtained.IntroductionIt is known that laterite ore resources account for an estimated 72% of the world's nickel resources, with sulfide sources accounting for the remaining 28%. Yet sulfide resources account for 58% of the world's primary nickel production while laterite resources account for the remaining 42% [I]. There are numerous reasons for this discrepancy, but the most important one is the mineralogical and compositional complexity that is associated with laterite ore deposits. For example, this complexity currently offers only limited opportunities for upgrading, thereby creating capital intensive whole ore processing facilities. It then follows logically that the identification and application of a low-cost processing option for the treatment of laterites could potentially open up an opportunity for exploiting these vast untapped laterite resources.To this end, a preliminary screening investigation was initiated by Xstrata Process Support to evaluate the potential application of the so-called (nickel) segregation process as a unit operation that could potentially be integrated into a laterite processing flow sheet. Laboratory bench tests were performed on this segregation process and this paper details some of the findings from this preliminary investigation."

Jan 1, 2011

By Jie Ma, Bo Wang, Jieyu Zhang, Jian Zhao, Guangxin Wu, Shunli Zhao

"Nucleation and growth model based on a 3D CAFE model, which was incorporated with macro heat transfer calculation within ProCAST software was used to predict the solidification microstructure of austenitic stainless steel in twin-roll strip casting. The simulation results of solidification microstructure agreed well with experimental results of austenitic stainless steel. The effect of different casting process parameters on the solidification microstructure was simulated. The predicted results show that solidification microstructure is obviously sensitive to superheat and convection heat transfer coefficient. With the increase of superheat, the grain density decrease and the proportion of columnar crystal increase. In addition, the proportion of columnar grains increases when convection heat transfer coefficient increases. Thus, it was demonstrated that the solidification microstructure evolution of twin-roll strip casting could be predicted reasonably by using this model.IntroductionNear-net-shape casting technology is an important research area in the iron and steel industry today. Twin-roll strip casting represents a major area of concentration of near-net-shape casting technology. It has been widely used for its outstanding advantages, such as extended solubility of alloying elements, refined solidification microstructure and reduced microsegregation [1]. Furthermore, it is the most environmentally friendly, energy saving, and C02-sensitive way to produce steel strips [2]. Therefore, much attention remains to be paid to this aspect. A lot of published works indicated that the solidification microstructure of twin-roll thin strip has obvious effect on the thin strip properties [3, 4]. For the accurate control of parameters of the process are made difficult due to the complicated process and the multi-fold factors, great attentions have been paid to numerical simulations to provide insight into the solidification behaviors of the thin strip formed by twin-roll strip casting [5, 6].Simulations of casting solidification can provide a method to predict microstructure and to improving strip quality by controlling the process parameters."

Jan 1, 2014

By Hao Deng, Hongmin Zhu, Jichao Li, Kai Huang

"Silicon and silicon carbide mixing micropowders obtained from the saw cutting industry of polycrystalline silicon ingot is separated by a simple sequential sedimentation. The Zeta potentials of the powders in the aqueous suspension are adjusted by varying the pHs with dilute acid or alkaline reagents. The dispersion and aggregation content of the microparticles is significantly influenced by pHs, and so their settlement velocity in the same hydraulic conditions are quite different, and silicon powders tend to suspend in the upper section of the suspension for its finer size and smaller density under the stronger Zeta potential repulsion force. The original content of the cutting powders with 30%wt silicon are separated into the Si-rich and SiC-rich powder respectively, and 62%wt Si-rich powder can be obtained after 4 times of sedimentation under pH = 8.0, showing the great potential for Si and SiC powder separation and recovery in a cost-effective way.IntroductionWith the fast development of photovoltaic (PV) technology these years, the market demand for the solar-grade high pure silicon material significantly increased, making the silicon recycling and recovery from the wire sawing slurry profitable and attractive[1]. Waste silicon slurry was produced in the multi-wire sawing process of a silicon ingot by using an ethylene glycol-based solution and silicon carbide abrasives as the slicing system. During this slicing process, about 30% of the silicon ingot will become the waste as the fine particles suspended in the slurry, which mainly consists of silicon kerf-loss particles, SiC fragmental particles, tiny iron fragments from the worn sawing wire and ethylene glycol-based solution [2]. The separation of above individual component is usually easy except for Si and SiC fine particles for their quite similar properties. So the biggest challenge for the effective recovery and recycling of silicon particles from the wire sawing slurry actually lies in the mutual separation of silicon and silicon carbide particles."

Jan 1, 2012

By Honorio Oliveros Gómez, Oscar Jaime B. Restrepo

"Colombia produces nine tons of electronic waste per year and there are approximately 60 tons accumulation generated in the last nine years. This work aims to establish a general methodology in the laboratory to recover gold, silver and platinum group present in electronic waste, also explore other forms of recovery of metals contained in electronic waste. We selected seven types of electronic cards present in the computers, which have their parent desoldering electronic components. Initially, we characterized the components of the cards through X-ray diffraction and SEM, to identify the metal species and composition. Tests were conducted laboratory hydrometallurgical recovery of metals. This paper proposes a methodology for laboratory-scale work.INTRODUCTIONColombia produces nine tonnes of electronic waste per year and build there in about 60 tons generated in the last 9 years [1], Computers, TVs, audio equipment, monitors, cell phones, remote controls, printers and operated toys battery, among others are part of this inventory, which mostly comes to landfills, because the lack of legislation to control the final destination of waste electrical and electronic equipment, and lack of efficient technologies to recover materials [2]. Under these circumstances which have environmental implications, technological and economic recovery is essential metals present in the electronic cards of computers, by hydrometallurgical with subsequent base metal electrodeposition [3]. Pyrometallurgical route is discarded by major implications for economic and environmental [4]. Recovery From this perspective, the determination of the metal fraction and the relationship between the different metals, using the SEM characterization techniques - BSE and XRD is indispensable [5] It follows with electrolytic dissociation processes in the leaching and electrodeposition [6], and unit operations in the laboratory to carry out successfully these processes on a larger scale. Were randomly selected computer twenty-four postcards for nine types of cards have different functions in the computer, which, through the absorption desoldering technique, they broke the resistance (thermal, surface, photoresist, power), capacitors (ceramic, electrolytic), diodes (silicon, germanium, high frequency), transistor (NPN, PNP), processors, integrated (high, medium and low frequency), the RAM card and pin parallel port serial"

Jan 1, 2011

By Zhou Jiemin

In order to fully understand the behavior of the rectangular six- electrode electric smelting furnace and improve its design and operation, a three-dimensional mathematical model has been developed which incorporates the electrical and thermal flows into numerical solutions, assuming a steady state regime. The model has been used to simulate the performance of the 16500 kVA nickel matte smelter at Jinchuan in China, and various factors have been investigated. The results of computation are in agreement with the measured data obtained from this furnace and its physical model. Application of this model is described and the calculation on the Jinchuan smelter shows that the operation expenses can be reduced by optimizing the furnace geometry and some operating parameters.

Jan 1, 1991

By Majid Sarkari, Hossein Atashi, Farhad Fazlollahi

"The aim of this research work was to prepare the efficient catalyst to purify pollutant output gases such as SO2 , NO2 and CO. This catalyst, lanthanum cobaltat (LaCo03) was prepared by the proper method in the analysis laboratory of Tabriz Oil .The first materials were chosen through calcination operation and temperatures of operation related to the Tamman temperature, therefore the basis for the first material of catalyst was nitrate and aqueous and since we had no availability to lanthanum nitrate, lanthanum oxide was used to prepare the nitrate one. Before all else, the first materials of catalyst were mixed together with the equal mole proportions and then, at the lower and upper temperatures of Tanunan temperature, calcination operation was carried out. To determine the molecular structure, the XRD analysis was utilized and specified that prepared lanthanum cobaltat was sixth aqueous and had the crystal structure type Triclinic.IntroductionLaCo03 has presented a vast interest because of its special electrical, magnetic and catalytic properties [1-4]. The catalyst LaCo03 can be prepared by means of several methods such as spray drying, freeze drying and also co-precipitation [5-12]. Some methods including hydrothermal, sol gel and citrate [13] This material usually has been synthesized by ceramic method and certainly the high temperature for the calcination operation. [14]. Lanthanum catalysts have been researched because of having such an active state [15]. One of the unique properties of this catalyst is the simultaneous conversion of pollutant elements. Nowadays CO oxidation has important applications in environment protection, such as indoor air cleaning and automotive exhaust treatment. LaCoO3 is one of the most important catalysts for CO oxidation."

Jan 1, 2013

By R. T. Jr. Faria, H. Vargas, R. Toledo, S. Cosin, V. P. Souza

"With the purpose of decrease environmental impact, caused by industrial residues (just discarded in the environment) and clay extraction in the ceramic industry, sanitary ware wastes were incorporated into clay. In contrast, it is important to evaluate not only the technological essays but also gases emissions in the ceramic firing process. The pollutant gases emitted in ceramic with residues can be in much larger concentrations than that in a pure clay ceramic firing or, on the other hand, can decrease the pollutant gas concentrations. With the aid of thermal analyses and photo acoustical techniques it was observed that sanitary ware waste can reduce the C02 emission. The gas emissions were shown as in function of firing temperature from 300 DC to 1100 DC. In order to analyze phase transformations during the firing process, clay samples and wastes were both analyzed by x-rays fluorescent chemical analysis and x-rays diffraction.IntroductionResearch works on the structural and physical changes that wastes, mainly industrially produced, cause to the final ceramic product has been rapidly expanding in these last two decades. See, for instance references in [1]. In spite of these examples of a continuous effort to incorporate wastes into clay ceramic motivated by technical and economical advantages, environmental issues are still a matter of concern. However, the gas emission due to the clay firing process and its related atmospheric pollution may be enhanced as a consequence of an incorporated waste [2]. It is known that the firing of clay ceramics in conventional furnaces using fuels such as wood, charcoal, heavy oil and natural gas generates appreciable amounts of gaseous components, mainly carbon dioxide (CO2), carbon monoxide (CO) and methane (CH4). Additionally to the atmospheric pollution, these gas sets could be harmful to the human health and can corrode equipments [3,4]."

Jan 1, 2012

By John Nauman

Liquid ferrous silicates that are related to cop- per slags have been studied as media for the transfer of heat in pyrometallurgical processes. The effective thermal diffusivities have been measured from 1025Oto 1400°C, and values in the range of 0.004 to 0.007 cm2/ sec have been obtained. The heat-transfer characteristics of these slags have been determined by measuring the rise of temperature of a cold nickel sphere immersed in the liquid slag. The sphere is spun about its vertical axis to obtain a well characterized flow of liquid about the sphere. The principal barrier to the transfer of heat from the bulk slag to the metal sphere is a solid shell of slag that forms around the sphere and subsequently melts. It appears that the detailed nature of this shell is important to theheat- transfer process. A mathematical model is used to predict the rate of heating of the sphere, and to evaluate various aspects of the system that can influence the transfer of heat.

Jan 1, 1976

By Farouk Tedjar

The growth of miniaturization in one hand and energy density need lead to rapid development of new chemistry for batteries as observed during last decade particularly in secondary systems. However dark side of the progress is always in environment impact and scarcity of resources. In the lithium segment a jump from six electrochemical series (all non rechargeable systems) before 1990 to more than 15 systems including new rechargeable systems has been observe during last decade. Lithium battery chemistry was enriched with new electrolytes, conductive salts and new oxide composition. In the same time, lithium ion battery safety was strongly improved during last period. The progress of these technologies was strongly boosted by the substantial growth of the mobile telephone market in the mid 1990's (+ 1% a month in 2000, and a 71% penetration rate in Europe in 2005 compared to just a few percent in 1996). This market is constantly in search of higher electrochemical performance (mainly energy density in front of increasing miniaturization. Recycling of end of life product could be managed not only in environment aspect, but also under resource conservation and economic aspect of arising technology (mainly on the effect of re-injection recovered materials) The Li-ion segment is a new branch in the cobalt market and impact of LiCoOx will be fitted with the actual increase of the demand for this battery. For this reason all the processes aim to valorize active and packaging material. RECUPYL process project was conducted in this direction to offer a new solution for recycling those lithium systems. The process has been developed at pilot industrial scales using synergy between new equipment (for mechanical pre-treatment step) and existing line at RECUPYL facility (for chemical treatment) and should lead to high valorization rate with a minimum hazardous co-products. The process was also developed in order to be able to recover news cathode materials introduced in electrode like LiFEPO4, LiMxCoyO2 and new anode composition in substitution with former carbon anode.

Jan 1, 2006

The merging of flash smelting with spray converting in one single furnace is proposed as a continuous copper making process. The proposed process is expected to produce blister copper, clean slag and gas with high sulfur dioxide concentration. Some high grade matte is an intermediate product recycled within the proposed furnace, spray-atomized and converted. The thermodynamic equilibria of the simultaneous oxidations which take place during copper smelting and converting are discussed in order to establish the gradient of oxygen potential along the furnace required for smooth operation. The proposed process is a dynamic system designed to reach equilibrium only close to the slag skimming end of the furnace. The process feasibility is based on the predesigned significant difference between the rates of converting reactions in a finely dispersed system and the rates of deconverting reactions between immiscible liquid phases of restricted interface area. The converting of small stationary droplets of matte, in a silica saturated system, was studied in the laboratory for extremely short oxidation times (10 to 120 seconds). These experiments led to some interesting observations on reaction mechanisms and kinetic trends. The droplet size and the matte grade affected very strongly the oxidation rate and the proportion of the different products obtained.

Jan 1, 1976

By K. H. Bech, S. T. Johansen

"The mass transfer at fluid-fluid interfaces due to turbulent agitation is investigated theoretically. In particular a theory is derived for interface stresses due to interface energy and surface renewal. This theory indicates that surface renewal may take place if the geometry is sufficiently large and if surface tension is sufficiently low.By using a model for a typical turbulent structure we compute the interface mass transfer for a stressless interface and a fully interface. Results for the general situation is not presently available. The computed results are used to derive analytical expressions for the mass transfer based on turbulent kinetic energy and free stream turbulent length scales.One important application of the theory is the mass transfer at the electrolyte side of the bath-metal interface in the Hall-Heroult process. For this process we show that mass transfer should be expected to be of the rigid surface type."

Jan 1, 1999

By U. Meyer, A. Alonso, P. Banios

The sampling of cathodes has changed with the introduction of the ISA-process in copper refineries. A Jernkontoret joint working group of refineries and rod plants from both primary and recycled copper plants has been investigating whether the actual sampling of cathodes is representative for this type of cathodes. As a first stage, samples were sent to the members of the working group with the objective to find an easy basis for a comparison of the results of the next stages. All samples show the same tendency for nearly all elements. In some cases, there may exist differences in calibration and for some elements the detection limits are too high, especially when Optical Spectrometry is used. In the second stage, discs were compared with melted samples to answer the question whether the punching of discs is sufficient for the quality control of the cathode. The analyses of the discs represent fairly well the cathode quality. There are differences between cathodes from different crops. Three punches are sufficient to determine the cathode quality. Finally, samples from various lots of cathodes were compared with samples from the rod produced from these cathodes. The impurity content of the rod corresponds to the impurity content of the cathode.

Jan 1, 2000

By Tim B. Vanderwood

The mineralogy of dusts from several locations in a lead smelting plant, remotely collected dusts and soils near the lead smelter, and dusts from a secondary copper smelter were examined by reflected light microscopy (RLM) to determine their m1neralogy, texture, and origins. Individual grams were further analyzed by microbeam techniques. Detailed petrographic analysis of the dust has been supplemented by automated scanning electron microscopy combined with energy dispersive x-ray spectroscopy (ASEM-EDS). This technique allows the rapid sizing and chemical analysis of thousands of individual particles in a dust sample, producing particle size distributions as well as statistically meaningful breakdown of a sample into chemical types (e.g., proportion of galena vs chalcopyrite).

Jan 1, 1992

By Donald I. Bleiwas

World primary nickel production in 1987 is projected to be 770,000 mt, slightly higher than that in 1986. Market economy country (MEC) production in 1987 is projected to be about 524,000 mt, an increase of almost 5 pct over 1986 production. Production cutbacks and closures at Japanese ferronickel plants in 1987 resulted primarily from the strong yen and higher energy prices. Cutbacks also caused reductions in ore production from Indonesia, New Caledonia, and the Philippines. Technical problems affected production, to varying degrees, in Botswana, Indonesia, and Yugoslavia. World primary nickel production for 1988 is projected to be 787,000 mt, of which 536,000 mt will be produced in MECs. Increased production is projected from Botswana, Canada, Cuba, and possibly Greece and Yugoslavia, while slight production decreases are projected for Indonesia, New Caledonia, the Philippines, and Zimbabwe. .. South African nickel production in 1988 could be severly curtailed by social strife. In the early 1990's Brazil and China could be major economic competitors to Western nickel producers.

Jan 1, 1988

By A. E. Clark

Rare earth compounds are widely known as possessing many extraordinary magnetic properties. In this paper, we focus on the huge magnetically induced displacements (magnetostrictions) which characterize the compounds of terbium with iron (Terfenol). Materials prepared commercially by both free-standing-zone (FSZ) and modified Bridgman (MB) techniques have now become available in large sizes and shapes. Prior to the development of the Terfenol alloys, it was possible to achieve giant magnetostrictions only at cryogenic temperatures. In the cubic Laves phase TbFe2 compound, saturation strains exceed 3000 x 10-6 at room temperature and above. Large magnetization 'jumps' can occur, causing huge spontaneous magnetostrictions with small triggering magnetic fields.

Jan 1, 1992

By R. W. Lawrence

A method by which it is possible at an oxidation potential below 680 mV SHE to achieve quantitative conversion of sulphide sulphur to elemental sulphur instead of sulphate in a biological leach of chalcopyrite and bornite has been investigated. The process chemistry, biological phenomena and process flowsheet options are discussed. Several copper concentrates have been evaluated and have been found to be amenable to th process. Results to study the progression of chalcopyrite decomposition during the leach are presented and mineralogical factors affecting the requirement for silver addition are discussed. A chloride addition method for improving silver recovery is described. The results of a small scale continuous leach test have demonstrated that continuous operation can be carried out with high copper extraction and stoichiometric conversion of sulphide sulphur to elemental sulphur.

Jan 1, 1985

By G. S. Hanumanth

Sedimentation of particles during the liquid metal processing of particulate metal-matrix composites can affect the homogeneity, and thereby the properties, of the cast product. A novel electrical probe has been developed to measure the in-situ volume fraction of ceramic particles in molten metal baths. Using this probe, sedimentation rates for 90 pm silicon carbide particles dispersed in molten aluminum A356 alloy were measured over a wide range of particle volume fraction, 0.05 to 0.3. The sedimentation rate was found to depend strongly on particle volume fraction; the time to clarify a 0.15 m depth increased from approximately 60 to 500 seconds as the volume fraction increased from 0.05 to 0.3. Measured sedimentation rates agree well with the predictions of a sedimentation model based on one-dimensional, two-phase flow theory in which the inter-phase drag function is derived from the momentum equation, utilizing the Richardson-Zaki Equation for sedimentation in aqueous systems. The implications for solidification are discussed.

Jan 1, 1993