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By Luben Savov

This paper presents recent research works on the removal of the tramp elements Cu, Sn, Zn and Pb from steel. The evaporation of Cu and Sn in iron-based melts treated at reduced pressure of the gas phase was studied in a vacuum induction melting furnace. The effect of chamber pressure, temperature and melt composition was investigated. Since the main source of contamination of steel with Sn and Zn is the recycling of tinplate and zinc coated steel, respectively, possibilities for the removal of meta1ic coatings in a scrap pre-treatment stage were studied, too. Tin was removed in the temperature range 400-5S0°C by treatment with reactive gases featuring high sulphur potential. Zinc can be removed by evaporation or by a combination of thermal and mechanical treatment. The paper discusses the thermodynamics of Pb in carbon-saturated iron melts, too.

Jan 1, 2001

By Dongxing Wang, Zhang Ting-an, Xiaolong Li, Yan Liu

Recent years, bottom blown oxygen copper smelting process has been widely used in China. Besides many advantages such as autothermal operation, this technology is still in developing stage. This topic aims at promoting the dispersion of materials charged into the bottom blown smelting furnace used in the process. Based on the similarity theory, a 1/5 scaled physical model of smelting furnace was constructed. Polypropene particles were used as charged materials. High-speed camera was used to record the phenomenon of the particles dispersion under different gas-flow rates, nozzle diameters and installation angles of nozzles. Image processing software was used for obtaining the particles concentration under different conditions. Results show that when the gas flow rate increases, charged materials disperse better. With the same gas flow, the increasing of nozzle diameter promotes the dispersion effect of materials. The effects of installation angles are opposite for nozzles with diameter of 2.50 and 5.92 mm.

Mar 1, 2017

By Stephan Mulch, Christian His, Patrick M. Stephan, Thibault Champion

"When fuel costs increase dramatically, waste to energy (WTE) conversion technologies become a good alternative to produce energy. The potential energy available in domestic wastes, in developed countries, could be upwards of 4% of their total energy needs. Due to low energy recovery and low level of treated domestic wastes in many countries, the energy coming from waste is generally less than 0.5% of the country needs.Domestic waste incineration can convert heat to electricity for industry and housing and allow waste volume reduction in countries where land fills are a scarce resource.There is a request to improve existing combustion technology by increasing energy recovery with better heat transfer in the boiler and also by increasing lining durability with more resistant materials and technologies.The knowledge of corrosion phenomena and material performance allows Saint-Gobain Group to develop and propose high performance refractory lining solutions.IntroductionThe interest in alternative energy has been growing dramatically in the two last decades due to several combined factors, such as global energy demand, fuels prices evolution (e.g. crude oil, Figure 1) or environmental and geopolitics factors"

Jan 1, 2008

By Kai Hu, Xuewei Lv, Run Zhang

An oxygen sensor of zirconia-based solid electrolytes for in situ measurements of oxygen potential in high titanium slag was developed in the present study. With the facility, series of measurements of electromotive force were successfully conducted for different titanium slags at 1998 K under an argon atmosphere. Oxygen potential in the slag was calculated by the measured EMF and simultaneous readings of temperature using the modified Nernst equation. In addition, the relationship between slag compositions and the oxygen potential in the slag was explored in detail. It has been found that the oxygen potential increases with increasing FeO content in the slag and decreases with the increasing Ti2O3 content in the slag. The oxygen potential in the slag has been calculated thermodynamically and compared with the experimental measurements. The results showed that oxygen potential in the slag may be controlled by FeO/Fe equilibrium reaction.

Mar 1, 2018

By Katie Schumacher, Greg Roset, Dayle Flynn

The Columbus Processing Complex of the Stillwater Mining Company began operations at Columbus, Montana in 1990 based on electric furnace smelting treating a precious metals concentrate from the nearby Stillwater mine and mill. Since that time, the smelter plant has been expanded in stages in order to treat recycled materials in addition to the concentrate. This paper describes a number of changes made at the plant to effectively handle recycled materials.

Jan 1, 2014

By Lin Zhu, Zheng Wei, Meng Li, Xueli Cao, Hanying Wen, Guodong Shi, Lei Yu, Wen-xin Tang, Tao Li

Low energy electron microscopy and photoemission electron microscopy (LEEM/PEEM), as powerful in-situ surface-sensitive electron microscopy, find wide applications in surface physics, chemistry and catalysis. The high reflectivity of incident low-energy electrons (0–100 eV), allows it to image the surface structures in the topmost few atomic layers within less than one second, while the sample can be heated up to 1200 °C in real time which is potentially very useful in metallurgy and materials fields. A unique three-prism aberration correction (ac-) LEEM was commissioned successfully in Chongqing University, with a lateral resolution below 2 nm. A multiple gas source in the ac-LEEM system was installed as well, which allowed us to observe chemical reactions of nanoscale mineral powders on metallic substrates. In this paper, the latest results on the applications of this three-prism ac-LEEM on oxidation and reduction processes on copper and iron polycrystalline surfaces are demonstrated.

Mar 1, 2018

By Yuanbo Zhang, Xiaoming Mao, Zhixiong You, Zhenyu Fan, Tao Jiang

"It is generally known that the formation of calcium ferrite is favorable during the iron ore sintering, which dominatingly contributes to the improvement of strength and reducibility of the finished sinters. In this study, effects of roasting temperature and 02 content of inlet gas on the sintering mineralization properties of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. The results showed the amount of calcium ferrite initially increased then decreased with the increase of the roasting temperature. The temperature of maximum calcium ferrite generation amount for different iron ores was determined as follows: hematite and limonite was 1275 °C, whereas specularite and magnetite was 1250 °C. Increasing 02 content of inlet gas was advantageous to the generation of calcium ferrite during the sintering. The sequence of 02 content affecting the mineralization properties of different iron ores was determined as follows: magnetite > hematite > specularite > limonite.IntroductionThe mineralization property of iron ore plays a significant role in the mineral composition and microstructure of finished sinters, which determine the quality and output of the sinters [1-2]. The mineralization process of sinters is composed of solid-phase reaction, formation of liquid-phase and crystallization. The formation and crystallization of liquid-phase is the foundation to the mineralization as the quality of the sinter is poor when concreted by solid-phase consolidation [3-4]. With respect to the iron ore sintering, liquid-phase regarded as bonding phase is generated between the iron ores and fluxes at high temperature [5]. Calcium ferrite is the most favorable liquid-phase among the bonding phases which dominatingly contributes to the improvement of strength and reducibility of the finished sinters [6-8]. Especially for high iron-low silicon sintering and high basicity sintering, making sure sufficient calcium ferrite quantity and reasonable distribution is crucial to the sinters [9-10]. Therefore, carrying out the researches on the high temperature reaction properties of iron ores is of great significance [11]."

Jan 1, 2013

By Xueqin Li, Xuewei Lv, Wenchao He, Jie Qiu, Jie Dang

Iron powders are mainly produced by Hoganas process and water atomization process, while both of which have the disadvantages of energy consumption. To obtain iron powders with higher particle sphericity, more uniform particle size distribution and higher proportion of total iron (TFe), a novel method considering of energy conservation was developed in this paper. The hot metal was transformed into granules with air cooling in a rotary disc atomizer, iron powder particles and hot off-gas were collected respectively. It was found that the property of the obtained iron powders was mainly controlled by the flow rate of the hot metal, the diameter of the rotary disc and the rotary speed and the heat of off-gas has a high level of value as well.

Mar 1, 2017

By Mingming Zhang, Udaya Bhaskar Kodukula, Marcelo Andrade

The physical and chemical properties of sinter feed are important factors that determine the productivity and quality of sinter product. In this study the feasibility of treating sinter feed by high pressure grinding rolls (HPGR) is investigated for selective cracks generation exploiting weak zones along grain boundaries of poor quality iron ores without generating much fines. The pre-treated sinter feed was characterized for size distribution, surface area, contact angle, and SEM analyses. The characterization results indicated that surface area of the pre-treated sinter feed sample increased about 20%. Pot-grate sintering tests results also indicated improvement on cold permeability, sintering yield and productivity, sinter Tumbler index, and low temperature degradation index (LTD) after HPGR pre-treatment.

Mar 1, 2018

By Fuqiang Zheng, Feng Chen, Wenting Duan, Yufeng Guo, Tao Jiang

High-quality titanium-rich material is of significance in the development of titanium industry as it is the main raw material to produce sponge titanium and titanium white using chloride process. Activation roasting of titanium slag with high Ca and Mg contents as adding H3PO4 followed by acid leaching was investigated to prepare titanium-rich material. The effects of H3PO4 dosage, roasting temperature and time, hydrochloric acid quantity, acid leaching temperature and time on TiO2 grade and removal of impurities were studied. The results show that after the finely ground titanium slag roasted with 8% H3PO4 at 1000 for 2h, most Mg impurities in anosovite solid solution structure were converted into simple acid–soluble compounds. The impurities such as Ca and Mg obviously decreased when the hydrochloric acid concentration was 20%, leaching at 100 °C for 2h, from which a titanium-rich material containing 82.56% TiO2 and 1.15% (CaO+MgO) was obtained.

Jan 1, 2016

By K. A. Elbarawy

Processing of Egyptian barite ore with a composition of 85.5% BaSO4; 2.75%SiO2;1.56%Fe2O3 and 5.1% Al2O3 was performed with the aim to prepare pure barium salts. The process took place through pelletization-solid state reduction and leaching steps. Each of these steps was optimized. Pure barium sulphate (99% < 0.82µm) and carbonate (99%<0.75µm )were the final products. This article deals with the reduction process that occur whn coal was added to the ore during pelletization in the ratio of 5:1 stoichiometry. Optimum reduction of pellets of 8-12mm in diameter was achieved after 60 minutes at 1050oC and under a rate of 5 lmin-1 of nitrogen atmosphere, where 87.79% of the ore was reduced. The kinetic studies showed that the reduction process could be modeled according to the core mechanism of diffusion control in which the effective diffusivity is based on the surface area of unreacted ore. The activation energy calculated was 92.7 kJmol-1.

Jan 1, 2006

By Katsunori Yamaguchi

The zinc, lead and alumina contents in copper smelting slag are increasing with the increase in waste recycling. The recovery of base metals such as lead and zinc from copper converter slag is important from both an economical and environmental perspective. As a fundamental study of the metal recovery by reduction process, activity coefficients of ZnO and PbO in the CaO-SiO2-FeOx-5mass%AlO1.5 slag under iron saturation at 1573K are derived from the data of slag-metal equilibrium experiments. On the basis of the obtained data, the activity coefficients of ZnO and PbO in the CaO-SiO2-FeOx-5mass%AlO1.5 slag were compared with those of the CaO-SiO2-FeOx ternary system. Addition of alumina increases activities coefficient of ZnO and PbO in SiO2 rich side of the slag, and decreases them in CaO rich side.

Jan 1, 2006

By Vineet Kumar Yadav, Akshay Dvivedi, Pradeep Kumar

Near-dry electric discharge machining (EDM) is a process variant of EDM, which uses two-phase flow of liquid and gas as dielectric medium. This article reports the results of an investigation pertaining to the drilling of holes on high speed steel (T2 grade) by a rotary tool near-dry EDM. The One-Factor-At-a-Time (OFAT) approach was used for experimentation. The effects of process parameters, viz. tool rotation speed, peak current, pulse duration, gas pressure and liquid flow rate on material removal rate (MRR) and overcut were investigated. The dielectric medium used was a mixture of glycerin-air. The experimental results reveal that rotation of the tool electrode along with high pressure of two-phase dielectric medium contribute in an effective flushing of inter electrode gap (IEG). Further, in rotary tool near-dry EDM process, higher values of current can be used. This improves process economics in terms of MRR. The MRR measured with rotary tool near-dry EDM was three to four times higher in comparison with conventional EDM. Additionally, appreciable surface quality was achieved.

Mar 1, 2017

By Bowen Li, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"Magnetic iron sulfide ore particles heat rapidly by microwave (MW) irradiation generating plasma during oxidation of surfaces. The high temperatures produced by the exothermic event decompose local portions of samples forming a differentiated flux of partially melted silicate (si-mt) with entrained metal-sulfide (sul-mt) droplets. The si-mt forms crystals of olivine (01) in Ca-rich pyroxene (Cpx) melt that resorbs a portion of iron sulfide (Po). The immiscible sul-mt droplets of (Fe,Ni,Cu)1-xS contain magnetic subsolidus Ni-pyrrhotite (Ni-Po) with Cr-bearing ferrospinel (Mag). Sub-micron sized flecks of Au are found on the surface of a sul-mt droplet with scanning electron microscope (SEM).IntroductionSulfide ore deposits supply the world's mineral resource in the production of non-ferrous metals. Particularly, Cu-Ni deposits are chemically enriched in metals from high sulfur saturation during magmatic formation that creates the proper geochemical environment for metals enrichment [1, 2]. The sulfur and oxygen fugacity control redox conditions of a differentiated silicate/sulfur magmatic melt with the concentration of iron playing a dominate role in the chemical partitioning of metals in sulfide liquid [3, 4]. The initial magnetic crystallization of (Fe,Ni)i-xS monosulfide solution (mss) from metal-sulfide liquid has an exclusive effect on the fractionation of mineral assemblages (zoning) [5].Phase equilibria of sulfide melt (sul-mt) components are related by a miscibility gap with mss forming Ni-rich pyrrhotite (Ni-Po) followed by the crystallization of (Fe,Cu)1-xS intermediate sulfide solution (iss) [6]. Precious metals form stable chacogenides and are retained in solution until the final liquid solidifies. The redistribution of metals now occurs by subsolidus cooling of mss and iss that exsolve low-temperature Fe-Cu-Ni bearing mineral assemblages [7]. The proper interpretation of ore genesis increases processing capabilities by isolating chemically enriched zones during extraction and should be used to aid in sustainable mine site development [8-11]."

Jan 1, 2013

By K. Prashant Sarswat

Isotopes are critical to a variety of applications including physical science analyses, biology, medicine, pharmaceuticals, and national security. In most cases isotopes must be relatively pure or highly enriched before they become useful. Current isotope separation technologies are relatively inefficient, capital and labor intensive, and often produced by a limited number of suppliers. In the category of isotopes, lithium is among other important candidates. Lithium is found naturally in two isotopes, 6Li which accounts for 7.5% of all lithium, and 7Li which makes up the balance of 92.5%. Each of these isotopes is important to the nuclear industry. 7Li is often used in the form of lithium hydroxide which is used to control pH in pressurized water reactors. The current supply of 7Li is based mostly outside of the United States, and its long-term supply is uncertain. Apart from supply issues, the use of mercury for 7Li separation is also a concern in commercial processing using the most common and efficient approach [1–3]. Hence, a reliable, environmentally friendly, and efficient technique is needed to produce 7Li. In this line of investigations, the authors used a two-compartment system and significant separation was achieved. In this piece of research, some preliminary results are presented including cell design and actual isotope ratio after enrichment. Applying an electro-potential across two electrodes can be used to drive electromigration of Li isotopes. The electromigration is in addition to normal diffusion. Note that 6Li diffuses faster and hence there will be a lowering of the 6Li concentration near the positively charged electrode and an enhancement in 6Li near the negative electrode during the separation process. Similarly, 7Li will be more prevalent near the positive electrode and less prevalent near the negative electrode during the initial separation stage [1].

By C. J. Lewis

This presentation concerns calcium oxide-better known as high calcium quick lime High calcium quicklime is produced by calcining high calcium limestone, mostly in the many rotary kilns located throughout the United States and Canada. This paper presents suggestions on the handling of lime based on field experience. The subjects covered are chemical analyses, transporta¬tion, lime storage, lime slaking to form a water slurry of calcium hydroxide solids, slurry transportation, slurry viscosity, and scaling of lime slurries. It is hoped that the comments on the foregoing areas will be of use to those designing or operating lime systems.

Jan 1, 1992

By Xueqin Li, Xuewei Lv, Yu Zhang, Wenchao He

In order to make full use of the chromium-bearing vanadium titanium magnetite with chromium, a new process of “direct reduction-electric furnace smelting separation” has been developed for recovering the iron, vanadium, titanium and chromium in recent years. In this paper, FactSage, one of the most frequently-used thermodynamic calculation software, was used to calculate the reduction degree of Fe, V and Cr with different n C/nO (mole ratio of carbon and oxygen). It was found that the suitable operating conditions of direct reduction process were n C/nO > 1.07 and T > 1473 K. In addition, the direct reduction experiment of Hongge vanadium titanium magnetite was carried out and the obtained samples after direct reduction were analyzed by XRD and chemical composition. The result shows that the metallization rate of carbon-containing pellet is nearly 90%.

Mar 1, 2018

By Markus A. Reuter, Antoinette van Schaik

"Product design engineers select from a wide range of materials and combine them into multimaterial product designs. These include various materials (metals and non-metals) which are complexly integrated (e.g. welded, glued, alloyed, layered). The recycling/recovery rate of consumer products are determined by the different materials and alloys used, but also by the particle size and multi-material particle composition after shredding (combination of materials due to design). Eco-design (for recycling) and Design for Recycling (DfR) can only be conducted if the interconnectivity of material/metal in various unliberated materials is accounted for and its effect on material and energy recovery can be linked back to design. This paper will discuss the basic principles of these DfR models and it is shown how these tools (i) are linked Computer Aided Design (CAD) and Life Cycle Assessment (LCA) software, (ii) affect conceptual design specifications of products, (iii) integrate the complex detail of the recycling system and recyclate quality and hence (iv) make recycling an integrated part of the product system. Furthermore, it is shown how these assessment tools and models can be applied for benchmarking of the recyclability and environmental damage created by the recycling of end-oflife consumer goods in order to e.g. (i) provide the (original) equipment manufacturer with knowledge and solutions to support product stewardship and Extended Producer Responsibility; (ii) create awareness of the consequences/benefits of design, products and recycling systems to manufacturer, designer, legislator, recycler etc.; and (iii) assist the consumer in their choice of consumer goods from an end-of-life point of view.IntroductionA first-principles basis is required in order to be able to simulate and predict the recycling/recovery behaviour of products facilitating Design for Recycling (DfR) and Eco- Design. This links recycling technology and the environmental consequences of recycling directly to product design."

Jan 1, 2008

By Rak-lun Choi

Plasma-induced damage of InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) has been studied in terms of forward turn-on and reverse breakdown voltages, together with etch rate and surface morphology. The physical degradation of sidewall along with rough surface morphology of n-GaN caused by increased ion scattering induced the deterioration of the forward and reverse voltages. It was found that the turn-on voltage is sensitive to the surface roughness of the etched n-GaN and the breakdown voltage is strongly affected by the sidewall contamination. Annealing under nitrogen after the mesa etching improved the electrical properties of the InGaN/GaN MQW LEDs. Efficient blue light-emitting diodes (LEDs) were fabricated using InGaN/GaN triangular MQWs. The LEDs with triangular QWs showed a lower operation voltage and 2.4 times higher light output power than those with the rectangular MQW LEDs at 20 mA and 20 °C. The intensity of electroluminescence (EL) at 20 mA was almost independent of ambient temperature in the triangular QW LED, but decreased substantially in the rectangular one.

Jan 1, 2003

By P. R. Seidl, R. C. C. Ribeiro, J. C. G. Correia

"More than 95% of asphalt pavement materials consist of aggregates. The highway and construction industries consume a huge amount of aggregates annually causing considerable energy and environmental losses. The aggregates are usually produced from neighborhood aggregate quarries or form natural aggregate sources. The use of marble and granite wastes from quarries as aggregates might help meet the increasing demands and slow down any detrimental effects on the environment. Chemical and physical results showed that the use of marble and granite wastes from quarries in the asphalt production is quite fusible. Consequently, granite sawmills would perform a clean technology. This technology would also have an economical impact by not spending on basalt extraction.IntroductionThe granite fines generated from sawmills of ornamental rocks comes as a great problem and it lacks undeletable solutions. This problem involves the preservation of the environmental and constitutes one of the subjects more critical the point of view of social beneficiation of the population. The Cachoeiro de Itapemirim County, Espírito Santo State, Brazil is an example, of this problem. In this area, the granite and marble fines generation is around 15.000 ton/year.The problems generated by these residues affect with more emphasis the animals, such as the cattle, which inhaled the water content fines of granite and this residue accumulate in their lungs. Other great problem observed is the sanded of the river and the reduction of aquatic life.This problem is beginning to be set out due to performance of Center of Mineral Technology (CETEM), and of several other organisms of Rio de Janeiro State, aiding the sawmills owner’s. This help consists of teaching the best procedure of discard the residues and studies for its use, for instance the production of mortars, tiles, bricks and road pavements [1]."

Jan 1, 2008