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By Guojun Ma

The entrainment of charge materials, evaporation or volatilization of elements and ejection of slag and metal by spitting or the bursting of gas bubbles are mechanisms whereby stainless steel plant dust are generated from the electric arc furnace and refining converter. TCLP and ASTM D 3987-85 tests on dust that was collected from the baghouse filter system of a South African Stainless Steel plant showed that this dust can be considered hazardous according to South African legislation, due to the high degree of Cr (VI) leachability (~13mg/l for TCLP and ~8mg/l for ASTM vs. regulation threshold of 0.05mg/l in drinking water). The dust is therefore considered to be harmful to both the environment and human health, due to its high solubility in water and carcinogenic properties. It should therefore be treated before being stockpiled or land filled. This paper consequently describes an investigation into the formation of Cr(VI)-containing stainless steel plant dust and the stabilisation thereof in a sintering process, whereby the dust was mixed with a silica-rich clay. It is postulated that Cr(VI) form when the (Mg,Fe,Mn,Cr)3O4spinel phase, CaO, Ca(OH)2 and CaF2 (all of which are present in the dust) react. This reaction was found to take place both at ambient and at high temperatures (1100°C). Stabilization of Cr(VI) in the dust could be achieved at an optimum sintering temperature of 1100°C for a 50mass% dust : 50mass% clay mixture. Chromium emission during the sintering process was found to be low, and within environmental limits.

Jan 1, 2006

By Marcela Morvová, Mário Janda, Morva Imrich

"The possibilities of greenhouse gas mitigation using various methods are brought out. The special case of utilization of mixture of CO2 with other greenhouse gases in a synergetic way inside non-thermal plasma based system is described in detail.Measurements on pilot system comprising pyrolysis chamber as alternative energy system (production of hydrogen and liquid tar) were made for various biomass and waste as the input material. The exhaust from this system was treated with non-thermal plasma gap suitable for up to 650Nm3/hour of exhaust gas flow. Condensable portion of exhaust is liquefied in distillation unit; produced hydrogen is stored on-line inside nano sized carbon of our own production.The CO2 removal efficiency varies depending on exhaust composition between 45 to 98%. Other oxides as CO, NOx, SOx and several hydrocarbons and VOC are also removed. The main product connected with CO2 removal is a solid powder of proteinoid nature. There exist strong probability, that precursor of the origin of life on the Earth from primary atmosphere were formed in the similar way as it is present in the electric discharge system used. Our system is equipped with on-line as well as ex-post analysis of all forms of products. We have also developed a system for recuperation of all forms of produced heat. It is stored inside as latent heat of waxes.IntroductionNatural greenhouse effect on the Earth is caused mainly by water vapour with the average absolute concentration about 4%. Other gases able to absorb long-wave radiation and thus this causing greenhouse effect are CO2, CH4, N2O, halocarbons and as precursors ozone and NOX. Some of them we produce and introduce into atmosphere in large quantities during production of energy and in transport. This factor leads to permanent increase of average temperature of air, sea and oceans, so called global warming.Nowadays large amount of data exists showing that the temperature of Earth in the last 150 years has been continually increasing. It represents about 03°C per ten years and the most of climatologist believe, that the increased concentration of greenhouse gases in the atmosphere is responsible for this effect.The most important greenhouse gas is carbon dioxide CO2. Majority of CO2 emissions comes from electric power stations working with fossil fuels, cars and industry. Burning of fossil fuels contribute up to 80% to world wide anthropogenetic emissions of CO2."

Jan 1, 2010

By Huanmei Yuan, Yuanyuan Wang, Hao Bai

Composite phase change materials are widely used in energy-saving and energy efficient process. Nano-encapsulated phase change materials are especially significant for making advanced working fluid applicable to waste heat recovery or storage. In this study, silica-coated stearic acid (SA) Nano composite phase change materials were prepared from tetraethyl orthosilicate (TEOS) and stearic acid (SA) via sol-gel process. The materials were investigated by Field emission scanning electron microscopy (FE-SEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy(FT-IR) and Differential scanning calorimeter (DSC).The FE-SEM and TEM results show that monodisperse microspheres with stable core– shell structure were formed and SA was encapsulated in the silicon dioxide shell. The FT-IR results show that there were no chemical reaction between silicon dioxide and SA, which is the chemical property of the composite material, is stable. The DSC results show that the composite phase change material has favorable heat capacity.

Jan 1, 2016

By Bo Zhou

During secondary aluminum recovery, complex aluminum scraps are melted and refined often in a rotary melting furnace and the aluminum metal has to pass through a molten salt layer and melt down in a bottom aluminum bath. Previous experimental study and industrial observations have indicated that salt shell formation and re-melting on the metal solids in the early stage plays a critical role in the overall melting process of the scrap. In the present paper, mathematical models are developed to simulate the process of salt shell formation and its re-melting, as well as aluminum melting in the molten melt. Influence of the salt layer properties, the residence time of the metal particles in the salt layer, the particle size, the temperature of bulk melt were investigated. Reasonable agreement with the measurement data was reached. The developed melting model will be used to construct a population balance model of the scrap melting behavior for a rotary melting furnace, taking into account the distributed characteristics of the scrap. Finally, an overall process model based on Computational Fluid Dynamics (CFD) for the rotary furnace will be constructed, coupling with the population balance model for the scrap melting.

Jan 1, 2003

By S. Yokoya

With increasing requirement of steel productivity and quality in continuous casting in the conventional casting system using an immersion nozzle, it is very difficult to establish a reasonable molten flow pattern. In order to overcome this difficulty, we propose a new method of imparting swirling motion onto the flow in the immersion nozzle and to control the flow pattern in the mold. Following results have been obtained during the studies. For the case of slab continuous casting mold: High amplitudes of oscillation with a period of 10 to 15 seconds are observed in the outlet flow of the immersion nozzle and meniscus flow in the conventional casting system, while these phenomena are remarkably suppressed using swirling motion in the immersion nozzle, which leads to very calm and uniform flow pattern at the outlets of the immersion nozzle, in the mold and on the meniscus in the mold; For the case of billet continuous casting mold: (1) heat and mass transfer near the meniscus can be remarkably activated compared with a conventional straight type immersion nozzle without swirl, and (2) Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable compared to that of straight nozzle. The findings, mentioned above, are very useful to control the flow pattern in the slab, and billet continuous casters. Such effectiveness of swirling flow in the SEN on the mold flow has been put into practical use. As a result, remarkable progress on the quality and production of continuous casting products has been observed in practical application.

Jan 1, 2006

By Philip Nash, Jie Zhou, Joshua Blackketter

"Large ingots tend to have internal defects such as shrinkage cavities and porosities, which have to be closed during the cogging stage to ensure sound internal quality of forged parts. In this work, finite element methods were used to simulate open die forging passes, with varying parameters that affect the void closure behavior profoundly. Numerical models ware constructed in ABAQUS, DEFORM and FORGE using data taken from footage of the forging process and material mechanical data obtained from the Gleeble compression tests. Forging variables such as pass rotation, reduction per pass, and feed ratio were studied with intense attention paid on the special properties of H13 steel, so that this study can be applied to solve real world problem.IntroductionCenterline defect closure is a frequently studied but still challenging topic in open die forging industry. In practice, open die forging is employed as an effective hot forming process to make desired shape of metal products as well as to ensure center consolidation of internal defects which result from the casting process. Nowadays, remarkable large forgings have been more and more required to meet industries demand. However, the increase in ingot size has tended to result in considerable macrosegregations and shrinkage cavities or voids, which need to be worked thoroughly during the forging process; but the size of the products and limitations of manufacturing capacity, such as the press load, make it difficult to achieve adequate local deformation to close those defects. Therefore, choosing optimal forging parameters under given work condition to ensure good internal quality of forged products is critically important."

Jan 1, 2012

By M. Misra

The prediction and assessment of the reactivity of acid mine tailings has been a subject of numerous studies. The conventional approaches such as sulfur content, pH, net acid generating capacity and conductivity are used for assessing reactivity of the tailings. In this paper a new non-invasive Impedance Spectroscopy (IS) technique is used for the determination of reactivity and acid mine potential of tailings. This technique is also used to establish the long term stability and leaching propensity of the tailings agglomerated with alkaline binders.

Jan 1, 1994

By Daoxin Wu, Zhong Cao, Yan Shi, Yu Ding, Huanli Yang, Zhongliang Xiao

"2-substituted benzimidazole-zinc and 2-substituted benzimidazole-copper complexes were main components of organic solderability preservative (OSP) in PCB producing process and affect the thermal stability of OSP film. So these four complexes were prepared by 2-substitutedbenzimidazole reacting with zinc ion and copper ion, the complexes crystals were determined by IR, its thermal stabilities were studied by TG method. The results indicated that the thermal stability of 2-substituted benzimidazole-zinc is higher than the 2-substituted benzimidazole copper,and the thermal decomposition mechanism was presentedIntroductionImidazole compounds which is an important heterocyclic compound shows the important value and outstanding prospects[I-3l in field of biological engineering, medicine, and high-performance composites. It's said that imidazole compounds is an excellent new metal surface treatment[4] agent, because it has good reaction activity with metals and can form a chemical layer on the metal surface. The complexes of imidazole were main components of organic solderability preservative (OSP) in PCB producing process and affect the thermal stability of OSP film. The mechanism of imodazole combined with metal and film deposited has been reported, but the opinions about thermal stability of film have bifurcation, let alone the thermal decomposition mechanism of film at high temperature. The complexes were prepared by combining of 2- substituted-benzimidazole with zinc and copper iron, which were studied by IR and TG method, in order to get thermal stability of different complexes."

Jan 1, 2011

"Recycling of solid wastes plays an important role in environmental protection. However, solid wastes are often contaminated with some undesired components so that many of these solid wastes are hardly economically recycled. Therefore, effective and efficient separation of undesired components from solid wastes becomes a crucial step for sustainable recycling of the solid wastes. There exist three general strategies of separation of undesired components from solid wastes: before-process separation, post-process separation and in-process separation. In this paper, different separation strategies are discussed in terms of energy requirement and availability, implementation complexity and additional need for environmental protection. It is concluded that of all separation strategies, in-process separation has the least energy requirement, the least implementation complexity and the minimum need for additional environmental protection.IntroductionIn industries, solid wastes almost come with every production process. Multi-million tons, if not billion tons, of solid wastes are being generated globally each year. These solid wastes are lowvalue materials in general, and often have very limited markets. As a matter of fact, many of these solid wastes have been stored on site or have been disposed of at landfills for many years, not only occupying lands, but also polluting environment. Therefore, effective and efficient recycling of solid wastes has been a very challengeable task and has played a very important role in environmental protection.One of the major barriers which hinder recycling of solid wastes is contamination of the solid wastes with some undesired components. These undesired components are components which are not wanted by production processes or applications where the solid wastes are consumed or recycled, since the undesired components often degrade qualities of the solid wastes, imposing negative effects on operations, facilities and product qualities of the production processes or applications. Sometimes, the undesired components may also pose severe environmental concerns. When undesired components are present in solid wastes at over-limit levels, the solid wastes tum to become destructive, useless and non-recyclable. Consequently, effective and efficient separation of undesired components from solid wastes becomes a crucial step for sustainable recycling of the solid wastes."

Jan 1, 2014

By Angus Hellawell

The application of the common tangent principle to free energy - composition surfaces is considered. It is shown that the construction requires that single phase surfaces on either side of a two phase volume must always exhibit the same sign of curvature - contrary to that shown in many published phase diagrams. In general, these curvatures will be such that the surfaces are mutually concave towards the more stable phase. A number of examples are discussed.

Jan 1, 1991

By Klaus-Markus Peters, James G. Hemrick, John Damiano

"Work was performed by Oak Ridge National Laboratory (ORNL), in collaboration with industrial refractory manufacturers, refractory users, and academic institutions, to employ novel refractory systems and techniques to reduce energy consumption of molten material processing vessels found in industries such as aluminum, glass and pulp and paper. The energy savings strategies discussed are achieved through reduction of chemical reactions, elimination of mechanical degradation caused by the service environment, reduction of temperature limitations of materials, and elimination of costly installation and repair needs. Key results of several case studies resulting from US Department of Energy (DOE) funded research programs are discussed with emphasis on applicability of these results to high temperature processing industries.IntroductionRefractory materials are limited in their application by many factors including chemical reactions between the service environment and the refractory material, mechanical degradation of the refractory material by the service environment, temperature limitations on the use of a particular refractory material, and the inability to install or repair the refractory material in a cost effective manner or while the vessel is in service. All of these limitations reduce the energy efficiency of the process as degraded refractory materials lead to loss of process heat (reduced insulation by refractories) and the need for maintenance through repair or replacement of refractory linings.This situation is conceptualized in Figure 1 which shows that when the thickness of the refractory wall is reduced by chemical or mechanical degradation, the heat losses through the wall increase exponentially. The subsequent maintenance to repair such conditions often requires cooling of the furnace or refractory lined vessel which entails loss of energy due to cooling and consumption of energy due to reheating. Additionally, production time and capability are sacrificed.Additionally, in most applications where refractories are used (metal melting furnaces, glass furnaces, steel making furnaces, gasifiers, etc.) wear of the refractory lining is not uniform. Very often, specific areas will wear (become thinner) more rapidly due to exposure to more corrosive or erosive conditions. This concept is illustrated in Figure 2, through the example of excessive metal line corrosion."

Jan 1, 2009

By H. K. Lin

Thermodynamics of Cu-C1-H2O system and the kinetics of copper dissolution in cupric chloride solution were studied with emphasis on possible difficulties which may occur during copper electrowinning. E,-pC1 diagram of this system wasestablished. Equilibriumdistributionof various copper chloride complexes of different valent states at the presence of metallic copper was computed through the relations of the simultaneous equilibria. The mechanism-of copper dissolution in the cupric chloride solutions was proposed and the mechanism of copper electroposition was discussed. The researched results were used for guiding the investigation of copper electrowinning from cupric chloride solution.

Jan 1, 1991

By William Gregg

Recent environmental and workplace safety legislation has Imposed more stringent limits on the amount and type of particulate emitted Into the air. In the past, the mass of particles contained In a volume of air was the governing criteria. Now the size and precise chemical nature of the particulate must be known and controlled In addition to it's ?mass. Processors of metallic materials have to implement stricter control practices and more efficient control equipment to meet the new regulations. Pulse-Jet dust collector systems are being used to control particulate emissions from various process gas streams. Pulse-jets :are also being used for maintaining a healthy environment In the workplace. this paper will discuss the impact of these regulations, the control techniques used to comply with such regulations, and the equipment needed for compliance.

Jan 1, 1992

By A. MacRae

Campaign life of the converting furnace has been limited by break-outs through the hearth and walls. Throughput of concentrate has increased by 60% since start-up of the copper operations in 1981. The Furnace Integrity program was initiated at Kidd in 1993 to improve the reliability and safety of the smelting-cleaning-converting furnace line. The converting furnace is undergoing a series of upgrades to overcome severe refractory wear to the roof, walls and hearth. A recent shut-down was held in March 1997 to implement improvements to the roof, walls and slag outlet. Wall modifications included a new upper shell, wall coolers which can be supported during a shut-down from outside of the vessel, and an increase in the number of cooling blocks. Improvements to the roof included increased cooling, a novel brick/cooler suspension system, and roof compression for gas tightness. Design is currently underway to deepen the refractory hearth, to decrease hearth erosion and increase resistance to flotation.

Jan 1, 1998

Laboratory trials were performed in an induction furnace to study droplet formation during lance blowing. Compressed air was blown on a molten iron bath consisting of iron alloyed with carbon and silicon. Steel droplets were collected using a specially designed sampler. The average steel droplet composition and the oxide layer thickness were determined using scanning electron microscopy combined with energy dispersed spectroscopy. In addition, the concentration gradient of elements was determined using a microprobe. It should be noted that a special technique had to be developed in order to prepare the droplet sample. The size distribution and composition of the droplets was also determined using the microprobe. It was found that the carbon content in the droplets was lower than the carbon content in the bulk.

Jan 1, 2006

By Qin Hua, Xiangru Chen, Qijie Zhai, Yongsheng Yan, Liang Chang

"In this paper, pure bainite ductile iron and their alloying form of 0.2wt% niobium were prepared by a controlled cooling heat-treatment. The effect of niobium alloying on the microstructure, hardness and impact toughness of bainite ductile iron was studied. The results show that adding niobium effectively improves the hardness and toughness of bainite ductile iron. The hardness and the impact toughness of niobium-alloyed bainite ductile iron were investigated by varying the temperature at which samples were fed to the incubator.IntroductionThere are two essential methods to prepare the bainite ductile iron: isothermal quenching [I-31, and alloying [4• 51• Isothermal quenching process is very time and energy consumable, concerned as a high cost technique for mass production. Besides, there are certain limitations on the size and shape of castings in this process. In addition, it potentially harms the environment. As for the alloying, Ni, Mo, and Cu have to be utilized to obtain bainite. However, the large demand and high cost of Ni makes it not feasible in practice.It is well known that niobium can promote the formation of carbon compound, and improves the stability ofundercooled austenite, which is preferred to the increase of the hardenability. Previous studies showed that niobium could refine the grain and improve the mechanical properties of gray cast iron [6-81 • Therefore, in the present work, the effects of niobium and the temperature at which samples were fed to the incubator on the microstructures and properties of niobium alloyed bainite ductile iron were investigated."

Jan 1, 2014

By Finn Olesen, Melina Garcia, Mark William Kennedy

"Furnace resistance is a function of the complex interrelationship between many factors including: operating practice, slag conductivity, temperature, power intensity, and geometry (electrode shape, diameter, spacing, immersion, slag depth, etc.).Accurate prediction of resistance is critical for success of the overall furnace design. The sizing of electrodes, columns, bus-bars, and transformers are all impacted. Estimation of minimum and maximum resistance or maximum operational current, as well as the maximum operating voltage are of fundamental importance.Various mathematical tools have been developed to assist designers with the selection of furnace dimensions and the prediction of resistance. Elkem found the methods of Downing and Urban 1965 and Westly 1975, to be particularly useful.In the current paper, comparisons are drawn between data from spent aluminum pot lining (SPL) demonstration testing at Elkem Bjolvefossen and predictions based on these classical tools and 3D finite element modeling (FEM) with COMSOL.®"

Jan 1, 2012

By Alexandre Bonan

This paper reports the results of a kinetic study on the oxidation of free cyanide and Cu-cyanide complex ions with HO,. The variables and respective ranges studied were the following: [CN] total =10 - 500 mg/l; pH=10-11; (H2O2/CN) mole ratio = 1- 3; (Cu/CN) mole ratio = 0.10 - 0.25. The results were interpreted by a semi-empirical model that incorporates the useful oxidation reactions and the parallel alkaline decomposition of H2O2

Jan 1, 1994

By Edgar Blanco

At the Deer Trail Mine, interest in recovering noble metals from oxide ore and tailings oxide ore with 6.0/1.0 g/t Au and 200/140 g/t Ag respectively has led to metallurgic studies focused on finding an adequate treatment for these materials. Using cyanide leaching, the silver/gold recoveries from oxide ore and oxide tailings were 39%/95% and 36%/96%, respectively. Since these recoveries were less than spectacular for silver, it was decided to explore a non-cyanide leaching process that would extract silver and gold better. Based on previous research the possibility of using aqua regia in combination with sulfuric acid was evaluated. On a laboratory scale, variables such as mineralogical composition, concentration of reagents, dissolved oxygen, reaction time, pH and temperature were evaluated. Under optimal conditions it was possible to achieve >65% silver recovery and >85% gold recovery for both oxide ore and tailings.

Jan 1, 2009

By Minge Zhao, Yuandong Pei, Zhixing Zhao, Zejun Ma, Lili Ban

"Confocal scanning laser microscope (CSLM) has been applied to carry out the in-situ observation of melting and solidifying characteristics during iron ore sintering process, accompanied with TG-DSC test. It can be found that apparent Liquid phase forming temperature(LFT) and ending solidifying temperature(EST) is about 1190? and 1160?, respectively. Forming liquid phase during sintering process goes through four courses, these are shrinking, expanding, shrinking and expanding coexisting and expanding totally. For Yandi fine, the corresponding temperature of these four courses is about 1120-1160?, 1190-1196?, 1218-1220? and 1233-1270?, respectively. Although CAJ fine has more difficulty in forming initial liquid phase, but when liquid phase expands, it may have better fluidity and easier for liquid phase formation. Adding enough CaO, CAJ fine takes on high fluidity like Yandi fine, because liquid phase during sintering process is formed mainly by reaction between CaO and Fe2O3.IntroductionConfocal scanning laser microscope (CSLM for short) has been applied to carry out the in-situ observation of metallurgical phenomena, especially in steelmaking process. Recently, many researches on ironmaking process were conducted with CLSM. While for high temperature properties during sintering process, there are limited reports on in situ observation1-2). In this paper, melting and solidifying characteristics of iron ore were observed with CLSM under simulated sintering temperature, and high temperature properties of iron ore during sintering process was clarified based on the in situ observation results and TG-DSC research."

Jan 1, 2012